Amorphous Glass Phase Research Articles

High‐temperature behavior and self‐enhancing mechanisms of oxide‐bonded SiC porous ceramics

AbstractOxide‐bonded SiC porous ceramics (SCPCs), synthesized via reaction bonding, exhibit significant potential for high‐temperature applications. However, incorporating sintering aids inevitably results in a considerable quantity of amorphous glass phase within SCPCs, thereby introducing risks to their high‐temperature mechanical performance. In this study, we employ in‐situ characterization techniques to investigate the high‐temperature behavior of SCPCs. Our findings reveal that SCPCs demonstrate remarkable high‐temperature self‐enhancing properties, with a critical bending strength at 800°C. Beyond this temperature, the strength declines sharply. Intriguingly, the critical bending strength is 36.6% greater than at ambient temperature. Moreover, elevated temperatures enhance the elastic modulus and promote the transition of SCPCs from multilinear to nonelastic fracture. The neck phase, which imparts strength to the SCPCs, is composed of four distinct layers along the depth direction: silicate glass, oxygen‐containing, silicon‐rich, and SiC region, as revealed by FIB‐TEM. The transformation from α to β‐cristobalite in the oxygen‐containing region improves the thermal expansion match with SiC, thereby mitigating local stress concentration. Furthermore, the compressive stress within the neck region intensifies with increasing temperatures, thereby inhibiting crack propagation. This work provides a basis for the high‐temperature applications of SCPCs.

Understanding the role of different phases in γ-C2S based carbonatable clinkers

Accelerated carbonation of carbonatable clinkers into building products is an effective way of CO2 utilization. However, due to insufficient understanding on the phase characteristics of carbonatable clinkers, there is still a lack of guidance on the selection and design of carbonatable clinkers. In this study, three γ-C2S based carbonatable clinkers were designed and synthesized, covering the carbonation active phase, the unavoidable C2AS and amorphous glass phases when using industrial feedstocks. The differences in the carbonation activity, mechanical properties and microstructure were compared. Results show that the uncarbonated phases have a significant impact on the mechanical properties of carbonated matrix. The presence of unreacted γ-C2S with self-pulverization induced cleavage planes and the amorphous glass phase with poor binding to the adjacent calcium carbonate crystals leads to reduced compressive strength. The carbonation reactivity of γ-C2S formed in composite system is significantly higher than that of pure γ-C2S. Benefiting from the higher degree of carbonation, carbonatable clinkers only need to contain >40 wt% of γ-C2S to obtain comparable compressive strength as the pure γ-C2S system.

A composite photoluminescent probe based on Er/Yb co-doped tellurite glass powder for dual-parameter measurement of temperature and UV radiation

To cope with the cross-sensitivity of simultaneous measurement of ultraviolet (UV) irradiance and temperature, we propose and experimentally demonstrate a miniature composite photoluminescent probe that is formed by thoroughly mixing Er/Yb co-doped tellurite glass powder into a resin adhesive substrate. Utilizing tellurite glass in form of powder not only guarantees its thorough mixing into the liquid resin base, but also retains its amorphous glass phase for hosting Er/Yb ions, thus breaking the limitations of studying tellurite glass only in bulk or fibrous form. Co-excited by UV radiation and NIR pumping, the composite probe produces a superimposed fluorescence emission spectrum, where the intensity change rate of the 488 nm dip can be used for UV irradiance measurement, and the fluorescence intensity ratio (FIR) of the 524 nm and 545 nm peaks for temperature measurement. Based on the sensitive specificity of the resin substrate and the Er/Yb co-doped tellurite glass, we have realized the simultaneous measurement of UV and temperature without cross-sensitivity.

