Sharif Digital Repository

Mordenite (MOR) nanocrystals were synthesized using the hydrothermal method. Sol–gel and deposition methods were utilized to modify the zeolite surface with TiO2 and then AgBr or AgCl particles. Photocatalysts were characterized by using X-ray diffraction, Brunauer–Emmett–Teller (BET), and scanning electron microscopy techniques. Activity was evaluated by photodegradation of Acid Blue 92 as an azo dye. The effect of silver halide deposition on the photocatalytic behavior of the prepared nanocomposites was studied under both ultraviolet (UV) and visible light, and the results were compared. The results showed that AgCl/TiO2/MOR was more active under UV, while with visible source,... 

Depletion of fossil fuels has increased the pressure on energy systems to operate in the most efficient and economical mode. This tendency promotes energy systems to operate at optimum operating conditions, which maximizes the system profit over lifetime. Recently, there have been many attempts to maximize lifetime profit. Most of them concentrate on the power generation aspect without incorporating further aspects such as system degradation and profitability through lifetime. However, the main intention of the system operators is to optimize the profitability of system at the moment of operation and not the total profitability through the system lifetime. In this study a novel approach is... 

Zeolite-based photocatalysts were prepared by the sol-gel and deposition methods. The photocatalysts were characterised by X-ray diffraction, nitrogen adsorption-desorption isotherms, FTIR spectroscopy, scanning electron microscopy and energy-dispersive X-ray spectrometry. The activity of the prepared photocatalysts was evaluated by the UV-induced degradation of acid blue 92, a textile dye in common use. The effect of various parameters, such as catalyst concentration, initial dye concentration, thiosulphate concentration and pH, on the rate and efficiency of the photocatalytic degradation of acid blue 92 was investigated. The results showed that each parameter influenced the degradation... 

In this work, the effect of addition of ZrO2 to TiO2 and catalyst geometry on photocatalytic properties of the nanocomposite TiO2/ZrO2 was investigated. The traditional use of powdery photocatalyst for the degradation of organic compounds has post-treatment problems which means much higher time and costs. A novel method to minimize these problems is immobilization by insertion onto an inert substrate. Several geometries of TiO2–10%ZrO2 (T-10Z) nano-photocatalysts (powder, fiber, film, and network-shaped) were produced using different templates. The products were characterized by X-ray diffraction, field emission scanning electron microscopy, Brunauer–Emmett–Teller, and diffuse reflectance... 

The sol-enhanced pulse plating (PP) technique was utilized to deposit the Ni-TiO2/TiO2 multilayers on copper substrates from a Watts bath containing a TiO2 sol, and the obtained coatings were heat treated at various temperatures. The characteristics of coatings were examined using scanning electron microscopy (SEM), X-ray diffraction (XRD), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and UV-visible spectrophotometry. In order to estimate the wettability of these nanostructured multilayers after exposure to UV light, the contact angle of water droplets were measured, and the photocatalytic (PC) efficiency of the multilayers were analyzed by the degradation of methyl... 

In this study, the interaction effect of K2S2O8 (PDS) and H2O2 (as two powerful oxidants) was investigated on the solar degradation of 2-nitrophenol (2-NF) in the two systems, i.e. absence and presence of Ag/S/TiO2 photocatalyst. Experiments were designed based on the central composite design, and two methods of response surface methodology (RSM) and artificial neural network (ANN) were developed for modeling of the systems. Concentrations of PDS and H2O2 were considered as independent variables and 2-NF degradation efficiency was selected as the response. It was revealed that the predictive capacity of ANN model is more than RSM model according to their corresponding R2, R2 adj RMS, MAE,... 

In this work, a novel photoactive cellulose-based hydrogel was prepared by simultaneous AgCl formation and entrapment inside Al (III) and Fe (III) cross-linked carboxymethyl cellulose beads. Physio-chemical and optical properties of the synthesized composites were well characterized by X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, elemental mapping, Fourier transform infrared (FTIR) spectroscopy, photoluminescence (PL), and diffuse reflectance spectroscopy (DRS). The photocatalytic activity of hydrogels was evaluated by the degradation of rhodamine B (RhB), as a model environmental pollutant. A comparative study showed that... 

A new magnetic composite was synthesized by integration of ZnFe2O4 and MIL-53(Fe) micro-rods by a solvothermal method. This composite served as a heterogeneous catalyst to overcome the high electron-hole recombination rates of ZnFe2O4 and to enhance the degradation of Direct Red 23 under visible light irradiation. Different analytical techniques, including XRD, FTIR, SEM, DRS, VSM, and PL, were employed to characterize the synthesized heterojunction nanocomposite and to evaluate its photocatalytic activity. The ZnFe2O4/MIL-53(Fe)/Vis-light system resulted in significantly higher dye degradation as compared with pristine ZnFe2O4 and MIL-53(Fe) semiconductors at the optimum pH of 3.1 and... 

Impact and tensile strength of polystyrene and nylon 6 samples, which have been produced by injection molding before and after annealing in different conditions are obtained. Polystyrene samples that are heated on vacuum conditions can deform highly even in temperatures much less than polystyrene glass temperature. This phenomenon is reduced significantly by heating samples to annealing temperature in atmospheric pressure and then removing air from sample environment in constant temperature. Deformation problems for nylon were not so important but due to high temperature implied for annealing of nylon parts, some color change due to oxidative degradation are observed. So for nylon parts a... 

