scholarly journals Structure formation processes and thermal conductivity features of light Al-Si alloys with additional alloying by iron

2020 ◽  
pp. 184-189
Author(s):  
A. S. Zhilin ◽  
O. I. Rebrin ◽  
I. M. Kovenskiy ◽  
V. A. Bykov ◽  
V. R. Yalunina
Keyword(s):  
Thermal Conductivity ◽  
Aluminum Alloys ◽  
Thermophysical Properties ◽  
Silicon Content ◽  
Structural Features ◽  
Metallographic Analysis ◽  
Simultaneous Increase ◽  
Formation Processes ◽  
Silicon Crystals ◽  
Different Temperatures

Metallographic analysis and thermal conductivity analysis of series of light aluminum alloys with silicon content from 0 to 12 % (by weight) and additionally alloyed with iron 1 % (by weight) were carried out. It is shown that with an increase in the silicon content in the alloy above 4–6 % (by weight), the size of silicon crystals increases significantly with a simultaneous increase in the values of thermal conductivity. The article assesses the effect of iron on thermophysical properties and shows the correlation of thermal conductivity at different temperatures with the morphology of silicon in alloys with silicon content from 0 to 12 % (by weight) and additionally alloyed with iron 1 % (by weight). It is shown that alloy with a silicon content of 4 % by weight has a balanced reserve of thermophysical properties due to the structural features of the morphology of the components.

ALCOA QC-10

Alloy Digest ◽  
2009 ◽  
Vol 58 (7) ◽  
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Aluminum Alloys ◽  
Physical Properties ◽  
Tensile Properties ◽  
Mold Material ◽  
Cast Products

Abstract Aluminum has long been accepted as a mold material. This alloy has a combination of faster machining, highest heat transfer, lighter weight, higher strength in thick sections, and greater thermal conductivity than other aluminum alloys. This datasheet provides information on physical properties, hardness, elasticity, and tensile properties. It also includes information on forming and machining. Filing Code: AL-423. Producer or source: Alcoa Forged and Cast Products.

scholarly journals Thermophysical Properties of Cement Mortar Containing Waste Glass Powder

Crystals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 488
Author(s):  
Oumaima Nasry ◽  
Abderrahim Samaouali ◽  
Sara Belarouf ◽  
Abdelkrim Moufakkir ◽  
Hanane Sghiouri El Idrissi ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Specific Heat ◽  
Thermophysical Properties ◽  
Glass Powder ◽  
Cement Mortar ◽  
Soda Lime ◽  
Waste Glass ◽  
Soda Lime Glass ◽  
Volumetric Specific Heat ◽  
Waste Glass Powder

This study aims to provide a thermophysical characterization of a new economical and green mortar. This material is characterized by partially replacing the cement with recycled soda lime glass. The cement was partially substituted (10, 20, 30, 40, 50 and 60% in weight) by glass powder with a water/cement ratio of 0.4. The glass powder and four of the seven samples were analyzed using a scanning electron microscope (SEM). The thermophysical properties, such as thermal conductivity and volumetric specific heat, were experimentally measured in both dry and wet (water saturated) states. These properties were determined as a function of the glass powder percentage by using a CT-Meter at different temperatures (20 °C, 30 °C, 40 °C and 50 °C) in a temperature-controlled box. The results show that the thermophysical parameters decreased linearly when 60% glass powder was added to cement mortar: 37% for thermal conductivity, 18% for volumetric specific heat and 22% for thermal diffusivity. The density of the mortar also decreased by about 11% in dry state and 5% in wet state. The use of waste glass powder as a cement replacement affects the thermophysical properties of cement mortar due to its porosity as compared with the control mortar. The results indicate that thermal conductivity and volumetric specific heat increases with temperature increase and/or the substitution rate decrease. Therefore, the addition of waste glass powder can significantly affect the thermophysical properties of ordinary cement mortar.

scholarly journals Improved Copper–Epoxy Adhesion by Laser Micro- and Nano-Structuring of Copper Surface for Thermal Applications

