Glass-ceramic Composites Research Articles

Techniques for the restorative management of localized and generalized tooth wear

This narrative review describes techniques and materials available to restore the worn dentition. Emphasis is given to application of composite resin as this material can be bonded to worn surfaces and is easily adjusted either within an existing or at an increased vertical dimension. The relevance of the differences in the composition of glass ceramics and polycrystalline ceramics for restoration in various wear scenarios are discussed. Removable dentures are still appropriate in certain circumstances, but require an understanding of their limitations. CPD/Clinical Relevance: Young and old patients with a range of aetiologies and presentations expect dentists to know how best to restore their disordered, worn dentition.

Microstructure and mechanical properties of an experimental lithium disilicate dental glass-ceramic

After testing over 50 experimental lithium disilicate (LS2)-based glass-ceramic (GC) compositions and evaluating their glass-forming ability and the effect of various heat treatments on their crystallized fraction, crystal size, and morphology, a particularly promising formulation was selected for the optimization of the mechanical properties of materials. The specimens were divided into groups submitted to a nucleation heat treatment at different times and temperatures, i.e., T1 (500 °C/90′), T2 (500 °C/180′), T3 (500 °C/360′) and T4 (480 °C/360′), followed by a crystal growth treatment to induce the lithium metasilicate (700 °C) and LS2 (840 °C) phases. However, a third (minor) phase, lithium phosphate, also precipitated. IPS e.max CAD was used as the control group (C, 500 °C/360′). The elastic modulus (E) was measured by the impulse excitation technique (ASTM E 1876-15), while the Vickers hardness (HV) and biaxial flexural strength (BFS) were determined by indentation and the piston-on-three balls test (ISO 6872), respectively. The E and HV results were analyzed by ANOVA one-way with Games–Howell post-hoc test, whereas the BFS data were investigated by Kruskal-Wallis with Dunn's post-hoc test (α = 0.05). The E of all GCs were within the expected range for commercial LS2 glass-ceramics. The T2 and T4 GCs exhibited the best properties when compared to the C group, and despite their relatively small crystallized fraction (∼57 %), they showed a hardness of 5.8 ± 0.2 GPa, a value that is adequate and statistically equal to that of the control group. The same groups reached BFS values of 359 ± 89 MPa and 493 ± 147 MPa, respectively, which are also statistically equal to that of the C group (338 ± 61 MPa). The mechanical properties of the material studied was successfully optimized through variations in the nucleation temperature and time, reaching values comparable to (but not better than) commercial dental glass-ceramics.

Glass-Ceramic Na3+x[(Zr/Cr)x(Sc/Ti)2-x(PO4)3 Electrolyte Materials for Na-Ion Full-Cell Application

Na3+x[(Zr/Cr)x(Sc/Ti)2-x(PO4)3] glass-ceramic material compositions containing NASICON-type crystalline phases might be a good candidate as an efficient electrolyte exclusively for Na-ion batteries. All-solid-state Na-ion full cells are designed with the three-layered pellets (NaCo0.7(VO)0.3PO4/Na3.5Zr0.5Sc1.5(PO4)3 (NZSP) and Na3.5Cr0.5Ti1.5(PO4)3) (NCTP)/Na-metal foil). The electrical conductivity of the NZSPglass-ceramic powder sample achieves to be highest (9.47 × 10−04 S/cm) due to its lower grain boundary resistance (R gb) as observed in SEM images and also exhibits best electrochemical stability against conductivity when the samples kept in ambient air for 60 d. The charge/discharge capacities for the initial cycle are 75/69 and 60/53 mAhg−1 to both NZSP and NCTP of two full cells, respectively. However, discharge capacities are boosted up for both these cells without much loss in coulombic efficiency even after 10 cycles.

