Alumina Particles Research Articles

Mechanical Properties of Sandwiched Construction with Composite and Hybrid Core Structure

In the field of lighter substitute materials, sandwich plate models of composite and hybrid foam cores are used in this study. Three core structures: composite core structure and then the core is replaced by a structure of a closed and open repeating cellular pattern manufactured with 3D printing technology. It finally integrated both into one hybrid open-cell core filled with foam and employed the same device (WBW-100E) to conduct the three-point bending experiment. The test was conducted based on the international standard (ASTM-C 393-00) to perform the three-point bending investigation on the sandwich structure. Flexural test finding, with the hybrid polyurethane/polytropic acid (PUR/PLA) core, the ultimate bending load is increased by 127.7% compared to the open-cell structure core. In addition, the maximum deflection increased by 163.3%. The simulation results of three-point bending indicate that employing a hybrid combination of PUR-PLA led to an increase of 382.3%, and for PUR–TPU by 111.8%; however, the highest value recorded with PUR/PLA, which has the slightest stress error among the tests. Also, it is reported that when the volume fraction of reinforced aluminum particles is increased, the overall deformation becomes more sufficient, and the test accuracy improves; for example, rising from 0.5% to 3%, the midspan deflection of composite (foam-Al) is increased by 40.34%. There were noticeable improvements in mechanical properties in the 2.5% composite foam-Al.

The Influence of Contamination and Different Cleaning Methods and the Effect of Plasma Treatment of CoCr Alloy on Tensile Bond Strength to Composite Resin.

To investigate the influence of contamination and different cleaning methods on resin bonding to cobalt-chro- mium (CoCr) alloy disks. A total of 160 CoCr disks were divided into 3 groups. The first group (N = 64) was air abraded with alumina particles and contaminated with a silicone disclosing agent and saliva; the second group (N = 64) was air abraded but not contaminated; the third group (N = 32) was neither air abraded nor contaminated. The first two groups were di- vided into 4 subgroups (N = 16) according to the cleaning method: ultrasonic bath in 99% isopropanol, use of a cleaning suspension of zirconium oxide particles, use of a cleaning suspension based on 10-MDP salt, and treatment with atmo- spheric plasma. The third group was divided into 2 subgroups (N = 16): treatment with atmospheric plasma and no treat- ment. All CoCr specimens were bonded to plexiglas tubes filled with a bonding resin that contained phosphate monomer. Tensile bond strength (TBS) was examined by tensile testing after 3 and 150 days of water storage plus 37,500 thermal cy- cles (N = 8). After contamination, TBS was significantly reduced after 150 days of water storage. Groups without air abrasion showed initially low TBS and debonded spontaneously after 150 days of water storage. None of the cleaning methods was able to remove saliva and silicone disclosing agent on CoCr-alloy sur- faces. Surface activation by plasma treatment has no long-term effect on the bond strength.

Investigating the Origin of Non-Metallic Inclusions in Ti-Stabilized ULC Steels Using Different Tracing Techniques

Since steel cleanness comes to the fore of steel producers worldwide, it is necessary to understand the formation mechanism and modification of non-metallic inclusions (NMIs) in more detail. One central point is the identification of the source of especially interfering NMIs to prevent their evolution in the future. The present study applies two approaches to determine the source of NMIs in Ti-stabilized ultra-low carbon (ULC) steels—the active and the passive tracing. Both approaches are applied to an industrial experiment. The active tracing technique is focused on investigating the clogging layer formation in submerged entry nozzles and, hence, the origin of alumina particles. This method adds rare earth elements (REEs) directly to the melt to mark pre-existing deoxidation products at a certain point of the steelmaking process. The main concern of the passive method, the so-called REE fingerprint, is the determination of the source of mesoscopic NMIs. For the REE fingerprint, the pre-existing concentration of REEs in different potential sources and the investigated NMIs are measured by using an inductively coupled plasma mass spectrometer (ICP-MS). The resulting patterns are compared after normalizing the contents to chondrites, and the NMIs’ origins are identified. Concerning the EDS analysis and the resulting patterns from the REE fingerprint, the mold slag and, respectively, the casting powder were the sources of the investigated NMIs.

