CN1344682A - Prepn of nano-cobaltosic oxide powder - Google Patents

Abstract

The present invention relates to chemical industry technology. The preparation of nanometer cobaltosic oxide powder includes purifying material, cobalt salt deposition, solid-liquid separation and solid calcination. Cobalt sheet is dissolved in nitric acid while being heated and high purity water is added to regulate solution density and pH value so as to obtain cobalt nitrate solution of 1.5-1.65 g/cu cm density and pH 4-5; ammonium bicarbonate suspension in 14-30 wt% is prepared with ammonium bicarbonate and water; cobalt nitrate solution is added into the suspension slowly to result in weight ratio of carbonate radical to cobalt ion being 2.4-2.6; and the wet cobalt carbonate material is heated to 300-450 deg.c for 3-6 hr to obtain black Co3O4 powder.

Description

The preparation method of nano-cobaltosic oxide powder

(1) technical field

The present invention relates to a kind of nano material Co ₃O ₄Powder preparation method belongs to the chemical industry technical field.

(2) background technology

As multifunctional material, metal oxide solid powder purposes is a lot.Be widely used as gas sensing material, humidity sensor material, temperature sensing material, infrared reflective material at present; In petrochemical complex industry, be used as catalyzer; In coating, pigment, ceramic industry, be used as additive etc.The synthetic of research metal oxide can not be ignored following two fields: the one, prepare the solid material of the different composition of various patterns, size, shape, vesicularity homogeneous, and develop the difference in functionality of different-shape material or make the existing capability of material more excellent; The 2nd, study the preparation method of simple and easy to do metal oxide nano-material.

Its character of different types of oxide compound is different with function, and the character of same a kind of metal oxide of different-shape and function also have difference, and the material with special appearance often has special property and function.Compare with tabular crystal, whisker mixes generally has better reinforcement in pottery, the plastics.At present, most of whiskers are as the toughener of polymer, metal, stupalith, and this also is the initial and topmost purposes of exploitation whisker.The shape difference of whisker is to the reinforced effects difference of material.With ZnO is example, when needle-like whisker is used as the toughener of matrix material, because the homogenizing that is difficult to accomplish three-dimensional in body material causes matrix material to present anisotropy.And when using four horn shape ZnO whiskers to mix in the body material, eliminated anisotropy, obviously improved reinforced effects.And for example to have fluidised form character good for the fusiform magnetic, easily realizes filming thin layerization helping improving advantages such as recording density.The shape characteristics such as edge that these advantages and its even particle size, branch be few, almost do not have a sharp corners are closely related.

Except adding the material, has the Co of spinel structure as gas sensitive and pottery ₃O ₄Can also be as eelctro-catalyst, oxygen, chlorine separates out on the catalyticing anode; Replace expensive RuO during electrolytic saltwater ₂As active material of positive electrode; Also be hopeful in fuel cell, to use as cathod catalyst.

No matter be the film or the preparation of powder, preparation method's difference is very big to the influence that material property produces.Preparation Co ₃O ₄Method commonly used mainly contains cobalt salt pyrolysis method, sol-gel method, chemical spray method etc.Wherein back two kinds of methods are usually used in preparing thin-film material on different matrix.Commercial scale production cobalt/cobalt oxide powder is used the chemical heat solution always.

The direct pyrolysis of cobalt salt is one of common method of preparation metal oxide.Adopt chemical precipitation agent with the form precipitation of the metal ion in the electrolyte solution with oxygenatedchemicals such as carbonate, oxalate, oxyhydroxide, heating makes its decomposition then.Perhaps direct heating decomposes nitrate, the acetate of cobalt.Cobalt/cobalt oxide manufacturing enterprise generally uses these class methods at present, and it is simple to operate, and not strict to operating parameters control, Heating temperature generally surpasses 600 ℃, and soaking time reaches 12 hours.Therefore powder granule size, the pattern that obtains is inhomogeneous, and granularity is generally micron order, and dopant species is many and content is high, can not satisfy the requirement of emerging industry to the every index of raw material fully.

The powder of Hydrothermal Preparation have crystal grain grow complete, size of microcrystal is little and be evenly distributed, do not have reunion, good dispersity, do not need characteristics such as calcination processing, often is used to prepare ultra-fine, the ultrapure powder of oxide compound.This method has successfully prepared sheet and fibrous Mg (OH) ₂, Al ₂O ₃, the uniform powder of pattern such as cobalt/cobalt oxide.Compare with the cobalt salt pyrolysis method, the hydrothermal synthesis method complicated operation, the cost height is more suitable for preparing the powder with special appearance feature.

