Solid State Communications
Considering the image potential, we calculate the binding energies of a shallow donor impurity placed on the centre of a quantum box using the variational approach. The results we have obtained show that there is a great difference of the effects of image potential between the cases including impurity ion image potential and including the image potentials of impurity ion and electron simultaneously. The results also show that the image potential is important, especially when the dimensions of quantum box become small.
关键词:
well;gaas-ga1-xalxas;states
李德江
,
宋泉吾
,
张勇
,
韩青
,
周云宗
,
戴立新
,
王成龙
黄金
doi:10.3969/j.issn.1001-1277.2003.07.005
在玲珑金矿田地质特征基础上,详细研究分析了175号脉群地质特征.根据矿段矿体赋存规律,对175支脉成矿进行预测,并对部分地段投入工程验证,获得了比较好的探矿效果.
关键词:
玲珑金矿田
,
175号脉特征
,
矿体赋存规律
,
成矿预测
L. H. Lang
,
D. C. Kang
,
S. H. Zhang
,
Z. R. Wang
,
S. J. Yuan
,
K. B. Nielsen and J. Dancket 1) Department of Materials Engineering
,
Harbin Institute of Technology
,
Harbin 150001
,
China 2) Aalberg University
,
Denmark
金属学报(英文版)
In this paper, the forming features of tapered rectangular box during hydrodynamic deep drawing are studied by means of FEM.The effect rules of square blank corner corner amount on body wrinkling are recognized and corresponding methods are discussed. At last, the results of FEM are verified by experi- ment.
关键词:
sheet metal forming
,
null
,
null
蔡彪
,
李劲风
,
贾志强
,
李朝兴
,
郑英鹏
,
蔡圳阳
材料热处理学报
采用拉伸性能测试、剥落腐蚀实验及透射电镜观察研究了175℃回归时7150-RRA铝合金力学性能、剥蚀行为及微观组织,并与T6及T73时效工艺进行了比较研究.结果表明,7150-T6铝合金强度高而剥蚀敏感性大;7150-T73铝合金强度降低而耐腐蚀性大幅度提高.175℃回归时,7150-RRA铝合金剥蚀敏感性随回归时间延长而降低;回归时间延长至3h,7150-RRA铝合金可保持7150-T6的高强度,而其剥蚀敏感性与7150-173接近.
关键词:
7150-RRA铝合金
,
回归再时效(RRA)
,
力学性能
,
剥落腐蚀
Qunqiang FU
材料科学技术（英文）
At first, a series of finite element method (FEM) simulation tests were used to find the critical forming conditions of hot-galvanized sheet steel during the rectangular box drawing processing when constant blank holder forces were applied. According the test results, the reasonable alteration scope of initial variable blank holder force (VBHF) was as 1.9~2.3 T. Then, based on the test productions of blank holder force, 12 typical VBHF curves were applied to perform the simulation tests by the simulation software of DYNAFORM. The simulation test results showed that VBHF had great effects on drawing formability of hot-galvanized sheet steel during the rectangular box drawing. However, the different VBHF curves were applied to control the whole drawing and it would get great different effects. At the same tine, the VBHF had great effects on the maximum thick thinning ratio, but had little effect on the maximum thick incrassation ratio. So, reasonable application of the VBHF would greatly decrease the fractures. When the VBHF profile is taken as curve L, the best effect of drawing formability could be obtained. When curve I is used, contrary effect could be gotten. The other types of curves would cause effects between above two types of VBHF curves. Finally, the actual tests were applied to check the validity of the FEM simulation tests. The results show that the FEM simulation tests are good ways for predicting and optimizing the VBHF.
关键词:
Drawing process
,
变压边力
,
热镀锌钢板
Insup Lee
,
Kwang-Ho Jeong
材料科学技术（英文）
Plasma nitrocarburizing and plasma oxidizing treatments were performed to improve the wear and corrosion resistance of SKD 61 steel. Plasma nitrocarburizing was conducted for 12 h at 540℃ in the nitrogen, hydrogen and methane atmosphere to produce the ε-Fe2–3 (N,C) phase. The compound layer produced by plasma nitrocarburising was predominantly composed of ε-phase, with a small proportion of γ′-Fe4(N,C) phase. The thickness of the compound layer and the diffusion layer are about 10 μm and about 200 μm, respectively. Plasma post oxidation was performed on the nitrocarburized samples with various oxygen/hydrogen ratio at constant temperature of 500℃ for 1 h. The very thin magnetite (Fe3O4) layer of 1–2 μm in thickness on top of the compound layer was obtained. Anodic polarization test revealed that plasma nitrocarburizing process contributed a significant improvement of corrosion resistance of SKD 61 steel. However, the corrosion characteristics of the nitrocarburized compound layer was deteriorated by oxidation treatment.
