Pokročilé povlaky

Browse

Now showing 1 - 5 of 25

Biodegradable WE43 Mg alloy/hydroxyapatite interpenetrating phase composites with reduced hydrogen evolution
(KEAI PUBLISHING LTD, 2024-12-01) Drotárová, Lenka; Slámečka, Karel; Bálint, Tomáš; Remešová, Michaela; Hudák, Radovan; Živčák, Jozef; Schnitzer, Marek; Čelko, Ladislav; Montufar Jimenez, Edgar Benjamin
Biodegradable magnesium implants offer a solution for bone repair without the need for implant removal. However, concerns persist regarding peri-implant gas accumulation, which has limited their widespread clinical acceptance. Consequently, there is a need to minimise the mass of magnesium to reduce the total volume of gas generated around the implants. Incorporating porosity is a direct approach to reducing the mass of the implants, but it also decreases the strength and degradation resistance. This study demonstrates that the infiltration of a calcium phosphate cement into an additively manufactured WE43 Mg alloy scaffold with 75 % porosity, followed by hydrothermal treatment, yields biodegradable magnesium/hydroxyapatite interpenetrating phase composites that generate an order of magnitude less hydrogen gas during degradation than WE43 scaffolds. The enhanced degradation resistance results from magnesium passivation, allowing osteoblast proliferation in indirect contact with composites. Additionally, the composites exhibit a compressive strength 1.8 times greater than that of the scaffolds, falling within the upper range of the compressive strength of cancellous bone. These results emphasise the potential of the new biodegradable interpenetrating phase composites for the fabrication of temporary osteosynthesis devices. Optimizing cement hardening and magnesium passivation during hydrothermal processing is crucial for achieving both high compressive strength and low degradation rate.
Study of the Synthesis of Multi-Cationic Sm-Co-O, Sm-Ni-O, Al-Co-O, Al-Ni-O, and Al-Co-Ni-O Aerogels and Their Catalytic Activity in the Dry Reforming of Methane
(MDPI, 2024-05-01) Cihlář, Jaroslav; Tkachenko, Serhii; Bednaříková, Vendula; Cihlář, Jaroslav; Částková, Klára; Trunec, Martin; Čelko, Ladislav
Dense multi-cationic Sm-Co-O, Sm-Ni-O, Al-Co-O, Al-Ni-O, and Al-Ni-Co-O oxide aerogels were prepared by epoxide-driven sol-gel synthesis. Catalysts for dry reformation of methane, Sm2O3/Co, Sm2O3/Ni, Al2O3/Co, Al2O3/Ni, Al2O3/Co, and Ni were prepared by reduction of aerogels with hydrogen and their catalytic activities and C-deposition during dry reformation of methane were tested. Catalytic tests showed high methane conversion (93-98%) and C-deposition (0.01-4.35 mg C/gcat.h). The highest content of C-deposits after catalytic tests was determined for Al2O3/Co and Al2O3/Ni catalysts, which was related to the formation of Al alloys with Co and Ni. A uniform distribution of Co0 and Ni0 nanoparticles (in the form of a CoNi alloy) was found only for the Al2O3/Co and Ni catalysts, which showed the highest activity as well as low C deposition.
The Corrosion Resistance of Hard Anodised EN AW 7075 T6 Alloy
(Electrochemical Society, 2021-08-22) Kusmič, David; Klakurková, Lenka; Juliš, Martin; Gejdoš, Pavel; Čech, Ondřej
In this paper, commercially cold-rolled and artificial aged EN AW 7075 T6 alloy has been used. To ensure increased corrosion resistance, surface hardness, scratching resistance, and aesthetic features, this aluminium alloy was subsequently hard anodised and hot-water sealed (AC-A). The hard anodizing and sealing process increased surface hardness up to 304 13 HV 1 from an initial surface hardness of 194 3 HV 1. Also, the microhardness of the anodised layer and bulk material has been documented. Scanning electron microscopy (SEM) was used for microstructure and trapped precipitates investigation in the 42.9 1.4 thick formed anodised layer investigation. The T6 treated (AC) and hard anodised together with sealed (AC-A) EN AW 7075 alloy corrosion properties were evaluated using the anodic potentiodynamic polarisation tests (PPT) in a neutral 2.5% NaCl deaerated solution. The corrosion rate CR (mm/y) decreased approx. 39-times for the hard anodised and sealed EN AW 7075 alloy (AC-A), associated with the shift of the E corr (mV) to more positive values, degreased Icorr (µA) and increased Rp (Ohm) values compared to the artificial aged (AC) alloy. Additionally, the pitting was evaluated using laser confocal microscopy, and the pitting coefficient was also calculated.
Flow-through Gas Phase Photocatalysis Using TiO2 Nanotubes on Wirelessly Anodized 3D-Printed TiNb Meshes
(American Chemical Society, 2023-07-12) Sopha, Hanna Ingrid; Kashimbetova, Adelia; Baudys, Michal; Chennam, Pavan Kumar; Sepúlveda Sepúlveda, Lina Marcela; Rusek, Jakub; Kolíbalová, Eva; Čelko, Ladislav; Montufar Jimenez, Edgar Benjamin; Krýsa, Josef; Macák, Jan
In this work, for the first time 3D Ti-Nb meshes of differentcomposition,i.e., Ti, Ti-1Nb, Ti-5Nb, and Ti-10 Nb, were produced by direct inkwriting. This additive manufacturing method allows tuning of the meshcomposition by simple blending of pure Ti and Nb powders. The 3D meshesare extremely robust with a high compressive strength, giving potentialuse in photocatalytic flow-through systems. After successful wirelessanodization of the 3D meshes toward Nb-doped TiO2 nanotube(TNT) layers using bipolar electrochemistry, they were employed forthe first time for photocatalytic degradation of acetaldehyde in aflow-through reactor built based on ISO standards. Nb-doped TNT layerswith low concentrations of Nb show superior photocatalytic performancecompared with nondoped TNT layers due to the lower amount of recombinationsurface centers. High concentrations of Nb lead to an increased numberof recombination centers within the TNT layers and reduce the photocatalyticdegradation rates.
Aerogel-Based Materials in Bone and Cartilage Tissue Engineering-A Review with Future Implications
(MDPI, 2023-09-13) Lázár, István; Čelko, Ladislav; Menelaou, Melita
Aerogels are fascinating solid materials known for their highly porous nanostructure and exceptional physical, chemical, and mechanical properties. They show great promise in various technological and biomedical applications, including tissue engineering, and bone and cartilage substitution. To evaluate the bioactivity of bone substitutes, researchers typically conduct in vitro tests using simulated body fluids and specific cell lines, while in vivo testing involves the study of materials in different animal species. In this context, our primary focus is to investigate the applications of different types of aerogels, considering their specific materials, microstructure, and porosity in the field of bone and cartilage tissue engineering. From clinically approved materials to experimental aerogels, we present a comprehensive list and summary of various aerogel building blocks and their biological activities. Additionally, we explore how the complexity of aerogel scaffolds influences their in vivo performance, ranging from simple single-component or hybrid aerogels to more intricate and organized structures. We also discuss commonly used formulation and drying methods in aerogel chemistry, including molding, freeze casting, supercritical foaming, freeze drying, subcritical, and supercritical drying techniques. These techniques play a crucial role in shaping aerogels for specific applications. Alongside the progress made, we acknowledge the challenges ahead and assess the near and far future of aerogel-based hard tissue engineering materials, as well as their potential connection with emerging healing techniques.

Browse

Recent Submissions