Presence Of Al2O3 Research Articles

Synthesis of furo[2,3-c]carbazoles as potent α-glucosidase and α-amylase inhibitors

The carbazole-3-carbaldehyde 2, produced by N-ethyl carbazole via Vilsmeier-Haack reaction, was subjected to Dakin type oxidation with H2O2 and H2SO4 in methanol to produce the carbazole-3-ol 3. The reaction of 3 with a range of commercially available α-haloketones 4a–f in the presence of Al2O3 as catalyst in xylene led to their regio-selective cyclization to afford the furo[2,3-c]carbazoles 5a–f. Identification of the furo[2,3-c]carbazoles 5a–f were performed through 1H NMR,13C NMR, FT-IR and high resolution mass spectrometry. Single crystal X-ray diffraction analysis was employed to further confirm the structures of the some of the targeted compounds. In vitro antidiabetic activities of the newly synthesized furocarbazoles 5a–e were investigated utilizing α-glucosidase and α-amylase enzymes. The biological evaluation revealed the obvious efficiencies of the targeted molecules toward the α-glucosidase enzyme inhibition with the potent IC50 values compared to the standard acarbose. In the case of α-glucosidase inhibition, the furo[2,3-c]carbazoles chloro substituted 5c and nitro substituted 5f were found to be more potent than acarbose with the values of 215.0 and 162.70 μM, respectively. On the other hand, the compound 5f was found to be only promising candidate for α-amylase enzyme but not as effective as the standard acarbose.

Surface Charge: An Advantage for the Piezoelectric Properties of GaN Nanowires

The optimization of the new generation of piezoelectric nanogenerators based on 1D nanostructures requires a fundamental understanding of the different physical mechanisms at play, especially those that become predominant at the nanoscale regime. One such phenomenon is the surface charge effect (SCE), which is very pronounced in GaN NWs with sub-100 nm diameters. With an advanced nano-characterization tool derived from AFM, the influence of SCE on the piezo generation capacity of GaN NWs is investigated by modifying their immediate environment. As-grown GaN NWs are analysed and compared to their post-treated counterparts featuring an Al2O3 shell. We establish that the output voltages systematically decrease by the Al2O3 shell. This phenomenon is directly related to the decrease of the surface trap density in the presence of Al2O3 and the corresponding reduction of the surface Fermi level pinning. This leads to a stronger screening of the piezoelectric charges by the free carriers. These experimental results demonstrate and confirm that the piezo-conversion capacity of GaN NWs is favoured by the presence of the surface charges.

GMP/Al2O3/ZnO/PDMS thermal interface materials with anisotropic thermal conductivity and electrical insulation ability obtained by 3D‐printing method

AbstractDue to the continuous increase in power density and power consumption, thermal management has become a crucial issue in electronic devices like integrated circuits. Polymer‐based thermal conductive composites possess excellent thermal and mechanical properties, making them ideal materials for thermal management in the modern microelectronic industry. In this work, we present a combination of filler hybridization strategy and 3D‐printing technology to synergistically enhance the thermal conductivity of graphite microplatelets (GMP)/alumina (Al2O3)/zinc oxide (ZnO)/polydimethylsiloxane (PDMS) composite (o‐GAZP). When the content of GMP reaches 4.5 vol%, the 3D‐printed composite material exhibits a directional thermal conductivity of up to 4.51 W m−1 K−1. This value is significantly higher than the thermal conductivity of a randomly mixed GMP/Al2O3/ZnO/PDMS composite (1.98 W m−1 K−1). The remarkable thermal conductivity can be attributed to the anisotropic structural design, which benefits from the orientation of GMP and the creation of a multi‐scale dense structure through filler compounding. Additionally, the presence of Al2O3 and ZnO effectively separates the GMP particles, preventing the formation of electron transfer pathways and improving the electrical insulation performance of the composites. Furthermore, the impact of the anisotropic structural design on the thermal conductivity of the composites was verified through finite element simulation. This study demonstrates that constructing efficient thermally conductive and electrically insulating pathways by densely packing highly oriented two‐dimensional anisotropic graphite‐based fillers with uniformly dispersed thermally conductive and electrically insulating fillers is a simple and effective method to enhance the composites' thermal conductivity, electrical resistivity, and mechanical properties simultaneously. These findings hold great potential for various scalable thermal‐related applications. By implementing this approach, composites can exhibit excellent thermal conductivity, high electrical resistivity, and superior mechanical performance.

