CN1197820C - Method for preparing superfine powder - Google Patents
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- CN1197820C CN1197820C CN01120379.XA CN01120379A CN1197820C CN 1197820 C CN1197820 C CN 1197820C CN 01120379 A CN01120379 A CN 01120379A CN 1197820 C CN1197820 C CN 1197820C
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- 239000000843 powder Substances 0.000 title claims abstract description 84
- 238000000034 method Methods 0.000 title claims abstract description 44
- 238000006243 chemical reaction Methods 0.000 claims abstract description 31
- 239000000203 mixture Substances 0.000 claims abstract description 27
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 25
- 239000001301 oxygen Substances 0.000 claims abstract description 25
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 25
- 229910052797 bismuth Inorganic materials 0.000 claims abstract description 20
- 239000002243 precursor Substances 0.000 claims abstract description 19
- 229910052745 lead Inorganic materials 0.000 claims abstract description 18
- 238000010438 heat treatment Methods 0.000 claims abstract description 13
- 230000008569 process Effects 0.000 claims description 16
- 230000009466 transformation Effects 0.000 claims description 15
- 238000001816 cooling Methods 0.000 claims description 5
- 239000000463 material Substances 0.000 abstract description 17
- 238000002360 preparation method Methods 0.000 abstract description 9
- 238000009472 formulation Methods 0.000 abstract 1
- 230000007704 transition Effects 0.000 abstract 1
- 239000002245 particle Substances 0.000 description 10
- 229910044991 metal oxide Inorganic materials 0.000 description 6
- 150000004706 metal oxides Chemical class 0.000 description 6
- 238000005245 sintering Methods 0.000 description 6
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 5
- 238000007669 thermal treatment Methods 0.000 description 5
- 229910052799 carbon Inorganic materials 0.000 description 4
- 230000015572 biosynthetic process Effects 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 239000010419 fine particle Substances 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 238000005096 rolling process Methods 0.000 description 3
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 2
- 230000008901 benefit Effects 0.000 description 2
- 238000002485 combustion reaction Methods 0.000 description 2
- 239000000446 fuel Substances 0.000 description 2
- 238000000227 grinding Methods 0.000 description 2
- 238000005498 polishing Methods 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 230000000630 rising effect Effects 0.000 description 2
- 238000005118 spray pyrolysis Methods 0.000 description 2
- QNRATNLHPGXHMA-XZHTYLCXSA-N (r)-(6-ethoxyquinolin-4-yl)-[(2s,4s,5r)-5-ethyl-1-azabicyclo[2.2.2]octan-2-yl]methanol;hydrochloride Chemical compound Cl.C([C@H]([C@H](C1)CC)C2)CN1[C@@H]2[C@H](O)C1=CC=NC2=CC=C(OCC)C=C21 QNRATNLHPGXHMA-XZHTYLCXSA-N 0.000 description 1
- 229910015901 Bi-Sr-Ca-Cu-O Inorganic materials 0.000 description 1
- 229910004247 CaCu Inorganic materials 0.000 description 1
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 229910002651 NO3 Inorganic materials 0.000 description 1
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 description 1
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 238000010923 batch production Methods 0.000 description 1
- 229910021386 carbon form Inorganic materials 0.000 description 1
- 239000003575 carbonaceous material Substances 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 230000001276 controlling effect Effects 0.000 description 1
- RKTYLMNFRDHKIL-UHFFFAOYSA-N copper;5,10,15,20-tetraphenylporphyrin-22,24-diide Chemical compound [Cu+2].C1=CC(C(=C2C=CC([N-]2)=C(C=2C=CC=CC=2)C=2C=CC(N=2)=C(C=2C=CC=CC=2)C2=CC=C3[N-]2)C=2C=CC=CC=2)=NC1=C3C1=CC=CC=C1 RKTYLMNFRDHKIL-UHFFFAOYSA-N 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- RVPVRDXYQKGNMQ-UHFFFAOYSA-N lead(2+) Chemical compound [Pb+2] RVPVRDXYQKGNMQ-UHFFFAOYSA-N 0.000 description 1
- 238000003701 mechanical milling Methods 0.000 description 1
- 229910001960 metal nitrate Inorganic materials 0.000 description 1
- 230000006911 nucleation Effects 0.000 description 1
