NaX分子筛吸附分离CO2/CH4的巨正则蒙特卡洛模拟

采用巨正则蒙特卡洛模拟与理想吸附溶液理论相结合的方法,研究了CO₂、CH₄分子在NaX分子筛上的吸附性能。通过对比实验数据在不同吸附理论模型下的拟合结果并计算相应的吸附热,描述了CO₂、CH₄气体的吸附分离过程。结果表明,CH₄分子的吸附强度比CO₂分子弱,更贴近理想吸附;CO₂分子的吸附选择性随其在空气中的体积分数升高而降低,在低压条件下随温度的升高而降低。因此,低温低压更有利于CO₂分子的分离。     

温度及压力对CO2置换CH4的影响

利用潞安和寺河煤样进行了不同温度和压力条件下CO2/CH4混合气体的等温吸附/解吸实验,根据Langmuir等温吸附模型及其扩展形式,结合分离因子和单位压降解吸率两个参数,分别分析了温度和压力对CO2置换CH4影响的效果,提出了低温、低压条件下具有更好的置换效果,认为低温低压下置换反应主要向解吸需要能量低、吸附释放能量高的方向进行,即需要能量较小的CO2吸附—CH4解吸方向.研究结果表明:同等条件下CO2吸附能力比CH4吸附能力更强;在3MPa注入压力条件下,随着温度逐渐升高CO2对CH4的分离因子依次减小,显示出温度为20℃时置换效果更佳;在30℃温度条件下,随着压力的的升高,CH4单位压降解吸率依次降低,显示出压力为2MPa时置换效果更好;CO2的吸附能高于CH4的吸附能,在低温、低压的低能量条件下CO2具有相对更好的吸附能力.     

CH3CH2F与O（3P）反应机理的量子化学研究

用量子化学从头算MP2(full)/6-311G(d,p)方法研究了CH3CH2F与O(3P)反应的反应机理.在QCISD(T)/6-311++G(d,p)水平上精确计算了各反应物种的能量.结果表明:CH3CH2F与O(3P)反应共存在4类反应9个反应通道,分别为抽提氢反应,消氢反应,碳碳键断裂反应和消氟化氢反应,抽提氢反应为主反应通道.     

煤对N2/CH4/CO2混合气体竞争吸附特征与机理研究

为研究煤对N₂,CH₄及CO₂混合气体的竞争吸附特征及其机理,通过混合气体吸附/解吸装置,结合穿透曲线法,对大柳塔(DLT)、硫磺沟(LHG)、瑞能(RN)、山阳(SY)和屯宝(TB)5种煤样,开展了温度为20℃、注气压力为0.25 MPa条件下N₂,CH₄和CO₂等比例混合气体的竞争吸附试验,得到了不同煤样对混合气体竞争吸附的规律;通过低温氮气吸附法,分析了5种煤样的孔隙结构,研究了孔隙对混合气体竞争吸附的影响.结果表明：DLT,LHG和RN煤样中N₂和CH₄先达到吸附平衡,一段时间后这2种气体在装置出口端的体积分数均超过其初始体积分数,而SY和TB煤样中只有N₂的出口端体积分数超过了其初始体积分数.试验结果与Yoon-Nelson模型拟合结果较好,线性相关系数R²基本可达0.9以上;各煤样传质速率常数均有k(N₂)>k(CH_4<...     

N2与CH4对CO2非混相驱油效果的影响

在矿场应用中,注入CO2中混有的杂质气体会影响其驱油效果.为制定更加合理有效的开发方案,有必要研究杂质气体对CO2驱的影响.利用油藏数值模拟方法,在纯CO2气体注入参数优化的基础上,研究了N2与CH4两种杂质气体对CO2非混相驱体积波及系数、驱油效率、油井见气时间和采收率的影响;以尽量提高原油采收率为目标,确定了注入气中杂质气体的临界含量.结果表明,杂质气体的存在会导致CO2非混相驱体积波及系数增大,驱油效率降低,油井见气时间缩短;注入的CO2中N2的摩尔分数最高不应超过5%,CH4的摩尔分数最高不应超过14%.     

