Browse Topic: Ceramics
For brake and clutch components of aircraft vehicles which require higher mechanical strength and wear resilient, light-weight aluminium composites were developed infusing solid lubricant. In this study, hybrid composites were developed using powder metallurgy route with aluminum alloy AA356 and various amounts of zirconium oxide (ZrO2) (0, 5, 10, 15, and 20 wt.%) as reinforcements. A solid lubricant hexagonal boron nitride (hBN) at a fixed 5 wt.% is considered. Following the appropriate ASTM guidelines, the specimens were mechanically characterized by measuring their density, porosity, micro-hardness, compression strength, impact strength, and flexural strength, among other properties. The findings showed that the composites' mechanical and physical behaviour were greatly affected by the inclusion of ZrO2. Porosity increased as a result of particle clustering and interfacial voids, while density increased gradually as ceramic content increased. Consistently increasing ZrO2 addition led to micro-hardness improvements; at 20 wt.% reinforcement, values reached their maximum, indicating that the hard ceramic phase contributed to better surface resistance. The best balance between particle reinforcement and matrix continuity was suggested by the compression and flexural strengths peaking at 15 wt.% ZrO2. However, when the addition was raised to 20 wt.%, brittleness and porosity began to marginally deteriorate. Unreinforced and lower ZrO2 composites had superior toughness in impact, whereas materials with a higher content had a poorer energy absorption capacity. The 5 wt.% hBN improved fracture arresting capabilities and helped load transmission over the interface. Inclusion of hBN provides solid-lubricating tribofilm formation that enhances the tribological performance. This study reveals that AA356/ZrO2-hBN hybrid composites have good hardness and compressive strength improvements, with 15 wt.% ZrO2 being the best composition with good strength, toughness, and wear resistance.
Hybrid bearings, which pair traditional bearing-steel raceways with ceramic rolling elements, can offer improved performance over full-metal bearings, particularly in aerospace applications. Because rolling-element bearings are critical components, effective condition monitoring is essential to prevent in-flight failures and support proactive maintenance strategies. Wear-debris monitoring is widely used in these applications to detect and diagnose bearing fault modes. To compare degradation behavior and monitoring signatures, bearing life tests were conducted on hybrid and full-metal bearings under matched Hertzian stress conditions. The results showed that differences in degradation curves between the two bearing types were small relative to the overall variability in bearing life. Additionally, hybrid bearings that develop rolling-element pitting were observed to progress toward raceway spall formation. This paper was presented at ERF Forum 51 but has been updated with new findings addressing questions over the effect of impact energy on the degradation rate between hybrid and full-metal bearings.
Certain materials — such as quartz, some ceramics, and even bone — produce an electrical charge when they are squeezed, pressed, or vibrated. This is piezoelectricity, which comes from the Greek “piezein” meaning to press. Modern vehicles rely on piezo components in fuel injectors, parking sensors, airbag systems, and other functions.
Researchers have pioneered a 3D printing method that grows metals and ceramics inside a water-based gel, resulting in exceptionally dense, yet intricate constructions for next-generation biomedical technologies.
Researchers have demonstrated a new technique that uses lasers to create ceramics that can withstand ultra-high temperatures, with applications ranging from nuclear power technologies to spacecraft and jet exhaust systems. North Carolina State University, Raleigh, NC A new technique that leverages the concept of sintering, can be used to create ceramic coatings, tiles or complex three-dimensional structures, which allows for increased versatility when engineering new devices and technologies. “Sintering is the process by which raw materials - either powders or liquids - are converted into a ceramic material,” says Cheryl Xu, co-corresponding author of a paper on this research and a Professor of Mechanical and Aerospace Engineering at North Carolina State University (NCSU). “For this work, we focused on an ultrahigh temperature ceramic called hafnium carbide (HfC). Traditionally, sintering HfC requires placing the raw materials in a furnace that can reach temperatures of at least 2,200 degrees Celsius - a process that is time-consuming and energy intensive.
A new technique that leverages the concept of sintering, can be used to create ceramic coatings, tiles or complex three-dimensional structures, which allows for increased versatility when engineering new devices and technologies.
This specification, in conjunction with the general requirements for peening media covered in AMS2431, establishes the requirements for the procurement of ceria-zirconia ceramic shot.
