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1.
为了取得贴近切削加工的临界切削厚度,本文提出了一种采用金刚石刀具对KDP晶体进行螺旋刻划、基于所得刻槽微观形貌特征参数计算临界切削厚度的新方法;分析了切削速度和材料各向异性对临界切削厚度的影响;通过切削实验验证所得临界切削厚度.结果表明,晶体材料的各向异性对临界切削厚度有显著影响;在低速切削范围内,切削速度对临界切削厚度影响不显著;基于所得临界切削厚度选择切削参数,实现了KDP晶体全晶向延性域切削,取得了表面粗糙度为2.57 nm(Ra)的超光滑表面. 相似文献
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以玻璃陶瓷为加工对象,通过单因素车削实验研究了硬脆性材料车削机理,分析了车削深度、车削速度和进给速度对表面粗糙度的影响规律.已加工表面质量观测结果表明,随着切削深度的增加,刀具与工件挤压作用增强,表面损伤加重;随着切削速度的增加,刀具与工件作用时间减小,裂纹扩展缩短,表面破坏减弱;将切削过程分为挤压与切削两个阶段,随着进给速度的增加,在挤压阶段刀尖和工件的接触区域产生更深层裂纹,切削阶段材料崩碎加剧.测量已加工表面粗糙度,结果表明:粗糙度随切削深度和进给速度增加而增加,随切削速度增加而减小. 相似文献
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为了研究各向同性热解石墨切削过程中单晶金刚石刀具磨损及其对加工质量的影响,对各向同性热解石墨材料进行了切削试验.观测了刀具磨损形貌的演变过程,分析了刀具磨损机理以及刀具磨损对加工表面质量的影响.研究结果表明,在切削距离逐渐增加的情况下,单晶金刚石刀具后刀面磨损区域逐渐增大,磨损形貌分为平行沟槽和微细网状两种.切削过程中产生的颗粒状切屑和交变应力分别是导致磨粒磨损和解理磨损的主要原因.切削距离300 m内,试件加工表面粗糙度值Ra在0.2~0.4 μm之间波动,切削距离达到l000 m以后,试件加工表面粗糙度值明显增大,但是保持了相对稳定,表面粗糙度值Ra约为0.8μm. 相似文献
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采用不同碳源浓度金刚石涂层刀具与未涂层刀具铣削石材,研究切削参数对切削力及加工表面质量的影响,分析刀具磨损机理,找到金刚石刀具最佳切削参数,进而实现切削优化.采用正交实验法,通过测力仪测量出不同刀具、不同切削参数下的切削力,测试已加工材料的表面粗糙度,观测刀具磨损情况.结果表明,对铣削分力Fx、Fz影响最大的是涂层碳源浓度;对铣削分力Fy影响最大的是切削深度;对表面粗糙度影响最大的是进给速度;当主轴转速达到n=3000 r/min、进给速度为vf=300 mm/min、切削深度d=1.0 mm、涂层碳源浓度为3;时,刀具切削性能最佳;3;涂层碳源浓度金刚石刀具较其他碳源浓度(含未涂层)刀具,加工后的石材表面粗糙度最低、切削力最小、耐磨性高,提高了加工精度,延长刀具的使用寿命. 相似文献
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为了探究硅片器件精密磨削加工的切削特征与机理,运用三棱锥形状的金刚石磨粒以不同加载压力划刻单晶硅材料表面模拟磨削加工过程,分析了划痕形貌特征、切削力与切削深度的演变规律,阐释了单晶硅的微米级切削加工机理。单晶硅微破碎去除发生的临界条件为法向切削力80 mN,临界切削深度2.03 μm;剥落去除发生的临界条件为法向切削力800 mN,切削深度5.65 μm。切削深度、切削力比在不同切削机理条件下具备可区分的差异化特征。平均切削深度随加载压力的变化规律呈现出鲜明的自相似性特征。此外,还分别构建了塑性去除、微破碎去除、剥落去除三个阶段的切削力方程,更准确地描述了切削力与切削深度的密切关系。 相似文献
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4H碳化硅(4H-SiC)单晶具有禁带宽度大、载流子迁移率高、热导率高和稳定性良好等优异特性,在高功率电力电子、射频/微波电子和量子信息等领域具有广阔的应用前景。经过多年的发展,6英寸(1英寸=2.54 cm)4H-SiC单晶衬底和同质外延薄膜已得到了产业化应用。然而,4H-SiC单晶中的总位错密度仍高达103~104 cm-2,阻碍了4H-SiC单晶潜力的充分发挥。本文介绍了4H-SiC单晶中位错的主要类型,重点讲述4H-SiC单晶生长、衬底晶圆加工以及同质外延过程中位错的产生、转变和湮灭机理,并概述4H-SiC单晶中位错的表征方法,最后讲述了位错对4H-SiC单晶衬底和外延薄膜的性质,以及4H-SiC基功率器件性质的影响。 相似文献
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采用数值模拟研究PVT法Φ150 mm 4H-SiC单晶生长的功率、频率选择、坩埚位置及保温厚度等关键生长参数.研究表明Φ150 mm 4H-SiC单晶生长功率是2inch 4H-SiC生长功率的2倍,优化的加热频率在5 kHz以下,系统分析不同生长参数下生长腔内径向及轴向温度梯度的变化规律.在此基础上初步的进行了Φ150 mm 4H-SiC单晶的生长工作,获得了无裂纹、直径完整的高质量SiC衬底材料.拉曼光谱Mapping测量显示Φ150 mm SiC衬底全片无多型,均为4H-SiC晶型.X光摇摆曲线显示半宽小于30 arcsec.采用掺杂过渡金属V杂质,获得了电阻率超过5×109 Ω·cm的150mmSiC衬底. 相似文献
11.
