Showing papers on "Ammonium hydroxide published in 2011"

A Facile Hydrothermal Conversion of Rice Husk Ash to ZSM‐5 Zeolite Powders

Abstract: The ZSM-5 zeolite powders were prepared through in situ extraction (extraction and conversion in single step process) of silica from rice husk ash in the presence of other aqueous-based precursors (sodium aluminate and tetrapropyl ammonium hydroxide) following a simple hydrothermal condition at 130 degrees C170 degrees C. The powders were characterized by X-ray diffraction (XRD), thermogravimetry analysis (TGA), differential thermal analysis (DTA), Fourier transform infrared (FTIR) spectroscopy, N2 physisorption measurements, and field emission scanning electron microscopy (FESEM). Crystallizations of ZSM-5 were noticed at 130 degrees C/96 h, 150 degrees C/24 h, and 170 degrees C/12 h. The exothermic peak at 422 degrees C in DTA curve indicated the removal of tetrapropyl ammonium ions (TPA+) used as structure directing agent (SDA). The vibration bands at around 550 and 1221 cm-1 indicated the presence of double 5-ring in ZSM-5. The 150 degrees C170 degrees C-treated samples exhibited higher BET surface area and pore volume compared to those of 130 degrees C-treated powders. The FESEM images showed coffin-shaped morphology of the powders, and their sizes increased with increase in both reaction temperature and time.

Electrochemical Deposition of γ-Phase Zinc-Nickel Alloys from Alkaline Solution

Abstract: Zinc-nickel alloys with 8-15% nickel were deposited onto stainless steel for corrosion protection Alkaline deposition conditions were utilized given that alkaline systems have been found to offer superior substrate coverage which results in better corrosion protection of the metal substrate (stainless steel) compared to acid bath depositions This method utilizes ammonium hydroxide as the base source with a working pH range of 9-95 Sodium acetate was used as the complexing ligand as it was found to stabilize the metal ions in the electrolytic solution Strongly adhering, quality deposits were obtained with electrodeposition at room temperature Bath compositions and applied potential had an effect on morphology of the films as seen in scanning electron microscopy Upon examination by x-ray diffraction and atomic absorption spectroscopy, all deposits were confirmed as γ phase zinc-nickel alloys with a nickel content of 8-15% The corrosion potential for the γ-phase coatings was improved over the pure zinc coatings

Process for the production of alcohols from biomass

Abstract: Alcohols useful as fuel compositions are produced from biomass by pretreating the biomass prior to hydrolysis and fermentation. In the pretreatment, the biomass is contacted with an aqueous solution containing a dilute acid with concentration of up to 10 wt % producing a predigested stream containing an aqueous liquor that contains at least a portion of hemicelluloses and a residual biomass that contains celluloses and lignin; separating at least a portion of the aqueous liquor from the residual biomass providing an aqueous liquor stream and a pre-digested biomass stream; then contacting the pre-digested biomass stream with a cooking liquor containing at least one alkali selected from the group consisting of sodium hydroxide, sodium carbonate, sodium sulfide, potassium hydroxide, potassium carbonate, ammonium hydroxide, and mixtures thereof and water. A process that allows for higher recovery of carbohydrates and thereby increased yields is provided.

Optimization of dynamic pH junction for the sensitive determination of amino acids in urine by capillary electrophoresis

Abstract: A capillary electrophoresis method with UV-absorbance detection was studied and optimized for the determination of underivatized amino acids in urine. To improve concentration sensitivity the utility of in-capillary analyte stacking via dynamic pH junction was investigated with phenylalanine (Phe) and tyrosine (Tyr) as model amino acids. Before sample injection, a plug of ammonium hydroxide solution was injected to enable analyte concentration. Samples were 1:1 (v/v) mixed with background electrolyte (1 M formic acid) prior to injection. The effect of the injected sample volume, and the injected ammonium hydroxide volume and concentration on analyte stacking and separation performance was investigated. The optimal volume of ammonium hydroxide depended on the injected sample volume. Using a dynamic pH junction good resolution (1.4) was obtained for a sample injection volume of 10% of the capillary (196 nl) with Phe and Tyr dissolved in water. Limits of detection (LODs) were 0.036 and 0.049 μM for Phe and Tyr, respectively. For urine samples, the optimized procedure comprised a 1.7-nl injection of 12.5% ammonium hydroxide, followed by a 196-nl injection of urine spiked with Phe and Tyr. Satisfactory resolution was obtained and amino acid peak widths at half height were only 1.6 s indicating efficient stacking. Calibration plots for Phe and Tyr in urine showed good linearity (R 2 > 0.96) in the concentration range 10–175 μM, and LODs for Phe and Tyr were 0.054 and 0.019 μM, respectively. RSDs for peak area and migration time for Phe and Tyr were below 7.5% and 0.75%, respectively.

