Lithium Aluminum Silicate Research Articles

Nitrogen-doped modified graphene aerogel enhancing interfacial bonding with lithium aluminium silicate ceramics for broadband microwave absorption

The swift progression of e-communication technology has resulted in significant electromagnetic pollution, necessitating the urgent need for effective microwave-absorbing materials to mitigate this issue. Augmenting heterogeneous phase interfaces and incorporating heteroatoms constitute viable strategies for enhancing the electromagnetic properties of functional materials. In this study, a series of lithium aluminium silicate glass-ceramic/nitrogen-doped graphene (LAS/N-GF) aerogels was synthesised via the hydrothermal and freeze-drying methods. An innovative bonding mechanism for the heterogeneous phase interface was revealed, in which nitrogen doping enabled the formation of lattice defects in LAS ceramic particles and graphene and promoted a closed approach for unsaturated carbon and silicon atoms to form carbon-silicon bonds through the electrostatic force generated by interfacial polarisation. Given that covalent bonds are widely recognized as stable carrier channels, the presence of carbon-silicon bonds at the interface facilitates electron migration, ultimately leading to improved microwave absorption. The maximum absorptivity of the LAS/N-GF aerogels could reach -47.98 dB at 8.96 GHz with a filler loading as low as 10 wt.%. It is noteworthy that the LAS/N-GF aerogel exhibits an effective absorption bandwidth of 8.34 GHz, which fully spans the entire X-band and more than two-thirds of the Ku-band. Such exceptional performance is rarely observed in dielectric loss materials. Finally, the application potential of the LAS/N-GF aerogels in microwave absorbers was simulated and analysed. The unique chemical phenomenon stemming from the bonding at the carbon material-ceramic interface offers a fresh perspective in interface science, enabling a deeper comprehension of the underlying mechanism of microwave absorption.

Advancing High‐Power Laser Lighting: Designing a Novel YAGG:Ce Color Converter in Li–Al–Si Glass Ceramic

AbstractIn laser illumination, there is considerable interest in phosphor‐converted laser diodes that boast high efficiency and exceptional thermal stability. Phosphor‐in‐glass (PiG) and phosphor‐in‐glass film (PiF) are highly favored for their efficiency, cost‐effectiveness, and ease of fabrication. To tackle the issue of low thermal conductivity of glass, a novel lithium–aluminum–silicate glass is innovatively developed. This glass induces the precipitation of spodumene crystalline phase, enhancing material stability. Utilizing solid‐state sintering techniques, Y3Al3.5Ga1.5O12:Ce3+ (YAGG:Ce) PiG is fabricated, which exhibited a luminous flux (LF) of 866.76 lm under 450 nm blue light with 3.88 W input power. Benefiting from the high thermal conductivity of sapphire substrate and the high‐intensity glass system, YAGG:Ce PiF demonstrated a saturation threshold of 10.20 W, yielding an impressive LF of 2178.1 lm, which is 2.5 times that of PiG samples. Notably, the thermal conductivity increased significantly from 2.2 W m−1K−1 (PiG) to 7.0 W m−1K−1 (PiF), surpassing traditional organic resin materials. To validate the practicality of the two‐color converters, it integrates them into both starlight lamp and laser flashlight modules for encapsulation, thereby generating attractive green light in various environments. This design holds the potential to become the ideal choice for the next generation of high‐power, high‐brightness laser illumination.

The effect of nucleating temperature on the crystallization, phase formation and properties of lithium aluminum silicate (LAS) glass-ceramics

To study the influence of the nucleation mechanism in lithium aluminosilicate glass, a composition similar to commercially produced glass was used. The glass-ceramics was obtained as a result of two-stage heat treatment, differing in the nucleation temperature and coinciding in the temperature and time of crystal growth. Scanning electron microscopy (SEM) and x-ray diffraction (XRD) were used to study the formed nanocrystals. It was shown that the change of nucleation temperature in the glass transition interval Tg ±15 °C significantly affects the coefficient of thermal expansion, which is due to the formation of a different number of nanocrystals of the general composition LixAlxSi1-xO2 with x = 0.33 with the size less than 50 nm.

