scholarly journals Manufacturing and investigation of physical properties of polyacrylonitrile nanofibre composites with SiO2, TiO2 and Bi2O3 nanoparticles

2016 ◽  
Vol 7 ◽  
pp. 1141-1155 ◽  
Author(s):  
Tomasz Tański ◽  
Wiktor Matysiak ◽  
Barbara Hajduk
Keyword(s):  
Dielectric Constant ◽  
Refractive Index ◽  
Physical Properties ◽  
Band Gap ◽  
Electrospinning Process ◽  
Nanocomposite Polymer ◽  
Dispersion Of Nanoparticles ◽  
Gap Width ◽  
Band Gap Width ◽  
Constant Refractive Index

The aim of this study was to produce nanocomposite polymer fibres, consisting of a matrix of polyacrylonitrile (PAN) and a reinforcing phase in the form of SiO2/TiO2/Bi2O3 nanoparticles, by electrospinning the solution. The effect of the nanoparticles and the electrospinning process parameters on the morphology and physical properties of the obtained composite nanofibres was then examined. The morphology of the fibres and the dispersion of nanoparticles in their volume were examined using scanning electron microscopy (SEM). All of the physical properties, which included the band gap width, dielectric constant and refractive index, were tested and plotted against the concentration by weight of the used reinforcing phase, which was as follows: 0%, 4%, 8% and 12% for each type of nanoparticles. The width of the band gap was determined on the basis of the absorption spectra of radiation (UV–vis) and ellipsometry methods. Spectroscopic ellipsometry has been used in order to determine the dielectric constant, refractive index and the thickness of the obtained fibrous mats.

Study on Linear Relationship between Refractive Index Difference and Band Gap Width of the 1-D PCs

2017 ◽  
Vol 872 ◽  
pp. 3-7 ◽  
Author(s):  
Yun Gao Cai ◽  
Ying Hong Dong
Keyword(s):  
Refractive Index ◽  
Band Gap ◽  
Linear Growth ◽  
Characteristic Matrix ◽  
One Dimensional ◽  
Refractive Index Difference ◽  
The One ◽  
Gap Width ◽  
Band Gap Width ◽  
Relationship Equation

Set the Refractive Indexes of the One-Dimensional Photonic Crystals (1-D Pcs) were n2 and n3, Keeping n2=1.5 Unchanged and Adjusting n3 in the Range of 2.5--3.5, the Dispersion Curves were Obtained through Characteristic Matrix Method (CMM). The Results Show that when n3 Increased from 2.5 to 3.5, the Band Gap Width Also Increased from about 0.086 to 0.140 Correspondingly. Furthermore, the Results Show that it’s a Linear Growth Process between the Refractive Index Difference and the Band Gap Width of the 1-D Pcs, for the First Propose Quantitatively, there is a Relationship Equation Δω=0.0537(Δn)+0.0336(Δn=n3-n2) Approximately.

scholarly journals Characteristics of Poly(vinyl Alcohol) (PVA) Based Composites Integrated with Green Synthesized Al3+-Metal Complex: Structural, Optical, and Localized Density of State Analysis

Polymers ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1316
Author(s):  
Shujahadeen B. Aziz ◽  
Muaffaq M. Nofal ◽  
Hewa O. Ghareeb ◽  
Elham M. A. Dannoun ◽  
Sarkawt A. Hussen ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Refractive Index ◽  
Metal Complex ◽  
Band Gap ◽  
Optical Band Gap ◽  
Complex Dielectric Constant ◽  
Poly Vinyl Alcohol ◽  
Optical Parameters ◽  
Dispersion Energy ◽  
Casting Technique

