title: Fabrication of advanced heat sink materials by powder metallurgy approach

authors: Chang, Yaqi

abstract: To guarantee a safe work environment for high-end chips, electronic packaging materials should have high thermal conductivity, matched coefficient of thermal expansion to semiconductor, low density, good impact toughness, and tensile strength. Diamond/graphite flakes-reinforced composites are considered as the new generation of heat sink material, however, the poor chemical affinity between copper and diamond and between copper and graphite flakes hinder the composites from achieving high thermal conductivity. The interface between copper matrix and diamond reinforcement or graphite flakes reinforcement is the key factor for improving heat transfer of the composites. 

This study aims to investigate the mechanisms of how the interface improves the thermal conductivity of the diamond/graphite flakes-reinforced composites. The primary research includes: (1) study the effect of vacuum sintering process on the formation of carbide layer; (2) investigate the effect of the volume fraction of diamond particles on relative density and thermal conductivity of the copper/diamond composites, and (3) explore the feasibility to fabricate graphite flakes reinforced copper composites by powder forging and investigate the effect of graphite flakes’ volume fraction on the thermal conductivity of the fabricated composites.

Tungsten carbide (WC) can be formed during the vacuum sintering process, however, the formed WC were broken during the subsequent 1050 ℃ hot forging process. The WC can be formed during the vacuum sintering process above 550 ℃ for 30mins, on both diamond -{100}facet and -{111}facet. Cu-55WDia-1050HF has a thermal conductivity of 230.5W/(mK) which is higher than Cu-55WDia-VS800C2h-1050 of 195.1W/(mK). With the volume fraction of diamond from 45vol% to 65vol%, the thermal conductivity reduced from 250.8 to 65.1W/(mK). For copper/graphite flakes composites, the addition of carbide forming element Ti helped to improve the thermal conductivity. Because of the excessive copper fluidity in Cu-Ti-50GFs-1050HF, Cu-Ti-50GFs-1050HF has the lower thermal conductivity of 202.7 W/(mK) than thermal conductivity of Cu-Ti-50GFs-950HF which is 375.0 W/(mK). With the volume fraction of the graphite flakes from 30% to 70%, the relative density changed from 100% to 83.3%.

text: Fabrication of advanced heat sink materials by powder metallurgy approach To guarantee a safe work environment for high-end chips, electronic packaging materials should have high thermal conductivity, matched coefficient of thermal expansion to semiconductor, low density, good impact toughness, and tensile strength. Diamond/graphite flakes-reinforced composites are considered as the new generation of heat sink material, however, the poor chemical affinity between copper and diamond and between copper and graphite flakes hinder the composites from achieving high thermal conductivity. The interface between copper matrix and diamond reinforcement or graphite flakes reinforcement is the key factor for improving heat transfer of the composites. 

This study aims to investigate the mechanisms of how the interface improves the thermal conductivity of the diamond/graphite flakes-reinforced composites. The primary research includes: (1) study the effect of vacuum sintering process on the formation of carbide layer; (2) investigate the effect of the volume fraction of diamond particles on relative density and thermal conductivity of the copper/diamond composites, and (3) explore the feasibility to fabricate graphite flakes reinforced copper composites by powder forging and investigate the effect of graphite flakes’ volume fraction on the thermal conductivity of the fabricated composites.

Tungsten carbide (WC) can be formed during the vacuum sintering process, however, the formed WC were broken during the subsequent 1050 ℃ hot forging process. The WC can be formed during the vacuum sintering process above 550 ℃ for 30mins, on both diamond -{100}facet and -{111}facet. Cu-55WDia-1050HF has a thermal conductivity of 230.5W/(mK) which is higher than Cu-55WDia-VS800C2h-1050 of 195.1W/(mK). With the volume fraction of diamond from 45vol% to 65vol%, the thermal conductivity reduced from 250.8 to 65.1W/(mK). For copper/graphite flakes composites, the addition of carbide forming element Ti helped to improve the thermal conductivity. Because of the excessive copper fluidity in Cu-Ti-50GFs-1050HF, Cu-Ti-50GFs-1050HF has the lower thermal conductivity of 202.7 W/(mK) than thermal conductivity of Cu-Ti-50GFs-950HF which is 375.0 W/(mK). With the volume fraction of the graphite flakes from 30% to 70%, the relative density changed from 100% to 83.3%.

year: 2021

title: Theories of governance and pacific microstates: The cautionary tale of Tuvalu.

authors: Goldsmith, Michael

subjects: governance

abstract: This paper questions the popularity of governance frameworks in explaining development failures and proposing new models of development for Pacific states. Such popularity is attributed to how problems are selected and framed (the doomsday scenario of demographic and environmental collapse, weakening of the state, and an upsurge in corruption) but also, and most importantly, to the recent hegemony of neo-liberal theory in political economy. Taking the MIRAB microstate of Tuvalu as a counterexample, each of those pillars of governance theory is seen to be lacking or to require a more nuanced form of understanding. A brief analysis of how the dominant Protestant church fits into traditional and modern systems of administration illustrates the complexity of local issues. The essay concludes with a discussion of how the neo-liberal governance orthodoxy lacks the critical insight into power and agency afforded by Foucault's concept of governmentality.

