Positive Effect Of Heat Treatment Research Articles

Thermal Conductivity of AlSi10MnMg Alloy in Relation to Casting Technology and Heat Treatment Method.

Nowadays, with the development of electromobility, the requirements not only for the mechanical properties but also for the thermal conductivity of castings are increasing. This paper investigates the influence of casting and heat treatment technology on the thermal diffusivity and thermal conductivity of an AlSi10MnMg alloy. The thermal diffusivity was monitored as a function of temperature in the range of 50-300 °C for the material cast by high-pressure die casting (HPDC) and also by gravity sand casting (GSC) and gravity die casting (GDC). This study also investigated the effect of the T5 heat treatment temperature (artificial ageing without prior solution treatment-HT200, HT300, and HT400) on the thermal conductivity of the material cast by different technologies. Experiments confirmed that the thermal diffusivity or thermal conductivity of the alloy depends on the casting technology. The slower the cooling rate of the casting, the higher the thermal conductivity value. For the alloy in the as-cast condition, the thermal conductivity at 50 °C is in the range of about 125 to 138 [W·m-1·K-1]. Regardless of the casting method, the thermal conductivity tends to increase with temperature (50-300 °C). Furthermore, a positive effect of heat treatment without prior solution treatment (HT200, HT300, and HT400) on the thermal conductivity was demonstrated. Regardless of the casting method of the samples, the thermal conductivity also increases with increasing heat treatment temperature. The results further showed that when artificial ageing is performed in industrial practice on castings to increase mechanical properties in the temperature range of 160-230 °C, this heat treatment has a positive effect on thermal conductivity.

Biological value of zaanen goats' pasteurized milk proteins

Goat's milk is positioned as biologically complete, suitable for the creation of functional products and baby food products. This is explained by the qualitative and quantitative composition of its main nutrients: proteins, lipids, carbohydrates, biologically active substances, micro- and macro-elements. The biological value of food raw materials is assessed by its ability to satisfy protein needs. Strict thermal treatment regimens are used for goat milk. This is caused by the quantitative ratio of casein and albumin fractions in goat milk and its specific organoleptic properties. Pasteurization of milk causes partial destruction of proteins, enzymes, hormones and evaporation of gaseous. This contributes to the improvement of sensory properties of dairy goat raw materials. The effect of high temperatures on goat milk proteins and its biological value has been little studied. The effect of pasteurization regimes on proteins was studied and indicators of the biological value of the samples were determined: without heat treatment; heat treatment 63 ± 2 °С, duration 30 minutes; heat treatment 87 ± 2 °С duration 5-6 minutes. The amino acid composition of the test samples was determined by acid hydrolysis on an LC2000 amino acid analyzer (Biotronik, Germany). Indicators of the biological value of proteins of pasteurized goat milk were calculated – coefficient of difference of amino acid composition, biological value, coefficient of utilitarian amino acid composition, coefficient of rationality of amino acid composition, coefficient of comparative redundancy. The general analysis of the obtained data revealed a positive effect of heat treatment on the indicators of the biological value of goat milk. The amino acid score of the limiting amino acid increased by 14.82–14.92 %; biological value – 11.4–13.02 %; the PDCAAS indicator – by 14.18–14.29 %; changes in the values of formalized indicators had the same tendency. The biological value of proteins for the application of thermal regimes is at the same level. It has been proven that pasteurization has a positive effect on the biological value of goat milk proteins. This makes the product safe and useful for all segments of the population and can be recommended for feeding children from 0 to 6 months. Prospects for further research are the development of milk drinks of a combined composition of raw materials with an improved recipe in order to enrich the product with limiting amino acids.

