Effective Electrodynamic Parameters of Nano-Composite Media and the Theory of Homogenisation

2019 ◽  
pp. 4-14 ◽  
Author(s):  
Leon A. Apresyan
Keyword(s):  
Heterogeneous Media ◽  
Transport Coefficients ◽  
Optoelectronic Devices ◽  
Initial Point ◽  
Dielectric Permeability ◽  
Nano Particles ◽  
Effective Parameters ◽  
Nano Composite ◽  
The Media ◽  
Percolation Thresholds

When creating new lighting and optoelectronic devices, great attention in recent years is paid to use nano-composite materials, i.e. the media containing impregnations of nanometre size, such as nano-particles of metals, quantum points, carbon nanotubes, graphenes, etc. This allows obtaining media with new, formerly unattainable characteristics. An initial point when describing properties of such medias is usually evaluation of their effective parameters (dielectric permeability, conductivity, heat conduction and of other similar transport coefficients) in the model of macroscopically heterogeneous media, in other words, media containing macroscopic impregnations with known or determined from experiments characteristics. Main approaches used in such cases are known Maxwell Garnett and Bruggeman approximations. In this review, methodical questions connected with various approaches to obtain these approximations and of their generalisations are discussed. Also some new results are given, which connected with evaluations of percolation thresholds within generalised Bruggeman approximations in the event of multi-component media.

scholarly journals Space Charge Characteristics and Electrical Properties of Micro-Nano ZnO/LDPE Composites

Crystals ◽  
2019 ◽  
Vol 9 (9) ◽  
pp. 481
Author(s):  
Jun-Guo Gao ◽  
Xia Li ◽  
Wen-Hua Yang ◽  
Xiao-Hong Zhang
Keyword(s):  
Electrical Properties ◽  
Space Charge ◽  
Synergistic Effects ◽  
Nano Particles ◽  
Breakdown Field ◽  
Nano Composite ◽  
Nano Zno ◽  
Additive Particles ◽  
Ldpe Composites ◽  
Short Connection

The synergistic effects of zinc oxide (ZnO) Micro/Nano particles simultaneously filled in low-density polyethylene (LDPE) on the space charge characteristics and electrical properties has been investigated by melt blending micro-scale and nanoscale ZnO additive particles into LDPE matrix to prepare Micro-ZnO, Nano-ZnO, and Micro-Nano ZnO/LDPE composites. The morphological structures of composite samples are characterized by Polarizing Light Microscopy (PLM), and the space charge accumulations and insulation performances are correlated in the analyses with Pulse Electronic Acoustic (PEA), DC breakdown field strength, and conductance tests. It is indicated that both the micro and nano ZnO fillers can introduce plenty of heterogeneous nuclei into the LDPE matrix so as to impede the LDPE spherocrystal growth and regularize the crystalline grains in neatly-arranged morphology. By filling microparticles together with nanoparticles of ZnO additives, the space charge accumulations are significantly inhibited under an applied DC voltage and the minimum initial residual charges with the slowest charge decaying rate have been achieved after an electrode short connection. While the micro-nano ZnO/LDPE composites acquire the lowest conductivity, the breakdown strengths of the ZnO/LDPE nanocomposite and micro-nano composite are, respectively, 13.7% and 3.4% higher than that of the neat LDPE material.

Experimental investigation of electrodeposited Ni-Al2O3/ZrO2 nano composite on HSLA ASTM A860 alloy

2021 ◽  
Author(s):  
Chandrasekhara Sastry Chebiyyam ◽  
Pradeep N ◽  
Shaik AM ◽  
Hafeezur Rahman A ◽  
Sandeep Patil
Keyword(s):  
Grain Size ◽  
Corrosion Resistance ◽  
Composite Coating ◽  
Base Alloy ◽  
Composite Coatings ◽  
Nano Particles ◽  
Alloy Sample ◽  
Nano Composite ◽  
Nano Coating ◽  
Nano Composite Coating

Abstract Nano composite coatings on HSLA ASTM A860 alloy, adds to the barrier efficacy by increase in the microhardness, wear and corrosion resistance of the substrate material. Additionally, reduction of delamination of the nano composite coating sample is ascertained. Ball milling is availed to curtail the coating samples (Al2O3/ZrO2) to nano size, for forming a electrodeposited product on the substrate layer. The curtailment in grain size was ascertained to be 17.62% in Ni-Al2O3/ZrO2 nano composite coating. During the deposition process, due to the presence of Al2O3/ZrO2 nano particles an increase in cathode efficiency is ascertained. An XRD analysis of the nano composite coating indicates a curtailment in grain size along with increase in the nucleation sites causing a surge in the growth of nano coating layer. In correlation to uncoated HSLA ASTM A36 alloy sample, a surge in compressive residual stress by 47.14%, reduction of waviness by 32.14% (AFM analysis), upsurge in microhardness by 67.77% is ascertained in Ni-Al2O3/ZrO2 nano composite coating. Furthermore, in nano coated Ni-Al2O3/ZrO2 composite a reduction is observed pertaining to weight loss and friction coefficients by 27.44% and 13% in correlation to plain uncoated alloy respectively. A morphology analysis after nano coating indicates, Ni-Al2O3/ZrO2 particles occupy the areas of micro holes, reducing the wide gaps and crevice points inside the matrix of the substrate, enacting as a physical barrier to upsurge the corrosion resistance by 67.72% in correlation to HSLA ASTM A860 base alloy.

