CN1569617A

CN1569617A - Detonation method for synthesizing oxide powder

Info

Publication number: CN1569617A
Application number: CN 200410020553
Authority: CN
Inventors: 李晓杰
Original assignee: Dalian University of Technology
Current assignee: Dalian University of Technology
Priority date: 2004-05-13
Filing date: 2004-05-13
Publication date: 2005-01-26

Abstract

The invention discloses a detonation method for synthesizing oxide powder, wherein the oxide precursor can be used to compose stable detonation explosive, through which the oxide precursor can produce under high temperature and high pressure of detonation oxide powder, nano oxide powder, inter-molecule mixed compound oxide powder, the explosive can be added by inert particles so as to synthesize nano oxide coated powder.

Description

Detonation synthesis method of oxide powder

Technical Field

The invention belongs to the field of physical or chemical methods, and particularly relates to a method for synthesizing oxide powder by using detonation at high temperature and high pressure.

Background

The nano powder is in nano order of magnitude (10)^-9m) of ultrafine particles, the size range of which is 1 to 100nm. Because the particles are very fine, the number of atoms on the grain boundary is more than that in the interior of the crystal grains, the crystal grain boundary has high concentration, and a large number of atoms are positioned in the defect center in the crystal grains. Therefore, the nano powder has the effects of small size, surface and interface, quantum size, macroscopic quantum tunneling and the like, and compared with large-particle micro powder consisting of the same components, the nano material often shows unique properties such as superplasticity, low elasticity and low density which are incomparable with other structural materialsHigh strength, large magnetic reluctance, low thermal conductivity, unusual soft ferromagnetism, considerable magnetocaloric effect and considerable specific surface area and transparency, etc. The nanometer material has such characteristics, so that the nanometer material has wide application prospects in the aspects of aerospace technology, electronics, metallurgy, chemistry, biology, medicine and the like. In the early 80 s, with the advent of nano materials, the new material has attracted great attention. At present, the preparation and property research of nano materials has become a very active and powerful hotspot in the field of material science. And is gaining more and more attention in the industry.

The nano-oxide has a wide range of industrial applications. In addition to being excellent high temperature ceramic materials, e.g. nano TiO₂Nano ZnO, nano MgO and nano SiO₂Nano Al₂O₃Nano mica, nano iron oxide and the like can be used as chemical catalysts, sterilization materials, photodegradation materials, ultraviolet and infrared absorption materials, electromagnetic or infrared stealth materials and the like.

In addition, many complex oxide ceramics have been used widely, such as yttrium barium copper oxide, lanthanum strontium copper oxide, etcHigh temperature superconductivity is found; y is₂O₃:Eu³⁺、Y₂O₃:Tb³⁺Is an excellent luminescent material; the rare earth activated alkaline earth aluminate and alkaline earth silicate are high-quality long afterglow materials; the nano ferrite is a magnetic material; lead titanate, barium titanate, lead zirconate titanate, and the like can be used as the piezoelectric crystal material; zirconium tungstate is an excellent negative thermal expansion material, lithium manganate is a new positive electrode material of a lithium battery, and the composite oxide is also used as acousto-optic, magneto-optic, electro-optic materials and the like.

The synthesis of these oxides, especially the synthesis of nano-oxides, is rather complicated and tedious, and complex oxide ceramics often require uniformity on the molecular scale, which makes the process conditions often difficult to control, the synthesis cost greatly increased, and the yield often extremely low.

Currently, the commonly used methods for synthesizing nanopowders can be roughly classified into three major types, solid phase, liquid phase and gas phase synthesis.

The solid phase method is to prepare nanometer powder by mechanical crushing, electric spark explosion, high-energy mechanical ball milling and other methods. Among them, the high energy mechanical ball milling method is a method capable of mass-producing nano-powder, which has been developed in recent years, without supplying heat energy from the outside. High-energy ball milling is carried out in a dry environment, so that large grains are changed into small grains. The solid phase method can be used for preparing simple substance nano materials, and can also be used for directly synthesizing the nano ceramic powder composite material through the solid phase reaction among particles. The solid phase method has the advantages of simple operation, low cost, easy preparation of the mixture and the like, but impurities are easy to introduce, so that the purity of the product is reduced, the particle distribution is not uniform, and the mixture is difficult to uniformly mix.

