scholarly journals FORECAST EVALUATION OF HEAT PROTECTION AND MECHANICAL PROPERTIES OF INSULATING CONSTRUCTION CERAMIC MATERIALS

2021 ◽  
pp. 68-74
Author(s):  
Liudmyla Pavlivna Shchukina ◽  
Yaroslav Olegovych Halushka ◽  
Larysa Oleksanrivna Yashchenko ◽  
Stanislav Leonidovych Lihezin
Keyword(s):  
Mechanical Properties ◽  
Thermal Conductivity ◽  
Rational Design ◽  
Structural Model ◽  
Ceramic Matrix ◽  
Integrated Approach ◽  
Ceramic Materials ◽  
Operating Conditions ◽  
Construction Ceramic ◽  
Heat Shielding

An integrated approach to determine the rational design of wall ceramic products based on modeling their behavior under operating conditions is proposed. This approach was used in the development of technology for heat–efficient insulating construction ceramic materials for energy–saving construction. For two models of porous–hollow ceramic products with a porous frame (40 % of voids) and a dense frame (60 % of voids), a predictive assessment of their heat–shielding and mechanical properties was carried out. Calculations of the equivalent coefficient of thermal conductivity of models based on Fourier’s law established that with a decrease in the voidness of products with a porous wall, the coefficient of their thermal conductivity decreases by 12 %, which improves the heat–shielding properties. Based on the results of computer simulation of the behavior of models under the influence of static power loads, it was determined that porosity of the ceramic framework of products leads to degradation of mechanical strength almost proportionally to a decrease in voidness. The stress–strain state of 3D models of ceramic structures with different pore geometry (spherical, globular, ellipsoidal) is analyzed and it is shown that stresses are concentrated in the contact zones of a ceramic matrix with pores. It is shown that the most durable is the structural model with spherical pores. The expediency of organizing such a structure, the need to strengthen the ceramic matrix of materials and zones surrounding the pores, as the most vulnerable structural sites, is shown. The results of predictive calculations have been experimentally confirmed in the development of technology for structural and heat–insulating composite–type ceramic materials based on low–melting loam and ash microspheres, which provide a given structural picture of the ceramic material.

Effect of α-Alumina as a Seed in Alumina/Silicon Carbide Composites

2006 ◽  
Vol 317-318 ◽  
pp. 115-118
Author(s):  
Seong Min Choi ◽  
Uraiwan Leela-adisorn ◽  
Sawao Honda ◽  
Shinobu Hashimoto ◽  
Hideo Awaji
Keyword(s):  
Mechanical Properties ◽  
Silicon Carbide ◽  
Fracture Strength ◽  
Vickers Hardness ◽  
Ceramic Matrix Composites ◽  
Ceramic Matrix ◽  
Ceramic Materials ◽  
Matrix Composites ◽  
Pulse Electric Current ◽  
Pulse Electric

Intra-type structure of ceramic matrix composites (CMCs) can improve the mechanical properties of ceramic materials. In this work, we used γ-alumina as a matrix including nano-pore for fabricating alumina/silicon carbide composites using pressure-less sintering and pulse electric current sintering (PECS) techniques. We added α-alumina as a seed in order to improve densification of this commercially available γ-alumina. The mixture was sintered from 1250 to 1450 by pressure-less sintering and PECS techniques. Densification of the specimen sintered by pressure-less sintering is very difficult and bulk density of the specimen sintered at 1450 showed lower than 3.0 g/cc. In the case of the PECS technique, the density was improved to 3.8 g/cc in seed added specimen sintered at 1450. Maximum Vickers hardness and maximum fracture strength were obtained 17 GPa and 500 MPa for the seed added specimens sintered at 1450, respectively.

Correlation of Thermal Conduction Properties With Mechanical Deformation Characteristics of a Set of SiC–Si3N4 Nanocomposites

2010 ◽  
Vol 133 (1) ◽  
Author(s):  
Vikas Tomar ◽  
Vikas Samvedi
Keyword(s):  
Mechanical Properties ◽  
Thermal Conductivity ◽  
Optimal Control ◽  
High Temperature ◽  
Fracture Strength ◽  
Thermal Conduction ◽  
Volume Fraction ◽  
Ceramic Materials ◽  
Thermal And Mechanical Properties ◽  
Sic Particles

