Wasan Alkaron, Tamás Kolonits, Katalin Balázsi
et al.
New eco-friendly fiber composites were developed by electrospinning cellulose acetate (CA) combined with calcium oxide (CaO) derived from thermally treated waste eggshells. CA solutions were prepared at varying concentrations to optimize the ideal concentration for producing smooth, continuous, and beads-free fibers. Various amounts of CaO were then added to assess its impact on fiber structure, crystallinity, and swelling characteristics.FTIR examinations demonstrated that CaO was effectively integrated without altering the CA structure, however XRD investigations revealed reduction in crystallinity with increasing CaO content. The swelling capacity remarkedly increased to 710% at 4% CaO, attributed to enhanced porosity and hydrophilicity, before showing a slight decline at higher concentrations due to particle aggregation. These results highlight a sustainable method for producing functional CA/CaO composites with tailored properties for promising applications in biomedical and environmental fields. Our further aim is to study the biocompatibility, cytotoxicity and the photocatalytic activity of the prepared composites.
ABSTRACT Nanostructured thermal barrier coatings (TBCs, Cr/CoAlY/8 wt% Y2O3‐ZrO2 ceramic top coatings) were deposited on superni‐718 substrates by the magnetron sputtering method on different process parameters. The effect of magnetron sputtering power on microstructure and mechanical properties of TBC was studied in the present research work. The structural properties of the deposited TBC coatings were characterized by X‐ray diffraction (XRD) and field emission scanning electron microscope (FE‐SEM) and chemical composition of thermal barrier coatings was characterized by energy dispersive X‐ray spectroscopy (EDS). XRD results showed that the coatings deposited at a low power has much more amorphous nature as compared to coatings deposited at a high power has crystalline nature.The XRD analysis revealed the tetragonal phase which is the stable phase in TBC coating, since the temperature is constant in both depositions. Mechanical properties of the TBC coatings were studied by nano indentation. The results revealed that coatings deposited at lower power exhibited 50% increase in hardness values as compared to coating deposited as higher power. Furthermore, coating thickness has enhanced from 957 nm to 1.34 µm thus there has been 28% enhancement in coating thickness in changing process parameters specifically power of magnetron.
High-entropy ceramics have emerged as a research hotspot in the field of ceramics due to their single-crystal structure and excellent physicochemical properties. In this paper, an innovative approach is adopted to synthesize high-entropy nitride ceramics (TiVCrNbZr1-x)Ny. To achieve this, the non-stoichiometric compound TiN0.3 was introduced as a sintering additive and the Spark Plasma Sintering (SPS) technique was employed. By adding TiN0.3, successfully preparing high-entropy nitride ceramics at 1500°C, which introduces vacancy defects that provide additional space for the diffusion and migration of atoms, allowing for more efficient migration and diffusion within the crystal structure, thereby accelerating the sintering process. The (TiVCrNbZr1-x)Ny- xZrO2 samples achieved outstanding mechanical properties when sintered at 1700°C, owing to the mechanisms of solid solution strengthening and second-phase diffusion toughening. Specifically, the samples exhibited a hardness of 25.42 ± 1.58 GPa, a flexural strength of 888 ± 32 MPa, and a fracture toughness of 6.23 ± 0.27 MPa·m1/2. This innovative sintering route provides an efficient method for preparing high-entropy nitride ceramics at relatively low temperatures without sacrificing quality. This approach not only enhances production efficiency but also expands the potential practical applications of these ceramics.
Thermistors with negative temperature coefficient (NTC) of resistivity are important components for temperature sensors and actuators. High material constant (B value) of NTC thermistor, i.e. high-temperature sensitivity, is one of key focuses. Herein, Bi/Mg modified NiO based ceramics for NTC thermistors were prepared by conventional solid-state reaction method. Introduction of Bi2O3 significantly enhances the sintering ability of ceramics and reduces the sintering temperature from 1380 to 1250°C. Mg-doping (i.e. preparation of Ni1-xMgxO ceramics, where x=0, 0.02, 0.05, 0.07 and 0.1) has significant effect on room temperature resistivity (ρ25). Phase composition, microstructure, electrical property and electrical stability were investigated. All prepared ceramics have the phase with rock-salt structure and show typical NTC characteristics with B values higher than 5300K. The electrical stability with an optimized resistance-change rate of 1.02%after being aged at 150°C for 500 h is achieved. The electrical properties of the ceramics were analysed by combining X-ray photoelectron spectra with complex impedance spectra.
