反应溶剂对Bi2S3粉体形貌的影响

利用溶剂热法在不同反应溶剂中制备了不同尺寸的Bi2S3纳米管和纳米棒.利用XRD、SEM、TEM、选区电子衍射(SAED)和高分辨透射电镜(HRTEM)对其结构和形貌进行了表征.结果表明,所制备的产物是结晶良好的正交相Bi2S3,反应溶剂的表面张力、粘度大小和反应溶剂中的比例影响纳米粉体的形貌和尺寸.紫外-可见光吸收光谱测量表明,由于尺寸效应所有粉体的吸收谱相对于正交相的Bi2S3块体都出现蓝移.     

Zn_2GeO_4纳米棒的制备及发光性质

采用水热合成法制备了纯菱形相的Zn_2GeO_4纳米棒,研究了水热制备前驱体溶液的pH值对材料尺寸及形貌的影响以及Zn_2GeO_4纳米棒的光学性质。扫描电子显微镜(SEM)测试结果表明,随着前驱体溶液pH值的变化样品逐渐由微米级块状结构生长成为纳米颗粒,并且进一步形成纳米棒结构。纳米棒的尺寸由长200 nm变化到500 nm。室温光致发光(PL)光谱中观察到位于450和530 nm两个不同的发光峰,其分别源于Zn_2GeO_4的不同缺陷能级。     

Zn2GeO4纳米棒的制备及发光性质

采用水热合成法制备了纯菱形相的Zn₂GeO₄纳米棒,研究了水热制备前驱体溶液的pH值对材料尺寸及形貌的影响以及Zn₂GeO₄纳米棒的光学性质。扫描电子显微镜（SEM）测试结果表明,随着前驱体溶液pH值的变化样品逐渐由微米级块状结构生长成为纳米颗粒,并且进一步形成纳米棒结构。纳米棒的尺寸由长200 nm变化到500 nm。室温光致发光（PL）光谱中观察到位于450和530 nm两个不同的发光峰,其分别源于Zn₂GeO₄的不同缺陷能级。     

Influence of Microwave Synthesis Parameters on the Size and Morphology of the Resulting MgAl2O4 Nanoparticles

In the present study, Nano-sized magnesium aluminate powders were successfully synthesized via microwave process based on the reaction between Mg (NO₃)₂·6H₂O and Al (NO₃)₃·9H₂O in distilled water, at various conditions. The products were characterized by X-ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy, photoluminescence (PL) spectroscopy, and EDAX analysis. The effects of different parameters such as reaction time and microwave power on the morphology, particle size, and PL properties of the product were studied by SEM images and the PL.     

铌源和掺杂位置对LiFePO4/C电化学性能的影响

使用Nb2O5和Nb(OC6H5)5为铌源对LiFePO4/C中的锂位和铁位分别掺杂,采用碳热还原法合成掺杂Nb的磷酸铁锂系列材料。运用X射线衍射仪、扫描电镜、循环伏安、交流阻抗谱和恒电流充放电测试等对材料进行表征。结果表明:相比掺杂位置,铌源对材料的颗粒形貌和粒径分布影响更大,而颗粒大小对材料的电化学性能,尤其是大倍率性能的提高有重要作用;掺杂在Li位的Nb元素比在Fe位能更好的稳定晶体结构,从而有利于提高循环性能。     

A study of the selenites of cerium

The solubilities of the systems CeO₂-SeO₂-H₂O and Ce₂O₃-SeO₂-H₂O were studied at 100°C. The field of crystallization of Ce(SeO₃)₂ was established in the system CeO₂-SeO₂-H₂O, and fields of crystallization of Ce₂(SeO₃)₃ and Ce₂(SeO₃)₃H₂SeO₃ were established in the system Ce₂O₃-SeO₂-H₂O. The compound obtained were identified by means of chemical, X-ray and derivatograph analysis. The mechanism of thermal dissociation of Ce(SeO₃)₂, Ce₂(SeO₃)₃ and Ce₂(SeO₃)₃·H₂SeO₃ was studied. This revised version was published online in August 2006 with corrections to the Cover Date.     

