Effects of ceramic-based CrN,TiN, and AlCrN interlayers on wear and friction behaviors of AlTiSiN+TiSiN PVD coatings

In this study, the wear and friction behavior of cathodic arc physical vapor deposited AlTiSiN+TiSiN coatings on H13 tool steels were investigated by using CrN, TiN and AlCrN interlayers with tribometer tests both under unlubricated and boundary lubricated conditions. 6 mm alumina balls were used as counter surfaces to test ceramic hard coatings. Surface coatings were characterized through nanoindentation, scanning electron microscopy coupled with an energy-dispersive X-ray spectrometer (SEM/EDXS), optical profilometry, and atomic force microscopy (AFM) techniques. The results showed that especially AlTiSiN+TiSiN coating with TiN interlayer resulted in a much more enhanced tribological performance of the tool steels at both unlubricated and the boundary lubricated conditions even at elevated contact pressures.     

Mixed oxide nanotubes in nanomedicine: A dead-end or a bridge to the future?

Nanomedicine has seen a significant rise in the development of new research tools and clinically functional devices. In this regard, significant advances and new commercial applications are expected in the pharmaceutical and orthopedic industries. For advanced orthopedic implant technologies, appropriate nanoscale surface modifications are highly effective strategies and are widely studied in the literature for improving implant performance. It is well-established that implants with nanotubular surfaces show a drastic improvement in new bone creation and gene expression compared to implants without nanotopography. Nevertheless, the scientific and clinical understanding of mixed oxide nanotubes (MONs) and their potential applications, especially in biomedical applications are still in the early stages of development. This review aims to establish a credible platform for the current and future roles of MONs in nanomedicine, particularly in advanced orthopedic implants. We first introduce the concept of MONs and then discuss the preparation strategies. This is followed by a review of the recent advancement of MONs in biomedical applications, including mineralization abilities, biocompatibility, antibacterial activity, cell culture, and animal testing, as well as clinical possibilities. To conclude, we propose that the combination of nanotubular surface modification with incorporating sensor allows clinicians to precisely record patient data as a critical contributor to evidence-based medicine.     

Interface properties of Ti3SiC2/Al2O3 ceramics: Combined experiments and first-principles calculations

The synthesis, characterization, and first-principles calculations of Ti₃SiC₂/Al₂O₃ ceramics were reported. X-ray diffraction measurements showed that the composite ceramics were highly pure. Scanning electron microscopy and transmission electron microscopy were used to characterize the interface information for Ti₃SiC₂ and Al₂O₃ crystals. Surface energies and interface properties were calculated using the first-principles method. The results suggested that Ti₃SiC₂ with Ti terminations and Al₂O₃ with O terminations are more stable than other terminations crystals. Thus powerful attraction between the coordinatively unsaturated Ti and O atoms on the Ti₃SiC₂∥Al₂O₃ interface would result in higher work of adhesion (Wad) and shorter boundary distance, demonstrating the intercrystalline strengthening of Ti₃SiC₂/Al₂O₃ composite ceramics.     

Highly compressible ceramic/polymer aerogel-based piezoelectric nanogenerators with enhanced mechanical energy harvesting property

Ceramic piezoelectric materials have orders of magnitude higher piezoelectric coefficients compared to polymers. However, their brittleness precludes imposition of large strains in mechanical energy harvesting applications. We report here that ice templating affords low bulk modulus lead-free aerogel piezoelectric nanogenerators (PENG) with unprecedented combination of flexibility and high piezoelectric response (voltage and power density). A modified ice templating protocol was used to fabricate piezoelectric nanocomposites of surface modified BaTiO₃ (BTO) nanoparticles in crosslinked polyethylene imine. This protocol allowed incorporating a significantly high fraction of BTO particles (up to 83 wt %) in the aerogel, while retaining remarkably high compressibility and elastic recovery up to 80% strain. The output voltage, at an applied compressive force of 20 N (100 kPa), increased with BTO loading and a maximum output voltage of 11.6 V and power density of 7.22 μW/cm² (49.79 μW/cm³) was obtained for PENG aerogels containing 83 wt% BTO, which is orders of magnitude higher than previously reported values for foam-based piezoelectric energy harvesters. The BTO/PEI PENGs also showed cyclic stability over 900 cycles of deformation. PENGs with higher porosity showed better elastic recovery and piezoelectric properties than lower porosity and higher BTO content aerogels. To the best of our knowledge, this is the first report to demonstrate the piezoelectric properties of high ceramic content aerogels having very high compressibility and elastic recovery.     

