On morphometric uniformity of diamond micron powders

The paper presents the findings of characterization of initial diamond powders and products of their flotation separation, analysis of the adequacy of mean values of morphometric characteristics and assessment of powder uniformity by a system-criterion method. The separation is demonstrated to provide a significant improvement of powder uniformity in dimensional characteristics and shape index. The flotation products have been found to feature the best uniformity which explains their higher abrasive ability. The flotation separation method has proved to be a suitable tool for improving morphometric uniformity of diamond micron powders, and the proposed system of computer-aided analytical methods has been demonstrated to offer an efficiency means for quantitative analysis of morhometric characteristics of the powders.     

Physico-mechanical properties and structure of diamond polycrystalline composite materials produced from variously dispersed powders

A nanostructural diamond composite material having grains of average size 0.08 μm and hardness corresponding to the hardness of diamond composite materials with grains of average size 30 μm has been produced using nanotechnologies of powder materials. Temperature dependences of hardness of nanostructural diamond composites of various dispersions have been compared. The thermostability of a diamond composite has been shown to depend not only on the composition of a sintering aid but on the size of diamond powders as well. Our findings have indicated that the material obtained holds promise in finishing products of nonferrous metals and alloys instead of natural diamonds.     

复合粉制备工艺对自反应喷射成形TiC-TiB2复合陶瓷坯件的影响

以Ti粉、B4C粉、石墨和蔗糖（C的前驱体）为原料，采用机械粘结法制备了Ti-B4C-C系复合粉，采用前驱体法制备了Ti-B4C-C-蔗糖系复合粉，并分别利用两种复合粉进行自反应喷射成形试验，获得了Ti（C，N）-TiB2复合陶瓷坯件。通过XRD、SEM等方法观察了复合粉与喷射沉积坯件的组织结构，分析了其相组成，并测试了成形坯件的孔隙率及断裂韧性等力学性能，对比分析了复合粉制备工艺对喷射成形材料组织结构及性能的影响。研究结果表明：与机械粘结法制备的，Ti-B4C-C系复合粉相比，采用前驱体法制备的Ti-B4C-蔗糖系复合粉内部粘结强度稍低，但粉体内部混合更均匀，各组元间接触更充分，因而自反应喷射成形过程中的SHS反应更加充分。二者喷射成形所得材料均以Ti（C，N）-TiB2主相、部分钛的氧化物为副产物相，并有一定孔隙。但Ti-B4C-蔗糖系复合粉喷射沉积坯件副产物相少，组织均匀致密，且材料的断裂韧性高，综合性能明显优于Ti-B4C-C系复合粉喷射沉积坯件。     

纳米TiO2/微米Cu复合粒子的制备及可见光活性

利用钛酸丁酯为原料,通过室温强迫水解的方法制备了具有可见光活性的纳米TiO2/微米Cu复合粒子.XPS分析表明复合粒子的表面存在Cu2 、Ti4 、Sn2 元素.场发射扫描电镜观察表明,4nm左右的TiO2颗粒覆盖在铜粉表面形成纳米/微米复合结构,利用空载实验获得表面包覆的TiO2颗粒样品,XRD结果显示TiO2颗粒呈现锐钛矿型,粒径约3.5nm.TG-DTA结果表明复合粒子与原始铜粉具有不同的高温氧化过程,表明TiO2与铜粉之间存在较强的相互作用,而不仅是简单的物理吸附.以甲基橙为模型化合物的降解实验显示出纳米TiO2/微米Cu复合粒子的可见光活性和可重复使用性,8h时照射后甲基橙的降解率达到97%,重复3次实验的降解率保持不变.     

