纳米晶SnO2粉体的合成

Crystalline tin oxide nanoparticles were synthesized by the direct precipitation from the starting material granulated tin. TG-DTA of the precursor showed a heavy weight loss at about 130℃ accompanied by an endothermic peak， two exothermic peaks above 200℃ accompanied by small weight loss indicated the decomposition and the oxidation of residual NO₃^- ion and PEG. XRD showed that obtained particles agreed well with the determination result of bulk SnO₂. The broadened XRD patterns became sharper as the calcining temperature turned to higher， it was indicated that the growth of the particle was exhibited. The surface area of the particles calcined at 300℃ was 161.1m²·g^-1 and declined as the calcining temperature turned to higher. TEM showed an heavier agglomeration at higher temperature.     

TiO2胶粒在铝合金表面的电泳沉积及所制薄膜的光催化性能研究

TiO₂ membranes were prepared on aluminum-alloy thin plates by electrophoretic deposition and dip coating in a colloid solution of TiO₂, respectively. The photocatalytic activity of TiO₂ membrane was compared using ethylene as reactant, and the crystal and morphological structure of the membrane were characterized by XRD and SEM. The results showed that a more compact membrane with high loading of TiO₂ but lower photocatalytic activity of unit TiO₂ mass was obtained by electrophoresis compared with dip coating method. The addition of polyethylene glycol (PEG) to the sol of TiO₂ could improve the specific photocatalytic activity (ethylene conversion per unit mass TiO₂ and unit area of membrane piece) of the electrophoresis-membrane prepared from the sol, but could not change the specific photocatalytic activity of the dip-coating membrane from the sol. The ethylene conversion on the electrophoresis membrane prepared from the sol containing PEG (50 g·L^-1) was 9 times of that on the dip coating membrane. The effect of PEG on the properties of electrophoresis-membrane of TiO₂ was attributed to the change of electrokinetic properties of sol. Addition of PEG decreased ζ potential value of the sol and the mobility of the sol particle, increased viscidity of the colloid, thus decreasing both the electrophoresis deposition velocity of colloid particles and the electroosmosis velocity of diffuse layer of colloid particles. These favored the formation of a low compact and porous membrane on the electrode in electric field, and thus increasing the availability of TiO₂ in photocatalytic process.     

纳米二氧化钛粉末的溶胶-凝胶法合成及晶相转化

Nanosized TiO₂ powder with anatase and rutile structures was synthesized by a sol-gel method using TiCl₄ ethanol solution as a precursor.The grain size of TiO₂ powder was about 63nm after the precursor was calcined at 600℃ for 2 hours .The experimental techniques of XRD,TEM and Particle Distribution were used to characterize the synthesized specimens. Various special effects were investigated for their contribution to crystal structure and the size of TiO₂ powder .The formation of anatase as well as the rutile phase of TiO₂ was indicted from the XRD when the reaction temperature was above 30℃ and when the sol was irradiated by infrared rays .However, an anatase TiO₂ powder formed after the heat treatment of the dried gel in a temperature range from 300℃ to 500℃.Under the vacuum drying and with the calcined time below 3hours ,the anatase phase was gained .As well as with the increase of gelatinizing time, the anatase TiO₂ powder was obtained.     

从不同氧化态锡盐水热合成法制备纳米SnO2粉体

Nanocrystalline SnO₂ were prepared by a novel gel hydrothermal route from alcoholic solutions of tin(Ⅱ) and tin(Ⅳ) salts. X-ray diffraction analysis and transmission electron microscopy showed that the resulting oxides were both in the form of powders having crystallites of about 5 nm in diameter. The formation procedures of the two precursors and the gas-sensing properties of the two SnO₂ nanocrystals were compared.     

共沉淀法制备负热膨胀性ZrW2O8粉体及其粒径控制初探

Negative thermal expansion (NTE) material ZrW₂O₈ powders were synthesized using co-precipitation route. The precursor of ZrW₂O₈ was studied by Thermogravimetric and differential scanning calorimetry (TG-DSC). The structure and morphology of the resulting powders were characterized by Powder X-ray diffraction (XRD) and Scanning electron microscopy (SEM), respectively. The results showed that the samples were single phase of α-ZrW₂O₈ with regular shape. High temperature X-ray diffraction measurement indicated that the thermal expansion coefficient of ZrW₂O₈ was -10.35 × 10^-6 K^-1 in the temperature range from room temperature to 150 ℃, -3.08 ×10^-6 K^-1 from 200 ℃ to 600 ℃ and the average value was -5.38 × 10^-6 K^-1. At the same time, polyethylene glycol (PEG) was used as dispersant to primary control the size of ZrW₂O₈.     

