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1.
Phys Chem Chem Phys ; 25(46): 31781-31790, 2023 Nov 29.
Artigo em Inglês | MEDLINE | ID: mdl-37965932

RESUMO

Thermal conductivity (κ, which consists of electronic thermal conductivity κe and lattice thermal conductivity κl), as an essential parameter in thermal management applications, is a critical physical quantity to measure the heat transfer performance of materials. To seek low-κ materials for heat-related applications, such as thermoelectric materials and thermal barrier coatings. In this study, based on a complex cluster design, we report a new class of two-dimensional (2D) transition metal dichalcogenides (TMDs): T-Au6X2 (X = S, Se, and Te) with record ultralow κl values. At room temperature, the κl values of T-Au6S2, T-Au6Se2, and T-Au6Te2 are 0.25 (0.23), 0.30 (0.21), and 0.12 (0.10) W m-1 K-1 along the x-axis (y-axis) direction, respectively, exhibiting good thermal insulation. The ultralow κl originates from strong phonon softening and suppression, especially for the phonon with frequency 0-1 THz. In addition, T-Au6Te2 holds the lowest group velocity and phonon relaxation time among the three T-Au6X2 monolayers. Our study provides an alternative approach for achieving ultralow κl through complex cluster replacement. Meanwhile, this new class of TMDs is expected to shine in thermal insulation and thermoelectricity due to their ultralow κl values.

2.
Front Chem ; 11: 1295589, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-37901161

RESUMO

Monoelemental two-dimensional (2D) materials, which are superior to binary and ternary 2D materials, currently attract remarkable interest due to their fascinating properties. Though the thermal and thermoelectric (TE) transport properties of tellurium have been studied in recent years, there is little research about the thermal and TE properties of multilayer tellurium with interlayer interaction force. Herein, the layer modulation of the phonon transport and TE performance of monolayer, bilayer, and trilayer tellurium is investigated by first-principles calcuations. First, it was found that thermal conductivity as a function of layer numbers possesses a robust, unusually non-monotonic behavior. Moreover, the anisotropy of the thermal transport properties of tellurium is weakened with the increase in the number of layers. By phonon-level systematic analysis, we found that the variation of phonon transport under the layer of increment was determined by increasing the phonon velocity in specific phonon modes. Then, the TE transport properties showed that the maximum figure of merit (ZT) reaches 6.3 (p-type) along the armchair direction at 700 K for the monolayer and 6.6 (p-type) along the zigzag direction at 700 K for the bilayer, suggesting that the TE properties of the monolayer are highly anisotropic. This study reveals that monolayer and bilayer tellurium have tremendous opportunities as candidates in TE applications. Moreover, further increasing the layer number to 3 hinders the improvement of TE performance for 2D tellurium.

3.
Nanoscale Horiz ; 8(12): 1695-1699, 2023 Nov 20.
Artigo em Inglês | MEDLINE | ID: mdl-37698845

RESUMO

Defect sites present on the surface of catalysts serve a crucial role in different catalytic processes. Herein, we have investigated defect engineering within a hybrid system composed of "soft" polymer catalysts and "hard" metal nanoparticles, employing the disparity in their thermal expansions. Electron paramagnetic resonance, X-ray photoelectron spectroscopy, and mechanistic studies together reveal the formation of new abundant defects and their synergistic integrability with plasmonic enhancement within the hybrid catalyst. These active defects, co-localized with plasmonic Ag nanoparticles, promote the utilization efficiency of hot electrons generated by local plasmons, thereby enhancing the CO2 photoreduction activity while maintaining the high catalytic selectivity.

