Search Results (78)

Nano-titanium dioxide ceramic coatings exhibit excellent wear resistance, corrosion resistance, and self-cleaning properties, showing great potential as multifunctional protective materials. This study proposes a synergistic reinforcement strategy by encapsulating micron-sized Al₂O₃ particles with nano-TiO₂. A core-shell structured nanocomposite coating composed of 65 wt% nano-TiO₂ encapsulating 30 wt% micron-Al₂O₃ was precisely designed and fabricated via a slurry dip-coating method on Q235 steel substrates. The microstructure and surface morphology of the coatings were characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD). Comprehensive performance evaluations including densification, adhesion strength, wear resistance, and thermal shock resistance were conducted. Optimal coating properties were achieved under the conditions of a binder-to-solvent ratio of 1:15 (g/mL), a heating rate of 2 °C/min, and a sintering temperature of 400 °C. XRD analysis confirmed the formation of multiple crystalline phases during the 400 °C curing process, including titanium pyrophosphate (TiP₂O₇), aluminum phosphate (AlPO₄), copper aluminate (Cu(AlO₂)₂), and a unique titanium phosphate phase (Ti₃(PO₄)₄) exclusive to the 2 °C/min heating rate. Adhesion strength tests revealed that the coating sintered at 2 °C/min exhibited superior interfacial bonding strength and outstanding performance in wear resistance, hardness, and thermal shock resistance. The incorporation of nano-TiO₂ into the 30 wt% Al₂O₃ matrix significantly enhanced the mechanical properties of the composite coating. Mechanistic studies indicated that the bonding between the nanocomposite coating and the metal substrate is primarily achieved through mechanical interlocking, forming a robust physical interface. These findings provide theoretical guidance for optimizing the fabrication process of metal-based ceramic coatings and expanding their engineering applications in various industries. Full article

High-temperature adsorption is a promising technology for carbon mitigation, and it can be applied in direct carbon capture and the integration with utilization. Lithium-based adsorbents, known for their high CO₂ uptake and rapid kinetics, have garnered significant interest. However, adsorption performance, cycling stability, and degradation behavior of this type of adsorbent are rarely reported and compared under comparable conditions. In this work, nine lithium-based adsorbents were synthesized and characterized for their physicochemical properties. Dynamic and isothermal thermogravimetric analysis were conducted to determine adsorption/desorption equilibrium temperatures, evaluate CO₂ adsorption characteristics under varying thermal conditions, and assess cycling stability over 20 adsorption–desorption cycles. The results reveal exceptional initial CO₂ capacities for α-Li₅AlO₄, Li₅GaO₄, Li₅FeO₄, and Li₆ZnO₄; however, these values decline to 30.2 wt.%, 24.3 wt.%, 41.6 wt.%, and 44.2 wt.% after cycling. In contrast, Li₂CuO₂ and Li₄SiO₄ exhibit lower initial capacities but possess superior cycling stability with final values of 21 wt.% and 21.6 wt.%. Phase composition and microstructural analysis identify lithium carbonate and metal oxides as primary products, and microstructural sintering was observed during cycling. This study could provide insights into the trade-offs between the initial capacity and cycling stability of lithium-based adsorbents, offering guidelines for adsorbent optimization through doping or pore engineering to advance high-temperature CO₂ capture technologies. Full article

