用微量热法测定稀土含硫有机配合物的比热容

推导了用改进的RD496-III型微热量计测定固态物质比热容的计算式. 用Joule 效应确定了仪器在298.15 K时的量热常数和相对标准偏差分别为(63.901±0.030) μV•mW^－1和0.08%, 用Peltier效应测定总不平衡热. 在该仪器上测定的两种标准物质(基准苯甲酸和α-Al₂O₃)比热容的计算值与文献值相差在0.4%以内. 用本法测定了13种固态配合物RE(PDC)₃(phen) (RE＝La, Pr, Nd, Sm～Lu; PDC＝ )的比热容值, 总偏差在1.0%, 与稀土原子序数Z_RE作图呈现“三分组现象”, 说明配合物中RE^3＋与配体间的化学键有一定程度的共价性, 显示了稀土离子4f电子云的扩大效应.     

大尺寸电阻加热式碳化硅晶体生长热场设计与优化

大尺寸低缺陷碳化硅(SiC)单晶体是功率器件和射频(RF)器件的重要基础材料,物理气相传输(physical vapor transport, PVT)法是目前生长大尺寸SiC单晶体的主要方法。获得大尺寸高品质晶体的核心是通过调节组分、温度、压力实现气相组分在晶体生长界面均匀定向结晶,同时尽可能减小晶体的热应力。本文对电阻加热式8英寸(1英寸=2.54 cm)碳化硅大尺寸晶体生长系统展开热场设计研究。首先建立描述碳化硅原料受热分解热质输运及其多孔结构演变、系统热输运的物理和数学模型,进而使用数值模拟方法研究加热器位置、加热器功率和辐射孔径对温度分布的影响及其规律,并优化热场结构。数值模拟结果显示,通过优化散热孔形状、保温棉的结构等设计参数,电阻加热式大尺寸晶体生长系统在晶锭厚度变化、多孔介质原料消耗的情况下均能达到较低的晶体横向温度梯度和较高的纵向温度梯度。     

La掺杂TiO2薄膜的制备及其光电流研究

采用溶胶凝胶-浸渍提拉法在ITO导电玻璃表面制备了纯TiO2薄膜和La掺杂TiO2薄膜,对其进行350℃、450℃、550℃保温2h热处理.利用XRD、SEM、EDS、XPS对样品结构、形貌、成分进行表征,利用电化学工作站对薄膜进行光电流测试,研究了La掺杂以及不同热处理温度对TiO2薄膜结构及光电流的影响.结果表明:La掺杂有细化TiO2晶粒和抑制锐钛矿相向金红石相转变的作用.随热处理温度提高,纯TiO2薄膜与La掺杂TiO2薄膜光电流密度均先增大后减小,450℃热处理后纯Ti02薄膜光电流密度为180 μA·cm-2,此温度下La掺杂TiO2薄膜光电流密度为650 μA·cm-2,是纯TiO2薄膜的3.6倍.     

Smectic A-Nematic and Nematic-Isotropic Liquid Transitions in 8CB Liquid Crystal: Comparative Analysis

A differential heat flux calorimeter has been used to study the Smectic A-Nematic and Nematic-Isotropic Liquid transitions in 8CB liquid crystal. The Faktor and Hanks model under our working conditions enables us to distinguish first-order from second-order transitions by analysis of differential signal. The critical exponent values obtained justify the proportionality between Cp evolution and the normalized differential signal (differential signal divided by the scanning rate).     

热屏结构对泡生法蓝宝石单晶炉功率影响研究

蓝宝石晶体因优异的综合性能被广泛用于航空航天等高性能要求领域.泡生法是目前生产大直径蓝宝石单晶的主要方法,热场对生产工艺、产品质量和单晶炉功率具有重要影响;并将影响生产成本.本文对氧化锆及钼金属组合式热屏中氧化锆材料内置、外置及材料不同组合方式对泡生法蓝宝石单晶炉功率的影响进行研究,得到合理的热场结构;并与实际生产结果进行验证.结果表明:相比于传统的15层钼保温结构,加入氧化锆保温层会明显降低单晶炉能耗,其中氧化锆内置的热场结构对单晶炉能耗降低影响更为明显;随着氧化锆层由0增加至15层,单晶炉能耗显著降低,相比传统15层钼保温结构,15层氧化锆保温结构炉体功率降低了38;.     

Pr掺杂量对镨锆黄陶瓷颜料性能的影响

以氯氧化锆、正硅酸乙酯为主要原料,氧化镨作为着色剂,采用溶剂热法制备镨锆黄陶瓷颜料前驱体,经1050℃煅烧得到镨锆黄陶瓷颜料,考察镨掺杂量对该颜料呈色的影响.采用扫描电镜和X射线衍射仪对样品的显微结构进行分析,样品性能采用色度分析、粒度分析和紫外-可见光光谱分析仪测试.实验结果表明:相对于其它掺镨样品,当镨掺杂含量为0.15 g,样品的ZrSiO4结晶度较高且Pr4+固溶到ZrSiO4晶格中,颗粒尺寸分布较小且较均匀,使样品在400~480 nm对蓝紫光有非常强的吸收,样品呈现较纯正的黄色色调.     