text: Theories of governance and pacific microstates: The cautionary tale of Tuvalu. This paper questions the popularity of governance frameworks in explaining development failures and proposing new models of development for Pacific states. Such popularity is attributed to how problems are selected and framed (the doomsday scenario of demographic and environmental collapse, weakening of the state, and an upsurge in corruption) but also, and most importantly, to the recent hegemony of neo-liberal theory in political economy. Taking the MIRAB microstate of Tuvalu as a counterexample, each of those pillars of governance theory is seen to be lacking or to require a more nuanced form of understanding. A brief analysis of how the dominant Protestant church fits into traditional and modern systems of administration illustrates the complexity of local issues. The essay concludes with a discussion of how the neo-liberal governance orthodoxy lacks the critical insight into power and agency afforded by Foucault's concept of governmentality.

year: 2005

title: Community Based Coastal Monitoring: Developing Tools For Sustainable Management

authors: Rickard, Darcel

subjects: Science

abstract: Burgeoning coastal development, recreational use, and the future affects of climate change are placing increasing strain on regulators to manage risk associated with coastal hazards.  Low-lying coastal communities in particular are vulnerable to a range of natural hazards including coastal erosion, storm surge inundation, tsunami and water safety that come with varying levels of risk to life and property. New Zealand's coastal hazard monitoring network is patchy and resources are limited. As a consequence there is considerable potential for coastal communities are going to need to take a more active role in monitoring their environment and building data bases and knowledge that can be used to better manage their coast. This paper describes simple methodologies based on the needs of various community groups and sound science principles that can be used to monitor beaches and the coastal environment. By employing these tools councils, technical experts and community groups will be able to make better-informed decisions for managing activities in the coastal environment. 
One of the keys to the successful uptake of a monitoring programme by a community group is its relevance to the group. The programme and the tools provided must fit the interests, needs, capability and resources of the group. This project develops tools for coastal monitoring and targets coastal community groups such as Coast Care, Coastal Hapu, Secondary Schools, and Surf Life Saving Clubs. The monitoring methodologies have been developed in consultation with Tainui ki Whaingaroa hapu, Raglan Area School, and the Waikato Beach Care and Coast Care Bay of Plenty.
Successful methodologies for measuring changes on the coast are also those that are matched to the type of beach, use appropriate equipment, collect structured data, provide data to which analysis can be applied, incorporate local knowledge of the environment, and feed results back to the community and other interested parties such as councils and science organisations. This project provides the target groups with simple monitoring methodologies, field forms/checklists, and appropriate survey and measurement equipment (which have undergone field trials) to carry out coastal monitoring.  A web-based facility has been developed to input, check and store data; and provide immediate feedback using graphs and images. It also provides background information on coastal processes relevant to monitoring programmes.  In this manner, a scientifically robust data set is collected and stored within a secure and future proofed archive, providing valuable information to coastal groups for years to come.
Although the primary objective of this research is to develop a means for coastal communities to monitor changes in their environment, there are additional benefits associated with engaging communities in the study of their environment. These benefits include increasing awareness of coastal hazards, capacity building, providing valuable educational resources, and improving the temporal and spatial data coverage of information for the New Zealand coastline.

text: Community Based Coastal Monitoring: Developing Tools For Sustainable Management Burgeoning coastal development, recreational use, and the future affects of climate change are placing increasing strain on regulators to manage risk associated with coastal hazards.  Low-lying coastal communities in particular are vulnerable to a range of natural hazards including coastal erosion, storm surge inundation, tsunami and water safety that come with varying levels of risk to life and property. New Zealand's coastal hazard monitoring network is patchy and resources are limited. As a consequence there is considerable potential for coastal communities are going to need to take a more active role in monitoring their environment and building data bases and knowledge that can be used to better manage their coast. This paper describes simple methodologies based on the needs of various community groups and sound science principles that can be used to monitor beaches and the coastal environment. By employing these tools councils, technical experts and community groups will be able to make better-informed decisions for managing activities in the coastal environment. 
One of the keys to the successful uptake of a monitoring programme by a community group is its relevance to the group. The programme and the tools provided must fit the interests, needs, capability and resources of the group. This project develops tools for coastal monitoring and targets coastal community groups such as Coast Care, Coastal Hapu, Secondary Schools, and Surf Life Saving Clubs. The monitoring methodologies have been developed in consultation with Tainui ki Whaingaroa hapu, Raglan Area School, and the Waikato Beach Care and Coast Care Bay of Plenty.
Successful methodologies for measuring changes on the coast are also those that are matched to the type of beach, use appropriate equipment, collect structured data, provide data to which analysis can be applied, incorporate local knowledge of the environment, and feed results back to the community and other interested parties such as councils and science organisations. This project provides the target groups with simple monitoring methodologies, field forms/checklists, and appropriate survey and measurement equipment (which have undergone field trials) to carry out coastal monitoring.  A web-based facility has been developed to input, check and store data; and provide immediate feedback using graphs and images. It also provides background information on coastal processes relevant to monitoring programmes.  In this manner, a scientifically robust data set is collected and stored within a secure and future proofed archive, providing valuable information to coastal groups for years to come.
Although the primary objective of this research is to develop a means for coastal communities to monitor changes in their environment, there are additional benefits associated with engaging communities in the study of their environment. These benefits include increasing awareness of coastal hazards, capacity building, providing valuable educational resources, and improving the temporal and spatial data coverage of information for the New Zealand coastline.

year: 2008