Aluminum Content Research Articles

The Effect of La, Ce Rare‐Earth Elements on the MnS Inclusion Precipitation and Distribution in U75V Heavy‐Rail Steel

The quality of heavy rail steel is significantly influenced by the distribution and morphology of MnS inclusions. With the help of experimental methods and thermodynamic predictions, the evolution of inclusions in heavy rail steels with different rare‐earth (RE: La + Ce) additions is investigated, and the relationship between RE inclusions and MnS is better interpreted by the classical two‐dimensional mismatch degree theory. The results show that the deoxidizing ability of RE elements added to the steel is greater than the desulfurizing ability. The best data for physical parameters of inclusions in steel are obtained at a RE addition of 122 ppm. The MnS inclusion particles are roughly spherical around the REAlO3 inclusion particles when the aluminum content in the RE inclusion is high. The MnS inclusion particles are better able to fit flatly around the RE2O2S inclusion particles when the sulfur content of the RE inclusion is high. By computing the two‐dimensional mismatch between the interfaces of different inclusions, it is discovered that the heterogeneous nucleation efficiency is comparatively low between MnS and REAlO3, relatively high between MnS and RE2O2S, and highest between MnS and RE2O3.

Fiber morphological characteristics of bamboo Ferrocalamus strictus culms from different geographical distribution regions

The fiber index including fiber length, width, wall thickness and lumen diameter of Ferrocalamus strictus culms (1, 2, and ≥ 3 years) from Jinping, Mojiang and Lvchun counties of Yunnan Province was determined and the elemental content of the soil was also determined to analyze the fiber characteristics. The average relative fiber index measured for F. strictus culms were fiber length (1.30 mm), width (21.57 μm), slenderness ratio (60.79 μm), wall thickness (4.21 μm), lumen diameter (7.22 μm), and runkel ratio (1.22 μm), which belonged to the range of middle and long fibers. The fiber length increased with the culm age. The proportion of long fiber increased while short fibers decreased along with culm maturing. The fiber morphology did not show a specific trend with the culm height. Fiber length reached the maximum in the bottom portions of the culms. There is a correlation between fiber morphology and soil elements, the content of organic matter, total potassium, total sulfur, total aluminum, total zinc, total iron, total boron, alkali-hydrolyzed nitrogen and available silicon in the soil affects fiber morphology. The content of organic matter, total boron and alkali-hydrolyzed nitrogen in the soil from Mojiang County was largest. Comparatively, the culm fiber in Mojiang County had the best fiber index performance for utilization, since the greatest proportion of medium and long fibers and the optimal distribution of fiber length frequency was obtained from the culms in Mojiang County. This study can provide a theoretical basis for large-scale bamboo forest cultivation and the development and utilization of bamboo culm fiber.

Effect of Nattokinase in D-galactose- and Aluminum Chloride-induced Alzheimer's Disease Model of Rat.

Alzheimer's disease (AD) is the most common form of dementia worldwide. Nattokinase is a serine protease extracellularly produced by natto, a fermented product of Bacillus subtilis var. natto. In this study, we investigated the therapeutic effects of nattokinase in a rat model of AD induced by aluminum and D-galactose. Forty Wistar rats were randomly divided into four groups: normal, vehicle, and orally administered nattokinase (NK65 and NK130 groups). Except for the normal group, all groups were treated with AlCl3 and D-galactose for 10 weeks. The NK65 and NK130 groups additionally received 65 mg/kg/day and 130 mg/kg/day nattokinase, respectively. We analyzed β-amyloid levels in the cerebrospinal fluid (CSF), and the spatial reference test was evaluated using the Morris water maze test. After the Morris water maze test, rats of all groups were subjected to micro-computed tomography (μCT) to assess constructional changes in the brain. Aluminum concentration and β-amyloid levels were analyzed by histochemical staining in all brain tissues. Oral administration of nattokinase in the AD rat model increased free-form β-amyloid levels in the CSF and improved aluminum and amyloid plaque accumulation in the brain. Brain μCT images showed enhanced brain volume with fewer constructional changes after treatment with nattokinase. In the behavioral tests, both the escape latency time in the spatial reference test and the time taken to cross the platform area in the spatial probe test improved partially. The results suggest that nattokinase has potential therapeutic applications in the treatment of AD.

