Sharif Digital Repository

In this study, a comprehensive investigation was carried out on the effects of environmental condition on physical and chemical properties of Cold-Briquetted Iron and Carbon (CBIC), Cold Direct Reduced Iron (CDRI), and Hot-Briquetted Iron (HBI). The results showed that cold briquetting of CDRI decreases its specific surface area by 51%, which has a significant effect on its oxidation resistance and mechanical strength. Microscopic observations revealed that the oxidation products are formed in near-surface porosities during aging, which protects the fresh material underneath from environmental oxidants, resulting in retarding further oxidation. The oxidation behavior of the samples showed... 

Ni-Fe and the Ni-Fe-Cr-Mo alloy films were electrodeposited from a chloride solution containing complexing compounds on ITO/glass substrates. AFM studies revealed a spherical structure for the alloy films with roughnesses from 10 up to 50 nm. The Ni-Fe-Cr-Mo alloy films were found to have a fine-grain structure. The quaternary alloy compounds containing up to 4% Cr and 2% Mo showed higher resistivity and little decrease in magnetoresistance (MR) relative to the Ni80Fe20 alloy compound. The MR of the quaternary alloy compounds was decreased for higher Cr and Mo contents. Moreover, the anisotropy (AMR) was also decreased by the addition of Cr and Mo to Permalloy films. Auger studies indicated... 

Palm oil (PO) and sunflower oil (SFO) blends with varying proportions were subjected to enzymatic interesterification (EIE) using a 1,3-specific immobilised lipase. The interesterified blends were evaluated for their slip melting point (SMP), solid fat content (SFC) at 10-40°C, p-anisidine value, peroxide value, free fatty acids (FFA), induction period of oxidation at 110°C (IP110) and composition of fatty acids by gas chromatography. Under EIE treatment, the blends of PO and SFO in different proportions (20:80, 40:60, 50:50, 60:40 and 80:20) had saturated and unsaturated fatty acid content in the range of 37.6-52.0% and 48.0-62.4%, respectively. The blends showed a considerable reduction in... 

A silicon carbide coating was formed on the surface of graphite flakes by reaction of molten Si with carbon at 1100-1300. °C in a 95%KCl-5%NaF molten salt under Ar atmosphere. The effect of temperature and Si/graphite ratio in the initial mixture on the quality and the amount of SiC were investigated by XRD and SEM/EDS analyses. Also, the water wettability, oxidation resistance and zeta potential of un-coated and coated graphite were examined by TGA analysis and sedimentation test. The results show the amount of coating to increase in the coated flakes with increasing temperature and Si/graphite ratio. The SiC coating improves water wettability of graphite and acts as a protective layer to... 

Many benefits of the MgO-C refractory bricks such as excellent corrosion resistance, high thermal shock resistance, good mechanical strength at high temperatures, and permeability have attracted attention of consumers in various industries. But on the other hand, the low oxidation resistance of these refractory bricks at high temperatures has restricted their application. For this purpose, in this research study, the impact of Nano-ZrSiO4 addition on microstructure and performance of MgO-C refractory was investigated. 0, 0.5, 1, 1.5, and 2 wt % of Nano-ZrSiO4 was added to compositions. After samples preparation, all specimens tempered and fired (in a coke bed) at the 250 °C and 1600 °C for 8... 

The effects of graphite content on the density and oxidation behavior of MgO-C refractory samples were studied. The samples were formulated with various amounts of graphite and their oxidation behavior was investigated (in an isothermal condition); using a Thermo Gravimetric system (TG), in air and at temperatures ranging from 900"C to 1450"C. The preliminary results showed that the porosity and density of tempered samples were decreased when the graphite content was increased. However, after heating the samples at higher temperatures, the decreasing rate of porosity was lowered. At the beginning of the oxidation process, the rate of weight loss was high, but was gradually decreased when the... 