The vapor phase method mainly refers to a method for synthesizing nano-powder by using evaporation, chemical vapor deposition and vapor phase chemical reaction. The heating method of heating and evaporating metal and its compounds in Inert Gas and condensing vapor can prepare nano particles with clean surface, also called Inert Gas Condensation method (IGC), and its heating method includes electric heating, electric explosion, laser, electric arc, plasma heating, etc., but this method is suitable for preparing nano particles with low melting point and single component of metal, etc., in recent decades, though MgO, Al and other elements are successfully prepared by changing heating method, such as electric arc method, plasma method and laser beam, etc. to heat precursor₂O₃、ZrO₂And Y₂O₃And nano powder with high melting point. However, these improvements are costly, such thatIts large-scale application is limited. Chemical Vapor Deposition (CVD) is a method in which metal, metal compound, etc. are used as raw materials, and they are gasified by the action of heat source, electron beam, laser radiation, plasma, and then Chemical reaction is carried out in the gas phase, and the coagulation and growth of the product are controlled, and finally the nano-powder is obtained. CVD allows the synthesis of nanomaterials at temperatures well below the melting point of the material, thus almost replacing the inert gas condensation method in the synthesis of non-metallic particles and high melting point compounds. The CVD prepared nano powder has high purity, and the reaction atmosphere can be controlled so as to control the granularity, but the technical equipment requirement is higherHigh yield and low output. One of the most mature synthesis methods in the Gas phase synthesis method is Gas phase combustion synthesis (Gas phase synthesis), for example, synthesis of nano titanium oxide by high temperature Gas phase hydrolysis, which utilizes the combustion of hydrogen-oxygen mixture and titanium tetrachloride to synthesize a large amount of nano titanium oxide with various crystal forms; the other method is a gas phase oxidation method, namely heating the mixed gas of oxygen and titanium tetrachloride at high temperature to decompose the mixed gas into chlorine and nano titanium oxide; the two methods are also used for preparing nano silicon dioxide in large quantity; although the gas-phase combustion and the gas-phase oxidation can prepare a large amount of nano titanium oxide and silicon oxide, the energy consumption is high on one hand, and a large amount of corrosive gas is generated on the other hand, so that the requirements on equipment are extremely high. The nanometer powder obtained by the general gas phase method has better dispersibility and higher chemical purity, and the mixed oxide is difficult to obtain.

The liquid phase method, i.e. wet chemical method, is a field which is widely applied and active in the preparation of nano materials. Such methods can be largely classified into a solvent evaporation method, a microemulsion method, a precipitation method, and a sol-gel method. The solvent evaporation method is to atomize the salt solution with high solubility into small droplets to make the salt in the solution precipitate out uniformly and rapidly, and then to heat and decompose the precipitate to obtain fine oxide nano powder. It also includes three kinds of freeze drying method, spray thermal decomposition method and spray drying method. The method has the characteristics of continuous operation, high preparation capacity, fine prepared particles, good dispersibility and the like. However, the requirements for the operating conditions are high and a large amount of chemical solvent is required. The microemulsion method is that metal salt and certain precipitant are mixed to form microemulsion, and the nucleation and growth of colloidal particles are controlled in a smaller micro-area, and then the nano-particles are obtained by heat treatment. The method is used for Fe₂O₃、Cr₂O₃Etc., which have good monodispersity of particles but are difficult to control the particle diameter, and can be preparedThe surface of the particles of (a) is often coated with surfactant molecules. The precipitation method is one of the more important methods for preparing nano-powder in wet chemistry. The principle is to hydrolyze the solution in a fluid such as an aqueous solution or steam by adding a precipitant or under high temperature and high pressure. Thereby forming insoluble hydroxides orSalt, washing and thermal decomposing to obtain nanometer oxide. The nanoparticles prepared by the method are many, such as: ZrO (ZrO)₂、Cr₂O₃-Al₂O₃、Al₂O₃-SiO₂、TiO₂、PbTiO₃And the like. The most promising of these synthetic methods is the hydrothermal method and the microwave hydrothermal method has emerged in recent years.

