Search Results (253)

This study evaluated the surface functionalization of a non-equiatomic TiZrNbTaMo high-entropy alloy (HEA) by micro-arc oxidation (MAO) in Cu-rich electrolytes to tailor its performance for biomedical implants. The Cu content was varied, and the resulting coatings were investigated for their morphology, phase constitution, chemical structure, wettability, and cytocompatibility. X-ray diffraction (XRD) measurements of the substrate indicated a body-centered cubic (BCC) matrix with minor HCP features, while the MAO-treated samples depicted amorphous halo with sparse reflections assignable to CaCO₃, CaO, and CaPO₄. Chemical spectroscopic analyses identified the presence of stable oxides (TiO₂, ZrO₂, Nb₂O₅, Ta₂O₅, MoO₃) and the successful incorporation of bioactive elements (Ca, P, Mg) together with traces of Cu, mainly as Cu₂O. MAO treatment increased surface roughness and rendered a hydrophilic behavior, which are features typically favorable to osseointegration process. In vitro cytotoxic assays with MC3T3-E1 cells (24 h) showed that Cu addition did not induce harmful effects, maintaining or improving cell viability and adhesion compared to the controls. Collectively, MAO in Cu-rich electrolyte yielded porous, bioactive, and Cu-incorporated oxide coatings on TiZrNbTaMo HEA, preserving cytocompatibility and supporting their potential for biomedical applications like orthopedic implants and bone-fixation devices. Full article

One-dimensional (1D) multiferroic composite nanofibers are known to exhibit enhanced magnetoelectric (ME) coupling compared to their thin-film and bulk counterparts with similar compositions. While measuring their local ME coupling at the nanoscale is essential for understanding multiferroic interactions, it remains challenging due to their complex structure. In this work, multiferroic Pb(Zr_0.52Ti_0.48)O₃-CoFe₂O₄ (PZT-CFO) Janus-type nanofibers were synthesized by electrospinning. This unique structure is expected to provide a more compact and continuous interface between the ferroelectric and ferromagnetic phases compared to core–shell configurations. X-ray diffraction confirmed the coexistence of the perovskite PZT and spinel CFO phases without detectable impurities. The Janus configuration was directly verified by scanning electron microscopy and Kelvin probe force microscopy, which revealed a distinct surface potential contrast between the two halves of a single nanofiber. Magnetic hysteresis loops demonstrated the macroscopic ferromagnetic behavior of the nanofiber assembly. Local magnetoelectric coupling was probed using piezoresponse force microscopy under an applied magnetic field. An enhancement of the intrinsic piezoresponse from 15 pm to 19 pm. was observed upon applying an 8000 Oe magnetic field, providing direct evidence of strain-mediated ME coupling at the nanoscale. Although no ferroelectric domain switching was observed, likely due to the substrate clamping effect, the observed piezoresponse modulation confirms the functional ME interaction. These findings suggest that the Janus nanofibers hold promise for applications in one-dimensional multiferroic devices. Full article

The development of cost-effective non-noble metal catalysts for the partial oxidation of methane (POM) remains a key strategy for producing hydrogen-rich syngas while mitigating greenhouse gas emissions. In this study, cobalt-supported alumina (Co/Al₂O₃) catalysts were prepared using 5 wt.% of Co and calcined at 600, 700, and 800 °C. Subsequently, Co/Al₂O₃ catalysts were promoted with 10 wt.% Mg, Si, Ti, and Zr at the optimized calcination temperature. The catalysts were systematically characterized by FT-IR, XRD, N₂ physisorption, H₂-TPR, and XPS analyses. Catalytic activity tests for POM of CH₄ were conducted at 600 °C (CH₄/O₂ = 2 and GHSV = 14,400 mL g⁻¹ h⁻¹). Catalysts calcined at 700 °C (5Co/Al_700) exhibited the highest activity among unpromoted samples, with CH₄ conversion of 43.9% and H₂ yield of 41.8%. The superior performance was attributed to its high surface area and the abundance of reducible Co³⁺ species, generating a greater number of Co⁰ active sites. XPS results confirmed the structural stability of γ-Al₂O₃ and preserved Co–Al interactions across calcination temperatures, while promoters mainly modulated Co dispersion and redox accessibility. Among the promoted catalysts, the activity order followed: 5Co/10ZrAl > 5Co/10MgAl> unpromoted-5Co/Al_700 > 5Co/10SiAl > 5Co/10TiAl. Si and Ti promoted catalysts acquired less concentration of active sites and less activity as well. The concentration of reducible species as well as initial activity towards POM are comparable over Zr and Mg-promoted catalysts. However, earlier one has a higher edge of reducibility and sustained constant activity over time in a stream study. The Zr-promoted catalyst exhibited superior reducibility and remarkable stability, achieving 47.3% CH₄ conversion and 44.4% H₂ yield sustained over 300 min time-on-stream. TEM analysis of spent 5Co/10ZrAl indicated that Zr promotion suppressed graphitic carbon formation. Full article

