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A system for sputter deposition of thin (10 1000 nm) metal and ceramic coatings onto vibro-fluidized beds of microparticles has been fabricated. Coatings are sputtered onto microparticles of various sizes, shapes, and materials. Experiments show that the coating deposition rate onto particles decreases with decreasing particle size for the case of a fixed total bed mass. Factors affecting particle coating thickness also include sputter power and fluidized bed container size. Coating surface morphology is evaluated using scanning electron microscopy. Lower sputter deposition powers create smoother, less porous coatings. Fluidizing parameters such as driving amplitude and frequency are also shown to affect coating morphology. Barrier coatings on salt microparticles are produced and shown to slow the dissolution of the coated salt particles in water. Dual-layer memetal-ceramicoatings are also demonstrated using the sputter deposition technique. A dual-layer aluminum/tin-oxide coating is produced on glass microspheres, which are then shown to have distinct reflectance characteristics and colors. A model is developed to estimate coating thickness based on size, shape, and number of particles., The original document contains color images.

This paper describes the development of a new analysis and crystal growth method for next generation infrared materials, namely, dilute nitride III-V semiconductors, which may be used in future low-cost night vision systems. The key to this method is isotopic enrichment of nitrogen-15 during material growth via molecular beam epitaxy, which allows enhanced detection of nitrogen using resonant nuclear reaction analysis. Films of GaAsN have been synthesized using nitrogen gas enriched in nitrogen-15, and examined using x-ray diffraction, secondary ion mass spectroscopy, and nuclear reaction analysis. This analysis has confirmed the incorporation of nitrogen-15 into the material corresponds with the expected enrichment of the feed gas, and opens up the possibility of examining the material using ion beam channeling methods to ascertain the lattice position of the incorporated nitrogen atoms., See also ADM002187. Published in the Proceedings of the Army Science Conference (26th) Held in Orlando, Florida on 1-4 December 2008. The original document contains color images.

The surface properties of poly(ethylene glycol) (PEG) films have been modified using gold particles functionalized with block copolymer-based ligands of poly(styrene) (PS) and PEG. The ligands were synthesized using Diels-Alder chemistry to join the PS and PEG blocks into linear diblock copolymers, which were attached to gold particles with a thiol terminal functionality on the PS block. The block copolymer ligands compatibilized the Au particles by creating a PEG shell around the Au and PS core. The Diels-Alder linkage, however, is temperature sensitive, and by annealing the films at 90 C, the PEG blocks of the ligand were separated from the PS-functionalized Au core. The Au particles were thus rendered immiscible in the PEG matrices and migrated to the film surfaces., The original document contains color images.

Polymer composites are attractive candidates for lightweight armor applications and can be made transparent by matching constituent refractive indices (RIs). Unfortunately, RI matching is difficult since the indices must be matched to approximately the third decimal place, and the matrix RI is very sensitive to factors such as temperature and stress state. Therefore, index matched systems are transparent only over a narrow temperature range. In order to capitalize on the superior properties of polymer composites in transparent armor applications, novel techniques are needed that can dynamically account for small changes in the RI. In this report, we investigate transparent composites that utilize polymer matrices whose RIs can be modulated in real time. Glass-reinforced composites are manufactured using polymers that incorporate nonlinear optical (NLO) chromophores small molecules whose RI can be changed with an applied electric field. We find that by utilizing typical NLO chromophores, the polymer matrix has insufficient electro-optical response for significant RI modulation., The original document contains color images.

Novel additives for polymeric coatings have been developed based on modified hyperbranched polymers. The additives are polyfunctional and have been prepared to spontaneously segregate to the surface of the polymer in which they are dispersed. They ave been used to install active sites in polymeric films, with little or no change in the formulation, bulk properties, or application of the coating., The original document contains color images.

The overall goal of this paper was to determine which factors of silane/silica chemistry most influenced surface coverage and surface roughness of glass surfaces. Nanotexturing of glass fibers has shown the potential to improve impact properties of glass reinforced composites. Previous work by Army researches determined that modifying fiber surfaces using a mixture of silane coupling agents that were both reactive and non-reactive towards the matrix phase, in conjunction with nanoscale colloidal silica, yielded a simultaneously high strength and tough composite. The focus of this work was to ascertain which factors of the silane and silica treatments were most influential in controlling the silica deposition on solid surfaces. The basis of the silane chemistry involves controlling the number of amine-functional groups on the fiber surface. Propyltrimethoxylsilane (PTMO) and aminopropyltrimethoxysilane (APS) are silanes that contain a propyl group and a primary amine, respectively. By varying the ratio of these silanes in solution, the concentration of amine groups on the fiber surface can be controlled. The amine groups on the fiber surface act as potential sites for epoxy-amine reactions. Two routes were chosen for affixing silica to the surface using the amine groups. In the first route, a reverse silane reaction is carried out; where the epoxy groups of a non-hydrolyzed glycidylpropyltrimethoxysilane (GPS) react with surface amine groups. Upon hydrolysis, the methoxy groups of the silane are converted to hydroxyl groups that undergo a condensation reaction with the silica. The second route for silica deposition involves the functionalization of the silica. In a separate step, hydrolyzed GPS is reacted with the silica to yield epoxy-functional silica. The epoxy groups on the silica can react with the amine groups on the glass surface., Presented at the Army Science Conference (25th), "Transformational Army Science and Technology - Charting the future of S&T for the Soldier," held in Orlando, Florida on 27-30 Nov 2006. Published in proceedings of the same. See also ADM002075. The original document contains color images.

