Size Of Al2O3 Research Articles

Cut/puncture resistance and mechanisms of protective composite textiles reinforced with inorganic powder

This study presents a soft-rigid unified structure (SRUS) textile composed of an inorganic powder (IP) reinforced epoxy resin block (EIPB) array and a soft textile substrate via a pattern-controllable integrated molding method. The influence of IP content and alumina particle size on the cut and puncture resistance of the resulting SRUS textile was systematically investigated. Furthermore, the anti-puncture and anti-cutting mechanisms of the SRUS textile were comprehensively evaluated based on the analysis of damage morphology and process. The experimental results demonstrated a significant enhancement in the puncture and cut resistance of the SRUS textile upon the incorporation of IP. Moreover, the cut/puncture resistance of the SRUS textile increased with an increase in IP content and the size of Al2O3, and the optimal cut/puncture resistance was observed at 60 mesh-50 wt.%. Additionally, the anti-puncture mechanism of the SRUS textile was attributed to the presence of hard passivation at the EIPB, as well as friction self-locking at the gaps. The anti-cutting mechanism was ascribed to the reverse cutting action exerted by the hard particles on the blade, preventing further penetration. Overall, these findings provide valuable insights into the underlying mechanisms that contribute to its enhanced protective performance.

Fabrication and luminescence properties of Al2O3-Ce:LuAG composite phosphor ceramics for solid-state laser lighting

Introducing Al2O3 as a secondary phase into Ce:LuAG phosphor ceramics has been realized by solid-state reaction method, but there is much room for improvement on the ingredient uniformity and performance of Al2O3-Ce:LuAG composite phosphor ceramics (CPCs). In this work, the excess of Al3+ in (Ce,Lu)3Al5O12 was regulated to synthesize a series of Al2O3-Ce:LuAG multiphase powders by the co-precipitation method, and homogeneous Al2O3-Ce:LuAG CPCs (the uniform volume fraction between Al2O3 and Ce:LuAG phases) were obtained by vacuum sintering (1775 °C × 10 h). With an increase in the Al3+ content, the morphology of the multiphase powders changes from small irregular shapes to porous flocs and flakes interwoven, and Lu3Al5O12 phases tend to convert to LuAlO3 phases. When the Al2O3 content is 78–89 mol% in the CPCs, the average grain sizes of Al2O3 are close to those of Ce:LuAG. Among all CPCs with an Al2O3 content of 68–95 mol%, the 85 mol% Al2O3-Ce:LuAG CPCs initially perform the best in terms of both excitation and emission intensity at room temperature, and their photoluminescence intensities only decrease 4.3% from 25 to 225 °C. A solid-state laser lighting device was constructed by using a 450 nm laser source and Al2O3-Ce:LuAG CPCs in a reflection mode. The CPCs with 85 mol% Al2O3 content based on 0.9 W laser diodes (LDs) show the optimum luminous flux (LF) and luminous efficiency (LE) of 244 lm and 266 lm∙W−1, respectively. Additionally, the LF of all CPCs based on LDs continues to increase without showing luminescence saturation when the power density increases from 1 to 20 W mm−2. When the 85 mol% Al2O3-containing CPCs are excited by a 20 W mm−2 LD, the maximum LF reaches 3624 lm, and the LE decreases only by 12.4% (compared to the data under 1 W mm−2 excitation). Al2O3-Ce:LuAG CPCs have excellent luminescence properties and improved thermal stability, which are promising for the application in solid-state laser lighting.

Al2O3–Ce:YAG composite phosphor ceramics for white laser lighting: Novel preparation and regulatable properties