Improvement in dielectric properties and energy storage performance of barium strontium niobate glass ceramics by Sm2O3 addition

High power density and high energy density glass ceramics have important applications in the field of miniaturized, lightweight and integrated pulsed power devices. Barium strontium niobate glass ceramics with different additive amount of Sm2O3 were successfully prepared. The effects of different additions of Sm2O3 on the phase composition, dielectric properties, breakdown strength, interfacial polarizations and energy storage properties of glass ceramics were investigated. The results of phase structure show that Ba0.5Sr0.5Nb2O6 of tungsten bronze structure and BaAl2Si2O8 two phases are precipitated from the glass matrix. The optimum Sm2O3 addition can increase the Ba0.5Sr0.5Nb2O6 phase content of tungsten bronze structure in the glass ceramics, thus increasing the dielectric constant of strontium barium niobate glass ceramics. A moderate amount of Sm2O3 addition improves the microstructure of the barium strontium niobate glass ceramics and reduces the interfacial activation energy of the glass ceramics, thus increasing the breakdown strength of the glass ceramics. For 3 mol% Sm2O3 addition, the breakdown strength of the glass ceramics reaches 1590 kV/cm with a corresponding dielectric constant of 98.4 and a maximum energy storage density of 12.44 J/cm3, which is 2.62 times higher than that of the barium strontium niobate glass ceramics without Sm2O3 addition. It is concluded that the increased energy density of glass ceramics can be attributed to the fact that the appropriate additive amount of Sm2O3 (1–3 mol%) increases the crystallinity of the glass ceramics and at the same time reduces the interfacial activation energy of the glass ceramics, thus increasing the dielectric properties of the glass ceramics with respect to the breakdown strength.

Zirconolite Matrices for the Immobilization of REE–Actinide Wastes

The structural and chemical properties of zirconolite (ideally CaZrTi2O7) as a host phase for separated REE–actinide-rich wastes are considered. Detailed analysis of both natural and synthetic zirconolite-structured phases confirms that a selection of zirconolite polytype structures may be obtained, determined by the provenance, crystal chemistry, and/or synthesis route. The production of zirconolite ceramic and glass–ceramic composites at an industrial scale appears most feasible by cold pressing and sintering (CPS), pressure-assisted sintering techniques such as hot isostatic pressing (HIP), or a melt crystallization route. Moreover, we discuss the synthesis of zirconolite glass ceramics by the crystallization of B–Si–Ca–Zr–Ti glasses containing actinides in conditions of increased temperatures relevant to deep borehole disposal (DBD).

LTCC glass-ceramics based on diopside/cordierite/Al2O3 for ultra-high frequency applications

In this work, three glass-ceramic composites based on a commercial SiO2-B2O3-Al2O3-CaO-MgO glass and cordierite, diopside or Al2O3 were used for preparation of green tapes and low temperature cofired ceramics (LTCC) substrates. The thermal behavior, phase composition, microstructure and dielectric properties of the fabricated glass-ceramics were characterized using a heating microscope, thermal analysis, X-ray diffraction, scanning electron microscopy and time domain spectroscopy. The applicability of the developed materials for LTCC technology was demonstrated by the preparation of test multilayer substrates. The glass-ceramic substrates exhibit advantageous properties for ultra-high frequency LTCC applications, including low sintering temperatures of 900-980°C, good compatibility with commercial Ag and AgPd conductive pastes and a low dielectric permittivity of 3.5-7 at 1 THz.

Al-26 and O-18 tracer diffusion in a titania-coated sodium aluminosilicate glass

Although TiO2 is a common nucleating agent in the production of aluminosilicate glass-ceramics, its role as a catalyst for the nucleation of the functional crystal remains unclear. Therefore, the Ti, Al and O mobility was studied in situ using 26Al and 18O tracer diffusion and Ti chemical diffusion experiments in an aluminosilicate melt of albite composition. The albite glass serves as a surrogate for lithium and magnesium aluminosilicate glass-ceramic compositions, as it allows to study atomic mobilities free of crystallisation artefacts. The depth profiles showed that Al mobility increased significantly and became comparable to that of oxygen when Ti simultaneously diffused into the glass. In the absence of Ti, the diffusivity of Al was two orders of magnitude lower than that of oxygen. The co-diffusion coefficients of Ti and Al seem to confirm a proposed preferential structural linkage between Al and Ti species in the network structure of aluminosilicate melts.

