Non-isothermal crystallization of MaterBi-Z/clay nanocomposites

Non-isothermal crystallization of MaterBi-Z (starch-polycaprolactone blend) and its nanocomposites with different clay contents (0, 2.5 and 5 mass%) was studied. The experimental data show that clay can be act both as nucleating or retarding agent depend on the clay content. Kinetic parameters obtained by using a non-linear regression method, i.e., Kamal’s model and Dietz’s modification, were able to describe the non-isothermal crystallization behavior of the studied materials. A full model that takes into account the induction and growth of the crystal during cooling under non-isothermal conditions was used to obtain a continuous cooling transformation diagrams.     

尼龙6/蒙脱土纳米复合材料非等温结晶动力学和透明性研究

将有机化的蒙脱土与尼龙6(PA6)在Haake共混机中共混,制备出尼龙6/蒙脱土纳米复合材料(PA6N);对尼龙6/蒙脱土纳米复合材料和纯尼龙6分别进行差示扫描量热法非等温结晶试验,以了解蒙脱土在尼龙6/蒙脱土纳米复合材料中的成核作用、扩大尼龙6在包装领域的应用范围.与此同时,采用偏光显微镜测定了样品的结晶形态;采用紫...     

Thermal stability of fluorochloroindate glasses

New fluorindate glass compositions have been investigated in order to improve optical transmission as well as thermal properties. Chloride inclusion extends transmission of a fluoride matrix to longer wavelength in infrared region. In the present work thermal parameters of an IZnBS composition, based on InF₃, ZnF₂, BaF₂ and SrF₂, with various amounts of alkaline chlorides were investigated by differential scanning calorimetry. The chloride presence decreased all characteristic temperatures and increased both thermal stability and glass forming ability up to 10% of MCl content, where M=Li, Na, K and Rb. The presence of NaCl promoted glass phase separation. For samples containing same concentration of NaCl, this effect is accentuated for increasing the contents of SrF₂. This revised version was published online in August 2006 with corrections to the Cover Date.     

不同Pr2O3含量硼铝硅酸盐玻璃析晶性能研究

采用高温熔融法制备了不同Pr2O3掺量的SiO2-B2O3-Al2O3-BaO玻璃,利用DTA,XRD,TEM以及IR等手段研究了稀土氧化物掺入量对玻璃热稳定性、析晶行为、玻璃结构的影响。结果表明：当稀土掺入量逐渐增加时,玻璃的热稳定性递减;在高于Tx的温度下进行热处理,玻璃析晶产物逐渐由PrAl2.03（B4O10）O0.54向PrBO3转变;Pr^3＋填充在[SiO4],[BO4]和[BO3]等结构单元组成的混合网络的空隙之中,网络中间离子Al^3＋随稀土氧化物的增加,发生从网络变性离子向网络形成离子的转变。     

Thermal crystallization studies on Ga−Te glasses

Semiconducting Ga_xTe_100?x (17≤x≤25) glasses have been prepared by melt quenching method and thermal crystallization studies carried out using differential scanning calorimetry. On heating, virgin Ga_xTe_100?x glasses exhibit one glass transition and two crystallization reactions. The first crystallization reaction corresponds to the precipitation of hexagonal Te and the second one to the crystallization of the matrix into zinc blende Ga₂Te₃ phase. If Ga_xTe_100?x glasses are quenched to ambient temperature fromT _crl and reheated, they exhibit the phenomenon of double glass transition.     

Phase diagram of V2O5-MoO3-Ag2O

Phase equilibria in the V₂O₅-Ag₂O system were investigated at a constant pressure of oxygen (0.2 atm) and the phase diagram found under these conditions was compared with the results of the authors who investigated the same system in vacuum and at an oxygen pressure of 1 atm. On the basis of all these results, an attempt was made to construct the hypothetical diagram of V₂O₅-Ag₂O-O₂.     

Non-isothermal crystallization of UHMWPE filled during polymerization with inorganic fillers

The non-isothermal crystallization of UHMWPE, filled with different inorganic fillers during the polymerization on the catalyst system TiCl₄/(C₂H₅)₂AlCl/(C₆H₅)₂Mg has been studied by DSC and polarization microscopy. The melting conditions of UHMWPE have been established before the crystallization experiments. It is shown that the fillers act as nucleating agents only when the crystallization is carried out from a melt, obtained at temperature above the flow temperature of UHMWPE, and at slow cooling rate. It was established that the efficiency of nucleation passes through maximum at 50 wt.% of the filler. It is assumed that this is due to the reduction of the heterogeneous sites, because of the aggregation of the filler with high concentration. The non-isothermal crystallization kinetics is studied by Harnisch and Muschik method. The Avrami exponents do not change in the presence of a filler with concentration up to 90 wt.%.     

