| 1. |
- Žerjav, Gregor, et al.
(författare)
-
Effect of Au loading on Schottky barrier height in TiO 2 + Au plasmonic photocatalysts
- 2022
-
Ingår i: Applied Surface Science. - : Elsevier BV. - 0169-4332. ; 579
-
Tidskriftsartikel (refereegranskat)abstract
- Composites of TiO2 and different amounts of plasmonic noble metal Au (0.25–2 wt%) were synthesized by employing the wet impregnation technique. The results of SEM, TEM, XRD and N2 physisorption analyses reveal that the morphologies of the prepared composites are similar to the morphology of bare TiO2 support and are not influenced by the increasing amount of deposited Au nanoparticles. On the other hand, the size of Au ensembles in the TiO2 + Au composites increased from 27.1 to 54.9 nm with the increasing amount of Au. With the increase of the diameter of Au ensembles, the intensity of the surface plasmon resonance (SPR) effect of Au ensembles in the UV–Vis diffuse reflectance spectra of the composites increased. The X-ray photoelectron spectroscopy (XPS) analysis of the valence band maxima (VBM) of the investigated photocatalysts revealed that the height of the Schottky barrier (SBH) at the Au/TiO2 junction in the investigated TiO2 + Au composites decreased from 0.4 to 0.15 eV with the increasing amount of Au (and their size). Therefore, the visible-light-generated “hot electrons” in Au ensembles of TiO2 + 2% Au composite have to overcome a lower energy barrier during the injection into the conduction band (CB) of the TiO2 support than “hot electrons” in the Au ensembles in the TiO2 + 0.25% Au composite. This makes the “hot electrons” in the TiO2 + 2% Au composite less accessible for the recombination with the visible-light generated holes, as the “hot electrons” do not agglomerate at the Schottky barrier (SB). This phenomenon was well expressed in the results of electrochemical impedance spectroscopy (EIS) analysis: under visible-light illumination, the TiO2 + 2% Au composite generated the highest amount of charge carriers among all investigated photocatalysts. The beneficial effect of the low SBH in the TiO2 + 2% Au solid was also expressed in the photoluminescence (PL) emission spectra, where the TiO2 + 2% Au composite showed the lowest charge carrier recombination rate. Further, the TiO2 + 2% Au composite expressed the highest visible-light triggered photocatalytic activity in the hydroxyl radical (OH·) generation and water-dissolved bisphenol A (BPA) oxidation test.
|
|
| 2. |
- Gangwani, Prashant, et al.
(författare)
-
Effect of multi-scale fillers on the tribological behavior of UHMWPE composites in water-lubricated contacts
- 2024
-
Ingår i: Tribology International. - : Elsevier. - 0301-679X .- 1879-2464. ; 196
-
Tidskriftsartikel (refereegranskat)abstract
- This study investigates the impact of graphite, hexagonal boron nitride and short carbon fibers, acting as micro- and nano-fillers, on the tribological performance of ultra-high-molecular-weight polyethylene (UHMWPE) hybrid composites. The tribological performance is evaluated under boundary-lubrication conditions with distilled water at contact pressures in the range from 5 and 15 MPa. The fillers were found to work synergistically, with the best performance recorded when the compositions incorporated fillers of all scales. The most effective composite, consisting of short carbon fibers, micro-scale graphite, micro-scale hBN and nano-scale hBN, reduced the coefficient of friction by 75 %, reaching a value of 0.06, and the specific wear rate by two orders of magnitude to 2 × 10−7 mm3/Nm, compared to pure UHMWPE. The fillers' size also played an important role. Composites with nano-boron nitride led to 40 % lower friction compared to micro-scale fillers only. However, all the fillers reduced the amount of abrasive wear, especially the boron nitride, as a consequence of the tribochemical reaction between the boron nitride and water at the interface. Additionally, the formation of a transfer film was observed on the steel discs, with only short carbon fibers and graphite contributing to its formation from among the fillers used.
|
|
| 3. |
- Jamnig, Andreas, et al.
(författare)
-
3D-to-2D Morphology Manipulation of Sputter-Deposited Nanoscale Silver Films on Weakly Interacting Substrates via Selective Nitrogen Deployment for Multifunctional Metal Contacts
- 2020
-
Ingår i: ACS APPLIED NANO MATERIALS. - : AMER CHEMICAL SOC. - 2574-0970. ; 3:5, s. 4728-4738
-
Tidskriftsartikel (refereegranskat)abstract
- The ability to reverse the inherent tendency of noble metals to grow in an uncontrolled three-dimensional (3D) fashion on weakly interacting substrates, including two-dimensional (2D) materials and oxides, is essential for the fabrication of high-quality multifunctional metal contacts in key enabling devices. In this study, we show that this can be effectively achieved by deploying nitrogen (N-2) gas with high temporal precision during magnetron sputtering of nanoscale silver (Ag) islands and layers on silicon dioxide (SiO2) substrates. We employ real-time in situ film growth monitoring using spectroscopic ellipsometry, along with optical modeling in the framework of the finite-difference time-domain method, and establish that localized surface plasmon resonance (LSPR) from nanoscale Ag islands can be used to gauge the evolution of surface morphology of discontinuous layers up to a SiO2 substrate area coverage of similar to 70%. Such analysis, in combination with data on the evolution of room-temperature resistivity of electrically conductive layers, reveals that presence of N-2 in the sputtering gas atmosphere throughout all film-formation stages: (i) promotes 2D growth and smooth film surfaces and (ii) leads to an increase of the continuous-layer electrical resistivity by similar to 30% compared to Ag films grown in a pure argon (Ar) ambient atmosphere. Detailed ex situ nanoscale structural analyses suggest that N-2 favors 2D morphology by suppressing island coalescence rates during initial growth stages, while it causes interruption of local epitaxial growth on Ag crystals. Using these insights, we deposit Ag layers by deploying N-2 selectively, either during the early precoalescence growth stages or after coalescence completion. We show that early N-2 deployment leads to 2D morphology without affecting the Ag-layer resistivity, while postcoalescence introduction of N-2 in the gas atmosphere further promotes formation of three-dimensional (3D) nanostructures and roughness at the film growth front. In a broader context this study generates knowledge that is relevant for the development of (i) single-step growth manipulation strategies based on selective deployment of surfactant species and (ii) real-time methodologies for tracking film and nanostructure morphological evolution using LSPR.
|
|
| 4. |
- Kumar, Anuj, et al.
(författare)
-
Influence of liquefied wood polyol on the physical-mechanical and thermal properties of epoxy based polymer
- 2017
-
Ingår i: Polymer testing. - : Elsevier. - 0142-9418 .- 1873-2348. ; 64, s. 207-216
-
Tidskriftsartikel (refereegranskat)abstract
- Epoxy resins are mostly produced from petroleum-based bisphenol A and epicholorhydrin. Bisphenol A is synthesized from non-renewable petroleum-based phenol and acetone. Biomass derived epoxy-based polymers (EBPs) are becoming the most promising alternative for petroleum-based counterparts, but still these biomass-based EBPs have inferior properties. In the present work, two types of epoxy resins were prepared with different weight percentages of resin (bisphenol A) and hardener. They were then modified with different weight percentages of liquefied wood from spruce sawdust. The derived EBPs were analysed in terms of tensile strength and tensile modulus, fractured surface morphology, thermal stability, long-term water adsorption and resistance to brown-rot fungus decay. The results revealed that the percentages of hardener and liquefied wood significantly influenced the overall properties of the EBPs.
|
|
