Alumina Research Articles

MACHINE LEARNING METHODS AS APPLIED TO MODELLING THERMAL CONDUCTIVITY OF EPOXY-BASED COMPOSITES WITH DIFFERENT FILLERS FOR AIRCRAFT

The thermal conductivity coefficient of epoxy composites for aircraft, which are reinforced with glass fiber and filled with aerosil, γ-aminopropylaerosil, aluminum oxide, chromium oxide, respectively, was simulated. To this end, various machine learning methods were used, in particular, neural networks and boosted trees. The results obtained were found to be in good agreement with the experimental data. In particular, the correlation coefficient in the test sample was 0.99%. The prediction error of neural networks in the test samples was 0.5; 0.3; 0.2%, while that of boosted trees was 1.5; 0.9%.

Exploring the impact of aluminum oxide nanoparticles on waste transformer biodiesel blend under variable injection timing

This study investigated the use of nano-blended biodiesel, made by mixing waste transformer biodiesel with nanoscale aluminum oxide particles. A fuel blend ratio containing both diesel and biodiesel components was created with 100 parts per million of alumina nanoparticles. All tests were conducted at various loads in an engine, using diesel, biodiesel, and nano-blended biodiesel fuel. The outcomes demonstrated that adding nanoparticles improved engine thermal efficiency and reduced emissions, especially at higher fuel injection timings. The greatest increase in brake thermal efficiency, 6% higher than diesel mode, was achieved with a nano-blended biodiesel formulation containing 100 ppm of aluminum oxide, at a fuel injection timing of 27 before top dead center under full load conditions. With a constant nanoparticle-blended biodiesel content and fuel injection timing of 27 before top dead center, reductions of 1.5% in smoke, 33% in hydrocarbon, and 8% in carbon monoxide emissions were observed, with a 9.7% increase in NO emissions.

The chemical compatibility of oxide ceramic candidates in static PbLi for advanced breeding blanket channel components

The use of a PbLi eutectic alloy is extended in the Dual Coolant Lead Lithium (DCLL) and Water Coolant Lead Lithium (WCLL) Breeding Blanket (BB) design concepts in future fusion reactors. However, the reactivity of PbLi is a challenging problem, as the flow liquid metal can damage metallic and ceramic materials. For the development of BB technologies, to conduct chemical compatibility studies of materials that will be exposed to the liquid metal is therefore critical. The advanced DCLL concept considers the use of ceramic channels, which could help to extend the BB operating window above 550 °C while improving the tritium-breeding ratio. Since BB components will be highly exposed to neutrons, the influence of PbLi in neutron-like damaged components is also of high concern as compositional changes may modify properties and functionality of the exposed material. Consequently, selected ceramics were submitted to long-term chemical compatibility experiments using COES, a lab-scale facility located at the Liquid Metal Laboratory at CIEMAT, Spain. Commercial Al2O3 ceramics were tested in the as-received and light-ion-implanted conditions, the resultant surfaces after static PbLi exposition being studied by SEM-EDX microstructural and SIMS analytical techniques. The conclusions after the long-term chemical compatibility experiments suggest that the use of bulk alumina ceramics in contact with PbLi is promising. Although lithium diffuses inside the ceramic transforming the initial alumina stequiometry, the surface structural damage is limited to the first 50 µm in the worst case, and could be still considered as a candidate ceramic material for the advanced DCLL BB.

Temperature dependent structural and magnetic properties of permalloy (Ni80Fe20) nanotubes

One dimensional Permalloy (Ni80Fe20) nanotubes (NTs) were successfully fabricated using Anodic Aluminum Oxide (AAO) templates with 100 nm diameter by employing a low-cost electrodeposition route at room temperature. As prepared Ni80Fe20 NTs morphology, elemental analysis and structural details have been investigated by using field-emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS) and X-Ray diffraction (XRD) respectively. The structure of prepared Permalloy nanostructures has face centered cubic (FCC) phase with polycrystalline in nature. The Ni80Fe20 NTs were annealed at 200 °C, 400 °C and 600 °C. The vibrating sample magnetometer (VSM) measurements showed that all the samples exhibit ferromagnetic nature. Furthermore, VSM has been employed to study the saturation magnetization (MS), Squareness (SQ) and Coercivity (HC) as the function of annealing temperature. A comparative study of magnetization reversal mechanism has also been conducted. The easy axis lies in the direction perpendicular to the NTS axis due to the dominance in shape anisotropy. Annealing temperature improved the magnetic properties of Permalloy (PA) NTs. This work will provide significant applications in the field of spintronics and high-density data storage devices.

