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Topic Review
Zirconia-Based Ceramics Reinforced by Carbon Nanotubes
The use of CNTs (carbon nanotubes) as a secondary phase in a zirconia matrix is motivated by their outstanding crack self-healing ability, the possibility to tailor the desired nano-structural properties, and their exceptional wear behavior. Therefore, a detailed investigation into CNT features has been provided. The debate of using the different Vickers indentation fracture toughness equations to estimate the resistance of crack propagation was critically reviewed according to crack characteristics.
  • 722
  • 16 Aug 2023
Topic Review
Room Temperature Gas Sensors Based on 2D MXenes
Owing to their large surface area, two-dimensional (2D) semiconducting nanomaterials have been extensively studied for gas-sensing applications in recent years. In particular, the possibility of operating at room temperature (RT) is desirable for 2D gas sensors because it significantly reduces the power consumption of the sensing device. Furthermore, RT gas sensors are among the first choices for the development of flexible and wearable devices.
  • 667
  • 18 Dec 2023
Topic Review
Fine-Grained YSZ–NiO(Ni) Anode Material
Reduction–oxidation (redox) cycling of a solid oxide fuel cell (SOFC) due to leakage of a fuel or standby and shutdown cycling is an issue that has attracted the attention of many research groups for a long time. The researchers mainly note the harmful effects of redox cycling on the microstructure of SOFC constituents and search for ways to mitigate or diminish them.
  • 489
  • 10 Jul 2023
Topic Review Peer Reviewed
From Fundamentals to Industrial Prospects: Ion-Imprinted Polymers for Metal Ion Separation
Ion-imprinted polymers (IIPs) are advanced adsorbents featuring selective recognition cavities for targeted metal ion capture, offering a promising route to high-efficiency separation in extractive metallurgy. In the present work, the evolution, design principles, synthesis strategies, separation mechanisms, and practical applicability of IIPs for metal recovery from complex aqueous matrices are overviewed. Key material components, including functional monomers, crosslinkers, template ions, initiators, solvents, and support materials, are discussed in relation to adsorption capacity, selectivity, kinetics, stability, and recyclability. Major preparation routes, such as surface imprinting, bulk polymerization, in situ polymerization, and sol–gel methods, are critically compared to clarify their advantages and limitations. Recent applications for base metals, precious metals, and rare-earth elements demonstrate that IIPs can achieve high specificity and rapid equilibrium under optimized conditions. However, their translation from simulated solutions to real leachates remains constrained by interfering ions, organic contaminants, mass transfer resistance, incomplete template removal, and matrix complexity. Mitigation strategies, including sample pretreatment, improved polymer architecture, and hybrid supports, are therefore emphasized. Additionally, chemometric modelling, machine learning, or artificial intelligence-assisted design may be implemented to advance the prospects of IIPs in industry. Conclusively, IIPs represent a strong separation platform, yet industrial deployment requires robust validation with real feed streams and scalable regeneration protocols during column operation, as well as under chemically aggressive conditions at scale.
  • 100
  • 06 Aug 2026
Topic Review Peer Reviewed
Towards High-Strength Transparent Glass-Ceramics: Processing, Microstructure, and Applications
Glass-ceramics are inorganic, non-metallic materials obtained by controlled crystallization of glasses through different processing routes; they contain at least one functional crystalline phase together with a residual glass, and the crystallized fraction may range from trace levels to nearly complete crystallization. Transparent glass-ceramics (TGCs) constitute the optically transparent subset of this class and combine a controlled crystalline microstructure with a residual amorphous matrix. Their transparency distinguishes them from conventional opaque glass-ceramics and is achieved by minimizing light scattering through careful control of crystallite size, volume fraction, spatial distribution, and refractive-index mismatch between the crystalline and glassy phases. Unlike conventional sintered ceramics, TGCs retain many of the processing advantages of glass while incorporating crystalline phases that can enhance mechanical, thermal, optical, or functional properties. Depending on their composition and microstructure, TGCs may exhibit improved hardness, fracture toughness, thermal stability, chemical durability, luminescence, nonlinear optical response, or ion-exchange strengthening capability. These features make TGCs attractive for applications requiring both optical clarity and advanced performance, including protective cover glass, transparent armour, precision optical substrates, laser and photonic components, optical sensors, and multifunctional host materials for rare-earth ions and nanoparticles.
