Refractory Characteristics Research Articles

Fabrication of impregnated activated carbon promoted by iron nitrate and its application for adsorptive removal of organic matters from actual reverse osmosis concentrate

In this study, the potential of a highly efficient composite of activated carbon with iron oxide active substances was explored for removing organic matters from reverse osmosis concentrate. The water quality characteristics indicated that the organic matters were mainly small molecular with molecular weight less than 1 kDa, and composed of hydrophilic-alkali, hydrophilic-neutral and hydrophobic-neutral substances. The specific surface area of the activated carbon composite was 482.96 m2/g, with 91.97% of the total specific surface area being microporous. Iron oxide active substances was loaded on activated carbon skeletons, mainly forming Fe2O3 and Fe3O4. The adsorption process was fitted with pseudo-second-order and Langmuir isotherm models, with the active site playing an important role in the adsorption capacity and the adsorption was spontaneous and endothermic. Combined with the refractory characteristics of the wastewater quality, electrostatic interactions, hydrogen bonding and functional group complexation were the main forces involved in the adsorption process, taking into account the refractory nature of the wastewater.

Influence of granulated graphite on fracture behavior of MgO–C refractories based on Brazilian splitting test with digital image correlation method and acoustic emission technique

Flake graphite is prone to preferential orientation distribution owing to its flat geometric structure, resulting in significant anisotropy of the physical properties of MgO-C refractories, thus affecting their service performance. The preferential orientation of flake graphite within the material can be suppressed by granulation. In this study, the influence of granulated graphite on fracture behavior of MgO-C refractories was investigated based on the Brazilian splitting test combined with digital image correlation method and acoustic emission technique. The thermal shock resistance of the MgO-C refractories was compared using oil quenching method. The results showed that in the Brazilian splitting test, MgO-C refractories exhibited peak values for tensile strength, fracture energy, and maximum horizontal strain at fracture when θ=0º (θ: angle between loading and shaping direction), followed by a subsequent decrease with increasing θ. Moreover, the introduction of granulated graphite effectively mitigated the anisotropy of mechanical and deformation characteristics of MgO-C refractories. Additionally, the addition of granulated graphite reduced the maximum thermal expansion coefficient and its anisotropy in MgO-C refractories, and promoted the generation of a higher proportion of shear or mixed crack modes, thereby contributing to enhancing the thermal shock resistance of MgO-C refractories.

Refractory ceramics based on magnesium–aluminate spinel and periclase of the Satka deposit

The article is aimed at evaluating the promising approach to the management of the performance characteristics of ceramic refractories based on magnesia-aluminate spinel and periclase made from natural components extracted from the Satka deposit. The essence of the approach is the mechanical activation of initial coarse powders to decrease the mean particle size and dispersion, as well as to clean particle surfaces, and the variation of sintering parameters to improve the quality of adhesion between particles during sintering. It is shown that these changes in production technology allow for achieving a significant superiority of refractories obtained from activated powders over industrial samples made of powders not subjected to this kind of treatment. The obtained materials particularly have multiple higher strengths and fracture toughness. The thermal conductivity and thermal shock resistance of the obtained materials are not inferior to or superior to the corresponding characteristics of industrial refractories of similar phase composition. The analysis showed that the mechanical and thermophysical characteristics of ceramics synthesized from mechanically activated natural powders are not inferior to those of ceramics synthesized in laboratory conditions from pure precursors. The results of the study indicate a possibility of significant improvement of the mechanical and thermal characteristics of industrial periclase-spinel refractories by additional mechanical activation of mixtures of coarse powders obtained from mined natural components.

Silicon Carbide–Silicon Nitride Refractory Materials: Part 1 Materials Science and Processing

Silicon carbide and silicon nitride materials were intensively studied in the end of the past century, yet some aspects of its physical chemistry require investigation. The strength characteristics of Si3N4-SiC refractories are moderate; however, these materials sometimes demonstrate “stress–strain” behavior, more typical for composite materials than for the brittle ceramics. These materials may be considered to be ceramic composites because they consist of big grains of silicon carbide surrounded by small grains of silicon nitride, with strict interfaces between them. There is no direct certainty whether Si3N4-SiC compositions may be called composite materials or brittle ceramic materials from the viewpoint of mechanics and strength. The balance of α/β modifications of silicon nitride in Si3N4-SiC composite material and, the occurrence and the role of silicon oxynitride Si2ON2 are also a matter of scientific interest in processing of Si3N4-SiC composite material. The same may be said about the particles of silicon nitride between the grains of silicon carbide—there is no direct understanding whether silicon nitride grains will be isometric grains or needle-like crystals.

