A novel technique for the fabrication of 3D nanofibrous scaffolds using simultaneous positive voltage electrospinning and negative voltage electrospinning

2013 ◽  
Vol 94 ◽  
pp. 116-120 ◽  
Author(s):  
Ho-Wang Tong ◽  
Min Wang
Keyword(s):  
Negative Voltage ◽  
Novel Technique ◽  
Nanofibrous Scaffolds ◽  
Positive Voltage

Effect of Applied DC Voltage to Stainless Steel Pin and CNx Coated Disk in Pin-on-Disk Sliding Test on Tribological Properties

2005 ◽  
Author(s):  
Noritsugu Umehara ◽  
Takahiro Yamamoto ◽  
Yoshio Fuwa
Keyword(s):  
Stainless Steel ◽  
Friction Coefficient ◽  
Friction And Wear ◽  
The Other ◽  
Electric Voltage ◽  
Dc Voltage ◽  
Negative Voltage ◽  
Positive Voltage ◽  
Sliding Test ◽  
Pin On Disk

The effect of applied DC voltage on the friction and wear of CNx sliding against stainless steel pin in air was clarified. Friction coefficient decreased with the increasing negative voltage to apply to the ball and disk in air. On the other hand, positive voltage increased friction coefficient. Friction coefficient of CNx in air decreased from 0.22 to 0.05 by applying electric voltage of DC −200 V. Specific wear rate was decreased with the increasing applied positive and negative voltage. It was considered that the oxidation of CNx was controlled by electric field.

A Wettability Tunable Surface of Nafion® with Controlling the Flip-Flop Property by DC Applied Voltage

2014 ◽  
Vol 616 ◽  
pp. 77-81 ◽  
Author(s):  
X. Wei ◽  
I. Mogami ◽  
G. Kawamura ◽  
Hiroyuki Muto ◽  
Atsunori Matsuda
Keyword(s):  
Thin Film ◽  
Applied Voltage ◽  
Flip Flop ◽  
Negative Voltage ◽  
Positive Voltage

The flip-flop property is an attractive phenomenon on the surface of Nafion® thin film. The sulfonic groups which are hydrophilic can change the wettability of the surface by lift up or curling down. In this study, an applied voltage makes the control of sulfonic groups become available. It has been proved that when a positive voltage is loading to the film through a conductive droplet, the flip-flop property can be enhanced. Being the opposite, it also can be inhibited by a negative voltage.

Influence of Voltage Parameters on Formation Process of MAO Ceramic Coating on Aluminum Alloy

2011 ◽  
Vol 189-193 ◽  
pp. 931-936
Author(s):  
Feng Guo ◽  
Rong Ming Liu ◽  
Peng Fei Li
Keyword(s):  
Aluminum Alloy ◽  
Phase Composition ◽  
Surface Morphology ◽  
Formation Process ◽  
Mass Fraction ◽  
Ceramic Coating ◽  
Outer Side ◽  
Thickness Increase ◽  
Negative Voltage ◽  
Positive Voltage

In this paper, the influence of positive and negative voltages to the formation process of ceramic coating on aluminum alloy was studied. The result indicates that, increasing of positive or negative voltage is favorable to the thickness increase and uniformity of the ceramic coating, the thickness of ceramic coating is linear correlation to the positive electrical quantity which is relative to loaded voltages. The ceramic coating is composed of α-Al2O3, γ-Al2O3 and mullite phases, and the voltages, especially negative voltage can increase the mass fraction of α-Al2O3 phase in the outer side of ceramic coating. The effects of voltage parameters on surface morphology of ceramic coating, thickness of ceramic coating and phase composition of ceramic coating is evident, in which the positive voltage is a decisive factor and the negative voltage is an important assistant factor.

scholarly journals Piezoelectric Properties of Lead Zirconate Titanate Ceramics at Low and High Temperatures

2020 ◽  
Author(s):  
Mitsuhiro Okayasu ◽  
Masakazu Okawa
Keyword(s):  
Thermal Stress ◽  
Lead Zirconate Titanate ◽  
Domain Switching ◽  
Low Voltage ◽  
Lead Zirconate ◽  
Negative Voltage ◽  
Zirconate Titanate ◽  
Positive Voltage ◽  
Warming Rate ◽  
The Difference

Abstract The material properties and damage characteristics of lead zirconate titanate (PZT) ceramics were investigated at various temperatures (–190 °C to 180 °C). A positive voltage was obtained when the sample was cooled from 20 °C to –190 °C, while a negative voltage was obtained when the sample was warmed from –190 °C to 180 °C. The difference between the positive and negative values depended on the thermal stress. Compressive stress generated a more positive voltage in the cooling process, while tensile stress led to a more negative voltage in the warming process). The voltage values also depended on the cooling (or warming) rate of the sample, e.g., the greater the cooling (or warming) rate, the greater the voltage. When cyclic loading was conducted mechanically at –190 °C, the voltage reduced, but it was recovered after warming to 20 °C. Damage of the PZT ceramic (90° domain switching) was detected when the sample was cooled to –190 °C. This was due to the high thermal stress, resulting in a low voltage.

