Mixture Of Nitric Acid Research Articles

Effect of cavitation erosion in the sonochemical exfoliation of activated graphite for electrocatalysis of acebutolol

This study mainly covered the cavitation erosion in probe sonication and its electrochemical behavior. The activated graphite was exfoliated by the probe sonication wherein the titanium alloy (TA) is used as a probe (micro-tip). The sonication performed in the aqueous solution contains a mixture of sulfuric acid and nitric acid (1:1). The exfoliated graphite (EG) was examined by field emission scanning electron microscope, Raman and X-ray diffraction pattern analysis. The results showed that some TA particles dissolute from the TA micro-tip accompanied with graphite exfoliation. This dissolution experienced from the cavitation erosion, because the acoustic cavitation makes severe deformation on probe tips due to the bubble collapse. The dissolution rate increased when increasing sonication time; the resultant TA particles are randomly distributed over the EG. These EGTAs applied to the electrochemical oxidation of acebutolol which revealed an appreciable electrochemical performance and also exhibited better analytical performances to the electrochemical determinations. The obtained analytical parameters viz., sensitivity (0.234 µA µM−1 cm−2), linear range (0.01–15.1 µM), and limit of detection (0.003 µM) are highly comparable with the previous reports. Moreover, it has an acceptable tolerance with the interfering substances.

Facile and Scalable Fabrication of Porous g‐C3N4 Nanosheets with Nitrogen Defects and Oxygen‐Doping for Synergistically Promoted Visible Light Photocatalytic H2 Evolution

A facile and scalable approach is firstly presented to fabricate novel O‐doped nitrogen defective porous g‐C3N4 nanosheets (PNV‐CN) through thermal polymerization of a guanylurea nitrate (GLUN) precursor that forms by a nitric acid assisted heating reaction process of dicyandiamide (DCDA), in which nitrate ions act as the intensified gas template function for producing pores and carbon nitride nanosheet structures and the oxidant for forming nitrogen defects. PNV‐CN demonstrates a high visible light photocatalytic activity of 62.4 μmol h−1 and an apparent quantum efficiency of 4.0% at 420 nm with 17.3 and 5.5 times higher hydrogen evolution rate (HER) than bulk g‐C3N4 (B‐CN) prepared by thermal polymerization of DCDA and the loose g‐C3N4 (LB‐CN), prepared via thermal polymerization of a mixture (DMDN) consisting of dicyandiamide nitrate (DN), GLUN, and their hydrogen‐bonding macromolecular compounds by drying the physical mixture of DCDA and nitric acid, respectively. The outstanding photocatalytic properties of PNV‐CN for visible light‐driven hydrogen evolution originate from the enhanced charge separation and migration, extending visible light absorption tails, promoting recombination of charge carriers, increased active sites, and strengthened mass transfer process that results from the synergistically promoting effect of hierarchical porous morphology, as‐formed nitrogen defects, O‐doping and the unique nanosheet structure.

The Clinical performance of all ceramic zirconia-veneered crowns after different surface treatments of zirconia framework: 30 months clinical assessment

