Alumina Particles Research Articles

Time-domain analysis of mode competition in ZnO nanowire lasers in inhomogeneous environments

Zinc oxide (ZnO) nanowire lasers are increasingly integrated into complex optoelectronic devices as a source of coherent radiation. To enable the rational design of these devices, it is crucial to understand how both the nanowire resonator and its surrounding environment influence mode competition and the three-dimensional structure of lasing modes. Additionally, realistic models of the lasing process must account for transient gain dynamics. In order to investigate the impact of an inhomogeneous environment, composed of various materials and structures, on mode competition, we conducted Finite-Difference Time-Domain (FDTD) simulations of the dominant lasing modes in different ZnO nanowire laser configurations. Our model describes how key parameters such as nanowire diameter, length, and substrate choice affect the field distribution in the lasing regime. We show that metallic substrates support lasing in thin nanowires in two distinct coupling regimes. Furthermore, we show that metallic particles attached to the nanowire end facets as a result of established nanowire growth techniques significantly influence lasing threshold, field distribution and competition between counter-propagating modes. We show that attaching an aluminum particle at the end facet of a ZnO nanowire leads to a threshold reduction, a switching of the dominant lasing mode and a mono-directional power flow inside a large segment of the nanowire.

Evaluation of different surface treatments on the bond strength of CAD/CAM PMMA denture teeth to heat-polymerized acrylic denture base

This in vitro study aims to evaluate various surface treatments on the shear bond strength and failure mode of CAD/CAM PMMA teeth to the heat-polymerized acrylic denture base. The study sample consisted of 100 teeth that were divided equally into five groups: Group 1: denture artificial teeth (control), Group 2: PMMA teeth without surface treatment, Group 3: PMMA teeth with MMA etching, Group 4: PMMA teeth with sandblasting (aluminum oxide particles), and Group 5: PMMA teeth with perpendicular grooves. The shear bond strength test was performed using a universal testing machine and the failure mode was recorded. Data were analyzed using ANOVA followed by Tukey’s post-hoc tests (α = 0.05). MMA increased the shear bond strength compared with other surface treatments (sandblasting and perpendicular grooves; P < 0.001). Sandblasting and perpendicular grooves showed no significant difference in the shear bond strength (P = 0.548 and 0.061; respectively). There were statistically significant differences in the frequencies of failure mode between the studied groups (P < 0.001). The control, PMMA, and PMMA + Sandblasting groups showed the weakest bonding. MMA application improved the shear bond strength for CAD/CAM PMMA teeth, the perpendicular groove seems to be not sufficiently effective, while the sandblasting cannot be considered as a surface treatment.

Experimental study on compression mechanical properties of functionally graded shape memory alloys

Functionally graded shape memory alloy (FG-SMA) hold considerable promise for diverse applications in aerospace and micro electro mechanical system (MEMS) fields, owing to their elevated ceramic hardness and distinctive phase transition characteristics. To investigate the mechanical properties and phase transition behaviors of FG-SMA, an FG-SMA specimen was fabricated for the first time using the spark plasma sintering and ball-mill mixing method. Subsequently, microstructure, phase transformation, hardness, compression fracture and shape memory effect testing experiments were carried out. The results revealed a microstructure of the FG-SMA without noticeable pores in the alumina content range of 0.1% to 0.6%. Alumina particles were effectively integrated into the NiTi matrix, enhancing the FG-SMA’s compressive strength. Varied alumina gradients in the FG-SMA cross-section led to distinct phase transitions. The addition of alumina increased the hardness of the NiTi matrix, resulting in higher fracture stress and strain in the FG-SMA. The elastic recovery strain of FG-SMA augmented with increasing alumina content, although the recoverable strain associated with the shape memory effect gradually decreased. This study provides valuable insights for the preparation, optimization, and practical applications of FG-SMAs. At the same time, the research in this article can lay an experimental foundation for the application of FG-SMA in the field of aerospace and MEMS.

