Polymer-derived non-oxide ceramics are candidate materials for various applications especially in... more Polymer-derived non-oxide ceramics are candidate materials for various applications especially in the high-temperature regime above l 200°C, where conventionally liquid-phase sintered ceramics start to fail due to softening of their glassy grain boundary phase. The polymer-to-ceramic approach uses high-purity educts from polymer chemistry. It allows for an additive-fr ee synthesis of ceramic materials and thus avoids the presence of glassy grain boundary phases in the body. In this work, the oxidation behaviour of poly(hydridomethyl)silazane NCP200-derived ceramic materials is investigated in more detail. Therefore, after standardised crosslinking and ceramisation the amorphous ceramic material was milled and sieved to a powder fraction with r s; 32µm. These powders with high surface-to-volume ratio were isothermally oxidised for 20 h using a TGA at temperatures between 1000°C and l 500°C in steps of I 00K, each a sample of approx. 120mg in an alumina crucible. Preliminary results on the oxidation behaviour of the specimens are reported and the mechanisms of oxidation are outlined.
The Eu 3+-doped transparent aluminas were prepared by wet shaping technique followed by pressure-... more The Eu 3+-doped transparent aluminas were prepared by wet shaping technique followed by pressure-less sintering and hot isostatic pressing. The effect of dopant amount on microstructure, real in-line transmission (RIT), photoluminescence (PL) properties, hardness and fracture behaviour was studied. The RIT decreased with increasing amount of the dopant. The PL emission spectra of Al2O3:Eu 3+ ceramics exhibited predominant red light emission with the highest intensity (under 394 nm excitation) for material containing 0.125 at.% of Eu 3+ and colour coordinates (0.645, 0.355) comparable with commercial red phosphors. The doping resulted in hardness increase from 26.1 GPa for undoped alumina to 27.6 GPa for Eu-doped sample. The study of fracture surfaces showed predominantly intergranular crack propagation micro-mechanism.
Metallic materials such as stainless steel (SS), titanium (Ti), magnesium (Mg) alloys, and cobalt... more Metallic materials such as stainless steel (SS), titanium (Ti), magnesium (Mg) alloys, and cobalt-chromium (Co-Cr) alloys are widely used as biomaterials for implant applications. Metallic implants sometimes fail in surgeries due to inadequate biocompatibility, faster degradation rate (Mg-based alloys), inflammatory response, infections, inertness (SS, Ti, and Co-Cr alloys), lower corrosion resistance, elastic modulus mismatch, excessive wear, and shielding stress. Therefore, to address this problem, it is necessary to develop a method to improve the biofunctionalization of metallic implant surfaces by changing the materials’ surface and morphology without altering the mechanical properties of metallic implants. Among various methods, surface modification on metallic surfaces by applying coatings is an effective way to improve implant material performance. In this review, we discuss the recent developments in ceramics, polymers, and metallic materials used for implant applications. ...
Polysilazane-based double layer composite coatings consisting of a polymer-derived ceramic (PDC) ... more Polysilazane-based double layer composite coatings consisting of a polymer-derived ceramic (PDC) bond-coat and a PDC top-coat that contains ceramic passive and glass fillers were developed. To investigate the environmental protection ability of the prepared coatings, quasi-dynamic corrosion tests under hydrothermal conditions were conducted at 200 °C for 48–192 h. The tested PDC coatings exhibited significant mass loss of up to 2.25 mg/cm2 after 192 h of corrosion tests, which was attributed to the leaching of elements from the PDC coatings to the corrosion medium. Analysis of corrosion solutions by inductively coupled plasma optical emission spectrometry (ICP-OES) confirmed the presence of Ba, Al, Si, Y, Zr, and Cr, the main component of the steel substrate, in the corrosion medium. Scanning electron microscopy (SEM) of the corroded surfaces revealed randomly distributed globular crystallites approximately 3.5 µm in diameter. Energy-dispersive X-ray spectroscopy (EDXS) of the preci...
