NaOH Alkaline Solution Research Articles

Effect of super-absorbent polymer on swelling pressure of compacted bentonite infiltrated by alkaline solutions

The application of bentonite in geological disposal of radioactive waste is still under evaluation, especially concerning the decreased swelling pressure of pure bentonite exposed to alkaline groundwater. In this paper, in order to improve the chemical resistance of bentonite to alkaline solutions, super-absorbent polymer (SAP), a hydrophilic polymer with much higher swelling ability than that of bentonite, was dry-blended with Gaomiaozi (GMZ) bentonite and compacted into blocks of different dry densities. Swelling pressure of the bentonite-SAP composites infiltrated with deionized water, NaOH and KOH alkaline solutions were tested, accompanied with scanning electron microscopy (SEM), mercury intrusion porosimetry (MIP) and X-ray diffractometer (XRD) tests conducted on the selected specimens. Results showed that, for the specimens hydrated by deionized water, the swelling pressure increased with increasing SAP content, dry density and concentration of NaOH solutions. With increasing concentration of KOH solutions, however, the swelling pressure decreased obviously and tended to undergo a slow long-term degradation. Results of SEM, MIP and XRD indicate that the SAP hydrogels swell extensively to clog the inter-aggregate pores and coat the aggregates (for high density specimens) or montmorillonite stacks (for low density specimens), while do not insert into the interlayer spaces. The swelling pressure was therefore mainly contributed by the crystalline swelling of montmorillonite and the osmotic swelling of SAP. The SAP chains could be associated with the montmorillonite crystallites, protecting them from chemical attack and thus improving the chemical resistance of bentonite to alkaline solutions.

Process intensification for fast SrFe12O19 nanoparticle production from celestite under supercritical hydrothermal conditions

The Sr-ferrite nanoparticle preparation process was intensified using supercritical hydrothermal conditions by employing mineral SrSO4 and acidic Fe3+ solution. The new approach consists of two unit operations: the mineral (SrSO4) dissolution in a mild alkaline NaOH solution; and the Sr/Fe hydroxide coprecipitation using a Fe3+ acid solution. In the first stage, a Sr-Fe gel colloid (Sr/Fe = 0.5) prepared by mixing acid Fe3+ and alkaline Sr2+ liquors (obtained from SrSO4 feedstock) was treated under supercritical hydrothermal conditions at 400 °C for 10 min at 30 MPa, resulting in Sr-ferrite particle crystallization. The second stage comprises increasing the production efficiency by reducing the Sr/Fe ratio to 0.2 coupled with Sr-Fe gel dehydration. The intensified processing proposed has demonstrated high efficiency through continuous flow preparation, which proceeded at a feeding rate of 50 g/L at 400 °C for a 40 s residence time.

In Situ Observation of ZnO Nanoparticle Formation by a Combination of Time-Resolved X-ray Absorption Spectroscopy and X-ray Diffraction.

The formation of ZnO nanomaterials from different Zn acetylacetonate precursor solutions was studied in situ by employing simultaneous, time-resolved X-ray diffraction (XRD) and X-ray absorption spectroscopy (EXAFS) at the Zn K-edge. The precursor solutions were heated from room temperature to the desired reaction temperatures in a hermetically sealed cell dedicated to X-ray experiments. In general, the first indications for the formation of hexagonal ZnO were found for elevated temperatures of about 80 °C both by XRD and EXAFS, and the contributions increase with temperature and time. However, no reaction intermediates could be proved in addition to the Zn precursors and the formed hexagonal ZnO materials. Furthermore, the results show that the efficiency of the reaction, i.e., the conversion of the precursor material to the ZnO product, strongly depends on the solvent used and the reaction temperature. ZnO formation is accelerated by an increased temperature of 165 °C and the use of 1-octanol, with a conversion to ZnO of more than 80% after only a ca. 35 min reaction time according to a detailed analysis of the EXAFS data. For comparison, an identical concentration of Zn acetylacetonate in water or dilute alkaline NaOH solutions and a reaction temperature of around 90 °C leads to a smaller conversion of approximately 50% only, even after several hours of reaction. The particle size determined from XRD for different orientations shows a preferred orientation along the c-direction of the hexagonal crystal system, as well in accordance with scanning electron microscopy. The LaMer model explained this highly non-uniform growth of needle-like ZnO crystallites.

