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In the past decade, it has been observed that polymer nanocomposite industrialisation is increasing due to several advantages. So, this area is becoming vital for researchers for making new material as per technical applications. Polymer nanocomposite can be made from different types of polymers and involves one or more nanofillers coupled with it. A major application of such polymer is in the aerospace and automotive industries. In this review, several metal oxide nanofillers and their hybrid state are chosen for understanding benefits in tribology throughout recent decades. Observation of friction and wear enhancement with several other technical circumstances are taken into account from various articles of metal oxide nanofiller in polymer nanocomposite. Alumina, zinc oxide, and titanium oxide are found to be most used among other metallic nanofillers for most polymer nanocomposite fabrication in the tribology area. [ABSTRACT FROM AUTHOR]

AbstractEvaluate the remnants of blasted alumina particles after cleaning by different protocols on intact, or resin coated dentine substrates, before or after aging. Seventy-eight mid-coronal dentine specimens were prepared. Six of them were kept intact as negative control (NC) group. At the same time, the other seventy-two were divided into three groups. They received three different dentine treatments: (1) sandblasted (S), (2) resin coated and blasted (RS), (3) resin coated, aged one week, and sand blasted (RAS). Subsequently, each group was cleaned via four sub-group protocols: (1) not cleaned, (2) air/water spray (A/W), (3) etched & A/W, and (4) water jet. Finally, five FE-SEM micrographs were taken from each tooth, and the number of remaining Al2O3 particles was counted on each picture. The numerical data were compared with each other using Two Way ANOVA and LSD post hoc tests (α = 0.05). Most Al2O3 particles were detected on uncleaned specimens, while all the other sub-groups displayed very few or no Al2O3 particles. Statistical analyses revealed that the dentine treatment and cleaning protocol significantly affected the remaining Al2O3 particles (p = 0.000 and 0.000, respectively). Moreover, the interaction of dentine treatment and cleaning protocol was statistically significant (p = 0.000). Cleaning protocols (A/W, etching, and water jet) could effectively remove the remnant of Al2O3 particles from the blasted dentine surface, either resin coated or not. [ABSTRACT FROM AUTHOR]

The need for alternative green energy to fossil fuels has increased research interest in creating energy storage technologies. One of the important components of an energy storage device is electrolytes. Previously, the use of liquid electrolytes (LEs) was dominant; nevertheless, LEs were reported to be flammable. Recently, attempts have been made to switch out the LEs for solid polymer electrolytes (SPE). SPE has a variety of merits; however, their limited ionic conductivity and high operating temperatures impede their development into practical application. Thus, fillers such as alumina (Al2O3) as an additive are introduced to enhance their performance. Recent progress in the use of Al2O3 has shown promising advancements in enhancing the electrochemical performance of SPEs while the future direction includes examining the cost-effectiveness of Al2O3-filled SPEs for large-scale applications, thereby paving the way for their integration into commercial energy storage technologies. This article provides a discussion on the effect of Al2O3 on the conductivity, and electrochemical stability of SPEs. Additionally, the review discusses the impact of various factors such as functionalization on the overall performance of SPEs-filled Al2O3. The review concluded by highlighting the potential applications, prospects, challenges, and recommendations for using Al2O3-filled SPEs in advanced energy storage devices. [ABSTRACT FROM AUTHOR]

Graphene-oxide/alumina (GO/Al2O3) nanocomposite was synthesized and applied for the removal of phosphate from water through adsorption. Various parameters like the influence of adsorbent dose, adsorption time, solution pH, and initial phosphate concentration on the phosphate removal capacity were examined. It was observed that the second-order kinetics model fitted better compare to the first-order kinetics. The adsorption isotherm was best fitted with Langmuir isotherm compare to Freundlich isotherm. The GO@Al2O3 nanocomposite showed maximum phosphate adsorption capacity 33.2 mg/g at pH 6 and room temperature 30 °C.The new phosphate adsorbents can be produced in a variety of structures using a simple technique and are likely to be applied to industrial applications in phosphate contaminated wastewater management. [ABSTRACT FROM AUTHOR]

A series of highly reusable heterogeneous catalysts (10-40 wt.% SiMo12/Al2O3), consisting of molybdosilicic acid (SiMo12) impregnated on alumina (Al2O3) support was synthesized by the wetness impregnation method. The physicochemical properties of synthesized catalyst were studied using FT-IR, XRD, SEM, EDX, TEM, BET and TG-DTA analysis techniques. The study proves that the synthesized SiMo12 catalyst efficiently incorporated on the surface of Al2O3. The catalytic activity of prepared catalyst was investigated for the synthesis of pyranopyrazole(6-amino-4-phenyl-3-methyl-2,4-dihydropyrano[2,3-c]pyrazole-5carbonitrile) via cyclocondensation reaction of aldehydes, malononitrile, hydrazine hydrate and ethyl-acetoacetate under solvent-free conditions. Among different catalysts, 30% SiMo12 supported on to Al2O3 showed the highest catalytic activity. High yield, shorter reaction time, operational simplicity, solvent-free conditions and reusability of the catalyst are the distinct features of this protocol. An economic, sustainable, and straightforward environmentally friendly synthesis of pyranopyrazole derivatives in presence of catalytic amount of SiMo12/Al2O3 under solvent-free condition. Excellent yields, and environmentally sustainability are the main advantages of the present method. [ABSTRACT FROM AUTHOR]

This review article presents the current status of various micromachining techniques used to create microfeatures in alumina ceramic. Alumina has emerged as an advanced substrate in various radio-frequency communication and automotive packaging applications due to its superior electrical resistivity, lower dielectric loss, higher wear resistance, and dimensional stability at high temperatures. However, creating complex-shaped microfeatures in alumina is challenging due to its hard and brittle nature. Traditional contact-based methods fail to create microsized shapes in alumina; thus, the researchers are exploring novel machining methods, like abrasive, thermal, chemical, and hybrid micromachining processes. This review article comprehensively summarizes various micromachining methods used to create microfeatures in alumina ceramics. The mechanism, unique features, pros/cons, novelty, and applications of ultrasonic machining, laser ablation, electrochemical discharge machining, abrasive-jet machining, etc., are presented. The associated processing challenges in various alumina micromachining and the potential remedies to produce high-quality alumina microparts for microelectronics applications are discussed. [ABSTRACT FROM AUTHOR]

