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Copper oxide films were reduced to copper with an atmospheric pressure argon and hydrogen plasma at temperatures between 25 and 300 °C. A 50-nm-thick CuO layer on a Cu-coated Si wafer, 200 mm in diameter, was fully reduced by the plasma in 200 s at 200 °C. The activation energy for the reaction was found to be 3.7 kcal/mol. X-ray photoelectron spectroscopy confirmed that the copper oxide was reduced to metallic copper. Cross-sectional scanning electron microscopy revealed that voids appeared between the oxide and the base metal layer when the CuO was thicker than 20 nm. These voids remained at the interface after reduction of the copper oxide back to copper metal.

In this report, networks of carbon nanotubes (CNTs) are transformed into composite yarns by infusion, mechanical consolidation and polymerization of dicyclopentadiene (DCPD). The microstructures of the CNT yarn and its composite are characterized by scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), and a focused ion beam used for cross-sectioning. Pristine yarns have tensile strength, modulus and elongation at failure of 0.8 GPa, 14 GPa and 14.0%, respectively. In the composite yarn, these values are significantly enhanced to 1.2 GPa, 68 GPa and 3.4%, respectively. Owing to the consolidation and alignment improvement, its electrical conductivity was increased from 1.0 × 105 S/m (raw yarn) to 5.0 × 105 S/m and 5.3 × 105 S/m for twisted yarn and composite yarn, respectively. The strengthening mechanism is attributed to the binding of the DCPD polymer, which acts as a capstan and increases frictional forces within the nanotube bundles, making it more difficult to pull them apart.

Nutplates are commonly used on aircraft to allow installation and removal of components and panels for maintenance and repair. The use of bonded nutplates over riveted ones reduces manufacturing complexity and leads to weight savings. In this work, plasma surface preparation has been examined for bonding stainless steel nutplates to aluminum structures. Preparation of these bond surfaces is often accomplished through an abrasion process or using only a solvent wipe. These methods are difficult to control and can lead to variation in the performance of bonded nutplates. Successful installation of bonded nutplates requires the generation of a highly clean and active bonding surface. A small, portable plasma device was used to clean individual nutplates within a few seconds. In addition, a handheld plasma tool was used to prepare the nutplate installation site. The plasma process eliminates operator variability by removing surface contaminants in a matter of seconds with no other cleaning steps required. The bond surface is rendered active for bonding and converted to a high surface energy, hydrophilic state. This new technology eliminates interfacial bond failures while increasing push-off strength from 441 +/- 34 lbs to 845 +/- 74 lbs and torque-out strength from 100 +/- 18 in.lbs to 159 +/- 27 in.lbs when compared with abrasion. Furthermore, the plasma has been shown to reduce preparation time, decrease variability and lower the instances of nutplate failures both in manufacturing and in the aircraft service environment. Transitioning to a plasma-based surface preparation thereby offers the potential to save millions of dollars over the life cycle of an aircraft.

The creation of more robust biocompatible printed electronics devices requires an understanding of interactions between conductive inks and substrates to achieve desired printing and functional properties. In this study, we present a water-based conductive ink that can provide a readily achieved thin film deposition on a highly hydrophobic surface such as poly(dimethylsiloxane) (PDMS). We also show that surface treatments with atmospheric plasma can be utilized to tailor the surface energy of hydrophobic substrates to improve the deposition of inks not custom made for such applications. By using a tailored Ag nano-particle ink, we have successfully printed conductive traces onto a hydrophobic (PDMS) substrate without any surface modification. It was also shown that when introducing atmospheric plasma treatment to the PDMS substrate prior to printing with the tailored ink poor printing resulted. The proposed mechanism for the cause of this poor wetting and deposition is an adverse interaction between the ink and PDMS surface caused by surface oxidation resultant of plasma treatment. The results show that the generally accepted rule that a difference between the substrate and ink surface energy of 10 mN/m for good print quality does not necessarily hold true in the case of functional printing.