Titanium-based bulk metallic glasses (BMGs) offer high strength, lower stiffness than Ti-6Al-4V, and superior corrosion resistance, but conventional Ti glass-forming systems often contain toxic Ni, Be, or Cu. This work investigates five novel Ti-based alloys free of these elements—Ti₄₂Zr₃₅Si₅Co_12.5Sn_2.5Ta₃, Ti₄₂Zr₄₀Ta₃Si₁₅, Ti₆₀Nb₁₅Zr₁₀Si₁₅, Ti₃₉Zr₃₂Si₂₉, and Ti_65.5Fe_22.5Si₁₂—synthesized by arc melting and suction casting. Single-track laser remelting using a selective laser melting (SLM) system was performed to simulate additive manufacturing and examine microstructural evolution, cracking behavior, mechanical properties, and cytocompatibility. All alloys solidified into fully crystalline α/β-Ti matrices with Ti/Zr silicides; no amorphous structures were obtained. Laser remelting refined the microstructure but did not induce glass formation, consistent with the known limited glass-forming ability of Cu/Ni/Be-free Ti systems. Cracking was observed at low laser energies but crack density decreased as laser energy increased. Cracks were eliminated above ~0.4 J/mm for most alloys. Ti₄₂Zr₃₅Si₅Co_12.5Sn_2.5Ta₃ exhibited the lowest stiffness (~125 GPa), while Ti₆₀Nb₁₅Zr₁₀Si₁₅ showed the highest due to silicide precipitation. Cytotoxicity tests (ISO 10993-5) confirmed all alloys to be non-toxic, with some extracts even enhancing fibroblast proliferation. This rapid laser-remelting approach enables cost-effective screening of Ti-based glass-forming alloys for additive manufacturing. Ti–Zr–Ta–Si systems demonstrated the most promising properties for further testing using the powder bed method. Full article

The investigation of the behavior of ZrB₂-SiC-based ultra-high temperature ceramic (UHTC) materials under high-velocity CO₂ plasma flow is of significant importance and relevance for evaluating their prospective use in the exploration of planets such as Venus or Mars. Accordingly, the degradation process of a ZrB₂-30 vol.% SiC ceramic composite, fabricated by hot-pressing at 1700 °C with a 15 vol.% Ti₂AlC sintering aid, was examined using a high-frequency induction plasmatron. It was found that the modification of the ceramic’s elemental and phase composition during consolidation, resulting from the interaction between ZrB₂ and Ti₂AlC, leads to the formation of an approximately 400 µm-thick multi-layered oxidation zone following 15 min stepwise thermochemical exposure at surface temperatures reaching up to 1970 °C. This area consists of a lower layer depleted of silicon carbide and an upper layer containing large pores (up to 160–200 µm), where ZrO₂ particles are distributed within a silicate melt. SEM analysis revealed that introduction of more refractory titanium and aluminum oxides into the melt upon oxidation, along with liquation within the melt, prevents the complete removal of this sealing melt from the sample surface. This effect remains even after 8 min exposure at an average temperature of ~1960–1970 °C. Full article

