CN1180344A - Method for firing sol-gel alumina particles - Google Patents

Abstract

Sol-gel alumina that is dried but unfired can be explosively comminuted by feeding the dried gel into a furnace held at temperatures above those at which vaporizable materials are eliminated from the particles of gel. At suitably elevated temperatures the firing is sufficient to form fully densified alpha alumina particles of a size suitable for direct use as abrasive grits.

Description

The method of firing sol-gel alumina particles

Background of invention

The present invention relates to alumina abrasive grain, particularly relate to sol-gel method alumina abrasive with improvement nonferromagnetic substance.

The general preparation method of sol-gel method alumina abrasive is the colloidal sol or the gel of dried alpha alumina precursor between about 125-200 ℃ (normally, but needing not to be boehmite), removes the moisture in the gelinite; The exsiccant gel is ground into the particle of abrasive particle desired size; May form the passage type of aluminum oxide also with this particle roasting (general under about 400-800 ℃ temperature); Be converted under the high temperature of αYang Hualv baked particle is calcined being enough to passage type with gamma-alumina and so on then.The case history of simple sol-gel method is in United States Patent (USP) 4,314,827; 4,518,397; 4,881,951 and UK Patent Application 2,099,012 in.Though once other additive metal oxide that forms agent and zirconium white, yttrium oxide, rare-earth oxide, titanium oxide and transition metal oxide and so on the spinel of the property-modifying additive of a spot of silicon-dioxide and so on, magnesium oxide and so on was reduced to about 1-10 micron with the crystalline size of this class sol-gel alumina, improve its some physicals, but it still can have 25 microns or bigger grain-size.

In a kind of good especially sol-gel method, be use identical with the crystalline structure of αYang Hualv own, the material " introducing crystal seed " in the αYang Hualv precursor that lattice parameter is approaching as far as possible." crystal seed " that add should be thin as far as possible, and be dispersed in whole colloidal sol or the gel.Crystal seed can add when beginning or on-the-spot formation.The effect of this crystal seed is under the temperature much lower than no crystal seed the time, all precursors to be converted into αYang Hualv equably.In the crystalline structure that this method makes, each αYang Hualv crystal grain (is meant that inside has identical crystalline orientation basically, the zone of being separated by the high angle grain boundary with adjacent crystal) size is very even, and crystal diameter is submicron order (for example about 0.1-0.5 micron) basically.Suitable crystal seed material comprise αYang Hualv itself and α ferric oxide, at a low price chromic oxide and nickel titanate and so on other compound and many to have similar lattice parameter to αYang Hualv and be enough to carrying out when not having this kind crystal seed under the lower temperature of the conventional temperature that transforms precursor conversion be other compound of αYang Hualv.The sol-gel method that this class adds crystal seed is documented in United States Patent (USP) 4,623,364; 4,774,802; 4,954,462; 4,964,883; 5,192,339; 5,215,551; Among 5,219,806 grades.

At high temperature to calcine the required time in order reducing, should to carry out roasting (and roasting generally is dispensable) the collosol and gel of drying.This is because the task of calcining step is transition alumina to be converted into alpha-type aluminum oxide and to its sintering, to eliminate remaining space, to guarantee that particle has the suitable abundant density and hardness of making abrasive particle.Known in calcining temperature (the collosol and gel material for adding crystal seed is generally 1300-1400 ℃, and unseeded collosol and gel material is high approximately 100 ℃) down if overlong time, can cause that crystal grows up.Because growing up, crystal generally is considered as being not suitable for, thus it is believed that to separate and carry out roasting earlier, to reduce the time under calcining high temperature.Though this method need be kept the operation of two comparatively high tempss and increase cost, but still use.

Because will pulverize and sieve operation after the drying operation, so particle needs cool to room temperature, the used heat of dried particles is released in the environment as a result.Yes that efficient is low-down for this.

Carry out crushing operation after drying, this is because the material of drying regime is pulverized easily, if just carry out crushing operation behind calcination operation, then because the hardness of material is very high, just needs too much energy.Therefore, normally before calcining, carry out crushing operation.And think carry out calcination efficiency after pulverizing can be higher because small-particle can reach calcining temperature quickly.

Have now found that energy expenditure required in the time of to reduce with sol-gel method production aluminum oxide widely.To come the step of design process, can accomplish this point with the antipodal mode of thinking directly perceived of design ordinary method.This novel method can be produced the alpha alumina particles of the form that caters to the need very much, and this alpha alumina particles is fine and close fully, is applicable to very much the abrasive material purposes.In addition, this novel method is again very flexibly, can design to obtain required abrasive particle.

