CN103332945B - Preparation method of crack-free coating fiber - Google Patents

Abstract

The invention relates to a preparation method of a crack-free coating fiber, and belongs to the technical field of preparation of a composite material. After initial tensile stress sigma o is exerted to continuous single fibers or fiber bundles, an anti-oxidation coating is evenly deposited on the surface by using a CVD (chemical vapor deposition) method and the like under the condition of tensile stress; the initial tensile stress sigma o is unloaded under the condition that the initial tensile stress is greater than or equal to the crack generating temperature TC of the coating after deposition is ended; the anti-oxidation coating is integrally cooled to room temperature after the initial tensile stress sigma o is unloaded, so as to obtain the crack-free coating fiber. By adopting the preparation method, a thermal stress crack caused by mismatching of thermal expansion of the fiber and the coating is avoided; a channel of an oxidizing medium is cut off; the fiber is prevented from being oxidized; anti-oxidation protection of a full-temperature section is achieved. Thus, the integrality, the safety and the reliability of the composite material are improved; the preparation method is suitable for preparation of heat-resistant, anti-oxidation and high-temperature creep-resistant reinforced composites. Therefore, the preparation method is continuous and simple in preparation technology, and convenient to industrially produce.

Description

A kind of preparation method of flawless coated fibre

Technical field

The present invention relates to a kind of preparation method of flawless coated fibre; Belong to matrix material preparing technical field.

Background technology

C fiber reinforcement SiC based composite ceramic material (CMC-SiC); properties is obvious to all; but because C fiber does not mate and causes SiC MATRIX CRACKING with the thermal expansion of SiC matrix; at high temperature originally there is the SiC matrix of extraordinary antioxygen property and defencive function; but due to matrix cracking, oxidizing medium is had an opportunity to take advantage of.Due to the oxidation passage that crackle provides, have a strong impact on the performance of CMC-SiC.Oxidized in order to prevent C fiber, investigator has thought various ways, and relatively effective means has at present: 1. crack closure method, and utilize exactly the difference of fiber and matrix thermal expansivity to carry out healed cracks, oxidizing medium cannot be entered.As, NASA SiC _fstrengthen the matrix material of C matrix ^[1], lower than under preparation temperature, due to α _siCf> α _m(α represents linear expansivity, and f represents fiber, and m represents matrix), SiC _fapply stress to C matrix, make the appearance of C matrix flawless or crackle in closure state, add the SiC coating protection of material surface, through evidence, its antioxidant property is fine.Aforesaid method is no doubt good, but the Zhang Litong academician of Northwestern Polytechnical University points out ^[2], owing to providing, the fortifying fibre of selection is less, moreover not resistance to oxidation of C base, also treats better method.2. CMC-MS method is that multi-component multi-layer self-healing is legal, and its effect is also fine; But shortcoming is: 1) due to B ₂o ₃the temperature that becomes viscous state more than 650 DEG C, and C fiber 370 DEG C started oxidation, that is to say that 370 DEG C～650 DEG C temperature section matrix crackings cannot be by liquid B ₂o ₃carry out packing, and CMC-SiC is relatively many at the crackle of this temperature section, makes its oxidation-resistance very poor.2) B ₂o ₃very sensitive to water vapour, easily make B ₂o ₃layer peels off, in addition, in the time that temperature reaches 815 DEG C, B ₂o ₃the diffusivity of oxygen very high, when more than 1000 DEG C, B ₂o ₃vapour pressure excessive, the diffusivity of oxygen is excessive, and no longer has a defencive function ^[3], and the higher volatilization of temperature is more serious.3) SiO ₂high temperature steam pressure less, the diffusivity of oxygen is very little, but SiO ₂more than 1000 DEG C, temperature just can have fluid-tight function, uses SiO so simple ₂fluid-tight, when 370 DEG C～1000 DEG C of temperature sections, could not play a protective role.Although so this method effect is better, high-temperature behavior need to improve ^[4].

At C _fin the research of/SiC matrix material, the antioxidant property of material below preparation temperature is far below the oxidation-resistance more than preparation temperature.Its major cause is, because the axial thermal expansion coefficient of C fiber is-0.1～-0.26 × 10 ^-6k ^-1, the thermal expansivity of SiC matrix is 4.8 × 10 ^-6k ^-1, fiber axially all exists thermal expansivity not mate with matrix, thereby produces internal stress ^[5].Higher than preparation temperature situation, matrix fiber axially in compressive stress state, its crackle is healed, and makes oxidizing medium cannot enter inside.But, when temperature is during lower than preparation temperature, due to the thermal expansion mismatch of SiC matrix and low-expansion carbon fiber, must cause producing crack due to thermal stress in matrix, even if matrix and fiber thermal expansion matching are (as SiC _f/ SiC matrix material), the matrix of the low strain of high-modulus is also easily ftractureing compared with under low-stress ^[6].When SiC matrix is during lower than preparation temperature (general 1000 DEG C), wherein crackle and hole are easy to oxidized medium (H ₂o and O ₂) by and be diffused into fiber and the interface of CMC-SiC, accelerate the oxidation of PyC (pyrolytic carbon layer) interface and C fiber ^[7].And fiber and interface are posting and load bearing unit, both damages may cause Failure Analysis of Composite Materials very much, have a strong impact on the work-ing life of CMC-SiC ^[8].

At present, C fiber is prepared oxidation resistant coating technique and is mainly adopted CVD legal system standby, wherein it is worth noting, the SiC fiber (C fiber core) that CVD legal system is standby, due to the thermal stresses of C core and outer field SiC, after cooling along axis direction, SiC layer is in tensile stress state, SiC layer is thinner, and its drawing stress on surface is just larger, easily fracture.Therefore after the SiC layer that only deposition is thicker on C core, could alleviate and reduce the tensile stress of SiC layer, could increase the tensile strength of SiC fiber, certainly will cause like this diameter of this fiber to become very thick, woven performance is very poor ^{[9] [10]}, the high-temperature creep resistance of SiC is poor compared with carbon fiber.

