Hours Of Heat Treatment Research Articles

Quantum-plasmonic engineering to improve the 1.53 µm radiative emission in Er3+-doped tellurite glasses under controlled temperature

The plasmonic applications at low temperatures of metallic nanoparticles in glasses doped with rare-earth ions are not yet covered in-depth analysis in the literature. This paper insights into the coupling between gold nanoparticles and Er3+ embedded in tellurite glasses via luminescence enhancement of the emission centred at 1.53 µm under controlled temperature. This enhancement is obtained for the sample with 24 h of heat treatment (TErAu24) concerning the Er3+ single doped (TEr) at room temperature under 980 nm excitation. The enhancement remains under cooling conditions, consequence of the strong coupling between the plasmon and the Er3+, attributed to an increment of the localized plasmon mode volume at low temperatures. Further, the band area increment of the TErAu24 sample comparing the spectra at 98 and 348 K is 414 %, whereas for the TEr is about 348 %. These findings provide advanced understanding of the plasmonics on quantum emitters engineering.

Phase and microstructure evolutions of fiber reinforced aerogel composites with different fiber components during calcination

In the high temperature industry, controlling the external surface temperature of the kiln shell is crucial for reducing heat loss, energy consumption, and carbon emissions. While aerogels are esteemed for their superior thermal insulation properties and considered as optimal materials in the thermal insulation layer of energy saving lining for burning zone of cement rotary kiln, their structural integrity at elevated temperatures confines their applications to medium and low temperature settings. To overcome this limitation, the fiber-reinforced aerogel composites have been developed to bolster the high-temperature endurance of aerogel products. Notably, composites containing ZrO2-enhanced fibers exhibit significantly higher resistance to thermal degradation from local overheating, such as flame impingement, compared to their counterparts without ZrO2. However, the mechanisms of performance degradation and the reinforcing role of ZrO2 in fiber reinforced aerogel composites at high temperatures especially above 1000 °C, remain unclear. This study specifically focuses on the thermal conductive properties of commercial aerogel felts, both with and without the inclusion of ZrO2 across a range of temperatures, and examines the subsequent phase transitions and microstructural evolutions upon thermal treatment. Critical analyses of heat flow, mass change, density, linear shrinkage, and pore size distribution during the calcination process were conducted. After 6 h of heat treatment, composites with ZrO2-enhanced fibers retained an 81.44 % porosity, unlike composites without ZrO2 which sintered and became denser. The experimental findings demonstrate that the performance of fiber reinforced aerogel composites mainly depends on the fiber’s framework microstructure and fiber-aerogel reactions, which provides the references for developing excellent aerogel composites and evaluating of the usability in high temperature zone of kiln.

Advanced Ceramics with Dual Functions of Healing and Decomposition.

This study developed advanced ceramic materials with both healing and decomposition functions using a metastable product generated under superheated steam. The developed composite material comprises ZrC particles dispersed in a yttria-stabilized zirconia (YSZ) matrix. After introducing a surface crack of approximately 120 μm on the composite specimen, it showed a complete strength recovery rate after one hour of heat treatment under superheated steam at 400 °C, while it exhibited a decomposition behavior after one hour of heat treatment in air at 400 °C. The XRD analysis of the heat-treated specimens showed that the final product was monoclinic ZrO2 under both steam and air conditions. In other words, full strength recovery in superheated steam was achieved by a chain reaction involving metastable intermediate products derived from H2O, unlike the reaction in air.

