Strong Localization Effect of Oxygen Deficiency on Carriersin T1 Based Superconductors

Investigation on the effect of Fe-doped T1-1223 superconductors has been carried out by the simultaneousmeasurements of the spectra of positron annihilation lifetime and Doppler broadening of position annihilation,together with the measurement of Hall coefficient. The results of samples with different doping level show that theoccupation of Fe atoms on Cu sites results in a linear decrement of superconducting transition temperature. The electron concentration in Cu-O layer has been enhanced by Fe doping. The difference in valence between Fe3+ andCu+ induces extra oxygen into the lattice and forms the extra oxygen defects. This Fe dopant leads to a stronglocalization of the electrons in the Cu-O layer. So the decrement of the concentration of the itinerant electronsresults in a decline of the superconducting transition temperature.     

不同抗衡阴离子自旋交叉分子的制备与表征

基于三氮唑（1,2,4-1H-triazole,Htrz）体系的Fe（II）的配合物是一类非常重要的在室温附近发生自旋转变的自旋交叉分子,具有潜在的应用。本文报道了2种基于三氮唑体系的Fe（II）的配合物的制备与表征,分别为［Fe（Htrz）₂（trz）］（CF₃SO₃）和［Fe（Htrz）₂（trz）］（BF₄）,并研究了抗衡阴离子对自旋转变行为的影响。自旋交叉分子的制备由2种前驱体简单混合反应而得,结构表征表明三氮唑参与反应,并且产物中的Fe元素基本为Fe（II）,磁性测试证实了这2种分子存在自旋转变特性,并且这种自旋转变具有温度磁滞效应。实验结果还表明抗衡阴离子对于自旋交叉分子的自旋转变行为有重要的影响。抗衡阴离子空间位阻越小、抗衡阴离子的电负性越强、结构越对称规整,则自旋转变温度越高。     

内壳层电子对过渡金属铁熔化温度的影响

在第一性原理密度泛函理论及其微扰理论的基础上,采用GGA、LDA两种交换关联能近似和TM赝势方法,计算过渡金属铁有8个外层价电子和16个外层价电子两种情况下的晶格结构和原胞参数的变化关系。提出了在计算过渡金属Fe的熔化温度时应把3s²3p⁶当作外层电子看待。     

Thermodynamic Study on Self-propagating High Temperature Synthesis of TiB_2/Fe Composites

Based on the experimental analysis and theoretical calculation, the self-propagating high temperature synthesis of TiB_2/Fe composite was studied. The experimental results show that the interfacial between TiB_2 and Fe was smooth and clear, and the composite bending strength increased with the addition of Fe, however, the hardness decreased accordingly. The thermodynamics of the composites preparation process was calculated. The calculation results show that the primary chemical reaction was the reaction between Ti and B. The extra B can react with Fe, producing the brittle phase Fe_2 B. By increasing Ti, the production of Fe_2B will decrease and a few of Ti-Fe intermetallic compound will be produced by the reaction between Ti and Fe in the composites. Finally, according to the Merzhanov condition of the adiabatic system, it is concluded that the Fe content must be selected between 16.3% and 54.3% by the thermodynamics temperature of reaction calculation.     

Oxygen adsorption on pyrite （100） surface by density functional theory

Pyrite (FeS2) bulk and (100) surface properties and the oxygen adsorption on the surface were studiedby using density functional theory methods. The results show that in the formation of FeS2 (100) surface, there exists a process of electron transfer from Fe dangling bond to S dangling bond. In this situation, surface Fe and S atoms have more ionic properties. Both Fe^2 and S^2- have high electrochemistry reduction activity, which is the base for oxygen adsorption. From the viewpoint of adsorption energy, the parallel form oxygen adsorption is in preference The result also shows that the state of oxygen absorbed on FeS2 surface acts as peroxides rather than O2.     

高能振动球磨作用对纳米Al2O3相变温度的影响

为了探讨球磨作用对纳米A l2O3颗粒相变温度的影响,利用高能振动球磨机分别对纳米A l2O3进行不同时间的球磨,并将球磨作用后的A l2O3粉末在不同温度下进行退火处理。采用XRD、TEM、FT-IR及DTA等方法测定处理前后A l2O3粉末的结构、物相组成及相变温度。结果表明:随着球磨时间的增长,A l2O3的相变温度降低,当球磨时间达50 h时,-γA l2O3到θ-A l2O3相变以及-θA l2O3到-αA l2O3相变的温度均降低了100℃左右;球磨作用促进了A l2O3的晶化,同时可以造成纳米氧化铝的晶格缺陷,是导致相变温度降低的主要原因。     

Fe3+/TiO2纳米薄膜的制备及光催化活性

采用溶胶凝胶法制备含铁二氧化钛复合纳米薄膜．实验表明，铁离子可以形成电荷陷阱，促进空穴的界面传递反应，含铁二氧化钛复合纳米薄膜的光催化活性明显提高。     

<Emphasis Type="Italic">Ab initio</Emphasis> study of doping mechanisms in BaTiO<Subscript>3</Subscript>-BiYO<Subscript>3</Subscript>

A density functional plane-wave pseudopotential method is used to study the doping mechanisms of impurity defects(Bi_Ba, Y_Ti) in BaTiO₃-BiYO₃. Single Bi_Ba and Y_Ti impurities have little structure distortion. Bi forms ionic bond with nearby O atom in single Bi impurity, Y formed [YO₆] octahedral in single Y impurity. However, in the co-doped Bi_Ba and Y_Ti structure, Bi formed three valence bonds with nearby O atom, which causes the large structure distortion. The doped ion makes the mobile of Ti⁴⁺ difficult and loss local ferroelectricity, which will broaden the dielectric constant temperature curve and increase the temperature stability of BaTiO₃ ceramic matrix.     