Three types of flash calcined powders with different specific surfaces and phases were selected to make alumina granules. The granulation was performed in a pan granulator as the spherical form. The hydrothermal and calcination conditions were applied to the granules. Physical, chemical and microstructural studies were applied to the hydrated and calcined granules. This study focussed on the thermal historical effects of the initial powders derived from bauxite on the granules. The least physical changes and the highest specific surface area were obtained for the granules prepared with flash calcined powder at 650°C. The hydrated granules can have boehmite, gamma and bayerite phases with rod, porous and plate morphologies, respectively. The presence of rod boehmite phase increases the strength of hydrated granules and plays an important role in the final strength. In the calcination stage, the phases transformed into the transition alumina and gamma phases with the growth of nanometer-sized crystals. [ABSTRACT FROM AUTHOR]

This research study explores the influence of NaF/Al2O3 catalysts on the process of hydrothermal liquefaction (HTL) of Crambe Orientalis. Three distinct catalysts were prepared and examined through a multitude of methodologies including FT-IR, BET, XRD and SEM/EDX/EDS. The HTL were made at temperatures ranging from 275 to 350°C for a duration of 0 to 60 minutes. The liquid products obtained were subjected to elemental, GC-MS, FT-IR, and1 H NMR analyses. The findings of this study demonstrate that NaF/Al2O3 catalysts effectively enhance the yield of liquid products. The liquid products that were obtained displayed an exceptionally elevated carbon content, with a maximum value of 80.97% achieved at a temperature of 350°C. These liquid products exhibit superior heating values (HHV), which vary between 37.64 and 29.31 MJ/kg. The catalysts demonstrated efficacy in enhancing the liquid product yield, characterized by a heightened proportion of aliphatic compounds and a diminished ratio of oxygen constituents. It was determined that the obtained catalysts may have the potential to obtain liquid products with high carbon content and energy values. [ABSTRACT FROM AUTHOR]

In pursuit of cleaner energy, this study explored the role of support materials in NiO's desulfurization capacity and selectivity in diesel fuel, thereby offering insight into sustainable fuel production. Nickel oxide (NiO) was loaded on different supports (activated carbon (AC), SiO2, Al2O3, and TiO2) for desulfurization. The adsorbent system was characterized using various techniques including FTIR, XRD, SEM, TPD-pyridine, TGA, and BET. At a low loading of approximately 5%NiO/support, the addition of NiO enhanced the adsorbent activity for all four supports at 30°C. However, increased NiO loading led to decreased adsorption activity due to agglomeration. The loading of NiO affected the selectivity of the adsorbents toward high molecular weight sulfur compounds differently. There was a decrease in selectivity for AC and Al2O3, a positive effect on SiO2, and no effect on TiO2. The positive effect on SiO2 resulted from NiO-SiO2 synergy. Additionally, NiO loading on SiO2 reduced hydrocarbon adsorption, thereby improving overall relative selectivity. When real diesel was used, the addition of 5%NiO on SiO2 and AC at a higher temperature (60°C) increased adsorption activity. This higher activity at elevated temperatures was attributed to poor adsorption of polyaromatic hydrocarbons and increased involvement of chemical-bonds. Lastly, all adsorption reactions were exothermic. [ABSTRACT FROM AUTHOR]

The coating's purpose is to enhance the tribological conditions at the tool-workpiece and chip–tool interfaces. In comparison to commercial coatings, the current work offers a coating for high-speed steel (HSS) equipment that is thinner and less expensive. A single-point AISI T6 high-speed steel tool having a square cross-section was used to prepare the cutting inserts for turning purpose. The best conditions for coating the HSS insert with ceramic oxides using the sol–gel process were determined. These precursor conditions involved: viscosity, PH, dispersion materials, and the ageing period. The deposition conditions were the number of coating cycles, the immersion time, the calcination temperature, and dry temperature that affects the layer thickness, adhesion, surface roughness, and homogeneity for coating layer. Titanium tetra-isopropoxide (TTIP), a catalyst HCl, and a dispersion material (triethanolamine) were employed to prepare the precursor (titanium hydroxide). The PH, the viscosity, and the ageing time, of the produced precursor were 6.46 and 8.74 cP, and 6 h, respectively. After the dip coating of the cutting inserts for 5 sec immersion time and two number of coating cycle in titania precursor, the inserts were dried at 355℃ for 1 hour. Then, to form the alumina coating film, the inserts were dipped in the alumina hydroxide sol, which was made by combining aluminium isopropoxide IPA, deionised water H2O, and nitric acid (HNO3). The produced precursor had a PH of 5.83, viscosity of 8.11 cP, with an ageing time of 12 h. The immersion time and number of coating cycles in the alumina precursor were 25 sec, and two, respectively. The inserts were dried at 355℃ for 1 hour, then calcinated at 500°C for 2 h to achieve the appropriate film thickness for the machining test. The study investigates the thermal and tribological properties of coated with single and multiple layers as well as uncoated cutting inserts. The results indicated that the hardness is 1393.3 HV with a thickness of 6 µm for multilayer. X-ray diffraction-phase analysis confirms the presence of phases originating from the coatings and substrate. EDS analysis of the chemical composition of the studied coatings indicates the presence of titanium and aluminium, as well as oxygen. Atomic force microscopy (AFM) was used to examine the surface morphologies of coated surfaces. Scratch hardness is measured in GPa and differs between monolayers (alumina) and multilayers (titania/alumina). Monolayer alumina has a value of 0.374 GPa, whereas multilayer alumina/titania has a value of 1.010 GPa. Multilayer coated inserts, on the other hand, have a lower wear rate than monolayer coated and uncoated inserts. The thermal expansion coefficient of the titania layer is often relatively near to the thermal expansion coefficient of the bulk HSS (11 × 10−6, 13 × 10−6 1/K) that reduces mismatch between substrate HSS and top coating layer (alumina). [ABSTRACT FROM AUTHOR]

Adhesive technology can joint dissimilar lightweight materials that are used in the automotive industry to improve fuel efficiency. However, the strength of the adhesive bonding is often reduced by oil contaminants on the adherend surfaces. Adhesives should repel the oil layer and diffuse onto the adherend surface, but there is no general design for reliable adhesion on contaminated adherends because of the poor molecular-level understanding of oil-surface adhesion. Here, we report the direct observation of oil-surface adhesion at a two-part epoxy adhesive/aluminum oxide (AlOx) interface via sum frequency generation (SFG) spectroscopy, a method that can probe buried interfaces. The AlOx surface is intentionally contaminated with commercial silicone oil. The SFG spectra of the cured epoxy adhesive/oil-contaminated AlOx interface suggest that the silicone oil remains after curing, explaining the reduction in adhesion strength. Triethylenetetramine, a hardener used in this study, can repel the oil layer, whereas bisphenol A epoxy resin is much less effective at removing the oil layer upon contact. Thus, the migration of both adhesive components onto the AlOx surface is key to securing sufficient oil-surface adhesion. We also applied SFG to second-generation acryl adhesive (SGAA)/AlOx interface and found that SGAA completely repels the oil from the aluminum interface. [ABSTRACT FROM AUTHOR]

