title: Fabrication and properties of thin-walled SOFC electrolyte tubes

authors: Hatchwell, Charles Edward

abstract: The object of this thesis was to fabricate tubular solid oxide fuel cell (SOFC) systems operating with both high and medium temperature electrolytes, and then to study their electrical behaviour using various current collection methods. The research has demonstrated that yttria-stabilised zirconia (YSZ) and Ce₀.₈Gd₀.₂O₁.₉ tubular electrolytes can be used as a basis for fabricating excellent high thermal shock resistant, rapid start up SOFC systems. The feasibility of using current collection materials with the Ce₀.₈Gd₀.₂O₁.₉ electrolyte system at operational and co-firing temperatures has also been established via chemical compatibility studies. 

Three methods of cathode current collection were investigated. These included silver coatings applied as strips along the cathode, Nimonic 90 alloy wires, and grooved metal Cr5Fe1Y₂O₃ plates. 

Conductive coatings were applied to the surface of the Nimonic 90 wires and Cr5Fe1Y₂O₃ plates. The effect these coatings had on cell performance was studied. For example, an 8 mol % YSZ tubular based SOFC was used in combination with an Ag-La₀.₈Sr₀.₂CrO₃ coated Cr5Fe1Y₂O₃ metal plate. At 900°C and 0.7 V, using H₂ bubbled through H₂O at 25 cm³ min⁻¹, a current density of 40 mA cm⁻² was achieved for the coated Cr5Fe1Y₂O₃ as compared to 16 mA cm⁻² for the non-coated. 

Dense (98% relative to theoretical), gas-tight, Ce₀.₈Gd₀.₂O₁.₉ electrolyte tubes were successfully fabricated using an extrusion process. Processing parameters, such as the modification of the Ce₀.₈Gd₀.₂O₁.₉ particle size by heat-treatment and addition of the correct proportions of organic extrusion aids, were shown to determine the quality of the final sintered tube. Electrodes were added to the electrolyte tube and the cell tested. At 600°C, using H₂ bubbled through H₂O at 25 cm³ min⁻¹, an open circuit voltage of 0.911 V was achieved. 

The chemical compatibility of the Ce₀.₈Gd₀.₂O₂ electrolyte with perovskite current collect coatings and Cr₂O₃ (the scale formed on the surface of Cr-based metal interconnects) was studied. The Cr₂O₃ and phase pure (La,Sr)CrO₃ perovskite were shown to be chemically compatible with the electrolyte at typical operating temperatures, and at co-firing temperatures. Second phases associated with the perovskite coatings were, however, shown to react with Ce₀.₈Gd₀.₂O₁.₉ at co-firing temperatures, digesting and reacting with the electrolyte. The reaction products formed were considered to be Cr based perovskite phases.

This thesis concludes with recommendations for future study.

text: Fabrication and properties of thin-walled SOFC electrolyte tubes The object of this thesis was to fabricate tubular solid oxide fuel cell (SOFC) systems operating with both high and medium temperature electrolytes, and then to study their electrical behaviour using various current collection methods. The research has demonstrated that yttria-stabilised zirconia (YSZ) and Ce₀.₈Gd₀.₂O₁.₉ tubular electrolytes can be used as a basis for fabricating excellent high thermal shock resistant, rapid start up SOFC systems. The feasibility of using current collection materials with the Ce₀.₈Gd₀.₂O₁.₉ electrolyte system at operational and co-firing temperatures has also been established via chemical compatibility studies. 

Three methods of cathode current collection were investigated. These included silver coatings applied as strips along the cathode, Nimonic 90 alloy wires, and grooved metal Cr5Fe1Y₂O₃ plates. 

Conductive coatings were applied to the surface of the Nimonic 90 wires and Cr5Fe1Y₂O₃ plates. The effect these coatings had on cell performance was studied. For example, an 8 mol % YSZ tubular based SOFC was used in combination with an Ag-La₀.₈Sr₀.₂CrO₃ coated Cr5Fe1Y₂O₃ metal plate. At 900°C and 0.7 V, using H₂ bubbled through H₂O at 25 cm³ min⁻¹, a current density of 40 mA cm⁻² was achieved for the coated Cr5Fe1Y₂O₃ as compared to 16 mA cm⁻² for the non-coated. 

