Negative axial thermal expansion coefficient of carbon nanotubes: Experimental determination based on measurements of coefficient of thermal expansion for aligned carbon nanotube reinforced epoxy composites

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.

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

MRS Proceedings ◽

10.1557/proc-369-325 ◽

1994 ◽

Vol 369 ◽

Cited By ~ 1

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.

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High Temperature Stability of Zirconium Tungstate

Materials Science Forum ◽

10.4028/www.scientific.net/msf.993.771 ◽

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.

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

Journal of Nanoscience and Nanotechnology ◽

10.1166/jnn.2021.19262 ◽

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.

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