The influence of dispersing Al-metal complex on the optical properties of PVA was investigated using UV–visible spectroscopy. Polymer composite films with various Al3+-complex amounts in the PVA matrix were arranged by solution casting technique by means of distilled water as a widespread solvent. The formation of Al3+-metal complex was verified through Ultraviolet–visible (UV-Vis) and Fourier-transform infrared spectroscopy (FTIR) examinations. The addition of Al-complex into the polymer matrix led to the recovery of the optical parameters such as dielectric constant (εr and εi) and refractive index (n). The variations of real and imaginary parts of complex dielectric constant as a function of photon wavelength were studied to calculate localized charge density values (N/m*), high-frequency dielectric constant, relaxation time, optical mobility, optical resistivity, and plasma angular frequency (ωp) of electrons. In proportion with Al3+-complex content, the N/m* values were amplified from 3.68 × 1055 kg−1 m−3 to 109 × 1055 kg−1 m−3. The study of optical parameters may find applications within optical instrument manufacturing. The optical band gap was determined from Tauc’s equation, and the type of electronic transition was specified. A remarkable drop in the optical band gap was observed. The dispersion of static refractive index (no) of the prepared composites was analyzed using the theoretical Wemple–DiDomenico single oscillator model. The average oscillator energy (Eo) and oscillator dispersion energy (Ed) parameters were estimated.

scholarly journals Effect of thickness on the optical properties of Gaas thin films

2013 ◽  
Vol 37 (1) ◽  
pp. 83-91 ◽  
Author(s):  
Chitra Das ◽  
Jahanara Begum ◽  
Tahmina Begum ◽  
Shamima Choudhury
Keyword(s):  
Thin Films ◽  
Dielectric Constant ◽  
Refractive Index ◽  
Band Gap ◽  
Optical Band Gap ◽  
Visible Region ◽  
Solar Spectrum ◽  
Band Gap Energy ◽  
Optical Parameters ◽  
Gap Energy

Effect of thickness on the optical and electrical properties of gallium arsenide (GaAs) thin films were studied. The films of different thicknesses were prepared by vacuum evaporation method (~10-4 Pa) on glass substrates at a substrate temperature of 323 K. The film thickness was measured in situ by a frequency shift of quartz crystal. The thicknesses were 250, 300 and 500 nm. Absorption spectrum of this thin film had been recorded using UV-VIS-NIR spectrophotometer in the photon wavelength range of 300 - 2500 nm. The values of some important optical parameters of the studied films (absorption coefficient, optical band gap energy and refractive index; extinction co-efficient and real and imaginary parts of dielectric constant) were determined using these spectra. Transmittance peak was observed in the visible region of the solar spectrum. Here transmittance showed better result when thicknesses were being increased. The optical band gap energy was decreased by the increase of thickness. The refractive index increased by increasing thickness while extinction co-efficient and real and imaginary part of dielectric constant decreased. DOI: http://dx.doi.org/10.3329/jbas.v37i1.15684 Journal of Bangladesh Academy of Sciences, Vol. 37, No. 1, 83-91, 2013

Wave propagation in acoustic metamaterials with resonantly shunted cross-shape piezos

2018 ◽  
Vol 29 (13) ◽  
pp. 2744-2753 ◽  
Author(s):  
Shengbing Chen
Keyword(s):  
Wave Propagation ◽  
Band Gap ◽  
Vibration Isolation ◽  
Band Gaps ◽  
Acoustic Metamaterials ◽  
Resonant Frequencies ◽  
Piezoelectric Patch ◽  
Transmission Properties ◽  
Gap Width ◽  
Band Gap Width

Cross-shape piezoelectric patches were originally proposed to improve the band-gap properties of acoustic metamaterials with shunting circuits. The dispersion curves are characterized through the application of finite element method. Also, the theoretical band-gap predictions are verified by simulation results obtained from COMSOL. The investigation results show that the proposed scheme distinguishes itself from the conventional square patches by broader band gaps, whose bandwidth is almost doubled. The inherent capacitance of the piezoelectric patch is strongly related to the boundary conditions, so the local resonant band gap is strongly affected by the shape of piezoelectric patches as well. As a result, the band-gap width and location of metamaterials with different shape patches are rather different, even with the same size patches. Also, negative modulus (NM) and Poisson’s ratio were observed around the resonant frequencies. The transmission properties of finite periods agree well with band-gap predictions. An obvious attenuation zone (AZ) is produced around the band-gap location, in which the wave propagation is decayed strongly. Similarly, the width of AZ of the proposed metamaterial is much larger than that of the conventional one. Hence, the proposed scheme demonstrates more advantages in the application to vibration isolation when compared with the conventional.

