Engineering and Technology Journal

Rice crop may be subjected to several heavy metals contamination due to various causes such as contaminated irrigating water, fertilizers containing certain heavy metals and other agricultural applications. This work was designed to examine several heavy metals (Lead, Chromium, Arsenic and Copper) in rice crop imported from India, USA, Brazil, Thailand, Paraguay and Uruguay in addition to locally cultivated rice. Rice samples were collected from local markets and subjected to the examination of above heavy metal content using acidic digestive method and heavy metal ions were determined by Atomic Absorption Spectrophotometer. It has been found that these examined rice crops have shown significant variations in terms of heavy metal content and importing countries where in case of Lead ion, Iraqi rice had the highest mean (19.27 ± 0.25 mg/kg ) content while India 1 showed the lowest (9.51 ± 0.08 mg/kg) mean value. For rice Chromium content, it was found that USA rice gave the highest (4.02 ± 0.51 mg/kg) mean value and the lowest mean content (0.15 ± 0.02 mg/kg) was detected in the Iraqi rice. Regarding rice Arsenic content, all examined rice crops had As content varying from minimum mean value of 0.2 ± 0.012 mg/kg in India2 to a maximum value of 0.37 ± 0.021 mg/kg in India1. For Copper rice content, this study has found the Iraqi crop had the highest (4.50 ± 0.07 mg/kg)

Galvanic corrosion between law alloy steel and copper couple in 4 % NaCl solution was studied and the effect of some variable were investigated. The effect of area ratio, temperature and rotational speed through the electrolyte have been investigated. An increase in galvanic current was observed when we increased the area ratio of law alloy steel to copper and the galvanic potential moved to extra negative direction. When the temperature of solution increase led to increase the galvanic current and shifting the galvanic potential to extra negative direction. The galvanic current rises clearly with increasing of rotational velocity of agitator with shifting the galvanic potential to extra positive due to mass transfer control the process. In addition, increase the diffusion of oxygen from bulk of electrolyte to the metals surface.

The present work aims to study the effect of particles shape and size of copper powder on physical, mechanical properties and wear resistance of copper-13vol%graphite composites prepared by powder metallurgy technique.Spherical and dendritic copper powder particles were used as a matrix besides a mixture of both shapes with three particle size ranges [(25>),(38-45),(53-63)]m. 13vol%graphite powder with a grain size of(63 (≤ was added as reinforcement. All powder mixtures were mixed mechanically for 2 hours. The mixed powders were cold pressed uniaxially at (700Mpa) for 30seconds and sintered at (900 oC) for one hour.
The results showed that the relative density, both electrical and thermal conductivities and compressive strength of dendritic copper composites are higher than those of spherical copper composites, for example, the maximum values for both electrical and thermal conductivities for dendritic copper (53-63)m+13vol%graphite composite were 36.01 (.m)-1, 295.55 W/m.oK respectively, while wear rate of dendritic copper composites was lower than that of spherical copper composites where the minimum value for dendritic copper composites was (1.068×10-9 g/cm) for dendritic copper (53-63)m+13vol%graphite composite. It was found through the results of the present work that relative density, hardness and compressive strength increases with decreasing copper particle size. On the other hand an improvement in wear resistance was found on decreasing the particle size.

In this work, we study a diagnostic of a copper-plasma in air using a fundamental wavelength of a Nd: YAG laser system. The optical emission spectra of copper-plasma that have been detected using a spectrum analyzer (Thorlabs GmbH) have been used to extract the excited plasma temperature via the Saha-Boltzmann method, and measure the electron number density by McWhirter criterion. Measured values of Ne and (Te) is in the range of (14890.827 K°) and (Ne) is (2.7*1015 cm-3) at the fundamental wavelength.

Metal samples such as Copper and Aluminum and alloy as Brass were prepared and machined as discs (plane sample) and as a half rings (curvature sample). The samples were polished by using metallographic paper with different grades. The micro roughness and the initial weight were measured for all samples before wear tests, and then the samples were subjected to wear testing system under lubricated condition, fixed normal load of 15N, sliding time 30 min and sliding speed of 750 rpm. During the running of wear testing system the temperature of the samples were measured .The wear rate was calculated by employing the weighing method. It is clear from the results that micro roughness values increasing leads to increase in weight loss , wear rate and the temperature of samples .The effect of sample shape on weight loss , wear rate and sample heat is also obvious when noticing that the different measurements of weight loss, wear rate and sample heat of curvature samples are higher than that of plane samples .

The corrosion behavior of copper in deaerated and oxygenated 0.1 H2SO4
solutions has been investigated using the rotating cylinder electrode under turbulent
flow conditions. Potentiostatic polarization measurements were carried out at different
bulk temperatures of 283, 288, 293 and 298 K and various speeds of rotation viz 100,
200, 300 and 400 r.p.m. The anodic dissolution of copper and the hydrogen evolution
reaction, in deaerated and oxygenated solutions, are activation controlled processes
dependent on the temperature of the solution. The anodic dissolution of copper is not
mass transfer controlled. The results are consistent with a mechanism which suggests
that oxidation of copper takes place in two steps of one electron each. The second step,
i.e., cuprous ion (Cu+) oxidation, is the rate controlling. Moreover, the mechanism of
hydrogen evolution reaction is a proton discharge upon the metal surface. The charge
transfer of the oxygen reduction reaction is a 2e process in the range of bulk
temperatures employed, i.e., the oxygen reduction is controlled by 2e process.
Furthermore, the limiting current density value of the oxygen reduction reaction
increases as the velocity of the fluid increases. The results, at a constant bulk
temperature are consistent with Eisenberg et al theory for mass transfer to a rotating
cylinder electrode surface