- 238000010899 nucleation Methods 0.000 description 1
- 150000002894 organic compounds Chemical class 0.000 description 1
- 239000011368 organic material Substances 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000012827 research and development Methods 0.000 description 1
- 230000004044 response Effects 0.000 description 1
- 229910052709 silver Inorganic materials 0.000 description 1
- 239000004332 silver Substances 0.000 description 1
- 230000002269 spontaneous effect Effects 0.000 description 1
- 238000001694 spray drying Methods 0.000 description 1
- 238000005482 strain hardening Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 239000002887 superconductor Substances 0.000 description 1
- 239000000725 suspension Substances 0.000 description 1
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- Inorganic Compounds Of Heavy Metals (AREA)
- Compositions Of Oxide Ceramics (AREA)
Abstract
The present invention relates to a preparation method for superfine powder, more specifically to a preparation method for superconductive precursor powder. The formulation and the transition degree of the phase are controlled by changing material parameters and technological parameters, such as the content of Pb in Bi and Pb (2212), reaction temperatures, oxygen partial pressure, heat treatment time and different temperature raising and reducing modes. Fine superconductive precursor powder can be prepared by utilizing the method, and accordingly, the performance of superconductive materials is obviously raised.
Description
Technical field
The present invention relates to the preparation method of the very thin superconducting precursor powder of a kind of granularity, utilize this method can control the composition of phase and mutually transformation degree, prepare tiny superconducting precursor powder, thereby significantly improve the performance of superconducting material.
Background technology
Since superconducting material was found, material supplier author had in research and development and has carried out extensive and deep exploration and research aspect the high-quality long superconducting wire.Because the performance of forerunner's powder has determined the current capacity of superconductivity wire to a great extent, therefore, prepare the prerequisite that the superconducting precursor powder with better chemistry and physicals becomes the high-quality superconductivity wire of preparation.
Superconducting precursor powder is generally the heterogenetic mixture, and its particle diameter is preferably less than 1 μ m.Oarse-grained forerunner's powder reaction energy is lower, in follow-up technology, be difficult to react with other particles, as in the preparation process of Bi-based high-temperature superconductive lead, oarse-grained forerunner's powder can finally be unfavorable for Bi (2212) transformation of Bi (2223) phase in opposite directions, forms the CuO, the Ca that account for larger proportion
2PbO
4, Pb
3(Sr, Bi)
3Ca
2CuO
y, Sr
8Ca
6Cu
24O
41, Ca
2CuO
3, CaCuO
2, CaO and the two-phase of SrO grade in an imperial examination, thereby reduce the quality of lead.It is long-pending that tiny forerunner's powder particles can enlarge reacted surface, the reaction energy of increase in follow-up sintering, reduce the atomic diffusion distance that forms superconducting phase, thereby increase speed of response, promote the formation of superconducting phase, and tiny forerunner's powder can also form the superconducting phase with better texture, thereby makes the superconductivity wire of preparation have higher critical current density.
The composition of phase also has very big influence to the quality of superconductivity wire in forerunner's powder.As in the preparation process of Bi-based high-temperature superconductive lead, except principal phase Bi, Pb (2212) or Bi (2212) also can contain CuO, Ca in addition in forerunner's powder
2PbO
4, Pb
3(Sr, Bi)
3Ca
2CuO
y, Sr
8Ca
6Cu
24O
41, Ca
2CuO
3, CaCuO
2, CaO and the two-phase of SrO grade in an imperial examination, select the composition of suitable phase, help Bi, the formation of Pb (2223) or Bi (2223), thus improve the quality of lead.
