用纳米石墨作碳源在Fe粉作用下合成金刚石的研究

在国产 6× 12 0 0吨铰链式六面顶压机上 ,以Fe粉为触媒 ,在 5 1GPa和 95 0K～ 14 2 0K的条件下 ,首次用纳米石墨进行了金刚石的合成实验。实验结果表明 :约在 12 5 0K～ 1330K的高温范围内 ,有金刚石生成 ,颗粒大小在 5～ 2 0 μm左右 ,呈球形和块状。初步探讨了用纳米石墨合成金刚石能降低合成温度的原因     

Fe+Ni+C体系合成粗颗粒金刚石单晶的生长特征

在配备有高精密化控制系统SPD6×1670T型国产六面顶压机上,采用Fe80Ni20粉末触媒和高纯石墨开展粗颗粒金刚石单晶的生长特征研究。在粉末触媒技术合成金刚石的基础上,引入旁热式组装,以及采用优选粒度的触媒,特别是通过优化合成工艺严格地控制了合成腔体内晶体的成核量及生长速度。最终,在高温高压条件下(约5.4GPa、1435℃)成功合成出尺寸达到0.95mm(18/20目)的优质的粗颗粒金刚石单晶,分析了粗颗粒金刚石的生长特征和晶体缺陷,期待研究的结果有助于我国高品级粗颗粒金刚石的发展。     

纳米金刚石颗粒的长大实验研究

本文研究了炸药爆轰合成的纳米金刚石粉的小颗粒在高温 (～ 10 0 0K)和高压(5 2GPa)条件下的长大行为。将纳米金刚石粉放入特制的模具中压制成小圆片 ,将纳米金刚石小园片相互叠加起来放入钼套中 ,压实。然后将钼套置于石墨套中再放到叶蜡石块中 ,于高温高压下进行长大实验。实验结果表明 :在此高温高压条件下 ,纳米金刚石粉没有石墨化 ;纳米金刚石粉的纳米颗粒长大 ,可长成 1微米尺寸的金刚石颗粒 (温度为 10 0 0K左右 )。这一现象表明 ,纳米金刚石颗粒表面的活性使得它可以在较低的温度长成较大的金刚石颗粒     

高温高压合成含硼金刚石单晶制备工艺初探

本文以掺入不同含量硼铁的铁基合金为触媒,以石墨为碳源,在高温高压条件下合成了含硼金刚石单晶体.利用扫描电镜(SEM)观察了金刚石及触媒的组织形貌;利用金相显微镜观察了金刚石颗粒的颜色和形态;利用拉曼光谱仪(RS)确认了人造金刚石单晶体中硼的存在;利用低温电阻测量仪验证了合成的含硼金刚石单晶颗粒具有半导体性能.实验结果表明,在金刚石的合成中,触媒中硼铁含量为2wt%的合成效果相对最好.     

纳米金刚石颗粒的长大实验研究

本文研究了炸药爆轰合成的纳米金刚石粉的小颗粒在高温（－1000K）和高压（5．2GPa)条件下的长大行为。将纳米金刚石粉放入特制的模具中压制成小圆片,将纳米金刚石小圆片相互叠加起来放相钼套中,压实,然后将钼套置于石墨套中再放到叶蜡石块中,于高温高压下进行长大实验。实验结果表明,在此高温高压条件下,纳米金刚石粉没有石墨化;纳米金刚石粉的纳米颗粒长大,可长成1微米尺寸的金刚石颗粒（温度为1000K左右）,这一现象表明,纳米金刚石颗粒表面的活性使得它可以在较低的温度长成较大的金刚石颗粒。     

一种制备金属钨纳米针的新方法

采用H2／N2／H2O混合气体在850℃下还原含有少量Ni／Fe／Co的氧化钨混合粉末的方法，制备出金属钨纳米针．用SEM、TEM和EDS分析等方法对金属钨纳米针进行了表征．结果表明：纳米针的顶部直径为30-70nm，根部直径为150-200nm，长度为2—10μm；纳米针具有完好的BCC单晶结构，沿（100）方向生长；在纳米针的生长过程中Ni／Fe／Co起到了顶端催化作用．     

