Eu2O3修饰对纳米TiO2热稳定性及光催化活性的影响

通过浸渍过程实现了Eu2O3对溶胶水热法合成的锐钛矿相TiO2纳米粒子的表面修饰改性.重点研究了表面修饰对纳米锐钛矿相热稳定性及光催化活性的影响.结果表明,Eu2O3表面修饰抑制了锐钛矿相向金红石相的转变,相变温度由550℃左右升高到700℃左右,提高了纳米锐钛矿相TiO2的热稳定性,这与Eu2O3修饰在表面而阻碍了锐钛矿纳米粒子的直接接触有关.与未修饰的TiO2相比,经过700℃高温热处理的Eu2O3修饰的TiO2样品表现出了较高的光催化活性,这与其结晶度提高而有利于光生电荷分离有关.     

磷酸修饰对纳米Fe2O3热稳定性及光催化性能的影响

通过溶液浸渍蒸干过程实现了磷酸对Fe₂O₃纳米粒子的表面修饰, 研究了磷酸修饰对纳米Fe₂O₃的热稳定性及光催化活性的影响. 结果表明, 磷酸修饰显著提高了Fe₂O₃的热稳定性, 主要归因于磷酸修饰在样品表面抑制了粒子之间的团聚生长. 同时, 在光催化降解气相乙醛和液相苯酚的测试中, 磷酸修饰后热处理温度为600 ℃的样品表现出了最佳的可见光催化性能, 这主要归因于该样品具有高晶化度、 小粒子尺寸及大比表面积, 并且适量的修饰有利于其光催化性能的提高.     

微乳法合成纳米SiO2/TiO2及其光催化性能

采用聚乙二醇辛基苯基醚(Triton X-100)/正己醇/环己烷/氨水微乳体系合成了纳米TiO2和SiO2/TiO2复合物,用X射线衍射、红外光谱和透射电镜对其结构进行了表征,并以甲基橙降解评价了其光催化性能,讨论了SiO2/TiO2摩尔比、晶相组成及粒径与光催化活性的关系.结果表明,SiO2/TiO2催化剂中形成了新的Ti-O-Si键和无定形SiO2;在纳米TiO2中复合SiO2能有效抑制锐钛矿向金红石的转变,增加锐钛矿的稳定性,并阻止TiO2晶粒的聚集生长.催化剂的光催化活性随金红石含量的增加而降低,加入适量SiO2能明显提高TiO2的光催化活性,其中摩尔比为1/7的SiO2/TiO2光催化活性最高.     

低温水热合成异形TiO2纳米晶及其表征

70 ℃下在钛酸四丁酯(TBOT)水热合成TiO2过程中, 加入油酸, 控制TiO2颗粒的生长方向, 无需热处理, 直接得到针状和纺锤形锐钛矿TiO2纳米晶. 应用透射电子显微镜、X 射线衍射仪对TiO2纳米晶进行了形貌观察和晶体结构的测定. 红外光谱分析表明, 油酸分子以静电作用吸附于针状TiO2纳米晶的表面. 根据UV-Vis吸收峰, 计算了TiO2纳米晶的禁带宽度. 纺锤形TiO2纳米晶具有较高的光催化活性, 60 min内催化降解了90%的罗丹明B.     

液相沉积法制备光催化活性TiO2薄膜和纳米粉体

采用液相沉积法 ,在 3 5℃通过向六氟钛酸铵水溶液中添加硼酸和结晶诱导剂锐钛矿型TiO2 纳米晶 ,沉积出具有光催化活性的TiO2 薄膜和纳米粉体 .用XRD ,AFM ,阶梯仪 ,UV vis ,BET法对TiO2 薄膜和粉体的沉积条件、结构、厚度和性能进行了测定和表征 ,并用亚甲兰的降解 ,评价了TiO2 薄膜和纳米粉体的光催化活性 .结果表明 ,当反应物六氟钛酸铵与硼酸的摩尔比为 1∶2～ 1∶4时 ,沉积的粉体和薄膜含有锐钛矿相TiO2 ;经 3 0 0℃热处理的TiO2 薄膜和纳米粉体具有最高的光催化活性 ,它的光催化活性是未经热处理前的 5倍 .本文还解释了经 3 0 0℃热处理的薄膜和纳米粉体具有最高光催化活性的原因     

