title: Synthesis, Microstructure and Mechanical Properties of Titanium with Controlled Levels of Porosity

authors: Xu, Qian

subjects: Titanium

abstract: Porous titanium (Ti) products have many applications due to their excellent corrosion resistance, high strength-to-weight ratio, high specific surface area, etc. However, the major limitation is the expensive cost of porous Ti products because of the high raw materials costs and the difficulty of processing. The novelty of this research work is concerned with a study of a ceramic casting technique, slip casting, to create porous Ti products and the effect of porosity on the mechanical properties and gas permeability of Ti compacts. 

An optimised Ti slurry was developed from 43 vol.% of Ti powder, 0.3 dw.% of dispersant, 0.8 dw.% of plasticiser and 0.8 dw.% of binder, mixed with a balance of distilled water, which produced a viscosity of 290 cP. It was then poured into a plaster mould to form compacts with a green density of 45%. Thermal debinding was carried out at 320°C with an argon flow for 2 hours, followed by vacuum sintering different samples at 1000°C and 1200°C for 0.5 hours, respectively. The porous sintered compacts had satisfactory tensile strength with some plastic deformation. The increase in oxygen and carbon content during processing was minor. The results from this investigation suggested that slip casting is a potentially low-cost, simple manufacturing route for porous Ti products.

Porous Ti compacts with porosity in the range of 12.3 vol.% to 35.3 vol.% were fabricated by slip casting. The mechanical properties, fracture morphology, gas permeability, pore size analysis and pore shape factors for the porous Ti compacts were determined for different porosity levels. A decreasing porosity level resulted in less open porosity and gas permeability, reduced pore size, and an increased tensile stress and elongation. The mechanical properties of porous Ti compacts produced by slip casting were comparable with more conventional press and sintered materials at the same porosity levels. Theoretical models for tensile stress and ductility as a function of porosity were examined and incorporated into the results and differences between the theoretical models and experimental results are discussed. The pore shape factor analysis showed that tensile loading would stretch the pores in the compacts to produce more irregular pores, which were acting as linkage sites to allow the propagation of cracks. Additionally, a novel interconnected pore characterisation method using ammonium meta-tungstate solution is presented. By using backscatter scanning electron microscopy, the interconnected pores can be directly observed. 

The packing behaviour and sintering behaviour of Ti compacts fabricated with different particles size distribution were characterised and studied, in terms of porosity, pore size analysis, tensile properties and gas permeability. Two different particles size (avg. 14 μm & avg. 56 μm) of pure Ti hydride-dehydride powder were used in five volume proportions (20:80, 40:60, 60:40, 80:20 & 100:0). A theoretical model predicted that the green density reaches a maximum when the volume fraction of fine particles is 0.35. It was found that although experimental results showed similar behaviour there was no well-defined maximum green density. The sintered compacts showed that an increase in the volume fraction of fine powder particles reduced the porosity, permeability level and pore size, and increased the tensile properties. The relationship between permeability and porosity level was non-linear and this was caused by the differences in pore diameters in the compacts. The capillary tube model was used to discuss the relationship between the permeability, pore diameter and porosity. Using this information, a graded porosity compact was designed and fabricated by slip casting. A future study on this graded porosity compacts is recommended to undertake in more depth.

text: Synthesis, Microstructure and Mechanical Properties of Titanium with Controlled Levels of Porosity Porous titanium (Ti) products have many applications due to their excellent corrosion resistance, high strength-to-weight ratio, high specific surface area, etc. However, the major limitation is the expensive cost of porous Ti products because of the high raw materials costs and the difficulty of processing. The novelty of this research work is concerned with a study of a ceramic casting technique, slip casting, to create porous Ti products and the effect of porosity on the mechanical properties and gas permeability of Ti compacts. 

An optimised Ti slurry was developed from 43 vol.% of Ti powder, 0.3 dw.% of dispersant, 0.8 dw.% of plasticiser and 0.8 dw.% of binder, mixed with a balance of distilled water, which produced a viscosity of 290 cP. It was then poured into a plaster mould to form compacts with a green density of 45%. Thermal debinding was carried out at 320°C with an argon flow for 2 hours, followed by vacuum sintering different samples at 1000°C and 1200°C for 0.5 hours, respectively. The porous sintered compacts had satisfactory tensile strength with some plastic deformation. The increase in oxygen and carbon content during processing was minor. The results from this investigation suggested that slip casting is a potentially low-cost, simple manufacturing route for porous Ti products.

