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Thermophysical Properties of Materials

A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Materials Physics".

Deadline for manuscript submissions: closed (20 March 2023) | Viewed by 33280

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Department of Physics, Faculty of Natural Sciences and Informatics, Constantine the Philosopher University in Nitra, Nitra, Slovakia
Interests: ceramic and building materials; thermophysical and mechanical properties; thermal analysis
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Special Issue Information

Dear Colleagues,

Thermophysical (heat capacity, thermal expansion, thermal conductivity, and diffusivity) properties of materials (building, ceramic, composite, plastic, metallic, or noncrystalline) are known for their practical applications. Therefore, it is crucial to study the relationship between these key properties and individual details of the manufacturing process from a experimental or theoretical point of view. The description of the behavior of materials and products under nonstationary thermal boundary conditions in a broader temperature interval requires the knowledge of dilatometric characteristics of the materials, the dependence of the thermal conductivity or diffusivity on the temperature, and also the temperature dependencies of heat capacity. The knowledge of thermophysical properties provides the opportunity for optimization of thermal processing of materials and thermal strain of products. Additionally, detailed knowledge on a given material and its properties provides the opportunity to find its specific practical applications. In the field of the measurement of thermophysical properties, there exist a large number of experimental methods: differential thermal analysis, differential scanning calorimetry, thermogravimetry, thermodilatometry, calorimetry, steady-state methods, and transient methods.

It is my pleasure to invite you to submit a manuscript for this Special Issue of Materials. Full papers, short communications, and reviews are all welcome.

Dr. Anton Trník
Guest Editor

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Keywords

  • Heat capacity
  • Thermal conductivity
  • Thermal diffusivity
  • Thermal expansion
  • Heat transfer
  • Measurement methods
  • Ceramic materials
  • Composite materials
  • Noncrystalline materials
  • Thermal insulation materials.

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Related Special Issue

Published Papers (13 papers)

