Interfacial Barrier Research Articles

Tuning the mechanical properties of Mo-W alloyed Ni-based multilayered films upon post-annealing at 600 °C via modulation of individual layer thickness

Ni-based multilayered film is attractive due to its high good thermal conductivity, oxidation resistance and mechanical properties. However, the influence of individual layer thickness on the microstructure thermal stability and mechanical properties have seldom been investigated. Hence, the 5 at.% Mo and 5 at.% W co-added in Ni/NiAl multilayers with individual layer thicknesses ranging from 10 nm to 160 nm were synthesized using co-sputtering. Upon post-annealing at 600 °C, the phase separation of γ-Ni solid solution in multilayer occurs, precipitating dispersed nano-sized α-W phases in major when individual layer thicknesses are lower than 40 nm. The periodical layer interfaces of these multilayers are maintained with excellent thermal stability. The hardness of multilayer is enhanced with reduction of individual layer thicknesses due to grain boundary relaxation, increased layer interfacial barriers and W-related precipitations as obstruction for dislocations movement, showing anneal hardening significantly. Due to crack deflection at the layer interfaces, less brittle W-relative phase precipitation and bare columnar crystals growth, the superior toughness is achieved for 600 °C annealed multilayer with individual layer thicknesses of 40 nm. Therefore, 5 at.% MoW co-alloyed Ni-based multilayer are suitable for high-temperature applications with excellent mechanical properties by modulation of individual layer thicknesses.

Individual Layer Thickness Dependence of Microstructure and Mechanical Properties of Magnetron Sputtering Mo-W-Doped Ni/Ni3Al Multilayers

The mechanical properties of nanocrystalline pure Ni films are degraded due to grain coarsening with exposure for a long time in ambient. In order to further improve the mechanical properties of Ni-based thin films, as-sputtered Mo-W co-doped Ni/Ni3Al multilayered structures were constructed. When the individual layer thickness (h) is lower than 40 nm, both the average grain sizes and the crystallinity degrees are degraded, showing a tendency for the formation of the amorphous phase. With h = 40 nm, nano-twins were observed as (111) twining interfaces for the multilayers due to the reduction of the stacking fault energy by the co-doping of Mo-W, whereas the nucleation and growth of the nano-twins were limited, without observations for the Mo-W co-doped Ni/Ni3Al multilayer with h = 10 nm. The hardness of the multilayers was enhanced, and the elastic modulus was reduced at a lower h, owing to the grain refinements and layer interface barriers for strengthening, and the existence of the amorphous phase with the inferior modulus, respectively. The resistance against the fracture was enhanced due to toughening by the lamellar structure for the Mo-W doped Ni/Ni3Al multilayer at h ≤ 40 nm. Comprehensively, the Mo-W-doped Ni/Ni3Al multilayer with 10 nm displays a superior mechanical performance.

Cu/CuO/ZnO/PPy heterojunction material was prepared for Hg2+ anti-interference detection in seawater

Hg2+ pollution poses a major threat to human health and the ecological environment, but there is still a lack of direct and sensitive Hg2+ detection technology. In this study, Cu/CuO/ZnO wires were prepared by alkaline oxidation and hydrothermal methods. Polypyrrole (PPy) was covered on the surface of the material by electrochemical polymerization. Using the principle of electrochemical signal response driven by p-n junction barrier, the material was used for the direct electrochemical detection of Hg2+ and was tested by differential pulse voltammetry. The composite has a good linear relationship in the Hg2+ concentration range of 200–1600 nmol/L, and has ultra-high sensitivity (1,010.82 μA∙L/(nmol∙cm2)) and ultra-low detection limit (2.1 pmol/L). The new sensing mode based on the interface barrier eliminates the interference of other ions. The recovery rate of Hg2+ in tap water, river water and sea water is 97.3%–105.0%, and the RSD is 1.8%–5.6%. This method using p-n junction barrier can be extended to the development and research of other sensors for detecting heavy metal ions.

Vacancy-induced tensile strain of CdS/Bi2S3 as a highly performance and robust photocatalyst for hydrogen evolution

Lattice strain is a new strategy for promoting photocatalytic activity in order to source more sustainable energy. Vacancy-induced strain is an effective tactic for lattice deformation. Herein, a CdS/Bi2S3 heterojunction structure containing sulfur vacancies (CdS/Bi2S3-VS) is synthesized by a one-step solvothermal method. When there are sulfur vacancies in the Bi2S3 lattice (Bi2S3-VS), the surrounding atoms move toward sulfur vacancies. This phenomenon lengthens the bonds between surrounding atoms, resulting in tensile stress. Strain engineering adjusts the energy band structure to reduce the interface barrier height, thus effectively improving the interface charge transfer rate. Moreover, density functional theory (DFT) calculations explore the influence of different strain levels on the band structure and Gibbs free energy. The strain-regulated band structure provides a new approach and effectively reduce the interface barrier.

