Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1021/acs.jpclett.9b00718

Repository Public URL： http://hdl.handle.net/2324/4787549

Language：English   Publishing type：Research paper (scientific journal)  

Thermal property measurement of individual micro- and nano-materials has been very challenging and the development of measurement methods is crucial for the experimental investigation of microscale and nanoscale heat transfer. Here we present a noncontact frequency-domain Raman method to measure thermal diffusivity of individual 1D microfibers and nanowires without the need of knowing laser absorptivity. Cosine-wave modulated laser is used to heat the sample, while the laser-intensity-weighted spatiotemporal average temperature is simultaneously detected from the sample's Raman band shift. Transient heat conduction models under periodic heating are established and analytically solved in the frequency domain with considerations of the Gaussian laser distribution and thermal contact resistance. By varying the laser modulation frequency as well as the laser spot size, we can eliminate the laser absorptivity by a normalization technique and extract the thermal diffusivity with high sensitivity. Typically, if the thermal diffusivity is on the order of 10 ⁻⁴ m ² /s, we need to use the modulation frequencies on the order of 10 Hz to measure millimeter long microfibers, and ∼MHz frequencies to measure micrometer long nanowires. We also demonstrate that any kind of periodic laser modulation can be decomposed to a series of cosine modes and readily analyzed by this frequency-domain approach, which can greatly broaden the applications of transient Raman techniques.

DOI： 10.1016/j.ijheatmasstransfer.2019.01.057

Repository Public URL： http://hdl.handle.net/2324/4377872

Language：English   Publishing type：Research paper (scientific journal)  

Thermal contact resistance (TCR) between individual carbon fibers (CFs) can dominate heat dissipation rates in CF-based composite materials. Here, we develop a totally non-contact “laser-flash Raman mapping” method to simultaneously measure the TCR at the CF-CF junction and their thermal conductivities. Laser power is used to heat the sample and the laser absorptivity is experimentally determined by a transient laser-flash Raman technique. The laser heating positions are changed along two connected CFs, and the change of temperature rise with varying positions is in-situ measured from the temperature dependent Raman band shifts. The high spatial resolution of the micro-Raman mapping allows direct observation of the abrupt jump of thermal resistance at the CF-CF junction, from which we extracted the TCR as well as the thermal conductivity. The laser absorptivity of the 11 μm-diameter CFs is measured to be 0.12 ± 0.03, the thermal conductivities of the individual CFs are around 200 W/mK, and the TCR of the CF-CF junction is (2.98 ± 0.92) × 10⁵ K/W. This work provides indispensable knowledge for the design of CF-based composite for thermal management, and the novel non-contact measurement method can stimulate characterization and manipulation of contact/interface heat conduction between various micro- and nano-materials.

DOI： 10.1016/j.carbon.2018.09.034

Repository Public URL： http://hdl.handle.net/2324/4377863

Language：English   Publishing type：Research paper (scientific journal)  

The last decade has seen the rapid growth of research on two-dimensional (2D) materials, represented by graphene, but research on their thermophysical properties is still far from sufficient owing to the experimental challenges. Herein, we report the first measurement of the specific heat of multilayer and monolayer graphene in both supported and suspended geometries. Their thermal conductivities were also simultaneously measured using a comprehensive Raman optothermal method without needing to know the laser absorption. Both continuous-wave (CW) and pulsed lasers were used to heat the samples, based on consideration of the variable laser spot radius and pulse duration as well as the heat conduction within the substrate. The error from the laser absorption was eliminated by comparing the Raman-measured temperature rises for different spot radii and pulse durations. The thermal conductivity and specific heat were extracted by analytically fitting the temperature rise ratios as a function of spot size and pulse duration, respectively. The measured specific heat was about 700 J (kg K)−1 at room temperature, which is in accordance with theoretical predictions, and the measured thermal conductivities were in the range of 0.84–1.5 × 103 W (m K)−1. The measurement method demonstrated here can be used to investigate in situ and comprehensively the thermophysical properties of many other emerging 2D materials.

