Surface Resistance Of Films Research Articles

Thickness Effects on the Thermal Expansion Coefficient of Indium Tin Oxide/Polyethylene Terephthalate Film

Indium tin oxide/polyethylene terephthalate (ITO/PET) thin film/flexible substrates are widely applied in dye-sensitized solar cells, touch screens, and energy efficient windows, In this study, an application of the digital image correlation (DIC) method was used to determine the coefficient of thermal expansion (CTE) of ITO/PET thin films, and the effects of thickness variations of ITO and PET on the CTE of the samples. The observation range of the experimental temperature was selected from room temperature to the glass transition temperature of PET, which is 70°C. A novel DIC experimental process reduces errors caused by variations in the refractive index of the surrounding heated air is proposed. As a result, the error of the CTE measurement was reduced from 15 to 23% to less than 4%. The experimental results demonstrated that the CTE of the ITO/PET sample was anisotropic. Furthermore, the CTE of an ITO/PET sample increased by decreasing the thickness of PET flexible substrates, and increased by increasing the thickness of ITO film, and thus decrease the surface resistance of ITO film.

Effects of precursor parameters on the optical and electrical properties of AZO nano-composite films

Al doped ZnO (AZO) nano-composite films were synthesized on glass substrates with the sol–gel spin-coating method at the room temperature. The activation energy of AZO nano-composite films was calculated to be 49kJ/mol for the particles growth. The electrical, structural and optical properties of AZO films were determined by changing ZnO:water and ZnO:Al ratios. ZnO:water and ZnO:Al ratios play an important role in controlling the electrical conductivity of the AZO nano-composite films. The optimum doping ratio of Al was found to be 2% in terms of the lowest resistivity, and above 2% Al-doping concentration, the surface resistivity of AZO nano-composite films starts to increase. The optical highest transmittance of the films of 86% in visible region, and low surface resistivity of 70Ω/□ can be obtained for the optimum doping ratio of Al.

Fabrication and Protein Conjugation of Aligned Polypyrrole-Poly(L-lactic acid) Fibers Film with the Conductivity and Stability.

The conducting composite scaffold, including fiber-cores of aligned poly(L-lactic acid) (PLLA) and shell-layer of polypyrrole (PPy), was fabricated, and then bovine serum albumin (BSA) was conjugated on the PPy shell-layer. Aligned PLLA fibers (about 300 nm diameter) were obtained by electrospinning and rotating drum collection, and then coated by PPy nanoparticles (NPs, about 50 nm diameter) via chemical oxidation. The surface resistivity of PPy-PLLA fibers film were 0.971, 0.874 kΩ. cm at the fiber's vertical and parallel directions, respectively. The results of PPy-PLLA fibers film immersed in phosphate buffer saline for 8 d indicated that the fibers morphology and the film conductivity were not significantly changed, and the fluorescent images showed that FITC-labeled BSA (FITC-BSA) were successfully conjugated in the fibers film with carbodiimide chemistry, and the largest amount of FITC-BSA conjugated in the fibers film from 100 μg/mL proteins solution was 31.31 μg/cm2 due to lots of poly(glutamic acid) in surface-nanogrooves of the fibers surface. Under electrical stimulation of 100 mV, the fibers film was accompanied the release of all conjugated FITC-BSA with the detachment of some PPy NPs. These results suggested that PPy-PLLA fibers film would be potentially applied in the construction of degradable tissue engineering scaffold with protein factors, especially neurotrophic factors for nerve tissue repair.