Dense (98% relative to theoretical), gas-tight, Ce₀.₈Gd₀.₂O₁.₉ electrolyte tubes were successfully fabricated using an extrusion process. Processing parameters, such as the modification of the Ce₀.₈Gd₀.₂O₁.₉ particle size by heat-treatment and addition of the correct proportions of organic extrusion aids, were shown to determine the quality of the final sintered tube. Electrodes were added to the electrolyte tube and the cell tested. At 600°C, using H₂ bubbled through H₂O at 25 cm³ min⁻¹, an open circuit voltage of 0.911 V was achieved. 

The chemical compatibility of the Ce₀.₈Gd₀.₂O₂ electrolyte with perovskite current collect coatings and Cr₂O₃ (the scale formed on the surface of Cr-based metal interconnects) was studied. The Cr₂O₃ and phase pure (La,Sr)CrO₃ perovskite were shown to be chemically compatible with the electrolyte at typical operating temperatures, and at co-firing temperatures. Second phases associated with the perovskite coatings were, however, shown to react with Ce₀.₈Gd₀.₂O₁.₉ at co-firing temperatures, digesting and reacting with the electrolyte. The reaction products formed were considered to be Cr based perovskite phases.

This thesis concludes with recommendations for future study.

year: 1999

title: The ColorDex DJ system: a new interface for live music mixing

authors: Villar, Nicolas

subjects: computer science

abstract: This paper describes the design and implementation of a new interface prototype for live music mixing. The ColorDex system employs a completely new operational metaphor which allows the mix DJ to prepare up to six tracks at once, and perform mixes between up to three of those at a time. The basic premises of the design are: 1) Build a performance tool that multiplies the possible choices a DJ has in respect in how and when tracks are prepared and mixed; 2) Design the system in such a way that the tool does not overload the performer with unnecessary complexity, and 3) Make use of novel technology to make the performance of live music mixing more engaging for both the performer and the audience. The core components of the system are: A software program to load, visualize and playback digitally encoded tracks; the HDDJ device (built chiefly out of a repurposed hard disk drive), which provides tactile manipulation of the playback speed and position of tracks; and the Cubic Crossfader, a wireless sensor cube that controls of the volume of individual tracks, and allows the DJ to mix these in interesting ways.

text: The ColorDex DJ system: a new interface for live music mixing This paper describes the design and implementation of a new interface prototype for live music mixing. The ColorDex system employs a completely new operational metaphor which allows the mix DJ to prepare up to six tracks at once, and perform mixes between up to three of those at a time. The basic premises of the design are: 1) Build a performance tool that multiplies the possible choices a DJ has in respect in how and when tracks are prepared and mixed; 2) Design the system in such a way that the tool does not overload the performer with unnecessary complexity, and 3) Make use of novel technology to make the performance of live music mixing more engaging for both the performer and the audience. The core components of the system are: A software program to load, visualize and playback digitally encoded tracks; the HDDJ device (built chiefly out of a repurposed hard disk drive), which provides tactile manipulation of the playback speed and position of tracks; and the Cubic Crossfader, a wireless sensor cube that controls of the volume of individual tracks, and allows the DJ to mix these in interesting ways.

year: 2007

title: Manaakitia te paharakeke: an insight into the daily operational challenges facing Te Whakaruruhau

