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This study investigated the possibility of obtaining dense silicon carbide sinters with the use of a spark plasma sintering (SPS) process by changing the composition of SiC α/β polymorphs in a starting powder mixture. Amorphous boron was used as the basic additive to activate the sintering processes. Some of the compositions were prepared with additional carbon in two different forms: multilayer graphene flakes and carbon black. The well-described effect of the β–α transition in the form of elongated lamellar grains in the sintered structure was confirmed. The obtained sinters were analyzed qualitatively and quantitatively in terms of the microstructure and density. The hardness and the participation of the polytypes in the sinter structures were examined. During the study, SPS sintering allowed us to obtain a material with a density close to the theoretical (relative density of 99.5% and hardness of 27 MPa) without the addition of carbon. It was found that the role of carbon was not limited to the activation of the sintering process. Additional effects accompanying its presence, depending on the initial α/β composition, included grain size reduction and an influence on the transformation kinetics.

In this study, AA6061 matrix composites reinforced with multilayer graphene and MoS2 were analyzed. The composites were prepared by powder metallurgy using the spark plasma sintering and spark plasma texturing methods. Microstructure, physical and mechanical properties were investigated and compared with unreinforced AA6061 sinter and AA6061 sheet plate. The results showed that the application of spark plasma texturing positively influences the relative density and compressive yield strength of AA6061 matrix composites. Moreover, in composites with MoS2, significant differences in compressive yield strength between the centre and the edge of the sintered compacts were noticed. These differences are related to the formation of the MoAl12 phase as a result of the temperature gradient generated in the graphite die during sintering by the spark plasma texturing.

This paper introduce the formation of alumina matrix composites reinforced with multilayered graphene, graphene oxide and nickel-phosphorus coated multilayered graphene. The powder metallurgy technique followed by the Spark Plasma Sintering (SPS) method were utilized to fabricate the specimens. The influence of graphene-family material additions on microstructure was investigated, and correlated with measurements of mechanical properties. The emphasis of the research has been placed on the tribological performance conducted with the use of the ball-on-disc method under loads of 10 N and 30 N. Both the wear tracks of composites and the corresponding counterparts were carefully analysed, to evaluate the combined influence of mechanical properties and tribofilm formation on the measured wear rates. All results were compared to pure alumina as a reference specimen.

The effect of graphene-based materials: multilayer graphene (MLG), graphene oxide (GO), and nickel-coated graphene (Gn-Ni-P) addition on the mechanical properties of commercial Al2O3–ZrO2 and Al2O3–Ti(C,N) materials is discussed in this paper. The influence of used reinforcements on relative density, microstructure, hardness, and fracture toughness was investigated. Moreover, the combination of strengthening effects deriving from the addition of graphene-based materials and the presence of zirconia or carbon nitride titanium particles was analysed. In order to determine the wear resistance of the obtained composites, tribology test was conducted. The added reinforcement had an evident effect on hardness of the obtained composites in both series, an almost 150 HV5 increase was observed for the TAZ+0.2 wt%GO composites. Fracture toughness remained unchanged or decreased, which was related to the complexity of the Al2O3 + ZrO2 + Ti (CN) + Graphene Family Nanomaterials system. Moreover, an almost 800% decrease of wear rate for the TACN based composite with a 0.2 wt% addition of GO was noted. Other composites also showed an increase in wear resistance depending on the type of matrix, the type of reinforcements and the load applied during the tribology test.

