Glass formation in the GexTe100−x binary system: Synthesis by twin roller quenching and co-thermal evaporation techniques

The Ge–Te system exhibits one main composition domain where glasses can be easily prepared by melt quenching technique; this domain is centered on the eutectic composition Ge₁₅Te₈₅. In this work, bulk flakes and films of composition Ge_xTe_100−x with x  50 at.% were prepared by two different quenching techniques: (i) the twin roller quenching for bulk flakes and, (ii) the co-thermal evaporation for films (with thickness comprised between 2 and 14 μm). Electron Probe Micro-Analysis was used to check the composition of the materials while X-ray diffraction allowed identifying the amorphous state and/or the crystalline phases present in the Ge_xTe_100−x samples. Thermal properties for both types of materials were investigated by differential scanning calorimetry. The glass-forming regions were: 11.7–22.0 at.% Ge for bulk flakes and 10.2–35.9 at.% Ge for films. A similar thermal behavior of bulk flakes and thick films was highlighted by Differential Scanning Calorimetry.     

水热条件下不同形貌和晶相碳酸钙的形成和转化

利用碳酸氢钙水热分解制备了具有不同形貌和晶相的碳酸钙.在水热情况下,得到了多种形貌的方解石和霰石碳酸钙,研究了碳酸氢钙浓度、添加剂氯化镁浓度、反应时间和温度等对碳酸钙形貌和晶相的影响.以X射线衍射(XRD)和扫描电镜(SEM)对制备的碳酸钙进行了表征.研究发现,水热条件对碳酸钙形貌和晶相的形成以及演化过程有重要影响.水热条件下发现了稳定的碳酸钙晶相向亚稳定相转化的反常相变,对相关的形成及转化机理进行了相应的阐述.     

ZnSb2O4纳米正三角形的合成与生长机理讨论

以混合的ZnO粉和金属Sb作为前驱物,通过化学气相沉积方法在Si衬底上合成了ZnSb2O4纳米正三角形.利用场发射扫描电子显微镜、透射电子显微镜以及附带的能谱仪对它们的结构和成分进行了表征.并对ZnSb2O4纳米正三角形的生长机理进行了讨论.     

Preparation of palladium clusters protected by silica-supported,crosslinking, partially phosphorylated poly(vinyl alcohol) and their catalytic activity

The palladium cluster protected by silica-supported, crosslinking, partially phosphorylated poly(vinyl alcohol) (P-PVA) was prepared from a crosslinking P-PVA–Pd(II) complex by reduction in alcohol. The P-PVA–Pd complex and the palladium cluster protected by P-PVA were analyzed by electron spectroscopy, X-ray photoelectron spectrometry and transmission electron microscopy. The complex formation between the Pd(II) ion and phosphoric acid groups in P-PVA was important in the formation of a fine palladium cluster. Palladium clusters protected by silica-supported crosslinking P-PVA were used as catalysts for the hydrogenation of nitrobenzene or acrylic acid at 30°C under atmospheric pressure. The palladium cluster protected by crosslinking P-PVA supported on silica was the most active catalyst, was stable and had no by-products, compared with the palladium cluster protected by silica-supported noncrosslinking P-PVA or PVA.     

环氧溴丙烷或环氧氯丙烷/溴代萘/β-环糊精三元包接络合物的燐光性质

在β-环糊精溶液中,环氧溴丙烷(EBH)或环氧氯烷(ECH)能够诱导α-溴代萘(α-BrN)和β-溴代萘(β-BrN)强的室温燐光(RTP).结果证明,EBH比ECH有更强的重原子增强效应(HAEE);α-BrN/ECH/β-CD三元包接合物的稳定性比β-BrN/ECH/β-CD稳定性更强.     

Alkaline hydrolysis of ethylp-nitrophenyl chloromethylphosphonate in the reverse micellar AOT—decane—water system

The influence of cluster formation of micelles on the rate of alkaline hydrolysis of ethylp-nitrophenyl chloromethylphosphonate in the reverse micellar sodium bis(2-ethylhexyl) sulfosuccinate (AOT)—decane—water system was found. The applicability of the pseudo-phase model of micellar catalysis below and above the percolation threshold was shown. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2266–2270, December, 1999.     