Sequential hydrolysis of hemicellulose and lignin in lignocellulosic biomass by two-stage percolation process using dilute sulfuric acid and ammonium hydroxide

Abstract: To obtain the total fractionation and pretreatment of the corn stover, two-stage percolation process was investigated. This process consists of two steps: use of 0.07 wt% sulfuric acid for hemicellulose recovery in first stage and ARP (ammonia recycled percolation) in the following stage for lignin recovery. Among tested conditions, the best conditions of two-stage process were as follows: 1st stage; 170 °C, 2.5 ml/min, 30 minutes using 0.07 wt% sulfuric acid and 2nd stage; 170 °C, 5.0 ml/min, 60minutes using 15 wt% ammonium hydroxide. At above two-stage treatment conditions, the hemicellulose in corn stover was easily hydrolyzed (95%) and recovered with high yields (86%) and the extent of the lignin removal was 81%. After two-stage process, the treated biomass contained nearly pure glucan (85%). Two-stage treatment brought about enzymatic digestibility of 90% and 89% with 60 and 15 FPU/g glucan cellulase enzyme loadings, respectively.

The preparation of conducting polyaniline–silver and poly( p -phenylenediamine)–silver nanocomposites in liquid and frozen reaction mixtures

Abstract: The oxidation of aniline with silver nitrate in 1 mol L−1 acetic acid at 20 °C yielded a composite of two conducting components, polyaniline and silver; the acceleration with 1 mol% of p-phenylenediamine is needed for efficient synthesis. The yield and molecular weight increased when aniline was copolymerized with 10 mol% p-phenylenediamine. Such product displayed metallic conductivity below 180 K and semiconductor type above this temperature. As the result, the conductivity was the same at 100 and 300 K. The oxidation of p-phenylenediamine alone with silver nitrate also produced a conducting composite having the conductivity of 1,750 S cm−1 despite the assumed nonconductivity of poly(p-phenylenediamine). The present study demonstrates that all oxidations proceeded also in frozen reaction mixtures at −24 °C, i.e., in the solid state. In most cases, molecular weights of polymer component increased, the conductivity of composites with silver improved, to 2,990 S cm−1 for poly(p-phenylenediamine)–silver, and remained high after deprotonation with 1 mol L−1 ammonium hydroxide.

Mn–ferrite nanoparticles via reverse microemulsions: synthesis and characterization

Abstract: Mn–ferrite nanoparticles were synthesized by thermal treatment at 800 °C of manganese and iron oxo-hydroxides obtained via water-in-oil microemulsions consisting of n-hexanol as continuous phase, cetyl trimethyl ammonium bromide (CTAB) as the cationic surfactant and aqueous solutions of metal salts and precipitant agent (tetramethyl ammonium hydroxide) as reagents. Nanoparticles were synthesized using a multi-microemulsion approach. Two different co-precipitation routes are described depending on the Fe(II) or Fe(III) precursor salts. The influence of salt concentration and digestion process on the final products was examined. The nanoparticles were characterized by X-ray diffraction accompanied by Rietveld analysis, transmission electron microscopy, thermal analysis, infrared spectroscopy, and SQUID magnetometry. In all the synthesis reported in this study MnFe2O4 was observed only after thermal treatment at 800 °C of the as-prepared precursors. Almost spherical nanocrystalline MnFe2O4 ranging from 12 to 39 nm was obtained starting from chlorides or mixed chloride–sulfate salts as precursors. Low values of reduced remanent magnetization (M r/M s) and coercive field (H c) induce to believe that a fraction of superparamagnetic particle is present at room temperature.

Synthesis of In2O3@SiO2 core-shell nanoparticles with enhanced deeper energy level emissions of In2O3.

Abstract: In2O3@SiO2 core–shell nanoparticles were prepared using an organic solution synthesis approach and reverse-microemulsion technique. In order to explore the availability of various silica encapsulations, a partial phase diagram for this ternary system consisting of hexane/cyclohexane (1:29 wt), surfactant (polyoxyethylene(5)nonylphenyl ether, i.e., Igepal CO-520), and aqueous solution containing ammonium hydroxide was also established. It is realized that the shell-thickness can be tuned by several parameters such as the concentration of In2O3 nanocrystal suspension and the dose of the Si-precursor, tetraethyl orthosilicate. It was observed that the deeper energy level emissions of In2O3 were apparently enhanced when In2O3 was confined by the silica-shell in such core–shell nanoparticles. However, this enhancement could be degraded by increasing the shell-thickness.