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Research

13 pages, 5772 KiB  
Article
A New Theoretical Method for Studying Effects of Microstructure on Effective Thermal Conductivity of Vermicular Graphite Cast Iron
by Ailong Jiang, Anchen Shao, Lin Song, Minghao Hua, Hongliang Zheng, Xiaofu Zhang, Xuelei Tian and Xiaohang Lin
Materials 2023, 16(6), 2158; https://doi.org/10.3390/ma16062158 - 7 Mar 2023
Cited by 2 | Viewed by 1618
Abstract
To provide the basis for thermal conductivity regulation of vermicular graphite cast iron (VGI), a new theoretical method consisting of shape interpolation, unit cell model and numerical calculation was proposed. Considering the influence of the graphite anisotropy and interfacial contact thermal conductivity (ICTC), [...] Read more.
To provide the basis for thermal conductivity regulation of vermicular graphite cast iron (VGI), a new theoretical method consisting of shape interpolation, unit cell model and numerical calculation was proposed. Considering the influence of the graphite anisotropy and interfacial contact thermal conductivity (ICTC), the effective thermal conductivity of a series of unit cell models was calculated by numerical calculation based on finite difference. The effects of microstructure on effective thermal conductivity of VGI were studied by shape interpolation. The experimental results were in good agreement with the calculated ones. The effective thermal conductivity of VGI increases in power function with the decrease in graphite shape parameter, and increases linearly with the increase in graphite volume fraction and thermal conductivity of matrix. When the graphite volume fraction increases by 1%, the thermal conductivity of nodular cast iron increases by about 0.18 W/(m·K), while that of gray cast iron increases by about 3 W/(m·K). The thermal conductivity of cast iron has the same sensitivity to the thermal conductivity of matrix regardless of the graphite shape parameter. The thermal conductivity of matrix increased by 15 W/(m·K) and the thermal conductivity of cast iron increased by about 12 W/(m·K). Moreover, the more the graphite shape deviates from the sphere, the greater the enhancement effect of graphite anisotropy on thermal conductivity than the hindrance effect of interface between graphite and matrix. This work can provide guidance for the development of high thermal conductivity VGI and the study of thermal conductivity of composites containing anisotropic dispersed phase particles with complex shapes. Full article
(This article belongs to the Special Issue Thermophysical Properties of Materials)
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39 pages, 11695 KiB  
Article
Thermodynamic Relationships for Perfectly Elastic Solids Undergoing Steady-State Heat Flow
by Anne M. Hofmeister, Everett M. Criss and Robert E. Criss
Materials 2022, 15(7), 2638; https://doi.org/10.3390/ma15072638 - 3 Apr 2022
Cited by 4 | Viewed by 2404
Abstract
Available data on insulating, semiconducting, and metallic solids verify our new model that incorporates steady-state heat flow into a macroscopic, thermodynamic description of solids, with agreement being best for isotropic examples. Our model is based on: (1) mass and energy conservation; (2) Fourier’s [...] Read more.
Available data on insulating, semiconducting, and metallic solids verify our new model that incorporates steady-state heat flow into a macroscopic, thermodynamic description of solids, with agreement being best for isotropic examples. Our model is based on: (1) mass and energy conservation; (2) Fourier’s law; (3) Stefan–Boltzmann’s law; and (4) rigidity, which is a large, yet heretofore neglected, energy reservoir with no counterpart in gases. To account for rigidity while neglecting dissipation, we consider the ideal, limiting case of a perfectly frictionless elastic solid (PFES) which does not generate heat from stress. Its equation-of-state is independent of the energetics, as in the historic model. We show that pressure-volume work (PdV) in a PFES arises from internal interatomic forces, which are linked to Young’s modulus (Ξ) and a constant (n) accounting for cation coordination. Steady-state conditions are adiabatic since heat content (Q) is constant. Because average temperature is also constant and the thermal gradient is fixed in space, conditions are simultaneously isothermal: Under these dual restrictions, thermal transport properties do not enter into our analysis. We find that adiabatic and isothermal bulk moduli (B) are equal. Moreover, Q/V depends on temperature only. Distinguishing deformation from volume changes elucidates how solids thermally expand. These findings lead to simple descriptions of the two specific heats in solids: ∂ln(cP)/∂P = −1/B; cP = nΞ times thermal expansivity divided by density; cP = cVnΞ/B. Implications of our validated formulae are briefly covered. Full article
