Papers by Keyword: Acid Treatment

Abstract: Ti-12Ta-9Nb-6Zr-3V-O alloy, one of the shape-memory alloys with lower Young’s modulus in comparison with conventional titanium alloy, was treated with sulfuric acid to form roughened surface on the substrate. In order to impart hydroxyapatite formation ability to the Ti-12Ta-9Nb-6Zr-3V-O alloy, apatite nuclei (AN) were precipitated on the roughened surface using simulated body fluid (SBF) adjusted at higher pH than physiological condition. By this treatment, AN-precipitated Ti-12Ta-9Nb-6Zr-3V-O alloy was obtained. The AN-precipitated Ti-12Ta-9Nb-6Zr-3V-O alloy showed high hydroxyapatite formation ability in physiological SBF.

Abstract: Waste lignin (WL) obtained from paper mills, was studied for its potential application in preparing carbon nanoparticles (CNPs) with high porosity. This was done by impregnation of 0, 5, 10 and 20% concentrations of phosphoric acid under various carbonization temperatures (600, 700, 800 and 900°C). The physicochemical properties of CNPs were characterized through nitrogen sorption, X-ray diffraction (XRD), Scanning electron microscopy (SEM), and Fourier transforms infrared spectroscopy (FTIR). Nitrogen sorption revealed that the condition using 10% concentration of phosphoric acid treatment at a carbonization temperature of 700°C formed carbon nanoparticles with a highly porous structure (Surface area 27.65 m²/g and pore volume 0.07 cm³/g). Additionally, in order to high surface area, porosity and concentrated carbon nanoparticle.

Abstract: We aimed to clarify the effect of sulfuric acid treatment and oxygen plasma treatment on changes in surface condition of PEEK substrates during fabrication process of bioactive apatite nuclei (AN) precipitated PEEK. We treated PEEK substrate by sulfuric acid treatment. This treatment contributed to provide micropores and sulfo groups on the surface of the PEEK. Next, we treated the PEEK with oxygen plasma at 200 W for 4 minutes. By this treatment, both generation of carboxyl groups and increase of sulfo groups were occurred and significant improvement of hydrophilicity of the surface of the PEEK was occurred. Finally, we precipitated AN on the surface of the PEEK. By this treatment, high apatite-forming ability was achieved.

Abstract: Oxidation by acid treatment is one of the chemical methods used to introduce surface oxygen functional group (SOFG) and defects on the surface of carbon nanofibers (CNFs). Therefore, many researchers used this method to improve the dispersion ability of CNFs in aqueous media. However, only few researchers used combination of chemical and mechanical method for oxidation of CNFs. In this work, as-received CNFs were treated using chemical method with an addition of mechanical method. On the first experiment (Method A) concentrated sulphuric acid and nitric acid were used and followed by combinations of mechanical method using ultrasonication water bath under reflux. The addition mechanical method through reflux was eliminated and different times of ultrasonication were used in method B and method C. Outer diameter of each CNFs samples were determined from FESEM images and were found to be in range of 50 nm–190 nm. Whereas, Raman spectroscopy was used to analyse any structural defects of CNFs samples during each treatment methods. From the findings, acid treatment of CNFs with addition of mechanical method using ultrasonication showed remarkably effect on the CNFs morphology.

Abstract: Efficient utilization of agricultural residue is the need of today’s environment. Teff straw is one such agricultural residue which is available in high amount in east African continent particularly Ethiopia. In the present study, combination of heat and acid treatment has been used to extract nano-silica from teff straw. X-ray fluorescence (XRF) analysis showed presence of high amount of silicon dioxide (≈52%) in raw teff straw. Thermal treatment at 600°C for 4 hour increased the SiO₂ concentration to ≈ 92% in its ash. Further acid treatment increased the concentration to ≈97%. Fourier transform infrared (FTIR) spectroscopy also confirmed increase in SiO₂ after thermal and acid treatment. X-ray diffraction (XRD) analysis showed the silica of amorphous nature in teff straw ash before acid treatment (S-BAT) whereas crystallinity increased after acid treatment (S-AAT). Transmission electron microscopy (TEM) showed presence of uniform nano-disks shaped particles of 50 nm average particle size in acid treated teff straw ash. Compared to other agricultural residues high amount of silica availability as raw and its small diameter anatomy structure will make teff straw better source of silica material at lower heat and chemical treatment.