Repository Public URL： http://hdl.handle.net/2324/4787543

Language：English   Publishing type：Research paper (scientific journal)  

2D nanomaterials have been attracting extensive research interests due to their superior properties and the accurate thermophysical characterization of 2D materials is very important for nanoscience and nanotechnology. This paper presents a transient "laser flash Raman spectroscopy" method for measuring the thermal diffusivity of 2D nanomaterials in the supported form without knowing the laser absorption coefficient. Square pulsed laser rather than continuous laser is used to heat the sample and the accumulated Raman signals are used to determine the time-averaged temperature rise of both the supported 2D material and the substrate. The laser absorption coefficient can be eliminated by comparing the temperature rises measured with different laser spot sizes and laser pulse durations. The method sensitivity is also analyzed by case studies for typical 2D nanomaterials. This method is useful for measuring the thermophysical properties of 2D materials in the most applicable forms and figuring out the difference between the supported and free-standing 2D material.

DOI： 10.1016/j.ijheatmasstransfer.2015.12.065

Repository Public URL： http://hdl.handle.net/2324/4787548

Language：English   Publishing type：Research paper (scientific journal)  

Thermophysical characterization of graphene is very important for both fundamental and technological research. While most of the existing thermal conductivity measurements are for graphene sheets with sizes larger than 1 μm, the thermal conductivities for suspended submicron graphene ribbons are still very few, although the thermal conductivity of graphene ribbons at the submicron scale is predicted to be much smaller than large graphene and strongly size dependent for both length and width due to the 2D nature of phonon transport. Here, we report the temperature dependent thermal conductivity of a 169-nm wide and 846-nm long graphene ribbon measured by the electrical self-heating method. The measured thermal conductivities range from (12.7 ± 2.95) W/m/K at 80 K to (932 ± 333) W/m/K at 380 K, being (349 ± 63) W/m/K at 300 K, following a ∼ T^2.79 law for the full temperature range of 80 K to 380 K and a ∼ T^1.23 law at low temperatures. The comparison of the measured thermal conductance with the ballistic transport limit indicates diffusive transport in this narrow and short ribbon due to phonon-edge as well as phonon-defect scattering. The data were also combined with an empirical model to predict possible width dependence of thermal conductivity for suspended graphene ribbons. These results help understand the 2D phonon transport in suspended submicron graphene ribbons and provide knowledge for controlling thermophysical properties of suspended graphene nanoribbons through size manipulation.

DOI： 10.1063/1.4907699

Repository Public URL： http://hdl.handle.net/2324/4354937

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1007/s10765-023-03209-y

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.ultramic.2023.113747

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.applthermaleng.2022.119821

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1007/s11630-022-1668-8

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1007/s11630-022-1670-1

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1007/s11630-022-1594-9

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.ijheatmasstransfer.2021.122001

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1021/acs.langmuir.1c01589

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1021/acsami.0c22814

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.ijheatmasstransfer.2021.121115

Other Link： https://www.sciencedirect.com/science/article/abs/pii/S0017931021002180

Repository Public URL： http://hdl.handle.net/2324/4363564

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.30919/esmm5f430

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1039/d0ra08861g

Language：English   Publishing type：Research paper (scientific journal)  

The rapid development in the synthesis and device fabrication of two-dimensional (2D) materials provides new opportunities for their wide applications in a variety of fields including thermoelectric energy conversion, thermal management, and thermal logics. As one important research direction, the possibly poor thermoelectric performance of the pristine 2D materials can be dramatically improved with patterned nanostructures, and stacking of different 2Ds to form layered heterostructures, as well as electrostatic gating, which allow the fine-tuning of both the quasi Fermi level and phonon transport. This article reviews the recent advancement in this direction, with an emphasis on both fundamental understanding and practical problems.

