title: Synthesis, characterisation, and properties of powder metallurgy transition metal-based high entropy alloys for electrocatalytic application

authors: Kumar, Ashok

subjects: Powder metallurgy

abstract: Water electrolysis is an eco-friendly route for hydrogen production when compared to other routes such as steam reforming, coal gasification, biomass gasification etc, however only 4% of hydrogen is being produced through water electrolysis. Water electrolysis proceeds via two half-cell reactions namely oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). HER is a two-electron transfer process while OER is a four electron/proton transfer process. Hence OER is energy intensive and affects the overall efficiency of water electrolysis. To improve the efficiency of water electrolysis, it is necessary to develop an efficient electrocatalyst for OER process. Ir and Ru based oxides are the state-of-the-art electrocatalysts for OER, however their natural abundance is minuscule, hence they are expensive. Transition metal based electrocatalysts are emerging materials for OER applications due to their high natural abundance and low cost. However, these materials exhibit poor conductivity and consequently poor catalytic activity. Hence to overcome the shortcomings of conventional electrocatalysts a new class of multi component alloys termed as high entropy alloys (HEAs) are getting popular for electrocatalytic applications. However, most of the HEAs for OER are not self-supporting and being synthesised in powder form are often coated onto conductive substrates such as Ni foam and carbon fibre. Hence this powder based electrocatalysts are not suitable for industrial scale hydrogen production. In addition, most synthesised HEAs consist of Co which is an inherently expensive material. To overcome these current drawbacks in this field, this thesis considered three Co free self-supporting HEA combinations namely NiMnFeCu, NiMnFeCrCu and NiMnFeCr which were successfully synthesized. Among the synthesized HEAs examined, NiMnFeCr was found to exhibit an overpotential of 300 mV after it was subjected to 100 cycles of cyclic voltammetry (CV) activation. Furthermore, the NiMnFeCr HEA synthesised exhibited a compressive yield stress of 306 MPa manifesting the excellent combined properties of not only catalytic activity but also mechanical strength. The research showed that NiMnFeCr was a suitable candidate material for industrial scale water electrolysis and hence can be considered as a potential replacement for the conventional, prominently used electrocatalysts such as Raney nickel, Ir and Ru oxide- based catalysts. The excellent catalytic activity demonstrated by the HEA NiMnFeCr could also be attributed to its work function of 3.02 eV which is the lowest value of work function of other studied HEAs.

text: Synthesis, characterisation, and properties of powder metallurgy transition metal-based high entropy alloys for electrocatalytic application Water electrolysis is an eco-friendly route for hydrogen production when compared to other routes such as steam reforming, coal gasification, biomass gasification etc, however only 4% of hydrogen is being produced through water electrolysis. Water electrolysis proceeds via two half-cell reactions namely oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). HER is a two-electron transfer process while OER is a four electron/proton transfer process. Hence OER is energy intensive and affects the overall efficiency of water electrolysis. To improve the efficiency of water electrolysis, it is necessary to develop an efficient electrocatalyst for OER process. Ir and Ru based oxides are the state-of-the-art electrocatalysts for OER, however their natural abundance is minuscule, hence they are expensive. Transition metal based electrocatalysts are emerging materials for OER applications due to their high natural abundance and low cost. However, these materials exhibit poor conductivity and consequently poor catalytic activity. Hence to overcome the shortcomings of conventional electrocatalysts a new class of multi component alloys termed as high entropy alloys (HEAs) are getting popular for electrocatalytic applications. However, most of the HEAs for OER are not self-supporting and being synthesised in powder form are often coated onto conductive substrates such as Ni foam and carbon fibre. Hence this powder based electrocatalysts are not suitable for industrial scale hydrogen production. In addition, most synthesised HEAs consist of Co which is an inherently expensive material. To overcome these current drawbacks in this field, this thesis considered three Co free self-supporting HEA combinations namely NiMnFeCu, NiMnFeCrCu and NiMnFeCr which were successfully synthesized. Among the synthesized HEAs examined, NiMnFeCr was found to exhibit an overpotential of 300 mV after it was subjected to 100 cycles of cyclic voltammetry (CV) activation. Furthermore, the NiMnFeCr HEA synthesised exhibited a compressive yield stress of 306 MPa manifesting the excellent combined properties of not only catalytic activity but also mechanical strength. The research showed that NiMnFeCr was a suitable candidate material for industrial scale water electrolysis and hence can be considered as a potential replacement for the conventional, prominently used electrocatalysts such as Raney nickel, Ir and Ru oxide- based catalysts. The excellent catalytic activity demonstrated by the HEA NiMnFeCr could also be attributed to its work function of 3.02 eV which is the lowest value of work function of other studied HEAs.

