Glass Softening Temperature Research Articles

A novel non-crystallizing Na2O-K2O-TiO2 silicate glass sealant for protonic ceramic fuel cell applications

Sealants play an indispensable role in the fabrication of proton ceramic fuel cell (PCFC) stacks. A TiO2-containing silicate glass, primarily composed of Na2O-K2O-TiO2-SiO2, was developed for sealing BaZr0.1Ce0.7Y0.1Yb0.1O3-δ (BZCYYb) electrolyte and Crofer 22 H interconnect. The coefficient of thermal expansion of the glass sealant is 11.6 × 10−6 K−1, and its glass transition temperature and softening temperature are 566 °C and 601 °C, respectively. The structure of the glass was investigated by XRD, Raman and FT-IR, indicating that it is not sensitive to high temperatures up to 800 °C. The wettability of the glass on BZCYYb and Crofer 22 H substrates was tested. An intact and defect-free BZCYYb/Crofer 22 H joint was sealed by the glass sealant at 750 °C for 30 min. The elemental distribution demonstrates that no violent reaction or diffusion of elements occurs at the interface, indicating that the Na2O-K2O-TiO2-SiO2 glass is capable of sealing PCFC stacks.

Structure, properties and wetting behaviour on Si substrates of lead-free low melting-temperature Li2O-ZnO-B2O3-WO3 glasses

Li2O–ZnO–B2O3-WO3 (LZBW) sealing glasses for Si substrates were prepared and the effect of WO3 on the structure, thermal properties, and sintering behaviour was investigated. As the WO3 increases from 0 to 12 mol%, the glass transition temperature and softening temperature reach the lowest values of 448 °C and 479 °C, respectively, at which time the glass network has the lowest degree of polymerization. The thermal expansion coefficient increases from 6.959 × 10−6/°C to 8.476 × 10−6/°C with increasing WO3 contents. It is verified that the introduction of WO3 can effectively improve the conductivity. The sealing property of the glasses was evaluated by the wetting angle of the glasses after co-sintering with Si substrate for 10 min at 860 °C, and the 25Li2O-7ZnO-2.7Bi2O3-1.3P2O5-55B2O3-9WO3 glass had the minimum wetting angle of 34.07°. The excellent thermal properties, conductivity, and wetting behaviour of the LZBW glasses make it a potential material as a binder material for positive silver pastes.

Strengthening functional properties and competitive crystallization behavior of La2O3-BaO-CaO-Al2O3-B2O3-SiO2 glass-ceramic for solid oxide fuel cells: Agglomeration effect of rare-earth oxide

In this paper, the agglomeration effect of rare-earth oxide has been confirmed through that the thermal properties, viscosity, crystalline phase, and high temperature resistivity of the 35BaO-(15-x)CaO-5Al2O3–10B2O3–35SiO2-xLa2O3 (x = 1, 3, 5, 7, 9 mol%, BABSCLa) glass system were systematically investigated. With the increase of the La2O3/CaO molar ratio, the results of Raman and infrared spectra of the BABSCLa glass showed that the Q4, Q3, and Q2 units of [SiO4] decrease, while Q1 and Q0 units increased in the BABSCLa glass structure, because the La2O3 as the glass network modifier can create more non-bridging oxygen than the CaO. However, the "agglomeration" effect of La ions with the high field strength could adsorb the oxygen in glass to form the La–O–La (Si) bond, resulting that the glass transition temperature and softening temperature of the BABSCLa glass continued to increase with the addition of La2O3, and the coefficient of thermal expansion (CTE) of annealed glass decreased from 11.37 to 10.87 × 10–6K–1, respectively. Simultaneously, the main crystalline phase of the BABSCLa glass-ceramic gradually changed from the low crystallization activation energy BaSiO3 phase with 287 kJ/mol to Ba3La6(SiO4)6 phase with 454 kJ/mol duo to the "agglomeration" effect of La ions. The CTE of the BABSCLa glass-ceramic increased from 12.35 to 13.05 × 10–6K–1 and then decreased to 11.75 × 10–6K–1. The direct-current (DC) resistivity of the BABSCLa glass-ceramic was higher 105 Ω•cm at a high temperature of 750 °C, which had good high-temperature electrical insulation. This demonstrated the La2O3 strengthening BaOCaO-Al2O3-B2O3-SiO2 glass-ceramic system was an effective method for the preparation of hermetic glasses.

