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1.
ACS Appl Bio Mater ; 7(7): 4760-4771, 2024 Jul 15.
Article in English | MEDLINE | ID: mdl-38916249

ABSTRACT

Laccase is an oxidase of great industrial interest due to its ability to catalyze oxidation processes of phenols and persistent organic pollutants. However, it is susceptible to denaturation at high temperatures, sensitive to pH, and unstable in the presence of high concentrations of solvents, which is a issue for industrial use. To solve this problem, this work develops the synthesis in an aqueous medium of a new Mn metalloenzyme with laccase oxidase mimetic catalytic activity. Geobacillus thermocatenulatus lipase (GTL) was used as a scaffold enzyme, mixed with a manganese salt at 50 °C in an aqueous medium. This leads to the in situ formation of manganese(IV) oxide nanowires that interact with the enzyme, yielding a GTL-Mn bionanohybrid. On the other hand, its oxidative activity was evaluated using the ABTS assay, obtaining a catalytic efficiency 300 times higher than that of Trametes versicolor laccase. This new Mn metalloenzyme was 2 times more stable at 40 °C, 3 times more stable in the presence of 10% acetonitrile, and 10 times more stable in 20% acetonitrile than Novozym 51003 laccase. Furthermore, the site-selective immobilized GTL-Mn showed a much higher stability than the soluble form. The oxidase-like activity of this Mn metalloenzyme was successfully demonstrated against other substrates, such as l-DOPA or phloridzin, in oligomerization reactions.


Subject(s)
Laccase , Manganese , Laccase/metabolism , Laccase/chemistry , Manganese/chemistry , Materials Testing , Geobacillus/enzymology , Particle Size , Biocompatible Materials/chemistry , Biocompatible Materials/chemical synthesis , Biocompatible Materials/metabolism , Lipase/metabolism , Lipase/chemistry
2.
Sci Rep ; 14(1): 11106, 2024 May 15.
Article in English | MEDLINE | ID: mdl-38750130

ABSTRACT

Transforming amines with low boiling points and high volatilities into protic salts is a versatile strategy to utilize low molecular weight compounds as precursors for N-doped carbon structures in a straightforward carbonization procedure. Herein, conventional mineral acids commonly used for the synthesis of protic salts were replaced by bio-derived phytic acid, which, combined with various amines and amino acids, yielded partially or fully bio-derived protic salts. The biomass-based salts showed higher char-forming ability than their mineral acid-based analogs (up to 55.9% at 800°), simultaneously providing carbon materials with significant porosity (up to 1177 m2g-1) and a considerable level of N,P,O-doping. Here, we present the first comprehensive study on the correlation between the structure of the bio-derived protic precursors and the properties of derived carbon materials to guide future designs of biomass-derived precursors for the one-step synthesis of sustainable carbon materials. Additionally, we demonstrate how to improve the textural properties of the protic-salt-derived carbons (which suffer from high brittleness) by simply upgrading them into highly flexible nanocomposites using high-quality single-walled carbon nanotubes. Consequently, self-standing electrodes for the oxygen reduction reaction were created.

3.
Materials (Basel) ; 17(6)2024 Mar 18.
Article in English | MEDLINE | ID: mdl-38541538

ABSTRACT

Proton-exchange membrane fuel cells are one of the most promising energy conversion technologies for both automotive and stationary applications. Scientists are testing a number of solutions to increase the durability of cells, especially catalysts, which are the most expensive component. These solutions include, among others, the modification of the composition and morphology of supported nanoparticles, the platinum-support interface, and the support itself. A detailed understanding of the mechanism of platinum degradation and the subsequent improvement of the durability of the entire cell requires the development of methods for effectively monitoring the behavior of catalytic nanoparticles under various cell operating conditions. The Identical-Location Transmission Electron Microscopy (IL-TEM) method makes it possible to visually track structural and morphological changes in the catalyst directly. Because the tests are performed with a liquid electrolyte imitating a membrane, they provide better control of the degradation conditions and, consequently, facilitate the understanding of nanoparticle degradation processes in various operating conditions. This review is primarily intended to disseminate knowledge about this technique to scientists using electron microscopy in the study of energy materials and to draw attention to issues related to the characterization of the structure of carbon supports.

