Contribution à l'étude de la lixiviation de la chalcopyrite

A study of the kinetics of chalcopyrite dissolution in sulfuric acid medium under oxygen pressure of 70 psia (0.48 MPa) was made on a chalcopyrite concentrate as function of acid concentration, temperature, and grain size. An evaluation of the real surface, an examination of the surface of the grains by scanning electronic microscope, and an analysis of the residue by energy dispersion of X-rays were carried out for different leaching periods. The dissolution kinetics vary sensibly with grain size, leaching temperature and normality of the original solution. 80% of copper can be leached out of the concentrate after 10 hours of dissolution at 90'C with a solution of 1.8 N sulfuric acid and for a grain dimension of 5 pm. An exponential function is found suitable to explain the kinetics of leaching till the slowing of the copper dissolution is achieved. The nature of the attack is electrochemical with different forms. Crevice corrosion under deposits is an important contributing factor in dissolution and in slowing of the dissolution at the end of the process.     

La Lixiviation de concentres de sulfures de nickel par le chlorure ferrique

The effectiveness of ferric chloride leaching of nickel sulphide concentrates and of a nickel sulphide matte has been demonstrated. Ferric chloride concentrations ranged from 1 M to 5.7 M for treatment of the concentrates and 0.6 M to 3.8 M for that of the matte; experiments were carried out at 80 ± 1°C.The rate of the reaction was markedly slower after the dissolution of ～ 70% of the Ni. Concentrations of ferric chloride have a significant effect upon the quantity of elemental sulphur obtained. During leaching, a part of the iron from the leachant precipitated out. β-NiS is formed during the treatment of a nickel sulphide matte with ferric chloride.The reaction was followed by continuous measurements of pH, conductivity, redox potential and spectrophotometric intermittent measurements concerning nickel concentrations.     

A Time Frequency-Based Approach for Defect Detection in Composites Using Nonstationary Thermal Wave Imaging

Russian Journal of Nondestructive Testing - Characterization of various industrial components without impairing their future utility increases the necessity of nondestructive testing (NDT)...     

Electrochemical behaviour of rapidly solidified and conventionally cast Cu-Ni-Sn alloys

The corrosion behaviour of microcrystalline Cu-Ni-Sn alloys produced by rapid solidification was studied and compared to that of conventionally cast alloys. Due to the great chemical homogeneity provided by rapid solidification, the corrosion resistance of the microcrystalline material was superior to that of conventional material. The former material developed a more uniform and homogeneous barrier layer in 3% NaCl solutions. The electrochemical behaviour of the studied alloys was dependent on the Sn content. The influence of the Ni content on the corrosion performance of both types of materials is also discussed.     

Chitosan hydrogel‐coated cotton fabric: Antibacterial,pH‐responsiveness,and physical properties

In this work, chitosan hydrogel has been synthesized and used to impart pH‐sensitivity and antimicrobial finish to cotton fabric. In order to enhance the incorporation rate of hydrogel, anionic, and cationic activation of the textile surface was applied and then compared. The antibacterial activity of the fabric was then studied. The results revealed an enhancement of the antibacterial activities of the modified fabrics against Escherichia coli, Listeria monocytogene, and Staphylococcus aureus bacteria's. The capacity of material to respond to pH change was studied and confirmed using contact angle method. The anionic fabric treated with hydrogel showed a better pH‐responsiveness. Scanning electron microscopic testing results has also confirmed that the deposition of hydrogel was clearly better with the anionic activation. The characteristics of breathability of the fabrics were analyzed. The results show that the moisture management behavior of the finished materials is significantly better than the control one. Although the permeability to air has reduced by 10%, the permeability to water vapor remained practically unchanged. Furthermore, the effects of the antibacterial finishing on the physical properties of the cotton fabrics were also investigated. It was established that the functionalized samples have changed structure parameters, thickness, air permeability, tensile strength, and resistance to wrinkles. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46645.     

