CA2134631A1 - Finely divided metal, alloy and metal compound powders - Google Patents
Finely divided metal, alloy and metal compound powdersInfo
- Publication number
- CA2134631A1 CA2134631A1 CA002134631A CA2134631A CA2134631A1 CA 2134631 A1 CA2134631 A1 CA 2134631A1 CA 002134631 A CA002134631 A CA 002134631A CA 2134631 A CA2134631 A CA 2134631A CA 2134631 A1 CA2134631 A1 CA 2134631A1
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F9/00—Making metallic powder or suspensions thereof
- B22F9/16—Making metallic powder or suspensions thereof using chemical processes
- B22F9/18—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds
- B22F9/28—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds starting from gaseous metal compounds
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B19/00—Selenium; Tellurium; Compounds thereof
- C01B19/007—Tellurides or selenides of metals
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B21/00—Nitrogen; Compounds thereof
- C01B21/06—Binary compounds of nitrogen with metals, with silicon, or with boron, or with carbon, i.e. nitrides; Compounds of nitrogen with more than one metal, silicon or boron
- C01B21/0632—Binary compounds of nitrogen with metals, with silicon, or with boron, or with carbon, i.e. nitrides; Compounds of nitrogen with more than one metal, silicon or boron with gallium, indium or thallium
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G1/00—Methods of preparing compounds of metals not covered by subclasses C01B, C01C, C01D, or C01F, in general
- C01G1/02—Oxides
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G1/00—Methods of preparing compounds of metals not covered by subclasses C01B, C01C, C01D, or C01F, in general
- C01G1/12—Sulfides
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/51—Particles with a specific particle size distribution
- C01P2004/52—Particles with a specific particle size distribution highly monodisperse size distribution
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/60—Particles characterised by their size
- C01P2004/62—Submicrometer sized, i.e. from 0.1-1 micrometer
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/60—Particles characterised by their size
- C01P2004/64—Nanometer sized, i.e. from 1-100 nanometer
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/12—Surface area
Abstract
Finely divided metal. alloy and metal compound powders Abstract The present invention relates to finely divided metal, alloy and metal compound powders MeX, wherein Me means Al, Ga, In, Th, Ge, Sn, Pb, As, Sb, Bi, Se, Te, Cu, Ag, Au, Zn, Cd, Hg, Pt, Pd, Ir, Rh, Ru, Os, Re, Y, La, Ce, Th, Pr, Nd, Sm, Eu, Gd, and X means C, N, B, Si, Se, Te, P, O and S or combinations thereof, with the exception of AlN and Al2O3.
Description
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Finelv divided metal, alloy and metal compound powders The present invention relates to finely divided metal, alloy and metal compound powders MeX wherein Me means Al, Ga, In, Tl, Ge, Sn, Pb, As, Sb, Bi, Se, Te, Cu, Ag, Au, 7.n, Cd, Hg, Pt, Pd, Ir, Rh, l~u, Os, Re, Y, La, Ce, Th, Pr, Nd, Sm, Eu, Gd and X means C, N, B, Si, Se, Te, P, O and S or combinations thereof, with the exception of AIN and Al2O3.
Finely divided powders of the various compositions above are becoming increasingly important industrially. For example, mirrors may be produced by applying a suspension of such finely divided metal powder onto a substrate. ;~
Many processes have become known for the industrial production of fine metal and metal compound powders.
Apart from purely mechanical size reduction and classifying processes, which have . ~;, the disadvantage that it is only possible to produce powders down to a certain ~ ~:
fineness and with a relatively wide grain distribution, a plurality of gas-phaseprecipitation processes has been proposed.
Partly due to sometimes very small energy sources, such as for example thermal p1asma or laser beam, or in turbulent flames? such as for example in a chlorine 2 0 detonating gas burner, the grain distribution and grain size of the resultant powders cannot be exactly controlled and the reaction conditions customarily result in a very wide grain distribution and the occurrence of individual particles with diameters which are a multiple of the average grain size.
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Using currently known large-scale industrial powder production processes, it is scarcely possible, or only with great difficulty, to produce powders with average grain sizes of < 0.5 ~,lm, measured by FSSS (and not individual particle size). In these conventionally produced powders it is virtually impossible to prevent the ;;
presence of a certain percentage of coarse grains in the material which have a deleterious effect on the mechanical properties of components produced from them. A very wide grain distribution is also obtained in conventional grinding processes, which even air classification carmot substantially narrow in these powders.
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Currently known processes for the production of ultra-fine powders via the gas phase operate in some cases in two stages, wherein the purpose of the second stage is to convert the intermediate product, which is to a greater or lesser extent - .
amorphous, into crystalline form and to separate unwanted secondary products from the reaction.
, , . . ,~ . .
15 Other gas phase processes do not operate with a flow-optimised hot wall reactor, but instead use a plasma flame or other energy source such as laser beams for the reaction. The disadvantages of these processes essentially relate to the reaction conditions which, in practice, are uncontrollable in various areas of the reaction ; . , .
zone with very large temperature gradients and/or turbulent flow. Such phenomena . ;
2 0 result in powders with a wide grain distribution. ;
Many processes have been proposed for the production of ultra-fine powders of YL~,: ".f., ~, hard material, all of which, however, have disadvantages. Thus, the process disclosed in US-A 4,994,107, in which a tubular reactor for the production of a .
uniform, non-agglomerated powder is described, has considerable practical disadvantages. Since all the reactants are mixed together before the hot zone, there is no defined beginning to the nucleation reaction. Wall reactions also cannot be prevented. This increases the risk that large particles will enter the otherwise fine powder and will thereafter be impossible to remove.
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EP-A 0 379 910 describes a two-stage process for the production of Si3N4 from ~ : -the gas phase, in which the starting halide is injected as a liquid into the reaction zone through a two-fluid nozzle. It is not possible to prepare a satisfactory powder ~ r`, using this process either. . ~ ~ ;
- ;
5 Other proposals for the production of very fine, uniform powders include reaction under reduced pressure, as well as various sol-gel processes. These proposals also ~;
have disadvantages, such as being multi-stage operations, being poorly controllable in terms of grain size, grain distribution and being batch processes.
The proposed plasma, laser or explosion processes (EP-A 0 152 957, EP-A 0 151 -10 490) also exhibit the stated disadvantages.
The production of fine powders by specially controlled magnesiothermal reaction . .
of the corresponding metal chlorides in order to produce, for example, TiN or TiC
also does not achieve the fineness and uniformity of the powders produced - :
according to the proposed process (G.W. Elger, Met. Transactions 20 B, 8, 1989, p. 493 497).
- ' .
The process disclosed in US-A 4,642,207, US-A 4,689,075, EP-A 152 957 and EP-A 151 490, which relate to the vaporisation of metal by electric arc or electron `
beam and to the reaction of gaseous reactants in a glow discharge, likewise do not fulfil the requirements for a process which may be operated econornically for the 20 production of very uniform and very fine powders.
Amorphous Si3N4 powders with a grain size of 0.1 to 1 ~lm and crystalline Si3N4 powders with grain sizes of 0.15 to 1.0 llm are known from DE-A 3 536 933. DE-A 3 833 382 describes AlN powders with a smallest grain size of approximately . -~
0.3,um.
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".- .. .
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In the search for materials made from metals and metal compounds with improved mechanical, electrical, optical and magnetic properties, there is a requirement for ever finer powders.
It is already possible to produce ultra-fine nanometre range powders using the 5 noble gas condensation process. This process may, however, only be used to produce quantities in the milligram range. The powders are also not produced with a narrow particle size distribution. ;~
The object of this invention is thus to provide powders which do not exhibit thedescribed disadvantages of prior art powders.