(This article belongs to the Special Issue Thermophysical Properties of Materials)
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14 pages, 2447 KiB  
Article
Optimization of Single α-Phase for Promoting Ferromagnetic Properties of 44Fe–28Cr–22Co–3Mo–1Ti–2V Permanent Magnet with Varying Co Concentration for Energy Storage
by Inam Ullah Khan, Vineet Tirth, Ali Algahtani, Rajwali Khan, Mohammad Sohail, Amjad Ali, Saiful Islam and Kashif Irshad
Materials 2022, 15(7), 2344; https://doi.org/10.3390/ma15072344 - 22 Mar 2022
Cited by 5 | Viewed by 1697
Abstract
The thermal stability and structural, microstructural and magnetic properties of (40 + x) Fe–28Cr–(26 − x) Co–3Mo–1Ti–2V magnets with x = 0, 2, 4 addition in cobalt content were investigated and presented. The magnetic alloys were synthesized by vacuum arc melting and casting [...] Read more.
The thermal stability and structural, microstructural and magnetic properties of (40 + x) Fe–28Cr–(26 − x) Co–3Mo–1Ti–2V magnets with x = 0, 2, 4 addition in cobalt content were investigated and presented. The magnetic alloys were synthesized by vacuum arc melting and casting technique in a controlled argon atmosphere. Magnetic properties in the alloys were convinced by single-step isothermal field treatment and subsequent aging. The alloys were investigated for thermal stability, structural, microstructural and magnetic properties via differential thermal analysis (DTA), X-ray diffractometery (XRD), optical microscopy (OM), field emission scanning electron microscope (FESEM) and DC magnetometer. Metallurgical grains of size 300 ± 10 μm were produced in the specimens by casting and refined by subsequent thermal treatments. The magnetic properties of the alloys were achieved by refining the microstructure, the optimization of conventional thermomagnetic treatment to modified single-step isothermal field treatment and subsequent aging. The best magnetic properties achieved for the alloy 44Fe–28Cr–22Co–3Mo–0.9Ti–2V was coercivity Hc = 890 Oe (71 kA/m), Br = 8.43 kG (843 mT) and maximum energy product (BH)max = 3 MGOe (24 kJ/m3). The enhancement of remanence and coercivity enabled by the isothermal field treatment was due to the elongation of the ferromagnetic phase and step aging treatment due to the increase in the volume fraction. This work is interesting for spin-based electronics to be used for energy storage devices. Full article
(This article belongs to the Special Issue Thermophysical Properties of Materials)
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9 pages, 3080 KiB  
Article
Thermal and Mechanical Properties of Amorphous Silicon Carbide Thin Films Using the Femtosecond Pump-Probe Technique
by Yun Young Kim
Materials 2022, 15(6), 2165; https://doi.org/10.3390/ma15062165 - 15 Mar 2022
Cited by 4 | Viewed by 2627
Abstract
Nanoscale amorphous silicon carbide (a-SiC) thin films are widely used in engineering applications. It is important to obtain accurate information about their material properties because they often differ from those of the bulk state depending on the fabrication technique and process parameters. In [...] Read more.
Nanoscale amorphous silicon carbide (a-SiC) thin films are widely used in engineering applications. It is important to obtain accurate information about their material properties because they often differ from those of the bulk state depending on the fabrication technique and process parameters. In this study, the thermal and mechanical properties of a-SiC thin films were evaluated using the femtosecond pump-probe technique, which provides high spatial and temporal resolutions sufficient to measure films that have a thickness of less than 300 nm. a-SiC films were grown using a plasma-enhanced chemical vapor deposition system, and the surface characteristics were analyzed using ellipsometry, atomic force microscopy, and X-ray reflectometry. The results show that the out-of-the-plane thermal conductivity of the films is lower than that of bulk crystalline SiC by two orders of magnitude, but the lower limit is dictated by the minimum thermal conductivity. In addition, a decrease in the mass density resulted in a reduced Young’s modulus by 13.6–78.4% compared to the literature values, implying low Si-C bond density in the microstructures. The scale effect on both thermal conductivity and Young’s modulus was not significant. Full article
(This article belongs to the Special Issue Thermophysical Properties of Materials)
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18 pages, 1404 KiB  
Article
