NaOH Alkaline Solution Research Articles

Synthesis of Kaolin Geopolymer as Ceramic Reinforcement in Lead-Free Solder

This paper elucidates the fabrication of kaolin geopolymer as the ceramic material. The kaolin geopolymer ceramic (KGC) was used as a new potential reinforcement in the lead-free solder. The fabrication of KGC was started through combination of alkaline solution of NaOH and Na2SiO3 reaction with kaolin material. The mixture of kaolin geopolymer were prepared and the homogenised mixture were curing for 24 hours. The kaolin geopolymer is sintered at 1200°C and then crushed to produces a fine kaolin geopolymer. The KGC were then mixed with lead-free solder through powder metallurgy technique. The elemental distribution in the KGC was investigated by using Synchrotron Micro-XRF. Meanwhile, the phase analysis involved in KGC and composite solder with addition of KGC were investigated as well.

Metakaolin Addition to Improve Geopolymerization Process and Properties of Waste Clay-Based Materials

The exploitation of different kind of clayey waste (halloysitic, smectitic/illitic, kaolinitic) for the production of geopolymers in the view of a circular economy of mines is the main goal of this study. In particular, the addition of low percentages of metakaolin (5-15%) was evaluated to improve the chemical-physical properties and the consolidation degree of geopolymeric formulations produced with clays classified as mine’s by-products. In fact, these secondary raw materials are often not sufficient alone to obtain chemically stable formulations with acceptable mechanical properties but require the addition of reactive fillers. All samples contained thermally treated clays (600°C-700°C) and metakaolin as aluminosilicate precursors, alkaline solution of NaOH and Na2SiO3, and were cured at room temperature. The influence on the final products with MK addition was monitored with the evaluation of the chemical stability in water (pH and ionic conductivity measures), the comparison of setting times (Vicat needle) and mechanical performance.

A Study on Chemical Ageing of Composite Ribbed GFRP Bars under Load

Here we explored the chemical durability of glass fiber-reinforced polymer (GFRP) bars under load. Three batches of ribbed GFRP bar specimens were fabricated using binder matrices: ED-22+isomethyltetrahydrophthalic anhydride (iso-MTGFA), ED-22+Ethal-450 and NPPN-631+ iso-MTGFA. As the reinforcing filler, we used an EC17 glass roving (for all the specimen batches). The specimens of each batch were aged in a 1 N alkaline NaOH solution at 60 °C for 2000 hrs. The ageing was performed under a 300 MPa load (30% of the failure stress). The tensile strength of the specimens from each batch following ageing was measured. The tensile test results demonstrated that that the strength loss of the specimens following chemical ageing was 58.9% for batch 1 based on ED-22+iso-MTGFA, 6.6% for batch 2 based on ED-22+Ethal-450, and 33.6% for batch 3 based on NPPN-631 + iso-MTGFA. The specimens of batch 2 based on ED-22+Ethal-450 exhibited the greatest resistance to the NaOH alkaline solution (a strength loss of 6.6%).

Synthesis and Application of Graphdiyne Oxide-Polyurethane Nanocomposite Yield a Highly Sensitive Non-Enzyme Glucose Sensor

Graphdiyne is a new carbon nanomaterial after graphene. It has excellent electrical properties and can be chemically modified. Here, a graphdiyne oxide-polyurethane nanocomposite (GDYO-PU) was synthesized by chemical coupling and characterized with Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and scanning electron microscopy (SEM). A GDYO-PU modified glassy carbon electrode (GCE) was applied as a non-enzymatic glucose electrode. The electrochemical property of the GDYO-PU electrode was investigated by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and amperometry in the presence of [Fe(CN)6]3−/4− in 0.1 M NaOH alkaline solution and at the bias potential of 0.2 V. Fast electro-deposition was observed for the electrochemical deposition of Fe(CN)6 3−/4− on the GDYO-PU electrode surface. Under the optimized conditions, the calibration curve of the nano electrode is linear over the concentration range of 0.2 to 6.4 μM, with high sensitivity of 377 μAmM−1cm−2 as well as a low detection limit (LOD) of 0.1 μM (S/N = 3). The GDYO-PU nanocomposite based non-enzyme glucose electrode is therefore promising for analysis of tiny volume of biological samples, which meets the requirement of minimal invasive measurement in clinic and family care.