Enhancing wear resistance in Al-7075 composites through conventional mixing and casting techniques

Aluminium 7075 alloy composite are highly sought after materials because of their superior strength, light weight and exhibiting enhanced tribological characteristics. An electric resistance furnace and the metal die process were used to develop this aluminium (Al 7075) alloy hybrid composites, with reinforcing provided by E-glass short fibres and aluminium oxide (Al2O3) particulates. The Al 7075 alloy composites have been cast by employing stirring technique at various weight percentages of E-glass short fibres (2 %, 4 %, 6 %, and 8 %) and Al2O3 particles (3 %, 6 %, 9 %, and 12 %). Microscopic examination demonstrates that Al2O3 particle distribution within Aluminium matrix has been uniform. Hardness of the in-situ Al–Al2O3-E-glass-based composites rose by 10.58 %, 22.35 %, 50.58 %, and 41.17 % in comparison to its base alloy. Tensile strength of the 2 to 8 wt% E-glass with 3–12 wt% Al2O3 stir-cast composites increased by 9.08 %, 15.91 %, 19.09 %, and 7.27 % when compared with the aluminium matrix, whereas ductility reduced by 8.9 %, 12.5 %, 18.75 %, and 25 %. An experiment on wear rate was carried out using a pin-on-disk benchtop test equipment. The examination was performed at varying weights and sliding speeds, and the resulted demonstrated that composite materials exhibit higher wear resistance than Al matrix. Furthermore, the presence of Al2O3 and E-glass resulted in lower wear loss across all applied loads and sliding velocities. Lower wear rates in these composites were attributed to hardness and the interfacial bonding between the Al alloy and the in-situ reinforcement.

High temperature innovative zirconia-alumina ramming mass

Zirconia and high alumina ramming masses stand out as efficacious variants within the domain of unshaped refractories. In the interface between these materials, the utilization of transitional zirconia-alumina ramming mass is recommended. This study delves into the impact of alumina additive on the fundamental properties of ramming mass samples based on calcium oxide-stabilized zirconia, employing a phosphate bond. The investigation encompasses both the characterization of these samples, ranging from cold to heat-treated states across temperatures spanning 200–2100 °C, and an analysis of phase evolution throughout these conditions. The alterations in ZrO2 phases during thermal processing in the presence of Al2O3 and P2O5, along with the ramifications of these transformations on the properties of the ramming mass, are elucidated. Notably, the most comprehensive interaction between P2O5 and cubic ZrO2 materializes within the temperature interval of 1200–1400 °C, resulting in a marked destabilization of the cubic ZrO2 phase accompanied by a marginal reduction in sample strength that remains acceptable. The process of cubic ZrO2 phase destabilization reaches completion at 1700 °C. Elevating the heat treatment temperature of samples from 1700 to 2000 °C engenders the disintegration of aluminium, calcium, and zirconium phosphates, consequently leading to the re-stabilization of ZrO2. This, in turn, fosters densification and fortification of the sample structure. Designed for constituting the functional layer of linings at the interface of combustion and reaction zones within carbon black production reactors, the zirconia-alumina ramming mass with a phosphate bond showcases noteworthy potential. Experimental validation of this developed ramming mass at a carbon black plant has yielded favourable outcomes.

Simple Synthetic Approach to N-(Pyridin-2-yl)imidates from Nitrostyrenes and 2-Aminopyridines via the N-(Pyridin-2-yl)iminonitriles as Intermediates.

