Exothermic Crystallization Research Articles

Emulsion Stability and Rheological Properties of Emulsions Prepared with Ozonized Hazelnut Oil

In this study, physical and rheological characteristics of the emulsion stabilized with whey protein isolate (WPI) at a concentration of 0.25% (w/w) and containing ozone applicated hazelnut oil (OHO) were studied. The hazelnut oil was subjected to ozone gas exposure for durations of 1, 5, 30, 60, 180, and 360 min. The emulsions made with both control (HO) and OHO were analysed to assess emulsion properties. It was observed that as the duration of ozone application increased, the emulsion activity index (EAI) experienced a decrease. Specifically, ozone applications of 30, 60, and 180 min significantly reduced emulsion stability index (ESI). The creaming ratio of emulsions formulated with OHO for durations of 1, 5, 30, 60, and 180 min were found to be 23%, 20%, 18%, 16%, and 44%, respectively. Optical microscopy revealed that significant flocculated droplet formed in emulsions including OHO. The longer time the ozone application resulted that the emulsions exhibited more solid-like behaviour. Furthermore, differential scanning calorimeter (DSC) was utilized to assess the changes in the melting and cooling profiles of hazelnut oil after being applicated with ozone. An increase in ozone application duration led to the melting peaks broadening and shifting towards lower temperatures. Also, ozone application caused that the sharp exothermic crystallization shifted towards lower temperatures and become broader and less pronounced as the duration of the application increased.

Isothermal crystallization kinetics of commercial PA66 and PA11

This study is aimed at investigating the crystallization kinetics of two structurally related polymers, Nylon 6,6 (PA66) and Nylon 11 (PA11), by differential scanning calorimetry (DSC) in the scope of a logistic-based model using a model fitting approach. By this method, the values of the rate parameters for each specific temperature are obtained from fitting all points of the crystallization exotherm that were accurately recorded at that temperature. This method differs from Arrhenius-based model fitting approaches, in which the initial and final parts of the exotherm do not usually match the shape of Arrhenius-based models and are therefore discarded for fitting. Furthermore, in other kinetic approaches that fall outside the scope of this article, kinetic parameters are typically obtained from specific points in the crystallization exotherm, and good fits cannot generally be obtained nor is that the goal of those approaches. The DSC curves of both polymers obtained at different temperatures are analysed to determine the crystallization kinetics. One of the most insightful parameters of the model is the crystallization rate. Its dependence on temperature is analysed for both polymers and compared to others. The other parameters can also help to better understand some of the crystallization features of these polymers. In addition, the information retrieved from this study can be useful to adjust processing conditions.

Transition mechanism and thermokinetic analysis of Sr0.5Zr2(PO4)3–Ce0.5Sm0.5PO4 composite ceramics for nuclear waste forms based on in-situ synthesis

In this study, the novelly designed Sr0.5Zr2(PO4)3–Ce0.5Sm0.5PO4 composite ceramics were utilized as nuclear waste form to simultaneously immobilize simulated fission products Sr and actinide nuclides. The phase transition mechanism, thermokinetics and densification behavior of Sr0.5Zr2(PO4)3–Ce0.5Sm0.5PO4 composite ceramics based on in-situ synthesis were systemically analyzed by XRD, in-situ XPS, TG-DSC, SEM and density measurements. The results demonstrate that the formation of Ce0.5Sm0.5PO4 solid solution phase preceded that of Sr0.5Zr2(PO4)3 phase, of which there is a valence change of Ce from Ce4+ to Ce3+ before 1023 K. Additionally, as for the exothermic crystallization enthalpy, change of exothermic crystallization enthalpy and activation energy, the values of Sr0.5Zr2(PO4)3 and Ce0.5Sm0.5PO4 phases in composite ceramics are 286.17 – 515.61 mJ, 19.11 – 35.38 J/g, 702.45 kJ/mol and 145.21 – 232.44 mJ, 9.26 – 15.44 J/g, 450.04 kJ/mol, respectively. It is then indicated that the formation of Ce0.5Sm0.5PO4 phase is definitely more favorable than that of Sr0.5Zr2(PO4)3 phase. Simultaneously, the relative densities of Sr0.5Zr2(PO4)3–Ce0.5Sm0.5PO4 composite ceramics are more than 95 % when the sintering temperature exceeds 1273 K.

