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Liquid hydrogen carriers have garnered considerable interest in long-distance and large-scale hydrogen storage owing to their exceptional hydrogen storage density, safety, and compatibility. Nonetheless, their practical application is hampered by the low hydrogen production rate and high cost, stemming from poor thermal utilization and heavy reliance on noble metals in solar bulk dehydrogenation platforms. To conquer these challenges, we devise an economical all-in-one architecture comprising the photothermal catalytic termination-vacant MXene and a highly insulated melamine substrate. This design floats on the air–reactant interface to efficiently drive solar interfacial dehydrogenation. The melamine enables interfacial heat localization to improve the thermal utilization, providing a high reaction temperature. Meanwhile, the MXene with termination vacancies exposes rich active sites for formic acid dehydrogenation, and simultaneously high performance and cost-effectiveness can be realized. This work offers fresh perspectives on the design and application of photothermal catalytic MXene, broadening the prospects for hydrogen storage using liquid hydrogen carriers.

A broadband high-data-rate ${D}$ -band OOK transmitter (TX) is designed in this article for high-speed communication. The TX consists of an adjustable signal source, a broadband high-speed OOK modulator, and a wideband low-noise power amplifier (LNPA). The proposed LNPA can be utilized simultaneously in both the TX and the receiver to improve the RF bandwidth of the system, thus increasing the data transmission rate. Additionally, a dual-mode balun was utilized, which is compatible with single-ended and differential interfaces. The TX was fabricated in a 28-nm bulk CMOS process and achieved more than 5-dBm output power under 1-V supply voltage with 167-mW dc power consumption. For testing purposes, the TX is connected to a receiver via wire bonding, achieving a data rate of 32 Gbps in the OOK modulation scheme. Moreover, a wideband antenna was designed and implemented on printed circuit board (PCB) for the over-the-air (OTA) transmission, supporting data rates of 20 Gbps at a distance of 6 cm. To the best of our knowledge, this work demonstrates the widest RF bandwidth and the highest data rate in TXs without predistortion and equalization, which can provide excellent performance for ${D}$ -band high-speed communication.

In this paper, the thermal transport characteristics of penta-CN2and -BCN, which can be seen as the analogues of penta-graphene, are systematically studied by first-principles calculation and solving the phonon Boltzmann transport equation. The results reveal that, in contrast to the traditional two-dimensional materials, the three-phonon scattering process is insufficient to adequately characterize the thermal transport mechanisms of the above two materials, and the four-phonon scattering process has an enormous impact on their thermal transport processes. The thermal conductivity of penta-CN2at room temperature is reduced by 44.1% after considering four-phonon scattering, and that of penta-BCN is dropped by 60.0% in the same case. Combining with phonon analysis, it can be found that four-phonon scattering mainly affects the phonons in the ZA branch, which is mainly due to the extremely isolated distribution of the ZA branch. Further, it can also be noticed that the number of the phonon scattering channel involved in the redistribution process is significantly higher than those of the other two four-phonon scattering processes, i.e., splitting and recombination processes, and even reaches the level of the three-phonon scattering processes. Under the influence of the above factors, the four-phonon scattering process plays an extremely important role in the thermal transport properties of penta-CN2and -BCN. Considering that the dispersion curves of the two structures do not have an obvious phonon bandgap, we can notice that the impact mechanism of four-phonon scattering in penta-CN2and -BCN is significantly different from those of other structures, which are also greatly affected by four-phonon scattering, e.g., BAs. The results in this work provide strong theoretical support for expanding the application of penta-structures and four-phonon scattering processes in the field of nanoscale heat transfer.

This article presents a prototype of a two-way differential power-combining sub-terahertz (sub-THz) power amplifier (PA) utilizing a coupled-line-balun network in a 0.13- $\mu \text{m}$ SiGe BiCMOS process with $f_{t}/f_{\text {max}}$ = 350/450 GHz. To achieve optimum load impedance matching and power combining simultaneously in a sub-THz band, a modified design method based on the characteristic impedance and electrical length of a coupled line is proposed. This method employs offset coupled lines and additional compensated transmission lines (T-lines) to obtain a wide single-ended-to-differential impedance transformation range. Furthermore, the influence of bypassed capacitances on common-mode performance is also analyzed, and the metal–oxide–metal (MOM) capacitor is used in the balun design. The proposed power combiner and splitter occupy a compact area of less than $125\times 90\,\,\mu \text {m}^{2}$ . The sub-THz four-stage PA utilizing the proposed techniques exhibits a peak gain of 21.4 dB at 259 GHz, a 3-dB small-signal bandwidth of 33 GHz (242–275 GHz), and a 3-dB saturated power bandwidth of 41 GHz (241–282 GHz). A measured maximum saturated power of 12.5 dBm and the corresponding power-added efficiency (PAE) of 2.26% at 265 GHz verifies the effectiveness of the proposed modified design method.

The temperature of a friction pair exerts considerable influence on the tribological behavior of a system. In two cases, one with and the other without Cu (copper) nanoparticles, the temperature increase in friction pairs caused by frictional heating and its tribological properties at various temperatures are studied by using the molecular dynamics approach. The results show that temperature distribution and surface abrasion are significantly improved by the presence of Cu nanoparticles. This is one of the reasons for the improvements in tribological properties achieved in the presence of nanoparticles. The temperature and range of influence of frictional heating for the model without nanoparticles are significantly increased with the increase in the sliding velocity; however, in the model with nanoparticles, the temperature gradient is confined to the area near the Cu film. With an increase in the temperature of the friction pair, the improvement in anti-wear properties associated with the presence of Cu nanoparticles becomes more significant.