4.
Food Chem ; 428: 136762, 2023 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-37418884

RESUMO

Effect of stearic acid-based lipophilic emulsifiers (sorbitan monostearate (Span-60), sucrose ester S-170, and lactic acid esters of monoglycerides (LACTEM)) and oleic acid-based lipophilic emulsifiers (sorbitan monooleate (Span-80) and sucrose ester O-170) on the crystallization of fat blend and the stability of whipped cream were studied. Span-60 and S-170 possessed strong nucleation inducing ability and good emulsifying properties. Thus, tiny and uniform crystals were formed in fat blends, small and ordered fat globules were distributed in emulsions, and air bubbles were effectively wrapped in firmly foam structures. The crystallization of the fat blend and the stability of whipped cream were slightly modified by LACTEM due to its poor nucleation inducing ability and moderate emulsifying characteristic. Span-80 and O-170 had weak nucleation inducing ability and poor emulsifying properties, therefore, loose crystals were formed in fat blends and some big fat globules were separated in emulsions, thereby decreasing the stability of whipped creams.


Assuntos
Emulsificantes , Ácido Oleico , Emulsões/química , Cristalização , Emulsificantes/química , Monoglicerídeos/química , Ésteres
5.
Small ; 19(37): e2301468, 2023 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-37140080

RESUMO

2D 2H-phase MoS2 is promising for electrocatalytic applications because of its stable phase, rich edge sites, and large surface area. However, the pristine low-conductive 2H-MoS2 suffers from limited electron transfer and surface activity, which become worse after their highly likely aggregation/stacking and self-curling during applications. In this work, these issues are overcome by conformally attaching the intercalation-detonation-exfoliated, surface S-vacancy-rich 2H-MoS2 onto robust conductive carbon nanotubes (CNTs), which electrically bridge bulk electrode and local MoS2 catalysts. The optimized MoS2 /CNTs nanojunctions exhibit outstanding stable electroactivity (close to commercial Pt/C): a polarization overpotential of 79 mV at the current density of 10 mA cm-2 and the Tafel slope of 33.5 mV dec-1 . Theoretical calculations unveil the metalized interfacial electronic structure of MoS2 /CNTs nanojunctions, enhancing defective-MoS2 surface activity and local conductivity. This work provides guidance on rational design for advanced multifaceted 2D catalysts combined with robust bridging conductors to accelerate energy technology development.

6.
Proc Natl Acad Sci U S A ; 120(3): e2212075120, 2023 01 17.
Artigo em Inglês | MEDLINE | ID: mdl-36634137

RESUMO

Liquid methanol has the potential to be the hydrogen energy carrier and storage medium for the future green economy. However, there are still many challenges before zero-emission, affordable molecular H2 can be extracted from methanol with high performance. Here, we present noble-metal-free Cu-WC/W plasmonic nanohybrids which exhibit unsurpassed solar H2 extraction efficiency from pure methanol of 2,176.7 µmol g-1 h-1 at room temperature and normal pressure. Macro-to-micro experiments and simulations unveil that local reaction microenvironments are generated by the coperturbation of WC/W's lattice strain and infrared-plasmonic electric field. It enables spontaneous but selective zero-emission reaction pathways. Such microenvironments are found to be highly cooperative with solar-broadband-plasmon-excited charge carriers flowing from Cu to WC surfaces for efficient stable CH3OH plasmonic reforming with C3-dominated liquid products and 100% selective gaseous H2. Such high efficiency, without any COx emission, can be sustained for over a thousand-hour operation without obvious degradation.

7.
Phys Chem Chem Phys ; 24(39): 24447-24456, 2022 Oct 12.
Artigo em Inglês | MEDLINE | ID: mdl-36190779

RESUMO

Searching for materials with a high thermoelectric figure of merit (ZT) has always been the goal of scientific researchers in the energy field. Here, we combine first-principles calculations to obtain the thermoelectric characteristics of Tl3XSe4 (X = V, Nb, or Ta). First, we compared the phonon thermal transport characteristics of Tl3XSe4 by solving the Boltzmann transport equation and calculated the thermal conductivity. After that, we obtained the thermoelectric properties of Tl3XSe4 through the relaxation time approximation theory. The results show that Tl3XSe4 has a high Seebeck coefficient, high electrical conductivity, high power factor (PF) and low thermal conductivity contributed by both phonons and electrons. At the same time, the ZT value of Tl3XSe4 shows that it is a potential thermoelectric material with excellent performance. This work demonstrates the thermoelectric transport characteristics of Tl3XSe4 to explore its potential applications in many other fields of thermoelectricity and energy.