authors: Kurei, Anna

subjects: Women's refuge

abstract: This report is based on participant observations of the daily operations at Te Whakaruruhau, Hamilton. The observations represent the fieldwork element of an undergraduate paper contributing to the co-author, Anna Kurei’s Bachelor’s degree at the University of Waikato. Anna’s participation and observations over several weeks included attending meetings, shadowing Advocates, contributing (as appropriate) to operations and observing interactions between Advocates and the women in living in the service’s residential housing. 
Founded by Ruahine Albert and Ariana Simpson in 1986, Te Whakaruruhau Incorporated (Waikato women's refuge) was the first Māori women's refuge in Aotearoa. Since its inception, Te Whakaruruhau has been a Kaupapa driven service, with Māori cultural practices consciously employed throughout all its operations. Māori tikanga is fluid and adaptable by nature and can therefore meet the needs of people from multiple cultures and backgrounds. The current service has grown from humble beginnings in a four-bedroom state owned house providing emergency housing, to now include a twenty-four-hour crisis service, residential housing and a broadened community outreach programme. Staff numbers have increased from 7 to 36 paid staff and the twenty-fourhour crisis service has allowed the refuge to provide services for high risk cases that would otherwise be turned away. 
Funding is critical to the successful operation of the service. The refuge provides wrap-around services to meet clients’ needs and help them navigate through a maze of government and community services. The needs of women and families who have lived with domestic violence are deep-seated and complex. Achieving a stable, healthy, independent life is frequently a long-term process. Funding however, is not only limited, but is tied to expectations of achieving successful outcomes in the short-term. It was quickly evident during the fieldwork that Te Whakaruruhau is desperately under-resourced. In the year to June 2015 the Refuge provided services for 6575 cases, but had contracted funds for less than 1600. The consequences of such starkly inadequate resources are dire – for both clients and staff.
Advocates (case workers) are frequently exhausted as they try to assist women and children with high and complex needs with very little resources on a highly restricted budget. Many times, workers were observed relegating their own interests (including their own health and safety) in order to meet the demands and needs of their clients. Similarly, the successful rehabilitation of clients is jeopardised by restricted options, insufficient capacity in the system and at times even the simplest of requirements such as transport to essential services. We know that when women and children become free of violence they have better health, employment and education outcomes. These outcomes benefit not only themselves but their communities and the wider social and economic landscape. Higher levels of funding - with a longer term focus- would therefore ultimately reduce the costs of domestic violence overall. Further to this, Kaupapa-based services at Te Whakaruruhau offer a culturally meaningful response to the high representation of Maori women seeking assistance. Its success in the face of such high levels of under-resourcing suggests that expectations around funding also need to be altered.

text: Manaakitia te paharakeke: an insight into the daily operational challenges facing Te Whakaruruhau This report is based on participant observations of the daily operations at Te Whakaruruhau, Hamilton. The observations represent the fieldwork element of an undergraduate paper contributing to the co-author, Anna Kurei’s Bachelor’s degree at the University of Waikato. Anna’s participation and observations over several weeks included attending meetings, shadowing Advocates, contributing (as appropriate) to operations and observing interactions between Advocates and the women in living in the service’s residential housing. 
Founded by Ruahine Albert and Ariana Simpson in 1986, Te Whakaruruhau Incorporated (Waikato women's refuge) was the first Māori women's refuge in Aotearoa. Since its inception, Te Whakaruruhau has been a Kaupapa driven service, with Māori cultural practices consciously employed throughout all its operations. Māori tikanga is fluid and adaptable by nature and can therefore meet the needs of people from multiple cultures and backgrounds. The current service has grown from humble beginnings in a four-bedroom state owned house providing emergency housing, to now include a twenty-four-hour crisis service, residential housing and a broadened community outreach programme. Staff numbers have increased from 7 to 36 paid staff and the twenty-fourhour crisis service has allowed the refuge to provide services for high risk cases that would otherwise be turned away. 
Funding is critical to the successful operation of the service. The refuge provides wrap-around services to meet clients’ needs and help them navigate through a maze of government and community services. The needs of women and families who have lived with domestic violence are deep-seated and complex. Achieving a stable, healthy, independent life is frequently a long-term process. Funding however, is not only limited, but is tied to expectations of achieving successful outcomes in the short-term. It was quickly evident during the fieldwork that Te Whakaruruhau is desperately under-resourced. In the year to June 2015 the Refuge provided services for 6575 cases, but had contracted funds for less than 1600. The consequences of such starkly inadequate resources are dire – for both clients and staff.
Advocates (case workers) are frequently exhausted as they try to assist women and children with high and complex needs with very little resources on a highly restricted budget. Many times, workers were observed relegating their own interests (including their own health and safety) in order to meet the demands and needs of their clients. Similarly, the successful rehabilitation of clients is jeopardised by restricted options, insufficient capacity in the system and at times even the simplest of requirements such as transport to essential services. We know that when women and children become free of violence they have better health, employment and education outcomes. These outcomes benefit not only themselves but their communities and the wider social and economic landscape. Higher levels of funding - with a longer term focus- would therefore ultimately reduce the costs of domestic violence overall. Further to this, Kaupapa-based services at Te Whakaruruhau offer a culturally meaningful response to the high representation of Maori women seeking assistance. Its success in the face of such high levels of under-resourcing suggests that expectations around funding also need to be altered.

year: 2016