Objective: To evaluate the clinical performance of zirconia-veneered crowns after different surface treatment of zirconia frameworks named as; no surface treatment, sandblasting, silicatization (CoJetTM sand) , Selective infiltration etching (SIE) and the novel acids mixture.Materials and methods: A total of 50 patients of age ranged from 20 to 35 years were presented with root canal-treated molar teeth that needed post-retained restorative treatment. They were divided into 5 groups according to surface treatment of zirconia frameworks (10cases each); Group S1: Zirconia frameworks received no surface treatment. Group S2: Zirconia frameworks received sandblasting with 110µm aluminum oxide airborne particle abrasives.GroupS3: Zirconia frameworks received CoJet sand surface treatment. Group S4: Zirconia frameworks received selective infiltration etching surface treatment. Group S5: Zirconia frameworks received a specially formulated mixture of hydrofluoric acid (HF 9 wt%) and nitric acid (HNO3 26 wt%) at a ratio of (4:1) for 5 min. All Zirconia frameworks received IPS e.max Ceram veneering porcelain. They received all ceramic zirconia based single crowns using Cerec in-Lab CAD/CAM technology for designing and milling zirconia frameworks. Teeth preparation was performed to achieve 2mm occlusal clearance, 1.5mm axial reduction and 1mm rounded shoulder subgingival finish line. Secondary impression was taken for each case using addition silicone rubber base impression material and poured using special reflective cerec stone (CAM Base) to facilitate scanning of the preparation using the in-Lab extra oral scanner “inEos”. 3D virtual models were obtained that were used for designing zirconia frameworks. Then, milling of zirconia blocks were performed using inLab Cerec 3 milling machine to obtain zirconia frameworks followed by sintering procedures for the zirconia frameworks. After try in of sintered zirconia frameworks in the patient’s mouth, they received different types of surface treatment. After that, porcelain build up was conducted by layering technique. All ceramic zirconia based crowns were then cemented using dual-cured resin cement (Multilink Auto Mix) and were subjected to a period of 6, 12, 18, 24 and 30 months clinical observation according to the modified USPHS criteria for indirect restorations, where prosthodontic results were recorded. Statistical analysis was performed using a commercially available software program (SPSS 19; SPSS, Chicago, IL, USA). Values were presented as number and percentages. Chi square test was used to compare categorical data.The level of significance was set at P < 0.05. Results: It was found that at 6 months, score A was recorded in all specimens of IPS e.max Ceram, with no statistically significant difference between different surface treatments (p=1). At 12 months, score A was recorded in all specimens, with no statistically significant difference between different surface treatments (p=1). At 18 months, score A was recorded in 100% specimens of CoJet and acid mixture surface treatment, in 90% of specimens of no treatment and in 80% of specimens of sandblasting and SIE; with no statistically significant difference between different surface treatments (p=0.815). At 24 months, score A was recorded in 80% specimens of sandblasting, CoJet and acid mixture surface treatment, in 66.7% of specimens of no treatment and in 22.2% of SIE; with a statistically significant difference between different surface treatments (p=0.045). At 30 months, score A was recorded in 80% specimens of sandblasting, 88.9% CoJet and 77.8% of acid mixture surface treatment, in 44.5% of specimens of no treatment and in 11.1% of SIE; with a statistically significant difference between different surface treatments (p=0.0024). Conclusions: (1) In all cases, the tested systems showed chipping of the comparable low-strength veneering ceramic but no fracture of the high-strength core or the natural tooth in clinical cases. (2) The treatment of the surface zirconia framework with Cojet system was able to maintain acceptable clinical performance at 24 months and 30 months recall periods. However, the other surface treatments showed lesser performance. (3)No direct correlation between zirconia framework surface treatments and long term bonding to veneering ceramic could be addressed; however, it could be multifactorial such as lack of proper framework support, internal defects, direction, magnitude and frequency of the applied load as well as the residual stresses induced by processing.

Graphene-based materials produced by graphite electrochemical exfoliation in acidic solutions: Application to Sunset Yellow voltammetric detection

Two graphene-based materials were prepared by exfoliation of graphite rod with pulses of current. The first material (denoted EGr-1) was exfoliated in a mixture of sulphuric and nitric acid (3:1 ratio; 0.5 M each; pH 1) giving a material composed of graphene (40% few-layer; 32% multi-layer) and graphene oxide (28%). The second material (denoted EGr-2) was prepared by exfoliation of the graphite rod in 0.05 M boric acid (pH 5.1) in which 0.05 M NaCl was added to increase the electrolyte conductivity. After preparation, the materials were used for the modification of two glassy carbon (GC) electrodes, denoted GC/EGr-1 and GC/EGr-2, respectively. The performances of each electrode toward Sunset Yellow (SY) detection were tested in laboratory solutions (pH 6 PBS) containing increasing concentrations of SY (3 × 10−7–1 × 10−4 M). It is important to emphasize that the sensitivities, linear ranges and the limits of detection of the two electrodes were different. Hence, in the case of the electrode covered with graphene prepared in strong acidic solution (GC/EGr-1) the sensitivity was 0.017 A·M−1, the linear range between 6 × 10−6 and 1 × 10−4 M, the LOD was 1.8 × 10−6 M. In contrast, the electrode covered with the material prepared in weak acidic solution (GC/EGr-2) has higher sensitivity (0.021 A·M−1) wider linear range (1 × 10−6–1 × 10−4 M) and lower LOD (3 × 10−7 M).

