Composite Materials for Passive Antiradar Camouflage

In this study, a new solution for the development of an antiradar camouflage by overlaying several mono-pigment polymeric structures in a composite structure is provided. In this respect, powder materials with antiradar properties (carbon nanotubes, graphite, active charcoal, aluminum trioxide) were embedded in polymeric matrices. The performances of the developed products were tested using an experimental device for the measurement of electromagnetic efficiency within the frequency range from 1 to 18 GHz.

Surface Conditioning Methods and Polishing Techniques Effect on Surface Roughness of a Feldspar Ceramic

Objective: To investigate the effects of three surface conditioning methods on shear bond strength (SBS) and on surface roughness (Ra) of a feldspathic ceramic, and to compare the efficiency of three polishing techniques. Materials and Methods: A total of 106 feldspathic specimens were used. Thirty specimens were divided into three groups according to the surface conditioning methods: air-particle abrasion (APA) with 25-μm aluminum trioxide (Al2O3) (group A); hydrofluoric acid (HFA) (group H); APA and HFA (group AH). Metal brackets were bonded and subjected to SBS testing. Sixty-three specimens were divided into three groups according to the surface conditioning method. Ra was evaluated profilometrically. Then, each group was divided into three subgroups according to the polishing technique, ie, adjustment kit, diamond polishing paste, adjustment kit + diamond polishing paste. Following polishing, the second Ra values were obtained. Results: The lowest SBS was obtained for group H. This value was significantly different from the values of groups A and AH (P < .05). The lowest Ra value was observed for group H (P < .001). There was no significant difference between groups A and AH (P > .05). No significant differences between the subgroups in which a polishing paste was used were observed (P > .05). There was no significant difference between the adjustment kit and the adjustment kit + a diamond polishing paste (P > .05). Conclusion: APA or APA + HFA created rougher porcelain surfaces than HFA alone. Both adjustment kit use and the adjustment kit + polishing paste application were effective to smooth the porcelain, but one was not found superior to the other.