The industrial method for preparing superconducting precursor powder commonly used is a mechanical milling method.This method is to mix various metal oxides, and mechanical mill then reduces powder size, and sintering, grinding again obtains tiny forerunner's powder.Related to this class methods in U.S. Pat 5284822, at first selecting mean diameter is the metal oxide of 10mm, adds ethanol then and mixes, and puts into the wet type grinding in ball grinder 24 hours, at last oven dry.The result shows that powder might be polluted in mechanical mill, the powder after the mechanical mill has work hardening, out-of-shape, flowability degenerates and features such as agglomerate occur.
A kind of method of utilizing the spray pyrolysis process to prepare forerunner's powder has been described in international monopoly WO 90/14307.This process comprise metal-nitrate solutions and organic compound or (with) carburetted hydrogen gas (acting as a fuel) mixes and sends into reactor, between fuel and the nitrate solution spontaneous combustion takes place in reactor, thereby obtain forerunner's powder.The advantage of this method is to expand the scale of production easily, to adapt to industrialization demands, but also there is the shortcoming of at least two aspects in it, at first be that temperature of reaction reaches more than 2000 ℃, it is controlled to make that volatile metal oxide such as the PbO content in forerunner's powder is difficult to, and in addition, oxycarbide can cause containing in the last superconducting material that forms the carbon of larger proportion, these carbon form the carbonate of high stable easily, thereby reduce the quality of superconducting material.
In European patent O371211, U.S. Pat 5814585, related to another kind of spray pyrolysis process.This process mainly is containing in the solution of supercondutive powder material or the reactor that suspension is ejected into gaseous combustion, to obtain forerunner's powder.Because the temperature of reaction height, so be difficult to volatile metal oxide of control such as the content of PbO in forerunner's powder.
A kind of method for preparing nano level forerunner powder has been proposed in U.S. Pat 5447708.This method is that various metal oxides are mixed with organic or carbonaceous material, and the droplet of these mixtures is heated to sufficiently high temperature to cause organic burning, and metal oxide evaporates nucleation or diffusible oxydation, thereby obtains nano level forerunner's powder.Because this method has related to carbon, thereby has also had the shortcoming that carbon causes.
People such as Q.Li propose with spray-drying process (Q.Li et al, Physica C 217 (1993) 360) the manufacturing superconducting precursor powder, the advantage of this method is that prepared powder has better chemical consistence, high movable energy and low carbon content, but according to forerunner's powder degree of this method preparation in 40 μ m, very big distribution range is arranged, influenced the homogeneity of powder.
In sum, need to propose a kind of new method for preparing forerunner's powder, to obtain the tiny superconducting precursor powder of particle.
The Bi-based high-temperature superconductive material is one of superconducting material the most promising in the present superconducting material, contains three kinds of superconducting phases, i.e. Bi in Bi-Sr-Ca-Cu-O
2(Sr, Ca)
2CuO
6+ δ(Bi (2201)), Bi
2Sr
2CaCu
2O
8+ δ(Bi (2212)) and Bi
2Sr
2Ca
2Cu
3O
10+ δ(Bi (2223)), critical temperature mutually is about 20K, 85K respectively to Bi (2201) with Bi (2212) mutually, and the critical temperature of Bi (2223) is 110K, because Bi (2223) has the highest critical temperature, so present Bi system high-temperature superconducting generally adopts Bi (2223) phase mutually, and partly substitute Bi with Pb in mutually, thereby reduce the formation temperature of this phase at this, accelerate it and form, improve the quality of this phase.In order to prepare Bi, Pb (2223) phase, at first need prepared sizes little contain Bi, Pb (2212) or Bi (2212) principal phase and a small amount of second mutually the superconducting precursor powder.For these reasons, will analyze at the thinning process of this kind superconducting precursor powder below.