In this study, a comprehensive molecular dynamics (MD) study on the structural evolution of alumina nanoparticles during sintering has been performed using two-sphere model. The effect of variation in particle size and heating rate are investigated. A power-law equation is proposed to explain the increase of dimensionless neck radius, with the increasing sintering time. Two important parameters are extracted from the equation: a characteristic time related to the initiation of neck formation and an exponent related to the rate of neck growth. The variation of shrinkage and density of particles are also used to characterise the sintering of alumina nanoparticles. One of the novel findings is that instead of temporal variation of dimensionless neck radius, its variation with shrinkage can be used to correlate simulation and experimental results. From the results of the variation of heating rate, it is revealed that a lower heating rate initiates neck formation at a lower temperature. The sintering temperature has been successfully estimated for micron-sized particles from the results of molecular dynamics simulation using Herring's scaling law. Moreover, it is evident from experimental validation that the developed MD model can successfully predict the average dimensionless neck size value of micro injection moulded alumina, at sintered state, and thereby can be effectively used as a process control tool. [ABSTRACT FROM AUTHOR]

Electromagnetic pollution has become a major problem affecting human health, which requires the scientific community to characterise materials that can solve this problem. In the present work, we studied the microwave absorption properties and complex permittivity of ZrB2/Al2O3 ceramic composites in the X-band by simulation. The composites studied are based on alumina and reinforced with ZrB2 particles. The concentration of ZrB2 particles by volume in these composites are 0%, 5%, 10% and 15%. The results obtained show, on the one hand, that the complex permittivity depends on the frequency, and on the other hand, the high content of ZrB2 remarkably increases the complex permittivity and improves the microwave absorption properties. The ZrB2/Al2O3 composite with 5% by volume of ZrB2 particles has better microwave absorption property than others. In this case, the minimum reflection loss is −26.36 dB at 11.5 GHz. For this composite, the RL bandwidth of less than −10 dB is 1.72 GHz, and it is obtained in the frequency range from 9.4 GHz to 10.5 GHz. The simulation results are in good agreement with the published experimental results. In addition, they indicate that the composites studied are favourable for microwave absorption applications in the X band. [ABSTRACT FROM AUTHOR]

A novel composite porous scaffold of hydroxyapatite (HA) and alumina was fabricated using the gelation freezing method. First, the microstructure was observed using scanning electron microscopy. The addition of alumina to HA led to an improved pore orientation attributed to the improved latent heat release during the freezing process owing to its higher thermal conductivity. The appropriate sintering temperature for composites consisting of different ceramics, HA, and alumina exceeded 1450 °C. Next, a compression test was conducted with fracture behavior monitoring using an acoustic emission method. The proposed HA-alumina composite porous scaffold exhibited better mechanical properties with higher porosity compared to scaffolds with randomly oriented pores. Furthermore, it was observed that the alumina addition and sintering temperature affected the macrofracture and microfracture behaviors, respectively. [ABSTRACT FROM AUTHOR]

A novel composite ceramic porous scaffold consisting of calcium phosphate ceramics and alumina was fabricated using the gelation freeze-casting method. Notably, the temperature is important for the simultaneous sintering of different ceramics. A denser microstructure with better mechanical properties was obtained at a sintering temperature of 1450 °C. At sintering temperatures above 1500 °C, liquid-phase sintering occurred, resulting in substantial changes to the microstructure. The addition of alumina accelerated the phase transformation of hydroxyapatite into α-tricalcium phosphate. Furthermore, it was suggested that a mixture of calcium phosphate and alumina was formed at a sintering temperature of 1550 °C. Additionally, Young's modulus and compressive strength increased with increasing sintering temperature. The increase in compressive strength was due to the smoothening of the microstructural surface via liquid-phase sintering. [ABSTRACT FROM AUTHOR]

Two-phase porous materials are extensively employed in industries and their thermal characteristics decide on the overall efficiency of the system. Several dependent parameters such as geometry, its structure, heat transfer mechanism, and contact ratio, strongly influence the effective thermal conductivity (ETC) of the two-phase system. There are various literatures on analytical and experimental prediction of ETC of two-phase porous materials such as packed beds, foams, and sponges. However, numerical studies are limited with the consideration of few influential parameters. This present study has attempted to investigate the thermal behavior of two-phase porous materials numerically using square and circular geometries with the consideration of all primary and secondary criterions at different pressures and elevated temperatures. The numerical results are correlated against the experimental data of different porous insulation materials and packed bed materials. Further, the square and circular models are assessed for their stability in predicting the ETC at higher temperatures. Even at elevated temperatures, the present models hold better accuracy and consistency in prediction. [ABSTRACT FROM AUTHOR]

Ceramic membranes are one of the emerging separation technologies with extremely high separation factors. In this work, natural Kaolin clay collected from the western of Algeria was characterized in detail to see its feasibility in a ceramic membrane preparation. The ceramic membrane was prepared by solid-state reactive firing under the slip casting method. The aim is to favor the mullite phase, once the alumina is added a part will be dispersed in the mullite matrix to form a mullite-alumina composite. The mineralogical, morphological structure, particle size distribution, thermal stability, and chemical composition of prepared alumina oxide membrane were carried out using several techniques. They reveal the apparition of two main phases the mullite and the alumina. The kaolin provides the membrane with a well homogeneous morphology, good hydrophobicity, and thermal stability. The obtained membrane presented a mesoporous membrane character that can use successfully for ultrafiltration applications.. [ABSTRACT FROM AUTHOR]

Natural fibre reinforced polymer nanocomposites are gaining recognition in various technical areas like aerospace, defence, construction, and automobiles due to their low cost and environmental friendliness. However, the incompatibility between natural fibre and polymer matrices and the higher water absorption percentage of natural fibre is restricting their utilization in structural and semi-structural applications. To overcome these limitations, surface treatment of natural fibre and nanofiller addition into the polymer matrices have become among the most valuable ways to improve natural fibre composite performance. This work examined the alkaline-treated and untreated flax/polylactic acid (PLA) fibre reinforced epoxy hybrid nanocomposites, in which alumina and magnesia were used as nanofillers. The effect of surface treatment and nanofillers was explored in terms of mechanical properties (compression and interlaminar shear), water absorption behaviour, and morphology of composites. Substantial enhancements in compressive and interlaminar shear strengths were reported, as well as a notable reduction in the amount of water absorbed. The optimal nanofiller concentration was 3% in alkaline-treated and untreated flax/PLA fibre reinforced epoxy hybrid nanocomposite. The results reveal that nanofillers combined with surface treatment can appreciably improve developed laminates' mechanical and water absorption properties, making them feasible for furniture, packaging, automobiles, and structural applications. [ABSTRACT FROM AUTHOR]