Comprehensive parametric investigation of hot air erosion behavior in 3D-printed Scalmalloy

This study explores the erosion characteristics of 3D-printed Scalmalloy, an advanced aluminum–magnesium–scandium alloy, through a comprehensive investigation of varied process parameters. The erosion behavior was quantified through careful measurement of material loss, while the morphological changes on the surface were analyzed using scanning electron microscope (SEM) analysis. As the discharge of erodent increases, the kinetic energy of the particles is heightened, leading to augmented material removal and subsequently causing elevated erosion rates on the workpiece. An increase in the nozzle angle, the perpendicular force exerted by the particles, known as the normal force, decreases, while the parallel force, referred to as the tangential force, increases. The erosion rate increased from 30° to 45° due to increasing sliding wear, although it plateaued at 45° and 60° before falling at higher angles. According to the connection, the rate of erosion rose rapidly up to 60 m/s, plateaued between 60 and 120 m/s, and then increased marginally over 120 m/s. The rise in erosion rate from 6.33E-05 to 7.97E-05 (6.3–8%) with increased discharge is attributed to stronger impact forces and more particle interactions, resulting in greater material removal. The drop-in erosion rate between 325 and 350 °C indicates that higher ductility at elevated temperatures reduces adhesion and improves fracture resistance. At 25 m/s velocity and 60° angle, alumina particles likely strike with sufficient force to exceed the fracture toughness of Scalmalloy at 325 °C.

Global Climate Effect from Space Debris Reentry: Engineering and Policy Implications

Space objects are routinely reentered into Earth’s atmosphere for disposal. During reentry, space objects demise and produce ablation by-products, including alumina ([Formula: see text]) particles that can interact with Earth’s radiative balance, and possibly influence climate change. In this work, we model a future reentry scenario with [Formula: see text] of alumina entering into the South Pacific from controlled reentries to estimate the implications of a hypothetical policy that requires all reentries to demise over this region. We find that reentry alumina particles remain aloft in the atmosphere for 714 days, generating a direct radiative cooling effect of [Formula: see text] at the top of the atmosphere and [Formula: see text] at the tropopause. These South Pacific reentries create a concentration of particles in the southern stratosphere, leading to asymmetrical radiative forcing. When compared to aviation, the direct radiative forcing from a single reentry is greater in magnitude than a single commercial airliner flight, but reentries as a whole produce less radiative forcing per dollar of industry revenue than commercial aviation. These results support policies that encourage satellite design for demise and reentry as a form of decommissioning but warn against limiting reentry to the South Pacific only.

Numerical Study on Pressure Oscillations in a Solid Rocket Motor with Backward Step Configuration Under Two-Phase Flow Interactions

The pressure oscillation caused by vortex–acoustic coupling is one of the main gain factors that results in the combustion instability of motors. Focusing on a solid rocket motor with a backward step configuration that can generate a corner vortex, this study aims to investigate the pressure oscillation characteristics in a combustion chamber under two-phase flow interactions through numerical simulations. The two-phase flow discrete phase model (DPM) was chosen to study particle motion and two-phase interactions. The numerical methodology was hence established by coupling the DPM with the large eddy simulation (LES) method. Taking the Clx motor as a reference and introducing aluminum oxide particles, two important particle parameters (diameter and concentration) and the key geometric parameters of the backward step were numerically studied. The numerical results show that both increased particle diameter and concentration can decrease the frequency and amplitude of pressure oscillations; additionally, the effects of geometric parameters on the pressure oscillations of the backward step, such as the downstream aspect ratio, the expansion ratio, and the step position, are basically consistent under both pure gas and two-phase flows. The influences of those geometric parameters are mainly reflected in defining the space for the development of upstream flow instability and the motion of downstream vortices. Compared with the pure-gas flow, the presence of aluminum oxide particles in two-phase flow globally decreases the vortex shedding frequency, the primary frequency, and the amplitude of pressure oscillations. It can also weaken the effects of vortex–acoustic coupling due to increased turbulent viscosity, which hinders the orderly development of vortices.

Assessing shear bond strength of various surface treatments of 3D-printed provisional material with bis-acryl relining material

