Heterogeneous exchange of precipitates

Summary The heterogeneous exchange of ferric ion between a labelled aqueous ferric chloride solution and some differently prepared ferric (hydr)oxides [(1) a freshly formed “amorphous” ferric (hydr)oxide, (2) ferric oxide obtained by drying the freshly formed precipitate in the air at 165 °C for 4.5 hours, (3) ferric oxide obtained by boiling the freshly formed precipitate in water at 100 °C for 4.5 hours] was investigated at room temperature. The exchange rate decreased in the sequence: (1), (2), (3), that sequence being attributed to the recrystallization of the solid phase in the sense of lattice ordering and particle growth, related to the treatment of freshly formed precipitate before the solid was put in contact with the ferric chloride and labelled. System (1) corresponded to a positively charged precipitate near the equivalency of the system FeCl₃ + NaOH, and the exchange was governed by a rapid recrystallization (particle growth), initiated by labelling⁵⁹FeCl₃ solution in an acid (HCl) medium. In the system (2) selfdiffusion is indicated as the exchange governing process. The radionuclide⁵⁴Mn, being present without isotopic carrier in labelling⁵⁹FeCl³ solution and introduced into the liquid phase, remained in the liquid phase of systems (2) and (3). Contribution number 112 from the Department of Physical Chemistry, Faculty of Sciences, University of Zagreb.     

Fe(AsO4): a new iron(III) arsenate synthesized from thermal treatment of (NH4)[Fe(AsO4)F

The new orthorhombic Fe(AsO4) phase has been synthesized by thermal treatment at 525 degrees C of a new (NH4)[Fe(AsO4)F] compound, with a [Fe(AsO4)F]- skeleton showing channels where the ammonium cations are located. The crystal structure of Fe(AsO4) has been solved from single-crystal data. The structure is formed by layers of edge-sharing dimeric octahedra, and interconnected by chains of alternating FeO6 octahedra and AsO4 tetrahedra.     

Evidence of desulfurization in the oxidative cyclization of thiosemicarbazones. Conversion to 1,3,4-oxadiazole derivatives

The addition of pyridine-2-carbaldehyde 4N-methylthiosemicarbazone (C8H10N4S) to an aqueous solution of copper(II) nitrate yields [[Cu(C8H9N4S)(NO3)]2] (1). This complex consists of centrosymmetric dinuclear entities containing square-pyramidal copper(II) ions bridged through the sulfur thioamide atoms. The oxidation of 1 with KBrO3 or KIO3 gives rise to a compound with formula [[Cu(C8H8N4O)(H2O)2(SO4)]2]*2H2O (2) (C8H8N4O = 2-methylamino-5-pyridin-2-yl-1,3,4-oxadiazole). The structure of 2 is made up of centrosymmetric dimers where the copper(II) ions exhibit a distorted octahedral coordination and are connected by the oxadiazole moiety. The metal ions in 2 can be removed by addition of K4[Fe(CN)6], and then the oxadiazole ligand can be isolated and recrystallized as (C8H8N4O)*3H2O (3).     

高功率准连续半导体激光阵列中应变对独立发光点性能的影响

为了解决阵列中每个发光点性能分布不均的问题,研究了微通道水冷封装的960nm半导体激光器阵列,阵列包含38个发光点,腔长为2mm,在驱动电流为600A、占空比为10%的条件下,输出的峰值功率达到665.6 W,电光转换效率为63.8%,中心波长为959.5nm.通过对应力的理论分析,给出了各个发光点应变的表达式;通过搭建单点测试系统获得阵列中每个发光点的阈值电流、斜率效率、光谱和功率等光电特性;结合应变理论分析可知,器件中发光点的性能与应变大小和类型密切相关,压应变会导致器件波长蓝移、阈值电流降低、功率和斜率效率升高,张应变会导致波长红移、阈值电流升高、功率和斜率效率降低.研究表明,影响器件内部发光点的性能不仅与热效应有关,而且与封装后残余的应变密切相关,通过应力的分布可以预测阵列性能的变化规律,可为高峰值功率、高可靠性的半导体激光阵列的研制提供参考.     

多氯萘的研究

多氯萘(polychlorinated naphthalenes,PCNs)是一类理化性质相似的持久性有机污染物,共有75个同类物.从20世纪70年代起,在全球范围内已陆续停止了PCNs的生产和使用,目前环境中PCNs的污染主要来自历史上生产和使用PCNs以及现有废弃物焚烧、金属冶炼及其它类似过程的废气排放.PCNs广泛分布于各类环境介质中,其造成的环境污染已有所显现,PCNs的相关研究成为近年来环境科学研究的一个热点,PCNs的污染控制已成为一些国家和地区环境管理的新任务.本文重点介绍了PCNs的特性、环境中PCNs的来源、分析检测方法、环境污染水平、环境化学行为与环境归宿.同时还讨论了我国有关PCNs研究的一些初步结果,展望了有关多氯萘的研究发展趋势.     

Synthesis of metal complexes of polyalkylene(arylene) phosphorous amides

Reactions of phosphorous triamides with symmetrical diols in equimolar ratio were studied. These reactions result in formation of unique poly(oligo)amidophosphorous systems. The products obtained are used as ligands for the synthesis of metal complexes of a new type.     

Synthesis of zirconium dioxide nanotubes, nanowires, and nanocables by concentration dependent solution deposition

Nanowires and nanotubes of ZrO₂ were successfully synthesized in this study by concentration dependent solution deposition (CDSD) using Zr[O(CH₂)₃CH₃]₄ as the precursor and anodic aluminum oxide (AAO) as the substrate. Here, we synthesized one-dimensional zirconium dioxide with a simple and efficient method by sucking the precursor solution though the AAO channels. In these experiments, the key factor in the formation of nanowires and nanotubes is the concentration of the precursor, Zr[O(CH₂)₃CH₃]₄ butanol solution. Concentrated Zr[O(CH₂)₃CH₃]₄ solutions cause the formation of solid one-dimensional materials, whereas dilute precursor solutions form hollow nanotubes. The dimensions of the nanomaterials synthesized correspond to the scope of the AAO template are 200–450 nm in diameter and about 60 μm in length. Furthermore, the cable structures of these nanomaterials, wire-in-tube and tube-in-tube, were synthesized by alternately operating the processes. We are reporting an uncomplicated, fast and versatile method applicable to a wide range of materials, taking advantage of the sol–gel process to prepare a vast variety of nanocomposite full of potential applications, especially cable nanomaterials.