title: Microstructure, Thermal Stability and Consolidation of Nanostructured and Ultrafine Structured Cu based Metal Matrix Composite and Alloy Powders Produced by High Energy Mechanical Milling

authors: Mukhtar, Aamir

subjects: high energy mechanical milling

abstract: Ultrafine grained and/or nanostructured Cu and Cu-(2.5-10)vol.%Al2O3 composite balls/granules/powder particles were produced using two high energy mechanical milling (HEMM) routes respectively. The microstructural evolution of the as-milled Cu and Cu-Al2O3 composite balls/granules/powder particles produced using Route 1 (12hours) and Route 2 (Route 1 + 12 hours milling under another condition) of milling was studied using scanning electron microscopy (SEM), transmission electron microcopy (TEM), scanning transmission electron microscopy (STEM) and energy dispersive X-ray (EDX) mapping. The study confirmed that HEMM can be effectively used to disperse (2.5-10)vol.%Al2O3 nanoparticles into a ultrafine grained or nanocrystalline Cu matrix after both routes of milling.

The as-milled Cu and Cu-Al2O3 composite balls/granules/powder particles were heat treated at 150, 300, 400 and 500 C for 1 hour, respectively, to determine the thermal stability of the microstructure and corresponding microhardness change as a function of annealing temperature. It was found that for Cu and Cu-2.5vol.%Al2O3 composites after heat treatment at 150 C, the Cu grain sizes decreased due to recrystallisation, and increasing the annealing temperature to 300 C causes slight coarsening of the Cu grains. Further increasing the annealing temperature to 500 C caused significant coarsening of the Cu grains and the Al2O3 nanoparticles. With increasing the volume fraction of Al2O3 nanoparticles, (i) the thermal stability of the Cu-Al2O3 composite increases, (ii) the microstructure of the Cu matrix became finer, and (iii) the coarsening of Cu grains in the composite powder particles after annealing at 500 C become less severe.

The average microhardness of the Cu-Al2O3 composites decreased after annealing at 150 C due to decrease of dislocation density, then remained almost unchanged with increasing the annealing temperatures to 300 C and 400 C. Further increasing the annealing temperature to 500 C caused significant decrease in average microhardness due to reduction in dislocation density and grain coarsening, suggesting that Cu-Al2O3 composites are thermally stable at temperatures up to 400 C.

Pure copper powder and Cu-Al2O3 composite powders produced using Route 2 were compacted by hot pressing at 350 C followed powder compact forging. Increasing the volume fraction of Al2O3, the average microhardness increased for the forged Cu-Al2O3 composites. A decrease in tensile fracture strength was examined for the Cu-Al2O3 composites with the increase of the volume fraction of Al2O3 as 2.5% to 10%.

Nanostructured Cu-(1-4)at.%Pb alloy powder particles were produced using Route 1 of high energy mechanical milling. The microstructural evolution and thermal stability of microstructure of powder particles as a function of annealing temperature were examined. It was found that heat treatment at 150 C caused slight coarsening of the Cu grains, and increasing the annealing temperatures to 300 and 500 C caused significant coarsening of the Cu grains. The average microhardness of the Cu-Pb alloy powder particles decreased after annealing at 150 C due to decrease of dislocation density, and then remained almost unchanged with increasing the annealing temperature to 300 C. Further increasing the annealing temperatures to 400 C and 500 C caused significant decrease in average microhardness due to reduction in dislocation density and grain coarsening, suggesting that Cu-Pb alloy powders are thermally stable at temperatures up to 300 C.

text: Microstructure, Thermal Stability and Consolidation of Nanostructured and Ultrafine Structured Cu based Metal Matrix Composite and Alloy Powders Produced by High Energy Mechanical Milling Ultrafine grained and/or nanostructured Cu and Cu-(2.5-10)vol.%Al2O3 composite balls/granules/powder particles were produced using two high energy mechanical milling (HEMM) routes respectively. The microstructural evolution of the as-milled Cu and Cu-Al2O3 composite balls/granules/powder particles produced using Route 1 (12hours) and Route 2 (Route 1 + 12 hours milling under another condition) of milling was studied using scanning electron microscopy (SEM), transmission electron microcopy (TEM), scanning transmission electron microscopy (STEM) and energy dispersive X-ray (EDX) mapping. The study confirmed that HEMM can be effectively used to disperse (2.5-10)vol.%Al2O3 nanoparticles into a ultrafine grained or nanocrystalline Cu matrix after both routes of milling.

The as-milled Cu and Cu-Al2O3 composite balls/granules/powder particles were heat treated at 150, 300, 400 and 500 C for 1 hour, respectively, to determine the thermal stability of the microstructure and corresponding microhardness change as a function of annealing temperature. It was found that for Cu and Cu-2.5vol.%Al2O3 composites after heat treatment at 150 C, the Cu grain sizes decreased due to recrystallisation, and increasing the annealing temperature to 300 C causes slight coarsening of the Cu grains. Further increasing the annealing temperature to 500 C caused significant coarsening of the Cu grains and the Al2O3 nanoparticles. With increasing the volume fraction of Al2O3 nanoparticles, (i) the thermal stability of the Cu-Al2O3 composite increases, (ii) the microstructure of the Cu matrix became finer, and (iii) the coarsening of Cu grains in the composite powder particles after annealing at 500 C become less severe.

