电弧离子镀制备CrN_x薄膜中熔滴的结构表征与形成机制

应用电弧离子镀技术,在不同的氮气分压(0.5~2.5 Pa)和脉冲偏压(0~-300 V)条件下对TC4基体沉积CrNx薄膜,采用扫描电镜和透射电镜对镀膜过程中产生的熔滴现象进行分析研究。结果表明,升高氮气分压能减少靶材排出粒子团数量,改变等离子体轰击作用,从而控制熔滴数量及尺寸,改善薄膜表面平整度;脉冲偏压能够使熔滴与薄膜紧密结合,改变熔滴成分,在一定范围内能促进靶材成分熔滴的形成。     

锰酸锂动力电池滥用条件下安全性能研究

采用商品化的LiMn2O4和石墨作为正负极材料制作锰酸锂动力电池(347080-16Ah),测试其热冲击,穿刺,短路和过充安全实验。研究发现,电池经过热冲击、穿刺和短路测试后,电池未发生爆炸起火现象。但是3C/10V过充后,电池发生爆炸,并放出大量黑烟,电池表面最高温度达到290℃。黑烟的主要成分是CO2、CO、H2、CH4、C2H6、C2H4和炭黑,爆炸后的粉末主要成分为C、MnO和Li2CO3。     

铈对D6冷作模具钢中共晶碳化物的影响

针对某集团生产的模铸D6钢中经常出现共晶碳化物对超标现象,在模铸过程中添加稀土元素铈.在坯料和钢材上取样,采用光学显微镜观察侵蚀后钢的组织形貌.结果表明,随着铈含量的增加,共晶碳化物网格尺寸变小,当坯料中铈含量由0.038％增加到0.073％时,网格尺寸减小约50％,网格厚度变薄,甚至网状结构被破坏;钢材中共晶碳化物的级别随铈含量的增加而降低.铈对铸态组织的细化作用导致了最终产品中共晶碳化物的细化.     

Improving the electrochemical performance of LiMn<Subscript>2</Subscript>O<Subscript>4</Subscript>/graphite batteries using LiF additive during fabrication

LiMn2O4/graphite batteries using LiF additive were fabricated and their electrochemical performance including discharge,cycling and storage performances were tested and compared with LiF-free LiMn2O4/graphite batteries.The LiMn2O4/graphite battery with LiF added shows better capacity (107.5 mAh/g),cycling performance (capacity retention ratio of 93% after 100 cycles),and capacity recovery ratio (98.1%) than the LiF-free battery.The improvement in electrochemical performance of the LiF-added LiMn2O4/graphite...     

尖晶石型铁氧体纤维的制备及磁性能

以柠檬酸和金属盐为原料, 采用有机凝胶-热分解法制备了MeFe₂O₄(Me=Zn, Ni_0.5Zn_0.5, Ni_0.4Zn_0.4Cu_0.2)铁氧体纤维.通过FT-IR、XRD、TG-DSC、SEM和VSM等测试技术对纤维前驱体凝胶的结构、热分解过程及热处理产物的物相、形貌以及纤维的磁性能等进行了表征.结果表明, 在凝胶形成过程中, 金属离子单齿或双齿螯合配位于柠檬酸根阴离子, 形成线型分子结构, 使凝胶有较好的可纺性. 所制得的纤维具有较大的长径比, 纤维直径在0.5～20.0μm之间.这些纤维在室温下都具有软磁特性, 化学组成、晶粒大小及形貌对纤维的磁性能有着显著影响.ZnFe₂O₄、Ni_0.5Zn_0.5Fe₂O₄和Ni_0.4Zn_0.4Cu_0.2Fe₂O₄纤维的饱和磁化强度分别为2.6、12.7和40.0A·m²·kg^-1, 相应的矫顽力分别为4.77、5.82和4.04kA·m^-1.     