This manuscript presents a systematic and detailed study of ion release from 45S5 bioactive glass... more This manuscript presents a systematic and detailed study of ion release from 45S5 bioactive glass to develop a methodology to directly monitor dissolved ions in a simulated fluid via inductively coupled plasma optical emission spectrometry (ICP OES). For the kinetic study, two dynamic tests, an inline ICP test and a flow-through test, are performed with the same flow rate, temperature, pH, ionic strength of the solution, and sample surface to leaching solution volume ratio. The flow-through test allows for the measurement of an initial dissolution rate, as well the maximum amount of any species released from the surface of the glass. In addition, the data from the inline ICP test are obtained by immediate and direct monitoring of ions from the first minutes of contact of the glass with aqueous fluids with pH values of 4 and 7.4. The overall dissolution rates of the tested commercial bioactive glass in simulated body fluid (SBF) (pH 7.4) were significantly lower compared to the initi...
Fiber glass waste (FGW) was subjected to alkali activation in an aqueous solution with different ... more Fiber glass waste (FGW) was subjected to alkali activation in an aqueous solution with different concentrations of sodium/potassium hydroxide. The activated materials were fed into a methane–oxygen flame with a temperature of around 1600 °C. X-ray diffraction analysis confirmed the formation of several hydrated compounds, which decomposed upon flame synthesis, leading to porous glass microspheres (PGMs). Pore formation was favored by using highly concentrated activating alkali solutions. The highest homogeneity and yield of PGMs corresponded to the activation with 9 M KOH aqueous solution.
The present study illustrates the manufacturing method of hierarchically porous 3D scaffolds base... more The present study illustrates the manufacturing method of hierarchically porous 3D scaffolds based on åkermanite as a promising bioceramic for stereolithography. The macroporosity was designed by implementing 3D models corresponding to different lattice structures (cubic, diamond, Kelvin, and Kagome). To obtain micro-scale porosity, flame synthesized glass microbeads with 10 wt% of silicone resins were utilized to fabricate green scaffolds, later converted into targeted bioceramic phase by firing at 1100 °C in air. No chemical reaction between the glass microspheres, crystallizing into åkermanite, and silica deriving from silicone oxidation was observed upon heat treatment. Silica acted as a binder between the adjacent microspheres, enhancing the creation of microporosity, as documented by XRD, and SEM coupled with EDX analysis. The formation of ‘spongy’ struts was confirmed by infiltration with Rhodamine B solution. The compressive strength of the sintered porous scaffolds was up t...
2021 13th International Conference on Measurement, 2021
Bi-doped calcium aluminosilicate glass materials (CAS), with the concentration of Bi3+ ions 0.5, ... more Bi-doped calcium aluminosilicate glass materials (CAS), with the concentration of Bi3+ ions 0.5, 1.0 and 3.0 mol %, were prepared by conventional melting. The basic properties and thermal behavior were studied by X-ray diffraction (XRD), He-pycnometry, X_Ray Fluorescence (XRF) and differential thermal analysis (DTA). XRD analysis showed the presence of crystalline gehlenite traces in samples with the highest Bi content. Crystallization of gehlenite in all prepared samples and crystallization of Bi2O3 in case of samples with 1 and 3 mol.% Bi3+ content was observed by a combination of DTA and XRD analysis. The increasing ability to crystallize was correlated with the increasing Bi content in the samples.
International Journal of Applied Glass Science, 2021
Aluminum is one of the most important strategic resources, but the Bayer process, typically appli... more Aluminum is one of the most important strategic resources, but the Bayer process, typically applied for the purification of ores, leads to vast amounts of alkaline slurry waste, known as red mud. Though interesting for potential reprocessing, red mud is still predominantly stored in big slurry pools, due to high levels of toxic metals. Toxic ions can be easily immobilized by vitrification, but the high costs of this solution need to be balanced by the reuse of the obtained glass. The present paper is dedicated to the transformation of waste-derived glass into new binders for the construction industry, according to both "conventional melting" and "smelting" approaches. In the first case, red mud was included in a mixture of waste, designed to yield a reactive glass (CMG), that is, forming stable gels after activation in an alkaline aqueous solution. In the second approach, red mud was subjected to a thermal treatment in a reductive atmosphere, implying the separation of molten iron alloy. The remaining glassy slag, according to its chemical composition (CaO and Al 2 O 3-rich) underwent gelation by simple interaction with pure water, without any alkaline activator, thus configuring a new "glass cement."
