Measurements of the thermal conductivity of liquid R32, R124, R125, and R141b

This paper reports measurements of the thermal conductivity of refrigerants R32, R124, R125, and R141b in the liquid phase. The measurements, covering a temperature range from 253 to 334 K and pressure up to 20 MPa, have been performed in a transient hotwire instrument employing two anodized tantalum wires. The uncertainty of the present thermal-conductivity data is estimated to be ±0.5%. The experimental data have been represented by polynomial functions of temperature and pressure for the purposes of interpolation. A comparison with other recent measurements is also included.     

碳纳米管/聚丙烯腈基复合材料的热导率研究

采用原位聚合法制备了碳纳米管/聚丙烯腈(CNT/PAN)复合材料,用MDSC的测试方法研究了复合材料的热性能,并由此推导了复合材料的热导率.应用Cheng-Vachon、Nielsen-Lewis和Okamoto-Ishida 3种导热理论模型对CNT/PAN复合材料的热导率进行估算.对比实验测试与导热理论模型的计算结果,考虑到碳纳米管在聚合物基体中的分散和取向情况,得出Nielsen-Lewis理论在低填充含量及室温条件下可以较准确地估算无规分散的CNT/PAN复合材料体系的热导率.     

冷轧辊的硬度和残余应力在回火过程中的变化规律

本文利用x射线分析法和大截面试样的逐次剥层法研究了冷轧辊在低温回火中残余应力与硬度的变化规律,以及淬硬层与试样尺寸对回火应力松弛的影响。找到了冷轧辊淬火后的合理回火工艺制度。     

单向纤维复合材料导热性预测

本文利用均匀化方法预测复合材料导热性。采用这一方法给出了单向纤维复合材料沿纤维方向的导热性表达式;将该方法与有限元技术结合得到了在垂直于纤维方向上复合材料导热性数值形式的预测结果。根据这些结果我们用曲线形式给出了材料导热性同各组分体分比间的关系,分析了体分比、纤维截面形状和分布方式、纤维和基体间的相对导热系数等因素对材料整体导热性影响。注意到纤维分布的随机性,本文还研究了纤维相对位置对材料导热性的影响,指出相对位置的变化可导致材料的各向异性导热性。本文指出基体相导热性对材料整体导热性的影响比纤维相的影响更重要。和已有的理论和实验结果的比较说明,本文提出的方法是很有效的。      

Study of Physical Properties of SiCw/Al Composites During Unloaded Thermal Cycling

The thermal expansion coefficient of SiCw/Al composites squeeze cast during unloaded thermal cycling was determined and analyzed. The study had shown that the thermal expansion coefficient of SiCw/Al composites reduced greatly with temperature raising. The thermal expansion coefficient of artificial ageing treatment SiCw/Al composites during unloaded thermal cycling reduced gradually, while the thermal expansion coefficient of squeezing SiCw/Al composites increased gradually. In addition, the thermal expansion coefficient of SiCw/Al composites reduced drastically with fiber fraction increasing.     

DCJTB掺杂的荧光型白光有机电致发光器件

本文基于为ITO/2-TNATA(20 nm)/NPB(30 nm)/BePP2:DCJTB(45 nm:X%)/Alq3(30 nm)/LiF(1 nm)/Al(100 nm)的白光器件结构(X为DCJTB的掺杂浓度(质量分数))。采用真空热蒸镀的方法,在高精度膜厚测控仪的监控下分别制备了发光层掺杂浓度为1,1.5,2.0,2.5,3.0不同器件,并对各器件性能进行了测试。实验结果表明:当DCJTB的掺杂浓度为2.0%时,平衡了器件中电子和空穴的传输能力,使载流子复合形成激子的几率增加,既使载流子的传输能力明显改善,并且有效地抑制了器件的荧光猝灭效应。在12 V电压下,可以获得发光亮度最高达到9 868cd/m2,发光效率大于7.2 cd/A,且色坐标为(0.334,0.337)的较理想白光有机发光器件。     

聚酰亚胺薄膜气相沉积的研究进展

综述了气相沉积聚合设备、制备过程、影响因素、性能表征方法及近年来国内外的研究现状.气相沉积聚合聚酰亚胺薄膜相比于传统湿法成型具有纯度高、无溶剂、膜厚可控、致密均匀、可在复杂表面成型等优点.展望了气相沉积的应用以及今后的发展前景.     

水性丝印荧光油墨色彩再现研究

目的为了更好地研究加色法成像机理,改善红色水性荧光丝印油墨的荧光性能,进而对三色荧光油墨的呈色性能进行研究。方法通过改变不同红色荧光材料的含量研究红色水性荧光丝印油墨的荧光性能,接着在此基础上,得出红、绿、蓝三色荧光油墨的色域,比较不同呈色方式对三色油墨荧光性能的影响,并探讨2种不同的承印物对三色油墨呈色性能的影响。结果当荧光粉质量分数为6%时,红色水性丝印荧光油墨的荧光强度最好。三色荧光油墨的色域范围比s RGB范围略小,可以满足色彩再现的研究需要。丝印时,网点并列比网点叠合更有利于荧光油墨彩色信息的真实再现。不含荧光剂的承印物有利于荧光油墨的色彩再现,纸张比pc膜色调再现能力好。结论最终制备的水性丝印荧光油墨具备优良的荧光性能,可以再现s RGB色域内的大部分色彩。     

Aeroelastic stability of heated functionally graded cylindrical shells containing fluid

The article is concerned with the analysis of panel flutter of heated circular clamped cylindrical shells made of functionally graded (FG) material, which are subject to a simultaneous action of the external supersonic gas flow and the internal flow of ideal compressible fluid. The effective properties of the material change throughout the thickness of the shell according to a power law and depend on temperature. The aerodynamic pressure is calculated based on the quasi-static aerodynamic theory. The behavior of the fluid is described in the framework of the potential theory. A mathematical formulation of the dynamic problem for elastic structure is developed based on the classical theory of shells and the principle of virtual displacements. Based on the results of numerical simulation the influence of different consistencies of the examined FG materials, thermal load, and internal flow velocity on the boundary of aeroelastic stability is analyzed.     

Transport properties of 1,1,1,2-tetrafluoroethane (R134a)

New equations for the thermal conductivity and the viscosity of R134a that are valid in a wide range of pressures and temperatures are presented. They were obtained through a theoretically based, critical evaluation of the available experimental data, which showed considerable inconsistencies between data sets, in particular in the vapor phase. In the critical region the observed enhancement in the thermal conductivity is well represented by a crossover model for the transport properties of fluids. Since thermodynamic properties enter into the calculation of the critical enhancement of the transport properties, a new fundamental equation for the critical region was developed also.Paper dedicated to Professor Joseph Kestin.