Bulk glass formability for Cu–Hf–Zr–Ag and Cu–Zr–Ag–Si alloys

The effects of the gradual substitution of Zr by Hf on glass formability and thermal stability in the Cu₄₅Zr_45?xHf_xAg₁₀ alloys and the effects of small additions of Si on glass formability in the Cu₄₅Zr₄₅Ag₁₀ alloy are reported and discussed. The samples were prepared as ribbons of thickness in the range 25–200 μm by melt spinning and as conical bulk shapes, with a length of 50 mm and cone base diameters in the range 2–10 mm, by suction die casting. The alloy Cu₄₅Zr₄₅Ag₁₀ had a critical cylindrical rod diameter for glass formation, d_c, of 3.5 mm but substitution of 1.5 and 3.5 at.% Zr by Hf resulted in substantial increases to 5.5 and 4.5 mm, respectively. However, for x in the range 5–40 at.%, d_c was reduced to <1 mm_. The small addition of Si proved to be beneficial to the glass forming ability (GFA), increasing d_c up to 5.5 mm for 0.5 at.% Si. Thus the chemical and atomic size similarities of Hf and Zr do not guarantee that bulk glass formation will be maintained on substituting large proportions of Zr by Hf though small substitutions of Hf and of minor additions of Si were beneficial to the GFA. These effects are discussed in terms of the possible influence of the alloying additions on the liquid structure and on the number density of heterogeneous nucleants.     

硅基Pt/Ba0.6Sr0.4TiO3/Pt电容器不同温度下的漏电机理研究

利用脉冲激光沉积技术在Pt(111)/TiO2/SiO2/Si(001)衬底上生长了厚度约为200 nm的Ba0.6 Sr04TiO3(BST)薄膜,构架了Pt/BST/Pt平行板电容器,测量了Ba06Sr0.4TiO3薄膜电容器在不同温度下的漏电流,研究了BST薄膜的结构和性能.结果表明BST薄膜为多晶钙钛矿结构,随着测量温度的降低,漏电流密度也随之降低,但是正负偏压下的J-V曲线并不对称,这主要归因于上下Pt电极与BST的界面热处理不同.通过不同导电机理对漏电流密度拟合发现,在负向偏置电压下,Pt/BST/Pt电容器均基本符合欧姆导电机制;而对于正向偏置电压,在低电压下符合欧姆导电机制,并且符合欧姆导电机制的电压范围在不断扩大,在高电压下符合空间限制电流(SCLC)导电机制.     

非晶 Ti-Al 过渡层对 Pt/Ba0.6Sr0.4TiO3/Pt电容器结构和性能的影响

应用磁控溅射法在 Pt/Ti/SiO2/Si(001)衬底上制备 5 mm 厚超薄非晶 Ti-Al 薄膜作为过渡层,利用脉冲激光沉积法制备 Ba0.6 Sr0.4TiO3 薄膜,构造了 Pt/Ba0.6Sr0.4TiO3/Pt(Pt/BST/Pt)和 Pt/Ti-Al/Ba0.6Sr0.4TiO3/Ti-Al/Pt(Pt/Ti-Al/BST/Ti-Al/Pt)结构的电容器,研究了 Ti-Al 过渡层对 Pt/BST/Pt 电容器结构及其性能的影响.实验表明,过渡层的引入有效地阻止了 Pt 电极和 BST 薄膜的互扩散,降低了 BST 薄膜氧空位的浓度,提高了铁电电容器的介电性能.当测试频率为 1 kHz、直流偏压为0 V时,介电常数由引入过渡层前的 530 增大到引入后的 601,介电损耗则由0.09减小到0.03.而且过渡层的引入有效地降低了 BST 薄膜的漏电流,使正负向漏电流趋于对称,在测试电压为5 V 时,漏电流密度由3.8×10-5 A/cm2 减小到 8.25 ×10-6 A/cm2.     

Microstructure and properties of spark plasma sintered Fe–Cr–Mo–Y–B–C bulk metallic glass

Fabrication of Fe-based amorphous alloy using spark plasma sintering (SPS) process has been reported. Fully amorphous compacts with ～95% relative density were successfully sintered at temperature about 100 °C lower than glass transition temperature (T_g: 575 °C). Formation of crystalline Fe₂₃(C, B)₆ phases within near-fully dense (～99%) amorphous matrix is observed at sintering temperatures (>550 °C) close to glass transition temperature. Microstructure evolution in sintered compacts indicated that density, degree of crystallinity, and mechanical properties can be effectively controlled by optimizing SPS parameters.     