A novel concept for the additive manufacturing of three-dimensional glass-ceramic scaffolds, to b... more A novel concept for the additive manufacturing of three-dimensional glass-ceramic scaffolds, to be used for tissue engineering applications, was based on fine glass powders mixed with a reactive binder, in the form of a commercial silicone. The powders consisted of 'silica-defective glass' specifically designed to react, upon firing in air, with the amorphous silica yielded by the binder. By silica incorporation, the glass was intended to reach the composition of an already known CaOeNa 2 OeB 2 O 3 eSiO 2 system. Silica from the binder provided up to 15 wt% of the total silica. With the same overall formulation, silicone-glass powder mixtures led to nearly the same phase assemblage formed by the reference system, crystallizing into wollastonite (CaSiO 3) and Ca-borate (CaB 2 O 4). Samples from silicone-glass powder mixtures exhibited an excellent shape retention after firing, which was later exploited in highly porous reticulated scaffolds, obtained by means of direct ink writing (DIW).
Transparent oxyfluoride glass-ceramics (GCs) with embedded β-Na1.5Y1.5F6 crystals doped with Er3+... more Transparent oxyfluoride glass-ceramics (GCs) with embedded β-Na1.5Y1.5F6 crystals doped with Er3+ ions were fabricated by a melt-quenching method with subsequent heat-treatment. The structural characterizations and spectroscopic techniques were performed to verify the precipitation of β-Na1.5Y1.5F6 crystals and partition of the Er3+ dopant into the crystals. Bright green up-conversion (UC) emission was achieved in Er3+-doped glass-ceramic (Er-GC). Furthermore, the temperature-dependent visible UC behavior based on thermally coupled energy levels (TCLs) and non-thermally coupled energy levels (NTCLs) was also examined in the temperature range 298 k to 823 K with maximum relative sensitivity (Sr) of 1.1% K−1 at 298 K for TCLs in Er-G and Er-GC samples.
This work is aimed at the development and investigation of the oxidation behavior of ferritic sta... more This work is aimed at the development and investigation of the oxidation behavior of ferritic stainless-steel grade AISI 441 and polymer-derived ceramic (PDC) protective coatings. Double-layer coatings of a PDC bond coat below a PDC top coat with glass and ceramic passive fillers’ oxidative resistance were studied at temperatures up to 1000 °C in a flow-through atmosphere of synthetic air and in air saturated with water vapor. Investigation of the oxide products formed at the surface of the samples in synthetic air and water vapor atmospheres, at different temperatures (900, 950, 1000 °C) and exposure times (24, 96 h) was carried out on both uncoated steel and steel coated with selected coatings by scanning electron microscopy (SEM) and X-Ray diffraction (XRD). The Fe, Cr2O3, TiO2, and spinel (Mn,Cr)3O4 phases were identified by XRD on oxidized steel substrates in both atmospheres. In the cases of the coated samples, m- ZrO2, c- ZrO2, YAG, and crystalline phases (Ba(AlSiO4)2–hexacel...
