Conductivity Of Wood Research Articles

Pristine Wood-Supported Electrodes With Intrinsic Superhydrophilic/Superaerophobic Surface Intensify Hydrogen Evolution Reaction.

Wood, as a renewable material, has been regarded as an emerging substrate for self-supporting electrodes in large-scale water electrolysis due to numerous merits such as rich pore structure, abundant hydroxyl groups, etc. However, poor conductivity of wood can greatly suppress the performance of wood-based electrodes. Carbonization process can improve wood's conductivity, but the loss of hydroxyl groups and the required high energy consumption are the drawbacks of such a process. Here, a facile strategy is developed to prepare pristine wood-supported electrode (Ni-NiP/W) for enhanced hydrogen evolution reaction (HER); this improves electrical conductivity of wood while retaining its excellent intrinsic properties. The preparation process involves the deposition of copper on the untreated wood followed with the loading of Ni-NiP catalyst at room temperature. Encouragingly, the Ni-NiP/W exhibits conductive and inherited pristine wood's superhydrophilic and superaerophobic properties, that effectively boost mass and charge transfer. It demonstrates high activity and excellent stability in acidic, alkali, and seawater conditions as well as high current densities of up to 2000mA cm-2; particularly a record-low HER overpotential of 206mV in acidic conditions at 1000mA cm-2. This work fully unlocks the admiring potential of pristine wood as superior substrate for high-performance electrochemical electrodes.

Li–Na metal compounds inserted into porous natural wood as a bifunctional hybrid applied in supercapacitors and electrocatalysis

As a green and sustainable natural resource, wood is regarded as a feasible candidate material for developing green and sustainable energy due to its natural porous structure. However, the conductivity of wood is poor, which restricts its application in energy storage. In this research, a novel material with Li–Na metal compounds inserted into porous carbonized lignin free wood (PCLFW) as a bifunctional hybrid is synthesized. This material with a high specific capacitance, high power density and excellent electrocatalytic activity is synthesized. The final product shows a high specific capacitance of 255 F g−1, high energy density of 31.88 Wh kg−1 and power density of 3188 W kg−1. Moreover, after experiencing 5000 cycles, the specific capacitance is maintained at 239 F g−1 (capacitance retention of 93%). In addition, the hybrid exhibits excellent hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) activities in alkaline solution, with overpotentials of 349 mV (Tafel = 192 mV dec−1) and 484 mV (Tafel = 184 mV dec−1), respectively. Meanwhile, the hybrid also shows a larger initial and half-wave potentials of −0.12 V and −0.22 V, reflecting an outstanding oxidation-reduction reaction (ORR) property. In a word, this work provides a new idea for us to fabricate wood-based hybrid for high-performance energy storage devices and carbon-based catalysts.

Determination of the Coefficient of Thermal and Moisture Conductivity of Wood by the Transient Moisture Current Method

Consideration is given to the method of determining the coefficient of thermal and moisture conductivity of wood by measuring the transient moisture current in its cross grains. Results of experiments conducted with birchwood are in good agreement with analogous data obtained earlier.

Research of the opportunity of using bran as a building material

As a result of the functioning of the agro-industrial complex, several million tons of bran that require recycling are annually produced in Russia. At present, there is no resource-efficient way of utilizing bran, which ensures its ecological compatibility and economic efficiency. In this regard, the purpose of the paper is to investigate the possibility of using wheat bran as a building material. The article presents the prerequisites for the construction of low-rise buildings using wheat bran as a building material: an experiment was carried out for the manufacture of bran blocks, and their thermophysical characteristics, maximum crushing strength, and moisture resistance were measured. Building blocks made from bran have a thermal conductivity comparable to the thermal conductivity of wood. The high strength of the bran blocks to squeeze indicates the possibility of their use for the construction of low-rise buildings without any strengthening of their design. However, this blocks exhibit hydrophilic properties, which requires the application of a protective layer. For example, a conventional wood varnish can be use as such a coating.

Effects of Temperature and Time of Carbonization on the Properties of Bamboo (Dendrocalamus asper) Carbon

Lignocellulosic materials such as wood and bamboo have special characteristics when carbonized at high temperature. For example the electrical conductivity of wood and bamboo increases when carbonized at temperature of 800°C or higher. This property can be used for developing smart materials such as fiber reinforced concrete which has function as sensors for load, damage or temperature. In this experiment, betung bamboo (Dendrocalamus asper) was carbonized at different temperatures and times of carbonization. The purpose of this experiment was to observe the effect of temperature and time of carbonization on the properties of bamboo carbon. Bamboo in the form of particles were carbonized at temperature of 400°C for 300 min and continued at temperatures of 700, 800, or 900°C for 45, 60, or 90 min. Carbon properties such as yield, fixed carbon, volatile matters, and ash content were determined. Structure properties were studied by X Ray Diffraction (XRD), morphological properties were observed by Scanning Electron Microscope (SEM), and electrical conductivity was measured using LCR meter. Result shows that increasing temperature and time of carbonization have significant effects on the structure and other properties of bamboo carbon. Carbonization at temperature of 800°C for 60 min was considered as an optimum condition.

