Search

Metal halide perovskites are promising semiconductors for next-generation light-emitting diodes (LEDs) due to their high luminance, excellent color purity, and handily tunable band gap. However, it remains a great challenge to develop perovskite LEDs (PeLEDs) with pure red emission at the wavelength of 630 nm. Herein, we report a spectrally stable and efficient pure red PeLED by employing sequential ligand post-treated CsPbI3 quantum dots (QDs). The synthesized CsPbI3 QDs with a size of ∼5 nm are treated in sequential steps using the ligands of 1-hydroxy-3-phenylpropan-2-aminium iodide (HPAI) and tributylsulfonium iodide (TBSI), respectively. The CsPbI3 QD films exhibit improved optoelectronic properties, which enables the fabrication of a pure red PeLED with a peak external quantum efficiency (EQE) of 6.4% and a stable EL emission centered at the wavelength of 630 nm. Our reported sequential ligand post-treatment strategy opens a new route to improve the stability and efficiency of PeLEDs based on QDs.

In this study, carbon nanotubes with Fe cores (Fe-CNTs) were successfully prepared by the vapor deposition method, which used raw coal as a carbon source. The brookite crystal Ti3+-doped TiO2 (Ti3+...

As one fundamental property of light, polarization has a huge impact in quantum optics and optoelectronics through light-matter interactions. However, the bright and near-unity polarized light emissions in the visible range by solid crystalline materials are scantly realized. Here, we report well-defined quasi two-dimensional (2D) hybrid crystals based on the linear alignment of Cu2I2-dimer/bidentate ligand hybrid clusters for achieving bright and near-unity linearly polarized light emissions. Using first-principle calculations, we demonstrate that the superaligned transition dipole moments are the key for the observed excellent polarized light emissions. To further enhance the photoluminescence (PL) polarization degree, we fabricate Cu2I2-dimer-based hybrid nanobelts, which display high PL quantum yield (up to 64%) and ultrahigh PL polarization degree (∼0.99). Our reported copper iodine cluster-based luminescent hybrid materials for bright and highly polarized light emissions will have great potential for future quantum optics applications.

In this article, the design of the hourglass truss sandwich structure is improved by optimizing the number of layers to enhance the compressive strength of both the core and the face sheet and then its mechanical performance. The hourglass truss structures characterized by three different numbers of layers are manufactured using an interlocking and vacuum brazing method. The effect of the layer number of the hourglass core panels on their out-of-plane compression and in-plane compression performance is investigated, and the results from calculations and experiments are in reasonable agreement. The results show that as the layer number of the hourglass core increases, the out-of-plane compressive strengths show little change, but their energy absorption properties are effectively increased. The in-plane compressive failure mechanism maps are constructed, and the specimens are designed to examine the local elastic and inelastic buckling failure modes of the face sheets. The results suggest that as the number of layers of the hourglass core increases, its maximum in-plane compressive load increases. The maximum in-plane compressive loads of the two-layer hourglass truss panels are 57%–70% higher than those of the single-layer panels. It can also be concluded that the out-of-plane and in-plane compression mechanical properties of the multilayer hourglass truss outperform those of the pyramidal truss. Furthermore, the number of layers of the hourglass core is optimized in consideration of both mechanical properties and fabrication cost.

Low angle dependence single green polystyrene colloidal crystal films were prepared by vertical deposition method using polystyrene microspheres with size of 380 ± 10 nm as raw material and further modified by adding nano-carbon. Without nano-carbon addition, the film showed various colors with changing the angle of incident light under natural light. With nano-carbon addition, saturation and angle dependence of the polystyrene colloidal crystal film were remarkably improved. With 0.01 wt % nano-carbon addition, since the stray light of other wavelengths other than the band gap light was absorbed by the added nano-carbon, the film showed only green color under different angles of incident light, suggesting that the film had low angle dependence. It is significant in the research of color behavior and is helpful to obtain single color polystyrene colloidal crystal film.