ObjectiveMarginal adaptation of the provisional restoration often requires relining from relining materials. This study determined the effects of surface treatments on the shear bond strength (SBS) between 3D-printed provisional and bis-acryl relining materials.Materials and methodsThe 3D-printed provisional specimens (9 × 9 × 2 mm3) were prepared using methacrylate-based material. Five test groups (n = 15) based on surface treatments were evaluated; (1) no treatment (CT), (2) ethanol (ET), (3) universal adhesive; CLEARFIL TRI-S BOND Universal Quick (UA), (4) airborne-particle abrasion with 50 μm aluminum oxide particles (AA), and (5) airborne-particle abrasion followed by universal adhesive (AA-UA). The specimens were bonded with relined bis-acryl resin material and left at room temperature for 24 h, allowing the complete polymerization. Then, shear bond strength was performed using a universal testing machine with a knife-edge blade parallel to the bonded surface at a crosshead speed of 1 mm/min until failure occurred. The fracture surfaces were examined under stereomicroscopy (20X) and scanning electron microscopy (50X).ResultsThe CT group had the lowest shear bond strength (1.92 ± 0.26 MPa), which was no statistically significant difference from ET (2.11 ± 0.23 MPa). The significantly highest shear bond strength was obtained from AA-UA (14.39 ± 1.07 MPa) (p < 0.05), followed by AA (6.39 ± 0.59 MPa) and UA (3.34 ± 0.21 MPa), respectively. Failure modes obtained were varied, with mixed and cohesive failures in AA-UA (46.6% mixed failures) and AA groups (66.6% mixed failure) whereas primarily adhesive failures were observed in CT (93.5%), ET (86.6%), and UA groups (86.6%).ConclusionsWithin the limitation of this study, the optimal bond strength was obtained when airborne-particle abrasion and universal adhesive were applied on the 3D-printed provisional material and relined with bis-acryl relining material.

3D‐printed porous mullite lattice structures by hybrid direct ink writing of silicone suspension‐emulsions

AbstractSilicones added with nano‐sized alumina particles are already known as starting materials for phase pure mullite ceramics, synthesized at quite low temperatures. The present paper deals with a fundamental upgrade, based on a novel suspension‐emulsion concept, for the easy fabrication of highly porous lattice structures. An aqueous suspension of γ‐Al2O3 nanoparticles in water was first distributed as emulsion within an “oily phase,” consisting of a silicone/acrylates blend, with the help of a surfactant. The mixture was later employed to fabricate highly porous structures (∼80% open porosity), by direct ink writing, that is, an extrusion‐based 3D printing technology requiring specific rheological behavior of the feedstock ink. Finally, the structures were rapidly stabilized through a photo‐polymerization step (configuring a form of “hybrid” direct ink writing). The presence of water also allowed the application of a freeze‐curing procedure, for a second series of samples. The abundant water vapor release from the starting mixtures, upon firing (up to 1300°C), led to structures with enhanced pore interconnectivity. The freeze‐curing protocol proved beneficial to the homogeneity of pore distribution and to the achievement of high strength‐to‐density ratios.

Obtaining Metal-Ceramic Layers by Laser Cladding using Alumina Powder Mixtures

In the paper a comparative analyse of laser cladding behaviour of metal-ceramic powder mixture was studied. The use of In718 alloy as a matrix material, with a lower melting range than SS304, allowed the reduction of the overheating of the cladding layer, for the same values ​​of the laser deposition parameters. At the same time, the greater fluidity of the In718 alloy led to an increase in the width of the cladded layer compared to the SS304 alloy. The use of spherical alumina particles led to the improvement of the appearance and adhesion to the substrate of the laser deposited layers. The analysis of the results obtained with laser cladding and metal matrix composite (MMC) manufactured using different proportions of Al2O3, SS304 or In718 highlighted that the optimal value of the laser melting power was of 500W for a deposition speed of 10mm/sec.

Comparison of shear bond strength of metallic orthodontic brackets bonded to zirconia models underwent different surface conditioning methods and different primer systems

Objectives: This study aimed to compare the shear bond strength (SBS) of metal brackets bonded to zirconia models with different surface treatment methods and two types of primers and to determine the adhesive remnant index (ARI). With the increase in demand for orthodontic treatment by adults and most adult patients having acrylic resin, amalgams, gold, composite resin, zirconia, or porcelain restorations, bonding of orthodontic braces to these surfaces is now a necessity. Brackets bonding to zirconia prostheses are a challenge in orthodontics because they need special surface conditioning. Material and Methods: In this in vitro study, 60 zirconia models were divided randomly into two groups of 30 models according to the primer material used (Assure® Plus and Transbond™ XT). The labial surface of each model was subjected to one of the following three surface preparation: No surface treatment (control group), sandblasting with 50 µm aluminum oxide (Al2O3) particles, and acid etching with 9.6% hydrofluoric acid (HF). Metal orthodontic brackets (Dentaurum) were bonded to zirconia models using Assure® Plus or Transbond™ XT adhesives. The SBS was measured using a universal testing machine at a crosshead speed of o.5 mm/min. The labial surfaces of models were inspected under a stereomicroscope, and the ARI scores were determined. Raw data were analyzed using Statistical Package for the Social Sciences program through analysis of variance and the Kruskal–Wallis test (P ≤ 0.05). Results: The Al2O3 air abrasion with the Assure® Plus group had the highest mean of SBS values, while HF groups with Transbond™ XT adhesive or Assure® Plus gave rise a significantly lower SBS values than that obtained for the Al2O3 group. A significant difference was noted among the groups in the ARI scores. In Al2O3 group bonded with Transbond™ XT had scores 1 and 2, which was designated as a mix-type failure, indicating a favorable failure mode. Conclusion: This study showed that air abrasion of zirconia models had a significant effect on the SBS of metal brackets bonded to zirconia surface, and the Transbond™ XT adhesive is a suitable primer material.