球磨-溶剂热诱导法合成WS2纳米棒及其摩擦性能

采用行星式高能球磨机，将WS₂与S粉末混合球磨，得到纳米片状结构的前驱体，然后添加分散剂聚乙二醇(PEG)用溶剂热诱导的方法使纳米片状前驱体发生结构转变，制备了棒状结构的WS₂纳米材料。用XRD、SEM、TEM等方法对WS₂纳米棒进行了形貌和结构表征，并对其作为润滑油添加剂的摩擦性能进行了初步的研究。     

Sol-Emulsion-Gel Synthesis of Alumina-Zirconia Composite Microspheres

Oxide microspheres in the system Al₂O₃-ZrO₂ (AZ), with the Al₂O₃:ZrO₂ molar ratios as 87:13, 78:22, 74:26 and 64:36 were obtained from emulsified bi-component sols by the sol-emulsion-gel method. The surfactant concentration and viscosity of the sols were found to affect the characteristics of the derived microspheres. The gel and calcined microspheres were investigated by using thermogravimetry analysis (TGA), differential thermal analysis (DTA), X-ray diffraction (XRD), optical and scanning electron microscopy (SEM) and particle size analysis. TGA indicated the removal of most of the volatiles, i.e. 40 ± 2 wt% up to about 500°C. Crystallization of gel microspheres at about 900°C was confirmed by DTA and XRD. XRD results also indicated the retainment of tetragonal (t-)ZrO₂, in the absence of stabilizers, at 1600°C. The optical and scanning electron microscopy confirmed the spherical morphology of the gel and calcined particles. The particle size distribution of the AZ microspheres calcined at 1200°C for 1 h exhibited a size range of 5–60 m with the average particle size (d ₅₀) varied from 23 to 26 m.     

Synthesis and properties of a novel plugging agent based on the PAN microspheres with sodium carbonate

A new plugging agent, which derived from the copolymer of polyacrylonitrile, was successfully synthesized by using acrylonitrile as monomer, poly(ethylene glycol) diacrylate as cross-linker, AIBN as initiator, cyclohexane as solvent, and anhydrous sodium carbonate as the alkaline additive, its structure and surface morphology were characterized using FTIR and SEM. As key investigation parameters, in an aqueous environment, the gel viscosity η and distribution of particle size with different dosage of Na₂CO₃, the gel viscosity η with aging time, and the slow release mechanism of Na₂CO₃ in resulting plugging agent were investigated, its gel procedure was also described.     

Pr4(SeO3)2(SeO4)F6 und NaSm(SeO3)(SeO4): Selenit‐Selenate der Selten‐Erd‐Elemente

Pr₄(SeO₃)₂(SeO₄)F₆ and NaSm(SeO₃)(SeO₄): Selenite‐Selenates of Rare Earth Elements Light green single crystals of Pr₄(SeO₃)₂(SeO₄)F₆ have been obtained from the decomposition of Pr₂(SeO₄)₃ in the presence of LiF in a gold ampoule. The monoclinic compound (C2/c, Z = 4, a = 2230.5(3), b = 710.54(9), c = 835.6(1) pm, β = 98.05(2)°, R_all = 0.0341) contains two crystallographically different Pr³⁺ ions. Pr(1)³⁺ is attached by six fluoride ions and two chelating SeO₃^2– groups (CN = 10), Pr(2)³⁺ is surrounded by four fluoride ions, three monodentate SeO₃^2– and two SeO₄^2– groups. One of the latter acts as a chelating ligand, so the CN of Pr(2)³⁺ is 10. The selenite ions are themselves coordinated by five and the selenate ions by four Pr³⁺ ions. The coordination number of the F^– ions is three and four, respectively. The linkage of the coordination polyhedra leads to cavities in the crystal structure which incorporate the lone pairs of the selenite ions. The reaction of Sm₂(SeO₄)₃ and NaCl in gold ampoules yielded light yellow single crystals of NaSm(SeO₃)(SeO₄). The monoclinic compound (P2₁/c, Z = 4, a = 1066.9(2), b = 691.66(8), c = 825.88(9) pm, β = 91.00(2)°, R_all = 0.0530) contains tenfold oxygen coordinated Sm³⁺ ions. The oxygen atoms belong to five SeO₃^2– and two SeO₄^2– ions. Two of the SeO₃^2– groups as well as one of the SeO₄^2– groups act as a chelating ligand. The sodium ions are surrounded by five SeO₄^2– ions and one SeO₃^2– group. One of the selenate ions is attached chelating leading to a coordination number of seven. Each selenite group is coordinated by six (5 × Sm³⁺ and 1 × Na⁺), each selenate ion by seven cations (5 × Na⁺ and 2 × Sm³⁺).     