A facile, green, synthetic protocol of several substituted N-(pyridin-2-yl)imidates from nitrostyrenes and 2-aminopyridines via the corresponding N-(pyridin-2-yl)iminonitriles as intermediates is reported. The reaction process involved the in situ formation of the corresponding α-iminontriles under heterogeneous Lewis acid catalysis in the presence of Al2O3. Subsequently, α-iminonitriles were selectively transformed into the desired N-(pyridin-2-yl)imidates under ambient conditions and in the presence of Cs2CO3 in alcoholic media. Under these conditions, 1,2- and 1,3-propanediols also led to the corresponding mono-substituted imidates at room temperature. The present synthetic protocol was also developed on one mmol scale, providing access to this important scaffold. A preliminary synthetic application of the present N-(pyridin-2-yl)imidates was carried out for their facile conversion into the N-heterocycles 2-(4-chlorophenyl)-4,5-dihydro-1H-imidazole and 2-(4-chlorophenyl)-1,4,5,6-tetrahydropyrimidine in the presence of the corresponding ethylenediamine and 1,3-diaminopropane.

Pentachlorophenol degradation in the heterogeneous catalytic o zonation process using Al2O3as a catalyst agent

In this study, the catalytic ozonation of pentachlorophenol (PCP) in the presence of aluminum oxide (Al2O3) and the formation of byproducts during ozonationhas been studied. Results showed that catalytic ozonation in the presence of Al2O3 can substantially enhance PCP degradation efficiency compared with the using only ozonation process. The influences of severalenvironmental parameters including pH of the solution, initial PCP concentration, dosage of Al2O3 and dissolved ozone concentration were also investigated. The highest degradation efficiency of PCP was achieved at conditions: pH 8, 1.87 g/LAl2O3, and 0.49 g/L dissolved ozone concentration. The catalytic activity of Al2O3 was linked to highly hydroxylated surface. The surface hydroxyl groups on Al2O3 were the active places during catalytic ozonation. According to the drastic changes in the color of solution during ozonationin this study and results of some previous researches, formation of the intermediate reaction products during ozonationwas verified.Free chloride ion released, which was favored at slightly alkaline solution, was also followed in catalytic ozonation process.

Pentachlorophenol degradation in the heterogeneous catalytic o zonation process using Al2O3as a catalyst agent

In this study, the catalytic ozonation of pentachlorophenol (PCP) in the presence of aluminum oxide (Al2O3) and the formation of byproducts during ozonation has been studied. Results showed that catalytic ozonation in the presence of Al2O3 can substantially enhance PCP degradation efficiency compared with the using only ozonation process. The influences of several environmental parameters including pH of the solution, initial PCP concentration, dosage of Al2O3 and dissolved ozone concentration were also investigated. The highest degradation efficiency of PCP was achieved at conditions: pH 8, 1.87 g/LAl2O3, and 0.49 g/L dissolved ozone concentration. The catalytic activity of Al2O3 was linked to highly hydroxylase surface. The surface hydroxyl groups on Al2O3 were the active places during catalytic ozonation. According to the drastic changes in the color of solution during ozonation this study and results of some previous researches, formation of the intermediate reaction products during ozonation was verified. Free chloride ion released, which was favored at slightly alkaline solution, was also followed in catalytic ozonation process.

Experimental Study of the Combined Effects of Al2O3, CaO and MgO on Gas/Slag/Matte/Spinel Equilibria in the Cu–Fe–O–S–Si–Al–Ca–Mg System at 1473 K (1200ºC) and p(SO2) = 0.25 atm

The combined effects of Al2O3, CaO and MgO slagging components on phase equilibria and thermodynamics in the basic Cu–Fe–O–S–Si system have been evaluated at 1473 K (1200 ºC) and p(SO2) = 0.25 atm for a range of oxygen partial pressures and matte compositions. The experimental technique included high-temperature equilibration of the samples on a spinel substrate under controlled gas atmosphere (CO/CO2/SO2/Ar), followed by rapid quenching and subsequent measurement of the equilibrium phase compositions using Electron Probe X-ray Microanalysis (EPMA). The experimental data have been compared with the results of thermodynamic calculations undertaken using FactSage software and an internal thermodynamic database. Both the experimental results and the calculations results revealed that the presence of Al2O3, CaO and MgO reduced both the sulphur and copper concentrations in the slag phase for a given set of process conditions. The data have been used for further optimisation of the parameters of the thermodynamic database describing multicomponent metallurgical systems. The resulting thermodynamic database is capable of predicting, with high accuracy, the phase equilibria and the distribution of all elements between the phases in the Cu–Fe–O–S–Si–(Al, Ca, Mg) system.Graphical