Elaboration of geopolymer binder from pharmaceutical glass waste and optimization of its synthesis parameters

The objective of this study is to manufacture a new geopolymer binder from pharmaceutical glass waste as a main raw material. The geopolymer synthesis followed a chemical procedure whereby the effect of several parameters, namely, the glass particle size, the concentration of the alkaline solution and the cure temperature were optimized. Several techniques were used to characterize the raw material and the obtained geopolymers: X-ray diffraction, X-ray fluorescence, Fourier-transform infrared, scanning electron microscopy and thermo-gravimetric analysis. The compressive strength of the produced geopolymers was determined by mechanical tests. The results show that the pharmaceutical glass waste produces geopolymer binder of high mechanical performance. Contrary to metakaolin-based geopolymers, no sodium silicate is required for the setting and hardening of this geopolymer type. The thermal activation by increasing the cure temperature improves the geopolymerization kinetics and leads to a high compressive strength, which exceeds 60 MPa for 60 °C and NaOH alkaline solution molarity of 8 M.

Flashpoint and Flame Spread Analysis of Material Coconut Fiber (Cocus Nucifera) Using Chemical Treatment of Alkali NaOH as a Sound Absorber Material in Ship

The use of sound absorbers on many ships made from glass wool. Glass wool has a negative impact on health, which can irritate the skin and disrupt the respiratory system. Therefore, it is necessary to have an alternative sound insulation material that is eco-friendly which has capabilities comparable to glass wool, and can also be used as heat insulation on ships. These alternative ingredients are materials from natural fiber. This research made sound absorbers using coconut fiber by soaking fiber into an alkali NaOH solution. Materials are selected based on density, economic value, and ease in the manufacturing process. The sound absorbers are modified using coconut fiber which is given a soaking treatment of alkaline NaOH solution and distilled water with a percentage of 15%. Soaking aims to remove lignin content and improve the mechanical properties of coconut fiber. In this research, 9 variations were made with different compositions. Tests are based on ASTM E84 to determine the flashpoint value and the safe flame spread on the ship. From the test results, it was found that coconut coir material was given a soaking treatment of alkaline NaOH solution with a percentage of 15% for 2 hours with a density of 0.3 gr/cm3 and thickness 30 mm and using a polyurethane adhesive. The time to reach the flashpoint is 20.45 seconds and the average temperature of flame spread is low when compared to other specimens including glass wool. The conclusion obtained is that the sound absorbers are safe when used on a ship.

Effect of Mixing Procedure and Chemical Composition on Physical and Mechanical Performance of Geopolymers

Nowadays geopolymer is promising and relevant material that can be effectively used in wide range of application areas. It is possible because of there are a lot of potential sources of raw materials for geopolymer synthesis. Raw components are the one of the key parameters that effect on geopolymer performance. On the other hands, the technological stages of geopolymer synthesis is no less important factor. The purpose of this study was to determine effect of technological parameters of geopolymer synthesis such as component composition of solid state phase, alkaline activator preparation and its introduction onto geopolymer paste as well as curing temperature on performance characteristics of geopolymer. Fly-ash based geopolymer samples were prepared with adding of different mineral components: Portland cement (PC), kaolin, metakaolin; different curing temperature conditions: ambient temperature and temperature treatment at 70 °C in oven during 24 hours; different methods of preparation and application of alkaline activator: using of fresh alkaline solution and using alkaline solution after 24 hours of cooling. The results show that efficiency of curing temperature conditions strongly depend on component composition of geopolymer paste. Samples, containing PC and metakaolin demonstrate better characteristics after curing under ambient temperature. Samples, containing kaolin and reference composition (fly ash only) the temperature treatment in oven is the best curing method (increasing in compressive strength up to 13 times). Using alkaline solution of NaOH after 24 hours of cooling gives a good effect on geopolymerization process and provides increasing in compressive strength value from 13 to 84 % for all experimental geopolymer pastes. However, average density for all compositions is varied slightly.

