Thermal diffusivity, specific heat, thermal conductivity, coefficient of thermal expansion, and refractive-index change with temperature in AgGaSe_2

2005 ◽  
Vol 44 (13) ◽  
pp. 2673 ◽  
Author(s):  
R. L. Aggarwal ◽  
T. Y. Fan
Keyword(s):  
Thermal Conductivity ◽  
Refractive Index ◽  
Thermal Expansion ◽  
Thermal Diffusivity ◽  
Specific Heat ◽  
Thermal Conductivity Coefficient ◽  
Coefficient Of Thermal Expansion ◽  
Refractive Index Change ◽  
Index Change

Effects of Particle Size on Microstructures and Properties of Si/Al Composites

2013 ◽  
Vol 873 ◽  
pp. 361-365 ◽  
Author(s):  
Wei Chen Zhai ◽  
Zhao Hui Zhang ◽  
Fu Chi Wang ◽  
Shu Kui Li
Keyword(s):  
Thermal Conductivity ◽  
Particle Size ◽  
Thermal Expansion ◽  
Flexural Strength ◽  
Spark Plasma Sintering ◽  
Thermal Conductivity Coefficient ◽  
Coefficient Of Thermal Expansion ◽  
High Strength ◽  
Plasma Sintering ◽  
Spark Plasma

Si/Al composites with different Si particle sizes were fabricated using spark plasma sintering process for electronic packaging. The density, thermal conductivity, coefficient of thermal expansion and flexural strength of the composites were investigated. Effect of Si particle size on structure and properties of the Si/Al composites were studied. The results showed that the Si/Al composites synthesized by spark plasma sintering were composed of Si and Al. Al was uniformly distributed among the Si phase, leading to a high thermal conductivity (>120 W/m·k). The relative density of the Si/Al composites decreased with increasing Si particle size. Small Si particle size produced small grains, leading to a low coefficient of thermal expansion and a high strength. There is an optimal matching among the thermal conductivity, coefficient of thermal expansion and flexural strength when the Si particle size was 44 um.

scholarly journals Thermal Properties of Bayfol® HX200 Photopolymer

Materials ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 5498
Author(s):  
Pierre-Alexandre Blanche ◽  
Adoum H. Mahamat ◽  
Emmanuel Buoye
Keyword(s):  
Refractive Index ◽  
Thermal Properties ◽  
Coefficient Of Thermal Expansion ◽  
Uv Light ◽  
Refractive Index Change ◽  
Visible Region ◽  
Wave Theory ◽  
Industrial Applications ◽  
Holographic Recording ◽  
Index Change

Bayfol® HX200 photopolymer is a holographic recording material used in a variety of applications such as a holographic combiner for a heads-up display and augmented reality, dispersive grating for spectrometers, and notch filters for Raman spectroscopy. For these systems, the thermal properties of the holographic material are extremely important to consider since temperature can affect the diffraction efficiency of the hologram as well as its spectral bandwidth and diffraction angle. These thermal variations are a consequence of the distance and geometry change of the diffraction Bragg planes recorded inside the material. Because temperatures can vary by a large margin in industrial applications (e.g., automotive industry standards require withstanding temperature up to 125°C), it is also essential to know at which temperature the material starts to be affected by permanent damage if the temperature is raised too high. Using thermogravimetric analysis, as well as spectral measurement on samples with and without hologram, we measured that the Bayfol® HX200 material does not suffer from any permanent thermal degradation below 160°C. From that point, a further increase in temperature induces a decrease in transmission throughout the entire visible region of the spectrum, leading to a reduced transmission for an original 82% down to 27% (including Fresnel reflection). We measured the refractive index change over the temperature range from 24°C to 100°C. Linear interpolation give a slope 4.5×10−4K−1 for unexposed film, with the extrapolated refractive index at 0°C equal to n0=1.51. This refractive index change decreases to 3×10−4K−1 when the material is fully cured with UV light, with a 0°C refractive index equal to n0=1.495. Spectral properties of a reflection hologram recorded at 532 nm was measured from 23°C to 171°C. A consistent 10 nm spectral shift increase was observed for the diffraction peak wavelength when the temperature reaches 171°C. From these spectral measurements, we calculated a coefficient of thermal expansion (CTE) of 384×10−6K−1 by using the coupled wave theory in order to determine the increase of the Bragg plane spacing with temperature.