Influence of the cold sintering process and post annealing on the microstructure and Li-ion conductivity of LiTa2PO8 solid electrolyte

Recently, LiTa₂PO₈ (LTPO) has attracted interest as a potential Li-ion solid electrolyte material because of its high bulk ionic conductivity and low grain boundary ionic conductivity. However, most ceramic-based solid electrolytes are fabricated via the high-temperature sintering process (typically above 1000 °C); such temperatures can cause the evaporation of Li from the compound. To replace high-temperature sintering of ceramics, the cold sintering process (CSP) was introduced; this process enables the densification of ceramics and composites at extremely low temperatures (below 300 °C). In this work, we investigate the effect of using the CSP and post annealing on the microstructure and Li-ion conductivity of LTPO pellets. It is found that the CSP pellets have an amorphous phase between particles. This intermediate amorphous phase creates a better contact between particles and is hypothesized to lead to more Li-ion migration paths. The CSP pellet is found to have a high density and high ionic conductivity of (1.19 × 10^?5 S/cm). The pellet obtained via the CSP has Li-ion conductivity similar to that of the pellet obtained via dry pressing after it has been annealed. The CSP pellet after post annealing shows good connections between particles and a high Li-ion conductivity of 1.05 × 10^?4 S/cm, which is comparable to the conductivity of a pellet obtained via high-temperature sintering. This work provides new evidence that the CSP is a promising alternative to high-temperature sintering for fabricating ceramic solid electrolytes.     

A comprehensive exploration on the development of nano Y2O3 dispersed in AA 7017 by mechanical alloying and hot-pressing technique

The main objective of the present study is to develop AA 7017 alloy matrix reinforced with yttrium oxide (Y₂O₃, rare earth element) nanocomposites by mechanical alloying (MA) and hot pressing (HP) techniques for armor applications. AA 7017+10 vol % Y₂O₃ nanocomposites were synthesized in a high-energy ball mill with different milling times (0, 5, 10, and 20 h) to explore the structural refinement effect. The phase analysis and homogeneous dispersion of Y₂O₃ in AA 7017 nanocrystallite matrix were investigated by X-ray diffraction (XRD), various electron microscopes (HRSEM, and HRTEM), Particle Size Analyzer (PSA), and Differential Thermal Analysis (DTA). The nanostructured powders were hot-pressed at 500 MPa pressure with a temperature of 673k for 1hr. The consolidated sample results revealed significant grain refinement and the enhanced mechanical properties with the function of milling time in which the 20h sample exhibited improvement in the hardness (142 VHN - 260 VHN) and ultimate compressive strength (514 MPa–906.45 MPa) due to effective dispersion of Y₂O₃. The various strengthening mechanisms namely, grain boundary (27.02–32.69 MPa), solid solution (57.21 MPa), precipitate (189.79–374.62 MPa), Orowan (135.68–206.92 MPa), and dislocation strengthening (84.99–149.82 MPa) were determined and correlated to the total strength.     