Development of alpha tracks measurement with thermal oven as an etching technique for SSNTDs

Abstract In the present work, Thermal oven as a heating technique in chemical etching process has been tested to investigate the track density and compares with a traditional technique water bath (WB). Thermal oven induced chemical etching has been employed in reducing the etching duration. Two solid-state nuclear track detectors (SSNTDs) CR-39 and LR-115 are utilized in this comparison. Detectors are exposed to 226Ra alpha source (5 µ ci). Several pieces of CR-39 and LR-115 detectors were exposed to 226Ra source at three different times of exposure (5, 10 and 15sec). Chemically Etching carry out with NaOH alkaline solution (6.25 N) at 70 °C for CR-39 and (2.5 N) at 60 °C for LR-115. For (5, 10 and 15sec) exposure time, the estimated maximum track densities of CR-39 detector at 90 min for thermal oven compared with 120 min for water bath. LR-115 detector maximum track densities were founded at 40 min compared with 50 min for the water bath technique. Finally, the etching parameters (the diameter of the tracks (D), etching efficiency (ɳ), bulk etching rate (VB), track etching rate (VT), and the sensitivity (V)) were calculated and compared.

MnOOH nanoparticles integrated nitrogen doped porous nanosheet-like carbon network as a non-noble catalyst for electro-oxidation of sodium borohydride

Nitrogen doped carbon-supported with various ratio of electro-active manganite nanoparticles (MnO–NPCs) as a facile, low-cost, and non-noble electrocatalyst is synthesized for electro-oxidation of borohydride. Transmission electron micrographs show the size of MnO nanoparticles in NPC is about 3.8 ± 0.2 nm with a definite lattice parameter and randomly distributed into the entire nanosheet-like porous carbon network. Survey X-ray photoelectron spectrum (XPS) of MnO–NPCs sample reveals the presence of Mn element; and Mn–O–Mn and Mn–O–H peaks from O 1s, indicating the effective insertion of MnO nanoparticles onto the NPC surface. Electrochemically transformed MnOOH–NPCs are further explored as effective catalysts toward the electro-oxidation of borohydride in 1.0 M alkaline NaOH solution. Among the catalysts with different ratios, MnOOH–NPC-2 displays higher catalytic performance (~19.9 mA ⋅ cm−2) with low-onset polarization potential (−0.65 V) towards borohydride electro-oxidation. The obtained results are mainly owing to (i) the unique nanosheet-like structure of nitrogen doped carbon network access large amount of MnOOH nanoparticles (without any aggregation) through their numerous porous-structure with high-specific surface area (821 m2 g−1), (ii), the presence of intrinsic synergetic activity between porous carbon nanosheets and MnOOH nanoparticles, and (iii) the effective interaction of Mn2+ ions with OH− ions to form Mn(OH)2, which mediates improved catalytic activity of borohydride electro-oxidation.

Rapid one-pot hydrothermal reaction for preparing BaCu2Si2O7 fine particles with controlled blue colour tonality

A new chemical approach to control the preparation of BaCu2Si2O7 fine particles employing alkaline NaOH solutions coupled with a variation of the nominal mixed Cu2+ content was investigated aiming to crystallise BaCu2Si2O7 particles successfully. The concentration of the NaOH solutions varied between 0.25 and 3.0 M, and the mixed Cu2+ content varied between 1.6 and 2.0 mol. The synthesis of the BaCu2Si2O7 particles occurred at 180 °C for an interval as short as 24 h, even in a 0.25 M NaOH solution with a Cu2+ content of 2.0 mol. The crystallisation of BaCu2Si2O7 particles, free of by-products, was carried out via a one-pot process involving a single-step reaction. The crystallisation of fine octahedral-shaped particles with a size varying from 75 to 200 nm occurred in a 0.25 M NaOH solution at 200 °C for 6 h. These particles exhibited a 3D self-assembling process forming semi-spherical shaped agglomerates (2.25 μm average size) with a pale blue hue. On the contrary, the optical reflectance of the BaCu2Si2O7 particles was tuned in the UV–vis, and blue tonality occurred when the mixed Cu2+ content varied between 1.7 and 1.9 mol. The brighter blue colour tonalities with high UV–vis reflectance is favoured by the formation of fine block-like shaped particles with sizes within the range of 60–125 nm; these particles formed oval-shaped 3D hierarchical agglomerates with an average size of 0.6 μm. All the powders prepared by the present method exhibited CIE-L*a*b* values that correspond to the Han blue colour spectral space, but the differences in the colour values are strongly affected by the particle morphological variations.