THE EFFECTS OF NANOADDITIVES ON A SINGLE CYLINDER DIESEL ENGINE USING PROSOPIS JULIFLORA BIODIESEL

This study looks at how a Prosopis Juliflora methyl ester-powered one-cylinder direct injection diesel engine burns, works, and gives off emissions when titanium nanoadditives are added at two different concentrations: 25 ppm and 50 ppm. The test engine should be run at 1500 rpm continuously with 17.5 compression and 23-degree BTDC timing. A magnetic agitator and an ultrasonic converter are used to mix aluminium nano-additive materials. Due to the high surface-to-area-volume ratio of alumina particles with smaller-scale alumina nanometrics, combustion is boosted and emissions are minimised, according to experimental studies. Furthermore, the alumina blend greatly improved brake thermal efficiency, lowering fuel consumption by 6.56 percent initially and 7.37 percent thereafter. In terms of combustion efficiency, this leads to a modest reduction in NOx, CO, HC, and smoke emissions.

Application investigations of force fields for molecular dynamic simulations of medical aluminum particles

The phase transition of metals is a research hotspot in molecular dynamic (MD) simulation. With the increase of the development of MD, different force fields with different requirements have emerged, which helps to select the appropriate force field and also increases the difficulty of selection. In addition, previous studies have been affected by particle size, which affects the melting point accuracy. MD simulation of the melting and condensing behavior of Aluminum (Al) particles was carried out by using EAM force fields from different sources. The thermal behavior of phase transition was studied by means of potential energy, specific heat, MSD, FCC lattice number, etc. The melting and condensation process of 2–10[Formula: see text]nm cubic without boundary under the NPT system was simulated, and the steady-state simulation was discussed by means of an isometric temperature point. It is proved that the borderless simulation can completely eliminate the boundary effect. The parameter setting of efficient use of EAM is widely discussed by using this method, and the effectiveness of the EAM force field is compared, so as to improve the efficiency of scholars engaged in related research and avoid the difficult choice of force field files. The results show that the borderless simulation has quite high advantages in terms of phase transition potential energy and melting point, while the current EAM force field is inherently deficient in this kind of discussion, and the development of new force field is urgent.

Development of engineering coating based on alumina nanoparticles incorporated into a Ni-Co alloy matrix: Effect of current density and alumina bath loading on microstructure and electrochemical corrosion behavior

The construction of electrodeposited coatings (EDCs) with enhanced microstructural characteristics and superior electrochemical corrosion behavior is of enduring concern for the industrial applications. In this study, alumina (Al2O3) nanoparticles were incorporated into a Ni-Co alloy matrix to improve its morphological and electrochemical behaviors. The primary objective was to assess the impact of varying electrodeposition current densities (20, 40, and 60 mA/m2) and different contents of alumina (3, 5, and 7 g/L) on the properties of a ternary Ni-Co-Al2O3 composite coating. EDX analysis was employed to investigate the effects of deposition current density and alumina bath loading on cobalt/nickel (Co/Ni) ratio and alumina content in the coatings. The results revealed that both the Co/Ni ratio and alumina content in the coatings increased with increasing current density and bath loading, but only up to certain thresholds (40 mA/m2 and 5 g/L). XRD analysis was conducted to assess the phase composition, crystal structure, crystallite size values, and preferred orientation of the fabricated EDCs. The mechanical properties of the deposited coatings were also evaluated using Vickers microhardness testing. The electrochemical corrosion behavior of the as-prepared EDCs was assessed using potentiodynamic polarization (Tafel) and electrochemical impedance spectroscopy (EIS) techniques. The 40 mA/cm2 and 5 g/L samples exhibited lower corrosion current density (jcorr), higher charge transfer resistance (Rct), and lower double layer capacitance (CPEdl) values, suggesting that the increased cobalt and alumina particles in the coatings improved the corrosion resistance. Consequently, the optimal current density and alumina bath content for achieving the most favorable properties were found to be 40 mA/m2 and 5 g/L, respectively.