Structural and Electrochemical Properties of Li2O-V2O5-B2O3-Bi2O3 Glass and Glass-Ceramic Cathodes for Lithium-Ion Batteries

In this study, 20Li₂O-60V₂O₅-(20 − x)B₂O₃-xBi₂O₃ (x = 5, 7.5, 10 mol%) glass materials have been prepared by the melt-quenching method, and the structure and morphology of the glass materials have been characterized by XRD, FTIR, Raman, and FE-SEM. The results show that the disordered network of the glass is mainly composed of structural motifs, such as VO₄, BO₃, BiO_3, and BiO₆. The electrochemical properties of the glass cathode material have been investigated by the galvanostatic charge-discharge method and cyclic voltammetry, and the results show that with the increases of Bi₂O₃ molar content, the amount of the VO₄ group increases, and the network structure of the glass becomes more stable. To further enhance the electrochemical properties, glass-ceramic materials have been obtained by heat treatment, and the effect of the heat treatment temperature on the structure and electrochemical properties of the glass has been studied. The results show that the initial discharge capacity of the glass-ceramic cathode obtained by heat treatment at 280 °C at a current density of 50 mA·g⁻¹ is 333.4 mAh·g⁻¹. In addition, after several cycles of charging and discharging at a high current density of 1000 mA·g⁻¹ and then 10 cycles at 50 mA·g⁻¹, its discharge capacity remains at approximately 300 mAh·g⁻¹ with a capacity retention rate of approximately 90.0%. The results indicate that a proper heat treatment temperature is crucial to improving the electrochemical properties of glass materials. This study provides an approach for the development of new glass cathode materials for lithium-ion batteries.     

Phase diagram of the V2O5-MoO3-Ag2O system

The phase diagram of the MoO₃-Ag₂O system was constructed. A comparison of the phase diagram presented here with the phase diagram of MoO₃-Ag₂MoO₄ system presented in [2] revealed some discrepancies.It was found that phase equilibrium in MoO₃-Ag₂O system could be reached only after cooling the previously melted mixtures of silver and molybdenum oxides.

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Zusammenfassung Es wurde das Phasendiagramm des Systemes MoO₃-Ag₂O erstellt. Der Vergleich dieses Phasendiagrammes mit dem des in (2) beschriebenen Systemes MoO₃-Ag₂MoO₄, ergeben sich einige Unterschiede.Man fand, da\ ein Phasengleichgewicht im System MoO₃-Ag₂O nur nach Abkühlen des zuvor geschmolzenen Gemisches aus Silber- und MolybdÄnoxides erreicht werden kann.

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The author wishes to thank Professor M. Figlarz from Université de Picardie, Amiens for giving the possibility of carrying out in his laboratory a part of the experiments described.     

Non-isothermal studies on crystallization kinetics of tellurite 20Li<Subscript>2</Subscript>O-80TeO<Subscript>2</Subscript> glass

Structural and thermal properties of the 20Li₂O-80TeO₂ glass were studied using X-ray diffraction analysis and differential scanning calorimetry techniques to understand and control the crystallization process on this glass. The γ-TeO₂, α-TeO₂ and α-Li₂Te₂O₅ phases were identified during the crystallization in this glass. Activation energies and Avrami exponent n were calculated from non-isothermal measurements for glasses with different particle size. The mean values of Avrami exponent were obtained for glasses with 63–75 and 45–63 μm particle sizes such as , but glasses with particle size 38–45 μm and smaller than 38 g,m presented .     

Non-isothermal crystallization kinetics of hot drawn polyester films

The non-isothermal crystallization kinetics of hot drawn poly(ethylene terephthalate) films were studied using the Kissinger and Ozawa equations. The influence of the initial drawing on the crystallization kinetics was investigated. The values of the apparent activation energy and of the Avrami exponent indicates that the nucleation and growth of crystallites depend greatly on the stress submitted to the samples.     

一维链状配位聚合物{[Cu(H2bttc)(H2O)3]·3H2O}n的非等温反应动力学和晶体结构

为研究配位聚合物{[Cu(H₂bttc)(H₂O)₃]·3H₂O}_n(H₂bttc=1，2，4，5-benzenetetracarboxylate)的热分解机理和非等温反应动力学进行了DSC和TG-DTG热分析。由热分析结果和FTIR光谱推测了其热分解机理；将Kissinger法、Ozawa法、积分法和微分法得到的动力学参数进行比较确定了第一个失重过程最可能的动力学模型函数。配位聚合物的X射线单晶结构分析表明它由 [Cu(H₂bttc)(H₂O)₃]_n分子链组成，并有客体水分子通过分子间氢键附着在分子链上。这一结构特点与热分析结果相一致。还有一种氢键将分子链连接起来形成二维框架，这一框架在失去配位水和结晶水后到553 K开始分解。     

Thermal Study of A2O–(MoO3)2–P2O5 (A=Li, Na) Glasses

Alkali phosphomolybdate glasses have been prepared by quenching melted mixtures of P₂O₅, MoO₃ and A₂O(A=Li, Na). The composition dependence of the transition temperature of glasses belonging to ternary A₂O–(MoO₃)₂–P₂O₅ (A=Li, Na) systems is studied for several series of glasses corresponding to either a fixed A₂O rate or a constant Mo/P ratio. The interpretation of the results is based on the presence of different types of molybdenum and phosphorous structural groups and P–O–M (M=P, Mo) linkages in glasses. This revised version was published online in August 2006 with corrections to the Cover Date.     

