scholarly journals Combining good dispersion with tailored charge trapping in nanodielectrics by hybrid functionalization of silica

e-Polymers ◽  
2021 ◽  
Vol 21 (1) ◽  
pp. 897-909
Author(s):  
Xiaozhen He ◽  
Ilkka Rytöluoto ◽  
Rafal Anyszka ◽  
Amirhossein Mahtabani ◽  
Minna Niittymäki ◽  
...  
Keyword(s):  
Surface Layer ◽  
Trap Depth ◽  
Charge Trapping ◽  
Polymeric Matrix ◽  
Electron Microscopic ◽  
Depolarization Current ◽  
Good Dispersion ◽  
Dielectric Performance ◽  
Ethylene Copolymer ◽  
The One

Abstract Fumed silica-filled polypropylene (PP)-based nanodielectrics were studied in this work. To not only improve the dispersion of the silica but also introduce deep charge traps into the polymeric matrix, five types of modified silicas were manufactured with different surface modifications. The modified silica surfaces comprise an inner and a surface layer. The inner layer contains a polar urethane group for tailoring the charge trap properties of the PP/propylene–ethylene copolymer nanocomposites, whereas the surface layer consists of hydrocarbons (ethyl-, tert-butyl-, cyclopentyl-, phenyl-, or naphthalenyl moieties) in order to gain a good dispersion of the silica in the unpolar polymer blend. Scanning electron microscopic pictures proved that these tailored silicas show a much better dispersion than the unmodified one. Thermally stimulated depolarization current measurements revealed the ability of the silica to introduce deep charge traps with low trap density. The trap depth distribution depends on the type of the unpolar surface layer consisting of the different hydrocarbons. Among these five differently modified silicas, the introduction of the one with a surface layer consisting of tert-butyl moieties resulted in the lowest charge injection and the lowest charge current in the nanocomposite, proving good dielectric performance. Additionally, this silica exhibits good dispersion in the polymeric matrix, indicating a promising performance for nanodielectric application.

scholarly journals Surface Modification of Fumed Silica by Dry Silanization for PP/POE-based Dielectric Nanocomposites

2019 ◽  
pp. 32-36
Author(s):  
Xiaozhen He ◽  
Ilkka Rytöluoto ◽  
Amirhossein Mahtabani ◽  
Eetta Saarimäki ◽  
Kari Lahti ◽  
...  
Keyword(s):  
Surface Modification ◽  
Dielectric Properties ◽  
High Voltage ◽  
Silica Surface ◽  
Trap Depth ◽  
Charge Trapping ◽  
Depolarization Current ◽  
Dry Process ◽  
Green Approach ◽  
Silica Surface Modification

A systematic study of the influence of surface modification of nanosilica with coupling agents having different polarities on the dielectric properties of a PP/POE/silica blend was performed. The main goal of this investigation was to tailor the chemical composition of the silica surface, in order to modify the charge trapping properties of the nanocomposites. For the modification of the silica surface, a “green” approach was utilized: a dry silanization method, which is performed without the need of a solvent. The results of the thermogravimetric analysis (TGA) indicate that the dry process is an effective method to perform silica surface modification using alkoxysilanes.The charge trapping properties were studied by Thermally Stimulated Depolarization Current (TSDC) measurements. The obtained TSDC results show significant differences in charge trapping properties of PP/POE composites filled with differently modified silicas. Polar functional groups attached to the surface of the silica appear to have a strong effect on the charge trapping properties: The trap depth distribution becomes deeper and the trap density decreases to significantly lower levels.All results show that incorporation of surface modified nanosilica into a PP/POE matrix is a promising approach to tailor its dielectric properties. Further development of these composites may lead to benefits for application in high-voltage cable and capacitor applications.Keywords: silica surface modification, dry silanization, charge trapping, PP, POE, TSDC, high voltage cable.

The effect of boundaries on wave propagation in a liquid-filled porous solid: VI. Love waves in a double surface layer

1964 ◽  
Vol 54 (1) ◽  
pp. 417-423
Author(s):  
H. Deresiewicz
Keyword(s):  
Wave Propagation ◽  
Surface Layer ◽  
Dispersion Relation ◽  
Energy Loss ◽  
Classical Solution ◽  
Specific Energy ◽  
Classical Case ◽  
Specific Energy Loss ◽  
Double Surface ◽  
The One

abstract The classical solution of Stoneley and Tillotson is generalized by considering the outer one of the pair of layers to be porous. Although the dispersion relation turns out, for practical purposes, to be identical with the one governing the classical case, the motion in the present instance is shown to be dissipative and the expression is exhibited for the specific energy loss.