FE Investigation of Design and Quality Control-Related Issues Contributing to Metal-On-Metal Hip Implant Failures

High levels of cobalt and chromium ions were detected in the bodies of multiple recipients of modular cobalt chrome molybdenum metal-on-metal hip implants, necessitating the revision of their implants. A forensic engineering investigation of provided discovery documents and existing literature regarding the design, manufacturing, and clinical testing of these modular hip implants was performed. The investigation revealed that the modular interfaces of the implant allowed for micromotion to induce mechanically assisted crevice corrosion at these surfaces. The debris from this corrosion resulted in the release of metal ions into the bodies of the users, forming pseudotumors and compromising the user’s health and wellbeing. The effect of this corrosion was enhanced by the galvanic couple that existed between the modular components of the implant. In addition, scanning electron microscopy (SEM) and electron dispersive spectroscopy (EDS) analysis identified silicon carbide (SiC) and aluminum oxide (AL2O3 ) particles left behind from polishing, which were embedded in the ball and liners. These particles accelerated the wear of the hip implant and further exacerbated the release of metal ions. The designers of future hip implants should take care in preventing the occurrence of the above-stated factors.

Osteoblast Attachment on Bioactive Glass Air Particle Abrasion-Induced Calcium Phosphate Coating.

Air particle abrasion (APA) using bioactive glass (BG) effectively decontaminates titanium (Ti) surface biofilms and the retained glass particles on the abraded surfaces impart potent antibacterial properties against various clinically significant pathogens. The objective of this study was to investigate the effect of BG APA and simulated body fluid (SBF) immersion of sandblasted and acid-etched (SA) Ti surfaces on osteoblast cell viability. Another goal was to study the antibacterial effect against Streptococcus mutans. Square-shaped 10 mm diameter Ti substrates (n = 136) were SA by grit blasting with aluminum oxide particles, then acid-etching in an HCl-H2SO4 mixture. The SA substrates (n = 68) were used as non-coated controls (NC-SA). The test group (n = 68) was further subjected to APA using experimental zinc-containing BG (Zn4) and then mineralized in SBF for 14 d (Zn4-CaP). Surface roughness, contact angle, and surface free energy (SFE) were calculated on test and control surfaces. In addition, the topography and chemistry of substrate surfaces were also characterized. Osteoblastic cell viability and focal adhesion were also evaluated and compared to glass slides as an additional control. The antibacterial effect of Zn4-CaP was also assessed against S. mutans. After immersion in SBF, a mineralized zinc-containing Ca-P coating was formed on the SA substrates. The Zn4-CaP coating resulted in a significantly lower Ra surface roughness value (2.565 μm; p < 0.001), higher wettability (13.35°; p < 0.001), and higher total SFE (71.13; p < 0.001) compared to 3.695 μm, 77.19° and 40.43 for the NC-SA, respectively. APA using Zn4 can produce a zinc-containing calcium phosphate coating that demonstrates osteoblast cell viability and focal adhesion comparable to that on NC-SA or glass slides. Nevertheless, the coating had no antibacterial effect against S. mutans.

"Load-Unload" Effect of Manganese Oxides on Phosphorus in Surface Water of the Pearl River Estuary

Phosphorus (P) conveyed by surface runoff plays an essential role in regulating nutrient balance and primary production in estuarine waters. In this study, basic physiochemical properties, total phosphorus (TP, including speciation), particulate iron (PFe), particulate manganese (PMn), and particulate aluminum (PAl) of the surface water in the Pearl River Estuary (PRE) in different seasons were determined to investigate the spatiotemporal distribution characteristics of P and to identify the crucial factor controlling P migration and transformation in the freshwater-saltwater interaction zone. TP concentrations (28.88-233.68 μg·L-1) decreased with increasing salinity gradient owing to deposition and dilution. The proportions of P speciation followed a decreasing order as dissolved inorganic phosphorus (DIP, 37.3%) &gt; particulate inorganic phosphorus (PIP, 22.7%) &gt; dissolved organic phosphorus (DOP, 21.0%) &gt; particulate organic phosphorus (POP, 19.0%). PIP was positively related to PFe, PMn, and PAl (P &lt; 0.05), confirming their concurrent migration behaviors. In addition, the increase in salinity promoted the desorption of phosphate on the suspended particulate matters, which mainly took place near the freshwater-saltwater interface. A significant positive correlation (P &lt; 0.001) between the solid-liquid phase partitioning coefficient (Kd) of phosphate and salinity indicated that PIP was present mainly in more stable forms in the brackish water. Most importantly, a better relationship between Kd and PMn (P &lt; 0.01) supported our scientific hypothesis of the "load-unload" effect of Mn oxides on P:particulate-carrying phosphates transported from the freshwater zone tend to be desorbed and released into the brackish water.

