Nanoporous Polymeric Periodic Structures Fabricated by Emulsion-assisted Holographic Patterning

2009 ◽  
Vol 1228 ◽  
Author(s):  
Vincent K.S Hsiao ◽  
Wei-Ting Chang
Keyword(s):  
Periodic Structure ◽  
Periodic Structures ◽  
Polar Phase ◽  
Acrylate Monomer ◽  
Uniform Size ◽  
Aqueous Emulsion ◽  
Emulsion Droplets ◽  
Sodium Dioctyl ◽  
A New Technique ◽  
Average Size

AbstractWe report a new technique of creating a nanoporous polymeric nanostructure by photo-patterning emulsions generated from a formamide (polar phase) and an acrylate-monomer (nonpolar phase). Formamide is a highly polar solvent that forms well dispersed, non-aqueous emulsion droplets within the monomer-containing nonpolar phase before holographic patterning. Photochemically initiated polymerization of the nonpolar phase (acrylate monomer) forces the formation of ordered formamide emulsions defined by the holographic interference. Evaporation of the formamide from the ordered structure yields a periodic structure with high optical reflectivity and a wide reflection bandwidth. The average size and the size distribution of formamide droplets in the photopolymer fluid must be controlled to fabricate a periodic structure with high reflectivity. Furthermore, we found that the addition of sodium dioctyl sulfosuccinate (AOT) surfactant helps to stabilize the formamide emulsion which further facilitates the formation of the ordered nanopores with uniform size.

Excitation of Rotationally Periodic Structures

1979 ◽  
Vol 46 (4) ◽  
pp. 878-882 ◽  
Author(s):  
S. J. Wildheim
Keyword(s):  
Periodic Structure ◽  
Periodic Structures ◽  
Resonance Condition ◽  
Forced Response ◽  
Closed Ring ◽  
Additional Resonance ◽  
Rotationally Symmetric ◽  
Deformation Patterns ◽  
Frequency Diagram ◽  
Rotationally Periodic Structure

A rotationally periodic structure consists of a finite number of identical substructures forming a closed ring. The vibrational behavior of such structures is considered, especially the forced response due to a rotating force. It is known that for a rotationally symmetric structure, excited by a rotating force, resonance for the n nodal diameters mode is obtained when the corresponding natural frequency is ωn = nΩ, where Ω is the angular velocity of the force. This resonance condition also holds for a rotationally periodic structure. But then additional resonance possibilities exist, given by ωn = (kN ± n)Ω, where N is the number of substructures and k = 0, 1, 2,… These resonance conditions give a zigzag line in the nodal diameters versus frequency diagram, which here is introduced as the ZZENF diagram. The deformation patterns at the resonances are both forward and backward traveling waves.

Molten Salts Synthesis of Relaxor Ferroelectrics PMN-PT Powders

2007 ◽  
Vol 336-338 ◽  
pp. 10-13 ◽  
Author(s):  
Shi Xi Zhao ◽  
Qiang Li ◽  
Feng Bing Song ◽  
Chun Hong Li ◽  
De Zhong Shen
Keyword(s):  
Molten Salt ◽  
Solid Solutions ◽  
Molten Salts ◽  
Processing Parameters ◽  
Relaxor Ferroelectrics ◽  
Molten Salt Synthesis ◽  
Uniform Size ◽  
Compositional Homogeneity ◽  
Average Size ◽  
Temperature Time

Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) solid solutions with composition near the morphotropic phase boundary (MPB) (33mol% PT) were successfully synthesized by the molten salt synthesis (MSS) method at 800°C for 30min using Li2SO4-Na2SO4 and NaCl-KCl molten salts as a medium of reaction, respectively. The influences of processing parameters, such as temperature, time, and type of salts, on the formation and the micrographs characteristics of the PMN-PT powders were discussion. It was found that the PMN-PT powder obtained by the MSS method has a relatively uniform size distribution and a better dispersivity of particle, and an average size of PMN-PT particles with smooth surface was around 0.3∼0.5 μm. With other conditions being kept same, chloride molten salt is more propitious to the formation of PMN- PT solid solutions, and improving the compositional homogeneity of PMN-PT powders.

Synthesis of LiCoO2 particles with tunable sizes by a urea-based-homogeneous-precipitation method

2020 ◽  
Vol 111 (4) ◽  
pp. 347-355
Author(s):  
Munekazu Motoyama ◽  
Hiroki Iwasaki ◽  
Miyuki Sakakura ◽  
Takayuki Yamamoto ◽  
Yasutoshi Iriyama
Keyword(s):  
Size Distribution ◽  
Average Diameter ◽  
Precipitation Method ◽  
Homogeneous Precipitation ◽  
Uniform Size ◽  
Homogeneous Precipitation Method ◽  
Wide Range ◽  
Size Uniformity ◽  
Average Size ◽  
Uniform Size Distribution

Abstract This paper reports the synthesis of monodisperse spherical LiCoO2 particles in a wide range of average diameter using a urea-based-uniform-precipitation method. The average diameter of LiCoO2 particles can be varied from 2 to 14 lm with a uniform size distribution. The effective approach to maintain the size uniformity while changing the average size of LiCoO2 particles is to keep the ratio of [CO(NH2)2] to [CoSO4] at 8 even when the CoSO4 and urea concentrations are changed.

