Au/ZrO2催化CO氧化反应中ZrO2纳米粒子的尺寸效应

从同一ZrO(OH)₂出发制备了三种不同尺寸的ZrO₂纳米颗粒(ZrO₂-CP: 40～200 nm, ZrO₂-AN: 18～25 nm, ZrO₂-AD: 10～15 nm), 采用沉积-沉淀方法制备了相应的Au/ZrO₂催化剂. 用XRD, XRF, TEM和低温N₂吸附对ZrO₂和Au/ZrO₂进行了表征. XRD和TEM分析表明Au/ZrO₂样品中Au粒子的平均尺寸为4～5 nm, 而ZrO₂的晶相和颗粒大小没有因为“负载”Au粒子而发生变化. CO催化氧化反应的结果表明, Au/ZrO₂催化活性随着ZrO₂纳米粒子尺寸的减小活性明显增加. TEM/HRTEM结果表明, Au/ZrO₂催化剂中Au粒子与ZrO₂颗粒接触界面随ZrO₂颗粒尺寸的减小而明显增加, 这很可能是含有更小尺寸ZrO₂纳米粒子的Au/ZrO₂催化剂具有更高催化活性的重要原因.     

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。     

(ZrO2)0.86(Sm2O3)0.14纳米粉体的水热法合成及其烧结体的电性能

以湿化学法制得Zr(OH)₄和Sm(OH)₃的共沉淀为前驱体, 在碱性介质中用水热法合成了(ZrO₂)_0.86(Sm₂O₃)_0.14及(ZrO₂)_0.88(Sm₂O₃)_0.12纳米粉体. 将纳米粉体在较低温度(1450 ℃)下烧结制得了致密的固体电解质陶瓷样品, 比通常高温固相反应法采用的烧结温度(＞1600 ℃)降低了150 ℃以上. XRD测定结果表明, (ZrO₂)_0.86(Sm₂O₃)_0.14纳米粉体及其烧结体均为立方相, 但(ZrO₂)_0.88(Sm₂O₃)_0.12纳米粉体为立方相, 它的烧结体为立方相和单斜相的混合相. 用交流阻抗谱法、氧浓差电池法及氧泵(氧的电化学透过)法研究了(ZrO₂)_0.86(Sm₂O₃)_0.14陶瓷样品在600～1000 ℃下的离子导电特性. 结果表明, 该陶瓷样品在600～1000 ℃下氧离子迁移数为1, 氧离子电导率的最大值为3.2×10^－2 S•cm^－1, 是一个优良的氧离子导体; 它的氧泵性能明显地优于YSZ.     

Au@ZrO2空心纳米微球的制备及其催化性质

以Stober法合成了不同粒径的SiO₂微球。以这些SiO₂微球为硬模板,通过ZrOCl₂前驱体吸附和水解制备得到了ZrO₂@SiO₂复合物,然后用HF溶解去除二氧化硅模板剂,制备得到ZrO₂空心球。以ZrO₂空心球为载体,采用沉积-沉淀法（DP）合成了Au@ZrO₂纳米空心微球。考察了Au@ZrO₂纳米空心微球在对硝基苯胺还原反应中的催化性能。研究结果表明,所合成的SiO₂微球粒径大小均一、形状规则、分散性好;ZrO₂空心微球大小及比表面积可以通过硬模板SiO₂微球粒径进行有效控制;与Au@ZrO₂实心微球相比,Au@ZrO₂空心微球在对硝基苯胺还原反应中表现出良好的催化性能,当反应温度为45℃、反应7 min时,对硝基苯胺能够完全转化为对苯二胺。     

表面活性剂模板在空气-水界面ZrO2薄膜中的稳定性

采用模板——十二烷基苯磺酸(DBS-H)在空气-水界面组装ZrO₂薄膜，研究了DBS-H在ZrO₂自组装薄膜中的水溶性、化学稳定性、热稳定性和光化学稳定性。模板的各类稳定性将直接控制ZrO₂薄膜结构，主要表现在层间距变化上。从模板与Na₂SiO₃反应的研究中获得了一种制备ZrO₂ / SiO₂复合氧化物薄膜的新方法，并推测出该复合薄膜的结构。     