Effect of partial substitution of barium oxide by lanthanum oxide on the structure and properties of iron-based aluminosilicate glass

Silica-aluminum borates (SiO2-R2O3-R2O-RO-ZrO2 system) with La2O3 replacing BaO were preparing using the conventional melt quenching process. The impact of substituting BaO with La2O3 on the glass structure was examined using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and Raman. The density, thermal properties, alkali resistance and dielectric properties of the glasses were measured and compared using Archimedes, Differential Scanning Circuit (DSC), Thermal Expansion Calorimetry (TEC), Weight Reduction and Impedance Spectroscopy. The viscosity of the glass system was calculated from the thermal properties and discussed in comparison with the wetting angle at 1000 °C. The results showed that the glass does not undergo precipitation. With the increase of La2O3 to BaO substitution, the Q4 in the glass network structure transforms to Q0+Q1 and Q2, causing depolymeriation of the glass structure. This results in an increase in the density of the glass, as well as an increase and subsequent decrease in the thermal expansion coefficient. Additionally, the glass transition temperature and glass softening temperature decrease and then increase, which was due to the high field strength of La3+. When substituting 5 wt% of BaO with La2O3, The glass displayed the lowest dielectric constant and dielectric loss, along with the best alkali resistance. Viscosity calculations showed that the viscosity gradually increases at 1000 °C with the increase of La2O3 substitution, which was consistent with the wettability results. The glass components in the 0-5 wt% weight range all satisfy the iron-sealed glass wetting angle requirements.

Preparation of anisotropic polyimide aerogels for thermal protection with outstanding flexible resilience using the freeze-drying method.

Polyimide aerogels (PIAs) not only possess excellent thermodynamic properties but also have a high porosity structure, making them an exceptional protective and thermal insulation material, and further broadening their application scope in aerospace and other cutting-edge fields. In this work, a series of anisotropic polyimide aerogels (3,3',4,4'-biphenyltetracarboxylic dianhydride (S-BPDA), p-phenylenediamine (PDA), 4,4'-diaminodiphenyl ether (ODA)) with excellent properties were prepared. These PIAs were obtained by unidirectional freeze-drying and thermal amination of two different precursor solutions mixed in proportion. These PIAs possess an irregularly oval tubular structure, exhibiting pronounced anisotropy. (PIA-2 exhibits outstanding flexible resilience in the radial direction. It can still regain its original form after half an hour of compression by a universal testing machine, yet it cannot do so in the axial direction. The thermal diffusivity of PIA-5 in the radial direction at room temperature is as low as 0.067 mm2 s-1, and even at 200 °C, the thermal diffusivity is as low as 0.057 mm2 s-1. Meanwhile, the thermal diffusivity in the axial direction at room temperature is 0.11 mm2 s-1, surpassing the value of 0.106 mm2 s-1 of aerogels prepared from monomeric raw materials and dried under supercritical conditions). PIAs exhibit outstanding thermal stability (the axial strength and modulus retention of PIA-8 at 200 °C are as high as 52.63% and 44.82%), and its weight loss temperature of 5% is as high as 603 °C and it has a glass softening temperature of 387 °C. PIAs also demonstrate exceptional flame retardancy in imitation flame retardant experiments and exhibit outstanding thermal insulation performance when heated on a 150 °C heating plate for 10 minutes (the radial surface temperature of PIA-5 was only 49.9 °C). These anisotropic PIAs materials exhibit outstanding flexible resilience, and thermal protection performance, holding significant importance for their widespread adoption as thermal insulation materials in aerospace, high-precision electronic components, and other domains.