In the present work, WC preforms with varied amounts of ZrC nanopowder (0–3.5 vol.%) were prepare... more In the present work, WC preforms with varied amounts of ZrC nanopowder (0–3.5 vol.%) were prepared using gel-casting base on nontoxic sodium alginate and then reactively infiltrated by molten Zr2Cu through displacive compensation of porosity method. The influence of ZrC nanopowder addition on the relative density, phase composition, microstructure, and properties of the final composites were investigated. The relative density, Vickers hardness, and flexural strength of the resulted composites prepared by reactive infiltration first increased and then decreased with increasing fraction of ZrC nanopowder in WC preforms. When the added fraction of ZrC nanopowder was 1.5 vol.%, the relative density, hardness, and flexural strength of the resulted composite reached their maximum values of about 97.3± 1%, 10.9± 0.3 GPa, and 503± 3 MPa, respectively. Fractography studies revealed that the fracture mode of composites was predominately intergranular. The W-ZrC composite was ablated by an oxyacetylene flame for 60 s. The mean value of mass and linear ablation rates of the composite were 2.1 ± 0.1 mg/s and 2.9 ± 0.3 μm/s, respectively. W-ZrC composites fabricated in complex and near net shapes at modest temperature and at ambient pressure by a reactive infiltration process can be utilized in aerospace applications. Graphical abstract Graphical abstract
In this paper, we report the preparation of visible-light active direct Z-scheme Cu2O/WO3 nanocom... more In this paper, we report the preparation of visible-light active direct Z-scheme Cu2O/WO3 nanocomposite photocatalyst by a solid-state reaction avoiding the otherwise inevitable formation of CuWO4 phase in wet syntheses. Structure, morphology, and thermal and optical properties of prepared WO3 nanoplatelets decorated by Cu2O were investigated by XRD, Raman spectroscopy, SEM/TEM, combined thermogravimetric (TG)/differential scanning calorimetry (DSC) analysis, and UV–VIS spectroscopy. The photocatalytic performance of the prepared samples under UV and visible light was studied through monitoring discoloration of methylene blue under illumination by selected wavelengths, allowing for the distinguishing between the contributions of the two semiconductive components. Experimental results showed that the decoration of WO3 nanoplates by Cu2O nanoparticles led to an improvement in photocatalytic performance, regardless of used LED (Light-Emitting Diode) wavelength, even at low concentratio...
Silicone resins, filled with phosphates and other oxide fillers, yield upon firing in air at 1100... more Silicone resins, filled with phosphates and other oxide fillers, yield upon firing in air at 1100 °C, a product resembling Biosilicate® glass-ceramics, one of the most promising systems for tissue engineering applications. The process requires no preliminary synthesis of parent glass, and the polymer route enables the application of direct ink writing (DIW) of silicone-based mixtures, for the manufacturing of reticulated scaffolds at room temperature. The thermal treatment is later applied for the conversion into ceramic scaffolds. The present paper further elucidates the flexibility of the approach. Changes in the reference silicone and firing atmosphere (from air to nitrogen) were studied to obtain functional composite biomaterials featuring a carbon phase embedded in a Biosilicate®-like matrix. The microstructure was further modified either through a controlled gas release at a low temperature, or by the revision of the adopted additive manufacturing technology (from DIW to digit...
Polymer-derived non-oxide ceramics are candidate materials for various applications especially in... more Polymer-derived non-oxide ceramics are candidate materials for various applications especially in the high-temperature regime above l 200°C, where conventionally liquid-phase sintered ceramics start to fail due to softening of their glassy grain boundary phase. The polymer-to-ceramic approach uses high-purity educts from polymer chemistry. It allows for an additive-fr ee synthesis of ceramic materials and thus avoids the presence of glassy grain boundary phases in the body. In this work, the oxidation behaviour of poly(hydridomethyl)silazane NCP200-derived ceramic materials is investigated in more detail. Therefore, after standardised crosslinking and ceramisation the amorphous ceramic material was milled and sieved to a powder fraction with r s; 32µm. These powders with high surface-to-volume ratio were isothermally oxidised for 20 h using a TGA at temperatures between 1000°C and l 500°C in steps of I 00K, each a sample of approx. 120mg in an alumina crucible. Preliminary results on the oxidation behaviour of the specimens are reported and the mechanisms of oxidation are outlined.
The Eu 3+-doped transparent aluminas were prepared by wet shaping technique followed by pressure-... more The Eu 3+-doped transparent aluminas were prepared by wet shaping technique followed by pressure-less sintering and hot isostatic pressing. The effect of dopant amount on microstructure, real in-line transmission (RIT), photoluminescence (PL) properties, hardness and fracture behaviour was studied. The RIT decreased with increasing amount of the dopant. The PL emission spectra of Al2O3:Eu 3+ ceramics exhibited predominant red light emission with the highest intensity (under 394 nm excitation) for material containing 0.125 at.% of Eu 3+ and colour coordinates (0.645, 0.355) comparable with commercial red phosphors. The doping resulted in hardness increase from 26.1 GPa for undoped alumina to 27.6 GPa for Eu-doped sample. The study of fracture surfaces showed predominantly intergranular crack propagation micro-mechanism.
