SHS/QC legal system has the microstructure of compound pottery and porcelain studies TiC/Al₂O₃

The Phase And Microstructure Characteristics Of TiC/Al2O3 Composite Ceramics Made Under Various Conditions Of Preheating Temperature And Diluent Were Investigated.

The Results Show That As Preheating Temperature Is Raised, the Combustion Is Transferred From Unstable Spiral Model To Stable Planar Model, materials Are Easy To Be Formed, and Reaction Is More Complete But The Microstructure Of Reaction Product Was Gross.

On The Contrary, the Particles Of TiC And Al2O3 Produced By Reaction Were Fine, but Cracks Are Easy To Appear In The Forming Process Of Consolidation.

The Combustion Characteristic Parameters Of This System Were Measured By Experiments And The Reaction Mechanisms Were Also Discussed In The Paper.

Pottery and porcelain of TiC/Al2O3 of 　 of 　 of Combustion Model of 　 of 　 Preheating Temperature of SHS/QC of 　 of Keywords 　 TiC/Al2O3 Composite Ceramics is a kind of good cutting tool stuff. But the hot pressing agglomeration that uses a convention, heat static pressure wait for craft, technology is sophisticated, cost is high, and use novel SHS to react - fast pressurization law, the complex rate that can lower craft greatly [1 ～ 3] . Using the discovery when combustion is synthesized, the craft parameter such as the initiative condition of temperature of feature of the photograph of material, organization and combustion mode, warm-up, reactant concerns close. Research discovers [2] , the combustion way that TiO2+C+Al system leaves in normal temperature is not stable helix to burn more, lift as warm-up temperature, combustion mode produces change. Because this article basically considered to be below different technology condition, change along with combustion mode, make feature of the photograph of TiC/Al2O3 compound pottery and porcelain, organization, discussed the reaction mechanism of this system from this. Stuff of this good to using this craft to synthesize function cutting tool of TiC/Al2O3 pottery and porcelain has important sense. Place of test of 1 experiment means uses Al, tiO2, al2O3, carbon black pink is respectively: 29 μ M, 0.

5 μ M, 30 μ M, 0.

5 μ M. Press them different match evener than mixing, sampling the sample of 30mm of × of 40mm of φ of Leng Yacheng  , send density ～ relatively 50% . If the graph is shown 1 times,experiment place uses vacuum pressurization device. After using sample of tungsten filament ignition, await pressurization of proper time immediately, make material. To velocity of wave of combustion temperature, combustion determine to be not had in vacuum pressure undertake below condition. Through be on sample, can beg on the time temperature curve that leaves place to place thermocouple place to obtain take tendril to light time, achieve combustion rate thereby, observe through peephole tendril lights a course. Bougie of diffractive to be being made so that X undertook after material sampling analysis, electron and can chart analysis. Graph 1 vacuum pressurization is compact Fig of device sketch map.

Result of test of 1 　 Schematic Representation Of Consolidatedvacuum Equipment2 and analysis 2.

1 combustion feature and analysis pursue 2 it is the relation that speed of combustion temperature, combustion and tendril light a form to follow initiative temperature and thinner Al2O3 to join quantitative change to change. Can see, follow warm-up temperature to reduce, thinner Al2O3 joins a quantity to increase, bring about speed of combustion temperature, combustion to reduce, combustion burns to transfer to not stable helix combustion by stable plane. Because content of low, thinner adds warm-up thermal drop,this is make radiative quantity reduces SHS process, make between reactant diffuse each other more difficult be caused by. By still can discover in the graph, combustion temperature appeared around 2040 ℃ a constant platform, this is Al2O3(its melting point is 2040 ℃ ) produce fused result. With this correspondence, discovery drops from 2040 ℃ above when combustion temperature come here near temperature when, combustion speed is reduced very remarkable, this specification reaction gets diffusion control apparent, of Al2O3 fused quickened reactant between diffuse, thereby enkindle rate rises greatly. Graph 3 it is to use determining velocity of wave and combustion temperature, according to equation of velocity of wave [1] : Graph the relation of temperature of 2 combustion temperature and combustion speed and thinner Al2O3 content, warm-up (the relation of content of Al2O3 of A) combustion temperature and warm-up temperature, thinner; (The relation Fig of content of Al2O3 of B) combustion speed and warm-up temperature T0, thinner.

2 　 The Relationships Among Combustion Temperature And Speed And Diluent(Al2O3) Content And Preheating Temperature pursues of 3 systems - the relation curve Fig of Ln(v/Tc) and 1/Tc.

3 　 Plot Showing The Relationship Between-ln(V/Tc) And 1/Tc In The System among them: V is combustion wave spreads speed; F(n) is the function of kinetic progressional N; Tc combustion temperature; R is gas constant; K0 is invariable; The activation that E  is a process can; K is child specific heat; Q is reaction heat; ρ is child density from - Ln(V/Tc) can see to the relation curve of 1/Tc, determines dot distributings approximately linear, undertake planning to close to these dots, the slope with linear basis is calculable the activation that gets this system can be 323kJ/mol, discover it and Ti-C spread oneself systematic reaction activations can [1] 310kJ/mol is adjacent, two around that this specification produces in systematic Al-TiO2-C are consecutive reaction process [2] : (A)Al+TiO2; (B) [Ti] + C, actual be by hind function is controlled since the response that one pace answers whole system instead, compare C to diffuse in TiC activation can [4] (234 ～ 410kJ/mol) , can think, [Ti] + the C in C reaction diffuses mediumly in TiC the operating ring section that the process is whole reaction. Graph the 4 results that are X diffraction analysis, increase certain amount when thinner Al2O3 content it is thus clear that by the graph when (right now combustion is not stable helix combustion form) , appeared in reaction child a few leftover photograph TiO2. By before in narrating the addition of content of knowable thinner Al2O3 to cause this system no matter be Al+TiO2, or [Ti] + C reacts diffuse it is more difficult that the process undertakes, cause reaction finally consequently not complete. Graph the X diffractive result of 4 products of combustion (0wt% of content of A) thinner Al2O3, 25 ℃ of T0 ＝ ; (20wt% of content of B) thinner Al2O3, 25 ℃ of T0 ＝ Fig.

