Diamond Channel Research Articles

Investigating the impact of cooling configurations on heat transfer coefficient and friction coefficient under rotating state

A comprehensive study was conducted to compare the heat transfer coefficients (HTC) of four different pin–fin structures in a rotating state. The HTC were evaluated within specific conditions: the inlet Reynolds number (Re) varied from 10,000 to 70,000, the rotation number (Ro) ranged from 0 to 1.0, the temperature ratio (TR) spanned 0.04 to 0.22, and the Buoyancy number (Buo) ranged 0 to 2.55. The diamond pin-fins channel exhibited optimal HTC performance, whereas the elliptical pin-fins channel exhibited the least HTC. Remarkably, the droplet pin-fins channel demonstrated enhanced cooling effects near the channel entrance compared to the circular pin-fins channel, but in the latter part of the channel, the circular pin-fins channel exhibited higher HTC. Overall, the circular and droplet pin-fins channels had lower HTC than the diamond pin-fins channel but surpassed the elliptical pin-fins channel. The incorporation of pin-fins increased the interaction area between the coolant and the surface, leading to enhanced turbulence and coolant blending, thereby improving HTC. The pin-fins structure design was instrumental in boosting HTC. Research findings indicated a gradual enhancement in heat transfer effectiveness as the pin-fins structure transitioned from elliptical to diamond. Moreover, the study analyzed the influence of TR and Re on HTC, unveiling the complex interplay among pin-fins structures, fluid dynamics, and heat transfer efficiency.

Molecular Dynamics Simulation of the Adsorption and Diffusion of C8 Aromatic Isomers in MIL-47(V).

The separation of C8 aromatic isomers (oX: o-xylene, pX: p-xylene, mX: m-xylene, and EB: ethylbenzene) remains an enormous challenge in industrial production due to their similar molecular structures and physical properties. Porous materials with suitable pore structures and selective recognition sites to discriminate the slight structural differences of isomers are imminently needed. In this paper, MIL-47(V) with a three-dimensional (3D) grid structure of 10.5 × 10.5 Å2 and a one-dimensional (1D) diamond channel was selected as the adsorbent. However, the mechanism of the adsorption and separation of C8 aromatic isomers in porous materials still needs to be understood. Given the importance of C8 aromatic isomers' confinement in MIL-47(V) for adsorption and diffusion applications, it is important to understand C8 aromatic isomers' behavior in MIL-47(V). Here, we demonstrated from a simulation perspective that metal-organic frameworks MIL-47(V) with one-dimensional (1D) diamond channels can identify C8 aromatic isomers. Molecular dynamics (MD) simulations have shown that organic ligands with guest response sites of MIL-47(V) can effectively distinguish between C8 aromatic isomers by adaptation to the shape of a specific isomer. MIL-47(V) has high adsorption and an excellent separation sequence between C8 aromatic isomers: oX > pX ≈ mX > EB. Significant differences exist in π-π superposition interactions between C8 aromatic isomers and between C8 aromatic isomers and the skeletons. This phenomenon is mainly caused by the unique pore structure and guest response characteristics of MIL-47(V). This work is identified as a supplementary instruction to experimental research and is expected to provide profound insights into research on developing C8 aromatic isomers' adsorption and separation and theoretical support.

Flow and heat transfer performance of bionic heat transfer structures with hybrid triply periodic minimal surfaces

Efficient energy conversion technologies are essential for mitigating the environmental impact of industrial activities. The development and application of high-efficiency heat exchangers are key components in this endeavor. Heat exchangers based on triply periodic minimal surfaces (TPMS) are widely acknowledged for their exceptional thermal-hydraulic performance. However, current research mainly focuses on the design and optimization of heat exchangers with standard TPMS structures. In this study, a hybrid process is utilized to construct ten novel heat exchangers, followed by comprehensive investigations of their internal flow fields using three-dimensional numerical simulations. In order to establish a baseline, five standard TPMS structures are also introduced as reference cases. The results reveal that complex secondary flow distributions and velocity variations are critical factors influencing the thermal-hydraulic performance. Moreover, the influence of different standard TPMS cells on the flow and heat transfer characteristics varies during the hybridization process. Specifically, the inclusion of the Schwarz cell generally leads to an improvement in heat transfer, while the presence of the Lindinoid cell may result in a deterioration of heat transfer. The Diamond and Lindinoid cells have an adverse impact on the flow characteristics, while the Gyroid and Neovius cells enhance the flow characteristics. To evaluate the overall thermal-hydraulic performance of different channels, a comprehensive performance assessment is introduced. The Diamond channel and the Gyroid-Neovius channel show superior overall performance in their respective Reynolds number regions, with the former exhibiting better flow characteristics and the latter has outstanding heat transfer performance.

