一步还原法制备纳米铁粉（英文）

采用一种新方法——一步还原法制备了纳米铁粉颗粒。过量的柠檬酸在620℃有助于形成纯相、结晶高的α-Fe。纳米铁粉被X射线衍射(XRD)、透射电子显微镜(TEM)、振动样品磁强计(VSM)进行了表征,形貌观察表明产物形成了粒径在30 nm左右的近球形的纳米颗粒。磁滞回线说明了纳米铁颗粒的饱和磁化强度为198.97 A·m~2/kg,作为磁性材料具有很好的铁磁性能。一步还原法生产的颗粒粒径分布窄、可控、流程短,可用于大规模生产。     

开口型SnO_2空心球表面载银制备及其表征

以锡酸钠和尿素为原料,采用一步水热法和两步原位化学还原法分别制备出SnO_2空心球表面载有银亚纳米颗粒的复合粉体,通过X射线衍射(XRD)、扫描电子显微镜(SEM)、能谱仪(EDS)、透射电子显微镜(TEM)等研究了表面银颗粒的厚度及分布均匀性。结果表明,2种方法均能制备出平均粒径为1~4μm、分散性良好的空心微球;一步水热法制备的SnO_2空心球表面银颗粒细小且有团聚现象,而采用两步原位化学还原法在SnO_2空心球表面获得了一层由亚纳米银颗粒组成的厚度均匀的银壳,银颗粒的粒径为100~300nm;还原剂葡萄糖的浓度对银颗粒粒径及分布影响明显。     

氧化亚铜纳米颗粒的制备及其释放速率测定

针对涂料中氧化亚铜纳米颗粒作为防污剂在海水中存在释放速率不稳定的问题,采用化学还原法,通过控制溶液中葡萄糖的浓度和pH值制备出具有不同形状和粒径的氧化亚铜纳米颗粒,利用扫描电子显微镜(SEM)、X射线衍射仪(XRD)以及动态光散射粒度分析仪(DLS)表征所合成的氧化亚铜纳米颗粒的形状、粒径以及物相,利用电感耦合等离子体发射光谱仪(ICP)考察多种形状和粒径的氧化亚铜纳米颗粒在人工海水中的释放速率。结果表明:对于形状而言,球形释放速率最快,其次为正八面体,立方形释放速率最慢;在同一形状下,粒径越小释放速率越快,其中球形粒径在398.5nm的释放速率最快,立方形粒径在801.5nm的氧化亚铜释放速率最慢。     

间接电还原法合成银纳米颗粒及纳米银粉的抗菌性能

利用Keggin结构的12-磷钨酸（PTA,下同）作为还原剂,采用间接电还原法还原硝酸银制备了银纳米颗粒,考察了12-磷钨酸与Ag+离子不同摩尔配比对Ag纳米颗粒大小的影响。用透射电子显微镜(TEM)、紫外可见吸收光谱(UV-vis)、X射线光电子能谱(XPS)、X射线衍射(XRD)等手段对制备的银纳米颗粒的形貌、组分、粒径和相结构进行了表征。测试了银纳米颗粒对大肠杆菌和金黄色葡萄球菌的抗菌性能,结果表明,制备的Ag纳米颗粒的平均粒径随磷钨酸和硝酸银的摩尔比的减小而增大。纳米银对大肠杆菌和金黄色葡萄球菌生长具有较好的抑制作用,且抗菌性能稳定。     

热注入法制备银纳米颗粒及其结构表征

采用热注入法,以AgNO_3为前躯体、乙二醇为还原剂,聚乙烯吡咯烷酮为稳定剂和分散剂,制备银纳米颗粒。利用透射电子显微镜(TEM)、X射线衍射(XRD)仪和紫外-可见光分光光度计(UV-Vis)对产物银颗粒的尺寸形貌、晶体结构以及光学性能进行表征,同时根据Mie散射理论对消光谱进行模拟计算。结果表明,同传统的一步化学还原法相比,利用热注入法制备的银纳米颗粒粒径分布更加均匀,分散性更好。所制备的银颗粒呈类球形,粒度约为20 nm,其共振吸收谱线同模拟计算的结果基本符合。     