GENERAL DESCRIPTION OF INVENTION

The inventive method is at least 5% weight with volatile matter content, drying but directly join in the stove that remains on certain temperature more than 400 ℃ without the incinerating sol-gel alumina, the controlled temperature and the residence time, produce the explosive aluminum oxide of pulverizing.In some stove, under the enough high and sufficiently long condition of the residence time of temperature, can directly sol-gel alumina be converted into alpha-type aluminum oxide, and it is sintered to have 95% theoretical density.

Sol-gel alumina generally forms after drying and is of a size of several millimeters larger particles, and it is an exsiccant boehmite basically, the residual water of may not removed fully when its each molecule all has associating water molecules and some dry.The useful properties-correcting agent that usually in collosol and gel, adds magnesium oxide, yttrium oxide, rubidium oxide, Cs2O or rare earth metal or transition metal oxide and so in addition with solvable nitrate type form.These materials also make and contain volatile component (as nitrogen oxide) in the desiccant gel.If when collosol and gel is carried out peptization, use the acid of nitric acid or acetate and so on, in the exsiccant collosol and gel, also have the acid of this remnants.The total content of volatile matter is generally about 5-50% weight in the desiccant gel, is about 10-45% weight preferably, better is about 20-40% weight.Drying is carried out under the temperature below 200 ℃ usually, more commonly carries out in much lower temperature.Therefore, the desiccant gel of packing in the stove contains quite a large amount of volatile matter.

Though the present invention is primarily aimed at the explosivity of dry collosol and gel material and pulverizes, these materials also can contain the component that its itself is not a volatile matter.Therefore, as long as the total content of volatile matter remains on more than 5% weight in the drying composite, in the collosol and gel material, also can contain the composition of α or gamma-alumina powder, silicon carbide (granule type and whisker type), zirconium white, cubic boron nitride and other abrasive material and so on.

When the collosol and gel larger particles of drying was put into stove, volatile matter wherein just expanded explosively, and larger particles is scattered, and produced to be highly suitable for grinding the small-particle of purposes.If the residence time sufficiently long in stove, the small-particle of generation changes into the α phase rapidly, and very rapidly sinters into fine and close fully basically.Because this process is very fierce, so it is called " the explosive pulverizing " intuitively,, and comprises and be sintered into the α phase though present method exceeds the scope of pulverizing in a preferred embodiment, also sinter to theoretical density in some cases basically.When temperature was low, the degree of pulverizing may reduce, and mainly is broken into bigger fragment, and has produced linear discontinuities in these fragments, makes it cracked easily in crushing operation subsequently.Yet this also is counted as explosive the pulverizing.

Therefore, when the exsiccant sol-gel alumina particles is added in the stove, and when under need not the condition of any external force, being fragmented into smaller particles at least in part, just think the particulate matter that has formed " the explosive pulverizing ".

If the residence time in stove is lower than temperature in short or the stove, when then material was discharged from stove, sintering process may be carried out not exclusively, even also may not be converted into the α phase fully.In this case, part or all of particle may be porous to a certain extent.These loose macrobeads can be pulverized through slighter grinding operation earlier, then in another stove or sinter density into greater than 95% theoretical density by rotary oven for the second time.Sometimes plant way and be well because very the explosive pulverizing of intensive may produce a large amount of very fine particles, and these very fine particle is inapplicable concerning some grinds purposes.Relatively mild explosive pulverizing can produce does not have the broken particle of opening in appearance, and the operation afterwards of these particles is easy to pulverize.Sometimes a better way is, can with not by explosive fully pulverize through calcined material (porosity is often arranged) the volatile liquid dipping of water and so at least in part, and then finish crushing process by rotary oven.

Regulating above-mentioned porous product that calcination condition produces can also flood with the modifier solution of soluble salt aqueous solution of magnesium, yttrium, transition element, rubidium, caesium or rare earth metal and so on.This material through dipping of sintering can produce very effective modified oxide usually, also produces other volatile matter that can play explosive porphyrization simultaneously.

Have now found that if before dry gel is pushed, the extrusion die orifice that less extrusion die orifice is bigger is better.For example, be that the gel of 1.6 millimeters nib extruding has better explosive smashing capability than the gel that the nib that is 6 millimeters pushes with diameter with diameter.In addition, circular extrudate is better than dihedral extrudate (as making with the right angle nib).

The abrasive particle that makes with aforesaid method has unexpected good nonferromagnetic substance than the abrasive particle that makes with ordinary method usually.Its theoretical principle may be because this crushing technology does not apply mechanical strain to the material that is produced, thereby does not produce microdefect in the abrasive particle structure.No matter how to explain that in theory the improvement of this performance is wondrous and significant after all.