An Inverse Analysis for Establishing the Temperature-Dependent Thermal Conductivity of a Melt-Cast Explosive across the Whole Solidification Process
by Lei Ni, Xiangrong Zhang, Lin Zhou, Xiufen Yang and Bo Yan
Materials 2022, 15(6), 2077; https://doi.org/10.3390/ma15062077 - 11 Mar 2022
Viewed by 2037
Abstract
Thermal conductivity is one of the most important thermophysical properties of a melt-cast explosive. However, the temperature-dependent thermal conductivity of such explosives cannot be easily measured across the whole solidification process (including the liquid, semi-solid, and solid states). This study used an inverse [...] Read more.
Thermal conductivity is one of the most important thermophysical properties of a melt-cast explosive. However, the temperature-dependent thermal conductivity of such explosives cannot be easily measured across the whole solidification process (including the liquid, semi-solid, and solid states). This study used an inverse analysis method to estimate the temperature-dependent thermal conductivity of a 2,4-dinitroanisole/cyclotetramethylenetetranitramine (DNAN/HMX) melt-cast explosive in a continuous way. The method that was used is described here in detail, and it is verified by comparing the estimated thermal conductivity with a prespecified value using simulated measurement temperatures, thereby demonstrating its effectiveness. Combining this method with experimentally measured temperatures, the temperature-dependent thermal conductivity of the DNAN/HMX melt-cast explosive was obtained. Some measured thermal conductivity values for this explosive in the solid state were used for further validation. Full article
(This article belongs to the Special Issue Thermophysical Properties of Materials)
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11 pages, 15341 KiB  
Communication
Thermal Kinetics of Monocationic and Dicationic Pyrrolidinium-Based Ionic Liquids
by Asyraf Hanim Ab Rahim, Noraini Abd Ghani, Noorhafizah Hasanudin, Normawati M. Yunus and Ninna Sakina Azman
Materials 2022, 15(3), 1247; https://doi.org/10.3390/ma15031247 - 8 Feb 2022
Cited by 3 | Viewed by 2027
Abstract
This work presents an in-depth kinetic thermal degradation comparison between traditional monocationic and the newly developed dicationic ionic liquid (IL), both coupled with a bromide (Br) anion by using non-isothermal thermogravimetric analysis. Thermal analyses of 1-butyl-1-methylpyrrolidinium bromide [C4MPyr][Br] and [...] Read more.
This work presents an in-depth kinetic thermal degradation comparison between traditional monocationic and the newly developed dicationic ionic liquid (IL), both coupled with a bromide (Br) anion by using non-isothermal thermogravimetric analysis. Thermal analyses of 1-butyl-1-methylpyrrolidinium bromide [C4MPyr][Br] and 1,4-bis(1-methylpyrrolidinium-1-yl)butane dibromide [BisC4MPyr][Br2] were conducted at a temperature range of 50–650 °C and subjected to various heating rates, which are 5, 10, 15, 20 and 25 °C/min. Thermogravimetric analysis revealed that dicationic IL, [BisC4MPyr][Br2] is less thermally stable compared to monocationic [C4MPyr][Br]. A detailed analysis of kinetic parameters, which are the activation energy (Ea) and pre-exponential factor (log A), was calculated by using Kissinger-Akahira-Sunose (KAS), Flynn-Wall-Ozawa (FWO) and Starink. This study revealed that the average Ea and log A of [BisC4MPyr][Br2] are lower than [C4MPyr][Br], which may be contributed to by its low thermal stability. Conclusively, it proved that the Ea and log A of ILs are strongly related to the thermal stability of ILs. Full article
(This article belongs to the Special Issue Thermophysical Properties of Materials)
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14 pages, 4789 KiB  
Article
Fiber Optic-Based Thermal Integrity Profiling of Drilled Shaft: Inverse Modeling for Spiral Fiber Deployment Strategy
by Wen Deng, Ruoyu Zhong and Haiying Ma
Materials 2021, 14(18), 5377; https://doi.org/10.3390/ma14185377 - 17 Sep 2021
Cited by 2 | Viewed by 1974
Abstract
The current state of practice to interpret the thermal integrity profiling (TIP) data of drilled shaft is the so-called effective radius method. It uses the concrete pouring log and average temperature to construct a relationship between temperature distribution and effective radius that can [...] Read more.