Crystallization mechanism and properties of CaO-B2O3-SiO2-Nb2O5 (CBSN) glass-ceramics

CaO-B2O3-SiO2Nb2O5 (CBSN) glass-ceramics were produced by melt water quenching and isothermal heat treatment in this paper. The FTIR results showed that with the addition of Nb2O5, the combination of B-O and Si-O would be destroyed, resulting in a decrease in the number of [BO3] and [SiO4] units. The results about DSC of glass powder showed that with the increase of Nb2O5 doping amount, the softening temperature (Tg) of glass, the initial temperature of the crystallization peak (Tc), the temperature corresponding to the endothermic peak intensity (Tp) of exothermic peaks and the activation energy values of the CaSiO3 and CaB2O4 crystal phase moved to high values, indicating that the crystallization of the CaSiO3 and CaB2O4 phase became difficult. The results of crystallization kinetics showed that the nucleation rate and crystallization rate decreased near Tc1 and Tc2, indicating that the crystal phase crystallization near Tc1 and Tc2 was inhibited. The critical cooling rate decreased with the addition of Nb2O5, indicating that the viscosity of the glass system increased. The XRD results of glass-ceramics showed that the main crystal phase of the sample changed from α-CaSiO3 to β-CaSiO3 and finally to CaNb2O6 with the addition of Nb2O5.The CBSN2 glass-ceramics sintered at 865 °C for 15 min had excellent dielectric properties: εr = 6.42 and tanδ = 1.049 × 10−3 (1 MHz). The results indicated that CBSN glass-ceramics could be a potential LTCC substrate material.

Assigning Viscosity Values in the Glass Softening Temperature Range

A new optical method for assigning glass viscosity values in the softening temperature range is presented. In this method, an irregular particle, a few millimeters in size, laying on an alumina plate, is heated up to temperature T, and then remains at this temperature. T should be within the softening temperature range of the glass. There are no external applied shear stresses, the only acting shear forces are those coming from the particle's own surface energy. At the fixed temperature T, the surface free energy of the sample decreases by viscous flow while its shape evolves from a polyhedron or irregular shape towards a spherical or rounded shape. This shape evolution is recorded using a photographic camera. From each image, the sample's roundness is determined, obtaining a characteristic time τ from the roundness against time. Simultaneously, using the available software, a value for the viscosity η was calculated, at temperature T, allowing for building sets of T, τ, η, namely three data values. Accordingly, if T, τ are considered as independent variables, a master function η = η (T, τ) can be built. Now, if we measure T, τ data on a glass of an unknown viscosity, the master function makes it possible to assign a η value. When incipient crystallization or liquid-liquid phase separations are present, effective viscosity values are obtained. This method requires a high temperature microscope, as well as tridimmensional samples with a few cubic millimeters of volume. Each isothermal τ determination can take from minutes to several hours. We tested the method with two glasses of known viscosity values: borosilicate glass (VG98) and alumimoborosilicate glass (SG7), both of which are used for radioactive waste immobilization and have assigned log(η) values between 6 and 7.3 with η in Pa s. The discrepancy between the log(η) values assigned here and those values fitted with a VFT function on the values measured for the SG7 and VG98 glasses were within ±14%.