8.
Phys Chem Chem Phys ; 24(18): 11268-11277, 2022 May 11.
Artigo em Inglês | MEDLINE | ID: mdl-35481990

RESUMO

In recent years, the energy crisis and global warming have been urgent problems that need to be solved. As is known, thermoelectric (TE) materials can transfer heat energy to electrical energy without air pollution. High-throughput calculations as a novel approach are adopted by screening promising TE materials. In this paper, we use first-principles calculations combined with the semiclassical Boltzmann transport theory to estimate the TE performance of monolayer Ir2Cl2O2 according to the prediction that Ir2Cl2O2 has potential as a good TE material via high-throughput calculations. The low thermal conductivities of 1.73 and 4.68 W mK-1 of Ir2Cl2O2 along the x- and y-axes are calculated, respectively, which exhibits the strong anisotropy caused by the difference in group velocities of low-frequency phonon modes. Then, the electronic transport properties are explored, and the figure of merit ZT is eventually obtained. The maximum ZT value reaches 2.85 (0.40) along the x-axis (y-axis) at 700 K, revealing that the TE properties of the Ir2Cl2O2 monolayer are highly anisotropic. This work reveals that the anisotropic layer Ir2Cl2O2 exhibits high TE performance, which confirms that it is feasible to screen excellent TE materials via high-throughput calculations.

9.
Adv Mater ; 34(36): e2104113, 2022 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-35451528

RESUMO

Owing to the rapid developments to improve the accuracy and efficiency of both experimental and computational investigative methodologies, the massive amounts of data generated have led the field of materials science into the fourth paradigm of data-driven scientific research. This transition requires the development of authoritative and up-to-date frameworks for data-driven approaches for material innovation. A critical discussion on the current advances in the data-driven discovery of materials with a focus on frameworks, machine-learning algorithms, material-specific databases, descriptors, and targeted applications in the field of inorganic materials is presented. Frameworks for rationalizing data-driven material innovation are described, and a critical review of essential subdisciplines is presented, including: i) advanced data-intensive strategies and machine-learning algorithms; ii) material databases and related tools and platforms for data generation and management; iii) commonly used molecular descriptors used in data-driven processes. Furthermore, an in-depth discussion on the broad applications of material innovation, such as energy conversion and storage, environmental decontamination, flexible electronics, optoelectronics, superconductors, metallic glasses, and magnetic materials, is provided. Finally, how these subdisciplines (with insights into the synergy of materials science, computational tools, and mathematics) support data-driven paradigms is outlined, and the opportunities and challenges in data-driven material innovation are highlighted.

