Moisture Intrusion in Sio2/Epoxy Interfaces

1989 ◽  
Vol 154 ◽  
Author(s):  
Ken M. Takahashi
Keyword(s):  
Water Adsorption ◽  
Diglycidyl Ether ◽  
Interfacial Bond ◽  
Conduction Path ◽  
Low Frequencies ◽  
Impedance Measurements ◽  
Diethylene Triamine ◽  
Diffusion Controlled ◽  
Property Changes

In-situ interfacial impedance measurements were used to study the effects of moisture at 80 ° C on the interface between oxidized silicon and a diglycidyl ether of bisphenol A (DGEBA) epoxy cured with diethylene triamine (DETA). Using two electrode configurations, admittances attributable to bulk and interfacial conduction processes were distinguished. Bulk impedance measurements followed Randles behavior; conduction in the bulk epoxy was ionic, and was diffusion controlled at low frequencies. Equivalent circuit models were used to demonstrate that an apparent interfacial conduction process was caused by distributed current leakage into the silicon subphase, not a true interfacial conduction path that would indicate water adsorption or interfacial aggregation. However, transitions in diffusivity and bulk epoxy permittivity behavior above a 70–80% relative humidity threshold were observed. Effective epoxy permittivity (εc) jumped to values indicative of a water cluster induced Maxwell-Wagner relaxation. The humidity threshold corresponds to a level that has been associated with adhesion loss in epoxies. It appears that epoxy adhesion losses result from bulk epoxy property changes at high humidity rather than interfacial bond displacement or delamination.

Moisture Intrusion in Sio2/Epoxy Interfaces

1989 ◽  
Vol 153 ◽  
Author(s):  
Ken M. Takahashi
Keyword(s):  
Water Adsorption ◽  
Diglycidyl Ether ◽  
Interfacial Bond ◽  
Conduction Path ◽  
Low Frequencies ◽  
Impedance Measurements ◽  
Diethylene Triamine ◽  
Diffusion Controlled ◽  
Property Changes

SummaryIn-situ interfacial impedance measurements were used to study the effects of moisture at 80 °C on the interface between oxidized silicon and a diglycidyl ether of bisphenol A (DGEBA) epoxy cured with diethylene triamine (DETA). Using two electrode configurations, admittances attributable to bulk and interfacial conduction processes were distinguished. Bulk impedance measurements followed Randles behavior; conduction in the bulk epoxy was ionic, and was diffusion controlled at low frequencies. Equivalent circuit models were used to demonstrate that an apparent interfacial conduction process was caused by distributed current leakage into the silicon subphase, not a true interfacial conduction path that would indicate water adsorption or interfacial aggregation. However, transitions in diffusivity and bulk epoxy permittivity behavior above a 70-80% relative humidity threshold were observed. Effective epoxy permittivity (∈c) jumped to values indicative of a water cluster induced Maxwell-Wagner relaxation. The humidity threshold corresponds to a level that has been associated with adhesion loss in epoxies. It appears that epoxy adhesion losses result from bulk epoxy property changes at high humidity rather than interfacial bond displacement or delamination.

Low Wave Number Radar Image Energy Influence on Determining Current

2012 ◽  
Vol 433-440 ◽  
pp. 6054-6059
Author(s):  
Gan Nan Yuan ◽  
Rui Cai Jia ◽  
Yun Tao Dai ◽  
Ying Li
Keyword(s):  
Wave Spectrum ◽  
Surface Current ◽  
Sea Surface ◽  
Radar Image ◽  
Wave Number ◽  
Sea State ◽  
Low Frequencies ◽  
In Situ Data ◽  
Main Effects

In the radar imaging mechanism different phenomena are present, as a result the radar image is not a direct representation of the sea state. In analyzing radar image spectra, it can be realized that all of these phenomena produce distortions in the wave spectrum. The main effects are more energy for very low frequencies. This work investigates the structure of the sea clutter spectrum, and analysis the low wave number energy influence on determining sea surface current. Then the radar measure current is validated by experiments. By comparing with the in situ data, we know that the radar results reversed by image spectrum without low wave number spectrum have high precision. The low wave number energy influent determining current seriously.

