Glass transition temperature-structural studies of tungstate tellurite glasses

Raman, IR and DSC studies have been carried on the (100 − x)TeO₂–xWO₃ (TW) glasses with 10 ≤ x ≤ 40 mol%. The Raman, IR spectra of these samples show that glass network consists of [TeO₃]/[TeO₃₊₁], [TeO₄], [WO₄] and [WO₆] groups as basic structural units. The W ion coordination state changes from 4 to 6 when WO₃ concentration increases beyond 30 mol%. Addition of WO₃ oxide to the TW glasses increases the amount of lower coordination of [TeO₃]/[TeO₃₊₁] units and decreases the higher coordination [TeO₄] units, Te–O–Te chains. From DSC thermogram, thermal properties such as the glass transition temperature (T_g), onset crystallization (T_o) of the glass systems were calculated. The compositional variation of glass transition temperature (T_g) is found to linear with an increase in WO₃ content.     

Effect of hydroxyl content on the physical properties of calcium metaphosphate glasses

The hydroxyl (OH) content of calcium metaphosphate glasses has been controlled in the range 50–800 ppm by melting calcium dihydrogen phosphate in air, under vacuum and with fluoride addition. Density, refractive index and glass transition temperature of the glasses increase with decrease in OH content while the coefficient of thermal expansion remains almost unchanged. With gradual decrease in OH, the UV cutoff initially shifts towards shorter and finally towards longer wavelengths. IR spectroscopic study shows that the OH groups exist exclusively in the hydrogen bonded states. Correlations of the glass properties with OH content have been explained in terms of structural rearrangement leading to the change in P-O bond length and O-P-O/P-O-P bond angles of the PO₄ tetrahedral units of (PO ₃ ⁻ ) _n chains. These changes are caused due to conversion of non-bridging oxygens (NBOs) of the H-bonded OH groups into bridging oxygens (BOs) during progress of dehydroxylation.     

The Effects of Casting Temperature on the Glass Formation of Zr‐Based Metallic Glasses

The glass1‐forming ability of two alloys, Zr_64.9Al_7.9Ni_10.7Cu_16.5 and Zr₄₇Cu_37.5Ag_7.5Al₈, prepared by arc‐melting a mixture of Zr, Cu, Al, Ni and Ag elements is studied as a function of casting temperature. Other processing parameters such as the alloy melt mass, and the vacuum and injection pressures during the copper‐mold‐casting process are kept constant so just the influence of the casting temperature is considered. The casting temperature determines the characteristics of the liquid melt and the cooling rate. The glass‐forming ability is discussed in terms of dissipation of pre‐exiting, metastable local‐ordering clusters that act as nucleation sites promoting crystallization, the cooling rate at high casting temperatures, and the presence of oxygen in the alloys, which is increased at high casting temperatures. It is found that the glass‐forming ranges of alloys shrink as the glass‐forming size approaches a critical value. The optimum temperatures are around 1450 K and 1550 K for Zr_64.9Al_7.9Ni_10.7Cu_16.5 and Zr₄₇Cu_37.5Ag_7.5Al₈ alloys respectively. The alloys were studied by XRD, TEM, oxygen‐level determination, and DSC.     

Glass formation and properties of novel GeS2-Sb2S3-In2S3 chalcogenide glasses

Novel chalcogenide glasses based on GeS₂-In₂S₃-Sb₂S₃ system were prepared by conventional melt-quenching method and their physicochemical properties, e.g. glass transition temperature, density, and Vickers micro-hardness, were studied in detail. The results show that the thermal, mechanical, and optical properties depend largely on four-coordinated Ge or In entities and are sensitive to the variation of the connectivity in the GeS₂-In₂S₃-Sb₂S₃ glass network. It is a promising chalcogenide glass system suitable for rare earth doping or crystallization of rare earth doped crystals, which aims at optical applications of IR optical amplifier or efficient solid state laser.     