The assembly of paddle-wheel Ru2 building units affords a new trimetallic carbonate, Cs3Cd(H2O)6[{Cd(H2O)3}2{Ru2(CO3)4}3]·10H2O (1), that contains structurally near-perfect kagome layers, {Ru2(CO3)4}n3n-, linked by octahedral Cd(H2O)32+ into a nanoscale kagome network exhibiting ferromagnetic ordering below 3.5 K. The investigation of influences of the grinding method on the crystal samples of compound 1 reveals that the coercivity increases from ∼2.5 Oe to 44.0 Oe upon a grinding treatment for 180 minutes. The results demonstrate that compound 1 can vary from a soft magnet to a hard magnet simply by manually grinding the crystal samples to the nanoscale.

Control of magnetic performances of molecular magnets is essential but few efforts have been documented. A green and efficient sonication assisted synthesis of a new heterometallic diruthenium(II,III) carbonate, Na[Ni(H2O)4Ru2(CO3)4]·3H2O (1), was carried out by self-assembling in aqueous solution. Compound 1 exhibits spin-glass behavior below ∼5.0 K, and a systematic investigation of the ultrasonic irradiation influence on the powder samples reveals that their coercivity increases from 50 Oe to 743 Oe with the control of ultrasonic power under appropriate conditions.

A Dielectric Fabry Perot Cavity Antenna (FPCA) is proposed in this paper. It consists of a dual-layer superstrate with the same size placed on top of a square ground plane. It is fed by a waveguide attached at the bottom surface of the ground plane. It has an impedance bandwidth of 6.09 % and an antenna gain of 13.80 dBi. It achieved an antenna gain enhancement of more than 3dB compared with its single-layer counterpart.

A low profile cavity-backed dual-band antenna based on half mode substrate integrated waveguide (HMSIW) technology is designed. HMSIW technology is used to make semicircular resonant cavity. An additional resonance can be generated by loading a U-shaped strip outside the radiation aperture of HMSIW cavity, thus realizing the dual-band performance. The reflection characteristics of single-band and dual-band HMSIW cavity-backed antennas are studied. The simulated results show that the resonant frequencies can be controlled easily by changing the antenna parameters. The proposed antenna has the characteristics of low profile, high gain and low cross polarization.

In this paper the enhanced lattice topology (defined as hourglass), with the improved resistance to tearing of face sheets, is used to improve the underwater blast impact performance of lattice truss structures. The stainless-steel lattices are fabricated by an interlocking and vacuum brazing method, all with a core relative density of about 4%. Their mechanical behaviors are investigated under quasi-static out-of-plane compression and underwater blast impact, in the latter case using an underwater shock simulator. Results show that the quasi-static compressive strength of the hourglass lattice is similar to that of the pyramidal lattice for the relative density chosen in this paper. The failure modes of the hourglass lattice panels subjected to underwater blast impact consist of core truss buckling, node imprinting and stretching of the front face sheets. The obtained results confirm that the hourglass lattice sandwich panel shows an approximately 60% reduction in the maximum panel deflection with respect to a monolithic plate of equal mass per unit area. Furthermore, the underwater blast impact performance of the hourglass lattice panels outperforms that of the pyramidal lattice panels of equal weight per unit area in the sense of resistance to stretching and tearing of the face sheets. Therefore, sandwich structure with the hourglass lattice design is a potential candidate for protective structures.

Exploring lightweight sandwich structures with excellent load-bearing and vibration damping performances is one of the important topics in structural and functional applications. The aim of the present work is to design, fabricate novel metallic sandwich structures with Hourglass truss cores and investigate their modal characteristics and vibration isolation performances by comparing with the traditional pyramidal sandwich structure experimentally and numerically. It is shown that the natural frequencies of the Hourglass sandwich structures are much higher than that of the pyramidal sandwich structures under free-free boundary condition and equal relative density of the truss cores. The torsional modes and transverse bending modes of the Hourglass sandwich structures separately play a dominant role in lower and higher modes of vibration, which are opposite to the pyramidal sandwich structures. From the results of the acceleration frequency responses and vibration level difference (VLD), it is indicated that the Hourglass sandwich structures exhibit better vibration isolation performance than the pyramidal sandwich structures. Furthermore, experimentally validated finite element analysis (FEA) models are developed to study the influences of truss inclination angles and boundary conditions on the modal characteristics of the present sandwich structures. Some conclusions are summarized, which may be useful for understanding the vibration behavior of such kinds of lattice sandwich structures.