year: 2023

title: Isolation and characterization of soda lignin from OPEFB and evaluation of its performance as wood adhesive

authors: Toma, Farhana Sultana

subjects: Black Liquor

abstract: The purpose of this study was to explore the mechanical properties of plywood panels that had been bound with lignin-phenol-formaldehyde (LPF) adhesive. LPF, composed of lignin that was extracted from Oil Palm Empty Fruit Bunch (OPEFB) fiber by soda pulping method and characterized by Fourier Transform Infrared (FT-IR), Nuclear Magnetic Resonance (HNMR), and Thermal Gravimetric Analyzer (TGA) analysis. Then, various compositions of soda lignin (10-50 wt %) were used as a phenol substitute in LPF synthesis. The characteristics of the synthesized adhesive were compared to the properties of phenol formaldehyde (PF) adhesive. Plywood was fabricated with LPF and its mechanical properties were studied and evaluated using industrial standards. The result indicates that the increase of phenol substitution with soda lignin, up to 40%, improves the mechanical properties of plywood. This research demonstrated the use of lignin as a renewable replacement of phenol in PF adhesive formulation.

text: Isolation and characterization of soda lignin from OPEFB and evaluation of its performance as wood adhesive The purpose of this study was to explore the mechanical properties of plywood panels that had been bound with lignin-phenol-formaldehyde (LPF) adhesive. LPF, composed of lignin that was extracted from Oil Palm Empty Fruit Bunch (OPEFB) fiber by soda pulping method and characterized by Fourier Transform Infrared (FT-IR), Nuclear Magnetic Resonance (HNMR), and Thermal Gravimetric Analyzer (TGA) analysis. Then, various compositions of soda lignin (10-50 wt %) were used as a phenol substitute in LPF synthesis. The characteristics of the synthesized adhesive were compared to the properties of phenol formaldehyde (PF) adhesive. Plywood was fabricated with LPF and its mechanical properties were studied and evaluated using industrial standards. The result indicates that the increase of phenol substitution with soda lignin, up to 40%, improves the mechanical properties of plywood. This research demonstrated the use of lignin as a renewable replacement of phenol in PF adhesive formulation.

year: 2023-09

title: Two Decades After Siaan Nathan’s (1999) Study: Revisiting the Responsiveness of Professional Clinical Psychology Programmes

authors: Chan, Joanna

abstract: Clinical psychology training programmes in Aotearoa New Zealand are predominantly monocultural and centred on perspectives from Western Europe and North America. Several initiatives have sought to address the monocultural dominance of Western psychology in training programmes, with limited sustainability. We surveyed clinical psychology programme directors (N=6) to assess the progress of programmes towards meeting Te Tiriti o Waitangi obligations across five key domains (Māori representation across programme staff and students, advisory group, admissions process and programme content). Promisingly, progress regarding the inclusion of Māori-focused content and faculty representation was identified. However, all directors reported that the increase in Māori student representation was slow, with half (n=3) reporting the number of tauira Māori applicants to programmes was an ongoing concern. The limited progress towards ensuring increased Māori representation was thought to reflect system constraints. The findings highlight the pressing need for clinical psychology training to fulfil Te Tiriti o Waitangi obligations to support tino rangatiratanga for Māori that leads to transformative change. Notably, equity for Māori was identified as a priority through the provision of sufficient and sustainable resourcing for kaupapa Māori psychologies.

text: Two Decades After Siaan Nathan’s (1999) Study: Revisiting the Responsiveness of Professional Clinical Psychology Programmes Clinical psychology training programmes in Aotearoa New Zealand are predominantly monocultural and centred on perspectives from Western Europe and North America. Several initiatives have sought to address the monocultural dominance of Western psychology in training programmes, with limited sustainability. We surveyed clinical psychology programme directors (N=6) to assess the progress of programmes towards meeting Te Tiriti o Waitangi obligations across five key domains (Māori representation across programme staff and students, advisory group, admissions process and programme content). Promisingly, progress regarding the inclusion of Māori-focused content and faculty representation was identified. However, all directors reported that the increase in Māori student representation was slow, with half (n=3) reporting the number of tauira Māori applicants to programmes was an ongoing concern. The limited progress towards ensuring increased Māori representation was thought to reflect system constraints. The findings highlight the pressing need for clinical psychology training to fulfil Te Tiriti o Waitangi obligations to support tino rangatiratanga for Māori that leads to transformative change. Notably, equity for Māori was identified as a priority through the provision of sufficient and sustainable resourcing for kaupapa Māori psychologies.

year: 2025