SnO—BaO—P2O5系统无铅封接玻璃的结构与性质

以SnO—BaO—P2O5三元系统玻璃为研究对象,利用差示量热扫描分析仪、热膨胀仪、拉曼光谱仪,分析了玻璃的结构以及玻璃转变温度和热膨胀系数与玻璃组成的关系．获得了该体系玻璃的形成区域,测得该系统的玻璃转变温度为260～360℃和热膨胀系数为12～14×10^-6℃．研究发现,当P2O5=45mol％不变时,玻璃转变温度随着SnO含量的增加而降低;当BaO=10mol％不变时,玻璃转变温度随着SnO含量的增加先降低后升高．研究表明,该体系玻璃可以作为低温环保封接玻璃潜在的基质材料．     

Tribological properties of transition metal di-chalcogenide based lubricant coatings

Transition metal di-chalcogenides MX₂ (X= S, Se, Te; and M= W, Mo, Nb, Ta) are one kind of solid lubricant materials that have been widely used in industry. The lubricant properties of such lubricant coatings are dependent not only on microstructure, orientation, morphology, and composition of the coatings, but also on the substrate, the interface between substrate and lubricant coatings, and the specific application environment. In this review, the effects of parameters on tribological properties of such kind of lubricant coatings were summarized. By comparing advantages and disadvantages of those coatings, the special treatments such as doping, structural modulation and post-treatment were suggested, aiming to improve the tribological performance under severe test conditions (e.g. high temperature, oxidizing atmosphere or humid condition).     

过渡金属/活性炭电极的电容性能研究

选用微孔和中孔活性炭采用浸渍法负载金属离子,考察在水性电解质中用于超级电容器的活性炭复合电极的电化学性能,探讨活性炭在负载前后的放电容量变化情况.采用低温氮吸附和直流恒流循环实验考察活性炭复合电极的孔结构及电容性能.研究表明:金属Cu、Mn具有比较明显的准电容效应,Co、Ni可提高中孔活性炭的放电容量,而金属Mo、Fe和Y的准电容效应不显著;中孔活性炭负载金属的作用明显强于微孔活性炭;中孔活性炭负载金属Cu时,放电容量随负载量的增加而上升.     

Balancing benefits of strength,plasticity and glass-forming ability in Co-based metallic glasses

Development of advanced metals materials with ultrahigh strength,large plasticity and high thermosta-bility is one of the most attractive aims for materials researchers.Co-based bulk metallic glasses(BMGs)with the highest strength(up to 6 GPa)and special strength(up to 650 Nm/g)among all of metals mate-rials so far we known have received extensive attentions.In this paper,a family of Co-Ta-B-Si BMGs with high glass-transition temperature(above 870 K),large compressive plasticity(up to 6.4％)and high strength(above 5.5 GPa),and high glass-forming ability(the critical diameter,Dc:up to 4 mm)was devel-oped by accurately tuning metalloid element contents of Si and B in the parental alloy of Co55Ta10B35.The changes of glass formation and plasticity caused by the adjustment of the constituent metalloid elements were evaluated by the combination of experimental and calculated results.The reason for the significant improvement of plastic deformation is revealed by the analysis of the self-organization behaviors of high-density shear bands.     

用AEAM模型研究Ti与过渡族bcc金属二元合金的结构

运用AEAM模型理论,计算了Ti金属的总能量,并和Rose方程的结果作了比较;同时系统地研究了Ti与bcc金属组成的二元合金系统形成焓,并对计算结果进行了分析,给出了Ti与bcc金属组成的各合金结构稳定性与成分关系,为AEAM模型理论研究二元合金结构及稳定性提供了思路.     

