High Permeability of Boron along the Transverse Direction of Wood under High-Voltage Electrostatic Field (HVEF) Treatment

Permeability of wood preservative is one of the most significant factors for protection of wood construction.Ani-sotropic flow permeability was involved in different directions of wood with higher flow resistance in the trans-verse and lower longitudinal directions.In this study,boron acid solution was brushed onto the tangential section of air-dried wood cubes and boron penetration along wood transverse direction was investigated under free dif-fusion,vacuum and HVEF treatments.Multi-scale boron distribution,FTIR measurement,leaching property,mechanical properties and fungistatic characteristic were investigated for free diffusion,vacuum and HVEF trea-ted samples respectively.The results revealed that boron exhibited high permeability along the transverse direc-tion with the penetration depth of≈35 mm for HVEF treated samples and≈1 mm for free diffusion and vacuum treated samples.For HVEF treated samples,no significant decrease of hardness,compression modulus of elasti-city and strength were found in the treated samples.Better fungistatic characteristic was showcased in HVEF trea-ted samples exposed to white rot fungi.Thus,HVEF treatment has a positive effect on boron permeability and the improvement of penetration depth of preservatives hence playing a significant role in wood protection and prolonging the service life of wood construction.

Tensile Behavior of Strain Hardening Cementitious Composites (SHCC) Containing Reactive Recycled Powder from Various C&D Waste

This work investigates the feasibility of utilizing reactive recycled powder(RP)from construction and demolition(C&D)waste as supplementary cementitious material(SCM)to achieve a ductile strain hardening cementitious composites(SHCC).The recycled mortar powder(RMP)from mortar waste,recycled concrete powder(RCP)from concrete waste and recycled brick powder(RBP)from clay brick waste were first prepared,and the micro-properties and tensile behavior of SHCC containing various types and replacement ratios of RPs were determined.The incorporated RP promotes pozzolanic and filler effects,while the hydration products in cementitious materials decrease with RP incorporation;therefore,the incorporated RP decreases the compressive strength of SHCC.Attributed to the reduction in the matrix strength,the incorporated RP increases the crack-bridging extent and ductility of SHCC;the irregular micro-structure and high reactivity of RP also help the strain-hardening performance of the prepared SHCC.In addition,the strainhardening performance of SHCC containing RMP and RBP is surperior to that of SHCC with RCP and is slightly lower than that of SHCC with fly ash(FA);for instance,the ultimate strain of SHCC containing 54%FA,RMP,RCP and RBP is 3.67%,3.61%,2.52%and 3.53%,respectively.In addition,the strain-hardening behavior of an SHCC doubled mix with FA and RMP or RBP has a similar ultimate strain and a higher ultimate stress than SHCC containing only FA.

Enhanced visible-light photocatalytic hydrogen evolution using two-dimensional carbon nitride sheets with the removal of amine groups

Two-dimensional(2D)carbon nitride sheets(CNs)with atomically thin structures are regarded as one of the most promising materials for solar energy conversion.However,due to their substantially enlarged bandgap caused by the strong quantum size effect and their incomplete polymerisation with a large number of non-condensed surface amino groups,the practical applicability of CNs in photocatalysis is limited.In this study,CNs with broad visible-light absorption were synthesised using a 5-min fast thermal annealing.The removal of uncondensed amine groups reduces the bandgap of CNs from 3.06 eV to 2.60 eV,increasing their absorption of visible light.Interestingly,the CNs were distorted after annealing,which can differentiate the spatial positions of electrons and holes,enhancing the visible-light absorption efficiency.As a result,when exposed to visible light,the photocatalytic hydrogen production activity of atomically thin 2D CNs rose by 8.38 times.This research presents a dependable and speedy method for creating highly effective visible-light photocatalysts with narrowed bandgaps and improved visible-light absorption.

