As-prepared Porous Ceramics Research Articles

Preparation of nanocarbon modified vermiculite ceramics with excellent adsorption capacity

sNanocarbon modified vermiculite porous ceramics with hydrophobicity were prepared using vermiculite as the starting materials and polyethylene terephthalate (PET) as the carbon precursor via the catalytic reaction method. The microstructures, hydrophobicity, and adsorption capacity of as-prepared porous ceramics were characterized by scanning electron microscope, water contact angle testing, and weight gaining, respectively. The results revealed that the nano-carbon generated from the pyrolysis of PET formed on the surface of the pores in ceramics. The water contact angle of as-prepared modified porous ceramics with 82% porosity was up to 123 °. The as-prepared porous ceramics showed highly efficient adsorption to oils and were very durable, and would be excellent candidate materials to separate the oil from the water/oil mixture.

Structure and properties of Al2O3-bonded porous fibrous YSZ ceramics fabricated by aqueous gel-casting

To meet requirements for high porosity and high strength, novel aqueous gel-casting process has been successfully developed to fabricate Al2O3-bonded porous fibrous YSZ ceramics with ρ-Al2O3 and YSZ fibers as raw materials. Microstructure, phase composition, apparent porosity, bulk density, thermal conductivity, and compressive strength of fabricated porous ceramics were investigated, and effects of fiber content on properties were discussed. According to results, bird nest 3D mesh with interlaced YSZ fibers and Al2O3 binder was formed, ensuring the ability to obtain high performance, lightweight ceramics. An increase in the number of YSZ fibers led to more complex interlaced arrangement of fibers and denser network structure of porous ceramics at retaining their stability. Furthermore, their apparent porosity and bulk density increased, whereas thermal conductivity and compressive strength decreased with increasing the fiber content. In particular, comparatively high porosity (71.1–72.7%), low thermal conductivity (0.209–0.503 W/mK), and relatively high compressive strength (3.45–4.24 MPa) were obtained for as-prepared porous ceramics, making them promising for applications in filters, thermal insulation materials, and separation membranes.

Preparation of porous ceramics with waste zeolites as raw material

ABSTRACT Nepheline porous ceramics with improved strength and well thermal insulation performance were synthesised at 850–1000°C by a foam-gelcasting technology, using waste zeolite powders, triethanolamine lauryl sulphate and xanthan gum respectively as the starting materials, foaming agent and gelling agent. The effect of sintering temperatures and solid contents on the physical and thermal properties of final samples were investigated. The strengths of foams increased with the firing temperatures and solid levels, and the sample possessing the porosity of 71.9% exhibited the highest compressive strength of 2.9 MPa 1, respectively. Moreover, the one with a solid content of 20 wt-% and fired at 950°C containing 76.9% porosity and having compressive strengths respectively of 1.8 MPa showed the lowest thermal conductivity of 0.10 W/(m oC) at 25°C, suggesting that as-prepared porous ceramics could be potentially used as a good thermal insulation material.

Porous silica/mullite ceramics prepared by foam-gelcasting using silicon kerf waste as raw material

Porous silica/mullite ceramics with high porosity, sufficient compressive strength and low thermal conductivity were successfully prepared by foam-gelcasting method using silicon kerf waste as raw material. Microstructures of the as-prepared porous ceramics were found complex, depicting large-sized spherical pores, circular window pores, and small-sized pores present on internal walls. Effects of temperature on porosity, bulk density, compressive strength, and thermal conductivity were investigated. The thermal conductivity of the samples with a bulk density of 0.65 g/cm3, a porosity of 86.7%, and a compressive strength of 3.19 MPa was 0.178 W/(m·K), indicating that it can be used in the field of thermal insulation materials.

Facile fabrication of nanofibrous network reinforced hierarchical structured porous Si3N4-based ceramics based on Si-Si3N4 binary particle-stabilized foams

A facile method for preparation of SiC nanofibrous network reinforced hierarchical structured porous Si3N4 based ceramics via annealing Si-Si3N4 binary particle-stabilized foam in coke bed is reported in this work for the first time. The atmosphere created by coke bed enables the fabrication of Si3N4 based porous ceramics at 1450 °C without using sintering additives. As prepared specimens possess a relative high compressive strength due to the partial oxidation of Si3N4 particles. This novel structure with three levels of hierarchy characterized by flexible SiC nanofibrous network, cell walls and unit cells can be characterized. The vaporization of silicon powder results in formation of Si(g), SiO(g) and allows subsequent generation of SiC nanofibrous network, leading to a considerable number of micro-pores on cell walls simultaneously. As-prepared porous ceramics contained 76.7% porosity and had compressive strength of 10.81 MPa.