非晶态高分子粉体玻璃化转变温度的影响因素及测试技术

非晶态高分子粉体的玻璃化转变温度，是分析其结块原因、采取预防结块措施的重要依据。本文分析了影响非晶态高分子粉体玻璃化转变温度的主要因素；介绍了常用玻璃化温度测试技术；建立了用膨胀法测试非晶态粉体玻璃化转变温度的装置与方法，并讨论了其有效性与准确性。     

Thermal properties of ion beam irradiated polycarbonate films

Semicrystalline polycarbonate (PC) films were irradiated under vacuum at room temperature by C⁺⁵ beam of 55 MeV energy at fluences of 3 × 10¹¹ and 3 × 10¹³ ions cm². Ion induced modifications were studied by X-ray diffraction (XRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and thermally stimulated discharge current (TSDC) techniques. With increasing ion fluence significant loss of average crystallite size, percentage crystallinity, stability and glass transition (T_g) temperature were observed. TSDC shows that activation energy, released charge, α-relaxation peak, and charge carrier mobility decrease while relaxation time and peak current increase.     

Thermal, structural and optical properties of new tungsten lead–pyrophosphate glasses

Crystalline lead–pyrophosphate precursor was prepared in aqueous solution from lead nitrate and phosphoric acid and characterized by X-ray diffraction, thermogravimetry and Raman scattering. This crystalline lead–phosphate was then used to prepare glass samples in the binary system Pb₂P₂O₇–WO₃. Dependence of WO₃ content on thermal, structural and optical properties were investigated by thermal analysis (DSC), Raman spectroscopy, UV–visible and near-infrared absorption and M-Line technique to access refractive index values. Incorporation of WO₃ in the lead–pyrophosphate matrix enhances the glass transition temperature and thermal stability against devitrification, favors formation of POW bonds and WO₆ clusters. In addition, optical properties are strongly modified with a redshift of the optical bandgap with WO₃ incorporation as well as an increase of the refractive index from 1.89 to 2.05 in the visible.     

Critical evaluation of the thermodynamic properties of cobalt

The thermodynamic properties and the pressure-temperature phase diagram of Co have been evaluated from experimental information using thermodynamic models for the Gibbs energy of the various phases. For hcp and fcc Co the model describes the magnetic contribution to the molar volume, expansivity, and compressibility and the efect of pressure upon the Curie temperature. Experimental data of many different types are satisfactorily described by the evaluated model parameters.This work was supported by the Swedish Board for Technical Development, and by Sandvik Hard Materials, Stockholm, Sweden.     

Processing and characterization of functionally graded materials through mechanical properties and glass transition temperature

Functionally graded materials (FGMs) were prepared by construction based layering method through dispersion of carbon nanoparticles in the styrene butadiene rubber matrix. The gradation of material property i.e., ‘glass transition temperature’ was brought in the nanocomposite by varying the concentration of process oil. Glass transition temperature (T_g) of FGMs was varied from − 56 to − 80 °C along the span of 3 mm thick sheet. The gradation of oil in FGMs also changes other properties like tensile strength, elongation at break, modulus, etc. Tensile strength and modulus at 100% drops down while elongation at break continuously increases while moving from one end to other end along the sheet thickness. Thermal analysis of FGMs verifies the compositional changes as well as the change in T_g along the thickness.     

PbO－Bi_2O_3－B_2O_3－SiO_2系重金属氧化物玻璃的结构与光学性

通过密度、可见光光谱、红外吸收光谱、Ｃｏ－６０辐照损伤试验及荧光光谱的测试，研究了ＰｂＯ－Ｂｉ２Ｏ３－Ｂ２Ｏ３－ＳｉＯ２玻璃系的光学性能与结构．密度最高可达８．４６４ｇ／ｃｍ３其紫外吸收达截止波长随Ｐｂ２＋及Ｂｉ３＋含量升高而红移．玻璃熔化温度低达８５０℃．在ＰｂＯ－Ｂｉ２Ｏ３－Ｂ２Ｏ３系玻璃中加人ＳｉＯ２可使玻璃结构更致密．室温下该系统玻璃在３６０ｎｍ有一个宽的激发峰，能产生４１８ｕｍ及４３８ｕｍ两个弱的发射峰．该系统玻璃的结构是由［ＳｉＯ４］４－、［ＢＯ３］３－、［ＢＯ４］５－、［ＰｂＯ４］６－及［ＢｉＯ６］９－构成．其中部分Ｐｂ２＋及Ｂｉ３＋以网络外体进入玻璃．     

