Detection of Different Interfaces in Percolated Networks of Antimony Tin Oxide: Borosilicate Glass Composites by Impedance Spectroscopy

2020

Mater. Res. Express

The objective of this study was to determine the effect of processing on the electrical properties and microstructure of MWCNTs/PMMA nanocomposites made by compression molding. Three different mixing methods were used: mechanical, solution, and melt mixing of the same starting materials. The composite microstructures were found to be segregated, agglomerated, and randomly distributed respectively. Electrical property measurements indicate that the mechanically mixed composites have the lowest percolation threshold of 0.05 phr (0.028 vol% MWCNT). Melt mixed composites have the highest percolation threshold of 4 phr (2.161 vol% MWCNT) while solution mixed composites have a percolation threshold of 2 phr (1.102 vol% MWCNT). These results indicate that the segregated microstructure allows for the CNTs to form a percolated network through the composite more easily than the other two methods. Fitted equivalent circuits to the measured impedance spectra show that after percolation the CNTs dominate the electrical properties as represented by an increase in the number of inductance circuit elements. Before or at percolation, the presence of PMMA plays a stronger role in the circuit. This article is novel in that this is the first study where direct comparison of the properties and microstructure of composites fabricated utilizing three different mixing methods using the same source materials can be made.

Section: Resultsmentioning

confidence: 99%

Effect of processing on the properties and morphology of MWCNT-polymer networks

Watt

2020

Mater. Res. Express

“…In addition, such modeling allowed for separation of the electrical responses from the constituent phases and interfaces, which provided additional insight into how microstructure and phase distribution were affected. The foundation for finding appropriate, physically justifiable models was based on a model previously developed for a similar material system, [18] which, upon independent verification in the current work, was found to be the most appropriate model for the ITO-borosilicate composites. The model was derived by finding circuits, which fit impedance data from tests of the isolated constituents and combinations of them, as shown in Figure 2a-d.…”

Section: Development Of Equivalent Circuit Modelsmentioning

confidence: 94%

“…This composition was chosen because its electrical response was just above the percolation threshold [17] and was expected to be very sensitive to small changes in the connectivity of the particles. [11,18] SPS was carried out using three different SPS equipment: a Thermal Technologies L.L.C model SPS 10-4, a Thermal Technologies L.L.C model SPS 25-10, and a Fuji Electronic Industrial Co., Ltd. Dr. Sinter model SPS-211Lx. These different equipment were designated as UA, TT, and GT, respectively.…”

Section: Methodsmentioning

confidence: 99%

Effect of Spark Plasma Sintering Current and Voltage on the Microstructure and Electrical Properties of Borosilicate Glass–Indium Tin Oxide Composites

Rudzik

2020

Adv Eng Mater

Self Cite

Borosilicate glass–indium tin oxide (ITO) composites made from glass microspheres and ITO nanoparticles provide a unique model system to monitor the effect of spark plasma sintering (SPS) parameters on the resultant electrical properties of the composites. Composite sets containing different ITO content (up to 10 phr), fabricated under the same SPS conditions, are used as the starting point for the equivalent circuit analysis. The effect of changing the various SPS parameters such as heating rate, hold temperature, and applied pressure on the current and voltage profiles experienced by samples containing 2.5 phr (2.44 wt%) ITO, and their resultant electrical response are reported. Experiments are carried out varying a single SPS parameter at a time while keeping others constant. The applied pressures used range from 5 to 40 MPa; the hold temperature is varied from 610 to 680 °C; and the heating rate is tested between 2 and 200 °C min−1. It is demonstrated that not only do the current and voltage profiles change in all of these instances but also the microstructure and resultant electrical properties of the composite samples being fabricated. Results indicate that all of these parameters are interdependent and can affect the electrical properties of the fabricated samples by many orders of magnitude in some cases.

“…This will have to be addressed in another publication where the quality of contact between the individual ITO nanoparticles can be evaluated. Previous research in our group has indicated that the quality of contact can be obtained by conducting careful impedance and dielectric spectroscopy measurements, but that falls outside the scope of this study. Additional details regarding the application of the ITO in inkjet printing and inkjet printing details are provided in the Supporting Information.…”

Section: Methodsmentioning

confidence: 99%

Three-Dimensional Nanoscale Mapping of Porosity in Solution-Processed ITO Multilayer Thin Films for Patternable Transparent Electrodes

Xia

Lauter

2019

ACS Appl. Nano Mater.

Self Cite

Indium tin oxide (ITO) films constitute components of many layered heterostructures used for emergent technologies beyond conventional optoelectronics. Compositional and morphological changes have a direct impact on the device’s performance. Hence control over the morphology with advanced multimodal characterization approaches is required to evaluate the devices. Herein multilayer ITO films deposited by spin-coating were quantified in nanoscale detail in three dimensions by combining results from depth-sensitive neutron reflectometry (NR), noncontact topographic AFM images, and cross-sectional SEM images. Films with a different number of deposited layers were visually transparent even though the topmost layer was as high as 60% porous, with porosity gradually decreasing as the number of the underneath sublayers increased. Surface and interfacial roughness through the total film and individual layer thickness were obtained. NR data also furnished quantitative depth information on the films’ chemical composition and layer-by-layer bulk density, which has never been obtained before, providing a way to monitor and ultimately control the sheet resistivity via the pore network. When the same formulation is used for inkjet printing patterns, the larger pores disappear, and the optical properties are improved to >90% transmittance at all visible wavelengths. All 5L films achieved sheet resistivities as low as 10–2 Ω cm and can therefore be used as patternable transparent electrodes for many devices including liquid crystal displays.