Wood densification can improve the strength of low density wood species and extend wood product applications. To enhance the wood compressive quality, chemical pretreatments for pristine wood have ...widely been used. Densified
Abies
wood was fabricated by combining NaOH/Na
2
SO
3
solution treatment, hot-pressing and post mechanical fixation. The appearance, color, chemical composition, and physiology and mechanical properties before and after the densification treatment were examined by the colorimeter, FTIR and mechanical testing machine, respectively. Surface color of
Abies
wood was changed obviously after the densification. The values of brightness
L
* and
b
* decreased but the value of
a
* showed a slight increase in the densified wood. FTIR results confirmed that the color changes can be explained by the degradation of hemicellulose and lignin in wood cell walls and migration of extractives during the densification process. Sufficient removal of wood polymers resulted in the average compression ratio of about 80% in the radial direction of the natural wood. The density of densified wood increased with the wood thickness up to 1.227 g cm
−1
, accounting for a 169% increase compared to that of the pristine wood. Modulus of rupture (MOR) and modulus of elasticity (MOE) in the thickness direction of densified wood also markedly enhanced. Degradation of polymers in wood cell walls also was reconfirmed by the difference of fracture interface. All the results suggested that the densified softwood can be easily fabricated using the proposed method and the new densified softwood can be appropriately used as interior decoration materials.
Transparent wood samples were fabricated from an environmentally-friendly hydrogen peroxide (H2O2) bleached basswood (Tilia) template using polymer impregnation. The wood samples were bleached ...separately for 30, 60, 90, 120 and 150 min to evaluate the effects on the changes of the chemical composition and properties of finished transparent wood. Experimental results showed decreases in cellulose, hemicellulose, and lignin content with an increasing bleaching time and while decreasing each component to a unique extent. Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscope (SEM) analysis indicated that the wood cell micro-structures were maintained during H2O2 bleaching treatment. This allowed for successful impregnation of polymer into the bleached wood template and strong transparent wood products. The transparent wood possessed a maximum optical transmittance up to 44% at 800 nm with 150 min bleaching time. Moreover, the transparent wood displayed a maximum tensile strength up to 165.1 ± 1.5 MPa with 90 min bleaching time. The elastic modulus (Er) and hardness (H) of the transparent wood samples were lowered along with the increase of H2O2 bleaching treatment time. In addition, the transparent wood with 30 min bleaching time exhibited the highest Er and H values of 20.4 GPa and 0.45 GPa, respectively. This findings may provide one way to choose optimum degrees of H2O2 bleaching treatment for transparent wood fabrication, to fit the physicochemical properties of finished transparent wood.
Metallic oxides are promising electrochemically active materials which can supply large energy density and capacitance, while always suffer from weak electrical conductivity and structural stability. ...Herein, a green and low-tortuosity wood-derived anisotropic carbon is developed to stabilize CuO and improve its conductivity. The low tortuosity and large surface area of anisotropic carbon is capable to act as an electrolyte storage to supply fast transport channels for the ionic migration, which is verified by the kinetic analysis. As expected, the composite electrode has superior electrochemical performances with a large specific capacitance of 694.8 F g−1 at the current density of 0.5 A g−1 (131.5% and 344.2% higher than that of the individual CuO (300.1 F g−1) and the individual carbon (156.4 F g−1)) and high cycling stability. As the current density dramatically increases 100 times to 50 A g−1, the composite electrode still retains 46.7% of the original capacitance, reflecting its outstanding rate capability. More importantly, the composite acts as an advanced cathode material to assemble hybrid supercapacitors, possessing a high cell voltage of 1.5 V and good cycling stability (91.2% capacitance retention after 5000 cycles) and high energy density (13.6 W h kg−1 at 350.3 W kg−1).
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•A low-tortuosity wood-derived anisotropic carbon is developed to stabilize CuO.•A 17.3% improvement for b value verifies the carbon contribution to ionic migration.•The integration of carbon leads to a 131.5% improvement in the specific capacitance.•As current density increases 100 times, 46.7% of capacitance retention is achieved.•The devices achieve a wide voltage range and high energy density of 13.6 W h kg−1.