1-Decanoic Acid와 Tri-n-octylphosphine을 이용하여 화학적 환원법으로 제조된 은 나노입자의 특성 및 전기적 전도체 적용

Silver nanoparticles were prepared by chemical reduction-protection method using 1-decanoic acid and tri-n-octylphosphine as surfactants, and using as a reducing agent. The silver nanoparticles were also studied for their formation, structure, morphology and size using UV-Visible spectroscopy, XRD, TEM and SEM. Further the viscosity of the silver paste and the surface resistance of the silver metal film produced by screen coating onto a PET film were investigated. Well dispersed and quasispherical silver nanoparticles with the size of 10-200 nm were obtained under the optimal molar ratio of $NaBH_4/AgNO_3

Preparation and properties of epoxy‐modified tung oil waterborne insulation varnish

ABSTRACTThis work aimed to develop a novel epoxy‐modified tung oil waterborne insulation varnish with blocked hexamethylene diisocyanate as a curing agent. The Diels–Alder reaction between tung oil and maleic anhydride, and the ring‐opening esterification reaction of epoxy resin were confirmed. The conversion rate of epoxy was explored as a function of reaction time and temperature. The effects of epoxy resin content on the thermal stability, water absorption and insulation properties (insulation strength, volume resistivity, and surface resistivity) of films were investigated, and the resistances of films to salted water were evaluated. The increase in epoxy resin contents could improve the thermal stability and insulation properties of films, and decreased the water adsorption of films, but when the epoxy resin content reached 30% and above, the water solubility of resin became poor. After being immersed in 3.5 wt % NaCl solution, the electrical insulation strength of films were lower than that in dry state, and decreased as the immersed time prolonged. In particular, the electrical insulation strength loss of films increased significantly for epoxy resin content at 15% and below. Furthermore, the increase of epoxy resin content could improve the hardness and adhesion of films, but the flexibility of films became worse. On the basis of experimental, the epoxy resin content at 25% was appropriate to prepare waterborne epoxy‐modified tung oil resin. The resulting varnish may have potential as an immersing insulation varnish for the spindle of electric motor. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42755.

Effect of 750 keV Argon ion irradiation on nc ZnO[sbnd]SiOx thin films

Nanocomposite (nc) ZnOSiOx thin films were grown using rf magnetron sputter deposition technique and post-deposition annealing at 750°C. These films were irradiated with 750keV Argon ions at fluences in the range from 1×1015 to 1×1017ions/cm2, using Low Energy Ion Beam Facility (LEIBF) at IUAC. X-ray diffraction (XRD) patterns of the as-deposited irradiated films show decrease in intensity of ZnO peaks relative to pristine film. Fourier transform infrared (FT-IR) spectroscopy measurements of the as-deposited irradiated films indicate the breakage of ZnO, ZnOSi and SiOSi bonds in them, which is substantiated by FT-IR measurements of 750°C annealed films that were irradiated at a fluence of 1016ions/cm2. Photoluminescence (PL) measurements show drastic decrease of visible PL emission from as-deposited irradiated films. Current−Voltage (I–V) measurements show decrease in surface resistance of irradiated films by three orders of magnitude. The results suggest that 750keV argon ion irradiation of nc ZnO−SiOx films has resulted in the formation of non-radiative defects in ZnO phase and damage in SiOx, and amorphization in Zinc silicate phase. These results are explained on the basis of the dominant energy loss mechanism of low energy ions in materials.

Understanding the Origin of Enhanced Performances in Core-Shell and Concentration-Gradient Layered Oxide Cathode Materials.

Core-shell and concentration-gradient layered oxide cathode materials deliver superior electrochemical properties such as long cycle life and outstanding thermal stability. However, the origin of enhanced performance is not clear and seldom investigated until now. Here, a specific structured layered oxide (LiNi0.5Co0.2Mn0.3O2) consisting of concentration-gradient core, transition layer, and stable outer shell, is designed and achieved from double-shelled precursors to overcome the great challenge by comparison with the normal layered LiNi0.5Co0.2Mn0.3O2. As expected, the specific structured layered oxide displays excellent cycle life and thermal stability. After numerous cycles, the valence state of Ni and Co at normal layered oxide surface tends to a higher oxidation state than that of the specific structured oxide, and the spinel phase is observed on particle surface of normal layered oxide. Also, the deficient spinel/layered mixed phases lead to high surface film and charge-transfer resistance for normal layered oxide, whereas the specific structured one still remains a layered structure. Those results first illustrate the origin of improved electrochemical performance of layered core-shell and concentration-gradient cathode materials for lithium-ion batteries.

