魔方状微纳结构BaTiO3的制备及其压电催化性能

在简单溶剂热条件下,通过控制钡、钛物质的量之比制备了魔方状微纳结构BaTiO₃粉体,并以5 mg·L^-1罗丹明B (RhB)溶液为降解对象测试其压电催化性能。采用扫描电子显微镜、X射线衍射、傅里叶变换红外光谱对所制备粉体的物化性质进行详细表征,并测试其压电、光催化活性及循环稳定性。结果表明,钡、钛物质的量之比为1∶1时,合成的粉体为由立方体组装而成的魔方状四方相结构的BaTiO₃。在40 kHz、360 W的超声条件下,180 min内的降解率达90%,5次循环后的降解率为79.7%,变化率为11.4%,优于其光催化性能,具备优异的压电催化活性及循环稳定性。     

反应温度对微波水热法合成Bi2WO6粉体及光催化性能影响的研究

以Na₂WO₄·2H₂O和Bi(NO₃)₃·5H₂O为原料,用微波水热法在140~200 ℃保温1 h合成出不同形貌的正交晶相粉体。利用 XRD、FE-SEM、BET、DRS等分析手段表征了Bi₂WO₆粉体,以RhB溶液为目标降解物,对不同反应温度下合成粉体的光催化性能进行了研究,结果表明：反应温度对合成Bi₂WO₆粉体的物相、形貌及光催化性能均有较大影响,180 ℃时合成的绒线团状Bi₂WO₆粉体比表面积为25.63 m²·g^-1,禁带宽度为2.92 eV,因光在粉体催化剂内产生了漫反射,光催化效果最佳,在可见光照射下3h时RhB溶液降解率达到了96%,紫外光照射下2 h时RhB溶液降解率达到了98%以上。     

三种化学方法合成K0.5Bi0.5TiO3粉体的机理比较

采用溶胶-凝胶法、水热法和溶胶-凝胶-水热法三种化学方法合成K_0.5Bi_0.5TiO₃ (KBT)无铅压电陶瓷粉体. 用X射线衍射(XRD)分析产物的结构, 用扫描电镜(SEM)和透射电镜(TEM)观察产物的形貌. 实验结果表明, 三种化学方法均可获得纯钙钛矿相KBT粉体, 但不同工艺获得的粉体在形貌和生成机制上有很大的不同. 溶胶-凝胶法属高温固相扩散机制, 需要700 ℃以上温度煅烧才可获得KBT纯相, 且粉体颗粒度大、团聚严重. 水热法符合溶解-结晶机制, 生长出四方形的KBT纳米片. 溶胶-凝胶-水热法利用了凝胶团聚体空间链状结构的模板作用, 通过原位结晶机制生长出KBT纳米线.     

纳米CaMgSi2O6粉体的低温合成与微波介电性能

以硝酸锂、偏钒酸铵、硝酸钙、硝酸镁、正硅酸乙酯为原料，采用溶胶-凝胶法低温合成纳米CaMgSi₂O₆微波介质陶瓷粉体，研究了不同粒径粉体的烧结行为与微波介电性能。结果表明，通过在钙镁硅溶胶中引入锂钒烧结助剂可大大降低陶瓷粉体的晶相合成温度，干凝胶在750 ℃煅烧后可获得主晶相为CaMgSi₂O₆、分散性良好、粒径为78～98 nm的陶瓷粉体，可满足微型片式元器件用超薄陶瓷介质层的制备要求;该粉体在890 ℃烧结后获得致密结构的陶瓷，具有良好的微波介电性能:介电常数为7.68，品质因数为24 542 GHz，频率温度系数为-57.25×10^-6 ℃^-1。     

质子导体BaCe0.4Zr0.4M0.2O3-δ (M=In，Y，Gd，Sm)化学稳定性及电性能

采用高温固相法制备了不同阳离子掺杂的BaCe_0.4Zr_0.4M_0.2O_3-δ (M=In,Y,Gd,Sm)系列质子导体。运用X射线衍射仪、扫描电子显微镜分别对四类质子导体的物相结构、微观形貌进行了表征,应用IM6e型电化学工作站测定了其不同温度下的阻抗谱,并对样品在CO₂和沸水中的稳定性进行了研究。结果表明：除Sm³⁺掺杂的质子导体有少量的杂质相Sm₂O₃外,其他3种均为单相立方晶钙钛矿结构;对CO₂和沸水皆表现良好的化学稳定性;Y³⁺掺杂的质子导体具有高的电导率,800 ℃约为2.07×10^-2 S·cm^-1,空气气氛电导活化能为72.34 kJ·mol^-1。     

共沉淀-熔盐法制备BaMoO4∶Eu3+及其发光性能研究

以KCl-NaCl为熔盐,采用共沉淀前躯体-熔盐辅助焙烧法合成了红色发光材料BaMoO₄∶Eu³⁺。运用X射线粉末衍射(XRD)、扫描电子显微镜(SEM)及荧光光谱(PL)等测试手段,研究了熔盐辅助焙烧温度对粉体相结构、形貌和发光性能的影响,并对比了直接采用共沉淀法合成BaMoO₄∶Eu³⁺的结构与发光性能。结果表明：采用两种方法制备的BaMoO₄∶Eu³⁺均是纯相,粒径随温度升高而增大。当KCl-NaCl复合熔盐焙烧温度大于700 ℃,BaMoO₄晶粒在熔盐中实现了(111)面取向生长,得到均一的尖晶石型BaMoO₄∶Eu³⁺微晶。光谱研究表明：共沉淀前躯体-熔盐辅助焙烧法合成样品在615 nm处的Eu³⁺的⁵D₀-⁷F₂发射明显得到加强,样品发出明亮的红色发射光。     