Free volume and viscosity of Fe–Co–Cr–Mo–C–B–Y bulk metallic glasses and their correlation with glass-forming ability

In this work, the variation of the glass-forming ability (GFA) in Fe–Co–Cr–Mo–C–B–Y alloy system with Co addition has been investigated from the viewpoints of non-isothermal viscosity and free volume. The best GFA for the alloy containing 7% Co is found to closely relate with its highest viscosity, and the minimum sizes and lowest concentrations of the intermediate and largest open volumes. The results may provide more insights into the formation mechanism of metallic glasses.     

Fabrication and ionic conductivity of amorphous Li–Al–Ti–P–O thin film

Li⁺ ion conducting Li–Al–Ti–P–O thin films were fabricated on ITO-glass substrates at various temperatures from 25 to 400 °C by RF magnetron sputtering method. When the substrate temperature is higher than 300 °C, severe destruction of ITO films were confirmed by XRD (X-ray diffraction) and the abrupt transformation of one semi-circle into two semi-circles on the impedance spectra. These as-deposited Li–Al–Ti–P–O solid state electrolyte thin films have an amorphous structure confirmed by XRD and a single semicircle on the impedance spectra. Good transmission higher than 80% in the visible light range of these electrolyte thin films can fulfill the demand of electro-chromic devices. Field emission scanning electron microscopy and atomic force microscopy showed the denser, smoother and more uniform film structure with the enhanced substrate temperature. Measurements of impedance spectra indicate that the gradual increased conductivity of these Li–Al–Ti–P–O thin films with the elevation of substrate temperature from room temperature to 300 °C is originated from the increase of the pre-exponential factor (σ₀). The largest Li-ion conductivity can come to 2.46 × 10^? 5 S cm^? 1. This inorganic solid lithium ion conductor film will have a potential application as an electrolyte layer in the field such as lithium batteries or all-solid-state EC devices.     

Electronic conduction in (Bi,Pb)–Sr–Ca–Cu–O granular superconductors

Granular superconductors are very interesting materials owing to their untypical electrical properties caused by the presence of Coulomb effects, electron tunnelling, Josephson coupling between granules and various aspects of disorder. The electrical properties of (Bi,Pb)–Sr–Ca–Cu–O granular superconductors obtained by the solid state crystallization method have been studied in this paper. The materials may be considered as a system of granules of a high-temperature suprconductor embedded in the insulating matrix. The main parameter which determines the properties of granular materials is the tunnelling conductivity between the neighboring grains. Composed of small weakly coupled granules they are characterized by hopping conductivity exponential dependence. Samples containing relatively large granules of the 2212 phase (above 30 nm), with larger inter-grain conductivity, above the transition temperature, exhibit a logarithmic temperature dependence of resistivity.     

Pt掺杂CdS光学性质的第一性原理研究

采用基于密度泛函理论的平面波超软赝势方法分析了CdS和Pt掺杂CdS的几何、电子结构和光学性质,计算结果表明Pt掺杂的CdS结构引入了由Pt贡献的导电载流子,增强了CdS的电导率,另外,费米能级下移进入价带.研究表明,Pt掺杂的CdS结构在费米能级附近出现了杂质能级,这是由Pt的5d态电子所形成;在光学性质上,Pt掺杂的CdS在可见光区的吸收系数比理想CdS高,能量损失峰出现红移现象,可见,Pt掺杂的CdS晶体具有更高的光催化活性.     

Effect of Mo–Fe substitution on glass forming ability and thermal stability of Fe–C–B–Mo–Cr–W bulk amorphous alloys

Amorphous Fe_67?xC₁₀B₉Mo_7+xCr₄W₃ (x = 1–7 at.%) plates with 0.64 mm thickness were prepared by copper mold casting. The thermal properties and microstructural development during heat treatments were investigated by a combination of differential scanning calorimetry, differential thermal analysis, and X-ray diffraction. The glass forming ability (GFA) and activation energy for crystallization have a distinct dependence on Mo content. Fe₆₂C₁₀B₉Mo₁₂Cr₄W₃ was the best glass former in this study, demonstrating a supercooled liquid region, ΔT_x = 51 K, and an activation energy for crystallization, Q = 453 kJ/mol. The GFA of alloys in this system was governed by elastic strain optimization resulting directly from the variation in Mo content. Heat treatments were performed to demonstrate resistance to crystallization under typical processing conditions. Alloys in this system exhibited a three phased evolution during crystallization. A second set of heat treatments was performed to identify each phase. An analysis of phase evolution revealed a distinct dependence of phase evolution with stepwise substitution of Mo for Fe in this system.     

