基于第一性原理的WC-Co(0001)/cBN(111)界面结合性能研究

基于第一性原理方法,建立WC-Co/cBN4B、WC-Co/cBN4N、WC-Co/cBN1B-near OA、WC-Co/cBN1N-near OA、WC-Co/cBN1N-near OB和WC-Co/cBN1B-near OB六种界面模型,计算其界面粘附功、断裂韧性.结果 表明:WC-Co/cBN4B界面具有最大粘附功值9.705 J·m-2,界面最稳定,粘附功大于WC(0001)w界面的断裂韧性7.824 J·m-2,裂纹倾向于出现在基体中;WC-Co/cBN4N界面有最小粘附功4.470 J·m-2,界面最不稳定,粘附功小于WC(000l)w界面的断裂韧性,裂纹倾向于出现在界面处.在此基础上,为从电荷转移、成键方式和价电子分布的深层次角度解释界面稳定性,进行了差分电荷密度、态密度和Mulliken布居分析,结果表明:WC-Co/cBN4B模型中,界面处Co、B原子之间存在电荷转移,由Co-d、B-p轨道杂化成强Co-B共价键;WC-Co/cBN4N模型中,界面处Co、N原子之间亦存在电荷转移,由Co-d、N-p轨道杂化成弱Co-N共价键.两种模型的界面处,Co-B共价键的布居数更大且键长更小、键能更大,Co-B共价键的作用强于Co-N共价键作用,因此,WC-Co/cBN4B界面结合性能更好,界面更稳定.     

硅晶体生长固液界面形貌研究

结合杰克逊界面理论、分子动力学模拟(MD)和密度泛函理论(DFT),对硅晶体(100)和(111)面生长过程中固液界面形貌进行研究,包括界面自由能变化、结构变化和生长位置吸附能等.通过杰克逊界面理论计算,发现(100)界面晶相原子和流体相原子在表面各占约50;时吉布斯自由能达到极小值,而(111)界面在表面占比约0;或100;时达到极小值,说明当热力学平衡时,(100)面趋向于粗糙面,(111)面趋向于光滑面;分子动力学模拟显示,随着生长的进行,初始光滑的固液界面在(100)面上会逐渐转变为粗糙界面,而(111)面则始终保持光滑界面生长;且在生长过程中,(100)面的生长速率明显高于(111)面,因为(100)面始终为粗糙面生长;DFT计算发现,(100)面上的所有生长位置吸附能接近,可以实现连续生长,(111)面吸附能则存在明显的差值,生长原子需要吸附在台阶处才能进行层状生长.     

拓扑半金属α2-Ti3Al(0001)表面的电子结构理论研究

采用基于密度泛函理论的第一性原理方法对α2-Ti3Al(0001)表面的电子结构进行计算.结果 表明:(1)α2-Ti3Al(0001)表面的表面能为2.03 J/m2,表面功函数为4.265 eV;(2)表面的总态密度在费米能级处达到极大值,系统呈现金属性,与块体的半金属差异明显,Ti-s、Ti-p和Al-s轨道受层数的影响较小,而Ti-d和Al-p轨道受层数的影响较大,均在费米能级处出现极大值;(3)能带结构未呈现块体的节线环,而是在费米能级附近以下的Γ点,出现一个类电子型的三带交叉点,在费米能级以上的Γ点,出现一个类空穴型的两带交叉点.     

铜锡钛合金钎焊金刚石及立方氮化硼磨粒界面特征分析

采用一种铜基合金(Cu-Sn-Ti)作为活性钎料,在高真空炉中钎焊连接金刚石、立方氮化硼与45#钢基体,将其牢固钎焊在基体表面.通过扫描电镜(SEM)、能谱仪(EDS)和X射线衍射仪进一步研究活性元素Ti在Cu基合金与金刚石及立方氮化硼结合界面的扩散现象.结果表明:活性元素Ti向金刚石、立方氮化硼表面发生偏聚,生成TiC、TiN、TiB和TiB2;活性元素Ti在向金刚石和立方氮化硼磨粒的扩散存在一定的差异性;铜基合金和钢基体的结合界面发生元素扩散生成铁钛金属间化合物.     