To retain the advantageous properties of Al2O3 ceramics, their electrical conductivity must be controlled using a small amount of the conducting phase by pressure-less sintering in an air atmosphere. In this study, the electrical conductivity of Al2O3 ceramics was successfully increased from 10−16 to over 10° S/cm by precipitating a small amount of indium tin oxide (ITO) grain boundary phase. An ITO phase of only 3-mol% (4.45 vol. %) was propagated three-dimensionally in pressure-less sintered Al2O3. Electric discharge machining (EDM) showed the machinability of electrically conductive Al2O3/3-mole% ITO grain boundary composites. Furthermore, the temperature dependency of the electrical conductivity was identified as metallic, exhibiting an electrical conductivity that decreases slightly with increases in measurement temperature, as observed in metals and ITO. The temperature dependence of the electrical conductivity of ITO was maintained in the Al2O3/ITO grain boundary composites. [ABSTRACT FROM AUTHOR]

A series of extruded H-ZSM-5/alumina composite catalysts were prepared and characterized using N2 sorption isotherm, transmission electron microscopy, scanning electron microscopy, infrared spectroscopy, X-ray diffraction, NH3-TPD, and pyridine adsorption. The methanol conversion over the as-prepared catalyst as well as its components was studied at 500 °C. The catalysts with H-ZSM-5/alumina ratio 3/1 and 1/1 (by mass) catalyst exhibited the highest ethylene selectivity (up to 44%) and the ethylene/propylene ratio up to 10/1, whereas zeolite H-ZSM-5 demonstrated the propylene selectivity up to 30% and the ethylene/propylene ratio 1/8. In contrast, the catalyst with the H-ZSM-5/alumina ratio 1/3 demonstrated no activity toward olefins synthesis. The as-prepared H-ZSM-5/alumina catalysts have a long lifetime in the methanol-to-hydrocarbons conversion, which is several times higher compared to pure zeolite H-ZSM-5. The catalyst regeneration results in recovering the initial catalytic activity. The obtained findings reveal that embedding microporous zeolite in the mesoporous alumina matrix facilitates the mass transfer limitations and decreases the number of strong acid sites. These factors govern an essential performance of the as-prepared catalyst in the methanol-to-ethylene reaction. [ABSTRACT FROM AUTHOR]

Plasma electrolytic oxidation (PEO) coatings on commercial pure titanium (Cp-Ti) and hot-dip aluminised Cp-Ti surfaces were prepared in an alkaline electrolyte. The morphological, structural, wear, and corrosion characteristics of the coatings were studied by using SEM, EDS, XRD, electrochemical polarisation, and dry sliding wear tests. The experimental results showed that the main compositions of the PEO coating on Cp-Ti are TiO2 and Al2TiO5 phases, while the PEO coating on hot-dip aluminised (HDA'ed) Cp-Ti mainly consists of the Al2O3 phase. The single PEO coating exhibited more porosity with small diameter micro-pores compared to the PEO coating on the HDA'ed sample. Electrochemical polarisation tests revealed that the PEO coating on the HDA'ed sample exhibited approximately 4.6 times more polarisation resistance than the single PEO coating and 10 times that of the bare Cp-Ti sample. According to the wear test results, the wear resistance of the bare Cp-Ti was doubled by hot-dip aluminising (HDA) and PEO treatments, while the single PEO treatment resulted in better resistance against dry sliding wear. [ABSTRACT FROM AUTHOR]

Structural models of the (110) termination of α-Al2O3 and α-Fe2O3 are studied using Density Functional Theory (DFT) calculations and thermodynamics to determine the details of the mineral-water interface structure and stability. Prior experiments have characterised these interfaces, but the X-ray reflectivity techniques used cannot identify the distribution of protons on surface sites. In addition, the alumina (110) surface displays two different surface structures stable in water, with their occurrence dependent on sample preparation conditions. We use theory and modelling to determine the thermodynamically preferred surface structures, including protonation states of surface oxygen functional groups, as a function of temperature and pressure. Consistent with studies of other facets of alumina and hematite, we find that thermodynamically unfavourable defect structures, upon hydration and hydroxylation, show comparable stability to the hydrated forms of ideal terminations. The model results are compared to experimental characterisation of hydrated (110) alumina and hematite surfaces with good agreement between the best-fit structures from experiments and the lowest surface free energy structures from theory and modelling. Electronic structure analysis of the exposed surface functional groups is presented, and we highlight instances in which the electronic density of states differs between oxygen functional groups that have similar coordination environments. [ABSTRACT FROM AUTHOR]

In this work, the effect of water on the packing and flow properties of cohesive powders was experimentally investigated. Two cohesive powders with small particle sizes were studied with weight percentages of added water of 0, 10, 25, 40, and 50%. Particle properties including conditioned bulk density, porosity, compressibility, flow function coefficient, cohesion, etc., were tested using the Freeman FT4 Powder Rheometer and examined as a function of water content. Results show that water content has a significant effect on the packing and flow of the powders. With small amounts of water added, the particle beds became more cohesive, due to the formation of liquid bridges, and the bed volume increased roughly in proportion to the mass of water added leading to a fairly constant conditioned bulk density. When greater amounts of water were added to the particle beds, there was a substantial increase in conditioned bulk density. The bulk densities of both powders increased from around 0.3–0.55 g/ml when the added water was increased from 40% to 50%. As the water weight fraction increased, there was generally an increase in basic flow energy and cohesion, while the porosity and pressure drop generally decreased. [ABSTRACT FROM AUTHOR]

Experimental analysis of tool wear in alumina micromachining by multi-tip Electrochemical Discharge Machining (ECDM) technique is reported. Multi-tip tool electrodes having a tip size of 300 µm and length of 10 mm are created in stainless steel by wire-EDM. Experiments are conducted at different tool feed rates, i.e., 0.25 µm/s, 0.50 µm/s, 0.75 µm/s. Tool wear of 3 × 3 array electrode is categorized into three different zones, i.e., outer-most tip, outer-middle tip wear, and central-tip. The experimental results reveal that the outer-most tips are worn out rapidly compared to other tips due to the localization of higher current density and easier availability of fresh electrolytes. The tool wear is severe at a slower feed rate due to prolonged exposure to the higher temperature generated during the ECDM. However, at a higher tool feed rate (≥0.50 µm/s), the tool-tips are in physical contact with the alumina substrate. The central tip has a sideways bending beyond tool travel of 400 µm that would have led to the breakage of thin alumina substrate. The experimental results are useful in understanding the tool wear pattern in multi-tip electrodes during the ECDM process used in the micromachining of alumina and other non-conductive materials. [ABSTRACT FROM AUTHOR]

