CN1063410C - Method of preparing foamed ceramic material by self-overgrowth high-temp. synthesis control - Google Patents

Abstract

The present invention relates to a method for preparing a foamed ceramic material by the control of self-propagating high-temperature synthesis(SHS), which belongs to the material field. The present invention comprises two kinds or more than two kinds of reactant powder materials which are utilized according to the stoichiometry to make an SHS reaction and generate partial liquid measure, and 1 to 40% of additive substances are added in the reactant powder materials. The sintering process is finished under the TK temperature by the SHS method in an ignition mode. The present invention is characterized in that the powder materials for prescription are directly pressed into a base body after being mixed, the porosity of the prepared foamed ceramic material can be controlled within the range of 50 to 80%, and the hole diameter of the prepared foamed ceramic material can be controlled within the range of 0.1 to 0.5mm. The present invention has the main advantages of short sintering time, simple technology, no need of a high-temperature sintering furnace, good high-temperature performance of a product, and low cost; in addition, the refractability of the present invention is higher than 1800 DEG C.

Description

A kind of synthetic method for preparing foam ceramic material of self propagating high temperature of utilizing

The present invention relates to the preparation of the last stupalith of bubble, belong to the material field.

Foamed ceramics has the good temperature resistance energy, and flourishing surface and very high activity can be widely used in industrial circles such as exhaust gases of internal combustion engines filtration and chemical catalyst carrier.Therefore, the research of foam ceramic material is Materials science worker research always, the advanced subject of discussion.

Patent Office of the People's Republic of China accepts the patent application that is entitled as " a kind of synthetic method for preparing foam ceramic material of self propagating high temperature of utilizing " on August nineteen ninety-five 28, and its application number is 95111958.3.The technological line of this patent is: utilize self propagating high temperature to synthesize (Self-propagating High-temperature Synthesis, abbreviation SHS) legal system is equipped with foam ceramic material, and its technological process realizes by pulp preparation, dipping, oven dry and four steps of sintering.In pulp preparation, by stoichiometry add granularity greater than 200 purposes two or more, can carry out SHS reaction and generating unit branch amount of liquid phase calculated value θ ₀The reactant powder, comprise the additive that accounts for reactant gross weight 1～40wt%, add binding agent after, press the formulated component of slurry, after adding entry, stirring becomes slurry; Will be as the slurry carrier, and the polyurethane foam plastic with φ 0.3～3.0mm aperture makes the big or small body of requirement, it is immersed in the slurry about 10～15 minutes, take out and extrude redundant sizing agent; The polyurethane foam plastic base substrate that is stained with mixture paste is heated to 200～300 ℃, dries, make the porous plastics volatilization, the base substrate typing; Sintering process is to utilize the SHS method to finish, in the SHS reaction of finishing, and the amount of liquid phase θ that is controlled in the system ₁Or θ _1cBe 40～80Wt%; Utilize the actual ignition temperature of SHS reaction pair blank sintering to be Tk, carry out the electrically heated igniting in the Tk temperature with metal W silk or Mo silk and finish preparation process.This invention has overcome in the past prior art can only be with the deficiency of High Temperature Furnaces Heating Apparatus sintered foam stupalith, prepare with short production cycle, processing method is fairly simple, cost is low, refractoriness has the good foam ceramic material of high-temperature behavior simultaneously greater than 1800 ℃, but it also has the following disadvantages: processing step is more relatively, prepared finished product void content and aperture can only be determined by the aperture of polyurethane foam plastic, void content and aperture can not be controlled, and more can't prepare the foam ceramic material of pore less than 0.3mm.

Purpose of the present invention and task are: overcoming prior art, to prepare the foam ceramic material processing step various, can not control the deficiency in product void content and aperture, and it is simple to prepare material formula, the body preparation work simplification, can control the aperture of product and the foam ceramic material of void content, for utilizing the SHS reaction to realize the production of the foam ceramic material in 0.1～0.5mm aperture, particularly to the production of 0.1～0.3mm aperture foam ceramic material, the spy proposes technical solution of the present invention.

The present invention is according to the SHS reaction process, the formation of its foam ceramic material is a kind of principle of high heat-producing chemical reaction process, utilize the SHS method that necessary energy is being provided to system, be under the prerequisite of certain temperature, the local chemical reaction that produces of the system of bringing out, after this, because this chemical reaction process is proceeded under the support of self emitting high calorie, at last, the combustion reactions ripple spread to the characteristics of whole system and according to the characteristics of the experiment of base substrate actual density and foamed ceramics product aperture and void content relation, thereby prepare required stupalith.

Basic design of the present invention is, utilize the SHS reaction, can finish the powder of the present invention's prescription of SHS reaction, need not add entry and binding agent, also need not any carrier, by the density of control base substrate, directly prepare satisfactory base substrate, and then with the preparation base substrate be placed in the stove, utilize the direct ignition of SHS method to realize task of the present invention.