The glass transition temperature of anhydrous amorphous calcium carbonate

Abstract Amorphous calcium carbonate (ACC) is the least stable polymorph of calcium carbonates. It has been identified to play an important role in nature (e.g., biomineralization and speleothem formation), where it acts as a precursor for the transformation to more stable polymorphs such as calcite. Furthermore, the use of ACC in technical applications requires a robust understanding of the material’s properties. We present the first study that reveals the existence of a glass transition for synthetic and anhydrous ACC. The glass transition occurs at 339 °C. Such measurements are impossible with conventional differential scanning calorimetry (DSC) due to the high tendency of ACC to crystallize. Fast scanning DSC with heating rates of 500 °C/s and higher, however, can be used to separate the endothermic glass transition signature from the exothermic crystallization event since crystallization is shifted to higher temperatures. This allows the detection and quantification of the glass transition for ACC. These observations indicate that ACC is a structural glass and are especially significant because the synthesis of ACC, precipitation from a solution followed by lyophilization, contrasts with the more conventional and well-known route of glass formation–the rapid cooling of a melt. Moreover, we prove that a structural glass can be produced from a simple single-component carbonate system.

Establishing patterns in the structure formation of polymer nanocomposites based on polyamide 6 during their crystallization processes

This paper reports experimental and computational studies on patterns in the structure formation of polymer nanocomposites when different types of fillers are used. The study was conducted for nanocomposites based on polyamide 6 filled with carbon nanotubes or silicon dioxide nanoparticles. In the course of research, the mass fraction of the filler varied from 0.2 % to 4.0 %, and the cooling rate of the melt composite varied from 0.5 K/min up to 20 K/min. Data on experimental and theoretical studies into the mechanisms of structure formation of composites according to the method, which includes two stages, are given. According to the first stage, crystallization exotherms of nanocomposites were experimentally obtained when they are cooled from the melt at a given constant rate. The dependence of various characteristics of the crystallization process on the mass fraction of the filler and the cooling rate of the composite was established. At the second stage, based on the analysis of the obtained crystallization exotherms, theoretical studies were performed to determine the mechanisms of structure formation of nanocomposites at different stages of crystallization. For the initial stage, according to the nucleation equation, the presence of two mechanisms of structure formation – planar and volumetric – has been shown. Within the framework of the Kolmogorov-Avrami equation, the mechanisms of structure formation at the next stage of crystallization were established, which corresponds to the formation of ordered structures in the material within the volume of the polymer composite as a whole. The research was carried out assuming the existence of a mechanism of crystallization of the polymer matrix itself, which is realized on fluctuations in the density of the polymer, and a mechanism of crystallization, the centers of which are filler particles. The use of the proposed nanocomposites is promising for the manufacture of parts of energy equipment, electronic equipment, elements of chemical, processing, defense industry installations, etc.

Microfluidic Assembly of Degradable, Stereocomplexed Hydrogel Microparticles.