Thermal interface materials (TIMs) are a critical component of thermal management systems, with efforts being made to improve their thermal conductivity (k) to enhance their thermal-management performance in electronic devices. However, the heat flow management ability should be the key factor for determining thermal-management performance, instead of the kof the TIMs alone as commonly assumed. Systematically looking for what factors will affect the heat flow management ability and understanding how they can influence the thermal-management performance is urgent. In this work, we combined both experiments and simulations to clarify this issue in a TIM-based thermal management system. The heat flow management ability of TIMs was classified into two categories based on the heat flow directions: the heat transport ability, responsible for transferring heat from the chip to heat sink in through-plane direction; and the heat flow dispersion ability, pertaining to the in-plane dispersion of heat flow within the chip. These two kinds of ability of TIMs were found to be affected by different properties beyond just k: the former was proportional to the thermal resistance of TIMs and the contact area between TIMs and chips, while the latter was influenced by the area and anisotropic kof TIMs. Through systematic analysis of heat flow, a clear understanding of the heat flow management ability was obtained, leading to the proposal of design criteria grounded in the perspective of heat flow management. These criteria aim to guide the development of efficient materials design and further enhance thermal-management performance.

Zinc oxide (ZnO) is a wide band-gap semiconductor material with versatile applications in high-tech fields. Under high pressure, ZnO exhibits multiple phase transitions, which are of great significance for the development of photocatalysts, micro-devices with stress-controlled elements, and the investigation of relevant structure-activity relationships. However, previous studies have reported only theoretical calculations of its thermal transport properties under high pressure due to the challenges of experimental methodology. In this work, we employed a combination of the time-domain thermoreflectance technique and diamond anvil cell to characterize the anisotropic thermal properties of ZnO crystal under 0–20 GPa. Simultaneously, we studied the micro-structure of ZnO in the same pressure range by Raman spectra. Our proposed modified Leibfried-Schlomann equation adequately explained the non-monotonic trend of the thermal conductivity within 10 GPa observed in measurement results. Additionally, we report the ZnO thermal conductivity during the decompression process for the first time. Our experimental results and theoretical analysis advance the understanding of the thermal transport mechanism of wide-gap semiconductors under high pressure and pave the way for their high-pressure modification.

• Thermal properties of GaAs with multi-structure were measured up to ∼23 GPa. • Diverse heat carriers play a central role in κ Al/GaAs in different regimes. • Lattice defects enable released GaAs to exhibit glass-like κ. • Both intrinsic and extrinsic factors enhance G Al/GaAs with compression. • The released G Al/GaAs is 2.6 times higher than that of the initial. High-pressure has been widely utilized to improve material performances such as thermal conductivity κ and interfacial thermal conductance G. Gallium arsenide (GaAs) as a functional semiconductor has attracted extensive attention in high-pressure studies for its technological importance and complex structure transitions. Thermal properties of GaAs under high pressure are urgent needs in physics but remain elusive. Herein, we systematically investigate κ GaAs and G Al/GaAs of multi-structure up to ∼23 GPa. We conclude that: (1) in pressurization, phonon group velocity, lattice defects, and electrons play a central role in κ GaAs in elastic, plastic, and metallization regions, respectively. The increased phonon density of states (PDOS) overlap, group velocity, and interfacial bonding enhances G Al/GaAs. (2) In depressurization, electrons remain the dominant factor on κ GaAs from 23 to 13.5 GPa. G Al/GaAs increases dramatically at ∼12 GPa due to the larger PDOS overlap. With decompressing to ambient, lattice defects including grain size reduction, arsenic vacancies, and partial amorphization reduce κ GaAs to a glass-like value. Remarkably, the released G Al/GaAs is 2.6 times higher than that of the initial. Thus our findings open a new dimension in synergistically realizing glass-like κ and enhancing G , which can facilitate thermoelectric performance and its potential engineering applications. [Display omitted] [ABSTRACT FROM AUTHOR]

Self-heating is a severe problem for high-electron-mobility transistors (HEMTs). Graphene and thin graphite films are attractive candidates for heat spreader materials at the transistor level due to their ultrahigh in-plane thermal conductivity. However, a realistic and systematic simulation study of how they can improve the thermal management of HEMTs has not been carried out yet and is needed to push the method into practical use and realize industrialization. This study systematically investigated the effect of graphene and thin graphite films, and the most practical boundary condition in the simulations was primarily selected with comparisons. Then, the thermal properties consisting of thermal conductivity and interfacial thermal resistance (ITR) between graphite and other materials were fully investigated, which may bottleneck the actual improvement of the thermal management in applications. Our steady-state results indicated that the ITR between graphite and SiO2 determined the whole improvement in thermal management performance through the added graphite heat bridge. Subsequently, the transient thermal analysis was conducted on the HEMTs to explore the effect of graphene and thin graphite films under repeated joule heating pulses on a microsecond time scale, and we obtained the effect of graphene and thin graphite films on each heating and cooling process. Finally, based on all the results and analysis mentioned above, we can confirm that the graphite-based heat-spreader structures can still offer efficient heat dissipation under near-real conditions, thereby indicating ways of the optimization of HEMTs heat dissipation.

Porous materials have been widely used to encapsulate phase change materials (PCMs) and enhance their thermal performances. However, the original porous materials possess monotonic properties and cannot endow PCMs with multiple functions, thus limiting their applications. Therefore, various surface strategies have been explored to modify the porous materials to extend the application scenarios of PCMs. Herein, we comprehensively review the surface-modified porous materials based on various modifiers, such as carbon-based materials, metallic/metallic oxide materials, MXenes, metal-organic frameworks, elements, and molecules. Those modifiers form a thin adlayer on the porous substrate and endow it with multiple features, such as high thermal/electrical conductivity, large loading capacity of PCMs, hydrophilicity/hydrophobicity, full-spectrum light adsorption, and flame retardant. The preparation and modification methods for surface-modified porous materials are elaborated upon in this paper. Finally, we summarize the significant current achievements, future challenges, and opportunities for the gradual development of novelties in thermal energy storage.

