Effect Of Al2O3 Addition Research Articles

Reaction mechanism, hygroscopic behavior, and properties of aluminum phosphate adhesive

The lack of basic research is a principal reason restricting the widespread application of aluminum phosphate adhesive, such as its reaction mechanism is not yet clear. Herein, we investigate the dissolution behavior of aluminum oxide (Al2O3) in acid aluminum phosphate (AAP) solution and the effects of Al2O3 addition, calcination temperature and phosphorus to aluminum (P/Al) ratio of the AAP solution on the thermal evolution, phase development and hygroscopic behavior of aluminum phosphate adhesive. The dissolution process of Al2O3 in AAP solution is controlled by external diffusion. The thermal evolution of aluminum phosphate adhesives is a complex process that is a function of Al2O3 addition and calcination temperature. Although it is a linear process, many of the reactions are largely coupled and occur simultaneously. The hygroscopic mechanism of aluminum phosphate adhesives is associated to the hydrophilicity of the hydroxyl groups (P–OH). Increasing the calcination temperature and the Al2O3 addition can improve the hygroscopicity resistance properties. Finally, the mechanical and dielectric properties of the quartz fiber cloth reinforced aluminum phosphate matrix composites (SiO2f/aluminum phosphate composites) were also investigated. The results demonstrate that the composites have the characteristics of light weight, high strength, and excellent dielectric properties, suggesting that they have attractive applications in radome materials.

Effects of Al2O3 addition on sintering behaviour, microstructure, and physical properties of Al2O3/vitrified bond CBN composite

The effects of Al2O3 content on the sintering behaviour, microstructure, and physical properties of Al2O3/vitrified bonds (SiO2–Al2O3–B2O3–BaO–Na2O–Li2O–ZnO–MgO) and Al2O3/vitrified bond cubic boron nitride (CBN) composites were systematically investigated using X-ray diffraction, differential scanning calorimetry, dilatometry, scanning electron microscopy, and X-ray photoelectron spectroscopy. Various amounts of Al2O3 promoted the formation of BaAl2Si2O8 and γ-LiAlSi2O6, increasing the relative crystallinity of the Al2O3/vitrified composite from 85.0 to 93.2%, resulting in residual compressive stress on BaAl2Si2O8, thereby influencing the thermal behaviour and mechanical properties of the Al2O3/vitrified composite. The bulk density, porosity, flexural strength, hardness, and thermal conductivity of 57.5 wt% Al2O3 sintered at 950 °C were 3.12 g/cm3, 6.1%, 169 MPa, 90.5 HRC, and 4.17 W/(m·K), respectively. The coefficient of thermal expansion of the bonding material was 3.83 × 10−6 °C−1, which was comparable to that of CBN, and the number of N–Al bonds were increased, which boosted the flexural strength of the Al2O3/vitrified CBN composite to 81 MPa. The excellent mechanical properties, compact structure, and suitable interfacial bonding state with the CBN grains of the Al2O3/vitrified composite make it a promising high-performance bonding material for superhard abrasive tools.

Effects of Al2O3 addition on microstructure and luminescence of transparent germanosilicate glass-ceramics with incorporated spinel Ga-oxide nanocrystals

Ga-oxide spinel nanocrystals are wide band gap systems, which can be incorporated in a glass matrix by phase separation mechanisms. In suitable conditions, this kind of processes can give rise to transparent nanostructured glass-ceramics with UV excitation and luminescence properties potentially interesting in several technological areas. Nanophase size dispersion and volume fraction have been demonstrated to be controllable, at some extent, by suitable thermal treatments for nucleation and nano-crystallization in low-alkali gallium germanosilicate system. Here we report the results on the role of Al2O3 additions on the microstructure and optical response of the glass-ceramics fabricated in this system. Data of differential scanning calorimetry, X-ray diffraction, transmission electron microscopy, absorption and fluorescence spectroscopy show that Al2O3 addition, up to 4.5 mol%, turns out to have a considerable impact on the size and number density of precipitated nanocrystals, which are solid solutions of γ-Ga2-xAlxO3 resulting from the partial incorporation of Al3+ ions into the crystalline phase. We show that the use of Al2O3 as an additive in the composition of gallium germanosilicates facilitates glass melting and leads to glass-ceramics with significantly modified photoluminescence characteristics such as decay lifetime and integrated intensity of light emission. The possible reasons are discussed.