NiO纳米片和多孔纳米片自组装的空心微球的无模板水热法制备与磁学性质

报道一种非常简单的制备NiO和Ni(OH)₂空心微球的无模板水热法, 即通过NiCl₂与氨水在140 ℃水热反应12 h, 制备了Ni(OH)₂纳米片自组装的空心微球, 经400 ℃热处理2 h得到了NiO空心微球. 采用X射线衍射仪、扫描电镜和透射电子显微镜对产物进行表征, 并在室温下测试了它的磁学性能, 结果表明, Ni(OH)₂空心微球的直径约为3～4 μm, 它是由尺寸1.1～1.3 μm左右的六方相结构的Ni(OH)₂纳米片组装而成; NiO空心微球是由立方相纳米片和多孔纳米片组装而成, 它具有弱的铁磁性, 其矫顽力为583 Oe, 剩余磁化强度为0.213 emu/g. 研究了氨在Ni(OH)₂纳米片的形成与组装过程中的作用, 提出了可能的生长机理.     

Pt/ZrO2-Al2O3催化剂催化氧化C3H6和CO性能

采用共沉淀法合成了ZrO₂与Al₂O₃的不同质量比的ZrO₂-Al₂O₃复合氧化物,并以此为载体通过等体积浸渍法制备了1.5% Pt/ZrO₂-Al₂O₃（w/w）催化剂。以C₃H₆和CO为反应物的催化性能评价显示,在系列催化剂中以Pt/Zr（0.4）-Al催化剂催化氧化活性最为优异,其C₃H₆和CO的起燃温度（T₅₀）小于125℃,完全转化温度（T₉₀）小于150℃。采用XRD、低温N₂吸附、H₂-TPR、CO脉冲吸附等分析表征技术探索了催化剂物相结构、比表面积、颗粒尺寸等对催化活性的影响规律。结果发现,ZrO₂-Al₂O₃复合氧化物具有Al₂O₃材料的介孔织构和大比表面积特性,且产生了Al_xZr_1-xO_y固溶体新物相。适当的ZrO₂与Al₂O₃的质量比,是改善Pt与ZrO₂-Al₂O₃的相互作用强度,促进贵金属Pt的分散,提升Pt/ZrO₂-Al₂O₃催化剂的低温氧化活性的关键。     

溶胶-凝胶涂附电纺纳米纤维制备ZrO2纳米管

Stable zirconia sol was prepared using inorganic salt(zirconia chloride octahydrate) as the precursor and H₂O₂ as the catalyst. ZrO₂-PBS coaxial nanofibers were fabricated using the sol-gel coating technique to filling poly butylenes succinate(PBS) fibers with zirconium dioxide by electrospun. ZrO₂ nanotubes were obtained via calcining ZrO₂-PBS coaxial nanofibers. The ZrO₂ nanotubes were characterized by TG, SEM and TEM, respectively. The results show that ZrO₂ nanotubes with a diameter of 50～100 nm are obtained after calcining ZrO₂-PBS coaxial nanofibers at 450 ℃.     

用原位红外技术研究Ag-MoO3/ZrO2催化丙烯气相环氧化反应

制备了对丙烯直接气相环氧化具有优良催化性能的Ag-MoO₃/ZrO₂催化剂, 采用原位FT-IR技术研究了丙烯、环氧丙烷及丙烯和氧气混合气在载体和催化剂上的吸附及反应行为. 研究表明, 丙烯在ZrO₂载体和20%Ag-4%MoO₃/ZrO₂催化剂上吸附后, 均不发生化学反应, 而环氧丙烷在ZrO₂载体上吸附后于400 ℃发生开环反应, 在20%Ag-4%MoO₃/ZrO₂催化剂上吸附后于300 ℃发生开环反应. 当丙烯和氧气混合气在ZrO₂载体上共吸附后, 随着反应温度从室温升高至400 ℃, 二者开始反应生成CO₂和H₂O; 混合气在20%Ag-4%MoO₃/ZrO₂催化剂上共吸附后于350 ℃开始反应. 对比非负载型Ag-MoO₃催化剂的研究结果可见, ZrO₂载体的存在使催化剂的活性下降的同时, 提高了对产物环氧丙烷的选择性.     