微晶石墨对Ⅱa型宝石级金刚石单晶生长的影响

将除氮剂Ti(Cu)添加到FeNiCo合金触媒中在高温高压下合成出优质Ⅱa型宝石级金刚石单晶.在压力5.4GPa、温度1600K的条件下沿{111)面合成Ⅱa型宝石级金刚石过程中伴随有黑色粉末析出.采用X射线衍射(XRD)和扫描电子显微镜(SEM)对该黑色石墨粉末的测试表明其为微晶石墨.随着生长时间的延长,这种微晶石墨...     

纳米晶Fe5C2/α-Fe双相复合材料结构与磁性的研究

用机械合金化方法制备了具有单斜晶体结构的纳米晶、硬磁性、单相Fe5C2化合物粉末和软磁性好的纳米晶Fe55Ni45(f.c.c)过饱和固溶体粉末及纯α-Fe(b.c.c)超细粉末.并将上述硬磁和软磁粉末按一定的原子百分比混合后继续球磨10h,生成Fe5C2/α-Fe双相结构的复合材料.发现制备态复相材料的饱和磁化强度Ms高于制备态单相Fe5C2,而矫顽力Hc比制备态Fe5C2略低.当样品在相变温度以下进行低真空退火后其磁性得到更大提高.发现400C真空退火后,成分为(Fe5C2)94(Fe55Ni45)6的复相样品,其饱和磁化强度Ms和矫顽力Hc比制备态单相Fe5C2样品分别高出37%和48%,比退火态单相Fe5C2样品分别高出18%和12%.实验证实纳米晶Fe5C2/α-Fe双相复合材料具有较优的综合硬磁性,有望成为一种新的磁记录介质,并对这一实验结果进行了讨论.     

用激光法合成纳米金刚石

使脉冲激光与石墨粉在空气中相互作用，并对其氧化提纯．对产物进行的显微激光拉曼光谱（Raman）与高分辨电子显微镜（HRTEM）分析表明，产物中含大量纳米金刚石颗粒，其尺寸为5nm左右，且具有较多的晶体缺陷和残余内应力．提出了石墨转变为金刚石纳米晶的机理：在脉冲激光产生的高温高压的条件下，具有石墨结构的原子团发生快速滑移切变，形成立方金刚石晶核，碳等离子体中高化学活性的碳粒子集团使金刚石晶核迅速长大，形成金刚石微晶．     

新型三元锂离子正极材料Li_2Ru_(1/3)Co_(1/3)M_(1/3)O_3的合成及其电化学性能

利用高温固相反应法制备了新型三元锂离子电池正极材料Li2Ru1/3Co1/3M1/3O3(M=Mn、Ni、Fe)。通过X射线衍射技术和电化学性能测试对Li2Ru1/3Co1/3M1/3O3的微观结构及其电化学性能进行了表征。研究结果表明,Li2Ru1/3Co1/3Ni1/3O3和Li2Ru1/3Co1/3Fe1/3O3为六方层状结构,空间群为R-3M,而Li2Ru1/3Co1/3Mn1/3O3保持了单斜结构;电化学性能测试表明Li2Ru1/3Co1/3Mn1/3O3的电化学性能优于掺杂Fe和Ni的三元材料,该材料具有良好的循环性能,在电流密度为16 m A/g情况下,首次充电容量达到190 m Ah/g,首次放电容量为171 m Ah/g,50次循环后容量保持率为98%。     

Ni12P5微球的溶剂热合成与表征

以硫酸镍(NiSO4.7H2O)作为镍源,以乙二醇和水作为混合溶剂,利用溶剂热法成功地制备了磷化镍(Ni12P5)微球。X射线粉末衍射(XRD)、扫描电子显微镜(SEM)、透射电镜(TEM)和高分辨透射电镜(HRTEM)等分别对所制备样品进行了表征。结果表明,所得产物为纯的四方相磷化镍(Ni12P5)微球,粒径约为2～5μm;研究了不同实验参数对样品尺寸、形貌及微球形成过程等的影响。最后对磷化镍微球的发光性进行了研究。     