10 Powders have now been developed which do fulfil these requirements. These powders constitute the subject matter of the present invention.
. '''" . ~ ~ ~
The present invention thus provides finely divided metal alloys, and metal compound powders MeX, wherein . ~ :
Me = Al, Ga, In, Tl, Ge, Sn, Pb, As, Sb, Bi, Se, Te, Cu, Ag, Au, Zn, Cd, 15Hg, Pt, Pd, Ir, Rh, Ru, Os, Re, Y, La, Ce, Th, Pr, Nd, Sm, Eu, Gd and X = C, N, B, Si, Se, Te, P, O and S or combinations thereof, with the exception of AIN and Al2O3, wherein they have a particle size of between l.0 nm and l,000 nm and less than 20 1% of the individual particles deviate by more than 40%, and no individual particle deviates by more than 60% from the average grain size.
Preferably, less than 1% of the individual particles deviate by more than 20%, and .
no individual particle deviates by more than 50% from the average grain size, in STA 66-~oreign Countries - 4 -2~ 3~fi3~ ~ :
.:
p~ticular less than 1% of the individual particles deviate by more than 10% and no individual particle deviates by more than 40% from the average grain size.
:
Preferred metal and metal compound powders are: Ag, AgxAuy, GaxInyNz, PbSe, :
AIxGayP. The powdcrs according to the invention have high purity and an extremely n~ow particle size distribution. .
The oxygen content of non-oxides is preferably less than 5,000 ppm, particularly ; .~
preferably less than 1,000 ppm. Particularly pure powders according to the - .;. .
invention are thus characterised in that they have an oxygen content of less than 100 ppm, preferably less than 50 ppm.
.-,~ ~.
0 The quantities of non-oxide impurities are also very low. Thus, the sum of ~
impurities, with the exception of oxide impurities, is preferably less than 5,000 ppm, particularly preferably less than 1,000 ppm. ~ s -~:
In a very particularly preferred embodiment, the sum of impurities, with the exception of oxide impurities, is less than 200 ppm.
;' 15 The powders according to the invention may be obtained on an industrial scale, . .,;. ~
and thus can be produced in quantities of greater than 1 kg.
The powders according to the invention may be obtained in a process for the production of finely divided ceramic powders by the reaction of appropriate metal . ~ ~.. '.','!,,.
compounds and appropriate gas phase coreactants -C~-, wherein the metal 2 0 compound(s) and fur~er coreactants are reacted in a reactor in a gaseous state, are .
directly homogeneously condensed from the gas phase with complete exclusion of .;~
wall reactions and are then separated from the reaction medium, which process is ~ ~ i characterised in that the metal compounds and coreactants are separately ~ .-.. :.. ~`
introduced into the reactor at least at the reaction temperature. In the event that . `~
two or more metal compounds and/or coreactants are to be introduced, the - ~`.; ..
particular gas mixtures should be selected such that no reaction leading to solid .. .
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reaction products occurs during heating. This process may be particularly advantageously performed in a tubular reactor. It is particularly favourable if the metal compounds, the coreactants and the product particles pass through the reactor with laminar flow. . .~
By means of separate preheating of the process gases to at least the reaction ~ ,'~',~',!
temperature (in the case of decomposition reactions of the metal component, the temperature of this educt stream is selected such that no solids are produced before entry into the reactor), it is possible to delimit the location of nucleation.
Laminar flow within the reactor ensures a narrow dwell time distribution of the nuclei or particles. In this manner, a very narrow grain size distribution may be achieved. -~
The metal compounds and coreactants should thus preferably be introduced into the reactor as coaxial laminar partial streams.
However, in order to ensure thorough mixing of the two coaxial partial strearnsj a 15 Karman vortex street of defined intensity and divergence is generated by incorporating an obstacle in the otherwise strongly laminar flow.
A preferred embodiment of this process thus consists in the coaxial, laminar partial streams of the metal compound(s) and coreactants being mixed in a defined manner by means of a Karman vortex street.
2 0 In order to prevent the energetically strongly preferred precipitation of the .
reactants onto the reactor wall, the reaction medium is preferably shielded from ~ '.''i7 .. ,.
the reactor wall by a layer of inert gas. This may be achieved by introducing an . - .
inert gas stream through specially shaped annular slots in the reactor wall, which stream lies against the reactor wall due to the (: oanda effect. The ceramic powder particles produced in the reactor by homogeneous precipitation from the gas phase with typical dwell times of between lO and 300 msec, leave the reactor together with the gaseous reaction products (for example HCI), the unreacted reactants and '`' ~ ~ ` ' `'' `
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the inert gases which are injected as carrier gas, scavenging gas and in order to reduce HCl adsorption. Using the process according to the invention, it is possible to achieve yields of up to 100% related to the metal component.
Separation of the ceramic powder is preferably perfor ned at temperatures above 5 the boiling or sublimation temperatures of the metal compounds, coreactants used and/or the inevitably occurring products formed during the reaction. Separation may here advantageously be performed in a blow-back filter. If this filter is operated at elevated temperatures of, for example, 600C, it is possible to maintain low levels of adsorption of gases, in particular non-inert gases such as HCl, NH3, 10 GaCl3 etc., onto the very large surface area of the ceramic or metal powders. In particular, the formation of NH4Cl is prevented (at above 350C) during nitride production.
Any still remaining disruptive substances adsorbed onto the surfaces of the powder may be further removed in a downstream vacuum container, preferably again at 15 temperatures of approximately 600C. The finished powders should then be discharged from the unit with exclusion of air.
Preferred metal compounds pursuant to this invention are one or more compounds from the group of metal halides, partially hydrogenated metal halides, metal hydrides, metal alkoxides, metal alkyls, metal amides, metal azides, metal 20 hydridoborates and metal carbonyls.
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Preferred further coreactants are one or more substances from the group H2, NH3,hydrazine, amines, CH4, other alkanes, alkenes, alkynes, aryls, 2~ air, BCl3, . .` . .' borates, boranes, SiCl4, other chlorosilanes and silanes. . ~
' ' ~" ''' ' ' '``' The powders according to the invention may be nano- or microdisperse (crystalline . `~
or amorphous) metal or metal compound powders, wherein preferred powders are :~
carbides, nitrides, borides, silicides, phosphites, sulphides, oxides, selenides, '..' `''-' ',~'.
STA 66-Foreign Countries - 7 -.., ~ ... ..
--` ~13 4 ~ 31 tellurides and/or combinations thereof of the elements Al, Ga, In, Tl, Ge, Sn, Pb, ;~
As, Sb, Bi, Ag, Au, Pt, Pd or these elements alone or combined together. -It is possible using this process to produce powders with a particle.size adjustable between l and 1,000 nm (1 ~,lm), which have an extremely narrow particle size 5 distribution. A characteristic feature. of the particles according to the invention is the complete absence of particles which are substantially larger than the average ;
grain size. ~ .r^~
Further characteristics of the powders are their high purity, high surface purity and ~ ..
good reproducibility.
Depending upon the grain size and material, the powders according to the invention may be very air-sensitive to pyrophoric. In order to eliminate this property, these powders may be provided with defined surface modification by .
- ~,s.
exposure to gas,vapour mixtures.
Pigure 1 is a schematic representation of an apparatus with which this process may be performed. Performance of this process is explained below using figure 1.The process, material and/or equipment parameters explicitly stated here are merely options selected from amongst many and thus do not restrict the invention.
The solid, liquid or gaseous metal compounds are metered into an externally located vaporiser (1) or a vaporiser (la) located within the high temperature furnace, are vaporised there at temperatures of 200C to 2,000C and transportedwith an inert carrier gas (N2, Ar or He) into the gas preheater (2a~. The further coreactants (3) such as H2, NH3 and CH4 are also heated in a gas preheater (2).