Silver nanoparticles modified by water-soluble leaning tower[6]arenes for sensing and catalysis

2021 ◽  
Author(s):  
Yi-Nan Zhang ◽  
Zheng Li ◽  
Suriguga Meng ◽  
Alideertu Dong ◽  
Ying-Wei Yang
Keyword(s):  
Silver Nanoparticles ◽  
Hybrid Material ◽  
Water Soluble ◽  
One Pot ◽  
Sodium Salts ◽  
Good Dispersion ◽  
One Pot Synthesis ◽  
The One ◽  
Excellent Stability

Carboxylated leaning tower[6]arene sodium salts are used as an efficient stabiliser for the one-pot synthesis of silver nanoparticles. The resulting hybrid material with good dispersion, excellent stability and narrow size...

scholarly journals Biotinylphallotoxins: preparation and use as actin probes.

1989 ◽  
Vol 37 (7) ◽  
pp. 1035-1045 ◽  
Author(s):  
H Faulstich ◽  
S Zobeley ◽  
U Bentrup ◽  
B M Jockusch
Keyword(s):  
Actin Filaments ◽  
Ultrastructural Level ◽  
Microscopic Level ◽  
Electron Microscopic Level ◽  
Electron Microscopic ◽  
Permeabilized Cells ◽  
High Affinity ◽  
Double Label ◽  
The One

We describe the synthesis of four phalloidin derivatives conjugated with biotin. An aminomethyldithiolane derivative of ketophalloidin was used as a reactive starter compound, and biotin residues were coupled to this molecule either directly, separated by spacer chains comprised of one or two glycyl residues, or of a 12-atom long chain constructed from succinic acid and hexamethylendiamine. Although all products still displayed a high affinity for F-actin, as seen in competition experiments with [3H]-demethylphalloidin, only the one with the longest spacer (BHPP) showed specific and high-affinity decoration of actin filaments in permeabilized cells, in conjunction with FITC-coupled avidin and fluorescence microscopy. Combined with gold-streptavidin, BHPP decorated the actin filament system at the light and electron microscopic level faithfully and with satisfactory density. Actin filaments polymerized in vitro from purified protein were not as densely labeled as had been expected. However, in all these experiments the new phalloidin probe, when combined with avidin or streptavidin, yielded clear and highly specific labeling of F-actin. Therefore, this system is useful to identify and localize actin unambiguously in microfilaments, independent of actin antibodies, and should facilitate double-label experiments on cytoskeletal components at the ultrastructural level.

The occurrence of submicrovillar endotube (modified terminal web) and associated cytoskeletal structures in the intestinal epithelia of nematodes

1984 ◽  
Vol 306 (1125) ◽  
pp. 1-18 ◽  
Keyword(s):  
Brush Border ◽  
Haemonchus Contortus ◽  
Luminal Surface ◽  
Blunt Dissection ◽  
Electron Microscopic ◽  
Free Living ◽  
Intestinal Epithelia ◽  
Terminal Web ◽  
The One ◽  
Living Group

The intestines of 22 genera of nematodes from five different orders were examined for the presence of an endotube, the submicrovillar entity previously described for Haemonchus contortus , a member of the order Strongylida. The endotube can be obtained by blunt dissection as a complex with the microvilli essentially free of the rest of the cytoplasm. Representatives of all three suborders and eight families of the order Strongylida possessed an endotube but of the representatives of the four other parasitic orders and the one free-living group examined only one genus, Strongyloides (Rhabditida) possessed this structure. The thickness of the endotube ranged from about 80 nm in Metastrongylus up to 6 μm in Strongylus . In all samples the filamentous cores of the microvilli, whether formed into an axial bundle (as usual) or dispersed in a net (as in Dictyocaulus ), which extended 0.1-0.5 μm below the base of the microvilli terminated in the luminal surface of the endotube. The basal side of the endotube was usually associated with a layer of microfibrils. The depth and distribution of the microfibrillar layer determined the extent to which the endotube-brush-border complexes could be dissected free from other cytoplasmic components. There was electron microscopic evidence for an endotube-like entity not associated with the microvilli in the intestine of Syphacia (Ascarida). A survey of published electron micrographs of nematode intestines indicated that the true submicrovillar endotube occurred only in members of the order Strongylida and the genus Strongyloides (Rhabditida) in which the structure here described as an endotube has previously been described as terminal web.