微胶囊铜粉对铜复合浆料性能的影响

为提高铜浆料的导电性,利用微胶囊技术在铜粉表面包覆液体石蜡,增强铜粉的抗氧化性,并添加少量导电性能优异的碳纳米管作为导电增强相,制备碳纳米管-铜复合浆料.利用四探针测试仪、扫描电镜等测试方法研究了液体石蜡含量对包覆铜粉性能的影响以及微胶囊铜粉作为主导电相,碳纳米管作为导电增强相对浆料导电性能的影响.结果表明:液体石蜡包覆含量为4 wt%的微胶囊铜粉具有良好的导电性和抗氧化性,其电导率为44.32%IACS;微胶囊铜粉作为碳纳米管-铜浆料的主导电相,制备浆料膜层电阻率为22.59 mΩ·cm,相比于未包覆的铜粉为主导电相制备的浆料膜层电阻率降低了12.44%;碳纳米管作为导电增强相所制备的浆料相比于纯铜浆料,电阻率降低31.74%.     

Fe/C复合纳米炭粉的制备及其磁学性能研究

以高温煤焦油沥青为原料,以体积比7∶3的浓硫酸和浓硝酸混合酸为氧化剂,制备水性中间相沥青;采用溶胶-凝胶法先形成碳基溶胶,加入FeCl3后进一步形成复合Fe/C凝胶;凝胶经醇水交换、常温干燥和900℃炭化制备出Fe/C复合磁性纳米炭粉。利用FT-IR、XRD、TG和TEM等对水性中间相沥青、磁性纳米炭原粉以及磁性纳米炭粉进行表征。结果表明:采用溶胶-凝胶和常温干燥的方法可以制备出粒度均匀、形状近似于椭圆形的Fe/C复合磁性纳米炭;其磁性纳米炭粉的平均粒径约5 nm,以聚集成粒度为20 nm～30 nm的团聚体形式存在。磁性纳米炭粉中的碳以无定型结构的形式存在,Fe元素以α-Fe、Fe2O3和Fe3C的形式存在,Fe/C复合磁性纳米炭粉具有软磁性和较高的磁响应性。     

软磁复合材料铁芯电机特性的仿真研究

为了发挥软磁复合材料的高电阻率,低损耗,易于再利用的特点,仿真模拟将其应用在永磁电机的铁芯上.以12槽4极直流电机为仿真对象,把三维计算问题转化成二维模型,用JMAG软件对电机进行建模,阐述SMC与硅钢片铁芯差异,先用两种材料进行仿真,结果说明只靠替换铁芯材料对电机性能改进并不会产生很大改善,改进模型,得出不同延伸高度铁芯延伸长度增加引起的电流和转矩特性与功率变化的关系.利用所建模型将Somaloy500的软磁复合材料与50CS800的硅钢片制备的铁芯进行模拟实验,结果表明:相同条件下软磁复合材料铁芯的效率要更高一些.最低转速时效率增加5%,最高转速时效率增加10%;软磁复合材料铁芯模型抑制电流输出,各向同性的优势明显.结论为SMC材料在低转速电机的开发中依旧能够发挥优势,实现电机性能的提高.     

Structure and mechanical properties of reaction-sintered ceramic composite materials based on titanium and hafnium diborides

The structure and mechanical characteristics of ceramic composite materials based on titanium and hafnium diborides produced by reaction sintering in the course of hot pressing have been studied. It has been shown that ultradispersed structure is responsible for high mechanical characteristics of the synthesized composites.     

HA-n-ZrO2核壳层复合陶瓷微粉材料的制备与表征

采用水热-沉积原位分步反应法.制备了羟基磷灰石(HA)-氧化锆(ZrO2)复合微粉,采用XRD和TEM对复合微粉的物相、形貌和大小进行了表征.对复合微粉进行模压成型、热处理制备了复合陶瓷试样,并测试其力学性能.结果表明:所得复合微粉以纳米级四方相ZrO2为"核心",逐层包覆HA,形成核-壳层结构(HA-n-ZrO2);...     