The sol-gel method is to hydrolyze metal alkoxide and inorganic salt to form sol, then to polymerize to form gel, to obtain sol-gel with uniform chemical composition, and finally to dry and bake to obtain nano powder. The method for preparing sol-gel by using nitrate and then synthesizing nano oxide powder by combustion has the most development potential. The method is characterized in that cheap raw materials and simple equipment are adopted, and the obtained sample has small particle size, high purity and certain dispersibility. The method has the disadvantages of high heat energy consumption in the processes of sol-gel drying and roasting and simultaneously generating a large amount of polluting gases.

The detonation method has the characteristics of high synthesis reaction speed, simple synthesis equipment and easy mass production amplification. However, the detonation synthesis method has only one application at present, namely, the excess carbon in the TNT mixed explosive is used for synthesizing nano diamond powder, and some reports are that graphite powder is added into the explosive to perform high-pressure physical crushing on the graphite. The output of the nano-diamond synthesized by the detonation synthesis method can reach 8% of the explosive amount, and the explosive is a mixture of high-energy explosives such as TNT and RDX or PETN, so that the cost of the explosive is high, and the explosive accounts for about 200-350 yuan/kg in the cost of synthesizing the diamond.

Disclosure of Invention

The purpose of the invention is: provides a method for synthesizing various oxides, double oxides and nano oxides, realizes the homogenization of the double oxides on the molecular scale, and can coat the nano oxides on the surface of powder with general scale. Meanwhile, the problem of accurate control of nano oxide synthesis is solved, pollution is reduced, and energy consumption is reduced.

The technical scheme for realizing the invention is as follows:

the oxide precursor is detonated to decompose at high temperature and high pressure and react with oxygen, water and combustible matter in the detonation gas to synthesize oxide, compound oxide and nanometer oxide.

The industrial explosive is generally divided into two categories of single-substance explosives and mixed explosives, wherein the mixed explosives consist of an oxidant, a combustible agent, a sensitizer and a performance regulator, and the dosage forms can be liquid, solid or gas. Typical oxidizing agents are nitrates, nitrites, hypochlorites, chlorates, perchlorates, metal oxides, and also nitric acid, perchloric acid, gaseous and liquid oxygen, etc.; the combustible agent generally comprises wood powder, fuel oil, hydrogen, metal powder and other combustible substances; the sensitizer can be elementary explosive, bubbles and the like, and mainly increases the sensitivity of detonation; the performance regulator is mainly used as an additive for regulating the performance of the explosive according to different purposes, and can be active or inert. Therefore, in the method for synthesizing the nano oxide, the oxide precursor can be an elementary explosive, can also be added as an oxidant, or can be added as a combustible agent, a sensitizer and a regulator, and the adopted oxide precursor has a wide selection range.

The reaction process of the oxide precursor in the detonation wave is very complex, and the reaction process has great relation with the structure, the chemical activity, the chemical reaction form and the gas product amount of the oxide precursor. Oxide precursor zones can be broadly classified into a high activity, high gas production class; high activity, no gas or gas production; low activity pyrolysis and inert substances.

For the precursors with high activity and large gas production, metal ions (or semiconductors and rare earth elements) in the oxide precursors fully participate in the detonation reaction during the detonation. The precursor of the oxide can be quickly ionized under high temperature and high pressure in the detonation reaction zone, after the reaction is finished, the metal ions and the oxygen ions are polymerized in the gaseous detonation product, and then crystallized and grown, but because the high-pressure detonation product is quickly expanded and cooled, the growth process of the crystal grains of the oxide is stopped, and then the nano oxide with extremely small size can be generated. In addition, the preferred growth direction of the crystal grains is not greatly acted in the high-speed particle agglomeration process, so that spherical particles are easily formed. Such oxide precursors include a large number of inorganic and organic compounds containing metal ions (or semiconductors, rare earth elements), including elemental compounds (i.e., explosives) that decompose explosively on their own, oxidizers that provide a large amount of oxygen, fuels that provide a large amount of heat of combustion and generate a large amount of gas after combustion, and compounds that react strongly with detonation products.

