Surface Integrity of Ball Burnished 316L Stainless Steel

316L is a type of austenitic stainless steel that offers a good combination of mechanical properties, corrosion resistance, and biocompatibility. In some industrial applications, it is necessary to proceed to finish treatments to extend the lifetime of the mechanical parts. In the present chapter, ball burnishing treatment is applied to improve the surface integrity of 316L since the performance behavior of parts is directly dependant on the surface properties of the used material. Both surface topography and surface microhardness of 316L after subjection to ball burnishing are studied. The number of burnishing passes is varied by up to five to investigate its effect on the results. Optical profilometer and atomic force microscopy (AFM) were used to analyze the surface roughness and surface topography texture while measurements of microhardness Vickers were proceeded to investigate the changes in surface hardening.

Surface and Subsurface Quality Assessment of Polished Lu2O3 Single Crystal Using Quasi-Brewster Angle Technique

The sesquioxide Lu2O3 single crystal has attracted tremendous attention as potential host material for high-power solid-state lasers. As polishing is the terminal process of conventional ultra-precision machining, the quality of polished crystal directly impacts the crucial performance indicators of optics. The high melting point of Lu2O3 single crystal makes crystal preparation difficult. Therefore, investigations on the surface/subsurface quality inspection of polished Lu2O3 single crystal are scarce. In this paper, we utilize the quasi-Brewster angle technique (qBAT) based on ellipsometry to inspect the quality of polished Lu2O3 single crystal, achieving fast, non-destructive, and high-sensitive surface/subsurface damage assessment. A systematic crystal processing scheme is designed and polished Lu2O3 crystal samples are obtained. To verify the results of qBAT, the surface and subsurface quality are tested using optical profilometer and transmission electron microscope, respectively. The consistency of the test results demonstrates the feasibility, high sensitivity, and accuracy of the qBAT. To our knowledge, this is the first time that the qBAT is applied to investigate the polished surface/subsurface quality of Lu2O3 single crystal. In conclusion, this method provides a powerful approach to the high-precision characterization of the surface/subsurface quality of Lu2O3 single crystal, and has significant potential for material property study and process optimization during ultra-precision machining.

Influence of weather conditions on the durability of acrylic-polyurethane car coatings in an industrial area

The influence of weather conditions on the durability of acrylic-polyurethane car coatings during their exposure to industrial plants (Grupa Azoty, Zakłady Chemiczne "Police" SA) was investigated. The surface structure and the general appearance of the paint coatings (after 16 months of the test) were examined using an optical microscope and a scanning electron microscope, an optical profilometer and a gloss meter. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) were used to study the composition and chemical structure of the coatings. Convex spots of various sizes were observed on the surface of the tested coatings. Quantitative profilometric analysis showed a clear increase in surface roughness. However, the results of the XPS and FTIR tests did not confirm the chemical degradation of the tested samples. It was shown that the convexities observed on the surfaces of the aged coatings were atmospheric deposits consisting mainly of oxygen, calcium, phosphorus, iron, silicon and carbon. Thorough cleaning of the surfaces resulted in their complete removal.

Discerning the painter’s hand: machine learning on surface topography

Attribution of paintings is a critical problem in art history. This study extends machine learning analysis to surface topography of painted works. A controlled study of positive attribution was designed with paintings produced by a class of art students. The paintings were scanned using a chromatic confocal optical profilometer to produce surface height data. The surface data were divided into virtual patches and used to train an ensemble of convolutional neural networks (CNNs) for attribution. Over a range of square patch sizes from 0.5 to 60 mm, the resulting attribution was found to be 60–96% accurate, and, when comparing regions of different color, was nearly twice as accurate as CNNs using color images of the paintings. Remarkably, short length scales, even as small as a bristle diameter, were the key to reliably distinguishing among artists. These results show promise for real-world attribution, particularly in the case of workshop practice.

Discerning the painter’s hand: machine learning on surface topography

Attribution of paintings is a critical problem in art history. This study extends machine learning analysis to surface topography of painted works. A controlled study of positive attribution was designed with paintings produced by a class of art students. The paintings were scanned using a confocal optical profilometer to produce surface data. The surface data were divided into virtual patches and used to train an ensemble of convolutional neural networks (CNNs) for attribution. Over a range of patch sizes from 0.5 to 60 mm, the resulting attribution was found to be 60 to 96% accurate, and, when comparing regions of different color, was nearly twice as accurate as CNNs using color images of the paintings. Remarkably, short length scales, as small as twice a bristle diameter, were the key to reliably distinguishing among artists. These results show promise for real-world attribution, particularly in the case of workshop practice.

