离子色谱电感耦合等离子体质谱研究痕量氯金酸在弱碱性体系中金(Ⅲ)的形态

采用离子色谱电感耦合等离子体质谱联用方法研究弱碱性体系下痕量氯金酸中Au(Ⅲ)的形态。结果表明:在弱碱性条件下,总金含量在4.0～30 ng之间,Au(Ⅲ)主要以[AuCl2(OH)2]μ和[AuCl(OH)3]μ的形式存在。与较高含量的氯金酸溶液相比,痕量氯金酸溶液中的[AuCl2(OH)2]μ至少可以在pH 7.0～10.0范围内存在。溶液外加的Cl-可使[AuCl2(OH)2]-含量升高同时降低[AuCl(OH)3]μ含量;当pH=7.0或Clμ浓度高于0.050 mol/L,会产生不随色谱流出的金络合物,根据水解过程推断该络合物为[AuCl3(OH)]μ。在pH 8.0～10.0,Cl-浓度在0.000～0.020 mol/L时,[AuCl2(OH)2]μ+OHμ幑幐[AuCl(OH)3]μ+Clμ的水解平衡常数为不定值,说明痕量氯金酸的水解不仅受pH值和Clμ浓度影响,还受其它因素影响。

真菌介导的纳米金合成及其应用研究进展

纳米金(AuNPs)凭借其独特的物理化学性质在多个领域得到了广泛的应用。相比于传统的化学、物理合成方法,微生物合成AuNPs凭借其环境友好、条件温和、绿色低毒等优势成为纳米技术领域的研究热点。相较于其他微生物,真菌能够分泌大量胞内或胞外蛋白/酶以及生物小分子,能够耐受较高浓度的AuCl_4^-,并且合成AuNPs的速度快、产量高、尺寸较为均一,因此具有大规模生产AuNPs的潜力。文章主要从合成AuNPs的真菌资源、影响纳米粒子形态的因素、合成机制与应用等方面进行综述,提出利用人工真菌群落合成AuNPs的新概念,并对未来该研究方向进行展望。

青海某难处理含砷金矿石工艺矿物学研究

青海某难处理含砷金矿矿石性质较为复杂,产出的金精矿金品位及回收率均较低。为充分掌握矿石性质、提高金品位及回收率,利用偏光显微镜、场发射扫描电子显微镜(SEM)等手段对矿石进行了系统的工艺矿物学研究。结果表明:①不同矿区金品位分布极不均匀,平均Au品位3.0 g/t;矿石中主要金属矿物为黄铁矿,少量闪锌矿和方铅矿以及微量黄铜矿,并且含有少量毒砂,主要非金属矿物为石英和长石,以及部分绿帘石、透辉石、绢云母、方解石。②矿石中金矿物主要为含量81.58%的银金矿,其余为含量14.80%的自然金与含量3.62%的金银矿;矿石中金矿物颗粒细小,细粒金占93.39%,微粒金占6.64%,最大粒径为31μm,最小粒径为2μm,平均粒径为10μm;金矿物的赋存状态有包裹金、晶隙金和裂隙金3种,包裹金占79.30%,晶隙金占12.76%,裂隙金占7.94%;金矿物的形态以圆粒状为主,其余为长条状与不规则状。③矿石中主要载金矿物为黄铁矿和少量毒砂,相比理想黄铁矿中铁含量,矿石中普通黄铁矿与载金黄铁矿中Fe含量分别低2.06个百分点和2.66个百分点,表现出低铁高硫的特征;普通毒砂与载金毒砂中的Fe、As含量相较于理想含量低,其中普通毒砂Fe、As含量分别低1.65个百分点、3.30个百分点;载金毒砂Fe、As含量分别低0.50个百分点、6.15个百分点,普通毒砂与载金毒砂中S含量分别比理想含量高4.28个百分点和6.65个百分点。④矿石中主要载金矿物为黄铁矿,且金的粒度为微细粒,建议通过细磨提高黄铁矿的单体解离度,同时强化黄铁矿的捕收,以进一步增加金的回收率。

