Preparation of Mo/Cu composites by SLS method and its post-treatment techniques

A multi-component polymer-coated molybdenum powder was chosen for selective laser sintering（SLS）. The powder was prepared by coating polymer on Mo particles and frozen by grinding techniques. The laser sintering activities and sound densification response were obtained by optimizing the process parameters. The post-treatment process of SLS samples was developed, which was high temperature sintering Mo framework combined with Cu impregnation. Then, the Mo/Cu composites are gained. The microstructure evolution of post-treatment samples was investigated by scanning electron microscopy. Mo grains frequently string together. The microstructural characterization of Mo/Cu composites is homogeneous compound structure of adhesive phase Cu linked with Mo grains. There is little ellipsoidal Mo grains singly existing around Cu phase. Between Mo grains and Cu zone, there is a medium changing zone with width of 10-20 nm. Post-treatment mechanism is Mo framework sintering of solid phase and Cu impregnation of melting/solidification. The mechanical and thermal properties concluding tensile strength, elastic modulus, elongation and linear expansion of Mo/Cu composites were studied.     

Modification of tribological properties of polyarylate by supercritical fluid impregnation of copper(II) hexafluoroacetylacetonate

Polyarylate has been used as a model polymer to study its tribological property alteration during impregnation of copper(II) hexafluoroacetylacetonate in a supercritical carbon dioxide environment followed by thermal decomposition of the copper compound in air. The initial, impregnated and thermally treated polymer samples were tested by various tribological techniques to compare their wear resistance, friction coefficient f_k and surface microhardness H. SEM, EDX and ESCA have been applied to determine surface and internal domain morphology, profiles of copper complex concentration, its types and influence on the tribological properties of the samples. Dramatic surface layer modification and significant enhancement of its wear resistance (more than 400%) due to this process have been observed and discussed. This revised version was published online in June 2006 with corrections to the Cover Date.     

Carbonized Wood Decorated with Cobalt-Nickel Binary Nanoparticles as a Low-Cost and Efficient Electrode for Water Splitting

Using an inexpensive and eco-friendly wood substrate, herein, a one-step calcination method is developed to deposit Co-Ni binary nanoparticles into aligned wood channels and an effective carbonized wood (CW) electrode (termed as Co/Ni-CW) is fabricated. Well distributed Co-Ni nanoparticles are achieved by the coordination bonds between the hydroxyl groups on wood matrix and soaked metal cations. Subsequently, high-temperature calcination promotes the nucleation of Co-Ni nanoparticles and the formation of CW. With the uniform distribution of Co-Ni nanoparticles and porous wood structure, not only is a high active surface area, but also the electron and mass diffusion pathways are enhanced. Thus, the as-prepared Co/Ni-CW affords the current density of 10 mA cm^–2 at low overpotentials of 330 and 157 mV for oxygen and hydrogen evolution, respectively. Remarkably, when the wood-based bifunctional electrocatalyst is used as both the anode and cathode, a low cell voltage of 1.64 V is required to reach the current density of 10 mA cm^–2. Compared with most substrates used in bifunctional electrocatalysts, the abundance, low cost, eco-friendliness, and easy operation of wood-based catalysts allow for an active and scalable electrode for water splitting and many other energy storage devices.     

聚磷酸铵/次磷酸铝协效阻燃聚丙烯/木粉复合材料

以聚磷酸铵(APP)和次磷酸铝(AHP)为阻燃剂,马来酸酐接枝聚丙烯(MA-g-PP)为界面相容剂,通过熔融共混制备了聚丙烯(PP)/木粉(WF)复合材料。采用UL-94垂直燃烧、氧指数(LOI)、热重分析(TGA)探究了阻燃PP/WF复合材料的阻燃性和热分解过程。实验表明,当APP与AHP质量比为9∶1时,LOI值为28.3%,垂直燃烧UL-94达到V-0级。TGA和DTG测试表明,APP与AHP复配能降低木纤维的分解温度,使复合材料提前成炭,达到阻燃作用;加入APP与AHP的PP/WF复合材料的成炭率提高了141%,其高温稳定性也得到提高。通过SEM观察到,当m(APP)∶m(AHP)=9∶1时,木塑复合材料可形成致密的炭层,具有更好的隔热、隔氧作用,从而提高了阻燃性。结果表明在聚磷酸铵中加入少量的协效剂次磷酸铝可明显提高PP/WF复合材料的阻燃性。     

Evaluation of thin-layer models for describing drying kinetics of poplar wood particles in a fluidized bed dryer

In this study, fluidized bed drying experiments were conducted for poplar wood particles (Populus deltoides) at temperatures ranging from 90°C to 120°C and air velocities ranging from 2.8 m s^?1 to 3.3 m s^?1. The initial moisture content (MC) and the bed height of the poplar wood particles were 150% (on an oven-dry basis) and 2 cm, respectively. The results showed that the drying rate increased by increasing the drying temperature and air velocity. The constant drying rate period was only observed at the early stages of the drying process and most of the drying processes were found in the falling rate period. The experimental data of the drying process were put into e11 models. Among these models, Midilli, Kucuk, and Yapar (2002 Midilli, A., H. Kucuk, and Z. Yapar. 2002. A new model for single-layer drying. Drying Technology 20:1503–13. doi:10.1081/DRT-120005864[Taylor &; Francis Online], [Web of Science ®] , [Google Scholar]) and Henderson and Pabis (1961 Henderson, S. M., and S. Pabis. 1961. Grain drying theory I. Temperature effect on drying coefficient. Journal of Agriculture Engineering Research 6 (3):169–74. [Google Scholar]) were found to satisfactorily describe the drying characteristics of poplar wood particles. The effective moisture diffusivity of wood particles increased from 7E-6 to 8.46E-6 and 7.65 E-6 to 1.44E-5 m² s^?1 as the drying air temperature increased from 90°C to 120°C for 2.8 m s^?1 and 3.3 m s^?1 of velocities, respectively. Also, the activation energies of diffusion were 34.08 kJ mol^?1 and 64.70 kJ mol^?1 for the air velocities of 2.8 m s^?1 and 3.3 m s^?1, respectively.     