4.
J Funct Biomater ; 14(9)2023 Aug 28.
Article in English | MEDLINE | ID: mdl-37754857

ABSTRACT

The main purpose of these studies was to obtain carbon-carbon composites with a core built of carbon fibers and a matrix in the form of pyrolytic carbon (PyC), obtained by using the chemical vapor deposition (CVD) method with direct electrical heating of a bundle of carbon fibers as a potential electrode material for nerve tissue stimulation. The methods used for the synthesis of PyC proposed in this paper allow us, with the appropriate selection of parameters, to obtain reproducible composites in the form of rods with diameters of about 300 µm in 120 s (CF_PyC_120). To evaluate the materials, various methods such as scanning electron microscopy (SEM), scanning transmission electron microscope (STEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and tensiometer techniques were used to study their microstructural, structural, chemical composition, surface morphology, and surface wettability. Assessing their applicability for contact with nervous tissue cells, the evaluation of cytotoxicity and biocompatibility using the SH-SY5Y human neuroblastoma cell line was performed. Viability and cytotoxicity tests (WST-1 and LDH release) along with cell morphology examination demonstrated that the CF_PyC_120 composites showed high biocompatibility compared to the reference sample (Pt wire), and the best adhesion of cells to the surface among all tested materials.

5.
Sci Rep ; 12(1): 18531, 2022 Nov 02.
Article in English | MEDLINE | ID: mdl-36323701

ABSTRACT

Ni-Mo alloy coatings were deposited on a copper base material from a non-aqueous plating bath based on a deep eutectic solvent (DES) of choline chloride and propylene glycol in a 1:2 molar ratio containing 0.2 mol dm-3 NiCl2 · 6H2O and 0.01 mol dm-3 (NH4)6Mo7O24·4H2O. Uniform and adherent Ni-Mo deposits with a nodular morphology were obtained at all the deposition potentials investigated (from - 0.5 to - 0.9 V vs. Ag). By shifting the potential from - 0.5 to - 0.9 V, the deposition current density increased from - 0.4 to - 1.5 mA cm-2 and the overall surface roughness increased. It was also accompanied by an increase in the Mo content from ~ 7 to ~ 13 wt% in the potential range from - 0.5 to - 0.7 V. A further change in the potential from - 0.8 to - 0.9 V caused a decrease in the Mo content to ~ 10 wt% and a deterioration in the quality of the coating. For the most uniform coating, deposited at - 0.6 V and having a thickness of ca. 660 nm, the crystallite size did not exceed 10 nm. With the content of Ni (89 at.%) and Mo (11 at.%), the selected area electron diffraction (SAED) analysis allowed us to identify the cubic phase Ni3.64Mo0.36. The corrosion resistance of Ni-Mo coatings in 0.05 mol dm-3 NaCl solution generally increased during exposure of 18 h, as evidenced by ever higher polarization resistance. Finally, regardless of the applied deposition potential, low corrosion currents (in the range of 0.1-0.3 µA cm-2) have been measured for the coatings. EIS revealed that charge transfer resistances were the highest (57-67 kΩ cm2) for coatings deposited at - 0.5 V, - 0.6 V and - 0.7 V. Further increase in the deposition potential in the negative direction was unfavorable.