DOI： 10.30919/es8d1136

Other Link： https://www.espublisher.com/journals/articledetails/323

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1039/D0CP01719A

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1021/acsomega.0c01207

Language：English   Publishing type：Research paper (scientific journal)  

We report on the in situ thermal measurement of a carbon nanofiber (CNF) modified by focused ion beam (FIB) irradiation. The FIB irradiation led to local amorphization of the crystalline structure of the CNF. The in situ measurement was improved by correcting for the effect of the scattered ions on the sensor. The low effective thermal conductivity of the pristine CNF (∼39 W/mK) resulted from the anisotropic structure made of many individual graphitic fibers. The first FIB irradiation decreased the thermal conductivity by approximately 3.2%. This relatively small decrease is attributed to the structure of the CNF consisting of many individual fibers, with some fibers remaining pristine even after the FIB irradiation. Analysis using a thermal-circuit model suggested that the thermal transport in the CNF could include a ballistic feature of phonons in the micrometer range. Our proposed in situ thermal measurement method can be extended to the study of thermal transport in various structurally modified nanomaterials.

DOI： 10.1016/j.carbon.2019.07.056

Language：English   Publishing type：Research paper (scientific journal)  

We report a quasi-three-dimensional observation of electron-beam-induced nanobubbles inside a 1000 nm thick layer of water using the liquid cell electron microscopy. In the early stage of observation, heterogeneous bubble nucleation occurred, and small bubbles coalesced with the adjacent bubbles when they come in contact with each other. However, for the first time, we found that after prolonged electron beam irradiation heterogeneous nucleation did not occur more, and then homogeneous nucleation started even though a solid surface was available for heterogeneous nucleation. We conclude that the Ostwald ripening effect prevents heterogeneous nucleation from occurring and that the lower surface tension due to the generation of ions and radicals boosts the homogeneous nucleation. It was also discovered that the generation sites of homogeneous nucleation are beneath the three-phase contact lines of existing interfacial bubbles.

DOI： 10.1021/acs.jpcc.8b09200

Language：Others   Publishing type：Research paper (scientific journal)  

Nanoparticles are widely used in composite materials and nanoscale devices. Thus, characterization of the thermophysical properties of a single nanoparticle is of great importance for both nanotechnology and nanoscience applications. However, conventional measurement methods cannot be used to determine the thermophysical properties of a single nanoparticle. Due to their small size and small mass, the specific heat of a nanoparticle is extremely tiny. Thus, the temperature variations with time for a nanoparticle are very hard to measure by a contact sensor. Non-contact measurement methods are high speed measurements to resolve the temperature rise of the nanoparticle. However, there are no effective heat flux meters for non-contact measurements. Thus, the thermal parameters cannot be easily separated by non-contact measurement methods. This study characterizes the thermophysical properties of a single nanoparticle by combining non-contact measurement data with contact measurements to decouple the various parameters. The measurements combine a contact Joule heating method with a non-contact laser flash tip-enhanced Raman spectroscopy method to characterize the specific heat of a single nanoparticle. A contact probe is first used to heat the single nanoparticle with the heating power measured with and without contact with the nanoparticle to determine the effective heat transfer coefficient to the nanoparticle. A series of square laser pulses are used to heat the sample with the temperatures then measured by their Raman band shifts, which gives the temperature changes for a lumped parameter model. The tip-enhanced Raman spectroscopy method gives high spatial resolution. The laser light absorptivity of the nanoparticle is then eliminated by comparing the temperature rises measured using different laser pulse widths. The specific heat of the nanoparticle is then extracted by fitting the normalized temperature rise curves. The lumped model is shown to be accurate when Bi<0.11 and 1/Fo>1.2 for which the maximum temperature difference within the nanoparticle is less than 10%. The nanoparticle can then be regarded as a zero-dimensional model and the lumped model will give reasonable results. Simulations with typical nanoparticle properties show that the temperature measurements need to be faster with lower specific heats. For a 100 nm diameter nanoparticle with a specific heat of about 1×10 ² J/(kg K), the temperature rise will approach steady state within about 20 ns, so the smallest pulse width should be about 1 ns. However, for a specific heat on the order of 10 ³ J/(kg K), the smallest pulse width can be 10-50 ns. The influence of ignoring the temperature rise of the substrate is also discussed. Simulation of typical conditions shows that the nanoparticle temperature rise is about 10 ⁴ times the highest temperature rise of the substrate. Therefore, the temperature rise in the substrate can be neglected. Other possible difficulties of this method are also analyzed in this paper.

