Microstructural and auger microanalytical characterization of Cu-Hf and Cu-Ti catalysts.

Degradation processes occurring at the surface and in the bulk of Cu-based amorphous alloys during cathodic hydrogen charging were used for promoting the catalytic activity of such alloys. These processes modifying the structure, composition, and morphology of the substrate proved to be useful methods for transforming Cu-Hf and inactive Cu-Ti amorphous alloy precursors into active and durable catalysts. Indeed, their catalytic activity for dehydrogenation of 2-propanol increased up to a conversion level of approximately 60% at selectivities to acetone of about 99% for Cu-Ti and to conversion of approximately 90% at selectivities of approximately 95% for Cu-Hf. Previous attempts carried out by aging in air or hydrogen charging from the gas phase resulted in a maximum conversion level up to 15% for Cu-Hf and up to 3% for Cu-Ti. High resolution Auger spectroscopy allowed changes occurring during the activation process to be identified, namely, the formation of small Cu particles on the HfO2 surface and the formation of highly porous particles containing mostly Cu and some Ti and O (Cu-Ti-O) on a Cu-Ti substrate. Differences in the chemistry and structure of both catalysts are discussed, and the implications for catalytic function are considered. A probable configuration of active sites on the Cu-Ti-O/Ti-O-Cu catalyst for dehydrogenation of 2-propanol is proposed.     

Metal oxide monolithic columns

Metal oxide monoliths composed of ZrO2 and HfO2 have been synthesized in situ inside capillary columns. The material shows globular-like structure and through pores. Capillary electrochromatography and capillary liquid chromatography were performed in a monolithic column with the HfO2 material. Separation of a simple sample mixture showed the potential of the new metal oxide monolithic columns.     

Synthesis of aluminium borate-boron oxide and binary titanium-boron and zirconium-boron oxides from metal alkoxides and (MeO)3B3O3 in non-aqueous solvents

The reaction of metal alkoxides M(OR)4 (M = Ti, Zr; R = organyl) with (MeO)3B3O3 (1 : 0.67) in dry propan-2-one at room temperature led to gels which when dried and calcined in air for 24 h at 500-1000 degrees C afforded bi-phased mixed-oxide materials formulated as 4TiO2 x 3B2O3 and ZrO2 x B2O3 in high ceramic yields and purity; the B2O3 phases of these materials were amorphous. The materials remained amorphous upon calcination at lower temperatures. The TiO2 phase of the 4TiO2 x 3B2O3 was crystalline when calcined at higher temperatures with either anatase (600 degrees C) or rutile (>800 degrees C) being obtained. The ZrO2 phase of the ZrO2 x B2O3 was crystalline when calcined at higher temperatures and was obtained as a metastable tetragonal phase (<700 degrees C) or baddeleylite (>800 degrees C). In a similar reaction, Al(O(i)Pr)3 (2 : 1) gave a bi-phased aluminium borate-boron oxide (Al18B4O(33).7B2O3) after calcination at >700 degrees C. The dried gels and oxide materials were all characterized by elemental analysis, TGA-DSC, and powder XRD.     

Formation and Characterization of ZrO3 and HfO3 Molecules in Solid Argon

ZrO3 and HfO3 molecules were prepared via reactions of metal monoxides with dioxygen in solid argon and were characterized using matrix isolation infrared absorption spectroscopy as well as theoretical calculations. Unlike the titanium monoxide molecule, which reacted spontaneously with dioxygen to form TiO3, the ZrO and HfO molecules reacted with dioxygen to give the ZrO3 and HfO3 molecules only under visible light irradiation. Density functional calculations predicted that both the ZrO3 and HfO3 molecules possess a closed-shell singlet ground state with a non-planar C8 geometry, in which the side-on coordinated O2 falls into the peroxide category.     

CO2加氢合成甲醇的超细Cu-ZnO-ZrO2催化剂的表征

采用原位顺磁共振（ＥＰＲ）、原位Ｘ射线光电子能谱（ＸＰＳ）和程序升温还原（ＴＰＲ）等手段,对ＣＯ２加氢合成甲醇用的不同粒度的超细Ｃｕ－ＺｎＯ－ＺｒＯ２催化剂各组分的相互作用进行了研究。结果表明,ＺｒＯ２的加入改变了催化剂的表面结构和配位状态,增加了活性组分的分散度,提高了催化剂的稳定性。实验还发现,催化剂的粒度对各组分的相互作用有着重大的影响,催化剂的粒度较小时,Ｃｕ＾２＋主要以团簇的形式存在,易     

