Analysis of the Various Effects of Coating W Tips with Dielectric Epoxylite 478 Resin or UPR-4 Resin Coatings under Similar Operational Conditions

2020 ◽  
Vol 13 (3) ◽  
pp. 191-199
Keyword(s):  
Epoxy Resins ◽  
Dielectric Material ◽  
Electrochemical Etching ◽  
Dielectric Thin Films ◽  
Operational Conditions ◽  
Critical Comparison ◽  
Composite Systems ◽  
Current Voltage ◽  
Before And After ◽  
New Type

Abstract: The objective of this work is to study the differences that occur in behavior and properties of the emitted electron beam from tungsten (W) tips before and after coating these tips with a thin layer of a good proven dielectric material. Core metallic tips have been prepared from a polycrystalline (99.995% purity) tungsten (W) wire. Analysis has been carried out for clean W emitters before and after coating these tips with two differences types of epoxy resins; namely: (Epoxylite 478 and UPR-4). For critical comparison and analysis, several tungsten tips with various apex- radii (very sharp) have been prepared with the use of electrochemical etching techniques. The tips have been coated by dielectric thin films of various thicknesses. Their characteristics have been recorded before and after the process of coating. These measurements have included the current-voltage (I-V) characteristics, Fowler-Nordheim (F-N) plots, visible light microscope (VLM) image and scanning electron microscope (SEM) micrographs to measure the influence of the Epoxylite resin coating’s thickness on the tips after coating. Special distributions have been recorded from the phosphorescent screen of a field electron emission microscope as well. Comparing the two sets of composite systems tested under similar conditions has provided several advantages. Recording highly interesting phenomena has produced a wide opportunity to develop a new type of emitter that includes the most beneficial features of both types. Keywords: Cold field emission, Epoxylite 478, Epoxylite UPR-4.

Composite Metallic Nano Emitters Coated with a Layer of Insulator Covered by Au Layer

2020 ◽  
Vol 13 (3) ◽  
pp. 253-262
Keyword(s):  
Thin Layer ◽  
Dielectric Material ◽  
Electrochemical Etching ◽  
Emission Current Density ◽  
Composite Cathode ◽  
Emission Current ◽  
Dielectric Thin Films ◽  
Current Voltage ◽  
Before And After ◽  
New Type

Abstract: In this work, the differences in the behavior and properties of the emitted electron beam from tungsten (W) tips were studied before and after coating these tips with a thin layer of dielectric material followed by a thin layer of gold, to improve the emission current density, stability and emission current pattern concentration. The core of the composite cathode is made of high-purity tungsten (W). Measurements have been made with clean W emitters before and after coating these tips with two types of epoxy resins (epoxy 478 resins or epoxy UPR- 4 resins) followed by a thin layer of gold. For critical comparison, several tungsten tips with various apex-radii have been prepared using electrochemical etching techniques. The emitters have been coated by dielectric thin films of various thicknesses and the layer of Au used for coating the Epoxy layer has the same thicknesses. Their behavior has been recorded before and after the process of coating. These measurements include the current-voltage (I-V) characteristics and Fowler-Nordheim (F-N) plots. Imaging has also been done using a visible light microscope (VLM), along with a scanning electron microscope (SEM) to help in characterizing the epoxy layer thickness on the tip surface after coating. Besides, the emission patterns have been recorded from the phosphorescent screen of a field electron emission microscope (FEM). Having two types of composite systems tested under similar conditions provided several advantages. These measurements helped in producing a new type of emitters that have more suitable features with each of the two resins. Keywords: Cold field emission, Nano emitter, Dielectric coating, Au layer.

Deterioration of Local Mechanical Properties of HVOF-Sprayed Stellite 6 after Exposure to High-Temperature Corrosion

2015 ◽  
Vol 662 ◽  
pp. 115-118 ◽  
Author(s):  
Zdeněk Česánek ◽  
Jan Schubert ◽  
Šárka Houdková ◽  
Olga Bláhová ◽  
Michaela Prantnerová
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
High Temperature Corrosion ◽  
Corrosion Testing ◽  
Time Interval ◽  
Coating Properties ◽  
Operational Conditions ◽  
Stellite 6 ◽  
Coating Surface ◽  
Before And After

Coating properties determine its behavior in operation. The simulation of future operational conditions is therefore the best quality test. The evaluation during operation is usually not possible to perform, and the coatings are therefore frequently characterized by their physical or mechanical properties. This text deals with the high temperature corrosion of HVOF sprayed Stellite 6 coating and with changes of its local mechanical properties before and after the corrosion testing. High temperature corrosion is defined as a corrosion in the presence of molten salts. In this case, the mixture of salts in composition of 59% Na2(SO)4 with 34.5% KCl and 6.5% NaCl was used. Two exposure temperatures 525 °C and 575 °C were selected and the tests for both temperatures were performed in the time interval of 168h in the autoclave. The coating with salt mixture layer was analyzed using scanning electron microscopy and nanoindentation. The high temperature resistance of Stellite 6 coating was evaluated according to the changes in the coating surface and by the occurrence of individual phases formed on the coating surface during the test. Generally, it can be said that the Stellite 6 alloys deposited by HVOF technology show selective oxidation under the salt film. This fact was also proved in this study. Furthermore, the nanoindentation measurements of Stellite 6 coating were performed before and after the corrosion testing. These measurements were used to evaluate the change of local mechanical coating properties.

