纳米Cu/Al_2O_3组装体模板合成与光吸收

以有序的多孔氧化铝为模板,利用交流电在孔洞中沉积金属铜得到纳米Cu粒子/Al2O3组装体系.透射电镜观察显示随着交流电沉积时间的延长,孔洞中纳米Cu粒子数量增加.测量了纳米Cu粒子/Al2O3组装体系的紫外可见光吸收光谱,发现随着孔洞中纳米Cu粒子数量增加,纳米Cu粒子/Al2O3组装体系的吸收带边大幅度红移;根据雷利散射引起的消光增强解释了组装体吸收带边红移的原因.同时发现Cu粒子的表面等离子共振吸收峰消失及组装体在吸收带边区光吸收值满足间接带隙半导体光吸收边的表达式.     

MoO3/Al2O3催化剂中Mo分散的正电子研究

用浸渍法制备了一系列不同Mo含量的MoO₃/Al₂O₃催化剂.测量了这些样品的正电子湮没寿命谱(PALS)与符合多普勒展宽(CDB)谱,以研究其孔洞结构以及Mo分散.正电子寿命测量结果表明,Al₂O₃载体中存在两种不同尺寸的孔洞.掺入MoO₃之后,Mo原子主要进入Al₂O₃的大孔中,使孔洞体积减小.符合多普勒展宽谱结果表明,当MoO 关键词： 3/Al₂O₃催化剂')" href="#">MoO₃/Al₂O₃催化剂 正电子湮没寿命谱 符合多普勒展宽 Mo 分散     

Al2O3薄膜/纳米Ag颗粒复合结构的光吸收谱及增强Raman散射光谱研究

Al₂O₃介质薄膜与纳米Ag颗粒构成的复合结构,被应用于表面增强Raman散射探测实验中,其中Al₂O₃介质薄膜对纳米Ag颗粒的吸收谱及增强Raman散射光谱的影响被特别关注.该复合结构的光学特性表征出纳米Ag颗粒的偶极振荡特性.从光吸收谱中可以看到,其共振吸收谱随Al₂O₃介质薄膜厚度增加而在整个谱域上发生红移,表明纳米Ag颗粒的周围介电常数随Al₂O₃介质薄膜厚度的增加而增大.采用罗丹明6G作为探针原子,6个Raman特征峰的平均增益值作为表征表面增强Raman散射衬底增益程度的量度.实验结果表明,Al₂O₃介质薄膜层的引入提高了纳米Ag颗粒的衬底介电常数,并引起了散射共振的增强,从而使表面增强Raman散射强度提高. 关键词： 纳米Ag薄膜 共振吸收 表面增强Raman散射 介电常数     

微弧等离子喷涂碳纳米管/纳米Al2O3-TiO2复合涂层的吸波性能研究

将碳纳米管与纳米Al₂O₃-TiO₂陶瓷粉末超声共混制备了碳纳米管/纳米Al₂O₃-TiO₂复合粉末,测试了复合粉末在2—18GHz波段的电磁参数.研究表明：随着碳纳米管质量分数的增加,碳纳米管/纳米Al₂O₃-TiO₂复合粉末的复介电常数和损耗角不断增大.当碳纳米管质量分数和厚度增加时,复合粉末对电磁波的反射率峰值先增加后减小,而谐振频率不断向低频移动.采用微弧等离子喷涂制备了7wt%碳纳米管/纳米Al₂O₃-TiO₂复合吸波涂层,当厚度为1.5mm时,涂层最小反射率为-24.0dB,当厚度为2.0mm时,涂层小于-10dB的频带宽为3.60GHz,当温度为500℃高温时,1.0mm厚的涂层最小高温反射率为-12.2dB,小于-10dB频带宽为2.0GHz.复合涂层的实际厚度D与理论厚度d呈线关系：d=0.898D+0.515. 关键词： 等离子喷涂 碳纳米管 2O₃-TiO₂')" href="#">纳米Al₂O₃-TiO₂ 吸波性能     