温度对陶瓷/铁基金属结合剂性能与结构的影响

采用粉末冶金法制备低温陶瓷/铁基金属结合剂.结合材料电子万能试验机、SEM、XRD等检测手段,研究了烧结温度对低温陶瓷/铁基金属结合剂性能与结构的影响.结果表明:当热压烧结温度为740 ℃时,低温陶瓷/铁基金属结合剂具有最佳的力学性能(抗折强度206 MPa,冲击强度6.4 kJ/m2);温度升高促进了低温陶瓷与铁基结合剂界面之间元素的相互渗透,铁基金属结合剂与低温陶瓷达到最佳的机械嵌合,提高结合剂强度.     

Cu/Hg3In2Te6欧姆接触形成机制的研究

采用电流-电压特性测试和X射线光电子能谱测试对Cu/Hg3In2Te6接触特性及其形成机制进行了研究.研究发现,当所加电压不超过10 V时,Cu/Hg3In2Te6接触的电流-电压特性曲线均呈现出良好的线性关系,表现为欧姆接触特性.经拟合,在1V、3V、5V和10 V电压下的Cu/Hg3In2Te6接触的欧姆特性系数分别为0.99995、0.99981、0.99968和0.99950.当电压增加至12 V及以上时,由于Cu/Hg3In2Te6接触势垒被击穿,导致Cu/Hg3In2Te6欧姆接触被破坏.通过X射线光电子能谱深度剖析,发现界面处的元素存在显著的扩散现象,因而导致界面元素的化学环境发生改变,引起了界面上各元素的结合能发生偏移,其中Cu2p结合能向高能方向偏移0.15 eV,而Te3d结合能向低能方向偏移0.15 eV.研究表明界面元素互扩散是促进Cu/Hg3In2Te6欧姆接触形成的主要原因.     

c-BN含量对(Ti,W)C/WC/Co金属陶瓷刀具材料力学性能的影响

采用真空热压烧结工艺制备了(Ti,W)C/WC/c-BN/Co金属陶瓷刀具材料,分析了(Ti,W)C/WC/c-BN/Co金属陶瓷刀具材料的微观结构、元素成分和物相组成,研究了不同含量c-BN对(Ti,W)C/WC/c-BN/Co金属陶瓷刀具材料微观结构和力学性能的影响.研究结果表明:适量添加c-BN 能有效细化颗粒,减少气孔等缺陷,提高材料的相对密度,(Ti,W)C/WC/c-BN/Co金属陶瓷刀具材料的断裂模式为穿/沿晶混合断裂模式;当c-BN含量为1wt;时,(Ti,W)C/WC/c-BN/Co金属陶瓷刀具的综合力学性能最优,其抗弯强度、断裂韧性和维氏硬度分别为769.32±10.21 MPa、6.69±0.18 MPa·m1/2和22.83±0.46 GPa.     

低压Ar气氛下用PS/OCS/Si (111)叠层热解制备单晶4H-SiC薄膜及层错缺陷抑制机理

在一定压力的Ar气氛中对Si (111) 衬底上的PS/OCS(硅的有机化合物)凝胶叠层进行热处理,制备出单晶4H-SiC薄膜.用XPS、XRD、TEM、TED和SEM研究了热处理温度和压力对薄膜结晶质量和晶型的影响.XPS分析显示薄膜中C/Si比为1.09.SEM分析表明薄膜的表面平整,SiC/Si(111)界面清晰、无层错缺陷形成.进一步讨论了层错缺陷形成及抑制的机理.     