Review on the thermal characteristics and applications of silicon nitride ceramics

As the heat generation problem is predicted to intensify due to the trend of integration and high density of the power semiconductor power module responsible for the electric drive of the electric vehicle, which has recently been in full swing, high-reliability materials and It is essential to secure large-area heat dissipation substrate manufacturing process technology, and technical obstacles to maintain reliability even in environmental changes such as severe cold/excessive heat are becoming issues.In the case of silicon nitride ceramic material, which is in the spotlight as a heat dissipation substrate material, a balance that meets the user’s needs is required. In order to realize excellent heat dissipation performance, it is necessary to reduce the thickness of the silicon nitride substrate, increase the thickness of the metal junction, and improve the thermal conductivity of the silicon nitride material. Therefore, the task of technological progress beyond the complementary relationship between heat conduction-intensity still remains.In this paper, various technical considerations for increasing the thermal conductivity of silicon nitride ceramics are described, and the direction of technological progress is described along with detailed examples. In order to improve thermal conductivity, it is necessary to minimize the inflow of impurities into the raw material powder, appropriately select sintering additives required for liquid phase sintering, and optimize the microstructure through minimization of the amorphous glass phase and control of grain growth by the gas pressure sintering process.

Rare earth element recovery and aluminum-rich residue production from high alumina fly ash by alkali pre-desilication enhance the mechanochemical extraction process

Recycling rare earth elements (REEs) from coal fly ash by conventional acid leaching may generate large amounts of harmful waste acid, and the obtained acid residues have low utilization value. Accordingly, a green non-acid leaching approach for REE recovery and Al-rich residue production from high alumina fly ash (HAFA) was developed based on the alkali pre-desilication enhanced mechanochemical extraction process. REEs mainly existed in the chemically stable amorphous aluminosilicate glass phase of HAFA, which hindered the leaching of REEs. Thus, NaOH solution (150 g/L) was used to dissolve the glass phase and release REEs from the glass phase under a mild condition (80 °C, 2 h). The released REEs could be easily extracted by green EDTA during the mechanochemical extraction process. The extraction rates of La, Ce, Pr and Nd were about 82.03–88.71%, and valuable Al-rich residue (68.23% Al2O3 content and 2.51 Al/Si ratio) can be obtained when the mass ratio of the pre-desilication residue to EDTA, milling time, rotary speed, and liquid-solid ratio were 2:3, 2 h, 500 rpm, and 0.8, respectively. The used EDTA and REEs in the extracted solutions can be recycled by pH adjusting and organic solvent extraction. Thus, this study provides a new idea for green and high-value utilization of HAFA.

Enhancement of elastic properties and surface plasmon resonance with the addition of boron oxide to the ZnO−SiO2 glass system

Glass substrates, with their ultrasonic and enhanced Raman signals, are ever-demanding for medical applications. This paper reports the effect of boron addition to the enhancement of the elastic properties and Raman shifting in the Surface Plasmon Resonance results for the zinc borosilicate glass substrate that can be used for optical biosensor applications. Such glasses were prepared by melt–the quenching method and characterized using a densimeter, X-ray diffraction measurement, Fourier transforms infrared spectroscopy, ultrasonic, and surface plasmon resonance spectroscopy. Results from the current study demonstrated how the composition of the glass influences the physical and elastic moduli of the boron-doped zinc silicate series. The physical characteristics of the zinc silicate glasses were predicted to alter significantly after adding boron as a modifier. The glass density decreased from 3392 to 2983 kg/m3 as the percentage of boron increased from 0.10 to 0.20 wt.%, then increased to 3191 kg/m3 at 0.30 wt.%. The X-ray diffraction and Fourier transforms infrared spectroscopy techniques verified the amorphous glass phase. The ultrasonic method determined the glass's ultrasonic longitudinal and shear velocity at a 5 MHz resounding recurrence at room temperature to study elastic moduli. When boron content is added, the longitudinal, Young, shear, and bulk moduli exhibit a decreasing and increasing trend. As the boron content increases and behaves as a modifier, the number of non-bridging oxygen will increase, which will cause the glass network to expand. In addition, the increase in Eopt occurs from 3.4883 to 3.4331 because the sample has a higher number of non-bridging oxygen. The shift for Otto configuration of the SPR results occurs with the increase of boron concentration. The fabricated glass can potentially be used to construct an integrated silicon-based glass substrate for an optical sensor.

