球形纳米银粉的制备研究

在较高浓度的硝酸银溶液中，采用水合肼为还原剂，PVP为保护剂的化学还原法制备了纳米银粉。通过对还原剂、保护剂用量和硝酸银浓度、温度、还原剂的加入方式、pH值等因素对纳米银粉粒度和形貌影响的考察，获得了制备纳米银粉的工艺。在AgNO3浓度为0．6mol／L，PVP／Ag摩尔比为1．5，水合肼浓度为0．6mol／L，pH值为5～6，温度为60℃的条件下，制备出了粒度均匀且粒度在50nm左右的纳米银粉。     

Triton X-100／Vc／H2O微乳液中纳米金的合成

在Triton X-100/Vc/H2O微乳液中,用0.001 mol·L-1HAuCl4溶液代替组分水,以Vc作还原剂制备纳米金.用紫外-可见光谱和透射电镜进行分析.结果表明,所制备的金纳米粒子的平均粒度在20 nm左右,且粒子的粒度分布范围较窄.无论是在固定0.001 mol.L-1HAuCl4/Vc质量比下改变Triton X-100的含量,还是在固定Triton X-100/0.001 mol·L-1 HAuCl4质量比下改变Vc的含量,所得的金纳米粒子大小与形状都没有明显的变化.初步探讨了在Triton X-100/Vc/H2O微乳液中合成纳米金的机制.     

氯金酸的浓度对纳米金形态的影响

采用Zn置换HAuCl4溶液的方法制备了具有不同形貌的纳米金,并研究了HAuCl4溶液的浓度对纳米金形貌的影响.实验结果表明,纳米金的形貌主要取决于HAuCl4溶液的浓度.当HAuCl4溶液的浓度为0.01 mmol/L时,置换反应进行5 min后的产物是金纳米颗粒,其粒径为10～50 nm,24 h后金颗粒的粒径超过100 nm,金颗粒团聚成金花状.当HAuCl4溶液的浓度为1 mmol/L时,金颗粒的粒径为数百纳米,部分金颗粒团聚成金花状.当HAuCl4溶液的浓度为10 mmol/L时,在金颗粒中出现由纳米金片组成的多晶枝晶,多晶枝晶随后通过OA和OR机制转变成单晶枝晶.当HAuCl4溶液的浓度为30 mmol/L时,反应时直接生成金枝晶.因此,通过控制HAuCl4溶液的浓度,可制备具有不同形貌的纳米金.     

SDS／Vc／H2O微乳液中纳米金的合成

在SDS／Vc／H2O微乳液中用0．001mol·L^-1HAuCl4溶液代替组分水，以Vc作还原剂制备纳米金。紫外一可见光谱和扫描电镜实验结果表明，所制备的金纳米粒子的粒径在5-20nm之间；在固定SDS／Vc的质量比为50／50条件下，粒子的粒径随微乳液中HAuCl4（aq）含量的增加而增加。初步探讨了在SDS／Vc／H2O微乳液中合成纳米金的机制。     

水相法制备小粒径金溶胶

采用柠檬酸三钠还原氯金酸法制备金溶胶.研究了还原剂用量、试剂加入顺序、反应时间、搅拌速度等因素对金溶胶浓度、粒径、形貌和分散性的影响,使用紫外-可见分光光度计和透射电子显微镜对金溶胶的光学特性、粒径、形貌及结构进行表征.结果表明:制备小粒径金溶胶的最优条件为柠檬酸三钠(0.034 mol/L)与氯金酸(0.024 mol/L)溶液体积比为3:1,将氯金酸加入柠檬酸三钠溶液中为宜,反应时间6 min,搅拌速度约650 r/min;在此最优条件下可成功制备出形貌均一、分散性好、稳定性佳的金溶胶,其平均粒径约6～7 nm.     