Novel Nanostructured Pd/Co-Alumina Materials for the Catalytic Oxidation of Atmospheric Pollutants.

Cobalt-doped alumina catalysts were prepared using different methods, either conventional wet impregnation (WI) and/or advanced spray impregnation (SI), and they were evaluated as novel oxidation catalysts for CO and MeOH oxidation. The spray impregnation technique was used with the aim of achieving the synthesis of core-shell catalytic nanostructures to secure the chemical/thermal stability of active sites on the catalyst carrier. The catalysts were further promoted with a low Pd content (0.5 wt.%) incorporated via either incipient wetness impregnation (DI) or spray impregnation. The results revealed the superior performance of the spray-impregnated catalysts (Co/γ-Al2O3-SI) for both reactions. The deposition of Co oxide on the outer surface of the alumina particle (SEM images) and the availability of the active Co phase resulted in the enhancement of the Co/γ-Al2O3 catalysts' oxidation activity. Pd incorporation increased the catalysts' reducibility (TPR-H2) and improved the catalysts' performance for both reactions. However, the Pd incorporation method affected the catalytic performance; with the SI method, the active phase of Co3O4 was probably covered with PdO and was not available for the oxidation reactions. On the contrary, the incorporation of Pd with the DI method resulted in a better dispersion of PdO all over the Co/Al catalyst surface, maintaining available Co active sites and a better Pd-Co interaction. MeOH desorption studies revealed the methanol oxidation mechanism: the Co/Al catalysts promoted the partial oxidation of MeOH to formaldehyde (HCHO) and dehydration to dimethyl ether (DME), while the Pd-based Co/Al catalysts enhanced the complete oxidation of methanol to CO2 and H2O.

Enhancement of silk fabric knife-stabbing resistance for soft body armor

Traditional silk, known for its strength, flexibility, and comfort, shows promise as a lightweight, comfortable material for stab-resistant armor. This study explores enhancing silk’s knife-stabbing resistance for soft body armor through surface treatments. This study aims to augment the knife-stabbing resistance of silk fabric for soft body armor. Designed a falling tower setup to investigate fabric responses under impact. Exploring the addition of layers with coatings like silicon dioxide deposition, rice ash deposition, and aluminum oxide particles, the investigation revealed significant enhancements. A solitary silk layer exclusively coated with resin exhibited improvements of approximately 37.07%, 29.21%, and 13.47% in stab resistance for rice ash, aluminum oxide, and silicon oxide particles, respectively. The specific knife penetration depth indicated that the coating is more effective in diminishing penetration depth. The research identified that 7 layers of pure silk and 3 layers coated with rice ash satisfy National Institute of Justice Standard–0115.00, S1 as 26 layers of silk fabric, demonstrating a reduction without compromising protective efficacy.

Cyclic Fatigue Properties of Titanium Alloys for Application in Dental Implants.

The present study investigated the cyclic fatigue properties of titanium alloys (Ti-6Al-4V and Ti-6Al-7Nb) as implant materials and compared their properties with those of commercially pure titanium. Ti-6Al-4V and Ti-6Al-7Nb cylinders with diameters of 3.0 mm were examined. The surfaces of the cylinders were roughened by sand blasting with alumina particles and acid etching. Static and cyclic tests were performed according to ISO 14801:2016. The yield force in the static test (YS) was measured in 5 specimens of each alloy using a universal testing machine. The yield force in a cyclic test (YC) was measured in 20 specimens of each alloy using the staircase method, which involved applying a cyclic load at a frequency of 10 Hz for 106 cycles. After the cyclic loading tests, cross-sections of the specimens were examined under an optical microscope. The YS values for Ti-6Al-4V and Ti-6Al-7Nb were 1463 N±93 N and 1405 N±79 N, respectively, and the YC values were 870 N±58 N and 853 N±202 N, respectively. Microscopic observation revealed cracks on the tensile side of some of the specimens, including run outs and failures. The results of this study suggest that the YC values for Ti-6Al-4V and Ti-6Al-7Nb were 40% less than those for YS. The yield force of Grade-4 Cp-Ti significantly decreased after cyclic loading. The YC values for Ti-6Al-4V and Ti-6Al-7Nb were approximately 900 N, which was markedly greater than that for commercially pure, Grade-4 titanium (700 N).