Effect of network connectivity on behavior of synthetic Broborg hillfort glasses

AbstractThere is wide industrial interest in developing robust models of long‐term (>100 years) glass durability. Archeological glass analogs, glasses of similar composition, and alteration conditions to those being tested for durability can be used to evaluate and inform such models. Two such analog glasses from a 1500‐year‐old vitrified hillfort near Uppsala, Sweden have previously been identified as potential analogs for low concentration Fe‐bearing aluminosilicate nuclear waste glasses. However, open questions remain regarding the melting environment from which these historic glasses were formed and the effect of these conditions on their chemical durability. A key factor to answering the previous melting and durability questions is the redox state of Fe in the starting and final materials. Past work has shown that the melting conditions of a glass‐forming melt may influence the redox ratio value (Fe+3/∑Fe), a measure of a glass's redox state, and both melting conditions and the redox ratio may influence the glass alteration behavior. Synthetic analogs of the hillfort glasses have been produced using either fully oxidized or reduced Fe precursors to address this question.In this study, the melting behavior, glass transition temperature, oxidation state, network structure, and chemical durability of these synthesized glass analogs is presented. Resulting data suggests that the degree of network connectivity as impacted by the oxidation state of iron impacted the behavior of the glass‐forming melt but in this case does not affect the chemical durability of the final glass. Glasses with a lower degree of melt connectivity were found to have a lower viscosity, resulting in a lower glass transition temperature and softening temperature, as well as in a lower temperature of foam onset and temperature of foam maximum. This lower degree of network connectivity most likely played a more significant role in accelerating the conversion of batch chemicals into glass than the presence of water vapor in the furnace's atmosphere. Future work will focus on using the results from this work with outcomes from other aspects of this project to evaluate long‐term glass alteration models.

Study on preparation and properties of boron bismuth/fluorooxy glass and glass-ceramics

Boron-bismuth/fluorine-oxygen glass was prepared by the traditional high-temperature melting annealing method. By studying and analyzing the effects of B2O3 and CaF2 on the density, molar volume, thermal expansion coefficient and glass softening temperature of these two component glasses, it can be gained a deeper understanding of the structure and performance of the glass system. As the B2O3 content in boron-bismuth glass increases, some [BO3] triangles in the glass will transform into [BO4] tetrahedrons, the glass network structure will shrink, and the thermal stability of the glass will increase. With the increase of CaF2 content in fluorinated oxygen glass, the phenomenon of F− replacing O− occurs in the glass network structure, the breaking of the bridge oxygen bond makes the glass network loose, and the thermal stability of the glass decreases. To select the glass with good comprehensive performance and pre-formulate the corresponding heat treatment system are to obtain glass ceramics with good crystallinity.

Accelerating design of matching glass for phosphate fiber cores: Multi-parameter inversion model

Based on twelve phosphate glasses compositions and properties, a composition-property model was established to predict the properties of matching glass for phosphate fiber cores, including thermal expansion coefficient (CTE), glass softening temperature (Ts), glass transition temperature (Tg), and refractive index (nd). Under the composition constraints of this model, sensitivity analysis showed that the positive influence of these compositions on CTE, Ts, Tg and nd followed the order of Sb2O3 > BaO > Na2O > K2O > P2O5 > Nb2O5 > La2O3 > GeO2 > Al2O3 > Y2O3, Nb2O5 > Y2O3 > Al2O3 > GeO2 > BaO > P2O5 > La2O3 > Na2O > K2O > Sb2O 3, Nb2O5 > Sb2O3 > Al2O3 > GeO2 > BaO > P2O5 > La2O3 > Na2O > K2O > Y2O3, Sb2O3 > Y2O3 > Nb2O5 > GeO2 = Al2O3 > BaO > Na2O > P2O5 > K2O > La2O3. Constraint-based probability distributions of properties were predicted via numerical simulation. This model can be extended to study multi-composition glasses, accelerating the glass design.

