Preparation of PbS and PbSe nanocrystals by a new solvothermal route

A new solvothermal route for the preparation of nanocrystals of PbS and PbSe, involving the reaction of lead stearate with sulfur or selenium and tetralin (tetrahydronaphthalene) in toluene solvent is described. Tetralin in the presence of S/Se gives H₂S/H₂Se and gets aromatized to naphthalene. The nanocrystals have been characterized by powder X-ray diffraction and electron microscopy. Use of surfactant Triton X-100 (polyoxyethylene(10)isooctylphenyl ether) resulted in both nanorods and nanoparticles of PbSe. Capping by citric acid and malonic acid reduce the particle sizes to less than 10 nm.     

Preparation and characterization of ionic liquid intercalation compounds into layered zirconium phosphates

In this work, immobilizing a series of ionic liquids (ILs) 1-alkyl-3-methylimidazolium chloride [C _n mim]Cl (n = 2, 4, 6, 8) on the layered zirconium phosphates were investigated. [C₄mim]Cl was used to explore in detail the factors affecting intercalation. By comparing several starting materials including α-zirconium phosphate (α-ZrP), γ-zirconium phosphate (γ-ZrP) and the corresponding alkylamine preintercalated composites, it was found that the α-ZrP · 2BA (i.e., preintercalated BA were arranged in a bilayer mode at the galleries of α-ZrP) was a suitable host for intercalating ILs. Intercalation was verified with X-ray diffraction (XRD), Raman, UV–Vis and other instrumental approaches. pH effect on immobilization was investigated. Other ionic liquids including [C _n mim]Cl (n = 2, 6, 8) intercalation compounds were prepared. Based on XRD data, the interlayer distances of the studied intercalation compounds were similar, suggesting that the ionic liquids were arranged in an approximately planar manner, as confirmed by molecular modeling.     

乙二醇溶剂热法制备纳米TiO2

用乙二醇溶剂热法制备了锐钛矿相纳米TiO2,用X射线粉末衍射(XRO)、红外光谱仪(FTIR)、热重分析(TG-DTA)和透射电子显微镜(TEM)对制备的样品进行了表征,研究了乙二醇浓度、含水量、反应温度和反应时间对纳米TiO2晶型和晶粒尺寸的影响.结果表明:所得的纳米TiO2粒径分布窄,单分散性好.随着溶剂热反应温度的升高,纳米TiO2的晶粒尺寸逐渐变大,但随着溶剂热反应时间的延长,纳米TiO2的晶粒尺寸却几乎不变.     

溶剂热法制备不同微米结构的氧化亚铜

以乙酸铜为原料,采用溶剂热法合成了球形直径约为2~3μm和八面体粒径大小约为4μm的氧化亚铜颗粒。通过选用不同的还原剂如三乙醇胺和乙二醇,系统研究了不同反应体系中如反应温度、溶剂、原料配比和添加表面活性剂十六烷基三甲基溴化铵(CTAB)对微米结构氧化亚铜晶型与形貌的影响,选出制备氧化亚铜八面体和球形的最佳条件,并初步探讨了氧化亚铜微米颗粒的生长机理。     

Synthesis of CoO nanoparticles by esterification reaction under solvothermal conditions

A new esterification reaction under solvothermal conditions was first applied to synthesize CoO nanoparticles in this paper. Esterification reaction of cobalt acetate and anhydrous ethanol under solvothermal conditions results in the formation of CoO nanoparticles. The concentrations of cobalt acetate, reaction temperature and surfactant to as-synthesized CoO have been explored. SEM, TEM and XRD were employed to characterize the size, morphology and crystalline structure of the as-synthesized CoO nanoparticles. It is revealed that the FCC-structured CoO nanoparticles are of uniform tetragonal projected shape with good dispersion. Typically, CoO nanoparticles with an average size of 35 nm were obtained at 150 °C for 24 h using 0.08 mol/L solution of Co(CH₃COO)₂·4H₂O in ethanol under solvothermal conditions.     