Nonvolatile bipolar resistive switching characteristics of aluminum oxide grown by thermal oxidation processes

This study proposes a bipolar resistive random-access memory (RRAM), which is fabricated using an aluminum oxide (AlO x ) resistive switching (RS) layer. The RRAM shows a large memory window of 106 at a low read voltage of 0.5 V. In addition, high switching speed, long retention time, and superior read-disturb immunity are observed. AlO x layers are prepared by a thermal oxidation growth process. Aluminum metal films deposited on n+-Si wafers are oxidized at O2/(O2 + N2) flow rate ratios of 50%–100%. Al/AlO x /n+-Si device shows no RS behavior when the AlO x is grown in a pure O2 environment. As the O2/(O2 + N2) flow rate ratio decreases to 50%, Al/AlO x :N/n+-Si device reveals stable bipolar RS characteristics. A filamentary mode based on oxygen interstitial and Al vacancy is proposed to explain the difference in electrical characteristics of AlO x devices prepared at different O2 flow rates.

The Influence of the Structural Parameters of Nanoporous Alumina Matrices on Optical Properties

In this work, two types of nanoporous alumina membranes were prepared and tested. Structural features of the samples obtained by using different acids were investigated by scanning electron microscopy (SEM). And further SEM-images were analyzed by different types of fractal dimension estimation methods. The transmission and scattering of accelerated He+ ions were studied in experiments on the ion irradiation of dielectric channels based on porous alumina. An ion accelerator was used as a source of the He+ beam with an energy of 1.7 MeV. Ion scattering was studied by Rutherford backscattering spectrometry. Helium transition through nanoporous alumina at various angles between the normal to the sample and the beam direction were observed. It is shown that the porous structure of anodic aluminum oxide is excellent as a dielectric matrix of nanocapillaries. Owing to the small angle scattering, it allows for the transportation of the accelerated charged particles through the dielectric capillaries, and, as a result, the localization of high energy ion irradiation effects. Additionally, according to the transmission of UV–V is spectra, the energy gaps of samples obtained were calculated.

Thermal radiation and heat source/sink influence on MHD heat transmission of copper (Cu)–aluminum oxide (Al2O3) Hybrid nanofluid flow with velocity and thermal slips along a stretching sheet

The primary aim of this study is to examine the Magneto radiative flow characteristics of Hybrid nanofluid, a subject of contention within the framework of a stretching sheet including porous material and a heat source/sink. The remarkable ability of hybrid nanoparticles to enhance heat transmission has fascinated several experts, prompting them to further investigate the properties of the working fluid. This work specifically examines the Hybrid Nanofluid flow with MHD and heat transfer on an elongating surface, taking into account radiation and chemical reaction. The study utilizes a mixture of copper ( Cu ) and aluminum oxide ( A l 2 O 3 ) nanoparticles combined with water ( H 2 O ) as the underlying fluid. The process of similarity conversion is used to translate the governing partial differential equations (PDEs) of the fluid flow model into nonlinear ordinary differential equations (ODEs). The whole set of non-linear coupled ODEs, together with the boundary circumstances, are numerically solved by means of the Keller-Box approach. Two unique fluids, known Cu/water (nanofluid) and as A l 2 O 3 − Cu / water (hybrid nanofluid), are used to investigate the flow factors affecting heat transportation phenomena. Comparing the numerical data with the findings reported in the prior works reveals a strong agreement. This research explores the impacts of convective heat transfer, thermal radiation, heat absorption, and MHD. Nanofluid technology has several technical and industrial uses, including power production, sun collecting, and heat exchangers for cooling. Although nanofluids have the highest heat transfer rate compared to traditional fluids, there are several limitations to their effectiveness.

