The effect of carbon nanotube (CNT) functionalization in altering the properties of Epoxy-CNT composites is presented. The presence of functional groups effectively influenced the colloidal behavior of CNTs in the precursor epoxy resin and the hardener triethylenetetramine (TETA), which affected the synthesis process and eventually the interfacial interactions between the polymer matrix and the CNTs. The physical, thermal and electrical properties of the composites exhibited strong dependence on the nature of functionalization. At a 0.5 wt% CNTs loading, the enhancement in tensile strength was found to be 7.2, 11.2, 11.4 and 14.2 percent for raw CNTs, carboxylated CNTs, octadecyl amide functionalized CNTs and hydroxylated CNTs, respectively. Glass transition temperatures (Tg) also varied with the functionalization and composite prepared using hydroxylated CNTs showed the maximum enhancement of 34%.

No abstract

In this study the wear resistance, corrosion resistance, and oxidation resistance of boronized metallic alloys were investigated. Thermochemical treatment was performed by powder pack boronizing process at temperature 850-950°C for 4 h. Saw-tooth morphology and smooth interface microstructures were observed with an optical microscope; microhardness was measured across the coating depth. The phases present in the boron coatings depend on the substrate material. High-temperature oxidation resistance was investigated and it was found that boron coating on ferrous alloys can resist temperatures up to 800°C. The corrosion resistance of the boronized samples was improved and the corrosion rate was calculated for boronized and plain specimens. Wear testing was conducted by following the procedures of ASTM G99, ASTM D2526, and ASTM D4060. The obtained experimental results revealed that boronizing significantly improves the wear-resistance, corrosion-resistance, and oxidation resistance of metallic alloys.

This paper presents the effects of boronizing on ferrous alloys such as plaincarbon steel AISI 1018, high-strength alloy steel AISI 4340, and austenitic stainless steel AISI 304. The coatings were produced by thermochemical treatment with powder mixtures at temperatures of 850°C for 4 h. The microstructure of obtained coatings was investigated, the microhardness was measured, and the corrosion resistance and oxidation resistance were tested. By metallographic analyses, the thickness of the coatings was measured. Microhardness of the boron coatings was measured using loads of 10 gf, 25 gf, and 50 gf. Corrosion tests were performed in 5% HCl, 10% HCl, and 15% HCl at room temperature.To determine the oxidation resistance of the coatings, the isothermal method was used to observe the weight change at a temperature of 600°C for 12 h. Results indicated that the presence of boronized coatings on ferrous alloys greatly improved their microhardness, oxidation resistance, and corrosion resistance.

The high-temperature oxidation behavior of boron coating on plain lowcarbon steel AISI 1018 was studied at 500, 600, 700, 800 and 900°C in air. The oxidation resistance of unboronized (uncoated) and boronized (boron-coated) specimens was studied isothermally in a thermogravimetric analyzer. The oxidation-rate constant represented as a parabolic rate constant (k p ) was evaluated with the parabolic rate law. The activation energy of oxidation on unboronized and boronized steel specimens was determined by Arrhenius law. Optical microscopy, XRD and SEM were used for surface characterizations. The experimental results show that boronized coating increases the oxidation resistance of plain low carbon steel AISI 1018 about five times and prevents oxygen from penetrating into the steel substrate at temperatures below 900°C.