Ultrasound‐Induced Luminescence from Cr3+‐Doped ZnGa2O4 Glass–Ceramic Composites

An intense ultrasound‐induced luminescence (USL) from Cr3+‐activated glass–ceramic composites, obtained by direct precipitation of nanoscale ZnGa2O4 from silicate melts upon cooling, is reported. The USL band overlaps with the first near‐infrared transmission window of biological tissue and spans further into the visible red spectral range, generating interest for visible data encryption and labeling as well as for photophysical stimulation with a remote, non‐optical energy source. Time‐resolved observations of luminescence build‐up and decay, US heating, and persistent luminescence reveal thermal de‐trapping as the origin of the observed US sensitivity. The spectroscopic performance is very similar to that of phase‐pure ZnGa2O4, the fabrication process leads to a robust, dense, and biocompatible composite without requiring secondary encapsulation.

Effect of Temperature–Time Parameters on the Structure and Properties of Glass–Ceramic Composites Based on Molybdenum Disilicide

Composite materials based on molybdenum disilicide, boron and aluminum oxide were obtained by heat treatment of mixtures of initial components in the form of finely dispersed powders in air. In the course of chemical reactions, a glass-forming melt is formed, which encapsulates the initial powder particles, which provides increased heat resistance of the composite material. The effect of temperature–time parameters on the phase composition and microstructure of glass–ceramic composites has been determined.

One-Step Crystallization of Gahnite Glass-Ceramics in a Wide Thermal Gradient

The glass crystallization regime plays a crucial role in the fabrication of glass ceramics: it affects both phase composition and microstructure, and thus the properties of the final product. In the search for new glass-ceramic materials, the development of a proper heat-treatment schedule involves the utilization of numerous glass samples that need to be thermally treated and then investigated to determine the values of the target characteristics. In this study, we evaluated the effect of crystallization temperature on the glass structure, phase composition, and hardness of glass ceramics in the ZnO-MgO-Al2O3-SiO2 system containing TiO2 and ZrO2 as nucleators. To maximize the number of heat treatments, we performed polythermal crystallization of the glass in a wide temperature range with the help of a gradient furnace. Using X-ray diffraction, Raman spectroscopy, and transmission electron microscopy, we showed the precipitation of gahnite nanocrystals as the main phase in the bulk of a single glass sample and observed a gradual change in its microstructure, transparency, and hardness. The dependence of Vickers hardness values on heat treatment temperature was found to follow a non-linear trend, revealing the optimal thermal range for glass crystallization.

Production of sintered glass-ceramic composites from low-cost materials

Considering that wastes are harmfull for the environment and human health due to certain physical, chemical and biological reasons; the necessity of systematic implementation of waste management comes to the fore. Waste management provides advantages to for industrial manufacturing with less pollut on, cheaper and competitively superior products. With the waste recycling, the needs for raw materials and the impact of production on the environment will decrease. This study proposed to produce low-cost sintered glass-ceramic composite by adding a mixture of molten mining tailings, recycled glasses and alumina platelets at different rates. The results showed that glass-ceramic composite made by 50 wt % molten tailings, 25 wt % recycled borosilicate glass and 25 wt % alumina platelets exhibited the best properties (2.39 g/cm3 bulk density, 0.22 ± 0.01% water absorption and 84± 9 MPa bending strength). In this study, considering the consumptions of raw material resources, it was seen that glass and mine residues can be used as secondary raw materials in glass ceramic composite production when cost and environmental issues are matter.

