Structure composite powders

The nebulization was also employed to generate composite powders for specific applications, such as in ceramics, by hydrolyzing with water vapor droplets containing Al(5ec-OBu) and silicon methoxide in the atomic ratio Al/Si = 3. This ratio of alkoxides was chosen in order to produce mullite, which was achieved by calcination of the resulting amorphous particles at rather high temperatures (up to I400 C) (52). In another approach a mixed Al-Mg-Si ethoxide was first synthesized, and then nebulized and hydrolyzed as usual (77). Depending on the experimental conditions, the powders calcined at 500 C exhibited structures of pure cordierite, or mixed with forsterite. In all of these described cases the nebulization yielded spherical but polydisperse particles. 

Polyimides (PI) were among the earliest candidates in the field of thermally stable polymers. In addition to high temperature property retention, these materials also exhibit chemical resistance and relative ease of synthesis and use. This has led to numerous innovations in the chemistry of synthesis and cure mechanisms, structure variations, and ultimately products and applications. Polyimides (qv) are available as films, fibers, enamels or varnishes, adhesives, matrix resins for composites, and mol ding powders. They are used in numerous commercial and military aircraft as structural composites, eg, over a ton of polyimide film is presendy used on the NASA shutde orbiter. Work continues on these materials, including the more recent electronic applications. 

The method for the study of crystal structure, including mineral composition, is x-ray diffraction. It is a semiquantitative method (Klug and Alexander 1954 Warren 1999) for the study of mineral composition. Powder samples of rocks are studied, and the place of the peaks (in nanometer or diffraction angle) and their relative intensity are observed. The diffractogram is usually compared to that of known substances that can be found in databases (ICDD 2009). In order to accurately quantify the rock samples, x-ray diffraction must be complemented with other quantitative techniques, including chemical analysis (Section 4.1.1), thermal, infrared analyses (Chapter 2, Section 2.1.2) and surface area (Chapter 1, Section 1.3.4.1.5 Section 4.1.3) measurements. 

In the present work, the nanostructured Co-Cu powders with different Co/Cu ratio are prepared after 2-3 h of ball milling. As a precursor we use the Co/Cu composite powders with particles consisting of amorphous Co-P alloy core and Cu shell [3]. The structural and magnetic characteristics are analyzed for different Cu content and compared with the Co-Cu alloys produced by traditional mechanical alloying techniques. Also the aim of this work is to obtain additional information on Co-Cu alloy structure formed during the ball-milling process. 

Les] Lesnik, N.D., Minakova, R.V., Khomenko, E.V., Chromium-Copper System Adhesion Characteristics, Doping, the Structure of Phase Boundary and Composites , Powder Metall. Met. Ceram., 40(7-8), 432-440 (2001) (Experimental, Morphology, Phys. Prop., Interface Phenomena, 12)... 

N. M. P. Low, Fabrication of Cellular Structure Composite Material from Recycled Soda-Lime Glass and Phlogopite Mica Powders, J. Mat. Sci. 15, 1509-1517 (1980). 

Structural composites and the principles of their construction have been known and used for literally thousands of years. Adobe brick, concrete, and laminated wood are the earliest known examples. The Assyrians and Babylonians are known to have used a type of concrete based on clay. A more robust type of concrete made from heated powdered clam and oyster shells that used lime (calcium oxide) as the binding agent was developed in ancient Egypt. Laminated structures such as wood pieces that have been mechanically fastened together or bonded together with an adhesive material of some kind have a similarly long history. 

Typically, dicyandiamide is used at levels of 5-7 parts per 100 parts liquid epoxy, and at 3-4 parts per 100 solid epoxy resin. It can be used for one-component formulations with long shelf life. The moderately high curing temperature can be reduced by adding accelerators such as amines, imidazoles, or urea derivatives. Applications include prepregs and composites, printed circuit boards, structural adhesives, powder coatings, and lacquers and varnishes. 

Besides diffusion problems, fractal analysis can be applied to such problems as lamination of composites, powder and pellet resin coalescence, latex paint structure, internal weld line shape, and tack of uncured elastomers. In this area, theory is ahead of experiment. 

Cabot s Dynalyst family of electrocatalysts is designed for use in applications ranging from cost-sensitive to performance-driven PEM fuel cell applications. Dynalyst electrocatalyst powders are manufactured to meet specific performance requirements based on their structure, composition and precious metal loading in the electrode layers. Dynalyst 20SR1 - 20% Pt/C electrocatalyst has excellent electrochemical performance at low precious metal loadings in the MEA. A loading of 0.1-0.3 mg Pt/cm in the electrode layer is recommended to achieve optimum performance and Pt utilization. 

The fundamental goal of nanoparticle research is to assemble atoms in a controllable way and design nanostructured materials with the desired physical and chemical properties. A major part of the research in the field of nanoscience is dedicated to the development of synthesis routes to nanoparticles and nanostructures. Conventionally, solid-state reactions between powders have successfully been employed for the low-cost production of bulk metal oxides. However, to obtain metal oxide nanoparticles with well-defined shape, size, and composition, these solid-state routes are unsuitable. In contrast to these high-temperature processes, liquid-phase synthesis routes, and in particular sol-gel routes, offer better possibility to control the variation of structural, compositional, and morphological features of the final nanomaterials [1,2]. 

Based upon a piezoelectric 1-3-composite material, air-bome ultrasonic probes for frequencies up to 2 MHz were developped. These probes are characterized by a bandwidth larger than 50 % as well as a signal-to-noise ratio higher than 100 dB. Applications are the thickness measurement of thin powder layers, the inspection of sandwich structures, the detection of surface near cracks in metals or ceramics by generation/reception of Rayleigh waves and the inspection of plates by Lamb waves. 

In wide sectors of industry there is a growing need of inspection methods which go without liquid coupling media. The excitation of bulk and surface waves by means of air-coupled ultrasonic probes is therefore an attractive tool for NDE. This is tme e.g. for the rapid scanning of large composite structures in the aerospace industry [1]. In other cases, the use of liquid couplants is prohibitive like the thickness measurement of powder layers. 

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