AbstractIn this work, a series of Al2O3–Ce:YAG phosphor powders were synthesized by regulating the excess Al3+ of (Y,Ce)3Al5O12 via coprecipitation method for the first time, where Al3+, Ce3+, and Y3+ elements were uniformly distributed. With the increase of Al3+ content, the morphology of the powders changed from wormlike shapes to flaky shapes, and Y3Al5O12 phases had a tendency to convert to YAlO3 phases. The x wt.% Al2O3–(Y0.999Ce0.001)3Al5O12 (x = 20, 30, 40, 50, 60, and 70) composite phosphor ceramics (CPCs) were obtained by vacuum sintering (1775°C × 10 h), where Al2O3 and Ce:YAG phases were also well‐distributed. When the Al2O3 content was 30–40 wt.%, the average grain size of Al2O3 was close to that of Ce:YAG. A solid‐state laser lighting device was constructed by a 450 nm laser source and CPCs in a reflection mode. By adjusting the laser power, the correlated color temperature (CCT) values of white laser diodes (LDs) were achieved close to the standard white light of 6500 K. Impressively, the white LDs equipped with the 40 wt.% Al2O3‐containing CPCs showed the optimum CCT of 6498 K (color coordinates: 0.31 and 0.38), as well as a high luminous flux of 1169 lm and efficiency of 166 lm/W at the LD power of 7.05 W. This work has provided a potential idea to optimize the composition uniformity of Al2O3–Ce:YAG CPCs as also to explore their excellent performance in the application of white laser lighting.

Microstructure and oxidation behavior of the Y/Ta/Hf co-doped AlCoCrFeNi high-entropy alloys in air at 1100 ℃

The grain morphology and oxidation behavior of the Y/Ta/Hf co-doped AlCoCrFeNi high-entropy alloy (HEA) were investigated in air at 1100 ℃. The Y/Ta/Hf co-doped significantly improves the high-temperature oxidation resistance of the alloy. Hf doped AlCoCrFeNiYTa HEA presents the larger grain sizes of Al2O3, which effectively reduces the inward diffusion of O along the grain boundaries. In addition, Y/Ta/Hf co-doped AlCoCrFeNi HEA accelerates the transformation metastable Al2O3 to α-Al2O3. The oxide pegs formed at the oxide/substrate interface have a positive effect on improving the adhesion of the oxide scale, and Ta increased the probability of oxide peg formation.

Effect of Doping Content of MgO on Solar Absorptivity to IR Emissivity Ratio of Al2O3 Coatings

High-emissivity coatings are often used on the surfaces of solar probes to block heat from the sun. Therefore, improving the thermal control ability is the standard for determining the quality of the coatings. In this study, MgO was doped into Al2O3 to improve the thermal control ability of the coatings and to analyse the effect of different MgO doping contents. The solar absorptivity to infrared (IR) emissivity ratio (α/ε) was used to evaluate the thermal control ability of the coatings. The results showed that 5 wt.% MgO doping content is the best choice. The main reason for the change in α/ε is related to the doping of MgO, which affects the grain size of Al2O3.

Experimental Investigation of Thermal Conductivity of Alumina (Al2O3)-Multi-Walled Carbon Nanotubes (MWCNT) in Water-Ethylene Glycol Hybrid Nanofluid

Thermal conductivity and stability of hybrid nanofluid containing Al2O3and MWCNT nanoparticles (90:10 weight% or 87:13 volume%) in the base fluid of Water and Ethylene Glycol (EG) mixture (80:20 volume%) had been experimentally investigated. Nanofluid was prepared using the two-step method, i.e., by dispersion the nanoparticles into base fluid using ultra-sonication. The stability of nanofluids was determined by UV-VIS-NIR spectroscopy by measuring maximum absorbance (along with the corresponding wavelength) for all samples. CTAB surfactant of 1/10th weight of nanoparticle was used to prevent agglomeration. The nanofluid absorbance was observed after 1, 10, 20 and 30 days of storage. Nanofluid having a concentration of 0.028%, was found to be stable up to 20 days. Higher concentrations or longer duration made the nanofluid unstable within 20 days. Thermal conductivity measurements were conducted in the temperature range T = 25 °C–50 °C (6 levels) and volume concentrationφ= 0.004%–0.028% (8 levels). Scherrer’s equation was applied to XRD data to compute the average crystalline size of Al2O3nanoparticles as 43 nm. FESEM showed good morphology of nanoparticles. EDX stoichiometric analysis confirmed that the nanofluid contained only Al, O, C elements. Experimental results showed that thermal conductivity increases with an increase in volume concentration and temperature. Maximum thermal conductivity of 0.5416 W/mK (8.47% increase over base fluid) was observed at T = 50 °C andφ= 0.028%. Maxwell, Weber, Hashin-Shtrikman, Bruggeman’s theoretical models and their experimental data showed a significant deviation. Hence regression equations that are suitable for these data were developed for better prediction purposes.