ASSESSMENT OF THE REFRACTORY AND PLASTIC PROPERTIES OF CLAY MINERAL DEPOSITS IN UHONMORA, OWAN WEST LOCAL GOVERNMENT AREA IN EDO STATE , NIGERIA

In order to assess the plastic and thermal behaviour of the clay mineral deposits at Uhonmora, Edo State, Nigeria, the chemical, mineralogical and physical properties were evaluated. The results of the study showed that the deposits consisted of phyllosilicate minerals such as kaolinite, illite and clinochlore; other mineral present were quartz, sanidine high, geonalite, diaspore and and lepidocrocite. The clay minerals exhibited moderate swelling characteristics and medium plasticity; the linear shrinkage and apparent porosity were within the accepted values for refractory clays. It is reddish-brown colour on account of the presence of coloured iron mineral lepidocrocite. The clay minerals also exhibited good thermal shock resistance and refractoriness above 1200oC. The properties of the clay mineral deposits were reflection of the combined effects of the properties of the clay minerals and other non-clay mineral constituents. The study revealed that the clay mineral deposits studied had good refractory characteristics and can be used at operating temperature conditions above 1200oC.

Physical and mechanical characteristics of refractories for the vitrification furnace of highly active waste

The results of experimental measurements of mechanical and physical characteristics of refractory materials are presented: TCLE, thermal conductivity, heat capacity, dynamic and static modulus of elasticity. The study was carried out to select the material for the manufacture of the vault of a glass furnace for curing radioactive waste. It is shown that the materials of the MKRV-53 and AZS- 60SB brands are superior in their characteristics to the material of the BMKrF brand. The obtained results are used for mathematical modeling of the operating modes of the electric furnace arch. Ill. 3. Ref. 7. Tab. 7.

Smart and Generalizable Cytarabine Derivative-Triggered Nanoparticles for Synergistic Therapy of Relapsed/Refractory Acute Myeloid Leukemia.

Acute myeloid leukemia (AML) is rapidly progressed hematologic malignancy with relapsed and refractory characteristics. Cytarabine combined with the BCL2 inhibitor venetoclax showed impressive response rates in the treatment of relapsed/refractory acute myeloid leukemia (R/R AML), while it requires complicated administration regimens and brings added toxicity. In this work, we synthesized a mercaptopropionic acid-substituted derivative of Ara-C (Ara-SH) and used it as the trigger to fabricate a smart cytarabine and venetoclax-coloaded nanoparticle (AV-NP) through self-assembly. The AV-NP characterized with redox-responsive drug release, rapid uptake by leukemia cells, and long retention in circulation had the potential to accumulate in leukemia-enriched sites. It generated a remarkable synergistic effect with higher antileukemia activity in vitro and better safety in the hematologic system compared with free drugs and significantly improved the therapeutic effect on orthotopic AML mice in vivo. These similar results were also confirmed in primary cells from R/R-AML patients. Besides, the AV-NP has the superiority of facile fabrication and generalizability, rendering it easy for clinical translation.

Overlooked great role of wind erosion in terrestrial dissolved organic matter input to lake ecosystem in cold and arid regions

Lakes in cold and arid regions have weak hydrological connectivity to their watersheds and serious soil erosion by wind, and are particularly sensitive to changes in underlying surface process and global climate changes, which may result in unique carbon cycles across the terrestrial-aquatic interface and ecological impacts. However, the roles of input pathways of terrestrial dissolved organic matter (TDOM) to lakes in cold and arid regions, especially the effects of possible TDOM input caused by wind erosion, has not been fully understood. Taking a typical lake in cold and arid regions as an example, this study comprehensively investigated the characteristics and contributions of dissolved organic matter (DOM) input from different TDOM input pathways, ultimately highlighted the impacts of wind erosion from composition characteristics, historical changes and universal proofs. The results showed that DOM introduced by wind erosion contributed 37.34 % to all TDOM input, and exhibited the strongest humification and aromaticity, and greatest molecular weight and stability. The considerable input and refractory characteristics led to the differences in the TDOM distribution and DOM composition between the near-wind and far-wind shores of the lake. Moreover, historical analysis showed that wind erosion became the main way driving the changes in buried terrestrial organic matter in the lake through a combined action of precipitation and land cover changes after 2008. The pervasive importance of wind erosion pathways on TDOM inputs in the cold and arid regions was further demonstrated through the proof from two other representative lakes. The findings also shed light on the possible impacts of wind erosion on material distribution, aquatic productivity, and energy input in lake ecosystems. The study provides new insights to broaden the content of global lake-landscape interactions and regional ecosystem conservation.