Role of nitrogen and tantalum in the high-temperature oxidation behavior of AlCoCr0.5NiTaxTi(N) alloys synthesized by laser in situ synthesis

Laser cladding was used to synthesize the coatings of the AlCoCr0.5NiTaxTi (N) alloys on a Ti–6Al–4 V substrate. As the Ta content increased, the alloy evolved from columnar crystals composed of dendritic face-centered cubic (FCC)/L12 phases and interdendritic Laves phases to a eutectic structure. The high-valence state of Ta diminished oxygen vacancies in TiO2, which reduced the diffusion rate, so an appropriate Ta content improved high-temperature oxidation resistance. In the cladding process, nitrogen from the protective gas was partially dissolved in the alloy and partially formed Ti2N, both of which act as diffusion barriers for titanium, inhibiting the formation of titanium oxide and promoting the formation of continuous single aluminum oxide, thereby improving oxidation resistance at high temperatures.

Характеристика вогнетривких відходів на основі MgO та Al2O3, як часткова заміна геополімеру на основі золи

Green process is a manufacturing technologies method without harming the environmental, one of the green process is reclaiming and reuse the manufacturing waste into applicable products. Geopolymer is one of the examples of green process products. Geopolymer are a material from synthesized aluminosilicate and alkali silicate that formed polymeric SiO4 and AlO4 structure. Geopolymer can be applicated for building or refractory material. Aluminosilicate material such as fly ash is used for Geopolymer precursor. In this study, fly ash as precursor is substituted by magnesium oxide (MgO) and aluminum oxide (Al2O3)-based refractory waste. It was then activated by activator consist of sodium hydroxide (NaOH) and Na2SiO3 (water glass). Results shown that the compressive strength of Al2O3 refractory waste based geopolymer are generally higher than MgO refractory waste based geopolymer. The result showed an addition of Al2O3 refractory waste improved the compressive strength of geopolymer specimen. XRD and FTIR characterization conducted to analyse the morphological compound and bonding of resulting geopolymer. The substance that contained in MgO and Al2O3 refractory based geopolymer are Quartz, Periclase, Corundum and Albite. FTIR results shows the siloxo and sialate bond as proof of geopolymerization has successfully occured.

Chemical constraints and tectonic setting of the Ginebra ophiolite complex

The occurrence and types of ophiolites in the Central Cordillera of the Colombian Andes have not been identified in terms of their tectonic settings and geochemical features. Therefore, the study of the tectonic setting and subduction zones in the ophiolites’ magmatic evolution becomes a significant issue. The Ginebra Ophiolitic Complex (GOC) is located on the western flank of the Central Cordillera in the Valle del Cauca Department, southwest of Colombia, assigned to the Lower Cretaceous period, as indicated by the contact of the GOC with the Buga Batholith. The GOC is formed by three main lithologies: amphibolite, gabbro, and ultramafic rocks (pyroxenite and peridotite), according to Ossa (2007). The rocks in the Puente Piedra section, located in the northeast of Ginebra municipality, are part of the gabbroic cumulates within the ophiolitic sequence. This sequence comprises interspersed layers of gabbroic cumulates, gabbrodiorites, and diorites; interpreted as a result of crystal accumulation and fractional crystallization processes. The mafic rocks of the GOC are sub-alkaline and correspond to the low potassium (K2O wt% 0.03-0.06) tholeiitic series. Geochemically, they have SiO2 wt% ranging from 49 to 61 and an aluminum oxide saturation index of approximately ~0.4 and ~0.8, indicating a metaluminous type. The geochemistry of the studied rocks from Puente Piedra section indicates that the GOC formed through fractional crystallization and accumulation processes from a single magma source. Cluster analysis, used to compare the geochemistry of GOC rocks and the Amaime Complex basalts, suggests a similar magma source, possibly linked to multiple recharge events that underwent fractional crystallization, melt extraction, and accumulation processes. The geochemical parameters are indicative of a suprasubduction zone ophiolite, characterized by a low potassium tholeiitic series affinity, TiO2 values typically <1.2 wt%, Th enrichment typical of subduction zones, high Pb content, and low values of Ti, Y, Yb, Ta, Nb, Zr, and Hf.