Effect of SrO Content on Structure, Thermal Properties and Chemical Stability of Bi2O3-B2O3-ZnO-SrO Low-melting Glass for Si-Al Alloy Package

The 40Bi2O3-30B2O3-(30−x)ZnO-xSrO (x=0–15mol%, BBZSr) glass system was prepared by the conventional melt quenching method. The effect of SrO addition on structure, thermal properties, chemical stability and sealing performance of BBZSr glass were investigated thoroughly. The experimental results show that the total proportions of [BO3] group and [BO4] group decrease and the vibrations of [BiO3] group and [BiO6] group become weaker with the increase of SrO addition content, suggesting the glass network structure is strengthened owing to the SrO addition. Hence, both the thermal and chemical stability were significantly improved as the SrO content was increased. When the SrO content increased from 0 to 15mol%, the glass transition temperature and softening temperature slightly increased from 380 to 388 °C and from 392.7 to 402.2 °C, respectively, meanwhile the coefficient of thermal expansion also increased from 10.49×10−6 to 11.16× 10−6/°C (30–300 °C). The BBZSr glass with 15mol% SrO exhibited excellent comprehensive properties with low glass transition temperature(384.9 °C), low softening temperature(400.3 °C), high coefficient of thermal expansion (11.14×10−6 C, 30–300 °C), good thermal and chemical stability. Besides, the glass had the good wetting behavior and sealing performance for Al-50%Si alloy.

Ethanol-Precursor-Mediated Growth and Thermochromic Applications of Highly Conductive Vertically Oriented Graphene on Soda-Lime Glass.

Direct growth of vertically oriented graphene (VG) nanowalls on soda-lime glass has practical significance in extending the application of graphene to daily-life-related areas, such as gas sensors and conductive electrodes, via combining their complementary properties and applications. However, VG films derived by low-temperature deposition (e.g., on glass) usually present relatively low conductivity and optical transparency. To tackle this issue, an ethanol-precursor-based, radio-frequency plasma-enhanced chemical vapor deposition (rf-PECVD) route for the synthesis of VG nanowalls is developed in this research, at around the softening temperature of soda-lime glass (∼600 °C) templates. The average sheet resistance, i.e., ∼2.4 kΩ·sq-1 (at transmittance ∼81.6%), is only one-half of that achieved by a traditional methane-precursor-based PECVD route. Based on the highly conductive and optically transparent VG/glass, as well as its scalable size up to 25 in. scale, high-performance reversible thermochromic devices were successfully constructed using VG/glass as transparent heaters. Hereby, this work should propel the scalable synthesis and applications of highly conductive VG films on glass in next-generation transparent electronics and switchable windows.

Influence of La/B ratio on the structure, sinterability and crystallization of La2O3–B2O3–CaO glass–ceramics

To have a better understanding on the characteristics of La2O3–B2O3–CaO (LBC) glass–ceramics designed for low temperature co-fired ceramic applications, LBC glass–ceramics with La/B ratio changing from 1:6.0 to 1:3.0 were prepared, and the network structure, sinterability, crystalline phase composition and crystallization kinetics of synthesized LBC glass–ceramics were investigated. The increase of La/B ratio would reduce the content of [BO4] units in the network structure, and decrease the glass transition temperature as well as the softening temperature of LBC glass–ceramics. But low La/B ratio of glass could cause serious foaming during sintering process. The change of La/B ratio would influence the position as well as intensity of crystalline peaks on DSC curves, and the composition and microstructure of crystalline phases were also affected. The crystallization activation energies of LBC glass–ceramics were 157.9–498.7 kJ/mol, which raised up with the increase of La/B ratio.

Effect of ZnO content on microstructure, crystallization behavior, and thermal properties of xZnO-30B2O3-(65-x)Bi2O3-5BaO glass

xZnO-30B2O3-(65-x)Bi2O3-BaO (x = 40–60 mol%) glasses were prepared by the melt quenching method. The microstructure, crystallization behavior, and thermal properties of the glasses were investigated. The results show that the samples with 40–55 mol% ZnO possess an amorphous structure after melting at 950 °C. When the ZnO content increases to 60 mol%, the sample possesses strip-shaped Zn3B2O6 crystals after melting at 950 °C, and becomes homogenous glass at 1050 °C. The thermal expansion coefficient (TEC) decreases from 10.294 to 7.43 × 10−6/°C when the ZnO content increases from 40 to 60 mol%. Both the glass transition temperature and glass softening temperature increase with increasing ZnO content. In addition, needle-shaped Bi2ZnB2O7 crystals are observed on the glass surface after annealing at crystallization temperatures for 1 h, and the amount of crystals decreases with increasing ZnO content. Furthermore, the weight loss ratio of the glasses increases gradually as the content of ZnO increases. After 48 h, the magnitude of weight loss value in 6 wt% of HNO3 or NaOH solution at 90 °C is 10−3 g/cm3∙min while it is 10−7 g/cm3∙min in deionized water.