This article presents an attempt to determine the effect of the MXene phase addition and its decomposition during sintering with the use of the spark plasma sintering method on mechanical properties and residual stress of silicon carbide based composites. For this purpose, the unreinforced silicon carbide sinter and the silicon carbide composite with the addition of 2 wt.% of Ti

This paper discusses the effects of the environment and temperature of the Ti3C2 (MXene) oxidation process. The MXene powders were annealed at temperatures of 1000, 1200, 1400, 1600, and 1800 °C in argon and vacuum using a Spark Plasma Sintering (SPS) furnace. The purpose of the applied annealing method was to determine the influence of a high heating rate on the MXene degradation scheme. Additionally, to determine the thermal stability of MXene during the sintering of SiC matrix composites, SiC–C–B–Ti3C2 powder mixtures were also annealed. The process parameters were as follows: Temperatures of 1400 and 1600 °C, and pressure of 30 MPa in a vacuum. Observations of the microstructure showed that, due to annealing of the SiC–C–B–Ti3C2 powder mixtures, porous particles are formed consisting of TiC, Ti3C2sym, and amorphous carbon. The formation of porous particles is a transitional stage in the formation of disordered carbon structures.

A broad family of two-dimensional (2D) materials - carbides, nitrides, and carbonitrides of early transition metals, called MXenes, became a newcomer in the flatland at the turn of 2010 and 2011 (over ten years ago). Their unique physicochemical properties made them attractive for many applications, highly boosting the development of various fields, including biotechnological. However, MXenes' functional features that impact their bioactivity and toxicity are still not fully well understood. This study discusses the essentials for MXenes's surface modifications toward their application in modern biotechnology and nanomedicine. We survey modification strategies in context of cytotoxicity, biocompatibility, and most prospective applications ready to implement in medical practice. We put the discussion on the material-structure-chemistry-property relationship into perspective and concentrate on overarching challenges regarding incorporating MXenes into nanostructured organic/inorganic bioactive architectures. It is another emerging group of materials that are interesting from the biomedical point of view as well. Finally, we present an influential outlook on the growing demand for future research in this field.

This article presents new findings related to the problem of the introduction of MXene phases into the silicon carbide matrix. The addition of MXene phases, as shown by the latest research, can significantly improve the mechanical properties of silicon carbide, including fracture toughness. Low fracture toughness is one of the main disadvantages that significantly limit its use. As a part of the experiment, two series of composites were produced with the addition of 2D-Ti3C2Tx MXene and 2D-Ti3C2Tx surface-modified MXene with the use of the sol-gel method with a mixture of Y2O3/Al2O3 oxides. The composites were obtained with the powder metallurgy technique and sintered with the Spark Plasma Sintering method at 1900 °C. The effect adding MXene phases had on the mechanical properties and microstructure of the produced sinters was investigated. Moreover, the influence of the performed surface modification on changes in the properties of the produced composites was determined. The analysis of the obtained results showed that during sintering, the MXene phases oxidize with the formation of carbon flakes playing the role of reinforcement. The influence of the Y2O3/Al2O3 layer on the structure of carbon flakes and the higher quality of the interface was also demonstrated. This was reflected in the higher mechanical properties of composites with the addition of modified Ti3C2Tx. Composites with 1 wt.% addition of Ti3C2Tx M are characterized with a fracture toughness of 5 MPa × m0.5, which is over 50% higher than in the case of the reference sample and over 15% higher than for the composite with 2.5 wt.% addition of Ti3C2Tx, which showed the highest fracture toughness in this series.

This article presents new findings related to the problem of the introduction of MXene phases into the silicon carbide matrix. The addition of MXene phases, as shown by the latest research, can significantly improve the mechanical properties of silicon carbide, including fracture toughness. Low fracture toughness is one of the main disadvantages that significantly limit its use. As a part of the experiment, two series of composites were produced with the addition of 2D-Ti3C2Tx MXene and 2D-Ti3C2Tx surface-modified MXene with the use of the sol-gel method with a mixture of Y2O3/Al2O3 oxides. The composites were obtained with the powder metallurgy technique and sintered with the Spark Plasma Sintering method at 1900 °C. The effect adding MXene phases had on the mechanical properties and microstructure of the produced sinters was investigated. Moreover, the influence of the performed surface modification on changes in the properties of the produced composites was determined. The analysis of the obtained results showed that during sintering, the MXene phases oxidize with the formation of carbon flakes playing the role of reinforcement. The influence of the Y2O3/Al2O3 layer on the structure of carbon flakes and the higher quality of the interface was also demonstrated. This was reflected in the higher mechanical properties of composites with the addition of modified Ti3C2Tx. Composites with 1 wt.% addition of Ti3C2Tx M are characterized with a fracture toughness of 5 MPa × m0.5, which is over 50% higher than in the case of the reference sample and over 15% higher than for the composite with 2.5 wt.% addition of Ti3C2Tx, which showed the highest fracture toughness in this series.