Novel additives for polymeric coatings have been developed based on modified hyperbranched polymers (HBP). The additives are polyfunctional, and have been prepared to spontaneously segregate to the surface of the polymer in which they are dispersed. They have been used to install "active" sites in polymeric films, with little or no change in the formulation, bulk properties, or application of the coating., See also ADM002075. Presented at the Army Science Conference (25th) held in Orlando, Florida on 27-30 November 2006. The original document contains color images.

Nanotechnology offers the ability to create new material systems as well as dramatically improve the performance of existing systems through the introduction of new physical mechanisms not found in the original material. Nanomaterial modification of fibers and textiles has been used to increase fabric performance in areas ranging from biocidal capability to stain resistance and water repellency. In this study we use scalable methods to modify nanoscale features on organic materials to probe the potential for increased impact energy absorption and mechanical properties in composite applications. Specifically atmospheric plasma treatment and wetchemistry methods were utilized to create nanoscale chemical scaffolding and surface textures on model polyethylene films and fibers. This approach was successful at modifying the surfaces of these fibers and scaling to high speed web manufacturing is easily envisioned., See also ADM002075. Presented at the Army Science Conference (25th) held in Orlando, FL on 27-30 November 2006. The original document contains color images.

ARL has recently made discoveries in the area of interior ballistic propellant combustion product interactions with a gun tube bore. These discoveries were based on two hypotheses. The first was that the products could and are dynamically nitriding the bore of the gun, thus creating a nitride coating which inhibits the dissociation of CO and subsequently reducing the amount of carbon uptake. The second was that the combustion products richer in nitrogen have a lower temperature upon expansion in our experimental fixture as well as in a gun barrel. This is due to Joule and or Joule-Thomson cooling effects. Both of these hypotheses were proven and validated through numerical and experimental methods. Higher nitrogen containing combustion products have definitively been shown to have relatively lower erosivity with respect to those having lower nitrogen content. These results have revolutionized the gun propellant development community in that for the first time there is guidance for erosivity control through propellant chemical constituent formulation., See also ADM001736, Proceedings of the Army Science Conference (24th) held in Orlando, FL on 29 Nov-2 Dec 2004. The original document contains color images.

The U.S. Army Research Laboratory (ARL) has demonstrated that a bonded bimetallic stratified nanocomposite structure can, with a small electrical or thermal initiation, completely and quickly (<10 ms) separate two adhesively coupled surfaces. The bimetallic layers are typically composed of metals such as nickel/aluminum or titanium/aluminum that are vapor deposited onto surfaces. To date these bi-layer films have been deposited onto brass, aluminum, graphite composite, and mylar. Unlike other debonding approaches, this method allows for fast, remote and oncommand separation of structurally bonded materials. ARL has engineered the materials to create directly applied reactive nano-coatings that allow new methods of assembling and separating structural systems. The technology is being developed to meet critical design needs for development of a non-lethal frangible 155MM artillery munition., See also ADM001736, Proceedings for the Army Science Conference (24th) Held on 29 November - 2 December 2005 in Orlando, Florida. , The original document contains color images.

Novel Pt/Ti/WSi/Ni composite ohmic contacts to n-SiC were investigated as a function of annealing temperatures up to 1000 C. The onset of ohmic behavior occurred after annealing at 900 C. Annealing at temperatures between 950 and 1000 C yielded excellent ohmic behavior. At these temperatures the contact-SiC interface was smooth, defect free and characterized by a narrow Ni2Si reaction region. The annealed contacts possessed smooth surface morphologies and exhibited minimal contact expansion. The residual carbon, resultant from SiC decomposition, was constrained by reaction with the WSi and Ti metallization layers forming carbide phases of W and Ti. The locations of the carbide phases were spatially distant from the metal semiconductor interface. The anneal optimized (annealed at 950 and 1000 C for 30 s) Pt/Ti/WSi/Ni ohmic contacts to n-SiC were evaluated for thermal stability via pulsed/cyclic thermal fatigue and aging experiments at 650 C. Negligible changes in the electrical properties, micro structure, and surface morphology/roughness were observed for both annealed ohmic contacts in response to 100 cycles of acute cyclic thermal fatigue. Aging of the 950 C annealed contact for 75 hours at 650 C resulted in electrical failure and chemical interdiffusion/ reaction between the contact and SiC substrate. The 1000 C annealed contact retained omicity after 100 h of aging and was found to be chemically and micro structurally stable. These findings indicate that the 1000 C annealed Pt/Ti/WSi/Ni ohmic contact to n-SiC is thermally stable and merits strong potential for utilization in high temperature and pulsed power devices., Pub. in IEEE Lester Eastman Conference on High Performance Devices,vII-4, p65-74, 2002. This article is from ADA423729 Proceedings IEEE Lester Eastman Conference on High Performance Devices at University of Delaware, Newark, Delaware, August 6, 7, and 8. 2002

Ni2Si Ohmic contacts were fabricated via pulsed laser deposition on n-SiC. The contacts' electrical, structural, compositional, and surface morphological properties were investigated as a function of annealing temperatures ranging from 700 to 950 deg C. The as-deposited and 700 deg C annealed contacts were non-Ohmic. Annealing at 950 deg C yielded excellent Ohmic behavior, an abrupt void-free interface, and a smooth surface morphology. No residual carbon was present within the contact metallization or at the contact-SiC interface, and the contact showed no appreciable thickness increase as a result of the annealing process. The results demonstrate that aside from maintaining the desirable electrical integrity associated with Ni and Ni/Si Ohmic contacts, the Ni2Si Ohmic contacts possessed improved interfacial, compositional, microstructural, and surface properties which are required for reliable high temperature and high power device operation.