Glass Crystallization Temperature Research Articles

Synthesis of transparent tin-doped indium oxide (ITO)-containing glass-ceramic coating by the sol-gel route for UV/NIR-shielding

Transparent glass-ceramic containing tin-doped indium oxide nano-crystalline phase was synthesized using the sol-gel method. The prepared sol, which was based on sodium aluminoborosilicate glass composition, was applied on soda-lime-silicate glass substrate through the dip-coating technique. Developing such glass-ceramics can offer several advantages, including reducing the total cost of production, enhanced chemical durability and a low-temperature synthesis process. The thermal behavior of the dried gels was investigated using simultaneous thermal analysis (STA), to determine the decomposition temperature of the nitrate salts in the gel, its glass crystallization temperature, and finally to optimize the heat treatment regime and optical properties as well. UV–Vis–NIR spectroscopy of the coated samples after heat treatment at 500 °C for 10 h revealed high visible transparency (T>70%) while indicating significant UV/NIR shielding, i.e. near zero and 10 % transmission, respectively. Phase analysis and crystallization behavior studies were conducted using XRD and FE-SEM to evaluate the morphology and size of the precipitated crystallites. According to the results, the optimum heating program for ITO crystallization was heating temperature and soaking time of 500 °C and 10 h, respectively. The undesirable crystalline phase of InBO3 was precipitated as the main crystalline phase by increasing the heat treating temperature to 550 °C. Furthermore, the glass structure was studied using FTIR spectroscopy demonstrating a highly polymerized glassy network for the coating. The effect of the precursors-to-solvent ratio during the synthesis process on the final optical properties was also investigated.

BATCH COMPOSITION INFLUENCE ON SINTERING AND CRYSTALLIZATION PROCESSES OF CORDIERITE GLASSES OBTAINED BY THERMAL PLASMA MELTING

This article focuses on the production of glasses and glass-ceramic materials with a cordierite (2MgO∙2Al2O3∙5SiO2) composition. The processes of crystallization and sintering of cordierite glasses, which are based on natural raw materials, pure oxides and pre-synthesized cordierite, have been investigated. It has been determined that cordierite glasses produced via plasma melting exhibit high structural defects attributed to rapid heating and cooling rates. The relaxation of microstresses in the glasses takes place within the temperature range of 480 – 490 °C. Glasses based on synthesized cordierite exhibit a crystallization temperature of 930 – 1020 °C, depending on the presence and type of nucleating agents. This is approximately 20 – 50 °C lower compared to glasses based on component mixtures. The primary crystallization product of studied glasses at 900 °C is the high-quartz solid solution with formula MgO∙Al2O3∙3SiO2, which is dissociate above 1000 °C with the formation of cordierite. The addition of 5% ZrO2 to the batch increases the viscosity of softened glasses and their crystallization temperature, resulting in increased activity of glass powders in the sintering processes due to the higher impact of liquid-phase sintering on the general densification process of glass-ceramics. This allows for the production of glass-ceramics with open porosity of 2 – 4% at 1300 – 1350 °C. The addition of 5% TiO2 to the batch reduces the glass crystallization temperature. However it does not significantly effect on the cordierite glass-ceramics sintering processes. For citation: Sharafeev S.M., Shekhovtsov V.V., Zvyagina E.E. Batch composition influence on sintering and crystallization processes of cordierite glasses obtained by thermal plasma melting. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2024. V. 67. N 7. P. 80-87. DOI: 10.6060/ivkkt.20246707.7032.

Glass transition and crystallization of Se95Te5 chalcogenide glassy semiconductor

The study is dedicated to the investigation of thermo-physical characteristics of Se95Te5 chalcogenide glassy semiconductor during its glass formation and crystallization processes, employing various scanning rates of 5, 10, 15 and 20 K/min in non-isothermal modes through DSC measurement. Analysis of the structural relaxation kinetics involves the Kissinger’s, Augis and Bennett's, as well as Matusita’s approaches. Experimental data yield contains the determination of crucial parameters such as glass transition (𝑇𝑇𝑔𝑔), crystallization(𝑇𝑇𝑐𝑐), and melting temperatures alongside factors like reduced temperature of glass transition (𝑇𝑇𝑟𝑟𝑟𝑟), Hruby’s parameter (𝐾𝐾𝑔𝑔𝑔𝑔), fragility index (𝐹𝐹𝑖𝑖), Avrami exponents (n, m), glass transition (140.24 kJ/mol) and crystallization (Ec = 95.11 kJ/mol) energies, respectively. The results confirm that Se95Te5 chalcogenide system as an efficient glass former. Matusita’s method reveals that the crystallization mechanism (n = 2.51, m = 1.9) corresponds to volumetric nucleation with two-dimensional growth.

