Failure mechanisms in in-situ SEM micropillar compressions of pre-crystallized and crystallized zirconia-containing lithium silicate glass-ceramics

Microscale microstructure-property relations for zirconia-containing lithium silicate glass-ceramics (ZLS) are critical for their applications as load-bearing restorations. This study investigated in-situ scanning electron microscopy (SEM) micropillar compression responses of pre-crystallized and crystallized ZLS materials with a flat diamond punch. Micromechanical properties (moduli, strength, ductility, resilience and toughness) of the two materials were determined. Pre-crystallized and crystallized ZLS materials showed distinct ductile-brittle failure mechanisms. Pre-crystallized ZLS containing weaker lithium metasilicate crystals and higher concentrated glass matrix revealed its ductile mode featured with bending and delamination, and side-splitting fractures originated from fragmentation and microcracking. Crystallized ZLS with stronger lithium disilicate crystals and lower concentrated glass matrix demonstrated bending and shear-band initiation, shear fracture from shear-band expansion and fragmentation. Further, crystallized ZLS yielded much higher moduli, strength, ductility, resilience and toughness than pre-crystallized ZLS. This study provides vital insights into the basic understanding of micromechanical behavior of ZLS materials for load-bearing applications.     

Role of vanadium oxide on the lithium silicate glass structure and properties

The structural role of V in 28Li₂O–72SiO₂ (in mol%) lithium silicate glass doped with 0.5 mol% V₂O₅ was assessed using ²⁹Si and ⁵¹V Nuclear Magnetic Resonance (NMR), Fourier-transform infrared (FTIR), and X-ray photoelectron (XPS) spectroscopy techniques. Despite the low amount of V₂O₅ used, the structural information obtained or deduced from the statistical analysis of the NMR data could explain the evolution of glass properties after V₂O₅ addition. The XPS results indicated that all vanadium exists in 5+ oxidation state. Both the ²⁹Si NMR and FTIR data point toward an increase in the polymerization of the silicate network, caused by the V₂O₅ acting as network former, capable to form various tetrahedral units (for n = 0, 1, and 2) in the glasses. These units, which are similar to phosphate units, scavenge the Li⁺ ions and cause the silicate network to polymerize. However, in an overall balance, the entire glass network is depolymerized due to the additional nonbridging oxygens contributed by the vanadium polyhedra. The addition of vanadium causes the network to expand and increases the ionic conductivity.     

Crystallization and thermal expansion behavior of lithium zinc silicate sealing glass

Effect of heat treatment schedule on the crystallization and thermal expansion behavior of a lithium zinc silicate glass system was investigated by differential scanning calorimeter (DSC), X-ray diffraction, and linear thermal expansion test. Two well-defined crystallization exothermic peaks were observed from the DSC trace. According to the apparent activation energies and avrami parameter values calculated from the two crystallization exothermal peaks, the first crystallization exothermal peak was attributed to a combining surface and internal crystallization behavior, while the second one was found to be internal crystallization. Additionally, the phase evolution and the thermal expansion behavior with increasing heat treatment temperature were found to be closely related. Interestingly, it was found in comparison with previous reports that addition of CaO varies the phase composition of the resulting glass–ceramic in an opposite way to K₂O and the deep rooted reason has been discussed which may cast light on the modulation of properties of glass–ceramic involved crystalline phase of quartz or cristobalite. At last, average thermal expansion coefficient of 7.99–15.38×10⁻⁶ K⁻¹ in the temperature range of 25–400 °C has been obtained with different heat treatment schedules.     

Cutting characteristics of dental glass ceramics during in vitro dental abrasive adjusting using a high-speed electric handpiece