烧结温度对陶瓷/青铜结合剂性能与显微结构的影响

通过粉末冶金法制备出陶瓷/青铜结合剂,青铜结合剂(mCu∶mSn=85∶15)与陶瓷结合剂质量比3∶1.结合电子万能试验机、洛氏硬度仪、扫描电子显微镜(SEM)、X射线衍射仪等,研究了烧结温度对陶瓷/青铜结合剂性能及结构的影响.结果表明:随烧结温度的升高,陶瓷/青铜结合剂密度、抗折强度和抗冲击强度呈先上升后下降的趋势;且烧结温度为620 ℃时,陶瓷/青铜结合剂综合性能较优,其密度为5.43 g/cm3、抗折强度为170 MPa、抗冲击强度为9.76 kJ/m2、硬度(HRB)为126;温度升高促进铜锡元素合金化及陶瓷与青铜结合剂界面之间元素的相互渗透;且经620 ℃烧结后,铜锡之间全部以α+δ共析相存在,金属和陶瓷界面结合性好,提高了陶瓷/青铜结合剂的综合性能.     

InGaN/GaN微米阵列结构的生长及发光性能研究

采用金属有机化学气相外延技术,在图形化蓝宝石衬底上通过选区外延可控生长了三种不同形貌的InGaN/GaN微米阵列结构,阵列尺寸均为6μm.其中,六方片状阵列结构以(0001)c面为主,高度为0.6μm;六棱台状阵列结构包括一个(0001)c面和六个等效的(10-11)半极性面,高度为1.2μm;六棱锥状阵列结构以(10...     

Structure of (chloranilato)bis(tri-n-butylphosphine)palladium(II)

(Chloranilato)bis(tri-n-butylphosphine)palladium(II), [Pd(C₆Cl₂O₄){P(C₄H₉)₃}₂] (chloranilic acid=2,5-dichloro-3,6-dihydroxy-p-benzoquinone): FW=718.02,P2₁/c,a=21.729(6),b=17.293(5),c=21.010(9) Å,=112.62(3)°,V=7287.42 ų,Z=8,D _c=1.309mg m^–3, Mo, =0.710730 Å,=0.76 mm^–1,F(000)=3008, finalR=0.087, 2594 observed reflections. Palladium is ligated by a distorted square planar P₂O₂ coordination sphere in the title compound. The two molecules per asymmetric unit differ in the arrangement of phosphine n-butyl chains, yielding two unique metal centers.     

Structure of (N-(2-hydroxyphenyl)-salicylaldiminopiperidino) Ni(II) complex

The crystal and molecular structure of the title complex, C₁₈H₁₉N₂O₂Ni, has been determined by direct methods. The compound crystallizes in the monoclinic crystal system witha=22.973(1),b=5.212(1),c=27.076(1)Å, β=106.46(1)°, space groupC2/c,V=3109.1(6)ų, Z=8, andD _x=1.51g cm^?3. The nickel atom is in a slightly distorted square-planar environment of two oxygens [Ni(1)?O(1) 1.824(3) and Ni(1)?O(2) 1.856(3)Å] and two nitrogens [Ni(1)?N(1) 1.849(3) and Ni(1)?N(2) 1.932(3)Å] with O?Ni?N angles between 85.7(1) and 97.1(1)°. The nickel atom is 0.006 Å out of the plane of its ligands.     

Crystal structure of triphenylphosphine-(1-(di(trifluoromethyl)-hydroxymethyl)-cyclopentadienyl)-(1,2-di(carboxymethyl) ethylene-1-yl) ruthenium (0)

The structure of triphenylphosphine — (1 — (di(trifluoromethyl) — hydroxymethyl) — cyclopentadienyl) — (1,2 — di(carboxymethyl)ethylene — 1 — yl) — ruthenium (0) has been studied by single-crystal X-ray diffraction techniques. This compound, [C₅ H₄(CF₃)2 COH] Ru(PPh₃)C2(CO₂Me)₂H, crystallizes in the triclinic space groupP¯1 witha =10.131,b= 15.107,c= 10.798 Å, = 102.14, = 107.04, = 89.64° andZ = 2. The structure was refined by block-diagonal least-squares methods to a finalR value of 0.042, including hydrogen atoms. The compound contains a dicarboxymethylethylene ligand coordinated to ruthenium both through a ketonic oxygen and through a metal--carbon -bond. An intramolecular hydrogen bond is observed. Details of the structure are reported, and the structures of several Ru(0) complexes are compared.     