玻璃基体上电沉积Ni-Co合金镀层的性能研究

对玻璃基体上电沉积Ni Co合金镀层的工艺及镀层的性能进行了研究 ,对底镀层的形貌、成分、结构进行了观察和分析 ,并测定了镀层的耐腐蚀性。结果表明 ,镀层在 0 .5mol/LH2 SO4 和 5%NaCl(pH =3 )中的耐蚀性与 1Cr18Ni9Ti相当     

Ni（OH）2水热氢还原制备超细Ni粉

采用ＮｉＳＯ４加过量碱制取的Ｎｉ（ＯＨ）２水浆（ｐＨ１２－１３），经氢还原￣３０ｍｉｎ制得平均粒度２０ｎｍ以下的Ｎｉ粉。碱是否过量对Ｎｉ粉粒度影响较大；催化剂和温度对反应速度也有较大影响。氢还原反应机制不是液相中的Ｎｉ离子还原，而昌Ｎｉ（ＯＨ）２固体微粒与活性氢之间的反应。     

富锂锰基正极材料Li1.2Ni0.13Co0.13Mn0.54O2的Zn2+掺杂改性

采用高温固相合成法制备富锂锰基正极材料Li_(1.2)Ni_(0.13)Co_(0.13)Mn_(0.54-x)Zn_xO_2(x=0,0.03,0.06,0.10),Zn~(2+)掺杂对Li_(1.2)Ni_(0.13)Co_(0.13)Mn_(0.54)O_2的表面特性和电化学性能都有影响。通过X射线衍射(XRD)、扫描电子显微镜(SEM)、拉曼光谱分析、充放电测试、倍率特性测试、循环性能测试,分析了该合成材料的晶体结构、形貌特征、微观结构和电化学性能。富锂锰基正极材料为a-NaFeO_2层状结构,R-3m空间群,结晶度高,结构稳定性好,其中Li_(1.2)Ni_(0.13)Co_(0.13)Mn_(0.48)Zn_(0.06)O_2的电化学性能较好。掺杂Zn~(2+)可以提高富锂锰基正极材料的充放电比容量、倍率性能、循环性能等电化学性能。     

Synthesis, densification, and mechanical properties of TaB2

Tantalum diboride (TaB₂) was synthesized by reducing Ta₂O₅ using B₄C and graphite at 1600 °C under flowing Ar. The powder had an average particle size of 0.4 μm with both needle-like and rounded particles. The TaB₂ powder was hot pressed to relative densities of 97% at 2000 °C (3.6 μm grain size) and 98% at 2100 °C (5.3 μm grain size). Mechanical properties were measured for TaB₂ hot pressed at 2100 °C and were comparable to those of the commonly studied diborides, ZrB₂ and HfB₂. The Young's modulus was 551 GPa, Vickers' hardness was 25.6 GPa, flexure strength was 555 MPa, and fracture toughness was 4.5 MPa-m^1/2.     

Sintering behaviour of the diamond-super invar alloy system at high temperature and pressure

In the diamond-super invar alloy system, effect of the grain size of the starting diamond powder on the sintering behaviour was investigated at 5.8 G Pa and 1300 to 1500 ° C for 30 to 60 min. Abnormal grain growth was often observed in the sintered diamond using fine diamond powder, but a homogeneous sintered diamond was easily synthesized using 5 to 10m diamond. By the rigorous control of sintering conditions, a 3m grain size homogeneous sintered diamond was synthesized under conditions of 5.8 G Pa and 1350 ° C for 30 min. The Vickers hardness and thermal resistance of the fine grained sintered diamond was examined.     