Polymers ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1721
Author(s):  
Mario Mora ◽  
Hippolyte Amaveda ◽  
Luis Porta-Velilla ◽  
Germán F. de la Fuente ◽  
Elena Martínez ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Bonding Strength ◽  
Copper Surface ◽  
Heat Sinks ◽  
Electrical Insulation ◽  
Cryogenic Temperatures ◽  
Shear Tests ◽  
Patterned Structures ◽  
Different Temperatures ◽  
Mechanical Tensile

The objective of this work is the enhancement of metal-to-metal bonding to provide high thermal conductivity together with electrical insulation, to be used as heat sinks at room and cryogenic temperatures. High thermal conductive metal (copper) and epoxy resin (Stycast 2850FT) were used in this study, with the latter also providing the required electrical insulation. The copper surface was irradiated with laser to induce micro- and nano-patterned structures that result in an improvement of the adhesion between the epoxy and the copper. Thus, copper-to-copper bonding strength was characterized by means of mechanical tensile shear tests. The effect of the laser processing on the thermal conductivity properties of the Cu/epoxy/Cu joint at different temperatures, from 10 to 300 K, is also reported. Using adequate laser parameters, it is possible to obtain high bonding strength values limited by cohesive epoxy fracture, together with good thermal conductivity at ambient and cryogenic temperatures.

scholarly journals Influence of Temperature and Moisture Content on Thermal Performance of Green Roof Media

Energies ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2421
Author(s):  
Bohan Shao ◽  
Caterina Valeo ◽  
Phalguni Mukhopadhyaya ◽  
Jianxun He
Keyword(s):  
Thermal Conductivity ◽  
Moisture Content ◽  
Green Roof ◽  
Green Roofs ◽  
Power Functions ◽  
Thick Substrate ◽  
Different Temperatures ◽  
Test Cells ◽  
Substrate Moisture ◽  
Phase Transition Zone

The influence of moisture content on substrate thermal conductivity at different temperatures was investigated for four different commercially available substrates for green roofs. In the unfrozen state, as moisture content increased, thermal conductivity increased linearly. In the phase transition zone between +5 and −10 °C, as temperature decreased, thermal conductivity increased sharply during the transition from water to ice. When the substrate was frozen, thermal conductivity varied exponentially with substrate moisture content prior to freezing. Power functions were found between thermal conductivity and temperature. Two equally sized, green roof test cells were constructed and tested to compare various roof configurations including a bare roof, varying media thickness for a green roof, and vegetation. The results show that compared with the bare roof, there is a 75% reduction in the interior temperature’s amplitude for the green roof with 150 mm thick substrate. When a sedum mat was added, there was a 20% reduction in the amplitude of the inner temperature as compared with the cell without a sedum mat.

Thermal conductivity investigations of granular and powdered silica aerogels at different temperatures and pressures

2016 ◽  
Vol 118 ◽  
pp. 226-231 ◽  
Author(s):  
Gaosheng Wei ◽  
Lixin Wang ◽  
Chao Xu ◽  
Xiaoze Du ◽  
Yongping Yang
Keyword(s):  
Thermal Conductivity ◽  
Silica Aerogels ◽  
Different Temperatures

EXAMINATION OF THERMOPHYSICAL CHARACTERISTICS OF A HEAT-PROTECTIVE MATERIAL BASED ON FIBERGLASS DURING DESTRUCTION

2021 ◽  
pp. 91-97
Author(s):  
D.Ya. Barinov ◽  
◽  
S.Yu. Shorstov ◽  
M.G. Razmahov ◽  
A.I. Gulyaev ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Heat Capacity ◽  
Thermophysical Properties ◽  
Thermal Effects ◽  
Space Technology ◽  
Muffle Furnace ◽  
Thermophysical Characteristics ◽  
Initial State ◽  
Protective Material ◽  
Temperature Dependences

When designing advanced samples of aviation and rocket and space technology, during the operation of which the temperature on the surface of the material can exceed the temperature of destruction, it is important to have an understanding of the values of thermophysical properties. The work investigates the thermophysical properties of fiberglass in the initial state and after the binder is burned out in a muffle furnace. The temperature dependences of thermal effects, heat capacity, thermal diffusivity and thermal conductivity were determined, density was measured, and thermogravimetric analysis was carried out. Using a stereomicroscope, the microstructure of the lateral cut of the samples was examined and its evolution was determined during the burning of the binder.

