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Hydroxyapatite (HAp) has been investigated for the removal of heavy metals in environmental application. However, little is known about the influences of surface modifications of the HAp. In this paper nano-HAp-polyvinyl alcohol (PVAL) gel was synthesized under pH control and the formed gel was used for removing nickel ions. The influence of nickel ions on the surface of HAp was studied. Reaction mechanisms were followed by ICP-MS and discussed via continuous variations method (CVM), mole ratio method (MRM) and slope-ratio method (SRM). The formed gel with nickel ions was characterized by various methods including UV, FTIR, XRD, and SEM. The ICP-MS was used to analyze the supernatant solution to confirm the presence of Ca and/or Ni ions. The nickel ions were found to reduce the degree of crystallinity of the synthesized HAp phase. The present results indicate that nickel ions were completely adsorbed on the HAp structure with its anion. The validation of the nature of HAp gel as chelating agent, or complex formation as well as physical sorption was discussed.

The advent of imaging seekers in the range of (8-12) µm band poses a new challenge in the area of infrared countermeasures. The application of camouflaging tent in this field is one of the effective methods which are used to decrease the thermal signature of the targets and hot bodies in the field.In this paper a white duck textile barrier treated with white emulsion paint, aluminum metal in different forms was used to reduce the thermal image of hot plate (100 o C). The effect of aluminum powder, aluminum spray, and aluminum foil on the reduction of the thermal image was studied. The results show that, as the aluminum powder content increase from 4.2 to 8.37 mg/cm 2 the reduction in thermal image decreases from 90% to 87.3%. However, for aluminum spray, as the areal density increases from 3.7 mg/cm 2 to 11.1 mg/cm 2 the percent reduction increases from 84% to 90%. In addition to that, the application of a stream of air with volumetric flow rate of 1.2 lit/s between two identical samples improves this percent to 98.4%. The results also show that, aluminum foil supported on white duck textile has the greatest effect, where it gives 99.7% percent reduction in the thermal image. KEY WORDSThermal image, Aluminum. _______________________________________________________________ * Egyptian Armed Forces.

The reduction of radar signature for textile fabric by treating with carbon black powder dissolved in shellac solution (shellac dissolved in ethanol) is investigated. In this study, carbon black was added with known concentration in shellac solution and mixed until solution formula was homogenous. Also, the textile fabrics were chosen from the commercially available ones with known specifications and characterizations. All of them were obtained before dyeing and without any further treatment and they were prepared with known dimensions. Another different polymeric compound was used with carbon black which was commercial epoxy resin. The prepared textile fabric was treated with the solution of carbon black and dissolved shellac by impregnation of the textile sample or by coating in case of using carbon black mixed with epoxy resin. After treatment of textile fabric with the chemical solution containing carbon black, the obtained textile sample was tested by microwave reflectometer to measure the reduction in reflected radar power and so the reduction of radar signature. The results of these measurements were recorded.

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