Features of structure and phase transformations in shape memory TiNi-based alloys after severe plastic deformation

Amorphous and nanostructured TiNi-based alloys (Ti₅₀Ni₅₀, Ti_49.5 Ni_50.5, Ti₅₀Ni₄₉Fe₁, in at.%) were first produced using two techniques of severe plastic deformation (SPD), namely high pressure torsion (HPT) and equal channel angular pressing (ECAP). X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to examine the structural states and phase compositions of initial and SPD specimens, their thermostability on annealing and cooling, including in situ experiments. The nanocrystallization temperatures of the amorphous alloys and critical points of martensitic transformations in the crystalline alloys were also determined by means of measurements of the temperature dependence of electrical resistance. It was shown that martensitic transformations in the sequence B2↔R↔B19′ occur in nanostructured TiNi-based alloys or, on the contrary, only a single B2↔R transition can occur in the amorphous-nanocrystalline alloys. In nanostructured SPD-alloys cooled to below the M_s′ or M_s temperatures, nucleation and growth of R- and B19′-martensites occur by a “B2-austenite single nanocrystal — martensite single crystal” mechanism without microtwinning. Only in submicrocrystalline SPD-alloys with coarser B2-grains (larger than 100 – 200 nm) the R and B19′ martensites had a twinned packet morphology.     

作为Be2+磷光探针的含9-冠-3的铱配合物

以4′-(2-苯并噻唑基)苯并-9-冠-3(BTZ9C3)为主配体,用2,2′-联吡啶(bpy)及3-三氟甲基-5-(2′-吡啶基)-1,2-二唑(Hfppz)辅助配体分别合成了离子型铱配合物[Ir(BTZ9C3)2(bpy)]PF6(1)和中性铱配合物[Ir(BTZ9C3)2(fppz)](2)。配合物的结构通过核磁、高分辨质谱进行了表征,并测定了配合物1的单晶结构。对它们光物理性能的研究表明,2种配合物掺杂在PMMA中的发光为黄绿光发射,配合物1的发光波长为535 nm,配合物2的发光波长为541 nm,发光量子效率分别为10.8%,45.0%,发光寿命分别为3.01和2.58μs,为典型的磷光发射。通过循环伏安法测得配合物1和2的HOMO能级分别为-5.60和-5.35 eV。2种配合物对Be2+都有发光增强的选择性识别效果,化学计量比为1∶2,最低检测限低至6.0μmol·L-1。抗干扰能力方面,离子型配合物1的抗干扰能力较好,而中性配合物2受Al3+的干扰较大。     

Crystal Structures and Electrochemical Properties of R1.5Ca1.5MgNi14(R=Nd,Gd and Er)Hydrogen Storage Alloys

Ca₃MgNi₁₄, Nd_1.5Ca_1.5MgNi₁₄, Gd_1.5Ca_1.5MgNi₁₄ and Er_1.5Ca_1.5MgNi₁₄ alloys were prepared by high frequency induction melting and sintering. Characterization and analysis were performed by X-ray diffraction/Rietveld full-spectrum fitting, gaseous P-C-T hydrogen storage test and electrochemical properties tests. It can be found that all alloys consist of Gd₂Co₇-type 3R phase and Ce₂Ni₇-type 2H phase. Although the hydrogen storage capacities of Nd_1.5Ca_1.5MgNi₁₄, Gd_1.5Ca_1.5MgNi₁₄ and Er_1.5Ca_1.5MgNi₁₄ decrease to some extent compared to that of Ca₃MgNi₁₄, their equilibrium pressures for absorption and desorption increase markedly. Moreover, R_1.5Ca_1.5MgNi₁₄ alloys have better cycling stabilities and high-rate discharge(HRD) properties as compared to Ca₃MgNi₁₄. The hydrogen diffusion in alloy electrodes is the main factor to influence the HRD performance.     

Theoretical Study on Reaction Mechanism of Aluminum-Water System

在B3LYP/6-311+G(d,p)和QCISD(T)/6-311++G(d,p) 水平上,对气相中铝与水的反应进行了计算. 理论计算结果表明,铝水反应经过了三条可能的反应通道并且涉及了四个异构体、七个过渡态和两种产物. 其中两条反应通道所涉及的中间物和产物已被实验测得. 同时,在298 K和2000 K计算了铝水反应的焓变和吉布斯自由能,一些计算结果与以前的计算和实验结果吻合较好.     