Metallic materials such as stainless steel (SS), titanium (Ti), magnesium (Mg) alloys, and cobalt... more Metallic materials such as stainless steel (SS), titanium (Ti), magnesium (Mg) alloys, and cobalt-chromium (Co-Cr) alloys are widely used as biomaterials for implant applications. Metallic implants sometimes fail in surgeries due to inadequate biocompatibility, faster degradation rate (Mg-based alloys), inflammatory response, infections, inertness (SS, Ti, and Co-Cr alloys), lower corrosion resistance, elastic modulus mismatch, excessive wear, and shielding stress. Therefore, to address this problem, it is necessary to develop a method to improve the biofunctionalization of metallic implant surfaces by changing the materials’ surface and morphology without altering the mechanical properties of metallic implants. Among various methods, surface modification on metallic surfaces by applying coatings is an effective way to improve implant material performance. In this review, we discuss the recent developments in ceramics, polymers, and metallic materials used for implant applications. ...
Polysilazane-based double layer composite coatings consisting of a polymer-derived ceramic (PDC) ... more Polysilazane-based double layer composite coatings consisting of a polymer-derived ceramic (PDC) bond-coat and a PDC top-coat that contains ceramic passive and glass fillers were developed. To investigate the environmental protection ability of the prepared coatings, quasi-dynamic corrosion tests under hydrothermal conditions were conducted at 200 °C for 48–192 h. The tested PDC coatings exhibited significant mass loss of up to 2.25 mg/cm2 after 192 h of corrosion tests, which was attributed to the leaching of elements from the PDC coatings to the corrosion medium. Analysis of corrosion solutions by inductively coupled plasma optical emission spectrometry (ICP-OES) confirmed the presence of Ba, Al, Si, Y, Zr, and Cr, the main component of the steel substrate, in the corrosion medium. Scanning electron microscopy (SEM) of the corroded surfaces revealed randomly distributed globular crystallites approximately 3.5 µm in diameter. Energy-dispersive X-ray spectroscopy (EDXS) of the preci...
This manuscript presents a systematic and detailed study of ion release from 45S5 bioactive glass... more This manuscript presents a systematic and detailed study of ion release from 45S5 bioactive glass to develop a methodology to directly monitor dissolved ions in a simulated fluid via inductively coupled plasma optical emission spectrometry (ICP OES). For the kinetic study, two dynamic tests, an inline ICP test and a flow-through test, are performed with the same flow rate, temperature, pH, ionic strength of the solution, and sample surface to leaching solution volume ratio. The flow-through test allows for the measurement of an initial dissolution rate, as well the maximum amount of any species released from the surface of the glass. In addition, the data from the inline ICP test are obtained by immediate and direct monitoring of ions from the first minutes of contact of the glass with aqueous fluids with pH values of 4 and 7.4. The overall dissolution rates of the tested commercial bioactive glass in simulated body fluid (SBF) (pH 7.4) were significantly lower compared to the initi...
Fiber glass waste (FGW) was subjected to alkali activation in an aqueous solution with different ... more Fiber glass waste (FGW) was subjected to alkali activation in an aqueous solution with different concentrations of sodium/potassium hydroxide. The activated materials were fed into a methane–oxygen flame with a temperature of around 1600 °C. X-ray diffraction analysis confirmed the formation of several hydrated compounds, which decomposed upon flame synthesis, leading to porous glass microspheres (PGMs). Pore formation was favored by using highly concentrated activating alkali solutions. The highest homogeneity and yield of PGMs corresponded to the activation with 9 M KOH aqueous solution.
The present study illustrates the manufacturing method of hierarchically porous 3D scaffolds base... more The present study illustrates the manufacturing method of hierarchically porous 3D scaffolds based on åkermanite as a promising bioceramic for stereolithography. The macroporosity was designed by implementing 3D models corresponding to different lattice structures (cubic, diamond, Kelvin, and Kagome). To obtain micro-scale porosity, flame synthesized glass microbeads with 10 wt% of silicone resins were utilized to fabricate green scaffolds, later converted into targeted bioceramic phase by firing at 1100 °C in air. No chemical reaction between the glass microspheres, crystallizing into åkermanite, and silica deriving from silicone oxidation was observed upon heat treatment. Silica acted as a binder between the adjacent microspheres, enhancing the creation of microporosity, as documented by XRD, and SEM coupled with EDX analysis. The formation of ‘spongy’ struts was confirmed by infiltration with Rhodamine B solution. The compressive strength of the sintered porous scaffolds was up t...