Effect of Al2O3 and NiO Nanoparticle Additions on the Structure and Corrosion Behavior of Sn—4% Zn Alloy Coating Carbon Steel

The application of a higher corrosion resistance coating modified with nano additions can effectively decrease or prevent corrosion from occurring. In the present work, a novel method is successfully developed for the modification of carbon steel surfaces aiming for high corrosion resistance using Sn—4% Zn alloy/nanoparticle composite (NiO+ Al2O3) coating. Sn—4% Zn alloy/nanoparticle composite (NiO+ Al2O3) coatings were deposed on carbon steel using a direct tinning process that involved a power mixture of Sn—4% Zn alloy along with a flux mixture. Regular coating and interface structures were achieved by individual Al2O3 and both NiO and Al2O3 nanoparticle combined additions in the Sn-Zn coating. The maximum coating thickness of 70 ± 1.8 µm was achieved for Al2O3 nanoparticles in the Sn-Zn coating. Interfacial intermetallic layer thickness decreased with all used nanoparticle additions in individual and hybrid conditions. The minimum intermetallic layer thickness of about 2.29 ± 0.28 µm was achieved for Al2O3 nanoparticles in the Sn—Zn coating. Polarization and impedance measurements were used to investigate the influence of the incorporated Al2O3, NiO, and hybrid Al2O3/NiO nanoparticles on the passivation of the low-carbon steel (LCS) corrosion and the coated Sn—Zn LCS in sodium chloride solution. It was found that the presence of Al2O3, NiO, and Al2O3/NiO nanoparticles remarkably improved the corrosion resistance. The corrosion measurements confirmed that the corrosion resistance of the coated Sn-Zn carbon steel was increased in the presence of these nanoparticles in the following order: Al2O3/NiO > NiO > Al2O3.

Synthesis and wear properties of near eutectic Al-Si-TiB2/Al2O3 hybrid composites

In metal matrix composites a metal/alloy is often combined with non-metallic/inter-metallic phases to produce a novel material possessing attractive engineering attributes of its own. AMCs or Aluminium matrix composites refer to the group of light weight, high performance, aluminium based material systems which are employed to meet the demand of automotive and aerospace sectors. The present study emphasises on casting of Al–11.8 wt% Si metal-matrix composites with the help of an exothermic reaction among the melt and halide salts (K2TiF6 and KBF4) to incorporate 2 and 3 wt% TiB2 in the base alloy matrix. Al2O3 particles (0.5, 1 and 2 wt%) were also mixed with these in-situ prepared composites to produce hybrid composites which were characterized using optical microscopy. Optical Emission Spectroscopy revealed some amount of silicon loss during casting. XRD analysis indicated the presence of Al2O3 and TiB2 in the cast composites. Hardness, density and dry sliding wear tests were carried out and analysed. The results of the present investigation revealed that the wear rate of the composites decreases when there is an increase in the TiB2 content but this behaviour is limited to 1 wt% reinforcement in case of Al2O3. Increasing load promoted wear rate. At higher sliding distances wear rate decreased though wear volume was more. Density values of the composites were found to increase with increasing amounts of reinforcements. Increasing Al2O3 up to 1 wt%, the hardness of the composites was found to increase. Further increase in Al2O3 to 2 wt% revealed lower hardness values of the composites due to agglomeration of the particles.

