CN1125780C - Process for preparing nm-class VO2 powder and nm-class ceramics - Google Patents

Abstract

The present invention relates to a preparation method for VO2 and the adulterant of nanometer powder and nanometer ceramics. The method reduces V2O5 to prepare a VOCl2 solution, and vanadyl (IV) basic ammonium carbonate precursors are prepared from the VOCl2 solution, the VO2 nanometer powder is prepared by the thermal decomposition of the precursors, and finally, VO2 nanometer ceramics can be prepared through tabletting and sintering. The present invention has the advantages of simple process, low energy consumption, little investment, low cost, high strength of the ceramics and good thermoelectric performance, and is convenient for scale production.

Description

The preparation method of vanadium dioxide nano powder and hotchpotch nano-powder thereof

Technical field

The invention relates to the preparation method of vanadium dioxide nano powder and hotchpotch nano-powder thereof.

Background technology

As everyone knows, VO ₂The about 68 ℃ transformations that have a low temperature monocline (semi-conductor phase) to high temperature four directions (metallographic phase).During the phase transformation, some physical propertiess such as electric conductivity, magnetic moment and ir transmissivity generation hop; Particularly to VO ₂When mixing, transformation temperature (Tc) can be regulated change, and its variable quantity is relevant with kind of mixing impurity and quantity.For example mix Cr and increase Tc, V _0.976Cr _0.024O ₂Tc be 72 ℃.And whenever mix the 1%Mo atom, and Tc reduces 11 ℃, whenever mixes the 1%W atom, and Tc reduces 26 ℃.VO ₂These special propertys, can be used to contactless thermoelectric switch, thermorelay, hygrosensor and temperature equilibrator, photoswitch, optical storage material, inverting element and multiple sensors.And, for powder body material, except that being used for preparation pottery and thin layer, at critical temperature resistor (CTR), conductive polymer composite, electrode material of lithium battery, except that O ₂Agent, catalyzer, pigment and multiple space flight occasion have special application.Therefore for many years to VO ₂Research from uninterruptedly.Though in recent years to VO ₂The synthetic of fine powder body has considerable progress, but the high and economical and practical preparation nanometer VO of quality is not arranged as yet ₂The processing method of powder.Use the induced with laser gas-phase reaction and decompose VOCl ₃Though, can obtain＜VO of 100nm ₂Powder, but the right cost of this Faxian is high, can not produce in enormous quantities.

Summary of the invention

The purpose of this invention is to provide a kind of manufacturing VO ₂The practical approach of nano-powder and hotchpotch nano-powder thereof, its technological process is simple, and energy consumption is low, can better control the whole ratio property of powder.

The present invention is with the compound V of vanadium ₂O ₅Reduction is mixed, and makes vanadyl (IV) the basic carbonate ammonium as presoma, after thermolysis gets VO ₂Nano-powder and hotchpotch nano-powder thereof, concrete preparation process is:

1. use H ₂C ₂O ₄2H ₂O and N ₂H ₂2HCl in hydrochloric acid medium with V ₂O ₅Reduction preparation VOCl ₂Solution: with prevailing vanadium compound V ₂O ₅Be starting raw material, in hydrochloric acid medium with oxalic acid or xitix prereduction V ₂O ₅, water hydrazine or hydrazine hydrochloride further reduce and prepare VOCl again ₂Solution.Also directly water hydrazine or hydrazine hydrochloride the reduction V ₂O ₅Preparation VOCl ₂Solution.For the preparation of hotchpotch, can be at VOCl ₂Add corresponding doped metal ion in the solution according to actual needs and obtain VOCl ₂Doped solution, the mol ratio of controlled doping ion and vanadium is regulated impurity at VO ₂In content ratio.When mixing Cr, can add CrCl ₃When mixing Mo, can add MoO ₂Cl ₂Or (NH ₄) ₂MoO ₄In hydrochloric acid medium by hydrazine hydrochloride reductive solution, also can be at NH in step 2 ₄HCO ₃Or (NH ₄) ₂CO ₃Middle (the NH that adds ₄) ₂MoO ₄When mixing W, can add WO ₂Cl ₂, also can be with (NH in step 2 ₄) ₂WO ₄Be added in NH ₄HCO ₃Or (NH ₄) ₂CO ₃In the solution.

