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21.
A. D’Angio’ J. Zou J. Binner Hai-Bin Ma G.E. Hilmas W.G. Fahrenholtz 《Journal of the European Ceramic Society》2018,38(2):391-402
The effect of ZrC on the mechanical response of ZrB2 ceramics has been evaluated from room temperature to 2000 °C. Zirconium diboride ceramics containing 10 vol% ZrC had higher strengths at all temperatures compared to previous reports for nominally pure ZrB2. The addition of ZrC also increased fracture toughness from for nominally pure ZrB2 to due to residual thermal stresses. The toughness was comparable with ZrB2 up to 1600 °C, but increased to at 1800 °C and 2000 °C. The increased toughness above 1600 °C was attributed to plasticity in the ZrC at elevated temperatures. Electron back-scattered diffraction analysis showed strong orientation of the ZrC grains along the [001] direction in the tensile region of specimens tested at 2000 °C, a phenomenon that has not been observed previously for fast fracture (crosshead displacement rate = 4.0 mm min?1) in four point bending. It is believed that microstructural changes and plasticity at elevated temperature were the mechanisms behind the ultrafast reorientation of ZrC. 相似文献
22.
X.M. Wang K.B. Ma D.N. Wijesundera B. Liu J.R. Liu W.K. Chu 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2009,267(20):3466-3470
Rutherford Backscattering Channeling (RBSC) is often used in the studies of single crystalline materials with regard to issues hinging upon the location of specific atomic species within the crystal lattice. Results are deduced from the characteristics of an angular scan curve representing the yield of close collision events from the constant scattering of the probing projectiles from the crystalline sample in a sequence of directions lying in a plane perpendicular to one particular crystal lattice direction. Such angular scans exhibit dips near major channels, and their angular widths are of concern. On a fundamental level, accurate determination of these angular widths in the case of axial channeling and their interpretation come up against uncertainties arising out of the absence of a preferred choice for the plane of scan. Here, we shall illustrate these uncertainties in a representative case, channeling of 2 MeV He+ ions in the 1 0 0 direction of Si. 相似文献
23.
R. Mitdank D. HabelO. Görke M. HarthH. Schubert H. Winter 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2011,269(3):345-352
TiO2/V2O5 based ceramic materials applied in catalysis were investigated. Structural properties like the grain diameter of these pressed ceramic powders were analysed by means of Rutherford backscattering (RBS) making use of an analytic model to describe the energy spectra of porous rough samples. Grain diameters of these samples were deduced as function of process temperature and chemical composition and related to a phase transition from the TiO2-Anatase/V2O5-Shcherbinaite to Rutile solid solution (Rutile-ss) structure. RBS data were compared to results of scanning electron microscopy (SEM). The activation energy for the sintering at the phase transition was estimated to 5.4 eV. 相似文献
24.
采用连通式双反应室高温MOCVD系统在Si衬底上外延ZnO薄膜,通过卢瑟福背散射/沟道(RBS/C)及高分辨X射线衍射(HR-XRD)技术对不同衬底条件的ZnO外延膜进行了组分及结构分析,结果表明在采用SiC缓冲层后,Si(111)衬底上ZnO(0002)面衍射峰半高宽明显减小,缺陷密度降低,单晶质量显著变好,c轴方向应变由0.49%变为-0.16%,即由拉应变变为压应变且应变值变小,说明SiC缓冲层可以有效地减小ZnO与Si衬底晶格失配带来的应变,改善外延膜质量,实现Si衬底上单晶ZnO的生长. 相似文献
25.
Electron backscatter pattern analysis has been used to characterise, using the coincidence site lattice model, the distribution of grain boundary structures in a series of BaTiO3 based positive temperature coefficient of resistance (PTC) thermistors, prepared with 0, 1.0, 2.0 and 3.0 at.% SiO2 additions. As the SiO2 content was raised, the proportion of random, high-angle grain boundaries in the microstructure increased steadily from 85.7% to 89.6%, while the proportion of grain boundaries indexable in the range Σ3–Σ29 decreased from 14.3% to 10.4%, and the Σ3 grain boundary population fell from 5.9% to 3.6%. At the same time the proportion of Σ3 twin boundaries remained approximately constant at 3.0 ± 0.3%. Significantly more Σ3 grain boundaries than would be expected in a randomly oriented, untextured material were observed in all samples. The variation in grain boundary types with SiO2 addition is discussed in terms of grain boundary energy and its effect on PTC performance. 相似文献
26.