CaTiO3纳米粉体溶胶-凝胶法合成、表征及介电特性

采用无机盐溶胶-凝胶法制备了CaTiO₃纳米粉体，采用TG-DTA、XRD、TEM等技术进行了表征，并探讨了CaTiO₃纳米粉体烧结特性及介电效应。结果表明，干凝胶800 ℃低温煅烧可获得粒径分布较窄、平均粒径为60～70 nm的单相CaTiO₃纳米粉。纳米CaTiO₃粉具有较大的比表面积，使作为粉体烧结驱动力的表面能剧增，促使CaTiO₃在1 200 ℃实现致密烧结，比固相法制备的微米粉烧结降低100～200 ℃，且具有较宽的烧结温区。与微米级粉体烧结体介电特性相比，纳米粉具有更高的Q_f值。纳米CaTiO₃粉制备的陶瓷在1 250 ℃烧结2 h，获得优良的介电性能：ε_r=172，Q_f=4 239 GHz，τ_f=+7.68 × 10^-4 ℃^-1。     

Li3V2(PO4)3的溶胶-凝胶法合成及其性能研究

以LiOH·H₂O、NH₄VO₃、H₃PO₄和柠檬酸等为原料采用溶胶-凝胶法合成了锂离子二次电池正极材料磷酸钒锂(Li₃V₂(PO₄)₃)。考察了煅烧温度和配位剂种类等条件对产物组成及电化学性能的影响。研究了优化条件下制得样品的循环伏安、充放电性能和循环性能。0.1 C条件下,样品首次放电比容量达129.81 mAh·g^-1，经过100次循环后容量几乎没有衰减，仍保持在128 mAh·g^-1。X射线衍射研究表明合成单一Li₃V₂(PO₄)₃晶体所需温度比固相法低；并考察了循环20次后材料充电到各个单相的晶体结构，通过X射线衍射和最小二乘法计算给出了其晶胞参数变化过程，证实了循环嵌Li过程中晶体结构能够得到重现。     

B2O3-Bi2O3-ZnO-Al2O3玻璃助烧剂对BaTiO3陶瓷烧结条件、晶体结构和介电性能的影响

通过调节B₂O₃‐Bi₂O₃‐ZnO‐Al₂O₃(BBZA)玻璃的添加量研究其对钛酸钡(BaTiO₃)陶瓷烧结条件、晶体结构和介电性能的影响。结果表明：添加适量的BBZA玻璃能够有效地将BaTiO₃陶瓷烧结温度由1350℃降至950℃,并使其致密化。同时,添加BBZA玻璃后,BaTiO₃的晶体结构随着烧结温度的升高而发生转变(立方相→四方相)。另外,BBZA玻璃的引入使BaTiO₃陶瓷的居里峰得到了有效的抑制和拓宽。陶瓷微观形貌显示,玻璃相均匀分布在BaTiO₃晶粒表面。优化的BaTiO₃陶瓷制备条件如下：BBZA添加量(质量分数)为2.0%,烧结温度为950℃。在该条件下制备的BaTiO₃陶瓷介电常数达到1364,介电损耗低至1.2%。     

Cr2(WO4)3和Cr2(MoO4)3的负热膨胀特性研究

用液相反应-前驱物烧结法制备了Cr₂(WO₄)₃和Cr₂(MoO₄)₃粉体。298～1 073 K的原位粉末X射线衍射数据表明Cr₂(WO₄)₃和Cr₂(MoO₄)₃的晶胞体积随温度的升高而增大, 本征线热膨胀系数分别为(1.274±0.003)×10^-6 K^-1和(1.612±0.003)×10^-6 K^-1。用热膨胀仪研究了Cr₂(WO₄)₃和Cr₂(MoO₄)₃在静态空气中298～1 073 K范围内热膨胀行为，即开始表现为正热膨胀，随后在相转变点达到最大值，最后表现为负热膨胀，其负热膨胀系数分别为(-7.033±0.014)×10^-6 K^-1和(-9.282±0.019)×10^-6 K^-1。     

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.     

B2O3-Bi2O3-ZnO-Al2O3玻璃助烧剂对BaTiO3陶瓷烧结条件、晶体结构和介电性能的影响

通过调节B₂O₃-Bi₂O₃-ZnO-Al₂O₃(BBZA)玻璃的添加量研究其对钛酸钡(BaTiO₃)陶瓷烧结条件、晶体结构和介电性能的影响。结果表明：添加适量的BBZA玻璃能够有效地将BaTiO₃陶瓷烧结温度由1 350℃降至950℃,并使其致密化。同时,添加BBZA玻璃后,BaTiO₃的晶体结构随着烧结温度的升高而发生转变(立方相→四方相)。另外,BBZA玻璃的引入使BaTiO₃陶瓷的居里峰得到了有效的抑制和拓宽。陶瓷微观形貌显示,玻璃相均匀分布在BaTiO₃晶粒表面。优化的BaTiO₃陶瓷制备条件如下：BBZA添加量(质量分数)为2.0%,烧结温度为950℃。在该条件下制备的BaTiO₃陶瓷介电常数达到1 364,介电损耗低至1.2%。     

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.