From Wood to Textiles: Top‐Down Assembly of Aligned Cellulose Nanofibers

Advanced textiles made of macroscopic fibers are usually prepared from synthetic fibers, which have changed lives over the past century. The shortage of petrochemical resources, however, greatly limits the development of the textile industry. Here, a facile top‐down approach for fabricating macroscopic wood fibers for textile applications (wood‐textile fibers) comprising aligned cellulose nanofibers directly from natural wood via delignification and subsequent twisting is demonstrated. Inherently aligned cellulose nanofibers are well retained, while the microchannels in the delignified wood are squeezed and totally removed by twisting, resulting in a dense structure with approximately two times higher mechanical strength (106.5 vs 54.9 MPa) and ≈20 times higher toughness (7.70 vs 0.36 MJ m^?3) than natural wood. Dramatically different from natural wood, which is brittle in nature, the resultant wood‐textile fibers are highly flexible and bendable, likely due to the twisted structures. The wood‐textile fibers also exhibit excellent knitting properties and dyeability, which are critical for textile applications. Furthermore, functional wood‐textile fibers can be achieved by preinfiltrating functional materials in the delignified wood film before twisting. This top‐down approach of fabricating aligned macrofibers is simple, scalable, and cost‐effective, representing a promising direction for the development of smart textiles and wearable electronics.     

湘东地区的民间传统竹木制蒸炊器具设计研究

目的 分析湖湘饮食特色中“蒸炊”的竹木制器物的特点,探寻其设计理念,扩展认识湖湘文化的新视角。方法 对株洲、浏阳、长沙等湘东地区的民间蒸炊器具进行调查,并测得其主要尺寸,运用功能分析法把典型器具分为甑、蒸盖、箅、舀水器等。结合当地的饮食习惯和传统文化,运用形式分析、逻辑推理等方法,对用材、形式、功能、结构等进行具体分析。结论 湘东地区民间传统蒸炊器具具有世俗性、科学性、艺术性等特点,其设计遵循“取材因地制宜、制器功能至上、造型简朴规整”的造物规律。     

Exploring a Multi‐modal Experimental Approach to Investigation of Local Embedment Behaviour of Wood under Steel Dowels

A multi‐modal experimental approach for analysing the embedment behaviour of timber connections with steel dowels is proposed in this study. In this approach, a standard mechanical embedment test on single‐dowel connections is combined with an optical measurement of surface deformations of the connection based on digital image correlation principle and an X‐ray micro‐computed tomography examination of the deformations in the dowel‐wood interface. The latter is conducted on cylindrical cores including the dowel hole, physically extracted from the loaded specimen at three characteristic points of the load‐deformation curves. The major challenge of this procedure is disrupted load transfer between the cylindrical core specimens and the external material they were plugged in for further analysis. Despite its challenges and limitations, the method revealed a potential for an unprecedented insight into the micromechanics of dowel connections and for effective correlation of the micro‐level observations with the external macroscopic load‐deformation characteristics.     

壳聚糖-二氧化硅复合湿凝胶的改性及其对木家具中有害物质吸附性能的研究

采用改性共溶胶-凝胶法制备多孔壳聚糖气凝胶通过扫描电镜、红外、X射线能谱、BET等手段对其进行分析。结果表明:制备的壳聚糖-二氧化硅复合气凝胶既保留了气凝胶的轻质结构和介孔特性,又含有壳聚糖所具有的烷基、羟基、氨基、酰胺基等活泼有机基团,且通过改性提高其活性,使其能吸附木家具中挥发性有机物和重金属。其中以戊二醛改性的壳聚糖-二氧化硅复合湿凝胶吸附能力最好,其对乙酸丁酯和正十一烷的吸附率为85%~95%,对重金属的吸附率大于50%,其吸附VOCs的能力为二氧化硅凝胶的1.92倍,吸附重金属能力为二氧化硅凝胶的6.86倍。     

A Highly Conductive Cationic Wood Membrane

Here, a highly conductive cationic membrane is developed directly from natural wood via a two‐step process, involving etherification and densification. Etherification bonds the cationic functional group (? (CH₃)₃N⁺Cl^?) to the cellulose backbone, converting negatively charged (ξ‐potential of ?27.9 mV) wood into positively charged wood (+37.7 mV). Densification eliminates the large pores of the natural wood, leading to a highly laminated structure with the oriented cellulose nanofiber and a high mechanical tensile strength of ≈350 MPa under dry conditions (20 times higher than the untreated counterpart) and ≈98 MPa under wet conditions (×5.5 increase compared to the untreated counterpart). The nanoscale gaps between the cellulose nanofibers act as narrow nanochannels with diameters smaller than the Debye length, which facilitates rapid ion transport that is 25 times higher than the ion conductance of the natural wood at a low KCl concentration of 10 × 10^?3 m . The demonstrated cationic wood membrane exhibits enhanced mechanical strength and excellent nanofluidic ion‐transport properties, representing a promising direction for developing high‐performance nanofluidic material from renewable, and abundant nature‐based materials.