九州大学-研究者情報 [李秦宜 (准教授) 工学研究院航空宇宙工学部門]

李秦宜（りちんい）

データ更新日：2024.04.23

准教授　／　工学研究院航空宇宙工学部門航空宇宙熱・流体力学講座

原著論文

1.	Naoya Sakoda, Qin-Yi Li, Editor’s Preface for the Special Issue on Asian Thermophysical Properties Conference (ATPC2022), International Journal of Thermophysics, 10.1007/s10765-023-03209-y, 44, 7, 100, 2023.05.
2.	Sota Hirokawa, Hideaki Teshima, Pablo Solís-Fernández, Hiroki Ago, Qin-Yi Li, Koji Takahashi, Random but limited pressure of graphene liquid cells, Ultramicroscopy, 10.1016/j.ultramic.2023.113747, 250, 113747, 2023.04.
3.	Jiajun Zhang, Xiaoling Wu, Dan Zhou, Qin-Yi Li, Xinxi Li, Kai Chen, Experimental and numerical investigation on efficient optimization of battery thermal management systems, Applied Thermal Engineering, 10.1016/j.applthermaleng.2022.119821, 221, 119821, 2022.12.
4.	Dawei Li, Qin-Yi Li, Koji Takahashi, Thermal resistance mapping along a single cup-stacked carbon nanotube with focused electron beam heating, International Journal of Heat and Mass Transfer, 10.1016/j.ijheatmasstransfer.2022.123418, 198, 123418, 2022.09, The structural non-uniformity in low-dimensional materials, including interfaces and defects, makes it highly desirable to map the thermal property distribution with a high spatial resolution. Meanwhile, eliminating the error of thermal contact resistance at the sample-sensor junction has remained a critical challenge in nanoscale thermal conductivity measurement. Here, we combine the electron beam (EB) heating with two suspended line-shaped heat flux sensors and have achieved the in-situ thermal resistance mapping along a single cup-stacked carbon nanotube (CNT) in a scanning electron microscope (SEM). The CNT is anchored between the two suspended metal lines, and the focused electron beam heats the CNT locally with a nanometer-range spatial resolution, while the two metal lines simultaneously measure the heat fluxes induced by the EB heating. By sweeping the focused EB along the CNT, we can obtain the spatially resolved thermal resistance, from which the true thermal conductivity of the CNT was extracted to be around 40 W/m·K without the thermal contact resistance error. This SEM-based in-situ thermal measurement method can accelerate high-resolution nanomaterials characterization and the elucidation of nanoscale heat transfer..
5.	Kuan-Ting Chen, Qin-Yi Li, Koji Takahashi, Slip Flow on Graphene: Current Status and Perspective, Journal of Thermal Science, 10.1007/s11630-022-1668-8, 31, 4, 1115-1134, 2022.07.
6.	Weigang Ma, Tengfei Luo, Hua Bao, Tingting Miao, Qin-Yi Li, Special Issue on Nano/Microscale Heat Transfer, Journal of Thermal Science, 10.1007/s11630-022-1670-1, 31, 4, 975-975, 2022.07.
7.	Ryo Abe, Yuki Sekimoto, Shirkant Saini, Koji Miyazaki, Qinyi Li, Dawei Li, Koji Takahashi, Takashi Yagi, Masakazu Nakamura, Round Robin Study on the Thermal Conductivity/Diffusivity of a Gold Wire with a Diameter of 30 μm Tested via Five Measurement Methods, Journal of Thermal Science, 10.1007/s11630-022-1594-9, 2022.05, [URL].
8.	Li, Dawei; Li, Qin-Yi; Ikuta, Tatsuya; Takahashi, Koji, Concurrent thermal conductivity measurement and internal structure observation of individual one-dimensional materials using scanning transmission electron microscopy, APPLIED PHYSICS LETTERS, 10.1063/5.0079153, 120, 4, 2022.01, The thermal conductivity of individual nanomaterials can vary from sample to sample due to the difference in geometries and internal structures, and thus, concurrent structure observation and thermal conductivity measurement at the nanoscale are highly desired but challenging. Here, we have developed an experimental method that allows concurrently the in situ thermal conductivity measurement and the real-time internal structure observation of a single one-dimensional (1D) material using scanning transmission electron microscopy (STEM) in a scanning electron microscope. In this method, the two ends of the 1D nanomaterial are bonded on a tungsten probe and a suspended platinum nanofilm, respectively. The platinum nanofilm serves simultaneously as a heater and a resistance thermometer, ensuring highly sensitive thermal measurements. The platinum nanofilm is fabricated on the edge of the silicon wafer so that the electron beam can transmit through the 1D material and be detected by the STEM detector, which caters for real-time observation of the inner nanostructure. Using this method, we in situ measured the thermal conductivities of two cup-stacked carbon nanotubes and concurrently observed the internal hollow structures. We found that the sample with more structural disorders had a lower thermal conductivity. Our measurement method can pave the way to the sample-by-sample elucidation of the structure–property relationship for 1D materials..