GENETIC ANALYSIS AND EXPRESSION PROFILING OF TAHSP90A TRANSCRIPTS CONFER HEAT TOLERANCE IN WHEAT

Heat stress has emerged as a chief problem impeding wheat crop productivity. In several crops, specific HSP90A genes have intensively managed induced fluctuations in temperature. A wheat plant with TaHSP90A transcripts had the potential to cope with temperature stress. It enables plants to survive in transient extremes of temperature and under heat stress. The presented study design enhanced temperature tolerance plasticity with high yield in wheat through a line × tester mating design containing lines (12) and testers (4) having a differential expression of TaHSP90A transcripts (TraesCS2A02G033700.1, TraesCS5B02G258900.3, and TraesCS5D02G268000.2), then hybridized to get the F1 (48) wheat hybrids. For heat treatment, temperature raising was only in the daytime, through the tunnel at anthesis (for two weeks). Data recording for several morphological and physiological parameters went along with the relative expression of TaHSP90A transcripts for hybrid evaluation. After one hour of heat treatment, the relative expression of TaHSP90A transcripts’ determination in the flag leaf followed. The manifestation of TaHSP90A transcripts’ upregulation was two folds in several hybrids after heat treatment. Best lines, testers, and selected crosses having TaHSP90A transcripts with high yield and heat tolerance compared with parents can further benefit breeding programs aiming toward tolerance against heat stress in changing climate scenarios.

Characteristics and Biological Applications of Green Nickel Oxide Synthesised by Hibiscus Sabdariffa Flowers

This study used Hibiscus sabdariffa flowers to prepare and characterise nickel oxide nanoparticles that are non-toxic and environmentally advantageous (green synthesis). After two hours of heat treatment at 600 °C, XRD was employed to validate the cubic crystal structure of NiO-NPs. The crystal plane (200) corresponded to the optimal peak on the XRD, With an average crystalline size, as per Williamson-Hall's formula, is 46.26 nm, while as per Scherrer's formula, it is 24.40 nm. At 524, 420, and 468 cm-1, the FT-IR spectrum revealed a Ni-O vibration band. Throughout the surface microscopic analysis, Field-Emission Scanning Electron Microscopy (FE-SEM) revealed smooth, cylindrical rod-like crystals. As per the UV-Vis spectral curve, NiO-NPs had a direct bandgap (Eg) of 2.91 eV. NiO-NPs nanoparticles were shown to be more effective against gram-negative bacteria in terms of biological activities. P. aeruginosa was significantly more severely harmed than S. aureus.

EFFECT OF HEAT-TREATMENT TEMPERATURE ON THE MECHANICAL AND MICROSTRUCTURAL PROPERTIES OF AISI 4140 STEEL

Heat treatment is a metallurgical process for removing residual stresses in metals, improving their mechanical properties, reducing surface hardness, and preventing the formation of brittle fractures or cracks. The tempering (age hardening) process, which is a type of heat treatment in tempered steels, affects the mechanical and microstructural properties of the steel more than the other steel types. In this study, the base material test specimens with 13 HRC hardness and 12.5 mm diameter were heat-treated and tempered, and the effect of the heat treatment process on the mechanical and microstructural properties was investigated. AISI 4140 tempered steel was tempered at 600°C for 3 hours after 3 hours of heat treatment at 880°C, 850°C and 820°C and cooled in oil. While the base material has a tensile strength of 654.16 ± 12 MPa, the maximum tensile strengths were determined as 1022.44 ± 10 MPa, 1006.24 ± 9 MPa and 987.454 ± 11 MPa, respectively, after heat treatment at 880°C, 850°C and 820°C. The strength of the material increased by 56.29% by applying heat treatment at 880°C temperature. This increase in strength is associated with the transformation of the existing microstructure from ferritic to martensitic structure. The needle-like structure in the martensitic structure increased and lath martensite structure was formed with the combination of grain boundaries with increasing heat treatment temperature. Strength and hardness increased while the heat treatment temperature is increasing. It was observed that ductility decreased. Hereby, the temperature parameter in the heat treatment process is effective on the strength and the heat treatment has high advantages in terms of material saving in machine designs

Genome-wide identification, characterization and expression of HSP 20 gene family in dove.