The average microhardness of the Cu-Al2O3 composites decreased after annealing at 150 C due to decrease of dislocation density, then remained almost unchanged with increasing the annealing temperatures to 300 C and 400 C. Further increasing the annealing temperature to 500 C caused significant decrease in average microhardness due to reduction in dislocation density and grain coarsening, suggesting that Cu-Al2O3 composites are thermally stable at temperatures up to 400 C.

Pure copper powder and Cu-Al2O3 composite powders produced using Route 2 were compacted by hot pressing at 350 C followed powder compact forging. Increasing the volume fraction of Al2O3, the average microhardness increased for the forged Cu-Al2O3 composites. A decrease in tensile fracture strength was examined for the Cu-Al2O3 composites with the increase of the volume fraction of Al2O3 as 2.5% to 10%.

Nanostructured Cu-(1-4)at.%Pb alloy powder particles were produced using Route 1 of high energy mechanical milling. The microstructural evolution and thermal stability of microstructure of powder particles as a function of annealing temperature were examined. It was found that heat treatment at 150 C caused slight coarsening of the Cu grains, and increasing the annealing temperatures to 300 and 500 C caused significant coarsening of the Cu grains. The average microhardness of the Cu-Pb alloy powder particles decreased after annealing at 150 C due to decrease of dislocation density, and then remained almost unchanged with increasing the annealing temperature to 300 C. Further increasing the annealing temperatures to 400 C and 500 C caused significant decrease in average microhardness due to reduction in dislocation density and grain coarsening, suggesting that Cu-Pb alloy powders are thermally stable at temperatures up to 300 C.

year: 2010

title: Reasoning and Religion: The Relevance of the Academic Study of Religion to Critical Thinking Pedagogy

authors: Goldberg, Ilan Yaakov

subjects: Critical Thinking

abstract: In this thesis I inquire into method and theory debates within the academic study of religion, arguing for the potential of this broad field to enrich critical thinking pedagogy, especially with regard to worldviews and problems associated with the influences of worldviews on reasoning. I highlight the growing recognition within critical thinking literature that critical thinking pedagogy ought to include a sizable component devoted to worldviews, and argue for the relevance of the academic study of religion to this worldview component. An inquiry into three popular method and theory debates within the academic study of religion concerning the definition, comparison, and evaluation of religion(s), and into interreligious dialogue, helps cement this assertion. In my treatment of definition I attempt to put the close connection between religions and worldviews on firm ground. I also describe common misconceptions of religion and worldviews that should be of concern to critical thinking educators, and for which the academic study of religion is particularly apposite. Next I concentrate on how comparison of religions and worldviews is justified within the academic study of religion and on good and bad forms of comparison. My discussion of evaluation repeats this pattern: I look at debates over what constitutes good and bad evaluation in and of religions and worldviews, and the relevance of this subject to critical thinking. My foray into interreligious or cross-worldview dialoguing focuses on difficulties that are germane within the critical thinking domain. Although I do recommend the inclusion of these four subjects within critical thinking pedagogy, I take them primarily as a sample of a wider field of inquiry. This sample is meant to support a broader recommendation, namely: Just as education should be infused with critical thinking, so too should critical thinking be infused with the philosophy of the academic study of religion, and the fruits of its inquiry. This recommendation does not come without reservation. In the last chapter I discuss some of the problems that my suggestions bring up, first among which is the religious bias evident in much of what can be found under the auspices of the academic study of religion.

text: Reasoning and Religion: The Relevance of the Academic Study of Religion to Critical Thinking Pedagogy In this thesis I inquire into method and theory debates within the academic study of religion, arguing for the potential of this broad field to enrich critical thinking pedagogy, especially with regard to worldviews and problems associated with the influences of worldviews on reasoning. I highlight the growing recognition within critical thinking literature that critical thinking pedagogy ought to include a sizable component devoted to worldviews, and argue for the relevance of the academic study of religion to this worldview component. An inquiry into three popular method and theory debates within the academic study of religion concerning the definition, comparison, and evaluation of religion(s), and into interreligious dialogue, helps cement this assertion. In my treatment of definition I attempt to put the close connection between religions and worldviews on firm ground. I also describe common misconceptions of religion and worldviews that should be of concern to critical thinking educators, and for which the academic study of religion is particularly apposite. Next I concentrate on how comparison of religions and worldviews is justified within the academic study of religion and on good and bad forms of comparison. My discussion of evaluation repeats this pattern: I look at debates over what constitutes good and bad evaluation in and of religions and worldviews, and the relevance of this subject to critical thinking. My foray into interreligious or cross-worldview dialoguing focuses on difficulties that are germane within the critical thinking domain. Although I do recommend the inclusion of these four subjects within critical thinking pedagogy, I take them primarily as a sample of a wider field of inquiry. This sample is meant to support a broader recommendation, namely: Just as education should be infused with critical thinking, so too should critical thinking be infused with the philosophy of the academic study of religion, and the fruits of its inquiry. This recommendation does not come without reservation. In the last chapter I discuss some of the problems that my suggestions bring up, first among which is the religious bias evident in much of what can be found under the auspices of the academic study of religion.

