High-temperature Phase Separation Research Articles

Effect of B2O3 and Basic Oxides on Network Structure and Chemical Stability of Borosilicate Glass

Glass properties play crucial roles in ensuring the safety and reliability of electronic packaging. However, challenges, such as thermal expansion and resistance to acid corrosion, pose long-term service difficulties. This study investigated the impact of the microstructure on acid resistance by adjusting the glass composition. A glass material with excellent acid resistance was obtained by achieving a similar coefficient of thermal expansion to tantalum; it exhibited a weight loss rate of less than 0.03% when submerged in 38% sulfuric acid at 85 °C for 200 h. Theoretically, this glass can be used to seal wet Ta electrolytic capacitors. Differential scanning calorimetry (DSC) was used to analyze the glass transition temperature and thermal stability of borosilicate glasses. X-ray diffractometry (XRD), scanning electron microscopy (SEM), and Raman spectroscopy were used to study the microstructure of the amorphous phase of the borosilicate glass, which revealed a close relationship between the degree of network phase separation in the borosilicate glass and the degree of polymerization (isomorphic polyhedron value, IP) of the glass matrix. The IP value decreased from 3.82 to 1.98 with an increasing degree of phase separation. Boron transitions from [BO4] to [BO3] within the glass network structure with increasing boron oxide content, which diminishes the availability of free oxygen provided by alkaline oxide, resulting in a lower acid resistance. Notably, the glass exhibited optimal acid resistance at boron trioxide and mixed alkaline oxide contents of 15% and 6%, respectively. Raman experiments revealed how the distributions of various bridging oxygen atoms (Qn) affect the structural phase separation of the glass network. Additionally, Raman spectroscopy revealed the depolymerization of Q4 into Q3, thereby promoting high-temperature phase separation and highlighting the unique advantages of Raman spectroscopy for phase recognition.

Effect of Zr on the Microstructure and High-Temperature Phase Separation Evolution of SiOC Aerogels.

SiZrOC aerogels were synthesized through the pyrolysis of the zirconium source-doped SiOC system using zirconyl chloride octahydrate (ZrOCl2·8H2O) at temperatures ranging from 900 to 1300 °C. This study investigates the microstructure evolution and phase separation of SiOC and SiZrOC aerogels during the pyrolysis process. Upon pyrolysis, both aerogels exhibited a Si-O-C structure with a high thermal stability. The introduction of zirconium elements significantly enhanced the pore volume (3.20 cm3/g) and porosity (96.0%) and reduced the thermal conductivity (0.023 W·m-1·K-1) of the organic-inorganic precursor aerogel. Moreover, the three-dimensional pore structure was retained even under high-temperature pyrolysis conditions. SiZrOC-1100 displayed a high specific surface area of 273.52 m2/g, a high pore volume of 1.70 cm3/g, and a low thermal conductivity of 0.033 W·m-1·K-1. At high temperatures, the SiZrOC phase transformation produces tetragonal ZrO2, which inhibits the graphitization process of free carbon and the growth of SiC grains. Furthermore, the phase separation process of the SiOxCy matrix structure generated oxygen-rich SiOxC4-x units, while carbon-rich SiOxC4-x units were negligible below a pyrolysis temperature of 1200 °C. Between 900 and 1200 °C, SiZrOC is composed of amorphous SiOC, amorphous ZrO2, microcrystalline t-ZrO2, and free carbon phase. These findings provide valuable insights into the preparation of high-performance SiOC aerogels.

Ordering–separation phase transitions in a Co3V alloy

The microstructure of the Co3V alloy formed by heat treatment at various temperatures is studied by transmission electron microscopy. Two ordering–separation phase transitions are revealed at temperatures of 400–450 and 800°C. At the high-temperature phase separation, the microstructure consists of bcc vanadium particles and an fcc solid solution; at the low-temperature phase separation, the microstructure is cellular. In the ordering range, the microstructure consists of chemical compound Co3V particles chaotically arranged in the solid solution. The structure of the Co3V alloy is shown not to correspond to the structures indicated in the Co–V phase diagram at any temperatures.