2021 13th International Conference on Measurement, 2021
Bi-doped calcium aluminosilicate glass materials (CAS), with the concentration of Bi3+ ions 0.5, ... more Bi-doped calcium aluminosilicate glass materials (CAS), with the concentration of Bi3+ ions 0.5, 1.0 and 3.0 mol %, were prepared by conventional melting. The basic properties and thermal behavior were studied by X-ray diffraction (XRD), He-pycnometry, X_Ray Fluorescence (XRF) and differential thermal analysis (DTA). XRD analysis showed the presence of crystalline gehlenite traces in samples with the highest Bi content. Crystallization of gehlenite in all prepared samples and crystallization of Bi2O3 in case of samples with 1 and 3 mol.% Bi3+ content was observed by a combination of DTA and XRD analysis. The increasing ability to crystallize was correlated with the increasing Bi content in the samples.
International Journal of Applied Glass Science, 2021
Aluminum is one of the most important strategic resources, but the Bayer process, typically appli... more Aluminum is one of the most important strategic resources, but the Bayer process, typically applied for the purification of ores, leads to vast amounts of alkaline slurry waste, known as red mud. Though interesting for potential reprocessing, red mud is still predominantly stored in big slurry pools, due to high levels of toxic metals. Toxic ions can be easily immobilized by vitrification, but the high costs of this solution need to be balanced by the reuse of the obtained glass. The present paper is dedicated to the transformation of waste-derived glass into new binders for the construction industry, according to both "conventional melting" and "smelting" approaches. In the first case, red mud was included in a mixture of waste, designed to yield a reactive glass (CMG), that is, forming stable gels after activation in an alkaline aqueous solution. In the second approach, red mud was subjected to a thermal treatment in a reductive atmosphere, implying the separation of molten iron alloy. The remaining glassy slag, according to its chemical composition (CaO and Al 2 O 3-rich) underwent gelation by simple interaction with pure water, without any alkaline activator, thus configuring a new "glass cement."
A novel concept for the additive manufacturing of three-dimensional glass-ceramic scaffolds, to b... more A novel concept for the additive manufacturing of three-dimensional glass-ceramic scaffolds, to be used for tissue engineering applications, was based on fine glass powders mixed with a reactive binder, in the form of a commercial silicone. The powders consisted of 'silica-defective glass' specifically designed to react, upon firing in air, with the amorphous silica yielded by the binder. By silica incorporation, the glass was intended to reach the composition of an already known CaOeNa 2 OeB 2 O 3 eSiO 2 system. Silica from the binder provided up to 15 wt% of the total silica. With the same overall formulation, silicone-glass powder mixtures led to nearly the same phase assemblage formed by the reference system, crystallizing into wollastonite (CaSiO 3) and Ca-borate (CaB 2 O 4). Samples from silicone-glass powder mixtures exhibited an excellent shape retention after firing, which was later exploited in highly porous reticulated scaffolds, obtained by means of direct ink writing (DIW).
Transparent oxyfluoride glass-ceramics (GCs) with embedded β-Na1.5Y1.5F6 crystals doped with Er3+... more Transparent oxyfluoride glass-ceramics (GCs) with embedded β-Na1.5Y1.5F6 crystals doped with Er3+ ions were fabricated by a melt-quenching method with subsequent heat-treatment. The structural characterizations and spectroscopic techniques were performed to verify the precipitation of β-Na1.5Y1.5F6 crystals and partition of the Er3+ dopant into the crystals. Bright green up-conversion (UC) emission was achieved in Er3+-doped glass-ceramic (Er-GC). Furthermore, the temperature-dependent visible UC behavior based on thermally coupled energy levels (TCLs) and non-thermally coupled energy levels (NTCLs) was also examined in the temperature range 298 k to 823 K with maximum relative sensitivity (Sr) of 1.1% K−1 at 298 K for TCLs in Er-G and Er-GC samples.
