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1.
Synthesis of TiAl3 from Ti + 3Al powder mixtures in thermal explosion mode was found to proceed by the equilibrium mechanism in case of smaller Ti particles (55 μm) and by the non-equilibrium mechanism in case of larger Ti particles (130 μm). In the latter case, the product was found to contain the phases of TiAl3, TiAl, Ti3Al, Ti-based solid solution, and no unreacted Al.   相似文献   

2.
The mathematical model of thermal explosion and synthesis of products in a mechanically activated 3Ni + Al mixture is simulated in macroscopic approximation. It is shown that activation of original components significantly increases the formation rate of a Ni3Al intermetallide. The experimental data are used to determine the thermophysical and kinetic constants of the process.  相似文献   

3.
Chernogolovka. Translated from Fizika Goreniya i Vzryva, Vol. 24, No. 3, pp. 67–74. May–June, 1988.  相似文献   

4.
反应热喷涂的发展   总被引:4,自引:0,他引:4  
反应热喷涂是自蔓延高温合成(SHS)同热喷涂技术相结合而发展起来的新技术。本文综述反应热喷涂的工艺,过程和涂层结构及性能。  相似文献   

5.
Combustion of Cr2O3 + Al powder mixtures in a coflow of inert gas (Ar) was investigated upon variation in green density in the presence/absence of blowing agents (borax, baking soda). The results were rationalized in terms of the convection-conduction theory for combustion in heterogeneous condensed systems. For Part 4, see Int. J. SHS, 2008, vol. 17, no. 3, pp. 199–205.  相似文献   

6.
For Cr + B mixtures, we investigated the influence of mechanoactivation (MA) on the thermal effect of SHS reaction, burning velocity, and combustion temperature, and optimized MA conditions. Using the technique of forced SHS compaction, we manufactured the CrB2-based compacts up to 125 mm in diameter (residual porosity 3–5%) from green mixtures subjected to MA under optimized conditions.   相似文献   

7.
Thermal explosion in (Ni + Al)/Nb/(Ni + Al + Nb) sandwiches was found to results in formation of (a) NiAlNb composite containing NiAl, NiAlNb, and trace amounts of Nb5Ni and (b) good joining with a transition zone.  相似文献   

8.
A new method is developed for obtaining powder nanocomposites consisting of a metallic or intermetallic matrix and ceramic nanometer particles as a reinforcing phase. This method involves the following consecutive processes: short-time mechanical activation of the mixture of powder reagents in a high-energy planetary ball mill, self-propagating high-temperature synthesis, and additional mechanical activation of the synthesis products. Specific features of the reinforcing phase synthesis in matrices are examined by an example of TiB2-Cu and TiB2-TiNi systems. Compaction conditions that allow obtaining volume nanostructural materials with high strength characteristics are found. __________ Translated from Fizika Goreniya i Vzryva, Vol. 43, No. 2, pp. 58–71, March–April, 2007.  相似文献   

9.
A new method is developed for specimen preheating with subsequent loading by shock waves and conservation of the products of shock consolidation; the method is based on the use of the chemical furnace energy produced by a thermal explosion or combustion of SHS systems. The use of the thermal explosion expands the range of pre-shock heating temperatures up to 3000 °C and the range of mean pressures in the cylindrical ampoule up to 25 GPa. Two variants of preheating are considered: an inert specimen is heated by heat release in a reacting SHS system or the specimen under study itself is an SHS system.Translated from Fizika Goreniya i Vzryva, Vol. 41, No. 1, pp. 129–135, January–February, 2005.  相似文献   

10.
The factors responsible for the transition from reagent interaction involving a liquid phase in ordinary SHS powder mixtures to solidstate combustion after preliminary activation of these mixtures in an energyintensive planetary mill were studied for Ni + 13 wt. % Al and Ni + 45 wt. % Ti compositions. The dependences of the burning rate and temperature on the duration and conditions of mechanical activation were determined. It is found that the occurrence of solidstate SHS in a powdermixture is due to the formation of laminated composites, in which the reagents are ground to ultrafine size, the area of their contact increases severalfold, and the concentration of nonequilibrium defects is high. In activated samples, heat release proceeds in several stages and at lower temperature than in powder mixtures.  相似文献   

11.
Data on the mechanoactivation (MA) of SHS processes and systems obtained over the past 15 years are overviewed. Analysis of these data is used to formulate some recommendations for appropriate application of MA to SHS.   相似文献   

12.
The effect of mechanical activation conditions in a planetary ball mill on the main parameters of SHSprocesses and combustion product composition was studied for Ni + 13 wt. % Al and Ni + 45 wt. % Ti compositions. From results of experiments at elevated initial temperatures, it is concluded that because of reverse quenching, the defects produced by mechanical activation are not annealed in the heating zone and are retained in the sample until the beginning of chemical interaction in the leading zone of the SHS wave. The process of annealing of the activated samples was studied in situ on a transmission electron microscope and a synchrotron radiation diffractometer. The energy stored in the samples as a result of mechanical activation is estimated by calorimetric studies.  相似文献   

13.
化学反应系统热爆炸判据   总被引:4,自引:0,他引:4       下载免费PDF全文
应用摄动方法 ,研究了放热化学反应系统在发生失控 (即“热爆炸”)时 ,其化学动力学参数的临界值 ,在进行量纲 1化后 ,得到了热爆炸判据δcr的渐近分析公式 ,该公式给出了δcr随ε的变化 .  相似文献   