A kind of synthetic method that prepare foam ceramic material of self propagating high temperature of utilizing proposed by the invention mainly comprises: by stoichiometry get granularity greater than 200 purposes two or more, can carry out SHS and react also generating unit branch amount of liquid phase calculated value θ ₀Ti+B or Zr+Cr ₂O ₃Or Al+TiO ₂+ C or Al+TiO ₂+ B ₂O ₃Or Al+Cr ₂O ₃The reactant powder and account for refractory metal Ti, Cr, Zr, Mo, W powder and the ceramic Al of reactant gross weight 1～40wt% ₂O ₃, SiO ₂, ZrO ₂Component prescription with SiC powder additive; The making of base substrate and sintering method; 40～80% the amount of liquid phase θ that in finishing the self propagating high temperature building-up reactions, is controlled in the system ₁Or θ _1c, and by preheating temperature T ₀Or T _0cThe actual ignition temperature T k of definite blank sintering, it is characterized in that: base substrate be by reactant powder and additive powder behind uniform mixing, directly compacting forms base substrate control of density d _kBe by product foamed ceramics theoretical density D ₀And experiment parameter is definite, is d _k=0.20 D ₀～0.5D ₀+ 5%～10%; When requiring to react the corresponding void content of after product and be 65～80%, then the control of density of base substrate is d _k=0.2 D ₀～0.35D ₀+ 5%～10%; When requiring to react the corresponding void content of after product and be 50～65%, then the control of density of base substrate is d _k=0.35D ₀～0.5D ₀+ 5%～10%.The manufacture craft of control preparation foam ceramic material is: with the material of the present invention's prescription, uniform mixing is 15～20 minutes in ball mill, directly is pressed into shape and the density d that requires base substrate with spacing method in mould _k, again base substrate is placed in the stove, be heated to actual ignition temperature of reaction Tk, and under this temperature, carry out sintering ignition with oxy-acetylene flame or metal W, the electrically heated of Mo silk, finish the self propagating high temperature synthetic reaction process, be made into the foam ceramic material product.

Added additive accounts for the concrete span of control of reactant gross weight 1～40wt% and is in the present invention batching: to the Ti+B system, add the Al that accounts for Zr, Mo, the W metal-powder additive of reactant gross weight 1～10wt% and account for reactant gross weight 1～15wt% ₂O ₃, ZrO ₂The ceramic powder additive, but add fashionablely when mixing, its two adding total amount should be 1～15wt%; To Zr+Cr ₂O ₃System adds the Al that accounts for reactant gross weight 10～30wt% ₂O ₃, SiO ₂The ceramic powder additive; To Al+TiO ₂+ C system adds the Al that accounts for Ti, Cr, Zr, Mo, the W metal-powder additive of powder gross weight 1～10wt% and account for reactant gross weight 1～15wt% ₂O ₃, SiO ₂The ceramic powder additive, but add fashionablely when mixing, its two adding total amount should be 1～15wt%; To Al+TiO ₂+ B ₂O ₃System adds the Al that accounts for Ti, Cr, Zr, Mo, the W metal-powder additive of reactant gross weight 1～10wt% and account for reactant gross weight 1～20wt% ₂O ₃, SiO ₂The ceramic powder additive, but add fashionablely when mixing, its two adding total amount should be 1～20wt%: to Al+Cr ₂O ₃System adds the Al that accounts for reactant gross weight 20～40wt% ₂O ₃, SiO ₂, SiC ceramic powder additive; The design preheating temperature T of base substrate ₀Upper and lower bound or minimum preheating design temperature T _0c, all be in guarantee system, to carry out SHS when reaction, there is 40～80% amount of liquid phase θ ₁Or θ _1cPrerequisite under, draw through calculation of thermodynamics.Base substrate in SHS reaction, 40～80% amount of liquid phase θ that controlled in the system ₁Or θ _1cBe according to amount of liquid phase calculated value θ ₀, and by controlling kind and the amount that adds additive, determine through calculation of thermodynamics and experiment; Base substrate control amount of liquid phase θ ₁Or θ _1cShould in the scope of 40～80Wt% specifically be; To Ti+B and Zr+Cr ₂O ₃System should be controlled θ ₁Or θ _1cIn 40～60Wt% scope to calculate T ₀Or T _0c, to Al+TiO ₂+ C system should be controlled θ ₁Or θ _1cIn 50～70Wt% scope to calculate T ₀Or T _0c: to Al+TiO ₂+ B ₂O ₃System and Al+Cr ₂O ₃System should be controlled θ ₁Or θ _1cIn 60～80Wt% scope to calculate T ₀Or T _0cThe obtaining value method of the actual ignition temperature T k of base substrate is: when adding the additive of specified amount, if preheating temperature changes continuously, and the amount of liquid phase θ that controls ₁In specialized range, also change continuously, and can make the amount of liquid phase θ that controls ₁Reach the upper and lower bound of the preheating temperature of specialized range, this upper limit and lower limit are design preheating temperature T ₀Upper and lower bound, Tk then should get design preheating temperature T ₀The mean value of upper and lower bound; When adding the additive of specified amount,,, temperature can not make the amount of liquid phase θ that controls along with raising if preheating temperature changes continuously ₁Reach the upper limit of the amount of liquid phase of regulation, and only can make θ ₁Reach the stationary value θ in the standard solution phase weight range _1c, and make the amount of liquid phase θ that controls ₁Reach this fixed value θ _1cMinimum preheating temperature be minimum design preheating temperature T _0c, then Tk should get T _0cAdd 300～400 ℃ again, get 350 ℃ usually.