This work is aimed at the development and investigation of the oxidation behavior of ferritic sta... more This work is aimed at the development and investigation of the oxidation behavior of ferritic stainless-steel grade AISI 441 and polymer-derived ceramic (PDC) protective coatings. Double-layer coatings of a PDC bond coat below a PDC top coat with glass and ceramic passive fillers’ oxidative resistance were studied at temperatures up to 1000 °C in a flow-through atmosphere of synthetic air and in air saturated with water vapor. Investigation of the oxide products formed at the surface of the samples in synthetic air and water vapor atmospheres, at different temperatures (900, 950, 1000 °C) and exposure times (24, 96 h) was carried out on both uncoated steel and steel coated with selected coatings by scanning electron microscopy (SEM) and X-Ray diffraction (XRD). The Fe, Cr2O3, TiO2, and spinel (Mn,Cr)3O4 phases were identified by XRD on oxidized steel substrates in both atmospheres. In the cases of the coated samples, m- ZrO2, c- ZrO2, YAG, and crystalline phases (Ba(AlSiO4)2–hexacel...
In the present work, WC preforms with varied amounts of ZrC nanopowder (0–3.5 vol.%) were prepare... more In the present work, WC preforms with varied amounts of ZrC nanopowder (0–3.5 vol.%) were prepared using gel-casting base on nontoxic sodium alginate and then reactively infiltrated by molten Zr2Cu through displacive compensation of porosity method. The influence of ZrC nanopowder addition on the relative density, phase composition, microstructure, and properties of the final composites were investigated. The relative density, Vickers hardness, and flexural strength of the resulted composites prepared by reactive infiltration first increased and then decreased with increasing fraction of ZrC nanopowder in WC preforms. When the added fraction of ZrC nanopowder was 1.5 vol.%, the relative density, hardness, and flexural strength of the resulted composite reached their maximum values of about 97.3± 1%, 10.9± 0.3 GPa, and 503± 3 MPa, respectively. Fractography studies revealed that the fracture mode of composites was predominately intergranular. The W-ZrC composite was ablated by an oxyacetylene flame for 60 s. The mean value of mass and linear ablation rates of the composite were 2.1 ± 0.1 mg/s and 2.9 ± 0.3 μm/s, respectively. W-ZrC composites fabricated in complex and near net shapes at modest temperature and at ambient pressure by a reactive infiltration process can be utilized in aerospace applications. Graphical abstract Graphical abstract
In this paper, we report the preparation of visible-light active direct Z-scheme Cu2O/WO3 nanocom... more In this paper, we report the preparation of visible-light active direct Z-scheme Cu2O/WO3 nanocomposite photocatalyst by a solid-state reaction avoiding the otherwise inevitable formation of CuWO4 phase in wet syntheses. Structure, morphology, and thermal and optical properties of prepared WO3 nanoplatelets decorated by Cu2O were investigated by XRD, Raman spectroscopy, SEM/TEM, combined thermogravimetric (TG)/differential scanning calorimetry (DSC) analysis, and UV–VIS spectroscopy. The photocatalytic performance of the prepared samples under UV and visible light was studied through monitoring discoloration of methylene blue under illumination by selected wavelengths, allowing for the distinguishing between the contributions of the two semiconductive components. Experimental results showed that the decoration of WO3 nanoplates by Cu2O nanoparticles led to an improvement in photocatalytic performance, regardless of used LED (Light-Emitting Diode) wavelength, even at low concentratio...
Silicone resins, filled with phosphates and other oxide fillers, yield upon firing in air at 1100... more Silicone resins, filled with phosphates and other oxide fillers, yield upon firing in air at 1100 °C, a product resembling Biosilicate® glass-ceramics, one of the most promising systems for tissue engineering applications. The process requires no preliminary synthesis of parent glass, and the polymer route enables the application of direct ink writing (DIW) of silicone-based mixtures, for the manufacturing of reticulated scaffolds at room temperature. The thermal treatment is later applied for the conversion into ceramic scaffolds. The present paper further elucidates the flexibility of the approach. Changes in the reference silicone and firing atmosphere (from air to nitrogen) were studied to obtain functional composite biomaterials featuring a carbon phase embedded in a Biosilicate®-like matrix. The microstructure was further modified either through a controlled gas release at a low temperature, or by the revision of the adopted additive manufacturing technology (from DIW to digit...
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