50 research outputs found
Potential Use of Wollastonite as a Filler in UF Resin Based Medium-Density Fiberboard (MDF)
No full textUrea-formaldehyde (UF) resins are primary petroleum-based, increasing their potential environmental footprint. Identifying additives to reduce the total amount of resin needed without adversely affecting the panel properties could reduce these impacts. Wollastonite is a mineral containing calcium and silica that has been used as an additive in a variety of materials and may be useful as a resin extender. Nanoscale wollastonite has been shown to enhance the panel properties but is costly. Micron-scale wollastonite may be a less costly alternative. Medium-density fiberboards were produced by blending a hardwood furnish with UF alone, micron-sized wollastonite alone, or a 9:1 ratio of UF to wollastonite. Panels containing of only wollastonite had poor properties, but the properties of panels with 9:1 UF/wollastonite were similar to the UF-alone panels, except for the internal bond strength. The results suggest that small amounts of micron-sized wollastonite could serve as a resin extender. Further studies are suggested to determine if the micron-sized material has similar positive effects on the resin curing rate
Penetration of Different Liquids in Wood-Based Composites: The Effect of Adsorption Energy
No full textThe penetration properties of three different liquids on the surface of medium-density fiberboard (MDF) and particleboard panels were studied. Water, as a polar liquid, was compared to two other less polar liquids (namely, ethanol and kerosene) with significantly larger molecules. Measurement of penetration time and wetted area demonstrated significantly higher values for water in comparison with the other two liquids, in both composite types. Calculation of adsorption energies, as well as adsorption distances, of the three liquid molecules on hemicellulose showed higher potentiality of water molecules in forming bonds on hemicellulose. However, comparison of the adsorption energies of cellulose with hemicellulose indicated a higher impact of the formation of bonds between hydroxyl groups in water and cellulose in hindering the penetration of water molecules into the composite textures. It was concluded that the formation of strong and stable bonds between the hydroxyl groups in water and cellulose resulted in a significant increase in penetration time and wetted area
First-Principles Study of Twin 4–8 Graphene in Carbon and Boron Nitride Nanostructures: Implications for Mechanical and Optoelectronic Nanodevices
No full textA nanosheet with the name twin 4–8
graphene composed
of
4- and 8-membered rings is suggested. The structural, mechanical,
electronic, and optical properties of carbon (C) twin 4–8 graphene
and twin 4–8 graphene-like boron nitride (BN) sheets are studied
by using density functional theory. These sheets exhibit dynamic stability
as well as good energetic and thermal stability, especially at room
temperature. The C and BN twin graphene sheets are softer and more
prone to deformation compared to graphene. Thus, they can be used,
particularly when softer materials are required rather than graphene.
The C twin 4–8 graphene exhibits semiconductor properties,
while the BN twin 4–8 graphene is an indirect band gap insulator.
An anisotropic behavior is observed for the optical properties of
the sheets. These sheets could store energy and filter out harmful
ultraviolet radiation due to their high dielectric constants and optical
absorption, particularly in the ultraviolet region. These nanosheets
are well suited for use in nanomechanics and nano-optoelectronics
due to their favorable mechanical, electronic, and optical characteristics
Mechanical properties of novel forms of graphyne under strain: A density functional theory study
No full textStructural and Electronic Properties of α2-Graphyne Nanotubes: A Density Functional Theory Study
No full textSensing Caffeine and Nicotine with Biphenylene Carbon, α-Graphyne Sheet and Nanotube: A Density Functional Theory Study
No full textWe have used density functional theory to study adsorption of caffeine and nicotine on carbon based nanostructures. The effect of caffeine and nicotine molecules on the electronic properties of α-graphyne, biphenylene carbon, and (4,0) nanotube based on α-graphyne were studied. It was found that caffeine and nicotine molecules were adsorbed strongly on these sheets and nanotube. The charges were transferred from molecules to the sheets and nanotube. Because of adsorption of these donor molecules, biphenylene carbon, α-graphyne sheet and nanotube become n-type semiconductors. Sensitivity of the electronic properties of these sheets and nanotube to adsorption of caffeine and nicotine indicate the carbon based nanostructures can be used for detection of caffeine and nicotine molecules.</jats:p
BAND GAP MODULATION OF GRAPHENE AND GRAPHYNE VIA TETRACYANOETHYLENE ADSORPTION
Get PDFAdsorption of tetracyanoethylene molecule on graphene and graphyne was investigated in view of finding an effective way to control their electronic properties. The electronic properties of graphene, α-, β- and γ- graphyne were studied by using the density functional theory. The binding energy, equilibrium adsorption distance, amount of charge transfer, electronic band structure, and density of states were calculated. The small adsorption energy and large adsorption distance identified physisorption of tetracyanoethylene molecule on graphene and graphyne sheets. It was found that charge is transferred from sheets to tetracyanoethylene molecule. In the presence of this acceptor molecule, the graphene and α-, β- and γ-graphynes, with semimetallic properties, show semiconducting behaviour. The tetracyanoethylene molecule has no considerable effect on the semiconducting property of γ-graphyne. Our results reveal that adsorption of organic molecules, such as tetracyanoethylene, is a proper method to open a band gap in graphene and graphyne
BAND GAP MODULATION OF GRAPHENE AND GRAPHYNE VIA TETRACYANOETHYLENE ADSORPTION
Get PDFAdsorption of tetracyanoethylene molecule on graphene and graphyne was investigated in view of finding an effective way to control their electronic properties. The electronic properties of graphene, α-, β- and γ- graphyne were studied by using the density functional theory. The binding energy, equilibrium adsorption distance, amount of charge transfer, electronic band structure, and density of states were calculated. The small adsorption energy and large adsorption distance identified physisorption of tetracyanoethylene molecule on graphene and graphyne sheets. It was found that charge is transferred from sheets to tetracyanoethylene molecule. In the presence of this acceptor molecule, the graphene and α-, β- and γ-graphynes, with semimetallic properties, show semiconducting behaviour. The tetracyanoethylene molecule has no considerable effect on the semiconducting property of γ-graphyne. Our results reveal that adsorption of organic molecules, such as tetracyanoethylene, is a proper method to open a band gap in graphene and graphyne
Engineering the band gap of BN and BC2N nanotubes based on T-graphene sheets using a transverse electric field: Density functional theory study
Get PDFA new class of nanotubes formed by rolling boron nitride (BN) and boron carbonitride (BC2N) sheets in the form of T-graphene is suggested in this work. The structural and electronic properties of these nanotubes, named T-BNNTs and T-BC2NNTs, are systematically studied by density functional theory (DFT) calculations. The tubes with different chirality and size are considered. Their structural stability is evaluated by calculation of cohesive energy and ab-initio molecular dynamics simulation. The results confirm the thermal stability of the considered T-BNNTs and T-BC2NNTs. The calculated electronic band structures and density of states reveal that the T-BNNTs are insulators, independent of their size and chirality. The T-BC2NNTs show both metallic and semiconducting properties. Our results indicate that the electronic properties of T-BNNTs and T-BC2NNTs can be successfully tuned by applying an external electric field, which makes the application of these tubes in nanoelectronic devices more promising