For finishing preparation process of the present invention, satisfying the additive amount that adds under the prescribed condition, make under the prerequisite of its amount of liquid phase that in carrying out the SHS reaction, reaches defined, determine that base substrate carries out the actual ignition temperature T k of SHS reaction.For this reason, determining and should gather in the clear and definite following step Tk:

1. at first, utilize thermodynamic balance equations calculate SHS be reflected at standard state following 25 ℃ when carrying out chemical reaction theoretical adiabatic temperature Tad and the theoretical amount of liquid phase θ of part that is produced ₀,

2. secondly, by adding 1～40% additive, after reaching control SHS reaction, have the amount of liquid phase θ of regulation ₁Or θ _1cBe under the condition of 40～80Wt%, utilize thermodynamic balance equations to calculate the design preheating temperature T of base substrate again ₀Or T _0c

3. last, according to the design preheating temperature T of base substrate ₀Or T _0cTo determine the actual ignition temperature T k of final base substrate when carrying out the SHS reaction.

Now the general process with regard to the SHS reaction illustrates computation process of the present invention:

The principle of utilizing thermodynamic balance equations to calculate is suppose that reaction is to take place under adiabatic condition, and reactant 100% to carry out heat release SHS reaction, H ° of its institute's liberated heat Δ by stoichiometry ₂₉₈All be used to heat resultant, so,, then have if take place under the standard state when being reflected at 25 ℃:

-Δ H ° ₂₉₈=∑ n _i(H ° _Tad-H ° ₂₉₈) _{The i resultant}

In the formula (H ° _Tad-H ° ₂₉₈)-be material mol relative enthalpy

n _iThe mol number of-resultant

Δ H ° ₂₉₈Reaction heat effect in the time of-25 ℃

The physical significance of following formula is: SHS reaction, promptly the heat effect of high heat-producing chemical reaction or claim enthalpy change makes resultant be warmed up to Tad, i.e. the resultant heat effect that equals to react from 25 ℃ of enthalpy change total amounts that are raised to adiabatic temperature Tad.

If reactant is through being preheated to T ₀Or T _0cUnder the off-rating of temperature, remix reacts, and just has:

∑ n _i(H ° _{TO or Toc}-H ° ₂₉₈) _{The i reactant}-Δ H ° ₂₉₈=∑ n _i(H ° _Tad-H ° ₂₉₈) _{The i resultant}

The essential meaning of following formula is, is reflected at H ° of heat effect Δ under the standard state normal temperature in order to use SHS ₂₉₈, convenient calculating, according to law of Hess, this SHS reactant is by T that preheating reached ₀Or T _0cWhen reducing to 298K, its liberated heat just equals the heat that it absorbed, and uses ∑ n _i(H ° _{TO or Toc}-H ° ₂₉₈) _{The i reactant}Expression, because supposition is adiabatic process, H ° of this heat and heat effect Δ ₂₉₈All absorbed, thereby improved the resultant temperature by product.

Add and be preheated to T as additive ₀During temperature, the molecular balance equation becomes:

∑ n _j(H ° _TO-Δ H ° ₂₉₈) _{The j additive}+ ∑ n _i(H ° _TO-Δ H ° ₂₉₈) _{The i reactant}-Δ H ° ₂₉₈=∑ n _k(H ° _Tad-H ° ₂₉₈) _{The k resultant}+ ∑ n _j(H ° _Tad-H ° ₂₉₈) _{The j additive}

N in the formula _jThe mol number of-additive

n _kThe mol number of-resultant

During concrete calculating, it should be noted that the adiabatic temperature Tad and the theoretical amount of liquid phase θ of SHS reaction ₀Closely related with reaction heat effect and product fusing point, existing reacting to each other with A material and B material generates the AB material, and reaction formula is: Be example, be illustrated, if the fusing point of AB is T _{M (AB)}, its latent heat of fusion is △ H _{M (AB)}, then Tad and θ ₀Calculating has three kinds of situations:

First kind of situation, if:

C in the formula _{PS (AB)}The solid-state thermal capacitance of-AB

At this moment, heat effect is less, and product A B did not melt still for solid-state when SHS finished, amount of liquid phase θ ₀=0, Tad＜Tm (AB), calculation formula is:

Second kind of situation, if:

At this moment, heat effect Δ H ° ₂₉₈Bigger, when SHS finishes, product A B partial melting, Tad=T _{M (AB)}, calculation formula is:

Can obtain AB fusing umber, i.e. amount of liquid phase θ ₀The third situation, if $-\mathrm{\Δ}{H}_{298}>{\∫}_{298}^{T_{m\left(\mathrm{AB}\right)}}{C}_{\mathrm{ps}\left(\mathrm{AB}\right)}\mathrm{dT}+\mathrm{\Δ}{H}_{m\left(\mathrm{AB}\right)}$

At this moment, heat effect is big, and when SHS finished, product all melted, and Tad＞T _{M (AB)}, calculation formula is: $-\mathrm{\Δ}{H}_{298}={\∫}_{298}^{T_{m\left(\mathrm{AB}\right)}}{C}_{\mathrm{ps}\left(\mathrm{AB}\right)}\mathrm{dT}+\mathrm{\Δ}{H}_{m\left(\mathrm{AB}\right)}+{\∫}_{298}^{\mathrm{Tad}}{C}_{\mathrm{ps}\left(\mathrm{AB}\right)}\mathrm{dT}$

C in the formula _{PL (AB)}The liquid thermal capacitance of-AB

The present invention all lists the enforcement controlled variable of aforementioned calculation method and each reaction system thereof in subordinate list 1.Now with two examples (A) below in the subordinate list 1 and (B), definite to the calculating of subordinate list 1 and controlled variable thereof gives simple declaration:

(A)

(B)

1) calculates Tad and θ ₀:

