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排序方式: 共有579条查询结果,搜索用时 15 毫秒
1.
《Ceramics International》2021,47(22):31852-31859
The primary purpose of this work is to introduce the second phase of graphene (G) into non-stoichiometric TiO1.80 successfully and optimize the thermoelectric properties of this composite material through high pressure and high temperature (HPHT) technology. The purpose of doping Ti powder under high pressure is to create a closed reducing atmosphere to change the ratio of titanium to oxygen in the titanium oxide base. The addition of graphene can considerably improve the electrical properties of the material and reduce its resistivity. An X-ray diffractometer, X-ray photoelectron spectrometer, scanning electron microscope, and transmission electron microscope were used to analyze and characterize the phase structure, chemical bond, micro morphology and crystal morphology of the samples. An abundance of grain boundaries and lattice dislocation defects can inhibit the lattice thermal conductivity. We also tested and analyzed the thermoelectric performance of the high-temperature and high-pressure synthetic samples through a variable temperature system. The variation of the absorption intensity of the ultraviolet UV spectrum with wavelength shows that high pressure can reduce the band gap, which is beneficial to the carrier transition and improves the conductivity of semiconductors. HPHT optimizes both the electrical and the thermal parameters of the sample. At a final sintering pressure of 5.0 GPa, the dimensionless figure of merit (zT) of the bulk composite material G/TiO1.80 was found to be 0.23 at 700 °C. 相似文献
2.
《Sensors and actuators. A, Physical》2006,125(2):223-233
To characterize the thickness of a corrosive fluid system's coated facilities, such as pipes, tubes, tanks, and structural members, a complex ultrasonic transducer capable of measuring multilayered parts was fabricated and the time and frequency responses were evaluated. The target transducer was constructed with two active dual elements made from tape-cast PbNb2O6 sheets and an additional thin-film active element made from sol–gel spin-coated Pb(Zr0.52Ti0.48)O3 films. After adjusting the properties of each active element, a complex transducer was assembled after matching the impedance of each element and considering the minimal interference between the active layers. The impulse response of the assembled complex transducer shows excellent characteristics. Moreover, the assembled transducer's capability of accurately measuring the thickness assures that it can be directly applied to related industries. 相似文献
3.
Xuexin Guo Jinbao Zhang Mucui Ni Li Liu Hongwei Lian Han Wang 《Journal of Materials Science: Materials in Electronics》2016,27(11):11262-11267
Hollow and porous α-Fe2O3 nanotubes were successfully synthesized by single nozzle electrospinning method followed by annealing treatment. The crystal structures and morphologies of the as-prepared materials were characterized by X-ray diffraction and scanning electron microscopy, respectively. The as-prepared materials were applied to construct gas sensor devices which gas sensing properties were further investigated. The obtained results revealed that porous α-Fe2O3 nanotube gas sensors exhibit a markedly enhanced gas sensing performance compared with hollow α-Fe2O3 nanotube gas sensors, which was about three times higher to 100 ppm acetone at 240 °C. Interestingly, hollow and porous α-Fe2O3 nanotube gas sensors both showed fast response–recovery time and good selectivity, but the porous ones possessed the shorter recovery time. The improved properties could be attributed to the unique morphology of porous nanotubes. Thus, further improvement of performance in metal-oxide-semiconductors materials could be realized by preparation the unique porous structures of nanotubes. Moreover, it is expected that porous metal-oxide-semiconductors nanotubes could be further design as promising candidates for gas sensing materials. 相似文献
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The influence of oxidizing environments on single crystal diamond and polycrystalline chemical vapor deposited CVD diamond films was studied using the near edge X-ray absorption fine structure (NEXAFS) pre-edge region in both bulk and surface sensitive modes. The NEXAFS of (100) oriented single crystal diamond was measured following (i) exposure to a microwave (MW) hydrogen plasma, (ii) annealing to 1000 °C, (iii) exposure of the as annealed surface to H2O, and (iv) exposure of the as annealed surface to O2. From these measurements particular surface bonding configurations have been assigned to features in the pre-edge structure. The NEXAFS of microcrystalline CVD diamond films was studied following different oxidative treatments using (i) a thermal atomic oxygen (AO) environment, (ii) a hyperthermal (5 eV) AO source, and (iii) an RF oxygen plasma exposure. The nature of the surface layer was found to be different for differently oxidized surfaces. These treatments were carried out as part of a study of CVD diamond durability in the low Earth orbit space environment. 相似文献
7.
WC/Co mining bits from a drill head used for drilling holes for roof support bolts in a mine were examined using a focused ion beam scanning electron microscope (FIB-SEM). This was combined with energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) analyses to study the chemical interaction between the drill bit and the rock. It was found that at the surface of the buttons there was depletion of cobalt, change in chemistry of the remaining binder regions, and changes to the morphology of the WC grains. Tribochemistry calculations were done to understand the possible formation of silicides at the surface of the drill bits, and thus emphasise the importance of quartz content in rock on wear. The evidence of mechanical damage combined with chemical reactions is another step towards understanding the complete wear process in hardmetal mining tools. 相似文献
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Induced polarization shows a significant influence on dielectric permittivity of 0–3 polymer composites containing Si-based semi-conductive fillers. The nature of induced polarization is the increased electric conductivity or decreased band gap in Si-based semi-conductive fillers. In this work, the dependence of induced polarization onto particle size of α-SiC filler together with polarity of polymer matrix and Si-based semi-conductive filler has been elaborately investigated by detecting the permittivity of composites. It was found that increasing the grain size of SiC filler, improving the polarity of polymer matrix and reducing the band-gap of Si-based semi-conductive filler could favor the enhancement of the overall induced polarity in the composites. As a result, the significantly improved dielectric permittivity of composites higher than both of the neat polymer and filler was observed depending on the constituents of the composites. The highest dielectric permittivity of ~215@1 kHz was achieved in poly(vinyl alcohol) based composite filled with 60 vol% of 12 µm SiC particles. The dielectric permittivity of these 0–3 composites could be well tuned in a wide range through altering their constituents. This work might open a facile route to obtain the promising high-performance dielectric composite materials by regulating the degree of induced polarization. 相似文献
10.
《Carbon》2014
We report a muon spin relaxation investigation of Li6C60 and Na10C60 fullerides, which have been recently demonstrated to be efficient and reversible H2 absorbers above 570 K. We prove that, differently from other fullerides, a sizeable fraction of implanted muons form C60 muonium adduct radicals, with hyperfine coupling depending on the C60 hydrogen coverage. Surprisingly, the fraction of radicals was found to increase up to 65% when lowering T to 5 K in Na10C60Hy. This indicates that hydrogen interaction in these systems is enhanced even at cryogenic temperatures, while the high T needed for hydrogen absorption is only required to overcome the H2 dissociation barrier mediated by alkali metals. 相似文献