Abstract: Effect of acid and heat treatments of multi-walled carbon nanotubes (MWCNTs) on benzene detection was investigated. For acid treatment, MWCNTs were treated by hydrochloric acid (HCl) for 1 h meanwhile other batches of MWCNTs were treated by heating under air ambient at 500^°C for 1 h. Pristine, HCl-treated and heat-treated MWCNTs were separately coated with ethyl cellulose (EC) by spin-coating prior to fabrication of three different sensors named as EC/pristine MWCNTs, EC/HCl-MWCNTs and EC/heat-MWCNTs sensors, respectively. Each fabricated sensor was exposed to benzene vapor at room temperature for testing its sensing performance based on an increase in its electrical resistance which was sensitive to benzene vapor. Response of the sensors fabricated from EC/HCl-MWCNTs and EC/heat-MWCNTs were 3.66 and 1.92 times higher than that of EC/pristine MWCNTs, respectively. Sensitivity of all sensors would be attributed to swelling of EC, resulting in loosening of MWCNT network after benzene vapor exposure. In addition, the difference of sensing response of the EC/pristine MWCNTs when compared with those of EC/HCl-MWCNTs and EC/heat-MWCNTs would be ascribed to different crystallinity and functionalization of MWCNTs sidewalls, suggesting that acid and heat treatments of MWCNTs would be promising techniques for improvement of benzene detection.

Abstract: The effects of hydrochloric acid (HCL) modification of the surface area, morphology and physico-chemical properties of Sayong kaolinite clay was investigated in this study. Sayong kaolinite clay was refluxed with different concentration of HCL (1M, 5M and 10M) at 100 °C for 4 hours and followed by calcination at 500 °C at 1 hour. The samples of untreated and treated clay were characterized by different analytical equipment such as BET Surface Area Analyzer, X-Ray Fluorescence (XRF), Fourier Transform Infrared (FTIR), Thermogravimetric Analyzer (TGA) and Field Emission Scanning Electron Microscopy (FESEM). The acid treatment increased the surface area of the Sayong kaolinite clay almost three times from 24.46 m²/g to the maximum value which is 64.04 m²/g once treated with 5M HCL. The increasing of the surface area is due to the formation of amorphous silica phase and removal of the octahedral Al³⁺ cations and other impurities (such as Mg²⁺, K⁺, Ca⁺ etc.) when the acid strength is increasing as reported in XRF analysis. FTIR study shows the change of the peak intensity of several types of structural OH groups that presently in the untreated and acid treated samples. TGA-DTA profiles shows that acid treatment increased the amount of physisorbed water as the acid concentration is increased. There are three of endothermic peaks was observed in the untreated sample which centered at 49 °C, 275 °C and 520 °C. However, when the clay samples treated with acid, it has increased the physisorbed water and decreased the structural and coordinated water which caused the change in the endothermic curves in the treated sample.

Abstract: The application of carbon nanotubes as a catalyst support has received considerable attention recently. The influence of acid and thermal treatments on the properties of multi-walled carbon nanotubes (MWCNTs) is presented in this paper. MWCNTs were treated with 65 wt% HNO₃ at the 120 °C for 14 h in order to open the caps and introduce functional groups on the MWCNTs. Then thermal treatment was carried out at 600, 700, 800, 900 °C for 3 h in flowing Ar gas in a tubular furnace. The MWCNTs were characterized by N₂- adsorption, FESEM and Raman spectroscopy. The thermal treatment resulted in slight morphological changes of the MWCNTs. The acid and thermal treatments also increased the BET surface areas and pore volumes of the MWCNTs.

Abstract: A new purification procedure was used for the purification of multiwalled carbon nanotube (MWCNTs) based on nitric acid oxidation. Using thermogravimetric analysis (TGA), and Energy dispersive X-ray analysis (EDX) to characterize the morphologies of MWCNTs oxidized under various conditions. The TGA provided clear evidence for the presence of carboxylic groups (COOH) attached to the surface of MWCNTs resulting from the acid treatment.

Abstract: To achieve lower price and high performance of pitch carbon fiber, coal tar pitch has to restructure through high-purity process, thermal and acid treatment process, and separation process. Thermal treatment and different oxidation treatments were used to increase the softening point and yield of the precursor pitch for carbon fiber. These treatments have the effect on the properties of carbon fiber because they cause considerable change in the chemical composition of pitches. Low molecular weight materials could be removed by the thermal treatment. The oxygen containing structure formed by the acid treatments would promote the poly-condensation and polymerization reactions. The oxidation treatment with sulfuric acid, nitric acid, and air blowing would lead to the remarkable change in the chemical composition of pitches, and resulted in considerable increase in the softening point and yield of the pitches.