DOI： 10.1360/N972018-00294

Language：English   Publishing type：Research paper (scientific journal)  

Stacked layers of different atomically thin 2D materials is called the van der Waals (vdW) heterostructure, which has become a rapidly developing research field due to its extraordinary and tunable properties. In this paper, we develop a variable-spot-size laser-flash Raman method to in-situ measure the thermal properties as well as the laser absorption in the supported 2D vdW heterostructure with arbitrary layers. The extracted thermal properties include the in-plane thermal conductivity and diffusivity of each layer, and interfacial thermal conductance between every two adjacent layers. A three-dimensional transient heat conduction model is developed and analytically solved to describe the process of pulsed Gaussian laser heating supported n-layer heterostructure. The temperature of each atomic layer can be simultaneously non-contact detected from their distinct Raman peaks whose positions are temperature dependent. The laser spot sizes and pulse durations are varied to generate multiple temperature curves. The multiple thermal properties as well as the laser absorption can be extracted by simultaneously fitting these temperature curves into the analytical solutions at multiple spot sizes or/and pulse durations. We also establish the approach of sensitivity and uncertainty analysis for the multi-response multi-parameter least-square fitting in our proposed measurement methods. Case studies show that the transient temperature curves are generally more sensitive to the thermal properties than the steady-state temperatures at variable spot sizes. All the unknown thermal properties and laser absorption can be extracted with sufficiently high accuracy if multiple transient temperature curves at multiple spot sizes are simultaneously fitted into the analytical solution. The measurement method and uncertainty analysis approach presented here are useful for investigating the thermal transport in the emerging 2D materials and vdW heterostructures.

DOI： 10.1016/j.ijheatmasstransfer.2018.05.011

Repository Public URL： http://hdl.handle.net/2324/4377871

Language：English   Publishing type：Research paper (scientific journal)  

Two-dimensional (2D) layered materials have been the focus of materials research for more than a decade. Stacking different 2D nanosheets and 3D substrates with van der Waals interactions in between has opened up new ways to sophisticated design of novel device functionalities and platforms for new physics. The performance of van der Waals heterostructure (vdWH) devices can be most often limited by the heat dissipation issue, but the thermal transport in vdWHs has rarely been studied yet. This paper presents a novel heater assisted Raman method to accurately measure interfacial thermal conductance between every two layers in the vdWH, which is suitable to detect interfacial thermal transport between all kinds of nanosheets no matter whether the neighboring layer is electrical conductor or insulator. In this method, a transparent insulating thin layer and a patterned transparent conducting indium-tin-oxide (ITO) layer are successively sputtered on top of the vdWH. The ITO layer is electrically heated to provide vertical heat flux, while the temperatures of each atomic layer and the substrate surface are simultaneously detected from their temperature dependent Raman band shifts, thus the interfacial thermal conductance between every two layers can be accurately determined from the ITO's Joule heating power and the Raman-measured temperatures. With high sensitivity and accuracy, the measurement method proposed here provides a general way to experimentally investigate interfacial thermal transport across both electrically conducting and insulating van der Waals interfaces in 2D-material-based devices.

DOI： 10.1615/ihtc16.nmt.021756

Language：Others   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1103/PhysRevLett.119.179601

Repository Public URL： http://hdl.handle.net/2324/4355058

Language：English   Publishing type：Research paper (scientific journal)  

Metallic nanofilms are important components of nanoscale electronic circuits and nanoscale sensors. The accurate characterization of the thermophysical properties of nanofilms is very important for nanoscience and nanotechnology. Currently, there is very little specific heat data for metallic nanofilms, and the existing measurements indicate distinct differences according to the nanofilm size. The present work reports the specific heats of 40-nm-thick suspended platinum nanofilms at 80-380 K and ∼5�10^-4 Pa using the 3ω method. Over 80-380 K, the specific heats of the Pt nanofilms range from 166-304 J/(kg•K), which are 1.65-2.60 times the bulk values, indicating significant size effects. These results are useful for both scientific research in nanoscale thermophysics and evaluating the transient thermal response of nanoscale devices.

