Investigation of Thermal Properties of Heavily Doped 4H-SiC Crystals by a Picosecond Transient Grating Technique

2009 ◽  
Vol 615-617 ◽  
pp. 319-322
Author(s):  
Patrik Ščajev ◽  
Arunas Kadys ◽  
Kęstutis Jarašiūnas
Keyword(s):  
Thermal Properties ◽  
Thermal Diffusivity ◽  
Picosecond Laser ◽  
Spatial Modulation ◽  
Temperature Dependences ◽  
Carrier Absorption ◽  
Heavily Doped ◽  
Dynamic Grating ◽  
532 Nm ◽  
Picosecond Dynamic

We applied a picosecond dynamic grating technique for investigation of thermal diffusivity, sound velocity, thermo-optic and photoelastic coefficients in heavily doped 4H-SiC substrates. Spatial modulation of thermal properties was achieved by intraband carrier absorption at excitation by an IR picosecond laser pulse (1064 nm) and subsequent carrier thermalisation. Decay of dynamic grating at its various periods and sample temperatures was monitored at 532 nm wavelength. The thermal diffusivity DT = 0.94 cm2/s, thermo-optic coefficient dn/dT = 3.610–5 K-1 and effective photoelastic constant = – 0.10 were determined at 300 K. DT value increased at lower temperatures and saturated below 100 K. Temperature dependences of thermo-optic coefficient and thermal expansion were found in good correlation with heat capacity peculiarities.

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.

Free carrier absorption in heavily doped silicon layers

2004 ◽  
Vol 84 (13) ◽  
pp. 2265-2267 ◽  
Author(s):  
Joerg Isenberg ◽  
Wilhelm Warta
Keyword(s):  
Free Carrier ◽  
Free Carrier Absorption ◽  
Doped Silicon ◽  
Carrier Absorption ◽  
Heavily Doped

Clearance of yellow tattoo ink with a novel 532-nm picosecond laser

2015 ◽  
Vol 47 (4) ◽  
pp. 285-288 ◽  
Author(s):  
Hamad Alabdulrazzaq ◽  
Jeremy A. Brauer ◽  
Yoon-Soo Bae ◽  
Roy G. Geronemus
Keyword(s):  
Picosecond Laser ◽  
532 Nm

Experimental Study on Thermal Properties of Hollow Sphere Structures

2021 ◽  
Vol 407 ◽  
pp. 185-191
Author(s):  
Josef Tomas ◽  
Andreas Öchsner ◽  
Markus Merkel
Keyword(s):  
Thermal Conductivity ◽  
Experimental Study ◽  
Thermal Properties ◽  
Thermal Diffusivity ◽  
Specific Heat ◽  
Hollow Sphere ◽  
Plane Source ◽  
Source Method ◽  
Transient Plane Source ◽  
Transient Plane Source Method

Experimental analyses are performed to determine thermal conductivity, thermal diffusivity and volumetric specific heat with transient plane source method on hollow sphere structures. Single-sided testing is used on different samples and different surfaces. Results dependency on the surface is observed.

scholarly journals Synthesis and Thermal Properties of Cerium-Dysprosium Oxide

2016 ◽  
Vol 61 (2) ◽  
pp. 965-969 ◽  
Author(s):  
M. Mikuśkiewicz ◽  
M. Stopyra ◽  
G. Moskal
Keyword(s):  
Thermal Properties ◽  
Phase Composition ◽  
Thermal Diffusivity ◽  
Solid State ◽  
Cerium Oxide ◽  
Solid State Reaction ◽  
Synthesis And Characterization ◽  
Equimolar Ratio ◽  
Dysprosium Oxide

Abstract The paper presents results of investigation on synthesis and characterization of cerium-dysprosium oxide. The input powders - dysprosium oxide Dy2O3 and cerium oxide CeO2 - were mixed so as to obtain equimolar ratio of cations, milled in alcohol and synthesized via solid state reaction process at 1350°C under 15MPa in vacuum for 2h. The microstructure, phase composition and thermal properties were analyzed. The obtained material was multiphase. Non-stoichiometric compounds were identified. Thermal diffusivity of investigated material decreased in the temperature range of 25-1000°C from 0,71 to 0,45 mm2/s.

scholarly journals Application of sonication and freezing as initial treatments before microwave-vacuum drying of cranberries

2019 ◽  
Vol 2 (22) ◽  
pp. 151-167 ◽  
Author(s):  
Izabela Staniszewska ◽  
Szymon Staszyński ◽  
Magdalena Zielińska
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Thermal Diffusivity ◽  
Physical Properties ◽  
Color Change ◽  
Vacuum Drying ◽  
Drying Time ◽  
Dried Fruits ◽  
Microwave Vacuum Drying ◽  
Drying Kinetic

The aim of study was to determine the influence of sonication and freezing on the kinetic of the microwave-vacuum drying, energy consumption and physical properties of whole cranberries as well as evaluate the applicability of sonication instead of freezing in order to change their physical properties and the drying kinetic of whole cranberries. Microwave-vacuum drying of whole cranberries with/without initial treatments took from 12 ± 1 to 14.5 ± 0.5 minutes. All of treatments did not significantly shorten the drying time of cranberries. However, they increased SMER values even by 31%. Despite of cryogenic freezing, all of treatments significantly increased the values of Dew. Sonication combined with drying allowed to obtain dried berries characterized by the lowest cohesiveness (0.19±0.02), springiness (0.62±0.02) and chewiness (3.4±0.8 N), while cryogenic freezing combined with drying allowed to obtain dried fruits characterized by highest springiness (0.75±0.03) and low chewiness (3.3±0.5 N). The highest lightness (32.2±0.7), redness (32.6±0.8), and yellowness (11.1±0.7) were found for fruits subjected to initial convective freezing before drying. The efficiency of sonication in color change was comparable to cryogenic freezing and much lower than convective freezing. All of initial treatments increased such thermal properties of dried cranberries as thermal conductivity and thermal diffusivity.

