铅/钡摩尔比对铅酸钡陶瓷薄膜电阻率的影响

铅酸钡(BaPbO3)导电薄膜是目前最有潜力的锆钛酸铅(lead zirconate titanate,PZT)铁电器件底电极替代材料之一.用溶胶-凝胶法在氧化铝(Al2O3)基片上旋涂成型BaPbO3薄膜.由于氧化铅(PbO)的高温挥发性,因此有必要研究薄膜中的铅/钡摩尔比与薄膜电阻率之间的关系.实验比较了常规热处理(conventional thermal annealing,CTA)和快速热处理(rapid thermal annealing,RTA)方式,用X射线衍射和能量散射X射线能谱研究了热处理方式和热处理制度对薄膜方阻的影响,分别得到了CTA和RTA热处理条件下BaPbO3薄膜的最低方阻性能,与CTA热处理相比,RTA热处理技术需要更高的热处理温度,因此,CTA热处理技术更为适合BaPbO3薄膜的合成.     

Thermal response characteristics of fire blanket materials

The thermal response characteristics of over 50 relatively thin (0.15–3.7 mm) fire blanket materials from four different fiber groups (aramid, fiberglass, amorphous silica, and pre‐oxidized carbon) and their composites have been investigated. A plain or coated fabric sample was subjected to a predominantly convective or radiant heat flux (up to 84 kW/m²) using a Meker burner and a cone heater, respectively. In addition to conventional thermal protective performance ratings for protective clothing, two transient thermal response times (for the fabric back‐side temperature to reach 300 °C and for the through‐the‐fabric heat flux to reach 13 kW/m²) and a steady‐state heat‐blocking efficiency (HBE) were introduced for both convective and radiant heat sources. For most woven fabrics, the HBE values were approximately 70 ± 10% for both convection and radiation and only mildly increased with the fabric thickness or the incident heat flux. Nonwoven (felt) fabrics with low thermal conductivity exhibited significantly better insulation (up to 87%) against convective heat. Highly reflective aluminized materials exhibited exceptionally high HBE values (up to 98%) for radiation, whereas carbon and charred aramid fabrics showed lower HBEs (down to 50%) because of efficient radiation absorption. A relatively thin fire blanket operating at high temperatures can efficiently block heat from a convective source by radiative emission (enhanced by its T⁴‐dependence and high surface emissivity) coupled with thermal insulation and from a radiant heat source by surface reflection while the aluminum surface layer remains. Copyright © 2013 John Wiley & Sons, Ltd.     

Heat treatment of thin carbon films and the effect on residual stress, modulus, thermal expansion and microstructure

Thin carbon films are used to hermetically seal and improve the performance of devices exposed to extreme conditions. Such films, which are deposited by chemical vapor deposition, develop residual thermal stresses due to a mismatch in the coefficient of thermal expansion between the film and substrate. Residual stresses reduce the adhesion of the film, and are a common cause of coating failure. This work investigates heat treatment as a potential technique to reduce residual stresses in thin carbon films. The magnitude of the residual stress has been challenging to measure due to the associated size scales and mechanical properties. In this study, experimental measurements of mechanical properties and residual stresses in thin carbon films are performed using nanoindentation and Raman spectroscopy. The results relate surface residual stresses to film thickness and heat treatment temperature. The approach presented in this study is a nondestructive and non-intrusive method for measuring residual surface stress and properties in thin films, and is ideal for small or curved-surface specimens such as optical fibers and other photonic devices.     

Interface Contributions to Localized Heating of Dielectric Thin Films

Measurements of the thermal conductivity of thin dielectric films in the last ten years have established that thin film thermal conductivity may be much lower than that of the corresponding bulk solid, by as much as two orders of magnitude, and that significant interfacial thermal resistance may be present along the film/substrate interface. We review such measurements of thin film thermal conductivity and interfacial thermal resistance, and use the heat conduction equation to determine their implications for the localized heating of thermally anisotropic thin films bonded to substrates. It is found that for surface heating an equivalent isotropic film can be established and that the presence of large interfacial thermal resistance leads to a strong dependence of film thermal conductivity on film thickness, especially for thin films. A microscopic model of the film/substrate interface is used to establish the dependence of the interfacial thermal resistance on porosity along the interface.     