Therefore, the present invention also comprises novel alumina abrasive grain.Have now found that the abrasive particle that makes with explosive comminuting method has unique shape and size-grade distribution.This also may be the reason that produces above-mentioned good nonferromagnetic substance.They are different with the abrasive particle of uniform mold pressing of cross section or extruding, do not have the uniform cross-sectional area shape, and shape is irregular, and are especially very irregular on perpendicular to the cross section of longest dimension direction, and this is to pulverize gained particulate feature.

In general, make abrasive particle, exactly the material of relatively large shape is pulverized with non-manufacturing process.Existing two kinds of basic conventional breaking methods: impact grinding and roll extrusion are pulverized.The impact grinding method can produce the comparatively abrasive particle of piece shape, its L/D, and promptly long-width ratio (longest dimension L with perpendicular to the overall dimension D of this longest dimension ratio) approaches 1.And the roll extrusion comminuting method can produce more weak abrasive particle, and in fact this be meant that its mean aspect ratio is greater than 1.Certain abrasive particle that makes for the roll extrusion comminuting method, the long-width ratio scope of a reality of existence, but the long-width ratio of most of abrasive particles is basically less than 2.

" granularity " measured with the different sieve of a series of screen sizes usually.If abrasive particle can determine that then the controlling dimension of " granularity " is second largest size with three orthogonal characterization of size, because it will determine the size of the minimum aperture that can pass through when abrasive particle when longest dimension is orientated.If the conventional abrasive particle of abrasive particle average specific of the present invention is a little longer, then its each abrasive particle obviously has bigger average-volume.Have now found that it is this situation really.

Alumina abrasive grain of the present invention is being asymmetrical perpendicular to longitudinal size, and in arbitrary granularity grades of the abrasive particle that makes, the abrasive particle that long-width ratio was at least 2: 1 accounts for more than 25%, and situation accounts for 30% at least preferably, and better situation accounts for 50% at least.

Have now found that the alumina abrasive grain that conventional roll extrusion is pulverized is made in arbitrary granularity grades of abrasive particle of state in its pulverizing, long-width ratio is that 2: 1 or higher abrasive particle are no more than 25%, only about usually 19-25%.It seems that this is relevant with the concrete grammar of pulverizing, rather than relevant with the aluminum oxide concrete form that constitutes alumina abrasive grain.Therefore, abrasive particle of the present invention is significantly different with existing abrasive particle.Shown in embodiment just described as follows, the nonferromagnetic substance that abrasive particle of the present invention has improved has greatly very clearly proved this point.

Accompanying drawing

Fig. 1 represents to add the differential thermal analysis curve of the sol-gel alumina of crystal seed.

Fig. 2 represents to be applicable to the upright synoptic diagram of looking of the device of an embodiment in the inventive method.

The detailed description of invention

A kind of differential thermal analysis curve that adds the crystal seed collosol and gel when curve shown in Fig. 1 is the temperature rising. This curve shows that an endothermic peak is arranged in the time of about 400 ℃. It shows the volatile materials that loses water, acid and salt catabolite and so on. The release of this volatile materials has caused explosive pulverizing just. Obvious this release is faster, and the explosivity of decomposition is larger. The volatile materials amount that will remove during to about 600 ℃ has obviously reduced, and the conversion that changes into the anhydrous alumina phase of gamma-alumina and so on also becomes complete. When higher temperature, begin to be converted into the α phase. For the sol gel film that adds crystal seed, at about 1150 ℃ or lower temperature place this conversion occurs. This conversion is shown in the peak among Fig. 1. In unseeded collosol and gel, except the α conversion peaks occurred in higher temperature (being about 1250 ℃), its curve was very similar.

In order to implement the present invention, only need be heated to the temperature that volatile matter begins to volatilize. Obviously, the temperature heating more than lowest decomposition temperature is conducive to very rapidly decompose, thereby produces maximum explosive effect. If yet heating is enough fast, the moderate temperature heating at above-mentioned scope lower limit place also is effective.

If use the temperature (under this temperature, also not forming alpha-aluminium oxide) at above-mentioned scope lower limit place, necessary the material of pulverizing through explosivity is further calcined, with finish to the conversion of α phase also (if any must) this material is sintered near solid density (generally above solid density 95%). Although this needs extra-pay, it can use the revolving burner tube material more solid than carborundum boiler tube, that cost is lower. Although the carborundum boiler tube is the standard boiler tube that carries out simultaneously all these operations.

