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71.
Asmita Kumari 《Journal of solid state chemistry》2007,180(7):2013-2019
New cubic-AGaSnS4 (A=Na, K, Rb, Cs, Tl) and orthorhombic-NaGaSnS4 compounds were synthesized by solid-state reactions and characterized by X-ray diffraction and diffuse reflectance spectroscopy. Single crystals of orthorhombic-Na1.263Ga1.263Sn0.737S4 were obtained in the crystal growth attempts of sodium compound. All six new compounds have orthorhombic AgGaGeS4 and cubic BaGa2S4 structures, as determined from single crystal X-ray structures of Na1.263Ga1.263Sn0.737S4 and cubic-AGaSnS4 (A=Na, K, Rb). Orthorhombic-NaGaSnS4 and known layered-KGaSnS4 undergo structural transformation to thermodynamically stable cubic form. 相似文献
72.
The growth rate of isotactic polypropylene is deduced from microscopic observations during isothermal crystallizations. A change in the growth regime is observed at 138 C and interpreted as a Regime III Regime II transition, according to Hoffman's kinetic theory of polymer crystallization. A Regime II Regime I transition is also theoretically predicted at 155 C, i. e. at a temperature outside the investigated temperature range. The Regime III Regime II transition is related to the positive to negative change in the spherulite birefringence, which is generally attributed to a change in the organization of crystalline lamellae: quadritic arrays of intercrossing lamellae atT
c < 138 C (Regime III) and preferentially radiating lamellae atT
c > 138 C (Regime II). It is suggested that such a morphological change could be interpreted using the concept of non-adjacent re-entry introduced in Hoffman's kinetic theory. This interpretation could also explain the interspherulitic ruptures observed in negative spherulites. 相似文献
73.
Elena Laukhina Vladislava Tkacheva Salavat Khasanov Leokadia Zorina Jordi Gómez-Segura Angel Pérez del Pino Jaume Veciana Vladimir Laukhin Concepció Rovira 《Chemphyschem》2006,7(4):920-923
Temperature has great impact on the structure and size of the linked crystallites of the conducting topmost layer formed at the surface of a polycarbonate film via the reaction BEDT-TTF+IBr [BEDT-TTF=bis(ethylenedithio)tetrathiafulvalene]. We show that fine temperature control permits formation of a semiconducting topmost layer of alpha'-(BEDT-TTF)(2)(I(x)Br(1-x))(3) crystallites with either micro- or nanometre size, a result that opens a route to miniaturized conducting plastic materials. 相似文献
74.
A thin film of manganese hexacyanoferrate (MnHCF) was electrochemically formed on a glassy carbon (GC) electrode to prepare a chemically modified electrode (CME). The mechanism of film formation of MnHCF and its growth process were investigated in detail by cyclic voltammetry. The results show that the stoichiometric composition of MnHCF is Mn^ⅢFe^Ⅲ(CN)6, an analogue of prussian yellow. There exist three clear-cut stages in the whole modification process and the last stage is indispensable to the fabrication of homogenized, stable MnHCF film and must last for an appropriate time. The surface morphology of MnHCF/GC electrode was characterized by scanning electron microscopy (SEM), which further verified the effective deposition of MnHCF film on GC. The kinetic constants of MnHCF/GC electrode process were also evaluated. The resulting MnHCF film modified electrode presented good stability and high electrocatalytic activity toward the oxidation of H2O2, indicating that MnHCF film possesses function of catalase and can be expected for analytical purposes. 相似文献
75.
In this work, Ba(NO3)2 crystals with single crystal face were induced by using the the method of bio-mimetic mineralization and double LB films of behenic acid (BA) as the template. The crystals were characterized by Scanning Electron Microscope (SEM) and X-Ray Diffraction (XRD). The crystals were observed in regular square shape with uniform size about 5~8 μm by SEM, and they were found by XRD to grow along the (111) plane. From these experiments, we can conclude that the good selection of the (111) crystal face of Ba(NO3)2 is due to the electrostatic interactions , the match between this crystal face and the definite lattice structure of the LB films. 相似文献
76.
