Continuous ice-templating of macro-porous materials with uniformly ordered architecture

Ice-templating technique offers a viable means for constructing ordered macro-porous architectures in materials;nevertheless,it is generally limited by a low efficiency for fabrication,large difficulty for manipulation,along with the small dimension,and poor structural uniformity of icetemplated materials.Here,a new approach was exploited for continuous ice-templating of uniformly ordered macro-porous materials based on the establishment of a large,stable temperature gradient with specific bi-directional designs at the freezing front by descending the front toward the cooling medium to accommodate its upward growth.The freezing rate was markedly increased with the dimension of frozen body notably enlarged as compared with the case for conventional static ice-templating technique.The macro-porous architecture of materials,taking zirconia ceramics as an example,was made much finer and more uniform over the entire sample,and exhibited better ordering of alignment and enhanced inter-connectivity between lamellae.This led to an improvement in the compressive strength and its stability along the height direction for ice-templated materials than those made by the static ice-templating technique at a similar porosity.This study may facilitate the scale up of ice-templating techniques and promote the exploitation and application of new high-performance materials.

Friction and wear behavior of bioinspired composites with nacre-like lamellar and brick-and-mortar architectures against human enamel

Friction and wear performance is critical for dental materials which are inevitably subject to reciprocating friction against opposing teeth in applications.Here in-vitro friction and wear behavior of bioinspired ceramic-polymer composites,which possess nacre-like lamellar and brick-and-mortar architectures and resemble human teeth in their stiffness and hardness,against human tooth enamel were quantitatively investigated to imitate actual service conditions in line with standardized testing configuration.The composites were revealed to exhibit different wear mechanisms and lead to differing extents of wear to the opposing tooth enamel depending on their specific architectural types and orientations.In particular,the brick-and-mortar architecture displayed much less wear than the lamellar one,without obviously roughening the contact surfaces with enamel owing to its high ceramic content,and as such did not accelerate the wear of enamel as compared to smooth ceramics.Such characteristics,combined with its unique stiffness and hardness matching those of human enamel as well as the good fracture toughness and machinability,endow the composite with a promising potential for dental applications.This work may provide an experimental basis to this end and may also give insights towards designing new bioinspired wear-resistant materials for reducing friction and wear.