Abstract
In this article, we present a simple, advanced method to produce lightweight tailor-made materials based on capillary suspensions that are made from locally bonded hollow glass spheres with a high total porosity in the range of 70% at apparent densities of 200 kg/m3, having a compressive strength of 0.6 MPa. The amount of added liquid and the particle surface treatment determine the network structure in the pastes and the resulting microstructure of the porous material in a straightforward manner. This structure has a strong impact on the porosity, pore size, and mechanical properties of the final body. The most promising porous materials were made of surface treated hollow glass spheres that create a sample-spanning network in the capillary state, where the added liquid wets the particles worse than the bulk fluid. These samples approach the density of natural balsa wood and they may find application in fields where either weight or structure are important, such as in insulation materials, filters, and membranes, as well as lightweight construction materials for automotive or aerospace engineering.
Highlights
Porous materials are found in a broad field of applications, such as separation and filtering techniques, as well as thermal insulation materials or even catalytic materials [1], while the pore size is a key property
We present an advanced method using capillary suspensions to create self-organized porous bodies with open porosities of up to 67% at an apparent density of only 200 kg/m3 and a compressive strength of 0.6 MPa
The porous materials were made from capillary suspensions containing glass spheres, glycerol as bulk fluid, and an epoxy resin as secondary phase, inducing the formation of a strong sample-spanning network
Summary
Porous materials are found in a broad field of applications, such as separation and filtering techniques, as well as thermal insulation materials or even catalytic materials [1], while the pore size is a key property. The changes can be detected by, e.g., a strong increase of the yield stress, which is caused by a transition from fluid-like to gel-like behavior due to structure formation within the suspension This small amount of secondary liquid phase is distributed as capillary bridges between the micron-sized particles, leading to a particle network due to the capillary attraction. If the secondary fluid preferentially wets the particles (θS,B < 90◦ ), the particles are directly connected by capillary bridges and the system is in the pendular state Both of the arrangements lead to a sample-spanning network, but they show significant differences in the overall structure. The process route is very simple, low cost, consumes little energy, and is environmentally friendly
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