An underground gas storage company adopted bimetallic composite pipes for gas transmission. The pipelines were inspected with industrial camera, it was found that a large number of pipelines had liner collapsed, and some of collapsed liner had suspected cracks. In order to analyze the reasons for the collapse and cracking of the liner, visual inspection, non-destructive testing, material examination, crack analysis, bend fatigue test and pressure test were conducted. The results showed that the material properties of the bimetal composite pipe meet standard requirements. The external pressure test was imposed on Φ168 composite pipe, the liner collapse under the pressure of 1.76MPa which is lower than the calculated value. The cause of collapse was analyzed from manufacturing process and service condition. There are micro-cracks around the main crack of the liner, the fracture showed fatigue striations and thickness thinning characteristic. The root cause of the liner collapse is that the water enters the interlayer during the manufacturing of bimetallic composite pipe, and the thermal expansion coefficient of base pipe and lining pipe is different. When external anti-corrosion coating was manufactured and temperature changed during operation, collapse tendency of the liner increased. The root cause of the crack of the liner is bending fatigue, and the load originates from pressure fluctuations during operation. In order to avoid such incidents, the online inspection should be performed for the effusion part of the pipeline to check whether the remaining wall thickness of the base pipe meets the requirements for safe operation. The carbon steel pipe with regular pigging was recommended for this application situation.

This paper focuses on strengthening carbon fiber hierarchical composite square honeycomb structures (HCSH) by selecting high-modulus hierarchical phase and optimizing its thickness. HCSH have been manufactured from carbon fiber composite foam sandwich structures by a simple snap-fit and bonding method. The measured compressive and shear strengths are shown to be well predicted by micromechanics failure models of HCSH. Compared to the monolithic composite square honeycomb structures (CSH), the measured specific out-of-plane compressive strength of HCSH improves to approximately 330% and the specific shear strength improves to about 180%. Furthermore, the relationships between hierarchical phase modulus and its optimum thickness are developed to design the optimum HCSH. Carbon fiber HCSH are found to exhibit better mechanical properties than other cellular structures, and thus provide new opportunities for light-weight multifunctional sandwich structures.

We propose a novel two-dimensional (2D) SnP3 crystal that possesses low indirect band gaps of 0.67 eV (monolayer) and 1.03 eV (bilayer) and high kinetic and thermal stability until 500 K. The 2D SnP3 shows strong interlayer quantum confinement effects, resulting in a band gap increase from mono- to bilayer, and then a band gap decrease from bi- to triple layer leading to a semiconductor–metal transition. Monolayer SnP3 has large hole mobility (992 cm2 V–1 s–1), whereas bilayer SnP3 has high electron mobility (8002 cm2 V–1 s–1) which is comparable to that of phosphorene. The static dielectric constants of mono- and bilayer SnP3 are 3.21 and 5.24, respectively. Both monolayer and bilayer SnP3 show strong light absorption in the visible and ultraviolet regions. The indirect band gap of monolayer SnP3 decreases under biaxial compressive strain and increases under biaxial tensile strain. Especially, when the biaxial compressive strain reaches to 6%, monolayer SnP3 has a transition from semiconductor to metal. ...