According to people (R Fl ü kiger et al such as R Fl ü kiger, Supercond.Sci.Technol.10 (1997) A68-A92) model of Ti Chuing, original powder is being prepared in the process of required forerunner's powder, Bi (2212) Bi is in opposite directions taking place under certain condition, the transformation of Pb (2212) phase.Original powder is by big flaky Bi (2212) phase and some little erose Pb of being rich in and the phase composite of being rich in Cu, experimental result (Hiroki Fujii et al according to people such as Hiroki Fujii, Physica C 331 (2000) 79-84), Bi (2212) phase and Bi, the transformation between Pb (2212) phase is reciprocal about 800 ℃.When this reaction forward is carried out, Ca
2PbO
4Phase decomposition goes out lead ion and enters Bi (2212) phase structure, main Bi (2212) Bi in opposite directions that takes place in this process, the chemical reaction that Pb (2212) changes mutually, reaction be accompanied by structural variation, Bi (2212) is changed to rhombic system (also claiming the O phase) from counterfeit tetragonal system (also claiming the T phase), the Bi that forms, Pb (2212) grows up mutually gradually, and Bi (2212) phase and Ca
2PbO
4Particle dwindles gradually, and on the contrary, when reaction during reverse carrying out, Pb reduces in the solubleness of Bi (2212) in mutually, and Bi (2212) mutually and Ca
2PbO
4Particle begins to grow up, and Bi, Pb (2212) phase and alkaline earth cuprate begin to dwindle, thereby can allow reaction forward carry out earlier by the equilibrium conditions between the above reciprocal reaction control reaction, and Bi, Pb (2212) begin to grow up mutually, and Bi (2212) phase and Ca
2PbO
4Particle begins to dwindle, and works as Bi, and Pb (2212) grows up mutually to a certain degree, allows reverse the carrying out of reaction again, and Pb reduces in the solubleness of Bi (2212) in mutually, and Bi (2212) mutually and Ca
2PbO
4` grain is grown up gradually, and Bi, Pb (2212) phase and alkaline earth cuprate dwindle gradually, allow like this and react forward or reverse carrying out repeatedly, and the degree of control variation, causing crystalline-granular texture mutually and the repeatedly variation of O between mutually, thereby cause the variation of grain size, reach the purpose of crystal grain thinning at T.
The important technical parameter of controlling this reaction is oxygen partial pressure and temperature of reaction.It is reported (P.Majewski et al, Physica C 3221 (1 994) 295; A.L.Crossley et al, Physica C314 (1999) 12; J.Shimoyama et al, Adv.Supercond.10 (1998) 279), Pb can be along with the reduction of the rising of temperature of reaction and oxygen partial pressure in the solubleness of Bi (2212) in mutually and is increased.
The specification sheets page 4 is replaced page or leaf:
People such as Hiroki Fujii propose (Hiroki Fujii e tal, Physica C 331 (2000) 79-84) temperature and Bi under the different oxygen partial pressure as shown in Figure 1, relation curve between Pb/ (Bi+Pb+Sr+Ca+Cu) ratio of Pb (2212) in mutually, Ca2PbO4 can reduce along with the rising of temperature, so can control equilibrium conditions between the reaction by control oxygen partial pressure and temperature.
In technology, can also control reaction process with the different heating and cooling mode of employing by the control heat treatment time.Heat treatment time can influence the performance of superconducting phase, and heat treatment time is the function of thermal treatment temp and superconductor particles size, and along with the reduction of temperature, heat treatment time can corresponding prolongation.Intensification in the heat treatment process and the cooling can be continous way also can be stepped, the lifting of temperature can be adopted different speed.
Summary of the invention
Based on above analysis, the present invention proposes a kind of method for preparing superconducting precursor powder, in the thinning process of described superconducting precursor powder, the composition of the phase of forerunner's powder lives through twice different transformation at least, the transformation of phase is by changing Bi, Pb (2212) mutually in Pb content, temperature of reaction, oxygen partial pressure and heat treatment time realize that the scope of Bi wherein, Pb (2212) the Pb content in mutually is to make the Bi of finally prepd Bi-based high-temperature superconductive lead
2-yPb
ySr
2Ca
2Cu
3O
10+x0＜y＜0.6 in (Bi (2223)), the span of control of temperature of reaction are 720 ℃ to 805 ℃, and the span of control of oxygen partial pressure is 0.01 to 1 normal atmosphere, and the span of control of heat treatment time is 1-7 hour.