This article describes the manufacturing of silicon carbide composites with the addition of quasi-two-dimensional titanium carbide Ti3C2, known as MXene. The composites were obtained by the powder metallurgy technique, consolidated with the use of the Spark Plasma Sintering method at 1900 °C and dwelled for 30 min. The influence of the Ti3C2 MXene addition on the microstructure and mechanical properties of the composites was investigated. The structure of the MXene phase after the sintering process was also analyzed. The results showed a significant increase (almost 50%) of fracture toughness for composites with the addition of 0.2 wt% Ti3C2 MXene. In turn, the highest hardness, 23.2 GPa, was noted for the composite with the addition of the 1.5 wt% Ti3C2 MXene phase. This was an increase of over 10% in comparison to the reference sample. The analysis of chemical composition and observations using a transmission electron microscope showed that the Ti3C2 MXene phase oxidizes during sintering, resulting in the formation of crystalline, highly defected, disordered graphite structures. The presence of these structures in the microstructure, similarly to graphene, significantly affects the hardness and fracture toughness of silicon carbide.

Among two-dimensional (2D) materials, such as graphene, a new family of 2D anisotropic carbides and nitrides of early transition metals (MXenes) is very interesting because of the potential applications in electronics, medicine, and photocatalysis. In this paper, preparation, morphostructural characterization, band gaps determination, and salicylic acid photodegradation ability of Ti2C MXene and six nanocomposites consisting of the MXene modified by TiO2, Ag2O, Ag, PdO, Pd, and Au are reported. It was confirmed using electron diffraction studies, energy dispersive X-ray spectroscopy, and high-resolution transmission microscopy that metals and metal oxides occur on the MXene flakes as nanoparticles in a shape of spots. The band gaps determined experimentally using Tauc's method are placed in the region of 0.90-1.31 eV. In recent years, the method of photocatalytic decomposition of pollutants using semiconductor photocatalysts and UV-vis energy has become increasingly important. The MXene based nanocomposites revealed high activity in the salicylic acid (SA) photodegradation reaction (86.1-97.1% of degraded SA after 3 h, concentration of SA initial solution 100 μM, the circulation rate of the SA solution 0.875 cm3/min). The interfacial charge transfer mechanism and the role of the metallic and metal oxide nanoparticles in the photocatalytic activity of the MXene based nanocomposites are presented and discussed.

Photothermal therapy (PTT) has shown significant potential for anti-cancer modality. In this report, according to our best knowledge, we explore for the first time Ti2C-based MXene as a novel, highly efficient and selective agent for photothermal therapy (PTT). Ti2C superficially modified with PEG was obtained from the layered, commercially available Ti2AlC MAX phase in the process of etching aluminum layers using concentrated HF, and characterized by scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HREM) as well as X-ray photoelectron spectroscopy for chemical analysis (ESCA-XPS). The PEG-coated Ti2C flakes showed a satisfactory photothermal conversion efficacy (PTCE) and good biocompatibility in wide range of the tested concentrations. Through in vitro studies, the PEG-modified Ti2C demonstrated notable NIR-induced ability to cancerous cells' ablation with minimal impact on non-malignant cells up to the concentration of 37.5 μg mL−1. The applied doses of Ti2C_PEG in our work were even 24 times lower comparing other MXene-based photothermal agents. This work is expected to expand the utility of 2D MXenes to biomedical applications through the development of entirely novel agents for photothermal therapy. This work is expected to expand the utility of 2D MXenes to biomedical applications through the development of entirely novel agents for photothermal therapy.

