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951.
在引进型300MW和600 MW汽轮发电机组中,高温螺栓大量采用GH4145合金,这种材料的晶粒粗大,可达-3级[1],在运行中经常断裂,影响机组安全.本文采用低频、窄脉冲、双晶爬波探头检测GH415螺栓,可以发现深度大于等于0.5 mm的模拟裂纹.  相似文献   
952.
本文研究了陶瓷结合剂中Li2O的含量对陶瓷结合剂性能的影响。实验表明结合剂的耐火度随Li2O含量的增加而降低,而在碱金属总量不变的情况下,结合剂的耐火度随Li2O含量的增加反而有所上升。当结合剂中碱金属氧化物含量较低时结合剂的抗折强度随Li2O含量的增高而提高,当R2o/(B2O3,+Al2O3)的摩尔比为1.03时强度达到最高值;同时Li2O的加入可以改善结合剂与CBN磨料的润湿性。  相似文献   
953.
1 Introduction As one of the most promising cathode materials for lithium ion batteries, spinel LiMn2O4 has received much attention in recent years. This material has reversible capacities at both 3 V and 4 V plateaus[1]. However, the Li insertion and ex…  相似文献   
954.
The effects of electric field intensity and treatment temperature on the microstructures of GH4199 superalloy after long-term aging were investigated. The results show that the number and size of carbides and TCP(σ phase and μ phase) phase in the alloy increase with increasing electric field intensity at the same heat treatment temperature and holding time. While the number and size of carbides and TCP phase are weekly influenced by treatment temperature with lower electric field intensity of 2 kV/cm. When the treat temperature is up to 1 093 K, annealing twins appear in the alloy, and the number of twins increases with increasing holding time. Since the electric field can provide the enough energy for the movement of vacancies and atom, it is considered that the nucleus of the twins formed with formation stack faults due to the mismatch of local atom in crystal caused by the vacancies, and the twins will grow with the increase of holding time. Meanwhile, such promoting effects on atom movement of the electric field increase with the increase of the electric field intensity, meantime the carbides and TCP phase grow fast with the increase of electric field intensity.  相似文献   
955.
HPLC-DAD及HPLC-MS研究干燥工艺对中药粗榧化学成分的影响   总被引:1,自引:0,他引:1  
用高效液相色谱-二极管阵列检测器及高效液相色谱-质谱联用技术,发现常压及减压干燥能使粗榧提取物中两个主要的化合物(1号峰和2号峰)发生降解。减压干燥后两个化合物分别减少了20.2%和45.6%,常压干燥后,两个化合物均检测不到。与干燥前相比,减压干燥和常压干燥使3号峰面积分别增加了1.90倍和5.74倍。1~3号峰均具有特征性的黄酮化合物的两个紫外吸收带(240~280 nm和300~400 nm),被推测为黄酮化合物,质谱研究推测1~2号峰发生了苷键断裂生成3号峰。用AB-8大孔吸附树脂,葡聚糖凝胶LH-20,反相硅胶(ODS)柱色谱分离纯化得到1~3号峰的3个化合物,对其进行了红外和核磁测定,鉴定出芹菜素-5-O-α-L-吡喃鼠李糖基(1→4)-β-D-吡喃葡萄糖苷和芹菜素-5-O-α-L-吡喃鼠李糖基(1→4)-6″-O-乙酰基-β-D-吡喃葡萄糖苷两个黄酮苷,干燥过程使它们苷键断裂生成了苷元芹菜素(3号峰)。  相似文献   
956.
Application of room temperature ionic liquids to Li batteries   总被引:1,自引:0,他引:1  
Novel electrolyte materials, room temperature ionic liquids (RTILs) were applied to the Li battery system and their characteristics in Li-metal batteries are discussed, partly reviewing authors work in the past. Quaternary ammonium (QA) cation-imide RTIL was focused on because of the excellent stability in cathodic environment of Li. Li/LiCoO2 cell performance and Li cycling efficiency using the selected QA-imide RTIL was almost satisfactory. In addition, thermal stability of selected QA-imide RTIL with the charged positive electrode and Li was the advantage for Li battery. On the other hand, further improvement in the conducting properties is required with balanced approach for both electrochemical stability and thermal stability in order to use the RTIL electrolyte practically in batteries.  相似文献   
957.