直流电弧等离子体法制备In(Sn)-O及Sn(In)(Sb)-O系纳米颗粒

采用一种新的直流电弧等离子体法,通过对熔融的金属进行爆破(或气化),制备出了单相SnO₂、In₂O₃纳米颗粒以及In₂O₃:Sn (ITO)、SnO₂:Sb (ATO)和SnO₂:In:Sb (IATO)多元复合纳米颗粒。XRD结果表明,所制备的SnO₂和In₂O₃基多元复合纳米颗粒均为单相结构,没有其它杂相;TEM结果表明,直流电弧等离子体所制备的单相纳米颗粒分散性好,尺寸约20-50nm。该法合成的纳米ITO和ATO颗粒所制备的ITO靶材和SnO₂电极密度高、电阻率低,表明所制备的ITO和ATO纳米颗粒可以应用于平板显示和导电电极领域。     

铜纳米添加剂的制备及其摩擦学性能分析

采用KBH4液相还原法制备了纳米铜颗粒,通过X射线衍射和透射电镜分析,得出所制备的纳米铜颗粒的粒径约为20nm的圆球形颗粒。分析了表面修饰的纳米铜颗粒作为润滑油添加剂的摩擦学性能和作用机理,结果表明纳米铜的加入,能在磨损表面形成一层润滑性的铜膜,从而能够有效地改善润滑油的抗磨减摩性能,降低润滑油的摩擦因数,减小摩擦副的磨损量,并得出纳米铜添加剂的最佳用量。     

微纳米铁粉热稳定性实验研究

利用管式电阻炉和X射线衍射仪(XRD)实施了对恒温退火处理100、200、300和500 nm 4种粒径的微纳米铁粉热稳定特性实验研究,通过函数拟合衍射峰图谱计算其微观应变,分析退火过程中微纳米铁粉晶粒长大现象。结果表明:微观应变的大小和晶粒长大过程密切相关,随着退火温度升高,微观应变逐渐减小,晶粒尺寸增大。100、200和300 nm微纳米铁粉200℃以下晶粒长大迅速,200℃以上长大速度减小;500 nm铁粉晶粒200℃以下长大速度比较缓慢,200℃以上晶粒迅速长大。低温下大粒径铁粉热稳定性优于小粒径铁粉。     

纳米锑掺杂对回流焊Sn-3.0Ag-0.5Cu-xSb焊点界面IMC生长的影响机理

研究了纳米锑掺杂对回流焊过程中Sn-3.0Ag-0.5Cu-xSb(x=0,0.2%,1.0%和2.0%)焊点界面金属间化合物(IMC)生长动力学的影响.借助扫描电镜(SEM)观察了焊点的微观结构,利用X射线能谱分析(EDX)及X射线衍射谱仪(XRD)确定了IMC的相和成分.结果表明,部分纳米锑颗粒溶解在富锡相中形成SnSb二元相,部分纳米锑颗粒溶解在Ag₃Sn相中形成Ag₃Sb相,剩余部分沉降在界面Cu₆Sn₅金属间化合物层表面.随着纳米锑含量的增加,IMC厚度减小.当纳米锑的含量为1.0%时,IMC厚度最小.通过曲线拟合,确定出界面IMC层生长指数和扩散系数.结果表明,IMC层生长指数和扩散系数均随着纳米锑含量的增加而减小.当纳米锑的含量为1.0%,IMC层生长指数和扩散系数均有最小值,分别为0.326和10.31×10^-10 cm²/s.由热力学相图和吸附理论可知,Sn,Sb元素之间易形成SnSb化合物,引起Sn元素的活性、Cu-Sn金属间化合物形成的驱动力和界面自由能下降,从而导致Cu₆Sn₅金属间化合物生长速率下降,抑制IMC生长.     

纳米银粉的制备及表征

采用化学还原法制备了纳米Ag粉,并通过X射线衍射(XRD)、透射电子显微镜(TEM)、红外吸收光谱(FT-IR)、热失重分析(TGA)和差示扫描量热分析(DSC)等测试手段对样品进行性能表征.结果表明:在所选择的实验条件下制备了类球形分布、分散性好的Ag纳米颗粒,其粒径主要分布在10～50nm范围,平均粒径为26nm,晶体结构与相应的块体材料基本相同,为fcc结构,具有很强的吸附性.     

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.     

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.     

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.     

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.