One-Pot Synthesis of Alumina-Titanium Diboride Composite Powder at Low Temperature.

Alumina-titanium diboride (Al2O3-TiB2) composite powders were synthesised via aluminothermic reduction of TiO2 and B2O3, mediated by a molten chloride salt (NaCl, KCl, or MgCl2). The effects of salt type, initial batch composition, and firing temperature/time on the phase formation and overall reaction extent were examined. Based on the results and equilibrium thermodynamic calculations, the mechanisms underpinning the reaction/synthesis processes were clarified. Given their evaporation losses at test temperatures, appropriately excessive amounts of Al and B2O3 are needed to complete the synthesis reaction. Following this, phase-pure Al2O3-TiB2 composite powders composed of 0.3–0.6 μm Al2O3 and 30–60 nm TiB2 particles were successfully fabricated in NaCl after 5 h at 1050 °C. By increasing the firing temperature to 1150 °C, the time required to complete the synthesis reaction could be reduced to 4 h, although the sizes of Al2O3 and TiB2 particles in the resultant phase pure composite powder increased slightly to 1–2 μm and 100–200 nm, respectively.

Microstructure refinement-homogenization and flexural strength improvement of Al2O3 ceramics fabricated by DLP-stereolithography integrated with chemical precipitation coating process

In this study, the chemical precipitation coating (CP) process was creatively integrated with DLP-stereolithography based 3D printing for refining and homogenizing the microstructure of 3D printed Al2O3 ceramic. Based on this novel approach, Al2O3 powder was coated with a homogeneous layer of amorphous Y2O3, with the coated Al2O3 powder found to make the microstructure of 3D printed Al2O3 ceramic more uniform and refined, as compared with the conventional mechanical mixing (MM) of Al2O3 and Y2O3 powders. The grain size of Al2O3 in Sample CP is 64.44% and 51.43% lower than those in the monolithic Al2O3 ceramic and Sample MM, respectively. Sample CP has the highest flexural strength of 455.37±32.17 MPa, which is 14.85% and 25.45% higher than those of Samples MM and AL, respectively; also Sample CP has the highest Weibull modulus of 16.88 among the three kinds of samples. Moreover, the fine grained Sample CP has a close thermal conductivity to the coarse grained Sample MM because of the changes in morphology of Y3Al5O12 phase from semi-connected (Sample MM) to isolated (Sample CP). Finally, specially designed fin-type Al2O3 ceramic heat sinks were successfully fabricated via the novel integrated process, which has been proven to be an effective method for fabricating complex-shaped Al2O3 ceramic components with enhanced flexural strength and reliability.

Study on the Al2O3p/Al composites prepared by Al-calcined kaolin system

In this study, in-situ Al2O3p/Al composite was prepared by the exothermic dispersion method from Al-calcined kaolin system. Thermodynamic analysis was carried out by calculating Gibbs free energy. The reaction kinetics of the system was studied by differential scanning calorimetry and Kissinger equation. The effects of heating temperature and holding time on the microstructure of the composites were analysed. The results showed that the reaction activation energy of the system continued to increase with the progress of the reaction. With the extension of the reaction time at 800°C, the particle size of Al2O3 increased slowly. When the holding time was 50 min, the density and hardness of the composite material were 2.7 g cm−3 and 64HV respectively.

Distribution characteristics of inclusions along with the surface sliver defect on the exposed panel of automobile: A quantitative electrolysis method

The specific distribution characteristics of inclusions along with the sliver defect were analyzed in detail to explain the formation mechanism of the sliver defect on the automobile exposed panel surface. A quantitative electrolysis method was used to compare and evaluate the three-dimensional morphology, size, composition, quantity, and distribution of inclusions in the defect and non-defect zone of automobile exposed panel. The Al2O3 inclusions were observed to be aggregated or chain-like shape along with the sliver defect of about 3–10 µm. The aggregation sections of the Al2O3 inclusions are distributed discretely along the rolling direction, with a spacing of 3–7 mm, a length of 6–7 mm, and a width of about 3 mm. The inclusion area part is 0.04%–0.16% with an average value of 0.08%, the inclusion number density is 40 mm−2 and the inclusion average spacing is 25.13 µm. The inclusion spacing is approximately 40–160 µm, with an average value of 68.76 µm in chain-like inclusion parts. The average area fraction and number density of inclusions in the non-defect region were reduced to about 0.002% and 1–2 mm−2, respectively, with the inclusion spacing of 400 µm and the size of Al2O3 being 1–3 µm.