Davidia involucrata is a significant living fossil with high abiotic stress tolerance. Although heat shock protein 20 (HSP20) has already been linked to heat stress, nothing is known about HSP20 family protein activities in D. involucrata. The functional dynamics of the D. involucrata HSP20 (DiHSP20) gene family were identified and characterized using a thorough genome-wide investigation. From the genome of D. involucrata, a total of 42 HSP20 genes were identified, which are distributed across 16 chromosomes. The DiHSP20 proteins were grouped into seven separate subfamilies by our phylogenetic analysis, which was validated by the conserved motif composition and gene structure studies. Segmental duplication events were shown to play a crucial role in the expansion of the DiHSP20 gene family. Synteny analysis revealed that 19 DiHSP20 genes of D. involucrata shared a syntenic connection with Arabidopsis genes, 39 with C. acuminata genes, and just 6 with O. sativa genes. Additionally, heat stress differently enhanced the expression levels of D. involucrata HSP20 genes. After 1 hour of heat treatment, the expression levels of most DiHSP20 genes, particularly DiHSP20-7, DiHSP20-29, DiHSP20-30, DiHSP20-32, and DiHSP20-34, were dramatically increased, suggestted that they might be employed as heat tolerance candidate genes. Overall, these findings add to our knowledge of the HSP20 family genes and provide helpful information for breeding heat stress resistance in D. involucrata.

Conversion of carbohydrates to carboxylic acids during hydrothermal and oxidative treatment of concentrated kraft black liquor

Black liquor, a side stream of the kraft pulping process, contains valuable low molecular weight carboxylic acids and carbohydrates. Hydrothermal treatment and wet oxidation of black liquor with a dry matter content of 43 % were investigated as an approach to convert these carbohydrates to carboxylic acids to increase their concentration. Wet oxidation with H2O2 or O2 at 115–185 °C led to partial degradation of carbohydrates, but no significant formation of the investigated carboxylic acids, glycolic, lactic, formic and acetic acid, was detected. Treatment under N2 atmosphere at 185 and 220 °C finally led to an increase of the hydroxy acid concentration. After two hours of heat treatment at 220 °C, 90 % of the carbohydrates were degraded, coupled with a high carbon conversion efficiency of 32 % based on the formation of lactic acid and glycolic acid, of which the concentrations increased by 51 and 73 %, respectively.

Effect of aging time on microstructural and mechanical properties of 6061 aluminum alloy

Aluminum alloy 6061 have moderate strength, good formability, and excellent corrosion resistance, it has a wide use in several engineering sectors. Age hardening is the main feature of this alloy. In this study, some mechanical characteristics of Aluminum 6061 samples aged to different times has been studied. The specimen’s mechanical properties were improved in general; best mechanical properties were achieved after 2 hours of heat treatment at 200oC. Ultimate tensile stress, yield stress, ductility and microhardness variation with aging time are discussed regarding to the microstructural alteration caused by heat treatment. We found that the Mg2Si initiation and growth was a function for aging time, which was the main cause for improvement of the alloy mechanical features.

Obtaining of hematite from industrial steel waste using dry-milling and high temperature

In this work, the mill scale (MS) of hot rolling, a waste of steel processing, composed by a complex mixture of iron oxides, is transformed in a nanocrystalline powder containing only the hematite (α-Fe 2 O 3 ) phase. For that, the MS was dry-milled using a high-energy ball mill for 30 min and heat-treated up to 1200 °C for 25 min. The samples of this study were characterized by X-ray diffraction, Thermogravimetric Analysis and Vibrating Sample Magnetometry. The milling process decreases the amount of FeO phase content (FeO:Fe 3 O 4 phase ratio from 3:1 to 1:1), reduces the average crystallite size and increases the micro-strain of the iron oxides. The high-temperature experiments showed the complete transformation of the Fe 3 O 4 and FeO nanophases to the nanocrystalline α-Fe 2 O 3 with average crystalline domains greater than 180 nm after few hours of heat treatment. The thermal expansion coefficient of the α-Fe 2 O 3 nanophase was obtained considering anisotropic effects, mainly for the a -axis. Thermogravimetric analysis shows the oxidation of Fe 3 O 4 to α-Fe 2 O 3 . The milled MS sample shows a mixed magnetism that transforms to a weak ferromagnetism (or antiferromagntism) after thermal treatment. The temperature of the Morin transition of the α-Fe 2 O 3 nanophase at 110 K and a second magnetic transition at 50 K, related to a spin-glass state, seems to be strongly affected by the nanometric size of crystalline domains (about 180 nm).