Before carrying out the explosivity pulverizing, sol-gel alumina is generally dry 200 ℃ of following temperature, and is dry under the lower temperature between about 75-175 ℃ better.

As mentioned above, need to heat as quickly as possible the collosol and gel bulky grain material of drying, farthest expand and explosive the pulverizing in order to produce. The cut-away section of Fig. 2 is vertical to be looked the device shown in the schematic diagram and is suitable for satisfying these requirements. The not pulverizing sol-gel alumina dried particles that diameter is about 0.5-1 centimetre adds in the material bin 1, with vibrating feeder (conveyer) 2 it is added the second feeder 3 from hopper 1. The second feeder is sent this particle into air ejector 4. Air ejector uses again the compressed air of coming in from arm 5 to flow these Particle Accelerations. Compressed air stream transmits these particles and enters in the revolving burner 7 at 8 places, position by pipeline 6. This revolving burner has top and bottom. Position 8 is close to the high-temperature region in the stove. In operation, particle enters the high-temperature region and blasts, and the particle after the pulverizing is discharged from the lower end 9 of stove.

In the blast comminuting method, heat rapidly the gel bulky grain of drying, to reach maximum explosive effect. Although also can satisfy this requirement from several furnace design different among Fig. 2, the stove that is highly suitable for implementing this method is the revolving burner with a boiler tube that tilts at angle with horizontal line and pivot. Described boiler tube is from external heat. The rotation of boiler tube has guaranteed that the size particles in the pipe all always is in the continuous motion, like this, contacts and is heated with boiler tube with regard to the part that can not only have particle, and the not heated situation of another part. The rotary speed of boiler tube and angle of inclination have determined the time of staying of particle in stove. Regulate these parameters, just can guarantee best that volatile materials promptly volatilizees from oarse-grained inside, rather than little by little carry out. Granule that this just can make that bulky grain is explosive forms after pulverizing can maximally utilise the time of staying and calcine with densified.

Also can use other furnace design, comprise batch kiln that fluid bed maybe can be housed and the stove of heating using microwave or eddy-current heating.

The revolving burner that uses under the sintered alumina temperature generally adopts the carborundum boiler tube. This is because it has the performance that satisfies the requirement of this method process physics, and described physics requires to comprise variations in temperature on the boiler tube length direction and the different mechanical loads of diverse location. Carborundum is the issuable sour gas of ability also, such as the nitrate residue that discharges. If yet want to occur to carry out explosivity pulverizing under the fully sintered temperature and to change into the α type being lower than, can use ability up to the metal alloy of about 1200 ℃ of temperature, such as " inconel ".

When using revolving burner, the inventive method requires to be about 1 second to 30 minutes in the time of staying of high-temperature region, is 2 seconds to 20 minutes preferably. In order to obtain this time of staying, the elevation angle of pipe is about 1 ° to 60 °, and more preferably 3 ° to 20 °, preferably about 0.5-20 rev/min of rotary speed, more preferably about 1-15 rev/min.

When calcining added the sol-gel alumina of crystal seed, the calcining heat of high-temperature region was about 400-1500 ℃ usually in the revolving burner, better for about 600-1400 ℃. When the unseeded sol-gel alumina of calcining, the calcining heat of high-temperature region is about 400-1650 ℃ usually in the revolving burner, better for about 600-1550 ℃.

Have obviously large length-width ratio with the present invention's particle that comminuting method makes that explodes, namely particle has a size more much longer than other any one size more. This class particle is specially adapted to the purposes of coated abrasives.

The inventive method is applicable to produce all types of sol-gal process particles, particularly is applicable to produce grind purposes. Collosol and gel can add crystal seed or not add crystal seed. Unique difference of used condition is when not adding crystal seed in the collosol and gel, generally needs higher sintering temperature. The inventive method also can be used for the aluminium oxide of sintering, namely is to make finely divided alpha alumina particles form bulk by partially sintering, and then liquid infiltration with its explosive pulverizing, is made abrasive particle again.

Because the inventive method can be without mechanical disintegration step commonly used in the prior art, so the gel of drying directly can be sent in the stove from drier. Considerable time and energy consumption have been saved like this.

The description of preferred embodiment

The sol-gel alumina that concrete now reference calcining in rotary oven adds crystal seed comes the inventive method is described.These embodiment only are used for indicative purpose, do not mean qualification to base region of the present invention.