热等离子体雾态气化制备薄膜技术

热等离子体雾态气化制备薄膜技术(mist plasma evaporation, MPE)以液态源物质溶液为先体,采用超声雾化将先体溶液雾化为细小液滴,用载气将雾化液滴输运到射频感应热等离子体中,利用热等离子体的超高温,将液滴中的源物质彻底气化和分解为其组分粒子,通过气相输运,最终在基片上沉积薄膜.MPE制备薄膜技术采用单一先体溶液,源物质来源广泛,沉积速率快,不需后续热处理.本文介绍了MPE制备薄膜技术原理及工艺,综述了近年来在制备薄膜方面的研究进展.     

AlN薄膜的研究进展

AlN薄膜是宽带隙绝缘材料,在热、电、光和机械等方面具有非常良好的综合性能。本文对近些年来AlN薄膜的制备方法和性能研究作了简要的回顾介绍,阐述了AlN薄膜的应用现状及前景。     

Glass Coatings Based on Electric Precipitator Dust

Compositions based on electric precipitator dust are developed for producing thin films on sheet glass with heat-shielding and decorative properties. A method for conversion of the pigment in the form of solid waste into a solution is developed. The obtained films absorb 39 – 25% thermal radiation in the IR spectrum range.     

界面接触热阻的研究进展

界面接触热阻（TCR）是电子器件冷却、低温超导薄膜等领域研究中的一个热点。综合评述了对接触热阻的传热机理的研究方法、测量方法以及减小接触热阻的主要措施,介绍了近年来国内外对接触热阻的最新研究成果和进展,现有的研究表明：对于界面接触热阻这一特殊物理问题,其理论研究既要从宏观上定量分析又要在微观上综合考虑声子、电子的散射、辐射等机理;在实验方面,目前的测量精度不够高,实验测量工作有待进一步地完善;在减小接触热阻方面,除了常用的方法外,可以通过在接触表面生长新型的高性能导热材料（碳纳米管等）来实现。对已报道的研究工作进行了总结,指出了今后的研究方向。     

Thermal ageing of electrical conductivity in carbon nanotube/polyaniline composite films

The influence of carbon nanotubes on the thermal ageing effect of the electrical conductivity of composite thin films is presented. The composite thin films comprise carbon nanotube/polyaniline nanofibers. When subject to thermal treatment, the presence of nanotubes retards the loss of dopants from the polyaniline and enhances the thermal stability in electrical conductivity of the composite thin films. Specifically, an increase in temperature for the conductivity degradation and a significant reduction in the rate of the conductivity degradation of the composite thin films are observed. Upon prolonged heating, the composite thin films exhibit relative large conductivity at high nanotube content, while the polyaniline thin films become insulating.     

复合热源太阳能热泵热水系统性能模拟

提出了一种复合热源太阳能热泵热水系统,通过阀门切换,可以根据不同的天气状况改变运行模式,以空气和太阳辐射作为热源制取生活用水。针对设计的150 L热水系统建立了数学模型,对不同运行模式下的性能进行了计算机模拟分析,分析了太阳辐射强度及环境温度对系统性能的影响,并计算了系统的全年运行状况。从模拟结果可以看出,热泵串联集热器模式（HP+SC）比集热器串联热泵模式（SC+HP）耗时稍长,但COP更高,各月总热效率前者略高于后者。COP及总热效率均随太阳辐射强度及环境温度的升高而升高。在4～10月的晴朗天气下,应尽量优先采用集热器模式（SC）,仅在完全没有太阳辐射时才使用热泵模式（HP）。     

The heat pulse technique for measuring specific heat and thermal diffusivity applied to thin polymeric films

Summary A heat pulse technique has been developed and applied to thin polymeric films in order to obtain specific heat and thermal diffusivity data. This technique allows the determination of time dependence of thermal properties, and therefore information on molecular high speed processes may be available.     