正交设计优化纳米银粉制备的研究

在较高浓度的AgNO3溶液中,采用聚乙烯吡咯烷酮(PVP)为保护剂,次磷酸钠(NaH2PO2·H2O)为还原剂,通过化学还原法成功制备出纳米银粉.采用设计3因素3水平的正交实验L9(33),考察了还原剂浓度、保护剂用量及反应温度对纳米银粉粒度及形貌的影响,获得制备纳米银粉的最佳条件:在AgNO3浓度为1.0 mol/L时,NaH2PO2·H2O浓度为0.1 mol/L,PVP,AgNO3(质量比)为1:1,溶液pH值为1～2,反应温度为40℃的条件下,制备出类球形、分散均匀、纯度高的纳米银粉,其粒度主要分布在30～50 nm范围.     

晶种法制备单分散的金纳米粒子及光学性能研究

加入聚乙烯吡咯烷酮(PVP)做稳定化试剂,用硼氢化钾还原氯金酸,结合晶种生长法制备了单分散性、粒径小的胶体金。通过晶种生长法,在反应中加入PVP试剂,用抗坏血酸做还原剂,制备了单分散的金纳米棒。结果表明,PVP试剂对金纳米粒子的形貌有重要的影响;加入PVP试剂得到的金纳米粒子(胶体金和金纳米棒)分散性好,无明显的团聚现象。应用透射电镜,纳米粒度分析仪和紫外-可见分光光度计对不同粒径的纳米金进行了表征。     

水热合成法制备HfO_2薄膜(英文)

以HfOCl2·8H2O为前驱体采用水热合成法制备了HfO2溶胶,采用旋涂法制备了HfO2-PVP薄膜。利用透射电镜和粒度分析仪观察和表征HfO2溶胶的微观结构和粒度分布。实验发现,通过调整不同的水热合成温度、反应物前驱体浓度、溶液的pH值和水热合成时间等制备条件,可以在3～100nm范围内对HfO2溶胶颗粒的大小进行控制。分别采用椭偏仪,原子力显微镜,傅里叶红外变换光谱对HfO2–PVP薄膜的形貌和结构进行了表征和测量。结果表明,旋涂法制备的HfO2-PVP薄膜的粗糙度小于0.5nm,折射率达1.75左右。实验还发现,HfO2薄膜的激光损伤阈值达到15J/cm3(1064nm,1ns),HfO2-PVP薄膜的激光损伤阈值可高达20J/cm3(1064nm,1ns)。还对HfO2-PVP薄膜中有机粘结剂PVP在激光诱导损伤过程中的作用机理进行了初步探讨。     

溶胶-凝胶法制备纳米MoCu复合粉体

以硝酸铜和二钼酸铵为原料，采用溶胶-凝胶法制备了纳米MoCu复合粉体，研究了热处理工艺，溶液pH值，添加剂等对纳米粒子形貌及粒径的影响。结果表明，在600℃热处理的钼铜氧化物通过氢气还原之后可以得到粒径小于60nm的纳米MoCu复合粉体；溶液中添加剂的用量影响微粒的粒径，当添加剂用量K为0．5时，能得到尺寸较小，粒度均匀的纳米粉体；不同酸度条件下所得粉体的粒径各不相同，当pH值在1～4之间变化时粒径随pH值的增大而增大，pH值取1较合适。     

溶胶-凝胶法合成La_(1-x)Sr_xCoO_3粉末

在醋酸镧、硝酸锶和硝酸钴溶液中，加入乙二醇溶液，用溶胶-凝胶法合成了La（1-x）SrxCoO3（x＝0．2）粉末。通过电镜分析研究了干凝胶分解温度、制备干凝胶时乙二醇的浓度及溶液pH值等工艺条件对粉末性能的影响；通过X射线衍射分析研究了粉末的变化过程。研究表明：干凝胶的分解温度为800℃，乙二醇的浓度为0.2mol／L，溶液的pH＝6.5时，粉末的粒度分布范围相对最窄，且平均粒度最小（75nm）；粉末的烧成温度为1100℃。     