Stepwise ordering under nano-scale confinement in thin silica films

The phase transition from an amorphous 2D structure to a crystalline 3D structure under confinement is a fascinating and challenging problem in materials science and condensed matter physics. This work reports the Field Emission Scanning Electron Microscopy (FESEM) and energy dispersive analysis of X-rays (EDAX), X-ray diffraction (XRD), X-ray reflectivity (XRR), Fourier Transform Infrared Spectroscopy (FTIR) studies on pristine silica thin films. Silica was deposited on pristine Al (001) substrate (Alfa-Aesar) from tetraethyl orthosilicate (TEOS) precursor and thin films were spin-coated at different spinning frequencies under ambient conditions. The samples are highly porous and in-plane porosity varies from 30% to 60% as analyzed from both the FESEM and XRR and with increasing spinning frequency pores become more ordered. XRR shows that the samples are composed of two layers, a thick layer of aluminum oxide (Al2O3) as buffer layer and a layer of SiO2 on the top of the film. XRR shows sharp ordering rather than any layering. The film thickness varies from 90[Formula: see text]Å to 200[Formula: see text]Å and it shows a linear decay in the thickness of silica layer. In between 1000 and 1500[Formula: see text]rpm, XRR shows a sharp drop in the thickness of silica layer where thickness of this layer falls below the unit-cell dimension indicating higher-ordered crystallization under strained condition. XRD shows that there are no crystalline peaks coming from silica at lower rpm except the peaks of Al coming from the substrate. At 1000, 1200 and 1500[Formula: see text]rpm there is peak corresponding to the quartz, highly crystalline phase of SiO2 and where the substrate is slightly modified Al2O3. Reflection from (101) plane is prominent in all the films and it gives indication of formation 3D crystalline phase. Whereas FTIR shows that the Si–O stretching modes exhibit sharper and more defined reflectance peak compared to the broad bands observed in the samples in lower rpm. Observations suggest a clear indication of progressive ordering under confinement. To one extent, the results of XRR and FESEM will suggest the mechanism of transition from 2D amorphous to 3D crystalline phase under geometrical confinement effect and total confinement effect arising from thinning of the films with the increasing rpm, interfacial effect and on the other hand XRD and FTIR results will explain high ordering under confinement without any layering.

Engineering Compounds for the Recovery of Critical Elements from Slags: Melt Characteristics of Li5AlO4, LiAlO2, and LiAl5O8.

Engineered artificial minerals (EnAMs) are the core of a new concept of designing scavenger compounds for the recovery of critical elements from slags. It requires a fundamental understanding of solidification from complex oxide melts. Ion diffusivity and viscosity play vital roles in this process. In the melt, phase separations and ion transport give rise to gradients/increments in composition and, with it, to ion diffusivity, temperature, and viscosity. Due to this complexity, solidification phenomena are yet not well understood. If the melt is understood as increments of simple composition on a microscopic level, then the properties of these are more easily accessible from models and experiments. Here, we obtain these data for three stoichiometric lithium aluminum oxides. LiAlO2 is a promising EnAM for the recovery of lithium from lithium-ion battery pyrometallurgical processing. It is obtained through the addition of aluminum to the recycling slag melt. The high temperature properties spanning from below to above the liquidus temperature of three stoichiometric Li-Al-Oxides: Li5AlO4, LiAlO2, and LiAl5O8 are determined using molecular dynamic simulations. The compounds are also synthesized via the sol-gel route. The Li+ ion exhibits the largest diffusivity. They are quite mobile already below the liquidus temperature, i.e., for LiAlO2 at T = 1700 K, the diffusion coefficient of the lithium ion equals D = 3.0 × 10-9 m2 s-1. The other ions Al3+ and O2- do not move considerably at that temperature. The diffusivity of Li+ is largest in the lithium-rich compound Li5AlO4 with D = 32 × 10-9 m2 s-1 at 2500 K. The lower the viscosity, the higher the lithium content. The Li5AlO4 exhibits a viscosity of η = 2.2 mPa s at 1328 K which matches well with the experimentally determined 2.5 mPa s at this temperature. The viscosity of LiAlO2 at 1800 K is more than two times higher. These data sets can help to describe the melts on a microscopic level and understand how the melt properties will change due to gradients in the Li/Al concentration.

