Surface and barrier properties of hybrid nanocomposites containing silica and PEO segments

Hybrid organic–inorganic nanocomposites containing PEO segments linked to a methacrylate network were prepared through a dual‐curing process, which involved photopolymerization and condensation of alkoxysilane groups. A system based on an α,ω‐dimethacrylate PEO oligomer (BEMA 1400) added with methacryloyl‐oxypropyl‐trimethoxysilane (MEMO) and tetraethoxysilane (TEOS) was used. The surface properties of the obtained films were investigated through XPS analyses and contact angle measurements. A selective enrichment of the MEMO additive towards the outermost layers of the films was evidenced either in the presence or in the absence of TEOS. SEM analyses were performed on the cross section of the films coated on PET substrates, determining the film composition at different depth by EDS analysis. The Si content was found constant, moving from the PET surface towards the air–surface of the films. The barrier properties, with respect to oxygen, of the hybrid films coated on a PET substrate were measured. A decrease of the permeability and of the oxygen transmission rate using hybrid coatings was observed. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 4107–4115, 2007     

High-quality and efficient transfer of large-area graphene films onto different substrates

We used a two-layer structure consisting of polyethylene terephthalate (PET) and silicone to transfer graphene grown by chemical vapor deposition onto various rigid and flexible substrates through dispersive adhesion. It only takes a few seconds to transfer graphene from PET/silicone to the target substrates at ambient conditions. And the recycling of the PET/silicone decreases the production cost greatly. The transferred graphene films were characterized by optical and atomic force microscopy, Raman spectroscopy, electrical analyses, and optical transmittance measurements, and the results show that the graphenes transferred by PET/silicone have a cleaner and more continuous surface, lower doping level, and higher optical transmittance and conductivity than those transferred by thermal release tape. Considering its high efficiency, low cost, large area and high quality, the PET/silicone transfer method would be particularly useful for graphene’s electronic applications such as field-effect transistors and transparent conducting electrodes.     

Extracting the Optical Parameters of the Fabricated (Al/Bare Borosilicate Crown Glass,BK-7/Ag) Multiple Layers

Significant effort has been devoted in this work to convert bare glass substrate with high transmittance, into reflective layers to know its suitability for modern applications. The glass substrate has been carefully chosen for its durability, high permeability, and ability to withstand any external stresses as a result of the accumulation of layers that reduce its permeability to convert it with the thin films coated on it into reflective materials. In parallel, the thin layer to be coated on the substrate is selected from films that can withstand external influences and their great optical properties, not to mention that they are cheap and can produce highly reflective surfaces. The optical measurements (transmittance and reflectance spectra) have been performed in the UV, Vis and NIR regions of the spectrum, that is, in the range between 300 and 1200 nm. Such measurements have been made for the bare glass substrate, the glass substrate with the Al (top side), and the glass substrate with Ag on it (bottom side), and then the optical measurements have been made for the three layers. The corresponding optical parameters of each layer have been calculated and ultimately a reflective layer with high electrical conductivity and excellent optical properties has been obtained that can be adapted for different application purposes.

     

Assembly and benign step-by-step post-treatment of oppositely charged reduced graphene oxides for transparent conductive thin films with multiple applications

We report a new approach for the fabrication of flexible and transparent conducting thin films via the layer-by-layer (LbL) assembly of oppositely charged reduced graphene oxide (RGO) and the benign step-by-step post-treatment on substrates with a low glass-transition temperature, such as glass and poly(ethylene terephthalate) (PET). The RGO dispersions and films were characterized by means of atomic force microscopy, UV-visible absorption spectrophotometery, Raman spectroscopy, transmission electron microscopy, contact angle/interface systems and a four-point probe. It was found that the graphene thin films exhibited a significant increase in electrical conductivity after the step-by-step post-treatments. The graphene thin film on the PET substrate had a good conductivity retainability after multiple cycles (30 cycles) of excessively bending (bending angle: 180°), while tin-doped indium oxide (ITO) thin films on PET showed a significant decrease in electrical conductivity. In addition, the graphene thin film had a smooth surface with tunable wettability.     

