The effect of crystalline phase (anatase, brookite and rutile) and size on the photocatalytic activity of calcined polymorphic titanium dioxide (TiO2)

© 2018 Elsevier Ltd. The effect of thermal treatment on the morphology (crystalline phase and size) and photocatalytic activity of freshly prepared TiO 2 nano-powder is communicated. TiO 2 nano-powders, prepared by hydrolyzing titanium tetraisopropoxide at room temperature, were all dried at 382 K and subsequently calcined at different temperatures, for 1 h, up to 1172 K. Raman analysis of each thermally treated sample exhibited different titania phase structures. Up to 772 K a mixture of brookite and anatase phases was observed, while a mixture of all three phases, i.e. anatase, brookite and rutile, was observed at 872 K, with a rutile only phase at 1097 K and above. The photocatalytic activity of all samples was assessed by means of the photocatalytic degradation of methyl orange dye (MeO). All anatase-brookite compositions exhibited high photocatalytic activity with the rate of degradation decreasing with increasing calcination temperature, which coincides with (i) a slight increase of the anatase phase, (ii) a slight decrease of the brookite phase, and (iii) a gradual increase of the crystallite size of all phases. The greatest photocatalytic activity was observed for the sample calcined at 382 K, which contained the highest amount of brookite (in the presence of anatase as the dominant phase), while the lowest rate was observed for the pure rutile sample

Use of ion-assisted sputtering technique for producing photocatalytic titanium dioxide thin films: Influence of thermal treatments on structural and activity properties based on the decomposition of stearic acid

Titanium dioxide thin films were deposited by the reactive ion-assisted sputtering method from titanium targets at various partial pressures and deposition parameters. The films were deposited onto substrates at temperatures ranging from room-temperature conditions to 722 K. A selection of thin films was post-deposited annealed at temperatures up to 972 K for 10 min and characterized by micro-Raman spectroscopy and scanning electron microscopy (SEM) and subsequently analysed to assess their photocatalytic activity. Micro-Raman characterization revealed that the as-deposited films had either predominant amorphous, rutile-like structures, anatase-like structures or anatase-rutile mixed structures. The thin films deposited with a high substrate temperature and with energy assistance from the ion source tended to be amorphous, while films deposited on a hot substrate without ion energy assistance tended to have a mixed crystalline phase. On subsequent annealing the amorphous films changed to a rutile structure at temperatures above 672 K, while mixed anatase-rutile films changed to predominant rutile structures only after thermal treatments above 872 K. Thus, this study has revealed an astonishing persistence of the anatase-rutile mixed phase at very high temperatures and showed the possible existence of a key transition temperature at 672 K, where it was possible to see a transformation from amorphous or mixed phase to a rutile or dominant rutile mixed phase. Photocatalytic tests were undertaken by using a novel method consisting of observing the degradation of a film of stearic acid by the thin films under artificial UV radiation. Of the films investigated those with anatase-rutile mixed phases showed the greatest photoactivity. This work was essential in the understanding of the correlation between growth deposition conditions, phase transitions and photocatalytic activity. This set of experiments demonstrated that titania made under a highly oxidizing atmosphere, with no temperature applied on the substrate during fabrication and using an ion sputtering method, is a useful and valuable novel method for creating active TiO2thin films

Comparison of tonic spinal cord stimulation, high-frequency and burst stimulation in patients with complex regional pain syndrome: a double-blind, randomised placebo controlled trial

BACKGROUND: Complex Regional Pain Syndrome (CRPS) is a disabling disease that is sometimes difficult to treat. Although spinal cord stimulation (SCS) can reduce pain in most patients with CRPS, some do not achieve the desired reduction in pain. Moreover, the pain reduction can diminish over time even after an initially successful period of SCS. Pain reduction can be regained by increasing the SCS frequency, but this has not been investigated in a prospective trial. This study compares pain reduction using five SCS frequencies (standard 40 Hz, 500 Hz, 1200 Hz, burst and placebo stimulation) in patients with CRPS to determine which of the modalities is most effective. DESIGN: All patients with a confirmed CRPS diagnosis that have unsuccessfully tried all other therapies and are eligible for SCS, can enroll in this trial (primary implantation group). CRPS patients that already receive SCS therapy, or those previously treated with SCS but with loss of therapeutic effect over time, can also participate (re-implantation group). Once all inclusion criteria are met and written informed consent obtained, patients will undergo a baseline assessment (T0). A 2-week trial with SCS is performed and, if successful, a rechargeable internal pulse generator (IPG) is implanted. For the following 3 months the patient will have standard 40 Hz stimulation therapy before a follow-up assessment (T1) is performed. Those who have completed the T1 assessment will enroll in a 10-week crossover period in which the five SCS frequencies are tested in five periods, each frequency lasting for 2 weeks. At the end of the crossover period, the patient will choose which frequency is to be used for stimulation for an additional 3 months, until the T2 assessment. DISCUSSION: Currently no trials are available that systematically investigate the importance of variation in frequency during SCS in patients with CRPS. Data from this trial will provide better insight as to whether SCS with a higher frequency, or with burst stimulation, results in more effective pain relief. TRIAL REGISTRATION: Current Controlled Trials ISRCTN3665525

Towards practical applications of EQCN experiments to study Pt anchor Sites on carbon surfaces

This work investigates the viability and outlines the current challenges in electrochemical quartz crystal nanobalance (EQCN) experiments on supported Pt catalysts. EQCN experiments involving Pt supported on 2-D “surface-treated graphite sputtered onto quartz crystal” (Pt/MFG-H) catalysts were compared to standard polycrystalline Pt (Ptpoly), which showed similarities in frequency versus potential trends; however, the Pt/MFG-H catalysts obtained higher frequencies due to the support capacitance. The physical characterizations (XRD and XPS) and electrochemical responses, mainly cyclic voltammetry in acidic media and the ferri/ferrocyanide couple, of the 2-D Pt/MFG-H were compared to the representative 2-D Pt supported on treated highly orientated pyrolytic graphite (Pt/HOPG-H), in order to make assertions on the similarities between the two catalysts. The XRD diffraction patterns and the XPS valence band structure for the treated and untreated MFG (-H and -P, respectively) and HOPG (-H and -P, respectively) demonstrated similarities. Nevertheless, the cyclic voltammograms and peak positions of the ferri/ferrocyanide couple between the treated and untreated MFG and HOPG catalysts were dissimilar. However, EQCN may be used qualitatively between the two different 2-D catalysts since the same trends in electrochemical responses before and after treatment of the MFG and HOPG catalysts were seen. Hence, the EQCN technique can be used in future studies as an alternative method to study degradation mechanisms of Pt and carbon for PEFCs

Improvement of software development processes, balancing internal and external organizational aspects

Actual results of software process improvement projects happen to be quite disappointing in practice. Although many software development organisations have adopted improvement models such as CMMI, it appears to be difficult to improve software development processes in the right way. This paper presents a new approach to determine the direction of improvement for an organisation. This approach is based on literature research as well as an empirical investigation among software development organisations in The Netherlands. The results of the research show that software development organisations can be classified on the basis of their internal and external entropy, c.q. the level of (dis)order in the business system and its environment. Based on a possible imbalance between the internal and external entropy, directions for software process improvement can be determined. As such the new approach can complement and improve the application of current software process improvement methodologies, e.g. CMMI