Machinability is an important characteristic of dental ceramics for restorative dentistry because machining is not only commonly employed in dental CAD/CAM systems but also essential in dental adjustments for occlusal fitting and restorative quality. This paper reports on an in vitro study on machinability of dental ceramics by quantifying cutting characteristics of feldspar and leucite glass ceramics in simulated dental adjusting using a high-speed electric handpiece and diamond burs. Cutting forces, force ratio, energy, surface integrity and bur topography were evaluated as functions of clinically relevant cutting conditions. The results indicate that tangential and normal forces and specific cutting energy for both materials exhibited significant dependences (p<0.01) on both the bur depth of cut and the bur feed rate. Surface roughness showed a weak influence by the choice of the material (0.05>p>0.01) but no correlations with the cutting conditions applied (p>0.05). At the slower feed rates or smaller depths of cut the cutting behaviors for the two materials were very similar in terms of cutting forces and specific cutting energy. At the deeper depths of cut or faster feed rates, normal forces for leucite glass ceramic were significantly higher than those for feldspar glass ceramic (p<0.01). However, leucite glass ceramic produced better cutting surfaces with less fracture areas compared with feldspar ceramic due to its lower index of brittleness and higher force threshold for brittle–ductile transition. This research provides a methodological qualification in evaluating cutting characteristics of dental ceramics and quality control in clinical dentistry.     

Microstructural influence on damage-induced zirconia surface asperities produced by conventional and ultrasonic vibration-assisted diamond machining

Zirconia surface asperities associated with machining-induced damage and deformation jeopardize the quality of zirconia products. Conventional and emerging ultrasonic vibration-assisted machining processes are used to shape zirconia materials. However, a deep understanding of how zirconia microstructures and ultrasonic vibration amplitudes affect material removal mechanisms and surface quality in these processes is missing, rendering the proper mechanical process selection challenging. This paper reports on the 3D characterization of damage-induced surface asperities and the investigation of material removal mechanisms of pre-sintered porous and sintered dense zirconia materials in conventional and ultrasonic vibration-assisted diamond machining processes. 3D white light profilometry was used to measure surface asperities in terms of texture parameters, together with scanning electron microscopy (SEM) for imaging damage and deformation morphologies. The results show that removal mechanisms and damage-induced zirconia surface asperities depended on material microstructures and ultrasonic vibration amplitudes. Both porous and dense zirconia materials had a brittle-ductile mixed removal mode in conventional and ultrasonic vibration-assisted diamond machining processes. However, brittle fracture was dominant for the porous state and ductile deformation was presiding for the dense state. Thus, there were significantly higher fracture damage area ratios with much higher average and maximum roughness values, and maximum peak and valley heights on machined porous surfaces than dense ones. Ultrasonic assistance at an optimal vibration amplitude promoted brittle-ductile transitions on both porous and dense zirconia surfaces, resulting in reduced brittle fracture damage areas with reduced surface asperities. This microstructure-process-surface quality relation provides insights into manufacturing processes for zirconia products.     

硅酸镁锂的有机改性及物化性质研究

以十六烷基三甲基溴化铵(CTAB)、十六烷基溴化吡啶(CPB)及十八胺(ODA)为有机改性剂,采用阳离子交换法对硅酸镁锂进行有机改性。并用小角度X射线衍射仪(XRD)、傅里叶变换红外光谱仪(FT-IR)、热失重分析仪(TG)及扫描电子显微镜(SEM)对样品进行了表征;采用孔分布及比表面积测试仪测定了样品的孔分布情况及比表面积。实验结果表明3种改性试剂均插入硅酸镁锂层间,硅酸镁锂的层间距得到增大,其中十八胺-硅酸镁锂层间距增大到2.09nm;硅酸镁锂经有机改性后在有机溶剂及聚合物单体中的分散性得到提高。     

Capture of carbon dioxide over porous solid adsorbents lithium silicate,lithium aluminate and magnesium aluminate at pre-combustion temperatures

The capturing process for carbon dioxide over porous solid adsorbents such as lithium silicate, lithium aluminate, and magnesium aluminate at pre- combustion temperatures was studied. Lithium silicate was prepared by the sol gel and solid fusion methods. The lithium silicate adsorbent was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), nuclear magnetic resonance (NMR), and surface area. The capturing of carbon dioxide over lithium silicate, lithium aluminate, and magnesium aluminate was explored at different experimental conditions such as exposure time, temperature variation, and exposure carbon dioxide pressure. The capturing process for carbon dioxide was investigated over these adsorbents with variation of their metal mole ratios. The effect of the addition of (promoter) sodium, potassium, and cesium in the lithium silicate adsorbent was explored to investigate the variation of the capture of carbon dioxide over these adsorbents.     