Fabrication of sustainable magnesium phosphate cement micromortar using design of experiments statistical modelling: Valorization of ceramic-stone-porcelain containing waste as filler

Magnesium phosphate cement (MPC) is a potential sustainable alternative to Portland cement. It is possible to lower the total CO₂ emissions related to MPC manufacturing by using by-products and wastes as raw materials. When by-products are used to develop MPC, the resultant binder can be referred to as sustainable magnesium phosphate cement (sust-MPC). This research incorporates ceramic, stone, and porcelain waste (CSP) as a filler in sust-MPC to obtain a micromortar. Sust-MPC is formulated with KH₂PO₄ and low-grade MgO (LG-MgO), a by-product composed of 40–60 wt% MgO. CSP is the non-recyclable glass fraction generated by the glass recycling industry. The effect of water and CSP addition on the mechanical properties of sust-MPC was analyzed using design of experiments (DoE). A statistical model was obtained and validated by testing ideally formulated samples achieved through optimization of the DoE. The optimal formulation (15 wt% of CSP and a water to cement ratio of 0.34) was realized by maximizing the compressive strength at 7 and 28 days of curing, resulting in values of 18 and 25 MPa respectively. After one year of curing, the micromortar was physico-chemically characterized in-depth using backscattered scanning electron microscopy (BSEM-EDS) and Fourier transform infrared-attenuated total reflectance spectroscopy (FTIR-ATR). The optimal formulation showed good integration of CSP particles in the ceramic matrix. Thus, a potential reaction between silica and the K-struvite matrix may have occurred after one year of curing.     

In-situ growth flower-like binder-free 3D CuO/Cu2O-CTAB with tunable interlayer spacing for high performance lithium storage

Copper-based oxides are attractive anode materials for lithium-ion batteries (LIBs) due to their abundant resources, low cost, non-toxic and high capacity. However, copper-based oxides will produce a huge volume change during lithiation/delithiation, and the structural strain caused by periodic volume changes may cause the exfoliation of active materials. Herein, a flower-like binder-free three-dimensional (3D) CuO/Cu₂O-CTAB was prepared by introducing CTAB, which homogeneously grew in situ on a copper mesh framework. The binder-free 3D sample guarantees direct contact between the active material and the copper mesh, maintaining the structure stability. The flower-like CuO/Cu₂O-CTAB with a small size reveals larger active interfaces and provides more active sites. The introduction of CTAB enlarges the interlayer spacing of CuO/Cu₂O, increases the active sites for lithium storage, and adapts to the volume change of the material during lithiation/delithiation. In addition, the expanded interlayer structure helps decrease the ion diffusion energy barrier for accelerating electrochemical reaction kinetics. Therefore, CuO/Cu₂O-CTAB exhibits better lithium storage performance (2.9 mAh cm^?2 at 0.5 mA cm^?2) than bare CuO/Cu₂O (1.8 mAh cm^?2 at 0.5 mA cm^?2).     

Investigation of processes of obtaining cerium dioxide sol with polyvinyl alcohol having bioactive properties

Cerium dioxide sols are widely used in photocatalysis, catalysis, medicine and cosmetics. It is believed that sols with a CeO₂ size of up to 10 nm have the most active biological properties. The method of sols preparation affects their functional properties. They are usually obtained through the stage of separating the oxide in the solid phase from the solution, which can lead to particle agglomeration, and then transferring the oxide to a colloidal solution under the action of various stabilizers. In this study, we propose the method of CeO₂ sol obtaining without step of solid phase oxide separation. The stabilizer (polyvinyl alcohol (PVA)) is present at the stage of formation of weakly aggregated CeO₂ nanoparticles from cerium(III) salt with an ammonia and hydrogen peroxide solution. Using IR, UV spectroscopy, viscometry and titration it was found that H₂O₂ eventually oxidizes Ce(III) in solution to Ce(IV) and does not oxidize PVA. The intermediate formed after the addition of ammonia solution to cerium(IV) salt has the composition Ce(ООН)₃OН?nH₂O, which is confirmed by the data of proton magnetic resonance, weight and thermal analyses. The process of CeO₂ sol formation stabilized by PVA goes through the stages of Ce(ООН)₃ОН dissolution accompanying with an endothermic effect, followed by decomposition. Peroxide compounds in the solid phase are stable in air up to 90–100 °C. The prepared sol has the composition CeO₂–PVA–ammonium nitrate, exhibit antioxidant properties, is not a nutrient medium for E. Coli and S. Aureus and is capable to form a calcium-phosphate layer on its surface from a model solution of SBF.     