Microwave Losses in YBCO Coplanar Waveguide Resonators at Low Power and Millikelvin Range

We have investigated the temperature dependence of microwave losses in the low-power limit and millikelvin temperature range of a thin-film YBa2Cu3O7-x (YBCO) λ/2 coplanar waveguide resonator patterned on a (La0.3Sr0.7) (Al0.65Ta0.35)O3 (LSAT) substrate covered by a CeO2 seed layer. The unloaded quality factor is mainly governed by the surface resistance of the YBCO film and the dielectric losses caused by resonant absorption due to a bath of two-level fluctuators in the dielectrics. The value of the unloaded quality factor at 20 mK and low power, i.e., Q0∼2000, allows for the realization of YBCO microwave quantum circuits implementing biepitaxial grain-boundary Josephson junctions.

(Invited) Uniform Nanostructures for Highly Efficient and Reproducible Perovskite Solar Cells

Organo-lead trihalide perovskites (CH3NH3PbX3, X = I, Br or Cl) as light absorption materials have attracted great attention recently in photovoltaic research. By virtue of their high absorptivity and long carrier diffusion length, the power conversion efficiency (PCE) was rapidly increased from 3.8% to above 17% within the short five years. In this presentation, I will report some our latest researches in this field. Firstly, the hole-blocking layer is required to prevent holes formed in the perovskie or HTL layer from reaching the FTO electrode, which would otherwise short-circuit the cell. Optimization of the blocking layer is a key factor for improving the device performance of perovskite solar cells. We systematically examined the different blocking layer fabricated by three different methods. The surface morphology and film resistance shows that atomic layer deposition (ALD) based TiO2 compact layer contains much lower density of nano-scaled pinholes with respect to spin-coating and spray pyrolysis ones. The ALD-TiO2 layer acts as an efficient hole-blocking layer in perovskite solar cells, which offers a large shunt resistance and enables a high power conversion efficiency of 12.56%. Secondly, uniform, highly crystalline perovskite film is important for sequential deposition processed perovskite solar cells. We develop a new method to enable an efficient deposition of perovskite film with enhanced conversion rate and surface morphology. By this approach, the energy conversion efficiency of mesoporous-free perovskite solar cells was twice as high as that of using traditional method. Figure 1

Improvement in physical and electrical properties of poly(vinyl alcohol) hydrogel conductive polymer composites

ABSTRACTWith an aim to develop anti‐electrostatic discharge materials based on biodegradable polymers, poly(vinyl alcohol) films composited with two different conductive fillers (carbon black and aluminium) at various fillers contents (20−60%wt), were manufactured using solvent‐casting technique. The mechanical properties of such the films were investigated through tensile stress‐strain tests. Wettability and morphology of the composite films were performed by water contact angle measurement and SEM, respectively. Young's modulus of the composite films can be increased with the addition of conductive fillers. The surface of the composite films showed non‐homogeneous appearance, in which the phase boundary within the composites was clearly observed and the conductive fillers formed aggregation structure at high filler concentration. In addition, the composite films exhibited better hydrophobicity when higher conductive filler content was added. TGA results suggested that both carbon black and aluminum have proven their efficiency to enhance thermal stability of poly(vinyl alcohol). Investigation of cross‐cut adhesion performance of the prepared composite films revealed that carbon black‐filled composites exhibited excellent adhesion strength. The effect of conductive filler content on surface resistivity of the composite films was also examined. The experimental results confirmed that both the fillers used in this study can improve the electrical conductivity of poly(vinyl alcohol) hydrogel. The surface resistivity of the composite films was reduced by several orders of magnitude when the filler of its critical concentration was applied. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42234.

