在美国Argonne国家实验室连接有IVEM-Tandem National Facility加速器的Hi-tatch3000电子显微镜上,通过400KeV Xe^+离子就位辐照研究了TiNiCu形状记忆合金的常温晶态-非晶态转变。入射的Xe离子通过级联碰撞,从0.05 dpa开始辐照诱发TiNiC...在美国Argonne国家实验室连接有IVEM-Tandem National Facility加速器的Hi-tatch3000电子显微镜上,通过400KeV Xe^+离子就位辐照研究了TiNiCu形状记忆合金的常温晶态-非晶态转变。入射的Xe离子通过级联碰撞,从0.05 dpa开始辐照诱发TiNiCu合金化学无序,非晶化过程和化学无序几乎同时进行;0.2dpa后,马氏体变体的衬度明显减小,变得非常模糊;在0.4dpa非晶化转变完成,马氏体变体的衬度完全消失。展开更多
Ge^＋ ions are implanted into fused silica glass at room temperature and a fluence of 1 × 10^17 cm^-2. The as-implanted samples are annealed in O2, N2 and Ar atmospheres separately. Ge^0, GeO and GeO2 coexist in ...Ge^＋ ions are implanted into fused silica glass at room temperature and a fluence of 1 × 10^17 cm^-2. The as-implanted samples are annealed in O2, N2 and Ar atmospheres separately. Ge^0, GeO and GeO2 coexist in the as-implanted and annealed samples. Annealing in different atmospheres at 600℃ leads each composite to change its content. After annealing at 1000℃, there remains some amount of Ge^0 in the substrates. However, the content of Ge decreases due to out-diffusion. After annealing in N2, Si N composite is formed. The absorption peak of GeO appears at 240 nm after annealing in O2 atmosphere, and a new absorption peak occurs at 418 nm after annealing in N2 atmosphere, which is attributed to the Si N composite. There is no absorption peak appearing after annealing in Ar atmosphere. Transmission electron microscopic images confirm the formation of Ge nanoparticles in the as-implanted sample and GeO2 nanoparticles in the annealed sample. In the present study, the GeO content and the GeO2 content depend on annealing temperature and atmosphere. Three photolumineseence emission band peaks at 290, 385 and 415 nm appear after ion implantation and they become strong with the increase of annealing temperature below 700℃ and their photoluminescences recover to the values of as-grown samples after annealing at 700℃. Optical absorption and photoluminescence depend on the annealing temperature and atmosphere.展开更多
The microstructural evolution of zircaloy-4 was studied, including the amorphization and recrystallization of Zr（Fe, Cr）2 precipitates, and the density of dislocations under in situ Ne ion irradiation and post annea...The microstructural evolution of zircaloy-4 was studied, including the amorphization and recrystallization of Zr（Fe, Cr）2 precipitates, and the density of dislocations under in situ Ne ion irradiation and post annealing. The results show that irradiation at a relatively high temperature and dose induces the formation of nanocrystals in pre-amorphized Zr（Fe, Cr）2 precipitates. The recrystallized nanocrystals also have the structure of hcp-Zr（Fe, Cr）2. The formation of the nanocrystals is thought to be the consequence of competition between atomistic disordering and the recrystallization of precipitates under ion irradiation. The free energy of the nanocrystal is lower than that of the amorphous state, which is another reason for the recrystallization of the precipitates. With increased annealing temperature, the density of the nanocrystals is increased. The dislocation density sharply decreases with the increase in the annealing temperature, and its size increases.展开更多
The soft deposition of Cu clusters on a Si （001） surface was studied by molecular dynamics simulations. The embedded atom method, the Stillinger-Weber and the Lennar-Jones potentials were used to describe the intera...The soft deposition of Cu clusters on a Si （001） surface was studied by molecular dynamics simulations. The embedded atom method, the Stillinger-Weber and the Lennar-Jones potentials were used to describe the interactions between the cluster atoms, between the substrate atoms, and between the cluster and the substrate atoms, respectively. The Cu13, Cu55, and Cu147 clusters were investigated at different substrate temperatures. We found that the substrate temperature had a significant effect on the Cn147 cluster. For smaller Cu13 and Cu55 clusters, the substrate temperature in the range of study appeared to have little effect on the mean center-of-mass height. The clusters showed better degrees of epitaxy at 800 K. With the same substrate temperature, the Cu55 cluster demonstrated the highest degree of epitaxy, followed by Cu147 and then Cu13 clusters. In addition, the Cu55 cluster showed the lowest mean center-of-mass height. These results suggested that the Cu55 cluster is a better choice for the thin-film formation among the clusters considered. Our studies may provide insight into the formation of desired Cu thin films on a Si substrate.展开更多