Carbon doped with binary heteroatoms (N,X–C,where X = P,B, or S) derived from polypyrrole for enhanced electromagnetic wave absorption at microwave frequencies

Dual heteroatom-doped carbon materials show great promise as electromagnetic wave absorbers. However, synthesizing carbons containing multiple heteroatoms at controlled heteroatom doping levels has provided challenges to date. Herein, we report a simple method for manufacturing dual heteroatom doped carbons (N,X–C, where X = P, B, or S) by direct carbonization of polypyrrole synthesized in the presence of H₃PO₄, H₃BO₃, or H₂SO₄, respectively. The heteroatom content of the N,X–C products could be precisely tuned by varying amounts of acid dopant used in the polypyrrole synthesis. The N,X–C materials showed excellent electromagnetic wave absorption properties, especially N,S₁–C (prepared using equimolar amounts of pyrrole and H₂SO₄) which offered a wide absorption bandwidth up to 6.6 GHz (11.38–18 GHz), and a RL_min of ?32.3 dB (14.2 GHz) at 2.5 mm at a ?ller loading of 9.0 wt%. The outstanding electromagnetic wave absorption performance of N,S₁–C was attributed to the presence of N dopant species, defects, C–S, and C–SO_x groups, which optimized dipole polarization and conduction loss in the dielectric loss leading to excellent impedance matching.     

Room-temperature densification of MgO bulk ceramics with dispersed nitride phosphor particles

Wave conversion materials with high thermal conductivity are necessary for high-power semiconductor lighting. Ceramics have higher thermal conductivity than existing matrices such as resin or glass in which phosphor particles are dispersed. However, the high densification of ceramics generally requires high-temperature sintering, which degrades and alters the phosphor particles. In this study, we aimed to achieve the high densification of MgO ceramics at room temperature. Applying high hydrostatic pressure with water addition improved the sample packing ratio and promoted the formation of Mg(OH)₂. As a result, the relative density was ≥95%. Additionally, various nitride phosphor particles (CaAlSiN₃:Eu²⁺, β-SiAlON:Eu²⁺, and α-SiAlON:Eu²⁺) were dispersed in the MgO matrix at room temperature without degrading the luminescence property. The thermal conductivity of the obtained sample was about 8 W m^?1K^?1, 40 times higher than that of the epoxy matrix.     

Oxygen-ion conductivity and mechanical properties of Lu2O3-doped ZrO2 as a solid electrolyte

The characteristics of Lu₂O₃-doped ZrO₂ as a solid electrolyte material were investigated in terms of its oxygen ion conductivity and flexural strength to realize its electrolytic function at intermediate and high temperatures. The effect of doping Lu³⁺, which has a high nuclear charge electric field strength, was examined through impedance spectroscopy, open-circuit potential measurements, and bending tests. The results with Lu₂O₃ dopant were compared with those obtained with a widely used dopant, Y³⁺, having a similar ionic radius with Lu³⁺, as well as a dopant that provides high ionic conduction, Sc³⁺, having a smaller ionic radius with Zr⁴⁺. The results revealed that, at the same dopant concentration, both the ionic conductivity and the flexural strength of Lu₂O₃-doped ZrO₂ are higher than those of the widely used Y₂O₃-doped ZrO₂. The conductivity of 8 mol% Lu₂O₃-doped ZrO₂ surpassed that of 8 mol% Sc₂O₃-doped ZrO₂ in the range of 800–950 °C (0.153 S/cm vs. 0.121 S/cm at 900 °C). These results indicate the potential of Lu³⁺ as a dopant for enhancing the performance of ZrO₂ solid electrolytes.     