Embodiment 1

In Luo Si (Ross) mixing tank, add 74657 gram deionized water and αYang Hualv crystal seed slurries.The BET surface-area of described crystal seed is about 120 meters ²/ gram.Described slurry is the 6000 deionized water slurries that restrain 6% crystal seed to be added in the 10000 gram deionized waters make.Add 36.00 kilograms of boehmites (CondeaGmbH sells, and trade mark is " Disperal ") again, mixture was vacuumized and stirs 5 minutes.Keep under the condition of vacuum in this mixture after being mixed then, add the solution of 1671 grams, 70% nitric acid with 5014 gram deionized water dilution back gained.Restir 5-10 minute.After Vacuum solutions removed, the limit was injected mixture with 1671 grams, 70% nitric acid with the solution of 5014 gram deionized waters dilution back gained, and an on-line mixing homogenizer is passed through with this mixture in the limit, makes this mixture gelation.

With the gained gel drying, be fragmented into the macrobead that size is about 0.25-1 centimetre again, directly add in the rotary oven then.This rotary oven is used is that a length is that 213 centimetres, diameter are 15 centimetres carborudum tube, and it has temperature to remain on 50 centimetres of high-temperature zones of 1405 ℃.Boiler tube and horizontal pitch angle are 6 °, and rotating speed is about 18 rev/mins.

Have a size range after described macrobead blast is pulverized, the abrasive particle of therefrom isolating the 50T size is used for mechanical testing.Calcined materials is about 1-2 minute by the time of rotary oven.The density of calcining back abrasive particle surpasses 3.8 gram per centimeters, and they are that diameter is about 0.2 micron alumina crystallites body.

For the purpose of comparison, by the dry identical sol-gel recipe of identical mode, roll extrusion makes by 24 purpose particles after pulverizing again, after about 800 ℃ of roastings, calcines in conventional rotary oven according to a conventional method.The gained abrasive particle is and the present invention's identical submicron order alumina crystallites body that comminuting method makes that explodes.

Use identical amount of abrasive, backing, initial adhesion coating and sizing menting property then, these two kinds of abrasive particle samples are made grinding belt respectively.The wide of every grinding belt is 6.4 centimetres, and length is 152.4 centimetres.Bonding amount of abrasive is 590 grams on every per square meter of surface area.Make grinding belt with 9000 surface rice/minute the speed running, apply 6.8 kilograms power and under the refrigerant effect, be used to cut 304 stainless steel bars, last 4 minutes.

During this period of time, the grinding belt cutting 74 made from conventional abrasive particle restrains, and pulverizes grinding belt cutting 94 grams that abrasive particle is made with blast, and is higher by 27% than conventional grinding belt.

Embodiment 2

With main equipment as shown in Figure 2 at room temperature the exsiccant granularity be about+directly to add temperature in the rotary oven be 1000 ℃ high-temperature zone for the crystal seed sol-gel alumina macrobead that adds of 24T, the speed of adding be about the 2.25-4.5 kilogram/hour.Except that the rotating speed of pipe be about 10 rev/mins and be 7 ° with horizontal pitch angle, stove used among this rotary oven and the embodiment 1 is identical.Gel particle is pulverized by blast in stove, and its size-grade distribution is listed in the table below in 1.

Table 1

Size range	Amount in the scope
		????+30	????41％
????-30+40	????31％
		????-40+50	????11％
????-50+60	????3％
		????-60	????4％

In another operation, above-mentioned blast material crushed is further sintered to density greater than 3.8 gram per centimeters ³The size range of material is listed in the following table 2 behind the sintering.

In these two kinds of abrasive particles, aluminum oxide all is the submicron crystallite form.

Table 2

Size range	Amount in the scope
		????+30	????22％
????-30+40	????38％
		????-40+50	????23％
????-50+60	????9％
		????-60	????8％

Embodiment 3

Abrasive particle of present embodiment explanation novelty of the present invention and preparation method thereof.

Prepare the unprocessed crystal seed alumina gel that adds as follows:

In the high solids Jaygo mixing machine of two sigma shape blades and an extrusion screw is housed, add 148 kilograms of boehmites (available from Condea GmbH, registered trademark is " Disperal ") and 40 kilograms of deionized waters.Under the screw rod opposite spin, this mixture was stirred 5 minutes.(29 kilogram of 4% αYang Hualv solid dispersion, the BET surface-area of this αYang Hualv is greater than 110 meters to add the αYang Hualv water slurry then ²/ gram), continues to stir after 8 minutes, add 30 kilogram of 22% nitric acid, continue again to stir 20 minutes.Last positive dirction is rotated extrusion screw, extrudes formed gel through one 6.3 millimeters extrusion die.Then this gel extrudate is dried to water content and is about 30-35% weight, be divided into two parts again.