  • 38
  • 17 Sep 2026
Topic Review
Chalcogenide Glasses
Chalcogenide glasses are a family of non-oxide amorphous solids formed from one or more chalcogen elements—sulfur, selenium, or tellurium—combined with network-forming elements such as germanium, arsenic, silicon, or antimony, and with modifier elements, so that the material lacks long-range crystalline order [1]. Because the constituent atoms are heavier and more polarizable than those of silica, these glasses possess a high refractive index and a broad optical transmission window extending into the mid-infrared, well beyond the transparent range of silicate glasses. Their structure is a covalent, disordered network in which the average coordination number and the connectivity of the chalcogen chains determine glass-forming ability, thermal stability, and properties such as the glass transition temperature. The glasses also exhibit pronounced infrared transparency, high nonlinear optical response, and photosensitivity, in which illumination can induce structural or refractive changes. The material is therefore defined as an amorphous, covalently bonded infrared-transmitting chalcogen network rather than an oxide glass [2]. Their behavior is governed by the chemical bonding and rigidity of the disordered chalcogen network [3].
  • 22
  • 26 Sep 2026
Topic Review
Hydrothermal Synthesis
Chemical transformations carried out in water (or a water-rich fluid) above ambient temperature under the autogenous pressure of the closed vessel constitute hydrothermal synthesis. The solvent is superheated water, whose decreased permittivity, altered ion product, and enhanced solubility of inorganic species enable dissolution–reprecipitation and crystallization pathways that are inaccessible in open aqueous solution. Hydrothermal crystallization is the defining industrial and laboratory route to many zeolites, in which aluminosilicate gels reorganize into microporous frameworks [1]. Controlled hydrothermal growth produces ZnO nanorods with a defined diameter regime [2]. Selective control of hydrothermal conditions can also determine whether α- or β-MnO2 single-crystal nanowires form [3]. The concept is a synthetic method specified by the aqueous, high-temperature, closed-system medium, not by a single product class: molecular organic reactions, carbonized polymer dots, and inorganic crystals can all be formed hydrothermally. Solvothermal synthesis is the analogue in nonaqueous solvents. Ambient-pressure aqueous precipitation and dry solid-state calcination lie outside the term.
  • 13
  • 19 Oct 2026
Topic Review
Ceramic Sintering
Ceramic sintering is a thermal consolidation process in which a compacted, porous green body of ceramic powder is heated to a temperature below the melting point of its principal constituent, causing the particles to bond together and the body to densify through the motion of atoms rather than by bulk fusion [1]. At the sintering temperature, solid-state diffusion, viscous flow of a transient liquid phase, evaporation–condensation, and grain-boundary transport operate to reduce the total solid–vapor interfacial area: material is transported from particle contacts to fill the interparticle pores, necks grow between adjacent grains, and the porosity shrinks and eventually becomes isolated. Because densification and grain growth proceed simultaneously, the final microstructure—grain size, pore size, and residual porosity—is determined by the balance between the driving force for shrinkage, which scales with surface energy, and grain-boundary mobility [2]. The process is governed by powder particle size, packing homogeneity, temperature, time, atmosphere, and the presence of sintering additives that form a transient liquid phase. Sintering is therefore defined as the heat-induced, diffusional bonding and densification of a particulate ceramic compact in the solid state or with a minor liquid phase, distinct from melting and casting [3].
  • 13
  • 26 Sep 2026
Topic Review
Transparent Ceramics
Transparent ceramics are polycrystalline inorganic bodies that transmit light in the visible or the infrared, made possible by reducing the residual porosity to a level where scattering becomes negligible. Pores are the dominant scatterer because their refractive index differs sharply from that of the grains, so the processing target is full densification without grain growth, and pressure-assisted sintering is the route most taken to reach it [1]. Hot isostatic pressing after sintering closes the remaining closed porosity, and the order in which the two steps are applied changes both the trajectory and the final in-line transmittance [2]. Reactive sintering from mixed powders, followed by a short hold, is an alternative that avoids a separate calcination [3]. The optical and the mechanical properties do not improve together: the conditions that give the highest transmittance are not those that give the highest strength, and in laminated bodies the two are often traded against each other deliberately [4]. The same approach extends to infrared-transmitting chalcogenide hosts [5]. Grain-boundary phases and dopant segregation, rather than porosity, then set the remaining loss.
  • 9
  • 08 Oct 2026
Topic Review
Constitutive Modeling
Constitutive modeling is the formulation of the relation between stress and strain, or between flux and driving force, that closes a boundary-value problem. In crystal plasticity the constitutive law, the kinematics, and the homogenisation scheme have to be chosen together, and the three are reviewed as one subject [1]. Shape memory alloys need a law that carries the transformation strain as well as the plastic strain into the finite element solution [2]. Cyclic crack propagation in concrete is modelled with a scaled boundary formulation coupled to a cohesive law [3]. Confinement of non-circular columns by fibre-reinforced polymer is treated with an evolutionary potential law [4]. Indentation-induced superelasticity is reproduced with a three-dimensional law of the same class [5].