Interfacial study for the effect of Al2O3 addition on the microstructure and micro-hardness of the Al2O3/AA6061 semi-solid cast composite

ABSTRACT Interfaces and processing input parameters are the two key potential candidates for an analysis of semi-solid cast composites. These elements are mostly influenced by various combinations such as pressurized solidifications, type and size of reinforcements particulates, cooling and solidification rate for an improvement in properties of composite/s. However, in this experimental study, Al2O3-reinforced AA6061 semi-solid cast composite is investigated according to the interfacial effect on the cast microstructure and its effect on micro-indentation hardness. In the synthesis, ball-milled Al2O3/Al powder was fed inside the AA6061 semi-solid melt under argon gas protection to prepare a slurry, which was flowed inside the mould via free vortex flow. Obtained results are analyzed according to interfacial mechanism and its effect of Al2O3 particles on the micro-indentation hardness for reinforcement, matrix, and interface regimes. Micro-indentation result shows an increment of 10.1% higher values for 4% Al2O3 addition for 2% Al2O3 addition.

Effect of Al2O3 addition on the microstructure and oxidation behavior of SiC coating prepared by pack cementation on C/C composites

The study addresses the effects of Al2O3 on the SiC coating fabricated by pack cementation by preparing coatings with different Al2O3 contents on C/C composite. After the in-depth analysis of various characterization results, including XRD, SEM, EDS, and XPS, the competition brought by Al2O3 between enhancing coatings qualities and affecting oxidation behaviors was revealed. One insight into the microstructure of as-prepared coatings is that Al2O3 could boost internal exchange and the diffusion of parent materials, which is conducive to resisting oxidation by improving the qualities of the layers. Another insight about the coating oxidation is obtained from the SiC–Al2O3 volatility diagram, where the multiple roles of Al2O3 plays in the transition of oxidative mechanisms are elucidated. The beneficial impact that stables the oxide layer and reduces the coating consumption takes the upper hand comparing to the adverse effect, including breaking the structure of SiO2.

Effect of Al2O3 Addition on Magnetoelectric Properties of Ni0.5Zn0.5Fe2O4/Ba0.8Sr0.2TiO3 Composite Ceramics

Effect of Al2O3 Addition on Magnetoelectric Properties of Ni0.5Zn0.5Fe2O4/Ba0.8Sr0.2TiO3 Composite Ceramics

Glass-ceramics in Li1+xAlxGe2-x(PO4)3 system: The effect of Al2O3 addition on microstructure, structure and electrical properties

Abstract Glass-ceramics of the Li1+xAlxGe2-x(PO4)3 series (0 ≤ x ≤ 0.65) was obtained by glass crystallization under the same conditions of heat treatment. The influence of the heating rate (1, 3 and 8 °C min−1) and the different heat treatment times (2, 8 and 12 h) on the lithium-ion conductivity of glass-ceramics were studied. The impact of Al2O3 addition on the phase composition, microstructure, transport properties and molecular structure of lithium germanophosphate was investigated by XRD, SEM, impedance spectroscopy and Raman spectroscopy, respectively. The obtained electrolytes have the NASICON-type structure with space group R-3c. Glass-ceramics is single-phase when 0.3 ≤ x ≤ 0.5, but impurity phases Li4P2O7, AlPO4, and GeO2 appear at x = 0.65. An increase in Al2O3 content leads to the formation of larger crystallites. A significant improvement in ionic conductivity was observed in Al-doped samples. The conductivity of undoped LiGe2(PO4)3 was found to be 4 orders of magnitude lower compared to the Al-doped solid electrolytes. Among the Li1+xAlxGe2-x(PO4)3 glass-ceramics, the composition of Li1·5Al0.5Ge1.5(PO4)3 (x = 0.5) has the highest lithium-ion conductivity, which is 5.03 × 10-4 S cm−1 at 25 °C. The electron conductivity of solid electrolyte at x = 0.5 is 4 × 10−9 S cm−1 at 25 °C. Ionic transference number was found to be close to 0.99.

Effect of Al2O3 addition on hardness and wear behavior of Cu–Al2O3 electro-less coated Ag nanocomposite

The present paper represents the experimental examination on the additions of Al2O3 coated Ag percent on the properties of Cu–Al2O3 coated Ag nanocomposites. With the object of enhancement dispersion of high weight fraction of Al2O3 nanoparticles and wettability in Cu matrix, nano Al2O3 particles were electroless coated via Ag particles. Four different Al2O3 content, 3, 6, 9 and 12wt.% are considered to highlight its effect on the characteristics of the fabricated nanocomposite. High-energy ball milling is applied for mixing powders and compaction and sintering are applying for consolidation. Microstructural explanations displayed a homogenous distribution of Al2O3. The relative density decreases with increasing the content of Al2O3 nanoparticles. In addition, microhardness is increased gradually via the addition of nano Al2O3 coated Ag. Sliding wear rate decrease via increasing the Al2O3 coated Ag nanocomposite content and increase with increasing the applied load. Also, the coefficient of friction decreases via increasing the nano Al2O3 coated Ag nanocomposite content and increasing applied load.

