稀土铈/纳米TiO2复合抗菌剂的研究

制备出稀土铈掺杂锐钛型纳米TiO2复合抗菌功能材料,该抗菌材料与不掺杂的纳米TiO2相比,在可见光下对大肠杆菌、金黄色葡萄球菌、枯草芽孢杆菌的混合菌具有较好的抑菌效果,随着Ce4+的摩尔浓度增加,制备的试样的抗菌能力越强.其原因(1)铈掺杂激活纳米TiO2在可见光下的催化活性,使其光催化杀菌能力增强,(2)Ce4+本身具有较好的杀抑菌能力.     

阴离子掺杂型TiO2可见光活性研究进展

阴离子掺杂改性TiO2光催化材料是目前光催化材料界的一个研究热点.综述了阴离子掺杂改性TiO2可见光活性的研究进展,重点探讨了N、C和S等元素掺杂TiO2材料的原理,实验工艺,效果以及优缺点.并对TiO2光催化材料可见光活性未来发展趋势进行了展望.     

共掺杂改性TiO2光催化剂的研究进展

TiO2具备化学稳定性好、催化活性高、无污染、价格低廉等优点,在光催化领域有广阔的发展前景,但禁带宽度较大、可见光吸收能力差等缺点影响了TiO2在生产生活中的推广利用.本文综述了共掺杂改性TiO2在光催化领域的研究进展,介绍了纳米TiO2的光催化机理,分析比较了金属与金属共掺杂、非金属与非金属共掺杂、金属与非金属共掺杂三种改性方式对TiO2光催化性能的影响;指出共掺杂改性可以通过降低禁带宽度、产生可见光效应、抑制光生电子空穴复合等方式提高TiO2的光催化活性;总结了有关共掺杂作用机理和离子间协同作用的研究成果,提出了当下共掺杂改性TiO2研究存在的不足之处,并对今后的研究方向进行了展望.     

Ce掺杂TiO2/SiO2的制备及其光催化降解罗丹明B

采用溶胶-凝胶法制备了纯TiO2和掺杂不同含量Ce的TiO2/SiO2复合纳米粒子.并用FT-IR,UV-Vis对样品结构进行了表征,并以罗丹明B(RB)的光催化降解为探针反应,评价了其光催化性能.结果表明,TiO2/SiO2催化剂中形成了新的Ti-O-Si键,Ce的掺杂使TiC2/SiO2光谱响应范围向可见光区拓展.与未掺杂的TiO2/SiO2相比较,掺杂的TiO2/SiO2具有更高的催化性能.Ce掺杂的最佳值为x(Ce)∶x(Ti)=0.0090,光催化剂最佳投放量为30mg.     

溶胶-凝胶法制备N-卤素共掺杂TiO_2可见光催化材料

为满足低温制备N掺杂TiO2可见光催化材料的需要,采用溶胶-凝胶法,以十六烷基三甲基氯(溴、碘)化铵为掺杂剂,在回流条件下与TiO2纳米晶溶胶直接反应,制备TiO2光催化材料T5100-C、T5100-B、T5100-I。通过XPS分析,只有样品T5100B成功地在TiO2晶格中掺入了N、Br。UV-Vis漫反射吸收光谱和亚甲基兰(MB)的可见光降解实验表明,样品T5100-B具有良好的可见光响应和光催化活性;而样品T5100-C和T5100-I没有明显的可见光响应和可见光催化活性。N的掺杂使得样品T5100-B具有明显的可见光吸收,而Br的掺杂可以阻止光生电子/空穴对的复合,二者共同提高可见光催化活性。     

非金属元素掺杂TiO2的可见光催化活性研究进展

TiO2(锐钛矿)的禁带宽度限制了其光诱导特性的广泛应用,非金属元素掺杂为TiO2在可见光辐射环境下的应用提供了新的机会.详细介绍了非金属元素(N、C、S、F)掺杂TiO2的制备方法和可见光催化活性研究的最新进展,讨论了制备工艺与掺杂TiO2可见光催化活性的关系,深入分析了非金属元素对TiO2可见光催化活性的诱导机理.制备工艺显著影响了掺杂元素的化学态和含量,从而决定了掺杂TiO2带隙中局域态的特征.带隙中局域态特征正是影响掺杂TiO2可见光催化活性的关键因素.文章也对未来的研究方向进行了展望.     

