复合铝热剂配方及其性能研究

为了改善铝热剂的点火和燃烧性能，采用均匀设计法对Al-Fe₃O₄、Al-Ba(NO₃)₂和Al-MnO₂进行配方优化设计，然后选用SPSS(statistical program for social sciences)软件进行二次回归分析，确定了一种铝热剂配方，并外掺占其质量25%的黏结剂,获得复合铝热剂。研究其燃烧性能，试验结果表明，该复合铝热剂点燃性能好，燃烧过程分成两个阶段，整个燃烧时间持续约140 s，最高燃烧温度达1 893.32 K，能够形成较好的高温纵火效果，30 g复合铝热剂能够可靠熔穿2 mm铝板。     

NC体系发射药烤燃点火的响应特性

选用制式的硝化棉(NC)体系发射药进行了烤燃试验,研究了NC体系发射药的配方组成对烤燃作用下的自点火温度和燃烧性能的影响。结果表明,NC体系发射药的配方组分对烤燃响应的自点火温度和燃烧性能影响明显,随着烤燃温度上升,NC体系发射药烤燃响应时经历了热分解—点火燃烧—冲破约束强度造成剧烈响应的过程。单基药中NC的自热反应和硝胺发射药中RDX的气相燃爆反应使得发射药迅速完成热分解到燃烧反应的转变,压力增长速度较快;单基药的自点火温度约为157.5 ℃,增加较低温度开始分解的NG和增塑剂TEGDN提前了发射药的自点火温度;发射药烤燃点火后,压力增长速率与发射药配方组成和弧厚有明显关系,与烤燃响应类型和冲击压力规律相符;增加弧厚对发射药烤燃作用下的热分解无影响,降低了点火后压力的上升速率,有利于降低发射药烤燃响应剧烈程度。     

电点火头发火过程的时间结构的研究

该文设计了一种测试电发火过程时间结构的测试方法和测试系统,该方法可以同时测试电发火过程中桥丝的升温时间和点火药的爆发延滞期,实验表明,KP,K1K和LTNR电点火头发火的时间参数与点火电流,通电时间和点火药的燃烧特性有关,影响发火时间的主要因素是点火药的燃烧特性。     

氧气含量对超音速火焰喷涂燃烧特性的影响

超音速火焰喷涂过程中,火焰特征对涂层的形成产生重要的影响,应用β-PDF(Probability DensityFunction)湍流燃烧模型对喷枪燃烧室的燃烧过程进行了数值模拟,研究了混合状态与燃烧状态之间的关系.研究表明,随着氮气含量的增加,燃气温度下降,燃烧的最高温度点向低混合分数靠近,温度梯度增大,最高理论燃烧温度从3417K下降到2000 K;燃烧过程中存在大量中间产物,随着氮气的增加,燃烧过程中大量的单质碳析出,燃烧过程向低温燃烧转化.随着氮气含量和燃油的增加,燃烧产物中CO2的含量在最高温度点附近出现最高点,H2O次之,最后生成CO,C的含量呈现逐步递增的趋势.     

钛合金叶片燃烧后冷却过程的三维热流耦合数值模拟

为了理解航空发动机钛火发生后叶片的冷却过程,采用有限元方法结合ROTOR37转子模型,分别对550℃阻燃钛合金(TF550钛合金)和600℃高温钛合金(TA29钛合金)燃烧后压气机通道内温度场、流场进行数值模拟研究。结果表明:相对马赫数对于压气机通道内叶片散热有一定的影响,其中叶尖燃烧区域在0.7~1的低马赫数区域散热能力最佳;相对于前缘燃烧区域,叶尖燃烧区域的冷却过程更为复杂,且冷却速率比前缘燃烧区域低一个数量级;在叶尖燃烧区域内,TF550钛合金和TA29钛合金的冷却温度差异比较显著,在1000~2500K温度区间内的差别最大,前者比后者低100K以上,在300~500K温度区间内前者比后者低30K以内;叶尖燃烧区域流场的温度畸变会增加喘振的剧烈程度,设计叶片时应充分考虑燃烧对喘振裕度的影响。     

K2MnAl11O19六铝酸盐催化剂的制备及其催化甲烷燃烧性能的研究

采用共沉淀法、溶胶-凝胶法和反相微乳液法制备六铝酸盐催化剂K2MnAl11O19,利用XRD、BET和TG-DTA技术及甲烷燃烧活性对催化剂进行了表征和活性验证。结果表明,3种方法所制备催化剂经1200℃焙烧4h后均可以形成完整的六铝酸盐晶型,同时都具有高的催化性能和高温稳定性,其中反相微乳液法制备的K2MnAl11O19催化剂具有较高的比表面积和甲烷催化燃烧活性,起燃温度T10%=458℃,至676℃(T90%)甲烷完全转化。     