Cutting Performance and Wear Mechanisms of an Al2O3-Based Micro-Nano-Composite Ceramic Tool

2010 ◽  
Vol 443 ◽  
pp. 244-249 ◽  
Author(s):  
Yong Hui Zhou ◽  
Jun Zhao ◽  
Xing Ai
Keyword(s):  
Failure Modes ◽  
Cutting Tools ◽  
Tool Material ◽  
Composite Ceramic ◽  
Cutting Performance ◽  
Nano Particles ◽  
Ceramic Tool ◽  
Nano Composite ◽  
Micro Particles ◽  
1045 Steel

An Al2O3-based composite ceramic cutting tool material reinforced with (W, Ti)C micro-particles and Al2O3 micro-nano-particles was fabricated by using hot-pressing technique, the composite was denoted as AWT. The cutting performance, failure modes and mechanisms of the AWT micro-nano-composite ceramic tool were investigated via continuous turning of hardened AISI 1045 steel in comparison with those of an Al2O3/(W, Ti)C micro-composite ceramic tool SG-4 and a cemented carbide tool YS8. Worn and fractured surfaces of the cutting tools were characterized by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The results of continuous turning revealed that tool lifetime of the AWT ceramic tool was higher than that of the SG-4 and YS8 tools at all the tested cutting speeds. The longer tool life of the AWT composite ceramic tool was attributed to its synergistic strengthening/toughening mechanisms induced by the (W, Ti)C micro-particles and Al2O3 nano-particles.

Trapezoidal traction–separation laws in mode II fracture in nano-composite and nano-adhesive joints

2018 ◽  
Vol 37 (11) ◽  
pp. 780-794 ◽  
Author(s):  
P Ghabezi ◽  
M Farahani
Keyword(s):  
Experimental Investigation ◽  
Data Reduction ◽  
Beam Theory ◽  
Calibration Method ◽  
Adhesive Joints ◽  
Nano Particles ◽  
Mode Ii ◽  
Nano Composite ◽  
Mode Ii Fracture ◽  
Beam Method

The main focus of this paper is on the experimental investigation and comparison between different bridging laws. For mode II fracture in the presence of nano-particles, these laws are calculated from three data reduction schemes for describing the bridging zone and trapezoidal traction–separation law parameters. For the calculation of the energy release rate in mode II fracture, three corresponding data reduction schemes, compliance calibration method, corrected beam theory and compliance-based beam method, have been utilized for different percentages of nano-particles in the adhesives and the adherents.

Design Issues of 4G-Network Mobility Management

2014 ◽  
pp. 210-238
Author(s):  
D. H. Manjaiah ◽  
P. Payaswini
Keyword(s):  
Heterogeneous Networks ◽  
Mobile Networks ◽  
Mobility Management ◽  
Heterogeneous Media ◽  
Fourth Generation ◽  
Network Information ◽  
Ieee 802.21 ◽  
Research Areas ◽  
Media Independent Handover ◽  
The Media

Fourth Generation wireless networking (4G network) is expected to provide global roaming across different types of wireless and mobile networks. In this environment, roaming is seamless and users are always connected to the best network. Moreover, 4G networks will be packet switched systems entirely based on the IPv6 protocol. The essentiality of Quality of Service (QoS) and the heterogeneous nature of 4G pose high demands onto the mobility management technology. Due to this, one of the most challenging research areas for the 4G network is the design of intelligent mobility management techniques that take advantage of IP-based technologies to achieve global roaming among various access technologies. In order to address the issue of heterogeneity of the networks, IEEE 802.21 working group proposed Media Independent Handover (MIH). The scope of the IEEE 802.21 MIH standard is to develop a specification that provides link layer intelligence and other related network information to upper layers to optimize handovers between heterogeneous media. The IEEE 802.21 group defines the media independent handover function that will help mobile devices to roam across heterogeneous networks and stationary devices to switch over to any of the available heterogeneous networks around it.

