Advances in Science and Technology Vol. 179

Abstract: Traditional Portland cement production generates substantial CO₂ emissions, hindering sustainable low-carbon building materials. This study develops a cement-free alkali-activated geopolymer using metakaolin as the primary binder, blended with 0%, 10%, and 20% ground granulated blast-furnace slag (GGBFS) by weight, activated by sodium hydroxide and sodium silicate. It examines physical properties, including setting time, compressive strength, and volumetric stability, under varying GGBFS levels, with chemical analysis via FTIR and DTG. Increasing GGBFS accelerates polymerization, reducing initial setting time from 4 hours (0% GGBFS) to 2 hours (20% GGBFS), with final setting time similar. Compressive strengths (MPa) under ambient curing at 1, 7, and 28 days for M100S0, M90S10, and M80S20 are 8.34/13.34/26.28 at 1 day, 31.77/45.90/45.68 at 7 days, and 34.8/45.4/42.1 at 28 days. Early-age strength improves with higher GGBFS due to additional calcium facilitating C-S-H gel formation, while strengths stabilize beyond 28 days. Volumetric stability shows no significant shrinkage or expansion within three days across mixtures, with maximum strain below 0.12%, indicating excellent stability. FTIR shows enhanced Si-O-Al bond intensity (~1050 cm⁻¹) in GGBFS samples, reflecting greater Al incorporation into silicate tetrahedra and denser amorphous structure. The O-H stretching peak (~3400 cm⁻¹) narrows slightly, signifying reduced water and improved polymerization. DTG corroborates enhanced polymerization efficiency with GGBFS. These results highlight superior mechanical properties and stability of GGBFS-blended metakaolin geopolymers, positioning them as promising for subgrade soil stabilization, improving early bearing capacity and long-term durability for sustainable construction.

Abstract: Smart construction systems require materials capable of autonomously detecting structural damage with high precision and reliability. This study develops self-sensing cementitious composites and evaluates their feasibility using a damage-mechanics-based framework. Mechanical loading tests were performed while monitoring electrical resistance, and the correlation between fractional change in resistance and damage variable was quantitatively assessed. The conductive network generated by dispersed functional fibers enabled deformation-induced electrical variation, providing real-time sensing capability. Unlike prior studies focusing solely on electrical response, this work integrates continuum damage mechanics to establish a predictive electro-mechanical relationship. Results demonstrate a strong correlation between electrical response and internal damage evolution, validating the feasibility of applying these self-sensing composites to smart structural systems for health monitoring and early-stage damage detection.

Abstract: This study investigated the feasibility of using hydrogels based on 2-acrylamido-2-methylpropane sulfonic acid sodium salt (AMPS-Na⁺) as rigid solvent gels for cleaning art surfaces. Hydrogels were synthesized from AMPS-Na⁺ (10–50 %w/v) using ethylene glycol dimethacrylate (EGDM, 0.05–0.25 mol%) as a crosslinker and 2,2′-azobis (2-methylpropionamidine) dihydrochloride (CPAD, 0.05–0.25 mol%) as an initiator under UV irradiation. The gel formation, swelling capacity, and water retention were evaluated to determine the optimal composition. Results showed that 50% AMPS combined with 0.25 mol% EGDM and 0.25 mol% CPAD produced a stable, transparent hydrogel with excellent swelling ability (6,793%) and structural uniformity. FTIR spectra confirmed successful copolymerization of AMPS, EGDM, and CPAD, maintaining functional groups such as –SO₃⁻ and C=O without chemical degradation. DSC thermograms revealed improved thermal stability and homogeneity at higher CPAD concentrations. The optimized hydrogel exhibited high water uptake, controlled evaporation, and reusability, suggesting strong potential as a safe and effective cleaning.

Abstract: Porous starch (PS) was used as a carrier agent for cinnamon essential oil (CEO) for the development of an active food packaging film. This study aimed to investigate polyvinyl alcohol (PVA), PVA incorporated with CEO (PVA-CEO), and a composite PVA film enriched with PS loaded with CEO (PVA-PSCEO). The results showed that the PVA-PSCEO film exhibited a tensile strength (TS) of 24.48 ± 0.70 MPa, an elongation at break (EAB) of 365.94 ± 6.76%, and a water vapor permeability (WVP) of 4.3523×10⁻⁸± 3.1008×10⁻⁸ gH2O.m/m²·h·Pa. The PVA-PSCEO significantly increased thickness and UV-protection ability compared with PVA and PVA-CEO. The CEO release profile of the PVA-PSCEO film also demonstrated a slow-release behavior. Films containing either CEO or PS-CEO both exhibited antioxidant activity and antimicrobial properties. SEM analysis revealed that the loading of CEO into PS improved the dispersion of CEO within the film. FTIR spectra indicated the presence of interactions among PVA, PS, and CEO. Therefore, this slow-release active film shows strong potential for food packaging applications.

