Polymer encapsulations of two different grades of water-dispersible, surface-sulfonated carbon black, Sterling-4620 with an aggregate size of 260
nm and Black Pearls-800 (BP-800) with an aggregate ...size of 45.7
nm, were carried out using surfactant-free emulsion polymerisation of butyl acrylate, methyl methacrylate and allyl methacrylate. High levels of initiator were required because carbon black acts as an efficient radical trap. Although polymerisation in the presence of Sterling-4620 proceeded satisfactorily using ammonium persulfate (APS), the much larger specific surface area of BP-800 inhibited polymerisation with APS and the sodium salt of 4,4′-azobis(4-cyanopentanoic acid), a non-oxidising initiator, was necessary for effective polymerisation in the presence of BP-800. Several polymer-encapsulated Sterling-4620 and BP-800 products were prepared successfully using different amounts and compositions of polymer, and have been characterised using solvent extraction, pyrolysis, thermogravimetry, infrared spectroscopy, transmission electron microscopy, differential scanning calorimetry and dynamic mechanical thermal analysis.
Inside a spacecraft, the temperature and humidity, suitable for the human crew onboard, also creates an ideal breeding environment for the proliferation of bacteria and fungi; this can present a ...hazard to human health and create issues for the safe running of equipment. To address this issue, wear-resistant antimicrobial thin films prepared by magnetron sputtering were developed, with the aim to coat key internal components within spacecrafts. Silver and copper are among the most studied active bactericidal materials, thus this work investigated the antibacterial properties of amorphous carbon coatings, doped with either silver, silver and copper, or with silver clusters. The longevity of these antimicrobial coatings, which is heavily influenced by metal diffusion within the coating, was also investigated. With a conventional approach, amorphous carbon coatings were prepared by cosputtering, to generate coatings that contained a range of silver and copper concentrations. In addition, coatings containing silver clusters were prepared using a separate cluster source to better control the metal particle size distribution in the amorphous carbon matrix. The particle size distributions were characterized by grazing-incidence small-angle X-ray scattering (GISAXS). Antibacterial tests were performed under both terrestrial gravity and microgravity conditions, to simulate the condition in space. Results show that although silver-doped coatings possess extremely high levels of antimicrobial activity, silver cluster-doped coatings are equally effective, while being more long-lived, despite containing a lower absolute silver concentration.
Amorphous carbon films were deposited by means of closed-field unbalanced magnetron sputtering (CFUBMS). The silicon content was fixed at 1.3 at. %, while the chromium content was increased by ...modification of the current applied to the chromium magnetrons, with two doping levels, 0.3 and 2.7 at. %. Both, hardness and thermal stability were found to decrease as result of increasing chromium. Ball-on-disk tests revealed friction coefficients of 0.06 at room temperature with similar specific wear rate in all films (~4 × 10−13 m3 N−1 m−1). Increasing annealing temperatures were found to reduce the coefficient of friction compared to room temperature values, while increasing the specific wear rate for all films.
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•Chromium doping reduced the relative fraction of Si–O–C, which plays a role in the friction.•Hardness, reduced Young's modulus and the C–C sp3 fraction were found to be reduced as result of increasing chromium doping.•Increasing chromium content reduced the thermal stability of the films and promoted the clustering of the films.•Specific wear rate was increased for the chromium containing films as result of increasing temperature.
This paper provides a description of the transmission function of an X‐ray photoelectron spectroscopy (XPS) instrument operating with exchangeable Al Kα (1486.6 eV) and Ag Lα (2984.3 eV) sources. ...Both sources use the same quartz crystal monochromator and illuminate the same area of the sample. The transmission‐function–corrected data from sputter cleaned gold provides a useful reference material to calibrate other instruments of the same type. Sensitivity factors for Ag Lα and Al Kα are calculated from photoionisation cross sections and electron effective attenuation lengths. These compare well with previous experimental values and data acquired from ionic liquids. The intensity of the Ag Lα source is found to be approximately 50 times lower than the Al Kα source. This, coupled with generally lower photoemission efficiencies, results in noisier data or extended acquisition times. However, there are clear advantages to using the Ag Lα source to analyse certain elements where additional core levels can be accessed and for many technologically important elements where interference from Auger electron peaks can be eliminated. The combination of calibrated data from both sources provides direct and easily interpreted insight into the depth distribution of chemical species. This could be particularly important for topographic samples, where angle resolved experiments are not always helpful. We also demonstrate, using thin coatings of chromium and carbon, that the inelastic background in Ag Lα wide‐scan spectra has a significantly increased information depth compared with Al Kα.