A new theoretical model based on the extended high order sandwich panel theory is established to predict the mechanical response of sandwich panels under static loads with the bilinear constitutive stress–strain relation in the core. The constitutive relations of normal stresses related to the longitudinal and vertical normal strains in the bilinear isotropic hardening core are first formulated. The influence of the in-plane rigidity on the elastoplastic response of sandwich structures is analyzed. An in-plane loaded sandwich structure with the bilinear core is first studied based on extended high order sandwich panel theory, and the effect of the bilinear ratio on the mechanical response is evaluated. The governing equations are derived from the principle of minimum potential energy, and a Ritz-based half-analytical method is applied to get the solutions. The plastic response is acquired by an iterative procedure along with the convergence criteria. The results reveal that the local effect can be captured when the axial rigidity of the core is considered. The bilinear characteristic of the core decreases the maximum normal stress with an increase of the average value. The equivalent plastic region extends with the increase of the bilinear ratio when the sandwich structure is loaded in plane. By comparison with open literatures and finite element results, the present theoretical model is proved to be effective and efficient.

This research focuses on the dynamic response of sandwich panels with multilayered graded hourglass lattice core subjected to blast loading. A three-layer lattice core configuration is proposed to improve the absorption efficient of kinetic energy resulted from blast shock wave. The relative density of each core layer is changed with sectional dimension of core truss members to regulate the energy absorption of each core layer. Three-dimensional numerical simulation analyses of dynamic response are carried out, and the applied impulsive pressure distribution on the surface of the panels is calculated using the CONWEP code. The panels are made of stainless steel AL6XN, which is assumed to follow bilinear strain hardening and strain rate-dependence. Peak back sheet deflection and energy absorption of core layers for four types of hourglass lattice panels are comparatively analyzed and the effects of load intensity on the peak deflection are discussed. Furthermore, the near-optimal configuration under blast loadings is proposed.

Topological-reinforcement and material-strengthening were used and employed to improve the mechanical properties of lattice truss sandwich structures. This new type of three-dimensional aluminum alloy lattice truss (named enhanced lattice truss) sandwich structure, with a relative density ranging from 1.7% to 4.7%, was designed and fabricated by interlocking and vacuum-brazing method. The out-of-plane compression and shear properties of the enhanced lattice truss sandwich structures (both as-brazed and age-hardened cores) were experimentally and analytically investigated. Good correlations between analytical predictions and experiment results were achieved. Experimental results showed that the mechanical properties of the enhanced lattice truss cores were sensitive to the unit-cell size and parent-alloy properties (i.e. inelastic buckling and tangential modulus). The compressive and shear characteristics of enhanced lattice truss sandwich structures were discussed and found superior to competing lattice truss structures in low density area (0.046–0.124 g/cm3) of material property charts. The combination of topological-reinforcement and material-strengthening provided a way to achieve lightweight sandwich structures with high specific strengths and low densities.

A quantum dot coupled to two electrodes with spin-dependent splitting of chemical potentials (spin bias) is proposed as a detector of an individual electron spin. Spin polarized transport properties through the quantum dot have been investigated theoretically by means of the nonequilibrium Green's function formalism. We found that the direction of current flow is dependent on the electronic spin state in quantum dot. Measuring the direction of the current flow through the devices, we can determine the direction of the electronic spin state in quantum dot. This proposed detector provides a practical and all electrical approach to detect the electronic spin state in quantum dot structure.

Quantum memory is a crucial component for the large-scale quantum networks. Rare-earth-ion doped crystals have been a promising candidate for the practical quantum memory because of its very long coherence time. However, doped ions cause unwanted lattice distortion, and consequently reduce the optical depth and the storage efficiency. The stoichiometric rare-earth crystals have low lattice distortion and high rare earth ion density, and thus are expected to enable high-efficiency storage. EuCl3·6H2O is a promising material for quantum memory applications because its optical inhomogeneous broadening can be smaller than its hyperfine splitting and the theoretically predicted spin coherence time is up to 1000 seconds. Despite the numerous efforts in solid-state quantum memory based on rare-earth ion doped crystals, optical memory and quantum memory have not been implemented with stoichiometric rare-earth crystals yet. Here, we report the atom frequency comb optical storage using a EuCl3·6H2O crystal. A coherence time of 55.7 μs is obtained by photon echo measurements on \begin{document}$^7{\rm{F}}_0 \rightarrow {}^5{\rm{D}}_0$\end{document} transition. The two-level atomic frequency comb storage is demonstrated with a storage efficiency of 1.71% at a storage time of 1 μs, showing the potential capability of optical quantum storage of this material. Based on the analysis of the line shift of \begin{document}$^7{\rm{F}}_0 \rightarrow {}^5{\rm{D}}_0$\end{document} depending on the sample temperature, we highlight the challenge of achieving high-efficiency optical pumping in this material, which imposes a limit on the achievable efficiency.