3D Printed hybrid rocket fuels with μAl core-shell particles coated with polyvinylidene fluoride and polydopamine: enhanced combustion characteristics

3D printing technology enhances the combustion characteristics of hybrid rocket fuels by enabling complex geometries. However, improvements in regression rate and energy properties of monotonous 3D printed fuels have been limited. This study explores the impact of poly (vinylidene fluoride) and polydopamine-coated aluminum particles on the thermal and combustion properties of 3D printed hybrid rocket fuels. Physical self-assembly and anti-solvent methods were employed for constructing composite μAl particles. Characterization using SEM, XRD, XPS, FTIR, and μCT revealed a core-shell structure and homogeneous elemental distribution. Thermal analysis showed that PVDF coatings significantly increased the heat of combustion for aluminum particles, with maximum enhancement observed in μAl@PDA@PVDF (denoted as μAl@PF) at 6.20 kJ/g. Subsequently, 3D printed fuels with varying pure and composite μAl particle contents were prepared using 3D printing. Combustion tests indicated higher regression rates for Al@PF/Resin composites compared to pure resin, positively correlating with particle content. The fluorocarbon-alumina reaction during the combustion stage intensified Al particle combustion, reducing residue size. A comprehensive model based on experiments provides insights into the combustion process of PDA and PVDF-coated droplets. This study advances the design of 3D-printed hybrid rocket fuels, offering strategies to improve regression rates and energy release, crucial for enhancing solid fuel performance for hybrid propulsion.

Quantifying dispersion and light emission for aluminum powder suspensions with varied surface energy

The dust combustion of aluminum (Al) particles post ballistic impact was studied bi-spectrally in the visible (VIS) and near-infrared (NIR) using high-speed imaging. Powders were delivered loosely via a novel sabot design into a chamber and impacted an anvil at speeds of 1050 m/s. Two identically sized Al powders were studied, one was untreated (UN), the other processed using a thermal annealing and quenching treatment called superquenched (SQ). The SQ Al powder had reduced surface energy compared to UN Al powder, which was induced by the annealing–quenching treatment. Particle dispersion and emission during reaction was quantified by introducing a field emission fraction metric that characterizes the burning powder cloud and relates to particle combustibility. In the case of SQ Al, VIS light emission from dispersed powder decays slower compared to UN Al. High-speed NIR imaging shows UN Al agglomerates resulting in high concentrations of unreacted Al. The differences in powder dispersion and emission were attributed to different combustion regimes and further confirmed by x-ray diffraction analysis of post-burn products, which demonstrated different residue phase compositions. This study demonstrates that a field emission fraction is a quantitative analysis tool to simultaneously evaluate dispersion and emission of dust combustion.

The Effect of Various Surface Treatment on the New Digitally Manufactured Materials Versus the Conventional Materials – In Vitro Study

Background: Clinical benefits of resilient denture liners have been recognized in prosthodontic practice for many years. The elastic behavior of the soft lining materials is designed to distribute functional and non-functional stress on denture-supporting tissues. Materials and Methods: A total of 30 dumbbell-shaped test specimens were prepared from two different heat cure denture base materials. They are divided into two groups. Group (A) was prepared from heat cure poly-methylmethacrylate resin (PMMA) and Group (B) was prepared from computeraided design and computer-aided manufacturing (CAD/CAM) acrylic resin denture base material. A temporary soft-liner type was used. The denture base specimens of (Group A and Group B) were subdivided equally into three subgroups. 3 mm was marked and sectioned on the specimens with fissure burs and removed to create a uniform space for the application of soft liner. The interface surface of each specimen and the denture base resin surface were conditioned by three surface treatment modalities: 1 – specimens were polished using silicone carbide papers of grit size, 2 – using air abrasion by 50 μm aluminum oxide particle, 3 – by application of 3 M Scotchbond dental adhesive. Tensile bond strength (TBS) was tested for the specimens of each subgroup after thermocycling. Results: The mean of TBS of subgroup (A3) and subgroup (B3) specimens treated with 3M Scotch bond was significantly higher than the other subgroups. Conclusion: The surface treatment of PMMA and CAD/CAM denture base specimens with primer followed using an adhesive bond of 3M Scotch bond had an effective and superior TBS.

