Magnetic Wood Research Articles

Magnetic properties of NdFeB-coated rubberwood composites

Magnetic properties of composites prepared by coating lacquer containing neodymium iron boron (Nd-Fe-B) powders on rubberwood were characterized by vibrating sample magnetometry (VSM), magnetic moment measurements, and attraction tests with an iron-core solenoid. The Nd-Fe-B powders were recycled from electronic wastes by the ball-milling technique. Varying the milling time from 20 to 300 min, the magnetic squareness and the coercive field of the Nd-Fe-B powders were at the minimum when the powders were milled for 130 min. It followed that the coercive field of the magnetic wood composites was increased with the milling time increasing from 130 to 300 min. For the magnetic wood composites using Nd-Fe-B obtained from the same milling time, the magnetic squareness and the coercive field were rather insensitive to the variation of Nd-Fe-B concentration in coating lacquer from 0.43 to 1.00 g/cm3. By contrast, the magnetization and magnetic moment were increased with the Nd-Fe-B concentration increasing. Furthermore, the electrical current in the solenoid required for the attraction of the magnetic wood composites was exponentially reduced with the increase in the amount of Nd-Fe-B used in the coating.

Electromagnetic Wave Absorption Characteristics Adjustment Method of Recycled Powder-Type Magnetic Wood for Use as a Building Material

The purpose of this paper is to demonstrate the electromagnetic wave absorption characteristics of powder-type magnetic wood by changing the mixing ratios for the Mn-Zn ferrite and Ni-Zn ferrite powder. The results show that the matching frequency of the electromagnetic wave absorption characteristics can be controlled by changing the mixing ratios of the magnetic materials and the thickness of the board. We obtained electromagnetic wave absorption of close to 20 dB over the 2.5 GHz-6.2 GHz frequency range. The powder-type magnetic wood boards used in these experiments satisfy JIS standards for wood surface materials in terms of bending strength and deflection. The results from our studies can be used to design indoor powder-type magnetic wood wave absorbers for a specified absorption frequency.

Electromagnetic Wave Absorption Characteristics of Half Carbonized Powder-Type Magnetic Wood

A new technique for designing the material composition for a powder-type magnetic wood to achieve a specific matching frequency for an electromagnetic wave absorber is proposed and validated experimentally. The complex permittivity of the wood powder is changed by heating the powder-type magnetic wood until the surface is carbonized (referred to as half- carbonized) and has a conductive property. The changed complex permittivity of the wood powder alters the frequency at which peak absorption takes place. The experimental results for this study show that the electromagnetic wave absorption characteristics of the half- carbonized Mn-Zn ferrite powder-type (40 volume%) magnetic wood can be controlled by adjusting the processing temperature. The correct matching frequency and an acceptable bending strength are achieved if the material is processed at 250°C. The powder-type magnetic wood boards used in these experiments satisfy JIS standards for wood surface materials in terms of bending strength. The results from our studies can be used to design indoor powder-type magnetic wood wave absorbers with a specified absorption frequency.

Preparation of Thermoplastic Magnetic Wood via Etherification and In-Situ Synthesis of Iron Oxide

Wood flour (WF) was converted not only to thermoplastic material but also to carrier matrix for in-situ synthesis of iron oxide nano-particles by a set of etherification; namely, considerable hydroxypropylation and modest carboxymethylation. A sequence of procedure for the in-situ synthesis of iron oxides includes ferrous ion-absorption of the etherified WF, precipitation of ferrous hydroxide by an alkaline treatment, and oxidation of the ferrous hydroxide. Magnetometry measurements revealed that the magnetic woody composite showed superparamagnetism (SPM) at room temperature. The observation of SPM may be of significance in the perceptibility to an external magnetic stimulus only on demand and without energy loss.

Study of electromagnetic wave absorption characteristics and component parameters of laminated-type magnetic wood with stainless steel and ferrite powder for use as building materials

The purpose of this paper is to propose that a laminated-type magnetic wood using ferrite powder and stainless steel powder can serve as a wood building material of suitable quality for an indoor electromagnetic wave absorber. The experimental results for the gigahertz frequency band show that the laminated-type magnetic wood which has volume content ratio of 20vol%, an inside ratio of stainless steel to ferrite powder 2:3, and a thickness of magnetic layer 4.0mm has an electromagnetic wave absorption characteristic of 45.18dB at 2.62GHz. This laminated board can be used to prevent radio interference for indoor wireless LANs, which mainly use the 2.4GHz frequency band.