Recyclability of novel energy harvesting and storage technologies for IoT and wireless sensor networks

This paper aims to present a set of separation and recycling methods designed to recover valuable materials and components from innovative high-performance piezoelectric (PEG) and thermoelectric (TEG) generators and monolithic supercapacitors (SC) developed within the InComEss project. This project, a part of the European Horizon H2020 research program, focuses on creating environmentally friendly, cost-effective, and highly efficient Energy Harvesting Systems (EHSs) for powering wireless sensor networks. It combines advanced polymer-based composite materials for piezoelectric, thermoelectric, and supercapacitors, capable of harvesting and storing electrical energy from mechanical or waste heat sources. The authors initially identified key recoverable components. In PEG, these includes Polyvinylidene fluoride (PVDF), silver electrodes, polyimide, fiberglass/resin composite and copper. In TEG the highest-value components are single walled carbon nanotubes (SWCNTs) and polymeric matrices, along with the SWCNTs, while in SC, aluminium, polyethylene terephthalate (PET) and carbon particles are targeted. This paper proposes a range of separation and recycling techniques involving mechanical, thermal, and chemical processes. These methods include microwave-assisted and pyrolysis thermal processes, various mechanical fragmentation and separation processes, hydrometallurgical recovery processes, and solvent-based dissolution methods. However, a comprehensive understanding of the end-of-life waste stream of these devices is necessary for further advancements. The authors are currently conducting a thorough laboratory assessment of the recovery methods to pinpoint the most effective recyclable options. The outcomes of this assessment will be shared in a subsequent article.

Nitriding Titanium by Plasma Ion Implantation: Surface Properties and Initial Osteoblast Cell Response

This in vitro study aimed to investigate the effect of plasma ion implantation nitriding on titanium's surface properties and initial cell response. Grade 4 titanium discs (12.7 × 2 mm) were blasted with aluminum oxide particles to create moderately rough surfaces. The experimental discs (TiN) were nitrided using the plasma ion implantation technique in a vacuum chamber. Surface characterization was performed using laser confocal microscopy, atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). Surface wettability was assessed by measuring the contact angle of a sessile drop using a goniometer. Human osteoblast cells were seeded on the discs to evaluate cell attachment and proliferation at 1, 3, 5, and 7 days of culture using a tetrazolium compound assay. Alkaline phosphatase (ALP) activity was measured at day 7 to assess cell differentiation. Cell morphology was examined by scanning electron microscopy (SEM) and confocal laser scanning microscopy. The TiN group exhibited similar micro-roughness to the control group; however, it displayed a higher density of nanostructures, increased nitrogen content, and slightly improved wettability. Cell proliferation and ALP activity were similar between the groups after seven days of culture. In conclusion, plasma ion implantation nitriding enhances surface nanofeatures and wettability without compromising the biocompatibility of titanium, making it a promising surface modification technique for dental and orthopedic implants.

Effect of Phytic Acid Etching and Airborne-Particle Abrasion Treatment on the Resin Bond Strength.