Anomalous Scatter of Forward Current-Voltage Characteristics of He+-Irradiated Ni/4H-SiC Schottky Diodes

2016 ◽  
Vol 858 ◽  
pp. 749-752 ◽  
Author(s):  
Anatoly M. Strel'chuk ◽  
Viktor V. Zelenin ◽  
Alexei N. Kuznetsov ◽  
Joseph Tringe ◽  
Albert V. Davydov ◽  
...  
Keyword(s):  
Series Resistance ◽  
Degradation Mechanism ◽  
Schottky Diodes ◽  
Defect Structures ◽  
Induced Current ◽  
Forward Current ◽  
Current Voltage ◽  
Before And After ◽  
Current Voltage Characteristics

A study of forward current-voltage characteristics of Ni/4H-SiC Schottky diodes (SDs) before and after irradiation with He+ ions revealed features that characterize defect structures and reveal the degradation mechanism of the diodes. These features are the presence of excess currents of certain type in the unirradiated SDs, their appearance in forward-biased originally ideal SDs, and a >10 orders of magnitude scatter of the series resistance of the SDs upon their irradiation with He+ ions. A model of localized defect-induced current paths (shunts) in the form of unintentionally produced SDs with the substrate is suggested.

Isometric Stress Analysis and Current-Voltage Characteristics of Some Nanoclay Dielectric Elastomer Compounds

2007 ◽  
Author(s):  
N. Nurminen ◽  
A. Ellman ◽  
V. Jouppila ◽  
M. Paajanen ◽  
M. Karesoja
Keyword(s):  
Material Model ◽  
Dielectric Elastomer ◽  
Adhesive Tape ◽  
Electromechanical Properties ◽  
Dependent Behavior ◽  
Current Voltage ◽  
New Type ◽  
Current Voltage Characteristics ◽  
Compound Materials ◽  
Different Levels

The electromechanical properties of elastomer material change when different levels of stretching are applied to the elastomer film. The generated stress and expansion of the EAP material depend on the electric field across the material and its relative permeability. Some of the best known commercial dielectric elastomer materials are based on acrylic elastomers, e.g. 3M VHB 4910 or 4905 adhesive tape. In this work, the VHB 4910 tape was used as a reference material for different types of acrylic nanoclay compound materials. These new type of nanoclay elastomer compounds were tested because the addition of clay into the elastomer was assumed to increase its actuating performance. Different voltage and pre-stretching levels were used in the measurements. Current-voltage characteristics and isometric stress measurements were used to study the energy efficiency, frequency dependent behavior, reactivity and isometric stress performance of the EAP materials. Based on the electromechanical characterization and material properties, a general hyperelastic material model was developed. According to the preliminary tests, the nanoclay compound seems to be a bit stiffer than VHB 4910 resulting in a greater isometric stress response.

scholarly journals Synthesis of epoxy resins derivatives of naphthalene-2,7-diol and their cross-linked products

2019 ◽  
Vol 138 (6) ◽  
pp. 4349-4358 ◽  
Author(s):  
K. Fila ◽  
M. Gargol ◽  
M. Goliszek ◽  
B. Podkościelna
Keyword(s):  
Fourier Transform ◽  
Epoxy Resins ◽  
Attenuated Total Reflectance ◽  
Cross Linking ◽  
Total Reflectance ◽  
Before And After ◽  
Ft Ir ◽  
The Cross ◽  
Derivatives Of ◽  
Epoxy Groups

Abstract The aim of this study was the synthesis of three different epoxy compounds based on naphthalene-2,7-diol (2,7-NAF.EP, 2,7-NAF.WEP, 2,7-NAF.P.EP) and then their cross-linking by triethylenetetramine (TETA). All epoxides were prepared by the reaction of naphthalene-2,7-diol with epichlorohydrin but under different conditions and with other catalysts. The structures of the obtained compounds before and after the cross-linking reactions were confirmed by the attenuated total reflectance Fourier transform infrared spectroscopy (ATR/FT-IR). The ATR/FT-IR spectra of cross-linked compounds show disappearance of the C–O–C bands (about 915 cm−1) derived from the epoxy groups. DSC and TG/DTG measurements indicated that the obtained materials possess good thermal resistance; they are stable up to about 250 °C. The hardness of the cross-linked products was determined using the Shore D method. The highest value of hardness was obtained for the 2,7-NAF.EP-POL. Additionally, the UV–Vis absorption spectra of the obtained polymers were registered and evaluated.