New developments in high temperature ceramic materials technology have focused on obtaining nanocomposite materials with nanoscale features for an optimal control of thermal and mechanical properties. One example is the silicon carbide (SiC)–silicon nitride (Si3N4) nanocomposites with nanosized SiC particles placed either in microsized Si3N4 grains or along Si3N4 grain boundaries (GBs). This work focuses on analyzing the influence of GBs, interfaces, and impurities on thermal and mechanical properties of a set of SiC–Si3N4 nanocomposites at three different temperatures (300 K, 900 K, and 1500 K). Nanocomposite thermal conductivity values predicted in this study are smaller in comparison to the bulk Si3N4 values (∼30 W/m K). Even with the volume fraction of SiC phase being limited to maximum 40%, it is shown that the thermal conductivity values could be reduced to less than those of the bulk SiC phase (∼3 W/m K) by microstructural feature arrangement. Nanocomposite phonon spectral density values show a short rage structural order indicating a high degree of diffused phonon reflection. Visual analyses of the atomistic arrangements did not reveal any loss of crystallinity in the nanocomposites at high temperatures. This indicates that structural arrangement, not the phase change, is a factor controlling thermal conduction as a function of temperature. The nanocomposite deformation mechanism is a trade-off between the stress concentration caused by SiC particles and Si3N4–Si3N4 GB sliding. The temperature increase tends to work in favor of GB sliding leading to softening of structures. However, microstructural strength increases with increase in temperature when GBs are absent. GBs also contribute to reduction in thermal conductivity as well as increase in fracture strength. Replacement of sharp GBs by diffused GBs having C/N impurities, lowered thermal conductivity, and increased fracture strength. Decrease in SiC–Si3N4 interfaces by removal of SiC particles tends to favor an increase in thermal conductivity as well as fracture resistance. Overall, it is shown that for high temperature mechanical strength improvement, judicious placement of SiC particles and optimal control of GB atomic volume fraction are the main controlling factors.

scholarly journals Two-sided Estimates of Thermal Conductivity Coefficient of a Porous Body Skeleton

2018 ◽  
pp. 45-60
Author(s):  
V. S. Zarubin ◽  
O. V. Novozhilova ◽  
E. S. Sergeeva
Keyword(s):  
Thermal Conductivity ◽  
Porous Material ◽  
Porous Materials ◽  
Porous Body ◽  
Structural Model ◽  
Thermal Conductivity Coefficient ◽  
Solid Sphere ◽  
Operating Conditions ◽  
Porous Composite ◽  
Coefficient Of Thermal Conductivity

Porous composite materials are widely used in engineering as structural and heat-insulating materials. The presence of pores in such materials is due to both the technology of their manufacture and the operating conditions.One of the most important factors in the process of designing products from a porous composite is the complex of thermophysical characteristics of the material. This characteristic determines the application area of the material.Among the thermophysical properties the leading role is played by the coefficient of thermal conductivity. This coefficient for some porous materials can be determined experimentally, however, in order to reduce the time and resources needed, a theoretical study of this characteristic is more relevant.Theoretical investigation of the thermal conductivity coefficient of a porous composite allows us to predict its possible values depending on the composition of the material and its porosity. Such information about the composite is necessary at various stages of working with the material from its preparation to the construction of a structure from it.There are many works devoted to approaches to the theoretical evaluation of the coefficient of thermal conductivity of a porous material. However, due to a significant spread of its values, an actual task is to construct guaranteed two-sided estimates of the possible values of this material characteristic.As is well known, there are some difficulties in constructing lower estimates of the properties of a porous material. In this paper, to overcome this difficulty, a modification of the structural model of the porous body was used in conjunction with the dual formulation of the stationary heat conduction problem in an inhomogeneous solid.The modification of the structural model of a porous body in this paper is as follows: a hollow spherical particle is replaced by a solid sphere with an equal external radius. The solid sphere in turn is represented by a composite ball consisting of an inner ball of some conventional material and an outer spherical layer of the carcass material of the porous body. The equivalent thermal conductivity of the material of the inner ball is to be determined.The modification of the structural model of the porous body proposed in the work allowed to obtain two-sided estimates of the possible value of this coefficient. Also, the obtained estimates were compared with unimprovable upper bound for this characteristic.The obtained results will allow us to predict two-sided estimates of the thermal conductivity coefficient of perspective heat-insulating and structural porous materials.

scholarly journals Structure and properties of ceramic brick colored by manganese-containing wastes

2018 ◽  
Vol 143 ◽  
pp. 02009 ◽  
Author(s):  
Andrey Stolboushkin ◽  
Danil Akst ◽  
Oksana Fomina ◽  
Aleksandr Ivanov
Keyword(s):  
Mechanical Properties ◽  
Raw Materials ◽  
Physical And Mechanical Properties ◽  
Ceramic Matrix Composites ◽  
Ceramic Matrix ◽  
Ceramic Materials ◽  
Strength Properties ◽  
Ceramic Brick ◽  
Color Code ◽  
Decorative Ceramic