DOI： 10.1088/1674-1056/25/11/114401

Repository Public URL： http://hdl.handle.net/2324/4787547

Language：English   Publishing type：Research paper (scientific journal)  

Recently, a noncontact technique based on the temperature dependent Raman band shift has been applied for thermophysical characterization of low dimensional nanomaterials. However, the difficulty of accurately determining the laser absorption significantly limits the accuracy of this Raman technique. This paper presents a transient "laser flash Raman spectroscopy" method to characterize the thermal diffusivity, thermal conductivity and thermal contact resistance of 2D nanomaterials and the laser absorption can be easily eliminated by a normalization technique. The thermophysical properties can be determined by fitting the curves of the normalized temperature rise versus the laser heating time for various laser spot radii. Moreover, if the thermal contact resistance is neglected, the data analysis process is much more convenient and the relative error caused by neglecting the thermal contact resistance is only 1%.

DOI： 10.1016/j.tca.2014.08.011

Language：English   Publishing type：Research paper (scientific journal)  

The accurate thermal property characterization of micro/nano fibers is crucial for precise micro/nano technology. We developed a non-contact T-type Raman spectroscopy method for combined determination of micro/nano fibers' laser absorption, thermal conductivity and air heat transfer coefficient. The accuracy of laser absorption measurement is independent of the fiber properties or thermal contact resistance. When determining the thermal conductivity, the thermal contact resistance can be easily eliminated. Moreover, the air heat transfer coefficient is determined based on the accurate laser absorption and thermal conductivity data of the same sample. Case studies show that this method is sensitive and accurate for micro/nano fiber characterization.

DOI： 10.1016/j.tca.2014.01.023

Language：English   Publishing type：Research paper (scientific journal)  

Prediction of CO₂ leakage into biosphere is very important for risk assessment in geological carbon storage projects. Underground CO₂ can be transported into biosphere through short term leakage due to fractures of wellbores or cap rocks, which has been extensively investigated, and long term leakage due to diffusion, which has few relevant studies. This paper presents a diffusive model for CO₂ gradual leakage into biosphere during a long period after CO₂ injection. First, the paper describes a general diffusive model with long term secondary trapping effects for CO₂ fluxes from underground into biosphere. Secondly, a simplified one-dimensional model is presented and solved for the CO₂ concentrations in groundwater. The results show that the groundwater CO₂ concentration will reach the maximum value at about 50th year after CO₂ injection and then slowly decrease due to secondary trapping effects. Moreover, the partition coefficient is the dominant parameter for predicting the groundwater CO₂ concentration while the convective mass transfer coefficient plays an insignificant role.

DOI： 10.1007/s11434-014-0506-0

Language：English   Publishing type：Research paper (scientific journal)  

Viscosity measurement of supercritical fluids is very important for industry applications. We developed a non-contact optical method for determining supercritical fluids' viscosity based on the pressure dependence of fluids' Raman spectra and Poiseuille flow principles. Firstly, we investigated the pressure dependence of Raman spectra for methane mixtures and carbon dioxide mixtures. We can use Raman spectra to accurately obtain the total pressure of methane mixtures, but the Raman spectra method for determining the total pressure of carbon dioxide mixtures needs further investigation. Further, we theoretically designed the measurement system and analyzed the sensitivity of the method. The measurement system consists of gas tanks, a pressure-controlling high pressure syringe pump, a temperature controlling plate, a capillary tube array plate and a Raman spectrometer. The pressures vary significantly between the inlet and outlet of the capillary tube array and this method is very sensitive for measuring viscosity of methane mixtures.

