Advanced Materials Research Vols. 295-297

Abstract: The properties of a silicone-based elastomeric thermal pad filled with inexpensive ceramic additives were studied in this research. The effects of the content, particle size and mixing ratio of two additives upon the thermal and di-electrical property of the thermal pad are investigated. The result shows that the higher the content, the higher the thermal and dielectric properties are. In addition, the thermal conductivity of two particles filled thermal pads are higher than that of a single particle filled thermal pad. The thermal conductivity of the two kind of particle sizes (14 and 2 um) of 60 % (vol.) SiC filled thermal pad is the highest (2.14 W/m·K).

Abstract: Single crystalline Cd(OH)2 low-dimensional nanostructures, such as nanowires, nanobelts, and nanorolls have been controlled synthesized through a convenient, low-temperature hydrothermal method. Moreover, the shape and diameter of 1D Cd(OH)2 nanostructures can be facilely controlled through adjusting the experiment factors. The influences of the ammonia concentration, temperature on the morphology of Cd(OH)2 are investigated, and a possible mechanism involved adjustable growth properties from kinetic growth stage to thermodynamic growth stage has been discussed. This work has also provided a general, simple, and effective method to control the shape of other transition-metal carbonate.

Abstract: Silicon dioxide-based nanocomposites offer large loading capacity for various doping chemicals or molecular complexes, high surface to volume ratio and customizable surface chemistry for the creation and development of novel sensors and devices [1-2]. When compared with other sol-gel materials, xerogels represent a class of nanocomposites that are relatively easy to fabricate but with unique thermal, acoustic, optical and mechanical properties for rapid sensor or device prototyping development [3-4]. Xerogels in solids are formed by controlled evaporation of the liquid in the hydro-gel. Their porosity and morphology depend largely on the temperature, gel chemical compositions and pH in the fabrication process. When impregnated with fluorescent compounds in their nanosize cavities, the doped xerogels exhibit strong and stable fluorescence properties that are useful for the developing of ion-exchange sensors and optical devices. However, the use of these fluorescently doped xerogels in forensic applications was still largely unexplored.

Abstract: Since rapid development of wireless network technologies and individuals and enterprises’ urgent demands on application of wireless network, the use of wireless network has been spread rapidly and it is becoming more close to our life. It’s very essential for us to correctly understand and evaluate the characters and performance of wireless network by correctly understanding and studying the errors, using network analog software to simulate the error environment. This paper gives theoretical analyses and discussions to the IEEE 802.11 Protocol wireless networks on the basis of the simulator Tool –NS.

Abstract: This study is mainly to investigate the early age cracking due to the addition of silica fume (SF) into concrete and to propose Densified Mixture Design Algorithm (DMDA) method as a trouble-shooting strategy. Specimens with different water-to-binder ratio (W/B) and silica fume content were prepared with ACI concrete (W/B = 0.23, 0.35 and 0.47; SF content = 0%, 10%, 20% and 30%) and DMDA concrete (W/B = 0.23, 0.35 and 0.47; coating paste thickness t = 5, 15 and 25 μm). Adding silica fume to the concrete system to replace part of cement may increase the crack intensity, and the rate of water absorption; but reduce the heat of hydration. DMDA method as a problem-shooting technique shows to have a better performance in reducing the crack intensities up to 41% with W/B = 0.23 and the better durability index than that of ACI method.

Abstract: This thesis presents and summarizes the theory of multi-domain feature mapping in details and provides a basis of the conversion from design domain features to cost domain feature. It studies the current cost modeling techniques based on cost feature, and describes the whole process of cost feature modeling. This thesis lays a foundation for cost estimation.

Abstract: The micro-PECM (Pulse Electrochemical Machining) combining synchronous ultrasonic vibration is proposed as a new technology for to solve the difficulty machining problems of conductive hard and tough materials. The feasibility of micro-PECM combining synchronous ultrasonic vibration is studied. The synchronous way is analyzed; the synchronous electrical circuit is designed and made. The synchronous electrochemical micro-machining system combining ultrasonical vibration are built and improved，which machining parameters can be adjusted in a wide ranges, and the synchronous target of the ultrasonical vibration with the voltage of micro-PECM can be realized. The micro-machining electrodes are manufactured in different sections and sizes by combined electrical discharge machining. The mechanism tests of micro-PECM are carried, which kentaniums （YBD151、YG8）and stainless steel are machined and the results are analyzed and discussed. Contrast with the single micro-USM, the micro-PECM combining ultrasonic vibration has high productivity, good machining accuracy and surface quality; furthermore, its cathode wastage is low. The micro-PECM combining synchronous ultrasonic vibration has the best machining precision and surface quality.

Abstract: Copper coated nano-SiO₂ composite particles were prepared by mechanical milling technology. The effects of milling time on morphology, granularity, component and microstructure of the composite particles were characterized by scanning electronic microscope, laser particle size analyzer, energy depressives spectrometer and transmission electron microscope, respectively. Results showed that dendrite composite particles change to the flaky, and then to spherical ones with the milling time increasing. The particle size decreases firstly and then increases with the milling time increasing. The n-SiO₂ particles disperse more homogeneously in the composite particles with the milling time increasing.

Abstract: Graphene/CdS-nanobelt nanocomposites were prepared using a simple mixing process of graphene with CdS nanobelts in distilled water at room temperature. Prior to the preparation of such nanomaterials, graphene was obtained using modified Hummers method and characterized by various measurement techniques. The measurement results demonstrate that graphite oxide in high-concentration hydrazine hydrate solution can be easily reduced into graphene under hydrothermal condition. The measurement results of nanocomposites show that the addition and mixing of CdS nanobelts has not affected on the structure of graphene.

Abstract: Fe-doped anatase TiO₂ nanobelts were prepared using layered titanate nanobelts as precursor by two-step hydrothermal process. Various measurement techniques were employed to investigate the morphology and structure of products. The results show that Fe-doped TiO₂ still remain nanobelt-like and structure as pure TiO₂ nanobelts. Fe-cations doped in TiO₂ nanobelts lead to the red-shift of the absorption edge of TiO₂ nanobelts. The visible-light photodegradation of Rhodamine B on the products exhibits that Fe-doped products with low Fe-content show higher photocatalytic activity than that of TiO₂ nanobelts or Fe-doped product with high Fe-content.