First part of gel roll extrusion pulverized,, in rotary oven, sinter to more than 97% of theoretical density then 600-800 ℃ of temperature roasting.The agglomerating abrasive particle is sieved, isolate the abrasive particle that granularity is 50T, measure the long-width ratio and the nonferromagnetic substance of these abrasive particles then.It is represented, and conventional roll extrusion is pulverized, the sol-gel alumina abrasive particle of weak shape.

Except earlier material crushed to be exploded being sized to+10 orders, remove beyond the fine particle, by the method described in the embodiment 2 second part of gel is machined to density and surpasses 97% of theoretical density.From the blast crushed products, sieve out the identical abrasive particle that granularity is 50T.Also this fraction is carried out the long-width ratio analysis, and estimate its nonferromagnetic substance.

Long-width ratio is analyzed

For the 50T granularity, the abrasive particle that will carry out the long-width ratio analysis is sized to-45+50; For the 36T granularity, the abrasive particle that will analyze is sized to-30+35.

The equipment that uses is a DageMTIO PA-81 high resolution grayscale camera that 55 millimeters macroshot lenss of Nikon Micro Nikkor are housed, and is installed on the Bencher M2 photographic camera bracing frame, in order to take the abrasive particle photo.During shooting, abrasive particle is dispersed on the black paper (for white abrasive particle), takes the photo of several abrasive particles in the visual field.

Only, avoid shade and excessive high light with the illumination of top fluorescent lamp.

Photographic camera is installed on the photographic camera bracing frame with the centre hole at the top-portion apertures on the anchor and the photographic camera back side, and the vertical shifting scale on the photographic camera bracing frame is locked in about 44 centimeters.The camera gun aperture settings is at F-2.g.On the base plate of photographic camera bracing frame, place a bar metric system ruler, photographic camera is focused on and set the line (it is actually 10 millimeters, promptly 10000 microns) of desired length, camera system is calibrated.

The black paper that is placed with abrasive particle is moved, produce the different visuals field, analyze different abrasive particles.

Take pictures, and analyze with Compix C Imaging 1280/Simple 51 software system.In testing process, aim at the abrasive particle edge better, carry out the clear image operation by the image intensification mode in order to help.Produce a binary image (binary image) then, the abrasive particle image is compiled, guarantee that two abrasive particles taking are not in contact with one another and eliminate the image of obvious distortion.In order to get rid of background noise relevant with paper in the image, the minimum particle size scope that detects abrasive particle is set in 200 square microns.Have now found that, set this minimum value and do not have the abrasive particle that perforated detects.

The area, maximum length and the maximum width that comprise each abrasive particle in the visual field with the data of Simple 51 software collections.These parameters of 200-250 abrasive particle are measured in this test at least to per sample (p.s.).Then with data input Microsoft ' the s Excel that collects ^(Release 5.0) software, calculating mean value, standard deviation, long-width ratio and relevant cumulative data.

The assessment nonferromagnetic substance

By the standard glue spread abrasive particle electrostatic precipitation is being scribbled on the cloth backing of aerodux coating.Tackiness agent is solidified.These are coated with the glued coating of resol above abrasive particle after, make its curing.With this coated abrasives system grow into 152.4 centimetres, wide be 6.35 centimetres annular grinding belt.With 914.4 surface rice/minute linear velocity, with water coolant, under the effect of 6.8 kilogram forces, stainless steel 304 rods are carried out grinding, by the constant force mode grinding belt is tested.Write down steel stock removal total in 20 minutes during off-test.

All abrasive particles have the microlitic structure that is about 0.2-0.4 micron (measuring with the mean intercept method) αYang Hualv crystallite formation by diameter.

The result of assessment

Relative % nonferromagnetic substance in per 100 abrasive particles of sample

L/D＞/=2.0 GMS grind the amount of disappearing/20

The relative % number of abrasive particle minute

Embodiment 3 54 207 284

Comparative Examples 3 25 100 199

Can clearly be seen that from above-mentioned data the abrasive particle that blast is pulverized has quite superior nonferromagnetic substance, the weak shape abrasive particle of it and control sample has a great difference.Wherein L/D is more much higher than the ratio more than or equal to 2.0 abrasive particle.

Embodiment 4

Except using slightly different sol-gel method, present embodiment is undertaken by embodiment 3 similar methods.All other sides and these two embodiment are identical.