Experimental study on electromagnetic wave absorbing control of coating-type magnetic wood using a grooving process

This paper proposes a new electromagnetic wave absorbing control technique involving the coating-type magnetic wood in order to take advantage of the easy processing of wood materials. The experimental results show that, by changing the shape and size of the surface, the electromagnetic wave absorption characteristics can be controlled. The magnetic wood board with embedded grid lines demonstrated the best electromagnetic wave absorption characteristics among the various types that were studied.

Magnetic Wood Achieving a Harmony between Magnetic and Woody Functions

Magnetic wood, which was first introduced and developed by the Oka group in 1991, achieves a good balance of both woody and magnetic functions through the active addition of magnetic characteristics to the wood itself. In addition to showing magnetic characteristics, this magnetic wood also offers a woody texture, low specific gravity, humidity control, acoustic absorption and is very easy to process.

Effects of humidity on the magnetic and woody characteristics of powder-type magnetic wood

Among three types of proposed magnetic wood, powder-type magnetic wood can be made of recycled magnetic materials from IT devices, consumer electronics and waste wood. Because of its wood powder content, powder-type magnetic wood shows special characteristics different from those of typical magnetic materials. We focused on the relationship between humidity and magnetic characteristics of powder-type magnetic wood. The magnetic powder ratio, wood powder density and magnetic binder density were all examined as parameters for AC permeability.

Knock on wood

Some time ago, actor Laurence Fishburne interrupted a Broadway performance to give a piece of his mind to a member of the audience whose cell phone had gone off during the show. I am sure that, at one point or another, you have been similarly annoyed in a public place by an inconsiderate cell-phone user. How can a restaurant or theater owner provide a quiet zone for its customers? IEEE member Hideo Oda of Iwate University (Japan) and his colleagues have been perfecting another line of defense against irresponsible cell-phone users in public places. Based on a patented design, wood magnetic material (1994), Dr. Oda's magnetic wood can be used to panel a room to shield from cell-phone signals. The Japanese investigators settled on wood because it offers more natural, aesthetic options to interior design.

Experimental study on actuation functions of coating-type magnetic wood

Magnetic wood, which was proposed by the authors in 1991, magnetically attracts in spite of the fact that material itself is essentially wood. In addition to strong magnetic characteristics, this magnetic wood also offers a wood texture, low specific gravity, and it is very easy to process. Experimental results show good agreement with theoretical results. The parameters that determine the actuation function of the coating-type magnetic wood are presented.

Manufacturing methods and magnetic characteristics of magnetic wood

The relationship between wood construction and DC magnetic characteristics for three types of magnetic wood was experimentally investigated. The results show that the magnetic characteristics of each type of magnetic wood are dependent on the magnetic materials, the density of the magnetic material and the construction of the wood. Furthermore, it was determined that the relationship between the fiber direction and the magnetic path direction of the magnetic wood influenced the wood's magnetic characteristics.

Effects of humidity on the magnetic and woody characteristics of powder-type magnetic wood

Among three types of proposed magnetic wood, powder-type magnetic wood can be made of recycled magnetic materials from IT devices, consumer electronics and waste wood. Because of its wood powder content, powder-type magnetic wood shows special characteristics different from those of typical magnetic materials. We focused on the relationship between humidity and magnetic characteristics of powder-type magnetic wood. The magnetic powder ratio, wood powder density and magnetic binder density were all examined as parameters for AC permeability.

Laminated impregnated magnetic wood manufacturing methods and magnetic characteristics from DC to 13.5 GHz band

Summary form only given. Since the introduction of magnetic wood, the authors have proposed various functions such as heating, attraction and electromagnetic wave absorption. The impregnated type magnetic wood, which is manufactured by impregnating magnetic fluid through conduit pipes, has the best woody characteristics among the three types of magnetic woods (impregnated type, powder type and coating type). In spite of the merits, the manufacturing methods up until now have been unsuccessful in producing an impregnated type magnetic wood with good magnetic characteristics, because it is difficult to impregnate a sufficient amount of magnetic fluid into the wood board. The purpose of this paper is to suggest a new impregnating method and report on the experimental results of DC and AC magnetic characteristics. The manufacturing method involves taking a thin layer of film from the wood and impregnating this section with a magnetic fluid. Next, these layers are laminated and adhered to create a board. Comparative measurements were made of the specific gravity of the laminated impregnated type and impregnated type magnetic woods. The experimental results for the proposed laminated impregnated type show that uniform magnetic characteristics are obtained and apparently good characteristics are shown from DC to 13.5 GHz.