Abstract: This study aimed to develop β-cyclodextrin (β-CD) microcapsules containing cold-pressed avocado oil (AO) using an optimized co-precipitation method. The AO was extracted by cold pressing, yielding 31.12%. Prior to microencapsulation, the antioxidant activity and total phenolic content of AO were analyzed, showing an antioxidant activity of 85.25 ± 1.22% and a total phenolic content of 95.34 ± 1.10 mg GAE/L of oil. The effect of varying ethanol concentrations (30%, 40%, 60%, 80%, and 100% v/v) on encapsulation efficiency was systematically investigated. Using β-cyclodextrin as the encapsulating agent and 80% ethanol produced the highest encapsulation performance, with a microcapsule recovery yield of 89.45 ± 0.71% and an encapsulation efficiency of 75.25 ± 0.54% for AO. Characterization of the AO-β-cyclodextrin inclusion complex by scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and thermal analysis revealed notable changes in spectra and thermal profiles, confirming the formation of the inclusion complex. The antioxidant activity and total phenolic content of the microcapsules prepared with 80% ethanol and an AO-to-β-cyclodextrin ratio of 1:0.5 w/w were evaluated after 1.5 months of storage. The results demonstrated the antioxidant activity and total phenolic content of 87.01±0.54% and 98.29±0.19 mg GAE/L of oil, respectively. The results indicated that the microcapsules effectively stabilized AO. These findings suggest that the AO-β-cyclodextrin inclusion complex is a promising bioactive system for the development of functional foods and cosmetic formulations.

Abstract: This research aims to fabricate and analyze asymmetric polylactic acid (PLA) membranes and evaluate their performance in the removal of methyl orange (MO) dye through a microfiltration process. The asymmetric PLA membranes were synthesized via the non-solvent induced phase separation (NIPS) method. A polymer solution containing 14 wt.% PLA dissolved in 86 wt.% N,N-dimethylacetamide (DMAc) was prepared with varying amounts of TiO₂ (0, 0.5, and 1.0 wt.%). The cast membranes were immersed in a coagulant bath consisting of methanol and distilled water in an 80:20 ratio. Several characterization methods were employed: membrane porosity was measured using the gravimetric method and hydrophilicity was assessed by water contact angle. Membrane performance was evaluated in terms of water flux and permeability under a transmembrane pressure of 1 bar, as well as the removal efficiency of methyl orange dye. In addition, the photocatalytic activity of the membranes was investigated to determine its effect on dye removal. The results showed that membrane porosity decreased with increasing TiO₂ content (from 53.7% to 45.1%), while water contact angle also decreased (from 72.7° to 56.1°), indicating improved hydrophilicity. The incorporation of TiO₂ enhanced water flux (11,526.8–14,628.4 L/m²h), permeability (5763.4–7314.2 L/m²h·bar), and methyl orange removal efficiency (65–69.8%). Furthermore, photocatalytic reactions further improved dye removal efficiency with increasing TiO₂ content (up to 84.3%).

Abstract: This study investigates the production and application of biochar derived from Nannochloropsis gaditana residue for sustainable soil amendment. Pyrolysis conditions were optimized by varying temperature and residence time: 300°C for 30 minutes (Sample A), 500°C for 60 minutes (Sample B), and 700°C for 90 minutes (Sample C). Biochar characterization included SEM (morphology), FTIR (functional groups), pH analysis, and ICP-MS (trace elements). Sample B, produced at 500°C for 60 minutes, showed the most favorable properties; high porosity, balanced functional groups, and optimal alkalinity (pH 9.41). Sample C was highly porous and alkaline (pH 9.83) but lacked reactive groups, while Sample A retained labile nutrients with moderate porosity and pH (7.64). These results demonstrate the potential of microalgae-based biochar to improve nutrient-poor, acidic soils and support environmentally friendly alternatives to chemical fertilizers in Malaysia.

Abstract: In this study, flexible aerogels were fabricated using carrot cellulose nanofibers (CCNF) combined with graphene oxide (GO) or reduced graphene oxide (RGO). GO was thermally treated to produce RGO in order to enhance the material's thermal conductivity, while retaining some functional groups that react with CCNF to form the aerogel. The 3D porous structure of these aerogels effectively supports phase change materials (PCMs). Magnesium nitrate hexahydrate (MNH) was then adsorbed onto the aerogels as the PCM to form the phase change aerogels. These phase change aerogels can adsorb up to 96.0% of MNH, and their phase change enthalpy reaches 100.9 J/g. The thermal conductivity of the aerogels is 0.4021 W/m·K, and the photothermal conversion storage efficiency reaches 0.591. Therefore, this composite phase change material, with its outstanding photothermal conversion and storage properties, shows promising potential for use as a solar thermal energy storage material.

Abstract: Ice thermal energy storage offers an effective solution for sustainable infrastructure cooling by producing ice during off-peak hours and utilizing the stored cooling during peak demand. The performance of such systems is strongly influenced by the geometry and material selection of the embedded heat exchangers, which determine heat transfer, durability, and fabrication feasibility. This study presents a novel direct comparison of helical and finned tube coils under identical operating conditions, rarely addressed in prior ITES research. Both configurations, fabricated from copper tubing, were tested in a 200-liter insulated tank using water as the secondary refrigerant. Performance was evaluated through ice formation rate, cooling capacity delivery, and overall efficiency. The helical coil consistently outperformed the finned tube coil, producing more uniform ice distribution, a greater ice mass of 58.4 kilograms compared with 49.83 kilograms, and an extended cooling duration of 5 hours and 30 minutes compared with 4 hours and 15 minutes. The originality of this work lies in isolating coil geometry effects on ITES performance, offering reproducible evidence for design optimization. Limitations include the use of a single refrigerant and a laboratory-scale system, which may affect scalability to real applications. Nevertheless, the findings provide practical guidance for selecting coil designs that improve efficiency and reliability in infrastructure cooling systems.