Effect Of High-temperature Heating Research Articles

Effect of High Temperature Heating on Chemical Compounds in Magnesium Composite Materials

Effect of High Temperature Heating on Chemical Compounds in Magnesium Composite Materials

Влияние неоднородной теплозащиты на характеристики излучения антенны космического аппарата

Introduction: Knowledge of the electrical characteristics of the onboard antenna on the trajectory of the descent of the spacecraft makes it possible to assess the presence or absence of radio communication. Under conditions of aerodynamic heating, the thermal protection of the onboard antenna heats up unevenly in thickness and becomes electrically inhomogeneous. Purpose of the work: Determination of the radio technical characteristics of the onboard antennas of the returning spacecraft with the effect of high-temperature heating on the thermal protection of the antenna based on calculations using the developed mathematical model of the antenna with thermal protection. Methods: Expressions for the structure of the radiation field of a rectangular waveguide under the above conditions were derived by the WKB method. Of the well-known analytical methods of solution, it is possible to use the method of integral transformations and the method of eigenfunctions. Both of these methods were used in this work. Results: The obtained theoretical results are new, they allow predicting the radio technical characteristics of the onboard antenna, taking into account uneven heating across the thickness of the thermal protection at low temperature gradients. A mathematical model of the spacecraft's onboard antenna on the descent trajectory has been developed, taking into account the inhomogeneity of thermal protection under conditions of aerodynamic heating. Practical significance: The development of a mathematical model of the main radio technical characteristics of onboard antennas, taking into account the impact of high-temperature aerodynamic heating, as well as the results of numerical calculations, can be applied in the development of recommendations for choosing thermal protection and recommendations for reducing the effect of temperature changes in the electrical parameters of thermal protection on the characteristics of onboard antennas and reducing time loss of radio communication or loss recovery.

THE EFFECTS OF HIGH TEMPERATURE HEATING ON COLOUR AND WEIGHT CHANGES IN GIC AND RMGIC (A STUDY TO SUPPORT IDENTIFICATION OF FIRE VICTIMS)

Background: The temperature reached by fire disaster was varies. The disaster can cause fatalities and thus human identification is required. Dental restorative materials have properties that are resistant to high temperatures and play a role in identification process of fire victims. The identification process can be observed from the change in colour and weight of the restorative material. GIC and RMGIC are some of the most commonly used restorative material because they have good aesthetics properties, biocompatible, economical, and can release fluoride. Purpose: To determine the effect of high temperature heating on colour and weight changes in GIC and RMGIC as a support for forensic identification. Method: A total of 30 GIC and RMGIC samples used in this study were made in the form of cylinder with a size 3x2 mm. Each material was heated at four temperature groups of 30°C-200°C, 30°C-400°C, 30°C-800°C dan 30°C-1100°C using a furnace. The study was continued with the examination of colour using the Vitapan Classical Shade Guide and weight changes using a digital scale. Results: GIC and RMGIC experienced changes in colour and weight changes due to hight temperatures of 30°C-200°C, 30°C-400°C, 30°C-800°C dan 30°C-1100°C. High temperature heating shows the difference of each material. This is indicated by the p value <0,001 in the Two Way Anova Test and Post Hoc LSD which means that there is a significant difference in weight difference between GIC and RMGIC at each temperature interval. Conclusion: High temperature heating affects the colour and weight changes of GIC and RMGIC. Keywords: Forensic identification, GIC, High temperature heating, RMGIC

Effect of high temperature heating on the microstructure and performance of cesium-based geopolymer reinforced by cordierite

Cesium-based geopolymer is more refractory than K+ and Na+ based geopolymers after the transformation to ceramic material, whose thermal resistance feature is highly appreciated by some industries, especially in the engineering field where the materials in some cases are exposed to environments with high temperatures. In this study, cesium-activated geopolymer composites (CsGPc), with 5–35 wt% cordierite reinforcements, were prepared and evaluated on the high temperature performance. When 35 wt% cordierite was added, the compressive strength increased by 72% compared to the reference plain CsGP. Residual compressive strength (after heating at 1400 °C) of CsGPc with 35 wt% cordierite increased by 106% compared to the specimen before the thermal exposure. After thermal exposure up to 1400 °C, the geopolymer matrix was transformed into a pollucite-based ceramic composite. Amorphous phases in CsGPc gradually crystallized to form pollucite as the main phase with cordierite as secondary phase. The microstructure of CsGPc and the obtained ceramics showed a clear sintering process and crystallization of pollucite. Shrinkage was reduced and the coefficient of thermal expansion (CTE) varied from 4.50 to 1.89 × 10−6 K−1 with the cordierite inclusion. The performance of obtained ceramic composites was superior compared to the initial CsGPc, which would be excellent for heat resistance applications.