The Basic Technology of Steaming and Drying of Wood

Drying is a complex heat and mass transfer process which is affected by operating parameters environment and thermophysical properties of wood. Basis for classification of methods of drying is a method of transmission of heat to material. The basic method of drying is convective, but it is accompanied by a conductivity of wood (from the material surface to its center) and thermal radiation. The research investigates the processes of initial heating and steaming of beech wood in the form of profile pieces, which describes the dynamics of change in temperature of wood in general and particularly of surface and inner layers of wood, as well as changing the thermal properties (coefficients of heat-conducting, diffusivity and specific heat capacity) of wood. The change of thermal properties of wood causes the change of heat-exchange criteria of Fourier and Nusselt. So the use of differential equalization of heat-conducting of Fourier is possible only for the certain period of process of heating. Firstly, experimental studies of process of drying of profile workpiece (firewoods) are undertaken with a previous steaming and without a previous steaming; the corresponding sizes of speed of drying, coefficients of moisture conductivity and output of moisture are found. Consequently, taking into account the criterion of Reynolds the coefficient of drying and mass transfer coefficient of Fourier and Nusselt it is possible to synthesize the physical-mathematical model of process of drying. In the course of the study we have elaborated the structure of technological process of drying of firewoods. It is proved to include such successive technological operations as the initial heating, steaming, drying, that allows considerably to intensify mass transfer processes and, to the eventual result, shorten duration of process of drying on 25 % and accordingly to economize the charges of thermal energy. As a conclusion the author proposes structure of the technological process of drying wood that involves the use of environmentally-friendly drying agent for heating and steaming, and drying process steam-air mixture received from the combustion of waste wood. In general, the structure provides an energy saving of realization of technological process and reduces its overall duration.

Design Properties of Log Walls with Respect to Building Physics

The paper deals with the construction of walls of log wood houses of Canadian type in terms of thermal insulation, with the focus shifted onto the comparison of alternative structural solutions of such walls. The main aim of the research done was to assess the different Canadian type massive log wood walls, with various thermally insulating materials placed between the logs. The computer simulations of wall models were done in ANSYS software. Massive wooden walls unfortunately do hardly meet today's ever increasing requirements given for thermal resistance, heat conductivity and heat losses of a building, since the bed joints are weakened and also because of the thermal conductivity of wood itself. Thus, mainly the contact surface temperature was observed, which also became one of the evaluation factors describing the quality of construction.

Experimental Determination of Hydraulic Conductivity of Pine Samples in the Longitudinal Direction During Convective Drying

In studying the process of drying wood samples, the hydraulic conductivity of pine samples exposed to a convective air flow was measured in the direction perpendicular to the cross-sectional plane of the tree (along the wood grain). The kinetic curves of the drying process were treated with a technique based on the approximate solution of the one-dimensional diffusion equation for hydraulic conductivity of wood with a boundary condition of the third kind. The technique was tested on the basis of the known value of hydraulic conductivity in the direction tangential to annual rings of the tree. It is shown that the hydraulic conductivity in the longitudinal direction is 17 times the hydraulic conductivity in the direction tangential to the annual rings in the cross-sectional plane of the tree. By means of numerical simulation of the process, based on solving the initial-boundary problem for the two-dimensional linear equation of hydraulic conductivity, the effect of anisotropy of hydraulic conductivity coefficients on the dependence of the mean humidity on time and on the local humidity distribution is studied.

Brief report on theoretical research upon wood thermal property

In this paper, the theoretical expressions of the specific heat and thermal conductivity of wood are first derived from the micro-structure of wood by applying some basic principles in statistical thermodynamics and physical mechanics. Tested by a great many experiments, the average error of theoretical values is about 5%, much less than that of all kinds of exiting empiric equations in the world.

Sapwood water storage: its contribution to transpiration and effect upon water conductance through the stems of old‐growth Douglas‐fir

Abstract Enough water is stored in the sapwood of large Douglas‐fir to significantly contribute to transpiration. Sapwood water content falls through the season, causing the wood's conductivity to fall. This leads to low leafwater potentials, stomatal closure, and reduced photosynthesis by the trees.The amount of water stored in the sapwood of Douglasfir 50‐60 m tall, growing in the Cascade Mountains of Oregon, was estimated periodically over two seasons from measurements of sapwood relative water content (Rs). The relationship between Rs and volume of water contained in the sapwood was determined in the laboratory, and an equation describing the variation of relative conductivity (K) with Rs was derived from the literature. Stomatal conductance (ks) and leaf water potentials were measured in the field.The relative conductivity of the sapwood was calculated from estimates of the flow rate through the tree and differences in water potential between dawn and the time of comparison. Flow rate was assumed to equal transpiration rate, calculated from the Penman‐Monteith equation using measured ks values. A sixfold decrease in K during the summer was attributed to changes in Rs. The maximum observed diurnal variation in K would require a change in RS estimated at 25%.About 270 m3 ha−1 (27 mm) of water were stored in sapwood, and 75% of that was in the stemwood. Withdrawal from this store reached 1.7 mm day−1 on clear days after cloudy or rainy weather. Recharge could be almost as fast (up to 1.6 mm day−1) after rain, but was very slow if the foliage remained wet.

Seasonal Variation in Specific Conductivity of Wood in Tropical Plants with Reference to Leaf Fall

1. There is a fundamental distinction between monopodial and sympodial growth, the conductivity in the latter falling off rapidly from the base to the apex. 2. The distinction drawn by Farmer between deciduous and evergreen trees refers primarily to the respective demands made by them on the water supply for purposes of transpiration. 3. There is a correlation between the period of leaf fall and the increased capacity of the wood for conducting water.

2. On the Application of Angström's Method to the Conductivity of Wood

This was an account of a series of experiments made in the Natural Philosophy Laboratory of the University, to test the applicability of Angström's method of periodic variations of temperature to the determination of low conductivity. The wood was cut into discs of a standard thickness, and these were very tightly secured together, after the interposition of copper-iron thermo-electric junctions (of very fine wire). One series of discs was cut parallel, the other perpendicular, to the fibre. The results were obtained very easily, and accorded satisfactorily with those obtained by more laborious methods.