Fang Liang Zhao Zhengyu Wang Feng Su Fanfan 《Frontiers of Electrical and Electronic Engineering in China》2007,2(4):415-419
The real-time information of the distant ionosphere can be acquired by using the Wuhan ionospheric oblique backscattering
sounding system (WIOBSS), which adopts a discontinuous wave mechanism. After the characteristics of the ionospheric echo Doppler
spectra were analyzed, the signal preprocessing was developed in this paper, which aimed at improving the Doppler spectra.
The results indicate that the preprocessing not only makes the system acquire a higher ability of target detection but also
suppresses the radio frequency interference by 6–7 dB.
__________
Translated from Journal of Wuhan University (Natural Science), 2006, 52(1): 114–118 [译自: 武汉大学学报(理学版)] 相似文献
27.
J. Vacik V. Hnatowicz J. Cervena H. Naramoto S. Yamamoto D. Fink 《Fullerenes, Nanotubes and Carbon Nanostructures》2001,9(2):197-209
To determinate the stopping cross section in fullerite a feasible approach, taking into account the high radiation sensitivity and mechanical fragility of fullerite films, should be employed. In this work, the stopping cross sections of 1H, 3H, 4He and 7Li ions for several selected energies were measured by Rutherford backscattering, neutron depth profiling and alpha spectroscopy using sandwich structures of samples composed of fullerite deposited on a firm substrate (Si, steel) with an intermediate marker (Au, N, Li, B, Pu). In addition, ion transmission through a thin C film supporting a fullerite layer was also utilized. The measured stopping cross sections follow the theoretical predictions calculated for carbon, but are systematically (10-35%) higher than the theoretical ones (with the exception of 5 — 5.5 MeV 4He). The observed deviation of the experimental data can partly be explained by the chemical state effects in fullerite, which accounts for about 20-50% of the difference. The measured energy straggling exceeds Bohr's value by a factor of about 2 for alpha spectroscopy and ion transmission, and 2.5 or 9.5 for Rutherford backscattering and neutron depth profiling, respectively. The discrepancy can be explained by a thickness variation, such as surface roughness of the fullerite films. 相似文献
28.
29.
K. Z. Baba-Kishi 《Scanning》1998,20(2):117-127
Electron backscatter Kikuchi diffraction patterns (BKDPs) recorded in the scanning electron microscope (SEM) require measurements on the plane of the photographic film or on the recording screen. The parameters that require measurements are the equivalent electron source point on the pattern, or pattern centre, specimen-to-film distance, true interzonal angles, true interplanar angles, Bragg angles, and interplanar spacing. In this paper, the geometry and the methods of calculation of these parameters on BKDPs recorded directly on film are described in detail. The methods described are suitable for practical purposes, providing speed of calculation but limited accuracy. The inherent factors that limit the accuracy of any measurements on BKDPs are the limitations of the gnomonic projection, resulting in projected distortions in Kikuchi bands and diffuseness of Kikuchi band edges originating from inelastic scattering of electrons. The methods described are applied to crystallographic analysis of BKDPs recorded from silicon and polycrystalline copper. 相似文献
30.
An experimental evaluation of spatial distribution for deeply penetrating protons in carbon material
Mitsuo Tosaki Daisuke Ohsawa Yasuhito Isozumi 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2005,230(1-4):59-62
The peak profile of the 4.8-MeV resonance by the 12C(p,p)12C reaction in backscattering geometry has been analyzed to examine two kinds of stragglings of proton, i.e. the depth straggling in the incoming path and the energy loss straggling in the outgoing path. The analysis, which is combined with existing theoretical treatments for the stopping process and the energy loss straggling, has made it possible to deduce the penetration depth and its spread at the resonance position in carbon materials. The present method, as a new tool for direct inspection of ion beams inside target material, is explained in detail. 相似文献