title: Valorization of wood ash for sustainable in situ reinforced Ti composites with tailorable mechanical behavior manufactured via powder metallurgy

authors: Bolzoni, Leandro

subjects: composites

abstract: The aim of this work is to investigate the feasibility of revalorizing commonly disposed wood ash as source to produce more sustainable in situ reinforced Ti composites. We propose a manufacturing process based on the powder metallurgy green technology and further increase the energy efficiency of the process by analyzing reactive induction sintering as the primary consolidation method. The feasibility of the proposed approach is demonstrated through the characterization of the physical, microstructural, and mechanical performance. It is found that compressibility decreases and the amount of residual porosity increases (6.0–11.7% for pressureless sintering) with the amount of wood ash used (0–0.25 wt%). However, the effective in situ creation of the reinforcement is always guaranteed by the proposed approach. Furthermore, minor adjustments of the manufacturing route can be used to maximize the amount of ash to be added for higher sustainability. The in situ reinforced Ti composites are commonly characterized by both elastic and plastic deformation and fail non-catastrophically, where for vacuum sintering ductility decreases (13.7 → 8.7%) but strength (497 → 653 MPa) and hardness (47.8 → 55.0 HRA) increase with the amount of ash used. The in situ reinforced Ti composites produced from revalorized wood ash have overall comparable or better mechanical properties in comparison to other Ti-based composites bearing a higher amount of generally more expensive reinforcements.

text: Valorization of wood ash for sustainable in situ reinforced Ti composites with tailorable mechanical behavior manufactured via powder metallurgy The aim of this work is to investigate the feasibility of revalorizing commonly disposed wood ash as source to produce more sustainable in situ reinforced Ti composites. We propose a manufacturing process based on the powder metallurgy green technology and further increase the energy efficiency of the process by analyzing reactive induction sintering as the primary consolidation method. The feasibility of the proposed approach is demonstrated through the characterization of the physical, microstructural, and mechanical performance. It is found that compressibility decreases and the amount of residual porosity increases (6.0–11.7% for pressureless sintering) with the amount of wood ash used (0–0.25 wt%). However, the effective in situ creation of the reinforcement is always guaranteed by the proposed approach. Furthermore, minor adjustments of the manufacturing route can be used to maximize the amount of ash to be added for higher sustainability. The in situ reinforced Ti composites are commonly characterized by both elastic and plastic deformation and fail non-catastrophically, where for vacuum sintering ductility decreases (13.7 → 8.7%) but strength (497 → 653 MPa) and hardness (47.8 → 55.0 HRA) increase with the amount of ash used. The in situ reinforced Ti composites produced from revalorized wood ash have overall comparable or better mechanical properties in comparison to other Ti-based composites bearing a higher amount of generally more expensive reinforcements.

year: 2024

title: Coordination polymers and isomerism; a study using silver(I) and a ∏-stacked ligand

authors: Caradoc-Davies, Paula L.

subjects: chemistry

abstract: The ligand 2,5-bis(2-pyridylmethylsulfanylmethyl)pyrazine (L) was prepared by the base coupling of 2-(sulfanylmethyl)pyridine and 2,5-bis(chloromethyl)pyrazine. This new ligand was treated with AgClO₄ in a 1   1 metal-to-ligand ratio and with AgNO₃in a 2   1 metal-to-ligand ratio to give coordination polymers. The crystal structures of {[Ag(L)]ClO₄}∞ ( 1) and {[Ag₂(L)](NO₃)₂}∞ ( 2) were determined. The Ag(I) ions in the one-dimensional polymeric chains of 1 adopted square-pyramidal geometries with the pyridine and pyrazine N donors coordinated in an extremely bent fashion. The structure of 2 revealed two isomeric polymer chains in the one crystal forming a single supramolecular array. The isomeric polymers differed in the donor atoms about the Ag(I) ions and in the arrangement of adjacent ligands along the chain. A feature of both structures was that L adopted a three-layer ∏-stacked arrangement.