Sol-gel method is the another kind of method for preparing high purity, monodisperse particles.Compare with traditional method, it has the low advantage of thermal treatment temp.Mustapha El Baydi et al. adopts Prepared by Sol Gel Method Co ₃O ₄, and contrasted pattern granularity, specific surface area and the electro catalytic activity of sol-gel method, solid nitric acid salt pyrolysis method and nitrate solution spray pyrolysis gained material.Although find the Co of Prepared by Sol Gel Method ₃O ₄Particle size range narrowly distributing (2-4nm), specific surface area are bigger, but material does not show better electro catalytic activity.And nano material has special surface effects and volume effect because particle diameter is little.As control Co ₃O ₄Granularity in nanometer range the time, its catalytic activity can improve greatly.For example, Co ₃O ₄The oxidizing reaction of catalysis CO, grain graininess are the principal elements that influences its catalytic activity.Work as Co ₃O ₄Granularity when reaching several nanometer, the conversion rate of oxidation of CO still can reach 100% in the time of-78 ℃.When small particle size enters nanometer scale, itself have quantum size effect, small-size effect, surface effects and macro quanta tunnel effect, show many distinctive character.Therefore, nano material has broad application prospects at aspects such as catalysis, optical filtering, medicine, magneticmedium and novel materials.But nano material has very high surfactivity, very easily produces and reunites.People such as Dierstein A. adopt the electrochemical deposition method (EDOC) under the oxidizing atmosphere and use suitable stablizer to prepare the narrow nano Co of particle size distribution range ₃O ₄Powder.Adopt simple and easy to do method to prepare good dispersion, pattern and even particle size, nano Co that foreign matter content is low ₃O ₄Powder effectively solves the agglomeration traits of nano-powder material, is important research project.

In recent years, along with the secondary lithium battery demand constantly increases, to its positive electrode material LiCoO ₂Demand also constantly increase.The oxide compound of cobalt is preparation LiCoO ₂One of important source material.Secondary lithium battery positive electrode material LiCoO ₂The component target of the oxide compound of its raw material cobalt is required quite high, the Ni of trace, Na, Mn, Cu, impurity such as Fe are to material LiCoO ₂Chemical property damaging influence is arranged.If with Co ₃O ₄Be raw material production LiCoO ₂, the content of various impurity all should be ppm level (quality index sees table 1 for details) in the raw material.Solid phase method synthesizes LiCoO ₂General technology be earlier two kinds of raw materials to be ground refinement respectively, batch mixing, roasting then.Yet solid material is difficult for mixing, and the material mass transfer velocity is slow in the solid powder, causes solid state reaction temperature height, and long reaction time causes prepared product LiCoO ₂Pattern is inhomogeneous.This will directly influence LiCoO ₂Chemical property.Produce LiCoO and adopt cobalt/cobalt oxide that rough production technique produces all can not satisfy in the past at aspects such as the chemical ingredients of product, purity, granularity, crystal formations ₂Requirement.And use nano level Co ₃O ₄Powder can improve the problems referred to above as one of raw material.Because nano-powder has great surface-area and reactive behavior, not only can simplify mixing procedure, makes batch mixing easier, more even, and can reduce temperature of reaction, shortening reaction times effectively.At present inside the province and even domesticly still do not have a Co ₃O ₄Nano-powder manufacturer, but Co ₃O ₄Nano-powder at home and abroad holds out broad prospects.Therefore, research preparation well-crystallized, even particle size distribution, highly purified cobalt/cobalt oxide have important theory and practical significance.

Table 1: nano Co ₃O ₄The composition index of powder (content by weight percentage)

Cobalt contents	Nickel content	Sodium content	Iron level	Manganese content	Copper content
						????70-74	????≤0.1	????≤0.07	????≤0.017	????≈0.005	????≈0.005

(3) summary of the invention

The present invention is directed to the deficiency of prior art, provide a kind of chemical precipitation-pyrolysis method to prepare high purity, nano Co ₃O ₄The preparation method of powder.Technical process mainly comprises: the purification of raw material, cobalt salt precipitation, solid-liquid separation, solid roasting and product post-treating and other steps.

