Thermal Conductivity Measurements Research Articles

Non-contact SThM thermal conductivity measurements of GeSbTe thin films sputtered on silicon and glass substrates

Abstract Chalcogenide materials based on germanium-antimony-tellurium (GST) are typically used in phase change memory applications. The thermal conductivity of GST films is an important factor in predicting the temperature evolution and the structural alterations of the material in response to rapid thermal transitions inherent in memory operations. While several techniques have been used to determine the thin film thermal conductivity of GSTs, they require fabricating metal heaters or thermometers on test samples. In this paper we report using a non-contact scanning thermal microscopy (SThM) technique to measure the thermal conductivity of GST thin-films while circumventing the need for sample preparation. A Wollaston wire probe of a 5-µm diameter was used as a Joule-heated thermometer to measure the probe thermal resistance in air far away and at 100 nm away from the sample surface. Detailed heat transfer modeling between the probe, sample, and ambient, which considers the non-classical heat transfer across the gap between the SThM probe and sample surface was used to determine the thermal resistance of several GST films sputtered with different powers on glass and silicon substrates. The thermal conductivity of GST thin film shows a reducing trend from 0.7 to 0.2 W m-1 K-1 when the thickness reduces from 159 nm to 24 nm. The reasons for thermal conductivity reduction are discussed based on analytical heat transfer modeling.

Quantitative noncontact measurement of thermal Hall angle and transverse thermal conductivity by lock-in thermography

Quantitative noncontact measurement of thermal Hall angle and transverse thermal conductivity by lock-in thermography

Thermal Conductivities of Molten Na2O–SiO2 Slags from the Perspective of Depolymerization of the Silicate Network

The thermal conductivities of molten KNO3, molten NaCl, and molten xNa2O–(100−x)SiO2 (x = 20, 33, and 40) (mol%) are measured over the temperature ranges between 623–723 K, 1173–1473 K, 1173–1573 K, respectively, by nonstationary hot‐wire method to elucidate the relationship between thermal conductivities of molten Na2O–SiO2 slags and silicate network structures. 1) The thermal conductivity measurements of molten KNO3 reveal that the measurements are successfully made without the influence of electrical leakage from the bare metallic wire to the melt as the present data are in good agreement with the reported data measured by the nonstationary hot‐wire method with ceramic‐coated hot‐wires. 2) The thermal conductivity measurements of molten NaCl measured at 1173 and 1273 K agree well with the recommended data. However, the data at 1373 and 1473 K are much smaller than the recommended data due to some electrical noise affecting the voltage changes ΔV between the potential leads. 3) The thermal resistivities of molten Na2O–SiO2 at liquidus temperatures ρLT increase with an increase in the number of nonbridging oxygens (NBO) per tetrahedrally coordinated atoms (e.g., Si, Al), i.e., NBO/T, and have a linear relationship between ρLT and NBO/T.

Compatibility Study of Synthesized Materials for Thermal Transport in Thermoelectric Power Generation

This study investigates the compatibility of synthesized materials for optimized thermal transport within thermoelectric modules. Experimental procedures involved the synthesis of candidate materials followed by characterization using techniques such as scanning electron microscopy, and thermal conductivity measurements. The research employs electrodeposition of HoSbxTex on the synthesized materials using AAo as a template in the electrolyte composed of 2mm TeO2, 2.5mm Bi(No3)3, 0.33mm SeO2, and 0.2m HNO3. Compatibility assessments were conducted within simulated thermoelectric modules to evaluate the materials’ performance under realistic operating conditions. The findings reveal crucial insights into the interplay between material properties and thermal transport mechanisms, guiding the selection and optimization of materials for enhanced thermoelectric power generation. Moreover, this study underscores the importance of tailored material design to achieve synergistic enhancements in both thermal and electrical conductivity, thereby advancing the efficiency and viability of thermoelectric energy conversion technologies. This research contributes to the ongoing efforts to enhance thermoelectric power generation and supports the global transition to sustainable energy systems.