THERMO-MECHANICAL ANALYSIS OF HETEROGENEOUS SOLID ROCKET PROPELLANT

The article presents results of thermo-mechanical analysis of heterogeneous solid rocket propellant H2, with special attention devoted to determining the glass transition temperature and softening temperature. Mechanical properties such as storage modulus (E’), loss modulus (E’’) and tan(δ) were measured using NETZSCH DMA 242C analyzer within temperature range from -120oC to +80oC at 2 K/min of heating rate and frequency of applied force f = 1 Hz. Relative thermal expansion as well as the Coefficient of Linear Thermal Expansion (CLTE) of H2 sample were determined using NETZSCH DIL 402C dilatometer within temperature range from 30oC to 80oC at 1 K/min of heating/cooling rate. The thermophysical properties including thermal conductivity, thermal diffusivity, and specific heat were determined within temperature range from -20oC to +80oC using KD2 Pro apparatus.

Spectroscopic and thermal analysis of lead-free multipurpose radiation shielding glasses

The genetic algorithm was used to identify glasses, of the composition 50Bi2O3-(50-x) B2O3-xBaO with 25≥x≥5 wt%, that have a similar half-value layer (HVL) and neutron removal cross-section. The structure of these glasses was further explored using a combination of spectroscopic and thermal analysis in order to ascertain whether they possess advantageous physical properties comparable to traditional materials used in nuclear reactor design. Differential scanning calorimetry (DSC) analysis was used to examine the thermal profile of the glass system and to identify glass transition temperature Tg and softening temperature Ts. Glass of the composition 50Bi2O3–30B2O3–20BaO had exhibited the highest thermal stability. Analysis of the Raman spectra of the samples confirmed the presence of BiO6 octahedrons and B-O-B bonds in poly borate chains. A deconvolution of the IR spectra was carried out to determine the relative proportions of BO3 triangles to BO4 tetrahedral units in the glass network that would affect the density and bulk modulus. Optical absorption spectrum of the samples exhibited absorption peaks in the blue region along with a broad band of absorption at longer red wavelengths associated with excitation of bismuth ions. When compared to traditional heavy concretes used in radiation shielding, the bismuth-barium borate glasses exhibited superior performance over conventional barite concrete as a gamma-radiation shield and was comparable to limonite concrete as a neutron radiation shield. The bulk modulus of the glass series was also found to be comparable to that of regular concrete at approximately to 30 GPa.

Silica‐free sealing glass for sodium‐beta alumina battery

AbstractA CaO‐Bi2O3‐Al2O3‐B2O3 glass system was studied as a sealant for sodium‐sulfur battery. The thermal properties such as thermal expansion coefficient, glass transition, and softening temperature were determined by dilatometry and differential scanning calorimetry. Selected glasses, based on the thermal properties, were bonded with α‐alumina substrate followed by aging in air at 400°C for 100 hours and in sodium vapor at 350°C for 100 hours. The interfacial compatibility and resistance to sodium vapor corrosion of the bonded and aged samples were evaluated by structural and microstructural analysis using X‐ray diffractometer (XRD) and scanning electron microscope (SEM) attached with energy dispersive spectroscope (EDS). Helium leakage test was performed at room temperature to examine the sealing ability of the select glass. It is found that Bi2O3 increases the thermal expansion coefficient, decreases the glass transition and softening temperature, shows excellent interfacial compatibility and thermal cycling resistance, improves sealing ability, and degrades sodium corrosion resistance.

