影响金刚石合成的粉末触媒形态因素

采用相同成分体系的片状、球状Ni-Mn-Cu粉末触媒体为原料,在六面顶压机上进行人造金刚石高温、超高压合成的对比实验.结果表明:具有片状等不规则形状的NiMnCu粉末触媒合成工艺较球状同类粉末触媒合成工艺更稳定、易于掌握.针对上述结果,结合金刚石成核、生长过程中合成腔体内温度变化对上述实验结果进行了讨论.     

粉末法合成人造金刚石技术的研究与应用

目前,工业人造金刚石的合成是在高温高压条件下通过触媒作用将碳元素的排序由石墨结构转变成金刚石结构.传统的片状合成技术成本高,转化率低,已逐步被先进的粉末合成技术取代.粉末合成技术解决了原材料的研制、粉末柱的制备、合成结构及合成工艺的确定等关键技术问题.随着粉末合成技术的推广应用,我国人造金刚石得到快速发展,生产成本大幅降低,金刚石产量及质量大幅提高.     

金刚石合成用触媒的应用及展望

金刚石是集多种极限性能于一身并可在各种严苛环境下工作的理想材料.触媒材料能降低金刚石高温高压合成条件并使金刚石合成得以工业化.触媒对金刚石的科学研究和工业技术的提高是十分重要的.本文介绍了触媒材料的发现历程及触媒在金刚石合成中的作用机理;从触媒所包含的金属触媒和非金属触媒两大类分别综述了各种触媒的研究现状.在研究上述各触媒在金刚石合成中的合成条件及合成效果的基础上对这两类触媒的使用特点进行了总结.由此指出金属触媒中的合金触媒最适合应用在工业生产上,非金属触媒有利于模拟天然金刚石的成因,具有潜在的研究价值.最后本文对今后触媒的发展方向进行了展望.     

金刚石单晶合成效果与合成后铁基触媒组织的相关性研究

采用粉末冶金法制备铁基触媒片,在六面顶压机上高温高压合成金刚石单晶.利用扫描电子显微镜(SEM)、光学显微镜(OM)等表征了不同成分的触媒以及同一触媒在不同合成时间条件下金刚石单晶的合成质量和合成后的铁基触媒组织.结果表明:当金刚石单晶合成质量较好时,合成后铁基触媒组织特征表现为初生板条状渗碳体分布较均匀,呈平行生长的条束,渗碳体的板条两边缘较平直,而且数量较多.触媒成分和合成时间是影响铁基触媒组织中初生渗碳体的数量和形态的主要因素.     

NiMnCo粉末触媒合成金刚石特征的研究

本文采用扫描电子显微镜(SEM)、图象分析仪和金刚石性能测试仪分别对粉末状和片状NiMnCo触媒合成的金刚石形貌、(111)、(100)结晶面的微形貌、包裹体分布及其力学性能进行分析.研究结果表明:与片状触媒合成的金刚石相比,NiMnCo粉末触媒合成的金刚石呈典型的六-八面体,晶型完整率高;(111)、(100)结晶面完整无缺陷,透明度高、包裹体少且细小分散.因此,NiMnCo粉末触媒合成的金刚石具有较高的静压强度和热稳定性.     

FeMn粉末触媒制备及金刚石合成条件的研究

利用气雾化法制备了FeMnX1、FeMnX2NiY2、FeMnX2CoY2(X1=X2+Y2,X2＞Y2,0＜Y2≤10)粉末触媒.利用金相显微镜、扫描电镜和X射线衍射仪对粉末进行了表征.分析表明:制备的粉末大多为球形颗粒,D50约为23.6 μm,晶格常数约为0.36108 nm;按触媒与石墨粉的比例为4: 6制备合成柱并进行了合成实验,结果表明用FeMn基粉末触媒合成金刚石的温度、压力均要高于使用FeNi30触媒,在5.4～5.6 GPa压力、温度高于1450 ℃时才可以合成出金刚石,添加Y2;的Ni或Co元素后合成温度和压力稍微降低,且金刚石形核量有所增加.此外,利用晶体的价电子结构和界面电子密度连续理论分析了不同的M3C型碳化物对合成条件的影响,解释了FeMn基触媒合成金刚石条件高于FeNi触媒的原因.     

添加不同硼源时金刚石的高温高压合成

在压力6.5 GPa、温度1290～1350℃实验条件下,研究了合成体系中分别添加单质硼、六角氮化硼(h-BN)时金刚石的合成.由于合成体系中添加剂的存在,导致所合成的金刚石颜色发生了明显的改变.傅里叶显微红外光谱(FTIR)测试表明,当合成体系中h-BN添加量较少时,所合成金刚石中含有替代式的氮杂质,且金刚石中有sp2杂化的硼-氮、硼-氮-硼结构存在.当合成体系中h-BN添加量达到2 wt;时,金刚石中的氮仅以硼-氮-硼的结构存在.此外,霍尔效应测试结果表明,硼掺杂金刚石具有p型半导体特性,而合成体系中添加h-BN所制备的金刚石表现为绝缘体.     

NiFe合金粉末触媒合成金刚石研究

本文介绍了人工合成金刚石的一种新方法.研究中采用NiFe合金粉末作为原料,并对NiFe合金粉末坯块进行活化处理,在超高压、高温的条件下,做为触媒材料经一定的工艺流程合成了金刚石.结果表明,这种触媒材料采用这种新方法所合成的金刚石产品具有其明显的特征,可显著提高金刚石的粗粒度百分比且粒度集中,金刚石样品质量高,金刚石的颜色黄且单产高.     