Temperature effect on elastic and fracture behaviour of lead-free piezoceramic BaTiO3

Ferroelectric ceramics, especially piezoceramics, are widely used in the field of sensors, micromanipulators, and capacitors. Barium titanate and its derivates are the first choices between lead-free materials. The main aim of the paper is to clarify fundamental processes taking place in the vicinity of Curie temperature with a focus on the fracture behaviour of pure polycrystalline barium titanate. The explanation of observed changes in the mechanical behaviour of this material is based on the experimental approach supported by numerical simulations utilising features of the real microstructure on the grain level. Several model materials with various grain microstructures were manufactured from the submicron barium titanate powder sintered at various temperatures. Two resulting materials with a suitable distribution of grains were selected for further investigation. The grain size influenced not only the exact position of the temperature of the Curie point but also the kinetics of the lattice transformation, elastic, and fracture properties. The significant drop observed in the fracture resistance was attributed to the development of localised internal thermal stresses, which was supported by the results of the performed numerical simulations. The coincidence of the volume change of neighbouring grains due to lattice transformation together with a significant variation in elastic properties can lead up to a 20% decrease in the measured fracture toughness. Understanding this behaviour is essential for the processing and correct application of lead-free barium titanate materials.     

Efficient nitric oxide sensing on nanostructured La2MMnO6 (M: Co,Cu, Zn) electrodes

Selective detection of nitric oxide (NO) is a challenge for automotive exhaust monitoring systems due to the instability of sensing architectures operating under extreme environments. Herein, yttria-stabilized zirconia (YSZ) solid-electrolyte-based electrochemical gas sensor was developed using double perovskite electrodes (DPO) for selective detection of NO. The La₂MMnO₆ (M: Co, Cu, Zn) phases were synthesized by sol-gel processing of constituent salts and characterized for physicochemical and sensing properties to investigate the impact of transition metal cations present in octahedral environments on charge transport properties. The La₂ZnMnO₆ with a predominant Zn²⁺–Mn⁴⁺ charge ordering excelled in the sensing characteristics with high sensitivity (33 mV/decade for 3–80 ppm NO concentration), fast response/recovery time (52/42 s) and significant NO selectivity at 500 °C. The sensing behavior of double perovskites was comprehensively explored and found to abide by the mixed-potential model. Moreover, stable sensing properties over a period of three weeks indicate the here-described sensors to be potentially competitive for onboard exhaust monitoring in automobiles.     

Development of magnetic nanoparticle based nanoabrasives for magnetorheological finishing process and all their variants

Efficacy and the outcome of the magnetorheological finishing (MRF) related processes depends on two crucial factors, (i) a finishing abrasive and (ii) a magnetic particle. However, the magnetic particles although necessary, become a hindrance for non-magnetic abrasive particles in directly reaching the surface to be finished. This study relates to the development of SPION-based smart material for MRF and all their variant processes. The SPION particles possess dual nature such as nanoabrasives and magnetic nanoparticle. The superparamagnetic property of the developed SPION particle has been confirmed by alternating gradient magnetometer with the saturation magnetization value of 82.23 emu/g. The polishing performance of the developed SPION-based particle as abrasive has been investigated on a BK-7 optical glass and the polishing is done via a 5-axes automated ball end magnetorheological finishing (BEMRF). The developed SPION abrasive enhanced the finishing process of the BEMRF technique and provided surface finishing on the BK-7 substrate up to the surface roughness (Ra) values of 22.3 nm with the Ra improvement of 88.14%.     

A novel composition of bioactive glass with potent haemostatic action and antibacterial competence

Haemorrhagic bleeding is a crucial area of concern related to military as well as civilian trauma. In recent years, bioactive glass is gaining attention in a number of healthcare applications, including haemostasis. Herewith, we report a unique composition of bioactive glass, 70 SiO₂: (30-x-y) CaO: x.Al₂O₃: y.ZnO, where x = 10–18 mole% and y = 0–8 mole%, (Al-BAG) exhibiting haemostatic property as well as antibacterial activity. The as-prepared glass was characterized using XRD, SEM-EDX, FTIR and TG-DSC along with in-vitro degradation study and biological studies e.g., cytocompatibility, haemocompatibility, in-vitro thrombus formation, in-vitro blood absorption capacity, blood coagulation assays (PT, aPTT), in-vitro antibacterial assay against Staph. aureus as well as in-vivo acute dermal toxicity followed by histopathological analysis) and in-vivo haemostasis efficacy were undertaken. The novel bioactive glass composition exhibits promises to be an efficient haemostatic agent with antibacterial activity.     

