Cai Hua Huang

Effect of Characteristic Size on the Effective Thermal Conductivity of Anodic Aluminum Oxide (AAO) Porous Thin Films

Based on the surface morphology, a model is presented to investigate the heat transfer in anodic aluminum oxide (AAO) porous thin films. The extra thermal resistance from the micropores will inevitably cause a change in thermal properties, which can be analyzed by the Fourier law. The effect of the characteristic size on the thermal conductivity is discussed in details by means of the theory of phenomenological model of phonon scattering. Considering the effects of porosity and the distribution of micropores reflected by parameter D, the function of the effective thermal conductivity of AAO porous thin films expressed by two independent variables, εp and D. The temperature field is simulated with the effective thermal conductivity and the result demonstrates a bigger temperature rise in AAO porous thin films.

Influence of Substrate Temperature on the Structural, Electrical and Optical Properties of Al-Doped ZnO Films by RF Magnetron Sputtering

Transparent conducting aluminum-doped zinc oxide (AZO) films have been prepared on soda-lime glass substrates by radio frequency magnetron sputtering using a high density ceramic target at different substrate temperatures. The structural, morphology, electrical, and optical properties of the AZO thin films were investigated by X-ray diffraction, scanning electron microscope, Hall measurement, and optical transmission spectroscopy, and which were strongly influenced by substrate temperatures. Films with better texture, higher transmission, lower resistivity and larger carrier concentration were obtained for the samples fabricated at higher substrate temperature. The AZO film with the lowest resistivity of 4.63×10−4 Ω.cm and an average optical transmission of 92% in the visible range was deposited on the substrate heated at 450 °C. The optical bandgap depends on the deposition condition, and was in the range of 3.35~3.59 eV.

Discussion on High-Quality Curriculum Construction of Welded Structure in Local Comprehensive Universities

The curriculum construction is a very important work leading to the excellent course. Welded Structure (including 40 class hours) is one of main and compulsory course for the major of Material Molding and Control Engineering in our university. It is very important and necessary to construct the course in time. Based on the project of High Quality Curriculum Construction for Welded Structure undertaken by the authors, this paper makes a discussion on the original ideas, goals and contents, strategies and measures of the project. Meanwhile, the course construction and reform of Welded Structure are introduced from following aspects, such as curriculum setting, teaching contents and methods, teaching staffs, teaching quality management and supervision, online teaching resource construction. The purpose of the paper is to provide beneficial references and experiences to facilitate the further curriculum construction and reform in higher school.

Research on Thermal Effect Caused by Absorbing Inclusion in Dielectric Irradiated by Pulse Laser

The thermal effect caused by absorbing inclusion irradiated by pulse laser is affected by size of inclusions, pulse duration, repetition interval and number of pulse laser. The temperature both in the center of inclusion and the interface between inclusion and dielectric increases firstly with the increase of the size of inclusion, then trends to a constant value when the size is over the critical radius. Pulse duration and repetition interval of pulse change the energy acumulation in inclusion then have influence on the peak temperature in the center and interface. The temperature fluctuates periodically but the overall assumes the trend of increase.

Colloidal Dispersion of High Solid Loading ZnO Powders with 2 wt% Al2O3 Stabilized with Polyelectrolyte

The high solid loading slurries with ZnO-Al2O3 powders stabilized with polyelectrolytes have been studied. The influence of Sodium poly(acrylate) (PA 30) on the fluidity and stablility of the slurries was investigated. Morphological features of ZnO-Al2O3 powders in suspension and fracture surface of green compact were observed using TEM and SEM. The slurries with pH 9 were prepared after milled using ZnO mixed powders and the PA 30 solution of pH 8. As 0.2 wt% PA 30 added, the lowest viscosity and the highest sediment were obtained. ZnO and Al2O3 particles had been homogeneous dispersed. The maximum density (66.7 %TD) of green compact was obtained.

The Temperature Field Caused by Sphere Inclusion in Dielectric Irradiated by Single Pulse Laser

The thermal effect arisen from absorbing inclusions is the main factor which causes the damage of optical materials or component irradiated by the longer pulse duration laser. The unsteady heat conduction depends markedly on both the thermal properties of inclusions and the parameters of laser. Based on the differential equation of heat conduction, the temperature distribution caused by single absorbing inclusion is solved by use of finite difference method. The effect of the laser intensity and the pulse duration on temperature field is analyzed in detail. The result demonstrates that the smaller size inclusion and the smaller pulse duration cause relative safe thermal effect, consequently, the less probability to be damaged by thermal effect.

Influence of Thickness on the Structural, Electrical and Optical Properties of Al-Doped ZnO Films Deposited by RF Magnetron Sputtering

Transparent conducting aluminum-doped zinc oxide (AZO) films with different film thickness had been prepared on soda-lime glass substrates by radio frequency magnetron sputtering using a high density ceramic target. The structural, morphology, electrical, and optical properties of the AZO thin films were investigated by X-ray diffraction, scanning electron microscope, Hall-effect measurement and optical transmission spectroscopy, which were strongly influenced by film thickness. With the film thickness increasing from 140 nm to 710 nm, the resistivity decreases from 9.78 × 103 to 3.23 × 103 Ω.cm and an average optical transmission decreases from 88% to 80% in the visible range and the optical bandgap decreases from 3.47 to 3.24 eV.

Orientation Control and Dielectric Properties of Ba0.6Sr0.4TiO3 Thin Films on Pt/Ti/SiO2/Si Substrates with PbO Seeding Layer

Ba0.6Sr0.4TiO3 (BST) thin films were fabricated by solgel technique on Pt/Ti/SiO2/Si substrate without and with PbO seeding layer from precursor solutions with different concentrations. The crystal structure, surface morphology, dielectric properties and leakage current density of BST thin films are investigated as functions of the concentration of PbO precursor solution. Its found that the growth orientation of BST thin films with PbO seeding layer can be modulated through adjusting the concentration of PbO precursor solution. BST thin film with PbO seeding layer from 0.05 M precursor solution shows the highest dielectric constant and tunability, which may be attributed to the high crystallization and amplitude of the polarization in high (100) preferred orientated films. The leakage current density of BST films increases with the increasing concentration of PbO precursor solution and agrees well with the space-charge-limited current mechanism at room temperature.

Thermal Effects Caused by Inclusions in Optical Films Irradiated by CW Laser

A steady thermal conduction model was presented to study the temperature field and thermal stress distribution in film irradiated by continuous wave laser. The thermal effects may arise from either the absorbing inclusions or the intrinsic absorption of film. Based on the plane thermal conduction assumption, the characteristics of damage resulted from local melting or evaporation and thermal stress were discussed. The damage region resulted from local melting or evaporation smaller than that from thermal stress. The circumferential stress σθ is the main cause accounting for the stress damage. The normal stress perpendicular to the interface between film and substrate is the direct cause of drum type damage. The characteristics of damage in unsteady thermal conduction caused by pulse laser can be analyzed qualitatively by means of this model.

Thermal Effects Induced by Absorbing Inclusions in Laser Optical Films

The thermal transportation caused by absorbing inclusions in optical films under the radiation of laser pulse is unsteady heat conduction. The temperature distribution in films is ununiform and time-dependent. Considering the small size of inclusions, the absorbing inclusions were treaded as dot-heat sources. Based on this assumption, the unsteady heat conduction model was brought out and the temperature distribution in films was figured out and discussed, the mechanism that the catastrophic damage may avoid with micro-damage or micro-deformation in films through the release of stress concentration is presented. By comparing the thermal effects caused respectively by single inclusion and assembling ones, the effect of inclusion size on thermal damage in films was discussed.