Development of a simple method for fabrication of transparent conductive films with high mechanical strength

Abstract

We have developed a simple method of fabricating transparent conductive films with a high mechanical strength on glass and indium tin oxide substrates. It does not require a large excess of organic solvents and polymerization catalysts and can yield smooth films by spin-coating of a mixture of a commercially available aqueous dispersion of poly(3,4-ethylenedioxythiophene)-poly(4-styrene sulfonate) and a neat liquid of tetraethyl orthosilicate. Preparation conditions such as feed ratio, kinds of additives, and annealing temperature and time were optimized to give highly conductive, transparent and mechanically strong films.     

Fabrication of conducting poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) thin films by ultrasonic spray-assisted mist deposition method

Transparent conducting polymer, poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) thin films were fabricated by a vapor-deposition technique, ultrasonic spray-assisted mist deposition method. The thickness was well controlled from 40 to 600 nm, keeping reasonable conductivity of 300-450 S/cm. The films with thickness less than 180 nm have high (> 80%) transmission over a wide (270-800 nm) spectral region. In addition, formation of ring-dot electrode pattern with a hard-mask was demonstrated, achieving lithography-less patterning. The results encourage that this deposition method is developed as an actual process technology of transparent electrodes in devices.     

Experimental study of culture for mouse fibroblast used conductive polymer films

The purpose of this study is to develop electrodes for electrical stimulation of the nervous system using conductive polymers, polypyrrole (PPy) and/or poly(3,4-ethylenedioxythiophene), PEDOT. We evaluated biocompatibility in fibroblast and/or myoblast of mouse. Cultured cells on PPy and/or PEDOT extended their neuritis and survived over a week. These experiments have demonstrated that conductive polymers such as PPy, PEDOT, etc. have high biocompatibility, and PPy and/or PEDOT are applicable to nerve stimulation electrodes.     

Drift in the resistance of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) printed films during thermal cycling

We report on the investigation of the suitability of printed poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) films for temperature sensing devices. Gravure printing with the advantage of low cost production was used to prepare thin films of PEDOT:PSS on a flexible foil substrate. The electrical resistance was studied during thermal cycling and exposure to elevated constant temperatures. A drift of the resistance which depends on time, temperature and sample makes the usage as simple temperature sensors not possible. However, a closer look on the drift of relative resistances reveals that integrated temperature-time-profiles can be measured, which might be interesting in connection with monitoring of conditions of storing and transport of sensitive goods.     

A hybrid material of graphene and poly (3,4-ethyldioxythiophene) with high conductivity, flexibility, and transparency

A novel hybrid material prepared from graphene and poly (3,4-ethyldioxythiophene) (PEDOT) shows excellent transparency, electrical conductivity, and good flexibility, together with high thermal stability and is easily processed in both water and organic solvents. Conductivities of the order of 0.2 S/cm and light transmittance of greater than 80% in the 400–1800 nm wavelength range were observed for films with thickness of tens of nm. Practical applications in a variety of optoelectronic devices are thus expected for this transparent and flexible conducting graphene-based hybrid material. Electronic Supplementary Material  Supplementary material is available in the online version of this article at http://dx.doi.org/ and is accessible free of charge.     

Synthesis of c-axis preferred orientation ZnO:Al transparent conductive thin films using a novel solvent method

Transparent aluminum doped zinc oxide (ZnO:Al, AZO) conducting thin films with a high-preferential c-axis orientation were synthesized using a new sol-gel formula. The films were deposited using a spin-coating route onto borosilicate glass substrates. We used propylene glycol methyl ether (PGME) as the solvent in place of ethylene glycol monomethyl ether (EGME), which is commonly used because it is easier to deposit onto the substrates. PGME is also superior in terms of health and safety. PGME solvent does not need to settle for several days before use and can be spin-coated as soon as the raw material and solvent are mixed. The effects of this novel solvent on the structural, morphological, electrical and optical properties are discussed using XRD, SEM, a four-point probe and UV-VIS spectrophotometry. It was found that the films produced with PGME showed a high-preferential c-axis orientation and compact microstructure in comparison films produced using EGME. The electrical resistivity of AZO thin films produced with PGME solvent was lowered to 3.474 × 10^− 3Ω cm after annealing in 95 N₂/5H₂ atmosphere. In addition, the optical transmittances of AZO thin films on glass plates were higher than 90% in the visible wavelength region.     