In a word, at present C fiber is prepared the coating that oxidation resistant coating technique prepares and all can be had thermal stresses tiny crack, greatly reduces the provide protection of coating.As B ₄the coating such as C, SiC, but due to thermal mismatching, these coatings fibre axis to tensile stress excessive, cause coating, matrix to occur the crackle of vertical fibers axis direction, then cannot protect C fiber, to this, due to C _fc fiber in/SiC cannot be protected, thereby has to change C fiber into SiC fiber, but SiC _fthe creep-resistant property of/SiC temperature more than 1600 ° becomes very poor, C _fthe creep-resistant property of/SiC is far above SiC _f/ SiC.SiC at present _fthe life-time service temperature of/SiC is 1450 DEG C, C _fthe life-time service temperature of/SiC reaches 1650 DEG C, therefore solves C _fc in/SiC _foxidation-resistance be C _fthe gordian technique of/SiC pottery ^[11], namely solve C fiber axially and coating or matrix because the coefficient of expansion does not mate, cause the thermal stress issues of coating or MATRIX CRACKING; But also there is no desirable method sealing at present or stop thermal stress cracking, stoping C fiber and PyC interface oxidized.

Summary of the invention

For the problems referred to above, the object of the invention is just to provide a kind of preparation method of the flawless coated fibre that can stop C fiber and interface oxidation.

The preparation method of a kind of flawless coated fibre of the present invention realizes by following proposal:

Apply initial tensile stress sigma at fiber or fibrous bundle two ends _o, then uniform deposition inoxidzable coating; After deposition, be more than or equal to coating crack generation temperature T _ccondition under, the initial tensile stress sigma of removal _o, treat initial tension stress σ _oafter removal, entirety is cooled to room temperature, obtains flawless coated fibre.

The preparation method of a kind of flawless coated fibre of the present invention, first at fiber or fibrous bundle surface deposition transition layer PyC or BN, obtain conjugated fibre or bundle of composite fibers, then, conjugated fibre or bundle of composite fibers two ends are applied to initial tension stress, uniform deposition inoxidzable coating.

The preparation method of a kind of flawless coated fibre of the present invention, is applied to the initial tension stress σ on fiber or fibrous bundle _opress formula (11) calculative determination:

$\frac{({\mathrm{\α}}_f-{\mathrm{\α}}_m)E_f\mathrm{\Δ}{T}_1(E_m{V}_m+E_f{V}_f)}{E_m-({\mathrm{\α}}_f-{\mathrm{\α}}_m)E_f{V}_f\mathrm{\Δ}{T}_1}\≤{\mathrm{\σ}}_o\≤0.8f_{\mathrm{pk}\·\·\·\·\·\·}.---\left(11\right)$

Wherein: E _m, E _fbe respectively the Young's modulus of coating and fiber under room temperature;

V _m, V _fbe respectively the volume fraction of coating and fiber under room temperature, V _m+ V _f=1;

α _m, α _fthe thermal expansivity of coating and fiber respectively;

σ _ofor the initial tension stress of fiber or fibrous bundle;

F _pkfor the standard tensile strength of fiber or fibrous bundle;

Δ T ₁poor for room temperature and coating depositing temperature, i.e. Δ T ₁=RT-T _f, RT is expressed as room temperature, and coating depositing temperature is coating preparation temperature T _f.

σ _othe derivation of calculation formula is as follows:

If the initial tension stress that fiber or fibrous bundle produce pulling force is σ _o, adopt some theoretical formulas to calculate here.There is following hypothesis:

Be σ to the initial tension stress of fiber _o, adopt some theoretical formulas to calculate here.There is following hypothesis:

1, the interface of fiber and coating is without slippage;

2, coated fibre each several part is without temperature head;

3, fiber and coating in the following temperature of ultimate-use temperature in elastic stage.

Because coated fibre is unidirectional fibrous composite materials, Poisson's ratio is less on its impact, so stress formula does not below count the impact of Poisson's ratio in deriving.

If fiber original length is l, after stretch-draw, elongation is Δ x ₁, the original length of coating is l+ Δ x ₁, only consider the effect of fibre machinery restorer, after fiber is put, due to the restoring force of fiber, the compress variation of coating is Δ x ₂, according to hooke's law:

$F_f=\frac{E_f{A}_f}{l}({\mathrm{\Δx}}_1-{\mathrm{\Δx}}_2)---\left(1\right)$

$F_m=\frac{E_m{A}_m}{l+{\mathrm{\Δx}}_1}{\mathrm{\Δx}}_2---\left(2\right)$

By equilibrium of forces, F _f=F _m,

$\frac{E_m{A}_m}{l+{\mathrm{\Δx}}_1}{\mathrm{\Δx}}_2=\frac{E_f{A}_f}{l}({\mathrm{\Δx}}_1-{\mathrm{\Δx}}_2)---\left(3\right)$

${\mathrm{\Δx}}_2=\frac{E_f{A}_f{\mathrm{\Δx}}_1}{\frac{E_m{A}_{m}l}{l+{\mathrm{\Δx}}_1}+E_f{A}_f}---\left(4\right)$

The stress of coating under the effect of fibre machinery restorer:

${{\mathrm{\σ}}^p}_m=E_m{\mathrm{\ϵ}}_m=E_m\frac{{\mathrm{\Δx}}_2}{l+{\mathrm{\Δx}}_1}---\left(5\right)$

Formula (4) substitution formula (5) is obtained:

${{\mathrm{\σ}}^p}_m=\frac{E_m{E}_f{A}_f{\mathrm{\Δx}}_1}{E_m{A}_{m}l+E_f{A}_f(l+{\mathrm{\Δx}}_1)}---\left(6\right)$