10.
Phys Chem Chem Phys ; 23(41): 23718-23729, 2021 Oct 27.
Artigo em Inglês | MEDLINE | ID: mdl-34642727

RESUMO

Thermoelectric materials with excellent performance can efficiently and directly convert waste heat into electrical energy. In today's era, finding thermoelectric materials with excellent performance and adjusting the thermoelectric parameters are essential for the sustainable development of energy in the context of the energy crisis and global warming. Through first-principles calculations, we notice that two-dimensional (2D) orthogonal ScX2 (X = C and N) compounds show great potential in the field of thermoelectricity. Different from most materials containing C or N atoms, which are generally accompanied by high lattice thermal conductivity (TC), the 2D o-ScX2 exhibited a rather low and anisotropic lattice TC. The κ3L (the lattice thermal conductivity including the effect of three-phonon scattering and isotope scattering) of o-ScC2 along the X and Y directions are 2.79 W m-1 K-1 and 1.55 W m-1 K-1, and those of o-ScN2 are 1.57 W m-1 K-1 and 0.56 W m-1 K-1. By calculating the fourth-order interatomic force constants (IFCs), we obtain the κ3+4L with the additional four-phonon scattering effect. Our results clearly show that four-phonon scattering plays an important role in the TC of the two materials, the κ3+4L of o-ScC2 is only half of its κ3L. Furthermore, it can be noticed that the low lattice TCs of o-ScX2 (X = C and N) are the result of many factors, e.g., heavy atom doping, the strong anharmonicity caused by the vibration of Sc atoms in the out-of-plane direction and C(N) atoms in the in-plane direction, important four-phonon scattering and strongly polarized covalent bonds between X atoms and Sc atoms. Moreover, it is interesting to find that the thermal transport properties of o-ScX2 are led by a different phonon mechanism, e.g., the different TCs of o-ScC2 and o-ScN2 are determined by the anharmonic characteristic, and the harmonic characteristic plays a more important role in the anisotropy of o-ScX2 (X = C and N). In general, our research can be expected to provide important guidance for the application of o-ScX2 (X = C and N) in the thermoelectric field.

11.
Phys Chem Chem Phys ; 23(24): 13633-13646, 2021 Jun 23.
Artigo em Inglês | MEDLINE | ID: mdl-34116567

RESUMO

With the ability to alter the inherent interatomic electrostatic interactions, modulating external electric field strength is a promising approach to tune the phonon transport behavior and enhance the thermoelectric performance of two-dimensional (2D) materials. Here, by applying an electric field (Ez = 0.1 V Å-1), it is predicted that an ultralow value of the lattice thermal conductivity (0.016 W m-1 K-1) at 300 K of 2D indium selenide (InSe) is nearly three orders of magnitude lower than that under an electric field of 0 V Å-1 (27.49 W m-1 K-1). Meanwhile, we calculated the variations in the electrical conductivities, electronic thermal conductivities, Seebeck coefficients, and figure of merit (ZT) of 2D InSe along with the carrier (hole and electron doping) concentrations under some representative electric fields. Owing to the smaller total thermal conductivity along the armchair and zigzag directions, p-type doped 2D InSe at Ez = 0.1 V Å-1 exhibits a larger ZT value (∼1.6) compared to the ZT value (∼0.1) without an electric field at room temperature. The peak ZT value (∼0.53) of the n-type 2D InSe at Ez = 0.1 V Å-1 is much higher than that without an electric field (∼0.02) at the same temperature. Our results pave the way for applying an external electric field to modulate the phonon transport properties and greatly promote the thermoelectric performance of some specific 2D semiconductor materials without altering their crystal structure.

12.
Small ; 17(12): e2100024, 2021 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-33656246

RESUMO

Crystallographic facets in a crystal carry interior properties and proffer rich functionalities in a wide range of application areas. However, rational prediction, on-demand customization, and accurate synthesis of facets and facet junctions of a crystal are enormously desirable but still challenging. Herein, a framework of machine learning (ML)-aided crystal facet design with ionic liquid controllable synthesis is developed and then demonstrated with the star-material anatase TiO2 . Aided by employing ML to acquire surface energies from facet junction datasource, the relationships between surface energy and growth conditions based on the Langmuir adsorption isotherm are unveiled, enabling to develop controllable facet synthetic strategies. These strategies are successfully verified after applied for synthesizing TiO2 crystals with custom crystal facets and facet junctions under tuning ionic liquid [bmim][BF4 ] experimental conditions. Therefore, this innovative framework integrates data-intensive rational design and experimental controllable synthesis to develop and customize crystallographic facets and facet junctions. This proves the feasibility of an intelligent chemistry future to accelerate the discovery of facet-governed functional material candidates.