Parametric Study on Rectangular Sonic Crystal

2012 ◽  
Vol 152-154 ◽  
pp. 281-286 ◽  
Author(s):  
Arpan Gupta ◽  
Kian Meng Lim ◽  
Chye Heng Chew
Keyword(s):  
Band Gap ◽  
Periodic Structure ◽  
Parametric Study ◽  
Sound Propagation ◽  
Periodic Structures ◽  
Sound Attenuation ◽  
Experimental Results ◽  
Center Frequency ◽  
Sonic Crystal ◽  
Sonic Crystals

Sonic crystals are periodic structures made of sound hard scatterers which attenuate sound in a range of frequencies. For an infinite periodic structure, this range of frequencies is known as band gap, and is determined by the geometric arrangement of the scatterers. In this paper, a parametric study on rectangular sonic crystal is presented. It is found that geometric spacing between the scatterers in the direction of sound propagation affects the center frequency of the band gap. Reducing the geometric spacing between the scatterers in the direction perpendicular to the sound propagation helps in better sound attenuation. Such rectangular arrangement of scatterers gives better sound attenuation than the regular square arrangement of scatterers. The model for parametric study is also supported by some experimental results.

Optimization of Axial Vibration Attenuation of Periodic Structure With Nonlinear Stiffness Without Addition of Mass

2020 ◽  
Vol 142 (6) ◽  
Author(s):  
Diego P. Vasconcellos ◽  
Marcos Silveira
Keyword(s):  
Periodic Structure ◽  
Total Mass ◽  
Periodic Structures ◽  
Original Structure ◽  
Dynamical Response ◽  
Nonlinear Stiffness ◽  
Optimal Position ◽  
Simplified Approach ◽  
Vibration Attenuation ◽  
Linear And Nonlinear

Abstract We explore the vibration attenuation of a periodic structure when one absorber with nonlinear cubic stiffness is included without increasing the total mass. Metastructures, and specifically periodic structures, present interesting characteristics for vibration attenuation that are not found in classical structures. These characteristics have been explored for automotive and aerospace applications, among others, as structures with low mass are paramount for these industries, and keeping low vibration levels in wide frequency range is also desirable. It has been shown that the addition of vibration absorbers in a periodic arrangement can provide vibration attenuation for shock input without increasing the total mass of a structure. In this work, the dynamical response of a metastructure with one nonlinear vibration absorber, with same mass as original structure, optimized for vibration attenuation under harmonic input is compared with a base metastructure without absorbers and a metastructure with linear absorbers via the evaluation of the H2 norm of the frequency response. A simplified approach is used to compare linear and nonlinear stiffness based on deformation energy, by considering linear and nonlinear restoring forces to be equal at mean deformation. The dynamical response of the optimal system is obtained numerically, and an optimization procedure based on sequential quadratic programming (SQP) is proposed to find the optimal position and stiffness coefficients of only one nonlinear absorber, showing that it results in lower level of vibrations than original structure and than structure with linear absorbers, while almost the same level as a structure with all nonlinear absorbers.

Synthesis and Characterization of Nanometer Copper Ferrite by Auto-Combustion

2011 ◽  
Vol 347-353 ◽  
pp. 3472-3476
Author(s):  
Guang Xiu Cao ◽  
Tian Liu ◽  
Qing Hong Zhang ◽  
Hong Zhi Wang
Keyword(s):  
Raw Materials ◽  
Combustion Process ◽  
Copper Nitrate ◽  
Copper Ferrite ◽  
X Ray Diffraction ◽  
Uniform Size ◽  
Simple Method ◽  
Transmission Electron ◽  
Auto Combustion ◽  
Average Size

A simple method for preparing nanoscale copper ferrite particles with narrow distribution and uniform size was developed by auto-combusting the precursor using copper nitrate, iron nitrate, and malic acid as raw materials. The constituents and the thermal decomposition process of the precursor were studied by Fourier transform infrared (FT-IR), thermogravimetry-differental thermal analysis (TG-DTA) and X-ray diffraction (XRD). The results showed that the carboxyl and nitrate ion take part in the reaction during the auto-combustion process. The precursor decomposed completely at about 199 °C, to yield single phase product. Transmission electron microscopy (TEM) indicated that the average size of the as-burnt sample was about 90 nm.