2. the VOCl that step 1 is made ₂Solution is with (NH ₄) ₂CO ₃Or NH ₄HCO ₃Reaction, preparation vanadyl (IV) basic carbonate ammonium presoma (NH ₄) ₅[(VO) ₆(CO ₃) ₄(OH) ₉] 10H ₂O or doping presoma.Presoma or its dopant precursor in dehydrated alcohol with ultrasonic disruption to granularity≤2 μ m.

3. the presoma that step 2 is made or its dopant precursor obtain VO at inert atmosphere or contain thermolysis in the oxygen inert atmosphere ₂And the hotchpotch nano-powder, 350～700 ℃ of Heating temperatures.The NH that emits in the presoma thermal decomposition process ₃Can be with part of V ⁴⁺Be reduced to V ³⁺One of characteristic of the present invention is to comprise O in the air-flow by the thermolysis system ₂Concentration, the logical O that contains ₂The time of air-flow and the selection of pyrolysis temperature, V in the control product ³⁺And V ⁵⁺Content, thereby obtain the whole high-quality powder of various differences than property.Adopt method of the present invention, can also control the granularity and the crystal form of powder.In 350～450 ℃ of scopes, can obtain amorphous or be main contain a small amount of B phase crystal, the powder of granularity＜10nm with amorphous.Between 450～560 ℃, can obtain accurate crystalline A phase powder, granularity＜20nm.Between 560～700 ℃, can obtain the A phase powder of better crystallinity degree, granularity＜30nm.

The preparation vanadium dioxide is mixed Cr ³⁺The step of nano-powder is:

1) uses H ₂C ₂O ₄2H ₂O and N ₂H ₂2HCl in hydrochloric acid medium with V ₂O ₅Reduction preparation VOCl ₂Solution; At VOCl ₂Add Cr in the solution ³⁺, the mol ratio of Cr and V in the control solution, thus the control presoma mix Cr ³⁺Amount;

2) vanadyl that makes with step 1) (IV) basic carbonate ammonium is mixed Cr ³⁺Presoma, in dehydrated alcohol with the presoma ultrasonication to granularity≤2 μ m;

3) with step 2) make mix Cr ³⁺Presoma is at inert atmosphere or contain that thermolysis gets V in the oxygen inert atmosphere _1-xCr _xO ₂Nano-powder, 0＜x≤0.06 wherein, 350～700 ℃ of Heating temperatures.

The step that the preparation vanadium dioxide is mixed the Mo nano-powder is:

1) uses H ₂C ₂O ₄2H ₂O and N ₂H ₂2HCl in hydrochloric acid medium with V ₂O ₅Reduction preparation VOCl ₂Solution; At VOCl ₂Add MoO in the solution ₂Cl ₂Or (NH ₄) ₂MoO ₄By hydrazine hydrochloride reductive solution, perhaps at NH ₄HCO ₃Or (NH ₄) ₂CO ₃Add (NH in the solution ₄) ₂MoO ₄Solution, the mol ratio of Mo and V in the control solution, thus the control presoma is mixed the Mo amount;

2) vanadyl that makes with step 1) (IV) basic carbonate ammonium is mixed the Mo presoma, in dehydrated alcohol with the presoma ultrasonication to granularity≤2 μ m;

3) with step 2) make mix the Mo presoma at inert atmosphere or contain that thermolysis gets V in the oxygen inert atmosphere _1-xMo _xO ₂Nano-powder, 0＜x≤0.045 wherein, 350～700 ℃ of Heating temperatures.

