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Bioactive ions (Mg, Sr, Zn) doped carbonated hydroxyapatite powders (dHAp) and pure carbonated hydroxyapatite (HAp) powders were prepared by wet chemical precipitation method. The bioactive ions were incorporated into the HAp matrix by co-precipitation from solution containing the appropriate amount of chloride salt of different ions. The morphology of pure HAp was mainly needle-like in nanometre size and the particles were disordered showing quasi-amorphous structure. The ion doping changed the morphology of particles, the dHAp particles had distorted spheroid shapes. Owing to the ion addition, the crystallinity of particles decreased. Particle aggregations can also be observed in both types of samples. HAp and dHAp loaded biopolymer polyvinylpyrrolidone (PVP) composite materials have also been developed by novel electrospinning technique. It has been shown that both the HAp and dHAp particles can be successfully incorporated into the PVP fibre web matrix and simultaneously the bioceramic powders were attached to the surface of polymer fibres. The surface of fibres was not fully covered with the particles. The ceramic powder addition to the polymer solution caused the polymer fibres to become more entangled and the diameters of fibres varied over a wider range compared to the base polymer fibres without bioceramic powder addition.

Alumina dispersion-strengthened 316L stainless steels were successfully produced using attrition milling and spark plasma sintering. Two different composites (316L/0.33 wt% and 316L/1 wt% Al2O3) were prepared by powder technology. The attrition milling produced a significant morphological transformation of the globular 316L starting powders and provided a homogeneous distribution of the nanosized alumina particles. The XRD results confirmed that the 316L steel was an austenitic γ-Fe3Ni2. The formation of a ferrite α-Fe phase was detected after milling; this was transformed to the austenitic γ-Fe3Ni2 after the sintering process. The addition of nanosized alumina particles increased the composites’ microhardness significantly to 2.25 GPa HV. With higher amounts of alumina, the nanosized particles tended to agglomerate during the milling process. The friction coefficient (FC) of the 316L/0.33 wt% Al2O3 and the 316L/1 wt% Al2O3 decreased because of the increase in the composite’s hardness; FC values of 0.96, 0.93 and 0.85, respectively, were measured respectively for the 316L reference, the 316L/0.33 wt% and the 316L/1 wt% Al2O3. The 316L/0.33 wt% Al2O3 composite had a higher flexural strength of 630.4 MPa compared with the 316L/1 wt% Al2O3 with 386.6 MPa; the lower value of the latter was related the agglomeration of the alumina powder during attrition milling.

Pathogenic microbes, such as bacteria and viruses, can spread quickly via contaminated surfaces. Most of these pathogenic microorganisms can survive on surfaces for a long time. Touching these surfaces can lead to the transmission of the microorganisms to the human body and cause serious illnesses. ZrN-Cu coatings containing different amounts of Cu were deposited using an industrial PVD system, and their ability to inhibit bacteria and inactivate the SARS-CoV-2 virus was tested. Microstructural studies showed the formation of two distinct ZrN and Cu phases when Cu content was sufficiently high. Hardness and elastic modulus were inversely proportional to the Cu content. The coatings showed outstanding bactericidal properties against Escherichia coli and Pseudomonas aeruginosa, especially when Cu content was more than 12 at.% and exposure time was longer than 40 min. The coatings, however, did not exhibit any significant virucidal properties. Good mechanical properties, along with excellent antibacterial effects, make these coatings suitable for use as self-sanitizing surfaces on objects that people regularly touch and that are prone to bacterial contamination. Their use would thus allow for only minimal transmission or multiplication of bacteria, and the treated surface would not serve as another source of infection.

The multilayer ceramic composites (MLC) consist of two ceramic materials insoluble in each other and sequentially piled in a symmetric manner whereas they can be divided into two groups: multilayer composites with weak interfaces and composites with strong interfaces. The graphene added multilayer ceramic sandwich (GMCS) composite was developed. The multilayer stack of Si3N4 with 5 and 30 wt% graphene addition were stratified in sandwich structure. So formed multilayer stacks with 5 and 7 layers were sintered by hot issostatic pressing (HIP). The homogenity of graphene addition, the effect of layered structures and the position of layers with lower and higher graphene content on the final properties were studied.