红色荧光粉Ca3La3（BO3）5:Eu3+的制备及光学性能

由于红色荧光粉具有提高白光发光二极管（LED）显色指数以及降低色温等优点,因此开发性能优异的白光LED用红色荧光粉一直是白光LED领域研究的重要课题。通过传统的高温固相法制备了系列Ca₃La₃（BO₃）_5:3xEu³⁺红色荧光粉,并通过X射线衍射仪、荧光分光光度计和色坐标分析了荧光粉样品的晶体结构及光学性能。实验结果表明掺杂的Eu³⁺进入了Ca₃La₃（BO₃）₅（CLBO）主晶格,并且掺杂少量的Eu³⁺的CLBO主晶格无杂相生成,得到的Ca₃La₃（BO₃）_5:3xEu³⁺荧光粉的结构与CLBO主晶格一致。该荧光粉被紫外光激发后能发射红光。通过对Ca₃La₃（BO₃）_5:3xEu³⁺荧光粉的光致发光光谱进行计算发现在不同波长光的激发下,色坐标都非常接近美国国家电视系统委员会红光标准。Ca₃La₃（BO₃）_5:3xEu³⁺荧光粉是一种性能优异的白光LED用红色荧光粉。     

掺杂Nd3+离子CsCdBr3晶体光谱的理论分析

运用稀土自由离子理论和晶体场理论,通过对掺杂Nd3+离子的CsCdBr3晶体的发光光谱的计算分析,分别拟合了实验光谱数据中的28、47和65条能级,得出理论晶场能级与实验值的标准差分别为3.83,12.367和25.852 cm-1。该结果比已有的拟合结果小得多,表明此计算结果与实验光谱吻合得较好,说明拟合过程和方法是合理的。同时得到了合理的自由离子参量和晶场参量,为进一步研究稀土离子在晶体材料中受到晶体场作用的各种物理机制打下基础。     

晋城无烟煤煤中CH4和CO2运移规律研究

基于三轴应力条件下,煤岩有效应力、吸附膨胀量和渗透率的一体测试,研究了晋城无烟煤吸附甲烷和二氧化碳后,渗透性随有效应力改变和煤岩吸附膨胀效应的变化规律.认为煤岩吸附膨胀量和孔隙压力的关系可用兰氏方程描述;煤岩渗透性同有效应力、吸附膨胀量均呈负指数函数关系,同时结果表明:甲烷和二氧化碳在晋城无烟煤中的扩散方式不同,煤岩对甲烷的吸附膨胀符合单孔气体扩散模型,而对二氧化碳的吸附膨胀符合双孔气体扩散模型,且甲烷的吸附膨胀速率小于二氧化碳的吸附膨胀速率;煤岩饱和吸附后,各孔隙压力条件下的初始渗透率与孔隙压力呈幂函数关系减小.针对晋城无烟煤,同等条件下煤岩吸附甲烷后的渗透率为吸附二氧化碳后渗透率的1.14～1.51倍,大部分在1.30倍左右.     

Bi2O3和Fe2O3掺杂对BaTiO3陶瓷显微结构的影响

利用扫描电子显微镜(SEM)、透射电子显微镜(TEM)和X射线能量色散谱(EDAX)等结构分析技术,研究了施主(Bi     

2BaTiO3/1SrTiO3/1CaTiO3超晶格的纵向挠曲电系数计算

采用基于密度泛函理论的第一性原理方法,研究了由²BaTiO₃/¹SrTiO₃/¹CaTiO₃所构成的超晶格材料的纵向挠曲电系数。构建了三种超晶胞构型,钛酸钡、钛酸锶和钛酸钙的层数比都为2：1：1,并且保持超晶胞的总层数为16层。对三种超晶胞构型,分别施加余弦应变,分析超晶格中各原子的位移和应变,以及每种构型的纵向挠曲电系数。结果表明,构型Ⅱ的纵向挠曲电系数可达5.63 nC/m,比单晶BaTiO₃、单晶SrTiO₃材料分别提升了16倍和6倍。本文的研究结果对遴选纵向挠曲电系数的材料具有较好的指导意义。     

