Oxygen and hydrogen profiles in metal surfaces following plasma immersion ion implantation of helium

Helium ion implantation into metals can be used to form nanoscale cavities in high concentration in the surface. These cavity structures have unique features which offer potential for applications such as catalysis. Most previous studies have used ion accelerators to carry out the helium implantations. Here helium implantation using pulsed plasma immersion ion implantation (PI3 TM) is investigated. Previously we have reported results for PI3 implantations of 40-keV helium, and 20-keV oxygen, into Ti metal and two Ti alloys (including Ti-6Al-4V). Here we extend this work and examine in detail the depth profiles, determined by HERDA, of helium, hydrogen and oxygen in these metals following implantations of helium only, at several helium dose levels and two helium energies. It is found that the profiles for casual hydrogen and oxygen are strongly influenced by the depth profile and fluence of the implanted helium. The effect on the profiles of subsequent PI3 oxygen implantation is also reported

The effect of ventilation on air particulate matter in school classrooms

Health problems and respiratory diseases are associated with indoor air particulate matter (PM) mass. This is specially a concern in schools as children spend most of their time indoors. Understanding factors that affect PM mass such as occupant activities, ventilation and the infiltrating outdoor environment are important to safeguard occupant health. We investigated the air quality inside and outside two low decile primary school classrooms (children ages 7–9) over a three-week period during the southern hemisphere winter season in Palmerston North, New Zealand. Both classrooms were heated with wall mounted inverter heat pumps and in addition one classroom roof was fitted with a solar air heated ventilation unit (treatment). Particulate matter was continuously sampled and monitored to identify particles less than 10 µm in aerodynamic diameter (PM10) both outside and inside both classrooms to compare their indoor air quality. Significantly higher PM10 concentrations occurred within both classrooms during school hours (0845–1500), but the ventilated treatment classroom had PM10 concentrations on average 66% lower than those measured in the unventilated control classroom. Elemental composition and source apportionment of hourly samples showed that outdoor sources of PM10 infiltrated indoors, with similar contributions in both classrooms to those measured outdoors. However, the increased PM10 in the classrooms was predominantly from crustal sources, thought to be soil tracked in from outside on children's footwear and re-suspended during activities within the classrooms. Our results indicate that ventilation plays an important role in the quality of indoor air of classrooms and will contribute to the wellbeing of the students. In addition, there is a need to improve dust exposure mitigation strategies (carpet cleaning regime, dust reducing carpet) in classrooms fitted with carpets