Chemical vapor transport and solid-state exchange synthesis of new copper selenite bromides

A new dimorphic copper selenite bromide, Cu₅(SeO₃)₄Br₂ was obtained via chemical transport reactions. α-Cu₅(SeO₃)₄Br₂, monoclinic (1m) and β-Cu₅(SeO₃)₄Br₂, triclinic (1a) polymorphs were produced simultaneously upon reaction of amorphous, partially dehydrated copper selenite and copper bromide. 1m is similar to Cu₅(SeO₃)₄Cl₂, whereas 1a is distantly related to Ni₅(SeO₃)₄Br₂ and Co₅(SeO₃)₄Br₂. Attempts to reproduce synthesis of 1a via exchange reaction between Na₂SeO₃ and CuBr₂ resulted in a new Na₂[Cu₇O₂](SeO₃)₄Br₄ (2). Current study demonstrates for the first time, that both chemical vapor and exchange reactions can be employed in preparation of new selenite halides.     

Syntheses, crystal structures and characterizations of BaZn(SeO3)2 and BaZn(TeO3)Cl2

Two new barium zinc selenite and tellurite, namely, BaZn(SeO₃)₂ and BaZn(TeO₃)Cl₂, have been synthesized by the solid state reaction. The structure of BaZn(SeO₃)₂ features double chains of [Zn(SeO₃)₂]²⁻ anions composed of four- and eight-member rings which are alternatively along a-axis. The double chains of [Zn₂(TeO₃)₂Cl₃]³⁻ anions in BaZn(TeO₃)Cl₂ are formed by Zn₃Te₃ rings in which each tellurite group connects with three ZnO₃Cl tetrahedra. BaZn(SeO₃)₂ and BaZn(TeO₃)Cl₂ are wide bandgap semiconductors based on optical diffuse reflectance spectrum measurements.     

Three modifications of BaCu(SeO3)2 and the compound SrCu(SeO3)2: Preparation and crystal structure determination

The crystal structures of four hydrothermally synthesized alkaline earth-copper-selenites were determined: BaCu(SeO₃)₂-I [a = 5.247(1), B = 13.353(2), C = 8.981(1) Å, space group Pnm2₁, Z = 4, R_w = 0.024 for 1270 reflections], BaCu(SeO₃)₂-II [a = 5.256(1), B = 13.231(2), C = 8.933(1) Å, β = 90.19(1)°, space group P2₁/c, Z = 4, R_w = 0.046 for 2238 reflections], BaCu(SeO₃)₂-III [a = 8.031(1), B = 5.185(1), C = 15.823(2) Å, β = 90.83(1)°, space group C2/c, Z = 4, R_w = 0.038 for 1866 reflections], and SrCu(SeO₃)₂ [a = 7.929(1), B = 5.132(1), C = 14.997(2) Å, β = 90.53(1)°, space group C2/c, Z = 4, R_w = 0.028 for 1414 reflections; isotypic with BaCu(SeO₃)₂-III].BaCu(SeO₃)₂-I and -II contain Cu(SeO₃)₂ sheets lying parallel to (100) formed by CuO₄ “squares” and selenite groups. These sheets are topologically different: in BaCu(SeO₃)₂-I they are formed by the connection of Cu₂(SeO₃) and Cu₆(SeO₃)₄ rings while in BaCu(SeO₃)₂-II they are formed by Cu₂(SeO₃)₂ and Cu₆(SeO₃)₆ rings. The Cu(SeO₃)₂ sheets are rugged in BaCu(SeO₃)₂-I and they are slightly waved in BaCu(SeO₃)₂-II. In both compounds they are connected to each other by a fifth Cu---O bond and by the Ba atoms. In BaCu(SeO₃)₂-III and in its isotypic Sr analog the CuO₄ “squares” and the selenite groups form parallel chains [010], which are connected by the alkaline earth atoms.     

