Enhanced dehydrogenation of hydrazine bisborane for hydrogen storage

NiCl₂ and CoCl₂ were adopted to enhance the dehydrogenation of hydrazine bisborane (HBB), respectively, of which NiCl₂ showed better performance. By adding 2.0 mol. % NiCl₂, the dehydrogenation property of HBB was significantly improved, for example, the impurity of NH₃ during the dehydrogenation of HBB was totally suppressed with more than 13.0 wt. % of pure hydrogen evolved. By Kissinger method, the apparent activation energies of the first step for HBB and Ni-doped HBB were calculated to be 143.2 and 60.7 kJ mol⁻¹, respectively. DSC result showed that the addition of NiCl₂ did not change the enthalpy change of HBB dehydrogenation. Based on theoretical analysis and literature review, the improved dehydrogenation property of HBB was potentially ascribed to the solid state interaction of Ni²⁺ with the electronegative N in the NH₂ group of HBB.     

Synthesis and properties of poly(methyl methacrylate-2-acrylamido-2-methylpropane sulfonic acid)/PbS hybrid composite

The synthesis of a new hybrid composite based on PbS nanoparticles and poly(methyl methacrylate-2-acrylamido-2-methylpropane sulfonic acid) [P(MMA-AMPSA)] copolymer is reported. The chemical synthesis consists in two steps: (i) a surfactant-free emulsion copolymerization between methyl methacrylate and 2-acrylamido-2-methylpropane sulfonic acid and (ii) the generation of PbS particles in the presence of the P(MMA-AMPSA) latex, from the reaction between lead nitrate and thiourea. The composite was studied by scanning electron microscopy (SEM), X-ray diffraction, FTIR spectroscopy, thermogravimetric analysis and differential scanning calorimetry. The microstructure observed using SEM proves that the PbS nanoparticles are well dispersed in the copolymer matrix. The X-ray diffraction measurements demonstrate that the PbS nanoparticles have a cubic rock salt structure. It was also found that the inorganic semiconductor nanoparticles improve the thermal stability of the copolymer matrix.     

低等规聚丙烯的等温结晶动力学

利用 DSC法研究了低等规度聚丙烯 ( LIPP)的等温结晶动力学。根据 Avrami方程求出了各个结晶温度下的结晶动力学参数 k( T)、n和 t1/ 2 ,研究了 L IPP的结晶度及结晶速率与结晶温度的关系。利用Hoffman等温结晶理论 ,求出 LIPP的 σe 为 3.0 7× 10 -2 J/ m2 。     

差示扫描量热法分析防火涂料的膨胀体系

利用差示扫描量热法（DSC）探讨了膨胀体系的作用机理。通过对典型膨胀体系（即聚磷酸铵、三聚氰胺、季戊四醇）中单一活性物质及其混合物的DSC分析，探讨了不同组分之间热效应的桑加现象和相互作用，从热效应角度分析了膨胀反应，初步探索了复杂膨胀现象中物理化学变化的热特征。利用在较低的温度下复杂体系中季戊四醇的晶型转变吸热峰独立存在的特点，根据其在不同混合体系中的焓变，确定该组分在混合体系及涂料中的质量百分数。     

Effects of Pre-Ageing Treatment on Subsequent Artificial Ageing Characteristics of an Al-1.01Mg-0.68Si-1.78Cu Alloy

The influences of pre-ageing temperature and natural ageing time on subsequent artificial age hardening behavior and precipitation sequence of new type Al-1.01Mg-0.68Si-1.78Cu alloy were investigated by hardness test, differential scanning calorimetry (DSC) test and transmission electronic microscopy (TEM) observations. When pre-ageing temperature is 20℃ (natural ageing), the peak hardness of subsequent artificial aged alloy is lower than that of T6 treated alloy (negative effect), while a positive effect a...     