Make A=A _m+ A _f,

By the molecule denominator on the right of formula (6) with divided by Al,

${{\mathrm{\σ}}^p}_m=\frac{E_m{E}_f{V}_f{\mathrm{\ϵ}}_f}{E_m{V}_m+E_f{V}_f(1+{\mathrm{\ϵ}}_f)}---\left(7\right)$

Again

substitution formula (7) has fiber to apply compression stress ot to coating ^p _m:

${{\mathrm{\σ}}^p}_m=\frac{E_m{V}_f{\mathrm{\σ}}_o}{E_m{V}_m+E_f{V}_f+V_f{\mathrm{\σ}}_o}---\left(8\right)$

The thermal stress producing while only considering coating temperature variation, Young's modulus and the coefficient of expansion of matrix material are respectively ^[11,12]:

E _c=V _fE _f+V _mE _m

${\mathrm{\α}}_c=\frac{{\mathrm{\α}}_m{V}_m{E}_m+{\mathrm{\α}}_f{V}_f{E}_f}{V_m{E}_m+V_f{E}_f}$

After stress equilibrium, the thermal stresses that coating and fiber produce because the coefficient of expansion is poor ^[12]:

σ ^T _m=E _c(α _c-α _m)ΔT=(α _f-α _m)E _fV _fΔT (9)

Both stress stacks, the stress of coating is:

${\mathrm{\σ}}_m={{\mathrm{\σ}}^T}_m-{{\mathrm{\σ}}^p}_m=({\mathrm{\α}}_f-{\mathrm{\α}}_m)E_f{V}_f\mathrm{\ΔT}-\frac{E_m{V}_f{\mathrm{\σ}}_o}{E_m{V}_m+E_f{V}_f+V_f{\mathrm{\σ}}_o}---\left(10\right)$

Wherein: σ ^p _mfor only considering the stress value of coating under the effect of fibre machinery restorer;

σ ^t _mfor only considering the stress value of coating in thermal stress situation;

σ _mfor considering the stress value of thermal stress and mechanical recovery force coating;

E _m, E _fbe respectively the Young's modulus of coating and fiber under room temperature;

V _m, V _fbe respectively the volume fraction of coating and fiber under room temperature, V _m+ V _f=1;

A _m, A _fbe respectively the section area of coating and fiber, A _m+ A _f=A;

α _m, α _fthe thermal expansivity of coating and fiber respectively;

ε _mfor being coated with the strain after layer equilibration; ε _ffor the initial stretching strain of fiber;

Δ T is the poor of coating temperature and coating depositing temperature, and in the time that coating temperature is less than coating depositing temperature, Δ T is negative, and in the time that coating temperature is greater than coating depositing temperature, Δ T is positive number.

σ _ofor the initial tension stress of fiber or fibrous bundle; When after the kind and Determination of quantity of coating and fiber, E _m, E _f, V _m, V _f, α _m, α _fbe just constant; When coating temperature is that room temperature is Δ T=Δ T ₁=RT-T _f, σ _m≤ 0 o'clock, coating was zero condition in stress or stress, considers the physical properties of fiber or fibrous bundle and coating, so initial tension stress σ _oscope be:

$\frac{({\mathrm{\α}}_f-{\mathrm{\α}}_m)E_f{\mathrm{\ΔT}}_1(E_m{V}_m+E_f{V}_f)}{E_m-({\mathrm{\α}}_f-{\mathrm{\α}}_m)E_f{V}_f{\mathrm{\ΔT}}_1}\≤{\mathrm{\σ}}_o\≤0.8f_{\mathrm{pk}}---\left(11\right)$

F _pkfor the standard tensile strength of fiber or fibrous bundle;

If only consider the anti-oxygen of coated fibre, do not consider that the situation of crackle appears in coating in temperature range (room temperature is to being oxidized threshold temperature), and coating temperature is in oxidation threshold temperature T _tor when its following temperature, coating crack is just closed, can stop oxidizing medium to enter.Therefore, Δ T=Δ T ₂=T _t-T _f, σ _m≤ 0, coating is zero condition in stress or stress, considers the physical properties of fiber or fibrous bundle and coating, so initial tension stress σ _oscope be:

$\frac{({\mathrm{\&alpha;}}_f-{\mathrm{\&alpha;}}_m)E_f{\mathrm{\&Delta;T}}_2(E_m{V}_m+E_f{V}_f)}{E_m-({\mathrm{\&alpha;}}_f-{\mathrm{\&alpha;}}_m)E_f{V}_f{\mathrm{\&Delta;<figure-callout\; id="2"\; label="T"\; filenames="HDA00003351706900031.png"\; state="\{\{state\}\}">T</figure-callout>}}_2}\&le;{\mathrm{\&sigma;}}_o\&le;0.8f_{\mathrm{pk}}---\left(12\right)$

The preparation method of a kind of flawless coated fibre of the present invention, described inoxidzable coating is by the nitride of Si, Al, Cr, Ti, Zr, Mg, B, Y, W, Hf, V, Nb, Ta, carbide, carbonitride, oxynitride, boride, silicide, at least one forms; Described fiber or fibrous bundle are selected from the one in carbon fiber or carbon fiber bundle.

The preparation method of a kind of flawless coated fibre of the present invention, described inoxidzable coating is by SiC, B ₄a kind of formation in C, TaC.

The preparation method of a kind of flawless coated fibre of the present invention, described inoxidzable coating adopts chemical vapor deposition method to deposit; Chemical vapour deposition temperature T _fbe more than or equal to coating crack and generate temperature T _c; When deposition, protective atmosphere used is argon gas or nitrogen, and carrier gas used and diluent gas are hydrogen.