桂东大瑶山地区六安金矿床金的赋存状态研究

桂东大瑶山地区是我国南方重要的黄金生产基地,多期次的构造–岩浆活动,为金及多金属矿化提供了优越的成矿条件。但是,从找矿实践来看,由于成矿理论研究相对滞后和薄弱,以致找矿思路依然局限于“就矿找矿”,虽然陆续发现了200多个金矿床(或矿化点),但总体表现为“只见星星,不见月亮”,找矿成果与该地区超强的金地球化学异常和优越的成矿地质条件严重不匹配。蚀变岩型金矿是大瑶山地区未来重要的矿产勘查类型,但有关该类型金矿的基本成矿特征研究却相对薄弱,鉴于此,本次研究选择六安蚀变岩型金矿为对象,通过详细的野外地质调查,利用显微镜、扫描电镜和电子探针等分析手段,研究矿床基本特征、典型矿石矿物组合和金的赋存状态,以期为后续矿产勘查和资源开发提供必要的依据。研究结果表明,六安金矿主要的围岩蚀变为硅化、黄铁矿化、绢云母化、绿泥石化、褐铁矿化;金的赋存状态主要为包裹金和晶格金,其中包裹金以银金矿的形式赋存于黄铁矿之中,粒度一般为10 μm;晶格金主要以类质同象形式赋存于晶型较完整的黄铁矿之中。

合质金、金泥及旧金饰品化学提纯方法研究与应用

本文根据传统提纯金方法对有害元素铅提不净的缺点,综合目前国内各种除铅技术,着重对不同形态金的除铅的新方法、基本原理,进行了论述,提出用MR化合物沉淀分离铅的方法,并通过实例验证可行。

Flow softening behavior and microstructure evolution of Al-5Zn-2Mg aluminum alloy during dynamic recovery

The flow stress behavior and microstructure development of Al-5Zn-2Mg （7005） aluminum alloy were studied by hot compression tests at deformation temperatures between 300-500 ＆#176;C and strain rates between 0.05-50 s-1. The deformed structures of the samples were observed by optical microscopy （OM）, transmission electron microscopy （TEM） and electron backscattering diffraction （EBSD） analysis. The calculated activation energy is 147 kJ/mol, which is very close to the activation energy for lattice self-diffusion in aluminum （142 kJ/mol）. Dynamic recovery is the dominant restoration mechanism during the deformation. At high strain rate of 50 s-1, temperature rise due to deformation heating leads to a significant flow softening. Microstructure observations indicated that the remaining softening after deformation heating correction at high strain rate and the softening observed at high temperature are associated with grain coarsening induced by grain boundary migration during dynamic recovery process.

Ecological risk assessment of heavy metals in sediments of Xiawan Port based on modified potential ecological risk index

Modified potential ecological risk index （MRI） was proposed based on the potential ecological risk index （RI） and risk assessment code （RAC） by modifying an index. The modified index was relevant to the chemical speciation of heavy metals. Xiawan Port, a typical region contaminated by industrial production, was selected as a case study area. The total concentrations and chemical speciation of heavy metals in sediments of Xiawan Port were analyzed. The experimental data indicate that Xiawan Port is seriously polluted by heavy metals, especially by Cd. The risks of heavy metals are evaluated by RI, RAC and MRI, respectively. The resluts of MRI show that the risks of heavy metals are in the decreasing order of Cd〉Pb〉Cu〉Zn. Comparison of results by different methods reveals that MRI integrates the characters of RI and RAC. MRI is recognized to be useful for risk managemnt of heavy metals in sediments.

