制备工艺对NiFe2O4分解CO2活性的影响

随着大气中CO2浓度的增加,温室效应日趋严重,促使人们对大气中CO2的转化与消除这一课题更加重视。1990年Yutaka Tamaura[1]发现氧缺位磁铁矿几乎可以100%分解CO2后,为解决温室效应提供了一条新的探索途径。通过对不同铁酸盐MFe2O4(M=Fe,Mn[2],Co[3],Zn[4],Ni[5]等)分解CO2活性的考察,发现铁酸镍在300℃分解CO2的活性比其它铁酸盐都好。NiFe2O4的制备最常采用的是共沉淀法、柠檬酸溶胶凝胶法和水热法,3种方法由于制备     

Li2ZrO3材料吸收CO2性能的进一步研究

用不同结构的ZrO₂合成了一系列在高温下吸收CO₂的Li₂ZrO₃材料，并详细的研究了反应物质的物理和化学性质对生成物吸收CO₂性能的影响。采用SEM、XRD以及TG分析法分别进行了材料结构及其吸收CO₂性能的表征，并使用XPS法测定了材料表面的元素组成。实验结果表明，使用不同结构的ZrO₂合成的Li₂ZrO₃，其吸收CO₂的性能明显的不同。用ZrO₂(t)(四方)合成的Li₂ZrO₃吸收CO₂的速度快，在500 ℃下，20% CO₂（80%空气）的气氛中保持3h，其吸收量可达25（±0.6）%（wt），而以ZrO₂(m)(单斜)为原料制备的Li₂ZrO₃在上述吸收条件下重量仅增加9（±0.6）%（wt）。此外，实验结果还表明化学元素的掺杂对用ZrO₂(m)合成的Li₂ZrO₃的CO₂吸收速度及吸收容量影响较大。     

溶剂热氧化少层Ti3C2 MXene制备二维TiO2/Ti3C2复合光催化剂

为了改善TiO_2光催化剂光生电子-空穴对复合率高、太阳光利用率低的缺陷,采用溶剂热法控制氧化剥离的少层Ti_3C_2MXene(DL-Ti_3C_2),制备TiO_2/DL-Ti_3C_2复合光催化剂,并通过降解罗丹明B溶液,研究其光催化性能。结果表明,TiO_2/DL-Ti_3C_2复合光催化剂能有效吸收可见光,且光催化性能明显优于DL-Ti_3C_2和P25。当溶剂热氧化温度为160℃时,复合材料具有最佳的光催化性能。当氧化温度过低时,催化剂中形成的TiO_2量不足,产生的光生电子-空穴对数量较少,导致催化剂性能较差;当氧化温度过高时,DL-Ti_3C_2减少,降低了材料导电性,光生电子-空穴对复合效率高,导致催化剂性能变差。因此,通过改变DL-Ti_3C_2的氧化温度,可以调控TiO_2/DL-Ti_3C_2复合材料中TiO_2和DL-Ti_3C_2的相对含量,使二者产生协同作用提高复合光催化剂的可见光催化活性。     

CeO2改性Ag-V2O5/TiO2催化剂的甲基吡啶氧化脱甲基性能

以锐钛矿TiO_2为载体,考察了CeO_2改性对Ag-CeO_2-V_2O_5/TiO_2催化3-甲基吡啶氧化脱甲基性能的影响,并优化了催化剂组成与制备条件.结果表明:Ce掺杂改性不仅能够与V物种作用形成Ce VO_4,而且促进V_2O_5分散,改善活性组分的氧化还原性能,从而提高3-甲基吡啶脱甲基转化率与选择性,改善Ag-V_2O_5/TiO_2催化性能.适宜的催化剂组成为V_2O_5负载量15%,Ce/V的摩尔比0.33,Ag质量分数1.0%.过高的焙烧温度将导致TiO_2载体向金红石型转变,Ag-CeO_2-V_2O_5/TiO_2适宜制备条件为450℃焙烧4 h.     

Li2O-TiO2-SiO2-P2O5和Li2O-TiO2-Al2O3-P2O5体系锂离子固体电解质的制备及性能研究

一些具有NASICON型网格结构的固体电解质具有高的电导率和好的稳定性,NASICON的意思是Na Super Ionic Conductor[1]。当NaZr2(PO4)3中P5 被Si4 部分取代时便可以得到具有NASICON结构的Na1 xZr2SixP3-xO12体系,其具有高的钠离子电导率。然而有相同结构的Li1 xZr2SixP3-xO12体系的离子电导率却很低,这是因为Li 半径太小,而NASICON三维网格结构的离子通道太大,两者不匹配而使电导率下降[2]。但当LiZr2(PO4)3中Zr4 被离子半径小些的Ti4 取代,所得LiTi2(PO4)3的通道就与Li 半径相匹配,适合于锂离子的迁移,从而使其电导率…     