Historical ferrous slag induces modern environmental problems in the Moravian Karst (Czech Republic)

Ferrous slag produced by a historic smelter is washed from a slagheap and transported by a creek through a cave system. Slag filling cave spaces, abrasion of cave walls / calcite speleothems, and contamination of the aquatic environment with heavy metals and other toxic components are concerns. We characterize the slag in its deposition site, map its transport through the cave system, characterize the effect of slag transport, and evaluate the risks to both cave and aqueous environments. The study was based on chemical and phase analysis supported laboratory experiments and geochemical modeling. The slag in the slagheap was dominated by amorphous glass phase (66 to 99 wt%) with mean composition of 49.8 ± 2.8 wt% SiO2, 29.9 ± 1.6 wt% CaO, 13.4 ± 1.2 wt% Al2O3, 2.7 ± 0.3 wt% K2O, and 1.2 ± 0.1 wt% MgO. Minerals such as melilite, plagioclase, anorthite, and wollastonite / pseudowollastonite with lower amounts of quartz, cristobalite, and calcite were detected. Slag enriches the cave environment with Se, As, W, Y, U, Be, Cs, Sc, Cd, Hf, Ba, Th, Cr, Zr, Zn, and V. However, only Zr, V, Co, and As exceed the specified limits for soils (US EPA and EU limits). The dissolution lifetime of a 1 mm3 volume of slag was estimated to be 27,000 years, whereas the mean residence time of the slag in the cave is much shorter, defined by a flood frequency of ca. 47 years. Consequently, the extent of slag weathering and contamination of cave environment by slag weathering products is small under given conditions. However, slag enriched in U and Th can increase radon production as a result of alpha decay. The slag has an abrasive effect on surrounding rocks and disintegrated slag can contaminate calcite speleothems.

A meshfree peridynamic model for brittle fracture in randomly heterogeneous materials

In this work we aim to develop a unified mathematical framework and a reliable computational approach to model the brittle fracture in heterogeneous materials with variability in material microstructures, and to provide statistical metrics for quantities of interest, such as the fracture toughness. To describe the material responses such as the nucleation and growth of fractures in a uniform setting, we consider the peridynamics model. In particular, a stochastic state-based peridynamic model is developed, where the micromechanical parameters are modeled by a finite-dimensional random field, e.g., a combination of truncated random variables determined by the Karhunen–Loève decomposition or the principal component analysis (PCA). To solve this stochastic peridynamic problem, probabilistic collocation method (PCM) is employed to sample the random field that represents the micromechanical parameters. For each sample, the corresponding peridynamic problem is solved by an optimization-based meshfree quadrature rule. We present rigorous analysis for the proposed scheme and verify the convergence rate with a number of benchmark problems. The proposed scheme not only possesses the asymptotic compatibility spatially but also achieves an algebraic or sub-exponential convergence rate in the parametric random space when the number of collocation points grows. Finally, to validate the applicability of this approach on real-world fracture problems, we consider the problem of crystallization toughening in glass-ceramic materials, in which the material at the microstructural scale contains both amorphous glass and crystalline phases. The proposed stochastic peridynamic solver is employed to capture the crack initiation and its growth of the glass-ceramics with different crystal volume fractions, and the averaged fracture toughness are also calculated accordingly. The numerical estimates of fracture toughness show good consistency with data from experimental measurements.

Ceramic granite production wastes use for enhancement asphalt concrete construction and technical properties

Bitumen concrete construction and technical properties improvement when used as refuse finely-fragmented layer inorganic material formed in production of ceramic granite, ceramic construction material, is conditioned by its phase composition and structure. The set of physicochemical studies has established that the high physical and technical properties of ceramic granite are associated with its microstructure, which presents glassceramic composite consisting of amorphous glass phase permeated with mullite crystals and silica-containing phases of quartz and cristobalite, that provides low material porosity. The density of natural granite containing only β-quartz in an amount of about 35% with its density and the density of other minerals in the granite, in particular field spars, is 2.6… 2.7 g/cm3. The density of ceramic granite decreases due to less dense β-cristobalite, but at the same time its porosity decreases due to glass crystal structure. Use of non-porous refuses of ceramic granite as finely-fragmented inorganic material reduces amount of bitumen in bitumen concrete mixture, increases water resistance, compressive strength, shear resistance of bitumen concrete, which can increase service life of road surface.