Ferroelectric polarization controlled surface potential and charge transport across ITO-Nd-doped BiFeO3 polycrystalline ceramic bulk for photoelectrochemical solar water splitting

The spontaneous polarization in ferroelectrics provides an effective way to engineer interfacial charge distribution at the ferroelectric heterojunctions, thereby depletion width in p-n junction and energy band structures. Here, we integrated p-type multiferroic 7% neodymium-doped bismuth ferrite Bi0.93Nd0.07FeO3 (BFO7Nd) polycrystalline ceramic bulk with n-type transparent conductive indium tin oxide (ITO) to demonstrate the influence of ferroelectric polarization on surface potential and its effect on photoelectrochemical (PEC) water reduction. Kelvin probe force microscopy (KPFM) results reveal the surface potential change during ferroelectric polarization switching, suggesting that the polarization bound charges may have an effect on space charge region between ITO-BFO7Nd, thus dominating surface potential at the electrode/electrolyte interface. This implies that the interface barrier between ITO and BFO7Nd can be easily modulated by polarization bound charges. The electron lifetime of upward-polarization (P-up) ITO-BFO7Nd is estimated 29.30 ms, about 15 times longer than unpoled ITO-BFO7Nd. The photocurrent density of P-up ITO-BFO7Nd is ∼1.2 × 10−6 A/cm2 (at 0 V vs RHE), which is one-order higher compared to that of the unpoled and P-down states under illumination with an intensity of 100 mWcm−2. This work shows that ferroelectric polarization combined with photogenerated carriers is an effective approach for effective charge transfer in multiferroic ceramic to boost PEC solar water splitting.

Laser Manufactured Nano‐MXenes with Tailored Halogen Terminations Enable Interfacial Ionic Stabilization of High Performance Perovskite Solar Cells

AbstractFormamidinium (FA)‐based perovskite promises high power conversion efficiency in photovoltaics while it faces awkward spontaneous yellow phase transition even at ambient conditions. This has spurred intensive efforts which leave a formidable challenge on robust anchoring of the soft perovskite lattice. Present work pioneers the rational design of interfacial ionic‐bonding between halogen‐terminated nano‐MXenes and perovskite for effective retarding of the lattice instability in FA‐based perovskites. The robust heterointerface between perovskite and nano‐MXenes results also in effectively modulating the deep‐energy‐level defects, lowering the interfacial charge transfer barrier, and tuning the work function of perovskite films. Benefiting from these merits, unencapsulated FA‐based perovskite solar cells after the ionic stabilization (champion efficiency up to 24.17%), maintain over 90% of their initial efficiency after operation at maximum power point under continuous illumination for 1000 h, and retain more than 85% of their initial efficiency even after annealing for 1000 h at 85 °C in inert atmosphere.

Effects of electron- and hole-current hysteresis on trap characterization in organo-inorganic halide perovskite

Charge trap density and carrier mobility of perovskite materials are the critical properties of perovskite solar cells. The space charge limited current (SCLC) method, which measures a dark current–voltage (I-V) curve of a single-carrier device has found extensive use for studying the trap density and charge carrier mobility in perovskite materials. Herein, it was found that the electron- and hole-current in organo-lead perovskite-based single-carrier device undergoes significant hysteresis under forward and reverse scanning due to the mobile ions. In addition, it was also observed that measuring history has a detrimental effect on hysteresis resulting in possible overestimation or underestimation of the extracted electrical values from the SCLC measurement. In the forward/reverse scanning process, the mobile ionic defects enhance/shield the charge in the traps due to ionic charging/discharging, thereby increasing/reducing the interface barrier and net charge in the I-V scanning, which in turn affects the determination of transport properties of the carrier. These results raise quite a few doubts over the direct application of classical SCLC measurements for the accurate characterization of intrinsic transport properties of the mixed ionic-electronic perovskite.

