Papers by Keyword: Ammonia

Abstract: The process of sorption-electrochemical cleaning of rinse waters, obtained after ammonia etching of printed circuit boards from copper ions, is proposed. Cation exchanger KU-2×8 and ampholyte Lewatit MonoPlus TP 207 for the extraction of copper were tested. Capacity up to breakthrough of Lewatit MonoPlus TP 207 is 0.11 g/g and a full dynamic exchange capacity for copper of 0.15 g/g. Various options of a pregnant ion exchanger desorption are considered. The best stripping ability has a 20% solution of sulfuric acid. The possibility of desorption by a partially de-coppered eluate was studied. This scheme allows the use of acid formed in the process of copper electro-winning. The effect of concentrations of NH₄Cl and NH₄OH on the sorption of copper was studied. It was shown that, with an increase in the concentration of NH₄Cl to 100 g/dm³, the capacity of the ion exchanger decreases by 10.42%. Thus, the ion exchanger Lewatit MonoPlus TP 207 effectively absorbs copper even at high salt background. A combined sorption-electrochemical technology has been proposed for treatment of rinse waters. The proposed technology will reduce consumption of fresh water and ammonia for printed circuit boards washing and extract copper in the form of elemental metal.

Abstract: This paper is focused on the effect of treatment of fly ash after selective non-catalytic reduction (SNCR) with tannin on autoclaved aerated concrete (AAC) production in order to reduce or stop ammonia leakage from the fresh mixture due to its alkalinity. A pure form of tannin and a tannin-based product „Farmatan“ were used as a treatment in dosage ranging from 0,5 g – 3 g of agent per 1 kg of fly ash. Efficient dosage was determined at 2 wt.% of fly ash by the speed of an indicator change due to gaseous ammonia diluted in water. The rheological properties of fresh mixtures were observed by consistency test in Viskomat showing that Farmatan causes delay of hydration. The results of bulk density and compressive strength testing revealed that Farmatan causes an increase of bulk density and at higher amount decreases the compressive strength because of thermal crack formation due to combined effect of delayed hydration and thixotropy. Using x-ray diffraction (XRD) analysis there were no differences in phase composition observed.

Abstract: ZnSe quantum dots (QDs) with high intrinsic fluorescence quantum efficiency (QY) and low defect luminescence were prepared by hydrothermal method assisted with ammonia, in which the selenium powder and zinc acetate were used as Se and Zn source, and the mercaptopropionic acid (MPA) was used as ligand. Effect of ammonia amount, Zn/Se ratio, Zn/MPA ratio, and reaction time was investigated in detail in this study. The as-prepared ZnSe QDs were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-visible absorption spectrum (UV-Vis), fluorescence spectrum (PL). ZnSe QDs assisted with ammonia were sphalerite, and with emission peak in the range of 380~405nm. The optimal condition was following: Zn/Se ratio was 5, Zn/MPA ration was 0.25, reaction temperature was 110 °C and reaction time was 6 h. Under the optimal condition, ZnSe QDs with intrinsic emission QY of 47% and diameter of 3.8±0.3 nm can be obtained. The ZnSe QDs prepared in this study were expected to replace toxic Cd-related QDs in biomarkers, violet and blue light solid luminescent devices, and provide excellent parent materials for the doped ZnSe QDs system.

Abstract: The internal gelation process was used to prepare cerium dioxide microspheres. The effect of ammonia on the stability of the precursor solutions was investigated with the NH₃∙H₂O/Ce (NH₄)₂(NO₃)₆ molar ratio from 0 to 1.25. The surface morphology and microstructure of the sintered CeO₂ microspheres were analyzed. With the increase of NH₃∙H₂O/Ce (NH₄)₂(NO₃)₆ molar ratio, the solutions became more unstable, which indicated that their gelation was initiated. When the NH₃∙H₂O/Ce (NH₄)₂(NO₃)₆ ratio varied from 0 to 0.75, the surface of the microspheres became rougher and grain size became larger. Further increase in the NH₃∙H₂O/Ce (NH₄)₂(NO₃)₆ ratios to 1 and 1.25 led to CeO₂ microspheres with smooth surface and compact structure.

Abstract: This study aimed to determine the ammonia (NH₃) gas sensing ability of zinc oxide (ZnO) films deposited on glass tube substrates via successive ionic layer adsorption and reaction (SILAR) technique. The fabricated films were annealed at different temperatures. The sensor films were exposed to different volumes of ammonium hydroxide (NH₄OH), converted to parts per million (ppm). The change in voltage from concentrations 595ppm up to 1189ppm exhibited a linear trend. However, no trend was revealed in concentrations 2378ppm and 3964ppm due to film saturation. Results showed that the films annealed at 250 °C, 300 °C, 350 °C, and 400 °C presented sensitivities of 2.7×10^-4 V/ppm, 1.0×10^-4 V/ppm, 2.3×10^-4 V/ppm, and 1.5×10^-4 V/ppm with R² values of 0.997, 0.994, 0.904, 0.999 and resolutions of 3.7 ppm/mV, 9.9 ppm/mV, 4.4 ppm/mV, and 6.6 ppm/mV, respectively. Furthermore, this research study had proven that high quality gas sensors may be fabricated at a lower cost.

