Transparent, photocatalytic, titania thin films formed at low temperature

Tim Kemmitt,Najeh. I. Al-Salim,Jiaxin Lian,Vladimir B. Golovko,Jan-Yves Ruzicka 한국물리학회 2013 Current Applied Physics Vol.13 No.1

A convenient method for the preparation of transparent, photocatalytic titania thin films is described. The films do not require annealing or thermal processing to develop photoactivity, thus can be applied to many thermally-sensitive substrates. Oxalic acid is used in place of the usual mineral acids to peptize the precipitated hydrous titania formed from the hydrolysis of titanium iso-propoxide. This leaves no inorganic residues in the film resulting in a higher quality film. The mineral phase and the photocatalytic activity produced are strongly influenced by the ratio of oxalic acid:titanium iso-propoxide employed. The peptization is carried out at 65 C with vigorous stirring for 1 h in water containing 15% v/v ethanol, followed by a hydrothermal step at 95 C. High oxalic acid:Ti molar ratios (0.5:1) result in rutile free sols, while lower ratios (0.25:1) result in anatase, rutile, brookite and TiO2(B) in varying proportions. The films were exposed to low level UV light to cure, and photodecompose the residual organic components in the film. The photodecomposition of residual oxalic acid in the cast films were monitored using infrared spectroscopy. Photo-activity of the UV-cured films was compared by monitoring the decoloration of methylene blue stains on the film, by UVeVis spectroscopy. Transmission was greater than 99% across the visible light region (400e800 nm).

Photocatalytic titania coatings

T. Kemmitt,N. I. Al-Salim,M. Waterland,V. J. Kennedy,A. Markwitz 한국물리학회 2004 Current Applied Physics Vol.4 No.2-4

Thin coatings of titania and titania/silica were deposited onto aluminium and anodised aluminium substrates from an aqueous precursor. The titania precursor sol was prepared using a proprietary method, and applied onto cleaned or polished substrates by spray coating. Two-stage heat processing at 160 and up to 650 C densified and crystallised the film. Crack-free, transparent coatings up to 1.00 lm thickcan be produced from a single application using this precursor system. X-ray diffraction was used to identify the crystal phase of the films as anatase, and resonant nuclear reaction (RNRA) experiments were carried out to assess the degree of aluminium migration from the aluminium substrates into the films. Photocatalytic oxidation of an organic dye on the surface was monitored by a novel fluorescence method. Water droplet contact angles were measured on the film surfaces before and after UV illumination to investigate the photoactivated hydrophilicity of the films. The activities were compared with films prepared on glass and ceramic substrates.

Thermal Development from Hybrid Gels of Compounds for Use in Fibre-Reinforced Oxide Ceramics

MacKenzie, Kenneth J.D.,Kemmitt, Tim,Meinhold, Richard H.,Schmucker, Martin,Mayer, Lutz The Korean Ceramic Society 1998 The Korean journal of ceramics Vol.4 No.4

Mixed oxide compounds of potential usefulness for fibre coatings (hexagonal celsian, $BaAl_2Si_2O_8$ and lanthanum hexaluminate, $LaAl_{11}O_{18}$) or for matrix materials (yttrium aluminium garnet, $Y_3Al_5O_{12}$) were prepared by hybrid sol-gel synthesis and their thermal crystallisation was monitored by thermal analysis, X-ray diffraction and multinuclear solid state MAS NMR. All the gels convert to the crystalline phase below about $12200^{\circ}C$, via amorphous intermediates in which the Al shows and NMR resonance at 36-38 ppm sometimes ascribed to Al in 5-fold coordination. Additional information about the structural changes during thermal treatment was provided by $^{29}Si$, $^{137}Ba$ and $^{89}Y$ MAS NMR spectroscopy, showing that the feldspar framework of celsian begins to be established by about $500^{\circ}C$ but the Ba is still moving into its polyhedral lattice sites about $400^{\circ}C$ after the sluggish onset of crystallization. Lanthanum hexaluminate and YAG crystallise sharply at 1230 and $930^{\circ}C$ respectively, the former via $\gamma-Al_2O_3$, the latter via $YAlO_3$. Yttrium moves into the garnet lattice sites less than $100^{\circ}C$ after crystallisation.

