天然与Fe-C(H)系高温高压合成金刚石多晶的光学属性对比研究及意义(下)

山东蒙阴天然金刚石多晶与Fe-C(H)系高温高压(HPHT)合成金刚石多晶的光学显微镜、拉曼光谱、光致发光谱及红外光谱等的对比研究表明,相似的金刚石晶粒形态、表面生长台阶、结构功能团及缺陷等决定着两者存在成因上的联系;而自金刚石多晶的深部至表面,缺陷的不同变化规律及金刚石晶粒间聚集方式的差异等暗示着两者的生长历史并不完全相同;天然金刚石多晶的形成可能经历早期快速成核一长大、中期长大及漫长的后期改造三个阶段;基于晶体成核、长大及后期改造的思想,从微结构、微成分的角度厘定金刚石多晶中的标型信息,有利于拓展金刚石找矿、地球深部重大科学问题探讨等的思路和方法,也有利于为高品级金刚石多晶的合成提供新的科学线索.     

Fe—C（H）系高温高压合成金刚石多晶的RAMAN与PL光谱研究

Fe-C(H)系高温高压合成金刚石多晶的FESEM,RAMAN和PL光谱研究表明:构成多晶的金刚石晶粒多为八面体形态,同时其形成环境比较稳定.在金刚石晶粒中存在与氮相关、与镍相关及塑性形变等缺陷,且不同金刚石晶粒中的缺陷不完全相同.基于镍易在金刚石中形成发光中心及氢可以加速金刚石多晶的形成,为了提高金刚石单晶的质量,应该尽量在压腔中使用纯铁作为触媒,且在引入氢的同时除氮.     

高温高压下Fe-Ni-C系合成金刚石单晶的机理研究(下)

2 金属包覆膜物相结构的系统表征[16]2．1 金属包覆膜的形成片状工艺中金刚石在触媒与碳片界面处形核,优先向碳源充足的碳片一侧生长,生长前端总是包覆着一层金属熔体。     

高温高压下Fe-Ni-C系合成金刚石单晶的机理研究(上)

从三个方面综合介绍了本课题组近几年来采用Fe-Ni-C系在高温高压下合成优质金刚石单晶的研究成果:1)采用单质金属铁、镍粉和石墨粉以及粉末冶金方法制备出新型铁基触媒,利用六面顶压机合成了高品位的金刚石单晶;2)采用现代分析测试方法对金刚石单晶外的金属包覆膜物相结构进行了系统表征和分析;3)基于固体与分子经验电子理论(EET理论)和托马斯-费米-狄拉克-程开甲理论(TFDC理论)对金刚石合成过程中相关物相(金刚石、石墨、Fe3C((Fe,Ni)3C)和γ-(Fe,Ni)等)的价电子结构进行了计算和论证。实验分析与理论研究结果表明,单质金属粉辅以粉末冶金方法同样可以实现高品位金刚石单晶的合成;金属包覆膜中存在大量的Fe3C、(Fe,Ni)3C类型的金属碳化物和γ-(Fe,Ni)型金属中间相,且γ-(Fe,Ni)与金属碳化物的对应晶面之间存在相互平行的位向关系;金刚石与石墨主要晶面间的平均共价电子密度在一级近似条件下均不连续,而Fe3C与金刚石或Fe3C与γ-(Fe,Ni)之间存在界面电子密度连续性,因此证明Fe3C/金刚石界面能够满足金刚石生长的边界条件。研究结果表明,金刚石单晶生长的碳源并非直接来源于石墨,而来源于在金属中间相的催化作用下,由金属碳化物过渡相中脱溶出的、具有类SP3杂化态的C-C原子团,因此从实验和理论上进一步支持了金刚石合成的"溶剂-催化"理论。     

4(3H)-喹唑啉酮类化合物的合成

综述了4(3H)-喹唑啉酮类化合物的几种主要合成方法,并进行简要的评述。     

2-取代喹唑啉-4(3H)-酮的合成研究进展

喹唑啉-4(3H)-酮类化合物具有良好的生物活性和药物作用,正因如此,喹唑啉-4(3H)-酮类化合物尤其是2-取代喹唑啉-4(3H)-酮的合成受到了有机合成化学家的关注.本文从不同的反应物出发,总结了近几十年里2-取代喹唑啉-4(3H)-酮的合成研究进展.     

