Cooling Effectiveness Measurements for Air Film Cooling of Thermal Barrier Coated Surfaces in a Burner Rig Environment Using Phosphor Thermometry

Science.gov (United States)

Eldridge, Jeffrey I.; Shyam, Vikram; Wroblewski, Adam C.; Zhu, Dongming; Cuy, Michael D.; Wolfe, Douglas E.

2016-01-01

While the effects of thermal barrier coating (TBC) thermal protection and air film cooling effectiveness are usually studied separately, their contributions to combined cooling effectiveness are interdependent and are not simply additive. Therefore, combined cooling effectiveness must be measured to achieve an optimum balance between TBC thermal protection and air film cooling. In this investigation, surface temperature mapping was performed using recently developed Cr-doped GdAlO3 phosphor thermometry. Measurements were performed in the NASA GRC Mach 0.3 burner rig on a TBC-coated plate using a scaled up cooling hole geometry where both the mainstream hot gas temperature and the blowing ratio were varied. Procedures for surface temperature and cooling effectiveness mapping of the air film-cooled TBC-coated surface are described. Applications are also shown for an engine component in both the burner rig test environment as well as an engine afterburner environment. The effects of thermal background radiation and flame chemiluminescence on the measurements are investigated, and advantages of this method over infrared thermography as well as the limitations of this method for studying air film cooling are discussed.

The Effect of Thermal Radiation on Entropy Generation Due to Micro-Polar Fluid Flow Along a Wavy Surface

Directory of Open Access Journals (Sweden)

Kuei-Hao Chang

2011-09-01

Full Text Available In this study, the effect of thermal radiation on micro-polar fluid flow over a wavy surface is studied. The optically thick limit approximation for the radiation flux is assumed. Prandtl’s transposition theorem is used to stretch the ordinary coordinate system in certain directions. The wavy surface can be transferred into a calculable plane coordinate system. The governing equations of micro-polar fluid along a wavy surface are derived from the complete Navier-Stokes equations. A simple transformation is proposed to transform the governing equations into boundary layer equations so they can be solved numerically by the cubic spline collocation method. A modified form for the entropy generation equation is derived. Effects of thermal radiation on the temperature and the vortex viscosity parameter and the effects of the wavy surface on the velocity are all included in the modified entropy generation equation.

Tuning the surface chemistry of lubricant-derived phosphate thermal films: The effect of boron

Energy Technology Data Exchange (ETDEWEB)

Spadaro, F. [Laboratory for Surface Science and Technology, Department of Materials, ETH Zurich, Vladimir-Prelog-Weg 5, CH-8093 Zurich (Switzerland); Rossi, A., E-mail: antonella.rossi@mat.ethz.ch [Laboratory for Surface Science and Technology, Department of Materials, ETH Zurich, Vladimir-Prelog-Weg 5, CH-8093 Zurich (Switzerland); Dipartimento di Scienze Chimiche e Geologiche, Università degli Studi di Cagliari, Cittadella Universitaria di Monserrato, I-09100, Cagliari (Italy); Lainé, E.; Woodward, P. [Enabling Research, Infineum UK Ltd., Milton Hill, Steventon, Oxfordshire OX13 6BD (United Kingdom); Spencer, N.D., E-mail: nicholas.spencer@mat.ethz.ch [Laboratory for Surface Science and Technology, Department of Materials, ETH Zurich, Vladimir-Prelog-Weg 5, CH-8093 Zurich (Switzerland)

2017-02-28

Highlights: • The additives bulk interactions in “neat” blends at high temperatures is evaluated. • The competition among the different additives to react with air-oxidized steel surfaces under pure thermal condition is investigated. • Different thermal films are grown, their in depth-composition and thickness is determined by ARXPS. • A reaction mechanism is proposed for elucidating the composition of the thermals films. - Abstract: Understanding the interactions among the various additives in a lubricant is important because they can have a major influence on the performance of blends under tribological conditions. The present investigation is focused on the interactions occurring between ZnDTP and dispersant molecules in an oil formulation, and on their reactivity under purely thermal conditions in the presence of air-oxidized iron surfaces. Nuclear magnetic resonance spectroscopy (NMR) was performed on undiluted blends at different temperatures, while angle-resolved X-ray photoelectron spectroscopy (ARXPS) was exploited to investigate the surface reactivity on oxidized iron surfaces. The results indicate that the dispersant, generally added to blends for preventing the deposition of sludge, varnish and soot on the surface, might also inhibit the reaction of all other additives with the steel surface.

Investigation on the Temporal Surface Thermal Conditions for Thermal Comfort Researches Inside A Vehicle Cabin Under Summer Season Climate

Directory of Open Access Journals (Sweden)

Zhang Wencan

2016-01-01

Full Text Available With the proposes of improving occupant's thermal comfort and reducing the air conditioning power consumption, the present research carried out a comprehensive study on the surface thermal conductions and their influence parameters. A numerical model was built considering the transient conduction, convective and radiation heat transfer inside a vehicle cabin. For more accurate simulation of the radiation heat transfer behaviors, the radiation was considered into two spectral bands (short wave and long wave radiation, and the solar radiation was calculated by two solar fluxes (beam and diffuse solar radiation. An experiment was conducted to validate the numerical approach, showing a good agreement with the surface temperature. The surface thermal conditions were numerically simulated. The results show that the solar radiation is the most important factor in determining the internal surface thermal conditions. Effects of the window glass properties and the car body surface conditions were investigated. The numerical calculation results indicate that reducing the transitivity of window glass can effectively reduce the internal surface temperature. And the reflectivity of the vehicle cabin also has an important influence on the surface temperature, however, it's not so obvious as comparison to the window glass.

Thermal effects of λ = 808 nm GaAlAs diode laser irradiation on different titanium surfaces.

Science.gov (United States)

Giannelli, Marco; Lasagni, Massimo; Bani, Daniele

2015-12-01

Diode lasers are widely used in dental laser treatment, but little is known about their thermal effects on different titanium implant surfaces. This is a key issue because already a 10 °C increase over the normal body temperature can induce bone injury and compromise osseo-integration. The present study aimed at evaluating the temperature changes and surface alterations experienced by different titanium surfaces upon irradiation with a λ = 808 nm diode laser with different settings and modalities. Titanium discs with surfaces mimicking different dental implant surfaces including TiUnite and anodized, machined surfaces were laser-irradiated in contact and non-contact mode, and with and without airflow cooling. Settings were 0.5-2.0 W for the continuous wave mode and 10-45 μJ, 20 kHz, 5-20 μs for the pulsed wave mode. The results show that the surface characteristics have a marked influence on temperature changes in response to irradiation. The TiUnite surface, corresponding to the osseous interface of dental implants, was the most susceptible to thermal rise, while the machined surfaces, corresponding to the implant collar, were less affected. In non-contact mode and upon continuous wave emission, the temperature rose above the 50 °C tissue damage threshold. Scanning electron microscopy investigation of surface alterations revealed that laser treatment in contact mode resulted in surface scratches even when no irradiation was performed. These findings indicate that the effects of diode laser irradiation on implant surfaces depend on physical features of the titanium coating and that in order to avoid thermal or physical damage to implant surface the irradiation treatment has to be carefully selected.

Effects of radiation and thermal diffusivity on heat transfer over a stretching surface with variable heat flux

International Nuclear Information System (INIS)

Seddeek, M.A.; Abdelmeguid, M.S.

2006-01-01

The effect of radiation and thermal diffusivity on heat transfer over a stretching surface with variable heat flux has been studied. The thermal diffusivity is assumed to vary as a linear function of temperature. The governing partial differential equations have been transformed to ordinary differential equations. The exact analytical solution for the velocity and the numerical solution for the temperature field are given. Numerical solutions are obtained for different values of variable thermal diffusivity, radiation, temperature parameter and Prandtl number

Thermal crackling: study of the mechanical effects of quick temperature fluctuations on metallic surfaces

International Nuclear Information System (INIS)

Pradel, P.

1984-05-01

After a brief overview of the thermohydraulical conditions of liquid sodium leading to important temperature fluctuations near the metallic surfaces, the author examines the transfer modes of these fluctuations in the structure thickness and the long term mechanical effects. Dimensioning models based on thermal and metallurgical properties are under study for structures subject to such sodium loads [fr

Surface modification of montmorillonite on surface Acid-base characteristics of clay and thermal stability of epoxy/clay nanocomposites.

Science.gov (United States)

Park, Soo-Jin; Seo, Dong-Il; Lee, Jae-Rock

2002-07-01

In this work, the effect of surface treatments on smectitic clay was investigated in surface energetics and thermal behaviors of epoxy/clay nanocomposites. The pH values, X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR) were used to analyze the effect of cation exchange on clay surface and the exfoliation phenomenon of clay interlayer. The surface energetics of clay and thermal properties of epoxy/clay nanocomposites were investigated in contact angles and thermogravimetric analysis (TGA), respectively. From the experimental results, the surface modification of clay by dodecylammonium chloride led to the increases in both distance between silicate layers of about 8 A and surface acid values, as well as in the electron acceptor component (gamma(+)(s)) of surface free energy, resulting in improved interfacial adhesion between basic (or electron donor) epoxy resins and acidic (electron acceptor) clay interlayers. Also, the thermal stability of nanocomposites was highly superior to pure epoxy resin due to the presence of the well-dispersed clay nanolayer, which has a barrier property in a composite system.

Local thermal property analysis by scanning thermal microscopy of an ultrafine-grained copper surface layer produced by surface mechanical attrition treatment

Energy Technology Data Exchange (ETDEWEB)

Guo, F.A. [Suzhou Institute for Nonferrous Metals Processing Technology, No. 200 Shenxu Road, Suzhou Industrial Park, Suzhou 215021 (China) and Unite de Thermique et d' Analyse Physique, Laboratoire d' Energetique et d' Optique, Universite de Reims, BP 1039, 51687 Reims Cedex 2 (France)]. E-mail: guofuan@yahoo.com; JI, Y.L. [Suzhou Institute for Nonferrous Metals Processing Technology, No. 200 Shenxu Road, Suzhou Industrial Park, Suzhou 215021 (China); Trannoy, N. [Unite de Thermique et d' Analyse Physique, Laboratoire d' Energetique et d' Optique, Universite de Reims, BP 1039, 51687 Reims Cedex 2 (France); Lu, J. [LASMIS, Universite de Technologie de Troyes, 12 Rue Marie Curie, Troyes 10010 (France)

2006-06-15

Scanning thermal microscopy (SThM) was used to map thermal conductivity images in an ultrafine-grained copper surface layer produced by surface mechanical attrition treatment (SMAT). It is found that the deformed surface layer shows different thermal conductivities that strongly depend on the grain size of the microstructure: the thermal conductivity of the nanostructured surface layer decreases obviously when compared with that of the coarse-grained matrix of the sample. The role of the grain boundaries in thermal conduction is analyzed in correlation with the heat conduction mechanism in pure metal. A theoretical approach, based on this investigation, was used to calculate the heat flow from the probe tip to the sample and then estimate the thermal conductivities at different scanning positions. Experimental results and theoretical calculation demonstrate that SThM can be used as a tool for the thermal property and microstructural analysis of ultrafine-grained microstructures.

The effect of polyether functional polydimethylsiloxane on surface and thermal properties of waterborne polyurethane

Science.gov (United States)

Zheng, Guikai; Lu, Ming; Rui, Xiaoping

2017-03-01

Waterborne polyurethanes (WPU) modified with polyether functional polydimethylsiloxane (PDMS) were synthesized by pre-polymerization method using isophorone diisocyanate (IPDI) and 1,4-butanediol (BDO) as hard segments and polybutylene adipate glycol (PBA) and polyether functional PDMS as soft segments. The effect of polyether functional PDMS on phase separation, thermal properties, surface properties including surface composition, morphology and wettability were investigated by FTIR, contact angle measurements, ARXPS, SEM-EDS, AFM, TG and DSC. The results showed that the compatibility between urethane hard segment and PDMS modified with polyether was good, and there was no distinct phase separation in both bulk and surface of WPU films. The degradation temperature and low temperature flexibility increased with increasing amounts of polyether functional PDMS. The enrichment of polyether functional PDMS with low surface energy on the surface imparted excellent hydrophobicity to WPU films.

Thermal impact of waste emplacement and surface cooling associated with geologic disposal of nuclear waste

Energy Technology Data Exchange (ETDEWEB)

Wang, J.S.Y.; Mangold, D.C.; Spencer, R.K.; Tsang, C.F.

1982-08-01

The thermal effects associated with the emplacement of aged radioactive wastes in a geologic repository were studied, with emphasis on the following subjects: the waste characteristics, repository structure, and rock properties controlling the thermally induced effects; the current knowledge of the thermal, thermomechanical, and thermohydrologic impacts, determined mainly on the basis of previous studies that assume 10-year-old wastes; the thermal criteria used to determine the repository waste loading densities; and the technical advantages and disadvantages of surface cooling of the wastes prior to disposal as a means of mitigating the thermal impacts. The waste loading densities determined by repository designs for 10-year-old wastes are extended to older wastes using the near-field thermomechanical criteria based on room stability considerations. Also discussed are the effects of long surface cooling periods determined on the basis of far-field thermomechanical and thermohydrologic considerations. The extension of the surface cooling period from 10 years to longer periods can lower the near-field thermal impact but have only modest long-term effects for spent fuel. More significant long-term effects can be achieved by surface cooling of reprocessed high-level waste.

Thermal impact of waste emplacement and surface cooling associated with geologic disposal of nuclear waste

International Nuclear Information System (INIS)

Wang, J.S.Y.; Mangold, D.C.; Spencer, R.K.; Tsang, C.F.

1982-08-01

The thermal effects associated with the emplacement of aged radioactive wastes in a geologic repository were studied, with emphasis on the following subjects: the waste characteristics, repository structure, and rock properties controlling the thermally induced effects; the current knowledge of the thermal, thermomechanical, and thermohydrologic impacts, determined mainly on the basis of previous studies that assume 10-year-old wastes; the thermal criteria used to determine the repository waste loading densities; and the technical advantages and disadvantages of surface cooling of the wastes prior to disposal as a means of mitigating the thermal impacts. The waste loading densities determined by repository designs for 10-year-old wastes are extended to older wastes using the near-field thermomechanical criteria based on room stability considerations. Also discussed are the effects of long surface cooling periods determined on the basis of far-field thermomechanical and thermohydrologic considerations. The extension of the surface cooling period from 10 years to longer periods can lower the near-field thermal impact but have only modest long-term effects for spent fuel. More significant long-term effects can be achieved by surface cooling of reprocessed high-level waste

OBSERVED ASTEROID SURFACE AREA IN THE THERMAL INFRARED

Energy Technology Data Exchange (ETDEWEB)

Nugent, C. R. [Infrared Processing and Analysis Center, California Institute of Technology, Pasadena, CA 91125 (United States); Mainzer, A.; Masiero, J.; Bauer, J.; Kramer, E.; Sonnett, S. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Wright, E. L. [Department of Physics and Astronomy, University of California, Los Angeles, CA 90095 (United States); Grav, T. [Planetary Science Institute, Tucson, AZ (United States)

2017-02-01

The rapid accumulation of thermal infrared observations and shape models of asteroids has led to increased interest in thermophysical modeling. Most of these infrared observations are unresolved. We consider what fraction of an asteroid’s surface area contributes the bulk of the emitted thermal flux for two model asteroids of different shapes over a range of thermal parameters. The resulting observed surface in the infrared is generally more fragmented than the area observed in visible wavelengths, indicating high sensitivity to shape. For objects with low values of the thermal parameter, small fractions of the surface contribute the majority of thermally emitted flux. Calculating observed areas could enable the production of spatially resolved thermal inertia maps from non-resolved observations of asteroids.

Experimental and Numerical Investigation of Design Parameters for Hydronic Embedded Thermally Active Surfaces

DEFF Research Database (Denmark)

Marcos-Meson, Victor; Pomianowski, Michal Zbigniew; E. Poulsen, Søren

2015-01-01

This paper evaluates the principal design parameters affecting the thermal performance of embedded hydronic Thermally Active Surfaces (TAS), combining the Response Surface Method (RSM) with the Finite Elements Method (FEM). The study ranks the combined effects of the parameters on the heat flux i...

Thermal performance of a phase change material on a nickel-plated surface

International Nuclear Information System (INIS)

Nurmawati, M.H.; Siow, K.S.; Rasiah, I.J.

2004-01-01

Thermal control becomes increasingly vital with IC chips becoming faster and smaller. The need to keep chips within acceptable operating temperatures is a growing challenge. Thermal interface materials (TIM) form the interfaces that improve heat transfer from the heat-generating chip to the heat dissipating thermal solution. One of the most commonly used materials in today's electronics industry is phase change material (PCM). Typically, the heat spreader is a nickel-plated copper surface. The compatibility of the PCM to this surface is crucial to the performance of the TIM. In this paper, we report on the performance of this interface. To that end, an instrument to suitably measure critical parameters, like the apparent and contact thermal resistance of the TIM, is developed according to the ASTM D5470 and calibrated. A brief theory of TIM is described and the properties of the PCM were investigated using the instrument. Thermal resistance measurements were made to investigate the effects of physical parameters like pressure, temperature and supplied power on the thermal performance of the material on nickel-plated surface. Conclusions were drawn on the effectiveness of the interface and their application in IC packages

Thermographic method for evaluation of thermal influence of exterior surface colour of buildings

Science.gov (United States)

Wu, Yanpeng; Li, Deying; Jin, Rendong; Liu, Li; Bai, Jiabin; Feng, Jianming

2008-12-01

Architecture colour is an important part in urban designing. It directly affects the expressing and the thermal effect of exterior surface of buildings. It has proved that four factors affect the sign visibility, graphics, colour, lighting condition and age of the observers, and colour is the main aspect. The best method is to prevent the exterior space heating up in the first place, by reflecting heat away room the exterior surface.The colour of paint to coat building's exterior wall can have a huge impact on energy efficiency. While the suitable colour is essential to increasing the energy efficiency of paint colour during the warm summer months, those products also help paint colour efficiency and reduce heat loss from buildings during winter months making the interior more comfortable all year long. The article is based on analyzing the importance of architecture color design and existing urban colour design. The effect of external surface colour on the thermal behaviour of a building has been studied experimentally by Infrared Thermographic method in University of Science and technology Beijing insummer.The experimental results showed that different colour has quietly different thermal effect on the exterior surface of buildings. The thermal effect of carmine and fawn has nearly the same values. The main factor which is color express, give some suggest ting about urban color design. The investigation reveals that the use of suitable surface colour can dramatically reduce maximum the temperatures of the exterior wall. Keywords: architectural colour, thermal, thermographic

Thermal repellent properties of surface coating using silica

Science.gov (United States)

Lee, Y. Y.; Halim, M. S.; Aminudin, E.; Guntor, N. A.

2017-11-01

Extensive land development in urban areas is completely altering the surface profile of human living environment. As cities growing rapidly, impervious building and paved surfaces are replacing the natural landscape. In the developing countries with tropical climate, large masses of building elements, such as brick wall and concrete members, absorb and store large amount of heat, which in turn radiate back to the surrounding air during the night time. This bubble of heat is known as urban heat island (UHI). The use of high albedo urban surfaces is an inexpensive measure that can reduce surrounded temperature. Thus, the main focus of this study is to investigate the ability of silica, SiO2, with high albedo value, to be used as a thermal-repelled surface coating for brick wall. Three different silica coatings were used, namely silicone resin, silicone wax and rain repellent and one exterior commercial paint (jota shield paint) that commercially available in the market were applied on small-scale brick wall models. An uncoated sample also had been fabricated as a control sample for comparison. These models were placed at the outdoor space for solar exposure. Outdoor environment measurement was carried out where the ambient temperature, surface temperature, relative humidity and UV reflectance were recorded. The effect of different type of surface coating on temperature variation of the surface brick wall and the thermal performance of coatings as potential of heat reduction for brick wall have been studied. Based on the results, model with silicone resin achieved the lowest surface temperature which indicated that SiO2 can be potentially used to reduce heat absorption on the brick wall and further retains indoor passive thermal comfortability.

Apparent thermal inertia and the surface heterogeneity of Mars

Science.gov (United States)

Putzig, Nathaniel E.; Mellon, Michael T.

2007-11-01

Thermal inertia derivation techniques generally assume that surface properties are uniform at horizontal scales below the footprint of the observing instrument and to depths of several decimeters. Consequently, surfaces with horizontal or vertical heterogeneity may yield apparent thermal inertia which varies with time of day and season. To investigate these temporal variations, we processed three Mars years of Mars Global Surveyor Thermal Emission Spectrometer observations and produced global nightside and dayside seasonal maps of apparent thermal inertia. These maps show broad regions with diurnal and seasonal differences up to 200 J m -2 K -1s -1/2 at mid-latitudes (60° S to 60° N) and 600 J m -2 K -1s -1/2 or greater in the polar regions. We compared the seasonal mapping results with modeled apparent thermal inertia and created new maps of surface heterogeneity at 5° resolution, delineating regions that have thermal characteristics consistent with horizontal mixtures or layers of two materials. The thermal behavior of most regions on Mars appears to be dominated by layering, with upper layers of higher thermal inertia (e.g., duricrusts or desert pavements over fines) prevailing in mid-latitudes and upper layers of lower thermal inertia (e.g., dust-covered rock, soils with an ice table at shallow depths) prevailing in polar regions. Less common are regions dominated by horizontal mixtures, such as those containing differing proportions of rocks, sand, dust, and duricrust or surfaces with divergent local slopes. Other regions show thermal behavior that is more complex and not well-represented by two-component surface models. These results have important implications for Mars surface geology, climate modeling, landing-site selection, and other endeavors that employ thermal inertia as a tool for characterizing surface properties.

Thermal performance enhancement of erythritol/carbon foam composites via surface modification of carbon foam

Science.gov (United States)

Li, Junfeng; Lu, Wu; Luo, Zhengping; Zeng, Yibing

2017-03-01

The thermal performance of the erythritol/carbon foam composites, including thermal diffusivity, thermal capacity, thermal conductivity and latent heat, were investigated via surface modification of carbon foam using hydrogen peroxide as oxider. It was found that the surface modification enhanced the wetting ability of carbon foam surface to the liquid erythritol of the carbon foam surface and promoted the increase of erythritol content in the erythritol/carbon foam composites. The dense interfaces were formed between erythritol and carbon foam, which is due to that the formation of oxygen functional groups C=O and C-OH on the carbon surface increased the surface polarity and reduced the interface resistance of carbon foam surface to the liquid erythritol. The latent heat of the erythritol/carbon foam composites increased from 202.0 to 217.2 J/g through surface modification of carbon foam. The thermal conductivity of the erythritol/carbon foam composite before and after surface modification further increased from 40.35 to 51.05 W/(m·K). The supercooling degree of erythritol also had a large decrease from 97 to 54 °C. Additionally, the simple and effective surface modification method of carbon foam provided an extendable way to enhance the thermal performances of the composites composed of carbon foams and PCMs.

Thermal impact of waste emplacement and surface cooling associated with geologic disposal of nuclear waste

International Nuclear Information System (INIS)

Wang, J.S.Y.; Mangold, D.C.; Spencer, R.K.; Tsang, C.F.

1982-01-01

The age of nuclear waste - the length of time between its removal from the reactor cores and its emplacement in a repository - is a significant factor in determining the thermal loading of a repository. The surface cooling period as well as the density and sequence of waste emplacement affects both the near-field repository structure and the far-field geologic environment. To investigate these issues, a comprehensive review was made of the available literature pertaining to thermal effects and thermal properties of mined geologic repositories. This included a careful evaluation of the effects of different surface cooling periods of the wastes, which is important for understanding the optimal thermal loading of a repository. The results led to a clearer understanding of the importance of surface cooling in evaluating the overall thermal effects of a radioactive waste repository. The principal findings from these investigations are summarized in this paper

[Study on Hollow Brick Wall's Surface Temperature with Infrared Thermal Imaging Method].

Science.gov (United States)

Tang, Ming-fang; Yin, Yi-hua

2015-05-01

To address the characteristic of uneven surface temperature of hollow brick wall, the present research adopts soft wares of both ThermaCAM P20 and ThermaCAM Reporter to test the application of infrared thermal image technique in measuring surface temperature of hollow brick wall, and further analyzes the thermal characteristics of hollow brick wall, and building material's impact on surface temperature distribution including hollow brick, masonry mortar, and so on. The research selects the construction site of a three-story-high residential, carries out the heat transfer experiment, and further examines the exterior wall constructed by 3 different hollow bricks including sintering shale hollow brick, masonry mortar and brick masonry. Infrared thermal image maps are collected, including 3 kinds of sintering shale hollow brick walls under indoor heating in winter; and temperature data of wall surface, and uniformity and frequency distribution are also collected for comparative analysis between 2 hollow bricks and 2 kinds of mortar masonry. The results show that improving heat preservation of hollow brick aid masonry mortar can effectively improve inner wall surface temperature and indoor thermal environment; non-uniformity of surface temperature decreases from 0. 6 to 0. 4 °C , and surface temperature frequency distribution changes from the asymmetric distribution into a normal distribution under the condition that energy-saving sintering shale hollow brick wall is constructed by thermal mortar replacing cement mortar masonry; frequency of average temperature increases as uniformity of surface temperature increases. This research provides a certain basis for promotion and optimization of hollow brick wall's thermal function.

Mars Surface Heterogeneity From Variations in Apparent Thermal Inertia

Science.gov (United States)

Putzig, N. E.; Mellon, M. T.

2005-12-01

Current techniques used in the calculation of thermal inertia from observed brightness temperatures typically assume that planetary surface properties are uniform on the scale of the instrument's observational footprint. Mixed or layered surfaces may yield different apparent thermal inertia values at different seasons or times of day due to the nonlinear relationship between temperature and thermal inertia. To obtain sufficient data coverage for investigating temporal changes, we processed three Mars years of observations from the Mars Global Surveyor Thermal Emission Spectrometer and produced seasonal nightside and dayside maps of apparent thermal inertia. These maps show broad regions with seasonal and diurnal differences as large as 200 J m-2 K-1 s-½ at mid-latitudes (60°S to 60°N) and ranging up to 600 J m-2 K-1 s-½ or greater in the polar regions. Comparison of the maps with preliminary results from forward-modeling of heterogeneous surfaces indicates that much of the martian surface may be dominated by (1) horizontally mixed surfaces, such as those containing differing proportions of rocks, sand, dust, duricrust, and localized frosts; (2) higher thermal inertia layers over lower thermal inertia substrates, such as duricrust or desert pavements; and (3) lower thermal inertia layers over higher thermal inertia substrates, such as dust over sand or rocks and soils with an ice table at depth.

Increasing the Thermal Conductivity of Graphene-Polyamide-6,6 Nanocomposites by Surface-Grafted Polymer Chains: Calculation with Molecular Dynamics and Effective-Medium Approximation.

Science.gov (United States)

Gao, Yangyang; Müller-Plathe, Florian

2016-02-25

By employing reverse nonequilibrium molecular dynamics simulations in a full atomistic resolution, the effect of surface-grafted chains on the thermal conductivity of graphene-polyamide-6.6 (PA) nanocomposites has been investigated. The interfacial thermal conductivity perpendicular to the graphene plane is proportional to the grafting density, while it first increases and then saturates with the grafting length. Meanwhile, the intrinsic in-plane thermal conductivity of graphene drops sharply as the grafting density increases. The maximum overall thermal conductivity of nanocomposites appears at an intermediate grafting density because of these two competing effects. The thermal conductivity of the composite parallel to the graphene plane increases with the grafting density and grafting length which is attributed to better interfacial coupling between graphene and PA. There exists an optimal balance between grafting density and grafting length to obtain the highest interfacial and parallel thermal conductivity. Two empirical formulas are suggested, which quantitatively account for the effects of grafting length and density on the interfacial and parallel thermal conductivity. Combined with effective medium approximation, for ungrafted graphene in random orientation, the model overestimates the thermal conductivity at low graphene volume fraction (f 10%). For unoriented grafted graphene, the model matches the experimental results well. In short, this work provides some valuable guides to obtain the nanocomposites with high thermal conductivity by grafting chain on the surface of graphene.

Thermal Bridge Effects in Walls Separating Rowhouses

DEFF Research Database (Denmark)

Rose, Jørgen

1997-01-01

In this report the thermal bridge effects at internal wall/roof junctions in rowhouses are evaluated. The analysis is performed using a numerical calculation programme, and different solutions are evaluated with respect to extra heat loss and internal surface temperatures.......In this report the thermal bridge effects at internal wall/roof junctions in rowhouses are evaluated. The analysis is performed using a numerical calculation programme, and different solutions are evaluated with respect to extra heat loss and internal surface temperatures....

Structured thermal surface for radiative camouflage.

Science.gov (United States)

Li, Ying; Bai, Xue; Yang, Tianzhi; Luo, Hailu; Qiu, Cheng-Wei

2018-01-18

Thermal camouflage has been successful in the conductive regime, where thermal metamaterials embedded in a conductive system can manipulate heat conduction inside the bulk. Most reported approaches are background-dependent and not applicable to radiative heat emitted from the surface of the system. A coating with engineered emissivity is one option for radiative camouflage, but only when the background has uniform temperature. Here, we propose a strategy for radiative camouflage of external objects on a given background using a structured thermal surface. The device is non-invasive and restores arbitrary background temperature distributions on its top. For many practical candidates of the background material with similar emissivity as the device, the object can thereby be radiatively concealed without a priori knowledge of the host conductivity and temperature. We expect this strategy to meet the demands of anti-detection and thermal radiation manipulation in complex unknown environments and to inspire developments in phononic and photonic thermotronics.

Arc-textured metal surfaces for high thermal emittance space radiators

International Nuclear Information System (INIS)

Banks, B.A.; Rutledge, S.K.; Mirtich, M.J.; Behrend, T.; Hotes, D.; Kussmaul, M.; Barry, J.; Stidham, C.; Stueber, T.; DiFilippo, F.

1994-01-01

Carbon arc electrical discharges struck across the surfaces of metals such as Nb-1% Zr, alter the morphology to produce a high thermal emittance surface. Metal from the surface and carbon from the arc electrode vaporize during arcing, and then condense on the metal surface to produce a microscopically rough surface having a high thermal emittance. Quantitative spectral reflectance measurements from 0.33 to 15 μm were made on metal surfaces which were carbon arc treated in an inert gas environment. The resulting spectral reflectance data were then used to calculate thermal emittance as a function of temperature for various methods of arc treatment. The results of arc treatment on various metals are presented for both ac and dc arcs. Surface characterization data, including thermal emittance as a function of temperature, scanning electron microscopy, and atomic oxygen durability, are also presented. Ac arc texturing was found to increase the thermal emittance at 800 K from 0.05. to 0.70

External Thermal Insulation Composite Systems: Critical Parameters for Surface Hygrothermal Behaviour

Directory of Open Access Journals (Sweden)

Eva Barreira

2014-01-01

Full Text Available External Thermal Insulation Composite Systems (ETICS are often used in Europe. Despite its thermal advantages, low cost, and ease of application, this system has serious problems of biological growth causing the cladding defacement. Recent studies pointed that biological growth is due to high values of surface moisture content, which mostly results from the combined effect of exterior surface condensation, wind-driven rain, and drying process. Based on numerical simulation, this paper points the most critical parameters involved in hygrothermal behaviour of ETICS, considering the influence of thermal and hygric properties of the external rendering, the effect of the characteristics of the façade, and the consequences of the exterior and interior climate on exterior surface condensation, wind-driven rain, and drying process. The model used was previously validated by comparison with the results of an “in situ” campaign. The results of the sensitivity analyses show that relative humidity and temperature of the exterior air, atmospheric radiation, and emissivity of the exterior rendering are the parameters that most influence exterior surface condensation. Wind-driven rain depends mostly on horizontal rain, building’s height, wind velocity, and orientation. The drying capacity is influenced by short-wave absorbance, incident solar radiation, and orientation.

Thermal Radiation Effects on Thermal Explosion in Polydisperse Fuel Spray-Probabilistic Model

Directory of Open Access Journals (Sweden)

Ophir Navea

2011-06-01

Full Text Available We investigate the effect of thermal radiation on the dynamics of a thermal explosion of polydisperse fuel spray with a complete description of the chemistry via a single-step two-reactant model of general order. The polydisperse spray is modeled using a Probability Density Function (PDF. The thermal radiation energy exchange between the evaporation surface of the fuel droplets and the burning gas is described using the Marshak boundary conditions. An explicit expression of the critical condition for thermal explosion limit is derived analytically and represents a generalization of the critical parameter of the classical Semenov theory. Because we investigated the model in the range where the temperature is very high, the effect of the thermal radiation is significant.

HIGH VELOCITY THERMAL GUN FOR SURFACE PREPARATION AND TREATMENT

Directory of Open Access Journals (Sweden)

I.A. Gorlach

2012-01-01

Full Text Available Many surface preparation and treatment processes utilise compressed air to propel particles against surfaces in order to clean and treat them. The effectiveness of the processes depends on the velocity of the particles, which in turn depends on the pressure of the compressed air. This paper describes a thermal gun built on the principles of High Velocity Air Fuel (HVAF and High Velocity Oxy Fuel (HVOF processes. The designed apparatus can be used for abrasive blasting, coating of surfaces, cutting of rocks, removing rubber from mining equipment, cleaning of contaminations etc.

Thermal control surfaces on the MSFC LDEF experiments

International Nuclear Information System (INIS)

Wilkes, D.R.; Whitaker, A.F.; Zwiener, J.M.; Linton, R.C.; Shular, D.; Peters, P.N.; Gregory, J.C.

1992-01-01

There were five Marshall Space Flight Center (MSFC) experiments on the LDEF. Each of those experiments carried thermal control surfaces either as test samples or as operational surfaces. These materials experienced varying degrees of mechanical and optical damage. Some materials were virtually unchanged by the extended exposure while others suffered extensive degradation. The synergistic effects due to the constituents of the space environment are evident in the diversity of these material changes. The sample complement for the MSFC experiments is described along with results of the continuing analyses efforts

Surface Thermal Insulation and Pipe Cooling of Spillways during Concrete Construction Period

Directory of Open Access Journals (Sweden)

Wang Zhenhong

2014-01-01

Full Text Available Given that spillways adopt a hydraulic thin concrete plate structure, this structure is difficult to protect from cracks. The mechanism of the cracks in spillways shows that temperature stress is the major reason for cracks. Therefore, an effective way of preventing cracks is a timely and reasonable temperature-control program. Studies show that one effective prevention method is surface thermal insulation combined with internal pipe cooling. The major factors influencing temperature control effects are the time of performing thermal insulation and the ways of internal pipe cooling. To solve this problem, a spillway is taken as an example and a three-dimensional finite element program and pipe cooling calculation method are adopted to conduct simulation calculation and analysis on the temperature fields and stress fields of concretes subject to different temperature-control programs. The temperature-control effects are then compared. Optimization results show that timely and reasonable surface thermal insulation and water-flowing mode can ensure good temperature-control and anticrack effects. The method has reference value for similar projects.

Clinical effect of vitamin A palmitate eye gel on early ocular surface reconstruction after thermal or chemical injuries

Directory of Open Access Journals (Sweden)

Fen-Dui Zhang

2015-11-01

Full Text Available AIM: To evaluate the clinical effect of vitamin A palmitate eye gel on early ocular surface reconstruction after thermal or chemical injuries. METHODS: Seventy-eight cases with thermal or chemical injuries to eyes were selected and divided into two groups by randomized, double-blind, positive drug parallel controlled method: group A(40 cases were treated with vitamin A palmitate eye geland group B \\〖38 cases were treated with basic fibroblast growth factor(bFGF\\〗. The bFGF and vitamin A palmitate eye gel were used 4 times a day. The treatment course was 14d. Restoration of epithelial defect, Schirmer's test values, tear break-up time(BUT, and subjective assessment of symptoms and signs were observed on D1, D3, D5, D7, D10 and D14.RESULTS: In group A, 31 cases were cured, 5 cases were effective, with the cure rate of 76% and efficiency 90%. In group B, 32 cases were cured, 3 cases were effective, with the cure rate of 84% and efficiency 92%. There were no significant differences between the two groups(P>0.05. However, there were significant differences on the results of Schirmer's test and BUT(PPCONCLUSION: Vitamin A palmitate eye gel is valuable and safe on early ocular surface reconstruction of the eyes suffered from thermal or chemical injuries.

Control of surface thermal scratch of strip in tandem cold rolling

Science.gov (United States)

Chen, Jinshan; Li, Changsheng

2014-07-01

The thermal scratch seriously affects the surface quality of the cold rolled stainless steel strip. Some researchers have carried out qualitative and theoretical studies in this field. However, there is currently a lack of research on effective forecast and control of thermal scratch defects in practical production, especially in tandem cold rolling. In order to establish precise mathematical model of oil film thickness in deformation zone, the lubrication in cold rolling process of SUS410L stainless steel strip is studied, and major factors affecting oil film thickness are also analyzed. According to the principle of statistics, mathematical model of critical oil film thickness in deformation zone for thermal scratch is built, with fitting and regression analytical method, and then based on temperature comparison method, the criterion for deciding thermal scratch defects is put forward. Storing and calling data through SQL Server 2010, a software on thermal scratch defects control is developed through Microsoft Visual Studio 2008 by MFC technique for stainless steel in tandem cold rolling, and then it is put into practical production. Statistics indicate that the hit rate of thermal scratch is as high as 92.38%, and the occurrence rate of thermal scratch is decreased by 89.13%. Owing to the application of the software, the rolling speed is increased by approximately 9.3%. The software developed provides an effective solution to the problem of thermal scratch defects in tandem cold rolling, and helps to promote products surface quality of stainless steel strips in practical production.

Evaluation of Surface Modification as a Lunar Dust Mitigation Strategy for Thermal Control Surfaces

Science.gov (United States)

Gaier, James R.; Waters, Deborah L.; Misconin, Robert M.; Banks, Bruce A.; Crowder, Mark

2011-01-01

Three surface treatments were evaluated for their ability to lower the adhesion between lunar simulant dust and AZ93, AlFEP, and AgFEP thermal control surfaces under simulated lunar conditions. Samples were dusted in situ and exposed to a standardized puff of nitrogen gas. Thermal performance before dusting, after dusting, and after part of the dust was removed by the puff of gas, were compared to perform the assessment. None of the surface treatments was found to significantly affect the adhesion of lunar simulants to AZ93 thermal control paint. Oxygen ion beam texturing also did not lower the adhesion of lunar simulant dust to AlFEP or AgFEP. But a workfunction matching coating and a proprietary Ball Aerospace surface treatment were both found to significantly lower the adhesion of lunar simulants to AlFEP and AgFEP. Based on these results, it is recommended that all these two techniques be further explored as dust mitigation coatings for AlFEP and AgFEP thermal control surfaces.

Thermal and UV Hydrosilylation of Alcohol-Based Bifunctional Alkynes on Si (111) surfaces: How surface radicals influence surface bond formation.

Science.gov (United States)

Khung, Y L; Ngalim, S H; Scaccabarozi, A; Narducci, D

2015-06-12

Using two different hydrosilylation methods, low temperature thermal and UV initiation, silicon (111) hydrogenated surfaces were functionalized in presence of an OH-terminated alkyne, a CF3-terminated alkyne and a mixed equimolar ratio of the two alkynes. XPS studies revealed that in the absence of premeditated surface radical through low temperature hydrosilylation, the surface grafting proceeded to form a Si-O-C linkage via nucleophilic reaction through the OH group of the alkyne. This led to a small increase in surface roughness as well as an increase in hydrophobicity and this effect was attributed to the surficial etching of silicon to form nanosize pores (~1-3 nm) by residual water/oxygen as a result of changes to surface polarity from the grafting. Furthermore in the radical-free thermal environment, a mix in equimolar of these two short alkynes can achieve a high contact angle of ~102°, comparable to long alkyl chains grafting reported in literature although surface roughness was relatively mild (rms = ~1 nm). On the other hand, UV initiation on silicon totally reversed the chemical linkages to predominantly Si-C without further compromising the surface roughness, highlighting the importance of surface radicals determining the reactivity of the silicon surface to the selected alkynes.

Effect of Surface Impulsive Thermal Loads on Fatigue Behavior of Constant Volume Propulsion Engine Combustor Materials

National Research Council Canada - National Science Library

Zhu, Dongming

2004-01-01

.... In this study, a simulated engine test rig has been established to evaluate thermal fatigue behavior of a candidate engine combustor material, Haynes 188, under superimposed CO2 laser surface impulsive thermal loads (30 to 100 Hz...

D Surface Generation from Aerial Thermal Imagery

Science.gov (United States)

Khodaei, B.; Samadzadegan, F.; Dadras Javan, F.; Hasani, H.

2015-12-01

Aerial thermal imagery has been recently applied to quantitative analysis of several scenes. For the mapping purpose based on aerial thermal imagery, high accuracy photogrammetric process is necessary. However, due to low geometric resolution and low contrast of thermal imaging sensors, there are some challenges in precise 3D measurement of objects. In this paper the potential of thermal video in 3D surface generation is evaluated. In the pre-processing step, thermal camera is geometrically calibrated using a calibration grid based on emissivity differences between the background and the targets. Then, Digital Surface Model (DSM) generation from thermal video imagery is performed in four steps. Initially, frames are extracted from video, then tie points are generated by Scale-Invariant Feature Transform (SIFT) algorithm. Bundle adjustment is then applied and the camera position and orientation parameters are determined. Finally, multi-resolution dense image matching algorithm is used to create 3D point cloud of the scene. Potential of the proposed method is evaluated based on thermal imaging cover an industrial area. The thermal camera has 640×480 Uncooled Focal Plane Array (UFPA) sensor, equipped with a 25 mm lens which mounted in the Unmanned Aerial Vehicle (UAV). The obtained results show the comparable accuracy of 3D model generated based on thermal images with respect to DSM generated from visible images, however thermal based DSM is somehow smoother with lower level of texture. Comparing the generated DSM with the 9 measured GCPs in the area shows the Root Mean Square Error (RMSE) value is smaller than 5 decimetres in both X and Y directions and 1.6 meters for the Z direction.

Surface state of GaN after rapid-thermal-annealing using AlN cap-layer

Energy Technology Data Exchange (ETDEWEB)

El-Zammar, G., E-mail: georgio.elzammar@univ-tours.fr [Université François Rabelais, Tours, GREMAN, CNRS UMR 7347, 10 rue Thalès de Milet CS 97155, 37071 Tours Cedex 2 (France); Khalfaoui, W. [Université François Rabelais, Tours, GREMAN, CNRS UMR 7347, 10 rue Thalès de Milet CS 97155, 37071 Tours Cedex 2 (France); Oheix, T. [Université François Rabelais, Tours, GREMAN, CNRS UMR 7347, 10 rue Thalès de Milet CS 97155, 37071 Tours Cedex 2 (France); STMicroelectronics, 10 rue Thalès de Milet CS 97155, 37071 Tours Cedex 2 (France); Yvon, A.; Collard, E. [STMicroelectronics, 10 rue Thalès de Milet CS 97155, 37071 Tours Cedex 2 (France); Cayrel, F.; Alquier, D. [Université François Rabelais, Tours, GREMAN, CNRS UMR 7347, 10 rue Thalès de Milet CS 97155, 37071 Tours Cedex 2 (France)

2015-11-15

Graphical abstract: Surface state of a crack-free AlN cap-layer reactive sputtered on GaN and annealed at high temperature showing a smooth, pit-free surface. - Highlights: • We deposit a crystalline AlN layer by reactive magnetron sputtering on GaN. • We show the effect of deposition parameters of AlN by reactive magnetron sputtering on the quality of the grown layer. • We demonstrate the efficiency of double cap-layer for GaN protection during high temperature thermal treatments. • We show an efficient selective etch of AlN without damaging GaN surface. - Abstract: Critical issues need to be overcome to produce high performance Schottky diodes on gallium nitride (GaN). To activate dopant, high temperature thermal treatments are required but damage GaN surface where hexagonal pits appear and prevent any device processing. In this paper, we investigated the efficiency of cap-layers on GaN during thermal treatments to avoid degradation. Aluminum nitride (AlN) and silicon oxide (SiO{sub x}) were grown on GaN by direct current reactive magnetron sputtering and plasma-enhanced chemical vapor deposition, respectively. AlN growth parameters were studied to understand their effect on the grown layers and their protection efficiency. Focused ion beam was used to measure AlN layer thickness. Crystalline quality and exact composition were verified using X-ray diffraction and energy dispersive X-ray spectroscopy. Two types of rapid thermal annealing at high temperatures were investigated. Surface roughness and pits density were evaluated using atomic force microscopy and scanning electron microscopy. Cap-layers wet etching was processed in H{sub 3}PO{sub 4} at 120 °C for AlN and in HF (10%) for SiO{sub x}. This work reveals effective protection of GaN during thermal treatments at temperatures as high as 1150 °C. Low surface roughness was obtained. Furthermore, no hexagonal pit was observed on the surface.

Characteristics of Turbulent Airflow Deduced from Rapid Surface Thermal Fluctuations: An Infrared Surface Anemometer

Science.gov (United States)

Aminzadeh, Milad; Breitenstein, Daniel; Or, Dani

2017-12-01

The intermittent nature of turbulent airflow interacting with the surface is readily observable in fluctuations of the surface temperature resulting from the thermal imprints of eddies sweeping the surface. Rapid infrared thermography has recently been used to quantify characteristics of the near-surface turbulent airflow interacting with the evaporating surfaces. We aim to extend this technique by using single-point rapid infrared measurements to quantify properties of a turbulent flow, including surface exchange processes, with a view towards the development of an infrared surface anemometer. The parameters for the surface-eddy renewal (α and β ) are inferred from infrared measurements of a single-point on the surface of a heat plate placed in a wind tunnel with prescribed wind speeds and constant mean temperatures of the surface. Thermally-deduced parameters are in agreement with values obtained from standard three-dimensional ultrasonic anemometer measurements close to the plate surface (e.g., α = 3 and β = 1/26 (ms)^{-1} for the infrared, and α = 3 and β = 1/19 (ms)^{-1} for the sonic-anemometer measurements). The infrared-based turbulence parameters provide new insights into the role of surface temperature and buoyancy on the inherent characteristics of interacting eddies. The link between the eddy-spectrum shape parameter α and the infrared window size representing the infrared field of view is investigated. The results resemble the effect of the sampling height above the ground in sonic anemometer measurements, which enables the detection of larger eddies with higher values of α . The physical basis and tests of the proposed method support the potential for remote quantification of the near-surface momentum field, as well as scalar-flux measurements in the immediate vicinity of the surface.

Low thermal budget surface preparation of Si and SiGe

International Nuclear Information System (INIS)

Abbadie, A.; Hartmann, J.M.; Holliger, P.; Semeria, M.N.; Besson, P.; Gentile, P.

2004-01-01

Using a two-step cleaning, we have investigated the low thermal budget surface preparation of Si and Si 1-x Ge x (x=0.2-0.33). It consists of an ex situ 'HF-last' wet-cleaning and an in situ low thermal budget H 2 bake in a reduced pressure-chemical vapor deposition reactor. Using secondary ion mass spectrometry, we have evaluated the effects of different H 2 bake temperatures (in between 750 and 850 deg. C for 2 min) on the removal efficiency of C, O and F atoms still present on the surface of Si and SiGe virtual substrates after the 'HF-last' wet-cleaning. We have then examined the impact of the (wet-cleaning+H 2 bake) combination on the surface cross-hatch of SiGe as-grown virtual substrates, focusing on the analysis, notably by atomic force microscopy, of the surface topography before and after the miscellaneous thermal treatments. In situ hydrogen baking steps in between 775 and 850 deg. C do not modify the surface morphology and roughness. An easy and rapid optical characterization method, i.e. the optical interferometry, is presented as well to monitor in line the morphological changes induced by such processing steps as chemical mechanical polishing, wet-cleaning, H 2 bake, etc. Despite the lower resolution of the optical profilometer, the surface roughness values coming from it have been correctly correlated with those obtained from AFM. An optimized 'HF-last' wet-cleaning using a diluted chemistry in conjunction with a H 2 bake at 800 deg. C for 2 min (775 deg. C, 2') is a good compromise for SiGe (Si) surface preparation

Acid Aging Effects on Surfaces of PTFE Gaskets Investigated by Thermal Analysis

Directory of Open Access Journals (Sweden)

C. Fragassa

2016-12-01

Full Text Available This paper investigates the effect of a prolonged acid attack on the surface of PTFE by Thermogravimetric Analysis (TGA and Differential Scanning Calorimetry (DSC. PTFE is very non-reactive, partly because of the strength of carbon–fluorine bonds and for its high crystallinity, and, as a consequence, it is often used in containers and pipework with reactive and corrosive chemicals. The PTFE under analysis is commercialized by two alternative producers in form of Teflon tapes. These tapes are adopted, as gaskets, in process plants where tires moulds are cleaned by acid solutions inside a multistage ultrasonic process. In this case, PTFE shows, in a relatively short operation time, inexplicably phenomena of surface degradation, which could be related, in general terms, to an acid attack. But, even considering the combined effect of ultrasonic waves, temperature, humidity and acid attack, the PTFE properties of resistance nominally exclude the risk of the extreme erosion phenomena as observed. The present experimental research aim at investigating this contradiction. A possible explanation could be related to the presence in the cleaning solution of unexpected fluorides, able to produce fluorinating agents and, thus, degrade carbon-fluorine bonds. Considering more the 300 chemical elements a tire compound consists in, it is really complex to preserve the original chemical composition of the cleaning solution. In this research PTFE samples have been treated with different mixtures of acids with the aim at investigating the different aging effects. The thermal analysis has permitted the experimental characterization of PTFE surface properties after acid attack, providing evidence of the degradation phenomena. In particular, the different acid treatments adopted for accelerating the aging of gaskets have highlighted the different behaviour of the PTFE matrix, but also differences between manufacturers.

Construction of mechanically durable superhydrophobic surfaces by thermal spray deposition and further surface modification

Science.gov (United States)

Chen, Xiuyong; Gong, Yongfeng; Suo, Xinkun; Huang, Jing; Liu, Yi; Li, Hua

2015-11-01

Here we report a simple and cost-effective technical route for constructing superhydrophobic surfaces with excellent abrasion resistance on various substrates. Rough surface structures were fabricated by thermal spray deposition of a variety of inorganic materials, and further surface modification was made by applying a thin layer of polytetrafluoroethylene. Results show that the Al, Cu, or NiCrBSi coatings with the surface roughness of up to 13.8 μm offer rough surface profile to complement the topographical morphology in micro-/nano-scaled sizes, and the hydrophobic molecules facilitate the hydrophobicity. The contact angles of water droplets of ∼155° with a sliding angle of up to 3.5° on the samples have been achieved. The newly constructed superhydrophobic coatings tolerate strong abrasion, giving clear insight into their long-term functional applications.

Surface properties of thermally treated composite wood panels

Science.gov (United States)

Croitoru, Catalin; Spirchez, Cosmin; Lunguleasa, Aurel; Cristea, Daniel; Roata, Ionut Claudiu; Pop, Mihai Alin; Bedo, Tibor; Stanciu, Elena Manuela; Pascu, Alexandru

2018-04-01

Composite finger-jointed spruce and oak wood panels have been thermally treated under standard pressure and oxygen content conditions at two different temperatures, 180 °C and respectively 200 °C for short time periods (3 and 5 h). Due to the thermally-aided chemical restructuration of the wood components, a decrease in water uptake and volumetric swelling values with up to 45% for spruce and 35% for oak have been registered, comparing to the reference samples. In relation to water resistance, a 15% increase of the dispersive component of the surface energy has been registered for the thermal-treated spruce panels, which impedes water spreading on the surface. The thermal-treated wood presents superior resistance to accelerated UV exposure and subsequently, with up to 10% higher Brinell hardness values than reference wood. The proposed thermal treatment improves the durability of the finger-jointed wood through a more economically and environmental friendly method than traditional impregnation, with minimal degradative impact on the structural components of wood.