This adiabatic temperature Tad and product amount of liquid phase theoretical value θ ₀, be at 25 ℃, the data during no additive.For (A) formula, tentative calculation belongs to aforesaid second kind of situation as can be known, and promptly after the reaction of carrying out SHS, Tad equals resultant TiB ₂Fusing point 3193K, TiB ₂Partial melting calculates θ ₀The thermodynamics formula be:

In the formula -TiB ₂Solid-state hot melt

-TiB ₂Melting heat

θ ₀-TiB ₂Fusing umber wt% draws as calculated: θ ₀=35%

For (B) formula, tentative calculation as can be known, after SHS reaction, Al ₂O ₃All fusings, TiB ₂For solid-state, and $\mathrm{Tad}>T_{m\left({\mathrm{Al}}_2{O}_3\right)},$ It is similar to aforesaid the third situation, and amount of liquid phase is by the Al of fusing ₂O ₃Can calculate, consider under heat of fusion, the phase transformation situation, through calculating Tad=2465K, Al ₂O ₃All fusings account for 70.8% of system total amount, i.e. θ in reaction ₀=70.8%

2) calculate T ₀Or T _0c:

For guaranteeing θ ₁=40～80%, face adds additive 1～40% o'clock, calculates T ₀Or T _0cValue at this moment, can add a kind of separately or the mixing several additives,

For (A) formula, for guaranteeing this system control amount of liquid phase θ ₁=40～60%, should make additive 100% fusing in the SHS reaction, and part TiB ₂Be in melted state, therefore, reaction Tad is TiB ₂Fusing point, i.e. Tad=3193K.At this moment, carry out the SHS reaction in different preheating temperatures, the design amount of liquid phase changes between 40～60% continuously, so, to (A) formula, account for reactant 10%Al with independent adding ₂O ₃Be example, calculate T ₀Method be, according to TiB ₂The mol molecular weight, should add Al ₂O ₃Amount is that 7.0 to be converted to the mol umber be 0.686, system Tad=3193K, Al ₂O ₃All fusings according to thermodynamic balance equations, get θ through zooming in the reaction ₁=40% o'clock, T ₀The following 770K. θ that is limited to ₁=60% o'clock, T ₀On be limited to 1020K, when promptly preheating temperature changed between 770K～1020K, this system amount of liquid phase changed between 40～60%.

Be example with (B) formula more below, it is right to illustrate that metal adds with pottery, tries to achieve T _0cSituation, account for reactant gross weight 5%Cr and 10%SiO with adding ₂Be example:

When this system does not have 25 ℃ of reactions of additive, Tad=2465K, θ ₀=70.8%.After adding additive, when the design preheating temperature is carried out the SHS reaction,, make Tad＞2303K, i.e. Al when the design preheating temperature raises ₂O ₃Fusing point, the design preheating temperature that continues again to raise is right, can find out at Tad greater than 2303K to 3193K, promptly at Al ₂O ₃Fusing point and TiB ₂In the melting range, amount of liquid phase is stable fixed value θ _1c, and θ _1c=74.6%, therefore, this system is only calculated and is made θ _1c=74.6% o'clock minimum design preheating temperature T _0c, at this moment, Al ₂O ₃All Tad=2303K is got in fusing, during calculating, according to total mol molecular weight of system reactant, adds SiO ₂Weight to be converted to the mol umber be 1.2mol, it is 0.692mol that the weight that adds Cr is converted to the mol umber, can calculate T by thermodynamic balance equations _0C=417K.

Calculate above-mentioned T _0cFormula be:

In the formula, the required heat of solid-state phase changes is not expressed, but has taken into account when calculating, and formula programming zooming draws T thus _0c=417K, in the aforementioned calculation, the temperature error scope is ± 5 ℃.

3) definite principle of Tk:

When adding the additive of specified amount, Tk gets and can make control amount of liquid phase θ ₁Reach the design preheating temperature T of specialized range ₀The mean value or get of upper and lower bound make control amount of liquid phase θ ₁Reach fixed value θ _1cMinimum design preheating temperature T _0cAdd 300～400 ℃ again.Tk gets T _0cThe empirical method that adds 300～400 ℃ is: to Zr+Cr ₂O ₃System is generally taken off limit, promptly gets Tk=T _0c+ 300 ℃, to Al+TiO ₂+ C system, general capping is promptly got Tk=T _0c+ 400 ℃, to Al+TiO ₂+ B ₂O ₃System is generally averaged, and promptly gets Tk=T _0c+ 350 ℃.

Realize that conception of the present invention prepares the key of desirable foam ceramic material and be, base substrate control of density d _kDetermine and the technology controlling and process of prepared foam ceramic material, promptly reach the control in product foam ceramic material void content and aperture by the control of blank density, finish SHS in the igniting of Tk temperature at last and react.

System is finished the SHS reaction, when Tad is lower than additive and product volatilization temperature, the material gross weight remains unchanged before and after the reaction, and base substrate volume and product volume are constant substantially, therefore the density of the preceding base substrate of reaction reflects the actual density and the void content of product indirectly, while is closely related with the product aperture again, has controlled the density of base substrate when therefore carrying out the SHS reaction, has also just controlled the void content and the aperture of product simultaneously.Specify as follows:

Press the actual density of base substrate in theory, can directly draw the theoretical density and the void content of product.If the material gross weight remains unchanged before and after the reaction, and the base substrate volume is with the product volume when identical, and so, the density of base substrate is exactly the actual density that reacts after product before the reaction, also can draw according to its void content of theoretical density of product.Because base substrate has about 5% volumetric shrinkage before and after the actual SHS reaction, also has 5%～10% sealed porosity in the product simultaneously, causes density and void content and notional result deviation to some extent.The present invention is on experiment basis, according to the theoretical density D of product ₀Provide by base substrate control of density d _kControl the method for product void content, that is: work as d _k=0.2D ₀～0.35D ₀+ 5%～10% o'clock, the corresponding void content of igniting reaction after product was 65%～80%; Work as d _k=0.35 D ₀～0.5D ₀+ 5%～10% o'clock, the corresponding void content of igniting reaction after product was 50%～65%.

