Papers by Keyword: Crystallization

Abstract: The crystallization kinetics of Cu47.5Zr47.5Al5 BMG was studied by differential scanning calorimetry (DSC) using the mode of continuous heating and isothermal annealing. It is found that Tg, Tx, and Tp, display a dependence on the heating rate in the case of continuous heating. The activation energies, Eg, Ex and Tp determined by the Kissinger method, yield 445, 264 and 285 kJ/mol, respectively. The local activation energy, E(x), was determined by the Doyle-Ozawa method, which gives the average activation energy 204 kJ/mol. On the other hand, the isothermal kinetics was modeled by the Johnson-Mehl-Avrami (JMA) equation, the Avrami exponent versus crystallization fraction was calculated at different temperatures. Details of nucleation and growth behaviors are discussed in terms of the local Avrami exponent and local activation energy during the isothermal crystallization. X-ray shows that the quenched BMG only includes the glass single phase. The BMG heated to 873 K has the precipitation of the body-center cubic (BCC) CuZr.

Abstract: Polypropene (PP)/graphite oxide (GO) nanocomposite was prepared via solution blending and studied by adopting polarized optical microscopy observations, X-ray diffraction analysis and differential scanning calorimetry analysis. It is found that GO acts as an effective heterogeneous nucleation agent. The addition of GO doesn’t change the crystalline structure of PP, but leads to the decrease of spherulite dimension. GO makes the temperature of the crystallization exothermic peak increase, the crystallization temperature range and the half width of the crystallization peak narrow.

Abstract: The effects of Amide type nucleating agents SX , talc and nucleating agents SX combination with talc on crystallization behavior of poly (L-lactic acid）(PLLA) were analyzed by means of Differential scanning calorimetry (DSC)．The results of non-isothermal crystallization showed that SX is an efficient nucleating agent. The crystallization peak temperature and degree of crystallization of PLLA sample with 0.6 wt% SX are both higher than that of PLLA sample with 4 wt% Talc，which proved that the nucleating ability of SX is stronger．Nucleating agent SX and talc combination has obvious coordination effects, the sample of PLLA/0.2 wt % SX + 4 wt % talc has the minimal crystallization undercooling temperature, the highest crystallization peak temperature and crystallinity. Isothermal crystallization kinetics of PLA showed that when the four nucleating agents added in are all with the Avrami exponent n between 2.1-2.5, crystallization tended to be heterogeneous nucleation. When the nucleating agents added in are 0.6 wt%, the crystallization time is greatly decreased to 0.75min. Meanwhile, the PLLA crystallinity could be significantly increased by adding SX nucleating agents; besides, with the decrease of the isothermal crystallization temperature, the half crystallization time of the PLLA/0.6 wt% SX sample was decreased.

Abstract: Fused quartz granules (d₅₀=19 μm) were used as raw material, and Gd₂O₃-Nd₂O₃ (1:1, in mass) was used as additive with dosages of 1% (in mass, similarly hereinafter), 2% and 3%. Fused quartz ceramic materials were fabricated in reduction atmosphere at 1300 °C, 1350 °C and 1400 °C for 1 h. The apparent porosity, bending strength and thermal expansion ratios of the samples were examined and the samples were further analysed by means of XRD and SEM. The results showed that the sample sintered at each temperature with 3% Gd₂O₃-Nd₂O₃ had the lowest apparent porosity, the highest bending strength and more compact microstructure. This indicated that 3% Gd₂O₃-Nd₂O₃ was helpful to sintering of fused quartz ceramic materials. The results of XRD and thermal expansion ratio analysis showed that 3% Gd₂O₃-Nd₂O₃ compound additive had better effect on inhibiting crystallization of the samples sintered at 1300 °C and 1350 °C, but had a little effect on inhibiting crystallization of the sample sintered at 1400 °C.

Abstract: Fused quartz granules (d₅₀=19 μm) were used as raw material, and Si₃N₄-Nd₂O3 (1:1, in mass) was used as additive with dosages of 1% (in mass, similarly hereinafter), 2% and 3%. Fused quartz ceramic materials were fabricated in reduction atmosphere at 1300 °C, 1350 °C and 1400 °C for 1 h. The apparent porosity, bending strength and thermal expansion ratios of the samples were studied and the samples were further analysed by means of XRD and SEM. The results showed that the sample sintered at each temperature with 3% Si₃N₄-Nd₂O₃ had the lowest apparent porosity, the highest bending strength and more compact microstructure. This indicated that 3% Si₃N₄-Nd₂O₃ was useful to the sintering of fused quartz ceramic materials. The results of XRD and thermal expansion ratio analysis showed that 3% Si₃N₄-Nd₂O₃ compound additive had better effect on inhibiting crystallization of the samples sintered at 1300 °C, 1350 °C and 1400 °C.