TiN/Al2O3纳米多层膜的共格外延生长及超硬效应

采用多靶磁控溅射法制备了一系列具有不同Al₂O₃调制层厚度的TiN/Al₂O₃纳米多层膜. 利用X射线能量色散谱、X射线衍射、扫描电子显微镜、高分辨透射电子显微镜和微力学探针表征了多层膜的成分、微结构和力学性能. 研究结果表明，在TiN/Al₂O₃纳米多层膜中，单层膜时以非晶态存在的Al₂O₃层在厚度小于1.5 nm时因TiN晶体层的模板效应而晶化，并与TiN层形成共格外延生长，相应地，多层膜产生硬度明显升高的超硬效应，最高硬度可达37.9 GPa. 进一步增加多层膜中Al₂O₃调制层的层厚度，Al₂O₃层逐渐形成非晶结构并破坏了多层膜的共格外延生长，使得多层膜的硬度逐步降低. 关键词： 2O₃纳米多层膜')" href="#">TiN/Al₂O₃纳米多层膜 外延生长 非晶晶化 超硬效应     

SHS等离子喷涂制备FeAl2O4-Al2O3-Fe纳米复合涂层的研究

利用SHS等离子喷涂技术，将经过机械团聚法制备的Fe₂O₃-Al复合粉体送入等离子焰流，沉积出厚度约为400 μm的复合涂层.利用XRD，SEM 和TEM等检测手段对涂层的成分和组织进行了分析，测定了涂层的显微硬度、断裂韧性以及耐磨性.结果表明涂层为具有纳米结构的FeAl₂O₄-Al₂O₃-Fe纳米复合组织；涂层的显微硬度为HV_100g870；断裂韧性是普通Al₂O₃涂层的2倍；无润滑磨损的耐磨性是普通Al₂O₃涂层的2.5倍. 关键词： SHS等离子喷涂 纳米涂层 断裂韧性     

基于透射光谱确定溅射Al2O3薄膜的光学（已撤稿）

基于反应磁控溅射Al₂O₃薄膜的紫外—可见—近红外透射实验光谱,采用Swanepoel方法结合Wemple-DiDomenico色散模型,方便地导出了Al₂O₃薄膜在200—1100 nm波长范围内的光学常数,包括折射率、色散常数、膜层厚度、吸收系数及能量带隙.研究发现反应磁控溅射Al₂O₃薄膜具有高折射率(1.556— 1.76,测试波长为550 nm)、低吸收和直接能量带隙(3.91—4.20 eV)等光学特性,而且其光学常数对薄膜制备过程中的重要工艺参数——膜层后处理温度表现出强烈的依赖性.此外,在膜层的弱吸收和中等吸收光谱区域内,计算得到的折射率色散曲线与分光光度法的测试结果基本符合,说明本实验中所建立的计算方法在确定反应磁控溅射Al₂O₃薄膜光学常数方面的可靠性. 关键词： 光学常数 Swanepoel方法 2O₃薄膜')" href="#">Al₂O₃薄膜 热处理     

Er3+掺杂SiO2复合的Al2O3粉末结构及光致发光特性

采用溶胶-凝胶(sol-gel)工艺制备0.1 mol% Er³⁺掺杂Al₂O₃体系和SiO₂-Al₂O₃复合体系粉末. 实验结果表明：5 mol%的SiO₂复合加入Al₂O₃抑制γ→θ和θ→α相转变. 掺0.1 mol%Er³⁺:Al₂O₃体系粉末，900℃烧结，在1.47—1.63μm波段内光致发光(PL)谱为中心波长1.53 μm、半高宽56 nm的单一宽峰，1000—1200℃烧结，劈裂为多峰PL谱. 掺0.1 mol%Er³⁺:SiO₂-Al₂O₃复合体系粉末，在高达1200℃烧结，仍保持中心波长1.53 μm的单一宽峰PL谱，由于—OH更完全的脱除，PL强度较900℃烧结Al₂O₃体系，SiO₂-Al₂O₃复合体系均提高1个数量级. 关键词： 2-Al₂O₃复合体系')" href="#">SiO₂-Al₂O₃复合体系 掺铒 溶胶-凝胶工艺 光致发光     