The sintering of ceramic matrix composites is usually carried out by raising the sintering temperature below the melting point of components. Spark plasma sintering (SPS) has the capability to densify ceramics at a relatively low temperature in a very short time. Two different additions, multilayered graphene (MLG) and graphene oxide (GrO), were added to Si3N4 ceramic matrix in various amount, 5 wt% and 30 wt%. The influence of reinforcing phase on final properties of spark plasma sintered Si3N4 composite was studied. The uniaxial-pressure-assisted SPS sintering resulted in a preferential alignment of both type of graphene in the Si3N4 ceramic matrix, leading to highly anisotropic properties with lower mechanical behavior but better tribological and electrical properties.

Si3N4/3wt.% multi-walled carbon nanotubes (MWCNTs) composites were prepared from oxidized ?-Si3N4 powders and sintering additives by hot isostatic pressing (HIP). The Si3N4 powders were oxidized at 1000?C in ambient air environment for 10 and 20 h and the powder mixture was sintered at 1700?C for 3 h under the pressure of 20MPa in nitrogen. The relationship between oxidation, microstructure, tribology and mechanical properties was studied. The dispersion of MWCNTs was not optimal, as they were found mainly in the form of bundles between the ?-Si3N4 grains. Neither Si2N2O nor other oxide phase were observed after the sintering. This was probably caused by the presence of MWCNTs at the grain boundaries of the Si3N4 grains causing reduction of oxide phases. The density, hardness, bending strengths and friction coefficient of the composites increased with the oxidation time of the Si3N4 powder.

Biocompatible ceramics are extremely important in bioengineering, and very useful in many biomedical or orthopedic applications because of their positive interactions with human tissues. There have been enormous efforts to develop bioceramic particles that cost-effectively meet high standards of quality. Among the numerous bioceramics, calcium phosphates are the most suitable since the main inorganic compound in human bones is hydroxyapatite, a specific phase of the calcium phosphates (CaPs). The CaPs can be applied as bone substitutes, types of cement, drug carriers, implants, or coatings. In addition, bioresorbable bioceramics have great potential in tissue engineering in their use as a scaffold that can advance the healing process of bones during the normal tissue repair process. On the other hand, the main disadvantages of bioceramics are their brittleness and poor mechanical properties. The newest advancement in CaPs doping with active biomolecules such as Mg, Zn, Sr, and others. Another set of similarly important materials in bioengineering are biopolymers. These include natural polymers such as collagen, cellulose acetate, gelatin, chitosan, and synthetic polymers, for example, polyvinyl pyrrolidone (PVP), polyvinyl alcohol (PVA), and polycaprolactone (PCL). Various types of polymer have unique properties that make them useful in different fields. The combination of CaP particles with different biopolymers gives rise to new opportunities for application, since their properties can be changed and adjusted to the given requirements. This review offers an insight into the most up-to-date advancements in the preparation and evaluation of different calcium phosphate–biopolymer composites, highlighting their application possibilities, which largely depend on the chemical and physical characteristics of CaPs and the applied polymer materials. Overall, these composites can be considered advanced materials in many important biomedical fields, with potential to improve the quality of healthcare and to assist in providing better outcomes as scaffolds in bone healing or in the integration of implants in orthopedic surgeries.

A new method for preparing multi-layered graphene oxide powder was developed. In this method, the raw material was commercially available micro-sized graphite powder. The graphite powder was milled...