This study evaluates the wear and corrosion resistance of the Cu-50Ni-5Al alloy reinforced with CeO₂ nanoparticles for potential use as anodes in molten carbonate fuel cells (MCFCs). Cu–50Ni–5Al alloys were synthesized, with and without the incorporation of 1% CeO₂ nanoparticles, by the mechanical alloying method and spark plasma sintering (SPS). The samples were evaluated using a single scratch test with a cone-spherical diamond indenter under progressive normal loading conditions. A non-contact 3D surface profiler characterized the scratched surfaces to support the analysis. Progressive loading tests indicated a reduction of up to 50% in COF with 1% NPs, with specific values drop-ping from 0.48 in the unreinforced alloy to 0.25 in the CeO₂-doped composite at 15 N of applied load. Furthermore, the introduction of CeO₂ decreased scratch depths by 25%, indicating enhanced wear resistance. The electrochemical behavior of the samples was evaluated by electrochemical impedance spectroscopy (EIS) in a molten carbonate medium under a H₂/N₂ atmosphere at 550 °C for 120 h. Subsequently, the corrosion products were characterized using X-ray diffraction (XRD), scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS), and X-ray photoelectron spectroscopy (XPS). The results demonstrated that the CeO₂-reinforced alloy exhibits superior electro-chemical stability in molten carbonate environments (Li₂CO₃-K₂CO₃) under an H₂/N₂ atmosphere at 550 °C for 120 h. A marked reduction in polarization resistance and a pronounced re-passivation effect were observed, suggesting enhanced anodic protection. This effect is attributed to the formation of aluminum and copper oxides in both compositions, together with the appearance of NiO as the predominant phase in the materials reinforced with nanoparticles in a hydrogen-reducing atmosphere. The addition of CeO₂ nanoparticles significantly improves wear resistance and corrosion performance. Recognizing this effect is vital for creating strategies to enhance the material’s durability in challenging environments like MCFC. Full article

Powder metallurgy enables the production of composite materials, which are of great interest to different branches of the automotive, aerospace, and medical industries. This work investigated the sintering of an Al-xCu and Al-xCu-0.1Sn alloy, with copper concentration between 3.5 and 4.5% and tin added in the range of 0.1%. Compressibility curves were drawn, and the samples were sintered in a high-purity nitrogen-controlled atmosphere furnace. The composites were subjected to subsequent solubilization heat treatment, with cooling in low concentration polymer solutions and artificial aging (T6). The samples were studied using optical, scanning electron, Vickers microhardness, and X-ray diffraction techniques. The results indicated the effectiveness of cooling the samples after solubilization in polymer solutions, the influence of the addition of tin on the aging time, and the mechanical properties of the alloys as a function of the T6 cycles applied. Full article

This paper reports on the influence of various processing parameters and different SiC_p proportions on the outcome of mechanical, tribological, microstructural, and microcompositional investigations of Al-Cu based composites used as potential brake friction materials for eco-friendly vehicle parts. The composites were obtained by powder metallurgy, and then the sintered composite was treated at 515 ± 5 °C/6 h, quenched in water, and artificially aged at different temperatures and times. The microstructural and microcompositional investigations of the composites were made using an environmental scanning electron microscopy (ESEM), energy-dispersive X-ray spectroscopy (EDS). After analyzing the microstructures in correlation with the results of the hardness tests, the optimal proportion of SiC_p and optimal heat treatment parameters were determined. The composite samples with the best properties were chosen for tribological investigation. The friction and wear tests of samples were made under dry sliding conditions using a “pin on disc” machine, at a contact pressure of 0.35 to 1.15 MPa, 2 to 4.5 m/s relative speed, and the prediction of tribological behavior was made using a linear factorial design approach. Full article

Nature has created a unique combination of materials, and the design and material compositions used in nature are not successfully employed for industrial applications. Metallic multimaterials (MMMs) are a unique class of materials that combine the properties of various metallic constituents (both matrix and reinforcement(s)) to improve the functionality, performance in real-time, and application spectrum. Accordingly, this study explores the fabrication perspective of MMMs by combining both additive manufacturing (AM) and powder metallurgical (PM) routes. Ti6Al4V structures were fabricated via the laser powder-bed fusion (LPBF) process, and the reinforcement powders were added into the spark plasma sintering (SPS) mold where the Ti6Al4V structures were placed. Different reinforcement compositions including Mg, Al, Fe, Ni, and Cu were explored. Since the present study is focused on the variation of hardness, the hardness profile of the MMM composite was explored showing a sinusoidal trend. This study stands as a testimonial of fabricating MMM composites via a combination of AM and PM processes. Full article