Magnetic‐field‐assisted electrospinning highly aligned composite nanofibers containing well‐aligned multiwalled carbon nanotubes

ABSTRACTComposite nanofiber meshes of well‐aligned polyacrylonitrile (PAN)/polyvinylpyrrolidone (PVP) nanofibers containing multiwalled carbon nanotubes (MWCNTs) were successfully fabricated by a magnetic‐field‐assisted electrospinning (MFAES) technology, which was confirmed to be a favorable method for preparation of aligned composite nanofibers in this article. The MFAES experiments showed that the diameters of composite nanofibers decreased first and then increased with the increase of voltage and MWCNTs content. With the increase of voltage, the degree of alignment of the composite nanofibers decreased, whereas it increased with increasing MWCNTs concentration. Transmission electron microscopy observation showed that MWCNTs were parallel and oriented along the axes of the nanofibers under the low concentration. A maximum enhancement of 178% in tensile strength was manifested by adding 2 wt % MWCNTs in well‐aligned composite nanofibers. In addition, the storage modulus of PAN/PVP/MWCNTs composite nanofibers was significantly higher than that of the PAN/PVP nanofibers. Besides, due to the highly ordered alignment structure, the composite nanofiber meshes showed large anisotropic surface resistance, that is, the surface resistance of the composite nanofiber films along the fiber axis was about 10 times smaller than that perpendicular to the axis direction. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41995.

Study on the Properties of UHMW-PE Film

Some physicochemical properties of UHMW-PE film such as gas permeability, tensile strength, and corrosion resistance in acid with different immersion time, various concentrations and various solutions and rattler testing were studied. The obtained results showed that the values of gas permeability, tensile strength, elongation at break, and the temperature of dissociation at weight loss 5% was 546.57 cm3·m﹣2·24 h·0.1 MPa, 37.22 MPa, 368.00%, 360°C, respectively. In different concentration acid, the surface resistance of film accumulated to some extent with immersion time increasing, together with that the higher acid concentration was, the lower the surface resistance of film was. Moreover, the contact angle of films gradually increased with the acid concentration decreasing and the increase of immersion time. After wear testing, the mass of UHMW-PE film did not nearly change, while the contact angle became larger with the number of turning increasing and the value was more than 90°.

Optical and Electrical Properties of CH<sub>3</sub>NH<sub>3</sub>PbI<sub>3</sub> Perovskite Thin Films Transformed from PbO-PbI<sub>2</sub> Hybrid Films

Organic-inorganic halide perovskites have been shown to be outstanding photovoltaic materials, achieving remarkably high power conversion efficiency (15%) of sunlight to electricity within the past 4 years. The controllable synthesis of organic-inorganic halide perovskites is fundamental to their applications in photovoltaic devices. Here we explore a novel strategy to prepare a typical halide peroskite CH3NH3PbI3 by transforming PbO-PbI2 hybrid materials. CH3NH3PbI3 thin films were deposited on glass substrates by reacting ultrasonic-assisted successive ionic layer adsorption and reaction (SILAR)-derived PbO-PbI2 hybrid films with CH3NH3I vapor at 110 °C. The microstructure and crystallinity of the films, together with the optical and electrical properties were characterized. Results show that CH3NH3PbI3 thin films possess perovskite crystal structure and uniform surface morphology with grain size up to 400 nm. In the visible band, CH3NH3PbI3 thin films showed low transmittance (below 10%), with a band gap of 1.58 eV. The surface resistivity of CH3NH3PbI3 thin films was as high as 1000 MΩ, indicating the dielectric nature of obtained CH3NH3PbI3 films, with a dielectric constant of er(100 Hz)=155 on low frequency. The current work opens an effective route toward high quality organic- inorganic halide perovskite films with good crystallinity and optical properties, which make them suitable for application in photovoltaic devices, and other optical and electrical applications.

