Additive manufacturing (AM) of co-fired low temperature ceramics offers a unique route for fabrication of novel 3D radio frequency (RF) and microwave communication components, embedded electronics and sensors. This paper describes the first-ever direct 3D printing of low temperature co-fired ceramics/floating electrode 3D structures. Slurry-based AM and selective laser burnout (SLB) were used to fabricate bulk dielectric, Bi 2 Mo 2 O 9 (BMO, sintering temperature = 620-650°C, ε r = 38) with silver (Ag) internal floating electrodes. A printable BMO slurry was developed and the SLB optimised to improve edge definition and burn out the binder without damaging the ceramic. The SLB increased the green strength needed for shape retention, produced crack-free parts and prevented Ag leaching into the ceramic during co-firing. The green parts were sintered after SLB in a conventional furnace at 645°C for 4 h and achieved 94.5% density, compressive strength of 4097 MPa, a relative permittivity (ε r) of 33.8 and a loss tangent (tan δ) of 0.0004 (8 GHz) for BMO. The feasibility of using SLB followed by a postprinting sintering step to create BMO/Ag 3D structures was thus demonstrated.

No abstract

No abstract

The effectiveness, kinetics and mechanism of oxidation of maleic acid in solution using a novel modified polyacrylonitrile (PAN) catalyst/hydrogen peroxide system was studied. The modified PAN catalyst contains immobilised Fe

A kinetic model has been developed that expresses the oxidation of maleic acid in solution using a novel modified (polyacrylonitrile) PAN catalyst=hydrogen peroxide system. The novel modified PAN catalyst contains immobilised Fe 3 þ and its reaction with hydrogen peroxide is thought to generate reactive hydroxyl radicals according to Fenton's reaction as well as another active iron oxo species. The model takes into account the presence of both hydroxyl radicals and active iron oxo species as well as hydroperoxyl radical and hydrogen peroxide in the oxidation process. Kinetic constants for the modified PAN=H 2 O 2 system towards the decomposition of maleic acid were determined, and their sensitivity analysed. Predicted concentration profiles of the radical species ( ? OH, HO ? 2 , O ? À 2 ), as well as iron species (Fe(III), Fe(II) and FeO) helped in gaining a better understanding the oxidation process. This model, with the new set of kinetic parameters, provides a superior fit to the experimental data compared to kinetic constants from the literature.