Abstract: Fused quartz granules (d₅₀=19 μm) were used as raw material, and Si₃N₄-Y₂O₃ (1:1, in mass) was used as additive with dosages of 1%, 2% and 3% (in mass). Fused quartz ceramic materials were fabricated in reduction atmosphere at 1300 °C, 1350 °C and 1400 °C for 1 h. The effect of Si₃N₄-Y₂O₃ on crystallization and sintering of the fused quartz ceramic materials were researched by measurements of apparent porosity, bending strength and thermal expansion rate (RT~1200 °C), and by the analyses of XRD and SEM. The results showed that the samples sintered at each temperature with 3% Si₃N₄-Y₂O₃ had the lowest apparent porosity, the highest bending strength and more compact microstructure. This indicated that 3% Si₃N₄-Y₂O₃ was conducive to sintering of fused quartz ceramic materials. The results of XRD and thermal expansion rate showed that addition of 3% Si₃N₄-Y₂O₃ compound had obvious effect on inhibiting crystallization of the samples sintered at various temperatures. It can be deduced that the Si3N4-Y2O3 compound plays the best role in inhibiting crystallization and facilitating sintering of fused quartz ceramic materials.

Abstract: Fused quartz granule (d₅₀=0.019 mm) was used as raw material, nano-ZnO (size<0.08 μm) was used as additive with dosages of 1% (in mass, similarly hereinafter), 2% and 3%. Fused quartz ceramic materials were fabricated in reduction atmosphere at 1300 °C, 1350 °C and 1400 °C for 1 h. Properties of samples were researched by measurements of apparent porosity, bending strength and thermal expansion rate, and analyzed by XRD and SEM. The results showed that additive nano-ZnO had excellent inhibiting effect on crystallization of fused quartz sintered at 1300 °C and 1350 °C. As dosages of nano-ZnO increased, thermal expansion rate, diffraction peak intensity and bending strength were improved, and microstructure of the samples became more compact. It can be deduced that for fused quartz ceramic materials, with add dosage of nano-ZnO increasing, the inhibiting effect on crystallization decline, but the facilitating effect on sintering enhance.

Abstract: A diacid monomer was prepared from trimellitic anhydride and aminobenzoic acid,and a novel poly(ester-imide) was synthesized through the diacid monomer and the 1, 4-butanediol.The structure and chemical resistance, intrinsic viscosity and thermal property and crystallization of the poly(ester -imide) were characterized by FT-IR spectra,various organic solvents,a capillary Ubbelohde viscometer,differental scanning calorimetry (DSC) and thermogravimetric analysis (TGA) and crystallization rate instrument.The results showed that the poly(ester-imide) has excellent chemical resistance and thermal property,its intrinsic viscosity is 0.46dL/g,it has high glass transition temperature (Tg) and relatively low melting temperature (Tm).Moreover,the novel poly(ester-imide) has obvious crystallization and excellent property to spin into fibers.

Abstract: A series of N-octadecylated polyethyleneimine (PEI18C) comblike polymers with different grafting ratios, through N-alkylation method, have been successfully prepared. The chemical structure and thermal behavior of PEI18C comblike polymers with different grafting ratios has been characterized by Fourier transformed infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). Experimental shows that C18 alkyl groups have been successfully grafted onto PEI backbones, and the thermal behavior of PEI18C comblike polymers with different grafting ratios exhibit the linear increment with the grafting ratio of alkyl groups. It can be attributed to the effect of the grafting density of alkyl side groups along PEI backbones. The detailed investigation and discussion is carried out from the viewpoint of side chain crystallization and molecular packing behaviors.

Abstract: This paper investigates a combination of Ni acetate solution induced crystallization and microwave induced crystallization of a-Si thin film. Ni acetate solution was coated over amorphous Si thin film for evenly spread of Ni metal source. The Ni inducing source was formed from Ni acetate powder dissolved in de-ionized water or ethanol. The crystallization using Ni acetate solution was a Ni-silicide mediated process, the same process used with Ni metal layer. Compared to Ni metal layer induced crystallization by conventional furnace annealing, it finds that the crystallization temperature was lowered to 450 °C and the time of crystallization was reduced. Using Ni acetate solution induced crystallization is propitious to big area crystallization. After the processing, the poly-Si grain size was found about 0.1-0.5μm. The crystallization of a-Si thin films was enhanced by applying microwaves and Ni acetate solution to the thin films. The technique that combines Ni solution induced crystallization with microwave annealing has potential applications in thin-film transistors (TFT’s) and solar cell.