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.

Investigation of the Dilation of Epoxy with Negative Thermal Expansion Fillers

2010 ◽  
Vol 44-47 ◽  
pp. 2950-2953
Author(s):  
Sheng Yi Chang ◽  
Hsi Hsun Tsai ◽  
Sheng Ching Wang
Keyword(s):  
Thermal Expansion ◽  
Coefficient Of Thermal Expansion ◽  
Ceramic Powder ◽  
Negative Thermal Expansion ◽  
Negative Coefficient ◽  
Silica Powder ◽  
Silica Filler ◽  
The One ◽  
Silicon Based ◽  
Electronic Elements

The bonding glue is well used in packaging of the opto-electronic elements. The light paths of the elements are aligned accurately before bonding, the coefficient of thermal expansion of bonding glue is much more large than the one of silicon based optoelectronic elements, the light paths of the elements are thus misalignment after the bonding. The silica filler is usually mixed into the bonding glue for lowering the coefficient of thermal expansion. In this paper, the ceramic powder of the ZrW2O8 with negative coefficient of thermal expansion is thus mixed the commercial bonding glue for deriving of the extra low dilation adhesion. The thermal expansion of the composite bonding glue with negative coefficient of thermal expansion fillers is measured accurately to compare with the filler of silica powder. The results show that a composite glue with the very low coefficient of thermal expansion is therefore acquired for packaging of optoelectronic elements.

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.

Very high or close to zero thermal expansion by the variation of the Sr/Ba ratio in Ba1−xSrxZn2Si2O7 – solid solutions

2016 ◽  
Vol 45 (11) ◽  
pp. 4888-4895 ◽  
Author(s):  
Christian Thieme ◽  
Christian Rüssel
Keyword(s):  
Thermal Expansion ◽  
Solid Solutions ◽  
Coefficient Of Thermal Expansion ◽  
Positive Coefficient ◽  
Negative Coefficient ◽  
Very High

The compound BaZn2Si2O7 shows a highly positive coefficient of thermal expansion, while replacement of more than 10% of Ba2+ by Sr2+ results in a negative coefficient of thermal expansion.

The Stabilization of Central Wavelength of Fiber Bragg Gratings by Thermal Contraction Effect of Kovar Substrate

2010 ◽  
Vol 160-162 ◽  
pp. 1270-1275
Author(s):  
Sheng Ching Wang ◽  
Hsi Hsun Tsai
Keyword(s):  
Communication Network ◽  
Thermal Expansion ◽  
Optical Fiber ◽  
Ambient Temperature ◽  
Coefficient Of Thermal Expansion ◽  
Fiber Bragg Gratings ◽  
Bragg Gratings ◽  
Tension Force ◽  
Negative Coefficient ◽  
Central Wavelength

A stabilized laser is essential for optical fiber communication network. One of the passive technique for stabilization of central wavelength of laser is based on the application of fiber Bragg gratings. Due to the positive coefficient of thermal expansion of optical fiber, the Bragg gratings within the fiber written by excimer laser gives about 0.01nm/oC shift on the central wavelength respect to the ambient temperature which leads serious problem in the communication network. Since both the temperature and tension force are linearly proportional to the central wavelength of fiber Bragg gratings. A feasible approach to derive the wavelength stabilization is to decrease the tension force of fiber Bragg gratings respect to the increase of ambient temperature. In this paper, a Kovar substrate with negative coefficient of thermal expansion is used to decrease the tension force while the environmental temperature increases. The experimental results show that the coefficient of thermal expansion of the Kovar substrate is negative and linearly proportional to the temperature. Thus, this Kovar substrate differing from the constant negative coefficient of thermal expansion ceramic substrate induces about 0.0085nm/C on the fiber Bragg gratings, which shows the well application of this Kovar for athermalization of the fiber Bragg gratings in optical communication system.

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.

Atomic and Electronic Structure of Zinc and Copper Pyrovanadates with Negative Thermal Expansion

2010 ◽  
Vol 63 ◽  
pp. 358-363 ◽  
Author(s):  
Tatiana Krasnenko ◽  
Nadezhda Medvedeva ◽  
Vitalii Bamburov
Keyword(s):  
Thermal Expansion ◽  
Thermal Deformation ◽  
Structural Parameters ◽  
Negative Thermal Expansion ◽  
Structural Data ◽  
Interband Transitions ◽  
Negative Coefficient ◽  
Total Energies ◽  
Zigzag Shape ◽  
Atomic And Electronic Structure

Zinc and copper pyrovanadates are promising materials for micro- and optoelectronics due to their negative coefficient of volume thermal expansion (NTE). Besides, solid solutions on the base of these compounds can be used to obtain grade materials with variable thermal coefficients. Thermal deformation of both Zn2V2O7 and Cu2V2O7 structures was studied. According to the structural data, NTE of these substances is provided by the zigzag shape of zinc (copper) chains alongside with stable distances between layers. The structural and electronic characteristics depending on temperature were studied for α-Zn2V2O7 and α-Cu2V2O7 by using the first principle method. Our results demonstrate that the lowest total energies corresponds to the structural parameters at 400° C and 200° C for α-Zn2V2O7 and α-Cu2V2O7, respectively. We predict that α- Zn2V2O7 is a semiconductor with the band gap of 1,5 эВ and the bottom of conduction band is determined by the vanadium 3d states with small addition of antibonding oxygen 2р-states. For α- Cu2V2O7, the lowest interband transitions correspond to energy of 1,6 eV and involve also the O2p and V 3d states.

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