Herbert DaCosta

CO2 adsorption at nitrogen-doped carbons prepared by K2CO3 activation of urea-modified coconut shell

This article reports on the synthesis and characterization of porous nitrogen-doped carbons synthesized by carbonization of coconut shell followed by urea modification and K2CO3 activation. The as-synthesized samples were carefully characterized by various techniques. This series of samples demonstrate high CO2 uptake at 1bar, up to 3.71mmol/g at 25°C in addition to 5.12mmol/g at 0°C. Furthermore, these sorbents possess fast CO2 adsorption kinetics, stable reusability, moderate heat of CO2 adsorption, reasonable CO2/N2 selectivity, and high dynamic CO2 capture capacity under simulated flue gas conditions. It is found that, in addition to nitrogen content and narrow micropore volume, the pore size distribution of narrow micropore also plays a major role in determining the CO2 capture capacity under ambient condition. This work is intended to provide useful information and to inspire ways to develop new carbonaceous sorbents for removing CO2 from combustion flue gas.

Tribological Properties of CrAlN and TiN Coatings Tested in Nano- and Micro-scale Laboratory Wear Tests

We investigated the tribological properties of CrAlN and TiN coatings produced by electron beam plasma-assisted physical vapor deposition by nano- and micro-scale wear tests. For comparison, we also conducted nano-indentation, nano-scanning wear tests, and pin-on-disk tribotests on uncoated M2 steel. The results indicate that, after nano-scale sliding tests against diamond indenter and pin-on-disk tests against ceramic alumina counterface pins, the CrAlN coating presents superior abrasive wear resistance compared to the TiN-coated and uncoated M2 steel samples. Against aluminum counterface, aluminum is more prone to attach on the CrAlN coating surface compared to TiN coating, but no apparent adhesive wear was observed, which has occurred on the TiN coating.

Borate’s effects on coatings by PEO on AZ91D alloy

ABSTRACT This research is to produce corrosion protection coatings on magnesium alloys (AZ91D) with good performance and less time and less power consumption by optimising the electrolytes used in plasma electrolytic oxidation processes. Coatings were produced in a NaAlO2 solution and two composite electrolytes, namely NaAlO2/NaBO2 and NaAlO2/NaBO3. The effects of borate additives on the coating formation processes, phase structure, microstructure, and corrosion property are discussed. The results indicate that borate additives can greatly increase the coating growth rate and improve the corrosion property by strengthening the micro-arcing growth process and accelerating coating’s fuse and re-crystallisation. The coating can have a thickness of about 40 μm with NaBO3 additives in NaAlO2 electrolyte after 50-min treatment. The coating thickness is only 8 μm using NaAlO2 electrolyte. Specifically, the coating produced in NaBO3–NaAlO2 solution achieves the best corrosion resistance among all the coatings due to its uniform, dense, and thick structure.