Papers by Keyword: High Purity

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Authors: Hui Li Shao, Xian Jue Zhou, Xue Chao Hu
Abstract: Synthesis of Poly(L-lactide) (PLLA) by the ring-opening polymerization (ROP) of L-lactides in supercritical carbon dioxide (SC-CO2) with co-solvent were studied. Effects of kinds of co-solvent on the molecular weight (MW) and the molecular weight distribution (MWD) of the resultant polymers were investigated by the gel permeation chromatography (GPC). The resultant polymers were also characterized with 1H NMR, 13C NMR and FT-IR. It was found that PLLA with high purity and almost without racemization could be obtained by this technology and the acetone is the best co-solvent for this kind of polymerization. By using stannous octoate as initiator and acetone as co-solvent, PLLA having a weight-average molecular weight (Mw) near to 9×104 and polydispersity index (PDI) of 1.7 was successfully synthesized.
1377
Authors: Kosei Sato, Toshinori Kokubu, Kensuke Nishioka
Abstract: High purity nanoporous silica was fabricated using Shirasu volcanic ash as a starting material. The starting materials were placed into a platinum crucible and were melted at 1400°C. A mother glass was formed by quenching the melt in pure water. Leaching was performed by immersing the mother glass into an HCl solution. Nonsilica phases formed by phase separation in the mother glass were leached out with acid solution. The obtained porous silica was more than 99% pure and had pore size smaller than 2 nm. In order to control the pore size, post heat treatment was performed. The pore size could be controlled from 3.1 to 21.7 nm by changing the post treatment temperature.
970
Authors: Sashiro Ezaki, M. Saito, K. Ishino
155
Authors: Jin Jiang He, Shu Qin Liu, Jun Feng Luo, Yue Wang, Yan Gao, Xiao Dong Xiong
Abstract: High-purity precious metal and its alloy targets make a very important role in semiconductor manufacturing. In this paper, the preparation methods of high performance sputtering targets (including silver, platinum and its alloy, ruthenium materials) for advanced semiconductor manufacturing were introduced. The relationships between deposited film behaviors and sputtering target properties in some applications were also discussed. In order to acquire high quality thin film, the properties of sputtering target such as density, alloy composition homogeneity, grain size and uniformity et al. have to be well controlled by proper fabrication techniques.
61
Authors: Kosei Sato, Toshinori Kokubu, Kensuke Nishioka
Abstract: High purity nanoporous silica was fabricated using Shirasu a volcanic ash as a starting material. The starting materials were melted at 1400°C. A mother glass was formed by quenching the melt in pure water. Leaching was performed by immersing the mother glass into an HCl solution. Nonsilica phases formed by phase separation in the mother glass were leached out with acid solution. The obtained porous silica was more than 99% pure and had pore size smaller than 2 nm. In order to control the pore size, post heat treatment was performed. The treatment temperature was varied from 540 to 600°C for 12 h. The treatment time was varied from 6 to 12 hours at 600°C. The pore size was controlled from 3.1 to 23.4 nm with changing temperature and time for the post heat treatment.
547
Authors: Sang Woo Kim, Shin Young Kim
Abstract: The effect of phase transformation and fine particle dispersion on densification behavior of high purity nanocrystalline alumina was investigated. The γ/α phase ratio of the mixture compacts were affected detrimentally by sinterability and phase transformation of α-phase alumina ceramics. The densification was significantly deteriorated with increasing γ-phase owing to faceted pores which are caused by the formation of a colony. The faceted pores were not existed in the α- Al2O3 ceramics with 10% γ-phase. Densification of the 10% γ-phase dispersed α-Al2O3 ceramics was significantly enhanced by rapid transformation of α-alumina. The grain growth was effectively inhibited by a small amount of nanoparticle dispersion for the alumina ceramics. As a result, dense nanostructured alumina can be achieved in the 10% γ-phase dispersed α-Al2O3 ceramics, even sintering at 1400oC for 3 hours.
831
Authors: Fu Jun Wang, Hui Rong Zhu, Qi Di Xiu, Jing Luo
Abstract: In this paper, the physical and chemical properties of LaB6 Ceramics are introduced, the influence of fabrication techniques on the microstructure and properties of LaB6 Ceramics are discussed. The combustion synthesis process was considered as the proper method for fabrication of LaB6 Ceramic powder with high purity. The results showed that the control additive has a great influence on the synthesis processand the nanoLaB6 Ceramic powder with high purity can be produced made when the content of the control additive is 30%.
135
Authors: Yang Song, Chang An Wang, Chun Qing Peng, Yong Huang
Abstract: High-pure bulk Ti3SiC2 samples were fabricated by directly hot-pressing (HP) high-pure Ti3SiC2 powder without any additives at 1200°C to 1500°C for 0.5–2 hours in flow argon atmosphere. X-ray diffraction (XRD) and scanning electron microscope (SEM) were used for phase identification and microstructure evaluation. The fabricated Ti3SiC2 materials have relative high density with high purity, flexural strength of 500-700MPa and fracture toughness of 9-12MPa·m1/2. The influence of sintering temperature and soaking time on the mechanical properties of Ti3SiC2 materials was discussed. The sintering mechanism for Ti3SiC2 powder without any additives was considered to be related with the fragile-ductile transformation of Ti3SiC2 at 1100°C.
958
Authors: Miao Qin Chen, Jin Jiang He, Zhao Chong Ding, Xin He
Abstract: MgO ceramics with the purity higher than 99.99% have been fabricated by a hot-isostatic press (HIP) technique of hot-pressed MgO compacts using nanometer MgO powder with an average particle size of 300 nm. The densification and grain growth behavior of MgO compacts during HIP process were investigated. The results indicate that the high-purity MgO ceramic with an average grain size of 9.76 μm and a density approximately to the theoretical density can be obtained by HIP method at 1350°C and 150 MPa for 60 min. HIP can significantly enhance the densification process of MgO compacts and cause a slightly change of grain size distribution.
1693
Authors: Chun Qing Peng, Chang An Wang, Liang Qi, Yong Huang
Abstract: In this work, a new method to fabricate high-purity Ti3AlC2 powder by pressureless sintering (PLS) was reported through adding a little amount of B2O3 as a low-temperature aid. The elemental Ti, Al, and active carbon powders were used as raw materials with the molar ratio of 3 : 1.2 : 2. The effect of sintering temperature on the purity of Ti3AlC2 was investigated at the range of 800°C to 1400°C. The results showed that high-purity Ti3AlC2 powders, in which almost no TiC phase could be found, were stably fabricated by pressureless synthesis at 1400°C for 5 mins in flow Ar atmosphere. The roles of B2O3 addition were discussed in the paper.
1247
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