Silica-doped alumina–supported catalyst, containing manganese oxides, doped with cobalt oxide, was prepared in situ by wet impregnation, vacuum drying, and calcination at 700°C. Potassium permangan...

This work presents a comprehensive study on the surface-property changes of 2D flakes of MXenes (Ti3C2 and Ti2C) upon interacting with the model cationic protein – lysozyme, using time-resolved dynamic light scattering and zeta potential. The study was also aimed at investigating how MXenes stoichiometry, structure, surface chemistry and exposure concentration effects its interactions with lysozyme. We found that the adsorption of lysozyme on 2D Ti2C and Ti3C2 flakes occurred effectively, leading to changes in MXenes zeta potential in a concentration-dependent manner. The lysozyme adsorption efficiency varied, depending on the surface chemistry and stoichiometry of the investigated MXenes. The results showed that the Ti3C2 MXene exhibited a higher adsorption of lysozyme in comparison to Ti2C MXene. The zeta potential assays revealed that the adsorption mechanism for MXenes was mainly electrostatic. We also demonstrated the lysozyme release from the MXene surface during pH changes to basic environment. Our findings highlight the importance of evaluating MXenes interactions with biomacromolecules and the mechanism for potential protein adsorption prior to designing e.g. drug delivery systems. We have shown that protein adsorption dramatically changes the surface-physicochemical properties of the MXenes, which may have a significant impact on the effectiveness and safety of future delivery, separation and purification systems dedicated to particular proteins.

Within this paper, it is explored how two-dimensional Ti2C sheets addition affects silicon carbide matrix composites in terms of the microstructure and mechanical properties. In order to consolidate the powder mixtures, powder metallurgy processing followed by Spark Plasma Sintering was performed to prepare the sinters. According to our knowledge, this is the first attempt to apply delaminated MXene phases as a reinforcing phases of ceramic matrix composites. The delaminated MXene phases were characterized using a high-resolution transmission microscope (HRTEM) and X-ray photoelectron spectroscopy (XPS). Significant improvement of the fracture toughness and hardness for the composites reinforced with 1.5 wt% 2D Ti2C compared to the reference sample were observed. It is expected that the applied reinforcing phase will have an influence on the fracture mechanism, and so this has also been investigated. Two of the main mechanisms of crack propagations (crack deflection and bridging) were observed.

Fabrication of alumina matrix composites reinforced with montmorillonite (MMT) is introduced in this work. Specimens were prepared with the use of powder metallurgy and consolidated using the Spark Plasma Sintering (SPS) method. Investigations were then carried out on the influence of MMT addition on microstructure, mechanical properties and tribological performance of the alumina matrix composites. Scanning Electron Microscopy (SEM) revealed significant changes in microstructure where elongated, abnormally overgrown grains of alumina can be observed in areas contacted with montmorillonite. This unusual bimodal microstructure greatly influenced the measured mechanical properties and friction study. Tribological examinations exhibited outstanding results, where samples with montmorillonite addition demonstrate significant improvement in the wear in comparison to pure unmodified alumina sinters.

In the present research, mechanical properties of silicon carbide sintered with four carbon forms as a sintering aid were examined. As the source of carbon, the following substrates were used: multilayer graphene (MLG), carbon black, highly oriented pyrolytic graphite (HOPG) and synthetic graphite. The sinters were prepared with the use of powder metallurgy technique and consolidated at 1900 °C using the Spark Plasma Sintering (SPS) method. The influence of carbon form on mechanical properties, such as microhardness, hardness, fracture toughness, and elastic properties such as Young's modulus was investigated. Transmission electron microscope (TEM) analysis of the obtained sinters was also performed. Differences between mechanical properties were observed for samples with varied forms of carbon. An analysis of the obtained results shows that the form of carbon can determine the mechanical properties of silicon carbide and generate significant differences in hardness and fracture toughness despite the similarities in the microstructure.