Processing of lithium aluminium silicate glass-ceramics and investigations of fracture behaviour and its correlation with the microstructural features

Lithium Aluminium Silicate (LAS) samples were fabricated through a melt casting process using Lithium carbonate, Aluminium hydroxide, Silica and other additives as raw materials. The melt was drain casted at 1300 °C in a pre-heated mould followed by annealing and ceramization at 850 °C. Ceramized samples were subjected to X-ray diffraction. The density of the samples was found to be in the range of 2.53–2.54 g/cm3. The sample was found free from bubbles and inclusions after optically polishing. Mechanical properties including hardness, flexural strength, fracture toughness and compressive strength of LAS samples were evaluated. Knoop hardness of the LAS samples was found to be 597–669 kg/mm2. LAS sample exhibited a peak flexural strength of 110–114 MPa and compressive strength of 221 MPa before fracture. Additionally, the total fracture energy release rate (Jc) of LAS samples along with R-curve and fractography were also studied. R-curve exhibited an increasing trend of Jc with respect to normalised displacement without any sign of saturation indicating the scope for optimisation of quantification of crystals fraction in the glass matrix to obtain the predominant toughening behaviour. Finally, the physico-chemical, microstructural and optical properties were measured and correlated with the mechanical properties observed. Near to theoretical density, high crystallinity and superior mechanical properties of processed LAS glass-ceramic can be used in strategic and civilian applications.

Evolution of electrical, structural, and chemical properties of Li‐aluminosilicate glass during crystallization

AbstractStructural, chemical, and microstructural changes in lithium aluminum silicate glass during ceramming are tracked by in‐situ impedance spectroscopy, X‐ray diffraction and transmission electron microscopy. The glass’ electric and dielectric properties are found to evolve during the ceram cycle. Scaling of frequency‐dependent electrical conductivity and dielectric properties provides temperature‐independent information of bulk phases and interfaces in presence.The initial glass is an ion conductor with Li‐ion mobility following simple Arrhenius‐type behavior. At the nucleation onset, a badly defined, broad feature appears in the impedance spectra, that represents early‐stage nuclei with their interfaces and evolves over time into separate contributions from internal interfaces and ion mobility in crystalline phase. Impedance tracking suggests that nuclei form by de‐mixing and phase separation of the glass, first producing interfaces in a very defective structure before the well‐defined structure and chemistry of crystalline β‐quartz crystal develop in a second time. Findings are supported by XRD and TEM.

Lithium-aluminium-silicate glass: A novel high-quality glass for preparing LuAG: Ce colour converter for laser illumination

Phosphor-in-glass (PiG) plays an indispensable role as a highly tunable and easily prepared phosphor material for new-generation high-brightness and high-collimation laser lighting (blue laser diodes + colour converters). However, at low power (<5 W), the poor thermal stability and brittleness of PiGs make it challenging to develop high-intensity, high-brightness PiG materials because of their susceptibility to rupture and sudden drop in luminous efficiency (LE) owing to thermal accumulation under high-energy laser irradiation. In this study, a performance-tunable lithium-aluminium-silicate (LAS) glass system was used to adjust the glass composition and synthesise LAS-glasses that can be sintered at low temperatures. In addition to LuAG: Ce phosphor, LuAG: Ce phosphor-in-LAS (LuAG: Ce-PiGLAS) has been successfully developed, which can withstand an 8.24-W laser irradiation without heat dissipation, achieving a luminous flux of 1248 lm and LE of 204 lm/W. Furthermore, a pre-thermal treatment was used to precipitate the lithium disilicate phase to enhance the resistance of the glass to laser ablation, resulting in a power increase to 8.62 W at 1485 lm and maximum LE increase to 212 lm/W with a 2.5% attenuation at 498 K. High-brightness illumination performance was demonstrated in both transmission and reflection modules. This study is anticipated to generate new prospects for PiG applications and accelerate the development of laser lighting.