2(5H)-呋喃酮的过氧化氢氧化法合成与表征

用过氧化氢氧化糠醛法合成2（5H）-呋喃酮,详细讨论了投料比例、反应温度、滴加方式、反应时间等对产率的影响,产物用FT-IR、UV、^1HNMR、MS等进行了表征.     

氢预处理与高压影响下石墨的Raman光谱研究及在金刚石高温高压合成中的意义

氢预处理及高压作用后石墨的Raman光谱的研究表明：酸浸泡及氢等离子体预处理均可以在石墨中造就有利于金刚石成核的-CH3：C—H类金刚石碳区，并使石墨的有序度显著降低；5．4GPa高压作用后，氢预处理石墨的有序度会有所提高．但不会超过常压下未经氢预处理石墨的有序度；高压下石墨向金刚石转变，石墨片层确实有褶曲，但在此之前可能存在一个石墨与氢等造就类金刚石碳区有关的必然环节。     

苯并呋喃-2(3H)-酮的合成

在乙醇钠催化下邻硝基甲苯与草酸二乙酯缩合后,经水解、双氧水氧化、盐酸酸化得到邻硝基苯乙酸,收率为62%。邻硝基苯乙酸再经硫化铵还原、重氮化反应、水解得到苯并呋喃-2(3H)-酮。考察了重氮化反应时间和水解温度对反应的影响,适宜的重氮化反应时间为30 m in,适宜的水解温度135℃,在此条件下苯并呋喃-2(3H)-酮的收率为51%。两步总收率为32%。     

1-(2-氯苯基)-5(4H)-四唑啉酮的合成研究

1 (2 氯苯基 ) 5 (4H) 四唑啉酮 (Ⅰ)可由 2 氯硝基苯经三步合成反应制得。首先 ,2 氯硝基苯经铁粉还原得 2 氯苯胺 (Ⅱ) ,Ⅱ与碳酸二 (三氯甲基 )酯反应得 2 氯苯基异氰酸酯 (Ⅲ ) ,Ⅲ在DMF溶剂中 ,无水三氯化铝催化下与叠氮钠缩合得Ⅰ。三步收率分别为 90 %、80 %、90 % ,总收率为 6 5 %(以邻氯硝基苯计 ) ,产品质量分数达 95 %。     

A study of radiation dosimeters based on synthetic HPHT diamond

We investigated the applicability of synthetic diamond crystals routinely produced by the HPHT (High Pressure High Temperature) technique for the detection of ionising radiation. Split-sphere-type multi-anvil equipment was used to produce these HPHT diamonds. Both as-grown type Ib and HPHT treated type IaA diamonds were examined at the Centre of Oncology in Kraków using a therapeutic Co-60 γ-ray beam. Detectors fabricated from type IaA diamonds showed, on average, better performance than those based on type Ib diamonds. IaA- type synthetic diamonds containing up to 150-200 ppm nitrogen showed sensitivity up to 160 nC/(Gy mm³), charge collection distance up to 180 μm and close to linear dose-rate response. Considerable variations in the detecting characteristics were observed for the devices containing similar concentrations of nitrogen. From our preliminary qualitative analysis we conclude that the observed response variations may be associated with varying concentration of the nickel impurity present in these diamond crystals.     

Effects of zinc additive on the HPHT synthesis of diamond in Fe-Ni-C and Fe-C systems

In the series of experiments at 5.0-7.0 GPa and 1300-1800 °C with the duration from 15 min to 2 h, the diamond crystals were synthesized in the Fe-Ni-C and Fe-C systems with zinc additive and the capability of zinc for converting graphite to diamond were also investigated in this work. Compared with the diamond synthesis using conventional catalysts, much higher temperatures are required for the nucleation and growth of diamond in Fe-Ni-Zn-C and Fe-Zn-C systems. The morphology of synthesized diamond crystals changes regularly from cub-octahedron to octahedron in the Fe-Ni-C system with increasing zinc additive, while only octahedral diamonds form in the Fe-Zn-C system. The diamond growth is accelerated by appropriate addition of zinc in conventional catalysts while the excessive zinc additive may have a suppressive effect on the diamond nucleation. We also estabish the essential dependence of diamond nucleation and morphology on the composition of crystallization medium in the Fe-Ni-Zn-C and Fe-Zn-C systems. Based on our analysis of the diamond surface configuration, we suggest that the formation of the different defects on the {100} and {111} faces is most likely due to the two simultaneous growth process on the {111} faces.     

