机械合金化制备纳米晶铁-铜合金粉体

利用机械合金化方法制备了纳米晶铁-铜合金粉体,采用XRD、SEM和粒度分析仪对粉体在球磨过程中的固态相变、微观形貌和粒径变化进行了分析。结果表明:球磨20 h后,粉体的衍射峰宽化并形成固溶体,随球磨时间延长,粉体的晶粒尺寸逐渐减小,微观应变和晶格常数逐渐增大;粉体颗粒首先被碾压成扁平状并相互焊合使颗粒尺寸粗化,然后随球磨的继续进行变成球状的小颗粒,使颗粒尺寸逐渐减小;球磨65 h后,颗粒形貌和组织趋于稳定,获得了平均粒径为5.80～7.76μm的纳米晶粉体,粉体平均晶粒尺寸达到8 nm左右。     

消息

纳米金刚石粉研磨抛光剂由甘肃凌云纳米材料有限公司研制成功的“纳米金刚石延伸产品研磨抛光剂”,在兰州通过鉴定 ,该纳米金刚石研磨剂性能处于国内领先 ,研磨效果与效率达到国际先进水平。甘肃凌云公司生产的纳米金刚石粉具有 4nm～ 1 6 nm的颗粒尺寸 ,并具备接近天然金刚石的硬度 ,是理想的研磨材料。而在此基础上研制的抛光剂的外观、流变性能和储存稳定性良好 ,形成了年产 5 0 0 kg的生产能力。用凌云公司研制的纳米金刚石研磨膏对陶瓷球的研磨使其表面粗糙度达到 6 .3 nm,优于常规的微米金刚石研磨膏 ,粗糙度已超过最高级 (3级 )精度…     

SiO2气凝胶常压合成新工艺

以正硅酸乙酯为硅源,HF为催化剂,采用溶胶-凝胶法常压下制备出了SiO2气凝胶,并研究了水、催化剂、乙醇等制备因素对其溶胶-凝胶过程的影响.用透射电镜(TEM)、比表面(BET)、傅里叶变换红外光谱仪、激光粒度仪等方法对其微结构测试.结果表明所制备的SiO2气凝胶具有大的比表面和纳米多孔结构(骨架颗粒约为10 nm,空洞尺寸为10～30 nm),平均粒径＜20 μm,为介孔结构.     

水热法制备板钛矿型TiO_2纳米颗粒及其表征

采用水热法成功合成板钛矿型TiO2纳米颗粒。利用X射线衍射仪、透射电子显微镜、拉曼光谱仪、激光粒度分析仪对样品进行分析表征,结果表明TiO2纳米颗粒为棒状,直径约为10nm,长度约为100nm。发现所合成的样品随着反应时间,其长度有明显的增加,而直径没有明显的变化。     

高纯纳米α-Al2O3的连续批量制备与表征

通过 HLG-30型纳米化粉碎机批量制备纳米 Al2O3,使用纳米激光粒度仪分析其粒度及粒度分布,并用扫描电子显微镜（SEM）和透射电子显微镜（TEM）观察其大小和形貌,采用 X 射线衍射（XRD）表征其晶型结构,通过电感耦合等离子体发射光谱（ICP-AES）检测杂质元素的含量,研究其纯度。结果表明,制备所得的 Al2O3粒度分布窄,大部分颗粒的粒径〈40 nm,为α型晶体,并且纯度〉99.99%,具有广阔的应用前景。     

表面活性剂SPAN80对水热法制备SrTiO_3粉体物相、形貌与极性的影响

以硝酸锶、钛酸四丁酯和氢氧化钾为原料,采用水热法制备了纳米SrTiO3粉体,用XRD、SEM、激光粒度分析仪等研究了制备过程中非离子表面活性剂SPAN80含量对纳米SrTiO3粉体物相、形貌、粒径和极性的影响。结果表明:表面活性剂SPAN80的添加对SrTiO3粉体晶型结构没有影响,且有效减弱了粉体的团聚;在SPAN80最佳添加量10%(体积分数)的条件下,制备得到SrTiO3粉体的颗粒尺寸约为39nm,并呈球形;极性的SrTiO3粉体被SPAN80包裹后变成了非极性粉体。     

纳米金刚石颗粒粒度的测量与表征

介绍了用负氧平衡炸药在密闭容器内爆轰制备的纳米金刚石。用 X射线衍射线线宽法 (谢乐公式 )、透射电镜观察法 (TEM)、激光拉曼散射法、比表面积法和 X射线小角散射法等手段 ,对合成的纳米金刚石颗粒粒度进行了测量 ,结果表明炸药爆轰法制备的纳米金刚石具有立方金刚石结构 ,颗粒呈球形或椭球形 ,平均粒径为 6 .7nm。在五种测量方法中 ,X射线衍射线线宽法 (谢乐公式 )得到的平均粒径值最小 ,而其它四种测量方法所得到的粒径值基本一致     