Definitive screening design for the development of alkali resistant PECVD coatings for returnable PET bottles

Definitive screening design is put to test for the development of plasma polymeric silicon organic coatings as protective coatings for polyethylene terephthalate (PET) against the influence of strong NaOH alkaline solutions (c = 0.5 mol/L). To evaluate the protection performance of the coatings, oxygen transmission rate measurements are employed after washing experiments under application-oriented conditions. Parameter influences on the maintained OTR values after exposure to NaOH solution are derived by statistical correlation and used for optimization. Significant optimization is achieved for two coatings, that are subjected to long term performance evaluation and characterized in regard to their topography as well as atomic and chemical composition in dripping tests. Long term stability of two optimized coatings was lost after 50 minutes of exposure. Optimization was shown to be primarily achieved by an increase of the microwave pulse length. Both coatings showed similar atomic compositions and functional groups. Coatings System B showed chemical integrity of its functional groups up to 120 min of exposure to NaOH. Therefore, a denser structure with few pinholes was attributed, that was reinforced by lower roughness values. Defect and pin hole free coating structure as well as a high carbon content could be identified as beneficial properties.

Alkali Niobate Powder Synthesis Using an Emerging Microwave-Assisted Hydrothermal Method.

For more than five decades, alkali niobate-based materials (KxNa1−xNbO3) have been one of the most promising lead-free piezoelectric materials researched to be used in electronics, photocatalysis, energy storage/conversion and medical applications, due to their important health and environmentally friendly nature. In this paper, our strategy was to synthetize the nearest reproductible composition to KxNa1−xNbO3 (KNN) with x = 0.5, placed at the limit of the morphotropic phase boundary (MPB) with the presence of both polymorphic phases, orthorhombic and tetragonal. The wet synthesis route was chosen to make the mix crystal powders, starting with the suspension preparation of Nb2O5 powder and KOH and NaOH alkaline solutions. Hydrothermal microwave-assisted maturation (HTMW), following the parameter variation T = 200–250 °C, p = 47–60 bar and dwelling time of 30–90 min, was performed. All powders therefore synthesized were entirely KxN1−xNbO3 solid solutions with x = 0.06–0.69, and the compositional, elemental, structural and morphological characterization highlighted polycrystalline particle assemblage with cubic and prismatic morphology, with sizes between 0.28 nm and 2.95 μm and polymorphic O-T phase coexistence, and a d33 piezoelectric constant under 1 pC/N of the compacted unsintered and unpoled discs were found.

Reinforced Composite as a Feeder for 3D Printing Application

Kenaf fibre has a low environmental impact because it is recyclable, light density and strong to be used as a product. Natural fibres, especially kenaf fibre, are undertilised and understudied in 3D printing technology. 3D technology is gaining traction to replace traditional methods because it saves cost and production time. This study focuses on producing kenaf composite materials that can be used as a feeder for 3D printing. This study used different fibre compositions (20,25,30) % mixed with polypropylene set at 190 ˚C temperature, 45 rpm speed, and 25 minutes. The material was left to cool to form clot to go through for the rheology process, and injection analysis was performed using Autodesk Moldflow Insight 2014. This study showed that a mixing temperature of 190 ˚C was suitable for forming a high shear mechanism. Kenaf fibre was treated in an alkaline solution of NaOH to 3 hours to prevent damage to the surface of the filler fibre in composites. Kenaf fibre at 6% of NaOH solution reaches a higher value for mechanical strength and roughness, resulting in better mechanical interlocking between the fibres and the matrix. In addition, analysis from Autodesk Moldflow Insight 2014 reveals that at 200 ˚C injection temperature pretend, the shear rate is higher creating smoother melt flow characteristics.

