Removal of Phosphorus in Silicon by the Formation of CaAl2Si2 Phase at the Solidification Interface
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Directional solidification
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Cathodoluminescence is generated when a suitable specimen, such as a polished thin section, is bombarded with a beam of high-energy electrons. Some of the earliest observations of cathodoluminescence were made in the early 1960s by using an electron probe microanalyzer (EPMA), commonly referred to as an electron probe or electron microprobe (e.g., Long, 1963; Long and Agrell, 1965; Stenstrom and Smith, 1964; Smith and Stenstrom, 1965). In spite of this early application to CL study, the EPMA has not subsequently been used extensively for this purpose. Although CL images can be viewed in an EPMA, the EPMA is used primarily for compositional analysis.
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Characterization
BORO
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For further study on leaf boron forms of rape (Brassica napus L.) with different boron efficient at flowering stage, two boron efficient (9589,9590), two boron inefficient rape cultivars (9141,95105) and their four F 1 hybrid (95105×9589, 95105×9590, 9141×9589, 9141×9590) were used in this pot experiment. The results showed that the water soluble boron(S B) content and bound boron(B B) content in boron efficient cultivars was lower, while the semi bound boron(SB B)content was higher, on the contrary, in the boron inefficient cultivars, and the results in F 1 hybrid were just between that in boron efficient cultivars and in boron inefficient cultivars. A balance of boron forms was established, which showed boron forms had a close relation with boron efficiency, and it may uncover the physiological mechanism of boron efficiency.
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Applications of Electron Probe Microanalyzer for Measurement of Cl Concentration Profile in Concrete
Electron probe microanalysis (EPMA) has been applied for the quantitative evaluation of Cl ingress into concrete. In order to obtain quantitative data on Cl concentration, the measurement conditions were discussed statistically in detail and sample measurement conditions were introduced. The absolute concentrations of Cl obtained through EPMA were found to be equivalent with wet analysis and the effect of matrix differences to be negligible. By using the difference in chemical composition between cement paste and aggregate measured by EPMA with a spatial resolution of 100 μm, it was possible to discriminate the paste part in concrete. Since Cl penetrates into concrete through the paste part, the Cl concentration profile obtained by EPMA is useful for the estimation of the apparent Cl diffusion coefficient, Da. The quantified value of Cl concentrations obtained with EPMA were confirmed through comparison with traditional slicing and grinding methods. Based on the measurement results, the Da value was calculated for various concrete mixtures and the results were found to be equivalent with those yielded by conventional methods.
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凹凸が生じた金属材料表面上に存在する介在物の分析に斜出射EPMA法を応用し、その有効性を検討した.斜出射EPMA法は,平坦な表面上に分析対象物が存在することを必要とする.この条件のために,応用範囲が狭く,応用例が少なかった.本研究では,一般の走査型電子顕微鏡(SEM+EDS)で斜出射EPMA法を行う方法として,試料のZ軸上の位置を変化させてX線の取り出し角度を調整する方法を開発した。そして、この方法を腐食を施したステンレスの凹凸面上に観察された微小な介在物(約0.3ミクロン)の分析に応用した.その結果,斜出射EPMA法によって介在物の構成元素を正確に同定できることが分かった。介在物はMg,Al,Si,Ca,Ti,CrおよびMnを含む複合酸化物であり,Fe,Niは含まれていなかった.
Electron probe microanalysis
Microanalysis
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The element distribution and the microstructures of directionally solidified ingots of Ti-45Al-8Nb and Ti-46Al-8Nb alloys were studied by scanning electron microscope (SEM) and electron probe microanalyzer (EPMA) equipped with wavelength-dispersive X-ray spectroscope (WDS). At high solidification rates, e.g., more than 50 μm/s, the ingot solidified in columnar β dendrites, while at low solidification rates, e.g., less than 30 μm/s, the solidification path changed from initial β solidification to L + β→α peritectic solidification, forming cellular dendrites with the β phase matrix surrounded by the α phase. The difference of Ti content in dendritic arms and interdendritic regions was not pronounced. The composition segregation was mainly caused by the mutual conversion of Al and Nb contents. Therefore, it was difficult to distinguish the variation of Ti in microstructure by EPMA-WDS map and line profiles. The composition of the peritectic α phase was different from that of the α phase transformed directly from the β phase. The Al content of the former was about 1 at% higher than that of the latter, while the Nb content was about 1 at% lower. The change of solidification path in the final solidified part resulted from the more severe segregation caused by slow solidification.
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Abstract Boron is an important element, used in applications from superhard materials to superconductors. Boron exists in several forms (allotropes) and, surprisingly, it was not known which form (α or β) is stable at ambient conditions. Through experiment, we quantify the relative stability of α‐boron and β‐boron as a function of temperature. The ground‐state energies of α‐boron and β‐boron are nearly identical. For all temperatures up to 2000 K, the complicated β‐boron structure is more stable than the simpler α‐boron structure at ambient pressure. Below 1000 K, β‐boron is entropically stabilized with respect to α‐boron owing to its partially occupied sites, whereas at higher temperatures β‐boron is enthalpically stabilized with respect to α‐boron. We show that α‐boron only becomes stable on application of pressure.
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Abstract. When measuring boron (B) in tourmalines calibrated with schorl, no deviations in the peak intensities could be detected with a proven analysis protocol and using the Mo/B4C multilayer crystal LDEB. It is only when boron is detected in natural and experimental samples, some with significantly lower boron concentrations than in tourmalines, that irregularities in the analysis become visible. This phenomenon is known but has not been analytically investigated so far. Using four natural and artificial solids with boron concentrations from 0.035 wt %–3.14 wt % B, an apparent linear trend line was drawn. The intersect of that trend line with the y axis represents the detection limit of boron, which is of about 0.25 wt % B. The discrepancy between the apparent and the true value trend lines at boron concentrations of 0.25 wt %–2.1 wt % B shows that a correction is necessary. At higher boron concentrations, the discrepancy between the apparent and true value trend lines is within the uncertainty of electron microprobe analysis (EPMA) and disappears completely up to boron concentrations of about 3 wt %.
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Abstract Boron is an important element, used in applications from superhard materials to superconductors. Boron exists in several forms (allotropes) and, surprisingly, it was not known which form (α or β) is stable at ambient conditions. Through experiment, we quantify the relative stability of α‐boron and β‐boron as a function of temperature. The ground‐state energies of α‐boron and β‐boron are nearly identical. For all temperatures up to 2000 K, the complicated β‐boron structure is more stable than the simpler α‐boron structure at ambient pressure. Below 1000 K, β‐boron is entropically stabilized with respect to α‐boron owing to its partially occupied sites, whereas at higher temperatures β‐boron is enthalpically stabilized with respect to α‐boron. We show that α‐boron only becomes stable on application of pressure.
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