FeCl_3-Al(i-Bu)_3-phen胶体催化剂制备方法对催化活性的影响

研究了 Fe Cl3- Al( i- Bu) 3- phen胶体催化剂各组分的配比、加入顺序、陈化等制备方式影响催化活性的原因。在加氢汽油介质中 ,较佳 [Al]/[Fe]比值 ,能将 Fe Cl3颗粒表面的 Fe3+ 还原成 Fe2 + ,又与 Al( i- Bu) 3形成双电层使胶粒稳定。较佳的 [phen]/[Fe]比值保证有充分的 phen与 Fe2 +生成稳定的配合物 ,阻止 Al( i- Bu) 3将 Fe2 +还原成低价态 ( Fe+ ,Fe0 ) ,同时较佳配比制得的胶体催化剂颗粒小而均匀。因为生成活性位的反应是快速反应 ,只有 phen、Fe Cl3先于 Al( i- Bu) 3加入 ,才能有效阻止深度还原。所以最好的加料顺序是 phen+ Fe Cl3+ Al( i- Bu) 3;由于本体系是较稳定的胶体体系 ,在陈化时间为 4h、陈化温度在 - 1 5℃～ 2 0℃范围内几乎不影响催化剂活性。因为丁二烯聚合物能增加胶粒的稳定性 ,所以加丁二烯陈化优于不加丁二烯陈化     

Calculation of electron structure by density function theory and electrochemical process of surface （100） of FeS2

The electron structure of FeS2 surface (100) was computed by DFT (density function theory) and the process of electron transfer in sulfide flotation was simulated through ab-initio calculation. The results show that the interaction between xanthate and FeS2 is controlled by the energy of valence band. The products and degree of the reaction depend on the density of state of valence band and concentration of positive hole in valence band. Interaction between xanthate and pyrite can be changed by modifying the election structure of the surface of pyrite. Xanthate is adsorbed on the surface of intrinsic pyrite. But the amount of xanthate adsorbed on the surface of the pyrite with sulfur vacancy is more than that on the surface of the intrinsic pyrite due to the higher electron and vacancy density. Xanthate is not adsorbed on the surface of pyrite with Fe vacancy because of its high Fermi energy.     

Ab Initio Study of Doping Mechanisms in Ba TiO_3-BiYO_3

A density functional plane-wave pseudopotential method is used to study the doping mechanisms of impurity defects(Bi_(Ba),Y_(Ti)) in BaTi O_3-BiYO_3. Single Bi_(Ba) and Y_(Ti) impurities have little structure distortion. Bi forms ionic bond with nearby O atom in single Bi impurity, Y formed [YO_6] octahedral in single Y impurity. However, in the co-doped Bi_(Ba) and Y_(Ti) structure, Bi formed three valence bonds with nearby O atom, which causes the large structure distortion. The doped ion makes the mobile of Ti~(4+) difficult and loss local ferroelectricity, which will broaden the dielectric constant temperature curve and increase the temperature stability of BaTiO_3 ceramic matrix.     

溶胶-凝胶法制备TiO_2和掺铁TiO_2及其纳米粒子的局域结构分析

采用溶胶-凝胶法分别在500℃和600℃烧结温度下制备了掺铁TiO2,而且在相同条件下制备了纯TiO2.XRD测量结果表明：纯TiO2和掺杂0.07%（摩尔分数）铁的TiO2样品均为锐钛矿相,粒径范围为10～25nm;样品粒径随烧结温度的升高而增大,但是掺铁样品的粒径比相同条件下制备的纯TiO2样品的要小.钛原子K-吸收端的EXAFS分析表明：与纯TiO2样品相比,掺铁TiO2样品的氧配位距离缩小,氧配位数增加,减少了氧空位;在不同烧结温度下制备的掺铁TiO2样品中,铁原子都进入了钛原子位置.     

Environmental embrittlement of intermetallic compounds in Fe-Al alloys

First,it is proposed that hydrogen atoms occupy the interstitial sites in Fe3Al and FeAl.Then the environmental embrittlement of intermetallic compounds in Fe-Al alloys is studied in the light of calculated valence electron structures and bond energy of Fe3Al and FeAl containing hydrogen atoms.From the analyses it is found that the states of metal atoms will change,in which more lattice electrons will become covalent electrons to bond with hydrogen atoms when the atomic hydrogen diffuses into the intermetallic compounds in Fe-Al alloys,which will result in the decrease of local metallicity in Fe3Al and FeAl.Meanwhile,it is found that the crystal will easily cleave since solute hydrogen bonds with metal atoms and severely anisotropic bonds form.As a conclusion,these factors result in the environmental embrittlement of Fe3Al and FeAl.     