Study on Density Functional Theory of Zn1-xMgxO Alloy

2014 ◽  
Vol 556-562 ◽  
pp. 177-180
Author(s):  
Fu Chun Zhang ◽  
Hong Wei Cui ◽  
Xing Xiang Ruan ◽  
Wei Hu Zhang
Keyword(s):  
Density Functional Theory ◽  
Band Gap ◽  
Density Functional ◽  
High Energy ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Research Findings ◽  
Gap Width ◽  
Band Gap Width ◽  
Mg Doped

Geometric structure and electronic structures of Zn1-xMgxO alloy under different Mg doped concentrations have been investigated by performing the first-principle calculations based on density functional theory under the generalized gradient approximation (GGA). The calculated results show that there is substantial change in electronic structure of Mg doped MgxZn1-xO alloy, with the constant increase of Mg content, cell parameter a shall be on the gradual increase, with c on gradual decrease and band gap width of MgxZn1-xO alloy on the increase. The research findings show that the position of conduction band bottom is dependent on Mg 2p and Zn 4s. Mg doping results in drift of Mg 2p and Zn 4s toward high energy region, being the root cause for the increase in band gap width,the research results in the paper are in accordance with other experimental results. The above results provide theoretical guidance to the preparation of Zn1-xMgxO alloy in experiment.

Preparation and Optical Properties of One-Dimensional Ag/SiOx Photonic Crystal

2014 ◽  
Vol 576 ◽  
pp. 27-31
Author(s):  
Gai Mei Zhang ◽  
Can Wang ◽  
Yan Jun Guo ◽  
Wang Wei ◽  
Xiao Xiang Song
Keyword(s):  
Photonic Crystal ◽  
Band Gap ◽  
Electromagnetic Waves ◽  
Photonic Band Gap ◽  
Incident Angle ◽  
One Dimensional ◽  
The One ◽  
Photonic Band ◽  
Gap Width ◽  
Band Gap Width

The photonic crystal has the property that electromagnetic waves with interval of frequency in photonic band gap (PBG) can not be propagated, so it has important applying and researching value. The traditional one-dimensional photonic crystal is with narrow band gap width, and the reflection within the band is small, especially the band gap is sensitive to the incident angle and the polarization of light. A new photonic band gap (PBG) structure, metallodielectric photonic crystal by inserting metal film in the medium can overcomes the shortcomings mentioned above. The one-dimensional Ag/SiOx photonic crystal was prepared, and theoretical and experimental researches were developed. The results show that photonic band gap appears gradually and the band gap width increase with increasing of period of repeating thickness. With the thickness of Ag film increasing, the band gap width increases, but the starting wavelength of the photonic band gap keeps unchanged. With thickness of SiOx film increasing, the band gap width of photonic band gap also increases, but it is not obvious and starting wavelength increases.

Variation of Optical Band Gap Width of PVA Films Doped with Aluminum Iodide

2011 ◽  
Vol 383-390 ◽  
pp. 3257-3263 ◽  
Author(s):  
Omed Ghareb Abdullah ◽  
Sarkawt Abubakr Hussen
Keyword(s):  
Dielectric Constant ◽  
Band Gap ◽  
Localized States ◽  
Complex Dielectric Constant ◽  
Energy Gaps ◽  
Solution Cast ◽  
Aluminum Iodide ◽  
Gap Width ◽  
Solution Cast Method ◽  
Composite Samples

Polymer composite of polyvinyl alcohol (PVA), Aluminum Iodide have been prepared by solution cast method for different doping concentrations. The absorption of pure and doped films have been investigated in the visible and ultraviolent wavelength regions. It was found that the optical absorption is due to direct and indirect transitions, and the optical energy gaps values shifted to lower energies on Aluminum Iodide doping concentration for all transitions, while the band edge width of the tail localized states increase with increasing Aluminum Iodide concentration. The band gap of all films shows to be decrease after thermal treatment. The optical constants refractive index n, extinction coefficient k, the complex dielectric constant have been also calculated. The dielectric constant increased in the composite samples as compared with the pure PVA sample prepared by the same method.

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