EFFECT OF NANOPARTICLES ON CLAY STABILITY IN WATER: IMPLICATION FOR WATER BASED DRILLING MUD

Clay stability in water is essential in chemical and manufacturing processes. In water based drilling fluids, montmorillonite dispersed in water is commonly used to maintain fluid density that counter-balances pressure effects from formation layers. However, due to gravity, clay particles settlement at the bottom of holes is inevitable especially if operations in holes are suspended for technical reasons such as during fishing operations and dislodging of stuck pipes. This necessitates the introduction of additives that can enhance dispersion of clay particles in water columns. It has been reported that some nanoparticles can enhance clay stability in water; hence the primary objective in this work is to identify nanoparticles that have potentials to enhance clay stability and nanoparticles that promote clay instability in distilled water and brine of 30 g/l. In the experimental work, clays and different kinds of nanoparticles were dispersed in columns of water and the volumes of settled particles were plotted against time. Experimental results show that nanoparticles of silicon, zirconium, iron, tin, nickel and magnesium oxides all have the capacity to improve clay stability in water, while the presence of Al2O3 and ZnO nanoparticles promote clays instability in water. It is therefore recommended that further research on desirable drilling fluid properties be conducted with nanoparticle oxides that promote clay stability in water to investigate their suitability as additives in water based drilling muds.

The solid-state combustion synthesis of in-situ hybrid (Al3Ni+Al2O3)/Al composites and evaluation of its mechanical properties

In-situ hybrid (Al3Ni+Al2O3)/Al composites with bimodal size particles distributions were fabricated via an Al-NiO solid-state combustion reaction and subsequent hot extrusion process. The reaction system between Al and NiO was investigated by differential thermal analysis (DTA). The presence of Al2O3 and Al3Ni in the matrix was verified by XRD/EDS analysis. The in-situ formed Al3Ni phase with varying morphologies and sizes such as particle, plate, strip and flake at different sintering temperatures were observed. And the exothermic reaction of Al-NiO can be reduced to below the melting point of Al, and the desirable sintering temperature was. 600 ℃. In hot-extruded samples, both nano Al2O3 and Al3Ni particles distributed homogeneously, and most of Al3Ni particles is smaller than 2 µm in size. When NiO content increases from 8% to 12%, Al matrix grains in composites can be refined from 1.7510 µm to 1.2050 µm. The mechanical properties of composites are enhanced significantly due to the introduction of Al3Ni and Al2O3 particles, and can be up a YS of 322 MPa and a UTS of 407 MPa in the 15% NiO-Al composite. In addition, when the content of NiO increases from 10% to 12%, the strength of composites enhances without obvious sacrifice of EI. The strengthening and toughening mechanisms also was discussed in detail.

Improved electrical parameter of graphene in Si/SiO2/Al2O3/graphene heterostructure for THz modulation

We proposed the extraction of necessary electrical parameters of graphene (Gr) on Si/SiO2/Gr and Si/SiO2/Al2O3/Gr heterostructure THz modulators using the THz measurement technique. The obtained average THz absorption is 24.5% more on Si/SiO2/Al2O3/Gr as compared to the Gr on Si/SiO2. The calculated value of the carrier mobility of graphene on Si/SiO2/Al2O3 is 2.33 times more than that on Si/SiO2. The presence of Al2O3 may play a role of a barrier for diffusion of trap and impurity charges from Si/SiO2 to graphene which may lead to higher mobility and higher THz absorption. THz modulation measurements by optical pumping were also performed. Maximum modulation depth was 18.54% on Si/SiO2/Al2O3/Gr modulator at 2W pumping power which is 16.54% higher as compared to Gr on Si/SiO2. This shows that graphene on Si/SiO2/Al2O3 heterostructure exhibits great potential for the development of an efficient electro-optical THz modulator as compared to Si/SiO2/Gr modulator.

Analyzing the impact of adding aluminum oxide and cerium oxide nanoparticles to waste cooking biodiesel on engine performance, combustion and emissions characteristics

The purpose of this research is to analyze the emission, combustion, and performance parameters of a CRDI diesel engine fueled by waste cooking oil (WCO) biodiesel (B20%), diesel (80%), and their blend with two distinct metal-based nanoparticles cerium oxide (CeO2) and aluminum oxide (Al2O3). Transesterification was used to produce biodiesel from waste cooking oil (WCO). An ultrasonication procedure was used to gradually mingle the nanoparticles with a B20-diesel fuel blend in mass fractions of 50 and 100 ppm. The developed nanoparticle fuel samples were designated as (B20 + 50 Al2O3, B20 + 100 Al2O3, B20 + 50 CeO2, B20 + 100 CeO2). The CRDI engine was run at a constant speed with four different engine loads: 3 kg, 6 kg, 9 kg, and 12 kg. The result showed that the presence of Al2O3 in the blended fuel improved the BTE by 11.39%, reduced the SFC by 13.74%, and increased the cylinder pressure and heat release rate (HRR) by 16.77% and 21.48% respectively compared to B20 fuel at peak load condition. Regarding harmful emissions, CO emissions decreased by 15.06% for B20 + 50 Al2O3 than B20 and HC emissions decreased by 50% for B20 + 50 CeO2 than diesel at peak load. Further, NOx is reduced by 18.29% for B20 + 50 CeO2 than B20 at peak loads.