Cu-bearing titanium alloys exhibit promising antibacterial properties for clinical use. A novel Ti6Al4V-Ti5Cu composite alloy is developed using powder bed fusion (selective laser sintering, SLM) and spark plasma sintering (SPS). SLM produces a triple periodic minimal surface (TPMS) lattice structure from Ti6Al4V, which is then filled with Ti-5Cu powders and sintered using SPS. Microstructural analysis confirms a well-bonded interface between Ti6Al4V and Ti-5Cu could be achieved through SLM-SPS technology. The composite primarily showcases laths α phase, with Ti₂Cu precipitates in the Ti-5Cu region. Electrochemical assessments reveal superior corrosion resistance in the Ti6Al4V-Ti5Cu composite compared to SLM-Ti6Al4V and SPS-Ti-5Cu. The antibacterial rate of the TPMS structure exceeds 90%, and that of TCCU-90 reaches as high as 99%, manifesting robust antibacterial activity. These findings suggest a strategy for creating biomimetic alloys that seamlessly combine structure and multifunctionality within biomedical materials. Full article

This study fabricated (Al₆₃Cu₂₅Fe₁₂)₉₉Ce₁ quasicrystal-enhanced aluminum matrix composites using the hot-pressing method to investigate their interfacial reaction traits. Microstructure analysis revealed that at 490 °C for 30 min of hot-pressing, the interface between the matrix and reinforcement was clear and intact. Chemical diffusion between the I-phase and aluminum matrix during sintering led to the formation of Al₇Cu₂Fe, AlFe, and AlCu phases, which, with their uniform and fine distribution, significantly enhanced the alloy’s overall properties. Regarding compactness, it first increased and then decreased with different holding times, reaching a maximum of about 98.89% at 490 °C for 30 min. Mechanical property analysis showed that compressive strength initially rose and then fell with increasing sintering temperature. After 30 min at 490 °C, the reinforcement particles and matrix were tightly combined and evenly distributed, with a maximum compressive strength of around 790 MPa. Additionally, the diffusion dynamics of the transition layer were simulated. The reaction rate of the reaction layer increased with hot-pressing temperature and decreased with holding time. Selecting a lower temperature and appropriate holding time can control the reaction layer thickness to obtain composites with excellent properties. This research innovatively contributes to the preparation and property study of such composites, providing a basis for their further application. Full article

In this study, we fabricated Ti-Cu-based friction composites containing waste-metal (Ti, CuZn, stainless steel (SSt), MgAl), Al₂O₃ due to improving properties and its good compatibility with copper and graphene nanoplatelets as reinforcement and lubricant component, using planetary ball mill and technique based on Spark Plasma Sintering (SPS). Understanding the wear behaviour of such engineered friction composites is essential to improve their material design and safety, as these materials could have the potential for use in public and industrial transportation, such as high-speed rail trains and aircraft or cars. This is why our study is focused on wear behaviour during friction between function parts of devices. We investigated the composite materials designed by us in order to clarify their microstructural state and mechanical properties. Using different loading conditions, we determined the Coefficient of Friction (COF) using a ball-on-disc tribological test. We analysed the state of the samples after the mentioned test using a Scanning Electron Microscope (SEM), then Energy-Dispersive X-ray Spectroscopy (EDS), and confocal microscopy. Also, a comparative analysis of friction properties with previously studied materials was performed. The results showed that friction composites with different compositions, despite the same conditions of their compaction during sintering, can be defined by different wear characteristics. Our study can potentially have a significant contribution to the understanding of wear mechanisms of Ti-Cu-based composites with incorporated metal-waste and to improving their material design and performance. Also, it can give us information about the possibilities of reusing metal-waste from different machining operations. Full article