Electrical behavior of PET films coated with nanostructured organic–inorganic hybrids

Hybrid coatings, based on poly(ethylene oxide) (PEO) or polycaprolactone (PCL) and silica (SiO₂), at different organic–inorganic compositions have been used to coat PET films employed in the electric industry to produce capacitors. The overall electrical behavior of the coated films has been investigated. The electrical strength of the coated films increases up to 10–15% of the uncoated ones regardless of polymer type (PEO/PCL) and amount of inorganic phase, as far as the thickness of the coating is below 5 μm. A systematic increase of surface electrical conductivity is found in all coated samples which however still behave as insulators. Permittivity and loss factor also increase particularly at low frequencies (< 10 Hz) on account of the presence of ions deriving from the sol–gel process and on the presence of interfacial polarization probably related to the coatings nanostructurated morphology which leads to phase separation. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4870–4877, 2006     

不同衬底上ZnO:Al透明导电薄膜的性能

室温下,采用射频磁控溅射法在玻璃和聚对苯二甲酸乙二醇酯（polyethylene terephthalate,PET）上沉积了掺铝的氧化锌（ZnO：Al,AZO）透明导电薄膜。通过X射线衍射仪分析不同衬底上AZO薄膜的结构,采用四探针测试仪及紫外可见光分光光度计测试薄膜的光电性能。结果表明：沉积在两种衬底上的AZO薄膜都具有六方纤锌矿结构,最佳取向均为[002]方向;玻璃衬底和PET衬底上制备的AZO薄膜的方阻分别为19/sq和45/sq,薄膜透光率均高于90%。实验表明,柔性衬底透明导电氧化物薄膜可以代替硬质衬底透明导电薄膜使电子器件向小型化、轻便化方向发展。     

Hybrid laser processes for thick silver coating fabrication on AlN substrate

Aluminum nitride (AlN) are particularly suitable as integrated circuits (ICs) substrates due to its high thermal conductivity and excellent electricity insulation. However, its poor weldability with metals limits its usage. Recent research on surface metallization of AlN provides possible solutions to tackle this defect. Nevertheless, these solutions show some shortages such as complicated processes or insufficient electrical conductivity. In this paper, we report a method that consists of laser induced surface metallization and laser sintering of silver (Ag) coatings. A nanosecond laser was applied to induce a 10 μm thick aluminum (Al) layer from the AlN substrate. Afterwards, laser sintering of Ag layers was implemented, which could enhance the conductivity and the bonding performance between layers. With optimized laser parameters applied, both the electrical conductivity and the bonding tests demonstrated excellent physical properties. Finally, simulation and EDS analysis illustrated the melting evolution and confirmed a metallurgical combination of Al and Ag, thus enhancing bonding strength. Thanks to the small size of focused laser spot, electrical circuits width could be greatly narrowed if these findings were applied; hence highly dense ICs on AlN substrate become potentially available.     

Room temperature sputtering deposition of high-haze Ga-doped ZnO transparent conductive thin films on self-textured bio-based poly(ethylene 2, 5-furandicarboxylate) substrates

In this work, bio-based poly(ethylene 2,5-furandicarboxylate) (PEF) films were prepared by drop-casting method and used as substrates for depositing Ga-doped ZnO (GZO) transparent conductive thin films. Results showed that the 300-nm GZO thin films deposited on PEF substrates exhibited haze values above 65% at 550 nm without post-treatment. The high haze value was because of the large surface roughness of PEF films. The total optical transmittance and electrical properties of GZO thin films on PEF were comparable to those of GZO thin films on PET. The present study provides a simple way for the sputtering deposition of high-haze transparent conductive thin films on flexible substrates.     

Physical properties of Al-doped ZnO films deposited on nonwoven substrates by radio frequence magnetron sputtering

In this study, the polyethylene terephthalate (PET) spunbonded nonwoven materials were used as substrates for creating electro-optical functional nanostructures on the fiber surfaces. A magnetron sputter coating was used to deposit Al-doped ZnO (AZO) films onto the nonwovens. The influences of the deposition time on the structural, optical, and electrical properties of AZO films were investigated. Atomic force microscopy (AFM) was employed to examine the topography of the fibers. The AFM observation revealed a significant difference in the morphology of the fibers before and after the AZO sputter coating. The examination by UV–visible spectrophotometer analysis showed that the nonwovens deposited with transparent nanostructure AZO films had better UV absorption, and an average transmittance was approximately 50% in the visible light wavelength region. The surface conductivity of the materials was analyzed using a four-probe meter, and it was found that electrical resistance was significantly decreased as the sputtering time increased.     