year: 2011

title: Words on walls: The linguistic landscape of Kirikiriroa primary school classrooms

authors: Burnette, Jessie

abstract: Language contact between te reo Māori and English has resulted in one of the central features of New Zealand English (NZE): the integration of loanwords from the Indigenous, donor language, te reo Māori, into a dominant Lingua Franca (Hay et al., 2008). Previous works have analysed the presence and presentation of these loanwords across a number of mediums. Our study, however, examines data directed at a previously unexamined demographic: primary school-aged children.

We aim to establish which loanwords children are regularly exposed to, and thus examine a most relevant domain: the classroom. Considering the linguistic landscape of classrooms (schoolscapes) offers insight into the language use that occurs within them. Further, the classroom is educational in the traditional sense, but also in the developmental sense, in the acquisition of broader social meaning. Previous schoolscapes research has highlighted not only their pedagogical importance, but their influence in the construction and transmission of language ideologies (Pzymus and Huddleston 2021; Brown 2012), making these particularly valuable spaces to study.

This study presents a schoolscape investigation of nine Waikato classrooms by analysing loanwords arising in educational artefacts directed at primary-aged children (7-11) in an English-medium school setting. We make the following contributions: (1) a systematic schoolscape method for analysing contact-induced language phenomena; (2) quantitative and qualitative analyses of loanwords identified in our data; (3) a detailed taxonomic expansion of te reo Māori loanword categories (semantic and syntactic) in present day NZE.

In this talk, we ask the following questions:

RQ1) What type of te reo Māori (loan)words are children regularly exposed to through schoolscapes in A/NZ?

RQ2) What is their distribution across schools/classrooms/years?

We find that, in the classes examined, children encounter both high levels of exposure to te reo Māori (loan)words and high levels of variation in the types of words present. On average, children encounter one te reo Māori token for every ten English tokens. As in previously identified trends (Macalister, 2006b), most loanwords found are nouns belonging to semantic categories pertaining to the environment, place names and social culture items. However, we also identify prominently occurring words and word types that have not previously been identified in corpora. We show that, within classrooms, children regularly encounter a landscape richer in te reo Māori (loan)words than previously seen, but also one characterised by substantial variation.

text: Words on walls: The linguistic landscape of Kirikiriroa primary school classrooms Language contact between te reo Māori and English has resulted in one of the central features of New Zealand English (NZE): the integration of loanwords from the Indigenous, donor language, te reo Māori, into a dominant Lingua Franca (Hay et al., 2008). Previous works have analysed the presence and presentation of these loanwords across a number of mediums. Our study, however, examines data directed at a previously unexamined demographic: primary school-aged children.

We aim to establish which loanwords children are regularly exposed to, and thus examine a most relevant domain: the classroom. Considering the linguistic landscape of classrooms (schoolscapes) offers insight into the language use that occurs within them. Further, the classroom is educational in the traditional sense, but also in the developmental sense, in the acquisition of broader social meaning. Previous schoolscapes research has highlighted not only their pedagogical importance, but their influence in the construction and transmission of language ideologies (Pzymus and Huddleston 2021; Brown 2012), making these particularly valuable spaces to study.

This study presents a schoolscape investigation of nine Waikato classrooms by analysing loanwords arising in educational artefacts directed at primary-aged children (7-11) in an English-medium school setting. We make the following contributions: (1) a systematic schoolscape method for analysing contact-induced language phenomena; (2) quantitative and qualitative analyses of loanwords identified in our data; (3) a detailed taxonomic expansion of te reo Māori loanword categories (semantic and syntactic) in present day NZE.

In this talk, we ask the following questions:

RQ1) What type of te reo Māori (loan)words are children regularly exposed to through schoolscapes in A/NZ?

RQ2) What is their distribution across schools/classrooms/years?

We find that, in the classes examined, children encounter both high levels of exposure to te reo Māori (loan)words and high levels of variation in the types of words present. On average, children encounter one te reo Māori token for every ten English tokens. As in previously identified trends (Macalister, 2006b), most loanwords found are nouns belonging to semantic categories pertaining to the environment, place names and social culture items. However, we also identify prominently occurring words and word types that have not previously been identified in corpora. We show that, within classrooms, children regularly encounter a landscape richer in te reo Māori (loan)words than previously seen, but also one characterised by substantial variation.

year: 2024