A general process for in situ formation of functional surface layers on ceramics

Abstract

Ceramics are often prepared with surface layers of different composition from the bulk, in order to impart a specific functionality to the surface or to act as a protective layer for the bulk material. Here we describe a general process by which functional surface layers with a nanometre-scale compositional gradient can be readily formed during the production of bulk ceramic components. The basis of our approach is to incorporate selected low-molecular-mass additives into either the precursor polymer from which the ceramic forms, or the binder polymer used to prepare bulk components from ceramic powders. Thermal treatment of the resulting bodies leads to controlled phase separation ('bleed out') of the additives, analogous to the normally undesirable outward loss of low-molecular-mass components from some plastics; subsequent calcination stabilizes the compositionally changed surface region, generating a functional surface layer. This approach is applicable to a wide range of materials and morphologies, and should find use in catalysts, composites and environmental barrier coatings.

Structural, electronic, and hyperfine properties of pure and Ta-dopedm-ZrO2

“…[16][17][18][19][20][21] In particular, Coey et al reported ferromagnetism above room temperature in undoped HfO 2 thin films fabricated by conventional out-of-equilibrium pulsed-laser deposition. 22,23 Such unexpected ferromagnetism has also been reported in CaO, ZnO, CaB 6 , and ZrO 2 thin films and nanoparticles. [24][25][26][27] From a theoretical point of view, it has been shown that point defects such as cation or oxygen vacancies or electron trapping at an impurity site can be the origin of the magnetism.…”

“…In its various forms and (sometimes) with the addition of small amounts of impurities, ZrO 2 has applications, for example, in refractory materials, solid oxide fuel cell electrolytes, catalyst substrates, protective coatings, functional ceramics, ceramic glazes, oxygen sensors, electro-ceramics, and abrasives and grinding media, etc. [5][6][7][8][9][10][11] Moreover, zirconia is one of the most radiation-resistant ceramics currently known; [12][13][14] therefore it has a particular importance in the nuclear industry. Also it was proposed, together with HfO 2 , as a gate dielectric material in metal-oxide semiconductor devices.…”

Affecting glass fibre surfaces and composite properties by two stage sizing application

“…Interphases between reinforcement and matrix are formed by the inter-diffusion of sizing and matrix [4], resulting in different compositions and properties compared to the bulk matrix. Interphases with gradual or monotonic change of mechanical properties and composition rather than homogeneous properties are highly expected, since in such case mechanical stresses can be efficiently transferred from matrix to reinforcement and the concentration of mechanical and thermomechanical stresses at this area can be greatly avoided [5]. Recent progresses in mechanical characterisation on interphases in combination with adhesion strength measurement and real composite mechanical tests indicated the presence of an interphase with mechanical property gradients leading to high mechanical properties [6][7][8][9][10][11].…”

Synthesis of SiOC Base Fibers from Silicone Resin with Low Carbon Content and Control of Surface Functionality by Metal Chloride Treatment in Vapor

“…The TiO 2 grains on the fiber acts as surface defects, and the strength is apparently low. Ishikawa et al reported the successful production of flexible SiO 2 -TiO 2 fibers by using polycarbosilane (PCS) base precursor [8,9]. To be used as fabrics, like such previous SiO 2 -TiO 2 fibers derived from polycarbosilane, the amount of TiCl 4 captured in the silicone resin fiber must be controlled at a low content to reduce the resin fiber swelling during the curing and the TiO 2 crystal growth at the fiber surface during the pyrolysis.…”