Lithium aluminium silicate–based low–coefficient of thermal expansion materials obtained by colloidal and low–temperature approaches

Glass ceramics based on lithium aluminosilicates are interesting because they have low coefficients of thermal expansion (CTEs) and are adjustable to different processes by adjusting their chemical composition. However, their typical production is complex, requiring high process temperatures and long grinding times to obtain micrometric particles. This study presents the synthesis of low–CTE lithium aluminium silicate nanoparticles obtained through a colloidal approach from the heterocoagulation of a lithium source (lithium acetate obtained by the reaction of carbonate with acetic acid), silica, and alumina from different sizes. The concentrated suspensions were dried, and the powders were thermally treated at 750–900 °C to form the crystalline phases projected by the solid–state reaction. The samples were characterized by thermal and structural analysis. The use of alumina nanoparticles in the synthesis of powders yielded mostly the crystalline phases β–spodumene and β–eucryptite, which were thermally treated at 850 °C and showed a low CTE (1.25 × 10−6 °C−1). Powders were successfully synthesized, which with some adjustments in the synthesis conditions may yield higher levels of β–eucryptite and therefore much lower CTE powders.

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).

In-situ study of phase changes in glass by impedance spectroscopy and scaling

Transformation in “evolving glass” in ion-conducting silicate glasses, glass ceramics or ceramics containing an intergranular glass is studied by in-situ impedance spectroscopy and scaling laws. Approaches are developed to scale frequency-dependent electrical conductivity and dielectric properties of multiphase ion-conducting materials to derive temperature-independent information on bulk phases and interfaces in presence. A material's scaled electric conductivity provides a unique response over a range of temperature, if the material remains unaltered, but changes, once modifications in the material occur. Therefore, impedance spectroscopy in combination with scaling can be used for tracking modifications in structure, organization, chemistry and microstructure in “evolving (ion-conducting) glass”.In a first part of this work, our approach is validated through application to stable silicate glasses and glass ceramics. Then “evolving glass” is studied in bulk glasses and ceramics with intergranular glass. Examples include ceramming of glass under formation of a glass ceramic, glass-glass phase separation, modification of intergranular glass in ceramics as result of chemical reactions or melt corrosion.Our approach allows to determine onset of phase separation, nucleation or reaction with high precision. It further reveals that nucleation in our exemplary lithium aluminum silicate glass starts with formation of interfaces (phase separation) prior to forming a well-organized crystal lattice. During phase separation in glass, early capacitive contributions in the impedance spectra indicate that the formation of glass-glass interface precedes the compositional changes in the bulk glass.Impedance of refractories is monitored during thermal treatments or corrosion in glass melt at temperatures up to 1600 °C, and glass characteristics of refractories with glass content as low as 3% are extracted. Conductivity and/or level and/or interconnectivity of the refractory's glass are shown to change during thermal treatments due to reactions between glass and crystalline refractory phases, due to phase transformation or, in case of melt corrosion, due to melt infiltration and ion exchange with the melt.In-situ tracking of impedance and application of scaling laws is shown to be able to reveal changes in bulk glass and intergranular glass.

Dual effect of ZrO2 on phase separation and crystallization in Li2O–Al2O3–SiO2–P2O5 glasses

AbstractZrO2 is an effective nucleation agent for low‐expansion lithium–aluminum silicate (LAS) glass–ceramic (GC) with high Al2O3 content. However, the effect of ZrO2 is still not fully understood in LAS glasses with low contents of Al2O3 and P2O5. In this work, the effect of ZrO2 on the phase separation and crystallization of Li2O–Al2O3–SiO2–P2O5 glasses were investigated. The results revealed that ZrO2 significantly increased Tg and the crystallization temperature of Li2SiO3 and Li2Si2O5 crystals. Li3PO4 crystals precipitated preferentially in the glass containing 3.6‐mol% ZrO2, wherein Zr was stable in the network and no precipitation of ZrO2 nanocrystals was observed. Moreover, the separation of phosphate‐rich phases in the as‐quenched glasses increased with the addition of ZrO2. The findings of the study revealed a dual role of ZrO2. First, ZrO2 acted as a glass network former rather than a nucleation agent, increasing glass viscosity and the nucleation barrier of Li2SiO3 through its strong network connectivity. Second, as Zr preferentially combined with non‐bridging oxygen to form Si–O–Zr linkages, a sufficient amount of charge‐balancing Li+ ions existed in the network, which promoted the separation of phosphate‐rich phases. It indicated that the incorporation of ZrO2 contributes to the activation of the nucleation role of P2O5, thus contributing to the formation of nanocrystals and fine microstructure of GCs.