碳纳米管超晶格结构吸附Fe原子的电子机理

为了提高碳纳米管与Fe基体之间的润湿性,构造出N掺杂有限长碳纳米管超晶格结构.第一性原理能量计算结果表明,新型超晶格结构的埋置能正向升高,结构稳定性降低,但可以显著提高外壁对Fe原子的吸附能力.差分电荷密度结果表明,掺杂体系中N原子与邻近C原子间的π键出现了畸变,使得N原子易与Fe原子发生结合.布居数和电荷转移情况表明,N原子的掺入导致Fe原子失电子能力降低,但Fe—N间共价键强度提高.超晶格结构在一定的扭转和剪切变形下仍能保持对Fe原子的吸附能力.     

铁微量掺杂对二钛酸钡陶瓷介电性能的影响

采用常规固相反应法,以碳酸钡、二氧化钛和三氧化二铁为原料,制备微量铁掺杂的二钛酸钡陶瓷,研究了铁掺杂含量对二钛酸钡陶瓷的相纯度、相对密度和介电性能的影响.采用X射线粉末衍射仪检测二钛酸钡陶瓷的相成分,利用精密阻抗分析仪测量其介电性能.结果表明,微量铁元素进入了二钛酸钡晶格,能够获得单相二钛酸钡陶瓷的最大铁掺杂量在0.5%～1%之间.随着铁含量的增加,铁电相变居里温度快速减小,从未掺杂时的415 ℃降至铁含量为0.02%时的376 ℃和铁含量为0.5%时的324 ℃.同时介电常数逐渐减小,介电峰不断发生宽化,但并没有导致弛豫性铁电体的出现.微量铁元素的掺杂在实验测量误差范围内对陶瓷的密度影响不大.     

大功率MIP中激发温度和电子密度的测定

在假设局部热力学平衡的前提下,分别采用Boltzmann作图法和Saha-Eggert解离平衡计算法测定了大功率微波诱导氮等离子体的激发温度和电子密度。实验结果表明,当选择的元素和光谱线不同、引用的跃迁几率等文献参数不同时,会导致激发温度和电子密度的测定结果显著不同。     

Mechanism of Fixation of Ozone and Its Medical Value

Because of both ozone gas and ozone solution are instable which limits the application of ozone, to solve the storage problem, it is necessary to find a kind ofideal ozone carrier which can combine ozone as an "ozonic compound" in which the bond strength between ozone and carrier should not be too high or too low, to appropriately release ozone from the ozonic compound. Combining Criegee's three-step reaction mechanism of ozone and olefins, the charge, covalent bond levels and energy levels of ozone, ethylene, butadiene and their ozonic compounds were calculated by the first-principles calculation method based on density functional theory methods. The stability of the ozonide, or the bond strength between ozone and ions of carrier were controlled felicitously to release ozone from the ozonide with proper velocity. Ozone antimicrobial was composed on the above principle. It can be used conveniently, especially for common families.     

A molecular dynamics-based comparison of defect production in collision cascades during the bombardment of iron with different ions

We present a computer simulation study on the influence of incident ions on the energy transferred to primary knock-on atoms(PKAs)and defects produced in the cascade collision of irons.Three types of ions(H,Fe,and Xe,which are frequently used in irradiation experiments)with an energy of 3 MeV were simulated.According to the calculation results of SRIM,the average energy transferred to PKAs by Fe ions was the highest among the three types.Then,cascade collisions induced by PKAs with different energies were simulated by the molecular dynamics method.The maximum number of defects produced during irra-diation increased,and the time taken by defect number peak formation was extended with the increased energy of PKAs.The difference in radial distribution function between pre-and post-irradiation irons showed that a higher energy of PKA transferred resulted in a flatter curve.Besides,the law of defects varying in temperature was also investigated.All the researches imply that heavy ions can substitute for neutrons in irradiation experiments which is a practicable way,but the influence of conditions must be taken into account.     

Calculation of the valence electron structures of alloying cementite and its biphase interface

The valence electron structures of alloying cementite θ-(Fe, M)3C and ε-(Fe, M)3C and those of the biphase interfaces between them and α-Fe are calculated with Yu' s empirical electron theory of solid and molecules. The calculation results accord with the actual behavior of alloys.     

密度泛函理论研究CH_3Cl与Cl~(4/)的亲核取代反应

用DFT理论的B3LYP/6 31 1 + +G 水平上对反应Cl- +CH3Cl→ClCH3+Cl-的电子转移的振动光谱进行研究。此反应包括旧键断裂 ,新键生成以及分子间的电子转移。分析了反应物 ,前驱配合物 ,过渡态 ,后继配合物和产物的振动频率及振动模式。它们之间的关系和变化验证了键的断裂、键的生成及电子转移过程