The utilization of red mud in the production of ceramic products represents an efficient approach for harnessing red mud resources. Composite ceramics were prepared from Al₂O₃, red mud, and Cr₂O₃ by atmospheric pressure sintering, and the phase composition and microscopic morphology of the composite ceramics were investigated by XRD, SEM, and EDS. The flexural strength and fracture toughness of composite ceramics were measured by three-point bending and SENB methods. The results showed that the composite ceramics sintered at 1500 °C with the addition of 1.5 wt.% Cr₂O₃ had a flexural strength of 297.03 MPa, a hardness of 17.44 GPa, and a densification of 97.75% and fracture toughness of 6.57 MPa·m^1/2. The addition of Cr₂O₃ helps to improve the low strength of red mud composite ceramic samples. The CaAl₁₂O₁₉ phase can form a similar “endo-crystalline” structure with Al₂O₃ grains, which changes the fracture mode of the ceramics and thus significantly improves the fracture toughness. The wettability tests conducted on Cu and RM–Al₂O₃ composite ceramic materials revealed that the composites exhibited non-wetting behavior towards Cu at elevated temperatures, while no interfacial reactions or elemental diffusion were observed. Composites have higher surface energy than Al₂O₃ ceramic at high temperatures. The present study provides a crucial foundation for enhancing the comprehensive utilization value of red mud and the application of red mud ceramics in the field of electronic packaging. Full article

The Ti₃SiC₂TiSi_x ceramic composite was synthesized in situ from a mixture of 3Ti:1.5Si:1.2C powders under pressures ranging from 2 to 5 GPa and temperatures of 1150 °C to 1400 °C. At medium and high temperatures (4–5 GPa and 1400 °C), Ti₃SiC₂ dissolves into the cubic TiC phase. SEM analysis revealed that the high-pressure-produced multilayer structure of Ti₃SiC₂ remained intact. The friction properties of Ti₃SiC₂-TiSi_x composites combined with copper and aluminum were studied under both dry and lubricated conditions. After the break-in period, the Ti₃SiC₂-TiSi_x/Al combination exhibited the lowest friction coefficient: approximately 0.2. In dry-sliding conditions, the friction coefficient varies between 0.5 and 0.8. The wear mechanisms for Ti₃SiC₂-TiSi_x composites paired with aluminum primarily involve pear groove wear and adhesive wear during dry friction. Irregularly shaped aluminum balls accumulate in the pear grooves and adhere to each other. With increasing sintering pressure, the average friction coefficient of Ti₃SiC₂-TiSi_x composites against Cu ball pairs first increases and then decreases. The wear rate of the samples did not vary significantly as the sintering pressure increased, whereas the wear rate of Cu balls decreased with increasing sintering pressure. The adhesive wear of the Ti₃SiC₂-TiSi_x composite with its Cu counterpart is stronger than that of the Al counterpart. Abrasive chips of Cu balls appeared in flake form and adhered to the contact interface. Full article

The exploration of unleaded free-cutting Cu40Zn brass with excellent mechanical and tribological properties has always drawn the attention of researchers. Due to its attractive properties combining metals and ceramics, Ti₃AlC₂ was added to Cu40Zn brass using high-energy milling and hot-pressing sintering. The effects of Ti₃AlC₂ on the microstructure, mechanical and tribological properties of Cu40Zn-Ti₃AlC₂ composites were studied. The results showed that Ti₃AlC₂ could suppress the formation of ZnO by adsorbing oxygen impurity and promote the formation of the β phase by releasing the β-forming element Al to the substrate. The hardness and wear resistance of Cu40Zn-Ti₃AlC₂ composites increased with increasing Ti₃AlC₂ content from 0 to 5 wt.%. The proper Ti₃AlC₂ additive was beneficial to both the strength and plasticity of the composites. The underlying mechanisms were discussed. Full article

A study of the combustion processes of Ti/CuO and Ti/CuO/NC nanothermites prepared via electrospraying was conducted in this work. For this purpose, the compositions were thermally conditioned at 350, 550 and 750 °C, as selected based on our initial differential scanning calorimetry-thermogravimetry (DSC/TG) investigations. The tested compositions were analysed for chemical composition and morphology using SEM-EDS, Raman spectroscopy and XRD measurements. Additionally, the thermal behaviour and decomposition kinetics of compositions were explored by means of DSC/TG. The Kissinger and Ozawa methods were applied to the DSC curves to calculate the reaction activation energy. SEM-EDS analyses indicated that sintering accelerated with increasing equivalence ratio and there was a strong effect on the sintering process due to cellulose nitrate (NC) addition. The main combustion reaction was found to start at 420–450 °C, as confirmed by XRD and Raman study of samples annealed at 350 °C and 550 °C. Moreover, increasing the fuel content in the composition led to lower E_a, higher reaction heats and a more violent combustion process. Conversely, the addition of NC had an ambiguous effect on E_a. Finally, a multi-step combustion mechanism was proposed and is to some extent in line with the more general reactive sintering (RS) mechanism. However, unusual mass transfer was observed, i.e., to the fuel core, rather than the opposite, which is typically observed for Al-based nanothermites. Full article