Normally-off operation in vertical diamond MOSFETs using an oxidized Si-terminated diamond channel

We fabricated (001) vertical diamond metal-oxide-semiconductor field-effect transistors (MOSFETs) with oxidized Si-terminated (C–Si–O) diamond channels on the surfaces and trench sidewalls. The C–Si–O diamond surface is approximately 1.0 eV weaker in negative electron affinity than the hydrogen-terminated (C–H) diamond surface, resulting in a smaller valence band bending between the interface of C–Si–O diamond surface and Al2O3, and larger the difference between the energy values of the fermi level and the valence band on the top (EF−EV), and the threshold voltage (Vth) shifts in the negative direction. As a result, the maximum drain current density was 108 mA/mm, the Vth was −9.0 V. Compared with conventional vertical diamond FETs using a C–H channel, the Vth was shifted more than 20 V in the negative direction to reach normally-off mode. The normally-off operation was achieved while maintaining high current density, which is the first case of normally-off operation that has been observed in vertical diamond FETs. In, addition, it was confirmed that the diode functions as a freewheeling diode by adding a reverse drain voltage and allowing current to flow, and the change of current-voltage characteristics was also investigated by swapping the source and drain positions and performing measurements.

Optimization design and numerical study on thermal performance of a novel diamond-type channel cold plate

Heat dissipation capacity is of great importance object for the battery thermal management system (BTMS). To obtain a simple and efficient liquid cooling method for rectangular lithium-ion battery, three types of diamond channel (line, inner arc and outer arc) cold plate were established. Firstly, the temperature rise of line diamond microchannel cold plate under basic conditions were simulated. Then, an experimental device for measuring the surface temperatures of cold plate was designed, and the numerical simulation results were verified. The results showed that the errors between the avenge temperature (Tavg) of experiment and simulation were between 0.66% and 2.1%, and the inner arc diamond-type channel cold plate had better cooling effectiveness. Then the effects of the connection form of the intermediate channel, structural parameters and the layout of the inlet and outlet on the cooling performance of the cold plate were discussed. The pressure drop (ΔP) and Tavg of the best results reach 5.33Pa and 36.52 °C respectively. Compared with the initial condition, ΔP was decreased by 32.81Pa (86.03%) and Tavg was decreased by 0.69 °C (1.9%). The above research results depict that the new diamond-shaped cold plate proposed in this paper could greatly enhance the cooling performance of the liquid-cooling system.

Synergistic Effects of Lewis Acid-Base Pair Sites─Hf-MOFs with Functional Groups as Distinguished Catalysts for the Cycloaddition of Epoxides with CO2.

The incorporation of Lewis acid-base sites in catalysts has been considered as a significant approach to fabricating bifunctional catalysts with efficient catalytic activity for CO2 fixation. In this paper, a series of Hafnium-based metal-organic frameworks (Hf-MOFs), NU-912(Hf) and NU-912-X(Hf)-X (X = -NH2, -Br, -CN, and -I) derivatives assembled by Lewis acidic Hf6(μ3-O)4(μ3-OH)4(H2O)4(OH)4 (Hf6) clusters and Lewis base-attached organic linkers, are successfully synthesized by a facile ligand functionalization method. These isostructural Hf-MOFs, which exhibit diamond channels of 1.3 nm diameter, great chemical stability, and CO2 adsorption capacity, have been evaluated as catalysts for the CO2 cycloaddition reaction with epoxides. Catalytic experiments reveal that the micropore environments of these MOFs have an outstanding impact on catalytic activity. Remarkably, NU-912(Hf)-I serves as an efficient heterogeneous catalyst for this catalytic reaction under mild conditions due to the high density of Lewis acid Hf6 cluster centers and strong Lewis base functional groups, surpassing most of the reported MOF-based catalysts.

