• Journal of the Korean Home Economics Association
• /
• v.25 no.4
• /
• pp.9-18
• /
• 1987

This study is conducted to investigate the influence of addition of quarternary ammonium salt(cetyl trimethyl ammonium bromide: CTAB) when polyester(PET) fabric is treated with sodium hydroxide(NaOH), depending on experimental variables such as CTAB concentration, NaOH concentration, time & temperature, and the change in physical & chemical properties of alkaline-hydrolyzed PET fabrics depending on their weight loss. The results are as follows: 1. By adding CTAB in aqueous NaOH, the weight loss of PET fabric is increased remarkably and until the concentration of CTAB is reached at its cmc, and the higher the concentration of CTAB are, the more weight loss on PET fibrics are. 2. The addition of CTAB in aqueous NaOH is most effective at lower NaON concentration(2%) among various NaOH concentration, on increasing the amount of weight loss, while there are almost similar results through various treatment time and temperature. 3. As the amount of weight of weight loss on PET fabric is increased, the increase of void space in the PET yarn, of softness & dyeability of PET fabric and the decrease of tensile strength are found. On the other hand, the moisture regain shows a little increase by alkaline-hydrolysis on PET fabric while vertical absorption test & water retention value are not sufficiently sensitive to distinguish between the hydrophillicity of untreated and treated PET fabric. The shrinkage of PET fabric is induced by swelling in hot aqueous NaOH regardless of NaOH concentration & addition of CTAB.

• Resources Recycling
• /
• v.26 no.6
• /
• pp.91-96
• /
• 2017

Tungsten (W) recovery from tungsten carbide (WC) was researched by alkali melt followed by water leaching. The experiments of alkali melt were carried out with the change of the sort of alkali material, heating temperature, and the heating duration. Water leaching of W was performed in the fixed conditions ($25^{\circ}C$, 2 hr., slurry density: 10 g/L). From the mixture of WC and sodium nitrate ($NaNO_3$) in the molar ratio of 1:2, treated at $400^{\circ}C$ for 6 hours, only 63.3% of W might be leached by water leaching. With the increase of sodium hydroxide (NaOH) as a melting additive, the leachability increased. Finally it reached to 97.8 % with the melted mixture of ($WC:NaNO_3:NaOH$) in the ratio of (1:2:2). This imply that NaOH may play a role as a reaction catalyst by lowering Gibb's free energy for alkali melt reaction for WC.

• Resources Recycling
• /
• v.14 no.6 s.68
• /
• pp.3-9
• /
• 2005

In this study, the separation and recovery of cerium hydroxide was investigated from the wasted cerium polishing powders. Waste cerium polishing powder contains $64.5\;wt\%$ of rare earth oxide and the content of cerium oxide is $36.5\;wt\%$. Since cerium oxide, $56.3\%$ of rare earths, is the most stable state in rare earth, the dissolution of cerium oxide in acid solution is not easy. Therefore the process of rare earth oxide by sulfation and water leaching was examined in order to increase the recovery of rare earth. Rare earth elements were recovered in the form of $\Re{\cdot}Na(SO_{4})_{2}$ by the addition of sodium sulfate to leached solution. The slurry of rare earth hydroxide was prepared by the addition of $\Re{\cdot}Na(SO_{4})_{2}$ to sodium hydroxide solution. After the oxidation of cerous hydroxide($CE(OH)_{3}$) to ceric hydroxide($CE(OH)_{3}$) by aeration, ceric hydroxide was separated from other rare earth hydroxides by controlling the acidity of solution.

• Advances in concrete construction
• /
• v.13 no.1
• /
• pp.25-34
• /
• 2022

The production of geopolymer is considered as a cleaner process due to much lower CO₂ emission than that from the production of Portland cement. This paper presents a study of the potential use of recycled steel fibre (RSF) coming from the recycling process of the old tires in geopolymer mortars. Ground expanded perlite (EP) is used as a source of alumino-silicate and sodium hydroxide (NaOH=5, 10, 15, and 20M) is used as alkaline medium for geopolymer synthesis. RSFs were added to the mortar mixtures in four different volume fractions (0, 0.5, 1.0, and 1.5% of the total volume of mortar). The unit weight, ultrasound pulse velocity, flexural and compressive strength of expanded perlite based geopolymer mortar (EPGM) mixtures were determined. The microstructures of selected EPGMs were examined by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) analyses. The optimum molarity of sodium hydroxide solution was found to be 15M for geopolymer synthesis by EP. The test results revealed that RSFs can be successfully used for fibre-reinforced geopolymer production.

• KOREAN JOURNAL OF CROP SCIENCE
• /
• v.29 no.1
• /
• pp.98-101
• /
• 1984

Endorcarp inhibited the embryo growth of ginseng seeds. This inhibition is not due to impermeability to water, but is probably caused by mechanical resistance. The embryo growth rate was enhanced by endocarp injury by soaking for 10 to 30 minutes in 2.5% solution of sodium hydroxide. But sulfuric acid did not affect on the embryo growth of ginseng seed.