As a typical two-dimensional material, graphene (Gr) has shown great potential to be used in thermal management applications due to its ultrahigh in-plane thermal conductivity (k). However, low interface thermal conductance (ITC) between Gr and metals to a large extent limits the effective heat dissipation in Gr-based devices. Therefore, having a deep understanding on heat transport at Gr–metal interfaces is essential. Because of the semimetallic nature of Gr, electrons would possibly play a role in the heat transport across Gr–metal interfaces as heat carriers, whereas, However, how much the electron can participate in this process and how to optimize the total ITC considering both electron and phonon transportations have not yet been revealed yet. Therefore, in this work, hydrogenation-treated Gr (H-Gr) was sandwiched by nickel (Ni) nanofilms to compare with the samples containing pure Gr for investigating the interfacial electron behaviors. Moreover, both Gr and H-Gr sets of the samples were prepared with different layer numbers (N) ranging from 1 to 7, and the corresponding ITC was systematically studied based on both time-domain thermoreflectance measurements and theoretical calculations. We found that a larger ITC can be obtained when Nis low, and the ITC may reach a peak value when Nis 2 in certain circumstances. The present findings not only provide a comprehensive understanding on heat transport across Gr-metal interfaces byconsidering a combined effect of the interfacial interaction strength, phonon mode mismatch, and electron contributions, but also shed new lights on interface strucure optimiazations of Gr-based devices.

Accurately and directly characterizing the thermal properties of graphene and thin-graphite films (GFs) is of fundamental importance for understanding the heat transport mechanism and of practical interest in possible applications of thermal management. However, due to the lack of experiment data, the mechanism of the thickness dependence of GFs thermal properties has not been fully understood yet. In this study, a 90-nm-thick GF is characterized by the time-domain thermoreflectance method, and the obtained GFs in-plane thermal conductivity and interfacial thermal conductance between GFs and gold are (1354±297) W/(m·K) and (38±6) MW/(m2·K), respectively. Two theoretical models are also applied for comparison and discussion, and we conclude that the influence from the surface perturbation by supporting materials on the phonon transport of graphite nano-films will beyond the near surface layers to the more inner ones. This work not only provides a better understanding of the fundamental mechanisms of the thermal transport size effect in GFs, but also facilitates the possible applications of GFs as heat spreaders in the future.

An ionization-engineered hydrogel with electronegativity polymer chains to impede salt ions was designed.The hydrogel evaporator exhibited salt impedance in 20 wt% brine for 15 days with a high evaporation efficiency of 95.6%.An all-day high-salinity brine treatment with zero liquid discharge was proposed.

Knowledge acquisition is one of the important issues in granular computing. In recent years, scholars have paid much attention to this problem and proposed the rule-based acquisition algorithms. However, a large number of the decision rules mined by the existing algorithms are not comprehensible. At the same time, the long detailed rules are easy to lead to over-fitting. In order to generate simpler and easier-to-comprehensible rules and improve human decision-making, a hierarchical sequential three-way decision model is proposed by combining sequential three-way decisions with hierarchical rough set model. Specifically, we generalize the concepts of the conditional attributes through the concept hierarchy tree, design the multi-hierarchical decision table with multiple levels of granularity, and illustrate the corresponding algorithm to acquire the generalized rules step by step. The experimental results demonstrate that the proposed model can mine hierarchical sequential three-way decision rules under different levels of granularity. [ABSTRACT FROM AUTHOR]

Angle-resolved ellipsometry with back focal plane imaging has been found to be of increasing importance in recent industrial sensing by virtue of its rich information provided at various incident and azimuthal angles. To achieve high sensing accuracy, the incident angles of a back focal plane must be accurately calibrated. For this purpose, a simple and robust incident angle calibration method based on full-field Brewster angle fitting is proposed, without expensive tools or complex operations. With this method, a back focal plane image is first captured from boundary reflectance through a high-numerical-aperture objective. By extracting annular data from the image, radius-dependent ellipsometric parameters $ (\psi,{\Delta)}$ are calculated. At the end, the radii of the back focal plane are mapped to the angle of incidence by using a fitted Brewster angle as the reference. The method is validated by simulation and experiments using a homemade angle-resolved ellipsometer and a commercial spectroscopic ellipsometer. The results show that the proposed method provides a 75% error reduction approximately from generally used methods.

Spiral fins have been widely used to enhance the heat transfer of latent heat thermal energy storage (LHTES) systems. However, owing to the inhomogeneous melting of solid-liquid phase change materials (PCMs) driven by convective heat transfer, the uniform spiral fins always have poor enhancing performance. In the present work, we proposed structural-optimized spiral fins, including optimized fin thickness, optimized fin height, and optimized fin pitch, to uniformly and efficiently transfer the heat from fins to PCM. By comparing their melting results with the original-uniform model, we found that negative models with larger fin volume at the bottom are more efficient in accelerating the melting process, and they can maximally reduce the complete melting time of PCM by 15.01% compared with the original one. On the contrary, the positive model with a smaller fin volume at the bottom slows down the melting of the LHTES unit. The heat transfer mechanism along the whole melting process is analyzed by comparing the thermal parameters (including liquid fraction, average temperature, average liquid velocity, and heat flux) of the original and optimized models. The enhancements of the negative models are owing to their benefits to the developments of convective heat transfer in the top region and conductive heat transfer at the bottom. According to the results of this paper, researchers can design novel high-performance LHTES systems using optimized spiral fins.

