Damian Kowalski

Self-healing ion-permselective conducting polymer coating

The present work demonstrates a new approach to self-healing polymers that have the ability to repair artificial defects and restore the passive state of an underlying metal substrate. An intrinsically conducting polymer (ICP) with a well designed function of doped ions possesses specific permselective properties, restricting incorporation of aggressive chlorides from corrosive electrolyte. The cation permselective membrane controls the release of healing ions to the defect zone when artificial defects are formed, efficiently inhibiting corrosion of the underlying metal substrate.

High Proton Conductivity in Anodic ZrO2/WO3 Nanofilms

The proton conductivity of the anodic ZrO2–WO3–SiO2 nanofilms prepared by anodizing of sputter-deposited Zr37W47Si16 alloy at several formation voltages for 1.8 ks in 0.1 mol dm phosphoric acid electrolyte at 20C has been examined below 250C in various environments. The proton conductivity activated by thermal treatment at 250C is not influenced by the presence of O2 and H2O in the atmosphere. However, the conductivity is enhanced by one order of magnitude in H2-containing atmosphere. The H2-induced conductivity enhancement is reversible; the enhanced conductivity is returned to an original value by exposing again in an O2containing atmosphere.

Self-healing Ability of Conductive Polypyrrole Coating with Artificial Defect

Graduate School of Engineering, Hokkaido University, Sapporo 060-8628, JAPAN . A bi-layered PPy film consisting of an inner layer doped with Keggin-structure anions of PMo12O40 and HPO4 (PPy-PMo12) and an outer layer doped with organic anions of dodecyl sulfate (PPy-DoS) exhibited a self-healing property when coated on steel. When a defect was introduced into the PPy-coated steel immersed in 3.5% NaCl aqueous solution, the potential initially decreased and activation of the coated steel occurred. After a few hours, the potential was recovered to the passive region, and the passivation continued for another 20 hours. Without any damage, the release of PMo12 doped in the inner layer was inhibited by the outer PPy layer doped with DoS. When a defect was introduced into the PPy film, the inner PPy layer released phosphate and molybdate anions to the damaged zone due to their decomposition via hydrolysis. Both anions work as passivation inhibitors and helped to repassivate the damaged zone on the steel.

Enhanced hydrogen permeability of hafnium nitride nanocrystalline membranes by interfacial hydride conduction

Hydrogen permeability based on mixed hydride ion electron conduction was demonstrated for hafnium nitride HfNx (film thickness of 100–500 nm, x = 0.8 and 1.0) nanocrystalline membranes. Nanocrystalline films with a (100) orientation and crystallite sizes of a few tens of nanometers were prepared on porous alumina supports by radio frequency (RF) reactive sputtering. Combined spectroscopic, permeability, and microbalance analysis suggests that the nanocrystalline matrices were readily hydrogenated by the formation of Hf–H terminal groups on the internal grain surfaces at ambient temperature and thus efficient hydrogen permeation took place due to an enhanced diffusion of hydridic defects through the grain boundaries; this was further aided by the Hf–H bond exchange process. Hence, membranes with an average crystallite size of 11 nm yielded a hydrogen flux of 6 × 10−7 mol cm−2 s−1 at 25 °C at an applied hydrogen partial pressure of 50 kPa; this value is higher than those exhibited by the current state-of-the-art Pd membranes. These findings establish a new concept for Pd alternatives based on the pronounced hydric conductivity of transition metal nitride nanomaterials.

High-Efficiency Direct Ammonia Fuel Cells Based on BaZr0.1Ce0.7Y0.2O3− δ /Pd Oxide-Metal Junctions

Abstract A direct ammonia‐type intermediate temperature fuel cell is examined by means of a hydrogen membrane fuel cell (HMFC) comprising 1‐µm‐thick BaZr0.1Ce0.7Y0.2O3− δ (BZCY) thin‐film electrolyte and Pd solid anode. It generates the maximum power density of 0.58 W cm−2 at 600 °C with ammonia fuels, and this value is found to be three times larger than the champion data of the recently reported direct ammonia‐type proton‐conducting ceramic fuel cells (PCFCs). AC impedance spectroscopy is performed to determine the interfacial polarization resistances, disclosing that the anodic overpotentials of HMFCs are at least one order of magnitude smaller than those of anode‐supported PCFC under relatively high DC outputs. The anode reactions are driven by the oxidation of monoatomic hydrogen dissolving at the BZCY/Pd solid–solid interface, mediated via proton transfer from Pd to BZCY. The electrochemical analysis reveals that the BZCY/Pd junction forms Ohmic contact without growth of wide depletion layer and thus facilitates the proton transfer reactions because the interfacial region beneath Pd electrode can accommodate amounts of protonic defects as well as the bulk of BZCY due to the small depletion of holes under hole–proton thermodynamic equilibrium.

Characterization of Amorphous Anodic Nb2O5 Nanofilm for Gas Sensing

Amorphous Nb2O5 film of 167 nm thickness was fabricated by anodic oxidation of sputter deposited niobium and characterized by TEM, GD-OES and AFM. The electric properties of the anodic films with sputter-deposited circular gold electrodes were studied by AC impedance spectroscopy in ambient gas atmospheres of air, argon, oxygen or hydrogen in the temperature range of 25 – 200C. The amorphous Nb2O5 showed the character of n-type semiconductor. The conductivity of the film, following the Arrhenius behaviour, was independent of the oxygen partial pressure, but was largely dependent on hydrogen partial pressure. The conductivity of the Nb2O5 film at room temperature in dry hydrogen was 2.2 orders of magnitude as high as that in air. The enhanced conductivity could be associated with partial reduction of Nb in dry hydrogen atmosphere. The addition of water vapor to hydrogen atmosphere reduced conductivity probably due to suppressing the reduction of Nb2O5.