Incomplete diesel combustion emits soot and CO. The use of biomass-derived, oxygen-containing diesel additives has been proposed as an effective mitigation strategy. Among these, long-chain ethers have been widely regarded as one of the most promising additive classes. Guided by this, carbonyl compounds were targeted as intermediates for the synthesis of long-chain ethers. Py-GC/MS was used to assess eight oxides (CaO, ZrO₂, NiO, CeO₂, TiO₂ (rutile), TiO₂ (anatase), Fe₂O₃, CuO) during fast pyrolysis of native holocellulose. Relative content of carbonyl compounds was increased by all catalysts, with CaO exhibiting the highest value (69.47%). CaO raised the content of linear ketones from 18.25% to 27.61%, while it sharply reduced the relative content of acetic acid (from 11.56% to 3.19%). TiO₂ (rutile) increased cyclic ketones from 11.09% to 15.01%. CuO boosted furans and acids to 17.48% and 17.91%, respectively. Levoglucosan dropped from 11.24% to 4.83% over CuO, which also increased furfural content from 3.25% to 5.63%. Full article

Suitable nitride coating deposition could improve the wear resistance of WC/Co carbide tools when cutting Ti₂AlNb typical difficult-to-machine alloy. However, there is no clear conclusion on which nitride series coating is suitable for improving the friction characteristics between WC/Co carbide and Ti₂AlNb alloy. In this research, the CrAlN, CrAlN/(CrAlB)N/CrAlN, and TiAlN/ZrN coatings were deposited on WC/Co carbide with the only variable of coating type, which were utilized to conduct the high-temperature pin disc experiments with Ti₂AlNb alloy at 600 °C, respectively. The high-temperature friction characteristics were analyzed by the friction coefficient with time, the alloy wear rate, the surface morphology, and element distribution after wear. The results showed that the three types of coating all improved the high temperature friction and wear characteristics of WC/Co carbide. The Ti₂AlNb alloy also exhibited good surface morphology after wear with TiAlN/ZrN-coated carbide. It is speculated that TiAlN/ZrN coating was the suitable coating deposition on WC/Co carbide tools to improve cutting performance of Ti₂AlNb alloy. Full article

In this study, a highly conductive nickel (Ni) layer was deposited onto a P-type (Zr,Ti)Co(Sn,Sb) half-Heusler (HH) thermoelectric (TE) material using a low-cost electro-brush plating technique. Before depositing Ni on the TE material, the plating process was optimised on a stainless steel (SS) substrate. An optimal medium-rate deposition voltage of 6V was identified on the SS substrate, with the desired thickness, superior mechanical performance, reduced sheet resistance and surface roughness, and enhanced electrical conductivity. The optimised deposition condition was then applied to the P-type (Zr,Ti)Co(Sn,Sb) material, resulting in a Ni layer that significantly enhanced its electrical and thermal stability. After thermal exposure at 500 °C for 10 h, the Ni coating effectively protected the TE surface against oxidation and sublimation, suggesting that the interfacial contact properties of P-type (Zr,Ti)Co(Sn,Sb) TE material can be effectively enhanced by depositing a highly conductive, oxidation-resistant Ni layer using the cost-effective, straightforward electro-brush plating technique. Full article

The selective hydrogenation of the C=O bond over the C=C bond in α,β-unsaturated aldehydes remains a well-known challenge. This work investigates the liquid-phase catalytic transfer hydrogenation of crotonaldehyde to crotyl alcohol over ReOx-based catalysts, using formic acid (FA) as an in situ hydrogen donor. A series of 10 wt% Re catalysts supported on G200, g-C₃N₄, TiO₂, and ZrO₂ were synthesized and tested in a batch reactor at 20 bar and temperatures of 140–180 °C. Catalysts were characterized by XRD, BET, NH₃-TPD, and XPS to correlate their physicochemical properties with catalytic behavior. Among the studied materials, ReO_x/ZrO₂ and ReO_x/g-C₃N₄ exhibited the highest crotyl alcohol selectivity above 57% for all reaction temperatures, evaluated at crotonaldehyde conversion of 25%. The nature of the support strongly influenced the dispersion and oxidation state of Re species, as well as the surface acidity, which governed the activation of both the carbonyl group and the FA decomposition. Compared with molecular hydrogen, FA improved both conversion and selectivity due to its superior hydrogen-donating ability in the aqueous phase. These findings demonstrate that tailoring the acid–base characteristics of ReO_x catalysts and employing biomass-derived hydrogen donors represent an effective strategy for selective hydrogenation of α,β-unsaturated aldehydes. Full article