scholarly journals A NEW FREEZING-ULTRAMICROTOME

1961 ◽  
Vol 10 (1) ◽  
pp. 1-13 ◽  
Author(s):  
H. Moor ◽  
K. Mühlethaler ◽  
H. Waldner ◽  
A. Frey-Wyssling
Keyword(s):  
The Other ◽  
Wide Field ◽  
Cell Organelles ◽  
Electron Microscopic ◽  
Preliminary Results ◽  
Biological Objects ◽  
Shadow Casting ◽  
Internal Structures ◽  
The One ◽  
Microscopic Investigations

The difficulties in sectioning frozen biological objects for electron microscopic investigations are overcome by Steere's freezing-etching method. In order to test this method and to open up a wide field of application, the new freezing-ultramicrotome has been designed. The apparatus consists of the combination of an ultramicrotome with freezing-drying and shadow-casting installations in the same vacuum container. The preliminary results show, on the one hand, the practicability of all preparational steps and, on the other, that it is possible to resolve internal structures of cell organelles and even macromolecular patterns.

Influence of Crystallite Size on Consolidation of Carbon Nanotube Reinforced AA 4032 Composite Powders by Equal Channel Angular Pressing

2011 ◽  
Vol 471-472 ◽  
pp. 127-132
Author(s):  
M.S. Senthil Saravanan ◽  
K. Sivaprasad ◽  
S.P. Kumaresh Babu
Keyword(s):  
Crystallite Size ◽  
Equal Channel Angular Pressing ◽  
Ultrafine Grain ◽  
Electron Microscopic ◽  
Composite Powders ◽  
Powder Consolidation ◽  
Angular Pressing ◽  
Grain Structures ◽  
Transmission Electron ◽  
The One

Equal channel angular pressing (ECAP) is the one of the promising methods of severe plastic deformation to obtain bulk ultrafine grain structures. However, ECAP can also be used for powder consolidation. In the present study, fully dense bulk AA 4032 alloy was consolidated from nanocrystalline and microcrystalline powders. These materials were processed by ECAP until four passes at ambient temperature. It is observed that hardness and densification increased significantly with increase in number of ECAP passes. Transmission electron microscopic and scanning electron microscopic examinations evidenced that crystallite size of the nanopowders are unaltered, however a significant crystallite size reduction from around 50 µm down to submicron size is observed. Moreover, higher densification is achieved in microcrystalline powders than nano powders, whereas higher hardness in the case of nanopowders compared to microcrystalline powders.

Ultra-low dielectric closed porous materials via incorporating surface-functionalized hollow silica microspheres: preparation, interface property and low dielectric performance

RSC Advances ◽  
2016 ◽  
Vol 6 (3) ◽  
pp. 1870-1876 ◽  
Author(s):  
Xiaonan Wei ◽  
Cuijiao Zhao ◽  
Jiajun Ma ◽  
Yawen Huang ◽  
Ke Cao ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Porous Materials ◽  
Polymeric Matrix ◽  
Silica Microspheres ◽  
Hollow Silica ◽  
Interface Property ◽  
Low Dielectric ◽  
Dielectric Performance

One effective route to reduce the dielectric constant is to directly incorporate hollow silica (HoSiO2) microspheres into a polymeric matrix.

scholarly journals The Present State of Surface Conditioning in Cutting and Grinding

2021 ◽  
Vol 5 (3) ◽  
pp. 92
Author(s):  
Benedict Stampfer ◽  
Germán González ◽  
Michael Gerstenmeyer ◽  
Volker Schulze
Keyword(s):  
Surface Layer ◽  
Review Article ◽  
Manufacturing Processes ◽  
Lightweight Construction ◽  
Surface Conditioning ◽  
The One ◽  
Robust Process ◽  
Abrasive Process ◽  
Deutsche Forschungsgemeinschaft ◽  
Priority Program

All manufacturing processes have an impact on the surface layer state of a component, which in turn significantly determines the properties of parts in service. Although these effects should certainly be exploited, knowledge on the conditioning of the surfaces during the final cutting and abrasive process of metal components is still only extremely limited today. The key challenges in regard comprise the process-oriented acquisition of suitable measurement signals and their use in robust process control with regard to the surface layer conditions. By mastering these challenges, the present demands for sustainability in production on the one hand and the material requirements in terms of lightweight construction strength on the other hand can be successfully met. In this review article completely new surface conditioning approaches are presented, which originate from the Priority Program 2086 of the Deutsche Forschungsgemeinschaft (DFG).

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