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Aluminum oxynitride (AlON) exhibits excellent mechanical properties and good optical transparency in the ultraviolet to near-infrared range and can be used in military and civilian fields. However, the troublesome molding of AlON, especially for complex shapes, limits its promotion and application. Therefore, transparent AlON ceramics with complex morphologies were prepared for the first time by a novel spontaneous coagulation casting (SCC) and pressureless sintering method. In this study, we report a simple carbothermal reduction and nitridation (CRN) method for synthesizing high-purity AlON powder, which is especially suitable for wet casting without anti-hydration treatment. The dispersion and gelation behavior of AlON slurries by isobutene maleic anhydride copolymer (Isobam104) and tetramethylammonium hydroxide (TMAH) were extensively investigated. With the addition of 0.9 wt% Isobam104 and 15 mL/L TMAH, the AlON slurries can achieve a solids loading of up to 45 vol% with the lowest viscosity (460.4 mPa·s-10 r/min) and the AlON green body is free of cracks and deformation during drying and demolding processes. Finally, the AlON green bodies with square and polygonal irregular morphologies were fabricated via a simple SCC method. High transparent AlON ceramics of a maximum transmittance up to 77.3% at 2000 nm and 72.2% at 632 nm were obtained by pressureless sintered at 2000 °C for 6 h. The SCC method has great potential in preparing ceramics with controllable shapes. [ABSTRACT FROM AUTHOR]

The study explored the treatment of different wastewater by producing microelectronic components. It proposed using aerobic biological treatment for the first effluent containing tetramethyl ammonium hydroxide and chemical-physical processes for the other two streams having fluorides, phosphates, nitrates and acetic acid. The novel integrated process significantly reduced environmental impacts by an average of 50 % compared to current disposal methods. The economic analysis indicates a 30 % reduction in treatment costs for the first effluent and lesser reductions for the other two effluents. The study revealed that treating all three effluents in an integrated manner is cost-effective, reducing investment and operating costs.

The Sample Analysis at Mars (SAM) instrument aboard the Curiosity Rover at Gale crater can characterize organic molecules from scooped and drilled samples via pyrolysis of solid materials. In addition, SAM can conduct wet chemistry experiments which enhance the detection of organic molecules bound in macromolecules and convert polar organic compounds into volatile derivatives amenable to gas chromatography‐mass spectrometry analyses. Specifically, N‐tert‐butyldimethylsilyl‐N‐methyltrifluoroacetamide (MTBSTFA) is a silylation reagent whereas tetramethylammonium hydroxide (TMAH) is a thermochemolysis methylation reagent. Shortly after arriving at Mars, the SAM team discovered that at least one of the MTBSFTA cups was leaking, contributing to a continuous background inside SAM with the potential to interfere with future TMAH reactions. Therefore, here we characterized possible interactions between the two reagents to determine byproducts and implications for the detection of indigenous organics. SAM‐like pyrolysis experiments supplemented with flash pyrolysis were accordingly conducted with fragments of the Murchison meteorite as a reference for exogenous organic matter delivered to Mars. Flash TMAH experiments yielded various aromatic acids, dicarboxylic acids, and amino acids while SAM‐like pyrolysis presented mixtures of methylated and non‐methylated compounds due to decreased reaction efficiency at slower ramp rates. All experiments in the presence of simulated MTBSTFA vapor produced pervasive silylated byproducts which co‐elute and obscure the identification of Murchison‐derived compounds. Despite challenges, a significant diversity of pyrolyzates and TMAH derivatives could still be identified in flash pyrolysis in presence of MTBSTFA. However SAM‐like experiments with TMAH and MTBSTFA are hindered by both decreased methylation yields and additional co‐eluting compounds. Plain Language Summary: The Sample Analysis at Mars (SAM) instrument aboard the Curiosity Rover on Mars can detect and analyze organic molecules that might be used by life as we know it. SAM does this by heating scooped soil or drill samples in order to vaporize and uncover any organic content that might be present. In addition, SAM can detect different types of organics that have more direct similarities to those used by modern organisms by adding one of two different kinds of chemical reagents prior to heating. However, shortly after arriving at Mars, it was discovered that one type of reagent, called MTBSTFA, was leaking inside of SAM with the potential to eventually interfere with the other, called TMAH, whenever it might be utilized. This study therefore reports on the chemical interactions between the two reagents and how they might impact the detection of indigenous organics on Mars. We determined heating samples in the presence of both reagents produces a series of byproducts which obscure the identification of organic compounds of interest. Still, despite analytical challenges, it is possible SAM may detect different types of organics which have yet to be detected on Mars with TMAH despite interference from leaking MTBSTA. Key Points: TMAH experiments with Murchison meteorite produces various aromatic acids, dicarboxylic acids, and amino acidsSAM‐like TMAH pyrolysis presents mixtures of methylated and non‐methylated compounds due to decreased reaction yields at slower ramp ratesAll experiments with simulated MTBSTFA vapor produce byproducts that obscure the identification of Murchison‐derived compounds [ABSTRACT FROM AUTHOR]

A simple and dependable technique, known as THAM method, has been developed to detect and measure ethyl eicosapentaenoate (EE-EPA) and ethyl docosahexaenoate (EE-DHA) in encapsulated fish oils. This technique involves using tetramethylammonium hydroxide (TMAH) as a catalyst, followed by analysis using gas chromatography equipped with a flame ionization detector. Recoveries of EE-EPA and EE-DHA spiked between 5 mg/g and 20 mg/g were found to be between 90.8% and 95.2%, with coefficients of variation ranging from 0.2% to 2.5%, demonstrating the accuracy and precision of the technique. Additionally, its limitation of quantitation of EE-EPA and EE-DHA in fish oil samples was 0.2%. When compared with the direct injection method, the TMAH method yielded relative percent differences of no more than 3.8% in the amounts of ethyl esters of EPA and DHA in fish oil, while preventing contamination and maintaining its performance over time. Furthermore, when compared the total amounts of EPA and DHA with the boron trifluoride method, the relative percent differences were no more than 4.7% by the TMAH method. The advantages of using the TMAH method in distinguishing the ester forms of EPA and DHA and determining the total content of fatty acids in fish oils, which can provide an auxiliary check for evaluating the compliance of applications with the regulation related to the purity and form of EPA and DHA. [ABSTRACT FROM AUTHOR]