Test Research on the Suppressing Radio Interference of DC Transmission Lines by Ferrite Cores

2013 ◽  
Vol 805-806 ◽  
pp. 987-990
Author(s):  
Hong Zhang ◽  
Zhi Bin Zhao ◽  
Yang Liu ◽  
Lei Liu ◽  
Fang Wang
Keyword(s):  
Corona Discharge ◽  
Transmission Lines ◽  
Power Grids ◽  
Radio Interference ◽  
Test Results ◽  
Inhibitory Effects ◽  
Research Results ◽  
Negative Voltage ◽  
Positive Voltage ◽  
Better Than

Radio interference (RI) of DC transmission lines due to the corona discharge has become a restraining factor of power grids design and operation, so the suppression of RI is very important. In this paper, a new idea for suppressing RI by mounting ferrite cores on the conductor is proposed. By measuring and comparing RI values of the test stranded wire with and without ferrite cores, test results show this approach to suppress RI is effective. Further research results also show inhibitory effects at negative voltage are better than positive voltage and the material of ferrite cores affects the inhibition effects.

TUNABLE PROPERTIES OF LSCO BUFFERED PMN-PT THIN FILM CAPACITOR

2011 ◽  
Vol 04 (03) ◽  
pp. 241-244
Author(s):  
Y. HE ◽  
X. M. LI ◽  
X. D. GAO ◽  
R. K. ZHENG ◽  
X. LENG ◽  
...  
Keyword(s):  
Thin Film ◽  
Strong Influence ◽  
Asymmetric Distribution ◽  
Negative Voltage ◽  
Voltage Bias ◽  
Tunable Properties ◽  
Positive Voltage ◽  
Capacitance Voltage ◽  
Charged Defects ◽  
Ferroelectric Capacitors

The tunable properties of Pt/PMN-PT/LSCO/Ir capacitor have been studied under different applied voltages and frequencies. The PMN-PT thin film exhibited good dielectric tunability. A tunability of 70.3% at 12 V and 100 kHz is obtained for the film under negative voltage bias. For the positive voltage bias, the tunability is 68.7% which is smaller than the value under negative voltage bias. The asymmetric distribution of charged defects is suggested as possible causes of the asymmetric capacitance–voltage (C–V) behaviors of ferroelectric capacitors. On the other hand, the frequency dependency of the capacitance's tunability indicated that the interface has strong influence on the frequency stable of tunability.

DESIGN, FABRICATION AND USE OF A NOVEL PENNING DISCHARGE SOURCE TO SYNTHESIZE CARBON AND CARBON NITRIDE FILMS

2008 ◽  
Vol 22 (24) ◽  
pp. 2373-2382 ◽  
Author(s):  
B. Q. YANG ◽  
P. X. FENG
Keyword(s):  
Carbon Nitride ◽  
Plasma Source ◽  
Plasma Discharge ◽  
Discharge Voltage ◽  
Sputtering Deposition ◽  
Raman Scattering Spectroscopy ◽  
Negative Voltage ◽  
Gas Plasma ◽  
Positive Voltage ◽  
Gas Pressures

The Penning discharge (PD) sputtering deposition technique was developed and used to synthesize carbon and carbon nitride films. This novel PD source, which was very different from traditional penning electrodes, was based on configurations of two hollow interpenetrating cylindrical electrodes. The discharge voltage, current, and spectral emissions of the plasma source had been characterized. In the pulsed gas beam plasma discharge, the intensity of spectral emission from discharge plasma supplied by the positive voltage was higher than that supported by using the negative voltage. In the static gas plasma discharge, the negative voltage discharge yielded a stable and concentrated plasma source, and the discharge current linearly increased with an increase of the discharge voltage. The phase change of the discharge following the variation of gas pressures was observed. After characterization, the PD source was used in the sputtering deposition of both carbon and carbon nitride films. Microscope images of samples indicated that nanostructured films had been obtained. All samples were characterized by using Raman scattering spectroscopy.