Crystallization kinetics and enhanced Bi NIR luminescence of transparent silicate glass‐ceramics containing Sr2YbF7 nanocrystals

Bismuth‐doped glasses and crystals have been widely investigated due to their intriguing potential applications in superbroadband fiber amplifier and lasers in new NIR spectral range. However, few reports have been devoted so far to bismuth‐doped transparent glass‐ceramics. Here, this work reports on bismuth‐doped silicate glasses and glass‐ceramics, which were prepared by melt‐quenching and consequent annealing processes, respectively. On the basis of the analyses on crystallization kinetics, nucleation and growth rate of crystalline phase can be modulated and Sr₂YbF₇ nanophase can, therefore, be precipitated uniformly inside the glass matrix in a controlled way to maintain proper transparence especially in optical telecommunication windows. Once the nanophase comes into being, enhanced bismuth NIR luminescence can be observed by more than 40 times upon excitation of 470 nm. Similar enhancement can appear upon different excitation schemes and the mechanism is discussed accordingly. Such Bi doped transparent glass‐ceramics with improved luminescence efficiency might find application in fiber lasers for future optical fiber communication.     

Enhanced near-infrared to green upconversion from Er3+-doped oxyfluoride glass and glass ceramics containing BaGdF5 nanocrystals

In this work, effect of glass composition as well as ceramization on visible and near-infrared (NIR) luminescence properties along with their decay dynamics of Er³⁺ ions has been compared considering two different oxyfluoride glasses yielding BaF₂ and BaGdF₅ nanocrystals. Both the glass systems have exhibited an intense normal and upconversion green emission under ultraviolet (378 nm) and NIR (978 nm) excitations, respectively. A remarkable enhancement of these emission intensities is observed for gadolinium-(Gd) containing glasses. Interestingly, NIR fluorescence intensity from Er³⁺ ions at 1540 nm has showed marginal decrease in gadolinium-containing glass which is attributed to occurrence of strong excited-state absorption (ESA) due to higher fluorine content ensuing an augmentation of upconversion green emission with a concomitant decrease in NIR emission. The quadratic dependence of upconversion green emission intensity on its pump power for all the samples revealed biphotonic absorption process from ground-state ⁴I_15/2 to the excited-state ⁴I_11/2 followed by ESA of second photon to the ⁴F_7/2 level. The intense green upconversion emission as well as enhanced NIR fluorescence lifetimes indicate the suitability of these glass/glass ceramics for upconversion lasers and amplification in the third telecom window.     

Crystallization of a highly viscous multicomponent silicate glass: Rigidity percolation and evidence of structural heterogeneity

A magnesium bearing multicomponent silicate glass was annealed at the temperature slightly above glass transition temperature (T_g) for various periods of time. The crystalline phase of fluorophlogopite with the chemical formula of NaMg₃AlSi₃O₁₀F₂ is precipitated in the floppy regions, which leads to the formation of a core-shell structure. Considering that there exists only four- or six-fold coordinated Mg²⁺ in the studied glass, the fraction of four-fold coordinated Mg²⁺ is determined by comparing the maximum size of the crystallite and the floppy region according to the percolation theory. In addition, a striking phenomenon of endotherm above glass transition in heat capacity (C_p) curve is observed for the first time when prolonging the annealing time, which is ascribed to the amorphous heterogeneous structure surrounding the crystallites.     

Suppression of diamond tool wear in machining of tungsten carbide by combining ultrasonic vibration and electrochemical processing

As an important ceramic material, tungsten carbide (WC) is utilized as the typical mold in precision glass molding, which has replaced conventional grinding and polishing to provide a highly replicative process for mass manufacturing of optical glass components. Ultra-precision grinding, which is time consuming and has low reproducibility, is the only method to machine such WC molds to high profile accuracy. Although diamond turning is the most widely used machining method for fabrication of optical molds made of metals, diamond turning of WC is still considered challenging due to fast abrasive wear of the diamond tool caused by high brittleness and hardness of WC. Ultrasonic vibration cutting has been proven to be helpful in realizing ductile-mode machining of brittle materials, but its tool life is still not long enough to be utilized in practical diamond turning of optical WC molds. In the current study, a hybrid method is proposed to combine electrochemical processing of WC workpiece surface into the diamond turning process. Cutting tests on WC using poly-crystalline diamond tools were conducted to evaluate its effect on improvement of tool wear and surface quality. Validation cutting tests using single crystal diamond tools has proven that the proposed hybrid method is able to significantly reduce the diamond tool wear and improve the surface quality of machined ultra-fine grain WC workpiece compared to ultrasonic vibration cutting without electrochemical processing.     

