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Porowata ceramika infiltrowana metalami i polimerami

Szafran M., Rokicki G., Lipiec W., Konopka K., Kurzydłowski K.

Kompozyty

2002

R. 2, nr 5

313-317

Przedstawiono wstępne wyniki badań nad otrzymywaniem nowych kompozytów na bazie porowatej ceramiki infiltrowanej metalami i polimerami. Uzyskane wyniki wskazują na możliwość uzyskania tą drogą nowych materiałów o właściwościach łączących pozytywne cechy składników kompozytu, w którym osnową jest tworzywo ceramiczne, a fazą modyfikującą metal lub polimer organiczny. Poprzez dobór rodzaju tworzywa ceramicznego, jego porowatości otwartej oraz wielkości i rozkładu wielkości porów można uzyskać osnowę o parametrach optymalnych z punktu widzenia zastosowań kompozytu ceramika-metal czy ceramika-polimer. Właściwości kompozytu mogą być także kontrolowane poprzez zmianę rodzaju i sposobu wprowadzenia metalu lub polimeru w pory ceramicznego tworzywa porowatego.

In this paper, preliminary results of studies of ceramic-metal and ceramic-polymer composites obtained via infiltration of porous ceramic matrix are reported. Ceramic-metal composites based on porous ceramic material are usually obtained employing the method in which melted metal at high temperature is infiltrated into open pores of ceramic under pressure lower than 50 MPa. This type of composites amalgamates properties of both materials: hardness and elasticity. The image of Al2O3-Fe composite, presented in Figure 1 reveals the interlayer consisting of FeAl2O4. The presence of this interlayer between ceramic and metallic phases, which is formed at high temperature leads to the composite exhibiting mechanical strength higher than that of both metal and ceramic material. It is known that mechanical strength, especially compressive and tensile strengths of some human as well as animal bones is unexpectedly high. The bones are natural inorganic-organic composites. Thus, human and animal bones are examples of ceramic-polymer composites, in which the intercellular matrix of bone is bonded with the natural polymer - fibrous proteins of molecular weight up to several million. These two components are intimately bound, with the mineral crystals wrapped around and embedded among the protein. The hard mineral crystals provide great compressive strength, making bone an excellent load-bearing material. The protein fibers add elasticity and high tensile strength, enabling bone to withstand tension forces. The heat treatment of bones at temperature, at which the organic material is decomposed and removed, leads to the porous ceramic material, mainly consisting of hydroxyapatite, and additionally indicating the porosity gradient. The SEM picture of an animal bone after firing at 700°C is presented in Figure 2. Ceramic-polymer composites mimicking bones were prepared via introducing of monomer or reactive resin into pores of porous ceramic material and subsequent the monomer polymerization and resin curing. It was shown that the mechanical properties of resulting composites depend on a kind of monomer and reactive resin used as an organic material (Table 1). The problem of the composite preparation is the residual open porosity due to polymerization shrinkage which is immanent for polymerization process as well as crosslinking of reactive resins (Fig. 3). However, it is possible to use special monomers exhibiting low shrinkage or even the volume expansion during polymerization, which can result in an additional strengthen of the composite. Closing a flammable polymer in the porous structure of the ceramic material additionally can reduce ignition and flame susceptibility of the polymer. It is especially true for the ceramics-polymer composites, characterized by porosity gradient.

Kompozyty z włókien miedzi infiltrowane ołowiem

Cyunczyk A., Sosnowy P.

Kompozyty

2002

R. 2, nr 3

81-84

Wytworzono kompozyty Cu-Pb metodą infiltrowania ciekłym ołowiem szkieletów z włókien miedzi. Celem pracy było dokonanie oceny przydatności nieregularnych, nitkowych kryształów miedzi uzyskanych w sposób podobny do metody hodowania wiskerów metalowych. Wykorzystano w tym celu zmodyfikowaną metodę Brennera. Dla porównania wykorzystano również włókna otrzymane z ciągnionego drutu miedzi. Zbadano wybrane właściwości mechaniczne kompozytów zawierających 30 i 40% ołowiu.

The investigations for producing a pseudoalloy Cu-Pb have been made. The Cu-Pb composites containing 60 and 70 volume per cent copper fibrous skeleton were fabricated by infiltration technique. Two kinds of copper fibres were applied: (1) the filamentary vapour-grown crystals of copper and (2) a cold-drawn copper wire. The Brenner technique for metallic whiskers growing from halides salts was used as a method of production of filamentary crystals, but modificated experimental conditions were applied (Figs 1 and 2). The filamentary crystals unexpected in shape were obtained instead of the perfect whiskers (Fig. 4). The cold-drawn 0.1 mm diameter copper wire was cut into 4:6 mm length and etched in nitric acid. For the slurry felting method both kinds of copper fibres were beaten in to a slurry with a glycerine (Fig. 3). The product of felting was pressed and sintered and samples with porosity of 30 and 40% were obtained. During infiltration by gravity method all the pores were filled with lead. The mechanical properties of obtained composites are given in Table 1. The presented paper indicates that mechanical properties of Cu-Pb composites could be improved by incorporation of vapour-grown filament copper crystals.