较为宽松条件下水热合成铁酸铋粉体

Bismuth ferrite(BiFeO₃) powders were hydrothermally synthesized by using FeCl₃·6H₂O and BiCl₃ as staring materials, NaOH as a mineralizer and NH₄Cl as an additive. The results show that pure BiFeO₃ powders can be synthesized under loose hydrothermal conditions of reaction temperature ranging from 140 to 230 ℃ and NaOH concentration ranging from 2 mol·L^-1 to 5 mol·L^-1. Moreover, the morphologies of the products can be controlled by changing the hydrothermal conditions.     

Sr3Al2O6∶Eu2+红色发光纳米晶的新型形貌与发光性能的研究

A red luminescent Sr₃Al₂O₆∶Eu²⁺ nanocrystallites with new morphology were synthesized by sol-gel route assisted by microwave irradiation. The phosphor powders were characterized by X-ray diffraction (XRD)， scanning electron microscopy (SEM) and fluorescence spectroscopy. The results reveal that the calcination temperature of the Sr₃Al₂O₆∶Eu²⁺ phosphor crystallites greatly affects its morphology. With temperature increasing， the phosphor crystallites morphology showed primarily from nanorod-like， mixture of nanorod and flower-like to homogeneous flower-like morphology. The effects of new morphology on luminescent properties of phosphors were investigated. Uniformly dispersed flower-like Sr₃Al₂O₆∶Eu²⁺ phosphor powders showed the strongest luminescent intensity and the longest afterglow time.     

有机体系中纳米TiO2 / ZrO2修饰电极的制备及电催化活性

The complexes Ti(OCH₂CH₂O)₂ and Zr(OCH₂CH₂O)₂ were directly synthesized by using HOCH₂CH₂OH dissolution in 50 mL flask. The nano-ZrO₂ / TiO₂ powders were prepared by a direct sol-gel synthesis using the above solution and followed by drying at 400 ℃ for 2 h. The complexes were characterized by FTIR and ¹H NMR. XRD and TEM were used to investigate the structure of nano-ZrO₂ / TiO₂. The results show that the complexes containing ^-OCH₂CH₂O^- group could prevent the precursor from agglomeration and sintering during the hydrolysis and calcination process. The ZrO₂ / TiO₂ powders of 20～35 nm was thus obtained in a high purity. The highly active nano-ZrO₂ / TiO₂ modified electrode was prepared by using daubing and calcination. The electro-catalytic activities of this electrode in (COOH)₂ were investigated. The discharge current of nano-ZrO₂ / TiO₂ electrode increased obviously. In preparative electrolysis under optimal conditions, the average yield and current efficiency for HOOC-CHO were 84.7% and 91.6 %, respectively.     

锂离子电池正极材料LiMn2O4的合成与晶体结构（英）

Spinel LiMn₂O₄ powders were prepared using two-step synthesis method consisting of solid-state reaction method and citrate modified sol-gel method. The effects of the calcination temperature and the Li/Mn ratio of raw materials were studied on the physicochemical and electrochemical properties of the spinel LiMn₂O₄ powders, such as crystallinity, lattice constant and density. The title compound was characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Polycrystalline LiMn₂O₄ powers calcined at 750 ℃ were found to be composed of very uniformly-sized microcrystal with an average particle size of 300 nm. The improvement in electrochemical properties was mainly attributed to the process of re-grinding by absolute alcohol.     

超细掺锑SnO2制备工艺中前驱体洗涤分离的研究

Sb-doped SnO₂ ultrafine powders were prepared via oxidation-coprecipitation. Also the relation between surface characteristic (i.e. charged status and solvation) and precursor separation was studied. The results showed that the filter washing speed of precursor can be improved by reduced Precursor |ζ| values or lessen Precursor solvation. For example, adding to little organic solvents (such as ethanol )in Washing liquid morely accelerates to separation speed of precursor. This method and principle of washing and separation precursor can be used by other nona powders preparation with precipitation method, also sb doped SnO₂ ultrafine powders will be prepared easily in industry with it.     