Characteristics and biocompatibility of Na2O–K2O–CaO–MgO–SrO–B2O3–P2O5 borophosphate glass fibers

A novel Na₂O–K₂O–CaO–MgO–SrO–B₂O₃–P₂O₅ borophosphate glass fiber is prepared. The thermal properties including differential thermal analysis (DTA) and viscosity measurement of the glass were presented. The tensile strength of the glass fiber is measured. The reaction of the glass fibers in the SBF solution is characterized by XRD, FTIR and SEM. XRD and FTIR indicate that the carbonate hydroxyapatite has formed rapidly on the glass. Cell attachment, spreading and proliferation on the glass are determined by MTT [3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide] assay method using Human osteosarcoma MG-63 cells. The bioactivity and biocompatibility of the glass fiber make it a good potential prospect in the field of tissue engineering.     

TiO_2/Pt复合纳米材料的可控合成及其表征

用两步水热法合成了TiO2/Pt复合纳米材料,并用TEM、XRD、EDS、BET、Zeta电位和EIS对TiO2/Pt复合纳米材料的形貌、晶体结构、成分及其物理和化学性质进行了表征。结果表明:与纯的TiO2纳米材料相比,TiO2/Pt复合纳米材料具有不同的物理和化学性质如晶体结构、比表面积、表面电荷性质和电子转移性质,而且随着Pt掺杂量的变化,这些物理和化学性质呈现规律性的变化。     

陶瓷单晶(100)基底上外延生长Pt薄膜

用对靶溅射技术在MgAl2O4 (100) (MAO) 和SrTiO3 (100) (STO)单晶基底上制备Pt薄膜.基底温度为700℃时,Pt薄膜外延生长为(200)取向,Pt/STO 薄膜的电阻率很低,而Pt/MAO 薄膜表现出高电阻特征.此外,Pt (50nm)/La0.67Ca0.33MnO3 (50nm)/STO的制备和研究表明,在包括庞磁电阻材料的器件设计中,Pt是一种较好的电极材料.     

Pt/Co-N-C电催化材料的制备及其碱性ORR性能

金属有机框架材料(MOFs)是一种制备过渡金属-氮-碳(M-N-C)氧还原电催化材料的有效前驱体，但在热解过程中结构坍塌等问题限制了其实际应用。本研究通过表面活性剂F-127包覆以及Zn掺杂对ZIF-67进行改性，并对改性后的Zn-ZIF-67@F-127在氩气气氛下进行热解，制得结构完整的Co-N-C载体。通过在Co-N-C载体表面进行Pt的负载，制备了Pt/Co-N-C复合氧还原反应(ORR)催化剂，并对其在碱性电解液中的ORR催化性能进行了探究。实验结果表明，F-127的加入提高了Zn-ZIF-67@F-127在热解过程中的形貌保持率，Pt/Co-N-C在O₂饱和的0.1 mol·L^-1 KOH中，催化剂的起始电位、半波电位、极限扩散电流密度分别为1.027 V、0.836 V和5.51 mA·cm^-2,与商用20%Pt/C性能相近。Pt与Co-N-C的协同作用使得催化剂不仅对ORR的四电子路径显示出高选择性，更在计时电流测试中表现出接近于商用20%Pt/C的稳定性与较商用20%Pt/C更优的抗甲醇性能。     

Effect of Mo element on the properties of Fe–Mo–P–C–B bulk metallic glasses

Bulk Fe_80?xMo_xP₁₀C_7.5B_2.5 (x = 5–10 at.%) metallic glasses are synthesized by copper mold casting, which have a critical diameter up to 3 mm, fracture strength over 3000 MPa, plastic strain up to 2.5% and saturation magnetization reaching 1.1 T. Results show that the glass forming ability and strength increase with increasing Mo content, while the plasticity and saturation magnetization do otherwise. These Mo content dependent properties are illuminated with the atomic interactions in the alloys that could be strengthened by suitable addition of Mo element. The effects of Mo on the properties of the alloys imply that proper Mo element should be chosen in designing Fe-based glassy alloys with desired properties.     