Theoretical analysis of initial adsorption of high-κ metal oxides on In(x)Ga(1-x)As(0 0 1)-(4×2) surfaces

Ordered, low coverage to monolayer, high-κ oxide adsorption on group III rich InAs(0 0 1)-(4×2) and In(0.53)Ga(0.47)As(0 0 1)-(4×2) was modeled via density functional theory (DFT). Initial adsorption of HfO(2) and ZrO(2) was found to remove dangling bonds on the clean surface. At full monolayer coverage, the oxide-semiconductor bonds restore the substrate surface atoms to a more bulklike bonding structure via covalent bonding, with the potential for an unpinned interface. DFT models of ordered HfO(2)/In(0.53)Ga(0.47)As(0 0 1)-(4×2) show it fully unpins the Fermi level.     

Photoelectron spectroscopy of the molecular anions, ZrO-, HfO-, HfHO-, and HfO2H-

Negative ion photoelectron spectra of ZrO(-), HfO(-), HfHO(-), and HfO(2)H(-) are reported. Even though zirconium- and hafnium-containing molecules typically exhibit similar chemistries, the negative ion photoelectron spectral profiles of ZrO(-) and HfO(-) are dramatically different from one another. By comparing these data with relevant theoretical and experimental studies, as well as by using insights drawn from atomic spectra, spin-orbit interactions, and relativistic effects, the photodetachment transitions in the spectra of ZrO(-) and HfO(-) were assigned. As a result, the electron affinities of ZrO and HfO were determined to be 1.26 ± 0.05 eV and 0.60 ± 0.05 eV, respectively. The anion photoelectron spectra of HfHO(-) and HfO(2)H(-) are similar to one another and their structural connectivities are likely to be H-Hf-O(-) and O-Hf-OH(-), respectively. The electron affinities of HfHO and HfO(2)H are 1.70 ± 0.05 eV and 1.73 ± 0.05 eV, respectively.     

Electronic structure differences in ZrO2 vs HfO2

Although ZrO2 and HfO2 are, for the most part, quite similar chemically, subtle differences in their electronic structures appear to be responsible for differing MO2/Si (M = Zr, Hf) interface stabilities. To shed light on the electronic structure differences between ZrO2 and HfO2, we have conducted joint experimental and theoretical studies. Because molecular electron affinities are a sensitive probe of electronic structure, we have measured them by conducting photoelectron spectroscopic experiments on ZrO2(-) and HfO2(-). The adiabatic electron affinity of HfO2 was determined to be 2.14 +/- 0.03 eV, and that of ZrO2 was determined to be 1.64 +/- 0.03 eV. Concurrently, advanced electronic structure calculations were conducted to determine electron affinities, vibrational frequencies, and geometries of these systems. The calculated CCSD(T) electron affinities of HfO2 and ZrO2 were found to be 2.05 and 1.62 eV, respectively. The molecular results confirm earlier predictions from solid state calculations that HfO2 is more ionic than ZrO2. The excess electron in MO2(-) occupies an sd-type hybrid orbital localized on the M atom (M = Zr, Hf). The structural parameters of ZrO2 and HfO2 and their vibrational frequencies were found to be very similar. Upon the excess electron attachment, the M-O bond length increases by ca. 0.04 A, the OMO angle increases by 2-4 degrees, and frequencies of all vibrational modes become smaller, with the stretching modes being shifted by 30-50 cm(-1) and the bending mode by 15-25 cm(-1). Together, these studies unveil significant differences in the electronic structures of ZrO2 and HfO2 but not in their structural or vibrational characteristics.     

Colloidal Self‐Assembly of Catalytic Copper Nanoclusters into Ultrathin Ribbons

Metal nanoclusters (NCs) with diameter below 2 nm are promising catalysts in oxygen reduction reactions (ORR). However, the high surface energy of ultra‐small clusters leads to structural instability, shedding doubt on practical applications. Herein, we demonstrate a self‐assembly method to improve the durability of catalytic metal NCs, employing copper NCs capped by 1‐dodecanethiol (DT) to form free‐standing ribbons in colloidal solution. By tuning the cooperation between the dipolar attraction between Cu NCs and the van der Waals attraction between DT, the thickness of ribbons is adjusted to a single NC scale. Such free‐standing ribbons exhibit excellent catalytic activity and durability in ORR.     

