title: A Replication of the St. Louis Test for New Zealand

authors: Ng, Ah Kan

abstract: Monetary theory is less abstract than some economic theory in the sense that it cannot avoid a relation to reality. Its development has been to a considerable extent prompted by the experiences encountered by the writers in their own time, and monetary disturbances have always acted as a catalyst in its development. It seems that the role of money in an econmy has appeared to be more important in some periods than others, and writers on monetaryu issues, have therefore, had to adjust their theories accordingly.

text: A Replication of the St. Louis Test for New Zealand Monetary theory is less abstract than some economic theory in the sense that it cannot avoid a relation to reality. Its development has been to a considerable extent prompted by the experiences encountered by the writers in their own time, and monetary disturbances have always acted as a catalyst in its development. It seems that the role of money in an econmy has appeared to be more important in some periods than others, and writers on monetaryu issues, have therefore, had to adjust their theories accordingly.

year: 1973

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 state of the Rotorua Lakes in 2017

authors: Hamilton, David P.

abstract: I have been asked to give an overview of the Rotorua Te Arawa Lakes and then focus on just four of the lakes. Chris McBride will pick up other lakes.  I would like to acknowledge Warwick Silvester who set up the Lakes Chair, Simon Stuart who is working outside the rohe, on Lake Taupō, but has a great body of knowledge on the food chain in that lake, with potential applications to the Te Arawa lakes. Also to Kohji Muraoka who helped me over the last 24 hours, putting data together which enabled me to synthesise my thoughts on these lakes.

text: The state of the Rotorua Lakes in 2017 I have been asked to give an overview of the Rotorua Te Arawa Lakes and then focus on just four of the lakes. Chris McBride will pick up other lakes.  I would like to acknowledge Warwick Silvester who set up the Lakes Chair, Simon Stuart who is working outside the rohe, on Lake Taupō, but has a great body of knowledge on the food chain in that lake, with potential applications to the Te Arawa lakes. Also to Kohji Muraoka who helped me over the last 24 hours, putting data together which enabled me to synthesise my thoughts on these lakes.

year: 2017