Liquid and Glass Phases of an Alkylguanidinium Sulfonate Hydrogen-Bonded Organic Framework.

Glassy phases of framework materials feature unique and tunable properties that are advantageous for gas separation membranes, solid electrolytes, and phase-change memory applications. Here, we report a new guanidinium organosulfonate hydrogen-bonded organic framework (HOF) that melts and vitrifies below 100 °C. In this low-temperature regime, non-covalent interactions between guest molecules and the porous framework become a dominant contributor to the overall stability of the structure, resulting in guest-dependent melting, glass, and recrystallization transitions. Through simulations and X-ray scattering, we show that the local structures of the amorphous liquid and glass phases resemble those of the parent crystalline framework.

A mixture of innate cryoprotectants is key for freeze tolerance and cryopreservation of a drosophilid fly larva.

Insects that naturally tolerate internal freezing produce complex mixtures of multiple cryoprotectants (CPs). Better knowledge on composition of these mixtures, and on the mechanisms of individual CP interactions, could inspire development of laboratory CP formulations optimized for cryopreservation of cells and other biological material. Here, we identify and quantify (using high resolution mass spectrometry) a range of putative CPs in larval tissues of a subarctic fly, Chymomyza costata, which survives long-term cryopreservation in liquid nitrogen. The CPs proline, trehalose, glutamine, asparagine, glycine betaine, glycerophosphoethanolamine, glycerophosphocholine and sarcosine accumulate in hemolymph in a ratio of 313:108:55:26:6:4:2.9:0.5 mmol l-1. Using calorimetry, we show that artificial mixtures, mimicking the concentrations of major CPs in hemolymph of freeze-tolerant larvae, suppress the melting point of water and significantly reduce the ice fraction. We demonstrate in a bioassay that mixtures of CPs administered through the diet act synergistically rather than additively to enable cryopreservation of otherwise freeze-sensitive larvae. Using matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI), we show that during slow extracellular freezing trehalose becomes concentrated in partially dehydrated hemolymph where it stimulates transition to the amorphous glass phase. In contrast, proline moves to the boundary between extracellular ice and dehydrated hemolymph and tissues where it probably forms a layer of dense viscoelastic liquid. We propose that amorphous glass and viscoelastic liquids may protect macromolecules and cells from thermomechanical shocks associated with freezing and transfer into and out of liquid nitrogen.

Study on the composition and structure characteristics and dry decarbonization separation of coal water slurry gasification fine slag

Efficient separation and high-valued utilization of coal gasification ash or slag limit the clean and green development of coal chemical industry. In this paper, a coal-water slurry gasification fine slag (CWSFS) was studied by wet screening and classification. The relationship between the particle composition with different sizes and the structural characteristics was investigated by means of proximate analysis, XRF, XRD, BET and SEM. A classification method of CWSFS was proposed to guide the high-valued utilization of coal gasification slag. Then, dry separation of a coal-water slurry gasification fine slag was carried out using a combined treatment method of crushing and dissociation and airflow classification. The results show that the CWSFS particles of different sizes have obvious differences in fixed carbon content, ash composition and mineral types. For the CWSFS with the particle size above 74 μm, the fixed carbon content is more than 60%, the calorific value is more than 20 MJ/kg, the specific surface area is relatively high and the main component is the residual carbon that contains magnetite and brookite. For the CWSFS with particle sizes between 13–74 μm, the fixed carbon content is between 20%–60%, the calorific value is between 11–19 MJ/kg, the specific surface area is small and the main mineral types are pyroxene, marcasite and hematite, etc. For the CWSFS with a particle size between 0–13 μm, the fixed carbon content is less than 20% and the calorific value is less than 10 MJ/kg, which mainly includes the amorphous glass phase that was rich in aluminum, iron and calcium, quartz and a small amount of fayalite, muscovite and other minerals. According to the fixed carbon content of CWSFS with different particle sizes, the above three components with varying particle size ranges are defined as high-carbon component, medium-carbon component and low-carbon component, respectively. The dry separation test shows that the air flow crushing and classification process can achieve a higher product yield of 29.60% and a high ignition loss of 93.76%, compared to the traditional disc crushing-classification process. Airflow crushing was proved to be able to effectively increase the dissociation degree of residual carbon and greatly improve the separation and enrichment rate of residual carbon.