Catalytic abatement of CO and volatile organic compounds in waste gases by gold catalysts supported on ceria-modified mesoporous titania and zirconia

Mesoporous oxides TiO2 and ZrO2, synthesized by surfactant templating via a neutral C13(EO)6–Zr(OC3H7)4 assembly pathway, and ceria‐modified TiO2 and ZrO2, prepared by a deposi‐tion–precipitation (DP) method, featuring high surface areas and uniform pore size distributions were used as supports for gold catalysts. The supported gold catalysts were assessed for the cata‐lytic abatement of air pollutants, i.e., CO, CH3OH, and (CH3)2O. The gold was supported on the mes‐oporous oxides by a DP method. The supports and catalysts were characterized by powder X‐ray diffraction, high‐resolution transmission electron microscopy, N2 adsorption–desorption analysis, and temperature‐programmed reduction technique. A high degree of synergistic interaction be‐tween ceria and mesoporous ZrO2 and TiO2 as well as a positive modification of the structural and catalytic properties by ceria was observed. The ceria additive interacts with the mesoporous oxides and induces a strong effect on the reducibility of the supports. The catalytic behavior of the catalysts was discussed to determine the role of the ceria modifying additive and possible interaction be‐tween the gold nanoparticles and ceria‐mesoporous oxide supports. The gold catalysts supported on ceria‐modified mesoporous ZrO2 displayed superior catalytic activity (~100%conversion of CO at 10 °C and CH3OH at 60 °C). The high catalytic activity can be attributed to the ability of the sup‐port to assist oxygen vacancies formation. The studies indicate that the ceria‐modified mesoporous oxide supports have potential as supports for gold‐based catalysts.     

Dimethyl methylphosphonate decomposition on Cu surfaces: supported Cu nanoclusters and films on TiO2(110)

The thermal decomposition of dimethyl methylphosphonate (DMMP), which is a simulant molecule for organophosphorus nerve agents, has been investigated on Cu clusters as well as on Cu films deposited on a TiO(2)(110) surface. Scanning tunneling microscopy studies were conducted to characterize the cluster sizes and surface morphologies of the deposited Cu clusters and films. Temperature-programmed desorption experiments demonstrated that the surface chemistry of DMMP is not sensitive to the size of the Cu clusters over the range studied in this work. DMMP reaction on an annealed 40 monolayer Cu film resulted in the desorption of H(2), methane, methyl, formaldehyde, methanol, and molecular DMMP, and reaction on the small (4.4 +/- 0.9 nm diameter, 1.8 +/- 0.6 nm height) and large (10.7 +/- 1.9 nm diameter, 4.8 +/- 1.0 nm height) Cu clusters generated similar products. Formaldehyde and methane production is believed to occur via a methoxy intermediate on the Cu surface. These products are favored on the higher coverage Cu films that completely cover the TiO(2) surface since competing reaction pathways on TiO(2) are suppressed. X-ray photoelectron spectroscopy studies showed that DMMP begins to decompose on the Cu clusters upon adsorption at room temperature and that atomic carbon, atomic phosphorus, and PO(x) remain on the surface after DMMP decomposition.     

Highly mixed phases in ball-milled Cu/ZnO catalysts: an EXAFS and XANES study

New highly mixed phases have been identified in Cu/ZnO systems by EXAFS and XANES at both the Cu and Zn K-edge. The phases were generated by ball-milling Cu(2)O/ZnO mixtures under three different atmospheres of synthetic air (SA), SA + CO(2) and CO(2). The system milled in CO(2) shows disproportionation of Cu(2)O into Cu(0), Cu(1+) (cuprite Cu(2)O-type phase) and Cu(2+) (tenorite CuO-type phase), while most of the Zn(2+) is transformed into a nanocrystalline/amorphous ZnO-type zincite that forms a superficial mixture of oxide and carbonate phases. When synthetic air is added to the CO(2) atmosphere, ball milling results in the oxidation of nearly half the Cu(1+) into Cu(2+) with no Cu metal formed. The copper phase in this material is almost entirely amorphous. In SA, a significant amount of Cu(2+)- and Zn(2+)-based phases appears to react to form a nanocrystalline/amorphous Cu(1-x)Zn(x)O (x approximately 0.3) solid solution. This distorted rock saltlike solid solution, in which Zn and Cu feature different octahedral environments, was never reported before. It is thought to be formed by incorporation of Zn(2+) in the Cu fcc sublattice of the cuprite Cu(2)O matrix and the concomitant oxidation of Cu(1+) into Cu(2+). The formation of such a highly mixed Cu(1-x)Zn(x)O phase indicates strong Cu/Zn interaction in the Cu/ZnO system, which also suggests the presence of highly mixed phases in conventionally prepared activated catalysts.     