Analysis of mechanical and shape memory properties of biocompatible shape memory polymers with different Fe3O4 contents

Shape memory polymers (SMPs) can recall their original shape when exposed to environmental factors like heat, light, or magnetic fields. These SMPs are extensively used in medical applications, notably in stents, due to their shape memory and biocompatibility after implantation in the human body. However, conventional stents require balloons for expansion, limiting their flexibility. To address this, the study developed an SMP material that can regain its original shape without the need for a balloon. To effectively induce self-response, magnetically responsive Fe3O4 nanoparticles at concentrations of 10%, 15%, and 20% were integrated, and their dispersion was verified using scanning electron microscopy. The study also utilized differential scanning calorimetry to measure the glass transition temperature, crystallization temperature, and melting point of the synthesized polymers. The confirmation of uniformly dispersed nanoparticles revealed that the synthesized polymers exhibited a high shape memory ratio (84%–93%). Shape memory ratio represents the ability to return from a temporarily deformed state to the initial, original shape. Therefore, the biocompatible, magnetic-responsive SMP developed in this study has the potential to be utilized in various medical devices as an advanced shape-memory material.

Effect of composition on the thermal properties and structure of M-Al-Si-O-N glasses, M = Na, Mg, Ca

The primary objective of this study is to explore the relationship between the composition, structure, and thermal characteristics of M-Al-Si-O-N glasses, with M representing sodium (Na), magnesium (Mg), or calcium (Ca). The glasses were prepared by melting in a quartz crucible at 1650 °C and AlN precursor (powder) was utilized as a nitrogen source. The measured thermal properties studied were glass transition temperature (Tg), crystallization temperature (Tc), glass stability, viscosity, and thermal expansion coefficient (α). The findings indicate that increasing the aluminum content leads to higher glass transition, crystallization temperatures, and viscosities. In contrast, fragility values increase with the Al contents, while modifier elements and silicon content influence thermal expansion coefficient values. FTIR analysis revealed that in all glasses, the dominant IR bands are attributed to the presence of Q2 and Q3 silicate units. The effect of Al is observed as a progressive polymerization of the silicate network resulting from the glass-forming role of Al2O3. In most samples, the Q4 silicate mode was also observed, strongly related to the high Al content. Overall, the study shows that the complexity of composition-property correlations where the structural changes affect the properties of Mg/Ca-based oxynitride glasses has potential implications for their use in various technological fields.

Correlation of thermal and electrical properties of silver germanophosphate glasses with their structural analysis by Raman and NMR spectroscopy

In present study glasses of the system Ag2O-GeO2-P2O5 were studied in the compositional series (50−x)Ag2O-xGeO2-50P2O5 with x = 0−40 mol%. Ag2O substitution by GeO2 results in a significant increase of both glass transition temperature, Tg, and crystallization temperature, Tc, up to 628 °C (Tg) and 851 °C (Tc) at x = 40 mol% GeO2. The glass structure was investigated from the analysis of 31P MAS NMR and Raman spectra. Both methods show transformation of phosphate glass network formed mainly by Q2 units to germanate-phosphate network formed by Q1xGe and Q21Ge phosphate units and germanate units. Raman spectra, in addition, reveal evolution of P‒O‒P linkages to P‒O‒Ge and Ge‒O‒Ge linkages through the glass series. DC conductivity trend upon GeO2 addition showed non-monotonic behaviour, which is related to structural changes in the glass-network.