SYNTHESIS AND PHOTOELECTROCHEMICAL PROPERTIES OF SU2O-CU3VO4 COMPOSITE FILMS

Cu2O-Cu3VO4 films were obtained by elect­rochemical synthesis. The analysis of polarization curves and Pourbaix diagrams for copper and vanadium ions made it possible to analyze the possible reactions that occur during the deposition of films. At potentials from 0 to -0.2V, mainly monovalent copper oxide Cu2O with Cu3VO4 impurities precipitated in the working solution. At the same time, there are two competing processes of acidification of the near-electrode layer as a result Cu2O formation reaction and alkalinization as a result of the chemical interaction of Cu2O with HVO42-. The formation of an excess of OH- ions can inhibit the reaction rate of the formation of Cu3VO4, accelerating the reaction of the formation of Cu2O. Thus, deposition of Cu3VO4 will take place to a lesser extent compared to Cu2O. Accordingly, to increase the yield of Cu3VO4, an attempt was made to reduce the deposition current, which, according to literature, helps to reduce the effect of the pH change near the electrode layer. Where, as known the critical current limit at change pH starts from 5 or more mA/cm2. For the synthesis of the films, a current of up to 1 mA/cm2 selected, which contributed to the production of the Cu3VO4 - Cu2O composite, as was established further from the analysis of X-ray patterns. It is shown that their photoelectrochemical pro­perties depend on the heat treatment conditions. This is expressed by the difference in the spectral characteristics of the quantum yield and the value of the photocurrent in the samp­les annealed in air and argon. Using the X-ray phase analysis method, it was established that heat treatment in argon contributes to the formation of a Cu3VO4 and Cu2O composite, in contrast to heat treatment in air, where a mixture of CuO and V2O5 oxides is mainly formed. In the film annealed in air due to impact of wide-band oxide compounds, a smaller value of the quantum yield of the photoelectrochemical current and a narrower spectral dependence were observed. The stretching of the spectrum into the region of visible light on the spectral curves of the photocurrent quantum yield is caused by the contribution of copper vanadate with Eg = 1.5 eV. Analysis of photo­current quantum output spectra and X-ray patterns showed that an increase in monovalent copper in the film structure contributes to the growth of photocurrent in the wavelength range of 450-600nm at a potential of -0.2 relative. h.s.e in 2 times. This indicates a positive effect of heat treatment in argon on increasing the efficiency of photocathodes based on a composite of Cu3VO4 and Cu2O for photoelectrochemical cells.

Study of heating kinetics and temperature fields of melon fruits under IR irradiation

This article is devoted to the study of heating kinetics, temperature fields, as well as determining the laws of non-stationary heat transfer processes during treatment of melon fruits with IR rays. These studies, in turn, make it possible to determine the heating time to the desired temperature under different radiation conditions, which is a necessary condition for achieving a positive effect of heat treatment in infrared radiation. At the same time, the study of temperature fields and heating kinetics is carried out in order to reach the optimal regime obtained in the treatment of melon fruits with IR rays as a result of planning the experiment. The optimization of the process shows that the most appropriate mode of heat treatment of melon fruits during drying is IR irradiation at an incident flux density of 23-24 kW/m2 in a pulsed mode: τ=95 (-40)+60 (-30)+60 sec. The analysis of heating kinetics and temperature field confirms the correct selection of the optimal modes obtained in controlling the process of treatment of melon fruits with IR rays and allows to establish the laws of heat-mass transfer.

Properties of basalt-fiber-reinforced polyamide-6 filled by polymerization at the synthesis stage

The composition, physical-mechanical and structural features of polyamide-6 modified at the stage of synthesis by basalt fillers are investigated. The influence of the introduced fillers on the structural features, deformation-strength, technological and physic-chemical properties of the synthesized polymer is established. The positive effect of heat treatment of fillers on their adhesion interaction with the polymer matrix in the synthesis of the composite is revealed. It is shown that with the introduction of a fibrous filler of more than 7.5 wt%, there is a tendency to increase the physical and mechanical characteristics of the synthesized polymer. The behavior of the synthesized composite under high temperature conditions was evaluated by thermogravimetric analysis, which showed that the thermal treatment of basalt fiber can significantly increase the activation energy of destruction, which confirms the effectiveness of the thermal modification of the basalt thread. With the help of infrared spectroscopy, it is shown that the synthesized polymer is fully identified with the spectral pattern characteristic of polyamide-6.

Facile fabrication of electrospun regenerated cellulose nanofiber scaffold for potential bone-tissue engineering application

In this study, cellulose acetate (CA) solutions (9–15% w/v) prepared in acetone-water (80:20 & 90:10 v/v) system were subjected to electrospinning for fabricating non-woven nanofibrous CA scaffolds (CAS) with average fiber diameters from 300 to 600 nm. Further, regenerated cellulose scaffold (RCS) was obtained by deacetylation of electrospun CAS in alkaline media for varying time periods to find the ideal time required for complete deacetylation. Following deacetylation, RCS was subjected to varying temperatures (60 °C, 80 °C) to observe the possible positive effect of heat treatment on the improvement of mechanical strength. The RCS was characterized using ATR FTIR, SEM for studying its surface chemistry and morphology along with other physio-chemical characterizations such as micro-tensile strength, swelling property, porosity, degradation rate in acidic conditions. The results were analyzed and co-related with variation of composition in solvent system, deacetylation time and heat treatment temperatures to determine the optimal fabricating conditions for RCS. In vitro studies using MC3T3-E1 osteoblast cells were also conducted on the selected RCS samples to evaluate cell adhesion and cell proliferation using SEM and MTT assay analysis. The primary results indicate positive outcome regarding the viability of RCS as potential biomaterial for bone-tissue engineering.