Structural,electric modulus and complex impedance analysis of ZnO/TiO2 composite ceramics

ZnO/TiO₂ composite ceramics have been prepared by solid‐state reaction technique at 900°C. The X‐ray diffraction results revealed the formation of secondary phases referred to as spinel Zn₂TiO₄ and hexagonal ZnTiO₃. The structural analysis showed that all the composites that have been prepared have a polycrystalline nature and a hexagonal wurtzite structure. The complex modulus (M) and electric impedance of the samples have been investigated by broadband dielectric spectroscopy in a wide range of temperature (40°C‐110°C) and frequency (0.1 Hz to 10 MHz). The modulus plots (M′′, M′) illustrate the presence of non‐Debye type of relaxations attributed to the effects of interfacial and dipolar polarizations. The real and the imaginary parts of the impedance are well fitted to equivalent circuit models. At high temperatures, Z″_max varies from 0.03 × 10⁶ to 4.9 × 10⁶ Ω when the TiO₂ doping concentration increases from 1 to 7 wt%. From the obtained results, the secondary phase ZnTiO₃ plays an important role in the electrical properties.     

Influence of different parameters on compression strength of foam steel produced by slip reaction foam sintering

In this study, a 2⁴ factorial design was used to investigate the magnitude effects of sintering temperature, mill scale, carbon content and starch additions on compression strength of produced foam steel. The design was based on experimental results of compression test of steel foam with additions of mill scale up to 20%, carbon up to 0.5%, sintering temperatures from 1000 to 1200°C with starch (from 3 to 12%). MatLab was used to carry out the required calculations. Regression models were used to deduce a mathematical formulation to predict the influence of different parameters on compression strength of foam steel.

The results showed that mill scale addition has the highest positive effect while the interaction combination between starch with carbon has the highest negative effect on compression strength. The results of the driven model were found to be in good agreement with the experiments and publishing work.     

Composite electronic materials based on poly(3,4-propylenedioxythiophene) and highly charged poly(aryleneethynylene)-wrapped carbon nanotubes for supercapacitors

Supercapacitor charge storage media were fabricated using the semiconducting polymer poly(3,4-propylenedioxythiophene) (PProDOT) and single-walled carbon nanotubes (SWNTs) that were helically wrapped with ionic, conjugated poly[2,6-{1,5-bis(3-propoxysulfonicacidsodiumsalt)}naphthylene]ethynylene (PNES). These PNES-wrapped SWNTs (PNES-SWNTs) enable efficient dispersion of individualized nanotubes in a wide range of organic solvents. PNES-SWNT film-modified Pt electrodes were prepared by drop casting PNES-SWNT suspensions in MeOH; high stability, first-generation PProDOT/PNES/SWNT composites were realized via electropolymerization of the ProDOT parent monomer (3,4-propylenedioxythiophene) in a 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide/propylene carbonate solution at the PNES-SWNT-modified electrode. The electrochemical properties of PProDOT and PProDOT/PNES/SWNT single electrodes and devices were examined using cyclic voltammetric methods. The hybrid composites were found to enhance key supercapacitor figures of merit (charge capacity and capacitance) by approximately a factor of 2 relative to those determined for benchmark Type I devices that exploited a classic PProDOT-based electrode material. The charge/discharge stability of the supercapacitors was probed by repeated rounds of cyclic voltammetric evaluation at a minimum depth of discharge of 73%; these experiments demonstrated that the hybrid PProDOT/PNES/SWNT composites retained ~90% of their initial charge capacity after 21,000 charge/discharge cycles, contrasting analogous data obtained for PProDOT-based devices, which showed only 84% retention of their initial charge capacity.     

Optimized solar-powered liquid desiccant system to supply building fresh water and cooling needs

This paper studies the feasibility of using a solar-powered liquid desiccant system to meet both building cooling and fresh water needs in Beirut humid climate using parabolic solar concentrators as a heat source for regenerating the liquid desiccant. The water condensate is captured from the air leaving the regenerator. An integrated model of solar-powered calcium chloride liquid desiccant system for air dehumidification/humidification is developed. The LDS model predicted the amount of condensate obtained from the humid air leaving the regenerator bed when directed through a coil submerged in cold sea water. An optimization problem is formulated for selection and operation of a LDS to meet fresh water requirement and air conditioning load at minimal energy cost for a typical residential space in the Lebanon coastal climate with conditioned area of 80 m² with the objective of producing 15 l of fresh drinking water a day and meet air conditioning need of residence at minimum energy cost. The optimal regeneration temperature increases with decreased heat sink temperature with values of 50.5 °C and 52 °C corresponding to sink temperatures of 19 °C and 16 °C.