19 research outputs found
Dialkyldithiophosphate Acids (HDDPs) as Effective Lubricants of Sol–Gel Titania Coatings in Technical Dry Friction Conditions
The goal of this study was the investigation of
the effectiveness of dialkyldithiophosphate acids (HDDPs)
films in improving the tribological properties of thin, sol–
gel derived titania coatings. Amorphous, anatase, and rutile
titania coatings were obtained using sol–gel dip–coating
deposition after treatment at 100, 500, and 1,000 C,
respectively. Titania coatings were then modified from the
liquid phase by HDDPs acids having dodecyl-(C12), tetradecyl-(C14),
and hexadecyl-(C16) alkyl chains deposited by
dip–coating (DC) and Langmuir–Blodgett (LB) methods.
The influence of the deposition procedure, the length of the
HDDPs alkyl chain and the type of titania substrate on the
surface morphology and tribological properties were studied.
It was found, using wetting contact angle measurements,
that these modifications of titania coatings decrease
the surface free energy and increase its hydrophobicity.
The surface topography imaged by Atomic force microscopy
(AFM), exhibit island-like or agglomerate features for
the DC deposition method, while smooth topographies
were observed for LB depositions. Tribological tests were
conducted by means of a microtribometer operating in the
normal load range 30–100 mN. An enhancement of tribological
properties was observed upon modification, as
compared to unmodified titania
Structural analysis and corrosion studies on an ISO 5832-9 biomedical alloy with TiO2 sol–gel layers
The aim of this study was to demonstrate the
relationship between the structural and corrosion properties
of an ISO 5832-9 biomedical alloy modified with titanium
dioxide (TiO2) layers. These layers were obtained via the
sol–gel method by acid-catalyzed hydrolysis of titanium
isopropoxide in isopropanol solution. To obtain TiO2 layers
with different structural properties, the coated samples
were annealed at temperatures of 200, 300, 400, 450, 500,
600 and 800 C for 2 h. For all the prepared samples,
accelerated corrosion measurements were performed in
Tyrode’s physiological solution using electrochemical
methods. The most important corrosion parameters were
determined: corrosion potential, polarization resistance,
corrosion rate, breakdown and repassivation potentials.
Corrosion damage was analyzed using scanning electron
microscopy. Structural analysis was carried out for selected
TiO2 coatings annealed at 200, 400, 600 and 800 C. In
addition, the morphology, chemical composition, crystallinity,
thickness and density of the deposited TiO2 layers
were determined using suitable electron and X-ray measurement
methods. It was shown that the structure and
character of interactions between substrate and deposited
TiO2 layers depended on annealing temperature. All the
obtained TiO2 coatings exhibit anticorrosion properties, but
these properties are related to the crystalline structure and
character of substrate–layer interaction. From the point of
view of corrosion, the best TiO2 sol–gel coatings for stainless steel intended for biomedical applications seem to
be those obtained at 400 C.This study was supported by Grant No. N N507
501339 of the National Science Centre. The authors wish to express
their thanks to J. Borowski (MEDGAL, Poland) for the Rex 734 alloy
Superfícies fotocatalíticas de titânia em substratos cerâmicos: Parte I: Síntese, estrutura e fotoatividade
Właściwości tarciowe i zużyciowe powłok tlenku glinu wytwarzanych metodą zol-żel
In this study, alumina coatings were prepared by the sol-gel method using the dip-coating technique. All samples were prepared on silicon wafers Si (100) with the use of aluminium sec-butoxide as a precursor. The surface topographies of alumina coatings were imaged by an atomic force microscope (AFM). Tribological properties were characterised using a microtribometer and an optical microscope. The results show a strong dependence of antiwear and antifrictional properties of alumina coatings on the annealing temperatures. The best performance was exhibited by coatings heated to 1000°C due to the formation of hard alfa-Al2O3.Badane powłoki tlenku glinu zostały otrzymane w oparciu o metodę zol-żel z wykorzystaniem techniki zanurzeniowej (dip-coating). Na powierzchnie płytek krzemowych nanoszono roztwory prekursora, którym był sec-butoksyglin. Analizę topografii powierzchni wytworzonych powłok tlenku glinu przeprowadzono z wykorzystaniem Mikroskopu Sił Atomowych (AFM). Właściwości tribologiczne zostały scharakteryzowane z użyciem mikrotribometru (T-23) i mikroskopu optycznego. Uzyskane wyniki wskazały istnienie zależności między właściwościami przeciwtarciowymi i przeciwzużyciowymi powłok tlenku glinu a temperaturą wygrzewania próbek. Najlepsze właściwości wykazały powłoki wygrzewane w 1000°C, co spowodowane jest obecnością fazy alfa-Al2O3