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International audience; This study aimed to characterize Phase Change Materials (PCM) by improving their properties using shape stabilization; this was achieved by adding nanoparticles as a support material. PCM soy wax was modified using two nanoparticles, graphene, and MAXene Ti3AlC2. The synthesis process comprised stirring using a magnetic stirrer and ultrasonication using an ultrasonic processor with various percentages of 0.1, 0.5, and 1 wt.% of soy wax with nanoparticles. Based on the results, the morphologies of graphene and MAXene Ti3AlC2 were found to be in the form of sheets. These sheets had a large surface area, so soy wax could adsorb more nanoparticles to increase the stability of the material. The thermal conductivity increased with increasing percentage addition of nanoparticles. The highest values from the synthesis with graphene and MAXene Ti3AlC2 were 0.89 W/mK and 0.85 W/mK, respectively. The thermal conductivity of soy wax increased with the ratio of pure soy wax and nano-soy wax; the thermal conductivity was 6.01 for soy wax+graphene and 5.71 for soy wax+Ti3AlC2. Differential scanning calorimetry (DSC) results showed an increase in the melting and solidifying points of pure soy wax. The modified soy wax with 0.1 wt.% graphenes experienced a reduction in the melting and solidification points up to 15% and 14%, respectively. Similar results were obtained for 0.1 wt.% MAXene Ti3AlC2. In this case, there was a reduction in the melting and solidifying points by 16% and 13%, respectively. Finally, the addition of MAXene improved the material stability and thermal conductivity of soy wax and has the potential to be used as a thermal energy storage material for building applications.

The growth and crystallization processes of the Cu2ZnSnS4 (CZTS) phase typically rely on high-temperature sulfurization, which involves a harmful chalcogen-containing atmosphere. Together with the use of high-toxicity solvents, these processes could hinder the widespread adoption of this technology in the mass production of CZTS semiconductors for solar cell application. Thus, we studied the formation of CZTS films from ethanol-based precursors without the sulfurization step, fully employing the non-toxic solvent and avoiding the environmentally harmful sulfur-containing atmosphere. The certain addition of 2-mercaptopropionic acid led to the formation of a clear and stable sulfur-containing precursor. The precursors were successfully deposited onto soda lime glass by employing spin coater. CZTS crystallinity in the identified XRD patterns was vanishingly small in the case of eliminating the sulfurization process. Moreover, the carbon concentration and grain size of the resulting films were controlled by changing the time period of drying treatment during film fabrication. A drying time of 120 minutes, which demonstrated a CZTS grain size of ± 1 µm with a direct optical energy gap around 1.4 eV, was confirmed as the ideal condition. These results may provide a useful route toward environment-friendly strategies for the production of a CZTS semiconductor that is compatible with the absorber application in thin-film solar cells.

Die soldering occurs when molten aluminum sticks to the surface of a die material and remains there after the ejection of the part. This resulted in low productivity and economic value in the foundry industry. Nitriding surface treatment is considered as an effective way in enhancing the service life of AISI H13 steel dies and to prevent soldering effect. The focus of this paper is to investigate the influence of three different surface conditions in terms of roughness, gas nitriding and pretreatment prior to gas nitriding on the soldering effect. Three kind of samples made of AISI H13 steel were pretreated (quenched and tempered) and followed by : shot peened, gas nitrided and shot peening followed by gas nitriding, were immersed in liquid melted ADC 12 Aluminium alloy at 30 seconds, 30 minutes, 2 hours and 5 hours, at a constant temperature of 680oC in a holding furnace. Characterizations on the surface of the steel were focused on the optical microstructure, microhardness profile, FE SEM observation and enegy dispersive spectrometry mapping. It was found that shot peening prior to nitriding gives a higher surface hardness and depth of nitride layer of H13 tool steel, 1140 HV (>70 HRC) and 120.5 μm, than the nitriding only process, 1033 HV (68 HRC) and 105 μm. The higher the hardness and depth of nitride layer expected would reduce the die soldering effect at the surface of the H13 tool steel dies. It was also found that the only shot peening treatment resulted in a tendency of soldering accompanied by the formation of intermetallic layers ; while soldering is not found on the nitrided and shot peened-nitrided samples.

Hydroxyapatite/chitosan (HApC) composite has been prepared by precipitation method and used for removal of heavy metals (Cr6+, Zn2+and Cd2+) from aqueous solution. The HAp and 3H7C composite with HAp:chitosan ratio of 3:7 (wt%) were characterized by Fourier transform infrared spectroscopy, X-ray diffraction and scanning electron microscopy-energy dispersive X-ray spectroscopy. The SEM results showed that HAp is spherical-shaped and crystalline, while chitosan has a flat structure. SEM micrograph of 3H7C composite reveals crystalline of HAp uniformly spread over the surface of chitosan. The crystal structure of HAp is maintained in 3H7C composite. Chitosan affects the adsorption capacity of HAp for heavy metal ions; it binds the metal ions as well as HAp. The kinetic data was best described by the pseudo-second order. Surface adsorption and intraparticle diffusion take place in the mechanism of adsorption process. The binding of HAp powder with chitosan made the capability of composite to removal of Cr6+, Zn2+and Cd2+from aqueous solution effective. The order of removal efficiency (Cr6+> Cd2+> Zn2+) was observed.