The current state of practice to interpret the thermal integrity profiling (TIP) data of drilled shaft is the so-called effective radius method. It uses the concrete pouring log and average temperature to construct a relationship between temperature distribution and effective radius that can be used to reconstruct a drilled shaft model. While this effective radius method is computationally inexpensive and has good operationality, it is not good at predicting the dimensions and shape of shaft defects. Upgrading the sensor used in conventional TIP from thermocouples/thermal wires to fiber optic sensors, the spatial resolution of the measured temperature will be enhanced. By using the newly proposed spiral fiber deployment strategy, we can improve the reconstruction of shaft defects in the integrity testing of drilled shafts. The corresponding inverse modeling of defected shaft reconstruction for spiral deployment is proposed in this paper based on the temperature distribution pattern that is learned from forward modeling. Through inverse modeling, the details of defects in drilled shafts can be reconstructed numerically. An analysis of the results shows that the prediction by inverse modeling has good agreement with the forward modeling set up initially. This work helps the evolution of the TIP from the nondestructive testing stage to the quantitative nondestructive evaluation stage. Full article
(This article belongs to the Special Issue Thermophysical Properties of Materials)
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24 pages, 3883 KiB  
Article
Industrial Thermal Insulation Properties above Sintering Temperatures
by Amalie Gunnarshaug, Maria-Monika Metallinou and Torgrim Log
Materials 2021, 14(16), 4721; https://doi.org/10.3390/ma14164721 - 21 Aug 2021
Cited by 1 | Viewed by 3164
Abstract
Processing highly flammable products, the oil and gas (O&G) industry can experience major explosions and fires, which may expose pressurized equipment to high thermal loads. In 2020, oil fires occurred at two Norwegian O&G processing plants. To reduce the escalation risk, passive fire [...] Read more.
Processing highly flammable products, the oil and gas (O&G) industry can experience major explosions and fires, which may expose pressurized equipment to high thermal loads. In 2020, oil fires occurred at two Norwegian O&G processing plants. To reduce the escalation risk, passive fire protection may serve as a consequence-reducing barrier. For heat or cold conservation, equipment and piping often require thermal insulation, which may offer some fire protection. In the present study, a representative thermal insulation (certified up to 700 °C) was examined with respect to dimensional changes and thermal transport properties after heat treatment to temperatures in the range of 700 °C to 1200 °C. Post heat treatment, the thermal conductivity of each test specimen was recorded at ambient temperature and up to 700 °C, which was the upper limit for the applied measurement method. Based on thermal transport theory for porous and/or amorphous materials, the thermal conductivity at the heat treatment temperature above 700 °C was estimated by extrapolation. The dimensional changes due to, e.g., sintering, were also analyzed. Empirical equations describing the thermal conductivity, the dimensional changes and possible crack formation were developed. It should be noted that the thermal insulation degradation, especially at temperatures approaching 1200 °C, is massive. Thus, future numerical modeling may be difficult above 1150 °C, due to abrupt changes in properties as well as crack development and crack tortuosity. However, if the thermal insulation is protected by a thin layer of more robust material, e.g., passive fire protection to keep the thermal insulation at temperatures below 1100 °C, future modeling seems promising. Full article
(This article belongs to the Special Issue Thermophysical Properties of Materials)
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16 pages, 4028 KiB  
Article
Influence of the Direction of Mixture Compaction on the Selected Properties of a Hemp-Lime Composite
by Przemysław Brzyski, Piotr Gleń, Mateusz Gładecki, Monika Rumińska, Zbigniew Suchorab and Grzegorz Łagód
Materials 2021, 14(16), 4629; https://doi.org/10.3390/ma14164629 - 17 Aug 2021
Cited by 13 | Viewed by 2156
Abstract
The aim of the research presented in the article was to check the differences in the hygro-thermal and mechanical properties of hemp-lime composites with different shives fractions, depending on the direction of mixture compaction. The research part of the paper presents the preparation [...] Read more.
