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排序方式: 共有126条查询结果,搜索用时 31 毫秒
101.
T. Bak J. Nowotny C. C. Sorrell M. F. Zhou E. R. Vance 《Journal of Materials Science: Materials in Electronics》2004,15(10):635-644
The present paper reports the electrical conductivity of polycrystalline undoped CaTiO3 in the temperature range 973–1323 K under controlled oxygen partial pressure (10–105 Pa). The electrical conductivity data are considered in terms of defect disorder and related semiconducting properties of CaTiO3. The values of the p(O2) exponent of electrical conductivity at high p(O2), that vary between 1/4.3 and 1/6.2 at 973 and 1323 K, respectively, are considered in terms of theoretical defect disorder model of p-type CaTiO3 and increasing effect of minority charge carriers (electrons) with temperature on p-type conduction. The activation energy of the electrical conductivity, assuming 125.3 kJ/mol at 10 Pa and 94.4 kJ/mol at 72 kPa, has been considered in terms of the formation of defect and their mobility. The band gap, determined from the minimum of electrical conductivity corresponding to the n–p transition is equal to 2.77 eV. 相似文献
102.
Hangjuan Ren Thomas Dittrich Hongyang Ma Judy N. Hart Steffen Fengler Sheng Chen Yibing Li Yu Wang Fuyang Cao Mauricio Schieda Yun Hau Ng Zhirun Xie Xin Bo Pramod Koshy Leigh R. Sheppard Chuan Zhao Charles C. Sorrell 《Advanced materials (Deerfield Beach, Fla.)》2019,31(8)
Conductive metal oxides represent a new category of functional material with vital importance for many modern applications. The present work introduces a new conductive metal oxide V13O16, which is synthesized via a simplified photoelectrochemical procedure and decorated onto the semiconducting photocatalyst BiVO4 in controlled mass percentages ranging from 25% to 37%. Owing to its excellent conductivity and good compatibility with oxide materials, the metallic V13O16‐decorated BiVO4 hybrid catalyst shows a high photocurrent density of 2.2 ± 0.2 mA cm?2 at 1.23 V versus reversible hydrogen electrode (RHE). Both experimental characterization and density functional theory calculations indicate that the superior photocurrent derives from enhanced charge separation and transfer, resulting from ohmic contact at the interface of mixed phases and superior electrical conductivity from V13O16. A Co–Pi coating on BiVO4–V13O16 further increases the photocurrent to 5.0 ± 0.5 mA cm?2 at 1.23 V versus RHE, which is among the highest reported for BiVO4‐based photoelectrodes. Surface photovoltage and transient photocurrent measurements suggest a charge‐transfer model in which photocurrents are enhanced by improved surface passivation, although the barrier at the Co–Pi/electrolyte interface limits the charge transfer. 相似文献
103.
Interfacial Reactions Between Anorthite (CaAl2Si2O8) and Al 7075 Alloy at 850°C and 1150°C 下载免费PDF全文
Esmaeil Adabifiroozjaei Pramod Koshy Ebad Rastkerdar Charles C. Sorrell 《Journal of the American Ceramic Society》2016,99(5):1694-1708
The present work reports an investigation of the interactions of Al 7075 alloy and anorthite at 850°C (150 h) and 1150°C (24 h). Transmission electron microscopy, electron probe microanalysis, X‐ray diffraction, and scanning electron microscopy coupled with energy‐dispersive spectroscopy were used to identify the mineralogical and microstructural changes at the metal–ceramic interface. At 850°C, the phase formation mechanisms were (a) Si4+–Al3+ interdiffusion between the Al alloy and anorthite to form calcium dialuminate (CA2) and Ca2+–Mg2+ interdiffusion between the Al alloy and calcium dialuminate to form spinel. At 1150°C, spinel + Al2O3 and calcium hexaluminate (CA6) + CA2 were the major and minor phase mixtures, respectively in the corroded area. A thin layer of calcium monoaluminate (CA), gehlenite, and Si was present in the immediate vicinity of anorthite. The early stages of corrosion at 1150°C and 850°C were identical. However, due to thickening of the corroded region (viz., spinel formation) and enhanced evaporation of Mg at the higher temperature, the interdiffusion path evolves from Si4+–Al3+ + Ca2+–Mg2+ to Si4+–Al3+ + Ca2+–Al3+, thus establishing the following phase evolution path at the interface: 相似文献
104.