On the occasion of Alexis T. Bell's fiftieth year at Berkeley, we are honored to discuss a few aspects of his extensive contributions to catalysis, reaction engineering, and understanding of molecular-scale structure in catalytic processes. The illustrations provided here help reveal some of his traits most valued by our community: a drive to employ the best methods of instrumentational and computational analysis available; the instinct to search for the essence of the most important problems at hand, and the skill to write about them with exceptional clarity; and the formation and nurturing of collaborative teams to focus on the most essential questions.

Wide angle X-Ray scattering was used to measure the progression of alignment when stretching carbon nanotube (CNT) sheets. The nanotubes were grown by an aerogel chemical vapor deposition process and drawn onto a drum rotating at a draw rate of 15 m/min to form a sheet. Samples were cut from this sheet at 0 degrees, 10 degrees, 25 degrees, 45 degrees and 90 degrees with respect to the drawing direction. Samples stretched along the drawing direction reached 28% elongation at failure, whereas samples stretched 90 degrees to the drawing direction reached 44% elongation at failure. In spite of this, the 0 degrees sample had 50% of its nanotubes aligned along the stretching axis, while the 90 degrees sample had 40% of its nanotubes aligned within +/- 10 degrees of the stretching axis. The strength and modulus of samples cut along the growth direction were 1.8x and 4.9x higher than those cut in the 90 degrees direction, with a smooth drop in strength observed as the cutting direction increased from 0 degrees to 90 degrees. This work reveals the relationship between sheet scale deformation and micro scale CNT reorientation. (C) 2016 Elsevier Ltd. All rights reserved.

Transitional metal oxides hold great potential for high capacity anodes. However, the low electron conductivity of such materials leads to poor cycling stability and inferior rate capability. We reported herein the use of a novel hydrogen plasma technology to improve the conductance of metal oxides, which leads great success in improving the rate performance of CuO nanotube based anodes. This method has the potential to be widely adopted in the field of lithium ion batteries and supercapacitors.

A low-temperature, atmospheric pressure helium and oxygen plasma has been used for the surface preparation of aluminum 2024 prior to adhesive bonding. The plasma converted the aluminum from a water contact angle (WCA) of 79 degrees to down to 38 degrees within 5 s of exposure, while sanding reduced the WCA to only 51 degrees. Characterization of the aluminum surface by X-ray photoelectron spectroscopy revealed a decrease in carbon contamination from 70 to 36% and an increase in the oxygen content from 22 to 50% following plasma treatment. Similar trends were observed for sanded surfaces. Lap shear results demonstrated bond strengths of 30 +/- 2 MPa for the sanded aluminum vs. 33 +/- 1 MPa for plasma-treated aluminum, where sol-gel and primer coatings were added to the surface preparation. Following seven days of aging, wedge crack extension tests revealed cohesive failure percentages of 86, 92, and 96% for sanded, plasma-treated, and sanded/plasma-treated aluminum, respectively. These results indicate that atmospheric pressure plasmas are an attractive alternative to acid treatment or abrasion techniques for surface preparation prior to bonding.

An atmospheric pressure helium and oxygen plasma has been used for the surface preparation of 410 stainless steel and carbon-fiber epoxy laminates prior to bonding to themselves or to each other. Lap shear results for stainless steel coupons and carbon-fiber epoxy laminates demonstrated an 80% and a 150% increase in bond strength, respectively, after plasma activation. Following 7 days of aging, wedge crack extension tests revealed a crack extension length of 7.0 mm and 2.5 mm for the untreated and plasma-activated steel. The untreated stainless steel had 30% cohesive failure compared to 97% for steel activated with the plasma. Surface analysis by X-ray photoelectron spectroscopy showed that carbonaceous contamination was removed by plasma treatment, and specific functional groups, e.g. carboxylic acids, were formed on the surface. These functional groups promoted strong chemical bonding to the epoxy film adhesive. Atmospheric pressure plasmas are an attractive alternative to abrasion techniques for surface preparation prior to bonding.