The regulation and characterization of nanomaterials in foods are of great interest due to the potential risks associated with their exposure and the increasing number of applications where they are used within the food industry. One factor limiting the scientifically rigorous regulation of nanoparticles in foods is the lack of standardized procedures for the extraction of nanoparticles (NPs) from complex matrices without alteration of their physico-chemical properties. To this end, we tested and optimized two sample preparation approaches (enzymatic- and alkaline-based hydrolyses) in order to extract 40 nm of Ag NP, following their equilibration with a fatty ground beef matrix. NPs were characterized using single particle inductively coupled plasma mass spectrometry (SP-ICP-MS). Fast sample processing times (<20 min) were achieved using ultrasonication to accelerate the matrix degradation. NP losses during the sample preparation were minimized by optimizing the choice of enzymes/chemicals, the use of surfactants, and the product concentration and sonication. The alkaline approach using TMAH (tetramethylammonium hydroxide) was found to have the highest recoveries (over 90%); however, processed samples were found to be less stable than the samples processed using an enzymatic digestion based upon pork pancreatin and lipase (≈60 % recovery). Low method detection limits (MDLs) of 4.8 × 106 particles g−1 with a size detection limit (SDL) of 10.9 nm were achieved for the enzymatic extraction whereas an MDL of 5.7 × 107 particles g−1 and an SDL of 10.5 nm were obtained for the alkaline hydrolysis. [ABSTRACT FROM AUTHOR]

This study investigated efficiency of tetramethyl ammonium hydroxide pentahydrate (TMAH) in removal of heavy metal ions from heavy oils obtained from Nigerian oil sands by Soxhlet-extraction technique. Metals were removed from the heavy oils at variable temperatures using TMAH. Elemental analysis was done using Atomic absorption spectrophotometry (AAS). Percentage recovery was ≥92.85%, confirming reliability of results. Total metal concentrations followed order: Ni > Pb > Mn > Cu > Cr > Cd. Analysis of variance results showed that F

Graphene/silicon (Gr/Si) Schottky junction solar cells have attracted extensive research interest due to their simple structure and potential low-cost. Surface texturing is an important part of high-efficiency solar cells. In this paper, the effects of TMAH concentration, IPA concentration and etching time on the structure and anti-reflection ability of silicon pyramid array (SiPa) were systematically studied to obtain uniform and reliable pyramid array. Under the optimized conditions, a large scale SiPa with uniform size distribution was obtained and applied to Gr/Si solar cells. The results show that the TMAH etched SiPa has a better Schottky junction contact between graphene and the SiPa surface, and the SiPa can further improves the ability of collecting photogenerated carriers. Compared with Gr/Si solar cells, the power conversion efficiency (PCE) of Gr/SiPa device is 1.66 times higher than that of Gr/Si solar cells. Finally, Gr/SiPa devices with PCE of 5.67% is successfully obtained by HNO3 doping. This work proposes a new strategy for TMAH etching SiPa to improve the performance of Gr/Si solar cells. Highlights: The effects of TMAH concentration, IPA concentration and etching time on silicon pyramid structure were studied. Uniform silicon pyramid arrays with low reflectivity were prepared. The results show that the TMAH etched SiPa has a better Schottky junction contact between graphene and the SiPa surface. The PCE of Gr/SiPa solar cells could reach up to 5.67%. [ABSTRACT FROM AUTHOR]

The dissolution behavior of a simple combination of poly(4-hydroxystyrene) films and tetramethylammonium hydroxide aqueous solution was analyzed to gain a fundamental understanding of the effects of film thickness and alkaline concentration on the dissolution kinetics of chemically amplified resists. Films of four different thicknesses, from thick (approximately 900 nm) to thin (approximately 50 nm), were developed in 22 different developers of different concentrations. The dissolution behavior of each combination was observed using a quartz crystal microbalance. Differences in dissolution kinetics due to film thickness were observed even between relatively thick films such as 900 and 500 nm thick films in dilute developers. These differences were considered to be caused by the diffusion of the solution into the films. Thin films also showed characteristic behavior with dilution. This behavior was due to the interaction between the substrate and the films, unlike in the case of thick films. [ABSTRACT FROM AUTHOR]

Abstract Wet anisotropic etching is extensively employed in silicon bulk micromachining to fabricate microstructures for various applications in the field of microelectromechanical systems (MEMS). In addition, it is most widely used for surface texturing to minimize the reflectance of light to improve the efficiency of crystalline silicon solar cells. In wet bulk micromachining, the etch rate is a major factor that affects the throughput. Slower etch rate increases the fabrication time and therefore is of great concern in MEMS industry where wet anisotropic etching is employed to perform the silicon bulk micromachining, especially to fabricate deep cavities and freestanding microstructures by removal of underneath material through undercutting process. Several methods have been proposed to increase the etch rate of silicon in wet anisotropic etchants either by physical means (e.g. agitation, microwave irradiation) or chemically by incorporation of additives. The ultrasonic agitation during etching and microwave irradiation on the etchants increase the etch rate. However, ultrasonic method may rupture the fragile structures and microwave irradiation causes irradiation damage to the structures. Another method is to increase the etching temperature towards the boiling point of the etchant. The etching characteristics of pure potassium hydroxide solution (KOH) is studied near the boiling point of KOH, while surfactant added tetramethylammonium hydroxide (TMAH) is investigated at higher temperature to increase the etch rate. Both these studies have shown a potential way of increasing the etch rate by elevating the temperature of the etchants to its boiling point, which is a function of concentration of etch solution. The effect of various kinds of additives on the etch rate of silicon is investigated in TMAH and KOH. In this paper, the additives which improve the etch rate have been discussed. Recently the effect of hydroxylamine (NH2OH) on the etching characteristics of TMAH and KOH is investigated in detail. The concentration of NH2OH in TMAH/KOH is varied to optimize the etchant composition to obtain improved etching characteristics especially the etch rate and undercutting which are important parameters for increasing throughput. In this article, different methods explored to improve the etch rate of silicon have been discussed so that the researchers/scientists/engineers can get the details of these methods in a single reference.

Abstract Background Tetramethylammonium hydroxide (TMAH) is a quaternary ammonium compound that is both a base corrosive and a cholinergic agonist, and it is widely used in the photoelectric and semiconductor industries. It causes corrosive skin injuries and systemic cholinergic toxicity with death primarily resulting from respiratory failure without efficacious early decontamination. Methods A retrospective observational study was performed of all cases of TMAH exposure reported to the Taiwan Poison Control Center between July 2010 and October 2017. Retrieved medical records were independently reviewed by two trained clinical toxicologists. Results Despite immediate (

Objective:In order to efficiently remove TMAH from the wastewater generated by the TFT-LCD manufacturing process, the oxidation of TMAH was tested by applying an UV/persulfate. The optimum reaction conditions for high concentration TMAH oxidation were investigated by evaluating and comparing the removal efficiency according to the factors affecting TMAH oxidative degradation. Methods:In this study, TMAH was decomposed by sulfate radical (SO4-∙) and hydroxyl radical (OH∙) generated from persulfate activated by UV. Factors affecting on the treatment efficiency were try to be optimized by comparing and evaluating the removal efficiency depending on the initial pH, oxidant concentration, and initial TMAH concentration. Results and Discussion:Depending on initial pH (2, 7, 12), persulfate addition (0, 50, 100, 150, 200 mM), initial TMAH concentration (100, 300, 500, 700 mg/L) degradation rates of TMAH were compared. When UV/persulfate was applied, the removal efficiency of TMAH was close to 90% regardless of the initial pH and, at initial pH 12, was the highest with 89%. It was confirmed that the generation pattern of intermediate formed were different depending on the initial pH. When the oxidizing agent was not added, there was little change in TMAH concentration. The removal efficiency was highest when 100 mM persulfate was added. However the efficiency was rather low when 150 mM persulfate was added. When the initial TMAH concentration was 100 mg/L, it was decreased within 150 minutes. As the initial concentration increased, the removal efficiency and reaction rate constant decreased. Conclusions:As a results, during the oxidation of 750 mg/L TMAH by using UV/persulfate, the removal efficiency was highest with initial pH 12 and 100 mM of persulfate addition.