Influence of sandblasting parameters and luting materials on microshear bond strength to a CAD/CAM hybrid ceramic material

Objective: To assess the influence of sandblasting parameters (applied pressure and grain particle size) on the microshear bond strength (μSBS) of Vita Enamic (VE) CAD/CAM hybrid ceramic to two different resin cements. Materials and Methods: One-hundred VE specimens were fabricated and allocated to 5 pretreatment groups (n=20/group): no treatment, 50 μm Al2O3 (2 bar), 50 μm Al2O3 (3.5 bar), 110 μm Al2O3 (2 bar) and 110 μm Al2O3 (3.5 bar). After pretreatment, surface roughness (Ra) was determined using a profilometer. The topography of pretreated surfaces was examined with Scanning Electron Microscopy (SEM). Each group was further divided into two subgroups according to type of luting material; subgroup (a): G-CEM LinkAce and subgroup (b): Single bond universal and RelyX Ultimate. After bonding, μSBS was measured with a Universal Testing Machine. Data were statistically analyzed using ANOVA and Tukey HSD tests (α=.05). Results: Specimens air-abraded with 110 μm Al2O3 and pressure 2 bar showed the highest but insignificant μSBS compared to other sandblasted groups (P 50 μm (2 bar) > 110 μm (3.5 bar) > 50 μm (3.5 bar) > control. Regardless the Al2O3 size, μSBS improved when sandblasting pressure was 2 bar while decreased with 3.5 bar groups. RelyX Ultimate showed higher μSBS than G-CEM LinkAce. Conclusions: Sandblasting of VE surface by (2 bar) pressure and the use of conventional resin cement in association with universal adhesive system were required to achieve satisfactory bond strength values.

Modeling and Optimization of the Fabrication of Al<sub>2</sub>O<sub>3</sub>- Based Ceramocomposites Reinforced with Carbon Nanotubes

The physico-mechanical properties of ceramic-matrix Al2O3-based composites are strongly influenced by the particle size of Al2O3, the presence of carbon nanotubes (CNTs), and the temperature regimes of sintering. In order to obtain the very low porosity ceramic composites with high rates of flexural strength and crack resistance, mathematical models were developed for grinding the particles of Al2O3 and spark plasma sintering of the composite. Mathematical models were based on the equations of the balance of the number of particles by size taking into account their grinding (for the grinding stage), the balance of pores in the composite by the size (for the sintering stage). The kinetic parameters of mathematical models were determined and a good agreement was reached between the calculated and experimental results. The developed models were used to determine the optimal modes of grinding and sintering stages, which made it possible to obtain, in particular, the composite Al2O3 - CNT (20 vol. %) with bending strength 540 MPa, and crack resistance 6.3 MPa·m1/2.

Processing and characterization of fiber-reinforced and layered alumina - graphene composites

The aim of the present contribution is the processing and characterization of fiber-reinforced and layered alumina - graphene composites, prepared by the combination of electrospinning, calcination, chemical vapor deposition (CVD) and spark plasma sintering (SPS). The fiber-reinforced composite contains homogenously distributed graphene-coated polycrystalline alumina microfibers in the Al2O3 matrix. The layered composites contain Al2O3 layers and layers of graphene-coated alumina microfibers or layers of graphene-coated alumina grains of submicron size. The systems with high density, 99.5–99.9 %, show different grain sizes of Al2O3 in their constituents, changing from 0.08 to 1.9 μm in comparison to the monolithic alumina with the average grain size of 2.6 μm. The composites and their layers show increased electrical conductivity, hardness, and fracture toughness by approximately five orders of magnitude, 31 %, and 8%, respectively, in comparison to the monolithic alumina due to the presence of graphene layers, small grain-sized alumina, and microfibers in the composites.