The treatment of polymer surfaces with atmospheric pressure and vacuum plasmas for enhanced adhesion is examined in this chapter. Poor wetting and adhesion can occur in microelectronic packages in key manufacturing steps such as applying epoxy molding compound to the substrate and applying epoxy underfill to the flip chip module. Low-pressure plasmas have long been utilized by the packaging industry to activate polymer surfaces prior to bonding. However, atmospheric pressure plasmas (APPs) have been developed which provide reactive species concentrations that are several thousand times higher than in vacuum plasmas, which suggests that the APP treatment may provide higher process throughput. Here, the physics and chemistry of atmospheric and vacuum discharges are examined. Then a rigorous comparison is made between these two technologies for the activation of flame-retardant 4 (FR-4) and polyimide substrates for adhesion to epoxy underfill. The data indicate that both low-pressure and atmospheric pressure plasmas are well suited for enhancing adhesion. The selection of one method over the other should be based on other considerations, such as throughput, cost, and yield.

In order to avoid using polyvinyl alcohol (PVA), an eco-friendly sizing technology with atmospheric pressure plasma treatment and green sizing recipes has been developed and evaluated with respect to sizing properties and desizing efficiency. The results show that the eco-friendly sizing technology can endow cotton yarn with better sizing properties, including significantly improved size-pick-up, breaking strength, breaking elongation, abrasion resistance and substantially reduced yarn hair, than the traditional sizing technology with the use of PVA. Compared with a typical traditional sizing technology using PVA and modified starch, the optimized eco-friendly sizing technology can impart the yarn an increase of 19.4%, 5.3%, 3.4% and 169.2% for the size-pick-up, breaking strength, breaking elongation and the abrasion resistance time, respectively, and a reduction of 59.3% for the yarn hairiness index value at level 1. The sizing properties can be obviously improved by the atmospheric pressure plasma treatment, which can roughen the fiber surface, etch away the hydrophobic cuticle layer and introduce polar groups. The glycerol in the green sizing recipes can effectively reduce the yarn hairiness and increase size-pick-up and abrasion resistance. The eco-friendly sizing technology has no observable negative influence on desizing of cotton fabrics. Furthermore, a better water diffusion in the fabric can be achieved because of the improved hydrophilicity by using the plasma treatment.

Carbon nanotube yarn and sheet were activated using radio frequency, atmospheric pressure, helium and oxygen plasmas. The nanotubes were exposed to the plasma afterglow, which contained 8.0×1016cm−3 ground state O atoms, 8.0×1016cm−3 metastable O2 (1Δg), and 1.0×1016cm−3 ozone. X-ray photoelectron spectroscopy and infrared spectroscopy revealed that 30s of plasma treatment converted 25.2% of the carbon atoms on the CNT surface to oxidized species, producing 17.0% alcohols, 5.9% carbonyls, and 2.3% carboxylic acids. The electrical resistivity increased linearly with the extent of oxidation of the CNT from 4 to 9×10−6Ωm. On the other hand, the tensile strength of the yarn was decreased by only 27% following plasma oxidation.

Gold rush: Nanoporous palladium particles are decorated with gold clusters by galvanic replacement. The bimetallic pPd@Au nanocatalysts feature a well-defined nanoporous morphology coupled to a highly accessible surface area with segregated Au clusters, and are highly active in both benzyl alcohol oxidation and formic acid electro-oxidation. The amount of Au in the catalyst system determines the extent of alloying as well as the accessibility to catalytically more active Pd surface atoms.

This innovation consists of a pyrotechnic initiator and piezoelectric initiation system. The device will be capable of being initiated mechanically; resisting initiation by EMF, RF, and EMI (electromagnetic field, radio frequency, and electromagnetic interference, respectively); and initiating in water environments and space environments. Current devices of this nature are initiated by the mechanical action of a firing pin against a primer. Primers historically are prone to failure. These failures are commonly known as misfires or hang-fires. In many cases, the primer shows the dent where the firing pin struck the primer, but the primer failed to fire. In devices such as "T" handles, which are commonly used to initiate the blowout of canopies, loss of function of the device may result in loss of crew. In devices such as flares or smoke generators, failure can result in failure to spot a downed pilot. The piezoelectrically initiated ignition system consists of a pyrotechnic device that plugs into a mechanical system (activator), which on activation, generates a high-voltage spark. The activator, when released, will strike a stack of electrically linked piezo crystals, generating a high-voltage, low-amperage current that is then conducted to the pyro-initiator. Within the initiator, an electrode releases a spark that passes through a pyrotechnic first-fire mixture, causing it to combust. The combustion of the first-fire initiates a primary pyrotechnic or explosive powder. If used in a "T" handle, the primary would ramp the speed of burn up to the speed of sound, generating a shock wave that would cause a high explosive to go "high order." In a flare or smoke generator, the secondary would produce the heat necessary to ignite the pyrotechnic mixture. The piezo activator subsystem is redundant in that a second stack of crystals would be struck at the same time with the same activation force, doubling the probability of a first strike spark generation. If the first activation fails to ignite, the device is capable of multiple attempts. Another unique aspect is in the design of the pyrotechnic device. There is an electrode that aids the generation of a directed spark and the use of a conductive matrix to support the first-fire material so that the spark will penetrate to the second electrode.