Molecular structure and spectral characteristics of bis(S-methyl-N-(2-pyridyl)methylendithiocarbazato)nickel(II), (Ni(NNS)2)

A nickel(II) complex of the pyridine-2-aldehyde Schiff base of S-methyldithiocarbazate (HNNS) has been synthesized and characterized by means of elemental analysis, IR and UV-vis spectra. The crystal structure of the complex has been determined by single-crystal X-ray diffraction. The complex crystallizes in the monoclinic, space P2₁/c, with a = 14.092(2), b = 16.886(2), c = 8.857(2)Å; = 105.78(3) °, V = 2028.2(6) ų, and Z = 4. The nickel atom is octahedrally coordinated by two uninegatively charged tridentate Schiff base in a mer-configuration via the pyridine nitrogen atom, azomethine nitrogen atom, and mecaptide sulfur atom.     

Structures of Azomethine Imines of the Pyrazolidone-(3)-type (I). The Structure of 1-(4-Nitrobenzylidene-pyrazolidone-(3)-betaine

1-(4-Nitrobenzylidene)-pyrazolidone-(3)-betaine crystallizes in the orthorhombic space group Pbca with eight molecules per unit cell. The lattice parameters are a = 11.025 Å; b = 22.995 Å; c = 7. 677 Å. With X-ray diffraction data, collected on a automatical four circle diffractometer, the crystal structure was solved by direct methods and refined to an R-value of 0.047 for 1516 symmetrically independent reflections. The structure determination has been performed to contribute to the explanation of the photochromic behaviour of this special class of azomethine imines.     

Synthesis, spectroscopy, and X-ray structures of fac-(CO)3(dppe)MnSC(S)H, fac-(CO)3(dppe)ReSC(S)H, fac-(CO)3(dppp)ReSC(S)H, and fac-(CO)3(dppb)ReSC(S)H

The monodentate dithioformato complexes, fac-(CO)₃(dppe)MnSC(S)H (1), fac- (CO)₃(dppe)ReSC(S)H (2), fac-(CO)₃(dppp)ReSC(S)H (3), and fac-(CO)₃ (dppb)ReSC(S)H (4), where dppe is 1,2-bis(diphenylphosphino)ethane, dppp is 1,3-bis(diphenylphosphino)propane, and dppb is 1,4-bis(diphenylphosphino)butane, were synthesized from the treatment of the corresponding hydrides, fac-(CO)₃ (P-P)MSC(S)H with CS₂. Compounds 1–4 crystallize in the monoclinic crystal system: for 1, space group = P2₁/c, a = 15.3139(3) Å, b = 9.7297(4) Å, c = 19.0991(6) Å, = 105.928(1), V = 2736.5 ų, Z = 4; for 2, space group = P2₁/c, a = 15.6395(8) Å, b = 9.8182(5) Å, c = 19.4153(11) Å, = 106.741(1), V = 2854.9(3) ų, Z = 4; for 3, space group = P2₁/n, a = 11.3570(10) Å, b = 19.465(2) Å, c = 15.5702(14) Å, = 104.776(2), V = 3328.3(5) ų, Z = 4; and for 4, space group = C2/c, a = 32.078(2) Å, b = 10.4741(6) Å, c = 19.0608(9) Å, = 94.315(2), V = 6386.1(6) ų, Z = 8.     

