Energetic Films Research Articles

Preparation and characterisation of nanofibrous CuO/Al metastable intermolecular composite films

Metastable intermolecular composite (MIC) has been widely touted for their potential to fulfil the objectives of high energetic materials and nanotechnology. In this study, nanofibrous CuO/Al MIC films on the silicon substrate were successfully synthesised by evaporating and depositing Al on the surface of nanoporous CuO films, which were prepared by calcinating polyvinylpyrrolidone (PVP)/Cu(NO3)2 films obtained through the electrospinning process. The structures and energetic properties of the nanofibrous CuO/Al MIC films were characterised by a scanning electron microscope, X-ray diffraction, Fourier transform-infrared spectroscopy, TGA–DSC and open-air combustion experiments. The results revealed that the electrospinning process was an effective way to prepare energetic films. The optimised calcination temperature of the PVP/Cu(NO3)2 composite films was 500°C, and the starting reaction temperature of the nanoporous CuO/Al MIC film was 532°C.

Biomimetics in thin film design – Wrinkling and fracture of pulsed laser deposited films in comparison to human skin

The goal of the current work is the biomimetic comparison of wrinkling effects on the nano- and micrometer scale in thin films and on the micro- and millimeter scale of human skin. Ti, Ag, Au, W, C, and TiN thin films with 10 to 500nm thickness were deposited by pulsed laser deposition (PLD) on smooth polyurethane, polycarbonate, polyamide 6, and polyimide polymer substrates. Such high energetic conditions like in PLD plasma lead to stiffening of the polymer surface layers by pseudodiffusion during the initial stages of film growth. Both the high intrinsic film stresses due to high energetic film growth and the huge difference in elastic properties of films and polymer substrates result in hierarchical and self-adapting nanowrinkling phenomena. Intrinsic stresses are a reason for the hierarchical and self-adapting wrinkling of human skin too, being mechanically treated quite similar to the coated polymers as a hard layer (stratum corneum) on a soft foundation (viable epidermis and dermis). Mechanically, the wrinkles have high impact on the elongation behavior: In the elastic region of the stress–strain curve, they are smoothing out at increasing strain.In fracturing, the wrinkles are an origin of cracking (channeling cracks) and afterwards fragmentation of both thin film and stratum corneum islands, respectively, as proofed with in-situ tensile straining experiments of the thin films in scanning electron microscopy.

Fabrication and Performance Characterization of Al/Ti Multilayer Energetic Films

Al/Ti multilayer films with bilayer thicknesses of 50nm, 100nm and 200nm were prepared by RF magnetron sputtering alternate Al and Ti layers. The relative thickness of Al and Ti layers was maintained at a 1:1 ratio in order to obtain a 1:1 atomic ratio. XRD measurements show that the compound of AlTi is the final product of the exothermic reactions. DSC curves show that the values of heat release in Al/Ti multilayer films with bilayer thicknesses of 50nm, 100nm and 200nm are 457.99 J∙g-1, 493.42 J∙g-1 and 696.81 J∙g-1, respectively. The exothermic reaction in Al/Ti multilayer films lead to more intense electric explosion. Al/Ti multilayer bridge films with modulation period of 50nm explode more rapidly and intensely than other bridge films because decreasing the bilayer thickness results in an increased reaction velocity.

Corrigendum: The Burning Rate of Energetic Films of Nanostructured Porous Silicon

Corrigendum: The Burning Rate of Energetic Films of Nanostructured Porous Silicon

The Burning Rate of Energetic Films of Nanostructured Porous Silicon

A systematic study of nanoenergetic films consisting of nanostructured porous silicon impregnated with sodium perchlorate is carried out. The explosive properties of these films are investigated as a function of thickness, porosity, and confinement. The films' burning rates are investigated using fiber-optic velocity probes, demonstrating that flame-front velocities vary between approximately 1 and 500 m s(-1) and are very sensitive to the films' structural characteristics. Analysis of the flame profile by high-speed video is also presented, suggesting that the reaction type is a deflagration rather than a detonation. A strong plume of flame is emitted from the surface, indicating the potential for this material to perform useful work either as an initiator or as a propellant. The shape of the flame front transitioned from an inverted V at thin-film thicknesses to a neat square-shaped front once the material became self-confining at 50 μm.