Exchange bias effect in CuCr2O4/Cr2O3 nanogranular systems

We have successfully synthesized the CuCr2O4/Cr2O3 nanogranular system through a high-temperature phase separation route from Cu doped Cr2O3 nanoparticles, which are confirmed by X-ray diffraction measurements. Magnetic susceptibility shows two magnetic transitions at 130 K and 310 K corresponding to the ferrimagnetic and antiferromagnetic phases of CuCr2O4 and Cr2O3, respectively. Significant exchange bias behavior could be observed in the field cooling magnetic hysteresis loop at low temperatures. Both exchange bias field (HEB) and coercive field (HC) decrease with increasing temperature and disappear near 200 K. This exchange bias behavior is discussed in terms of the existence of exchange coupling between the ferrimagnetic CuCr2O4 and antiferromagnetic Cr2O3. The uncompensated spins in antiferromagnetic phase frozen along field cooling direction provide the pinning force on the ferrimagnetic spins leading to the exchange bias effect.

Thermoelectric properties of p-type PbTe/Ag2Te bulk composites by extrinsic phase mixing

We investigated the thermoelectric properties of PbTe/Ag2Te bulk composites, synthesized by hand milling, mixing, and hot press sintering. From x-ray diffraction and energy dispersive x-ray spectroscopy measurements, we observed Ag2Te phase separation in the PbTe matrix without Ag atom diffusion. In comparison with previously reported pseudo-binary (PbTe)1−x(Ag2Te)x composites, synthesized by high temperature phase separation, the PbTe/Ag2Te bulk composites fabricated with a low temperature phase mixing process give rise to p-type conduction of carriers with significantly decreased electrical conductivity. This indicates that Ag atom diffusion in the PbTe matrix changes the sign of the Seebeck coefficient to n-type and also increases the carrier concentration. Effective p-type doping with low temperature phase separation by mixing and hot press sintering can enhance the thermoelectric performance of PbTe/Ag2Te bulk composites, which can be used as a p-type counterpart of n-type (PbTe)1−x(Ag2Te)x bulk composites.

Phase transitions ordering–phase separation in the Co3V alloy

An electron microscopic study of the Co3V alloy microstructure formed after heat treatment at different temperatures has been conducted. Two phase transitions ordering–phase separation have been discovered, which occur in the alloy at temperatures of about 450 and 800°C. At high-temperature phase separation, the microstructure consists of bcc vanadium atom particles and a fcc solid solution; at low-temperature phase separation, it is a cellular structure, in which the cellular boundaries are enriched in vanadium. In the region of ordering, it consists of particles of the Со3V chemical compound, randomly distributed in the solid solution. It is shown that at none of the temperatures do these microstructures correspond to those shown in the Со–V phase diagram.

Structural and phase transformations in high-nitrogen austenitic steel 05Kh20AG10N3MF during thermal action

The structural and phase transformations in high-nitrogen austenitic steel 05Kh20AG10N3MF under various thermal actions are studied. The transformations are shown to occur only in the Fe-Cr diffusion couple, and they resemble the phase transformations in an Fe-20% Cr binary alloy. At 1200°C, hightemperature phase separation is detected; at 550°C or below, low-temperature separation is detected; and at 700 and 800°C, ordering with the formation of a Laves phase is observed. The ordering-low-temperature separation phase transition in the steel differs substantially from that occurring in Fe-Cr binary alloys.

Deformation-induced nanoscale high-temperature phase separation in Co–Fe alloys at room temperature

Instead of applying severe plastic deformation, high-temperature heat treatment or high pressure, grain refinement and high-temperature phase separation induced by deformation in single-phase body-centered-cubic (bcc) coarse-grained Co–Fe alloys have been achieved by simple room-temperature compression. The alloys exhibit large plasticity over 140% without fracture. Phase separation from the bcc phase to nanoscale face-centered-cubic Fe and Co phases, which generally occurs at high temperature above ∼1150K, is formed in the deformed samples. The possible mechanisms are shear deformation and deformation-enhanced atomic diffusion rather than the temperature rise during deformation.