Language：English   Publishing type：Research paper (scientific journal)  

Optical absorptance is an important property of carbon nanotubes for practical applications but has rarely been accurately measured. We developed a T type thermal probe method to measure the optical absorptance of an individual multiwall carbon nanotube. In this method, one end of the carbon nanotube (CNT) is attached to the center of a platinum nanofilm in a T shape and the Pt nanofilm acts as a thermometer. A laser beam irradiates at the CNT and the absorbed laser power can be determined by measuring the average temperature rise of the Pt nanofilm based on the temperature dependence of the electric resistance. Experimental results showed that a 100-nm-diameter multiwall CNT could absorb 13.2% of the 514-nm-wavelength laser power with the laser spot diameter being 1 μm. This method is useful for determining the optical absorptance of CNTs and other one-dimensional nanostructures such as Si/Ge nanowires for various optical wavelengths in their photovoltaic, photoelectrolysis and other optical applications.

DOI： 10.1063/1.4824494

Language：English   Publishing type：Research paper (scientific journal)  

Utilization of wind and solar energies coupled with heat pumps is a promising technology for energy conservation and emission reduction. This paper describes a rooftop wind solar hybrid heat pump system for building hot water, heating and cooling loads and presents energy and exergy analyses as well as an environmental benefit assessment. The system consists of a shrouded wind-lens turbine subsystem, a flat-plate solar thermal subsystem and a water/air source heat pump subsystem, where the wind and solar subsystems are compactly installed on the rooftop. The solar collector heats water for supplying domestic hot water and increasing the heat pump evaporation temperature for room heating. Heat pumps are used for room heating and cooling and auxiliary heating domestic hot water. Wind power contributes to satisfying the heat pump power demand. Energy and exergy analyses show that the solar thermal subsystem is exergetically inefficient and thus a better design of the solar collector can improve the system exergy efficiency. Wind power can provide 7.6% of the yearly heat pump power demand to satisfy the thermal loads of a 198 m² residential building in Beijing. The system can yearly reduce 31.3% carbon dioxide emission compared with conventional energy systems.

DOI： 10.1016/j.enbuild.2013.05.048

Language：English   Publishing type：Research paper (scientific journal)  

The flat-plate solar collector is an important component in solar-thermal systems, and its heat transfer optimization is of great significance in terms of the efficiency of energy utilization. However, most existing flat-plate collectors adopt metallic absorber plates with uniform thickness, which often works against energy conservation. In this paper, to achieve the optimal heat transfer performance, we optimized the thickness distribution of the absorber with the constraint of fixed total material volume employing entransy theory. We first established the correspondence between the collector efficiency and the loss of entransy, and then proposed the constrained extreme-value problem and deduced the optimization criterion, namely a uniform temperature gradient, employing a variational method. Finally, on the basis of the optimization criterion, we carried out numerical simulations, with the results showing remarkable optimization effects. When irradiation, the ambient temperature and the wind speed are 800 W/m ², 300 K and 3 m/s, respectively, the collector efficiency is enhanced by 8.8% through optimization, which is equivalent to a copper saving of 30%. We also applied the thickness distribution optimized for wind speed of 3 m/s in heat transfer analysis with different wind speed conditions, and the collector efficiency was remarkably better than that for an absorber with uniform thickness.

DOI： 10.1007/s11434-011-4811-6

Event date： 2021.4

Language：English   Presentation type：Oral presentation (general)  

Venue：Online   Country：China  

Event date： 2021.4

Language：English  

Country：Japan  

Event date： 2020.6

Language：English  

Country：China  

Event date： 2020.6

Language：Japanese  

Country：Japan  

Event date： 2020.6

Language：English  

Country：United Kingdom  

Event date： 2020.6

Language：English  

Country：China  

Event date： 2020.6

Language：English  

Country：Japan  

Event date： 2020.6

Language：English  

Country：China  

Event date： 2020.6

Language：English  

Country：Japan  

Event date： 2019.6

Language：Japanese   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2019.6

Language：English   Presentation type：Oral presentation (general)  