Binding and Ionophoric Properties of Polyamide Compounds. Lead Selectivity

The extraction and transport properties of macrocyclic dioxa-, dithia- and diazatetralactams are reported along with those of open-chain analogous compounds. The preference of three of them for lead over alkali, alkaline-earth or other heavy metal cations is discussed.     

甲烷在Mo/HZRP-1催化剂上无氧脱氢芳构化反应Ⅰ.Mo/HZRP-1催化剂的催化性能和积炭行为

用高 硅含磷五 员环 沸 石 分子 筛（ 商 品 代号 Ｈ Ｚ Ｒ Ｐ１） 作 为 载体 ,制 备 了 Ｍｏ／ Ｈ Ｚ Ｒ Ｐ１ 催化剂． 与 Ｍｏ／ Ｈ Ｚ Ｓ Ｍ５ 相比, Ｍｏ／ Ｈ Ｚ Ｒ Ｐ１ 对 甲烷无 氧脱氢芳 构化反 应也表现 出较好的 催化 性能 ． 实验过程 中,在反 应气中添 加 Ｎ２ 作 为内标 物,给出包 括甲烷 在 Ｍｏ／ Ｈ Ｚ Ｒ Ｐ１ 上 的结焦量 、转化率 及各产物选 择性在内 的总碳 物料平衡 计算结果 ． 考 察了不同 Ｍｏ 担 载量对催 化剂性 能和 积炭 行为 的影响; 重点考察 了不同 温度焙烧 后２０ ％ Ｍｏ／ Ｈ Ｚ Ｒ Ｐ１ 催化剂 的性能和 积炭行 为． 在 反应的初 始阶段 ,６ ％ Ｍｏ／ Ｈ Ｚ Ｒ Ｐ１ 表 现出 很 高 的 活 性： 反 应 进 行 ３０ ｍｉｎ 时, 甲 烷 转 化 率 为 １１ ％ , 芳 烃 选 择 性 达８１ ％ , 而催化 剂的结焦 选择性 仅为１２ ％ ． Ｂ Ｅ Ｔ, Ｎ Ｈ３ Ｔ Ｐ Ｄ 和 催 化反 应等 表 征结 果表 明： Ｍｏ 物种的数量 和状态, 分子筛的 酸强度和 酸量以 及分子筛 的孔道 结构是 决定 甲烷 无氧 脱氢 芳构 化反 应性能和积 炭行为 的关键因 素．     

Mechanism of [3+2] Cycloaddition of Alkynes to the [Mo3S4(acac)3(py)3][PF6] Cluster

A study, involving kinetic measurements on the stopped‐flow and conventional UV/Vis timescales, ESI‐MS, NMR spectroscopy and DFT calculations, has been carried out to understand the mechanism of the reaction of [Mo₃S₄(acac)₃(py)₃][PF₆] ([ 1 ]PF₆; acac=acetylacetonate, py=pyridine) with two RC?CR alkynes (R=CH₂OH (btd), COOH (adc)) in CH₃CN. Both reactions show polyphasic kinetics, but experimental and computational data indicate that alkyne activation occurs in a single kinetic step through a concerted mechanism similar to that of organic [3+2] cycloaddition reactions, in this case through the interaction with one Mo(μ‐S)₂ moiety of [ 1 ]⁺. The rate of this step is three orders of magnitude faster for adc than that for btd, and the products initially formed evolve in subsequent steps into compounds that result from substitution of py ligands or from reorganization to give species with different structures. Activation strain analysis of the [3+2] cycloaddition step reveals that the deformation of the two reactants has a small contribution to the difference in the computed activation barriers, which is mainly associated with the change in the extent of their interaction at the transition‐state structures. Subsequent frontier molecular orbital analysis shows that the carboxylic acid substituents on adc stabilize its HOMO and LUMO orbitals with respect to those on btd due to better electron‐withdrawing properties. As a result, the frontier molecular orbitals of the cluster and alkyne become closer in energy; this allows a stronger interaction.