scholarly journals Photothermocapillary Method for the Nondestructive Testing of Solid Materials and Thin Coatings

Sensors ◽  
2021 ◽  
Vol 21 (19) ◽  
pp. 6671
Author(s):  
Aleksandr Zykov ◽  
Vladimir Vavilov ◽  
Marina Kuimova
Keyword(s):  
Thermal Conductivity ◽  
Surface Tension ◽  
Monochromatic Light ◽  
Small Diameter ◽  
Solid Material ◽  
Destructive Testing ◽  
Solid Materials ◽  
Ptc Effect ◽  
Maximal Diameter ◽  
Thermally Conductive

The photothermocapillary (PTC) effect is a deformation of the free surface of a thin liquid layer on a solid material that is caused by the dependence of the coefficient of surface tension on temperature. The PTC effect is highly sensitive to variations in the thermal conductivity of solids, and this is the basis for PTC techniques in the non-destructive testing of solid non-porous materials. These techniques analyze thermal conductivity and detect subsurface defects, evaluate the thickness of thin varnish-and-paint coatings (VPC), and detect air-filled voids between coatings and metal substrates. In this study, the PTC effect was excited by a “pumped” Helium-Neon laser, which provided the monochromatic light source that is required to produce optical interference patterns. The light of a small-diameter laser beam was reflected from a liquid surface, which was contoured by liquid capillary action and variations in the surface tension. A typical contour produces an interference pattern of concentric rings with a bright and wide outer ring. The minimal or maximal diameter of this pattern was designated as the PTC response. The PTC technique was evaluated to monitor the thickness of VPCs on thermally conductive solid materials. The same PTC technique has been used to measure the thickness of air-filled delaminations between a metal substrate and a coating.

Modeling the interaction of a beam of elastic vibrations with the surface of an object under acoustic non-destructive testing

2020 ◽  
pp. 55-57
Author(s):  
N.P. Aleshin ◽  
M.V. Grigorev ◽  
N.V. Kryisko ◽  
A.G. Kusyiy
Keyword(s):  
Mathematical Model ◽  
Transverse Wave ◽  
Small Diameter ◽  
Non Destructive Testing ◽  
Destructive Testing ◽  
Liquid Immersion ◽  
Elastic Transverse ◽  
Elastic Transverse Wave ◽  
Physical And Mathematical Models ◽  
Non Destructive

Physical and mathematical models are developed that describe the refraction by a concave cylindrical surface of a field of an elastic transverse wave arbitrarily incident on a surface from a liquid. Immersion control of a small-diameter pipeline is considered. Keywords acoustics, ultrasound, immersion control, physical and mathematical model, bent surface, small-diameter pipeline. [email protected]

Highly thermally conductive UHMWPE/NG composites with the segregated structure and their application for heat spreader

2020 ◽  
pp. 089270572096564
Author(s):  
Xiao Wang ◽  
Hui Lu ◽  
Jun Chen
Keyword(s):  
Thermal Conductivity ◽  
Laser Flash ◽  
Heating Process ◽  
X Ray Diffraction ◽  
Heat Spreader ◽  
Conductive Composites ◽  
Compression Direction ◽  
Thermal Analyzer ◽  
Thermally Conductive ◽  
Plane Direction

In this work, ultra-high molecular weight polyethylene (UHMWPE)/natural flake graphite (NG) polymer composites with the extraordinary high thermal conductivity were prepared by a facile mixed-heating powder method. Morphology observation and X-ray diffraction (XRD) tests revealed that the NG flakes could be more tightly coated on the surface of UHMWPE granules by mixed-heating process and align horizontally (perpendicular to the hot compression direction of composites). Laser flash thermal analyzer (LFA) demonstrated that the thermal conductivity (TC) of composites with 21.6 vol% of NG reached 19.87 W/(m·K) and 10.67 W/(m·K) in the in-plane and through-plane direction, respectively. Application experiment further demonstrated that UHMWPE/NG composites had strong capability to dissipate the heat as heat spreader. The obtained results provided a valuable basis for fabricating high thermal conductive composites which can act as advanced thermal management materials.

scholarly journals Enhancement of the Thermal Performance of the Paraffin-Based Microcapsules Intended for Textile Applications

Polymers ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 1120
Author(s):  
Virginija Skurkyte-Papieviene ◽  
Ausra Abraitiene ◽  
Audrone Sankauskaite ◽  
Vitalija Rubeziene ◽  
Julija Baltusnikaite-Guzaitiene
Keyword(s):  
Thermal Conductivity ◽  
Thermal Performance ◽  
Comparative Method ◽  
Multiwall Carbon Nanotubes ◽  
Acrylic Resin ◽  
Positive Influence ◽  
Outer Shell ◽  
Ir Camera ◽  
Spacer Fabric ◽  
Thermally Conductive