Michal Kukielski, Weronika Bulejak, Paulina Wiecinska
et al.
Ceramic-graphene composites had been considered very promising for both their conductivity and superior fracture toughness compared to nonreinforced materials. However, agglomeration of graphene flakes occurring during the shaping process causes the properties of obtained composites to differ from theoretical values. Authors investigate slip casting as the alternative to the granulation and powder metallurgy route. Slip casting as a near-net-shape technique results in fewer steps compared to the standard routes of ceramic-graphene composites preparation. To enable slip casting of such materials stable ceramic-graphene suspensions of low viscosity are required. The influence of dispersing agents on zeta potential and viscosity of obtained suspensions had been investigated. Authors define possible interactions between graphene and alumina powder within suspension and their influence on the properties of suspensions. The composite materials have been well densified by pressureless sintering in a reductive atmosphere. The composites exhibited much higher fracture toughness in comparison to pure alumina samples.
Control of nanomaterial morphology has been investigated to utilize for the desired application. 1D nanomaterials are ideal for various applications because of their excellent carrier transportability and huge specific surface area. Due to their advantages, various methods have been developed to grow in a specific direction. Herein, we introduced a simple synthesis method of freestanding Zinc hydroxidefluoride (ZnOHF) nanobelt as 1D material without seed or substrate using aqueous solutions. The ZnOHF nanobelt was synthesized using zinc fluoride and hexamethylenetetramine (HMT) at 80°C for 3 h. Even though low synthesis temperature, ZnOHF demonstrated good crystallinity and a homogeneous nanobelt structure. The ZnOHF nanobelts were grown over several μm to <010> direction with less than 100 nm width. In addition, the growth direction of the nanobelt was controlled by the concentration of HMT. The width of the nanobelt was broader by a decrease in HMT concentration. It was considered that crystal nucleation and growth of ZnOHF could be influenced by OH− and NH4+ ions generated from HMT decomposition.
This paper investigates the main parameters influencing the plastic behavior of clays used for traditional ceramics production. For this, twenty-six clayey pastes were selected from twelve traditional ceramic plants around the city of Marrakech (Morocco). According to the lithology, six different types of materials are used as raw material in the ceramic industry of this region. Emphasis is placed on the impact of the characteristics of these clayey materials upon the plastic behavior of these clays. The pastes were characterized through their consistency using the Atterberg limits. It has been concluded that the gain size, the mineralogical and the clay mineral composition and content, the effect of diagenesis and the presence of talc-pyrophyllite association play the most important role in the control of the plasticity behavior.
Syed Zaighum Abbas Bukhari, Jang-Hoon Ha, Jongman Lee
et al.
Oxidation bonding is a technique used to produce porous SiC ceramics at low temperatures. The oxidation behavior of SiC particles depends on various factors, including the oxidation environment, temperature, time, particle size, and impurities. The key properties required for a porous ceramic membrane are a controlled pore morphology, high strength, and high permeability. In this study, SiC powders with different particle sizes (0.55 and 7 μm) were used to fabricate porous ceramic membranes. First, the oxidation behavior of the SiC powders was evaluated. Then, the feasibility of using their mixture to create supports for microfiltration applications was analyzed. Through this study, not only were the ideal conditions for fabricating microfiltration supports quantified but also the conditions where specimens could be made with zero size change. Finally, a membrane fabricated from a powder mixture composed of 92% of the 7 μm powder and 8% of the 0.55 μm powder and sintered at 1450°C was proposed, which had a 37% porosity, 1.42 μm pore size, 49.6 MPa flexural strength, and L cm-2 min-1 bar-1 air permeability.
Christian Bechteler, Achim Rübling, Ralf Girmscheid
et al.
