Phase change materials incorporation into 3D printed geopolymer cement:A sustainable approach to enhance the comfort and energy efficiency of buildings

The advent of 3D printing has revolutionized conventional construction, offering cost-effective and fast construction of complex structures. Nevertheless, there remain challenges to be addressed regarding the effective integration of functional additives into 3D printing construction materials. Herein, we present a straightforward and environmentally friendly approach to promote sustainable buildings while reducing energy consumption. This is achieved by integrating Macroencapsulated Phase Change Materials (MEPCM) into a 3D printable geopolymer paste (GPP) derived from fly ashes. The research followed a systematic methodology, encompassing the assessment of fresh and hardened properties of geopolymer pastes with varying amounts of MEPCM, analyzing their thermal properties, and investigating the thermal performance by printing miniature houses without and with 20 vol% MEPCM. Notably, MEPCM demonstrated its dual functionality as a thermal energy management component and a viscosity modifier for 3D printable geopolymer paste. Overall, this study paves an innovative path toward sustainable construction, highlighting the significance of energy efficiency and waste reduction.</p

MXene/rGO grafted sponge with an integrated hydrophobic structure towards light-driven phase change composites

While phase change materials (PCMs) have great potential for use in solar energy storage, they suffer from a lack of shape stability and energy conversion ability. In this study, proper amination of melamine sponge (MS) was designed to construct an integrated MXene and reduced graphene oxide (rGO) structure. The MXene/rGO layer is sufficiently robust to endure the capillary pressure caused by solvent evaporation during the airdrying process. In addition, the reduction of GO using oleylamine (OA) contributes to the protection of MXene from oxidation by preventing the surface of MXene nanosheets from being exposed to oxygen and moisture. The as-designed MXene/rGO sponges have been shown to effectively enhance the thermophysical and photo absorption properties of paraffin wax (PW) in the composite PCM. The composite with the highest amount of MXene/rGO maintained 93.3% of the latent heat of pure PW. The photothermal storage efficiency can reach as high as 93.0% at an MXene content of around 1%. A thermal conductivity enhancement of 66.9% can be achieved compared to the pure MS/PW composite. Therefore, this study presents a new approach for designing of high-performance phase change composites for waste-heat recovery and solar thermal energy storage applications.</p

Dynamic response of ladder track rested on stochastic foundation under oscillating moving load

The ladder track is a new type of an elastically supported vibration-reduction track system that has been applied to several urban railways. This paper is devoted to the investigation of dynamic behavior of a ladder track under an oscillating moving load. The track is represented by an infinite Timoshenko beam supported by a random elastic foundation. In this regard, equations of motion for the ladder track are developed in a moving frame of reference. In continuation, by employing perturbation theory and contour integration, the response of the ladder track is obtained analytically and its results are verified using the stochastic finite element method. Finally, using the verified model, a series of sensitivity analyses are accomplished on effecting parameters including velocity and load frequency

Investigation of thermal conductivity and rheological properties of nanofluids containing graphene nanoplatelets

In the present study, stable homogeneous graphene nanoplatelet (GNP) nanofluids were prepared without any surfactant by high-power ultrasonic (probe) dispersion of GNPs in distilled water. The concentrations of nanofluids were maintained at 0.025, 0.05, 0.075, and 0.1 wt.% for three different specific surface areas of 300, 500, and 750 m(2)/g. Transmission electron microscopy image shows that the suspensions are homogeneous and most of the materials have been well dispersed. The stability of nanofluid was investigated using a UV-visible spectrophotometer in a time span of 600 h, and zeta potential after dispersion had been investigated to elucidate its role on dispersion characteristics. The rheological properties of GNP nanofluids approach Newtonian and non-Newtonian behaviors where viscosity decreases linearly with the rise of temperature. The thermal conductivity results show that the dispersed nanoparticles can always enhance the thermal conductivity of the base fluid, and the highest enhancement was obtained to be 27.64% in the concentration of 0.1 wt.% of GNPs with a specific surface area of 750 m(2)/g. Electrical conductivity of the GNP nanofluids shows a significant enhancement by dispersion of GNPs in distilled water. This novel type of nanofluids shows outstanding potential for replacements as advanced heat transfer fluids in medium temperature applications including solar collectors and heat exchanger systems