Characterization of surface properties of chitosan/bentonite composites beads by inverse gas chromatography

Chitosan/bentonite (CSBt) composites beads were prepared by dropwise of a solution containing chitosan and bentonite to an alkaline NaOH solution. Fourier Transform Infrared Spectroscopy, X-ray diffraction analysis, X-ray photoelectron spectroscopy, XPS and Brunauer-Emmett-Teller BET analysis have been used to provide new insights on the composition and morphology of CSBt composites beads surface. In this study, inverse gas chromatography (IGC) was implemented to characterize physico-chemical properties of CSBt composites surface. IGC at infinite dilution (IGC-ID) was used to understand the effect of CS on dispersive component of the surface energy of the bentonite. The increasing amount of CS leads to significantly decrease of Bt γsd emphasizing the Bt coating with CS. The IGC at finite concentration (IGC-FC) was also implemented allowing us to reach several parameters such as: specific surface area with organic probes and the distribution functions of the adsorption energy sites on the solid surface. In this case, the most significant decreases were observed in the specific surface area obtained with the octane and isopropanol probes. The distribution function of the adsorption energy sites obtained with isopropanol revealed the decrease in the number of the high energy sites with increase of CS/Bt mass ratio.

Structural characterization and inhibitions on α-glucosidase and α-amylase of alkali-extracted water-soluble polysaccharide from Annona squamosa residue

A novel acidic polysaccharide, named as AWPA, was extracted form Annona squamosa residue by 0.1 M NaOH alkaline solution and purified by DEAE-cellulose and Sephadex G-150. HPLC analysis indicated that AWPA was a homogeneous polysaccharide with molecular weight of 3.08 × 103 kDa. The monosaccharide composition of AWPA, determined by ion chromatography, was consisted of L-arabinose, D-galactose, d-glucose, D-mannose, D-galacturonic acid in a percentage of 15.58:13.48:60.14:9.02:1.78, respectively. The results of FT-IR, methylation and NMR showed that the sugar residue of AWPA were mainly composed of α-L-Araf-(1→, →4)-α-D-Glcp-(1→, →4)-β-D-Galp-(1→, →6)-β-D-Glcp-(1→, →4,6)-β-D-Galp(1→, →3,6)-α-D-Manp-(1→, respectively. The Congo red experiment on AWPA showed that there was helix conformation. The microstructure of AWPA was detected by scanning electron microscopy, showing that the shape of AWPA was reticular and its structure was irregular. AWPA had effectively α-glucosidase inhibitory activity and α-amylase inhibitory activity with IC50 of 0.667 mg/mL and 1.360 mg/mL, respectively. The inhibitory effects of AWPA on α-glucosidase and α-amylase were both reversible with mixed type and competitive type competition, respectively. The significance of manuscript was not only to avoid the waste of Annona squamosa residue, but provided alternative in the developments of inhibitors of α-glucosidase and α-amylase.

Study of fly ash based zeolite by using slow positrons

After coal fly ash activation with alkaline NaOH solution by the hydrothermal method, it was possible to synthesize the zeolites type Cancrinite and Analcime. Slow positron beam experiments have been performed on two set of samples. One in which the NaOH concentration was varied and another one in which the synthesis temperature range was varied. The mineralogical composition was determined by X ray diffraction, the morphology of one of the zeolite samples as compared with the coal fly ash was observed by 3D X-ray imaging. Positron results suggest that increasing the NaOH concentration produces an increase in open volume and/or defects while increasing the temperature in the sample preparation diminishes it.

