scholarly journals Auxetic-Inspired Honeycomb Macrostructures With Anomalous Tailormade Thermal Expansion Properties Including “Negative” Heat-Shrinking Characteristics

2021 ◽  
Vol 8 ◽  
Author(s):  
James N. Grima-Cornish ◽  
Daphne Attard ◽  
Kenneth E. Evans ◽  
Joseph N. Grima
Keyword(s):  
Thermal Expansion ◽  
Coefficient Of Thermal Expansion ◽  
Negative Thermal Expansion ◽  
Geometric Parameters ◽  
Anomalous Property ◽  
Plane Direction ◽  
Anomalous Thermal Expansion

Negative thermal expansion (NTE) materials and structures exhibit the anomalous property of shrinking rather than expanding when heated. This work examines the potential of multi-material planar re-entrant and non-re-entrant honeycombs to exhibit anomalous thermal expansion properties. Expressions for the coefficient of thermal expansion as a function of the geometric parameters and intrinsic thermal expansion properties were derived for any in-plane direction. It was shown that re-entrant honeycombs, a metamaterial which is well known for its auxetic characteristics, can be made to exhibit NTE in specific directions when constructed from conventional positive thermal expansion (PTE) materials, provided that the slanting ligaments expand more than the vertical ligaments when heated and that the geometry is amenable. Conversely, it was shown that the construction of such honeycombs from NTE components will not necessarily result in a system which exhibits NTE in all directions. Furthermore, conditions which result in honeycombs demonstrating zero thermal expansion (ZTE) coefficients in specific directions were also explored.

scholarly journals Thermal Expansion Behavior in the A2M3O12 Family of Materials

Solids ◽  
2021 ◽  
Vol 2 (1) ◽  
pp. 87-107
Author(s):  
Hongfei Liu ◽  
Weikang Sun ◽  
Zhiping Zhang ◽  
La’Nese Lovings ◽  
Cora Lind
Keyword(s):  
Thermal Expansion ◽  
Physical Properties ◽  
Coefficient Of Thermal Expansion ◽  
Negative Thermal Expansion ◽  
Future Studies ◽  
The Past ◽  
Expansion Behavior ◽  
Wide Range ◽  
Anomalous Thermal Expansion ◽  
Published Research

Over the past several decades, research on anomalous thermal expansion materials has been rapidly growing, and increasing numbers of compounds exhibiting negative thermal expansion (NTE) have been reported. In particular, compounds with formula A2M3O12 have attracted considerable attention. A2M3O12 family materials offer a wide range of possible compositions due to the chemical flexibility of the A and M sites. According to published research, more than half of them possess NTE properties. This paper reviews the range of physical properties displayed by materials in the A2M3O12 family. Research on improving material imperfections and controlling the coefficient of thermal expansion in the A2M3O12 family are systematically summarized. Finally, challenges and questions about the developments of these A2M3O12 NTE compounds in future studies are also discussed.

scholarly journals A Proposal for a Composite with Temperature-Independent Thermophysical Properties: HfV2–HfV2O7

Materials ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 5021
Author(s):  
Philipp Keuter ◽  
Anna L. Ravensburg ◽  
Marcus Hans ◽  
Soheil Karimi Aghda ◽  
Damian M. Holzapfel ◽  
...  
Keyword(s):  
Thermal Expansion ◽  
Temperature Coefficient ◽  
Thermophysical Properties ◽  
Coefficient Of Thermal Expansion ◽  
Negative Thermal Expansion ◽  
Phase Fraction ◽  
Formation Temperature ◽  
Oxygen Mobility ◽  
Zero Temperature ◽  
Coefficient Of Elasticity

The HfV2–HfV2O7 composite is proposed as a material with potentially temperature-independent thermophysical properties due to the combination of anomalously increasing thermoelastic constants of HfV2 with the negative thermal expansion of HfV2O7. Based on literature data, the coexistence of both a near-zero temperature coefficient of elasticity and a coefficient of thermal expansion is suggested for a composite with a phase fraction of approximately 30 vol.% HfV2 and 70 vol.% HfV2O7. To produce HfV2–HfV2O7 composites, two synthesis pathways were investigated: (1) annealing of sputtered HfV2 films in air to form HfV2O7 oxide on the surface and (2) sputtering of HfV2O7/HfV2 bilayers. The high oxygen mobility in HfV2 is suggested to inhibit the formation of crystalline HfV2–HfV2O7 composites by annealing HfV2 in air due to oxygen-incorporation-induced amorphization of HfV2. Reducing the formation temperature of crystalline HfV2O7 from 550 °C, as obtained upon annealing, to 300 °C using reactive sputtering enables the synthesis of crystalline bilayered HfV2–HfV2O7.