The simple substance includes silver, Mg (NO)₃)₂·3C₂H₅OH, picrate, perchlorate, and the like;

the oxide precursor is in the form of oxidant, that is, the compound which is decomposed into oxide and releases a large amount of oxygen under heating state and the solution form of the compound are used as the precursor, such as: nitrate, oxynitrate, nitrite, chlorite, chlorate, perchlorate, higher oxides, etc., the precursor of the oxide will be decomposed as follows (where M represents a metal or semiconductor element, Q represents the heat of reaction, and x represents the valence which may be fractional):

decomposition of nitrate:

nitrite decomposition:

chlorate decomposition:

decomposition of perchlorate:

decomposition of chlorite:

hypochlorite decomposition:

bromate, iodate, and chromic anhydride, ammonium dichromate, and the like may also be used for chromium oxide synthesis.

When the form of the flammable agent is selected as the oxide precursor, a compound that can be burned in oxygen or a compound that causes a strong hydrolysis reaction is used as the precursor, such as organic salts of hydrides, nitrides, sulfides, phosphides, chlorides, oxalates, acetates, alkoxides, etc., alkane derivatives of silanes, boranes, etc., and the like. The oxide precursor will undergo the following oxidation and hydrolysis reactions in the active oxygen produced by detonation:

oxidation of oxalate:

chloride oxidation:

chloride hydrolysis:

for the high activity, non-gassing or gettering type of precursors, the precursors may undergo melting, gasification and high speed surface reactions during detonation reactions. The gasification will fully react with oxygen, and the reaction process is similar to the former; for the precursor which is melted, the precursor is crushed and atomized into nano particles under the strong pressure of detonation waves and high-speed airflow, and the nano particles are oxidized into oxides; melting and vaporizing type precursors can also produce spherical nanopowders. For the precursors which generate solid surface chemical reaction, the precursors react with oxygen and water in detonation gas and are broken into irregular nano powder by high-temperature, high-pressure and high-speed gas flow. The precursor is mainly composed of simple substance powder and oxygen-deficient oxide, and the following oxidation reaction occurs in the detonation process.

Metal powder oxidation:

oxidation of suboxide:

for low-activity thermal decomposition type precursors, the precursors do not participate in detonation chemical reaction, but are pyrolyzed in the detonation reaction to release a large amount of gas substances. Such as hydrous oxides (especially oxides containing water of crystallization), hydroxides, oxo acids and their salts which can be pyrolyzed to solid oxides, oxide colloids, carbonates, sulfates, etc., belong to this class. The material absorbs a large amount of reaction heat and non-isentropic compression heat in a detonation reaction zone, but because the detonation pressure in the reaction zone is far higher than the critical pressure of a gas substance in a precursor, the gas product in the detonation reaction zone cannot overflow the precursor in a large amount, and in an expansion zone of the detonation product, the external pressure of the precursor is rapidly reduced, the gas product in the precursor can expand at a high speed, evaporated water and decomposed gas can form huge pressure in the oxide, the gas can strongly overflow to the outside of the oxide, and the oxide particles can be blasted from the inside, so that the particles can be crushed and refined, and simultaneously gasification holes are formed on the particles, and the particles with large specific surface area are formed. A representative such reaction is as follows:

pyrolysis of hydrous oxide:

hydroxide pyrolysis:

carbonate pyrolysis:

the last type of precursor is a completely inert oxide particle or other friable compound, and when the precursor is added to an explosive as an inert component, the formation of nanoparticles relies primarily on the thermomechanical effect to produce fragmentation. The fragile precursor particles can form uneven temperature rise under the high temperature of detonation, the uneven temperature rise generates thermal stress and thermal cracks, and the particles can be further physically crushed under the high pressure of detonation. There is no essential difference from the grinding effect other than the heat removal, the only advantage being that no other solid impurities are mixed in when the detonation product is entirely gaseous. However, if the completely inert precursor is added into the explosive together with other precursors for detonation, the method provides a new method for coating the surface of the inert precursor with the nano oxide. In this case, we can use various stable ceramic powder, metal, carbon, etc. as nano-carrier, and add oxide precursor with strong activity into explosive, and the new oxide will deposit and grow on the surface of carrier particles during detonation, so as to produce composite particles with surface coated with nano-oxide.