多层硅材料微型燃烧器的组件装配、检测结构设计及性能评定

本文系《基于硅材料的微型气体涡轮机中微型燃烧器的设计和加工》之续篇,阐述了一种由7层硅片组成的微型燃烧器的组件装配,检测结构设计及其性能评定。用氢气作为燃料,成功地引燃了该燃烧器并使其保持持续稳定的燃烧。用微型K-type热电偶测试和评定了燃烧腔出口处的温度分布以及腔壁的温度。经实验证实,在特定的燃-气比率及流量的条件下,燃烧腔出口处的最高温度可达1700K,且排出的废气中残留氢气的含量甚微。     

K_2O对白榴石生成的影响

以钾长石、碳酸钾为主要原料,设计高、中、低3种不同钾含量的配方固相合成白榴石晶体,探讨K2O的含量对白榴石生成的影响。通过实验发现,适当地提高配方中K2O的含量对白榴石生成是有利的,但当配方中K2O远高于其在白榴石中的理论含量时,其在高温下完全熔融成玻璃熔态物质,没有白榴石晶体的生成;当K2O的含量为25.4%,在1250℃熔融保温60min,其热膨胀系数为20.74×10-6℃-1(30～700℃),平均晶粒尺寸为3μm。     

镁氢化和镁镍共晶反应对氢化燃烧合成产物储氢性能的影响

通过改变氢化燃烧合成Mg2Ni中镁氢化反应的保温时间,以及镁镍合成反应温度和合成保温时间,来研究镁氢化反应、镁镍燃烧合成反应对产物Mg2Ni储氢性能的影响。实验结果表明,镁氢化反应保温120min时,产物的首次吸氢动力学性能变差;合成温度的提高有利于吸氢量的提高（合成温度850K时,吸氢量最大可达3．36wt％）;保温时间的延长对于产物吸氢量的影响随合成温度的差异而表现不同。     

用液氮点代替氩三相点检定83.8058K～273.16K的铂电阻温度计

本文介绍了在检定83.8058K～273.16K温度范围铂电阻温度计时,用液氮点代替氩三相点的有关装置、检定方法和检定结果处理,以及用液氮点与用氩三相点检定结果的比较。     

MSP试验法评价Mo/PSZ系复合材料的强度特性(Ⅱ)

首先利用图像处理系统对Mo/PSZ系两相复合材料的微观组织进行了定量分析,然后在不同的实验温度下利用MSP试验法对该系复合材料的高温力学性能进行了测试,详细讨论了该系复合材料不同温度下的MSP强度与其组成,特别是与其对应的微观组织结构特征的关系.实验结果表明,不同温度下复合材料的MSP强度显示出不同的组织依存性,室温时呈W形状变化,在873K、1273K时分别在Mo分散组成和两相连续组成范围呈极大值,这种变化趋势依赖于复合材料所具有的微观组织结构.     

Crystallization behaviour of amorphous Zr1-xCox alloys with 0.20 ≤ x ≤ 0.41

The crystallization of melt-spun amorphous Zr_1-xCo_x alloys with 0.20 ≤ x ≤ 0.41 has been studied under both isothermal and non-isothermal conditions by use of DSC-technique. Up to three peaks were observed. The crystallization temperature varies with composition from 631 K for x = 0.20 to 746 K for x = 0.41. Isothermal annealing of x = 0.41 shows that the kinetics of the crystallization can be described by the Johnson-Mehl-Avrami equation with n ≈ 2.85 at lower annealing temperatures (712.5 – 725 K) while in the temperature range 725 K to 740 K n increases with increasing annealing temperature. The phases formed during the crystallization process have been identified by means of X-ray diffraction techniques and electron microscope studies. For compositions around x = 0.33 microcrystalline phases are formed upon crystallization.     

La(1−x)SrxCoO3 for thin film thermocouple applications

In this study, the LSCO (lanthanum strontium cobalt oxide) family has been investigated for thin film thermocouple applications. Thin films of La_(1−x)Sr_xCoO₃ (x=0.3,0.5,0.7) were prepared on sapphire substrates by pulsed laser deposition. The films were annealed at different temperatures in air and characterized for phase, composition and microstructure to determine their thermal stability. From the phase and composition analyses, it is clear that as the Sr content in LSCO increases, the thermal stability decreases. Among the three compositions studied, x=0.3 had the best phase and chemical stability, and microstructural properties. It was observed that La_0.7Sr_0.3CoO₃ possesses excellent phase, composition and microstructural stability up to 1273 K. Above 1273 K, however, LSCO decomposes resulting in the loss of cobalt and formation of individual oxide phases. Electrical resistivity and Seebeck coefficients were measured in situ as a function of temperature in air up to 1023 K. The electrical and Seebeck coefficient properties were found to be stable for all the three compositions up to 1023 K and studies indicated that electrical conduction occurs through a small polaron hopping mechanism. In conclusion, LSCO possessed good thermal stability in air up to 1273 K and exhibits excellent potential in thin film thermocouple applications.     

Drop Calorimetric Measurements on Binary Bi–In System

Measurements of integral enthalpies of mixing of Bi–In system have been taken at 767, 813 and 855 K by a drop calorimeter over the entire composition range. Bismuth was used as the base metal, and indium was dropped by motorized dropping device. Calibration of the calorimeter was done by dropping four pieces of α-Al₂O₃ at the drop temperatures. The measured enthalpies of mixing are plotted against indium composition and found exothermic in nature for all the compositions. The minimum enthalpies were observed in the range of compositions x_In?~?0.40–0.50. A slight temperature dependency of enthalpy was observed for each composition. The experimental data were used to determine the binary interaction parameters using Redlich–Kister polynomial at 767, 813 and 855 K.     