Heterologous Expression of Histidine Acid Phytase From Pantoea sp. 3.5.1 in Methylotrophic Yeast Pichia Pastoris

Background and Objective:The major storage form of phosphorus in plant-derived feed is presented by phytates and not digested by animals. Phytases are able to hydrolyze phytates and successfully used as feed additives. Nevertheless, nowadays, there is a constant search of new phytases and expression systems for better production of these enzymes. In this study, we describe cloning and expression of gene encoding histidine acid phytase fromPantoeasp. 3.5.1 using methylotrophic yeastPichia pastorisas the host.Methods:The phytase gene was placed under the control of the methanol-inducible AOX1 promoter and expressed inP. pastoris. Experiments of small-scale phytase expression and activity assays were used to test recombinant colonies. Four different signal peptides were screened for better secretion of phytase byP. pastoris. After 36 h of methanol induction in shake flasks, the maximum extracellular phytase activity (3.2 U/ml) was observed inP. pastorisstrain with integrated construct based on pPINK-HC vector andKluyveromyces maxianusinulinase gene signal sequence. This phytase was isolated and purified using affinity chromatography.Results:Recombinant phytase was a glycosylated protein, had a molecular weight of around 90 kDa and showed maximum activity at pH 4.0 and at 50°C. Recombinant phytase had excellent thermal stability – it retained high residual activity (100% ± 2%) after 1 hour of heat treatment at 70°C.Conclusion:The enhanced thermostability of the recombinant phytase, its expression provided by strong inducible promotor and the effectively designed expression cassette, the simple purification procedure of the secreted enzyme, and the possibility of large-scale expression make the foundation for further production of this bacterial phytase inP. pastorisat an industrial scale.

Effects of sodium nitrate and heat treatment atmosphere on the synthesis of α–NaFeO2 layered oxide

α-NaFeO2 type layered oxides shows reversible intercalation/de-intercalation of sodium ions between the oxide layers, which is suitable as regenerable CO2 absorber and cathode material for secondary batteries. This paper reports a critical effect of heating atmosphere to synthesize pure α-NaFeO2 from equimolar sodium nitrate and iron oxide. Reaction of NaNO3 with γ-Fe2O3 was much faster in nitrogen than oxygen atmosphere and high-purity α-NaFeO2 was yielded in a few hours of heat treatment in nitrogen while in oxygen atmosphere the reaction was sluggish, resulting in partially sodiated γ-Fe2O3. Inert atmosphere thermodynamically enhances nitrate decomposition, which controls the reaction rate of NaNO3 with γ-Fe2O3, and increases the solubility of γ-Fe2O3 in molten NaNO3 to promote topotactic phase transformation to α-NaFeO2. Molten NaNO3 works as a solvent for ferric ions and a redox buffer for maintaining the lattice oxygen structure and oxidation state of γ-Fe2O3. Larger iron oxide crystal was found to be suitable for production of high-purity α-NaFeO2 in a wide temperature range.

Effect of Heat Exposure on Grain Growth and Oxidation Behavior of Cobalt Based Composite Powders by Facile Suspension Synthesis

In this study the intermetallic-matrix composite powders CoNiCrAlY-2wt. %Al2O3 were characterized in order to investigate the effect of heat exposure time on morphologies, grain growth and phases formed by facile suspension route synthesis. The as-synthesized powders were examined by Scanning Electron Microscopy (SEM), Energy Dispersive X-ray (EDX) and X-ray diffraction (XRD). The formation of NiAl phase was noticed after 1 hour of heat treatment. The average particle size of intermetallic-matrix composite powders CoNiCrAlY-2wt.%Al2O3 increased as the heat exposure time increased. It is found that the reinforcement of alumina allowed the particles to uniformly distributed when the sample was heated for 10 hours. The formation of NiAl started when the sample was heated at 1 hour and NiAl continued to form when heated at 10 hours.