The role of ZnO in the catalytic behaviour of Zn-Al mixed oxides in aldol condensation of furfural with acetone

The manuscript describes the key aspects of Zn-Al mixed oxides prepared by different methods (the so-called urea method and co-precipitation methods using either NaOH/Na2CO3 alkaline solution or solution of NaOH) affording high conversion and selectivity values in aldol condensation of furfural with acetone. The structure, composition and acid-base properties of Zn-Al mixed oxides were described by using of TGA, XRD, N2-adsorption, TPD-NH3/CO2 and in-situ diffuse reflectance spectroscopy and correlated with the catalytic performance of a series of Zn-Al mixed-oxides catalysts. Along with the impact of specific surface area and basicity on the furfural conversion, the conversion of furfural also increased with the increasing value of the edge of UV-vis spectrum of Zn-Al mixed oxide reflecting ZnO-Al2O3 interaction. We have introduced a simple method based on diffuse reflectance spectroscopy with a potential to predict furfural conversion over Zn-Al mixed oxides in aldol condensation of furfural with acetone.

Alternately Dipping Method to Prepare Graphene Fiber Electrodes for Ultra-high-Capacitance Fiber Supercapacitors.

SummaryFlexible fiber supercapacitors are promising candidate for power supply of wearable electronics. Fabrication of high-performance fibers is in progress yet challenging. The currently available graphene fibers made from wet-spinning or electro-deposition technologies are far away from practical applications due to their unsatisfactory capacitance. Here we report a facile alternately dipping (AD) method to coat graphene on wire-like substrates. The excellent mechanical properties of the substrate with greatly diverse choices can be carried over to the fiber supercapacitors. Under such guideline, the graphene fiber with a titanium core made by our AD method (AD:Ti@RGO) shows an ultra-high specific capacitance of up to 1,722.1 mF cm−2, which is ∼1,000 times that of wet-spinning- and electro-deposition-fabricated neat graphene fibers and presents the highest specific capacitance to date. With excellent mechanical properties and striking electrochemical performances, the AD:Ti@RGO-based supercapacitors light the path to the next-generation technologies for wearable devices.

Rapid microwave-assisted hydrothermal green synthesis of rGO/NiO nanocomposite for glucose detection in diabetes

Diabetes is one of the fastest growing diseases worldwide that can lead to dangerous complications. Therefore, the demand for the development of optimal glucose sensors has increased for diabetes disease management. In this study, a non-enzymatic glucose sensor based on a reduced graphene oxide and nickel oxide (rGO/NiO) nanocomposite was developed. This novel rGO/NiO nanocomposite was synthesized using a facile and rapid green economic microwave-assisted hydrothermal method in the absence and presence of organic/reducing agents and subcritical water, respectively. The morphology and composition of the as-prepared rGO/NiO nanocomposite were characterized via X-ray diffraction, Fourier transform infrared, energy-dispersive X-ray spectrometry, and field emission scanning electron microscopy. The electrochemical performance of the rGO/NiO-modified electrode was examined by cyclic and square wave voltammetric techniques under optimal conditions. The results indicated that the developed rGO/NiO electrode exhibited a good performance toward glucose detection in 0.1 M NaOH alkaline solution with two linear electrochemical responses to glucose ranging from 20 μM to 80μM and from 1mM to 15 mM. Moreover, the detection limit was 19.35 μM ([S/N] = 3). The fabricated sensor was also investigated for the detection of glucose in the presence of common interfering species. Thus, the sensor exhibited good sensitivity and selectivity and was repeatable, stable, and economical for non-enzymatic glucose detection. Additionally, the proposed sensor was successfully applied for glucose detection in human serum samples with satisfactory recoveries.