Hydrogel microparticles (HMPs) have been investigated widely for their use in tissue engineering and drug delivery applications. However, translation of these highly tunable systems has been hindered by covalent cross-linking methods within microparticles. Stereocomplexation, a stereospecific form of physical cross-linking, provides a robust yet degradable alternative for creating translationally relevant HMPs. Herein, 4-arm polyethylene glycol (PEG) stars were used as macromolecular initiators from which oligomeric poly(l-lactic acid) (PLLA) was polymerized with a degree of polymerization (DPn) of 20 on each arm. Similarly, complementary propargyl-containing ABA cross-linkers with enantiomeric poly(d-lactic acid) (PDLA) segments (DPn = 20) on each arm. Droplets of these gel precursors were formed via a microfluidic organic-in-oil-in-water system where microparticles self-assembled via stereocomplexation and were stabilized after precipitation in deionized water. By varying the flow rate of the dispersed phase, well-defined microparticles with diameters of 33.7 ± 0.5, 62.4 ± 0.6, and 105.7 ± 0.8 μm were fabricated. Gelation due to stereocomplexation was confirmed via wide-angle X-ray scattering in which HMPs exhibited the signature diffraction pattern of stereocomplexed PLA at 2θ = 12.2, 21.2, 24.2°. Differential scanning calorimetry also confirmed stereocomplexation by the appearance of a crystallization exotherm (Tc = 37 °C) and a high-temperature endotherm (Tm = 159 °C) that does not appear in the homocrystallization of PLLA or the hydrogel precursors. Additionally, the propargyl handle present on the cross-linker allows for pre- or post-assembly thiol-yne "click" functionalization as demonstrated by the addition of thiol-containing fluorophores to the HMPs.

On polymorphic crystal growth in a Ti-Ni-Cu-Fe system metallic glass at the glass-transition temperature

A polymorphic crystallization reaction forming spherical cP2/B2 crystals in a Ti50Ni22Cu22Fe6 metallic glass close to the glass-transition temperature was studied. The phase transformation was investigated by differential scanning calorimetry. X-ray diffractometry indicated the formation of the cP2/B2 crystalline phase after the initial exothermic crystallization reaction. In situ transmission electron microscopy observation allowed direct measurement of a crystal growth rate at a constant temperature close to the glass-transition temperature while the usage of an analytical microscope confirmed the polymorphic nature of the phase transformation. The results are interpreted in line with the diffusion data suggested from the viscosity obtained in creep experiments with a thermo-mechanical analyzer. Thermodynamic considerations are also taken into account.

Investigating the thermal behavior of acyclovir

Viruses are a significant health, economic and social issue. Acyclovir (ACV) is an antiviral agent analogous to the guanine nitrogenous base that acts by interrupting the multiplication of DNA of virus in infected cells. The thermal decomposition mechanism of ACV was evaluated by thermoanalytical techniques Thermogravimetry/derivative thermogravimetry (TG/DTG), differential thermal analysis (DTA), evolved gas analysis by thermogravimetry coupled to vibrational infrared spectrometry in gas phase (TG-FTIR), differential scanning calorimetry (DSC), hot stage microscopy (HSM) and mass spectrometry (MS). TG/DTG and DTA curves were performed under N2 and air atmospheres. Under N2, four stages of mass loss were observed from the TG curve between 523-1273 K, while under air decomposition occurred in a similar way, however, the additional burning of carbonaceous material was found in air. DSC curves were obtained in heat-cool-heat mode, from 233 to 543 K, under N2 atmosphere and presented two endothermic peaks related to water loss and phase transition followed by exothermic crystallization of a new form, followed by melting associated with decomposition in agreement with HSM images. Powder X-ray diffraction (PXRD) profiles confirmed the phase transitions. From the TG-FTIR characterization, it was suggested that decomposition undergoes by release of water, 1,3-dioxolane, isocyanic acid, carbon dioxide, carbon monoxide, and ammonia. MS spectrum of the residue collected at 543 K revealed the presence of guanine free base as decomposition product in agreement with the release of dioxolane ring in gas phase.

Biodegradable Polyhydroxyalkanoates with a Different Set of Valerate Monomers: Chemical Structure and Physicochemical Properties.