Electrical conductivity of （Na3AlF6-40%K3AlF6）-AlF3-Al2O3 melts

The effects of contents of AlF3 and Al2O3, and temperature on electrical conductivity of （Na3AlF6-40%K3AlF6）- AlF3-Al2O3 were studied by continuously varying cell censtant （CVCC） technique. The results show that the conductivities of melts increase with the increase of temperature, but by different extents. Every increasing 10 ℃ results in an increase of 1.85 × 10^-2, 1.86× 10^-2, 1.89 × 10^-2 and 2.20 × 10^-2 S/cm in conductivity for the （Na3AlF6-40%K3AlF6）-AlF3 melts containing 0%, 20%, 24%, and 30% AlF3, respectively. An increase of every 10 ℃ in temperature results an increase about 1.89× 10^-2, 1.94 × 10^-2, 1.95 × 10^-2, 1.99× 10^-2 and 2.10× 10^-2 S/cm for （Na3AlF6-40%K3AlF6）-AlF3-Al2O3 melts containing 0%, 1%, 2%, 3% and 4% Al2O3, respectively. The activation energy of conductance was calculated based on Arrhenius equation. Every increasing 1% of AlF3 results in a decrease of 0.019 and 0.020 S/cm in conductivity for （Na3AlF6-40%K3AlF6）-AlF3 melts at 900 and 1 000 ℃, respectively. Every increase of 1% Al2O3 results in a decrease of 0.07 S/cm in conductivity for （Na3AlF6-40%K3AlF6）-AlF3-Al2O3 melts. The activation energy of conductance increases with the increase in content of AlF3 and Al2O3.     

Electrolysis expansion performance of semigraphitic cathode in [K3AlF6/Na3AlF6]-AlF3-Al2O3 bath system

The electrolysis expansion of semigraphitic cathode in [K₃AlF₆/Na₃AlF₆]-AlF₃-Al₂O₃ bath system was tested by self-made modified Rapoport apparatus. A mathematical model was introduced to discuss the effects of α _CR (cryolite ratio) and β _KR (elpasolite content divided by the total amount of elpasolite and sodium cryolite) on performance of cathode electrolysis expansion. The results show that K and Na (potassium and sodium) penetrate into the cathode together and have an obvious influence on the performance of cathode electrolysis expansion. The electrolysis expansion and K/Na penetration rate increase with the increase of α _CR. When α _CR=1.9 and β _KR=0.5, the electrolysis expansion is the highest, which is 3.95%; and when α _CR=1.4 and β _KR=0.1, the electrolysis expansion is the lowest, which is 1.28%. But the effect of β _KR is correlative with α _CR. When α _CR=1.6 and 1.9, with the increase of β _KR, the electrolysis expansion and K/Na penetration rate increase. However, when α _CR=1.4, the electrolysis expansion and K/Na penetration rate firstly increase and then decrease with the increase of β _KR. 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     

Reaction dynamics in the combustion synthesis system of Al-CrO3-Al2O3-NaF-N2-O2

A new material with heat-resistant and adiabatic characteristics and high strength was prepared using the combustion synthesis method by mixed powders of CrO3, Al, Al2O3, and NaF in atmospheric gas. The reaction dynamic process of the Al-CrO3-NaF-Al2O3-N2-O2 new material system by the combustion synthesis method was discussed based on the observation results by SEM, EDS, and XRD in combination with the combustion front quenching method （CFQM） and the relation curves between reaction free enthalpies and the corresponding temperatures. The combustion synthesis mechanism and the formation reasons of the phase in the combustion product were analyzed.     

Modification of LiCo1/3Ni1/3Mn1/3O2 cathode material by CeO2-coating

LiCo_1/3Ni_1/3Mn_1/3O₂ was coated by a layer of 1.0 wt% CeO₂ via sol-gel method. The bared and coated LiMn_1/3Co_1/3Ni_1/3O₂ was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), cyclic voltammogram (CV) and galvanotactic charge-discharge test. The results show that the coating layer has no effect on the crystal structure, only coating on the surface; the 1.0 wt% CeO₂-coated LiCo_1/3Ni_1/3Mn_1/3O₂ exhibits better discharge capacity and cycling performance than the bared LiCo_1/3Ni_1/3Mn_1/3O₂. The discharge capacity of 1.0 wt% CeO₂-coated cathode is 182.5 mAh·g⁻¹ at a current density of 20 mA·g⁻¹, in contrast to 165.8 mAh·g⁻¹of the bared sample. The discharge capacity retention of 1.0 wt% CeO₂-coated sample after 12 cycles reaches 93.2%, in comparison with 86.6% of the bared sample. CV results show that the CeO₂ coating could suppress phase transitions and prevent the surface of cathode material from direct contact with the electrolyte, thus enhance the electrochemical performance of the coated material.     