The given paper investigates the influence of manganese-containing wastes on bulk coloring and physical and mechanical properties of wall ceramic materials with matrix structure. Conventional research methods to study physical and mechanical properties of ceramic specimens were used in the present study. The structure and phase state of decorative ceramic materials were investigated by means of physical-chemical analysis. Authors suggested the model to form coloring layer in ceramic matrix composites based on argillaceous raw materials and coloring pigment. Macrostructure was studied on ceramic samples manufactured according to the developed method from clay loam of moderate plasticity and wastes of manganese mining. The paper provides results of pilot testing on production of colored ceramic brick. It was found that incorporation of coloring component does not decrease strength properties of ceramic matrix materials. Authors defined the palette and color code for decorative ceramic specimens manufactured with different content of coloring component of manganese mining wastes according to RGB color codes chart.

Microstructural Evolution of Alumina-Zirconia Nanocomposites

2014 ◽  
Vol 805 ◽  
pp. 621-626 ◽  
Author(s):  
C.L. Ojaimi ◽  
Adriana Scoton Antonio Chinelatto ◽  
Adilson Luiz Chinelatto ◽  
E.M.J.A. Pallone ◽  
R.E.P. Salem
Keyword(s):  
Mechanical Properties ◽  
Microstructural Evolution ◽  
Ceramic Matrix ◽  
Ceramic Materials ◽  
Nanosized Particles ◽  
Ceramic Processing ◽  
Sintering Process ◽  
Transformation Toughening ◽  
The Matrix ◽  
Processing Control

Ceramic materials have limited use due to their brittleness. The inclusion of nanosized particles in a ceramic matrix, which are called nanocomposites, and ceramic processing control by controlling the grain size and densification can aid in obtaining ceramic products of greater strength and toughness. Studies showed that the zirconia nanoinclusions in the matrix of alumina favor an increase in mechanical properties by inhibiting the grain growth of the matrix and not by the mechanism of the transformation toughening phase of zirconia. In this work, the microstructural evolution of alumina nanocomposites containing 15% by volume of nanometric zirconia was studied. From the results it was possible to understand the sintering process of these nanocomposites.

Parametric Study of Photovoltaic Thermal Solar Collector Using An Improved Parallel Flow

2020 ◽  
Vol 2 (1) ◽  
pp. 19-24
Author(s):  
Sakhr Mohammed Sultan ◽  
Chih Ping Tso ◽  
Ervina Efzan Mohd Noor ◽  
Fadhel Mustafa Ibrahim ◽  
Saqaff Ahmed Alkaff
Keyword(s):  
Thermal Conductivity ◽  
Energy Balance ◽  
Parametric Study ◽  
Solar Collector ◽  
Parallel Flow ◽  
Operating Conditions ◽  
Balance Equations ◽  
Conductivity Type ◽  
Pv Module ◽  
Sunny Weather

Photovoltaic Thermal Solar Collector (PVT) is a hybrid technology used to produce electricity and heat simultaneously. Current enhancements in PVT are to increase the electrical and thermal efficiencies. Many PVT factors such as type of absorber, thermal conductivity, type of PV module and operating conditions are important parameters that can control the PVT performance. In this paper, an analytical model, using energy balance equations, is studied for PVT with an improved parallel flow absorber. The performance is calculated for a typical sunny weather in Malaysia. It was found that the maximum electrical and thermal efficiencies are 12.9 % and 62.6 %, respectively. The maximum outlet water temperature is 59 oC.

An analysis of the transport properties and mechanical stability of rapidly solidified Al-Sb alloy

2015 ◽  
Vol 10 (2) ◽  
pp. 2663-2681
Author(s):  
Rizk El- Sayed ◽  
Mustafa Kamal ◽  
Abu-Bakr El-Bediwi ◽  
Qutaiba Rasheed Solaiman
Keyword(s):  
Mechanical Properties ◽  
Thermal Conductivity ◽  
Melt Spinning ◽  
Elastic Moduli ◽  
Mechanical Stability ◽  
Microstructural Analysis ◽  
Alloy System ◽  
Antimony Content ◽  
The Stability ◽  
Rapidly Solidified

The structure of a series of AlSb alloys prepared by melt spinning have been studied in the as melt–spun ribbons  as a function of antimony content .The stability  of these structures has  been  related to that of the transport and mechanical properties of the alloy ribbons. Microstructural analysis was performed and it was found that only Al and AlSb phases formed for different composition.  The electrical, thermal and the stability of the mechanical properties are related indirectly through the influence of the antimony content. The results are interpreted in terms of the phase change occurring to alloy system. Electrical resistivity, thermal conductivity, elastic moduli and the values of microhardness are found to be more sensitive than the internal friction to the phase changes. 