A. L. Bingham J. E. Drake C. Gurnani M. B. Hursthouse M. E. Light M. Nirwan R. Ratnani 《Journal of chemical crystallography》2006,36(10):627-630
Triethyl ammonium Salt of O,O′-bis(p-tolyl)dithiophosphate and O,O′-bis(m-tolyl)dithiophosphate have been obtained by reaction of p- and m-cresol, respectively with P2S5 in toluene and have been characterized by elemental analysis, IR, 1H and 31P NMR spectroscopy. The molecular structure of O,O′-bis(p-tolyl)dithiophosphate has been determined. Crystal data: [Et3NH]+[(4-MeC6H4O)2PS2]−: Monoclinic, P21/c, a=15.2441(9) ?, b=10.415(2) ?, c=3.9726(9) ?, β=91.709(7)°, V=2217.5(1) ?−3, Z=4.Supplementary materials Additional material available from the Cambridge Crystallographic Data Centre (CCDC no. 600927 for [Et3NH]+[(4-MeC6H4O)2PS2]− comprises the final atomic coordinates for all atoms, thermal parameters, and a complete listing of bond distances and angles. Copies of this information may be obtained free of charge on application to The Director, 12 Union Road, Cambridge CB2 2EZ, UK (fax: +44-1223-336033; email: deposit@ccdc.cam.ac.uk or www:http://www.ccdc.cam.ac.uk). 相似文献
12.
Lin Zhu Karl Seff Thomas Witzke Lutz Nasdala 《Journal of chemical crystallography》1997,27(5):325-329
The structure of Zn4Na(OH)6SO4Cl·6H2O, a secondary mineral from Hettstedt, Germany, was determined by single-crystal X-ray diffraction. The crystals are hexagonal,a=8.413(8),c=13.095(24) Å, space group $P\bar 3$ , Z=2. The structure was refined to R=0.0554 and Rw=0.0903 for 970 reflections with I≥3σ(I). The structure can be described as zinc hydroxide layers perpendicular toc, from which sulfates and chlorides extend. The layers are held together by a system of hydrogen bonds involving hexaaquo Na+ ions which occupy the interlayer space. 相似文献
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Jerry P. Jasinski Ray J. Butcher Anil N. Mayekar H. S. Yathirajan B. Narayana B. K. Sarojini 《Journal of chemical crystallography》2009,39(10):761-765
Abstract The title compound, C18H18BrN3O3S, a derivative of 1,3,4-oxadiazole, crystallizes in the triclinic space group P-1 with unit cell parameters a = 6.8731(3), b = 8.9994(4), c = 15.7099(6) ?, α = 92.779(3)°, β = 130.575(3)°, γ = 107.868(4)°, Z = 2. The dihedral angle between the mean planes of the planar naphthyl and morpholine (chair) rings with the planar oxadiazol
ring is 50.1(8) and 76.8(6)°, respectively. The planar naphthyl ring is twisted 52.2(5)° with the mean plane of the morpholine
ring. A group of four intermolecular close contacts are observed between a bromine atom and hydrogen atoms from the closely
packed naphthyl, morpholine and oxy–methyl groups in the unit cell. These molecular interactions in concert with an additional
series of π–π stacking interactions that occur between the center of gravity of the two 6-membered rings of the naphthalene
group influence the twist angles of each of these three groups. A MOPAC AM1 calculation of the conformation energy of the
crystal structure [226.0128(9) kcal] compared to that of the minimum energy structure after geometry optimization [29.9744(1) kcal]
reveals a significantly reduced value. The twist angles of the three groups above also change after the AM1 calculation giving
support to the influence of both intermolecular C–H···Br short-range interactions and Cg π–π stacking interactions on these
angles which therefore play a role in stabilizing crystal packing.