Plastics and Food Sources: Dietary Intervention to Reduce BPA and DEHP

Purchasing fresh, unpackaged foods and avoiding the use of plastic food processing and storage equipment may help consumers minimize their exposure to bisphenol A (BPA) and bis(2-ethylhexyl) phthalate (DEHP), according to a small but systematic study of associations between diet and people’s levels of these chemicals [EHP 119(7):914–920; Rudel et al.]. At the time of this January 2010 study, BPA and DEHP were used widely in food packaging, including cans, plastic wraps, and food storage containers.1 Evidence from in vitro and animal studies demonstrates BPA’s potential to disrupt endocrine function in a number of organ systems. Animal studies have linked exposure to DEHP to inhibition of testosterone synthesis and adverse effects on the developing male reproductive system. Some epidemiologic evidence also links urinary levels of phthalate metabolites to effects on boys’ reproductive development, male hormone levels, semen quality, and neurobehavioral end points. Although some scientists believe diet is likely to be a major source of exposure to BPA and DEHP, few empirical data exist to verify this belief. One of the stated goals of the current study was to assess the relative importance of food packaging as a source of exposure to these chemicals. BPA and DEHP are relatively easy to study because they have short biological half-lives and exposure biomarkers that can be measured in urine. The study involved five 4-person families, including adults and children, who were chosen in part because they reported frequently eating canned foods. Urine samples were collected over 8 days. On days 3–5 family members consumed only food prepared by a caterer who avoided using plastic (including plastic utensils and storage containers) in preparing and packaging the meals and snacks made from fresh ingredients. Families were given stainless steel water bottles and lunch boxes and advised to use only the containers provided. Coffee drinkers were instructed to use a French press or ceramic drip in place of a plastic coffee maker. When consuming their customary diets, family members’ urine levels of biomarkers for both BPA and DEHP were in the range of the general U.S. population’s, as estimated by the Centers for Disease Control and Prevention’s National Health and Nutrition Examination Survey program. During the time the families were on the fresh-food diet, the geometric mean concentration of BPA dropped by 66%, and mean concentrations of DEHP metabolites decreased by 53–56%. The researchers note they cannot determine exactly which changes in food sourcing and handling caused the observed exposure changes. In addition, their intervention did not completely eliminate all sources of BPA and DEHP. They state food contamination may occur during premarket processing of whole foods or from the presence of phthalates and BPA in the environment where the food originates.

The microstructure and magnetic behavior of Co nanostructured film prepared by energetic cluster beam deposition

Cobalt nanostructured films were successfully prepared by depositing Co clusters onto a Si(100) substrate in our home-made cluster beam deposition apparatus. During preparation, the energy of the cluster beam was accelerated by applying an external electric field. The effect of the cluster beam energy on the microstructure, phase transformation and magnetic behavior was investigated for the cluster-assembled film in the case of both low energy cluster deposition and energetic cluster deposition. The scanning electron microscopy observation confirms that the films are assembled by the regular spherical nanoclusters. Compared with the low-energy Co cluster-assembled film, the magnetization of the energetic Co cluster-assembled film was improved significantly. The present work describes an effective way to prepare the magnetic nanostructured films.

Monte Carlo simulation of interactions between energetic electron and cellulose film

Monte Carlo method of simulating the interactions between energetic electron and organic compound is presented. This method is based on the Mott cross-section and Rutherford cross-section for the elastic scattering of electrons in different energy regions and the cross-section derived by dielectric response theory with exchange effect included for the inelastic scattering of electrons. The comparisons have been done to show the reliability of the described method. Using this method, the systematic calculations of the mean energy loss of transmitted electrons through the cellulose films with different thickness for different primary energies have been performed. The dependence of the mean energy loss of transmitted electrons on cellulose film thickness is analyzed. A method to evaluate the mean energy loss of the transmitted electrons for the cellulose film with a fixed thickness at a given primary energy is proposed.

Characterization of surface enhancement of carbon ion-implanted TiN coatings by metal vapor vacuum arc ion implantation

The modification of the surfaces of energetic carbon-implanted TiN films using metal vapor vacuum arc (MEVVA) ion implantation was investigated, by varying ion energy and dose. The microhardness, microstructure and chemical states of carbon, implanted on the surface layer of TiN films, were examined, as functions of ion energy and dose, by nanoindenter, transmission electron microscopy, Auger electron spectroscopy, X-ray photoelectron spectroscopy and X-ray diffraction. Results revealed that the microhardness increased from 16.8 up to 25.3 GPa and the friction coefficient decreased to approximately 0.2, depending on the implanted ion energy and dose. The result is attributed to the new microcrystalline phases of TiCN and TiC formed, and carbon concentration saturation of the implanted matrix can enhance the partial mechanical property of TiN films after MEVVA treatment. The concentration distribution, implantation depth and chemical states of carbon-implanted TiN coatings depended strongly on the ion dose and energy.

Energetic deposition using filtered cathodic arc plasmas

Energetic film deposition techniques, film properties, and some applications are briefly reviewed. Energetic deposition can be defined as a film deposition process in which a significant fraction of particles arrives at the substrate surface with a kinetic energy greater than the bulk displacement energy. Examples of energetic deposition processes include ion-beam-assisted deposition, plasma immersion ion deposition, pulsed laser deposition, and cathodic arc deposition. This work focuses on the production, properties, and use of filtered cathodic arc plasmas. The pulsed biasing technique of metal plasma immersion ion implantation and deposition extends the possibilities of tuning film properties such as density, stress, adhesion, surface roughness, hardness, elastic modulus, and optical constants via the energy of film-forming ions. The difference between kinetic and total ion energy, atomic scale heating, nucleation, intermixing, subplantation, and the relaxation of compressive stress by relatively high-energy ions are discussed.