Biomass-derived photothermal conversion materials are considered to be promising evaporator choices for cost-effective, sustainable, and environmentally friendly solar vapor generation. Herein we demonstrate a double-layer flamed straw, which is a typical solar-driven interfacial evaporator that can directly convert solar energy into heat and then localize heat at interface for vapor generation. Benefiting from the unique structure of a natural corn straw, the flamed straw exhibits a high solar absorbance of 91%, ultralow thermal conductivity (0.042 W m–1K–1), and a sufficient water supply. Notably, the flamed-straw evaporator achieves a fast evaporation rate of 1.497 kg m–2h–1and a high photothermal efficiency of 86% under 1 sun illumination, showing comparable efficiency with the reported studies. Our work highlights the promise of using the low-cost biomass-derived materials as highly effective solar vapor generators in the realm of seawater desalination and wastewater treatment.

The Moving Least Squares (MLS) and Moving Total Least Squares (MTLS) method are widely used for approximating discrete data in many areas such as surface reconstruction. One of the disadvantages of MLS is that it only considers the random errors in the dependent variables. The MTLS method achieves a better fitting accuracy by taking into account the errors of both dependent and independent variables. However, both MLS and MTLS suffer from a low fitting accuracy when applied to the measurement data with outliers. In this work, an improved method named as α-MTLS method is proposed, which uses the Total Least Square (TLS) method based on singular value decomposition (SVD) to fit the nodes in the influence domain and introduces a geometric characteristic parameter αto associated with the abnormal degree of nodes. The generated fitting points are used to construct the parameter and quantify the abnormal degree of the nodes. The node with the largest parameter value is eliminated and the remaining nodes are used to determine the local coefficients. By trimming only one node per influence domain, multiple outliers of measurement data can be effectively handled. There is no need to set threshold values subjectively or assign weights which avoids the negative influence of manual operation. The performance of the improved method is demonstrated by numerical simulations and measurement experiment. It is shown that the α-MTLS method can effectively reduce the influence of the outliers and thus has higher fitting accuracy and greater robustness than that of the MLS and MTLS method.

Interfacial solar-driven evaporation is an effective and sustainable approach to convert solar energy to heat for desalination. However, maintaining a rapid evaporation rate and long-term stability is a critical challenge that needs to be addressed urgently to facilitate practical applications of this technology. Here, taking advantage of the inherent porosity, wettability, and low thermal conductivity of wood, we develop a flexible and mildew-resistant aerogel derived from natural wood as the substrate of evaporators for stable and efficient solar desalination. The wood-derived aerogel not only possesses good hydrophilicity, low thermal conductivity, and light weight, which are favorable to realize heat localization and efficient water evaporation, but also avoids fragility and mildew problems that seriously restricted long-term stability of wood-based evaporators. With high absorbance (>95%) of Au–rGO coating, the evaporator showed a high solar to vapor efficiency of 90.1% and an evaporation rate of 1.394 kg m–2h–1under 1 sun. During 120 h desalination, the evaporator transports brine for evaporation in the day and achieves dissolution of salt residues in the night, exhibiting a repetitive self-cleaning behavior, which enables the recovery of desalination stability. The multiple functionalities of the wood-derived aerogel make the evaporator promising as an attractive device for stable and continuous solar desalination.

For white-light spectral interferometry, the phase information is usually retrieved via the Fourier transform method and the temporal phase-shifting method. In comparison, the synchronous phase-shifting method can be used to synchronously acquire interferometric signals with good accuracy and reduced noise. Therefore, it has potential for online measurement and is suitable for application in precision industries and for ultrahigh-speed measurement. In this work, a white-light spectral interferometer for synchronous phase shifting based on polarization interference was built, and the two-step phase-shifting algorithm was used to retrieve phase information. A variety of spectral interferometric signals were simulated based on the mathematical model of the two-step phase-shifting algorithm to illustrate the effects of differences in intensity and envelope shape, random noise, and phase-shift error on measurement of the absolute distance. Measurements of the absolute distance were conducted, and they indicated that the system had high accuracy.

Chemical looping reforming of biomass is a promising avenue for hydrogen generation. Both the design of reactor configurations and the screening of oxygen carriers represent major challenges in chemical looping technologies. Here, we synthesize three oxygen carriers (referred to as Ni–Al, NiW–Al, and W–Al) by a continuous coprecipitation method and first test them in a fixed-bed reactor. The NiW–Al showed the highest coke resistance, reducibility, and glycerol conversion. We employ an Ellingham diagram to explain the superior performance of the NiW–Al and screen operational temperatures from the standpoint of thermodynamics. Then, using the NiW–Al oxygen carriers, we investigate the effect of Ni-to-glycerol ratio, fuel reactor temperature, and steam-to-glycerol ratio in moving-bed reactors. Establishing two sets of five-stage equilibrium models in Aspen Plus, we compare the experimental results with simulations, discovering good agreement with each other. An isothermal and coke-free operational window was optimized at a fuel reactor temperature of 650 °C, a Ni-to-glycerol ratio of 0.9, and a steam-to-glycerol ratio of 4.5, achieving an average H2yield of 1.5 mol-H2/mol-C. This work highlights the promise of combining moving-bed reactors with oxygen carriers with high oxygen storage capacity to utilize biomass by chemical looping reforming for continuous H2generation.