An alternative sequential extraction scheme for the determination of trace elements in ferrihydrite rich sediments

Sequential extraction schemes (SES) were evaluated to investigate the fractionation of Al, As, Cd, Cs, Cr, Co, Cu, Fe, Mn, Mo, Pb, Sr, U and Zn between the different mineral phases in iron oxide rich deposits of a former uranium mining site. Ineffective dissolution of iron oxide was observed when applying the BCR sequential extraction scheme. The hydroxylamine hydrochloride reagent in nitric acid could not effectively dissolve the iron oxide phase, even after several consecutive extractions. The use of sodium pyrophosphate to remove organic matter prior to the dissolution of the iron oxides and the use of oxalic acid buffer and dithionite citrate buffer to dissolve the amorphous and crystalline iron oxides was evaluated. An alternative six step SES for iron oxide rich sediments is proposed consisting of F1) Exchangeable-Carbonate fraction using acetic acid/ sodium acetate buffer (pH 5) F2) Labile organic fraction using sodium pyrophosphate, F3) Easily reducible amorphous oxides using an oxalic acid buffer, F4) Organic and Sulfide fraction using hydrogen peroxide, followed by ammonium acetate extraction, F5) Poorly reducible crystalline oxides using sodium dithionite and F6) residual fraction using a microwave digestion step with hydrofluoric acid, nitric acid and hydrochloride acid mixture. A good correspondence between the sum of the sequential extraction steps and total metal concentrations was found. Both the BCR method and new method were also applied to the CRM BCR 701 providing indicative values for non-certified elements with the BCR method and indicative values for the method presented.

Validation of a simple sample preparation method for multielement analysis of bovine serum.

Here we propose a single acid digestion (SAD) sample preparation method for ICP-MS analysis of animal serum samples to determine trace element contents. The method was evaluated in comparison with a commonly used procedure involving dilution of samples in an alkaline solution (AKD). In the SAD procedure, aliquots (1 mL) of bovine serum samples were treated at low temperature with a mixture of concentrated nitric acid and hydrogen peroxide. Trace elements (As, B, Ba, Cd, Co, Cr, Cu, Fe, Hg, Li, Mn, Mo, Ni, Pb, Sb, Se, Sr, U, and Zn) were directly determined by ICP-MS analysis of diluted solutions of samples. Both methods were sufficiently sensitive to enable quantification of most trace elements, with the exception of the AKD method for Cd, Hg and Pb. The quality of the data was verified by using certified reference material. Good results were obtained for the SAD procedure and all elements, but recoveries were unacceptable with the AKD procedure for Se (recovery: 57%), Cd (154%) and Fe (139%). Strong associations (R2>0.90, P = 0.000) between the data obtained by both methods were demonstrated for the elements considered. The proposed SAD sample preparation method produced satisfactory results for determining most toxic and essential trace elements targeted in monitoring studies.

Thermally-treated and acid-etched carbon fiber cloth based on pre-oxidized polyacrylonitrile as self-standing and high area-capacitance electrodes for flexible supercapacitors

The fast development of portable devices has greatly stimulated the demand for flexible supercapacitors (FSCs). The key to assembling FSCs lies in the development of electrodes with high-performance and good flexibility. In this work, oxygeneous groups modified nitrogen-doped carbon fibers cloth (ONCC) was obtained through annealing the pre-oxidized polyacrylonitrile cloth (PPC), followed by a facile oxidation process using a mixture of concentrated sulfuric acid and concentrated nitric acid. By changing annealing temperature, the nitrogen content can be controlled in the obtained ONCC. It was found that the PPC annealed at 950 °C followed by acid etching for 60 min could deliver the excellent areal and gravimetric specific capacitance of 1385 mF cm−2 and 294.7 F g−1 at the current density of 1 mA cm−2, outstanding rate performance and superb cycling stability. Furthermore, the assembled FSC delivered a high energy density of 19.8 μWh cm−2 (4.03 Wh kg−1) at a power density of 50.1 μW cm−2 (10.2 W kg−1) and good flexibility under different bending conditions. This work provides a facile and efficient route to prepare high-performance carbon fiber based electrode materials in large scale for flexible all-solid-state energy storage devices.

