scholarly journals A Method Of Calculating Thermal Diffusivity And Conductivity For Irregularly Shaped Specimens In Laser Flash Analysis

2015 ◽  
Vol 22 (4) ◽  
pp. 521-530 ◽  
Author(s):  
Jerzy Szałapak ◽  
Konrad Kiełbasiński ◽  
Jakub Krzemiński ◽  
Anna Młożniak ◽  
Elżbieta Zwierkowska ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Heat Flow ◽  
Computer Software ◽  
Simulated Data ◽  
Laser Flash ◽  
Silver Layer ◽  
Joint Properties ◽  
Measurement Results ◽  
Laser Flash Analysis ◽  
Plate Area

AbstractThe Low Temperature Joining Technique(LTJT) using silver compounds enables to significantly increase the thermal conductivity between joined elements, which is much higher than for soldered joints. However, it also makes difficult to measure the thermal conductivity of the joint.The Laser Flash Analysis(LFA) is a non-intrusive method of measuring the temperature rise of one surface of a specimen after excitation with a laser pulse of its other surface. The main limitation of the LFA method is its standard computer software, which assumes the dimensions of a bonded component to be similar to those of the substrate, because it uses the standard Parker’s formula dedicated for one-dimensional heat flow. In the paper a special design of measured specimen was proposed, consisting of two copper plates of different size joined with the sintered silver layer. It was shown that heat properties of these specimens can also be measured after modifying the LFA method. The authors adapted these specimens by masking the false heat signal sourced from the uncovered plate area. Another adaptation was introducing a correcting factor of the heat travel distance, which was calculated with heat-flow simulations and placed into the Parker’s formula. The heat-flow simulated data were compared with the real LFA measurement results, which enabled estimation of the joint properties,e.g.its porosity.

scholarly journals Heat Dissipation in Epoxy/Amine-Based Gradient Composites with Alumina Particles: A Critical Evaluation of Thermal Conductivity Measurements

Polymers ◽  
2018 ◽  
Vol 10 (10) ◽  
pp. 1131 ◽  
Author(s):  
Matthias Morak ◽  
Philipp Marx ◽  
Mario Gschwandl ◽  
Peter Filipp Fuchs ◽  
Martin Pfost ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Heat Dissipation ◽  
Critical Evaluation ◽  
Laser Flash ◽  
Element Analysis ◽  
Epoxy Amine ◽  
Alumina Particles ◽  
Laser Flash Analysis ◽  
Key Aspects ◽  
Guarded Heat Flow Meter

Abstract: For the design of the next generation of microelectronic packages, thermal management is one of the key aspects and must be met by the development of polymers with enhanced thermal conductivity. While all polymer classes show a very low thermal conductivity, this shortcoming can be compensated for by the addition of fillers, yielding polymer-based composite materials with high thermal conductivity. The inorganic fillers, however, are often available only in submicron- and micron-scaled dimensions and, consequently, can sediment during the curing reaction of the polymer matrix. In this study, an epoxy/amine resin was filled with nano- and submicron-scaled alumina particles, yielding a gradient composite. It was found that the thermal conductivity according to laser flash analysis of a sliced specimen ranged from 0.25 to 0.45 W·m−1·K−1 at room temperature. If the thermal conductivity of an uncut specimen was measured with a guarded heat flow meter, the ‘averaged’ thermal conductivity was measured to be only 0.25 W·m−1·K−1. Finite element analysis revealed that the heat dissipation through a gradient composite was of intermediate speed in comparison with homogeneous composites exhibiting a non-gradient thermal conductivity of 0.25 and 0.45 W·m−1·K−1.

