High Mechanical Adhesion Research Articles

Nanocarbon ohmic electrodes fabricated by coaxial arc plasma deposition for phosphorus-doped diamond electronics application

n-Type (phosphorus-doped) diamond is a promising material for diamond-based electronic devices. However, realizing good ohmic contacts for phosphorus-doped diamonds limits their applications. Thus, the search for non-conventional ohmic contacts has become a hot topic for many researchers. In this work, nanocarbon ohmic electrodes with enhanced carrier collection efficiency were deposited by coaxial arc plasma deposition. The fabricated nanocarbon ohmic electrodes were extensively examined in terms of specific contact resistance and corrosion resistance. The circular transmission line model theory was used to estimate the charge collection efficiency of the nanocarbon ohmic electrodes in terms of specific contact resistance at a specific voltage range (5–10 V); they exhibited a specific contact resistance of 1 × 10−3 Ωcm2. The result revealed one order reduction in the specific contact resistance and, consequently, a potential drop at the diamond/electrode interface compared to the conventional Ti electrodes. Moreover, the fabricated nanocarbon electrodes exhibited high mechanical adhesion and chemical inertness over repeated acid treatments. In device applications, the nanocarbon electrodes were evaluated for Ni/n-type diamond Schottky diodes, and they exhibited nearly one order enhancement in the rectification ratio and a fast charge collection at lower biasing voltages.

Custom-made lipid nanotubes as a tissue and hydrogel adhesive

Recently, nanomaterial-based adhesives have arised as alternatives to be used in the industrial field or to provide the next generation of biomedical adhesives with their enhanced mechanical properties and adhesion strengths. In this work, we developed a method for achieving adhesion between two PDMA (Poly dimethylacrylamide) hydrogel surfaces by using different nanomaterial-based adhesive dispersions with different sizes and shapes that have high mechanical adhesion strength. We obtained a new adhesive consisting of a lipid-based nanotube formed by the special custom-made molecule AQua (C25H29NO4) and measured the adhesion force between the hydrogel surfaces. Our results revealed that lipid AQua nanotube dispersions, which also has a high potential as drug delivery agents, showed efficient adhesion by strongly binding the hydrogel strips together and exhibit better adhesive effects in comparison with other nanomaterials that are used for this purpose. This high adhesion capability is also valid for various hydrogels that have different chemical properties or rigidities and soft tissues such as calf livers. So, the system developed here is believed to have a usage potential in different industrial and biomedical areas.

Determination of Mechanical Adhesion Energy of Thermal Oxide Scales on Steel Produced from Medium and Thin Slabs Using Tensile Test

The mechanical adhesion of thermal oxide scales formed on industrial hot-rolled steel strips produced through the electric-arc-furnace route was studied. The samples as-received steel were prepared with the specific shape fitting to the micro-tensile machine in the SEM chamber for observation of surface failure during the test. It was found that oxide transverse cracking and scale spallation are observed. This paper also presented a theoretical model for evaluate adhesion energy from strain and stress values at the first spallation. It was found that the oxide scales on the medium slab exhibited high mechanical adhesion energy. This might be due to the existence of oxide contained Si at steel-scale interfaces. It can promote adhesive interactions between steel-scale interfaces.

Fabrication of highly electro catalytic active layer of multi walled carbon nanotube/enzyme for Pt-free dye sensitized solar cells

Highly dispersed conductive suspensions of multi walled carbon nanotubes (MWCNT) can have intrinsic electrical and electrochemical characteristics, which make them useful candidate for platinum (Pt)-free, dye sensitized solar cells (DSSCs). High energy conversion efficiency of 7.52% is demonstrated in DSSCs, based on enzyme dispersed MWCNT (E-MWCNT) layer deposited on fluorine doped tin oxide (FTO) glass. The E-MWCNT layer shows a pivotal role as platform to reduce large amount of iodide species via electro catalytically active layer, fabricated by facile tape casting under air drying technique. The E-MWCNT layer with large surface area, high mechanical adhesion, and good interconnectivity is derived from an appropriate enzyme dispersion, which provides not only enhanced interaction sites for the electrolyte/counter electrode interface but also improved electron transport mechanism. The surface morphology and structural characterization were investigated using field emission-scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), x-ray photoelectron spectroscopy (XPS), Raman spectroscopy and electronic microscopy techniques. Electro catalytic activity (ECA) and electrochemical properties of E-MWCNT counter electrode (CE) were investigated using cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) measurements. The high power conversion efficiency (PCE) of E-MWCNT CE is associated with the low charge transfer resistance (RCT=1.39Ωcm2) and excellent electro catalytic activity on the redox of the iodide/tri-iodide pair, as discovered by the cyclic voltammetry and electrochemical impedance spectroscopy investigations. This facile E-MWCNT configuration provides a concrete fundamental background towards the development of the third generation photovoltaic devices.

