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Synthesis of metallic copper nanoparticles and metal-metal bonding process using them
Kobayashi, Yoshio,Nakazawa, Hiroaki,Maeda, Takafumi,Yasuda, Yusuke,Morita, Toshiaki Techno-Press 2017 Advances in nano research Vol.5 No.4
Metallic copper nanoparticles were synthesised by reduction of copper ions in aqueous solution, and metal-metal bonding by using the nanoparticles was studied. A colloid solution of metallic copper nanoparticles was prepared by mixing an aqueous solution of $CuCl_2$ (0.01 M) and an aqueous solution of hydrazine (reductant) (0.2-1.0 M) in the presence of 0.0005 M of citric acid and 0.005 M of n-hexadecyltrimethylammonium bromide (stabilizers) at reduction temperature of $30-80^{\circ}C$. Copper-particle size varied (in the range of ca. 80-165 nm) with varying hydrazine concentration and reduction temperature. These dependences of particle size are explained by changes in number of metallic-copper-particle nuclei (determined by reduction rate) and changes in collision frequency of particles (based on movement of particles in accordance with temperature). The main component in the nanoparticles is metallic copper, and the metallic-copper particles are polycrystalline. Metallic-copper discs were successfully bonded by annealing at $400^{\circ}C$ and pressure of 1.2 MPa for 5 min in hydrogen gas with the help of the metalli-ccopper particles. Shear strength of the bonded copper discs was then measured. Dependences of shear strength on hydrazine concentration and reduction temperature were explained in terms of progress state of reduction, amount of impurity and particle size. Highest shear strength of 40.0 MPa was recorded for a colloid solution prepared at hydrazine concentration of 0.8 M and reduction temperature of $50^{\circ}C$.
Tailored Materials for High‐Performance MgB<sub>2</sub> Wire
Kim, Jung Ho,Oh, Sangjun,Kumakura, Hiroaki,Matsumoto, Akiyoshi,Heo, Yoon‐,Uk,Song, Kyeong‐,Se,Kang, Yong‐,Mook,Maeda, Minoru,Rindfleisch, Matt,Tomsic, Mike,Choi, Seyong,Dou, Shi Xue WILEY‐VCH Verlag 2011 Advanced Materials Vol.23 No.42
<P><B>Carbon‐encapsulated crystalline boron nanopowder</B> and coarse magnesium powder are used as inexpensive tailored starting materials for the fabrication of high‐performance MgB<SUB>2</SUB> superconducting wire. A low sintering temperature leads to a high critical current density, as a result of nanometer‐sized boron powder, surface oxidation preclusion by carbon encapsulation, and grain alignment by elongated magnesium coarse powder.</P>
Tsuneaki Takao,Seiji Okada,Yuichiro Morishita,Takeshi Maeda,Kensuke Kubota,Ryosuke Ideta,Eiji Mori,Itaru Yugue,Osamu Kawano,Hiroaki Sakai,Takayoshi Ueta,Keiichiro Shiba 대한척추외과학회 2016 Asian Spine Journal Vol.10 No.3
Study Design: Retrospective case series. Purpose: To clarify the influence of cervical spinal canal stenosis (CSCS) on neurological functional recovery after traumatic cervical spinal cord injury (CSCI) without major fracture or dislocation Overview of Literature: The biomechanical etiology of traumatic CSCI remains under discussion and its relationship with CSCS is one of the most controversial issues in the clinical management of traumatic CSCI. Methods: To obtain a relatively uniform background, patients non-surgically treated for an acute C3–4 level CSCI without major fracture or dislocation were selected. We analyzed 58 subjects with traumatic CSCI using T2-weighted mid-sagittal magnetic resonance imaging. The sagittal diameter of the cerebrospinal fluid (CSF) column, degree of canal stenosis, and neurologic outcomes in motor function, including improvement rate, were assessed. Results: There were no significant relationships between sagittal diameter of the CSF column at the C3–4 segment and their American Spinal Injury Association motor scores at both admission and discharge. Moreover, no significant relationships were observed between the sagittal diameter of the CSF column at the C3-4 segment and their neurological recovery during the following period. Conclusions: No relationships between pre-existing CSCS and neurological outcomes were evident after traumatic CSCI. These results suggest that decompression surgery might not be recommended for traumatic CSCI without major fracture or dislocation despite pre-existing CSCS.
Microscopic role of carbon on MgB2 wire for critical current density comparable to NbTi
Kim, Jung Ho,Oh, Sangjun,Heo, Yoon-Uk,Hata, Satoshi,Kumakura, Hiroaki,Matsumoto, Akiyoshi,Mitsuhara, Masatoshi,Choi, Seyong,Shimada, Yusuke,Maeda, Minoru,MacManus-Driscoll, Judith L,Dou, Shi Xue Nature Publishing Group 2012 NPG Asia Materials Vol.4 No.-