Machining mechanism of CoCrFeNiAlX high entropy alloys via ultrasonic elliptical vibration cutting

Abstract This study investigates the micro-cutting mechanism of CoCrFeNiAl X high entropy alloys, focusing on the impact of amplitude, vibration frequency, cutting depth, and the Al element content. The mechanical response of the material is analyzed using simulation methods for both conventional cutting and ultrasonic elliptical vibration assisted cutting (UEVAC). The results show that under different vibration parameters and cutting depth, the cutting temperature produced by UEVAC is significantly higher than that of conventional cutting temperature. When the Y-axis amplitude is reduced from 90 μm to 30 μm, the cutting temperature is reduced by 50%. In addition, the cutting temperature is positively correlated with the Al content, and when the molar ratio is 20%, the cutting temperature is about 2.1 times that of 13%. While keeping the cutting parameters unchanged, the cutting force generated by UEVAC is significantly reduced compared to conventional cutting. It is worth noting that when the X-axis amplitude is 40 μm, the Y-axis amplitude is 90 μm, and the vibration frequency is 25 KHz, the cutting force of UEVAC is the smallest, which is only about 13% of the conventional cutting force. With the increase of the mole ratio of aluminum in the high entropy alloy, when the mole ratio of aluminum increases from 0% to 13%, the cutting force begins to decrease by about 33%. However, when the molar ratio increases from 13% to 20%, the cutting force increases by about 214%. On the surface of the workpiece (within the range of 0–3 μm from the machining surface), the residual stress generated by UEVAC is mainly manifested as compressive stress or tensile stress, which is significantly less than the residual stress generated by conventional cutting. The relation of residual compressive stress of workpiece under different aluminum content is Al1 > Al0.6 > Al0.

Characterization of Some Local Clay Minerals and Fabrication into Ceramic Floor-Tiles

Clay minerals deposits, which include, kaolin, ball-clay, fireclay and zircon, were investigated and used in fabrication of ceramic floor tiles. X-ray diffractometer (XRD-6100, Japan), was used to examine the various compositions and structures of the clay samples. 2000 grams of 0.005 mm grain size of each sample were homogeneously mixed into dough, compressed in metallic mould of 12 mm × 36 mm dimension, and allowed to dry for about 5 hours. Kiln draught oven, at 1200°C was set for glazing and firing of the moulded tiles, to ensure glossy appearance, smoothness and improved strength. XRD test showed higher content of alumina (Al<sub>2</sub>O<sub>3</sub>) and Silicon (iv) oxide (SiO<sub>2</sub>) in all the clay samples. The percentage composition of Critobalite, Diphosphorus trioxide (P<sub>2</sub>O<sub>3</sub>), Potassium Oxide (K<sub>2</sub>O) and Sodium Oxide (Na<sub>2</sub>O), were reasons for their excellent workability, improved mechanical and rheological properties of ceramics floor-tiles. Water absorption, chemical resistance, shrinkage properties of the different ceramic tiles were compare to some commercial products. This investigation had shown that locally available clay minerals could be fully integrated into ceramic industries to reduce cost of ceramic importation and create job opportunities for youths.

Dual-gate AlGaN channel HEMTs: advancements in E-mode performance with N-shaped graded composite barriers