Effect of surface conditions on blast wave propagation

International Nuclear Information System (INIS)

Song, Seung Ho; Li, Yi Bao; Lee, Chang Hoon; Choi, Jung Il

2016-01-01

We performed numerical simulations of blast wave propagations on surfaces by solving axisymmetric two-dimensional Euler equations. Assuming the initial stage of fireball at the breakaway point after an explosion, we investigated the effect of surface conditions considering surface convex or concave elements and thermal conditions on blast wave propagations near the ground surface. Parametric studies were performed by varying the geometrical factors of the surface element as well as thermal layer characteristics. We found that the peak overpressure near the ground zero was increased due to the surface elements, while modulations of the blast wave propagations were limited within a region for the surface elements. Because of the thermal layer, the precursor was formed in the propagations, which led to the attenuation of the peak overpressure on the ground surface

Transient thermal stresses in an orthotropic finite rectangular plate due to arbitrary surface heat-generations

International Nuclear Information System (INIS)

Sugano, Y.

1980-01-01

The transient thermal stresses in an orthotropic finite rectangular plate due to arbitrary surface heat-generations on two edges are studied by means of the Airy stress function. The purposes of this paper are to present a method of determing the transient thermal stresses in an orthographic rectangular plate with four edges of distinct thermal boundary condition of the third kind which exactly satisfy the traction-free conditions of shear stress over all boundaries including four corners of the plate, and to consider the effects of the anisotropies of material properties and the convective heat transfer on the upper and lower surfaces on the thermal stress distribution. (orig.)

Impacts of thermal and chemical discharges to surface water

International Nuclear Information System (INIS)

Stober, Q.J.

1974-01-01

Various aspects of thermal and chemical discharges to surface water are outlined. The major impacts of nuclear power plants on aquatic resources are disruption during construction, intake of cooling water, discharge problems, and interactions with other water users. The following topics are included under the heading, assessment of aquatic ecology: identification of flora and fauna; abundance of aquatic organisms; species-environment relationships; and identification of pre-existing environmental stress. The following topics are included under the heading, environmental effects of plant operation: entrapment of fish by cooling water; passage of plankton through cooling system; discharge area and thermal plume; chemical effluents; and plant construction. (U.S.)

Formation of hydrophobic coating on glass surface using atmospheric pressure non-thermal plasma in ambient air

International Nuclear Information System (INIS)

Fang, Z; Qiu, Y; Kuffel, E

2004-01-01

Non-thermal plasmas under atmospheric pressure are of great interest in material surface processing because of their convenience, effectiveness and low cost. In this paper, the treatment of a glass surface for improving hydrophobicity using a non-thermal plasma generated by a dielectric barrier corona discharge (DBCD) with a needle array-to-plane electrode arrangement in atmospheric air is conducted, and the surface properties of the glass before and after the DBCD treatment are studied using contact angle measurement, surface resistance measurement and the wet flashover voltage test. The effects of the plasma dose (the product of average discharge power and treatment time) of DBCD on the surface modification are studied, and the mechanism of interaction between the plasma and glass surface is discussed. It is found that a layer of hydrophobic coating is formed on the glass surface through DBCD treatment, and the improvement of hydrophobicity depends on the plasma dose of the DBCD. It seems that there is an optimum plasma dose for the surface treatment. The test results of thermal ageing and chemical ageing show that the hydrophobic layer has quite stable characteristics

Reverse Non-Equilibrium Molecular Dynamics Demonstrate That Surface Passivation Controls Thermal Transport at Semiconductor-Solvent Interfaces.

Science.gov (United States)

Hannah, Daniel C; Gezelter, J Daniel; Schaller, Richard D; Schatz, George C

2015-06-23

We examine the role played by surface structure and passivation in thermal transport at semiconductor/organic interfaces. Such interfaces dominate thermal transport in semiconductor nanomaterials owing to material dimensions much smaller than the bulk phonon mean free path. Utilizing reverse nonequilibrium molecular dynamics simulations, we calculate the interfacial thermal conductance (G) between a hexane solvent and chemically passivated wurtzite CdSe surfaces. In particular, we examine the dependence of G on the CdSe slab thickness, the particular exposed crystal facet, and the extent of surface passivation. Our results indicate a nonmonotonic dependence of G on ligand-grafting density, with interfaces generally exhibiting higher thermal conductance for increasing surface coverage up to ∼0.08 ligands/Å(2) (75-100% of a monolayer, depending on the particular exposed facet) and decreasing for still higher coverages. By analyzing orientational ordering and solvent penetration into the ligand layer, we show that a balance of competing effects is responsible for this nonmonotonic dependence. Although the various unpassivated CdSe surfaces exhibit similar G values, the crystal structure of an exposed facet nevertheless plays an important role in determining the interfacial thermal conductance of passivated surfaces, as the density of binding sites on a surface determines the ligand-grafting densities that may ultimately be achieved. We demonstrate that surface passivation can increase G relative to a bare surface by roughly 1 order of magnitude and that, for a given extent of passivation, thermal conductance can vary by up to a factor of ∼2 between different surfaces, suggesting that appropriately tailored nanostructures may direct heat flow in an anisotropic fashion for interface-limited thermal transport.

Effect of rapid thermal treatment on optical properties of porous silicon surface doped lithium

Energy Technology Data Exchange (ETDEWEB)

Haddadi, Ikbel, E-mail: haded.ikbel@yahoo.fr; Slema, Sonia Ben; Amor, Sana Ben; Bousbih, Rabaa; Bardaoui, Afrah; Dimassi, Wissem; Ezzaouia, Hatem

2015-04-15

In this paper, we have studied the effect of rapid thermal annealing on the optical properties of porous silicon layers doped with lithium (Li/PS). Surface modification of As-deposited Li/PS samples through thermal annealing were investigated by varying the temperature from 100 °C to 800 °C in an infrared (IR) heated belt furnace. A decrease in the reflectivity to about 6% for Li/PS annealed at 200 °C was obtained. From Photoluminescence (PL) spectra, a blue-shift of the gap was observed when the temperature is increased to 800 °C; we correlate these results to the change in chemical composition of the layers in order to find the optimized conditions for a potential application in silicon solar cells. - Highlights: • We have varied the annealing temperature of PS doped with Li. • PL intensity shows significant variation as function of temperature. • We observe reduce of Si–O–Li bands with increasing temperature. • Concurrent with the loss of Li we observe a decrease of the PL.

Methane Lunar Surface Thermal Control Test

Science.gov (United States)

Plachta, David W.; Sutherlin, Steven G.; Johnson, Wesley L.; Feller, Jeffrey R.; Jurns, John M.

2012-01-01

NASA is considering propulsion system concepts for future missions including human return to the lunar surface. Studies have identified cryogenic methane (LCH4) and oxygen (LO2) as a desirable propellant combination for the lunar surface ascent propulsion system, and they point to a surface stay requirement of 180 days. To meet this requirement, a test article was prepared with state-of-the-art insulation and tested in simulated lunar mission environments at NASA GRC. The primary goals were to validate design and models of the key thermal control technologies to store unvented methane for long durations, with a low-density high-performing Multi-layer Insulation (MLI) system to protect the propellant tanks from the environmental heat of low Earth orbit (LEO), Earth to Moon transit, lunar surface, and with the LCH4 initially densified. The data and accompanying analysis shows this storage design would have fallen well short of the unvented 180 day storage requirement, due to the MLI density being much higher than intended, its substructure collapse, and blanket separation during depressurization. Despite the performance issue, insight into analytical models and MLI construction was gained. Such modeling is important for the effective design of flight vehicle concepts, such as in-space cryogenic depots or in-space cryogenic propulsion stages.

Surface modification of cellulose acetate membrane using thermal annealing to enhance produced water treatment

Energy Technology Data Exchange (ETDEWEB)

Kusworo, T. D., E-mail: tdkusworo@che.undip.ac.id; Aryanti, N., E-mail: nita.aryanti@gmail.com; Firdaus, M. M. H.; Sukmawati, H. [Chemical Engineering, Faculty of Engineering, Diponegoro University Prof. Soedarto Street, Tembalang, Semarang, 50239, Phone/Fax : (024)7460058 (Indonesia)

2015-12-29

This study is performed primarily to investigate the effect of surface modification of cellulose acetate using thermal annealing on the enhancement of membrane performance for produced water treatment. In this study, Cellulose Acetate membranes were casted using dry/wet phase inversion technique. The effect of additive and post-treatment using thermal annealing on the membrane surface were examined for produced water treatment. Therma annealing was subjected to membrane surface at 60 and 70 °C for 5, 10 and 15 second, respectively. Membrane characterizations were done using membrane flux and rejection with produced water as a feed, Scanning Electron Microscopy (SEM) and Fourier Transform Infra Red (FTIR) analysis. Experimental results showed that asymmetric cellulose acetate membrane can be made by dry/wet phase inversion technique. The results from the Scanning Electron Microscopy (FESEM) analysis was also confirmed that polyethylene glycol as additivie in dope solution and thermal annealing was affected the morphology and membrane performance for produced water treatment, respectively. Scanning electron microscopy micrographs showed that the selective layer and the substructure of membrane became denser and more compact after the thermal annealing processes. Therefore, membrane rejection was significantly increased while the flux was slighty decreased, respectively. The best membrane performance is obtained on the composition of 18 wt % cellulose acetate, poly ethylene glycol 5 wt% with thermal annealing at 70° C for 15 second.

Surface modification of cellulose acetate membrane using thermal annealing to enhance produced water treatment

International Nuclear Information System (INIS)

Kusworo, T. D.; Aryanti, N.; Firdaus, M. M. H.; Sukmawati, H.

2015-01-01

This study is performed primarily to investigate the effect of surface modification of cellulose acetate using thermal annealing on the enhancement of membrane performance for produced water treatment. In this study, Cellulose Acetate membranes were casted using dry/wet phase inversion technique. The effect of additive and post-treatment using thermal annealing on the membrane surface were examined for produced water treatment. Therma annealing was subjected to membrane surface at 60 and 70 °C for 5, 10 and 15 second, respectively. Membrane characterizations were done using membrane flux and rejection with produced water as a feed, Scanning Electron Microscopy (SEM) and Fourier Transform Infra Red (FTIR) analysis. Experimental results showed that asymmetric cellulose acetate membrane can be made by dry/wet phase inversion technique. The results from the Scanning Electron Microscopy (FESEM) analysis was also confirmed that polyethylene glycol as additivie in dope solution and thermal annealing was affected the morphology and membrane performance for produced water treatment, respectively. Scanning electron microscopy micrographs showed that the selective layer and the substructure of membrane became denser and more compact after the thermal annealing processes. Therefore, membrane rejection was significantly increased while the flux was slighty decreased, respectively. The best membrane performance is obtained on the composition of 18 wt % cellulose acetate, poly ethylene glycol 5 wt% with thermal annealing at 70° C for 15 second

Thermal desorption study of physical forces at the PTFE surface

Science.gov (United States)

Wheeler, D. R.; Pepper, S. V.

1987-01-01

Thermal desorption spectroscopy (TDS) of the polytetrafluoroethylene (PTFE) surface was successfully employed to study the possible role of physical forces in the enhancement of metal-PTFE adhesion by radiation. The thermal desorption spectra were analyzed without assumptions to yield the activation energy for desorption over a range of xenon coverage from less than 0.1 monolayer to more than 100 monolayers. For multilayer coverage, the desorption is zero-order with an activation energy equal to the sublimation energy of xenon. For submonolayer coverages, the order for desorption from the unirradiated PTFE surface is 0.73 and the activation energy for desorption is between 3.32 and 3.36 kcal/mol; less than the xenon sublimation energy. The effect of irradiation is to increase the activation energy for desorption to as high as 4 kcal/mol at low coverage.

Surface-environment effects in spin crossover solids

Energy Technology Data Exchange (ETDEWEB)

Gudyma, Iu., E-mail: yugudyma@gmail.com; Maksymov, A.

2017-06-15

Highlights: • The spin-crossover nanocrystals were described by modified Ising-like model. • The ligand field on the surface is a function of external fluctuations. • The thermal hysteresis with surface and bulk interactions of the lattice was studied. • The system behavior with fluctuating ligand field on the surface was examined. • The fluctuations enlarge the hysteresis, but smaller surface interaction narrows it. - Abstract: The impact of surface effects on thermal induced spin crossover phenomenon is a subject of a broad and current interest. Using the modified Ising-like model of spin crossover solids with the ligand field as function of the molecule’ positions and random component on surface by means of Metropolis Monte Carlo algorithm the thermal spin transition curves were calculated. The analysis of spin configuration during transition gives a general idea about contribution of molecules from the surface and inside the lattice into resulting magnetization of the systems. The behavior of hysteresis loop for various surface coupling and fluctuations strength has been described.

Effects of surface proteins and lipids on molecular structure, thermal properties, and enzymatic hydrolysis of rice starch

Directory of Open Access Journals (Sweden)

Pan HU

Full Text Available Abstract Rice starches with different amylose contents were treated with sodium dodecyl sulfate (SDS to deplete surface proteins and lipids, and the changes in molecular structure, thermal properties, and enzymatic hydrolysis were evaluated. SDS treatment did not significantly change the molecular weight distribution, crystalline structure, short-range ordered degree, and gelatinization properties of starch, but significantly altered the pasting properties and increased the swelling power of starch. The removal of surface proteins and lipids increased the enzymatic hydrolysis and in vitro digestion of starch. The influences of removing surface proteins and lipids from starch on swelling power, pasting properties, and enzymatic hydrolysis were different among the various starches because of the differences in molecular structures of different starch styles. The aforementioned results indicated that removing the surface proteins and lipids from starch did not change the molecular structure but had significant effects on some functional properties.

Study of thermal effects in superconducting RF cavities

International Nuclear Information System (INIS)

Bousson, S.; Caruette, A.; Fouaidy, M.; Hammoudi, N.; Junquera, T.; Lesrel, J.; Yaniche, J.F.

1999-01-01

A high speed thermometric system equipped with 64 fixed surface thermometers is used to investigate thermal effects in several 3 GHz cavities. An evaluation of the time response of our thermometers is presented. A method based on RF signal analysis is proposed to evaluate the normal zone propagation rate during thermal breakdown. (authors)

Urban Soil: Assessing Ground Cover Impact on Surface Temperature and Thermal Comfort.

Science.gov (United States)

Brandani, Giada; Napoli, Marco; Massetti, Luciano; Petralli, Martina; Orlandini, Simone

2016-01-01

The urban population growth, together with the contemporary deindustrialization of metropolitan areas, has resulted in a large amount of available land with new possible uses. It is well known that urban green areas provide several benefits in the surrounding environment, such as the improvement of thermal comfort conditions for the population during summer heat waves. The purpose of this study is to provide useful information on thermal regimes of urban soils to urban planners to be used during an urban transformation to mitigate surface temperatures and improve human thermal comfort. Field measurements of solar radiation, surface temperature (), air temperature (), relative humidity, and wind speed were collected on four types of urban soils and pavements in the city of Florence during summer 2014. Analysis of days under calm, clear-sky condition is reported. During daytime, sun-to-shadow differences for , apparent temperature index (ATI), and were significantly positive for all surfaces. Conversely, during nighttime, differences among all surfaces were significantly negative, whereas ATI showed significantly positive differences. Moreover, was significantly negative for grass and gravel. Relative to the shaded surfaces, was higher on white gravel and grass than gray sandstone and asphalt during nighttime, whereas gray sandstone was always the warmest surface during daytime. Conversely, no differences were found during nighttime for ATI and measured over surfaces that were exposed to sun during the day, whereas showed higher values on gravel than grass and asphalt during nighttime. An exposed surface warms less if its albedo is high, leading to a significant reduction of during daytime. These results underline the importance of considering the effects of surface characteristics on surface temperature and thermal comfort. This would be fundamental for addressing urban environment issues toward the heat island mitigation considering also the impact of urban

Stagnation point flow on bioconvection nanofluid over a stretching/shrinking surface with velocity and thermal slip effects

Science.gov (United States)

Chan, Sze Qi; Aman, Fazlina; Mansur, Syahira

2017-09-01

Nanofluid containing nanometer sized particles has become an ideal thermal conductivity medium for the flow and heat transfer in many industrial and engineering applications due to their high rate of heat transfer. However, swimming microorganisms are imposed into the nanofluid to overcome the instability of nanoparticles due to a bioconvection phenomenon. This paper investigates the stagnation point flow on bioconvection heat transfer of a nanofluid over a stretching/shrinking surface containing gyrotactic microorganisms. Velocity and thermal slip effects are the two conditions incorporated into the model. Similarity transformation is applied to reduce the governing nonlinear partial differential equations into the nonlinear ordinary differential equations. The transformed equations are then solved numerically. The results are displayed in the form of graphs and tables. The effects of these governing parameters on the skin friction coefficient, local Nusselt number, local Sherwood number and the local density of the motile microorganisms are analysed and discussed in details.

Effects of ion concentration on thermally-chargeable double-layer supercapacitors

Science.gov (United States)

Lim, Hyuck; Lu, Weiyi; Chen, Xi; Qiao, Yu

2013-11-01

The concept of thermally-chargeable supercapacitor was discussed and validated experimentally. As two double-layer supercapacitor-type devices were placed at different temperatures and connected, due to the thermal dependence of surface charge structures, the electrode potentials became different, and thermal energy could be harvested and stored as electric energy. The important effect of ion concentration was investigated. The results were quite different from the prediction of conventional surface theory, which should be attributed to the unique behaviors of the ions confined in the nanoporous electrodes.

The Response of the Ocean Thermal Skin Layer to Air-Sea Surface Heat Fluxes

Science.gov (United States)

Wong, Elizabeth Wing-See

There is much evidence that the ocean is heating as a result of an increase in concentrations of greenhouse gases (GHGs) in the atmosphere from human activities. GHGs absorb infrared radiation and re-emit infrared radiation back to the ocean's surface which is subsequently absorbed. However, the incoming infrared radiation is absorbed within the top micrometers of the ocean's surface which is where the thermal skin layer exists. Thus the incident infrared radiation does not directly heat the upper few meters of the ocean. We are therefore motivated to investigate the physical mechanism between the absorption of infrared radiation and its effect on heat transfer at the air-sea boundary. The hypothesis is that since heat lost through the air-sea interface is controlled by the thermal skin layer, which is directly influenced by the absorption and emission of infrared radiation, the heat flow through the thermal skin layer adjusts to maintain the surface heat loss, assuming the surface heat loss does not vary, and thus modulates the upper ocean heat content. This hypothesis is investigated through utilizing clouds to represent an increase in incoming longwave radiation and analyzing retrieved thermal skin layer vertical temperature profiles from a shipboard infrared spectrometer from two research cruises. The data are limited to night-time, no precipitation and low winds of less than 2 m/s to remove effects of solar radiation, wind-driven shear and possibilities of thermal skin layer disruption. The results show independence of the turbulent fluxes and emitted radiation on the incident radiative fluxes which rules out the immediate release of heat from the absorption of the cloud infrared irradiance back into the atmosphere through processes such as evaporation and increase infrared emission. Furthermore, independence was confirmed between the incoming and outgoing radiative flux which implies the heat sink for upward flowing heat at the air-sea interface is more

Effect of treatment duration on surface nanocrystallization induced by fast multiple rotation rolling and its thermal stability

Energy Technology Data Exchange (ETDEWEB)

Chui Pengfei; Liu Yi; Liang Yanjie; Li Yang [Key Laboratory for Liquid-Solid Structure Evolution and Processing of Materials (Ministry of Education), Shandong University, Jinan 250061 (China); Fan Suhua [Key Laboratory for Liquid-Solid Structure Evolution and Processing of Materials (Ministry of Education), Shandong University, Jinan 250061 (China); Shandong Women' s University, Jinan 250300 (China); Sun Kangning, E-mail: sunkangning@sdu.edu.cn [Key Laboratory for Liquid-Solid Structure Evolution and Processing of Materials (Ministry of Education), Shandong University, Jinan 250061 (China)

2012-12-15

Highlights: Black-Right-Pointing-Pointer Effect of treatment time on surface nanocrystallization of a low carbon steel. Black-Right-Pointing-Pointer The grain size decreases gradually with the increase of treatment duration. Black-Right-Pointing-Pointer The microhardness of FMRR treated sample reaches 284 HV. Black-Right-Pointing-Pointer The nanocrystalline layer is stable during annealing treatment up to 400 Degree-Sign C. - Abstract: A nanocrystalline surface layer of low carbon steel induced by fast multiple rotation rolling (FMRR) was determined by optical microscopy and transmission electron microscopy. The results show that the grain size decreases gradually with the increase of treatment duration. Equiaxed nanocrystalline with the average grain size about 20 nm is obtained in the top surface layer after FMRR treatment for 30 min. With the increase of treatment duration (60 min), the average grain size further reduces to about 9 nm. At the same time, the microhardness of surface layer for treated sample is improved correspondingly owing to grain refinement and work-hardening. Compared with original sample, the microhardness of FMRR treated sample is increased by more than 200%. After annealing treatment, the investigation of thermal stability of nanocrystalline layer indicates that the grains begin to grow obviously at annealing for 400 Degree-Sign C, and abnormal grain growth also occurs in individual grains. Due to grain growth and stress relaxation during annealing, the microhardness slightly decreases at 400 Degree-Sign C. In spite of this, the majority of grains are still nanocrystalline, ranging from about 30 to 60 nm. It demonstrates that the nanocrystalline layer has high thermal stability.

Effect of surface tension and coefficient of thermal expansion in 30 nm scale nanoimprinting with two flexible polymer molds

International Nuclear Information System (INIS)

Kim, Jae Kwan; Cho, Hye Sung; Jung, Ho-Sup; Suh, Kahp-Yang; Lim, Kipil; Kim, Ki-Bum; Choi, Dae-Geun; Jeong, Jun-Ho

2012-01-01

We report on nanoimprinting of polymer thin films at 30 nm scale resolution using two types of ultraviolet (UV)-curable, flexible polymer molds: perfluoropolyether (PFPE) and polyurethane acrylate (PUA). It was found that the quality of nanopatterning at the 30 nm scale is largely determined by the combined effects of surface tension and the coefficient of thermal expansion of the polymer mold. In particular, the polar component of surface tension may play a critical role in clean release of the mold, as evidenced by much reduced delamination or broken structures for the less polarized PFPE mold when patterning a relatively hydrophilic PMMA film. In contrast, such problems were not notably observed with a relatively hydrophobic PS film for both polymer molds. In addition, the demolding characteristic was also influenced by the coefficient of thermal expansion so that no delamination or uniformity problems were observed when patterning a UV-curable polymer film at room temperature. These results suggest that a proper polymeric mold material needs to be chosen for patterning polymer films under different surface properties and processing conditions, providing insights into how a clean demolding characteristic can be obtained at 30 nm scale nanopatterning. (paper)

Impact of the surface quality on the thermal shock performance of beryllium armor tiles for first wall applications

Energy Technology Data Exchange (ETDEWEB)

Spilker, B., E-mail: b.spilker@fz-juelich.de; Linke, J.; Pintsuk, G.; Wirtz, M.

2016-11-01

Highlights: • Different surface qualities of S-65 beryllium are tested under high heat flux conditions. • After 1000 thermal shocks, the loaded area exhibits a crucial destruction. • Stress accelerated grain boundary oxidation/dynamic embrittlement effects are linked to the thermal shock performance of beryllium. • Thermally induced cracks form between 1 and 10 pulses and grow wider and deeper between 10 and 100 pulses. • Thermally induced cracks form and propagate independently from surface grooves and the surface quality. - Abstract: Beryllium will be applied as first wall armor material in ITER. The armor has to sustain high steady state and transient power fluxes. For transient events like edge localized modes, these transient power fluxes rise up to 1.0 GW m{sup −2} with a duration of 0.5–0.75 ms in the divertor region and a significant fraction of this power flux is deposited on the first wall as well. In the present work, the reference beryllium grade for the ITER first wall application S-65 was prepared with various surface conditions and subjected to transient power fluxes (thermal shocks) with ITER relevant loading parameters. After 1000 thermal shocks, a crucial destruction of the entire loaded area was observed and linked to the stress accelerated grain boundary oxidation (SAGBO)/dynamic embrittlement (DE) effect. Furthermore, the study revealed that the majority of the thermally induced cracks formed between 1 and 10 pulses and then grew wider and deeper with increasing pulse number. The surface quality did not influence the cracking behavior of beryllium in any detectable way. However, the polished surface demonstrated the highest resistance against the observed crucial destruction mechanism.

Improved the Surface Roughness of Silicon Nanophotonic Devices by Thermal Oxidation Method

Energy Technology Data Exchange (ETDEWEB)

Shi Zujun; Shao Shiqian; Wang Yi, E-mail: ywangwnlo@mail.hust.edu.cn [Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, No. 1037, Luoyu Street, Wuhan 430074 (China)

2011-02-01

The transmission loss of the silicon-on-insulator (SOI) waveguide and the coupling loss of the SOI grating are determined to a large extent by the surface roughness. In order to obtain smaller loss, thermal oxidation is a good choice to reduce the surface roughness of the SOI waveguide and grating. Before the thermal oxidation, the root mean square of the surface roughness is over 11 nm. After the thermal oxidation, the SEM figure shows that the bottom of the grating is as smooth as quartz surface, while the AFM shows that the root mean square of the surface is less than 5 nm.

A thermal monitoring sheet with low influence from adjacent waterbolus for tissue surface thermometry during clinical hyperthermia.

Science.gov (United States)

Arunachalam, Kavitha; Maccarini, Paolo F; Stauffer, Paul R

2008-10-01

This paper presents a complete thermal analysis of a novel conformal surface thermometer design with directional sensitivity for real-time temperature monitoring during hyperthermia treatments of large superficial cancer. The thermal monitoring sheet (TMS) discussed in this paper consists of a 2-D array of fiberoptic sensors embedded between two layers of flexible, low-loss, and thermally conductive printed circuit board (PCB) film. Heat transfer across all interfaces from the tissue surface through multiple layers of insulating dielectrics surrounding the small buried temperature sensor and into an adjacent temperature-regulated water coupling bolus was studied using 3-D thermal simulation software. Theoretical analyses were carried out to identify the most effective differential TMS probe configuration possible with commercially available flexible PCB materials and to compare their thermal responses with omnidirectional probes commonly used in clinical hyperthermia. A TMS sensor design that employs 0.0508-mm Kapton MTB and 0.2032-mm Kapton HN flexible polyimide films is proposed for tissue surface thermometry with low influence from the adjacent waterbolus. Comparison of the thermal simulations with clinical probes indicates the new differential TMS probe design to outperform in terms of both transient response and steady-state accuracy in selectively reading the tissue surface temperature, while decreasing the overall thermal barrier of the probe between the coupling waterbolus and tissue surface.

Thermal equilibrium of pure electron plasmas across a central region of magnetic surfaces

Science.gov (United States)

Hahn, Michael; Pedersen, Thomas Sunn

2009-06-01

Measurements of the equilibria of plasmas created by emission from a biased filament located off the magnetic axis in the Columbia Non-neutral Torus (CNT) [T. S. Pedersen, J. P. Kremer, R. G. Lefrancois et al., Fusion Sci. Technol. 50, 372 (2006)] show that such plasmas have equilibrium properties consistent with the inner surfaces being in a state of cross-surface thermal equilibrium. Numerical solutions to the equilibrium equation were used to fit the experimental data and demonstrate consistency with cross-surface thermal equilibrium. Previous experiments in CNT showed that constant temperatures across magnetic surfaces are characteristic of CNT plasmas, implying thermal confinement times much less than particle confinement times. These results show that when emitting off axis there is a volume of inner surfaces where diffusion into that region is balanced by outward transport, producing a Boltzmann distribution of electrons. When combined with the low thermal energy confinement time this is a cross-surface thermal equilibrium.

Thermal equilibrium of pure electron plasmas across a central region of magnetic surfaces

International Nuclear Information System (INIS)

Hahn, Michael; Pedersen, Thomas Sunn

2009-01-01

Measurements of the equilibria of plasmas created by emission from a biased filament located off the magnetic axis in the Columbia Non-neutral Torus (CNT) [T. S. Pedersen, J. P. Kremer, R. G. Lefrancois et al., Fusion Sci. Technol. 50, 372 (2006)] show that such plasmas have equilibrium properties consistent with the inner surfaces being in a state of cross-surface thermal equilibrium. Numerical solutions to the equilibrium equation were used to fit the experimental data and demonstrate consistency with cross-surface thermal equilibrium. Previous experiments in CNT showed that constant temperatures across magnetic surfaces are characteristic of CNT plasmas, implying thermal confinement times much less than particle confinement times. These results show that when emitting off axis there is a volume of inner surfaces where diffusion into that region is balanced by outward transport, producing a Boltzmann distribution of electrons. When combined with the low thermal energy confinement time this is a cross-surface thermal equilibrium.

Thermal Effects Induced by Laser Irradiation of Solids

International Nuclear Information System (INIS)

Galovic, S.

2004-01-01

A part of incident energy is absorbed within the irradiated sample when a solid is exposed to the influence of laser radiation, to more general electromagnetic radiation within the wide range of wavelengths (from microwaves, to infrared radiation to X-rays), or to the energy of particle beams (electronic, protonic, or ionic). The absorption process signifies a highly selective excitation of the electronic state of atoms or molecules, followed by thermal and non-thermal de-excitation processes. Non-radiation de-excitation-relaxation processes induce direct sample heating. In addition, a great number of non-thermal processes (e.g., photoluminescence, photochemistry, photovoltage) may also induce heat generation as a secondary process. This method of producing heat is called the photothermal effect.The photothermal effect and subsequent propagation of thermal waves on the surface and in the volume of the solid absorbing the exciting beam may produce the following: variations in the temperature on the surfaces of the sample; deformation and displacement of surfaces; secondary infrared radiation (photothermal radiation); the formation of the gradient of the refractivity index; changes in coefficients of reflection and absorbtion; the generation of sound (photoacoustic generation), etc. These phenomena may be used in the investigation and measurement of various material properties since the profile and magnitude of the generated signal depend upon the nature of material absorbing radiation. A series of non-destructive spectroscopic, microscopic and defectoscopic detecting techniques, called photothermal methods, is developed on the basis of the above-mentioned phenomena.This paper outlines the interaction between the intensity modulated laser beam and solids, and presents a mathematical model of generated thermal sources. Generalized models for a photothermal response of optically excited materials have been obtained, including thermal memory influence on the propagation

Surface roughness effects on heat transfer in Couette flow

International Nuclear Information System (INIS)

Elia, G.G.

1981-01-01

A cell theory for viscous flow with rough surfaces is applied to two basic illustrative heat transfer problems which occur in Couette flow. Couette flow between one adiabatic surface and one isothermal surface exhibits roughness effects on the adiabatic wall temperature. Two types of rough cell adiabatic surfaces are studied: (1) perfectly insulating (the temperature gradient vanishes at the boundary of each cell); (2) average insulating (each cell may gain or lose heat but the total heat flow at the wall is zero). The results for the roughness on a surface in motion are postulated to occur because of fluid entrainment in the asperities on the moving surface. The symmetry of the roughness effects on thermal-viscous dissipation is discussed in detail. Explicit effects of the roughness on each surface, including combinations of roughness values, are presented to enable the case where the two surfaces may be from different materials to be studied. The fluid bulk temperature rise is also calculated for Couette flow with two ideal adiabatic surfaces. The effect of roughness on thermal-viscous dissipation concurs with the viscous hydrodynamic effect. The results are illustrated by an application to lubrication. (Auth.)

Thermal limiting effects in optical plasmonic waveguides

International Nuclear Information System (INIS)

Ershov, A.E.; Gerasimov, V.S.; Gavrilyuk, A.P.; Karpov, S.V.; Zakomirnyi, V.I.; Rasskazov, I.L.; Polyutov, S.P.

2017-01-01

We have studied thermal effects occurring during excitation of optical plasmonic waveguide (OPW) in the form of linear chain of spherical Ag nanoparticles by pulsed laser radiation. It was shown that heating and subsequent melting of the first irradiated particle in a chain can significantly deteriorate the transmission efficiency of OPW that is the crucial and limiting factor and continuous operation of OPW requires cooling devices. This effect is caused by suppression of particle's surface plasmon resonance due to reaching the melting point temperature. We have determined optimal excitation parameters which do not significantly affect the transmission efficiency of OPW. - Highlights: • The thermodynamic model was developed to study thermal effects at nanoscale. • Developed model considers temperature-dependent permittivity of the nanoparticles. • Thermal effects significantly suppress transmission efficiency of plasmonic chains. • Optimal parameters for stable operation of plasmonic chains were defined.

STUDY ON SHADOW EFFECTS OF VARIOUS FEATURES ON CLOSE RANGE THERMAL IMAGES

Directory of Open Access Journals (Sweden)

C. L. Liao

2012-07-01

Full Text Available Thermal infrared data become more popular in remote sensing investigation, for it could be acquired both in day and night. The change of temperature has special characteristic in natural environment, so the thermal infrared images could be used in monitoring volcanic landform, the urban development, and disaster prevention. Heat shadow is formed by reflecting radiating capacity which followed the objects. Because of poor spatial resolution of thermal infrared images in satellite sensor, shadow effects were usually ignored. This research focus on discussing the shadow effects of various features, which include metals and nonmetallic materials. An area-based thermal sensor, FLIR-T360 was selected to acquire thermal images. Various features with different emissivity were chosen as reflective surface to obtain thermal shadow in normal atmospheric temperature. Experiments found that the shadow effects depend on the distance between sensors and features, depression angle, object temperature and emissivity of reflective surface. The causes of shadow effects have been altered in the experiment for analyzing the variance in thermal infrared images. The result shows that there were quite different impacts by shadow effects between metals and nonmetallic materials. The further research would be produced a math model to describe the shadow effects of different features in the future work.

Effects of flow and colony morphology on the thermal boundary layer of corals

DEFF Research Database (Denmark)

Jimenez, Isabel M; Kühl, Michael; Larkum, Anthony W D

2011-01-01

The thermal microenvironment of corals and the thermal effects of changing flow and radiation are critical to understanding heat-induced coral bleaching, a stress response resulting from the destruction of the symbiosis between corals and their photosynthetic microalgae. Temperature microsensor...... measurements at the surface of illuminated stony corals with uneven surface topography (Leptastrea purpurea and Platygyra sinensis) revealed millimetre-scale variations in surface temperature and thermal boundary layer (TBL) that may help understand the patchy nature of coral bleaching within single colonies....... The effect of water flow on the thermal microenvironment was investigated in hemispherical and branching corals (Porites lobata and Stylophora pistillata, respectively) in a flow chamber experiment. For both coral types, the thickness of the TBL decreased exponentially from 2.5 mm at quasi-stagnant flow (0...

MHD natural convection from a heated vertical wavy surface with variable viscosity and thermal conductivity

International Nuclear Information System (INIS)

Choudhury, M.; Hazarika, G.C.; Sibanda, P.

2013-01-01

We investigate the effects of temperature dependent viscosity and thermal conductivity on natural convection flow of a viscous incompressible electrically conducting fluid along a vertical wavy surface. The flow is permeated by uniform transverse magnetic field. The fluid viscosity and thermal conductivity are assumed to vary as inverse linear functions of temperature. The coupled non-linear systems of partial differential equations are solved using the finite difference method. The effects of variable viscosity parameter, variable thermal conductivity parameter and magnetic parameter on the flow field and the heat transfer characteristics are discussed and shown graphically. (author)

'Thermal ghosts': apparent decay of fixed surfaces caused by heat diffusion

International Nuclear Information System (INIS)

Livadiotis, George

2007-01-01

The behaviour concerning classical heat diffusion on fixed thermal surfaces, studied by observations, still holds surprises. As soon as convective and radiative processes are negligible within the medium, this is considered to be free from energy sources and sinks. Then, the heat diffusion equation is conveniently solved using standard Fourier methods. Some considerations about the contrast effect suggest that the surface boundary would rather be observed to follow specific area decay dynamics than remaining fixed and static. Here it is shown that the apparent boundary lies on a specific isothermal spatiotemporal curve, which depends on the observing device. This is characterized by a slight, though determinative, difference between its radiance and that of the ambient background. Thereafter, the heat diffusion yields apparent boundary shrinkage with the passing of time. This phenomenon is particularly notable for two reasons: its lifetime and final decay rate depend only on the medium thermal properties, while being independent of the apparent boundary spatiotemporal curve. Thus, the former provides a suitable method for measuring the medium thermal properties via the observational data. The latter strongly reveal a kind of universality of some characteristic properties of the phenomenon, common to all observers

Evolution of surface topography in dependence on the grain orientation during surface thermal fatigue of polycrystalline copper

CERN Document Server

Aicheler, M; Taborelli, M; Calatroni, S; Neupert, H; Wuensch, W; Sgobba, S

2011-01-01

Surface degradation due to cyclic thermal loading plays a major role in the Accelerating Structures (AS) of the future Compact Linear Collider (CLIC) In this article results on surface degradation of thermally cycled polycrystalline copper as a function of the orientation of surface grains are presented Samples with different grain sizes were subjected to thermal fatigue using two different methods and were then characterized using roughness measurements and Orientation Imaging Scanning-Electron-Microscopy (OIM-SEM) Samples fatigued by a pulsed laser show the same trend in the orientation-fatigue damage accumulation as the sample fatigued by pulsed Radio-Frequency-heating (RF) it is clearly shown that 11 1 1] surface grains develop significantly more damage than the surface grains oriented in {[}100] and three reasons for this behaviour are pointed out Based on observations performed near grain boundaries their role in the crack initiation process is discussed The results are in good agreement with previous f...

Surface modification of biphasic calcium phosphate scaffolds by non-thermal atmospheric pressure nitrogen and air plasma treatment for improving osteoblast attachment and proliferation

International Nuclear Information System (INIS)

Choi, Yu-Ri; Kwon, Jae-Sung; Song, Doo-Hoon; Choi, Eun Ha; Lee, Yong-Keun; Kim, Kyoung-Nam; Kim, Kwang-Mahn

2013-01-01

Surface modifications induced by non-thermal plasma have been used extensively in biomedical applications. The attachment and proliferation of osteoblast cells are important in bone tissue engineering using scaffolds. Hence the effect of non-thermal plasma on hydroxyapatite/β-tri-calcium phosphate (HA/β-TCP) scaffolds in terms of improving osteoblast attachment and proliferation was investigated. Experimental groups were treated with non-thermal plasma for 10 min and 20 min and a control group was not treated with non-thermal plasma. For surface chemistry analysis, X-ray photoelectron spectroscopy (XPS) analysis was carried out. The hydrophilicity was determined from contact angle measurement on the surface. Atomic force microscopy analysis (AFM) was used to test the change in surface roughness and cell attachment and proliferation were evaluated using MC3T3-E1 osteoblast cells. XPS spectra revealed a decreased amount of carbon on the surface of the plasma-treated sample. The contact angle was also decreased following plasma treatment, indicating improved hydrophilicity of plasma-treated surfaces compared to the untreated disc. A significant increase in MC3T3E-1 cell attachment and proliferation was noted on plasma-treated samples as compared to untreated specimens. The results suggest that non-thermal atmospheric pressure nitrogen and air plasma treatments provide beneficial surface characteristics on HA/β-TCP scaffolds. - Highlights: ► Non-thermal plasma increased OH- and decreased C on biphasic scaffold. ► Non-thermal plasma had no effect on surface roughness. ► Non-thermal plasma resulted in hydrophilic surface. ► Non-thermal plasma resulted in better cell attachment and proliferation. ► Non-thermal plasma treatment on biphasic scaffold is useful for tissue engineering

Influence of deposition temperature of thermal ALD deposited Al2O3 films on silicon surface passivation

Directory of Open Access Journals (Sweden)

Neha Batra

2015-06-01

Full Text Available The effect of deposition temperature (Tdep and subsequent annealing time (tanl of atomic layer deposited aluminum oxide (Al2O3 films on silicon surface passivation (in terms of surface recombination velocity, SRV is investigated. The pristine samples (as-deposited show presence of positive fixed charges, QF. The interface defect density (Dit decreases with increase in Tdep which further decreases with tanl up to 100s. An effective surface passivation (SRV<8 cm/s is realized for Tdep ≥ 200 °C. The present investigation suggests that low thermal budget processing provides the same quality of passivation as realized by high thermal budget process (tanl between 10 to 30 min.

Self-Healing Thermal Annealing: Surface Morphological Restructuring Control of GaN Nanorods

Energy Technology Data Exchange (ETDEWEB)

Conroy, Michele; Li, Haoning; Zubialevich, Vitaly Z.; Kusch, Gunnar; Schmidt, Michael; Collins, Timothy; Glynn, Colm; Martin, Robert W.; O’Dwyer, Colm; Morris, Michael D.; Holmes, Justin D.; Parbrook, Peter J.

2016-12-07

With advances in nanolithography and dry etching, top-down methods of nanostructuring have become a widely used tool for improving the efficiency of optoelectronics. These nano dimensions can offer various benefits to the device performance in terms of light extraction and efficiency, but often at the expense of emission color quality. Broadening of the target emission peak and unwanted yellow luminescence are characteristic defect-related effects due to the ion beam etching damage, particularly for III–N based materials. In this article we focus on GaN based nanorods, showing that through thermal annealing the surface roughness and deformities of the crystal structure can be “self-healed”. Correlative electron microscopy and atomic force microscopy show the change from spherical nanorods to faceted hexagonal structures, revealing the temperature-dependent surface morphology faceting evolution. The faceted nanorods were shown to be strain- and defect-free by cathodoluminescence hyperspectral imaging, micro-Raman, and transmission electron microscopy (TEM). In-situ TEM thermal annealing experiments allowed for real time observation of dislocation movements and surface restructuring observed in ex-situ annealing TEM sampling. This thermal annealing investigation gives new insight into the redistribution path of GaN material and dislocation movement post growth, allowing for improved understanding and in turn advances in optoelectronic device processing of compound semiconductors.

STRESSES IN CEMENT-CONCRETE PAVEMENT SURFACING CAUSED BY THERMAL SHOCK

Directory of Open Access Journals (Sweden)

M. K. Pshembaev

2016-01-01

Full Text Available It is necessary to mention specially so-called thermal shock among various impacts on highway surface. Ice layer is formed on a concrete surface during the winter period of pavement surfacing operation. Sodium chloride which lowers temperature of water-ice transition temperature and causes ice thawing at negative temperature is usually used to remove ice from the pavement surface. Consequently, temperature in the concrete laying immediately under a thawing ice layer is coming down with a run that leads to significant stresses. Such phenomenon is known as a thermal shock with a meaning of local significant change in temperature. This process is under investigation, it has practical importance for an estimation of strength and longevity of a cement-concrete pavement surfacing and consequently it is considered as rather topical issue. The purpose of investigations is to develop a mathematical model and determination of shock blow permissible gradients for a cementconcrete road covering. Finite difference method has been used in order to determine stressed and deformed condition of the cement-concrete pavement surfacing of highways. A computer program has been compiled and it permits to carry out calculation of a road covering at various laws of temperature distribution in its depth. Regularities in distribution of deformation and stresses in the cement-concrete pavement surfacing of highways at thermal shock have been obtained in the paper. A permissible parameter of temperature distribution in pavement surfacing thickness has been determined in the paper. A strength criterion based on the process of micro-crack formation and development in concrete has been used for making calculations. It has been established that the thermal shock causes significant temperature gradients on the cement-concrete surfacing that lead to rather large normal stresses in the concrete surface layer. The possibility of micro-crack formation in a road covering is

Robust and thermal-healing superhydrophobic surfaces by spin-coating of polydimethylsiloxane.

Science.gov (United States)

Long, Mengying; Peng, Shan; Deng, Wanshun; Yang, Xiaojun; Miao, Kai; Wen, Ni; Miao, Xinrui; Deng, Wenli

2017-12-15

Superhydrophobic surfaces easily lose their excellent water-repellency after damages, which limit their broad applications in practice. Thus, the fabrication of superhydrophobic surfaces with excellent durability and thermal healing should be taken into consideration. In this work, robust superhydrophobic surfaces with thermal healing were successfully fabricated by spin-coating method. To achieve superhydrophobicity, cost-less and fluoride-free polydimethylsiloxane (PDMS) was spin-coated on rough aluminum substrates. After being spin-coated for one cycle, the superhydrophobic PDMS coated hierarchical aluminum (PDMS-H-Al) surfaces showed excellent tolerance to various chemical and mechanical damages in lab, and outdoor damages for 90days. When the PDMS-H-Al surfaces underwent severe damages such as oil contamination (peanut oil with high boiling point) or sandpaper abrasion (500g of force for 60cm), their superhydrophobicity would lose. Interestingly, through a heating process, cyclic oligomers generating from the partially decomposed PDMS acted as low-surface-energy substance on the damaged rough surfaces, leading to the recovery of superhydrophobicity. The relationship between the spin-coating cycles and surface wettability was also investigated. This paper provides a facile, fluoride-free and efficient method to fabricate superhydrophobic surfaces with thermal healing. Copyright © 2017. Published by Elsevier Inc.

Transient thermal stresses in a transversely isotropic finite hollow circular cylinder due to arbitrary surface heat generations

International Nuclear Information System (INIS)

Sugano, Yoshihiro; Nakanishi, Takanori.

1980-01-01

The materials macroscopically regarded as anisotropic materials such as fiber-reinforced composite materials have become to be used for the structural elements at elevated temperature, and the studies on the problem of thermal stress in anisotropic bodies are carried out actively. The unsteady thermal stress in anisotropic finite circular cylinders has not been analyzed so far. In this study, the problem of unsteady thermal stress in an anisotropic finite circular cylinder having arbitrary surface heat generation in axial direction on the internal and external surfaces, and emitting heat from both ends and the internal and external surfaces, was analyzed. For the analysis of temperature distribution, generalized finite Fourier transformation and finite Hankel transformation were used, and thermal stress and thermal displacement were analyzed by the use of the stress function of Singh. By adopting the function used for the transformation nucleus in generalized finite Fourier transformation as the stress function, the analysis was made without separating symmetric and opposite symmetric problems. Numerical calculation was carried out on the basis of the analytical results, and the effects of the anisotropy in thermal conductivity, Young's modulus and linear expansion on unsteady temperature distribution, thermal stress and thermal displacement were quantitatively examined. (Kako, I.)

A thermal spike analysis of low energy ion activated surface processes

International Nuclear Information System (INIS)

Gilmore, G.M.; Haeri, A.; Sprague, J.A.

1989-01-01

This paper reports a thermal spike analysis utilized to predict the time evolution of energy propagation through a solid resulting from energetic particle impact. An analytical solution was developed that can predict the number of surface excitations such as desorption, diffusion or chemical reaction activated by an energetic particle. The analytical solution is limited to substrates at zero Kelvin and to materials with constant thermal diffusivities. These limitations were removed by developing a computer numerical integration of the propagation of the thermal spike through the solid and the subsequent activation of surface processes

Effects of thermal efficiency in DCMD and the preparation of membranes with low thermal conductivity

Energy Technology Data Exchange (ETDEWEB)

Li, Zhehao, E-mail: ccgri_lzh@163.com [Changchun Gold Research Institute, 130012 (China); Peng, Yuelian, E-mail: pyl@live.com.au [Department of Chemistry and Chemical Engineering, College of Environmental and Energy Engineering, Beijing University of Technology, Beijing 100124 (China); Dong, Yajun; Fan, Hongwei [Department of Chemistry and Chemical Engineering, College of Environmental and Energy Engineering, Beijing University of Technology, Beijing 100124 (China); Chen, Ping [The Research Institute of Environmental Protection, North China Pharmaceutical Group Corporation, 050015 (China); Qiu, Lin [Institute of Engineering Thermophysics, Chinese Academy of Sciences, Beijing 100190 (China); Jiang, Qi [National Major Science and Technology Program Management Office for Water Pollution Control and Treatment, MEP, 100029 (China)

2014-10-30

Highlights: • The effects on vapor flux and thermal efficiency were simulated. • The conditions favoring vapor flux also favored thermal efficiency. • Four microporous polymer membranes were compared. • The SiO{sub 2} aerogel coating reduced the thermal conductivity of polymer membranes. • A 3ω technique was used to measure the thermal conductivity of membranes. - Abstract: The effects of the membrane characteristics and operational conditions on the vapor flux and thermal efficiency in a direct contact membrane distillation (DCMD) process were studied with a mathematical simulation. The membrane temperature, driving force of vapor transfer, membrane distillation coefficient, etc. were used to analyze the effects. The operating conditions that increased the vapor flux improved the thermal efficiency. The membrane characteristics of four microporous membranes and their performances in DCMD were compared. A polysulfone (PSf) membrane prepared via vapor-induced phase separation exhibited the lowest thermal conductivity. The PSf and polyvinylidene difluoride (PVDF) membranes were modified using SiO{sub 2} aerogel blending and coating to reduce the thermal conductivity of the membrane. The coating process was more effective than the blending process toward this end. The changes in the structure of the modified membrane were observed with a scanning electron microscope. Si was found on the modified membrane surface with an energy spectrometer. The PVDF composite and support membranes were tested during the DCMD process; the composite membrane had a higher vapor flux and a better thermal efficiency than the support. A new method based on a 3ω technique was used to measure the thermal conductivity of the membranes.

Effects of thermal efficiency in DCMD and the preparation of membranes with low thermal conductivity

International Nuclear Information System (INIS)

Li, Zhehao; Peng, Yuelian; Dong, Yajun; Fan, Hongwei; Chen, Ping; Qiu, Lin; Jiang, Qi

2014-01-01

Highlights: • The effects on vapor flux and thermal efficiency were simulated. • The conditions favoring vapor flux also favored thermal efficiency. • Four microporous polymer membranes were compared. • The SiO 2 aerogel coating reduced the thermal conductivity of polymer membranes. • A 3ω technique was used to measure the thermal conductivity of membranes. - Abstract: The effects of the membrane characteristics and operational conditions on the vapor flux and thermal efficiency in a direct contact membrane distillation (DCMD) process were studied with a mathematical simulation. The membrane temperature, driving force of vapor transfer, membrane distillation coefficient, etc. were used to analyze the effects. The operating conditions that increased the vapor flux improved the thermal efficiency. The membrane characteristics of four microporous membranes and their performances in DCMD were compared. A polysulfone (PSf) membrane prepared via vapor-induced phase separation exhibited the lowest thermal conductivity. The PSf and polyvinylidene difluoride (PVDF) membranes were modified using SiO 2 aerogel blending and coating to reduce the thermal conductivity of the membrane. The coating process was more effective than the blending process toward this end. The changes in the structure of the modified membrane were observed with a scanning electron microscope. Si was found on the modified membrane surface with an energy spectrometer. The PVDF composite and support membranes were tested during the DCMD process; the composite membrane had a higher vapor flux and a better thermal efficiency than the support. A new method based on a 3ω technique was used to measure the thermal conductivity of the membranes

Investigation of thermal effect on exterior wall surface of building material at urban city area

Energy Technology Data Exchange (ETDEWEB)

Md Din, Mohd Fadhil; Dzinun, Hazlini; Ponraj, M.; Chelliapan, Shreeshivadasan; Noor, Zainura Zainun [Institute of Environmental Water Resources and Management (IPASA), Faculty of Civil Engineering, Universiti Teknologi Malaysia, 81310 UTM Skudai, Johor (Malaysia); Remaz, Dilshah [Faculty of Built Environment, Universiti Teknologi Malaysia, 81310 UTM Skudai, Johor (Malaysia); Iwao, Kenzo [Nagoya Institute of Technology, Nagoya (Japan)

2012-07-01

This paper describes the investigation of heat impact on the vertical surfaces of buildings based on their thermal behavior. The study was performed based on four building materials that is commonly used in Malaysia; brick, concrete, granite and white concrete tiles. The thermal performances on the building materials were investigated using a surface temperature sensor, data logging system and infrared thermography. Results showed that the brick had the capability to absorb and store heat greater than other materials during the investigation period. The normalized heat (total heat/solar radiation) of the brick was 0.093 and produces high heat (51% compared to granite), confirming a substantial amount of heat being released into the atmosphere through radiation and convection. The most sensitive material that absorbs and stores heat was in the following order: brick > concrete > granite > white concrete tiles. It was concluded that the type of exterior wall material used in buildings had significant impact to the environment.

Thermal Infrared Spectra of Microcrystalline Sedimentary Phases: Effects of Natural Surface Roughness on Spectral Feature Shape

Science.gov (United States)

Hardgrove, C.; Rogers, A. D.

2012-03-01

Thermal infrared spectral features of common microcrystalline phases (chert, alabaster, micrite) are presented. Spectra are sensitive to mineralogy and micron-scale (~1-25 µm) surface roughness. Roughness is on the scale of the average crystal size.