For the first time, χ-Al2O3 was investigated as a sorbent for the simultaneous separation of copper and molybdenum from rhenium. This work finds the optimal conditions of the process. In an acetate buffer solution with a pH of 5.5 under the action of ultrasound for 30 min, the Langmuir adsorption capacity for copper and molybdenum on this sorbent was 46 mg⋅g−1 and 44 mg⋅g−1, respectively, rhenium remained in the solution. The adsorption corresponded to the pseudo-second-order kinetics model. It has been shown that under the indicated conditions, over 80% of molybdenum and 95% of copper can be removed from synthetic solutions containing 100- and 1000-fold mass excess of copper and molybdenum. In nitric acid or sulfuric acid solutions, the same results can be achieved at a pH of 2.5–3.0. It was found that the recovery of rhenium by inductively coupled plasma atomic emission spectrometry after matrix separation was improved; on average, a threefold reduction in the relative standard deviation (n = 5) was achieved. The mechanism of adsorption of Cu, Re, and Mo ions on the surface of χ-Al2O3 was proposed, based on the interaction of ions with an electric double layer of sorbent particles. [ABSTRACT FROM AUTHOR]

This article investigates the effect of ceramic powder bath heat-treatment on the sintering of α-alumina (α-Al2O3) for potential ceramic tool application. Three different ceramic sintering mediums were used i.e., (i) Pure alumina powder bath, (ii) Pure graphite powder bath, and (iii) Alumina Graphite Powder Bath (AGPB). The hardness and microstructural analysis were carried out using Vickers hardness, Field Emission Scanning Electron Microscopy (FESEM), and Scanning Electron Microscopy (SEM). The experimental results revealed that the novel Alumina Graphite Powder Bath (AGPB) sintering mechanism proposed in this research provided better hardness and microstructure as compared to the rest. The heating mechanism of alumina and graphite powder mixture was compared with published Thermogravimetric analysis (TGA) results. The Alumina Graphite Powder Bath (AGPB) sintering method improved the mean hardness and relative density by 23% and 13%, respectively. Further, an orderly crystalline corundum microstructure with closed porosity was revealed from Scanning Electron Microscopy (SEM) micrographs. The conversion of convection-radiation to conduction mode of heat transfer in Alumina Graphite Powder Bath (AGPB) sintering technique was the reason behind this property enhancement. [ABSTRACT FROM AUTHOR]

The spark plasma sintering behavior of the alumina ceramic composite that is modified by the spatial distribution of electrically semi-conductive sub-micron scale titanium carbide particles was investigated. Titanium Carbide was reinforced to the alumina composites in different weight percent concentrations of 20, 25, 30, and 35. The influence of titanium carbide particle distribution on the thermal profile, micro-hardness, and wear resistance of alumina ceramic composites was studied. Homogenous spatial distribution of sub-micron scale semi-conductive titanium carbide particles in the composite were noticed through scanning electron microscopy, excluding the 35 weight percent sintered sample. In the spark plasma sintering processed samples, X-ray diffraction results revealed strong α-alumina and titanium carbide peaks. The obtained experimental results show that a higher titanium carbide concentration causes an earlier onset of shrinkage temperature, which positively impacts densification. The addition of titanium carbide particles accelerates the sintering kinetics and improves the properties. Among all composites, the sample with 30 weight percent has the highest relative density of 98.80% and hardness of 20.56 GPa. Besides, the highly densified sample of 30 weight percent has superior wear resistance to all other composites, and can be used for high-temperature sliding applications. [ABSTRACT FROM AUTHOR]

Fluoride concentration in drinking water has become a global challenge due to its effects on the human body. While small level (1–1.5 mg·L−1) strengthens enamel and bone formation, higher concentration (>1.5 mg·L−1) leads to dental and skeletal fluorosis. Globally, over 200 million people drink fluorinated water and more than 70 million people suffer from fluoride related diseases. As such, treating fluorinated water through the adsorption method has been the most ideal method due to its low cost, availability of adsorbents, pollution-free treated water and environmental friendliness. This review article summarizes the use of alumina and aluminum-based composites for fluoride removal. These adsorbents have been classified into three categorize based on their modifications thus: raw alumina-based adsorbents/geomaterials, activated alumina and modified activated alumina and aluminum-based adsorbents. Minimal activation (300–400 °C) and modification improve their overall adsorption capacity by increasing their specific surface area (250–1000 m2·g−1) which ultimately improves the pore size and volume. Also, some can remediate as high as 450 mg·g−1 of fluoride at a wider pH range (3–12) with stable thermodynamic properties. This grants them the ability to easily form aluminumfluoro complexes (AlFx) for enhanced adsorption at near-neutral pH (5.5–6.5) making them the most ideal adsorbents. [ABSTRACT FROM AUTHOR]

Micromachining of alumina has gained a lot of interest due to unique combinations of electrical resistivity and good thermal conductivity, thus being a potential substrate for microsystems packaging in high-power electronics. Creating multiple through-holes simultaneously in alumina is difficult due to its hard and brittle nature. In this article, the formation of multiple through-holes in a 425 µm thick alumina substrate is demonstrated for the first time using the combined pulse-feed approach of the ECDM process with multi-tip array tool to improve productivity. Initial experiments are conducted with a single-tip electrode to understand the effect of duty factor, pulse frequency, and feed rate. A combined pulse-feed approach is adopted to create deep microholes (>600 µm). Later, multiple through-holes are formed using 3 × 3 multi-tip array tool to achieve an average etch rate of 24 µm/min using the combined pulse-feed approach. A duty factor of 70% and a pulse frequency of 20 kHz are suggested for stable electrochemical discharge. A low feed rate (<1 µm/s) is recommended to avoid physical contact between the tool and workpiece. These multiple through-holes can be filled with electroplated copper to form 3D interconnects for upcoming radio-frequency MEMS applications. [ABSTRACT FROM AUTHOR]

Polymer systems like epoxies are not generally used in the manufacturing of structures on their own since they possess an ordinary level of mechanical properties. Hence, different reinforcing fibres and nanofillers are incorporated into polymer systems, thereby combining some of the properties of the resin with those of the fibres, thus making the resultant composite superior to even some metals. In this research study, the hybrid fibre fillers are added to epoxy composites with alumina nano-filler reinforcement are fabricated and tested to improve the flexural strength of the hybrid composites for use in various applications like automobiles, aerospace, civil engineering, military, motorsports etc. Effects of Alumina nanoparticles on flexural strength of Glass-Nylon hybrid composite have been studied. The factors, levels of factors and number of test model have been considered for the experiments as well as for the analysis is decided based on Design of Experiment method by Taguchi. The experimental results have shown that hybrid composite with an increase in the percentage of nanofiller, increases the flexural strength. The increase in flexural strength is noticed due to the addition of nanoparticles to epoxy, and the nucleating effect of nanofillers that were dispersed thoroughly within the matrix. [ABSTRACT FROM AUTHOR]