Effect of High-Temperature Heating on the Structure, Phase Composition, and Properties of Small Stampings Made of a VMD16 Magnesium Alloy

Effect of High-Temperature Heating on the Structure, Phase Composition, and Properties of Small Stampings Made of a VMD16 Magnesium Alloy

Effects of high-temperature heating and cryogenic quenching on the physico-mechanical properties of limestone

This paper is designed to investigate the influence of high-temperature heating and cryogenic quenching using liquid nitrogen (LIN) cooling on the physico-mechanical properties of limestone such as compressive strength, tensile strength, ultrasonic pulse velocity (UPV) and morphological characterization. The main aim is to provide a better understanding on influence of the temperature shock including high temperature pre-treatments and combined process with heating followed by LIN quenching on the physico-mechanical properties of rock. The samples were subjected to different thermal treatment using high-temperature of 100 °C, 200 °C, 400 °C and 600 °C for 4 h. In addition, the combined process of heating at 600 °C for 4 h and LIN quenching for 15 min, 30 min, 45 min and 60 min has also been explored. The obtained results indicate that pre-treatments in limestone depict decreasing trend in strength values. Limestone samples show 62% drop in uniaxial compressive strength (UCS) and 84% drop in Brazilian tensile strength (BTS) for 600 °C pre-treatment for 4 h, whereas the decrease in 70% of UCS and 89% of BTS are also observed for the combined process with 60 min of LIN quenching. The influence of pre-treatment on UPV and microstructure of rock has been investigated in detail. Due to thermal stress, very low UPV has been obtained for the pre-treated samples compared to untreated. SEM analysis has been carried out to understand the fracture morphology for both untreated and treated rock samples.

On the possibility of using detonation ceramic coatings as microwave energy absorbers

The developed absorbing microwave energy coatings of TiO2 and Al2O3/TiO2 deposited by the detonation method were investigated in this work. Thermal cyclic tests of the obtained samples of different layer thickness on copper substrates were carried out, the phase composition of the obtained coatings was investigated, the effect of high-temperature heating in hydrogen on the phase composition of the coating and its stability was determined. The gas emission was studied on evacuated and degassed experimental model.

The Effect of High Temperature Heating on Indentation Resistance of Cobalt Chromium Alloy Plates as Denture Labeling for Forensic Identification ( Research Report )

The labeled denture is important to identify people who have memory loss or identify of bodies in mass disasters, mainly due to the fires. Denture labeling made of tinfoil or paper laminated, but this form can easily be damaged if exposed to high temperatures. Cobalt Chromium (CoCr) Alloy metal is resistant to high temperatures which has melting point 1150º-1500ºC, so that possibility can be used as a tool in identification. Purpose: To determine indentation resistance of CoCr alloy plates on heating with high temperatures and be expected the use of its can be alternatives as denture labeling for forensic identification. Methods: Experimental Laboratory with sample form of plates made of CoCr metal cast and measuring 30X10X2 mm, with depth of indentation is 1.5 mm. The plates were heated with temperatures 400º, 800º,1050ºC and duration 5 and 15 minutes in the preheating furnace machine. 42 samples were divided into 3 groups (temperature of heating) and each group was divided into 2 groups again (duration of heating). Results: The size of depth and width of indentation (mm) of plate for all groups, there was no significant difference between before and after heating, except in groups heating to a temperature of 1050°C for 15 minutes (P<0.05). Conclusions: Heating with high temperature is not enough to make the plate damaged and deformed, so labeling indentation can still be read clearly. The use of CoCr plate can be alternatives as denture labeling.

The effects of high temperature heating on the gas permeability and porosity of a cementitious material

This experimental study investigates variations in the transfer properties (permeability) and porosity, of a normalized mortar heated up-to 600°C. New experimental techniques allow simultaneous measurements of permeability and porosity variations, under confining pressure. The main results show that when temperature raises from 105°C to 600°C, the permeability increases by 2 to 3 orders of magnitude, and nearly 50% in relative porosity (from 17% to 24% in absolute value). The higher the temperature, the greater the sensitivity to confinement of the permeability (and porosity), thus indicating substantial cracking and the irreversible nature of the material's behaviour. The application of confining pressure leads to irreversible crack closure and crushing of the pores. Various poro-mechanical measurements also revealed a considerable loss in stiffness for strongly heated material, providing complementary information concerning the porosity variation under loading, the amplitude of which is too high to be due to crack closure alone.

Study of fire-resistance of reinforced concrete slab of a new type

Reinforced concrete structures with complex inner geometry under the effect of high temperatures considering void former materials were examined. The analysis of strain-stress state of new type of architectural and construction system ‘Monofant’ under the effect of high temperature heating in standard fire mode, considering the change of design pattern was carried out. Numerical study of concrete slab with given reinforcement and complex inner geometry was carried out with use of software packages based on finite element method. Temperature fields throughout the depth of cross section of the slab of new type of architectural and construction system ‘Monofant’ upon heating in standard fire mode for time interval 0-240 min. were obtained. The carrying capacity of sections exposed to high temperatures was determined by deformation method. Offered the algorithm that considers the transformation of design patterns depending on temperature values and excessive pressure in thermal insulation cavities taking into account influence of deformation fields on temperature distribution.