在1000 ℃用活性炭把二氧化锡粉末还原成单质锡, 锡作为催化剂, 硅片作为硅源同时作为收集衬底, 在硅片上制备出了非晶SiO2纳米灯笼. 灯笼的一端连在硅片上, 另一端为一个锡球, 中间是一些圆弧状的SiO2纳米线把两端相连. 纳米灯笼具有良好的对称性. 利用扫描电子显微镜(SEM)、高分辨透射电子显微镜(HRTEM)、选区电子衍射(SAED) 和HRTEM自带的能谱分析仪(EDS)对样品的表面形貌、微观结构和成分进行了分析研究. 结果表明, 灯笼中SiO2纳米线为非晶态, 结点是晶态锡, 结点表面覆盖一层非晶态的硅的氧化物. 结合实验条件对纳米灯笼的生长机理进行了讨论, 提出了纳米灯笼生长的一个模型. 相似文献
77.
Timothy B. Hutson Ming J. W. Chang Joseph T. Keller David J. Long 《Mikrochimica acta》1988,94(1-6):339-341
Fourier transform infrared techniques were used to monitor mammalian cell growth plated on attenuated total reflection (ATR) crystals. Consistently, the growth kinetics plots generated from the obtained spectra demonstrated a sigmoidal curve representing a sequence of slow, rapid, then tapering cell growth which correlated well with non-spectral cell growth determinations. Significant advantages over traditional methods of measuring cell growth kinetics are demonstrated. The technique has promising potential to be used to study events in areas such as toxicology and cell biology. 相似文献
78.
H. Moon S. W. Kim J. Lee S. K. Rhee E. S. Choi H. A. Kang I. H. Kim S. I. Hong 《Applied biochemistry and biotechnology》2003,111(2):65-79
As a novel feeding strategy for aptomizing human epidermal growth factor (hEGF) production with a recombinant Hansenula polymorpha DL-1 using the methanol oxidase (MOX) promoter in H. polymorpha DL-1, independent exponential feeding of two substrates was used. A simple kinetic model considering the cell growth on two
substrates was established and used to calculate the respective feeding rates of glycerol and methanol. In the fedbatch culture
with methanol-only feeding, the optimal set point of specific growth rate on methanol was found to be 0.10 h−1. When the fed-batch cultures were conducted by the independent feeding of glycerol and methanol, the actual specific growth
rate on glycerol and methanol was slightly lower than the set point of specific growth rate. By the uncoupled feeding of glycerol
and methanol the volumetric productivity of hEGF increased from 6.4 to 8.0 mg/(L·h), compared with methanol-only feeding. 相似文献
79.
贫水电解质体系制备多孔阳极氧化铝模板的研究 总被引:3,自引:0,他引:3
在有机溶剂为主的含草酸电解质中,研究了大孔径有序度高的阳极氧化铝(AAO)的一步法电化学制备.实验证实,电解质中水含量的降低能够有效抑制铝的电氧化速率和溶解速率,使得其氧化膜孔道的生长能够稳定进行,所得到的六方孔道排列有序度明显高于纯水溶剂制备的电解质体系下的产物.考察了水含量、有机溶剂种类以及电解质浓度对AAO模板孔道形貌的影响.结果表明,有机溶剂贫水电解质体系使得电氧化电压的选取范围比水溶液电解质体系更宽,孔径连续可调,反应条件温和.该方法适合于制备均匀大孔径的AAO模板. 相似文献
80.
Mojumdar S. C. Kozánková J. Chocholoušek J. Majling J. Fábryová D. 《Journal of Thermal Analysis and Calorimetry》2004,78(1):73-82
Fluoroapatite containing glass-ceramics were prepared from Li2O-CaO-CaF2-P2O5-SiO2 system. The glass was melted at 1480°C for 1 h. The object of observation was the preparing crystal phase of fluoroapatite
in amorphous glass matrix. The morphology of lithium disilicate glass-ceramics was studied by SEM. The crystal growth and
thermal properties of fluoroapatite were studied by X-ray diffraction and DTA. The more the content of P2O5, the more the presence of fluoroapatite particles. SEM investigation clearly indicated the phase separation and formation
of a primary crystalline phase of fluoroapatite in the studied glass-ceramics. DTA curves of the fluoroapatite samples exhibit
exothermic effects in the temperature range 337-694°C depending on the composition of the materials. The position of exothermic peak for lithium disilicate on DTA curves moves with increasing specific surfacetowards lower temperatures which points on its preferential surface crystallization. As far as physical qualities are concerned,
mainly color and gloss, the best qualities of all observed materials belong to glass-ceramics with 10% P2O5.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献