The aim of the research presented in the article was to check the differences in the hygro-thermal and mechanical properties of hemp-lime composites with different shives fractions, depending on the direction of mixture compaction. The research part of the paper presents the preparation method and investigation on the composites. Thermal conductivity, capillary uptake, as well as flexural and compressive strengths were examined. Additionally, an analysis of the temperature distribution in the external wall insulated with the tested composites was performed. The results confirm that the direction of compaction influences the individual properties of the composites in a similar way, depending on the size of the shives. The differences are more pronounced in the case of the composite containing longer fractions of shives. Both thermal conductivity of the material and the capillary uptake ability are lower in the parallel direction of the compaction process. Composites exhibit greater stiffness, but they fail faster with increasing loads when loaded in the direction perpendicular to compaction. Full article
(This article belongs to the Special Issue Thermophysical Properties of Materials)
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19 pages, 5904 KiB  
Article
Thermal Stability and Decomposition Kinetics of 1-Alkyl-2,3-Dimethylimidazolium Nitrate Ionic Liquids: TGA and DFT Study
by Jianwen Meng, Yong Pan, Fan Yang, Yanjun Wang, Zhongyu Zheng and Juncheng Jiang
Materials 2021, 14(10), 2560; https://doi.org/10.3390/ma14102560 - 14 May 2021
Cited by 11 | Viewed by 2303
Abstract
The thermal stability and decomposition kinetics analysis of 1-alkyl-2,3-dimethylimidazole nitrate ionic liquids with different alkyl chains (ethyl, butyl, hexyl, octyl and decyl) were investigated by using isothermal and nonisothermal thermogravimetric analysis combined with thermoanalytical kinetics calculations (Kissinger, Friedman and Flynn-Wall-Ozawa) and density functional [...] Read more.
The thermal stability and decomposition kinetics analysis of 1-alkyl-2,3-dimethylimidazole nitrate ionic liquids with different alkyl chains (ethyl, butyl, hexyl, octyl and decyl) were investigated by using isothermal and nonisothermal thermogravimetric analysis combined with thermoanalytical kinetics calculations (Kissinger, Friedman and Flynn-Wall-Ozawa) and density functional theory (DFT) calculations. Isothermal experiments were performed in a nitrogen atmosphere at 240, 250, 260 and 270 °C. In addition, the nonisothermal experiments were carried out in nitrogen and air atmospheres from 30 to 600 °C with heating rates of 5, 10, 15, 20 and 25 °C/min. The results of two heating modes, three activation energy calculations and density functional theory calculations consistently showed that the thermal stability of 1-alkyl-2,3-dimethylimidazolium nitrate ionic liquids decreases with the increasing length of the alkyl chain of the substituent on the cation, and then the thermal hazard increases. This study could provide some guidance for the safety design and use of imidazolium nitrate ionic liquids for engineering. Full article
(This article belongs to the Special Issue Thermophysical Properties of Materials)
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18 pages, 3988 KiB  
Article
Influence of Polypropylene, Glass and Steel Fiber on the Thermal Properties of Concrete
by Marcin Małek, Mateusz Jackowski, Waldemar Łasica and Marta Kadela
Materials 2021, 14(8), 1888; https://doi.org/10.3390/ma14081888 - 10 Apr 2021
Cited by 28 | Viewed by 3695
Abstract
The variety of approaches to tackle climate change reflects the size of this global problem. No technology will act as a panacea to cure the greenhouse gas emissions problem, but new building materials with byproducts or even wastes have the potential to play [...] Read more.
The variety of approaches to tackle climate change reflects the size of this global problem. No technology will act as a panacea to cure the greenhouse gas emissions problem, but new building materials with byproducts or even wastes have the potential to play a major role in reducing the environmental impacts of the building sector. In this study, three potential solutions of concrete with dispersed reinforcement in the form of recycled fibers (polypropylene, glass and steel) were examined. The aim is to present a detailed analysis of the thermal properties of new building materials in an experimental approach. Concrete mixtures were prepared according to a new, laboratory-calculated recipe containing granite aggregate, a polycarboxylate-based deflocculant, Portland cement (52.5 MPa) and fibers. This experimental work involved three different contents of each fiber (0.5%, 0.75% and 1.0 wt.%), and all tests were carried after the complete curing cycle of concrete (28 days). Full article
(This article belongs to the Special Issue Thermophysical Properties of Materials)
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14 pages, 3796 KiB  
Article
Heat Losses Caused by the Temporary Influence of Wind in Timber Frame Walls Insulated with Fibrous Materials
by Piotr Kosiński, Przemysław Brzyski, Zbigniew Suchorab and Grzegorz Łagód
