Tensile properties of Fe-3Mn-0¿6/0¿7C steels sintered in semiclosed containers in dry hydrogen, nitrogen and mixtures thereof

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Mentor-Mentee Experiences Amidst COVID-19: A Teaching Practice Case Study

Preparing student teachers for the world of work is seen globally as a challenge. This research aims to explore mentors and mentees experiences in teaching practice during the COVID-19 period. In order to explore the challenge in this study, the following research question guided the paper: What are the teaching practice experiences of mentors and mentees at a school during COVID-19? The research question is a result of limited research done on the experiences of two groups during COVID-19. Informed by the realist social theory, we generated data via telephonic interviews with mentors and mentees in one school. The data was generated through semi-structured Interviews and thematic analysis was a method employed in the analysis of the data. The results present challenges experienced by mentees which, amongst others, include a feeling of inadequacy or a lack of confidence in their abilities to bring about order to the classroom and a feeling of being excluded in meetings and extra-curricular activities. On the other hand, mentors receive mentees without any prior warning or without arrangements made to accommodate them and the absence of the university officials except for assessment. Based on the results, a collaborative approach should be employed to deal with some of the challenges experienced by mentors and mentees

Microstructure and mechanical properties of sintered (2-4)Mn-(0¿6.-0¿8)C steels

YesMechanical properties of 2¿4% manganese PM steels were determined in tension and in bending following laboratory sintering in dry, hydrogen rich atmospheres. Young's modulus determined by an extensometric technique was about 115 GPa; when measured by an ultrasonic method it was about 153 GPa, in accordance with the`law of mixtures¿. The microstructures, significantly devoid of oxide networks, were predominantly pearlitic, but frequently with variability for specimens similarly processed, resulting in appreciable variations in the stresses for macroscopic yielding and fracture. The majority of the experiments were conducted on 3 and 4Mn¿0·6C alloys and for these R0·1 was in the range 275¿500 MPa, tensile strength (TS) 300¿600 MPa, and (apparent) transverse rupture strength (TRS) 640¿1260 MPa. Statistical techniques were employed to analyse the data. When careful control of processing was maintained, the Weibull modulus was highest, at about 17, for TS of furnace cooled specimens, and lowest, about 6, for TRS of the rapidly cooled specimens. In order to interpret the significant differences between the TRS and the TS values, both apparently measuring the critical stress for cracking after strains of up to 7%, a two stage normalising technique for TRS was adopted. By taking account of the plastic strains preceding failure, the elastic`strength of materials¿ formula was modified to allow true fracture stresses to be calculated. It was also postulated that failure was initiated from a population of flaws of variable size and then the `normalised¿ bend strengths, smaller than TRSs, were shown to correspond well with TSs. It is suggested that this combined plasticity correction and Weibull analysis approach, which has a sound scientific basis, should be employed to interpret bend test data in preference to empirical correlations between TS and TRS

Managing the Culture of COVID-19 "New Normal" as a Motivation for University Students in South Africa

The advent of COVID-19 and its implication on university education has been the bone of contention in recent times. The COVID-19 emergency has led to a change in knowledge inputs, processes, and outputs. This trajectory has demotivated student approaches to their learning. In response to this revolution, this study provides motivational strategies through students' perspectives to respond to the underside of new normal among South African university students. Ubuntu underpins the study within the Transformative Paradigm lens and Participatory Research as a research design. Ten students of a particular module in a selected university in South Africa were chosen to participate in the study. They were selected using the snowballing sampling technique because the participants were under level 3 lockdown with little or no access to campus at the time of the study. Online interview via phone calls, email and WhatsApp, was conducted with the students, and the data were analysed using Thematic Analysis. The study revealed a lack of visualised physical engagement between students and their lecturers and unstable internet access and lack of the internet as the major challenges.  The study, therefore, recommends solutions that there should be adequate provision of effective online audio-visual sessions with enough space for student-lecturer’s interactions and low-tech online sessions and content deliveries