The Surface Chemistry of the Mild Steel and Glass Substrates for Thermal Spray

The surface chemical condition of substrates plays a key role in single splats formation. Single splats are the foundation of thermal spray coatings. In this study, the surface chemistry of the mild steel and glass substrates were investigated. The result indicated that the 100 °C heat treatment released the absorbents of mild steel substrates. The adsorbed water disappears from the surface of the mild steel sample after one hour of heat treatment at 100 °C; there is no adsorbed water on the surface of the glass sample.

Effect of Experimental Aging on the Performance of Al-7.9Mg-13.3Zn and Al-10.5Mg-8.6Zn Alloys as Sacrificial Anodes

Light aluminum alloys have a great importance in industry owing to generally accessible costs, low density, good machinability, and corrosion resistance under certain environments. The present work studies aging treatments that preform important roles on the distribution and microstructural changes of two AlMg-Zn alloys, and the resulting effect on the corrosion behavior. The experimental AlMg-Zn alloys were cast and then heat treated at 200 °C, after the solubilization treatments were made, using different treatment times. These alloys showed important changes in their corrosion mechanisms, but mainly, corrosion started at AlxMgyZnz complex phases in both alloys. The optimal corrosion rates were reached after 5 and 24 hours of heat treatment. These results were obtained through electrochemical techniques in NaCl solutions, and by metallographic analysis using SEM and optical microscopy.

Synthesis and Characterization of Leucite Using a Diatomite Precursor

Leucite is nowadays an important component in ceramic restoration systems with particular suitability to dental porcelains. The leucite synthesis from a hydrothermally-derived precursor is here presented. A silicate solution was prepared by mixing a naturally derived amorphous silica (diatomitic rock from Crotone, southern Italy) with potassium hydroxide and an aluminate solution was obtained by mixing aluminium hydroxide and potassium hydroxide. Three mixtures of varying ratios of aluminate and silicate solutions were prepared and submitted to hydrothermal treatment at 150 °C for one hour. Subsequently these hydrothermal precursors were subjected to calcination at the temperature of 1000 °C for variable time intervals, thus resulting in 3 series of syntheses. The synthesis run 3 turned out to be the best from the point of view of temporal yield showing the crystallization of the leucite after only 15 hours of heat treatment. The products of synthesis run 3 were fully characterised by Powder X-Ray Diffraction, Inductively Coupled Plasma Optical Emission Spectrometry, Infrared Spectroscopy and Thermal Analysis. The amorphous phase in the synthesis powders was estimated by quantitative phase analysis using the combined Rietveld and reference intensity ratio methods. Density of leucite was also achieved by He-pycnometry. The use of a cost effective starting material such as a diatomite in the experimental route makes the process highly attractive for expansion to an industrial scale especially considering that both the chemical and physical characterizations of our leucite product are highly satisfactory. Last but not least we explain some inferences that can be obtained from this process of synthesis in order to a better understanding of some natural occurrences of leucite in geologic systems related to basaltic magmas.

Thermal stability of lithium metasilicate produced under high pressure from lithium disilicate glass

AbstractCrystalline lithium disilicate, Li2Si2O5 (LS2c) is usually produced at atmospheric pressure by suitable heat treatment of the glass with the same stoichiometric composition (LS2g). At this pressure, the orthorhombic phase of lithium disilicate is thermodynamically stable. The heat treatment of LS2g under high pressure (7.7 GPa) induces the crystallization of lithium metasilicate Li2SiO3 (LSm) phase, which remains metastable after pressure release. In this work, distinct heat treatments under high pressure were chosen to produce lithium metasilicate crystals with different grain sizes embedded in the glass matrix: smaller than 10 µm, about 100 µm and larger than 100 µm. Thermal stability of this set of samples was investigated during subsequent heat treatments at atmospheric pressure. All samples were analyzed by X‐ray diffraction, Raman spectroscopy and optical microscopy. Small LSm crystals produced under high pressure remained detectable only up to 1 hour of heat treatment at 610°C at atmospheric pressure while for longer heating times, the formation of quartz and crystalline LS2c was observed. On the other hand, for the samples containing larger LSm crystals produced under high pressure, the metasilicate phase remained detectable up to 9.5 hours of subsequent heat treatment, forming spherulitic configurations.