The conductive CuCo2O4 spinel coating is applied on the surface of the AISI 430 ferritic stainless steel by the dip-coating sol-gel process and it is evaluated in terms of the microstructure, oxidation resistance and electrical conductivity. The results show that the CuCO2O 4 coating forms a double-layer scale consisting of a Cr, Fe-rich subscale and Cu-Co spinel top layer after 500 h in air at 800 °C. This scale is protective, acts as an effective barrier against Cr migration into the outer oxide layer and alleviates the cathode Cr-poisoning. The oxidation resistance is significantly enhanced by the protective coating with a parabolic rate constant of 5.8 × 10-13 gr2 cm-4 s -1, meanwhile... 

Electro-oxidation of methanol on Ni in NaOH solutions with the alkali concentration in the range of 0.05-0.5 M and in the presence of 0.5 M Na 2SO4 supporting electrolyte is studied. All the mentioned species compete for adsorption on Ni and OH- is essential for the electro-oxidation process. The electro-oxidation seems to proceed through the electro-chemical reactions of adsorbed methanol and hydroxide species and the removal of the resulting intermediate by adsorbed hydroxyl groups. The mechanism is consistent with the cyclic voltammetry and impedance spectroscopy results and can semi-quantitatively account for the appearance of capacitive, inductive and negative resistance loops as well... 

Coating of graphite flakes with MgO/carbon nanocomposite was carried out via gaseous state reaction between mixture of Mg metal, CO gas and graphite flakes at 1000 °C. XRD and FE-SEM analysis of coating showed that the coating was comprised of MgO nano particles and amorphous carbon distributed smoothly and covered the graphite surface evenly. Thermodynamic calculations were employed to predict the reaction sequences as well as phase stability. The effect of coating on water wettability and oxidation resistance of graphite was studied using contact angle measurement and TG analysis, respectively. It was demonstrated that the reaction between Mg and CO could result in MgO/C nanocomposite... 

Abstract: This work describes coating of NiCoCrAlY on IN-738LC superalloy by high-velocity oxygen fuel (HVOF) process. Properties of the coatings are significantly influenced by oxygen/fuel ratio and other spraying parameters. The effect of oxygen/fuel ratio on the oxidation behavior, bond strength, hardness, roughness and microstructure including porosity, inclusion formation and unmelted particles are discussed here. The porosity and inclusion in C1 coating are maximal. C2 coating with oxygen/fuel ratio of 2 has the highest bond strength and the lowest unmelted particles. C3 coating with the lowest total porosity and inclusion has the minimal roughness and the highest oxidation resistance... 

This work describes coating of NiCoCrAlY on IN-738LC superalloy by high-velocity oxygen fuel (HVOF) process. Properties of the coatings are significantly influenced by oxygen/fuel ratio and other spraying parameters. The effect of oxygen/fuel ratio on the oxidation behavior, bond strength, hardness, roughness and microstructure including porosity, inclusion formation and unmelted particles are discussed here. The porosity and inclusion in C1 coating are maximal. C2 coating with oxygen/fuel ratio of 2 has the highest bond strength and the lowest unmelted particles. C3 coating with the lowest total porosity and inclusion has the minimal roughness and the highest oxidation resistance and... 

Synthesis of colloidal metal oxides with controllable size and morphology is burgeoning field of research in nanoscience. Low band gap gray Zn/ZnO colloidal nanoparticles were fabricated by plasma-liquid interaction of DC arc discharge in water. Scanning electron microscopy, X-ray diffraction and UV–vis spectroscopy were employed for morphology, crystal structure and optical characterizations respectively. Optical emission spectroscopy was used to investigate the plasma properties during the synthesis and formation mechanism of nanoparticles. Nanoparticles with different size and shape were fabricated only by adjusting discharge current during synthesis without introducing any chemical... 

Catalytic ozonation has recently been used as a new means of contaminant removal from water and wastewater. In this study, bone charcoal (BC), a new catalyst prepared under laboratory conditions, was used to catalyze the ozonation of humic substances (HS) in aqueous solutions. The catalytic effect of bone charcoal and the relevant parameters of this ozonation process (solution pH, temperature, scavenger effect, humic acids concentration and BC dosage) were investigated. In the catalytic ozonation experiments, the degradation kinetics was investigated. The reaction rate and the rate constant were determined. The results showed that using a BC catalyst in the ozonation of HS produced a 1.43-...