Papers by Keyword: Alkali

Abstract: Composite (FRP) reinforcement is used in the construction industry mainly because of its high resistance to aggressive environments. The production technology and design of straight FRP members is now very well understood. However, when designing concrete elements, it is usually necessary to adapt the reinforcement to the requirements of the construction and to design curved (bent) members. These then undergo structural changes in their cross-section during manufacture, which can have a major effect on their service life and load-bearing capacity. This paper describes the problem of degradation of shaped composite reinforcement in an aggressive alkaline environment and presents experimentally determined values of tensile strength.

Abstract: Here we investigate the durability of glass fiber-reinforced polymer bars that were held for a long time (up to 360 days) at temperatures of 20 ºС, 60 ºС and 80 ºС in a NaOH solution (pH=13). A total of 22 specimen groups, including a control group of initial specimens, were tested. The fracture strength tests were performed by the longitudinal bend technique. The durability of the bars when held in alkali at 60 ºС and 80 ºС for up to 55 days was found to decline gradually and constituted 0.86 and 0.84 of the initial strength (86% and 84 %). After 55 days, the point of inflection occurred, and the durability began to decrease sharply, reaching the values of 0.49 (at 60 ºС) and 0.24 (at 80 ºС) at a residence time of 360 days. The durability diminished gradually at a room temperature of 20−23 ºС to attain the value of 0.91 at a holding time of 360 days. A mathematical model is suggested that approximates test results with reasonable accuracy, R²=0.9967, and the time when the conditions change (inflection of strength-to-time curve) was experimentally found to be 60 days.

Abstract: Studies have been conducted to assess the possibility of refining a lead collector containing precious metals, with the aim of obtaining lead using an economically viable technology. Studied the patterns of anodic oxidation of lead and impurities in alkaline-water-glycerate electrolytes, depending on the concentration of sodium hydroxide and glycerol in the electrolyte, the potential sweep rate.

Abstract: Empty fruit bunches fibre (EFB) consisting of 44 % cellulose, 16 % lignin and 35 % hemicelluloses component was treated using microwave-alkali (Mw-A) agitated pre-treatment so as to disrupt the recalcitrant structures in the fibre. Morphology and chemical changes of treated EFB were used as indicators to the effectiveness of Mw-A treatment. The results obtained were compared with conventional pre-treatment process. The morphology of the treated fiber was observed using scanning electron microscope. The reduction in the EFB composition during Mw-A treatment was justified by measuring the total extract cellulose; remaining lignin and hemicellulose, and ash content after the process was performed. Results revealed that Mw-A pre-treatment technique exhibited a more effective removal of lignin and hemicelluloses as compared to the conventional or chemical treatment.

Abstract: The requirements regarding the properties of fibres are closely linked to their further application. The demands for garment and home textile considerably differ from requirements for fibres that are used for technical purposes. This paper presents the results on investigation of raw flax and hemp fibres after their initial treatment with two step method (cold or hot alkaline, enzyme treatment and bleaching as after-treatment). The properties of hemp and flax fibres are evaluated by colorimetric analysis, mechanical testing, and microscopy of the surface of fibres.

Abstract: Copper indium gallium selenide/sulfide (CIGS) and copper zinc tin selenide/sulfide (CZTS) are two thin film photovoltaic materials with many similar properties. Therefore, three new processing steps – which are well-known to be beneficial for CIGS solar cell processing – are developed, optimized and implemented in CZTS solar cells. For all these novel processing steps an increase in minority carrier lifetime and cell conversion efficiency is measured, as compared to standard CZTS processing. The scientific explanation of these effects is very similar to its CIGS equivalent: the incorporation of alkali metals, ammonium sulfide surface cleaning, and Al₂O₃ surface passivation leads to electrical enhancement of the CZTS bulk, front surface and reduced front interface recombination, respectively.

Abstract: The dissolution of wool in 4g/L NaOH solution at 65°C is used to be a standard test method for the damage of wool in the processing. This suggests that alkali can cause wool keratin and the linkage between molecule chains broken. Fortunately, the dissolution of wool at low temperature is mainly limited on the surface scales because the swelling of wool in water solution at lower temperature is quite small. In this paper, the dissolution of wool in alkali solution and the changes of the fiber structure and performance at different temperature were investigated. The results showed clearly that the wool surface keratin could be dissolved in different extent with the varying of the temperature and this could be applied to develop an AOX free modification of wool for shrinkage resistance.

Abstract: The crystallization activation energies and crystalline phases of lithium-iron-phosphate (LIP) glasses with alkali and alkali-earth metal oxides have been studied and compared. The results indicate that the alkali and alkali-earth metal oxides reduce the glass crystallization. Moreover, the alkali metal oxides result in the changes in the crystalline phase, while the alkali-earth metal oxides make the glass crystallization more sensitive to the thermal treatment conditions.

Abstract: A study was conducted for production of activated carbon (AC) from industrial bamboo waste using carbonization and Microwave-alkali (Mw-A) activation techniques. The aim of the study is to produce activated carbon with higher surface area via Mw-A activation techniques. The study was focused on the effect of activation (KOH soaking and Mw-A) and carbonization temperature (400^oC and 500^oC) on the physical and chemical structure of AC. The analysis was conducted using proximate analysis, BET surface area, FESEM and FTIR analysis. The morphology and characteristic study on activated carbon shown that Mw-A activation techniques gave higher BET surface area and well develop pore structure. The results indicated that Mw-A activation of activated carbon gave BET surface area of 950m²g^-1, whereas by using steam activation only 719 m²g^-1 of BET surface area was recorded. Higher carbonization temperature for Mw-A treated bamboo produced higher surface area of AC. At 500^oC, 1578m²g^-1 BET surface area of AC was achieved. This work highlighted, Mw-A activation can be applied and further enhanced to obtain higher surface area of activated carbon derived from industrial bamboo waste.

Abstract: 1,4-Bis (dimethyl) benzyl octyl ethylene diammonium bromide chloride has been synthesized, characterized and applied as new phase transfer catalyst in the alkaline hydrolysis of PET leading to depolymerisation. The new phase transfer catalyst has been compared with the alkaline hydrolysis of PET using zinc sulfate as catalyst in the depolymerization. It was found that the newly synthesized phase transfer catalyst exhibited excellent conversion than the alkaline hydrolysis of PET using zinc sulfate as catalyst.