Porous Fiber Materials Research Articles

Properties of high-porosity materials from refractory compound fibers

1. A study was made of the hydraulic properties, pore sizes, pore channel tortuosity, and compressive strength of high-porosity materials from extruded titanium carbide fibers. 2. So far as the quantity q and itsdependence onvarious factors are concerned, the materials investigated approach wire filters atθ=40–70% and filters from nonspherical powders atθ<28–30%. 3. The parameters Dmax, Dhydr, andβ substantially grow with increase inθ and d, but are less strongly affected by changes in the lengthl. Dmax is not a unique characteristic of the stopping power of a porous fiber material. The greater the surface roughness of the fibers, the higher is the value ofβ at a constant value of Dmax. 4. The variation ofσp withθ is quite accurately described by the equation σp=σb(1-θ)m. The values of the exponent m (m=3–5) for the materials investigated approach those for sintered powder materials. 5. The variation ofσp as a function of fiber diameter is almost linear, the actual degree of the influence exerted by d onσp being determined by the porosityθ. The fiber length affectsσp up to a certain value ofl, above whichσp remains virtually unchanged.

Hydraulic characteristics and structure of porous metal fiber materials

Hydraulic characteristics and structure of porous metal fiber materials

Hydraulic characteristics and structure of porous metal fiber materials Part I

Hydraulic characteristics and structure of porous metal fiber materials Part I

Manufacture and properties of powder metallurgical refractory compound fibers and porous fiber materials

1. Using titanium carbide and titanium and zirconium diborides as typical examples, a study was made of the extrusion of fibers from plasticized powder mixtures. The optimum mixture compositions and extrusion conditions, ensuring stability of filament discharge, were determined. 2. Certain characteristic features of the sintering behavior of refractory compound fibers were discovered. Conditions securing maximum possible strength in sintered refractory fibers were determined. Ways of further increasing their strength are discussed. 3. Porous materials were produced from sintered fibers. It is shown that the hydraulic properties of fiber filters approach those of filters from wire fibers. Fiber filters are comparable in strength to porous materials from powders and can be expected to surpass them in stopping power.

Changes in dimensions of porous metal fiber materials subjected to pressing and sintering

1. During pressing and sintering, high-porosity materials from metal fibers exhibit dimensional changes induced by residual stress relaxation, which may attain several tenths. 2. The total strain observed, which exceeds the purely elastic strain of a porous fiber material by one order of magnitude or more, is associated with the structural characteristics of the material. 3. To suppressthe undesirable material “growth” phenomenon occurring during sintering as a result of residual stress relaxation, a two-stage heat treatment may be employed.

The electrical conductivity of porous sintered materials from copper fibers

1. An expression is derived for the electrical conductivity of porous sintered fiber materials as a function of porosity and contact imperfection, using the model of an infinite cylinder arbitrarily oriented in space. Analysis of this expression leads to the conclusion that the electrical conductivity of a porous fiber material has a finite value in the absence of contacts along the fiber generatrices. 2. Satisfactory agreement between theoretical and experimental results was obtained, but further study will be required to elucidate the effect of contact imperfection on electrical conductivity.

Some problems of fiber metallurgy

Problems of the preparation and sintering of fibers are discussed, and the properties of porous and dense copper fiber materials are studied. Fiber metals differ from powder metals by the following characteristics: pronounced anisotropy, considerable elastic recovery during sintering and compacting, greater dependence of properties on intraparticle factors, and lesser dependence on interparticle contact factors.