This work deals with the cementation of copper from sulfate solution on moving zinc beads as sacrificial metal using magnetic stirring. The efficiency of zinc beads in copper recovery has been estimated in terms of kinetic and apparent mass transfer coefficients according to operating parameters such as initial copper ion concentration, rotational speed, zinc beads diameter as well as temperature. Kinetic investigation showed that the copper cementation reaction follows a first order reaction and the activation energy was calculated. The rate of diffusion controlled cementation of copper ions was expressed in terms of the mass transfer coefficient; the data were correlated with the following dimensionless correlation: Sh = 0.7485 Sc0.33Re0.53. The resulting samples of zinc beads surface and copper precipitate were characterized by two analysis methods, scanning electron microscopy (SEM) and X-Ray (EDX) which confirmed that about 99% of copper can be recovered from the sulfate solution.
An electrochemical biosensor for sensitive detection of perfluorooctane sulfonate (PFOS) was developed based on the PFOS inhibition influence on the biocatalysis process of enzymatic biofuel cell (BFC). The one-compartment BFC was prepared used multi-walled carbon nanohorns (MWNHs) modified glassy carbon electrodes (GCE) as the substrates for both bioanode and biocathode, and glutamic dehydrogenase (GLDH) and bilirubin oxidase (BOD) acted as biocatalysts of bioanode and biocathode, respectively. The BFC generated an open circuit potential (Voc) of 30.65 mV and a maximum power density of 27.5 µW/cm2. After interaction times of 20 min, a wide linear range from 5 to 500 nmol/L between ΔVoc and PFOS concentration was achieved with good correlation R2 = 0.976 and number of measurements is three times (n = 3), and the detection limit was 1.6 nmol/L. Furthermore, we choose 4 kinds of perfluorinated chemicals, whose structures are similar with PFOS, including perfluorooctanoic acid (PFOA), nonafluorobutanesulfonic acid potassium (PFBSK), perfluorooctanesulfonamide (PFOSA) and heptadecafluorononanoic acid (PFNA), and 2 kinds of chemicals (SMNBS and SDS), which co-exist with PFOS in micro-polluted water and could possibly disturb the PFOS detection. The electrochemical biosensor exhibited good selectivity for PFOS against these chemicals. High precision with relative standard deviation (RSD) (n = 3) from 3.6 to 7.7% for PFOS detection in real water samples was also demonstrated by the standard addition method. Results obtained in this study indicated that this electrochemical biosensor could be successfully used for selective detection of PFOS in real micro-polluted water.
In order to reduce chip damage during bonding, high-temperature thick Al-0.5 mass%Cu wire bonding technology was investigated. In a previous study, we found that the reliability of the 300-µm-diameter Al-0.5 mass%Cu wire bonds was higher than conventional Al-Ni wire bonds. As the hardness of Al-Cu wire is higher than that of Al-Ni wire, the former has a higher possibility of chip damage occurrence. In this paper, by using a heated substrate, we have carried out thick Al-0.5 mass%Cu wire bonding and investigated chip damage occurrence and the reliability of the Al-0.5 mass%Cu wire bonds as a function of bonding temperature. Chip damage was evaluated by measuring the gate-emitter voltage. Al-0.5 mass%Cu wire joined at 423 K required the lowest ultrasonic power and shortest bonding time compared with 373 K and RT conditions. Also, Al-0.5 mass%Cu wire joined at both 423 and 373 K had the lowest number of damaged chips compared with RT. We also found that the reliability of Al-0.5 mass%Cu wire bonds joined at both 373 and 423 K was the same level as that of Al-0.5 mass% Cu wire bonds joined at RT.
The rate equation of hydrogen evolution reaction on spheroidal graphite cast iron which has different areas of graphite particles has been studied in sulfuric acid solutions at 298 K. The cathodic Tafel slope of −0.125 V/decade and the reaction order with respect to the activity of hydrogen ion of 1 are obtained by linear potential sweep technique. The cathodic current density due to hydrogen evolution reaction does not depend on the area of graphite particles. There is no difference in hydrogen evolution reaction mechanism between pure iron and spheroidal graphite cast iron.
A fiber-type Li-Mn-O electrode was developed for use as the positive electrode of Li-ion batteries. For the electrode preparation process, a Mn3O4 layer was formed on a carbon fiber by electrodeposition, and then the Mn3O4 plated fiber was hydrothermally treated in a LiOH aqueous solution. A structural analysis based on the synchrotron X-ray diffraction pattern indicated that the hydrothermally-treated sample contains 70 wt% orthorhombic LiMnO2 phases in addition to the 15 wt% cubic LiMn2O4 ones. After cycling, the electrode consisted of 78 wt% LiMn2O4 and 6 wt% LiMnO2 phases, indicating that the LiMnO2 phases were transformed into the LiMn2O4 ones during the cycling.
Au wire bond strength on Cu interconnects printed wiring boards was investigated for electroless Au/Pd/Ni-P pads plating prepared with knocking substrates in plating baths. A scanning electron microscope revealed that the surface of Ni-P plating formed with knocking was smoother than that of Ni-P plating formed without knocking. Furthermore, X-ray photoelectron spectroscopy indicated that no a Ni peak was recognized on Au/Pd/Ni-P plating formed with knocking, while a Ni peak was observed on ones formed without knocking. The wire bond strength to Au/Pd/Ni-P plating pads formed with knocking was larger than that to ones formed without knocking. These findings are due to removing hydrogen from a Ni-P surface by knocking substrates during formation of Ni-P plating.
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