Synthesis and fungicidal activity of novel 3,5-diarylpyrazole derivatives

(E)-3-(2-chlorophenyl)-1-(2,4-dichlorophenyl) prop-2-en-1-one was prepared from 2-chlorobenzaldehyde followed by cyclization with hydrazine monohydrate. Eight new 3-(2,4-Di-chlorophenyl)-5-(2-chlorophenyl)-4,5-dihydro-N-acylpyrazole derivatives were synthesized and characterized by elemental analysis, IR and ¹H NMR spectroscopy. The experimental results show that the inhibition ratio of compounds 3f towards H. Oryzae and P. oryzae at 50 mg·L⁻¹ is 55.2% and 57.1%, respectively. The inhibition ratio of compounds 3g towards H. Oryzae, P. oryza, S. Sclerotiorum at 50 mg·L⁻¹ is 53.3%, 60.0%, 50.4% respectively. __________ Translated from Chinese Journal of Applied Chemistry, 2007, 27(7): 835–837     

硼、氮共掺杂多孔碳的制备及其超电容性能

分别以含氮菲咯啉、四硼酸钾和醋酸锌为碳源、活化剂和模板,制备了B、N共掺杂多孔碳(BN-PC),并探究模板质量对BN-PC结构和储电性能的影响。当醋酸锌质量为5 g时,所得BN-PC₅中B、N杂原子含量分别为20.21%、18.29%。电化学测试结果表明,以6 mol·L^-1KOH为电解液,BN-PC₅电极展现出高的比电容(在0.05 A·g^-1电流密度下为255 F·g^-1)、优异的倍率性能(在20 A·g^-1电流密度下为188 F·g^-1)和卓越的循环稳定性(在5 A·g^-1的电流密度下循环10 000次比电容保持率为97%)。以3mol·L^-1ZnSO₄为电解液,在平均功率密度为56 W·kg^-1时,BN-PC₅电容器的能量密度可达27 Wh·kg^-1。     

Graphene materials-based chemiluminescence for sensing

Graphene has attracted considerable attention in multidisciplinary research fields and shown various promising applications due to its unique structure and extraordinary physicochemical properties. This review covers the latest advances in graphene materials-based chemiluminescence (CL) for sensing. Chemiluminescence resonance energy transfer and luminescence quenching of graphene materials are discussed. Graphene materials, such as graphene nanosheets, graphene quantum dots, graphene oxide, and reduced graphene oxide have been employed successfully in CL systems in recent years. Graphene materials can be utilized as catalysts, platforms, and energy acceptors to improve the performance of CL. Possible challenges and future perspective on this topic are also presented.     

采用正方元胞的Ising模型实空间重正化群解

在二维正方形晶格上,将元胞取为4格点正方形,采用3种不同的规则定义块自旋状态,进行了重正化群计算,得出了更为精确的结果;解决了元胞内格点数为偶数的重正化群计算问题.     

Magnetic properties of terbium dihydrides

Magnetization measurements of terbium dihydride samples with different hydrogen concentration, TbH_1.92, TbH_1.99, TbH_2.03 and TbH_2.09, in the temperature range from 1.8 to 300 K and at an applied field of 1 kOe are reported. Two first-order antiferromagnetic transitions have been registered in the narrow temperature range between 15–18 K for all hydride compositions. Isothermal magnetization ($\sigma {\left(H\right)}_{T=\mathrm{const}}$) measurements at several temperatures in the vicinity of magnetic transitions have been carried out and used for the magnetic-entropy change, $\Delta S_{\sigma }$, calculations. The magnetic-entropy changes have negative values, and in an applied magnetic field of 5 T they reach 2.5 J/kg K, which is only about 26% of the $\Delta S_{\sigma }\left(H\right)$ value expected from thermal measurements. A much larger magnetic field must be applied for terbium hydrides to be used as refrigerant materials for low-temperature needs.