表面修饰Bi纳米微粒的制备及摩擦学性能

为研究低熔点金属纳米微粒作为润滑油抗磨添加剂的摩擦学性能,采用原位表面修饰液相化学还原的方法,制备了硬脂酸修饰B i纳米微粒,通过XRD,TEM,FT-IR等分析手段对其形貌和结构进行了表征,在四球摩擦磨损试验机上考察了所制备表面修饰B i纳米微粒添加在液体石蜡中的减摩抗磨性能。结果表明,所合成的纳米微粒具有斜方晶型B i的晶体结构,平均粒径10~20 nm,分散好,颗粒之间无团聚现象,有机修饰层的存在防止了B i纳米微粒的氧化。硬脂酸修饰B i纳米微粒在中低负荷下作为润滑油添加剂具有良好的减摩性能和较好的抗磨性。     

以滤纸为模板制备多孔CeO_2纤维及其催化性能

以滤纸为模板,合成了具有滤纸微观形貌和纳米级孔均匀分布的CeO2纤维,利用热重分析、X射线衍射、电镜观察、氮气吸/脱附等方法对其进行表征,考察了前驱体溶液浓度对其微观结构的影响,最后研究了CeO2纤维的催化性能。结果表明:前驱体溶液浓度为0.02mol·L-1时,合成的CeO2纤维的比表面积最大,约为84.7cm2·g-1,纤维长为0.5~5mm,直径为5~20μm,纤维结构由5~10nm的CeO2纳米晶组成,纳米孔径约为3nm,此多孔CeO2纤维具有良好的CO催化氧化活性,在450℃时的CO转化率可达100%;随着前驱体溶液浓度的增加,由于颗粒堆积,影响了产物对模板的复制效果。     

铜包覆纳米碳化硅复合粉体的制备及表征

利用非均匀形核法制备了铜包覆纳米SiC复合粉体，通过XRD、SEM、EDS、TEM等手段对复合粉体进行了微观测试和表征。结果表明：纳米SiC颗粒表面的铜包覆层均匀、连续，铜晶粒平均粒径约38nm，部分氧化成CuzO，氧化率为11．54％。用质量分数为0．5％的PEG-20000作为分散剂，能有效地分散纳米SiC颗粒，并阻止包覆在纳米SiC颗粒表面的铜晶粒过度长大。     

Controlled Synthesis and Optical Properties of Pure Gold Nanoparticles

Abstract

Gold nanoparticles were synthesized by laser ablation of a gold metallic disc at wavelengths of 532 nm and 355 nm with 7 ns pulse duration in the pure water. The colloidal gold nanoparticles were characterized by ultraviolet-visible absorption spectroscopy, transmission electron microscopy, and fluorescence spectrometry. The presence of a surface plasmon resonance peak around ～ 524 nm indicates the formation of gold nanoparticles. The formation efficiencies of gold nanoparticles in colloids were found to increase when ablating the gold metallic disc with a laser having a longer wavelength. The size distributions of the gold nanoparticles thus produced were measured by transmission electron microscopy. A reduction in mean diameter of the particles was observed with a decrease in the laser wavelength under the irradiation at a high fluence of 25 mJ/pulse. The fluorescence spectroscopy demonstrated that these gold nanoparticles are fluorescent, showing a strong blue emission intensity at 458 nm.     

粒径对油溶性Cu纳米颗粒抗磨性能的影响

用两相法合成了表面为双正十二烷氧基二硫代磷酸(DDP)修饰的Cu纳米颗粒,通过改变反应物的添加比例有效控制了Cu纳米颗粒的粒径,并利用四球摩擦磨损试验机考察了DDP修饰Cu纳米颗粒作为润滑油添加剂的抗磨性能。结果表明,所制备的Cu纳米颗粒粒径越小,其作为润滑油添加剂的抗磨性能越好。     

受控部分还原法制备Fe3O4纳米粒子及其性能研究

采用受控部分还原法(CPRM)制备Fe3O4纳米粒子。由于反应乳液中的大分子表面活性剂限制了成核和核的生长过程,使得纳米粒子的粒径分布很好,且系统中纳米粒子的含量较微乳液法有明显提高。改变反应物浓度可使反应系统中的Fe2 稍过量,故采用CPRM时,反应系统无须惰性气体保护,合成的Fe3O4纳米粒子经TEM、X-ray、动态光散射和振动磁强计等进行表征,结果表明Fe3O4磁性粒子的平均粒径为16 nm,且粒径分布窄,具有极好的超顺磁性。CPRM法使得在一般条件下合成高质量的纳米粒子和Fe3O4磁流体成为可能。     

Fullerene-like MoS<Subscript>2</Subscript> Nanoparticles and Their Tribological Behavior