scholarly journals Thermal conductivity of titanium slags

2019 ◽  
Vol 116 (6) ◽  
pp. 635 ◽  
Author(s):  
Juhani Heimo ◽  
Ari Jokilaakso ◽  
Marko Kekkonen ◽  
Merete Tangstad ◽  
Anne Støre
Keyword(s):  
Thermal Conductivity ◽  
Room Temperature ◽  
Laser Flash ◽  
Analysis Method ◽  
Additional Experiment ◽  
Titanium Slag ◽  
Freeze Lining ◽  
Laser Flash Analysis ◽  
Increasing Temperature ◽  
Additional Sample

In ilmenite smelting furnaces, a freeze lining of solidified slag is used to protect the furnace refractories against the aggressive titanium slag. Freeze lining thickness cannot be measured directly due to harshness of conditions inside the process, thus process modelling is required. Several parameters influence the thickness of the freeze-lining, one of them being thermal conductivity of the frozen slag. However, there is a lack of thermal conductivity values for high titanium slags −especially as a function of temperature. In this study, thermal conductivity of three titanium slag samples and an additional sample of freeze-lining was measured from room temperature to 1100/1400 °C with the laser flash analysis method. In addition, thermal expansion and microstructures of the samples were studied to provide an extensive understanding of how microstructure will affect thermal conductivity. The thermal conductivity of the slag samples was found to increase from 1.2 to a maximum of 2.4 W/(m K) when increasing temperature from room temperature to 1100 °C. An additional experiment at 1400 °C showed that the thermal conductivity increased further as the temperature increased. The freeze-lining sample behaves differently, with conductivity being the highest at room temperature, 2.2 W/(m K).

Experimental Study of VACNT Arrays as Thermal Interface Material

2013 ◽  
Author(s):  
Yulong Ji ◽  
Gen Li ◽  
Hongbin Ma ◽  
Yuqing Sun
Keyword(s):  
Thermal Conductivity ◽  
Chemical Vapor ◽  
Laser Flash ◽  
Thermal Interface Material ◽  
Chemical Vapor Deposition Method ◽  
Free Standing ◽  
Thermal Interface ◽  
Thermal Paste ◽  
Laser Flash Analysis ◽  
Contact Thermal Conductivity

In order to improve thermal interface material (TIM), vertically aligned carbon nanotube (VACNT) arrays were synthesized by the chemical vapor deposition method, and then transferred by dipping in hydrofluoric acid (HF acid) solution to get a free standing VACNT array. Different TIM samples with sandwiched structures were fabricated by inserting the free standing VACNT arrays between two copper plates with and without bonding materials. The laser flash analysis method was applied to measure the overall thermal conductivity of these samples. Results show that: compared with two copper plates in direct contact, thermal conductivity of samples only with VACNT arrays as TIM can be enhanced about 142%–460% depending on the thickness of VACNT arrays. Conventional TIM made up of thermal paste (TG-550 with thermal conductivity of 5 W/mK) and a thermal pad (TP-260 US with thermal conductivity of 6 W/mK) was used as a bonding material between copper plates and VACNT arrays, thermal conductivity has been shown to further improve with the highest values at 8.904 W/mK and 10.17 W/mK corresponding to the different bonding materials and different thicknesses of VACNT arrays used. Results also show that the thicker the VACNT array is when used as a TIM, the lower the overall thermal conductivity of the corresponding samples. This lower thermal conductivity caused by more defects in amorphous carbon of thicker VACNT arrays and lower density of the corresponding sandwiched samples.

scholarly journals Enhanced Thermal Conductivity of Silicone Composites Filled with Few-Layered Hexagonal Boron Nitride

Polymers ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 2072
Author(s):  
Wei-Cheng Cheng ◽  
Yi-Ting Hsieh ◽  
Wei-Ren Liu
Keyword(s):  
Thermal Conductivity ◽  
Boron Nitride ◽  
Heat Dissipation ◽  
Hexagonal Boron Nitride ◽  
Low Cost ◽  
Laser Flash ◽  
Force Microscopy ◽  
Surface Areas ◽  
Laser Flash Analysis ◽  
Surface Morphologies