Heat Transfer and Pressure Loss of Additively Manufactured Internal Cooling Channels With Various Shapes

AbstractAdditive manufacturing (AM) provides the ability to fabricate highly customized internal cooling passages that are relevant to gas turbine components. This experimental study examines the pressure loss and heat transfer performance of a range of fundamental channel shapes that were produced using direct metal laser sintering. Circular, hexagonal, pentagonal, elliptical, diamond, square, rectangular, trapezoidal, and triangular channel cross sections were investigated. To maintain the same convective surface area between shapes, the wetted perimeters of the channel cross sections were kept constant. Parallel computational fluid dynamic simulations were performed to understand the relationships in cooling performance between several channel shapes. Several characteristic length scales were evaluated to scale the pressure loss and heat transfer measurements. Among the channel shapes investigated, the diamond channel showed the lowest Nusselt number and friction factor. The pentagon exhibited a similar Nusselt number as the circular channel despite having a lower friction factor. There was no difference in scaling the friction factor or Nusselt number results of the different channel shapes between using the square root of cross-sectional area compared to hydraulic diameter as the characteristic length scale

Study of a diamond channel cut monochromator for high repetition rate operation at the EuXFEL: FEA thermal load simulations and first experimental results

The recent start of the European X-ray Free-Electron Laser (EuXFEL) provides a unique pulsed X-ray source of high spectral brilliance and high photon flux at a high repetition rate and opens the possibility for new scientific opportunities. However, the EuXFEL beam has a high peak power that is converted into a high cyclic thermal load on the optical elements, such as mirrors and monochromators, and is impossible to fully mitigate within the pulse train pattern. In the single crystal based X-ray monochromators, the increase of temperature leads to deformation of the crystal structure which affects the rocking curve and consequently the performance of these devices and the quality of the transmitted X-ray beam. To address the increase of temperature, we propose the use of a diamond channel-cut monochromator as an alternative to the current silicon monochromators. In this work we present the design and parameters of the diamond monochromator, heat load simulations and the surface and crystalline quality characterisation. The heat load simulations indicate a high performance of the monochromator under the pulse train of the EuXFEL and the characterisation demonstrates high crystal quality and its functionality as a double crystal monochromator.

Analysis and optimization of flow and heat transfer performance of active thermal protection channel for hypersonic aircraft

This paper presents a numerical simulation on the thermal–hydraulic performance of multiple parallel cooling channels to realize active thermal protection of hypersonic aircraft. The fluid velocity is set in the range of 0.5–2.5 m/s, with the corresponding Reynolds number of 4300 to 22,000, and results show that the rectangular and triangular channel have the best cooling performance on outer wall and inner wall with water as coolant, respectively. Further, “Diamond” channel is proposed to improve the cooling performance, and aviation kerosene RP–3 is used as coolant. Three inlet temperatures (243, 253 and 263 K) are applied to investigate the thermal protection performance of Diamond channel. The cooling performance of RP–3 is better than water, and total pump power of RP–3 is only 60% of water. It is found that the conspicuous symmetric longitudinal swirls generated at the leading edge effectively enhance the heat convection performance. Under the studied ranges of fluid velocity and inlet temperatures, outer and inner wall temperatures can be controlled below 700 K and 330 K, respectively. Subsequently, the preliminary parameters of the “Diamond” are investigated and optimized. Model with L = 16 mm, Yc = 3 and X = 8.8 mm has better thermal protection performance and mechanical properties.