Hybrid ceramic membrane microfiltration and electrolysis process for Cu-removal from aqueous solutions

This study aims to fabricate a low-cost ceramic microfiltration membrane by mixing kaolin 4.2 wt%, silica 5.8 wt%, starch 20 wt%, graphite 30 wt%, and sodium silicate 40 wt%. The produced paste was molded into a cylinder (1.0 cm high, 5 cm diameter) and dried in an oven at 90°C for 1 h, and then sintered in a furnace at 650 °C for 2 h. The characterization of the produced ceramic membrane was performed by X-ray diffraction analysis, Fourier transformed infra-red spectroscopy, and scanning electron microscopy. Furthermore, the contact angle of the membrane surface was measured, thus demonstrating that the surface is hydrophilic. The fabricated ceramic membrane was investigated for its chemical resistance in strongly acidic and alkaline media. The mass loss of membrane in HCl solution at pH = 2 for 200 h was not more than 0.18%, while it was 2% in alkaline NaOH solution (pH = 12). The fabricated ceramic membrane was combined with an electrolysis process for applying as a new hybrid process for copper ions removal from an aqueous solution. The effects of three operating parameters of electric voltage, initial pH, and initial copper concentration on the performance of copper removal percentage were investigated. To investigate the independent effect of the hybrid electrolysis process versus microfiltration, two experiments with and without an electric field were conducted in 100 min. The copper concentration was decreased from 350 to 160 ppm only by applying the microfiltration method, whereas hybrid electrolysis and microfiltration decreased the copper concentration from 350 to 10 ppm. The regeneration of the composite membrane was evaluated in four consecutive cycles. The percentage of copper ions removal after 4 cycles without washing is about 97%. The proposed process is effective and fast for copper ions removal from the solution, with an excellent yield of 97.4%.

Effects of pH and exposure time to alkaline solutions on the mineralogy of the Opalinus Clay from the lower sandy facies of Mont Terri site

The Opalinus Clay is a claystone considered as potential host rock for deep geological disposal of radioactive wastes in Switzerland and Gemany. During the operational phase of the repository, an increase in underground water pH, from 7.5 to a value as high as 13.5 is expected, due to the release of alkaline plumes from concrete degradation, resulting in possible changes in the mineralogy of the host rock. While clay mineral dissolution is known to occur and affect the hydro-mechanical properties of the host rock, the dissolution of other minerals present in claystone, i.e., quartz and calcite, can also take place. This study focuses on identification of such dissolutions by considering NaOH, Ca(OH)2 and KOH alkaline solutions at different pHs (8.5, 11.5 and 13.5). A low pH = 8.5 was investigated to consider the gradual increase in pH of the underground water resulting from the progressive infiltration of alkaline plumes. Series of Opalinus Clay samples from the lower sandy facies of Mont Terri site were immersed in these solutions for six months and for one year. It was found that quartz dissolution occurred significantly at pHs higher than 11.5, but also at pHs as low as 8.5. The longer the exposure time, the more significant the quartz dissolution. Calcite dissolution was observed after six months at pH higher than 11.5, and after one year at pH higher than 8.5. Thus, the quartz dissolution seemed to be governed by the exposure time, while the calcite dissolution seemed to depend on both exposure time and pH value, due to carbonation phenomenon. While generally attention has been paid to the effect of alkalinity on clay minerals, this paper meticulously studies the dissolution of quartz and calcite initially present in significant proportions in the Opalinus Clay from the lower sandy facies of Mont Terri site by investigating a wide range of pHs. The dissolution of such minerals will undoubtedly affect the hydraulic and mechanical properties of the claystone. Thereby, it is of paramount importance to study this phenomenon in order to ensure the long-term safety of the nuclear waste disposal. Furthermore, by investigating a wide range of pHs, attention is paid to both the early stage of site water pH increase (low pHs) and the late stage (high pHs).

Indirect Additive Manufacturing: A Valid Approach to Modulate Sorption/Release Profile of Molecules from Chitosan Hydrogels.