Investigation the optical and structural properties of Mn-doped Sb2S3 nanocrystals embedded in host glass

The search for earth-abundant and non-toxic elements is essential for the manufacture of sustainable optical devices. In this context, dilute magnetic semiconductor (DMS) xMn-doped Sb2S3 nanocrystals (NCs) embedded in host glass were synthesized by the fusion method. Differential Thermal Analysis shows evidence of Sb2S3 phase crystallization peak and changes in glass transition and crystallization temperatures of the host glass with the presence of xMn-doped Sb2S3 NCs. Transmission electron microscopy images show the formation of xMn-doped Sb2S3 NCs with increasing size (2.1–3.8 nm) as a function of concentration (x = 0.00 to 0.40), respectively. X-ray diffraction measurements reinforced the evidence for the orthorhombic structure of xMn-doped Sb2S3 NCs embedded in glass. Energy dispersive X-ray spectroscopy analyses confirm the S, Sb and Mn precursor elements of DMS NCs. Atomic and magnetic force microscopy measurements show the magnetic contrast patterns resulting from the incorporation of Mn atoms into the Sb2S3 structure. The electronic paramagnetic resonance spectrum confirms the presence of Mn2+ ions (3d5) located in the crystal field of the Sb2S3 semiconductor due to six hyperfine transitions. The redshift of the Raman vibrational mode (1Ag) with increasing xMn concentration gives strong evidence for the presence of Mn2+ ions in sulfur vacancies (VS) in the Sb2S3 unit cell. Optical absorption and photoluminescence (PL) spectroscopy measurements for xMn-doped Sb2S3 NCs show the subtle tunable redshift of the band gap and excitonic recombination in the green-red region, with increasing x concentration. PL confirms that dopant Mn2+ ions fill VS2 that are dominant in Sb2S3. Therefore, the position of the energy states after the increasing concentration of Mn2+ dopant ions gives rise to insight into luminescence for future research scenarios and applications involving sustainable DMS NCs.

Effect of substituting Li2O with ZnO on the crystallization and properties of Li2O–Al2O3–SiO2 transparent glass ceramics

The transparent glass ceramic Li2O–Al2O3–SiO2 (LAS) was successfully prepared through a melting method. The impact of ZnO substitution for Li2O on the crystallization and properties of LAS glass ceramics was investigated. The results revealed that with the increase in ZnO substitution from 0% to 4%, the Q4 structural units in the base glass increased, reinforcing the integrity of the glass network structure. This led to an elevation in the glass transition temperature (from 533.5°C to 545.7°C), crystallization temperature (from 728.6°C to 832.3°C), and Vickers hardness (from 5.98 to 6.44 GPa). Additionally, the primary crystalline phases in the glass ceramics transformed from Li2Si2O5 and LiAlSi4O10 to cristobalite, and the multiphase crystalline structure transitioned to a single phase with a spherical morphology of the crystalline grains. The discussion delved into the size distribution of crystals in the glass ceramics, revealing that the increase in ZnO content refined the size and homogenized the distribution of the cristobalite crystals. Glass ceramics with 0% and 4% ZnO substitution, nucleated at 570°C for 4 h and crystallized at 700°C for 2 h, yielded lithium disilicate glass ceramic and cristobalite glass ceramic, respectively, with maximum transmittances (at 550 nm) of 86.92% and 88.79%. The study indicated that the type and size of precipitated crystalline phases significantly influenced the whiteness of the glass ceramics, with minimal impact on other color parameters. Moreover, the presence of fine grains in the glass ceramics, compared with the base glass, imparted a higher hardness. The addition of ZnO exhibited an increasing trend in the toughness of the glass ceramics. At a ZnO substitution of 4% and a crystallization temperature of 700°C, the glass ceramic with cristobalite as the crystalline phase demonstrated optimal comprehensive performance.