Gasless combustion-driven heating elements for materials experiments in space

The novel concept of using gasless combustible mixtures as heating elements for materials processing in space and in ground-based microgravity facilities is presented. The unique properties of metal-sulfur combustible compositions (i.e., high flame temperatures, low ignition temperatures, liquid combustion products, nonporous charges, and gasless reactions) make them ideally suited for such heating applications. Heating elements based on metal-sulfur combustion have an energy density more than order of magnitude greater than electrical batteries, can be easily integrated with processing samples, and can operate under high pressures and in different gaseous environments. Demonstration prototypes of the gasless combustion-driven furnaces have already demonstrated peak temperatures close to 2300 K and heating rates above 200 °C/s.     

Determination of the hydrogen isotopic compositions of organic materials and hydrous minerals using thermal combustion laser spectroscopy

Hydrogen isotopic compositions of hydrous minerals and organic materials were measured by combustion to water, followed by optical isotopic analysis of the water vapor by off-axis integrated cavity output spectroscopy. Hydrogen and oxygen isotopic compositions were calculated by numerical integration of the individual isotopologue concentrations measured by the optical spectrometer. Rapid oxygen isotope exchange occurs within the combustion reactor between water vapor and molecular oxygen so that only hydrogen isotope compositions may be determined. Over a wide range in sample sizes, precisions were ±3-4 per mil. This is comparable but worse than continuous flow-isotope ratio mass spectroscopy (CF-IRMS) methods owing to memory effects inherent in water vapor transfer. Nevertheless, the simplicity and reduced cost of this analysis compared to classical IRMS or CF-IRMS methods make this an attractive option to determine the hydrogen isotopic composition of organic materials where the utmost precision or small sample sizes are not needed.     

Determination of the thermal conductivity of xenon-helium mixtures at high temperatures by the shock-tube method

The thermal conductivity of gases at high temperatures has been measured by the shock-tube method, which is uniquely suited to measure thermal conductivities of gases at high temperatures above 2000 K. A consistent set of thermal-conductivity data over a wide range of temperatures has been obtained from optimum combinations of shock-tube experiments at high temperatures, previously published data at lower temperatures, and a theoretical correlation of the temperature dependence. In the present study, the thermal conductivity of xenon-helium mixtures has been determined at compositions of 10 and 30 mol% xenon over the temperature range from 300 to 4800 K. Even though there is a large difference between the thermal conductivity of pure xenon and that of helium, it is interesting that the dependences of the thermal conductivity of the mixture on temperature and composition are linear. The experimental results are in good agreement with the predicted values based on the corresponding-states principle and the mixing rule. From these experimental results, interpolating the corresponding-states correlation data, we represent the equation of xenon-helium gas mixtures for thermal conductivity in terms of temperature and composition.     

Gas pressure combustion sintering and hot isostatic pressing in the Ti-Si-C system

The processing of materials in the Ti-Si-C system produced by gas pressure combustion sintering (GPCS) and hot isostatic pressing (HIP) was studied. By variation of the raw material composition it was possible to produce different materials containing Ti₅Si₃, Ti₃SiC₂, TiSi₂, TiC, SiC and titanium. The different phase compositions of samples with the same reactants obtained by GPCS and HIP are due to the duration of each of the processes; in GPCS the equilibrium state was not achieved. The properties of the specimen are strongly related to their chemical behaviour during processing at high temperatures. Not all phases built up at the high temperatures during the GPCS and HIP processes are stable at lower temperatures, and some reactions occur during cooling, which influence densification, microstructure and properties of the bodies finally obtained.     

Vapour-liquid equilibria of the CH4ArCO system

Isothermal-isobaric vapour-liquid equilibrium compositions were determined for the CH₄ArCO system at temperatures of 123.4, 137.1, and 164.0 K and, where possible, at pressures of 10.00, 20.00, and 35.00 atm abs. At the above temperatures respectively none, one, and two of the components are supercritical. The equilibrium ratios calculated from the experimental data are found to depend strongly on temperature and pressure, whereas they depend very little on the composition. As a first approximation, the ternary phase diagram is found to be completely characterized by the constituent binary phase diagrams.     

研究延期药燃烧过程及规律的分段压制测试法

文章介绍了一种研究延期药燃烧过程及规律的新方法——分段压制测试法。首先，将延期药压制成长度不同的延期体，然后分别测试其延期时间，再逐点计算其燃速，最后拟合燃烧曲线并分析。对B-CuO延期药燃速的研究结果表明，用分段压制测试法可以清楚地反映延期药从点燃到燃烧结束时存在的几个燃烧阶段以及各段的燃烧规律。该方法对延期药配方设计、延期体结构设计、延期药的延期精度等方面的研究具有重要的意义。