检索结果-南通市图书馆

Rapid Dendrite growth in Solidification of Highly Undercooled Alloys

在线全文

学校读者我要写书评

暂无评论

Journal of Wuhan University of Technology(Materials Science) 2021年第2期36卷 259-261页

作者： AN Hong’en YANG Jine ZHANG Xiaobing YANG Shaopei College of Mechanical and Electronic Engineering Huanghe Jiaotong UniversityJiaozuo 454950China Jiangsu Yingchuang Power Technology Co. Ltd.Suzhou 215000China Henan Engineering Technology Research Center on Intelligent Manufacturing Technology and EquipmentJiaozuo 454950China

Nonequilibrium thermodynamics and transportation kinetics near the propagating solid-liquid interface dominates the rapid solidification process,which is far from a thermodynamically stable *** solidification process can be described more precisely using quantitative thermodynamic calculation of phase diagram with nonlinear liquidus and solidus and evaluating the nonequilibrium effect in diffusion *** on these basic principles,we used a current nonequilibrium dendrite growth model to describe rapid solidification process of deeply undercooled *** of the key fundamental solidification parameters was also evaluated.

关键词： solid solutions solidification growth from melt natural crystal growth

growth,Structure,and Spectroscopic Characteristics of the Nd^(3+):LiGd(WO_4)_2 Crystal

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Structural Chemistry 2011年第1期30卷 85-96页

作者：黄新阳王国富 Institute of Research on the Functional Matter Jiangxi University of Finance and Economy Institute of Research on the Structure of Matter Chinese Academy of Sciences

The Nd^3＋：LiGd（WO4） 2 crystal with dimensions of 25mm×28mm×16mm was grown by the top-seeded solution growth method from the 60 mol% Li2W2O7 flux. LiGd（WO4） 2 crystallizes in the tetragonal system with space group I41/a（C4h^6） and cell parameters： a = 5.1986 and c = 11.2652A. The hardness is about 5.0 Mohs＇ scale. The specific heat is 0.40 J·g^-1·K^-1 at 50 oC. The thermal expansion coefficients for a-and c-axes are 1.314×10^-5 and 2.052×10^-5 K^-1,respectively. The room-temperature polarized absorption and emission spectra and the fluorescence decay curve was measured. The parameters of oscillator strengths,the spontaneous transition probabilities,the fluorescence branching ratios,the radiative lifetimes,and the emission cross sections have been investigated based on Judd-Ofelt theory and Füchtbauer-Ladenburg method. The absorption cross-section is 5.19×10^-20 cm^2 at 805 nm for π-polarization and its line width is 15 nm; the emission cross section is 1.726×10^-19 cm^2 at 1060.5 nm for π-polarization. The fluorescence and radiative lifetimes are 86 and 158 μs,respectively. The fluorescence quantum efficiency is 54.43%.

关键词： optical microscopy growth from melt Nd^3+:LiGd(WO4)2 crystal solid state laser materials

Structural and photoluminescence studies on europium-doped lithium tetraborate(Eu:Li2B4O7)single crystal grown by microtube Czochralski(μT-Cz)technique

在线全文

学校读者我要写书评

暂无评论

Chinese Physics B 2016年第5期25卷 429-433页

作者： A Kumaresh R Arun Kumar N Ravikumar U Madhusoodanan B S Panigrahi K Marimuthu M Anuradha GRD Centre for Materials Research PSG College of TechnologyCoimbatoreIndia Department of Physics PSG College of TechnologyCoimbatoreIndia Radiation Safety Division Indira Gandhi Centre for Atomic ResearchKalpakkamIndia Department of Physics Gandhigram Rural UniversityDindigulIndia PSG Institute of Advanced Studies CoimbatoreIndia

Rare earth europium（Eu（3＋））-doped lithium tetraborate（Eu：Li_2B_4O_7） crystal is grown from its stoichiometric melt by microtube Czochralski pulling technique（μT-Cz） for the first time. The grown crystals are subjected to powder x-ray diffraction（PXRD） analysis which reveals the tetragonal crystal structure of the crystals. UV–vis–NIR spectral analysis is carried out to study the optical characteristics of the grown crystals. The crystal is transparent in the entire visible region, and the lower cutoff is observed to be at 304 nm. The existence of BO_3 and BO_4 bonding structure and the molecular associations are analyzed by Fourier transform infrared（FTIR） spectroscopy. The results of excitation and emission-photoluminescence spectra of europium ion incorporated in lithium tetraborate（LTB） single crystal reveal that the observations of peaks at 258,297, and 318 nm in the excitation spectra and peaks at 579, 591, 597, 613, and 651 nm are observed in the emission *** chromaticity coordinates are calculated from the emission spectra, and the emission intensity of the grown crystal is characterized through a CIE 1931（Commission International d＇Eclairage） color chromaticity diagram.