1. the purification of raw material and preparation

At present chemical industry to Co ₃O ₄The powder chemical ingredients requires harsh present situation, must the raw materials used chemical ingredients of control.It is the cobalt source that present method adopts the cobalt sheet, wherein contains impurity metal ions such as relatively large Fe, Ni, purifies by pH value and the recrystallizing technology of regulating cobalt nitrate solution.The concrete practice is: at first, the cobalt sheet is dissolved in volume ratio (1～2) under heating condition: the nitric acid of (1～2), constantly add the density and the pH of high purity water regulator solution in the dissolution process, and finally obtaining density is 1.30～1.40g/cm ³, the pH value is the cobalt nitrate solution of 4-5, leaves standstill the solids removed by filtration throw out one day; Again with the pH=1-2 of an amount of nitric acid regulator solution, evaporating solvent carefully, obtaining density is 1.50g/cm ³～1.65g/cm ³Cobalt nitrate solution, leave standstill, the cooling, separate out cobalt nitrate crystals.

The Fe constituent content is lower than 0.004% in the above-mentioned cobalt nitrate crystals of analysis revealed, the Ni constituent content is lower than 0.025%.

Above-mentioned cobalt nitrate crystals is dissolved in the high purity water, and making density is 1.50g/cm ³～1.65g/cm ³Cobalt nitrate solution stand-by.

Chemical precipitation agent adopts food grade NH ₄HCO ₃, the Na constituent content is lower than 0.02%.Adding water, to make concentration be that the bicarbonate of ammonia suspension liquid of 14～30% weight percents is stand-by.

2. the chemical precipitation pyrolysis method is produced the cobalt salt precipitation

Under agitation condition, the density that slow adding has been purified in the bicarbonate of ammonia suspension liquid is 1.50g/cm ³～1.65g/cm ³Cobalt nitrate solution, make the ratio of the weight of material: CO ₃ ^2-/ Co ²⁺=2.4～2.6, and pH=6.5～7.0 of clear liquid behind the conditioned reaction.After reinforced the finishing, continue to stir 2～2.5 hours.Leave standstill centrifugation.The control solid contains the cobalt amount 18～22%, separates the clear liquid that obtains and recycles.

Traditional chemical pyrolysis legal system is equipped with cobalt/cobalt oxide and adopts thermal degradation Xiao Suangu solid method, and the decomposition temperature height produces a large amount of oxides of nitrogen gas polluted airs in the decomposition course.Present method adopts the chemical precipitation pyrolysis method, earlier the solubility cobalt salt is converted into carbonate deposition, and thermal degradation carbonate under design temperature has been avoided the generation of toxic gas again, helps environment protection; Select NH ₄HCO ₃Be precipitation agent, the precipitation that obtains does not need washing, has not only saved a large amount of bath wateies, and has avoided introducing Na ⁺In addition, control sedimentary water content, promptly controlled the amount of residual ammonium nitrate, take place when being heated violent the decomposition, send a large amount of heat and gas by centrifugal means.Can reduce Co effectively ₃O ₄Synthesis temperature, shorten soaking time, also help and obtain tiny, the finely dispersed Co of particle ₃O ₄Powder, also helpful to solving the particulate agglomeration traits.

3. nano Co ₃O ₄The preparation of powder:

The cobaltous carbonate wet feed that the last step was obtained places appropriate containers, and feeding quantity is 1/2～2/3 of a container, is warming up to 300～450 ℃ and be incubated 3～6 hours, obtains black powder.

4. the aftertreatment of product:

Product cools off under the exsiccant closed environment, vacuum packaging.

Because nano grain surface is long-pending greatly, surfactivity is high, easily reunites, easily absorbs airborne moisture content.The sample cooling should be carried out in dry closed environment, and adopts vacuum-packed.

The present invention adopts the chemical pyrolysis legal system that is fit to the commercial scale production powder body material to be equipped with Co ₃O ₄Nano-powder has characteristics such as technological operation is simple, parameter is easy to control, suitable large-scale industrial production.Compared with the prior art details are as follows for excellent results of the present invention.

