1,721,091 research outputs found
Preliminary investigations on the use of preceramic polymers to produce metal matrix composites, via powder metallurgy techniques
No full textCeramic-reinforced metal matrix composites were produced by means of preceramic polymers, as precursors for the ceramic phase and powders of the metal alloy.
The use of preceramic polymers as precursors for a reinforcing ceramic phase in metallic components represents a well known technique to produce 3d interpenetrating composites .
However it was poorly investigated so far, the use of preceramic polymers in powder metallurgy. Only few results were published in the literature, concerning the use of polycarbosilane in Ti or Fe-Cr alloy. In the present work the use of a polysiloxanes (as precursor for a SiOC reinforcing and /or reacting phase) dispersed within a metal matrix is investigated. Powders of alloys of commercial interest (i.e. Al12Si, Ti6Al4V) were investigated and the properties of the produced composites were compared to the pure alloys, produced via a similar technique
Use of cryogenic machining to improve the adhesion of sphene bioceramic coatings on titanium substrates for dental and orthopaedic applications
No full textEtching of SiOC ceramic foams
No full textPolymer derived SiOC microcellular foams were etched by means of a 20 vol.-%HF solution. An increase in one order of magnitude in specific surface area (SSA) values compared to the unetched samples was observed. This SSA increase was accompanied by micro- and mesopores formation. The limited increase in the specific surface area was attributed to several factors: the smaller dimension of the etchable SiO2 nanodomains and the more amorphous nanostructure of these polymer derived ceramics compared to the sol–gel derived ones. Moreover a possible role of the carbon residue deriving from polymethylmetacrylate (PMMA) microbeads used as porosity source was supposed. Higher SSA values (up to 65 m2 g−1) were reached by inducing a slight phase separation, accompanied by a growth of the nanodomains size, and by an oxidative treatment that partly removed the residual carbon. Microcellular ceramic foams with a bimodal pore size distribution were produced
In situ formation of ceramic micro reinforcement in Ti-based composites
No full textThe development of metal matrix composites using ceramic particles at the micro and nano range is finding widespread interest in the scientific community. However the use of preceramic polymers as precursors for the dispersion at the micro and nano level of the ceramic reinforcement has not been deeply investigated so far.
Preceramic polymers are a specific class of polymers (polysiloxanes) widely used in the production of advanced ceramics. They give, upon pyrolisis run under inert or reducing atmosphere, SiOC, SiCN or SiC compositions, depending on the polymer composition. Only few exemples in the literature show the use of preceramic polymers as precursors for ceramic reinforcing particles dispersed within a metallic matrix.
In the present work, Ti6Al4V micropowders were mixed at different conditions with 20 vol.% of polymers and the effect of processing parameters on the properties of the material were investigated. Properties such as hardness, wear resistance and Young modulus were related to the morphology and composition of the novel composite material produced and compared to standard Ti6Al4V cast alloy
Polymer-derived microcellular SiOC foams with magnetic functionality
No full textSiOC microcellular ceramic foams possessing
soft-ferromagnetic properties were produced from a preceramic
polymer, poly-methyl-methacrylate microbeads
(PMMA) (used as sacrificial pore formers) and iron silicide
micro-powders (as functional filler). The interactions
between the matrix and the filler were studied as a function
of the amount of powders introduced and the pyrolysis
temperature. Magnetic and mechanical properties were also
investigated
Development and characterization of Ti6Al4V matrix composites, formed in Situ via the preceramic polymer route
No full textGas permeability of microcellular ceramic foams
No full textSiOC microcellular ceramic foams were prepared by means of a commercially available preceramic polymer and poly(methyl methacrylate) microbeads acting as a sacrificial filler. Microfoams having cell sizes in the range of 10−150 μm and cell window sizes in the range 10−50 μm were prepared. To test the applicability of such materials in the fluid flow field, gas permeability measurements were performed. The relationship between the permeability constant and morphological parameter were analyzed. An aerosol filtration process was simulated on the samples and revealed the feasibility of this process only for larger cell size foams
Characterization of the morphology of cellular ceramics by 3D image processing of X-ray tomography
No full textX-ray tomography images of different cellular ceramics have been obtained using appropriate tomography setups. The samples exhibited a wide range of cell sizes (View the MathML source m to mm) but a narrow range of porous fraction (75–85 vol.%). The images have been processed to retrieve the local fraction of ceramic. The average value of this measurement have been compared with a standard method based on image analysis of optical micrographs. The thickness distribution of both pores and ceramics was also retrieved using three-dimensional (3D) mathematical morphological operation on the images. The average value of these granulometry measurements was compared to optical and electron microscopy measurements
Polymer-derived sphene biocoating on cpTi substrates for orthopedic and dental implants
No full textSphene coatings were prepared by a novel process involving the use of a preceramic polymer containing nanosized
and micro-sized active fillers as precursors for the formation of the desired ceramic phase. A commercially
available airbrush was used to cold-spray the suspension on the cpTi substrate, and the samples were heat
treated to transform the precursor and fillers mixture into a ceramic coating. The processing conditions were
optimized in order to obtain cracks free coatings, characterized by good adhesion to the substrate and a desired
phase assemblage
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