جستجوی مقالات مرتبط با کلیدواژه « Heat treatment » در نشریات گروه « شیمی »

Heat treatment is a promising approach to reducing the viscosity and improving the combustion behavior of black liquor. The bagasse-based kraft black liquor was heated in a series digester at a constant temperature of 180˚C in three batches for 15, 20, and 25 min to investigate its physicochemical and rheological properties before and after heat treatment. Black liquor heated for 25 min showed the highest residual active alkali consumption of 28.37%. The optimum heat treatment time was 20 min, and the heat-treated black liquor at this condition exhibited residual active alkali 5.02% as Na2O and an increase in swelling volume ratio from 12 ml/g to 18 ml/g. Rheological studies of original and heat-treated black liquors were carried out in a rotational rheometer at 90˚C and 105˚C in the shear rate range of 1-100 s-1. 20 min heat-treated black liquor showed 74.09% and 71.56% reduction in viscosity at 90˚C and 105˚C, respectively, for 65% solids concentration. The effect of temperature and solids content on the rheological properties of black liquor was discussed. The results showed that black liquors obtained after heat treatment were non-Newtonian (pseudoplastic) in nature with a power law index less than unity (n<1). The power law (Ostwald de Waele) model best fits the obtained viscosity data of heat-treated bagasse black liquor. The work presented here gives an insight into the importance of the heat treatment process for the viscosity reduction of bagasse black liquor. It may help better understand various Physicochemical properties and the flow behavior of heat-treated bagasse black liquor for chemical recovery.

Austenitic stainless steel 316's role in industrial applications has spurred extensive but fragmented studies, presenting challenges in synthesizing its diverse properties. This study comprehensively investigates its fracture properties, analyzing the interplay of mechanical traits, microstructural nuances, strain rates, operational temperatures, hydrogen and helium impacts, heat treatment effects, and fracture behaviors across varying operational parameters. Analysis reveals a robust correlation between microstructure and mechanical characteristics, specially yield stress and fracture topography. Predictive models like Hall-Petch equation and Gibson-Ashby micromechanical model adeptly project these mechanical attributes. Deformation strain-rate surpasses relative porosity density in impact. Higher relative density prompts increased slip bands and grain deformation at constant strain rates, indicating local shear as the primary fracture mode, evident from observed shear bands. Hydrogen's influence, though delayed, assumes a secondary dominant deformation mechanism. While low strain rates do not alter failure modes due to hydrogen damage, its primary impact lies in reducing stress required for dislocation displacement and crack propagation, thereby diminishing tensile strength. External hydrogen exhibits a pronounced effect in some instances. Heat treatment significantly modifies the ferrite-cementite phase interface, impacting fracture morphology, notably at higher temperatures. Controlled annealing enhances fracture resistance at the expense of potential strength reduction, necessitating cautious execution due to heightened hydrogen embrittlement risk from reduced grain boundary chromium. This study seeks to consolidate insights into 316 SS fracture behavior, offering future research directions and practical implications for optimizing its performance in varied industrial settings.

A new type of unsaturated poly ester-amide was prepared by melt polycondensation and characterized completely. Influence of heat treatment conditions and cross-linking content on mechanical and degradation properties of unsaturated polyester-amide were studied. Results suggested that the newly synthesized unsaturated poly(ester-amide) possessed good heat stabilization properties. Mechanical and degradation properties of cross-linked poly (ester-amide) were determined by heat treatment conditions and cross-linker content. Different initiation-accelerating agent systems and their content differences have an insignificant influence on the cross-linking time at Room Temperature (RT). Increasing heat treatment time increased the retention rate of mechanical properties during the degradation process and decreased hydrolysis rate in alkaline solution.

Electrochemical synthesis followed by heat-treatment is a facile and easy method for preparation of nanostructured metal oxides. Herein we report nanostructured Mn5O8 prepared through pulse cathodic deposition followed by heat-treatment for the first time. For the preparation of Mn5O8 nanorods, pulse cathodic electrodeposition was first done from 0.005M Mn(NO3)2 at the current density of 5 mA cm-2 which yield Mn3O4 precursor. Then, heat-treatment of the deposited precursor was performed to obtain final Mn5O8 product. The structural and morphological properties of the prepared product were investigated by XRD, FT-IR, SEM and TEM techniques. The analysis results revealed that the prepared sample has pure Mn5O8 composition with rod morphology at nanoscale. Mechanism of deposit formation during pulse deposition was proposed and discussed. The formation of Mn5O8 nanorods via calcination of Mn3O4 precursor was also studied by thermogravimetric analysis. The results suggested that the cathodic electrodeposition-heat treatment method can be considered as simple and facile route for preparation of Mn5O8 nanorods.

We reported here a simple electro-synthesis procedure to synthesize an extremely high specific surface area (SSA) yttrium oxide (Y2O3) nanopowder. The mesoporous (pore diameter, d≈8 nm) Y2O3 powder was deposited by a two-step process involving the pulse cathodic electro-deposition (PC-ED) of yttrium hydroxide film from nitrate bath at 70 oC temperature followed by calcination at 600 C in air for 3 h. The applied pulse parameters i.e. peak current density, on-time and off-time were Ip=25 mA/cm2, ton=1ms and toff=5ms, respectively. The products were characterized by means of scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR) spectroscopy methods. The obtained data proved that the fabricated product had pure cubic Y2O3 crystal structure and is composed thin wall-like morphology with SAA value of 243.7 m2/g and mean pore size of 9 nm. From these findings, the PC-ED procedure was proposed for facile fabrication of high-SSA Y2O3 nanopowder.