Reactive metal additive manufacturing: Surface near ZrN–metallic glass composite formation and mechanical properties

ZrN formation in a Zr-based bulk metallic glass is observed after processing using reactive laser powder bed fusion. Two processing routes employing nitrogen as a reactive process gas are explored: (1) Standard inert processing in argon followed by reactive remelting in nitrogen and (2) reactive processing in nitrogen. Incorporation of nitrogen is depth-dependent and both approaches result in a dispersion of ZrN nanocrystals in the amorphous matrix close to the surface. The process parameters can be adjusted to control the volume fraction of crystalline phases formed. Hence, it is shown that reactive additive manufacturing can be utilised to form bulk metallic glass–ceramic composites in surface near regions. Thereby we demonstrate that the reactive gas atmosphere utilised during additive manufacturing enables local tailoring of structure, composition, and mechanical properties in the vicinity of the surface.

Glass-Zirconia Composites as Seals for Solid Oxide Cells: Preparation, Properties, and Stability over Repeated Thermal Cycles.

This study focuses on the preparation and characterization of composite gaskets designed for the sealing of the solid oxide cell stacks operating below 700 °C. The seals were fabricated with the addition of various amounts (10-90 wt.%) of 3 mol.% yttria partially stabilized zirconia to a BaO-Al2O3-CaO-SiO2 glass matrix. The sample gaskets in the form of thin frames were shaped by tape casting. The quality of the junctions between the composites and Crofer 22APU steel commonly used as an SOC interconnect was evaluated after thermal treatment of heating to 710 °C, then cooling to the working temperature of around 620 °C and then leaving them for 10h in an air atmosphere, before cooling to room temperature. The samples were also studied after 3, 5, and 10 thermal cycles to determine the changes in microstructure and to evaluate the porosity and possible crystallization of the glass phase. The compression of the seals was calculated on the basis of differences in thickness before and after thermal treatment. The influence of zirconia additions on the mechanical properties of the seals was studied. The experimental results confirmed that glass-ceramic composites are promising materials for gaskets in SOC stacks. The most beneficial properties were obtained for a composite containing 40 wt.% of YSZ.

Modifying the composition of oxyfluoride glass-ceramics containing Eu2+-doped nepheline and LaF3 crystals for white LED

An oxyfluoride glass-ceramic containing Eu2+-doped nepheline and LaF3 crystals was synthesized with varying compositions to modify its color conversion and quantum efficiency under ultra-violet light emitting diode (UV-LED) excitation. Glass composing elements such as SiO2, Na2O and Al2O3 were exchanged with LaF3 to influence the formation of nepheline crystals within the glass matrix. Among the various combinations, when Al2O3 was replaced by LaF3 there was improvement in the observed emission intensity and photo-luminescence quantum yield (PL-QY). The optimum composition of Al2O3 and LaF3 content was investigated to improve PL-QY. X-ray diffractometer (XRD) was used to monitor structural changes in the crystals within the glass-ceramic. A white LED, with a high color rendering index (CRI) comparable to commercial white LEDs, was successfully demonstrated using the modified glass-ceramic as a color converter in structures of phosphor in silicone and phosphor in glass.

Light-Transmitting Lithium Aluminosilicate Glass-Ceramics with Excellent Mechanical Properties Based on Cluster Model Design.

In this study, for the first time, a cluster-plus-glue-atom model was used to optimize the composition of lithium aluminosilicate glass-ceramics. Basic glass in glass-ceramics was considered to be a 16-unit combination of three-valence {M2O3} and one-valence {Li2O} units. By adjusting the ratio of {M2O3} and {Li2O}, the composition of basic glass could be optimized. After optimization, the average cation valence of the base glass was increased to 2.875. After heat treatment of the optimized base glass, it is found that the crystal size, proportion, and crystallinity changed obviously compared with that before optimization. The main crystalline phases of all the lithium aluminosilicate glass-ceramics prepared in this work were Li2Si2O5 and LiAlSi4O10. All optimized glass-ceramics had an obvious improvement in the crystallinity, with one of the largest having a crystallinity of over 90%. Furthermore, its bending strength was 159 MPa, the microhardness was 967 Hv, and the visible light transmission rate exceeded 90%. Compared with the widely used touch panel cover glass, the optical properties were close, and the mechanical properties were greatly improved. Due to its excellent performance, it could be used in microelectronics, aerospace, deep-sea exploration, and other fields.