The aim of this study is to present a novel, lower sintering temperature preparation, processing, structural, mechanical, and tribological testing of the AlN-Al2O3 ceramics. The precursor powder of AlN was subjected to oxidation in ambient environment at 900 °C for 3, 10, and 20 h, respectively. These oxidized powders were characterized by SEM and XRD to reveal their morphology, phase, and crystal structure. The SEM results showed coarse powder particles and the presence of aluminum oxide (Al2O3) phase at the surface of aluminum nitride (AlN). The XRD analysis has shown increasing aluminum-oxy-nitride conversion of aluminum nitride as the holding time of oxidation increased. The highest percentage of conversion of AlN powder to AlN-Al2O3 was observed after 10 h. Simultaneously the powders were compacted and sintered using the hot isostatic pressing (HIP) under inert environment (N2 gas) at 1700 °C, 20 MPa for 5 h. This led to the compaction and increase in density of the final samples. Mechanical tests, such as bending test and tribology tests, were carried out on the samples. The mechanical properties of the samples were observed to improve in the oxidized samples compared to the precursor AlN. Moreover, applying longer oxidation time, the mechanical properties of the sintered samples enhanced significantly. Optimum qualitative (microstructure, oxide percentage) and quantitative (tribology, hardness, and bending tests) properties were observed in samples with 10-h oxidation time.

Silicon nitride (SiNx) and hydrogenated silicon nitride (SiNx:H) thin films enjoy widespread scientific interest across multiple application fields. Exceptional combination of optical, mechanical, and thermal properties allows for their utilization in several industries, from solar and semiconductor to coated glass production. The wide bandgap (~5.2 eV) of thin films allows for its optoelectronic application, while the SiNx layers could act as passivation antireflective layers or as a host matrix for silicon nano-inclusions (Si-ni) for solar cell devices. In addition, high water-impermeability of SiNx makes it a potential candidate for barrier layers of organic light emission diodes (OLEDs). This work presents a review of the state-of-the-art process techniques and applications of SiNx and SiNx:H thin films. We focus on the trends and latest achievements of various deposition processes of recent years. Historically, different kinds of chemical vapor deposition (CVD), such as plasma enhanced (PE-CVD) or hot wire (HW-CVD), as well as electron cyclotron resonance (ECR), are the most common deposition methods, while physical vapor deposition (PVD), which is primarily sputtering, is also widely used. Besides these fabrication methods, atomic layer deposition (ALD) is an emerging technology due to the fact that it is able to control the deposition at the atomic level and provide extremely thin SiNx layers. The application of these three deposition methods is compared, while special attention is paid to the effect of the fabrication method on the properties of SiNx thin films, particularly the optical, mechanical, and thermal properties.

The effect of the ultrafine grained silicon nitride and yttria addition to the morphological, structural, mechanical and magnetic properties of the ceramic dispersion strengthened 316 L stainless steels prepared by powder technology has been studied. Four composites have been prepared: 316 L/0.33 wt.% Si3N4, 316 L/1 wt.% Si3N4 (CDS) and 316 L/0.33 wt.% Y2O3, 316 L/1 wt.% Y2O3 (ODS). Spark plasma sintering (SPS) was used for fast compaction of milled composite powders. The hardness values have been found to be significantly higher in the cases of CDS and ODS samples in comparison to reference sample, whereas the ODS composites had lower smaller hardness than the CDS composites regardless the content of additives. The magnetic characterization of samples demonstrated that the samples exhibit ferromagnetic property already before ageing and a larger ferromagnetic component was observed as a result of thermal aging. It was proven that in the case of ODS and CDS samples with a low amount of Y2O3 or Si3N4 the saturation magnetization was slightly dependent on ageing time, however, it exhibited a noticeable change with ageing both at 600 and 800 °C for samples containing higher amount of additives.

In this work multiwall carbon nanotubes (MWCNTs) reinforced 8 mol.% yttria-stabilized zirconia (8YSZ) composites were prepared using attrition milling and spark plasma sintering (SPS, at 1400 °C) in different compositions (0, 1, 5, 10 wt% MWCNTs). The effect of sliding speed at low (V1 = 0.036 m/s) and high (V2 = 0.11 m/s) values has been investigated. Outstanding wear improvement at both low/high sliding speed has been reported with the addition of 1 wt% of MWCNTs. This was most likely attributed to two main factors: 1) the formation of a perfectly continuous and uniform tribo-film. 2) the improved flexural strength, fracture toughness and density.