The number of investigations regarding the application of 2D nanosheets of MXenes in different technological areas is growing rapidly. Different surface modifications of MXenes have been introduced to date in order to tailor their properties. As a result, surface-modified MXenes could be released in the environment from filtration membranes, adsorbents, or photocatalysts. On the other hand, assessment of their environmental impact is practically unexplored. In the present study, we examined how modification of the antimicrobial Ti3C2 MXene with ceramic oxide and noble metal nanoparticles affects its toxic behavior. The expanded 2D sheets of the Ti3C2 MXene phase were modified with Al2O3/Ag, SiO2/Ag, and SiO2/Pd nanoparticles using the sol–gel method and extensively characterized. The obtained 2D nanocomposite structures were characterized by antibacterial properties. The ecotoxicological assays considered green algae (Desmodesmus quadricauda) as well as two higher plants: sorghum (Sorghum saccharatum) and charlock (Sinapis alba). Our results revealed that obtained nanomaterials can cause both stimulating and inhibiting effects towards algae, and the ecotoxicity depended on the concentration and the type of modification. The study reveals the intriguing property of pristine Ti3C2 which highly stimulated green algae growth at low concentrations. It also shows that modification of pristine Ti3C2 MXene with different nanoparticles changes the ecotoxicological effects of the resulting nanocomposite 2D structures. We have also indicated nanocomposite structures that does not revealed the toxic effect on tested organisms i.e. the Ti3C2 MXene surface-modified with Al2O3/Ag was not phyto- and eco-toxic. This work helps with better understanding of the reactivity of surface-modified MXenes towards chosen organisms, giving more information concerning the potential impact of tested nanocomposites on the ecosystems.

This study presents new findings related to the incorporation of MXene phases into ceramic. Aluminium oxide and synthesised Ti3C2 were utilised as starting materials. Knowing the tendency of MXenes to oxidation and degradation, particularly at higher temperatures, structural modifications were proposed. They consisted of creating the metallic layer on the Ti3C2, by sputtering the titanium or molybdenum. To prepare the composites, powder metallurgy and spark plasma sintering (SPS) techniques were adopted. In order to evaluate the effectiveness of the applied modifications, the emphasis of the research was placed on microstructural analysis. In addition, the mechanical properties of the obtained sinters were examined. Observations revealed significant changes in the MXenes degradation process, from porous areas with TiC particles (for unmodified Ti3C2), to in situ creation of graphitic carbon (in the case of Ti3C2-Ti/Mo). Moreover, the fracture changed from purely intergranular to cracking with high participation of transgranular mode, analogously. In addition, the results obtained showed an improvement in the mechanical properties for composites with Ti/Mo modifications (an increase of 10% and 15% in hardness and fracture toughness respectively, for specimens with 0.5 wt.% Ti3C2-Mo). For unmodified Ti3C2, enormously cracked areas with spatters emerged during tests, making the measurements impossible to perform.

Background The biological activity of MXenes has been studied for several years because of their potential biomedical applications; however, investigations have so far been limited to 2D titanium carbides. Although monolayered Ti2NTx MXene has been expected to have biological activity, experimental studies revealed significant difficulties due to obstacles to its synthesis, its low stability and its susceptibility to oxidation and decomposition. Results In this paper, we report our theoretical calculations showing the higher likelihood of forming multilayered Ti2NTx structures during the preparation process in comparison to single-layered structures. As a result of our experimental work, we successfully synthesized multilayered Ti2NTx MXene that was suitable for biological studies by the etching of the Ti2AlN MAX phase and further delamination. The biocompatibility of Ti2NTx MXene was evaluated in vitro towards human skin malignant melanoma cells, human immortalized keratinocytes, human breast cancer cells, and normal human mammary epithelial cells. Additionally, the potential mode of action of 2D Ti2NTx was investigated using reactive oxygen tests as well as SEM observations. Our results indicated that multilayered 2D sheets of Ti2NTx showed higher toxicity towards cancerous cell lines in comparison to normal ones. The decrease in cell viabilities was dose-dependent. The generation of reactive oxygen species as well as the internalization of the 2D sheets play a decisive role in the mechanisms of toxicity. Conclusions We have shown that 2D Ti2NTx in the form of multilayered nanoflakes exhibits fair stability and can be used for in vitro studies. These results show promise for its future applications in biotechnology and nanomedicine.