14.
Specific features of heating of a mechanically activated 3Ni + Al mixture during synthesis in the thermal explosion mode are considered. Based on the authors’ criterion of the minimum curvature of the heating rate logarithm as a function of inverse temperature, the activation energies of the synthesis process in the above-mentioned system are determined and the temperature intervals of the Arrhenius dependence and self-deceleration segments on thermograms are found. A kinetic function structure analysis shows that synthesis follows the laws of homogeneous kinetics with the reaction order close to unity. The calculated activation energies are anomalously low, as compared with conventional self-propagating high-temperature synthesis in this system.  相似文献   

15.
A model of phase-formation processes in the regime of a static thermal explosion of a powder mixture at temperatures higher than the melting point of the low-melting component is developed on the basis of the equilibrium diagram of state of a Ti-Al system. Numerical diagrams of the critical parameters of the system are constructed for different ratios of the original components. The dynamics of motion of the boundaries of phase homogeneity regions is calculated. For the ratio of the components in the mixture corresponding to the TiAl compound, the composition of the resultant product of the synthesis is demonstrated to depend on the conditions of heat transfer between the system and the ambient medium, which may offer a principal possibility of controlling phase-formation processes in the system mentioned.  相似文献   

16.
陶瓷基Al3+掺杂硅胶吸附剂材料的制备与性能   总被引:2,自引:2,他引:2  
陶瓷纤维纸经水玻璃、铝盐及其它添加剂顺次浸渍得到新型陶瓷基Al^3 掺杂硅胶吸附剂材料。探讨浸渍条件对材料吸附性能的影响;反应的优化条件为:水玻璃质量分数26.6%,铝盐质量分数为10%,反应温度60℃。由于铝替代硅进入硅胶网络,红外光谱显示Si-OH对称伸缩振动峰由968cm^-1移至Si(Al)-OH的954cm^-1;扫描电镜图表明Al^3 掺杂硅胶能较好地分布在陶瓷纤维表面及其孔隙中;X射线能谱(EDS)揭示材料表面微区Al^3 的存在与含量;多孔介质孔隙分析显示材料起吸附作用的主要为中孔。由于Al^3 掺杂,新型材料的吸附性能、耐热性能及机械强度等均优于同等条件下反应生成的硅胶。  相似文献   

17.
Ni/Ni3Al—TiC系梯度功能材料的热应力缓和特性设计   总被引:1,自引:0,他引:1  
沈强  张联盟 《硅酸盐通报》1997,16(2):34-36,40
本文选择Ni/NiAl-TiC体系的FGM,对其在制备过程中的残余絷应力进行了计算机有限元模拟。在综合考虑热应力最小,应力强度比值最小以及纯TiC侧应力状态等因素的基础上,完成了FGM体系的热应力缓和特性设计,得到组成分布指数P=1.6的最佳设计结果。  相似文献   

18.
选择粒径为15μm鳞片石墨(FG)和3μm Al2O3混杂导热填料,采用新型同向非对称双螺杆挤出机,当Al2O3质量分数为20%时,改变FG的质量分数,制备PP/FG/Al2O3导热复合材料,研究混沌混合加工对导热复合材料性能的影响。结果表明,随着FG含量的增加,导热复合材料的拉伸强度和弯曲强度均呈现先增大后减小的趋势,而断裂伸长率、冲击强度逐渐减小,弯曲弹性模量逐渐增大,加工流动性能变差。当FG质量分数为40%时,导热复合材料的拉伸强度和弯曲强度有最大值,分别为32.76,46.88 MPa;抵抗热变形能力和热稳定性能逐渐提高,热导率逐渐增大。当FG质量分数为50%时,维卡软化温度提高7.2℃,负载变形温度提高38.6℃,最大分解速率温度提高13.7℃,热导率是未填充FG的6.6倍、纯PP的7.9倍。制备的导热复合材料具有优异的力学、耐热、导热性能。  相似文献   

19.
This paper gives the results of temperature measurements at the beginning of fast decomposition of nine commercial azo dyes under heating. The enthalpies of formation of three azo dyes are measured, and the parameters of their explosive transformation are calculated. It is shown that for the flash temperatures obtained using the kinetic parameters of decomposition reactions and calculated heats of explosion of azo dyes, the average deviation from experimental values is 4.5%. __________ Translated from Fizika Goreniya i Vzryva, Vol. 44, No. 5, pp. 93–97, September–October, 2008.  相似文献   

20.
Layered double hydroxide (LDH) containing different metal constituents (Zn, Co, and Ni) was intercalated with different organic anions and has been used as fillers in low-density polyethylene (LDPE), and its thermal and flammability behavior was evaluated. The best thermal stability (∆T0.5 = 21 °C) was obtained with the LDPE-Ni/Al-dodecyl sulfate (4 wt %) nanocomposite. Addition of hydrophobic LDHs systematically decreases the enthalpy of melting and crystallization compared to the neat polymer. In LDPE-Co/Al-dodecyl sulfate (2 wt %) nanocomposite, the melting and crystallization enthalpies declined by about 45 J/g, indicating a good interaction of the filler with the polymer matrix. A reduction of 20% of the flammability for the LDPE-Ni/Al-stearate (4 wt %) nanocomposite was obtained. On the other hand, Zn–Co LDH as filler in LDPE nanocomposite did not affect effectively the same property. In an innovative study, results indicate that different metal constituents and interlayer anion of LDH as filler can change thermal and flammability properties of the polymer nanocomposite. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48737.  相似文献   

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