Core–shell structures in pressureless-sintered undoped Pb(Fe2/3W1/3)O3 ceramics

Core–shell structures have been found by both scanning and transmission electron microscopy in undoped Pb(Fe_1/3W_2/3)O₃ ceramics when a solid-state-reacted powder of stoichiometric composition was sintered at 800°C. The presence of superlattice reflections of the {1/2 1/2 1/2}-type, often termed F-spots, indicates that the existence of nanoscale ordered domains of 2–5 nm size in both core and shell is due to chemical ordering of the B-site cations with alternating Fe³⁺ and W⁶⁺ along the <111> direction. The ceramic is densified by the assistance of a low-temperature liquid eutectic at ∼690°C. A formation mechanism of core–shell structures in Pb(Fe_1/3W_2/3)O₃ ceramic is proposed. It can be described by solution-reprecipitation and phase transformation subsequently to perovskite Pb(Fe_1/3W_2/3)O₃, involving at least two intermediate phases which are formed at temperatures below and above the low-temperature liquid eutectic point and related to pyrochlore (Pb₂FeWO_6.5). The cores are characterised by “black dots” and contain relatively Fe-excess. The shells exhibiting featureless contrast are free of “black dots” but contain W-excess relative to the cores. Long term sintering at 800°C has facilitated the inward diffusion of W⁶⁺ to the grain interior when the distribution of the B-site cations is improved. As a result, the shell increases its size at the expense of the core.     

Research on the dynamic recrystallization behavior of GCr15 steel

The dynamical recrystallization (DRX) of GCr15 steel was investigated at deformation temperatures of 950–1150 °C and strain rates of 0.1–10 s^?1 on a Gleeble-3800 thermo-mechanical simulator. The stress–strain curves at lower strain rates are typical of the occurrence of DRX and exhibit a peak in the flow stress before reaching steady state. The flow stress at higher strain rates increases rapidly to the maximum too, but followed by a steady region. The microstructures after deformation certify that DRX takes place in all specimens. And the results show that DRX occurs more easily with the decrease of strain rate and the increase of deformation temperature. Using regression analysis, the DRX activation energy of the steel, the relationship of critical strain and deformation conditions were determined. In order to determine the recrystallized fraction under different conditions, an approximate model based on the stress–strain curves was investigated, and the kinetic model for DRX was established.     

Diversity in nutritional composition of wild jack bean (Canavalia ensiformis L. DC) seeds collected from south India

Nine accessions of the wild jack bean (Canavalia ensiformis L. DC) seeds collected from nine different locations of south India were analysed for proximate composition and mineral profiles. The major findings of the study were as follows: crude protein ranged from 28.9 to 35.0%, crude lipid 3.4–4.7%, crude fibre 7.0–10.7%, ash 3.0–5.8%, carbohydrates 46.1–54.5% and energy levels 1469–1574 kJ 100 g⁻¹ DM. Significant (P<0.05) diversity was observed in crude protein and carbohydrate contents among the accessions collected from different locations based on analysis of variance (ANOVA) analysis. Potassium was the most abundant mineral, which ranged from 634 mg 100 g⁻¹ in Dasukuppam accession to 1017 mg 100g⁻¹ in Valacode accession. Sodium and magnesium levels are generally low with mean values of 63 and 250 mg 100 g⁻¹, respectively. In the present study, in all minerals, significant diversity was observed among the accessions collected from different locations.     

Light scattering study of stereocomplex behaviour in solutions of poly(methyl methacrylate)

The behaviour of mixtures of iso- and syndiotactic poly(methyl methacrylate) (PMMA) as a function of time and polymer whole concentration in several solvents has been studied by light scattering and laser light scattering. The different solvents investigated in this study are acetonitrile, ethyl acetate, dimethylformamide (DMF), tetrahydrofuran (THF) and 1,4-dioxane. We have found that the last one behaves as a weakly complexing solvent, while the others show a complexing power decreasing from acetonitrile to THF.An increase in polymer whole concentration induces a higher aggregation of the macromolecular coil, while the compaction process of stereocomplex particles is not strongly influenced. The influence of time in stereocomplex behaviour depends on the nature of the solvent employed. In strongly complexing solvents there is initially a strong increase in the aggregation process and a decrease in compaction. However, in weakly complexing solvents these kinetic processes are less important.     

A mass spectrometric investigation of the thermal oxidative reactivity of ethylene glycol

The thermal oxidative stability of ethylene glycol was investigated over the temperature range of 100–126°C. Aqueous ethylene glycol were heated in sealed tubes in the presence of metallic copper and without metal. Mass spectrometric analysis was used to determine the rates of O₂ consumption and CO₂ evolution during heating. Copper had a catalytic effect of the glycol degradation. It was found that the rate limiting step in the thermal oxidative process was not related to oxygen consumption, suggesting that the rate limiting step involved the formation of a free radical which subsequently reacts with O₂. The evolution of CO₂ continued to occur after total consumption of the O₂. This suggested that the CO₂ is evolved from one of the thermal oxidation products of ethylene glycol.