Effect of baking processes on properties of TiB2/C composite cathode material

Pitch and TiB₂/C green composite cathode material were respectively analyzed with simultaneous DSC-TGA, and effects of three baking processes of TiB₂/C composite cathode material, i.e. K25, K5 and M5, on properties of TiB₂/C composite cathode material were investigated. The results show that thermogravimetric behavior of pitch and TiB₂/C green composite cathode is similar, and appears the largest mass loss rate in the temperature range from 200 to 600°C. The bulk density variation of sample K5 before and after baking is the largest (11.9%), that of sample K25 is the second, and that of sample M5 is the smallest (6.7%). The crushing strength of sample M5 is the biggest (51.2 MPa), that of sample K25 is the next, and that of sample K5 is the smallest (32.8 MPa). But, the orders of the electrical resistivity and electrolysis expansion of samples are just opposite with the order of crushing strength. The heating rate has a great impact on the microstructure of sample. The faster the heating rate is, the bigger the pore size and porosity of sample are. Compared with the heating rate between 200 and 600° of samples K25 and K5, that of sample M5 is slower and suitable for baking process of TiB₂/C composite cathode material. Foundation item: Project (2005CB623703) supported by the Major State Basic Research and Development Program of China; Project (2008AA030502) supported by the National High-Tech Research and Development Program of China     

Synthesis and electrochemical performance of TiO2-B as anode material

TiO₂-B was synthesized by solid-state reaction. The structures, surface morphologies and electrochemical performances of TiO₂-B were characterized by X-ray diffractometry (XRD), scanning electron microscopy (SEM) and electrochemical measurement, respectively. The effects of calcining temperature, molar ratio of K₂O to TiO₂ and calcining time on the characteristics of TiO₂-B were investigated. The results show that the calcining time exerts a significant influence on the electrochemical performances of TiO₂-B. The TiO₂-B is obtained with good crystal structure and suitable size by using K₂Ti₄O₉, which is prepared at 950°C for 24 h under the condition of x(K₂O)/x(TiO₂)=1:3.5. The TiO₂-B delivers all initial discharge capacity of 231.6 mA·h/g. And the rate capacity is 73.2 mA·h/g at 1 675 mA/g, which suggests that TiO₂-B is a promising anode material for the lithium ion batteries.     

Structure characterization and electrochemical properties of new lithium salt LiODFB for electrolyte of lithium ion batteries

Lithium difluoro（axalato）borate （LiODFB） was synthesized in dimethyl carbonate （DMC） solvent and purified by the method of solventing-out crystallization. The structure characterization of the purified LiODFB was performed by Fourier transform infrared （FTIR） spectrometry and nuclear magnetic resonance （NMR） spectrometry. The electrochemical properties of the cells using 1 mol/L LiPF6 and 1 mol/L LiODFB in ethylene carbonate （EC）/DMC were investigated, respectively. The results indicate that LiODFB can be reduced at about 1.5 V and form a robust protective solid electrolyte interface （SEI） film on the graphite surface in the first cycle. The graphite/LiNi1/3Mn1/3Co1/3O2 cells with LiODFB-based electrolyte have very good capacity retention at 55 ℃, and show very good rate capability at 0.5C and 1C charge/discharge rate. Therefore, as a new salt, LiODFB is a most promising alternative lithium salt to replace LiPF6 for lithium ion battery electrolytes in the future.     

不锈钢表面粉末渗铝及其抗高温氧化性能研究

研究了316L不锈钢表面的固体粉末渗铝以及渗铝处理前后不锈钢的抗高温氧化性.结果表明,研究所用粉末渗铝法可在不锈钢表面形成厚度约100 μm的渗层,渗层主要由NiAl相和Ni3Al相组成,渗层与基体之间结合紧密;对渗铝不锈钢进行热氧化处理,可在其表面形成致密均匀、且主体成分为氧化铝的表面膜;与没有处理的不锈钢相比,渗铝处理后不锈钢的抗高温氧化性能明确增强,这主要是由于渗铝层在高温下所形成的致密氧化膜层阻止了氧化性气体对基体金属的进一步氧化.     