关键词:
Plasma nitrocarburizing
,
null
,
null
,
null
,
null
,
null
,
null
Lixing HUO
,
Furong CHEN
,
Yufeng ZHANG
,
Li ZHANG
,
Fangjun LIU
,
Gang CHEN
材料科学技术（英文）
The electron beam local post-weld heat treatment (EBLPWHT) is a rather new method that provides the advantages of high precision, flexibility and efficiency, energy saving and higher productivity. This paper studies the effect of two post-weld heat treatment processes on the microstructure, mechanical properties and fracture toughness of an electron beam welded joints in 30CrMnSiNi2A steel. EBLPWHT, in a vacuum chamber, immediately after welding and a traditional furnace whole post-weld heat treatment (FWPWHT) were compared. The experimental results show that, after EBLPWHT treatment, the main microstructure of weld was changed from coarse acicular martensite into lath martensite, HAZ was changed from lath martensite, bainite into lower bainite, and base metal was changed from ferrite and pearlite into upper bainite and residual austenite. The microstructures of different zones of joints in FWPWHT condition were tempered sorbite. The properties of welded joints can be improved by the EBLPWHT in some extent, and especially largely for the fracture toughness of welded joints. However the value of fracture toughness of base metal is comparatively low, so appropriate heat treatment parameters should be explored in the future.
关键词:
Post-weld heat treatment
,
null
,
null
,
null
Carbon
A combined in situ and post-synthesis gas phase oxidation approach for selective removal of metallic single-walled carbon nanotubes (m-SWCNTs) is reported. The in situ oxidation is performed by introducing a small amount of oxygen during the synthesis of SWCNTs by floating catalyst chemical vapor deposition, and the post-synthesis oxidation is conducted by heat-treating the synthesized SWCNTs in air at 400 C. A combination of characterization techniques shows that m-SWCNTs were selectively removed as a result of their higher reactive activity to oxygen compared to semiconducting SWCNTs, and the diameter distribution of the SWCNTs is narrowed to a range of 1.5-2.0 nm. The mechanism of the combined in situ and post-synthesis oxidation approach is discussed. (C) 2010 Elsevier Ltd. All rights reserved.
关键词:
field-effect transistors;preferential destruction;absorption-spectroscopy;fluorescence;irradiation;separation
Physica B-Condensed Matter
We have studied the effects of Si ion implantation and post-annealing on yellow luminescence (YL) from GaN. Two types of GaN samples grown by the metal-organic chemical vapor deposition method and labeled as GaN1 and GaN2 were studied. The PL spectrum of the as-grown GaN1 sample was dominated by a strong YL and that of the as-grown GaN2 sample was almost free from YL. After Si ion implantation with doses of both 1.3 x 10(13) and 1.0 x 10(16)cm(-2), the intensity ratios of YL to near band edge (NBE) emission (I-Y/I-NBE) for the GaN1 samples decreased markedly compared with those of the corresponding unimplanted ones both before and after post-annealing at temperatures up to 950degreesC. However, for the Si-ion-implanted GaN2 sample with a dose of 1.3 x 10(13)cm(-2), I-Y/I-NBE increased compared with that of the as-grown one both before and after post-annealing. Besides, the I-Y/I-NBE for Si-ion-implanted GaN1 with a dose of 1.3 x 10(13) cm(-2) increased monotonically with annealing temperature. Our results show that only the Si ion implantation being accompanied with high-temperature post-annealing could produce YL. The possible reasons for the marked reduction in I-Y/I-NBE for the GaN1 sample after Si-ion-implantation have been discussed. (C) 2002 Elsevier Science B.V. All rights reserved.
关键词:
photoluminescence;yellow luminescence;ion implantation;GaN;detected magnetic-resonance;vapor-phase epitaxy;laser-diodes;undoped;gan;photoluminescence;vacancies;layers;origin