For the first time, an experiment has been conducted to investigate synthetic jet laminar vortex rings impinging onto porous walls with different geometries by time-resolved particle image velocimetry. The geometry of the porous wall is changed by varying the hole diameter on the wall (from 1.0 mm to 3.0 mm) when surface porosity is kept constant ($\unicode[STIX]{x1D719}=75\,\%$). The finite-time Lyapunov exponent and phase-averaged vorticity field derived from particle image velocimetry data are presented to reveal the evolution of the vortical structures. A mechanism associated with vorticity cancellation is proposed to explain the formation of downstream transmitted vortex rings; and both the vortex ring trajectory and the time-mean flow feature are compared between different cases. It is found that the hole diameter significantly influences the evolution of the flow structures on both the upstream and downstream sides of the porous wall. In particular, for a porous wall with a small hole diameter ($d_{h}^{\ast }=0.067$, 0.10 and 0.133), the transmitted finger-type jets will reorganize into a well-formed transmitted vortex ring in the downstream flow. However, for the case of a large hole diameter of $d_{h}^{\ast }=0.20$, the transmitted vortex ring is not well formed because of insufficient vorticity cancellation. Additionally, the residual vorticity gradually evolves into discrete jet-like structures downstream, which further weaken the intensity of the transmitted vortex ring. Consequently, the transmitted flow structures for the $d_{h}^{\ast }=0.20$ case would lose coherence more easily (or probably even transition to turbulence), resulting in a faster decay of the axial velocity and stronger entrainment of the transmitted jet. For all porous wall cases, the velocity profile of the transmitted jet exhibits self-similar behaviour in the far field ($z/D_{0}\geqslant 6.03$), which agrees well with the velocity distribution of free synthetic jets. With the help of the control-volume approach, the time-mean drag of the porous wall is evaluated experimentally for the first time. It is shown that the porous wall drag increases with the decrease in the hole diameter. Moreover, for a porous wall with a small hole diameter ($d_{h}^{\ast }=0.067$, 0.10 and 0.133), it appears that the porous wall drag mainly derives from the viscous effect. However, as $d_{h}^{\ast }$ increases to 0.20, the form drag associated with the porous wall geometry becomes significant.

All‐inorganic cesium lead halide perovskite colloidal nanocrystals (NCs) (CsPbX3, X = Cl, Br, I) have emerged as potential candidates for next‐generation light‐emitting diodes (LEDs). However, high trap states on the surface of CsPbX3 NCs caused by ionic nature and dynamic bonding of organic ligands limit the performance of CsPbX3 NCs‐based LEDs. Herein, a microemulsion (ME)‐modified strategy to decorate CsPbBr3 NC cores with inorganic PbWO4 is developed. It is demonstrated that ME‐assisted modification plays a crucial role in bridging the WO42− anion solution and the CsPbBr3 NC suspension. Compared with pristine CsPbBr3 NCs, the obtained PbWO4‐modified NCs exhibit improved photoluminescence efficiency. The corresponding NC films also show enhanced stability at elevated temperature and also in humid atmosphere. Consequently, the PbWO4‐modified NCs‐based LED exhibits a pronounced improvement of electroluminescence with an external quantum efficiency from 0.2% to 5.7% and twofold enhancement of the operational lifetime through PbWO4 passivation in comparison with that of pristine CsPbBr3 NCs‐based LED. These results show a promising pathway by ME‐induced anionic modification for high‐performance and stable LEDs based on perovskite NCs.

