Papers by Keyword: Metals

Abstract: Wetting behavior and interfacial characteristic of the Sn-3.5Ag/Ni system are investigated by sessile drop method at the temperature range of 523~773K. The reactive wetting processes demonstrate that: contact angles between the solder and Ni substrate decrease as exponential decay and the equilibrium contact angles decrease monotonously with the temperature increasing. Triple-line mobility is enhanced as the temperature increases. Compositions of the Sn-3.5Ag/Ni interface are identified by EPMA and EDS analysis as Ni₃Sn₄ adjacent to the solder and Ni₃Sn adjacent to the Ni substrate, respectively. The formation of the interface IMC was known to greatly improve the reliability of the solder joints in integrated circuits.

Abstract: In recent years, the number of End-of-Life Vehicle has increased dramatically, the prevention and control pollution and resource recycling become increasingly serious. The paper analyzes the scrapped automobiles recycling methods in metal materials, non-metallic materials, such as plastic, rubber, glass, specially, propose the new composite materials recycling method. Through these materials recycling method, provide references for the scrap automobile materials recycling in our country.

Abstract: Thespreading of nitrogenous compounds into the environment is a common challenge duringmining industries. Typical explosives used in mining are N-based compoundswhich lead to nitrogen contamination of groundwater and water bodies. In goldextraction, cyanide used as lixiviant is also another source of nitrogen pollution.The present work aims to investigate the effect of heavy metals ondenitrification using batch bioassays. Cu, Ni, Co and Fe influence ondenitrification process was studied at pH 7.0. Below the soluble concentrationof 62 mg/L, Ni did not inhibit denitrification, whereas denitrification wasrepressed at soluble Ni concentration above 62 mg/L. At 122 mg/L of soluble Ni,50% inhibition of denitrification was observed. Below soluble concentration of86 mg/L, Co exerted no inhibitory effect on nitrate removal but moderatelydecreased the denitrification rate. Cu slowed denitrification down resulting in40% of nitrate removal averagely at the soluble concentration below 1 mg/L. Onthe contrary, Fe supplementationresulted in iron oxidation and soluble Fe concentrations ranging from 0.4-1.6mg/L that stimulated denitrification. Thepresent work indicates that denitrification can tolerate heavy metals and canbe suitable for acid mine drainage remediation.

Abstract: Molybdenum films with flat and smooth surfaces were prepared on Si (100) substrates using a pulsed laser deposition method. results indicate that increased laser fluence results in narrower diffraction peak, higher surface roughness, and transition from amorphous state into polycrystalline state with gradually increased grain size. The growth mechanism of the films and the effects of particle energy on the growth of the films are discussed based on an analysis of the changes in the crystallization process with laser fluence.

Abstract: The quenching and partitioning (Q&P) process was performed on high strength steel WHT1300HF at 250-350 °C for 30 to 90 s, respectively, for the improvement of its product of strength and plasticity (PSP). ε-carbide precipitation was observed in all the specimens partitioned at each temperature for different periods of time due to inadequate amount of Si in the composition of WHT1300HF steel. The volume fraction of retained austenite at room temperature in the partitioned specimens is extremely low due to the lack of carbon enrichment in untransformed austenite at the partitioning temperature as a result of the carbide precipitation. The decrease of tensile strength and increase of elongation are caused by the partitioning treatment, a maximum value of the PSP (17.6 GPa%) is achieved by partitioning at 300 °C for 60 s.

Abstract: In order to make clear about the effect of cryogenic temperature on the microstructure evolution of alloy, the as-cast AZ91 magnesium alloy was subjected to the cryogenic treatment after solution treatment (415°C,5h) and aging treatment (190°C, 16h) with the protection of graphite power. Transmission Electron Microscope was utilized to characterize the microstructure of as-treated sample. The results show that a high volume fraction of nanocrystalline can be found in the treated alloys with the average sizes are about 55nm. The phenomenon highlights the importance of cryogenic temperature in forming nanostructures. During the continuous contraction of alloy the micro dynamic plastic deformation induces the generation, movement and accumulation of high-density dislocations that give rise to the formation of nanocrystalline during recovery and recrystallization.

Abstract: 7055 aluminum alloy was processed by circular cryogenic-aging treatments for four times. Some characters such as precipitates, dislocation density, crystal structure and micro hardness were studied in detail. It is showed that the sizes of precipitates are decreased from several hundred nanometers to 100nm with the increase of cycle index. The main components are AlZn or AlZnMg phases. The hardness test result illustrates that the micro hardness arrives at 232HV after circular cryogenic-aging treatment for twice. The corresponding precipitates exhibit high density and complex sizes. The sizes are in the range of 50-200nm.

Abstract: The presence of heavy metals in the environment can be detrimental to a variety of living species including human. River crabs are sensitive to heavy metals .The concentrations of cadmium, copper, lead and zinc were analyzed in muscles, hepatopancreas, gills and exoskeletons using ICP-MS . Zinc was greater in muscles and hepatopancreas, whereas copper was greater in muscles and gills. Cadmium and lead were within the range of limits for hazardous substance about the pollution-free food. Then river crab can be an effective bioindicator for assessing metal levels in environment.

Abstract: The recombinant Saccharomyces cerevisiae expressing human hepatic metallothionein (MT) was constructed for biosorption of cadmium (II). The gene sequence of mt was modified for codon preference of S. cerevisiae and synthesized using chemical method. The maximal biosorption capability of cadmium compounds Cd²⁺ of the recombinant increased more than 25.8% compared with the control. For MT-expressed recombinant strains, a rapid adsorption occurred within the first 30 min with a significant level of Cd²⁺ (55.75mg/g). For comparison, S. cerevisiae cells reach its maximal Cd²⁺ adsorption capacity (45.02 mg/g) until 2h. Furthermore, recombinant strain were able to withstand the toxicity of Cd²⁺ and grow. The results indicated that recombinant should be useful in enhancement the tolerance and biosorption of cadmium in practice.

Abstract: Biochar has caused great interest due to its sequestrating carbon and improving soil fertilities. It has been increasing attracted and applied to agriculture systems. However, many toxic compounds (e.g., polycyclic aromatic hydrocarbons (PAHs), volatile organic compounds (VOCs),heavy metals) are likely to be formed during biochar production. These compounds may be existed in biochar matrix and even bioavailable to exposed organisms. Therefore, the formation and impact factors as well as the concentrations and bioavailability of these compounds are reviewed.