Preparations of Polystyrene/Aluminum Hydroxide and Polystyrene/Alumina Composite Particles in an Ionic Liquid

Abstract: Polystyrene (PS)/aluminum hydroxide (Al(OH)3) composite particles were successfully prepared by the sol−gel process of aluminum isopropoxide (Al(OPri)3) in a hydrophilic ionic liquid, 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF4]) using ammonium hydroxide (NH4OH) as a catalyst in the presence of PS seed. Transmission electron microscopy observation of ultrathin cross-sections of the composite particles revealed that the composite particles had a core−shell morphology consisting of a PS core and a Al(OH)3 shell having high crystallinity. The amount of secondary nucleated Al(OH)3 could be reduced by dropwise addition of NH4OH. Moreover, PS/η-Al2O3 composite particles were successfully prepared by heat treatment of PS/Al(OH)3 at 300 °C in N2 atmosphere, which is below the decomposition temperature of PS.

Direct nickel electrodeposition on magnesium alloy in pyrophosphate electrolyte

Abstract: Direct nickel electrodeposition on a Mg alloy, AZ31B, was conducted in an electrolyte containing potassium pyrophosphate, nickel sulfate, potassium fluoride and ammonium hydroxide. The effect of potassium fluoride on the Mg alloy in a pyrophosphate nickel electrolyte was investigated using polarization and EIS methods. The chemical state of the Mg alloy was also analyzed by XPS. The effect of added ammonium hydroxide on electroplated nickel layer was observed by FE–SEM. A magnesium fluoride film, which was formed by added potassium fluoride, inhibits the dissolution of the Mg alloy in the electrolyte. The current efficiency was increased and surface cracks on the nickel layer were also eliminated by adding ammonium hydroxide to the electrolyte. The direct nickel electrodeposited Mg alloy showed significantly improved corrosion resistance compared to the uncoated Mg alloy. A successful and protective electrodeposited nickel layer was formed on the Mg alloy in pyrophosphate nickel electrolyte due to the addition of potassium fluoride and ammonium hydroxide.

Aqueous alkaline etching and cleaning composition and method for treating the surface of silicon substrates

Abstract: An aqueous alkaline etching and cleaning composition for treating the surface of silicon substrates, the said composition comprising: (A) a quaternary ammonium hydroxide; and (B) a component selected from the group consisting of water-soluble acids and their water-soluble salts of the general formulas (I) to (V): (R1-S03-)nXn+ (I), R-P03 2- (Xn+)3-n (II); (RO-S03-)nXn+ (III), RO-P03 2- (Xn+)3-n, (IV), and [(RO)2P02-] nXn+ (V); wherein the n = 1 or 2; X is hydrogen or alkaline or alkaline-earth metal; the variable R1 is an olefinically unsaturated aliphatic or cycloaliphatic moiety and R is R1 or an alkylaryl moiety; the use of the composition for treating silicon substrates, a method for treating the surface of silicon substrates, and methods for manufacturing devices generating electricity upon the exposure to electromagnetic radiation.

Effect of Surfactant Concentration on the Physico-chemical Characteristics of Mesoporous Molecular Sieve

Abstract: A series of mesoporous molecular sieve samples have been synthesized hydrothermally by using cetyltrimethylammonium bromide (CTAB) as a template, tetraethyl orthosilicate (TEOS) as a silica source, tetramethyl ammonium hydroxide as a base source and water as a solvent. The samples were prepared by adding required amount of surfactant, TEOS, water and TMAOH to maintain pH, then the obtained mixture was stirred for 10 min. and then transferred into autoclave. pH of the gel was adjusted to 10. The molar ratio of surfactant (CTAB) and TEOS was kept at 0.11:0.48, 0.165:0.48, 0.22:0.48 and 0.274:0.48 for samples A-I, A-II, A-III and A-IV respectively, while the aging time was kept 4 days and temperature remained constant at 393 K. The as-synthesized samples were thoroughly washed with distilled water and then dried at 373 K for 24 h. The as-synthesized samples were calcined at 723 K for 6 h in air. The as-synthesized samples were characterized for its morphology using Field Emission Scanning Electron Microscopy (FESEM), elemental analysis by using Energy Dispersive X-Ray (EDX), thermal stability by using Thermogravimetric Analysis (TGA), the functional groups within the samples before and after calcination was analyzed using Fourier Transform InfraRed Spectroscopy (FTIR). Formation of the mesoporous material depends on the surfactant, which act as a structure directing agent. Micelles of the surfactant arrange themselves and interact with the silicate ions to form the mesoporous material. In this study, the effect of concentratiohn was studied on the synthesis and found that due to increase in concentration of surfactant, more silica polymerized and formation of material increases.