Cyclic Voltammetry, Impedance Measurements and In-Situ EPR Studies of Conjugated Polymers

1991 ◽  
Vol 21 ◽  
pp. 139-162 ◽  
Author(s):  
L. Wuckel ◽  
M. Schwarzenberg ◽  
A. Bartl ◽  
H.G. Döge
Keyword(s):  
Cyclic Voltammetry ◽  
Conjugated Polymers ◽  
Impedance Measurements

In-Situ, Time Resolved, Kinetics of Reactions in Co-Ge thin Films

1991 ◽  
Vol 237 ◽  
Author(s):  
R. M. Walser ◽  
Byung-Hak Lee ◽  
Alaka Valanju ◽  
Winston Win ◽  
M. F. Becker
Keyword(s):  
Depth Profiling ◽  
Laser Interferometry ◽  
Semiconductor Interface ◽  
Time Resolved ◽  
Interface Reactions ◽  
Valuable Adjunct ◽  
Diffusion Controlled ◽  
Sputter Deposited ◽  
Time Required

ABSTRACTWe report the first kinetic study of metal-semiconductor interface reactions using in-situ, time resolved, laser interferometry. Diffusion couples with Co/Ge thicknesses of 1500 Å/1500 Å were sputter deposited on silicon wafers, and vacuum-annealed at temperatures between 300°C-400°C. Under these conditions polycrystalline CoGe was expected to form [1]. Real time laser (HeNe 6328 Å) interferograms for each anneal were recorded in-situ. These data were supplemented by information from AES and X-ray.For temperatures below 400°C the diffusion controlled formation of CoGe was observed. The composition was confirmed by Auger depth profiling that showed uniform Co and Ge concentrations when the reaction went to completion. The well defined interferences fringes were formed by the dissolution of amorphous Ge. The activation energy = 1.6 eV for the formation of CoGe were determined with precision from the temperature dependence of the time required to anneal the fixed λ/4 distance between adjacent minima and maxima of the interferogram. We discuss the evidence for formation of an intermediate Co-rich compound following the initial diffusion of Co into Ge. The results of these experiments indicate that optical interferometry will be a valuable adjunct to other techniques used to study metal-semiconductor interface reactions.

scholarly journals Metallic conduction through van der Waals interfaces in ultrathin $$\hbox{Bi}_2\hbox{Te}_3$$ films

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Shinichiro Hatta ◽  
Ko Obayashi ◽  
Hiroshi Okuyama ◽  
Tetsuya Aruga
Keyword(s):  
Photoelectron Spectroscopy ◽  
Van Der Waals ◽  
Vertical Direction ◽  
Conductivity Measurement ◽  
Spatial Separation ◽  
Mean Free Path ◽  
Conduction Path ◽  
Conductivity Increase ◽  
The Impact

AbstractWhile the van der Waals (vdW) interface in layered materials hinders the transport of charge carriers in the vertical direction, it serves a good horizontal conduction path. We have investigated electrical conduction of few quintuple-layer (QL) $$\hbox {Bi}_2\hbox {Te}_3$$ Bi 2 Te 3 films by in situ four-point probe conductivity measurement. The impact of the vdW (Te–Te) interface appeared as a large conductivity increase with increasing thickness from 1 to 2 QL. Angle-resolved photoelectron spectroscopy and first-principles calculations reveal the confinement of bulk-like conduction band (CB) state into the vdW interface. Our analysis based on the Boltzmann equation showed that the conduction of the CB has a long mean free path compared to the surface-state conduction. This is mainly attributed to the spatial separation of the CB electrons and the donor defects located at the Bi sites.

scholarly journals Morphology, Thermal, Mechanical Properties and Rheological Behavior of Biodegradable Poly(butylene succinate)/poly(lactic acid) In-Situ Submicrofibrillar Composites

Materials ◽  
2018 ◽  
Vol 11 (12) ◽  
pp. 2422 ◽  
Author(s):  
Zhiwen Zhu ◽  
Hezhi He ◽  
Bin Xue ◽  
Zhiming Zhan ◽  
Guozhen Wang ◽  
...  
Keyword(s):  
Lactic Acid ◽  
Cold Drawing ◽  
Mechanical Analysis ◽  
Poly Lactic Acid ◽  
Fiber Morphology ◽  
Molding Process ◽  
Butylene Succinate ◽  
Low Frequencies ◽  
Biodegradable Poly