Seafloor hydrothermal fluids, Ben Nevis area, Abitibi Greenstone Belt: Implications for Archean (∼2.7 Ga) seawater properties

A central part of the ∼2.7 Ga Abitibi Greenstone Belt, between the Destor-Porcupine and Cadillac-Larder Lake structures, has been subjected to sub-greenschist facies metamorphism ( T < 300 °C). Quartz-filled vesicles and interstitial and drainage cavity quartz from pillowed flows are considered to be the best host for Archean seawater-related fluid inclusions. Petrology revealed primary depositional textures, indicating a lack of significant metamorphism or recrystallization. Hence, the material is considered to be of primary origin, containing primary, Archean trapped fluids. The majority of observed fluid inclusions are two-phase and liquid-dominated with a vapor bubble volume of ∼10%. Microthermometry on 58 samples (∼1100 fluid inclusions) and eutectic temperatures between −45 and −30 °C indicate the presence of at least one significant divalent cation in the fluids; hence, salinity is calculated as wt.% CaCl 2 equiv. The peak of the salinity distribution of inclusions from vesicles, and interstitial and drainage cavity quartz, falls between ∼4 and ∼10 wt.% CaCl 2 equiv.; a small subset of inclusions yielded salinities between 18 and 22 wt.% CaCl 2 equiv. Most homogenization temperatures fall in an interval between ∼110 and ∼160 °C. A geothermal gradient estimated from the data of ∼10–15 °C/km is reasonable and consistent with the interpretation of the area as a regional seafloor recharge zone. Primary porosity in the modern ocean floor does not show the rapid precipitation of quartz that is indicated for the Archean; however, the global occurrence of silica-rich banded iron formations and the lack of silica consuming marine organisms in the Precambrian indicates that marine geochemistry and SiO 2-precipitation mechanisms may have been different during the Precambrian. The total salinity of a fluid is dependent primarily on its total chlorinity; hence water–rock interactions with ion exchange cannot be the only reason for the higher salinities encountered in this study. Indications for boiling or high temperature phase separation are not evident, suggesting that these options are not a reason for the observed high salinities. Our data are in agreement with six other data sets—from the 3.75 Ga Isua Greenstone Belt (W. Greenland), the 3.24 Ga Pilbara region (W. Australia), the ∼3.2 Ga Barberton Greenstone Belt (South Africa; 2), the ∼2.7 Ga Matagami area (Abitibi Greenstone Belt, Canada), and the Proterozoic (∼2.2 Ga) Ongeluk Formation (South Africa). The consistency of fluid inclusion data suggests that Archean and early Proterozoic seawater may have been more saline, and potentially stratified, compared to modern seawater.

Assimilation of seawater-derived components in an oceanic volcano: evidence from matrix glasses and glass inclusions from Loihi seamount, Hawaii

We report major element, H 2O, Cl, B, and Be analyses of matrix glass and olivine-hosted glass inclusions from two pillow lava samples dredged from 4200 m on the southern rift zone of Loihi seamount, Hawaii. Matrix glasses (MgO∼9 wt.%) have H 2O, Cl, and B contents considerably in excess of the values expected from mantle melting or fractional crystallization of parental Loihi magmas. Glass inclusions have H 2O, Cl, and B contents ranging from the high values of the matrix glasses to lower concentrations that are more typical of Hawaiian magmas. Concentrations of other incompatible elements (e.g., K 2O, P 2O 5, and Be) in matrix glasses and glass inclusions are uncorrelated with their H 2O, Cl, and B contents. Glass inclusions show considerable scatter in major element compositions compared to matrix glasses, but except for H 2O, Cl, and B, the average glass inclusion composition corresponds well to the matrix glass compositions. We propose that the glass inclusions represent compositionally diverse liquids present within the magmatic plumbing system at Loihi that were mixed and homogenized to produce the liquid that quenched to the matrix glass on eruption. This range of liquid compositions present at depth was trapped by crystallizing olivine prior to blending and homogenizing and therefore preserves a compositional diversity not present in erupted whole rocks. The high H 2O, Cl, and B contents of matrix glasses and some glass inclusions, and the range of H 2O, Cl, and B concentrations in glass inclusions, are best explained by variable extents of assimilation by Loihi magmas of H 2O–Cl–B-rich, seawater-derived components prior to eruption. The required assimilants range from material similar in composition to seawater to materials with Cl/H 2O and B/H 2O ratios much higher than seawater. Our preferred explanation (similar to that suggested for MORB by Michael and Schilling, 1989) [Michael, P.J., Schilling, J.-G., 1989. Chlorine in mid-ocean ridge magmas: Evidence for assimilation of seawater-influenced components. Geochim. Cosmochim. Acta, 53, pp. 3131–3143.] is that most of the assimilated materials were brines (or rocks containing brines in inclusions or along grain boundaries) enriched in Cl by high temperature phase separation of seawater in sub-sea-floor hydrothermal circulation systems. Addition of ∼1.0 wt.% of a 15 wt.% NaCl brine can explain the H 2O and Cl contents of the matrix glasses. Addition of altered basalt cannot readily account for the Cl and H 2O contents of matrix glasses and glass inclusions, but may be required to account for their elevated B contents. The enrichment in Cl and contamination with atmospheric noble gases observed in other samples from Loihi could also result from assimilation of Cl-enriched, seawater-derived components.

