冲击压缩对TiO2粉末结构和热处理相变的影响

为研究动高压加载下TiO2的冲击改性特点,利用平面冲击波加载技术对TiO2粉体进行冲击压缩实验,以XRD和Raman光谱为主要手段,对样品的结构和热处理相变行为进行了表征和比较.结果表明:冲击压缩作用使TiO2的衍射峰宽化,在样品中形成较大的晶格畸变和应力;飞片速度对TiO2晶粒的粉碎细化效果影响较大.经飞片2258 m/s高速冲击后,微结构中的晶格畸变和应力使TiO2在热处理时的相变温度降低约100℃.TiO2在高速冲击后生成了一种具有锆钛矿结构的同素异构体.     

Superconductivity of the FeSe/SrTiO_3 Interface in View of BCS–BEC Crossover

In paired Fermi systems,strong many-body effects exhibit in the crossover regime between the Bardeen-CooperSchrieffer(BCS)and the Bose-Einstein condensation(BEC)limits.The concept of the BCS-BEC crossover,which is studied intensively in the research field of cold atoms,has been extended to condensed matters.Here by anal.yzing the typical superconductors within the BCS-BEC phase diagram,we find that FeSe-based superconductors are prone to shift their positions in the BCS-BEC crossover regime by charge doping or substrate substitution,since their Fermi energies and the superconducting gap sizes are comparable.Especiall.y at the interface of single-layer FeSe on SrTiO_3 substrate,the superconductivity is relocated closer to the crossover unitary than other doped FeSe-based materials,indicating that the pairing interaction is effectively modulated.We further show that hole-doping can drive the interfacial system into the phase with possible pre-paired electrons,demonstrating its flexible tunability within the BCS-BEC crossover regime.     

冲击合成PZT95/5的X 射线电子能谱

以Pb3O4、ZrO2 和TiO2 粉体为原料,利用柱面冲击波合成了单一的钙钛矿相Pb(Zr0.95Ti0.05)O3 (即PZT95/5)粉体,用X射线衍射(XRD)和X射线电子能谱(XPS)对PZT的物相、元素化学态、分子结构和 成分含量进行了表征。冲击合成粉体和制备陶瓷的XPS结果表明,除表面存在少量的吸附氧外,样品中存在 PZT结构中的Pb、Zr 和O,陶瓷的元素定量计算接近样品的配比。且冲击压缩造成PZT 中 Zr O 、Pb O 键的键长降低,引起冲击合成粉体的Pb4f、Zr3d结合能增大。利用固相合成粉体制备陶瓷 的Zr3dXPS比冲击合成粉体制备陶瓷的Zr3dXPS多2个峰,对应于少量游离ZrO2 被还原的低价锆离子。     

Single-Walled Carbon Nanotubes Acting as Controllable Transport Channels

The motion and equilibrium distribution of water molecules adsorbed inside neutral and negatively charged singlewalled carbon nanotubes (SWNTs) have been studied using molecular dynamics simulations (MDSs) at room temperature based on CHARMM (Chemistry at HARvard Molecular Mechanics) potential parameters. We find that water molecules have a conspicuous electropism phenomenon and regular tubule patterns inside and outside the charged tube wall. The analyses of the motion behaviour of water molecules in the radial and axial directions show that by charging the SWNT, the adsorption efficiency is greatly enhanced, and the electric field produced by the charged SWNTs prevents water molecules from flowing out of the nanotube. However, water molecules can travel through the neutral SWNT in a fluctuating manner. This indicates that by electrically charging and uncharging the SWNTs, one can control the adsorption and transport behaviour of polar molecules in SWNTs for using as a stable storage medium or long transport channels. The transport velocity can be tailored by changing the charge on the SWNTs, which may have a further application as modulatable transport channels.     

混合基体改进剂石墨炉原子吸收法测定锗的方法研究

石墨炉原子吸收法，涂钼热解管，Ｐｔ－Ｎｉ混合基体改进剂，Ｚｅｅｍａｎ效应扣除背景，在１４００℃灰化温度下直接测定锗，方法简单，结果满意。特征质量为２０．３ｐｇ／０．００４Ａ。     

一类新的正定函数

§1.引言 本文讨论下述数学问题:已知R(t)在区间(-t_0,t_0)上为正定函数,问是否存在实轴上定义的正定函数g(t),它在(-t_0,t_0)上与R(t)相同,且它对应的平稳过程X(t).(指X(t)的相关函数恰为g(t))满足性质,t>0,有E(X_t|X_τ,τ≤0)=E(E_1|X_τ,-τ_0≤τ≤0)成立.这里假定E(X_t| X_τ,τ≤0)是X_t,在{X_τ,τ≤0}生成的线性子空间上正交投影.EX_t≡0.用E[X_t·X_s]定义内积,记为,‖X‖~2=。     

凸角域上的椭圆Neumann问题的H^2正则性

对凸角域上的Neumann问题△u au＝finΩ，эu/эn＝0onэΩ，这里α≥0是Ω上的有界可测函数且不恒为0，我们证明了：若f∈L^2（Ω)，则解u∈H^2(Ω)，且有正则性估计‖u‖2.0≤C‖f‖0.Ω。     

鈧与釷之分离及测定 Ⅲ.以四氯邻苯二甲酸作试剂

本文报告以四氯邻苯二甲酸作钪的沉淀剂。适宜于沉淀的溶液酸度为pH2.4—4.4。每一克原子钪需2.5—3克分子沉淀剂,而多至8克分子沉淀剂亦无影响。测定范围在1—102毫克氧化钪之间。本文尚列有四氯邻苯二甲酸的钪盐和钍盐之热分解曲线,钪盐之曲线在80—150℃之间有一平台,经分析证明其钪盐之粗成为C_6Cl_4(COO)-2Sc(OH)·H_2O。另在670—960℃(高于960℃未测)有一平台(形成氧化钪)。钍盐之热分解曲线形式与钪盐相仿,亦有二平台,(a)在80—150℃之间和(b)在720—960℃之间,分别相当于[C_6Cl_4(COO)_2]_2Th·3H_2O及氧化钍之形式。两盐经在120℃干燥后均适于作称衡形式。文中尚报告数种阴离子和碱金属盐之影响,以及与希土元素之分离情形,经两次沉淀轻希土虽多至一百倍而钇多至十倍亦不干扰。在pH2.5—3.4之间希土与本斌剂的沉淀极少(0.3—2毫克希土氧化物)。同时尚设计测定钪和钍的方法,系先在pH1.0—1.1之间两次沉淀钍,再将滤液调节至pH3.0沉淀钪,曾试验Sc_2O_3:ThO_2重量比在1:2.5至1:9.8时结果良好,绝对误差在±0.0至 0.7毫克二氧化钍和 0.1至 0.3毫克氧化钪范围内。