Deposition of nickel nanoparticles onto aluminum powders using a modified polyol process

Aluminum is commonly used as fuel additive for propellants. The main limitation to its use lies in comparatively slow ignition and oxidation/combustion kinetics. Combustion performance of aluminized propellants can be improved through the use of Ni-coated Al particles. Nanoparticles, with its increased reactivity, also improve combustion performance. Hence, in this work, nano-sized Ni particles coated onto commercially available micron-sized Al powders using a modified polyol process were synthesized and evaluated. Ni-coated Al powders of various compositions produced by this method showed significant improvement in the oxidation kinetics as compared to untreated Al powders. The onset oxidation temperatures for the Ni-coated Al powders were found to be significantly reduced as compared to pure untreated Al. Other than the oxides, the intermetallic compound, Al₃Ni was also detected in the 10 wt% Ni-Al powders that were heated to temperature above 1050 °C.     

醇类保护剂对猪软骨低温膨胀过程的DSC研究

在对关节软骨进行低温保存时,由于冰晶的生长而造成的热膨胀效应是其低温断裂的主要原因。本论文采用非等温热分析仪和修正的Avrami动力学方程,考察了分别添加不同浓度的四种醇类低温保护剂时,猪关节软骨低温保存过程中热力学及结晶动力学参数的变化。研究表明,软骨结晶峰随降温速率的增大而变宽,从而导致结晶越不完善;在-60~0℃温度范围,只有添加4.5 mol/L 1,2-丙二醇时,其Avrami指数为4.156,冰晶以均相三维球晶方式生长。且与其他保护剂相比,1,2-丙二醇保护效果最好。同时降温速率对结晶及热膨胀不同的影响结果也说明,低温损伤并不完全是由冰晶生长所决定,还与其胞外基质的缓冲作用有关。     

Study of omeprazole-gamma-cyclodextrin complexation in the solid state

The possibility of obtaining inclusion complexes between omeprazole (OME) and γ-cyclodextrin (γ-CD) by kneading, spray-drying, coprecipitation, and freeze-drying was evaluated. All these methods lead to the isolation of a true inclusion compound, as evidenced by differential scanning calorimetry (DSC), infrared spectroscopy, and X-ray diffractometry on powder (PXRD). Moreover, PXRD and scanning electron microscopy (SEM) afforded data concerning crystallinity and surface characteristics of the solid phases obtained. In all cases, a significant increase of the release rate with respect to the drug alone was found, and it was attributed to the formation of an inclusion compound. Among the solid phases obtained, the coprecipitated product presented the highest dissolution rate.     

Reaction kinetics studies on Ti-Al-Cr-Nb-B intermetallics

In reaction synthesis (RS) route of powder metallurgy, heat of reaction between elemental powders is utilised to obtain intermetallic compounds. Prior to reaction synthesis of quaternary alloy Ti48Al2Cr2Nb (with 10 at. % B), reaction kinetics studies were carried out. Powder mixture was prepared and Differential Scanning Calorimetry (DSC) experiments were carried out at 3 different heating rates. Activation energy and Avrami Index ‘n’ are obtained by Johnson-Mehl-Avrami (JMA) equation. Formation of Al₃Ti was confirmed through X-ray diffraction (XRD). Reaction mechanisms are identified in accordance with ‘n’ values. In the temperature range of 1060–1150K, it proceeds as instantaneous nucleation and three dimensional growth with an activation energy of 176 kJ mole⁻¹.     

锆基大块非晶合金的非等温晶化动力学效应

采用非等温差示扫描量热法(DSC)研究了锆基非晶合金Zr60Al15Ni25、Zr65Al10Ni10Cu15的晶化动力学.结果显示,随着升温速率的加快,这两种非晶合金的特征温度Tg、Tx、Tp均向高温区移动,且过冷液相区逐渐加宽,表明非晶合金的玻璃化转变和晶化均具有动力学效应.分别采用Kissinger法和Ozawa法计算各非晶合金的激活能,两种方法的计算结果相近.从激活能数据得出,两种锆基非晶合金的热稳定性均较强;与非晶合金Zr60Al15Ni25相比,Zr65Al10Ni10Cu15虽较难形成玻璃化转变和开始晶化,但其晶化一旦开始则随后的过程反而更容易进行.