The properties, features of thermal behavior and crystallization of copolymers containing various types of valerate monomers were studied depending on the set and ratio of monomers. We synthesized and studied the properties of three-component copolymers containing unusual monomers 4-hydroxyvalerate (4HV) and 3-hydroxy-4-methylvalerate (3H4MV), in addition to the usual 3-hydroxybutyrate (3HB) and 3-hydroxyvalerate (3HV) monomers. The results showed that P(3HB-co-3HV-co-4HV) and P(3HB-co-3HV-co-3H4MV) terpolymers tended to increase thermal stability, especially for methylated samples, including an increase in the gap between melting point (Tmelt) and thermal degradation temperature (Tdegr), an increase in the melting point and glass transition temperature, as well as a lower degree of crystallinity (40-46%) compared with P(3HB-co-3HV) (58-66%). The copolymer crystallization kinetics depended on the set and ratio of monomers. For terpolymers during exothermic crystallization, higher rates of spherulite formation (Gmax) were registered, reaching, depending on the ratio of monomers, 1.6-2.0 µm/min, which was several times higher than the Gmax index (0.52 µm/min) for the P(3HB-co-3HV) copolymer. The revealed differences in the thermal properties and crystallization kinetics of terpolymers indicate that they are promising polymers for processing into high quality products from melts.

Extraction, physicochemical characterization, functionality, and excipient ability of corn fiber gum-starch isolate from corn milling industry waste

Corn processing industries generate an extensive fibrous byproduct consisting of corn fiber gum (CFG) and residual starch (S). The present study hypothesized that CFG and S could be isolated as a single crosslinked conjugate. The isolated CFG-S conjugate was acidic, with a pKa value of 11.49, and a swelling index of 99.60%. Henderson–Hasselbalch equation predicted negligible ionization throughout the gastrointestinal pH range. The DSC thermogram highlights glass transition and temperature-specific structure stabilization through the exothermic crystallization domain. FTIR, SEM & XRD confirmed the structural conjugation and integrity of the conjugate. Tablets containing Venlafaxine hydrochloride as a model drug were prepared using CFG-S (14 and 57%) as excipient by wet granulation method. Percentage cumulative drug release with low concentration was up to 99.67175 ± 0.09 % in 5 h whereas with high concentration, it was extended to 12 h (P < 0.05). Korsemayer-Peppas release exponent indicates zero order (R2 = 0.9935) kinetics with super case-II anomalous transport showing diffusion and erosion as drug release mechanisms. The results confirmed that CFG-S isolate could act as a good binding agent at low concentrations and release extending cross-linked matrix former at a higher concentration for release retardant excipient.

Effect of Monomers of 3-Hydroxyhexanoate on Properties of Copolymers Poly(3-Hydroxybutyrate-co 3-Hydroxyhexanoate)

The properties of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) P(3HB-co-3HHx) copolymers with different ratios of monomers synthesized by the wild-type strain Cupriavidus necator B-10646 on sugars, and an industrial sample from Kaneka synthesized by the recombinant strain C. necator NSDG-ΔfadB1 on soybean oil, were studied in a comparative aspect and in relation to poly(3-hydroxybutyrate) P(3HB). The copolymer samples, regardless of the synthesis conditions or the ratio of monomers, had reduced values of crystallinity degree (50–60%) and weight average molecular weight (415–520 kDa), and increased values of polydispersity (2.8–4.3) compared to P(3HB) (70–76%, 720 kDa, and 2.2). The industrial sample had differences in its thermal behavior, including a lower glass transition temperature (−2.4 °C), two peaks in its crystallization and melting regions, a lower melting point (Tmelt) (112/141 °C), and a more pronounced gap between Tmelt and the temperature of thermal degradation (Tdegr). The process, shape, and size of the spherulites formed during the isothermal crystallization of P(3HB) and P(3HB-co-3ННx) were generally similar, but differed in the maximum growth rate of the spherulites during exothermic crystallization, which was 3.5–3.7 μm/min for P(3HB), and 0.06–1.25 for the P(3HB-co-3HHx) samples. The results from studying the thermal properties and the crystallization mechanism of P(3HB-co-3HHx) copolymers are important for improving the technologies for processing polymer products from melts.