Abstract This work evaluates the performance of dual gate AlGaN channel HEMTs on SiC substrate. The study analyzes two HEMT structures that differ only in barrier design, one design consists of fixed composite barriers (FCB-HEMT) i.e. there is fixed Aluminum composition x = 0.48 in the first Al x Ga1−x N barrier and x = 0.42 in the second Al x Ga1−xN barrier while the other design comprises N-shaped graded composite barriers (NGCB-HEMT) i.e. the Aluminum content varies gradually from 0.4 to 0.48 in the first AlGaN barrier and from 0.34 to 0.42 in the second AlGaN barrier. The paper concentrates on energy band diagrams, electron concentration profile, electric field distribution, drain and transfer characteristics, and the effects of high temperature on drain characteristics and mobility of the NGCB-HEMT. It has been reported that at zero gate bias, the FCB-HEMT has a drain current density of 0.137 A mm−1 while it decreases to 0.0058 A mm−1 in the case of NGCB-HEMT, thus presenting a novel approach towards enhancement-mode AlGaN HEMTs. Hence, grading can be optimized in the composite barriers to achieve enhancement mode operation of AlGaN channel HEMTs. Furthermore, the study reveals that the critical electric field of FCB-HEMT is 6.9975 M V cm−1, while that of NGCB-HEMT is 5.3124 M V cm−1, demonstrating their usefulness in electronic devices that operate at high voltages and harsh temperatures. Moreover, at higher temperatures, the phenomenon of optical phonon scattering leads to decreased mobilities, which in turn causes low drain currents relative to the drain voltage.

Soil Analysis by Mobile Multinuclear NMR: Quantification of Phosphorus, Aluminum, and Sodium.

Soil analyses are essential to ensure economically and environmentally sustainable crop production while maintaining the soil fertile for future use. Unfortunately, common soil analyses may be highly demanding in terms of time, chemicals, and costs. This applies, in particular, when total quantities of elements are desired. As an easy and fast alternative without consumption of chemicals, we here present mobile 31P, 27Al, 23Na, and 1H NMR for quantification of phosphorus, aluminum, and sodium contents in soil. This enables accurate on-site analysis and is suitable for direct measurement on fresh, undried soil samples since the water content is quantified as well. For demonstration, 40 various Danish agricultural soil samples were analyzed using a mobile NMR sensor, and the results were compared with external laboratory analyses for P, Al, and Na. The laboratory analyses were conducted with ICP-OES after four-acid digestion, which additionally were compared with aqua regia digestion, showing inadequacies in the performance of the latter. Good agreement between NMR and laboratory analyses (correlation coefficients 0.91 for P, 0.98 for Al, and 0.90 for Na, in the concentration ranges 250-1200 ppm P, 1.4-5% Al, and 0.3-1% Na) were obtained with high accuracy using NMR measuring times of 20 min to 1 h for P, 4-12 min for Al, and 6-20 min for Na. Additionally, the NMR measurements provide information on the amount of P associated with paramagnetic centers (e.g., Fe3+). Good correlations were also observed to other parameters such as the clay content, which is predictable from the intensity of the more fast-relaxing of three 27Al NMR components.

Aluminum exposure levels in workers at electrolytic production

Introduction. Occupational exposure to aluminum has been established to lead to accumulation of metal in tissues and create a risk of functional impairment in the central nervous system. The aim of the work was to assess the levels of external and internal aluminum exposure in workers at the electrolytic production of aluminum under modern occupation conditions. Materials and methods. Two hundred fifty measurements of the average shift aluminum oxide concentration were analyzed at various stages of the technological process. The urine aluminum concentration urine was determined by the atomic absorption method. Results. The aluminum oxide concentration in the housings with the unbaked anode technology varied from 0.59 to 17.95 mg/m3. The MPC was exceeded at the electrolyzer workplace in 10% of measurements, the anode maker — in 40%, and the crane operator – in 50%. In housings with a baked anode, the aluminum oxide concentration in all measurements did not exceed the MPC. The highest aluminum emission was observed in occupational groups associated with unbaked anodes. A trend model was constructed for the dependence of urine aluminum concentration on the aluminum dioxide level in the air, which has the form of an exponential curve. The bend in the curve begins with an air aluminum dioxide content of about 4.2 mg/m3. Limitations. The study is limited by the number of examined workers who underwent periodic medical examination. Conclusion. The results of biomonitoring showed the elimination of aluminum with urine to reflect the level of exposure to the toxicant. The equation of the dependence of the urine aluminum concentration on the air aluminum dioxide level was calculated.

