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Composite materials are identified to be an alternate solution for the present-day problems pertaining to the reduction of the weight of the components without compromising on their strength and stiffness. The application of the different reinforcements improves the mechanical or thermal properties of the base matrix material related to the application and the heterogeneous nature of the composite material adds flexibility in the design. The manufacturing methods of the composites have also improved in the recent past to ensure that the Reinforcements are properly distributed in the base matrix. Machining a hard composite using conventional techniques is tedious, time-consuming, and will lead to higher tool wear. Therefore, non-conventional machining processes were adopted for the machining of the composite material which can be carried out using inexpensive tooling, The present work aims at optimization of the machining parameters and helps in providing better productivity and cost-effectiveness. The material identified for the optimization was AA6351-SiC-B4C hybrid composites which have widespread application in the nuclear industry. This work aimed at the optimization of the parameters by employing Analysis of Variance (ANOVA) and Response Surface Methodology (RSM) for the identification of the optimum parameters. The current was identified to be the major contributing parameter for the machining of the composite for the output parameters considered. The optimum values for all the composites were identified to be at 12A current.100 µs Pulse on time and feed rate of wire at 8m/min irrespective of the percentage variation of B4C. It can be identified that the optimum values identified are independent of the reinforcement percentage and therefore, can be adopted for all the percentages of B4C in the composite. [ABSTRACT FROM AUTHOR]

The aim of this article is to analyse the changes of apparent activation energy (Ea) of alkali-activated materials (AAM) at temperatures up to 100°C. Apparent activation energy (Ea) refers to the minimum amount of energy is required for the occurrence of reaction. The existing AAM research is based on assumptions about Portland cement (OPC). A number of studies have been conducted on the development of concrete strength depending on, inter alia, the duration of seasoning and the liquid to solid ratio (L/S). Based on the apparent activation energy and taking into account the effect of time and temperature at the same time, the physical and mechanical properties of OPC can also be predicted. The influence of the activator on the solidification process should also be taken into account for alkali-activated materials. This article shows the effect of changes in the concentration of the alkaline solution used in the AAM process on activation energy. The synthesized AAM material uses a solution based on water glass, sodium hydroxide, sand and volatile ash from the ‘Skawina’ coal-fired power plant (located in Skawina, Lesser Poland). The chemical composition of the material used is classified as class F ash. The concentration of the alkaline solution was 8M, 10M, 12M and 14M. The described research method was based on the use of thermistors with a negative temperature factor. It enabled prediction of the physical and mechanical properties of the materials tested. The results clearly indicate that this method can be used to determine the activation energy of the AAM. However, when determining apparent activation energy (Ea), the time and activation temperature of the binding processes of these types of materials should be taken into consideration.

Currently, hydrogel materials are being widely developed and investigated. Factors affecting their properties may be mentioned, such as the types and the amounts of the reagents used for the synthesis of the hydrogel matrix and modifiers; thus, the main aim of the investigations was to check the impact of the amount of photoinitiator applied during the UV-induced polymerization of polyvinylpyrrolidone-based hydrogels incorporated with vitamin C and Aloe vera juice. The experiments that were performed were focused on determining the hydrogels' swelling capability, behavior in simulated body fluids, hydrophilicity, chemical structure (using FT-IR spectroscopy), as well as their surface morphology and roughness. It was proven that developed materials had relatively rough surfaces, they did not degrade in simulated physiological liquids, and their swelling ratios in these media were 2.0–3.0 g/g. The only change in the pH of the incubation media—a slight decrease—was caused by the release of the modifiers into the tested liquids. Subsequently, it was demonstrated that as the amount of the photoinitiator (2-hydroxy-2-methylpropiophenone) increased, the percentage elongation decreased, and the tensile strength increased. The content of the photoinitiator in the hydrogels also influenced their wettability. All samples showed hydrophilicity; the more photoinitiator in the hydrogel structure, the lower wetting angle for water. Moreover, the greater the amount of 2-hydroxy-2-methylpropiophenone, the smoother and more homogeneous the hydrogel surface; thus, considering the demonstrated physicochemical properties of developed materials, they seem to show application potential for more advanced research regarding the development of innovative dressing materials. [ABSTRACT FROM AUTHOR]