As well as having corrosion resistance and mechanical properties, medical metallic biomaterials used in metal implants must allow imaging by MRI for prognostic diagnosis. Alloys based on Ti, Fe, Co, etc., have the disadvantage that those constituent elements have higher magnetic susceptibility than the tissue surrounding the metallic implant, and this condition results in defects and distortions (“artifacts”) in MR images during MRI imaging. In consideration of this issue, MRI-compatible low-magnetic-susceptibility materials are currently being researched and developed. In this study, microstructural control of Zr-based alloys by alloy design and heat treatment was investigated. The problem with pure Zr is its low corrosion resistance due to the α-phase of its hexagonal-close-packed (HCP) structure. However, alloys that were alloyed and solution heat-treated to a β-phase (body-centered cubic (BCC) structure) showed high corrosion resistance. In particular, when Zr-15Nb-5Ti-3Cr, which has relatively high corrosion resistance, was subjected to aging heat treatment at 673 K for 1.8 ks, precipitation of fine ω-phase in the β-phase was confirmed. The metallographic structure in which the ω-phase precipitated in the β-phase provided high corrosion resistance [≧1000 mV (vs. SHE)] derived from the β-phase, as well as low magnetic susceptibility (approximately 1.2 × 10⁻⁶ cm³/g), due to the effect of the ω-phase. This study provides guidelines for microstructural control to achieve both low magnetic susceptibility and high corrosion resistance in Zr-based metallic biomaterials for medical use. Full article

Background/Objectives: A comparative study of silver (Ag), titanium nitride (TiN), zirconium nitride (ZrN), and copper (Cu) coatings on titanium (Ti) disks, considering the specifications of a microporous skin- and bone-integrated titanium pylon (SBIP), was performed to assess their biocompatibility, osseointegration, and mechanical properties. Methods: To assess cytotoxicity and biocompatibility, Ti disks with various metal coatings were co-cultured with FetMSCs and MG-63 cells for 1, 3, 7, and 14 days and subsequently evaluated using a cell viability assay, as supported by SEM and confocal microscopy studies. The antimicrobial activity of the selected four materials coating the implants was tested against S. aureus by mounting Ti disks onto the surface of LB agar dishes spread with a bacterial suspension and measuring the diameter of the growth inhibition zones. Quantitative Real-Time Polymerase Chain Reaction (RT-PCR) analysis of the relative gene expression of biomarkers that are associated with extracellular matrix components (fibronectin, vitronectin, type I collagen) and cell adhesion (α2, α5, αV integrins), as well as of osteogenic markers (osteopontin, osteonectin, TGF-β1, SMAD), was performed during the 14-day follow-up period. Additionally, the activity of matrix metalloproteinases (MMP-1, -2, -8, -9) was assessed. Results: All samples with metal coatings, except the copper coating, demonstrated a good cytotoxicity profile, as evidenced by the presence of a cellular monolayer on the sample surface on the 14th day of the follow-up period (as shown by SEM and inverted confocal microscopy). All metal coatings enhanced MMP activity, as well as cellular adhesion and osteogenic marker expression; however, TiN showed the highest values of these parameters. Significant inhibition of bacterial growth was observed only in the Ag-coated Ti disks, and it persisted for over 35 days. Conclusions: The silver-based coating, due to its high antibacterial activity, low cytotoxicity, and biointegrative capacity, can be recommended as the coating of choice for microporous titanium implants for further preclinical studies. Full article

Detailed description of phase composition and geochemistry of the Muschelkalk carbonate rocks of the Upper Silesian Province in Poland were presented in this article. The tests were carried out to determine mineralogical features and geochemical properties. The samples were collected from the formations of the Lower Muschelkalk (Gogolin Unit), Middle Muschelkalk (Diplopore Dolomite Unit) and Upper Muschelkalk (Tarnowice Unit, Boruszowice Unit). The following research methods were used: macroscopic description, X-Ray Diffraction, Fourier transform infrared spectroscopy, X-Ray Fluorescence and Atomic spectrometry with plasma intensification. The following carbonate phases were identified: a low-Mg calcite, a high-Mg calcite, a proto-dolomite, an ordered dolomite and a huntite. The results of XRD analysis allowed the determination of the chemical formulas of the mineral phases. XRF and ICP AES analyses allowed to establish the content of following trace elements: Sr, Ba, Al, Si, Fe, Mn, K, Na, S, Cl, Ti, Cr, Ni, Zn, Rb, Zr, Pb, As, V, Be, B, Co, Cu, Br, Mo and Cd. Apart from Sr and Ba, they are not fundamental components of carbonate rocks. They indicate the presence of minerals such as silicates, aluminosilicates, oxides and sulfides. Full article