Evaluation of PAN Based Composite Sheet Films with Modified Carbon Nanotubes

An aqueous deposited polymerization method to fabricate PAN based composite sheet films after multiwall carbon nanotubes (CNTs) modified with concentrated nitric acid was presented. This paper disscussed the effect of CNTs modified with concentrated nitric acid on the thermal and the crystal properties of PAN based composite sheet films. The results indicated that the normal process of multiwall CNTs treated with concentrated nitric acid can change the crystallization properties of polymers but not change the basic structure of polymers. The crystallinity of pure PAN at 2θ≈17° was strengthened after preoxidation. With the addition of CNTs, the crystallization peak of composite sheet films at 2θ≈17° became weaker, and a sharp crystallization peak appeared at 2θ≈25°, as showed that the composite sheet films could carry out the cyclization at low preoxidation temperature. During their process of preoxidation and carbonization, modified CNTs could promote the formation of cyclization and cause the formation of aromatic ring structure, and the cyclization efficiency increased from 20.24% to 70.41%. TEM analysis indicated that the modified CNTs existed in the composite sheet films in two forms: the dispersion and reunite of the single state. The test results of the surface resistivity of the composite sheet films showed that when the CNT content was lower, the surface resistivity of film was very large. When the CNT content was 5% and 10%, the surface resistivity of the film was 5.74 MΩ and 0.15 MΩ, respectively. It was obvious that once the continuous conductive network of CNTs was formed, the surface resistivity of composite sheet films hardly changed.

Synthesis, characterization, and properties of acrylate‐modified tung‐oil waterborne insulation varnish

ABSTRACTAn acrylate‐modified tung‐oil waterborne insulation varnish was synthesized from tung oil, maleic anhydride, and acrylates via a Diels–Alder reaction and free‐radical polymerization, and the varnish could be solidified at a relatively low temperature with blocked hexamethylene diisocyanate as a curing agent. The resulting films were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, and differential scanning calorimetry. The insulation properties (electrical insulation strength, volume resistivity, and surface resistivity) of the varnish films were tested, and the resistances of films to salted water were evaluated. With an increase in the maleic anhydride content, the thermal stability of the film was improved, whereas the electrical insulation strength, volume resistivity, and surface resistivity decreased. The electrical insulation strength of the film after it was immersed in the NaCl solution was lower than that in dry state, and it decreased as the immersed time was prolonged. In particular, the electrical insulation strength loss of the film increased significantly at maleic anhydride contents beyond 25 wt %. Furthermore, the hardness of the film increased with increasing methyl methacrylate/N‐butyl acrylate ratio, whereas the flexibility and adhesion of film decreased to a certain degree at the same time. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41608.

Effect of Cr and Mo doping on the electrochemical properties of freeze-dried LiCoO2

Abstract In this study, LiCoO2 is doped with 2 mol.% Cr and Mo in order to determine the effect of these elements on the electrochemical performance. Precursors are synthesized by means of freeze drying. Calcination is applied at 750 °C for 24 h. Doping content and calcination temperature as well as duration are very important for producing impurity-free layered LiCoO2. If the doping content is larger than 2 mol.% or when the calcination temperature is decreased to 550 °C, impurity phases are seen. As a result, the sample doped with 2 mol.% Cr has better high charge and discharge rate capability, and cycleability, but discharge capacity is slightly lowered when compared to the undoped sample. Electrochemical impedance spectroscopy results show that surface film resistances of Cr-doped samples are lower than that of the undoped sample.

Promising in vitro performances of nickel-free nitrogen containing stainless steels for orthopaedic applications

The aim of the present work was to study the in vitro corrosion resistance in Hank’s solution and biocompatibility of indigenized low-cost Ni-free nitrogen containing austenitic stainless steels (HNSs) and to compare with conventionally used 316L and 316LVM. The electrochemical behaviour was assessed using electrochemical impedance spectroscopy, potentiostatic polarization and scanning electron microscopy. The MTT assay [3-(4,5-dimethythiazol 2-yl)-2,5-diphenyltetrazolium bromide] was performed using Dalton’s lymphoma cell line for cytotoxicity evaluation and cell adhesion test. The resistance of surface film was raised by increasing nitrogen content in stainless steel (SS). The corrosion current density was decreased with increase in nitrogen content and corrosion potentials for HNS were observed to be more positive. Shallower and smaller pits were associated with HNS, indicating that nitrogen suppresses the pit formation. The HNS had higher cell proliferation and cell growth and it increases by increasing the nitrogen content. The surface wettability of the alloys was also investigated by water contact-angle measurements. The value of contact angles was found to decrease with increase in nitrogen content. This indicates that the hydrophilic character increases with increasing nitrogen content, which is further attributed to enhance the surface free energy that would be conducive to cell adhesion, which in turn increases the cell proliferation.