Before entering the tubular reactor (4), the individual turbulent stream filaments leaving the gas preheaters (2) are shapred by nozzle (5) into two coaxial, laminar and rotationally syrnmetrical stream filaments.
STA 66-Poreign Countries - 8 -~3~3~
In the tubular reactor (4), the central stream filament (6), which contains the metal component, and the surrounding stream filament (7), which contains the remainingreactants, thoroughly mix together under defined conditions. The reaction here occurs at temperatures of between 500C and 2,000C, for example in accordance with the following particular examples~
AgCI + 1/2 H~ ~ Ag + HCI
GaCI3 + NH3 ~ GaN + 3 HCI
InCI3 + NH3 ~ InN + 3 HCI
PbI2 + SeCI4 + 3 H2 ~ PbSe + 4 HCI + 2 HI ~ .
In order to ensure thorough mixing of the two coaxial stream filaments, a Karmanvortex street may be generated in the otherwise strongly larninar flow by ;
incorporating an obstruction (17). On exiting from the nozzle, the two coaxial stream threads are separated by a weak stream of inert gas (16) in order to prevent `
fouling of the nozzle (5).
--~ ~ . .....
In order to suppress the energetically strongly preferred heterogeneous precipitation of these substances onto the hot reactor wall, the wall is swept with an inert gas stream (9) (N2, Ar or He) passing through annular slots (8), which ~ ~ :
stream lies against the reactor wall due to the Coanda effect. The ceramic powder pa ticles produced in the reactor by homogeneous precipitation from the gas phase leave the reactor together with the gaseous reaction products (for example HCI),the inert gases and the unreacted reactants and pass directly into a blow-back filter (10), in which they are precipitated. The blow-back filter (10) is operated at temperatures of between 300C and 1,000C, so ensuring that adsorption of gases,in particular non-inert gases such as HCI and NH3, onto the very large surface area of these powders is maintained at a low level. The formation of NH4CI from ~ -excess NEI3 (in the production of metal nitrides) and HCI is also suppressed. In a - :~
subsequent container (11), the residues of the gases adsorbed onto the powders are further reduced, preferably by alternate application of a vacuum and flooding with ,~, ,. "
STA 66-Foreign Countries - 9 -fi 3 :~ ~
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various gases at 300C to 1,000C. Good effects are achieved if gases such as Aror Kr are used. SF6 is particularly preferably used.
It is also possible to produce metastable material sys~ems and particles with a core/shell structure using this process. Metastable material systems are here 5 obtained by arranging very rapid rates of cooling in the lower part of the reactor.
The particles with a core/shell structure are obtained by introducing additionalreaction gases into the lower part of the reactor.
From the evacuation container (11), the powders pass into the cooling container (12) before passing through the lock (13) into the collection and shipping ; .
10 container (14). In the cooling container (12), the particle surfaces may be provided with defined surface modification by injecting various gas/vapour mixtures. . i . i;.. .
. - ., , ~, The material which may be used for those components which are exposed to temperatures of up to 2,000C and over, such as heat exchangers (2) and (3), nozzle (5), reactor (4) and reactor casing (15), is preferably coated graphite, in particular fine grained graphite. Coating may, for example, be necessary if the requisite chemical resistance of the graphite against the gases used, such as metal - . i.1,,i. ?"~
chlorides, HC1, H2, NH3 and N2, is inadequate at the temperatures involved or if - ``; .
erosion at higher flow velocities (O.S-SO m/sec) is very considerable or if gas-tightness of the graphite may be increased by such coating or if surface roughness 2 o of the reactor components may be reduced by this means. . .
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Layers which may be used are, for example, SiC, B4C, TiN, TiC and Ni (only up .. ~ S
to 1200C). Combinations of various layers, for example with a "species-specific"
outer layer, are also possible. These layers may advantageously be applied by means of CVD, plasma spraying and electrolysis ~
If only low temperatures are required, it is also possible to use metallic materials. .: ;
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Three approaches may simultaneously be used to adjust the particle sizes of the ceramic powder~
~ :',:.,, - setting a certain ratio between the reaction gases and inert gases.
- setting a certain pressure.
5 - setting a certain temperature/dwell time profile along the reactor axis.
The temperature/dwell time profile is adjusted as follows~
,- ~,...,; :
- by two of more heating zones from the beginning of the gas preheater (2) .~to the end of the tubular reactor (4). :;. .. - . .
- "' ~
- by varying the reactor cross section along its longitudinal axis.
~..,...- . ; .i..;
10 - by varying gas throughputs and consequently, for a given reactor cross section, flow velocities as well. `, ', ' ;: ' ,'!~
"''~ ',' j'~' :' A substantial advantage of variability of the ternperature/dwell time profile is the possibility of decoupling the nucleation zone from the nucleus growth zone. It is thus possible, in order to produce "coarser" powders (for example in range from :
15 approximately O.l ~,lm to approximately 0.5 ~,lm) at very low temperatures and a - short dwell time (i.e. small reactor cross section for a certain length), to permit the . ii formation of only few nuclei, which may then grow into "coarse" particles at . .
elevated temperature and long dwell time (large reactor cross section). It is also `
possible to produce "fine" powders (for example in the range from approximately ~:
20 3 nm to approximately 50 nm): very large numbers of nuclei are formed in a zone of elevated temperature with a relatively long dwell time, which nuclei grow only slightly in the further reactor at low temperatures and with a short dwell time (small reactor cross section). It is possible to set any intermediate position between the extremes qualitatively represented here.
STA 66-~orelgn Countries - 11 ~
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.
It is possible to passivate the sometimes very air-sensitive to pyrophoric powders in the cooling container (12) by injecting a suitable gas/vapour mixture. The surfaces of the particles of these ceramic powders may be coated both with an oxide layer of a defined thickness and with suitable organic comp.ounds such as 5 higher alcohols, amines or also sintering auxiliaries such as paraffins in aII inert carrier gas stream. Coating may also be provided with regard to possible furtheçprocessing of the powders.
The oxide layers may, for example, be applied with an inert gas/air stream with a ;~
defined moisture content and also with an inert gas/CO2 stream (preferably ~ ~: . `-10 suitable for carbides).
The nano-scale powders according to the invention are suitable, thanks to their ~
mechanical, electrical, optical and magnetic properties, for the production of novel -.
sensors, actuators, dye systems, pastes and mirrors.
The invention is further illustrated below by way of exarnple, although this -.
5 example should not be considered a limitation.
Example I
GaN was produced according to the reaction equation GaCI3 + NH3 ~GaN + 3 HCI
in an apparatus according to figure 1, wherein an excess of NH3 and H2 was . .
2 0 maintained.
.~:,. ~.- ':
To this end, 100 g/min of GaCI3 (solid, boiling point 201C) were metered into ~ ` : .
the vaporiser (la), vaporised and, together with 50 Nl/min of N2, heated to 800C.