General model for comparative tensile mechanical properties of composites fabricated from fly ash and virgin/recycled high‐density polyethylene 下载免费PDF全文
Imrana I. Kabir Charles C. Sorrell Mykanth R. Mada Sagar T. Cholake Sri Bandyopadhyay 《Polymer Engineering and Science》2016,56(10):1096-1108
The present work on the mechanical properties of ≤10 wt% fly ash additions in 2.5 wt% increments to recycled high‐density polyethylene (RHDPE) synthesizes experimental data from three similar published reports. The present work shows, as a function of increasing fly ash addition level, maxima at the initial fly ash addition level of 2.5 wt% for the tensile elastic modulus (+25%) and tensile strength (+10%); a slight general increase in the yield stress (+6%); and significant general decreases in the yield strain (?61%), elongation at break (?92%), and Charpy impact strength (?55%). Combining these data with data for higher‐level additions of fly ash (≤40 wt%/23 vol%) and cenospheres (≤39 vol%) to HDPE or RHDPE provides the basis for design parameters and a generalized model for the interpretation of failure of composites of hard brittle spherical dispersant additions in ductile polymeric matrices. The relevant load‐extension plots are characterized by three behavioral regions: ductile deformation (dispersion strengthening and stress concentration), crazing (debonding and cavitation), and brittle failure (fibril failure). The locations of these regions and their transitions are a function of five dependent variables: dispersant volume, dispersant particle size, intrinsic flaw size (viz., dispersant size), generated flaw size (viz., void size), and interfacial bond strength and associated load transfer. POLYM. ENG. SCI., 56:1096–1108, 2016. © 2016 Society of Plastics Engineers 相似文献
105.
Sang-Yoon Koo Gyeong-Geun Lee Suk-Joong L. Kang Janusz Nowotny Chris Sorrell 《Journal of the American Ceramic Society》2004,87(8):1483-1487
In an attempt to improve the dielectric properties of SrTiO3 -based boundary-layer capacitors (BLCs), the effects of infiltrant composition on the liquid film migration and dielectric properties in 0.2-mol%-Nb2 O5 -doped SrTiO3 were investigated. Powder compacts were sintered at 1480°C for 5 h in 5H2 ·95N2 and infiltrated with 80Bi2 O3 ·20( x CaO–(1 – x )BaO) at 1300°C for various times in air. When the value of x was 0, 0.2, 0.7, and 1.0, liquid film migration occurred, which formed a new solid-solution layer containing solute species. On the other hand, when x = 0.5, no liquid film migration was observed. The effective dielectric constant was the highest in the sample with x = 0.5 (no liquid film migration), and it decreased as the migration distance increased. In addition, the loss tangent was the lowest, <1%, in the sample with x = 0.5. Agreement between the estimated effective dielectric constants and the measured values showed that the suppression of liquid film migration improved the dielectric constant. The agreement further indicated that the prediction of the dielectric constant in SrTiO3 -based BLCs was possible using a two-layer model with a liquid-infiltrated layer and a SrTiO3 -based oxidized layer. 相似文献
106.
Ji-Ping Zhou Charles C. Sorrell Shi-Xue Dou Miles H. Apperley 《Journal of the American Ceramic Society》1991,74(7):1541-1546
The present work describes a new technique to synthesize aligned YBa2 Cu3 O7- x and Ag─YBa2 Cu3 O7- x superconducting composites from Ba- and Cu-deficient compositions (relative to YBa2 Cu3 O7- x ) plus BaCuO2 . For YBa2 Cu3 O7- x , high transition temperature midpoint Tc (91 K), temperature of zero resistivity T 0 (90 K), and critical current density Jc (>3000 A°Cm−2 at 77 K) were achieved by using this technique. This procedure provides the potential for using a reliable and reproducible densification and alignment technique alternative to partial or full melting. The composite is highly aligned, with an average grain size of ∼1 to 2 mm and domains of width greater than 5 mm. The initial phase assemblage consists of YBa2 Cu3 O7- x (123) as the major phase plus YBa2 CuO5 (211) CuO as minor phases. The BaCuO2 is added to the Ba- and Cu-deficient starting composition in order to assist in the formation of a CuO-rich liquid as well as to compensate for the Ba and Cu deficiences in 123. Since the liquid forms at ∼900°C and is compatible with 123, it can be used to facilitate alignment of 123 at ∼930°C. The addition of Ag to the system results in eutectic formation with the (solidified) liquid, substantial filling of the pores during sintering, and improved alignment. 相似文献
107.