Mechanical Properties and Fabrication of a Nanostructured Nb-Al2O3 Composite by High Frequency Induction Heating

Al2O3 has a high Young’s modulus (380 GPa), a low density (3.98 g· cm-3), good high-temperature mechanical properties, biocompatibility and excellent oxidation resistance. Al2O3 has been used for automotive, aerospace, bio-materials and various industrial applications. Despite its various merits, the low fracture toughness of the material below the brittle-ductile transition temperature has limited its use for wide application. To enhance its fracture toughness, the method commonly utilized has been to make a composite by the addition of a second phase to fabricate nanostructured materials. In the study, nano-powders of Al2O3 and Nb were synthesized during the ball milling according to the reaction(Nb2O5 + 10/3 Al → 2Nb + 5/3 Al2O3). The nanostructured Nb-Al2O3 composite was consolidated within a short time from the milled powders using high-frequency induction heated sintering. The average grain sizes of Al2O3 and Nb in composite sintered at 1400 °C were 63 and 250 nm, respectively. The relative density of the Nb-Al2O3 composite was about 99% under the simultaneous induced current and application of 80 Mpa pressure. The fracture toughness and hardness of the composite were about 8.7 MPa· m1/2 and 1460 kg/mm2, respectively. The fracture toughness of the nanostructured Nb-Al2O3 composite was higher than that of monolithic Al2O3. (Received June 7, 2019; Accepted September 10, 2019)

The Condition of Ni-Cr Alloy Surface After Abrasive Blasting with Various Parameters

The parameters of abrasive blasting process directly affect the condition of the metal surface, changing the degree of surface roughness and wettability, depending on the size of the used particle, the pressure or type of abrasive. The aim of this study was to analyze the condition of Ni-Cr alloy surface after abrasive blasting using various process variants. The samples were blasted by Al2O3 abrasive using various particle sizes and pressures of the process. Basic and specific roughness parameters were investigated, and a surface wettability test was performed, and the percentage share of abrasive particles penetrated in the surface after abrasive blasting was also examined. The most considerable differences in the condition of the surface were observed with the change in the particle size of Al2O3. Statistical analysis confirmed the statistical significance of all these relationships.

Assessment of the nano-fluid effects on the thermal reactivity feedback coefficients in the VVER-1000 nuclear reactor with nano-fluid as a coolant using thermal hydraulic and neutronics analysis

Increasing efficiency and improving energy consumption in the nuclear power plants have always been of interest for researchers. So, they try to improve the heat transfer in the applied systems. Hence, extensive research has been performed to apply an alternative fluid which has more suitable thermal properties instead of the conventional fluids such as water. One of these efforts is application of nanoparticles in a coolant fluid. The most important advantage of the nanoparticles is increase of the thermal conductivity and heat transfer coefficient. Considering the importance of the nanofluids effect as a coolant in the nuclear reactors on the reactor dynamic parameters, in this paper, for the first time, fuel and coolant temperature reactivity coefficients which have important contribution in the dynamic analysis and safety requirements of the nuclear reactors, are calculated in a VVER-1000 Nuclear Reactor with nanofluid as a coolant. In this study, using different volumetric percentages and sizes of Al2O3 (Alumina) nanoparticle, the important and fundamental parameters of the VVER-1000 reactor, including dynamic reactor parameters such as temperature reactivity coefficients are calculated. For this purpose, at the first, the equivalent cell of the fuel rod and the surrounding coolant nanofluid are simulated in the hexagonal fuel cell of the VVER-1000 reactor. Then, the thermal hydraulic calculations are carried out at different concentrations and sizes of the nanoparticle and their effects on the heat transfer parameters such as the heat transfer coefficient, temperature of coolant and fuel are assessed. Also, using the neutron calculating codes, the reactor core is simulated and the effect of coolant and fuel temperature changes on the effective multiplication factor is calculated and analyzed. Through the thermal hydraulic and neutronics calculations, the fuel and coolant temperature reactivity coefficients are calculated and analyzes versus variation of the concentration and size.

