title: Study of the Effects of Key Processing Parameters on the Cost and Quality of Ti-Al Powders Produced Using the TiPro Process

authors: Sichone, Kenneth

subjects: TiPro Process

abstract: The high cost of titanium has motivated a global drive to research and develop low-cost titanium production technologies. In New Zealand, the TiPro process has been invented at the University of Waikato. The process starts with a combustion reaction between TiO₂ and Al powders, followed by: solid/liquid separation by extrusion which separates the metal rich liquid from the Al₂O₃ solid. The metal-rich phase is subsequently purified to reduce its oxygen content to acceptable level (e.g. <0.3 wt%).
The aim of this study was to establish such key relationships required to maximise the yield of Ti-Al and quality of the Ti-Al powder product. An in-depth understanding of the effects of key process parameters (e.g. heating rate, temperature, time and pressure) and starting TiO₂/Al composite powder characteristics (e.g. microstructure and compressibility) on the quality, production rate and cost of Ti-Al based powders was achieved. The solid/liquid separation step was identified to be most critical in determining the quality and cost of Ti-Al powders produced using the TiPro process. The results indicated that the microstructure of reactant powders, wetting properties of TiAl alloy on the Al₂O₃ particles, the viscosity of the liquid TiAl and the degree of saturation of the combustion product with liquid TiAl are some of the major factors in the extraction of TiAl from the combustion product using extrusion as the solid/liquid separation technique. In the current state of the invention, where the alloy is extracted by extruding the combustion product, the TiPro process is not viable due to poor yields. The throughput, alloy product purity and yield of the TiPro process are constrained by the solid/ liquid separation unit operation. When extrusion is the sole separation technique, the alloy yields are limited to only 10% of total input. This falls far below the minimum yield, (60%) that is required to make the process economically viable. Therefore, unless the solid/ liquid separation is supplemented by other separation techniques, such as froth flotation and leaching, the cost of producing titanium alloy powders by the TiPro process will be high and the quality of the alloy poor, consequently making the process uneconomical. 
This study has demonstrated that froth flotation can recover 65.7 wt% of TiAl content of the extrusion by-product into a 71.0 wt% TiAl grade product. This corresponds to removing 20 wt% of the total Al₂O₃ contained in the extrusion by-product (flotation feed). The potential exists to increase the TiAl grade further by multiple flotation stages. However, further work is required to investigate more suitable reagents than the HF acid that was used to activate Al₂O₃ in this study.

text: Study of the Effects of Key Processing Parameters on the Cost and Quality of Ti-Al Powders Produced Using the TiPro Process The high cost of titanium has motivated a global drive to research and develop low-cost titanium production technologies. In New Zealand, the TiPro process has been invented at the University of Waikato. The process starts with a combustion reaction between TiO₂ and Al powders, followed by: solid/liquid separation by extrusion which separates the metal rich liquid from the Al₂O₃ solid. The metal-rich phase is subsequently purified to reduce its oxygen content to acceptable level (e.g. <0.3 wt%).
The aim of this study was to establish such key relationships required to maximise the yield of Ti-Al and quality of the Ti-Al powder product. An in-depth understanding of the effects of key process parameters (e.g. heating rate, temperature, time and pressure) and starting TiO₂/Al composite powder characteristics (e.g. microstructure and compressibility) on the quality, production rate and cost of Ti-Al based powders was achieved. The solid/liquid separation step was identified to be most critical in determining the quality and cost of Ti-Al powders produced using the TiPro process. The results indicated that the microstructure of reactant powders, wetting properties of TiAl alloy on the Al₂O₃ particles, the viscosity of the liquid TiAl and the degree of saturation of the combustion product with liquid TiAl are some of the major factors in the extraction of TiAl from the combustion product using extrusion as the solid/liquid separation technique. In the current state of the invention, where the alloy is extracted by extruding the combustion product, the TiPro process is not viable due to poor yields. The throughput, alloy product purity and yield of the TiPro process are constrained by the solid/ liquid separation unit operation. When extrusion is the sole separation technique, the alloy yields are limited to only 10% of total input. This falls far below the minimum yield, (60%) that is required to make the process economically viable. Therefore, unless the solid/ liquid separation is supplemented by other separation techniques, such as froth flotation and leaching, the cost of producing titanium alloy powders by the TiPro process will be high and the quality of the alloy poor, consequently making the process uneconomical. 
This study has demonstrated that froth flotation can recover 65.7 wt% of TiAl content of the extrusion by-product into a 71.0 wt% TiAl grade product. This corresponds to removing 20 wt% of the total Al₂O₃ contained in the extrusion by-product (flotation feed). The potential exists to increase the TiAl grade further by multiple flotation stages. However, further work is required to investigate more suitable reagents than the HF acid that was used to activate Al₂O₃ in this study.