It is raw material that the chemical heat solution generally adopts Xiao Suangu, cobalt oxalate and cobaltous carbonate, and heating makes it to decompose (being accompanied by oxidation sometimes), the preparation cobalt/cobalt oxide.The former is the solubility cobalt salt, when being directly used in thermal degradation, produces a large amount of deleterious oxynitride, atmosphere pollution; And decomposition temperature generally surpasses 600 ℃, and soaking time is long, causes product granularity and pattern inhomogeneous, can't satisfy battery industry user's needs.Both are difficulty soluble salt the back, need utilize chemical precipitation method to be transformed by the solubility cobalt salt earlier and obtain.Though technology can be avoided atmospheric pollution effectively than direct decomposing soluble cobalt salt slightly complicated.Wherein the oxalate price is higher, and still can produce a large amount of toxic gases in the decomposition course.And there are not these problems in carbonate decomposition.

When using rose vitriol to do the cobalt source, the very easy absorption of the cobaltous carbonate that chemical precipitation obtains sulfate ion wherein, and be difficult for washing, and cause and contain relatively large rose vitriol in the final product, influence product performance; And when adopting cobalt chloride to be raw material, the by product of precipitin reaction is an ammonium chloride, produces a large amount of ammonias and hydrogen chloride gas during decomposes, on the one hand CoCl ₂Transform not exclusively, cause the cobalt/cobalt oxide loss on the other hand, thereby product purity is reduced, it is lower to show as cobalt contents.And adopt Xiao Suangu is raw material, with NH ₄HCO ₃Generation cobaltous carbonate precipitation, wet feed needn't wash, and directly is warming up to design temperature from room temperature in process furnace, and insulation for some time prepares Co at highest temperature place ₃O ₄By product in the clear liquid decomposes simultaneously, emits the gentle body of big calorimetric, and the gas of generation is gone out from solid, helps obtaining the tiny product of particle diameter.This technology has not only been saved a large amount of bath wateies, and makes the Co of generation ₃O ₄Nano-powder is difficult for reuniting, and is convenient to the battery industry client and uses.

Table 2: the powder section results of elemental analyses (by weight percentage) that different precipitation agents and Xiao Suangu reactive chemistry precipitation heat solution obtain

Different precipitation agents	Ammonia	Sodium hydroxide	Yellow soda ash	Bicarbonate of ammonia
					The Na constituent content	Do not survey	????0.34	????0.16	????0.015
Cobalt element content	????70.42	????71.63	????71.32	????71.50

When with NH ₄HCO ₃Add fashionablely in cobalt nitrate solution, produce a large amount of gases, volumetric expansion is serious, and is wayward.And feed rate is too fast, and this phenomenon is serious more; The order of addition(of ingredients) that employing of the present invention is opposite with known technology slowly joins NH with cobalt nitrate solution ₄HCO ₃In the suspension liquid, obtained good effect.

The acidity of chemical precipitation reaction back supernatant liquid directly influences the yield of cobalt, even has influence on the granularity and the pattern of product.When the pH of supernatant liquid hour, the carbanion loss is serious, Xiao Suangu is excessive in the clear liquid.This solid-state intermediate of thermal degradation, the product cobalt contents that obtains is on the low side, and granularity is bigger, and particle agglomeration is more serious.And when the pH of supernatant liquid was big, the yield of cobalt obviously reduced.By regulating feed ratio, control feed rate, precipitin reaction is finished after the pH of supernatant liquid between 6.5～7.0, the yield of a production process cobalt can reach more than 91%, the result is the most satisfactory.

The present invention has carried out thermal analysis experiment from room temperature to 900 ℃ to solid-state intermediate.There are a significantly weightlessness in TG and DTG curve display between 290-310 ℃, in the time of 350 ℃, weightlessness is complete substantially.Almost imponderability variation between 350-900 ℃.In 300-900 ℃ of scope, carried out solid-state intermediate pyrolysis experiment.Degradation production under the differing temps is carried out XRD, TEM to be characterized.Fig. 4 is the product size value that calculates according to the XRD and the transmission electron microscope photo of product and the relation of maturing temperature.The Co that Fig. 5 obtains for different maturing temperatures ₃O ₄The powder transmission electron microscope photo.The result shows, all obtain pure phase Co in 300-900 ℃ of scope ₃O ₄Crystal, but wherein have a particle diameter sudden change, promptly when maturing temperature surpassed a certain particular value, particle diameter increased suddenly.Determined suitable maturing temperature in view of the above.In the suitability for industrialized production, consider furnace and factors such as container shapes, material thickness, maturing temperature can correspondingly change.