The preparation method of a kind of flawless coated fibre of the present invention, the fiber that will be discharged by actinobacillus wheel (11) or fibrous bundle (12) are through after chemical gas phase (CVD) deposition apparatus, be connected with wire drawing wheel (13), apply initial tension stress σ to fiber or fibrous bundle (12) by gravity type boat davit deceleration loading device (9) _o; Be synchronized with the movement by electric machine control actinobacillus wheel (11), wire drawing wheel (13), make fiber or fibrous bundle (12) in deposition apparatus, realize the deposition of inoxidzable coating; After deposition, be more than or equal to coating crack generation temperature T _ccondition under, the initial tensile stress sigma of removal _o, then cooling, obtains flawless coated fibre.Wherein, T _ccoating crack generates temperature and is determined by following formula:

If σ _cfor the room temperature tensile strength of coating, when coating temperature is down to T _c, i.e. Δ T=T _c-T _f, now coating is about to cracking has,

σ ^T _m=(α _f-α _m)E _fV _fΔT=(α _f-α _m)E _fV _f(T _C-T _F)=σ _C （13）

By formula (13) distortion,

$T_C=T_F+\frac{{\mathrm{\&sigma;}}_C}{({\mathrm{\&alpha;}}_f-{\mathrm{\&alpha;}}_m)E_f{V}_f}---\left(14\right)$

After coating material therefor and thickness are determined, σ _calso just determined now T _ccan be considered constant.

The preparation method of a kind of flawless coated fibre of the present invention, between actinobacillus wheel (11) and wire drawing wheel (13), be provided with silk thread regulating wheel (10), described gravity type boat davit deceleration loading device (9), between actinobacillus wheel (11) and silk thread regulating wheel (10), applies initial tension stress σ to fiber or fibrous bundle (12) _o.

In the preparation method of a kind of flawless coated fibre of the present invention, fiber is continuous carbon fiber; Described fibrous bundle is continuous carbon fiber bundle.

Principle and advantage

Ultimate principle of the present invention is exactly to allow continuous fiber or fibrous bundle under constant pulling force effect, adopts the methods such as CVD at the even inoxidzable coating of its surface deposition.Before deposition oxidation resistant coating, can deposit in advance RESEARCH OF PYROCARBON PyC or BN interfacial layer.In deposition process, coating at fibre axis in unstress state.After deposition, the tension force of removal to fiber, due to fiber and the strong combination of coating interface, both carry out interior stress balance as an entirety.This entirety is called the stress rib that prestores.Because fiber and coating are not completely according to axle center homogeneous symmetry, so after balance, form very faint wave bending, as long as the thickness of coating is more even, can not affect its use properties.

Because the compressive strength rate tensile strength of ceramic coating exceeds a lot, the present invention, by the part ultimate compression strength of sacrificial coatings, applies stress to fiber coat, offsets thermal stresses, makes coating from oxidation threshold temperature T _tto crackle generation temperature T _ctemperature section is in compressive stress state, or under the situation of crackle sealing, thereby can realize the antioxidant defense of total temperature section.In the time that flawless coated fibre uses as reinforcement, even if matrix occurs crackle under the effect of thermal stresses, and the coating of fiber is higher than T _ttemperature is in compressive stress state, at T _tto T _ctemperature section flawless passage, O ₂/ H ₂o cannot approach fiber and interface, makes it obtain provide protection, realizes from room temperature RT to ultimate-use temperature T _ltotal temperature section antioxidant defense.

In deposited coatings process, in the time that fiber or fibrous bundle and coating are different along the coefficient of expansion of axis direction, fiber or fibrous bundle be deposited coatings under tension force effect, does not apply stress to coating, the hot-drawn stress occurring while not offsetting because of cooling, coating ftractures under the effect of larger thermal stresses.Therefore, the fiber of deposited coatings or fibrous bundle be not before unloading, and its temperature must be controlled at crackle and generate temperature T _cabove temperature to prevent the cracking of coating, is carried out entirety cooling after the load of removal fiber or fibrous bundle.If only consider the anti-oxygen of coated fibre, do not consider that the situation of crackle appears in coating in temperature range (room temperature is to being oxidized threshold temperature), and coating temperature is in oxidation threshold temperature T _tor when its following temperature, coating crack is just closed, can stop oxidizing medium to enter, in the front and back of removal fiber or fibrous bundle load, without the temperature variations of considering the coated fibre beyond cvd furnace.

In order to make fiber or fibrous bundle possess the effect of extracting in the time rupturing, make the matrix material of its enhancing possess more high tenacity, first at fiber or fibrous bundle surface deposition RESEARCH OF PYROCARBON PyC or BN weak interface layer, then deposit oxidation resistant coating.At least one formation in the nitride of material Si, the Al of oxidation resistant coating, Cr, Ti, Zr, Mg, B, Y, W, Hf, V, Nb, Ta, carbide, carbonitride, oxynitride, boride, silicide, but prerequisite is under ultimate-use temperature, coating can not produce reaction and affect their intensity and performance with fiber or fibrous bundle and matrix.When oxidation resistant coating on fiber or fibrous bundle is laminated coating, can alleviate like this thermal stresses causing because of differing materials thermal expansivity, the material of each layer can be the collocation of inequality and formation advantage, as compound coating combination C core/PyC/SiC/B ₄c/SiC.

Aspect the proof stress of fiber or fibrous bundle and coating, the initial tension stress σ of fiber or fibrous bundle _odetermine by calculating.Work as σ _owhen excessive, deposit complete, preparation envrionment temperature unloading, the screen resilience that coating cannot balance fiber, will cause it by conquassation.σ _otoo small, when temperature is down to room temperature RT or oxidation threshold temperature T _ttime, because of excessive its cracking that causes of tensile stress of coating.Therefore, make the stressed condition 0.75f of coating _cpk≤ σ _m≤ 0(f _cpkfor the standard ultimate compression strength of coating, and be negative, negative number representation is stress), σ _omust be controlled at σ _o≤ 0.8f _pk(f _pkfor the standard tensile strength of fiber).The section area of fiber and coating is according to principle of moderation, to ensure the antioxidant effect of coating.