Adhesive bonding offers many advantages over mechanical fastening, but requires certification before it can be incorporated in primary structures for commercial aviation without disbond-arrestment features or redundant load paths. Surface preparation is widely recognized as the key step to producing robust and predictable adhesive bonds. Surface preparation by laser ablation provides an alternative to the expensive, hazardous, polluting, and less precise practices used currently such as chemical-dip, manual abrasion and grit blast. This report documents preliminary testing of a surface preparation technique using laser ablation as a replacement for the chemical etch and abrasive processes currently applied to Ti-6Al-4V alloy adherends. Surface roughness and surface chemical composition were characterized using interference microscopy and X-ray photoelectron spectroscopy, respectively. A technique for fluorescence visualization was developed which allowed for quantitative failure mode analysis. Wedge crack extension testing in a hot, humid environment indicated the relative effectiveness of various surface treatments. Increasing ablation duty cycle reduced crack propagation and adhesive failure. Single lap shear testing showed an increase in strength and durability as laser ablation duty cycle and power were increased. Chemical analyses showed trends for surface chemical species, which correlated with improved bond strength and durability.

A review is presented on the surface preparation of polymers and composites using atmospheric pressure plasmas. This is a promising technique for replacing traditional methods of surface preparation by abrasion. With suffi cient exposure to the plasma afterglow, polymer and composite surfaces are fully activated such that when bonded and cured with epoxy adhesives, they undergo 100% cohesive failure in the adhesive. Depending on the material, the lap shear strength and crack delamination resistance (GIC) can be increased several fold over that achieved by either solvent wiping or abrasion. In some cases, a plasma-responsive layer must be incorporated into the top resin layer of the composite to achieve maximum bond strength to the adhesive. Adhesion does not correlate well with water contact angle or surface roughness. Instead it correlates with the fraction of the polymer surface sites that are oxidized and converted into active functional groups, as determined by x-ray photoelectron spectroscopy and infrared spectroscopy.

Adhesive bonding offers many advantages over mechanical fastening, but requires certification before it can be incorporated in primary structures for commercial aviation without disbond-arrestment features or redundant load paths. Surface preparation is widely recognized as the key step to producing robust and predictable bonds. Laser ablation imparts both topographical and chemical changes to a surface which can lead to increased bond durability. A laser based process provides an alternative to chemical-dip, manual abrasion and grit blast treatments which are expensive, hazardous, polluting, and less precise. This report documents preliminary testing of a surface preparation technique using laser ablation as a replacement for the chemical etch and abrasive processes currently applied to Ti-6Al-4V alloy adherends. Failure mode, surface roughness, and chemical makeup were analyzed using fluorescence enhanced visualization, microscopy, and X-ray photoelectron spectroscopy, respectively. Single lap shear tests were conducted on bonded and aged specimens to observe bond strength retention and failure mode. Some promising results showed increasing strength and durability of lap shear specimens as laser ablation coverage area and beam intensity increased. Chemical analyses showed trends for surface chemical species which correlated with improved bond strength and durability. Combined, these results suggest that laser ablation is a viable process for inclusion with or/and replacement of one or more currently used titanium surface treatments. On-going work will focus on additional mechanical tests to further demonstrate improved bond durability.