Chemical durability of optical temperature sensors made of tellurite glass: Effect of the alumina concentration

Tellurite glass is an amorphous material commonly doped with rare earth ions for the development of optical temperature sensors. Considering the intrinsic properties of glasses, it is expected that these sensors could be used in acidic environments and withstand temperature changes. However, this has not been fully demonstrated since most of the literature is limited to demonstrate the sensor operation under normal conditions. Additionally, there is a lack of information regarding the chemical durability of these glasses and methods to improve it. In this work, a special tellurite glass composition was proposed for the development of optical temperature sensor. The effect of the alumina concentration on the structure, chemical durability and emission properties of the glasses was evaluated. Chemical durability was assessed by monitoring the weight loss of glass samples after immersion in hydrochloric acid solutions at room temperature, vegetable oil or air at 150 °C. The results indicate that the addition of alumina increases the chemical durability of the glass and improves its emission properties. It was found that the average temperature estimated by the optical sensor had a relative error of 1.3 % due to the degradation of the glass caused by remaining immersed in a 1 N HCl solution for 60 days.

Assessing the impact of leachate irrigation on Medicago sativa (alfalfa) growth, enzymatic responses, and heavy metal accumulation.

In light of the increasing water scarcity and the need for sustainable waste management, the use of landfill leachate for irrigation has emerged as both a solution and a concern, posing potential risks to soil health and plant vitality. This study examined the multifaceted impacts of leachate irrigation on the soil characteristics, plant growth, and enzymatic activities of Medicago sativa (M. sativa). By exposing alfalfa to different concentrations of leachate, we assessed the influence on heavy metal accumulation, physiological parameters, and enzyme functions. The physicochemical profile of the leachate indicated that the pH was within acceptable limits, but the chemical oxygen demand (COD), biochemical oxygen demand (BOD5), and concentrations of lead (Pb) and aluminum (Al) exceeded regulatory standards. Morphological parameters exhibited dual effects: stimulation at lower leachate doses and inhibition at higher leachate doses. Our findings show that soil acts as a buffer, reducing heavy metal uptake by plants. Enzymatic activities, including catalase, peroxidase, and succinate dehydrogenase, fluctuated significantly at higher leachate concentrations, indicating stress responses. This research underscores the interplay between leachate irrigation, plant physiology, and soil health, emphasizing sustainable management to optimize plant growth and minimize environmental impacts. It also stresses refining leachate application protocols to preserve soil and ecosystem health.

Full-zone optical spin injection in AlxGa1−xAs alloys

Abstract Full-zone optical spin injection in Al x Ga1−x As alloys is investigated by analyzing the degree of circular polarization (DCP) of luminescence in a quantum well architecture. Aluminium content in AlGaAs barrier layers is varied to explore both the direct- and indirect-bandgap regimes. For all the samples, experimental data are compared with a 30-band k .p model addressing the band structure of the alloy and the optical spin injection over the entire Brillouin zone. We observe circularly polarized luminescence arising from the spin generation either around Γ or the L valley. We interpret the specific shape of the DCP within a framework accounting for smaller electron spin relaxation at the higher k points of the X valley of the AlGaAs barrier layer. Moreover, it is found that the presence of strain plays a vital role in governing the magnitude and shape of the DCP spectra for near band-edge excitation while exciting spin-polarized carriers in the direct-bandgap AlGaAs. We believe that these findings are important for the realization of AlGaAs-based spin-photonic devices aiming at possible applications in quantum technology.

Sol-Gel Derived Alumina Particles for the Reinforcement of Copper Films on Brass Substrates.

