Papers by Keyword: Size Control

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Authors: Chun Gu, Guo Qiang Luo, Rui Zhi Zhang, Jian Zhang, Yuan Li, Mei Juan Li, Qiang Shen, Lian Meng Zhang
Abstract: In this work, monodispersed silver nanoparticles with controllable size have been successfully in situ synthesized in PMMA matrix. NaHS, HCl and poly (vinyl pyrrolidone) (PVP) were used to optimize the nucleation and growth of silver nanocrystalline. UV–vis analysis and transmission electron microscopy (TEM) were used to characterize the size and dispersion of silver nanoparticles in the Ag/PMMA nanocomposites. The results show that silver nanoparticles homogeneously distribute in PMMA/DMF sol and the particle size of silver nanoparticles increase with the increasing of time. The nucleation of Ag atoms can be facilitated through the addition of a trace amount of NaHS to generate Ag2S clusters as heterogeneous nuclei. Introducing a trace amount of Cl- into the reaction system can effectively reduce the growth rate of the nanoparticles and thus generating more uniform silver nanoparticles in PMMA matrix.
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Authors: Hyung Mi Lim, Hong Chul Shin, Soo Hyun Huh, Seung Ho Lee
Abstract: Nano size silica particles were produced by direct oxidation of silicon powder in the water with the base catalysts. The average size of 10~100 nm was successfully prepared from the starting material of silicon powder with variable procession parameters such as silicon solid content, choice of catalyst and amount, the order of mixing, etc. The sodium hydroxide and ammonium hydroxide was chosen for the base catalysts and their amount and addition order were found to control the size of silica particles in the oxidation reaction. The limited amount of NH4OH as the first catalyst seemed to limit the number of nucleus particles, and the limited amount of NaOH further feeded only for particle growing rather than nucleus formation, thereby it was observed to be able to control the average size of particles to be as large as 100 nm. The possible mechanism of particle growth was suggested by solubility of silica and relative affinity of NH4 + and Na+ ions to the surface of SiO2.
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Authors: Yong Kap Park, In Churl Cho, Y. Choi
Abstract: X-ray irradiation was applied to control the size of metal colloids in a silicate glass to make a high precise photosensitive glass containing K2O, Na2O, ZnO BaO, 0.01-0.05wt.% Au metal as sensitizer, <1.2wt.% Sb2O3 and SnO2 as thermal reducer. Colorimetry showed that X-ray irradiation effectively works to make the color of red system. Transmission electron microscopy revealed that the metal colloids were oxided and had uniform and spherical shape of 10-20 nm. Au colloid made various colors like pink after heating at 400°C, red at 500°C and dark-red at 600°C. Ag colloid made them like yellow-green at 400°C, yellow at 500°C and dark-brown, respectively.
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Authors: Qi Zhong Li, Dong Ming Zhang, Lian Meng Zhang
Abstract: Porous Al with controlled pore size was prepared by the spacer method including spark plasma sintering and the dissolution of space-holding NaCl particles. The NaCl of the controlled pore size (particle diameter control range of 5˰ڌm~20˰ڌm) were prepared by precipitation method. The effects of sintering condition such as the sintering electric current intensity, voltage and the size, morphology and content of NaCl powder on the porosity and size of porous Al are investigated. The porous Al with higher porosity of 69.41% and smaller pore size of 5 ڌm was obtained.
199
Authors: Xiao Ming Sheng, Xue Wu Hu, Yun Qing Xu
Abstract: Gripper with two claws of automatic placing and removing manipulator is designed in this paper, and structure characteristics, working theory and positional error analysis are introduced. This gripper has the function of automatic center aligning and size control. The chucking size of gripper can be modified automatically in order to be adaptable when clamping different work pieces and this gripper, which could shorten the time and improve the efficiency, is designed to place and remove workpiece at one time beat. The gripper has a virtue of better ability to locate and move, improving the precision of automatic feeding manipulator and lathe cutting. The grippers have the advantages of simple structure, small volume and weight, which can solve the problems of complicated structure and massive volume for typical translational gripper. They also could simplify the control system of manipulator; meet the demand of placing and removing workpiece instead of complicated and heavy manual work.
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Authors: Hao Shen Zhou, Takeo Yamada, Keisuke Asai, Itaru Honma, H. Uchida, T. Katsube
1985
Authors: Zhen Guang Shen, Zhi Jian Peng, Jing Wen Qian, Xiu Li Fu
Abstract: WO3 particles with different grain sizes were prepared by a thermal evaporation method. The composition, morphology, and optical properties of the samples were analyzed by powder X-ray diffraction, scanning electron microscopy, and UV–vis absorption and photoluminescence spectroscopy. Their photocatalytic properties were evaluated by decomposing methylene blue in aqueous phase. It was found that the smaller the grain size of the prepared WO3 particles, the better the degradation effect on methylene blue.
284
Authors: Xiao Lan Sun, Yan Hua Dong, Chao Li, Xiao Hong Liu
Abstract: The size of quantum dots (QDs), their shape, and ordered arrays have significant impact on electrical and optical properties of the QDs. We synthesized near-infrared-emitting PbSe QDs via an oil phase method in a noncoordinating solvent. Transmission electron microscopy (TEM) and photoluminescence (PL) spectroscopy were used to characterize the samples. Sizes of the QDs were accurately controlled from 4.2 nm to 10.2 nm through control of the reaction time as well as the growth temperature. The PL spectra showed strong size dependence, which is large red shift with increasing size of the QDs.
405
Authors: Yi Min Zhu, Yue Xin Han, Xiao Yu Wang, Xu Wang
Abstract: A precipitation-pyrolysis process was developed for the synthesis of MgO nano-particles with diameter of 20~100 nm by using organic reagent, glycol, n-butanol and N,N-Dimethylacetamide, as shape and size controller. XRD and TEM were used to study on composition, morphology and size of the as prepared MgO nanoparticles. The results indicate that organic crystal controller is one of the key factors affecting the sizes and shapes of the nano MgO particles. When using glycol as a crystal controller, the dispersion of nano MgO particles is better and olive-shaped particles with sizes of 20~40 nm are prepared. When nano MgO particles are synthesized by MgCl2 and Mg(NO3)2, their particle sizes are smaller and their particles with olive shape. During chemical reaction process, Mg(OH)2 particles are already formed to be nano scale. Calcination process at the temperature of 650°C can change the crystal shape slightly. FTIR results show that nano MgO particles have abnormal infrared absorption behaviors compared with that of micron scale.
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