Determination of Recrystallization Kinetics Model of 30Cr2Ni4MoV Steel Based on Dislocation Density

2017 ◽  
Vol 263 ◽  
pp. 59-66
Author(s):  
Peng Zhou ◽  
Qing Xian Ma
Keyword(s):  
Dislocation Density ◽  
Model Comparison ◽  
Kinetics Model ◽  
Structure Evolution ◽  
Metallographic Analysis ◽  
Recrystallization Kinetics ◽  
Proposed Model ◽  
Different Temperatures ◽  
Predicted Values ◽  
Experimental Values

A new model to predict the structure evolution of 30Cr2Ni4MoV steel is proposed based on the dislocation density in this research. Hot compression of 30Cr2Ni4MoV steel is carried out on Gleeble 1500 at different temperatures from 1233 K to 1473 K with a strain rate of 0.01 s-1 and the deformed samples are immediately quenched by water to frozen the austenite structure. The recrystallization kinetics model of 30Cr2Ni4MoV steel is successfully established by inverse analysis of the flow curve based on the relation between flow stress and dislocation density. In order to validate the proposed model, comparison between the predicted values and experimental values obtained by metallographic analysis is implemented. It is shown that the predicted results agree with the experimental results well.

scholarly journals Application and testing of a new simple experimental set-up for thermal conductivity measurements of liquids

2017 ◽  
Vol 21 (3) ◽  
pp. 1195-1202 ◽  
Author(s):  
Andrej Stanimirovic ◽  
Emila Zivkovic ◽  
Nenad Milosevic ◽  
Mirjana Kijevcanin
Keyword(s):  
Thermal Conductivity ◽  
Measurement Uncertainty ◽  
Thermophysical Properties ◽  
Deionized Water ◽  
Conductivity Measurements ◽  
Transient Hot Wire ◽  
Hot Wire ◽  
New Apparatus ◽  
Wire Method ◽  
Set Up

Transient hot wire method is considered a reliable and precise technique for measuring the thermal conductivity of liquids. The present paper describes a new transient hot wire experimental set-up and its initial testing. The new apparatus was tested by performing thermal conductivity measurements on substances whose reference thermophysical properties data existed in literature, namely on pure toluene and double distilled deionized water. The values of thermal conductivity measured in the temperature range 25 to 45 ?C deviated +2.2% to +3% from the literature data, while the expanded measurement uncertainty was estimated to be ?4%.

scholarly journals Thermal conductivity of silicon doped by phosphorus: ab initio study

2018 ◽  
Vol 35 (4) ◽  
pp. 717-724
Author(s):  
B. Andriyevsky ◽  
W. Janke ◽  
V.Yo. Stadnyk ◽  
M.O. Romanyuk
Keyword(s):  
Thermal Conductivity ◽  
Heat Conductivity ◽  
Phonon Scattering ◽  
Theoretical Calculations ◽  
Doped Semiconductors ◽  
Silicon Crystals ◽  
Coefficient Of Thermal Conductivity ◽  
Silicon Doped ◽  
Scattering Time ◽  
Phosphorus Doped

Abstract An original approach to the theoretical calculations of the heat conductivity of crystals based on the first principles molecular dynamics has been proposed. The proposed approach exploits the kinetic theory of phonon heat conductivity and permits calculating several material properties at certain temperature: specific heat, elastic constant, acoustic velocity, mean phonon scattering time and coefficient of thermal conductivity. The method has been applied to silicon and phosphorus doped silicon crystals and the obtained results have been found to be in satisfactory agreement with corresponding experimental data. The proposed computation technique may be applied to the calculations of heat conductivity of pure and doped semiconductors and isolators.

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