نشریه علم و مهندسی سرامیک
سال ششم شماره 3 (پیاپی 22، پاییز 1396)

Various adsorbent materials such as clays, calcium silicates and zeolite have been studied for their ability to remove nickel from industrial wastewater. The current research aims to investigate the thermal decomposition of three types of clay (Taiwan kaolin, Zonuz kaolin and Chah-Taleb Bentonite). Samples of pure clays, calcined clays and containing CaCO3 as additive were examination. The calcination was carried out at 700 and 800 °C for kaolins and bentonite, respectively. The XRD of the calcined samples containing 10 wt.% of CaO and sintered at 900 °C indicates the presence of a amorphous phase together with anorthite and wollastonite phases. To examine the absorption of nickel, one gram of each sample of absorbent materials was put in a solution of 50 mg /l for 24 h. Then, the remaining nickel was determined by Inductively Coupled Plasma (ICP). The results showed that the samples of pure Iranian kaolin, and Taiwan kaolin with 10 wt.% CaCO3 were the best adsorbent materials. However, adding more than 10 wt.% CaO to Iranian kaolins had a negative effect on absorption. The samples of pure bentonite and containing 10 wt.% CaO showed better absorption of nickel than that of calcined bentonite.

In this research (PANI/CNT) core/shell nanocomposite were synthesized via in situ chemical oxidative seeding polymerization‚ the results of SEM indicated the structure of synthesized nanocomposite. TEM‚ FTIR‚ UV-Vis‚ XRD analyses of samples showed that this nanocomposite is decorated with (Ni‚ Co) oxide nanoparticles. The VSM test of as prepared and annealed nanocomposite exhibited the saturated magnetization of 0.93‚ 1.96 emu/g, respectively; the coercivity values were also 26.5‚ 1200 Oe, respectively. The reflection loss characteristics of (Ni‚ Co) oxide- Pani- CNT core/shell nanocomposite were also investigated with a vector network analyzer‚ in the 12.4–18 GHz range (Ku band). The maximum absorption increases with enhancement of the dispersed nanoparticles percent in polyurethane matrix from 1 to 10%. The value of the maximum reflection loss in the absorption samples with 1% and 10% of nanoparticles is -3.84 dB at 15.80 GHz and -7.3 dB at 17.5 GHZ, respectively.

Thermal barrier coatings are used to insulate the components in the hot turbine parts to increase the working temperature and efficiency of these components. In this study, conventional and functionally graded thermal barrier coatings of NiCrAlY / YSZ were applied by plasma spraying on Hastelloy-x. The specimens were subjected to thermal shock with a defined cycle. The coatings were characterized using optical microscope, Scanning Electron Microscopy (SEM), Energy Dispersive x-ray Spectrometry (EDS), map analysis and X-Ray Diffraction (XRD). Moreover, thermal shock resistance of the coatings was determined. The thermal shock stress was measured by a new method. In this research, nano-indentation stress measurement method was used to measure the residual stress in thermal barrier coatings. The results of scanning electron microscopy analysis showed that microstructure, porosity and chemical composition changed gradually through the functionally graded coating. Surveying the surface of the samples after applying thermal shock showed that the separation of layers in the two-layer thermal barrier coatings occurred more than the graded coatings. The results of stress measurement by nano-indentation method indicated that the designed method for measuring stress, in contrast to other conventional methods, can measure stresses along the coating depth with acceptable accuracy, without damaging the sample.