Stable phosphate-based glass for low-temperature sealing applications: Effect of Si3N4 dopant

Phosphate glass is advantageous as a low temperature sealing material, especially in solar cells, micro-motor systems, vacuum engineering and the like, but the poor chemical stability restricts its wide application, especially in humid environments. To overcome this shortcoming, a certain proportion of silicon nitride is added to tailor the structural, chemical and thermal properties of phosphate glass. The results show that the addition of silicon nitride improves the water resistance and remarkably reduces the mass loss in humid environments from 60 to 3 wt% after 120 h. With the addition of silicon nitride, the softening temperature of glass is in the range of 330–372 °C. In particular, the coefficient of thermal expansion of phosphate glass can be tailored ranging from 14.9 × 10−6 K−1 to 17.4 × 10−6 K−1 by adjusting the content of silicon nitride, making it thermally compatible with various substrates. These findings provide useful information on the development of reliable low-temperature sealing glass.

RE2O3-alkaline earth-aluminosilicate fiber glasses: Melt properties, crystallization, and the network structures

Glasses and/or glass fibers of a new glass system, RE2O3 (RE = Sc,Y, La)-MgO-CaO-Al2O3-SiO2, were studied in detail, covering rare earth (RE) effects on high temperature viscosity, liquidus temperature and crystalline phases, softening and glass transition temperature, and speciation reactions of aluminum (AlOx, x = 4, 5) and silicate network (Qn, n = 4, 3, 2) using 27Al and 29Si MAS NMR and Raman spectroscopic methods. Rare earth oxides (RE2O3) were shown to have a dual functionality, i.e., decreasing melt viscosity like a network modifier depolymerizing glass network, but increasing viscosity at low temperature, i.e., glass softening temperature (Tsoft) and transition temperature (Tg), strengthening the glass network functioning like Al2O3. Liquidus temperature (TLiq) was found to be sensitive to the type of RE2O3 modifications in terms of their ionic field strength (IFS); Sc3+ of the highest IFS increased, but La3+ of the lowest IFS decreased TLiq. Effect of Y3+ (intermediate IFS) on TLiq resembles Sc3+ only at higher concentration. The overall results suggest that RE ions of different IFS have different “true” solubility limits in the host glass matrix, above which RE2Si2O7 crystallizes. All of the glasses with and without RE2O3 contained predominately four-fold coordinated aluminum, AlO4; yet replacement of CaO by RE2O3 increased AlO5 according to 27Al MQMAS NMR spectroscopic measurements. Raman spectroscopic results suggested that depolymerization of the silicate network.

Wide range temperature-dependent deformation and fracture mechanisms for 8701 under dynamic and static loading.

Although the RDX-based composite explosive 8701 explosive 8701 has been widely used to achieve military goals, its mechanical properties have not been carefully investigated. In the present study, we focused on the mechanical response of 8701 at a wide range temperature from −125 °C to 100 °C under both quasi-static (about 0.001 s−1) and high-rate compression loading (about 600 s−1). The stress–strain curves exhibit different tendencies at different temperatures for both quasi-static and high strain-rate loading. The failure stress and elastic/storage modulus present important temperature-dependence. Differential scanning calorimetry (DSC) tests showed that the glass transition temperature and softening temperature of 8701 are 11.61 °C and 15.14 °C respectively, which is lower than that of the binder (with glass transition temperature of 25 °C and softening temperature 38 °C). For the quasi-static loading, scanning electron microscopy (SEM) observations revealed that 8701 shows an interface debonding failure mode along the binder phase below 15 °C, while the mechanical behavior of 8701 is dominated by softening behavior of the binder above 38 °C. For high-rate loading, 8701 shows a mixture of interface debonding and trans-granular cleavage when below 15.14 °C.