It is as follows to be used to make the method that contrasts abrasive particle and abrasive particle of the present invention:

In a mixing vessel, pack into the αYang Hualv crystal seed slurry of 908 kilograms water, 118 kilograms of dilutions and 41 kilograms 21% nitric acid.Described αYang Hualv crystal seed slurry contains the surface-area of 4% weight above 120 meters ²The αYang Hualv crystal seed of/gram (making) by in the Sweco ball mill, grinding 8% submicron order αYang Hualv water dispersion with Diamonite low-purity oxidation aluminium mill Jie.This mixture stirs with high speed dispersion blade, and vacuumizes and remove bubble.The pH value that records is about 4.Then this mixture and 21% nitric acid are pumped in the online homogenizer together, feeding speed is 0.6 liter/minute, makes this mixture homogenization.Gel drying to the water content of gained is about 30-35%.

Then the exsiccant gel is divided into two parts, presses embodiment 3 described methods and further handle respectively and assessment.The result is as follows:

Relative % nonferromagnetic substance in per 100 abrasive particles of sample

L/D＞/=2.0 GMS stock removal/20 minute

The relative % number of abrasive particle

Embodiment 4 36 171 281

Comparative Examples 4 21 100 212

These data also show, for the method for low solid content, between abrasive particle that makes with ordinary method and the abrasive particle that makes with the inventive method tangible difference are arranged also.

Embodiment 5

Except the granularity difference of tested abrasive particle, the method for present embodiment is identical with embodiment 3.Here be to isolate the part that granularity grades is 36T, rather than the fraction of 50T, detect.The result is as follows:

Relative % nonferromagnetic substance in per 100 abrasive particles of sample

L/D＞/=2.0 GMS stock removal/20 minute

The relative % number of abrasive particle

Embodiment 5 27 142 259

Comparative Examples 5 19 100 149

Therefore, even the relative number of longer abrasive particle is only for to make 142% of abrasive particle with conventional roll extrusion comminuting method in the abrasive particle of the present invention, but the raising of its nonferromagnetic substance is still quite surprising.

Embodiment 6

Present embodiment shows the size and the changes in weight of seven kinds of materials.These seven kinds of materials have identical standard 45/50 granularity.Wherein three kinds of materials are various sample that add crystal seed sol-gel alumina material of pulverizing by the inventive method blast.Other three kinds is that roll extrusion is pulverized and to be added crystal seed sol-gel alumina material and make, and the described crystal seed sol-gel alumina material that adds is with identical by the abrasive particle of the inventive method pulverizing.Another kind of sample is commercially available alumina abrasive grain (available from 3M company, trade name is " 321 Cubitron ").It is said that this abrasive particle makes with unseeded sol-gel alumina method, this aluminum oxide is alumina modified with a spot of yttrium oxide and rare earth metal.It is reported that this abrasive particle is to make with the machinery method of pulverizing.The crystalline structure of this abrasive particle is the alpha-alumina crystals that diameter is about 1-7 micron (measuring with the mean intercept method).

The results are shown in as in the following table 3:

Table 3

Mean length width average center line average average-volume

Sample micron micron micron micron ³

Invent 1 754 400 179 3.95

Invent 2 872 399 269 3.90

Invent 3 673 424 254 3.19

Roll extrusion 1 597 450 299 2.22

Roll extrusion 2 615 414 282 2.92

Roll extrusion 3 601 450 226 2.87

321??????????649?????????396?????????231?????????2.27

Except also measuring the particulate height, use the measuring technology identical with embodiment 3 with the white light perturbation technique.Though these data show the size (width) in the sample scope only poor about 54 microns that determines granularity, this is because all samples have identical granularity (45/50), and the scope of all kinds of sample particulate center line averages and width average overlaps mutually, mean length and therefore weight in average then in visibly different scope, longer by the abrasive particle that the inventive method is pulverized than the abrasive particle of prior art roll extrusion pulverizing, and heavier.

Claims (32)

1. one kind contains drying but without the blast breaking method of the composition of incinerating sol-gel alumina, volatile matter content is at least 5% weight in the described composition, method is characterised in that it is that particle with composition directly joins temperature and remains in 400-1600 ℃ the stove and control residence time in the stove, produces the explosive alumina particle of pulverizing.

2. the method for claim 1 is characterized in that described stove is tubular rotary oven.

3. the method for claim 1, the residence time that it is characterized in that highest temperature zone in stove (high-temperature zone) is 1 second to 30 minutes.

4. method as claimed in claim 2 is characterized in that described boiler tube and horizontal pitch angle are 1 °-60 °.

5. method as claimed in claim 4, the rotating speed that it is characterized in that described pipe is 0.5-40 rev/min.

6. the method for claim 1 is characterized in that sending into the volatile matter that dry sol-gel alumina composition contains 5-60% weight that contains in the stove.

