scholarly journals THE INFLUENCE OF MORTAR MICROSTRUCTURE ON ITS THERMAL EXPANSION COEFFICIENT

2003 ◽  
Vol 9 (1) ◽  
pp. 45-51
Author(s):  
Darius Zabulionis ◽  
Gediminas Marčiukaitis
Keyword(s):  
Thermal Expansion ◽  
Bulk Modulus ◽  
Thermal Expansion Coefficient ◽  
Expansion Coefficient ◽  
Composite Structure ◽  
Parametric Study ◽  
Coefficient Of Thermal Expansion ◽  
Thermal Strain ◽  
Interfacial Transition Zone ◽  
Aggregate Fractions

Thermal strain is one of the factors causing additional stresses in a composite structure. It is necessary to calculate the coefficient of thermal expansion in evaluating thermal strains. According to the research, concrete is a material consisting of three phases: aggregate, interfacial transition zone (ITZ) and cement paste. The article presents the technique which enables the estimation of the thermal expansion coefficient of the mortar consisting of various aggregate fractions and covered with ITZ layer. A parametric study of various ITZ layer characteristics influencing the coefficient of thermal expansion has been carried out in the present paper. It has been determined that dry mortar or concrete could be treated as a material consisting of two components. While evaluating moist mortar or concrete it is necessary to take into account the depth of the ITZ the bulk modulus and the coefficient of thermal expansion.

Equation of State of α-Al2O3 (Corundum) from Quasi-Harmonic Atomistic Simulations

1998 ◽  
Vol 54 (6) ◽  
pp. 741-749 ◽  
Author(s):  
M. Catti ◽  
A. Pavese
Keyword(s):  
Thermal Expansion ◽  
Bulk Modulus ◽  
Thermal Expansion Coefficient ◽  
Expansion Coefficient ◽  
Interatomic Potential ◽  
Unit Cell ◽  
Atomistic Simulations ◽  
Ambient Conditions ◽  
Thermal Dependence ◽  
Α Al2o3

A two-body interatomic potential function, including fractional atomic charges and a shell model for oxygen, and supplemented by an O—Al—O bond-angle energy term, was fitted to the structural, elastic and vibrational properties of \alpha-Al2O3, corundum, at ambient conditions. Full quasi-harmonic calculations were then carried out on a p,T grid of 54 points in the domain 0–40 GPa and 300–1700 K. The crystal structure was equilibrated at each point, taking into account the anisotropy of vibrational pressure and the thermal dependence of elastic constants, so as to obtain unit-cell edges, atomic coordinates, bulk modulus, thermal expansion coefficient and other thermodynamic properties. Polynomial approximations were developed to represent the p,T dependence of these quantities. Comparison with experimental results for the separate p (T = 300 K) and T (p = 0) behaviours shows very good agreement, with average deviations of 0.1% for the unit-cell volume and 6% for the thermal expansion coefficient. The coupled p,T dependence of the properties of corundum is predicted to be very small for the bulk modulus (\partial^2K_T/\partial p\partial T=8.4\times10^{-5} K−1), but not at all negligible for the volume [(1/V)\partial^2V/\partial p\partial T in the range −1.2 to −7.5 × 10−7 GPa−1 K−1 over the p,T domain explored].

Bimaterial Micro-Structured Annulus With Zero Thermal Expansion Coefficient

2017 ◽  
Author(s):  
Yan Xie ◽  
Dengfeng Lu ◽  
Jingjun Yu
Keyword(s):  
Thermal Expansion ◽  
Thermal Expansion Coefficient ◽  
Expansion Coefficient ◽  
High Speed ◽  
Thermal Strain ◽  
Geometric Constraints ◽  
Geometrical Parameters ◽  
Thermal Behaviors ◽  
Lattice Cell ◽  
Triangular Cell

This paper mainly concentrates on the design and analysis of the annulus with zero thermal expansion coefficient (ZTE) aiming to solve the heat generation and deformation in high speed bearing. First, a fork-like lattice cell inspired by the basic triangular cell is put forward and further applied to construct an annulus. The stretch-dominated lattice cell utilizes the Poisson’s contraction effect to achieve the tailorable thermal expansion coefficient (CTE). The thermal behaviors differences between the continuous interfaces and lattice cells will lead to the internal stress. Thus, the CTE of the annulus consisting of the lattice cell can be tailored to zero even negative values through the offset between the thermal-strain and force-strain. Then a theoretical model is established with some appropriate assumptions to reveal the quantitative relations among the geometrical parameters, material properties and equivalent CTEs thoroughly. The prerequisites for realizing a zero CTE are further derived in terms of material limitations and geometric constraints. Finally, FEA method is implemented to verify and analyze the thermal behaviors of annulus. The proposed annulus design characterized by the CTE tunability, structure efficiency and continuous interfaces is hopefully to be applied in the high speed bearings, adapters between the shaft and collar and fastener screws.