Fe基非晶和纳米晶合金晶化及电化学腐蚀行为

应用单辊甩带法制备非晶态Fe78Si13B9和Fe73.5Si13.5B9Nb3Cu1薄带,并以非晶晶化退火法制备出纳米晶Fe73.5Si13.5B9Nb3Cu1薄带.利用X射线衍射(XRD)仪和示差扫描量热计(DSC)对该非晶薄带的非晶特性及其晶化过程进行了研究.并用电化学极化曲线的方法和电化学阻抗技术研究了非晶态Fe78Si13B9和纳米晶Fe73.5Si13.5B9Nb3Cu1合金在1mol/LNaOH溶液里的电化学腐蚀行为,用SEM对极化测试后的试样形貌进行了观察;同时还研究了不同的热处理温度对材料结构及在1mol/LNaOH溶液里耐腐蚀性能的影响.结果表明,该非晶薄带的晶化过程分为两步;纳米晶比非晶合金的耐腐蚀性要好;且随着热处理温度的升高,非晶和纳米晶的耐腐蚀性能都得到提高.     

Ti-ZrO_2系金属陶瓷的氧化性能研究

本文研究了由等体积比的Ti与 5Y TZP热压合成的金属陶瓷的抗氧化性能 .首先进行了热力学分析 ,证实在 0 .1MPa的空气氛中发生高温反应时 ,只发生氧化反应而不会氮化 .研究表明其氧化动力学规律与纯钛类似 ,只是材料中ZrO2 的存在使氧的扩散阻力增大 ,表现为扩散活化能远高于氧在钛氧固溶体中的扩散活化能 ;氧化初期恒温增重曲线符合抛物线规律 .XRD和TEM分析证明 ,氧化产物的主晶相为金红石结构的TiO2 ,此外还有少量的ZrTiO4 .氧化层表面和断面的SEM分析表明 ,氧化膜中存在两种类型的裂纹 ,ZrO2 /Ti(或TiO2 )的界面裂纹主要是由加热或冷却过程中因ZrO2 与Ti(或TiO2 )的热膨胀系数失配而造成的 .氧化层中出现平行于氧化表面的裂纹产生于氧化层与基体的界面应力 ,ZrO2 的存在能于一定程度上抑制此类裂纹的扩展     

Study of the Osteoimmunomodulatory Properties of Curcumin-Modified Copper-Bearing Titanium

Peri-implantitis can lead to implant failure. In this study, curcumin (CUR) was modified onto the copper-bearing titanium alloy (Cu-Ti) with the assistance of polydopamine (PDA) in order to study the bone immune response and subsequent osteogenesis. FE-SEM, XPS and water contact angle were utilized to characterize the coating surface. Bone marrow mesenchymal stem cells (BMSCs) and macrophages were cultured separately and together onto the CUR modified Cu-Ti. Cell activity, expression of relative genes and proteins, cell migration ability, and fluorescence staining of cells were performed. CUR modification slightly increased the activation of M1-type and M2-type cells under physiological conditions. In the inflammation state, CUR inhibited the overexpression of M1 macrophages and induced M2-type differentiation. In addition, the modification itself could provoke the expression of osteoblastic-related genes of BMSCs, while promoting the osteogenic differentiation of BMSCs through the activation of macrophages in both physiological and inflammatory states. The BMSCs migration was increased, the expression of osteogenic-related genes and proteins was up-regulated, and alkaline phosphatase activity (ALP) was increased. Thus, the modification of CUR can promote the osteointegration effect of Cu-Ti by bone immunomodulation and may, in addition, improve the success rate of implants.     