The present invention is prepared in flawless coated fibre process, in the time that fiber or fibrous bundle (12) and coating are different along the coefficient of expansion of axis direction, fiber or fibrous bundle (12) deposited coatings under tension force effect, do not apply stress to coating, the hot-drawn stress occurring while not offsetting because of cooling, coating ftractures under the effect of larger thermal stresses.Therefore, the fiber of deposited coatings or fibrous bundle (12) be not before unloading, and its temperature must be controlled at crackle and generate temperature T _cabove temperature, to prevent the cracking of coating.After the load of removal fiber or fibrous bundle (12), carry out entirety cooling.In order to make fiber or fibrous bundle (12) possess the effect of extracting in the time rupturing, make the matrix material of its enhancing possess more high tenacity, first at fiber or fibrous bundle (12) surface deposition RESEARCH OF PYROCARBON PyC or BN weak interface layer, then deposit oxidation resistant coating.At least one formation in the nitride of material Si, the Al of oxidation resistant coating, Cr, Ti, Zr, Mg, B, Y, W, Hf, V, Nb, Ta, carbide, carbonitride, oxynitride, boride, silicide, but prerequisite is under ultimate-use temperature, coating can not produce and react and affect their intensity and performance with fiber or fibrous bundle (12) and matrix.When oxidation resistant coating on fiber or fibrous bundle (12) is laminated coating, can alleviate like this thermal stresses causing because of differing materials thermal expansivity, the material of each layer can be the collocation of inequality and formation advantage, as compound coating combination C core/PyC/SiC/B ₄c/SiC.

In the time preparing the carbon fiber of flawless coating or carbon fiber bundle, because the radial swelling coefficient of carbon fiber or carbon fiber bundle is generally slightly larger than coating or close with it, when lower than preparation temperature, the hoop compression chord of coating, therefore can not cause the cracking of coating, without the problem of considering hoop coating cracking.

Compared with prior art, the invention has the advantages that: the present invention, by the part ultimate compression strength of sacrificial coatings, applies stress by fiber or fibrous bundle to coating, offset thermal stresses, prepare flawless coated fibre, due to the existence of flawless coating, make coating from oxidation threshold temperature T _tto crackle generation temperature T _ctemperature section is in compressive stress state or crackle closed state; avoid because the crack due to thermal stress appearance causing is not mated in fiber and the thermal expansion of coating; cut off the passage of oxidizing medium; even if matrix has crackle to occur; also can obtain the protection of flawless coating; thereby prevent that fiber is oxidized, realize the antioxidant defense of total temperature section, thereby increase greatly globality, the safety and reliability of matrix material.That the present invention is applicable to is high temperature resistant, anti-oxidant, the preparation of the composite material reinforcement body of high temperature creep-resisting.

Brief description of the drawings

The general oxidation behavior of accompanying drawing 1 coating C fiber;

The anti-oxidation mechanism of accompanying drawing 2 CMC-SiC;

Accompanying drawing 3 flawless coating preparation principle figure;

Accompanying drawing 4 flawless coated fibres are prepared schematic diagram;

Accompanying drawing 5 σ _o=560MPa, the relation curve of the stress of coat-thickness and coating;

Accompanying drawing 6 σ _o=625Pa, the relation curve of the stress of coat-thickness and coating;

Accompanying drawing 7 σ _o=675MPa, the relation curve of the stress of coat-thickness and coating;

Accompanying drawing 8 σ _o=610MPa, the relation curve of the volume fraction of fiber and the stress of coating;

9, accompanying drawing is subject to thermal stress, the relation curve of coat-thickness and coating tensile stress

The stress curve of accompanying drawing 10 coat-thicknesses from 0 to 3 μ m

Under accompanying drawing 11 preparation temperatures, the relation curve of the initial tensile stress of fiber and coating stress

The relation curve of the initial tensile stress of accompanying drawing 12 carbon fibers and the stress of coating

Accompanying drawing 13 SiC coated fibre preparation facilities figure;

Accompanying drawing 14 B ₄c coated fibre preparation facilities figure.

In Fig. 1, T _tfor oxidation threshold temperature (being 370 DEG C); T _ffor the preparation temperature (generally temperature preparation more than 1000 DEG C) of coating; T _cfor crackle generates temperature (in existing preparation method, below preparation temperature, temperature when coating and fibre axis crack to thermal expansion mismatch); T _lfor the ultimate-use temperature of coating; Crackle generates temperature T _cto ultimate-use temperature T _lbe called the anti-oxidation temperature range of intrinsic.At oxidation threshold temperature T _tto crackle generation temperature T _ctemperature section.The oxidation characteristic of coating C fiber is same as coating C/C, the oxidation threshold temperature T of coating C _tthe same with C/C, be 370 DEG C ^[13].Therefore as can be seen from Figure 1, realize the protection to C fiber, C matrix and PyC interface, key is to be oxidized threshold temperature T _tto crackle generation temperature T _cthe appearance of temperature section flawless or cracks are at closure state, and oxidizing medium can enter without passage, thereby realize from room temperature RT to ultimate-use temperature T _ltotal temperature section antioxidant defense.In Fig. 1, if the axial thermal expansion coefficient of fortifying fibre is less than the coefficient of expansion of matrix, the preparation temperature T of coating _fbe greater than crackle and generate temperature T _c; Otherwise, if the axial thermal expansion coefficient of fortifying fibre is greater than the coefficient of expansion of matrix, the preparation temperature T of coating _fbe less than crackle and generate temperature T _c, the T in figure _cat T _fthe right.And the present invention mainly considers that the axial thermal expansion coefficient of fortifying fibre is less than this situation of the coefficient of expansion of matrix.