The step that the preparation vanadium dioxide is mixed the W nano-powder is:

1) uses H ₂C ₂O ₄2H ₂O and N ₂H ₂2HCl in hydrochloric acid medium with V ₂O ₅Reduction preparation VOCl ₂Solution; At VOCl ₂Add WO in the solution ₂Cl ₂Solution is perhaps at NH ₄HCO ₃Or (NH ₄) ₂CO ₃Add (NH in the solution ₄) ₂WO ₄Solution, the mol ratio of W and V in the control solution, thus the control presoma is mixed the W amount;

2) vanadyl that makes with step 1) (IV) basic carbonate ammonium is mixed the W presoma, in dehydrated alcohol with the presoma ultrasonication to granularity≤2 μ m;

3) with step 2) make mix the W presoma at inert atmosphere or contain that thermolysis gets V in the oxygen inert atmosphere _1-xW _xO ₂Nano-powder, 0＜x≤0.028 wherein, 350～700 ℃ of Heating temperatures.

VO ₂The preparation method of nano ceramics: the nano-powder that makes with aforesaid method; the most handy crystal form or accurate crystalline powder; at 400～800MPa lower sheeting, then vacuumize or logical protection of inert gas under, the insulation 4～8 hours down in room temperature～800 ℃; slough adsorbed gas; 900～1100 ℃ of sintering 1 hour to 4 hours, can obtain grain fineness number＜150nm then, intensity is big; thermal circulation performance is good, has the nano ceramics of practical value.

VO ₂Material volume changes about 1% during phase transformation, consequent stress is huge to the body material, this causes in monocrystal material research, when carrying out resistance-temperature curve when measuring, even do not finish a thermal cycling and measure single crystal and just break, and to the polycrystalline micrometer ceramics, also just just break through several thermal cyclings.Therefore, this type of pottery commercialization of failing so far.For overcoming the transformation stress of material, main recently research mould material.But mould material is not suitable for the application scenario of high-voltage large current, and the cost height.Use the nano ceramics that method of the present invention is made, have high intensity, realized the practicability of this class pottery.In short, prepare VO with method of the present invention ₂And the hotchpotch powder, have following outstanding advantage:

1. raw material obtains easily, presoma synthetic easy, and can carry out multiple metal doping.

2. the presoma heat decomposition temperature is low, can prepare amorphous state, accurate crystal form, and the nano-powder of crystal form, and can accurately control the whole of powder than property and non-stoichiometric.

3. ceramic sintering temperature is low, physical strength and temperature-sensitive good stability.

4. whole art production process is simple, low for equipment requirements, invests for a short time, and energy consumption is low, easily produces in enormous quantities, and the product cost is low, helps commercialization.

5. technological process is not introduced detrimental impurity and is produced hazard residue thing, product purity height.Production process is not discharged objectionable impurities, belongs to friendly process.

Embodiment

The invention will be further described by the following examples.

Embodiment 1

1. prepare VO ₂Nano-powder:

1) preparation VOCl ₂Solution

Take by weighing 91g V ₂O ₅, add 100～200mL distilled water and size mixing, add 38g H ₂C ₂O ₄2H ₂O, heating, gradation under agitation adds 140～160mL concentrated hydrochloric acid, and little several minutes that boils drips N then ₂H ₄H ₂O makes solution change mazarine into.Perhaps at above-mentioned V ₂O ₅In the suspension liquid, repeatedly alternately add 120～140mL concentrated hydrochloric acid and 26～29g N in heating with under stirring ₂H ₄2HCl, dissolving obtains blue solution.Use a small amount of V ₂O ₅Or N ₂H ₄2HCl (N ₂H ₄H ₂O) be adjusted to solution and can't check VO ₂ ⁺And V ³⁺Ion.Cross the elimination insolubles in case of necessity, rare again to 500mL.VO ₂ ⁺And V ³⁺Detect and use ferrous phenanthroline and potassium dichromate process.