  • 8
  • 14 Oct 2026
Topic Review
Aluminum Nitride
Aluminum nitride is a covalently bonded III-V compound that combines high thermal conductivity with high electrical resistivity, and it is attractive where heat must be removed from a component that has to stay electrically insulated. The intrinsic lattice conductivity is high, and measurements on dense material established the baseline values against which later work is judged [1]; turning that into a commercial ceramic required control of the oxygen dissolved in the lattice, because the aluminium vacancies it creates scatter phonons and dominate the thermal resistance of a sintered body [2]. Oxide additions are what allow densification at practical temperatures, and they act by reacting with that dissolved oxygen to form an aluminate phase that removes the impurity from the grains, calcium oxide being the addition whose effect has been quantified most directly [3]. The residual grain-boundary film then sets both the thermal and the mechanical behaviour, so low-temperature routes are tuned to balance conductivity against strength [4]. Shaping by vat photopolymerisation is being developed for integrated packaging [5]. Bonding the ceramic to a metal substrate without introducing a thermal barrier remains the difficult step.
  • 7
  • 23 Sep 2026
Topic Review
Gallium Oxide
Gallium oxide is a wide-bandgap oxide semiconductor, the monoclinic beta polymorph being the stable form and the one developed for power electronics and solar-blind ultraviolet detection. Its bandgap near 4.8 electronvolts gives a critical breakdown field several times that of silicon or silicon carbide, which translates into a much lower on-resistance for a given blocking voltage, and the transparency that follows from the same wide gap is what makes the material attractive for detectors that must ignore visible light. Large single crystals can be grown from the melt by methods established for other oxides, which distinguishes it from gallium nitride and is one reason the material moved quickly from laboratory to device work [1]. Progress has not been uniform across the polymorphs, and the metastable phases present different opportunities and different problems [2]. Field-effect transistors on single-crystal substrates were demonstrated early and set the baseline for the technology [3]. Heterojunctions with a p-type oxide, nickel oxide among them, address the lack of usable p-type conduction [4], and the wide gap has been exploited in electromechanical transducers for dual-modality detection [5]. The absence of shallow p-type doping and the low thermal conductivity of the material remain the main obstacles.
  • 7
  • 24 Sep 2026
Topic Review
Ceramic-Metal Joining
Ceramic-metal joining denotes the set of processes by which a monolithic ceramic or ceramic component is bonded to a metal or alloy component to produce a single, load-bearing assembly that combines the high-temperature strength, hardness, and chemical stability of the ceramic with the ductility and toughness of the metal [1]. The central scientific difficulty is that the two materials are chemically and thermally mismatched: the ceramic is generally non-wetting to conventional molten braze alloys, and its lower coefficient of thermal expansion generates residual stress on cooling from the joining temperature. This is overcome by active metal brazing, in which a reactive element—most commonly titanium, zirconium, or hafnium—is alloyed into an Ag–Cu or Au–Ni filler so that it segregates to the ceramic interface and chemically reduces or reacts with the ceramic surface, forming a thin reaction layer of oxides, nitrides, or carbides that permits wetting and metallurgical adhesion [2]. Diffusion bonding, brazing through a prior metallized layer, and interlayer insertion are alternative routes that control the interfacial reaction and redistribute thermal stress. The resulting joint is therefore defined by an engineered interfacial reaction zone between the ceramic and the filler rather than by simple fusion welding [3].
  • 7
  • 28 Sep 2026
Topic Review
Sintering Temperature
Sintering temperature is the temperature at which a powder compact is held so that the necks between particles grow and the pore network closes. Densification and coarsening compete, and raising the temperature accelerates both, so the hottest treatment rarely gives the finest microstructure; in a field-assisted process the temperature also fixes phase composition and defect chemistry, and a nitrogen-containing ceramic can lose nitrogen as the temperature rises [1]. The usual way to lower the required temperature is to add a sintering aid that forms a transient liquid, the liquid providing a fast transport path while most of the solid stays undissolved [2]; activated and plasma-assisted routes push densification to lower temperatures by the same logic combined with an enhanced driving force [3]. Under the pressure applied in field-assisted sintering, part of the densification occurs by creep rather than by diffusion alone, so the mechanism depends on stress and temperature together [4]. The practical window is bounded from below by incomplete densification and from above by exaggerated grain growth, loss of a volatile constituent and reaction with the die, and hardness and thermal conductivity track the density reached within that window [5].
  • 4
  • 08 Oct 2026
Topic Review
Ion Conductivity
Ion conductivity is the ability of a medium to carry current by the migration of ions, expressed as current density per unit applied field [1]. The value is the sum over species of charge, concentration and mobility, so it depends both on how many mobile ions exist and on how freely they move [2]. In a crystalline solid electrolyte the ions hop between lattice sites or through an amorphous phase, and the activation energy of the hop sets the temperature dependence [1]. In a polymer electrolyte the motion couples to segmental relaxation of the chains above the glass transition, so conductivity follows free volume rather than a simple Arrhenius law [3]. The quantity is measured by impedance spectroscopy, which separates the bulk response from electrode polarisation [2].
  • 2
  • 06 Nov 2026
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