A novel approach to generate random surface thermal loads in piping

Energy Technology Data Exchange (ETDEWEB)

Costa Garrido, Oriol, E-mail: oriol.costa@ijs.si; El Shawish, Samir; Cizelj, Leon

2014-07-01

Highlights: • Approach for generating continuous and time-dependent random thermal fields. • Temperature fields simulate fluid mixing thermal loads at fluid–wall interface. • Through plane-wave decomposition, experimental temperature statistics are reproduced. • Validation of the approach with a case study from literature. • Random surface thermal loads generation for future thermal fatigue analyses of piping. - Abstract: There is a need to perform three-dimensional mechanical analyses of pipes, subjected to complex thermo-mechanical loadings such as the ones evolving from turbulent fluid mixing in a T-junction. A novel approach is proposed in this paper for fast and reliable generation of random thermal loads at the pipe surface. The resultant continuous and time-dependent temperature fields simulate the fluid mixing thermal loads at the fluid–wall interface. The approach is based on reproducing discrete fluid temperature statistics, from experimental readings or computational fluid dynamic simulation's results, at interface locations through plane-wave decomposition of temperature fluctuations. The obtained random thermal fields contain large scale instabilities such as cold and hot spots traveling at flow velocities. These low frequency instabilities are believed to be among the major causes of the thermal fatigue in T-junction configurations. The case study found in the literature has been used to demonstrate the generation of random surface thermal loads. The thermal fields generated with the proposed approach are statistically equivalent (within the first two moments) to those from CFD simulations results of similar characteristics. The fields maintain the input data at field locations for a large set of parameters used to generate the thermal loads. This feature will be of great advantage in future sensitivity fatigue analyses of three-dimensional pipe structures.

A novel approach to generate random surface thermal loads in piping

International Nuclear Information System (INIS)

Costa Garrido, Oriol; El Shawish, Samir; Cizelj, Leon

2014-01-01

Highlights: • Approach for generating continuous and time-dependent random thermal fields. • Temperature fields simulate fluid mixing thermal loads at fluid–wall interface. • Through plane-wave decomposition, experimental temperature statistics are reproduced. • Validation of the approach with a case study from literature. • Random surface thermal loads generation for future thermal fatigue analyses of piping. - Abstract: There is a need to perform three-dimensional mechanical analyses of pipes, subjected to complex thermo-mechanical loadings such as the ones evolving from turbulent fluid mixing in a T-junction. A novel approach is proposed in this paper for fast and reliable generation of random thermal loads at the pipe surface. The resultant continuous and time-dependent temperature fields simulate the fluid mixing thermal loads at the fluid–wall interface. The approach is based on reproducing discrete fluid temperature statistics, from experimental readings or computational fluid dynamic simulation's results, at interface locations through plane-wave decomposition of temperature fluctuations. The obtained random thermal fields contain large scale instabilities such as cold and hot spots traveling at flow velocities. These low frequency instabilities are believed to be among the major causes of the thermal fatigue in T-junction configurations. The case study found in the literature has been used to demonstrate the generation of random surface thermal loads. The thermal fields generated with the proposed approach are statistically equivalent (within the first two moments) to those from CFD simulations results of similar characteristics. The fields maintain the input data at field locations for a large set of parameters used to generate the thermal loads. This feature will be of great advantage in future sensitivity fatigue analyses of three-dimensional pipe structures

Thermal Stress of Surface of Mold Cavities and Parting Line of Silicone Molds

Directory of Open Access Journals (Sweden)

Bajčičák Martin

2014-06-01

Full Text Available The paper is focused on the study of thermal stress of surface of mold cavities and parting line of silicone molds after pouring. The silicone mold White SD - THT was thermally stressed by pouring of ZnAl4Cu3 zinc alloy with pouring cycle 20, 30 and 40 seconds. The most thermally stressed part of surface at each pouring cycle is gating system and mold cavities. It could be further concluded that linear increase of the pouring cycle time leads to the exponential increasing of the maximum temperature of mold surface after its cooling. The elongated pouring cycle increases the temperature accumulated on the surface of cavities and the ability of silicone mold to conduct the heat on its surface decreases, because the low thermal conductivity of silicone molds enables the conduction of larger amount of heat into ambient environment.

Near-surface thermal characterization of plasma facing components using the 3-omega method

International Nuclear Information System (INIS)

Dechaumphai, Edward; Barton, Joseph L.; Tesmer, Joseph R.; Moon, Jaeyun; Wang, Yongqiang; Tynan, George R.; Doerner, Russell P.; Chen, Renkun

2014-01-01

Near-surface regime plays an important role in thermal management of plasma facing components in fusion reactors. Here, we applied a technique referred to as the ‘3ω’ method to measure the thermal conductivity of near-surface regimes damaged by ion irradiation. By modulating the frequency of the heating current in a micro-fabricated heater strip, the technique enables the probing of near-surface thermal properties. The technique was applied to measure the thermal conductivity of a thin ion-irradiated layer on a tungsten substrate, which was found to decrease by nearly 60% relative to pristine tungsten for a Cu ion dosage of 0.2 dpa

Transient thermal stresses in an orthotropic rectangular plate with convective heat transfer at upper and lower surfaces

International Nuclear Information System (INIS)

Sugano, Yoshihiro; Nakanishi, Takanori; Ito, Masahiko; Saito, Koichi.

1982-01-01

Recently, anisotropic materials have been used widely for reactor core elements and fast flying objects, therefore, the problem of thermal stress in anisotropic bodies has been studied actively. In this study, the unsteady plane thermal stress in an orthotropic rectangular thin plate heated by the temperature of ambient medium was analyzed, taking the heat transfer on both surfaces into account. The influence that the anisotropy of material constants and the heat transfer on both surfaces exert on the temperature and thermal stress of the plate was examined. Moreover, in order to investigate into the effect of the aspect ratio of the plate on the temperature and thermal stress, the unsteady distributions of temperature and thermal stress in an orthotropic semi-infinite band, of which the end surfaces are heated by ambient medium, were analyzed. The numerical calculation was carried out, and the results are shown. Before, it was difficult to satisfy the boundary condition related to shearing stress, accordingly, the analysis has not been performed, but in this study, it was shown that the analysis is possible. (Kako, I.)

Thermal characteristics of thermobrachytherapy surface applicators for treating chest wall recurrence

International Nuclear Information System (INIS)

Arunachalam, K; Maccarini, P F; Craciunescu, O I; Stauffer, P R; Schlorff, J L

2010-01-01

The aim of this study was to investigate temperature and thermal dose distributions of thermobrachytherapy surface applicators (TBSAs) developed for concurrent or sequential high dose rate (HDR) brachytherapy and microwave hyperthermia treatment of chest wall recurrence and other superficial diseases. A steady-state thermodynamics model coupled with the fluid dynamics of a water bolus and electromagnetic radiation of the hyperthermia applicator is used to characterize the temperature distributions achievable with TBSAs in an elliptical phantom model of the human torso. Power deposited by 915 MHz conformal microwave array (CMA) applicators is used to assess the specific absorption rate (SAR) distributions of rectangular (500 cm 2 ) and L-shaped (875 cm 2 ) TBSAs. The SAR distribution in tissue and fluid flow distribution inside the dual-input dual-output (DIDO) water bolus are coupled to solve the steady-state temperature and thermal dose distributions of the rectangular TBSA (R-TBSA) for superficial tumor targets extending 10-15 mm beneath the skin surface. Thermal simulations are carried out for a range of bolus inlet temperature (T b = 38-43 deg. C), water flow rate (Q b = 2-4 L min -1 ) and tumor blood perfusion (ω b = 2-5 kg m -3 s -1 ) to characterize their influence on thermal dosimetry. Steady-state SAR patterns of the R- and L-TBSA demonstrate the ability to produce conformal and localized power deposition inside the tumor target sparing surrounding normal tissues and nearby critical organs. Acceptably low variation in tissue surface cooling and surface temperature homogeneity was observed for the new DIDO bolus at a 2 L min -1 water flow rate. Temperature depth profiles and thermal dose volume histograms indicate bolus inlet temperature (T b ) to be the most influential factor on thermal dosimetry. A 42 deg. C water bolus was observed to be the optimal choice for superficial tumors extending 10-15 mm from the surface even under significant blood perfusion

Thermal performance of climber greenwalls: Effects of solar irradiance and orientation

International Nuclear Information System (INIS)

Jim, C.Y.

2015-01-01

Highlights: • Field experiment tested solar irradiance effect on greenwall thermal performance. • Climber greenwalls were planted on four orientations of circular concrete tank. • High solar-energy input had high bare-surface temperature but maximum cooling. • Threshold solar intensity of 300 Wm −2 was needed for effective greenwall cooling. • Transpiration cooled anterior air better than shading and thermal insulation. - Abstract: Thermal performance of greenwalls, a critical and common concern, is regulated by solar irradiance vis-à-vis orientation and shading. A field experiment was conducted in humid-tropical Hong Kong to address the research question under typical summer-weather scenarios: sunny, cloudy and rainy. On a large circular concrete tank, climber-greenwall experimental plots were established with duplication in four cardinal compass directions. Air and infrared-radiometer surface temperature sensors monitored at different greenwall positions: ambient-air (control), bare-concrete-surface (control), vegetation-surface, behind-mesh-airgap, and behind-mesh-concrete surface. Pyranometers were installed vertically at four orientations and horizontally at tank-top (control) to monitor solar-energy input. Habitat verticality induces notable variations in solar-energy capture at four orientations by daily total, peak level, intensity, duration and timing. On sunny day, solar fraction reaching east side was only 37.1% of tank-top. Early morning sunshine striking east side nearly perpendicularly brings maximum intensity. South side facing the sun but at tangential incident angle has only 23.3% reception. Strong irradiance drives high control-surface temperature, but also induces notable vegetation-surface and adjacent ambient-air cooling by transpiration. A threshold solar intensity of about 300 Wm −2 is necessary to impart notable cooling-effect. Summer-sunny day and rainy-day sunshine-burst episodes could satisfy this condition; cloudy day and

Surface and sub-surface thermal oxidation of thin ruthenium films

Energy Technology Data Exchange (ETDEWEB)

Coloma Ribera, R.; Kruijs, R. W. E. van de; Yakshin, A. E.; Bijkerk, F. [MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede (Netherlands); Kokke, S.; Zoethout, E. [FOM Dutch Institute for Fundamental Energy Research (DIFFER), P.O. Box 1207, 3430 BE Nieuwegein (Netherlands)

2014-09-29

A mixed 2D (film) and 3D (nano-column) growth of ruthenium oxide has been experimentally observed for thermally oxidized polycrystalline ruthenium thin films. Furthermore, in situ x-ray reflectivity upon annealing allowed the detection of 2D film growth as two separate layers consisting of low density and high density oxides. Nano-columns grow at the surface of the low density oxide layer, with the growth rate being limited by diffusion of ruthenium through the formed oxide film. Simultaneously, with the growth of the columns, sub-surface high density oxide continues to grow limited by diffusion of oxygen or ruthenium through the oxide film.

Dispersion of Co/CNTs via strong electrostatic adsorption method: Thermal treatment effect

Energy Technology Data Exchange (ETDEWEB)

Akbarzadeh, Omid, E-mail: omid.akbarzadeh63@gmail.com; Abdullah, Bawadi, E-mail: bawadi-abdullah@petronas.com.my; Subbarao, Duvvuri, E-mail: duvvuri-subbarao@petronas.com.my [Department of Chemical Engineering, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, 31750 Tronoh, Perak (Malaysia); Zabidi, Noor Asmawati Mohd, E-mail: noorasmawati-mzabidi@petronas.com.my [Department of Fundamental and Applied Sciences, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, 31750 Tronoh, Perak (Malaysia)

2015-07-22

The effect of different thermal treatment temperature on the structure of multi-walled carbon nanotubes (MWCNTs) and Co particle dispersion on CNTs support is studied using Strong electrostatic adsorption (SEA) method. The samples tested by N{sub 2}-adsorption, field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). N{sub 2}-adsorption results showed BET surface area increased using thermal treatment and TEM images showed that increasing the thermal treatment temperature lead to flaky CNTs and defects introduced on the outer surface and Co particle dispersion increased.

Enhanced Thermal Conductivity of Copper Nanofluids: The Effect of Filler Geometry.

Science.gov (United States)

Bhanushali, Sushrut; Jason, Naveen Noah; Ghosh, Prakash; Ganesh, Anuradda; Simon, George P; Cheng, Wenlong

2017-06-07

Nanofluids are colloidal dispersions that exhibit enhanced thermal conductivity at low filler loadings and thus have been proposed for heat transfer applications. Here, we systematically investigate how particle shape determines the thermal conductivity of low-cost copper nanofluids using a range of distinct filler particle shapes: nanospheres, nanocubes, short nanowires, and long nanowires. To exclude the potential effects of surface capping ligands, all the filler particles are kept with uniform surface chemistry. We find that copper nanowires enhanced the thermal conductivity up to 40% at 0.25 vol % loadings; while the thermal conductivity was only 9.3% and 4.2% for the nanosphere- and nanocube-based nanofluids, respectively, at the same filler loading. This is consistent with a percolation mechanism in which a higher aspect ratio is beneficial for thermal conductivity enhancement. To overcome the surface oxidation of the copper nanomaterials and maintain the dispersion stability, we employed polyvinylpyrrolidone (PVP) as a dispersant and ascorbic acid as an antioxidant in the nanofluid formulations. The thermal performance of the optimized fluid formulations could be sustained for multiple heating-cooling cycles while retaining stability over 1000 h.

Optical and thermal properties in ultrafast laser surface nanostructuring on biodegradable polymer

Science.gov (United States)

Yada, Shuhei; Terakawa, Mitsuhiro

2015-03-01

We investigate the effect of optical and thermal properties in laser-induced periodic surface structures (LIPSS) formation on a poly-L-lactic acid (PLLA), a biodegradable polymer. Surface properties of biomaterials are known to be one of the key factors in tissue engineering. Methods to process biomaterial surfaces have been studied widely to enhance cell adhesive and anisotropic properties. LIPSS formation has advantages in a dry processing which is able to process complex-shaped surfaces without using a toxic chemical component. LIPSS, however, was difficult to be formed on PLLA due to its thermal and optical properties compared to other polymers. To obtain new perspectives in effect of these properties above, LIPSS formation dependences on wavelength, pulse duration and repetition rate have been studied. At 800 nm of incident wavelength, high-spatial frequency LIPSS (HSFL) was formed after applying 10000 femtosecond pulses at 1.0 J/cm2 in laser fluence. At 400 nm of the wavelength, HSFL was formed at fluences higher than 0.20 J/cm2 with more than 3000 pulses. Since LIPSS was less formed with lower repetition rate, certain heat accumulation may be required for LIPSS formation. With the pulse duration of 2.0 ps, higher laser fluence as well as number of pulses compared to the case of 120 fs was necessary. This indicates that multiphoton absorption process is essential for LIPSS formation. Study on biodegradation modification was also performed.

AN INVESTIGATION OF LOCAL EFFECTS ON SURFACE WARMING WITH GEOGRAPHICALLY WEIGHTED REGRESSION (GWR

Directory of Open Access Journals (Sweden)

Y. Xue

2012-07-01

Full Text Available Urban warming is sensitive to the nature (thermal properties, including albedo, water content, heat capacity and thermal conductivity and the placement (surface geometry or urban topography of urban surface. In the literature the spatial dependence and heterogeneity of urban thermal landscape is widely observed based on thermal infrared remote sensing within the urban environment. Urban surface warming is conceived as a big contribution to urban warming, the study of urban surface warming possesses significant meaning for probing into the problem of urban warming.The urban thermal landscape study takes advantage of the continuous surface derived from thermal infrared remote sensing at the landscape scale, the detailed variation of local surface temperature can be measured and analyzed through the systematic investigation. At the same time urban environmental factors can be quantified with remote sensing and GIS techniques. This enables a systematic investigation of urban thermal landscape with a link to be established between local environmental setting and surface temperature variation. The goal of this research is utilizing Geographically Weighted Regression (GWR to analyze the spatial relationship between urban form and surface temperature variation in order to clarify the local effects on surface warming, moreover to reveal the possible dynamics in the local influences of environmental indicators on the variation of local surface temperature across space and time. In this research, GWR analysis proved that the spatial variation in relationships between environmental setting and surface temperature was significant with Monte Carlo significance test and distinctive in day-night change. Comparatively, GWR facilitated the site specific investigation based on local statistical technique. The inference based on GWR model provided enriched information regarding the spatial variation of local environment effect on surface temperature variation which

Practical Calculation of Thermal Deformation and Manufacture Error uin Surface Grinding

Institute of Scientific and Technical Information of China (English)

周里群; 李玉平

2002-01-01

The paper submits a method to calculate thermal deformation and manufacture error in surface grinding.The author established a simplified temperature field model.and derived the thermal deformaiton of the ground workpiece,It is found that there exists not only a upwarp thermal deformation,but also a parallel expansion thermal deformation.A upwarp thermal deformation causes a concave shape error on the profile of the workpiece,and a parallel expansion thermal deformation causes a dimension error in height.The calculations of examples are given and compared with presented experiment data.

Thermal desorption and surface modification of He+ implanted into tungsten

International Nuclear Information System (INIS)

Fu Zhang; Yoshida, N.; Iwakiri, H.; Xu Zengyu

2004-01-01

Tungsten divertor plates in fusion reactors will be subject to helium bombardment. Helium retention and thermal desorption is a concerned issue in controlling helium ash. In the present study, fluence dependence of thermal desorption behavior of helium in tungsten was studied at different irradiation temperatures and ion energies. Results showed that helium desorption could start at ∼400 K with increasing fluence, while no noticeable peaks were detected at low fluence. Total helium desorption reached a saturation value at high fluence range, which was not sensitive to irradiation temperature or ion energy for the conditions evaluated. Surface modifications caused by either ion irradiation or thermal desorption were observed by SEM. The relationship of surface modifications and helium desorption behavior was discussed. Some special features of elevated irradiation temperature and lower ion energy were also indicated

Thermal surface characteristics of coal fires 1 results of in-situ measurements

Science.gov (United States)

Zhang, Jianzhong; Kuenzer, Claudia

2007-12-01

Natural underground coal fires are fires in coal seams occurring subsurface. The fires are ignited through a process named spontaneous combustion, which occurs based on a natural reaction but is usually triggered through human interaction. Coal mining activities expose coal to the air. This leads to the exothermal oxidation of the carbon in the coal with the air's oxygen to CO 2 and - under certain circumstances - to spontaneous combustion. Coal fires occur in many countries world wide - however, currently the Chinese coal mining industry faces the biggest problems with coal fires. Coal fires destroy the valuable resource coal and furthermore lead to many environmental degradation phenomena such as the deterioration of surrounding vegetation, land subsidence and the emission of toxic gasses (CO, N 2O). They additionally contribute to the emission of green house relevant gasses such as CO 2 and CH 4 to the atmosphere. In this paper we present thermal characteristics of coal fires as measured in-situ during a field campaign to the Wuda coal fire area in south-central Inner Mongolia, China. Thermal characteristics include temperature anomaly measurements at the surface, spatial surface temperature profiles of fire areas and unaffected background areas, diurnal temperature profiles, and temperature measurements inside of coal fire induced cracks in the overlying bedrock. For all the measurements the effects of uneven solar heating through influences of slope and aspect are considered. Our findings show that coal fires result in strong or subtle thermal surface anomalies. Especially the latter can easily be influenced by heating of the surrounding background material through solar influences. Temperature variation of background rocks with different albedo, slope, aspect or vegetation cover can substantially influence the detectability of thermal anomalies. In the worst case coal fire related thermal anomalies can be completely masked by solar patterns during the daytime

Effects of Anisotropic Thermal Conductivity in Magnetohydrodynamics Simulations of a Reversed-Field Pinch

International Nuclear Information System (INIS)

Onofri, M.; Malara, F.; Veltri, P.

2010-01-01

A compressible magnetohydrodynamics simulation of the reversed-field pinch is performed including anisotropic thermal conductivity. When the thermal conductivity is much larger in the direction parallel to the magnetic field than in the perpendicular direction, magnetic field lines become isothermal. As a consequence, as long as magnetic surfaces exist, a temperature distribution is observed displaying a hotter confined region, while an almost uniform temperature is produced when the magnetic field lines become chaotic. To include this effect in the numerical simulation, we use a multiple-time-scale analysis, which allows us to reproduce the effect of a large parallel thermal conductivity. The resulting temperature distribution is related to the existence of closed magnetic surfaces, as observed in experiments. The magnetic field is also affected by the presence of an anisotropic thermal conductivity.

Field induced decrystallization of silicon: Evidence of a microwave non-thermal effect

Science.gov (United States)

Nozariasbmarz, Amin; Dsouza, Kelvin; Vashaee, Daryoosh

2018-02-01

It is rather strange and not fully understood that some materials decrystallize when exposed to microwave radiation, and it is still debatable if such a transformation is a thermal or non-thermal effect. We hereby report experimental evidences that weight the latter effect. First, a single crystal silicon wafer exposed to microwaves showed strong decrystallization at high temperature. Second, when some areas of the wafer were masked with metal coating, only the exposed areas underwent decrystallization. Transmission electron microscopy analysis, x-ray diffraction data, and thermal conductivity measurements all indicated strong decrystallization, which occurred in the bulk of the material and was not a surface effect. These observations favor the existence of a non-thermal microwave effect.

Modeling of thermal effects on TIBER II divertor during plasma disruptions

International Nuclear Information System (INIS)

Bruhn, M.L.; Perkins, L.J.

1987-01-01

Mapping the disruption power flow from the mid-plane of the TIBER Engineering Test Reactor to its divertor and calculating the resulting thermal effects are accomplished through the modification and coupling of three presently existing computer codes. The resulting computer code TADDPAK (Thermal Analysis Divertor during Disruption PAcKage) provides three-dimensional graphic presentations of time and positional dependent thermal effects on a poloidal cross section of the double-null-divertor configured reactor. These thermal effects include incident heat flux, surface temperature, vaporization rate, total vaporization, and melting depth. The dependence of these thermal effects on material choice, disruption pulse shape, and the characteristic thickness of the plasma scrape-off layer is determined through parametric analysis with TADDPAK. This computer code is designed to be a convenient, rapid, and user-friendly modeling tool which can be easily adapted to most tokamak double-null-divertor reactor designs

Review on effect of chemical, thermal, additive treatment on mechanical properties of basalt fiber and their composites

Science.gov (United States)

Jain, Naman; Singh, Vinay Kumar; Chauhan, Sakshi

2017-12-01

Basalt fiber is emerging out the new reinforcing material for composites. To overcome some of the disadvantages of fibers such as poor bonding to polymers, low thermal stability and high moisture absorption fiber characteristics are modified with chemical, thermal and additive treatments. Chemical treatment corrosive resistance to alkali and acid were investigated which were used to clean and modify the surface of fiber for higher bonding with resins. To improve the thermal stability and reduce moisture uptake thermal treatment such as plasma and non thermal plasma were used which increased the surface roughness and change the chemical composition of surface of basalt fiber. Additive treatment is used to improve the mechanical properties of fibers, in basalt fiber additive treatment was done with SiO2 additive because of its chemical composition which contains major content of SiO2. In present investigation review on the effect of different treatment such as chemical, thermal and additive were studied. Effect of these treatment on chemical composition of the surface of basalt fiber and corrosion to acidic and alkali solution were studied with their effect on mechanical properties of basalt fiber and their composite.

Application of the thermal plasma technique in the treatment of stone surfaces

International Nuclear Information System (INIS)

Gonzalez A, Z.I.

2000-01-01

The stone materials which form part of the cultural heritage of Mexico, are degraded under the united action of water, atmospheric gases, air pollution, temperature changes and the microorganisms action; provoking on the stone: fissures, crevices, scalings, fragmentations, pulverizations, etc. Therefore, the purpose of this work is to study the possibilities to apply a protective coating on the stone surfaces, previously clean and consolidated, through the thermal plasma technique. The purpose is to analyse the physical and chemical properties of three types of stone materials: quarry, tezontle and chiluca, usually used in constructions of cultural interest such as: historical monuments, churches, sculptures, etc., before and after to be submitted to the action of thermal plasma in order to examine the feasibility in the use of this coating technique in this type of applications. The application of conventional techniques to determine: porosity, density, absorption, low pressure water absorption and crystallization by total immersion of nuclear techniques such as: neutron activation analysis, x-ray diffraction and scanning electron microscopy as well as of instrumental techniques: optical microscopy, mechanical assays of compression, flexure and surface area calculations, allowed to know the chemical and physical properties of the stone material before and after to be treated through the thermal plasma technique, projecting quartz on the stones surface at different distances and current intensity and showing the effect caused by the modifications or surface alterations present by cause of the application of that coating. the obtained results provide a general panorama of the application of this technique as an alternative to the maintenance of the architectural inheritance built in stone. (Author)

Mechanical, Thermal Degradation, and Flammability Studies on Surface Modified Sisal Fiber Reinforced Recycled Polypropylene Composites

Directory of Open Access Journals (Sweden)

Arun Kumar Gupta

2012-01-01

Full Text Available The effect of surface treated sisal fiber on the mechanical, thermal, flammability, and morphological properties of sisal fiber (SF reinforced recycled polypropylene (RPP composites was investigated. The surface of sisal fiber was modified with different chemical reagent such as silane, glycidyl methacrylate (GMA, and O-hydroxybenzene diazonium chloride (OBDC to improve the compatibility with the matrix polymer. The experimental results revealed an improvement in the tensile strength to 11%, 20%, and 31.36% and impact strength to 78.72%, 77%, and 81% for silane, GMA, and OBDC treated sisal fiber reinforced recycled Polypropylene (RPP/SF composites, respectively, as compared to RPP. The thermogravimetric analysis (TGA, differential scanning calorimeter (DSC, and heat deflection temperature (HDT results revealed improved thermal stability as compared with RPP. The flammability behaviour of silane, GMA, and OBDC treated SF/RPP composites was studied by the horizontal burning rate by UL-94. The morphological analysis through scanning electron micrograph (SEM supports improves surface interaction between fiber surface and polymer matrix.

Thermal effects on beryllium mirrors

International Nuclear Information System (INIS)

Weinswig, S.

1989-01-01

Beryllium is probably the most frequently used material for spaceborne system scan mirrors. Beryllium's properties include lightweightedness, high Young's modulus, high stiffness value, high resonance value. As an optical surface, beryllium is usually nickel plated in order to produce a higher quality surface. This process leads to the beryllium mirror acting like a bimetallic device. The mirror's deformation due to the bimetallic property can possibly degrade the performance of the associated optical system. As large space borne systems are designed and as temperature considerations become more crucial in the instruments, the concern about temporal deformation of the scan mirrors becomes a prime consideration. Therefore, two sets of tests have been conducted in order to ascertain the thermal effects on nickel plated beryllium mirrors. These tests are categorized. The purpose of this paper is to present the values of the bimetallic effect on typical nickel plated beryllium mirrors

Effects of Surface Nitrification on Thermal Conductivity of Modified Aluminum Oxide Nanofibers-Reinforced Epoxy Matrix Nanocomposites

International Nuclear Information System (INIS)

Kim, Byungjoo; Bae, Kyongmin; An, Kayhyeok; Park, Soojin

2012-01-01

Aluminum oxide (Al 2 O 3 ) nanofibers were treated thermally under an ammonia (NH 3 ) gas stream balanced by nitrogen to form a thin aluminum nitride (AlN) layer on the nanofibers, resulting in the enhancement of thermal conductivity of Al 2 O 3 /epoxy nanocomposites. The micro-structural and morphological properties of the NH 3 -assisted thermally-treated Al 2 O 3 nanofibers were characterized by X-ray diffraction (XRD) and atomic force microscopy (AEM), respectively. The surface characteristics and pore structures were observed by X-ray photoelectron spectroscopy (XPS), Zeta-potential and N 2 /77 K isothermal adsorptions. From the results, the formation of AlN on Al 2 O 3 nanofibers was confirmed by XRD and XPS. The thermal conductivity (TC) of the modified Al 2 O 3 nanofibers/epoxy composites increased with increasing treated temperatures. On the other hand, the severely treated Al 2 O 3 /epoxy composites showed a decrease in TC, resulting from a decrease in the probability of heat-transfer networks between the filler and matrix in this system due to the aggregation of nanofiber fillers

Effect of ion implantation on thermal shock resistance of magnesia and glass

International Nuclear Information System (INIS)

Gurarie, V.N.; Williams, J.S.; Watt, A.J.

1995-01-01

Monocrystals of magnesia together with glass samples have been subjected to ion implantation prior to thermal shock testing in an impulse plasma of continuously varied intensity. Measurements of the separation between fragments have been used to estimate the surface temperature. Fracture and deformation characteristics of the surface layer are measured in ion implanted and unimplanted samples using optical and scanning electron microscopy. Implantation-induced near-surface damage is analysed by ion channeling using 2 MeV He + ions. Ion implantation is shown to modify the near-surface structure of magnesia samples by introducing damage, which makes crack initiation easier under thermal stresses. The fracture threshold and maximum crack density are shifted towards the lower temperature range. Ion implanted MgO crystals show a ten fold increase in surface crack density. An increased crack density results in a decreased degree of damage characterised by the depth of crack penetration. The thermal stress resistance parameter of glass samples is increased at relatively small doses and decreased at higher doses. The results suggest that crack density and the degree of fracture damage in brittle ceramics operating under thermal shock conditions can be effectively controlled by ion implantation which provides crack initiating defects in the near-surface region. 23 refs., 7 figs

Wave propagation in fluid-conveying viscoelastic carbon nanotubes under longitudinal magnetic field with thermal and surface effect via nonlocal strain gradient theory

Science.gov (United States)

Zhen, Yaxin; Zhou, Lin

2017-03-01

Based on nonlocal strain gradient theory, wave propagation in fluid-conveying viscoelastic single-walled carbon nanotubes (SWCNTs) is studied in this paper. With consideration of thermal effect and surface effect, wave equation is derived for fluid-conveying viscoelastic SWCNTs under longitudinal magnetic field utilizing Euler-Bernoulli beam theory. The closed-form expressions are derived for the frequency and phase velocity of the wave motion. The influences of fluid flow velocity, structural damping coefficient, temperature change, magnetic flux and surface effect are discussed in detail. SWCNTs’ viscoelasticity reduces the wave frequency of the system and the influence gets remarkable with the increase of wave number. The fluid in SWCNTs decreases the frequency of wave propagation to a certain extent. The frequency (phase velocity) gets larger due to the existence of surface effect, especially when the diameters of SWCNTs and the wave number decrease. The wave frequency increases with the increase of the longitudinal magnetic field, while decreases with the increase of the temperature change. The results may be helpful for better understanding the potential applications of SWCNTs in nanotechnology.

Effects of surface and interface scattering on anomalous Hall effect in Co/Pd multilayers

KAUST Repository

Guo, Zaibing

2012-09-27

In this paper, we report the results of surface and interface scattering on anomalous Hall effect in Co/Pd multilayers with perpendicular magnetic anisotropy. The surface scattering effect has been extracted from the total anomalous Hall effect. By scaling surface scattering contribution with ρAHs∼ργss, the exponent γ has been found to decrease with the increase of surface scattering resistivity, which could account for the thickness-dependent anomalous Hall effect. Interface diffusion induced by rapid thermal annealing modifies not only the magnetization and longitudinal resistivity but also the anomalous Hall effect; a large exponent γ ∼ 5.7 has been attributed to interface scattering-dominated anomalous Hall effect.

Thermal Characteristics of Urban Landscapes

Science.gov (United States)

Luvall, Jeffrey C.; Quattrochi, Dale A.

1998-01-01

Although satellite data are very useful for analysis of the urban heat island effect at a coarse scale, they do not lend themselves to developing a better understanding of which surfaces across the city contribute or drive the development of the urban heat island effect. Analysis of thermal energy responses for specific or discrete surfaces typical of the urban landscape (e.g., asphalt, building rooftops, vegetation) requires measurements at a very fine spatial scale (i.e., less than 15 m) to adequately resolve these surfaces and their attendant thermal energy regimes. Additionally, very fine scale spatial resolution thermal infrared data, such as that obtained from aircraft, are very useful for demonstrating to planning officials, policy makers, and the general populace the benefits of the urban forest. These benefits include mitigating the urban heat island effect, making cities more aesthetically pleasing and more habitable environments, and aid in overall cooling of the community. High spatial resolution thermal data are required to quantify how artificial surfaces within the city contribute to an increase in urban heating and the benefit of cool surfaces (e.g., surface coatings that reflect much of the incoming solar radiation as opposed to absorbing it thereby lowering urban temperatures). The TRN (thermal response number) is a technique using aircraft remotely sensed surface temperatures to quantify the thermal response of urban surfaces. The TRN was used to quantify the thermal response of various urban surface types ranging from completely vegetated surfaces to asphalt and concrete parking lots for Huntsville, AL.

A 1-D Analytical Model for the Thermally Induced Stresses in the Mould Surface During Die Casting

DEFF Research Database (Denmark)

Hattel, Jesper; Hansen, Preben

1994-01-01

This paper presents an anlytically based method for predicting the normal stresses in a die mold surface exposed to a thermal load. A example of application of the method is the high-pressure di casting process where the surface stresses in critical cases lead to cracks. Expressions for the normal...... stresses as afunction of the thermal and mechanical properties have been developed for a casting both without and with a coating. Finally, the resulting relationships are derived and evaluated, with particular emphasis on the effect of the heat transfer coefficient between the casting and the mold....

Thermal Stability and Surface Wettability Studies of Polylactic Acid/Halloysite Nanotube Nanocomposite Scaffold for Tissue Engineering Studies

Science.gov (United States)

Nizar, M. Mohd; Hamzah, M. S. A.; Razak, S. I. Abd; Mat Nayan, N. H.

2018-03-01

This paper reports the preliminary study about the incorporation of halloysite nanotubes (HNT) into polylactic acid (PLA) scaffold to improve the thermal resistance and surface wettability properties. The fabrication of the porous scaffold requires a simple yet effective technique with low-cost materials within freeze extraction method. The thermal stability of PLA/HNT scaffold compared to neat PLA scaffold achieved with increased content of HNT by 5 wt%. Moreover, the surface wettability of the scaffold also shows a positive impact with high content of HNT by 5 wt%. This new nanocomposite scaffold may have high potential as a suitable template for tissue regeneration.

Experimentally Reproducing Thermal Breakdown of Rock at Earth's Surface

Science.gov (United States)

Eppes, M. C.; Griffiths, L.; Heap, M. J.; Keanini, R.; Baud, P.

2016-12-01

Thermal stressing induces microcrack growth in rock in part due to thermal expansion mismatch between different minerals, mineral phases, or crystalline axes and/or thermal gradients in the entire rock mass. This knowledge is largely derived from experimental studies of thermal microcracking, typically under conditions of very high temperatures (hundreds of °C). Thermal stressing at lower temperatures has received significantly less attention despite the fact that it may play an important role in rock breakdown at and near Earth's surface (Aldred et al., 2015; Collins and Stock, 2016). In particular, Eppes et al. (2016) attribute recorded Acoustic Emissions (AE) from a highly instrumented granite boulder sitting on the ground in natural conditions to subcritical crack growth driven by thermal stresses arising from a combination of solar- and weather-induced temperature changes; however the maximum temperature the boulder experienced was just 65 °C. In order to better understand these results without complicating factors of a natural environment, we conducted controlled laboratory experiments on cylindrical samples (40 mm length and 20 mm diameter) cored from the same granite as the Eppes et al. (2016) experiment, subjecting them to temperature fluctuations that reproduced the field measurements. We used a novel experimental configuration whereby two high temperature piezo-transducers are each in contact with an opposing face of the sample. The servo-controlled uniaxial press compensates for the thermal expansion and contraction of the pistons and the sample, keeping the coupling between the transducers and the sample, and the axial force acting on the sample, constant throughout. The system records AE, as well as P-wave velocity, both independent proxies for microfracture, as well as strain and temperature. Preliminary tests, heating and cooling granite at a rate of 1 °C/min, show that a large amount of AE occurs at temperatures as low as 100 °C. Ultimately, by

Lattice Boltzmann model for thermal free surface flows with liquid-solid phase transition

International Nuclear Information System (INIS)

Attar, Elham; Koerner, Carolin

2011-01-01

Purpose: The main objective of this work is to develop an algorithm to use the Lattice Boltzmann method for solving free surface thermal flow problems with solid/liquid phase changes. Approach: A multi-distribution function model is applied to simulate hydrodynamic flow and the coupled thermal diffusion-convection problem. Findings: The free surface problem, i.e. the reconstruction of the missing distribution functions at the interface, can be solved by applying a physical transparent momentum and heat flux based methodology. The developed method is subsequently applied to some test cases in order to assess its computational potentials. Practical implications: Many industrial processes involve problems where non-isothermal motion and simultaneous solidification of fluids with free surface is important. Examples are all castings processes and especially foaming processes which are characterized by a huge and strongly changing surface. Value: A reconstruction algorithm to treat a thermal hydrodynamic problem with free surfaces is presented which is physically transparent and easy to implement.

Thermal fatigue of austenitic stainless steel: influence of surface conditions through a multi-scale approach

International Nuclear Information System (INIS)

Le-Pecheur, Anne

2008-01-01

Some cases of cracking of 304L austenitic stainless steel components due to thermal fatigue were encountered in particular on the Residual Heat Removal Circuits (RHR) of the Pressurized Water Reactor (PWR). EDF has initiated a R and D program to understand assess the risks of damage on nuclear plant mixing zones. The INTHERPOL test developed at EDF is designed in order to perform pure thermal fatigue test on tubular specimen under mono-frequency thermal load. These tests are carried out under various loadings, surface finish qualities and welding in order to give an account of these parameters on crack initiation. The main topic of this study is the research of a fatigue criterion using a micro:macro modelling approach. The first part of work deals with material characterization (stainless steel 304L) emphasising the specificities of the surface roughness link with a strong hardening gradient. The first results of the characterization on the surface show a strong work-hardening gradient on a 250 microns layer. This gradient does not evolved after thermal cycling. Micro hardness measurements and TEM observations were intensively used to characterize this gradient. The second part is the macroscopic modelling of INTHERPOL tests in order to determine the components of the stress and strain tensors due to thermal cycling. The third part of work is thus to evaluate the effect of surface roughness and hardening gradient using a calculation on a finer scale. This simulation is based on the variation of dislocation density. A goal for the future is the determination of the fatigue criterion mainly based on polycrystalline modelling. Stocked energy or critical plane being available that allows making a sound choice for the criteria. (author)

Electronic and surface properties of pentacene films deposited on SiO2 prepared by the sol–gel and thermally grown methods

International Nuclear Information System (INIS)

Dai, Chi-Jie; Tsao, Hou-Yen; Lin, Yow-Jon; Liu, Day-Shan

2014-01-01

This study investigates the effect of different types of SiO 2 on the electronic and surface properties of pentacene films. Developing better contacts on dielectrics is one of the main challenges for pentacene-based transistor technology. The water contact angle variation indicates more hydrophobic thermally grown SiO 2 surfaces than sol–gel SiO 2 surfaces, suggesting that the thermally grown SiO 2 dielectric enables a better molecular arrangement as the pentacene layer is deposited. It is found that the carrier mobility in pentacene on thermally grown SiO 2 dielectrics is higher than that in pentacene on sol–gel SiO 2 dielectrics. The Hall-effect analysis by using the polaron theory revealed that the enhanced carrier mobility is due to the increased spacing between molecules. - Highlights: • The carrier mobility of pentacene on thermally grown and sol–gel SiO 2 was researched. • The enhanced carrier mobility of pentacene on thermally grown SiO2 was observed. • The dominance of tunneling (hopping) at low (high) temperatures was observed. • The carrier mobility is correlated with the morphology of pentacene films

Effect of high heating rate on thermal decomposition behaviour of ...

Indian Academy of Sciences (India)

Effect of high heating rate on thermal decomposition behaviour of titanium hydride ... hydride powder, while switching it from internal diffusion to chemical reaction. ... TiH phase and oxides form on the powder surface, controlling the process.

Thermal Characteristics of Pyranometers and Pyrgeometers in Atmosphere-Surface Energetic Measurements

Science.gov (United States)

Tsay, Si-Chee; Einaudi, Franco (Technical Monitor)

2000-01-01

Since the introduction of thermopile, pyranometers (solar, e.g., 0.3 - 3.0 microns) and pyrgeometers (terrestrial, e.g., 4 - 50 microns) have become instruments commonly used for measuring the broadband hemispherical irradiances at the surface in a long-term, monitoring mode for decades. These commercially available radiometers have been manufactured in several countries such as from the United States, Asia, and Europe, and are generally reliable and economical. These worldwide distributions of surface measurements become even more important in the era of Earth remote sensing in studying climate change. However, recent studies from field campaigns have pointed out that erroneous factors (e.g., temperature gradients between the filter dome and detector, emissivity of the thermopile) are responsible for the unacceptable level of uncertainty (e.g., 20 W/sq m). It is best to utilize an energy balance equation to describe the thermal dome effect of pyranometers and pyrgeometers. Therefore, quality of pyranometer and pyrgeometer measurements can be improved largely by applying proper knowledge of the thermal parameters affecting the operation of the thermopile systems. Data correction procedure and algorithm will be presented and discussed.

Analytical approach for evaluating temperature field of thermal modified asphalt pavement and urban heat island effect

International Nuclear Information System (INIS)

Chen, Jiaqi; Wang, Hao; Zhu, Hongzhou

2017-01-01

Highlights: • Derive an analytical approach to predict temperature fields of multi-layered asphalt pavement based on Green’s function. • Analyze the effects of thermal modifications on heat output from pavement to near-surface environment. • Evaluate pavement solutions for reducing urban heat island (UHI) effect. - Abstract: This paper aims to present an analytical approach to predict temperature fields in asphalt pavement and evaluate the effects of thermal modification on near-surface environment for urban heat island (UHI) effect. The analytical solution of temperature fields in the multi-layered pavement structure was derived with the Green’s function method, using climatic factors including solar radiation, wind velocity, and air temperature as input parameters. The temperature solutions were validated with an outdoor field experiment. By using the proposed analytical solution, temperature fields in the pavement with different pavement surface albedo, thermal conductivity, and layer combinations were analyzed. Heat output from pavement surface to the near-surface environment was studied as an indicator of pavement contribution to UHI effect. The analysis results show that increasing pavement surface albedo could decrease pavement temperature at various depths, and increase heat output intensity in the daytime but decrease heat output intensity in the nighttime. Using reflective pavement to mitigate UHI may be effective for an open street but become ineffective for the street surrounded by high buildings. On the other hand, high-conductivity pavement could alleviate the UHI effect in the daytime for both the open street and the street surrounded by high buildings. Among different combinations of thermal-modified asphalt mixtures, the layer combination of high-conductivity surface course and base course could reduce the maximum heat output intensity and alleviate the UHI effect most.

Thermal grafting of fluorinated molecular monolayers on doped amorphous silicon surfaces

International Nuclear Information System (INIS)

Sabbah, H.; Zebda, A.; Ababou-Girard, S.; Solal, F.; Godet, C.; Conde, J. P.; Chu, V.

2009-01-01

Thermally induced (160-300 deg. C) gas phase grafting of linear alkene molecules (perfluorodecene) was performed on hydrogenated amorphous silicon (a-Si:H) films, either nominally undoped or doped with different boron and phosphorus concentrations. Dense and smooth a-Si:H films were grown using plasma decomposition of silane. Quantitative analysis of in situ x-ray photoelectron spectroscopy indicates the grafting of a single layer of organic molecules. The hydrophobic properties of perfluorodecene-modified surfaces were studied as a function of surface coverage. Annealing experiments in ultrahigh vacuum show the covalent binding and the thermal stability of these immobilized layers up to 370 deg. C; this temperature corresponds to the Si-C bond cleavage temperature. In contrast with hydrogenated crystalline Si(111):H, no heavy wet chemistry surface preparation is required for thermal grafting of alkene molecules on a-Si:H films. A threshold grafting temperature is observed, with a strong dependence on the doping level which produces a large contrast in the molecular coverage for grafting performed at 230 deg. C

Influence of surface modification adopting thermal treatments on dispersion of detonation nanodiamond

International Nuclear Information System (INIS)

Xu Xiangyang; Yu Zhiming; Zhu Yongwei; Wang Baichun

2005-01-01

In order to improve the dispersion of detonation nanodiamonds (ND) in aqueous and non-aqueous media, a series of thermal treatments have been conducted in air ambient to modify ND surface. Small angle X-ray scattering (SAXS) technique and high resolution transmission electron microscopy (HRTEM) were introduced to observe the primary size of ND. Differential thermal analysis (DTA), X-ray diffraction (XRD) methodology, X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy were adopted to analyze the structure, bonds at surfaces of the treated ND. Malvern instrument Zetasizer3000HS was used for measuring the surface electric potential and the size distribution of ND. As thermal treatments can cause graphitization and oxidization of functional groups at the surface, ND treated at high temperature is correspondingly more negatively charged in an aqueous medium, and the increased absolute value of zeta potential ensures the electrostatic stability of ND particles. Specially, after being treated at a temperature more than 850K, ND can be well dispersed in various media

Thermal Molding of Organic Thin-Film Transistor Arrays on Curved Surfaces.

Science.gov (United States)

Sakai, Masatoshi; Watanabe, Kento; Ishimine, Hiroto; Okada, Yugo; Yamauchi, Hiroshi; Sadamitsu, Yuichi; Kudo, Kazuhiro

2017-12-01

In this work, a thermal molding technique is proposed for the fabrication of plastic electronics on curved surfaces, enabling the preparation of plastic films with freely designed shapes. The induced strain distribution observed in poly(ethylene naphthalate) films when planar sheets were deformed into hemispherical surfaces clearly indicated that natural thermal contraction played an important role in the formation of the curved surface. A fingertip-shaped organic thin-film transistor array molded from a real human finger was fabricated, and slight deformation induced by touching an object was detected from the drain current response. This type of device will lead to the development of robot fingers equipped with a sensitive tactile sense for precision work such as palpation or surgery.

Effect of Thermal Cycling on the Tensile Behavior of CF/AL Fiber Metal Laminates

Directory of Open Access Journals (Sweden)

Muhammad Farhan Noor

2017-09-01

Full Text Available The objective of this research work was to estimate the effect of thermal cycling on the tensile behavior of CARALL composites. Fiber metal laminates (FMLs, based on 2D woven carbon fabric and 2024-T3 Alclad aluminum alloy sheet, was manufactured by pressure molding technique followed by hand layup method. Before fabrication, aluminum sheets were anodized with phosphoric acid to produce micro porous alumina layer on surface. This micro-porous layer is beneficial to produce strong bonding between metal and fiber surfaces in FMLs. The effect of thermal cycling (-65 to +70ºC on the tensile behavior of Cf/Al based FML was studied. Tensile strength was increased after 10 thermal cycles, but it was slightly decreased to some extent after 30, and 50 thermal cycles. Tensile modulus also shown the similar behavior as that of tensile strength.

Ground-based thermal imaging of stream surface temperatures: Technique and evaluation

Science.gov (United States)

Bonar, Scott A.; Petre, Sally J.

2015-01-01

We evaluated a ground-based handheld thermal imaging system for measuring water temperatures using data from eight southwestern USA streams and rivers. We found handheld thermal imagers could provide considerably more spatial information on water temperature (for our unit one image = 19,600 individual temperature measurements) than traditional methods could supply without a prohibitive amount of effort. Furthermore, they could provide measurements of stream surface temperature almost instantaneously compared with most traditional handheld thermometers (e.g., >20 s/reading). Spatial temperature analysis is important for measurement of subtle temperature differences across waterways, and identification of warm and cold groundwater inputs. Handheld thermal imaging is less expensive and equipment intensive than airborne thermal imaging methods and is useful under riparian canopies. Disadvantages of handheld thermal imagers include their current higher expense than thermometers, their susceptibility to interference when used incorrectly, and their slightly lower accuracy than traditional temperature measurement methods. Thermal imagers can only measure surface temperature, but this usually corresponds to subsurface temperatures in well-mixed streams and rivers. Using thermal imaging in select applications, such as where spatial investigations of water temperature are needed, or in conjunction with stationary temperature data loggers or handheld electronic or liquid-in-glass thermometers to characterize stream temperatures by both time and space, could provide valuable information on stream temperature dynamics. These tools will become increasingly important to fisheries biologists as costs continue to decline.

Sea surface temperature mapping using a thermal infrared scanner

Digital Repository Service at National Institute of Oceanography (India)

RameshKumar, M.R; Pandya, R; Mathur, K.M.; Charyulu, R; Rao, L.V.G.

1 metre water column below the sea surface. A thermal infrared scanner developed by the Space Applications Centre (ISRO), Ahmedabad was operated on board R.V. Gaveshani in April/May 1984 for mapping SST over the eastern Arabian Sea. SST values...

Surface Temperature Mapping of the University of Northern Iowa Campus Using High Resolution Thermal Infrared Aerial Imageries

Directory of Open Access Journals (Sweden)

Ramanathan Sugumaran

2008-08-01

Full Text Available The goal of this project was to map the surface temperature of the University of Northern Iowa campus using high-resolution thermal infrared aerial imageries. A thermal camera with a spectral bandwidth of 3.0-5.0 μm was flown at the average altitude of 600 m, achieving ground resolution of 29 cm. Ground control data was used to construct the pixelto-temperature conversion model, which was later used to produce temperature maps of the entire campus and also for validation of the model. The temperature map then was used to assess the building rooftop conditions and steam line faults in the study area. Assessment of the temperature map revealed a number of building structures that may be subject to insulation improvement due to their high surface temperatures leaks. Several hot spots were also identified on the campus for steam pipelines faults. High-resolution thermal infrared imagery proved highly effective tool for precise heat anomaly detection on the campus, and it can be used by university facility services for effective future maintenance of buildings and grounds.

Surface Temperature Mapping of the University of Northern Iowa Campus Using High Resolution Thermal Infrared Aerial Imageries

Science.gov (United States)

Savelyev, Alexander; Sugumaran, Ramanathan

2008-01-01

The goal of this project was to map the surface temperature of the University of Northern Iowa campus using high-resolution thermal infrared aerial imageries. A thermal camera with a spectral bandwidth of 3.0-5.0 μm was flown at the average altitude of 600 m, achieving ground resolution of 29 cm. Ground control data was used to construct the pixel- to-temperature conversion model, which was later used to produce temperature maps of the entire campus and also for validation of the model. The temperature map then was used to assess the building rooftop conditions and steam line faults in the study area. Assessment of the temperature map revealed a number of building structures that may be subject to insulation improvement due to their high surface temperatures leaks. Several hot spots were also identified on the campus for steam pipelines faults. High-resolution thermal infrared imagery proved highly effective tool for precise heat anomaly detection on the campus, and it can be used by university facility services for effective future maintenance of buildings and grounds. PMID:27873800

Kinetic Monte Carlo study on the evolution of silicon surface roughness under hydrogen thermal treatment

Energy Technology Data Exchange (ETDEWEB)

Wang, Gang; Wang, Yu; Wang, Junzhuan; Pan, Lijia; Yu, Linwei; Zheng, Youdou; Shi, Yi, E-mail: yshi@nju.edu.cn

2017-08-31

Highlights: • The KMC method is adopted to investigate the relationships between surface evolution and hydrogen thermal treatment conditions. • The reduction in surface roughness is divided into two stages at relatively low temperatures, both exhibiting exponential dependence on the time. • The optimized surface structure can be obtained by precisely adjusting thermal treatment temperatures and hydrogen pressures. - Abstract: The evolution of a two-dimensional silicon surface under hydrogen thermal treatment is studied by kinetic Monte Carlo simulations, focusing on the dependence of the migration behaviors of surface atoms on both the temperature and hydrogen pressure. We adopt different activation energies to analyze the influence of hydrogen pressure on the evolution of surface morphology at high temperatures. The reduction in surface roughness is divided into two stages, both exhibiting exponential dependence on the equilibrium time. Our results indicate that a high hydrogen pressure is conducive to obtaining optimized surfaces, as a strategy in the applications of three-dimensional devices.