Abstract A process for the production of carbon nanotube (CNT)/alumina composites on the basis of an aqueous suspension and without any extensive pretreatment was developed. Pressureless sintering and hot‐pressing of the nanocomposites were extensively researched and optimized. The influence of varying CNT contents, different alumina powders, sintering temperature and pressure on mechanical properties were investigated. Optimal hot‐pressing conditions are specified at 1550°C, 15 min dwell time, and 80 MPa applied pressure. Dense nanocomposites up to 3 wt.% and 0.5 wt.% CNT content were achieved by hot‐pressing and pressureless sintering, respectively. Furthermore, a 20% increase in hardness for CNT contents below 1.0 wt.% was detected, which is independent from the applied force and the alumina matrix. A highly anisotropic fracture toughness at increased CNT contents was detected by an indentation‐based method. The developed process provides a possibility to produce CNT/alumina composites with improved mechanical properties under reasonable effort, which could also be used for industrial production.
Glassy materials can be broadly defined as any amorphous solid, which are important in nature and have significant societal value for their applications in daily life and industry. Although many methods have been applied, the fracture toughness of traditional glasses is still very low due to intrinsic brittleness, significantly limiting their use for structural applications. While nanoelements may be added into glasses and ceramics to form nanocomposites with enhanced properties, it is extremely difficult to distribute and disperse them inside the liquid glass/ceramic matrix with traditional processing methods. It is shown that a strong and tough glass can be fabricated through a direct‐solidification process using a nanoparticle self‐dispersion mechanism in a glass melt (2MgO·2Al2O3·5SiO2) with the assistance of B2O3, delivering a 6.1% strain limit and strength up to E/14 (E is elastic modulus), which is close to the theoretical limit of E/10 and one of the highest among all materials reported so far. The fracture toughness of the glass with 30 vol% SiC nanoparticles is significantly higher than any other inorganic glass tested under similar conditions. This new method opens up remarkable opportunities for glass and ceramic research, manufacturing, and applications.
Glass is one of the oldest human-made materials, it is produced in many forms and, theoretically, it is a 100 % recyclable material. There are many ways how to successfully recycle waste glass and the reuse of waste glass as an additive for traditional ceramics has also been studied extensively. Illitic clay (80 mass% of illite, 4 mass% of montmorillonite, 4 mass% of orthoclase, and 12 mass% of quartz) and kaolin (92 mass% of kaolinite, 6 mass% of muscovite, and 2 mass% of quartz) with addition of waste glass (car windshield glass) were studied using thermal analyses – differential thermal analysis (DTA), thermogravimetry (TG), and thermodilatometry (DIL). The presence of the waste glass was observable on the DIL and TG curves where an increase of overall shrinkage and a decrease in mass loss with an increasing amount of waste glass was observed, respectively.
Rafael Ribeiro Silveira, Christian Louter, Tillmann Klein
Chemically strengthened thin glass (t < 2 mm) is a material that is stronger and due to its small thickness, more flexible than conventional window glass. As such, thin glass offers the possibility for lightweight and flexible glass façades that could change shape depending on external conditions. This paper explores this concept and presents an MSc study on the use of this material in adaptive façade panels. The behavior of thin glass in this context depends on different factors. The glass thickness and strength define its bending limits, while the desired geometry and movement affect its overall stiffness and visual outcome. In order to integrate these factors, different configurations of panels were analyzed in numerical models. These analyses showed the importance of understanding the desired movement and geometry in order to correctly define the supports and degrees of freedom of the panel, avoiding stress concentration (particularly on the edges) and allowing for an unobstructed movement of the panel. The development of these analyses resulted in the conception of a design example of an adaptive façade panel, taking into consideration the design requirements developed in the research. Finally, as a proof of concept, a mock-up was built simulating the behavior of the design example developed in this research. Although there is still the need for research to be developed so that thin glass can become a building material, this research showed that this is possible and that interesting results, regarding visual effect, ventilation and dead load reduction (in larger scale, an environmental impact reduction is also possible) can be achieved. Besides that, using thin glass in adaptive panels challenges the concept of glass as a static material, opening new possibilities for its use.
The purpose of this paper, as part of a MSc graduation project, has been to explore to which extent the kinematic potential of folded geometries can benefit from the structural and architectural properties of glass plates. Using as a case study the covering in an adjustable way an outdoor swimming pool area, the course of this paper consists of form evolution based on structural performance and development of a dual purpose connection and deployment principle developed through experimental testing. Both aspects are examined independently, in parallel processes, and the findings are combined and further evaluated. This study has shown that it is possible to create a self-supporting structure made out of plate elements which is also directionally deployable, without compromising the system’s stability and thus provides an important beginning to implementing complex structures that make use of the benefits of glass.