As can be seen from Figure 2, there is crackle in matrix (matrix) under the effect of thermal stresses, and C fiber coat is higher than T _ttemperature is in compressive stress state, at T _tto T _ctemperature section flawless passage, O ₂/ H ₂o cannot approach C fiber and interface pyrolytic carbon layer PyC, makes it obtain provide protection, realizes from room temperature RT to ultimate-use temperature T _ltotal temperature section antioxidant defense.

As can be seen from Figure 3, by the tension force controllable device in figure, fiber or fibrous bundle (12) are applied to initial tension stress σ _o, depositing preparation, after removal pulling force, the stress of coating is σ _m; In figure, 3 is coating; 4 is fiber; 7 is flawless coated fibre or the stress rib that prestores.

In Fig. 4,9 is gravity type boat davit deceleration loading device; 10 is silk thread regulating wheel; 11 is wire wheel; 12 is fiber or fibrous bundle; 13 is wire drawing wheel.

As Fig. 5, the initial tensile stress of carbon fiber is 560MPa, and temperature declines, Δ T=-1100 DEG C, the nonlinearities change relation that is of the stress of coat-thickness variation and coating.When the thickness of coating is 0.5 μ m, the stress of coating is 2MPa.

As Fig. 6, the initial tensile stress of carbon fiber is 625MPa, temperature variation Δ T=-1100 DEG C, and along with the variation in thickness of coating, the stress of coating becomes thereupon, and is nonlinearities change.In the time that the thickness of coating is 1 μ m, the stress of coating is 1MPa.The below ordinate in diagram, negative number representation stress, positive number represents tensile stress.

As Fig. 7, the initial tensile stress of carbon fiber is 675MPa, temperature variation Δ T=-1100 DEG C, and along with the variation in thickness of coating, the stress of coating becomes thereupon, is nonlinearities change.In the time that the thickness of coating is 1.5 μ m, the stress of coating is 2MPa.

As Fig. 8, the initial tensile stress of carbon fiber is 610MPa, temperature variation Δ T=-1100 DEG C, the nonlinearities change relation of the volume fraction of fiber and the stress of coating.As can be seen from Fig., along with the volume of fiber constantly increases, the stress of coating becomes stress from the tensile stress starting.

If only consider the situation of thermal stress, as Fig. 9, temperature variation Δ T=-1100 DEG C, coat-thickness from 0 to 100 μ m, coating is thinner, and suffered hot-drawn stress is just larger, and maximum can approach 870MPa, so high tensile stress, coating cannot be born.

Figure 10 represents the stress curve of coat-thickness from 0 to 3 μ m.

When envrionment temperature is preparation temperature, now without thermal stress, only consider the elastic-restoring force of fiber, as Figure 11, temperature variation Δ T=0 DEG C, the initial tensile stress of fiber is from 0 to 1000Mpa, and the stress that coating is born increases thereupon, linear.

As Figure 12, the volume fraction 50% of fiber, temperature variation Δ T=-1100 DEG C, the initial tensile stress of carbon fiber and the stress of coating linear.As can be seen from Fig., along with the initial tensile stress of carbon fiber constantly increases, the stress of coating becomes stress from the tensile stress starting.Because the tensile strength of ceramic coating is very lowly lower than ultimate compression strength, so in the initial tensile stress of 0-1000Mpa fiber interval, coating is in tensile stress state, so be easy to cracking destruction in this interval, and in 1000-2000Mpa interval, coating, in compressive stress state, there will not be crackle.

Coating preparation facilities schematic diagram of the present invention is Figure 13 or Figure 14;

In Figure 13:

3 is coating; 4 is fiber; 7 is flawless coated fibre or the stress rib that prestores; 9 is gravity type boat davit deceleration loading device; 10 is silk thread regulating wheel; 11 is carbon fiber wire wheel; 12 is fiber or fibrous bundle; 13 is wire drawing wheel; 14 is hermetically sealed head; 15 is glass reaction tube; 16 is coaxial coupler; 17 is variable adjustment electric capacity; 18 is radio frequency generators; 19 for holding the container of dichloro methyl silane; 20 for holding the container of trichloromethyl silane; 21 is thermostat water bath; 22 is the metering control system of reactant gases; 23 is high-purity hydrogen; 24 is high-purity argon gas; 25 is argon gas intake line; 26 is reactant gases intake line; 27 is exhaust emissions pipeline; 28 is exhaust gas processing device;

In Figure 14:

30 is degumming stove; 31 is RESEARCH OF PYROCARBON high temperature deposition stove; 32 is B ₄c is coated with high temperature deposition stove.

Embodiment

Below in conjunction with drawings and Examples, the present invention is further elaborated.

Embodiment 1:

The present embodiment adopts T300 carbon fiber (12), SiC coating (3), and the correlation properties of SiC coating (3) and T300 carbon fiber (12) are in table 1; Prepare flawless coated fibre, gravity type boat davit deceleration loading device (9) adopts gravity type boat davit to load, and method is as follows:

Step 1, deposition weak interface layer.First at the temperature of 600 DEG C, come unstuck, then, at the upper uniform deposition 0.3 μ m RESEARCH OF PYROCARBON PyC interfacial layer of T300 carbon fiber (12), deposition apparatus adopts device as shown in figure 13, and raw material adopts high purity acetylene gas, and shielding gas adopts Ar gas.In CVD deposition process, because interfacial layer thickness is very thin, can apply tension force to T300 carbon fiber (12), also can deposit pyrolytic carbon layer without tension force, very little to oxidation resistant coating stressing influence.