6.
Chem Mater ; 34(17): 7916-7936, 2022 Sep 13.
Article in English | MEDLINE | ID: mdl-36117879

ABSTRACT

Understanding how reaction conditions affect metal-support interactions in catalytic materials is one of the most challenging tasks in heterogeneous catalysis research. Metal nanoparticles and their supports often undergo changes in structure and oxidation state when exposed to reactants, hindering a straightforward understanding of the structure-activity relations using only ex situ or ultrahigh vacuum techniques. Overcoming these limitations, we explored the metal-support interaction between gold nanoparticles and ceria supports in ultrahigh vacuum and after exposure to CO. A combination of in situ methods (on powder and model Au/CeO2 samples) and theoretical calculations was applied to investigate the gold/ceria interface and its reactivity toward CO exposure. X-ray photoelectron spectroscopy measurements rationalized by first-principles calculations reveal a distinctly inhomogeneous charge distribution, with Au+ atoms in contact with the ceria substrate and neutral Au0 atoms at the surface of the Au nanoparticles. Exposure to CO partially reduces the ceria substrate, leading to electron transfer to the supported Au nanoparticles. Transferred electrons can delocalize among the neutral Au atoms of the particle or contribute to forming inert Auδ- atoms near oxygen vacancies at the ceria surface. This charge redistribution is consistent with the evolution of the vibrational frequencies of CO adsorbed on Au particles obtained using diffuse reflectance infrared Fourier transform spectroscopy.

7.
Materials (Basel) ; 15(17)2022 Sep 02.
Article in English | MEDLINE | ID: mdl-36079493

ABSTRACT

Ceramic injection moulding and gas-pressure infiltration were employed for the manufacturing of alumina/AlSi10Mg composites. Porous ceramic preforms were prepared by mixing alumina powder with a multi-binder system and injection moulding the powder polymer slurry. Then, the organic part was removed through a combination of solvent and thermal debinding, and, finally, the materials were sintered at different temperatures. Degrading the binder enabled open canals to form. The sintering process created a porous ceramic material consisting of alumina without any residual carbon content. During infiltration, the liquid metal filled the empty spaces (pores) effectively and formed a three-dimensional network of metal in the ceramic. The microstructure and properties of the manufactured materials were examined using high-resolution transmission electron microscopy, porosimetry, and bending strength testing. Microscopy observations showed that the fabricated composite materials are characterised by a percolation type of microstructure and a lack of unfilled pores. The research confirmed the diversified nature of the connection at the particle-matrix interface. It was observed that the interphase boundary was characterised by the lack of a transition zone between the components or a continuous transition zone, with the thickness not exceeding 30 nm. Thanks to their increased mechanical properties and low density, the obtained composites could be used in the automotive industry as a material for small piston rings and rods, connecting rods, or even gears.

8.
Materials (Basel) ; 15(15)2022 Aug 05.
Article in English | MEDLINE | ID: mdl-35955344

ABSTRACT

This paper presents research on the microstructure and mechanical properties of an alloyed composite copper (Cu) surface layer, reinforced with a mixture of chromium-tungsten carbide (Cr-WC) powders. Copper alloying was performed using a high-power diode laser (HPDL). In the tests, three mixtures of powders with different percentage contents (75%Cr 25%WC, 50%Cr 50%WC, 25%Cr 75%WC) were injected into the melting pool during the laser surface alloying process. Microstructural evolution and the properties of the surface layer of copper after laser alloying were investigated. Structural investigations were performed using light microscopy, scanning and transmission electron microscopy (SEM, TEM) and X-ray diffraction (XRD). Microhardness and wear resistance of the modified surface layer were examined as well. After laser treatment the applied powders appear as uniformly distributed particles in the alloyed zone as well as nanoscale precipitates in the Cu matrix. Several types of precipitate characteristics, in terms of morphology, structure and chemical composition, were observed. Laser alloying of the surface layer modified the microstructure, which resulted in an increase in the hardness of the surface layers compared to the base material.