Novel silicon oxycarbide/spodumene glass-ceramic composites with tailored thermal expansion coefficient

Highly densified silicon oxycarbide (SiOC)/spodumene composites with low coefficient of thermal expansion (CTE) were obtained just selecting the spark plasma sintering temperature employed. For the first time we proposed the use of spodumene a cheap and natural available lithium aluminium silicate mineral as meltable/active filler for SiOC-derived composites, due to its powerful fluxing properties and also its very low CTE. SiOC/spodumene composites sintered at 1200 ⁰C display a very low CTE (0.128±0.004–1.902±0.002 × 10−6 K−1) due to the α,β-transformation of spodumene. At higher sintering temperatures the CTE increases to 3.288±0.004 × 10−6 and 4.516±0.006 × 10−6 K−1 (1300 and 1400 ⁰C) due to the β-SiC formation. In this range of temperature, spodumene promotes the phase separation of SiOC and subsequent crystallization of cristobalite and β-SiC. The maximum values of hardness (11.5 ± 0.5 GPa) and elastic modulus (91±4 MPa) are reached at 1300 ⁰C, where the SiOC/composite displays a neat densification and the lowest roughness (1.61±0.01 nm).

Composite Metamaterial: Ferrite Matrix with Ferroelectric Inclusions

A metamaterial based on periodic ferroelectric inhomogeneities in a magnetic ferrite matrix including a quantity of ferroelectric composite in a matrix, demonstrating relative low microwave losses and effective dielectric permittivity, was produced. Glass-ceramic composites, consisting of low-melting glass and barium-strontium titanate, were successfully synthesized and incorporated into the periodic holes of the ferrite matrix to build the meta-structure. Investigation of the structure showed dielectric permittivity, which increased with the volume of ferroelectric inclusions. The range of magnetically controlled interactions of the meta-structures with an electro-magnetic field was increased for the matrix with periodic holes filled by the ferroelectric composite in comparison with the basic ferrite matrix. The ferrite substrate completely determined the microwave losses of the sample and the ferroelectric inclusions increased the Q-factor of the meta-structure.

Metal and Nonmetal Protective Screens for Hypervelocity Debris Shielding

The protective properties of metallic and nonmetallic screens were experimentally investigated when penetrated by an aluminum shaped charge jet at collision velocities of 7–10 km/s. Such a projectile is an analog of an elongated fragment of man-made debris. For materials of protective screens, we used glass, B4C ceramics, and diamond-silicon carbide ceramic composite. The obtained results were compared with the data obtained for metal screens. In this paper, we show that the effectiveness of screen protection increases due to phase and structural transitions that occur during the interaction of elongated hypervelocity projectile with protective screens.

Effect of Al4B2O9 and Al18B4O33 whiskers synthesized in situ on the evolution of microstructure and mechanical properties of white fused alumina and Cubitron glass-ceramic composites

The present paper reports on the influence of in situ crystallization of aluminum borate whiskers on the evolution of the microstructure and mechanical properties of electrocorundum (white fused alumina) and microcrystalline alumina (Cubitron 321™) glass-ceramic porous composites. The investigated composites were obtained by sintering the white fused alumina (WFA) and Cubitron 321™ abrasive grains, glass-ceramic bond and various amounts of precursor for whisker growth. The results showed that in the presented technology, the crystallization of the composite reinforcing phases proceeds differently in both types of composites, which affects their microstructure and mechanical properties. An increase in the mechanical tensile strength of 36% was observed for both types of composites; however, depending on the type of abrasive grain, the composites with the highest tensile strength differed in the amount of whisker precursor added. A significant increase in the Young's modulus values was also observed for composites containing 40 wt% precursor: by 45% for WFA and by 52% for Cubitron 321™.

The effect of fluxing agents and heat treatment on the leucite crystallization in bio glass–ceramic composites

The effect of fluxing agents and heat treatment on the leucite crystallization in bio glass–ceramic composites