In conclusion, the detonation method can be used for preparing nano oxide particles with various forms and nano surface ceramics, and if mixed salt, especially solution and colloid which are mixed with molecules are used for decomposition in the detonation, the intermolecular uniform compound oxide, such as yttrium barium copper oxide, lanthanum strontium copper oxide and other high-temperature superconducting ceramics, can be prepared; y is₂O₃:Eu³⁺、Y₂O₃:Tb³⁺A light-emitting material; rare earth activated alkaline earth aluminates, alkaline earth silicates, nano ferrite, lead titanate, barium titanate, lead zirconate titanate, zirconium tungstate, lithium manganate and the like. Therefore, the detonation synthesis method is a general oxide synthesis method, and all elements capable of forming solid oxides on the periodic table of elements can be prepared into nano oxides, compound oxides and coated particles.

In addition, because the morphology of the nano particles synthesized by detonation has a great relationship with the detonation state and the selected precursor, the crystal form and the particle size of the nano oxide can be effectively controlled by adjusting the precursor, the state of the precursor, the detonation parameters such as detonation velocity, detonation pressure and detonation heat. These parameters can be controlled by the composition, density, morphology of the explosive and are also very easily fixed for a given explosive ratio. Therefore, the detonation synthesis method is a good method which is easy to adjust and control the size and the crystal form of the nano particles and can stabilize the particle size and the crystal form of the nano particles.

The specific technical scheme can be carried out according to the following steps:

firstly, selecting proper oxide precursor, calculating its oxygen balance according to explosive components, and adding proper oxidant and combustion agent according to the oxygen balance. In order to ensure that the mixture can be detonated normally, a certain sensitizing agent, such as elementary explosive, mixed explosive, pores and the like, is added. According to the characteristics of the oxide and the precursor to be prepared, powder explosive, pressedexplosive and cast explosive can be adopted, or liquid explosive, water gel explosive, emulsion explosive, slurry explosive, gas mixed type explosive and gas suspension type explosive can be prepared.

Then, the explosive is put into a sealed detonation container to detonate (the detonation mode is not limited, and can adopt the modes of detonator, high-voltage discharge, laser, microwave, high-energy particle beam and the like to detonate), and the solid product is recovered to obtain the required nano oxide. The parameters of the nano oxide such as size, crystal form, specific surface area and the like can be adjusted by the detonation parameter of the mixture.

The invention has the advantages that:

1. the invention relates to a universal method for synthesizing oxides, which can prepare all elements capable of forming solid oxides on a periodic table of elements into nano oxides, compound oxides and coated particles.

2. Has a large selection range of precursors, and can synthesize nano oxides by adopting a plurality of precursors. For example, aluminum powder, aluminum hydroxide, aluminum sol, aluminum nitrate and aluminum alkoxide can be used for synthesizing nano aluminum oxide; the nano titanium oxide is prepared by using titanium powder, common titanium oxide, metatitanic acid, titanium sol, titanium nitrate, titanyl nitrate, titanium tetrachloride, titanium trichloride, titanium dichloride, titanium alkoxide, titanium oxalate and the like. The method is favorable for synthesizing nano particles with various forms and reducing the synthesis cost, so that the synthesis method becomes a simple and cheap method for preparing nano oxides.

3. The invention is a method suitable for synthesizing mixed nano-oxides; for example, yttrium barium copper oxide compound can be prepared by taking nitrate of yttrium barium copper asa precursor; the nanometer barium titanate is prepared by barium nitrate and titanium nitrate.

4. The method can be used for preparing composite powder with a nano-oxide coated surface.

5. The performance of the synthesized nano powder can be stably controlled by controlling the detonation parameters of the explosive.

6. Because the detonation synthesis process is a gaseous synthesis process, the spherical nano powder with large specific surface area and good dispersibility can be synthesized.

7. Because the synthesis speed of the detonation synthesis process is very fast, and is in the magnitude of 1-10 microseconds, the metastable nanometer oxide can be synthesized.

8. The invention is a method suitable for synthesizing nano materials in large quantity, and generally 100-500 g of nano oxide can be produced per kilogram of mixture, so that the yield of the nano oxide is only limited by the size of an explosion container, and 50-250 kg of nano powder can be produced per day by blasting 5kg of the mixture container once and 100 times per day; when a large container or a plurality of containers are used for synthesis, the yield of the nano powder is greatly improved, and the method is completely possible to reach daily yield of ton to dozens of tons.