Effect of high-pressure torsion processing on the microstructure evolution and mechanical properties of consolidated micro size Cu and Cu-SiC powders

In this paper, micro size Cu and Cu-SiC composites powders were consolidated by powder metallurgy (PM) followed by sintering or high-pressure torsion (HPT) to study the effect of the different processing methods on microstructure evolution and mechanical properties. HPT contributes in producing fully dense samples with a relative density higher than those processed by PM followed by sintering. Bimodal and trimodal microstructures with a mixture of ultrafine grain (UFG) and micro or nano grain sizes were noted in the case of Cu and Cu-SiC HPTed samples, respectively. The increase of the SiC volume fraction (SiC%) produces smaller grain size with higher fractions of high angle grain boundaries (HAGBs) in the HPTed Cu-SiC samples than that in the case of HPTed Cu sample. The HPT under a pressure of 10 GPa and 15 revolutions was effective to achieve a complete fragmentation of SiC particles down to ultrafine particle size. HPT processing of Cu and Cu-SiC composites enhanced the mechanical properties (hardness and tensile strength) with conserving a reasonable degree of ductility (elongation%). The yield strength of the samples was estimated based on the microstructure observations and processing parameters by different models correctly with an error range of 5.1–1% from the experiential results.     

碳化钨粉末对聚晶金刚石复合片钻头胎体组织与力学性能的影响

以铸造碳化钨粉末混合镍粉作为骨架粉末,采用无压浸渍工艺制备了聚晶金刚石复合片（PDC）钻头胎体材料。研究了碳化钨的粉末粒形、粒度及质量分数对PDC钻头胎体的微观组织和力学性能的影响。结果表明,碳化钨的粉末粒形、粒度及质量分数是影响胎体微观组织和力学性能的重要因素。与破碎碳化钨相比,粉末粒度适中的球形碳化钨作为骨架制备的胎体组织更均匀、更致密,胎体的力学性能明显提高。采用150~180 μm的球形碳化钨混合13wt%的镍粉作为骨架粉末制备的胎体力学性能优于石油天然气行业标准SY/T 5217—2000,其硬度、冲击韧性和抗弯强度分别为HRC 34、6.7 J/cm2和820 MPa。      

酸蚀Al粉对Al-聚氨酯复合涂层光泽度与红外发射率的影响

在不明显升高Al-聚氨酯(PU)复合涂层红外发射率的前提下,通过酸蚀Al粉提高Al粉表面粗糙度的方法来明显降低涂层的光泽度。系统研究了Al粉酸蚀时间对Al-PU复合涂层的微结构、光泽度、红外发射率及力学性能的影响。结果表明:Al粉酸蚀可明显降低涂层的光泽度,酸蚀10min即可使涂层的光泽度从20.1降低为13.0,而Al粉酸蚀对涂层的微结构基本没有影响,对涂层发射率的影响非常有限,酸蚀50min仅使涂层的发射率从0.208增大为0.254,仍然具有较低的发射率。酸蚀20min可使涂层同时具有较低的光泽度和发射率,其值分别为12.8和0.228。涂层的力学性能对Al粉酸蚀处理并不敏感,处理前后涂层的硬度、附着力和耐冲击强度等力学性能分别可达到3H、1级和50kg·cm。     

Heat-insulating composite based on unwoven materials and organomineral binder

Composites based on unwoven cellulose-hydrate and carbon materials and an organomineral binder have been developed and investigated. Optimal compositions of the composites feature a higher fire resistance, a low density, and effective thermophysical characteristics. The composites are promising for use as heat-insulating materials with a rigid structure in different branches of the national economy and industry. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 82, No. 1, pp. 85–91, January–February, 2009.     

大尺寸掺硼宝石级金刚石单晶的高温高压合成及电学性质研究

在5.4GPa、1200～1400℃条件下,进行掺硼金刚石单晶的合成研究。成功合成出了重0.2g,径向尺寸达6.0mm的优质掺硼金刚石单晶。考察了合成体系中硼添加量对晶体透光度的影响。利用伏安特性和霍尔测试,得到了掺硼金刚石单晶常温电阻率、霍尔系数及霍尔迁移率和合成体系中硼添加量的关系。研究发现,随着合成体系中硼添加量的增加,晶体的电阻率和霍尔迁移率都呈下降趋势;霍尔系数随硼添加量的增加先下降后上升。随着硼添加量的增加:晶体常温电阻率下降,表明硼杂质已进入到金刚石晶体中。霍尔迁移率的下降,可能是晶体缺陷增多对载流子散射所致。霍尔系数先减小后增大,这可能与进入金刚石的硼元素量增大及晶体缺陷增多有关。     