In this paper, we introduce novel surface treatments of UV/Ozone and TMAH to solve the surface problem of gate recess of InAlAs/InGaAs InP-based HEMTs. The problem of nonstoichiometric surface of InP etch stopper layer was found to be the result of donor-like surface defects brought by HF damage, bringing troubles like kink effect, high gate leakage current and deteriorated noise performance. Through the method of surface treatments, the InAlAs/InGaAs InP-based HEMTs exhibit excellent DC performances, demonstrating a low gate leakage currents of 10 -8 A/um, a peak transconductance of 1100mS/mm, an improved subthreshold swing of 92.5mV/decade at Vds = 1.0V, and a positive threshold voltage shift of Vth = 300 mV. The ft of 260GHz and fmax of 440GHz were hardly influenced by the surface treatments while the noise performances were improved obviously. Two orders of magnitude smaller input noise spectral density shows the method of surface treatment can effectively reduce the surface defects and significantly improve the surface of gate recess of InAlAs/InGaAs InP-based HEMTs.

The effect of tetramethylammonium hydroxide (TMAH) treatment prior to gate dielectric deposition on the performance of recessed-gate AlGaN/GaN metal-insulator-semiconductor high electron mobility transistors (MIS-HEMTs) was investigated. Through the use of TMAH wet etching, a low roughness etched surface of 0.173 nm was obtained. The capacitance–voltage characteristics of MIS heterostructures showed that the interface states reduced by one order of magnitude. When the temperature was increased to 473 K, the treated MIS-HEMTs delivered a small threshold voltage shift (Δ V _TH ) of ∼−0.53 V. From the dynamic measurement, the Δ V _TH obtained without treatment was observed more severely (∼−1 V) when compared to the treated one (∼−0.01 V).

This paper presents a facile method of producing graphene nanosheets by organic liquid-assisted electrochemical exfoliation using tetramethyleammonium hydroxide (TMAH) as organic electrolyte. The process involves low-cost copper as ground electrode and carbon block as anode or cathode. The application of organic electrolyte eliminates the presence of unwanted metal ions on the graphene nanosheets. To the best of our knowledge, this is a maiden effort of producing graphene with pure organic electrolyte using TMAH with low-cost copper electrode. By the use of TMAH, conformal large-area graphene nanosheets of 4.3 nm thickness with an average sheet diameter of 3–4 μm have been obtained. Graphene nanosheets are characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, ultraviolet-visible spectroscopy, Fourier transform infrared, Raman spectroscopy, and atomic force microscopy. Raman characterization confirms the conservation of the intrinsic nature of few-layer graphene. Graphene nanosheets are dissolved in a polar aprotic solvent dimethylformamide and are drop coated on the Si/SiO2 substrate to make a thin film of graphene. Films are annealed to remove any residual solvent attached to it. Different annealing temperatures (50–200°C) were reported. Sheet resistances were measured before and after annealing, with a remarkable decrease afterward. Current-voltage characteristics were studied to evaluate the conductivity of the graphene nanosheets produced.

Wet anisotropic etching is extensively employed in silicon bulk micromachining to fabricate microstructures for various applications in the field of microelectromechanical systems (MEMS). In addition, it is most widely used for surface texturing to minimize the reflectance of light to improve the efficiency of crystalline silicon solar cells. In wet bulk micromachining, the etch rate is a major factor that affects the throughput. Slower etch rate increases the fabrication time and therefore is of great concern in MEMS industry where wet anisotropic etching is employed to perform the silicon bulk micromachining, especially to fabricate deep cavities and freestanding microstructures by removal of underneath material through undercutting process. Several methods have been proposed to increase the etch rate of silicon in wet anisotropic etchants either by physical means (e.g. agitation, microwave irradiation) or chemically by incorporation of additives. The ultrasonic agitation during etching and microwave irradiation on the etchants increase the etch rate. However, ultrasonic method may rupture the fragile structures and microwave irradiation causes irradiation damage to the structures. Another method is to increase the etching temperature towards the boiling point of the etchant. The etching characteristics of pure potassium hydroxide solution (KOH) is studied near the boiling point of KOH, while surfactant added tetramethylammonium hydroxide (TMAH) is investigated at higher temperature to increase the etch rate. Both these studies have shown a potential way of increasing the etch rate by elevating the temperature of the etchants to its boiling point, which is a function of concentration of etch solution. The effect of various kinds of additives on the etch rate of silicon is investigated in TMAH and KOH. In this paper, the additives which improve the etch rate have been discussed. Recently the effect of hydroxylamine (NH2OH) on the etching characteristics of TMAH and KOH is investigated in detail. The concentration of NH2OH in TMAH/KOH is varied to optimize the etchant composition to obtain improved etching characteristics especially the etch rate and undercutting which are important parameters for increasing throughput. In this article, different methods explored to improve the etch rate of silicon have been discussed so that the researchers/scientists/engineers can get the details of these methods in a single reference. [ABSTRACT FROM AUTHOR]

Hydrothermal spring deposits host unique microbial ecosystems and have the capacity to preserve microbial communities as biosignatures within siliceous sinter layers. This quality makes terrestrial hot springs appealing natural laboratories to study the preservation of both organic and morphologic biosignatures. The discovery of hydrothermal deposits on Mars has called attention to these hot springs as Mars-analog environments, driving forward the study of biosignature preservation in these settings to help prepare future missions targeting the recovery of biosignatures from martian hot-spring deposits. This study quantifies the fatty acid load in three Icelandic hot-spring deposits ranging from modern and inactive to relict. Samples were collected from both the surface and 2–18 cm in depth to approximate the drilling capabilities of current and upcoming Mars rovers. To determine the preservation potential of organics in siliceous sinter deposits, fatty acid analyses were performed with pyrolysis–gas chromatography–mass spectrometry (GC-MS) utilizing thermochemolysis with tetramethylammonium hydroxide (TMAH). This technique is available on both current and upcoming Mars rovers. Results reveal that fatty acids are often degraded in the subsurface relative to surface samples but are preserved and detectable with the TMAH pyrolysis-GC-MS method. Hot-spring mid-to-distal aprons are often the best texturally and geomorphically definable feature in older, degraded terrestrial sinter systems and are therefore most readily detectable on Mars from orbital images. These findings have implications for the detection of organics in martian hydrothermal systems as they suggest that organics might be detectable on Mars in relatively recent hot-spring deposits, but preservation likely deteriorates over geological timescales. Rovers with thermochemolysis pyrolysis-GC-MS instrumentation may be able to detect fatty acids in hot-spring deposits if the organics are relatively young; therefore, martian landing site and sample selection are of paramount importance in the search for organics on Mars. [ABSTRACT FROM AUTHOR]