Interface functionalization of composite electrolyte by Lix-CeO2 layer on the surface of Li6.4La3Zr1.4Ta0.6O12

The development of all-solid-state batteries has become an inevitable trend as safety is increasingly valued. Naturally, solid-state electrolytes(SSEs) have attracted extensive attention. The composite of superionic conductors and polymer is considered to be a material that can achieve both high energy density and safety. Nevertheless, the compatibility between the polymer and superionic conductors is poor due to the large differences in structure and electrochemistry, resulting in a high interfacial transport energy barrier of the cation. In this work, a functional Lix-CeO2(LCO) layer is synthesized on the surface of the superionic conductor. While broadening the cation transport path at the interface, the anion of lithium salt is successfully anchored and the concentration of lithium-ion is increased. In addition, the structural compatibility and adhesion between polymer and superionic conductors are improve. Compared with the pristine electrolyte, the ionic conductivity and the lithium-ion transference number (tLi+) of LLZTO@2%LCO are as high as 2.325 × 10−3 S cm−1(pristine sample is only 7.109 × 10−5 S cm−1) and 0.44 (pristine sample is only 0.27)respectively. At 2C, the discharge specific capacity of LiFePO4(LFP)|LLZTO@2%LCO-CSE|Li can reach 134.8mAh g−1. The outstanding performance of the composite electrolyte is attributed to the interface functionalized Lix-CeO2 compound coating. Therefore, polymer/ceramic interface engineering to promote the interaction between the two components should be one of the directions of future research.

Crystallization pathways and interfacial drivers for the formation of hierarchical architectures

The development of structural hierarchy on various length scales during crystallization process is ubiquitous in biological systems and is also observed in synthetic nanomaterials. The driving forces for the formations of complex architectures range from local interfacial interactions, that modify interfacial speciation, local supersaturation, and nucleation barriers, to macroscopic interparticle forces. Although it is enticing to interpret the formation of hierarchical architectures as the assembly of independently nucleated building blocks, often crystallization pathways follow monomer-by-monomer addition with structural complexity arising from interfacial chemical coupling and strongly correlated fluctuation dynamics in the electric double layers. Here, the mechanism of the development of structural hierarchy through heterogeneous nucleation, coupled interfacial nucleation and assembly, and oriented attachment of independently nucleated particles is discussed. The emphasis is made on the discussion of the underlying interfacial forces and chemical coupling that drives crystallization pathways towards the formation of structural hierarchy.

(Invited) Local and Macroscopic Probes of Semiconductor/Electrocatalyst Photochemical Interfaces

Charge-carrier-selective interfaces between electrocatalyst particles and semiconductor light absorbers are critical for solar photochemistry but controlling their properties is challenging. In this talk I will show that the nanoelectrode tip of an atomic-force-microscope cantilever can sense the surface electrochemical potential of thin-film and nanoscale electrocatalysts coating semiconductor photoelectrodes during operation. This technique allowed us to unambiguously show that metal (oxy)hydroxide layers act as both hole collectors and oxygen-evolution catalysts on metal-oxide photoanodes such as Fe2O3 and BiVO4. We also discovered the critical role that heterogeneous interfacial barrier heights, and a related nanoscale pinch-off effect, play in building carrier-selective interfaces in semiconductor photoelectrodes for generating fuel from sunlight. As specific example, thin films and nanoparticle of Pt hydrogen-evolution catalysts on p-InP, a high-performance photocathode material, along with macroscopic and nanoscopic electrical and chemical analysis, are used to show how hydrogen alloying, the pinch-off effect for nanoscale contacts, and the formation of a native surface oxides all play different roles in creating charge-carrier-selective junctions. These measurements are compared and contrasted to a new approach to “wirelessly” measure interfacial for different contact materials by analyzing shifts in element-specific shifts in x-ray photoelectron emission energies. The sum of these new insights can be broadly applied to photocathodes, photoanodes, and overall water-splitting systems to control charge-carrier selectivity and improve performance.

Determination of spin polarization of metals and gap of superconductors by spin-polarized Andreev reflection spectroscopy

Andreev reflection spectroscopy (ARS) is a unique technique that can determine the spin polarization of a metal as well as the gap of a superconductor but d-wave superconductors are seldomly used in ARS due to the lack of quantitative model to extract parameters from experiments. Here we calculate spin-polarized ARS based on the modified Blonder-Tinkham-Klapwijk model for both s- and d-wave superconductors of a three-dimensional (3D) interface with a point angle. We show that the 3D interface and the point angle can drastically affect the spectra for both s- and d-wave ARS. For s-wave, the 3D effect is similar to that of an interfacial barrier but it can generate a variety of rich features in d-wave ARS and induce Andreev bound states (ABS). The spin polarization can linearly suppress both s- and d-wave spectra including ABS. We show that the ABS states can be controlled by the spin polarization, the point angle and the interfacial barrier but very high polarization is required to completely suppress the ABS. Furthermore, the Fermi wavevector mismatch as well as the carrier effective mass mismatch can cause effects very similar to that of an interfacial barrier for both s- and d-wave ARS.