In2O3/CuO纳米异质结的制备和光催化性质研究

通过溶胶-凝胶结合静电纺丝过程制备了In₂O₃/CuO纳米异质结。XRD和Raman光谱的研究表明,随着前驱物中Cu/In比例的增加,CuO相的含量逐渐增加。吸收光谱研究表明,随着CuO含量的增加,复合纳米结构的可见光吸收明显增强。光催化实验研究结果表明,In₂O₃/CuO纳米异质结具有比单一相的In₂O₃和CuO更强的光催化性能,其主要来源于异质结所导致的增强的光生电子和空穴的分离效率。     

方腔内Cu/Al2O3水混合纳米流体自然对流的格子Boltzmann模拟

纳米流体作为一种较高的导热介质, 广泛应用于各个传热领域. 鉴于纳米颗粒导热系数和成本之间的矛盾, 本文提出了一种混合纳米流体. 为了研究混合纳米流体颗粒间相互作用机理和自然对流换热特性, 在考虑颗粒间相互作用力的基础上, 利用多尺度技术推导了纳米流体流场和温度场的格子Boltzmann方程, 通过耦合流动和温度场的演化方程, 建立了Cu/Al₂O₃水混合纳米流体的格子Boltzmann模型, 研究了混合纳米流体颗粒间的相互作用机理和纳米颗粒在腔体内的分布. 发现在颗粒间相互作用力中, 布朗力远远大于其他作用力, 温差驱动力和布朗力对纳米颗粒的分布影响最大. 分析了纳米颗粒组分、瑞利数对自然对流换热的影响, 对比了混合纳米流体(Cu/Al₂O₃-水)与单一金属颗粒纳米流体(Al₂O₃-水)的自然对流换热特性, 发现混合纳米流体具有更强的换热特性.     

Optical band-edge absorption of oxide compound SnO2

Tin oxide (SnO₂) is an important oxide for efficient dielectrics, catalysis, sensor devices, electrodes and transparent conducting coating oxide technologies. SnO₂ thin film is widely used in glass applications due to its low infra-red heat emissivity. In this work, the SnO₂ electronic band-edge structure and optical properties are studied employing a first-principle and fully relativistic full-potential linearized augmented plane wave (FPLAPW) method within the local density approximation (LDA). The optical band-edge absorption α(ω) of intrinsic SnO₂ is investigated experimentally by transmission spectroscopy measurements and their roughness in the light of the atomic force microscopy (AFM) measurements. The sample films were prepared by spray pyrolysis deposition method onto glass substrate considering different thickness layers. We found for SnO₂ qualitatively good agreement of the calculated optical band-gap energy as well as the optical absorption with the experimental results.     

Magnetic and structural study of Cu-doped TiO2 thin films

Transparent pure and Cu-doped (2.5, 5 and 10 at.%) anatase TiO₂ thin films were grown by pulsed laser deposition technique on LaAlO₃ substrates. The samples were structurally characterized by X-ray absorption spectroscopy and X-ray diffraction. The magnetic properties were measured using a SQUID. All films have a FM-like behaviour. In the case of the Cu-doped samples, the magnetic cycles are almost independent of the Cu concentration. Cu atoms are forming CuO and/or substituting Ti in TiO₂. The thermal treatment in air promotes the CuO segregation. Since CuO is antiferromagnetic, the magnetic signals present in the films could be assigned to Cu substitutionally replacing cations in TiO₂.     