Excellent field emission properties from carbon nanotube field emitters fabricated using a filtration-taping method

Abstract A filtration-taping method was demonstrated to fabricate carbon nanotube (CNT) emitters. This method shows many good features, including high mechanical adhesion, good electrical contact, low temperature, organic-free, low cost, large size, and suitability for various CNT materials and substrates. These good features promise an advanced field emission performance with a turn-on field of 0.88 V/mm at a current density of 0.1 mA/cm 2 , a threshold field of 1.98 V/mm at a current density of 1 mA/cm 2 , and a good stability of over 20 h. The filtration-taping technique is an effective way to realize low-cost, large-size, and high-performance CNT emitters. Key words: field emission properties, carbon nanotube, filtration-taping method 1. Introduction Due to their unique geometry and physical properties, carbon nanotubes (CNTs) are currently being investigated as next-generation field emitter materials for cold cathodes. Numerous papers can be found on field emission applications such as field emission displays, lamps, X-ray sources, high-resolution electron-beam instruments, and microwave amplifiers [1-5]. Up to now, various techniques have been developed for fabricating CNT field emitters using as-grown, spraying, electrophoresis, screen-printing, and attaching individual CNTs on tungsten probe methods, etc. [6-10]. However, these techniques suffer from weak me-chanical adhesion between CNT emitters and the cathode, or severe degradation of CNT emitters due to the organic binders used in the process, which lead to a short lifetime. There-fore, an efficient and organic binder-free technique for fabricating CNT emitters is still a great challenge. In this letter, we demonstrate an advanced organic-free technique named the filtration-taping method. The filtration-taping method is suitable to fabricate simple, large, and cost-effective CNT emitters that can ensure a high mechanical adhesion, good electri-cal contact, and damage-free CNT tips, resulting in enhanced field emission properties and excellent stability.

Gold nanoparticle thin films fabricated by electrophoretic deposition method for highly sensitive SERS application

We report an electrophoretic deposition method for the fabrication of gold nanoparticle (GNP) thin films as sensitive surface-enhanced Raman scattering (SERS) substrates. In this method, GNP sol, synthesized by a seed-mediated growth approach, and indium tin oxide (ITO) glass substrates were utilized as an electrophoretic solution and electrodes, respectively. From the scanning electron microscopy analysis, we found that the density of GNPs deposited on ITO glass substrates increases with prolonged electrophoresis time. The films possess high mechanical adhesion strength and exhibit strong localized surface plasmon resonance (LSPR) effect by showing high SERS sensitivity to detect 1 × 10−7 M rhodamine 6 G in methanol solution. Finally, the relationship between Raman signal amplification capability and GNP deposition density has been further investigated. The results of our experiment indicate that the high-density GNP film shows relatively higher signal amplification capability due to the strong LSPR effect in narrow gap regions between the neighboring particles on the film.

Toner Adhesion Measurement

Toner adhesion to printer components is an important factor in determining the force needed for good image quality. Controversy remains as to the dominance of electrical or mechanical (Van der Waals) forces as force measurements have yielded a large range of results. A new measurement tool has been developed to measure the cumulative distribution of toner adhesion from toner transferred onto an intermediate belt. The tool consists of a metered pulse of air directed perpendicularly onto a toner isopel pattern. Printed thin lines of toner were used to calibrate isopel removal to known air force. Air velocity at toner level was found through Navier-Stokes. Resulting removal distributions correlate to transfer field parameters. The last few percent of toner remain attached to the substrate due to toner damage which results in high mechanical adhesion.

The use of polyolefins-based hot melts for wood bonding

The shear strength of three-layer birch veneer/polyolefin/birch veneer lap joints has been investigated. It was found that the optimum technological parameters for producing three-layer laminated systems (plywood) at 180°C were a pressure time of 1-3 min (plus 3-min preheating) and pressure of 5-10 MPa. All the systems investigated exhibited relatively high values of shear strength, which were higher than those of the industrially produced plywood based on phenol-formaldehyde glues (3.5-5 MPa). It is shown that the use of interfacial modifiers can increase the shear strength by 50% compared with its initial values. The high shear resistance is explained by the high mechanical adhesion between the hot melts and the wood substrate. After a prolonged moisture influence (70 days at relative air humidity of 80%), all the systems investigated showed a considerable (up to 25%) increase in the shear strength. This can be explained by swelling of birch veneer, which gives rise to additional resistance forces between the hot melt and the substrate.

Determination of mechanical adhesion energy of thermal oxide scales on AISI 430Ti alloy using tensile test

The present paper deals with mechanical adhesion energy determination of thermal oxide scales on metallic alloys. AISI 430Ti alloy (Fe–18Cr–0·4Ti–0·5Si, wt-%) was isothermally oxidised at 900°C in Ar–20%O2 atmosphere to grow thermal oxide scales of various thickness. These oxide/metal systems were subjected to room temperature in situ tensile test in the SEM chamber allowing continuous observation of surface failure during the test. Characteristic observations were oxide transverse cracking and scale spallation. A theoretical model was developed to quantify stress and strain evolution in oxide during the test, allowing to derive adhesion energy from strain and stress values at spallation onset. It was found that oxide scales on AISI 430Ti exhibited high mechanical adhesion energy, decreasing from 163 to 38 J m−2 with increasing oxide thickness in the range from 0·3 to 2·2 μm. Excellent agreement was observed with adhesion energy values obtained using the inverted blister test on the same alloy.

Coating plywood with a thermoplastic

This work presents a method for the surfacing of wood sheets such as plywood with melt processable thermoplastic using extrusion coating. The method uses a direct coating of the plywood with a very hot low-viscosity coating. During the coating, the pressure of the melt is kept as low as possible. These factors produce a very high mechanical adhesion between the coating and the wood. In addition, the coating method uses a tool for preventing the formation of holes in the surface by the penetration of air expanding and water evaporating from the wood pores through the coating. In this work the method was applied to coating plywood with a copolymer of polypropylene. The adhesion between the wood and the polypropylene was improved by blending the polypropylene with maleated polypropylene wax. The experiments showed that the method produces sound and smooth polypropylene coated plywood. Addition of a modifying agent improves the adhesion between the polypropylene and the wood.