Papers by Keyword: Oxidant

Abstract: Hydrodesulfurization (HDS) technique is no longer applicable in achieving ultra-low sulfur diesel because of high operational cost, high operating temperature and low efficiency. Due to these disadvantage, catalytic oxidative desulfurization (Cat-ODS) has been introduced as a new technique in achieving ultra-low sulfur diesel. The performance of the Fe catalyst was investigated in Cat-ODS of model diesel using terbutyl hydroperoxide (TBHP) as oxidant and dimethylformamide (DMF) as an extracting solvent. The physicochemical analysis of this catalyst was accomplished using several characterization techniques such as BET, EDX and HRTEM. It posseses high surface area of 226 m²g^-1 with small particle sizes in the range of 6-7 nm and less metal leaching. Under optimize condition, about 90% of sulfur was removed from model diesel. In the absence of catalyst, only about less than 80% of organosulfur compounds were removed. The Cat-ODS system showed the promising technology to be compliment with hydrodesulfurization (HDS) to produce low sulfur diesel.

Abstract: The polypyrrole-coated cotton fabrics were prepared via in situ chemical oxidative polymerization. The polymerization time of 120 min and reaction temperature of 25 °C were employed in this study. The major factors on electricities of the fabrics, including types of oxidants and molar ratio of pyrrole monomer to oxidant, were studied. Ferric trichloride hexahydrate (FeCl₃·6H₂O), ammonium persulfate ((NH₄)₂S₂O₈) and sodium periodate (NaIO₄) were selected to carry out the synthesis of polypyrrole. When FeCl₃·6H₂O acted as oxidant, the optimum conductivity of 4×10^-3 S·cm^-1 could be obtained by changing molar ratio of Py to FeCl₃·6H₂O. By contrast, the highest conductivity of fabrics which used (NH₄)₂S₂O₈ as oxidant was 1.8 ×10^-4 S·cm^-1. The evolution of resistivities, morphology, surface chemistry and mechanical strength were characterized by a four-points probe resistivity system, scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FTIR) and mechanical test instrument.

Abstract: Over the past century, numbers of hydrometallurgical processing technologies have been conducted for gold leaching in mining and second resource, such as cyanidation, being with high toxicity and low reaction rate, and non-cyanide---thiosulphate leaching and thiourea leaching, etc, having relatively high reagent consumption. Recently, ammonium thiocyanate was selected as leaching reagent in the laboratory study. Just as some papers shown, thiocyanate can be complexed tightly with Au⁺ or Au³⁺ to form water-soluble complexes according to the dynamic and thermodynamic system of thiocyanate gold and regenerated or obtained as a by-product in technological processes. And the extraction process is affected by many factors, such as thiocyanate concentration, oxidant concentration, liquid-solid ratio, temperature, and reaction time, especially pH and the category of oxidants, which can be chosen properly to make the method extensively applied in industrialization. Recent studies have shown that the gold leaching with thiocyanate under alkaline conditions is also viable using oxygen as oxidant. Then this article compares and analyzes the use of different oxidants in acid or alkali environment reaching a 96% leaching efficiency and the techniques of gold recycle from thiocyanate gold solutions. However, as the restriction for post-processing cost of thiocyanate and the strict requirement for the equipment in the acidic conditions or high pressure conditions, additional research should be directed towards making incorporation with other extraction methods perfectly. Two development tendencies are presented in this paper: (1) as additive; (2) as the lixiviant under alkaline or neutral conditions.

Abstract: Single crystal diamond is widely used in high-tech fields for its remarkable performance on mechanics, calorifics, optics, acoustics, etc. High-quality diamond surface with small roughness and low scathe are required in these applications. However, the extreme hardness and high chemical inertness of diamond result in severe processing difficulties. Chemical mechanical polishing (CMP) is a promising processing method which can obtain super-smooth and low-damage diamond surface. Oxidant is a key issue for CMP of single crystal diamond. In this study, five different oxidants were used to polish diamond samples. The results indicated that Fenton reagent was an appropriate CMP oxidant and a super-smooth diamond surface of Ra 2.4 nm was achieved by using Fenton reagent in CMP.