Abstract: After introducing SNCR in coal combustion process in power plants, the valuable by-product such as fly ash remains contaminated with amount of ammonia in form of NH₄HSO₄, (NH₄)₂SO₄ respectively, which became undesirable in AAC technology because the toxic ammonia is released in the air during the mixing process. This paper deals with the effect of varying ammonia content in fly ash after selective non-catalytic reduction (SNCR) on the physical-mechanical properties of the fly ash based autoclaved aerated concrete (AAC) with the main focus on determination of the impact of the various content of ammonium ion in fly ash on the initial consistency of fresh slurry, the residual content of ammonium ion in hardened aerated matrix and also the impact on the bulk density, compressive strength and tobermorite formation after hydrothermal treatment. Seven batches of AAC, made out of fly ash with rising content of ammonium ion from 0 ppm to 250 ppm, were tested and based on the results obtained it was found out that ammonia is released during the mixing process entirely and doesn‘t remain in AAC after autoclaving, moreover it doesn‘t affect the properties of both fresh slurry (no apparent foaming effect noticed) and thermally treated samples of AAC. Formation of tobermorite wasn’t negatively affected.

Abstract: Silver nanoparticles were synthesized using silver nitrate as a silver precursor in the presence of tannic acid under UV radiation for 60 minutes. Various pH conditions were employed in the synthesis in order to study its effect on characteristics and ammonia sensing of the synthesized nanoparticles. The images obtained from transmission electron microscope revealed the formation of the spherical particles with average diameters in the range of 10-40 nm depending on pH conditions. It was found that using acidic condition resulted in yellow silver nanoparticles colloids with bigger particles and exhibiting a UV-visible absorbance peak at around 435 nm whereas using other conditions yielded greenish-yellow colloids with smaller particles and having two absorbance peaks at around 370 and 430 nm. After adding 100 ppm of ammonia, TEM images revealed the aggregation and the changes in size and shape of the silver nanoparticles. The color of the silver nanoparticles colloids synthesized using acidic condition changed to orange-yellow color. However, other pH conditions caused the color of the colloids became darker. These color changes were observed by the naked eyes.

Abstract: Various sizes SiO₂ colloidal particles in the size range of 260-950 nm were synthesized by the stöber method by adjusting the amount of ammonia from 9.0 ml to 3.0 ml while keeping 20.0 ml tetraethyl orthosilicate (TEOS), 125.0 ml ethanol, 6.0 ml ammonia and 18.0 ml distilled water fixed. In addition, X-ray diffraction (XRD) and scanning electron microscopy (SEM) were employed to analyze the crystallinity and morphology of the synthesized SiO₂ colloidal particles; the XRD result show that the SiO₂ colloidal particles are amorphous at room temperature; the SEM results demonstrated that the amount of ammonia could have significant effects on the size, size distribution and sphericity of the SiO₂ colloidal particles. SiO₂ colloidal particles were resulted with good monodispersity when the amount of ammonia was in the range of 6.0-90 ml, while SiO₂ colloidal particles with double size distribution were obtained when the range is 3.0-4.5 ml; on the other hand, SiO₂ spheres were resulted with good sphericity when the ammonia is in the range of 6.0-7.5 ml.

Abstract: Ab initio density functional theory employed to study the adsorption of hydrogen and nitrogen gas molecule on the α-Fe₂O₃ (111) surface for ammonia synthesis. The calculated adsorption energy is-4.70kcal/mol, -4.60kcal/mol,-4.38kcal/mol and-3.77kcal/mol for different orientations of adsorbed gas molecules and shows that system is stable and gas molecules have adsorbed. It can also be seen with adsorption of gas molecules the net spin of hematite enhanced from 0 to 2 hence confirms the activity of hematite surface. Hematite nanowires synthesized by oxidation method. Raman spectrum analyses demonstrates that the nanowires are single-crystalline. Field Emission Scanning Electron Microscopy (FESEM) reveals that the nanowires have lengths of 10-25 μm. The magnetic saturation of the nanowires is 15.6 emu/g investigated by vibrating sample magnetometer (VSM). Ammonia was synthesized by magnetic induction method using the hematite nanowires as catlyst and quantified by Kjeldahl method. It is found that the role of gases adsorption was able to enhance catalytic activity of hematite nanowires for the ammonia synthesis. This green synthesis method could be a contender to the Haber-Bosch process currently used by the industry.

Abstract: In order to evaluate the effect of repeated cleaning on EUV reticles, specifically, on the etched Mo/Si multilayer, wafer-based test structures with a mimic of this etched Mo/Si multilayer (“black-border”) were fabricated. The resistance of Mo and Si towards alkaline chemistries was tested and quantified using these test structures. The initial passivating film on Mo seems to play a role in delaying the Mo to further oxidize and dissolve in alkaline solutions. For the cleaning times used (minutes) the Mo surface, and thus the black-border edges, will probably stay passivated by that protective oxide in alkaline solution (pH 11), with no or only very limited Mo loss. Stirring and the amount of oxygen or other oxidizing species like H2O2 in solution could increase the oxidation rate of the Mo and/or Mo oxides into soluble Mo(VI) species.