This paper aims to propose a new theory on the elastoplastic transient response of sandwich beams under large displacement with moderate rotation, including an analysis strategy for multi-dimensional elastoplasticity and the corresponding numerical solving technique. The material behaviors follow the bilinear proportional hardening rule. According to the classifications of stress statuses, the updated structural stiffness of the sandwich beam in time history is acquired and a systematic procedure for the multi-dimensional elastoplastic dynamic analysis is subsequently developed. The dynamic governing equations involving geometric and material nonlinearities are solved by a modified Ritz-based approach, in association with the Newmark-beta technique. The closed linear solution and the finite element simulation validate the accuracy of the proposed nonlinear theory. Case study reveals that the strain hardening has significant effects on the dynamic response of sandwich beams. The application to the blast-resisting study of sandwich beams as sacrificial coatings on ship hulls further proves the effectiveness of the current theory.

A new dual-fed dual-frequency antenna that integrates a microwave hollow dielectric resonator antenna (DRA) with a high-gain millimeter-wave dielectric Fabry–Perot resonator antenna (FPRA) is investigated. To obtain the dual-frequency operation, the dielectric and air regions of the hollow DRA are designed to satisfy the resonance condition of the FPRA. The DRA and FPRA are excited by a strip and a WR-34 waveguide, respectively. For demonstration, a prototype that covers both 2.4- and 24-GHz ISM bands was fabricated and tested. The S-parameters, radiation pattern, antenna gain, and antenna efficiency are studied, and reasonable agreement between the measured and simulated results is found.

Steady state florescence and three-photon-absorption-induced upconversion fluorescence of two fluorene-based derivatives with different electron donors were investigated. The upconversion fluorescence intensity is cubic with the input intensity. The electron donors have great impact on the upconversion fluorescence property. The transition processes of the two molecules were investigated with TD SCF/DFT theory methods, the results of theory and experiments accord well with each other.

In order to explore a smart carrier which can control drug delivery in special pH environment, a type of nanometer material, namely, poly acrylic acid acrylamide (P(AA-AM)) was synthesized with acrylic acid and acrylamide as monomers. Its structure was determined using Fourier transform infrared spectroscopy (FTIR) and its swelling properties were tested by measuring its weight evolution. The drug delivery control potential was estimated by monitoring its swelling performances in the solutions of different pH values. The cycle characteristics were also investigated to determine its degradation properties in the environment. The results indicate that the synthesized material is sensitive to pH and is suitable for controlling drug delivery at the pH range from 10 to11 and below 7. Furthermore, this material can be automatic decomposition in the environment so that it is a degradable green material without causing burden to the environment.

The low through-thickness thermal conductivity limits the thermal management application of carbon fiber reinforced polymer-matrix (CFRP) composites. A simple method of constructing a 3D thermal conductive pathway is developed to improve the through-thickness thermal conductivity of CFRP laminated composites. Then, a z-filler laminated composite panel is fabricated by filling the copper spheres and coating the aluminum foils, and its effective thermal conductivity is investigated, both experimentally and theoretically. Analytical predictions agree well with measured values. The through-thickness thermal conductivity of z-filler laminated composites has been significantly improved by increasing the z-filler volume fraction but by decreasing the interface thermal resistance. A maximum improvement in the through-thickness thermal conductivity is up to approximately 12 times compared with the unmodified composite materials. Moreover, with high through-thickness thermal conductivity, z-filler laminated composites possess both low coefficient of thermal expansion (CTE) and adequate mechanical properties for structural applications. Thus, z-filler laminated composites can be considered as promising candidates for multifunctional material in the high-end heat dissipation fields.