Detection of Poor Contacts in Low-Voltage Electrical Installations

Effects of a reduced torque on heating and the electrical resistance of wire-screw terminal connections in an old (used) receptacle and two new receptacles with intentionally corroded connections were experimentally investigated in the laboratory. In one of the new receptacles, the corrosion process was accelerated by treating the line connection with a mixture of nitric acid and hydrochloric acid, and in the other by treating the neutral connection with sulfuric acid. It was shown that by using these acids, both the temperature rise and electrical behavior of long-serving receptacles can be simulated. The possibility to detect a poor contact in an electrical circuit by measuring both the line to earth (L-PE) resistance and the line to neutral (L-N) short circuit loop resistance during a periodic verification of low-voltage electrical installations was also analyzed. In the laboratory conditions, a test electrical circuit with a poor contact in each of the tested receptacles was formed and the influence of that contact on both of the mentioned resistances was observed during long-lasting heating processes. Based on the results of both the laboratory experiments and periodic verifications of low-voltage electrical installations in public and commercial buildings with the total of 11 243 receptacles, a new procedure for detecting poor contacts in low-voltage electrical installations, valid for the terra neutral protection system, is recommended. The procedure, intended for periodic verification, provides information about poor contacts and their location in the tested receptacle (on the phase, neutral, and/or equipment grounding conductor) by comparing both the L-PE resistance and the L-N short circuit loop resistance to the limit values obtained during the verification.

Oxidative Treatment of Multi-Walled Carbon Nanotubes and its Effect on the Mechanical and Electrical Properties of Green Epoxy based Nano-Composites

Oxidative treatment of Multi-Walled Carbon Nanotubes (MWCNT’s) was done by chemical functionalization by using the mixture acid, which is a mixture of sulfuric acid (H2SO4) and nitric acid (HNO3). Functionalization was governed by four parameters namely mixture acid concentration, temperature(T), time of heating(t) and the amount of MWCNTs used. After functionalization, functionalized MWCNT’s were then diluted in dimethylformamide (DMF) to analyse the percentage of soluble MWCNT’s. Also, by increasing the time of functionalization, it was observed that overall yield decreases but the percentage of functionalized product inside the yield quantity remains the same. Material characterization was also carried out at several steps to validate this theory.Chemical functionalization of MWCNT’s is generally significant for the manufacturing of polymer-based nanocomposites. Oxidative treatment enhances the dispersion and interfacial bonding within the epoxy matrix. In this research work, a bio-based epoxy resin was selected for the manufacturing of nanocomposite samples with various concentrations of pristine and functionalized MWCNTs. Mechanical and electrical characterization was finally carried out to increase the knowledge on the interaction of MWCNT’s with the selected green epoxy matrix system and their influence on the original properties of the resin.

A highly sensitive printed humidity sensor based on a functionalized MWCNT/HEC composite for flexible electronics application.

A novel functionalized multi-walled carbon nanotube (FMWCNT)/hydroxyethyl cellulose (HEC) composite-based humidity sensor was successfully developed for humidity monitoring applications. FMWCNTs were synthesized by covalently functionalizing multi-walled carbon nanotubes (MWCNTs) in a mixture of sulfuric and nitric acid to enhance their hydrophilicity. The FMWCNTs were characterized using transmission electron microscopy, Raman spectroscopy, Fourier transform infrared spectroscopy and dispersion analysis to verify the presence of functional hydroxyl and carboxyl groups. A FMWCNT/HEC (1 : 6 w/w) composite ink was formulated using the solution blending technique with 2.5 wt% FMWCNTs. A multi-layered humidity sensor was fabricated using additive print manufacturing processes on a flexible polyethylene terephthalate (PET) substrate. Screen printing and gravure printing processes were used to deposit the bottom silver (Ag) electrode and FWMCNT/HEC sensing layers, respectively. The capability of the fabricated humidity sensor was investigated by measuring its resistive response towards relative humidity (RH) varying from 20% RH to 80% RH. As the RH was increased from 20% RH to 80% RH in steps of 10% RH at 25 °C, it was observed that the resistance of the printed sensor increased linearly. The printed sensor demonstrated resistance changes as high as ≈290% at 80% RH, when compared to its base resistance at 20% RH. A sensitivity and a response time of 0.048/%RH and ≈20 s were obtained for the printed sensor, respectively. The results thus demonstrated the feasibility of employing additive print manufacturing processes to develop a highly sensitive sensor for humidity monitoring applications.