The aim of this study is to provide tailored alumina particles suitable for reinforcing the metal matrix film. The sol-gel method was chosen to prepare particles of submicron size and to control crystal structure by calcination. In this study, copper-based metal matrix composite (MMC) films are developed on brass substrates with different electrodeposition times and alumina concentrations. Scanning electron microscopy (FE-SEM) with energy-dispersive spectroscopy (EDS), TEM, and X-ray diffraction (XRD) were used to characterize the reinforcing phase. The MMC Cu-Al2O3 films were synthesized electrochemically using the co-electrodeposition method. Microstructural and topographical analyses of pure (alumina-free) Cu films and the Cu films with incorporated Al2O3 particles were performed using FE-SEM/EDS and AFM, respectively. Hardness and adhesion resistance were investigated using the Vickers microindentation test and evaluated by applying the Chen-Gao (C-G) mathematical model. The sessile drop method was used for measuring contact angles for water. The microhardness and adhesion of the MMC Cu-Al2O3 films are improved when Al2O3 is added. The concentration of alumina particles in the electrolyte correlates with an increase in absolute film hardness in the way that 1.0 wt.% of alumina in electrolytes results in a 9.96% increase compared to the pure copper film, and the improvement is maximal in the film obtained from electrolytes containing 3.0 wt.% alumina giving the film 2.128 GPa, a 134% hardness value of that of the pure copper film. The surface roughness of the MMC film increased from 2.8 to 6.9 times compared to the Cu film without particles. The decrease in the water contact angle of Cu films with incorporated alumina particles relative to the pure Cu films was from 84.94° to 58.78°.

Integrated environmental and social assessment of alum-contaminated water in An Giang province

ABSTRACT This study investigates alum-contaminated water in An Giang province within the Mekong Delta, emphasizing methodological approaches to assess its distribution and impacts. The research conducted from March to May 2021 involved surveys of residents, public sector employees, and provincial managers, complemented by expert interviews and extensive fieldwork. Surface water samples were collected during both rainy and dry seasons across three districts, with parameters such as turbidity, pH, and temperature measured onsite, and aluminum (Al), iron (Fe), and copper (Cu) concentrations analyzed in the laboratory using atomic absorption spectrometry. The data were further processed using QGIS software to create comprehensive maps illustrating seasonal variations in water quality. The findings revealed significant spatial and temporal variations in water quality, with pH levels fluctuating markedly between the dry and rainy seasons. Household surveys indicated a lack of awareness regarding effective water treatment methods, with most respondents relying on local authorities for solutions. The study highlights the need for community education and participation in addressing alum contamination, offering insights into the environmental and public health implications of water quality in the region. This research contributes valuable knowledge to the ongoing efforts in environmental conservation and water quality management in the Mekong Delta.

Influence of Low-Energy High-Current Electron Beam Exposure on the Phase Composition and Corrosion Resistance of the AM60 Magnesium Alloy

The surface of an AM60 (Al – 5.5, Zn – 0.2, Cu – 0.009, Fe – 0.005, Si – 0.1; Ni – 0.002, Mn – 0.3 wt.%, Mg – the rest) magnesium alloy was exposed to a low-energy high-current electron beam. After the irradiation, the content of the β-phase (Mg17Al12) decreases and the aluminum content increases in the alloy surface layer. After the exposure to the electron beam, the corrosion resistance of the alloy in a 1-molar NaCl solution increases significantly compared to the initial state. The physical reason for the increase in the alloy corrosion resistance after exposure to the electron beam is the higher corrosion resistance of the oxide film formed on the alloy surface due to the increased aluminum content.

Using Artificial Neural Networks to Predict Operational Parameters of a Drinking Water Treatment Plant (DWTP)