Li_(1.3)Ti_(1.7)Al_(0.3)(PO_4)_3,Na_(1.3)Ti_(1.7)Al_(0.3)(PO_4)_3的离子交换研究

研究了在不同温度下的NaNO3和AgNO3水溶液中Li1.3Ti1.7Al0.3(PO4)3和Na1.3Ti1.7Al0.3(PO4)3离子交换行为.实验表明Li1.3Ti1.7Al0.3(PO4)3和Na1.3Ti1.7Al0.3(PO4)3均显示出了高选择性与Na+和Ag+进行离子交换的特征,且对Ag+的选择性高于Na+.升高温度可显著提高Ag/Li和Ag/Na的交换反应速度.     

Crystal growth, structure determination, and optical properties of new potassium-rare-earth silicates K3RESi2O7 (RE=Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu)

Single crystals of K₃RESi₂O₇ (RE=Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) were grown from a potassium fluoride flux. Two different structure types were found for this series. Silicates containing the larger rare earths, RE=Gd, Tb, Dy, Ho, Er, Tm, Yb crystallize in a structure K₃RESi₂O₇ that contains the rare-earth cation in both a slightly distorted octahedral and an ideal trigonal prismatic coordination environment, while in K₃LuSi₂O₇, containing the smallest of the rare earths, lutetium is found solely in an octahedral coordination environment. The structure of K₃LuSi₂O₇ crystallizes in space group P6₃/mmc with a=5.71160(10) Å and c=13.8883(6) Å. The structures containing the remaining rare earths crystallize in the space group P6₃/mcm with the lattice parameters of a=9.9359(2) Å, c=14.4295(4) Å, (K₃GdSi₂O₇); a=9.88730(10) Å, c=14.3856(3) Å, (K₃TbSi₂O₇); a=9.8673(2) Å, c=14.3572(4) Å, (K₃DySi₂O₇); a=9.8408(3) Å, c=14.3206(6) Å, (K₃HoSi₂O₇); a=9.82120(10) Å, c=14.2986(2) Å, (K₃ErSi₂O₇); a=9.80200(10) Å, c=14.2863(4) Å, (K₃TmSi₂O₇); a=9.78190(10) Å, c=14.2401(3) Å, (K₃YbSi₂O₇). The optical properties of the silicates were investigated and K₃TbSi₂O₇ was found to fluoresce in the visible.     

Near infrared study of aqueous rare-earth ethylsulfates

The near infrared spectra of aqueous solutions of the ethylsulfates of La, Nd, Gd, Tb, Er, Yb, Lu, Y, and Na have been determined from about 0.2 mol-dm^–3 to nearly saturation. The extinction coefficients of water have been calculated taking into account the absorption of ethylslfate anions determined in separate experiments. Their values appeared to be nearly the same as that of pure water. The relative contents of free OH groups in 0.5 and 0.7M solutions have been estimated from the absorbances at 1160 nm. They were lower in solutions of the heavy rare-earth ethylsulfates (Tb, Er, Yb, Lu) than in equimolar solutions of the lighter ones (La, Nd), confirming our previous view that secondary hydration of the heavy trivalent rare-earth cations is distinctly stronger than that of the lighter ones. A comparison of the spectra of these aqueous ethylsulfates with those of perchlorates shows that the structure-breaking ability of the C₂H₅SO ₄ ^– ion is much smaller than that of perchlorate anion.     

Structural studies of five layer Aurivillius oxides: A2Bi4Ti5O18 (A=Ca, Sr, Ba and Pb)

The room temperature structures of the five layer Aurivillius phases A₂Bi₄Ti₅O₁₈ (A=Ca, Sr, Ba and Pb) have been refined from powder neutron diffraction data using the Rietveld method. The structures consist of [Bi₂O₂]²⁺ layers interleaved with perovskite-like [A₂Bi₂Ti₅O₁₆]²⁻ blocks. The structures were refined in the orthorhombic space group B2eb (SG. No. 41), Z=4, and the unit cell parameters of the oxides are a=5.4251(2), b=5.4034(1), c=48.486(1); a=5.4650(2), b=5.4625(3), c=48.852(1); a=5.4988(3), b=5.4980(4), c=50.352(1); a=5.4701(2), b=5.4577(2), c=49.643(1) for A=Ca, Sr, Ba and Pb, respectively. The structural features of the compounds were found similar to n=2-4 layers bismuth oxides. The strain caused by mismatch of cell parameter requirements for the [Bi₂O₂]²⁺ layers and perovskite-like [A₂Bi₂Ti₅O₁₆]²⁻ blocks were relieved by tilting of the TiO₆ octahedra. Variable temperature synchrotron X-ray studies for Ca and Pb compounds showed that the orthorhombic structure persisted up to 675 and 475 K, respectively. Raman spectra of the compounds are also presented.     