Solid-state intermediate is placed in the process furnace, under the chosen temperature condition, take out after 1,3,6,12 hours, carry out XRD and TEM and characterize respectively at insulation.The result shows that heating after three hours has been pure phase Co ₃O ₄, and crystalline condition is good.Consider in the industrial production, factors such as the shape of container, material thickness, furnace, roasting time can proper extension.Determine that thus roasting time is 3～6 hours.

Product of the present invention detects through Shandong Forecasting and Analysis Center, and the result is as follows:

Table 3: nano Co ₃O ₄Powder analysis of components result (analytical procedure: ICP, by weight percentage)

Cobalt contents	Nickel content	Sodium content	Iron level	Manganese content	Copper content
						????71.5	????0.035	????0.015	????0.011	????0.0047	????0.0055

The present invention is further illustrated below in conjunction with drawings and Examples.

(4) description of drawings

Fig. 1 is a nano Co of the present invention ₃O ₄The powder preparing process flow sheet.

Fig. 2 is Xiao Suangu and four kinds of precipitation agent ammonia, sodium hydroxide, yellow soda ash, the bicarbonate of ammonia X-ray powder diffraction figure through the powder of chemical precipitation pyrolysis preparation.

Fig. 3 is the Co that different precipitation agents obtain ₃O ₄The powder transmission electron microscope photo, wherein, A:NH ₃, B:NaOH, C:Na ₂CO ₃, D:NH ₄HCO ₃

XRD and Fig. 3 transmission electron microscope photo by Fig. 2 are analyzed, although all obtain pure phase Co under imposing a condition ₃O ₄, the product granularity is all less than 100nm.But table 1 analysis of components result shows, is that raw material satisfies the Chemical Composition quality index with cobalt nitrate crystals and bicarbonate of ammonia.

Fig. 4 is the product size value that calculates according to the XRD and the transmission electron microscope photo of product and the relation of maturing temperature.

The Co that Fig. 5 obtains for different maturing temperatures ₃O ₄The powder transmission electron microscope photo.

The powder X-ray diffractogram that Fig. 6 obtains for the present invention.Testing tool: D/max-γ A type rotating anode X-ray diffractometer (Japan of science), CuK alpha-ray, λ=0.154178nm, graphite monochromator, 40KV, 50mA, sweep limit 10 °≤2 θ≤70 °.

The Co of Fig. 7 chemical precipitation pyrolysis method preparation ₃O ₄The powder transmission electron microscope photo.Testing tool: JEM-100CXII transmission electron microscope (NEC company)

(5) embodiment

Embodiment 1.

At first, under heating condition the cobalt sheet is dissolved in 1: 1 nitric acid of volume ratio, constantly adds the density and the pH of high purity water regulator solution in the dissolution process, finally obtaining density is 1.35g/cm ³, the pH value is 4.5 cobalt nitrate solution, leaves standstill the solids removed by filtration throw out one day; Again with the pH=1.5 of nitric acid regulator solution, evaporating solvent carefully obtains density and is 1.57 cobalt nitrate solution, leaves standstill, and cobalt nitrate crystals is separated out in cooling.The Fe constituent content is lower than 0.004% in the above-mentioned cobalt nitrate crystals of analysis revealed, the Ni constituent content is lower than 0.025%.

Chemical precipitation agent adopts food grade NH ₄HCO ₃, the Na constituent content is lower than 0.02%.Making concentration with 25 parts of (weight part, down with) bicarbonate of ammonia and 100 kilograms of high purity waters is that the bicarbonate of ammonia suspension liquid of 20% weight percent is stand-by.

Under agitation condition, the density that slow adding has been purified in the bicarbonate of ammonia suspension liquid is 1.57g/cm ³Cobalt nitrate solution, make the ratio of the weight of material: CO ₃ ^2-/ Co ²⁺=2.5, and the pH=6.6 of clear liquid behind the conditioned reaction.After reinforced the finishing, continue to stir 2 hours.Leave standstill centrifugation.The control solid contains the cobalt amount 20%, separates the clear liquid that obtains and recycles.