This paper discusses the effect of modified multilayer graphene nanoplatelets (MLG-Ni-P) and unmodified multilayer graphene nanoplatelets (MLG) addition on the tribological properties of alumina matrix composites. The composites were prepared by powder metallurgy processing using Spark Plasma Sintering to consolidate the powders. The effect of the coated graphene addition on the strength properties was evaluated. Furthermore, the relative density, fracture toughness and tribological properties were investigated. The lowest wear rates (0.1 mm 3 /Nm for Al 2 O 3 -2 vol% Gn), despite lower mechanical properties (4.1 MPa m .5 for Al 2 O 3 -2 vol% Gn), were observed for composites reinforced with uncoated graphene. Moreover, the threshold volume of graphene addition was specified to achieve high tribological properties of composites.

In this work, sintering behaviour and microstructure changes of silicon carbide sintered with different additions (0.5, 1, 1.5, 2 wt%) of four forms of carbon as a sintering aid were examined. As the source of carbon, the following substrates were used: Multilayer graphene (MLG), Carbon Black, Highly oriented pyrolytic graphite (HOPG) and Synthetic graphite. In order to determine the morphology of the used carbon, the specific surface area, porosity, and SEM observations were performed. The Raman spectra was conducted with the purpose of determining the differences in the thickness of the analyzed platelets, as well as the physical properties of the surface. The sinters were consolidated at 1900 °C using the Spark Plasma Sintering (SPS) method. The influence of carbon morphology on the relative density, microstructure and phase composition of the sintered samples was investigated. Similar, almost non porous microstructures with equiaxed grains were obtained for carbons with markedly different morphology (spherical particles of Carbon Black and platelets particles of synthetic graphite), whereas significantly different microstructures were obtained for carbons with nearly identical morphology (synthetic graphite and HOPG).

Ni-free N-containing oxide dispersion strengthened (ODS) austenitic alloys were manufactured by mechanical alloying (MA) followed by spark plasma sintering (SPS). The phase evolutions during milling under a nitrogen atmosphere and after sintering were studied by X-ray diffraction (XRD). Transmission electron microcopy (TEM) and alloy contrast variation analysis (ACV), including small-angle neutron scattering (SANS) and ultra-small-angle X-ray scattering (USAXS), revealed the existence of nanoparticles with a diameter of 3–51 nm for the samples sintered at 950 °C. Sintering at 1000 °C for 5 and 15 min caused slight growth and a significant coarsening of the nanoparticles, up to 70 nm and 128 nm, respectively. The ACV analysis indicated the existence of two populations of Y2O3, e-martensite and MnO. The dispersive X-ray spectrometry (EDS) confirmed two kinds of nanoparticles, Y2O3 and MnO. The material was characterized by superior micro-hardness, of above 500 HV0.1.

The expanded Ti2C and Ti3C2 MXene phases were synthesized from their parent Ti2AlC and Ti3AlC2 MAX phases using the same conditions of the classical acidic aluminum extraction method. The assumption for the study was that the expanded Ti2C and Ti3C2 MXenes are composed of the same atoms and if are synthesized from MAX phases using the same conditions of the classical acidic aluminum extraction method, the observed bio-effects can be related only to the changes in their structures. The scanning electron microscope investigations indicated that the expanded Ti2C and Ti3C2 sheets formed the specific network of slit-shaped nano-pores. The x-ray photoelectron spectroscopy for chemical analysis (ESCA-XPS) showed almost no difference in surface chemistry of Ti2C and Ti3C2 MXenes. The high-resolution transmission electron microscope investigations revealed, however, differences in atomic structure of the individual Ti2C and Ti3C2 sheets. Measured distance between Ti-C atomic layers in Ti2C was 9.76 A and was larger by 0.53 A in comparison with Ti3C2 (9.23 A). Our investigations of bioactive properties toward model gram-negative Escherichia coli bacterial strain showed that the Ti2C MXene did not influence the viability of bacteria. Contrarily, the Ti3C2 MXene showed antibacterial properties. The results of the study indicate that the structure at the atomic scale may play a key role in the bioactivity of MXenes of the same chemical composition, but different stoichiometry, just like in case of Ti2C and Ti3C2.