关键词： crystal growth optical material growth from melt photoluminescence study

Advances of the Vertical Directional Solidification Technique for the growth of High Quality GaSb Bulk Crystals

在线全文

学校读者我要写书评

暂无评论

Journal of Chemistry and Chemical Engineering 2012年第1期6卷 65-73页

作者： Dattatray Bhairu Gadkari Crystal growth Research Lab Department of Physics Mithibai College Mumbai 400056 lndia

Advantages of the detached phenomena have influenced researchers to modify the conventional methods to promote it on the earth. Since 1994, the vertical directional solidification （VDS） technique has been employed for the growth of bulk crystals, without the seed, without contact to the ampoule wall, without coating and without external pressure. An automated furnace was designed and fabricated for the controlled temperature gradients, growth conditions and parameters. The typical ingots growths of GaSb have shown the gap of 20 μm-145 μm and mobility μn = 1125 cm^2/*** at 300 K. Mobility is highest and five times larger than the attached growths. Dislocation density is the order of 104/cm2 in the conical region, decreases in the direction of growth, and in many crystals reached less than 103/cm2. The spontaneous gap formation due to the meniscus depends on the pressure differences and thermal state. GaSb grown ingots have shown progress in the properties of crystal grown ever, and attributed to reduce thermal stress without contact to the ampoule wall.

关键词： Solidification growth from melt antimonides semiconduction Ⅲ-Ⅴ crystal structure detached growth.

Analysis of Acoustic Emission Signals Accompanying growth of Single Aluminum Crystals： Experimental Results and Theoretical Model of the Cluster

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Chemistry and Chemical Engineering 2012年第4期6卷 358-362页

作者： Vorontsov Vadlm Bonsovlch Zhuravlev Danila Victorovich Physics and Chemistry Department Ural State University of Railway Transport （USURT） Yekaterinburg 620034 Russia

The purpose of the work is to identify the acoustic emission （AE） signal in the melt and from the interphase during the crystal growth and to establish the connection between issue parameters： the number of signal events of frequency and the signal power with the growth conditions of temperature gradient and crystallization rate. Experiments on single crystal growth were carried out using hardware and software system which allows to perform spectral Fourier analysis of AE signals and to simultaneously remove the cooling curve for the entire period of crystallization. On the basis of spectral analysis of AE signals, a theoretical model of clusters in the aluminum melt was designed. The experimental results indicate an uneven abrupt advancement of the interface according to the configuration of each individual cluster.

关键词： growth models interfaces surface growth from melt single crystal growth Bridgman growth acoustic emission method metals sound conductor.

Advances of the Vertical Directional Solidification Technique for the growth of High Quality InSb Bulk Crystals

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Chemistry and Chemical Engineering 2012年第3期6卷 250-258页

作者： Dattatray Bhairu Gadkari Department of Physics Mithibai College

Since 1994, the vertical directional solidification （VDS） technique is employed for the growths of bulk crystals-without the seed, without contact to the ampoule wall, without coating and without external pressure, which leads to the detached growth. growth velocities ranged from 3 mm/h to 10 mm/h, and rotation rates 10-20 rpm have been used. Ingots, 10-20 mm diameter and 60-65 mm length, have been grown with the conical ampoule geometry and these ingots have shown symmetric detachment. Crystals grown under such conditions showed the relatively low dislocation density and the highest carrier mobility,/tn = 5.9 x 104 cm2＂Vl-sl than the crystal grown ever. For the detached crystals, the dislocation density is 104 cm＂2 in conical region, and reached less than 103 cm-2 in the direction of the growth, when the ingots are not in contact with the ampoule wall. Experiments for indium-antimonide （InSb） growth have shown that the 80% growth environments have detachment, 15% entrapped in conical region and 5% attached.

关键词： Antimonides growth from melt solidification detachment crystal structure semiconductor indium compound.