Venue：Beijing   Country：China  

Event date： 2019.6

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：名古屋   Country：Japan  

Event date： 2019.6

Language：English   Presentation type：Oral presentation (general)  

Venue：Levi, Lapland   Country：Finland  

Event date： 2019.6

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：仙台   Country：Japan  

Event date： 2019.6

Language：English   Presentation type：Oral presentation (general)  

Venue：Qingdao   Country：China  

Event date： 2016.1

Language：English  

Venue：Biopolis   Country：Singapore  

2D nanomaterials have been attracting extensive research interests due to their superior properties and the accurate thermophysical characterization of 2D materials is very important for nanoscience and nanotechnology. Recently, a noncontact technique based on the temperature dependent Raman band shifts has been used to measure the thermal conductivity of 2D materials. However, the heat flux, i.e. the absorbed laser power, was either theoretically estimated or measured by a laser power meter with uncertainty, resulting in large errors in thermal conductivity determination. This paper presents a transient "laser flash Raman spectroscopy" method for measuring the thermal diffusivity of 2D nanomaterials in both the suspended and supported forms without knowing laser absorption. Square pulsed laser instead of continuous laser is used to heat the sample and the laser absorption can be eliminated by comparing the measured temperature rises for different laser heating time and laser spot radii. This method is sensitive for characterizing typical 2D materials and useful for nanoscale heat transfer research.

Language：English  

Country：Other  

Language：English  

Country：Other  

Language：English  

Country：Other  

For supercritical fluids, viscosity determination is difficult by contact sensors because contact sensors may be affected by the high pressure, high temperature and distinctive properties of supercritical fluids. In this paper, a non-contact method is presented for determining viscosity of supercritical fluids based on the linear pressure dependence of fluid Raman spectra and the principles of laminar flow in rectangular micro channels. The pressure drop along a micro channel can be determined by mapping the Raman spectra along the channel and the flow rate can be simultaneously determined by mapping the pressures at adjacent locations with different cross areas based on the Bernoulli equation for gases. Thus, the fluid viscosity can be determined combined with the pressure drop and the flow rate. Cases of methane, carbon dioxide and hydrogen at various pressures and temperatures are simulated to analyze the sensitivity and uncertainty of this method. The total viscosity uncertainty for methane at 300 K and 10 MPa is 2.9%. The viscosity uncertainties for carbon dioxide at 313.15 K, 9 MPa and 313.15 K, 12 MPa are respectively estimated as 2.1% and 9.7%. For hydrogen, this method is most suitable at low temperatures. The viscosity uncertainty for hydrogen at 85 K and 5 MPa is 1.84% and increases to 24.1% at 315 K and 15 MPa. This Raman spectra method still remains to be experimentally validated.

Language：English  

Country：Other  

Language：English  

Country：Other  

Language：English  

Country：Other  

Language：Japanese  

Country：Other  

Language：English  

Country：Other  

Language：Japanese  

Country：Other  

Language：Japanese  

Country：Other  

Type：Competition, symposium, etc. 

Type：Competition, symposium, etc. 

Type：Competition, symposium, etc. 

Type：Academic society, research group, etc. 

Type：Competition, symposium, etc. 

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Type：Competition, symposium, etc. 

Number of participants：500

Type：Academic society, research group, etc. 

Type：Academic society, research group, etc. 

Type：Peer review 

Number of peer-reviewed articles in foreign language journals：7

Type：Competition, symposium, etc. 

Type：Peer review 

Number of peer-reviewed articles in foreign language journals：5

Type：Competition, symposium, etc. 

Type：Peer review 

Number of peer-reviewed articles in foreign language journals：6

Proceedings of International Conference Number of peer-reviewed papers：10

Type：Competition, symposium, etc. 

Type：Peer review 

Number of peer-reviewed articles in foreign language journals：5

Number of peer-reviewed articles in Japanese journals：0

Proceedings of International Conference Number of peer-reviewed papers：10

Proceedings of domestic conference Number of peer-reviewed papers：0