Purification and comprehensive utilization of sapphire kerf waste

Sapphire kerf waste (a fine powder) is a great potential source of high-purity α-Al2O3 and is currently discarded without reutilization, which is a waste of this resource and causes environmental problems, such as occupying space and generating dust. Herein, we report a feasible combined method to recycle valuable high-purity α-Al2O3 from sapphire kerf waste through the ultrasound-assisted leaching of nickel, diamond removal by bulk heating and a grinding process. The impurities in the waste were collected, and their existence states were characterized as independent metal nickel and diamond. The nickel impurity was removed from the waste by ultrasound-assisted leaching using a mixture of sulfuric acid and nitric acid, and the optimal leaching efficiency reached 99.67% under the conditions of sulfuric acid: nitric acid = 2:1 (v/v), 4 mol/L H+ concentration, 4 mL/g liquid-solid ratio, 45 °C, 30 min, 200 rpm, 240 W ultrasonic power and 45 kHz ultrasonic frequency. Subsequently, nickel ions in the lixivium were recycled in the form of nickel sulfate through extraction and stripping treatments. The diamond impurity was removed by bulk heating in flowing oxygen, and the optimal removal ratio was 99.65% under the conditions of 800 °C, 30 min and oxygen flow of 400 mL/min. High-purity α-Al2O3 was successfully recovered from the sapphire kerf waste after the grinding process, which had a purity higher than 99.99 wt% and an average diameter of 0.6 μm. In addition, the kinetics of leaching nickel and diamond removal were systematically analysed based on the shrinking model, and the chemical reaction was found to be the control step. The reaction mechanisms of the two processes were also studied. The economic evaluation revealed that the profit from dealing with 1 kg sapphire kerf waste with this method was $13.68. Therefore, the proposed method is promising for providing technical and economical guidance for industrial production.

Incorporation of mineralized human waste and fish waste as a source of higher plant mineral nutrition in the BTLSS mass exchange

The present study deals with the development of the principles and conditions of fish waste mineralization using the method of wet combustion with hydrogen peroxide in alternating electromagnetic field and describes testing mineralized human waste and fish waste as sources of nutrients for plants in the biotechnical human life support system (BTLSS). The study shows that mineralization of fish waste in the wet combustion reactor should be performed in the presence of readily oxidized organic matter, represented by human waste, as an activator of oxidation. Re-mineralization of the sediment in the mixture of hydrogen peroxide and nitric acid in the wet combustion reactor converts mineral elements bound in the sediment into the form available to plants. Using mineralized fish waste as an additional source of mineral elements in the nutrient solutions for growing plants based on mineralized human waste is a way to reduce the amounts of mineral elements added to the solution to replenish it, enabling fuller closure of material loops in the BTLSS.

Microwave-Assisted Digestion Procedures Using Diluted Oxidant Mixture for Elemental Analysis of Crustaceans by MIP OES.

The aim of this study was to evaluate three digestion procedures using a diluted oxidant mixture of nitric acid, hydrogen peroxide, and water for determination of Cu, Fe, K, Mg, Mn, and Zn in shrimp and crab samples from Northern Brazil by microwave-induced plasma optical emission spectrometry. The efficiency of the digestion procedure was evaluated by comparing the residual carbon content, residual acidity, and elemental concentrations obtained in the samples. Digestion procedure 2 (4mL HNO3 + 4mL H2O2 + 4mL H2O) was chosen due the adequate residual carbon content (5.85%) and low residual acidity (2.94molL-1). The recoveries obtained using the certified reference material (DORM-4) varied from 90 to 105%. High contents of K and Mg were found in the studied crustaceans. Also, it can give an excellent contribution to the recommended daily intake of Cu and Zn, indicating that these foods can be considered a good source of these minerals for the human diet.