This gas mixture was passed into gas preheater (2a). The coreactants H2 (200 Nl/min) and NH3 (95 Nl/min) were introduced into gas preheater (2). The STA 66-Foreign Countries - 12 - -~13 ~S31 :
coreactants were separately preheated to a temperature of approximately l,000C.Temperature measurement was made with a WSRe-W26Re thermocouple (18) at the point shown in figure l (1175C). Before entering the reaction tube (4), theindividual turbulent stream filaments leaving the gas preheaters (2) were shaped in the outer part of nozzle (5) into a homogeneous, rotationally symmetrical and larninar annular stream. The gas stream leaving gas preheater (2a) was also larninarised in the nozzle (5) and annular flow imparted to it. The nozzle (5) here comprised three coaxially arranged partial nozzles. An inert gas stream (16) exited from the central partial nozzle, so shifting the location of the beginning of the reaction, i.e. the meeting point of the two partial streams (6) and (7), away from the nozzle into the reaction tube. A Karman vortex street was generated in the inner stream filament with an obstruction (17) having a characterising dimensionof 3.0 mm (arranged in the longitudinal axis of the nozzle). The reaction tube had a total length of l,lO0 mm, an internal diameter of 40 mm at the nozzle outlet, an internal diameter of 30 mm at 200 mm below the nozzle and 50 mm at the outlet The internal cross section was here constantly changed in accordance with the laws of fluid mechanics. The reaction tube (4) comprised 18 segments, wherein the segments were each attached by a spacing and centring ring. An annular slot (8) was arranged at each of these points. The temperature of the reaction tube (4) was set at 1080C, measured on the outer wall of the reactor, 400 mm below the nozzle with the W5Re-W26Re thermocouple (l9). The pressure in the reaction tube (4) was virtually identical to the pressure in the blow-back filter (lO). This pressure was 200 mbar above atmospheric. The reactor wall was swept with 250 Nl/min of Ar passing through 18 annular slots (8). If the reactor wall is not swept with an inert gas, fouling may occur which may sometimes very rapidly proceed as far as to block the reactor so shutting down the process; in any case, however, the changing reactor geometry also results in changes to the product. In order to reduce the HCl partial pressure, 200 Nl/min of Ar was injected into the reactiontube (4) through the 6th annular slot from the bottom by means of an additional gas feed device. The product (GaN with a uniform particle size of approximately 10 nm) was separated from the gases (H2, NH3, HCl, Ar, N2) in the blow-back filter (lO) at a temperature of 600C.
STA 66-Foreign Countries - 13 -X ~ 6 3 1 This temperature was selected, on the one hand, in order to prevent the formation of NH4Cl (> 350C) and, on the other, to keep the primary occupation of the veryIarge particle surfaces (approximately 100 m2/g) with HC1 at a low level (approximately 1.5% Cl). . ~ - .
~ . -; -; ~...
The GaN produced in this manner was collected for 60 minutes (i.e. 2850 g) in the blow-back filter, in order then to be transferred into the evacuation container (11). Over a period of 50 minutes, 8 pumping/flooding cycles with final vacuums of 0.1 mbar abs. were performed in this container. On each occasion, the container was flooded with Ar to a pressure of 3,000 mbar abs.. After 50 minutes, the GaN
10 powder treated in this manner was transferred into the cooling container (12). It is possible purposefully to tailor surface properties in this container by the injection of various gas/vapour mixtures. Once the powder had cooled to < 50C, it was transferred through the lock (13) without contact with the extern21 air into thecollection and shipping container.
5 The pyrophoric GaN powder had an extremely narrow grain distribution at a BET
specific surface area of 98 m2/g, measured using the N2 single point method (DIN66 131), corresponding to 10 nm.
A scanning electron micrograph of this GaN powder with a specific surface area of 98 m2/g demonstrated the very narrow distribution of the particle dimensions 20 and the absence of oversize particles. According to the micrograph, less than 1%
of the individual particles deviate by more than 10% and no individual particle deviates by more than 40% from the average grain size. As measuring techniques currently stand, it is possible to make reliable statements as to the particle size distribution of such extremely fine po~ders Ohly on the basis of imaging 25 techniques (for example SEM, TEM).
:
Analysis of this GaN powder showed an oxygen content of 95 ppm and total non~
oxide impurities amounted to 400 ppm.
STA 66-Foreign Countries - 14 - ~ r~
Finelv divided metal, alloy and metal compound powders The present invention relates to finely divided metal, alloy and metal compound powders MeX wherein Me means Al, Ga, In, Tl, Ge, Sn, Pb, As, Sb, Bi, Se, Te, Cu, Ag, Au, 7.n, Cd, Hg, Pt, Pd, Ir, Rh, l~u, Os, Re, Y, La, Ce, Th, Pr, Nd, Sm, Eu, Gd and X means C, N, B, Si, Se, Te, P, O and S or combinations thereof, with the exception of AIN and Al2O3.
Finely divided powders of the various compositions above are becoming increasingly important industrially. For example, mirrors may be produced by applying a suspension of such finely divided metal powder onto a substrate. ;~
Many processes have become known for the industrial production of fine metal and metal compound powders.
Apart from purely mechanical size reduction and classifying processes, which have . ~;, the disadvantage that it is only possible to produce powders down to a certain ~ ~:
fineness and with a relatively wide grain distribution, a plurality of gas-phaseprecipitation processes has been proposed.
Partly due to sometimes very small energy sources, such as for example thermal p1asma or laser beam, or in turbulent flames? such as for example in a chlorine 2 0 detonating gas burner, the grain distribution and grain size of the resultant powders cannot be exactly controlled and the reaction conditions customarily result in a very wide grain distribution and the occurrence of individual particles with diameters which are a multiple of the average grain size.
STA 66-Foreign Countries - 1 - . ~ `
.- -~ -.. ...
;, .- ~.~,.
-- 213 ~3~ :
..
Using currently known large-scale industrial powder production processes, it is scarcely possible, or only with great difficulty, to produce powders with average grain sizes of < 0.5 ~,lm, measured by FSSS (and not individual particle size). In these conventionally produced powders it is virtually impossible to prevent the ;;
presence of a certain percentage of coarse grains in the material which have a deleterious effect on the mechanical properties of components produced from them. A very wide grain distribution is also obtained in conventional grinding processes, which even air classification carmot substantially narrow in these powders.
, ~
Currently known processes for the production of ultra-fine powders via the gas phase operate in some cases in two stages, wherein the purpose of the second stage is to convert the intermediate product, which is to a greater or lesser extent - .
amorphous, into crystalline form and to separate unwanted secondary products from the reaction.
, , . . ,~ . .
15 Other gas phase processes do not operate with a flow-optimised hot wall reactor, but instead use a plasma flame or other energy source such as laser beams for the reaction. The disadvantages of these processes essentially relate to the reaction conditions which, in practice, are uncontrollable in various areas of the reaction ; . , .
zone with very large temperature gradients and/or turbulent flow. Such phenomena . ;
2 0 result in powders with a wide grain distribution. ;
Many processes have been proposed for the production of ultra-fine powders of YL~,: ".f., ~, hard material, all of which, however, have disadvantages. Thus, the process disclosed in US-A 4,994,107, in which a tubular reactor for the production of a .
uniform, non-agglomerated powder is described, has considerable practical disadvantages. Since all the reactants are mixed together before the hot zone, there is no defined beginning to the nucleation reaction. Wall reactions also cannot be prevented. This increases the risk that large particles will enter the otherwise fine powder and will thereafter be impossible to remove.
- "~
., STA 66-Foreign Countries - 2 -, ....
- ~,, -, " : - ~ ~ , .. . . .
EP-A 0 379 910 describes a two-stage process for the production of Si3N4 from ~ : -the gas phase, in which the starting halide is injected as a liquid into the reaction zone through a two-fluid nozzle. It is not possible to prepare a satisfactory powder ~ r`, using this process either. . ~ ~ ;
- ;
5 Other proposals for the production of very fine, uniform powders include reaction under reduced pressure, as well as various sol-gel processes. These proposals also ~;
have disadvantages, such as being multi-stage operations, being poorly controllable in terms of grain size, grain distribution and being batch processes.
The proposed plasma, laser or explosion processes (EP-A 0 152 957, EP-A 0 151 -10 490) also exhibit the stated disadvantages.
The production of fine powders by specially controlled magnesiothermal reaction . .
of the corresponding metal chlorides in order to produce, for example, TiN or TiC
also does not achieve the fineness and uniformity of the powders produced - :
according to the proposed process (G.W. Elger, Met. Transactions 20 B, 8, 1989, p. 493 497).