CO2 as the main parent source of atomic oxygen in comet C/2017 K2 (Pan-STARRS)

C/2017 K2 (Pan-STARRS) is an Oort cloud comet discovered in May 2017. Ground observations have revealed that this long-period comet was active at heliocentric distance of 35 au. At such a distance, activity cannot be driven by the sublimation or the exothermic crystallization of water ice. We assume that the activity of comet C/2017 K2 may be driven by the sublimation of super-volatile ices such as CO and CO2. The nature of parent molecules driving the unprecedented activity of comet C/2017 K2 can be investigated by analyzing its spectrum. In particular, the analysis of atomic oxygen emission lines and the calculation of the green (5577.339 Å) to red (6300.304 and 6363.776 Å) line intensity ratio (hereafter G/R) can reveal the nature of molecules driving cometary activity. We report on the detection of atomic oxygen lines in the spectra of comet C/2017 K2 (Pan-STARRS) from high-resolution spectra obtained at the Telescopio Nazionale Galileo (TNG) on 24 June and 2 July 2022 using the High Accuracy Radial velocity Planet Searcher North (HARPS-N) echelle spectrograph. We found G/R ratios equal to 0.29±0.02 (24 July 2022) and 0.27±0.01 (2 July 2022), which are consistent with a cometary activity driven by CO2, even if located at 2.8 au from the Sun. To better define the nature of the driving molecule, we measured the width of the three oxygen lines and found that the green line in the spectrum of 24 July 2022 is wider than either of the two red lines. This allows us to argue that CO2 is dissociated by highly energetic solar photons that produce O(1S) with a large excess velocity.

Self-ignition of amorphous alloys activated by exothermic crystallization

Increasing importance has been paid to ignition and combustion of metals for their wide engineering applications. However, the ignition temperatures of pure metals are much higher than their melting points, leading to long ignition delays, agglomeration before ignition, slow burning rates and incomplete combustion. Here, we report on the ignition of amorphous alloys activated by exothermic crystallization, which is weakly dependent on oxygen. It is found that, though the crystallization enthalpy of an amorphous alloy is a constant value under different heating rates, its maximum available exothermic transition specific power (PT,transmax, W/g) during crystallization is considerably enhanced by several orders of magnitude due to a high-rate heating. For example, PT,transmax of the Zr60Al15Ni25 amorphous alloy is magnified from 2.96 W/g at a heating rate of 1 K/s to ∼2.70×104 W/g at a heating rate of 3.0 × 103 K/s. It is such a high PT,transmax that triggers a self-propagating exothermic solid-state reaction; as a result, a self-ignition is activated. Our finding sheds light on the ignition mechanism of amorphous alloys, which is scientifically important for their engineering applications as metalized energetic and reactive materials.

Binary decanoic acid/polyethylene glycol as a novel phase change material for thermal energy storage: Eutectic behaviors and energy conservation evaluation

This work developed a novel decanoic acid/polyethylene glycol binary eutectic (DA-PEG) phase change material (PCM) for thermal energy storage, wherein the mass ratio of DA and PEG was 1:1. DSC results indicated that DA-PEG eutectic had a suitable phase transition temperature of 22.9 °C for building thermal comfort, and its latent heat of 173.9 J/g was relatively large. Moreover, DA-PEG eutectic PCM had a superior crystallinity as compared to pure PEG, which was confirmed by the results in terms of supercooling degree, relative exothermic capacity and crystallization kinetics. ATR-FTIR and Raman spectra were used to reveal the mechanism behind. It turned out that the improved crystallization behaviors of PEG were achieved by the promoting effect of the intermolecular hydrogen bonding between DA and PEG on the ordered arrangement of PEG long chain. Furthermore, DA-PEG eutectic PCM presented good thermal and chemical stability in long-term use. Besides, energy and environmental assessment suggested that DA-PEG eutectic exhibited high cost performance and great potentials for energy conservation and emission reduction used in solar passive building.