In-situ XAS study on the Cu and Ce local structural changes in a CuO-CeO2/Al2O3 catalyst under propane reduction and re-oxidation

The redox behaviour of a CuO-CeO₂/Al₂O₃ catalyst is studied under propane reduction and re-oxidation. The evolution of the local Cu and Ce structure is studied with in-situ transmission X-ray absorption spectroscopy (XAS) at the Cu K and Ce L₃ absorption edges.CuO and CeO₂ structures are present in the catalyst as such. No structural effect on the local Cu structure is observed upon heating in He up to 873 K or after pre-oxidation at 423 K.Exposure to propane at reaction temperature (600-763 K) fully reduces the Cu²⁺ cations towards metallic Cu⁰. Quick EXAFS spectra taken during reduction show a small amount of intermediate Cu¹⁺ species. Parallel to the CuO reduction, CeO₂ is also reduced in the same temperature range. About 25% of the Ce⁴⁺ reduces rapidly to Ce³⁺ in the 610-640 K temperature interval, while beyond 640 K a further slower reduction of Ce⁴⁺ to Ce³⁺ occurs. At 763 K, Ce reduction is still incomplete with 32% of Ce³⁺.Re-oxidation of Cu and Ce is fast and brings back the original oxides.The propane reduction of the CuO-CeO₂/Al₂O₃ catalyst involves both CuO and CeO₂ reduction at similar temperatures, which is ascribed to an interaction between the two compounds.     

Structure and composition of the segregated Cu in V2O5/Cu system

We have investigated segregation of copper at the surface of V₂O₅ films deposited onto Cu substrate by employing surface analysis techniques. X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) confirmed that the Cu is segregated at the surface and its chemical state is Cu₂O. According to secondary ion mass spectroscopy (SIMS) and glow discharge spectroscopy (GDS), the Cu concentration inside the deposited V₂O₅ layer is low. Ultraviolet photoelectron spectroscopy (UPS) and scanning tunneling spectroscopy (STS) revealed the segregation alters the surface local density of states. Surface analysis of deposited samples in ultra high vacuum (UHV) condition verified that the segregation occurs during the deposition. We have extended kinetic tight binding Ising model (KTBIM) to explain the surface segregation during the deposition. Simulation data approve the possibility of surface segregation during room temperature deposition. These results point out that on pure Cu substrate, oxidation occurs during the segregation and low surface energy of Cu₂O is the original cause of the segregation.     

退火诱导亚稳态Fe80Cu20合金固溶体的结构相变

利用扩展x射线吸收精细结构和x射线衍射研究了机械合金化制备的体心立方(bcc)的亚稳态Fe₈₀Cu₂₀合金固溶体的结构随退火温度的变化特点.结果表明，在300—873 K温度范围内，随着退火温度的升高，bcc结构物相的晶格常数近于线性降低，这主要是由于Cu原子从bcc结构Fe₈₀Cu₂₀合金固溶体中逐渐偏析出来，生成面心立方(fcc)结构的Cu物相所致.经603K退火后，Cu原子的平均键长R_Cu—Cu增加了0.003 nm左右，大约有50%的Cu原子从bcc结构的Fe₈₀Cu₂₀合金固溶体中偏析出来.在773 K退火后，bcc结构Fe_８０Cu₂₀合金固溶体近于完全相分离，生成了bcc结构的α-Fe与fcc结构的Cu物相. 关键词： 扩展x射线吸收精细结构 x射线衍射 ８０Cu₂₀合金')" href="#">Fe_８０Cu₂₀合金 机械合金化     

Optical constants of Cu(In0.7Ga0.3)5Se8 and Cu(In0.4Ga0.6)5Se8 crystals

Variable angle spectroscopic ellipsometry has been applied to characterize the optical constants of bulk Cu(In_0.7Ga_0.3)₅Se₈ and Cu(In_0.4Ga_0.6)₅Se₈ crystals grown by the Bridgman method. The spectra were measured at room temperature over the energy range 0.8-4.4 eV. Adachi’s model was used to calculate the dielectric functions as well as the spectral dependence of complex refractive index, absorption coefficient, and normal-incidence reflectivity. The calculated data are in good agreement with the experimental ones over the entire range of photon energies. The parameters such as strength, threshold energy, and broadening, corresponding to the E₀, E_1A, and E_1B interband transitions, have been determined using the simulated annealing algorithm.     