Pectin degree of esterification influences rheology and digestibility of whey protein isolate-pectin stabilized bilayer oil-in-water nanoemulsions

Gelation in nanoemulsions happens at a lower oil volume fraction ( φ ) compared to conventional emulsions due to the increasing contribution of interfacial shell-layer thickness. In this study, the shell-layer thickness was increased by depositing a second layer of pectin on whey protein isolate (WPI)-stabilized nanodroplets. Pectin with two different degrees of esterification (DE), 33% and 73%, was used to investigate the effect of interfacial charge on the repulsive shell layer thickness. Excess WPI was removed from the primary 20 wt% canola oil-in-water nanoemulsion stabilized with 4 wt% WPI (pH 7) by ultracentrifugation before pectin addition. At pH 7, the added pectin remained in the continuous phase and led to almost two orders of magnitude increase in emulsion viscosity, but they were flowable. Changing to pH 3 led to electrostatic complexation of pectin with WPI either mostly in the aqueous phase for the emulsions with excess proteins (WTEP) or at the oil droplet surface for the emulsions without excess proteins (WOEP). The addition of pectin transformed the liquid primary emulsions into viscoelastic gels at only 20 wt% oil due to extensive droplet aggregation for the emulsion WTEP. For the emulsion WOEP, gelation was manifested by the close packing of repulsive droplets. The higher pectin charge (DE33) increased the gel strength of bilayer emulsions compared to the lower pectin charge (DE73) due to the charge cloud-induced enhanced interfacial repulsive barrier. The deposition of pectin also reduced lipid digestibility from 37.2% for the monolayer emulsions to 24.0% and 16.1% for DE73 and DE33-coated bilayer emulsions, respectively. Such findings can be used to better understand and modify the rheological and digestion properties of repulsive emulsion gels for application in reduced fat foods. • WPI-pectin bilayer nanoemulsion was created using layer-by-layer electrostatic deposition. • Excess whey protein in the continuous phase led to attractive gelation in nanoemulsion. • Removal of excess protein led to repulsive gelation in bilayer nanoemulsion. • Higher pectin charge was more effective in enhancing repulsive gelation in bilayer nanoemulsions. • Lipid digestibility was reduced with pectin bilayer and increasing pectin charge.

The examination of the electrical properties of Al/Mg2Si/p-Si Schottky diodes with an ecofriendly interfacial layer depending on temperature and frequency

The electrical properties of Al/Mg2Si/p-Si Schottky diodes fabricated were examined at various frequencies and temperatures. The structural and surface morphological features of the interface layer (Mg2Si) were analyzed by XRD, SEM, and EDX. For the fabricated diode, temperature-dependent measurements were made in the range of 120–340 K with an increment of 20 K. The frequency-dependent measurements were also performed in the range of 1 kHz–5 MHz. For the Al/Mg2Si/p-Si Schottky diode, the temperature-dependence of ideality factor (n), saturation current (I0), zero-bias barrier height (ΦB0), serial resistance (Rs) and interface state density (Nss) were investigated. Besides, diffusion potential (VD), Fermi energy (EF), concentration of acceptor atoms (NA), the depletion layer width (WD) and frequency dependent obstacle height (ΦB0C–V) values were calculated from frequency dependent measurements. It was found that the Al/Mg2Si/p-Si Schottky diode is suitable for use in electronic applications in a wide temperature and frequency range.

The choroid plexus: a missing link in our understanding of brain development and function.

Studies of the choroid plexus lag behind those of the more widely known blood-brain barrier, despite a much longer history. This review has two overall aims. The first is to outline long-standing areas of research where there are unanswered questions, such as control of cerebrospinal fluid (CSF) secretion and blood flow. The second aim is to review research over the past 10 years where the focus has shifted to the idea that there are choroid plexuses located in each of the brain's ventricles that make specific contributions to brain development and function through molecules they generate for delivery via the CSF. These factors appear to be particularly important for aspects of normal brain growth. Most research carried out during the twentieth century dealt with the choroid plexus, a brain barrier interface making critical contributions to the composition and stability of the brain's internal environment throughout life. More recent research in the twenty-first century has shown the importance of choroid plexus-generated CSF in neurogenesis, influence of sex and other hormones on choroid plexus function, and choroid plexus involvement in circadian rhythms and sleep. The advancement of technologies to facilitate delivery of brain-specific therapies via the CSF to treat neurological disorders is a rapidly growing area of research. Conversely, understanding the basic mechanisms and implications of how maternal drug exposure during pregnancy impacts the developing brain represents another key area of research.