13.
Nanoscale ; 12(24): 13095-13102, 2020 Jun 28.
Artigo em Inglês | MEDLINE | ID: mdl-32543632

RESUMO

Carbon nanotubes (CNTs) exhibit outstanding electrical and mechanical properties, but these superior properties are often compromised as nanotubes are assembled into bulk structures, which limits the use of CNT assemblies. Despite much work in this field, few studies have made in situ observations of the relationship between electrical conductivity and the amount of nanowelding within pristine CNT assemblies at the microscopic scale. Here, we report in situ transmission electron microscopy observations of electrical conductivity increase of CNT bundles. High-temperature Joule heating was applied to a CNT bundle to fuse adjacent carbon nanofibers with graphitic carbon bonds, as this causes the electrical conductivity of the CNT bundle to increase three orders of magnitude. Apart from the welding process of the cross-over CNT bundles, we further observed a new case of welding process of parallel CNT bundles. Here, we not only obtain the relationship between electrical conductivity of CNT bundles and their merging processes, but also show the effect of the relationship between electrical conductivity and Joule-heating induced temperature on CNT bundles, which follows the natural logarithm law. Improving effective inter-bonding between neighboring nanotubes would help facilitate large-scale development of high-performing, bulk-carbon-based materials from nanostructures in applications such as flexible devices, energy storage, and electrocatalysis.

14.
Environ Sci Pollut Res Int ; 27(14): 16404-16414, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32124306

RESUMO

The spent biological activated carbon (BAC) should be disposed properly; regeneration was a better choice. Performances of thermal and ultrasonic regeneration to the BAC with various service time (3 years, 5 years, and 10 years) were compared comprehensively; the recovery of the BAC's pore structure, variation of mechanical hardness, influence of bioactivity, and removal efficiency of typical pollutants in the reuse were examined. The results showed that thermal regeneration was an utterly regeneration, and almost all the pore structure was restored, whose recovery rate was above 90% for BAC used 3 years and disfavored by the longer BAC's service time (83% for the BAC used 5 years). Ultrasonic regeneration could recover part of the BAC's pores (including micropores) and the restoration mainly focused on the BAC's surface, so the recovery rate was not influenced by the BAC's service time, and the recovery values of specific surface areas and iodine value were kept at 120 m2/g and 200 mg/g, respectively. In addition, the ultrasonic treatment enhanced the BAC's biological activity even with a significant decrease of the biomass on the BAC. The mechanical hardness of BAC decreased from 95 to 89% for the first regeneration and further to 79% for the second regeneration, whereas relatively lower decrease happened for the ultrasonic regeneration (less than 10% after 5 regeneration cycles). The mass losses in the thermal and ultrasonic regeneration were about 13%, 0.5%, and 25%, 3% for the first and second regeneration, respectively. The thermal-regenerated activated carbon (AC) exhibited excellent adsorption ability, good adherence of biofilm, and maintain higher removal rate for more than 2 years, which were similar with that of the fresh AC, but relatively lower removal performance was found. However, the ultrasonic regenerated BAC retained the biodegradation ability, restored the fast-adsorption ability, and the higher removal process lasted about 6 months. Taking the regeneration cost, operation, variation of the AC's characteristics, and the removal performance in reuse, ultrasonic regeneration was more suitable for the BAC filter and better used as a regular measure to maintain the higher removal performance, whereas thermal regeneration was more applicable to the activated carbon adsorption tank.