Reliability assessment of a tanker using the model correction factor method based on the IACS-CSR requirement for hull girder ultimate strength

The model correction factor method (MCFM) is adopted to assess the reliability of a Suezmax oil tanker considering the ultimate vertical bending moment capacity of the hull girder as a limit state. The approach uses the incremental iterative method proposed by the International Association of Classification Societies (IACS) Common Structural Rules (CSR) to evaluate the hull girder ultimate strength as a response model that is calibrated iteratively at the design points calculated by the First Order Reliability method (FORM) by means of advanced non-linear Finite Element Analyses (FEA). The considered loads are the still water and the wave-induced bending moments in a typical seagoing operational condition of the oil tanker in the full load and ballast load conditions. First, the predictions of the hull girder bending capacities calculated by the IACS-CSR method and by non-linear FEA are compared and then the efficiency of the MCFM for hull girder reliability problems is illustrated. It is shown that using semi-empirical response models, which include the important mechanical features with respect to the bending capacity of the ship hull girder, the reliability evaluation can be performed with a limited number of non-linear FEAs (less than 10) promoting the application of advanced response and reliability methods to complex structures.     

A method for the preparation of PMMA-SiO2 nanocomposites with high homogeneity

It is possible to optimize the performance of the inorganic-organic composites dispersing the inorganic component in the organic matrix on a nanomiter length scale. If dry the inorganic phase cannot be intimately dispersed during the incorporation in the matrix. When the particle surface is organically modified, and the incorporation is made starting from a liquid dispersion (particles in polymer solution), the resulting composites exhibit an excellent homogeneity. Here, monolithic [poly(methyl methacrylate)/monodisperse silica particles] nanocomposites have been prepared and characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), dynamic light scattering (DLS), micro-hardness, and differential scanning calorimetry (DSC).     

Facile fabrication of ultrathin freestanding nanoporous Cu and Cu-Ag films with high SERS sensitivity by dealloying Mg-Cu(Ag)-Gd metallic glasses

Nanoporous metals prepared by dealloying have attracted increasing attention due to their interesting size-dependent physical,chemical,and biological properties.However,facile fabrication of metallic ultra-thin freestanding nanoporous films(UF-NPFs)by dealloying is still challenging.Herein,we report a novel strategy of facile preparation of flexible Cu,Cu3Ag,and CuAg UF-NPFs by dealloying thick Mg-Cu(Ag)-Gd metallic glass ribbons.During dealloying,the local reaction latent heat-induced glass transition of the precursor ribbons leads to the formation of a solid/liquid interface between the initially dealloyed nanoporous layer and the underlying supercooled liquid layer.Due to the bulging effect of in situ gen-erated H2 on the solid/liquid interface,Cu,Cu3Ag,and CuAg UF-NPFs with thicknesses of～200 nm can self-peel off from the outer surface of the dealloying ribbons.Moreover,it was found that the surface-enhanced Raman scattering(SERS)detection limit of Rhodamine 6G(R6G)on the Cu and CuAg UF-NPF substrates are 10-6 M and 10-11 M,respectively,which are lower than most of the Cu and Cu-Ag sub-strates prepared by other methods.This work presents a reliable simple strategy to synthesize a variety of cost effective and flexible metallic UF-NPFs for functional applications.     

Preparation of high quality spray-deposited fluorine-doped tin oxide thin films using dilute di(n-butyl)tin(iv) diacetate precursor solutions

Fluorine-doped tin oxide (FTO) thin films were prepared, at different substrate temperatures, using dilute precursor solutions of di(n-butyl)tin(iv) diacetate (0.1 M DBTDA) by varying the F⁻ concentration in the solution. It is noticed that conductivity of FTO film is increasing by increasing the fluorine amount in the solution. Morphology of SEM image reveals that grain size and its distribution are totally affected by the substrate temperature in which conductivity is altered. Among these FTO films, the best film obtained gives an electronic conductivity of 31.85 × 10² Ω^− 1 cm^− 1, sheet resistance of 4.4 Ω/□ (ρ = 3.14 × 10^− 4 Ω cm) with over 80% average normal transmittance between the 400 and 800 nm wavelength range. The best FTO film consists of a large distribution of grain sizes from 50 nm to 400 nm range and the optimum conditions used are 0.1 M DBTDA, 0.3 M ammonium fluoride, in a mixture of propan-2-ol and water, at 470 °C substrate temperature. The large distribution of grain sizes can be easily obtained using low DBTDA concentration (~ 0.1 M or less) and moderate substrate temperature (470 °C).     