Incorporation of Iraqi Rocks in the Production of Eco-Friendly Cement Mortar

2020 ◽  
Vol 38 (10A) ◽  
pp. 1522-1530
Author(s):  
Rawnaq S. Mahdi ◽  
Aseel B. AL-Zubidi ◽  
Hassan N. Hashim
Keyword(s):  
Mechanical Properties ◽  
Thermal Conductivity ◽  
Compressive Strength ◽  
Water Absorption ◽  
Structural Properties ◽  
Mechanical Milling ◽  
Cement Mortar ◽  
Cement Mortars

This work reports on the incorporation of Flint and Kaolin rocks powders in the cement mortar in an attempt to improve its mechanical properties and produce an eco-friendly mortar. Flint and Kaolin powders are prepared by dry mechanical milling. The two powders are added separately to the mortars substituting cement partially. The two powders are found to improve the mechanical properties of the mortars. Hardness and compressive strength are found to increase with the increase of powders constituents in the cement mortars. In addition, the two powders affect water absorption and thermal conductivity of the mortar specimens which are desirable for construction applications. Kaolin is found to have a greater effect on the mechanical properties, water absorption, and thermal conductivity of the mortars than Flint. This behavior is discussed and analyzed based on the compositional and structural properties of the rocks powders.

A Study of Some Mechanical and Physical Properties for Palm Fiber/Polyester Composite

2020 ◽  
Vol 38 (3B) ◽  
pp. 104-114
Author(s):  
Samah M. Hussein
Keyword(s):  
Mechanical Properties ◽  
Thermal Conductivity ◽  
Dielectric Constant ◽  
Date Palm ◽  
Volume Fraction ◽  
Unsaturated Polyester ◽  
Dielectric Strength ◽  
Palm Fiber ◽  
Mechanical And Physical Properties ◽  
Polyester Composite

This research has been done by reinforcing the matrix (unsaturated polyester) resin with natural material (date palm fiber (DPF)). The fibers were exposure to alkali treatment before reinforcement. The samples have been prepared by using hand lay-up technique with fiber volume fraction of (10%, 20% and 30%). After preparation of the mechanical and physical properties have been studied such as, compression, flexural, impact strength, thermal conductivity, Dielectric constant and dielectric strength. The polyester composite reinforced with date palm fiber at volume fraction (10% and 20%) has good mechanical properties rather than pure unsaturated polyester material, while the composite reinforced with 30% Vf present poor mechanical properties. Thermal conductivity results indicated insulator composite behavior. The effect of present fiber polar group induces of decreasing in dielectric strength, and increasing dielectric constant. The reinforcement composite 20% Vf showed the best results in mechanical, thermal and electrical properties.

Structure and properties of compact articles from high-alloyed iron powder with adding of boron nitride

2020 ◽  
pp. 39-48
Author(s):  
B. O. Bolshakov ◽  
◽  
R. F. Galiakbarov ◽  
A. M. Smyslov ◽  
◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Boron Nitride ◽  
Grain Boundary ◽  
Bending Strength ◽  
Physical And Mechanical Properties ◽  
Operating Conditions ◽  
Structure And Properties ◽  
Steam Turbines ◽  
Friction Forces ◽  
Wide Range

The results of the research of structure and properties of a composite compact from 13 Cr – 2 Мо and BN powders depending on the concentration of boron nitride are provided. It is shown that adding boron nitride in an amount of more than 2% by weight of the charge mixture leads to the formation of extended grain boundary porosity and finely dispersed BN layers in the structure, which provides a high level of wearing properties of the material. The effect of boron nitride concentration on physical and mechanical properties is determined. It was found that the introduction of a small amount of BN (up to 2 % by weight) into the compacts leads to an increase in plasticity, bending strength, and toughness by reducing the friction forces between the metal powder particles during pressing and a more complete grain boundary diffusion process during sintering. The formation of a regulated structure-phase composition of powder compacts of 13 Cr – 2 Mо – BN when the content of boron nitride changes in them allows us to provide the specified physical and mechanical properties in a wide range. The obtained results of studies of the physical and mechanical characteristics of the developed material allow us to reasonably choose the necessary composition of the powder compact for sealing structures of the flow part of steam turbines, depending on their operating conditions.

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