Effect of manganese on the structure of CMAS slag glass–ceramics

With the acceleration of industrialization, environmental issues have received great attention from governments and societies around the world. Utilizing solid wastes containing valuable heavy metals and exploring their role and application in materials is one of the focal issues of environmental protection in recent years. In this paper, in order to explore the effect of Mn content on the crystallization of CaO-MgO-Al2O3-SiO2 glass–ceramics, glass–ceramics with different content of MnO2 were prepared by sintering method and the effect of MnO2 doping on the crystalline properties, glass stability and heavy metal fixation properties of the stainless steel slag glass–ceramics was investigated by differential scanning calorimetry (DSC), Raman spectroscopy, X-ray diffraction (XRD) and scanning electron microscope (SEM). The analysis using crystallization kinetics showed that surface crystallization dominated the whole crystallization process in the range of 0% to 10% MnO2 content. The peak glass crystallization and depolymerisation temperatures of the glass–ceramics increased gradually with increasing MnO2 content, and the main crystallization mode of the samples was one-dimensional crystallization. The main crystalline phase of the resulting glass–ceramics was transformed from diopside to spinel, with a crystallization temperature of 860℃. Heavy metals solidified in the spinel phase. This study shows that heavy metals can be effectively immobilized in glass–ceramics. In summary, the use of solid waste to prepare final products with good environmental performance provides a feasible way to utilize solid waste resources.

Development of 3D Printing Filaments from Recycled PLA Reinforced with Nanoclay

This study focused on the development of 3D printing filaments suitable for fused deposition modeling (FDM) by recycling expired polylactic acid (PLA) filaments. The 3D printing filaments were processed into pellets by incorporating montmorillonite (MMT) nanoclay into the expired PLA filaments through twin-screw extrusion with varying concentrations of 1%, 3%, and 5 wt.%. These composite pellets were reprocessed to filaments through a filament extruder with a diameter of 1.75 mm. These filaments underwent different characterization techniques to test its mechanical and thermal properties. The thermal properties showed increasing values in the glass transition temperature, crystallization temperature, and melting temperature with a decrease in the specific heat upon incorporating increasing amount of MMT nanoclay. Furthermore, thermogravimetric analysis (TGA) showed a positive impact with better thermal stability when the MMT content was incorporated. In terms of mechanical properties, the study showed that the addition of 1 wt% MMT nanoclay, provided an increase in both the tensile strength and elastic modulus comparable to the virgin 3D printing PLA filament.

Extending the glass formation of alkali tellurites

The physical properties of low alkali content tellurite glasses of composition xM2O.(1−x)TeO2 (0≤x≤0·35) have been previously collected in this laboratory. The twin-roller rapid quenching technique (cooling rate>105°C/s), used within a nitrogen environment, successfully and significantly extended the glass-forming range in the lithium and sodium tellurite systems. The upper range for modification has been extended from x=0·35 to 0·80 and up to x=0·625 for the lithium and sodium systems, respectively. In the K, Rb and Cs tellurites, the glass forming ranges were not increased. Glass transition temperature (Tg), crystallisation temperature (Tx), density, molar volume, packing fraction, ionic conductivity and Raman spectra were obtained for these glasses. These results showed structural changes as a function of composition and carbonate retention in the glasses as the amount of alkali modifier increased above x=0·5.

A highly stable and conductive cerium‐doped Li7P3S11 glass‐ceramic electrolyte for solid‐state lithium–sulfur batteries

AbstractIn this report, a facile wet chemical method using acetonitrile combined with thermal annealing was used to prepare Li2S‐P2S5 (LPS) based glass‐ceramic electrolytes with (1 wt%, 3 wt%, and 5 wt% Ce2S3) and without Ce2S3 doping. The crystal structure, ionic conductivity, and chemical stability of Li7P3S11 glass‐ceramic electrolytes were examined at varying temperatures (250–350°C). The results indicated that the highest ionic conductivity of 3.15 × 10−4 S cm−1 for pure Li7P3S11 was observed at a temperature of 325°C. By incorporating 1 wt% Ce2S3 and subjecting it to a heat treatment at 250°C, the glass ceramic electrolyte attained a remarkable ionic conductivity of 7.7 × 10−4 (S cm−1) at 25°C. Furthermore, it exhibited a stable and extensive electrochemical potential range, reaching up to 5 volts when compared to the Li/Li+ reference electrode. By tuning the glass transition and crystallization temperature, cerium doping seems to make Li7P3S11 more chemically stable, compared to its original 70Li2S‐30P2S5 counterpart. According to Raman and X‐ray photoelectron spectroscopy analyses, cerium doping inhibits the decomposition of highly conductive P2S74‐ (pyro‐thiophosphate) to PS43− and P2S64−. Doped LPS has a greater crystallinity and more uniform microstructure than pure LPS, according to XRD, Raman spectroscopy, and scanning electron microscopy analysis. Consequently, Li7P2.9Ce0.1S11 electrolyte shows great potential as a solid‐state electrolyte for constructing high‐performance sulfide‐based all‐solid‐state batteries.