- ' .
The process disclosed in US-A 4,642,207, US-A 4,689,075, EP-A 152 957 and EP-A 151 490, which relate to the vaporisation of metal by electric arc or electron `
beam and to the reaction of gaseous reactants in a glow discharge, likewise do not fulfil the requirements for a process which may be operated econornically for the 20 production of very uniform and very fine powders.
Amorphous Si3N4 powders with a grain size of 0.1 to 1 ~lm and crystalline Si3N4 powders with grain sizes of 0.15 to 1.0 llm are known from DE-A 3 536 933. DE-A 3 833 382 describes AlN powders with a smallest grain size of approximately . -~
0.3,um.
. ~' .' .-.
".- .. .
STA 66-Foreign Countries - 3 ~
2~3 ~3~ : `
In the search for materials made from metals and metal compounds with improved mechanical, electrical, optical and magnetic properties, there is a requirement for ever finer powders.
It is already possible to produce ultra-fine nanometre range powders using the 5 noble gas condensation process. This process may, however, only be used to produce quantities in the milligram range. The powders are also not produced with a narrow particle size distribution. ;~
The object of this invention is thus to provide powders which do not exhibit thedescribed disadvantages of prior art powders.
10 Powders have now been developed which do fulfil these requirements. These powders constitute the subject matter of the present invention.
. '''" . ~ ~ ~
The present invention thus provides finely divided metal alloys, and metal compound powders MeX, wherein . ~ :
Me = Al, Ga, In, Tl, Ge, Sn, Pb, As, Sb, Bi, Se, Te, Cu, Ag, Au, Zn, Cd, 15Hg, Pt, Pd, Ir, Rh, Ru, Os, Re, Y, La, Ce, Th, Pr, Nd, Sm, Eu, Gd and X = C, N, B, Si, Se, Te, P, O and S or combinations thereof, with the exception of AIN and Al2O3, wherein they have a particle size of between l.0 nm and l,000 nm and less than 20 1% of the individual particles deviate by more than 40%, and no individual particle deviates by more than 60% from the average grain size.
Preferably, less than 1% of the individual particles deviate by more than 20%, and .
no individual particle deviates by more than 50% from the average grain size, in STA 66-~oreign Countries - 4 -2~ 3~fi3~ ~ :
.:
p~ticular less than 1% of the individual particles deviate by more than 10% and no individual particle deviates by more than 40% from the average grain size.
:
Preferred metal and metal compound powders are: Ag, AgxAuy, GaxInyNz, PbSe, :
AIxGayP. The powdcrs according to the invention have high purity and an extremely n~ow particle size distribution. .
The oxygen content of non-oxides is preferably less than 5,000 ppm, particularly ; .~
preferably less than 1,000 ppm. Particularly pure powders according to the - .;. .
invention are thus characterised in that they have an oxygen content of less than 100 ppm, preferably less than 50 ppm.
.-,~ ~.
0 The quantities of non-oxide impurities are also very low. Thus, the sum of ~
impurities, with the exception of oxide impurities, is preferably less than 5,000 ppm, particularly preferably less than 1,000 ppm. ~ s -~:
In a very particularly preferred embodiment, the sum of impurities, with the exception of oxide impurities, is less than 200 ppm.
;' 15 The powders according to the invention may be obtained on an industrial scale, . .,;. ~
and thus can be produced in quantities of greater than 1 kg.
The powders according to the invention may be obtained in a process for the production of finely divided ceramic powders by the reaction of appropriate metal . ~ ~.. '.','!,,.
compounds and appropriate gas phase coreactants -C~-, wherein the metal 2 0 compound(s) and fur~er coreactants are reacted in a reactor in a gaseous state, are .
directly homogeneously condensed from the gas phase with complete exclusion of .;~
wall reactions and are then separated from the reaction medium, which process is ~ ~ i characterised in that the metal compounds and coreactants are separately ~ .-.. :.. ~`
introduced into the reactor at least at the reaction temperature. In the event that . `~
two or more metal compounds and/or coreactants are to be introduced, the - ~`.; ..
particular gas mixtures should be selected such that no reaction leading to solid .. .
STA 66-Foreign Countries - 5 -; ; -: ,.- ..
6 3 ~
reaction products occurs during heating. This process may be particularly advantageously performed in a tubular reactor. It is particularly favourable if the metal compounds, the coreactants and the product particles pass through the reactor with laminar flow. . .~
By means of separate preheating of the process gases to at least the reaction ~ ,'~',~',!
temperature (in the case of decomposition reactions of the metal component, the temperature of this educt stream is selected such that no solids are produced before entry into the reactor), it is possible to delimit the location of nucleation.
Laminar flow within the reactor ensures a narrow dwell time distribution of the nuclei or particles. In this manner, a very narrow grain size distribution may be achieved. -~
The metal compounds and coreactants should thus preferably be introduced into the reactor as coaxial laminar partial streams.
However, in order to ensure thorough mixing of the two coaxial partial strearnsj a 15 Karman vortex street of defined intensity and divergence is generated by incorporating an obstacle in the otherwise strongly laminar flow.
A preferred embodiment of this process thus consists in the coaxial, laminar partial streams of the metal compound(s) and coreactants being mixed in a defined manner by means of a Karman vortex street.
2 0 In order to prevent the energetically strongly preferred precipitation of the .
reactants onto the reactor wall, the reaction medium is preferably shielded from ~ '.''i7 .. ,.
the reactor wall by a layer of inert gas. This may be achieved by introducing an . - .
inert gas stream through specially shaped annular slots in the reactor wall, which stream lies against the reactor wall due to the (: oanda effect. The ceramic powder particles produced in the reactor by homogeneous precipitation from the gas phase with typical dwell times of between lO and 300 msec, leave the reactor together with the gaseous reaction products (for example HCI), the unreacted reactants and '`' ~ ~ ` ' `'' `
STA 66-Foreign Countries - 6 - .g~ }~
:. - ~ . . .: .: ~ .`, 2~3~3~
the inert gases which are injected as carrier gas, scavenging gas and in order to reduce HCl adsorption. Using the process according to the invention, it is possible to achieve yields of up to 100% related to the metal component.
Separation of the ceramic powder is preferably perfor ned at temperatures above 5 the boiling or sublimation temperatures of the metal compounds, coreactants used and/or the inevitably occurring products formed during the reaction. Separation may here advantageously be performed in a blow-back filter. If this filter is operated at elevated temperatures of, for example, 600C, it is possible to maintain low levels of adsorption of gases, in particular non-inert gases such as HCl, NH3, 10 GaCl3 etc., onto the very large surface area of the ceramic or metal powders. In particular, the formation of NH4Cl is prevented (at above 350C) during nitride production.
Any still remaining disruptive substances adsorbed onto the surfaces of the powder may be further removed in a downstream vacuum container, preferably again at 15 temperatures of approximately 600C. The finished powders should then be discharged from the unit with exclusion of air.
Preferred metal compounds pursuant to this invention are one or more compounds from the group of metal halides, partially hydrogenated metal halides, metal hydrides, metal alkoxides, metal alkyls, metal amides, metal azides, metal 20 hydridoborates and metal carbonyls.
, ; ~.. ,~, ,.. ,,, ~
Preferred further coreactants are one or more substances from the group H2, NH3,hydrazine, amines, CH4, other alkanes, alkenes, alkynes, aryls, 2~ air, BCl3, . .` . .' borates, boranes, SiCl4, other chlorosilanes and silanes. . ~
' ' ~" ''' ' ' '``' The powders according to the invention may be nano- or microdisperse (crystalline . `~
or amorphous) metal or metal compound powders, wherein preferred powders are :~
carbides, nitrides, borides, silicides, phosphites, sulphides, oxides, selenides, '..' `''-' ',~'.