Effect of step heat treatment modes on the physical-mechanical properties of concrete

Heat treatment of waterproof heavy concrete samples using heated air in step modes is carried out. It is indicated that these experiments are an integral part of the research of the method of heat treatment of concrete and reinforced concrete products using the air heated in a solar energy collector (the products are in closed forms). It is noted that on cloudy days and in the cold period of the year, an electric heater is used.It is emphasizedthat in certain cases, the time of intermittent clouds during the day will be relatively short, and it can be assumed that under such conditions the decrease in concrete hardening intensity due to the break in the heated air flow to the chamber will be negligible.It is indicated that simulation of the air heating process in the solar energy collector is carried out using an infrared heater.It is determined that the investigated step modes of heat treatment of heavy concrete with heated air give an opportunity to increase the compressive strength of concrete 1.59...1.76 times compared with hardening in air conditions. It is shown that the higher the heating intensity of the concrete of the studied composition during the first hour of heat treatment (in the range from 4 to 8 °С), the greater theconcrete compressive strength at 1 day.It is recommended not to use an electricair heater for the purpose of energy saving in the warm period of the year in conditions of intermittent clouds.It is found that in the investigated cases, concrete temperature after heat treatment in step modes after 4 hours 15 minutes was 30 °C, and concrete temperature after 22 hours of hardening in the chamber was 26.3...27.2 °C. It is specified that this concrete temperature at the end of hardening in the chamber indicates that relatively intensive hydration of cement occurs. It is recommended for similar cases to analyze the expediency of extending the period of concrete thermosetting in the chamber

End-of-life of silicon PV panels: A sustainable materials recovery process

In this paper, the management of end-of-life PV modules based on an advanced eco-sustainable process has been presented and discussed. The thermal removal of the polymeric compounds contained in c-Si PV modules has been investigated to separate and recover Si, Ag, Cu, Al and glass. A two-step thermal process has been employed. In the first step, the rear polymeric layer has been removed without emissions of dangerous fluorinated substances. In the second step, the remaining polymers have been completely removed with low volatile organic compounds (VOCs) emissions. The polymers degradation has been studied at combustion equivalent ratios Φ varying from 0.5 to 2 and at 500 °C.The materials recovery has been evaluated from an environmental point of view and optimized by considering the energy cost, through the identification of the best operating conditions, in terms of temperature, time, atmosphere and gas flow. One hour of heat treatment and a slightly oxidizing atmosphere have been enabled to separate and recover the different materials of the module. The elemental compositions of the PV sample and the residue condensed organic products have been determined. The gaseous degradation products have been characterized by gas chromatographic analysis (GC).

Synthesis and Direct Sintering of Nanosized (MIV ,MIII )O2-x Hydrated Oxides as Electrolyte Ceramics.

Highly reactive and nanosized Th1-x Yx O2-x/2 or Ce0.8 Ln0.2 O1.9 mixed oxides were prepared through the initial precipitation of hydroxide precursors which were further dried under vacuum. Whatever the chemical system investigated, the characterization of the powdered samples evidenced a rapid aging process leading to hydrated oxides. The thermal behavior of these samples was further investigated and first showed a two-step dehydration process, with the successive departure of adsorbed and constitutive water, both yielding a drastic drop of the powders' reactivity (i.e. decrease of the specific surface area). Sintering experiments were then undertaken by starting directly from raw powders and revealed very rapid densification kinetics. Highly densified pellets (above 95 %TD) with a fine grain microstructure were obtained after only 1 hour of heat treatment at 1600 °C. This easy and versatile process of precipitation, that can be followed by direct densification of the powders, then appears as a promising option for the elaboration of homogenous ceramic electrolytes.