Thermal expansion behaviour of barium and strontium zirconium phosphates

Ba_1.5-xSr_xZr₄P₅SiO₂₄ compounds withx = 0, 0.25, 0.5, 0.75, 1.0, 1.25 and 1.5, belonging to the low thermal expansion NZP family were synthesized by the solid state reaction method. The XRD pattern could be completely indexed with respect to space group indicating the ordering of vacancy at the divalent cation octahedral sites. The microstructure and bulk thermal expansion coefficient from room temperature to 800°C of the sintered samples have been studied. All the samples show very low coefficient of thermal expansion (CTE), withx = 0 samples showing negative expansion. A small substitution of strontium in the pure barium compound changes the sign of CTE. Similarly,x = 1.5 sample (pure strontium) shows a positive CTE and a small substitution of barium changes its sign.X = 1.0 and 1.25 samples have almost constant CTE over the entire temperature range. The low thermal expansion of these samples can be attributed to the ordering of the ions in the crystal structure of these materials     

中低温固相反应法制备纳米级铈锆复合氧化物固溶体

以碳酸铈、碳酸锆、草酸为原料,用中低温固相反应法制备了纳米级铈锆复合氧化物(CexZr1-xO2)。通过XRD、TEM、BET等测试手段对产物进行了表征,结果表明:所得产物为单一的立方晶系固溶体,平均粒径<40nm,比表面积达98.94m2/g。采用中低温固相反应法制备纳米级铈锆复合氧化物无需溶剂、无废液、节能,是一种绿色化学新工艺。     

Preparation of ultrafine zirconium dioxide particles by thermal decomposition of zirconium alkoxide vapour

Ultrafine zirconia particles are produced by thermal decomposition of zirconium tetratertiary butoxide (ZrTB) vapour. The introduction of ZrTB vapour into the cylindrical electric furnace, is achieved by three different methods: (evaporator, pressurized nebulizer and ultrasonic nebulizer). The properties of the fine particles obtained by these methods are mainly analysed by X-ray diffraction and transmission electron microscopy. It is found that ultrafine zirconia particles produced at relatively low temperatures from 600 to 700° C are spherical in the diameter range 0.035 to 0.15 μm and of tetragonal phase. Furthermore, two-component fine particles of zirconia-ilver are generated by putting the silver solid inside the furnace containing alkoxide vapour, and are deposited by inertia on to a glass substrate under low pressure to form films having a thickness of 17 to 33 μm. The electrical characteristics of the films are evaluated, and the conductance of the film is found to increase with the content of the silver component.     

Synthesis, microstructure and dielectric properties of zirconium doped barium strontium titanate obtained by solvothermal method

(Ba_0.8Sr_0.2Zr_yTi_1?yO₃) (y = 0.05, 0.1, 0.15 and 0.2) nanosized powders is synthesized by solvothermal method. The formation of (Ba_0.8Sr_0.2Zr_yTi_1?yO₃) was confirmed by XRD, FT-IR and XPS analysis. The purity of the (Ba_0.8Sr_0.2Zr_yTi_1?yO₃) was examined using FT-IR spectroscopy. The X-ray analysis proves that all as-synthesized Ba_0.8Sr_0.2Zr_yTi_1?yO₃ powders have a cubic perovskite structure. The surface characterization indicates the powder contains Zr and Sr elements. SEM investigation shows that the average particle size is reduced with increasing the Zr content and the average particle size is in the range 37–50 nm, the well dispersed nano powders have narrow particle size distribution. The study of dielectric properties shows that the Curie peaks of dielectric constant become broader and shift towards lower temperature on the basis of Ba_0.8Sr_0.2TiO₃ and the dielectric loss decreases with increasing Zr content.     

Synthesis of high-surface-area complex zirconium phosphates via mechanochemical activation route

 High-power ball mill activation of the mixture of hydrated zirconium and lanthanum salts (oxonitrates, oxochlorides) with ammonium phosphate followed by hydrothermal treatment at temperatures not exceeding 200°C and a nearly neutral pH was found to yield crystalline dispersed phase of a cubic NH₄Zr₂(PO₄)₃ type along with admixtures of disordered orthorhombic compounds of a zirconium orthophosphate type. In the same conditions and at the same Zr/P ratio, hydrothermal treatment of gels obtained by reacting mixed zirconium and lanthanum nitrates solutions with ammonium phosphates yields no crystalline products, and only treatment in acid media generates a phase of the α-ZrPO₄(OH) type coexisting with the NH₄Zr₂(PO₄)₃ phase if polyethylene oxide is present. X-ray powder diffraction, transmission electron microscopy, ³¹MAS-NMR, FTIRS and thermal analysis were applied to elucidate factors affecting crystallization of complex zirconium phosphates in the hydrothermal conditions. The most essential factor appears to be generation of some nuclei of zirconium phosphates under high pressures developed in the course of mixed solids mechanical activation. These nuclei are embedded into matrix of such well-crystallized solid products as ammonium nitrate or chloride. Hence, metastable cubic or orthorhombic structure of the phases obtained via mechanical activation route can be assigned to the nuclei-matrix orientation relationship. Due to easily scaled-up synthesis procedure, these results appear to be very promising for manufacturing of dispersed framework zirconium phosphates as acid catalysts or fast proton conductors. Received: 18 November 1998 / Reviewed and accepted: 2 December 1998     