Phase changing materials (PCMs) microcapsules MPCM32D, consisting of a polymeric melamine-formaldehyde (MF) resin shell surrounding a paraffin core (melting point: 30–32 °C), have been modified by introducing thermally conductive additives on their outer shell surface. As additives, multiwall carbon nanotubes (MWCNTs) and poly (3,4-ethylenedioxyoxythiophene) poly (styrene sulphonate) (PEDOT: PSS) were used in different parts by weight (1 wt.%, 5 wt.%, and 10 wt.%). The main aim of this modification—to enhance the thermal performance of the microencapsulated PCMs intended for textile applications. The morphologic analysis of the newly formed coating of MWCNTs or PEDOT: PSS microcapsules shell was observed by SEM. The heat storage and release capacity were evaluated by changing microcapsules MPCM32D shell modification. In order to evaluate the influence of the modified MF outer shell on the thermal properties of paraffin PCM, a thermal conductivity coefficient (λ) of these unmodified and shell-modified microcapsules was also measured by the comparative method. Based on the identified optimal parameters of the thermal performance of the tested PCM microcapsules, a 3D warp-knitted spacer fabric from PET was treated with a composition containing 5 wt.% MWCNTs or 5 wt.% PEDOT: PSS shell-modified microcapsules MPCM32D and acrylic resin binder. To assess the dynamic thermal behaviour of the treated fabric samples, an IR heating source and IR camera were used. The fabric with 5 wt.% MWCNTs or 5 wt.% PEDOT: PSS in shell-modified paraffin microcapsules MPCM32D revealed much faster heating and significantly slower cooling compared to the fabric treated with the unmodified ones. The thermal conductivity of the investigated fabric samples with modified microcapsules MPCM32D has been improved in comparison to the fabric samples with unmodified ones. That confirms the positive influence of using thermally conductive enhancing additives for the heat transfer rate within the textile sample containing these modified paraffin PCM microcapsules.

scholarly journals Advances in Liquid Crystalline Epoxy Resins for High Thermal Conductivity

Polymers ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1302
Author(s):  
Younggi Hong ◽  
Munju Goh
Keyword(s):  
Thermal Conductivity ◽  
Network Structure ◽  
Epoxy Resins ◽  
Liquid Crystalline ◽  
Random Network ◽  
Three Dimensional ◽  
Heat Insulator ◽  
Liquid Crystalline Epoxy ◽  
Thermally Conductive ◽  
Substantial Interest

Epoxy resin (EP) is one of the most famous thermoset materials. In general, because EP has a three-dimensional random network, it possesses thermal properties similar to those of a typical heat insulator. Recently, there has been substantial interest in controlling the network structure of EP to create new functionalities. Indeed, the modified EP, represented as liquid crystalline epoxy (LCE), is considered promising for producing novel functionalities, which cannot be obtained from conventional EPs, by replacing the random network structure with an oriented one. In this paper, we review the current progress in the field of LCEs and their application to highly thermally conductive composite materials.

scholarly journals Improving the Actuation Speed and Multi-Cyclic Actuation Characteristics of Silicone/Ethanol Soft Actuators

Actuators ◽  
2020 ◽  
Vol 9 (3) ◽  
pp. 62 ◽  
Author(s):  
Boxi Xia ◽  
Aslan Miriyev ◽  
Cesar Trujillo ◽  
Neil Chen ◽  
Mark Cartolano ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Short Term Memory ◽  
Conductive Filler ◽  
Thermally Driven ◽  
Thermally Conductive ◽  
Ethanol Evaporation ◽  
Long Short Term Memory ◽  
Soft Actuators ◽  
Robotic Applications ◽  
Soft Composite

The actuation of silicone/ethanol soft composite material-actuators is based on the phase change of ethanol upon heating, followed by the expansion of the whole composite, exhibiting high actuation stress and strain. However, the low thermal conductivity of silicone rubber hinders uniform heating throughout the material, creating overheated damaged areas in the silicone matrix and accelerating ethanol evaporation. This limits the actuation speed and the total number of operation cycles of these thermally-driven soft actuators. In this paper, we showed that adding 8 wt.% of diamond nanoparticle-based thermally conductive filler increases the thermal conductivity (from 0.190 W/mK to 0.212 W/mK), actuation speed and amount of operation cycles of silicone/ethanol actuators, while not affecting the mechanical properties. We performed multi-cyclic actuation tests and showed that the faster and longer operation of 8 wt.% filler material-actuators allows collecting enough reliable data for computational methods to model further actuation behavior. We successfully implemented a long short-term memory (LSTM) neural network model to predict the actuation force exerted in a uniform multi-cyclic actuation experiment. This work paves the way for a broader implementation of soft thermally-driven actuators in various robotic applications.