Effects of Cold Rolling on Microstructure and Anomalous Thermal Expansion Behaviors of Ti-35Nb-2Zr-0.3O Alloy

2017 ◽  
Vol 729 ◽  
pp. 46-50
Author(s):  
Chun Bo Lan ◽  
Yu Wu ◽  
Feng Chen
Keyword(s):  
Thermal Expansion ◽  
Martensitic Transformation ◽  
Cold Rolling ◽  
Texture Evolution ◽  
Rolling Direction ◽  
Negative Thermal Expansion ◽  
Expansion Rate ◽  
Solution Treated ◽  
Treated Sample ◽  
Anomalous Thermal Expansion

Ti-35Nb-2Zr-0.3O (wt.%) alloy was melted under high-purity argon atmosphere in an electric arc furnace, followed by cold rolling. The effects of deformation process on microstructures and thermal expansion behaviors were investigated by OM, XRD and TMA. Results showed that the stress-induced α" martensitic transformation occurs after cold rolling. The solution treated sample exhibits normal thermal expansion along the rolling direction, and the thermal expansion rate increases with the increase of temperature. After cold rolling, thermal expansion behavior is polarized (negative thermal expansion occurs along rolling direction and normal thermal expansion higher than solution treated sample occurs along transverse direction). The thermal expansion rate along rolling direction decreases with the increase of reduction. The 40% cold deformed sample along rolling direction possesses Invar effect in a temperature range from 25°C to 350°C. The anomalous thermal expansion behaviors of cold rolled samples possibly relate to stress-induced α" martensitic transformation and β <110> texture evolution.

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.

scholarly journals Micro-structured medium with large isotropic negative thermal expansion

2019 ◽  
Vol 475 (2232) ◽  
pp. 20190468 ◽  
Author(s):  
Luigi Cabras ◽  
Michele Brun ◽  
Diego Misseroni
Keyword(s):  
Thermal Expansion ◽  
Coefficient Of Thermal Expansion ◽  
Negative Thermal Expansion ◽  
Simple Relation ◽  
Space Structures ◽  
New Class ◽  
Wide Range ◽  
Theoretical Predictions ◽  
Innovative Materials ◽  
New Generation

A challenge in nano- and micro-mechanics is the realization of innovative materials exploiting auxetic behaviour to tailor thermal expansion properties. For this purpose, a new class of micro-structured media possessing an extremely wide range of tunable (positive, negative or even zero) thermal expansion is proposed and analytically and experimentally assessed. For this class of isotropic Mechanical-Auxetic Thermal-Shrinking media, the effective coefficient of thermal expansion is explicitly linked to two microstructural variables via a simple relation, allowing the design with desired values. The theoretical predictions for the negative thermal properties are fully validated by the experimental and numerical outcomes. The simplicity of the proposed structure makes the design useful for the production of a new generation of advanced media, with applications ranging from micromechanical devices to large civil and space structures.

Size and crystal symmetry breaking effects on negative thermal expansion in ScF3 nanostructures

2021 ◽  
Author(s):  
Chunyan Wang ◽  
Dahu Chang ◽  
Junfei Wang ◽  
Qilong Gao ◽  
Yinuo Zhang ◽  
...  
Keyword(s):  
Thermal Expansion ◽  
Symmetry Breaking ◽  
Coefficient Of Thermal Expansion ◽  
Negative Thermal Expansion ◽  
Crystal Symmetry ◽  
Negative Coefficient ◽  
Membrane Vibration

New membrane vibration and surface symmetry breaking effects determine the negative coefficient of thermal expansion at the nanoscale.

scholarly journals Thermally stable and highly efficient red-emitting Eu3+-doped Cs3GdGe3O9 phosphors for WLEDs: non-concentration quenching and negative thermal expansion

2021 ◽  
Vol 10 (1) ◽  
Author(s):  
Peipei Dang ◽  
Guogang Li ◽  
Xiaohan Yun ◽  
Qianqian Zhang ◽  
Dongjie Liu ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Thermal Expansion ◽  
White Light ◽  
Coefficient Of Thermal Expansion ◽  
Internal Quantum Efficiency ◽  
Negative Thermal Expansion ◽  
Concentration Quenching ◽  
Excellent Thermal Stability ◽  
Red Phosphor ◽  
Highly Efficient

