Kinetics Study of the Thermal Decomposition of Post-consumer Poly(Ethylene Terephthalate) in an Argon Atmosphere

The thermal decomposition of post-consumer samples of a carbonated water bottle made of poly(ethylene terephthalate), PC-PET, was examined by linear temperature programing under an argon atmosphere to determine its mass loss kinetics. A simple kinetic model, called the first order pseudo single-component model, was used. The total weight-loss of each sample assumed to be in two periods, with each period corresponding to a one step decomposition of the PC-PET to volatiles. Three methods for determining the kinetic parameters by thermal gravimetric analysis were examined: differential analysis at a constant heating rate (differential), temperatures of a given conversion at a number of heating rates (isoconversional), and the maximum rate at multiple heating rates (peak temperature). The latter two multiple heating rates methods results were comparable to each other but they were not in agreement with the results from the differential method. The results of the differential method were insensitive to the heating rate and consistent with kinetics data reported in the literature for PET.     

Relationship of nanostructure and thermo-chemical response/thermal ablation of carbon aerogels

In this work, the interfacial mass balance relations combined with the non-parametric kinetic (NPK) analysis results were used for evaluating the thermo-chemical ablation process and oxidation mechanism of carbon aerogels with various porous structure. It was found that the two-parameter model of Nomen–Sempereis was able to describe the kinetics of the oxidation reaction and to reveal the structure-dependent contribution of two main processes with chemical and physical nature. The porosity of the carbon aerogel, rather than the other microstructural features, was realized more effective on the rate of ablation.     

The thermophysical properties of low‐temperature Pb plasma

The thermophysical properties of low‐temperature Pb plasma are calculated at temperatures 10–100 kK and densities below 0.2 of the solid‐state value. The thermodynamic values (pressure and internal energy) and transport coefficients (electrical conductivity, thermal conductivity, and thermal power) are considered. The plasma composition and thermodynamic parameters are obtained within the chemical approach, namely by means of the solution of the corresponding system of the coupled mass action law equations. Atom ionization up to +4 is taken into consideration. The electronic transport coefficients are calculated within the relaxation time approximation. The results obtained by means of the present model are compared with the available data of other models and experiments.     

Quantum states in fabricating poly-Si films

The quantum states are presented in these processions of fabricating poly-Si films. Amorphous silicon films prepared by PECVD has been crystallized by conventional furnace annealing (FA) and rapid thermal annealing (RTA), respectively. It is found that the thin films grain size present quantum states with the increasing of the gas flow ratios of SiH₄, H₂ mixture, substrate temperatures, frequency power, annealing temperature and time.     

基于微拉曼光谱技术的氧化介孔硅热导率研究

利用基于有效介质理论的介孔硅传热机理,提出一个用于分析氧化介孔硅热导率的理论模型,对影响氧化介孔硅有效热导率的因素进行了理论分析,得出用于计算氧化介孔硅有效热导率的计算公式. 采用双槽电化学腐蚀法制备介孔硅,利用微拉曼光谱技术研究了氧化介孔硅热导率随所制备介孔硅孔隙率的变化规律,比较了经不同温度处理的氧化介孔硅的导热性能差异. 孔隙率为60%,73.4%和78.8%的所制备介孔硅经300℃氧化处理后,其热导率值为8.625W/(m·K),3.846W/(m·K)和1.817W/(m·K);孔隙率为73.4 关键词： 理论模型 氧化介孔硅 微拉曼光谱 有效热导率     

石墨烯封装单层二硫化钼的热稳定性研究

将单层二硫化钼用石墨烯进行封装,构造了石墨烯和二硫化钼的范德瓦耳斯异质结构,并且分别在氩气（Ar）和氢气（H₂）氛围下,详细研究了被封装的二硫化钼的热稳定性.结果表明：在氩气氛围中,石墨烯封装的二硫化钼在400–1000℃下一直保持稳定,而石墨烯和氧化硅上裸露的二硫化钼在1000℃时几乎全部分解;在氢气氛围中,石墨烯封装的二硫化钼在400–1000℃下一直稳定存在,而石墨烯和氧化硅上裸露的二硫化钼在800℃下已经完全分解.综上可得,在氩气和氢气的氛围下,被石墨烯封装的二硫化钼的热稳定性得到了显著的提高.该研究通过用石墨烯将单层的二硫化钼进行封装以提高其热稳定性,在未来以单层二硫化钼作为基础材料的电子器件中,可以保证其在高温下能够正常工作.该研究也为提高其他二维材料的热稳定性提供了一种可行的方法和思路.     

Influence of quantum degeneracy on the performance of a gas Stirling engine cycle

Based on the state equation of an ideal quantum gas, the regenerative loss of a Stirling engine cycle working with an ideal quantum gas is calculated. Thermal efficiency of the cycle is derived. Furthermore, under the condition of quantum degeneracy, several special thermal efficiencies are discussed. Ratios of thermal efficiencies versus the temperature ratio and volume ratio of the cycle are made. It is found that the thermal efficiency of the cycle not only depends on high and low temperatures but also on maximum and minimum volumes. In a classical gas state the thermal efficiency of the cycle is equal to that of the Carnot cycle. In an ideal quantum gas state the thermal efficiency of the cycle is smaller than that of the Carnot cycle. This will be significant for deeper understanding of the gas Stirling engine cycle.     

采用曲率传感器测量热透镜焦距

分析了用光栅型波前曲率传感器测量热透镜焦距的基本原理,针对高功率固体激光器的工作特点,结合实验现象推导了在热透镜效应较强时热透镜焦距变化的计算公式。对半导体二极管(LD)侧面泵浦的百W级Nd:YAG激光棒在泵浦电流为15~25 A时的热透镜焦距值进行了测量,讨论了可能存在的误差。实验现象和理论分析一致,测量的热透镜焦距值与理论值符合得较好。     

光学读出微梁阵列红外成像及性能分析

在构建的光学读出微梁阵列(焦平面阵列FPA)非制冷红外成像系统中，实现了无硅基底FPA置于空气中对人体的热成像. 通过FPA在不同真空度环境条件下的成像结果进行比较，分析了热导和系统噪声值随气压变化的关系，以及对系统成像性能的影响，并对气体分子热运动自由程大于空气传热层特征尺度时的气体热传导模型进行了修正分析和实验验证. 实验结果表明：FPA置于空气中时，气体分子撞击微梁引起的微梁反光板无序振动产生的光学读出噪声成为系统噪声的主要来源. 当真空度小于1Pa时，总热导和光学读出噪声值的变化都趋于平缓；当真空度小于10^-2Pa时，空气热导的影响可忽略，总热导降低到微梁感热像素的辐射极限，光学读出噪声也降低到一极小值. 实验结果与理论分析相符合. 关键词： 非制冷红外成像 光学读出 双材料微梁阵列 热导     

介观物理系统中的噪声

描述了介观物理系统中噪声的研究现况. 对热噪声和散粒噪声的物理起源做了详细介绍，热噪声是系统的能态占据数发生涨落引起的，而散粒噪声源于载流子传输的微粒特性. 还介绍了研究噪声的主要理论——散射理论，并给出了其在马鞍形半导体量子线和铁磁/绝缘体/半导体双异质结两种介观系统中的应用，指出了噪声研究的实际物理意义. 关键词： 介观物理 热噪声 散粒噪声 散射理论