Laser-induced thermal size effects in micro-Raman thermal conductivity measurements

Thermal conductivity measurements of submicrometer structures are at the core of the efficient power design of semiconductor devices. Micro-Raman spectroscopy measures thermal conductivity in a fast, nondestructive, and non-contact manner. However, the focused laser heating in micro-Raman experiments may cause drastic thermal size effects. To date, the role of such effects in the accuracy and limitations of the measurement has not been addressed. Here, we present an advanced thermal model to capture the role of material properties, laser power, and film thickness in the thermal size effects, based on the three-dimensional (3D) gray phonon Boltzmann transport equation. Recalling that laser-induced thermal size effects can lead to unexpectedly high local temperatures, even damaging the measured materials, our advanced 3D model gains particular importance for the accurate measurements of directional thermal conductivities in submicrometer structures using future high-resolution optical pump–probe techniques.

Simultaneous measurement of thermal conductivity and interfacial thermal resistance of Sub-10 nm SWCNT bundle via Raman-probing of distinct energy transport states

Simultaneous measurement of thermal conductivity and interfacial thermal resistance of Sub-10 nm SWCNT bundle via Raman-probing of distinct energy transport states

Correction to: Numerical and Experimental Studies on the In-Situ Measurement of Thermal Conductivity of the Thermal Barrier Coating

Correction to: Numerical and Experimental Studies on the In-Situ Measurement of Thermal Conductivity of the Thermal Barrier Coating

Reduction in thermal conductivity of monolayer MoS2 by large mechanical strains for efficient thermal management

Two-dimensional (2D) materials such as graphene and transition metal dichalcogenides (TMDC) have received extensive research interests and investigations in the past decade. In this research, we report the first experimental measurement of the in-plane thermal conductivity of MoS2 monolayer under a large mechanical strain using optothermal Raman technique. This measurement technique is direct without additional processing to the material, and MoS2’s absorption coefficient is discovered during the measurement process to further increase this technique’s precision. Tunable uniaxial tensile strains are applied on the MoS2 monolayer by stretching a flexible substrate it sits on. Experimental results demonstrate that, the thermal conductivity is substantially suppressed by tensile strains: under the tensile strain of 6.3%, the thermal conductivity of the MoS2 monolayer drops approximately by 62%. A serious of thermal transport properties at a group of mechanical strains are also reported, presenting a strain-dependent trend. It is the first and original study of 2D materials’ thermal transport properties under a large mechanical strain (> 1%), and provides important information that the thermal transport of MoS2 will significantly decrease at a large mechanical strain. This finding provides the key information for flexible and wearable electronics thermal management and designs.

Methods for Thermal Conductivity and Thermal Diffusivity Measurements of Solid and Molten Mold Fluxes

This study provides an in‐depth overview of the methods for measuring thermal conductivity and diffusivity of solid and molten mold fluxes, focusing on the development, advantages, and disadvantages of stationary, non‐steady‐state, and transient methods. The study highlights the challenges associated with stationary and non‐steady‐state methods, such as large sample sizes, difficulty in maintaining constant‐temperature profiles, and effects of convection, radiation, and low thermal conductivity materials. It also emphasizes the benefits of transient methods, including short measurement times and low sample weights, which help preserve the initial chemical composition of the samples. Transient hot‐wire and laser‐flash methods are also discussed, along with their application, accuracy, and limitations. Detailed results of thermal conductivity and diffusivity measurements of slags are presented. This study is dedicated to Professor Seetharaman, who has worked extensively on measuring thermophysical properties, thereby contributing significantly to the study of mold fluxes.