scholarly journals Developments of Space Debris Laser Ranging Technology Including the Applications of Picosecond Lasers

2021 ◽  
Vol 11 (21) ◽  
pp. 10080
Author(s):  
Haifeng Zhang ◽  
Mingliang Long ◽  
Huarong Deng ◽  
Shaoyu Cheng ◽  
Zhibo Wu ◽  
...  
Keyword(s):  
Space Debris ◽  
New Technologies ◽  
Pulse Repetition Frequency ◽  
Average Power ◽  
Picosecond Laser ◽  
Laser Ranging ◽  
Telescope Array ◽  
High Pulse ◽  
First Time ◽  
532 Nm

Debris laser ranging (DLR) is receiving considerable attention as an accurate and effective method of determining and predicting the orbits of space debris. This paper reports some technologies of DLR, such as the high pulse repetition frequency (PRF) laser pulse, large-aperture telescope, telescope array, multi-static stations receiving signals. DLR with a picosecond laser at the Shanghai Astronomical Observatory is also presented. A few hundred laps of space debris laser-ranging measurements have been made. A double-pulse picosecond laser with an average power of 4.2 W, a PRF of 1 kHz, and a wavelength of 532 nm has been implemented successfully in DLR, it’s the first time that DLR technology has reached a ranging precision at the sub-decimeter level. In addition, the characteristics of the picosecond-pulse-width laser transmission with the advantages of transmission in laser ranging were analyzed. With a mode of the pulse-burst picosecond laser having high average power, the DLR system has tracked small debris with a radar cross-section (RCS) of 0.91 m2 at a ranging distance up to 1726.8 km, corresponding to an RCS of 0.1 m2 at a distance of 1000 km. These works are expected to provide new technologies to further improve the performance of DLR.

Optical Characterization of VLS+CVD Grown 3C-SiC Films by Non-Linear and Photoluminescence Techniques

2010 ◽  
Vol 645-648 ◽  
pp. 443-446 ◽  
Author(s):  
Georgios Manolis ◽  
Georgios Zoulis ◽  
Sandrine Juillaguet ◽  
Jean Lorenzzi ◽  
Gabriel Ferro ◽  
...  
Keyword(s):  
Nitrogen Concentration ◽  
Free Carrier ◽  
Free Carrier Absorption ◽  
Free Carrier Density ◽  
Temperature Dependences ◽  
Carrier Absorption ◽  
Data Investigation ◽  
The Impact ◽  
Sic Films

Thin 3C-SiC(111) epilayers grown on 6H-SiC(0001) substrate by VLS and CVD procedures were studied by low temperature photoluminescence (LTPL) and nonlinear optical techniques at room and low temperatures. Free carrier density ((0.3-7)×1017 cm-3) and nitrogen concentration (4×1016 cm-3) in the layers were determined from Raman and LTPL data. Investigation of non-equilibrium carrier dynamics by using transient grating and free carrier absorption techniques provided an ambipolar diffusion coefficient Da (~2.5 cm2/s) and carrier lifetime τR (2-4 ns) values at room temperature. The temperature dependences of Da and τR in 40-300 K range revealed the scattering processes in high density plasma as well the impact of defects.

Influence of Mesocarp Fibre Inclusion on Thermal Properties of Foamed Concrete

2021 ◽  
Vol 87 (1) ◽  
pp. 1-11
Author(s):  
Siti Shahirah Suhaili ◽  
Md Azree Othuman Mydin ◽  
Hanizam Awang
Keyword(s):  
Thermal Conductivity ◽  
Heat Capacity ◽  
Thermal Properties ◽  
Thermal Diffusivity ◽  
Specific Heat ◽  
Specific Heat Capacity ◽  
Volume Fraction ◽  
Thermal Constant ◽  
Volume Fractions ◽  
Foamed Concrete

The addition of mesocarp fibre as a bio-composite material in foamed concrete can be well used in building components to provide energy efficiency in the buildings if the fibre could also offer excellent thermal properties to the foamed concrete. It has practical significance as making it a suitable material for building that can reduce heat gain through the envelope into the building thus improved the internal thermal comfort. Hence, the aim of the present study is to investigate the influence of different volume fractions of mesocarp fibre on thermal properties of foamed concrete. The mesocarp fibre was prepared with 10, 20, 30, 40, 50 and 60% by volume fraction and then incorporated into the 600, 1200 and 1800 kg/m3 density of foamed concrete with constant cement-sand ratio of 1:1.5 and water-cement ratio of 0.45. Hot disk thermal constant analyser was used to attain the thermal conductivity, thermal diffusivity and specific heat capacity of foamed concrete of various volume fractions and densities. From the experimental results, it had shown that addition of mesocarp fibre of 10-40% by volume fraction resulting in low thermal conductivity and specific heat capacity and high the thermal diffusivity of foamed concrete with 600 and 1800 kg/m3 density compared to the control mix while the optimum amount of mesocarp fibre only limit up to 30% by volume fraction for 1200 kg/m3 density compared to control mix. The results demonstrated a very high correlation between thermal conductivity, thermal diffusivity and specific heat capacity which R2 value more than 90%.

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