9.	Chen, Kuan-Ting; Li, Qin-Yi; Omori, Takeshi; Yamaguchi, Yasutaka; Ikuta, Tatsuya; Takahashi, Koji, Slip length measurement in rectangular graphene nanochannels with a 3D flow analysis, CARBON, 10.1016/j.carbon.2021.12.048, 189, 162-172, 2021.12, Although many molecular dynamics simulations have been conducted on slip flow on graphene, experimental efforts remain very limited and our understanding of the flow friction on graphene remains far from sufficient. Here, to accurately measure the slip length in rectangular nanochannels, we develop a 3D capillary flow model that fully considers the nonuniform cross-section velocity profile, slip boundary conditions, and the dynamic contact angle. We show that the 3D analysis is necessary even for a channel with a width/height ratio of 100. We fabricated graphene nanochannels with 45-nm depth and 5-μm width, and measured slip lengths of about 30–40 nm using this 3D flow model. We also reevaluated the slip-length data for graphene obtained from capillary filling experiments in the literature: 30 nm instead of originally claimed 45 nm for a 25-nm-deep channel, and 47 nm instead of 60 nm for an 8.5-nm-deep channel. We discover a smaller slip length than existing experimental measurements due to our full 3D flow analysis considered in our method. This work presents a rigorous analysis approach while also providing a better understanding of slip flow in graphene nanochannels, which will benefit further innovation in nanofluidic applications, including electronics cooling and biomedical chips..
10.	Ryota Kimura, Hideaki Teshima, Qin-Yi Li, Koji Takahashi, Thermally induced mass transfer between nanobubbles and micropancakes, INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER, 10.1016/j.ijheatmasstransfer.2021.122001, 181, 2021.12.
11.	Sota Hirokawa, Hideaki Teshima, Pablo Solís-Fernández, Hiroki Ago, Qin-Yi Li, Koji Takahashi, Pinning in a Contact and Noncontact Manner: Direct Observation of a Three-Phase Contact Line Using Graphene Liquid Cells, LANGMUIR, 10.1021/acs.langmuir.1c01589, 37, 42, 12271-12277, 2021.10.
12.	Si Wu, Tingxian Li, Minqiang Wu, Jiaxing Xu, Jingwei Chao, Yihao Hu, Taisen Yan, Qin-Yi Li, Ruzhu Wang, Dual-Functional Aligned and Interconnected Graphite Nanoplatelet Networks for Accelerating Solar Thermal Energy Harvesting and Storage within Phase Change Materials, ACS APPLIED MATERIALS & INTERFACES, 10.1021/acsami.0c22814, 13, 16, 19200-19210, 2021.04.
13.	Si Wu, Qin-Yi Li, Tatsuya Ikuta, Kazuhiko Morishita, Koji Takahashi, Ruzhu Wang, Tingxian Li, Thermal conductivity measurement of an individual millimeter-long expanded graphite ribbon using a variable-length T-type method, International Journal of Heat and Mass Transfer, 10.1016/j.ijheatmasstransfer.2021.121115, 171, 2021.02.
14.	Qinyi Li, Compositional Engineering of Halide Perovskites, ES Materials and Manufacturing, 10.30919/esmm5f430, 12, 1-2, 2021.02.
15.	Hideaki Teshima, Naoto Nakamura, Qin-Yi Li, Yasuyuki Takata, Koji Takahashi, Zigzag gas phases on holey adsorbed layers, RSC ADVANCES, 10.1039/d0ra08861g, 10, 73, 44854-44859, 2020.12.
16.	Qin-Yi Li, Qing Hao, Tianhui Zhu, Mona Zebarjadi, Koji Takahashi, Nanostructured and Heterostructured 2D Materials for Thermoelectrics, Engineered Science, 10.30919/es8d1136, 13, 24-50, 2020.09, 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..