Glass transition kinetics of some Se-Te-Ag chalcogenide glasses

Summary The present paper reports the Differential Scanning Calorimetric (DSC) study of some Ag doped Se-Te chalcogenide glasses. DSC runs were taken at different heating rates. Well-defined endothermic and exothermic peaks were obtained at glass transition and crystallization temperatures. The variation of glass transition temperature T_gwith Ag concentration has been studied. It has been found that T_gdecreases with increase in Ag concentration. The heating rate dependence of T_gis used to evaluate the activation energy of glass transition (DE_t). The value of<span style='font-size:10.0pt; font-family:"SymbolProp BT";mso-bidi-font-family:"SymbolProp BT"'>DE_thas been found to increase with increase in Ag concentration followed by nearly constant value at higher concentrations of Ag.     

Crystallization kinetic of fluoro- zirconate glasses by non-isothermal analysis

Fluoride glasses have been extensively studied due to their high transparency in the infrared wavelength. The crystallization kinetics of these systems has been studied using DTA and DSC techniques. Most of the experimental data is frequently investigated in terms of the Johnson-Mehl-Avrami (JMA) model in order to obtain kinetic parameters. In this work, DSC technique has been used to study the crystallization of fluorozirconate glass under non-isothermal conditions. It was found that JMA model was not fit to be applied directly to these systems, therefore, the method proposed by Málek has been applied and the Šesták-Berggren (SB) model seems to be adequate to describe the crystallization process. This revised version was published online in July 2006 with corrections to the Cover Date.     

Non-isothermal crystallization of polyethylene blends with bimodal molecular weight distribution

Non-isothermal crystallization of polyethylene (PE) blends with bimodal molecular weight distribution (MWD) was investigated by differential scanning calorimetry (DSC) at various scanning rates. The bimodal PE blends were prepared by blending two unimodal polyethylenes with large difference in molecular weigh in different ratio in xylene solution. Different kinetic parameters such as the half-time of crystallization (t_1/2), crystallization rate constant (Z_c), F(T) and the effective activation energy were determined. Some complicated relationships between these parameters and the average molecular weight were found. The crystallization rate first increased and reached a maximum then decreased, and also correlated with the MWD. The Avrami index under non-isothermal conditions was analyzed with a method developed by Harnisch and Muschik; the results indicated that homogeneous nucleation and spherulitic growth regimes were present in all samples studied.     

Thermal expansion of phases formed in the system Nb2O5-MoO3

Studies on thermal expansion of phases formed in the system Nb₂O₅-MoO₃ (WO₃) have been carried out in the high-temperature X-ray diffraction attachment. In the case of Nb₁₄Mo₃O₄₄, Nb₁₂MoO₃₃ and Nb₁₂WO₃₃ the structure that consists of ReO₃ type blocks, the direction of minimal thermal expansion is consistent with direction in which the chains of corner-sharing polyhedra spread to infinity. On the contrary, for Nb₂Mo₃O₁₄, the structure of which resembles the structure of tetragonal tungsten bronzes, the maximal thermal expansion direction is consistent with above mentioned direction. This revised version was published online in July 2006 with corrections to the Cover Date.     

V2O5-MoO3-SiO2表面复合氧化物催化剂的制备与表征

采用表面改性法制备了V2O5-SiO2,MoO3-SiO2,V2O5-MoO3-SiO2复合氧化物催化剂,并用TPR和IR技术研究了催化剂的表面结构及V=O,M0=O的活性,同时用化学吸附IR技术研究了催化剂样品对异丁烷的化学吸附性能.实验结果表明:这些复合氧化物催化剂对异丁烷都有较高的化学吸附能力;SiO2能缓解表面Lewis碱位V=O和Mo=O的氧化能力,有利于选择氧化.     

Thermal analysis of gel-derived bioactive phospho-silicate glasses

Thermal reactions of model phospho-silicate gels of simple composition has been studied. The investigations demonstrate that the kind of compounds introducing P₂O₅ into the gel silicate network, H₃PO₄, PO(OC₂H₅)₃, POCl₃ influence the course and temperature and the xerogel formation. The amount of interstitial water and xerogel porosity is dependent on the cations, amorphous structure modifiers (Ca, Na) used. Thermal analysis curves appear the convenient carriers of informations about the processes in gel pores and the formation of xerogel and glass. This revised version was published online in July 2006 with corrections to the Cover Date.     

DTA/DSC study of nanocrystallization in oxyfluoride glasses

Crystallization of glasses of the Na₂O-Al₂O₃-SiO₂-LaF₃ system was studied by DTA/DSC, XRD and TEM methods. It has been found that the nanocrystallization of LaF₃ in the NAS-based glass strongly depends on ratio of Na₂O/(SiO₂+Al₂O₃) and amount of doped LaF₃. Analysis of the local atomic interactions in the structure of oxyfluoride glasses has been used to explain the course of the crystallization. This revised version was published online in July 2006 with corrections to the Cover Date.