The more effective use of readily available Ce in FeNdB sintered magnets is an important step towards more resource-efficient, sustainable, and cost-effective permanent magnets. These magnets have the potential to bridge the gap between high-performance FeNdB and hard ferrite magnets. However, for higher degrees of cerium substitution (>25%), the magnetic properties deteriorate due to the lower intrinsic magnetic properties of Fe₁₄Ce₂B and the formation of the Laves phase Fe₂Ce in the grain boundaries. In this paper, sintered magnets with the composition Fe70.9-(Ce_xNd_1-x)18.8-B5.8-M4.5 (M = Co, Ti, Al, Ga, and Cu; with Ti, Al, Ga, and Cu less than 2.0 at% in total and Co_bal; x = 0.5 and 0.75) were fabricated and analyzed. It was possible to obtain coercive fields for higher degrees of Ce substitution, which previous commercially available magnets have only shown for significantly lower degrees of Ce substitution. For x = 0.5, coercivity, remanence, and maximum energy product of µ₀H_c = 1.29 T (H_c = 1026 kA/m), J_r = 1.02 T, and (BH)_max = 176.5 kJ/m³ were achieved at room temperature for x = 0.75 µ₀H_c = 0.72 T (H_c = 573 kA/m), J_r = 0.80 T, and (BH)_max = 114.5 kJ/m³, respectively. Full article

TiC bonded diamond composites were prepared from a mixture of Ti, graphite, and diamond powders as raw materials, with Si as sintering additives, through high-temperature and high-pressure (HTHP) technology. The reaction between Ti and graphite under 4.5–5 GPa pressure and 1.7–2.3 kW output power can produce TiC as the main phase. The diamond particles are surrounded by TiC, and the interface is firmly bonded. The coefficient of friction (COF) of TiC–diamond composites with POM and PP balls decreases with increasing load for a specific friction velocity. However, the COF of TiC–diamond composites with agate, Cu and Al balls increases with the rising load because of the enhanced adhesive wear effect. The COF of PP, Cu and Al balls slightly increases with the increase in friction velocity at a certain load. SEM results show that the surface of agate balls has rough, pear-shaped grooves and shallow scratches. The scratches on the surface of POM balls are wrinkled. The PP balls have pear-shaped groove scratches on their wear surfaces. The wear mechanism of TiC–diamond composites with Cu ball pairs is primarily adhesive wear. The abrasion of TiC–diamond composites with Cu ball pairs remains almost unchanged as the load increases. However, the depth and width of the pear-shaped grooves on the wear surface of TiC–diamond composites are significantly increased. This phenomenon may be attributed to the high rotational speed, which helps to remove the residual abrasive debris from the friction grooves. As a result, there is a decrease in both the depth and width of the pear-shaped grooves, leading to a smoother overall surface. The wear mechanism of TiC–diamond composites with Al ball pairs is abrasive wear, which increases with an increasing load. When the load is constant, as the speed increases, the wear morphology of TiC–diamond composites with Al ball pairs transitions from rough to smooth and then back to rough again. This phenomenon may be attributed to the wear mechanism at low speeds being groove wear and adhesive wear. As the speed increases, the wear particles are more easily removed from the wear track, leading to a reduction in abrasiveness. As the speed increases, the wear surface becomes roughened by a combination of grooves and dispersed wear debris. This can be attributed to the increased dynamic interaction between surfaces caused by higher speed, resulting in a combination of abrasive and adhesive wear. In addition, Cu and Al ball wear debris appeared as irregular particles that permeated and adhered to the surface of the TiC phase among the diamond particles. The results suggest that TiC–diamond composites are a very promising friction material. Full article