Materials 2020, 13(23), 5514; https://doi.org/10.3390/ma13235514 - 3 Dec 2020
Cited by 10 | Viewed by 2274
Abstract
The paper presents the results of research concerning three fiber materials—mineral wool, hemp fiber and wood wool—as loose-fill thermal insulation materials. The analysis used the material parameters determined in previous works conducted by the authors, such as thermal conductivity and air permeability in [...] Read more.
The paper presents the results of research concerning three fiber materials—mineral wool, hemp fiber and wood wool—as loose-fill thermal insulation materials. The analysis used the material parameters determined in previous works conducted by the authors, such as thermal conductivity and air permeability in relation to bulk density. These materials exhibit open porosity; thus, convection is an essential phenomenon in the heat transfer process. The paper aimed at conducting thermal simulations of various frame wall variants which were filled with the above-mentioned insulation materials. The simulations were performed with the Control Volume Method using the Delphin 5.8 software. The studies accounted for the effect of wind pressure and the time of its influence on a wall insulated by means of fiber material with a thickness of 150 as well as 250 mm. The simulation enabled us to obtain such data as maximal R-value reduction and time to return to equilibrium after filtration for the analyzed materials. The study proved that heat transfer in these insulations strongly depends on the bulk density, thickness of the insulation and wind pressure. The decrease in R is reduced as the density increases. This results from the decreased air permeability characterizing the material. Wind washing causes lower R reduction than air filtration in all models. The greater the thickness, the longer it takes for the models to return to the equilibrium state following air filtration (and wind washing). This period is comparable for air filtration and wind washing. Hemp fibers were characterized with the strongest susceptibility to air filtration; in the case of wood wool, it was also high, but lower than for hemp fibers, while mineral wool was characterized with the lowest. Full article
(This article belongs to the Special Issue Thermophysical Properties of Materials)
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14 pages, 3432 KiB  
Article
Young’s Modulus of Different Illitic Clays during Heating and Cooling Stage of Firing
by Tomáš Húlan, Igor Štubňa, Ján Ondruška, Štefan Csáki, František Lukáč, Marek Mánik, Libor Vozár, Jurijs Ozolins, Tiit Kaljuvee and Anton Trník
Materials 2020, 13(21), 4968; https://doi.org/10.3390/ma13214968 - 4 Nov 2020
Cited by 9 | Viewed by 2521
Abstract
Dynamical thermomechanical analysis of 5 illite-based clays from deposits in Slovakia, Estonia, Latvia, and Hungary is presented. The clays consist of illite (37–80 mass%), quartz (12–48 mass%), K-feldspar (4–13 mass%), kaolinite (0–18 mass%), and calcite (0–3 mass%). Young’s modulus is measured during the [...] Read more.
Dynamical thermomechanical analysis of 5 illite-based clays from deposits in Slovakia, Estonia, Latvia, and Hungary is presented. The clays consist of illite (37–80 mass%), quartz (12–48 mass%), K-feldspar (4–13 mass%), kaolinite (0–18 mass%), and calcite (0–3 mass%). Young’s modulus is measured during the heating and cooling stages of firing (25 °C → 1100 °C → 25 °C). The liberation of the physically bound water increases Young’s modulus by ∼70% for all studied clays. By increasing the temperature, dehydroxylation and the α → β transition of quartz take place without a significant effect on Young’s modulus. Sintering, which starts at 800 °C, leads to an intensive increase in Young’s modulus up to the highest temperature (1100 °C). The increase remains also in the early stage of cooling (1100 °C → 800 °C). This increase of Young’s modulus is also the result of solidification of the glassy phase, which is finished at ∼750 °C. A sharp minimum of Young’s modulus is observed at around the β → α transition of quartz. Then, Young’s modulus still decreases its value down to the room temperature. The physical processes observed during heating and cooling do not differ in nature for the studied clays. Values of Young’s modulus vary at around 8 GPa, up to 800 °C. During sintering, Young’s modulus reaches values from 30 GPa to 70 GPa for the studied clays. The microstructure and composition given by the origin of the clay play a cardinal role for the Young’s modulus of the final ceramic body. Full article
(This article belongs to the Special Issue Thermophysical Properties of Materials)
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