Effect of BaTiO3 addition on the microwave dielectric properties of MgO–Al2O3–SiO2–TiO2 glass-ceramic

Barium titanate added MgO–Al2O3–SiO2–TiO2 (MAST) glass ceramic was prepared to obtain a range of dielectric constant 6–8 for microwave application using naturally occurring materials, e.g. talc, alumina and china clay. Firstly, the MAST glass was prepared by the conventional melt quench process. Barium titanate (BaTiO3) powder (5–30 wt%) was added to the obtained MAST glass frit. Ceramic pellets were prepared from homogeneously ground and mixed powders by uniaxial pressing. X-ray diffraction patterns of the sintered pellets (at 1200 °C) show well-defined peaks of cordierite, BaTi5O11 and Ba2Ti9O20, and some anorthite and magnesium titanium oxide phases. The evolution of BaTi5O11 and Ba2Ti9O20 compounds is very much desirable since they possess excellent microwave dielectric properties. Their high dielectric constant and high quality factor would increase the dielectric constant of the compositions without degrading the loss tangent value. The microstructure shows the crystalline and amorphous (glass) phases. The dielectric constant of the prepared glass ceramic samples varies in the range 6.0–8.0 with the tan delta of 10−2 in the X-band, depending on the composition, phase and microstructure of the specimens. The tailored dielectric constant glass ceramic will be useful for microwave device applications.

Magnetic Fractions of PM2.5, PM2.5–10, and PM10 from Coal Fly Ash as Environmental Pollutants

Characterization of magnetic particulate matter (PM) in coal fly ashes is critical to assessing the health risks associated with industrial coal combustion and for future applications of fine fractions that will minimize solid waste pollution. In this study, magnetic narrow fractions of fine ferrospheres related to environmentally hazardous PM2.5, PM2.5–10, and PM10 were for the first time separated from fly ash produced during combustion of Ekibastuz coal. It was determined that the average diameter of globules in narrow fractions is 1, 2, 3, and 7 μm. The major components of chemical composition are Fe2O3 (57–60) wt %, SiO2 (25–28 wt %), and Al2O3 (10–12 wt %). The phase composition is represented by crystalline phases, including ferrospinel, α-Fe2O3, ε-Fe2O3, mullite, and quartz, as well as the amorphous glass phase. Mössbauer spectroscopy and magnetic measurements confirmed the formation of nanoscale particles of ε-Fe2O3. Stabilization of the ε-Fe2O3 metastable phase, with quite ideal distribution of iron cations, occurs in the glass matrix due to the rapid cooling of fine globules during their formation from mineral components of coal.