Fundamental research on machining performance of diamond wire sawing and diamond wire electrical discharge sawing quartz glass

In reciprocating diamond wire sawing of quartz glass, the reversing and acceleration and deceleration will cause the position change of diamond wire, resulting in the discontinuous wire sawing in the reversing stage, so as to leave residual material on the processing surface and form wire marks. Also, the cutting load will cause diamond wire deformation as bow shape, and affect the machining accuracy. In this paper, the evaluation of DWS machining performance of quartz glass focus on the sawing time, cutting force and vibration, wire tension, machining surface flatness and roughness, surface morphology and wire state. The theoretical analysis of wire mark was carried out, and the simplified wire bow model of quartz glass sawing was established. The existence of wire mark and wire bow were verified by detecting the 3D contour of the slice. In addition, a diamond wire electrical discharge sawing (DWEDS) was performed to find the differences to DWS in the above indicators. Experiments were presented in jet cooling and bath cooling conditions. It was found that the cutting force, vibration, and wire tension of DWEDS are more stable than that of DWS. The DWEDS has been proved helpful to improve machining performance of quartz glass from surface roughness, sawing time, processing state, and wire bow control as it reduces the macro cutting force acting on the diamond wire although the discharge effect is weak. The SEM of slice surface and diamond wire showed no significant difference between DWEDS and DWS. Also, the influence of feed speed and cooling methods on machining performance was investigated.     

Effect of soluble Cr2O3 on the silicate network,crystallization kinetics,mineral phase,microstructure of CaO-MgO-SiO2-(Na2O) glass ceramics with different CaO/MgO ratio

Cr₂O₃ is often used as a glass additive to prepare glass ceramics. Chromium element exists mainly in two parts in the glass ceramics: chromium-containing spinel and soluble chromium in glass matrix. Herein, effect of soluble chromium on the CaO-MgO-SiO₂-(Na₂O) glass system is researched. Glass and glass ceramics were characterized by Raman spectrum, X-ray diffraction, scanning electron microscopy, energy dispersive spectrometry. It is found that the addition of Cr₂O₃ increased the Q²si structure unit in glass networks, especially in glass systems with high MgO content. The crystallization temperatures of the systems were increased with the addition of Cr₂O₃. Soluble chromium reduced the crystallization activation energy of the glass system slightly, but did not alter its crystallization behavior (surface crystallization). With the increase of MgO content, the mineral phases of the glass ceramics gradually changed from wollastonite to diopside. Cr₂O₃ reduced the lattice parameters of the mineral phases. The addition of Cr₂O₃ has a significant effect on grain refinement and structural compactness of the glass ceramics system with high MgO content.     

Growth behavior,morphology and properties of lithium aluminosilicate glass ceramics with different amount of CaO,MgO and TiO2 additive

Li₂O–Al₂O₃–SiO₂ glass with CaO, MgO and TiO₂ additive were investigated. With more CaO + MgO addition, the crystallization temperature (T_p) and the value of Avrami constant (n) decreased, the activation energy (E) increased. The mechanism of crystallization of the glass ceramics changed from bulk crystallization to surface crystallization. With more TiO₂ addition, the crystallization temperature decreased, E and n had a little change. The crystallization of the glass ceramics changed from surface crystallization to two-dimensional crystallization. Plate-like, high mechanical properties spodumene-diopside glass ceramics were obtained. The mechanical properties related with crystallization and morphology of glass ceramics.     

Preparation of V doped lanthanum silicate electrolyte ceramics by combustion method and study on conductance mechanism

Vanadium doped La_9.33Si_6−xV_xO_26+0.5x (x = 0.5, 1.0, 1.5) (LSVO) electrolyte powder was prepared by combustion method at 600°C for 5-7 min. The powder was sintered at 1500°C for 3 hours to prepare LSVO ceramics. XPS, IR, XRD, and EIS analysis show that V⁵⁺ doping replaces Si⁴⁺ in [SiO₄] to form [Si(V)O₄] tetrahedron. With the increase in x, the lattice volume increase. When x = 2.0, the LaVO₄ phase was formed, indicating that the limit doping amount of V⁵⁺ replacing Si⁴⁺ is x ≤ 1.5. The conductivity of LSVO increases significantly with the increase in x (x ≤ 1.0), which attributed to the defect reaction caused by V⁵⁺ doping. The addition of the interstitial oxygen Oi* in 6₃ channels and the increase of lattice volume leads to increased conductivity. When x = 1.0, the highest conductivity is 1.46 × 10⁻² S·cm⁻¹ (800°C). The doping enhancement conductivity mechanism is the Interstitial oxygen defect-Lattice volume composite enhancement mechanism.     