Wood permeability and compressibility are affected by cell wall structure and chemical composition. These properties can be improved by appropriate wood pretreatments. Low-density poplar wood was ...converted to a more dense structure by the following steps: First, lignin and hemicellulose were removed using a mixture of NaOH and Na2SO3. Second they were impregnated with polyethylene glycol (PEG, mean molecular weight of 1200), nano-SiO2, and a silane coupling agent at atmospheric temperature and pressure. Finally, impregnated wood was compressed at 150 °C. Results showed that the tracheid lumens on the transverse section of the compressed wood almost vanished. Specifically, the lumens in the wood cells, especially those that were compressed, were almost completely filled with PEG. In FTIR, the asymmetric absorption peaks of Si–O–Si at 1078–1076 cm−1 were clearly observed, which confirms the existence of bonding between nano-SiO2 and wood. The highest melting enthalpy and crystallization enthalpy showed a heat storage capacity of modified wood, which were 20.7 and 9.8 J/g, respectively. Such phase change capabilities may have potential applications in regulating the rate of change of room temperature. In summary, the modified wood could be utilized as material for construction to conserve energy.
Transparent wood (TW) was prepared by directly impregnating the wood cell wall and cavity with index-matched prepolymerized methyl methacrylate (MMA). In this process, lignin is retained compared ...with the preparation of transparent wood in the past, making the production faster and more energy-efficient. The innovation lies in that the prepared transparent wood retains the natural color and texture of the wood while transmitting light, especially under the illumination of a specific light source, which exist as the special visual effects. In order to enhance the practicality of the research and effectively expand the types of home decoration materials, six common wood species with different densities were selected in the experiment. Then the characteristics and mechanisms of wood, that is, color difference, light transmittance, microstructure, changes of chemical functional groups, and tensile strength, before and after PMMA impregnating were compared and analyzed. It is concluded that the light transmittance and mechanical properties of the wood have been improved, and a good synergistic effect between wood and PMMA has been confirmed by the analysis of scanning electron microscopy and infrared spectroscopy. The above highlights make pervious to transparent wood, which has the potential as an excellent functional decorative material.
Two common tree species of Betula alnoides (
) and New Zealand pine (
) were selected as the raw materials to prepare for the partially transparent wood (TW) in this study. Although the sample is ...transparent in a broad sense, it has color and pattern, so it is not absolutely colorless and transparent, and is therefore called partially transparent. For ease of interpretation, the following "partially transparent wood" is referred to as "transparent wood (TW)". The wood template (FW) was prepared by removing part of the lignin with the acid delignification method, and then the transparent wood was obtained by impregnating the wood template with a refractive-index-matched resin. The goal of this study is to achieve transparency of the wood (the light transmittance of the prepared transparent wood should be improved as much as possible) by exploring the partial delignification process of different tree species on the basis of retaining the aesthetics, texture and mechanical strength of the original wood. Therefore, in the process of removing partial lignin by the acid delignification method, the orthogonal test method was used to explore the better process conditions for the preparation of transparent wood. The tests of color difference, light transmittance, porosity, microstructure, chemical groups, mechanical strength were carried out on the wood templates and transparent wood under different experimental conditions. In addition, through the three major elements (lignin, cellulose, hemicellulose) test and orthogonal range analysis method, the influence of each process factor on the lignin removal of each tree species was obtained. It was finally obtained that the two tree species acquired the highest light transmittance at the experimental level 9 (process parameters: NaClO
concentration 1wt%, 90 °C, 1.5 h); and the transparent wood retained most of the color and texture of the original wood under partial delignification up to 4.84-11.07%, while the mechanical strength with 57.76% improved and light transmittance with 14.14% higher than these properties of the original wood at most. In addition, the wood template and resin have a good synergy effect from multifaceted analysis, which showed that this kind of transparent wood has the potential to become the functional decorative material.
