Electrical and Mechanical Behavior of Aerosol Jet–Printed Gold on Alumina Substrate for High-Temperature Applications

There is a growing interest in the development of microelectronics that can perform reliably and robustly at temperatures above 300 °C. Such devices require stable thermal properties, low thermal drift, and thermal cycling resistance. Conventional hybrid circuit technology demonstrates high-temperature packages, but the high costs and lead time are significant drawbacks. In contrast, additive manufacturing processes, including aerosol jet printing (AJP), offer cost and time benefits, as well as 3D structures and embedded features. However, the properties and reliability of additive packaging materials at extreme temperatures are not well known. Herein, the reliability at temperatures up to 750 °C in terms of electrical performance and mechanical strength of aerosol jet printed gold thick films onto ceramic substrates are assessed. Thermal coefficient of resistance of printed gold films is measured. The electrical resistance stability and leakage current of printed gold structures are also characterized during over 100 h of aging at temperatures up to 750 °C. Finally, the mechanical adhesion strength of the printed gold films is evaluated after aging for 100 h at temperatures up to 750 °C. The adhesion of the printed gold to the ceramic substrates remains high after aging, very stable resistances and minimal leakage currents have been observed.     

Using Selective Electron Beam Melting to Enhance the High-Temperature Strength and Creep Resistance of NiAl–28Cr–6Mo In Situ Composites

By increasing the density of interfaces in NiAl–CrMo in situ composites, the mechanical properties can be significantly improved compared to conventionally cast material. The refined microstructure is achieved by manufacturing through electron beam powder bed fusion (PBF-EB). By varying the process parameters, an equiaxed or columnar cell morphology can be obtained, exhibiting a plate-like or an interconnected network of the (Cr,Mo) reinforcement phase which is embedded in a NiAl matrix. The microstructure of the different cell morphologies is investigated in detail using scanning electron microscope, transmission electron microscopy, and atom probe tomography. For both morphologies, the mechanical properties at elevated temperatures are analyzed by compression and creep experiments parallel and perpendicular to the building direction. In comparison to cast NiAl and NiAl–(Cr, Mo), the yield strength of the PBF-EB fabricated specimens is significantly improved at temperatures up to 1,027 °C. While the columnar morphology exhibits the best improved mechanical properties at high temperatures, the equiaxial morphology shows nearly ideal isotropic mechanical behavior, which is a substantial advantage over directionally solidified material.     

三相反应器的气含率与液速分布和数值模拟

研究了一定操作条件下的气液固三相鼓泡床反应器的气含率和液体轴向速度分布,讨论了气、液表观速度对气含率和液体轴向速度分布的影响,比较了三相与两相鼓泡床中气含率和液体轴向速度分布,用拟两相的双流体模型计算了三相鼓泡床中的气含率和液体轴向速度．结果表明,模拟结果与实验结果一致．     

High-temperature oxidation of Al-deposited stainless-steel foils

The oxidation resistance of Al-deposited Fe–Cr–Al foils containing small amounts of La and Ce was assessed by a cyclic oxidation test with temperature varying between room temperature and 1323 K to 1423 K in static air. (1) The Al content of Fe–Cr–Al–La, Ce foils can be increased by depositing an Al layer from the vapor phase. The deposition of a 1-m-thick Al layer on both sides of the 50-m-thick foil is equivalent to a 1.5 mass% increase in the Al content. The deposited Al diffuses into the foil during heat treatment. The uniform distribution of Al is obtained by heating at 1273 K for 18 ks. (2) After the initial transition stage the oxidation follows the parabolic law until breakaway sets in. The scale consists mainly of -Al₂O₃ during the parabolic period. (3) The increase in the Al content by more than 5 mass% by the Al-deposition remarkably improves high-temperature oxidation resistance (smaller parabolic rate constant and longer protection time). (4) The Al-deposited foils have better oxidation resistance than the conventional foils with the same contents of Al and rare-earth elements. This is attributable to the different nature of the initially formed oxide on the Al-deposited foil. (5) The so-called rare-earth element effect was also observed for the Al-deposited foils. Predominant diffusion of oxygen through the Al₂O₃ scale and vacancy-sink mechanism are applicable to the present results.     