Investigation of the nonlinear absorption and optical limiting properties of two [Q]2[Cu(C3S5)2] compounds

The nonlinear absorption properties of two organometallic compounds, [(C₂H₅)₄N]₂[Cu(C₃S₅)₂] (DCu1) and [(C₄H₉)₄N]₂[Cu(C₃S₅)₂] (DCu2), have been investigated using an open-aperture Z-scan technique at 1064 nm with 40 ps pulse width and at 1053 nm with 18 ns pulse width. The reverse saturable absorption (RSA) which was observed in both samples with nanosecond pulse excitation was much larger than that observed with picosecond pulse excitation. The nonlinear absorption properties were analyzed theoretically by a five-level model. Optical limiting based on RSA was performed and limiting thresholds were evaluated for both samples under three conditions. DCu1 exhibited the better limiting characteristics because of its stronger RSA response.     

Radioluminescent mechanism of Li2B4O7:Cu crystal

The structure of the radioluminescent (RL) spectrum of Li₂B₄O₇:Cu crystal is complex, having no normal Gauss peaks. The RL spectrum recorded showed one sharp and strong peak near 365 nm. For the purpose of explaining this phenomenon, we used the self-trapped exciton (STE) model to analyze experimental data of absorption spectrum, emission spectrum, radioluminescence spectrum and decay-time curves. We found a short lifetime component (of the order of ns) from phosphorous signals of Li₂B₄O₇:Cu. We realized that the short lifetime component related to inherent signal of host lattice and the d-p transitions of Cu⁺. This result is applicable in the detector system with high time resolution.     

Optical absorption due to transitions between bands and local levels in CdCr2Se4

The theory of optical absorption due to transitions between a valence band and a hydrogen-like local level associated with a conduction band is modified to permit an arbitrary power-law dependence of energy on the magnitude of the wave-vector of carriers in the valence band. The observed absorption for photon energies below 1.6 eV in the ferromagnetic semiconductor CdCr₂Se₄ is discussed in terms of a combination of two types of terms. The first type of absorption is due to transitions to a local level from a band with two branches, in each of which there is an energy region with a width of 0.28 eV or more beginning 0.10–0.16 eV from the band edge, in which the energy measured from some origin near but not necessarily equal to the band-edge is approximately proportional to (wave-vector)^{($\text{1}\text{3}$)}. The second type of absorption has a dependence on photon energy ?ω of the form (?ω ? E₃)², where E₃ is a threshold energy probably connected with indirect transitions between bands as suggested by Sakai, Sugano and Okabe. After constraints on parameters appearing in the theory are imposed by use of results of these authors and of Shepherd, it is found that curves of Harbeke and Lehmann on optical absorption in CdCr₂Se₄ at 4.2, 78, 130 and 298 K in the photon-energy range 1.14–1.42 eV can be fitted to a mean accuracy of 3%, using an average of 3.75 adjustable parameters for each curve. The strength of the indirect band-to-band absorption does not have the temperature dependence expected for phonon-assisted indirect band-to-band transitions, but can be described by a term independent of temperature plus another term proportional to the square of the deviation of the magnetization from saturation. The fitting of the absorption curves requires that the ratio of the widths of the two branches of the bands varies from about 1.6 at low temperatures to 1.35 at 298 K and that the total width of the bands involved is less than 1 eV.     

多孔TiO2/Al/SiO2纳米复合结构的紫外光吸收特性研究

在SiO₂玻璃衬底上用脉冲激光沉积(PLD)技术，分别沉积Ti和Ti/Al膜，经电化学阳极氧化成功制备了多孔TiO₂/SiO₂和TiO₂/Al/SiO₂纳米复合结构. 其中TiO₂薄膜上的微孔阵列高度有序，分布均匀. 实验研究了Al过渡层对多孔TiO₂薄膜光吸收特性的影响. 结果表明：无Al过渡层的多孔TiO₂薄膜其紫外吸收峰在27