Low toxicity binder systems for tape cast Ce0.9Gd0.1O1.95 laminates

Conventional binder systems for tape casting contain toxic phthalate plasticizers and butanone (MEK) as part of the solvent. The effects of exchanging the phthalate with a non-toxic alternative, and butanone with ethanol, were studied on laminates of high-green density CGO (Ce_0.9Gd_0.1O_1.95) tapes. Samples were prepared with a binder system containing DBP (dibutyl phthalate) plasticizer and MEK solvent, and with a binder system based on a non-toxic non-phthalate plasticizer and ethanol. In both systems, the weight ratio of plasticizer to the PVB (polyvinyl butyral) binder was varied between 0.4 and 0.7. Substitution to the less toxic binder system had no adverse impacts on the microstructure. In fact, denser packing and improved homogeneity were observed with the non-phthalate-based system at ratio 0.5 indicating improved dispersion in this system. The denser packing also coincided with a maximum in z-shrinkage and molecular weight of the binder system, which could be related to the distribution of the binder system.     

Densification and grain growth during sintering of porous Ce0.9Gd0.1O1.95 tape cast layers: A comprehensive study on heuristic methods

The sintering behavior of porous Ce_0.9Gd_0.1O_1.95 (CGO10) tape cast layers was systematically investigated to establish fundamental kinetic parameters associated to densification and grain growth. Densification and grain growth were characterized by a set of different methods to determine the dominant sintering mechanisms and kinetics, both in isothermal and at constant heating rate (iso-rate) conditions. Densification of porous CGO10 tape is thermally activated with typical activation energy which was estimated around 440–470 kJ mol^?1. Grain growth showed similar thermal activation energy of ～427 ± 22 kJ mol^?1 in the temperature range of 1100–1250 °C. Grain-boundary diffusion was identified to be the dominant mechanism in porous CGO10 tapes. Grain growth and densification mechanism were found strictly related in the investigated temperature range. Porosity acts as a grain growth inhibitor and grain boundary mobility in the porous body was estimated around 10^?18–10^?16 m³ N^?1 s^?1 at the investigated temperature range.     

Densification and grain growth during early-stage sintering of Ce0.9Gd0.1O1.95−δ in a reducing atmosphere

The present work investigates the processes of densification and grain growth of Ce_0.9Gd_0.1O_1.95?δ (CGO10) during sintering under reduced oxygen partial pressure. Sintering variables were experimentally characterized and analyzed using defect chemistry and sintering constitutive laws. Based on the results achieved, the grain size–relative density relationship, the densification rate and the grain-growth rate were determined. The activation energies for densification and grain growth were evaluated, and the dominant densification mechanism was indicated. For comparison, the densification behavior of CGO10 sintered in air was also studied. Accelerated densification was observed in early-stage sintering of CGO10 in a reducing atmosphere. This might be attributed to the oxygen vacancies generated by the reduction of Ce⁴⁺ to Ce³⁺ in the reducing atmosphere, which facilitate the diffusion of ions through the lattice. The densification activation energy of CGO10 in the reducing atmosphere was evaluated to be 290 ± 20 kJ mol^?1 in the relative density range of 0.64–0.82, which was much smaller than that of CGO10 sintered in air (770 ± 40 kJ mol^?1). The grain-growth activation energy of CGO10 sintered in the reducing atmosphere was evaluated to be 280 ± 20 kJ mol^?1 in the grain size range of 0.34–0.70 μm. The present work describes a systematic investigation of sintering behavior of CGO10 under reduced oxygen partial pressure, which contributes to the first known determination of the fundamental parameters associated with densification and grain growth during early-stage sintering of CGO10 in a reducing atmosphere.     