A series of diamond-like carbon (DLC) coatings were deposited with increasing bias voltage using magnetron sputtering techniques. Structural changes were observed in the sp
2
-configuration across ...the films which were accompanied by a slight increase in the sp
3
fraction. With an increasing bias voltage, the thermal stability of the coatings increased from 300 to 450 °C. Oxygen diffusion was observed through the coating as a result of the high-temperature annealing and found to slow down with increasing bias voltage. Coefficients of friction (COF) remained stable with temperature for the individual coatings, with the softer films reporting the lowest COF. Our approach employed Raman spectroscopy to map the wear tracks at different temperatures, providing a deeper understanding of the coating performance and suggested maximum flash temperatures endured during testing.
Mechanically robust photocatalytic titanium oxide coatings can be deposited using reactive magnetron sputtering. In this article, we investigate the effect of doping on the activity of reactively ...sputtered TiO2. Silver, copper and stainless steel targets were used to co-deposit the dopants. The films were characterised using XRD, SEM and EDX. Adhesion and mechanical properties were evaluated using scratch testing and nano-indentation, respectively, and confirmed that the coatings had excellent adhesion to the stainless steel substrate. All coatings showed superhydrophilicity under UV irradiation. A methylene blue degradation test was used to assess their photocatalytic activity and showed all coatings to be photoactive to varying degrees, dependent upon the dopant, its concentration and the resulting coating structure. The results demonstrated that copper doping at low concentrations resulted in the coatings with the highest photocatalytic activity under both UV and fluorescent light irradiation.
The use of a diffusing-wave spectroscopy (DWS) technique for the particle size analysis of a series of suspensions of polymer latexes with diameters ranging between 90 nm and 1300 nm and volume ...fractions from 0.02 to 0.18 has been investigated. Particle sizes from DWS were in reasonable agreement with those from transmission electron microscopy and disc centrifuge photosedimentometry. Photon correlation spectroscopy was applicable only to the latexes with particle sizes less than 500 nm. For polymer latexes with volume fractions (V^sub f^) up to 0.09, the decay rate of the autocorrelation function from DWS was related to the particle size over the range of particle sizes examined. At the highest volume fraction (V^sub f^ = 0.18), it was possible to distinguish between particles with diameters of 740 and 1,300 nm from their autocorrelation functions, but not between particles with diameters of 90 and 430 nm.PUBLICATION ABSTRACT
Microbial populations on equipment surfaces of beverage filling lines were investigated as a function of surface coating type, location and time. Photocatalytic metal-ion doped (Ag or Mo) and ...non-doped TiO2 coatings deposited using reactive magnetron sputtering and spray coating methods were studied as means to reduce microbial numbers accumulating on the surfaces. The coatings were applied to stainless steel coupons, which were mounted to one canning and one glass bottle filling line for 3–5 months. After exposure microbial numbers on the coupons were evaluated by culturing, and bacterial community profiles were characterised with PCR-DGGE (denaturing gradient gel electrophoresis). The results showed that the longer the run time after washes the higher microbial numbers were detected, and that the two filling lines each had their characteristic bacterial community. The major species identified were members of Acinetobacter sp., lactic acid bacteria and enterobacteria. No clear effect of the different coating materials on the microbial numbers or bacterial community composition on the surfaces was shown. In conclusion, functional coatings with sufficient mechanical and chemical durability for industrial surfaces have been developed. Although these coatings have been previously reported to reduce the number of microorganisms on the surfaces in vitro, their efficacy in the challenging beverage process conditions was not proven.
•Microbial numbers on process surfaces followed the time from last washing cycle.•Each filling line had a characteristic bacterial community.•The major microbial groups were Acinetobacter sp., LAB and enterobacteria.•Coatings were not shown to function in the challenging beverage process conditions.
TiO2 coatings deposited using reactive magnetron sputtering and spray coating methods, as well as Ag- and Mo-doped TiO2 coatings were investigated as self-cleaning surfaces for beverage processing. ...The mechanical resistance and retention of the photocatalytic properties of the coatings were investigated over a three-month period in three separate breweries. TiO2 coatings deposited using reactive magnetron sputtering showed better mechanical durability than the spray coated surfaces, whilst the spray-deposited coating showed enhanced retention of photocatalytic properties. The presence of Ag and Mo dopants improved the photocatalytic properties of TiO2 as well as the retention of these properties. The spray-coated TiO2 was the only coating which showed light-induced hydrophilicity, which was retained in the coatings surviving the process conditions.
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