Vertical 3D diamond field effect transistors with nanoscale gate-all-around

Recent studies have shown that diamond field effect transistors (FETs) have great potential in high-power and high-frequency electronics, exhibiting the maximum leakage current of 1.35 A·mm−1 and the breakdown voltage of 2 kV. However, there is still a lack of preliminary exploration on diamond FETs with a three-dimensional (3D) architecture, which has been evidenced as a promising approach to increase device performance and density for silicon transistors. In this paper, we present a systematic investigation of 3D vertical gate-all-around (GAA) diamond transistors, combined with numerical simulation, device fabrication and characterization of device performance. The p-type conductivity of the diamond channel in a transistor is obtained by Boron-ion implantation. Our numberical simulations address the close correlation of transfer characteristics of the 3D vertical GAA diamond transistors with the ion implanted impurities. In the device fabrication, we introduce the focused ion and electron beam technology for the electrode interconnections in the 3D devices. Finally, we demonstrate that the 3D vertical GAA diamond transistor exhibits the on-off ratio of 2.5 × 103, subthreshold swing of 334.3 mV·dec−1, and threshold voltage of 0.64 V. And the temperature dependence of transfer characteristics of the 3D devices indicates that 3D vertical GAA diamond transistors have potential application prospects in extreme environments such as high temperature.

Simulation of silicon quantum dots with diamond-channel by simplified ME model

Developing novel silicon quantum dots (Si-QDs) on conventional CMOS process is one of the most important technologies in Si quantum computing to realize multi-bit integration with a large scale. In this paper, an analysis model based on master equation and realized by Python code is established to predict and optimize the performance of fabricated diamond channel Si-QDs for potential circuit applications. The model can fast describe the I-V characteristics of devices both in qualitative and semi quantitative method. The inherent tunneling process of Si-QDs can be well simulated by introducing additional parameters and the contribution of neighboring states can be analyzed by setting global parameters. In addition, the calculation speed and accuracy can be readily balanced by modifying the setting parameters. The simulation results of the model are in good agreement with the experimental results at low temperature, which lays a foundation for the performance prediction, structure and process optimization of the Si-QDs for a large scale circuit applications.

The Filtered Gaussian Primitive Diamond Channel

We investigate a special case of diamond relay comprising Gaussian channels with an identical frequency response from the user to the relays, and with lossless fronthaul links with limited rate from the relays to the destination. We use the oblivious compress and forward (CF) scheme with with distributed compression, and a decode and forward (DF) scheme, where each relay decodes the whole message and sends half of the bits to the destination. It is proved that optimal CF-DF time-sharing scheme is advantageous over the CF-DF superposition scheme. We derive an achievable rate by using time-sharing between CF and DF. The optimal time-sharing proportion between CF and DF, and the power and rate allocations are different for each frequency and are fully determined.

Fluorine-Terminated Polycrystalline Diamond Solution-Gate Field-Effect Transistor Sensor with Smaller Amount of Unexpectedly Generated Fluorocarbon Film Fabricated by Fluorine Gas Treatment.

In this study, a partially fluorine-terminated solution-gate field-effect transistor sensor with a smaller amount of unexpectedly generated fluorohydrocarbon film on a polycrystalline diamond channel is described. A conventional method utilizing inductively coupled plasma with fluorocarbon gas leads the hydrogen-terminated diamond to transfer to a partially fluorine-terminated diamond (C–F diamond); an unexpected fluorohydrocarbon film is formed on the surface of the diamond. To overcome this issue, we newly applied fluorine gas for the fluoridation of the diamond. Analytical results of X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry suggest that the fluorocarbon film does not exist or only a smaller amount of fluorocarbon film exists on the diamond surface. Conversely, the C–F diamond fabricated by the conventional method of inductively coupled plasma with a perfluoropropane gas (C3F8 gas) source possesses a certain amount of fluorocarbon film on its surface. The C–F diamond with a smaller amount of unexpectedly generated fluorohydrocarbon film possesses nearly ideal drain–source–voltage vs. gate–source–current characteristics, corresponding to metal–oxide–silicon semiconductor field-effect transistor theory. The results indicate that the fluorine gas (F2 gas) treatment proposed in this study effectively fabricates a C–F diamond sensor without unexpected semiconductor damage.