9.
Materials (Basel) ; 15(13)2022 Jun 21.
Article in English | MEDLINE | ID: mdl-35806498

ABSTRACT

The article presents the assessment of solutions and dried residues precipitated from solutions after the bioleaching process of Printed Circuit Boards (PCB) utilizing the Acidithiobacillus ferrooxidans. The obtained dried residues precipitated from bioleaching solution (leachate) and control solution were tested using morphology, phase, and chemical composition analysis, with particular emphasis on the assessment of crystalline and amorphous components. The analysis of the dried residues from leachate after bioleaching as well as those from the sterile control solution demonstrated a difference in the component oxidation-the leachate consisted of mainly amorphous spherical particles in diameter up to 200 nm, forming lacy aggregates. In the specimenform control solution larger particles (up to 500 nm) were observed with a hollow in the middle and crystalline outer part (probably Fe2O3, CuFeS2, and Cu2O). The X-ray diffraction phase analysis revealed that specimen obtained from leachate after bioleaching consisted mainly of an amorphous component and some content of Fe2O3 crystalline phase, while the dried residue from control solution showed more crystalline components. The share of the crystalline and amorphous components can be related to efficiency in dissolving metals during bioleaching. Obtained results of the investigation confirm the activity and participation of the A. ferrooxidans bacteria in the solubilization process of electro-waste components, with their visible degradation-acceleration of the reaction owing to a continuous regeneration of the leaching medium. The performed investigations allowed to characterize the specimen from leachate and showed that the application of complementary cross-check of the micro (SEM and S/TEM) and macro (ICP-OES and XRD) methods are of immense use for complete guidance assessment and obtained valuable data for the next stages of PCBs recycling.

10.
Materials (Basel) ; 15(3)2022 Jan 27.
Article in English | MEDLINE | ID: mdl-35160923

ABSTRACT

We present the study of pristine and calcined f-MWCNTs functionalized by nitrogen-containing functional groups. We focus on the structural and microstructural modification tuned by the previous annealing. However, our primary goal was to analyze the electronic structure and magnetic properties in relation to the structural properties using a multi-technique approach. The studies carried out by X-ray diffraction, XPS, and 57Fe Mössbauer spectrometry revealed the presence of γ-Fe nanoparticles, Fe3C, and α-FeOOH as catalyst residues. XPS analysis based on the deconvolution of core level lines confirmed the presence of various nitrogen-based functional groups due to the purification and functionalization process of the nanotubes. The annealing procedure leads to a structural modification mainly associated with removing surface impurities as purification residues. Magnetic studies confirmed a significant contribution of Fe3C as evidenced by a Curie temperature estimated at TC = 452 ± 15 K. A slight change in magnetic properties upon annealing was revealed. The detailed studies performed on nanotubes are extremely important for the further synthesis of composite materials based on f-MWCNTs.

11.
Materials (Basel) ; 15(4)2022 Feb 14.
Article in English | MEDLINE | ID: mdl-35207940

ABSTRACT

This article presents research on the structural and mechanical properties of an innovative metal matrix composite (MMC) coating designed for use in conditions of intense metal-mineral abrasive wear. The layer, which is intended to protect the working surface of drilling tools used in the oil and natural gas extraction sector, was padded using the multi-run technique on a sheet made of AISI 4715 low-alloy structural steel by Laser Direct Metal Deposition (LDMD) using a high-power fiber laser (FL). An innovative cobalt alloy matrix powder with a ceramic reinforcement of crushed titanium carbide (TiC) and tungsten-coated synthetic polycrystalline diamond (PCD) was used as the surfacing material. The influence of the preheating temperature of the base material on the susceptibility to cracking and abrasive wear of the composite coating was assessed. The structural properties of the coating were characterized by using methods such as optical microscopy, scanning electron microscopy (SEM), energy dispersion spectroscopy (EDS), transmission electron microscopy (TEM) and X-ray diffraction analysis (XRD). The mechanical properties of the hardfaced coating were assessed on the basis of the results of a metal-mineral abrasive wear resistance test, hardness measurement, and the observation of the abrasion area with a scanning laser microscope. The results of laboratory tests showed a slight dissolution of the tungsten coating protecting the synthetic PCD particles and the transfer of its components into the metallic matrix of the composite. Moreover, it was proved that an increase in the preheating temperature of the base material prior to welding has a positive effect on reducing the susceptibility of the coating to cracking, reducing the porosity of the metal deposit and increasing the resistance to abrasive wear.