Protection of internal weld using a silicate coating

The main disadvantage of steel pipes and pipeline parts is their sensitivity to corrosion, which leads to a huge waste of metal and reduces the pipeline service life. In the past 15 years, the oil and gas industry has seen a drastic increase in the production of internally coated pipes and pipes made from corrosion-resistant materials. Therefore, their connection must have the same strength, pressure tightness and corrosion resistance as the material of a main pipe. The need to protect the weld is due to the weld and the connected area is the most vulnerable point in the structure. Therefore, the purpose of this work is to develop a technology for enameling the steel pipeline weld with an internal vitreous silicate enamel coating. The components were weighed, mixed and melted. The resulting frit is an X-ray amorphous glass phase. On the basis of the obtained frit, enamel slurries of the required fineness and composition were prepared and tested for the main rheological properties: density; covering ability (amount of slurry retained on a metal product surface); fineness of grinding (degree of frit grinding in slurry suspension); sedimentation stability (resistance of system particles to settling). Slurry was applied to the pretreated steel samples by pouring method. Then the samples were dried for 7-10 minutes at a temperature of 70-90 °C. Fastening firing was carried out in an electric furnace in the temperature range of 750-950 °C for 5 minutes. The quality of the weld and the presence of defects were analyzed after cooling. The optimal composition was chosen. It is characterized by the following advantages: complete melting of the enamel; absence of “copper heads”; absence of bubble craters, as well as small bubbles in the enamel volume; absence of burnouts. Further, the main technical and operational properties of the protective coating for the pipe weld were investigated: chemical resistance to the acid and alkali solutions; “coating – metal” adhesion strength; wear resistance (abrasion resistance). The results obtained demonstrate high protection rates of the synthesized coating, its high durability and reliability. The work was supported by the Russian Science Foundation, Project # 18-19-00455 “Development of integrated protection technology for oil and gas pipelines, operated in the Far East of Russia” in the framework of the 2018 competition “Conducting fundamental scientific research and exploratory scientific research by individual scientific groups”.

Dependence on the distribution of valuable elements and chemical characterizations based on different particle sizes of high alumina fly ash

Understanding the influence of the particle size on the distribution of various elements of high alumina coal fly ash (HAFA) is of significance to the utilization of valuable elements in fly ash. The distribution of valuable elements and the chemical characterizations of various particle sizes of HAFA were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), and Brunauer–Emmett–Teller (BET) analysis etc. in this work. It indicated that the contents of most of the metal oxides, including Al2O3, Fe2O3, CaO, Ga2O3, TiO2, and Li2O, decreased as the particle sizes of HAFA increasing. The contents of the nonmetal oxides, including SiO2 and organics, however, increased with the sizes increasing. For the phases distribution, the spherical mullite crystalline phase and the corundum phase were more abundant in the smaller particle sizes, while the amorphous glass phase and quartz were more abundant in the larger particle sizes. In addition, the desilication efficiency increased from 38.08% to 39.30% though mechanical pretreatment method. Interestingly, it was observed that the glass phase Al2O3 reacted with the sodium silicate solution to form zeolites, which accounted for a 22.85% of the mass after desilication. Classification may be an important pretreatment step in the recovery of valuable elements from HAFA due to the differences between the different granularities.

Understanding the solidification and leaching behavior of synthesized Cr-containing stainless steel slags with varying Al2O3/SiO2 mass ratios

This study investigated the effect of Al2O3/SiO2 mass ratios on the equilibrium crystallization behavior of synthesized CaO–SiO2–MgO–Al2O3–Cr2O3 stainless steel slags to understand the selective concentration behavior of Cr into a primary Mg(Cr,Al)2O4 spinel phase during slag solidification and to determine the leaching stability of Cr-containing slags. The spinel solid solution was precipitated within the temperature range of 1600-1400 °C, where the Cr/(Cr+Al) mole ratio in the Mg(Cr,Al)2O4 spinel phase gradually decreased for slags with higher Al2O3/SiO2 mass ratios. When the Al2O3/SiO2 mass ratio increased from 0.125 to 0.5, the Cr content in the amorphous glass phase gradually decreased, with a subsequent increase in the Cr content in the crystalline phase. For slags with a unit Al2O3/SiO2 mass ratio and MgO mole percent comprising less than the combined sum of the Cr2O3 and Al2O3 mole percents, the Cr content in the amorphous glass phase increased, which was correlated with the enhanced substitution of Cr3+ with Al3+ in the spinel. The trend of the amount of Cr-related ions in the leachate was consistent with the trend of Cr in the amorphous glass phase: the amount decreased for slags with Al2O3/SiO2 mass ratios from 0.125 to 5 and then increased for slags with an Al2O3/SiO2 mass ratio of 1. The results suggest that the addition of appropriate amounts of Al2O3 to stainless steel slags could be conducive to stabilizing Cr into the primary spinel phase to minimize Cr leaching into the environment.