Catalytic pyrolysis of rice husk with SnCl2, Al2O3.4SiO2.H2O, and MoS2 for improving the chemical composition of pyrolysis oil and gas

Pyrolysis of Indian variety rice husk was carried out in a semi-batch reactor in the presence of SnCl2, Al2O3.4SiO2.H2O, and MoS2 catalysts at a fixed temperature (550 °C), heating rate (50 °C min−1), and N2 flow rate (0.3 L min−1). The yield of pyrolysis oil increased in the presence of Al2O3.4SiO2.H2O catalyst but deteriorated in presence of SnCl2, and MoS2 catalyst. At 550 °C, the maximum pyrolysis oil yield from non-catalytic pyrolysis (NCP) was 37.46 wt% and with Al2O3.4SiO2.H2O catalyst it was 38.41 wt%. The yield of H2 (7.27 mol %) in pyrolysis-gas after catalytic pyrolysis (CP) was 0.72 mol% higher than NCP (6.55 mol %). The gross calorific value (GCV) of pyrolysis-gas after CP increased to 5.99 MJ m−3 from 3.84 MJ m−3 (NCP). High lignin contained in rice husk gave a better CH4 yield of 10.13 mol. %. Reduction in water content (3.07–5.77 wt %) of pyrolysis oil after CP elevated the high heating value (HHV) to 28.61 from 22.41 MJ kg−1. A 3.0–4.58 mol. % reductions in the acidic compound content after CP impacted the pH and TAN of pyrolysis oils. The Al2O3.4SiO2.H2O catalyst elevated the area percentage of naphthenic (0.54 mol. %), olefinic (1.98 mol. %), aromatic (4.18 mol. %), and paraffinic (4.42 mol. %) compounds in pyrolysis oil. A 3.86 mol. % increase in the phenolic compounds was observed in presence of MoS2 catalyst. Approximately, 22 wt% loss in oxygen with 21 and 2.65 wt% increases in the carbon and hydrogen content of biochar elevated the HHV to 30.60 MJ kg−1 after CP.

Friction-induced motion evolution of reduced graphene oxide-Al2O3 at contact interface to achieve superior lubrication performance

Reduced graphene oxide-Al2O3 (rGO-Al2O3) nanoparticle (NP) was synthesized and applied as additive in water-based lubricants. Pin-on-disk tribological experiments indicated that rGO-Al2O3 nanofluid exhibited reinforced lubricity due to the formation of a double-layer tribofilm, contributing to 34.8 % ± 2.3 % and 78.2 % ± 2.5 % reduction in friction coefficient and wear rate. Combined with nonequilibrium molecular dynamics (NEMD) simulation, rGO-Al2O3 NP exerted synergistic effects of interlayer sliding, rolling, polishing and self-mending to obtain higher surface quality. A new parameter (p) was proposed to determine the motion modes of Al2O3. Al2O3 NP exhibited both rolling and sliding motion. The synergy of rGO and Al2O3 NPs increased the rolling motion proportion of Al2O3 from 78 % to 91 % compared to using alone. Similarly, about 12.6 % of the friction force in friction system was shared by the interlayer sliding of rGO monolayers in the presence of Al2O3 than the system with only rGO (9.5 %). Besides, rGO-Al2O3 had higher diffusion coefficient, which was more conducive to the formation of tribofilm. rGO nanosheets with large transverse size adsorbed on the Fe surface to prevent the embedding of high hardness Al2O3 to maintain its rolling effect. Meanwhile, Al2O3 can reversely stimulate the interlaminar sliding of rGO to enhance the lubrication performance of rGO-Al2O3 nanofluid.