Effect of Hydrogen Treatment on Room -Temperature Electric-Field Induced Properties in Narrow-Gap ZnCdHgTe Thin Films

2004 ◽  
Vol 813 ◽  
Author(s):  
Galina M. Khlyap ◽  
Petro G. Sydorchuk ◽  
Jacek Polit
Keyword(s):  
Thin Films ◽  
Room Temperature ◽  
Hydrogen Treatment ◽  
Narrow Gap ◽  
Glass Substrates ◽  
Semiconductor Thin Films ◽  
Visible Wavelength Range ◽  
Current Voltage ◽  
Before And After ◽  
First Time

ABSTRACTThe effect of hydrogen treatment on room temperature electric properties of narrow-gap semiconductor thin films ZnxCdyHg1−z−yTe (0 < x < 0.50, 0.20 < y < 0.40) is investigated for the first time. ZnCdHgTe films of 2 – 5 [.proportional]m thickness were grown on glass substrates by pulsed laser deposition technique. As-grown films were thermally treated in the flow of molecular H2 at 200°C during 24 hours. Comparison between electric characteristics measured before and after hydrogenation showed sufficient changes of the film resistance and appearance of photosensitivity in the visible wavelength range. Study of current-voltage characteristics of the films revealed appearance and significant change of diode-like properties.

Effect of Thermal Annealing on La2O3 Films Grown by Plasma Enhanced Atomic Layer Deposition

2015 ◽  
Vol 1088 ◽  
pp. 107-111
Author(s):  
Jian Shuang Liu ◽  
Fang Fang Zhu ◽  
Fei Lu ◽  
Lin Zhang
Keyword(s):  
Atomic Layer Deposition ◽  
Atomic Layer ◽  
Deposition Process ◽  
Flat Band ◽  
Interface Reactions ◽  
Layer Deposition ◽  
Current Voltage ◽  
Capacitance Voltage ◽  
Before And After ◽  
Current Voltage Characteristics

A plasma enhanced atomic layer deposition process has been demonstrated for Lanthanum oxide films using La (thd)3 precursor and oxygen plasma. The chemical and electrical properties of La2O3 ultra-thin films on Si (100) substrates before and after post-annealing in N2 ambient have been investigated. X-ray photoelectron spectroscopic revealed that interface reactions take place after annealing process which lead to oxygen insufficiency, as well as the balance band offset decreases with the increase of annealing temperature. The capacitance-voltage and current-voltage characteristics show La2O3 capacitors annealed at 900 °C have negligible hysteresis, smaller interface trap density in comparison with as-deposited samples, but larger flat band voltage and higher gate-leakage current density due to the appearance of oxygen vacancy in the La2O3 films.

A Study of the Irregularities Added in Apron Drafting

1969 ◽  
Vol 39 (2) ◽  
pp. 155-165 ◽  
Author(s):  
N. Balasubramanian
Keyword(s):  
Staple Fiber ◽  
Critical Comparison ◽  
Yarn Quality ◽  
Before And After

An assessment is made of irregularities added in apron drafting through comparisons of variance-length curves of fiber end density before and after drafting. In addition, the drafted products were examined for periodicities through correlograms. The investigations were made on a carded and a combed cotton and a cut staple fiber for a range of drafts. The studies were later extended to obtain relations of thickness irregularity with draft and hank of material fed. The implications of these results are discussed. Further, the effect of apron opening and doubling on yarn quality and a critical comparison of roller and apron drafting in regard to extent of irregularities added are presented.

scholarly journals Comparative investigations of in vitro and in vivo bioactivity of titanium vs. Ti–24Nb–4Zr–8Sn alloy before and after sandblasting and acid etching

RSC Advances ◽  
2020 ◽  
Vol 10 (40) ◽  
pp. 23582-23591
Author(s):  
Xin Liu ◽  
Yumei Niu ◽  
Weili Xie ◽  
Daqing Wei ◽  
Qing Du
Keyword(s):  
Young’S Modulus ◽  
Young's Modulus ◽  
Stress Shielding ◽  
Acid Etching ◽  
Implant Material ◽  
Before And After ◽  
New Type

To avoid the failure of clinical surgery due to “stress shielding” and the loosening of an implant, a new type of alloy, Ti–24Nb–4Zr–8Sn (TNZS), with a low Young's modulus acted as a new implant material in this work.

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