Crystal of catena-(μ2-terephthalato)-bis (N-methylimidazole)-copper(II)

A new one-dimensional chain complex [Cu(ta) (N-MeIm)₂]n (where ta = terephthalic acid dianion,N-MeIm =N-methylimidazole) has been synthesized and structurally characterized by single-crystal X-ray diffraction. The compound crystallizes in the Monoclinic space groupP2₁/c with the parameters:a = 5.2930(11)Å,b = 14.679(3)Å,c = 11.007(3)Å, β = 104.84(3)^°,V = 826.7(3)ų, withZ = 4 formula units. In the structure, each Cu atom is coordinated by a pair ofN-methylimidazole ligands and a pair of monodentate carboxylate groups, affording a square planar N₂O₂ geometry. Both carboxylate groups of the terephthalate dianion coordinate in a monodentate mode bridging two Cu(II) ions with formation of 1D zigzag chain along thec axis. This supramolecular compound exhibits a three-dimensional solid state structure constituted by hydrogen bonds and C–H–π stacking interactions.     

Structure of trans-aqua-bis(pyridine)dibenzoatocopper(II)

Crystals oftrans-aqua-bis(pyridine)dibenzoatocopper(II), Cu(NC₅H₅)₂(C₇H₅O₂)₂(H₂O), are monoclinic,P2₁/n, witha=5.9847(10),b=18.874(5),c=19.728(10)A,=92.97(4)°,Z=4, andV=2225.5(13)A³. The full-matrix least-squares refinement used 3030 reflections withI> 2.5(I) and converged toR=0.067. The benzoate ions bond as monodentate ligands in this five-coordinate complex. The copper ion is in a square pyrimidal environment with trans pyridine groups and benzoate ions in a slightly distorted square planar arrangement and a water ligand in the axial position. The Cu-O distance to the water molecule is significantly longer (2.273(4) Å) than the distances to the O atoms of the carboxyl groups (1.934(3) and 1.930(4)Å).     

X-ray crystal structure of trans-bis(monoethanolamine) bis(saccharinato)nickel(II)

The crystal structure of trans-bis(monoethanolamine)bis(saccharinato)nickel(II), [Ni(C₇H₄NO₃S)₂(C₂H₇NO)₂], has been determined from X-ray diffraction data. The metal complex is monoclinic, with a = 11.0555(5), b = 8.9103(4), c = 11.3890(5) Å, = 105.0230(10)°, Z = 2, and space group P2_1/c . The structure consists of individual molecules. Two monoethanolamine molecules and two saccharinate anions coordinate the nickel atom forming a distorted octahedron. The monoethanolamine molecules act as a bidentate ligand and form five-membered trans chelate rings, which constitute the plane of the coordination octahedron, while two saccharinate ions behave as a monodentate ligand occupying the axial positions. Intermolecular hydrogen bonds link the molecules to form a three-dimensional infinite structure.     

X-ray structures of tris(0-cyclohexyl-dithiocarbonato)bismuth(III) and tris(0-benzyl-dithiocarbonato)bismuth(III)

The crystal structures of two Bi tris xanthates are reported, namely [Bi(S₂CO-c-C₆H₁₁)₃ J and [Bi(S₂COCH₂C₆H₅)₃]. They exist as centrosymmetric dimers, owing to the presence of bridging xanthate ligands, with seven-coordinate Bi atoms. The presence of a stereochemically active lonepair of electrons in each structure distorts the coordination geometry defined by seven S atoms and causes the elongation of some of the Bi-S bond distances. Crystals of both compounds are triclinic, space groupP¯1 with unit cell dimensions for [Bi(S₂CO-c-C₆H₁₁)₃]:a=12.417(3),b=13.571(3),c=9.681(4) Å;=102.30(2),=109.21(2), =66.23(2)° andZ=2; and for [Bi(S₂COCH₂C₆H₅)₃]:a=14.747(2),b=15.966(2),c=5.991(1) Å;=95.08(1),=98.51(1), =104.92(1)° andZ=2. The structures were refined by a full-matrix least-squares procedure to finalR=0.045 using 4274 reflections for [Bi(S₂CO-c-C₆H₁₁)₃] and toR=0.027 using 3993 reflections for [Bi(S₂COCH₂C₆H₅)₃].