文摘在美国Argonne国家实验室连接有IVEM-Tandem National Facility加速器的Hi-tatch3000电子显微镜上,通过400KeV Xe^+离子就位辐照研究了TiNiCu形状记忆合金的常温晶态-非晶态转变。入射的Xe离子通过级联碰撞,从0.05 dpa开始辐照诱发TiNiCu合金化学无序,非晶化过程和化学无序几乎同时进行;0.2dpa后,马氏体变体的衬度明显减小,变得非常模糊;在0.4dpa非晶化转变完成,马氏体变体的衬度完全消失。
基金Project supported by the Foundation for Young Scholars of University of Electronic Science and Technology of China (Grant No.L08010401JX0806)
文摘Ge^＋ ions are implanted into fused silica glass at room temperature and a fluence of 1 × 10^17 cm^-2. The as-implanted samples are annealed in O2, N2 and Ar atmospheres separately. Ge^0, GeO and GeO2 coexist in the as-implanted and annealed samples. Annealing in different atmospheres at 600℃ leads each composite to change its content. After annealing at 1000℃, there remains some amount of Ge^0 in the substrates. However, the content of Ge decreases due to out-diffusion. After annealing in N2, Si N composite is formed. The absorption peak of GeO appears at 240 nm after annealing in O2 atmosphere, and a new absorption peak occurs at 418 nm after annealing in N2 atmosphere, which is attributed to the Si N composite. There is no absorption peak appearing after annealing in Ar atmosphere. Transmission electron microscopic images confirm the formation of Ge nanoparticles in the as-implanted sample and GeO2 nanoparticles in the annealed sample. In the present study, the GeO content and the GeO2 content depend on annealing temperature and atmosphere. Three photolumineseence emission band peaks at 290, 385 and 415 nm appear after ion implantation and they become strong with the increase of annealing temperature below 700℃ and their photoluminescences recover to the values of as-grown samples after annealing at 700℃. Optical absorption and photoluminescence depend on the annealing temperature and atmosphere.
基金Project supported by the Key Laboratory of Neutron Physics of China Academy of Engineering Physics(Grant No.2012AB02)the Fundamental Research Funds for the Central Universities of China(Grant No.ZYGX2012YB017)the Major Program of the National Natural Science Foundation of China(Grant No.91126001)
文摘The microstructural evolution of zircaloy-4 was studied, including the amorphization and recrystallization of Zr（Fe, Cr）2 precipitates, and the density of dislocations under in situ Ne ion irradiation and post annealing. The results show that irradiation at a relatively high temperature and dose induces the formation of nanocrystals in pre-amorphized Zr（Fe, Cr）2 precipitates. The recrystallized nanocrystals also have the structure of hcp-Zr（Fe, Cr）2. The formation of the nanocrystals is thought to be the consequence of competition between atomistic disordering and the recrystallization of precipitates under ion irradiation. The free energy of the nanocrystal is lower than that of the amorphous state, which is another reason for the recrystallization of the precipitates. With increased annealing temperature, the density of the nanocrystals is increased. The dislocation density sharply decreases with the increase in the annealing temperature, and its size increases.
基金Project supported by the National Natural Science Foundation of China (Grant No. 10375028)the US National Science Foundation Award (Grant No. CMMI-0700048)
文摘The soft deposition of Cu clusters on a Si （001） surface was studied by molecular dynamics simulations. The embedded atom method, the Stillinger-Weber and the Lennar-Jones potentials were used to describe the interactions between the cluster atoms, between the substrate atoms, and between the cluster and the substrate atoms, respectively. The Cu13, Cu55, and Cu147 clusters were investigated at different substrate temperatures. We found that the substrate temperature had a significant effect on the Cn147 cluster. For smaller Cu13 and Cu55 clusters, the substrate temperature in the range of study appeared to have little effect on the mean center-of-mass height. The clusters showed better degrees of epitaxy at 800 K. With the same substrate temperature, the Cu55 cluster demonstrated the highest degree of epitaxy, followed by Cu147 and then Cu13 clusters. In addition, the Cu55 cluster showed the lowest mean center-of-mass height. These results suggested that the Cu55 cluster is a better choice for the thin-film formation among the clusters considered. Our studies may provide insight into the formation of desired Cu thin films on a Si substrate.