放射性滑膜切除用镝锂硼玻璃的性能及红外光谱结构研究

测定了镝锂硼玻璃（DyLB）的密度和硬度,用红外吸收光谱测定了DyLB玻璃的结构,从组成一结构一性质的关系上分析了Dy2O3对DyLB系统玻璃结构及性能的影响。结果表明Dy2O3使DyLB玻璃中的[BO3]转变为[BO4],同时Dy^3＋具有积聚效应,使DyLB玻璃网络被强化,玻璃的密度、硬度均升高。     

St-BA共聚物玻璃化温度与转化率的关系

用溶液聚合的方法在不同投料比下合成了不同转化率的苯乙烯-丙烯酸丁酯无规共聚物,低转化率下共聚物的组成用1H-NMR测定,聚合物的玻璃化温度(Tg)用差示扫描量热法(DSC)测量。采用非线性最小二乘法(NLLS)计算得到单体的竞聚率rSt=0.831,rBA=0.187,不同转化率瞬时共聚物含量由竞聚率、投料比计算,Tg用前期提出的共聚物Tg-组成关系方程计算,累计产品的Tg由瞬时共聚物Tg用Fox公式加和而得,按此种方法预测的St-BA共聚物Tg-转化率关系与实验结果基本一致。     

聚甲基丙烯酸酯类运动单元结构与玻璃化转变温度的关系

玻璃化转变温度(Tg)是非晶态高聚物材料的一项很重要的参数。文中采用多元线性回归方法建立了56种聚甲基丙烯酸酯类高聚物Tg的结构-性能定量关系(QSPR)模型。模型所用参数从聚甲基丙烯酸酯类主链包含10个重复单元的运动单元计算得到。模型训练集(包含36种聚甲基丙烯酸酯类高聚物)的相关系数为0.971,标准误差为15.731K;模型测试集(包含20种聚合物)相关系数为0.946,均方根误差(rms)为17.286K;整个数据集(56种聚合物)相对误差为4.065%。结果表明,本文所得模型对聚甲基丙烯酸酯类高聚物Tg有着较强的预测能力。因此从高分子主链段运动单元得到分子参数预测Tg是可行的。     

Coordination and valence state of transition metal ions in alkali-borate glasses

Borate glasses of the 20R₂O·80B₂O₃ type, where R = Li, Na and K, were colored by doping with transition metal ions (Co, Ni, Cr and Mn). The glasses were obtained by melting at the temperature of 1150 °C. For these glasses optical absorption in UV–VIS–NIR range were recorded. Analysis of the spectra allows to be determined the coordination and oxidation states of the doping transition metal ions. Changes of their coordination or oxidation are presented as a function of the optical basicity Λ after Duffy. Cobalt and nickel are present in examined borate glasses as divalent ions (Co²⁺, Ni²⁺) in octahedral coordination mainly, but the tetrahedral coordination state of cobalt is also possible. Chromium and manganese are present in the borate glasses in various oxidation state, though Cr³⁺ and Mn³⁺ ions in the octahedral coordination are probably dominant. A decrease of the electronegativity of the modifiers (Li → Na → K) and an increase of the glass matrix basicity cause a shift of the oxidation/reduction equilibrium towards higher valences of the transition metals (Cr⁶⁺, Mn³⁺).     

PbI2-PbCl2-KCl系统玻璃的形成及其析晶行为研究

本文从阳离子的配位数、化学键的特性等角度出发，探讨了ＰｂＩ２－ＰｂＣｌ２－ＫＣｌ三元系统的玻璃形成特性，并以ＤＳＣ、ＳＥＭ和ＸＲＤ等为手段研究了组成为５０ＰｂＩ２３０ＰｂＫＣｌ（ｍｏｌ％）的玻璃的析晶行为。析晶学研究表明，所得玻璃的高、３氏温相变机量彼此不同，所得玻璃的析经能接近于较稳定的氟锆酸盐玻璃，因此在析晶温度睛表现出了较慢的析晶速率，通过适当的热处理，可以工餐透过与原始玻璃一致的微晶玻璃，