Optimising energy use in an existing commercial building: a case study of Australia’s Reef HQ Aquarium

Reef HQ Aquarium is a major tourism attraction in tropical North Queensland, Australia. In 8 years, a 50% reduction in grid electricity was achieved through targeted infrastructure investment, whilst growing the business. Initially, grid energy consumption was 2438 MWh per annum, with 490-kW peak demand and energy intensity of 1625 MJ m^?2 year^?1 used on typical equipment such as HVAC (heating, ventilation and air conditioning), machinery, lighting and catering equipment. Savings of 13% were achieved in the first year by increasing indoor air temperature set-points by 1.5 °C with no significant costs or impacts on occupant thermal comfort or worker productivity. Peak demand was decreased by 46% by upgrading the computerised building management system (BMS), HVAC, machinery and lighting; and by installing a 206-kW photovoltaic (PV) solar power system. This case study illustrates that (a) significant energy use reductions are possible at low cost; (b) capital investment in energy-efficient infrastructure can have short payback times and high direct and indirect benefits, particularly where equipment is ending its life. This study is unique as it examines how a commercial building with integrated chilled water thermal energy storage (TES) and a 3.2-ML chilled seawater aquarium system can be controlled by a BMS to optimise solar power to manage peak energy demand and also increase the utilisation of generated PV power in the absence of electrical battery storage. An interesting building is used to demonstrate efficiency methods with elements such as HVAC and lighting which usually consume over half commercial buildings’ energy use.     

Statistical heterospectroscopy, an approach to the integrated analysis of NMR and UPLC-MS data sets: application in metabonomic toxicology studies

Statistical heterospectroscopy (SHY) is a new statistical paradigm for the coanalysis of multispectroscopic data sets acquired on multiple samples. This method operates through the analysis of the intrinsic covariance between signal intensities in the same and related molecules measured by different techniques across cohorts of samples. The potential of SHY is illustrated using both 600-MHz 1H NMR and UPLC-TOFMS data obtained from control rat urine samples (n = 54) and from a corresponding hydrazine-treated group (n = 58). We show that direct cross-correlation of spectral parameters, viz. chemical shifts from NMR and m/z data from MS, is readily achievable for a variety of metabolites, which leads to improved efficiency of molecular biomarker identification. In addition to structure, higher level biological information can be obtained on metabolic pathway activity and connectivities by examination of different levels of the NMR to MS correlation and anticorrelation matrixes. The SHY approach is of general applicability to complex mixture analysis, if two or more independent spectroscopic data sets are available for any sample cohort. Biological applications of SHY as demonstrated here show promise as a new systems biology tool for biomarker recovery.     

Effects of co-sintering in self-standing CGO/YSZ and CGO/ScYSZ dense bi-layers

Viscoelastic properties and sintering mechanisms of tape-casted gadolinium-doped ceria (CGO), yttrium-stabilized zirconia (YSZ), and scandium–yttrium-stabilized zirconia (ScYSZ) are characterized in order to investigate the reciprocal thermo-mechanical compatibility when arranged as a self-standing bi-layered electrolyte system. The combined use of thermo-mechanical analysis, optical dilatometry, and scanning electron microscopy ensures a systematic characterization of both the individual layers and CGO/YSZ and CGO/ScYSZ bi-layered laminates. The results of the co-firing process of the bi-layers are critical due to the mismatch of thermo-mechanical and sintering properties among the materials. Despite the better sinteractivity of ScYSZ, the self-standing CGO/ScYSZ bi-layer presents more challenges in terms of densification compared with the CGO/YSZ bi-layer. In particular, above 1200 °C, ScYSZ and CGO show residual porosity, and at higher sintering temperatures, above 1300 °C, full densification is completely inhibited by constrained sintering phenomena.     

Manufacturing and characterization of metal-supported solid oxide fuel cells

A metal-supported solid oxide fuel cell design offers competitive advantages, for example reduced material costs and improved robustness. This paper reports the performance and stability of a recently developed metal-supported cell design, based on a novel cermet anode, on a 25 cm² (1 cm²/16 cm² active area) cell level. An electrochemical performance comparable to state-of-the-art anode-supported cells is demonstrated.Detailed electrochemical analysis allowed assignment of the overall polarization losses quantitatively to gas diffusion in the metal support, electrooxidation in the anode functional layer, oxygen reduction in the mixed ionic-electronic conducting cathode and an additional polarization process with a rather high relaxation frequency, which may be assigned to an insulating corrosion interlayer.The durability of the cells was investigated by means of galvanostatic operation for periods of up to 1000 h as well as the dynamic behavior, such as redox-, load- and thermal cycling tests.The galvanostatic stability tests indicated a fair, but significant degradation rate (∼5% decrease in cell voltage/1000 h at 650 °C and 0.25 A cm⁻²). Furthermore, the metal-supported cells underwent an endurance test of 100 redox cycles at 800 °C without severe degradation nor total failure.