This work studied the influence of hydrogel’s physical properties (geometry and hierarchical roughness) on the in vitro sorption/release profiles of molecules. To achieve this goal, chitosan (CS) solutions were cast in 3D-printed (3DP) molds presenting intricate shapes (cubic and half-spherical with/without macro surface roughness) and further immersed in alkaline solutions of NaOH and NaCl. The resulting physically crosslinked hydrogels were mechanically stable in aqueous environments and successfully presented the shapes and geometries imparted by the 3DP molds. Sorption and release profiles were evaluated using methyl orange (MO) and paracetamol (PMOL) as model molecules, respectively. Results revealed that distinct MO sorption/PMOL release profiles were obtained according to the sample’s shape and presence/absence of hierarchical roughness. MO sorption capacity of CS samples presented both dependencies of hierarchical surface and geometry parameters. Hence, cubic samples without a hierarchical surface presented the highest (up to 1.2 × greater) dye removal capacity. Moreover, PMOL release measurements were more dependent on the surface area of hydrogels, where semi-spherical samples with hierarchical roughness presented the fastest (~1.13 × faster) drug delivery profiles. This work demonstrates that indirect 3DP (via fused filament fabrication (FFF) technology) could be a simple strategy to obtain hydrogels with distinct sorption/release profiles.

Effect of Coir Fiber Reinforcement on Properties of Metakaolin-Based Geopolymer Composite

This study explored the use of coir fibers extracted from coconut husks, an agro-waste material that constitutes sanitation and environmental pollution problems, as a reinforcing element in the production of metakaolin-based geopolymer composites with improved properties. A series of sample formulations were produced with varying coir fiber content (0.5, 1.0, 1.5, and 2.0 percent weight of metakaolin powder). The investigation was conducted using a 10 M NaOH alkaline solution with a 0.24 NaOH:Na2SiO3 mass ratio. Samples were cured for 28 days and tested for bulk density, ultrasonic pulse velocity (UPV), and compressive and flexural strength. Microstructural examinations such as X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM) were also performed on samples. Compressive strength values up to 21.25 N/mm2 at 0.5% fiber content and flexural strength values up to 10.39 N/mm2 at 1% fiber content were achieved in this study. The results obtained showed a decreasing bulk density of geopolymer samples (2113 kg/m3 to 2045 kg/m3) with increasing coir fiber content. The geopolymer samples had UPV values varying from 2315 m/s to 2717 m/s. Coir fiber with 0.5–1.0% fiber content can be incorporated into metakaolin-based geopolymers to produce eco-friendly composite materials with improved mechanical properties for sustainable development.

CoP nanowires on carbon cloth for electrocatalytic NOx− reduction to ammonia

• Cobalt Phosphide (CoP) with uniform nanowire array morphology self-supported on carbon cloth (CC) was prepared and used as cathode. • The material demonstrated effective electrocatalytic activity for NO x − (NO 2 – and NO 3 – ) reduction in alkaline solution at low overpotentials. • The catalyst maintained robust electrocatalytic activity even after 10 repeated tests. Electrocatalysis provides a promising green solution to replace the industrial Haber-Bosch process for ammonia production under ambient conditions. The indirect method for ammonia synthesis (N 2 → NO x → NH 3 ) have recently received great attention and development of efficient catalysts for selective NO x conversion to NH 3 is of key importance. Herein, we report the preparation of uniform CoP nanwire arrays self-supported on carbon cloth as efficient catalyst for electrocatalytic nitrite (NO 2 – ) and nitrate (NO 3 – ) reduction to synthesize ammonia in alkaline NaOH solution. The material demonstrated efficient ammonia generation rate of 380 µg*h −1 *cm −2 for NO 2 – reduction and a faradic efficiency of 91.6% obtained at −0.3 V vs RHE, and 317 µg*h −1 *cm −2 for NO 3 – reduction and a faradic efficiency of 65% at −0.4 V vs RHE. More importantly, the CoP catalyst displayed robust stability and maintained its activity even after 10 cycles of elctrocatalysis. This work demonstrated the great potential of carbon cloth supported metal phosphides for efficient ammonia production through electrocatalytic NO x conversion.

Upconversion Properties and Temperature-Sensing Behaviors of Alkaline-Earth-Metal Scandate Nanocrystals Doped with Er3+/Yb3+ Ions in the Presence of Alkali Ions (Li+, Na+, and K+).