The scope of the present study is the estimation of key operational parameters of a drinking water treatment plant (DWTP), particularly the dosages of treatment chemicals, using artificial neural networks (ANNs) based on measurable in situ data. The case study consists of the Aposelemis DWTP, where the plant operator had an estimation of the ANN output parameters for the required dosages of water treatment chemicals based on observed water quality and other operational parameters at the time. The estimated DWTP main operational parameters included residual ozone (O3) and dosages of the chemicals used: anionic polyelectrolyte (ANPE), poly-aluminum chloride hydroxide sulfate (PACl), and chlorine gas (Cl2(g)). Daily measurable results of water sample analysis and recordings from the DWTP Supervisory Control and Data Acquisition System (SCADA), covering a period of 38 months, were used as input parameters for the artificial neural network (1188 values for each of the 14 measurable parameters). These input parameters included: raw water supply (Q), raw water turbidity (T1), treated water turbidity (T2), treated water residual free chlorine (Cl2), treated water concentration of residual aluminum (Al), filtration bed inlet water turbidity (T3), daily difference in water height in reservoir (∆H), raw water pH (pH1), treated water pH (pH2), and daily consumption of DWTP electricity (El). Output/target parameters were: residual O3 after ozonation (O3), anionic polyelectrolyte (ANPE), poly-aluminum chloride hydroxide sulfate (PACl), and chlorine gas supply (Cl2(g)). A total of 304 different ANN models were tested, based on the best test performance (tperf) indicator. The one with the optimum performance indicator was selected. The scenario finally chosen was the one with 100 neural networks, 100 nodes, 42 hidden nodes, 10 inputs, and 4 outputs. This ANN model achieved excellent simulation results based on the best testing performance indicator, which suggests that ANNs are potentially useful tools for the prediction of a DWTP’s main operational parameters. Further research could explore the prediction of water chemicals used in a DWTP by using ANNs with a smaller number of operational parameters to ensure greater flexibility, without prohibitively reducing the reliability of the prediction model. This could prove useful in cases with a much higher sample size, given the data-demanding nature of ANNs.

Effects of Al doping on structural, optical, morphological, and low-concentration CO2 gas sensing properties of ZnO nanoparticles synthesized by sol-gel method

Abstract This work examines the morphological, structural, optical, and gas-sensing characteristics of ZnO thin films doped with Al that were created by the sol-gel spin coating technique. The thin films, doped with varying aluminum concentrations (0%, 2%, and 5%), were characterized using XRD, UV-visible spectroscopy, and FE-SEM to assess their crystallinity, band gap, and surface morphology. XRD analysis confirmed the incorporation of Al into the ZnO lattice without forming secondary phases, while UV-visible spectroscopy revealed an increase in transmittance and band gap with higher Al doping. FE-SEM images showed a transition from agglomerated grains to smoother surfaces with increased Al content. Gas sensing performance was evaluated using low-concentration CO2 as the target gas. The results demonstrated that Al doping significantly enhances the CO2 sensing response, with the 5% Al-doped ZnO exhibiting the highest sensitivity due to increased carrier concentration and improved surface interaction. These findings suggest that Al-doped ZnO thin films are promising candidates for efficient CO2 gas sensors, combining enhanced structural and optical properties with superior gas sensing capabilities.

Potentially Toxic Metals Enrichment in Soils of Ishiagu Mining Community, Southeastern Nigeria

This Study was carried out to evaluate potentially toxic metals enrichment, pollution and potential ecological risk in the soils of Ishiagu. The concentrations of Cadmium (Cd), Chromium (Cr), Cobalt (Co), Copper (Cu), Lead (Pb), Manganese (Mn), Nickel (Ni), Zinc (Zn), Aluminum (Al) and Iron (Fe) in soil samples from the area were analyzed by Bureau Veritas Laboratory, Vancouver, Canada, using inductively-coupled plasma optic emission spectrometry (ICP-OES). Descriptive statistics, enrichment factor, pollution load and potential ecological risk indices were employed to analyze the data in order to understand the characteristics of potentially toxic metals in the study area. The potentially toxic metals statistic show the mean values (mg/kg-1 ) of Pb, Zn, Mn, Fe, Al, Cd, Cr, Ni, Co, and Cu to be 205.7, 162, 527, 35892, 11374, 1.3, 21.6, 15, 14.6 and 11.1 respectively. The soil enrichment varied considerably between mining and non-mining areas with mining area being extremely enriched with Pb, Zn and Cd, and significantly enriched with Co, Cu, Ni and Fe. Non- mining areas are minimally enriched with all investigated metals. The soils around the mines are polluted with Pb and Cd, where both metals also pose very high ecological risks.