Room-temperature ferromagnetism and piezoelectricity in metalfree 2D semiconductor crystalline carbon nitride

Two-dimensional(2D)materials that combine ferromagnetic,semiconductor,and piezoelectric properties hold significant potential for both fundamental research and spin electronic devices.However,the majority of reported 2D ferromagnetic-semiconductor-piezoelectric materials rely on d-electron systems,which limits their practical applications due to a Curie temperature lower than room temperature(RT).Here,we report a high-crystallinity carbon nitride(CCN)material based on sp-electrons using a chemical vapor deposition strategy.CCN exhibits a band gap of 1.8 eV and has been confirmed to possess substantial in-plane and out-of-plane piezoelectricity.Moreover,we acquired clear evidences of ferromagnetic behavior at room temperature.Extensive structural characterizations combined with theoretical calculations reveal that incorporating structural oxygen into the highly ordered heptazine structure causes partial substitution of nitrogen sites,which is primarily responsible for generating room-temperature ferromagnetism and piezoelectricity.As a result,the strain in wrinkles can effectively modulate the domain behavior and piezoelectric potential at room temperature.The addition of RT ferromagnetic-semiconductor-piezoelectric material based on sp-electrons to the family of two-dimensional materials opens up numerous possibilities for novel applications in fundamental research and spin electronic devices.

Constructing metal-free heterophotocatalyst using two-dimensional carbon nitride sheets and violet phosphorene for highly efficient visible-light photocatalysis

Two-dimensional(2D)carbon nitride sheets(CNs)with nanoscale thickness have great potential in solar energy conversion owing to their intrinsic bandgap.However,their photocatalytic efficiency falls far below the practical requirements because the generated electron-hole pairs rapidly recombine.We construct a metal-free 2D p–n junction heterophotocatalyst from CNs and violet phosphorene(VP)using a simple electrostatic self-assembly method.The experimental results and density functional theory calculations show that the built-in electric field of the p–n junction promotes photogenerated carrier transport at the heterojunction interface,thereby promoting the separation of photogenerated electron-hole pairs.Under visible-light illumination,the visible-light photocatalytic hydrogen and CO production rates of the CNs/VP heterojunction were increased by 5.85 and 1.51 times,respectively,when compared to that of CNs.This study provides new insights into the design of metal-free heterogeneous photocatalysts with high catalytic activity。

Designable heteronanocrystals via interface redox reaction

The synergistic interaction of different components in heteronanocrystals induces interfacial phenomena and novel functionalities.Nonetheless,effective technologies to design and fabricate heteronanocrystals with materials on demand are still missing.Rich heterostructures in a copper patina are known to form at room temperature and under atmospheric pressure.The redox process of copper tarnish inspired the discovery of a simple strategy to achieve heteronanocrystals that contained elements from group 3-11 and group 14-16.The interface redox-induced method is self-regulating at ambient conditions and applicable for metal,semiconductor,and dielectric materials.The enhanced interface bonding endows the heteronanocrystals with outstanding stability and catalytic performance,while the modular approach enables the design and fabrication of heteronanocrystals with intended materials to meet different purposes.

Rational Design of Biological Crystals with Enhanced Physical Properties by Hydrogen Bonding Interactions

Hydrogen bonds are non-covalent interactions and essential for assembling supermolecules into ordered structures in biological systems,endowing crystals with fascinating physical properties,and inspiring the construction of eco-friendly electromechanical devices.However,the interplay between hydrogen bonding and the physical properties is not fully understood at the molecular level.Herein,we demonstrate that the physical property of biological crystals with double-layer structures could be enhanced by rationally controlling hydrogen bonding interactions between amino and carboxyl groups.Different hydrogen bonding interactions result in various thermal,mechanical,electronic,and piezoelectric properties.In particular,the weak interaction between O and H atoms contributes to low mechanical strength that permits important ion displacement under stress,giving rise to a strong piezoelectric response.This study not only reveals the correlation between the hydrogen bonding and physical properties in double-layer structures of biological crystals but also demonstrates the potential of these crystals as functional biomaterials for high-performance energy-harvesting devices.Theoretical calculations and experimental verifications in this work provide new insights into the rational design of biomaterials with desirable physical properties for bioelectrical devices by modulating intermolecular interactions.