This study aimed at the characterization of the biosorption properties of RGO/Al 2 O 3 -M (where M = Ag, Au, or Pd) nanocomposite flakes in relation to various bacterial species, i.e. Escherichia coli , Staphylococcus aureus , Bacillus sp., and Sarcina sp. All the synthesized nanocomposite flakes were characterized as having good adsorption properties towards Bacillus sp. and E. coli bacteria in the near neutral pH range, which confirmed that their properties were applicable for water filtration. In particular, the RGO/Al 2 O 3 -Ag nanocomposite was considered the most effective material, due to the fact that it possessed both biosorption and biocidal properties. The latter was related to its nano-silver content. The combination of these two properties allowed for the effective attraction of bacterial cells towards the RGO/Al 2 O 3 -Ag nanocomposite surface and their subsequent complete deactivation.

MXenes are a novel family of 2D materials, the biological activity of which has been largely unexplored. The present study, for the first time, shows some aspects of the in vitro toxicity of 2D sheets of Ti3C2 MXene. The Ti3AlC2 MAX phase was used in an expansion and delamination process to obtain Ti3C2 material in the form of 2D sheets. The obtained 2D material was characterized using SEM, TEM, DLS, XPS, and zeta potential. The biological activity of the MXene was determined on two normal (MRC-5 and HaCaT) and two cancerous (A549 and A375) cell lines. The cytotoxicity results indicated that the observed toxic effects were higher against cancerous cells compared to normal ones. The mechanisms of potential toxicity were also elucidated. It was shown that MXene may affect the occurrence of oxidative stress and, in consequence, the generation of reactive oxygen species (ROS). The results of the present study provide the principal knowledge to date regarding the biological activity of the MXenes; the lack of such knowledge is the major obstacle on the MXenes’ road to further research and development on their applications in bioscience and biotechnology, e.g. as drug-delivery systems.

Extended lifetime of ceramic cutting plates is ever more desired. One way of approaching it entails sintering precursor materials with graphene-like nanoplatelets (GLPs) acting as solid lubricants. Therefore, Al 2 O 3 and Si 3 N 4 ceramic powders with addition of GLPs of grade 3 (fine) or grade 4 (coarse) were Spark Plasma Sintered. It is found that the 0.15 wt% GLPs addition of both grades allows to keep hardness practically at the same level as GLPs-free compacts (~16 GPa). Only larger GLPs additions (2 wt%) caused its evident decrease (down to 14−15 GPa). The ball-on-disc test revealed that only Al 2 O 3 +0.15 wt% GLPs(3) shows a 50% reduction in wear rate. The post mechanical test examination by SEM confirmed that Al 2 O 3 compacts with small GLPs showed smooth wear track, as opposed to those having a Si 3 N 4 matrix with large meandering cavities. TEM observations revealed that the wear damage caused by the ball was restricted to ~2 µm deep sub-surface areas, while, carbon is found to transfer from the GLPs agglomerates into tribo-film. The present experiments showed, that ceramic sinters with small addition of GLPs platelets could exhibit lower wear than GLPs-free ones and therefore show a potential for application as cutting plates.