Under step 2, tension force effect, uniform deposition oxidation resistant coating.The present embodiment deposition oxidation resistant coating is SiC, the thickness of target coating is 0.5 μ m, 1.0 μ m, 1.5 μ m, gravity type boat davit deceleration loading device (9) adopts gravitational load, in the time that the thickness of target coating is 0.5 μ m, and the initial tension stress σ of T300 carbon fiber (12) _ofor 560Mpa, in the time that the thickness of target coating is 1.0 μ m, the initial tension stress σ of T300 carbon fiber (12) _ofor 625Mpa, in the time that the thickness of target coating is 1.5 μ m, the initial tension stress σ of T300 carbon fiber (12) _ofor 675Mpa, preparation principle is as Fig. 4, and deposition apparatus adopts device as shown in figure 13.Wire wheel (11) and wire drawing wheel (13) are by synchronous machine control, gravity type boat davit deceleration loading device (9) applies constant load p to T300 carbon fiber (12), make T300 carbon fiber (12) have stretch-draw strain, T300 carbon fiber (12) enters from one end of CVD vapor phase growing apparatus, be in coating deposition under the effect of tension force at the T300 carbon fiber (12) between silk thread regulating wheel (10) and wire drawing wheel (13), depositing temperature is 1100 DEG C, and CVD sedimentation chemistry reaction formula has:

Wherein H ₂for carrier gas and diluent gas, shielding gas adopts Ar gas.

Step 3, wait to deposit after, keep 1100 DEG C of temperature, the pulling force of removal to T300 carbon fiber (12).

Step 4, cooling.Load removal to be tensioned, then entirety is cooled to room temperature, and therefore cooling extent is about 1100 DEG C (Δ T=1100 DEG C), completes the preparation of flawless coated fibre, calculates embodiment SiC coating (3) at axial stress σ by formula (10) _m, concrete numerical result is in table 2.When getting thickness and be 1.5 μ m flawless coated fibres and being warming up to 1100 DEG C again, i.e. Δ T=0 DEG C, is calculated the axial stress of coating: σ by formula (10) _m=-430MPa(presses).Because weak interface layer intensity is lower, less on the stress calculation impact of coating, so do not count in the axial stress of coating is calculated.

The correlation properties of table 1.SiC coating and C fiber (T300) ^{[14] [15]}.

Adapt with it C fiber subgroup table of initial tension stress of the SiC coating of table 2. different thickness.

Embodiment 2:

The present embodiment adopts carbon fiber (12), B ₄c coating (3), prepares flawless coated fibre, B ₄the correlation properties of C coating and C fiber are in table 3, and gravity type boat davit deceleration loading device (9) adopts gravitational load, and CVD deposition apparatus is as Figure 14, and method is as follows:

Step 1, deposition weak interface layer.First at the temperature of interior 600 DEG C of degumming stove 30, come unstuck; at the upper uniform deposition 0.3 μ m RESEARCH OF PYROCARBON PyC interfacial layer of carbon fiber (12); deposition apparatus adopts RESEARCH OF PYROCARBON high temperature deposition stove (31) as shown in figure 14, and raw material adopts high purity acetylene gas, and shielding gas adopts high-purity N ₂.In CVD deposition process, can apply tension force deposition pyrolytic carbon layer to carbon fiber (12).

Under step 2, tension force effect, uniform deposition oxidation resistant coating.The present embodiment deposition oxidation resistant coating is B ₄c, unstripped gas adopts BCl ₃, CH ₄, H ₂, wire travelling speed is suitable, the control volume fraction Vf=50% of coating, and gravity type boat davit deceleration loading device (9) adopts gravitational load, controls the initial tension stress σ of carbon fiber _o=1000MPa, preparation principle is as Fig. 4, and deposition apparatus can adopt B as shown in figure 14 ₄c is coated with high temperature deposition stove (32).Wire wheel (11) by synchronous machine control, applies constant load p to carbon fiber (12) by gravity type boat davit deceleration loading device (9) with wire drawing wheel (13), makes carbon fiber (12) have stretch-draw strain, the tension stress σ of carbon fiber (12) _ofor 1000MPa, carbon fiber (12) enters from one end of CVD vapor phase growing apparatus, be in coating deposition under the effect of tension force at the T300 carbon fiber (12) between silk thread regulating wheel (10) and wire drawing wheel (13), depositing temperature is 1100 DEG C, and CVD sedimentation chemistry reaction formula has:

Shielding gas adopts high-purity N ₂, H ₂for carrier gas and diluent gas.

Step 3, wait to deposit after, keep 1100 DEG C of temperature, the pulling force of removal to carbon fiber (12).

Step 4, cooling.Load removal to be tensioned, then entirety is cooled to room temperature, and therefore cooling extent is about 1100 DEG C, now B ₄c coating 3 is σ at axial stress _m=-38MPa(presses), complete the preparation of flawless coated fibre.When this flawless coated fibre is warming up to 1100 DEG C again, i.e. Δ T=0 DEG C, is calculated the axial stress σ of coating by formula (10) _m=-653MPa(presses).Because weak interface layer intensity is lower, less on the stress calculation impact of coating, so do not count in the axial stress of coating is calculated.

Table 3.B ₄the correlation properties of C coating and C fiber ^{[15] [16]}.

Reference

【1】JAMES M S,LARRY P Z.Performance of four ceramic matrix composite divergent flap inserts following ground testing on an F110 turb of an engine[J].Journal of the American Ceramic Society,2000,83(7):1727-1738.

[2] Zhang Litong, Cheng Laifei, Xu Yongdong, Liu Yongsheng, Zeng Qingfeng, Dong Ning, Luan Xingang. self-sealing silicon carbide ceramic based composite material research and application progress [J]. aeronautical material journal, 2006,26 (3): 226-232.

【3】Buchanan F J,Little J A.Corrosion Seience,1993,35(5-8):1243

[4] Li Siwei. the High Temperature Simulation environment Microstructure evolution of fiber reinforced self-sealing silicon carbide ceramic based composite material. doctorate paper [D], Xiamen University, 2008

[5] micromechanism of damage and the life prediction of the firm .3D C/SiC of Luan Xin in complicated coupling environment. doctorate paper [D], Northwestern Polytechnical University, 2007

【6】Wu S.J.，Cheng L.E，Zhang L.T.，et a1.Oxidation behavior of 2D C/SiC with a multi—layer CVD SiC coating[J].Surface and Coatings Technology,2006，200(14-l5)：4489-4492.