text: Coordination polymers and isomerism; a study using silver(I) and a ∏-stacked ligand The ligand 2,5-bis(2-pyridylmethylsulfanylmethyl)pyrazine (L) was prepared by the base coupling of 2-(sulfanylmethyl)pyridine and 2,5-bis(chloromethyl)pyrazine. This new ligand was treated with AgClO₄ in a 1   1 metal-to-ligand ratio and with AgNO₃in a 2   1 metal-to-ligand ratio to give coordination polymers. The crystal structures of {[Ag(L)]ClO₄}∞ ( 1) and {[Ag₂(L)](NO₃)₂}∞ ( 2) were determined. The Ag(I) ions in the one-dimensional polymeric chains of 1 adopted square-pyramidal geometries with the pyridine and pyrazine N donors coordinated in an extremely bent fashion. The structure of 2 revealed two isomeric polymer chains in the one crystal forming a single supramolecular array. The isomeric polymers differed in the donor atoms about the Ag(I) ions and in the arrangement of adjacent ligands along the chain. A feature of both structures was that L adopted a three-layer ∏-stacked arrangement.

year: 2001

title: Tangihanga: The ultimate form of Māori cultural expression - overview of a research programme

authors: Nikora, Linda Waimarie

subjects: Māori

abstract: Death, observed through the process of tangihanga (time set aside to grieve and mourn, rites for the dead) or tangi (to grieve and mourn), is the ultimate form of Māori cultural expression. It is also the topic least studied by Māori or understood by outsiders, even after televised funeral rites of Māori leaders and intrusive media engagements with more humble family crises. It has prevailed as a cultural priority since earliest European contact, despite missionary and colonial impact and interference, and macabre Victorian fascination. Change is speculative rather than confirmed. Tangi and death rituals have yet to be rigorously examined in the Māori oral canon, or in the archival and historic record that may be discarded or reinforced by current practice. As researchers we are committed to studying tangi, conscious of the belief that such work carries the inherent risk of karanga aituā (inviting misfortune or even death itself) by drawing attention to it. Contemporary Aotearoa New Zealand is constantly touched by aspects of tangi practice through popular media and personal exposure.

This volatile subject nevertheless demands careful and comprehensive scrutiny in order to extend and enrich the knowledge base, reveal the logic that guides ritual, inform the wider New Zealand community and, more importantly, support the cultural, social, ritual, economic and decision making processes of bereaved whānau (family, including extended family), people affiliated with marae (communal meeting complex) and iwi (tribe, tribal). This paper provides an overview of a research programme that began in July 2009, based at The University of Waikato. The programme is funded by Ngā Pae o te Māramatanga, the Marsden Fund of New Zealand and the Health Research Council of New Zealand.

text: Tangihanga: The ultimate form of Māori cultural expression - overview of a research programme Death, observed through the process of tangihanga (time set aside to grieve and mourn, rites for the dead) or tangi (to grieve and mourn), is the ultimate form of Māori cultural expression. It is also the topic least studied by Māori or understood by outsiders, even after televised funeral rites of Māori leaders and intrusive media engagements with more humble family crises. It has prevailed as a cultural priority since earliest European contact, despite missionary and colonial impact and interference, and macabre Victorian fascination. Change is speculative rather than confirmed. Tangi and death rituals have yet to be rigorously examined in the Māori oral canon, or in the archival and historic record that may be discarded or reinforced by current practice. As researchers we are committed to studying tangi, conscious of the belief that such work carries the inherent risk of karanga aituā (inviting misfortune or even death itself) by drawing attention to it. Contemporary Aotearoa New Zealand is constantly touched by aspects of tangi practice through popular media and personal exposure.

This volatile subject nevertheless demands careful and comprehensive scrutiny in order to extend and enrich the knowledge base, reveal the logic that guides ritual, inform the wider New Zealand community and, more importantly, support the cultural, social, ritual, economic and decision making processes of bereaved whānau (family, including extended family), people affiliated with marae (communal meeting complex) and iwi (tribe, tribal). This paper provides an overview of a research programme that began in July 2009, based at The University of Waikato. The programme is funded by Ngā Pae o te Māramatanga, the Marsden Fund of New Zealand and the Health Research Council of New Zealand.

year: 2010