Effects of carbon fiber modification with multiwall CNT on the electrical conductivity and EMI shielding effectiveness of polycarbonate/carbon fiber/CNT composites

ABSTRACTThe effect of carbon fiber (CF) modification with multiwall carbon nanotube (CNT) on the electrical, mechanical, and rheological properties of the polycarbonate (PC)/CF/CNT composite was investigated. The CF and multiwall CNT (MWCNT) were treated with sulfuric acid and nitric acid (3:1 wt %) mixture, to modify the CF with the CNT. For the PC with acid‐treated CNT (a‐CNT) modified acid‐treated CF (a‐CF) (PC/a‐CF/a‐CNT) composite, the electrical conductivity, and the electromagnetic interference shielding effectiveness (EMI SE) showed the highest values, compared with those of the PC/a‐CF and PC/a‐CF/CNT composites. The EMI SE of the PC/a‐CF (10 wt %)/a‐CNT (0.5 wt %) composite was found to be 26 (dB at the frequency of 10.0 GHz, and the EMI SE was increased by 91.2%, compared to that of the PC/a‐CF composite at the same amount of total filler content. Among the composites studied in this work, the PC/a‐CF/a‐CNT composite also showed the highest values of relative permittivity (εr) and dielectric loss factor. The above results suggest that the CF modification with the a‐CNT significantly affected the electrical conductivity and EMI SE of the composite, and the hybrid fillers of the a‐CNT and a‐CF resulted in good electrical pathways in the PC/a‐CF/a‐CNT composite. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47302.

Sulfonitric Treatment of Multiwalled Carbon Nanotubes and Their Dispersibility in Water.

In this study, Multiwalled carbon nanotubes (MWCNTs) were oxidized by a mixture of sulfuric acid and nitric acid (V:V = 3:1) at 70 °C for 1, 2, and 4 h, respectively. The oxidized MWCNTs were characterized by N2 adsorption, Fourier-transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), thermal gravimetric analysis (TGA), and Raman spectroscopy to determine the oxidation degree. The dispersion of the MWCNTs was investigated by UV-vis-NIR, SEM, and dynamic light scattering measurements. Results show that sulfonitric treatment increased the surface area and total pore volume and reduced the average pore diameter of MWCNTs. The treatment promoted the formation of oxidized species on the surface MWCNTs, as identified by FT-IR, TGA, and X-ray photoelectron spectroscopy measurements, and more oxygen-containing functional groups were generated when treatment time was extended. Moreover, a general relationship between oxidation degree and dispersibility of MWCNTs in water was established. UV-vis-NIR and dynamic light scattering measurements and SEM images revealed that MWCNTs with higher oxidation degree showed better dispersibility in water.

ANALISIS KANDUNGAN LOGAM BERAT TIMBAL (Pb) PADA CABAI MERAH (CAPSICUM ANNUUM L) YANG BEREDAR DI PASAR BATUSANGKAR

Research has been conducted to analyze the conten of the heavy metal content of lead (Pb) in red pepper (Capsicum Annuum L) circulating in Batusangkar market. Samples of five red peppers were taken from different places in Batusangkar market. The sample was dissolved by using a mixture of sulfuric acid and nitric acid. Furthermore, lead was measured by using atomic absorption spectrophotometry (SSA) at a wavelength of 283.3 nm. The results of the analysis showed that the lowest lead level of 0.2386 mg / kg and the highest lead level of 0.73642 mg / kg. From the five samples, it was found that there was one sample whose lead level exceeded the maximum limit set by National Standardization Council of 2009 about maximum limit of heavy metal contamination in food that is 0,5 mg / kg for lead, whereas for 4 other sample the value of lead level is less from 0.5 mg / kg. In addition, from the five samples, one sample did not meet the safe criteria and the other four samples meet the criteria.

Cellulose Nitrates from Unconventional Feedstocks

Samples of technical-grade cellulose isolated by nitric acid technique from unconventional feedstocks (oat hulls, Miscanthus, and intermediate flax straw) have been treated for the first time with a sulfuric acid–nitric acid mixture to give cellulose nitrates with a nitrogen content of 12.04–12.26%, viscosity 10–14 mPa s, and a solubility in an alcohol–ether mixture of at least 98%, which corresponds to industrial lacquer-purpose high-viscosity colloxylin and N-grade colloxylin. It has been confirmed by IR spectroscopy and differential scanning colorimetry that the cellulose nitrates from unconventional feedstocks correspond to industrial colloxylins in terms of the key absorption bands (1650–1635, 1279–1276, 831–825, 746, 687–672 cm–1), thermal degradation onset temperature (about 200°C), and specific heat of decomposition (6.28–7.54 kJ/g).