Broadband Spectrum Light-Driven PANI/Au/Beta-Cyclodextrin Nanocomposite and Its Light-Triggered Interfacial Carrier Transfer

Polyaniline/Au nanocomposites were synthesized by a novel method. Aniline monomers were loaded in the hydrophobic cavities of beta-cyclodextrin, and a polymerization reaction occurred at the interface of the beta-cyclodextrin cavities and the liquid phase of chloroauric acid. UV-vis absorbance indicated that the nanocomposite covered the range of visible light and NIR (near infrared). The photo-excitation experiment was carried out with typical wavelengths in the visible light (405 nm, 532 nm, and 650 nm) and NIR (780 nm, 808 nm, 980 nm, and 1064 nm) regions (10–200 mW) based on Au inter-digital electrodes on flexible polymer substrates casting a thick film. The nanocomposites exhibited photo-current switching behavior in visible light and NIR. The ratio of on/off was enormously dependent on the power and wavelength of incident light. The robust interface coupling between Au and PANi of the nanocomposite promoted the separation and transfer of electron/hole. The mechanism of carrier generation, separation, and transfer at interfaces of Au/conjugated polymer/non-conjugated small organic molecules by light inducement was discussed at the electron level. The results illustrate that the nanocomposites quickly produced free electrons and holes by low-power incident light, could prevent the recombination of electron/hole pairs to a certain extent, and could overcome the interface barriers between metal, conjugated polymer, and small organic molecules for transfer. This provides a simple and practical approach for developing multi-functional nanocomposites that have the potential act as intelligent nano-carriers, photo-current switches, NIR detectors, and for information storage.

Interphase mechanical behaviors of nickel/yttria-stabilized zirconia cermets: A study by nanoindentation and molecular dynamics simulations

The metal/ceramic interface is of great importance in a variety of basic science research and technological applications. In this paper, the interphase mechanical behaviors of the nickel/yttria-stabilized zirconia (Ni/YSZ) system serving as an anode material in solid oxide fuel cells are investigated by nanoindentation experiments and molecular dynamics (MD) simulations. The experimental results indicate that the interface effect can greatly enhance the Young's modulus and hardness of Ni near Ni/YSZ interface, while a reduction is observed in the aforementioned mechanical properties of YSZ near the interface. In addition, the change in the mechanical properties and the affected region of the YSZ component due to the interface effect are both much larger than those of its Ni counterpart. Our MD simulation results reveal that the different effects of Ni/YSZ interface on the mechanical properties of Ni and YSZ near the interface can be ascribed to different transport capabilities of deformations generated in these two components across the interface. Based on MD simulation results, an interface barrier model and a model considering the structural compliance are proposed here for theoretically predicting the interphase hardness and Young's modulus of the Ni/YSZ system.

NMR Study of Lithium Transport in Liquid-Ceramic Hybrid Solid Composite Electrolytes.

Despite their high conductivity, factors such as being fragile enough to face processing issues and interfacial incompatibility with lithium electrodes are some of the main drawbacks hindering the commercialization of inorganic (mainly oxide-based) solid electrolytes for use in all-solid-state lithium batteries. To this end, strategies such as the addition of solid polymer electrolytes have been proposed to improve the electrode-electrolyte interface. Hybrid electrolytes, which are usually composed of ceramic particles dispersed in a polymer, generally have a better affinity with electrodes and higher ionic conductivity than pure inorganic electrolytes. However, a significant downside of this strategy is that differences in lithium transportability between electrolyte layers can result in the formation of a high interfacial energy barrier across the cell. One strategy to ensure sufficient "wetting" of ceramics is to incorporate a liquid electrolyte directly into the solid inorganic electrolyte resulting in the formation of a hybrid liquid-ceramic electrolyte. To this end, liquid-ceramic hybrid electrolytes were prepared by adding LiG4TFSI, a solvate ionic liquid (SIL), to garnet, NASICON, and perovskite-type ceramic electrolytes. Although SIL addition resulted in increased ionic conductivity, comparisons between the pure SIL and the hybrid systems revealed that improvements were due to the SIL alone. A thorough investigation of the hybrid systems by solid-state nuclear magnetic resonance (NMR) revealed little to no lithium exchange between the ceramic and the SIL. This confirms that lithium conductivity preferentially occurs through the SIL in these hybrid systems. The primary role of the ceramic is to provide mechanical strength.