4 　 The XRD Results Of Combustion Products2.

The organization of 2 material and function are expressed 1 those who listed different pressurization pressure issues income data is relatively compact degree. Can see from this, send density to increase relatively along with what pressure increases material. Below 100MPa pressure, its send density to already was amounted to relatively 97.

4% . What the watch obtains data below 1 different pressure is relatively compact pressure of degree of pressurization of Relative Density Of Materials Prepared Undervarious Pressures of Table 1 　 / MPa2050100 sends density relatively / %90.

195.

997.

4 　 pursue the 5 microcosmic organization photographs that are material of the preparation below different warm-up temperature and different thinner content. Compare graph 5a, b can discover, as warm-up temperature elevatory, generated TiC grain becomes bulky (average size increases 2 μ M to control) from left and right sides of 1 μ M, and generated chunk shape Al2O3 has fused tendency, when warm-up temperature is more than 400 ℃ , reaction temperature exceeds Al2O3 melting point, generated Al2O3 joins together, and TiC grain is apparently thick change (5c seeing a picture, dimension achieves 3 μ M to control) . And the effect of adscititious thinner Al2O3 is as adverse as warm-up temperature (5d) seeing a picture, make generated TiC grain becomes petty, when thinner content achieves 10wt% , generated TiC is in about 0.

1 ～ 1.

0 μ M. And adscititious Al2O3 often is formed together with the Al2O3 adhesion that reaction generates get together conglomeration. Graph the constituent photograph of 5 preparation material (0wt% of content of A) thinner Al2O3, 25 ℃ of T0 ＝ ; (0wt% of content of B) thinner Al2O3, 200 ℃ of T0 ＝ (0wt% of content of C) thinner Al2O3, 400 ℃ of T0 ＝ ; (10wt% of content of D) thinner Al2O3, 25 ℃ of T0 ＝ Fig.

The kinetic feature that combustion of SHS of 　 of 　 of 5 　 Microstructure Photographs Of Fabricated Materials reacts is affecting the photograph that synthesizes material, organization greatly. To the SHS reaction of Al-TiO2-C system, its process was experienced early or late (A)Al-TiO2; (B) [Ti] + two paces of C react, by before narrate test result knowable, one pace reaction is the crucial link of process of this system SHS after, and C is in of reaction child TiC diffuse to have practical limitative effect to the process of reaction. This shows this system is medium, of production phase TiC generate with grown relatively Al2O3 is more difficult, all sorts of influences diffuse the bulk that the explicit condition of the process makes apparent change TiC grain. Of warm-up temperature elevatory, raised reaction temperature, prolonged the duration that SHS reaction issues in high temperature condition, make C atomic diffuses thereby more sufficient, reaction undertakes more easily, the growth of TiC is more so sufficient, particle size greatens. From the graph 5c can discover, warm-up temperature is elevatory, child Al2O3 happens after fusing, no matter this is right Al-TiO2, or [Ti] + between C diffuse reaction is advantageous, generated TiC happens to be brought up apparently. And the affiliation of thinner Al2O3, dropped reaction temperature on one hand, also increased Ti on the other hand, between C atom diffuse distance, make reaction more difficult, of TiC grain grown be restrained. Watch 2 listed determine the mechanical function of material. Can see, compare with the phase of data of TiC/Al2O3 pottery and porcelain with common method preparation, its each function is basic close. The hardness of TiC/wt% of function of Mechanical Properties Of Fabricated Materials of 　 of mechanical function Table 2 that expresses 2 preparation material / HV bending strength σ / MPa ruptures tenacity KIC/MPa*m-1/2 common method [2, 3] 2200600 ～ of 301900 ～ 8003.

8 ～ 4.

5SHS-QC3718435874.

53 conclusion 　 (1) uses combustion to synthesize - preparation of success of dynamic pressurization craft TiC/Al2O3 compound pottery and porcelain, the TiC that reaction generates distributings even, grain fine roundlet is whole, its dimension is in 0.

2 μ of 5 ～ M limits, of material send density to amount to relatively 97.

4% , its each mechanical function and the data that use common method preparation are close to basically. (2) as warm-up temperature elevatory, temperature of combustion velocity of wave, reaction is elevatory, particle size of reaction child TiC increases, when warm-up temperature achieves 400 ℃ , melt Al2O3 photograph appears in child, this is helpful for material shape. (The affiliation of 3) thinner Al2O3 dropped the reaction temperature of combustion velocity of wave, combustion mode burns to transfer to not steady helix combustion pattern by plane, often appear leftover reactant, and material be hard to compact, but generated TiC grain becomes more petty. CNC Milling