17.	Sota Hirokawa, Hideaki Teshima, Pablo Solís-Fernández, Hiroki Ago, Yoko Tomo, Qin-Yi Li, Koji Takahashi, Nanoscale Bubble Dynamics Induced by Damage of Graphene Liquid Cells, ACS omega, 10.1021/acsomega.0c01207, 2020.05.
18.	Hideaki Teshima, Qinyi Li, Yasuyuki Takata, Koji Takahashi, Gas Molecules Sandwiched in Hydration Layers at Graphite/Water Interfaces, Physical Chemistry Chemical Physics, 10.1039/D0CP01719A, 2020.05.
19.	Masahiro Narasaki, Qin Yi Li, Tatsuya Ikuta, Jin Miyawaki, Koji Takahashi, Modification of thermal transport in an individual carbon nanofiber by focused ion beam irradiation, Carbon, 10.1016/j.carbon.2019.07.056, 153, 539-544, 2019.11, [URL], 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..
20.	Qin Yi Li, Tianli Feng, Wakana Okita, Yohei Komori, Hiroo Suzuki, Toshiaki Kato, Toshiro Kaneko, Tatsuya Ikuta, Xiulin Ruan, Koji Takahashi, Enhanced Thermoelectric Performance of As-Grown Suspended Graphene Nanoribbons, ACS nano, 10.1021/acsnano.9b03521, 13, 8, 9182-9189, 2019.08, [URL], Conventionally, graphene is a poor thermoelectric material with a low figure of merit (ZT) of 10^-4-10^-3. Although nanostructuring was proposed to improve the thermoelectric performance of graphene, little experimental progress has been accomplished. Here, we carefully fabricated as-grown suspended graphene nanoribbons with quarter-micron length and â40 nm width. The ratio of electrical to thermal conductivity was enhanced by 1-2 orders of magnitude, and the Seebeck coefficient was several times larger than bulk graphene, which yielded record-high ZT values up to â0.1. Moreover, we observed a record-high electronic contribution of â20% to the total thermal conductivity in the nanoribbon. Concurrent phonon Boltzmann transport simulations reveal that the reduction of lattice thermal conductivity is mainly attributed to quasi-ballistic phonon transport. The record-high ratio of electrical to thermal conductivity was enabled by the disparate electron and phonon mean free paths as well as the clean samples, and the enhanced Seebeck coefficient was attributed to the band gap opening. Our work not only demonstrates that electron and phonon transport can be fundamentally tuned and decoupled in graphene but also indicates that graphene with appropriate nanostructures can be very promising thermoelectric materials..
21.	Qin-Yi Li, Ryo Matsushita, Yoko Tomo, Tatsuya Ikuta, Koji Takahashi, Water Confined in Hydrophobic Cup-Stacked Carbon Nanotubes beyond Surface-Tension Dominance, The Journal of Physical Chemistry Letters, 10.1021/acs.jpclett.9b00718, 2019.06.
22.	Qinyi Li, Koji Takahashi, Xing Zhang, Frequency-domain Raman method to measure thermal diffusivity of one-dimensional microfibers and nanowires, International Journal of Heat and Mass Transfer, 10.1016/j.ijheatmasstransfer.2019.01.057, 539-546, 2019.05, [URL], 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..
23.	Qinyi Li, Koki Katakami, Tatsuya Ikuta, Masamichi Kohno, Xing Zhang, Koji Takahashi, Measurement of thermal contact resistance between individual carbon fibers using a laser-flash Raman mapping method, Carbon, 10.1016/j.carbon.2018.09.034, 141, 92-98, 2019.01, [URL], 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..
24.	Yoko Tomo, Qinyi Li, Tatsuya Ikuta, Yasuyuki Takata, Koji Takahashi, Unexpected Homogeneous Bubble Nucleation near a Solid-Liquid Interface, Journal of Physical Chemistry C, 10.1021/acs.jpcc.8b09200, 122, 50, 28712-28716, 2018.12, [URL], 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..
25.	Aoran Fan, Qinyi Li, Weigang Ma, Xing Zhang, 一种测量单个纳米颗粒比热的焦耳加热-针尖增强拉曼闪光法, Kexue Tongbao/Chinese Science Bulletin, 10.1360/N972018-00294, 63, 27, 2896-2903, 2018.09, [URL], 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 Bi1.2 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..