Temperature-sensing media based on the fluorescence intensity ratio (FIR) of upconversion materials that suffer from low sensitivity owing to the small energy gap still have a need for new compounds with strong upconversion luminescence (UCL). In this work, a series of MSc2O4:Er3+/Yb3+ (M = Mg, Ca, Sr, and Ba) nanocrystals were prepared by a hydrothermal method using NaOH alkaline solution. The structure, morphology, and UCL characteristics of materials were investigated, and the red UCL of the CaSc2O4:Er3+/Yb3+ sample was dramatically enhanced by a factor of ∼12, ∼23, and ∼2000 compared with SrSc2O4, MgSc2O4, and BaSc2O4 samples, respectively. By adjusting alkali ions (Li+, Na+, K+), the UCL intensities of CaSc2O4:Er3+/Yb3+ and SrSc2O4:Er3+/Yb3+ samples were further improved, especially in the presence of Li+ ions. Excellent temperature-sensing behaviors are realized for CaSc2O4:Er3+/Yb3+ and SrSc2O4:Er3+/Yb3+ samples in the presence of Li+ ions, in which the maximum absolute sensitivity SA values are about 0.0041 and 0.0036 K-1 at 600 K and the corresponding relative sensitivity SR values are expressed as 1197/T2 and 1129/T2 (the current optimal SR = 1289/T2), respectively. The intense UCL and excellent SA and SR values indicate that CaSc2O4:Er3+/Yb3+ and SrSc2O4:Er3+/Yb3+ materials are promising candidates for application in high-temperature sensors working under 980 nm excitation.

Optimization of Soybean Protein Extraction Using By-Products from NaCl Electrolysis as an Application of the Industrial Symbiosis Concept

Defatted soybean flour is generated during the oil extraction process of soybean, and it has a protein content of ~50%. On the other hand, an alkaline solution of NaOH is produced during the electrolysis process of NaCl in a novel method used to make a potent disinfectant/antiseptic (HOCl). In the present work, we suggest using these two products to produce soy protein isolate (SPI), aiming to create an industrial symbiosis. A Box–Behnken experimental design was executed, and a surface response analysis was performed to optimize temperature, alkaline solution, and time used for SPI extraction. The SPI produced at optimal conditions was then characterized. The experimental results fit well with a second-order polynomial equation that could predict 93.15% of the variability under a combination of 70 °C, alkaline solution 3 (pH 12.68), and 44.7 min of the process. The model predicts a 49.79% extraction yield, and when tested, we obtained 48.30% within the confidence interval (46.66–52.93%). The obtained SPI was comparable in content and structure with a commercial SPI by molecular weight and molecular spectroscopy characterization. Finally, the urease activity (UA) test was negative, indicating no activity for trypsin inhibitor. Based on the functional properties, the SPI is suitable for food applications.

Mechanical and Thermal Evaluation of Diatomite Doped Fly Ash Based Geopolymers

In this work, the properties of alkali silicate geopolymer type materials and diatomite as additive to fly coal ash was investigated using thermic coal plant’s fly ash in alkaline solution. The reacted products of alumino-silicate geopolymers using fly ash plus diatomite were pseudo-amorphous aluminosilicate gel and calcite and their mechanical and thermal properties were evaluated by the addition of diatomite. The compressive strength of this geopolymer is similar to that of the Portland cement mortar of PC20 (± 20 %) when cured for 28 days while the density and thermal properties are much lower that indicates the insulator properties. Alkaline solution was produced by NaOH in different concentrations to determine the least alkaline solution molarity in the range of 1 M, 3 M and 5 M. The characterization of geopolymers were done by using XRD for phase analysis, SEM for surface and morphological evaluation, compression tests for mechanical properties and transient plane source thermal analysis for thermal insulation properties. The results showed that, 1 M of NaOH alkaline solution and 10wt% diatomite addition can provide enough strength of 18 MPa which is a good candidate for constructional materials. The thermal conductivity coefficient of 10 wt.% diatomite added geopolymer was evaluated as 0.0018 W/m×K which can also be a good candidate for insulator materials to be used in green lateral wall production.