Coagulation of the Ionized Combustion Products in a Dust Flame of Aluminum Particles

The addition-agent effect of atoms of alkali metals (K, Na, Li, and Cs) and halogens (Cl and I) introduced into the combustion zone of a dust flame of aluminum particles on the average size of Al2O3 nanoparticles is studied. A physical model of coagulation of a monodisperse aerosol is proposed. The model takes into account the formation of a complex plasma consisting of positive and negative ions, electrons, neutral gas molecules, and suspended particles of the condensed phase in the combustion zone. The effect of the forces of Coulomb repulsion of unipolarly charged Al2O3 particles as well as their possible attraction by ion wind on the constant of the coagulation rate is also taken into account. It is shown that at low ion concentrations in the plasma, the coagulation rate is determined by the Coulomb repulsion of the particles, and at ion concentrations greater than 1020 m−3 the coagulation rate is determined by the attraction of the particles by the ion wind. The results of calculations of the dependence of the average Al2O3 particle size on the concentration of the additives are in a good quantitative agreement with the experimental data. The combined effect of the additives and the equilibrium products of aluminum oxide (AlO, Al, and Al2O) evaporation on the concentration of positive and negative gas ions, electrons, and Al2O3 particle size in the condensation zone is analyzed. The peculiarities of the influence of the additives of electronegative gases (Cl and I atoms) on the coagulation rate of a thermally ionized aerosol and on the particle size of Al2O3 are considered.

Cathodic plasma electrolytic deposition of ZrO2/YSZ doped Al2O3 ceramic coating on TiAl alloy

Abstract ZrO2/yttria-stabilized zirconia (YSZ) doping Al2O3 ceramic coating was fabricated via cathodic plasma electrolytic deposition (CPED) technique. The microstructures and the chemical and phase compositions of the doped coating were characterized, the mechanical properties and the high temperature oxidation resistance were evaluated, and the doping mechanism was also discussed in detail. The results showed that, doped Zr4+ and Y3+ ions could effectively reduce the working voltage during CPED process and increase the content of metastable γ-Al2O3 in the coating. Accordingly, the doped ZrO2/YSZ significantly refined the grain size of Al2O3, as well as remarkably improved the high temperature oxidation resistance, the micro-structural compactness and hardness of the Al2O3 CPED coating. This study displayed here constructed an efficiently method for the fabrication of multifunctional coating on the surface of TiAl alloy.

Alumina nanoparticles size and crystalline phase impact on cytotoxic effect on alveolar epithelial cells after simple or HCl combined exposures

Applications using alumina nanoparticles (Al2O3 NPs) have incredibly increased in different fields of activity. In defense and aerospace fields, solid composite propellants use leads to complex combustion aerosols emissions containing high concentrations of Al2O3 NPs and hydrogen chloride gas (HCl). To better characterize potential hazard resulting from exposure to these aerosols, this study assesses cytotoxic effects of mixtures containing both compounds on human pulmonary alveolar epithelial cells (A549 cell line) after 24 h exposures.After all co-exposures cell viability was >80%. However co-exposures decrease normalized real-time cell index. Significant decreases of intracellular reduced glutathione pool were also observed after co-exposures to γ-10 nm or γ/δ-13 nm Al2O3 NPs and HCl. Co-incubations with γ/δ-13 nm or γ-500 nm Al2O3 particles and HCl induced significant DNA double-strand breaks increases. Moreover all co-exposures and HCl alone disrupted cell cycle (increased G1 phase cells). Transmission Electron Microscopy (TEM) observations revealed γ/δ-13 nm Al2O3NPs adsorption and internalization in cell cytoplasm only, suggesting indirect genotoxic effects.According to our results Al2O3 particles/HCl mixtures can induce cytotoxic effects and Al2O3 size and crystallinity are two main parameters influencing cytotoxic mechanisms.

Influence of Carbon Content on Aluminothermic Reduction of Ilmenite During Hot Pressing

Al2O3-TiCN-Fe composites were successfully prepared by hot pressing using natural ilmenite, aluminum, and carbon. The process of aluminothermic reduction of ilmenite and the influence of carbon on the phase evolution, synthetic products, microstructure, and properties were investigated using x-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), and mechanical analysis. The XRD results showed that the reduction process of the FeTiO3-2Al system was a gradual deoxygenation process. In the FeTiO3-2Al-xC systems, carbon participates in the reduction reaction to form TiN, which gradually transforms to TiCN. The carbon content had a great influence on the presence of titanium oxides during the reaction. In addition, the grain size of Al2O3, TiCN, and Fe phases became smaller as the carbon content was increased. When the carbon content was 0.88 mol, the synthesized products achieved comprehensive mechanical properties, i.e., bending strength and Vickers hardness of 375 MPa and 15.5 GPa, respectively.