燃烧合成铁掺杂TiO2纳米晶的染料敏化光催化性能

采用气相扩散火焰燃烧合成铁掺杂TiO2纳米晶，研究了铁掺杂TiO2纳米晶在可见光辐照下降解罗丹明B的活性，探讨了可见光染料敏化光催化机理．Fe^3＋掺杂可显著提高TiO2纳米晶的可见光催化活性，Fe^3＋最佳掺杂摩尔分数为0．12％．经过铁掺杂改性后，Fe^3＋的3d电子也可被可见光激发引发光催化反应，从而促进整个染料敏化光催化降解过程．     

氮掺杂TiO2光催化剂研究进展

对TiO2光催化剂进行改性,实现可见光催化活性是第二代光催化剂走向实用化的关键.氮掺杂TiO2是一种理想的具有可见光活性的光催化剂,由于N 2p态与O 2p态杂化,实现带隙窄化和吸收带边红移,对于实现可见光催化活性具有重要意义.评述了氮掺杂改性TiO2光催化剂的国内外研究现状,分析了不同掺杂方法对于实现TiO2可见光催化活性的掺杂机理和改性机理,提出研究合适的催化剂载体对TiO2进行氮等非金属负载是今后努力的方向,并且应该建立统一的催化剂性能评价标准.     

均匀水解低温晶化法氮掺杂TiO_2可见光催化剂的制备与表征

以硫尿为氮源,采用均匀水解低温晶化法制备了具有可见光活性氮掺杂的纳米TiO2。采用XRD、SEM、BET和UV-vis漫反射光谱等技术对其进行了表征。结果表明,所制备氮掺杂TiO2均为锐钛矿相,并且在可见光区域有明显的光吸收。以甲基橙溶液为模拟废水,研究氮掺杂TiO2在可见光下的光催化活性。实验表明,所制备的氮掺杂TiO2样品在可见光下具有高的光催化活性,可见光催化活性明显高于商业P25 TiO2光催化剂。     

TiO2包覆上转换发光材料Pr3+∶Y2SiO5的制备及其可见光催化性能的研究

为了提高TiO2对可见光的利用率,通过溶胶-凝胶法制备了TiO2包覆上转换发光材料Pr3+∶Y2SiO5的复合材料,并借助XRD、TEM、紫外-可见吸收光谱等对制备的样品进行了表征和研究。同时,研究了不同条件下制备的复合粉体对罗丹明B光降解效率。结果表明,该方法制备出的Pr3+∶Y2SiO5/TiO2复合材料较纯TiO2和简单机械混合两种粉体在可见光下具有较强的光催化效果。验证了Pr3+∶Y2SiO5作为上转换发光材料,可吸收可见光发射紫外线,从而满足TiO2光催化降解的要求。文中最后对Pr3+∶Y2SiO5/TiO2复合材料的光催化机理进行了研究。     

Structural and optical properties of AlxOy/Pt/AlxOy multilayer absorber

We report on the microstructure and optical properties of Al_xO_y–Pt–Al_xO_y interference-type multilayer films, deposited by electron beam (e-beam) deposition onto corning 1737 glass, silicon (1 1 1) and copper substrates. The structural properties were investigated by Rutherford backscattering spectrometry, X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy and atomic force microscopy. The optical properties were extracted from specular reflection/transmission, diffuse reflectance and emissometer measurements. The stratification of the coatings consists of a semi-transparent middle Pt layer sandwiched between two layers of Al_xO_y. The top and bottom Al_xO_y layers were non-stoichiometric with no crystalline phases present. The Pt layer is in the fcc crystalline phase with a broad size distribution and spheroidal shape in and between the rims of Al_xO_y. The surface roughness of the stack was found to be comparable to the inter-particle distance. The optical calculations confirm a high solar absorptance of ∼0.94 and a low thermal emittance of ∼0.06 for the multilayer stack, which is attributed not only to the optimized nature of the multilayer interference stacks, but also to the specific surface morphology and texture of the coatings. These optical characteristics validate the spectral selectivity of the Al_xO_y–Pt–Al_xO_y interference-type multilayer stack for use in high temperature solar-thermal applications.     