Ecological geopolymer produced with a ternary system of red mud, glass waste, and Portland cement

In this study, the use of residues from the processing of bauxite and glass powder as precursors for the preparation of geopolymers was evaluated. The route used was an alkaline solution of NaOH with three different molarities. Nine compositions of the percussion (waste) and the activator used were verified. XRF, XRD, laser granulometry, SEM, FTIR, BET, DTG, and compressive strength tests were used to verify the physical and chemical characteristics of the residues used and the geopolymers obtained. Some geopolymers developed efflorescence on their surfaces, indicating a higher alkali content. The compressive strength increased with the addition of small amounts of Portland cement (5%). The composition with the best performance exhibited a compressive strength of 11.35 ± 1.23 MPa after 28 days. The results of the chemical analysis showed the formation of the characteristic gel of the geopolymers. However, the primary finding was that the amount of activator (sodium hydroxide) proved to be inefficient because of the intrinsic alkaline properties of the red mud, which were already effective in the alkaline activation process.

Nanostructure engineering of Cu electrocatalyst for the selective C2+ hydrocarbons in electrochemical CO2 reduction

In recent years, the selective conversion of CO2 to fuels and chemicals has been deliberated as one of the key challenges in the electrochemical CO2 reduction reaction (CO2 RR). The copper (Cu)-based materials were demonstrated to achieve the selective products from the electrochemical CO2 RR and received significant attention due to the special morphological features, which enhance the mass transport and electrical conductivity. In present work, we modulated the morphology of Cu electrocatalysts by developing the Cu-aluminum (Al) (Cu80Al20) alloy on carbon paper through co-deposition of Cu and Al elements with a different ratio by a thermal evaporation method. Followed by etching the Al content by immersing in alkaline NaOH solution resulting the formation of nanostructured Cu-Al layer. Herein, the Cu layer showed the nanowire structure with the cupric oxide (Cu2O) phase. An interesting finding was that the faradic efficiency of the final products could be tuned by dealloying process where the composition of the Cu and Al elements has been changed. Thus, the electrocatalytic activity and selectivity of CO2 conversion into C2+ of the modified structure-dependent catalysts have been investigated. Herein, the as-deposited Cu, co-deposited Cu80Al20, and etched Cu80Al20 layers were adapted to evaluate the fundamental electrochemical properties for electrochemical CO2 RR using flow electrolyzer based on gas-diffusion electrodes in the 1 M KHCO3 electrolyte. The etched Cu80Al20 catalysts exhibited the highest C2+ faradaic efficiency (FEC2+) of 72.1% at −0.84 VRHE, higher than of the as-deposited Cu catalyst (11.7%) and co-deposited Cu80Al20 catalyst (46.0%), respectively. It can be attributed to the more active electrochemical surface area, low overpotential, and charge transfer resistance. Morever, the possible additional favorable adsorption states of intermediates (*CO-COH) on the surface of the etched Cu80Al20 catalysts layer.

Effect of Corrosive Media on the Chemical and Mechanical Resistance of IPS e.max® CAD Based Li2Si2O5 Glass-Ceramics.

The influence of 4% acetic acid (pH~2.4) and an alkaline solution of NaOH (pH~10) on the corrosion resistance and micromechanical properties of disilicate crystals containing glass-ceramics (LS2-GC’s) is studied. Partially crystallized lithium metasilicate crystal containing glass-ceramics (LS-GC’s) are annealed to fully LS2-GC’s using a one stage and a two-stage heating to induce nucleation. Materials with various chemical and wear resistance are prepared. The content of the crystalline phase in the material annealed in the two-stage process A is 60.0% and increases to 72.2% for the material heated in the one-stage process B. The main elements leached in the acidic medium are lithium and phosphorus, while lithium, silicon, and phosphorus leached into the alkaline environment. Material B exhibits better chemical resistance to the corrosive influence of 4% acetic acid under quasi-dynamic conditions. In the alkaline corrosion medium, silicon is leached from material A faster compared to the material B. After prolonged exposure to acidic or basic environments, both materials show evidence of surface structural changes. A decrease of the sliding wear resistance is observed after corrosion in the acidic environment under dynamic conditions. In both materials, the wear rate increases after corrosion.