12.
Sci Total Environ ; 820: 153308, 2022 May 10.
Article in English | MEDLINE | ID: mdl-35065111

ABSTRACT

This study investigates authigenic metal (Zn, Cd, and Pb) sulfides formed in the upper (4-20 cm) layer of severely degraded soil close to ZnPb smelter in CE Europe (southern Poland). The soil layer is circumneutral (pH 6.0-6.8), organic, occasionally water-logged, and contains on average 26,400 mg kg-1 Zn, 18,800 mg kg-1 Pb, 1300 mg kg-1 Cd, and 2500 mg kg-1 of sulfur. The distribution of the authigenic sulfide mineralization is uneven, showing close association with the remains of vascular plants (Equisetaceae, Carex, and herbs). A combination of focused ion beam (FIB) technology with scanning (SEM) and transmission electron microscopy (TEM) is used to reveal the structure and organization of the metal sulfides at micro- and nanoscale resolution. The sulfides form spheroidal and botryoidal porous aggregates composed of nanocrystalline (<5 nm) ZnCd sulfide solid solution and minor discrete PbS (galena) crystals up to 15 nm. The solid solution exists in a cubic (sphalerite) polytype over a whole Zn/Cd range. An intricate core-shell structure is found to be a characteristic feature of the aggregates in which high-Zn outer layers encapsulate Cd-rich sulfide core. PbS resides between the Cd-rich and Cd poor sulfide within nano sites of increased porosity. The study highlights the importance of nanoscale analyses for the prediction of metal behavior in soils. The sulfide self-organization into complex structures and Cd encapsulation inside high-Zn sulfide indicate the occurrence of a self-sustainable mechanism specific to polluted periodically water-logged soil that limits Cd mobility. However, as the reduced Cd mobility is obtained at the Zn expense, the soil gets Cd enriched relative to Zn over extended periods. Although the study proves PbS crystallization in the soil, the process seems environmentally irrelevant even at high Pb contents, being suppressed by other soil processes (e.g., Pb sorption on organic matter). Our findings are valuable in remediation strategies and the management of contaminated soils rich in organic matter that address the mobility of toxic metals and their transfer into living organisms.


Subject(s)
Metals, Heavy , Soil Pollutants , Cadmium/analysis , Metals, Heavy/analysis , Soil/chemistry , Soil Pollutants/analysis , Sulfides , Water , Zinc/analysis
13.
Materials (Basel) ; 14(24)2021 Dec 11.
Article in English | MEDLINE | ID: mdl-34947228

ABSTRACT

Li-ion batteries are widely used as energy storage devices due to their excellent electrochemical performance. The cubic Li7La3Zr2O12 (c-LLZO) compound is regarded as a promising candidate as a solid-state electrolyte for lithium-ion batteries due to its high bulk Li-ion conductivity, excellent thermal performance, and chemical stability. The standard manufacturing procedure involves the high-temperature and lengthy annealing of powders. However, the formation of the tetragonal modification of LLZO and other undesired side phases results in the deterioration of electrochemical properties. The mechanical milling of precursor powders can enhance the powders' reactivity and can result in an easier formation of c-LLZO. The aim of this work was to study the influence of selected milling and annealing parameters on c-LLZO compound formation. The starting powders of La(OH)3, Li2CO3, and ZrO2 were subjected to milling in various ball mills, under different milling conditions. The powders were then annealed at various temperatures for different lengths of times. These studies showed that the phase transformation processes of the powders were not very sensitive to the milling parameters. On the other hand, the final phase composition and microstructure strongly depended on heat treatment conditions. Low temperature annealing (750 °C) for 3 h produced 90% of c-LLZO in the powder structure.