Effect of parameters: Milling time and wt. % Al2O3 on mass density and hardness of Al2O3/Cu micro-composite

The new technologies require materials with multi-functional properties that cannot be met by conventional materials. Alumina (Al2O3) and pure copper (Cu) can be combined to form a multi-functional material with mechanical, tribological, and thermo-electrical properties. In this study, ceramic material Al2O3 with 0 wt.%, 1 wt. %, 2 wt. %, 3 wt. %, 4 wt. %, and 5 wt. % were added into the pure Cu matrix using a powder metallurgy method at various milling times. Different weight ratios of Al2O3 and Cu powders were pressed using a hydraulic press machine and sintered in a muffle furnace. A scanning electron microscope (SEM) and energy dispersive X-ray (EDX) were used to examine the surface morphograph and chemical elements of the micro-composite, respectively. The presence of Al2O3 in the sample is revealed by surface morphograph. The SEM images of the Al2O3/Cu micro-composite at various milling times show that the agglomeration tendency of the Al2O3 particles, as well as the Al2O3 particle size, decreases with increasing milling time. The presence of chemical elements such as Cu, Al, and O in the micro-composite is indicated by EDX analysis. The addition of Al2O3 particles into pure Cu reduces the mass density of the micro-composite samples and increases slightly as the milling time increases. The hardness analysis reveals that as the wt. % of Al2O3 particles and milling duration increases, the hardness value of pure Cu increases. The hardness of an Al2O3/Cu micro-composite is strongly dependent on the wt. % of Al2O3 particles, the Al2O3 particle size, the existence of porosity, the milling duration, and the distribution of the Al2O3 particles in the micro-composite samples.

Reactive Sintering of Al2O3–Y3Al5O12 Ceramic Composites Obtained by Direct Ink Writing

The main goal of this work was to obtain dense Al2O3–Y3Al5O12 ceramic composites by reactive sintering of three-dimensional samples, built by direct ink writing from a paste containing a mixture of Al2O3 and Y2O3 powders. To obtain a ceramic ink with proper rheological properties for extrusion-based printing, highly pure Al2O3 and Y2O3 powders in a percentage–weight ratio of 64:36 was mixed with 0.2 wt% MgO in a total solid loading of 42 vol% in aqueous media, adding carboxymethyl cellulose and polyethyleneimine solution as additives. The dried printed samples were sintered at final temperatures in the range of 1550 °C and 1650 °C; thus, relative densities of 83.7 ± 0.8%, 95.4 ± 0.4%, and 96.5 ± 0.5% were obtained for 1550 °C, 1600 °C, and 1650 °C, respectively. Rietveld refinement performed on the X-ray diffraction patterns indicated the presence of Al2O3 (42 to 47%) and Y3Al15O12 (58 to 61%) as crystalline phases, while micrographs showed the presence of equiaxial micrometric grains with average sizes of 1.8 ± 0.6 μm, for both phases and all sintering conditions. Samples sintered at 1600 °C and 1650 °C presented similar average Vickers hardness values of 14.2 ± 0.27 GPa and 14.5 ± 0.25 GPa, respectively. A slight increase in fracture toughness as sintering temperature increases was also stated, consistent with the densification.

Plasma-enhanced N2 fixation in a dielectric barrier discharge reactor: effect of packing materials

The effect of Al2O3 and BaTiO3 packing on the plasma-enhanced NO x synthesis from air was investigated in a packed-bed dielectric barrier discharge (DBD) reactor. The discharge characteristics are significantly influenced by packing different materials into the discharge gap. Compared with the DBD without packing, the presence of Al2O3 or BaTiO3 beads in the discharge effectively enhanced the charge accumulation, average electric field, and mean electron energy, all of which contribute to the enhanced production of NO x . The lowest energy consumption of 15.9 MJ mol−1 for NO x production was achieved when placing BaTiO3 beads in the DBD, which can be attributed to the increased mean electron energy using the BaTiO3 packing, facilitating the formation of more N2 excited species in the reaction. These results suggest that choosing proper packing materials can effectively reduce the energy cost for plasma NO x synthesis using DBD.