M. Rekas T. Bak J. Nowotny C. C. Sorrell Y. Zhao K. Foger E. R. Vance 《Journal of Materials Science: Materials in Electronics》2000,11(9):691-696
The present work reports equilibration kinetics for (La0.8,Sr0.2)CoO3(LSC) and (La0.72,Sr0.18)FeO3(LSF) in the temperature range 876–1114 K using a gravimetric method. Chemical diffusion determined in this way that depends on oxygen partial pressure, can be expressed by the following temperature dependence at low and high O2), respectively, for LSC:
and for LSF:
相似文献
108.
Jieyu Wang Hangjuan Ren Wen-Fan Chen Pramod Koshy Charles Christopher Sorrell 《Ceramics International》2018,44(5):4981-4989
Sn-doped anatase hollow spheres were fabricated using a template method involving polystyrene spheres as core and anatase coating as shell. The synthesis route included the preparation of PS spheres, followed by their coating by Sn-doped TiO2 sol-gel precursor and subsequent removal of the PS cores by pyrolysis and recrystallization at 500 °C for 2 h. The observation of minor amounts of rutile suggests that Sn promotes the anatase → rutile phase transformation. At doping levels of ≤ 1.0 mol% Sn, the unsaturated solubility and increasing defect densities enhanced nucleation. At 1.0–2.0 mol% Sn, the solubility remained unsaturated but increasing Sn incorporation reduced crystallinity owing to lattice deformation and partial amorphization. At 2.0–3.0 mol% Sn, solid solution saturation occurred, resulting in excess dopant precipitation, leading to grain boundary pinning and partial blockage of surface-active sites. Ionic radii, thermodynamic, phase equilibria, intervalence charge transfer, and defect chemistry considerations suggest that Sn4+ exhibits substitutional solid solubility in the TiO2 lattice. The photocatalytic performance was in the order 1.0 > 1.2 > 1.5 ≈ 0.7 > 2.0 > 0.0 > 3.0 mol% Sn. This ranking is consistent with the dominant role of crystallinity such that, at ≤ 1.0 mol% Sn, the performance increased owing to enhanced nucleation from low defect density and increasing crystallinity while, at 1.0–2.0 mol% Sn, the performance decreased from increased lattice strain and effective partial amorphization, and, at 2.0–3.0 mol% Sn, it decreased from maximal lattice strain and blockage of active sites. 相似文献
109.
Keng Ho Cheung Moreica Beatrice Pabbruwe Wen-Fan Chen Pramod Koshy Charles Christopher Sorrell 《Ceramics International》2021,47(2):1609-1624
TiO2 coatings were fabricated by anodization of Ti6Al4V in 1 M H3PO4 or H2SO4, at room temperature at 120 V for 10 min, and followed by annealing at 300° or 500 °C for 8 h. Analyses include mineralogy (GAXRD, Raman), chemistry (XPS), morphology and microstructure (FESEM, FIB, 3D confocal microscopy), thermodynamic, optical (UV–Vis), and photocatalytic performance (MB degradation). The present work highlights factors that govern the nature of the materials and their performance. The influence of the oxidation strength of the acid is pervasive in that it impacts on the crystallinity, microstructural homogeneity, coating thickness, Ti3+ concentration, gas generation during arcing to form pores, and resultant pore size and distribution density. A key observation is that the pores form a subsurface network of variable continuity, which has a significant impact on the surface area and associated density of photocatalytically active sites, access by liquids and gases inside the coating, penetration depth of incident radiation, gas condensation, and residual liquid trapping. These data and the related thermodynamic analyses of the acids, anodization processes, and oxidation processes facilitate the generation of schematic models for the anodization mechanisms and the resultant surface, bulk, and microstructural effects that dominate the photocatalytic performance. 相似文献
110.