A combined 2ω/3ω method for the measurement of the in-plane thermal conductivity of thin films in multilayer stacks: Application to a silicon-on-insulator wafer

A combined 2<i>ω</i>/3<i>ω</i> method for the measurement of the in-plane thermal conductivity of thin films in multilayer stacks: Application to a silicon-on-insulator wafer

Flexible 3ω sensors on submicron-thick parylene substrates for thermal conductivity measurements of liquids and soft materials

Flexible 3ω sensors on submicron-thick parylene substrates for thermal conductivity measurements of liquids and soft materials

A Method for Accurate Measurement of Anisotropic Thermal Conductivity of Impregnated Electrical Windings

A Method for Accurate Measurement of Anisotropic Thermal Conductivity of Impregnated Electrical Windings

Unveiling the intermolecular forces and unique properties of [EMIM][EtSO4] + [EMIM][MeSO3]

Unveiling the intermolecular forces and unique properties of [EMIM][EtSO4] + [EMIM][MeSO3]

Frequency-domain thermoreflectance with beam offset without the spot distortion for accurate thermal conductivity measurement of anisotropic materials.

The measurement of thermal conductivities of anisotropic materials and atomically thin films is pivotal for the thermal design of next-generation electronic devices. Frequency-domain thermoreflectance (FDTR) is a pump-probe technique that is known for its accurate and straightforward approach to determining thermal conductivity and stands out as one of the most effective methodologies. Existing research has focused on advancing a measurement system that incorporates beam-offset FDTR. In this approach, the irradiation positions of the pump and probe lasers are spatially offset to enhance sensitivity to in-plane thermal conductivity. Previous implementations primarily adjusted the laser positions by modifying the mirror angle, which inadvertently distorted the laser spot. Such distortion significantly compromises measurement accuracy, which is especially critical in beam-offset FDTR, where the spot radius has a crucial impact on measured values. This study introduces an advanced FDTR measurement system that realizes probe laser offset without inducing spot distortion, utilizing a relay optical system. The system was applied to measure the thermal conductivities of both isotropic standard materials and anisotropic samples, including highly oriented pyrolytic graphite and graphene. The findings corroborate those of prior studies, validating the measurement's reliability in terms of sensitivity. This development of a beam-offset FDTR system without laser spot distortion establishes a robust basis for accurate thermal conductivity values of anisotropic materials via thermoreflectance methods.

Range and accuracy of in-plane anisotropic thermal conductivity measurement using the laser-based Ångstrom method.

High heat fluxes in electronic devices must be effectively dissipated to prevent local hotspots, which are critical for long-term device reliability. In particular, advanced semiconductor packaging trends toward thin form factor products increase the need for understanding and improving in-plane conduction heat spreading in anisotropic materials. The 2D laser-based Ångstrom method, an extension of traditional Ångstrom and lock-in thermography techniques, measures in-plane thermal properties of anisotropic sheet-like materials. This method uses non-contact infrared temperature mapping to measure the thermal response to periodic laser heating at the center of a suspended sample. The spatiotemporal temperature data are analyzed via an inverse fitting algorithm to extract thermal conductivities in the in-plane orthotropic directions that best adhere to the governing heat conduction equation. Using this algorithm, we present an approach to simultaneously fit data across multiple heating frequencies, which improves measurement sensitivity because the thermal penetration depth varies with frequency. The accuracy of this technique is assessed by tuning experimental parameters such as sample dimensions and heating frequency. A standardized workflow is proposed for measuring unknown materials and for processing the data, including filtering out regions influenced by laser absorption and heat sink boundary effects. Numerical simulations validate the method across a wide range of thermal conductivities (0.1-1000W m-1 K-1) and material thicknesses (0.1-10mm), with accuracy demonstrated for anisotropy ratios up to 1000:1. Experimental measurements on isotropic and anisotropic materials agree well with the benchmark values. Ultimately, standardization of this technique supports the development of engineered anisotropic heat-spreading materials for thermal management and packaging applications.