电感耦合等离子体光谱法(ICP-AES)测定银精矿中铜、铅、锌、砷、镉、钙、镁、锰含量

针对银精矿样品复杂,难消解的特点,研究了不同酸溶法和碱熔法对样品的消解情况,建立了硝酸,盐酸,氢氟酸,高氯酸消解银精矿的方法。根据元素灵敏度和抗干扰性,选定各元素的测定波长。通过酸溶样和碱熔样测定结果比对,验证了方法准确性。建立了四酸消解-电感耦合等离子体光谱法测定银精矿中铜、铅、锌、砷、镉、钙、镁、锰含量的方法,元素的线性相关系数均在0.9999以上。通过共存元素干扰实验,确定了银精矿中高含量元素(铜、铅、锌、铁、锑、铋等)对测定元素结果没有影响。方法检出限：Cu 0.0063 mg/L, Pb 0.0159 mg/L ,Zn 0.0090 mg/L,As 0.0192 mg/L, Cd 0.0093 mg/L ,Ca 0.0084 mg/L, Mg 0.0075 mg/L, Mn 0.0081 mg/L。测定下限：Cu 0.0105mg/L,Pb 0.0265 mg/L, Zn 0.0150 mg/L, As 0.0320 mg/L, Cd 0.0155 mg/L, Ca 0.0140 mg/L, Mg 0.0125 mg/L,Mn 0.0135 mg/L。3个样品的相对标准偏差在0.87%~3.56%之间,加标回收率在95.00%~103.56%之间。方法流程短,操作简单,快速,灵敏度和再现性高,结果准确可靠,可以满足银精矿中铜、铅、锌、砷、镉、钙、镁、锰含量的测定。     

The crystal chemistry of Bi6TP2O15+x, T=Fe, Ni, Zn: Isomorphism and polymorphism, structural relationship to Bi6TiP2O16

The crystal structures of compounds with nominal compositions Bi₆FeP₂O_15+x (I), Bi₆NiP₂O_15+x (II) and Bi₆ZnP₂O_15+x (III) were determined from single-crystal X-ray diffraction data. They are monoclinic, space group I2, Z=2. The lattice parameters for (I) are a=11.2644(7), b=5.4380(3), c=11.1440(5) Å, β=96.154(4)°; for (II) a=11.259(7), b=5.461(4), c=11.109(7) Å, β=96.65(1)°; for (III) a=19.7271(5), b=5.4376(2), c=16.9730(6) Å, β=131.932(1)°. Least squares refinements on F² converged for (I) to R1=0.0554, wR₂=0.1408; for (II) R₁=0.0647, wR₂=0.1697; for (III) R₁=0.0385, wR₂=0.1023. The crystals are complexly twinned by 2-fold rotation about , by inversion and by mirror reflection. The structures consist of edge-sharing articulations of OBi₄ tetrahedra forming layers in the a-c plane that then continue by edge-sharing parallel to the b-axis. The three-dimensional networks are bridged by Fe and Ni octahedra in (I) and (II) and by Zn trigonal bipyramids in (III) as well as by oxygen atoms of the PO₄ moieties. Bi also randomly occupies the octahedral sites. Oxygen vacancies exist in the structures of the three compounds due to required charge balances and they occur in the octahedral coordination polyhedron of the transition metal. In compound (III), no positional disorder in atomic sites is present. The Bi-O coordination polyhedra are trigonal prisms with one, two or three faces capped. Magnetic susceptibility data for compound (I) were obtained between 4.2 and 350 K. Between 4.2 and 250 K it is paramagnetic, μ_eff=6.1 μ_B; a magnetic transition occurs above 250 K.     

