Inverse opal nanoassemblies : novel architectures for gas sensors the SnO2:Zn case

A novel technique is here presented, based on inverse opal metal oxide structures for the production of high quality macro and meso-porous structures for gas sensing. Taking advantage of a sol-gel templated approach. different mixed semiconducting oxides with high surface area, commonly used in chemical sensing application, were synthesized. In this work we report the
comparison between SnO₂ and SnO₂:Zn. As witnessed by Scanning and Transmission Electron Microscopy (SEM and TEM) analyses and by Powder x-ray Diffraction (PX RD), highly ordered meso-porous structures were formed with oxide crystalline size never exceeding 20 nm . The filled templates. in form of thick films, were bound to allumina substrate with Pt interdigitated contacts
and Pt heater, through in situ calcination, in order to perform standard electrical characterization. Pollutant gases like CO and NO₂ and methanol. as interfering gas, were used for the targeted electrical gas tests. All samples showed low detection limits towards both reducing and oxidizing species in low temperature measurements. Moreover, the addition of high molar percentages of Zn( II) affected the beha viour of electrical response improv ing the se lecti vity of the proposed system.

Structural studies of ambient temperature plastic crystal ion conductors

A number of novel organic ionic compounds based on the pyrrolidinium cation are described which have been found to be ion conductors in their solid states around room temperature. The properties of the compounds are consistent with their exhibiting plastic crystal phases. In order to understand some of the molecular origins of the plastic crystal behaviour and the ion conductivity that it promotes, a number of related compounds based on the imidazolium and ammonium cations are also described which have structural elements in common with the pyrrolidinium cation, but which do not show the plastic behaviour. It is found therefore that the nature of the cation is quite critical to the development of this behaviour. The alkyl methyl pyrrolidinium cation is found to produce plastic crystal phases when the alkyl chains are short, thereby preserving the ability of the cation to rotate with minimal steric hindrance. The ammonium and imidazolium cations of comparable size and structure are less able to produce these plastic phases, in many cases because the low temperature phase proceeds to melt rather than forming a stable rotator phase.

Evaluation of the thermal behaviour of bevelled cutting inserts using a numerical approach

The nose geometry of a hard and brittle metal cutting tool is generally modified in order to avoid the premature failure due to fracture under tensile stresses. While most research findings point to a favourable mechanical load pattern, the possible influence of the shape of the geometry on the thermal fields and the consequent changes in the stressed state of the tool seem to have attained less attention. The present work aims at establishing the thermal behaviour of bevelled tools under varying geometrical and process parameters. Data generated from statistically designed experiments and quick-stop chip samples are coupled to conduct numerical investigations using a mixed finite and boundary element solution to obtain the temperature distribution in bevelled carbide inserts. Due consideration is given to the presence of the stagnation zone and its size and shape. While the cutting forces and temperatures increased owing to the blunt shape of the tool, the possible absence of tensile stresses was found to be the likely effect of a more uniform temperature distribution resulting from a significant plastic contact on the principal flank and the consequent flank heat source. The characteristic low-temperature zones close to the nose of the conventional tool are taken over by the stagnation zone in bevelled tools. © IMechE 2007.

Solar industrial process heating in Australia - Past and current status

Thirty years ago in Australia, there was a significant research, development and demonstration programme in solar industrial process heating (SIPH). This activity was led principally by the Commonwealth Science and Industrial Research Organisation, the country’s main scientific research body. Other state government bodies also funded demonstration projects. Today, there is very little SIPH activity at any level in Australia. The contrast with the progress in other renewable energy technologies like wind and solar photovoltaic systems is striking. While the implementation of these technologies has progressed, SIPH has gone backwards. If Australia is to decarbonise its economy at the rate required, a massive deployment of solar thermal technology in those industries which use large quantities of low temperature hot water is also required. Recent developments nationally and internationally may rekindle new applications of solar thermal energy use by industry. This paper reviews the past achievements in SIPH in Australia and describes the lessons learned in order to better prepare for any new wave of SIPH activity.

Role of microstructure in the low cycle fatigue of multi-phase steels

The low cycle fatigue (LCF) behaviour of several commercially-produced multiphase steels was studied; including dual-phase (DP) and transformation induced plasticity (TRIP). In addition, a novel TRIP980 hybrid microstructure was examined that consisted of coarse ferrite grains along with low temperature bainite regions interspersed with retained austenite. Fully reversed strain controlled fatigue tests were conducted on the different steels to determine the cyclic stress response and strain to failure. The effects of the cyclic deformation on the microstructures were analysed using electron backscattered diffraction (EBSD) and X-ray diffraction (XRD). Results showed that the initial cyclic hardening behaviour and low cyclic softening ratio observed in the TRIP steels was not necessarily due to austenite to martensite transformation. Differences between the austenite transformation behaviour of the conventional and novel hybrid TRIP microstructures was related to the different surrounding phases and the size of the retained austenite.