Preparation of Ceramic Foam Filters With a Lithium-Containing Surface

Hydrogen in aluminum causes the formation of detrimental hydrogen porosity in castings. In order to reduce the formation of hydrogen pores, an approach was targeted using lithium as target for hydrogen. This approach utilizes the affinity of lithium for hydrogen, whereby spodumene (a lithium aluminum silicate) and lithium aluminate were used as lithium providers. Within the scope of this study, the preparation of ceramic foam filters with a coating of lithium-containing raw materials (spodumene) was investigated. Those investigations revealed that the spodumene coating has a detrimental influence on the bending strength of the foams when a certain level of spodumene is exceeded. This observation might be explainable by the intrusion of the spodumene into the alumina matrix of the skeleton foam. Two wetting tests at different temperatures were conducted, verifying the significant influence of the temperature on the reaction between the spodumene and AlSi7Mg. Furthermore, test filters coated with raw materials exhibiting different amounts of lithium were conducted. The hydrogen pores were evaluated by light microscopy and computed tomography. The analyzed pore size distribution in the aluminum did not elucidate the proximate influence of the lithium-coating on the ceramic foam filter on the hydrogen porosity in the aluminum.

Recovery of Li from lithium aluminum silicate (LAS) glass-ceramics after heat treatment at 1000 °C and Ca salt-assisted water leaching in two stages before and after calcination at 600 °C

In this study, the leaching of Li from lithium aluminum silicate (LAS) glass-ceramics was conducted using a Ca salt additive and water, with the content of other impurities at a minimum. LAS glass-ceramics were heat-treated at 1000 °C to increase the reactivity with leachate before the water leaching process. Various types of Ca salts were employed, and their effects on Li leaching were investigated. The reaction temperature, reaction time, and mass ratio of the Ca salt to the LAS glass-ceramics were considered as leaching parameters. Approximately 42.1% of Li was found to be leached by water at 100 °C via an ion exchange reaction between Li+ and Ca2+. X-ray diffraction revealed a peak shift of the leach residue, indicating that Li+ was substituted by Ca2+. When water leaching was conducted again after calcining the leach residue at 600 °C, Li leached from the LAS glass-ceramics exceeded 99.9%. Thus, Li can be recovered from LAS glass-ceramics using only a Ca salt and distilled water, without the requirement of other chemicals.

The effects of MgF2 in four complex nucleating agents on the performance and crystallization of lithium aluminum silicate glasses

Glasses and glass-ceramics in the LAS system containing four complex nucleating agents (TiO2+ZrO2+P2O5+MgF2) were prepared by the traditional melt quenching technology and two-step (nucleation-crystallization) method. The effects of MgF2 contents on the performances and crystallization behavior of parent glass were examined using XRD, SEM, DSC, Fourier transform infrared, Transmittance, TEC, Density, Bending strength, Vickers hardness and the Quality loss of Alkali (Acid) resistance. The result reveals that when the complex nucleating agents (TiO2+ZrO2+P2O5+MgF2) in a ratio of 2: 2: 5: 3, the parent glass has the most prominent performance and optimal crystallization promotion. Fluoride has the better promotion effect on the formation of ZrTiO4 when the MgF2 content is 2 wt%, regardless of whether β-quartz or β-spodumene solid solution used as main crystalline phase. Besides, fluoride may be hinder the precipitation of AlPO4 (in β-quartz solid solution) and has the limit impact on the formation of AlPO4 (in β-spodumene).

