Effect of Mechanical Milling and Cold Pressing on Co Powder

Absract: Cobalt (Co) is a transition metal used in electronics, magnetic recording [1], and hard materials [2–4]. Through thermal [5] and mechanical treatment [6–9], Co metal undergoes the allotropic HCP to FCC phase transformation. The current literature shows that metastable FCC phase is induced by ball milling (BM) [6], cold pressing [10], and thermal treatments [11]. It has been shown in the previous investigations that Co milled with W, V, and C powders forms the complex FCC Co-rich carbide with large lattice parameters [12]. Apart from the FCC phase, Co-based alloys undergo amorphization via electrodeposition [13, 14] and mechanical alloying (MA) [15–17] and during irradiation processes [18, 19]. It is worth noting that in the case of milling, the XRD peaks of nonmetallic elements such as Si in a mixture with Co vanish rapidly when subjected to BM and ultimately lead to amorphization [17]. Similar behaviour occurs when a mixture of Co and metallic elements is subjected to milling [15, 16, 20]..

Effect of Mechanical Milling and Cold Pressing on Co Powder

Absract: Cobalt (Co) is a transition metal used in electronics, magnetic recording [1], and hard materials [2–4]. Through thermal [5] and mechanical treatment [6–9], Co metal undergoes the allotropic HCP to FCC phase transformation. The current literature shows that metastable FCC phase is induced by ball milling (BM) [6], cold pressing [10], and thermal treatments [11]. It has been shown in the previous investigations that Co milled with W, V, and C powders forms the complex FCC Co-rich carbide with large lattice parameters [12]. Apart from the FCC phase, Co-based alloys undergo amorphization via electrodeposition [13, 14] and mechanical alloying (MA) [15–17] and during irradiation processes [18, 19]. It is worth noting that in the case of milling, the XRD peaks of nonmetallic elements such as Si in a mixture with Co vanish rapidly when subjected to BM and ultimately lead to amorphization [17]. Similar behaviour occurs when a mixture of Co and metallic elements is subjected to milling [15, 16, 20]..

Comparative study: the effect of annealing conditions on the properties of P3HT:PCBM blends

This paper presents a detailed study on the role of various annealing treatments on organic poly(3-hexylthiophene) and [6]-phenyl-C61-butyric acid methyl ester blends under different experimental conditions. A combination of analytical tools is used to study the alteration of the phase separation, structure and photovoltaic properties of the P3HT:PCBM blend during the annealing process. Results showed that the thermal annealing yields PCBM ‘‘needle-like’’ crystals and that prolonged heat treatment leads to extensive phase separation, as demonstrated by the growth in the size and quantity of PCBM crystals. The substrate annealing method demonstrated an optimal morphology by eradicating and suppressing the formation of fullerene clusters across the film, resulting in longer P3HT fibrils with smaller diameter. Improved optical constants, PL quenching and a decrease in the P3HT optical bad-gap were demonstrated for the substrate annealed films due to the limited diffusion of the PCBM molecules. An effective strategy for determining an optimized morphology through substrate annealing treatment is therefore revealed for improved device efficiency.Web of Scienc

The effect of lockdown regulations on SARS-CoV-2 infectivity in Gauteng Province, South Africa

Background. On 26 March 2020, the South African (SA) government initiated a 21-day national level 5 lockdown which was subsequently eased off and downgraded to level 4 on 1 May and to level 3 on 1 June. The effect of lockdown measures on SARS-CoV-2 infectivity is currently uncertain. In this article, we analyse the effects of the lockdown measures on the SARS-CoV-2 epidemic in one of the epicentres in SA.Objectives. To measure the effects of lockdown measures introduced in SA on SARS-CoV-2 attack rates (ARs, the percentage of individuals who tested positive in a specified time period) in Gauteng Province during a 4-month period (March - June 2020).Methods. In this retrospective cohort study, we used a comprehensive database from an independent pathology laboratory in Gauteng. We analysed trends of positivity rates of reverse transcription polymerase chain reaction tests done during the 4-month period. The ARs are reported over time (unweighted and age-weighted 14-day moving averages) by age groups, gender, and different regions/districts in Gauteng.Results. A total of 162 528 tests were performed at a private laboratory between 5 March and 30 June 2020, of which 20 574 were positive (overall AR 12.7%). These positive tests constituted 44.8% of all positive cases in the province (20 574/45 944). Sixty-two percent of all tests were done in June during lockdown level 3. There was an exponential increase in the AR in June (18.3%) when lockdown was eased to level 3, in comparison with 4.2% (March), 2.2% (April) and 3.3% (May). The increase in June was seen in all the age groups, although it was more pronounced in the 21 - 60 years age groups than the younger (0 - 20 years) and older (>60 years) age groups. The AR was significantly higher in males (13.2%) compared with females (12.1%) (χ2 test, p<0.0001).Conclusions. The findings of this study testify to the rapid increase in ARs resulting from easing of the lockdown regulations, especially to level 3 in June. Of concern is the upward trend in the AR across all age groups, especially <20 years (15.9%), which was not reported in other parts of the world. Population age dynamics should therefore be considered when taking future decisions about lockdown regulations

Thermally Induced Nano-Structural and Optical Changes of nc-Si:H Deposited by Hot-Wire CVD

We report on the thermally induced changes of the nano-structural and optical properties of hydrogenated nanocrystalline silicon in the temperature range 200–700 °C. The as-deposited sample has a high crystalline volume fraction of 53% with an average crystallite size of ~3.9 nm, where 66% of the total hydrogen is bonded as ≡Si–H monohydrides on the nano-crystallite surface. A growth in the native crystallite size and crystalline volume fraction occurs at annealing temperatures ≥400 °C, where hydrogen is initially removed from the crystallite grain boundaries followed by its removal from the amorphous network. The nucleation of smaller nano-crystallites at higher temperatures accounts for the enhanced porous structure and the increase in the optical band gap and average gap

Minimal information for studies of extracellular vesicles (MISEV2023): From basic to advanced approaches

Extracellular vesicles (EVs), through their complex cargo, can reflect the state of their cell of origin and change the functions and phenotypes of other cells. These features indicate strong biomarker and therapeutic potential and have generated broad interest, as evidenced by the steady year-on-year increase in the numbers of scientific publications about EVs. Important advances have been made in EV metrology and in understanding and applying EV biology. However, hurdles remain to realising the potential of EVs in domains ranging from basic biology to clinical applications due to challenges in EV nomenclature, separation from non-vesicular extracellular particles, characterisation and functional studies. To address the challenges and opportunities in this rapidly evolving field, the International Society for Extracellular Vesicles (ISEV) updates its 'Minimal Information for Studies of Extracellular Vesicles', which was first published in 2014 and then in 2018 as MISEV2014 and MISEV2018, respectively. The goal of the current document, MISEV2023, is to provide researchers with an updated snapshot of available approaches and their advantages and limitations for production, separation and characterisation of EVs from multiple sources, including cell culture, body fluids and solid tissues. In addition to presenting the latest state of the art in basic principles of EV research, this document also covers advanced techniques and approaches that are currently expanding the boundaries of the field. MISEV2023 also includes new sections on EV release and uptake and a brief discussion of in vivo approaches to study EVs. Compiling feedback from ISEV expert task forces and more than 1000 researchers, this document conveys the current state of EV research to facilitate robust scientific discoveries and move the field forward even more rapidly