Graphical Abstract Crystal structure of 5-{[(6-bromonaphthalen-2-yl)oxy]methyl}-3-(morpholin-4-ylmethyl)-1,3,4-oxadiazole-2(3H)-thione, C18H18BrN3O3S, is reported and its geometric and packing parameters described and compared to a MOPAC computational calculation.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
14.
Zun-Ting Zhang Xue-Ling Zhang Bo-Lun Yang Yao-Dong Zhang 《Journal of chemical crystallography》2006,36(7):407-411
Irisolidone (5,7-dihydroxy-6,4′-dimethoxyisoflavone) was isolated from the flowers of Pueraia lobata and its crystal structure was examined by X-ray single crystal diffraction. The crystal structure of irisolidone is monoclinic, space group P21/c with a = 15.491(9) ?, b = 7.895(4) ?, c = 13.321(7) ?, β = 110.546(9)° and Z = 4. Hydrogen bonding and aromatic π–π stacking assemble the title compound into a three-dimensional networking structure. 相似文献
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Maurizio Remelli Fernando Pulidori Remo Guerrini Valerio Bertolasi 《Journal of chemical crystallography》1997,27(9):507-513
The natural amino acid L-Spinacine (4,5,6,7-tetrahydro-1H-imidazo[4,5-c]pyridine-6-carboxylic acid) has been synthesized following a new pathway which gives a chemically and optically pure product with an excellent yield. The crystal structures of a synthetic intermediate, Nπ-hydroxymethyl-spinacine, and a spinacine derivative, Nα-methyl-spinaceamine, have been investigated through X-ray diffraction: Spi(πMeOH)·H2O, monoclinicP2 i,a=8.571(1),b=6.682(1),c=8.588(1) Å, and β=94.67(1)o. Spm(αMe)·2HCl·H2O, triclinicP l,a=7.492(4),b=10.799(3),c=7.040(2) Å, α=91.88(2), β=98.36(3) and γ=73.34(3)o. Spi(πMeOH) crystallizes with a water molecule and displays a zwitterionic character. The carboxylate group is in equatorial position and forms a short electrostatic interaction of 2.618(2) Å between one of its oxygens and the protonated nitrogen of the tetrahydropyridine ring. The crystal packing is assured by strong O?H???O, O?H???N, N?H???N intermolecular hydrogen bonds and C?H???O close contacts. The biprotonated compounds Spm(αMe) crystallizes with two Cl? anions and a water molecule. The positive charge on the imidazole ring is delocalized on the conjugated moiety N=C?N. The crystal is built up by clusters formed by two biprotonated Spm(αMe) molecules, four Cl? anions and two water molecules linked together by hydrogen bonds. 相似文献
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Maurizio Remelli Fernando Pulidori Remo Guerrini Valerio Bertolasi 《Journal of chemical crystallography》1991,27(9):507-513
The natural amino acid L-Spinacine (4,5,6,7-tetrahydro-1H-imidazo[4,5-c]pyridine-6-carboxylic acid) has been synthesized following a new pathway which gives a chemically and optically pure product
with an excellent yield. The crystal structures of a synthetic intermediate, Nπ-hydroxymethyl-spinacine, and a spinacine derivative, Nα-methyl-spinaceamine, have been investigated through X-ray diffraction: Spi(πMeOH)·H2O, monoclinicP2
i,a=8.571(1),b=6.682(1),c=8.588(1) ?, and β=94.67(1)o. Spm(αMe)·2HCl·H2O, triclinicP
l,a=7.492(4),b=10.799(3),c=7.040(2) ?, α=91.88(2), β=98.36(3) and γ=73.34(3)o. Spi(πMeOH) crystallizes with a water molecule and displays a zwitterionic character. The carboxylate group is in equatorial
position and forms a short electrostatic interaction of 2.618(2) ? between one of its oxygens and the protonated nitrogen
of the tetrahydropyridine ring. The crystal packing is assured by strong O−H−−−O, O−H−−−N, N−H−−−N intermolecular hydrogen
bonds and C−H−−−O close contacts. The biprotonated compounds Spm(αMe) crystallizes with two Cl− anions and a water molecule. The positive charge on the imidazole ring is delocalized on the conjugated moiety N=C−N. The
crystal is built up by clusters formed by two biprotonated Spm(αMe) molecules, four Cl− anions and two water molecules linked together by hydrogen bonds. 相似文献
17.