Isfahan province has a significant number of individual industrial soil deposits where some of them are utilized, but the silica and iron oxide impurities have deteriorate the run of mine quality and reduced the final product value extensively. The goal of this research was to eliminate the mentioned impurities to adopt the product quality with the tile and ceramic industry specifications, and for an additional added-value. Three feldspar samples were collected from Varzaneh, Naein, and Kashan regions, and chemical and mineralogical characterizations were conducted on the head samples after proper comminution and sieving analysis. The -250 µm head samples were treated by a 3 cm hydrocyclone to physically reduce the silica content, which, for all three samples and in the average, resulted in 4% silica reduction in the overflow product while alumina and unexpectedly iron oxide increased by 1.2 and 2%, respectively. Further reductions of iron oxide, 1% in average, were obtained once the overflow products were introduced to a high gradient magnetic separator. The dissolution of the amorphous silica along with iron oxides had made the magnetic products leaching, with sodium dithionite, practically ineffective. It is found that using oxalic acid as the leaching agent for the fresh run of mine feed would present the best results, as reduction of iron oxide below 1% was obtained for Kashan feldspar. Preliminary cost and benefit evaluations for a 150 t/y processing plant, determined a 50k Rl.s benefit per ton of processed product with almost 4 years of overall cost return period.

In this work, Mn1-xCoxFe2O4 (x=0, 0.1, 0.2, 0.3, 0.4 and 0.5) nanoparticles have been prepared by coprecipitation method. The effects of Co2 substitution on the cation distribution between tetrahedral and octahedral sites in spinel structure, magnetic properties and AC magnetically induced heating characteristics were investigated. The structure and cation distribution characterized by X-ray diffraction and Raman spectroscopy showed the substituted Co2 cations mainly entered to octahedral sites. The particle size of the as-coprecipitated powders observed by scanning electron microscopy decreased with cobalt additions. Magnetic properties of Mn1-xCoxFe2O4 nanoparticles studied by vibrating sample magnetometry showed the highest coercivity and saturation magnetization of 790 Oe and 32.8 emu/g for Mn0.7Co0.3Fe2O4 nanoparticles, respectively. The Mn0.7Co0.3Fe2O4 nanoparticles exhibited the AC heating temperature of 8 °C and specific loss power of 1.4 W/g in comparison with 4 °C and 0.35 W/g for the as-coprecipitated MnFe2O4 powders.

In the present research, silicon carbide synthesis via magnesiothermal method was investigated using MCM-48 as a silica source and different types of Carbon including CNT and MCM-48/CNTF nano composites through in-situ preparation. The experiments were accomplished with different molar ratios of MCM-48, carbon and magnesium at 650-700˚C in argon atmosphere. Properties of MCM-48, carbon nanotubes and synthesized samples were clarified using BET, XRD, FTIR, FESEM, EDX and TEM techniques. After preparation and characterization of MCM-48 and carbon nano tubes, the effect of amounts and types of carbon on reaction progress were also investigated for silicon carbide synthesis. Comparison of XRD phase analysis for samples consisting of different carbon sources showed that types and morphologies of carbon and also localization mode of reactors are important factors of silicon carbide synthesis. According to obtained results it was clear that micro structure of synthesized silicon carbide was fibrous and was dependent to CNT precursor pattern. Also functionalized carbon nano tube caused better contact between MCM-48 and CNT in magnesia thermal process, therefor efficiency of magnesia thermal reaction was improved.

In this study, the microstructure and corrosion properties of titanium oxide ceramic coatings formed in a carbonate electrolyte under the influence of the key factor of the density of the coating process were investigated. Plasma electrolytic oxidation coating made at current densities of 65, 82.5 and 100 mA/cm2, 1500 Hz and 11% duty cycles over a 10 minute and on a commercial titanium surface as the substrate. The results showed that the surface morphology and corrosion properties of the coatings depend on changes in the current density. The increase in the applied current density leads to changes in morphology, from pancreatic to pancake with volcanic spans, and the average diameter of the cavities increases from about 1 micrometer to 4 micrometers, which also increases surface roughness. Changes in the current density also cause variations in the voltage and intensity of the plasma around the samples, which directly affects the intensity of the microcirculation and the thermal gradient of the oxide film and causes the anatase oxidation phase to become more rutile. The corrosion resistance of the coatings increased with increasing current density, so that the corrosion current density decreased 10 times as compared to the uncoated sample, which caused a 2.5 times increase in the thickness of the coating and was more compact. The inner layer of the coating, reducing open path to the surface of the metal and the presence of the main rutile phase were attributed.