Search Results (4)

This study investigates hyperpolishing of Zerodur^® substrates via chemical-mechanical polishing (CMP) using silica (SiO₂) and ceria (CeO₂) nanoparticles as controlled nano-abrasives. A pre-polishing stress-mirror stage was combined with systematic use of nanoparticles of variable size to evaluate surface-state evolution via optical rugosimeter, HRSEM, cross-sectional HRTEM, and XPS. A set of hexagonal mirrors with a circumscribed diameter of 30 mm was polished for one hour with each nanoparticle type. All tested slurries significantly improved surface quality, with both the smallest (37 nm) and largest (209 nm) SiO₂ particles achieving similar final roughness, though larger particles showed a slight performance advantage that could be offset by longer polishing with smaller particles. CeO₂ nanoparticles (30 nm) produced even better process efficiency and surface finishes than 37 nm SiO₂, demonstrating higher chemical-mechanical polishing efficiency with CeO₂. Sequential polishing strategies, first with 209 nm SiO₂, then with 37 nm SiO₂ and 30 nm CeO₂, also enhanced surface quality, confirming trends from single-particle trials. One of the most effective protocols was adapted and scaled up to 135 mm Zerodur^® mirrors with spherical and plano geometries, representative of precision optical components. The strategic approach adopted to achieve a high-quality surface finish in a reduced processing time relies on the sequential use of nanoparticles acting as complementary nano-abrasives. Indeed, applying two hours of polishing with 209 nm SiO₂ followed by two hours with 37 nm SiO₂ yielded exceptional results, with area roughness (Sa) values of 1 Å for spherical and 0.9 Å for plano surfaces. These results demonstrate the capability of nanoparticle-assisted CMP to produce sub-nanometric surface finishes and offer a robust, scalable approach for high-end optical manufacturing. Full article

The long-term endurance of building stones must be assured since their longevity has repercussions for their economic and social value. Frequently, slabs for flooring and cladding are installed with polished finishing in outdoor environments for technical and ornamental purposes in cultural heritage sites and modern civil architecture. Compared to any other finishing, glossy surfaces are rather vulnerable to wear, particularly when they interact with slightly acidic rainwater. Several hydrophobic treatments are applied to prevent this damage by preventing contact between rain and stone; such treatments are efficient but sometimes non-durable. Stakeholders and conservation scientists need better methods to anticipate the future behaviour of this building material and hydrophobic solutions. Complying with this demand, a comparison is made between outdoor natural ageing and artificial weathering, reproduced by UVA radiation, moisture and spray accelerated weathering. Artificial weathering is applied to predict the behaviour of stones over time in the real environment. Data obtained through the measurement of gloss and colour parameters, the detection of micro-textures through SEM, and the calculation of micro-roughness using a digital rugosimeter demonstrate that weakly acidic rainwater is the main cause of superficial decay of stone finishing over just six months of outdoor exposure. This period corresponds to 7–14 days of artificial weathering. Furthermore, the loss of efficiency and durability of the hydrophobic coatings is detected by measuring the static contact angle. This highlights that even if a protective treatment was proficient, it could easily deteriorate in normal weathering conditions if applied on polished, low-porosity stone. Additionally, water vapour permeability indicates variations of regular vapour transmission through the stones due to ageing. The first solution to threats is the prevention of pathologies, including aesthetic ones. A careful choice of the most suitable lithotype finish and an environmental study represent an existing solution to the problem. It must be highlighted that aesthetic requirements should not be prioritised to detriment of the technical requirements of architectural quality, performance, durability, and safety. Full article

Background: The roughness of denture base materials is mainly affected by inherent material features, the polishing technique, and the operator’s manual skills. The surface irregularities of the denture base resin’s roughness profile is one of the components characterizing the superficial topography of dental prostheses, and it is a critical parameter for describing surface morphology. Generally, the increment of the surface roughness minimizes cleanability and promotes the rate of bacterial adherence, affecting the expression of bacterial adhesins. The purpose of this in vitro study was to investigate the roughness of four commercially available denture base resins employed for removable prosthodontics. Methods: Twenty-five specimens were realized and submitted to observation for three dimensions (vertically, horizontally, 45°). Average surface roughness (Ra), Rv, Rp, and Rq were measured with a calibrated mechanical roughness tester (Taylor Hobson Surtronic 25; Taylor Hobson, Leicester, UK). Data were analyzed through a Kruskal–Wallis test. Results: Significant differences in Ra between the groups were assessed. Baltic Denture System™ (Merz Dental GmbH; Lütjenburg, Germania) showed a lower surface roughness coefficient and a more homogeneous surface. Conclusions: The functional importance of surface roughness parameters for denture base materials must be explored, not only considering recognized surface features. Full article

Tribological performance of knee components are strongly related to the surface characteristics. Primarily, the roughness and its 3D distribution on the surfaces affect the joint performance. One of the main limitations related to the tribological study of knee prostheses is that most of the research studies report in vitro or in silico results, as knee retrievals are difficult to find or are too damaged to be analyzed. This paper is focused on the roughness characterization of retrieved metal femoral components of total knee replacements (TKR) by means of a rugosimeter and involving digital methods to reconstruct the 3D topography of the studied surfaces. The aim of this study is to investigate how changes and distribution of roughness are correlated between the medial vs. the lateral part and how the resulting digital topography can give insights about the wear behavior. Full article