Samuel B. Owens Jr. Abha A. Kaisare Gary M. Gray 《Journal of chemical crystallography》2007,37(10):655-661
Abstract X-ray crystal structures of [Et3NH][{(CO)5Mo(P(OCH2CMe2CH2O)O)}2H], 3, and (CO)5Mo{μ-Ph2POPPh2}Mo(CO)5, 2, are reported. Crystallization of 3 occurs in P-1 space group with a = 9.6944(19) ?, b = 10.814(2) ?, c = 19.730(4) ?, α = 94.24(3)°, β = 92.23(3)°, γ = 113.47(3)°,
Z = 4. Crystallization of 2 occurs in C2/c space group with a = 10.357(2) ?, b = 20.149(4) ?, c = 17.155(3) ?, α = 90°, β = 97.28(3)°, γ = 90°, Z = 8.
Compound 2 is a bimetallic complex with a P–O–P bridging group containing bond distances similar to that of other complexes in which
two metal centers are bridged by a single R2POPR2 ligand. Compound 3 contains intermolecular hydrogen bonded P–O–H–O–P linkages with bond distances comparable to those seen in similar structures
with intramolecular hydrogen bonding suggesting that the distance is a function of the nature of the bond and not affected
by the cis arrangement of the ligands about the metal center.
Graphical abstract
X-ray Crystal Structures of [Et
3
NH][{(CO)
5
Mo(P(OCH
2
CMe
2
CH
2
O)
O)}
2
H]
and (CO)
5
Mo{μ-Ph
2
POPPh
2
}Mo(CO)
5
, Two Complexes Derived from the Hydrolysis of Coordinated Chloro-Phosphorous-Donor Ligands
Samuel B. Owens Jr., Abha A. Kaisare and Gary M. Gray
X-ray crystal structures of [Et3NH][{(CO)5Mo(P(OCH2CMe2CH2O)O)}2H], 3, and
(CO)5Mo{μ-Ph2POPPh2}Mo(CO)5, 2, have been determined.
相似文献
18.
G. C. Das M. B. Hursthouse K. M. A. Malik M. M. Rahman M. T. Rahman T. Olsson 《Journal of chemical crystallography》1994,24(8):511-515
1,3,5-triphenyl-1,5-pentanedione, C23H20O2, has been prepared and characterized by spectroscopic methods and single crystal X-ray analysis. Crystals are monoclinic, space groupP21/n, a=28.124(4),b=5.997(1),c=10.434(1)Å, -98.42(1)Å,Z=4. The structure has been refined to a finalR-value of 0.040 for 1625 reflections withF
o>3(F
o). The compound contains the two carbonyl groups in a mutuallycis arrangement. 相似文献
19.
Andrzej Chmielewski W. Alexander Van Hook 《Molecular Crystals and Liquid Crystals》2013,570(1-2):27-36
The phase diagrams and heats of fusion and transition have been determined for the dodecyl amine (-NH2)/H2O and dodecyl amine (-ND2)/D2O systems using direct optical observation and differential scanning calorimetry. 相似文献
20.
P. M. Reshmi A. G. Kunjomana K. A. Chandrasekharan 《Crystal Research and Technology》2011,46(2):153-158
Different morphologies of indium telluride (In2Te3) including novel spherulites were crystallized using the physical vapour deposition (PVD) method, by varying the difference in the growth and source zone temperature (ΔT) of a dual zone horizontal furnace assembled indigenously. Whiskers and kinked needles of In2Te3were grown at ΔT = 250 K and 300 K respectively, maintaining the growth zone at 500 °C. At high supersaturation (Δ T = 400 K), spherulitic crystals were obtained. The stoichiometric composition of these crystals has been confirmed using energy dispersive analysis by x‐rays (EDAX). The structure of β‐In2Te3 spherulitic crystals is identified as zinc blende with lattice parameter a = 6.159 Å, from x‐ray diffraction (XRD) studies. The scanning electron microscope (SEM) images revealed the radial structure of the grown spherulites. The growth mechanism for the spherulitic crystallization of β‐In2Te3 crystals has been discussed based on the theoretical models. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献