Design,Facile Synthesis and Characterization of Porphyrin-Zirconium-Ferrite@SiO2 Core-Shell and Catalytic Application in Cyclohexane Oxidation

Silicon - In this study, a new magnetic ZrFe2O4@SiO2-TCPP nanocatalyst with high efficiency was used for the oxidation of cyclohexane to cyclohexanone (Ke) and cyclohexanol (Al). The mesoporous...     

The Determination of Optimum Forging Conditions for the Production of High Strength-High Impact Toughness Automotive Parts

The influences of various reheating and forging temperatures as well as cooling rates on the microstructure and mechanical properties, particularly impact energy, during the forging of a Nb-V microalloyed steel to be used for automotive safety parts were investigated. Increasing the prior austenite grain size increased the volume percent of acicular ferrite and reduced pearlite content in the microstructure even for very low post-forging cooling rates, resulting in improved toughness and tensile strength values. Increasing the cooling rate enhanced the acicular ferrite content, thereby increasing the impact energy properties. At lower reheating temperatures the yield strength and impact energy levels are determined by the percentage of pearlite present in the microstructure; while as the cooling rate is increased the amount of acicular ferrite and retained austenite are increased, improving the toughness and tensile strength of the forged part. This effect is more pronounced for the parts solutionized at 1250°C and is related to the presence of very fine carbonitride precipitates under these conditions, which contributes to improved yield strength, particularly at higher cooling rates. An optimized forging process was determined and adapted to a 25 MN production forging press to validate the experimental results on semi-industrial production scale. By adequate control of the above parameters, high-strength, high-toughness parts (T.S. = 800 MPa, CVN = 35 J) were forged and optimum mechanical properties were achieved without the need for any additional heat treatment.     

Preparation, Characterization and Photocatalytic Properties of Ba-Cd-Sr-Ti Doped Fe3O4 Nanohollow Spheres on Removal of Congo Red Under Visible-Light Irradiation

In this study, Ba-Cd-Sr-Ti doped Fe₃O₄ nanohollow spheres were successfully prepared via a simple solvothermal method. The crystal size, structure, morphology and elemental analysis of the as-prepared sample were investigated in detail by X-ray diffraction (XRD), FT-IR, scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectroscopy, respectively. Magnetic hysteresis measurement was carried out on a vibrant sample magnetometer (VSM) showing the soft ferromagnetic property at room temperature. The synthesized nanohollow spheres were employed as a photocatalyst to study the photocatalytic degradation of dye contaminations. The UV-Vis results showed that the specimen could well catalyze the decolorizing of congo red (CR) solution and a removal efficiency of 99.5 % was obtained at pH 6. The optical characteristic of the products was studied by estimating the band-gap energy based on diffuse-reflectance spectroscopy (DRS) which represented the doped magnetite with semiconductor metals to be more prone in the visible region as compared to UV region. Some factors such as initial dye concentration, pH, and contact time influencing the decomposition of CR were evaluated.     

CFD study of non-premixed swirling burners: Effect of turbulence models

This research investigates a numerical simulation of swirling turbulent non-premixed combustion. The effects on the combustion characteristics are examined with three turbulence models: namely as the Reynolds stress model, spectral turbulence analysis and Re-Normalization Group. In addition, the P-1 and discrete ordinate (DO) models are used to simulate the radiative heat transfer in this model. The governing equations associated with the required boundary conditions are solved using the numerical model. The accuracy of this model is validated with the published experimental data and the comparison elucidates that there is a reasonable agreement between the obtained values from this model and the corresponding experimental quantities. Among different models proposed in this research, the Reynolds stress model with the Probability Density Function (PDF) approach is more accurate (nearly up to 50%) than other turbulent models for a swirling flow field. Regarding the effect of radiative heat transfer model, it is observed that the discrete ordinate model is more precise than the P-1 model in anticipating the experimental behavior. This model is able to simulate the subcritical nature of the isothermal flow as well as the size and shape of the internal recirculation induced by the swirl due to combustion.     

Instability,heat transfer and flow regime in a two-phase flow thermosyphon loop at different diameter evaporator channel

In this study, the influence of different channel geometries on heat transfer, flow regime and instability of a two-phase thermosyphon loop, is investigated. Instabilities in flow regime and heat transfer, at low and high heat fluxes, are observed. Bubbly flow with nucleate boiling heat transfer mechanism, confined bubbly/slug flow with backflow for small channel height (H) and finally slug/churn flow at high heat fluxes are observed. This study shows that flow and thermal instability increases as channel height (H) decreases and also heat transfer coefficient increases with increasing channel height and heat flux. Bubbly flow characterizes the flow regime at high heat transfer coefficients while confined bubbles, backflow and intermittent boiling are more significant for low channel heights with lower heat transfer coefficient and critical heat flux.     