Influences of the wavy surface inserted in the middle of a circular tube heat exchanger on thermal performance

Energy Technology Data Exchange (ETDEWEB)

Jedsadaratanancai, Withada [King Mongkut' s Institute of Technology Ladkrabang, Bangkok (Thailand); Boonloi, Amnart [King Mongkut' s University of Technology North Bangkok, Bangkok (Thailand)

2015-09-15

Numerical investigations on flow topology, heat transfer behavior and performance evaluation in a circular tube inserted with various configurations of wavy surfaces, Inclined wavy surface (IWS), V-downstream wavy surface (VDWS), V-Upstream wavy surface (VUWS) are presented. The effects of the flow attack angles; 20 .deg., 30 .deg., 45.deg. and 60.deg. are studied for the Reynolds numbers, Re = 100-2000. The numerical results are compared with the smooth circular tube with no wavy surface and the previous works. It is found that the IWS, VDWS and VUWS can produce longitudinal vortex flow and impinging jet of the fluid flow like inclined baffle, V-downstream baffle and V-Upstream baffle, respectively, but give lower friction loss. The flow phenomena created by the wavy surfaces help to augment the heat transfer rate and thermal performance in the test tube. In the range studied, the order of enhancement for heat transfer rate is around 1.40-3.75, 1.60-6.25 and 1.30-5.80 times higher than the smooth tube for IWS, VDWS and VUWS, respectively. Moreover, the maximum thermal performance, presented in terms of the Thermal enhancement factor (TEF), is found to be about 1.60, 2.40 and 2.10, respectively, for IWS, VUWS and VDWS.

Electronic and surface properties of pentacene films deposited on SiO{sub 2} prepared by the sol–gel and thermally grown methods

Energy Technology Data Exchange (ETDEWEB)

Dai, Chi-Jie [Department of Physics, National Changhua University of Education, Changhua 500, Taiwan (China); Tsao, Hou-Yen [Institute of Photonics, National Changhua University of Education, Changhua 500, Taiwan (China); Lin, Yow-Jon, E-mail: rzr2390@yahoo.com.tw [Institute of Photonics, National Changhua University of Education, Changhua 500, Taiwan (China); Liu, Day-Shan [Graduate Institute of Electro-Optical and Materials Science, National Formosa University, Huwei 632, Taiwan (China)

2014-02-03

This study investigates the effect of different types of SiO{sub 2} on the electronic and surface properties of pentacene films. Developing better contacts on dielectrics is one of the main challenges for pentacene-based transistor technology. The water contact angle variation indicates more hydrophobic thermally grown SiO{sub 2} surfaces than sol–gel SiO{sub 2} surfaces, suggesting that the thermally grown SiO{sub 2} dielectric enables a better molecular arrangement as the pentacene layer is deposited. It is found that the carrier mobility in pentacene on thermally grown SiO{sub 2} dielectrics is higher than that in pentacene on sol–gel SiO{sub 2} dielectrics. The Hall-effect analysis by using the polaron theory revealed that the enhanced carrier mobility is due to the increased spacing between molecules. - Highlights: • The carrier mobility of pentacene on thermally grown and sol–gel SiO{sub 2} was researched. • The enhanced carrier mobility of pentacene on thermally grown SiO2 was observed. • The dominance of tunneling (hopping) at low (high) temperatures was observed. • The carrier mobility is correlated with the morphology of pentacene films.

Magnetohydrodynamic and thermal radiation effects on the boundary-layer flow due to a moving extensible surface with the velocity slip model: A comparative study of four nanofluids

Energy Technology Data Exchange (ETDEWEB)

Aly, Emad H., E-mail: efarag@uj.edu.sa [Department of Mathematics, Faculty of Science, University of Jeddah, Jeddah 21589 (Saudi Arabia); Department of Mathematics, Faculty of Education, Ain Shams University, Roxy, Cairo 11757 (Egypt); Sayed, Hamed M. [Department of Mathematics, Faculty of Education, Ain Shams University, Roxy, Cairo 11757 (Egypt); Department of Mathematics, Faculty of Sciences, Taibah University, Yanbu (Saudi Arabia)

2017-01-15

In the current work, we investigated effects of the velocity slip for the flow and heat transfer of four nanofluids over a non-linear stretching sheet taking into account the thermal radiation and magnetic field in presence of the effective electrical conductivity. The governing partial differential equations were transformed into a set of nonlinear ordinary differential equation using similarity transformations before being solved numerically by the Chebyshev pseudospectral differentiation matrix (ChPDM). It was found that the investigated parameters affect remarkably on the nanofluid stream function for the whole investigated nanoparticles. In addition, velocity and skin friction profiles of the four investigated nanofluids decreases and increases, respectively, with the increase of the magnetic parameter, first-order and second-order velocity slips. Further, the flow velocity, surface shear stress and temperature are strongly influenced on applying the velocity slip model, where lower values of the second-order imply higher surface heat flux and thereby making the fluid warmer. - Highlights: • A comparative study for four nanoparticles with MHD and thermal radiation effects was studied. • The effective electrical conductivity is mandatory; otherwise a spurious physical sight will be gained. • The investigated parameters affect remarkably on the nanofluids' flow. • The flow velocity, surface shear stress and temperature are strongly influenced by the slip model. • Lower values of the second-order imply higher surface heat flux and thereby making the fluid warmer.

Atmospheric effects on the remote determination of thermal inertia on Mars

International Nuclear Information System (INIS)

Haberle, R.M.; Jakosky, B.M.

1991-01-01

Measurements of the IR brightness temperature at the Martian surface at many different times of day are presently compared with temperatures predicted by thermal models which allow sunlight to reach the surface unattenuated, in order to determine the thermal inertia of the uppermost 1-10 cm of the Martian surface. The consequences of the assumptions made are assessed in view of results from a different thermal model which invokes radiation-transfer through a dusty CO2 atmosphere, as well as sensible heat-exchange with the surface. Smaller thermal inertias imply smaller particle sizes; the results obtained suggest that low thermal-inertia regions consist of 5-micron, rather than 50-micron, particle sizes. 52 refs

Size effect of the elastic modulus of rectangular nanobeams: Surface elasticity effect

International Nuclear Information System (INIS)

Yao Hai-Yan; Fan Wen-Liang; Yun Guo-Hong

2013-01-01

The size-dependent elastic property of rectangular nanobeams (nanowires or nanoplates) induced by the surface elasticity effect is investigated by using a developed modified core-shell model. The effect of surface elasticity on the elastic modulus of nanobeams can be characterized by two surface related parameters, i.e., inhomogeneous degree constant and surface layer thickness. The analytical results show that the elastic modulus of the rectangular nanobeam exhibits a distinct size effect when its characteristic size reduces below 100 nm. It is also found that the theoretical results calculated by a modified core-shell model have more obvious advantages than those by other models (core-shell model and core-surface model) by comparing them with relevant experimental measurements and computational results, especially when the dimensions of nanostructures reduce to a few tens of nanometers. (condensed matter: structural, mechanical, and thermal properties)

Experimental study of effective thermal conductivity of stainless steel fiber felt

International Nuclear Information System (INIS)

Li, W.Q.; Qu, Z.G.

2015-01-01

An experimental apparatus was designed to measure the effective thermal conductivity of porous stainless steel fiber felt under different operating pressures. The total effective thermal conductivity was studied by analyzing matrix heat conduction, air natural convection, and matrix thermal radiation at ambient pressure. The contribution of air natural convection was experimentally obtained by changing the ambient pressure to vacuum condition and the solid matrix heat conduction was evaluated using a theoretical model. The ratios of the three mechanisms to the total effective thermal conductivity were approximately 40%, 37.9%, and 22.1%, respectively. In addition, the effects of fiber diameter and porosity on the three mechanisms and on the total effective thermal conductivity were studied. The air natural convection was found to gradually intensify when the operating pressure increases from vacuum condition (15 Pa) to ambient pressure (1.0 × 10 5  Pa). With an increase in fiber diameter under fixed porosity, the solid matrix heat conduction remained unchanged, and air natural convection and thermal radiation decreased, thereby resulting in reduced effective thermal conductivity. With an increase in porosity under fixed fiber diameter, the air natural convection was almost unchanged, and solid matrix heat conduction and thermal radiation were reduced, thereby resulting in reduced effective thermal conductivity. - Highlights: • Matrix conduction, radiation and air convection were in the same order of magnitude. • Air natural convection was suppressed by reducing operating pressure. • Intensity of air convection was more sensitive to fiber diameter than porosity. • Surface area and permeability was comparable in air convection as fiber diameter fixed. • Interfacial area exerted dominant role in radiation and air convection as porosity fixed

The surface chemical properties of multi-walled carbon nanotubes modified by thermal fluorination for electric double-layer capacitor

Science.gov (United States)

Jung, Min-Jung; Jeong, Euigyung; Lee, Young-Seak

2015-08-01

The surfaces of multi-walled carbon nanotubes (MWCNTs) were thermally fluorinated at various temperatures to enhance the electrochemical properties of the MWCNTs for use as electric double-layer capacitor (EDLC) electrodes. The fluorine functional groups were added to the surfaces of the MWCNTs via thermal fluorination. The thermal fluorination exposed the Fe catalyst on MWCNTs, and the specific surface area increased due to etching during the fluorination. The specific capacitances of the thermally fluorinated at 100 °C, MWCNT based electrode increased from 57 to 94 F/g at current densities of 0.2 A/g, respectively. This enhancement in capacitance can be attributed to increased polarization of the thermally fluorinated MWCNT surface, which increased the affinity between the electrode surface and the electrolyte ions.

Effect of particle size on thermal decomposition of alkali metal picrates

International Nuclear Information System (INIS)

Liu, Rui; Zhang, Tonglai; Yang, Li; Zhou, Zunning

2014-01-01

Graphical abstract: The smaller-sized picrate has greater gas emission than do its larger counterpart. The small size effect reduces the thermal decomposition activation energy, accelerates the reaction rate, and promotes the reaction activity. - Highlights: • Picrates were prepared into three micron sizes by microemulsion synthesis. • Thermal decomposition kinetics and thermodynamics were studied by DPTA and DSC. • Smaller-sized picrate has higher activity and faster reaction rate. • Particle size effect on thermal decomposition kinetics and thermodynamics was revealed. - Abstract: Three alkali metal picrates, KPA, RbPA and CsPA, were prepared into three micron sizes by microemulsion synthesis, and their thermal decomposition behaviors were investigated by DPTA at different temperatures and by DSC at different heating rates. The smaller-sized picrate has greater gas emission and smaller kinetic and thermodynamic parameters than do its larger counterpart. It can be attributed to the decreasing particle size which leads to the high surface energy, the fast mass and heat transfer, and the increasing active sites on the reaction interface. The small size effect and surface effect cause the autocatalysis which reduces the activation energy and promotes the reaction activity. The particle size does not affect the reaction mechanism. However, the picrates with different central alkali metals exhibit different reaction mechanisms even though they are of the same size. This is because the central metal determines the bond energy and consequently affects the stability of picrate

Effect of particle size on thermal decomposition of alkali metal picrates

Energy Technology Data Exchange (ETDEWEB)

Liu, Rui; Zhang, Tonglai, E-mail: ztlbit@bit.edu.cn; Yang, Li; Zhou, Zunning

2014-05-01

Graphical abstract: The smaller-sized picrate has greater gas emission than do its larger counterpart. The small size effect reduces the thermal decomposition activation energy, accelerates the reaction rate, and promotes the reaction activity. - Highlights: • Picrates were prepared into three micron sizes by microemulsion synthesis. • Thermal decomposition kinetics and thermodynamics were studied by DPTA and DSC. • Smaller-sized picrate has higher activity and faster reaction rate. • Particle size effect on thermal decomposition kinetics and thermodynamics was revealed. - Abstract: Three alkali metal picrates, KPA, RbPA and CsPA, were prepared into three micron sizes by microemulsion synthesis, and their thermal decomposition behaviors were investigated by DPTA at different temperatures and by DSC at different heating rates. The smaller-sized picrate has greater gas emission and smaller kinetic and thermodynamic parameters than do its larger counterpart. It can be attributed to the decreasing particle size which leads to the high surface energy, the fast mass and heat transfer, and the increasing active sites on the reaction interface. The small size effect and surface effect cause the autocatalysis which reduces the activation energy and promotes the reaction activity. The particle size does not affect the reaction mechanism. However, the picrates with different central alkali metals exhibit different reaction mechanisms even though they are of the same size. This is because the central metal determines the bond energy and consequently affects the stability of picrate.

Thermal conductance of a surface phonon-polariton crystal made up of polar nanorods

Energy Technology Data Exchange (ETDEWEB)

Ordonez-Miranda, Jose; Joulain, Karl; Ezzahri, Younes [Univ. de Poitiers, Futuroscope Chasseneuil (France). Inst. Pprime, CNRS

2017-05-01

We demonstrate that the energy transport of surface phonon-polaritons can be large enough to be observable in a crystal made up of a three-dimensional assembly of nanorods of silicon carbide. The ultralow phonon thermal conductivity of this nanostructure along with its high surface area-to-volume ratio allows the predominance of the polariton energy over that generated by phonons. The dispersion relation, propagation length, and thermal conductance of polaritons are numerically determined as functions of the radius and temperature of the nanorods. It is shown that the thermal conductance of a crystal with nanorods at 500 K and diameter (length) of 200 nm (20 μm) is 0.55 nW.K{sup -1}, which is comparable to the quantum of thermal conductance of polar nanowires.

Modeling thermal effects in braking systems of railway vehicles

Directory of Open Access Journals (Sweden)

Milošević Miloš S.

2012-01-01

Full Text Available The modeling of thermal effects has become increasingly important in product design in different transport means, road vehicles, airplanes, railway vehicles, and so forth. The thermal analysis is a very important stage in the study of braking systems, especially of railway vehicles, where it is necessary to brake huge masses, because the thermal load of a braked railway wheel prevails compared to other types of loads. In the braking phase, kinetic energy transforms into thermal energy resulting in intense heating and high temperature states of railway wheels. Thus induced thermal loads determine thermomechanical behavior of the structure of railway wheels. In cases of thermal overloads, which mainly occur as a result of long-term braking on down-grade railroads, the generation of stresses and deformations occurs, whose consequences are the appearance of cracks on the rim of a wheel and the final total wheel defect. The importance to precisely determine the temperature distribution caused by the transfer process of the heat generated during braking due to the friction on contact surfaces of the braking system makes it a challenging research task. Therefore, the thermal analysis of a block-braked solid railway wheel of a 444 class locomotive of the national railway operator Serbian Railways is processed in detail in this paper, using analytical and numerical modeling of thermal effects during long-term braking for maintaining a constant speed on a down-grade railroad.

Thermal energy effects on articular cartilage: a multidisciplinary evaluation

Science.gov (United States)

Kaplan, Lee D.; Ernsthausen, John; Ionescu, Dan S.; Studer, Rebecca K.; Bradley, James P.; Chu, Constance R.; Fu, Freddie H.; Farkas, Daniel L.

2002-05-01

Partial thickness articular cartilage lesions are commonly encountered in orthopedic surgery. These lesions do not have the ability to heal by themselves, due to lack of vascular supply. Several types of treatment have addressed this problem, including mechanical debridement and thermal chondroplasty. The goal of these treatments is to provide a smooth cartilage surface and prevent propagation of the lesions. Early thermal chondroplasty was performed using lasers, and yielded very mixed results, including severe damage to the cartilage, due to poor control of the induced thermal effects. This led to the development (including commercial) of probes using radiofrequency to generate the thermal effects desired for chondroplasty. Similar concerns over the quantitative aspects and control ability of the induced thermal effects in these treatments led us to test the whole range of complex issues and parameters involved. Our investigations are designed to simultaneously evaluate clinical conditions, instrument variables for existing radiofrequency probes (pressure, speed, distance, dose) as well as the associated basic science issues such as damage temperature and controllability (down to the subcellular level), damage geometry, and effects of surrounding conditions (medium, temperature, flow, pressure). The overall goals of this work are (1) to establish whether thermal chondroplasty can be used in a safe and efficacious manner, and (2) provide a prescription for multi-variable optimization of the way treatments are delivered, based on quantitative analysis. The methods used form an interdisciplinary set, to include precise mechanical actuation, high accuracy temperature and temperature gradient control and measurement, advanced imaging approaches and mathematical modeling.

Reversible switching of wetting properties and erasable patterning of polymer surfaces using plasma oxidation and thermal treatment

Science.gov (United States)

Rashid, Zeeshan; Atay, Ipek; Soydan, Seren; Yagci, M. Baris; Jonáš, Alexandr; Yilgor, Emel; Kiraz, Alper; Yilgor, Iskender

2018-05-01

Polymer surfaces reversibly switchable from superhydrophobic to superhydrophilic by exposure to oxygen plasma and subsequent thermal treatment are demonstrated. Two inherently different polymers, hydrophobic segmented polydimethylsiloxane-urea copolymer (TPSC) and hydrophilic poly(methyl methacrylate) (PMMA) are modified with fumed silica nanoparticles to prepare superhydrophobic surfaces with roughness on nanometer to micrometer scale. Smooth TPSC and PMMA surfaces are also used as control samples. Regardless of their chemical structure and surface topography, all surfaces display completely reversible wetting behavior changing from hydrophobic to hydrophilic and back for many cycles upon plasma oxidation followed by thermal annealing. Influence of plasma power, plasma exposure time, annealing temperature and annealing time on the wetting behavior of polymeric surfaces are investigated. Surface compositions, textures and topographies are characterized by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and white light interferometry (WLI), before and after oxidation and thermal annealing. Wetting properties of the surfaces are determined by measuring their static, advancing and receding water contact angle. We conclude that the chemical structure and surface topography of the polymers play a relatively minor role in reversible wetting behavior, where the essential factors are surface oxidation and migration of polymer molecules to the surface upon thermal annealing. Reconfigurable water channels on polymer surfaces are produced by plasma treatment using a mask and thermal annealing cycles. Such patterned reconfigurable hydrophilic regions can find use in surface microfluidics and optofluidics applications.

Effect of high thermal expansion glass infiltration on mechanical ...

Indian Academy of Sciences (India)

This work studies the effect on the mechanical properties of alumina-10 wt% zirconia (3 mol% yttria stabilized) composite by infiltrating glass of a higher thermal expansion (soda lime glass) on the surface at high temperature. The glass improved the strength of composite at room temperature as well as at high temperature.

Thermal effects on vehicle emission dispersion in an urban street canyon

Energy Technology Data Exchange (ETDEWEB)

Xiaomin Xie; Zhen Huang; Jiasong Wang; Zheng Xie [Shanghai Jiao Tong Univ., School of Mechanical Engineering, Shanghai (China)

2005-05-15

The impact of the thermal effects on vehicle emission dispersion within street canyons is examined. The results show that heating from building wall surfaces and horizontal surfaces lead to strong buoyancy forces close to surfaces receiving direct solar radiation. This thermally induced flow is combined with mechanically induced flows formed in the canyon where there is no solar heating, and affects the transport of pollutants from the canyon to the layer aloft. The relative influence of each of these effects can be estimates by Gr/Re{sup 2}. When the windward wall is warmer than the air, an upward buoyancy flux opposes the downward advection flux along the wall; if Gr/Re{sup 2} > 2, the flow structure is divided into two counter-rotating cells, and pollutants are accumulated on the windward side of the canyon. When the horizontal surface is heated, and Gr/Re{sup 2} > 4, the flow structure is divided into two counter-rotating cells by upward buoyancy flux. Pollutants are accumulated at the windward side of the canyon. When the leeward side is heated, the buoyancy flux adds to the upward advection flux along the wall strengthening the original vortex and pollutant effects of transport compared to the isothermal case. (Author)

Fluorination effects on the thermodynamic, thermophysical and surface properties of ionic liquids

International Nuclear Information System (INIS)

Vieira, N.S.M.; Luís, A.; Reis, P.M.; Carvalho, P.J.; Lopes-da-Silva, J.A.; Esperança, J.M.S.S.; Araújo, J.M.M.; Rebelo, L.P.N.; Freire, M.G.; Pereiro, A.B.

2016-01-01

Highlights: • Surface tension of fluorinated ionic liquids. • Thermophysical properties of fluorinated ionic liquids. • Thermal properties and thermodynamic functions. - Abstract: This paper reports the thermal, thermodynamic, thermophysical and surface properties of eight ionic liquids with fluorinated alkyl side chain lengths equal or greater than four carbon atoms. Melting and decomposition temperatures were determined together with experimental densities, surface tensions, refractive indices, dynamic viscosities and ionic conductivities in a temperature interval ranging from (293.15 to 353.15) K. The surface properties of these fluorinated ionic liquids were discussed and several thermodynamic functions, as well as critical temperatures, were estimated. Coefficients of isobaric thermal expansion, molecular volumes and free volume effects were calculated from experimental values of density and refractive index and compared with previous data. Finally, Walden plots were used to evaluate the ionicity of the investigated ionic liquids.

The Effect of an Isogrid on Cryogenic Propellant Behavior and Thermal Stratification

Science.gov (United States)

Oliveira, Justin; Kirk, Daniel R.; Chintalapati, Sunil; Schallhorn, Paul A.; Piquero, Jorge L.; Campbell, Mike; Chase, Sukhdeep

2007-01-01

All models for thermal stratification available in the presentation are derived using smooth, flat plate laminar and turbulent boundary layer models. This study examines the effect of isogrid (roughness elements) on the surface of internal tank walls to mimic the effects of weight-saving isogrid, which is located on the inside of many rocket propellant tanks. Computational Fluid Dynamics (CFD) is used to study the momentum and thermal boundary layer thickness for free convection flows over a wall with generic roughness elements. This presentation makes no mention of actual isogrid sizes or of any specific tank geometry. The magnitude of thermal stratification is compared for smooth and isogrid-lined walls.

Modeling surface energy fluxes and thermal dynamics of a seasonally ice-covered hydroelectric reservoir.

Science.gov (United States)

Wang, Weifeng; Roulet, Nigel T; Strachan, Ian B; Tremblay, Alain

2016-04-15

The thermal dynamics of human created northern reservoirs (e.g., water temperatures and ice cover dynamics) influence carbon processing and air-water gas exchange. Here, we developed a process-based one-dimensional model (Snow, Ice, WAater, and Sediment: SIWAS) to simulate a full year's surface energy fluxes and thermal dynamics for a moderately large (>500km(2)) boreal hydroelectric reservoir in northern Quebec, Canada. There is a lack of climate and weather data for most of the Canadian boreal so we designed SIWAS with a minimum of inputs and with a daily time step. The modeled surface energy fluxes were consistent with six years of observations from eddy covariance measurements taken in the middle of the reservoir. The simulated water temperature profiles agreed well with observations from over 100 sites across the reservoir. The model successfully captured the observed annual trend of ice cover timing, although the model overestimated the length of ice cover period (15days). Sensitivity analysis revealed that air temperature significantly affects the ice cover duration, water and sediment temperatures, but that dissolved organic carbon concentrations have little effect on the heat fluxes, and water and sediment temperatures. We conclude that the SIWAS model is capable of simulating surface energy fluxes and thermal dynamics for boreal reservoirs in regions where high temporal resolution climate data are not available. SIWAS is suitable for integration into biogeochemical models for simulating a reservoir's carbon cycle. Copyright © 2016 Elsevier B.V. All rights reserved.

Investigation of ammonium nitrate effect on kinetics and mechanism of thermal decomposition of ammonium polyuranates

International Nuclear Information System (INIS)

Karelin, A.I.; Lobas, O.P.; Zhiganov, A.N.; Vasil'ev, K.F.; Zhiganova, A.A.

1987-01-01

A study was made on ammonium nitrate effect on the mechanism and kinetics of dehydration and thermal decomposition of ammonium polyuranates. Sufficient effect of nitrate ion content in ammonium polyuranate samples on their thermal stability was noted. Kinetic parameters of thermal decomposition of ammonium polyuranates were evaluated. Mechanism of dehydration and thermal decomposition of ammonium polyuranates in the presence of ammonium nitrate was suggested. It was shown that increase of ammonium nitrate content in ammonium polyuranate precipitate resulted to reduction of the specific surface of prepared uranium mixed oxide

Surface-finish effects on the high-cycle fatigue of Alloy 718

International Nuclear Information System (INIS)

Korth, G.E.

1981-06-01

Alloy 718 us a precipitation-hardening nickel-base superalloy that is being specified for various components for liquid-meal fast breeder reactors (LMFBRs). This alloy maintains high strength at elevated temperatures making it a desirable structural material. But the property that justifies most LMFBR applications is the alloy's resistance to thermal striping damage due to its high fatigue endurance strength. Thermal striping is a high-cycle fatigue phenomenon caused by thermal stresses from the fluctuating mixing action of sodium streams of differing temperatures impinging on the metal surfaces. Most of the design data is generated from laboratory fatigue specimens with carefully controlled surface finishes prepared with a low-stress grind and buffed to a surface finish 8--12 in. Since Alloy 718 has been shown to be quite notch sensitive under cyclic loading, the detrimental effect on the high-cycle fatigue properties caused by shop surface finishes of actual components has been questioned. This report examines some of the surface finishes that could be produced in a commercial shop on an actual component

Effective Thermal Conductivity For Drift-Scale Models Used In TSPA-SR

Energy Technology Data Exchange (ETDEWEB)

N.D. Francis

2001-01-25

The objective of this calculation is to develop a time dependent in-drift effective thermal conductivity parameter that will approximate heat conduction, thermal radiation, and natural convection heat transfer using a single mode of heat transfer (heat conduction). In order to reduce the physical and numerical complexity of the heat transfer processes that occur (and must be modeled) as a result of the emplacement of heat generating wastes, a single parameter will be developed that approximates all forms of heat transfer from the waste package surface to the drift wall (or from one surface exchanging heat with another). Subsequently, with this single parameter, one heat transfer mechanism (e.g., conduction heat transfer) can be used in the models. The resulting parameter is to be used as input in the drift-scale process-level models applied in total system performance assessments for the site recommendation (TSPA-SR). The format of this parameter will be a time-dependent table for direct input into the thermal-hydrologic (TH) and the thermal-hydrologic-chemical (THC) models.

Effective Thermal Conductivity For Drift-Scale Models Used In TSPA-SR

International Nuclear Information System (INIS)

N.D. Francis

2001-01-01

The objective of this calculation is to develop a time dependent in-drift effective thermal conductivity parameter that will approximate heat conduction, thermal radiation, and natural convection heat transfer using a single mode of heat transfer (heat conduction). In order to reduce the physical and numerical complexity of the heat transfer processes that occur (and must be modeled) as a result of the emplacement of heat generating wastes, a single parameter will be developed that approximates all forms of heat transfer from the waste package surface to the drift wall (or from one surface exchanging heat with another). Subsequently, with this single parameter, one heat transfer mechanism (e.g., conduction heat transfer) can be used in the models. The resulting parameter is to be used as input in the drift-scale process-level models applied in total system performance assessments for the site recommendation (TSPA-SR). The format of this parameter will be a time-dependent table for direct input into the thermal-hydrologic (TH) and the thermal-hydrologic-chemical (THC) models

Crystallite Size Effect on Thermal Conductive Properties of Nonwoven Nanocellulose Sheets.

Science.gov (United States)

Uetani, Kojiro; Okada, Takumi; Oyama, Hideko T

2015-07-13

The thermal conductive properties, including the thermal diffusivity and resultant thermal conductivity, of nonwoven nanocellulose sheets were investigated by separately measuring the thermal diffusivity of the sheets in the in-plane and thickness directions with a periodic heating method. The cross-sectional area (or width) of the cellulose crystallites was the main determinant of the thermal conductive properties. Thus, the results strongly indicate that there is a crystallite size effect on phonon conduction within the nanocellulose sheets. The results also indicated that there is a large interfacial thermal resistance between the nanocellulose surfaces. The phonon propagation velocity (i.e., the sound velocity) within the nanocellulose sheets was estimated to be ∼800 m/s based on the relationship between the thermal diffusivities and crystallite widths. The resulting in-plane thermal conductivity of the tunicate nanocellulose sheet was calculated to be ∼2.5 W/mK, markedly higher than other plastic films available for flexible electronic devices.

Relative importance of different surface regions for thermal comfort in humans.

Science.gov (United States)

Nakamura, Mayumi; Yoda, Tamae; Crawshaw, Larry I; Kasuga, Momoko; Uchida, Yuki; Tokizawa, Ken; Nagashima, Kei; Kanosue, Kazuyuki

2013-01-01

In a previous study, we investigated the contribution of the surface of the face, chest, abdomen, and thigh to thermal comfort by applying local temperature stimulation during whole-body exposure to mild heat or cold. In hot conditions, humans prefer a cool face, and in cold they prefer a warm abdomen. In this study, we extended investigation of regional differences in thermal comfort to the neck, hand, soles, abdomen (Experiment 1), the upper and lower back, upper arm, and abdomen (Experiment 2). The methodology was similar to that used in the previous study. To compare the results of each experiment, we utilized the abdomen as the reference area in these experiments. Thermal comfort feelings were not particularly strong for the limbs and extremities, in spite of the fact that changes in skin temperature induced by local temperature stimulation of the limbs and extremities were always larger than changes that were induced in the more proximal body parts. For the trunk areas, a significant difference in thermal comfort was not observed among the abdomen, and upper and lower back. An exception involved local cooling during whole-body mild cold exposure, wherein the most dominant preference was for a warmer temperature of the abdomen. As for the neck and abdomen, clear differences were observed during local cooling, while no significant difference was observed during local warming. We combined the results for the current and the previous study, and characterized regional differences in thermal comfort and thermal preference for the whole-body surface.

Desorption of surface positrons: A source of free positronium at thermal velocities

International Nuclear Information System (INIS)

Mills, A.P. Jr.; Pfeiffer, L.

1979-01-01

A direct measurement is reported of the velocity of positronium (Ps) ejected into a vacuum when 0- to 100-eV positrons (e + ) strike a negatively biased Cu(111) surface. At 30 0 C, about half the e + form Ps with normal energy component E-bar=3.4(3) eV. At 790 0 C, most of the remaining e + form Ps but with E-bar=0.14(1) eV, and a non-Maxwellian thermal distribution. We infer that surface-bound e + are thermally desorbed to form the extra Ps. These low Ps velocities suggest exciting possibilities for experiments on free Ps

Effects of vacuum thermal cycling on mechanical and physical properties of high performance carbon/bismaleimide composite

International Nuclear Information System (INIS)

Yu Qi; Chen Ping; Gao Yu; Mu Jujie; Chen Yongwu; Lu Chun; Liu Dong

2011-01-01

Highlights: → The level of cross-links was improved to a certain extent. → The thermal stability was firstly improved and then decreased. → The transverse and longitudinal CTE were both determined by the degree of interfacial debonding. → The mass loss ratio increases firstly and then reaches a plateau value. → The surface morphology was altered and the surface roughness increased firstly and then decreased. → The transverse tensile strength was reduced. → The flexural strength increased firstly and then decreased to a plateau value. → The ILSS increased firstly and then decreased to a plateau value. - Abstract: The aim of this article was to investigate the effects of vacuum thermal cycling on mechanical and physical properties of high performance carbon/bismaleimide (BMI) composites used in aerospace. The changes in dynamic mechanical properties and thermal stability were characterized by dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA), respectively. The changes in linear coefficient of thermal expansion (CTE) were measured in directions perpendicular and parallel to the fiber direction, respectively. The outgassing behavior of the composites were examined. The evolution of surface morphology and surface roughness were observed by atomic force microscopy (AFM). Changes in mechanical properties including transverse tensile strength, flexural strength and interlaminar shear strength (ILSS) were measured. The results indicated that the vacuum thermal cycling could improve the crosslinking degree and the thermal stability of resin matrix to a certain extent, and induce matrix outgassing and thermal stress, thereby leading to the mass loss and the interfacial debonding of the composite. The degradation in transverse tensile strength was caused by joint effects of the matrix outgassing and the interfacial debonding, while the changes in flexural strength and ILSS were affected by a competing effect between the crosslinking degree

Thermal Rate Coefficients and Kinetic Isotope Effects for the Reaction OH + CH4 → H2O + CH3 on an ab Initio-Based Potential Energy Surface.

Science.gov (United States)

Li, Jun; Guo, Hua

2018-03-15

Thermal rate coefficients for the title reaction and its various isotopologues are computed using a tunneling-corrected transition-state theory on a global potential energy surface recently developed by fitting a large number of high-level ab initio points. The calculated rate coefficients are found to agree well with the measured ones in a wide temperature range, validating the accuracy of the potential energy surface. Strong non-Arrhenius effects are found at low temperatures. In addition, the calculations reproduced the primary and secondary kinetic isotope effects. These results confirm the strong influence of tunneling to this heavy-light-heavy hydrogen abstraction reaction.

Thermal resistance matrix representation of thermal effects and thermal design in multi-finger power heterojunction bipolar transistors

Institute of Scientific and Technical Information of China (English)

Jin Dong-Yue; Zhang Wan-Rong; Chen Liang; Fu Qiang; Xiao Ying; Wang Ren-Qing; Zhao Xin

2011-01-01

The thermal resistance matrix including self-heating thermal resistance and thermal coupling resistance is presented to describe the thermal effects of multi-finger power heterojunction bipolar transistors. The dependence of thermal resistance matrix on finger spacing is also investigated. It is shown that both self-heating thermal resistance and thermal coupling resistance are lowered by increasing the finger spacing, in which the downward dissipated heat path is widened and the heat flow from adjacent fingers is effectively suppressed. The decrease of self-heating thermal resistance and thermal coupling resistance is helpful for improving the thermal stability of power devices. Furthermore, with the aid of the thermal resistance matrix, a 10-finger power heterojunction bipolar transistor (HBT) with non-uniform finger spacing is designed for high thermal stability. The optimized structure can effectively lower the peak temperature while maintaining a uniformity of the temperature profile at various biases and thus the device effectively may operate at a higher power level.

Thermal characteristics and surface morphology of char during co-pyrolysis of low-rank coal blended with microalgal biomass: Effects of Nannochloropsis and Chlorella.

Science.gov (United States)

Wu, Zhiqiang; Yang, Wangcai; Yang, Bolun

2018-02-01

In this work, the influence of Nannochloropsis and Chlorella on the thermal behavior and surface morphology of char during the co-pyrolysis process were explored. Thermogravimetric and iso-conversional methods were applied to analyzing the pyrolytic and kinetic characteristics for different mass ratios of microalgae and low-rank coal (0, 3:1, 1:1, 1:3 and 1). Fractal theory was used to quantitatively determine the effect of microalgae on the morphological texture of co-pyrolysis char. The result indicated that both the Nannochloropsis and Chlorella promoted the release of volatile from low-rank coal. Different synergistic effects on the thermal parameters and yield of volatile were observed, which could be attributed to the different compositions in the Nannochloropsis and Chlorella and operating condition. The distribution of activation energies shows nonadditive characteristics. Fractal dimensions of the co-pyrolysis char were higher than the individual char, indicating the promotion of disordered degree due to the addition of microalgae. Copyright © 2017 Elsevier Ltd. All rights reserved.

A Novel, Aqueous Surface Treatment To Thermally Stabilize High Resolution Positive Photoresist Images*

Science.gov (United States)

Grunwald, John J.; Spencer, Allen C.

1986-07-01

The paper describes a new approach to thermally stabilize the already imaged profile of high resolution positive photoresists such as ULTRAMAC" PR-914. ***XD-4000, an aqueous emulsion of a blend of fluorine-bearing compounds is spun on top of the developed, positive photoresist-imaged wafer, and baked. This allows the photoresist to withstand temperatures up to at least 175 deg. C. while essentially maintaining vertical edge profiles. Also, adverse effects of "outgassing" in harsh environments, ie., plasma and ion implant are greatly minimized by allowing the high resolution imaged photoresist to be post-baked at "elevated" temperatures. Another type of product that accomplishes the same effect is ***XD-4005, an aqueous emulsion of a high temperature-resistant polymer. While the exact mechanism is yet to be identified, it is postulated that absorption of the "polymeric" species into the "skin" of the imaged resist forms a temperature resistant "envelope", thereby allowing high resolution photoresists to also serve in a "high temperature" mode, without reticulation, or other adverse effects due to thermal degradation. SEM's are presented showing imaged ULTRAMAC" PR-914 and ULTRAMAC" **EPA-914 geometries coated with XD-4000 or XD-4005 and followed by plasma etched oxide,polysilicon and aluminum. Selectivity ratios are compared with and without the novel treatment and are shown to be significantly better with the treatment. The surface-treated photoresist for thermal resistance remains easily strippable in solvent-based or plasma media, unlike photoresists that have undergone "PRIST" or other gaseous thermal stabilization methods.

Combating Wear of ASTM A36 Steel by Surface Modification Using Thermally Sprayed Cermet Coatings

OpenAIRE

Shibe, Vineet; Chawla, Vikas

2016-01-01

Thermal spray coatings can be applied economically on machine parts to enhance their requisite surface properties like wear, corrosion, erosion resistance, and so forth. Detonation gun (D-Gun) thermal spray coatings can be applied on the surface of carbon steels to improve their wear resistance. In the present study, alloy powder cermet coatings WC-12% Co and Cr3C2-25% NiCr have been deposited on ASTM A36 steel with D-Gun thermal spray technique. Sliding wear behavior of uncoated ASTM A36 ste...

Thermal analysis of dry eye subjects and the thermal impulse perturbation model of ocular surface.

Science.gov (United States)

Zhang, Aizhong; Maki, Kara L; Salahura, Gheorghe; Kottaiyan, Ranjini; Yoon, Geunyoung; Hindman, Holly B; Aquavella, James V; Zavislan, James M

2015-03-01

In this study, we explore the usage of ocular surface temperature (OST) decay patterns to distinguished between dry eye patients with aqueous deficient dry eye (ADDE) and meibomian gland dysfunction (MGD). The OST profiles of 20 dry eye subjects were measured by a long-wave infrared thermal camera in a standardized environment (24 °C, and relative humidity (RH) 40%). The subjects were instructed to blink every 5 s after 20 ∼ 25 min acclimation. Exponential decay curves were fit to the average temperature within a region of the central cornea. We find the MGD subjects have both a higher initial temperature (p model, referred to as the thermal impulse perturbation (TIP) model. We conclude that long-wave-infrared thermal imaging is a plausible tool in assisting with the classification of dry eye patient. Copyright © 2015 Elsevier Ltd. All rights reserved.

Thermal Advantages for Solar Heating Systems with a Glass Cover with Antireflection Surfaces

DEFF Research Database (Denmark)

Furbo, Simon; Shah, Louise Jivan

2003-01-01

Investigations elucidate how a glass cover with antireflection surfaces can improve the efficiency of a solar collector and the thermal performance of solar heating systems. The transmittances for two glass covers for a flat-plate solar collector were measured for different incidence angles....... The two glasses are identical, except for the fact that one of them is equipped with antireflection surfaces by the company SunArc A/ S. The transmittance was increased by 5–9%-points due to the antireflection surfaces. The increase depends on the incidence angle. The efficiency at incidence angles of 08...... and the incidence angle modifier were measured for a flat-plate solar collector with the two cover plates. The collector efficiency was increased by 4–6%-points due to the antireflection surfaces, depending on the incidence angle. The thermal advantage with using a glass cover with antireflection surfaces...

Dentin surface treatment using a non-thermal argon plasma brush for interfacial bonding improvement in composite restoration

Science.gov (United States)

Ritts, Andy Charles; Li, Hao; Yu, Qingsong; Xu, Changqi; Yao, Xiaomei; Hong, Liang; Wang, Yong

2010-01-01

The objective of this study is to investigate the treatment effects of non-thermal atmospheric gas plasmas on dentin surfaces for composite restoration. Extracted unerupted human third molars were used by removing the crowns and etching the exposed dentin surfaces with 35% phosphoric acid gel. The dentin surfaces were treated by using a non-thermal atmospheric argon plasma brush for various durations. The molecular changes of the dentin surfaces were analyzed using FTIR/ATR and an increase in carbonyl groups on dentin surfaces was detected with plasma treated dentin. Adper Single Bond Plus adhesive and Filtek Z250 dental composite were applied as directed. To evaluate the dentin/composite interfacial bonding, the teeth thus prepared were sectioned into micro-bars as the specimens for tensile test. Student Newman Keuls tests showed that the bonding strength of the composite restoration to peripheral dentin was significantly increased (by 64%) after 30 s plasma treatment. However, the bonding strength to plasma treated inner dentin did not show any improvement. It was found that plasma treatment of peripheral dentin surface up to 100 s gave an increase in interfacial bonding strength, while a prolong plasma treatment of dentin surfaces, e.g., 5 min treatments, showed a decrease in interfacial bonding strength. PMID:20831586

Surface magnetic order and effects of the nature of the interactions

International Nuclear Information System (INIS)

Tsallis, C.; Chame, A.M.N.

1988-01-01

We discuss, within a real-space renormalization-group, interesting thermal effects (surface singularity at the bulk transition; Ising-Heisenberg crossover) concerning the free surface of a semi-infinite d=3 spin 1/2 anisotropic Heisenberg ferromagnet. Comparison with the Mermin-Wagner theorem and with experimental work is done. (author) [pt

Assessing thermal conductivity of composting reactor with attention on varying thermal resistance between compost and the inner surface.

Science.gov (United States)

Wang, Yongjiang; Niu, Wenjuan; Ai, Ping

2016-12-01

Dynamic estimation of heat transfer through composting reactor wall was crucial for insulating design and maintaining a sanitary temperature. A model, incorporating conductive, convective and radiative heat transfer mechanisms, was developed in this paper to provide thermal resistance calculations for composting reactor wall. The mechanism of thermal transfer from compost to inner surface of structural layer, as a first step of heat loss, was important for improving insulation performance, which was divided into conduction and convection and discussed specifically in this study. It was found decreasing conductive resistance was responsible for the drop of insulation between compost and reactor wall. Increasing compost porosity or manufacturing a curved surface, decreasing the contact area of compost and the reactor wall, might improve the insulation performance. Upon modeling of heat transfers from compost to ambient environment, the study yielded a condensed and simplified model that could be used to conduct thermal resistance analysis for composting reactor. With theoretical derivations and a case application, the model was applicable for both dynamic estimation and typical composting scenario. Copyright © 2016 Elsevier Ltd. All rights reserved.

A thermal control system for long-term survival of scientific instruments on lunar surface

Energy Technology Data Exchange (ETDEWEB)

Ogawa, K., E-mail: ogawa@astrobio.k.u-tokyo.ac.jp [Department of Complexity Science and Engineering, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba (Japan); Iijima, Y.; Tanaka, S. [Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo, Sagamihara, Kanagawa (Japan); Sakatani, N. [The Graduate University for Advanced Studies, Shonan Village, Hayama, Kanagawa (Japan); Otake, H. [JAXA Space Exploration Center, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo, Sagamihara, Kanagawa (Japan)

2014-03-15

A thermal control system is being developed for scientific instruments placed on the lunar surface. This thermal control system, Lunar Mission Survival Module (MSM), was designed for scientific instruments that are planned to be operated for over a year in the future Japanese lunar landing mission SELENE-2. For the long-term operations, the lunar surface is a severe environment because the soil (regolith) temperature varies widely from nighttime −200 degC to daytime 100 degC approximately in which space electronics can hardly survive. The MSM has a tent of multi-layered insulators and performs a “regolith mound”. Temperature of internal devices is less variable just like in the lunar underground layers. The insulators retain heat in the regolith soil in the daylight, and it can keep the device warm in the night. We conducted the concept design of the lunar survival module, and estimated its potential by a thermal mathematical model on the assumption of using a lunar seismometer designed for SELENE-2. Thermal vacuum tests were also conducted by using a thermal evaluation model in order to estimate the validity of some thermal parameters assumed in the computed thermal model. The numerical and experimental results indicated a sufficient survivability potential of the concept of our thermal control system.

A thermal control system for long-term survival of scientific instruments on lunar surface.

Science.gov (United States)

Ogawa, K; Iijima, Y; Sakatani, N; Otake, H; Tanaka, S

2014-03-01

A thermal control system is being developed for scientific instruments placed on the lunar surface. This thermal control system, Lunar Mission Survival Module (MSM), was designed for scientific instruments that are planned to be operated for over a year in the future Japanese lunar landing mission SELENE-2. For the long-term operations, the lunar surface is a severe environment because the soil (regolith) temperature varies widely from nighttime -200 degC to daytime 100 degC approximately in which space electronics can hardly survive. The MSM has a tent of multi-layered insulators and performs a "regolith mound". Temperature of internal devices is less variable just like in the lunar underground layers. The insulators retain heat in the regolith soil in the daylight, and it can keep the device warm in the night. We conducted the concept design of the lunar survival module, and estimated its potential by a thermal mathematical model on the assumption of using a lunar seismometer designed for SELENE-2. Thermal vacuum tests were also conducted by using a thermal evaluation model in order to estimate the validity of some thermal parameters assumed in the computed thermal model. The numerical and experimental results indicated a sufficient survivability potential of the concept of our thermal control system.

A thermal control system for long-term survival of scientific instruments on lunar surface

International Nuclear Information System (INIS)

Ogawa, K.; Iijima, Y.; Tanaka, S.; Sakatani, N.; Otake, H.

2014-01-01

A thermal control system is being developed for scientific instruments placed on the lunar surface. This thermal control system, Lunar Mission Survival Module (MSM), was designed for scientific instruments that are planned to be operated for over a year in the future Japanese lunar landing mission SELENE-2. For the long-term operations, the lunar surface is a severe environment because the soil (regolith) temperature varies widely from nighttime −200 degC to daytime 100 degC approximately in which space electronics can hardly survive. The MSM has a tent of multi-layered insulators and performs a “regolith mound”. Temperature of internal devices is less variable just like in the lunar underground layers. The insulators retain heat in the regolith soil in the daylight, and it can keep the device warm in the night. We conducted the concept design of the lunar survival module, and estimated its potential by a thermal mathematical model on the assumption of using a lunar seismometer designed for SELENE-2. Thermal vacuum tests were also conducted by using a thermal evaluation model in order to estimate the validity of some thermal parameters assumed in the computed thermal model. The numerical and experimental results indicated a sufficient survivability potential of the concept of our thermal control system

Thermal interaction effect on nucleation site distribution in subcooled boiling

International Nuclear Information System (INIS)

Zou, Ling; Jones, Barclay

2012-01-01

An experimental work on subcooled boiling of refrigerant, R134a, to examine nucleation site distributions on both copper and stainless steel heating surfaces was performed. In order to obtain high fidelity active nucleation site density and distribution data, a high-speed digital camera was utilized to record bubble emission images from a view normal to heating surfaces. Statistical analyses on nucleation site data were done and their statistical distributions were obtained. Those experimentally observed nucleation site distributions were compared to the random spatial Poisson distribution. The comparisons showed that, rather than purely random, active nucleation site distributions on boiling surfaces are relatively more uniform. Experimental results also showed that on the copper heating surface, nucleation site distributions are slightly more uniform than on the stainless steel surface. This was concluded as the results of thermal interactions between nucleation sites with different solid thermal conductivities. A two dimensional thermal interaction model was then developed to quantitatively examine the thermal interactions between nucleation sites. The results give a reasonable explanation to the experimental observation on nucleation site distributions.

Surface thermal analysis of North Brabant cities and neighbourhoods during heat waves

Directory of Open Access Journals (Sweden)

Leyre Echevarria Icaza

2016-03-01

Full Text Available The urban heat island effect is often associated with large metropolises. However, in the Netherlands even small cities will be affected by the phenomenon in the future (Hove et al., 2011, due to the dispersed or mosaic urbanisation patterns in particularly the southern part of the country: the province of North Brabant. This study analyses the average night time land surface temperature (LST of 21 North-Brabant urban areas through 22 satellite images retrieved by Modis 11A1 during the 2006 heat wave and uses Landsat 5 Thematic Mapper to map albedo and normalized difference temperature index (NDVI values. Albedo, NDVI and imperviousness are found to play the most relevant role in the increase of night-time LST. The surface cover cluster analysis of these three parameters reveals that the 12 “urban living environment” categories used in the region of North Brabant can actually be reduced to 7 categories, which simplifies the design guidelines to improve the surface thermal behaviour of the different neighbourhoods thus reducing the Urban Heat Island (UHI effect in existing medium size cities and future developments adjacent to those cities.

Toward intrinsic graphene surfaces: a systematic study on thermal annealing and wet-chemical treatment of SiO2-supported graphene devices.

Science.gov (United States)

Cheng, Zengguang; Zhou, Qiaoyu; Wang, Chenxuan; Li, Qiang; Wang, Chen; Fang, Ying

2011-02-09

By combining atomic force microscopy and trans-port measurements, we systematically investigated effects of thermal annealing on surface morphologies and electrical properties of single-layer graphene devices fabricated by electron beam lithography on silicon oxide (SiO(2)) substrates. Thermal treatment above 300 °C in vacuum was required to effectively remove resist residues on graphene surfaces. However, annealing at high temperature was found to concomitantly bring graphene in close contact with SiO(2) substrates and induce increased coupling between them, which leads to heavy hole doping and severe degradation of mobilities in graphene devices. To address this problem, a wet-chemical approach employing chloroform was developed in our study, which was shown to enable both intrinsic surfaces and enhanced electrical properties of graphene devices. Upon the recovery of intrinsic surfaces of graphene, the adsorption and assisted fibrillation of amyloid β-peptide (Aβ1-42) on graphene were electrically measured in real time.

Thermal Performance Analysis of Staging Effect of Solar Thermal Absorber with Cross Design

International Nuclear Information System (INIS)

Amir Abdul Razak; Zafri Azran Abdul Majid; Mohd Hafidz Ruslan; Kamaruzzaman Sopian

2015-01-01

The type and shape of solar thermal absorber materials will impact on the operating temperature and thermal energy storage effect of a solar air thermal collector. For a standard flat-plate design, energy gain can be increased by expanding the thermal absorber area along the collector plane, subject to area limitation. This paper focuses on the staging effect of a metal hollow square rod absorber of aluminium, stainless steel, and a combination of the two with a cross design, for the heat gain and temperature characteristics of a solar air collector. Experiments were carried out with three cross design set-ups, with 30 minutes of heating and cooling, phase, respectively, under 485 W/ m 2 solar irradiance value, and at a constant air speed at 0.38 m/ s. One set aluminium set-up delivered the highest output temperature of 41.8 degree Celsius, followed by two-sets aluminium and one aluminium set + one stainless steel set at 39.3 and 38.2 degree Celsius, respectively. The lowest peak temperature is recorded on three sets of the aluminium absorber at 35 degree Celsius. The bi-metallic set-up performed better than the two aluminium set-up where each set-up obtained a temperature drop against heat gain gradient value of -0.4186 degree Celsius/ W and -0.4917 degree Celsius/ W, respectively. Results concluded that by increasing the number of sets, the volume and surface areas of the absorber material are also increased, and lead to a decrease in peak temperature output for each increase of sets. (author)

Effective Thermal Conductivity of Graphite Materials with Cracks

Science.gov (United States)

Pestchaanyi, S. E.; Landman, I. S.

The dependence of effective thermal diffusivity on temperature caused by volumetric cracks is modelled for macroscopic graphite samples using the three-dimensional thermomechanics code Pegasus-3D. At high off-normal heat loads typical of the divertor armour, thermostress due to the anisotropy of graphite grains is much larger than that due to the temperature gradient. Numerical simulation demonstrated that the volumetric crack density both in fine grain graphites and in the CFC matrix depends mainly on the local sample temperature, not on the temperature gradient. This allows to define an effective thermal diffusivity for graphite with cracks. The results obtained are used to explain intense cracking and particle release from carbon based materials under electron beam heat load. Decrease of graphite thermal diffusivity with increase of the crack density explains particle release mechanism in the experiments with CFC where a clear energy threshold for the onset of particle release has been observed in J. Linke et al. Fusion Eng. Design, in press, Bazyler et al., these proceedings. Surface temperature measurement is necessary to calibrate the Pegasus-3D code for simulation of ITER divertor armour brittle destruction.