Composition–structure–property relationships in boroaluminosilicate glasses

The complicated structural speciation in boroaluminosilicate glasses leads to a mixed network former effect yielding nonlinear variation in many macroscopic properties as a function of chemical composition. Here we study the composition–structure–property relationships in a series of sodium boroaluminosilicate glasses from peralkaline to peraluminous compositions by substituting Al₂O₃ for SiO₂. Our results reveal a pronounced change in all the measured physical properties (density, elastic moduli, hardness, glass transition temperature, and liquid fragility) around [Al₂O₃]–[Na₂O] = 0. The structural origin of this change is elucidated through nuclear magnetic resonance analyses and topological considerations. Furthermore, we find that addition of 1 mol% Fe₂O₃ exerts a complicated impact on the measured properties.     

Self-catalyzed vapor–liquid–solid growth of InP/InAsP core–shell nanopillars

Indium phosphide/indium arsenide phosphide core–shell nanopillars have been prepared by the vapor–liquid–solid method using liquid indium droplets as the catalyst. The indium droplets were generated in situ in the deposition reactor. The hexagonal nanopillars exhibited hexagonal shaped sidewalls with average width and height of 150 and 250 nm, respectively. Cross-section transmission electron microscopy with selected area electron diffraction and X-ray dispersion energy analysis verified that an InAsP layer, approximately 10 nm thick, coated the pillars. Photoluminescence spectra at 77 K yielded an extremely intense band at 0.76 eV (1.63 μm), which was due to the InAsP shell on the pillars.     

Compositional dependence of optical parameters in Se–Bi–Te–Ag thin films

Compositional dependence of optical parameters in thermally evaporated amorphous Se_80.5Bi_1.5Te_18 ? yAg_y (for y = 0, 1.0, 1.5 and 2.0 at.%) quaternary thin films has been studied using well established Swanepoel method. The optical properties like, refractive index (n), extinction coefficient (k), absorption coefficient (α) and optical band gap (E_g) have been determined from the transmission spectra in the spectral range from 500 to 2500 nm. The optical band gap (E_g) has been estimated by using Tauc's extrapolation method and is found to increase with an increase in the Ag concentration. Present study shows that the refractive index, extinction coefficient and optical band gap increase with the increasing Ag content which is in agreement with the earlier studies. While the increase in the refractive index with Ag content over the entire spectral range can be attributed to the increased polarizability of larger Ag atomic radius (153 pm) compared to the Te atomic radius (135 pm), the increase in the optical band gap with increasing Ag concentration is correlated to an increase in the cohesive energy and decrease in the electronegativity of the films under study. The dielectric constant and optical conductivity (σ) of the thin films under study are also found to increase with the Ag concentration.     

On the decolorization property of Fe–Mo–Si–B alloys with different structures

Decolorization property of Fe–Mo–Si–B ribbons with different structures was investigated, and kinetic analyses elucidated that the decolorization process could be described by a pseudo-first-order kinetic model. Amorphous ribbons were proved to decolorize Acid Orange II solutions much more rapidly than amorphous/nanocrystalline ribbons at the same temperatures. Activation energies of the decolorization process by amorphous ribbons and amorphous/nanocrystalline ribbons were obtained according to Arrhenius equation, and they were proved more or less the same because of the existence of amorphous phase in both ribbons, while the different reactive site amount was considered to lead to the different decolorization rates for the two ribbons with different structures.     

Carrier collection characteristics of microcrystalline silicon–germanium p–i–n junction solar cells

We report on the carrier collection characteristics of hydrogenated microcrystalline silicon–germanium (μc-Si_1?xGe_x:H) p–i–n junction solar cells fabricated by low-temperature (～200 °C) plasma-enhanced chemical vapor deposition. Spectral response measurements reveal that the Ge incorporation into absorber i-layer reduces the quantum efficiencies at short wavelengths. Furthermore, the illumination of the solar cells for x ? 0.35, particularly in the wavelength range of <650 nm, induces a strong injection-level-dependent p–i interface recombination and a weak collection enhancement in the bulk. These results indicate that space charges near the p–i interface are largely negative, which gives rise to an electric field distortion in the i-layer. We attribute the negative space charges to the presence of the acceptor-like states that are responsible for the strong p-type conduction observed in undoped μc-Si_1?xGe_x:H films for large Ge contents.