Self‐assembly of novel architectural nanohybrid multilayers and their selective separation of solvent‐water mixtures

A new architectural nanohybrid multilayer has been explored and built on various substrates. The building blocks of positive and negative charged polyelectrolyte‐coated nanoparticles (NPs) could be obtained by tuning the electrical properties of the amphoteric oxide NPs in acid and basic environments. The nanohybrid films were, thereafter, formed by layer‐by‐layer (LbL) assembly of polycation‐ and polyanion‐coated NPs. It was demonstrated that this approach could incorporate single component NPs into both polycation and polyanion layers, and in turn improve the NP loading, maintain good dispersion of NPs within the film. For separation applications, a dynamic LbL assembly was attempted as a means of fabricating such nanohybrid multilayers on both 2‐D and 3‐D polymeric porous substrates. The nanohybrid multilayer membrane renders both much higher selectivity and flux in the separation of solvent‐water mixtures. Moreover, such assembly of nanohybrid multilayers allows us to efficiently simplify the procedures by reducing 30–40‐fold process cycles. © 2011 American Institute of Chemical Engineers AIChE J, 2012     

Preparation and characterization of silver nanocomposite textile

Nanostructured silver films of different thicknesses were deposited on surfaces of polypropylene nonwovens by magnetron sputter coating to obtain antibacterial and electrical conductive properties. The surface morphology of nanostructured silver films was investigated by atomic force microscopy (AFM). The antibacterial properties of the nonwovens coated with relatively thinner films were evaluated using the shake flask test. The conductivity of the nonwovens coated with relatively thicker films was examined using an ohm-meter. The results of the antibacterial test revealed that the antibacterial performance improved gradually as the film thickness increased from 0.5 to 3 nm. It is believed that the total amount of silver ions released from the coating was increased along with the increase in film thickness. As sputtering time prolonged, the grain sizes of the silver particles were increased and the coating became more compact. The results of the electrical conductivity test showed that the increased film thickness led to the improved electrical conductivity when the film was relatively thicker. The AFM images clearly revealed the change in surface morphology formed by sputter coating. The growth and coverage of the coating layer contributed to the improvement in its antibacterial and conductive properties.     

Electroactive PVDF thin films fabricated via cooperative stretching process

Ferroelectric polymers have obtained much attention in low cost and flexible electronics. As one representative ferroelectric polymer, poly(vinylidene fluoride) (PVDF) has been comprehensively studied. Due to its complicated phase composition, fabrication of electroactive phases has been an open question especially for PVDF thin films deposited on solid substrates. Here cooperative stretching process is introduced for the fabrication of electroactive PVDF thin films. PVDF thin films are coated on stretchable poly(vinyl alcohol) substrates and mechanically stretched under optimized stretching parameters. Structural, spectral, and electrical measurements indicate that cooperative stretching process can effectively convert the nonpolar α phase to the electroactive β and γ phases companied by an enhancement of film crystallinity. Stretched PVDF films present a reverse piezoelectric coefficient of ?37 pm/V, comparable with the results from films fabricated by the other techniques. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46324.     

[BN/CoPt]n/Ag薄膜的结构与磁性

采用磁控溅射方法在玻璃基片上制备了[BN/CoPt]n/Ag薄膜,并在600℃退火30min。结果表明,周期数（n）和Ag底层厚度（x）对CoPt薄膜结构和磁性有着重要的影响,周期数适当时（n=5）有利于易磁化轴（c轴）垂直于膜面取向,从而具有高的垂直磁各向异性;Ag底层可以诱导L10-CoPt相的形成并使c轴垂直择优取向,且Ag适量时（x=10nm）其诱导效应最强。     