Peptide-mediated deposition of nanostructured TiO2 into the periodic structure of diatom biosilica

2008 ◽  
Vol 23 (12) ◽  
pp. 3255-3262 ◽  
Author(s):  
Clayton Jeffryes ◽  
Timothy Gutu ◽  
Jun Jiao ◽  
Gregory L. Rorrer
Keyword(s):  
Titanium Dioxide ◽  
Electron Diffraction ◽  
Thermal Annealing ◽  
Periodic Structure ◽  
Outer Surface ◽  
Periodic Structures ◽  
Diatom Frustule ◽  
X Ray Diffraction ◽  
X Ray ◽  
Reported Study

Diatoms are single-celled algae that make silica shells called frustules that possess periodic structures ordered at the micro- and nanoscale. Nanostructured titanium dioxide (TiO2) was deposited onto the frustule biosilica of the diatom Pinnularia sp. Poly-l-lysine (PLL) conformally adsorbed onto surface of the frustule biosilica. The condensation of soluble Ti-BALDH to TiO2 by PLL-adsorbed diatom biosilica deposited 1.32 ± 0.17 g TiO2/g SiO2 onto the frustule. The periodic pore array of the diatom frustule served as a template for the deposition of the TiO2 nanoparticles, which completely filled the 200-nm frustule pores and also coated the frustule outer surface. Thermal annealing at 680 °C converted the as-deposited TiO2 to its anatase form with an average nanocrystal size of 19 nm, as verified by x-ray diffraction, electron diffraction, and SEM/TEM. This is the first reported study of directing the peptide-mediated deposition of TiO2 into a hierarchical nanostructure using a biologically fabricated template.

scholarly journals Number of Wavevectors for Each Frequency in a Periodic Structure

2017 ◽  
Vol 139 (5) ◽  
Author(s):  
Farhad Farzbod
Keyword(s):  
Periodic Structure ◽  
Degrees Of Freedom ◽  
Phonon Dispersion ◽  
Periodic Structures ◽  
Dispersion Curves ◽  
Neighbor Interaction ◽  
Phonon Dispersion Curves ◽  
Hexagonal Form ◽  
Vibration Properties ◽  
Unit Cells

Periodic structures have interesting acoustic and vibration properties making them suitable for a wide variety of applications. In a periodic structure, the number of frequencies for each wavevector depends on the degrees-of-freedom of the unit cell. In this paper, we study the number of wavevectors available at each frequency in a band diagram. This analysis defines the upper bound for the maximum number of wavevectors for each frequency in a general periodic structure which might include damping. Investigation presented in this paper can also provide an insight for designing materials in which the interaction between unit cells is not limited to the closest neighbor. As an example application of this work, we investigate phonon dispersion curves in hexagonal form of boron nitride to show that first neighbor interaction is not sufficient to model dispersion curves with force-constant model.

An Eigenvalue Inclusion Principle for Simple, Rotationally Periodic Structures

1993 ◽  
Author(s):  
I. Y. Shen
Keyword(s):  
Linear Combination ◽  
Periodic Structure ◽  
State Vector ◽  
Transfer Functions ◽  
Periodic Structures ◽  
The State ◽  
Degree Of Freedom ◽  
Single Degree Of Freedom ◽  
Inclusion Property ◽  
Single Degree

Abstract This paper describes an eigenvalue inclusion principle for a simple, rotationally periodic structure P whose i-th substructure Si is connected to a neighboring substructure Si+1 through a single-degree-of-freedom interface constraint Ii+1. The state vector vi+1 at the interface Ii+1, consisting of the displacement and the force at the interface, is represented in terms of the state vector vi at the interface Ii through transfer functions of the substructure Si. The periodicity of the structure P then requires that a linear combination of the transfer functions of Si be zero. As a consequence, a simple periodic structure P with period N will have exactly N eigenvalues lying between two consecutive eigenvalues of the substructure Si. Finally, this eigenvalue inclusion property is illustrated on a periodic structure with known exact eigensolutions.

Synthesis and Characterization of Antiferromagnetic Kmnf3 Nanoparticles

1999 ◽  
Vol 577 ◽  
Author(s):  
C. Sangregorio ◽  
E. E. Carpenter ◽  
C. J. O'connor
Keyword(s):  
Magnetic Properties ◽  
Reverse Micelles ◽  
Exchange Coupling ◽  
Hysteresis Loops ◽  
Size Control ◽  
Synthesis And Characterization ◽  
Uniform Size ◽  
Average Size ◽  
Aqueous Core

ABSTRACTThe magnetic properties of nanosized antiferromagnetic particles of KMnF3 are presented. The particles were synthesized using the microemulsion technique, i.e. by using the aqueous core of reverse micelles as constrained microreactors for the precipitation of the particles. The structural characterization of the samples, accomplished by TEM and XRD, reveal that the samples consist of cubic-shaped, crystalline KMnF3 nanoparticles of uniform size. Control over the average size of the particles was achieved by changing the reaction time. Four different samples of average size in the range 13-35 nm were prepared. DC magnetic susceptibility measurements revealed superparamagnetic behavior of the particles. Hysteresis loops measured after field cooling the samples through TN were shifted. The shift is ascribed to the exchange coupling between the antiferromagnetic core of the particles and the uncompensated spin shell surrounding it.

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