Design Issues of 4G-Network Mobility Management

2016 ◽  
pp. 634-662
Author(s):  
D. H. Manjaiah ◽  
P. Payaswini
Keyword(s):  
Heterogeneous Networks ◽  
Mobile Networks ◽  
Mobility Management ◽  
Heterogeneous Media ◽  
Fourth Generation ◽  
Network Information ◽  
Ieee 802.21 ◽  
Research Areas ◽  
Media Independent Handover ◽  
The Media

Fourth Generation wireless networking (4G network) is expected to provide global roaming across different types of wireless and mobile networks. In this environment, roaming is seamless and users are always connected to the best network. Moreover, 4G networks will be packet switched systems entirely based on the IPv6 protocol. The essentiality of Quality of Service (QoS) and the heterogeneous nature of 4G pose high demands onto the mobility management technology. Due to this, one of the most challenging research areas for the 4G network is the design of intelligent mobility management techniques that take advantage of IP-based technologies to achieve global roaming among various access technologies. In order to address the issue of heterogeneity of the networks, IEEE 802.21 working group proposed Media Independent Handover (MIH). The scope of the IEEE 802.21 MIH standard is to develop a specification that provides link layer intelligence and other related network information to upper layers to optimize handovers between heterogeneous media. The IEEE 802.21 group defines the media independent handover function that will help mobile devices to roam across heterogeneous networks and stationary devices to switch over to any of the available heterogeneous networks around it.

Cutting Performance and Tool Failure in Intermittent Turning Processes of an Al2O3-Based Micro-Nano-Composite Ceramic Tool

2012 ◽  
Vol 723 ◽  
pp. 56-61
Author(s):  
Yong Hui Zhou ◽  
Jun Zhao ◽  
Xiao Bin Cui
Keyword(s):  
Failure Modes ◽  
Composite Ceramic ◽  
Cutting Performance ◽  
Nano Particles ◽  
Ceramic Tool ◽  
Nano Composite ◽  
Micro Particles ◽  
Intermittent Turning ◽  
Shock Resistance ◽  
1045 Steel

An Al2O3-based micro-nano-composite ceramic cutting tool material reinforced with (W, Ti)C micro-particles and Al2O3 micro-nano-particles was fabricated by using hot-pressing technique, the composite was denoted as AWT. The cutting performance, failure modes and mechanisms of the AWT micro-nano-composite ceramic tool were investigated via intermittent turning of hardened AISI 1045 steel (44~48 HRC) in comparison with those of an Al2O3/(W, Ti)C micro-composite ceramic tool SG-4 and a cemented carbide tool YS8. Worn and fractured surfaces of the cutting tools were characterized by scanning electron microscopy (SEM). The results of intermittent turning revealed that shock resistance of the AWT ceramic tool was higher than that of the SG-4 and YS8 tools at all the tested cutting speeds. The excellent shock resistance of the AWT composite ceramic tool was attributed to its synergistic strengthening/toughening mechanisms induced by the (W, Ti)C micro-particles and Al2O3 nano-particles.

Polysaccharide nano crystal reinforced nanocomposites

2008 ◽  
Vol 86 (6) ◽  
pp. 484-494 ◽  
Author(s):  
Alain Dufresne
Keyword(s):  
Composite Materials ◽  
Physical Properties ◽  
High Performance ◽  
Volume Fraction ◽  
Thermal Stabilization ◽  
Nano Particles ◽  
Strong Interactions ◽  
Nano Composite ◽  
Practical Applications ◽  
Nano Crystal

There are numerous examples of animals or plants that synthesize extracellular high-performance skeletal biocomposites consisting of a matrix reinforced by nano sized crystalline domains. Cellulose and chitin are classical examples of these reinforcing elements, which occur as whisker-like microfibrils that are biosynthesized and deposited in a continuous fashion. In many cases, this mode of biogenesis leads to crystalline microfibrils that are almost defect-free, and whose axial physical properties therefore approach those of perfect crystals. During the last decade we have attempted to mimic biocomposites by blending cellulose or chitin whiskers from different sources with polymer matrices. Aqueous suspensions of such nano crystals can be prepared by acid hydrolysis of the substrate. The object of this treatment is to dissolve away regions of low lateral order so that the water-insoluble, highly crystalline residue may be converted into a stable suspensoid by subsequent vigorous mechanical shearing action. The resulting nano crystals occur as rod-like particles or whiskers, whose dimensions depend on the nature of the substrate. They are typically a few hundred nm long and between 5 and 20 nm in diameter. Starch can also be used as a source for the production of nano crystals. The constitutive nano crystals appear as platelet-like nano particles with a length ranging between 20 and 40 nm, a width ranging between 15 and 30 nm, and a thickness ranging between 5 and 7 nm. Since the first announcement of using cellulose whiskers as a reinforcing phase, they have been used extensively as model fillers in several kinds of polymeric matrices, including synthetic and natural ones. Casting mixtures of polysaccharide nano crystals and lattices led to the production of nano composite materials with drastically enhanced mechanical properties, especially at T > Tg of the matrix, by virtue of the formation of a whiskers network, even when the whisker volume fraction was only a few percent. The formation of this rigid network, resulting from strong interactions between whiskers, was assumed to be governed by a percolation mechanism. This hydrogen-bonded network induced a thermal stabilization of the composite up to 500 K, the temperature at which polysaccharides start to decompose. Any factors that perturb the formation of this percolating network directly affect the reinforcing effect of polysaccharide nano crystals. In addition to some practical applications, the study of these nano composite materials can help researchers understand such physical properties as the geometric and mechanical percolation effect.Key words: nano composites, polysaccharide, polymer, cellulose, nano crystal.

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