Synthesis and characterization of Mg3(PO4)2-coated Li1.05Ni1/3Mn1/3Co1/3O2 cathode material for Li-ion battery

Mg₃(PO₄)₂-coated Li_1.05Ni_1/3Mn_1/3Co_1/3O₂ cathode materials were synthesized via co-precipitation method. The morphology, structure, electrochemical performance and thermal stability were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), cyclic voltammetry(CV), electrochemical impedance spectroscopy(EIS), charge/discharge cycling and differential scanning calorimeter (DSC). SEM analysis shows that Mg₃(PO₄)₂-coating changes the morphologies of their particles and increases the grains size. XRD and CV results show that Mg₃(PO₄)₂-coating powder is homogeneous and has better layered structure than the bare one. Mg₃(PO₄)₂-coating improved high rate discharge capacity and cycle-life performance. The reason why the cycling performance of Mg₃(PO₄)₂-coated sample at 55 °C was better than that of room temperature was the increasing of lithium-ion diffusion rate and charge transfer rate with temperature rising. Mg₃(PO₄)₂-coating improved the cathode thermal stability, and the result was consistent with thermal abuse tests using Li-ion cells: the Mg₃(PO₄)₂ coated Li_1.05Ni_1/3Mn_1/3Co_1/3O₂ cathode did not exhibit thermal runaway with smoke and explosion, in contrast to the cells containing the bare Li_1.05Ni_1/3Mn_1/3Co_1/3O₂. Funded by the National Natural Science Foundation of China (No. 20273047)     

三氧化二铝是导致建筑物火灾的严重隐患

建筑物供电线路中的铜线与铝线连接处常常生成一种灰白物质－－三氧化二铝,极易引发建筑物火灾。着重介绍和分析这种灰白物质的成分、生成原因、危害以及防止其生成的主要措施。     

Comparative experiment on layered Li（Ni1/3Co1/3Mn1/3）O2 as the alternative material for LiCoO2

This work was financially supported by the National Natural Science Foundation of China （No.50472093）.     

Dielectric properties of Pb (Zn1/3 Nb2/3) O3?PbZrO3?PbTiO3 solid solution near morphotropic phase boundary

The dielectric properties of Pb(Zn_1/3Nb_2/3) O₃-PbZrO₃−PbTiO₃ (PZN-PZ-PT) system near the rhombohedral/tetragonal morphotropic phase boundary (MPB) are carefully studied in this paper. It is found that, for all samples, the curves around the temperatures of dielectric permittivity peak show the characteristics of diffuse phase transition. The change in PbZrO₃/PbTiO₃ ratio has much influence on the dielectric properties of the samples. The extent of diffuse phase transition increases with the increasing Zr/Ti ratio. The samples in rhombohedral region have typical diffuse phase transition in the temperature range measured. However, for the samples with tetragonal symmetry, a spontaneous normal ferroelectric-relaxor phase transition exists at temperature lower than that of permittivity peak. This normal ferroelectric-relaxor phase transition is confirmed by the experiment of thermally driven current. The analysis of TEM reveals that the samples in tetragonal region show a 90% macrodomain structure, while the samples in rhombohedral region have the configuration of microdomain structure.     

Structure of Bi2O3-ZnO-B2O3 system low-melting sealing glass

Bi_2O_3-ZnO-B_2O_3 system glass is a kind of lead-free low melting sealing glasses. The structure of Bi_2O_3-ZnO-B_2O_3 system low-melting sealing glass was investigated by DSC, FT-IR, XRD and SEM. The results show that with the increase of B_2O_3 content, the transition temperature Tg and softening temperature T_f of Bi_2O_3-ZnO-B_2O_3 system low-melting sealing glasses increase, which leads to the liquid phase precipitation temperature increasing and promotes the structure stability in the glass. With increasing the heat treatment temperature, a large number of liquid phases appear in samples and the sinter efficiency of the samples increases. The FT-IR spectra of the glasses show the presence of some bands that are assigned to vibrations of Bi-O bond from [BO_3] pyramidal and [BiO_6] octahedral units and B-O from [BO_3] and [BO_4] units. With the decrease of B_2O_3 content, the crystallization tendency of the glass increases. In glass samples B_1 and B_2, crystallization starts at 460 ℃ and 540 ℃, respectively. Both of them precipitate Bi-(24)B_2O_(39) phases.