Assuntos
Água Potável , Poluentes Químicos da Água/análise , Purificação da Água , Adsorção , Biodegradação Ambiental , Biofilmes , Carvão Vegetal
15.
Nanoscale ; 12(5): 3330-3342, 2020 Feb 06.
Artigo em Inglês | MEDLINE | ID: mdl-31976500

RESUMO

By performing first-principles calculations combined with the Boltzmann transport equation, we report a comprehensive study of the thermal and thermoelectric properties of monolayer triphosphides InP3, GaP3, SbP3 and SnP3. Firstly, we studied the structure and phonon dispersion, and discussed the long-range atomic interactions by analyzing the second-order interatomic force constants (IFCs). Next, we predicted the corresponding thermal conductivities of monolayer InP3, GaP3, SbP3 and SnP3 at 300 K to be 0.64 W m-1 K-1, 3.02 W m-1 K-1, 1.04 W m-1 K-1 and 0.48 W m-1 K-1, respectively. To study the thermoelectric properties, the carrier mobility and electron relaxation time of the four materials were predicted by the deformation potential theory method and explained by analyzing their energy band structures. Then, the Seebeck coefficient, electrical conductivity and thermoelectric figure of merit (ZT) at different temperatures were calculated by using the Boltzmann transport equation with relaxation time approximation. Finally, we predicted the maximum ZT values of InP3, GaP3, SbP3 and SnP3 to be up to 2.6, 0.9, 1.9 and 3.7 at 300 K and up to 4.6, 1.6, 3.5 and 6.1 at 500 K, respectively. With ultra-low thermal conductivity and high thermoelectric performance, monolayer triphosphides are considered as potential candidates for thermoelectric materials.

16.
Phys Chem Chem Phys ; 22(4): 1911-1922, 2020 Jan 29.
Artigo em Inglês | MEDLINE | ID: mdl-31912827

RESUMO

Manipulation of crystal symmetry is an important strategy to tune the thermoelectric performance. High-symmetry thermoelectric materials benefit from high band degeneracy. With first-principles calculations and Boltzmann transport theory, we systematically investigate the electronic and phononic transport properties of rhombohedral GeSe with higher symmetry. At optimized carrier concentrations, the maximum power factors are found to be 5.86 mW m-1 K-2 for the p-type and 4.45 mW m-1 K-2 for the n-type, respectively. The high p-type power factor originates from the highly degenerated L and Σ bands and small energy offset between them, while the n-type one results from the weak electron-phonon coupling. More importantly, rhombohedral GeSe possesses anisotropic and low lattice thermal conductivities of 3.58 W m-1 K-1 and 1.96 W m-1 K-1 at room temperature in the intralayer and interlayer directions, respectively, which is associated with the giant phonon anharmonicity driven by the resonant bonding. Combining the high power factor and low thermal conductivity, the predicted ZT values for p-type and n-type doping can reach 2.02 and 2.37 at 800 K. This study offers insights into the thermal and charge transport properties in rhombohedral GeSe, and demonstrates that both p-type and n-type GeSe are potential high-performance thermoelectric materials.

17.
Ultrason Sonochem ; 61: 104689, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31733452

RESUMO

Ultrasonic treatment has been shown to have a favorable effect on the regeneration of spent biological activated carbon (BAC) from drinking water treatment plants. In this study, the use of ultrasound as a regeneration method had a significant effect on the recovery of spent BAC after 7.5 years of use; it effectively increased the iodine value from 300 mg/g to 600 mg/g and restored the specific surface area and pore volume of BAC. Ultrasound effectively changed the structure of the biofilm inside and on the surfaces of BAC particles, on the basis of confocal laser scanning microscopy (CLSM) images. The thickness of the surface biofilm attached to BAC reached an "active" level (about 100 µm) at the regeneration frequency of 40 kHz. The dehydrogenase activity significantly improved from 4.50 mg TF/g BAC to 9.13 mg TF/g BAC, and the content of adenosine-triphosphate (ATP) in regenerated BAC was maintained at a high level (2.501 × 10-6g ATP/g BAC), thus allowing the development of microbial growth. The production of soluble microbial products (SMPs) from regenerated BAC decreased during the reuse process. The removal efficiency of DOC, CODMn, NH4+ and NO3- control increased by approximately 78%, 71%, 50% and 20%, respectively.