Porous Ti compacts with porosity in the range of 12.3 vol.% to 35.3 vol.% were fabricated by slip casting. The mechanical properties, fracture morphology, gas permeability, pore size analysis and pore shape factors for the porous Ti compacts were determined for different porosity levels. A decreasing porosity level resulted in less open porosity and gas permeability, reduced pore size, and an increased tensile stress and elongation. The mechanical properties of porous Ti compacts produced by slip casting were comparable with more conventional press and sintered materials at the same porosity levels. Theoretical models for tensile stress and ductility as a function of porosity were examined and incorporated into the results and differences between the theoretical models and experimental results are discussed. The pore shape factor analysis showed that tensile loading would stretch the pores in the compacts to produce more irregular pores, which were acting as linkage sites to allow the propagation of cracks. Additionally, a novel interconnected pore characterisation method using ammonium meta-tungstate solution is presented. By using backscatter scanning electron microscopy, the interconnected pores can be directly observed. 

The packing behaviour and sintering behaviour of Ti compacts fabricated with different particles size distribution were characterised and studied, in terms of porosity, pore size analysis, tensile properties and gas permeability. Two different particles size (avg. 14 μm & avg. 56 μm) of pure Ti hydride-dehydride powder were used in five volume proportions (20:80, 40:60, 60:40, 80:20 & 100:0). A theoretical model predicted that the green density reaches a maximum when the volume fraction of fine particles is 0.35. It was found that although experimental results showed similar behaviour there was no well-defined maximum green density. The sintered compacts showed that an increase in the volume fraction of fine powder particles reduced the porosity, permeability level and pore size, and increased the tensile properties. The relationship between permeability and porosity level was non-linear and this was caused by the differences in pore diameters in the compacts. The capillary tube model was used to discuss the relationship between the permeability, pore diameter and porosity. Using this information, a graded porosity compact was designed and fabricated by slip casting. A future study on this graded porosity compacts is recommended to undertake in more depth.

year: 2014

title: A decision support system for predicting the complications of diabetes mellitus: A design science research approach

authors: Madurapperumage, Anuradha

abstract: Health information systems (HIS) serve as the cornerstone of modern healthcare, seamlessly
weaving data into actionable insights and empowering professionals to make informed
decisions and elevate patient care. Decision support systems became a prominent research
area in the discipline of HIS, where clinical decision support systems (CDSSs) with the ability
to diagnose and prognosis of disease are recognised as the most common and beneficial
information systems. Moreover, the high prevalence and adverse effects of diabetes all over
the globe evidently make it vital to predict diabetes and its complications.
The current study aims to resolve an issue at Te Whatu Ora, by generating a CDSS which can
predict the complications of diabetes mellitus (CoDM) while answering the knowledge gap.
Although a rich data set of diabetes patients’ is maintained at Te Whatu Ora, their
involvement in decision-making is unsatisfactory. This study created a CDSS to resolve the
issue at Te Whatu Ora while considering two perspectives of the question: design and data
analysis. The system design followed design science research methodologies (DSRM) while
selecting suitable techniques in the steps of the empirical cycle to confirm their applicability
in the domain. The data analysis perspective of the study focused on survival analysis
methods due to their appropriateness in fulfilling the identified research gaps.
The created CDSS is the primary outcome of the research, which resolves the real-world issue
while addressing the recognised research gaps. The solution's design perspective confirms
the applicability of adopting design science research approaches in the context of a
systematic solution-design process. The data analytics perspective confirms the
appropriateness of survival techniques in the domain while validating the system’s
performance.
The outcome of this research has significant academical, and managerial implications. The
implemented CDSS is capable of providing a chronological risk percentage for 10 CoDM in a
cohort of New Zealand. The systematic procedure adopted in the research contributes to the
existing knowledge gaps while answering the design, implementation, and evaluation stages.
The managerial implications of the study expand through policy-makers, resource-allocators,
iii
and healthcare administrators to doctors, nurses, and patients. The predicted risk of CoDM
may be beneficial in managing the patients by issuing early warnings, starting treatment
plans, conducting diagnosis tests, recommending dietary/exercise routines and more from
the perspective of patient care. The visualisation of the statistical details and the survival
curves in the system may assist in managing diabetes data repositories efficiently.
This study creates a cohort-specific risk prediction model based on the New Zealand cohort.
The interoperability challenges in the CDSS could occur due to the variety of practices in real
life. Future research studies in this domain can concentrate on increasing the accuracy of the
models with more features of a rich dataset while protecting the patents’ confidentiality.
Additionally, the cohort specificity of the CDSS can be avoided with the engagement of a
global dataset.