Recovery of Li from Lithium Aluminum Silicate Glass-Ceramics by Ca Salt-Assisted Water Leaching

Recovery of Li from Lithium Aluminum Silicate Glass-Ceramics by Ca Salt-Assisted Water Leaching

Spodumene-containing glass-crystalline materials for technical purposes

The trends and current state of the glass-ceramic market from 2019 to 2024 have been analyzed, and an increase in demand for glass-crystalline materials for construction and technical purposes has been established. It has been determined that the orientation of world glass-ceramic market towards fragmentation will allow domestic producers to reduce import dependence and increase the competitiveness of domestic glass-ceramic materials in the world market.&#x0D; The aim of this work is to assess the technical and economic indicators of the technology developed spodumene-containing glass-ceramic materials for technical purposes and to conduct pilot laboratory tests.&#x0D; The study of the structure and phase composition of glass-ceramic materials was carried out using complementary methods of physicochemical analysis. The physicochemical properties of the materials were determined in accordance with the requirements of the current regulatory documents in silicate materials. Ballistic properties are determined according to GOST 8782: 2018.&#x0D; Compositions and technologies for the production of spodumene-containing glass-ceramic materials based on lithium-aluminum silicate glasses were selected for the production of domestic elements of armor protection, heat engineering and radio engineering, taking into account the aspects of energy and resource saving. The study of the developed materials structure made it possible to establish differences in mechanical, thermal, and optical properties, which makes it possible to select the recommended areas of their application.&#x0D; A comparative assessment of the performance properties and technical and economic indicators of known ceramic and glass-ceramic materials for body armor made it possible to establish the competitiveness of the developed domestic spodumene-containing materials as elements of individual protection.

The effect of phase formation on biomechanical and biological performance of Li2O-Al2O3-SiO2 glass-ceramics

Lithium aluminum silicate (LAS, Li2O-Al2O3-SiO2) glass-ceramics have been employed in dentistry as substitutes while seldom in orthopaedics. This is primarily due to difficulties with balancing the biomechanical and biological performance. This study aims to investigate the effects of SiO2 content and thermal treatment on the formation of Li2SiO3, Li2Si2O5 and LiAlSi2O6 in LAS glass-ceramics, and the effects of these crystalline phases on the biomechanical and biological performance. The preparation of LAS glass-ceramics were divided into two stages. In the first step, six components (C1, C2, C21, C22, C23 and C3) of LAS glass-ceramics were prepared and characterized. In the second step, the CN1, CN2 and CN3 with the principal phases of Li2SiO3, Li2Si2O5 and LiAlSi2O6 were obtained based on the C1, C22 and C3 and evaluated in biomechanics and biology. With the content of SiO2 increasing from 65.11% to 67.96%, the formation of Li2Si2O5 and LiAlSi2O6 correspondently increased. The extension of the holding time at 850 °C promoted the generation of LiAlSi2O6 at the expense of Li2Si2O5. The main crystalline phase coupled with Li2Si2O5 and LiAlSi2O6 (dominated by LiAlSi2O6) resulted in a high flexural strength of 378 ± 29 MPa and favorable cell viability of 115.21 ± 14.63%. The impressive biomechanical and biological results of CN3 indicate that this glass-ceramic may be a good candidate for orthopaedic applications.

Characteristics of Thermal Parameters and Some Physical Properties of Mineral Eutectic Type: Petalite-Alkali Feldspars.

The aim of the research was to check whether the system of three fluxes based on lithium aluminium silicate and alkali feldspars has a eutectic point, i.e., with the lowest melting temperature. Lithium was introduced into the mixtures in the form of petalite, which occurs naturally in nature (Bikita Zimbabwe deposit). Using naturally occurring raw materials such as petalite, sodium feldspar, and potassium feldspar, an attempt was made to obtain eutectics with the lowest melting point to facilitate thermal processing of the mineral materials. In addition, the high-temperature viscosity of the mineral alloys and physical parameters such as density, linear shrinkage, and open porosity were studied. The study showed that in these systems, there is one three-component eutectic at 1345 °C, with the lowest viscosity of 1·105 Pas and the highest density of 2.34g/cm3, with a weight content of petalite 20%, sodium feldspar 20%, and potassium feldspar 20%.