Numerical Simulation of the Effects of Water Surface in Building Environment

Science.gov (United States)

Li, Guangyao; Pan, Yuqing; Yang, Li

2018-03-01

Water body could affect the thermal environment and airflow field in the building districts, because of its special thermal characteristics, evaporation and flat surface. The thermal influence of water body in Tongji University Jiading Campus front area was evaluated. First, a suitable evaporation model was selected and then was applied to calculate the boundary conditions of the water surface in the Fluent software. Next, the computational fluid dynamics (CFD) simulations were conducted on the models both with and without water, following the CFD practices guidelines. Finally, the outputs of the two simulations were compared with each other. Results showed that the effect of evaporative cooling from water surface strongly depends on the wind direction and temperature decrease was about 2∼5°C. The relative humidity within the enclosing area was affected by both the building arrangement and surrounding water. An increase of about 0.1∼0.2m/s of wind speed induced by the water evaporation was observed in the open space.

Thermal stability studies on atomically clean and sulphur passivated InGaAs surfaces

Energy Technology Data Exchange (ETDEWEB)

Chauhan, Lalit; Hughes, Greg [School of Physical Sciences, Dublin City University, Glasnevin, Dublin 9 (Ireland)

2013-03-15

High resolution synchrotron radiation core level photoemission measurements have been used to study the high temperature stability of sulphur passivated InGaAs surfaces and comparisons made with atomically clean surfaces subjected to the same annealing temperatures. Sulphur passivation of clean InGaAs surfaces prepared by the thermal removal of an arsenic capping layer was carried out using an in situ molecular sulphur treatment in ultra high vacuum. The elemental composition of the surfaces of these materials was measured at a series of annealing temperatures up to 530 C. Following a 480 C anneal In:Ga ratio was found to have dropped by 33% on sulphur passivated surface indicating a significant loss of indium, while no drop in indium signal was recorded at this temperature on the atomically InGaAs surface. No significant change in the As surface concentration was measured at this temperature. These results reflect the reduced thermal stability of the sulphur passivated InGaAs compared to the atomically clean surface which has implications for device fabrication. (Copyright copyright 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Improving Energy Efficiency In Thermal Oil Recovery Surface Facilities

Energy Technology Data Exchange (ETDEWEB)

Murthy Nadella, Narayana

2010-09-15

Thermal oil recovery methods such as Cyclic Steam Stimulation (CSS), Steam Assisted Gravity Drainage (SAGD) and In-situ Combustion are being used for recovering heavy oil and bitumen. These processes expend energy to recover oil. The process design of the surface facilities requires optimization to improve the efficiency of oil recovery by minimizing the energy consumption per barrel of oil produced. Optimization involves minimizing external energy use by heat integration. This paper discusses the unit processes and design methodology considering thermodynamic energy requirements and heat integration methods to improve energy efficiency in the surface facilities. A design case study is presented.

Nucleation of 2D nanoislands in surface thermal spikes from swift heavy ions

International Nuclear Information System (INIS)

Volkov, Alexander E.; Sorokin, Michael V.

2003-01-01

Possibility of nucleation of nanoislands in the surface thermal spikes caused by swift heavy ions or intense femptosecond laser pulses is investigated. Nanoislands may occur when the characteristic nucleation time becomes shorter than that cooling down of the thermal spot. The values of system parameters favorable for the nucleation are estimated

Anthropogenic effects on the subsurface thermal and groundwater environments in Osaka, Japan and Bangkok, Thailand.

Science.gov (United States)

Taniguchi, Makoto; Shimada, Jun; Fukuda, Yoichi; Yamano, Makoto; Onodera, Shin-ichi; Kaneko, Shinji; Yoshikoshi, Akihisa

2009-04-15

Anthropogenic effects in both Osaka and Bangkok were evaluated to compare the relationships between subsurface environment and the development stage of both cities. Subsurface thermal anomalies due to heat island effects were found in both cities. The Surface Warming Index (SWI), the departure depth from the steady geothermal gradient, was used as an indicator of the heat island effect. SWI increases (deeper) with the magnitude of heat island effect and the elapsed time starting from the surface warming. Distributions of subsurface thermal anomalies due to the heat island effect agreed well with the distribution of changes in air temperature due to the same process, which is described by the distribution of population density in both Osaka and Bangkok. Different time lags between groundwater depression and subsidence in the two cities was found. This is attributed to differences in hydrogeologic characters, such as porosity and hydraulic conductivity. We find that differences in subsurface degradations in Osaka and Bangkok, including subsurface thermal anomalies, groundwater depression, and land subsidence, depends on the difference of the development stage of urbanization and hydrogeological characters.

Energy exchange in thermal energy atom-surface scattering: impulsive models

International Nuclear Information System (INIS)

Barker, J.A.; Auerbach, D.J.

1979-01-01

Energy exchange in thermal energy atom surface collisions is studied using impulsive ('hard cube' and 'hard sphere') models. Both models reproduce the observed nearly linear relation between outgoing and incoming energies. In addition, the hard-sphere model accounts for the widths of the outcoming energy distributions. (Auth.)

Thermal, spectral, and surface properties of LED light-polymerized bulk fill resin composites.

Science.gov (United States)

Pişkin, Mehmet Burçin; Atalı, Pınar Yılmaz; Figen, Aysel Kantürk

2015-02-01

The aim of this study was to evaluate the thermal, spectral, and surface properties of four different bulk fill materials – SureFil SDR (SDR, Dentsplay DETREY), QuixFil (QF, Dentsplay DETREY), X-tra base (XB, Voco) X-tra fil (XF, Voco) – polymerized by light-emitting diode (LED). Resin matrix, filler type, size and amount, and photoinitiator types influence the degree of conversion. LED-cured bulk fill composites achieved sufficient polymerization. Scanning electron microscope (SEM) analysis revealed different patterns of surface roughness, depending on the composite material. Bulk fill materials showed surface characteristics similar to those of nanohybrid composites. Based on the thermal analysis results, glass transition (T(g)) and initial degradation (T(i)) temperatures changed depending on the bulk fill resin composites.

Mathematical Modeling and Numerical Analysis of Thermal Distribution in Arch Dams considering Solar Radiation Effect

Science.gov (United States)

Mirzabozorg, H.; Hariri-Ardebili, M. A.; Shirkhan, M.; Seyed-Kolbadi, S. M.

2014-01-01

The effect of solar radiation on thermal distribution in thin high arch dams is investigated. The differential equation governing thermal behavior of mass concrete in three-dimensional space is solved applying appropriate boundary conditions. Solar radiation is implemented considering the dam face direction relative to the sun, the slop relative to horizon, the region cloud cover, and the surrounding topography. It has been observed that solar radiation changes the surface temperature drastically and leads to nonuniform temperature distribution. Solar radiation effects should be considered in thermal transient analysis of thin arch dams. PMID:24695817

Mathematical modeling and numerical analysis of thermal distribution in arch dams considering solar radiation effect.

Science.gov (United States)

Mirzabozorg, H; Hariri-Ardebili, M A; Shirkhan, M; Seyed-Kolbadi, S M

2014-01-01

The effect of solar radiation on thermal distribution in thin high arch dams is investigated. The differential equation governing thermal behavior of mass concrete in three-dimensional space is solved applying appropriate boundary conditions. Solar radiation is implemented considering the dam face direction relative to the sun, the slop relative to horizon, the region cloud cover, and the surrounding topography. It has been observed that solar radiation changes the surface temperature drastically and leads to nonuniform temperature distribution. Solar radiation effects should be considered in thermal transient analysis of thin arch dams.

Effects on heat transfer of multiphase magnetic fluid due to circular magnetic field over a stretching surface with heat source/sink and thermal radiation

Directory of Open Access Journals (Sweden)

A. Zeeshan

Full Text Available The purpose of the current article is to explore the boundary layer heat transport flow of multiphase magnetic fluid with solid impurities suspended homogeneously past a stretching sheet under the impact of circular magnetic field. Thermal radiation effects are also taken in account. The equations describing the flow of dust particles in fluid along with point dipole are modelled by employing conservation laws of mass, momentum and energy, which are then converted into non-linear coupled differential equations by mean of similarity approach. The transformed ODE’s are tackled numerically with the help of efficient Runga-Kutta method. The influence of ferromagnetic interaction parameter, viscous dissipation, fluid-particle interaction parameter, Eckert number, Prandtl number, thermal radiation parameter and number of dust particles, heat production or absorption parameter with the two thermal process namely, prescribed heat flux (PHF or prescribed surface temperature (PST are observed on temperature and velocity profiles. The value of skin-friction coefficient and Nusselt number are calculated for numerous physical parameters. Present results are correlated with available for a limited case and an excellent agreement is found. Keywords: Ferromagnetic interaction parameter, Dusty magnetic fluid, stretching sheet, Magnetic dipole, Heat source/sink, Thermal radiation

Silver Nanoparticle-Decorated Shape-Memory Polystyrene Sheets as Highly Sensitive Surface-Enhanced Raman Scattering Substrates with a Thermally Inducible Hot Spot Effect.

Science.gov (United States)

Mengesha, Zebasil Tassew; Yang, Jyisy

2016-11-15

In this study, an active surface-enhanced Raman scattering (SERS) substrate with a thermally inducible hot spot effect for sensitive measurement of Raman-active molecules was successfully fabricated from silver nanoparticle (AgNP)-decorated shape-memory polystyrene (SMP) sheets. To prepare the SERS substrate, SMP sheets were first pretreated with n-octylamine for effective decoration with AgNPs. By varying the formulation and condition of the reduction reaction, AgNP-decorated SMP (Ag@SMP) substrates were successfully prepared with optimized particle gaps to produce inducible hot spot effects on thermal shrink. High-quality SERS spectra were easily obtained with enhancement factors higher than 10 8 by probing with aromatic thiols. Several Ag@SMP substrates produced under different reaction conditions were explored for the creation of inducible hot spot effects. The results indicated that AgNP spacing is crucial for strong hot spot effects. The suitability of Ag@SMP substrates for quantification was also evaluated according to the detection of adenine. Results confirmed that prepared Ag@SMP substrates were highly suitable for quantitative analysis because they yielded an estimated limit of detection as low as 120 pg/cm 2 , a linear range of up to 7 ng/cm 2 , and a regression coefficient (R 2 ) of 0.9959. Ag@SMP substrates were highly reproducible; the average relative standard deviation for all measurements was less than 10%.

Analyzing Thermal Characteristics of Urban Streets Using a Thermal Imaging Camera: A Case Study on Commercial Streets in Seoul, Korea

Directory of Open Access Journals (Sweden)

Sugie Lee

2018-02-01

Full Text Available Due to continuing city growth and global warming over the past decades, urban heat island (UHI effects, referring to the phenomena wherein the ambient air temperatures in cities are higher than those in rural areas, have become a serious threat to urban populations. Impervious surfaces, buildings with low-albedo materials, and a lack of vegetated areas are the major causes of poor urban thermal environments, particularly during the summer. Previous research has focused primarily on the thermal characteristics of individual building units. Few studies consider the impact of the street-scale thermal environments on the surface temperature, which affects pedestrian thermal comfort. The purpose of this study is to analyze the thermal characteristics of various physical elements on urban streets using thermal imaging cameras, and present policy implications for improving pedestrian thermal comfort. This study examines street-scale thermal environments of three major commercial streets: Garosu road, Serosu road, and Narosu road, in Seoul, Korea. This study conducted field measurements both during the day and the night in June 2017 in order to investigate changes in the urban surface temperatures across time. The results show that street trees are the most effective mitigation element for reducing surface temperatures. With regard to building use types, the highest surface temperatures are typically measured near restaurant buildings. Building façades that are dark-colored or partially covered with a metal contribute to high surface temperatures. Similarly, the temperatures of artificial turf or wooden decks on urban streets are also significantly high during the daytime. The thermal characteristics of various urban street elements should be considered to reduce the surface temperature and mitigate the urban heat island effect.

Influence of surface morphology and microstructure on performance of CVD tungsten coating under fusion transient thermal loads

Energy Technology Data Exchange (ETDEWEB)

Lian, Youyun, E-mail: lianyy@swip.ac.cn [Southwestern Institute of Physics, Chengdu (China); Liu, Xiang; Wang, Jianbao; Feng, Fan [Southwestern Institute of Physics, Chengdu (China); Lv, Yanwei; Song, Jiupeng [China National R& D Center for Tungsten Technology, Xiamen Tungsten Co. Ltd, 361026 Xiamen (China); Chen, Jiming [Southwestern Institute of Physics, Chengdu (China)

2016-12-30

Highlights: • Thick CVD-W coatingswere deposited at a rapid growth rate. • The polished CVD-W coatings have highly textured structure and exhibited a very strong preferred orientation. • The polished CVD tungsten coatings show superior thermal shock resistance as compared with that of the as-deposited coatings. • The crack formation of the polished CVD-W was almost suppressed at an elevated temperature. - Abstract: Thick tungsten coatings have been deposited by chemical vapor deposition (CVD) at a rapid growth rate. A series of tungsten coatings with different thickness and surface morphology were prepared. The surface morphology, microstructure and preferred orientation of the CVD tungsten coatings were investigated. Thermal shock analyses were performed by using an electron beam facility to study the influence of the surface morphology and the microstructure on the thermal shock resistance of the CVD tungsten coatings. Repetitive (100 pulses) ELMs-like thermal shock loads were applied at various temperatures between room temperature and 600 °C with pulse duration of 1 ms and an absorbed power density of up to 1 GW/m{sup 2}. The results of the tests demonstrated that the specific surface morphology and columnar crystal structure of the CVD tungsten have significant influence on the surface cracking threshold and crack propagation of the materials. The CVD tungsten coatings with a polished surface show superior thermal shock resistance as compared with that of the as-deposited coatings with a rough surface.

Shallow crack effect on brittle fracture of RPV during pressurised thermal shock

International Nuclear Information System (INIS)

Ikonen, K.

1995-12-01

This report describes the study on behaviour of postulated shallow surface cracks in embrittled reactor pressure vessel subjected to pressurised thermal shock loading in an emergency core cooling. The study is related to the pressure vessel of a VVER-440 type reactor. Instead of a conventional fracture parameter like stress intensity factor or J integral the maximum principal stress distribution on a crack tip area is used as a fracture criteria. The postulated cracks locate circumferentially at the inner surface of the reactor pressure wall and they penetrate the cladding layer and open to the inner surface. Axisymmetric and semielliptical crack shapes were studied. Load is formed of an internal pressure acting also on crack faces and of a thermal gradient in the pressure vessel wall. Physical properties of material and loading data correspond real conditions in VVER-440 RPV. The study was carried out by making lot of 2D- and 3D- finite element calculations. Analysing principles and computer programs are explained. Except of studying the shallow crack effect, one objective of the study has also been to develop further expertise and the in-house developed computing system to make effectively elastic-plastic fracture mechanical analyses for real structures under complicated loads. Though the study concerns VVER-440 RPV, the results are of more general interest especially related to thermal loads. (orig.) (11 refs.)

The summer thermal behaviour of 'skin' materials for vertical surfaces in Athens, Greece, as a decisive parameter for their selection

Energy Technology Data Exchange (ETDEWEB)

Bougiatioti, F.; Evangelinos, E.; Poulakos, G.; Zacharopoulos, E. [National Technical University of Athens, School of Architecture, Department of Architectural Technology, 42, Patission Street, 10682 Athens (Greece)

2009-04-15

This paper analyses the thermal behaviour of the materials, which are widely used on the vertical surfaces of Greek cities. This analysis is based on surface temperatures measurements, which were carried out both in situ in various buildings of Athens, Greece and experimentally on samples of building materials exposed to solar radiation on a building's flat roof. The study includes surfacing materials, which are usually applied on building facades around Greece. The study leads to a number of conclusions concerning the effect of colour and orientation on the summer surface temperatures of materials, used on vertical city surfaces. These conclusions indicate how surfacing materials should be chosen in order to help mitigate the urban heat island and improve thermal comfort conditions in the outdoor spaces of Greek cities during the overheated summer period. (author)

An effect of surface properties on detachment of adhered solid to cooling surface for formation of clathrate hydrate slurry

Science.gov (United States)

Daitoku, Tadafumi; Utaka, Yoshio

In air-conditioning systems, it is desirable that the liquid-solid phase change temperature of a cool energy storage material is approximately 10 °C from the perspective of improving coefficient of performance (COP). Moreover, a thermal storage material that forms slurry can realize large heat capacity of working fluids. Since the solid that adheres to the heat transfer surface forms a thermal resistance layer and remarkably reduces the rate of cold storage, it is important to avoid the adhesion of a thick solid layer on the surface so as to realize efficient energy storage. Considering a harvest type cooling unit, the force required for removing the solid phase from the heat transfer surface was studied. Tetra-n-butylammonium Bromide (TBAB) clathrate hydrate was used as a cold storage material. The effect of the heat transfer surface properties on the scraping force for detachment of adhered solid of TBAB hydrate to the heat transfer surface was examined experimentally.

Effect of chemical treatment on thermal properties of fibers from pineapple

International Nuclear Information System (INIS)

Fernandes, Rafael I.M.; Mulinari, Daniella R.; Carvalho, Kelly C.C.; Conejo, Luiza dos Santos; Voorwald, Herman J.C.; Cioffi, Maria Odila H.

2009-01-01

In this work the effect of the chemical modification of natural fibres from of pineapple fibres with alkaline solution was studied. After modification the in nature and modified fibres were analyzed by XRD diffractometry and thermogravimetry with objective to evaluate influence chemical treatment in surface and in the thermal properties fibres. With the obtained results it was possible to verify an increase of 10.4 % in the crystallinity index of fibres beyond the increase around 4.5% in the degradation temperature, what it indicates an increase in the stability thermal of the fibres. (author)

Corrosion of ferritic steels by molten lithium: Influence of competing thermal gradient mass transfer and surface product reactions

International Nuclear Information System (INIS)

Tortorelli, P.F.

1987-10-01

An Fe-12Cr-1MoVW steel was exposed to thermally convective lithium for 6962 h. Results showed that the weight change profile of Fe-12Cr-1MoVW steel changed substantially as the maximum loop temperature was raised from 500 to 600 0 C. Furthermore, for a particular loop experiment, changes in the structure and composition of the exposed surfaces did not reflect typical thermal gradient mass transfer effects for all elements: the surface concentration of chromium was often a maximum at intermediate temperatures, while nickel (present at low concentrations in the starting material) tended to be transported to the coldest part of the loop. Such data were interpreted in terms of a qualitative model in which there are different dominant reactions or the various constituents of the ferritic steels (surface product formation involving nitrogen and/or carbon and solubility-driven elemental transport). This competition among different reactions is important in evaluating overall corrosion behavior and the effects of temperature. The overall corrosion rate of the 12Cr-1MoVW steel was relatively low when compared to that for austenitic stainless steel exposed under similar conditions

Effect of Insulation Thickness on Thermal Stratification in Hot Water Tanks

Directory of Open Access Journals (Sweden)

Burak KURŞUN

2018-03-01

Full Text Available One of the important factors to be considered in increasing the efficiency of hot water storage tanks used for thermal energy storage is thermal stratification. Reducing the temperature of the water at the base of the tank provides more utilization of the energy of the heat source during the heating of the water and improves the efficiency of the system. In this study, the effect of the insulation thickness on the outer surface of the tank and the ratio of the tank diameter to the height (D/H on the thermal stratification was investigated numerically. Numerical analyzes were carried out for the condition that the insulation thickness was constant and variable in the range of D/H=0,3-1. Water was used as the heat storage fluid and the analysis results were obtained for eight hours cooling period. Numerical results showed that the temperature difference between the bottom and top surfaces of the tank increased between 7-9 ° C for the range of D / H = 0,3-1 with changing the insulation thickness.

Thermal radiation effects on hydromagnetic flow

International Nuclear Information System (INIS)

Abdelkhalek, M.M.

2005-01-01

Numerical results are presented for the effects of thermal radiation, buoyancy and heat generation or absorption on hydromagnetic flow over an accelerating permeable surface. These results are obtained by solving the coupled nonlinear partial differential equations describing the conservation of mass, momentum and energy by a perturbation technique. This qualitatively agrees with the expectations, since the magnetic field exerts a retarding force on the free convection flow. A parametric study is performed to illustrate the influence of the radiation parameter, magnetic parameter, Prandtl number, Grashof number and Schmidt number on the profiles of the velocity components and temperature. The effects of the different parameters on the velocity and temperature profiles as well as the skin friction and wall heat transfer are presented graphically. Favorable comparisons with previously published work confirm the correctness of numerical results

Textural, surface, thermal and sorption properties of the functionalized activated carbons and carbon nanotubes

Directory of Open Access Journals (Sweden)

Nowicki Piotr

2015-12-01

Full Text Available Two series of functionalised carbonaceous adsorbents were prepared by means of oxidation and nitrogenation of commercially available activated carbon and multi-walled carbon nanotubes. The effect of nitrogen and oxygen incorporation on the textural, surface, thermal and sorption properties of the adsorbents prepared was tested. The materials were characterized by elemental analysis, low-temperature nitrogen sorption, thermogravimetric study and determination of the surface oxygen groups content. Sorptive properties of the materials obtained were characterized by the adsorption of methylene and alkali blue 6B as well as copper(II ions. The final products were nitrogen- and oxygen-enriched mesoporous adsorbents of medium-developed surface area, showing highly diverse N and O-heteroatom contents and acidic-basic character of the surface. The results obtained in our study have proved that through a suitable choice of the modification procedure of commercial adsorbents it is possible to produce materials with high sorption capacity towards organic dyes as well as copper(II ions.

Excellent c-Si surface passivation by thermal atomic layer deposited aluminum oxide after industrial firing activation

International Nuclear Information System (INIS)

Liao, B; Stangl, R; Ma, F; Mueller, T; Lin, F; Aberle, A G; Bhatia, C S; Hoex, B

2013-01-01

We demonstrate that by using a water (H 2 O)-based thermal atomic layer deposited (ALD) aluminum oxide (Al 2 O 3 ) film, excellent surface passivation can be attained on planar low-resistivity silicon wafers. Effective carrier lifetime values of up to 12 ms and surface recombination velocities as low as 0.33 cm s −1 are achieved on float-zone wafers after a post-deposition thermal activation of the Al 2 O 3 passivation layer. This post-deposition activation is achieved using an industrial high-temperature firing process which is commonly used for contact formation of standard screen-printed silicon solar cells. Neither a low-temperature post-deposition anneal nor a silicon nitride capping layer is required in this case. Deposition temperatures in the 100–400 °C range and peak firing temperatures of about 800 °C (set temperature) are investigated. Photoluminescence imaging shows that the surface passivation is laterally uniform. Corona charging and capacitance–voltage measurements reveal that the negative fixed charge density near the AlO x /c-Si interface increases from 1.4 × 10 12 to 3.3 × 10 12 cm −2 due to firing, while the midgap interface defect density reduces from 3.3 × 10 11 to 0.8 × 10 11 cm −2 eV −1 . This work demonstrates that direct firing activation of thermal ALD Al 2 O 3 is feasible, which could be beneficial for solar cell manufacturing. (paper)

Effect of engine-based thermal aging on surface morphology and performance of Lean NOx Traps

International Nuclear Information System (INIS)

Toops, Todd J.; Bunting, Bruce G.; Nguyen, Ke; Gopinath, Ajit

2007-01-01

A small single-cylinder diesel engine is used to thermally age model (Pt + Rh/Ba/γ-Al 2 O 3 ) lean NO x traps (LNTs) under lean/rich cycling at target temperatures of 600 C, 700 C, and 800 C. During an aging cycle, fuel is injected into the exhaust to achieve reproducible exotherms under lean and rich conditions with the average temperature approximating the target temperature. Aging is performed until the cycle-average NO x conversion measured at 400 C is approximately constant. Engine-based NO x conversion decreased by 42% after 60 cycles at 600 C, 36% after 76 cycles at 700 C and 57% after 46 cycles at 800 C. The catalyst samples were removed and characterized by XRD and using a microreactor that allowed controlled measurements of surface area, precious metal size, NO x storage, and reaction rates. Three aging mechanisms responsible for the deactivation of LNTs have been identified: (1) loss of dispersion of the precious metals, (2) phase transitions in the washcoat materials, and (3) loss of surface area of the storage component and support. These three mechanisms are accelerated when the aging temperature exceeds 850 C - the γ to (delta) transition temperature of Al 2 O 3 . Normalization of rates of NO reacted at 400 C to total surface area demonstrates the biggest impact on performance stems from surface area losses rather than from precious metal sintering. (author)

Measurements of Regolith Simulant Thermal Conductivity Under Asteroid and Mars Surface Conditions

Science.gov (United States)

Ryan, A. J.; Christensen, P. R.

2017-12-01

Laboratory measurements have been necessary to interpret thermal data of planetary surfaces for decades. We present a novel radiometric laboratory method to determine temperature-dependent thermal conductivity of complex regolith simulants under rough to high vacuum and across a wide range of temperatures. This method relies on radiometric temperature measurements instead of contact measurements, eliminating the need to disturb the sample with thermal probes. We intend to determine the conductivity of grains that are up to 2 cm in diameter and to parameterize the effects of angularity, sorting, layering, composition, and eventually cementation. We present the experimental data and model results for a suite of samples that were selected to isolate and address regolith physical parameters that affect bulk conductivity. Spherical glass beads of various sizes were used to measure the effect of size frequency distribution. Spherical beads of polypropylene and well-rounded quartz sand have respectively lower and higher solid phase thermal conductivities than the glass beads and thus provide the opportunity to test the sensitivity of bulk conductivity to differences in solid phase conductivity. Gas pressure in our asteroid experimental chambers is held at 10^-6 torr, which is sufficient to negate gas thermal conduction in even our coarsest of samples. On Mars, the atmospheric pressure is such that the mean free path of the gas molecules is comparable to the pore size for many regolith particulates. Thus, subtle variations in pore size and/or atmospheric pressure can produce large changes in bulk regolith conductivity. For each sample measured in our martian environmental chamber, we repeat thermal measurement runs at multiple pressures to observe this behavior. Finally, we present conductivity measurements of angular basaltic simulant that is physically analogous to sand and gravel that may be present on Bennu. This simulant was used for OSIRIS-REx TAGSAM Sample Return

Effects of thermal ageing on HMS-PP crystallinity

International Nuclear Information System (INIS)

Oliani, Washington L.; Parra, Duclerc F.; Lima, Luis F.C.P.; Lugao, Ademar B.

2009-01-01

The isotactic polypropylene is a linear polymer which exhibits low melt strength. Irradiation of PP under inert atmosphere causes a combination of chain scissioning and long-chain branching, and results in a material with significant enhanced melt strength. This process, which is sometimes termed visbreaking, thus provides improvement of rheological properties. HMS-PP (High Melt Strength Polypropylene) was obtained by the irradiation in atmosphere of acetylene as crosslinker agent. It was employed doses of 12.5 and 20 kGy of gamma radiation. The objective of this study is to investigate the effects of thermal ageing on the crystallinity level and chemical structure of HMS-PP. The thermal stability of the HMS-PP was evaluated after thermal ageing of samples using a stove at temperature of 90 deg C, in presence of air at different periods of time. The samples submitted to the thermal ageing were characterized by: thermogravimetry (TGA), differential scanning calorimetry (DSC), infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Since the long-term engineering properties of HMS-PP are intrinsically linked with the polymer microstructure, there is significant interest in understanding the effects of ageing, particularly due to prolonged exposure at service temperatures. In thermo-oxidative conditions, the formation of the oxidation products essentially involves a hydrogen abstraction by the peroxyl radicals, leading to hydroperoxides as primary products and chemical degradation in the immediate crack tips. Oxidative degradation on the network of HMS-PP, created by radiation process of PP, was revealed by the analytical results showing the susceptibility of HMS-PP to thermal oxidative degradation. Yellowing of the samples surface and oxidative products of degradation among other evidences were observed. (author)

Impacts of propagating, frustrated and surface modes on radiative, electrical and thermal losses in nanoscale-gap thermophotovoltaic power generators

Science.gov (United States)

Bernardi, Michael P.; Dupré, Olivier; Blandre, Etienne; Chapuis, Pierre-Olivier; Vaillon, Rodolphe; Francoeur, Mathieu

2015-01-01

The impacts of radiative, electrical and thermal losses on the performances of nanoscale-gap thermophotovoltaic (nano-TPV) power generators consisting of a gallium antimonide cell paired with a broadband tungsten and a radiatively-optimized Drude radiator are analyzed. Results reveal that surface mode mediated nano-TPV power generation with the Drude radiator outperforms the tungsten radiator, dominated by frustrated modes, only for a vacuum gap thickness of 10 nm and if both electrical and thermal losses are neglected. The key limiting factors for the Drude- and tungsten-based devices are respectively the recombination of electron-hole pairs at the cell surface and thermalization of radiation with energy larger than the cell absorption bandgap. A design guideline is also proposed where a high energy cutoff above which radiation has a net negative effect on nano-TPV power output due to thermal losses is determined. It is shown that the power output of a tungsten-based device increases by 6.5% while the cell temperature decreases by 30 K when applying a high energy cutoff at 1.45 eV. This work demonstrates that design and optimization of nano-TPV devices must account for radiative, electrical and thermal losses. PMID:26112658

The InSight Mars Lander and Its Effect on the Subsurface Thermal Environment

Science.gov (United States)

Siegler, Matthew A.; Smrekar, Suzanne E.; Grott, Matthias; Piqueux, Sylvain; Mueller, Nils; Williams, Jean-Pierre; Plesa, Ana-Catalina; Spohn, Tilman

2017-10-01

The 2018 InSight (Interior Exploration using Seismic Investigations, Geodesy and Heat Transport) Mission has the mission goal of providing insitu data for the first measurement of the geothermal heat flow of Mars. The Heat Flow and Physical Properties Package (HP3) will take thermal conductivity and thermal gradient measurements to approximately 5 m depth. By necessity, this measurement will be made within a few meters of the lander. This means that thermal perturbations from the lander will modify local surface and subsurface temperature measurements. For HP3's sensitive thermal gradient measurements, this spacecraft influence will be important to model and parameterize. Here we present a basic 3D model of thermal effects of the lander on its surroundings. Though lander perturbations significantly alter subsurface temperatures, a successful thermal gradient measurement will be possible in all thermal conditions by proper (>3 m depth) placement of the heat flow probe.

Modeling of thermal effects on TIBER II [Tokamak Ignition/Burn Experimental Reactor] divertor during plasma disruption

International Nuclear Information System (INIS)

Bruhn, M.L.; Perkins, L.J.

1987-01-01

Mapping the disruption power flow from the mid-plane of the TIBER Engineering Test Reactor to its divertor and calculating the resulting thermal effects are accomplished through the modification and coupling of three presently existing computer codes. The resulting computer code TADDPAK (Thermal Analysis Divertor during Disruption PAcKage) provides three-dimensional graphic presentations of time and positional dependent thermal effects on a poloidal cross section of the double-null-divertor configured reactor. These thermal effects include incident heat flux, surface temperature, vaporization rate, total vaporization, and melting depth. The dependence of these thermal effects on material choice, disruption pulse shape, and the characteristic thickness of the plasma scrape-off layer is determined through parametric analysis with TADDPAK. This computer code is designed to be a convenient, rapid, and user-friendly modeling tool which can be easily adapted to most tokamak double-null-divertor reactor designs. 14 refs

Temperature Mapping of Air Film-Cooled Thermal Barrier Coated Surfaces Using Cr-Doped GdAlO3 Phosphor Thermography

Science.gov (United States)

Eldridge, Jeffrey I.; Shyam, Vikram; Wroblewski, Adam C.; Zhu, Dongming; Cuy, Michael D.; Wolfe, Douglas E.

2016-01-01

It has been recently shown that the high luminescence intensity from a Cr-doped GdAlO3 (Cr:GdAlO3) thermographic phosphor enables non-rastered full-field temperature mapping of thermal barrier coating (TBC) surfaces to temperatures above 1000C. In this presentation, temperature mapping by Cr:GdAlO3 based phosphor thermometry of air film-cooled TBC-coated surfaces is demonstrated for both scaled-up cooling hole geometries as well as for actual components in a burner rig test environment. The effects of thermal background radiation and flame chemiluminescence on the measurements are investigated, and advantages of this method over infrared thermography as well as the limitations of this method for studying air film cooling are discussed.

Hyperspatial Thermal Imaging of Surface Hydrothermal Features at Pilgrim Hot Springs, Alaska using a small Unmanned Aerial System (sUAS)

Science.gov (United States)

Haselwimmer, C. E.; Wilson, R.; Upton, C.; Prakash, A.; Holdmann, G.; Walker, G.

2013-12-01

Thermal remote sensing provides a valuable tool for mapping and monitoring surface hydrothermal features associated with geothermal activity. The increasing availability of low-cost, small Unmanned Aerial Systems (sUAS) with integrated thermal imaging sensors offers a means to undertake very high spatial resolution (hyperspatial), quantitative thermal remote sensing of surface geothermal features in support of exploration and long-term monitoring efforts. Results from the deployment of a quadcopter sUAS equipped with a thermal camera over Pilgrim Hot Springs, Alaska for detailed mapping and heat flux estimation for hot springs, seeps, and thermal pools are presented. Hyperspatial thermal infrared imagery (4 cm pixels) was acquired over Pilgrim Hot Springs in July 2013 using a FLIR TAU 640 camera operating from an Aeryon Scout sUAS flying at an altitude of 40m. The registered and mosaicked thermal imagery is calibrated to surface temperature values using in-situ measurements of uniform blackbody tarps and the temperatures of geothermal and other surface pools acquired with a series of water temperature loggers. Interpretation of the pre-processed thermal imagery enables the delineation of hot springs, the extents of thermal pools, and the flow and mixing of individual geothermal outflow plumes with an unprecedented level of detail. Using the surface temperatures of thermal waters derived from the FLIR data and measured in-situ meteorological parameters the hot spring heat flux and outflow rate is calculated using a heat budget model for a subset of the thermal drainage. The heat flux/outflow rate estimates derived from the FLIR data are compared against in-situ measurements of the hot spring outflow rate recorded at the time of the thermal survey.

Control of propagation characteristics of spin wave pulses via elastic and thermal effects

Energy Technology Data Exchange (ETDEWEB)

Gómez-Arista, Ivan [Centro de Ciencias Aplicadas y Desarrollo Tecnológico, Universidad Nacional Autónoma de México, CU, 04510 D.F., México (Mexico); Kolokoltsev, O., E-mail: oleg.kolokoltsev@ccadet.unam.mx [Centro de Ciencias Aplicadas y Desarrollo Tecnológico, Universidad Nacional Autónoma de México, CU, 04510 D.F., México (Mexico); Acevedo, A.; Qureshi, N. [Centro de Ciencias Aplicadas y Desarrollo Tecnológico, Universidad Nacional Autónoma de México, CU, 04510 D.F., México (Mexico); Ordóñez-Romero, César L. [Instituto de Física, Universidad Nacional Autónoma de México, CU, 04510 D.F., México (Mexico)

2017-05-01

A study of the magnetoelastic (ME) and thermal effects governing the phase (φ) and amplitude of magnetostatic surface spin wave (MSSW) pulses propagating in Ga:YIG/GGG and permalloy magnonic waveguides is presented. The ME effects were studied in a flexural configuration, under punctual mechanical force (F). Thermally induced ME and demagnetization phenomena were controlled by optically injected thermal power P{sub th}. It was determined that in an unclamped Ga:YIG waveguide, the force F that induces the phase shift Δφ=π, decreases by a quadratic law in the range from 1 mN to nN, and the P{sub th} at which Δφ=π decreases linearly from mW to μW as the waveguide volume decreases from mm{sup 3} to nm{sup 3}. For nano-volume waveguides the ME control energy (E{sub me}) can be of order of aJ, and the thermal control energy (ΔE{sub th}) can be as small as 50 fJ. The response time of these effects lies in the ns time scale. Both the mechanical and the thermo-magnetic forces provide an effective control of MSSW pulse amplitude, in addition to its phase shift. The thermo-magnetic effect allows one to realize variable delays of a MSSW pulse. - Highlights: • The Magneto-elastic (ME) and optically induced thermal effects governing the phase and amplitude of magnetostatic surface spin wave (MSSW) pulses propagating in Ga:YIG/GGG and permalloy magnonic waveguides are presented. • A mechanical force that causes phase shift Δφ=π for spin waves in the waveguides decreases by a quadratic law in the range from 1 mN to nN, and the optical power that induces the phase shift Δφ=π, decreases linearly from mW to μW as the waveguide volume decreases from mm{sup 3} to nm{sup 3}. • The response time of these effects can lie in the ns time scale.

Thermal-driven attachment of gold nanoparticles prepared with ascorbic acid onto indium tin oxide surfaces

Energy Technology Data Exchange (ETDEWEB)

Aziz, Md. Abdul; Oyama, Munetaka, E-mail: oyama.munetaka.4m@kyoto-u.ac.jp [Kyoto University, Department of Material Chemistry, Graduate School of Engineering (Japan)

2013-05-15

Thermal-driven attachment of gold nanoparticles (AuNPs), of which size was less than 50 nm, onto the surfaces of indium tin oxide (ITO) is reported as a new phenomenon. This was permitted by preparing AuNPs via the reduction of hydrogen tetrachloroaurate (HAuCl{sub 4}) with ascorbic acid (AA). While the AuNPs prepared via the AA reduction sparsely attached on the surface of ITO even at room temperature, a heat-up treatment at ca. 75 Degree-Sign C caused denser attachment of AuNPs on ITO surfaces. The attached density and the homogeneity after the thermal treatment were better than those of AuNP/ITO prepared using 3-aminopropyl-trimethoxysilane linker molecules. The denser attachment was observed similarly both by the immersion of ITO samples after the preparations of AuNPs by AA and by the in situ preparation of AuNPs with AA together with ITO samples. Thus, it is considered that the thermal-driven attachment of AuNPs would occur after the formation of AuNPs in the aqueous solutions, not via the growth of AuNPs on ITO surfaces. The preparation of AuNPs with AA would be a key for the thermal-driven attachment because the same attachments were not observed for AuNPs prepared with citrate ions or commercially available tannic acid-capped AuNPs.

Morphological study of polymer surfaces exposed to non-thermal plasma based on contact angle and the use of scaling laws

Energy Technology Data Exchange (ETDEWEB)

Felix, T., E-mail: tsfelix81@gmail.com [Chemistry Department, Federal University of Santa Catarina, Campus Trindade, 88040-900 Florianópolis, SC (Brazil); Cassini, F.A.; Benetoli, L.O.B. [Chemistry Department, Federal University of Santa Catarina, Campus Trindade, 88040-900 Florianópolis, SC (Brazil); Dotto, M.E.R. [Physics Department, Federal University of Santa Catarina, Campus Trindade, 88040-900 Florianópolis, SC (Brazil); Debacher, N.A. [Chemistry Department, Federal University of Santa Catarina, Campus Trindade, 88040-900 Florianópolis, SC (Brazil)

2017-05-01

Highlights: • Polymeric surfaces were etched using non-thermal plasma at different intensities. • Polymers of low mechanical hardness reached the saturation level faster. • A mathematical model based on scaling laws was proposed. - Abstract: The experiments presented in this communication have the purpose to elaborate an explanation for the morphological evolution of the growth of polymeric surfaces provided by the treatment of non-thermal plasma. According to the roughness analysis and the model proposed by scaling laws it is possible relate to a predictable or merely random effect. Polyethylene terephthalate (PET) and poly(etherether)ketone (PEEK) samples were exposed to a non-thermal plasma discharge and the resulting surfaces roughness were analyzed based on the measurements from contact angle, scanning electron microscopy and atomic force microscopy coupled with scaling laws analysis which can help to describe and understand the dynamic of formation of a wide variety of rough surfaces. The roughness, R{sub RMS} (RMS- Root Mean Square) values for polymer surface range between 19.8 nm and 110.9 nm. The contact angle and the AFM (Atomic Force Microscopy) measurements as a function of the plasma exposure time were in agreement with both polar and dispersive components according to the surface roughness and also with the morphology evaluated described by Wolf-Villain model, with proximate values of α between 0.91{sub (PET)} and 0.88{sub (PEEK)}, β = 0.25{sub (PET)} and z = 3,64{sub (PET)}.

Morphological study of polymer surfaces exposed to non-thermal plasma based on contact angle and the use of scaling laws

International Nuclear Information System (INIS)

Felix, T.; Cassini, F.A.; Benetoli, L.O.B.; Dotto, M.E.R.; Debacher, N.A.

2017-01-01

Highlights: • Polymeric surfaces were etched using non-thermal plasma at different intensities. • Polymers of low mechanical hardness reached the saturation level faster. • A mathematical model based on scaling laws was proposed. - Abstract: The experiments presented in this communication have the purpose to elaborate an explanation for the morphological evolution of the growth of polymeric surfaces provided by the treatment of non-thermal plasma. According to the roughness analysis and the model proposed by scaling laws it is possible relate to a predictable or merely random effect. Polyethylene terephthalate (PET) and poly(etherether)ketone (PEEK) samples were exposed to a non-thermal plasma discharge and the resulting surfaces roughness were analyzed based on the measurements from contact angle, scanning electron microscopy and atomic force microscopy coupled with scaling laws analysis which can help to describe and understand the dynamic of formation of a wide variety of rough surfaces. The roughness, R_R_M_S (RMS- Root Mean Square) values for polymer surface range between 19.8 nm and 110.9 nm. The contact angle and the AFM (Atomic Force Microscopy) measurements as a function of the plasma exposure time were in agreement with both polar and dispersive components according to the surface roughness and also with the morphology evaluated described by Wolf-Villain model, with proximate values of α between 0.91_(_P_E_T_) and 0.88_(_P_E_E_K_), β = 0.25_(_P_E_T_) and z = 3,64_(_P_E_T_).

Urban thermal landscape characterization and analysis

International Nuclear Information System (INIS)

Xue, Y; Fung, T; Tsou, J

2014-01-01

Urban warming is sensitive to the nature (thermal properties, including albedo, water content, heat capacity and thermal conductivity) and the placement (surface geometry or urban topography) of urban surface. In this research, the pattern and variation of urban surface temperature is regarded as one kind of landscape, urban thermal landscape, which is assumed as the presentation of local surface heating process upon urban landscape. The goal of this research is to develop a research framework incorporating geospatial statistics, thermal infrared remote sensing and landscape ecology to study the urban effect on local surface thermal landscape regarding both the pattern and process. This research chose Hong Kong as the case study. Within the study area, urban and rural area coexists upon a hilly topography. In order to probe the possibility of local surface warming mechanism discrepancy between urban and rural area, the sample points are grouped into urban and rural categories in according with the land use map taken into a linear regression model separately to examine the possible difference in local warming mechanism. Global regression analysis confirmed the relationship between environmental factors and surface temperature and the urban-rural distinctive mechanism of dominating diurnal surface warming is uncovered

Thermal Inertia of near-Earth Asteroids and Strength of the Yarkovsky Effect

NARCIS (Netherlands)

Delbo, Marco; Dell'Oro, A.; Harris, A. W.; Mottola, S.; Mueller, M.

2006-01-01

Thermal inertia is the physical parameter that controls the temperature distribution over the surface of an asteroid. It affects the strength of the Yarkovsky effect, which causes orbital drift of km-sized asteroids and is invoked to explain the delivery of near-Earth asteroids (NEAs) from the main

Studies on thermal properties and thermal control effectiveness of a new shape-stabilized phase change material with high thermal conductivity

International Nuclear Information System (INIS)

Cheng Wenlong; Liu Na; Wu Wanfan

2012-01-01

In order to overcome the difficulty of conventional phase change materials (PCMs) in packaging, the shape-stabilized PCMs are proposed to be used in the electronic device thermal control. However, the conventional shape-stabilized PCMs have the drawback of lower thermal conductivity, so a new shape-stabilized PCM with high thermal conductivity, which is suitable for thermal control of electronic devices, is prepared. The thermal properties of n-octadecane-based shape-stabilized PCM are tested and analyzed. The heat storage/release performance is studied by numerical simulation. Its thermal control effect for electronic devices is also discussed. The results show that the expanded graphite (EG) can greatly improve the thermal conductivity of the material with little effect on latent heat and phase change temperature. When the mass fraction of EG is 5%, thermal conductivity has reached 1.76 W/(m K), which is over 4 times than that of the original one. Moreover, the material has larger latent heat and good thermal stability. The simulation results show that the material can have good heat storage/release performance. The analysis of the effect of thermal parameters on thermal control effect for electronic devices provides references to the design of phase change thermal control unit. - Highlights: ► A new shape-stabilized PCM with higher thermal conductivity is prepared. ► The material overcomes the packaging difficulty of traditional PCMs used in thermal control unit. ► The EG greatly improves thermal conductivity with little effect on latent heat. ► The material has high thermal stability and good heat storage/release performance. ► The effectiveness of the material for electronic device thermal control is proved.

A study on changes in body surface temperature and thermal effect according to ultrasound mode

Energy Technology Data Exchange (ETDEWEB)

Yang, Sung Hee [Dept. of Radiology, Ilsin Christian Hospital, Busan (Korea, Republic of); Lee, Jin Soo [Dept. of Radiology, University Haeundae Paik Hospital, Busan (Korea, Republic of)

2017-06-15

Recently, as the number of high-risk pregnancies increases, the use of new techniques such as Doppler, which have higher acoustic power than in the past, has been increasingly used in prenatal diagnosis and guidelines have been set up by various organizations to prevent excessive exposure. Therefore, in this study, we tried to investigate the temperature change of the body surface for each test mode according to the long time ultrasound examination and to examine the exposure time which is not influenced by the thermal effect. B mode, C mode, and PD mode according to time, and the temperature difference between exposed and unexposed sites were compared. As a result, the B mode showed a significant difference in the temperature change from 10 minutes, 50 minutes after exposed, 20 minutes from the C mode, and 30 minutes from the PD mode (p<0.01). In all three modes, the temperature difference was different(p<0.000), and PD mode was the most sensitive to temperature change. Also, it was found that the temperature rise time was shortened with the increase of the ultrasonic exposure time. Therefore, it is recommended that ultrasonography to observe the embryo or fetus should be used only for diagnostic purposes, avoiding excessive test time.

Hydromagnetic Rarefied Fluid Flow over a Wedge in the Presence of Surface Slip and Thermal Radiation

Directory of Open Access Journals (Sweden)

Das K.

2017-12-01

Full Text Available An analysis is presented to investigate the effects of thermal radiation on a convective slip flow of an electrically conducting slightly rarefied fluid, having temperature dependent fluid properties, over a wedge with a thermal jump at the surface of the boundary in the presence of a transverse magnetic field. The reduced equations are solved numerically using the finite difference code that implements the 3-stage Lobatto IIIa formula for the partitioned Runge-Kutta method. Numerical results for the dimensionless velocity and temperature as well as for the skin friction coefficient and the Nusselt number are presented through graphs and tables for pertinent parameters to show interesting aspects of the solution.

Non-thermal desorption from interstellar dust grains via exothermic surface reactions

Science.gov (United States)

Garrod, R. T.; Wakelam, V.; Herbst, E.

2007-06-01

Aims:The gas-phase abundance of methanol in dark quiescent cores in the interstellar medium cannot be explained by gas-phase chemistry. In fact, the only possible synthesis of this species appears to be production on the surfaces of dust grains followed by desorption into the gas. Yet, evaporation is inefficient for heavy molecules such as methanol at the typical temperature of 10 K. It is necessary then to consider non-thermal mechanisms for desorption. But, if such mechanisms are considered for the production of methanol, they must be considered for all surface species. Methods: Our gas-grain network of reactions has been altered by the inclusion of a non-thermal desorption mechanism in which the exothermicity of surface addition reactions is utilized to break the bond between the product species and the surface. Our estimated rate for this process derives from a simple version of classical unimolecular rate theory with a variable parameter only loosely constrained by theoretical work. Results: Our results show that the chemistry of dark clouds is altered slightly at times up to 106 yr, mainly by the enhancement in the gas-phase abundances of hydrogen-rich species such as methanol that are formed on grain surfaces. At later times, however, there is a rather strong change. Instead of the continuing accretion of most gas-phase species onto dust particles, a steady-state is reached for both gas-phase and grain-surface species, with significant abundances for the former. Nevertheless, most of the carbon is contained in an undetermined assortment of heavy surface hydrocarbons. Conclusions: The desorption mechanism discussed here will be better constrained by observational data on pre-stellar cores, where a significant accretion of species such as CO has already occurred.

Transient thermal effects in Alpine permafrost

Directory of Open Access Journals (Sweden)

J. Noetzli

2009-04-01

Full Text Available In high mountain areas, permafrost is important because it influences the occurrence of natural hazards, because it has to be considered in construction practices, and because it is sensitive to climate change. The assessment of its distribution and evolution is challenging because of highly variable conditions at and below the surface, steep topography and varying climatic conditions. This paper presents a systematic investigation of effects of topography and climate variability that are important for subsurface temperatures in Alpine bedrock permafrost. We studied the effects of both, past and projected future ground surface temperature variations on the basis of numerical experimentation with simplified mountain topography in order to demonstrate the principal effects. The modeling approach applied combines a distributed surface energy balance model and a three-dimensional subsurface heat conduction scheme. Results show that the past climate variations that essentially influence present-day permafrost temperatures at depth of the idealized mountains are the last glacial period and the major fluctuations in the past millennium. Transient effects from projected future warming, however, are likely larger than those from past climate conditions because larger temperature changes at the surface occur in shorter time periods. We further demonstrate the accelerating influence of multi-lateral warming in steep and complex topography for a temperature signal entering the subsurface as compared to the situation in flat areas. The effects of varying and uncertain material properties (i.e., thermal properties, porosity, and freezing characteristics on the subsurface temperature field were examined in sensitivity studies. A considerable influence of latent heat due to water in low-porosity bedrock was only shown for simulations over time periods of decades to centuries. At the end, the model was applied to the topographic setting of the Matterhorn

The effects of dune slopes and material heterogeneity on the thermal behavior of dune fields in Mars' Southern Hemisphere

Science.gov (United States)

O'Shea, P. M.; Putzig, N. E.; Van Kooten, S.; Fenton, L. K.

2015-12-01

We analyzed the effects of slopes on the thermal properties of three dune fields in Mars' southern hemisphere. Although slope has important thermal effects, it is not the main driver of observed apparent thermal inertia (ATI) for these dunes. Comparing the ATI seasonal behavior as derived from Thermal Emission Spectrometer (TES) data with that modeled for compositional heterogeneities, we found that TES results correlate best with models of duricrust overlying and/or horizontally mixing with fines. We measured slopes and aspects in digital terrain models created from High Resolution Imaging Science Experiment (HiRISE) images of dunes within Proctor, Kaiser, and Wirtz craters. Using the MARSTHERM web toolset, we incorporated the slopes and aspects together with TES albedo, TES thermal inertia, surface pressure, and TES dust opacity, into models of seasonal ATI. Models that incorporate sub-pixel slopes show seasonal day and night ATI values that differ from the TES results by 0-300 J m-2 K-1 s-½. In addition, the models' day-night differences are opposite in sign from those of the TES results, indicating that factors other than slope are involved. We therefore compared the TES data to model results for a broad range of horizontally mixed and two-layered surfaces to seek other possible controls on the observed data, finding that a surface layer of higher thermal inertia is a likely contributor. However, it is clear from this study that the overall composition and morphology of the dune fields are more complex than currently available models allow. Future work will combine slopes with other model parameters such as multi-layered surfaces and lateral changes in layer thickness. Coupling these improvements with broader seasonal coverage from the Thermal Emission Imaging System (THEMIS) at more thermally favorable times of day would allow more accurate characterization of dune thermal behavior.

Effect of layer thickness on the properties of nickel thermal sprayed steel

Energy Technology Data Exchange (ETDEWEB)

Nurisna, Zuhri, E-mail: zuhri-nurisna@yahoo.co.id; Triyono,, E-mail: triyonomesin@uns.ac.id; Muhayat, Nurul, E-mail: nurulmuhayat@staff.uns.ac.id; Wijayanta, Agung Tri, E-mail: agungtw@uns.ac.id [Department of Mechanical Engineering, Sebelas Maret University, Jl. Jr. Sutami 36 A, Surakarta (Indonesia)

2016-03-29

Thermal arc spray nickel coating is widely used for decorative and functional applications, by improving corrosion resistance, wear resistance, heat resistence or by modifying other properties of the coated materials. There are several properties have been studied. Layer thickness of nickel thermal sprayed steel may be make harder the substrate surface. In this study, the effect of layer thickness of nickel thermal sprayed steel has been investigated. The rectangular substrate specimens were coated by Ni–5 wt.% Al using wire arc spray method. The thickness of coating layers were in range from 0.4 to 1.0 mm. Different thickness of coating layers were conducted to investigate their effect on hardness and morphology. The coating layer was examined by using microvickers and scanning electron microscope with EDX attachment. Generally, the hardness at the interface increased with increasing thickness of coating layers for all specimens due to higher heat input during spraying process. Morphology analysis result that during spraying process aluminum would react with surrounding oxygen and form aluminum oxide at outer surface of splat. Moreover, porosity was formed in coating layers. However, presence porosity is not related to thickness of coating material. The thicker coating layer resulted highesr of hardness and bond strength.