Preparation and Electrochemical Performance of Yttrium-doped Li[Li0.20Mn0.534Ni0.133Co0.133]O2 as Cathode Material for Lithium-Ion Batteries

To improve the cycling performance and rate capability of the promising layered lithium-rich cathode materials, we substitute Co3+ in Li[Li0.20Mn0.534Ni0.133 Co0.133]O2 with unusually large Y3+ during coprecipitation and synthesize Li[Li0.20Mn0.534 Ni0.133Co0.133-x Yx]O2 (0 ≤ x ≤ 0.0665). The influences of yttrium content on the electrochemical properties of the lithium-rich materials are investigated by X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), galvanostatic charge–discharge tests and electrochemical impedance spectroscopy (EIS) techniques. The charge–discharge cycling tests suggest that after heating at 1223K in air for 10h, the material with x=0.00665 deliver a high discharge capacity of 349.7 mAhg−1 after 1 cycle and 225.2 mAhg−1 after 80 cycles with a current rate of 0.1C between 2.0 and 4.6V vs. Li/Li+. Electrochemical impedance spectroscopy indicates that Li[Li0.20Mn0.534Ni0.133Co0.133-xYx]O2 electrode has lower impedance during cycling. The higher capacity retention and high-rate capability of yttrium-substituted materials can be ascribed to the expanded Li+ diffusing channels in the layered structure, lower surface film resistance and lower charge transfer resistance of the electrode during cycling.

Effect of Al2O3 -coating on the electrochemical performances of Li3V2(PO4)3/C cathode material

The effect of Al2O3 -coating on Li3V2(PO4)3/C cathode material for lithium-ion batteries has been investigated. The crystalline structure and morphology of the synthesized powders have been characterized by XRD, SEM, and HRTEM, and their electrochemical performances are evaluated by CV, EIS, and galvanostatic charge/discharge tests. It is found that Al2O3 -coating modification stabilizes the structure of the cathode material, decreases the polarization of electrode and suppresses the rise of the surface film resistance. Electrochemical tests indicate that cycling performance and rate capability of Al2O3-coated Li3V2(PO4)3/C are enhanced, especially at high rates. The Al2O3-coated material delivers discharge capacity of 123.03 mAh g−1 at 4 C rate, and the capacity retention of 94.15 % is obtained after 5 cycles. The results indicate that Al2O3 -coating should be an effective way to improve the comprehensive properties of the cathode materials for lithium-ion batteries.

Dependences of microwave surface resistance of HTS thin films on applied dc magnetic fields parallel and normal to the substrate

We investigated the dc magnetic field and temperature dependences of microwave surface resistance (Rs) of high-temperature superconductor (HTS) films. Previously, we reported that the surface resistance RsRs(n) under a dc magnetic field applied normaly to the substrate increased when increasing the applied magnetic field. For NMR application, we have to examine the Rs(p) under the dc magnetic field parallel to the substrate. We measured the Rs(p) of the YBCO and DyBCO thin films with a thickness of 500 nm deposited on a MgO (100) substrate using the dielectric resonator method at 21.8 GHz, and a dc magnetic field of up to 5 T. In a zero magnetic field, the values of Rs(n) and Rs(p) were 0.35 mQ at 20 K. Under the dc magnetic field, the Rs(n) and the Rs(p) also increased with increasing magnetic field, however, the Rs(p) had a lower magnetic field dependence and the value was about 1/10 of that of the Rs(n). The Rs(p) at 16.4 T and at 700 MHz could be estimated by the two-fluid model. The Rs(p) value was about 1/2600 compared with that of copper at 20 K. As a result, we clarified that 500 nm thick YBCO and DyBCO thin films could provide advantages for NMR application.