Biskyrmion-based artificial neuron

Magnetic skyrmions are nanoscale magnetic whirls that are highly stable and can be moved by currents. They have led to the prediction of a skyrmion-based artificial neuron device with leak-integrate-fire functionality. However, so far, these devices lack a refractory process, estimated to be crucial for neuronal dynamics. Here we demonstrate that a biskyrmion-based artificial neuron overcomes this insufficiency. When driven by spin-orbit torques, a single biskyrmion splits into two subskyrmions that move towards a designated location and can be detected electrically, ultimately resembling the excitation process of a neuron that fires. The attractive interaction of the two skyrmions leads to a unique trajectory: Once they reach the detector area, they automatically return to the center to reform the biskyrmion but on a different path. During this reset period, the neuron cannot fire again. Our suggested device resembles a biological neuron with the leak, integrate, fire and refractory characteristics increasing the bio-fidelity of current skyrmion-based devices.

In-situ study of phase changes in glass by impedance spectroscopy and scaling

Transformation in “evolving glass” in ion-conducting silicate glasses, glass ceramics or ceramics containing an intergranular glass is studied by in-situ impedance spectroscopy and scaling laws. Approaches are developed to scale frequency-dependent electrical conductivity and dielectric properties of multiphase ion-conducting materials to derive temperature-independent information on bulk phases and interfaces in presence. A material's scaled electric conductivity provides a unique response over a range of temperature, if the material remains unaltered, but changes, once modifications in the material occur. Therefore, impedance spectroscopy in combination with scaling can be used for tracking modifications in structure, organization, chemistry and microstructure in “evolving (ion-conducting) glass”.In a first part of this work, our approach is validated through application to stable silicate glasses and glass ceramics. Then “evolving glass” is studied in bulk glasses and ceramics with intergranular glass. Examples include ceramming of glass under formation of a glass ceramic, glass-glass phase separation, modification of intergranular glass in ceramics as result of chemical reactions or melt corrosion.Our approach allows to determine onset of phase separation, nucleation or reaction with high precision. It further reveals that nucleation in our exemplary lithium aluminum silicate glass starts with formation of interfaces (phase separation) prior to forming a well-organized crystal lattice. During phase separation in glass, early capacitive contributions in the impedance spectra indicate that the formation of glass-glass interface precedes the compositional changes in the bulk glass.Impedance of refractories is monitored during thermal treatments or corrosion in glass melt at temperatures up to 1600 °C, and glass characteristics of refractories with glass content as low as 3% are extracted. Conductivity and/or level and/or interconnectivity of the refractory's glass are shown to change during thermal treatments due to reactions between glass and crystalline refractory phases, due to phase transformation or, in case of melt corrosion, due to melt infiltration and ion exchange with the melt.In-situ tracking of impedance and application of scaling laws is shown to be able to reveal changes in bulk glass and intergranular glass.

A new iron recovery and dephosphorization approach from high‑phosphorus oolitic iron ore via oxidation roasting-gas-based reduction and magnetic separation process

Deep dephosphorization of high‑phosphorus oolitic iron ore (HPOIO) is extremely difficult because of its refractory characteristics. A new approach for simultaneous iron recovery and dephosphorization from HPOIO by oxidation roasting–gas-based reduction (ORGR) and magnetic separation process was developed. The underlying mechanism was investigated using thermodynamic calculations, X-ray diffraction (XRD), and scanning electron microscopy combined with energy dispersive spectroscopy (SEM–EDS). The results showed that the powdery reduced iron produced contained 91.37% iron and 0.14% phosphorus, and the iron recovery was 92.81%, which is an ideal for steelmaking. The addition of Na2CO3 formed nepheline, which promoted the formation and coarsening of hematite during oxidation. Concurrently, Na2CO3 reacted with the phosphorus in the iron minerals and fluorapatite to form sodium calcium phosphate, which was embedded in hematite with a simple relationship. Hematite was subsequently converted into metallic iron, sodium calcium phosphate was not reduced, and metallic iron and phosphorus were separated efficiently.