An anion-functionalized zinc-organic framework for efficient C2H2/C2H4 separation

An anion-functionalized porous framework exhibits a 4,6-connected fsc topology with diamond channels along the b axis, which has high C 2 H 2 adsorption capacity and excellent separation selectivity for 1/99 C 2 H 2 /C 2 H 4 and 50/50 C 2 H 2 /C 2 H 4 . • An anion-functionalized porous framework FJI-W2 has been constructed using a four-connected TPB ligand. • FJI-W2 exhibits a 4,6-connected fsc topology with diamond channels along the b axis. • FJI-W2 manifests excellent separation selectivity for 1/99 C 2 H 2 /C 2 H 4 and 50/50 C 2 H 2 /C 2 H 4 . Separating acetylene from ethylene is a very significant process in the petrochemical industry. Herein, we have successfully synthesized an anion-functionalized porous framework [Zn(TPB)SiF 6 ] n (FJI-W2, TPB = 1,2,4,5-tetra(pyridin-4-yl)benzene). The single component gas sorption isotherms reveal that the adsorption capacity of C 2 H 2 can reach 95 cm 3 /g at 298 K and 1 bar. More notably, FJI-W2 has a high C 2 H 2 uptake of 28 cm 3 /g at 0.01 bar, significantly higher than that of C 2 H 4 (0.1 cm 3 /g). The isosteric adsorption enthalpies for C 2 H 2 and C 2 H 4 further prove that the adsorption affinity of FJI-W2 with C 2 H 2 is much stronger than C 2 H 4 . Ideal adsorbed solution theory shows that the separation selectivity of FJI-W2 for C 2 H 2 /C 2 H 4 (1/99, v/v) and C 2 H 2 /C 2 H 4 (50/50, v/v) can be up to 14.2 and 12.5, respectively.

Numerical Investigation of Thermal Hydraulic Performance of Printed Circuit Heat Exchanger of Periodic Diamond Channel Shape

One of the most recently important heat exchangers is the Printed circuit heat exchanger especially in the nuclear power plant and aerospace applications due to its very compact geometry and small print foot. This paper presents a 3D numerical investigation on the thermo-hydraulic performance of PCHE with new non-uniform channel design configuration. The new channel design is a rectangular cross section with repeated converging diverging sections or periodic diamond shape. The influence of three design parameters on the heat exchanger performance was studied and optimized, pitch length (p), length ratio (β) and the converging diverging angle (α). The computational models investigated in this study based on the operating conditions of the intermediate heat exchanger of very high temperature gas cooled reactor with helium as the working fluid under operating pressure of 3Mpa and inlet temperature of 800 K. The Reynolds number varied from 200 to 2000. Different Pitch lengths were used (1.59, 3.18, 6.36, and 12.73) mm, and different C-D angle (0, 4.5, 6, 7.5, 9, 10.5 and 12) and also different length ratios were used (0.2, 0.25 and 0.333). Three performance parameters were studied the Nusselt number, friction factor and the overall performance evaluation factor. Results show that the thermal performance enhanced with decreasing the pitch length and with increasing C-D angle and it was shown that this enhancement was found only at high Reynolds number above 1400. The best performance obtained at p=3.18, α=6 and β=0.25 based on the overall evaluation performance.

High-mobility p-channel wide-bandgap transistors based on hydrogen-terminated diamond/hexagonal boron nitride heterostructures

Field-effect transistors made of wide-bandgap semiconductors can operate at high voltages, temperatures and frequencies with low energy losses, and are important for power and high-frequency electronics. However, wide-bandgap p-channel transistors perform poorly compared with n-channel ones, making complimentary circuits difficult to achieve. Hydrogen-terminated diamond is a potential p-type material for such devices, but surface transfer doping—thought to be required to generate conductivity—limits performance because it requires ionized surface acceptors that can lead to hole scattering. Here we show that p-channel wide-bandgap heterojunction field-effect transistors can be created, without surface transfer doping, using a hydrogen-terminated diamond channel and hexagonal boron nitride gate insulator. Despite having a reduced density of surface acceptors, the transistors have a low sheet resistance (1.4 kΩ) and large ON current (1,600 μm mA mm−1) compared with other p-channel wide-bandgap transistors, due to a high room-temperature Hall mobility (680 cm2 V−1 s−1). The transistors also exhibit normally OFF behaviour with an ON/OFF ratio of 108. Wide-bandgap transistors with room-temperature hole mobility of 680 cm2 V−1 s−1 can be created without surface doping using hydrogen-terminated diamond/hexagonal boron nitride heterostructures.