Photoluminescence of GaN microcrystallites prepared by a new solvothermal process

GaN microcrystallites have been prepared by a solvothermal process. The influence of the synthesis temperature on the crystallinity of the resulting GaN has been studied on three samples, prepared at 400, 600 and 800°C in the same pressure conditions (150 MPa) and duration (6 h). The resulting powders were characterized by several techniques: X-ray diffraction to evaluate the reaction rate, scanning electron microscopy (SEM) to determine the morphology and size of the microcrystallites and photoluminescence to evaluate the quality of the powders.     

Recycling of fiber reinforced plastics using depolymerization by solvothermal reaction with catalyst

Fiber reinforced plastics (FRP) have been widely used as a high strength material. However, it is well known that the FRP is one of the most difficult materials to fractionate into elemental components, namely fiber, filler, and polymers in the waste recycling process. Therefore, the wastes are treated in the incineration or landfilling without any recycling approaches. We have developed a new recycling method using subcritical fluids where unsaturated polyester (UP) resin in FRP can be efficiently depolymerized to separate glass fiber from filler and polymer. Reactions were carried out with or without a catalyst (K₃PO₄) in diethyleneglycol monomethylethter (DGMM) and benzyl alcohol under their subcritical state at temperatures 463–623 K for 1–8 h in a batch reactor. The conversion of UP became fast as the catalyst/solvent molar ratio increased and it was enhanced in the presence of K₃PO₄ catalyst in subcritical BZA. The glass fiber recovered after the FRP treatment in subcritical BZA was relatively long, while it became short and somewhat damaged at temperature higher than 573 K. The similar trend was observed when DGMM was used as a solvent.     

Synthesis and morphological control of rare earth oxide nanoparticles by solvothermal reaction

Eu doped Y₂O₃ and some kinds of other rare earth oxides nanoparticles such as Er₂O₃, Nd₂O₃, Ho₂O₃, Lu₂O₃, and Dy₂O₃ were prepared by a simple co-precipitation-solvothermal treatment-calcination process, where the co-precipitated amorphous hydroxide precursors obtained by adding rare earth nitrate solutions in ammonia solutions were heated in solvents such as water, alcohols and glycols, followed by calcination in air. The morphology of rare earth oxide particles strongly depended on the solvothermal reaction medium but not related to the kind of rare earth oxide. The powders prepared in water and ethanol possessed nanowire structure, where the aspect ratio of powder treated in water was higher than that in ethanol. The powders prepared by co-precipition-solvothermal treatment-calcination process using ethylene glycol consisted of near-spherical nanoparticles whereas that prepared by conventional co-precipitation-calcination method consisted of hardly agglomerated submicron particles. The nanoparticles of Eu³⁺ doped Y₂O₃ prepared by co-precipition-solvothermal treatment-calcination process showed similar intensity of photoluminescence with the submicron particles by co-precipition-calcination process.     

Analyses of nano-crystalline LiCoVO4 prepared by solvothermal reaction

LiOH·H₂O, Co(NO₃)₂·6H₂O and NH₄VO₃ were used to prepare nano-crystalline LiCoVO₄ by 150 °C solvothermal reaction in isopropanol for 10–360 h and subsequent calcination at 300–500 °C for 6 h. XRD, TEM and selected area electron diffraction (SAED) revealed the presence of nano-crystalline LiCoVO₄ with inverse spinel structure. The V–O stretching vibration modes of VO₄ tetrahedrons were detected by FTIR over the range 617–835 cm^− 1 and by Raman spectrometer at 805.7 and 783.1 cm^− 1. Co, V and O were detected by EDX. TGA of solvothermal products shows weight loss due to the evaporation and decomposition processes at 40–648 °C.     