Lotus-Seedpod-Bioinspired 3D Superhydrophobic Diatomite Porous Ceramics Comodified by Graphene and Carbon Nanobelts.

Hydrophobic and oleophilic sorbents play an important role in the remediation processes of oil spills/leakages occurring globally from time to time. In this work, for the first time, lotus-seedpod-bioinspired 3D superhydrophobic diatomite porous ceramics with good mechanical strength and thermal stability were fabricated, using inexpensive porous diatomite as a substrate, and graphene/carbon nanobelts as modifiers. Thanks to the presence of graphene coating and in situ formed carbon nanobelts, the surface energy of the final porous ceramics was reduced and their surface roughness increased, conferring superhydrophobicity on them. As-prepared porous ceramics demonstrated 3-30 times higher adsorption capacity in oil/water separation than their conventional inorganic sorbent materials, and had compressive strength 70-270 times higher than that of a sponge/graphene-based sorbent material. The present work could additionally offer a new strategy for the treatment/recycle of waste plastics, the so-called "white pollution".

Foam-gelcasting preparation, microstructure and thermal insulation performance of porous diatomite ceramics with hierarchical pore structures

Hierarchically pore-structured porous diatomite ceramics containing 82.9∼84.5% porosity were successfully prepared for the first time via foam-gelcasting using diatomite powder as the main raw material. Sizes of mesopores derived from the raw material and macropores formed mainly from foaming were 0.02∼0.1μm and 109.7∼130.5μm, respectively. The effect of sintering temperature, additive content and solid loading of slurry on pore size and distribution, and mechanical and thermal properties of as-prepared porous ceramics were investigated. Compressive strength of as-prepared porous ceramics increased with sintering temperature, and the one containing 82.9% porosity showed the highest compressive strength of 2.1±0.14MPa. In addition, the one containing 84.5% porosity and having compressive strength of 1.1±0.07MPa showed the lowest thermal conductivity of 0.097±0.001W/(m·K) at a test temperature of 200 ̊C, suggesting that as-prepared porous ceramics could be potentially used as good thermal insulation materials.

Fabrication of porous Al 2O 3–MgAl 2O 4 ceramics using combustion-synthesized powders containing in situ produced pore-forming agents

Novel pore-forming agents as well as other starting materials were produced in situ via a solution combustion process and were used to fabricate porous Al 2O 3–MgAl 2O 4 ceramics. The relative fuel-to-oxidant ratios ( φ e) of 1.06, 1.28, 1.49 and 1.70 were achieved by varying the amount of starch in the precursors. Effects of φ e on the weight percent of the pore-forming agents in the powders, open porosity and Vickers hardness of the as-prepared porous ceramics were investigated. Experimental results revealed that the weight percent of the pore-forming agents in the powders increased significantly , while porosity of the as-prepared ceramics first increased and then decreased as φ e rose from 1.06 to 1.70. Meanwhile, pore size distribution became far narrower and the Vickers hardness of the porous ceramics increased as φ e increased.

Freeze casting of aqueous alumina slurries with glycerol for porous ceramics

Experiments have been performed to show that the mechanical properties of alumina porous ceramics may be improved by introducing glycerol into the raw slurries and then casting them under a constant cooling rate. The effects of glycerol on the freeze casting process and thereby on the microstructure and mechanical properties of porous ceramics obtained are investigated. It is shown that the addition of glycerol will increase both the slurry viscosity and sample sintered density. SEM images for microstructure of the final ceramics reveal that a good connection between ceramic lamellae has been promoted. This connection makes as-prepared porous ceramics obtain high mechanical properties. For the 30 vol.% alumina slurry with glycerol, the axial and radial compression strengths reach to, respectively, 255.1 MPa and 105.8 MPa.