Detection on Incipient Fungal Attack in Wood Using Magnetic Resonance Parameter Mapping Wood Studied by Liquid State NMR Measurements

Summary Magnetic resonance imaging delivers excellent, high-resolution spatial images of damp or wet wood that can supply information on internal defects of logs to optimise cutting patterns. In normal wood, the image contrast of magnetic resonance images is primarily influenced by the distribution of moisture content within the specimen. In the case of fungal attack, it is also affected by the inherent Spin-Lattice (T1) and Spin-Spin (T2) relaxation times. We investigate changes in relaxation times in beech wood (Fagus sylvatica L.) caused by fungal attack (Coniophora puteana (Schum.) Karst.) over 6 weeks. In addition, loss of compressive strength and mass loss were tested, allowing comparison to conventional methods. Magnetic resonance imaging showed superior sensitivity in detection of early stage of fungal decay in comparison to mass or strength loss assessment.

Experimental results on indoor electromagnetic wave absorber using magnetic wood

The purpose of this paper is to propose a new type of indoor electromagnetic wave absorber using magnetic wood. This magnetic wood has good electromagnetic wave absorbing characteristics, a low specific gravity, a wood texture and other wood characteristics and can be easily processed. Electromagnetic wave absorbing characteristics were measured for four types of magnetic wood. The sandwich-type magnetic wood demonstrated the best wave absorbing characteristics among the four types of magnetic wood that were studied. The experimental results showed that the proposed indoor electromagnetic wave absorber can be used to suppress the transmission and reception of cellular phone and Personal Handy Phone System (PHS) signals and can be used as a cross protection for indoor wireless Local Area Networks (LAN). This wood can be processed for use in furniture, building materials, and other applications.

Wood construction and magnetic characteristics of impregnated type magnetic wood

The results of experiments involving the AC and DC magnetic characteristics of impregnated type magnetic wood were studied by taking into consideration the wood construction and fiber direction. The experimental results show that the sufficient amount of impregnated magnetic fluid varies depending on the fiber direction and length, and the grain face of the wood material. The impregnated type magnetic wood sample that is fully impregnated by magnetic fluid has a 60% saturation magnetization compared to the saturation magnetization of magnetic fluid. Samples for which the wood fiber direction was the same as the direction of the magnetic path had a higher magnetization intensity and permeability.

磁性木材を用いた発熱ボードの作製とその発熱性能

This paper shows our experimental results for the heating characteristics of magnetic wood. We made a separate heating board and a multiple-ply heating board, to both of which were adhered magnetic wood and an excitation coil. The results showed that the multiple-ply heating board, which was combined with coated magnetic wood and a spiral coil, had superior heating characteristics and heating efficiency.

磁性木材の磁気特性と発熱特性に関する基礎的検討

磁性木材の磁気特性と発熱特性に関する基礎的検討

Composition and heating efficiency of magnetic wood by induction heating

The purpose of this paper is to propose a new combination type heating board with improved heating efficiency and heating characteristics. This article covers experimental results of measuring surface temperature, heating function, heating efficiency and leakage magnetic field intensity of magnetic combination type heating board by induction heating. The results showed that the heating board with magnetic coating layers and the exciting coil/magnetic binder layer had the highest heating characteristics and heating efficiency. The heating board we propose can be used in house building materials and medical equipment that require a warm and smooth surface.

Experimental study on magnetic and heating characteristics of magnetic wood

Magnetic wood, wood which demonstrates magnetic characteristics, was introduced by the Oka group in 1991. Based on previous studies, we have proposed that magnetic wood can be used as a heating board by induction heating, applying a high frequency magnetic field. This article covers experimental magnetic and heating characteristics for three types of magnetic wood: an impregnated type (the wood is impregnated with a water-based magnetic fluid), a powder type (Mn–Zn ferrite powder and wood powder are mixed and pressed into boards), and a coating type (Mn–Zn ferrite powder is coated onto a fiber board). Our results showed that the coating-type magnetic wood had the highest surface temperature when using a solenoid excitation coil. In this case the surface temperature rose 50 °C. The heating board we propose can be used in furniture and medical equipment that require a warm and smooth surface.