The aim of this laboratory study was to evaluate the fitting accuracy of complete-arch implant-supported fixed dental prostheses (ISFDPs) and the occurrence of possible constraint forces after ISFDP fixation using the All-on-four treatment concept. A titanium model was fabricated with support posts for implants in positions 15, 12, 22, and 25. The forces acting on these posts were assessed using strain gauge half bridges. Implants (BEGO Semados^® SCX Implantat 4.1 mm × 10 mm, BEGO Implant Systems, Bremen, Germany) were fixated on top of the support posts. Based on conventional impressions and intraoral scans, two 12-unit monolithic ISFDPs made from cobalt–chromium alloy (CoCr) and zirconia (ZrO₂) were fabricated, jointed with titanium adhesive abutments (PS TiB NH, BEGO), and successively attached to the model. Constraint forces caused by ISFDP fixation were measured for each implant without external force. After testing four ISFDPs with different materials and impression techniques, four new implants were fixated (n = 10 model situations). A standard linear mixed model was used to assess horizontal and vertical constraint forces. The horizontal constraint forces acting on the implants were oriented in the oral direction, indicating that the ISFDPs were too small. The highest constraint forces were measured on implant 22 in the horizontal and vertical directions. Within the limitations of the present laboratory study, the fitting accuracy of complete-arch CoCr and ZrO₂ ISFDPs based on the All-on-four concept was sufficient for clinical use. Restorations made using conventional impressions had better fitting accuracy and reliability than those made using intraoral scans. Full article

Electrochemical reduction processes enable the CO to be converted into a useful chemical fuel. Our study employs density functional theory calculations to analyze the (110) facets of the transition metal carbide surfaces for CO capture, incorporating the Mars–van Krevelen (MvK) mechanism. All the possible adsorption sites on the surface, including carbon, metal, and bridge sites, were fully investigated. The findings indicate that the carbon site is more active relative to the other adsorption sites examined. The CO hydrogenation paths have been comprehensively investigated on all the surfaces, and the free energy diagrams have been constructed towards the product. The results conclude that the TiC is the most promising candidate for the formation of methane, exhibiting an onset potential of −0.44 V. The predicted onset potential for CrC, MoC, NbC, VC, WC, ZrC, and HfC are −0.86, −0.61, −0.61, −0.93, −0.87, −0.61, and −0.81 V, respectively. Our calculated results demonstrate that MvK is selectively relevant to methane synthesis. Additionally, we investigated the stability of these surfaces against decomposition and conversion to pure metals concerning thermodynamics and kinetics. It was found that these carbides could remain stable under ambient conditions. The exergonic adsorption of hydrogen on carbon sites, requiring smaller potential values for product formation, and stability against decomposition indicate that these surfaces are highly suitable for CO reduction reactions using the MvK mechanism. Full article

The purpose of this study was to design a Pt/TiO₂–ZrO₂ catalytic-based treatment system to remove ethanol and oxygen (O₂) from a gaseous feed stream. The ultimate target application was the conversion of ethanol and O₂ to carbon dioxide (CO₂) and water (H₂O) from a feed stream of CO₂ in a commercial beer brewing operation. Bench-scale reactions were performed at 250 °C and 300 °C, representing two temperatures under practical consideration for a full-scale catalytic reactor. The target gaseous feed stream would be expected to have a relatively low (near-stoichiometric) concentration of O₂, so the effect of O₂ concentration was also studied. On the bench scale, ethanol was completely converted to CO₂ under low flow rate conditions, and the reactions proceeded through volatile and non-volatile reaction intermediates. Results from the bench-scale tests were used to make predictions for designing a pilot-scale catalytic reactor under conditions of high and low O₂ concentration. A pilot-scale reactor was constructed and installed in a commercial brewing facility, and results from testing the pilot-scale reactor are also presented. The pilot-scale system reduced the feed stream ethanol concentrations by 99.9% while concomitantly reducing the O₂ concentrations over the course of a six-day demonstration period without generating unacceptable levels of byproducts. Full article