RHEOLOGY FEATURE OF SIMPLE METAL MELT

The rheology feature of Sb, Bi melt and alloys was studied using coaxial cylinder high-temperature viscometer. The results showed that the curve of torsion-rotational speed for Sb melt presents a linear relation in all measured temperature ranges, whereas for the Bi melt, the curve presents obvious non-Newtonian feature within the low temperature range and at relative high shear stress. The rheology feature of Sb80Bi20 and Sb20Bi80 alloy melts was well correlated with that of Sb and Bi, respectively. It is considered that the rheology behavior of Sb melt plays a crucial role in Sb80Bi20 alloy and that of Bi melt plays a crucial role in Sb20Bi80 alloy.     

Microstructures and Mechanical Properties of a Newly Developed Austenitic Heat Resistant Steel

The effect of heat treatment on the microstructures and mechanical properties of a newly developed austenitic heat resistant steel(named as T8 alloy) for ultra-supercritical applications have been studied. Results show that the main phases in the alloy after solution treatment are γ and primary MX. Subsequent aging treatment causes the precipitation of M_(23)C_6 carbides along the grain boundaries and a small number of nanoscale MX inside the grains. In addition, with increasing the aging temperature and time, the morphology of M_(23)C_6 carbides changes from semi-continuous chain to continuous network.Compared with a commercial HR3C alloy, T8 alloy has comparable tensile strength, but higher stress rupture strength. The dominant cracking mechanism of the alloy during tensile test at room temperature is transgranular, while at high temperature, intergranular cracking becomes the main cracking mode, which may be caused by the precipitation of continuous M_(23)C_6 carbides along the grain boundaries. Typical intergranular cracking is the dominant cracking mode of the alloy at all stress rupture tests.     

The 15th Global Foundry Sourcing Conference 2014held in Qingdao China

Organized by Suppliers China Co., Ltd and co-organized by the National Technical Committee 54 on Foundry of Standardization Administration of China, the 15th Global Foundry Sourcing Conference 2014 （hereinafter referred to as FSC 2014） was successfully held on Sep. 23rd in Grand Regency Hotel, Qingdao. More than 500 delegates from home and abroad attended this conference, including over 130 purchasers from 20 countries and 380 domestic and foreign suppliers.     

LASER CLADDED TiCN COATINGS ON THE SURFACE OF TITANIUM

Laser cladded coatings of TiCN were produced on the surface of titanium. To obtain the optimal techniques, several conditions were tested by varying the laser scanning rate. The choice of shielding gas was also studied. The cladded coatings were then evaluated from the surface mechanics point of view based on their microhardness. The microstructure of some interesting samples was investigated by optical micrographs (OM). The results showed that under the condition of fixed pulse frequency and pulse width, the laser scanning rate and the shielding gas are the main factors influencing the components of coatings. TiCN coatings were decompounded and oxidized during the cladding process in the condition of no shielding gas of N2. X-ray diffraction results indicated that the composite coatings composed of TiCN, TiC, Ti2N, and TiO2 were produced using appropriate techniques. The results indicated that the best condition in terms of the surface microhardness is obtained when the scanning rate is 1.5mm / s, the pulse frequency is 15Hz, the pulse width is 3.0ms, and N2 is chosen as the shielding gas. The microhardness of the composite coatings is about 1331kg · mm - 2, which is about 4 times that of the substrate. The optical micrographs indicated that the cladding zone is made up of TiCN, TiO2, and some interdendritic Ti, but the diffusion zone mainly consists of the dendrites phase, and the cladded depth is about 80m, which is more than 2 times that of the laser nitrided sample. There were no microcracks or air bubbles in the cladded sample, which was cladded using the above optimal techniques.     