Effect of heat treatment on the roughness and mechanical properties of dental lithium disilicate glass-ceramics

In dental clinics, it is common to perform small fitting adjustments in dentures using a micro-grinding tool after testing them in the patient's mouth. This procedure increases local roughness and can lead to formation of microcracks on the prosthesis surface. This study aimed to investigate the benefits of a post-finishing heat treatment to surface roughness and crack healing and its effect on the flexural strength of lithium disilicate (LD) dental glass-ceramics. Commercially available lithium metasilicate, Li₂SiO₃, samples were heat treated at 840 °C for 7 min to induce the phase transformation into LD, Li₂Si₂O₅. The LD samples were characterized by X-ray Diffraction, Scanning Electron Microscopy, Vickers hardness, Young’s modulus, and fracture toughness. One of the surfaces of the LD samples was sanded aiming to simulate the denture fitting adjustments performed in the dentist’s laboratory, generating a rough surface, Group 1. Half of the LD samples had their biaxial flexural strength evaluated by the piston-on-three-ball test (P–3B) and the other half were submitted to a second short-term heat treatment (840 °C - 5 min), Group 2, and later assessed by the P–3B. Roughness parameters in both groups were measured by 3D optical profilometry. After the crystallization heat treatment, formation of elongated LD crystals, Li₂Si₂O₅, 35% amorphous phase, and residual Li₃PO₄ was observed. In addition, the following mechanical property values were obtained: Vickers hardness = 5.8 ± 0.1 GPa, fracture toughness = 2.2 ± 0.1 MPa m^1/2, and Young’s modulus = 100.3 ± 0.3 GPa. The samples in Group 1 showed bending strength of 206 ± 30 MPa and the following roughness parameters: Ra = 0.45 ± 0.16 μm, Rz = 22.7 ± 6.7 μm, and PV = 27.7 ± 7.1 μm. In the samples in Group 2, the Ra, Rz and PV roughness parameters were 0.31 ± 0.12 μm, 5.2 ± 2.5 μm, and 9.2 ± 4.7 μm, respectively. With this decrease in roughness, the bending strength increased by 62%, with a mean value of 331 ± 59 MPa. In the need for machine finishing of LD-based glass-ceramic dental prostheses, the use of a second short-term heat treatment at 840 °C for 5 min generates considerable gains in bending strength, increasing the lifecycle of the prosthesis as a result of reduced surface roughness caused by softening of the remaining amorphous phase in the glass-ceramic. These conditions can be adapted to each chemical and crystallographic composition of the glass-ceramic under study.     

Searching for correlations between vibrational spectral features and structural parameters of silicate glass network

Infrared (IR) and Raman spectroscopic features of silicate glasses are often interpreted based on the analogy with those of smaller molecules, molecular clusters, or crystalline counterparts; this study tests the accuracy and validity of these widely cited peak assignment schemes by comparing vibrational spectral features with bond parameters of the glass network created by molecular dynamics (MD) simulations. A series of sodium silicate glasses with compositions of [Na₂O]_x[Al₂O₃]₂[SiO₂]_98−x with x = 7, 12, 17, and 22 were synthesized and analyzed with IR and Raman. A silica glass substrate and a crystalline quartz were also analyzed for comparison. Glass structures with the same compositions were generated with MD simulations using three types of potentials: fixed partial charge pairwise (Teter), partial diffuse charge potential (MGFF), and bond order-based charge transfer potential (ReaxFF). The comparison of simulated and experimental IR spectra showed that, among these three potentials tested, ReaxFF reproduces the concentration dependence of spectral features closest to the experimentally observed trend. Thus, the bond length and angle distributions as well as Si–Qⁿ species and ring size distributions of silica and sodium silicate glasses were obtained from ReaxFF-MD simulations and further compared with the peak assignment or deconvolution schemes—which have been widely used since 1970s and 1980s—(a) correlation between the IR peak position in the Si–O stretch region (1050-1120 cm⁻¹) and the Si–O–Si bond angle; (b) deconvolution of the Raman bands in the Si–O stretch region with the Qⁿ speciation; and (c) assignment of the Raman bands in the 420-600 cm⁻¹ region to the bending modes of (SiO)_n rings with different sizes (typically, n = 3-6). The comparisons showed that none of these widely used methods is congruent with the bond parameters or structures of silicate glass networks produced via ReaxFF-MD simulations. This finding invokes that the adequacy of these spectral interpretation methods must be questioned. Alternative interpretations are proposed, which are to be tested independently in future studies.     