Surface Structures and Thermal Desorption Behaviors of Cyclopentanethiol Self-Assembled Monolayers on Au(111)

International Nuclear Information System (INIS)

Kang, Hun Gu; Kim, You Young; Park, Tae Sun; Noh, Jae Geun; Park, Joon B.; Ito, Eisuke; Hara, Masahiko

2011-01-01

The surface structures, adsorption conditions, and thermal desorption behaviors of cyclopentanethiol (CPT) self-assembled monolayers (SAMs) on Au(111) were investigated by scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), and thermal desorption spectroscopy (TDS). STM imaging revealed that although the adsorption of CPT on Au(111) at room temperature generates disordered SAMs, CPT molecules at 50 .deg. C formed well-ordered SAMs with a (2√3 x √5)R41".deg. packing structure. XPS measurements showed that CPT SAMs at room temperature were formed via chemical reactions between the sulfur atoms and gold surfaces. TDS measurements showed two dominant TD peaks for the decomposed fragments (C_5H_9 "+, m/e = 69) generated via C-S bond cleavage and the parent molecular species (C_5H_9SH"+, m/e = 102) derived from a recombination of the chemisorbed thiolates and hydrogen atoms near 440 K. Interestingly, dimerization of sulfur atoms in n-alkanethiol SAMs usually occurs during thermal desorption and the same reaction did not happen for CPT SAMs, which may be due to the steric hindrance of cyclic rings of the CPT molecules. In this study, we demonstrated that the alicyclic ring of organic thiols strongly affected the surface structure and thermal desorption behavior of SAMs, thus providing a good method for controlling chemical and physical properties of organic thiol SAMs

Functionalization of polymer surfaces by medium frequency non-thermal plasma

Science.gov (United States)

Felix, T.; Trigueiro, J. S.; Bundaleski, N.; Teodoro, O. M. N. D.; Sério, S.; Debacher, N. A.

2018-01-01

This work addresses the surface modification of different polymers by argon dielectric barrier discharge, using bromoform vapours. Atomic Force Microscopy and Scanning Electron Microscopy showed that plasma etching occurs in stages and may be related to the reach of the species generated and obviously the gap between the electrodes. In addition, the stages of flatten surface or homogeneity may be the result of the transient crosslinking promoted by the intense UV radiation generated by the non- thermal plasma. X-ray Photoelectron Spectroscopy analysis showed that bromine was inserted on the polymer surface as Csbnd Br bonds and as adsorbed HBr. The obtained results demonstrate that the highest degree of bromofunctionalization was achieved on polypropylene surface, which contains about 8,5% of Br. After its derivatization in ammonia, Br disappeared and about 6% of nitrogen in the form of amine group was incorporated at the surface. This result can be considered as a clear fingerprint of the Br substitution by the amine group, thus illustrating the efficiency of the proposed method for functionalization of polymer surfaces.

Thermally controlled growth of surface nanostructures on ion-modified AIII-BV semiconductor crystals

Science.gov (United States)

Trynkiewicz, Elzbieta; Jany, Benedykt R.; Wrana, Dominik; Krok, Franciszek

2018-01-01

The primary motivation for our systematic study is to provide a comprehensive overview of the role of sample temperature on the pattern evolution of several AIII-BV semiconductor crystal (001) surfaces (i.e., InSb, InP, InAs, GaSb) in terms of their response to low-energy Ar+ ion irradiation conditions. The surface morphology and the chemical diversity of such ion-modified binary materials has been characterized by means of scanning electron microscopy (SEM). In general, all surface textures following ion irradiation exhibit transitional behavior from small islands, via vertically oriented 3D nanostructures, to smoothened surface when the sample temperature is increased. This result reinforces our conviction that the mass redistribution of adatoms along the surface plays a vital role during the formation and growth process of surface nanostructures. We would like to emphasize that this paper addresses in detail for the first time the topic of the growth kinetics of the nanostructures with regard to thermal surface diffusion, while simultaneously offering some possible approaches to supplementing previous studies and therein gaining a new insight into this complex issue. The experimental results are discussed with reference to models of the pillars growth, abutting on preferential sputtering, the self-sustained etch masking effect and the redeposition process recently proposed to elucidate the observed nanostructuring mechanism.

Damage of first wall materials in fusion reactors under nonstationary thermal effects

International Nuclear Information System (INIS)

Maslaev, S.A.; Platonov, Yu.M.; Pimenov, V.N.

1991-01-01

The temperature distribution in the first wall of a fusion reactor was calculated for nonstationary thermal effects of the type of plasma destruction or the flow of 'running electrons' taking into account the melting of the surface layer of the material. The thickness of the resultant damaged layer in which thermal stresses were higher than the tensile strength of the material is estimated. The results were obtained for corrosion-resisting steel, aluminium and vanadium. Flowing down of the molten layer of the material of the first wall is calculated. (author)

Preparation and characterization of silicon nitride (Si−N)-coated carbon fibers and their effects on thermal properties in composites

Energy Technology Data Exchange (ETDEWEB)

Kim, Hyeon-Hye [R& D Division, Korea Institute of Carbon Convergence Technology, Jeonju 561-844 (Korea, Republic of); Nano& Advanced Materials Engineering, Jeonju University, Jeonju 560-759 (Korea, Republic of); Han, Woong [R& D Division, Korea Institute of Carbon Convergence Technology, Jeonju 561-844 (Korea, Republic of); Lee, Hae-seong [Nano& Advanced Materials Engineering, Jeonju University, Jeonju 560-759 (Korea, Republic of); Min, Byung-Gak [Department of Polymer Science & Engineering, Korea National University of Transportation, Chungju 380-702 (Korea, Republic of); Kim, Byung-Joo, E-mail: ap2-kbj@hanmail.net [R& D Division, Korea Institute of Carbon Convergence Technology, Jeonju 561-844 (Korea, Republic of)

2015-10-15

Graphical abstract: We report preparation and characterization of silicon nitride (Si−N)-coated carbon fibers and their effects on thermal properties in composites. Thermally composites showed enhanced thermal conductivity increasing from up to 59% by the thermal network. - Highlights: • A new method of Si−N coating on carbon fibers was reported. • Silane layer were successfully converted to Si−N layer on carbon fiber surface. • Si−N formation was confirmed by FT-IR, XPS, and EDX. • Thermal conductivity of Si−N coated CF composites were enhanced to 0.59 W/mK. - Abstract: This study investigates the effect of silicon nitride (Si−N)-coated carbon fibers on the thermal conductivity of carbon-fiber-reinforced epoxy composite. The surface properties of the Si−N-coated carbon fibers (SiNCFs) were observe using Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive spectroscopy, and X-ray photoelectron spectroscopy, and the thermal stability was analyzed using thermogravimetric analysis. SiNCFs were fabricated through the wet thermal treatment of carbon fibers (Step 1: silane finishing of the carbon fibers; Step 2: high-temperature thermal treatment in a N{sub 2}/NH{sub 3} environment). As a result, the Si−N belt was exhibited by SEM. The average thickness of the belt were 450–500 nm. The composition of Si−N was the mixture of Si−N, Si−O, and C−Si−N as confirmed by XPS. Thermal residue of the SiNCFs in air was enhanced from 3% to 50%. Thermal conductivity of the composites increased from 0.35 to 0.59 W/mK after Si−N coating on carbon surfaces.

Study of thermal effects in superconducting RF cavities; Etude des effets thermiques dans le cavites supraconductrices

Energy Technology Data Exchange (ETDEWEB)

Bousson, S.; Caruette, A.; Fouaidy, M.; Hammoudi, N.; Junquera, T.; Lesrel, J.; Yaniche, J.F. [Services Techniques, Inst. de Physique Nucleaire, Paris-11 Univ., 91 - Orsay (France)

1999-11-01

A high speed thermometric system equipped with 64 fixed surface thermometers is used to investigate thermal effects in several 3 GHz cavities. An evaluation of the time response of our thermometers is presented. A method based on RF signal analysis is proposed to evaluate the normal zone propagation rate during thermal breakdown. (authors) 2 refs., 3 figs.

Model of thermal fatigue of a copper surface under the action of high-power microwaves

Science.gov (United States)

Kuzikov, S. V.; Plotkin, M. E.

2007-10-01

The accelerating structures of modern supercolliders, as well as the components of high-power microwave electron devices operated in strong cyclic electromagnetic fields should have long lifetimes. Along with the electric breakdown, the surfaces of these microwave components deteriorate and their lifetimes decrease due to thermal strains and subsequent mechanical loads on the surface metal layer. The elementary theory of thermal fatigue was developed in the 1970s. In particular, a model of metal as a continuous medium was considered. Within the framework of this model, thermal fatigue is caused by the strains arising between the hot surface layer and the cold internal layer of the metal. However, this theory does not describe all the currently available experimental data. In particular, the notion of “safe temperature” of the heating, i.e., temperature at which the surface is not destroyed during an arbitrarily long series of pulses, which was proposed in the theoretical model, is in poor agreement with the experiment performed in the Stanford Linear Accelerator Center (SLAC, USA). In this work, the thermal-fatigue theory is developed on the basis of consideration of the copper polycrystalline structure. The necessity to take it into account was demonstrated by the results of the SLAC experiment, in which a change in the mutual orientation of copper grains and the formation of cracks at their boundaries was recorded for the first time. The developed theory makes it possible to use the experimental data to refine the coefficients in the obtained formulas for the lifetime of the metal surface and to predict the number of microwave pulses before its destruction as a function of the radiation power, the surface-temperature increase at the pulse peak, and the pulse duration.

Optimizing phonon scattering by tuning surface-interdiffusion-driven intermixing to break the random-alloy limit of thermal conductivity

Science.gov (United States)

Yang, Xiaolong; Li, Wu

2018-01-01

We investigate the evolution of the cross-plane thermal conductivity κ of superlattices (SLs) as interfaces change from perfectly abrupt to totally intermixed, by using nonequilibrium molecular dynamics simulations in combination with the spectral heat current calculations. We highlight the role of surface-interdiffusion-driven intermixing by calculating the κ of SLs with changing interface roughness, whose tuning allows for κ values much lower than the "alloy limit" and the abrupt interface limit in same cases. The interplay between alloy and interface scattering in different frequency ranges provides a physical basis to predict a minimum of thermal conductivity. More specifically, we also explore how the interface roughness affects the thermal conductivities for SL materials with a broad span of atomic mass and bond strength. In particular, we find that (i) only when the "spacer" thickness of SLs increases up to a critical value, κ of rough SLs can break the corresponding "alloy limit," since SLs with different "spacer" thickness have different characteristic length of phonon transport, which is influenced by surface-interdiffusion-driven intermixing to different extend. (ii) Whether κ changes monotonically with interface roughness strongly depends on the period length and intrinsic behavior of phonon transport for SL materials. Especially, for the SL with large period length, there exists an optimal interface roughness that can minimize the thermal conductivity. (iii) Surface-interdiffusion-driven intermixing is more effective in achieving a low κ below the alloy limit for SL materials with large mass mismatch than with small one. (iv) It is possible for SL materials with large lattice mismatch (i.e., bond strength) to design an ideally abrupt interface structure with κ much below the alloy limit. These results have clear implications for optimization of thermal transport for heat management and for the development of thermoelectric materials.

Relation between the Atmospheric Boundary Layer and Impact Factors under Severe Surface Thermal Conditions

Directory of Open Access Journals (Sweden)

Yinhuan Ao

2017-01-01

Full Text Available This paper reported a comprehensive analysis on the diurnal variation of the Atmospheric Boundary Layer (ABL in summer of Badain Jaran Desert and discussed deeply the effect of surface thermal to ABL, including the Difference in Surface-Air Temperature (DSAT, net radiation, and sensible heat, based on limited GPS radiosonde and surface observation data during two intense observation periods of experiments. The results showed that (1 affected by topography of the Tibetan Plateau, the climate provided favorable external conditions for the development of Convective Boundary Layer (CBL, (2 deep CBL showed a diurnal variation of three- to five-layer structure in clear days and five-layer ABL structure often occurred about sunset or sunrise, (3 the diurnal variation of DSAT influenced thickness of ABL through changes of turbulent heat flux, (4 integral value of sensible heat which rapidly converted by surface net radiation had a significant influence on the growth of CBL throughout daytime. The cumulative effect of thick RML dominated the role after CBL got through SBL in the development stage, especially in late summer, and (5 the development of CBL was promoted and accelerated by the variation of wind field and distribution of warm advection in high and low altitude.

Effects of thermal vapor diffusion on seasonal dynamics of water in the unsaturated zone

Science.gov (United States)

Milly, Paul C.D.

1996-01-01

The response of water in the unsaturated zone to seasonal changes of temperature (T) is determined analytically using the theory of nonisothermal water transport in porous media, and the solutions are tested against field observations of moisture potential and bomb fallout isotopic (36Cl and 3H) concentrations. Seasonally varying land surface temperatures and the resulting subsurface temperature gradients induce thermal vapor diffusion. The annual mean vertical temperature gradient is close to zero; however, the annual mean thermal vapor flux is downward, because the temperature‐dependent vapor diffusion coefficient is larger, on average, during downward diffusion (occurring at high T) than during upward diffusion (low T). The annual mean thermal vapor flux is shown to decay exponentially with depth; the depth (about 1 m) at which it decays to e−1of its surface value is one half of the corresponding decay depth for the amplitude of seasonal temperature changes. This depth‐dependent annual mean flux is effectively a source of water, which must be balanced by a flux divergence associated with other transport processes. In a relatively humid environment the liquid fluxes greatly exceed the thermal vapor fluxes, so such a balance is readily achieved without measurable effect on the dynamics of water in the unsaturated zone. However, if the mean vertical water flux through the unsaturated zone is very small (theoretical prediction is supported by long‐term field measurements in the Chihuahuan Desert. The analysis also makes predictions, confirmed by the field observations, regarding the seasonal variations of matric potential at a given depth. The conceptual model of unsaturated zone water transport developed here implies the possibility of near‐surface trapping of any aqueous constituent introduced at the surface.

Effects of surface finish and mechanical training on Ni-Ti sheets for elastocaloric cooling

Directory of Open Access Journals (Sweden)

Kurt Engelbrecht

2016-06-01

Full Text Available Elastocaloric cooling has emerged as a promising alternative to vapor compression in recent years. Although the technology has the potential to be more efficient than current technologies, there are many technical challenges that must be overcome to realize devices with high performance and acceptable durability. We study the effects of surface finish and training techniques on dog bone shaped polycrystalline samples of NiTi. The fatigue life of several samples with four different surface finishes was measured and it was shown that a smooth surface, especially at the edges, greatly improved fatigue life. The effects of training both on the structure of the materials and the thermal response to an applied strain was studied. The load profile for the first few cycles was shown to change the thermal response to strain, the structure of the material at failure while the final structure of the material was weakly influenced by the surface finish.

Evaluation of Haney-Type Surface Thermal Boundary Conditions Using a Coupled Atmosphere and Ocean Model

National Research Council Canada - National Science Library

Chu, Peter C; Chen, Yuchun; Lu, Shihua

2001-01-01

... (Russell et al,, 1995) was used to verify the validity of Haney-type surface thermal boundary condition, which linearly connects net downward surface heat flux Q to air / sea temperature difference DeltaT by a relaxation coefficient K...

Semiconductor surface diffusion: Nonthermal effects of photon illumination

International Nuclear Information System (INIS)

Ditchfield, R.; Llera-Rodriguez, D.; Seebauer, E. G.

2000-01-01

Nonthermal influences of photon illumination on surface diffusion at high temperatures have been measured experimentally. Activation energies and pre-exponential factors for diffusion of germanium, indium, and antimony on silicon change by up to 0.3 eV and two orders of magnitude, respectively, in response to illumination by photons having energies greater than the substrate band gap. The parameters decrease for n-type material and increase for p-type material. Aided by results from photoreflectance spectroscopy, we suggest that motion of the surface quasi-Fermi-level for minority carriers accounts for much of the effect by changing the charge states of surface vacancies. An additional adatom-vacancy complexation mechanism appears to operate on p-type substrates. The results have significant implications for aspects of microelectronics fabrication by rapid thermal processing that are governed by surface mobility. (c) 2000 The American Physical Society

Surface hopping, transition state theory, and decoherence. II. Thermal rate constants and detailed balance

Energy Technology Data Exchange (ETDEWEB)

Jain, Amber; Subotnik, Joseph E., E-mail: subotnik@sas.upenn.edu [Department of Chemistry, University of Pennsylvania, 231 South 34th Street, Philadelphia, Pennsylvania 19104 (United States)

2015-10-07

We investigate a simple approach to compute a non-adiabatic thermal rate constant using the fewest switches surface hopping (FSSH) dynamics. We study the effects of both decoherence (using our augmented-FSSH (A-FSSH) algorithm) and forbidden hops over a large range of parameters, including high and low friction regimes, and weak and strong electronic coupling regimes. Furthermore, when possible, we benchmark our results against exact hierarchy equations of motion results, where we usually find a maximum error of roughly a factor of two (at reasonably large temperatures). In agreement with Hammes-Schiffer and Tully, we find that a merger of transition state theory and surface hopping can be both accurate and efficient when performed correctly. We further show that detailed balance is followed approximately by A-FSSH dynamics.

Effect of Surrogate Aggregates on the Thermal Conductivity of Concrete at Ambient and Elevated Temperatures

Directory of Open Access Journals (Sweden)

Tae Sup Yun

2014-01-01

Full Text Available The accurate assessment of the thermal conductivity of concretes is an important part of building design in terms of thermal efficiency and thermal performance of materials at various temperatures. We present an experimental assessment of the thermal conductivity of five thermally insulated concrete specimens made using lightweight aggregates and glass bubbles in place of normal aggregates. Four different measurement methods are used to assess the reliability of the thermal data and to evaluate the effects of the various sensor types. The concrete specimens are also assessed at every 100°C during heating to ~800°C. Normal concrete is shown to have a thermal conductivity of ~2.25 W m−1 K−1. The surrogate aggregates effectively reduce the conductivity to ~1.25 W m−1 K−1 at room temperature. The aggregate size is shown not to affect thermal conduction: fine and coarse aggregates each lead to similar results. Surface contact methods of assessment tend to underestimate thermal conductivity, presumably owing to high thermal resistance between the transducers and the specimens. Thermogravimetric analysis shows that the stages of mass loss of the cement paste correspond to the evolution of thermal conductivity upon heating.

Surface Structures and Thermal Desorption Behaviors of Cyclopentanethiol Self-Assembled Monolayers on Au(111)

Energy Technology Data Exchange (ETDEWEB)

Kang, Hun Gu; Kim, You Young; Park, Tae Sun; Noh, Jae Geun [Hanyang University, Seoul (Korea, Republic of); Park, Joon B. [Chonbuk National University, Jeonju (Korea, Republic of); Ito, Eisuke; Hara, Masahiko [RIKEN-HYU Collaboration Center, Saitama (Japan)

2011-04-15

The surface structures, adsorption conditions, and thermal desorption behaviors of cyclopentanethiol (CPT) self-assembled monolayers (SAMs) on Au(111) were investigated by scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), and thermal desorption spectroscopy (TDS). STM imaging revealed that although the adsorption of CPT on Au(111) at room temperature generates disordered SAMs, CPT molecules at 50 .deg. C formed well-ordered SAMs with a (2√3 x √5)R41{sup .}deg. packing structure. XPS measurements showed that CPT SAMs at room temperature were formed via chemical reactions between the sulfur atoms and gold surfaces. TDS measurements showed two dominant TD peaks for the decomposed fragments (C{sub 5}H{sub 9} {sup +}, m/e = 69) generated via C-S bond cleavage and the parent molecular species (C{sub 5}H{sub 9}SH{sup +}, m/e = 102) derived from a recombination of the chemisorbed thiolates and hydrogen atoms near 440 K. Interestingly, dimerization of sulfur atoms in n-alkanethiol SAMs usually occurs during thermal desorption and the same reaction did not happen for CPT SAMs, which may be due to the steric hindrance of cyclic rings of the CPT molecules. In this study, we demonstrated that the alicyclic ring of organic thiols strongly affected the surface structure and thermal desorption behavior of SAMs, thus providing a good method for controlling chemical and physical properties of organic thiol SAMs.

Combating Wear of ASTM A36 Steel by Surface Modification Using Thermally Sprayed Cermet Coatings

Directory of Open Access Journals (Sweden)

Vineet Shibe

2016-01-01

Full Text Available Thermal spray coatings can be applied economically on machine parts to enhance their requisite surface properties like wear, corrosion, erosion resistance, and so forth. Detonation gun (D-Gun thermal spray coatings can be applied on the surface of carbon steels to improve their wear resistance. In the present study, alloy powder cermet coatings WC-12% Co and Cr3C2-25% NiCr have been deposited on ASTM A36 steel with D-Gun thermal spray technique. Sliding wear behavior of uncoated ASTM A36 steel and D-Gun sprayed WC-12% Co and Cr3C2-25% NiCr coatings on base material is observed on a Pin-On-Disc Wear Tester. Sliding wear performance of WC-12% Co coating is found to be better than the Cr3C2-25% NiCr coating. Wear performance of both these cermet coatings is found to be better than uncoated ASTM A36 steel. Thermally sprayed WC-12% Co and Cr3C2-25% NiCr cermet coatings using D-Gun thermal spray technique is found to be very useful in improving the sliding wear resistance of ASTM A36 steel.

Nature and analysis of chemical species: pollution effects on surface waters and groundwater

International Nuclear Information System (INIS)

Young, R.H.F.

1975-01-01

A literature review of 103 items covers: nutrients in surface waters; runoff and waste discharges primarily from energy-intensive activities; groundwater pollution causes, effects, controls and monitoring; land and subsurface wastewater disposal; radionuclides; biological effects; thermal effluents; and biological and mathematical models for rivers

Study of the effect of PH, surface finish and thermal treatment on the corrosion of AlFeNi aluminum alloy

International Nuclear Information System (INIS)

Nabhan, Diana

2013-01-01

The Jules Horowitz Reactor (JHR) is a research reactor under construction at the CEA Cadarache research center, France. It is scheduled to start operating by 2020. The fuel elements of this reactor core consist of eight concentric rows of cylindrical plates, each row being composed of three thin aluminum coated plates. Cooling water circulates between these plates through very thin gaps smaller than 2 mm. The aluminum alloy used to coat the fuel plates is an alloy called AlFeNi, which contains 1% wt. Fe, 1% wt. Ni and 1% wt. Mg. In the reactor environment, this alloy may undergo corrosion. The oxide layer formed on the AlFeNi alloy is composed of two different types of oxides: an inner oxide layer formed by a diffusion mechanism and an outer oxide layer formed by re-precipitation. As a consequence, formation of an oxide scale on the aluminum coating could reduce the gap between the cladding plates, thus allowing less water to circulate. This could in turn lead to local heating of the fuel cladding. In addition, the metal consumption and the softening of the metal at high temperatures can lead to a decrease of the mechanical strength of the cladding. In order to qualify the fuel elements of the JHR, several specimens of AlFeNi, representative of the future cladding, were corroded at 250 .deg. C for different durations (9 to 34 days) in distilled water of different pH: 4.9; 5.2 and 5.6. These pH values have been chosen to simulate the ones currently predicted for the JHR. The effect of surface finish (polished and not polished) and thermal treatment (annealed and not annealed) on the oxide growth rate was also investigated. For long tests over 30 days, the pH 5,6 appears to be more favorable than the pH 5,2 and 4,9 to limit the oxide thickness, but this pH effect is reduced on unpolished samples. In one hand, the effect of surface finish on the corrosion behavior as measured by optical microscopy appears to be strong. On the other hand, the effect of thermal

Study of the effect of PH, surface finish and thermal treatment on the corrosion of AlFeNi aluminum alloy

Energy Technology Data Exchange (ETDEWEB)

Nabhan, Diana [Comissariat a l' Energie Atomique, Paris (France)

2013-07-01

The Jules Horowitz Reactor (JHR) is a research reactor under construction at the CEA Cadarache research center, France. It is scheduled to start operating by 2020. The fuel elements of this reactor core consist of eight concentric rows of cylindrical plates, each row being composed of three thin aluminum coated plates. Cooling water circulates between these plates through very thin gaps smaller than 2 mm. The aluminum alloy used to coat the fuel plates is an alloy called AlFeNi, which contains 1% wt. Fe, 1% wt. Ni and 1% wt. Mg. In the reactor environment, this alloy may undergo corrosion. The oxide layer formed on the AlFeNi alloy is composed of two different types of oxides: an inner oxide layer formed by a diffusion mechanism and an outer oxide layer formed by re-precipitation. As a consequence, formation of an oxide scale on the aluminum coating could reduce the gap between the cladding plates, thus allowing less water to circulate. This could in turn lead to local heating of the fuel cladding. In addition, the metal consumption and the softening of the metal at high temperatures can lead to a decrease of the mechanical strength of the cladding. In order to qualify the fuel elements of the JHR, several specimens of AlFeNi, representative of the future cladding, were corroded at 250 .deg. C for different durations (9 to 34 days) in distilled water of different pH: 4.9; 5.2 and 5.6. These pH values have been chosen to simulate the ones currently predicted for the JHR. The effect of surface finish (polished and not polished) and thermal treatment (annealed and not annealed) on the oxide growth rate was also investigated. For long tests over 30 days, the pH 5,6 appears to be more favorable than the pH 5,2 and 4,9 to limit the oxide thickness, but this pH effect is reduced on unpolished samples. In one hand, the effect of surface finish on the corrosion behavior as measured by optical microscopy appears to be strong. On the other hand, the effect of thermal

Special problems: LBB, thermal effects

International Nuclear Information System (INIS)

Lin Chiwen

2001-01-01

This section presents the discussion of special problems in the reactor coolant system design, including LBB and thermal effects. First, the categories of fracture mechanics technology applicable to LBB is discussed. Two categories of fracture mechanics, namely: linear-elastic fracture mechanics (LEFM) and elastic-plastic fracture mechanics (EPFM) are discussed specifically. Next, basic concepts of LEFM are discussed. This will be followed by a discussion of EPFM, with more specific discussion of the methodology currently acceptable to NRC, with the emphasis on the J-integral approach. This is followed by a discussion of the NRC position and recommendations and basic requirements laid out by NRC. A specific example of LBB application to WPWR piping is used to identify the key steps to be followed, in order to satisfy the recommendations and requirements of NRC. An application of LBB to the WPWR reactor coolant loop piping is provided as further illustration of the methodology. This section focuses on the thermal effects which have not been addressed earlier, and the thermal effects which have caused particular concerns on potential reactor degradations, such as pressurized thermal shocks. The organization of this section is divided into the following subsections: linear-elastic fracture mechanics (LEFM); elastic-plastic fracture mechanics (EPFM); J concepts; NRC recommendations and requirements on the application of LBB; two specific applications of LBB to WPWR piping; PWR internals degradation; thermal fatigue considerations; a case study of pressurized thermal shock

Effects of thermal plasma on self-absorbed synchrotron sources in active galactic nuclei

International Nuclear Information System (INIS)

De Kool, M.; Begelman, M.C.

1989-01-01

The observable effects of a thermal background plasma in a self-absorbed synchrotron source are reviewed, in the context of a model for the central engine of an active galactic nucleus (AGN). Considering the effects of free-free absorption and emission, Thomson and Compton scattering, and spatial stratification, it is found that the observations set an upper limit on the thermal electron scattering optical depth in the central synchrotron-emitting region of an AGN. The upper limit, tau(max) about 1, results mainly from the apparent absence of induced Compton scattering and inverse thermal Comptonization effects. The low value of tau(max) poses some problems for nonthermal models of the AGN continuum that can be partly resolved by assuming a thin disk or layer-like geometry for the source, with (h/R) less than about 0.01. A likely site for the synchrotron-producing region seems to be the surface of an accretion disk or torus. 20 refs

Transient thermal driven bubble's surface and its potential ultrasound-induced damage

Science.gov (United States)

Movahed, Pooya; Freund, Jonathan B.

2017-11-01

Ultrasound-induced bubble activity in soft tissues is well-known to be a potential injury mechanism in therapeutic ultrasound treatments. We consider damage by transient thermal effects, including a hypothetical mechanism based on transient thermal phenomena, including viscous dissipation. A spherically symmetric compressible Navier-Stokes discretization is developed to solve the full governing equations, both inside and outside of the bubble, without the usual simplifications in the Rayleigh-Plesset bubble dynamics approach. Equations are solved in the Lagrangian framework, which provides a sharp and accurate representation of the interface as well as the viscous dissipation and thermal transport effects, which preclude reduction to the usual Rayleigh-Plesset ordinary differential equation. This method is used to study transient thermal effects at different frequencies and pressure amplitudes relevant to therapeutic ultrasound treatments. High temperatures achieved in the surrounding medium during the violent bubble collapse phase due to the viscous dissipation in the surrounding medium and thermal conduction from the bubble are expected to cause damage. This work was supported by NIH NIDDK Grant P01-DK043881.

Thermal etching of silver: Influence of rolling defects

Energy Technology Data Exchange (ETDEWEB)

Ollivier, M., E-mail: o.maelig@imperial.ac.uk [Department of Materials, Imperial College London, SW7 2AZ (United Kingdom); Harker, R.M. [AWE Aldermaston, Aldermaston, Reading RG7 4PR (United Kingdom); Chater, R.J.; Gourlay, C.M. [Department of Materials, Imperial College London, SW7 2AZ (United Kingdom)

2016-08-15

Silver is well known to be thermally etched in an oxygen-rich atmosphere and has been extensively studied in the laboratory to understand thermal etching and to limit its effect when this material is used as a catalyst. Yet, in many industrial applications the surface of rolled silver sheets is used without particular surface preparation. Here, it is shown by combining FIB-tomography, FIB-SIMS and analytical SEM that the kinetics of thermal etch pitting are significantly faster on rolled Ag surfaces than on polished surfaces. This occurs due to range of interacting phenomena including (i) the reaction of subsurface carbon-contamination with dissolved oxygen to form pores that grow to intersect the surface, (ii) surface reconstruction around corrosion pits and surface scratches, and (iii) sublimation at low pressure and high temperature. A method to identify subsurface pores is developed to show that the pores have (111) and (100) internal facets and may be filled with a gas coming from the chemical reaction of oxygen and carbon contamination. - Highlights: Thermal etching of industrial silver sheets vs. polished silver sheets Effect of annealing atmosphere on the thermal etching of silver: surface and subsurface characterization Link between etch pitting and defects induced by rolling. FIB-tomography coupled with EBSD for determining crystal planes of the facets of subsurface pores. FIB-SIMS characterization to probe the gas confined inside subsurface pores.

Aging effects on vertical graphene nanosheets and their thermal stability

Science.gov (United States)

Ghosh, S.; Polaki, S. R.; Ajikumar, P. K.; Krishna, N. G.; Kamruddin, M.

2018-03-01

The present study investigates environmental aging effects and thermal stability of vertical graphene nanosheets (VGN). Self-organized VGN is synthesized by plasma enhanced chemical vapor deposition and exposed to ambient conditions over 6-month period to examine its aging behavior. A systematic inspection is carried out on morphology, chemical structure, wettability and electrical property by scanning electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, water contact angle and four-probe resistivity measurements at regular intervals, respectively. Detailed microscopic and spectroscopic analysis substantiated the retention of graphitic quality and surface chemistry of VGN over the test period. An unchanged sheet resistance and hydrophobicity reveals its electrical and wetting stability over the time, respectively. Thermogravimetric analysis ensures an excellent thermal stability of VGN up to 575 °C in ambient atmosphere. These findings of long-term morphological, structural, wetting, electrical and thermal stability of VGN validate their potential utilization for the next-generation device applications.

Shukla-Spatschek diffusion effects on surface plasma waves in astrophysical turbulent plasmas

Science.gov (United States)

Lee, Myoung-Jae; Jung, Young-Dae

2017-02-01

The effects of Shukla-Spatschek turbulent diffusion on a temporal mode of surface waves propagating at the interface of an astrophysical turbulent plasma are investigated. The damping rates for high and low modes of surface wave are kinetically derived by employing the Vlasov-Poisson equation and the specular reflection boundary condition. We found that the diffusion caused by the fluctuating electric fields leads to damping for both high and low modes of surface waves. The high-mode damping is enhanced with an increase of the wavenumber and the diffusion coefficient, but suppressed by an increase of electron thermal energy. By contrast, the low-mode damping is suppressed as the wavenumber and the thermal energy increase although it is enhanced as the diffusion increases. The variation of the damping rate due to the Shukla-Spatschek turbulent diffusion is also discussed.

Effect of surface properties of NiFe2O4 nanoparticles synthesized by dc thermal plasma route on antimicrobial activity

Science.gov (United States)

Bhosale, S. V.; Ekambe, P. S.; Bhoraskar, S. V.; Mathe, V. L.

2018-05-01

The present work reports the role of surface properties of NiFe2O4 nanoparticles on the antimicrobial activity. The NiFe2O4 nanoparticles were synthesized by gas phase condensation and chemical co-precipitation route. These nanoparticles were extensively investigated using X-ray diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and electro-kinetic property measurements. The HRTEM was used to analyze surface morphology of nickel ferrite nanoparticles obtained by two different routes. Electro-kinetic properties of the nanoparticles under investigation were recorded, analyzed and correlated with the antimicrobial properties. It was observed that nickel ferrite nanoparticles synthesized by thermal plasma route (NFOTP) formed highly stable colloidal solution as compared to chemically synthesized (NFOCP), as the later tends to agglomerate due to low surface charge. The antimicrobial activity of NiFe2O4 nanoparticles were investigated on two Gram positive bacteria Staphylococcus aureus and Streptococcus pyogenes, two Gram negative bacteria Escherichia coli and Salmonella typhimurium and one fungal species Candida albicans. It was noted that the surface properties of NiFe2O4 particles have revealing effect on the antimicrobial activity. The NFOTP nanoparticles showed significant activity for gram negative E. coli bacteria however no activity was observed for other bacteria's and fungi under study. Moreover NFOCP particles did not show any significant activity for both bacteria's and fungi. Further, antimicrobial activity of nickel ferrite nanoparticles were studied even for different concentration to obtain the minimum inhibition concentration (MIC).

Thermal shock resistance behavior of a functionally graded ceramic: Effects of finite cooling rate

Directory of Open Access Journals (Sweden)

Zhihe Jin

2014-01-01

Full Text Available This work presents a semi-analytical model to explore the effects of cooling rate on the thermal shock resistance behavior of a functionally graded ceramic (FGC plate with a periodic array of edge cracks. The FGC is assumed to be a thermally heterogeneous material with constant elastic modulus and Poisson's ratio. The cooling rate applied at the FGC surface is modeled using a linear ramp function. An integral equation method and a closed form asymptotic temperature solution are employed to compute the thermal stress intensity factor (TSIF. The thermal shock residual strength and critical thermal shock of the FGC plate are obtained using the SIF criterion. Thermal shock simulations for an Al2O3/Si3N4 FGC indicate that a finite cooling rate leads to a significantly higher critical thermal shock than that under the sudden cooling condition. The residual strength, however, is relatively insensitive to the cooling rate.

Experimental investigation of thermal emittance components of copper photocathode

Directory of Open Access Journals (Sweden)

H. J. Qian

2012-04-01

Full Text Available With progress of photoinjector technology, thermal emittance has become the primary limitation of electron beam brightness. Extensive efforts have been devoted to study thermal emittance, but experiment results differ between research groups and few can be well interpreted. Besides the ambiguity of photoemission mechanism, variations of cathode surface conditions during cathode preparation, such as work function, field enhancement factor, and surface roughness, will cause thermal emittance differences. In this paper, we report an experimental study of electric field dependence of copper cathode quantum efficiency (QE and thermal emittance in a radio frequency (rf gun, through which in situ cathode surface parameters and thermal emittance contributions from photon energy, Schottky effect, and surface roughness are extracted. It is found the QE of a copper cathode illuminated by a 266 nm UV laser increased substantially to 1.5×10^{-4} after cathode cleaning during rf conditioning, and a copper work function of 4.16 eV, which is much lower than nominal value (4.65 eV, was measured. Experimental results also show a thermal emittance growth as much as 0.92  mm mrad/mm at 50  MV/m due to the cathode surface roughness effect, which is consistent with cathode surface morphology measurements.

Thermal Diffusion Processes in Metal-Tip-Surface Interactions: Contact Formation and Adatom Mobility

DEFF Research Database (Denmark)

Sørensen, Mads Reinholdt; Jacobsen, Karsten Wedel; Jonsson, Hannes

1996-01-01

and the surface can occur by a sequence of atomic hop and exchange processes which become active on a millisecond time scale when the tip is about 3-5 Angstrom from the surface. Adatoms on the surface are stabilized by the presence of the tip and energy barriers for diffusion processes in the region under the tip......We have carried out computer simulations to identify and characterize various thermally activated atomic scale processes that can play an important role in room temperature experiments where a metal tip is brought close to a metal surface. We find that contact formation between the tip...

Modeling the Effect of Grain Size Mixing on Thermal Inertia Values Derived from Diurnal and Seasonal THEMIS Measurements

Science.gov (United States)

McCarty, C.; Moersch, J.

2017-12-01

Sedimentary processes have slowed over Mars' geologic history. Analysis of the surface today can provide insight into the processes that may have affected it over its history. Sub-resolved checkerboard mixtures of materials with different thermal inertias (and therefore different grain sizes) can lead to differences in thermal inertia values inferred from night and day radiance observations. Information about the grain size distribution of a surface can help determine the degree of sorting it has experienced or it's geologic maturity. Standard methods for deriving thermal inertia from measurements made with THEMIS can give values for the same location that vary by as much as 20% between scenes. Such methods make the assumption that each THEMIS pixel contains material that has uniform thermophysical properties. Here we propose that if a mixture of small and large particles is present within a pixel, the inferred thermal inertia will be strongly dominated by whichever particle is warmer at the time of the measurement because the power radiated by a surface is proportional (by the Stefan-Boltzmann law) to the fourth power of its temperature. This effect will result in a change in thermal inertia values inferred from measurements taken at different times of day and night. Therefore, we expect to see correlation between the magnitude of diurnal variations in inferred thermal inertia values and the degree of grain size mixing for a given pixel location. Preliminary work has shown that the magnitude of such diurnal variation in inferred thermal inertias is sufficient to detect geologically useful differences in grain size distributions. We hypothesize that at least some of the 20% variability in thermal inertias inferred from multiple scenes for a given location could be attributed to sub-pixel grain size mixing rather than uncertainty inherent to the experiment, as previously thought. Mapping the difference in inferred thermal inertias from day and night THEMIS

Research on Land Surface Thermal-Hydrologic Exchange in Southern China under Future Climate and Land Cover Scenarios

Directory of Open Access Journals (Sweden)

Jianwu Yan

2013-01-01

Full Text Available Climate change inevitably leads to changes in hydrothermal circulation. However, thermal-hydrologic exchanging caused by land cover change has also undergone ineligible changes. Therefore, studying the comprehensive effects of climate and land cover changes on land surface water and heat exchanges enables us to well understand the formation mechanism of regional climate and predict climate change with fewer uncertainties. This study investigated the land surface thermal-hydrologic exchange across southern China for the next 40 years using a land surface model (ecosystem-atmosphere simulation scheme (EASS. Our findings are summarized as follows. (i Spatiotemporal variation patterns of sensible heat flux (H and evapotranspiration (ET under the land cover scenarios (A2a or B2a and climate change scenario (A1B are unanimous. (ii Both H and ET take on a single peak pattern, and the peak occurs in June or July. (iii Based on the regional interannual variability analysis, H displays a downward trend (10% and ET presents an increasing trend (15%. (iv The annual average H and ET would, respectively, increase and decrease by about 10% when woodland converts to the cultivated land. Through this study, we recognize that land surface water and heat exchanges are affected greatly by the future climate change as well as land cover change.

Improvement of Polytetrafluoroethylene Surface Energy by Repetitive Pulse Non-Thermal Plasma Treatment in Atmospheric Air

International Nuclear Information System (INIS)

Yang Guoqing; Zhang Guanjun; Zhang Wenyuan

2011-01-01

Improvement of polytetrafluoroethylene surface energy by non-thermal plasma treatment is presented, using a nanosecond-positive-edge repetitive pulsed dielectric barrier discharge generator in atmospheric air. The electrical parameters including discharging power, peak and density of micro-discharge current were calculated, and the electron energy was estimated. Surface treatment experiments of polytetrafluoroethylene films were conducted for both different applied voltages and different treating durations. Results show that the surface energy of polytetrafluoroethylene film could be improved to 40 mJ/m 2 or more by plasma treatment. Surface roughness measurement and surface X-ray photoelectron spectroscopy analysis indicate that there are chemical etching and implantation of polar oxygen groups in the sample surface treating process, resulting in the improvement of the sample surface energy. Compared with an AC source of 50 Hz, the dielectric barrier discharges generated by a repetitive pulsed source could provide higher peak power, lower mean power, larger micro-discharge current density and higher electron energy. Therefore, with the same applied peak voltage and treating duration, the improvement of polytetrafluoroethylene surface energy using repetitive pulsed plasma is more effective, and the plasma treatment process based on repetitive pulsed dielectric barrier discharges in air is thus feasible and applicable.

Study of thermal, radiation and environmental effects on serpentine

International Nuclear Information System (INIS)

Raje, Naina; Kalekar, Bhupesh B.; Dubey, K.A.

2016-01-01

Physical and chemical properties of a material, such as particle size surface area, magnetic properties, water content, radiation and thermal stability, viscosity, porosity, are responsible for their specific applications. Serpentine is a greenish, layer structured phyllosilicate, known as magnesium hydroxy silicate. The availability of large number of hydroxyl group makes serpentine a potential candidate for nuclear shielding material. Hence present studies have been carried out to understand the stability of serpentine with the variation in thermal, radiation and environmental parameters. Serpentine samples were received from Reactor Projects Division, BARC. An accurately weighed sample was subjected to simultaneous TG - DTA - EGA measurements in air as well as inert atmosphere at the heating rate of 10 °C/min. The sample was heated from room temperature to 1000 °C with a gas flow rate of 100 mL/min in Netzsch thermal analyzer (Model STA409 PC LUXX) connected to Bruker FTIR system (Model - Tensor27) via a 1m long capillary. The sample was subjected to gamma radiation in the range of 10 - 100 kGy using 60 Co gamma source in gamma chamber and was subjected to TG measurements to understand the effect of radiation on the thermal stability of serpentine and the results are being discussed here

Viscous Dissipation Effects on the Motion of Casson Fluid over an Upper Horizontal Thermally Stratified Melting Surface of a Paraboloid of Revolution: Boundary Layer Analysis

Directory of Open Access Journals (Sweden)

T. M. Ajayi

2017-01-01

Full Text Available The problem of a non-Newtonian fluid flow past an upper surface of an object that is neither a perfect horizontal/vertical nor inclined/cone in which dissipation of energy is associated with temperature-dependent plastic dynamic viscosity is considered. An attempt has been made to focus on the case of two-dimensional Casson fluid flow over a horizontal melting surface embedded in a thermally stratified medium. Since the viscosity of the non-Newtonian fluid tends to take energy from the motion (kinetic energy and transform it into internal energy, the viscous dissipation term is accommodated in the energy equation. Due to the existence of internal space-dependent heat source; plastic dynamic viscosity and thermal conductivity of the non-Newtonian fluid are assumed to vary linearly with temperature. Based on the boundary layer assumptions, suitable similarity variables are applied to nondimensionalized, parameterized and reduce the governing partial differential equations into a coupled ordinary differential equations. These equations along with the boundary conditions are solved numerically using the shooting method together with the Runge-Kutta technique. The effects of pertinent parameters are established. A significant increases in Rex1/2Cfx is guaranteed with St when magnitude of β is large. Rex1/2Cfx decreases with Ec and m.

Estimating envelope thermal characteristics from single point in time thermal images

Science.gov (United States)

Alshatshati, Salahaldin Faraj

Energy efficiency programs implemented nationally in the U.S. by utilities have rendered savings which have cost on average 0.03/kWh. This cost is still well below generation costs. However, as the lowest cost energy efficiency measures are adopted, this the cost effectiveness of further investment declines. Thus there is a need to more effectively find the most opportunities for savings regionally and nationally, so that the greatest cost effectiveness in implementing energy efficiency can be achieved. Integral to this process. are at scale energy audits. However, on-site building energy audits process are expensive, in the range of US1.29/m2-$5.37/m2 and there are an insufficient number of professionals to perform the audits. Energy audits that can be conducted at-scale and at low cost are needed. Research is presented that addresses at community-wide scales characterization of building envelope thermal characteristics via drive-by and fly-over GPS linked thermal imaging. A central question drives this research: Can single point-in-time thermal images be used to infer U-values and thermal capacitances of walls and roofs? Previous efforts to use thermal images to estimate U-values have been limited to rare steady exterior weather conditions. The approaches posed here are based upon the development two models first is a dynamic model of a building envelope component with unknown U-value and thermal capacitance. The weather conditions prior to the thermal image are used as inputs to the model. The model is solved to determine the exterior surface temperature, ultimately predicted the temperature at the thermal measurement time. The model U-value and thermal capacitance are tuned in order to force the error between the predicted surface temperature and the measured surface temperature from thermal imaging to be near zero. This model is developed simply to show that such a model cannot be relied upon to accurately estimate the U-value. The second is a data

Site-specific Pt deposition and etching on electrically and thermally isolated SiO2 micro-disk surfaces

International Nuclear Information System (INIS)

Saraf, Laxmikant V

2010-01-01

Electrically and thermally isolated surfaces are crucial for improving the detection sensitivity of microelectronic sensors. The site-specific in situ growth of Pt nano-rods on thermally and electrically isolated SiO 2 micro-disks using wet chemical etching and a focused ion/electron dual beam (FIB-SEM) is demonstrated. Fabrication of an array of micro-cavities on top of a micro-disk is also demonstrated. The FIB source is utilized to fabricate through-holes in the micro-disks. Due to the amorphous nature of SiO 2 micro-disks, the Ga implantation possibly modifies through-hole sidewall surface chemistry rather than affecting its transport properties. Some sensor design concepts based on micro-fabrication of SiO 2 micro-disks utilizing thermally and electrically isolated surfaces are discussed from the viewpoint of applications in photonics and bio-sensing.

Thermal interface pastes nanostructured for high performance

Science.gov (United States)

Lin, Chuangang

Thermal interface materials in the form of pastes are needed to improve thermal contacts, such as that between a microprocessor and a heat sink of a computer. High-performance and low-cost thermal pastes have been developed in this dissertation by using polyol esters as the vehicle and various nanoscale solid components. The proportion of a solid component needs to be optimized, as an excessive amount degrades the performance, due to the increase in the bond line thickness. The optimum solid volume fraction tends to be lower when the mating surfaces are smoother, and higher when the thermal conductivity is higher. Both a low bond line thickness and a high thermal conductivity help the performance. When the surfaces are smooth, a low bond line thickness can be even more important than a high thermal conductivity, as shown by the outstanding performance of the nanoclay paste of low thermal conductivity in the smooth case (0.009 mum), with the bond line thickness less than 1 mum, as enabled by low storage modulus G', low loss modulus G" and high tan delta. However, for rough surfaces, the thermal conductivity is important. The rheology affects the bond line thickness, but it does not correlate well with the performance. This study found that the structure of carbon black is an important parameter that governs the effectiveness of a carbon black for use in a thermal paste. By using a carbon black with a lower structure (i.e., a lower DBP value), a thermal paste that is more effective than the previously reported carbon black paste was obtained. Graphite nanoplatelet (GNP) was found to be comparable in effectiveness to carbon black (CB) pastes for rough surfaces, but it is less effective for smooth surfaces. At the same filler volume fraction, GNP gives higher thermal conductivity than carbon black paste. At the same pressure, GNP gives higher bond line thickness than CB (Tokai or Cabot). The effectiveness of GNP is limited, due to the high bond line thickness. A

Non linear thermal radiation effect on Williamson fluid with particle-liquid suspension past a stretching surface

Directory of Open Access Journals (Sweden)

K. Ganesh Kumar

Full Text Available A mathematical analysis of two-phase boundary layer flow and heat transfer of a Williamson fluid with fluid particle suspension over a stretching sheet has been carried out in this paper. The region of temperature jump and nonlinear thermal radiation is considered in the energy transfer process. The principal equations of boundary layer flow and temperature transmission are reformed to a set of non-linear ordinary differential equations under suitable similarity transformations. The transfigured equalities are solved numerically with the help of RKF-45 order method. The effect of influencing parameters on velocity and temperature transfer of fluid is examined and deliberated by plotted graphs and tabulated values. Significances of the mass concentration of dust particle parameter play a key role in controlling flow and thermal behavior of non-Newtonian fluids. Further, the temperature and concern boundary layer girth are declines for increasing values of Williamson parameter. Keywords: Two-phase flow, Williamson fluid, Nonlinear thermal radiation, Magnetic field, Temperature jump

A new approach to characterize the effect of fabric deformation on thermal protective performance

International Nuclear Information System (INIS)

Li, Jun; Li, Xiaohui; Lu, Yehu; Wang, Yunyi

2012-01-01

It is very important to evaluate thermal protective performance (TPP) in laboratory-simulated fire scenes as accurately as possible. For this paper, to thoroughly understand the effect of fabric deformation on basic physical properties and TPP of flame-retardant fabrics exposed to flash fire, a new modified TPP testing apparatus was developed. Different extensions were employed to simulate the various extensions displayed during different body motions. The tests were also carried out with different air gaps. The results showed a significant decrease in air permeability after deformation. However, the change of thickness was slight. The fabric deformation had a complicated effect on thermal protection with different air gaps. The change of TPP depended on the balance between the surface contact area and the thermal insulation. The newly developed testing apparatus could be well employed to evaluate the effect of deformation on TPP of flame-resistant fabrics. (paper)

A new approach to characterize the effect of fabric deformation on thermal protective performance

Science.gov (United States)

Li, Jun; Li, Xiaohui; Lu, Yehu; Wang, Yunyi

2012-04-01

It is very important to evaluate thermal protective performance (TPP) in laboratory-simulated fire scenes as accurately as possible. For this paper, to thoroughly understand the effect of fabric deformation on basic physical properties and TPP of flame-retardant fabrics exposed to flash fire, a new modified TPP testing apparatus was developed. Different extensions were employed to simulate the various extensions displayed during different body motions. The tests were also carried out with different air gaps. The results showed a significant decrease in air permeability after deformation. However, the change of thickness was slight. The fabric deformation had a complicated effect on thermal protection with different air gaps. The change of TPP depended on the balance between the surface contact area and the thermal insulation. The newly developed testing apparatus could be well employed to evaluate the effect of deformation on TPP of flame-resistant fabrics.

Effect of ZDDP concentration on the thermal film formation on steel, hydrogenated non-doped and Si-doped DLC

Energy Technology Data Exchange (ETDEWEB)

Akbari, S. [Laboratory for Tribology and Interface Nanotechnology, University of Ljubljana, Ljubljana (Slovenia); Kovač, J. [Jozef Stefan Institute, Jamova 19, 1000 Ljubljana (Slovenia); Kalin, M., E-mail: mitjan.kalin@tint.fs.uni-lj.si [Laboratory for Tribology and Interface Nanotechnology, University of Ljubljana, Ljubljana (Slovenia)

2016-10-15

Highlights: • The effect of the ZDDP concentrations onto the steel, H-DLC and Si-DLC surfaces is investigated. • ZDDP film structure on the DLC coatings is different from steel. • Different concentrations of ZDDP do not affect the final chemical structure of the ZDDP film on any of the studied surfaces. • The thickness of the thermal film is linear with the concentration for a given surface. • The reactivity of the ZDDP film is higher on the steel surface than on the DLC coatings. - Abstract: This work focuses on the ZDDP concentration (1, 5 and 20 wt%) to form a ZDDP film on surfaces during static thermal tests at 150 °C. Silicon-doped and hydrogenated DLC coatings, as well as steel as reference, were studied using Attenuated Total Reflection-Fourier Transform Infrared (ATR-FTIR) spectroscopy and X-ray Photoelectron Spectroscopy (XPS). The results show that, on the three surfaces, the structure of the ZDDP thermal film consists of identical groups of pyrophosphate and zinc oxide, while the sulphuric groups are dissimilar. On the steel surface, the sulphuric part consists of a mixture of organic sulphide and sulphohydryl groups, but on H-DLC and Si-DLC only organic sulphide groups are found; there are no sulphohydryl groups. Moreover, both ATR-FTIR and XPS show that different concentrations of ZDDP do not affect the final chemical structure of the ZDDP thermal film on any of the studied surfaces. In addition, the XPS results show that the thickness of the thermal film is linear with the concentration for the whole range from 1 to 20 wt%, supporting also its uniform chemical structure. These thicknesses further show that the reactivity of the ZDDP film is higher on the steel surface than on the DLC coatings.