Thermal performance of diamond field-effect transistors

In this report, the thermal performance of a hydrogen (H)-terminated diamond field-effect transistor (FET) is investigated using Raman spectroscopy and electrothermal device modeling. First, the thermal conductivity (κdiamond) of the active diamond channel was determined by measuring the temperature rise of transmission line measurement structures under various heat flux conditions using nanoparticle-assisted Raman thermometry. Using this approach, κdiamond was estimated to be 1860 W/m K with a 95% confidence interval ranging from 1610 to 2120 W/m K. In conjunction with measured electrical output characteristics, this κ was used as an input parameter for an electrothermal device model of an H-terminated diamond FET. The simulated thermal response showed good agreement with surface temperature measurements acquired using nanoparticle-assisted Raman thermometry. These diamond-based structures were highly efficient at dissipating heat from the active device channel with measured device thermal resistances as low as ∼1 mm K/W. Using the calibrated electrothermal device model, the diamond FET was able to operate at a very high power density of 40 W/mm with a simulated temperature rise of ∼33 K. Finally, the thermal resistance of these lateral diamond FETs was compared to lateral transistor structures based on other ultrawide bandgap materials (Al0.70Ga0.30N, β-Ga2O3) and wide bandgap GaN for benchmarking. These results indicate that the thermal resistance of diamond-based lateral transistors can be up to ∼10× lower than GaN-based devices and ∼50× lower than other UWBG devices.

Broadcast diamond channel: Transmission strategies and bounds

This paper proposes a new multiuser communication model in which a source with broadcast capabilities wants to transmit two different messages to two different destinations in the case that no direct links between the source and its destinations. In this channel model, two parallel half-duplex relays are used to extend the transmission. For this communication model, an outer bound to the achievable capacity is initially derived. Then, two distinctive transmission schemes are characterized such that the source can transmit to the two destinations. In each scheme, the transmission is split into two phases. Specifically, in the first phase, the source can broadcast different messages to the two relays. Then, in the second phase, the two relays can forward the source’s signals into their destinations. Based on the transmission on each scheme, the achievable rate region is characterized. Further, we derive the optimal duration of each phase. The theoretical analyses are followed by many numerical examples that compare between the different transmission techniques and also show the points at which the capacity is achieved.

Switching Response of Hydrogen-Terminated-Diamond-Based All-Solid-State Electric-Double-Layer Transistor