Effect of controllable decomposition of MAX phase (Ti3SiC2) on mechanical properties of rapidly sintered polycrystalline diamond by HPHT

Sintered polycrystalline diamond (PCD) was prepared via high temperature and high pressure (HTHP) process using Ti₃SiC₂ and Si as the binder. The effect of decomposition of Ti₃SiC₂ on comprehensive properties of PCD was investigated at different temperatures. Results show that Si formed liquid phase infiltrated diamond surface at high temperatures to inhibit diamond graphitization and to reduce defects significantly. In addition, strong covalent bond of Si-diamond was generated, which increased the strength of PCD. At suitable temperature, Ti₃SiC₂ would partially decompose to TiC and SiC with high activity. Strong covalent bond of TiC and SiC also increased relative density and hardness of PCD, and residual Ti₃SiC₂ enhanced the toughness of PCD. At 1500 °C, the hardness and toughness of PCD reached 54.35 GPa and 8.6 MPa m^1/2, respectively, which are 19% and 82%, respectively, higher than PCD sintered at 1350 °C.     

HPHT growth and characterization of diamond from a copper-carbon system

Diamond crystallization in the Cu-C system is studied at high pressure high temperature conditions of 7.0 GPa and 1500–1800 °C. The minimum temperature of diamond synthesis by spontaneous nucleation is found to be 1800 °C. Diamond layers of optical quality are grown on the seed crystals via the chemical-potential difference method. From the infrared absorption measurements it is found that the diamond layers grown on the (100) faces of the seed crystals contain nitrogen impurities in the form of A centers with concentration from 700 to 1100 ppm and show strong hydrogen-related absorption peak at 3107 cm^− 1. A number of specific optical centers are found in photoluminescence spectra recorded for diamond layers grown on both (100) and (111) faces of the seed crystals. The newly observed 1.748 eV center is tentatively assigned to defects involving Cu impurities. The 1.787 eV center is suggested to appear preferentially in diamonds with high contents of nitrogen and hydrogen impurities.     

(FeMn)xAl(1-x)-C体系金刚石的高温高压合成

利用FeMn-C体系以及添加剂Al,在国产六面顶压机上分别进行了合成金刚石单晶的实验,研究了在高温高压条件下(5.6～5.8 GPa ,1400℃～1600℃)(FeMn)xAl(1-x) - C (0≤x≤1)体系金刚石生长特性.通过光学成像显微镜、扫描电镜(SEM)和显微红外光谱、穆斯堡尔谱等分别对合成后的金刚石晶体的颜色与形貌,含氮量以及内部杂质进行了测试分析.研究结果表明,(FeMn)xAl(1-x)-C体系可合成晶面完整的八面体金刚石晶体;无Al(x=1) 添加时,合成晶体的生长速度较快,添加Al(x≠1)后,晶体生长速度明显变慢;无Al添加时,体系合成晶体的含氮量较高,而添加Al后,含氮量明显降低;无Al添加时,合成晶体内部的包裹体主要成分是Fe3C和Fe,添加Al以后,合成晶体内包裹体主要成分是FeAl合金.     

About orientation dependence of physico-chemical properties of HPHT diamond surfaces thermally treated in H2 and D2 environments

Recently [1] we reported on some preliminary results on different physico-chemical properties of diamond (100), (110) and (111) surfaces hydrogenated by using molecular hydrogen only. The main conclusions were that thermal hydrogenation was as efficient as plasma one and that the creation of the conducting surface channel was activated by a larger energy on the (100) surface with respect to the other two. The reason, at least in the case of the comparison between (100) and (111) surfaces, could be either attributed to the presence of a carbon – oxygen double bond before hydrogenation in the former case [2] or to a better coverage by carbon – hydrogen bonds in the latter one. In the present work, further results on surface conductivity after hydrogenation steps carried out at different temperatures are described and discussed, in order to discriminate between purely thermal and kinetic effects. Moreover, other results are reported on diamond powders (0.25 micrometer mean size) in order to draw some qualitative and quantitative conclusions about hydrogen presence and behavior at the diamond surfaces. In order to better clarify the results, a large part of chemical measurements were performed after deuteration steps carried out using the same conditions as thermal hydrogenation.     

A study of the charge collection properties of polycrystalline CVD diamond with synchrotron radiation

Polycrystalline CVD diamond samples have been prepared with different electrode configurations, allowing to produce an electric field parallel and perpendicular to the direction of the grain boundaries. A photon beam with an energy of 15 keV was used to study the response with a spatial resolution of about 7 μm. Results on the influence of the field direction on the signal, the pumping effect, and the signal response as a function of the film thickness were obtained.