Microstructure and Mechanical Properties of X80 Pipeline Steel Joints by Friction Stir Welding Under Various Cooling Conditions

X80 pipeline steel plates were friction stir welded(FSW) under air, water, liquid CO_2 + water, and liquid CO_2 cooling conditions, producing defect-free welds. The microstructural evolution and mechanical properties of these FSW joints were studied. Coarse granular bainite was observed in the nugget zone(NZ) under air cooling, and lath bainite and lath martensite increased signifi cantly as the cooling medium temperature reduced. In particular, under the liquid CO_2 cooling condition, a dual phase structure of lath martensite and fi ne ferrite appeared in the NZ. Compared to the case under air cooling, a strong shear texture was identifi ed in the NZs under other rapid cooling conditions, because the partial deformation at elevated temperature was retained through higher cooling rates. Under liquid CO_2 cooling, the highest transverse tensile strength and elongation of the joint reached 92% and 82% of those of the basal metal(BM), respectively, due to the weak tempering softening. A maximum impact energy of up to 93% of that of the BM was obtained in the NZ under liquid CO_2 cooling, which was attributed to the operation of the dual phase of lath martensite and fi ne ferrite.     

INDUSTRY NEWS

China Securities News reported on March 21, 2014： Guangdong Hongtu Wuhan Die Casting Co., Ltd. （Wuhan Hongtu）, a wholly owned subsidiary of Guangdong Hongtu Technology （Holdings） Co., Ltd., held a groundbreaking ceremony recently. With the registered capital of 50 million Yuan, Wuhan Hongtu has a total land area of 100,000 square meters and a plant construction area of 72,000 square meters. It is expected to have a production capacity of about 30,000 tonnes of aluminum castings annually after it is put into production.     

GROWTH MORPHOLOGIES OF A BINARY ALLOY WITH LOW ANISOTROPY IN DIRECTIONAL SOLIDIFICATION

Two new classes of growth morphologies, called doublons and seaweed, were simulated using a phase-field method. The evolution of doublon and seaweed morphologies was obtained in directional solidification. The influence of orientation and velocity on the growth morphology was investigated. It was indicated that doublons preferred growing with its crystallographic axis aligned with the heat flow direction. Seaweed, on the other hand, could be obtained by tilting the crystalline axis to 45°. Stable doublons could only exist in a range of velocity regime. Beyond this regime the patterns formed would be unstable. The simulation results agreed with the reported experimental results qualitatively.     

STUDY ON PROPERTIES OF PULSE ELECTRODEPOSITED RE-Ni-W-P-SiC COMPOSITE COATINGS

The effects of pulse frequency f and duty cycle r on the deposition rate, composition, morphology, and hardness of pulse electrodeposited RE （rare earth）-Ni-W-P-SiC composite coatings have been studied. The results indicate that pulse current can improve the deposition rate of RE-Ni-W-P-SiC composite coatings; W, P, and SiC contents in the coating decrease with the increase of pulse frequency and reach the lowest value at f = 33Hz, whereas the RE content in the composite coatings increases with the increase of pulse frequency. SiC content decreases with the increase of duty cycle, W content reaches the lowest value, and P content reaches the highest value at r = 0.4; pulse current and RE can lead to smaller size of the crystalline grains; however, the effects of different pulse frequency and duty cycle on the morphologies of RE-Ni-W-P-SiC composite coatings are not obvious. The hardness of RE-Ni-W-P-SiC composite coatings is the highest when the duty cycle is at 0.6 and 0.8 and pulse frequency is at 50Hz. At the same pulse frequency, the hardness of RE-Ni-W-P-SiC composite coatings at r= 0.8 is higher than that at r= 0.6.     

RELATIONSHIP BETWEEN J-INTEGRAL AND FRACTURE SURFACE AVERAGE PROFILE

To investigate the causes that led to the formation of cracks in materials, a novel method that only considered the fracture surfaces for determining the fracture toughness parameters of J-integral for plain strain was proposed The principle of the fracture-surface topography analysis （FRASTA） was used. In FRASTA, the fracture surfaces were scanned by laser microscope and the elevation data was recorded for analysis. The relationship between J-integral and fracture surface average profile for plain strain was deduced. It was also verified that the J-integral determined by the novel method and by the compliance method matches each other well.