高温水采暖系统内部氧腐蚀

对阜康冶炼厂高温水采暖系统内部产生氧腐蚀的原因进行分析，采取相应的措施，收到良好的效果     

Numerical analysis of magnetization AC losses in high-temperature superconducting slabs subjected to uniform strains

High-temperature superconductors in superconductor apparatuses are subjected to mechanical strains under operating conditions.These strains cause the degradation of the critical current densities and influence AC losses in the superconductors.Based on the dynamic process of thermomagnetic interaction,we report the results of numerical analysis of AC losses in an infinite high-temperature superconducting slab subjected to a uniform in-plane strain in an alternating external magnetic field parallel to the sample surface.The numerical analysis shows the details of electromagnetic phenomena in the slab and the dependences of AC loss on various external parameters including the uniform strain in the slab and the amplitude and frequency of the external magnetic field.In this paper,we find that whether the magnetic field fully penetrates the superconductor is the key factor that influences the features of AC loss.When the magnetic field cannot fully penetrate the superconductor,the loss rises with increasing strain or decreasing frequency.When the magnetic field can fully penetrate the superconductor,the feature is just opposite.We also analyze the effects of periodic strain on AC loss.It is interesting to find that when the periodic strain frequency equals the external magnetic field frequency,the AC loss reaches the maximum,regardless if the magnetic field fully penetrates the superconductor or not.     

900℃加热后热喷涂FeCrAl/AlSi复合涂层组织变化

为开发一种经济可靠的高温防护涂层,采用电弧喷涂方法在低碳钢表面制备FeCrAl/AlSi复合涂层,并对复合涂层试件进行900℃温度下的2400h加热,以考察其高温氧化表现和微观组织变化.实验结果表明：复合涂层中抗氧化元素的相互配合很好地保护了基体金属.900℃加热3h,防护涂层表面以及内部的氧化物以Al2O3为主,涂层/基体界面两侧形成Cr元素的扩散带.经过2400h加热后,复合涂层外表面氧化物层增厚,涂层/基体界面原位生成铬的氧化物,界面基体金属一侧存在约200μm宽的Cr元素扩散带.     

白光LED用荧光粉SrCaSiO_4:Eu~(2+)的制备及其光谱性能研究

采用高温固相法合成了SrCaSiO4:Eu,并研究了其光谱性能以及Eu的掺杂浓度对发射光谱强度的影响.研究表明,荧光粉SrCaSiO4:Eu2+的激发光谱位于250～400 nm的宽带,而发射光谱是主峰为500 nm的宽带,所以此荧光粉可以和紫外LED匹配,发射蓝绿光.SrCaSiO4:Eu中的激活剂Eu2+的猝灭浓度为0.5mol%.     

建筑用Q235钢在高温（火灾）条件下的力学性能研究

对建筑常用的Q235钢在火灾情况下的力学性能分析，获得了Q235钢在高温下的屈服强度、极限强度、弹性模量、伸长率等力学性能指标的变化规律，并在恒温加载和恒载加温两种试验下对Q235钢进行强度对比。     

凝析气藏油气水三相PVT相态特征测试及分析

常规凝析油气体系PVT相态测试方法忽略了气态凝析水对凝析油气体系相态的影响,而国内外凝析气藏开发实践表明,气态凝析水对凝析油气体系相态特征的影响不应被忽略.为了更有效地指导凝析气藏的开发,必须建立考虑气态凝析水的凝析油气体系PVT相态测试和计算方法.探索设计了富含气态凝析水的凝析油气体系PVT相态测试方法,并与常规凝析油-气两相平衡体系的PVT测试结果进行了对比,分析了考虑气态水组分的存在对凝析油气体系相态的影响.