Low-frequency noise (LFN) performances are investigated in a normally-off GaN metal-oxide-semiconductor field-effect transistor (MOSFET) fabricated by utilizing the tetramethylammonium hydroxide (TMAH) wet etching. The normalized power spectral densities ($\text{S}_{Id}/\text{I}_{d}^{2})$ are measured and perfectly matched with both the correlated mobility fluctuations (CMF) and Hooge mobility fluctuations (HMF) noise models. From the curves of ($\text{S}_{Id}/\text{I}_{d}^{2})$ dependent on the gate overdrive voltage (Vg – $\text{V}_{th})^{-1}$ , it is also confirmed that the mobility fluctuations prevail in the fabricated GaN device. The calculated Hooge constants ($\alpha _{H}$) according to the (Vg – $\text{V}_{th}$) are obtained to be 10−2 ~ 10−3. The reason for the dominance of the mobility fluctuations and the relatively low $\alpha _{H}$ is attributed that the TMAH wet etching effectively removes the plasma etching damage and fully recovers the crystal quality of GaN channel. [ABSTRACT FROM AUTHOR]

In this study, ozonation is coupled with other approaches for the degradation of tetramethylammonium hydroxide (TMAH) to increase the degradation efficiency and reduce the toxicity. A degradation of 70.9% was reached after the reaction of TMAH with ozone for 120 min at pH 11 with the ozone dosage of 16 g O3 per gram TMAH per hour (16 g O3 g−1 TMAH h−1). A mineralization of 47.6% was achieved and the cell viability increased from 60.6% (before treatment) to 83.8% (after treatment). When ozone was combined with H2O2 and ultraviolet (UV) irradiation, the reaction stimulated by UV light did not facilitate TMAH degradation, whereas the addition of H2O2 increased the production of ·OH, thereby increasing the TMAH degradation. The use of ultrafine bubble-enhanced ozonation reduced the required ozone dosage to 1/10 of that used for microbubble ozonation, but similar treatment efficiencies were achieved. The O3/H2O2 approach is favorable for TMAH degradation; under optimal conditions, a degradation of 82.3% and mineralization of 53.5% can be achieved. [ABSTRACT FROM AUTHOR]

The paper presents research on elaboration of well dispersed and stable aqueous suspensions of ZnO fine powder. Within the work the influence of the type and concentration (0.2 wt% - 1.2 wt%) of selected dispersing agents (i.a. poly(acrylic acid)-based polyelectrolyte and tetramethylammonium hydroxide), solid loading (30 - 50 vol%) and milling time (1–3 h) on the rheological properties of the slurries was investigated. Two-step sintering (970/920 °C, 2 h) was applied to sinter the green bodies obtained by slip casting. The lowest viscosity of ZnO suspensions was obtained for the addition of 0.4 wt% of poly(acrylic acid)-based polyelectrolyte (PAA) and TMAH. ZnO suspension containing PAA had negative zeta potential in the whole pH range. The highest solid loading obtained in the study was 50 vol%. The applied two-step sintering allowed to obtain samples of high density (above 96% of TD) and homogeneous microstructure of average grain size of 640 nm. ZnO sintered bodies were characterized by different electric properties at the core part and outer part of the sample which was caused by the differences in concentration of oxygen vacancies. [ABSTRACT FROM AUTHOR]

The study aimed at evaluation of the rheological properties of aqueous suspensions of SiC stabilized with either TMAH (tetramethyloammonium hydroxide) or NaOH in the amount of a given dispersant in the range of 0–1.0 wt% as calculated on the dry mass of SiC powder. The optimal amount of the dispersants was finally evaluated at 0.4–0.6 wt %, based on the results of rheological studies (flow curves and viscosity curves) and the sedimentation rate, which corresponded to the pH of the suspension within the range of 9.5–10.5. The amount of the dispersant here did not depend on the solid volume fraction in the suspension, but rather, according to the zeta potential measurement results, the pH range guaranteed the formation of a stable suspension. This effect allowed to propose a dispersant mechanism for stabilizing the suspension. The maximum amount of silicate anions formed, accordingly, in the pH range of 9.5–10.5 on the surface of SiC particles, which in turn could be able to adsorb Na+ or TMA+ cations and thus increase the thickness of the Stern layer, increasing electrostatic repulsion between the SiC particles and improving the stabilization of suspensions and their rheological properties. However, the increase in suspension pH deteriorated their stabilization – most likely due to the occurrence of polymerization of amorphous silica and the presence of additional cations in water increasing its ionic strength. These suggestions were confirmed by the results of XPS analysis of the chemical state of SiC particle surfaces. [ABSTRACT FROM AUTHOR]

Silicon carbide (SiC) powder was modified with γ-mercaptopropyl trimethoxysilane (KH590) and tetramethylammonium hydroxide (TMAH). The effects of modification were investigated following viscosity measurements, which confirmed the high dispersibility in water of the modified SiC powder. The maximum solids content of the slurry prepared using the modified SiC powder (ca. 76% vol.) was determined after optimization of the modification conditions. Overall, the results of viscosity and solid content indicate that the proposed modifications result in a SiC powder that is superior compared to that prepared by the Saint-Gobain's method. [ABSTRACT FROM AUTHOR]

In order to further understand the role of the cation when dissolving cellulose in aqueous solutions of hydroxide bases, different bases were combined in solution. Up to 5 wt.% of microcrystalline cellulose was dissolved using a combination of NaOH and the organic base tetramethylammonium hydroxide (TMAH) in water at low temperatures. Thermoscans of solutions containing both NaOH(aq) and TMAH(aq) indicated that cellulose interaction with TMAH seems to be favoured over NaOH. Dynamic rheology measurements of the solutions revealed that combining the two bases delayed gelation significantly when compared to cellulose dissolved in NaOH(aq) or TMAH(aq) alone. Intrinsic viscosity of cellulose in the combined NaOH- and TMAH(aq) solutions was slightly higher than that of the single-base solutions, indicating a slight increase in solvent quality. This shows that combining bases may lead to synergies that improve solvent stability without requiring the use of other additives. [ABSTRACT FROM AUTHOR]