Anode effects on energetic particle bombardment of the substrate in pulsed magnetron sputtering

Pulsed powering of a magnetron discharge in the medium frequency range (20–200 kilocycle) is the basis for a long-term stable run of reactive deposition processes at high deposition rates. Recent investigations indicated another important feature of pulsed powering, which is increased energetic particle bombardment of the substrate. In this paper causes of the strong substrate bombardment are investigated. Values for the thermal substrate load, ion current density onto a floating substrate, and self-bias voltage are compared for DC and pulsed powering. Systematic investigations in unipolar and bipolar pulsed-mode, for varied pulse parameters of duty cycle and frequency, and for several anode configurations are carried out. Different causes for the energetic substrate bombardment can be distinguished. The experiments show the essential influence of the anode configuration on the plasma density and electron temperature in the substrate region. Results suggest new techniques for influencing energetic substrate bombardment and film properties.

The growth dynamics of energetic cluster impact films

Dense and smooth thin films can be produced by the deposition of energetic clusters onto a solid surface. Roughnes, induced by random deposition of the clusters, is strongly suppressed by a downhill smoothing process. Molecular dynamic simulations of the impact of copper clusters onto tilted copper surfaces demonstrate that a downhill particle current proportional to the local slope of the surface is initiated. In the long wavelength limit the evolution of the surface profile is governed by the Edwards-Wilkinson equation. One parameter in this equation is related to the strength of the downhill movement due to the cluster impact and can be determined from the simulations. From the solution of the spatially Fourier transformed growth equation the power spectrum is calculated, which is in agreement with atomic force microscopy measurements for copper films.

Polymer Multi-Layer Processing of Thin Film Materials

AbstractPolymer Multi-Layer (PML) processing is a high speed industrial scale process for depositing thin polymer films. Moving substrates of arbitrary width can have one micron (typ.) polymer films deposited at speeds measured in hundreds of meters per minute. A wide variety of chemical functionality available in the precursor materials allows a variety of chemical, electrical, and optical applications. The polymer characteristics can be further augmented by subsequent deposition of inorganic materials. Recent advances with dielectric, electrolytic, photonic, barrier, chemical affinity, energetic, and piezoelectric thin film polymer materials are discussed.

On the low-temperature threshold for cubic boron nitride formation in energetic film deposition

The sharp threshold in substrate temperature below which cubic boron nitride (cBN) cannot be formed in energetic film-deposition processes was investigated. We found that cBN could be synthesized below the threshold temperature on top of cBN that had been previously formed above the threshold temperature. That the initial nucleation of cBN is more strongly dependent on temperature than its subsequent growth is suggested. How the structure of the sp 2-bonded BN that accompanied cBN growth changed with temperature was also investigated. Lowering the substrate temperature decreased the local ordering within the graphitic planes, and below the threshold temperature the separation of the graphitic planes increased dramatically. How these structural changes may influence the nucleation of cBN is discussed.

Energetic particles in PVD technology: particle-surface interaction processes and energy-particle relationships in thin film deposition

Energetic deposition techniques, including ion beam assisted deposition, ion plating, unbalanced magnetron sputtering, and cathodic-arc deposition, are playing an increasing role in the processing of coatings for mechanical, optical, and electronic applications, and for the protection of surfaces in hostile environments. Advantages of energetic film deposition include low temperature processing, improved adhesion to substrates, production of desired phases or compounds, and control of crystallographic orientation. There are certain fundamental physical processes common to these energetic deposition methods that involve the alloying of elements (ion implantation, condensate and gas adsorption), material removal (sputtering, desorption), collision-induced displacements, collision-stimulated thermal exchange, and collision-induced surface and bulk diffusion. The mechanisms by which these mechanisms affect film formation are under intense investigation. New Monte Carlo and molecular dynamics simulations of the effects of energetic atoms on surfaces as well as experimental investigations revealing relationships between deposition variables and phase formation are contributing to our understanding of thin film growth. This paper covers the above topics by first establishing the ‘ideal’ conditions for deposition of a film, indicates how different deposition processes attempt to approximate these conditions, and reviews known correlations between deposition variables and film characteristics.

Morphology Studies of Oxide Films Deposited by Rf Plasma Technique

AbstractRecently, an energetic film growth technique was developed. In this process, an RF (radio frequency) plasma was ignited in an ambient atmospheric environment. An aqueous solution was excited into mist, which was then fed into the plasma reactor. After vaporization, films were formed on substrates outside the plasma. As a by-product, small amount of powders were collected in the plasma reactor. Films studied were indium-tin oxide (ITO), aluminum oxide (Al2O3), and lanthanum strontium manganite oxides (LaSrMnO). Films and powders were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDAX, EDS), and Ultraviolet-Visible (UV-Vis) transmission measurements. Morphology of a film surface was dependent on deposition conditions, such as chemical composition of the precursor materials, precursor feeding rate, and/or substrate temperature.

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