7. the method for claim 1 is characterized in that directly the described composition that contains dry sol-gel alumina being added in the stove near the high-temperature zone.

8. the method for claim 1 is characterized in that the temperature in the stove is enough to form α mutually with the residence time, and sinters to 95% of theoretical density at least.

9. the method for claim 1 is characterized in that described stove remains below the temperature required following temperature of sintering αYang Hualv, and then explosive material crushed sintered to approaches theoretical density.

10. method as claimed in claim 9 is characterized in that before sintering, explosive material crushed is pulverized, with further adjusting granularity.

11. method as claimed in claim 9 is characterized in that before carrying out sintering operation, and is described through explosive material crushed with the soluble metal salt solution-treated that is selected from rare earth metal, transition metal, rubidium, caesium and yttrium.

12. one kind contains drying but without the blast breaking method of the composition of incinerating sol-gel alumina, volatile matter content is a 20-40% weight in the described composition, it is characterized in that it being that said composition is joined in the tubular rotary oven, the temperature in this furnace high-temperature district remains on 600-1500 ℃, pitch angle between boiler tube and sea line is 2 °-20 °, and rotating speed is 2-20 rev/min.

13. method as claimed in claim 12 is characterized in that the temperature in the stove is enough to form α mutually with the residence time, and sinters to 95% of theoretical density at least.

14. method as claimed in claim 12, it is characterized in that described stove remain below the sintering αYang Hualv the following temperature of temperature, and then explosive material crushed sintered to approach theoretical density.

15. method as claimed in claim 14 is characterized in that before sintering, explosive material crushed is pulverized, with further adjusting granularity.

16. method as claimed in claim 14 is characterized in that before carrying out sintering operation, and is described through explosive material crushed with the soluble metal salt solution-treated that is selected from rare earth metal, transition metal, rubidium, caesium and yttrium.

A 17. drying but do not add the blast breaking method of crystal seed sol-gel alumina without incinerating, volatile matter content is a 20-40% weight in the described composition, it is characterized in that it being that said composition is joined in the tubular rotary oven, the temperature in this furnace high-temperature district remains on 600-1650 ℃, pitch angle between boiler tube and sea line is 3 °-20 °, and rotating speed is 1-20 rev/min.

18. method as claimed in claim 17 is characterized in that the temperature in the stove is enough to form α mutually with the residence time, and sinters to 95% of theoretical density at least.

19. method as claimed in claim 17 is characterized in that described stove remains below the temperature required following temperature of sintering αYang Hualv, and then explosive material crushed sintered to approaches theoretical density.

20. method as claimed in claim 19 is characterized in that before sintering, explosive material crushed is pulverized, with further adjusting granularity.

21. method as claimed in claim 19 is characterized in that before carrying out sintering operation, and is described through explosive material crushed with the soluble metal salt solution-treated that is selected from rare earth metal, transition metal, rubidium, caesium and yttrium.

22. a bonding grinding tool is characterized in that it contains the abrasive particle that the useful blast of method is according to claim 1 pulverized.

23. a bonding grinding tool is characterized in that it contains the useful abrasive particle of pulverizing as method blast as described in the claim 12.

24. a bonding grinding tool is characterized in that it contains the useful abrasive particle of pulverizing as method blast as described in the claim 17.

25. a coated abrasive article is characterized in that it contains the abrasive particle that the useful blast of method is according to claim 1 pulverized.

26. a coated abrasive article is characterized in that it contains the useful abrasive particle of pulverizing as method blast as described in the claim 12.

27. a coated abrasive article is characterized in that it contains the useful abrasive particle of pulverizing as method blast as described in the claim 17.

28. alumina abrasive grain is characterized in that it is asymmetric with respect to longitudinal size, in all granularity grades of the abrasive particle that makes, all contains more than 25%, its long-width ratio was at least 2: 1 and density is at least the abrasive particle of 95% theoretical density.

29. alumina abrasive grain as claimed in claim 28 is characterized in that long-width ratio surpasses 2: 1 abrasive particle percentage ratio greater than 30%.

30. alumina abrasive grain as claimed in claim 28 is characterized in that it all is the sintered alumina crystal that is of a size of the 0.01-10 micron.

31. alumina abrasive grain as claimed in claim 30 is characterized in that described alpha-alumina crystals is a submicron order.

32. alumina abrasive grain as claimed in claim 28 is characterized in that it is the sintered alumina of using up to one or more oxide modifyings of 10%, described oxide compound is selected from the oxide compound of magnesium, zirconium, rare earth metal, transition metal, rubidium, caesium and yttrium.

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