Development of fast fabrication method for cylindrical-shaped grids and mechanical properties of CFRP pressure vessel reinforced with cylindrical-shaped grids

In order to reduce carbon dioxide and air pollution emissions, fuel cell vehicles (FCVs) are being developed, and CFRP pressure vessels have been used as the hydrogen storage systems for the FCVs. Since the FCVs are expected to increase driving distances of at least over 500 km, which is similar to those of conventional gasoline-fueled vehicles, the storage pressure of hydrogen must be raised from 35 to 70 MPa. It is important to decrease the amount of carbon fibers in order to reduce the cost and weight of the CFRP pressure vessels. In this study, a fast fabrication method for the cylindrical-shaped grids (CSG) composed of hoop stiffeners and helical stiffeners was developed with a particular mandrel and a 3-axis filament winding apparatus. Then, the CFRP pressure vessel was inserted into the CSG, and burst tests of the CFRP pressure vessels reinforced with and without the CSG were conducted. Moreover, their experimental results were compared with numerical ones obtained by a FEM analysis, and the mechanical properties and the reinforcement effects of the CFRP pressure vessels reinforced with the CSG were investigated.     

Effects of different sealing conditions on the seal strength of polypropylene films coated with a bio‐based thin layer

This paper presents the results of an investigation through the design of experiment technique regarding the influence of temperature, dwell time and bar pressure on the heat seal strength of oriented polypropylene films coated with a gelatin‐based thin layer. This chemometric approach allowed achieving a thorough understanding of the effect of each independent factor on the two different responses (maximum force and strain energy) considered in this work as a measure of the strength necessary to break the bond across the sealed interface. Surprisingly, the factor affecting both responses the most was the bar pressure rather than the sealing temperature. Moreover, whereas the bar pressure negatively affected the seal strength of coated polypropylene films, the sealing temperature had a positive effect. Dwell time did not have any significant influence as a main factor, while influencing negatively the seal strength as an interaction term (i.e. time × pressure), together with the further interaction temperature × pressure. The mathematical models obtained for the two responses provided different results in terms of fitting capability (R²) and prediction ability (Q²). In particular, for the maximum force response, R² and Q² were equal to 0.571 and 0.405, respectively, whereas the model supporting the strain energy response gave R² = 0.932 and Q² = 0.937, highlighting that for quantifying the seal strength, the energy necessary to break a seal is a better measure than the maximum force. The highest seal strength values obtained during this work were of 0.6615 N and 19.6 N·mm for maximum force and strain energy, respectively. Copyright © 2009 John Wiley & Sons, Ltd.     

Effect of ionic liquid dispersion on performance of a conducting polymer based Schottky diode

The effect of ionic liquid (IL) dispersion on the performance of Schottky diode fabricated with poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) has been investigated. Two kinds of ILs including 1-butyl-3-methylimidazolium hexafluorophosphate (BMIPF6, hydrophobic IL) and 1-butyl-3-methylimidazolium chloride (BMICL, hydrophilic IL) were dispersed to the PEDOT:PSS by mechanical stirring and sonication processes. Schottky diodes were fabricated with these mixtures. The forward current of Schottky diodes fabricated with PEDOT:PSS dispersed BMI PF6 (SD-BMIPF6)/BMICL (SD-BMICL) by mechanical stirring is slightly reduced compared with that of Schottky diodes fabricated with pristine PEDOT:PSS (SD-PEDOT). However, SD-BMIPF6 and SD-BMICL by sonication technique show higher forward current with respect to SD-PEDOT. Compared with SD-BMIPF6 and SD-BMICL, the forward current of SD-BMICL is much higher than that of SD-BMIPF6. Since the BMICL has hydrophilic nature, the enhancement of forward current might be due to the uniform dispersion of the BMICL on the PEDOT:PSS matrix.     