Radiationresistance and thermal stability of nylon 6, acrylonitrile copolymer and polyester fabrics

The thermal stability and radiation resistance of three polymers Nylon 6, acrylonitrile copolymer and polyester were investigated. The polymer samples were irradiated by low rate fission neutrons from a ²⁵²Cf source. The polyester showed a higher heat and radiation resistance than the two other polymers. It has to be recommended herein that polyester is the most suitable fiber for the manufacture of products in which heat buildup is produced during application, or products where radiation and heat resistance are required.     

Thermal diffusivity of heteroepitaxial diamond films: Experimental setup and measurements

The thermal diffusivity of heteroepitaxial CVD diamond films grown on iridium buffer layers has been measured using a combined laser flash and converging thermal wave setup. Absolute values and anisotropy for a fiber-textured reference sample were in the range of former reports in the literature. The in-plane thermal conductivity for three heteroepitaxial samples grown on Ir/YSZ/Si(001) as deduced from the diffusivity measurements was around 20 W/cm K, similar to high purity large grain polycrystalline films. Laser flash measurements of the perpendicular diffusivity suggest that the defect rich first microns of the heteroepitaxial films represent a thermal series resistance which limits the perpendicular heat transport especially for thin films. For the parallel component of the diffusivity the contribution of this shunt resistance is negligible. The absolute values for the parallel component in the heteroepitaxial films with in-plane angular spread of the crystal lattice below 0.5° were discussed in the framework of the model proposed by Klemens for phonon scattering by grain boundaries. The present data indicate that the remaining defects in heteroepitaxial diamond films with low mosaic spread are significantly less detrimental for the heat transport than large angle grain boundaries. In addition we speculate that the exclusive deposition on the {100} growth sector may also reduce the influence of nitrogen in the gas phase on the heat transport properties.     

INTERACTION OF THERMAL RADIATION IN THE LAMINAR PIPE FLOW OF OPTICALLY THIN GASES

The influence of thermal radiation on laminar forced convection of a gray gas in a pipe flow is studied semi-analytically. The gas is considered as an absorbing-emitting medium and the thin gas model approximation is used to describe the radiative heat flux in the energy equation. Invoking the method of lines (MOL), the nonlinear boundary value problem is reduced to an initial value problem which is eventually solved by a standard Runge-Kutta integration scheme. Numerical results are presented graphically for a selected group of thermal parameters encompassing the thin gas behavior. Additionally, it is found that limiting cases namely: laminar plug flow and laminar parabolic flow, both in the absence of radiation define an envelope for the curves of bulk temperature and total Nusselt number describing the combined thermal process for a thin gas in laminar motion. In general, the comparisons reveal that these asymptotic solutions are valid when the entrance-to-wall temperature ratio is less than 2.     

Applicability analysis of mathematical models for the combustion characteristics in the pool fire

A pool fire characterized by high temperature and heat radiation, is a common accident in chemical industry. The important combustion characteristic parameters are the heat radiation flux, the burning rate, the flame height, etc., but the most significant one is the heat radiation flux. The calculation model of the pool fire has an important role to assess the accident. There are three types of widely used pool fire models, the Shokri and Beyler model, the Mudan model, and the point source model. The models are used to calculate the combustion parameters of three different kinds of oils in tanks of different scales. The predictions of three models are compared with the simulation results. The analysis shows that the point source model has a large error for pool fires with the diameter greater than 10 m and the thermal radiation flux smaller than 5 kW/m², and the model is more applicable to heavy crude pool fires. The scope of application of the Mudan model is broader, and this model ensures higher accuracy if the thermal radiation flux is smaller than 5 kW/m². The Shokri and Beyler model is more suitable for the case where the pool fire diameter is greater than 40 m and the thermal radiation flux is above 5 kW/m², and the results for the light crude pool fire based on this model are more reasonable.     