(Zn1-xMnx)C2O4·2H2O在空气中的热分解动力学研究

用热分析（TG-DTG/DTA）、X射线衍射（XRD）技术和透射电镜（TEM）研究了固态物质Zn_1-xMn_xC₂O₄•2H₂O在空气中热分解的过程。热分析结果表明，Zn_1-xMn_xC₂O₄•2H₂O在空气中分两步分解，其失重率与理论计算失重率相吻合。 XRD和TEM结果表明，Zn_1-xMn_xC₂O₄•2H₂O分解的最终产物为Zn_1-xMn_xO,其颗粒大小约为10-13 nm。在非等温条件下对Zn_1-xMn_xC₂O₄•2H₂O的热分解动力学进行了分析。用Friedman法和Flynn-Wall-Ozawa(FWO)法求取了分解过程的活化能E，并用多元线性回归给出了可能的机理函数。Zn_1-xMn_xC₂O₄•2H₂O两步热分解的活化能分别为155.7513 kJ/mol 和215.9397 kJ/mol。     

(ZrO2)0.92(Gd2O3)0.08纳米晶的水热合成及其烧结体的电性能

用新制备的(Gd，Zr)(OH)_x·yH₂O共沉淀作前驱体，在强碱性介质中用水热法合成了(ZrO₂)_0.92(Gd₂O₃)_0.08纳米立方晶，考察了反应温度、pH值等水热反应条件对纳米晶粒大小的影响。将(ZrO₂)_0.92(Gd₂O₃)_0.08     

在CeO2-ZrO2中加入La2O3对改善单Pd三效催化剂性能的作用

浸渍法制备了CeO₂-ZrO₂-La₂O₃复合氧化物，用XRD、热分析（TG-DTA，DSC）、BET表面积、H₂-TPR等对合成样品进行表征，研究了La₂O₃的加入对CeO₂-ZrO₂和单钯Pd/CeO₂-ZrO₂/γ-Al₂O₃/蜂窝陶瓷催化剂性能和热稳定性的影响。结果表明，在CeO₂-ZrO₂-La₂O₃中，La的存在能促进CeO₂-ZrO₂固溶体的还原，提高贮氧能力；在Pd/CeO₂-ZrO₂/γ-Al₂O₃中加入La有利于提高催化剂的耐热稳定性，阻止γ-Al₂O₃在高温下的晶相转变，进一步稳定Al₂O₃的结构，保持其高的表面积。在贵金属Pd的负载量为1 g·L^-1的条件下，测定了Pd/CeO₂-ZrO₂-La₂O₃/γ-Al₂O₃/蜂窝陶瓷催化剂对CO、C₃H₈和NOx的三效催化净化活性。结果表明，在Pd/CeO₂-ZrO₂/Al₂O₃/蜂窝陶瓷催化剂中加入La₂O₃后，能明显地改善催化剂的低温活性和三效催化性能，经1 000 ℃老化10 h后，CO、C₃H₈和NO_x净化的起燃温度（T₅₀）分别为330 ℃、350 ℃和380 ℃。     

Fe2O3/Al2O3二元气凝胶合成高质量单壁纳米碳管

通过溶胶和超临界干燥方法制得了Fe₂O₃/Al₂O₃二元气凝胶，其比表面积和孔隙体积分别为246 m²·g^-1和1.89 cm³·g^-1，并具有较宽的孔径分布。以Fe₂O₃/Al₂O₃二元气凝胶作催化剂，通过甲烷催化裂解成功地合成了高质量的单壁纳米碳管。利用FESEM、TEM和HRTEM、Raman光谱等分析手段研究了反应温度对单壁纳米碳管生长的影响。结果表明在900 ℃时合成单壁纳米碳管的质量较高，并且合成的炭产物为毡状，该炭产物主要为高质量的单壁纳米碳管。     

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%。     

Effect of SiO2 coating layer morphology on TiH2 gas release characteristic

In this study, a uniform and compact SiO2 film-coating layer was prepared on the surface of TiH2 particles by sol-gel method using inexpensive raw materials. The preparation process of SiO2-coated TiH2 particles and the effect of the coating layer morphology on the gas release characteristic were investigated in detail. When the pH value of TiH2 suspending solution is about 4.0 and the concentration of silicic acid is more than 0.5 mol/L, the coating layer shows a SiO2 particle-coating morphology. While a homogeneous and dense film-coating layer can be obtained when the solution pH value and concentration of silicic acid are about 4.0 and 0.5 mol/L. The results of gas release at 700 degrees C show that TiH2 particles coated with silicon dioxide layers can efficiently delay the starting time of gas release of TiH2 powders to 60-100 s. Comparing the particle-coating layer, the SiO2 film-coating layer has a better delaying effect on gas release of TiH2 particles.     

