title: (Chloromethyl)pentacarbonylmanganese(I): a crystal structure with a non-crystallographic centre of symmetry

authors: Nicholson, Brian K.

subjects: chloromethyl

abstract: There are two molecules in the asymmetric unit of the P2₁/c unit cell of ClCH₂Mn(CO)₅, the first halomethyl complex of manganese to be structurally determined. The molecules are crystallographically independent, despite an apparent local centre of symmetry. The average bond parameters include Mn–Calkyl 2.128(8) Å, C–Cl 1.811(8) Å and Mn–C–Cl 116.4(4)°

text: (Chloromethyl)pentacarbonylmanganese(I): a crystal structure with a non-crystallographic centre of symmetry There are two molecules in the asymmetric unit of the P2₁/c unit cell of ClCH₂Mn(CO)₅, the first halomethyl complex of manganese to be structurally determined. The molecules are crystallographically independent, despite an apparent local centre of symmetry. The average bond parameters include Mn–Calkyl 2.128(8) Å, C–Cl 1.811(8) Å and Mn–C–Cl 116.4(4)°

year: 2008

title: Mechanical behaviour of Titanium, Ti-6Al-4V (wt %) alloy and Ti-47Al-2Cr (at %) alloy produced using powder compact forging

authors: Nadakuduru, Vijay Navaratna

subjects: mechanical behaviour

abstract: Powder compact forging was used to produce bulk consolidated titanium and Ti-6Al-4V (wt %) and Ti-47Al-2Cr (at%) alloy disks from hydrogenated and dehydrogenated (HDH) and gas atomised powders (GA) powders (in the case of titanium and Ti-6Al-4V) and a mechanically milled powder (in the case of Ti-47Al-2Cr alloy). The bulk titanium and Ti-6Al-4V (wt %) alloy have been produced by forging of the powder compacts. The Ti-47Al-2Cr (at %) alloy was produced using canned powder compact forging of a Ti/Al/Cr composite powder. The purpose of the present study is to investigate the deformation and fracture behaviour of the bulk consolidated as-forged materials, by conducting tensile testing at room temperature (RT) and examination of the fractured specimens which had near-α, α + β and γ phase structures, respectively. It was found that as-forged bulk titanium disk produced using HDH powder showed a yield point with a yield strength of ~700 MPa and with a considerable amount of ductility. While the as-forged Ti-6Al-4V (wt %) alloy produced using HDH powder, fractured prematurely without any yielding. On the other hand yielding was observed in the as-forged Ti-6Al-4V (wt %) alloy produced using GA powder, showing a yield strength of ~970 MPa and a considerable amount of plastic strain to fracture. The bulk consolidated Ti-47Al-2Cr (at %) alloy also fractured prematurely with fracture strength of ~125 MPa. The mechanical behaviour of the as-forged bulk materials was found to be dependent on several factors such as initial powders used, green density of the powder compact, forging parameters used during forging. It was expected that the entrapped gas in green compacts, absorbed oxygen, porosity and inter-particle bonding play an important role on the quality of the as-forged material, which in turn affected the mechanical behaviour of the bulk material.

text: Mechanical behaviour of Titanium, Ti-6Al-4V (wt %) alloy and Ti-47Al-2Cr (at %) alloy produced using powder compact forging Powder compact forging was used to produce bulk consolidated titanium and Ti-6Al-4V (wt %) and Ti-47Al-2Cr (at%) alloy disks from hydrogenated and dehydrogenated (HDH) and gas atomised powders (GA) powders (in the case of titanium and Ti-6Al-4V) and a mechanically milled powder (in the case of Ti-47Al-2Cr alloy). The bulk titanium and Ti-6Al-4V (wt %) alloy have been produced by forging of the powder compacts. The Ti-47Al-2Cr (at %) alloy was produced using canned powder compact forging of a Ti/Al/Cr composite powder. The purpose of the present study is to investigate the deformation and fracture behaviour of the bulk consolidated as-forged materials, by conducting tensile testing at room temperature (RT) and examination of the fractured specimens which had near-α, α + β and γ phase structures, respectively. It was found that as-forged bulk titanium disk produced using HDH powder showed a yield point with a yield strength of ~700 MPa and with a considerable amount of ductility. While the as-forged Ti-6Al-4V (wt %) alloy produced using HDH powder, fractured prematurely without any yielding. On the other hand yielding was observed in the as-forged Ti-6Al-4V (wt %) alloy produced using GA powder, showing a yield strength of ~970 MPa and a considerable amount of plastic strain to fracture. The bulk consolidated Ti-47Al-2Cr (at %) alloy also fractured prematurely with fracture strength of ~125 MPa. The mechanical behaviour of the as-forged bulk materials was found to be dependent on several factors such as initial powders used, green density of the powder compact, forging parameters used during forging. It was expected that the entrapped gas in green compacts, absorbed oxygen, porosity and inter-particle bonding play an important role on the quality of the as-forged material, which in turn affected the mechanical behaviour of the bulk material.

year: 2011

title: Ngā Whanaketanga: Minimising contradictions and maximising opportunities for teacher learning.

authors: Hohepa, Margie Kahukura

subjects: Māori medium teacher professional development

abstract: In 2010 the assessment of student progress and achievement against National Standards became mandatory in English medium schooling in Aotearoa New Zealand. In that same year information gathering and revision work was carried out on the then draft Whanaketanga, developed in 2009. The Whanaketanga are deemed to be the equivalent to National Standards for classrooms implementing Te Marautanga o Aotearoa, the curriculum for immersion Māori medium settings. The information gathering and revision work was carried out in readiness for mandatory implementation of the Whanaketanga in 2011. The work also provided important opportunities for Māori medium teacher professional learning and development. The introduction of National Standards has been controversial. The development of Whanaketanga has also been controversial and challenging in nature. The first half of this paper provides an overview of Whanaketanga development and the challenges its developers worked hard to address. The second part discusses implications for Māori medium teacher professional learning and development, drawn from findings from research case studies of the information gathering and revision work.

text: Ngā Whanaketanga: Minimising contradictions and maximising opportunities for teacher learning. In 2010 the assessment of student progress and achievement against National Standards became mandatory in English medium schooling in Aotearoa New Zealand. In that same year information gathering and revision work was carried out on the then draft Whanaketanga, developed in 2009. The Whanaketanga are deemed to be the equivalent to National Standards for classrooms implementing Te Marautanga o Aotearoa, the curriculum for immersion Māori medium settings. The information gathering and revision work was carried out in readiness for mandatory implementation of the Whanaketanga in 2011. The work also provided important opportunities for Māori medium teacher professional learning and development. The introduction of National Standards has been controversial. The development of Whanaketanga has also been controversial and challenging in nature. The first half of this paper provides an overview of Whanaketanga development and the challenges its developers worked hard to address. The second part discusses implications for Māori medium teacher professional learning and development, drawn from findings from research case studies of the information gathering and revision work.

year: 2012