NEGATIVE VOLTAGE ELECTROSPINNING AND POSITIVE VOLTAGE ELECTROSPINNING OF TISSUE ENGINEERING SCAFFOLDS: A COMPARATIVE STUDY AND CHARGE RETENTION ON SCAFFOLDS

Nano LIFE ◽  
2012 ◽  
Vol 02 (01) ◽  
pp. 1250004 ◽  
Author(s):  
HO-WANG TONG ◽  
MIN WANG
Keyword(s):  
Tissue Engineering ◽  
Solution Concentration ◽  
Polybutylene Terephthalate ◽  
Tissue Engineering Scaffolds ◽  
Negative Voltage ◽  
Fibrous Scaffolds ◽  
Positive Voltage ◽  
Initial Charge ◽  
Fibrous Membranes ◽  
Working Distance

Positive voltage electrospinning (PVES) has been mainly used for forming fibrous polymer scaffolds for different applications including tissue engineering. There is virtually no report on negative voltage electrospinning (NVES) of tissue engineering scaffolds. In this study, NVES of four biopolymers, namely, gelatin, chitosan, poly(lactic-co-glycolic acid) (PLGA), and polybutylene terephthalate (PBT), to form nanofibrous membranes was systematically investigated. For comparisons, PVES of these polymers was also conducted. It was found that chitosan fibers could not be produced using NVES. Under NVES or PVES, the fiber diameter of electrospun scaffolds generally increased with increasing needle inner diameter and polymer solution concentration but decreased with increasing working distance for all four polymers. Neither NVES nor PVES altered the chemical structure of gelatin, PLGA, and PBT. PVES and NVES resulted in fibrous membranes bearing positive charges and negative charges, respectively. PLGA and PBT fibrous membranes retained around 30% and 50%, respectively, of the initial charge one week after electrospinning. Charges on gelatin and chitosan fibrous membranes were almost completely dissipated within 60 min of electrospinning. For all four polymers, under either PVES or NVES, the retained charges on fibrous membranes increased with increasing applied electrospinning voltage. This study explored a new approach for forming fibrous scaffolds by using NVES and has opened a new area for developing negatively charged fibrous scaffolds for tissue engineering applications.

Controlled Release of Growth Factors from Tissue Engineering Scaffolds Made by Positive and Negative Voltage Electrospinning

2015 ◽  
Vol 815 ◽  
pp. 385-389 ◽  
Author(s):  
Qi Long Zhao ◽  
Yu Zhou ◽  
Min Wang
Keyword(s):  
Tissue Engineering ◽  
Growth Factor ◽  
Applied Voltage ◽  
Burst Release ◽  
Release Behavior ◽  
Tissue Engineering Scaffolds ◽  
Absolute Value ◽  
Negative Voltage ◽  
Positive Voltage

Emulsion electrospun nanofibrous tissue engineering scaffolds made by conventional positive voltage electrospinning (PVES) have various advantages for growth factor (GF) delivery. But problems such as high initial burst release still exist. Negative voltage electrospinning (NVES) may produce nanofiberous scaffolds that can modulate the release behavior of GFs which bear positive electrical charges. By using either PVES or NVES for emulsion electrospinng, the present study investigated the influence of NVES and applied voltage on the release behavior of a typical GF bearing the positive charge, basic fibroblast growth factor (bFGF), encapsulated in the nanofibers of poly (lactic-co-glycolic acid) (PLGA) scaffolds. Emulsions were firstly prepared by mixing a bFGF-containing aqueous solution and a PLGA solution. They were then subjected to electrospinning under either a positive voltage (10, 15, or 20 kV) or a negative voltage (-10, -15, or-20 kV). The morphology and structure of fibers and scaffolds were subsequently characterized. All scaffolds were nanofibrous and the nanofibers exhibited core-shell structures, with the bFGF-containing water phase forming the fiber core. Scaffolds exhibited the same type of electrical charges as the type of the applied voltage for electrospinning, i.e., scaffold made by PVES showed positive charges while scaffold fabricated by NVES possessed negative charges. The intensity of positive or negative charges borne by scaffolds and their retention time on scaffolds increased with an increase in the absolute value of the applied voltage (⏐V⏐). In vitro bFGF release experiments were conducted for scaffolds made by either NVES or PVES. Results showed that the bFGF release behavior was modulated by NVES.

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