Damage formation and suppression in rotary ultrasonic machining of hard and brittle materials: A critical review

Rotary ultrasonic machining (RUM) combines diamond grinding with small-amplitude tool vibration, to improve machining processes of hard and brittle materials. It has been successfully applied to the machining of a number of brittle materials from optical glasses to advanced ceramics as well as ceramic matrix composites. The emphasis of this literature review was on formation mechanism and suppression methods of machining induced damages that truly limit RUM machining efficiency improvement of brittle materials. In this review paper, material removal mechanism and cutting force modeling of RUM of brittle materials were presented, as well as all corresponding roles in the damage formation process. The critical processing capacity of RUM machine tools was described, which guarantees the RUM effectiveness and consequently constitutes the boundary condition of processing parameters determination. Formation mechanisms of edge chipping, tearing defects, subsurface damages, and their interactive effects were summarized. Advances in damage suppression methods were also described, including optimization of processing parameters, tool design of low damage, and other methods such as rotary ultrasonic elliptical machining.     

Improving white light emission and quantum yield of Ce@Eu co-doped silicate glass by reducing Eu3+ to Eu2+ with Si3N4

Rare-earth-doped transparent glass shows great potential in white light-emitting diodes (wLEDs) application due to its excellent optical and luminous properties. Currently reported commercial wLEDs have a drawback in red emission missing, which leads to a relatively low color rendering index (CRI) and a relatively high correlated color temperature (CCT). In this work, Ce@Eu Sr–Si–O glass is fabricated using a high-temperature quenching method. The white light is available when the ratio of Ce³⁺/Eu³⁺ equals 1, and the emitting color can be adjusted from blue to red by controlling the ratio of Ce³⁺/Eu³⁺. To further optimize the white light, Eu³⁺ ions can be reduced to Eu²⁺ according to the reaction of 6Eu³⁺ + 2N³⁻ → 6Eu²⁺ + N₂↑ by introducing Si₃N₄. As a result, the standard white light emission can be achieved in the Ce@Eu silicate glass contributed by the blue light from Ce³⁺, red light from Eu³⁺, and yellow–green light from Eu²⁺ (two elements, three emission). This glass shows excellent luminous properties, such as a color coordinate is (0.3651, 0.3269) in CIE 1931 color coordinate diagram, a CRI is over 70, a high quantum yield of 36.02%, and a CCT of 4117 K.     

Structural and spectroscopic properties of some neodymium-boro-germanate glasses and glass ceramics embedded with silver nanoparticles

Neodymium-boro-germanate glasses and glass ceramics (with Nd₂O₃ contents up to 40 mol%) embedded with silver metallic nanoparticles (AgNPs) were prepared by the melt-quenching technique. Two series of samples (with AgNPs and without AgNPs) were investigated by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, diffuse reflectance ultraviolet–visible (DR-UV–vis) spectroscopy and photoluminescence (PL) spectroscopy. XRD data reveal that for both series the samples with x < 40 mol% Nd₂O₃ are basically amorphous containing only small amounts of a crystalline phase (identified as crystalline B₂O₃) while for samples x = 40 mol% Nd₂O₃ an important amount of a crystalline phase (identified as the NdBO₃ orthorhombic phase) is present. FT-IR spectroscopy data show that addition of controlled amounts of Nd₂O₃ and AgNPs changes the structural units that build up the host glass ceramic network. These changes were confirmed also by the photoluminescence spectra that show that addition of AgNPs to the host matrix produces changes at the level of emission peaks. The positive values of bonding parameter (δ) calculated based on DR-UV–vis data indicate a covalent character of the bonds from the studied samples.