Thermal degradation behavior of multi-wall carbon nanotubes (MWCNTs)/ultra high molecular weight polyethylene (UHMWPE) nanocomposites, with different nanotubes contents (0.5, 1.5 and 3.5 wt%) prepared via in-situ polymerization technique have been investigated using thermal gravimetric analysis (TGA). TGA spectra revealed that these nanocomposites had enhanced thermal stability and no significant mass loss (<0.4 wt%) occurred up to 350°C. Thermal degradation of these UHMWPE/MWCNT nanocomposites was investigated in terms of parameters such as the onset temperature of degradation (T 10), the decomposition temperature at 50% wt loss (T 50), the degradation temperature of maximum rate of the... 

Space environments have a significant influence on advanced composite structures and adhesive joints. Degradation in the mechanical properties of aerospace materials changes the dynamic behavior of the structures and adhesive joints. In this paper, a typical tubular adhesive joint with material degradation due to geostationary orbit (GEO) thermal cycles has been studied numerically with Python scripts. Adhesive joint geometry and boundary conditions are the main parametric study parameters. The results show that the first non–zero natural frequencies of the clamped-free tubular adhesive joint decreased due to mechanical property degradation. A dynamic behavior comparison of the degradation... 

This research aimed to prepare a recoverable sonophotocatalyst, in which microfibrillated carboxymethyl cellulose (MFC) acted as the Zn-Cu-Mg-mixed metal hydroxide/graphitic carbon nitride (MMH/g-C3N4) carrier. The characteristics of bare and composite sonophotocatalysts were analyzed by the XRD, FT-IR, BET, DRS, PL and FE-SEM equipped with the EDX mapping. The performance of prepared composites (MMH/g-C3N4@MFC) with various weight ratios of the MMH/g-C3N4 was studied for the sonophotocatalytic degradation of sulfadiazine (SDZ) as the model emerging contaminant. 93% of SDZ was degraded using the most effective catalyst (MMH/g-C3N4@MFC3) with 15% weight ratio of the MMH/g-C3N4 under the... 

Azo dye degradation in wastewater treatment is a subject which has garnered the attention of many research studies. In this study, an innovative approach, namely, an integrated system of five batches (ISFB), was developed to investigate the capability of Saccharomyces cerevisiae ATCC 9763 for continuous degradation of methyl red as a representative azo dye. Toward this end, an expanded immobilized microbial bed (EIMB) reactor was established with a bed of encapsulated yeast cells in sodium alginate. EIMB reactor was run in two modes, single batch and ISFB. Moreover, durability of the microbial cells was evaluated by repeating the continuous decolourization eight sequential times in EIMB at... 

In the present study, the ACF-TiO2 catalyst was synthesised and used as a catalyst for the destruction of toxic cyanide in both synthetic and real industrial wastewaters. The ACF-TiO2 catalyst was found to be micro-porous with the BET surface area of 163 m2/g. The effect of different operational parameters such as catalyst concentration, cyanide concentration, operation time, and ozone concentration were target parameters in the present study. The findings show that 500 mg/L of catalyst is the optimum value for the photocatalytical process to completely oxidise 25 mg/L of cyanide within 10 min. While it was found that 300 mg/L of catalyst in the presence of 200 mg/h ozone is enough to remove... 

Predicting the residual-life (RL) of rolling element bearings (REBs) is an essential procedure of rotating machinery condition monitoring, in industries. Since the bearing fault propagation has a complicated stochastic nature, the multi-phase phenomenon is probable to happen in the degradation process. By occurrence of the multi-phase phenomenon, the degradation process experiences different phases, with distinct failure rate in each phase. Therefore, the mentioned phenomenon leads to large error in the prediction results of single-phase degradation models. The main concern of the present paper is to consider the effect of multi-phase phenomenon on the prediction confidence level of REBs. In... 

In this study, effects of glycerol (10, 20, and 30 wt%) and Sodium Montmorillonite (Na-MMT) (0%, 2.5%, and 5%) contents on the degradation of corn starch polymers were investigated. Films were prepared by casting corn starch solution using a modified method to enhance the nanoclay distribution. Biodegradability studies were performed by enzymatic and burial tests using pristine and enriched soils. The biodegradability of samples in pristine soil was faster, and all samples were fully degraded in 6 months. The effect of nanoparticles on the mass reduction in degradation was more pronounced than that of glycerol. In all glycerol concentrations, Na-MMT addition increased tensile strength. FTIR... 

In the present study, the ACF-TiO2 catalyst was synthesised and used as a catalyst for the destruction of toxic cyanide in both synthetic and real industrial wastewaters. The ACF-TiO2 catalyst was found to be micro-porous with the BET surface area of 163 m2/g. The effect of different operational parameters such as catalyst concentration, cyanide concentration, operation time, and ozone concentration were target parameters in the present study. The findings show that 500 mg/L of catalyst is the optimum value for the photocatalytical process to completely oxidise 25 mg/L of cyanide within 10 min. While it was found that 300 mg/L of catalyst in the presence of 200 mg/h ozone is enough to remove... 

In the present study, photo-Fenton degradation of catechol from aqueous solution was carried out using UV light and iron ions (Fe2+) as activators of persulfate (PS). Catechol degradation from solution was studied under different experimental variables such as solution pH (2.0–10.0), iron dosages (0.1–0.5 g/L), persulfate loadings (1.0–5.0 mM), initial catechol concentrations (20–100 mg/L) and scavengers (TBA and IPA). The comparative study of catechol removal showed that among the applied approaches, the order of degradation of catechol is as follows: PS/Fe2 +/UV > PS/Fe2 + > UV/PS > PS > UV. Furthermore, higher catechol degradation was observed with increasing iron dosage and PS...