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The main goal of this study is to improve the mechanical properties of low-alloy steels using an austempering heat treatment that involves combined molten bismuth and gallium (Bi-Ga) alloys. The cooling media is an alternative to the salt media, which is commonly used for austampering heat treatment. The steel was maintained at a constant temperature of 500 °C by immersing it in a cooling medium containing gallium and bismuth. The steel achieved an improvement of 229% in hardness and a 50% increase in tensile strength. Some slight decreases in thermal conductivity and diffusivity occurred as a result of the development of bainite in austempered steel, which affected the thermal behavior of the material. Through the process of bismuth diffusion into the steel grains, phase hardening was improved. To accomplish this, maintaining carbide stability and encouraging uniform carbon distribution were key. 500 °C was the best choice for austempering, where improved mechanical qualities were equally balanced. With its enhanced tensile strength, lightweight applications are now within reach, and the steel's enhanced hardness makes it perfect for uses requiring high durability and resistance to wear. This research emphasizes the potential of molten Bi-Ga austempering to enhance the performance of low-alloy steel across several industrial applications.

The development of transforming Belulang grass (Eleusine indica) fiber into high-value-added products has not been explored. Microcrystalline cellulose (MCC) is a promising natural material that has been widely used in several sectors. This study is focused on the MCC isolation from Belulang grass fibers using alkalization, bleaching, and acid hydrolysis. The effects of these treatments on the chemical composition, surface morphology, crystallinity, and thermal stability of the fibers were evaluated using various techniques. Fourier-transform infrared (FTIR) analysis confirmed the removal of lignin and hemicellulose content through treatments like alkalization and acid hydrolysis. Scanning electron microscopy (SEM) revealed a transformation in the fiber surface from a bundled structure to individual rods with average lengths of 15.64 μm after acid hydrolysis. Acid hydrolysis significantly increased the cellulose content by 119.2 %, while simultaneously reducing hemicellulose and lignin contents by 72.6 % and 84.1 %, respectively. X-ray diffraction (XRD) analysis demonstrated a remarkable increase in crystallinity index from 51.87 % to 75.76 % following hydrolysis. Moreover, thermogravimetric analysis (TGA) confirmed the enhanced thermal stability of MCC, with a decomposition temperature reaching up to 366.53 °C. These findings suggest that MCC derived from Belulang grass has the potential to be a sustainable alternative to synthetic materials for reinforcing biocomposites.

Sansevieria trifasciata fiber (STF) has a high cellulose content and considerable potential as a polymer composite reinforcement. This study aims to investigate the effect of alkali treatment on the physicochemical properties, tensile strength, thermal properties, and surface characteristics of STF. We explored the chemical changes in STF that had undergone alkali treatment and achieved an optimum increase in cellulose content of 51.8 % by weight. Soaking the STF for 120 minutes significantly changed its chemical composition. XRD analysis results indicated an increase in crystallinity index and fiber size by 75 % and 68 nm, respectively. After surface treatment, the density of STF increased to 1225 kg/m3, while the percentage of total weight decreased. Thermogravimetric testing provided relevant data for mechanical and thermal characteristics, including an increase in tensile strength to 535 MPa, a tensile modulus of 4.23 GPa, and thermal stability up to 371 °C. In addition, modification of the fiber surface by alkalization increased the wettability of the matrix, which in turn improved the ability of the fibers to interact with the resin. Observation of fiber morphology showed a reduction in lignin and hemicellulose content, which in turn improved the properties of the resulting composite. These results indicate that STF with optimized surface modification has the potential to be an excellent reinforcement for polymer composites.

Purun fiber (PF), which has been used as a raw material for handicrafts, can be used as a filler in composite materials. The purpose of this study is to determine the characteristics of polyester composites with the addition of PF filler at concentrations (5, 10, and 15 %) with arrangements, namely parallel, random, and woven. In this study, the method used was the press molding method with a size of 20 × 20 × 0.3 cm. The resulting composite was analyzed for functional groups, physical properties, morphological properties, mechanical properties, and thermal properties. The functional group results of PF treatment showed a sharp absorption at wave numbers 1724–2983 cm−1, indicating the presence of C=C vibrations in the aromatic ring. For all fiber arrangements, the addition of 10 % PF resulted in the best composite structure. The results of the highest composite physical properties include density, water absorption, and thickness swelling of 0.958 g/cm−3, 10.079 %, and 24.57 × 10−3, respectively. The results of the highest composite mechanical properties are tensile strength, tensile modulus, elongation, and flexural strength of 813.9519 MPa, 9345.737 MPa, 14.06 MPa, and 58.8399 MPa, respectively. While the results of the thermal properties that can be seen from the percent weight loss of the composite obtained the best results in random samples with a variation of 10 %, the effect of the PF filler ratio on composite heat flow obtained the best results, namely in samples parallel to 5 % with a temperature of 500.87 °C. It can be summarized that PF has the potential as a filler in the manufacture of composites.