Electrolytic polishing (2023)

The corrosion resistance and biocompatibility of 316L stainless steel implants depend on the surface characteristics and the nature of the passive film. The effects of electropolishing on surface topography, surface free energy, and surface chemistry were determined by atomic force microscopy, contact angle counter, and X-ray photoelectron spectroscopy. Electropolishing of 316L stainless steel is performed at the oxygen evolution potential (EPO) and below the oxygen evolution potential (EPBO). Compared to mechanically polished (MP) and EPO, the EPBO sample has a lower surface roughness (Ra=6.07 nm) and a lower surface free energy (44.21 mJ/m²).Relatively low corrosion rate (0.484mpy) and low passive current density (0.619µA/cm²) was determined by circular polarization scanning to be associated with OH, Cr(III), Fe(0), Fe(II) and Fe(III) species present on the surface. These species ensure the existence of a relatively uniform passivating oxide film on the EPBO surface. In addition, the relatively large charge transfer (R_ct) and passive film resistance (R_{to eat}) recorded from EPBO samples by impedance spectroscopy, confirming its better electrochemical performance. The in vitro response of these polished samples to MC3T3 preosteoblast cell proliferation was found to be directly related to their surface and electrochemical properties.

The effects of electropolishing variables such as stirring speed, solution temperature, applied potential, electropolishing time and volume percentage of perchloric acid in an ethanol-perchloric acid solution on the surface roughness of commercially pure aluminum plates (Al-1050, 99.5 %) using a fractional systematic factorial study design (FFD). Solution temperature, applied potential and electropolishing time were found to be the key factors affecting the surface roughness of Al-1050 plates, while the volume percentage of perchloric acid (or ethanol) showed complex interactions with these key factors. When performing electropolishing at 4 °C (ie low temperature solution level). These polished sheets can be effectively formed into a highly uniform, self-aligned anodized aluminum oxide (AAO) by performing an anodizing process in an aqueous solution consisting mainly of sulfuric and oxalic acids. The AAO pore size gradually decreases from approx. When the surface roughness of the aluminum plate increases from 3 to 30 nm, it is 90 to 60 nm.

Acta Biomaterials, Volume 10, Number 3, 2014, Pages 1475-1483

Numerous publications provide information on physiological and pseudophysiological corrosion of magnesium and its alloys for bioresorbable implants, but little attention has been paid to the properties of explanted materials. In this work, commercially pure magnesium wires were corroded in rat arteries for up to 1 month, then removed, and the major and surface products were characterized. Characterization of the surface using infrared spectroscopy revealed a dual structure consisting of highly magnesium-substituted hydroxyapatite, which later transformed into type A (carbonate-substituted) hydroxyapatite. To explain this transition, an ion exchange mechanism has been proposed. Elemental distribution of bioerosion products revealed Ca, P, Mg and O in the outer layer and Mg, O and P in the inner layer. No significant amount of carbon from the inner regolith was observed, suggesting that carbonates are not a ubiquitous weathering product. Cross-sectional electron backscatter shows that the thinning or loss of hydroxyapatite in the later stage of decomposition is associated with local thickening of the internal corrosion layer. Based on these experimental observations, a mechanism is proposed to describe the quasi-steady-state corrosion and final degradation process of magnesium samples.

Procedia Structural Integrity, Volume 43, 2023, Pages 270-275

This article deals with the phase transformation and austenitizing behavior of tool steel 1.2343. Dilation analysis of a series of samples with different cooling rates, selected within a range of 10°C s⁻¹do 0,05°C·s⁻¹The obtained experimental data are used to estimate the expansion curves for mapping the temperature scale for the transformation of austenite to pearlite, bainite or martensite. Microstructural analysis and hardness measurements were then performed on all experimental samples from the dilatation analysis to characterize the microstructure and hardness for each heat treatment regime investigated. At the end of the work, the generated CCT maps were compared with the JMatPro software to assess the accuracy.

Materials and Design, Volume 113, 2017, Pages 54-59

In this paper, the effect of post-weld heat treatment (solution + artificial aging) on ​​the microstructure and low-temperature fracture toughness of weld metal of VPTIG-welded AA2219 joints was investigated using the Crack Tip Opening Displacement (CTOD) Method. There are three classes: (i) Weld metal of welded joints, designated as Sample A. (ii) Weld metal for heat treated joints after welding, designated as Sample B. iii) Base metal is used for comparison and designated as BM. The results show that solid solution treatment dissolves the θ phase, and artificial aging treatment causes redeposition of the θ phase. After post-weld heat treatment, the strength of the weld metal increases, while the plasticity and fracture toughness decrease slightly. Regardless of the sample type, 77K tests are more intense than 298K due to lower frequencies of lattice vibrations and lower energy fluctuations. Also, the plasticity at 77 K is greater than that at 298 K because the Peierls-Nabarro force is insensitive to temperature. Therefore, fracture resistance is also better at 77K.

Journal of Chromatography A, Volume 1617, 2020, Article 460828

Materials Letters: X, Volume 2, 2019, Article 100007

Bioabsorbable materials are being investigated for their promising properties for application as implant materials. This study deals with the degradation and bioactive behavior of the magnesium scales that make up the dental ligament. Degradation behavior, including indentation during immersion tests, can be accurately observed using micro-computed tomography. Using bioactivity tests according to Kokub, it was shown that magnesium has a strong calcium phosphate layer formation associated with high degradability. Therefore, magnesium flakes seem to have great potential in the application of bone implants.

Journal of Amorphous Solids, Volume 512, 2019, p. 148-154 (view, other).

An attempt to prepare lithium hydrogen silicate glass ceramics through a solid state reaction between Li₂silicon dioxide₃Crystals and silicon₂Glass. Add 0.5 mol Li₂i₂this one₅With glass as a binder, the mixture was hot pressed at 840°C for 1 hour. The role of silicon₂Effect of content (1-2mol) on reaction sintering, microstructure and mechanical properties of Li₂i₂this one₅Glass ceramics were studied. Partial silicon₂The glass is crystallized in quartz so that at least 1.5 mol of SiO₂Requires complete reaction with 1 mole of LM crystal. Li particle size₂i₂this one₅The crystal increases with SiO₂The content depends on the degree of reaction. The flexural strength and fracture toughness of the samples first increased and then decreased with increasing SiO₂After the reaction, Lee Rod₂i₂this one₅Crystals tens of microns long can be obtained, several times larger than crystals crystallized directly from the mother glass. Such a reaction forms Li₂i₂this one₅These crystals apparently have an effective hardening effect without sacrificing other properties. Since 1mol of Li reacts completely₂silicon dioxide₃The crystals consist of 1.5 mol of SiO₂Glass in sample M1S1.5D0.5 has a higher bending strength of 373±12 MPa and a higher fracture strength of 3.35±0.12 MPa∙m^1/2is acquired. The improved properties are mainly attributed to flexural crack hardening and grain bridging mechanisms.