The spectral properties and colour functions of a radio frequency (RF)-based sputtering plasma source was monitored during consecutive sputter deposition of zinc doped indium oxide (IZO) thin films under argon and argon/hydrogen mix. The effect of target exposure to the hydrogen gas on charge density/mobility and spectral transmittance of the deposited films was investigated. We demonstrate that consecutive exposure to the hydrogen gas during the deposition process progressively affects the properties of thin films with a certain degree of continuous improvement in electrical conductivity while demonstrating that reverting to only argon from argon/ hydrogen mix follows a complex pathway, which has not been reported previously in such detail to our knowledge. We then demonstrate that this effect can be used to prepare highly conductive zinc oxide thin films without indium presence and as such eliminating the need for the expensive indium addition. We shall demonstrate that complexity observed in emission spectra can be simply identified by monitoring the colour of the plasma through its colour functions, making this technique a simple real-time monitoring method for the deposition process.
In recent years the quest for a circular economy approach and the upcycling of secondary raw materials have been pushed in the global political agenda. Increased interest has been taken by the recovery of materials from sludges, brines, contaminated waters and other media, all included in the larger umbrella identified as “low-grade” mineralisation. Contaminated soils have an interesting role in this process, and various methodologies have been developed using chemical, bacteriological and pyrometallurgical cleaning procedures. However, these procedures all involve the movement of high volume of materials and the disruption of the industrial landscape; furthermore, they often require the use of hazardous solvents and high energy processes. This work proposes to identify less impactful methods aimed at the recovery of metals from mining areas while preserving the landscape and avoiding environmental impacts such as the increase of CO2 for transport and increase hazard through use of solvents, this takes particular importance in areas of industrial heritage status. In particular, this work focuses on the use of Agrostis tenuis, an autochthonous species in mining areas of the UK, as a “mining tool” for the removal of lead. The selection of this plant is due to its visually non-invasive nature, as the plant is already present in these areas, it doesn’t grow above 10/15 cm and it also grows very fast and can be easily harvested with existing agricultural equipment. The experiments and results presented in this paper indicate: (1) Agrostis Tenuis shows the ability to adjust to contamination and increase its accumulation capacity; (2) the metal collected by the plant is fully transposed in the aerial part of the plant in a stable compound form and can consequently be harvested and further processed.
In recent years the quest for a circular economy approach and the upcycling of secondary raw materials have been pushed in the global political agenda. Increased interest has been taken by the recovery of materials from sludges, brines, contaminated waters and other media, all included in the larger umbrella identified as “low-grade” mineralisation. Contaminated soils have an interesting role in this process, and various methodologies have been developed using chemical, bacteriological and pyrometallurgical cleaning procedures. However, these procedures all involve the movement of high volume of materials and the disruption of the industrial landscape; furthermore, they often require the use of hazardous solvents and high energy processes. This work proposes to identify less impactful methods aimed at the recovery of metals from mining areas while preserving the landscape and avoiding environmental impacts such as the increase of CO2 for transport and increase hazard through use of solvents, this takes particular importance in areas of industrial heritage status. In particular, this work focuses on the use of Agrostis tenuis, an autochthonous species in mining areas of the UK, as a “mining tool” for the removal of lead. The experiments and results presented in this paper indicate: 1) Agrostis Tenuis shows the ability to adjust to contamination and increase its accumulation capacity; 2) the metal collected by the plant is fully transposed in the aerial part of the plant in a stable compound form.
In recent years the quest for a circular economy approach and the upcycling of secondary raw materials have been pushed in the global political agenda. Increased interest has been taken by the recovery of materials from sludges, brines, contaminated waters and other media, such as “mining” of waste. Contaminated soils have an interesting role in this process, and various methodologies have been developed using chemical, bacteriological and pyrometallurgical cleaning procedures. However, these procedures all involve the movement of high volume of materials and the disruption of the industrial landscape; furthermore, they often require the use of hazardous solvents and high energy processes. This work proposes to identify less impactful methods aimed at the recovery of metals from mining areas while preserving the landscape and avoiding environmental impacts such as the increase of CO2 for transport and increase hazard through use of solvents, this takes particular importance in areas of industrial heritage status. In particular, this work focuses on the use of Agrostis tenuis, an autochthonous species in mining areas of the UK, as a “mining tool” for the removal of lead. The selection of both the hyperaccumulator and the metal in this study are derived from the evaluation of the most common contamination in mining areas and the widespread prevalence of this hyperaccumulator and its resilience in highly contaminated abandoned mines. Aside from its presence within the mining areas, making it an autochthonous plant, Agrostis tenuis is selected for its visual morphology. Being a short grass, Agrostis does not change the visual appearance of the mining sites, most of which in the UK have a historic landscape status.
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