The cobaltous carbonate wet feed that the last step was obtained places appropriate containers, controls certain reinforced thickness and packing density, is warming up to 380 ℃ and be incubated 4 hours, obtains black powder.Product cools off under the exsiccant closed environment, vacuum packaging.

Embodiment 2. is as described in the embodiment 1, and different is:

Making concentration with 25 parts of bicarbonate of ammonia and 150 kilograms of high purity waters is that the bicarbonate of ammonia suspension liquid of 14.3% weight percent is stand-by.Under agitation condition, the density that slow adding has been purified in the bicarbonate of ammonia suspension liquid is 1.60g/cm ³Cobalt nitrate solution, make the ratio of the weight of material: CO ₃ ^2-/ Co ²⁺=2.6, and the pH=6.7 of clear liquid behind the conditioned reaction.After reinforced the finishing, continue to stir 2.5 hours.Leave standstill centrifugation.The control solid contains the cobalt amount 21%, separates the clear liquid that obtains and recycles.The cobaltous carbonate wet feed that the last step was obtained places appropriate containers, is warming up to 400 ℃ and be incubated 3.5 hours, obtains black powder.

This technology is initial feed with cobalt sheet and bicarbonate of ammonia, utilizes the replacement(metathesis)reaction between Xiao Suangu and the bicarbonate of ammonia, adopts the chemical precipitation pyrolysis method to prepare high purity, nano Co ₃O ₄Powder.Have advantages such as workable, that technology is simple, productive rate is high, pollution is little.The Co of preparation ₃O ₄Powder hardness is little, purity is high, is granular size, the uniform nanocrystal of pattern.Produce the oxide compound of a small amount of iron content, nickel in the purification of raw material, the dissolution process, they are nontoxic, tasteless, can be used as the building filler and handle.The mother liquor that recrystallization process produces is the higher relatively cobalt nitrate solution of nickel content, can as ceramic packing, not have the waste residue problem as producing low-level cobalt/cobalt oxide.The supernatant liquid that solid-liquid separation obtains can recycle, as the dissolving water, does not have the discharge of wastewater problem.The side goes out a large amount of gases in the roasting process, and major ingredient is water vapour and CO ₂Gas can not cause atmospheric pollution substantially.

Claims (2)

1. a chemical precipitation pyrolysis method prepares Co ₃O ₄The method of nano-powder mainly comprises it is characterized in that purification, cobalt salt precipitation, solid-liquid separation, the solid roasting of raw material,

(1) purification of raw material

At first, under heating condition, the cobalt sheet is dissolved in volume ratio (1～2): the nitric acid of (1～2), constantly add the density and the pH of high purity water regulator solution in the dissolution process, finally obtaining density is 1.30～1.40g/cm ³, the pH value is 4～5 cobalt nitrate solution, leaves standstill the solids removed by filtration throw out one day; Again with pH=1～2 of an amount of nitric acid regulator solution, evaporating solvent carefully, obtaining density is 1.50g/cm ³～1.65g/cm ³Cobalt nitrate solution, leave standstill, the cooling, separate out cobalt nitrate crystals; Above-mentioned cobalt nitrate crystals is dissolved in the high purity water, and making density is 1.50g/cm ³～1.65g/cm ³Cobalt nitrate solution stand-by;

Chemical precipitation agent adopts food grade NH ₄HCO ₃, adding water, to make concentration be that the bicarbonate of ammonia suspension liquid of 14～30% weight percents is stand-by;

(2) produce the cobalt salt precipitation

Under agitation condition, the density that slow adding has been purified in the bicarbonate of ammonia suspension liquid is 1.50～1.65g/cm ³Cobalt nitrate solution, make the ratio of the weight of material: CO ₃ ^2-/ Co ²⁺=2.4～2.6, and pH=6.5～7.0 of clear liquid behind the conditioned reaction, after reinforced the finishing, continue to stir 2～2.5 hours, to leave standstill, centrifugation separates the clear liquid that obtains and recycles;

(3) Co ₃O ₄The preparation of nano-powder

The cobaltous carbonate wet feed that the last step was obtained places appropriate containers, and feeding quantity is 1/2～2/3 of a container, is warming up to 300～450 ℃ and be incubated 3～6 hours, obtains black powder.

2. nano Co as claimed in claim 1 ₃O ₄The preparation method of powder is characterized in that, the aftertreatment of product: product cools off under the exsiccant closed environment, vacuum packaging.

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