High-Precision and Reliable Thermal Conductivity Measurement for Graphene Films Based on an Improved Steady-State Electric Heating Method

High-Precision and Reliable Thermal Conductivity Measurement for Graphene Films Based on an Improved Steady-State Electric Heating Method

Gold coating reduces thermal conductivity of oriented polypropylene fibers

Abstract Self-heating methods are widely used in thermal conductivity measurements of polymer fibers. In these methods, a thin metallic film needs to be coated on the fibers if the fibers are electrical insulators. In this paper, the thermal conductivities of oriented polypropylene (PP) fiber samples before and after gold coating were measured. The results show that the gold-coating process can reduce the thermal conductivity of oriented PP fibers by about 50%. Therefore, the self-heating methods are not appropriate for thermal conductivity measurements of insulative polymers. This finding is important to the research of thermal conductive polymers.

Prototype for thermal conductivity measurement of materials made in forest agroresidue

This research focuses on the development of a prototype machine to determine the thermal conductivity of insulating materials made from agroforestry residues and PET, following the ASTM C177 standard for the protected hot plate method. The study raises awareness of the importance of sustainable insulating materials as alternatives to conventional petroleum-based options. The prototype design incorporates a hot plate with heating elements, cold plates with peltier cells for cooling, and temperature sensors for data collection. The research provides a detailed description of the design process, material selection criteria based on their thermal properties, and construction phases. The results show the potential of the prototype in measuring the thermal conductivity of agroforestry residues and PET as sustainable insulating materials.

Influence of Nano Copper Oxide Addition on the Thermal, Rheological and Tribological Properties of Locally Sourced Avocado Oil Based Nanofluids

The goal of this study is to turn waste into value by producing lubricant from abandoned avocado fruits, as the globe looks for more environmentally friendly and sustainable lubricants than those derived from fossil fuels. In response to the growing need for high-performance, environmentally friendly products, we created a lubricant enriched with copper oxide nanoparticles (nCuO) using avocado oil as the foundation. The nano copper oxide was elucidated using XRD. To find out how these nanoparticles impact the oil’s viscosity, thermal stability, and other important characteristics, we introduced trace amounts of nCuO at concentrations of 0.4 wt%, 0.8 wt%, and 1.2 wt% in our studies. The nanofluids underwent 3.5 hours of ultrasonication at 75°C. The formulation with 0.8 weight percent nCuO proved to be the most effective, with a higher flash point of 220°C and viscosities of 7.5 cSt at 40°C and 2.7 cSt at 100°C, all of which satisfied the ASTM D445 standards. Furthermore, as compared to pure avocado oil, the ideal formulation demonstrated a 13.6% decrease in the coefficient of friction (COF) and a 16.9% decrease in wear rate. Good low-temperature performance was indicated by the pour point of -1°C and the cloud point of 15°C, respectively. According to the thermal conductivity measurements, the oil’s capacity for heat transport was improved by the addition of nCuO. These results imply that avocado oil-based nanofluids, especially those containing 0.8 weight percent nCuO, have great potential as high-performing, environmentally friendly substitutes for lubricating light-duty engines and other industrial uses.

Flexible, multimodal device for measurement of body temperature, core temperature, thermal conductivity and water content

Body core temperature is an important physiological indicator for self-health management and medical diagnosis. However, existing devices always fails to achieve continuous monitoring of core body temperature due to their invasive or motion-restricted measurement principles. Here, a wearable flexible device which can continuously monitor the core body temperature was developed. The flexible device integrated with fourteen temperature sensors and one thermal conductivity sensor on the polydimethylsiloxane substrate can be conformally attached to the human skin. With the wearable data processing module and wireless communication module, the continuous monitoring of the core body temperature for 24 h and the portable monitoring of the skin thermal conductivity were realized using this device. Owing to the annular distribution design of the temperature sensor and the directional heat transfer design of the thermal conductivity sensor, this device is comparable in accuracy and stability compared to standard instruments that require invasive or motion-restricted measurements.