Paste rheology and printing parameters contribute to a great extent to engineer the properties of ceramic parts produced through 3D printing process. Alumina paste, which showed shear thinning behavior, was prepared using optimum concentration of additives. Paste was 3D printed and effect of printing parameters such as printing speed, length to diameter (L/D) ratio of nozzle, self-standing distance of extrudate, filling pattern and filling angle have been studied. Additionally, effect of the substrate material on which the extrudate is printed was also elucidated. A printing speed of 5–6 mm/s, an L/D ratio of 25 mm and self-standing distance of 1.25 ± 0.25 mm are found to be optimum. Further, a filling pattern of rectilinear geometry along with filling angle of 90° is found to be desirable. Out of the substrates evaluated, polished metal surface is found to be relatively better to achieve close tolerances. The alumina samples printed under optimized conditions are found to possess integrity with respect to the structure and close to pre-designed dimensions. Sintered samples were found to be free of crack and exhibited a density of 3.88 g/cc (97.5% of theoretical density). Density and hardness (16.5 GPa) of printed part correlates well with the microstructure consisting of grains of average size of 9.68 μm. [ABSTRACT FROM AUTHOR]

Typically, synthesis of α-alumina (α-Al2O3) has been performed by annealing the aluminium hydroxide (AH) at temperatures higher than 1000°C, which leads to a high energy consumption. Accordingly, α-Al2O3 is desired to be synthesised by low-temperature processes for reducing energy consumption. This review describes our studies on the low-temperature synthesis of α-Al2O3 based on a sol-gel reaction. AHs were prepared by the hydrolysis of aluminium alkoxide and homogeneous precipitation from aluminium inorganic salt (alkoxide AH and inorganic AH, respectively). Alumina sols (ASs) were prepared by peptising the alkoxide AH and the inorganic AH with acids (alkoxide AS and inorganic AS, respectively). The ASs were converted to alumina gels (AGs) by dehydration in air at room temperature (alkoxide AG and inorganic AG, respectively). The ASs were seeded with α-Al2O3 nanoparticles and/or treated hydrothermally. Inorganic AS and AG were suitable to produce α-Al2O3 compared to alkoxide AS and AG. The use of formic acid as peptiser promoted crystallisation of AG to α-Al2O3. The seeding and the hydrothermal treatment also promoted the crystallisation. The alumina started to be crystallised to α-Al2O3 at a temperature as low as 400°C with the above three conditions. [ABSTRACT FROM AUTHOR]

The engineering properties of porous alumina ceramic composites such as sintering linear shrinkage, density, porosity, hardness, tensile strength and microstructure analysis were studied. Different sintering temperature of 1250°C, 1350°C, 1450°C, 1550°C was used. The alumina, rice husk ash, aluminium and sucrose solution binder were mixed and pressed through powder compaction technique. The porous structure and elemental analysis of the mixed powder have been characterised using field emission scanning electron microscopy (FESEM/EDX). For the phase identification, x-ray diffractiona nalysis has been performed. Results depicted that there is no contamination of the mixed powders. The pores structure reduced as the sintering temperature increased to 1550°C. The mechanical analysis revealed that the properties of the porous alumina ceramic composites sintered at 1550°C showed the best performances. Sintering linear shrinkage increased with increasing sintering temperature, resulting in higher volumetric changes. Thus, this effect increases densification and reduces total porosity while improving the tensile strength of the porous alumina ceramic composites. [ABSTRACT FROM AUTHOR]

The purification of Al(III) to alumina by bis(2,4,4-trimethylpentyl)phosphinic acid commonly called Cyanex®272 in kerosene diluent from aqueous aluminium leach liquor was investigated. The influences of parameters such as equilibrium pH and extractant concentration on the extent of Al(III) extraction were accordingly examined. After appropriate optimisation, an extraction efficiency of 98.6% Al(III) by 0.25 mol/L Cyanex®272 in kerosene diluent at 27 ± 2°C in the equilibrium pH range of 3.0–3.5 was achieved from an initial biotite-rich kaolinite leach liquor containing 1864.7 mg/L Al, 123.4 mg/L Fe, 70 mg/L Mn and 17.6 mg/L Ti as a major constituents. Other metal ion species detected including Ca and Mg was found to occur from low to trace amounts (≤1 mg/L). Total stripping of Al(III) from the loaded organic phase was carried out using 0.1 mol/L H2SO4 solution at an aqueous: organic (A:O) phase ratio 1: 1. The thermodynamic feasibility of extraction process to obtain high-grade alumina (Al2O3: 14-387-9021, melting point = 2056°C) gave the apparent standard enthalpy (ΔH), entropy (ΔS) and Gibb's energy (ΔG) of 3.87 kJ/mol, 10.57 J/K mol and −3177.6 J/mol respectively at 27 ± 2°C. [ABSTRACT FROM AUTHOR]

The importance of alumina and titania is exceptionally high for modern life since they appear in all materials science fields and perform essential tasks without which modern life would not be possible. Every day, the window of application of these oxides expands, including polymer science and technology. Alumina and titania as nanofillers are explored in the present work, aiming to expand the window of application of these oxides as a secondary phase in extruded PVDF composites. Unexpected findings lead to the belief that PVDF induces an unknown phase transition/oxidation in γ-alumina and anatase, which causes their composites to be dark and present unusual thermal behavior; Tmax decreased 75 and 61°C upon the incorporation of anatase and γ-alumina to PVDF matrix, respectively. All the titania and alumina composites possess lower mechanical properties and degradation temperatures than pure PVDF; however, the crystallinity degree is 3% higher for rutile, which could have positive application in membranes and pipes with selective permeability. The formation of the transformation mentioned above in γ-alumina and anatase decreased the viscosity of the polymer by 6 and 24% respectively, which is closely related to the unexpected thermal behavior of those composites and possess a new research subject about the causes of this transformation induced by polymer and its possibility for future applications. [ABSTRACT FROM AUTHOR]

High-temperature oxidation behaviour of an alumina-forming austenitic (AFA, Febalance–20Ni–14Cr–2.5Al–0.15Si–2Mn–2.5Mo–0.9Nb, in wt%) steel and W-substituted AFA steel was examined. The isothermal oxidation tests were performed on the two steels at 780°C for 2 weeks in air, which indicated that the substitution of W for Mo was beneficial to improve the oxidation resistance of the AFA steel. After oxidation at 780°C for 30 min, more compact and protective initial oxide layer against cation diffusion was formed on the W-substituted AFA steel than that of the original AFA steel, which was considered to be responsible for the reduced weight gain after the long-term oxidation. [ABSTRACT FROM AUTHOR]