Dually Modified Wide-Bandgap Perovskites by Phenylethylammonium Acetate toward Highly Efficient Solar Cells with Low Photovoltage Loss.

Wide-bandgap perovskites as a class of promising top-cell materials have shown great promise in constructing efficient perovskite-based tandem solar cells, but their intrinsic relatively low radiative efficiency results in a large open-circuit voltage (VOC) deficit and thereby limits the whole device performance. Reducing film flaws or optimizing interfacial energy level alignments in wide-bandgap perovskite devices can efficiently inhibit nonradiative recombination to boost device VOC and efficiency. However, the simultaneous regulation on both sides and their underlying mechanism are less explored. Herein, a bifunctional modification approach is proposed to optimize the wide-bandgap perovskite surface with an ultrathin layer of phenylethylammonium acetate (PEAAc) to synchronously decrease the surface imperfection and mitigate the interfacial energy barrier. This treatment effectively heals under-coordinated surface defects through the formation of chemical interaction between the perovskite and PEAAc, bringing about a much slower charge trapping process and dramatically decreasing nonradiative recombination losses. Meanwhile, the passivation-induced upshifted Fermi level of the perovskite contributes to accelerated electron extraction and larger Fermi-level splitting under illumination. Consequently, the PEAAc-modified wide-bandgap (1.68 eV) device achieves an optimal efficiency of 20.66% with a high VOC of 1.25 V, among the highest reported VOC values for wide-bandgap perovskite devices, enormously outperforming that (18.86% and 1.18 V) of the device without passivation. In addition, the radiative limit of VOC for both cells is determined to be 1.42 V, delivering nonradiative recombination losses of 0.24 and 0.17 V for the control and PEAAc-modified devices, respectively. These results highlight the significance of the bifunctional modification strategy in achieving high-performance wide-bandgap perovskite devices.

Efficiently photocatalytic H2O overall splitting within the strengthened polarized field by reassembling surface single atoms

Surface single atom Ni-coordinated carbon nitride fibers (Ni/C3N4Fs) were reassembled into tiny NiP nanoparticle-integrated C3N4Fs (NiP/C3N4Fs) with the strengthened polarized electric fields accompanied by a weakened interface barrier. Photogenerated e- and h+ dynamically transfer to the convex-integrated NiP and concave of C3N4Fs under the synergetic electric fields via inner single atoms of Ni as charge transfer bridges within C3N4Fs interlayers, which is confirmed by high-angle annular dark field scanning transmission electron microscopy, K-edge extended X-ray absorption fine structure, X-ray photoelectron spectroscopy and theoretical prediction. H2- and O2-evolution rates of 1.89 and 0.92 mmol g−1 h−1 with solar-to-hydrogen efficiency of 2.33% are obtained over NiP/C3N4Fs system under visible light irradiation. This research provides a rational strategy for constructing the connection of H2 fuel production with its practical application.

Tropocollagen-Inspired Hierarchical Spiral Structure of Organic Fibers in Epoxy Bulk for 3D High Thermal Conductivity.

Polymers are usually considered thermal insulators; however, significant enhancements in thermal conductivity (k) have been observed in oriented fibers and films. Despite being advantageous in real-world applications, extending the linear thermal-transport advantage of polymers into the 3D space in bulk materials is still limited due to the spatially interfacial phonon-conduction barriers. Herein, inspired by the structure of tropocollagen, it is discovered that weaving hierarchically arranged poly(p-phenylene benzobisoxazole) (PBO) fibers with a spiral configuration into an epoxy matrix can yield a 3D continuous thermal pathway. This achieves both a through-plane k of 10.85W m-1 K-1 and an in-plane k of 7.15W m-1 K-1 . Theoretical molecular simulations in combination with classical nonlinear modeling attribute the above spatially thermally conductive achievement to not only the hierarchical molecular, spiral and weaving structure of PBO, but also the noncrystalline chains that carry overlapping phonon density of states, thus thermally bridging adjacent high-k crystals in the PBO fiber. Consequently, the interfacial thermal resistance among high-k PBO crystals is suppressed to be on the order of 10-10 m2 K W-1 in both the through-plane and in-plane directions. Other advantages include being lightweight, mechanically strong, flexible, and non-combustible. This material creates opportunities for organic polymers in high-performance thermal management applications.