Titanium carbide/amorphous carbon (TiC/a:C) thin films have been extensively investigated in the past due to their wide applications in technology and industry. One of the most used preparation methods is a magnetron sputtering which provides a great flexibility and possibility for preparation of thin films with various structures. In this work, the effect of deposition temperature and Ti content on structure and mechanical properties of sputtered TiC/a:C coatings was studied. In the case of films with fully bounded Ti ions and columnar structure, the best mechanical properties were found. These films may be used as passivation layers for different applications because of their extremelly chemical stability and excellent mechanical properties.

The aim of present work was the examination of the role of the high efficient attrition milling on the structure and grain size of ZrO2 – 8 mol.% Y2O3 (YSZ) and on the distribution of multiwall carbon nanotubes (MWCNTs) in these powder mixtures. The microstructure of YSZ/MWCNTs powder mixtures with 1, 5, 10 wt.% MWCNTs was investigated. Detailed study confirmed the YSZ grain size decrease and simultaneously the non-destructive homogenization of MWCNTs in the ceramic powder mixtures. The best homogenization degree was achieved in the case of YSZ/1 wt.% MWCNT powder. Raman scattering measurements were performed to investigate the atomic bonding and structural integrity of carbon nanotubes. The presence of the G and D bands in each samples at ∼1590 and ∼1355 cm−1 confirmed the unaffected structural integrity of MWCNTs after the milling process. In addition to Raman measurements the high resolution transmission electron microscopy (HRTEM) studies have shown that the structure of MWCNTs remains intact after milling. Resumen: El propósito de este trabajo fue la evaluación del rol de la molienda por atrición en la estructura y tamaño de grano de ZrO2 – 8 mol.% Y2O3 (YSZ) y la distribución de tubos de carbono multipared(MWCNTs) en las mencionadas mesclas mixtas pulverizadas. Se investigó la microestructura de los polvos YSZ/MWCNT. El estudio detallado confirmó la disminución del tamaño de grano YSZ y, simultáneamente, la homogeneización no destructiva de MWCNT en las mezclas cerámicas pulverizadas. El mejor grado de homogenización fue alcanzado en el caso de YSZ al 1% en peso de MWCNT. Se realizaron mediciones de dispersión Raman para investigar la unión atómica y la integridad estructural de los nanotubos de carbono. La presencia de las bandas G y D en cada muestra a ∼1590 cm-1 y ∼1355 cm-1, confirmó que la integridad estructural de los MWCNT, no fue afectada después del proceso de molienda. Además de las mediciones de Raman, los estudios de microscopía electrónica de transmisión de alta resolución (HRTEM) demostraron que la estructura de los MWCNT permanece intacta después de la molienda. Keywords: MWCNT, Milling, Yttria-stabilized zirconia, Palabras clave: MWCNT, Fresado, Zirconia estabilizada con itria

Aluminium oxynitride (AlON) has a unique thermal and chemical stability that makes it the perfect candidate for a wide range of applications. This article provides a brief description and comparison of the most common AlON preparation methods along with their advantages and disadvantages. Although there has been extensive research on the material, especially more recently because of increased commercial interest, extensive systematic powder synthesis and processing studies have not been carried out to determine alternate, more cost efficient routes to fully dense transparent bodies. Further optimization of reaction sintering and transient liquid phase sintering could be important processing routes.

Composites consisting of 8 mol.% yttria-stabilized zirconia (8YSZ) and 1 wt%, 5 wt% and 10 wt% multiwall carbon nanotubes (MWCNTs) have been prepared by attrition milling and spark plasma sintering (SPS). The effect of sintering temperature and MWCNT content on the microstructural features including apparent density, phase transition, crystal size and mechanical properties were investigated. The phase transformation during the sintering process was observed with X-ray diffraction. The MWCNT stability was investigated by Raman spectroscopy. Vickers hardness and indentation fracture toughness of 8YSZ/MWCNTs composites were evaluated and compared with reference 8YSZ composite. The crack propagation mechanisms of composites were determined. MWCNT pull-out, crack bridging and crack deflections were found and constituted a key factor of fracture toughness enhancement in the composites with MWCNT addition.