Effects of Al2O3 Addition on the Microstructure and Properties of CoCr Alloys

Aluminum oxide (Al2O3) powder can be added to typical cobalt-chromium (CoCr) alloy powders. In the present study, we successfully prepared alloyed samples of various powder ratios by laser cladding and analyzed their microstructure and carbide structural characteristics, including the microhardness, biological properties, morphology (using scanning electron microscopy), and crystal structure (using X-ray powder diffraction). The elemental distribution was also determined by energy-dispersive X-ray spectroscopy. The results showed that an Al2O3 addition caused the alloy microstructure to change from slender columnar crystals to columnar grains that were similar in shape to equiaxed grains. In addition, Al2O3 agglomeration zones appeared, and carbide structures were altered. The mechanism of the observed performance changes was also analyzed.

Mg-1Sn/Al2O3 biodegradable composites: effect of Al2O3 addition on mechanical, in-vitro corrosion and bioactivity response

The present work investigates the mechanical, corrosion and bioactive behaviour of Mg-1Sn reinforced with 5, 10 and 15 wt% of Al2O3 fabricated by squeeze casting route. The phase analysis and microstructure of as-cast composites were characterized by x-ray diffraction (XRD) and scanning electron microscope (SEM) coupled with energy dispersive spectroscopy (EDS) respectively. Mechanical properties were evaluated by conducting the compression test. In order to evaluate the in-vitro corrosion properties of as-cast composites, Tafel and electrochemical impedance spectroscopy (EIS) techniques were performed in simulated body fluid (SBF). In-vitro bioactivity test was also carried out in SBF for 7 days of immersion period. Compression test results have showed that the increase in Al2O3 content up to 10 wt% in Mg-1Sn matrix would increase the compression strength and deteriorate on further increase Al2O3 content. The similar trend was observed in case of corrosion behaviour indicating that beyond 10 wt% of Al2O3, both mechanical and corrosion properties diminish. However, bioactivity performance was almost similar in case of all the composites and was better compared to Mg-1Sn alloy without the addition of Al2O3. Hence, it was concluded that the addition of Al2O3 increases the bioactivity of the Mg-1Sn alloy and up to the 10 wt% addition would enhance the mechanical and corrosion properties and further increase in Al2O3 content, they seem to be declining.

Structure, electrical, dielectric and ferroelectric properties of (1 − x)BiFeO3 − xAl2O3 ceramics

Lead-free ferroelectric composite ceramics of (1 − x)BiFeO3 − xAl2O3 (x = 0.00, 0.02, 0.04, 0.06, 0.08 and 0.10) were synthesized using the traditional solid-state reaction method. The effects of Al2O3 addition on structural (crystal data and microstructure), ferroelectric, dielectric properties, and leakage current characteristic were investigated. X-ray diffraction and scanning electron microscopy demonstrated that the addition of Al2O3 promoted the formation of the secondary phases (Bi2Fe4O9 and Bi24Al2O39) and the average grain size significantly reduced from 1.49 μm for x = 0.00 to 0.45 μm for x = 0.10. The samples with Al2O3 addition had lower dielectric constant and dielectric loss. The Curie temperature (TC) decreased gradually from 475 °C for x = 0.02 to 390 °C for x = 0.10. Leakage current density decreased significantly with the addition of the Al2O3, and the leakage conduction mechanism was changed from Ohmic relationship to space charge limited conduction (SCLC) mechanism. The ferroelectric hysteresis loops became more typical in shape with the addition of the Al2O3.

Effect of Al2O3 addition with concentration (x=0.1%, 0.2%, 0.4%) mol on the crystal structure and physical properties of permanent magnets barium hexaferrite (BaO6Fe2O3)

The effects of Al2O3 addition with various concentration (x=0.1%, 0.2%, 0.4% ) mol on the change of crystal structure and magnetic properties in Barium Hexaferrite (BaO6Fe2O3) has been made and analyzed by bulk metallurgy processes with raw material element BaCO3, Fe2O3 and Al2O3. Raw materials are mixed and calcined at 1150°C for 1 hour. After calcinations, the powder is mixed with 3% seluna, then press with a compressive force of 8000 kgf. Physical properties analysis is obtained from measurements of density and porosity. While the material phase structure is determined by XRD test and for magnetic properties using VSM. In the XRD test results, it can be seen that the sample is dominated by BaO6Fe2O3 phase and Al2O3 phase, with the dominant phase being BaO6Fe2O3. The evaluation results obtained the best value at a concentration of x=0.4% (gr/mol) with an optimum density of 4.13 gr/cm3 which has a porosity of 1.3% and for magnetic properties and material structure at x = 0.4% mol a remanence value of 2.02 emu/g is produced with coercivity of 0.531 kOe.