Assessment of skin sensitization potential of zinc oxide, aluminum oxide, manganese oxide, and copper oxide nanoparticles through the local lymph node assay: 5-bromo-deoxyuridine flow cytometry method

ABSTRACT The advent of nanotechnology has significantly spurred the utilization of nanoparticles (NPs) across diverse sectors encompassing industry, agriculture, engineering, cosmetics, and medicine. Metallic oxides including zinc oxide (ZnO), copper oxide (CuO), manganese oxide (Mn2O3), and aluminum oxide (Al2O3), in their NP forms, have become prevalent in cosmetics and various dermal products. Despite the expanding consideration of these compounds for dermal applications, their potential for initiating skin sensitization (SS) has not been comprehensively examined. An in vivo assay, local lymph node assay: 5-bromo-2-deoxyuridine-flow cytometry method (LLNA: BrdU-FCM) recognized as an alternative testing method for screening SS potential was used to address these issues. Following the OECD TG 442B guidelines, NPs suspensions smaller than 50 nm size were prepared for ZnO and Al2O3 at concentrations of 10, 25, and 50%, and Mn2O3 and CuO at concentrations of 5, 10, and 25%, and applied to the dorsum of each ear of female BALB/c mice on a daily basis for 3 consecutive days. Regarding the prediction of test substance to skin sensitizer if sensitization index (SI)≥2.7, all 4 NPs were classified as non-sensitizing. The SI values were below 2.06, 1.33, 1.42, and 0.99 for ZnO, Al2O3, Mn2O3, and CuO, respectively, at all test concentrations. Although data presented were negative with respect to adverse SS potential for these 4 NPs, further confirmatory tests addressing other key events associated with SS adverse outcome pathway need to be carried out to arrive at an acceptable conclusion on the skin safety for both cosmetic and dermal applications.

Experimental exploration of nano-phase change material composites for thermal management in Lithium-ion batteries

The present study reports an experimental investigation carried out for the thermal management of cylindrical lithium-ion battery simulators using aluminum oxide (nano particle)-eicosane (phase change material) composites. The experiment involves varying the power input from 4 to 10 W in 2 W increments and adjusting the weight percentage of nanoparticles (wt%) from 0.5 to 0.9 in 0.2 wt% intervals. The examination of battery temperature evolutions in response to heating power, a comprehensive heat transfer analysis incorporating the Nusselt number, the determination of the maximum temperature difference, thermal resistance analysis, and the exploration of temperature variations in the absence of Phase Change Material (PCM) are considered. The results show that an increase in the weight percentage of alumina nanoparticles in phase-change material cannot always improve the thermal performance. The results of the present study give guidelines for designing battery thermal management systems. The power levels used in the experiment vary from 4 W to 10 W in steps of 2 W. For a power level of 4 W, the heat flux is 1.088 kW/m2, and for a power level of 10 W, the heat flux is 2.72 kW/m2.

The Effect of Mechanical Alteration on Repair Bond Strength of S-PRG-Filler-Based Resin Composite Materials.