Mechanical Passive Compensation for Athermalisation Design of Infrared Optical System

2013 ◽  
Vol 552 ◽  
pp. 93-96
Author(s):  
Zhi Zhang ◽  
Zhao Hui Zhang ◽  
Zhe Yuan Fan ◽  
Aqi Yan ◽  
Jian Zhang ◽  
...  
Keyword(s):  
Refractive Index ◽  
Thermal Expansion ◽  
Optical System ◽  
Temperature Compensation ◽  
Refractive Index Change ◽  
Index Change ◽  
Aerospace Application ◽  
Temperature Range ◽  
Passive Compensation

Optical equipments especially those for aerospace application are expected to work over a wide temperature range. The change of temperature could cause the refractive index change of infrared glass elements. Furthermore, it would lead to the defocus of the image surface and the performance degradation, so the method of temperature compensation must be adopted, which could make sure that optical system would adapt to the change of ambient temperature. A method of temperature compensation with mechanical passive compensation is briefly described, and an example is also given. The quality of image could be optimized through mechanical passive compensation,depending on the differences of metal and non-metallic thermal expansion coefficient. The results show that the optical system works stablely in the designed temperature range. It is of great importance to the athermalisation design of infrared optical system.

Thermal Characterization of Carbon-Carbon Composites

2011 ◽  
Author(s):  
Messiha Saad ◽  
Darryl Baker ◽  
Rhys Reaves
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Thermal Diffusivity ◽  
Specific Heat ◽  
Critical Role ◽  
Carbon Composite ◽  
Flash Method ◽  
Carbon Composites ◽  
Energy Storage Devices ◽  
Graphitized Carbon

Thermal properties of materials such as specific heat, thermal diffusivity, and thermal conductivity are very important in the engineering design process and analysis of aerospace vehicles as well as space systems. These properties are also important in power generation, transportation, and energy storage devices including fuel cells and solar cells. Thermal conductivity plays a critical role in the performance of materials in high temperature applications. Thermal conductivity is the property that determines the working temperature levels of the material, and it is an important parameter in problems involving heat transfer and thermal structures. The objective of this research is to develop thermal properties data base for carbon-carbon and graphitized carbon-carbon composite materials. The carbon-carbon composites tested were produced by the Resin Transfer Molding (RTM) process using T300 2-D carbon fabric and Primaset PT-30 cyanate ester. The graphitized carbon-carbon composite was heat treated to 2500°C. The flash method was used to measure the thermal diffusivity of the materials; this method is based on America Society for Testing and Materials, ASTM E1461 standard. In addition, the differential scanning calorimeter was used in accordance with the ASTM E1269 standard to determine the specific heat. The thermal conductivity was determined using the measured values of their thermal diffusivity, specific heat, and the density of the materials.

scholarly journals Critical angle reflection imaging for quantification of molecular interactions on glass surface

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Guangzhong Ma ◽  
Runli Liang ◽  
Zijian Wan ◽  
Shaopeng Wang
Keyword(s):  
Refractive Index ◽  
Small Molecule ◽  
Molecular Interactions ◽  
Glass Surface ◽  
Critical Angle ◽  
Dynamic Range ◽  
Refractive Index Change ◽  
Label Free ◽  
Index Change ◽  
Sensing Range

AbstractQuantification of molecular interactions on a surface is typically achieved via label-free techniques such as surface plasmon resonance (SPR). The sensitivity of SPR originates from the characteristic that the SPR angle is sensitive to the surface refractive index change. Analogously, in another interfacial optical phenomenon, total internal reflection, the critical angle is also refractive index dependent. Therefore, surface refractive index change can also be quantified by measuring the reflectivity near the critical angle. Based on this concept, we develop a method called critical angle reflection (CAR) imaging to quantify molecular interactions on glass surface. CAR imaging can be performed on SPR imaging setups. Through a side-by-side comparison, we show that CAR is capable of most molecular interaction measurements that SPR performs, including proteins, nucleic acids and cell-based detections. In addition, we show that CAR can detect small molecule bindings and intracellular signals beyond SPR sensing range. CAR exhibits several distinct characteristics, including tunable sensitivity and dynamic range, deeper vertical sensing range, fluorescence compatibility, broader wavelength and polarization of light selection, and glass surface chemistry. We anticipate CAR can expand SPR′s capability in small molecule detection, whole cell-based detection, simultaneous fluorescence imaging, and broader conjugation chemistry.

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