Total concentrations and different fractions of heavy metals in sewage sludge from Guangzhou, China

Dewatered municipal sludge samples were collected from five municipal wastewater treatment plants （WWTPs） and one industrial WWTP in Guangzhou, China. A number of agricultural parameters and total metal concentrations in the sludge were determined. Metal speciation was also studied. The results showed that sewage sludge had high organic carbon, and was rich in such nutrients as N and P. The concentrations of Mn, Zn, and Cu were the highest, followed by Ni, Pb, and Cr, Cd had the lowest concentration. In addition, the concentrations of the aforementioned heavy metals in the sludge samples were higher than those recorded in the background data for crop soils. With the exception of Cu and Cd from site S1, and Ni from sites S1, $2, and $5, all other metal concentrations conformed to permissible levels prescribed by the national application standard of acid soil in China （GB 18918--2002）. The results of the BCR sequential extraction showed that the concentrations of Mn and Zn were predominant in acid-soluble/exchangeable and reducible fractions. Cu was principally distributed in oxidizable and residual fractions, whereas Cr was present in oxidizable and residual fractions, Pb was found in the state of residual fractions, and the distribution of Ni and Cd did not show significant characteristics.

Dynamic recovery and dynamic recrystallization of NiTi shape memory alloy under hot compression deformation

Mechanical behavior of nickel？titanium shape memory alloy（NiTi SMA） under hot deformation was investigated according to the true stress—strain curves of NiTi samples under compression at the strain rates of 0.001-1 s-1 and at the temperatures of 600？1000℃.Dynamic recovery and dynamic recrystallization of NiTi SMA were systematically investigated by microstructural evolution.The influence of the strain rates,the deformation temperatures and the deformation degree on the dynamic recovery and dynamic recrystallization of NiTi SMA was obtained as well.NiTi SMA was characterized by the combination of dynamic recovery and dynamic recrystallization at 600℃ and 700℃,but the complete dynamic recrystallization occurred at other deformation temperatures.Increasing the deformation temperatures or decreasing the stain rates leads to larger equiaxed grains.The deformation degree has an important influence on the dynamic recrystallization of NiTi SMA.There exists the critical deformation degree during the dynamic recrystallization of NiTi SMA,beyond which the larger deformation degree contributes to obtaining the finer equiaxed grains.

Hot deformation behavior of high Ti 6061 Al alloy

The hot deformation behavior of a high Ti 6061 aluminum alloy in the temperature range from 350 to 510 ℃ and strain rate range from 0.001 to 10 s^-1 was investigated using stress-strain curve analysis, processing map, transmission electron microscopy and electron backscatter diffraction analysis. The results show that the peak stress decreases with increasing deformation temperatures and decreasing strain rate. The average deformation activation energy is 185 kJ/mol in the parameter range investigated. The flow stress model was constructed. The main softening mechanism is dynamic recovery. The processing map was obtained using dynamic material model, and the suggested processing window is 400-440℃ and 0.001-0.1 s^-1.

Fracture behavior and microstructure of as-cast NiTi shape memory alloy

The as-cast ingot of equiatomic nickel-titanium shape memory alloy （NiTi SMA） was prepared by vacuum consumable arc melting. The tensile tests and the compressive tests with respect to as-cast NiTi SMA were performed to study its mechanical properties of fracture. The microanalysis of as-cast NiTi SMA as well as its fractured samples was performed so as to better understand microstructure evolution and fracture behavior of NiTi SMA. Under tensile loading, the as-cast NiTi SMA shows higher plasticity and is characterized by ductile fracture at 750℃, but it demonstrates poorer plasticity and is characterized by cleavage fracture as well as transcrystalline fracture at room temperature and -100 ℃. Under compressive loading at -100 ~C, the as-cast NiTi SMA is characterized by shear fracture where the normal to the shearing fracture surface inclines about 45° to the compressive axis, and belongs to cleavage fracture where the cracks exoand via transcrvstalline fracture.

Effects of external stress aging on morphology and precipitation behavior of θ'' phase in Al-Cu alloy

The exposure of Al-5Cu alloy to an external stress with normal aging was carried out. The effects of external stress-aging on the morphology and precipitation behavior of θ＂ phase were investigated by transmission electron microscopy （TEM）, differential scanning calorimetry （DSC） and first principle calculation. The size of the θ＂ phase precipitated plates in stress-aging （453 K, 6 h, 50 MPa） is 19.83 nm, which is smaller than that of those present （28.79 nm） in stress-flee aging （453 K, 6 h）. The precipitation process of θ＂ phase is accelerated by loading external stress aging according to the analysis of DSC results. The apparent activation energy for the external stress-aging is 10% lower than the stress-free one. The first principle calculation results show that the external stress makes a decrease of 6% in the interface energy. The effects of the stress on aging process of the alloy are discussed on the basis of the classical theory. The external stress changes the morphology and precipitation behavior of θ＂ phase because the critical nucleation energy is decreased by 19% under stress aging.

