Engineering Commons^™

Study Of The Effective Thermal Conductivity Of Polymer Composites With Varying Filler Arrangements, Debraliz Isaac Aragones, Rajath Kantharaj, Aaditya Candadai, Amy Marconnet

The Summer Undergraduate Research Fellowship (SURF) Symposium

Alternative thermal management solutions for electronic devices are being widely explored due to the increasing heat concentration that results from shrinking sizes and increasing power of modern electronics. Clearly, there is a need to spread the heat effectively in these systems, and polymer composites can potentially provide high thermal conductivity at low filler fraction while maintaining desirable mechanical properties for electronic packaging. The present study aims to investigate the effective thermal conductivity of various copper filler arrangements in a polymer matrix. The polymer composites are fabricated using laser cut acrylic templates to embed aligned copper rods in epoxy and create …

Spectral Phonon Relaxation Time Calculation Tool Based On Molecular Dynamics, Divya Chalise, Tianli Feng, Xiulin Ruan

The Summer Undergraduate Research Fellowship (SURF) Symposium

Thermal conductivity is an important material property which affects the performance of a wide range of devices from thermoelectrics to nanoelectronics. Information about phonon vibration modes and phonon relaxation time gives significant insight into understanding and engineering material’s thermal conductivity. Although different theoretical models have been developed for studying phonon modes and relaxation time, extensive knowledge of lattice dynamics and molecular dynamics is required to compute phonon modal frequencies and relaxation times. Therefore, a computational tool which can take simple inputs to calculate phonon mode frequencies and relaxation time will be beneficial. Through this research work, such computational tool has …

Thermomechanical Properties Of Novel Lanthanum Zirconate Based Thermal Barrier Coatings - An Integrated Experimental And Modeling Study, Xingye Guo

Open Access Dissertations

Thermal barrier coatings (TBCs) are refractory materials deposited on gas turbine components, which provide thermal protection for metallic components at operating conditions. The current state-of-art TBC material is yttria-stabilized zirconia (YSZ), whose service temperature is limited to 1200 celsius, due to sintering and phase transition at higher temperatures. In comparison, lanthanum zirconate (La2Zr2O7, LZ) has become a promising candidate material for TBCs due to its lower thermal conductivity and higher phase stability compared to YSZ.

The primary objective of this thesis is to design a novel robust LZ-based TBC system suitable for applications beyond 1200 celsius. Due to LZ’s low …

Carbon Nanotube Thermal Interfaces And Related Applications, Stephen L. Hodson

Open Access Dissertations

The development of thermal interface materials (TIMs) is necessitated by the temperature drop across interfacing materials arising from macro and microscopic irregularities of their surfaces that constricts heat through small contact regions as well as mismatches in their thermal properties. Similar to other types of TIMs, CNT TIMs alleviate the thermal resistance across the interface by thermally bridging two materials together with cylindrical, high-aspect ratio, and nominally vertical conducting elements. Within the community of TIM engineers, the vision driving the development of CNT TIMs was born from measurements that revealed impressively high thermal conductivities of individual CNTs. This vision was …

Effect Of Aggregation And Particle Size On The Thermal Conductivity Of Nickel-Epoxy Nanocomposites, Jacob M. Faulkner, Xiangyu Li, Xiulin Ruan Dr.

The Summer Undergraduate Research Fellowship (SURF) Symposium

Microprocessor advancements have been stunted in recent years by inadequate means of heat dissipation as power continues to grow and size continues to shrink. One way to increase thermal conductivity while maintaining electrical insulation is to add metal nanoparticles to a polymer matrix. This cheap material has become a popular thermal interface for this reason. However, optimization of the interface is dependent upon a number of factors including particle size, shape, orientation, and aggregation. Various theoretical models and numerical approximations have been developed to find the effective thermal conductivity of such nanocomposites, but none has been able to fully incorporate …

High-Temperature Thermal Properties Using Reflected Sample Generated Radiation, E. G. Wolff

International Thermal Conductivity Conference (ITCC) and the International Thermal Expansion Symposium (ITES)