Processing characteristics,structure development,and properties of uni and biaxially stretched poly(ethylene 2,6 naphthalate) (PEN) films

Poly(ethylene 2,6, naphthalene dicarboxilate), PEN, is very similar to poly(ethylene terephthalate), PET, in its chemical structure and was, therefore, expected to exhibit similar processing characteristics. We, however, observed a few problems during stretching of PEN, the most important of which was necking behavior at 145°C, which is between T_g (117°C) and T^cc (195°C). This is usually observed in PET only when it is stretched close to or below T_g. At temperatures between T_g and T_cc (cold crystallization temperature) PET stretches rather uniformly. The temperature window for film stretching appears to be rather wide, but our results indicate that this is not the case. Films stretched to high stretch ratios become uniform due to propagation and final disappearance of necks as a result of stress hardening. Our attempts at stretching these films at higher temperatures indicated that necking is eliminated, but so is stress induced crystallization, which causes stress hardening (unless high stretching rates are employed). The presence of stress hardening is essential for obtaining high quality, uniform films of these polymers. In addition, at high temperatures thermally activated crystallization which starts dominating the structure development, detrimentally affects the general appearance of the films. In brief, the PEN films we investigated have a narrower processing window than was anticipated based on their thermal behavior alone. At elevated temperatures the films are sensitive to the rate of stretching even more than typical PET processed at comparable conditions. The uniformity of the films depends on the stretch ratio, stretching mode, ratio(s) and rates and temperature. WAXS studies on the films indicate that the macromolecules packed into the low temperature crystal modification. In addition, WAXS pole figure studies suggest that naphthalene planes preferentially orient parallel to the film surface during biaxial stretching. The biaxially stretched films were observed to exhibit a bimodal chain orientation as evidenced by pole figure analysis of the (010) planes.     

Flexible IZO/Ag/IZO/Ag multilayer electrode grown on a polyethylene terephthalate substrate using roll-to-roll sputtering

We investigated the optical, electrical, structural, and surface properties of roll-to-roll [R2R] sputter-grown flexible IZO/Ag/IZO/Ag [IAIA] multilayer films on polyethylene terephthalate substrates as a function of the top indium zinc oxide [IZO] thickness. It was found that the optical transmittance of the IAIA multilayer was significantly influenced by the top IZO layer thickness, which was grown on identical AIA multilayers. However, the sheet resistance of the IAIA multilayer was maintained between the range 5.01 to 5.1 Ω/square regardless of the top IZO thickness because the sheet resistance of the IAIA multilayer was mainly dependent on the thickness of the Ag layers. Notably, the optimized IAIA multilayer had a constant resistance change (ΔR/R ₀) under repeated outer bending tests with a radius of 10 mm. The mechanical integrity of the R2R-sputtered IAIA multilayer indicated that hybridization of an IZO and Ag metal layer is a promising flexible electrode scheme for the next-generation flexible optoelectronics.     

Stretchable conductive films based on carbon nanomaterials prepared by spray coating

Stretchable conductive films consisting of a layer of carbon nanomaterials, that is, carbon nanotubes (CNTs), mechanically exfoliated graphene (GE), or chemically reduced graphene oxide (rGO), deposited on polydimethylsiloxane (PDMS) films were prepared by spray coating. The correlations among the concentration of the carbon nanomaterials, the electrical resistance and the optical transmittance of the spray‐coated films were investigated. The results show that the conductivity of the CNT coatings was better than that of the GE‐based coatings. When the CNT concentration of the dispersion for spraying increased from 0.01 to 0.075 mg/mL, the surface electrical resistance decreased from 7.8 × 10³ to 6.7 × 10² Ω, whereas for the GE or rGO coatings, the electrical resistance was several orders higher than that of the CNT coatings. The CNT spray‐coated films exhibited an optical transmittance of about 60% at a wavelength of 550 nm; this was higher than that of the GE or rGO spray‐coated films. The electric heating behaviors of the stretchable conductive films as functions of the applied voltage and the concentration of carbon nanomaterials and the electrical conductivity under tensile and bending strains were also investigated. The surface temperature of the CNT‐coated films rose rapidly up to 200°C within about 40 s when the applied voltage was 110 V. The stretchable conductive films have potential as electric heating elements because of their excellent conductive properties. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43243.     