The purpose of this study is to compare the effectiveness of wet acid, surfactant and alkaline digestion procedures for determination of heavy metals in cattle hair samples. Cattle hair samples were collected from the tails of Holstein cattle and washed sequentially with acetone, distilled water, and acetone for removal of external contaminations. Analyses were carried out by ICP-OES after applying to acid digestion (HNO3:H2O2), acid digestion under addition of surfactant (Triton X-100), and alkaline digestion using Tetramethylammonium hydroxide. The accuracies of methods for Cu, Cr, Fe, Mn, Ni and Zn metals were evaluated by using NCS ZC 8100 2b hair certified reference material. The results showed that Cu, Fe results obtained by application of Triton X-100 and Cr, Fe, Ni and Zn results obtained by application of Tetramethylammonium hydroxide were not compatible with certified values, whereas wet acid digestion method provided satisfactory recoveries for all examined metals in cattle hair samples. Relative standard deviations were found below %5 in wet acid digestion method. The concentrations of Zn, Cr, Ni, Cu, Fe and Mn in cattle hair samples were in the range of 88-157, 0.94-3.22, 0.00-2.96, 14.4-33.0, 36-101, 0.20-3.00 μg g-1 respectively. Our results indicated that wet digestion method was the most efficient for the analysis of Cu, Cr, Fe, Mn, Ni, and Zn in the cattle hair sample with excellent precision and recovery. [ABSTRACT FROM AUTHOR]

Featured Application: The process proposed in this study could be an effective method for the treatment of high-tech industrial wastewater to meet the new tetramethylammonium hydroxide (TMAH) discharge limit. Nitrogen-containing wastewater is an important issue in optoelectronic and semiconductor industries. Wastewater containing nitrogen compounds such as ammonium, monoethanolamine (MEA), and tetramethylammonium hydroxide (TMAH) must be properly treated due to concerns about health and environmental effects. MnCe-GAC (granular activated carbon) processes were developed in this study for the treatment of TMAH-contaminated wastewater in high-tech industries. The MnCe-GAC processes could effectively remove ammonium, MEA, and TMAH from aqueous solutions. The removal efficiencies of ammonium and MEA by these processes were better than observed for TMAH. Parameters affecting TMAH removal such as type of process, type of wastewater (synthetic or real), pH, salts, and t-butanol were investigated. In general, removal efficiencies of TMAH by various processes were in the following order: MnCe-GAC/O3/H2O2 > MnCe-GAC/O3 > MnCe-GAC/H2O2 > MnCe-GAC > GAC. The negative effect of sulfate and nitrate on pollutant removal might be due to the salting-out effect. Based on t-butanol experiments, the main degradation mechanisms of TMAH by the MnCe-GAC/O3/H2O2 process likely involved hydroxyl radicals. The process proposed in this study could be an effective alternative method for the treatment of high-tech industrial wastewater to meet the new TMAH discharge limit. [ABSTRACT FROM AUTHOR]

• An extraction method is developed for impurities in different edible oils using GFAAS. • It is simple and sensitive and does not use microwave or hot plate for digestion. • It is an alternative method to determine ultratrace impurities in various edible oils. • Applicable to different edible oils extracted from various seeds. • TMAH and EDTA together resulted in better detection limits for edible oils. A new method for extraction and determination of trace and ultratrace impurities from edible oils via an ultrasound-assisted extraction using tetramethylammonium hydroxide (TMAH) and ethylenediaminetetraacetic acid (EDTA) has been described. Method is simple and sensitive. Extraction variables like pH, concentrations of TMAH and EDTA, ultrasonication and centrifugation times were all optimised for analytes using engine-oil. Under optimised conditions, extraction of spiked analytes from all the edible oils into aqueous-medium were investigated and found to be quantitative (89–101%). Using this method, concentrations of impurities in edible-oils were determined by graphite furnace atomic absorption spectrometer (GFAAS) using standard-addition calibration method and validated with microwave-digestion method. The method was successfully applied to edible oils extracted from various seeds such as mustard oil, sun flower oil, sesame oil, ground nut oil, coconut oil, rice bran oil and corn oil containing ultratrace impurities. Accuracy of developed method for edible-oils was checked with corresponding results obtained by microwave digestion method. [ABSTRACT FROM AUTHOR]

Pyrolysis gas chromatography/mass spectrometry using tetramethylammonium hydroxide (TMAH) for thermally-assisted hydrolysis and methylation (THM-Py-GC/MS) is a powerful analytical technique for comprehensive characterization of organic materials in European lacquers. A daunting challenge, though, is systematically sorting through the vast number of chromatographic peaks in order to accurately locate marker compounds that are characteristic of lacquer artists' materials. AMDIS (Automated Mass spectral Deconvolution and Identification System) software, developed by NIST, is proven to be capable of extracting and locating library marker compounds in highly complex GC/MS data files. An AMDIS marker compound library of more than 1400 compounds representing Asian and European lacquer and a number of other artists' materials has been compiled from information in various publications and private communications. A customized Excel workbook was developed to semi-automatically analyse and interpret the marker compound information in the AMDIS search report, using interpretation guides based upon knowledge shared by experts in material characterization that aid in accurate identification. These software tools have been used in training workshops, organized by the Getty Conservation Institute, by scientists with varying levels of GC/MS experience to successfully identify artists' materials in complex samples from lacquered works of art. Based upon positive feedback from the workshop participants and successful application in their laboratories, we have concluded that the tools may be considered as an Expert System for Characterization with AMDIS Plus Excel (ESCAPE). Examples will be shown for using ESCAPE to identify a wide range of natural products in samples from lacquered objects and easel paintings. [ABSTRACT FROM AUTHOR]

Acids in diesel bring great harm to storage devices, transportation facilities and engines. Acids in diesel were removed by tetramethylammonium hydroxid (TMAH)/ammonia under nonylphenol ethoxylate as demulsifier. The effect of process parameters on removing acids was reviewed, such as volume ratio of TMAH to ammonia, volume ratio of deacidification agents to diesel, demulsifier dosage, deacidification temperature and deacidification time. The results showed that the optimum deacidification process was that volume ratio of TMAH to ammonia was 10:1, volume ratio of deacidification agents to diesel was 0.7:1, demulsifier dosage was 0.15 mL, deacidification temperature was 293 K and deacidification time was 5 min. Under the optimum process, deacidification rate of reached 88.36%. The deacidification process effectively removed acids in diesel, had a little effect on other physicochemical properties of diesel, moreover, the color of treated diesel also was greatly improved. [ABSTRACT FROM AUTHOR]