金刚石单晶合成工艺与铁基触媒中初生Fe3C形貌的关系

利用光学显微镜和X射线衍射等手段,表征了高温高压下合成金刚石单晶时不同合成工艺的铁基触媒合金组织结构.结果发现:金刚石合成效果较好时的触媒组织中Fe3C呈规则的条状,而合成效果不好时的触媒组织中局部出现了不规则的团絮状Fe3C.分析认为,Fe3C在不同的结晶条件下表现出不同的生长行为,高温高压下金刚石单晶的生长与触媒中Fe3C的生长行为有密切关系.     

NiMnCo-C-S系中掺硫金刚石单晶的研究

本文在5.5～5.7 GPa,1450～1550℃的条件下由镍锰钴-石墨-硫体系中合成金刚石单晶.合成的金刚石晶体具有完整的{111}和{100}面,内部有少量包裹体.晶体表面有凹坑,凹坑内有许多细小的孔洞,且有连晶出现.X射线荧光光谱检测结果表明,随着反应体系中硫含量的增加,晶体中硫和锰的含量明显增加,而镍和钴的含量却降低.这由于硫与触媒中的锰发生了反应,改变了合成触媒的成分配比,进而改变了触媒的性质.     

CsI-LiCl共晶材料的坩埚下降法生长与闪烁性能研究

本文采用坩埚下降法,在真空密封的石英坩埚中成功生长出CsI-LiCl与CsI-LiCl:Na共晶闪烁体。通过扫描电子显微镜(SEM)观察晶体微结构表明该共晶中LiCl相与CsI相存在周期性的层状排列,CsI相的厚度在5 μm左右。共晶样品的X射线激发发射谱显示在CsI-LiCl和CsI-LiCl:Na共晶样品存在缺陷发光,在CsI-LiCl样品中还观察到了纯CsI的自陷激子(STE)发光。CsI-LiCl样品在α粒子激发下的多道能谱中观察到明显的全能峰,这一结果证明CsI-LiCl共晶可用于热中子探测的潜力。     

静电纺丝法制备CeO2微纳米纤维及其除氟性能

以聚丙烯腈(PAN)为载体,六水合硝酸铈[Ce(NO₃)₃·6H₂O]为原料,采用静电纺丝法制备了Ce(NO₃)₃/PAN纤维,在空气中热处理得到CeO₂微纳米纤维,通过XRD、BET和SEM对CeO₂微纳米纤维进行表征。采用静态吸附实验探讨了CeO₂微纳米纤维去除水溶液中氟离子的性能,考察了溶液pH值、初始氟离子浓度及共存阴离子等对吸附性能的影响。结果表明,pH=3时,CeO₂微纳米纤维对F^-的吸附性能最佳,CeO₂吸附量随着F^-浓度的增大呈上升趋势。CeO₂微纳米纤维对F^-的吸附等温线遵循Langmuir模型,二级动力学模型能很好地描述CeO₂微纳米纤维对F^-的吸附过程。CeO₂微纳米纤维的除氟性能优良,可为其实际应用提供理论参考。     

First-principles coexistence simulations of supercooled liquid silicon

We perform first-principles coexistence simulations of the low-density and the high-density phases of supercooled liquid silicon and find a negative slope for the coexisting line in the temperature-pressure plane. Electron density maps and electron-localization function plots of the two phases of silicon show marked differences. The calculated differences suggest more localized electrons in the low-density liquid compared to the high-density liquid, coming from an increased population of covalent bonds, which further explain the calculated negative slope in the two phase coexistence regime. This is consistent with the presence of a pseudo-gap in low-density liquid silicon, absent in the high-density liquid which shows a metallic behavior.     

Crystal structures of thecis andtrans isomers of dithiahexahydro[3.3]metacyclophane

Structures of both thecis andtrans isomers of dithiahexahydro[3.3]metacyclophane, ?C₆H₄?CH₂SCH₂?C₆H₁₀?CH₂SCH₂?, have been determined, wherecis andtrans refer to the attachments to the cyclohexane ring. Thecis form crystallizes in the monoclinic space groupP2₁/c witha=8.4299(11)Å,b=21.772(2)Å,c=8.9724(13)Å, β=116.574(11)^o, andZ=4. Thetrans isomer packs into the monoclinic space groupP2₁ witha=8.159(16)Å,b=10.185(5)Å,c=9.558(2)Å, β=112.435(18)^o, andZ=2. The cyclohexane ring of thecis isomer is in the chair conformation, while the cyclohexane of thetrans isomer is found in a twisted boat conformation.     

CTAB与SDBS对碳酸锶粒子生长形态调控及机理研究

以表面活性剂CTAB和SDBS为化学添加剂,采用化学共沉淀法对碳酸锶晶体的生长形态进行调控,成功地制备出了实心的树枝状和花瓣为空心的花状碳酸锶粉体,并用X射线衍射(XRD)、扫描电子显微镜(SEM)和傅里叶变换红外光谱(FT-IR)等分析手段对样品进行了表征;最后重点对化学添加剂可能产生的影响机理进行了初步的探讨.结果表明,CTAB和SDBS在晶体生长的过程中能起到显著的影响作用,两者对粒子分散性能的作用效果相反,而且后者对晶体(013)和(213)晶面表面能降低的贡献明显大于前者.     

Triethyl ammonium salt of O,O′-bis(p-tolyl)dithiophosphate, [Et3NH]+[(4-MeC6H4O)2PS2]−

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).     

Crystal structure of Zn4Na(OH)6SO4Cl·6H2O

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 R_w=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.     

Synthesis and Crystal Structure of 5-[2-(6-bromonaphthalenyloxymethyl)]-3-(4-morpholinomethyl)-1,3,4-oxadiazole-2(3<Emphasis Type="Italic">H</Emphasis>)-thione

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.     

Crystal structure of irisolidone from the flowers of Pueraia lobata

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.