The Effect of Spray Distance on the Hot Corrosion Behavior of HVOF‐Sprayed NiCrAlY Coatings in a Simulated Gas Turbine Environment

ABSTRACTTo utilize the unique properties of coatings produced using the high‐velocity oxy‐fuel (HVOF) method, this study examined the effect of spray distance on the hot corrosion behavior of NiCrAlY coatings deposited on a steel substrate. The coating samples were obtained at spray distances of 20, 25, and 30 cm. The flow rates of oxygen and propane were maintained constant at 300 and 60 lit/min, respectively. Additionally, the powder feeding rate was 32 g/min. The samples were then subjected to the hot corrosion test in a salt mixture of Na2SO4−60% V2O5 at 900°C in an ambient atmosphere. The surface and the cross section of the samples were observed using a scanning electron microscope (SEM) and the chemical composition of different sections was determined by energy‐dispersive spectroscopy (EDS). The phases were also characterized using X‐ray diffraction analysis (XRD). The best corrosion resistance was found in the sample coating formed at a spraying distance of 20 cm, as the results showed that increasing the spraying distance led to a reduction in the thermal and kinetic energy of the flame, resulting in increased porosity in the coating. This behavior can be attributed to the low oxide content of the coating, the higher aluminum content, and the richer NiAl phase, which serves as a reservoir for aluminum.

Seeds Combining Pyrrolidine Control the Framework Al Distribution of FER Zeolite to Enhance Its Performance in the Skeletal Isomerization of n-Butene

FER zeolites have a unique framework structure and acid distribution, and are widely studied as a catalyst for reactions such as n-butene skeletal isomerization and dimethyl ether carbonylation. The Brönsted acid site (BAS) located in the 10-member ring (10-MR) of FER zeolites serves as the active site for the isomerization reaction of skeletal n-butene to produce isobutene. This study prepared five types of FER zeolites using different methods: using pyrrolidine (PY) alone as a template; using Na-form FER as seeds (SN) or H-form FER as seeds without organic structure directing agents (OSDAs); and combining the seeds of SN or SH with PY as OSDAs. The differences in the structure and acid distribution of the five zeolites were investigated, as well as their catalytic performance for the skeletal isomerization of n-butene. Experiments and characterization results showed that under hydrothermal synthesis conditions, the FER-PY+SH zeolites synthesized by using both H-form zeolites seeds and pyridine exhibited the highest aluminum concentrations at T1 and T3 sites, along with the greatest BAS located in the 10-MR. This unique composition contributed to the highest selectivity of isobutene. The FER-PY+SH catalyst was continuously used for 720 h at 350 °C, 0.1 MPa, and an n-butene mass space velocity of 2.0 h−1 for three cycles of 2160 h. During this period, the conversion of n-butene was over 39%, while the selectivity of isobutene exceeded 95%. The FER-PY+SH catalyst exhibited excellent stability and activity.

Effect of impregnation temperature and concentration of alumina sol on the properties of 3D printed silica ceramics

Due to the glass transition of molten quartz and the layer-by-layer 3D printing method, the strength of the finished ceramics is low. Therefore, it is necessary to find a suitable method to improve the mechanical properties of 3D printed silica ceramics used as casting molds for turbine blades. Vacuum impregnation is a very attractive method to introduce new phases into ceramic pores through liquid impregnation, thereby improving the mechanical properties of ceramic parts. In this study, 3D printed silica ceramics were impregnated with alumina sol, and the effect of impregnation temperature and concentration of alumina sol on the properties of the samples were investigated. The cristobalite content and mechanical properties of silica ceramics impregnated by alumina sol with different concentration and temperature were compared. The impregnation of alumina sol can promote the formation of cristobalite phase in the ceramics, and the appropriate amount of cristobalite can improve the mechanical properties of the ceramics. When the concentration of alumina is 15 wt% and the impregnation temperature is 60℃, the overall performance of alumina sol impregnated samples is the best, with a flexural strength of 22.70 ± 0.46 MPa, a bulk density of 1.70 ± 0.02 g /cm3, and a porosity of 25.89 ± 1.32 %.