Preparation of ZrO2-TiO2-CeO2 and Its Application in the Selective Catalytic Reduction of NO with NH3

TiO₂,ZrO₂-TiO₂,andZrO₂-TiO₂-CeO₂ were prepared by co-precipitation method and characterized by X-ray diffraction (XRD), specific surface area measurements (BET), temperature programmed desorption (NH₃-TPD), oxygen storage capacity (OSC), and temperature programmed reduction (H₂-TPR). The results showed that ZrO₂-TiO₂-CeO₂ exhibited large number of surface strong acid, possessed some oxygen storage capacity, and strong redox property. The three materials were used as supports and the monolith catalysts were prepared with 1% (w) V₂O₅ and 9% (w)WO₃ for selective catalytic reduction (SCR) of NO with ammonia in the presence of excessive O₂, and the results of catalytic activity showed that the catalyst used ZrO₂-TiO₂-CeO₂ as support yielded nearly 100% NO conversion at 275 °C at a gas hourly space velocity (GHSV) of 10000 h⁻¹, and it had the best catalytic activity and showed great potential for practical application.     

The Phase Relations in the System In2O3–TiO2–MgO at 1100 and 1350°C

The phase relations in the system In₂O₃–TiO₂–MgO at 1100 and 1350°C are determined by a classical quenching method. In this system, there are four pseudobinary compounds, In₂TiO₅, MgTi₂O₅ (pseudobrookite type), MgTiO₃ (ilmenite type), and Mg₂TiO₄ (spinel type) at 1100°C. At 1350°C, in addition to these compounds there exist a spinel-type solid solution Mg_2−xIn_2xTi_1−xO₄ (0≤x≤1) and a compound In₆Ti₆MgO₂₂ with lattice constants a=5.9236(7) Å, b=3.3862(4) Å, c=6.3609(7) Å, β=108.15(1)°, and q=0.369, which is isostructural with the monoclinic In₃Ti₂FeO₁₀ in the system In₂O₃–TiO₂–MgO. The relation between the lattice constants of the spinel phase and the composition nearly satisfies Vegard's law. In₆Ti₆MgO₂₂ extends a solid solution range to In₂₀Ti₁₇Mg₃O₆₇ with lattice constants of a=5.9230(5) Å, b=3.3823(3) Å, c=6.3698(6) Å, β=108.10(5)°, and q=0.360. The distributions of constituent cations in the solid solutions are discussed in terms of their ionic radius and site preference effect.     

Microstructures of Some Bi-W-Nb-O Phases

Microstructures of three Bi-W-Nb-O phases have been examined by using high-resolution transmission electron microscopy. Bi₁₇W₂Nb₃O₃₉ and Bi₁₇WNb₃O₃₆ have incommensurate superstructures derived from the defect fluorite-type δ-Bi₂O₃ and can be regarded as intermediate phases between the type II solid solutions in the Bi-Nb-O and Bi-W-O systems. Bi₈W₂Nb₂O₂₃ has a Bi₂WO₆-like subunit cell with a stepped superstructure. Formation mechanisms of various superstructures are discussed.     

Structure Study of Bi2.5Na0.5Ta2O9 and Bi2.5Nam−1.5NbmO3m+3 (m=2-4) by Neutron Powder Diffraction and Electron Microscopy

The crystal structures of Bi_2.5Na_0.5Ta₂O₉ and Bi_2.5Na_m-1.5Nb_mO_3m+3 (m=3,4) have been investigated by the Rietveld analysis of their neutron powder diffraction patterns (λ=1.470 Å). These compounds belong to the Aurivillius phase family and are built up by (Bi₂O₂)²⁺ fluorite layers and (A_m-1B_mO_3m+1)^2- (m=2-4) pseudo-perovskite slabs. Bi_2.5Na_0.5Ta₂O₉ (m=2) and Bi_2.5Na_2.5Nb₄O₁₅ (m=4) crystallize in the orthorhombic space group A2₁am, Z=4, with lattice constants of a=5.4763(4), b=5.4478(4), c=24.9710 (15) and a=5.5095(5), b=5.4783(5), c=40.553(3) Å, respectively. Bi_2.5Na_1.5Nb₃O₁₂ (m=3) has been refined in the orthorhombic space group B2cb, Z=4, with the unit-cell parameters a=5.5024(7), b=5.4622(7), and c=32.735(4) Å. In comparison with its isostructural Nb analogue, the structure of Bi_2.5Na_0.5Ta₂O₉ is less distorted and bond valence sum calculations indicate that the Ta-O bonds are somewhat stronger than the Nb-O bonds. The cell parameters a and b increase with increasing m for the compounds Bi_2.5Na_m-1.5Nb_mO_3m+3 (m=2-4), causing a greater strain in the structure. Electron microscopy studies verify that the intergrowth of mixed perovskite layers, caused by stacking faults, also increases with increasing m.