Low ductility and brittle deformation behaviors are major drawbacks of currently used commercial hard ceramic-based protective coatings. Recent ab-initio calculations revealed that the coexistence of metallic, boride and carbide bonds in a nanolaminate structure of crystalline W2BC system provides a combination of high hardness together with moderate ductility. The present paper deals with coatings containing W, B and C with different compositions and investigates the effect of the boron to tungsten ratio (B/W) on the structural and mechanical properties of W-B-C coatings prepared by pulsed-DC magnetron sputtering at a moderate temperature. Coatings with low B/W were deposited in a nanocomposite structure, whereas coatings with high B/W ratios were near-amorphous. The structure of the coatings was not a decisive factor in determining their mechanical properties. These were, however, directly correlated with the chemical bonds present. All the coatings exhibited high fracture resistance. These properties together with good adhesion to cemented tungsten carbides make W-B-C coatings promising candidates for the future protective coatings of tools which undergo large deformation in their working cycle.

In this work, amorphous hydrogen-free silicon nitride (a-SiNx) and amorphous hydrogenated silicon nitride (a-SiNx:H) films were deposited by radio frequency (RF) sputtering applying various amounts of hydrogen gas. Structural and optical properties were investigated as a function of hydrogen concentration. The refractive index of 1.96 was characteristic for hydrogen-free SiNx thin film and with increasing H2 flow it decreased to 1.89. The hydrogenation during the sputtering process affected the porosity of the thin film compared with hydrogen-free SiNx. A higher porosity is consistent with a lower refractive index. Fourier-transform infrared spectroscopy (FTIR) confirmed the presence of 4 at.% of bounded hydrogen, while elastic recoil detection analysis (ERDA) confirmed that 6 at.% hydrogen was incorporated during the growing mechanism. The molecular form of hydrogen was released at a temperature of ~65 &deg, C from the film after annealing, while the blisters with 100 nm diameter were created on the thin film surface. The low activation energy deduced from the Arrhenius method indicated the diffusion of hydrogen molecules.

Silicon nitride–zirconia–graphene composites with high graphene content (5 wt.% and 30 wt.%) were sintered by gas pressure sintering (GPS). The effect of the multilayer graphene (MLG) content on microstructure and fracture mechanism is investigated by multi-scale and in-situ microscopy. Multi-scale microscopy confirms that the phases disperse evenly in the microstructure without obvious agglomeration. The MLG flakes well dispersed between ceramic matrix grains slow down the phase transformation from α to β-Si3N4, subsequent needle-like growth of β-Si3N4 rods and the densification due to the reduction in sintering additives particularly in the case with 30 wt.% MLG. The size distribution of Si3N4 phase shifts towards a larger size range with the increase in graphene content from 5 to 30 wt.%, while a higher graphene content (30 wt.%) hinders the growth of the ZrO2 phase. The composite with 30 wt.% MLG has a porosity of 47%, the one with 5 wt.% exhibits a porosity of approximately 30%. Both Si3N4/MLG composites show potential resistance to contact or indentation damage. Crack initiation and propagation, densification of the porous microstructure, and shift of ceramic phases are observed using in-situ transmission electron microscopy. The crack propagates through the ceramic/MLG interface and through both the ceramic and the non-ceramic components in the composite with low graphene content. However, the crack prefers to bypass ceramic phases in the composite with 30 wt.% MLG.

Ta&ndash, B&ndash, C coatings were non-reactively sputter-deposited in an industrial batch coater from a single segmented rotating cylindrical cathode employing a combinatorial approach. The chemical composition, morphology, microstructure, mechanical properties, and fracture resistance of the coatings were investigated. Their mechanical properties were linked to their microstructure and phase composition. Coatings placed stationary in front of the racetrack of the target and those performing a 1-axis rotation around the substrate carousel are compared. Utilization of the substrate rotation has no significant effect on the chemical composition of the coatings deposited at the same position compared to the cathode. Whereas the morphology of coatings with corresponding chemical composition is similar for stationary as well as rotating samples, the rotating coatings exhibit a distinct multilayered structure with a repetition period in the range of nanometers despite utilizing a non-reactive process and a single sputter source. All the coatings are either amorphous, nanocomposite or nanocrystalline depending on their chemical composition. The presence of TaC, TaB, and/or TaB2 phases is identified. The crystallite size is typically less than 5 nm. The highest hardness of the coatings is associated with the presence of larger grains in a nanocomposite structure or formation of polycrystalline coatings. The number, density, and length of cracks observed after high-load indentation is on par with current optimized commercially available protective coatings.