Study of properties of guar gum and its use in development of packaging film

Discarded plastic materials are now a potential problem throughout the globe; therefore, researchers today attach huge importance and applicability to green chemistry and the sustainable development of biopolymer-based materials that can fulfil the needs of synthetic plastics and polymers and save the biological community of the globe. In this work, a new packaging film was developed by using polyvinyl alcohol (PVA) and guar gum (GG) modified with n-octenyl succinic anhydride (OSA). The objective of the work is to develop a water-resistant film for food packaging applications. In synthesizing the biomaterial film, PVA, glycerol, and guar gum with OSA are used to enhance the capability of water resistance, and the major aim of this study is to improve the hydrophobic nature of guar gum through modification with OSA. The glass transition temperature (Tg = 114.45 °C), crystallization temperature (Tc = 176.85 °C), and melting temperature (Tm = 191.28 °C) of the films indicated better thermal stability. In the characterization study, it was found that 30 % GG/PVA with 5 % OSA provides a better result.

Impact of impurities on the thermal properties of a Li2S–SiS2–LiPO3 glass

AbstractThe preparation of 0.58 Li2S + 0.315 SiS2 + 0.105 LiPO3 glass, and the impacts of polysulfide and P1P defect structure impurities on the glass transition temperature (Tg), crystallization temperature (Tc), working range (ΔT≡ Tc ‐ Tg), fragility index, and the Raman spectra were evaluated using statistical analysis. In this study, 33 samples of this glass composition were synthesized through melt‐quenching. Thermal analysis was conducted to determine the glass transition temperature, crystallization temperature, working range, and fragility index through differential scanning calorimetry. The quantity of the impurities described above was determined through Raman spectroscopy peak analysis. Elemental sulfur was doped into a glass to quantify the wt% sulfur content in the glasses. Linear regression analysis was conducted to determine the impact of polysulfide impurities and P1P defect impurities on the thermal properties. Polysulfide impurities were found to decrease the Tg at rate of nearly 12°C per 1 wt% increase in sulfur concentration. The sulfur concentration does not have a statistically significant impact on the other properties (α = 0.05). The P1P defect structure appears to decrease the resistance to crystallization of the glass by measurably decreasing the working range of the glasses, but further study is necessary to fully quantify and determine this.

Tunable emission and energy transfer of B2O3–Bi2O3–AlF3 glass system doped with Eu3+/Dy3+

The structure and luminescent properties of the B2O3–Bi2O–AlF3 glass system doped with Eu3+/Dy3+ ions in different molar ratios were studied. A series of glasses were synthesized by the conventional melt quenching technique. Glass transition and crystallization temperatures were examined by Differential Thermal Analysis (DTA) measurements. The amorphous character of the prepared samples was confirmed by the X-ray diffraction (XRD) method. Raman and FTIR spectra were collected and deconvoluted to investigate the glass micro-structure. Luminescence spectra revealed that the added rare-earth ions can be excited by a single wavelength. The emitted color can be tuned by changing the ratios of the Eu3+/Dy3+ ions and the excitation wavelength. Furthermore, the influence of the addition of AlF3 on the luminescence and decay times was investigated. In the glasses with 10 mol% AlF3 an enhancement of the emission and excitation spectra was detected. The energy transfer analysis confirms the energy transfer between Eu3+ and Dy3+ ions in the glass matrix. Additionally, the results of this study indicate that the B2O3–Bi2O–AlF3 glasses doped with Eu3+ and Dy3+ can be used as a color tunable phosphor.

