Solid State Phenomena Vol. 351

Abstract: In this paper a combination of colloidal silica and different gelling agents are studied in order to observe the effect of gelation rate on the formed sol-gel structure. Proper ratios of sol matrix materials and gelation agents were determined. Sets of samples based on these recipes were prepared with added filling material and tested for mechanical properties. Samples with added solution of NaCl gelling agent showed the highest flexural strength observed and also lower doses of this gelling agent are required for one of the studied sols which can positively effect the final price of product.

Abstract: The article investigates the influence of the sintering time with constant temperature on the development of the tricalcium silicate crystallinity using the Scherrer's and Rietveld method.One suitable raw material mixture consisting of only pure CaCO₃ and SiO₂ in their specific ratio of 73.6:26.3 wt.% was selected. This raw material powder was prepared using a wet milling process in the water medium in a PULVERISETTE 6 plan mill. Based on previous research in this area, a firing temperature of 1500 °C was chosen with sintering period of 5, 10, 15 and 20 minutes in an experimental furnace with a manipulator for isothermal sintering of laboratory samples developed by Dr. Chromy. This furnace requires special sample preparation, so a procedure for their preparation was designed and optimized. Thanks to this optimization, it is possible to repeatably prepare identical pellets with the exact parameters for this type of furnace. The resulting pellet weight is 73 mg at a volumetric weight of 2,285 g·cm^-3.The results of the firings with different sintering times and constant temperatures showed that the sintering processes and mineral conversion occur very quickly, since after 5 minutes 30.81 wt.% of the mineral tricalcium silicate was identified and after 20 minutes the raw powder was converted to tricalcium silicate in a significant amount, i.e., 72.02 wt.%. At the same time, the crystallinity was monitored using Scherrer's method and after 20 minutes of sintering, the crystallite size of tricalcium silicate reached 104.889 nm. Thus, there was a relatively rapid development of the crystallinity of Alite.

Abstract: In this study, an eco-friendly coconut oil-based polyol blend was synthesized for bio-based waterborne polyurethane (WBPU) and WBPU-silane composite coatings. It was demonstrated that an increase in silane content incorporated into the WBPU matrix significantly enhanced the corrosion protection of WBPU coatings. Results also show a fourfold increase in the adhesion strength of WBPU-silane composite coatings as compared to that of bare WBPU coatings. Further, the water contact angle revealed that hydrophobic properties increase as the silane content incorporated into the WBPU matrix increases. This work provides a novel route for enhanced corrosion protection utilizing a bio-based polyol blend.

Abstract: Polyurethane coating has been widely used as a protective coating due to its wide range of mechanical strength, excellent abrasion resistance, toughness, low-temperature flexibility, and chemical resistance, simplicity in production and application, and superior protection on corrosion to mild steel. No studies have been reported utilizing coconut-based/PPG blend polyols to produce polyurethane-based protective coatings on mild steel. Therefore, in this work, we fabricated polyurethane-based protective coating using coconut-based/PPG blend polyols for anti-corrosion application. Due to low adhesion strength of Polyurethane-based protective coating, the incorporation of nano-fillers into the polymer matrix improved the adhesion strength of the coating due to its functional benefits and its effects gave rise to increased intermolecular bonding, hydrogen bonding, van der waals, magnetism, and surface energy. Therefore, we fabricated PANI/PU composite coatings with varied amounts of polyaniline nanoparticles on mild steel using coconut-based/PPG blend polyols exposed in 3.5 wt% NaCl aqueous solution for anti-corrosion application. Characterizations like Fourier Transform Infrared Spectroscopy (FTIR), Potentiodynamic Polarization (Tafel plot), contact angle, adhesion test, FESEM, XRD, and UV-VIS were used in this study. Tafel plot revealed that PU-based and PANI/PU composite coatings exhibited a significant reduction in corrosion current density (I_corr), perhaps due to the adsorption of inhibitor in the surface of the mild steel which reduced corrosion rate of the metal by retarding the anodic process and impeding the corrosive species from the surroundings. Among all fabricated coatings, 0.5-PANI/PU composite coating was the best, having a less corrosion rate of 5.66x10^-5 mmpy compared to others. In addition, its surface was more compact, smooth, rigid, and no voids present at the interface according to the result of FESEM, suggesting better corrosion protection to mild steel. Hence, PU-based protective coating and PANI/PU composite coatings using coconut-based/PPG blend polyols inhibited the penetration of the corrosive species and served as an adequate barrier protection against corrosion for mild steel.

Abstract: In the Philippines, bananas are one of the most exported agricultural products, with up to 6 million metric tons of annual harvest. Because of this, harvesting bananas generates waste like banana pseudo-stems. Banana pseudo-stems offer a good source of nanocellulose, and it was found that these have very similar chemical compositions to jute and sisal fibers, which are the most common sources of cellulose today. This only indicates that banana pseudo-stems could be utilized for different industrial and engineering applications. Epoxy-based nanocomposite coatings have attracted attention in industrial and engineering applications. Epoxy/banana pseudo-stem nanocellulose (Epoxy/BPNC) composites as anti-corrosive fillers were prepared by incorporating BPNC into the epoxy matrix to improve the anti-corrosion performance of epoxy coatings on mild steel surfaces. Their anti-corrosion properties were explored by the Tafel polarization technique under immersion in 3.5 wt.% NaCl solutions as corrosive medium. According to the results, it can be observed that epoxy/BPNC composite coatings significantly improve the anti-corrosion performance on mild steel surfaces with a 1.5 wt.% BPNC loading ratio as the optimized concentration. Furthermore, it can be seen that the optimized concentration of the BPNC loading ratio (1.5 wt.%) has a lower corrosion rate (CR = 2.7109 x 10^-6 mm/year) compared to that of the bare mild steel (CR = 6.11190 x 10^-2 mm/year). Additionally, the SEM results showed that the presence of BPNC in the epoxy matrix has a significant protective effect compared to pure epoxy alone.