Sen Zhang 《Electrochimica acta》2007,52(25):7337-7342
Li[Ni1/3Co1/3Mn1/3]O2 cathode material for lithium ion batteries was prepared by mixing metal hydroxide, (Ni1/3Co1/3Mn1/3)(OH)2, with 6% excess LiOH followed by calcinations. The (Ni1/3Co1/3Mn1/3)(OH)2 with secondary particle of about 12 μm was prepared by hydroxide co-precipitation. The tap density of the obtained Li[Ni1/3Co1/3Mn1/3]O2 powder was 2.56 ± 0.21 g cm−3. The powder was characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), particle size distribution (PSD) and galvanostatic charge-discharge cycling. The XRD pattern of Li[Ni1/3Co1/3Mn1/3]O2 revealed a well ordered hexagonal layered structure with low cation mixing. Secondary particles with size of 13-14 μm and primary particles with size of about 1 μm can be identified from the SEM observations. In the voltage range of 2.8-4.3 V, the initial discharge capacity of the Li[Ni1/3Co1/3Mn1/3]O2 electrode was 166.6 mAh g−1, and 96.5% of the initial capacity was retained after 50 charge-discharge cycling.  相似文献   
958.
2091铝锂合金动态再结晶诱发超塑变形中的空洞行为   总被引:7,自引:1,他引:7  
研究了2091铝锂合金动态再结晶诱发超塑变形中的空洞行为.金相观察和图象分析表明,在最佳变形条件下,空洞率及空洞平均直径先随着变形增大而增大,变形至ε=1.03时,空洞率及空洞平均直径均减小,出现了超塑变形初期的空洞弥合现象.超塑变形初期的空洞形核取决于应变速率,最佳应变速率下断裂试样出现大量的圆角空洞,并且此时空洞率出现最大值.  相似文献   
959.
Silicon has been critically examined for its potential use as an electrode material for Li-ion batteries. Diffusive transport of Li-ions in the crystalline silicon anode is one of the key mechanisms that controls the deformation during lithiation, the rate of the charge–discharge cycle, and eventual mechanical failure. The use of amorphous silicon, instead of its crystalline counterpart, is considered to offer several advantages. The atomistic mechanisms underpinning diffusive transport of Li-ions in amorphous silicon are, however, poorly understood. Conventional molecular dynamics, if used to obtain atomistic insights into the Li-ion transport mechanism, suffers from several disadvantages: the relaxation times of Li ion diffusion in many of the diffusion pathways in amorphous Si are well beyond the short time scales of conventional molecular dynamics. In this work we utilize a sequence of approaches that involve the employment of a novel and recently developed potential energy surface sampling method, kinetic Monte Carlo, and the transition state theory to obtain a realistic evaluation of Li-ion diffusion pathways in amorphous Si. Diffusive pathways are not a priori set but rather emerge naturally as part of our computation. We elucidate the comparative differences between Li-ion diffusion in amorphous and crystalline Si as well as compare our results with past studies based on other methods.  相似文献   
960.
In this work specific film structures of Li-Nb-O/Li/Li-Nb-O are investigated by AC Impedance Spectroscopy measurements at different temperatures. This gives the opportunity to investigate properties of the material itself and, at the same time, to consider the influence of the grain boundaries on the ionic behavior of the polycrystalline Lithium Niobate. On the other hand, LiNbO3/Li/Cu multi-layers are studied as electrolyte/anode bi-layers and potential parts of “Li-free” microbatteries. The Li deficiency in the as deposited Li-Nb-O films is cured by forming a “sandwich” of Li-Nb-O/Li/Li-Nb-O, which after annealing becomes ionic conductor. The electrical behavior of an annealed film depends on two sources. The first is due to properties of the material itself and the second is based on the network of the grain boundaries. The average size of the grains is strongly influenced by the structure of the ohmic-contact/substrate. The electrical behavior of the electrolyte/anode interface of the “Li-free” structure LiNbO3/Li/Cu/Au is very similar to the impedance measurements of the single LiNbO3 single films. The whole multilayer structure, though, presents a third relaxation time which is consistent of a small resistance. This resistance is independent of temperature and it seems that is due to the metallic interface Li/Cu/Au.  相似文献   
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