Darstellung und Eigenschaften von Blei(lV)-selenit,Pb(SeO3)2, und der Alkali-triselenitoplumbate(IV), M2[Pb(SeO3)3])

Inhaltsübersicht. Blei(IV)-acetat reagiert in wäßriger Essigsäure mit seleniger Säure zu Blei(IV)-selenit, Pb(SeO₃)₂, welches unter geeigneten Versuchsbedingungen mit Alkaliselenitlösungen in die Alkalitriselenitoplumbate(IV), M₂[Pb(SeO₃)₃] übergeführt werden kann (M = NH₄, K, Rb, Cs). Die dargestellten Verbindungen sind kristallin. Preparation and Properties of Lead(IV) Selenite, Pb(SeO₃ )₂, and the Alkali Triselenito-plumbates(IV), M₂[Pb(SeO₃)₃] Lead(IV) acetate reacts in aqueous acetic acid with selenious acid to yield lead(IV) selenite, Pb(SeO₃)₂. Using suitable conditions of preparation lead(IV) selenite reacts with alkali-selenites to yield alkali triselenito-plumbates(lV). M₂[Pb(SeO₃)₃]. All the prepared compounds are cristalline.     

Nd2(SeO3)2(SeO4) · 2H2O – a Mixed‐Valence Compound containing Selenium in the Oxidation States +IV and +VI

Pale pink crystals of Nd₂(SeO₃)₂(SeO₄) · 2H₂O were synthesized under hydrothermal conditions from H₂SeO₃ and Nd₂O₃ at about 200 °C. X‐ray diffraction on powder and single‐crystals revealed that the compound crystallizes with the monoclinic space group C 2/c (a = 12.276(1) Å, b = 7.0783(5) Å, c = 13.329(1) Å, β = 104.276(7)°). The crystal structure of Nd₂(SeO₃)₂(SeO₄) · 2H₂O is an ordered variant of the corresponding erbium compound. Eight oxygen atoms coordinate the Nd^III atom in the shape of a bi‐capped trigonal prism. The oxygen atoms are part of pyramidal (Se^IVO₃)^2? groups, (Se^VIO₄)^2? tetrahedra and water molecules. The [NdO₈] polyhedra share edges to form chains oriented along [010]. The selenate ions link these chains into layers parallel to (001). The layers are interconnected by the selenite ions into a three‐dimensional framework. The dehydration of Nd₂(SeO₃)₂(SeO₄) · 2H₂O starts at 260 °C. The thermal decomposition into Nd₂SeO₅, SeO₂ and O₂ at 680 °C is followed by further loss of SeO₂ leaving cubic Nd₂O₃.     

Investigation of role of urea in morphologically controlled synthesis of calcium‐bismuth bimetallic nanoparticles from chicken egg shells and its catalytic and fuel additive applications

A comparative study on the role of urea in controlling the morphology of calcium‐bismuth (Ca₅Bi₃) bimetallic nanoparticles is carried out. Calcium‐bismuth bimetallic nanoparticles are synthesized in the presence and absence of urea using the solvothermal method. The morphology of the synthesized products is analyzed by scanning electron microscopy. The composition of the product is analyzed by energy‐dispersive X‐ray spectroscopic and X‐ray diffraction (XRD) analyses. Reitveld refinements are performed on the XRD data, and lattice parameters are optimized. Reitveld‐refined parameters are used to construct the structural model of the calcium‐bismuth product. The formation mechanism of needle like particles from an orthorhombic unit cell is also proposed. The degradation of Congo red dye is catalyzed by synthesized Ca₅Bi₃ bimetallic nanoneedles in an aqueous medium. The effect of catalyst dose on the apparent rate constant (k_app) of degradation is studied and compared with literature. Ca₅Bi₃ bimetallic nanoneedles are also used as an additive in commercial diesel obtained from Pakistan State Oil, Limited. The effect of an additive dose on the calorific value of diesel is studied. How the Ca₅Bi₃ additive influenced other fuel quality parameters such as flash point, fire point, pour point, cloud point, kinematic viscosity, and specific gravity is also studied.     