Reliability and lifespan of highly miniaturized and integrated devices will be effectively improved if excessive accumulated heat can be quickly transported to heat sinks. In this study, both molecular dynamics (MD) simulations and experiments were performed to demonstrate that self-assembled monolayers (SAMs) have high potential in interfacial thermal management and can enhance thermal transport across the polystyrene (PS)/silicon (Si) interface, modeling the common polymer/semiconductor interfaces in actual devices. The influence of packing density and alkyl-chain length of SAMs is investigated. First, MD simulations show that the interfacial thermal transport efficiency of SAM is higher with high packing density. The interfacial thermal conductance (ITC) between PS and Si can be improved up to 127 ± 9 MW m–2K–1, close to the ITC across the metal and semiconductor interface. At moderate packing density, the SAMs with less than eight carbon atoms in the alkyl chain show superior improvements over those with more carbons because of the assembled structure variation. Second, the time-domain thermoreflectance technique was employed to characterize the ITCs of a bunch of Al/PS/SAM/Si samples. C6-SAM enhances the ITC by fivefolds, from 11 ± 1 to 56 ± 17 MW m–2K–1. The interfacial thermal management efficiency will weaken when the alkyl chain exceeds eight carbon atoms, which agrees with the ITC trend from MD simulations at moderate packing density. The relationship between the SAM morphology and interfacial thermal management efficiency is also discussed in detail. This study demonstrates the feasibility of molecular-level design for interfacial thermal management from both the theoretical calculation and experiment and may provide a new idea for improving the heat dissipation efficiency of microdevices.

In this study, copper foam reinforced polymer-based composite phase change materials (CPCM) were prepared to solve the problems of low thermal conductivity, melting leakage, and poor mechanical strength in the realistic application of phase change materials. The CPCM consists of paraffin (PA) and styrene-ethylene-butylene-styrene (SEBS). Stability and mechanical tests were conducted and it was found that CPCM-90 (with a mass fraction of PA at 90 %) exhibited excellent leakage protection ability, shape stability, and bending resistance. The enthalpy of CPCM-90 is up to 168.11 J/g. After filling CPCM into copper foam (CF) with 98 % porosity, the thermal conductivity of the CF/CPCM-90 is improved up to 0.943 W/m·K, nearly 3 times higher than the thermal conductivity of CPCM-90. In addition, the reinforcement of copper foam allows CF/CPCM-90 before and after the phase transformation to withstand mechanical stress of 2 MPa and 0.7 MPa respectively with only 1 % strain. The CF/CPCM-90 also maintained its structural integrity during phase transformation, distinguishing it from CPCM, which commonly experiences cracking and deformation. Furthermore, CF/CPCM-90 maintains battery temperatures below 60 °C for 70 min at 7 W of heat generation and 34 min even at 13 W. Notably, at all heating powers, the duration below 60 °C of the CF/CPCM group is 3 times longer than in the copper foam group and 4 times longer than in the control group (no CF/CPCM-90 or CF). The CF/CPCM-90 shows very effective temperature control for LIBs and has great potential for realistic application regarding battery thermal management. Moreover, this paper provides ideas for further engineering applications of phase change materials in terms of synergistic enhancement of thermal conductivity, leakage prevention, and mechanical properties.

UiO-66 is one kind of zirconium-based metal-organic framework, and Zr6O4(OH)4clusters are the cornerstones of the three-dimensional framework. To obtain enough strength for desalination, a dense continuous UiO-66 membrane was synthetized by the seed-assisted solvothermal synthesis method on the alumina substrate. The thickness of the dense UiO-66 membrane on the alumina substrate could be reduced to 1 μm. The thin layer achieved a high permeate flux of 0.344 L m–2h–1μm–1with the ion rejections of Ca2+and Mg2+respectively reaching 82.1% and 98.2%. Such excellent performances were much better than those of reverse osmosis and nanofiltration membranes. Na+and K+could also be rejected by the UiO-66 membrane based on the ligand effect, whose ion rejections were 49.8% and 45.8%, respectively. Due to the exceptional chemical stability of UiO-66, no degradation of membrane performance was observed by test up to 180 h toward the saline solution. These results show that the UiO-66 membrane on the alumina substrate gives a good promise in the desalination application.

In dam works, air precooling of aggregate is a common and effective method to avoid temperature cracks in concrete structure. In order to offer a reliable design theory for the air precooling process to avoid unreasonable energy consumption, the transient heat transfer characteristics of the aggregate are intensively analyzed. The combined structure of the aggregate and the interstitial space in the hopper is treated as a porous structure, and the space-average method is used to simulate the transient heat transfer process. Simulation results show that size of the hopper and the average air velocity in the cross section have great influence on the transient heat transfer process of the aggregate, while the porosity in the range of 0.4‒0.5 has little influence. Nomograms are abstracted from simulation results, and then correlations of the compared excess temperature are precisely fitted to predict the air precooling transient heat transfer process of the aggregate.

Realizing “Power to Syngas” by electrifying chemical reactors via induction heating is one of the key enabling technologies to decarbonize the chemical industry. Nevertheless, developing catalysts for the induction heating process that can simultaneously serve as magnetic susceptors under high-temperature conditions remains challenging. Herein, we formulate a A-site vacancy induced electronic engineering strategy and, accordingly, synthesize a series of LaFe0.5Al0.5O3perovskite catalysts with different amounts of La vacancies (VLa) (LFAO, 1.5M-LFAO, and 3M-LFAO). In this way, we tune both the redox activity and the magnetocaloric effect (MCE) of perovskite and, for the first time, achieve induction heating methane partial oxidation coupled with CO2splitting for syngas production. Compared with the reported catalysts, the 3M-LFAO had not only superior syngas and CO yields (101.84L·kg cat-1/54.96Lkg cat-1) but also a great MCE (875°C). Spectroscopic investigations and DFT calculations rationalize these observations and demonstrate that the VLacause a unique Fe4+–O2-–Fe3+configuration in perovskite, accounting for an upshift of Fe 3d and O 2p band centers and therefore enhancing redox activity and MCE. This work deepens the understanding of the relationship between catalysis and MCE and unlocks the novel guidance to design induction heating chemical processes.