The control of density d of base substrate _kBe the ratio of preceding base substrate powder weight of SHS reaction and volume, the theoretical density of product can calculate according to product component, with Al ₂O ₃+ TiB ₂Foam ceramic material is that the concrete method of calculation of example are as follows: when not adding additive, the actual constituent of product is 5Al ₂O ₃+ 3TiB ₂, be converted to weight ratio and then be Al ₂O ₃: TiB ₂=710: 210, according to Al ₂O ₃And TiB ₂Theoretical density, can calculate the theoretical density of product, method of calculation are: according to the material physical property data, get Al ₂O ₃Theoretical density be 3.9g/cm ³, TiB ₂Theoretical density be 4.5g/cm ³, the theoretical density D of product ₀Calculating formula be: $D_0=\frac{{5W}_{A{l}_2{O}_3}+3W_{\mathrm{Ti}{B}_2}}{\frac{5W_{A{l}_2{O}_3}}{d{\mathrm{Al}}_2{O}_3}+\frac{3W_{\mathrm{Ti}{B}_2}}{\mathrm{dTi}{B}_2}}=\frac{5\×102+3\×70}{5\×102/3.9+3\×70/4.5}=4.06g/c{m}^3$ In the formula,

Be Al ₂O ₃And TiB ₂Molecular weight,

Be Al ₂O ₃And TiB ₂Theoretical density,

Can calculate the theoretical density of final product behind the adding additive by above-mentioned same procedure.

The relation in base substrate control of density and product aperture is: the density of base substrate is big more, and hole is few more between the particle, and the aperture of SHS reaction after product is also just more little, among the present invention, when the blank control of density at 25%～40% of product theoretical density, i.e. d _k=0.2D ₀～0.35D ₀+ 5%～10% o'clock, igniting reaction after product aperture was φ 0.25～φ 0.5mm, when the blank control of density at 40%～55% of product density, i.e. d _k=0.35 D ₀～0.5D ₀+ 5%～10% o'clock, igniting reaction after product aperture was φ 0.1～φ 0.25mm, in sum, has controlled the density of base substrate, has also just controlled the void content and the aperture of SHS reaction product simultaneously.

Technology of the present invention is: with the prescription of material of the present invention, uniform mixing is 15～20 minutes in ball mill, then, mixed powder is pressed into the base substrate of foam ceramic material in mould, again this base substrate is placed directly in the stove, be heated to actual ignition temperature of reaction Tk, and under this temperature, carry out sintering ignition with oxy-acetylene flame or metal W, the electrically heated of Mo silk, finish the SHS reaction process, be made into product, last, it is stand-by that this product is rebuild the qualified back of detection.

Utilize SHS prepared in reaction foam ceramic material, designed amount of liquid phase θ in its system ₁Or θ _1c, the kind of additive and addition, base substrate design preheating temperature T ₀Or T _0cAnd the actual SHS ignition temperature Tk scope in when reaction of carrying out, all list subordinate list 1～6 in, do not outline one by one at this.

Table 1 is the processing parameter of preparation foam ceramic material SHS reaction.Write up 5 kinds of equations that carry out the SHS reaction, theoretical parameter, process control parameter and manipulated variable in the table.

Table 2 is System prepares foam ceramic material processing parameter control calculated example.At length calculate in the table System is utilized SHS prepared in reaction foam ceramic material, different amount of liquid phase θ in the designed system ₁With for guaranteeing θ ₁Amount, the different sorts of controlling, the additives of different amounts, the design preheating temperature T of base substrate ₀And carry out relation between the actual ignition temperature T k of SHS reaction.

Table 3 is System prepares foam ceramic material processing parameter control calculated example.Detailed calculated goes out designed amount of liquid phase in the table, with the variation of the kind and the amount of additive, the fixed value θ that tends towards stability _1cAnd for guaranteeing θ _1cAmount, the additive of the difference amount of being controlled, the minimum design preheating temperature T of base substrate _1cAnd carry out relation between the actual ignition temperature T k of SHS reaction.

Table 4 is System prepares foam ceramic material processing parameter control calculated example.Detailed calculated goes out in the system variation with additive and amount thereof, the fixed value θ that the variation of amount of liquid phase also tends towards stability in the table _1c, and for guaranteeing θ _1cThe amount of value, institute adds the minimum design preheating temperature of different additives and amount and base substrate thereof T _1cAnd carry out relation between the actual ignition temperature T k of reaction of SHS.

Table 5 is System prepares foam ceramic material processing parameter control calculated example.Detailed calculated goes out the fixed value θ that the system amount of liquid phase still tends towards stability with the variation of different additives and amount thereof in the table _1c, and the θ for guaranteeing to be controlled _1cValue, and the difference amount that adds and the additive of composition, minimum design preheating temperature T _1cAnd carry out relation between the actual ignition temperature T k of SHS reaction.