AbstractRed phosphor materials play a key role in improving the lighting and backlit display quality of phosphor-converted white light-emitting diodes (pc-WLEDs). However, the development of a red phosphor with simultaneous high efficiency, excellent thermal stability and high colour purity is still a challenge. In this work, unique non-concentration quenching in solid-solution Cs3Gd1 − xGe3O9:xEu3+ (CGGO:xEu3+) (x = 0.1–1.0) phosphors is successfully developed to achieve a highly efficient red-emitting Cs3EuGe3O9 (CEGO) phosphor. Under the optimal 464 nm blue light excitation, CEGO shows a strong red emission at 611 nm with a high colour purity of 95.07% and a high internal quantum efficiency of 94%. Impressively, this red-emitting CEGO phosphor exhibits a better thermal stability at higher temperatures (175–250 °C, >90%) than typical red K2SiF6:Mn4+ and Y2O3:Eu3+ phosphors, and has a remarkable volumetric negative thermal expansion (coefficient of thermal expansion, α = −5.06 × 10−5/°C, 25–250 °C). By employing this red CEGO phosphor, a fabricated pc-WLED emits warm white light with colour coordinates (0.364, 0.383), a high colour rendering index (CRI = 89.7), and a low colour coordinate temperature (CCT = 4508 K). These results indicate that this highly efficient red-emitting phosphor has great potential as a red component for pc-WLEDs, opening a new perspective for developing new phosphor materials.

Zirconium tungstate reinforced cyanate ester composites with enhanced dimensional stability

2009 ◽  
Vol 24 (7) ◽  
pp. 2235-2242 ◽  
Author(s):  
Prashanth Badrinarayanan ◽  
Ben Mac Murray ◽  
Michael R. Kessler
Keyword(s):  
Thermal Expansion ◽  
Dimensional Stability ◽  
Coefficient Of Thermal Expansion ◽  
Negative Thermal Expansion ◽  
Thermomechanical Analysis ◽  
Dynamic Mechanical Properties ◽  
Filler Loading ◽  
Cyanate Ester ◽  
Scanning Calorimetry ◽  
Zirconium Tungstate

Zirconium tungstate (ZrW2O8) is a unique ceramic material characterized by isotropic negative thermal expansion behavior over a wide temperature range. Incorporation of ZrW2O8 is expected to improve the dimensional stability of polymers by reducing the overall coefficient of thermal expansion (CTE). In this work, the thermal and dynamic mechanical properties of a bisphenol E cyanate ester reinforced with various loadings of ZrW2O8 are examined. Thermomechanical analysis indicates that the incorporation of ZrW2O8 results in a decrease in CTE at temperatures above and below the glass transition temperature (Tg) of the neat resin. The dynamic storage moduli of the composites reinforced with ZrW2O8 are found to increase with increasing filler loading. Furthermore, the various phase behaviors exhibited by ZrW2O8 are also examined by differential scanning calorimetry measurements.

New Ti-Alloy with Negative and Zero Thermal Expansion Coefficients

2011 ◽  
Vol 495 ◽  
pp. 62-66 ◽  
Author(s):  
Mohamed Abdel Hady Gepreel
Keyword(s):  
Thermal Expansion ◽  
Thermal Expansion Coefficient ◽  
Expansion Coefficient ◽  
Coefficient Of Thermal Expansion ◽  
Cold Deformation ◽  
Negative Thermal Expansion ◽  
Expansion Factor ◽  
Thermal Expansion Coefficients ◽  
Ti Alloys ◽  
History Of

Most materials expand upon heating due to the anharmonicity of the atomic potential energy. This thermal expansion is one of the intrinsic properties of any material which is very difficult to be controlled. Recently, a negative thermal expansion factor was introduced to those Ti-alloys with high elastic softening when cold deformed. This negative thermal expansion factor is changeable in these types of alloys depending on the alloy composition, degree of cold deformation, and thermal history of the alloy. This change gives a lot of room to control the coefficient of thermal expansion (CTE) of those Ti-alloys to turn from positive though zero to negative values and vice versa. In this paper, the appearance of the NTE factor is discussed and the possible methods to control the final thermal expansion coefficient to achieve a zero thermal expansion coefficient are presented. The unique thermal expansion behavior of the alloys will locate them as an excellent candidate in sensing apparatus and other precious equipments.

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