A method for determining high-temperature thermal properties of thick solid materials involves short-term radiation pulses (20–200 s) on the front surface of a sample via a light guide, such as a quartz or sapphire rod. The magnitude of the flux absorbed must be accurately known for thermal conductivity, but not for thermal diffusivity. Power sources may include a lamp or laser but each has difficulties. For example, a lamp often has too little power and needs complex optics, and a laser beam may have excessive power that also lacks control. A heated sample transmits considerable radiation that varies with temperature …

Provisional Assessment Of Candidate High-Temperature Thermal Conductivity Reference Materials In The Emrp “Thermo” Project, J. Wu, R. Morrell, T. Fry, S. Gnaniah, D. Gohil, A. Dawson, J. Hameury, Alain Koenen, U. Hammerschmidt, E. Turzó-András, R. Strnad, A. Blahut

International Thermal Conductivity Conference (ITCC) and the International Thermal Expansion Symposium (ITES)

This article describes the provisional assessment of a short list of four candidate high-temperature thermal conductivity reference materials in a European research project, “Thermo.” These four candidate materials are low-density calcium silicate, amorphous silica, high-density calcium silicate, and exfoliated vermiculite. Based on initial tests on material composition and microstructure changes, dimensional stability, mechanical stability, chemical stability and uniformity, the best two candidate materials that would be considered for further detailed characterization in the next stage are low-density calcium silicate and high-density calcium silicate. These two materials are dimensionally, mechanically, and chemically stable, which are more robust and easier to handle …

Design Of A Guarded Hot Plate For Measuring Thin Specimens Of Polymer And Composite Materials, Clark Stacey, M. J. Parfitt, A. J. Simpkin, J. Wu

International Thermal Conductivity Conference (ITCC) and the International Thermal Expansion Symposium (ITES)

The National Physical Laboratory (NPL) has developed a new design of guarded hot plate apparatus specifically for absolute measurements on thin specimens of medium thermal conductivity materials, such as the polymer composites that are becoming more widely used in aerospace and other advanced manufacturing sectors. Although NPL has an existing measurement facility based on a commercially manufactured apparatus conforming to ASTM E1530, this current facility is not based on an absolute measurement technique and is not able to provide the low measurement uncertainty or flexibility that is increasingly being demanded by industrial users of this NPL service.

The target specification …

International Comparison Of Guarded Hot Plate Facilities At Low Temperature On Mineral Wool Insulation Material, Alain Koenen, Clark Stacey, Erik Rasmussen, Roland Schreiner, Grażyna Swołek

International Thermal Conductivity Conference (ITCC) and the International Thermal Expansion Symposium (ITES)

In 2000, the Institute for Reference Materials and Measurements (IRMM) proposed the creation of a new European certified reference material for the thermal conductivity measurements IRMM-440. A specific production batch of high density (64–78 kg/m³) resin-bonded glass fiber boards was manufactured and characterized by a group of six leading European laboratories with long-standing expertise in thermal conductivity measurements, including four national measurements institutes. The IRMM-440 has since been used as the European certified reference material for thermal conductivity measurements on thermal insulation covering temperatures between –10°C and 50°C, and most frequently to calibrate Heat Flow Meter apparatus making …

A New Facility For The Experimental Investigation On Nano Heat Transfer Between Gas Molecules And Ceramic Surfaces, D. Bayer, U. Gross, K. Raed

International Thermal Conductivity Conference (ITCC) and the International Thermal Expansion Symposium (ITES)

Since the last decade, the interest has risen in nanoscaled technological products, which have advantages through their size effect. The size effect also plays a significant role in the area of micro- and nanoscale heat transfers. Many applications were developed using this effect, such as nanostructured porous media, e.g. Aerogels or ceramics. This experimental work is focused on the determination of thermal accommodation coefficients (TAC) on ceramic surfaces considering several influencing factors. TAC is influenced by temperature, kind of gas, kind of wall material, roughness, and contamination with adsorbed gas layers. To determine TAC, a parallel plate apparatus is used, …

Simulation And Analysis Of An Integrated Device To Simultaneously Characterize Thermal And Thermoelectric Properties, Collier Miers, Amy Marconnet

International Thermal Conductivity Conference (ITCC) and the International Thermal Expansion Symposium (ITES)