Thermal analysis and non-isothermal crystallization kinetics of Ag–Ga2Te3–SnTe telluride glasses

In this paper, the microstructure evolutions and crystallization kinetics of the newly developed Agx-[(Ga2Te3)34(SnTe)66]100−x (x = 6, 8 and 10%) telluride glasses were comprehensively investigated under non-isothermal conditions. The microscopic structure of the investigated samples were analyzed by X-ray diffraction (XRD), transmission electron microscope (TEM) and the selected area electron diffraction (SAED). The crystalline products were identified as the SnTe phase (primary crystalline phase) and Ga6SnTe10 phase. The exothermic crystallization process for any investigated samples was actually on the envelope of two overlapped peaks and could be assigned to the first crystallization event of SnTe precipitation and followed by the second crystallization event of Ga6SnTe10 phase. The crystallization mechanism and activation energies were estimated by Matusita–Sakka model under continuous heating based on the differential scanning calorimeter (DSC). For the first crystallization event, the Avrami exponent n values for each of the three investigated samples was approximately 3, suggesting the crystallization occurred through the two-dimensional growth with increasing number of nucleation. The values of n for the second crystallization event of Ga6SnTe10 phase were close to 4, indicating three-dimensional growth with a increasing number of nuclei. The activation energy Ec for both the first and second crystallization events was gradually decreased as the Ag content increased.

Exploration of the fundamental factor for the synergistic modification of model waxy oil by EVA and asphaltene: An experiment and simulation study

It has been well documented that the synergistic effect of polymer pour point depressant (PPD) and asphaltenes improves the low-temperature rheology of waxy oil. However, the fundamental factor of this synergistic effect has been little studied. In this paper, we innovatively combine macroscopic rheology experiment, mesoscopic particle size test and microscopic molecular dynamics simulation, supplemented by crystallization exotherm test and wax crystal morphology observation, to investigate the effect of solvent composition on the synergistic modification ability between ethylene-vinyl acetate (EVA) PPD and asphaltene, and then reveal the fundamental factor of this synergistic effect. The results showed that the EVA's adsorption on the asphaltene surface is the key element influencing their synergistic effects. With the deterioration of asphaltene dispersion in the solvent, the ability of asphaltene and EVA to synergistically improve the low-temperature rheology of model waxy oil increases and then decreases. When the aromatic component in the solvent was too high, a large number of aromatic solvent molecules were distributed around the asphaltene molecules through π-π conjugation, which interfered with the adsorption of EVA on asphaltene due to the existence of spatial site resistance. When the content of saturated hydrocarbon component in the solvent was too high, the self-aggregation tendency of asphaltenes led to a decrease in the number of adsorption sites on their surfaces, resulting in the decline of the adsorption efficiency of EVA on the asphaltene surface, and the synergistic modification effect between them was reduced. This work offers fresh ideas for the design of waxy crude oil PPD, which is crucial for the efficient pipeline transmission of waxy crude oil.

Crystallizability of a biodegradable polymer as a criterion for assessing the degree of influence of the aquatic environment on its structure

The work is devoted to the study of the effect of an aqueous medium on a polymeric biodegradable material based on poly-3- hydroxybutyrate (PHB) by differential scanning calorimetry (DSC). To analyze the structural reorganizations of the polymer, we studied the effect of an aqueous medium on the process of polymer crystallization after soaking in distilled water. It is shown that after exposure to water, the forms of crystallization exotherms change, the rate of polymer crystallization decreases, and the heat of the process decreases insignificantly. To analyze the kinetics of non-isothermal crystallization, we used the kinetic crystallization parameter G [deg/min], which characterizes the rate of polymer crystallization in the non-isothermal mode. It has been established that the crystallizability of PHB decreases after exposure of the samples. The observed dependence of the parameter G on the scanning rate indicates a decrease in the mobility of polymer chains, a decrease in their flexibility after exposure to an aqueous medium, which is a consequence of a change in their structure.