This study investigates the impact of mechanical alteration on resin composite surfaces and its subsequent effect on repair bond strength. A total of 100 resin composite disks were prepared and were allocated for 24 h or 1 year of artificial aging. Specimens were embedded in epoxy resin, and the composite surfaces were mechanically altered using either diamond burs or air abrasion with aluminum oxide or glass beads. A universal bonding material was applied and a 2 mm circular and 3 mm high repair composite cylinder were prepared using a Teflon mold. Then, the specimens were tested for their shear bond strength, and the de-bonded specimens were observed under a scanning electron microscope to determine the failure pattern. SPSS 26.0 statistical software was used to analyze the data. Two-way ANOVA showed a statistically significant effect of mechanical alteration and aging on the shear bond strength of S-PRG-filler-based resin composite (p < 0.05). Surface modification with a fine diamond bur showed a significantly higher bond strength in both 24-h- and 1-year-aged specimens. Surface modification with alumina significantly increased the bond strength of 1-year-aged specimens; however, it was statistically insignificant for 24 h-aged specimens. Mechanical alteration with a fine diamond bur and 50-micron alumina can improve the repair bond strength of the composite.

Enhancing gamma and neutron radiation shielding efficiency of LDPE/PVC polymers using cobalt, aluminum, and magnesium oxide fillers

A procedure for creating and assessing LDPE/PVC polymers using Co, Al, and Mg oxides as fillers for use as radiation shielding material was conducted. The SEM/EDX equipment was utilized for elemental analysis and mapping in order to visually represent the morphology of the produced polymers. The characterizations indicate that the MgCo2O4 particles possess an irregular and tiny morphology, displaying a spherical form with an average diameter of less than 100 nm. In addition, the Al2CoO4 particles are characterized as being aggregated, diminutive, and exhibiting a spherical morphology, with an average diameter of less than 150 nm. The current study involved experimental investigation, simulation using FLUKA-MC code, and theoretical calculations using Phy-X-PSD code to examine the radiological properties of the shielding material. The results depend on several factors, including the half-value layer (HVL), the effective atomic number (Zeff), the effective electron number (Neff), the effective conductivity (Ceff), the exposure buildup factor (EBF), the energy-absorption buildup factor (EABF), and the fast neutron macroscopic removal cross-section (FNRC). The SR-NIEL-7 platform has been utilized to compute the mass-stopping power for protons (H+) and alpha particles (He++) based on their kinetic energy. The experimental findings indicate that the density of LDPE/PVC filled with MgCo2O4 is greater than that of Al2CoO4. Furthermore, polymer filled with MgCo2O4 exhibits higher values for MAC, LAC, and FNRCs than Al2CoO4 filler. The measured LAC and MAC conform to the simulated values.

Recycling of sludge residue as a coagulant for phosphorus removal from aqueous solutions.

Phosphorus pollution poses a significant challenge in addressing water contamination. The coagulant is one of the effective methods to remove phosphorus from wastewater. Abundant Al and Fe oxides in sludge residue make it have great potential to synthesize water treatment coagulants. However, the utilization of sludge residue for preparation of coagulant was seldom investigated. In this study, we fabricated a novel coagulant, polyaluminum ferric chloride (SM-PAC), using sludge residue as a raw material through acid leaching and polymerization processes. Characterization results confirm that the parameters of SM-PAC meet the specifications outlined in the national standard (GB/T 22627-2022). We investigated the effects of pH, dosage, initial phosphorus concentration, and contact time on the removal efficiency of SM-PAC. As anticipated, the prepared SM-PAC exhibited a significant efficacy in removing phosphorus, meeting the discharge standards set for municipal sewage. Furthermore, the adsorption kinetics analysis suggests that the predominant mode of phosphorus adsorption on SM-PAC is chemical adsorption. Furthermore, the SM-PAC was employed in the actual wastewater treatment plant and exhibited excellent efficiency in phosphorus removal. The utilization of SM-PAC can not only effectively address the issue of sludge disposal but also achieve the goal of "treating waste with waste." It is expected that the proposed method of reusing sludge residue as a resource can provide a sustainable way to synthesize a coagulant for phosphorus removal.