2) preparation presoma

Take by weighing 14～16g NH ₄HCO ₃, or 8.5～10g (NH ₄) ₂CO ₃, add 40～60mL distilled water, feed CO ₂(at NH ₄HCO ₃Situation also can lead to Ar or N ₂Gas).Under agitation dropwise splash into the above-mentioned VOCl of 28～30mL then ₂Solution.Left standstill 0.5～2 hour, and also can under secluding air, place and spend the night.Suction filtration is used saturated NH ₄HCO ₃Solution washing is to there not being Cl ^-, use a small amount of absolute ethanol washing 2 times again, obtain 8.0～9.5g presoma, productive rate 80～95%.Add 20～40mL dehydrated alcohol to this presoma, use the ultrasonic grinding crusher machine, suction filtration washs 2 times with a small amount of ether, suction filtration, dry the presoma of granularity≤2 μ m.Ethanol in the process and ether can reclaim or recycle.

3) preparation VO ₂Nano-powder

At diameter is in the quartz boat of 35mm, long 280mm, the 3g presoma is paved into thin layer and places the silica tube of φ 42mm.The N of feeding 99.99% ₂The mixed airflow of the airflow of air-flow (3L/ minute) and required flow rate 15 minutes preferably vacuumizes and uses N ₂Air purge is washed system.Feed mixed airflow then and be heated to temperature required, the insulation certain hour.The time of bubbling air can optionally suitably be controlled between soak, also can reduce the flow velocity of air gradually.From tube furnace, extract silica tube then out and in nitrogen gas stream, be cooled to room temperature, take out powder.Table 1 is listed the powder of 4 kinds of different pyrolytical conditions and is formed and character.The granularity of powder is by transmissioning electric mirror determining, and crystalline state is by the x ray diffraction determination.Powder composition chemical analysis.Powder is dissolved in H under the noble gas protection ₃PO ₄-H ₂SO ₄In, use ferrous phenanthroline-potassium bichromate titrimetric method titration then.For VO _{X ± y}, y value error is less than 0.001, and methods and results conforms to the thermogravimetry of oxygen level in the measurement powder.

Composition, crystalline state and the granularity of different pyrolytical conditions of table 1 and powder

Pyrolysis temperature (℃)	Air flow quantity (mL/ minute)	The blowing air time (branch)	Pyrolysis time (branch)	Powder is formed	Crystalline state	Granularity (nm)
							400	3.5	15	30	VO 2.028	Amorphous	＜10
450	5.0	20	20	VO 2.021	Amorphous+the B phase	＜10
							500	10.0	15	30	VO 2.000	Accurate crystallization	＜20
600	8.0	10	20	VO 1.989	Crystallization	＜30

Embodiment 2

When the Cr thing is mixed in preparation, at V _1-xCr _xO ₂The big I of x value is by VOCl in (0＜x≤0.06) ₂The change of the Cr/V mol ratio in the solution is regulated, the deviation of the repeated experiments of same x value＜3%.Be a specific examples below.At VOCl ₂Add CrCl in the solution ₃, making the Cr/V mol ratio is 0.065, synthesizes with embodiment 1 same method then and mixes Cr presoma, powder.Obtain the V that consists of of powder _0.955Cr _0.045O ₂

Embodiment 3

When the Mo thing is mixed in preparation, V _1-xMo _xO ₂The size of x value is regulated the deviation of the repeated experiments of same x value＜4% in (0＜x≤0.045) by the change of the Mo/V mol ratio in the presoma synthetic system.Lift an object lesson below.In hydrochloric acid medium, use N ₂H ₂2HCl is with (NH ₄) ₂MoO ₄Reduction.This reduzate adds VOCl ₂In the solution, making the Mo/V mol ratio is 0.11.Identical with embodiment 1 then method is synthetic mixes the Mo presoma, but NH ₄HCO ₃Consumption increase to 19～22g.Prepare powder with method, obtain V with embodiment 1 _0.985Mo _0.015O ₂Mix the Mo nano-powder.

Embodiment 4

When the hotchpotch of preparation W, V _1-xW _xO ₂The size of x value is by the decision of the W/V mol ratio in the presoma synthetic system, the deviation of the repeated experiments of same x value＜4% in (0＜x≤0.028).Lift an example below.In embodiment 1, with (NH ₄) ₂WO ₄Be added in NH ₄HCO ₃In the solution, making the W/V mol ratio is 0.12, the synthetic W presoma of mixing of identical with embodiment 1 then method.Same method obtains V _0.981W _0.019O ₂Adulterated powder.