Aspects of the Use of Conversion Calcium Carbonate — the Solution of the Ecological Problem of Utilization

Studies have been carried out to improve the quality of conversion calcium carbonate. The process of extraction of insoluble iron-containing impurities at the stage of obtaining calcium carbonate from calcium nitrate melt was studied. It has been determined that the preliminary removal of the acid-insoluble residue from the melt of Ca (NO3)2by filtration or settling allows the Fe2O3content to be reduced by more than 50 % in the form of magnetically susceptible impurities and further increases the whiteness of the final product. The effect of grinding and heat treatment of conversion calcium carbonate on the evolution of nitrogen-containing impurities is studied. It has been established that the amount of water-soluble substances in the sample increases exponentially with increasing shredding time of the material. Heat treatment can significantly reduce (in almost 3 times) the total content of water-soluble substances in the crushed product. Simultaneously with the removal of the "bound" nitrogen, the content of the main component increases by 1.5–2 %. A positive effect of heat treatment is also an increase in the rate of refinement of conversion calcium carbonate, which makes the dispersed composition of the product more homogeneous. A technological scheme for processing conversion calcium carbonate into a disperse filler with specified properties has been developed.

The effect of superabsorbent polymer on various scale of pore structure in ultra-high performance concrete

The addition of superabsorbent polymer (SAP) mainly has two opposite effects on the pore structure of ultra-high performance concrete (UHPC): the densification of microstructure due to internal curing (IC) and the increase of large voids by swollen SAP particles. To further elucidate these effects on various properties of UHPC, the pore structure of internally cured UHPC is studied in a wide range of 3 nm–10 mm (in diameter), by two methods of micro X-ray computed tomography (μ-CT) and mercury intrusion porosimetry (MIP). Owing to the different measurable pore scale, each method provides different total porosity and pore size distribution. The SAP voids significantly increase the porosity in the size range of 267 µm–2.7 mm, whereas IC makes the pore structure finer within 3–100 nm. In particular, the microstructural change due to the IC has a more decisive influence on the compressive strength than larger SAP voids. In addition, it is discovered that the positive effect of heat-treatment (HT) for UHPC is diminished due to the applied IC. The IC and HT have to share limited amounts of raw materials and space necessary to promote the hydration reaction. However, the IC consumes parts of them before the HT does, thereby limits conventional positive effect of the HT.

Catabolism of raw and cooked green pepper (Capsicum annuum) (poly)phenolic compounds after simulated gastrointestinal digestion and faecal fermentation

A total of 21 (poly)phenolic compounds (free and bound) were quantified in raw, olive oil fried, sunflower oil fried and griddled green pepper before and after a simulated gastrointestinal digestion. Flavonoids, particularly quercetin rhamnoside, were the main compounds. The bioaccessibility of (poly)phenolic compounds after gastrointestinal digestion was higher in cooked (>82%) than in raw (48%) samples, showing a positive effect of heat treatment on the release of (poly)phenols from the vegetal matrix. Additionally, a faecal fermentation was carried out for 24h. A time-dependent microbial metabolic activity was observed, which resulted firstly (<5h) in the hydrolysis of flavonoid glycosides and then in the formation of 3 catabolites, namely 3,4-dihydroxybenzoic acid, dihydrocaffeic acid and 3-(3′-hydroxyphenyl)propionic acid, this being by far the most abundant. Catabolic pathways for colonic microbial degradation of flavonoids and hydroxycinnamic acids have been proposed. Griddled pepper showed the highest amount of (poly)phenols both after gastrointestinal digestion and colonic fermentation.

Positive Effect of Heat Treatment on Carbon-Supported CoS Nanocatalysts for Oxygen Reduction Reaction

It is of increasing interest and an important challenge to develop highly efficient less-expensive cathode catalysts for anion-exchange membrane fuel cells (AEMFCs). In this work, we have directly prepared a carbon-supported CoS nanocatalyst in a solvothermal route and investigated the effect of heat-treatment on electrocatalytic activity and long-term stability using rotating ring-disk electrode (RRDE). The results show that the heat-treatment below 400 °C under nitrogen atmosphere significantly enhanced the electrocatalytic performance of CoS catalyst as a function of annealed temperature in terms of the cathodic current density, the half-wave potential, the HO2− product and the number of electrons transferred. The CoS catalyst that annealed at 400 °C (CoS-400) has exhibited a promising performance with the half-wave potential of 0.71 V vs. RHE (the highest one for non-precious metal chalcogenides), the minimum HO2− product of 4.3% at 0.60 V vs. RHE and close to the 4-electron pathway during the oxygen reduction reaction in 0.1 M KOH. Also, the CoS-400 catalyst has comparable durability to the Pt/C catalyst.