Thermal Expansion Coefficient of Ni Base Alloy Composite Coating Containing Spheroidal Ceramic Grains

2010 ◽  
Vol 44-47 ◽  
pp. 2148-2151
Author(s):  
Xie Quan Liu ◽  
Xin Hua Ni ◽  
Shu Qin Zhang ◽  
Wan Heng He
Keyword(s):  
Thermal Expansion ◽  
Thermal Expansion Coefficient ◽  
Composite Coating ◽  
Expansion Coefficient ◽  
Base Alloy ◽  
Thermal Strain ◽  
Phase Cell ◽  
Alloy Composite ◽  
Random Orientation ◽  
Two Phase

Ni base alloy composite coating containing spheroidal ceramic grains can be fabricated by a vacuum fusion sintering method. Composite coating was mainly composed of Ni base alloy and spheroidal ceramic grains with random orientation. The three-phase model is used to determine the thermal expansion coefficient of the composite coating. First, Eshebly-Mori-Tanaka method was used to determine thermal disturbance strain in two-phase cell aroused thermal inconsistency. Then, average thermal strain in the two-phase cell aroused by thermal inconsistency is gained by the means of volume equilibration. The two-phase cell is transverse isotropy and has two independent thermal expansion coefficients. Finely, based on mean strain of Ni base alloy ceramic composite coating containing spheroidal ceramic grains, the effective thermal expansion coefficient of the composite coating is obtained by considering random orientation of two-phase cells. Ni base alloy composite coating containing spheroidal ceramic grains is isotropy and has one independent thermal expansion coefficient.

Fabrication and Characterization of Low Thermal Expansion Cordierite/Spodumene/Mullite Composite Ceramic for Cookware

2018 ◽  
Vol 766 ◽  
pp. 276-281
Author(s):  
Pranee Junlar ◽  
Thanakorn Wasanapiarnpong ◽  
Lada Punsukmtana ◽  
Noppasint Jiraborvornpongsa
Keyword(s):  
Thermal Expansion ◽  
Water Absorption ◽  
Thermal Expansion Coefficient ◽  
Expansion Coefficient ◽  
Coefficient Of Thermal Expansion ◽  
Slip Casting ◽  
Ceramic Composites ◽  
Modulus Of Rupture ◽  
Mullite Phase ◽  
Low Thermal Expansion

Ceramic cookware can be taken a direct flame or stove top for the duration without damage. The selected materials must have low thermal expansion coefficient, high strength, low water absorption and high thermal shock resistance, reasonable in cost and easy to be produced. Cordierite and spodumene composite has been interested for ceramic cookware due to their fitted properties. In previous work, study in the cordierite-spodumene composite with low thermal expansion coefficient of 2.60 x 10-6 /°C when sintered at 1250 oC with a ratio of spodumene 60 wt% and cordierite 40 wt% can withstand the pot shape samples. However, the sample showed relatively high water absorption and low strength which was not appropriate for using in this application. In this research, mullite is added in the formula to improve strength and densification of ceramic composites. Spodumene, ball clay, calcined talc and calcined alumina are used as starting raw materials and formed by slip casting. All samples are sintered in a temperature range from 1250-1275 °C in an electric furnace. Water absorption and bulk density were tested by Archimedes method, modulus of rupture was tested by the three-point bending method, microstructure were investigated by SEM and the coefficient of thermal expansion was measured by dilatometer. It was found that the mullite phase was investigated when adding mullite more than 30 wt% in cordierite-spodumene composite.

Calculation of Defect Formation Energy from the Thermal Expansion Data for Lead Fluoride

1994 ◽  
Vol 369 ◽  
Author(s):  
Brenda J. Schuler ◽  
T. S. Aurora ◽  
D. O. Pederson ◽  
S. M. Day
Keyword(s):  
Thermal Expansion ◽  
Thermal Expansion Coefficient ◽  
Expansion Coefficient ◽  
Formation Energy ◽  
Defect Formation ◽  
Coefficient Of Thermal Expansion ◽  
Linear Thermal Expansion ◽  
Lead Fluoride ◽  
Defect Formation Energy ◽  
Thermal Expansion Data

AbstractLead fluoride is a superionic conductor with the fluorite structure. Results of the measurement of linear thermal expansion of lead fluoride (reported earlier in literature) showed a large increase in the thermal expansion coefficient near 700 K where the ionic conductivity has been shown to exhibit a sharp increase. It is believed that thermally-generated defects in a crystal lattice affect the thermal expansion coefficient. This idea was applied in the present analysis to calculate the defect formation energy (Ef) by using the literature values of the coefficient of thermal expansion. It was assumed that the thermal expansion in excess of that produced due to the lattice anharmonicity (δ∝) is proportional to the concentration of defects (n). With this assumption, one may write: δ∝ = c nº exp(-Ef/kT), where c is a constant. For lead fluoride, a plot of ln(δ∝) versus (l/T) yielded Ef = 0.56 eV which is lower than the literature values. The assumptions in this analysis and the discrepancy in the result are discussed.