Enhancement of leaching efficiency for Li by phase transformation from lithium aluminum silicate (LAS) glass-ceramics

The mechanism of Li leaching from lithium aluminum silicate glass-ceramics was investigated to facilitate the recovery of Li. The experimental process was divided into the phase transition of the crystal structure through heat treatment and the Li leaching process using NaOH. Phase transition of the crystal structure based on the reaction temperature and heat treatment time was examined through X-ray diffraction analysis. The effects of the NaOH concentration, particle size, stirring speed, reaction temperature, solid/liquid ratio, and reaction time on Li leaching from heat-treated LAS was investigated. The results show that the crystal structure of lithium aluminum silicate glass-ceramics transitioned from hexagonal to tetragonal, and the efficiency of Li leaching from lithium aluminum silicate glass-ceramics before and after heat treatment was 68% and 99.6%, respectively. Accordingly, heat treatment increased the Li leaching efficiency by approximately 1.5-fold. To investigate the cause of the improvement of leaching efficiency, we calculated the lattice constant by using the interplanar spacing and Miller indices obtained from the X-ray diffraction analysis results for the respective powder samples. The results show that the crystal structure expanded approximately four-fold, and the reactivity with NaOH increased.

Solid-state field-assisted ion exchange of Ag in lithium aluminum silicate glass-ceramics: A superfast processing route toward stronger materials with antimicrobial properties

Lithium-aluminum-silicate glass-ceramics (LAS) are of pivotal relevance in various applications as they combine excellent mechanical and functional properties. Due to their use in medical devices and cooking articles, antimicrobial properties are obviously of interest.Herein, we report the solid-state field-assisted (Ag→Li,Na) ion exchange in LAS glass-ceramics containing β-quartz and β-spodumene solid solutions. The ion-exchange is extremely rapid and deep silver penetration (>100 μm) can be achieved within a few minutes (<5 min), this being proportional to the treating time and applied current. The elemental profiles are characterized by a relatively complex shape which reflects the different alkali mobility in the different phases. The ion exchange initiates structural modifications involving: (i) β→α transition in spodumene; (ii) formation of lattice microstrain and quartz cell expansion; (iii) substantial changes in the IR absorption spectra. The obtained materials possess improved resistance to crack formation and antimicrobial activity against Staphylococcus aureus.

FEATURES OF THE STRUCTURE FORMATION OF SPODUMENS-CONTAINING GLASS-CRYSTAL MATERIALS AFTER HEAT TREATMENT

The promising areas of application of spodumene–containing glass–crystalline materials in various branches of science and technology, in particular, to increase the defense capability of the state, have been determined. The relevance of the development of lightweight high–strength sitalls based on them, taking into account the aspects of energy saving for obtaining armored elements, has been determined. It has been established that the use of IR spectroscopy is promising for studying the nanostructure of glass–crystalline materials. The compositions of lithium aluminum silicate glasses and the modes of their heat treatment have been developed. The features of the structure formation of spodumene–containing glass–crystalline materials obtained under the conditions of two–stage low–temperature heat treatment have been investigated. Taking into account the analysis of the nature of the IR spectra of chain silicates, the structure of glass–crystalline materials was investigated according to the IR spectra and the nature of structure formation was established depending on the initial composition of the glass. It has been established that the formation of a structural glass network with the participation of tetrahedra [AlO4], [BO4] and [SiO4] and the presence of cybotaxic groups [Si2O6] allows, under conditions of two–stage low–temperature treatment, to provide bulk crystallization of spodumene–containing glass–crystalline materials. It has been established that the formation of the vitrified structure of glass–crystalline materials allows to ensure their high values of Vickers hardness, microhardness and crack resistance and by the presence of a glass phase, which plays the role of a damper, to ensure their high armor resistance. This will increase the efficiency and make it possible to use them as an energy–destructive and energy–absorbing layer in the composition of the armor element «metal alloy – ceramics – sitall». The introduction of spodumene–containing glass–crystalline materials will increase the competitiveness of competitive domestic armored elements for personal protection.