An Alternative Process for Leaching Chalcopyrite Concentrate in Nitrate-Acid-Seawater Media with Oxidant Recovery

An alternative copper concentrate leaching process using sodium nitrate and sulfuric acid diluted in seawater followed by gas scrubbing to recover the sodium nitrate has been evaluated. The work involved leaching test carried out under various condition by varying temperature, leaching time, particle size, and concentrations of NaNO3 and H2SO4. The amount of copper extracted from the chalcopyrite concentrate leached with seawater, 0.5 M of H2SO4 and 0.5 M of NaNO3 increased from 78% at room temperature to 91% at 45 °C in 96 h and 46 h of leaching, respectively. Gas scrubbing with the alkaline solution of NaOH was explored to recover part of the sodium nitrate. The dissolved salts were recovered by evaporation as sodium nitrate and sodium nitrite crystals.

Microstructure and Catalytic Activity of Melt Spun Al-Cu-Fe Ribbons

The Al65Cu20Fe15 (in at.%) rapidly solidified ribbon in the form of brittle flakes was produced by melt-spinning technique. It consists the cell or dendrites of the icosahedral quasicrystalline I-phase surrounded by copper rich cubic τ-Al(Cu, Fe). The pulverized ribbon (fraction <32 μm) was subjected to NaBH4 or 20% aqueous NaOH treatment, which led to the formation of oxide in the form of thin flakes at the outer layer of the powder particles. Test of the catalytic properties of the as spun ribbon and powder before and after treatment was made in the reaction of phenylacetylene hydrogenation. It was shown that for as received ribbon, even at very mild conditions (60 °C, H2 pressure of 5 bar), 40% of phenylacetylene was converted to hydrogenation products with 0.7 styrene/ethylbenzene ratio. The use of pulverized ribbon resulted in improvement of activity, with the same ratio of reaction products. The effect of treatment with NaBH4 led to improvement of the catalyst activity, while strongly alkaline solution of NaOH worsened significantly the catalytic activity, but improved selectivity to styrene (styrene/ethylbenzene=1.2).

In-situ electrochemical oxidation of amorphous nanoporous NiZrO for enhanced non-enzymatic glucose sensing

Amorphous nanoporous NiZrO (npNiZrO) is fabricated by dealloying Ni64Zr36 metallic glass ribbon as non-enzymatic glucose sensor in this work. The npNiZrO supported by Ni64Zr36 metallic glass ribbon as self-supporting electrode can achieve a high sensitivity of 3.19 mA cm−2 mM−1 in 0.1 M NaOH alkaline solution. Furthermore, the sensitivity toward glucose sensing can be improved by in-situ electrochemical cyclic voltammograms (CV) activation, which is attributed to the oxidation of npNiZrO electrode. XPS results confirmed the formation of Ni2+/Ni3+ redox couple, which is acted as the active sites. The CV-activated npNiZrO electrode with an enhanced sensitivity of 4.81 mA cm−2 mM−1 is corresponding to the improved electrochemical active surface area (ECSA). The results in this work provide a basis for future production of enzyme-free glucose sensors based on amorphous nanoporous materials.

Synthesizing spindle-shaped anion exchange membranes to improve conductivity and stability

High ionic conductivity and excellent alkaline stability are very important for solid electrolyte. Therefore, spindle-shaped anion exchange membranes (AEMs) based on poly (arylene ether ketone) and 1-Bromo-N,N,N-trimethylhexane-6-aminium bromide (Br-QA) have been prepared. The obtained Br-QA can be grafted with poly (arylene ether ketone) main chains to form micro-phase separation structure enhancing the ionic conductivity. Especially, the grafting quaternary ammonium (QA) cation groups are separated by alkyl bromine endows the AEMs with alkaline stability features. Simultaneously, the OH− conductivity of the QA-PAEK-0.6 obtained membranes is 0.046 S/cm under fully hydrated conditions at 60 °C. After immersing into 1 M NaOH alkaline solution for 15 days at 60 °C, the anionic conductivity still high to 0.03 S/cm. Meanwhile, the poly (arylene ether ketone) backbones provide excellent mechanical properties and the Br-QA cation groups also possess good thermal stability, which satisfy the requirement of wide applications.