Experimental study of mechanical, morphological and thermal performance of bamboo-reinforced polylactic acid-based montmorillonite clay hybrid composite

Polylactic acid (PLA) is a promising, sustainable alternative to conventional petroleum-based polymers, but its mechanical and thermal properties limit its applications. This study introduces bamboo powders (BP) and montmorillonite clay particles (MMT) into the PLA matrix to prepare novel bio-based polymer hybrid composites using a unique combination of weight percentages of BP and MMT without chemical solvents through a stir casting process under optimised input parameters followed by compression moulding. Polymer hybrid composites were fabricated with different weight combinations, and their mechanical, morphological, and thermal properties were analysed. Tensile, flexural, and impact tests were performed to examine the mechanical performance, while thermogravimetric analysis and differential scanning calorimetry were used to assess thermal stability and characteristics. Microscopy observations showed a strong interaction between the bamboo, clay, and PLA matrix. The results revealed that the maximum tensile strength and modulus increased by 26.1 % and 40.8 %, respectively, with 10 wt% BP and 4 wt% clay content. Impact strength increased by 48 % with 15 wt% BP and 4 wt% clay content. Moreover, the thermal decomposition temperature, glass transition temperature (Tg), crystallisation temperature (Tc), and melting temperature (Tm) of the hybrid composites improved considerably with 10 wt% BP and 4 wt% clay content, increasing by 4 °C, 2 °C, and 8 °C, respectively. Based on the findings of this study, the controlled processing parameters were optimised to fabricate the bio-based composite with significantly improved mechanical and thermal properties. These properties make the composite suitable for various automotive and structural applications.

Advancing controlled-release phosphate glasses as sustainable fertilizers: Microelement-enhanced formulations and dissolution behavior analysis

In this study, we explore the potential of phosphate glasses as controlled-release fertilizers, addressing the need for sustainable nutrient management in agriculture. Our approach involves the systematic incorporation of microelements (Fe, Mn, Zn, B, Cu, Mo) into phosphate glasses to assess their impact on the glass's physicochemical properties. For this, seven phosphate glasses were synthesized using a combination of raw materials, and a series of experiments to analyze their thermal properties, structural characteristics, and dissolution behaviors were conducted. Results from the thermal analysis revealed an increase in glass transition, crystallization, and melting temperatures with progressively incorporating microelements indicating an enhancement in thermal stability. Structural characterizations unveiled a prevalent presence of Q2 units in the phosphate network, with discernible Q1 units existing as shorter phosphate chains within the matrix. The inclusion of microelements enhances the chemical durability of the glasses, with specific elements like iron and manganese significantly reducing dissolution rates. This enhanced chemical stability aligns with the requirements for controlled-release fertilizers as defined by ISO 18,644 standards. This study offers valuable insights into the interactions of microelements within phosphate glass matrices, highlighting their potential as effective and environmentally friendly controlled-release fertilizers. By meeting the ISO 18,644 criteria for controlled-release fertilizers, these glasses hold promise for sustainable agriculture practices.

Specific effects of Cr3+ dopant ions on diluted magnetic semiconductor Sb2-xCrxTe3 quantum dots in a glass matrix

Sb2-xCrxTe3 quantum dots (QDs) were synthesized in a host glass matrix through fusion and heat treatment methods. The results revealed the specific effects inherent to the doping of Cr3+ ions in diluted magnetic semiconductors (DMS) (Sb2-xCrxTe3 QDs embedded in glass matrix). Differential Thermal Analysis shows evidence of changes in glass transition and the host glass's crystallization temperatures with the presence of Sb2-xCrxTe3 QDs. Transmission electron microscopy (TEM) images and energy dispersive X-ray analysis evidenced the formation, size, and composition of these DMS QDs. The interplanar distances dhkl measured in TEM and the pattern observed in electron diffraction from the selected area reinforces the Sb2Te3 crystalline nature. Structural analyses of x-ray diffraction patterns confirm that all Sb2-xCrxTe3 QDs crystallize in the rhombohedral R3_m−D3d5 structure and that Cr3+-ions had replaced Sb3+-ions. Electronic paramagnetic resonance (EPR) spectra exhibit resonance signals confirming Cr3+ ion incorporation into the Sb2Te3 crystal lattice. Moreover, EPR shows that the sp-d exchange interactions become less pronounced with the formation of Cr3+ ─ Cr3+ pairs. Raman scattering spectroscopy confirmed the formation of Sb2-xCrxTe3 QDs. The red and blue shifts of the normal Raman- and IR-active vibrational modes characteristic of Sb2Te3 give strong evidence of the Cr3+ ion incorporation in QDs. Interestingly, the study results revealed better structural and magnetic properties. We believe that these Sb2-xCrxTe3 QDs in SNAB glass, with appropriate dopant concentration and chemical composition, are potentially efficient for thermoelectric, topological insulators, photovoltaic devices, solar cells, magnetic devices and spintronic applications.