In situ coating of flame-made TiO2 particles with nanothin SiO2 films

Rutile TiO2 particles made by flame spray pyrolysis (FSP) were coated in a single step with SiO2 layers in an enclosed flame reactor. This in situ particle coating was accomplished by a hollow ring delivering hexamethyldisiloxane (HMDSO) vapor (precursor to SiO2) through multiple jets in swirl cross-flow to Al-doped nanostructured rutile TiO2 aerosol freshly made by FSP of a solution of titanium tetraisopropoxide and aluminum sec-butoxide in xylene. The as-prepared powders were characterized by (scanning) transmission electron microscopy (STEM and TEM), energy dispersive X-ray analysis, X-ray diffraction, nitrogen adsorption, electrophoretic mobility, DC plasma optical emission (DCP-OES), and Fourier transform infrared (FT-IR) spectroscopy. The coating quality was assessed further by the photocatalytic oxidation of isopropyl alcohol to acetone. The effect of HMDSO injection point and vapor concentration on product particle morphology was investigated. The titania particles were uniformly SiO2-coated with controlled and uniform thickness at a production rate of about 30 g h(-1) and exhibited limited, if any, photoactivity. In contrast, spraying and combusting equivalent mixtures of the above Si/Al/Ti precursors in the above reactor (without delivering HMDSO through the hollow ring) resulted in particles segregated in amorphous (SiO2) and crystalline (TiO2) domains which exhibited high photocatalytic activity.     

Synthesis, structural and hydrogenation properties of Mg-rich MgH2-TiH2 nanocomposites prepared by reactive ball milling under hydrogen gas

MgH(2)-TiH(2) nanocomposites have been obtained by reactive ball milling of elemental powders under 8 MPa of hydrogen pressure. The composites consist of a mixture of β-rutile MgH(2), γ-orthorhombic high pressure MgH(2) and ε-tetragonal TiH(2) phases with nanosized crystallites ranging from 4 to 12 nm. In situ hydrogen absorption curves on milling reveal that nanocomposite formation occurs in less than 50 min through the consecutive synthesis of the TiH(2) and MgH(2) phases. The abrasive and catalytic properties of TiH(2) speed up the formation of the MgH(2) phase. Thermodynamic, kinetic and cycling hydrogenation properties have been determined for the 0.7MgH(2)-0.3TiH(2) composite and compared to nanometric MgH(2). Only the MgH(2) phase desorbs hydrogen reversibly at moderate temperature (523 to 598 K) and pressure (10(-3) to 1 MPa). The presence of TiH(2) does not modify the thermodynamic properties of the Mg/MgH(2) system. However, the MgH(2)-TiH(2) nanocomposite exhibits outstanding kinetic properties and cycling stability. At 573 K, H-sorption takes place in less than 100 s. This is 20 times faster than for a pure nanometric MgH(2) powder. We demonstrate that the TiH(2) phase inhibits grain coarsening of Mg, which allows extended nucleation of the MgH(2) phase in Mg nanoparticles before a continuous and blocking MgH(2) hydride layer is formed. The low crystallinity of the TiH(2) phase and its hydrogenation properties are also compatible with a gateway mechanism for hydrogen transfer from the gas phase to Mg. Mg-rich MgH(2)-TiH(2) nanocomposites are an excellent media for hydrogen storage at moderate temperatures.     

Sodium silicate route to coat polymer particles with silica

This paper presents a low-cost method to coat polymer particles with silica nanoparticles from inexpensive sodium silicate solution, which is a less-common precursor compared with tetraethyl orthosilicate for coating of polymer particles. The method is based on deposition of active silicic acid in the presence of polymer particles, prepared by emulsion polymerization of styrene involving poly(N-vinyl-2-pyrrolidone), under conditions that a dilute silica sol can be formed from this active silicic acid. The whole process was conducted in aqueous media. The effects of different reaction parameters, such as reaction temperature, amount of active silicic acid and solution pH, on the morphology and size of composite particles were investigated.     

Monodisperse and core-shell-structured SiO2@YBO3:Eu3+ spherical particles: synthesis and characterization

Y0.9Eu0.1BO3 phosphor layers were deposited on monodisperse SiO2 particles of different sizes (300, 570, 900, and 1200 nm) via a sol-gel process, resulting in the formation of core-shell-structured SiO2@Y0.9Eu0.1BO3 particles. X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), photoluminescence (PL), and cathodoluminescence (CL) spectra as well as lifetimes were employed to characterize the resulting composite particles. The results of XRD, FE-SEM, and TEM indicate that the 800 degrees C annealed sample consists of crystalline YBO3 shells and amorphous SiO2 cores, in spherical shape with a narrow size distribution. Under UV (240 nm) and VUV (172 nm) light or electron beam (1-6 kV) excitation, these particles show the characteristic 5D0-7F1-4 orange-red emission lines of Eu3+ with a quantum yield ranging from 36% (one-layer Y0.9Eu0.1BO3 on SiO2) to 54% (four-layer Y0.9Eu0.1BO3 on SiO2). The luminescence properties (emission intensity and color coordinates) of Eu3+ ions in the core-shell particles can be tuned by the coating number of Y0.9Eu0.1BO3 layers and SiO2 core particle size to some extent, pointing out the great potential for these particles applied in displaying and lightening fields.     

