Anode-support system for the direct electrorefining of cement copper Part III: Pretreatment and process conditions to refine industrial cement

This paper describes the final part of a study on the utilization of a special anode-support system for the electrorefining of industrial cement copper produced by small mines. This type of cement is obtained from the leaching solutions of copper oxide minerals by precipitation with iron scrap. The cement is highly contaminated with iron, different metallic and non-metallic compounds and chloride. Therefore it is necessary to purify the cement copper before the electrorefining process. A two-stage method of purification is proposed, washing with water (pH4) to eliminate chloride and soluble species and magnetic removal of the metallic iron. A circular cell provided with an annular AISI-316 stainless steel mesh supporting the mass of cement copper was utilized. A vertical rotary cylinder of AISI-316 stainless steel was used as the cathode. As operating conditions, a solution of CuSO4.5H2O: 150gdm-3 and H2SO4: 50gdm-3, jc: 5.0Adm-2, T: 40°C, u: 60rpm, were used. A cement copper of 85% purity was utilized. Under these recommended operating conditions it is possible to obtain copper sheets of good quality, meeting the ASTM B-11591 specification for commercial cathodes.     

Low-temperature inductively coupled plasma as a method to promote biomineralization on 3D printed poly(lactic acid) scaffolds

Journal of Materials Science - For bone tissue engineering, additive manufacturing offers promise in the development of biomimetic scaffolds; however, common polymers used in typical 3D printing...     

304 Stainless steel oxidation in sulfate and sulfate+ bicarbonate solutions

The electrochemical characterization of 304 stainless steel in 0.1–0.5m Na2SO4 and Na2SO4 + NaHCO3 aqueous solutions at pH8 was done in combination with SEM surface analysis. Passivation of the surface film without any pitting events is observed for the current–potential and current–time experiments, and no anodic current spikes, which are associated with depassivation events, are distinguishable above the background current level. However, SEM pictures of an electrode surface polarized at potentials above 0.4V show microscopic pit nucleation. Even when the metal may be regarded as passive from a current–time or current–potential characteristics, passivity is not stable and localized film breakdown can still occur. The events are ascribed to pit nucleation at the active inclusion sites. The pits do not grow even into the metastable state but die through repassivation by metal salt precipitation immediately after birth. The effect is ascribed to the solubility of metal salts with the electrolyte produced by dissolution in the nucleation sites. The results show that pit nucleation and pit growth are two distinct processes. The importance of solution composition and the protective effect of bicarbonate ions is also discussed.     

Analysis of the working process in a reciprocating expander in the region of wet vapor

By means of a numerical experiment with the example of methane, we analyze the features of the working process of a reciprocating expander with heat release associated with condensation, friction, and external heat exchange. The influence of the technical characteristics of expanders and inlet gas parameters is also considered. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 81, No. 3, pp. 524–529, May–June, 2008.     

Chemical stability of doped ZnO thin films

We present the results of a chemical etching stability study carried out on ZnO thin films doped with several elements deposited by spray pyrolysis. Prior to the etching, a structural study was done by X-ray diffraction and the texture of the samples was obtained by scanning electron microscopy. The samples were etched employing a solution of dilute hydrochloric acid. The etching rates obtained for the different samples depend on the dopant element and our results confirm that films doped with Cr present the highest stability against chemical etching.     

The influence of chemical treatment and suture on the elastic behavior of calf pericardium utilized in the construction of cardiac bioprostheses

Poor mechanical properties of biological tissue are known to cause wear, leading to the failure of cardiac bioprostheses made of calf pericardium. Different chemical agents such as sodium dodecyl sulfate (SDS) are presently being tested as possible inhibitors of the calcification process. The objective of this report was to determine the mechanical behavior of calf pericardium treated with SDS for 24 h and the influence of the suture on the mechanical properties of the tissue. Forty-eight samples were tested: 24 subjected to a standard treatment with glutaraldehyde (12 sewn with 4/0 silk suture thread) and 24 incubated with SDS for 24 h (12 sewn with the same suture thread). Each sutured and non-sutured sample was cut into two strips to yield paired samples. All were subjected to tensile stress to breaking point. The mean stress at breaking point in the non-sutured series treated with glutaraldehyde alone was 16.42 and 13.85 MPa depending on the region of the pericardium, while in the sutured samples subjected to glutaraldehyde the mean stress was 7.50 and 7.63 MPa, respectively, differences which were statistically significant (p = 0.03 and p = 0.003, respectively) when the means for non-sutured samples from equivalent regions treated with glutaraldehyde were compared. The stress at breaking point was lower in the SDS-treated series, ranging between 2.60 and 3.56 MPa. The mathematical functions that govern the stress/strain or deformation were obtained. In the series of pericardium treated with SDS, deformations of 10% were produced with stresses of under 0.4 MPa, an outcome that is intolerable from the constructive point of view. We established a regression model that enabled us to determine the mechanical behavior of a sutured sample by testing a contiguous piece of tissue, with a high correlation coefficient (r > 0.99). We consider this finding to be of interest in the selection of pericardium for use in the construction of leaflets for cardiac bioprostheses.     

Proposal of visual strength grading rules for Uruguayan pine timber

A previous database with bending and density data of 261 structural size specimens of currently produced Uruguayan slash pine and loblolly pine timber was adjusted to meet testing and characterization requirements of European standards. Visual parameters and mechanical properties for each specimen were evaluated and their relationship was statistically analyzed. Results suggested that all specimens can be grouped in one visual grade with engineered properties similar to those of European C14 strength class. Modulus of elasticity and characteristic bending strength were the defining properties for class assignation.     

A preliminary note on the detection and partial characterization of chicken muscle soluble proteins by immunoelectrophoresis in agarose gels

Immunoelectrophoresis in agarose gels has been used to detect and partially characterize specific protein precipitin bands of chicken muscle soluble proteins (CHSP), free of crossreactions with muscle soluble proteins of cow (CSP), pig (PSP) and horse (HSP). Six precipitin bands were obtained by reacting CHSP against an anti-CHSP antiserum produced by a rabbit. These precipitin bands did not appear when the protein extracts from cow, pig and horse were analyzed against the same anti-CHSP antiserum. The six precipitin bands were specific of the chicken muscle soluble proteins. This technique may have the potential to detect the presence of chicken meat in unheated ground meat products.     

Butyl substituents in n-butylamine and their influence on mild steel corrosion inhibition in hydrochloric acid

This paper describes a study of the influence of the butyl group as substituent in n-butylamine used as a mild steel corrosion inhibitor in hydrochloric acid solution. An inhibition mechanism is proposed. n-Butylamine, dibutylamine and tributylamine were studied in concentrations from 10–4 to 1 m and in the temperature range 278–308K using electrochemical, gravimetric and surface roughness techniques. The three inhibitors adsorbed on the mild steel according to a Frumkin isotherm.