Because of serious electromagnetic pollution caused by the widespread use of radio frequency equipment, the study of electromagnetic interference (EMI) shielding materials has been a long-standing ...topic. Carbon fiber and graphene composites have great potential as EMI shielding materials due to their unique microstructure and electrical conductivity. In this work, a novel kind of core-shell composite is fabricated based on the pore-rich pine needles-derived carbon fibers (coded as PNCFs) core and the graphene shell. The pore-rich PNCFs are created by KOH activation, and the integration between the pore-rich PNCFs and the graphene relies on a plasma-enhanced chemical vapor deposition (PECVD) method. The conductivity of the pore-rich PNCFs@graphene core-shell composite reaches 4.97 S cm−1, and the composite has an excellent EMI shielding effectiveness (SE > 70 dB over X-band (8.2−12.4 GHz)) and achieves a maximum value of ~77 dB at 10.4 GHz, which is higher than many biobased EMI shielding materials in the recent literature. By calculation and comparison, the large absorption loss (accounting for 90.8% of total loss) contributes to reducing secondary radiation, which is quite beneficial for stealth uses. Thus, this work demonstrates a promising design method for the preparation of green high-performance composites for EMI shielding and stealth applications (such as warcrafts, missiles, and stealth wears).
Due to its good physical properties, softened wood (SW) has been widely used in the fields of home furnishing, interior decoration, and construction, such as decorative panels, softened wood ...flooring, wooden bricks, and softened wood furniture. However, traditional methods of wood softening often fail to meet the requirements of enterprises for softening wood. Here, inspired by the research related to wood softening, we propose a method for directly preparing softened wood (SW) using a new type of “ionic liquid” eutectic solvent (DES) owing to its low cost, environmental friendliness, recyclability, and other advantages. To improve the adaptability of the study, a total of five types of DESs were designed and prepared, and by the microwave-assisted DES treatment of natural wood (NW), the purpose of softening wood was achieved. Then, we conducted a series of comparative analyses and performance tests on NW and SW, including microscopic images, chemical composition, color difference, and mechanical properties. The results show that the wood softened by DES has become a highly porous network structure, and partial lignin, hemicellulose, and cellulose have been removed. At the same time, different degrees of color change, lower hardness, excellent mechanical flexibility, and a compression rebound rate of up to about 90% are obtained. The above-mentioned various properties of SW provide great potential for its application in wood products.
As one of the fast-growth wood species, hybrid yellow poplar (YP-h, Liriodendron sino-americanum) has been extensively planted throughout China, however, little is known about its properties and ...applicability in structural and nonstructural applications such as construction and furniture. The aim of this study was to evaluate the properties of YP-h and examine its differences with yellow poplar (YP, Liriodendron tulipifera). The average vessel diameter of YP-h (55 μm) was 19 % lower than YP (68 μm), but, the density of YP-h was 37 % higher than YP and the dimensional change in YP-h was higher than YP. Comparable tensile strength and flexural modulus were found in YP-h and YP, however, the flexural, shear, and impact strength of YP-h was 35 %, 40 %, and 55 % higher than those of YP, respectively. The drilling, mortising, and turning processability of YP-h were superior to those of YP. Compared to the gluing and coating performance of YP, YP-h had inferior gluing properties and equivalent coating performance. Therefore, hybrid yellow poplar can be an ideal candidate for yellow poplar to be utilized in construction and furniture.
Tungsten trioxide films with sheet-like nanostructures were grown on wood surfaces through a simple low-temperature hydrothermal method using ethanol as an inducer. The morphologies, phase ...structures, compositions, optical properties and wetting behaviors of the WO
3
-treated wood surfaces were characterized. The ethanol content in the precursor solution played an important role in the morphologies and phase structures. It was observed that the WO
3
film based on the wood substrate was composed of 2D nanosheets with an edge length of 580-957 nm and a thickness of about 80 nm and was highly crystallized with a phase-pureness. The UV-vis analysis shows that the sample prepared with the 20% ethanol content responded to ultraviolet radiation of wavelength 270-350 nm very intensively. When the sample was irradiated under UV light (365 nm), there appeared an obvious color difference value (Δ
C
). The water contact angle (WCA) measurements demonstrated that the WO
3
-treated wood surfaces possessed superhydrophilic behavior and then converted to the superhydrophobic property through the octadecyltrichlorosilane (OTS) treatment. The AFM analysis indicated that a change in surface roughness of the film was responsible for photochromic and hydrophobic performances. The obtained wood surfaces exhibited photoresponsive and self-cleaning functions, which have potential applications such as information storage, smart sensors, and anti-fake materials.
Tungsten trioxide films with sheet-like nanostructures coated on wood substrates possessed photoresponsive behavior and superhydrophobic performance after OTS treatment.
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