Papers by Keyword: Phosphoric Acid

Abstract: Calcium sulfate (CaSO₄) scale formation during the phosphoric acid (H₃PO₄) production process presents significant operational challenges. Key variables influencing scale formation include temperature, pressure, stirring speed, and supersaturation. This study aims to evaluate the effect of varying concentrations of ATMP inhibitors on the mass of CaSO₄ scale in a 40% phosphoric acid solution and to analyze the composition of the resulting scale. The experimental procedure involved the addition of ATMP inhibitors at different concentrations, while temperature and stirring speed were varied. The solution was circulated through a sample housing for two hours, after which the mass of the formed scale was measured, and X-Ray Fluorescence (XRF) analysis was performed. The optimal concentration of ATMP inhibitors was found to be 9 ppm at a temperature of 40°C and a stirring speed of 235 rpm. Results indicated that the composition of the CaSO₄ scale produced with ATMP inhibitors was significantly lower than that of samples without inhibitors, with XRF analysis revealing an 8% reduction in CaSO₄ levels

Abstract: Creating waste-free technologies for the production of materials with high physical and thermal properties for the lining structures of thermal units is among the important environmental issues. Studies have shown that the waste of processing copper-zinc concentrates – ferrite-calcium slag crushed to pass through a sieve No. 0063 (the sieve residue is 1.2 % max.) can be used as a finely ground component of an iron phosphate binder. Studies have shown that under normal curing conditions at one-day age, refractory concretes based on an iron phosphate binder acquire strength sufficient for stripping, transportation, and installation of structures. At 7-day age, they acquire final strength, the value of which is determined by the aggregate properties. The iron phosphate binder refractoriness is 1,300 °C, and the working temperature of the concrete lining using expanded clay as coarse aggregate is 1,000 °C.

Abstract: Magnesium oxychloride cement (MOC) possesses rapid hardening, high mechanical strength, abrasion resistance, low alkali and low corrosive performances. However, its disadvantages of poor water resistance, easily deformation, moisture absorption and halogenations limit the application. A low cost-effective modifier H₃PO₄/Na₂O·xSiO₂·nH₂O was designed for MOC system. The results showed that the softening coefficient of the modified MOC reaches 0.988 by adding appropriate dosage of the modifier. Gelatinous substances in the modified MOC was produced after soaking in water, which effectively inhibit the hydrolysis of phase 5 (5Mg (OH)₂·MgCl₂·8H₂O) and the formation of Mg (OH)₂, thus improving the water resistance of MOC system. Keywords: Magnesium oxychloride cement; Water resistance; Phosphoric acid

Abstract: The adsorption of Pb (II) ions from aqueous solution by bio adsorbent from jackfruit wood sawdust treated with phosphoric acid was studied in a batch adsorption system. Characteristics of bio adsorbent investigated by Fourier transform infrared (FTIR). The functional group which involved in Pb (II) binding during adsorption process were amine N-H, amide C=O, alkyl C-H, and nitrile C≡N. The effects of phosphoric acid ratio to distilled water and soaking time on the adsorption capacity were investigated. Maximum adsorption of Pb (II) ions was carried out by bio adsorbent which modified by phosphoric acid with ratio to water 0.33. The experiment data of Pb (II) adsorption correlated well with pseudo second order kinetic model with correlation coefficient value 0.9988 and resulted adsorption capacity at equilibrium 1.4382 mg/g.

Abstract: In this work, a novel process integration scheme for p-MTJ devices’ passivation and contacting was proposed. The method can efficiently protect the ferromagnetic metals and the magnesium oxide which are the key building block of p-MTJs, and effectively make electrical contact with the interconnect metals for p-MTJs. The scheme consists of passivation of p-MTJs with dual dielectrics - silicon nitride and silicon oxide, followed by planarization and selective wet etch. The proposed integration scheme was successfully demonstrated with 80 nm size p-MTJ devices.

Abstract: This paper demonstrates a variety of metrology methods for high selective silicon nitride etch in different process baths. Capability of measuring full matrix components is also presented. For the measurement of H₃PO₄ and H₂O, both NIR spectroscopy and conductivity methods work well. Si measurement in the etchant that contains an organo-silicon compound requires a new reagent development in comparison with the original reagent method developed for regular process contains inorganic Si only.

Abstract: The etching of silicon nitride using phosphoric acid with silicon dioxide as a mask is an important process step used in the production of 3D NAND devices. This paper examines the theory of formation of a silica film onto the silicon dioxide surface during this etching step by performing a shell balance analysis of silica species in the etched out liquid volume of the 3D NAND structures. The method of moments is used to solve for the moments of the distribution of particle sizes, and this is used to solve for the potential energy barrier for silica particles to adhere to the silicon dioxide surface.

Abstract: The serious quality problem in the magnetic substrate during polishing process by using conventional lapping machine had generate the idea to develop a doubled-sided lapping machine of polishing stone manufactured of an abrasive and resin. After certain parameter of polishing process, the polishing stone starts to clog because of debris agglomeration from the polishing substrate, thus lead to the scratches on the magnetic substrate which will affect its performance. Three difference type of acid were used as to dissolve the debris agglomeration in the polishing stone. The influence of oxalic, phosphoric and citric acid at three different times were examined. It was found that oxalic acid is the best chelating agent in dissolving the debris in the polishing stone.

Abstract: In this study, porous anodic alumina was formed on aluminum alloy AA6061 by anodizing using mixture of 0.3 M oxalic acid and phosphoric acid with concentration ranged from 0.1 M to 1.0 M. AA6061 alloys were anodized at 40 V and 25°C for 60 minutes. FESEM images show that the uniformity of the pores arrangement of porous anodic alumina decreased with the increasing concentration of phosphoric acid in the electrolyte. Well-ordered porous anodic alumina was formed in mixture of 0.3 M oxalic acid and 0.1 M phosphoric acid while disordered porous anodic alumina were formed when the concentration of phosphoric acid were in the range of 0.3 M to 1.0 M. Pore size and interpore distance were found to increase with the concentration of phosphoric acid in the mixture. X-ray diffraction patterns show that to γ-Al₂O₃ were formed on the surface of AA6061 after the anodizing process, regardless of the concentration of phosphoric acid in the mixture electrolyte.

Abstract: Silica nanotubes with controlled diameter and length were synthesised by using a novel and modified template-sol-gel method. The consistency and order of silica nanotubes mainly depend on the anodic alumina membrane (AAO) template that was used during the preparation process. The AAO membrane was chemical etched using different concentrations (5, 7 and 10 wt %) of phosphoric acid. The obtained silica nanotubes had diameters in the range of 220-280 nm and thicknesses around 70-90 nm as observed by field emission scanning electron microscopy (FE-SEM). Scanning transmission electron microscopy (STEM) images enable us to view the arrangement of the hollow cylindrical silica nanotubes. Porosity of the silica nanotubes was investigated by nitrogen adsorption-desorption. The mesoporous silica nanotubes show characteristic type IV isotherm behaviour, with double capillary condensation step in the relative pressure range of 0.2-1.0 (p/p₀). Thermogravimetric (TGA) and differential thermal (DTA) analyses confirm the thermal stability of the silica nanotubes and their weight changes and endo and exothermic reactions. The structural and functional group analyses of the silica nanotubes were carried out by using X-ray diffraction (XRD) patterns and Fourier transform infrared spectroscopy (FT-IR).