Thin films comprising three dimensional germanium (Ge) quantum dot lattices formed by nitrogen (N) assisted magnetron sputtering deposition in alumina (Al2O3) matrix have been studied for light harvesting purposes. In order to expand the application of this material it is necessary to reduce germanium oxidation and to achieve stabilization of the germanium/alumina interface. Effects of tuning the N concentration, substrate temperature and Ge sputtering power during the films preparation are monitored. It is shown that the N presence not only reduces Ge oxidation during annealing but also affects the internal structure, size and arrangement of Ge quantum dots. Additionally, the deposition temperature and Ge sputtering power are used to tune the Ge quantum dot size, separation and the regularity of their positions. It is shown that the optical and electrical properties of the films, especially their photo-induced current, and quantum efficiency are strongly tunable by the deposition conditions. Moreover, a significant photo-response and effect of multiple exciton generation effect is observed. The materials presented could be used as a sensitive layer for photodetectors or photovoltaic light harvesting devices. The presented tools can be used for future fine tuning of the material to achieve the optimal quantum efficiency.

The formation of TiC and Ti phases and their influence on their mechanical properties was studied in this work. Thin layers were deposited by DC magnetron sputtering at room temperature in ultrahigh vacuum from Ti and C targets. Cubic TiC phase (c-TiC) was formed from 58 to 86 at.% Ti content. First formation of hexagonal Ti (h-Ti) occurred from 86 at.% Ti content. The c-TiC disappears from 90 at.% Ti content. Films with 86 at.% Ti content the c-TiC structure can transform to h-Ti by sequential stacking faults. Dominance of c-TiC(111) texture with increasing Ti content was observed. The hardness of thin films agree with structural observations. The highest hardness value (∼26 GPa) showed the c-TiC thin film with 67 at% Ti content. The nanohardness values showed decreasing character with increasing Ti content over 70 at.%. The lowest values of nanohardness (∼10 GPa) was observed for thin films with only h-Ti phase.

Preparation of coatings simultaneously exhibiting high hardness and enhanced fracture resistance is a hot topic, as nowadays used ceramic protective coatings show difficulties to cope with increased demands due to their inherent brittleness. Material exhibiting seemingly contradictory combination of mechanical properties like high hardness and moderate ductility enhancing the fracture resistance - was recently predicted by ab initio calculations in the crystalline X2BC system. The presented study is focused on the study of the influence of the C/W ratio on the microstructure, the content of different chemical bonds and the mechanical properties of WBC coatings prepared by magnetron sputtering at moderate temperature.

The current study was initiated in order to evaluate the adhesion strength of thin and porous hydroxyapatite (Hap) coatings on titanium (Ti) substrates deposited by the low temperature electrospraying method. The nanocrystalline hydroxyapatite powder was synthesized by coprecipitation method using eggshell biowaste as a nontoxic and natural source of the calcium precursor. Five hydroxyapatite coatings were electrosprayed onto Ti substrates by varying the concentration (0.05 and 0.1 wt%) of polyethylene glycol (PEG) and polyvinylpyrrolidone (PVP) polymers in Hap suspensions. It has been shown that the adhesion strength of composite polymer–Hap coatings increased with increasing polymer concentration and the highest value (8.75 ± 0.75 MPa) was measured for the sample containing 0.1 wt% of PVP. The reason for the change in bonding strength was ascribed owing to microstructural changes caused by polymer addition whereas on one hand lower adhesion strength in Hap–0.1PEG was caused by the presence of separated polymer contained islands, and hence, weaker adhesion to substrate was found in this sample. On the other hand, more uniform, homogeneous, and denser microstructure resulted in an increasing cohesive strength inside the Hap–0.1PVP layer which lead to stronger mechanical bonding at the coating–substrate interface.