Metribuzin and metamitron degradation using catalytic ozonation over tourmaline: Kinetics, degradation pathway, and toxicity

The reaction kinetics and degradation mechanisms of the herbicides metribuzin (MTZ) and metamitron (MTT) were evaluated during conventional and tourmaline-catalyzed ozonation processes. The tourmaline catalyst was characterized by X-ray diffraction, field emission-scanning electron microscopy, Brunauer-Emmett-Teller surface analysis and Fourier transform infrared spectroscopy. The reactivities of these two herbicides with ozone (O3) are low due to their refractory characteristics, so catalytic ozonation is an ideal way to effectively degrade them. The effects of catalyst dosage, pH, temperature and ozone concentration on catalytic degradation of MTZ and MTT were investigated. Based on the results from quenching experiments and calculation of second-order rate constants (kO3, MTZ (4.82 ± 0.42 M−1s−1), kO3, MTT (13.35 ± 0.62 M−1s−1) and k•OH, MTT ((6.90 ± 0.51) × 109M−1s−1)), it was found that oxidation of the pollutants was mediated by decomposition of O3 to produce •OH. Twelve MTZ degradation products and five MTT degradation products were identified by gas chromatography-mass spectrometry and liquid chromatography-tandem mass spectrometry, and the reaction mechanisms were analyzed. In addition, the potential toxicities of the derivatives formed during catalytic ozonation were examined. The degradation products of the two pollutants exhibited different toxicity profiles. The environmental-friendliness and efficient catalytic properties of tourmaline suggest that it has great potential as a heterogenous and green catalyst.

New insight of Mn(III) in δ-MnO2 for peroxymonosulfate activation reaction: Via direct electron transfer or via free radical reactions

Due to the increasing of industrial plastic waste and its refractory characteristics, it is extremely urgent to develop new degradation technology and environmentally friendly catalyst for industrial plastic waste. Manganese oxides are one of the most promising candidates for the catalytic degradation of plastic wastes. However, an improved understanding of the structural properties affecting their catalytic activity is required for high-efficient wastewater treatment. We herein report the surface reactivity effects of δ-MnO2 structural defects with regards to Bisphenol A (BPA) degradation/probe in the presence of peroxymonosulfate (PMS). Four δ-MnOx samples with different Mn(III) contents (different Mn(III)-deficient sample) were prepared and their structural properties as well as surface reactivity were characterized by batch test, ESR and XAFS analysis. For the Mn(III)-deficient sample, BPA removal was principally affected by direct electron transfer, with the adsorbed BPA degraded following hydroxylation. In contrast, a small fraction of Mn(III) substitution in δ-MnO2 could significantly encouraged the activation of PMS to produce SO4−☐and ☐OH, and a BPA degradation via beta scission. Moreover, the Mn(III)-rich δ-MnO2 demonstrate a high BPA removal rate even with a low sample load, which performed well following a reuse of five times. Our results provide a new way for the improvement of δ-MnO2 activity for the use of industrial plastic wastes treatment.

The effect of the addition of nanoscale SiO2 on the physical and mechanical characteristics and durability of an industrial batch of refractory products

The physicomechanical properties and structure of mullitecorundum unformed refractories were investigated and tests of a pilot batch of refractory products for various purposes were carried out. The effect of the addition of nanoscale SiO2 (1 wt. %) on strength, structural (density, porosity) and operational characteristics of unformed refractories. The results show that this additive contributes to the formation of a structure with high apparent density and compressive strength (2,93 and 2,98 g/cm3, 87,3 and 162,1 MPa, respectively, for two types of refractories), reduces open porosity from 20 to 14 %, and also increases the resistance of refractory products (by the duration of their operation) by 25‒35 % compared to the resistance of the base refractory. The use of SiO2 nanoparticle additives reduces the consumption of refractory products and raw materials for their production, and also increases the profitability of production. Ill. 2. Ref. 19. Tab. 4.