Biomorphic Silicon Carbide from Malaysian Hardwood

Porous silicon carbide with mimicking the original microstructure of wood are prepared by pyrolysis and subsequently impregnated with silicon by silicon melt infiltration. The infiltration process was performed at 1500 °C for 3 hours holding times in inert atmosphere. Two types of wood were used as precursor which is Kapur and dark red Meranti.The morphology of resulting porous SiC have been investigated using scanning electron microscope (SEM/EDX) and X-ray diffraction (XRD) analysis. The density of the samples was characterized by Archimedes methods. The excess of silicon was removed by etching with the mixture of hydrofluoric and nitric acid. The flexural strength was tested by the three-point flexural method at room temperature.It has been shown that the final SiC for both precursors have similar density. The existence of SiC was proved by the XRD result, whereas EDX analysis of silicon content revealed that the formation of silicon carbide in dark red Meranti is higher than that of Kapur. The flexural strength and modulus of dark red Meranti samples were much higher than those of the kapur samples because of higher formation of silicon carbide in dark red Meranti.

Smartphone-assisted Colorimetric Analysis of Manganese in Steel Samples

Background: Manganese, Mn, is an essential element that is present in steels, and determines steel’s mechanical properties. Traditionally, atomic absorption and X-ray photoelectron spectroscopic methods were used for Mn analysis and complicated instrument operations, sometimes of high cost, are associated, and spectrophotometry/colorimetry is another tool for Mn analysis with simple operations. Nowadays, smartphone is emerging as a new powerful tool with multiple advantages in analytical chemistry. Objective: This project aimed to develop a simple and reliable smartphone-assisted colorimetric method to analyze Mn in steel samples. Method: Steel samples were first dissolved in the mixture of nitric acid and phosphoric acid to convert the elemental form of Mn into Mn(II) ions. The Mn(II) ions were then oxidized into the colored permanganate ions whose color was determined via a smartphone. Quantification of Mn was performed by comparing the unknown signal with the standard calibration curve which was constructed by plotting the green value of the solution as a function of the permanganate concentration with a 2nd polynomial regression fitting. The results from the developed method were then compared with the manufacturer values and another UV/vis spectrophotometry, using the Student t-tests, to validate the method. Results: The concentration of Mn in steel samples was determined by the smartphone-assisted colorimetry to be in the range of 0.56% to 0.97%, which had the same accuracy as the classic spectrophotometry and was in agreement with the manufacturer’s values. Conclusion: The experimental results proved that the smartphone-assisted method is a good alternative tool for Mn analysis in steels. Keywords: Smartphone, colorimetry, manganese, steel, permanganate, spectrophotometry.

An experimental method for gold partitioning between two immiscible fluids: Brine and n-dodecane

Organic matter can be found in many different types of ore deposits, but its role in ore-forming processes is not yet fully understood. Here, we present an experimental method that can be used to determine the partition coefficient (DAuorg/aq: partition coefficient of Au between an hydrocarbon and an aqueous fluid) of gold between two immiscible liquids, and thus whether liquid hydrocarbon fluids such as petroleum can act as ore fluids and transport gold or other metals of interest. To investigate liquid hydrocarbons in the presence of an aqueous liquid doped with gold, we modified the HFS-340Z hydrothermal flow system (Coretest Systems, Inc.) to enable sampling at hydrothermal P-T conditions (≤150 °C and ~5 bar) of each of two density-stratified immiscible liquids. A saline aqueous solution (10 wt% NaCl) was doped with gold and heated with n-dodecane (CH3(CH2)10CH3) to 105 °C and 150 °C. Each brine sample was directly followed by an organic sample until three samples of each liquid were taken. Aqua regia was added to the brine samples to stabilize the gold before ICP-MS analyses. Each organic sample was digested chemically with a mixture of ultra-pure nitric acid and hydrogen peroxide to generate carbon free solutions prior to ICP-MS analysis. This procedure generates reproducible partition coefficients for gold, or presumably any other metal, between hydrocarbon and aqueous liquids, if passivation procedures of the HFS-340Z hydrothermal flow system are strictly followed and error sources are monitored rigorously. The preferred DAuorg/aq between n-dodecane and the brine is 0.05 ± 0.04.