贵州水银洞超大型金矿床矿石初步研究

通过对水银洞超大型金矿赋存于Sbt（构造蚀变体）中的金矿石初步研究，表明该类型矿石物质组成较复杂，矿石有用组分除Au外，Ag—As—S皆达综合利用指标，有两件样品中Tl含量在0．0015％～0．0122％之间，达综合利用指标。矿石中的金以包裹金为主，暴露金次之，硫化物中金的分配率为40．07％，仅为金的较主要载体，而碳酸盐矿物和硅酸盐矿物中金的分配率则高达34．79％。

板其金矿金的赋存状态研究

板其金矿属“卡林型”未氧化原生金矿,直接氰化的浸出率很低。本文着重研究了金在主要载体矿物——硫化物(黄铁矿、毒砂)、粘土矿物(水云母)及碳酸盐(方解石、铁白云石)、石英等矿物中的分布;测定了暴露金与包裹金的含量。得出工艺样中包裹金约占67％,主要包裹在硫化物中,少量在碳酸盐、石英中;暴露金约占33％,主要分布在水云母中。最后对矿石中金的赋存状态进行了探讨。矿石中包裹金主要以胶体分散金形式存在,金以溶胶状分散于黄铁矿、毒砂、方解石、石英等结晶矿物中。

Microstructure evolution of laser deposited Ti60A titanium alloy during cyclic thermal exposure

Cyclic thermal exposure tests of infrared heating to 800 ℃ in 120 s followed by compressed air cooling to 150 ℃ in 60 s were performed for the laser deposited Ti60A （Ti5.54Al3.38Sn3.34Zr0.37Mo0.46Si） alloy. The effects of thermal exposure cycles on length ofβphase, area fraction ofαphase and microhardness of alloy were examined by OM, SEM and EDS. The results indicate that thermal exposure cycles have significant effects on length ofβphase, area fraction ofαphase and microhardness of the alloy. The original fine basket-weaveβand 78.5%αtransform to transient wedge-likeβ, finally leaving granularβand 97.6%coarsenedαwith the increased thermal exposure cycles. The formation mechanism of coarsenedαand broken-upβmicrostructure is discussed. The alloy after 750 thermal exposure cycles has the maximum microhardness, 33.3%higher than that of the as-deposited alloy.

Effect of thermal exposure on microstructure and mechanical properties of Al-Si-Cu-Ni-Mg alloy produced by different casting technologies

The effect of thermal exposure at 350 ℃ for 200 h on microstructure and mechanical properties was investigated for Al-Si-Cu-Ni-Mg alloy, which was produced by permanent mold casting(PMC) and high pressure die casting(HPDC). The SEM and IPP software were used to characterize the morphology of Si phase in the studied alloys. The results show that the thermal exposure provokes spheroidization and coarsening of eutectic Si particles. The ultimate tensile strength of the HPDC alloy after thermal exposure is higher than that of the PMC alloy at room temperature. However, the TEPMC and TEHPDC alloys have similar tensile strength around 67 MPa at 350 ℃. Due to the coarsening of eutectic Si, the TEPMC alloy exhibits better creep resistance than the TEHPDC alloy under studied creep conditions. Therefore, the alloys with small size of eutectic Si are not suitably used at 350 ℃.

Comparative transcriptomics reveals genes involved in metabolic and immune pathways in the digestive gland of scallop Chlamysfarreri following cadmium exposure

Chlamys farreri is an economically important mollusk that can accumulate excessive amounts of cadmium(Cd). Studying the molecular mechanism of Cd accumulation in bivalves is difficult because of the lack of genome background. Transcriptomic analysis based on high-throughput RNA sequencing has been shown to be an efficient and powerful method for the discovery of relevant genes in non-model and genome reference-free organisms. Here, we constructed two c DNA libraries(control and Cd exposure groups) from the digestive gland of C. farreri and compared the transcriptomic data between them. A total of 227 673 transcripts were assembled into 105 071 unigenes, most of which shared high similarity with sequences in the NCBI non-redundant protein database. For functional classification, 24 493 unigenes were assigned to Gene Ontology terms. Additionally, Eu Karyotic Ortholog Groups and Kyoto Encyclopedia of Genes and Genomes analyses assigned 12 028 unigenes to 26 categories and 7 849 unigenes to five pathways, respectively. Comparative transcriptomics analysis identified 3 800 unigenes that were differentially expressed in the Cd-treated group compared with the control group. Among them, genes associated with heavy metal accumulation were screened, including metallothionein, divalent metal transporter, and metal tolerance protein. The functional genes and predicted pathways identified in our study will contribute to a better understanding of the metabolic and immune system in the digestive gland of C. farreri. In addition, the transcriptomic data will provide a comprehensive resource that may contribute to the understanding of molecular mechanisms that respond to marine pollutants in bivalves.

Evolution of surface roughness of a cast Al-Si-Cu piston alloy during thermal exposure

In the present work,samples of Al-Si-Cu piston alloy after T6 heat treatment were exposed for 2 h at temperatures ranging from 400 to 550°C.The evolution of surface roughness and microstructure of the alloy during thermal exposure was studied by combination methods of roughness profiles,optical and scanning electron microscopy as well as XRD analysis.It is found that the roughness and mass of the alloy increase with the raise of the thermal exposure temperature,and the increasing rates of them are slow as the exposure temperature is below 500°C,but accelerates abruptly when the temperature is higher than 500°C.The variation of surface roughness of the alloy is closely related to phase transformation and oxidation during the thermal exposure.