This study aimed to evaluate the bond strength of a universal adhesive to dentin (μTBS) using different time periods of airborne particle abrasion (APA) and two types of acid etching. Seventy-two human third molars were divided into 9 groups (n=8) according to dentin pretreatment: APA duration (0, 5, or 10s) and acid etching (no acid - NA, 37% phosphoric acid - PhoA, or 1% phytic acid - PhyA). APA was performed at a 0.5 cm distance and air pressure of 60 psi using 50 μm aluminum oxide particles. Afterwards, two coats of Single Bond Universal adhesive (3M) were applied to the dentin surface. Composite blocks were built using the incremental technique, sectioned into 1×1 mm slices and subjected to microtensile bond strength (μTBS) testing. Fracture patterns and surface topography of each dentinal pretreatment were evaluated using a Scanning electron microscope (SEM). Bond strength data were analyzed using two-way ANOVA and Bonferroni post-hoc tests. The group that received pretreatment with 5s APA and PhoA presented higher μTBS values among all groups, which was statistically different when compared with the PhoA, 10APA+PhoA, and 5APA+PhyA groups. PhyA did not significantly influence the bond strength of the air-abraded groups. Finally, adhesive failure was considered the predominant failure in all groups. Dentin pretreated by airborne particle abrasion using aluminum oxide demonstrated an increase in bond strength when abraded for 5 seconds and conditioned with phosphoric acid in a universal adhesive system.

Effect of Al-Ti complex deoxidation mode on steel cleanliness during RH refining of IF steels

The deoxidation in Ti containing Al killed IF steels is a vital parameter that directly influences the steel cleanliness. In this study, the evolution of steel compositions and inclusion characteristics during RH refining of IF steels were investigated by industrial trials involving three Al-Ti deoxidation modes, which were adding Ti-Fe 2 min after Al deoxidation in Mode I, adding Al and Ti-Fe simultaneously in Mode II, and adding Ti alloys with two equal batches at 3.2 min and 5 min after Al deoxidation in Mode III. The results showed that nitrogen pickup of several ppm was observed with Ti-Fe alloy addition. Therefore, nitrogen content in alloys should be strictly controlled. The main inclusions were single alumina particles, alumina clusters, alumina cluster with Al-Ti oxides, and Al-Ti complex oxides. Mode III had less amount of Al-Ti oxides compared with Mode I, and Mode II had a much higher proportion of Ti bearing inclusions than Mode I and Mode III at RH end. For Mode I &amp; Mode III, the inclusion removal rate was 0.33–0.35 min−1 before adding Ti, and slowed down to 0.14 min−1 for Mode I and 0.22 min−1 for Mode III after Ti-Fe addition. While for Mode II, the rate was only 0.18 min−1. Mode III was the recommended mode for its excellent steel cleanliness and high Ti yield with slight elongation of RH treating time.

Сравнительный анализ структуры и свойств керамик на основе оксида алюминия, полученных методами свободного и электроимпульсного плазменного спекания

The effect of the initial size of alumina particles on the density, microstructure, hardness, and fracture toughness of ceramics obtained by conventional and spark plasma sintering (SPS) has been studied. We studied ceramics obtained from commercial Al2O3 powders with an initial particle size of 40 – 50 nm, 0.2 mm, and 1 mm, and domestic fine powders with an initial particle size of 0.2 – 3 mm, and Al2O3 + 0.25 vol. % MgO and Al2O3 + 10 vol. % ZrO2. It is shown that the density of alumina ceramics nonmonotonically depends on the initial size of Al2O3 powder particles. It has been established that an increase in the grain size leads to a nonmonotonic change in the hardness of alumina ceramics. It has been established that the addition of 0.25 vol. % MgO accelerates the sintering of alumina. The addition of 10 vol. % ZrO2 makes it possible to provide an optimal combination of hardness and fracture toughness. It is shown that fine-grained ceramics obtained by the SPS method have a higher hardness. It has been suggested that SPS of submicron alumina powders with an amorphous layer on the surface, additionally stabilized by zirconia particles, is promising for further increasing the hardness of alumina ceramics.

Shear Bond Strength of Veneering Composite Versus Different Polyetheretherketone Materials after Various Surface Treatments: An In-vitro Study