Zinc(II) complexes of azadipyrromethene: Effect of nature and placement of solubilizing groups on structural, thermal, electrochemical and optical properties

Zinc(II) complexes of azadipyrromethenes are non-planar chromophores with strong absorption in the visible to NIR and are promising n-type materials for organic solar cells. To increase solubility and tune their properties, we incorporated hexyl or hexyloxy solubilizing groups either on the distal or proximal phenyls of bis[2,6-diphenylethynyl-1,3,7,9-tetraphenyl azadipyrromethene] zinc(II) (Zn(WS3)2). Crystal structures confirm the typical distorted tetrahedral geometry for these types of complexes and show that the solubilizing groups on the distal phenyls extend away from the conjugated core whereas groups on proximal phenyls interact with the other ligand. Differential scanning calorimetry measurement indicated that crystals of distal-substituted complexes have two endothermic peaks: solubilizing groups ‘melting’ and complex melting, whereas the proximal-substituted complexes show one exothermic crystallization peak and one endothermic melting peak. Electrochemical and optical properties varied as expected for ADP-based complexes: the presence of electron rich groups at the proximal substitutions resulted in lower oxidation potentials, higher HOMO levels, red-shifted absorption and lower optical gap than distal substitutions, and the effect was greater for hexyloxy than hexyl. Upon thermal annealing, films of the hexyloxy-substituted complexes strongly aggregated and showed crystal features under a polarized microscope, indicating that hexyloxy groups drive ordered self-assembly, especially when placed on distal phenyls. The ability to guide solid-state self-assembly of these non-planar chromophores using solubilizing groups have the potential to improve their charge carrier mobility and performance in opto-electronic applications such as organic solar cells, and photodetectors.

Effect of Ta2O5 addition on the structure, crystallization mechanism, and properties of CaO–B2O3–SiO2 glasses for LTCC applications

CaO–B2O3–SiO2–Ta2O5 (CBST) glass-ceramics, with different Ta2O5 content, (up to 6 mol%), have been prepared by using glass melt quenching followed by heat treatment between 800 and 880 °C. The Fourier Transform Infrared (FTIR) results showed that the stronger the attraction of Ta5+ to the oxygens in the BO33− and SiO32− structures, the more easily the B–O and Si–O bonds will be destroyed. The underlying reason is most probably the high field strength of Ta5+, which results in a weakening of the vibration intensities of the [BO3] and [SiO4] units. Moreover, the Differential Scanning Calorimetry (DSC) results showed that the softening point (Tg), crystallization starting temperature (Tc1), and exothermic crystallization peak temperature (Tp1), of the CaSiO3 phase, shifted to higher values with the addition of Ta2O5. Also, the crystallization activation energy (Ea) and the glass stability factor (ΔT) of the CaSiO3 phase increased, which indicated that the CaSiO3 phase of the glass became inhibited by the addition of Ta2O5. It was, thus, obvious that there was a need of glass characterization. The results of the crystallization kinetics showed that the critical cooling rate decreased with the addition of Ta2O5, which indicated that the viscosity of the system had increased. The CBST glass-ceramics, containing 1 mol% Ta2O5, that were sintered at 875 °C for 15 min showed excellent dielectric properties: εr = 6.22 and tanδ = 1.19 × 10−3 (1 MHz). To sum up, CaO–B2O3–SiO2–Ta2O5 glass-ceramics are potential low temperature co-fired ceramic substrate materials.

Dual-imaging-mode smart hydrogel information platform for illumination-independent covert decryption and read

ABSTRACT Smart hydrogel with color responsiveness is envisioned as one of the most promising materials for advanced information encryption and decryption platform, but the illumination-dependent way of decrypting and reading information leads to the worrying of concealment in some particular scenarios. Herein, we proposed a smart hydrogel information platform with dual imaging modes by utilizing the accompanying behaviors in transparency change and heat releasing after crystallization of supercooled solution. For this smart hydrogel information platform, the hidden information could be written and decrypted by ink of ethylene glycol and decryption tool of seed crystal, respectively. Furthermore, in addition to the traditional optical imaging mode with the assistance of light illumination, the decrypted information on dual-imaging-mode hydrogel platform also could be read by thermal imaging mode in dark environment owing to the exothermic crystallization. The illumination-independent read mode based on heat radiation helps to improve the secrecy and safety of the decryption and read process. This investigation provides a facile and feasible strategy to design illumination-independent information platform that enables reading the encrypted information in secret.