退火处理对非晶态Ni-P合金超细粉结构及磁性能的影响

采用液相脉冲放电技术,在NiSO4溶液中用NaH2PO2为还原剂,制备出了Ni-P合金超细粉体材料。将Ni-P合金粉在200～450℃下退火处理,并通过X射线衍射(XRD)、透射电镜(TEM)和场发射扫描电镜(FESEM)对退火前后Ni-P合金粉的结构、形貌进行了分析。用振动样品磁强计(VSM)对Ni-P合金粉进行了磁性能分析。结果表明所制备的超细Ni-P合金粉为非晶结构,颗粒直径在300～500nm之间,颗粒之间紧密结合成链枝状形貌。Ni-P合金粉在250～280℃退火后具有良好的软磁性能,250℃退火后矫顽力降低至0.437×10-4T。     

纳米氧化镁及其复合材料的抗菌性能研究

参考最近有关文献，认为抗茵材料已经成为传统材料与环境一体化的方向，作为新型陶瓷抗茵剂的纳米MgO系材料与其它抗菌剂相比，表现出独特的抗菌性和广泛的应用背景，对其研究已成为国外研究的新热点。本文总结了纳米MgO粉体的制备方法，分析了其抗菌机理，概述了其最新研究进展和复合制备技术，最后指出了存在的问题和研究方向。     

静压法合成含硼金刚石结构及电阻特性研究

采用在铁基触媒中加入硼铁粉的方法制成Fe-Ni-C-B系触媒,用静压法合成含硼金刚石。研究了含硼金刚石的形貌、晶体结构和电阻-温度曲线。实验结果表明,在不同温度区间内,金刚石具有不同的电离能,分析了其原因。同时测得此含硼金刚石的最高工作温度为773K左右。为高温半导体金刚石的研究提供了实验基础。     

基于太阳能供热的石墨烯/石蜡复合相变材料蓄放热特性实验研究

由于太阳能间歇性和不稳定性的缺点,给其在供热方面的应用带来了局限,采用相变储能法可改善太阳能供热应用的缺点。对此以石蜡为基液,向其中添加石墨烯通过"两步法"制备出石墨烯质量分数分别为0.1%、0.3%和0.5%的复合相变材料,搭建复合相变材料蓄放热实验台并记录数据。结果表明:在相同的实验条件下,石墨烯/石蜡复合相变材料随着石墨烯质量分数的增加,熔化速率也随之增加,在添加量为0.5%时增加了14.15%;凝固速率也随石墨烯质量分数的增加而增加,但效果不如熔化速率明显;复合相变材料在圆管外的蓄放热过程中,位于圆管底部的材料熔化与凝固效果均不理想。     

The effect of some color centers on the coloration of natural and synthetic diamonds

Mechanisms of the formation of diamond coloration caused by the light absorption by basic impurity defects, which are optically active in the visible region, have been studied. The analytical relationships between the relative concentration of each defect and the diamond main color tone and saturation have been derived. The influence of the centers under study on the diamond coloration has been compared.     

高压熔渗金刚石/铜复合材料的低温导热特性

为研究高压熔渗金刚石/铜复合材料导热率在低温区的变化规律,采用高压熔渗（HRF）的方法分别制备了不同粒度（100 μm,250 μm,400 μm）的金刚石/铜复合材料,利用扫描量热法分析评价了高压熔渗法制备的不同粒度金刚石/铜复合材料的低温导热特性,采用扫描电子显微镜（SEM）分析其显微组织。研究结果表明：由于高压熔渗制备的金刚石/铜复合材料中的部分金刚石发生聚晶反应,导致金刚石颗粒间晶界传热的热阻远小于界面传热热阻;高压熔渗条件下,金刚石颗粒内部变形破碎导致缺陷增多,且100~150 K低温下以声子为主要热载子的传热对裂纹和间隙等缺陷敏感,导致在较低温区内金刚石/铜复合材料的导热率低于普通压力熔渗（PF）所制备的金刚石/铜复合材料的导热率。