The Survival Strategy of the Soil Microbial Biomass

Philip Brookes,Sarah Kemmitt,Jianming Xu 한국토양비료학회 2014 한국토양비료학회 학술발표회 초록집 Vol.2014 No.6

Growth of AlPO4-5 within the pores of anodic alumina

Lilian Campbell,Tim Kemmitt,Mark Bowden,Alex Kirchner 한국물리학회 2008 Current Applied Physics Vol.8 No.3,4

We have conned the growth of crystals of the aluminophosphate AlPO4-5 within the nanochannels of an anodic alumina membrane.c-axis orientation. The degree of crystalalignment has been examined using XRD pole gures, and the relative degree of preferred orientation is over 200 for a typical membrane.Field emission SEM micrographs clearly show the aligned crystals within the pores. The inclusion of luminescent guest molecules withinthe pores of the zeolite has also been achieved. This paper will discuss the synthesis, characterization and potential application of thesemembranes.

High temperature superconductor films and devices for the microwave communication industry

N. J. Long,J. Joubert,T. Kemmitt,L. J. Campbell,A. J. Bubendorfer 한국물리학회 2004 Current Applied Physics Vol.4 No.2-4

High temperature superconductor (HTS) thin lms can be used to construct microwave devices such as lters and antennas withsuperior performance. We show how the lms can be manufactured using a solgel method which has the advantage of being able toproduce large area lms quickly, at low cost on simple equipment. We have developed a solgel precursor which has the additionalbenets of using commonly available non-toxic reagents, and which can be prepared quickly. HighTc and high Jc lms have beenmade with this precursor. These lms can be patterned to make microwave lters with better sensitivity and selectivity than con-ventional lters. Adesignfora microstriplayout ofaquasi-elliptic bandpass filter which can be implemented ona10 m×10mm film is described. Simulated results comparing lter implementations with metal and superconductor films operating at 77 K are given.

Preparation and high-temperature characterisation of nanostructured alumina ceramic membranes for gas purification

A. Kirchner,I.W.M. Brown,M.E. Bowden,T. Kemmitt,G. Smith 한국물리학회 2008 Current Applied Physics Vol.8 No.3,4

Porous anodic alumina discs supporting palladium lms as elements of hydrogen-purifying membranes have been examined for theirhigh-temperature behaviour. The method employed to fabricate the porous alumina support is the so-called ‘hard anodising’ technique,which oers substantially higher growth rates while producing mechanically robust lms. These alumina membranes were found to pos-sess a thermal stability better than commercial Anopore. membranes. Upon long-term exposure at 800.C they transform intoc-aluminawithout major deformation. Ultra-thin palladium lms deposited across the alumina pores by physical vapour deposition are continuousand stable in reducing atmospheres to at least 700.C but are oxidised and destroyed by heating in air.

Structural and thermal characterisation of nanostructured alumina templates

I.W.M. Brown,M.E. Bowden,T. Kemmitt,K.J.D. MacKenzie 한국물리학회 2006 Current Applied Physics Vol.6 No.3

Nanostructured anodic aluminium oxide materials containing a two dimensional array of high aspect ratio aligned pores of 200 nm.C. Thermal analysis shows two discrete irreversible exothermic eventsat 850.C and 1020 .C. XRD and27Al MAS NMR show the progressive development of local and long range order in the heated struc-tures and indicate a reaction sequence of amorphous Al2O3 ! h-Al2O3 ! a-Al2O3 (corundum). NMR shows the co-existence of alumin-ium in 4, 5 and 6-coordinated sites through most of the heating sequence until the stable (6-coordinated) corundum phase is established.Phosphorus impurities incorporated during the membrane fabrication process crystallise as an AlPO4 phase above 850 .C and play animportant role in directing the chemical, physical and structural outcomes of the heat treatment.