In this study, we demonstrate the use of silicone/few-layered hexagonal boron nitride (FL-hBN) composites for heat dissipation applications. FL-hBN is synthesized via a green, facile, low-cost and scalable liquid exfoliation method using a jet cavitation process. The crystal structures, surface morphologies and specific surface areas of pristine h-BN and FL-hBN were characterized by XRD, SEM, TEM and AFM (atomic force microscopy). The results confirmed that FL-hBN with a thickness of ~4 nm was successfully obtained from the exfoliation process. In addition, we introduced both pristine h-BN and FL-hBN into silicone with different ratios to study their thermal properties. The results of the laser flash analysis indicate that the silicon/FL-hBN composite exhibited a higher thermal conductivity than that of the silicone/h-BN composite. With the optimal loading content of 30 wt.% FL-hBN content, the thermal conductivity of the composite could be enhanced to 230%, which is higher than that of silicone/h-BN (189%). These results indicate that jet cavitation is an effective and swift way to obtain few-layered hexagonal boron nitride that could effectively enhance the thermal conductivity of silicone composites.

scholarly journals Investigation of Thermophysical Properties of Zr-Based Metallic Glass-Polymer Composite

Metals ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1412
Author(s):  
Adit Sharma ◽  
Mikhail Zadorozhnyy ◽  
Andrey Stepashkin ◽  
Aksar Kvaratskheliya ◽  
Artem Korol ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Metallic Glass ◽  
Laser Flash ◽  
Mechanical Analysis ◽  
Plasma Sintering ◽  
Laser Flash Analysis ◽  
Spark Plasma ◽  
Powder Characteristics ◽  
Supercooled Region ◽  
Composite Samples

Composites based on Zr65Cu17.5Ni10Al7.5 metallic glass (MG) and polytetrafluoroethylene (PTFE) were prepared by ball milling. Different composites (30/70, 50/50 and 70/30) were produced. Samples for dynamic mechanical analysis and laser flash analysis were fabricated in the supercooled region of the metallic glass and viscous region of the polymer. Spark plasma sintering (SPS) was performed at the supercooled region for the metallic glass powder. Characteristics such as thermal, mechanical, and structural properties were studied. A formation of the Zr2Cu and Zr2Ni intermetallic was found in the metallic glass after SPS. A formation of the nanocrystalline Zr2Cu was found in composite samples. Dynamical mechanical analysis (DMA) was used to study the mechanical behavior of the material. It was concluded that the 70/30-MG/PTFE composite sample had better thermal conductivity than the other composite samples. The thermal conductivity of the metallic glass was the highest among the samples and it increased with the MG content in composites.

scholarly journals Numerical and Experimental Evaluation of Thermal Conductivity: An Application to Al-Sn Alloys

Metals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 650
Author(s):  
Ziwei Li ◽  
Chiara Confalonieri ◽  
Elisabetta Gariboldi
Keyword(s):  
Thermal Conductivity ◽  
Composite Materials ◽  
Effective Thermal Conductivity ◽  
Laser Flash ◽  
Miscibility Gap ◽  
Two Phase ◽  
Lattice Monte Carlo ◽  
Three Phase ◽  
Laser Flash Analysis ◽  
Good Agreement

Evaluation of thermal conductivity of composite materials is extremely important to control material performance and stability in thermal applications as well as to study transport phenomena. In this paper, numerical simulation of effective thermal conductivity of Al-Sn miscibility gap alloys is validated with experimental results. Lattice Monte-Carlo (LMC) method is applied to two-phase and three-phase materials, allowing to estimate effective thermal conductivity from micrographs and individual phase properties. Numerical results are compared with literature data for cast Al-Sn alloys for the two-phase model and with a specifically produced powder metallurgy Al-10vol%Sn, tested using laser flash analysis, for a three-phase simulation. A good agreement between numerical and experimental data was observed. Moreover, LMC simulations confirmed the effect of phase morphology as well as actual phase composition on thermal conductivity of composite materials.

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