Polyethylene terephthalate/calcined kaolin composites: Effect of uniaxial stretching on the properties

This article is aimed at investigating the effect of a calcined kaolin filler (CKao) on polyethylene terephthalate (PET). The influence of a silane coupling agent, chain extension, and post extrusion uniaxial hot‐stretching on the final properties of the produced composites were studied as well. PET‐CKao films were prepared via melt blending using a twin‐screw extruder followed by stretching above the glass transition temperature at controlled conditions. The morphology of the composites before and after stretching was observed by SEM. Rheological measurements were also performed to characterize the polymer melts. Mechanical and optical properties as well as the oxygen transmission rate of the composites were also investigated. The results showed that addition of CKao particles, even at low filler content, improved drastically the mechanical and barrier properties compared to the neat PET. This effect was more pronounced in case of hot‐stretched samples. The main drawback observed with these CKao particle composites was an increased haze. Processing parameters including stretching temperature and stretching ratio were found to have a significant effect on the final properties; however, the influence of the stretching rate was negligible. POLYM. ENG. SCI., 55:1767–1775, 2015. © 2014 Society of Plastics Engineers     

Method of determination of transient and steady-state conductivity in polyethylene terephthalate ultrathin films

The determination of transient and/or steady-state conductivity of polyethylene terephthalate (PET) ultrathin films by means of electrode configurations involving any load or stress imposed on the measuring area during measurement usually leads to anomalous behaviours of the charging current and thus prevents a good evaluation of the electrical properties of the samples. This can be avoided by the use of a two-electrode system with lateral contacts, to obtain reproducible results without any requirement for previous mechanical, thermal, or electrical treatments (as is often recommended in the literature), and that permits the characterization of industrial films down to 1.5-μm thick in true storage conditions after production. © 1993 John Wiley & Sons, Inc.     

Properties investigation on electrically conductive adhesives based on acrylate resin filled with silver microsheets and silver plating carbon fibers

The introduction of highly electrically conductive fillers (Ag microsheets and silver plating carbon fiber) can functionally improve the electrical conductivity of acrylate resin. In this study, Ag microsheets and Ag/CF were thus introduced into acrylate polymer via solution blending method under ultrasonication in order to improve the electrical conductivity of the acrylate resin. The properties and microstructures of Ag microsheets, CF, Ag/CF and ECAs were performed by scan electron microscope (SEM), X-ray diffraction analysis (XRD), etc. SEM images and XRD results illustrated that the impurities in carbon fiber could be completely removed after the adequately alkali treatment. The SEM images showed that large numbers of metallic silver particles were uniformly and densely coated on the surface of the carbon fibers and hybrid fillers (silver microsheets and Ag/CF) could homogeneously disperse in acrylate resin. Electrical conductivity measurements demonstrated that the electrical conductivity of ECAs increased with the increasing content of hybrid fillers and the percolation threshold of ECAs was 5 wt%. The electrical conductivity of ECAs at its percolation threshold was 15.79 S/cm, which was two orders of magnitude higher than that of the ECAs based on acrylate resin filled with silver microsheets. The increment in Ag/CF contents may decrease 180° peel strength and raise shear strength with low content of Ag/CF. The overall performance of ECAs was optimum with 2 wt% Ag/CF. The TGA analysis indicated that ECAs possess excellent thermal stability.     

Relationship between electrical and thermal conductivity in graphene-based transparent and conducting thin films

We measured and modeled the electrical, optical and thermal properties of transparent and conducting thin films based on graphene and graphitic platelets. Thermal conductivity of our films decreases with increasing electrical conductivity. Our experiments indicate that, for sufficiently large platelets, the influence factor in controlling the thermal conductivity is represented by the junctions between neighboring graphene platelets. The thickness of such junctions is determined by the average number of graphene layers (N) forming each platelet. The fact that both the thermal and electrical properties depend on N allows us to establish a model that leads to a theoretical relationship between the thermal and electrical conductivity in our samples, which is general enough to be applied to a large class of graphene-based thin films.