The Mars Curiosity rover carries a diverse instrument payload to characterize habitable environments in the sedimentary layers of Aeolis Mons. One of these instruments is Sample Analysis at Mars (SAM), which contains a mass spectrometer that is capable of detecting organic compounds via pyrolysis gas chromatography mass spectrometry (py-GC-MS). To identify polar organic molecules, the SAM instrument carries the thermochemolysis reagent tetramethylammonium hydroxide (TMAH) in methanol (hereafter referred to as TMAH). TMAH can liberate fatty acids bound in macromolecules or chemically bound monomers associated with mineral phases and make these organics detectable via gas chromatography mass spectrometry (GC-MS) by methylation. Fatty acids, a type of carboxylic acid that contains a carboxyl functional group, are of particular interest given their presence in both biotic and abiotic materials. This work represents the first analyses of a suite of Mars-analog samples using the TMAH experiment under select SAM-like conditions. Samples analyzed include iron oxyhydroxides and iron oxyhydroxysulfates, a mixture of iron oxides/oxyhydroxides and clays, iron sulfide, siliceous sinter, carbonates, and shale. The TMAH experiments produced detectable signals under SAM-like pyrolysis conditions when organics were present either at high concentrations or in geologically modern systems. Although only a few analog samples exhibited a high abundance and variety of fatty acid methyl esters (FAMEs), FAMEs were detected in the majority of analog samples tested. When utilized, the TMAH thermochemolysis experiment on SAM could be an opportunity to detect organic molecules bound in macromolecules on Mars. The detection of a FAME profile is of great astrobiological interest, as it could provide information regarding the source of martian organic material detected by SAM. [ABSTRACT FROM AUTHOR]

Tetramethyl ammonium hydroxide (TMAH) is a corrosive and toxic chemical with a stable structure. Therefore, it is important to check whether surface water or wastewater contains TMAH. In addition to using ultrasound and ozone procedures to degrade TMAH in wastewater, in this study, the effects of TMAH degradation were explored by combining the two procedures while varying the reaction conditions. According to the experimental results, the degradation efficiency of TMAH by the single ultrasonic process was un-satisfactory, and the highest degradation ratio was only 8.4% after for 60 min, while the highest total organic carbon (TOC) mineralization ratio was only 7.1%. Ozonation is more effective for the degradation of TMAH, where the highest TMAH removal rate and mineralization rate can reach 58.4% and 21.8%, respectively. As the ultrasound is combined with the ozone procedure (named as sonozone) at the optimal condition, the TMAH removal ratio reaches 89.5% following by mineralization ratio of 77.5%. The toxicity test performed using the cell survival rate showed that ozonation and sonozone have better effects for improving the cell viability and reducing the toxicity of the water sample, and the sonozone process proves that the combination of two procedures indeed has synergistic oxidation efficiency. [ABSTRACT FROM AUTHOR]

Highlights • Doehlert design and desirability function allow optimize fish samples dissolution. • Ultrasound energy was used to increase the efficiency of the TMAH dissolution. • The method presents good analytical characteristics allowing simultaneous treatment. • Calcium, Mg, Fe and Zn were determinate from fillet fish samples using FAAS. Abstract Doehlert design and desirability function were used in the optimization of an ultrasound assisted dissolution method of fish fillet samples with tetramethyl ammonium hydroxide (TMAH) for the determination of Ca, Fe, Zn and Mg by flame atomic absorption spectrometry. The variables values after optimization were 620 μL (volume of TMAH), 25 min (sonication time) and 46 °C (bath temperature). The quantification limits for Ca, Mg, Fe and Zn were 56, 107, 23 and 2.9 μg g−1, respectively. Accuracy was evaluated by comparing the results generated from the analysis of the samples treated by the proposed method and by wet digestion. Additionally, accuracy for Fe and Zn was assessed by the analysis of certified reference materials Tort-3 (Lobster hepatopancreas), ERM-CE 278 (mussel tissue) and Dolt-4 (Fish liver). There were no significant differences between the results obtained at a 95% confidence level when results were evaluated by t -test application. [ABSTRACT FROM AUTHOR]

In this study, titanate nanotube arrays (TNAs) were prepared by using electrochemical anodization, and the silver nanoparticles were deposited on a titanate dioxide nanotube array (Ag/TNAs) by green synthesis methods. The Ag/TNAs was further applied to degrade tetramethylammonium hydroxide (TMAH) in a photoelectrochemical (PEC) system. SEM results showed that the diameter and length were 121.7 nm and about 3.45 µm, respectively, for TNAs. The deposited silver nanoparticles showed spherical and flaky shapes depending on using tea and coffee as green reducing agents, respectively. XPS showed that the atomic percentage of silver in Ag/TNAs-CTC5 and Ag/TNAs-CGA2.5 was 6.60% and 1.76%, individually. Results of UV–vis analyses indicated that the absorbance edge of TNAs red-shifts to a more extended wavelength region after silver modification. The photocurrents of Ag/TNAs-CTC5 (5.03 mA/cm2) and Ag/TNAs-CGA2.5 (3.63 mA/cm2) were 51% and 32% higher than that of TNAs (2.45 mA/cm2), illustrating that the photocatalytic ability of TNAs was significantly enhanced after silver nanoparticles modifying. Electrochemical impedance analysis (EIS) results confirmed that the electron lifetime of Ag/TNA-CTC and Ag/TNAs-CGA was 6.6 and 1.82 times longer than that of the TNA in the PEC system. Mott-Schottky analyses indicated that TNAs, Ag/TNAs-CTC5, and Ag/TNAs-CGA2.5 are n-type semiconductors with a density of dopants of 3.16 × 1019, 1.42 × 1020, and 9.49 × 1019 cm−3. The results of TMAH degradation showed that Ag/TNAs-CTC5 performed the highest efficiency at pH= 3 in the PEC system. EPR analyses of TNAs and Ag/TNAs-CTC5 showed a peak intensity of 1:2:2:1 which represented the characteristic DMPO−OH, revealing the dominant oxidants of the PEC system. [Display omitted] [ABSTRACT FROM AUTHOR]

1,2-Dihydro-1 -arylnaphtho[1,2-e][1,3]oxazine-3-one derivatives were synthesized in high yields using an efficient and one-pot condensation of 2-naphthol, aromatic aldehydes and urea catalyzed by tetramethylammonium hydroxide (TMAH) under solvent-free conditions. DOI: http://dx.doi.org/10.4314/bcse.v30i1.16

To create approximately spherical structures with curved sidewalls, this paper presents a method for building a series of decreasing slopes along the sidewall of a circular truncated cone. The multistep ring-edge etching technology of first reducing the concentric mask and then cutting the top off to create a mesa shape can be used to form the slopes. This wet-etching method avoids the constraints of crystallographic properties with surfactant-added Tetramethylammonium hydroxide (TMAH), enabling the manufacture of successive given inclination angles, the precise modulation of the spherical curvature by reduction design of concentric masks, and the setting of etching time. The newly approximated spherical Si microstructure patterns can be used for microlenses, quartz crystal resonators, micropulleys, and other applications. The present research is an approach to fabricate advanced microelectromechanical systems (MEMS) curved-surface structures, extending the range of 3D structures fabricated by silicon wet etching.