【7】Yin X.W，Cheng L.F.，Zhang L.T.，et a1.Microstructure and oxidation resistance of carbon/silicon carbide composites infiltrated with chromium silicide[J].Materials Science and Engineering A，2000，29(1-2)：89-94.

[8] Yin little Wei, the environmental oxidation behavior of 3D C/SiC matrix material. doctorate paper [D], Northwestern Polytechnical University, 2001.

[9] Lee is special, Xiao Peng, Xiong Xiang. the progress [J] of Continuous Fiber Reinforced Ceramic Matrix Composites. and Materials Science and Engineering of Powder Metallurgy, 2007,12 (1): 14-19.

[10] Liu Cuixia etc. the present Research of chemical Vapor deposition process continuous SiC fiber and development trend [J]. material Leader, 2006,20 (8): 35-40.

[11] beneficial little Su, Du Shanyi, Zhang Litong. Chinese material engineering grand ceremony: the 10th volume composite material engineering, 2006:468,616-632

[12] Li Longbiao etc. unidirectional fibre strengthens ceramic matric composite uniaxial extension behavior [J]. matrix material journal, 2008,25 (4): 154-160.

[13] Deng Jingyi, Liu Wenchuan, the research of Du Haifeng .C/C-SiC gradient based composites oxidation behavior. silicate journal, 1999,27(3): 357-361

[14] east of a river is bright, Li Long soil, and Ouyang's generation is amiable and compliant, Shi Jianlin. the grand ceremony of Chinese material engineering: the 8th volume materials science and engineering (on), 2006:180

[15] beneficial little Su, Du Shanyi, Zhang Litong. Chinese material engineering grand ceremony: the 10th volume composite material engineering, 2006:39

[16] east of a river is bright, Li Long soil, and Ouyang's generation is amiable and compliant, Shi Jianlin. the grand ceremony of Chinese material engineering: the 8th volume materials science and engineering (on), 2006:178,192

Claims (8)

1. a preparation method for flawless coated fibre, is characterized in that: apply initial tension stress σ at fiber or fibrous bundle two ends _o, then uniform deposition inoxidzable coating; After deposition, be more than or equal to coating crack generation temperature T _ccondition under, the initial tension stress σ of removal _o, treat initial tension stress σ _oafter removal, entirety is cooled to room temperature, obtains flawless coated fibre; Described initial tension stress σ _o, by formula (11) calculative determination:

$\frac{({\mathrm{\&alpha;}}_f-{\mathrm{\&alpha;}}_m)E_f\mathrm{\&Delta;}{T}_1(E_m{V}_m+E_f{V}_f)}{E_m-({\mathrm{\&alpha;}}_f-{\mathrm{\&alpha;}}_m)E_f{V}_f\mathrm{\&Delta;}{T}_1}\&le;{\mathrm{\&sigma;}}_o\&le;0.8f_{\mathrm{pk}}.......\left(11\right)$

Wherein: E _m, E _fbe respectively the Young's modulus of coating and fiber under room temperature;

V _m, V _fbe respectively the volume fraction of coating and fiber under room temperature, V _m+ V _f=1;

α _m, α _fthe thermal expansivity of coating and fiber respectively;

σ _ofor the initial tension stress of fiber or fibrous bundle;

F _pkfor the standard tensile strength of fiber or fibrous bundle;

Δ T ₁poor for room temperature and coating depositing temperature.

2. a kind of preparation method of flawless coated fibre according to claim 1, it is characterized in that: first at fiber or fibrous bundle surface deposition transition layer PyC or BN, obtain conjugated fibre or bundle of composite fibers, then, conjugated fibre or bundle of composite fibers two ends are applied to initial tension stress σ _o, uniform deposition inoxidzable coating.

3. a kind of preparation method of flawless coated fibre according to claim 1, is characterized in that: described inoxidzable coating is by the nitride of Si, Al, Cr, Ti, Zr, Mg, B, Y, W, Hf, V, Nb, Ta, carbide, carbonitride, at least one forms.

4. a kind of preparation method of flawless coated fibre according to claim 3, is characterized in that: described inoxidzable coating is by SiC, B ₄one in C, TaC forms.

5. a kind of preparation method of flawless coated fibre according to claim 1, is characterized in that: described inoxidzable coating adopts chemical vapor deposition method to deposit; Chemical vapour deposition temperature T _fbe more than or equal to coating crack and generate temperature T _c; When deposition, protective atmosphere used is argon gas or nitrogen, and carrier gas used and diluent gas are hydrogen.

6. the preparation method of a kind of flawless coated fibre according to claim 1, it is characterized in that: the fiber that will be discharged by actinobacillus wheel (11) or fibrous bundle (12) are through after chemical vapor deposition unit, be connected with wire drawing wheel (13), apply initial tension stress σ to fiber or fibrous bundle (12) by gravity type boat davit deceleration loading device (9) _o; Be synchronized with the movement by electric machine control actinobacillus wheel (11), wire drawing wheel (13), make fiber or fibrous bundle (12) in deposition apparatus, realize the deposition of inoxidzable coating; After deposition, be more than or equal to coating crack generation temperature T _ccondition under, the initial tension stress σ of removal _o, then cooling, obtains flawless coated fibre.

7. the preparation method of a kind of flawless coated fibre according to claim 6, it is characterized in that: between actinobacillus wheel (11) and wire drawing wheel (13), be provided with silk thread regulating wheel (10), described gravity type boat davit deceleration loading device (9), between actinobacillus wheel (11) and silk thread regulating wheel (10), applies initial tension stress σ to fiber or fibrous bundle (12) _o.

8. according to the preparation method of a kind of flawless coated fibre described in claim 1-7 any one, it is characterized in that: described fiber is carbon fiber; Described fibrous bundle is carbon fiber bundle.

Images