STA 66-Foreign Countries - 7 -.., ~ ... ..
--` ~13 4 ~ 31 tellurides and/or combinations thereof of the elements Al, Ga, In, Tl, Ge, Sn, Pb, ;~
As, Sb, Bi, Ag, Au, Pt, Pd or these elements alone or combined together. -It is possible using this process to produce powders with a particle.size adjustable between l and 1,000 nm (1 ~,lm), which have an extremely narrow particle size 5 distribution. A characteristic feature. of the particles according to the invention is the complete absence of particles which are substantially larger than the average ;
grain size. ~ .r^~
Further characteristics of the powders are their high purity, high surface purity and ~ ..
good reproducibility.
Depending upon the grain size and material, the powders according to the invention may be very air-sensitive to pyrophoric. In order to eliminate this property, these powders may be provided with defined surface modification by .
- ~,s.
exposure to gas,vapour mixtures.
Pigure 1 is a schematic representation of an apparatus with which this process may be performed. Performance of this process is explained below using figure 1.The process, material and/or equipment parameters explicitly stated here are merely options selected from amongst many and thus do not restrict the invention.
The solid, liquid or gaseous metal compounds are metered into an externally located vaporiser (1) or a vaporiser (la) located within the high temperature furnace, are vaporised there at temperatures of 200C to 2,000C and transportedwith an inert carrier gas (N2, Ar or He) into the gas preheater (2a~. The further coreactants (3) such as H2, NH3 and CH4 are also heated in a gas preheater (2).
Before entering the tubular reactor (4), the individual turbulent stream filaments leaving the gas preheaters (2) are shapred by nozzle (5) into two coaxial, laminar and rotationally syrnmetrical stream filaments.
STA 66-Poreign Countries - 8 -~3~3~
In the tubular reactor (4), the central stream filament (6), which contains the metal component, and the surrounding stream filament (7), which contains the remainingreactants, thoroughly mix together under defined conditions. The reaction here occurs at temperatures of between 500C and 2,000C, for example in accordance with the following particular examples~
AgCI + 1/2 H~ ~ Ag + HCI
GaCI3 + NH3 ~ GaN + 3 HCI
InCI3 + NH3 ~ InN + 3 HCI
PbI2 + SeCI4 + 3 H2 ~ PbSe + 4 HCI + 2 HI ~ .
In order to ensure thorough mixing of the two coaxial stream filaments, a Karmanvortex street may be generated in the otherwise strongly larninar flow by ;
incorporating an obstruction (17). On exiting from the nozzle, the two coaxial stream threads are separated by a weak stream of inert gas (16) in order to prevent `
fouling of the nozzle (5).
--~ ~ . .....
In order to suppress the energetically strongly preferred heterogeneous precipitation of these substances onto the hot reactor wall, the wall is swept with an inert gas stream (9) (N2, Ar or He) passing through annular slots (8), which ~ ~ :
stream lies against the reactor wall due to the Coanda effect. The ceramic powder pa ticles produced in the reactor by homogeneous precipitation from the gas phase leave the reactor together with the gaseous reaction products (for example HCI),the inert gases and the unreacted reactants and pass directly into a blow-back filter (10), in which they are precipitated. The blow-back filter (10) is operated at temperatures of between 300C and 1,000C, so ensuring that adsorption of gases,in particular non-inert gases such as HCI and NH3, onto the very large surface area of these powders is maintained at a low level. The formation of NH4CI from ~ -excess NEI3 (in the production of metal nitrides) and HCI is also suppressed. In a - :~
subsequent container (11), the residues of the gases adsorbed onto the powders are further reduced, preferably by alternate application of a vacuum and flooding with ,~, ,. "
STA 66-Foreign Countries - 9 -fi 3 :~ ~
.
various gases at 300C to 1,000C. Good effects are achieved if gases such as Aror Kr are used. SF6 is particularly preferably used.
It is also possible to produce metastable material sys~ems and particles with a core/shell structure using this process. Metastable material systems are here 5 obtained by arranging very rapid rates of cooling in the lower part of the reactor.
The particles with a core/shell structure are obtained by introducing additionalreaction gases into the lower part of the reactor.
From the evacuation container (11), the powders pass into the cooling container (12) before passing through the lock (13) into the collection and shipping ; .
10 container (14). In the cooling container (12), the particle surfaces may be provided with defined surface modification by injecting various gas/vapour mixtures. . i . i;.. .
. - ., , ~, The material which may be used for those components which are exposed to temperatures of up to 2,000C and over, such as heat exchangers (2) and (3), nozzle (5), reactor (4) and reactor casing (15), is preferably coated graphite, in particular fine grained graphite. Coating may, for example, be necessary if the requisite chemical resistance of the graphite against the gases used, such as metal - . i.1,,i. ?"~
chlorides, HC1, H2, NH3 and N2, is inadequate at the temperatures involved or if - ``; .
erosion at higher flow velocities (O.S-SO m/sec) is very considerable or if gas-tightness of the graphite may be increased by such coating or if surface roughness 2 o of the reactor components may be reduced by this means. . .
. :, :, . -, ,., ~
,, .: , ,~. .
Layers which may be used are, for example, SiC, B4C, TiN, TiC and Ni (only up .. ~ S
to 1200C). Combinations of various layers, for example with a "species-specific"
outer layer, are also possible. These layers may advantageously be applied by means of CVD, plasma spraying and electrolysis ~
If only low temperatures are required, it is also possible to use metallic materials. .: ;
STA 66-Foreign Countries - 10 - ~ ~ ~
, .' ~'' .. ~,,~
~ ~.
~^` 2 1 ~ -~ 6 3 ~ ~
Three approaches may simultaneously be used to adjust the particle sizes of the ceramic powder~
~ :',:.,, - setting a certain ratio between the reaction gases and inert gases.
- setting a certain pressure.
5 - setting a certain temperature/dwell time profile along the reactor axis.
The temperature/dwell time profile is adjusted as follows~
,- ~,...,; :
- by two of more heating zones from the beginning of the gas preheater (2) .~to the end of the tubular reactor (4). :;. .. - . .
- "' ~
- by varying the reactor cross section along its longitudinal axis.
~..,...- . ; .i..;
10 - by varying gas throughputs and consequently, for a given reactor cross section, flow velocities as well. `, ', ' ;: ' ,'!~
"''~ ',' j'~' :' A substantial advantage of variability of the ternperature/dwell time profile is the possibility of decoupling the nucleation zone from the nucleus growth zone. It is thus possible, in order to produce "coarser" powders (for example in range from :
15 approximately O.l ~,lm to approximately 0.5 ~,lm) at very low temperatures and a - short dwell time (i.e. small reactor cross section for a certain length), to permit the . ii formation of only few nuclei, which may then grow into "coarse" particles at . .
elevated temperature and long dwell time (large reactor cross section). It is also `
possible to produce "fine" powders (for example in the range from approximately ~:
20 3 nm to approximately 50 nm): very large numbers of nuclei are formed in a zone of elevated temperature with a relatively long dwell time, which nuclei grow only slightly in the further reactor at low temperatures and with a short dwell time (small reactor cross section). It is possible to set any intermediate position between the extremes qualitatively represented here.
STA 66-~orelgn Countries - 11 ~
2~3`163~ ~
.
It is possible to passivate the sometimes very air-sensitive to pyrophoric powders in the cooling container (12) by injecting a suitable gas/vapour mixture. The surfaces of the particles of these ceramic powders may be coated both with an oxide layer of a defined thickness and with suitable organic comp.ounds such as 5 higher alcohols, amines or also sintering auxiliaries such as paraffins in aII inert carrier gas stream. Coating may also be provided with regard to possible furtheçprocessing of the powders.