Effects of Al2O3 addition on the DC--bias-superposition characteristic of the low-temperature-fired NiCuZn ferrites

Low-temperature-fired NiCuZn ferrites with Al2O3 (0–2 wt%) addition were prepared via the conventional solid-state reaction. The effects of different Al2O3 doping contents on phase composition, microstructure and magnetic properties, especially DC-bias-superposition characteristic, were investigated. Results indicated that the addition of an appropriate amount of Al2O3 content to NiCuZn ferrites could increase coercivity and the thickness of the nonmagnetic grain boundaries, thereby increasing the demagnetising field and subsequently reducing the decrease rate of the magnetic permeability under superposition magnetic fields. Simultaneously, permeability and saturation flux density monotonously decreased with the increase in Al2O3 doping content. With the addition of 1.5 wt% Al2O3, the sample obtained relatively high permeability (∼70.7) and perfect DC-bias-superposition characteristic (H70%–840 A/m). This ferrite material has favourable application prospects for recognising chip inductors that can carry large currents.

Effect of Al2O3 addition on texturing in a rotating strong magnetic field and densification of B4C

The properties of ceramics can be improved by controlling the microstructure through texturing ceramics in a strong magnetic field. Fabricating dense boron carbide (B 4 C) requires high temperature sintering, therefore sintering additives are often used in order to densify B 4 C ceramics at lower temperatures. However, combined effect of texturing and sintering additives on densification of B 4 C has not been made clear yet. Here we report the effect of alumina (Al 2 O 3 ) sintering additive on texturing in a strong magnetic field and densification of B 4 C. Texturing was performed by rotating superconducting magnet at 12 T during slip casting process. Electron backscatter diffraction (EBSD) was used to observed the texturing projection. {0001} plane is clearly oriented in the plane parallel to rotating magnetic field. In addition, Lotgering factor was also calculated as quantitatively evaluation of texturing degree. Results on densification showed that addition of Al 2 O 3 successfully increased density of B 4 C sintered by spark plasma sintering (SPS) at 1800 o C to 97.8%. Formation of aluminum borate (Al 5 BO 9 ) as secondary phase was detected by X-Ray diffraction (XRD). It is considered that the generation of Al 5 BO 9 assisted finer densification of B 4 C ceramic. Textured B 4 C sintered at 1700 o C by SPS without alumina addition exhibited the highest orientation of c-axis. Addition of alumina caused decrease in degree of orientation of c-axis.

Investigation of the Effects of Al2O3 Content and Cooling Rate on Crystallization in Fe2O3–CaO–Al2O3 System Using In Situ Confocal Laser Scanning Microscopy

Sinter is a major Fe source, that is, used extensively in blast furnace processes worldwide. The chemical and physical properties of sinter are crucial factors that affect the operating stability of blast furnaces. The quality of sinter is largely determined by the phase fraction of the silico‐ferrite of calcium and aluminum (SFCA), which is a low‐melting‐point bonding phase formed during sintering. Calcium ferrite (CF)‐containing alumina is known to be the structural basis for SFCA and SFCA‐1, and provides basic information regarding the influence of Al2O3 on the formation of CF solid solutions. In this work, experiments are conducted to investigate the crystallization behaviors of an Fe2O3–CaO–Al2O3 system based on its Al2O3 content and cooling rate. The effects of Al2O3 additions are used to analyze changes in the phase formation temperature, phase ratio, and rate of decrease by using an in situ confocal laser‐scanning microscope, optical microscope, electron probe micro analyzer, and horizontal tube furnace. The temperatures at which the primary phase forms for various Al2O3 contents and cooling rates differ from the equilibrium temperatures, and the phase‐formation temperature ranges vary with the cooling rate.