Abstract: Chemical mechanical polishing (CMP) had been considered as the most practical and effective method of achieving an ultra-smooth and non-damage surface in manufacturing SiC crystal substrate. CMP slurry was one of the key factors of CMP technology. In this paper, through investigating the changes of several core factors to evaluate the performance of CMP, such as the material removal rate (MRR), surface roughness Ra, 3D surface profiler, etc., the influence of various slurry and its content on the polishing efficiency and surface finish quality had been studied. The research results showed that different oxidant had different chemical action mechanism, also affecting the stability of CMP slurry and surface quality of specimen; adding suitable an oxidant to slurry could effectively improve the CMP performance.

Abstract: In chemical mechanical polishing (CMP) of ultra-thin stainless steel, the oxidant of polishing slurry determines the material removal rate (MRR). In this paper, the influences of oxidant in slurry on MRR and surface roughness have been studied in CMP of ultra-thin 304 stainless steel based on alumina (Al₂O₃) abrasive. The research results show that, in the same conditions, the MRR increases with the increase of the oxidant C and the oxidant B, the MRR decreases with the increase of the oxidant A and the MRR is max with the oxidant C. It indicated that the oxidant C has a large effect on MRR in CMP of the 304 stainless steel. The research results can provide the reference for studying the slurry in CMP of ultra-thin stainless steel.

Abstract: this study intends to compare through the experiment research of potassium permanganate, Fenton reagent, sodium persulfate, hydrogen peroxide, four kinds of commonly used oxidant chlorobenzene in contaminated soil, the removal effect of O-O-dichlorobenzene;, selected a typical ground soil bioremediation is the best antioxidant effect. Research under the condition of different on the dose, 4 kinds of oxidants to chlorobenzene and O-O-dichlorobenzene; removal effect. Combined pollution ground soil properties screen of chlorobenzene in contaminated soil, the highest removal rate of dichlorobenzene oxidant and best delivery dosage, to apply typical ground soil bioremediation, the results show that the effect is the best Kmno4.

Abstract: Titanium nitride (TiN) is widely used as a hard mask film protecting the inter-level dielectric (ILD) before metal or plating seed layer deposition steps. It is common practice to use a wet etch in order to remove residues formed during the ILD dry-etch step, and at the same time to remove some or all of the exposed TiN. From its thermochemical properties, it might be predicted that wet etching of TiN should be easy, since it is quite unstable with respect to both plain and oxidative hydrolysis. For example, in acidic solutions at 25°C [1, :

Abstract: A differential thermal analyzer was used to analyse the thermal decomposition properties of samples mixed barium nitrate with 2 percent of CuO, Cu2O, Fe2O3, Fe3O4, CoO, NiO, SnO2, PbO, and MnO2 respectively. The samples were then made into firecrackers and tested on its displaying effect and mechanic sensitivity. The results show that the thermal decomposition temperature of barium nitrate added with Cu2O decreases by 45°C. Besides, the explosive sound ratio of CoO increases to 85% and its paper scrap ratio reaches to 65%. The mechanic sensitivity of all the samples increases slightly.

Abstract: In order to decrease the consumption of lixiviant, study on dissolution of pure gold and middle-refractory gold ore using a novel thiosulfate leaching system with ferricyanide as oxidant was carried out. The results showed that the advantage of the novel system is that the thiosulfate consumption is negligible though the potential of ferricyanide is much higher than that of traditional cupric ammine complex. And compared to the ferric oxalate system, novel system could be used at relatively high pH condition which benefit to the stability of thiosulfate because ferricyanide can’t transfer to iron hydroxide in base solution. It is unlikely that very high dissolution rate of gold can be obtained using an air saturated thiosulfate- ferricyanide system without thiourea catalyst. However gold dissolution rate was increased with the increasing of concentration of ferricyanid in 5 mmol/L to 30mmol/L. When 0.1mmol/L thiourea was presented, the dissolution of gold approximately 1.5 times faster than that of in the absence of thiourea. Leaching of middle-refractory gold ore show that both of the consumption of thiosulfate and leaching rate was decreased compare to the traditional copper–ammonia thiosulfate system. Thiourea is not stable in base solution, but it was found that gold dissolution rates can be increased with a little thiourea ,the mechanism is still unclear.