The oxide layers may, for example, be applied with an inert gas/air stream with a ;~
defined moisture content and also with an inert gas/CO2 stream (preferably ~ ~: . `-10 suitable for carbides).
The nano-scale powders according to the invention are suitable, thanks to their ~
mechanical, electrical, optical and magnetic properties, for the production of novel -.
sensors, actuators, dye systems, pastes and mirrors.
The invention is further illustrated below by way of exarnple, although this -.
5 example should not be considered a limitation.
Example I
GaN was produced according to the reaction equation GaCI3 + NH3 ~GaN + 3 HCI
in an apparatus according to figure 1, wherein an excess of NH3 and H2 was . .
2 0 maintained.
.~:,. ~.- ':
To this end, 100 g/min of GaCI3 (solid, boiling point 201C) were metered into ~ ` : .
the vaporiser (la), vaporised and, together with 50 Nl/min of N2, heated to 800C.
This gas mixture was passed into gas preheater (2a). The coreactants H2 (200 Nl/min) and NH3 (95 Nl/min) were introduced into gas preheater (2). The STA 66-Foreign Countries - 12 - -~13 ~S31 :
coreactants were separately preheated to a temperature of approximately l,000C.Temperature measurement was made with a WSRe-W26Re thermocouple (18) at the point shown in figure l (1175C). Before entering the reaction tube (4), theindividual turbulent stream filaments leaving the gas preheaters (2) were shaped in the outer part of nozzle (5) into a homogeneous, rotationally symmetrical and larninar annular stream. The gas stream leaving gas preheater (2a) was also larninarised in the nozzle (5) and annular flow imparted to it. The nozzle (5) here comprised three coaxially arranged partial nozzles. An inert gas stream (16) exited from the central partial nozzle, so shifting the location of the beginning of the reaction, i.e. the meeting point of the two partial streams (6) and (7), away from the nozzle into the reaction tube. A Karman vortex street was generated in the inner stream filament with an obstruction (17) having a characterising dimensionof 3.0 mm (arranged in the longitudinal axis of the nozzle). The reaction tube had a total length of l,lO0 mm, an internal diameter of 40 mm at the nozzle outlet, an internal diameter of 30 mm at 200 mm below the nozzle and 50 mm at the outlet The internal cross section was here constantly changed in accordance with the laws of fluid mechanics. The reaction tube (4) comprised 18 segments, wherein the segments were each attached by a spacing and centring ring. An annular slot (8) was arranged at each of these points. The temperature of the reaction tube (4) was set at 1080C, measured on the outer wall of the reactor, 400 mm below the nozzle with the W5Re-W26Re thermocouple (l9). The pressure in the reaction tube (4) was virtually identical to the pressure in the blow-back filter (lO). This pressure was 200 mbar above atmospheric. The reactor wall was swept with 250 Nl/min of Ar passing through 18 annular slots (8). If the reactor wall is not swept with an inert gas, fouling may occur which may sometimes very rapidly proceed as far as to block the reactor so shutting down the process; in any case, however, the changing reactor geometry also results in changes to the product. In order to reduce the HCl partial pressure, 200 Nl/min of Ar was injected into the reactiontube (4) through the 6th annular slot from the bottom by means of an additional gas feed device. The product (GaN with a uniform particle size of approximately 10 nm) was separated from the gases (H2, NH3, HCl, Ar, N2) in the blow-back filter (lO) at a temperature of 600C.
STA 66-Foreign Countries - 13 -X ~ 6 3 1 This temperature was selected, on the one hand, in order to prevent the formation of NH4Cl (> 350C) and, on the other, to keep the primary occupation of the veryIarge particle surfaces (approximately 100 m2/g) with HC1 at a low level (approximately 1.5% Cl). . ~ - .
~ . -; -; ~...
The GaN produced in this manner was collected for 60 minutes (i.e. 2850 g) in the blow-back filter, in order then to be transferred into the evacuation container (11). Over a period of 50 minutes, 8 pumping/flooding cycles with final vacuums of 0.1 mbar abs. were performed in this container. On each occasion, the container was flooded with Ar to a pressure of 3,000 mbar abs.. After 50 minutes, the GaN
10 powder treated in this manner was transferred into the cooling container (12). It is possible purposefully to tailor surface properties in this container by the injection of various gas/vapour mixtures. Once the powder had cooled to < 50C, it was transferred through the lock (13) without contact with the extern21 air into thecollection and shipping container.
5 The pyrophoric GaN powder had an extremely narrow grain distribution at a BET
specific surface area of 98 m2/g, measured using the N2 single point method (DIN66 131), corresponding to 10 nm.
A scanning electron micrograph of this GaN powder with a specific surface area of 98 m2/g demonstrated the very narrow distribution of the particle dimensions 20 and the absence of oversize particles. According to the micrograph, less than 1%
of the individual particles deviate by more than 10% and no individual particle deviates by more than 40% from the average grain size. As measuring techniques currently stand, it is possible to make reliable statements as to the particle size distribution of such extremely fine po~ders Ohly on the basis of imaging 25 techniques (for example SEM, TEM).
:
Analysis of this GaN powder showed an oxygen content of 95 ppm and total non~
oxide impurities amounted to 400 ppm.
STA 66-Foreign Countries - 14 - ~ r~
Claims (18)
1. A finely divided metal alloy or metal compound powder MeX, wherein Me represents Al, Ga, In, Te, Ge, Sn, Pb, As, Sb, Bi, Se, Te, Cu, Ag, Au, Zn, Cd, Hg, Pt, Pd, Ir, Rh, Ru, Os, Re, Y, La, Ce, Th, Pr, Nd, Sm, Eu, Gd and X represents C, N, B, Si, Se, Te, P, O and S or a combination thereof, with the exception of AlN and Al2O3, characterised in that they have a particle size of between 1.0 nm and 1,000 nm and less than 1% of the individual particles deviate by more than 40%, and no individual particle deviates by more than 60% from the average grain size.
2. A powder according to claim 1, characterised in that less than 1% of the individual particles deviate by more than 20%, and no individual particle deviates by more than 50% from the average grain size.
3. A powder according to claim 1, characterised in that less than 1% of the individual particles deviate by more than 10%
and no individual particle deviates by more than 40% from the average grain size.
and no individual particle deviates by more than 40% from the average grain size.
4. A powder according to claim 1, characterised in that the particle size ranges from 1 nm to less than 100 nm.
5. A powder according to claim 1, characterised in that the particle size ranges from 1 nm to less than 50 nm.
6. A powder according to claim 1, characterised in that the metal compound or alloy is GaxInyNz, Ag, AgxAuy, AlxGayP or PbSe.
7. A powder according to claim 1, which has an oxygen content of less than 5,000 ppm.
8. A powder according to claim 1, which has an oxygen content of less than 1,000 ppm.
9. A powder according to claim 1, which has an oxygen content of less than 100 ppm.
10. A powder according to claim 1, characterised in that the sum of the impurities, with the exception of oxide impurities, is less than 5,000 ppm.
11. A powder according to claim 1, characterised in that the sum of the impurities, with the exception of oxide impurities, is less than 1,000 ppm.
12. A powder according to claim 1, characterised in that the sum of the impurities, with the exception of oxide impurities, is less than 200 ppm.
13. A powder according to claim 1, which has an oxygen content of less than 50 ppm.
14. A powder according to claim 3, characterised in that the particle size ranges from 1 nm to 100 nm.
15. A powder according to claim 3, characterised in that the particle size ranges from 1 nm to 50 nm.
16. A powder according to claim 3, characterised in that the metal compound or alloy is GaxInyNz, Ag, AgxAuy, AlxGayP or PbSe.