This method is by regulating in forerunner's powder Bi (2212) Bi in opposite directions, the molecular balance condition that Pb (2212) changes mutually allows reaction forward or reverse carrying out, and the degree of control reaction, to cause particle volume in forerunner's powder and mutually variation, up to the composition and the particle size that obtain best phase.Utilize the present invention can prepare tiny forerunner's powder, and the purity height of material, good process repeatability, suitable batch production.The present invention is suitable for the preparation of forerunner's powder of superconducting material especially, and described superconducting material mainly is high temperature superconducting materia, especially Bi
2-yPb
ySr
2Ca
2Cu
3O
10+x(Bi (2223)), 0＜x＜1.5,0＜y＜0.6, because the stoichiometry of Bi (2223) phase is proximate, proximate with it composition is all within the scope of the present invention.In addition, powder is pressed into bulk or silver pipe that powder packed into after also can use present method refinement powder again.This method also can be used to prepare the fine materials of other kinds.
According to chemical reaction polishing of the present invention, can be by changing each material parameter and processing parameter, as Bi, Pb content, temperature of reaction, oxygen partial pressure, heat treatment time and the different heating and cooling mode of Pb (2212) in mutually controlled the composition of phase and mutually transformation degree, to form small grains.The chemical reaction polishing mainly can adopt following three kinds of modes:
1) when powder is handled, temperature remains unchanged, reduce oxygen partial pressure with promote Pb dissolve into Bi (2212) mutually in, and then raising oxygen partial pressure, Pb is separated out mutually from Bi (2212), and form second phase mutually with other, this process can be carried out repeatedly, by the composition and mutually transformation degree of phase in the control powder, so that powder reaches the composition and the granularity of best phase.
2) when powder is handled, it is constant that oxygen partial pressure keeps, improve temperature with promote Pb dissolve into Bi (2212) mutually in, and then cooling, Pb is separated out mutually from Bi (2212), and form second phase mutually with other, this process can be carried out repeatedly, by the composition and mutually transformation degree of phase in the control powder, so that powder reaches the composition and the granularity of best phase.
3) when powder is handled, 1) and 2) heat treating regime can interosculate, change temperature of reaction and oxygen partial pressure simultaneously and control mutually composition and mutually transformation degree, so that powder reaches the composition and the granularity of best phase.
Description of drawings
Below in conjunction with accompanying drawing specific examples of the present invention is described in detail, wherein:
Fig. 1 is temperature and Bi under different oxygen partial pressure, the relation curve between Pb/ (Bi+Pb+Sr+Ca+Cu) ratio of Pb (2212) in mutually;
Fig. 2 is Bi, and Pb (2212) is as the synoptic diagram of the function of oxygen partial pressure and temperature.
Embodiment
Forerunner's powder is by being principal phase mutually with Bi (2212) and containing Ca
2PbO
4The granulometric composition of phase.Powder is that 0.05 normal atmosphere, temperature are 805 ℃ of following sintering 1h in oxygen partial pressure, generates at last with Bi, and Pb (2212) is the fine particle of principal phase mutually.Filling Bi according to silver-colored sleeve pipe is oxide powder method (being the PIT method), and pack into silver-colored sleeve pipe and carry out drawing, rolling and thermal treatment of these powder, can make critical current density is 30000A/cm
2The superconductivity wire of (77K, self-fields).
Embodiment 2
Forerunner's powder is by with Bi, and Pb (2212) is the granulometric composition of principal phase mutually.Powder is that 0.2 normal atmosphere, temperature are 750 ℃ of following sintering 2h in oxygen partial pressure, generates at last with Bi (2212) to be principal phase mutually and to contain Ca
2PbO
4The fine particle of phase.Filling Bi according to silver-colored sleeve pipe is oxide powder method (being the PIT method), and pack into silver-colored sleeve pipe and carry out drawing, rolling and thermal treatment of these powder, can make critical current density is 30000A/cm
2The superconductivity wire of (77K, self-fields).