Influence of synthesis methods on tungsten dispersion, structural deformation, and surface acidity in binary WO3-ZrO2 system

WO3-ZrO2 catalysts were synthesized by precipitating the aqueous solutions of zirconium oxynitrate and ammonium metatungstate with ammonium hydroxide. The white slurry precipitate was treated under three different conditions. In the as-made materials, the amorphous phase was formed in the aged and refluxed samples, while well-crystallized tetragonal and monoclinic phases were obtained in the hydrothermally treated sample. The real amount of tungsten loaded in the samples was similar for the three samples, independently of the treatments; however, the tungsten surface atomic density in the annealed WO3-ZrO2 samples varied between 6 and 9 W atoms/nm2. Two different contrast types of aggregates were determined by scanning electron microscopy, the white particles which are rich in W, and the gray ones which are rich in zirconium; both of them were formed in the calcined solids prepared under aging or reflux condition. A very high dispersion of tungsten species on the zirconia surface was achieved in the hydrothermally treated sample. The degree of the interaction between WO(x) and ZrO2 surface strongly modified the Zr-O bond lengths and bond angles in the structure of tetragonal zirconia as proved by X-ray diffraction analysis and the Rietveld refinement. The catalyst obtained under hydrothermal condition exhibited the highest dispersion of tungsten species in the zirconia, which in turn causes strong structural deformation of the tetragonal ZrO2 phase responsible of the strongest surface acidity and, consequently, the optimum catalytic activity for n-hexane isomerization.     

Cux (x=1-4)团簇在CeO2(111)表面的吸附

用基于密度泛函理论的第一性原理方法研究了Cu团簇(Cu_x, x=1-4)在CeO₂(111)表面的吸附. 研究发现当团簇比较小时(x=2, 3), 倾向于平铺表面; 当x=4时, Cu团簇在CeO₂(111)表面以三维的四面体结构吸附较为稳定, 从Cu 3d到Ce 4f的电荷转移使Cu团簇带正电荷. 由二维的菱形结构到三维的四面体结构的转变势垒为1.05 eV, 并且其中一个Cu原子直接迁移到另外三个Cu原子的空位顶部的转变路径比较有利. 在Cu团簇与CeO₂的相互作用过程中, Cu-O和Cu-Cu相互作用的竞争最终决定了Cu团簇在CeO₂上的形貌. 这种CeO₂(111)负载的带正电的三维Cu团簇将对水分解, 进而对水煤气反应具有高的催化活性.     

Nickel catalysts based on porous nickel for methane steam reforming

The influence of synthesis conditions on the phase composition and texture of porous nickel supports as plates with a magnesium oxide underlayer were investigated by X-ray diffraction, low-temperature nitrogen absorption, and electron microscopy combined with X-ray microanalysis. Nickel catalysts supported on these plates were studied. Thermal treatment of Mg(NO₃)₂ in nitrogen yields a magnesium oxide underlayer with a small specific surface area (support I). The replacement of nitrogen with hydrogen leads to a larger surface area (support II). The formation of MgO is accompanied by the incorporation of Ni²⁺ cations from the oxide film into the underlayer. Upon subsequent reduction with hydrogen or under the action of the reaction medium, these cations form fine crystallites of nickel. The supports having an oxide underlayer show a higher activity in methane steam reforming than the initial metallic nickel. Nickel catalysts on supports I and II show similar activities. The activity of the catalysts was stable throughout 50-h-long tests; no carbon deposits were detected by TEM.     

Electronic coupling in iron oxide-modified TiO2 leads to a reduced band gap and charge separation for visible light active photocatalysis

In recent experiments Tada et al. have shown that TiO(2) surfaces modified with iron oxide display visible light photocatalytic activity. This paper presents first principles simulations of iron oxide clusters adsorbed at the rutile TiO(2) (110) surface to elucidate the origin of the visible light photocatalytic activity of iron oxide modified TiO(2). Small iron oxide clusters adsorb at rutile (110) surface and their presence shifts the valence band so that the band gap of the composite is narrowed towards the visible, thus confirming the origin of the visible light activity of this composite material. The presence of iron oxide at the TiO(2) surface leads to charge separation, which is the origin of enhanced photocatalytic efficiency, consistent with experimental photoluminesence and photocurrent data. Surface modification of a metal oxide is thus an interesting route in the development of visible light photocatalytic materials.     

氧化锆小团簇的结构和稳定性

利用密度泛函理论在广义梯度近似(GGA)和Perdew-Wang交换关联泛函条件下研究了小团簇Zr_mOn (1≤m≤5, 1≤n≤2m)的几何结构和稳定性. 结果表明: 所有团簇的最低能量结构可通过锆团簇的连续氧化获得, 一般情况下O原子占据在Zr团簇的桥位. (ZrO₂)₃和(ZrO₂)₅团簇的基态结构符合配位数规则和成键规律. 此外, 讨论了氧化锆团簇的分解通道和分解能, 值得指出的是在Zr原子数相同时Zr_mO_2m-1团簇(除了Zr₄O₇)存在最大的分解能.