Fractional distribution and risk assessment of heavy metal contaminated soil in vicinity of a lead/zinc mine

The pollution characteristics of Pb, Cd, Zn, Cu and Ni in soil of lead-zinc mining area were studied. The results indicate that the contamination degree followed the sequence of Cd〉Pb〉Zn〉Ni〉Cu and concentrations of Pb, Cd and Zn exceeded corresponding limits of the Chinese National Soil Environmental Quality Standard III. The soil was extremely polluted by Cd（Iego=5.26）, moderately to heavily polluted by Zn（Iego=2.38）, heavily to extremely polluted by Pb（Iego=4.13）. The results of BCR three-step sequential extraction procedure show that the active Cd, Pb and Zn were relatively high and might exert adverse effects on the plants grown in the soil, while Cu and Ni existed in soil with a relatively stable form. Potential ecological risk results indicate that soils were engaging in a high potential ecological risk by pollution of Cd and should be given rise to concern.

Preparation of semi-solid A380 aluminum alloy slurry by serpentine channel

The semi-solid slurry of A380 aluminum alloy was prepared by the serpentine channel. The effects of pouring temperature, curve number and curve diameter of the serpentine channel on the microstructure of the semi-solid A380 aluminum alloy slurry were investigated. The results show that the satisfactory semi-solid A380 aluminum alloy slurry could be obtained when the pouring temperature ranged from 630 to 650 °C. Under the same conditions, increasing the curve number or reducing the curve diameter of the serpentine channel would decrease the average diameter and increase the shape factor of the primary α（Al） grains. The ＂self-stirring＂ of the alloy melt in the serpentine channel was beneficial to the ripening of the dendrites and the spheroidizing of the primary α（Al） grains.

Microstructure evolution and segregation behavior of thixoformed Al-Cu-Mg-Mn alloy

A commercial wrought Al-Cu-Mg-Mn alloy（2024） was thixoformed based on the recrystallization and partial melting（RAP） route, and the microstructure evolution and segregation behavior during the indirect thixoforming process were studied. The results show that fine spheroidal microstructures can be obtained by partial remelting of commercial extruded 2024 alloys without additional thermomechanical processing. During the indirect thixoforming, the stress distribution can be optimized by increasing the thickness of base region. Under three-dimensional compression stress state, the microstructures are homogeneous among different regions with no evidence of liquid segregation and micro-porosities, and the grains in the columns are deformed plastically. The distribution of tensile mechanical properties is consistent with the microstructures. Moreover, the distribution of deformation mechanism was discussed, and a technical method for improving the stress distribution was proposed.

Deformation mechanism and softening effect of extruded AZ31 magnesium alloy sheet at moderate temperatures

The flow stress behavior of extruded AZ31 magnesium alloy sheet was investigated by means of compression tests at temperatures between 473 and 523 K and strain rates ranging from 0.001 to 1.0 s-1. The deformation activation energy of the sheet in extrusion direction （ED） was calculated, and the relationship between the softening effect and deformation mechanism was elucidated by optical microscopy and transmission electron microscopy. The results show that when the extruded AZ31 magnesium alloy samples were compressed at moderate temperatures in ED direction, the deformation activation energy is 174.18 kJ/mol, which means that dynamic recrystallization （DRX） is the main softening effect and is controlled by cross slip of thermal active dislocation. Dislocation slip is the main deformation mechanism in moderate-temperature deformation process except twinning. The main DRX effect at moderate temperatures can be considered to be continuous dynamic recrystallization accommodated with twinning DRX.