In this study, biodegradable poly(butylene succinate)/poly(lactic acid) (PBS/PLA) in-situ submicrofibrillar composites with various PLA content were successfully produced by a triple-screw extruder followed by a hot stretching−cold drawing−compression molding process. This study aimed to investigate the effects of dispersed PLA submicro-fibrils on the thermal, mechanical and rheological properties of PBS/PLA composites. Morphological observations demonstrated that the PLA phases are fibrillated to submicro-fibrils in the PBS/PLA composites, and all the PLA submicro-fibrils produced seem to have a uniform diameter of about 200nm. As rheological measurements revealed, at low frequencies, the storage modulus (G’) of PBS/PLA composites has been increased by more than four orders of magnitude with the inclusion of high concentrations (15 wt % and 20 wt %) of PLA submicro-fibrils, which indicates a significant improvement in the elastic responses of PBS melt. Dynamic Mechanical Analysis (DMA) results showed that the glass transition temperature (Tg) of PBS phase slightly shifted to the higher temperature after the inclusion of PLA. DSC experiments proved that fiber morphology of PLA has obvious heterogeneous nucleation effect on the crystallization of PBS. The tensile properties of the PBS/PLA in-situ submicrofibrillar composites are also improved compared to neat PBS.

scholarly journals Tetrathiafulvalene: A Gate to the Mechanochemical Mechanisms of Electron Transfer Reactions

Crystals ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 482
Author(s):  
Richard Chen ◽  
Mehmet Kerem Gokus ◽  
Silvina Pagola
Keyword(s):  
Mechanochemical Synthesis ◽  
Amorphous Material ◽  
In Situ Monitoring ◽  
Ex Situ ◽  
Mechanochemical Reaction ◽  
Charge Transfer Complexes ◽  
Spectroscopic Techniques ◽  
Diffusion Controlled ◽  
Mechanochemical Reactions

This report describes aspects of our previous studies of the mechanochemical synthesis of charge transfer complexes of the electron donor tetrathiafulvalene, which are relevant to the use of laboratory X-ray powder diffraction for ex situ monitoring of mechanochemical reactions toward investigating their mechanisms. In particular, the reaction of tetrathiafulvalene and chloranil was studied under neat mechanochemical conditions and liquid-assisted grinding with diethyl ether (1 μL/mg). The product in both cases is the green tetrathiafulvalene chloranil polymorph and the mechanism of the redox reaction is presumably the same. However, while the kinetic profile of the neat mechanochemical synthesis was fitted with a second-order rate law, that of the overall faster liquid-assisted grinding reaction was fitted with the Ginstling-Brounshtein 3D diffusion-controlled model. Hence, the diffusional processes and mass transfer bringing the reactants together and separating them from products must be different. Diffraction measurements sensitive to crystalline phases and amorphous material, combined with in situ monitoring by spectroscopic techniques, will ultimately afford a better understanding of mechanochemical reaction mechanisms, a hot topic in mechanochemistry.

scholarly journals Enhanced Foamability with Shrinking Microfibers in Linear Polymer

Polymers ◽  
2019 ◽  
Vol 11 (2) ◽  
pp. 211 ◽  
Author(s):  
Eric Kim ◽  
Heon Park ◽  
Carlos Lopez-Barron ◽  
Patrick Lee
Keyword(s):  
Strain Hardening ◽  
Polymer Processing ◽  
Expansion Ratio ◽  
Low Frequencies ◽  
Extensional Rheometry ◽  
Enhanced Strain ◽  
Linear Viscoelastic ◽  
Cost Efficient ◽  
Strain Hardening Behavior

Strain hardening has important roles in understanding material structures and polymer processing methods, such as foaming, film forming, and fiber extruding. A common method to improve strain hardening behavior is to chemically branch polymer structures, which is costly, thus preventing users from controlling the degree of behavior. A smart microfiber blending technology, however, would allow cost-efficient tuning of the degree of strain hardening. In this study, we investigated the effects of compounding polymers with microfibers for both shear and extensional rheological behaviors and characteristics and thus for the final foam morphologies formed by batch physical foaming with carbon dioxide. Extensional rheometry showed that compounding of in situ shrinking microfibers significantly enhanced strain hardening compared to compounding of nonshrinking microfibers. Shear rheometry with linear viscoelastic data showed a greater increase in both the loss and storage modulus in composites with shrinking microfibers than in those with nonshrinking microfibers at low frequencies. The batch physical foaming results demonstrated a greater increase in the cell population density and expansion ratio with in situ shrinking microfibers than with nonshrinking microfibers. The enhancement due to the shrinkage of compounded microfibers decreasing with temperature implies that the strain hardening can be tailored by changing processing conditions.

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