Co-valorization of marine sediments and construction & demolition wastes through alkali activation

In the present experimental study, the co-valorization potential of marine sediments and construction & demolition wastes (C&D wastes) through alkali activation is investigated. Specimens were produced by mixing raw materials, namely marine sediments and C&D waste components (tiles, bricks and concrete) with the activating solution consisting of KOH and sodium silicate solution. The produced specimens were then subjected to compressive strength testing. The effect of the molarity of the alkaline activating solution as well as the percentage of each waste in the initial mixture on the compressive strength of the final products was also assessed. Also, the effect of high temperature heating (400–800°C), immersion in water or seawater and subjection to freeze–thaw cycles on the structural integrity of the produced specimens was investigated. Analytical techniques, namely X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM) were used for the identification of the morphology and structure of the final products.

Valorization of construction and demolition (C&D) and industrial wastes through alkali activation

In the present experimental study, the valorization of construction and demolition (C&D) and industrial wastes, namely ferronickel slag and red mud, through alkali activation is investigated. Specimens were produced by mixing various proportions of the raw materials with NaOH and sodium silicate solutions. The paste was cast in cubic metal moulds with an edge of 5cm, cured at 80°C for 24h and then aged for 7days at room temperature. The produced specimens were subjected to compressive strength testing. The effect of the molarity of the activating solution, the mineralogy of the raw materials and the ratios of SiO2/Al2O3 and SiO2/(Al2O3+CaO) on the compressive strength of the final products was investigated. Also, the effect of high temperature heating (400–800°C) on the structural integrity of the produced specimens was assessed. The use of analytical techniques, namely X-ray diffraction, Thermogravimetric Analysis, Fourier Transform Infrared Spectroscopy and Scanning Electron Microscopy provided insights on the morphology, structure and thermal resistance of the produced specimens.

Silicide Ceramic Synthesis Based on Molybdenum Disilicide in a Combustion Regime Under High-Temperature Deformation Conditions

A fundamental possibility is demonstrated of using SHS-extrusion and SHS-compression methods, combining combustion and high-temperature deformation, for preparing compact materials and objects of silicide ceramics based on MoSi2. Formability of silicide ceramic by free SHS-compression is studied. The effect of holding time before high-temperature deformation, heating temperature, and metal binder content in an original charge workpiece, on the degree of synthesized material deformation is studied. Specimen macro- and microstructure, prepared by SHS-extrusion is provided, and the effect of high-temperature heating on specific electrical resistance is also studied.

Effect of High-Temperature Heating on the Structure and Properties of Aluminum Alloys in the Production of Drill Pipes

The effect of heating to 200 − 250°C for 3–10 min in hot fitting of locks in the process of production of drill pipes from aluminum alloys D16T and 1953T1 on their structure and mechanical properties is studied. Practical recommendations are given for operations of hot fitting of locks of drill pipes from aluminum alloys to provide increase in their operating capacity.

Effect of high-temperature treatment on the structure and properties of TiNi-base alloys

The effect of high-temperature heating (1100°C) of semiproducts from TiNi-base alloys melted by different methods and containing different volume fractions of Ti2Ni intermetallic phase on the structure and functional properties is investigated. The results obtained are used to study the possibility of application of such high-temperature methods of treatment as diffusion welding to semiproducts from TiNi-base alloys.

Simulation of degradation of the profile of nanoporous silicon in the course of annealing in an inhomogeneous temperature field

The results of simulation of processes of thermal annealing of porous silicon under the effect of high-temperature heating both in a homogeneous temperature field and under conditions of the presence of a linear temperature gradient in the system are reported.

HIGH-TEMPERATURE EFFECTS ON ANTIOXIDANT SYSTEMS AND TOXIC PRODUCT FORMATION IN NUTRITIONAL OILS

In this study, effects of high-temperature heating on antioxidant defense potential (AOP) and malondialdehyde (MDA) levels were investigated in several types of oils ingested by humans. Natural olive oil, refined olive oil, sunflower oil, and soy oil were examined. High-temperature heating to 180 C significantly decreased AOP. This was accompanied by a significant increase in MDA levels. The observed changes were quantitatively greater in soy and sunflower oil compared to olive oil. The loss in antioxidant defense potential and elevation in peroxidation products may be associated with enhanced disease processes.

Effect of high-temperature heating of bimetallic steel billets

A mathematical model of high-temperature induction heating of a two-layer bimetallic cylindrical specimen with an allowance for the effect of thermoelastoplastic loading has been developed on the basis of the inverse problem method. The results of a mathematical experiment on determining the optimum heating conditions connected with abrupt changes in the inductor's dynamic parameters are provided.

Molecular ordering of polypyromellitimide on heating to the temperature of thermolysis

Solid-body and wide-line high resolution 13C NMR methods have been used to investigate the effect of high temperature heating of films, fibres and powder of polypyromellitimide on the structure of the macromolecules and orientational properties of the fibres. It is shown that structural ordering induced by high temperature heating affects the diphenyl oxide part of the macromolecule. The orientation factor of the fibres on heating rises significantly. On subsequent thermolysis the macromolecules draw nearer as a result of their crosslinkage.

Effect of high-temperature heating on oxide inclusions

Effect of high-temperature heating on oxide inclusions