A green and efficient photocatalyst based on C and N co-doped titanium based nanorods (NRs) was prepared by facile hydrothermal synthesis and interlaminar bonding interaction between layered ${{\rm{Ti}}}_{3}{{{\rm{O}}}_{7}}^{2-}$ and tetramethylammonium hydroxide (TMAH). TMAH as one of quaternary ammonium-based compounds was used as the doping source of C and N elements. The results showed that C and N co-doping did not affect the anatase crystal structure of TiO _2 NRs. C, N-TiO _2 NRs showed excellent photocatalytic activity for degrading methyl orange under simulated sunlight irradiation. In particular, the 20:1 TiO _2 NRs catalyst showed the best catalytic performance, showing efficient photocatalytic rate of 90%. The photocatalytic reaction kinetics of undoped and doped catalysts was also studied. In addition, reactive species (RSs) experiments showed that hydroxyl radical ( ^· OH), superoxide radical anions ( ^· O _2 −) and photogenerated holes (h ^+ ) were major active species during the photocatalytic process. The mechanisms of the electrostatic attraction and potential photocatalytic degradation were proposed and discussed.

The magnetic hydrogels combining polyvinyl-alcohol (PVA) and Fe3O4 (magnetite)-TMAH (tetra-methyl ammonium hydroxide) have been successfully fabricated via a Freezing-thawing route. The magnetite nanoparticles were prepared from iron sands by using coprecipitation method. The transmission electron microscopy image revealed that the magnetite nanoparticles with a reaction temperature of 30 °C had the average particle size of 12 nm in clusters of aggregation. The result was similar to the particle size obtained from X-ray diffraction data analyzed by Scherer equation. Furthermore, synchrotron small angle X-ray scattering data were analyzed by using two lognormal distributions to calculate the distribution of the individual magnetite particles. Meanwhile, Teubner-Strey and Beaucage models were employed to observe the distribution of magnetite particles coated by TMAH as a surfactant. The data analysis showed that the magnetite particles within the magnetic hydrogels formed aggregations with diameters of cluster particles in the range from 13.1 to 31.8 nm. Interestingly, the diameter of clusters particle increased from 13.1 to 31.8 nm along with the increasing concentration of ferrofluids from 1 to 15 wt%. This phenomenon was predicted to result from the effect of TMAH as a surface reactant agent that prevented the aggregation by coating the surface of the magnetite nanoparticles. [ABSTRACT FROM AUTHOR]

Highlights • Because of the different mechanisms involved, comparisons of data from thermochemolysis and chemical methods must be done carefully. • Thermochemolysis should be viewed and used as a complementary method for the analysis of soil and sediment organic matter. • Thermochemolysis is a rapid and powerful tool suitable for routine analyses of soil organic compounds such as lignin, carbohydrates and lipids. Abstract Published data from different techniques used in the analysis of the main biomolecular families (lignin, carbohydrates and lipids) in 100 cm depth peat cores from the Sagnes peat bog (Limousin, France) were compared. Thermochemolysis using tetramethylammonium hydroxide was compared with the classical chemical degradation methods for lignin (CuO-NaOH oxidation) and carbohydrates (acid hydrolysis with HCl), and the Bligh and Dyer extraction method for lipids. Differences observed between the methods are mostly due to the different degradation mechanisms involved in each method. For lignin, the selective cleavage of β O 4 aryl ether bonds during thermochemolysis allowed identification of a more oxidized/degraded lignin pool in the deepest part of the peat core. For carbohydrates, the capacity of thermochemolysis to detect free (or terminal) carbohydrates showed an increase in microbial contribution at the interfaces between three distinct peat layers: the acrotelm, the upper part of the peat permanently above the water table; the mesotelm, the layer where water table fluctuations occur; and the catotelm, the bottom layer of peat that is permanently below the water table. For the lipid fraction, thermochemolysis revealed a lipid pool that was more influenced by microbial reworking. These results imply that, depending on the techniques used, the interpretation of the extent of degradation or source could differ. Therefore, TMAH thermochemolysis could be viewed and used as a complementary method of analysis, offering additional molecular data and contributing to a better understanding of the nature and sedimentation processes of organic matter in peat bogs. [ABSTRACT FROM AUTHOR]

In this paper, we present a gate-all-around silicon nanowire transistor (GAA SNWT) with a triangular cross section by simulation and experiments. Through the TCAD simulation, it was found that with the same nanowire width, the triangular cross-sectional SNWT was superior to the circular or quadrate one in terms of the subthreshold swing, on/off ratio, and SCE immunity, which resulted from the smallest equivalent distance from the nanowire center to the surface in triangular SNWTs. Following this, we fabricated triangular cross-sectional GAA SNWTs with a nanowire width down to 20 nm by TMAH wet etching. This process featured its self-stopped etching behavior on a silicon (1 1 1) crystal plane, which made the triangular cross section smooth and controllable. The fabricated triangular SNWT showed an excellent performance with a large Ion/Ioff ratio (~107), low SS (85 mV/dec), and preferable DIBL (63 mV/V). Finally, the surface roughness mobility of the fabricated device at a low temperature was also extracted to confirm the benefit of a stable cross section. [ABSTRACT FROM AUTHOR]

The thermal decomposition of cotton and hemp fibers was studied after mild alkaline treatments with tetramethyl-, tetraethyl- and tetrabutylammonium hydroxides with the goal of modeling the chemical activation during carbonization of cellulosic fibers. The thermal decomposition was studied by thermogravimetry/mass spectrometry and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). The treated samples decomposed in two temperature ranges during heating in the thermobalance. At lower temperature, tetraalkylammonium hydroxides (TAAH) ionically bonded to the cellulose molecules were decomposed; moreover, the alkaline agents initiated the partial decomposition of cellulose. Those fiber segments, which were not accessible for TAAH, decomposed at similar temperatures as the original cotton and hemp samples. It is known that quaternary ammonium hydroxides swell the cellulosic fibers; however, the results of this study proved that there was a chemical interaction between the alkaline swelling agents and cotton or hemp fibers at rather low temperatures (200-300 °C). The evolved products indicated that the alkaline chemicals reacted with the cellulose molecules and alkylated compounds were formed. This observation was confirmed by thermochemolysis experiments carried out by Py-GC/MS using tetramethylammonium hydroxide reagent. The thermochemolysis experiments under mild conditions resulted in the methylation of the glucoside units and levoglucosan, and no peeling reactions of the sugar units were observed as during strong alkaline conditions described in the literature. [ABSTRACT FROM AUTHOR]