14.
Materials (Basel) ; 14(16)2021 Aug 04.
Article in English | MEDLINE | ID: mdl-34442890

ABSTRACT

This paper presents the synergy of the effect of two surface engineering technologies-magnetron sputtering (MS-PVD) and atomic layer deposition (ALD) on the structure and properties of 316L steel. Recent studies indicate that PVD coatings, despite their thickness of a few micrometers, have many discontinuities and structural defects, which may lead to pitting corrosion after time. Applying an ALD layer to a PVD coating seals its structure and contributes to extending the service life of the coating. Investigations of the structure and morphology of the produced layers were carried out using a scanning electron microscope (SEM) and atomic force microscope (AFM). In addition, the structure of the coatings was investigated on the cross-section using a scanning-transmission electron microscope S/TEM. The tribological properties of the materials studied were determined by the ball-on-disc method. The corrosion resistance of the tested materials was determined by the electrochemical potentiodynamic method by recording the polarization curves of the anodes. Additional information about the electrochemical properties of the tested samples, including the quality, their tightness, and their resistivity, was obtained by electrochemical impedance spectroscopy (EIS). In addition, the main mechanisms of corrosion and tribological wear were determined by SEM observations after corrosion tests and after tribological tests. The study showed that the fabrication of hybrid layers by MS-PVD and ALD techniques allows obtaining coatings with electrochemical properties superior to those of layers fabricated by only one method.

15.
Chem Commun (Camb) ; 57(63): 7814-7817, 2021 Aug 14.
Article in English | MEDLINE | ID: mdl-34270643

ABSTRACT

The effect of the zeta potential of nano zero-valent iron (nZVI) and carbocatalyst on the activation of persulfate was investigated. The oxidation experiments were performed on three different compounds, with variously modified nZVI and three distinct carbocatalysts. From the obtained results, an evident linear correlation between nanoparticles' zeta potential and reaction rate constants of these three compounds oxidation may be observed. This phenomenon is not mechanism-specific and occurs for the radical and non-radical processes. The present work indicates the critical influence of the surface charge of nZVI and carbocatalysts on the persulfate catalytic activation.

16.
Materials (Basel) ; 14(13)2021 Jun 29.
Article in English | MEDLINE | ID: mdl-34209626

ABSTRACT

Halloysite nanotube (HNT) additions to the thermoplastic polyurethane (TPU) system were thoroughly evaluated in this study. The resultant composites have been designed for future personalized intervertebral disc implant applications, which requires additional technology to obtain the appropriate geometry unique to each patient. These requirements can be fulfilled using 3D printing. In this work, a technology was developed to produce filaments for fused deposition modeling (FDM). Nanocomposites were prepared using variable HNT content (1, 2, and 3 wt.%). The nanostructure of the resultant composites was confirmed using scanning transmission electron microscopy (STEM). Mechanical tests were used to measure the tensile modulus, stress, and elongation the composites and TPU matrix. Nanocomposites with 2% HNT content were able to withstand 26% increased stress and 50% increased elongation compared to pure TPU before fracturing in addition to a 13% reduction in the friction coefficient. A MTT cytotoxicity assay confirmed the cytotoxicity of all tested materials against human epidermal keratinocyte cells (HaCaT).

17.
Int J Mol Sci ; 22(10)2021 May 20.
Article in English | MEDLINE | ID: mdl-34065593

ABSTRACT

Interest in graphene oxide nature and potential applications (especially nanocarriers) has resulted in numerous studies, but the results do not lead to clear conclusions. In this paper, graphene oxide is obtained by multiple synthesis methods and generally characterized. The mechanism of GO interaction with the organism is hard to summarize due to its high chemical activity and variability during the synthesis process and in biological buffers' environments. When assessing the biocompatibility of GO, it is necessary to take into account many factors derived from nanoparticles (structure, morphology, chemical composition) and the organism (species, defense mechanisms, adaptation). This research aims to determine and compare the in vivo toxicity potential of GO samples from various manufacturers. Each GO sample is analyzed in two concentrations and applied with food. The physiological reactions of an easy model Acheta domesticus (cell viability, apoptosis, oxidative defense, DNA damage) during ten-day lasting exposure were observed. This study emphasizes the variability of the GO nature and complements the biocompatibility aspect, especially in the context of various GO-based experimental models. Changes in the cell biomarkers are discussed in light of detailed physicochemical analysis.