This manuscript reports a novel process of high-temperature laser shock peening (HTLSP) for surface strengthening of single-crystal ceramics such as sapphire and reveals its fundamental mechanisms. HTLSP at 1200°C can induce a high compressive residual stress on the surface of sapphire while minimize the damage of laser-driven shock waves. Transmission electron microscopy characterizations revealed high dislocation densities near the surface, suggesting that plastic deformation at an ultrahigh strain rate was generated by the high shock wave pressure. The HTLSP-induced compressive residual stress can significantly improve the hardness and fracture toughness of sapphire, while maintain its outstanding optical transmittance.This manuscript reports a novel process of high-temperature laser shock peening for surface strengthening of single-crystal ceramics, and reveals mechanisms related to the interactions between laser-driven shock waves and ceramics. [ABSTRACT FROM AUTHOR]

Black dross contains alumina, metal oxides and nitrides and some salts. In order to recover pure alumina from black dross, a hydrometallurgical process consisting of leaching and solution purification was investigated. Alkaline leaching of mechanically activated black dross resulted in an aluminate solution with 98% purity together with a small amount of silicate. In order to obtain pure aluminate solution, removal of silicate from alkaline leaching liquor was investigated by coagulation with polyacrylamide, which has never been reported. Most of silicate(IV) was removed at the optimum coagulation condition. The strong interaction of silicate(IV) with polyacrylamide was verified through Fourier-transform infrared spectroscopy (FT-IR), Ultraviolet-visible spectra and viscosity data. The application of this method is expected to have a significant impact on the recovery of pure alumina from black dross materials. [ABSTRACT FROM AUTHOR]

Biofuels are one of the most sought-after renewable energy sources to overcome the current energy crisis in the world. Diesel blended with esters derived from oils has shown appreciable results for its use in compression ignition engines. In this work, B20 (20% biodiesel + 80% diesel by volume) fuel blend comprising 80% diesel and 20% biofuel extracted from waste cooking oil is used as a fuel. Two different metallic oxide nanoparticles (NPs), namely, cerium oxide (CeO2) and aluminium oxide (Al2O3) each having size of 30 nm, are dispersed in B20 biodiesel blend and used to investigate their combined influence on engine combustion. Experiments are conducted to study the engine exhaust emissions of a single cylinder four-stroke diesel engine running at constant speed of 1,500 rpm with varying engine loads. Experiments are carried out with B20 fuel and adding mixtures of CeO2 and Al2O3 nanoparticles in 50–30, 40–40 and 30–50 ppm, respectively, to B20 biodiesel blend. Responses recorded are the emissions of CO, HC, CO2, NOx and smoke. The results reveal that, on adding the nanoparticles, the engine observed a smooth combustion with reduction in the exhaust emissions compared to neat B20 biodiesel operation. B20 blend with 50 ppm of CeO2 and 30 ppm of Al2O3 nanoparticles showed lower exhaust emissions compared to other fuel blends. For the best fuel blend, CO, HC, NOx and smoke are reduced by 57.3%, 22.3%, 24.3% and 7.36%, respectively, compared to neat B20 operation. [ABSTRACT FROM AUTHOR]

The multiscale nanocomposites are a new class of the designed materials that have nano and micro-scale reinforcements. The main purpose of this paper is to investigate the mechanical properties such as tensile and bending properties of a four-phase nanocomposite using molecular dynamics (MD) simulation and experimental evaluations. The nanocomposite constituents are carbon nanotubes (CNT), alumina nanoparticles (Al2O3), and glass fiber as reinforcements and epoxy resin as the matrix. Two atomistic models of nanocomposites were made with the cross-linked epoxy molecules as matrix and CNT and Al2O3 as reinforcements. After using NVT and NPT ensembles, the mechanical properties of the molecular models have been extracted using constant-strain method. An equation was proposed to predict the elastic modulus of the multiscale composite using the results of MD. Eight laboratory samples have been fabricated and empirical tensile and bending properties of these cases have been extracted. The characteristics of experimental samples were investigated using X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The obtained results show that adding CNT and alumina to the polymer increased the tensile and bending moduli by 163% and 11%, respectively. Moreover, the nanoscale reinforcements enhanced the tensile and flexural strengths of classic glass fiber composite by about 28% and 13%. Comparing the empirical and simulation results show slight differences between the experimental data and predicted values using formula. [ABSTRACT FROM AUTHOR]

This research work analyses the combustion, performance, and emissions characteristics of calophyllum inophyllum methyl ester or polanga biodiesel operated single-cylinder direct injection diesel engine appended with alumina nano-additives with two concentrations of 25 ppm and 50 ppm. The test engine was run at varying loads from 25%, 50%, 75%, and 100%. The test engine is to be operated at a constant speed of 1500 rpm speed along with compression ratio of 17.5 and injection timing of 23° bTDC. The magnetic stirrer and ultrasonicator are used for blending of alumina nano-additives. Based on experimental investigation, it is found that with smaller fraction alumina nano-additives, the combustion is improved and emissions are lowered owing to high surface-area-to-volume-ratio of alumina particles. In addition, the blending of alumina has escalated the brake thermal efficiency substantially and reduced brake specific fuel consumption by about 6.56% and 7.37% subsequently. Thus, the improvement in combustion efficiency is observed along with a marginal reduction in NOx, CO, HC, and smoke emissions. [ABSTRACT FROM AUTHOR]

In this study, aluminium foil waste was used as a raw material to prepare alumina (Al2O3) by the precipitation process. Then, the produced alumina was applied in the removal of reactive green-19 dye from the simulated wastewater. The purity of the prepared alumina was investigated by the X-ray florescence test, and it was more than 97%. The X-ray diffraction analysis displayed that the alumina sample calcined at 550°C had γ-Al2O3 phase. High-surface area and the pore volume obtained were 246 m2/g and 0.412 cm3/g, respectively. Also, the real and bulk densities were found to be 3 and 1.35 g/cm3, respectively. Batch adsorption experiments were carried out for removing RG dye from simulated wastewater using the prepared alumina. The effects of pH, contact time, agitation speed, alumina dose, and the initial concentration on the adsorption process were studied. The optimum conditions were as follows: pH = 3; contact time = 90 min; agitation speed = 200 rpm; and alumina dose = 0.25 g for initial dye concentration of 100 mg/L to have high removal efficiency (98.65%). Moreover, the results revealed that the experimental data fitted to both Freundlich and Langmuir isotherms. The maximum adsorption capacity was 133.33 mg/g. [ABSTRACT FROM AUTHOR]