Effects of Al2O3 addition on nanocrystal formation and crystallization kinetics in (1-x)Li2B4O7-xAl2O3 glasses

Effects of Al2O3 addition on nanocrystal formation and crystallization kinetics in (1-x)Li2B4O7-xAl2O3 glasses

Effect of Al2O3 Addition on Characteristics of Al-4Cu-4Mg Composites Produced By Thixoforming Process

Abstract Aluminium matrix composites have been widely developed due to its lightweight, therefore, Al composites have been potentially used for many application especially for vehicle components. Al-4Cu-4Mg reinforced Al2O3 has been successfully produced by the thixoforming process. In this study, Al-4Cu-4Mg as a matrix phase was prepared from Al ingot, Cu plate and Mg ingot and these materials were heated at 750°C, then Al2O3 particles with various from 5vf-% to 20vf-% were added into molten Al-4Cu-4Mg to produce composites using stir casting method. The stir cast composite was heated at 640°C to semi-solid state temperature then press as called thixoforming process. The effect of Al2O3 addition on characteristics and microstructure of stir cast and thixoformed composites are studied. The results show that thixoformed composites have better properties than that of stir cast composites, such as hardness, porosity and wear resistance. The porosities of thixoformed composites are lower with less Al2O3 content than that of high Al2O3content. The microstructures of stir cast composites are generally dendrite structure while thixoformed composites are columnar and globular which contributed to having better characteristic than that of dendrite structures. The hardness and wear resistance of thixoformed composites are higher than that of stir cast composite. It is also showed that composite containing 10vf-% Al2O3 provides optimum mechanical properties for both stir-cast and thixoformed composites.

Effect of Al2O3 Addition on Mineralogical Modification and Crystallization Kinetics of a High Basicity BOF Steel Slag

Basic oxygen furnace (BOF) steel slag is a main byproduct that is produced during the converter steelmaking process. The volume instability and fast crystallization of BOF slag limits its added-value application. This article aims to understand the effect of Al2O3 on the mineralogical modification and crystallization kinetics of a high basicity BOF steel slag. Continuous cooling transformation and time–temperature–transformation curves were constructed to determine the crystallization characteristics of BOF slag. The critical cooling rate to vitrify the slag was experimentally obtained. The crystallization sequence was clarified by integrating in situ and post-mortem observations with thermodynamic calculations. The results suggest that the addition of Al2O3 can effectively remove free lime, decrease the melting point, and improve the glass formation ability of the high basicity BOF slag. Undercooling the slag is enhanced by increasing the cooling rate and/or adding Al2O3. By steering the addition of Al2O3 and the cooling rate, BOF slag can be modified to obtain a more amorphous phase, presenting an enhanced potential to be a binder for added-value applications.

Effect of Al2O3 addition on the non-isothermal crystallization kinetics and long-term stability of BCABS sealing glass for IT-SOFCs

Owing to adjustable thermal expansion performance, BaO–CaO–Al2O3–B2O3–SiO2 (BCABS) glass has a promising commercialization prospect for intermediate temperature-solid oxide fuel cells (IT-SOFCs) sealing. Herein, Al2O3 with two different contents was added into the same glass formulation, referred to as A and B glass, respectively. In terms of the non-isothermal crystallization kinetic behavior, the effect of Al2O3 as the unique intermediate was innovatively studied on the long-term performance of BCABS sealing glass. After the heat treatment at 1023 K for 100 h, the change of the network structure and the expansion coefficient of the glass were characterized. The results showed that the addition of Al2O3 as a network forming body could enhance the structure of glass, and increase the activation energy for glass transition, which could effectively inhibit the crystallization ability of sealing glass. Therefore, the B glass with the higher Al2O3 content showed the better long-term sealing ability, which was greatly beneficial for IT-SOFCs sealing.

Non-linear effects of alumina concentration on Product Consistency Test response of waste glasses

The effect of alumina mole fraction on the 7-day Product Consistency Test (PCT) responses, ln[NLα], of simulated nuclear waste glasses was examined. It was found that the effect is highly non-linear. At low mole fractions of Al2O3 (xAl2O3 ≤ 0.035) the effect of Al2O3 additions is highly negative (dlnNLαdxAl2O3 = −72). At intermediate concentrations (0.035 <xAl2O3 ≤ 0.19) the effect of Al2O3 additions is moderately negative (dlnNLαdxAl2O3 = −11). At high concentrations (0.19 <xAl2O3) the effect of Al2O3 additions is highly positive (dlnNLαdxAl2O3 = +21). This variable impact of Al2O3 on ln[NLα] is speculated to be caused by the rates at which the glass corrosion process changes through various reaction regimes in static conditions at 90 °C. A model for prediction of ln[NLα] as a function of glass composition is presented. This model represents the data from 2669 glass compositions spanning a broad nuclear waste glass composition region and it is useful up to much higher Al2O3 concentrations than previous models (from ∼10 to 25 mol% Al2O3). The model was validated using data subset validation methods and shown to predict validation data in the same composition region with roughly equal certainty as the model fit data. The potential causes for non-linear effects of Al2O3 on ln[NLα] were discussed in context of the progression of glass corrosion rates. Time resolved static corrosion data is needed to better understand these non-linear effects.