Claims (4)

1. the preparation method of a vanadium dioxide nano powder is characterized in that this preparation method's step is:

1) uses H ₂C ₂O ₄.2H ₂O and N ₂H ₂2HCl in hydrochloric acid medium with V ₂O ₅Reduction preparation VOCl ₂Solution;

2) VOCl that makes with step 1) ₂Solution and (NH ₄) ₂CO ₃Or NH ₄HCO ₃Prepared in reaction vanadyl (IV) basic carbonate ammonium presoma, in dehydrated alcohol with the presoma ultrasonication to granularity≤2 μ m;

3) with step 2) presoma that makes is at inert atmosphere or contain that thermolysis gets VO in the oxygen inert atmosphere ₂Nano-powder, 350～700 ℃ of Heating temperatures.

2. preparation method that vanadium dioxide is mixed the Cr nano-powder is characterized in that this preparation method's step is:

1) uses H ₂C ₂O ₄2H ₂O and N ₂H ₂2HCl in hydrochloric acid medium with V ₂O ₅Reduction preparation VOCl ₂Solution; At VOCl ₂Add Cr in the solution ³⁺, the mol ratio of Cr and V in the control solution, thus the control presoma mix Cr ³⁺Amount;

2) vanadyl that makes with step 1) (IV) basic carbonate ammonium is mixed Cr ³⁺Presoma, in dehydrated alcohol with the presoma ultrasonication to granularity≤2 μ m;

3) with step 2) make mix Cr ³⁺Presoma is at inert atmosphere or contain that thermolysis gets V in the oxygen inert atmosphere _1-xCr _xO ₂Nano-powder, 0＜x≤0.06 wherein, 350～700 ℃ of Heating temperatures.

3. preparation method that vanadium dioxide is mixed the Mo nano-powder is characterized in that this preparation method's step is:

1) uses H ₂C ₂O ₄2H ₂O and N ₂H ₂2HCl in hydrochloric acid medium with V ₂O ₅Reduction preparation VOCl ₂Solution; At VOCl ₂Add MoO in the solution ₂Cl ₂Or (NH ₄) ₂MoO ₄By hydrazine hydrochloride reductive solution, perhaps at NH ₄HCO ₃Or (NH ₄) ₂CO ₃Add (NH in the solution ₄) ₂MoO ₄Solution, the mol ratio of Mo and V in the control solution, thus the control presoma is mixed the Mo amount;

2) vanadyl that makes with step 1) (IV) basic carbonate ammonium is mixed the Mo presoma, in dehydrated alcohol with the presoma ultrasonication to granularity≤2 μ m;

3) with step 2) make mix the Mo presoma at inert atmosphere or contain that thermolysis gets V in the oxygen inert atmosphere _1-xMo _xO ₂Nano-powder, 0＜x≤0.045 wherein, 350～700 ℃ of Heating temperatures.

4. preparation method that vanadium dioxide is mixed the W nano-powder is characterized in that this preparation method's step is:

1) uses H ₂C ₂O ₄2H ₂O and N ₂H ₂2HCl in hydrochloric acid medium with V ₂O ₅Reduction preparation VOCl ₂Solution; At VOCl ₂Add WO in the solution ₂Cl ₂Solution is perhaps at NH ₄HCO ₃Or (NH ₄) ₂CO ₃Add (NH in the solution ₄) ₂WO ₄Solution, the mol ratio of W and V in the control solution, thus the control presoma is mixed the W amount;

2) vanadyl that makes with step 1) (IV) basic carbonate ammonium is mixed the W presoma, in dehydrated alcohol with the presoma ultrasonication to granularity≤2 μ m;

3) with step 2) make mix the W presoma at inert atmosphere or contain that thermolysis gets V in the oxygen inert atmosphere _1-xW _xO ₂Nano-powder, 0＜x≤0.028 wherein, 350～700 ℃ of Heating temperatures.