17. A powder according to claim 3, which has an oxygen content of less than 1,000 ppm.
18. A powder according to claim 3, characterised in that the sum of the impurities, with the exception of oxide impurities, is less than 1,000 ppm.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DEP4337336.4 | 1993-11-02 | ||
| DE4337336A DE4337336C1 (en) | 1993-11-02 | 1993-11-02 | Finely divided metal, alloy and metal compound powders |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2134631A1 true CA2134631A1 (en) | 1995-05-03 |
Family
ID=6501593
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002134631A Abandoned CA2134631A1 (en) | 1993-11-02 | 1994-10-28 | Finely divided metal, alloy and metal compound powders |
Country Status (7)
| Country | Link |
|---|---|
| EP (1) | EP0650791B1 (en) |
| JP (1) | JPH07247106A (en) |
| CN (1) | CN1107085A (en) |
| CA (1) | CA2134631A1 (en) |
| DE (2) | DE4337336C1 (en) |
| IL (1) | IL111462A (en) |
| RU (1) | RU2136444C1 (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7749480B2 (en) | 2008-09-30 | 2010-07-06 | 5N Plus Inc. | Cadmium telluride production process |
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| JP2005097022A (en) * | 2003-09-22 | 2005-04-14 | Japan Science & Technology Agency | Synthetic method for group iiib nitride |
| DE10348643B3 (en) * | 2003-10-15 | 2005-05-19 | Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. | Workpiece transport device for press using carrier beams extending in transport direction each supported at either end via lever mechanism coupled to linear drive unit |
| JP5082213B2 (en) * | 2004-08-20 | 2012-11-28 | 三菱化学株式会社 | Metal nitride and method for producing metal nitride |
| KR101266776B1 (en) * | 2004-08-20 | 2013-05-28 | 미쓰비시 가가꾸 가부시키가이샤 | Metal nitrides and process for production thereof |
| JP4756239B2 (en) * | 2005-08-03 | 2011-08-24 | 独立行政法人物質・材料研究機構 | Hollow spherical particles made of gallium nitride and method for producing the same |
| RU2301058C1 (en) * | 2006-07-19 | 2007-06-20 | Валерий Сергеевич Комаров | Method for micronization of organic medicinal substance |
| JP5509731B2 (en) * | 2008-08-04 | 2014-06-04 | 株式会社三徳 | Rare earth nitride, method for producing the same, magnetic refrigeration material and cold storage material |
| RU2503748C2 (en) * | 2011-10-10 | 2014-01-10 | Федеральное государственное бюджетное образовательное учреждение высшего профессионального образования "Тамбовский государственный технический университет" (ФГБОУ ВПО ТГТУ) | Method of producing ultramicrodispersed nickel oxide powder using ac |
| RU2500502C1 (en) * | 2012-06-06 | 2013-12-10 | федеральное государственное бюджетное образовательное учреждение высшего профессионального образования "Тюменский государственный университет" | Method of production of rare-earth element fluorosulphide powders |
| CN102994856B (en) * | 2012-11-28 | 2015-08-12 | 太仓市天合新材料科技有限公司 | A kind of Heat expansion metal |
| RU2550070C1 (en) * | 2014-02-04 | 2015-05-10 | Федеральное государственное бюджетное образовательное учреждение высшего профессионального образования "Тамбовский государственный технический университет" | Procedure for production of ultra-micro-dispersed powder of nickel oxide |
| CN103754838B (en) * | 2014-02-08 | 2015-10-28 | 张家港绿能新材料科技有限公司 | A kind of method and apparatus preparing cadmium antimonide powder fast |
| EP3418344A4 (en) * | 2016-04-01 | 2019-03-27 | Sumitomo Metal Mining Co., Ltd. | Infrared-absorbing material, liquid dispersion of infrared-absorbing material, object including dispersed infrared-absorbing material, transparent base laminated with object including dispersed infrared-absorbing material, and infrared-absorbing transparent base |
| CN111468738A (en) * | 2020-03-02 | 2020-07-31 | 深圳市捷安纳米复合材料有限公司 | Nano silver-copper alloy material and preparation method thereof |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB919954A (en) * | 1960-11-10 | 1963-02-27 | Union Carbide Corp | Improvements in and relating to the production of ultra fine metal powders |
| GB950148A (en) * | 1961-05-03 | 1964-02-19 | Union Carbide Corp | Improvements in or relating to the production of ultrafine metal particles |
| JPS597765B2 (en) * | 1980-09-13 | 1984-02-21 | 昭宣 吉澤 | Manufacturing method of fine powder metal |
| JPS59227765A (en) * | 1983-06-04 | 1984-12-21 | 科学技術庁金属材料技術研究所長 | Manufacture of ceramic super fine particle |
| EP0151490B1 (en) * | 1984-02-09 | 1991-01-16 | Toyota Jidosha Kabushiki Kaisha | Process for producing ultra-fine ceramic particles |
| JPS60175537A (en) * | 1984-02-22 | 1985-09-09 | Toyota Motor Corp | Preparation of ultra-fine ceramic particles |
| JPS6193828A (en) * | 1984-10-16 | 1986-05-12 | Natl Res Inst For Metals | Preparation of ultra-fine particle mixture |
| DE3536933A1 (en) * | 1985-10-17 | 1987-04-23 | Bayer Ag | IMPROVED SILICON NITRIDE AND METHOD FOR THE PRODUCTION THEREOF |
| US4994107A (en) * | 1986-07-09 | 1991-02-19 | California Institute Of Technology | Aerosol reactor production of uniform submicron powders |
| DE3833382A1 (en) * | 1988-10-01 | 1990-04-05 | Bayer Ag | METHOD FOR PRODUCING FINE-PARTICLE CARBIDES AND NITRIDS FROM CERAMIC PRECURSOR COMPOUNDS |
| DE4214722C2 (en) * | 1992-05-04 | 1994-08-25 | Starck H C Gmbh Co Kg | Finely divided metal powder |
| DE4214723C2 (en) * | 1992-05-04 | 1994-08-25 | Starck H C Gmbh Co Kg | Finely divided metal powder |
-
1993
- 1993-11-02 DE DE4337336A patent/DE4337336C1/en not_active Expired - Fee Related
-
1994
- 1994-10-21 EP EP94116634A patent/EP0650791B1/en not_active Expired - Lifetime
- 1994-10-21 DE DE59402362T patent/DE59402362D1/en not_active Expired - Fee Related
- 1994-10-28 CA CA002134631A patent/CA2134631A1/en not_active Abandoned
- 1994-10-28 JP JP6287131A patent/JPH07247106A/en active Pending
- 1994-10-31 IL IL111462A patent/IL111462A/en not_active IP Right Cessation
- 1994-11-01 RU RU94040156A patent/RU2136444C1/en active
- 1994-11-02 CN CN94113789A patent/CN1107085A/en active Pending
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7749480B2 (en) | 2008-09-30 | 2010-07-06 | 5N Plus Inc. | Cadmium telluride production process |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH07247106A (en) | 1995-09-26 |
| EP0650791A1 (en) | 1995-05-03 |
| DE59402362D1 (en) | 1997-05-15 |
| RU94040156A (en) | 1997-02-27 |
| DE4337336C1 (en) | 1994-12-15 |
| IL111462A (en) | 1997-07-13 |
| RU2136444C1 (en) | 1999-09-10 |
| EP0650791B1 (en) | 1997-04-09 |
| IL111462A0 (en) | 1994-12-29 |
| CN1107085A (en) | 1995-08-23 |
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Legal Events
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| FZDE | Discontinued |