The study presents the results of the study on porous composite biomaterials obtained using lyophilization method based on polymer solutions: chitosan solution, sodium alginate solution, or polylactide solution, and ZnO-doped bioglass from CaO-SiO2-P2O5 system. The properties of zinc ions were used, which have bactericidal, immune-stimulating, and tissue-regenerating functions in the organism. The effects of the polymer type, granulation, and bioglass amount, as well as the amount of solvent on composite microstructure, were studied. SEM-EDS technique was used to visualize and describe the surface results occurring after incubation of composite in the Simulated Body Fluid (SBF). The selected method of preparation, used substrates, and the process conditions resulted in porous composites of the open, connected pore structure. It was proved that composite microstructure may be controlled by the appropriately selected amount of bioglass in relation to the polymer and its appropriate grain sizes. The morphology of the obtained composites is also affected by the amount of the solvent in lyophilizated dispersions. It was proved that bioactivity in composite material is induced by bioglass because after SBF incubation the surface layer is enriched with Ca and P, what may lead to a gradual formation of apatite layer. The obtained results enabled selection of the composites for further in vitro studies concerning cytotoxicity and antibacterial activity.

Graphene oxide (GO) reinforced alumina matrix composites have been fabricated by using graphene oxide synthesized by a modified Hummer's method. Samples were prepared by powder metallurgy and consolidated by Spark Plasma Sintering (SPS). The influence of GO addition on the microstructure and mechanical properties of the composites was investigated. Results show a significant increase (almost 35%) of the fracture toughness for composites containing 0.5 wt% graphene oxide compared to sintered pure alumina. In order to find reasons for this improvement Scanning/Transmission Electron Microscopy (SEM/TEM) observations were carried out. They reveal a good interface between the reinforcement and the matrix as well as such mechanisms like branching, deflection and bridging of crack propagation.

In the presented work 2 at% thulium doped yttrium oxide precursor powders were synthesized by the co-precipitation method using ammonium bicarbonate as a precipitation agent. The main aim of this work was to investigate the influence of co-precipitation parameters such as the process temperature (25°C–70 °C) and molar concentration of reagents on the morphology and luminescence properties of Tm:Y 2 O 3 . The lowest average particle size of about 20 nm and the highest value of the specific surface of 55.2 m 2 /g were obtained for powder co-precipitated at a temperature of 70 °C at a molar concentration of 0.1 M for thulium and yttrium nitrate. The emission spectra of the outcome powders were measured and compared and fluorescence dynamics behavior was presented and discussed.

The aim of this study was to compare the bioactivity of RGO/ceramic oxide-Ag nanocomposites. Different ceramic oxides (MexOy) i.e.: Al2O3, TiO2, SiO2 and ZnO2 were in situ co-deposited with Ag nanoparticles on the surface of RGO resulting in the formation of a nanocomposite structure of stacked flakes. The results of our investigations indicate that it is possible to obtain the targeted biocidal properties of the RGO/Ag system by choosing the appropriate ceramic oxide as a modificator of Ag nanoparticles. The strongest antimicrobial properties against E. coli, S. aureus and Bacillus sp. strains were achieved for RGO/SiO2-Ag nanocomposite whereas for Sarcina sp. bacteria the most effective biocide was RGO/TiO2-Ag nanocomposite.

This study aims to describe the influence of adding graphene oxide to TiO2-noble metal (Me=Ag, Au or Pd) composite nanoparticles on their bioactivity (formation of RGO/TiO2-Me nanocomposite system). The obtained nanocomposite flakes and reference TiO2-Me nanoparticles were characterized using SEM, HRTEM and XPS spectroscopy, N2 sorption analysis and helium pycnometer. The analysis of the antibacterial properties of synthesized nanocomposites revealed a growth inhibiting effect of TiO2-Ag particles on gram positive bacteria such as: Staphylococcus aureus, Sarcina lutea and Bacillus subtilis. In the case of nanocomposite flakes containing RGO the visible changes in bacteriostatic properties were observed, including unexpected reversal of the antimicrobial activity of silver-containing nanoparticles into the stimulation of growth of applied bacterial strains. The stimulation of growth was not observed for TiO2-Au and Pd nanoparticles deposited on the surface of RGO.