Using a novel technique to shape a refractory castable by Cold Isostatic Pressing and a study of the effect of pressure on the hydration reaction of high-alumina cement

Calcium aluminate cements are the most hydraulically setting cements used for refractory castables. The anhydrous phases of this type of cements incorporate CA, CA₂ and traces of C₁₂A₇ and alpha-alumina where C and A stand for CaO and Al₂O₃, respectively. Hydration starts to form the hexagonal crystals of CAH₁₀ (H denoting H₂O) and C₂AH₈, which convert to the cubic crystals of C₃AH₆ and AH₃ by the passage of hydration time. In this work, Al₂O₃−C (alumina-graphite) castables were shaped by cold isostatic pressing at 100 to 400 bars (≈100 to 400 Kg/cm²). Hydration and conversion reactions were studied using the Ratio of Slopes Method for quantitative XRD studies after 3 and 28 days. The results showed that by increasing the pressure, the kinetics of the hydration reaction will increase and higher strengths can be obtained, which supports the idea of forming this graphite containing castable by Cold Isostatic Pressing (CIP) in industrial applications for special refractories.     

Heat transfer in the evaporator of an advanced two-phase thermosyphon loop

As heat generation from electronic components increase and the limit of air-cooling is reached, the interest for using liquid cooling for high heat flux applications has risen. Thermosyphon cooling is an alternative liquid cooling technique, in which heat is transferred as heat of vaporization from evaporator to condenser with a relatively small temperature difference.The effect of fluid properties, the structure of wall surfaces, and the effect of system pressure was investigated and reported previously by the author. In this paper, the influence of heat flux, system pressure, mass flow rate, vapor fraction, diameter of evaporator channel and tubing distance between evaporator and condenser on the heat transfer coefficient of an advanced two-phase thermosyphon loop is reported. The tested evaporators were made from small blocks of copper with 7, 5, 4, 3 and 2 vertical channels with the diameters of 1.1, 1.5, 1.9, 2.5, and 3.5 mm, respectively and the length of 14.6 mm. Tests were done with isobutane at heat fluxes ranging between 28.3 and 311.5 kW/m².     

Void Formation and Plastic Deformation Mechanism of a Cold-Rolled Dual-Phase Steel During Tension

The void formation and plastic deformation micromechanisms of a cold-rolled DP600 steel during tensile loading were studied by scanning electron microscopy(SEM) and electron backscatter diffraction(EBSD).The SEM observations revealed that the main void nucleation mechanism in the DP600 steel is decohesion at the ferrite-martensite interfaces.The voids were mostly observed between the closely spaced martensite islands situated at the boundaries of relatively finer ferrite grains.The EBSD results indicated a strain gradient developed from the ferrite-martensite and ferrite-ferrite interfaces into the interior of ferrite grains during the tensile deformation,which led to a stress concentration at these interfaces.Moreover,it was demonstrated that local misorientation inside the finer ferrite grains surrounded by martensite islands was higher than that for the coarser ferrite grains,which made the former more prone to void initiation.     

Antiproliferative and antioxidative activities of cuttlefish (<Emphasis Type="Italic">Sepia pharaonis</Emphasis>) protein hydrolysates as affected by degree of hydrolysis

Bioactivities (including antioxidative and antiproliferative properties) of cuttlefish mantle protein hydrolysates (CPH) with the degree of hydrolysis (DH) of 20.9, 25.5, 30.6, 35.3 and 40.6% (shortened as 20, 25, 30, 35 and 40%, respectively) prepared using alcalase were evaluated. The results indicated that the CPH with 20, 30 and 40% DH showed the greatest activity against DPPH radical scavenging [5.2 µmol TE (torolox equivalent)/g sample], reducing power (0.4 absorbance at 700 nm) and total antioxidant capacity (0.6 mg ascorbic acid equivalent/g sample), which were 2.5, 6.5 and 13.8 times higher than the cuttlefish mantle protein isolate (CPI), respectively. The CPH with the DH of 20% had the highest effect against MDA-231 and T47D cancer cell lines with growth inhibition of 78.2 and 66.2%, which were 6.5 and 6 times higher activities compared to the CPI, respectively. The amino acid profile of CPH indicated that glutamine (15.7%) and asparagine (10.9%) were predominant.     

Tribological Properties of Nanostructured Al/Al_(12)(Fe,V)_3Si Alloys

Tribological behavior of nanostructured pure Al and Al–Al12(Fe,V)3Si alloys containing 27(FVS0812) and 37(FVS1212) vol% of Al12(Fe,V)3Si precipitates was investigated. All samples were prepared using mechanical alloying followed by hot pressing. Wear tests were performed at room temperature using a pin-on-disk machine. Results showed that the presence of Al12(Fe,V)3Si precipitates increases the wear resistance of nanostructured Al, and the wear resistance increases with increasing the Al12(Fe,V)3Si content. Scanning electron microscopy images of worn surfaces and wear debris demonstrated that abrasion and adhesion are the governing wear mechanisms for the nanostructured FVS0812 alloy at 2 and 5 N normal loads, whereas for the nanostructured FVS1212 alloy, the dominant wear mechanism is abrasion at these loads. A mechanically mixed layer(MML) containing Fe and O was formed on the worn surfaces of FVS0812 and FVS1212 samples at 10 N normal load. Formation and delamination of MML controls the wear behavior of these samples at the normal load of 10 N. It is also found that the presence of Al12(Fe,V)3Si precipitates decreases the friction coefficient of nanostructured Al.