• Transactions of the Korean hydrogen and new energy society
• /
• v.33 no.4
• /
• pp.343-352
• /
• 2022

Co/Al₂O₃ nanopowder was used as a catalyst to investigate the effect of catalyst support, reduction temperature, sodium borohydride (NaBH₄) concentration, sodium hydroxide (NaOH) concentration, and reaction temperature on the characteristics of NaBH₄ hydrolysis. The Co/Al₂O₃ nanopowder showed a high catalytic activity among various catalysts. Catalyst reduction at 250℃ exhibited a relatively good activity. The activity decreased with an increase in the NaBH₄ concentration. Conversely, the activity increased and then decreased with an increase in the NaOH concentration. Additionally, the activity increased with an increase in the reaction temperature. The value of apparent activation energy was 40.81 kJ/mol, which was lower than the other Co-based catalysts. Thus, Co/Al₂O₃ nanopowder catalyst can be widely used for NaBH₄ hydrolysis owing to its superior catalytic activity.

• Carbon letters
• /
• v.24
• /
• pp.62-72
• /
• 2017

The aim of this work was to evaluate the dielectric properties of impregnated and activated palm kernel shells (PKSs) samples using two activating agents, potassium carbonate ($K_2CO_3$) and sodium hydroxide (NaOH), at three impregnation ratios. The materials were characterized by moisture content, carbon content, ash content, thermal profile and functional groups. The dielectric properties were examined using an open-ended coaxial probe method at various microwave frequencies (1-6 GHz) and temperatures (25, 35, and $45^{\circ}C$). The results show that the dielectric properties varied with frequency, temperature, moisture content, carbon content and mass ratio of the ionic solids. PKSK1.75 (PKS impregnated with $K_2CO_3$ at a mass ratio of 1.75) and PKSN1.5 (PKS impregnated with NaOH at a mass ratio of 1.5) exhibited a high loss tangent ($tan{\delta}$) indicating the effectiveness of these materials to be heated by microwaves. $K_2CO_3$ and NaOH can act as a microwave absorber to enhance the efficiency of microwave heating for low loss PKSs. Materials with a high moisture content exhibit a high loss tangent but low penetration depth. The interplay of multiple operating frequencies is suggested to promote better microwave heating by considering the changes in the materials characteristics.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.22 no.3
• /
• pp.152-157
• /
• 2012

In this study, geopolymer was prepared with reject ash and blast furnace slag using NaOH as an alkali activator and water glass. The aim of this study was to investigate the compressive strength variation according to the contents of NaOH and water glass and replacement ratio of reject ash (RA) and blast furnace slag (BS). The compressive strength measured after 28 days was 38.91 MPa for the geopolymer which consist of 100 % of BS with 1 wt% NaOH and 3 wt% water glass. The major factor for improving compressive strength was the alkali activator proportion and the replacement ratio of RA and BS.

• Advances in concrete construction
• /
• v.8 no.3
• /
• pp.217-223
• /
• 2019

This paper presents the mechanical and microstructural properties of the geopolymer paste which was developed by utilizing the industrial by-products, rice husk ash (RHA) and ultra-fine slag. Ultra-fine slag particles with average particle size in the range of 4 to 5 microns. RHA is partially replaced with ultra-fine slag at different levels of 0 to 50%. Sodium silicate to sodium hydroxide ratio of 1.0 and alkaline liquid to binder (AL/B) ratio of 0.60 is taken. Setting time, compressive, flexural strengths were studied up to the age of 90 days with different concentrations of NaOH. The microstructure of the hybrid geopolymer paste was studied by performing the SEM, EDS, and XRD on the broken samples. RHA based geopolymer paste blended with ultrafine slag resulted in high compressive and flexural strengths and increased setting times of the paste. Strength increased with the increase in NaOH concentration at all ages. The ultra-small particles of the slag acted as a micro-filler into the paste and enhanced the properties by improving the CASH, NASH, and CSH. The maximum compressive strength of 70MPa was achieved at 30% slag content with 16M NaOH. The results of XRD, SEM, and EDS at 30% replacement of RHA with ultra-fine slag densified the paste microstructure.

• Proceedings of the Korean Fiber Society Conference
• /
• 2003.10a
• /
• pp.83-84
• /
• 2003

The microstructure and tensile properties of ramie treated with NaOH and crosslinked with 1, 2, 3, 4-butanetetracarboxylic acid were characterised. X-ray diffraction and FTIR were used to study the crystalline structure o f the resultant ramie yarns. Results showed that the maximum change in the structure of the modified ramie took place at 16% NaOH, which would completely transform Cellulose I to Cellulose II. Also, the crystallinity index and fibre orientation decreased to the minimum value while the absorption properties were enhanced. The average degree of polymerization of the treated ramie yams slightly decreased after NaOH treatment.