Characterization of h-WO3 nanorods synthesized by hydrothermal process

Hexagonal tungsten oxide nanorods have been synthesized by hydrothermal strategy using Na₂WO₄·2H₂O as tungsten source, aniline and sulfate sodium as structure-directing templates. Techniques X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy have been used to characterize the structure, morphology and composition of the nanorods. The h-WO₃ nanorods are up to 5 μm in length, and 50–70 nm in diameter.     

Untersuchung der Phasengleichgewichtein den Systemen Cs2SeO4-CoSeO4-H2Ound Cs2SeO4-NiSeO4-H2O bei 25.0°C

Zusammenfassung.  Die Phasengleichgewichte in den Systemen Cs₂SeO₄-CoSeO₄-H₂O und Cs₂SeO₄-NiSeO₄-H₂O bei 25.0°C wurden untersucht. Dabei wurde die Entstehung zweier kongruent l?slicher Doppelsalze (Cs₂Co(SeO₄)₂ċ6H₂O und Cs₂Ni(SeO₄)₂ċ6H₂O) festgestellt, die mittels chemischer, thermogravimetrischer und r?ntgenographischer Methoden identifiziert wurden.

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Investigation of the Phase Equilibria in the Systems Cs₂SeO₄-CoSeO₄-H₂Oand Cs₂SeO₄-NiSeO₄-H₂O at 25.0°C

Summary.  Phase equilibria in the systems Cs₂SeO₄-CoSeO₄-H₂O and Cs₂SeO₄-NiSeO₄-H₂O at 25.0°C were studied. Two congruently soluble double salts (Cs₂Co(SeO₄)₂ċ6H₂O and Cs₂Ni(SeO₄)₂ċ 6H₂O) were found to be formed which were identified by chemical, thermogravimetrical, and X-ray phase analysis.

Received October 14, 1999. Accepted (revised) February 1, 2000     

Wasserfreie Selenite des Lanthans: Synthese und Kristallstruktur von La2(SeO3)3 und LaFSeO3

Anhydrous Selenites of Lanthanum: Syntheses and Crystal Structures of La₂(SeO₃)₃ and LaFSeO₃ Colorless single crystals of La₂(SeO₃)₃ were obtained via the decomposition of La₂(SeO₄)₃ in the presence of NaCl in sealed gold ampoules. The compound crystallizes in the orthorhombic system (Pnma, Z = 4, a = 846.7(1), b = 1428.6(1), c = 710.3(2) pm, R_all = 0.0223) and contains La³⁺ in tenfold coordination of oxygen atoms which belong to seven SeO₃^2– groups. Hence, three of the latter act as bidentate ligands. The reaction of LiF with La₂(SeO₄)₃ in sealed gold ampoules yielded colorless single crystals of LaFSeO₃ (monoclinic, P2₁/c, Z = 12, a = 1819.8(3), b = 715.75(8), c = 846.4(1) pm, β = 96.89(2)°, R_all = 0.0352). The crystal structure contains three crystallographically different La³⁺ ions. La1 is surrounded by six oxygen atoms from five SeO₃^2– groups and four fluoride ions, La2 is coordinated by two bidentate SeO₃^2– ions and seven fluoride ligands. La3 is surrounded by oxygen atoms only with the coordination number and polyhedron being almost the same as found for La³⁺ in La₂(SeO₃)₃. Furthermore, the crystal structures of both compounds are strongly influenced by the lone pairs of the SeO₃^2– groups.     

Copper lanthanide selenite oxohalides with francisite structure: Synthesis and structural characteristics

The reaction of lanthanide oxohalides with CuO and SeO₂ gave the products Cu₃Ln(SeO₃)₂O₂X (Ln = lanthanide, X = Cl, Br). The oxochlorides are formed with all lanthanides, while oxobromides are formed only for Ln = La-Gd. The structures of the Cu₃Ln(SeO₃)₂O₂Cl phases for Ln = Nd (I) and Y (II) were determined by the Rietveld method. It was found that Cu₃Ln(SeO₃)₂O₂X has the structure of francisite (orthorhombic system, space group Pmmn), which does not change substantially upon the variation of the Ln³⁺ radius. No similar compounds with tellurium(IV) were found.