Effects of MgO and Fe2O3 Addition for Upgrading the Refractory Characteristics of Magnesite Ore Mining Waste/By-Products

In the context of a circular economy/zero-waste, the conversion of extractive wastes into new products is of particular importance. At the Grecian Magnesite SA mine (Chalkidiki, N. Greece), millions of tons of waste accumulate in the operation field. To achieve these goals, the effect of caustic calcined magnesia (MgO) at 10, 15, and 20 wt.% was investigated in combination with 0.5, 1, 2.5, and 5 wt.% Fe2O3 at 1300 °C and 1600 °C for 120 min. The main refractory properties were determined along with the mineralogical content. The morphological examination has been performed by SEM-EDS analysis. The addition of MgO increases the desired olivine and eliminates the unwanted pyroxenes, causing the formation of magnesium-ferrite and periclase. MgO wt.% addition resulted in the decrease of firing shrinkage at 1300 °C but increased with Fe2O3. At 1600 °C, firing shrinkage had a minimum value at the optimum MgO dose. Mechanical strength at 1600 °C achieved a maximum value at the optimum MgO dose plus 5 wt.% MgO and 2.5 wt.% Fe2O3 due to sintering process/magnesioferrite formation. These results indicate that MgO and Fe2O3 upgrade the refractoriness of magnesite mining wastes due to the diffusion of Fe2O3 in MgO excess.

The origin of gastric cancer stem cells and their effects on gastric cancer: Novel therapeutic targets for gastric cancer.

Gastric cancer (GC) is one of the most prevalent malignancies and the most common causes of cancer-related mortality worldwide. Furthermore, the prognosis of advanced GC remains poor even after surgery combined with chemoradiotherapy. As a small group of cells with unlimited differentiation and self-renewal ability in GC, accumulating evidence shows that GC stem cells (GCSCs) are closely associated with the refractory characteristics of GC, such as drug resistance, recurrence, and metastasis. With the extensive development of research on GCSCs, GCSCs seem to be promising therapeutic targets for GC. However, the relationship between GCSCs and GC is profound and intricate, and its mechanism of action is still under exploration. In this review, we elaborate on the source and key concepts of GCSCs, systematically summarize the role of GCSCs in GC and their underlying mechanisms. Finally, we review the latest information available on the treatment of GC by targeting GCSCs. Thus, this article may provide a theoretical basis for the future development of the novel targets based on GCSCs for the treatment of GC.

A RUNX-targeted gene switch-off approach modulates the BIRC5/PIF1-p21 pathway and reduces glioblastoma growth in mice

Glioblastoma is the most common adult brain tumour, representing a high degree of malignancy. Transcription factors such as RUNX1 are believed to be involved in the malignancy of glioblastoma. RUNX1 functions as an oncogene or tumour suppressor gene with diverse target genes. Details of the effects of RUNX1 on the acquisition of malignancy in glioblastoma remain unclear. Here, we show that RUNX1 downregulates p21 by enhancing expressions of BIRC5 and PIF1, conferring anti-apoptotic properties on glioblastoma. A gene switch-off therapy using alkylating agent-conjugated pyrrole-imidazole polyamides, designed to fit the RUNX1 DNA groove, decreased expression levels of BIRC5 and PIF1 and induced apoptosis and cell cycle arrest via p21. The RUNX1-BIRC5/PIF1-p21 pathway appears to reflect refractory characteristics of glioblastoma and thus holds promise as a therapeutic target. RUNX gene switch-off therapy may represent a novel treatment for glioblastoma.

Altered Functional Connectivity in Pain-Related Brain Regions and Its Correlation with Pain Duration in Bone Metastasis with Cancer Pain.