scholarly journals Polycrystalline SnSe with a thermoelectric figure of merit greater than the single crystal

2021 ◽  
Author(s):  
Chongjian Zhou ◽  
Yong Kyu Lee ◽  
Yuan Yu ◽  
Sejin Byun ◽  
Zhong-Zhen Luo ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Single Crystal ◽  
High Performance ◽  
Figure Of Merit ◽  
Waste Heat ◽  
Electric Energy ◽  
Cost Effective ◽  
Tin Selenide ◽  
Tin Oxides ◽  
Thermally Conductive

AbstractThermoelectric materials generate electric energy from waste heat, with conversion efficiency governed by the dimensionless figure of merit, ZT. Single-crystal tin selenide (SnSe) was discovered to exhibit a high ZT of roughly 2.2–2.6 at 913 K, but more practical and deployable polycrystal versions of the same compound suffer from much poorer overall ZT, thereby thwarting prospects for cost-effective lead-free thermoelectrics. The poor polycrystal bulk performance is attributed to traces of tin oxides covering the surface of SnSe powders, which increases thermal conductivity, reduces electrical conductivity and thereby reduces ZT. Here, we report that hole-doped SnSe polycrystalline samples with reagents carefully purified and tin oxides removed exhibit an ZT of roughly 3.1 at 783 K. Its lattice thermal conductivity is ultralow at roughly 0.07 W m–1 K–1 at 783 K, lower than the single crystals. The path to ultrahigh thermoelectric performance in polycrystalline samples is the proper removal of the deleterious thermally conductive oxides from the surface of SnSe grains. These results could open an era of high-performance practical thermoelectrics from this high-performance material.

Measuring the Thermal Conductivity of Porous, Transparent SiO2 Films With Time Domain Thermoreflectance

2011 ◽  
Vol 133 (6) ◽  
Author(s):  
Patrick E. Hopkins ◽  
Bryan Kaehr ◽  
Leslie M. Phinney ◽  
Timothy P. Koehler ◽  
Anne M. Grillet ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Time Domain ◽  
Optical Measurements ◽  
Conductivity Measurements ◽  
Glass Slides ◽  
Thermally Conductive ◽  
Surface Variability ◽  
Porous Nanomaterials ◽  
Structural Aspects ◽  
Nanoporous Structures

Nanocomposites offer unique capabilities of controlling thermal transport through the manipulation of various structural aspects of the material. However, measurements of the thermal properties of these composites are often difficult, especially porous nanomaterials. Optical measurements of these properties, although ideal due to the noncontact nature, are challenging due to the large surface variability of nanoporous structures. In this work, we use a vector-based thermal algorithm to solve for the temperature change and heat transfer in which a thin film subjected to a modulated heat source is sandwiched between two thermally conductive pathways. We validate our solution with time domain thermoreflectance measurements on glass slides and extend the thermal conductivity measurements to SiO2-based nanostructured films.

Static thermal conductivity methods for solid materials

Measurement ◽  
1983 ◽  
Vol 1 (4) ◽  
pp. 167-171
Author(s):  
Ir J-P. Issi ◽  
Ir B. Poulaert ◽  
Ir J. Heremans
Keyword(s):  
Thermal Conductivity ◽  
Solid Materials

Chemical-Vapor-Deposited Materials for High Thermal Conductivity Applications

MRS Bulletin ◽  
2001 ◽  
Vol 26 (6) ◽  
pp. 458-463 ◽  
Author(s):  
Jitendra S. Goela ◽  
Nathaniel E. Brese ◽  
Michael A. Pickering ◽  
John E. Graebner
Keyword(s):  
Thin Film ◽  
Thermal Conductivity ◽  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Chemical Vapor ◽  
High Thermal Conductivity ◽  
Solid Materials ◽  
Chemical Vapor Deposited

Chemical vapor deposition (CVD) is an attractive method for producing bulk and thin-film materials for a variety of applications. In this method, gaseous reagents condense onto a substrate and then react to produce solid materials. The materials produced by CVD are theoretically dense, highly pure, and have other superior properties.

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