Silver-alumina hybrid fillers (Ag/α-Al2O3) were synthesized by a simple 'heat and mix' technique to increase the thermal conductivity of epoxy resin. The nano and micro coalition of Ag/α-Al2O3 could facilitate the effective 3 D phonon transfer system throughout the insulative epoxy resin and consequently reduced the interfacial Kapitza resistance. The Ag/α-Al2O3hybrid filled epoxy composite with 55 wt % (Ag/αA-55Ep) expressed the 9.8 fold thermal conductivity improvement than pristine epoxy. The filler content was optimized to maximize the interfacial and cohesive bond strength of composites through lap shear tests. The Ag/αA-55Ep hybrid composite demonstrated glass transition temperature (Tg) of 118 °C evaluated through dynamic mechanical analysis (DMA). At 5% weight loss, the thermal stability of the Ag/αA-55Ep composite was 324 °C as measured using thermo-gravimetric analysis (TGA). The logarithm of electrical conductivity of Ag/αA-55Ep composite was 0.023 (Ω cm)−1 which signified the semiconducting material range. Surface morphology and conductive networks were determined from the fracture surface analysis of the composites. Agari's empirical model was adopted to analyze the obtained experimental thermal conductivity results. The Horowitz and Metzger method was also considered for activation energy analysis of optimized composite. [ABSTRACT FROM AUTHOR]

Using high aluminum gangue as a raw material, aluminum sulfate 18 hydrate was made by the sulfuric acid leaching method under certain conditions. The product was characterized using X-ray diffraction (XRD) analysis of the phases, x-ray-fluorescence (XRF) analysis of the aluminum and sulfur content and thermogravimetric analysis of the crystallized water [Al2(SO4)3·18H2O]. Change characteristics of the crystal form and morphology during pyrolysis of octadecahydrate aluminum sulfate were studied by thermogravimetric Analysis (TGA), differential scanning calorimetry (DSC), differential thermogravimetry (DTG), XRD and scanning electron microscope (SEM). The theoretical basis for the preparation of metallurgical alumina from octadecahydrate aluminum sulfate was provided. According to the characteristics of the crystal structure change, the pyrolysis process of octadecahydrate aluminum sulfate can be separated into three stages. The first stage (dehydration stage 87–250 °C) had a weight loss rate of 40.5% and a loss of 15 water molecules; the weight loss rate of the second stage (dehydration stage 280–414 °C) was 8.1% with three water molecules lost; the weight loss rate of the third stage (decomposition stage 770–900 °C) was 36.1%, where three SO3 molecules were lost. The pyrolysis products were mainly Al2O3. The activation energies of the three reaction stages were calculated using the Coats-Redfern method as 90.02 kJ/mol, 205.74 kJ/mol and 284.40 kJ/mol, respectively. [ABSTRACT FROM AUTHOR]

This study aims at evaluating the effectiveness of Powder-Mixed Electrical Discharge Machining (PMEDM) in improving the surface integrity. The surface quality has been analyzed in terms of surface roughness, waviness, surface texture, surface crack density (SCD), crack depth (Cd), residual stress, microhardness, and recast-layer thickness (RLT) followed by chemical analysis. It has been found that the addition of graphite and alumina powder improves the average surface roughness. But other critical parameters, viz., SCD, Cd, and RLT, improve only in graphite PMEDM, whereas they deteriorate in alumina PMEDM. Furthermore, maximum mean spacing (Psm) and least peak density (Rpc) confirmed the highest degree of spark distribution in graphite PMEDM. Apart from these, tool wear rate (TWR) and dimensional deviation of the machined profile have also been studied. Addition of powder has increased the TWR and hence taper in the machined profile. However, due to uniform distribution of spark in graphite PMEDM, maximum circularity is obtained. To analyze the observed results, all the dielectrics have been characterized. The improved surface integrity parameters of the machined surface are found to be in agreement with the changes in properties of dielectric due to addition of powders. [ABSTRACT FROM AUTHOR]

Our present study deals with the synthesis of a heterogeneous catalyst (CuL@Al2O3). Initially [CuL], having the formula [Cu(L)(H2O)](NO3) (HL = 2-[(3,5-dichloro-2-hydroxy-benzylidene)-amino]-2-hydroxymethyl-propane-1,3-diol, obtained from condensation between 3,5-dichloro-2-hydroxybenzaldehyde and 2-amino-2-(hydroxymethyl)propane-1,3-diol), has been synthesized, followed by immobilization of [CuL] on alumina to generate the catalyst. The catalyst has been characterized by SXRD, UV-vis, FT-IR and SEM. Ground-state structure of the homogeneous catalyst [CuL] was optimized by Density Functional Theory (DFT) and Time-Dependent DFT (TD-DFT) calculations. This catalyst exhibits appreciable catalytic activity towards oxidation of alcohols by using hydrogen peroxide as oxidant. Through ESI-MS study, it becomes possible to isolate intermediate species of the catalytic oxidation. Finally, a plausible mechanistic pathway has been proposed to elucidate the role of each substituent of the catalytic system. Prepared (CuL@Al2O3) offers a number of advantages such as easy work-up and separation of the catalyst from the reaction mixture by centrifugation, recyclability for six times with minimal loss of activity along with the high yield of product. [ABSTRACT FROM AUTHOR]

The solubility of chromium in alumina- and lime-containing (≈5 wt% Al2O3 and 0- ≈ 10 wt% CaO) iron silicate slags has been measured at 1,300°C. In order to avoid contamination and the effects of further elements in the slag, the measurements were carried out at silica saturation. The solubility of chromium was a function of oxygen partial pressure. At high oxygen partial pressures PO2 ≈ 10−5 atm, the solubility was about 0.15 wt% (Cr) and it increased to about 0.3 wt% (Cr) in reducing conditions of pO2 ≈ 10−10 atm. Alumina and lime seemed to increase the solubility slightly. [ABSTRACT FROM AUTHOR]

An α-Al2O3 bicrystal with a (10 1 ¯ 4)/[1 2 ¯ 10] Σ13 grain boundary was fabricated by joining two pieces of single crystal at 1500°C in an Ar–H2 mixture gas. The resultant grain boundary was characterised by scanning transmission electron microscopy (STEM) at the atomic level. STEM observations revealed that the grain boundary consists of two regions with different atomic structures. These two structures were identified to be the most and second-most stable structures by theoretical calculations and STEM image simulation. The coexistence of two different structures in the Σ13 grain boundary is discussed. [ABSTRACT FROM AUTHOR]