用原位红外技术研究Ag-MoO3/ZrO2催化丙烯气相环氧化反应

制备了对丙烯直接气相环氧化具有优良催化性能的Ag-MoO₃/ZrO₂催化剂, 采用原位FT-IR技术研究了丙烯、环氧丙烷及丙烯和氧气混合气在载体和催化剂上的吸附及反应行为. 研究表明, 丙烯在ZrO₂载体和20%Ag-4%MoO₃/ZrO₂催化剂上吸附后, 均不发生化学反应, 而环氧丙烷在ZrO₂载体上吸附后于400 ℃发生开环反应, 在20%Ag-4%MoO₃/ZrO₂催化剂上吸附后于300 ℃发生开环反应. 当丙烯和氧气混合气在ZrO₂载体上共吸附后, 随着反应温度从室温升高至400 ℃, 二者开始反应生成CO₂和H₂O; 混合气在20%Ag-4%MoO₃/ZrO₂催化剂上共吸附后于350 ℃开始反应. 对比非负载型Ag-MoO₃催化剂的研究结果可见, ZrO₂载体的存在使催化剂的活性下降的同时, 提高了对产物环氧丙烷的选择性.     

Silica-Zirconia Sol–Gel Coatings Obtained by Different Synthesis Routes

Homogeneous xSiO₂-(1−x)ZrO₂ coatings have been prepared onto glass-slides, monocrystalline Si and stainless steel (AISI 304) using sols prepared via acid and basic catalysis. Zirconium tetrabutoxide (TBOZr), zirconium n-propoxide (TPZ), tetraethoxysilane (TEOS) and methyltriethoxysilane (MTES) were used as precursors of zirconia and silica, respectively. The different parameters involved in the synthesis procedure, as molar ratios H₂O/alkoxides, NaOH/alkoxides, and sintering temperature have been analysed, correlating the stability and rheological properties of the sols. The evolution and structure of the sols and coatings have been studied by FTIR. Coatings have been prepared by dipping from acid and basic sols. Electrophoretic Deposition (EPD) technique has also been used to prepare coatings onto stainless steel from basic particulate sols in order to increase the critical thickness. A maximum thickness of 0.5 μ m was reached by both dipping and EPD process for 75SiO₂: 25 ZrO₂ composition. The critical thickness decreases with ZrO₂ amount depending strongly of the drying conditions. Si–O–Zr bonds have been identified by FTIR, indicating the existence of mixed network Si–O–Zr in the coatings obtained by the different routes. Crystallisation of ZrO₂(t) was only observed at high sintering temperature (900^∘C) by FTIR and confirmed by DRX.     

Silica-Zirconia Coatings Produced by Dipping and EPD from Colloidal Sol–Gel Suspensions

SiO₂-ZrO₂ sols have been prepared via acid catalysis using a commercial colloidal suspension of zirconia and two silica alkoxides; tetraethoxysilane (TEOS) and methyltriethoxysilane (MTES). Suspensions with 10, 15 and 25-mol% of ZrO₂ were prepared. The stability of the suspensions was followed by rheological measurements showing that the amount of water incorporated with the colloidal suspension is the factor that limits the maximum ZrO₂ content. Coatings have been prepared by dipping using the suspensions up to 25-mol% ZrO₂ onto glass-slides at different withdrawal rates. EPD process has been used to prepare coatings onto stainless steel AISI 304 using the suspension with 25-mol% ZrO₂ at different pHs. The parameters associated with the EPD process (current density, electric field, potential and deposition time) have been evaluated. The critical thickness for a ZrO₂ addition of 25-mol% was 0.8 μm and it increased for diminishing ZrO₂ content.     

Preparation and Evaluation of Octadecyl-Bonded ZrO2/SiO2

ZrO₂/SiO₂ particles, which were prepared by a layer-by-layer self-assemble technique and consist of micrometer-sized silica spheres as cores and nanometer-sized zirconia particles as surface coatings, have a higher surface area and pore volume than other zirconia supports have. Further more it is more stable than silica is. In this paper we made a reversed-phase support by bonding octadecyltrichlorosilane on ZrO₂/SiO₂ particles, it had a comparable high carbon amount of 9.62% and good chemical stability being stable up to pH 11. The chromatographic behavior showed that the support acted as a true reversed chromatographic stationary phase and had a hydrophobic selectivity. Basic and aromatic compounds are well separated and the peaks are symmetrical.     