Study of Glycerol as an Additive in Ni-Mo Electrodeposition

This paper evaluates the effect of adding glycerol to the electrodeposition bath on the deposition efficiency and characteristics of Ni-Mo coating in concentrations ranging from 0.07 to 0.82 mol.L-1. Evaluation of the corrosion resistance was performed by means of weight loss tests in four different periods of immersion. Electrochemical techniques, such as obtaining polarization curves, linear polarization resistance, corrosion current density, corrosion potential, and electrochemical impedance spectroscopy were applied. Corrosion measurements were obtained in 0.5 mol.L-1 NaCl acid solution and 0.5 mol.L-1 NaOH alkaline solution. The morphology and microstructures of electrodeposited were analyzed using Scanning Electron Microscopy and Spectrometry X-Ray Diffraction. The effect of glycerol on Ni-Mo hardness was evaluated by Vickers microhardness measurements. The presence of glycerol in the electrodeposition bath increased the grain size and decreased the hardness of the coating. However, it promoted the formation of a more compact and less porous coating, increasing the corrosion resistance of the coating. Moreover, the addition of 0.82 mol.L-1 glycerol increases current efficiency, thereby reducing the amount of energy consumed during electroplating.

Study on the influence of stacking pattern on mechanical behaviour of banana/snake grass fibers hybrid epoxy composite

The present work analyses the effect of staking order on the mechanical behaviour of a hybrid polymer composites. The composites were prepared by arranging the banana and snake grass fibers in a definite sequence within the epoxy-based polymer matrix. For achieving a better composite materials’ interaction characteristic, banana as well as snake grass fibers had been cleaned with NaOH alkaline solution. By utilizing a digitalized universal testing machine, the tensile, compressive and flexural characteristics of the hybrid composite samples with the pre-determined stacking orders were assessed. The results revealed that the stacking sequence strongly influenced the mechanical characteristics of the hybrid composites. The banana fibers at the ends and in alternative laminates had resulted in the maximization of mechanical strengths including tensile, compressive and flexural characteristics. Specifically, the augmentation in tension, compressive as well as flexural values had been recorded as 14.25%, 11.76%, and 20.6%, correspondingly for the composite material with banana fibers at the ends.

Effect of molarity of NaOH and alkalinity ratio on compressive strength of geo-polymer concrete

Concrete is the most copious man-made material in the planet. One of the main ingredients in a normal concrete mixture is Portland cement. However, the production of cement emits approximately 5% of the world’s carbon dioxide (Greenhouse gas). On the other hand, the climate change due to global warming and environmental protection has become major concerns. The production of Portland cement involves the emission of carbon dioxide, thus replacing of the Portland cement with industrial waste can be one of the solutions for reduction of the carbon dioxide emission. At the same time, thermal power plants produce fly ash in a very large amount and it creates a huge problem for its disposal. Disposal of this fly ash requires approximately 40,000 ha of land every year. In order to avoid the above environmental issues as well as the disposal problem, researchers have employed fly ash an alternative of cement in making of concrete exploiting the binding property of fly ash thereby it led to make attempt to carry out more research on the replacement of cement by fly ash in the concrete. Therefore, the focus to work in this direction acquainting with the idea that the replacement of cement is possible with 100% fly ash and this alternative to regular concrete is known as Geo Polymer Concrete (GPC). The theme of the present work is fully replacement of cement with fly ash to produce the GPC. To produce the GPC, the main constituent materials used are Fly Ash (which is a by-product obtained from thermal power plants) and the alkaline activators in addition to aggregates and water. The alkaline activators used in this study for the polymerization are sodium hydroxide (NaOH) in flakes form and sodium meta -silicate (Na2SiO3) in gel form. The objective of the present work is to study the effect of NaOH molarity and alkaline activator ratios on the compressive strength (3, 7 and 28 days) of GPC at a constant curing period and curing temperature and compare with controlled concrete prepared using ordinary Portland cement (OPC). In the present work 5 and 10 M of NaOH and 1:1, 1:1.5 and 1:2 alkaline ratios were considered with constant curing temperature of 90° C and 24 h curing time. M20 grade of concrete mix design was carried out as per BIS (IS: 10262–2009) for control concrete and the same mix proportion was adopted for GPC also. From the experimental results, it was found that the both NaOH molarity and alkaline solution ratio effecting the compressive strength at 3, 7 and 28 days and maximum compressive strength was obtained at higher NaOH molarity (10 M) and medium alkaline solution ratio (1:1.5). Further, it was found that the compressive strength of GPC was higher than the controlled concrete prepared using OPC.