Table 6 is System prepares foam ceramic material processing parameter control calculated example.Detailed calculated goes out system amount of liquid phase θ in the table ₁, with the variation of additive kind bigger variation is arranged, and designed amount of liquid phase θ ₁For guaranteeing θ ₁Value, add different amounts and different types of additive, the design preheating temperature T of base substrate ₀Carry out the relation between the actual ignition temperature T k of SHS reaction.

Major advantage of the present invention is: 1. technology is simple, saves high-temperature sintering apparatus, need not to add water and binding agent in the material formula, the base substrate straight forming, save the energy and investment, with low cost, 2. the production cycle can shorten greatly, general sintering time only is 10～40 seconds, 3. prepared product resistance to elevated temperatures and good thermal shock, refractoriness be greater than 1800 ℃, 4. the hot strength height, 1000 ℃ of ultimate compression strength are 2～5MPa, 5. can control the foam ceramic material of preparation aperture at 0.1～0.5mm.

Below in conjunction with specific examples of the present invention, further specify details of the present invention:

Embodiment 1:

A kind of ceramic foam filter that is used for purifying internal combustion engine tail gas test usefulness, its performance requriements is: aperture 0.2mm, void content is greater than 60%, refractoriness is greater than 1200 ℃, and ultimate compression strength is 4.0MPa under the normal temperature, when high temperature thermal shock resistance can 1000 ℃ greater than 50 times, be of a size of φ 150 * 50mm, prior art can not prepare the foam ceramic material of small-bore like this, adopts the inventive method preparation, and its step is as follows:

The first step, batching

Five kinds of given in the subordinate list 1 systems all can be used for making filter material, select Al at this ₂O ₃And TiB ₂, according to the SHS reaction equation: , according to the ceramic foam filter size, roughly can estimate its weight at 1400～1800 grams, therefore, get 200～270 order commercial offers powders respectively, Al powder 648g wherein, TiO ₂Powder 576g, B ₂O ₃Powder 504g, additive are Al ₂O ₃Account for above-mentioned reaction-ure mixture 10wt%, get 172.8g, do not add entry, also do not add any binding agent.Powder is directly put into ball mill mixed 20 minutes, make the powder that needs, gross weight is 1900.8 grams.

In second step, bad system is equipped with

Be theory of computation density, will add 10%Al ₂O ₃It is 0.705 that additive is converted to the mol number, so the product ultimate constituent consists of 5.705Al ₂O ₃+ 3TiB ₂, get Al ₂O ₃Theoretical density be 3.9g/cm ³, TiB ₂Theoretical density be 4.5g/cm ³, according to the theoretical density D of product ₀Calculating formula, D ₀Then be 4.03g/cm ³:

General foam materials void content is all a bigger scope, and operability is good.This strainer requires void content greater than 60%, therefore, and the control of density d of base substrate _k=0.35D ₀～0.50D ₀+ 5%～10%, the numerical value 0.35D in the formula ₀～0.50D ₀Get 0.4D ₀, and 5%～10% be used for balance by about 5% error that causes of volumetric shrinkage, gets 8% promptly 0.08.Take all factors into consideration desirable d _k=0.4D ₀+ 8%, calculate d _k=1.69g/cm ³

Product size is φ 150 * 50mm, and can calculate its volume is 883.1cm ³, this is the volume of base substrate, and the powder weight that can calculate base substrate thus is 883.1 * 1.692=1494.2 gram, considers active loss and easy to operate, can get 1500 gram powders, and the residue powder is preserved and is used.Because a little volume is shunk, and gets internal diameter 150.2mm, external diameter 180mm, the A3 steel die of high 110mm is put into mould with 1500 gram powders, powder is pressed into the shape of φ 150.2 * 50mm with spacing method.Take out base substrate, control of density d _kBe 1.69g/cm ³The foam ceramic material base substrate just prepared.

In the 3rd step, ignition temperature is determined

One, calculates Tad and θ ₀

According to calculation of thermodynamics or table look-at 1, the given data of table 5, the amount of liquid phase calculated value θ of this system when 298K reaction, no additive ₀Be 70.8%, adiabatic temperature T _Ad=2465K gets Tad=2303K during calculating.

Two, calculate T _0c

For guaranteeing control amount of liquid phase θ _1cAt 60～80Wt%, make the Al of adding ₂O ₃And the Al that generates ₂O ₃All fusings, at this moment, system temperature raises when making adiabatic temperature surpass 2303K, and the amount of liquid phase of control is a stationary value θ _1c, can calculate θ by the aforementioned hot theory of mechanics _1c=73.5%, T is calculated in substitution _0cFormula, calculate minimum design preheating temperature T _0c=444K.

Three, actual ignition temperature T k's determines

According to table 5 remarks column 1), to Al+TiO ₂+ B ₂O ₃System is got Tk=T _0c+ 350, so the actual ignition temperature T k=444+350=794K of base substrate, promptly 521 ℃.

The 4th step, sintering operation

With the base substrate of the foam ceramic material for preparing, put into chamber type electric resistance furnace, be heated to 521 ℃ ± 5 ℃, under this temperature,, to light a fire at an end of base substrate with the W silk electrically heated of φ 0.5mm, this moment, the voltage of W silk was 40V, electric current is 50A.One end is after igniting, and combustion wave is rapidly to the expansion of unreacted district, and about 33 seconds kinds are finished the SHS reaction, prepare desired foamed ceramic filter.

In the 5th step, product detects

Filter pore size 0.16～the 0.24mm of Zhi Zuoing after testing, void content is 62%, its effective ingredient is: Al ₂O ₃73.5%, TiB ₂26.5%, this strainer normal temperature ultimate compression strength is 4.3MPa, and 1000 ℃ of heat shock resistances are greater than 50 times, and refractoriness is greater than 1800 ℃.It is respond well to be applied to the purifying internal combustion engine tail gas test-filtration.