This study considers adding both the flat heat pipe (FHP) and phase change material (PCM) module to reinforce the lithium-ion battery thermal management (FHP-PCM-BTM) system, and it is compared with the system with only the FHP (FHP-assisted BTM system). Results show that the FHP-PCM-BTM system outperforms the FHP-assisted BTM system regardless of the discharge rate. It reduces the “cold start” behavior, which is harmful to the battery life. At the final of the discharging process with 3C, the maximum temperature of the FHP-assisted BTM system is 318.6 K, but it is 312.3 K of the FHP-PCM-BTM system. Meanwhile, the maximum temperature difference is reduced by 1.02 K. Throughout the cycling experiment, the maximum temperature of the FHP-PCM-BTM system is lower than 313.15 K, even with a discharge rate of 3C. The advantages of the FHP-PCM-BTM system are beneficial from the high thermal conductivity and large latent heat of the PCM module. This module, including copper boxes and PCM, plays a role of a giant heat sink to absorb sizeable heat from the battery pack, so the battery temperature is efficiently controlled. This study paves the way for achieving high-performance battery thermal management by simultaneously using heat pipe and PCM.

Interfacial thermal conductance (ITC) receives enormous consideration because of its significance in determining thermal performance of hybrid materials, such as polymer based nanocomposites. In this study, the ITC between sapphire and polystyrene (PS) was systematically investigated by time domain thermoreflectance (TDTR) method. Silane based self-assembled monolayers (SAMs) with varying end groups, -NH2, -Cl, -SH and -H, were introduced into sapphire/PS interface, and their effects on ITC were investigated. The ITC was found to be enhanced up by a factor of 7 through functionalizing the sapphire surface with SAM, which ends with a chloride group (-Cl). The results show that the enhancement of the thermal transport across the SAM-functionalized interface comes from both strong covalent bonding between sapphire and silane-based SAM, and the high compatibility between the SAM and PS. Among the SAMs studied in this work, we found that the ITC almost linearly depends on solubility parameters, which could be the dominant factor influencing on the ITC compared with wettability and adhesion. The SAMs serve as an intermediate layer that bridges the sapphire and PS. Such a feature can be applied to ceramic-polymer immiscible interfaces by functionalizing the ceramic surface with molecules that are miscible with the polymer materials. This research provides guidance on the design of critical-heat transfer materials such as composites and nanofluids for thermal management.

This research article investigates the effect that hydrodynamic cavitation has on flow-boiling characteristics in a single micro-channel. Flow and heat transfer characteristics have been investigated over a range of effective heat fluxes (71–330 W/cm2) and vapor quality (0.25–0.92) over a broad range of mass flow rates. The images of flow condition have been photographed. A fully developed cavitation flow, including inception, growth, and collapse of bubble, can be presented in the micro-channel. The intensity of bubble and length of the two-phase region increase with increase in the mass flow rates, and bubble flow pattern dominates the fully developed cavitation flow. Heat transfer coefficient has also been calculated at experimental conditions, and the coefficients decrease with increase in the vapor quality, but increase with increase in the heat fluxes.

In polymer-based electric microdevices, thermal transport across polymer/ceramic interface is essential for heat dissipation, which limits the improvement of the device performance and lifetime. In this work, four sets of polystyrene (PS) thin films/sapphire samples were prepared with different interface adhesion values, which was achieved by changing the rotation speeds in the spin-coating process. The interfacial thermal conductance (ITC) between the PS films and the sapphire were measured by time domain thermoreflectance method, and the interfacial adhesion between the PS films and the sapphire, as measured by a scratch tester, was found to increase with the rotation speed from 2000 to 8000 rpm. The ITC shows a similar dependence on the rotation speed, increasing up to a 3-fold from 7.0 ± 1.4 to 21.0 ± 4.2 MW/(m2K). This study demonstrates the role of spin-coating rotation speed in thermal transport across the polymer/ceramic interfaces, evoking a much simpler mechanical method for tuning this type of ITC. The findings of enhancement of the ITC of polymer/ceramic interface can shed some light on the thermal management and reliability of macro- and microelectronics, where polymeric and hybrid organic–inorganic nano films are employed.

Two-dimensional (2D) thermoelectric (TE) materials have been widely developed; however, some 2D materials exhibit isotropic phonon, electron transport properties, and poor TE performance, which limit their application scope. Thus, exploring excellent anisotropic and ultrahigh-performance TE materials are very warranted. Herein, we first investigate the phonon thermal and TE properties of a novel 2D-connectivity ternary compound named Ga2I2S2. This paper comprehensively studies the phonon dispersion, phonon anharmonicity, lattice thermal conductivity, electronic structure, carrier mobility, Seebeck coefficient, electrical conductivity, and the dimensionless figure of merit (ZT) versus carrier concentration for 2D Ga2I2S2. We conclude that the in-planelattice thermal conductivities of Ga2I2S2at room temperature (300 K) are found to be 1.55 W mK−1in the X-axis direction (xx-direction) and 3.82 W mK−1in the Y-axis direction (yy-direction), which means its anisotropy ratio reaches 1.46. Simultaneously, the TE performance of p-type and n-type doping 2D Ga2I2S2also shows significant anisotropy, giving rise to the ZTpeak values of p-type doping in xx- and yy-directions being 0.81 and 1.99, respectively, and those of n-type doping reach ultrahigh values of 7.12 and 2.89 at 300 K, which are obviously higher than the reported values for p-type and n-type doping ternary compound Sn2BiX (ZT∼ 1.70 and ∼2.45 at 300 K) (2020 Nano Energy67104283). This work demonstrates that 2D Ga2I2S2has high anisotropic TE conversion efficiency and can also be used as a new potential room-temperature TE material.