Heat treatment effect on erosion behavior of poly(methylmethacrylate) for optical transmittance efficiency

Influence of heat treatment on optical transmittance of poly(methyl methacrylate) (PMMA) samples was investigated under solid particle erosion. Heat treatment was employed at 85°C for 1, 2 and 3h. Effect of heat treatment on physical, chemical, mechanical and thermal properties of PMMA samples was investigated by differential scanning calorimeter (DSC), thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy, Vickers microhardness measurement methods. After these analysis, both pristine and heat treated PMMA samples were eroded at 15°, 30°, 45°, 60°, 75° and 90° impingement angles. Then, optical transmittance of all eroded PMMA samples was inspected by a UV–Vis spectrometer. Scanning electron microscopy (SEM) was used to explain the erosion mechanisms and to compare the roughness and optical transmittance of eroded PMMA surfaces.Heat treatment under glass transition temperature of PMMA increased the Tg and hardness values. According to erosion test results, both pristine and heat treated PMMA samples were showed ductile erosion behavior. However; maximum and minimum optical transmittance values of eroded pristine PMMA samples were obtained for the angles of 15° and 90°, respectively. A positive effect of heat treatment on optical transmittance of PMMA was obtained for all impingement angles, but most pronounced effect was seen for 15°.

The effect of heat treatment on selective separation of nickel from Cd–Ni zinc plant residues

Addressed is the effect of heat treatment on the dissolution behavior of zinc, cadmium and nickel from Cd–Ni zinc plant residues. The proposal was considered for possible positive effect of heat treatment on the separation of nickel present in the residue, due to some phase transformations. The leaching experiments were carried out with the heat-treated residues at identical leaching conditions. The residues were heat treated at 100–1000 °C for 1 h and water-leached after subsequent cooling down to the room temperature. The results obviously showed that the heat treatment necessarily reduces the dissolution of zinc but does not affect the dissolution of cadmium. However, the recovery of nickel was increased by 83.80% upon the temperature increase from 25 to 800 °C, whereas at temperatures above 800 °C, the recovery of nickel did not change. This work offers a possible vehicle for the separation of nickel from the residues. The increase in nickel dissolution was attributed to the formation of water-soluble nickel sulfate which was further verified by the XRD detection.

Isolation and characterization of the main small heat shock proteins induced in tomato pericarp by thermal treatment

In recent years, heat treatment has been used to prevent the development of chilling injury in fruits and vegetables. The acquired tolerance to chilling seen in treated fruit is related to the accumulation of heat shock proteins (HSPs). The positive effect of heat treatment has generally been verified for only a narrow range of treatment intensities and more reliable methods of determining optimal conditions are therefore needed. In this regard, quantitation of HSPs would seem to be an interesting tool for monitoring purposes. As a step toward the development of analytical methodology, the objective of this study was the isolation and characterization of relevant HSPs from plant tissues. Tomato fruits were exposed to a temperature of 38 degrees C for 0, 3, 20 and 27 h, and protein extracts from pericarp were analysed using SDS/PAGE. Analysis revealed the appearance of an intense 21 kDa protein band in treated samples. IEF of this band showed the presence of four major proteins (HSPC1, HSPC2, HSPC3 and HSPC4) with similar pI values. A monospecific polyclonal antiserum was raised in rabbits against purified HSPC1 protein, which cross-reacted with other small heat shock proteins. The major proteins were characterized by MS/MS analysis of tryptic peptides, all having blocked N-termini. The antiserum obtained proved suitable for detecting increased amounts of small heat shock proteins in tomatoes and grapefruits subjected to heat treatment for 24 and 48 h; these treatments were successful in preventing the development of chilling injury symptoms during cold storage. Our data are valuable for the future development of analytical methods to evaluate the optimal protection induced by heat treatment in different fruits.

Apple Cultivar Variations in Response to Heat Treatment and Minimal Processing

ABSTRACTEleven apple cultivars were subjected to heat treatments at various times and temperatures. Susceptibility to browning during heat treatment and after heat treatment was evaluated. Changes in firmness, respiration rate, soluble solids and acidity of slices prepared with heat treated apples were measured. Incidence of browning was dependent upon cultivar and heating temperature; Liberty, Monroe, RI Greening and Rome were very susceptive, while McIntosh, NY 674 and Empire were less susceptive. Golden Delicious and Delicious showed relative strong tolerance to heat. Apples that received heat treatment at 45°C produced slices with less browning and firmer texture compared to non‐treated apples. The positive effect of heat treatment might help produce high quality minimum processed fruits.