Introduction: Polyetheretherketone, also known as PEEK, is a semicrystalline thermoplastic material with many advantages. Since its grey material, it has to veneering with composite resin to enhance its aesthetic appeal. Bonding PEEK and composite veneers poses challenges due to its inert surface. Aim: To assess and compare the Shear Bond Strength (SBS) between various polyetheretherketone materials and veneering composites following various surface treatments. Materials and Methods: The in-vitro study was conducted at KSR Dental College and Hospital in Tiruchengode, Tamil Nadu, India, over a period of three months from December 2022 to February 2023. A total of 108 PEEK discs were prepared for the study, divided into three groups: unfilled PEEK, 30% carbon reinforced PEEK, and 10% carbon + 10% graphite + 10% Polytetrafluoroethylene (PTFE) reinforced PEEK. The specimens underwent different surface treatments, including no treatment, sandblasting with 110 um alumina particles, and acid etching with 98% sulphuric acid. Additionally, 108 composite discs were prepared and bonded to the PEEK specimens using adhesive and resin cement. The bonded specimens were immersed in distilled water for 24 hours, and the Shear Bond Strength (SBS) was determined using a universal testing machine. Statistical analysis was performed using one-way ANOVA, and mean values were compared using posthoc tests. Results: The results indicated significant variation in SBS among the three groups without treatment (p=0.011) and after sandblasting with 110 um alumina (p=&lt;0.001). The 30% carbon reinforced PEEK exhibited the highest SBS regardless of the surface treatments. Conclusion: Among the tested materials, 30% carbon reinforced PEEK demonstrated the highest SBS, regardless of the surface treatments. Acid etching yielded the highest SBS among the various surface treatments, irrespective of the type of PEEK material used.

Oxidation of fine aluminum particles: thermally induced transformations in particle shells and kinetics of oxide nucleation.

This paper investigates the process of oxidation of fine aluminum powder, consisting of spherical Al particles of 'metal core/oxide shell' type, when heated in air at temperatures below 550 °C. The highly dispersed aluminum powder 'Alex' used in this work (particle size: 0.05-1.5 μm and number average particle diameter (DN): 0.11 μm) was produced by electric explosion of a thin Al wire in argon with subsequent passivation in an oxygen-containing atmosphere. For the first time, the influence of the particle size on the oxidation process has been identified. During the reaction, individual γ-Al2O3 oxide nuclei grow at the surface of Al particles with diameters less than 300 nm without laterally overlapping to form a protective passivating layer, as typically occurs during the oxidation of micron-sized particles or bulk metal. The localization of γ-Al2O3 nuclei is determined by the regions where peeling of the primary amorphous oxide film from the surface of the metal core of an Al particle occurs due to the thermal decomposition of aluminum hydroxides (T ≈ 350 °C) present within the particle shells. A significant increase in the contributions of the following factors leads to a high oxidation rate: the diffusion within the disordered structure of a particle core and the surface diffusion of cations (Ea = 80.6 ± 5.3 kJ mol-1, 400-450 °C), the surface and grain boundary diffusion of oxygen during the growth of γ-Al2O3 crystallites (Ea = 108.3 ± 11.2 kJ mol-1, 470-500 °C) and the surface and grain boundary transport of anions through an amorphous and underlying nanocrystalline oxide layer with a constant thickness (Ea = 205.1 ± 8.6 kJ mol-1, 520-550 °C). The results obtained make it possible to expand the theoretical understanding of the manifestations of the size effect in solid-phase reactions and take into account its influence in practice.

Synthesis and Application of Bimetal Decorated Plant-Based Carbon Nanomaterial for Hydrogen Storage

Abstract: In this study, carbon nanomaterials (CNMs) were synthesized from waste cotton fibers and examined their hydrogen adsorption capacity. The CNMs were created by subjecting waste cotton fibers to high-temperature pyrolysis at 800°C, followed by activation with alkali solution. Nano-sized metallic particles of Nickel and Aluminium were decorated on the activated carbon fibers. Analysis through SEM, EDAX, Raman spectroscopy, X-ray diffraction and BET surface area confirmed the porous nature and presence of metal particles in the CNMs. These materials exhibited a notably larger specific surface area (SSA) compared to untreated carbon fibers, enhancing their hydrogen storage capabilities as it showed 8.08 wt% of hydrogen adsorption using a Sievert's apparatus. This work, shows the promising potential of these CNMs for hydrogen adsorption in various industrial applications.