We present a spectral domain low-coherence interferometry (SD-LCI) method that is effective for applications in on-line surface inspection because it can obtain a surface profile in a single shot. It has an advantage over existing spectral interferometry techniques by using cylindrical lenses as the objective lenses in a Michelson interferometric configuration to enable the measurement of long profiles. Combined with a modern high-speed CCD camera, general-purpose graphics processing unit, and multicore processors computing technology, fast measurement can be achieved. By translating the tested sample during the measurement procedure, real-time surface inspection was implemented, which is proved by the large-scale 3D surface measurement in this paper. ZEMAX software is used to simulate the SD-LCI system and analyze the alignment errors. Two step height surfaces were measured, and the captured interferograms were analyzed using a fast Fourier transform algorithm. Both 2D profile results and 3D surface maps closely align with the calibrated specifications given by the manufacturer.

The combustion chamber is an important component for the Stirling engine heated by natural gas. In the paper, we develop a combustion chamber for the Stirling engine which aims to generate 3∼5 kWeelectric power. The combustion chamber includes three main components: combustion module, heat exchange cavity and thermal head. Its feature is that the structure can divide “combustion” process and “heat transfer” process into two apparent individual steps and make them happen one by one. Since natural gas can mix with air fully before burning, the combustion process can be easily completed without the second wind. The flame can avoid contacting the thermal head of Stirling engine, and the temperature fields can be easily controlled. The designed combustion chamber is manufactured and its performance is tested by an experiment which includes two steps. The experimental result of the first step proves that the mixture of air and natural gas can be easily ignited and the flame burns stably. In the second step of experiment, the combustion heat flux can reach 20 kW, and the energy utilization efficiency of thermal head has exceeded 0.5. These test results show that the thermal performance of combustion chamber has reached the design goal. The designed combustion chamber can be applied to a real Stirling engine heated by natural gas which is to generate 3∼5 kWeelectric power.

A simulation for piston effect in supercritical carbon dioxide by employing a simple model is conducted. In the first place, the thermal properties of carbon dioxide near its liquid-vapor critical point are discussed. It is calculated that the heat capacity ratio and isobaric expansion coefficient of supercritical fluids are extremely high. Furthermore, the simulation for piston effect in supercritical carbon dioxide between two infinite vertical walls is presented. The numerical results prove that piston effect has a much faster speed of heat transfer than thermal conduction under microgravity conditions. Moreover, the piston effect turns out to be stronger when closer to the critical point.

The moving least squares (MLS) and moving total least squares (MTLS) are two of the most popular methods used for reconstructing measurement data, on account of their good local approximation accuracy. However, their reconstruction accuracy and robustness will be greatly reduced when there are outliers in measurement data. This article proposes an improved MTLS method (IMTLS), which introduces an improved random sample consensus (RANSAC) algorithm and a correction parameter in the support domain, to deal with the outliers and random errors. Based on the nodes within the support domain, firstly the improved RANSAC is used to generate a model for establishing the group of pre-interpolation and calculating the residual of each node. Subsequently, the abnormal degree of the node with the largest residual is evaluated by the correction parameter associated with the node residual and random errors. The node with certain abnormal degree will be eliminated and the remaining nodes are used to obtain the approximation coefficients. The correction parameter can be used for data reconstruction without insufficient or excessive elimination. The results of numerical simulation and measurement experiment show that the reconstruction accuracy and robustness of the IMTLS method is superior to the MLS and MTLS method.

The 3ω approach was used to measure the effective thermal conductivity of phase-change material microcapsules (PCMMs) based on urea formaldehyde and sliced paraffin. The effective thermal conductivities of PCMMs with different densities were measured within the phase-change temperature range. The relationships between effective thermal conductivity, density and temperature were analysed. The effective thermal conductivity reached peak values within the phase-change temperature range and the temperature peak value was consistent with the peak value of the phase-change temperature. The effective thermal conductivity increased with increasing density due to the decreased porosity of samples and their increased solid-phase conduction.

In order to study the theoretical cycle characteristic of [mmim]DMP (1-methyl-3-methylimidazolium dimethylphosphate) /methanol absorption refrigeration, the modified UNIFAC group contribution model and the Wilson model are established through correlating the experimental vapor pressure data of [mmim]DMP/methanol at T=280∼370 K and methanol mole fraction x= 0.529∼0.965. Thermodynamic performances of absorption refrigeration utilizing [mmim]DMP/methanol, LiBr/H2O and H2O/NH3are investigated and compared with each other under the same operating conditions. From the results, some conclusions are obtained as follows: 1) the circulation ratio of the [mmim]DMP /methanol absorption refrigeration is higher than that of the LiBr/H2O absorption refrigeration, but still can be acceptable and tolerable. 2) The COP of the [mmim]DMP/methanol absorption refrigeration is smaller than that of the LiBr/H2O absorption refrigeration, while it is higher than that of the H2O/NH3absorption refrigeration under most operating conditions. 3) The [mmim]DMP/methanol absorption refrigeration are still available with high COP when the heat source temperature is too high to drive LiBr/H2O absorption refrigeration.

Rectangular capillary microgrooves are processed on transparent borosilicate glass. Using high‐speed photography, bubble dynamic behaviors in the microgrooves are observed and analyzed. It is proved that no bubble departs from the bottom of microgroove. The results show that the whole bubble lifecycle can be divided into three distinct stages according to growing velocity. Compared with macroscopic pool boiling phenomenon, bubble life cycle shortens greatly. Experimental results about time‐varying micro bubble sizes are distinctly different from those of theoretical calculation results by the dynamic micro layer model for nucleate pool boiling heat transfer. © 2010 Wiley Periodicals, Inc. Heat Trans Asian Res; 39(7): 475–481, 2010; Published online 2 June 2010 in Wiley Online Library (). DOI 10.1002/htj.20309

lThe melting of the metal foam composite PCM is studied in pore-scale.lThe effect of the heat flux orientation on the melting is studied.lThe effect of the gradient porosity of metal foam is clarified.lThe whole melting performance is analyzed.