Assessment of non-ester monoterpenoids as biobased plasticizers for polylactide with improved ductile behaviour

Poly(lactide) (PLA) is a biodegradable aliphatic polyester derived from renewable resources. This material is characterized by high strength and stiffness; however, it has a high brittleness which makes it difficult to use in certain applications. In the present work, the plasticizing effect of different non-ester monoterpenoids, namely carvone, citral, citronellal and eucalyptol, on the mechanical, thermal, morphological, physical and chemical properties of PLA has been studied. In this case, different amounts (10 and 20 wt%) of each monoterpenoid were mixed with PLA in a twin-screw extruder and standardized samples were obtained by injection molding. The obtained results show how the addition of 20 wt% of the different monoterpenoids significantly improves the elongation at break of PLA, reaching values of 335.7 % for 20 wt% citral content, which represents an increase of about 4044 % with respect to pure PLA (8.1 %). In addition, a significant reduction in the tensile strength and Young's modulus of PLA has also been observed with the presence of monoterpenoids. The addition of monoterpenoids also leads to a decrease in the glass transition temperature and crystallization temperature of PLA due to the increased mobility of the polymeric chains caused by the plasticizing effect of the monoterpenoids, this decrease being more noticeable in the case of citral and citronellal, which are the monoterpenoids with the highest miscibility with PLA. Finally, it has been observed that the addition of monoterpenoids hardly affects the transparency of PLA, obtaining materials that may have a high potential in sectors such as food packaging. Therefore, it has been demonstrated that these non-ester monoterpenoids, especially citral, have a great potential to obtain environmentally friendly PLA formulations with improved toughness.

Effect of substituting Na2O with B2O3 on the crystallization and properties of MgO–Al2O3–SiO2 transparent glass-ceramics

MgO–Al2O3–SiO2 (MAS) transparent glass-ceramics were prepared with ZrO2 as a nucleating agent, and the substitution of B2O3 for Na2O on the properties of the MAS glass-ceramics was investigated systematically. The results show that the substitution of B2O3 increased the glass transition temperature, crystallization temperature, and crystallization activation energy. Additionally, there was no change in the main crystal phase of the glass-ceramics, which were ZrO2 (JCPDS PDF#.50-1089) and Al0.52Zr0.48O1.74 (JCPDS PDF#.53-0294). The crystal growth mode shifted from three-dimensional growth to two-dimensional growth, and the crystal morphology transformed from a spherical appearance to a star-shaped appearance. Moreover, the mechanisms of the property changes induced by B2O3 substitution are revealed and discussed. The transmittance of MAS glass-ceramics without B2O3 decreased from 88 % to 32 % as the crystallization temperature increased from 800 °C to 920 °C, and decreased from 90 % to 8 % when B2O3 was added. Additionally, the Vickers hardness of MAS glass-ceramics decreased from 6.37 GPa to 6.13 GPa, after the introduction of B2O3, while, the fracture toughness increased from 1.48 MPa m1/2 to 1.55 MPa m1/2. The scratch behaviour of glass-ceramics exhibits a negative correlation with the applied load, but a positive correlation with the crystallization temperature. In particular, the incorporation of B2O3 substantially enhances the scratch resistance of glass-ceramics. The conclusions provide researchers with the roles of B2O3 in crystallization kinetics, microstructure, transmittance, and mechanical properties of MAS transparent glass-ceramics for various applications such as covers.