DSC study of the miscibility of PPO and sulphonylated PPO in blends with alternating copolymers of β-substituted styrene derivatives with maleic anhydride and with N-substituted maleimides

The miscibility and phase behaviour of alternating copolymers of the type ▪CHPh—CHX—CH—CO—Y—CO—CH n (X is Me, OEt, O sec-Bu; Y is oxygen, N-Me, N-Ph) in blends with PPO and sulphonylated PPO (SPPO) have been studied by differential scanning calorimetry, and by visual observation of film clarity. Alternating copolymers of β-methylstyrene with maleic anhydrice (MAn) or with N-substituted maleimide (RMI) were found to be immiscible with PPO and SPPO copolymers in all proportions. The same was found for the blends of alternating copolymers of PhCH=CHOR with MAn or with NMeMI in blends with PPO and SPPO copolymers. It was also found that blends of poly(PhCH—CH—OR—alt—NPhMI) (R is Et, n-Bu) are miscible with SPPO having a degree of sulphonylation higher than 60 mol%, but they were immiscible with SPPO of a low degree of sulphonylation. The high-temperature phase separation in the miscible blends is a function of the degree of sulphonylation of SPPO and of the blend composition.

Miscibility study of the alternating copolymers of α-methylstyrene with maleimides m blends with PS, PPO or sulphonylated PPO

The miscibility of alternating copolymers of α-methylstyrene (αMeS) and maleimides (RMI; R = H, Me, Ph) in the blends with polystyrene (PS), with poly(2,6 dimethyl-1,4-phenylene oxide) (PPO) and with sulphonylated PPO (SPPO) copolymers of different degrees of sulphonylation was studied by differential scanning calorimetry (DSC) and by visual observation of film clarity. It was found that miscibility in these systems depends on the chemical structure of the blend components. Immiscibility was found for all alternating copolymer blends with PS and with PPO. The miscibility/immiscibility behaviour in the blends of SPPO with alternating copolymers depends on the degree of sulphonylation of SPPO copolymers as well as on the chemical structure of αMeS-RMI copolymers. High-temperature phase separation in the miscible blends is a function of the degree of sulphonylation of SPPO and blend composition. The results can be explained on the basis of the mean field theory of phase behaviour for copolymer-copolymer systems.

Miscibility and phase behaviour in poly(2,6-dimethyl-1,4-phenylene oxide) and poly(fluorostyrene-co-bromostyrene) blends

Copolymers of ortho(para)fluorostyrene and ortho(para)bromostyrene with a range of copolymer compositions were prepared by free radical polymerization in toluene solution using azobis(isobutyronitrile). The miscibility and phase behaviour of these copolymers in blends with poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) have been studied by differential scanning calorimetry. Of the four possible copolymer systems, miscibility was observed only for PPO/poly( o-fluorostyrene-co- p-bromostyrene) blends in which the copolymer contains between 11 and 73 mol% p-bromostyrene. High temperature phase separation in the miscible blends is a function of copolymer composition and of the thermal history. The results can be explained on the basis of the mean field theory of phase behaviour for homopolymer-copolymer systems.