纳米Au/TiO2光催化剂的XPS和SPS研究

 以溶胶-凝胶法制备的TiO2纳米粒子为载体,通过浸渍法制备了Au/TiO2样品,并利用XPS和SPS等技术对样品进行表征,考察了热处理温度和Au含量对TiO2纳米粒子光催化氧化苯酚活性的影响. 结果表明,Au是以金属纳米微晶的形式均匀地分散在TiO2纳米粒子表面. 用适量Au进行表面修饰不仅拓宽了TiO2对光的响应范围,而且改善了TiO2光生电子和空穴的分离效率,提高了样品对氧物种的吸附,并促进了光生电子向吸附氧的传输. 在光催化氧化苯酚反应中,500 ℃处理的Au/TiO2纳米粒子具有较高的光催化活性,这与XPS和SPS表征结果是一致的. 从电子能级匹配的角度揭示了Au对TiO2样品表面光电性质和光催化性能的影响机制.     

纳米TiO2 的制备及其光催化降解性能

采用低温水解沉淀法以TiCl4为原料制备了纳米TiO2,其结构经TEM和XRD表征。研究了太阳光激发下纳米TiO2对甲基橙的光催化降解性能,结果显示：纳米TiO2的分散性越好,粒径越小,光催化降解能力越强;以锐钛矿为主的复合纳米TiO2晶体比纯锐钛矿晶相具有更优异的光催化活性。     

超临界流体干燥法制备TiO2／C纳米粒子及光催化性能

以TiCl4为原料,采用溶胶凝胶法结合超临界流体干燥法(SCFD)制备了纳米级TiO2/C复合光催化剂.以苯酚的光催化降解对所得催化剂的催化活性进行了评价.结果表明,纳米TiO2/C复合粒子与单组分TiO2比较,复合粒子光催化活性高于单组分的TiO2,h苯酚降解率高达975 ％,COD为957%.并用XRD、TEM、 UV-Vis和XPS等手段进行了表征,iO2以锐钛矿型形式存在.比较了不同制备方法制得的TiO2/C复合催化剂,得出超临界干燥法制备的光催化剂具有粒径小,比表面积大,分散性好,光催化活性高等特点.     

纳米二氧化钛的制备及其光催化性能

分别采用水热法和溶胶-凝胶法制备了TiO2纳米粉体;利用X射线衍射仪和扫描电镜分析了两种方法制备的TiO2粉体的形貌和晶体结构,并测定了纳米TiO2粉体对罗丹明B的光催化降解活性.结果表明:采用水热法制备的TiO2纳米粉体含有锐钛矿相和金红石相,粒径较小,大约为50nm,而且分散均匀,光催化性能良好;采用溶胶-凝胶法制备的TiO2粉体经过550℃煅烧后仍然为锐钛矿相,而且粒径较大,大约为80nm.     

高活性二氧化钛光催化剂的低温水热合成

 以硫酸钛和尿素为原料,通过水热方法制备了锐钛矿相纳米晶二氧化钛光催化剂. 用X射线衍射(XRD)、扫描电镜(SEM)和N2吸附-脱附对所得催化剂的结构进行了表征,并通过空气中丙酮的光催化氧化反应考察了其光催化活性. 结果显示,通过水热方法不需要经过任何热处理就能制备结晶良好的锐钛矿相TiO2粉末,160 ℃水热反应3 h或180 ℃水热反应2 h制备的二氧化钛光催化剂显示出高的光催化活性,其光催化活性比Degussa P25高3倍多. 这可能是由于该方法所制备的二氧化钛光催化剂具有高的比表面积和小的晶粒尺寸引起的.     

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.     

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.     

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.     

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。     

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.     

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.