Subject(s)
Biocompatible Materials/chemistry , Biocompatible Materials/toxicity , Graphite/chemistry , Graphite/toxicity , Animals , Apoptosis/drug effects , Cell Survival/drug effects , DNA Damage/drug effects , Gryllidae/drug effects , Nanoparticles/chemistry , Nanoparticles/toxicity , Oxidation-Reduction/drug effects , Oxides/metabolism
18.
Materials (Basel) ; 14(8)2021 Apr 16.
Article in English | MEDLINE | ID: mdl-33923676

ABSTRACT

Cobalt-chromium-molybdenum alloys samples were obtained by the powder injection molding method (PIM). PIM is dedicated to the mass production of components and can manufacture several grades of dental screws, bolts, stabilizers, or implants. As a skeleton component, ethylene-vinyl acetate (EVA copolymer) with a low temperature of processing and softening point was used. The choice of a low-temperature binder made it necessary to use a coarse ceramic powder as a mechanical support of the green sample during sintering. The injection-molded materials were thermally degraded in N2 or Ar-5%H2 and further sintered in N2-5%H2 or Ar-5%H2 at 1300 or 1350 °C for 30 min. The structure of the obtained samples was characterized by X-ray diffraction and electron microscopy. Mechanical properties, including hardness and three-point bending tests, confirmed that a nitrogen-rich atmosphere significantly increases the bending strength compared to the material manufactured in Ar-5%H2. This is due to the precipitation of numerous fine nitrides and intermetallic phases that strengthen the ductile γ-phase matrix.

19.
Materials (Basel) ; 14(5)2021 Feb 26.
Article in English | MEDLINE | ID: mdl-33652601

ABSTRACT

The main purpose of the research was to analyze the influence of surface modification of the cobalt-based alloy used in dental prosthetics by applying zirconium oxide (ZrO2) layers using the ALD (Atomic Layer Deposition) method. The samples were made using the DMLS (Direct Metal Laser Sintering) technique, and their surfaces were prepared in accordance with the principles of removable partial dentures (RPDs). A 50 nm-thick zirconium oxide coating was applied to the prepared substrates. This paper deals with the issues of prosthetic stomatopathy, which is a complex of pathological changes occurring in approx. 40% of the Polish population using removable dentures. Often, these changes, occurring on the mucosa, are related to improper performance, allergic reactions or the multiplication of bacteria on the surface of partial dentures. An innovative method of surface modification was proposed, together with the analysis of its influence on the physicochemical properties of the alloy and the adhesion of bacteria to the surface.

20.
Materials (Basel) ; 14(1)2021 Jan 05.
Article in English | MEDLINE | ID: mdl-33466504

ABSTRACT

This paper describes the microstructure and properties of titanium-based composites obtained as a result of a reactive spark plasma sintering of a mixture of titanium and nanostructured (Ti,Mo)C-type carbide in a carbon shell. Composites with different ceramic addition mass percentage (10 and 20 wt %) were produced. Effect of content of elemental carbon covering nc-(Ti,Mo)C reinforcing phase particles on the microstructure, mechanical, tribological, and corrosion properties of the titanium-based composites was investigated. The microstructural evolution, mechanical properties, and tribological behavior of the Ti + (Ti,Mo)C/C composites were evaluated using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), electron backscatter diffraction analysis (EBSD), X-ray photoelectron spectroscopy (XPS), 3D confocal laser scanning microscopy, nanoindentation, and ball-on-disk wear test. Moreover, corrosion resistance in a 3.5 wt % NaCl solution at RT were also investigated. It was found that the carbon content affected the tested properties. With the increase of carbon content from ca. 3 to 40 wt % in the (Ti,Mo)C/C reinforcing phase, an increase in the Young's modulus, hardness, and fracture toughness of spark plasma sintered composites was observed. The results of abrasive and corrosive resistance tests were presented and compared with experimental data obtained for cp-Ti and Ti-6Al-4V alloy without the reinforcing phase. Moreover, it was found that an increase in the percentage of carbon increased the resistance to abrasive wear and to electrochemical corrosion of composites, measured by the relatively lower values of the friction coefficient and volume of wear and higher values of resistance polarization. This resistance results from the fact that a stable of TiO2 layer doped with MoO3 is formed on the surface of the composites. The results of experimental studies on the composites were compared with those obtained for cp-Ti and Ti-6Al-4V alloy without the reinforcing phase.

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