Lightweight vitreous carbon material: approaches to making open-pore cellular structure

Cellular vitreous carbons with the open-pore structure are attractive materials in some aerospace applications, such as the super-lightweight structural materials or sandwich core materials in the thermal protection systems. Cellular vitreous carbon (or VC foam) with the open-pore structure can be synthesized by pyrolysis of cellular precursor structures made from some types of resins, such as epoxy or phenolic resins. Several approaches elaborated at RPMI, Belarus can be applied to create the precursor resin foams. The replication approach ensures perfect open-pore structure with the porosity of >90% and high hydraulic permeability. The sacrificial template approach ensures lower porosity and hydraulic permeability, and higher specific strength. In the approach with the deformable space-holder granules in the sacrificial template, the foam porosity can be controlled in a wider range. The paper compares different methods of making the precursor resin foams and properties of VC structures synthesized by pyrolysis of these precursor foams

Nickel foams with oxidation-resistant coatings formed by combustion synthesis

A combustible mixture containing aluminum, titania and boron oxide powders was deposited onto the open-cell nickel foam structural elements. Heating the sample ensured formation of a protective coating based on titanium boride and alumina over the nickel foam struts via the combustion synthesis reaction. Oxidation rate of the resultant composite foam was remarkably lower compared to the bare nickel foam, the stress–strain behavior changed and was dependent on the coating thickness, and the original open-cell structure was retained

Porous titanium manufactured by a novel powder tapping method using spherical salt bead space holders: characterisation and mechanical properties

Porous Ti with open porosity in the range of 70–80% has been made using Ti powder and a particulate leaching technique using porous, spherical, NaCl beads. By incorporating the Ti powder into a pre-existing network of salt beads, by tapping followed by compaction, salt dissolution and “sintering”, porous structures with uniform density, pore and strut sizes and a predictable level of connectivity have been produced, showing a significant improvement on the structures made by conventional powder mixing processes. Parts made using beads with sizes in the range of 0.5-1.0 mm show excellent promise as porous metals for medical devices, showing structures and porosities similar to those of commercial porous metals used in this sector, with inter-pore connections that are similar to trabecular bone. The elastic modulus (0.86GPa) is lower than those for commercial porous metals and more closely matches that of trabecular bone and good compressive yield strength is retained (21MPa). The ability to further tailor the structure, in terms of the density and the size of the pores and interconnections has also been demonstrated by immersion of the porous components in acid

Прочностные и гидравлические свойства открытоячеистого пеностеклоуглерода, полученного разными методами

The paper reports on comparative studies of mechanical strength and hydraulic permeability of open-cell vitreous carbon foams manufactured by different methods. Vitreous carbon foam were manufactured either by infiltration of the epoxy precursor resin into a layer of pore-forming removable granules or by replication of a structure of polyurethane foam template with the phenolic precursor resin followed by pyrolysis of the precursor resins in neutral gaseous environment. It was stated that the vitreous carbon foams manufactured by the replication method had higher hydraulic permeability compared to the vitreous carbon foams manufactured by infiltration, but had poorer mechanical strength at similar cell diameter and within similar relative densities range. Recommendations for the use of the studied foams in various areas have been proposed.Проведены сравнительные исследования механической прочности и гидравлической проницаемости открытоячеистого пеностеклоуглерода, полученного разными методами. Пеностеклоуглерод получали инфильтрацией полимер-прекурсора в слой порообразующих удаляемых гранул и дублированием структуры высокопористого полимерного каркаса полимер-прекурсором с последующим пиролизом прекурсора в нейтральной газовой среде. Установлено, что при близком диаметре ячеек и в близком диапазоне относительных плотностей пеностеклоуглерод, полученный дублированием полимерного каркаса, превосходит по гидравлической проницаемости пеностеклоуглерод, полученный инфильтрацией, но уступает ему по механической прочности. Предложены рекомендации по применению исследованных пеноматериалов в различных областях

Open Celled Porous Titanium

Among the porous metals, those made of titanium attract particular attention due to the interesting properties of this element. This review examines the state of research understanding and technological development of these materials, in terms of processing capability, resultant structure and properties, and the most advanced applications under development. The impact of the rise of additive manufacturing techniques on these materials is discussed, along with the likely future directions required for these materials to find practical applications on a large scale