基于跨层设计的多判据AODV路由优化机制

针对无线Mesh网络中传统AODV协议路由判据单一从而导致路由性能较差的缺陷,提出一种多判据AODV跨层路由优化机制ACRO(AODV Cross-layer Routing Optimization).该机制基于跨层设计思想,采用最小跳数与来自物理层和MAC层的多种路由判据相互协作,考虑了传播环境和接入性能,在路由算法中定义了混合多维路由判据, 并提出多判据AODV跨层路由优化机制.理论分析和NS2仿真结果证明,这种路由优化机制提高了吞吐量,降低了网络时延和载荷,路由性能得到明显改善.     

沉淀法制备超细α-Al2O3

以Al2（SO4）3与（NH4）2CO3为原料，采用液相沉淀法，制备出前驱物碳酸铝铵（AACH），并烧结得到超细Al2O3粉末。通过分析AACH的热重曲线。确定了AACH的高温分解过程；并结合对AACH在不同烧结温度下所得产物XRD图谱的分析，确定了AACH的高温相变过程为：从AACH→AIOOH→Al2O3（无定型）→γ-Al2O3→θAl2O3→α-Al2O3。运用扫描电镜（SEM）对样品的形貌、分散情况进行表征，并估量出α-Al2O3颗粒的粒径大小；测定了α-Al2O3粉末的比表面积，并计算出α-Al2O3颗粒的粒径大小。结果表明，采用该方法能获得平均粒径约为50nm。形貌为球形且分散性良好的α-Al2O3粉体。     

石灰拜耳法赤泥沉降性能的研究

赤泥的沉降性能是关系到氧化铝生产过程能否顺行的重要指标之一。研究了石灰拜耳法新工艺过程中的赤泥沉降压缩性能，结果表明石灰拜耳法工艺过程的赤泥沉降性能略逊于常规拜耳法，但赤泥压缩性能良好，可以满足生产的要求。     

国内移动终端产业面临的机遇

文章首先从操作系统、技术标准、应用平台等方面对移动终端产业呈现的发展趋势进行了归纳,接着对我国终端产业在3G时代所面临的机遇进行了探讨。     

CaO掺杂对10NiO-NiFe2O4复合陶瓷致密化及导电性能的影响

研究了CaO的添加量和烧结温度对10NiO-NiFe2O4复合陶瓷的物相组成、致密度和导电性能的影响.结果表明:0%～4% (质量比,下同)CaO含量范围内,烧结样品的XRD图谱仅有NiO和NiFe2O4的衍射峰.CaO掺杂对10NiO-NiFe2O4复合陶瓷具有明显的助烧作用.材料在烧结温度为1 200 ℃,CaO掺杂量为2%时,致密度达到最大为98.75%,比相同温度下未掺杂CaO的样品提高20%左右.CaO掺杂量对1 200℃烧结的10NiO-NiFe2O4复合陶瓷的电导率影响显著.当CaO掺杂量为0%～1%时,材料电导率在500～650℃区间出现1～2个数量级的突降;当CaO质量分数为2%和4%时,材料电导率在30～960℃范围内随着测试温度的升高而增大;其中,添加2?O样品的电导率在960℃下可达到最大为16.29 S/cm.     

添加剂对超细α-Al2O3的制备及其性能影响

采用硫酸铝和碳酸铵为原料,通过沉淀法制备前驱体碱式碳酸铝铵,采用分散剂及添加剂(MC)防止粉体颗粒的团聚,着重考查了MC在干燥、煅烧过程中的作用.研究表明,MC能有效防止前驱体在干燥过程中的团聚,促进氧化铝在煅烧过程中的相变,大幅度降低了α-Al2O3的相变温度,同时还使颗粒维持在相对"动态"的煅烧状态,减轻了颗粒形成煅烧颈及其他硬团聚的趋势,从而改善了粉体颗粒的分散性能.BET及ICP分析结果表明,MC的引入还有利于产物α-Al2O3比表面积的提高,而且对煅烧产物的杂质元素含量没有影响,产物中氧化铝的质量分数高达99.97%.