Synthesis of a new perovskite Pb(Li14Nb34)O3

A high-pressure technique was adopted to obtain perovskite-type $\text{Pb(Li}{}_{\mathrm{<mtext>1</mtext><mtext>4</mtext>}}\text{Nb}{}_{\mathrm{<mtext>3</mtext><mtext>4</mtext>}}\text{)}\text{O}{}_3$. A new perovskite $\text{Pb(Li}{}_{\mathrm{<mtext>1</mtext><mtext>4</mtext>}}\text{Nb}{}_{\mathrm{<mtext>3</mtext><mtext>4</mtext>}}\text{)}\text{O}{}_3$ was characterized to have a cubic symmetry with $\text{a}{}_{\mathrm{<mtext>o</mtext>}}\text{= 4.069}\text{A}\text{?}$; Li and Nb ions in the B-site of perovskite lattice may be in a random arrangement.     

Bulk crystalline BaPb34Bi14O3: A ceramic superconductor

The preparation conditions of the high T_C ceramic superconductor Ba(Pb,Bi)O₃ is correlated with the superconducting transition. Transition onsets of all materials are similar, but transition widths and transition completeness is strongly dependent on firing temperature. Only materials prepared over a narrow temperature range, resulting in a nearly ideal weight loss, have a complete and narrow transition.     

Optimization of AlxOy/Pt/AlxOy multilayer spectrally selective coatings for solar-thermal applications

Spectrally selective Al_xO_y/Pt/Al_xO_y multilayer absorber coatings were deposited onto corning 1737 glass, Si (111) and copper substrates using electron beam (e-beam) vacuum evaporator at room temperature. The employment of ellipsometric measurements and optical simulation was proposed as an effective method to optimize and deposit multilayer solar absorber coatings. The optical constants (n and k) measured using spectroscopic ellipsometry, showed that both Al_xO_y layers, which used in the coatings, were dielectric in nature and the Pt layer was semi-transparent. The optimized multilayer coatings exhibited high solar absorptance α ∼ 0.94 ± 0.01 and low thermal emittance ? ∼ 0.06 ± 0.01 at 82 °C. The Rutherford backscattering spectroscopy (RBS) data of Al_xO_y/Pt/Al_xO_y multilayer absorber indicated the Al_xO_y layers present in the coating were nearly stoichiometry. The scanning electron microscope analysis (SEM) result indicated that the average diameter and inter-particles distance of Pt grains were statistically about 146 ± 0.17 nm and 6-10 ± 0.2 nm respectively.     

Electrostriction in Pb (Zn13Nb23)O3

The electrostriction in $\text{Pb (Zn}{}_{\mathrm{<mtext>1</mtext><mtext>3</mtext>}}\text{Nb}{}_{\mathrm{<mtext>2</mtext><mtext>3</mtext>}}\text{)}\text{O}{}_3$ crystals has been investigated using a strain gauge method. In the ferroelectric phase below 140 C, the strain vs the electric field shows a hysteresis, which is ascribed to the effect of ferroelectric domains. A quadratic relation holds between the strain x and the electric polarization P as x = QP² above about 170 C in the paraelectric phase. Values of the electrostrictive Q coefficients are determined from the measurements near 190 C, as Q₁₁ = 1.6·10^?2m⁴/C², Q₁₂ = ?0.86·10^?2m⁴/C², and Q₄₄ = 0.85·10^?2m⁴/C².     