Abstract: In this work, the dual-phase-lag (DPL) model of heat conduction is introduced in treating the transient heat conduction problems in finite rigid mediums under short-pulse-laser heating. Two-dimensional numerical solutions in a rectangular and an axially symmetric system are given by finite difference method. Calculations are performed to exhibit various two-dimensional lagging thermal behavior of conduction heat transfer, such as wavy, wavelike, and diffusive behavior. [Copyright &y& Elsevier]

•The perforated fin is used in the LHTES unit.•The mechanism of heat transfer enhancement of the perforated fin is clarified.•The effects of hole number, hole location, and hole diameter are analyzed.•An optimal model with the best heat storage performance is acquired.

Due to their good approximation accuracy and local fitting characteristics, the moving least squares (MLS) and moving total least squares (MTLS) methods are widely used in various engineering fields. However, neither of these two methods is robust and they cannot effectively deal with outliers in measurement data. To eliminate the negative influence of outliers and achieve robust reconstruction, a novel MTLS method is proposed in this paper, which introduces local Bayesian estimation combined with clustering using representatives (CURE) algorithm. In the support domain, this method adopts a two-step process to remove the abnormal points and adjust the weights of discrete points through compound weighting. Bayesian estimation is first performed on discrete points to derive the reference model, and the residuals are calculated as the input of CURE clustering. The points with large residuals are classified into one cluster and removed. The remaining points undergo repeated processing until the iteration concludes. A gradient weight function based on the residuals and a compact support weight function are combined to determine the final estimated value using weighted Bayesian estimation. The simulations and experiments demonstrate that the proposed reconstruction method achieves excellent accuracy and robustness, surpassing several existing methods when handling highly contaminated datasets. [ABSTRACT FROM AUTHOR]

Perovskite shows promising perspective in photoelectric and thermoelectric applications due to its mediate bandgap and low TC stemming from its intrinsic structure, i.e., organic-inorganic framework. While nanostructuring can reduce the thermal conductivity (TC) significantly which is important for the improvement of the corresponding thermoelectric performance, it is detrimental to the electrical and mechanical properties of materials, e.g., conductivity and strength. Nanotwinning has been proved to be an effective strategy to decouple the electrical and thermal properties, and improve the mechanical properties, and therefore it is one of the best candidates for the design of highly efficient thermoelectrics. Moreover, the introduction of nanotwinning can break the host structure of perovskite and regulate the proportions of liquid-convectional and solid-vibrational heat transport in some degree. Therefore, nanotwinning can be seen as an important method to face the challenge in the applications of perovskite in the field of thermoelectric conversion efficiency and thermal stability. Here, the multichannel heat transport in single-crystalline and twinned hybrid organic–inorganic halide perovskite is quantitatively characterized and compared by performing molecular dynamics simulations. Our results demonstrate that the solid-vibrational heat transport plays a dominant role in the whole thermal transport process even under high temperature, however, the contribution of convective term which is usually ignored in the previous studies also reaches to 20–30% of that of solid virial term. Furthermore, we notice that the convectional TC shows an unconventional temperature-independent trend and the cross term expresses a surprising negative TC. As for the twinned perovskite, it is surprising to find that the position of twin boundary plays an important role in controlling TC, i.e., the TC shows a first downward and then upward trend when the twin boundary is located at I atoms (I-model), while decreases when the center of twin is at Pb atoms (Pb-model). Moreover, the completely opposite trends of the TC-contributed ratios between convective and virial term have been found in the I- and Pb-model, respectively. Further, we also notice the TC contributed by fluid convective term is enhanced comparing with single-crystalline case and the cross term shows a much more significant negative TC, which results in the unexpected phenomenon that the total TC is even lower than that contributed by virial term. Our investigations provide a fundament understanding of the thermal transport properties of perovskite and propose the key mechanisms to guide the thermal management.

•The inner melting characteristic of the horizontal LHTES tube is clarified.•A hard-melting region located in the bottom tube is defined.•The effects of fin-thickness and fin-length at different locations are analyzed.•An optimal model with a faster charging process is acquired.

Clathrate hydrates are formed by water molecules and natural gas molecules under a certain temperature and pressure. Natural gas hydrates are mainly distributed in the marine sediments and the permafrost in nature. As a kind of potential clean energy, determining the structural characteristics of hydrates in sediments is the prerequisite for the safe and economic exploitation of natural gas hydrate. X‐ray computed tomography (CT) is a potential method to nondestructively detect the occurrence of natural gas hydrate. The basic physical properties such as porosity, hydrate saturation, and sediment permeability of the hydrate‐bearing sediments are analyzed by calculating the CT numbers or combining with the network model. Therefore, the X‐ray CT is used to study the hydrates produced in the laboratory and the hydrates formed in the nature by scientists all over the world. By summarizing the previous research, this article focuses on the important role of X‐ray CT in the hydrate research from the following three aspects: analyzing the basic physical properties of hydrate sediment, identifying the occurrence mode of hydrate in sediments, and measuring the hydrate formation and decomposition process. In response to the research progress and future research directions, relevant suggestions had been put forward. The application of X‐ray computed tomography (CT) in natural gas hydrate is summarized from the following perspectives: analyzing the basic physical properties of hydrate sediment, identifying the occurrence mode of hydrate in sediments, measuring the hydrate formation and decomposition process. In response to the research progress and future research directions, relevant suggestions are put forward.