改性壳聚精膜用于醇水混合液分离的研究──Ⅲ．超细粉末填充壳聚精膜

首次制备了用Ｓｉ３Ｎ４，ＳｉＯ２，ＴｉＨ４超细粉末填充的改性壳聚精膜，并将其用于乙醇／水混合液的分离中。实验表明壳聚糖膜经超细粉末填充后强度增大，溶胀度减小。用于乙醇／水混合液渗透蒸发分离时，分离因子和渗透通量都有提高，并在填充量为１６．７％附近出现极大值。随着料液中乙醇含量的增大，渗透通量减小，分离因子增大；随着料液温度的升高渗透通量显著增大，分离因子则稍有下降。并简单讨论了超细粉末在乙醇／水混合液分离中的作用。     

Influence of powder-characteristics on the microstructure of ceramic plasma spray coatings

Summary The relationship between the properties of plasma spray powders and the resultant coating has been investigated. ZrO₂ powders, differing in grain size, state of agglomeration and morphology, have been used and coating properties such as microstructure, porosity, roughness, hardness, and wear resistance are described. Agglomerated powders cause high porosity, while sphericalized particles yield very dense layers. The homogeneity of an agglomerate is also responsible for the homogeneity of the microstructure of the coating. By selecting powders with defined characteristics it is possible to produce plasma spray coatings with defined properties; the microstructure of the layers can be varied over a wide range.     

连续流微反应器中微纤结构化的Nafion/SiO2固体酸催化苯硝化反应

采用溶胶-凝胶组装方法制备了Nafion/SiO2胶体, 并涂附于烧结的316L不锈钢(SS-316L)金属微纤网络, 形成了空隙率为60%-75%(φ, 体积分数)的整体式微纤结构化的Nafion/SiO2固体酸催化剂. 使用傅里叶变换红外光谱(FT-IR), 热重分析(TGA), 扫描电子显微镜(SEM)及NH3吸附法对微纤结构化的Nafion/SiO2催化剂进行了表征. 结果显示, 溶胶-凝胶组装方法可以明显促进Nafion的分散, 导致酸性中心的暴露量显著增加; 结构化的Nafion/SiO2催化剂以200-400 nm颗粒堆积而成的多孔涂层形式存在. 在一种集换热、混合、催化(反应)功能于一体的微反应器中, 考察了整体式微纤结构化的Nafion/SiO2固体酸催化剂催化苯硝化的反应性能. Nafion在SiO2中的组装量为20%(w, 质量分数), 金属微纤网络上Nafion/SiO2担载量为36.3%(w)的优化催化剂上, 75 ℃时苯转化率为44.7%, 硝基苯选择性可达99.9%. 相近转化率下, Nafion/SiO2固体酸单位酸中心的催化效能约为硫酸的600倍.     

含硼片状锌热固涂层耐蚀性与结构的研究

片状锌热固涂层作为一项清洁生产的高新技术 ,一次完成多层涂覆和钝化 ,具有高抗蚀、无废水排放、无氢脆、高耐热和涂层薄 (一般小于1 0 μｍ)等显著优点 ,在应用前景上具有取代电镀锌的趋势[1] 。在盐水溶液中 ,这种涂层的耐蚀性最高可达电镀锌的 1 0倍 ,但在淡水中却不具有这样的优势。我们用硼酸部分取代铬酸配制涂层处理液 ,明显改善了涂层在淡水中的耐蚀性。为解释硼酸的作用机理 ,采用Ｘ 射线衍射 (ＸＲＤ)、Ｘ 射线光电子能谱 (ＸＰＳ)和核磁共振 (ＮＭＲ)等测试手段对膜层的结构进行了研究。1　实验部分1 1　仪器与药品ＨＤＶ 7Ｂ…     

研究硅酸聚合反应的新途经

用高分子反应统计理论研究了硅酸聚合反应.利用三甲基硅烷化-气相色谱法跟踪测定了聚合反应过程中各低聚态硅酸的含量变化,得到了分子数量分数分布.该分布符合含有内环化因子校正的A₁型缩聚反应统计理论,内环化反应是硅酸聚合反应的重要特征.