Assuntos
Biofilmes , Carbono/metabolismo , Sonicação , Análise da Demanda Biológica de Oxigênio , Microscopia Confocal , Purificação da Água/métodos
18.
Phys Chem Chem Phys ; 21(28): 15647-15655, 2019 Jul 17.
Artigo em Inglês | MEDLINE | ID: mdl-31268444

RESUMO

In this study, strain modulation of the lattice thermal conductivity of monolayer and bilayer penta-graphene (PG) at room temperature was investigated using first-principles calculations combined with the phonon Boltzmann transport equation. The thermal conductivities of both the monolayer and the bilayer PG exhibit a robust nonmonotonic up-and-down behavior under strain despite the effect of van der Waals (vdW) interactions, and the thermal conductivities of bilayer PG under strain are significantly reduced by up to 87%. Using phonon-level systematic analysis, the variation of thermal conductivity with the increasing strain was determined by increasing the phonon lifetime in specific phonon modes, and that with the reduction of strain was determined by the decrease of both phonon group velocity and phonon lifetime. Moreover, bilayer PG shows an unexpectedly different response to strain when compared with monolayer PG, and a significantly larger reduction (>60%) in the thermal conductivity of bilayer PG is achieved when the strain reaches 10% because the interlayer interactions enhance the phonon anharmonicity of the phonon modes of ultra-low frequency. Our study shows that bilayer PG will have tremendous opportunities for application in thermal management and two-dimensional nanoscale electronic devices owing to its largely tunable thermal conductivity.

19.
Sci Rep ; 9(1): 9490, 2019 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-31263221

RESUMO

In this paper, we systematically investigate the effect of hydrostatic pressure on the phononic and electronic transport properties of orthorhombic p-type GeSe using first-principles based Boltzmann transport equation approach. It is found that the lattice thermal conductivities along the a and c directions increase with pressure, whereas it experiences a decrease along the b direction. This anomalous pressure dependent lattice thermal conductivity is attributed to the combined effect of enhanced phonon group velocity and reduced phonon lifetime. Additionally, the optical phonon branches have remarkable contributions to the total lattice thermal conductivity. The electronic transport calculations indicate that the Seebeck coefficient undergoes a sign change from p-type to n-type along the a direction under pressure, and a dramatic enhancement of the power factor is observed due to the boost of electrical conductivity. The predicted ZT values along the a, b, and c directions are 1.54, 1.09, and 1.01 at 700 K and 8 GPa, respectively, which are about 14, 7.3, and 1.9 times higher than those at zero pressure at experimental carrier concentration of ~1018 cm-3. Our study is expected to provide a guide for further optimization of the thermal and charge transport properties through hydrostatic pressure.

20.
Phys Chem Chem Phys ; 21(11): 6011-6020, 2019 Mar 13.
Artigo em Inglês | MEDLINE | ID: mdl-30810132

RESUMO

In this paper, the interfacial thermal transport properties at the interfaces between the cubic compounds of boron with selected group V elements (BP, BN, BAs and BSb) and various substrates (Si, 6H-SiC and 3C-SiC) were studied by first-principles calculations. Systematic analysis of the effect of crystal information on interfacial thermal transport is performed based on the study of phonon density of states, atomic mass, crystal structure and spectral heat flux, respectively. The results show that the overlap of the phonon density of states of the two interface materials is related to the interfacial thermal conductance. Other crystal information, the atomic mass and lattice constant, which cannot directly reflect the trend of interfacial thermal conductance, can only play a predictive role. Further deep insight suggests that the interfacial thermal conductance also depends strongly on the phonon thermal transport characteristics of different materials and the frequency-dependent spectral heat flux. The results from this work unveil the fact that Si and SiC as the substrate materials do not have absolute superiority or inferiority, depending on the matching rate of many factors of the two materials at the interfaces. This study explores the phonon-level mechanisms for interfacial thermal transport between compounds of boron with group V elements and Si/SiC substrates and provides effective ways to improve the interfacial thermal transport in silicon based modern micro/nano-electronic devices.

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