Six cambic stagnohumic gley soil profiles located on marginal peatland between a gymnosperm plantation (Sitka spruce (Picea sitchensis (Bong.) Carr.)) and heather grassland in Wark Forest (northeast England), were analysed using 13C labelled tetramethylammonium hydroxide (TMAH) thermochemolysis to yield methylated phenolic and oxygenated aromatic products. The identification of aromatic compounds derived from the thermally assisted hydrolysis and methylation (THM) of vascular plant, Sphagnum and non- Sphagnum spp. allowed changes in vegetation both within the top 50 cm of peat (surficial peat) and across the site to be explored. Four sphagnum acid pyrolysis products reflected the presence of Sphagnum spp.; lignin phenols reflected the presence of vascular inputs; whilst 3,4-dimethoxybenzenepropanoic acid methyl ester reflected the presence of the non- Sphagnum moss Polytrichum commune. 210Pb dating of the surficial peat suggests that a historic change in vegetation identified by the changes in aromatic compound distribution with depth, coincide with the adjacent plantation of coniferous woodland. The peat closest to the plantation has seen a shift from grass dominated vegetation, to a species diverse vegetation cover, including Sphagnum spp. and vascular vegetation. These results suggest that Sphagnum spp. are able to survive not only perturbing environmental conditions, but are also able to establish themselves amongst non- Sphagnum species. This study demonstrates the ability of 13C-TMAH THM to be utilised as a screening method for the rapid characterisation of aromatic biomacromolecules in peat to identify key historic and current vegetation inputs. This technique in combination with peat dating helps identify the degradation patterns of these inputs and associated carbon dynamics, providing information on the resilience of current peat deposits to climate change and changing peat conditions. • Biomacromolecules were characterised by 13C-TMAH thermochemolysis in surficial peat. • Distinct aromatic compounds from Sphagnum spp. , non- Sphagnum mosses and vascular plants were identified. • Surficial peat was dated using 210Pb. • 13C-TMAH thermochemolysis can be used as a rapid screening method to identify vegetation inputs in peat. [ABSTRACT FROM AUTHOR]

Nitrogen-containing wastewater is an important issue in optoelectronic and semiconductor industries. Wastewater containing nitrogen compounds such as ammonium, monoethanolamine (MEA), and tetramethylammonium hydroxide (TMAH) must be properly treated due to concerns about health and environmental effects. MnCe-GAC (granular activated carbon) processes were developed in this study for the treatment of TMAH-contaminated wastewater in high-tech industries. The MnCe-GAC processes could effectively remove ammonium, MEA, and TMAH from aqueous solutions. The removal efficiencies of ammonium and MEA by these processes were better than observed for TMAH. Parameters affecting TMAH removal such as type of process, type of wastewater (synthetic or real), pH, salts, and t-butanol were investigated. In general, removal efficiencies of TMAH by various processes were in the following order: MnCe-GAC/O3/H2O2 > MnCe-GAC/O3 > MnCe-GAC/H2O2 > MnCe-GAC > GAC. The negative effect of sulfate and nitrate on pollutant removal might be due to the salting-out effect. Based on t-butanol experiments, the main degradation mechanisms of TMAH by the MnCe-GAC/O3/H2O2 process likely involved hydroxyl radicals. The process proposed in this study could be an effective alternative method for the treatment of high-tech industrial wastewater to meet the new TMAH discharge limit.

The control of environmental pollution has demanded increasingly determination of sulphur in a variety of matrices. Different analytical methods have been developed for the determination of this analyte in biodiesel fuel using various analytical techniques, including spectroanalytic and chromatographic methods. In this work a square-wave cathodic adsorptive stripping voltammetric (SW-AdCSV) procedure is proposed for the determination of sulphur in biodiesel, using a glassy carbon electrode modified with mercury-film (MFE). A buffer solution containing sodium acetate 1.4 mol L −1 and acetic acid 2% was used as supporting electrolyte in two different media (methanol an propanol). The voltammetric measurements were performed adding 70 μL of biodiesel sample previously treated with tetramethylammonium hydroxide (TMAH) to the supporting electrolyte. The method showed good linearity (r = 0.998) in the determination of sulphur in biodiesel (medium-concentration of 2.68 × 10 −8 mol L −1 (1.07 × 10 −3 mg kg −1 ) for a confidential level of 95%. Low values of limit of detection-LOD (3.29 × 10 −10 mol L −1 (1.32 × 10 −5 mg kg −1 ) and limit of quantification-LOQ (1.10 × 10 −9 mol L −1 (4.40 × 10 −5 mg kg −1 ) indicate a good sensitivity of the method. A validation of the procedure was carried out by comparing this procedure with the results obtained by an official method, using the same sample, through Teste- t of Student (confidence level of 95%). These results indicated that both methods are statistically equivalent, thus demonstrating the feasibility of the new method. [ABSTRACT FROM AUTHOR]

Anisotropic wet etching is a most widely employed for the fabrication of MEMS/NEMS structures using silicon bulk micromachining. The use of Si{110} in MEMS is inevitable when a microstructure with vertical sidewall is to be fabricated using wet anisotropic etching. In most commonly employed etchants (i.e. TMAH and KOH), potassium hydroxide (KOH) exhibits higher etch rate and provides improved anisotropy between Si{111} and Si{110} planes. In the manufacturing company, high etch rate is demanded to increase the productivity that eventually reduces the cost of end product. In order to modify the etching characteristics of KOH for the micromachining of Si{110}, we have investigated the effect of hydroxylamine (NHOH) in 20 wt% KOH solution. The concentration of NHOH is varied from 0 to 20% and the etching is carried out at 75 °C. The etching characteristics which are studied in this work includes the etch rates of Si{110} and silicon dioxide, etched surface morphology, and undercutting at convex corners. The etch rate of Si{110} in 20 wt% KOH + 15% NHOH solution is measured to be four times more than that of pure 20 wt% KOH. Moreover, the addition of NHOH increases the undercutting at convex corners and enhances the etch selectivity between Si and SiO. [ABSTRACT FROM AUTHOR]

The research complements the complex study carried out to understand the source of brown discolourations of ten marble statues in the Church of Orsanmichele in Florence, Italy. Originally located in exterior niches, the statues were restored to reverse the extensive alterations they had undergone throughout the centuries. One of the major alterations was the application of a dark brown patina that dated just after 1789. After the statues were placed indoors, brownish discolourations started to appear on their surfaces. Cross sections were examined using FTIR mapping and immunological methods. In parallel, the pyrolysis-gas chromatography/mass spectrometry (py-GC/MS) data already obtained from the statues' scrapings were compared with data from aged casein films applied to microscope glass slides and aged milk-treated marble. All the statues had been treated with milk-based substances before the time the bronze patina was applied. The values of temperature and illumination of the room were important factors in the ageing of organic substances and in the formation of calcium oxalates. It is likely that products of thermo-oxidation and photo-oxidation of the oils together with the oxalates caused the darkening. The marble samples corresponded to a Lunense provenance. [ABSTRACT FROM AUTHOR]