For many applications, multiple material properties impact device performance and characterization of multiple properties using a single sample is desirable. In this article, the authors focus on thermoelectric materials characterization, which requires the thermal conductivity, electrical conductivity, and Seebeck coefficient to be quantified. Specifically, the authors present a design analysis using numerical COMSOL simulations of the 3w technique to optimize a measurement structure for thermoelectric films while also including the capability for electrical measurements to be performed on the same sample without detachment or repositioning. Thermal optimization of the structure is achieved through investigation of temperature spatial uniformity, the …

Comparative Testing Of Thermal Conductivity For Thermal Insulation Products: The European Keymark Experience For More Than 50 Equipment At 25 Test Institutes, Erik Rasmussen, Clark Stacey, Alain Koenen, Eva-Lotta W. Kurkinen

International Thermal Conductivity Conference (ITCC) and the International Thermal Expansion Symposium (ITES)

This article describes comparative testing of thermal conductivity on a range of thermal insulation products used in the construction of buildings. This testing was arranged by the CEN Keymark scheme for voluntary certification of insulation within Europe, and measurements have been performed using over 50 instruments in more than 25 registered laboratories.

The uniformity of the material and a unique thermal conductivity value for each set of test specimens that were used in the comparison have been established according to the Keymark scheme rules, which were developed by experts from the most respected European laboratories. These experts include most of …

Bilateral National Metrology Institute Comparison Of Guarded-Hot-Plate Apparatus, Alain Koenen, Robert R. Zarr, William F. Guthrie

International Thermal Conductivity Conference (ITCC) and the International Thermal Expansion Symposium (ITES)

Two national metrology institutes have conducted an international interlaboratory comparison on thermal conductivity for two thermal insulation reference materials. The Laboratoire national de métrologie et d’essais (LNE), France, and the National Institute of Standards and Technology (NIST), United States, present measurements obtained by the guarded-hot-plate method. The study involved two materials: expanded polystyrene board (EPS) and fibrous glass board (FGB). The EPS was provided by the LNE and is issued as a transfer specimen; the FGB provided by NIST was issued as Standard Reference Material (SRM) 1450c. For each reference material, the study was based on four independent measurements at …

Microstructure And Thermal Conductivity Modeling Of Granular Nanoplatelet Assemblies, Ishan Srivastava, Timothy S. Fisher

International Thermal Conductivity Conference (ITCC) and the International Thermal Expansion Symposium (ITES)

Consolidation and sintering of bismuth telluride nanoplatelets is a cost-effective method of manufacturing high thermoelectric figure-of-merit materials. A structural optimization method is employed here to study the effects of columnar structures formed by nanoplatelet composites on thermal transport. The initially sparse and random distribution of nanoplatelets is compacted into a jammed state under an external hydrostatic stress, thereby simulating the compaction of nanopowders in experiments. The jammed morphology exhibits randomly oriented stacks of nanoplatelets and a discontinuous distribution of the pore phase within the microstructure. Grain and pore morphologies are statistically quantified using computational geometry techniques. High aspect ratio nanoplatelets …

Thermal Properties Of Soft Nanomaterials: Materials Synthesis And Fabrication, Meng Pan, Collier Miers, Amy Marconnet, Yu Han

The Summer Undergraduate Research Fellowship (SURF) Symposium

The properties of soft nanomaterials are hard to measure exactly due to their mechanical properties and unstable shape. In particular, hydrogels are a class of cross-linked polymers that can absorb large quantities of water changing their shape under the influence of various conditions such as humidity, temperature, and pH. This research addresses the fabrication of a material that has a significant contrast in properties under different conditions (e.g. temperature, wetting, and pH) and determine the physical mechanisms of heat transfer in this nanomaterial. The hydrogels are made using a several cycles of a freeze-thaw method. The method requires soluble material. …

Experimental And Theoretical Studies On Design Calculations For Latent Heat Storage, Dieter Lindemann

Open Access Theses

Research was conducted to obtain design data of latent heat-of-fusion thermal energy storage (LHTES) devices. The devices studied utilize a porous medium (PM) to increase the effective conductivity of the storage system. Therefore the melting and freezing process is accelerated. Metal shavings and metal spheres were used as porous media and water as the phase change medium (PCM). A simple experimental method to measure the conductivity of a water-metal mixture or ice-metal mixture was applied to obtain conductivity data. These measurements can be considered fairly accurate because measured conductivity of pure water and of pure ice agreed very well with …