High Temperature Stability of Zirconium Tungstate

2020 ◽  
Vol 993 ◽  
pp. 771-775
Author(s):  
Ping Zhai ◽  
Xiao Feng Duan ◽  
Da Qian Chen
Keyword(s):  
Thermal Expansion ◽  
High Temperature ◽  
Thermal Expansion Coefficient ◽  
Expansion Coefficient ◽  
Solid Phase ◽  
Coefficient Of Thermal Expansion ◽  
Negative Thermal Expansion ◽  
Tungstic Acid ◽  
High Temperature Stability ◽  
Zirconium Tungstate

In this paper, zirconium tungstate ceramic with negative thermal expansion coefficients was prepared from zirconium oxide and tungstic acid by solid phase synthesis and high temperature quenching technique with a sintering temperature of 1200 °C. The phase structure of the material was determined by X ray and the thermal expansion coefficient was measured by dilatometer, while the TG-DTA analysis of the prepared material was also carried out. The results showed that zirconium tungstate with high purity could be obtained by rapid chilled while fired at 1200 °C. The coefficient of thermal expansion at 300 °C was minus 8.5413 × 10-6K-1, which is identical with the theoretical value. The thermal expansion coefficient of the material was negative fired lower than 750 °C, while it was positive fired higher than 750 °C, and this indicates that the decomposition temperature of zirconium tungstate is about 750 °C.

Thermal Characteristics of Cu Matrix-SiC Filler Composite Using Nano-Sized Cu Powder

2021 ◽  
Vol 21 (9) ◽  
pp. 4964-4967
Author(s):  
Bok-Hyun Oh ◽  
Choong-Hwan Jung ◽  
Heon Kong ◽  
Sang-Jin Lee
Keyword(s):  
Thermal Conductivity ◽  
Thermal Expansion ◽  
Thermal Expansion Coefficient ◽  
Expansion Coefficient ◽  
Coefficient Of Thermal Expansion ◽  
Liquid Phase Sintering ◽  
High Thermal Conductivity ◽  
Ceramic Filter ◽  
Ceramic Filler ◽  
Significant Difference

A Cu metal-ceramic filter composite with high thermal conductivity and a suitable thermal expansion coefficient was designed to be applied to high performance heat dissipation materials. The purpose of using the ceramic filler was to decrease the high coefficient of thermal expansion of Cu matrix utilizing the high thermal conductivity of Cu. In this study, a SiC ceramic filler powder was added to the Cu sol including Zn as a liquid phase sintering agent. The final complex was produced by applying a PVB polymer to prepare a homogeneous precursor followed by sintering in a reducing atmosphere. The pressureless sintered composite showed lower thermal conductivity than pure bulk Cu due to the some residual pores. In the case of the Cu–SiC composite in which 10 wt% of SiC filler was added, it showed a thermal conductivity of 100 W/m·°C and a thermal expansion coefficient of 13.3×10−6/°C. The thermal conductivity showed some difference from the theoretical calculated value due to the pores in the composite, but the thermal expansion coefficient did not show a significant difference.

SIZE AND TEMPERATURE EFFECT ON THERMAL EXPANSION COEFFICIENT AND LATTICE PARAMETER OF NANOMATERIALS

2013 ◽  
Vol 27 (25) ◽  
pp. 1350180 ◽  
Author(s):  
RAGHUVESH KUMAR ◽  
GEETA SHARMA ◽  
MUNISH KUMAR
Keyword(s):  
Experimental Data ◽  
Thermal Expansion ◽  
Temperature Dependence ◽  
Thermal Expansion Coefficient ◽  
Expansion Coefficient ◽  
Size Dependence ◽  
Coefficient Of Thermal Expansion ◽  
Lattice Parameter ◽  
Model Predictions ◽  
Good Agreement

A simple theoretical model is developed to study the effect of size and temperature on the coefficient of thermal expansion and lattice parameter of nanomaterials. We have studied the size dependence of thermal expansion coefficient of Pb , Ag and Zn in different shape viz. spherical, nanowire and nanofilm. A good agreement between theory and available experimental data confirmed the model predictions. We have used these results to study the temperature dependence of lattice parameter for different size and also included the results of bulk materials. The temperature dependence of lattice parameter of Zn nanowire and Ag nanowire are found to present a good agreement with the experimental data. We have also computed the temperature and size dependence of lattice parameter of Se and Pb for different shape viz. spherical, nanowire and nanofilm. The results are discussed in the light of recent research on nanomaterials.

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