Detailed Description

Example 1

Mixing 1kg of aluminum nitrate nonahydrate and 1kg of Taian explosive powder respectively, adding 82 g of charcoal powder, and carrying out detonation according to the following chemical equation to achieve oxygen balance:

the explosive is put into a spherical container with the diameter of 3 meters and is detonated by a No. 8 detonator, 135g of nano alumina can be obtained, and the nano alumina is spherical powder with the diameter of less than 50 nm.

Example 2

Mixing magnesium nitrate hexahydrate and 1kg of Tyan explosive powder respectively, adding 9 g of charcoal powder, and carrying out detonation according to the following chemical equation to achieve oxygen balance:

the explosive is put into a spherical container with the diameter of 3 meters and is detonated by a No. 8 detonator, 157g of nano-magnesia can be obtained, and the nano-magnesia is spherical powder with the diameter of less than 50 nm.

Example 3

2kg of ammonium nitrate powder is mixed and added with 600g of titanium powder, and the detonation is carried out according to the following chemical equation, so that the oxygen balance is achieved:

the explosive is put into a spherical container with the diameter of 3 meters and is detonated by 50g of tai' an to obtain 1kg of nano titanium oxide.

Example 4

Mixing 2kg of ammonium nitrate powder, adding 600g of titanium powder, adding 200 g of metatitanic acid, and carrying out detonation according to the following chemical equation to achieve oxygen balance:

the explosive is put into a spherical container with the diameter of 3 meters and is detonated by 50g of tai' an, and 1.32kg of nano titanium oxide can be obtained.

Example 5

Mixing 1kg of aluminum nitrate nonahydrate and 1kg of Tyan explosive powder respectively, adding 82 g of charcoal powder, and then adding 500 g of silicon carbide micropowder, wherein the detonation is carried out according to the following chemical equation, so as to achieve oxygen balance:

the explosive is put into a spherical container with the diameter of 3 meters and is detonated by a No. 8 detonator, and 635g of silicon carbide powder with the surface coated by the nano aluminum oxide can be obtained.

Claims

1. A detonation synthesis method of oxide powder is characterized in that:

a) oxide precursor is used to compose stable detonation explosive, and the explosive is detonated to synthesize oxide powder, nano oxide powder and intermolecular mixed compound oxide powder in the detonation reaction product;

b) oxide precursor is used to constitute explosive with stable detonation, and stable inert powder particle is added to detonate the explosive to synthesize nanometer oxide in the detonation product, so that the nanometer oxide is deposited onto the surface of the stable inert particle to produce nanometer oxide coated powder.

2. The detonation synthesis process of an oxide powder according to claim 1, characterized in that: the oxide precursor is a detonation-stable elementary explosive and comprises inorganic or organic explosives in solid, liquid or gas forms.

3. The detonation synthesis process of an oxide powder according to claim 1, characterized in that: wherein the explosive containing oxide precursor stable detonation is inorganic, organic or a mixture of the inorganic, the organic or the mixture, and comprises solid, liquid, solution, colloid, aerosol, emulsion, gas or a mixed form of the solid, the liquid, the solution, the colloid, the aerosol, the emulsion and the gas.

4. The detonation synthesis process of an oxide powder according to claim 1 or 3, characterized in that: the precursor of the solid oxide is active and participates in detonation chemical reaction or thermal decomposition, and comprises simple substance elements, inorganic salts, organic salts, acids, alkalis, hydrous oxides and ceramics.

5. The detonation synthesis process of an oxide powder according to claim 1, 3 or 4, characterized in that: wherein the precursor of the solid oxide comprises nitrate, nitrite, chlorate, perchlorate, chlorite, hypochlorite, iodate, bromate, higher oxide, metal powder, lower oxide, alkoxide, hydride, carbide, nitride, chloride, oxalate, acetate, sulfide, phosphide, carbonate, hydroxide, oxide containing crystal water, oxyacid and salt of the solid oxide, and the mixture, compound, solution and mixed solution of the oxyacid and the salt.

6. The detonation synthesis process of an oxide powder according to claim 1 or 3, characterized in that:wherein the precursor of the solid oxide is inert and is oxide or compound oxide powder.

7. The detonation synthesis process of an oxide powder according to claim 1, characterized in that: wherein the inert powder particles are metal, oxide, carbide, nitride, silicide, boride, carbon particles or their mixture and compound.