Sintering microstructure and mechanical properties of PM manganese-molybdenum steels

YesThe effects of 0·5 wt-%Mo addition on the processing, microstructure, and strength of PM Fe¿3·5Mn¿0·7C steel are described. Water atomised and sponge irons, Astaloy 1·5Mo, milled ferromanganese, and graphite were the starting powders. During sintering in 75H2 /25N2 or pure hydrogen the dewpoint was controlled and monitored; in particular the effects of improving it from -35 to -60°C were investigated. Faster heating rates (20 K min-1), sufficient gas flowrates, milling the ferro alloy under nitrogen, a low dewpoint (<-60°C), and a getter powder can all contribute to the reduction or prevention of oxidation of the manganese, in particular formation of oxide networks in the sintered steels. For 600 MPa compaction pressure densities up to 7·1 g cm-3 were obtained; these were not significantly affected by sintering at temperatures up to 1180°C. The sintered microstructures were sensitively dependent on the cooling rate. Irrespective of the presence of Mo, slow furnace cooling at 4 K min-1 resulted in mainly pearlitic structures with some ferrite and coarse bainite, whereas fast cooling at 40 K min-1 produced martensite and some retained austenite, very fine pearlite, bainite, and some ferrite. Young's modulus, determined by tensile and ultrasonic tests, was in the range 110¿155 GPa. Sintering with -60°C dewpoint resulted in tensile and transverse rupture strengths of420 and 860 MPa for the Mn steel, rising to 530 and1130 MPa as a result of the Mo addition. This contrasts with strength decreases observed when processing included use of high oxygen containing ferromanganese and sintering with -35°C dewpoint

Trace species detection in the near infrared using Fourier transform broadband cavity enhanced absorption spectroscopy: Initial studies on potential breath analytes

Cavity enhanced absorption measurements have been made of several species that absorb light between 1.5 and 1.7 µm using both a supercontinuum source and superluminescent light emitting diodes. A system based upon an optical enhancement cavity of relatively high finesse, consisting of mirrors of reflectivity ∼99.98%, and a Fourier transform spectrometer, is demonstrated. Spectra are recorded of isoprene, butadiene, acetone and methane, highlighting problems with spectral interference and unambiguous concentration determinations. Initial results are presented of acetone within a breath-like matrix indicating ppm precision at &lt;∼10 ppm acetone levels. Instrument sensitivities are sufficiently enhanced to enable the detection of atmospheric levels of methane. Higher detection sensitivities are achieved using the supercontinuum source, with a minimum detectable absorption coefficient of ∼4 × 10(-9) cm(-1) reported within a 4 min acquisition time. Finally, two superluminescent light emitting diodes are coupled together to increase the wavelength coverage, and measurements are made simultaneously on acetylene, CO(2), and butadiene. The absorption cross-sections for acetone and isoprene have been measured with an instrumental resolution of 4 cm(-1) and are found to be 1.3 ± 0.1 × 10(-21) cm(2) at a wavelength of 1671.9 nm and 3.6 ± 0.2 × 10(-21) cm(2) at 1624.7 nm, respectively

Chemical reactions during sintering of Fe-Cr-Mn-Si-Ni-Mo-C-steels with special reference to processing in semi-closed containers

Sintering of Cr, Mn and Si bearing steels has recently attracted both experimental and theoretical attention and processing in semiclosed containers has been reproposed. This paper brings together relevant thermodynamic data and considers the kinetics of some relevant chemical reactions. These involve iron and carbon, water vapour, carbon monoxide and dioxide, hydrogen and nitrogen of the sintering atmospheres and the alloying elements Cr, Mn, Mo and Si. The paper concludes by presenting mechanical properties data for three steels sintered in local microatmosphere with nitrogen, hydrogen, nitrogen-5% hydrogen and air as the furnace gas