26.	Qinyi Li, Xing Zhang, Koji Takahashi, Variable-spot-size laser-flash Raman method to measure in-plane and interfacial thermal properties of 2D van der Waals heterostructures, International Journal of Heat and Mass Transfer, 10.1016/j.ijheatmasstransfer.2018.05.011, 125, 1230-1239, 2018.05, [URL], 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..
27.	Qin Yi Li, Koji Takahashi, Xing Zhang, Heater assisted raman method to measure interfacial thermal conductance in van der waals heterostructures, 16th International Heat Transfer Conference, IHTC 2018 International Heat Transfer Conference, 10.1615/ihtc16.nmt.021756, 2018-August, 7137-7143, 2018.01, [URL], 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..
28.	Aoran Fan, Qinyi Li, Weigang Ma, Xing Zhang, 焦耳加热和针尖增强拉曼闪光法测量单个纳米颗粒比热, Science Bulletin, 2018.
29.	Qinyi Li, Koji Takahashi, Xing Zhang, Comment on "divergent and Ultrahigh Thermal Conductivity in Millimeter-Long Nanotubes", Physical Review Letters, 10.1103/PhysRevLett.119.179601, 119, 17, 2017.10, [URL].
30.	Qinyi Li, Kailun Xia, Ji Zhang, Yingying Zhang, Qunyang Li, Koji Takahashi, Zhang Xing, Measurement of specific heat and thermal conductivity of supported and suspended graphene by a comprehensive Raman optothermal method, Nanoscale, 9, 10784-10793, 2017.07, 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..
31.	Qinyi Li, Masahiro Narasaki, Koji Takahashi, Tatsuya Ikuta, Takashi Nishiyama, Xing Zhang, Temperature-dependent specific heat of suspended platinum nanofilms at 80-380 K, Chinese Physics B, 10.1088/1674-1056/25/11/114401, 25, 11, 2016.11, [URL], 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 ∼5ï¿½10^-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..
32.	Qinyi Li, Wei Gang Ma, Xing Zhang, Laser flash Raman spectroscopy method for characterizing thermal diffusivity of supported 2D nanomaterials, International Journal of Heat and Mass Transfer, 10.1016/j.ijheatmasstransfer.2015.12.065, 95, 956-963, 2016.04, [URL], 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..
33.	Qinyi Li, Koji Takahashi, Hiroki Ago, Xing Zhang, Tatsuya Ikuta, Takashi Nishiyama, Kenji Kawahara, Temperature dependent thermal conductivity of a suspended submicron graphene ribbon, Journal of Applied Physics, 10.1063/1.4907699, 117, 6, 2015.02, [URL], 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..
34.	Qinyi Li, Xing Zhang, Yu Dong Hu, Laser flash Raman spectroscopy method for thermophysical characterization of 2D nanomaterials, Thermochimica Acta, 10.1016/j.tca.2014.08.011, 592, 67-72, 2014.09, [URL], 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%..
35.	Qinyi Li, Xing Zhang, T-type Raman spectroscopy method for determining laser absorption, thermal conductivity and air heat transfer coefficient of micro/nano fibers, Thermochimica Acta, 10.1016/j.tca.2014.01.023, 581, 26-31, 2014.04, [URL], 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..
36.	Qinyi Li, Qun Chen, Xing Zhang, CO₂ long-term diffusive leakage into biosphere in geological carbon storage, Science Bulletin, 10.1007/s11434-014-0506-0, 59, 28, 3686-3690, 2014.01, [URL], 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..
37.	Qinyi Li, Xing Zhang, Raman spectra method for measuring viscosity of supercritical fluids, Kung Cheng Je Wu Li Hsueh Pao/Journal of Engineering Thermophysics, 35, 4, 757-761, 2014.01, 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..
38.	Qinyi Li, Jin Hui Liu, Haidong Wang, Xing Zhang, Koji Takahashi, Optical absorptance measurement of an individual multiwall carbon nanotube using a T type thermal probe method, Review of Scientific Instruments, 10.1063/1.4824494, 84, 10, 2013.10, [URL], 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..
39.	Qinyi Li, Qun Chen, Xing Zhang, Performance analysis of a rooftop wind solar hybrid heat pump system for buildings, Energy and Buildings, 10.1016/j.enbuild.2013.05.048, 65, 75-83, 2013.07, [URL], 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..
40.	Qinyi Li, Qun Chen, Application of entransy theory in the heat transfer optimization of flat-plate solar collectors, Science Bulletin, 10.1007/s11434-011-4811-6, 57, 2-3, 299-306, 2012.01, [URL], 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..

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