Investigations on microstructure, hardness and tribological behaviour of AA7075-Al2O3 composites synthesized via stir casting route

Aluminium matrix composite (AMC) materials play an important role in the field of automobile and aerospace industries due to their excellent properties. In this research, aluminium alloy (AA7075) was reinforced with alumina (Al2O3) particles to improve their hardness and tribological behaviour of the base alloy. Four composites were prepared by varying the content (4, 8 and 12 wt.%) of Al2O3 particles through the stir casting technique. The surface morphology of the proposed composites ensured the uniform distribution of Al2O3 particles into the matrix alloy. The hardness of the composite was measured using a Brinell hardness tester and the maximum value of hardness was found in the AA7075 - 8 wt.% Al2O3 composite. Hence, a tribological investigation was carried out on this AA7075 - 8 wt.% Al2O3 composite. Load (P), sliding speed (V) and sliding velocity (D) were taken as the wear parameters for conducting the experiments. A Technique for Order Preference by Similarity to Ideal Preferred Solution (TOPSIS) approach has been applied to find out the optimal conditions of parameters to obtain the lowest wear rate (WR) and the co-efficient of friction (COF). The results showed that the lowest WR and COF was obtained at ‘P’ of 15 N, ‘V’ of 1 m•s-1 and ‘D’ of 1000 m•s-1. ANOVA results revealed that ‘P’ is the factor with the most significant contribution (38.36%), followed by ‘D’ (28.32%). The worn surface morphology of the confirmation experiment specimen was investigated by SEM and the wear mechanism was reported.

Enhancement effect of Li addition on nitriding reaction and combustion of Al-Li alloy in N2

For aluminum-based alloy particles, the addition of alloying element lithium (Li) with the properties of a high chemical activity and a low melting/boiling point can significantly improve the thermo-reactive properties of aluminum (Al) particles. To further reveal the combustion mechanism, this paper presents the nitriding reaction and combustion characteristics of Al-Li alloy in nitrogen (N2) through thermogravimetric analysis and differential scanning calorimetry (TG-DSC) analysis at a low heating rate and laser-induced ignition experiments at a high heating rate, considering the influences of two kinds of Li contents (1.0 wt% @ Al-1.0Li and 2.5 wt% @ Al-2.5Li) on these characteristics and making a comparison to the counterpart Al. Al-Li alloy powders as-prepared by gas atomization method showed the texture of the Li-rich eutectic phase compounds on the surface by scanning electron microscope (SEM) characterization. The TG-DSC results demonstrated that the thermal nitriding reaction of Al-Li alloy in N2 was significantly faster than that of pure Al. The nitriding reaction temperature decreased from 853 °C for pure Al to 245 °C for Al-2.5Li alloy with a reduction of 71 %. The final weight gain of Al-2.5Li alloy was almost three times higher than that of pure Al in N2. The SEM photograph of intermediate nitriding products revealed that the cracks and loose “island” structures in the Li-rich zone on the Al-Li surface were the key to preventing the formation of a “passivation effect” into Al and promoting N2 uptake during melting. In addition, Li also acts as a catalytic carrier and “oxygen absorber” to enhance the Al-N reaction. The combustion of single Al-Li alloy microparticles induced by laser showed two stages: preheating and rapid nitriding. Al-Li alloy particles were ignited more rapidly and showed typical gas-phase / surface combustion modes different from pure Al. According to these findings, the combustion mechanism was proposed to help guide the development of Al-based solid propellants containing Li and the synthesis of AlN/Al composites in nitrogen-rich environments.

Fabrication of alumina ceramic membrane supports using LCD 3D printing and titania nanoparticle doping

The integration of 3D printing technology into the production of ceramic membranes has garnered significant interest. Nonetheless, challenges persist in fabricating macroporous supports with both high porosity and strength through 3D printing. In this study, titania nanoparticles were introduced to facilitate the fusion of alumina nanoparticles. This freed the pores occupied by alumina nanoparticles and enhanced the connections between micron-sized alumina particles. Consequently, both the permeability and strength of the ceramic membrane supports were improved. The impact of ceramic slurry composition on photocuring performance, sintering processes, and the addition of titania nanoparticles on the microstructure and properties of the porous ceramic membrane support were investigated. The optimized membrane support featured a pore size of approximately 1.36 µm, achieving a porosity of 42.4% and a pure water permeance of 3700 L·m−2·h−1·bar−1. These findings provide a fundamental groundwork for subsequent endeavors in the development of high-performance ceramic membranes.