Researchers are developing soft sensor materials based on ceramics. Such sensors can feel temperature, strain, pressure, or humidity, for instance, which makes them interesting for use in medicine, but also in the field of soft robotics.
This specification, in conjunction with the general requirements for peening media covered in AMS2431, establishes the requirements for the procurement of yttria-zirconia ceramic shot.
The phenomenon of drop-wall interaction plays a crucial role in a wide range of industrial applications. When liquid droplets come into contact with a high-temperature surface, it can lead to thermal shock due to rapid temperature fluctuations. This abrupt temperature change can generate thermal stress within the solid wall material. If the thermal stress exceeds the material's strength in that specific stress mode, it can result in material failure. Therefore, it is imperative to delve into the evolving temperature patterns on high-temperature surfaces to optimize material durability. This study focuses on investigating drop-wall interactions within the context of engine environments. To achieve this, the Smoothed Particle Hydrodynamics (SPH) method is employed to simulate the impact of fuel droplets on a silicon nitride wall. The goal is to understand the heat transfer mechanisms, thermal penetration depths, and temperature distributions within the heated wall. Furthermore, this research explores the performance of ceramic materials, specifically silicon nitride, in terms of thermal stress. Thermal stress calculations are derived from temperature gradients and material properties. Results show that the silicon nitride glow plug can operate for infinite engine cycles if it is run under the relevant engine conditions.
Additive manufacturing enables unrivaled design freedom and flexible fabrication of components from a wide range of materials including metals, composites, polymers, and ceramics. The near net shape parts are made by processes like sequential melting or layer-by-layer material deposition with a complex set of processing variables. The sequential nature of the process means that every step can impact the next and thus, tools to evaluate that risk before and during manufacturing are necessary.
In this study, we have investigated the microstructural characteristics, the mechanical properties, and the dry sliding wear behavior of a ceramic coating consisting of zirconia (ZrO2) and alumina (Al2O3) deposited by flame spraying. A series of wear tests were carried out under a variety of loads and at two different sliding speeds. The evaluation included an examination of the coating microstructure, microhardness, coefficient of friction (COF), and wear resistance of the flame-sprayed coating. The results showed that the coatings had a perfectly structured micro-architecture and were metallurgically bonded to the substrate. The Al2O3 coating exhibited a fine granular structure with pores and oxides. The microstructure of Al2O3-10 wt.% ZrO2, on the other hand, showed a blocky structure with a uniform distribution of ZrO2 inclusions in the composite coating. X-ray diffraction (XDR) results showed that the phases in both coatings were predominantly α-Al2O3 with a minor presence of γ-Al2O3. However, in addition to residual ZrO2 in the tetragonal phase, the ZrO2-Al2O3 coating showed a predominance of ZrO2 in the monoclinic structure. To elucidate the intricacies of the wear mechanism and the characteristics of the wear debris, a comprehensive analysis of the wear performance of flame-sprayed ceramic coatings was carried out.
Billions of people around the world lack access to clean, drinkable water. A research team led by engineers at The University of Texas at Austin has developed a new water filtration system using locally sourced materials for members of the Navajo Nation in the Southwest.
Many of today’s high-performance technologies — nuclear reactors, spacecraft, concentrated solar plants, and hydrogen cells — require advanced materials. Advanced means they are made of metals and ceramics that can withstand extreme conditions or meet exacting specifications.
Photonics, the science and technology of light, relies on optical components that affect light transmission in very specialized ways. To achieve the precision required, the optical components must be precisely ground from standard forms of glass, ceramics, or other materials to exceedingly tight tolerances, in many cases with extreme levels of flatness and parallelism.
The impetus for advancing brittle ceramic materials used for armor applications has been identified as both an increased mass efficiency for greater weight reduction and enhanced performance against ballistic threats through manipulating the physics of failure.
This research developed and utilized advanced processing, modeling, and micromechanical tools to discover and demonstrate hierarchically structured diamond-based composites with exceptional mechanical and ballistic behavior. Understanding how nanoscale and mesoscale microstructural features in diamond–silicon carbide (SiC) composites influenced the physics of failure was critical in uncovering ways to improve performance for soldier protection and discover potential defeat mechanisms.
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