INTRODUCTION High-density electronic carrier control using an electric double layer (EDL) at electrolyte/electrode interfaces has been attracting attention for the application in various electronic devices. Specifically, the use of solid electrolyte is advantageous for practical use owing to its high compatibility with other peripheral devices.Recently, we have achieved an in situ modulation of hole density in hydrogen-terminated diamond (H-terminated diamond) using an all-solid-state electric double layer transistor (EDLT) [1]. The hole density increased from 1010 cm-2 to 1013 cm-2, a 3-order-of-magnitude difference, applying a negative gate voltage (V G). This indicates that the two-dimensional hole gas was electrostatically modulated by EDL charging at the solid electrolyte/H-terminated diamond interface. Then, we focus on a switching response speed, which is an important parameter for EDLTs. Towards further development of all-solid-state EDLTs for practical use, high switching response is desired. Because diamond is suitable for high-frequency electronic device owing to its high carrier mobility, diamond-based all-solid-state EDLT is a candidate to exceed the response speed of conventional all-solid-state EDLTs EXPERIMENTAL An H-terminated diamond thin film was homoepitaxially grown on the surface of an Ib-type HPHT diamond single crystal (100) using microwave plasma chemical vapor deposition. The channel area was fabricated by photolithography, and O2 plasma ashing. Source and drain electrodes were made of Pt/Pd. Gate electrode was made of LiCoO2 (LCO) and Pt films. We chose a Li+ conducting Li2O-ZrO2-SiO2 (LZSO) amorphous thin film as a solid-state-electrolyte. To compare response speed, we also fabricated EDLT with the same structure except for the gate electrode. The gate electrode of another EDLT was made of Au. Electrochemical measurements were performed using a Keithley 4200-SCS parameter analyzer and an atmosphere/temperature tunable prober system (Nagase). RESULTS AND DISCUSSION Figure 1 shows the switching characteristics of EDLTs measured at the drain voltage of 0.5 V. The measurements were performed in steps of 2 K. When a pulse (V G) is applied, drain current (i D) instantaneously decreases from the 10 microampere order to less than 10 nanoampere order. Thus, EDLTs are switched from an on-state to off-state. As explained in the introduction, this is attributed to the effect of EDL charging at the LZSO solid electrolyte/H-terminated diamond interface. In both EDLTs, the response time is shorter than 50 ms at 298 K. Because the speed is not affected even when the type of the gate electrode was changed, the effect of EDL charge and discharge at the LZSO/LCO interface can be ignored. Therefore, this response speed mainly resulted from EDL charge and discharge processes at the LZSO/H-terminated diamond interface. The response speed becomes faster with an increase in the temperature. This is attributed to an increase in the Li+ conductivity of LZSO. The conductivity of LZSO exhibited a thermally activated behavior with an activation energy of 0.66 eV; the conductivity of LZSO increased from 8×10-9 S/cm at 298 K to 2×10-7 S/cm at 340 K. Although the conductivity of the H-terminated diamond channel changed with an increase in the temperature, the variation was about 25%, which is sufficiently small compared to the variation in that of LZSO. Therefore, the rate of the response speed in EDLTs is determined by the conductivity of LZSO. At 340 K (Li+ conductivity: 2×10-7 S/cm), EDLTs show the response time of less than 800 μs. Thus, H-terminated diamond-based all-solid-state EDLT has a potential for ultrafast switching even at room temperature if an electrolyte with better conductivity is used. Since RbAg4I5 Ag+ superionic conductor (0.12 S/cm at RT [2]) was previously reported as an electrolyte for EDL capacitors [3], RbAg4I5 is a good candidate for ultrafast EDLTs, of which the response speed is expected to exceed 1 GHz.In the presentation, we will show the switching characteristics for H-terminated diamond-based all-solid-state EDLTs using various solid electrolytes. Acknowledgements This work was in part supported by JSPS KAKENHI Grant Number JP20H05816 (Grant-in-Aid for Scientific Research on Innovative Areas “Interface Ionics”), JP19K05279 and JP19J22244 (Grant-in-Aid for JSPS Fellows). REFERENCES [1] T. Tsuchiya, M. Takayanagi, M. Imura, Y. koide, T. Higuchi, and K. Terabe, Abstr. 22nd Intl. Conf. on Solid State Ionics, 2019, P-TUE-108.[2] J.N. Bradley and P.D. Greene, Trans. Faraday Soc., 63 (1967) 424.[3] J. E. Oxley, Proc. Power Sources Symp., 24, 20 (1970)Fig. 1. Switching characteristics of H-terminated diamond-based all-solid-state EDLTs in the temperature range of 298-340 K. The gate electrodes are (a) Pt/LCO and (b) Au. Figure 1

Numerical investigation on a multi-channel micro combustor fueled with hydrogen for a micro-thermophotovoltaic system

Targeting at improving the energy output of the micro-thermophotovoltaic (MTPV) system, the heat transfer performance and energy output of the conventional micro combustor (CMC) and the multi-channel micro combustor (MCMC) with various channel shapes in the MTPV system are compared. The mean outer wall temperature of the MCMC with diamond channel is improved by 86.5 K than that of the CMC at the inlet hydrogen mass flow rate (m˙in,hydrogen) of 1.64 × 10-6 kg/s. Furthermore, four arrangements of MCMC are compared in this work. The double-layer MCMC with layers counterflow exhibits the highest total energy conversion efficiency of 13.2% when the m˙in,hydrogen is 8.10 × 10−7 kg/s. The equivalence ratio (Φ) of premixed hydrogen/air plays a crucial role on the thermal performance of DMCMC-layer counter flow. The outer wall temperature and its uniformity becomes better as the equivalence ratio increases. The MPTV system with a DMCMC-layers counterflow can obtain an energy output of 19.3 W when the m˙in,hydrogen is 1.64 × 10-6 kg/s and Φ is equal to 1. Namely, the multi-channel micro combustor has the potential to be a novel energy resource for the MTPV system.