Advanced Materials Research Vols. 148-149

Abstract: The possible source of die edge cracking for Flip Chip Ceramic Ball Grid Array (FC-CBGA) package due to thermal cycling have been investigated in this study. Finite Element Analysis (FEA) models were used to analyze the effect of underfill fillet geometry on interfacial stresses between die edge and the underfill fillet. The input parameters of FC-CBGA from industry was used for simulation and the properties of commercial underfill were extracted by using Thermal Mechanical Analyzer (TMA) and Dynamic Mechanical Analyzer (DMA). Die stress distribution for different fillet height were generated to depict variation of stress due thermal loading. The variation of tensile stress due different fillet height and width were discussed for parameters optimization.

Abstract: The paper expatiates the nano material application on the nonwoven field and we carry on antibacterial test to the nonwoven fabric. All of these show that nano technology combine with nonwoven industry will have a great potential for widening product application field and promoting product overall performance, will create huge economical, social benefit on nonwoven industry in the future.

Abstract: A microwave sintering method was used to prepare C3S from Ca(OH)2, SiO2 and MexOy. f-CaO assay, X-ray diffraction and SEM were used to characterize the sintered samples.The results indicated that ion oxides played a very important role in C3S formation in conventional sintering, the use of MexOy as an additive was so effective in promoting C3S formation. The experimental results showed that samples were heated at an electric heating temperature(1500°C) and then further sintered with microwave for 30~60 min, tricalcium silicate could be formed with kilogram step. The new burning technique can greatly increase the forming speed of tricalcium silicate, MnO2, CuO and Ni2O3 could enhance the microwave sintering.

Abstract: Nano-FexOy (including γ-Fe2O3, α-Fe2O3 and Fe3O4) particles were prepared by acetylacetonate iron [Fe(C5H7O2)3] thermal decomposition under air condition at low temperature. X-ray diffusion (XRD), transmission electron microscopy (TEM), electron diffraction pattern (EDP), and specific surface area were carried out to characterized these nanoparticles. The influencing factors of experiment were discussed and studied, and the results show that γ-Fe2O3, α-Fe2O3 and Fe3O4 in different morphology can be obtained respectively by controlling the experiment conditions. The primary particle of Fe3O4 is about 16 nm; the primary particle of γ- Fe2O3 is about 20 nm and arranges compact. The second nanoparticle of γ- Fe2O3 presents catenarian and has the tendency to form an close space.

Abstract: The nanoindentation test and geometry measurement have been conducted to evaluate the hardness and geometry changes of bonded Au ball bonds towards the changes of the selected wire bonding parameters namely bonding power, bonding time and bonding force. Three indentations were made on the bonded ball bonds to evaluate the variation of hardness properties with the location of indentation. It was noted that the increase of bonding or ultrasonic power will increase the hardness value for the indentations 1 and 3 located at the periphery of bonded ball bonds. The increase of bonding power also increased the deformation of bonded ball bonds. It was also shown that the increment of bonding time will increase the hardness value across the bonded ball bonds in almost even distribution. The application of the bonding force in the wire bonding process has the least effect on the hardness and geometry changes on the bonded ball bonds.

Abstract: To improve the performances of LiFePO4, a positive material in lithium battery, research on the influence of doping amount and doping form of carbon nanotubes (CNTS) on electrical resistivity, specific capacity, specific surface area and particle size distribution of LiFePO4 powder was conducted. The results indicated that, addition of CNTS significantly reduced the electrical resistivity no matter in pure LiFePO4 or LiFe0.98Mg0.02PO4; with same usage, coating of CNTS as carbon source performed better than mechanical grinding and mixing with LiFePO4. With the increase of CNTS content, a rising trend of both specific surface area (BET) and particle size (D50) in LiFePO4 powder was observed, but seeing a slight drop in discharge capacity under the rates of 0.2C and 0.5C. When the content of CNTS reached 3% (by mass) respectively through mechanical mixing and being added as carbon source, electrical resistivity of pure LiFePO4 dropped from over 105Ω•cm to 1868Ω•cm and 27Ω•cm accordingly, and that of LiFe0.98Mg0.02PO4 dropped from over 105Ω•cm to 4800Ω•cm.

Abstract: Electrospinning is a novel processing technique for the production of nanofiber non-woven materials and nanofiber non-woven materials have extremely high surface-to-mass (or volume) ratio and a porous structure .for the advantages of electrospun nanofiber non-woven materials, it can be used many filed. This review introduction the progress of electrospun nanofibers and summarize the application of electro spun nanofibers in the medical materials filed.

Abstract: NixZn1-xFe2O4 (x=0.4, 0.6) powders are synthesized by sol-gel technique. The X-ray diffraction (XRD) measurements show their polycrystalline spinel structural characteristics. Both XRD and Atomic Force Microscopy demonstrate the samples are nanosized. At room temperature typical soft magnetism is exhibited by the samples. The reflection attenuation resulting from microwave absorption would reach to 1.9 dBm over the frequency range 6 GHz - 10 GHz when the samples are paved on a 10 cm  10 cm square aluminum plate with a thickness of about 0.35 mm.

Abstract: Spherical C@PSt microspheres with average size around 2 μm were successfully prepared using high-speed homogenization-assisted suspension polymerization of styrene in the presence of carbon black modified by oleic acid. The effects of initiator varieties and initiators concentration on the fractional conversion were investigated. Compared with BPO, AIBN has higher efficiency to initiate the polymerization. LPSA, SEM and OM results showed the prepared microspheres had spherical morphology with the carbon black in the core and PSt in the shell. About 10 weight percentages of carbon black were encapsulated in the complex microspheres proved by TGA results.

Abstract: Under microwave radiation and using trimethyl chlorosilane as modifier, hydrophobic SiO2 aerogel was prepared through fractional hydrophobic modification and ambient pressure drying of the raw material, tetraethoxysilane (TEOS), in the process of sol-gel and acid-base catalysis. Hydrophilic SiO2 aerogels were also prepared using the microwave method and water bath heating method. The SiO2 aerogels prepared using the three methods, including their morphology and chemical composition, were analyzed and compared using scanning electron microscopy, Brunauer-Emmett-Teller analysis method, Fourier transform infrared spectroscopy, X-ray diffraction, and themogravimetric-differential scanning calorimetry. The results indicate that by adopting the microwave reaction, the specific surface area of the SiO2 aerogels was effectively increased and the structure of the internal nanoscale pores of petal-coated shape was found to exist under the dense external surface of the SiO2 aerogels. Thermal stability of the hydrophobic SiO2 aerogels prepared through fractional modification assisted by the microwave method was increased with the hydrophobic angle at153°, which showed super hydrophobicity.