text: A decision support system for predicting the complications of diabetes mellitus: A design science research approach Health information systems (HIS) serve as the cornerstone of modern healthcare, seamlessly
weaving data into actionable insights and empowering professionals to make informed
decisions and elevate patient care. Decision support systems became a prominent research
area in the discipline of HIS, where clinical decision support systems (CDSSs) with the ability
to diagnose and prognosis of disease are recognised as the most common and beneficial
information systems. Moreover, the high prevalence and adverse effects of diabetes all over
the globe evidently make it vital to predict diabetes and its complications.
The current study aims to resolve an issue at Te Whatu Ora, by generating a CDSS which can
predict the complications of diabetes mellitus (CoDM) while answering the knowledge gap.
Although a rich data set of diabetes patients’ is maintained at Te Whatu Ora, their
involvement in decision-making is unsatisfactory. This study created a CDSS to resolve the
issue at Te Whatu Ora while considering two perspectives of the question: design and data
analysis. The system design followed design science research methodologies (DSRM) while
selecting suitable techniques in the steps of the empirical cycle to confirm their applicability
in the domain. The data analysis perspective of the study focused on survival analysis
methods due to their appropriateness in fulfilling the identified research gaps.
The created CDSS is the primary outcome of the research, which resolves the real-world issue
while addressing the recognised research gaps. The solution's design perspective confirms
the applicability of adopting design science research approaches in the context of a
systematic solution-design process. The data analytics perspective confirms the
appropriateness of survival techniques in the domain while validating the system’s
performance.
The outcome of this research has significant academical, and managerial implications. The
implemented CDSS is capable of providing a chronological risk percentage for 10 CoDM in a
cohort of New Zealand. The systematic procedure adopted in the research contributes to the
existing knowledge gaps while answering the design, implementation, and evaluation stages.
The managerial implications of the study expand through policy-makers, resource-allocators,
iii
and healthcare administrators to doctors, nurses, and patients. The predicted risk of CoDM
may be beneficial in managing the patients by issuing early warnings, starting treatment
plans, conducting diagnosis tests, recommending dietary/exercise routines and more from
the perspective of patient care. The visualisation of the statistical details and the survival
curves in the system may assist in managing diabetes data repositories efficiently.
This study creates a cohort-specific risk prediction model based on the New Zealand cohort.
The interoperability challenges in the CDSS could occur due to the variety of practices in real
life. Future research studies in this domain can concentrate on increasing the accuracy of the
models with more features of a rich dataset while protecting the patents’ confidentiality.
Additionally, the cohort specificity of the CDSS can be avoided with the engagement of a
global dataset.

year: 2024

title: What land is included?

authors: Oppatt, Neil

abstract: Neil has served the Rotorua District as both a Rotorua District Councillor for 15 years and now 9 years as a BOP Regional Councillor. Throughout this time Neil has been actively involved in the cleanup of Rotorua's lakes. He is presently a BOPRC appointee on the Rotorua Te Arawa Lakes Strategy Group and was an RDC appointee on its predecessor.
He has held positions as Chairman of RDC’s Finance Committee, BOPRC’s Operations and Regulations Committee and the Special Projects Committee set up to address Rotorua lake issues. Neil chaired the Lake Okareka Action Plan Committee and was a BOPRC appointee on the Lake Tarawera Action Plan Committee. Presently he is the BOPRC appointee on the Rotorua catchment Stakeholders Advisory Group.

text: What land is included? Neil has served the Rotorua District as both a Rotorua District Councillor for 15 years and now 9 years as a BOP Regional Councillor. Throughout this time Neil has been actively involved in the cleanup of Rotorua's lakes. He is presently a BOPRC appointee on the Rotorua Te Arawa Lakes Strategy Group and was an RDC appointee on its predecessor.
He has held positions as Chairman of RDC’s Finance Committee, BOPRC’s Operations and Regulations Committee and the Special Projects Committee set up to address Rotorua lake issues. Neil chaired the Lake Okareka Action Plan Committee and was a BOPRC appointee on the Lake Tarawera Action Plan Committee. Presently he is the BOPRC appointee on the Rotorua catchment Stakeholders Advisory Group.

year: 2013