Bone metastatic pain is thought to be a severe type of cancer pain that has refractory characteristics and a long duration. This study is aimed at exploring the brain functional connectivity (FC) pattern in lung cancer patients with bone metastatic pain. In this study, 27 lung cancer patients with bone metastatic pain (CP+), 27 matched lung cancer patients without pain-related complaints (CP−), and 27 matched healthy controls (HC) were recruited. All participants underwent fMRI data acquisition and clinical assessments. One-way ANOVA or a Mann–Whitney U test was applied to compare clinical data according to data distribution. Seventeen hypothesis-driven pain-related brain regions were selected as regions of interest (ROIs). FC values among pain-related brain regions across the three groups were computed by using ROI–ROI functional connectivity analysis. ANCOVA with a post hoc test was applied to compare FC differences among the three groups. p < 0.05 indicated statistical significance. Correlation analysis was conducted to explore the potential relationship between the FC values and clinical characteristics. Except for years of education, no significant differences were revealed among the three groups in age, gender, or neuropsychological assessment. In the CP+ group, FC alterations were mainly concentrated in the dorsal lateral prefrontal cortex (DLPFC), anterior cingulate cortex (ACC), secondary somatosensory cortex (SII), and amygdala compared to the CP− group. Among these brain regions with statistical differences, FC between the right DLPFC and the right ACC showed a positive correlation with the duration of cancer pain in the CP+ group. In addition, in the CP− group, altered FC was found in the bilateral SII, ACC, and thalamus compared to the HC group. Altered FC in pain-related brain regions may be a brain pattern of bone metastatic pain and may be associated with the long duration of cancer pain.

An investigation of the effect of tapered angle and boundary condition on natural frequency of different ceramic coated Ti-6Al-4V alloy with finite element analysis

In recent years, the interest in light metals has increased due to the increasing demand for components with high specific strength and long service life in the industry. In this context, titanium alloys have become very common and popular owing to their high strength/weight properties and superior refractory characteristics. In this study, the effect of boundary condition and tapered angle on the natural frequency and vibration behavior of the beam was investigated in Ti-6Al-4V beams coated with three different ceramic materials; Al2O3, AlN, and TiB2. Tapered angle values are considered as 0°, 0.2°, 0.4°, 0.6° and 0.8°. Besides, boundary conditions were evaluated in two conditions including left side fixed or both sides fixed. All analyzes were performed in the finite element-based Ansys APDL 19 program. According to the results obtained from the analyses, it was observed that there was a change in the natural frequency values according to the type of coating material, but no difference was found in terms of increase/decrease tendency. In addition, the resultant displacement values were determined for all samples. The results indicated that the resultant displacement values were severely affected by the tapered angle. A decreasing resultant displacement trend was observed in all samples with increasing tapered angle.

New insights into the transformation of effluent organic matter during Fe(II)-assisted advanced oxidation processes: Parallel factor analysis coupled with self-organizing maps

The negative effects of effluent organic matter (EfOM) on receiving aquatic environments and advanced treatment facilities pose significant concerns. However, the effective removal of EfOM is challenging due to its chemically complex nature and its refractory characteristics. In this study, two Fe(II)-assisted oxidation processes including UV/Fe(II)/H2O2 and UV/Fe(II)/persulfate (UV/Fe(II)/PS) were investigated to promote EfOM reduction. Fe(II) was essential for promoting EfOM degradation. The mineralization rate of EfOM increased from 7 to 29% with 2 mM Fe(II) addition in the UV/H2O2 process and to 23% with 0.8 mM Fe(II) addition in the UV/PS process. A preliminary experiment was conducted to obtain the optimal molar ratio of oxidant to Fe(II) for practical applications based on different indicators. The form of Fe(III) prevalent at different pH values strongly affected Fe(II)/Fe(III) cycling, thus determining the progress of EfOM degradation. A machine learning approach consisting of parallel factor analysis coupled with self-organizing maps (PARAFAC-SOM) was employed with fluorescence spectra to visualize the degradation behavior of EfOM in the different reaction systems. Four components (i.e., two humic-like substances, one fulvic acid, and one tryptophan-like substance) were eventually identified, and their reductions reached more than 62% during the Fe(II)-assisted oxidation processes. The degradation orders for each component in the different oxidation processes were initially evaluated by SOM analysis with Fmax percentage data. The degradation behavior of EfOM in the UV/Fe(II)/H2O2 and UV/Fe(II)/PS systems exhibited different trends based on the best matching unit map and component planes. The humic-like component was more refractory than the other three components in both oxidation processes. The microbial humic-like and high-molecular-weight fulvic acid substances showed higher reactivity with SO·4- than with ·OH, while the tryptophan-like substance was more reactive in the UV/Fe(II)/H2O2 system than in the UV/Fe(II)/PS system. The outcomes of this study provide new insights into the degradation behavior of EfOM, promoting the development of advanced wastewater treatments.