Determination of the Heat Transfer Coefficient of Metal Oxide Based Water Nanofluids in a Laminar Flow Regime Using an Adaptive Neuro-Fuzzy Inference System

In order to enhance the thermal properties of turbine oil (TO), three different nanoparticles (CuO, Al₂O₃, and TiO₂) are loaded into the TO. To measure the thermal performance of nanoparticle-based TO nanofluids at laminar flow and under constant heat flux boundary conditions, an experimental setup was applied. The obtained data clearly demonstrate the positive effect of all nanoparticles on the heat transfer rate of TO. As the most important factor, the heat transfer coefficient of the abovementioned two-phase systems is increased upon increasing both the volume concentration and the flow rate. An adaptive neuro-fuzzy inference system (ANFIS) is applied for modeling the effect of critical parameters on the heat transfer coefficient of nanoparticle-TO based nanofluids numerically. The results are compared with experimental ones for training and test data. The results suggest that the developed model is valid enough and promising for predicting the extant of the heat transfer coefficient. R² and MSE values for all data were 0.990208751 and 108.1150734, respectively. Based on the results, it is obvious that our proposed modeling by ANFIS is efficient and valid, which can be expanded for more general states.     

Adsorption of Carbon Dioxide on Activated Carbon

The adsorption of CO2 on a raw activated carbon A and three modified activated carbon samples B, C, and D at temperatures ranging from 303 to 333 K and the thermodynamics of adsorption have been investigated using a vacuum adsorption apparatus in order to obtain more information about the effect of CO2 on removal of organic sulfur-containing compounds in industrial gases. The active ingredients impregnated in the carbon samples show significant influence on the adsorption for CO2 and its volumes adsorbed on modified carbon samples B, C, and D are all larger than that on the raw carbon sample A. On the other hand, the physical parameters such as surface area, pore volume, and micropore volume of carbon samples show no influence on the adsorbed amount of CO2. The Dubinin-Radushkevich (D-R) equation was the best model for fitting the adsorption data on carbon samples A and B, while the Preundlich equation was the best fit for the adsorption on carbon samples C and D. The isosteric heats of adsorption on carbon samples A, B, C, and D derived from the adsorption isotherms using the Clapeyron equation decreased slightly increasing surface loading. The heat of adsorption lay between 10.5 and 28.4 kJ/mol, with the carbon sample D having the highest value at all surface coverages that were studied. The observed entropy change associated with the adsorption for the carbon samples A, B, and C (above the surface coverage of 7 ml/g) was lower than the theoretical value for mobile adsorption. However, it was higher than the theoretical value for mobile adsorption but lower than the theoretical value for localized adsorption for carbon sample D.     

Ti-50.8at%Ni马氏体相变中的电磁特性

研究Ti-50.8at%Ni合金在马氏体-奥氏体相变温度附近的电磁性质.由M-H曲线分析了传导电子的顺磁性以及少量局域电子引起的铁磁性.在M-T曲线中，降温曲线在180K附近有突降，升温曲线在230K附近有突升.在电阻率测量中，降温和升温的ρ-T曲线也有类似的突变.升温过程的质量热容c_p曲线在230K附近出现了由奥氏体相变引起的跳跃.这些实验结果表明，样品的马氏体相变温度约 关键词： TiNi合金 电磁性质 马氏体-奥氏体相变 质量热容     

热处理对NiTi形状记忆合金冲蚀磨损性能的影响

采用自制浆罐式砂水冲蚀磨损试验装置研究了4种经不同条件热处理的NiTi合金与1Cr18Ni9Ti不锈钢的冲蚀磨损性能;采用XL-30型扫描电子显微镜观察试样的冲蚀磨损表面形貌;采用MH-6型显微硬度计测量NiTi合金硬度;采用自制拉伸装置测量NiTi合金的力学性能.结果表明:5种试样的冲蚀磨损量随着冲蚀时间、冲蚀速度、砂水比及砂粒度的增加而增大,4种NiTi合金的耐冲蚀性能相近,均明显优于1Cr18Ni9Ti不锈钢,其中试样NiTi-3和NiTi-1表现出较好的耐冲蚀性能;硬度并非NiTi合金冲蚀磨损性能的决定因素,超弹性和超塑性是NiTi合金具有较好耐冲蚀性的主要原因,热处理使得NiTi合金的超弹性变形量减小,但增加了NiTi合金的塑性变形量;合金丝磨损表面不同部位的磨损机理不同,中部为典型的变形磨损,侧面为微切削磨损,5种试样均表现为典型的韧性材料冲蚀磨损特征.