Influence of serpentine channel pouring process parameters on semi-solid A356 aluminum alloy slurry

Semi-solid A356 aluminum alloy slurry was prepared by using serpentine channel pouring process, and the influences of the channel diameters and pouring temperatures on the semi-solid A356 aluminum alloy slurry were investigated. The experimental results show that when the channel diameter is 20 and 25 mm, respectively, and the pouring temperature is 640-680 ℃, the average diameter of primary α（Al） grains in the prepared A356 aluminum alloy slurry is 50-75 and 55-78 μm, respectively, and the average shape factor of primary α（Al） grains is 0.89-0.76 and 0.86-0.72, respectively. With the decline in the pouring temperature, the microstructure of semi-solid A356 aluminum alloy slurry is more desirable and a serpentine channel with smaller diameter is also advantageous to the microstructure imProvement. During the preparation of semi-solid A356 aluminum alloy slurry, a large number of nuclei can be produced by the chilling effect of the serpentine channel, and owing to the combined effect of the chilled nuclei separation and melt self-stirring, primary α（Al） nuclei can be multiplied and spheroidized finally.

Hot deformation behavior and processing map of Cu-Ni-Si-P alloy

The high-temperature deformation behavior of Cu-Ni-Si-P alloy was investigated by using the hot compression test in the temperature range of 600-800 ℃ and strain rate of 0.01-5 s-1. The hot deformation activation energy, Q, was calculated and the hot compression constitutive equation was established. The processing maps of the alloy were constructed based on the experiment data and the forging process parameters were then optimized based on the generated maps for forging process determination. The flow behavior and the microstructural mechanism of the alloy were studied. The flow stress of the Cu-Ni-Si-P alloy increases with increasing strain rate and decreasing deformation temperature, and the dynamic recrystallization temperature of alloy is around 700 ℃. The hot deformation activation energy for dynamic recrystallization is determined as 485.6 kJ/mol. The processing maps for the alloy obtained at strains of 0.3 and 0.5 were used to predict the instability regimes occurring at the strain rate more than 1 s-1 and low temperature （〈650 ℃）. The optimum range for the alloy hot deformation processing in the safe domain obtained from the processing map is 750-800 ℃ at the strain rate of 0.01-0.1 s i The characteristic microstructures predicted from the processing map agree well with the results of microstructural observations.

Preparation of semi-solid 7075 aluminum alloy slurry by serpentine pouring channel

The semi-solid slurry of 7075 aluminum alloy was prepared by a serpentine pouring channel （SCP）. Influences of pouring temperature and the number of turns on the microstructure of semi-solid 7075 alloy slurry were investigated. The results demonstrated that the semi-solid 7075 aluminum alloy slurry with satisfied quality could be generated by a serpentine pouring channel when the pouring temperature was in the range of 680-700 ℃. At a given pouring temperature, the equivalent size of the primaryα（Al） grains decreased and the shape factor increased with the increase of the number of turns. During the slurry preparation of semi-solid 7075 aluminum alloy, the flow direction of alloy melt changed many times when it flowed in a curved and closed serpentine channel. With the effect of“stirring”in it , the primary nuclei gradually evolved into spherical and near-spherical grains.

Simulation of temperature field and metal flow during continuous semisolid extending extrusion process of 6201 alloy tube

A continuous semisolid extending extrusion （CSEP） method was proposed. Temperature field and metal flow during continuous semisolid extending extrusion process of 6201 alloy tube were studied. During the process, the temperature in the roll-shoe cavity decreases gradually, and the isothermal lines of the alloy deviate from the shoe side to the work roll side in the roll–shoe gap. Metal flow velocity decreases gradually from the surface of the work roll to the surface of the shoe. In the extrusion mould, alloy temperature decreases gradually from the entrance to the exit and from the center to the sidewall of the mould. The extending cavity is radially filled with the alloy. The flow lines in the tube corresponding to the centers of the splitflow orifices and the welding gaps are dense, and the corresponding harness values are high; there are 8 transitional bands between them. In order to prepare 6201 alloy tubes with good surface quality, the pouring temperature from 750 ℃ to 780 ℃ was suggested.