PROSPECTS FOR THE INTEGRATED USE OF SLAG WASTES FROM FERROCHROME PRODUCTION FOR HEAT-RESISTANT MATERIALS

The research results of physicochemical and physicotechnical properties of slag wastes from ferrochrome production as raw materials for heat-resistant materials are presented. Chemical and mineralogical composition of slag from high-carbon ferrochrome production and slag from low-carbon ferrochrome production, as well as their constituent main crystalline phases, represented by magnesium and calcium aluminosilicates of complex composition, have been determined by physicochemical research methods. According to X-ray phase analysis, the slag from the high-carbon ferrochrome production is represented mainly by forsterite Mg2SiO4, spinel MgAl2O4, partially amorphous glass phase and admixture of calcium orthosilicate Ca2SiO4. In the slag from the low-carbon ferrochrome production, the main crystalline phase is calcium orthosilicate γ-Ca2SiO4, as well as magnesium orthosilicate forsterite Mg2SiО4. The research results of specific surface area, average particle size determination and sieve analysis have shown that the slag from the low-carbon ferrochrome production is a finely dispersed gray powder with the following characteristics: the specific surface area – 295 m2 /kg, the average particle size – 6.8 μm, the true density – 3.01 g/cm3 , the bulk density – 739 kg/m3 . The research of the physicochemical and physicotechnical properties has established that in terms of chemical, mineralogical composition and refractoriness indices, the slags from the high-carbon ferrochrome and low-carbon ferrochrome productions can be valuable raw materials for heat-resistant materials.

Immobilizing chromium in stainless steel slags with MnO addition

AbstractThis work investigates the stabilizing impact of MnO on the leaching behavior of hazardous Cr‐containing CaO‐SiO2‐Al2O3‐Cr2O3‐MnO stainless steel slags after equilibrating at various elevated temperatures and evaluates the potential immobilization of Cr into a MnCr2O4 spinel phase from the existing Cr2O3 phase. The MnCr2O4 spinel phase was found to be an excellent Cr‐stabilizer in stainless steel slags, where the leaching tendency of potentially hazardous Cr‐related ions decreased with higher MnO content and lower equilibration temperatures within the range of 0 to 15 mass pct. and 1500 to 1300°C, respectively. Thermodynamic calculations by conducting the phase stability diagram also showed that the MnCr2O4 spinel phase was relatively stable and the Ca3Si2O7 (Ca3‐xMnxSi2O7) phase was relatively unstable compared with other crystal phases in acid extractant with pH value of 3.2. Combined with the scanning electron microscopy and X‐ray powder diffraction results along with the thermodynamic calculations, the leached Cr‐related ions was predominantly originating from the unstable amorphous glass phase.

A new strategy to realize phase structure and morphology of BaTiO3 nanowires controlled in ZnO-B2O3-SiO2 glass

A novel strategy was designed to realise the control of the phase structure and morphology of BaTiO3 nanowires in ZnO-B2O3-SiO2 glass. BaTiO3 nanowire-(ZnO-B2O3-SiO2) glass-ceramics were fabricated and controlled by the sol-gel method and two-step sintering process. The influence of the amount of BaTiO3 nanowires on the glass-ceramics phase composition, morphology, and dielectric and energy storage properties was investigated. X-ray diffraction results show that all samples have a perovskite structure of BaTiO3 and a large amount of amorphous glass phases, which is the background, primarily distributed at 10-40°. With an increase in the amount of BaTiO3 nanowires in glass-ceramics, linear grains appear in the sample first, after which they transfer into rod grains as the linear grains are exhausted. The glass-ceramics dielectric constant and energy storage density first increase and then decrease with increasing amount of BaTiO3. For the sample of BaTiO3 nanowire-(ZnO-B2O3-SiO2) glass-ceramics with 30 wt% BaTiO3 nanowires, the linear grains, and the phase structure of BaTiO3 nanowires can be controlled by sintering the sample at 1200 °C for 30 min and then holding at 900 °C for 2 h. Most importantly, this work realised the control of the phase structure and morphology in glass-ceramics, which provides a significant baseline for exploring high-energy storage materials with optimal composition and structure.