Effect of Ni powder characteristics on the consolidation of ultrafine TiMoCN cermets by means of SPS and HIP technologies

Fully dense titanium carbonitride cermets have been consolidated from Ti(C,N)–Ni–Mo₂C–TiAl₃ powder mixtures either by spark plasma sintering or hot isostatic pressing techniques. Carbonyl Ni powders enhance the densification of the cermets produced by SPS (spark plasma sintering), a phenomenon likely related to a more efficient dissolution of Mo₂C additions and the possible precipitation of α″ phase. Both SPS and HIP (hot isostatic pressing) processes lead to materials with a bimodal Ti(C,N) grain size distribution containing a considerable fraction of nanometric grains. Unlike SPS, HIP induces significant graphite precipitation which could be explained by the destabilization of the carbonitride phase under high isostatic pressures at high temperature. Optimized compositions processed by SPS exhibit a combination of hardness and toughness close to the range covered by ultrafine WC–Co hardmetals of similar binder contents.     

镍氢动力电池正极材料的研究

为了研究镍氢动力电池正极材料氢氧化镍,收集目前常用的镍氢动力电池用正极材料——普通型及覆钴型氢氧化镍,制备独有技术产品钙镁掺杂型氢氧化镍。通过对该3大类产品进行高温大电流性能的测试表明,适用于镍氢动力电池的氢氧化镍正极材料为覆钴型及钙镁掺杂型氢氧化镍。再考察不同覆钴量的覆钴型氢氧化镍及不同配比的钙镁型氢氧化镍,对覆钴量及钙镁掺杂量进行研究,得出主要用于镍氢动力电池的氢氧化镍产品为覆钴量为Co3.5%的覆钴型氢氧化镍及Ca2Mg0.5、Ca1.5Mg0.2、Ca1Mg0.3等3种成分的钙镁型氢氧化镍。     

Bimetallic Nickel‐Substituted Cobalt‐Borate Nanowire Array: An Earth‐Abundant Water Oxidation Electrocatalyst with Superior Activity and Durability at Near Neutral pH

There is an urgent demand to develop earth‐abundant electrocatalysts for efficient and durable water oxidation under mild conditions. A nickel‐substituted cobalt‐borate nanowire array is developed on carbon cloth (Ni‐Co‐Bi/CC) via oxidative polarization of NiCo₂S₄ nanoarray in potassium borate (K‐Bi). As a bimetallic electrocatalyst for water oxidation, such Ni‐Co‐Bi/CC is superior in catalytic activity and durability in 0.1 m K‐Bi (pH: 9.2), with a turnover frequency of 0.33 mol O₂ s^?1 at the overpotential of 500 mV and nearly 100% Faradaic efficiency. To drive a geometrical catalytic current density of 10 mA cm^?2, it only needs overpotential of 388 mV, 34 mV less than that for Co‐Bi/CC, outperforming reported non‐noble‐metal catalysts operating under benign conditions. Notably, its activity is maintained over 80 000 s. Density functional theory calculations suggest that the O* to OOH* conversion is the rate‐determining step and Ni substitution decreases the free energy on Co‐Bi from 2.092 to 1.986 eV.     

Effects of added diamond powder on the reaction sintering behaviour of diamond in the graphite-nickel system

Polycrystalline diamond sintered compact was prepared under high pressure and temperature conditions (7 GPa, 1700°C, 10 to 30min) from the starting material with the composition of the system 50 wt% carbon (diamond + graphitized pitch coke (GPC))-50 wt% Ni. The effects of added diamond powder on the microstructure of the sintered compact and reaction sintering behaviour were investigated. The grain size of diamond in the sintered compact decreased remarkably from 20 to 40m to 2 to 3m on addition of 10 to 20 wt% diamond powder (grain size: 1m) to the GPC-Ni system. The grain size can be controlled by that of the added diamond powder. A sufficient supply of carbon from GPC plays an important role in the formation of a covalently bonded compact of diamond. The grain growth of the formed diamond is depressed by the coexistence of diamond powder, which controls the solubility of carbon in the metal-carbon system and also the grain growth process by solution-reprecipitation.