Cheap effective thermal solar-energy collectors

Energy Technology Data Exchange (ETDEWEB)

Highgate, D.J.; Probert, S.D. [Cranfield University, Bedford (United Kingdom). Dept. of Applied Energy

1996-04-01

A light-weight flexible solar-collector, with a wavelength-selective absorption surface and an insolation-transparent thermal-insulation protecter for its aperture, was built and tested. Its cheapness and high performance, relative to a conventional flat-plate solar-collector, provide a prima-facie case for the more widespread adoption of its design. (author)

Hydrological response and thermal effect of karst springs linked to aquifer geometry and recharge processes

Science.gov (United States)

Luo, Mingming; Chen, Zhihua; Zhou, Hong; Zhang, Liang; Han, Zhaofeng

2018-03-01

To be better understand the hydrological and thermal behavior of karst systems in South China, seasonal variations in flow, hydrochemistry and stable isotope ratios of five karst springs were used to delineate flow paths and recharge processes, and to interpret their thermal response. Isotopic data suggest that mean recharge elevations are 200-820 m above spring outlets. Springs that originate from high elevations have lower NO3 - concentrations than those originating from lower areas that have more agricultural activity. Measured Sr2+ concentrations reflect the strontium contents of the host carbonate aquifer and help delineate the spring catchment's saturated zone. Seasonal variations of NO3 - and Sr2+ concentrations are inversely correlated, because the former correlates with event water and the latter with baseflow. The mean annual water temperatures of springs were only slightly lower than the local mean annual surface temperature at the outlet elevations. These mean spring temperatures suggest a vertical gradient of 6 °C/vertical km, which resembles the adiabatic lapse rate of the Earth's stable atmosphere. Seasonal temperature variations in the springs are in phase with surface air temperatures, except for Heilongquan (HLQ) spring. Event-scale variations of thermal response are dramatically controlled by the circulation depth of karst systems, which determines the effectiveness of heat exchange. HLQ spring undergoes the deepest circulation depth of 820 m, and its thermal responses are determined by the thermally effective regulation processes at higher elevations and the mixing processes associated with thermally ineffective responses at lower elevations.

Aluminum nitride coatings using response surface methodology to optimize the thermal dissipated performance of light-emitting diode modules

Science.gov (United States)

Jean, Ming-Der; Lei, Peng-Da; Kong, Ling-Hua; Liu, Cheng-Wu

2018-05-01

This study optimizes the thermal dissipation ability of aluminum nitride (AlN) ceramics to increase the thermal performance of light-emitting diode (LED) modulus. AlN powders are deposited on heat sink as a heat interface material, using an electrostatic spraying process. The junction temperature of the heat sink is developed by response surface methodology based on Taguchi methods. In addition, the structure and properties of the AlN coating are examined using X-ray photoelectron spectroscopy (XPS). In the XPS analysis, the AlN sub-peaks are observed at 72.79 eV for Al2p and 398.88 eV for N1s, and an N1s sub-peak is assigned to N-O at 398.60eV and Al-N bonding at 395.95eV, which allows good thermal properties. The results have shown that the use of AlN ceramic material on a heat sink can enhance the thermal performance of LED modules. In addition, the percentage error between the predicted and experimental results compared the quadric model with between the linear and he interaction models was found to be within 7.89%, indicating that it was a good predictor. Accordingly, RSM can effectively enhance the thermal performance of an LED, and the beneficial heat dissipation effects for AlN are improved by electrostatic spraying.

Corrosion and biofouling on the non-heat-exchanger surfaces of an ocean thermal energy conversion power plant: a survey

Energy Technology Data Exchange (ETDEWEB)

Castelli, V.J. (ed.)

1979-05-01

Of the many foreseeable problems confronting economical ocean thermal energy conversion operation, two major items are the deterioration of the structural and functional components, which prevents efficient operation, and the biofouling of the surfaces, which adds excess weight to the floating ocean platform. The techniques required for effective long-term control of deterioration and corrosion have been investigated actively for many years, and successful solutions for most situations have been developed. For the most part, these solutions can be directly transferred to the ocean thermal energy conversion plant. The majority of problems in these areas are expected to be associated with scale-up and will require some advanced development due to the immensity of the ocean thermal energy conversion platform. Current antifouling control systems are not effective for long-term fouling prevention. Commercially available antifouling coatings are limited to a 3-year service life in temperate waters, and even shorter in tropical waters. However, underwater cleaning techniques and some fouling-control systems presently being used by conventional power plants may find utility on an ocean thermal energy conversion plant. In addition, some recent major advances in long-term antifouling coatings sponsored by the Navy may be applicable to ocean thermal energy conversion. 132 references.

Evaluation of mechanism of non-thermal plasma effect on the surface of polypropylene films for enhancement of adhesive and hemo compatible properties

Energy Technology Data Exchange (ETDEWEB)

Navaneetha Pandiyaraj, K., E-mail: dr.knpr@gmail.com [Surface Engineering Laboratory, Department of Physics, Sri Shakthi Institute of Engineering and Technology, L& T by pass, Chinniyam Palayam (post), Coimbatore-641062 (India); Deshmukh, R.R. [Department of Physics, Institute of Chemical Technology, Matunga, Mumbai-400 019 (India); Arunkumar, A.; Ramkumar, M.C. [Surface Engineering Laboratory, Department of Physics, Sri Shakthi Institute of Engineering and Technology, L& T by pass, Chinniyam Palayam (post), Coimbatore-641062 (India); Ruzybayev, I.; Ismat Shah, S. [Department of Physics and Astronomy, Department of Materials Science and Engineering, University of Delaware, 208 Dupont Hall, Newark (United States); Su, Pi-Guey [Department of Chemistry, Chinese Culture University, Taipei 111, Taiwan (China); Periayah, Mercy Halleluyah; Halim, A.S. [School of Medical Sciences, Health Campus, Universiti Sains Malaysia, 16150 Kubang Kerian, Kelantan (Malaysia)

2015-08-30

Highlights: • Investigated the mechanism of effect of various gaseous plasma treatments on the surface properties of Polypropylene (PP) films. • The improvement in surface energy is basically due to the incorporation of polar functional groups onto the PP films. • The extent of surface modification and hydrophobic recovery depends upon the type of plasma forming gas. • Due to the significant morphological and chemical changes induced by the gaseous plasma treatment, improved the blood compatibility as well as adhesive strength of the PP films. - Abstract: The hydro-carbon based polymers have attracted attention of scientists for its use in bio-medical field as various implants due to inherent flexibility. However, they have poor surface properties; particularly they have low surface energy (SE). Hence, blood components (platelets, blood proteins, etc.)-polymer surface interaction is the major concern when it comes in contact with blood. Thus, surface modification is required to develop the perfect antithrombogenic property without affecting the materials bulk. The present study describes the improvement in adhesive and blood compatible properties of polypropylene (PP) by low temperature (non-thermal) plasma of various gases such as Ar, O{sub 2}, air and Ar + O{sub 2} for biomedical applications. The changes in surface morphological, chemical and hydrophilic modification induced by the gaseous plasma treatment were analyzed by atomic force microscopy (AFM), X-ray photo electron spectroscopy (XPS), electron spin resonance (ESR) spectroscopy and contact angle measurements, respectively. Moreover, the stability of plasma effect was also studied for the different storage conditions. Variation in adhesive strength of the plasma treated PP film was studied by T-Peel and Lap-Shear strength tests. The blood compatibility of the surface modified PP films was investigated by in vitro analysis. It was found that gaseous plasma treatment improved the blood compatibility

Evaluation of mechanism of non-thermal plasma effect on the surface of polypropylene films for enhancement of adhesive and hemo compatible properties

International Nuclear Information System (INIS)

Navaneetha Pandiyaraj, K.; Deshmukh, R.R.; Arunkumar, A.; Ramkumar, M.C.; Ruzybayev, I.; Ismat Shah, S.; Su, Pi-Guey; Periayah, Mercy Halleluyah; Halim, A.S.

2015-01-01

Highlights: • Investigated the mechanism of effect of various gaseous plasma treatments on the surface properties of Polypropylene (PP) films. • The improvement in surface energy is basically due to the incorporation of polar functional groups onto the PP films. • The extent of surface modification and hydrophobic recovery depends upon the type of plasma forming gas. • Due to the significant morphological and chemical changes induced by the gaseous plasma treatment, improved the blood compatibility as well as adhesive strength of the PP films. - Abstract: The hydro-carbon based polymers have attracted attention of scientists for its use in bio-medical field as various implants due to inherent flexibility. However, they have poor surface properties; particularly they have low surface energy (SE). Hence, blood components (platelets, blood proteins, etc.)-polymer surface interaction is the major concern when it comes in contact with blood. Thus, surface modification is required to develop the perfect antithrombogenic property without affecting the materials bulk. The present study describes the improvement in adhesive and blood compatible properties of polypropylene (PP) by low temperature (non-thermal) plasma of various gases such as Ar, O 2 , air and Ar + O 2 for biomedical applications. The changes in surface morphological, chemical and hydrophilic modification induced by the gaseous plasma treatment were analyzed by atomic force microscopy (AFM), X-ray photo electron spectroscopy (XPS), electron spin resonance (ESR) spectroscopy and contact angle measurements, respectively. Moreover, the stability of plasma effect was also studied for the different storage conditions. Variation in adhesive strength of the plasma treated PP film was studied by T-Peel and Lap-Shear strength tests. The blood compatibility of the surface modified PP films was investigated by in vitro analysis. It was found that gaseous plasma treatment improved the blood compatibility as well

Effect of pyrolysis atmospheres on the morphology of polymer-derived silicon oxynitrocarbide ceramic films coated aluminum nitride surface and the thermal conductivity of silicone rubber composites

Science.gov (United States)

Chiu, Hsien T.; Sukachonmakul, Tanapon; Wang, Chen H.; Wattanakul, Karnthidaporn; Kuo, Ming T.; Wang, Yu H.

2014-02-01

Amorphous silicon oxycarbide (SiOC) and silicon oxynitrocarbide (SiONC) ceramic films coated aluminum nitride (AlN) were prepared by using preceramic-polysilazane (PSZ) with dip-coating method, followed by pyrolysis at 700 °C in different (air, Ar, N2 and NH3) atmospheres to converted PSZ into SiOCair and SiONC(Ar,N2andNH3) ceramic. The existence of amorphous SiOCair and SiONC(Ar,N2andNH3) ceramic films on AlN surface was characterized by FTIR, XRD and XPS. The interfacial adhesion between silicone rubber and AlN was significantly improved after the introduction of amorphous SiOCair and SiONC(Ar,N2andNH3) ceramic films on AlN surface. It can be observed from AFM that the pyrolysis of PSZ at different atmosphere strongly affected to films morphology on AlN surface as SiOCair and SiONCNH3 ceramic films were more flat and smooth than SiONCN2 and SiONCAr ceramic films. Besides, the enhancement of the thermal conductivity of silicone rubber composites was found to be related to the decrease in the surface roughness of SiOCair and SiONC(Ar,N2andNH3) ceramic films on AlN surface. This present work provided an alternative surface modification of thermally conductive fillers to improve the thermal conductivity of silicon rubber composites by coating with amorphous SiOCair and SiONC(Ar,N2andNH3) ceramic films.

Multi-sphere unit cell model to calculate the effective thermal conductivity in pebble bed reactors

International Nuclear Information System (INIS)

Van Antwerpen, W.; Rousseau, P.G.; Du Toit, C.G.

2010-01-01

A proper understanding of the mechanisms of heat transfer, fluid flow and pressure drop through a packed bed of spheres is of utmost importance in the design of a high temperature Pebble Bed Reactor (PBR). While the gas flows predominantly in the axial direction through the bed, the total effective thermal conductivity is a lumped parameter that characterises the total heat transfer in the radial direction through the packed bed. The study of the effective thermal conductivity is important because it forms an intricate part of the self-acting decay heat removal chain, which is directly related to the PBR safety case. The effective thermal conductivity is the summation of various heat transport phenomena. These are the enhanced thermal conductivity due to turbulent mixing as the fluid passes through the voids between pebbles, heat transfer due to the movement of the solid spheres and thermal conduction and thermal radiation between the spheres in a stagnant fluid environment. In this study, the conduction and radiation between the spheres are investigated. Firstly, existing correlations for the effective thermal conductivity are investigated, with particular attention given to its applicability in the near-wall region. Several phenomena in particular are examined namely: conduction through the spheres, conduction through the contact area between the spheres, conduction through the gas phase and radiation between solid surfaces. A new approach to simulate the effective thermal conductivity for randomly packed beds is then presented, namely the so-called Multi-sphere Unit Cell Model. The model is validated by comparing the results with that obtained in experiments. (authors)

Influence of a-Si:H deposition power on surface passivation property and thermal stability of a-Si:H/SiNx:H stacks

Directory of Open Access Journals (Sweden)

Hua Li

2012-06-01

Full Text Available The effectiveness of hydrogenated amorphous silicon (a-Si:H layers for passivating crystalline silicon surfaces has been well documented in the literature for well over a decade. One limitation of such layers however has arisen from their inability to withstand temperatures much above their deposition temperature without significant degradation. This limitation is of importance particularly with multicrystalline silicon materials where temperatures of at least 400°C are needed for effective hydrogenation of the crystallographic defects such as grain boundaries. To address this limitation, in this work the surface passivation quality and thermal stability of a stack passivating system, combining a layer of intrinsic a-Si:H and a capping layer of silicon nitride (SiNx:H, on p-type crystalline silicon wafers is studied and optimized. In particular the sensitivity of different microwave (MW power levels for underlying a-Si:H layer deposition are examined. Both effective minority carrier lifetime (ζeff measurement and Fourier transform infrared (FTIR spectrometry were employed to study the bonding configurations, passivating quality and thermal stability of the a-Si:H/SiNx:H stacks. It is established that the higher MW power could result in increased as-deposited ζeff and implied Voc (iVoc values, indicating likely improved surface passivation quality, but that this combination degrades more quickly when exposed to prolonged thermal treatments. The more dihydride-rich film composition corresponding to the higher MW power appears to be beneficial for bond restructuring by hydrogen interchanges when exposed to short term annealing, however it also appears more susceptible to providing channels for hydrogen out-effusion which is the likely cause of the poorer thermal stability for prolonged high temperature exposure compared with stacks with underlying a-Si:H deposited with lower MW power.

Thermal Effect on the Structural, Electrical, and Optical Properties of In-Line Sputtered Aluminum Doped Zinc Oxide Films Explored with Thermal Desorption Spectroscopy

Directory of Open Access Journals (Sweden)

Shang-Chou Chang

2014-01-01

Full Text Available This work investigates the thermal effect on the structural, electrical, and optical properties of aluminum doped zinc oxide (AZO films. The AZO films deposited at different temperatures were measured using a thermal desorption system to obtain their corresponding thermal desorption spectroscopy (TDS. In addition to obtaining information of thermal desorption, the measurement of TDS also has the effect of vacuum annealing on the AZO films. The results of measuring TDS imply part of the doped aluminum atoms do not stay at substituted zinc sites in AZO films. The (002 preferential direction of the AZO films in X-ray diffraction spectra shifts to a lower angle after measurement of TDS. The grain size grows and surface becomes denser for all AZO films after measurement of TDS. The carrier concentration, mobility, and average optical transmittance increase while the electrical resistivity decreases for AZO films after measurement of TDS. These results indicate that the AZO films deposited at 200°C are appropriate selections if the AZO films are applied in device fabrication of heat-produced process.

3D thermal model of laser surface glazing for H13 tool steel

Science.gov (United States)

Kabir, I. R.; Yin, D.; Naher, S.

2017-10-01

In this work a three dimensional (3D) finite element model of laser surface glazing (LSG) process has been developed. The purpose of the 3D thermal model of LSG was to achieve maximum accuracy towards the predicted outcome for optimizing the process. A cylindrical geometry of 10mm diameter and 1mm length was used in ANSYS 15 software. Temperature distribution, depth of modified zone and cooling rates were analysed from the thermal model. Parametric study was carried out varying the laser power from 200W-300W with constant beam diameter and residence time which were 0.2mm and 0.15ms respectively. The maximum surface temperature 2554°K was obtained for power 300W and minimum surface temperature 1668°K for power 200W. Heating and cooling rates increased with increasing laser power. The depth of the laser modified zone attained for 300W power was 37.5µm and for 200W power was 30µm. No molten zone was observed at 200W power. Maximum surface temperatures obtained from 3D model increased 4% than 2D model presented in author's previous work. In order to verify simulation results an analytical solution of temperature distribution for laser surface modification was used. The surface temperature after heating was calculated for similar laser parameters which is 1689°K. The difference in maximum surface temperature is around 20.7°K between analytical and numerical analysis of LSG for power 200W.

Application of Terrestrial Laser Scanner with an Integrated Thermal Camera in Non-Destructive Evaluation of Concrete Surface of Hydrotechnical Objects

Science.gov (United States)

Kaczmarek, Łukasz Dominik; Dobak, Paweł Józef; Kiełbasiński, Kamil

2017-12-01

The authors present possible applications of thermal data as an additional source of information on an object's behaviour during the technical assessment of the condition of a concrete surface. For the study one of the most recent propositions introduced by Zoller + Fröhlich company was used, which is an integration of a thermal camera with a terrestrial laser scanner. This solution enables an acquisition of geometric and spectral data on the surveyed object and also provides information on the surface's temperature in the selected points. A section of the dam's downstream concrete wall was selected as the subject of the study for which a number of scans were carried out and a number of thermal images were taken at different times of the day. The obtained thermal data was confronted with the acquired spectral information for the specified points. This made it possible to carry out broader analysis of the surface and an inspection of the revealed fissure. The thermal analysis of said fissure indicated that the temperature changes within it are slower, which may affect the way the concrete works and may require further elaboration by the appropriate experts. Through the integration of a thermal camera with a terrestrial laser scanner one can not only analyse changes of temperature in the discretely selected points but on the whole surface as well. Moreover, it is also possible to accurately determine the range and the area of the change affecting the surface. The authors note the limitations of the presented solution like, inter alia, the resolution of the thermal camera.

Distinct positive temperature coefficient effect of polymer-carbon fiber composites evaluated in terms of polymer absorption on fiber surface.

Science.gov (United States)

Zhang, Xi; Zheng, Shaodi; Zheng, Xiaofang; Liu, Zhengying; Yang, Wei; Yang, Mingbo

2016-03-21

In this article, the positive temperature coefficient (PTC) effect was studied for high-density polyethylene (HDPE)/carbon fiber (CF) composites. All of the samples showed a significant PTC effect during the heating processes without a negative temperature coefficient (NTC) effect, even at a temperature much higher than the melting point of the polymer matrix. An ever-increasing PTC intensity with increasing thermal cycles was observed in our study that had never been reported in previous research. The absence of a NTC effect resulted from the increased binding force between the matrix and fillers that contributed to the very special structure of CF surface. We incorporated thermal expansion theory and quantum tunneling effects to explain PTC effect. From the SEM micrographs for the HDPE/CF composites before and after the different thermal cycles, we found that the surface of CF was covered with a layer of polymer which resulted in a change in the gap length between CF and HDPE and its distribution. We believed that the gap change induced by polymer absorption on the fiber surface had a great effect on the PTC effect.

Effect of surface morphology and densification on the infrared emissivity of C/SiC composites

International Nuclear Information System (INIS)

Wang, Fuyuan; Cheng, Laifei; Zhang, Qing; Zhang, Litong

2014-01-01

Highlights: • The cauliflower-like microstructure improved the infrared emissivity multiply. • The infrared emissivity decreased continually with the improving surface flatness. • The densification process boosted the infrared emissivity. - Abstract: The effects of surface morphology and densification on the infrared emissivity of 2D C/SiC composites were investigated in 6–16 μm from 1000 °C to 1600 °C. As the sample surface was polished, the reflection and scattering for the electromagnetic waves of thermal radiation were reduced, causing a sustained decrease in the infrared emissivity. The space-variant polarizations caused by the cauliflower-like microstructure were enervated in the smooth surface, which enhanced the reduction trendy in the infrared emissivity. In densification process, the increasing SiC content and the growing amount of the cauliflower-like microstructure on sample surface improved the infrared emissivity of C/SiC composites, while the decreasing porosity decreased it. Due to the greater positive effects on the thermal radiation during the densification process, the infrared emissivity of C/SiC composites increased successively with density

Effect of surface morphology and densification on the infrared emissivity of C/SiC composites

Energy Technology Data Exchange (ETDEWEB)

Wang, Fuyuan, E-mail: wangfy1986@gmail.com; Cheng, Laifei; Zhang, Qing, E-mail: zhangqing@nwpu.edu.cn; Zhang, Litong

2014-09-15

Highlights: • The cauliflower-like microstructure improved the infrared emissivity multiply. • The infrared emissivity decreased continually with the improving surface flatness. • The densification process boosted the infrared emissivity. - Abstract: The effects of surface morphology and densification on the infrared emissivity of 2D C/SiC composites were investigated in 6–16 μm from 1000 °C to 1600 °C. As the sample surface was polished, the reflection and scattering for the electromagnetic waves of thermal radiation were reduced, causing a sustained decrease in the infrared emissivity. The space-variant polarizations caused by the cauliflower-like microstructure were enervated in the smooth surface, which enhanced the reduction trendy in the infrared emissivity. In densification process, the increasing SiC content and the growing amount of the cauliflower-like microstructure on sample surface improved the infrared emissivity of C/SiC composites, while the decreasing porosity decreased it. Due to the greater positive effects on the thermal radiation during the densification process, the infrared emissivity of C/SiC composites increased successively with density.

Stage I surface crack formation in thermal fatigue: A predictive multi-scale approach

International Nuclear Information System (INIS)

Osterstock, S.; Robertson, C.; Sauzay, M.; Aubin, V.; Degallaix, S.

2010-01-01

A multi-scale numerical model is developed, predicting the formation of stage I cracks, in thermal fatigue loading conditions. The proposed approach comprises 2 distinct calculation steps. Firstly, the number of cycles to micro-crack initiation is determined, in individual grains. The adopted initiation model depends on local stress-strain conditions, relative to sub-grain plasticity, grain orientation and grain deformation incompatibilities. Secondly, 2-4 grains long surface cracks (stage I) is predicted, by accounting for micro-crack coalescence, in 3 dimensions. The method described in this paper is applied to a 500 grains aggregate, loaded in representative thermal fatigue conditions. Preliminary results provide quantitative insight regarding position, density, spacing and orientations of stage I surface cracks and subsequent formation of crack networks. The proposed method is fully deterministic, provided all grain crystallographic orientations and micro-crack linking thresholds are specified. (authors)

Effective thermal conductivity of nanofluids: the effects of microstructure

International Nuclear Information System (INIS)

Fan Jing; Wang Liqiu

2010-01-01

We examine numerically the effects of particle-fluid thermal conductivity ratio, particle volume fraction, particle size distribution and particle aggregation on macroscale thermal properties for seven kinds of two-dimensional nanofluids. The results show that the radius of gyration and the non-dimensional particle-fluid interfacial area are two important parameters in characterizing the geometrical structure of nanoparticles. A non-uniform particle size is found to be unfavourable for the conductivity enhancement, while particle-aggregation benefits the enhancement especially when the radius of gyration of aggregates is large. Without considering the interfacial thermal resistance, a larger non-dimensional particle-fluid interfacial area between the base fluid and the nanoparticles is also desirable for enhancing thermal conductivity. The nanofluids with nanoparticles of connected cross-shape show a much higher (lower) effective thermal conductivity when the particle-fluid conductivity ratio is larger (smaller) than 1.

The effect of Y2O3 addition on thermal shock behavior of magnesium aluminate spinel

Directory of Open Access Journals (Sweden)

Pošarac Milica

2009-01-01

Full Text Available The effect of yttria additive on the thermal shock behavior of magnesium aluminate spinel has been investigated. As a starting material we used spinel (MgAl2O4 obtained by the modified glycine nitrate procedure (MGNP. Sintered products were characterized in terms of phase analysis, densities, thermal shock, monitoring the damaged surface area in the refractory specimen during thermal shock and ultrasonic determination of the Dynamic Young modulus of elasticity. It was found that a new phase between yttria and alumina is formed, which improved thermal shock properties of the spinel refractories. Also densification of samples is enhanced by yttria addition.

Remote sensing of land surface temperature: The directional viewing effect

International Nuclear Information System (INIS)

Smith, J.A.; Schmugge, T.J.; Ballard, J.R. Jr.

1997-01-01

Land Surface Temperature (LST) is an important parameter in understanding global environmental change because it controls many of the underlying processes in the energy budget at the surface and heat and water transport between the surface and the atmosphere. The measurement of LST at a variety of spatial and temporal scales and extension to global coverage requires remote sensing means to achieve these goals. Land surface temperature and emissivity products are currently being derived from satellite and aircraft remote sensing data using a variety of techniques to correct for atmospheric effects. Implicit in the commonly employed approaches is the assumption of isotropy in directional thermal infrared exitance. The theoretical analyses indicate angular variations in apparent infrared temperature will typically yield land surface temperature errors ranging from 1 to 4 C unless corrective measures are applied

Effect of thermal oxidation treatment on pH sensitivity of AlGaN/GaN heterostructure ion-sensitive field-effect transistors

Energy Technology Data Exchange (ETDEWEB)

Wang, Lei; Bu, Yuyu [Institute of Science and Technology, Tokushima University, Tokushima 770-8506 (Japan); Li, Liuan, E-mail: liliuan@mail.sysu.edu.cn [School of Electronics and Information Technology, Sun Yat-Sen University, Guangzhou 510275 (China); Ao, Jin-Ping, E-mail: jpao@ee.tokushima-u.ac.jp [Institute of Science and Technology, Tokushima University, Tokushima 770-8506 (Japan)

2017-07-31

Highlights: • AlGaN/GaN ISFETs were fabricated and evaluated with thermal oxidation treatment. • Sensitivity was improved to 57.7 mV/pH after 700 °C treatment. • Sensitivity became poor after 800 °C treatment. • The pure α-Al{sub 2}O{sub 3} crystal phase generated on the surface of the 700 °C treatment sample. • Ga{sub 2}O{sub 3} phase content in the metal oxide layer increased after 800 °C treatment. - Abstract: In this article, AlGaN/GaN heterostructure ion-sensitive field-effect transistors (ISFETs) were prepared and evaluated by thermal oxidation treatment on the AlGaN surface. The ISFETs were fabricated on the AlGaN/GaN heterostructure and then thermally oxidized with dry oxygen in 600, 700, and 800 °C, respectively. It indicates that the performance of the AlGaN/GaN heterostructure ISFETs, such as noise and sensitivity, has been improved owing to the thermal oxidation treatment process at different temperatures. The X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) results indicate that after thermal oxidation treatment at different temperatures, hydroxide who possesses high surface state density will transfer to oxide owing to the higher chemical stability of the latter. Moreover, a crystalline α-Al{sub 2}O{sub 3} phase generated at 700 °C can not only provide a relatively smooth surface, but also improve the sensitivity to 57.7 mV/pH for the AlGaN/GaN heterostructure ISFETs, which is very close to the Nernstian limit.

Envelope colour on thermal load in hot humid Hong Kong： Effect of hue, value, and chroma

Institute of Scientific and Technical Information of China (English)

VickyCHENG; EdwardNG

2003-01-01

Cooling energy consumption of a building can be significantly reduced by limiting solar heat gain through envelope, in which depends on the intensity of impinging solar radiation and on the colour of external surface. Albedo, from the thermal point of view, is the prime parameter of interest; however, it does appear to be too conceptual in practice. Architects, when considering choices of envelope colour, the actual decision is between various colours: yellow, blue, or green rather than a single numerical albedo. This study is to investigate the effect and magnitude of colour, in terms of visual qualities hue, value (lightness), and chroma (saturation), on thermal load of buildings. In the experiment, air temperatures inside test cells painted into different colours were measured, the results suggest that colour attribute: chroma has negligible effect on thermal performance of building envelope, while value has significant thermal effect. The effect of hue, as shown in this study, was insignificant, however further study might be needed as to obtain a clearer picture of its effect.

Numerical analysis for MHD thermal and solutal stratified stagnation point flow of Powell-Eyring fluid induced by cylindrical surface with dual convection and heat generation effects

Science.gov (United States)

Khalil-Ur-Rehman; Malik, M. Y.; Bilal, S.; Bibi, M.

The current analysis reports the untapped characteristics of magneto-hydrodynamic dual convection boundary layer stagnation point flow of Powell-Eyring fluid by way of cylindrical surface. Flow exploration is carried out with the combined effects of thermal and solutal stratification. The strength of temperature and concentration adjacent to the cylindrical surface is assumed to be greater than the ambient fluid. Flow conducting mathematically modelled equations are fairly transformed into system of coupled non-linear ordinary differential equations with the aid of suitable transformations. The computations are made against these resultant coupled equations through shooting technique by the support of fifth order Runge-Kutta algorithm. A parametric study is performed to examine the effect logs of various pertinent flow controlling parameters on the velocity, temperature and concentration flow regime. The achieved outcomes are validated by developing comparison with existing published literature. In addition, numerical values of skin friction coefficient and Nusselt number are presented graphically for two different geometries namely, plate and cylinder.

Effect of Non-Equilibrium Surface Thermochemistry in Simulation of Carbon Based Ablators

Science.gov (United States)

Chen, Yih-Kanq; Gokcen, Tahir

2012-01-01

This study demonstrates that coupling of a material thermal response code and a flow solver using non-equilibrium gas/surface interaction model provides time-accurate solutions for the multidimensional ablation of carbon based charring ablators. The material thermal response code used in this study is the Two-dimensional Implicit Thermal-response and AblatioN Program (TITAN), which predicts charring material thermal response and shape change on hypersonic space vehicles. Its governing equations include total energy balance, pyrolysis gas mass conservation, and a three-component decomposition model. The flow code solves the reacting Navier-Stokes equations using Data Parallel Line Relaxation (DPLR) method. Loose coupling between the material response and flow codes is performed by solving the surface mass balance in DPLR and the surface energy balance in TITAN. Thus, the material surface recession is predicted by finite-rate gas/surface interaction boundary conditions implemented in DPLR, and the surface temperature and pyrolysis gas injection rate are computed in TITAN. Two sets of nonequilibrium gas/surface interaction chemistry between air and the carbon surface developed by Park and Zhluktov, respectively, are studied. Coupled fluid-material response analyses of stagnation tests conducted in NASA Ames Research Center arc-jet facilities are considered. The ablating material used in these arc-jet tests was Phenolic Impregnated Carbon Ablator (PICA). Computational predictions of in-depth material thermal response and surface recession are compared with the experimental measurements for stagnation cold wall heat flux ranging from 107 to 1100 Watts per square centimeter.

The retrieval of two-dimensional distribution of the earth's surface aerodynamic roughness using SAR image and TM thermal infrared image

Institute of Scientific and Technical Information of China (English)

ZHANG; Renhua; WANG; Jinfeng; ZHU; Caiying; SUN; Xiaomin

2004-01-01

After having analyzed the requirement on the aerodynamic earth's surface roughness in two-dimensional distribution in the research field of interaction between land surface and atmosphere, this paper presents a new way to calculate the aerodynamic roughness using the earth's surface geometric roughness retrieved from SAR (Synthetic Aperture Radar) and TM thermal infrared image data. On the one hand, the SPM (Small Perturbation Model) was used as a theoretical SAR backscattering model to describe the relationship between the SAR backscattering coefficient and the earth's surface geometric roughness and its dielectric constant retrieved from the physical model between the soil thermal inertia and the soil surface moisture with the simultaneous TM thermal infrared image data and the ground microclimate data. On the basis of the SAR image matching with the TM image, the non-volume scattering surface geometric information was obtained from the SPM model at the TM image pixel scale, and the ground pixel surface's equivalent geometric roughness-height standard RMS (Root Mean Square) was achieved from the geometric information by the transformation of the typical topographic factors. The vegetation (wheat, tree) height retrieved from spectrum model was also transferred into its equivalent geometric roughness. A completely two-dimensional distribution map of the equivalent geometric roughness over the experimental area was produced by the data mosaic technique. On the other hand, according to the atmospheric eddy currents theory, the aerodynamic surface roughness was iterated out with the atmosphere stability correction method using the wind and the temperature profiles data measured at several typical fields such as bare soil field and vegetation field. After having analyzed the effect of surface equivalent geometric roughness together with dynamic and thermodynamic factors on the aerodynamic surface roughness within the working area, this paper first establishes a scale

Effects of growth conditions on thermal profiles during Czochralski silicon crystal growth

Science.gov (United States)

Choe, Kwang Su; Stefani, Jerry A.; Dettling, Theodore B.; Tien, John K.; Wallace, John P.

1991-01-01

An eddy current testing method was used to continuously monitor crystal growth process and investigate the effects of growth conditions on thermal profiles during Czochralski silicon crystal growth. The experimental concept was to monitor the intrinsic electrical conductivities of the growing crystal and deduce temperature values from them. In terms of the experiments, the effects of changes in growth parameters, which include the crystal and crucible rotation rates, crucible position, and pull rate, and hot-zone geometries were investigated. The results show that the crystal thermal profile could shift significantly as a function of crystal length if the closed-loop control fails to maintain a constant thermal condition. As a direct evidence to the effects of the melt flow on heat transfer processes, a thermal gradient minimum was observed when the crystal/crucible rotation combination was 20/-10 rpm cw. The thermal gradients in the crystal near the growth interface were reduced most by decreasing the pull rate or by reducing the radiant heat loss to the environment; a nearly constant axial thermal gradient was achieved when either the pull rate was decreased by half, the height of the exposed crucible wall was doubled, or a radiation shield was placed around the crystal. Under these conditions, the average axial thermal gradient along the surface of the crystal was about 4-5°C/mm. When compared to theoretical results found in literature, the axial profiles correlated well with the results of the models which included radiant interactions. However, the radial gradients estimated from three-frequency data were much higher than what were predicted by known theoretical models. This discrepancy seems to indicate that optical phenomenon within the crystal is significant and should be included in theoretical modeling.

Effects of surface cracks and strain rate on the tensile behavior of Balmoral Red granite

Directory of Open Access Journals (Sweden)

Mardoukhi Ahmad

2015-01-01

Full Text Available This paper presents an experimental procedure for studying the effects of surface cracks on the mechanical behavior of Balmoral Red granite under dynamic and quasi-static loading. Three different thermal shocks were applied on the surface of the Brazilian Disc test samples by keeping a flame torch at a fixed distance from the sample surface for 10, 30, and 60 seconds. Microscopy clearly shows that the number of the surface cracks increases with the duration of the thermal shock. After the thermal shock, the Brazilian Disc tests were performed using a servohydraulic materials testing machine and a compression Split Hopkinson Pressure Bar (SHPB device. The results show that the tensile strength of the rock decreases and the rate sensitivity of the rock increases as more cracks are introduced to the structure. The DIC analysis of the Brazilian disc tests shows that the fracture of the sample initiates at the center of the samples or slightly closer to the incident bar contact point. This is followed by crushing of the samples at both contact points with the stress bars.

Morphological study of polymer surfaces exposed to non-thermal plasma based on contact angle and the use of scaling laws

Science.gov (United States)

Felix, T.; Cassini, F. A.; Benetoli, L. O. B.; Dotto, M. E. R.; Debacher, N. A.

2017-05-01

The experiments presented in this communication have the purpose to elaborate an explanation for the morphological evolution of the growth of polymeric surfaces provided by the treatment of non-thermal plasma. According to the roughness analysis and the model proposed by scaling laws it is possible relate to a predictable or merely random effect. Polyethylene terephthalate (PET) and poly(etherether)ketone (PEEK) samples were exposed to a non-thermal plasma discharge and the resulting surfaces roughness were analyzed based on the measurements from contact angle, scanning electron microscopy and atomic force microscopy coupled with scaling laws analysis which can help to describe and understand the dynamic of formation of a wide variety of rough surfaces. The roughness, RRMS (RMS- Root Mean Square) values for polymer surface range between 19.8 nm and 110.9 nm. The contact angle and the AFM (Atomic Force Microscopy) measurements as a function of the plasma exposure time were in agreement with both polar and dispersive components according to the surface roughness and also with the morphology evaluated described by Wolf-Villain model, with proximate values of α between 0.91(PET) and 0.88(PEEK), β = 0.25(PET) and z = 3,64(PET).

Effect of surface oxidation on thermomechanical behavior of NiTi shape memory alloy wire

Science.gov (United States)

Ng, Ching Wei; Mahmud, Abdus Samad

2017-12-01

Nickel titanium (NiTi) alloy is a unique alloy that exhibits special behavior that recovers fully its shape after being deformed to beyond elastic region. However, this alloy is sensitive to any changes of its composition and introduction of inclusion in its matrix. Heat treatment of NiTi shape memory alloy to above 600 °C leads to the formation of the titanium oxide (TiO2) layer. Titanium oxide is a ceramic material that does not exhibit shape memory behaviors and possess different mechanical properties than that of NiTi alloy, thus disturbs the shape memory behavior of the alloy. In this work, the effect of formation of TiO2 surface oxide layer towards the thermal phase transformation and stress-induced deformation behaviors of the NiTi alloy were studied. The NiTi wire with composition of Ti-50.6 at% Ni was subjected to thermal oxidation at 600 °C to 900 °C for 30 and 60 minutes. The formation of the surface oxide layers was characterized by using the Scanning Electron Microscope (SEM). The effect of surface oxide layers with different thickness towards the thermal phase transformation behavior was studied by using the Differential Scanning Calorimeter (DSC). The effect of surface oxidation towards the stress-induced deformation behavior was studied through the tensile deformation test. The stress-induced deformation behavior and the shape memory recovery of the NiTi wire under tensile deformation were found to be affected marginally by the formation of thick TiO2 layer.

The effect of sediment thermal conductivity on vertical groundwater flux estimates

Science.gov (United States)

Sebok, Eva; Müller, Sascha; Engesgaard, Peter; Duque, Carlos

2015-04-01

The interaction between groundwater and surface water is of great importance both from ecological and water management perspective. The exchange fluxes are often estimated based on vertical temperature profiles taken from shallow sediments assuming a homogeneous standard value of sediment thermal conductivity. Here we report on a field investigation in a stream and in a fjord, where vertical profiles of sediment thermal conductivity and temperatures were measured in order to, (i) define the vertical variability in sediment thermal conductivity, (ii) quantify the effect of heterogeneity in sediment thermal conductivity on the estimated vertical groundwater fluxes. The study was carried out at field sites located in Ringkøbing fjord and Holtum stream in Western Denmark. Both locations have soft, sandy sediments with an upper organic layer at the fjord site. First 9 and 12 vertical sediment temperature profiles up to 0.5 m depth below the sediment bed were collected in the fjord and in the stream, respectively. Later sediment cores of 0.05 m diameter were removed at the location of the temperature profiles. Sediment thermal conductivity was measured in the sediment cores at 0.1 m intervals with a Decagon KD2 Pro device. A 1D flow and heat transport model (HydroGeoSphere) was set up and vertical groundwater fluxes were estimated based on the measured vertical sediment temperature profiles by coupling the model with PEST. To determine the effect of heterogeneity in sediment thermal conductivity on estimated vertical groundwater fluxes, the model was run by assigning (i) a homogeneous thermal conductivity for all sediment layers, calculated as the average sediment thermal conductivity of the profile, (ii) measured sediment thermal conductivities to the different model layers. The field survey showed that sediment thermal conductivity over a 0.5 m profile below the sediment bed is not uniform, having the largest variability in the fjord where organic sediments were also

Johnson noise and the thermal Casimir effect

International Nuclear Information System (INIS)

Bimonte, Giuseppe

2007-01-01

We study the thermal interaction between two nearby thin metallic wires, at finite temperature. It is shown that the Johnson currents in the wires give rise, via inductive coupling, to a repulsive force between them. This thermal interaction exhibits all the puzzling features found recently in the thermal Casimir effect for lossy metallic plates, suggesting that the physical origin of the difficulties encountered in the Casimir problem resides in the inductive coupling between the Johnson currents inside the plates. We show that in our simple model all puzzles are resolved if account is taken of capacitive effects associated with the end points of the wires. Our findings suggest that capacitive finite-size effects may play an important role in the resolution of the analogous problems met in the thermal Casimir effect

Suitability of thermal plasmas for large-area bacteria inactivation on temperature-sensitive surfaces – first results with Geobacillus stearothermophilus spores

International Nuclear Information System (INIS)

Szulc, M; Schein, S; Schaup, J; Zimmermann, S; Schein, J

2017-01-01

The application of thermal plasma for large-area bacteria inactivation on temperature-sensitive surfaces is not a common one. Nonetheless, there are thermal plasma generators which offer a high sheath homogeneity and have proven to be suitable for treatment of thermally sensitive materials in the past. To investigate the suitability of such plasmas, agar dishes plated with endospores of Geobacillus stearothermophilus have been treated with a long arc plasma generator called LARGE. The achieved results have been compared with a commercially available non-thermal plasma generator. A significant inactivation of the endospores could be observed only after 60 s of treatment with the thermal plasma source. This was not possible with the non-thermal generator. Moreover, no temperature damage or increase of the specimen could be detected. An attempt to determine the main agents responsible for the microbicidal effects have been made – the influence of plasma gas composition, discharge current and treatment time has been investigated. Significant improvements in the disinfection rates after adding small amounts of nitrogen to the plasma gas could be observed. A first discussion regarding the suitability of thermal plasmas for bacteria inactivation has been given. (paper)

Effect of thermal exposure on microstructure and nano-hardness of broached Inconel 718

Directory of Open Access Journals (Sweden)

Chen Zhe

2014-01-01

Full Text Available Inconel 718 is a high strength, heat resistant superalloy that is used extensively for components in hot sections of gas turbine engines. This paper presents an experimental study on the thermal stability of broached Inconel 718 in terms of microstructure and nano-hardness. The broaching process used in this study is similar to that used in gas turbine industries for machining fir-tree root fixings on turbine discs. Severe plastic deformation was found under the broached surface. The plastic deformation induces a work-hardened layer in the subsurface region with a thickness of ∼50 μm. Thermal exposure was conducted at two temperatures, 550 ∘C and 650 ∘C respectively, for 300 h. Recrystallization occurs in the surface layer during thermal exposure at 550 ∘C and α-Cr precipitates as a consequence of the growth of recrystallized δ phases. More recrystallized grains with a larger size form in the surface layer and the α-Cr not only precipitates in the surface layer, but also in the sub-surface region when the thermal exposure temperature goes up to 650 ∘C. The thermal exposure leads to an increase in nano-hardness both in the work-hardened layer and in the bulk material due to the coarsening of the main strengthening phase γ′′.

Structure and wettability property of the growth and nucleation surfaces of thermally treated freestanding CVD diamond films

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Pei, Xiaoqiang; Cheng, Shaoheng; Ma, Yibo; Wu, Danfeng; Liu, Junsong; Wang, Qiliang; Yang, Yizhou; Li, Hongdong

2015-08-01

This paper reports the surface features and wettability properties of the (1 0 0)-textured freestanding chemical vapor deposited (CVD) diamond films after thermal exposure in air at high temperature. Thermal oxidation at proper conditions eliminates selectively nanodiamonds and non-diamond carbons in the films. The growth side of the films contains (1 0 0)-oriented micrometer-sized columns, while its nucleation side is formed of nano-sized tips. The examined wettability properties of the as-treated diamond films reveal a hydrophilicity and superhydrophilicity on the growth surface and nucleation surface, respectively, which is determined by oxygen termination and geometry structure of the surface. When the surface termination is hydrogenated, the wettability of nucleation side converted from superhydrophilicity to high hydrophobicity, while the hydrophilicity of the growth side does not change significantly. The findings open a possibility for realizing freestanding diamond films having not only novel surface structures but also multifunction applications, especially proposed on the selected growth side or nucleation side in one product.

Role of the Soil Thermal Inertia in the short term variability of the surface temperature and consequences for the soil-moisture temperature feedback

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Cheruy, Frederique; Dufresne, Jean-Louis; Ait Mesbah, Sonia; Grandpeix, Jean-Yves; Wang, Fuxing

2017-04-01

A simple model based on the surface energy budget at equilibrium is developed to compute the sensitivity of the climatological mean daily temperature and diurnal amplitude to the soil thermal inertia. It gives a conceptual framework to quantity the role of the atmospheric and land surface processes in the surface temperature variability and relies on the diurnal amplitude of the net surface radiation, the sensitivity of the turbulent fluxes to the surface temperature and the thermal inertia. The performances of the model are first evaluated with 3D numerical simulations performed with the atmospheric (LMDZ) and land surface (ORCHIDEE) modules of the Institut Pierre Simon Laplace (IPSL) climate model. A nudging approach is adopted, it prevents from using time-consuming long-term simulations required to account for the natural variability of the climate and allow to draw conclusion based on short-term (several years) simulations. In the moist regions the diurnal amplitude and the mean surface temperature are controlled by the latent heat flux. In the dry areas, the relevant role of the stability of the boundary layer and of the soil thermal inertia is demonstrated. In these regions, the sensitivity of the surface temperature to the thermal inertia is high, due to the high contribution of the thermal flux to the energy budget. At high latitudes, when the sensitivity of turbulent fluxes is dominated by the day-time sensitivity of the sensible heat flux to the surface temperature and when this later is comparable to the thermal inertia term of the sensitivity equation, the surface temperature is also partially controlled by the thermal inertia which can rely on the snow properties; In the regions where the latent heat flux exhibits a high day-to-day variability, such as transition regions, the thermal inertia has also significant impact on the surface temperature variability . In these not too wet (energy limited) and not too dry (moisture-limited) soil moisture (SM

Effect of Electropulsing-Assisted Ultrasonic Nanocrystalline Surface Modification on the Surface Mechanical Properties and Microstructure of Ti-6Al-4V Alloy

Science.gov (United States)

Ye, Yongda; Wang, Haibo; Tang, Guoyi; Song, Guolin

2018-05-01

The effect of electropulsing-assisted ultrasonic nanocrystalline surface modification (EP-UNSM) on surface mechanical properties and microstructure of Ti-6Al-4V alloy is investigated. Compared to conventional ultrasonic nanocrystalline surface modification (UNSM), EP-UNSM can effectively facilitate surface roughness and morphology, leading to excellent surface roughness (reduced from Ra 0.918 to Ra 0.028 μm by UNSM and Ra 0.019 μm by EP-UNSM) and smoother morphology with less cracks and defects. Surface friction coefficients are enhanced, resulting in lower and smoother friction coefficients. In addition, the surface-strengthened layer and ultra-refined grains are significantly enhanced with more severe plastic deformation and a greater surface hardness (a maximum hardness value of 407 HV and an effective depth of 550 μm, in comparison with the maximum hardness value of 364 HV and effective depth of 300 μm obtained by conventional UNSM). Remarkable enhancement of surface mechanical properties can be attributed to the refined gradient microstructure and the enhanced severe plastic deformation layer induced by coupling the effects of UNSM and electropulsing. The accelerated dislocation mobility and atom diffusion caused by the thermal and athermal effects of electropulsing treatment may be the primary intrinsic reasons for these improvements.

Parameter optimization and evaluation of mechanical and thermal properties of nanographene reinforced Al 6060 surface composite using FSP

Science.gov (United States)

Kalyanamanohar, V.; Appalachari, D. Gireesh Chandra

2018-04-01

Friction stir processing (FSP) is emerging as a promising technique for making surface composites. FSP can improve surface properties such as hardness, strength, ductility, corrosion resistance, fatigue life and formability without affecting the bulk properties of the material. The literatures reported that FSP can produces very fine equiaxed and homogeneous grain structure for different Al alloys. Al 6060 is heat treatable alloy which has high thermal and electrical properties than remaining Al alloys. Al 6060 is being used where high rate of heat exchange is needed i.e. engine cylinders, heat exchangers etc. As derived from the carbon materials, like graphene and CNTs dissipates heat rapidly that improves the life of the engine cylinders and heat exchangers. In this work, nanographene is reinforced in the Al 6060 using friction stir processing at different rotational speeds, traverse speeds, and at constant load and tool tilt angle. After processed, the effect of process parameters on microstructure of the surface composite was investigated. The SEM studies shows that the FSP produces very fine and homogenous grain structure and it is observed that smaller grain size structure is obtained at lower traverse speed and higher rotational speeds. Significant improvement in ultimate tensile strength(22.9%) and hardness (22.44%) when compared friction stir processed plate at 1400 rotational speed and 20mm/min traverse speed with base Al 6060 plate. Coefficient of thermal expansion test of nanographene reinforced Al 6060 shows 7.33% decrease in its coefficient of thermal expansion as graphene has tendency to reduce the anisotropic nature.

Study of defects near molybdenum surface using thermal desorption spectrometer

International Nuclear Information System (INIS)

Naik, P.K.

1980-01-01

Thermal desorption spectrometry is utilized to study the migration of atoms and defects near molybdenum surface. The thermal desorption spectra of inert gas ions (neon, argon and krypton) injected with various energies (430-1950 eV) into a polycrystalline molybdenum target with various dosages (6.4 x 10sup(12) - 3.9 x 10sup(14) ions/cmsup(2)) are investigated. Four different states of binding of the trapped atoms corresponding to the activation energies for desorption have been revealed from the spectra. The activation energies are found to be relatively insensitive to the species of the bombarding ion, incident ion energy and the dosage. The patterns of the spectra are strongly influenced by the mean projected range of the ions into the solid. The activation energies deduced are in good agreement with those reported for the migration of atoms and defects in molybdenum. (auth.)

Coupled Monitoring and Inverse Modeling to Investigate Surface - Subsurface Hydrological and Thermal Dynamics in the Arctic Tundra

Science.gov (United States)

Tran, A. P.; Dafflon, B.; Hubbard, S. S.; Bisht, G.; Peterson, J.; Ulrich, C.; Romanovsky, V. E.; Kneafsey, T. J.; Wu, Y.