Nanocolumnar Preferentially Oriented PSZT Thin Films Deposited on Thermally Grown Silicon Dioxide

We report the first instance of deposition of preferentially oriented, nanocrystalline, and nanocolumnar strontium-doped lead zirconate titanate (PSZT) ferroelectric thin films directly on thermal silicon dioxide. No intermediate seed or activation layers were used between PSZT and silicon dioxide. The deposited thin films have been characterised using a combination of diffraction and microscopy techniques.     

Photoacoustic effect of piezoelectric ZnO thin films

This paper describes the photoacoustic (PA) effect of piezoelectric ZnO thin films. The one-dimensional theory of the PA-effect was derived. The relationships between PA-signals and modulation frequency, thin film properties such as piezoelectric coefficients, dielectric constant, specific heat and thermal conductivity coefficient were obtained. The experimental results on the PA-effect of sputter-deposited ZnO thin films exhibited good agreement with the theoretical analysis. The piezoelectric stress coefficients, e₃₃ and e₃₁, of some ZnO films were determined from the PA-signals, typical values of which are 0.82 C/m² and -0.43 C/m², respectively.     

Effects of radiation and heat source/sink on unsteady MHD boundary layer flow and heat transfer over a shrinking sheet with suction/injection

In this paper, an investigation is made to study the effects of radiation and heat source/sink on the unsteady boundary layer flow and heat transfer past a shrinking sheet with suction/injection. The flow is permeated by an externally applied magnetic field normal to the plane of flow. The self-similar equations corresponding to the velocity and temperature fields are obtained, and then solved numerically by finite difference method using quasilinearization technique. The study reveals that the momentum boundary layer thickness increases with increasing unsteadiness and decreases with magnetic field. The thermal boundary layer thickness decreases with Prandtl number, radiation parameter and heat sink parameter, but it increases with heat source parameter. Moreover, increasing unsteadiness, magnetic field strength, radiation and heat sink strength boost the heat transfer.     

Synchrotron radiation ablation of polymers having double bonds in their main chains

Polyacetylene (PA), poly(cis- and trans-1,4-butadiene)s (cis- and trans-PBs), and poly(p-phenylene vinylene) (PPV) were ablated by synchrotron radiation (SR), aiming to deposit thin, uniform films of each on a substrate. When PA was irradiated by SR, gaseous phenyl compounds were produced, and a thin amorphous film was deposited on the substrate, exhibiting no characteristics of PA. In the cases of PPV and trans-PB, the source materials were reproduced in the form of thin film on the substrate by SR ablation. When alkali halides, e.g. NaCl and KBr, were used as deposition substrates, PPV was deposited, in an ordered way, on their cleavage surfaces. However, the deposited film of trans-PB by SR ablation was non-crystalline, because it was produced as a copolymer by 1,4- and 1,2-addition polymerizations of ablated butadiene-based fragments. In comparison, thin films of these polymers were also prepared by thermally evaporating them in a vacuum. When trans-PB and PPV were thermally evaporated, thin films with chemically and structurally identical features to the source polymers were produced, respectively. In contrast, a deposited film from cis-PB by SR ablation consisted of carbon compounds, showing no sign of hydrocarbon compounds in it, while trans-PB was produced from cis-PB by thermal vapor deposition.     

Thin-film temperature sensor made from particle-filled polymer-derived ceramics pyrolyzed in vacuum

Thin-film sensors have wide applications in the fields of high-temperature measurement, such as in the hot section of aero engines. Polymer-derived ceramics (PDCs) are diversified, ease to shape, and resistant to thermal shock. However, they are seldom used as sensitive parts of thin-film sensors due to the oxidation of PDC thin films. To solve this challenging problem, pyrolysis of PDC thin films in vacuum is proposed in this work, and the anti-oxidation performances are verified in a high-temperature sensor based on such a PDC thin film. The temperature measurement experiment shows that the PDC thin-film temperature sensor with thickness of about 10 µm pyrolyzed in vacuum can measure temperature from room temperature to 800 ℃, which provides a feasible way for fabrication of high-temperature PDC thin-film sensors such as heat flux sensors and strain sensors.