Development of a new quantification method for a fire PSA

For an internal fire analysis, fire scenarios are developed carefully and quantified in a sequential and iterative way in a traditional fire Probabilistic Safety Assessment (PSA). However, there has been no proven explicit method to avoid these iterative quantifications till now. This study presents the Jung's Single Top And Run (JSTAR) method that facilitates a simultaneous single quantification of all fire scenarios. The JSTAR method could be employed at the fire PSA phases of a quantitative screening or detailed analysis. Using the JSTAR method, accurate fire risks of a fault tree that has many negates could be calculated by avoiding the frequent house event propagations of the fire scenario conditions. Furthermore, the proposed JSTAR method is a simple and explicit method to build a single-top external event PSA model for a risk-monitoring system.The JSTAR method could be implemented easily by developing a small automatic conversion tool. Depending on the maintenance policy of a fire PSA model, a single-top fire PSA model that is created by the conversion tool could be maintained permanently or it could be temporarily generated and discarded. The use of the JSTAR method is recommended for all external event PSAs such as an internal flooding risk analysis.     

Development of a liquid extraction method and comparison with dynamic thermal stripping–thermal desorption (DTS–TD) method: sorption of D‐limonene by flexible packaging films

The sorption of D ‐limonene into polymeric structures in contact with food simulant liquids (ethanol and acetic acid solutions) was determined using two methods, liquid extraction (LE) and dynamic thermal stripping–thermal desorption (DTS–TD). The polymeric films studied were PP (polypropylene), PE/nylon/EVOH/PE (polyethylene/nylon/ethylene vinyl alcohol/polyethylene) and metPET/VA EVA/LLDPE (metallized polyethylene terephthalate/ethylenevinyl acetate/linear low density polyethylene). Our assessment showed that both LE and DTS–TD techniques are valuable procedures. LE was evaluated as an alternative method with the advantage of being a simplified process. It was possible to measure the amount of D ‐limonene in the polymers using both methods. Correlation between methods was >82% and for the single layer polymers >92%. The respective sorption values obtained by the two methods were also found to be in good agreement. LE is simple and rapid to perform and, in general, gives slightly lower results compared to DTS–TS sorption tests conducted with adequate food simulants. The results indicate that the liquid extraction method is an excellent technique for the determination of sorbate concentration in polymeric structures. Copyright © 2004 John Wiley & Sons, Ltd.     

Numerical fatigue life analysis of a high frequency mechanical impact treated industrial component based on damage mechanics models

After post weld treatment with high frequency mechanical impact (HFMI) treatment of welds, a significant increase of fatigue life (up to a factor of 10) can be achieved. During the last years numerous experimental tests of welded joints with simple geometry under constant amplitude loading have been performed to quantify the positive effect of high frequency mechanical impact treatment. Due to the lack of methods for the prediction of the high frequency mechanical impact benefits, a widespread use of this process is not the case yet. Furthermore, it is still not clear if the results of these fatigue tests can be transferred to complex geometries and complex loading conditions such as in industrial applications. Therefore, an approach to assess the fatigue life of complex welded structures under variable amplitude loading was developed. For this purpose, high frequency mechanical impact treatment and fatigue load of simple welded specimen made of S690QL steel were simulated with finite element analysis (FEA) firstly. Then, the needed damage parameters for the fatigue life correlation were evaluated from the finite element post‐processing. The calculated life time to crack initiation was in good agreement with the experimental fatigue test results. In the next step, this procedure was implemented on a welded arm of an evacuator of type EW180B of the company Volvo Construction Equipment made of S700MC. The variable amplitude load measured under real service condition was transferred to single constant amplitude load cycles using a rainflow‐counting algorithm. By simulation and damage mechanics evaluation of each load cycle the total damage sum could be calculated and compared with the experimental results from Volvo Construction Equipment.     

Optimization of Polishing Parameters with Taguchi Method for LBO Crystal in CMP

Chemical mechanical polishing(CMP)was used to polish Lithium triborate(LiB3O5 or LBO)crystal.Taguchi method was applied for optimization of the polishing parameters.Material removal rate(MRR)and surface roughness are considered as criteria for the optimization.The polishing pressure,the abrasive concentration and the table velocity are important parameters which influence MRR and surface roughness in CMP of LBO crystal.Experiment results indicate that for MRR the polishing pressure is the most significant p...     

Determination of the high c/a ratio of hexagonal metals with a semi-empirical tight-binding method

A semi-empirical tight-binding potential is developed to reproduce the high c/a ratio of zinc and cadmium. In this scheme, we show that the calculation of the electronic energy by the standard recursion method with the Harrison model for the hopping integrals and their radius dependence is not able to predict c/a values higher than the ideal one . Only, the recursion method limited to first neighbours has permitted to get the right c/a ratio of zinc and cadmium. The calculated energies of different structures (2H, 4H, 6H and 3C) show that the hexagonal compact structure (2H) is always most stable.