A Novel Method for Preparing Nano‐ and Microcomposite Al2O3‐ZrO2 Ceramic Coatings

Nano‐ and microcomposite Al₂O₃‐ZrO₂ coatings were deposited on various substrates in a sol‐gel ceramic paint by a supercentrifugal force and a gradual sintering process. Fine metal oxide powders were dispersed in a sol‐gel solution by superpower ball milling so as to form a uniform stable ceramic paint. High‐resolution microscopy (FE‐SEM) was used to characterize the coating, indicating that the coating is composed of composite particle clusters with an average diameter of ～1 µm. The clusters consisted of larger particles with an average diameter of ～0.5 µm in center and smaller particles of ～100 nm surrounding the larger ones. The coating was relatively dense and increasingly dense toward the substrate surface.     

Study of the selectivity of a V2O5?ZrO2 catalyst for partial oxidation ofo-xylene at high temperatures

It has been established that at high temperatures (above 450°C) the V₂O₅−ZrO₂ catalyst exhibits a higher selectivity in the oxidation ofo-xylene to phthalic anhydride than does the conventional V₂O₅−TiO₂(a) catalyst. The catalyst selectivity is found to increase with respect to partial oxidation ofo-xylene, the valuable by-product maleic anhydride being obtained. Studies by different physicochemical methods have shown that V₂O₅−ZrO₂ undergoes no significant phase and structural changes under high-temperature conditions.     

Kinetic study of zirconia crystallization from amorphous ZrO2-SiO2 composite precursors processed by sol-gel chemistry

Powder precursor gels with composition xZrO₂·(100–x)SiO₂, with selected values of x=8, 24, 43 and 75 mol%, were processed by sol-gel chemistry. Differential thermal analysis (DTA) was used to study crystallization in (cubic/tetragonal)-ZrO₂ during the heating of the reactive amorphous precursors. Kinetic parameters such as activation energy, Avrami's exponent and frequency factor have been simultaneously calculated from the computed DTA data using a previously reported kinetic model. The crystallization temperature decreases relative to the increase in the amount of ZrO₂, the value of the kinetic parameter of the crystallization being related to the value of x.     

Catalytically Promoted NOx Sorption by ZrO2-Based Oxides

Metal promoted zirconia-based oxide sorbents, such as Pt–ZrO₂/Al₂O₃ for NO _x have been investigated. To clarify the role of the catalyst component, sorption of NO and NO₂ was compared using the samples with and without Pt. The catalytic oxidation of NO to NO₂ and successively to nitrate ions is an important role for the Pt catalyst. The experimental results indicate that a high-temperature calcination is essential to remove residual Cl from Pt–ZrO₂–Al₂O₃ prepared from H₂PtCl₆ in order to provide more active NO _x sorption sites. Of M–ZrO₂–Al₂O₃ samples investigated, ruthenium as well as Pt demonstrated relatively good performance as a catalyst component in the sorbent. The FT-IR spectra after sorption of NO and NO₂ demonstrated a strong band attributed to stored nitrate ions. The Pt catalyst was more resistant to sulfur poisoning than a base metal catalyst. However, the NO _x sorptive capacities of the Pt–ZrO₂/Al₂O₃ sorbents were expected to be deteriorated in dilute SO₂ as far as observed from FT-IR spectra.     

Synthesis of Biomorphic ZrO2-CeO2 Nanostructures by Silkworm Silk Template

A simple and green technique has been developed to prepare hierarchical biomorphic ZrO₂-CeO₂, using silkworm silk as the template. Different from traditional immersion technics, the whole synthesis process depends more on the restriction or direction functions of the silkwormsilk template. The analytic results showed that ZrO₂-CeO₂ exhibited a well-crystallized hierarchically interwoven hollow fiber structure with 16-28 μm in diameter. The grain size of the sample calcined at 800 oC was about 14 nm. Consequently, the interwoven meshwork at three dimensions is formed due to the direction of biotemplate. The action mechanism is summarily discussed here. It may bring the biomorphic ZrO₂-CeO₂ nanomaterials with hierarchical interwoven structures to more applications, such as catalysts.     

Acidity and Structure of Ca-Doped V2O5/ZrO2 Catalysts

Acidity and structure of Ca-doped V₂O₅/ZrO₂ catalysts have been studied by FTIR. Both Lewis and Brønsted acidity decreased with Ca loading. New surface vanadate species seemed to be formed by Ca addition.