Embodiment 2:

The ceramic foam filter of test usefulness, its performance requriements is: aperture 0.35mm, void content is greater than 70%, refractoriness is greater than 1400 ℃, and ultimate compression strength is 3.6MPa under the normal temperature, when high temperature thermal shock resistance can 1000 ℃ greater than 50 times, be of a size of φ 60 * 40mm, prior art prepares the foam ceramic material of small-bore like this has any problem, and adopts the inventive method preparation, and its step is as follows:

The first step, batching

Five kinds of given in the subordinate list 1 systems all can be used for making filter material, now select TiB for use ₂Ceramic material, for this reason, according to reaction formula , simultaneously according to the ceramic foam filter size, roughly can rough calculation go out its weight at 100～150 grams, therefore, getting granularity respectively is 250～320 purpose Ti powder, each 96g of B powder, 44g, additive is Al ₂O ₃Powder accounts for above-mentioned reactant gross weight 15%, is 21g.Do not add entry, also do not add any binding agent, powder is directly put into ball mill mixed 15 minutes, make the powder that needs, gross weight is 161 grams.

Second step, body preparation

For theory of computation density, with 15%Al ₂O ₃It is 0.103 that additive is converted to the mol number, so the product ultimate constituent consists of 0.103Al ₂O ₃+ 3TiB ₂, get Al ₂O ₃Theoretical density be 3.9g/cm ³, TiB ₂Theoretical density be 4.5g/cm ³, according to the theoretical density D of product ₀Calculating formula, D then ₀Be 4.41g/cm ³

General foam materials void content is all a bigger scope, and operability is good.This strainer requires void content greater than 70%, and therefore, the control of density of base substrate adopts d _k=0.25D ₀～0.30D ₀+ 5%～10%, the numerical value 0.25D in the formula ₀～0.30D ₀Value 0.25D ₀, and 5%～10% be used for balance by about 5% error that causes of volumetric shrinkage, gets 8% promptly 0.08.Take all factors into consideration desirable d _k=0.25D ₀+ 8%, calculate d _k=1.18g/cm ³

Product size is φ 60 * 40mm, and can calculate its volume is 113.0cm ³, this is the volume of base substrate, and the powder weight that can calculate base substrate thus is 113 * 1.18=133.5 gram, considers active loss and easy to operate, can get 135 gram powders, and the residue powder is preserved and is used.Because a little volume is shunk, and gets internal diameter 60.1mm, external diameter 75mm, the A3 steel die of high 75mm is put into mould with 135 gram powders, powder is pressed into the shape of φ 60.1 * 40mm with spacing method.Take out base substrate, control of density d _kBe 1.18g/cm ³The foam ceramic material base substrate just prepared.

In the 3rd step, ignition temperature is determined

One, calculates Tad and θ ₀

According to calculation of thermodynamics or table look-at 1, the given data of table 2, the amount of liquid phase calculated value θ of this system when 298K reaction, no additive ₀Be 35%, adiabatic temperature T _Ad=3193K.

Two, calculate T ₀

Learn by table 2, for guaranteeing Ti+B system control amount of liquid phase θ ₁At 40～60Wt%, add 15% additive Al ₂O ₃, as control amount of liquid phase θ ₁=40% o'clock, the T of design preheating temperature ₀Lower value is 1150K, as control amount of liquid phase θ ₁=60% o'clock, the upper limit T of design preheating temperature ₀Value is 1380K.

Three, actual ignition temperature T k's determines

Learn by table 2, Ti+B system Tk is got base substrate design preheating temperature T ₀The mean value of upper and lower bound, Tk=1265K=992 ℃.

The 4th step, sintering operation

With the base substrate for preparing, put into chamber type electric resistance furnace, be heated to 990 ℃ ± 5 ℃, under this temperature,, to light a fire at an end of base substrate with the W silk electrically heated of 0.5mm, this moment, the voltage of W silk was 30V, electric current is 45A.One end is after igniting, and combustion wave is rapidly to the expansion of unreacted district, and about 24 seconds kinds are finished the SHS reaction, prepare desired foamed ceramic filter.

In the 5th step, product detects

Filter pore size 0.27～the 0.33mm of Zhi Zuoing after testing, void content is 74%, its effective ingredient is: TiB ₂Account for 87.0%, Al ₂O ₃Account for 13.0%, mechanical property: normal temperature ultimate compression strength is 4.4MPa, and 1000 ℃ of heat shock resistances are greater than 50 times, and refractoriness is greater than 1800 ℃.Be applied to the tail gas clean-up test, the capture soot particle is respond well.

The following examples 3,4,5 because its preparation process is fully with the step of embodiment 1,2, therefore, are sketched the embodiment preparation process, can be referring to embodiment 1,2.3,4,5 of the following examples are provided the analysis of the key control parameter and the finished product composition of preparation.

Embodiment 3:

A kind ofly be used for the ceramic foam filter that exhaust gases of internal combustion engines is tested usefulness only, its performance requriements is: aperture 0.4mm, void content is 80%, refractoriness is greater than 1100 ℃, ultimate compression strength is 4.0MPa under the normal temperature, greater than 50 times, dimensional requirement was φ 150 * 70mm when high temperature thermal shock resistance can 1000 ℃, and its step is summarized as follows:

Use Al ₂O ₃, Cr and SiO ₂Material is made strainer.The SHS reaction equation is: , additive is SiO ₂Account for 40% of reaction mass gross weight.According to calculation of thermodynamics or table look-up 6 and learn, this system Tad=2303K, design preheating temperature T ₀On be limited to 775K, be limited to 990K down, get actual ignition service temperature TK=883K, promptly 610 ℃ ± 5 ℃.