Kuo-Chen Wei,1 Feng-Wei Lin,2 Chiung-Yin Huang,1 Chen-Chi M Ma,3 Ju-Yu Chen,1 Li-Ying Feng,1 Hung-Wei Yang2 1Department of Neurosurgery, Chang Gung Memorial Hospital, School of Medicine, Chang Gung University, Taoyuan, 2Institute of Medical Science and Technology, National Sun Yat-sen University, Kaohsiung, 3Department of Chemical Engineering, National Tsing Hua University, Hsinchu, Taiwan, Republic of China Abstract: To date, knowing how to identify the location of chemotherapeutic agents in the human body after injection is still a challenge. Therefore, it is urgent to develop a drug delivery system with molecular imaging tracking ability to accurately understand the distribution, location, and concentration of a drug in living organisms. In this study, we developed bovine serum albumin (BSA)-based nanoparticles (NPs) with dual magnetic resonance (MR) and fluorescence imaging modalities (fluorescein isothiocyanate [FITC]-BSA-Gd/1,3-bis(2-chloroethyl)-1-nitrosourea [BCNU] NPs) to deliver BCNU for inhibition of brain tumor cells (MBR 261-2). These BSA-based NPs are water dispersible, stable, and biocompatible as confirmed by XTT cell viability assay. In vitro phantoms and in vivo MR and fluorescence imaging experiments show that the developed FITC-BSA-Gd/BCNU NPs enable dual MR and fluorescence imaging for monitoring cellular uptake and distribution in tumors. The T1 relaxivity (R1) of FITC-BSA-Gd/BCNU NPs was 3.25mM-1s-1, which was similar to that of the commercial T1 contrast agent (R1=3.36mM-1s-1). The results indicate that this multifunctional drug delivery system has potential bioimaging tracking of chemotherapeutic agents ability in vitro and in vivo for cancer therapy. Keywords: drug tracking, fluorescence imaging, MR imaging, BSA nanoparticles, cancer therapy

A multifunctional composite square honeycomb sandwich structure (MCHSS) is developed which provides both high thermal conductivity and adequate mechanical property for a thermal management system. The out-of-plane thermal conductivity of MCHSS is improved by a simple method of coating highly oriented graphite film (HOGF), and investigated both theoretically and experimentally. There are two most efficient methods to further enhance the out-of-plane thermal conductivity of MCHSS: one is to increase the HOGF volume content, and the other, to decrease the interface thermal resistance. The maximum improvement is up to approximately 26 times for the measured out-of-plane thermal conductivity as compared with the traditional composite sandwich structures. Results indicate that, except for high specific thermal conductivity for thermal management, MCHSS also possess adequate mechanical properties for structural applications. Thus, MCHSS can be considered as a promising candidate for multifunctional structure material in the high-end heat dissipation field. Keywords: Multifunctional sandwich structures, Composite square honeycomb, Highly oriented graphite film, Thermal conductivity, Mechanical properties

This paper focuses on improving the strength of truss lattice sandwich structures by optimizing the topology structure. A new Hourglass truss lattice sandwich structure is then designed and fabricated by a snap-fit method. The out-of-plane and in-plane compressive properties of the Hourglass lattice sandwich structure are investigated theoretically and experimentally, and the measured results are compared with the analytical predictions. Results show that the low relative density Hourglass lattices have higher peak out-of-plane compressive strengths than the pyramidal lattices. Moreover, the peak in-plane compressive loads of Hourglass lattice sandwich structures are superior to the pyramidal sandwich structures. Therefore, the Hourglass lattice sandwich structure can be considered as a promising candidate in high specific strength lightweight structures.

The thermal conductivity prediction of a conductor/insulator composite with various geometrical structures of the conducting phase is one of the top challenges in disordered composites. To determine the effects of the geometrical structure of the second phase on the thermal conductivity of a conductor/insulator composite, Cu 2 O/Cu composites were prepared with spherical or branch-like Cu by hot-pressing technology. The box-counting fractal dimension was applied to characterize the geometrical structure of the second phase. The fractal dimension of branch-like Cu shows significantly lower values than the spherical Cu with a same filling content. The fractal dimension increasing rate with increasing Cu content was first introduced to predict the thermal conductivity of the composites. These results provide a pathway to determine the effects of the geometrical structure of the second phase on the thermal conductivity and shed some lights on building relationships between the tortuosity, fractal dimension, and overall performances of conductor/insulator composites.