Influence of the magnetic field on Al2O3-Cu/H2O hybrid nanofluid natural convection in a square cavity with heat sources and internal heat generation/absorption

In view of the growing interest in the numerical approach during the optimization phase of technical projects, this study proposes an in-depth analysis of the effects of several relevant parameters on the cooling of heat sources, part of the existing problems in the field of heat exchangers. The study focused on a natural convection problem inside a square cavity traversed by a vertical or horizontal magnetic field. This cavity contains four heating blocks, arranged at a uniform distance from each other and from the different surrounding walls. A hybrid nanofluid, composed of aluminum oxide (Al2O3) and copper (Cu) particles in equal proportions, was considered inside the cavity, imposing on it heat-generating or heat-absorbing behavior. The finite volume method was adopted as the solving approach for the adimensional governing equations, with the SIMPLE algorithm specifically chosen to handle the coupling between the momentum and continuity equations. Numerical results, covering a wide range of adimensional parameters such as Rayleigh number, Hartman number, volume fraction, internal heat value of the hybrid nanofluid, as well as for horizontal and vertical magnetic field orientations, have been grouped according to different scenarios to provide in-depth technical answers to fundamental questions related to the specific problem studied. These results have shown that increasing the flow regime leads to a transition from conductive to convective heat transfer, thus favoring an increase in heat exchange of up to 85% in certain scenarios. It is also clear that the cooling process of the heat sources is enhanced by the absorbing behavior of the hybrid nanofluid. Furthermore, the effects of the magnetic field (Ha) and the nanoparticle volume fraction (ϕ hnf) proved to be opposites: the former has an inhibiting effect, while the latter stimulates.

Alumina Ceramics for Armor Protection via 3D Printing Using Different Monomers.

Alumina ceramic is an ideal candidate for armor protection, but it is limited by the difficult molding or machining process. Three-dimensional printing imparts a superior geometric flexibility and shows good potential in the preparation of ceramics for armor protection. In this work, alumina ceramics were manufactured via 3D printing, and the effects of different monomers on the photosensitive slurry and sintered ceramics were investigated. The photosensitive slurries using dipropylene glycol diacrylate (DPGDA) as a monomer displayed the optimal curing performance, with a low viscosity, small volume shrinkage and low critical exposure energy, and each of the above properties was conducive to a good curing performance in 3D printing, making it a suitable formula for 3D-printed ceramic materials. In the 3D-printed ceramics with DPGDA as a monomer, a dense and uniform microstructure was exhibited after sintering. In comparison, the sample with trimethylolpropane triacrylate (TMPTA) showed an anisotropic microstructure with interlayer gaps and a porosity of about 9.8%. Attributed to the dense uniform microstructure, the sample with DPGDA exhibited superior properties, including a relative density of 97.5 ± 0.5%, a Vickers hardness of 19.4 ± 0.8 GPa, a fracture toughness of 2.6 ± 0.27 MPa·m1/2, a bending strength of 690 ± 54 MPa, and a dynamic strength of 3.7 ± 0.6 GPa at a strain rate of 1200 s-1.

Accumulation of Particles in an Annular Centrifugal Contactor Cascade and the Effect upon the Extraction of Nitric Acid

Centrifugal contactors (CCs) are a technology candidate for the development of advanced reprocessing flowsheets. While they offer many advantages, such as process intensification, there are still uncertainties regarding their industrial deployment. The presence of particles in the process streams in particular may present a challenge to both performance and operability. Preliminary studies have been undertaken to evaluate the accumulation of particles in the contactors and the effect upon the extraction behaviour of nitric acid. Aluminium oxide (Al2O3) particles were suspended in the aqueous feed solution during the operation of a three-stage, 40 mm diameter CC cascade. The presence of insoluble solid particles in the aqueous feed, up to 7 g/L, were not observed to affect phase separation and entrainment under the experimental conditions investigated. The particles were centrifuged out of solution and accumulated as a thin cake/bed in the rotors of each stage. This work also illustrates that particles do entrain through the cascade. The predominant effect on the rate of accumulation was particle concentration in the aqueous feed solution, and increasing solids loading was observed to have an impact upon the extraction of nitric acid across the cascade.