Magnetic,electrical and thermal studies on the V1−xMox02

The monoclinic-to-tetragonal structure transition of oxides V_1?xMo_x0₂ with $\text{0≤}\text{x}\text{≤0.20}$ has been studied by means of DTA, X-ray diffraction, magnetic susceptibility (powder samples) and electrical conductivity (single crystals) measurements within the temperature region 80 K to 400 K. A linear decrease of the transition temperature of 11 K per atom % Mo was observed. The magnetic susceptibility of the low temperature phase was found to be temperature independent paramagnetic for all preparations. Electrical conductivity measurements on the same phase showed crystals with $\text{x}\text{? 0.04}$ to be semiconducting, while a metallic behavior was observed in the region $\text{0.10 ?}\text{x}\text{? 0.14}$.     

n-PbTep+−Pb1−xSnxTe heterojunctions prepared by a modified hot wall technique

$\text{n-PbTe}\text{p}{}^{\mathrm{+}}\text{?}\text{Pb}{}_{\mathrm{1?x}}\text{Sn}{}_{\mathrm{x}}\text{Te}$ heterojunctions with a long wavelength spectral cutoff (λ_c ≈ 6 μm) were prepared using the double-channel hot wall technique. The electrical and photoelectrical properties of the heterojunctions at 77, 197 and 300 K were investigated. Detectors with R_oA equal to 170 Ω cm² and a quantum efficiency of 25–40% were obtained. Reasons for the shift of the long wavelength spectral cutoff of the heterojunctions towards shorter wavelengths are given.     

Reactive plasma deposited SixCyHz films

Si_xC_yH_z films have been prepared at 200°C by reactive plasma deposition from SiH₄ and CH₄ diluted in helium in a tubular reactor. These films have a ratio s (equal to $\text{Si}\text{(}\text{Si+C}\text{))}$ ranging from 0.2 to 0.8, a refractive index ranging from 1.96 to 2.6 and an optical energy band gap in the range 2.7-2.2 eV. The total quantity of hydrogen in the film is 40% when s=0.5. Infrared analysis shows that these films have large fractions of homonuclear bonds and that this material is best described as a polymer. Mass spectrometric measurements of the gaseous products formed in the SiH₄-CH₄-He plasma have been performed and the results are related to the composition of the deposited layers.     

Core-current-enhanced domain-wall pinning in nanocrystalline Fe/sub 73.5/Cu/sub 1/Nb/sub 3/Si/sub 15.5/B/sub 7/ ribbon

We have studied the influence of surface fields H/sub p/ (generated by either direct or alternating core current) on soft magnetic properties of amorphous and nanocrystalline Fe/sub 73.5/Cu/sub 1/Nb/sub 3/Si/sub 15.5/B/sub 7/ ribbon. While in an amorphous ribbon the coercive field H/sub c/ decreases with H/sub p/, in the same optimally annealed ribbon (H/sub c/=1.3 A/m, M/sub m//spl ap/M/sub s/) H/sub c/ increases with H/sub p/ for all the explored types of H/sub p/ (static and dynamic with different phases with respect to that of the magnetizing field H). The unexpected increase of H/sub c/ in nanocrystalline ribbon is associated with the influence of H/sub p/ on the surface and main (inner) domain structure. Here, we develop a model that takes into account this influence and explains the experimental results.     

Interfacial microstructure of NiSix/HfO2/SiOx/Si gate stacks

Integration of NiSi_x based fully silicided metal gates with HfO₂ high-k gate dielectrics offers promise for further scaling of complementary metal-oxide- semiconductor devices. A combination of high resolution transmission electron microscopy and small probe electron energy loss spectroscopy (EELS) and energy dispersive X-ray analysis has been applied to study interfacial reactions in the undoped gate stack. NiSi was found to be polycrystalline with the grain size decreasing from top to bottom of NiSi_x film. Ni content varies near the NiSi/HfO_x interface whereby both Ni-rich and monosilicide phases were observed. Spatially non-uniform distribution of oxygen along NiSi_x/HfO₂ interface was observed by dark field Scanning Transmission Electron Microscopy and EELS. Interfacial roughness of NiSi_x/HfO_x was found higher than that of poly-Si/HfO₂, likely due to compositional non-uniformity of NiSi_x. No intermixing between Hf, Ni and Si beyond interfacial roughness was observed.