The Erosive Potential of Acidic Candies: An Ex Vivo Study

Aim: The aim of this study was to evaluate the erosive potential of saliva on dental enamel sucking the acidic candies, and their effects on the pH, titratable acidity (TA) and buffering capacity (β) of saliva. Methodology: Human enamel specimens (n = 216) were randomly in 17 acidic candy groups and one negative control (paraffin wax) group. Three human volunteers sucked each candy for 5 min while spitting into a covered and chilled vial. The pH, TA and β were measured immediately after the saliva collection. For erosive challenge, each specimen was immersed in saliva at room temperature for 120 min without agitation. The erosion was measured by surface microhardness (SMH) tester and with 3D non-contact optical profilometer for depth of surface loos (DSL). Percentage of SMH change (%SMHC) was calculated. ANOVA followed by Tukey test and Pearson correlation were performed (α=0.05). Results: All candies lowered saliva pH below 5.5, and produced significant DSL (P<0.05) and %SMHC (P<0.01) on enamel, when compared to negative control. The Baby bottle Pop candy presented the lowest erosive potential. No significant differences were observed in DSL between all candies and the negative control, except for the PicoSitos candy. However, for the %SMHC almost all the candies were significantly different from negative control. Correlations were observed between the pH and TA and β, between TA and β, and between the %SMHC and DSL variables (P<0.05). Conclusion: Acidic candies can lower the saliva pH, hindering its buffering effect. The DSL and %SMHC analysis showed enamel dissolution with all candies investigated.

Antifungal Activity of Denture Base Resin Containing Nanozirconia: In Vitro Assessment of Candida albicans Biofilm

Objective. To evaluate the antimicrobial effects of different concentrations of zirconium dioxide nanoparticles (nano-ZrO2) reinforcement of poly(methyl) methacrylate (PMMA) on surface roughness and C. albicans biofilm. Methods. 20 heat-polymerized acrylic resin discs were conventionally made and divided into 4 groups (n = 5) according to nano-ZrO2 concentration: control (0% filler) and 3 experimental groups (2.5% (Z2.5), 5.0% (Z5.0), and 7.5% (Z7.5)). An optical profilometer was used for surface roughness evaluation, followed by Candida adherence assay. Specimens were sterilized, then immersed in cultured yeast (C. albicans), and incubated at 37°C for 48 hours. After that, discs were rinsed before extracting the clustered pellets of Candida. The attached C. albicans was counted using the direct method after spreading on agar media and incubating for 48 hours. Statistical analysis was performed using one-way ANOVA and Tukey’s post hoc test at α = 0.05. Results. Surface roughness was significantly increased with all modified groups compared with control ( P < 0.01 ), which showed the lowest roughness value (0.027 ± 0.004 μm). There was no significant difference in the roughness value among reinforced groups (2.5, 5.0, and 7.5%) ( P > 0.05 ), with Z7.5 showing the highest roughness value (0.042 ± 0.004 μm). Candida count was reduced as the nano-ZrO2 increased but not significantly ( P = 0.15 ). Conclusions. The addition of different concentrations of nano-ZrO2 particles to PMMA increased the surface roughness compared with control; in contrast, insignificant reduction of C. albicans biofilm was detected.

Fabrication of solderable intense pulsed light sintered hybrid copper for flexible conductive electrodes

Additively printed circuits provide advantages in reduced waste, rapid prototyping, and versatile flexible substrate choices relative to conventional circuit printing. Copper (Cu) based inks along with intense pulsed light (IPL) sintering can be used in additive circuit printing. However, IPL sintered Cu typically suffer from poor solderability due to high roughness and porosity. To address this, hybrid Cu ink which consists of Cu precursor/nanoparticle was formulated to seed Cu species and fill voids in the sintered structure. Nickel (Ni) electroplating was utilized to further improve surface solderability. Simulations were performed at various electroplating conditions and Cu cathode surface roughness using the multi-physics finite element method. By utilizing a mask during IPL sintering, conductivity was induced in exposed regions; this was utilized to achieve selective Ni-electroplating. Surface morphology and cross section analysis of the electrodes were observed through scanning electron microscopy and a 3D optical profilometer. Energy dispersive X-ray spectroscopy analysis was conducted to investigate changes in surface compositions. ASTM D3359 adhesion testing was performed to examine the adhesion between the electrode and substrate. Solder-electrode shear tests were investigated with a tensile tester to observe the shear strength between solder and electrodes. By utilizing Cu precursors and novel multifaceted approach of IPL sintering, a robust and solderable Ni electroplated conductive Cu printed electrode was achieved.

Erosive tooth wear inhibition by hybrid coatings with encapsulated fluoride and stannous ions

This study aimed to formulate a hybrid coating material (HC) and to modify this HC with fluoride (NaF) and stannous (SnCl2) ions, directly or encapsulated in nano containers, testing the effects of these materials against dental erosion and erosion–abrasion. Enamel and dentin specimens were treated with the HCs, and then tested in erosion or erosion–abrasion cycling models of 5 days (n = 10 for each substrate, for each model). Deionized water was the negative control, and a fluoride varnish, the positive control. Surface loss (SL, in µm) was evaluated with an optical profilometer, and data were statistically analyzed (α = 0.05). For enamel, in erosion, the positive control and HC without additives showed significantly lower SL than the negative control (p = 0.003 and p = 0.001). In erosion–abrasion, none of the groups differed from the negative control (p > 0.05). For dentin, in erosion, the positive control, HC without additives, HC with non-encapsulated F, and HC with encapsulated F + Sn showed lower SL than the negative control (p < 0.05). In erosion–abrasion, none of the groups differed significantly from the negative control (p < 0.05). HC without additives showed a promising potential for protecting the teeth against dental erosion (with upward trend for improved protection on dentin), but not against erosion–abrasion. The presence of additives did not improve the protective effect of the HC, on both substrates.