Investigation of the effects of alumina particle phase transition on internal flow field and engine performance in solid rocket motors

This study integrates theoretical modeling with numerical simulation methods to establish a comprehensive phase change dynamics model. The model encompasses critical stages of the phase change process, including undercooling, nucleation, solidification, and crystal phase transformation. We also utilize the latest drag coefficient model and heat transfer model in the two-phase flow field. Through numerical simulation, we delve into the impact of the phase change process of monodisperse particles on the flow field characteristics within a nozzle, extending our investigation to polydisperse particles phase change process. Furthermore, we systematically analyze the specific effects of variations in particle size distribution and particle loading on nozzle performance. In our simulation results, the most significant specific impulse enhancement was achieved under conditions of d43 = 2.63 μm and 20% particle loading, resulting in a specific impulse increase in approximately 0.53% compared to scenarios neglecting phase change. This work provides a solid theoretical foundation for accurately evaluating engine performance through numerical simulation.

Microstructure evaluation of Si-modified aluminide coatings on IN625 deposited by slurry aluminizing process

Si-modified aluminide coatings are promising for improving oxidation and corrosion resistance in superalloys at high temperatures. This study investigated the effect of different silicon levels in the aluminizing slurry on the morphology and structure of Si-modified aluminide coatings on IN625. This process involved spraying a slurry of aluminum and silicon particles in an aqueous PVA solution onto IN625 samples, followed by heat treatment under controlled conditions - two atmospheres (air and argon) and two heating ramps (regular and flash). Surface morphologies, cross-sectional structures, elemental compositions, and phase formations were analyzed using FE-SEM, SEM, EDS, and XRD methods, while DTA analysis assessed AlSi alloy formation during heating. The results showed that higher silicon content in the slurry increased silicon incorporation in the coatings but did not reduce aluminum activity enough to deposit a low-activity aluminide coating. The inert atmosphere (argon) and flash heating promoted the co-deposition of Si and Al, resulting in Cr and Mo silicide-enriched outer layers in some samples. The aluminum content in all slurries was sufficient for consistent β-NiAl formation across different silicon levels. The average silicon content in coatings ranged from 5 to 15 wt% and depended on the slurry composition and heat treatment conditions. The Al30Si slurry produced the thickest coatings (~90 μm), with further increases in Si leading to reduced thickness. This study suggests that slurry aluminizing can be optimized to control silicon incorporation, depositing Si-modified aluminide coatings for durable, high-performance applications.

The Impact of Nanocarbon Powder on the Characteristics of a Gel Propellant System with a High Concentration of Aluminum.

The addition of aluminum particles to a gel propellant has garnered attention through its potential for enhancing fuel properties. In order to enhance the energy performance of gel propellants, it is imperative to prepare gel propellants with high concentrations of aluminum. However, high-concentration aluminum-containing gels encounter two challenges. First, the combustion process leads to the agglomeration of aluminum particles, resulting in incomplete combustion. Additionally, elevated concentrations of aluminum particles increase the viscosity of the gel, impeding its atomization process and, subsequently, affecting combustion efficiency. These aforementioned issues pose practical obstacles for the application of high-concentration aluminum-containing gel propellants. In this research, a high-concentration aluminum-containing gel formulation was supplemented with nanocarbon powder. By investigating the impact of nanocarbon on various properties of the gel, its potential for addressing the above issues was analyzed. The investigation into the combustion performance of aluminum-containing gel blended with carbon powder revealed that the addition of 10 wt % nanocarbon powder to the gel system leads to a significant increase in the volumetric calorific value of the gel propellant by 21.21%. This enhancement not only improves the energy performance but also addresses the issue of incomplete combustion associated with aluminum. The rheology experiments conducted on gels demonstrate that the addition of nanocarbon powder results in an increased viscosity of the gel at lower shear rates, thereby enhancing its ability to withstand external disturbances during storage. Furthermore, this incorporation also enhances the gel's shear thinning properties, leading to a significant reduction in viscosity at higher shear rates and facilitating easier atomization of the gel system. In summary, the incorporation of nanocarbon powder can optimize the storage, atomization, and combustion processes of the gel, offering a straightforward and efficient approach to enhance the practical performance of metallized gel propellants.

Evaluating the remnants of Al2O3 particles on different dentine substrate after sandblasting and various cleaning protocols

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