Using a new quartz-made reactor, large amounts of fullerene-like (IF) MoS₂ nanoparticles were synthesized by reacting MoO₃ vapor with H₂S in a reducing atmosphere. The nanoparticles were found to be of high crystalline order; with an average size of 70 nm and consist of more than 30 closed shells. Extensive tribological testing of the nanoparticles in two types of synthetic oils- poly-alpha olefins (PAO)- was carried out and compared to that of bulk (2H platelets) MoS₂ and IF-WS₂. These tests indicated that under high pressure and relatively low humidity, the IF-MoS₂ exhibited a friction coefficient as low as 0.03 and the smallest wear rate of the measured systems. However, its performance was found to be lower in comparison to IF-WS₂ after 2500 cycles, due probably to its inferior chemical stability. This study indicates that the tribological performance of the IF nanoparticles depends strongly on their crystalline order and size.     

纳米Fe3O4粒子粒径对其作润滑油添加剂摩擦学性能的影响

采用化学共沉淀法和沉淀氧化法分别制备了粒径为10 nm和45 nm的球形Fe3O4粒子,研究了粒径对纳米Fe3O4粒子作润滑油添加剂摩擦学性能的影响。结果表明,纳米Fe3O4粒子的粒径对其作润滑油添加剂的减摩抗磨作用有明显影响。粒径为10 nm和45 nm的Fe3O4粒子作润滑油添加剂均具有较好的减摩抗磨作用,但是,粒径为10 nm的Fe3O4粒子的减摩抗磨效果优于粒径为45 nm的Fe3O4粒子的减摩抗磨效果。     

The Microstructure and Wear Characteristics of Cu–Fe Matrix Friction Material with Addition of SiC

The Cu–Fe matrix continuous braking friction materials using SiC as abrasive were fabricated by powder metallurgy technique, and the effect of content and size of SiC were investigated. The tribological properties of friction materials sliding against AISI 1045 steel ring were carried out on a block-on-ring tester at different loads and sliding speeds. The strengthening effect of nano-SiC (55 nm) was superior to that of micro-SiC (70 μm) of the tribological properties for friction materials. The friction coefficients of friction materials increased with increasing nano-SiC content. However, the wear rates decreased with increasing nano-SiC content and then increased when the content of nano-SiC particle exceeded 10 wt%. The specimen contained 10% nano-SiC had the best tribological properties at different testing conditions.     

Effect of matrix/reinforcement particle size ratio (PSR) on the mechanical properties of extruded Al–SiC composites

This paper studied the combined effects of matrix-to-reinforcement particle size ratio (PSR) and SiC volume fraction on the mechanical properties of extruded Al–SiC composites. A powder metallurgy technique (PM) of cold pressing at 500 MPa followed by hot extrusion at 580 °C was adopted to produce Al/SiC composite. Aluminum powder of size 60 μm and silicon carbide with different sizes, i.e., 50, 20, and 8 μm, were used. Three different volume fractions of SiC were employed, i.e., 5, 10, and 15 %, for each investigated size using a constant extrusion ratio of 14.36. The effect of matrix-to-reinforcement PSR on the reinforcement spatial distribution, fabricability, and resulting mechanical properties of a PM-processed Al/SiC composite were investigated. It has been shown that small ratio between matrix to reinforcement particle size resulted in more uniform distribution of the SiC particles in the matrix. As the PSR increases, the agglomerations and voids increase and the reinforcement particulates seem to have nonuniform distribution. In addition, the agglomerations increased as the volume fraction of the SiC increased. It has also been shown that homogenous distribution of the SiC particles resulted in higher yield strength, ultimate tensile strength, and elongation. Yield strength and ultimate tensile strength of the composite reinforced by PSR (1.2) are higher than those of composite reinforced by PSR (7.5), while the elongation shows opposite trend with yield strength and ultimate tensile strength.     

EDM of cast Al/SiC metal matrix nanocomposites by applying response surface method

The newly engineered metal matrix nanocomposite (MMNC) of Al 7075 reinforced with 0.5 wt% SiC nanoparticles was prepared by ultrasonic cavitation method. The high resolution scanning electron micrograph shows uniform distribution and good dispersion of the SiC nanoparticles within the aluminum metal matrix. Electrical discharge machining was employed to machine MMNC with copper electrode by adopting face-centered central composite design of response surface methodology. Analysis of variance was applied to investigate the influence of process parameters and their interactions. Further, a mathematical model has been formulated in order to estimate the machining characteristics.     

Observations of lattice defects using the weak-beam technique

The advantages of the weak-beam technique of electron microscopy for the study of small defects and dislocations are illustrated by micrographs taken of small loops in aluminium and Al–Ag alloys, GP zones and θ″ precipitates in Al + 4% Cu, and dislocation networks in Cu + 20% Zn. An estimate of 19·5 mJ m^?2 (erg cm^～2) is made for the stacking-fault energy of Cu–20% Zn from the size of extended nodes and the width of the dissociated dislocations imaged under weak-beam conditions.