Embodiment 3
Forerunner's powder is by with Bi, and Pb (2212) is the granulometric composition of principal phase mutually.Powder is that 0.2 normal atmosphere, temperature are 720 ℃ of following sintering 5h in oxygen partial pressure at first, is 0.10 normal atmosphere in oxygen partial pressure then, and temperature is 805 ℃ of following thermal treatment 2h, generates at last with Bi, and Pb (2212) is the fine particle of principal phase mutually.Filling Bi according to silver-colored sleeve pipe is oxide powder method (being the PIT method), and pack into silver-colored sleeve pipe and carry out drawing, rolling and thermal treatment of these powder, can make critical current density is 30000A/cm
2The superconductivity wire of (77K, self-fields).
Embodiment 4
Forerunner's powder is by with Bi, and Pb (2212) is the granulometric composition of principal phase mutually.Powder forms rod through isostatic cool pressing, is that 0.2 normal atmosphere, temperature are 750 ℃ of following sintering 2h in oxygen partial pressure, generates at last with Bi (2212) to be principal phase mutually and to contain Ca
2PbO
4The charge bar of phase.Charge bar is heat-treated, and making critical current density is 30000A/cm
2The superconducting material of (77K, self-fields).
Claims (4)
1. thinning method that Bi is the superconducting precursor powder end, it is characterized in that in the thinning process of described superconducting precursor powder, the composition of the phase of forerunner's powder lives through twice different transformation at least, the transformation of phase is by changing Bi, the middle mutually Pb content of Pb (2212), temperature of reaction, oxygen partial pressure and heat treatment time are realized, the scope of Bi wherein, Pb (2212) the Pb content in mutually is to make the Bi of finally prepd Bi-based high-temperature superconductive lead
2-yPb
ySr
2Ca
2Cu
3O
10+x0＜y＜0.6 in (Bi (2223)), the span of control of temperature of reaction are 720 ℃ to 805 ℃, and the span of control of oxygen partial pressure is 0.01 to 1 normal atmosphere, and the span of control of heat treatment time is 1-7 hour.
2. the method for preparing the superconducting precursor powder end according to claim 1, it is characterized in that described temperature of reaction remains unchanged, reduce oxygen partial pressure with promote Pb dissolve into Bi (2212) mutually in, and then the raising oxygen partial pressure, make Pb from Bi, Pb (2212) separates out in mutually, and form second phase mutually with other, this process can be carried out repeatedly, by the composition and mutually transformation degree of phase in the control powder, so that powder reaches the composition and the granularity of best phase.
3. the method for preparing the superconducting precursor powder end according to claim 1, it is characterized in that oxygen partial pressure keeps constant, improve temperature of reaction with promote Pb dissolve into Bi (2212) mutually in, and then cooling, make Pb from Bi, Pb (2212) separates out in mutually, and form second phase mutually with other, this process is carried out repeatedly, by the composition and mutually transformation degree of phase in the control powder, so that powder reaches the composition and the granularity of best phase.
4. the method for preparing the superconducting precursor powder end according to claim 1 is characterized in that changing simultaneously temperature of reaction and oxygen partial pressure, by the composition and mutually transformation degree of phase in the control powder, so that powder obtains the composition and the granularity of best phase.
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|---|---|---|---|
| CN01120379.XA CN1197820C (en) | 2001-08-29 | 2001-08-29 | Method for preparing superfine powder |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN01120379.XA CN1197820C (en) | 2001-08-29 | 2001-08-29 | Method for preparing superfine powder |
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|---|---|
| CN1401608A CN1401608A (en) | 2003-03-12 |
| CN1197820C true CN1197820C (en) | 2005-04-20 |
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|---|---|---|---|
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|---|---|
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