Preparation of spherical zirconium salt particles by homogeneous precipitation

Spherical basic zirconium sulphate particles were prepared by homogeneous precipitation in mixed solutions of zirconium sulphate and urea. Values of [SO ₄ ^2– ]/[Zr⁴⁺] and [urea]/[Zr⁴⁺] in starting mixed solutions and cooling rate may affect the formation of spherical particles. Complexes such as [Zr(OH)_n]^4–n could prevent the formation and thus lead to gel precipitation. In addition, spherical particles could only be obtained in the presence of SO ₄ ^2– ; for NO^3– and Cl^–, only gel precipitation occurred.     

Characterization of AgBiS2 nanostructured flowers produced by solvothermal reaction

AgBiS₂ nanostructured flowers were produced from CH₃COOAg, Bi(NO₃)₃.5H₂O and thiosemicarbazide (NH₂CSNHNH₂) using different solvents [ethylene glycol (EG), water (H₂O), polyethylene glycol with molecular weight of 200 (PEG200), and propylene glycol (PG)] in Teflon-lined stainless steel autoclaves. The phase and purity were detected using X-ray diffraction (XRD), controlled by the solvents. The product was purified AgBiS₂ produced by the 200 °C and 24 h reaction in EG, corresponding to selected area electron diffraction (SAED) and simulation patterns. Scanning and transmission electron microscopies (SEM and TEM) revealed the formation of nanostructured flowers — enlarged by the increase in the lengths of time and temperature. Their photoluminescence (PL) emissions were detected at the same wavelength of 382 nm (3.24 eV), although they were produced under different conditions.     

Preparation of barium titanate nanocube particles by solvothermal method and their characterization

Barium titanate (BaTiO₃) nanocube particles below 20 nm were prepared by solvothermal method. A selection of organic solvent and inorganic materials of Ba and Ti sources was most important for the preparation of nanocubes. A nucleation and particle growth of BaTiO₃ nanoparticles led to a formation of the BaTiO₃ nanocubes with a size of 10–15 nm at temperatures above 200 °C.     

Thermal expansion of NZP-family alkali-metal (Na, K) zirconium phosphates

The thermal expansion of the A _x Zr_2.25-0.25x(PO₄)₃ phosphates with A = Na(x = 0.5,1.0,2.0,3.0,4.0, 5.0) and K(x = 1.0, 3.0, 5.0), crystallizing in structures of the NaZr₂(PO₄)₃ type (sp. gr.R3c or C2/c), was studied by high-temperature x-ray powder diffraction in the range 20–700‡C. The lattice parametersa and c and thea- andc-axis thermal expansion coefficients (α_a and α_c) were determined. The thermal expansion of the phosphates was found to be highly anisotropic (α_a < 0, α_c > 0). The strongest anisotropy was found in NaZr₂(PO₄)₃ (α_a = -4.89 x 10^-6 K^-1, α_c = 22.02 x 10^-6 K^-1), KZr₂(PO₄)₃ (α_a =-5.30 x 10^-6 K^-1, α_c = 5.41 x 10^-6 K^-1), and Na₅Zr(PO₄)₃ (α_a = -5.82 x 10^-6 K^-1, α_c = 20.73 x 10^-6 K^-1). K₅Zr(PO₄)₃ exhibited the smallest thermal expansion and weak anisotropy (α_a = -2.14 x 10^-6 K^-1, α_c = 2.65 x 10^-6 K^-1). The effects of M(l) and M(2) site occupancies on α_a, α_c,a, and c were assessed. The relative magnitudes of crystal-chemical and thermal expansion in the Na and K compounds were analyzed.     

Thermal expansion behaviour of sodium zirconium phosphate structure type phosphates containing tin

Thermal expansion behaviour of sodium zirconium phosphate structure type phosphates of the formula AM³⁺SnP₃O₁₂ (A=Ca, Sr and Ba; M³⁺=Cr and Fe) was studied by high temperature X-ray diffraction and dilatometry in the temperature range 298-1073 K. The variation in the hexagonal lattice parameters of the Ca-containing compounds is in line with the ‘sodium zirconium phosphate behaviour’. However, the strontium- and barium-containing compounds display an altogether different behaviour of axial expansion. The results are explained based on the crystal chemistry of these compounds.