Press the step in embodiment 1 or 2, can produce ceramic foam filter, final composition is Al ₂O ₃Account for 35.4%, Cr accounts for 36.0%, SiO ₂Account for 28.6%.

Embodiment 4:

A kind ofly be used for the ceramic foam filter that purifying internal combustion engine tail gas is used, its performance requriements is: aperture 0.5mm, void content is 80%, refractoriness is greater than 1200 ℃, ultimate compression strength is 4.0MPa under the normal temperature, greater than 50 times, be of a size of φ 150 * 65mm when high temperature thermal shock resistance can 1000 ℃, its step is summarized as follows:

Use ZrO ₂+ Cr and Al ₂O ₃Material is made additive and is made strainer, and the SHS reaction equation is: , additive Al ₂O ₃Account for 10% of reaction mass gross weight.According to calculation of thermodynamics or table look-up 3 and learn, this system Tad=2303K, control amount of liquid phase θ _1c=41.8%, calculate minimum design preheating temperature T _0c=350K gets actual base substrate ignition temperature Tk=650K, promptly 377 ℃ ± 5 ℃.

Press the step in embodiment 1 or 2, can produce ceramic foam filter, final composition is: ZrO ₂Account for 58.1%, Cr accounts for 32.8%, Al ₂O ₃Account for 9.1%.

Embodiment 5:

A kind ofly be used for the ceramic foam filter that exhaust gases of internal combustion engines is tested usefulness only, its performance requriements is: aperture 0.1mm, void content is 60%, refractoriness is greater than 1250 ℃, ultimate compression strength is 4.0MPa under the normal temperature, greater than 50 times, be of a size of φ 150 * 40mm when high temperature thermal shock resistance can 1000 ℃, its step is summarized as follows:

Select Al for use ₂O ₃+ TiC stupalith is with Ti and SiO ₂Make the additive preparation strainer, according to reaction equation , additive Ti powder and SiO ₂Powder respectively accounts for additive 5%, according to calculation of thermodynamics or table look-up 4 and learn that this system is got Tad=2303K, and control amount of liquid phase θ _1cBe 57.4%, calculating minimum design preheating temperature is T _0c=535K, getting actual blank ignition temperature is TK=935K, i.e. TK=662 ± 5 ℃.

Press the step in embodiment 1 or 2, can produce ceramic foam filter, final composition is: Al ₂O ₃Account for 48.3%, TiC accounts for 42.6%, SiO ₂Account for 4.55%, Ti accounts for 4.55%.

It should be noted that about 1% impurity is not counted interior in the reactant, in the calculation of thermodynamics, does not also consider this influence when the composition of embodiment calculates.The processing parameter of table 1 preparation foam ceramic material SHS reaction

Table 2. System prepares foam ceramic material processing parameter control calculated example

Table 3 System prepares foam ceramic material processing parameter control calculated example

Table 4 System prepares foam ceramic material processing parameter control calculated example Table 5 System prepares foam ceramic material processing parameter control calculated example Table 6 System prepares foam ceramic material processing parameter control calculated example

Claims (1)

1. one kind is utilized the synthetic method for preparing foam ceramic material of self propagating high temperature, mainly comprises: by stoichiometry get granularity greater than 200 purposes two or more, can carry out self propagating high temperature building-up reactions and generating unit branch amount of liquid phase calculated value θ ₀Ti+B or Zr+Cr ₂O ₃Or Al+TiO ₂+ C or Al+TiO ₂+ B ₂O ₃Or Al+Cr ₂O ₃The reactant powder and account for refractory metal Ti, Cr, Zr, Mo, W powder and the ceramic Al of reactant gross weight 1～40% ₂O ₃, SiO ₂, ZrO ₂Component prescription with SiC powder additive; The making of base substrate and sintering method; 40～80% the amount of liquid phase θ that in finishing the self propagating high temperature building-up reactions, is controlled in the system ₁Or θ _1c, and by preheating temperature T ₀Or T _0cThe actual ignition temperature T k of definite blank sintering, it is characterized in that:

A) base substrate be by reactant powder and additive powder behind uniform mixing, directly compacting forms base substrate control of density d _kBe by product foamed ceramics theoretical density D ₀And experiment parameter is definite, is d _k=0.20 D ₀～0.5D ₀+ 5%～10%; When requiring to react the corresponding void content of after product and be 65～80%, then the control of density of base substrate is d _k=0.2 D ₀～0.35D ₀+ 5%～10%; When requiring to react the corresponding void content of after product and be 50～65%, then the control of density of base substrate is d _k=0.35D ₀～0.5D ₀+ 5%～10%,

B) manufacture craft of control preparation foam ceramic material is: with the material of prescription, uniform mixing is 15～20 minutes in ball mill, directly is pressed into shape and the density d that requires base substrate with spacing method in mould _k, again base substrate is placed in the stove, be heated to actual ignition temperature of reaction Tk, and under this temperature, carry out sintering ignition with oxy-acetylene flame or metal W, the electrically heated of Mo silk, finish the self propagating high temperature synthetic reaction process, be made into the foam ceramic material product.