2015-12-01

Quantitative characterization of the soil surface-subsurface hydrological and thermal processes is essential as they are primary factors that control the biogeochemical processes, ecological landscapes and greenhouse gas fluxes. In the Artic region, the surface-subsurface hydrological and thermal regimes co-interact and are both largely influenced by soil texture and soil organic content. In this study, we present a coupled inversion scheme that jointly inverts hydrological, thermal and geophysical data to estimate the vertical profiles of clay, sand and organic contents. Within this inversion scheme, the Community Land Model (CLM4.5) serves as a forward model to simulate the land-surface energy balance and subsurface hydrological-thermal processes. Soil electrical conductivity (from electrical resistivity tomography), temperature and water content are linked together via petrophysical and geophysical models. Particularly, the inversion scheme accounts for the influences of the soil organic and mineral content on both of the hydrological-thermal dynamics and the petrophysical relationship. We applied the inversion scheme to the Next Generation Ecosystem Experiments (NGEE) intensive site in Barrow, AK, which is characterized by polygonal-shaped arctic tundra. The monitoring system autonomously provides a suite of above-ground measurements (e.g., precipitation, air temperature, wind speed, short-long wave radiation, canopy greenness and eddy covariance) as well as below-ground measurements (soil moisture, soil temperature, thaw layer thickness, snow thickness and soil electrical conductivity), which complement other periodic, manually collected measurements. The preliminary results indicate that the model can well reproduce the spatiotemporal dynamics of the soil temperature, and therefore, accurately predict the active layer thickness. The hydrological and thermal dynamics are closely linked to the polygon types and polygon features. The results also enable the

Thermal effects on domain orientation of tetragonal piezoelectrics

Science.gov (United States)

Chang, Wonyoung

Thermal effects on electrical poling or mechanical grinding induced texture in tetragonal lead zirconate titanate (PZT) and lead titanate (PT) have been investigated using ex situ and in situ X-ray diffraction (XRD) with an area detector. According to previous results using ex situ XRD, domain configurations of poled samples after heat-treatment at or higher than the Curie temperature (TC) are similar to that of unpoled samples showing random domain distributions. The texture parameter called multiples of a random distribution (MRD) gradually decreases with increasing depoling temperature. On the other hand, using in situ XRD measurements, it was found that the MRD maximum for soft PZT initially increases with temperature up to approximately 100°C and then falls to unity at temperatures approaching the TC, whereas the MRD of hard PZT and PT initially undergoes a smaller increase or no change. Mechanical strain energy has an apparent effect on domain wall mobility. In contrast with previous results on electrical poling, mechanically-ground PT and soft PZT materials retained strong ferroelastic textures during thermal cycling, even after excursions to temperatures slightly above the TC . For the ground PT, it was found that repeated cycling above T C results in changes in both peak intensity and peak position, whereas the ground soft PZT undergoes the decrease in intensity of the (002) reflection after the first cycle of heating. Residual stresses in the surface region from grinding resulted in domain wall motion and the retention of textures in annealed samples. The research in this thesis demonstrates that the magnitude of loading applied to the sample surface, the speed used for grinding, or the grit size, can greatly affect the grinding induced damage zone and the depoling behavior of piezoelectric ceramics. Among the possible effects of grinding conditions on surface textures, one of particular interest is the effect of mechanical stresses produced during

Study on the effect of thermal property of metals in ultrasonic-assisted laser machining

International Nuclear Information System (INIS)

Lee, Hu Seung; Kim, Gun Woo; Park, Jong Eun; Cho, Sung Hak; Yang, Min Yang; Park, Jong Kweon

2015-01-01

The laser machining process has been proposed as an advanced process for the selective fabrication of electrodes without a mask. In this study, we adapt laser machining to metals that have different thermal properties. Based on the results, the metals exhibit a different surface morphology, heat-affected zone (HAZ), and a recast layer around the machined surface according to their thermal conductivity, boiling point, and thermal diffusivity. Then, we apply ultrasonic-assisted laser machining to remove the recast layer. The ultrasonic-assisted laser machining exhibits a better surface quality in metals with higher diffusivity than those having lower diffusivity

Measurement and evaluation of thermal effects in the intermixing zone at low power nuclear station outfall

International Nuclear Information System (INIS)

Kamath, P.R.; Gurg, R.P.; Bhat, I.S.; Vyas, P.V.

1978-01-01

Observations and evaluations of thermal effects in the lake near the RAPS-1 REACTOR, are reported. The coolant waters are drawn from the lake at a depth of 8-10 m below the surface and discharged through an open channel with a temperature rise of 10deg C. Temperature profiles and spread in the velocity of the outfall are mapped using in situ monitors. These studies show evidence of thermal stratification in the period following winter and the existence of a well established thermocline. Parasitism and eutrophication are also observed. The thermal effects are found to be accentuated by photosynthetic effects. Proposal to utilise waste heat for algal culture in the Kalpakkam nuclear site in South and mariculture (lobsters, prawns) in the heated effluents canal at the Tarapur Atomic Power Station near Bombay are discussed. (K.B.)

Experimental study of the surface thermal signature of gravity currents: application to the assessment of lava flow effusion rate

Science.gov (United States)

Garel, F.; Kaminski, E.; Tait, S.; Limare, A.

2011-12-01

During an effusive volcanic eruption, the crisis management is mainly based on the prediction of lava flows advance and its velocity. As the spreading of lava flows is mainly controlled by its rheology and the eruptive mass flux, the key question is how to evaluate them during the eruption (rather than afterwards.) A relationship between the heat flux lost by the lava at its surface and the eruption rate is likely to exist, based on the first-order argument that higher eruption rates should correspond to larger power radiated by a lava flow. The semi-empirical formula developed by Harris and co-workers (e.g. Harris et al., Bull. Volc. 2007) is currently used to estimate lava flow rate from satellite surveys yielding the surface temperatures and area of the lava flow field. However, this approach is derived from a static thermal budget of the lava flow and does not explicitly model the time-evolution of the surface thermal signal. Here we propose laboratory experiments and theoretical studies of the cooling of a viscous axisymmetric gravity current fed at constant flux rate. We first consider the isoviscous case, for which the spreading is well-know. The experiments using silicon oil and the theoretical model both reveal the establishment of a steady surface thermal structure after a transient time. The steady state is a balance between surface cooling and heat advection in the flow. The radiated heat flux in the steady regime, a few days for a basaltic lava flow, depends mainly on the effusion rate rather than on the viscosity. In this regime, one thermal survey of the radiated power could provide a consistent estimate of the flow rate if the external cooling conditions (wind) are reasonably well constrained. We continue to investigate the relationship between the thermal radiated heat flux and the effusion rate by using in the experiments fluids with temperature-dependent viscosity (glucose syrup) or undergoing solidification while cooling (PEG wax). We observe a

Computing Thermal Imbalance Forces On Satellites

Science.gov (United States)

Vigue, Yvonne; Schutz, Robert E.; Sewell, Granville; Abusali, Pothai A. M.

1994-01-01

HEAT.PRO computer program calculates imbalance force caused by heating of surfaces of satellite. Calculates thermal imbalance force and determines its effect on orbit of satellite, especially where shadow cast by Earth Causes periodic changes in thermal environment around satellite. Written in FORTRAN 77.

Effects of Nonuniform Incident Illumination on the Thermal Performance of a Concentrating Triple Junction Solar Cell

Directory of Open Access Journals (Sweden)

Fahad Al-Amri

2014-01-01

Full Text Available A numerical heat transfer model was developed to investigate the temperature of a triple junction solar cell and the thermal characteristics of the airflow in a channel behind the solar cell assembly using nonuniform incident illumination. The effects of nonuniformity parameters, emissivity of the two channel walls, and Reynolds number were studied. The maximum solar cell temperature sharply increased in the presence of nonuniform light profiles, causing a drastic reduction in overall efficiency. This resulted in two possible solutions for solar cells to operate in optimum efficiency level: (i adding new receiver plate with higher surface area or (ii using forced cooling techniques to reduce the solar cell temperature. Thus, surface radiation exchanges inside the duct and Re significantly reduced the maximum solar cell temperature, but a conventional plain channel cooling system was inefficient for cooling the solar cell at medium concentrations when the system was subjected to a nonuniform light distribution. Nonuniformity of the incident light and surface radiation in the duct had negligible effects on the collected thermal energy.

Thermally induced growth of ZnO nanocrystals on mixed metal oxide surfaces.

Science.gov (United States)

Inayat, Alexandra; Makky, Ayman; Giraldo, Jose; Kuhnt, Andreas; Busse, Corinna; Schwieger, Wilhelm

2014-06-23

An in situ method for the growth of ZnO nanocrystals on Zn/Al mixed metal oxide (MMO) surfaces is presented. The key to this method is the thermal treatment of Zn/Al layered double hydroxides (Zn/Al LDHs) in the presence of nitrate anions, which results in partial demixing of the LDH/MMO structure and the subsequent crystallization of ZnO crystals on the surface of the forming MMO layers. In a first experimental series, thermal treatment of Zn/Al LDHs with different fractions of nitrate and carbonate in the interlayer space was examined by thermogravimetry coupled with mass spectrometry (TG-MS) and in situ XRD. In a second experimental series, Zn/Al LDHs with only carbonate in the interlayer space were thermally treated in the presence of different amounts of an external nitrate source (NH4NO3). All obtained Zn/Al MMO samples were analysed by electron microscopy, nitrogen physisorption and powder X-ray diffraction. The gas phase formed during nitrate decomposition turned out to be responsible for the formation of crystalline ZnO nanoparticles. Accordingly, both interlayer nitrate and the presence of ammonium nitrate led to the formation of supported ZnO nanocrystals with mean diameters between 100 and 400 nm, and both methods offer the possibility to tailor the amount and size of the ZnO crystals by means of the amount of nitrate. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Thermal noise due to surface-charge effects within the Debye layer of endogenous structures in dendrites.

Science.gov (United States)

Poznanski, Roman R

2010-02-01

An assumption commonly used in cable theory is revised by taking into account electrical amplification due to intracellular capacitive effects in passive dendritic cables. A generalized cable equation for a cylindrical volume representation of a dendritic segment is derived from Maxwell's equations under assumptions: (i) the electric-field polarization is restricted longitudinally along the cable length; (ii) extracellular isopotentiality; (iii) quasielectrostatic conditions; and (iv) homogeneous medium with constant conductivity and permittivity. The generalized cable equation is identical to Barenblatt's equation arising in the theory of infiltration in fissured strata with a known analytical solution expressed in terms of a definite integral involving a modified Bessel function and the solution to a linear one-dimensional classical cable equation. Its solution is used to determine the impact of thermal noise on voltage attenuation with distance at any particular time. A regular perturbation expansion for the membrane potential about the linear one-dimensional classical cable equation solution is derived in terms of a Green's function in order to describe the dynamics of free charge within the Debye layer of endogenous structures in passive dendritic cables. The asymptotic value of the first perturbative term is explicitly evaluated for small values of time to predict how the slowly fluctuating (in submillisecond range) electric field attributed to intracellular capacitive effects alters the amplitude of the membrane potential. It was found that capacitive effects are almost negligible for cables with electrotonic lengths L>0.5 , contributes up to 10% of the signal for cables with electrotonic lengths in the range between 0.25thermal noise due to

Thermal motion in proteins: Large effects on the time-averaged interaction energies

International Nuclear Information System (INIS)

Goethe, Martin; Rubi, J. Miguel; Fita, Ignacio

2016-01-01

As a consequence of thermal motion, inter-atomic distances in proteins fluctuate strongly around their average values, and hence, also interaction energies (i.e. the pair-potentials evaluated at the fluctuating distances) are not constant in time but exhibit pronounced fluctuations. These fluctuations cause that time-averaged interaction energies do generally not coincide with the energy values obtained by evaluating the pair-potentials at the average distances. More precisely, time-averaged interaction energies behave typically smoother in terms of the average distance than the corresponding pair-potentials. This averaging effect is referred to as the thermal smoothing effect. Here, we estimate the strength of the thermal smoothing effect on the Lennard-Jones pair-potential for globular proteins at ambient conditions using x-ray diffraction and simulation data of a representative set of proteins. For specific atom species, we find a significant smoothing effect where the time-averaged interaction energy of a single atom pair can differ by various tens of cal/mol from the Lennard-Jones potential at the average distance. Importantly, we observe a dependency of the effect on the local environment of the involved atoms. The effect is typically weaker for bulky backbone atoms in beta sheets than for side-chain atoms belonging to other secondary structure on the surface of the protein. The results of this work have important practical implications for protein software relying on free energy expressions. We show that the accuracy of free energy expressions can largely be increased by introducing environment specific Lennard-Jones parameters accounting for the fact that the typical thermal motion of protein atoms depends strongly on their local environment.

Thermal motion in proteins: Large effects on the time-averaged interaction energies

Energy Technology Data Exchange (ETDEWEB)

Goethe, Martin, E-mail: martingoethe@ub.edu; Rubi, J. Miguel [Departament de Física Fonamental, Universitat de Barcelona, Martí i Franquès 1, 08028 Barcelona (Spain); Fita, Ignacio [Institut de Biologia Molecular de Barcelona, Baldiri Reixac 10, 08028 Barcelona (Spain)

2016-03-15

As a consequence of thermal motion, inter-atomic distances in proteins fluctuate strongly around their average values, and hence, also interaction energies (i.e. the pair-potentials evaluated at the fluctuating distances) are not constant in time but exhibit pronounced fluctuations. These fluctuations cause that time-averaged interaction energies do generally not coincide with the energy values obtained by evaluating the pair-potentials at the average distances. More precisely, time-averaged interaction energies behave typically smoother in terms of the average distance than the corresponding pair-potentials. This averaging effect is referred to as the thermal smoothing effect. Here, we estimate the strength of the thermal smoothing effect on the Lennard-Jones pair-potential for globular proteins at ambient conditions using x-ray diffraction and simulation data of a representative set of proteins. For specific atom species, we find a significant smoothing effect where the time-averaged interaction energy of a single atom pair can differ by various tens of cal/mol from the Lennard-Jones potential at the average distance. Importantly, we observe a dependency of the effect on the local environment of the involved atoms. The effect is typically weaker for bulky backbone atoms in beta sheets than for side-chain atoms belonging to other secondary structure on the surface of the protein. The results of this work have important practical implications for protein software relying on free energy expressions. We show that the accuracy of free energy expressions can largely be increased by introducing environment specific Lennard-Jones parameters accounting for the fact that the typical thermal motion of protein atoms depends strongly on their local environment.

Ion beam effects on the surface and near-surface composition of TaSi2

International Nuclear Information System (INIS)

Valeri, S.; Di Bona, A.; Ottaviani, G.; Procop, M.

1991-01-01

Low-energy (0.7-4.5 keV) ion bombardment effects on polycrystalline TaSi 2 at sputter steady state and in various intermediate steps have been investigated, in the temperature range up to 550degC, to determine the time and temperature dependence of the altered layer formation. This in turn enables a better knowledge of the synergistic effects of the processes mentioned above. At low temperatures (T≤410degC) the surface is silicon depleted, and the depletion is even more severe in the subsurface region up to a depth of several tens of angstroems; silicon preferential sputtering and radiation-enhanced segregation assisted by the displacement mixing-induced motion of atoms are assumed to be responsible for this composition profile, while thermally activated diffusion processes become operative above 410degC, reducing progressively the concentration gradient between the surface and the subsurface zone. The composition at different depths has been determined from Auger peaks for different kinetic energies, by varying the take-off angle and finally by sputter profiling at low in energy the high energy processed surfaces. Quantitative analysis has been performed by XPS and AES by using the elemental standard method. (orig.)

Effects of nano-void density, size and spatial population on thermal conductivity: a case study of GaN crystal

International Nuclear Information System (INIS)

Zhou, X W; Jones, R E

2012-01-01

The thermal conductivity of a crystal is sensitive to the presence of surfaces and nanoscale defects. While this opens tremendous opportunities to tailor thermal conductivity, true ‘phonon engineering’ of nanocrystals for a specific electronic or thermoelectric application can only be achieved when the dependence of thermal conductivity on the defect density, size and spatial population is understood and quantified. Unfortunately, experimental studies of the effects of nanoscale defects are quite challenging. While molecular dynamics simulations are effective in calculating thermal conductivity, the defect density range that can be explored with feasible computing resources is unrealistically high. As a result, previous work has not generated a fully detailed understanding of the dependence of thermal conductivity on nanoscale defects. Using GaN as an example, we have combined a physically motivated analytical model and highly converged large-scale molecular dynamics simulations to study the effects of defects on thermal conductivity. An analytical expression for thermal conductivity as a function of void density, size, and population has been derived and corroborated with the model, simulations, and experiments. (paper)

Thermal effects in concrete members

International Nuclear Information System (INIS)

Kar, A.K.

1977-01-01

The proposed method of analysis for concrete members subjected to temperature changes is consistent with the requirements of ultimate strength design. This also facilitates the provision of the same safety margin as for other loads. Due to cracks and creep in concrete, thermal stresses are nonlinear; they are dependent on the effective member stiffness, which in turn vary with the magnitude of loading. Therefore it is inconsistent to have an ultimate strength design in conjunction with an analysis based on the linear elastic theory. It is proposed that when the requirements of serviceability are met, the neutral axis corresponding to the ultimate load capacity conditions be considered for temperature-induced loadings. This conforms with the fact that the thermal load, because of creep and formation of cracks in the member, can be self-relieving as the failure load condition or ultimate capacity is approached. The maximum thermal load that can develop in dependent on the effective cross section of the member. Recommendations are made for determining the average effective member stiffness, which lies between the stiffness corresponding to the cracked (at ultimate condition) and the uncracked sections. In the proposed method, thermal stresses are not considered completely self-relieving. The stresses are considered simultaneously with stresses resulting from other causes. A step-by-step approach is presented for analysis and design of concrete members subjected to temperature changes

Preparing Al-Mg Substrate for Thermal Spraying: Evaluation of Surface State After Different Pretreatments

Science.gov (United States)

Lukauskaitė, R.; Valiulis, A. V.; Černašėjus, O.; Škamat, J.; Rębiś, J. A.

2016-08-01

The article deals with the pretreatment technique for preparing the surface of aluminum alloy EN AW 5754 before thermal spray. The surface after different pretreatments, including degreasing with acetone, chemical etching with acidic and alkali solutions, grit-blasting, cathodic cleaning, and some combinations of these techniques, has been studied. The investigation of pre-treated surfaces covered the topographical study (using scanning electron microscopy, atomic force microscopy, and 3D profilometry), the chemical analysis by x-ray photoelectron spectroscopy, the evaluation of surface wettability (sessile drop method), and the assessment of surface free energy. Compared with all the techniques used in present work, the cathodic cleaning and its combination with grit-blasting provide the most preferable chemistry of the surface. Due to the absence of hydroxides at the surface and, possible, due to the diffusion of magnesium to the surface of substrate, the surface wettability and the surface free energy have been significantly improved. No direct correlation between the surface topography and the surface wettability has been established.

Investigation of thermal fatigue behavior of thermal barrier coating systems

International Nuclear Information System (INIS)

Zhu Dongming; Miller, R.A.

1997-01-01

In the present study, the mechanisms of fatigue crack initiation and propagation, and of coating failure under thermal loads that simulate those in diesel engines are investigated. Surface cracks initiate early and grow continuously under thermal low cycle fatigue (LCF) and high cycle fatigue (HCF) stresses. It is found that, in the absence of interfacial oxidation, the failure associated with LCF is closely related to coating sintering and creep at high temperatures. Significant LCF and HCF interactions have been observed in the thermal fatigue tests. The fatigue crack growth rate in the ceramic coating strongly depends on the characteristic HCF cycle number, N* HCF which is defined as the number of HCF cycles per LCF cycle. The crack growth rate is increased from 0.36 μm/LCF cycle for a pure LCF test to 2.8 μm/LCF cycle for a combined LCF and HCF test at N* HCF about 20 000. A surface wedging model has been proposed to account for the HCF crack growth in the coating systems. This mechanism predicts that the HCF damage effect increases with heat flux and thus with increasing surface temperature swing, thermal expansion coefficient and elastic modulus of the ceramic coating, as well as with the HCF interacting depth. Good correlation has been found between the analysis and experimental evidence. (orig.)

Mixed convection boundary layer flow over a vertical surface embedded in a thermally stratified porous medium

International Nuclear Information System (INIS)

Ishak, Anuar; Nazar, Roslinda; Pop, Ioan

2008-01-01

The mixed convection boundary layer flow through a stable stratified porous medium bounded by a vertical surface is investigated. The external velocity and the surface temperature are assumed to vary as x m , where x is measured from the leading edge of the vertical surface and m is a constant. Numerical solutions for the governing Darcy and energy equations are obtained. The results indicate that the thermal stratification significantly affects the surface shear stress as well as the surface heat transfer, besides delays the boundary layer separation

An investigation of the effects of droplet impact angle in thermal spray deposition

International Nuclear Information System (INIS)

Smith, M.F.; Neiser, R.A.; Dykhuizen, R.C.

1994-01-01

It is widely held that spraying at off-normal angles can influence deposition efficiency and the properties of the deposited material. However, little quantitative information on such effects has been published. This paper reports on a series of experiments to investigate the angular dependence of deposition efficiency, surface roughness, and porosity for several thermal spray materials and processes at incidence angles ranging from 90 degree to 30 degree relative to the substrate surface. At incidence angles from 90 degree out to 60 degree, the observed changes were small and often statistically insignificant. Some significant changes began to appear at 45 degree, and at 30 degree significant changes were observed for nearly all materials and processes: deposition efficiency decreased while surface roughness and porosity increased. It is proposed that droplet splashing may cause some of the observed effects

Thermal effect of lubricating oil in positive-displacement air compressors

International Nuclear Information System (INIS)

Valenti, Gianluca; Colombo, Luigi; Murgia, Stefano; Lucchini, Andrea; Sampietro, Andrea; Capoferri, Andrea; Araneo, Lucio

2013-01-01

The isentropic efficiency of positive-displacement compressors may be improved in order to follow an increasing demand for energy savings. This work analyzes the thermal effect of the lubricating oil presence in the air during compression with the scope of exploiting it as a thermal ballast to mitigate both the gas temperature rise and its compression work. The bibliographic review shows that other authors suggested that oil can have positive effects if properly injected. Here an energy balance analysis is executed with the scope of deriving relations for the gas–liquid compression in analogy with those typical for the gas-only compression and of confirming that ideally the liquid presence may have beneficial effects, making the gas–liquid compression even better than 1- and 2-time intercooled gas compressions. Given these positive results, a heat transfer analysis is conducted to model the thermal interaction between gas and oil droplets within a mid-size rotary vane air compressor. A droplet diameter of the order of 100 μm leads to large reductions of both temperature increase and compression work: air can exit the discharge port at a temperature as low as 60 °C and compression work can be lowered by 23–28% with respect to conventional compressors. Finally, a test rig is constructed and operated to investigate a large-flow and large-angle oil nozzle taken from the market showing that, at the operating conditions of a compressor, oil breaks up into small droplets and undefined structures with large exchange surfaces. -- Highlights: ► Exploitation of thermal effect of oil in gas compressors is assessed numerically. ► Oil in 100 μm-diameter droplets mitigates effectively the gas temperature rise. ► Discharge temperature and compression work result to be much smaller than typical. ► An experimental setup is used to investigate oil atomization via commercial nozzles. ► A tested nozzle creates fine oil droplets and structures at conditions of

Surface reflectance drives nest box temperature profiles and thermal suitability for target wildlife.

Directory of Open Access Journals (Sweden)

Stephen R Griffiths

Full Text Available Thermal properties of tree hollows play a major role in survival and reproduction of hollow-dependent fauna. Artificial hollows (nest boxes are increasingly being used to supplement the loss of natural hollows; however, the factors that drive nest box thermal profiles have received surprisingly little attention. We investigated how differences in surface reflectance influenced temperature profiles of nest boxes painted three different colors (dark-green, light-green, and white: total solar reflectance 5.9%, 64.4%, and 90.3% respectively using boxes designed for three groups of mammals: insectivorous bats, marsupial gliders and brushtail possums. Across the three different box designs, dark-green (low reflectance boxes experienced the highest average and maximum daytime temperatures, had the greatest magnitude of variation in daytime temperatures within the box, and were consistently substantially warmer than light-green boxes (medium reflectance, white boxes (high reflectance, and ambient air temperatures. Results from biophysical model simulations demonstrated that variation in diurnal temperature profiles generated by painting boxes either high or low reflectance colors could have significant ecophysiological consequences for animals occupying boxes, with animals in dark-green boxes at high risk of acute heat-stress and dehydration during extreme heat events. Conversely in cold weather, our modelling indicated that there are higher cumulative energy costs for mammals, particularly smaller animals, occupying light-green boxes. Given their widespread use as a conservation tool, we suggest that before boxes are installed, consideration should be given to the effect of color on nest box temperature profiles, and the resultant thermal suitability of boxes for wildlife, particularly during extremes in weather. Managers of nest box programs should consider using several different colors and installing boxes across a range of both orientations and

A Novel Nonintrusive Method to Resolve the Thermal Dome Effect of Pyranometers: Radiometric Calibration and Implications

Science.gov (United States)

Ji. Q.; Tsay, S.-C.; Lau, K. M.; Hansell, R. A.; Butler, J. J.; Cooper, J. W.

2011-01-01

Traditionally the calibration equation for pyranometers assumes that the measured solar irradiance is solely proportional to the thermopile s output voltage; therefore, only a single calibration factor is derived. This causes additional measurement uncertainties because it does not capture sufficient information to correctly account for a pyranometer s thermal effect. In our updated calibration equation, temperatures from the pyranometer's dome and case are incorporated to describe the instrument's thermal behavior, and a new set of calibration constants are determined, thereby reducing measurement uncertainties. In this paper, we demonstrate why a pyranometer's uncertainty using the traditional calibration equation is always larger than a few percent, but with the new approach can become much less than 1% after the thermal issue is resolved. The highlighted calibration results are based on NIST traceable light sources under controlled laboratory conditions. The significance of the new approach lends itself to not only avoiding the uncertainty caused by a pyranometer's thermal effect but also the opportunity to better isolate and characterize other instrumental artifacts, such as angular response and nonlinearity of the thermopile, to further reduce additional uncertainties. We also discuss some of the implications, including an example of how the thermal issue can potentially impact climate studies by evaluating aerosol s direct radiative effect using field measurements with and without considering the pyranometer s thermal effect. The results of radiative transfer model simulation show that a pyranometer s thermal effect on solar irradiance measurements at the surface can be translated into a significant alteration of the calculated distribution of solar energy inside the column atmosphere.

Thermal protection system gap analysis using a loosely coupled fluid-structural thermal numerical method

Science.gov (United States)

Huang, Jie; Li, Piao; Yao, Weixing

2018-05-01

A loosely coupled fluid-structural thermal numerical method is introduced for the thermal protection system (TPS) gap thermal control analysis in this paper. The aerodynamic heating and structural thermal are analyzed by computational fluid dynamics (CFD) and numerical heat transfer (NHT) methods respectively. An interpolation algorithm based on the control surface is adopted for the data exchanges on the coupled surface. In order to verify the analysis precision of the loosely coupled method, a circular tube example was analyzed, and the wall temperature agrees well with the test result. TPS gap thermal control performance was studied by the loosely coupled method successfully. The gap heat flux is mainly distributed in the small region at the top of the gap which is the high temperature region. Besides, TPS gap temperature and the power of the active cooling system (CCS) calculated by the traditional uncoupled method are higher than that calculated by the coupled method obviously. The reason is that the uncoupled method doesn't consider the coupled effect between the aerodynamic heating and structural thermal, however the coupled method considers it, so TPS gap thermal control performance can be analyzed more accurately by the coupled method.

Point, surface and volumetric heat sources in the thermal modelling of selective laser melting

Science.gov (United States)

Yang, Yabin; Ayas, Can

2017-10-01

Selective laser melting (SLM) is a powder based additive manufacturing technique suitable for producing high precision metal parts. However, distortions and residual stresses within products arise during SLM because of the high temperature gradients created by the laser heating. Residual stresses limit the load resistance of the product and may even lead to fracture during the built process. It is therefore of paramount importance to predict the level of part distortion and residual stress as a function of SLM process parameters which requires a reliable thermal modelling of the SLM process. Consequently, a key question arises which is how to describe the laser source appropriately. Reasonable simplification of the laser representation is crucial for the computational efficiency of the thermal model of the SLM process. In this paper, first a semi-analytical thermal modelling approach is described. Subsequently, the laser heating is modelled using point, surface and volumetric sources, in order to compare the influence of different laser source geometries on the thermal history prediction of the thermal model. The present work provides guidelines on appropriate representation of the laser source in the thermal modelling of the SLM process.

Application of Terrestrial Laser Scanner with an Integrated Thermal Camera in Non-Destructive Evaluation of Concrete Surface of Hydrotechnical Objects

Directory of Open Access Journals (Sweden)

Kowalska Maria

2017-12-01

Full Text Available The authors present possible applications of thermal data as an additional source of information on an object’s behaviour during the technical assessment of the condition of a concrete surface. For the study one of the most recent propositions introduced by Zoller + Fröhlich company was used, which is an integration of a thermal camera with a terrestrial laser scanner. This solution enables an acquisition of geometric and spectral data on the surveyed object and also provides information on the surface’s temperature in the selected points. A section of the dam’s downstream concrete wall was selected as the subject of the study for which a number of scans were carried out and a number of thermal images were taken at different times of the day. The obtained thermal data was confronted with the acquired spectral information for the specified points. This made it possible to carry out broader analysis of the surface and an inspection of the revealed fissure. The thermal analysis of said fissure indicated that the temperature changes within it are slower, which may affect the way the concrete works and may require further elaboration by the appropriate experts. Through the integration of a thermal camera with a terrestrial laser scanner one can not only analyse changes of temperature in the discretely selected points but on the whole surface as well. Moreover, it is also possible to accurately determine the range and the area of the change affecting the surface. The authors note the limitations of the presented solution like, inter alia, the resolution of the thermal camera.

Effect of Air Gap Entrapped in Firefighter Protective Clothing on Thermal Resistance and Evaporative Resistance

Directory of Open Access Journals (Sweden)

He Hualing

2018-03-01

Full Text Available Heat and water vapor transfer behavior of thermal protective clothing is greatly influenced by the air gap entrapped in multilayer fabric system. In this study, a sweating hot plate method was used to investigate the effect of air gap position and size on thermal resistance and evaporative resistance of firefighter clothing under a range of ambient temperature and humidity. Results indicated that the presence of air gap in multilayer fabric system decreased heat and water vapor transfer abilities under normal wear. Moreover, the air gap position slightly influenced the thermal and evaporative performances of the firefighter clothing. In this study, the multilayer fabric system obtained the highest thermal resistance, when the air space was located at position B. Furthermore, the effect of ambient temperature on heat and water vapor transfer properties of the multilayer fabric system was also investigated in the presence of a specific air gap. It was indicated that ambient temperature did not influence the evaporative resistance of thermal protective clothing. A thermographic image was used to test the surface temperature of multilayer fabric system when an air gap was incorporated. These results suggested that a certain air gap entrapped in thermal protective clothing system could affect wear comfort.

Effects of heat transfer coefficient treatments on thermal shock fracture prediction for LWR fuel claddings in water quenching

International Nuclear Information System (INIS)

Lee, Youho; Lee, Jeong Ik; Cheon, Hee

2015-01-01

Accurate modeling of thermal shock induced stresses has become ever most important to emerging accident-tolerant ceramic cladding concepts, such as silicon carbide (SiC) and SiC coated zircaloy. Since fractures of ceramic (entirely ceramic or coated) occur by excessive tensile stresses with linear elasticity, modeling transient stress distribution in the material provides a direct indication of the structural integrity. Indeed, even for the current zircaloy cladding material, the oxide layer formed on the surface - where cracks starts to develop upon water quenching - essentially behaves as a brittle ceramic. Hence, enhanced understanding of thermal shock fracture of a brittle material would fundamentally contribute to safety of nuclear reactors for both the current fuel design and that of the coming future. Understanding thermal shock fracture of a brittle material requires heat transfer rate between the solid and the fluid for transient temperature fields of the solid, and structural response of the solid under the obtained transient temperature fields. In water quenching, a solid experiences dynamic time-varying heat transfer rates with phase changes of the fluid over a short quenching period. Yet, such a dynamic change of heat transfer rates during the water quenching transience has been overlooked in assessments of mechanisms, predictability, and uncertainties for thermal shock fracture. Rather, a time-constant heat transfer coefficient, named 'effective heat transfer coefficient' has become a conventional input to thermal shock fracture analysis. No single constant heat transfer could suffice to depict the actual stress evolution subject to dynamic heat transfer coefficient changes with fluid phase changes. Use of the surface temperature dependent heat transfer coefficient will remarkably increase predictability of thermal shock fracture of brittle materials and complete the picture of stress evolution in the quenched solid. The presented result

Quasi-Static Transient Thermal Stresses in an Elliptical Plate due to Sectional Heat Supply on the Curved Surfaces over the Upper Face

Directory of Open Access Journals (Sweden)

Lalsingh Khalsa

2018-01-01

Full Text Available This paper is an attempt to determine quasi-static thermal stresses in a thin elliptical plate which is subjected to transient temperature on the top face with zero temperature on the lower face and the homogeneous boundary condition of the third kind on the fixed elliptical curved surface. The solution to conductivity equation is elucidated by employing a classical method. The solution of stress components is achieved by using Goodier’s and Airy’s potential function involving the Mathieu and modified functions and their derivatives. The obtained numerical results are accurate enough for practical purposes, better understanding of the underlying elliptic object, and better estimates of the thermal effect on the thermoelastic problem. The conclusions emphasize the importance of better understanding of the underlying elliptic structure, improved understanding of its relationship to circular object profile, and better estimates of the thermal effect on the thermoelastic problem.

Thermal convection as a possible mechanism for the origin of polygonal structures on Pluto's surface

Science.gov (United States)

Vilella, Kenny; Deschamps, Frédéric

2017-05-01

High-resolution pictures of Pluto's surface obtained by the New Horizons spacecraft revealed, among other surface features, a large nitrogen ice glacier informally named Sputnik Planitia. The surface of this glacier is separated into a network of polygonal cells with a wavelength of ˜20-40 km. This network is similar to the convective patterns obtained under certain conditions by laboratory experiments, suggesting that it is the surface expression of thermal convection. Here we investigate the surface planform obtained for different convective systems in 3-D Cartesian geometry with different modes of heating and rheologies. We find that bottom heated systems, as assumed by previous studies, do not produce surface planforms consistent with the observed pattern. Alternatively, for a certain range of Rayleigh-Roberts number, RaH, a volumetrically heated system produces a surface planform similar to this pattern. We then combine scaling laws with values of RaH within its possible range to establish relationships between the critical parameters of Sputnik Planitia. In particular, our calculations indicate that the glacier thickness and the surface heat flux are in the ranges 2-10 km and 0.1-10 mW m-2, respectively. However, a difficulty is to identify a proper source of internal heating. We propose that the long-term variations of surface temperature caused by variations in Pluto's orbit over millions of years produces secular cooling equivalent to internal heating. We find that this source of heating is sufficient to trigger thermal convection, but additional investigations are needed to determine under which conditions it can produce surface patterns similar to those of Sputnik Planitia.

Environmental effects of thermal power plants

International Nuclear Information System (INIS)

Gerlitzky, M.; Friedrich, R.; Unger, H.

1986-02-01

Reviewing critically the present literature, the effects of thermal power plants on the environment are studied. At first, the loads of the different power plant types are compiled. With regard to the effects of emission reduction proceedings the pollutant emissions are quantified. The second chapter shows the effects on the ecological factors, which could be caused by the most important emission components of thermal power plants. Where it is possible, relations between immissions respectively depositions and their effects on climate, man, flora, fauna and materials will be given. This shows that many effects depend strongly on the local landscape, climate and use of natural resources. Therefore, it appears efficient to ascertain different load limits. The last chapter gives a suggestion for an ecological compatibility test (ECT) of thermal power plants. In modular form the ECT deals with the emission fields, waste heat, pollution burden of air and water, noise, loss of area and aesthetical aspects. Limits depending on local conditions and use of area will be discussed. (orig.) [de

Thermal-shock experiments with flawed clad cylinders

International Nuclear Information System (INIS)

Cheverton, R.D.; Bryson, J.W.; Alexander, D.J.

1989-01-01

The life expectancy of LWR pressure vessels is influenced by a reduction in fracture toughness that is the result of radiation damage. As the fracture toughness decreases, the probability of propagation of preexisting flaws (sharp, crack-like defects) in the wall of the vessel increases. The probability of propagation is also influenced by the type of loading condition and the type of flaws that might exist. A loading condition of particular concern is referred to as pressurized thermal shock (PTS), and a flaw of particular concern for PTS loading conditions is a shallow surface flaw. A sudden cooling (thermal shock) of the inner surface of the vessel results in relatively high tensile stresses and relatively low fracture toughness at the inner surface. In addition, the attenuation of the fast-neutron fluence also results in relatively low fracture toughness at the inner surface. Under some circumstances, this combination of high stress and low toughness at the inner surface makes it possible for very shallow surface flaws to propagate. The PTS issue has been under investigation for quite some time, but thus far possible beneficial effects, other than thermal resistance, of the cladding on the inner surface of the vessel have not been included in the analysis of flaw behavior. This document discusses this effect of cladding on surface flaws and crack propagation

Surface Composition of Trojan Asteroids from Thermal-Infrared Spectroscopy

Science.gov (United States)

Martin, A.; Emery, J. P.; Lindsay, S. S.

2017-12-01

Asteroid origins provide an effective means of constraining the events that dynamically shaped the solar system. Jupiter Trojan asteroids (hereafter Trojans) may help in determining the extent of radial mixing that occurred during giant planet migration. Previous studies aimed at characterizing surface composition show that Trojans have low albedo surfaces and fall into two distinct spectral groups the near infrared (NIR). Though, featureless in this spectral region, NIR spectra of Trojans either exhibit a red or less-red slope. Typically, red-sloped spectra are associated with organics, but it has been shown that Trojans are not host to much, if any, organic material. Instead, the red slope is likely due to anhydrous silicates. The thermal infrared (TIR) wavelength range has advantages for detecting silicates on low albedo asteroids such as Trojans. The 10 µm region exhibits strong features due to the Si-O fundamental molecular vibrations. We hypothesize that the two Trojan spectral groups have different compositions (silicate mineralogy). With TIR spectra from the Spitzer Space Telescope, we identify mineralogical features from the surface of 11 Trojan asteroids, five red and six less-red. Preliminary results from analysis of the 10 µm region indicate red-sloped Trojans have a higher spectral contrast compared to less-red-sloped Trojans. Fine-grain mixtures of crystalline pyroxene and olivine exhibit a 10 µm feature with sharp cutoffs between about 9 µm and 12 µm, which create a broad flat plateau. Amorphous phases, when present, smooth the sharp emission features, resulting in a dome-like shape. Further spectral analysis in the 10 µm, 18 µm, and 30 µm band region will be performed for a more robust analysis. If all Trojans come from the same region, it is expected that they share spectral and compositional characteristics. Therefore, if spectral analysis in the TIR reinforce the NIR spectral slope dichotomy, it is likely that Trojans were sourced from

Thermal effects and their compensation in Advanced Virgo

International Nuclear Information System (INIS)

Rocchi, A; Coccia, E; Fafone, V; Malvezzi, V; Minenkov, Y; Sperandio, L

2012-01-01

Thermal effects in the test masses of the gravitational waves interferometric detectors may result in a strong limitation to their operation and sensitivity. Already in initial LIGO and Virgo, these effects have been observed and required the installation of dedicated compensation systems. Based on CO 2 laser projectors, the thermal compensators heat the peripheral of the input test masses to reduce the lensing effect. In advanced detectors, the power circulating in the interferometer will increase, thus making thermal effects more relevant. In this paper, the concept of the compensation system for Advanced Virgo is described.

An atlast of XBT thermal structures and TOPEX/POSEIDON sea surface heights in the north Indian Ocean

Digital Repository Service at National Institute of Oceanography (India)

Gopalakrishna, V.V.; Ali, M.M.; Araligidad, N.; Shenoi, S.S.C.; Shum, C.K.; Yi, Y.

the Indian XBT Program were used to plot the sub-surface thermal structures of the Indian Ocean for 1993 to 2003. Since these in situ measurements are just along the ship tracks, sea surface height observations from the TOPEX altimeter were also plotted over...

Effects of kinematic hardening rules on thermal ratchetting analysis of cylinders subjected to cyclically moving temperature distribution

International Nuclear Information System (INIS)

Ohno, N.; Kobayashi, M.

1995-01-01

In the present work, thermal ratchetting in a cylinder subjected to a cyclically moving temperature front (i.e. liquid surface induced thermal ratchetting) was analyzed by implementing in a finite element method the four kinds of plasticity models with different kinematic hardening rules. The following findings were thus obtained concerning effects of the kinematic hardening rules on the analysis. (1) If transition nonlinear hardening after yielding is disregarded, the thermal ratchetting becomes significant, as seen in the results of the PP and LKH models. Especially the PP model, which does not express any strain hardening, predicts steady development of the thermal ratchetting. (2) If significant mechanical ratchetting is allowed in the modeling of kinematic hardening, the thermal ratchetting becomes marked, as seen in the results of the AF model. (3) Model dependence of the thermal ratchetting is more noticeable when the difference of temperature at the temperature front, ΔT, is smaller. (4) The OW model makes the thermal ratchetting stop at a smaller number of cycles when ΔT is smaller. On the other hand, the LKH and AF models allow that the thermal ratchetting to develop more constantly when ΔT is smaller. As seen from the above findings, the analysis of liquid surface induced thermal ratchetting has great dependence on the kinematic hardening rules employed. Especially the PP model, which has been used often to analyze the thermal ratchetting so far, gives too large development of the thermal ratchetting. Thus we may say that in order to improve the analysis it is necessary to use an appropriate kinematic hardening model which is capable of expressing appropriately both mechanical ratchetting and transient nonlinear hardening after yielding. (author)

Zirconium tungstate/epoxy nanocomposites: effect of nanoparticle morphology and negative thermal expansivity.

Science.gov (United States)

Wu, Hongchao; Rogalski, Mark; Kessler, Michael R

2013-10-09

The ability to tailor the coefficient of thermal expansion (CTE) of a polymer is essential for mitigating thermal residual stress and reducing microcracks caused by CTE mismatch of different components in electronic applications. This work studies the effect of morphology and thermal expansivity of zirconium tungstate nanoparticles on the rheological, thermo-mechanical, dynamic-mechanical, and dielectric properties of ZrW2O8/epoxy nanocomposites. Three types of ZrW2O8 nanoparticles were synthesized under different hydrothermal conditions and their distinct properties were characterized, including morphology, particle size, aspect ratio, surface area, and CTE. Nanoparticles with a smaller particle size and larger surface area led to a more significant reduction in gel-time and glass transition temperature of the epoxy nanocomposites, while a higher initial viscosity and significant shear thinning behavior was found in prepolymer suspensions containing ZrW2O8 with larger particle sizes and aspect ratios. The thermo- and dynamic-mechanical properties of epoxy-based nanocomposites improved with increasing loadings of the three types of ZrW2O8 nanoparticles. In addition, the introduced ZrW2O8 nanoparticles did not negatively affect the dielectric constant or the breakdown strength of the epoxy resin, suggesting potential applications of ZrW2O8/epoxy nanocomposites in the microelectronic insulation industry.

Effects of Magnetite Aggregate and Steel Powder on Thermal Conductivity and Porosity in Concrete for Nuclear Power Plant

Directory of Open Access Journals (Sweden)

Han-Seung Lee

2016-01-01

Full Text Available Among many engineering advantages in concrete, low thermal conductivity is an attractive property. Concrete has been widely used for nuclear vessels and plant facilities for its excellent radiation shielding. The heat isolation through low thermal conductivity is actually positive for nuclear power plant concrete; however the property may cause adverse effect when fires and melt-down occur in nuclear vessel since cooling down from outer surface is almost impossible due to very low thermal conductivity. If concrete containing atomic reactor has higher thermal conductivity, the explosion risk of conductive may be partially reduced. This paper presents high thermally conductive concrete development. For the work, magnetite with varying replacements of normal aggregates and steel powder of 1.5% of volume are considered, and the equivalent thermal conductivity is evaluated. Only when the replacement ratio goes up to 30%, thermal conductivity increases rapidly to 2.5 times. Addition of steel powder is evaluated to be effective by 1.08~1.15 times. In order to evaluate the improvement of thermal conductivity, several models like ACI, DEMM, and MEM are studied, and their results are compared with test results. In the present work, the effects of steel powder and magnetite aggregate are studied not only for strength development but also for thermal behavior based on porosity.

Comparison between alkali heat treatment and sprayed hydroxyapatite coating on thermally-sprayed rough Ti surface in rabbit model: Effects on bone-bonding ability and osteoconductivity.

Science.gov (United States)

Kawai, Toshiyuki; Takemoto, Mitsuru; Fujibayashi, Shunsuke; Tanaka, Masashi; Akiyama, Haruhiko; Nakamura, Takashi; Matsuda, Shuichi

2015-07-01

In this study, we investigated the effect of different surface treatments (hydroxyapatite (HA) coating, alkali heat treatment, and no treatment) on the ability of bone to bond to a rough arc-sprayed Ti metal surface, using rabbit models. The bone-to-implant contacts for untreated, HA-coated, and alkali heat-treated implants were 21.2%, 72.1%, and 33.8% at 4 weeks, 21.8%, 70.9%, and 30.0% at 8 weeks, and 16.3%, 70.2%, and 29.9% at 16 weeks, respectively (n = 8). HA -coated implants showed significantly higher bone-to-implant contacts than the untreated and alkali heat-treated implants at all the time point, whereas alkali heat-treated implants showed significantly higher bone-to-implant contacts than untreated implants at 4 and 16 weeks. The failure loads in a mechanical test for untreated, HA coated, alkali heat-treated plates were 65.4 N, 70.7 N, and 90.8 N at 4 weeks, 76.1 N, 64.7 N, and 104.8 N at 8 weeks and 88.7 N, 92.6 N, and 118.5 N at 16 weeks, respectively (n = 8). The alkali heat-treated plates showed significantly higher failure loads than HA-coated plates at 8 and 16 weeks. The difference between HA-coated plates and untreated plates were not statistically significant at any time point. Thus HA coating, although it enables high bone-to-implant contact, may not enhance the bone-bonding properties of thermally-sprayed rough Ti metal surfaces. In contrast, alkali heat treatment can be successfully applied to thermally-sprayed Ti metal to enhance both bone-to-implant contact and bone-bonding strength. © 2014 Wiley Periodicals, Inc.

Effective thermal conductivity of advanced ceramic breeder pebble beds

Energy Technology Data Exchange (ETDEWEB)

Pupeschi, S., E-mail: simone.pupeschi@kit.edu; Knitter, R.; Kamlah, M.

2017-03-15

As the knowledge of the effective thermal conductivity of ceramic breeder pebble beds under fusion relevant conditions is essential for the development of solid breeder blanket concepts, the EU advanced and reference lithium orthosilicate material were investigated with a newly developed experimental setup based on the transient hot wire method. The effective thermal conductivity was investigated in the temperature range RT–700 °C. Experiments were performed in helium and air atmospheres in the pressure range 0.12–0.4 MPa (abs.) under a compressive load up to 6 MPa. Results show a negligible influence of the chemical composition of the solid material on the bed’s effective thermal conductivity. A severe reduction of the effective thermal conductivity was observed in air. In both atmospheres an increase of the effective thermal conductivity with the temperature was detected, while the influence of the compressive load was found to be small. A clear dependence of the effective thermal conductivity on the pressure of the filling gas was observed in helium in contrast to air, where the pressure dependence was drastically reduced.

Thermal effect of Zn quantum dots grown on Si(111): competition between relaxation and reconstraint

Science.gov (United States)

Kao, Li-Chi; Huang, Bo-Jia; Zheng, Yu-En; Tu, Kai-Teng; Chiu, Shang-Jui; Ku, Ching-Shun; Lo, Kuang Yao

2018-01-01

Zn dots are potential solutions for metal contacts in future nanodevices. The metastable states that exist at the interface between Zn quantum dots and oxide-free Si(111) surfaces can suppress the development of the complete relaxation and increase the size of Zn dots. In this work, the actual heat consumption of the structural evolution of Zn dots resulting from extrinsic thermal effect was analyzed. Zn dots were coherently grown on oxide-free Si(111) through magnetron RF sputtering. A compensative optical method combined with reflective second harmonic generation and synchrotron x-ray diffraction (XRD) was developed to statistically analyze the thermal effect on the Zn dot system. Pattern matching (3 m) between the Zn and oxide-free Si(111) surface enabled Si(111) to constrain Zn dots from a liquid to solid phase. Annealing under vacuum induced smaller, loose Zn dots to be reconstrained by Si(111). When the size of the Zn dots was in the margin of complete relaxation, the Zn dot was partially constrained by potential barriers (metastable states) between Zn(111) and one of the six in-planes of Si〈110〉. The thermal disturbance exerted by annealing would enable partially constrained ZnO/Zn dots to overcome the potential barrier and be completely relaxed, which is obvious on the transition between Zn(111) and Zn(002) peak in synchrotron XRD. Considering the actual irradiated surface area of dots array in a wide-size distribution, the competition between reconstrained and relaxed Zn dots on Si(111) during annealing was statistically analyzed.

Use of X-ray photoelectron spectroscopy to study radiation and thermal effects in polytetrafluoroethylene

International Nuclear Information System (INIS)

Wheeler, D.R.; Pepper, S.V.

1990-01-01

X-ray photoelectron spectroscopy of the surface and mass spectroscopy of the gas evolved during irradiation and subsequent heating of irradiated polytetrafluoroethylene (PTFE) indicated that the effect of electron irradiation was the same as that of x-irradiation. Saturated fluorocarbon gas was evolved during irradiation and a cross-linked or branched network formed in the surface region. Heating irradiated PTFE to temperatures below 200C resulted in the evolution of additional saturated fluorocarbon gas but no change in the surface. From 200C to 300C, lightly damaged PTFE did not change further, but severely damaged PTFE emitted unsaturated fluorocarbons while the surface underwent apparent partial recovery. These observations demonstrate the thermal instability of the irradiated PTFE surface and allow elaboration of the existing model of radiation damage in PTFE

Thermal inertia of eclipsing binary asteroids : the role of component shape

NARCIS (Netherlands)

Mueller, Michael; van de Weijgaert, Marlies

2015-01-01

Thermal inertia controls the temperature distribution on asteroid surfaces. This is of crucial importance to the Yarkovsky effect and for the planning of spacecraft operations on or near the surface. Additionally, thermal inertia is a sensitive indicator for regolith structure.A uniquely direct way

Measuring Thermal Characteristics of Urban Landscapes

Science.gov (United States)

Luvall, Jeffrey C.; Quattrochi, Dale A.; Rickman, Doug L.

1999-01-01

The additional heating of the air over the city is the result of the replacement of naturally vegetated surfaces with those composed of asphalt, concrete, rooftops and other man-made materials. The temperatures of these artificial surfaces can be 20 to 40 C higher than vegetated surfaces. Materials such as asphalt store much of the sun's energy and remains hot long after sunset. This produces a dome of elevated air temperatures 5 to 8 C greater over the city, compared to the air temperatures over adjacent rural areas. This effect is called the "urban heat island". Urban landscapes are a complex mixture of vegetated and nonvegetated surfaces. It is difficult to take enough temperature measurements over a large city area to characterize the complexity of urban radiant surface temperature variability. However, the use of remotely sensed thermal data from airborne scanners are ideal for the task. In a study funded by NASA, a series of flights over Huntsville, Alabama were performed in September 1994 and over Atlanta, Georgia in May 1997. Analysis of thermal energy responses for specific or discrete surfaces typical of the urban landscape (e.g., asphalt, building rooftops, vegetation) requires measurements at a very fine spatial scale (i.e., energy regimes. Additionally, very fine scale spatial resolution thermal infrared data, such as that obtained from aircraft, are very useful for demonstrating to planning officials, policy makers, and the general populace, what the benefits are of the urban forest in both mitigating the urban heat island effect, in making cities more aesthetically pleasing and more habitable environments, and in overall cooling of the community. In this presentation we will examine the techniques of analyzing remotely sensed data for measuring the effect of various urban surfaces on their contribution to the urban heat island effect.

Ion beam effects on the surface and near-surface composition of TaSi sub 2

Energy Technology Data Exchange (ETDEWEB)

Valeri, S.; Di Bona, A.; Ottaviani, G. (Dipt. di Fisica, Univ. di Modena (Italy)); Procop, M. (Zentralinstitut fuer Elektronenphysik, Berlin (Germany))

1991-07-01

Low-energy (0.7-4.5 keV) ion bombardment effects on polycrystalline TaSi{sub 2} at sputter steady state and in various intermediate steps have been investigated, in the temperature range up to 550degC, to determine the time and temperature dependence of the altered layer formation. This in turn enables a better knowledge of the synergistic effects of the processes mentioned above. At low temperatures (T{<=}410degC) the surface is silicon depleted, and the depletion is even more severe in the subsurface region up to a depth of several tens of angstroems; silicon preferential sputtering and radiation-enhanced segregation assisted by the displacement mixing-induced motion of atoms are assumed to be responsible for this composition profile, while thermally activated diffusion processes become operative above 410degC, reducing progressively the concentration gradient between the surface and the subsurface zone. The composition at different depths has been determined from Auger peaks for different kinetic energies, by varying the take-off angle and finally by sputter profiling at low in energy the high energy processed surfaces. Quantitative analysis has been performed by XPS and AES by using the elemental standard method. (orig.).