year: 2015

title: Teaching formal methods lite via testing

authors: Utting, Mark

subjects: computer science

abstract: A new style of formal methods course is described, based on a pragmatic approach that emphasizes testing. The course introduces students to formal specification using Z, and shows how formal specification and testing can benefit each other, in both the validation and verification phases. It uses a tools-based approach, with practical work that reinforces formal specification techniques as well as traditional software engineering skills, such as unit and system testing, inspection and defensive programming with assertions. The two main results are to identify several practical uses of formal specifications that are not widely practised or taught and to demonstrate that teaching them results in a more interesting and relevant formal methods course.

text: Teaching formal methods lite via testing A new style of formal methods course is described, based on a pragmatic approach that emphasizes testing. The course introduces students to formal specification using Z, and shows how formal specification and testing can benefit each other, in both the validation and verification phases. It uses a tools-based approach, with practical work that reinforces formal specification techniques as well as traditional software engineering skills, such as unit and system testing, inspection and defensive programming with assertions. The two main results are to identify several practical uses of formal specifications that are not widely practised or taught and to demonstrate that teaching them results in a more interesting and relevant formal methods course.

year: 2001

title: Distributed agent-centric system for indigenous data sovereignty

authors: Noovao, Setephano

subjects: holochain

abstract: The sovereignty of indigenous data is a key issue facing indigenous communities. Holochain, a distributed ledger technology, has the potential to address some of the challenges indigenous communities face with respect to data sovereignty. The purpose of this thesis is to critically evaluate the feasibility of using holochain technology to support indigenous data sovereignty. This paper first explores the literature on holochain technology, examining its underlying architecture and features. The research employs a three-phase design science research methodology, conducting an experiment to explore the integration of a decentralized application, holochain, with a prominent cloud service provider. The first phase concentrates on emulating real data-sharing platforms that may utilize data at its disposal, following the principles of indigenous data sovereignty, where a centralized platform could be hosted on a cloud computing service with multiple services in operation. The second phase involves developing a holochain application guided by the principles of indigenous data sovereignty. The final phase seeks to combine the established centralized platform from the first phase with the outcomes of the holochain application from the second phase to experimentally assess whether both technologies can create a data sovereignty solution that aligns with the needs of indigenous data sovereignty. The results of the experiment will provide a solid foundation for understanding the current state of the field and identifying areas where holochain can potentially offer solutions. Furthermore, the results of our research indicate that holochain shows significant promise in tackling the issue of indigenous data sovereignty, although there are considerable limitations that must be addressed and resolved to achieve improved results.

text: Distributed agent-centric system for indigenous data sovereignty The sovereignty of indigenous data is a key issue facing indigenous communities. Holochain, a distributed ledger technology, has the potential to address some of the challenges indigenous communities face with respect to data sovereignty. The purpose of this thesis is to critically evaluate the feasibility of using holochain technology to support indigenous data sovereignty. This paper first explores the literature on holochain technology, examining its underlying architecture and features. The research employs a three-phase design science research methodology, conducting an experiment to explore the integration of a decentralized application, holochain, with a prominent cloud service provider. The first phase concentrates on emulating real data-sharing platforms that may utilize data at its disposal, following the principles of indigenous data sovereignty, where a centralized platform could be hosted on a cloud computing service with multiple services in operation. The second phase involves developing a holochain application guided by the principles of indigenous data sovereignty. The final phase seeks to combine the established centralized platform from the first phase with the outcomes of the holochain application from the second phase to experimentally assess whether both technologies can create a data sovereignty solution that aligns with the needs of indigenous data sovereignty. The results of the experiment will provide a solid foundation for understanding the current state of the field and identifying areas where holochain can potentially offer solutions. Furthermore, the results of our research indicate that holochain shows significant promise in tackling the issue of indigenous data sovereignty, although there are considerable limitations that must be addressed and resolved to achieve improved results.

year: 2024