Scanning pulsed laser ablation in liquids: An alternative route to obtaining biocompatible YbFe nanoparticles as multiplatform contrast agents for combined MRI and CT imaging

Ytterbium ferrites are being used in many promising applications, such as visible-light photocatalysis, solar cells, magnetooptic devices, electro-magnetic equipment, etc., due to their fantastic ferroelectric and ferromagnetic properties. However, despite their good magnetic and radiopaque features, the use of ytterbium ferrites as multiplatform contrast agents in magnetic resonance imaging (MRI) and X-ray computed tomography (CT) is still under-developed. This is mainly due to difficulties in obtaining stable and biocompatible aqueous colloidal dispersions of ytterbium ferrite nanoparticles. In order to overcome this limitation, this work explores an eco-friendly method to directly synthesize such dispersions by liquid-assisted pulsed laser ablation of ytterbium ferrite massive targets. First, orthorhombic bulk YbFeO₃ targets were obtained by a reaction-sintering method. Then, colloidal dispersions of nanoparticles were produced directly in both distilled water and ethanol by irradiating the bulk YbFeO₃ targets with high-power infrared nanosecond lasers pulses. A battery of techniques has been used to characterize the as synthesized YbFeO₃ targets and colloidal dispersions of YbFe nanoparticles to determine their composition, structure, magnetic properties, X-ray attenuation potentials, and colloidal properties. Moreover, the biocompatibility of the systems was also analysed by MTT cell viability assay. Results indicated that the use of distilled water as ablation medium yields colloidal dispersions consisted mainly of paramagnetic ytterbium ferrite nanoparticles. Contrarily, the use of ethanol as solvent leads to colloidal dispersions of polycrystalline nanoparticles with both ferromagnetic and paramagnetic behaviour, due to the coexistence, in each nanoparticle, of ytterbium ferrite, ytterbium oxide, and iron oxide crystalline phases. Both colloidal dispersions exhibit also high biocompatibility and suitable X-ray attenuation properties. Moreover, they show bio-safe hydrodynamic sizes (lower than 200 nm) with acceptable overall hydrodynamic polydispersity index values (under 0.4), being stable in water for several weeks. These results pave the way for the future evaluation of Yb–Fe based nanoparticles as multiplatform contrast agents in multimodal MRI and CT imaging.     

Corrosion behavior of carbon,Al2O3, and MgO refractories during the preparation of a Ti–Si–Al alloy via the aluminothermic reduction of a Ti-bearing blast-furnace slag

The extraction of Ti from Ti-bearing blast-furnace slag (TBFS) via aluminothermic reduction to prepare Ti–Si–Al alloy has several promising applications. However, the refractories of the furnace lining can dissolve into the molten slag and change the composition of the slag, not only shortening the life of the refractories, but also influencing the preparation of Ti–Si–Al alloys for industrial applications. The main purpose of this study was to explore the corrosion behavior of refractories (carbon, alumina, and magnesia bricks) and determine the most suitable refractories for the aluminothermic reduction of TBFS. Herein, for the first time, the dissolution equilibrium of refractories during the aluminothermic reduction of TBFS and its effect on aluminothermic reduction were revealed. The results revealed that the alumina and magnesia bricks were more effective for obtaining bulk Ti–Si–Al alloy and avoiding high mass loss of the Ti–Si–Al alloy compared to the carbon bricks. Furthermore, the corrosion of alumina and magnesia bricks increased with an increase in the content of the added CaO; however, the corrosion of the alumina bricks was more severe compared to the magnesia bricks. In addition, the largest extraction ratio of Ti (maximum value: 99.85%) was achieved when magnesia bricks were employed. The results of this study indicate that magnesia bricks are the optimal refractory for the preparation of Ti–Si–Al alloy via the aluminothermic reduction of TBFS. This work provides important experimental information for the industrial application of the aluminothermic reduction of TBFS in the preparation of Ti–Si–Al alloys.