Increasing Al2O3 Content Research Articles

Pilot-Scale Aluminothermic Production of Silicon Alloy and Alumina-Rich Slag.

As global demand for silicon (Si) and alumina continues to surge, the significance of developing more sustainable production methods has intensified. The SisAl process represents a path-breaking approach to producing Si and alumina by utilizing side streams from the silicon and aluminum industries. In the present work, a comprehensive series of pilot-scale trials was conducted to assess the scalability and validity of the SisAl process. The influences of reductant raw materials, charging methods, input material ratios, and other processing parameters were also investigated. On coupling between thermodynamic calculations and experimental results, it was demonstrated that the SisAl process is stable and controllable at a pilot scale. The typical composition of the produced Si alloy ranges from 70 to 75 wt % Si, 15-18 wt % Ca, and 8-10 wt % Al. The produced CaO-Al2O3-based slag has a composition of 48-57 wt % Al2O3, 40-45 wt % CaO, and 3-13 wt % SiO2. Furthermore, various reductants, including Al blocks, dross, and scraps, were evaluated in the pilot trials, yielding comparable outcomes, with alloy composition differences only within approximately 3 wt % under the same parameter conditions, demonstrating the versatility of raw materials selection in the SisAl process. Moreover, it was found that acidic slag exhibited better features for future upscaling than the neutral slags, with a 5 wt % higher Si content in the alloy and a 4 wt % increase in Al2O3 content in the slag phase. Additionally, the chemical composition of the products was shown to be controllable by adjusting the stoichiometry of the input materials (Al/SiO2 ratio). As the charged stoichiometry increases from 1 to 1.2, the Si content in the alloy significantly decreases from 73 to 63 wt %, while the Al content correspondingly increases from 9 to 18 wt %. Further investigation into processing parameters, such as charging method, slag prefusion, and stirring methods, has also revealed valuable insights toward the continued upscaling of the SisAl process to a potentially innovative, sustainable, low-carbon industrial process.

Effect of Al2O3 on the sintering process and the metallurgical performance of sinter

ABSTRACT The trend to process iron ore with increasing Al2O3 content has affected the performance of sinter and blast furnace operations. Formation of the primary melts and phase properties such as morphology and reducibility of the iron ore could be easily influenced by the Al2O3 content. In this paper, the effect of the Al2O3 content in the sinter samples, which range from 1.49 to 3.24 wt-% with a basicity of 2.0, MgO/Al2O3 ratio of 1.05, on the sintering process and the metallurgical performance were studied through a sinter pot experiment and a reduction experiment. The results show that an increase in the Al2O3 content deteriorated the sintering index, and the yield and tumble index decreased by 7.61% and 12.02%, respectively. The sintering index was relatively stable when the Al2O3 content was between 2.10 and 2.95 wt-%. Low-reduction columnar silico-ferrite of calcium and aluminum increased with the increasing Al2O3 content, hindered the reduction index of the sinter. The low-temperature reduction degradation index change was only around 2%, due to the higher MgO content of the sinter promoting magnetite formation.

Effects of sintering method and Al2O3 content on microstructure and mechanical properties of WC-10Co cemented carbide

Ultra-high toughness and ultra-high hardness WC-10Co-xAl2O3 cemented carbides were successfully prepared by vacuum liquid phase sintering (VS) and spark plasma sintering (SPS) using ultrafine WC and commercial Co powders as raw materials, respectively. The effects of nano-Al2O3 content and sintering process on the relative density, average grain size, microstructure and mechanical properties of WC-10Co alloys were investigated. The results showed that the densification degree of the samples decreased with the increase of Al2O3 content. In addition, the relative densities of the samples prepared by SPS were lower than those of the samples prepared by VS. For the samples prepared by VS, the average grain size increased first and then decreased as the Al2O3 content increased from 3 wt% to 9 wt%, and the percentage of coarse grain showed the same trend. When the addition of Al2O3 was 6 wt%, the average grain size reached the maximum value of 1.39 ± 1.03 μm. Meanwhile, the sample with 6 wt% Al2O3 had a typical inhomogeneous dual-grain structure, and the percentages of fine grain (< 1 μm) and coarse grain (> 1 μm) were about 50%, which displayed the highest fracture toughness of 18.59 MPa·m1/2. The dual-grain structure not only improved the toughness, but also compensated the loss of hardness. However, for the samples prepared by SPS, with the increase of Al2O3 content, the average grain size of WC decreased, while both hardness and toughness were continuously improved. When the Al2O3 content increased to 9 wt%, the grain size reached the minimum value of 0.25 ± 0.08 μm, and meanwhile, the hardness and toughness reached the maximum value of 19.69 GPa and 12.29 MPa·m1/2, respectively. Moreover, as the Al2O3 content increased, the transverse rupture strength (TRS) of the samples prepared by VS increased first and then decreased, and the TRS of sample with 3 wt% Al2O3 reached the maximum value of 1410 MPa. However, the TRS of the sample prepared by SPS showed a decreasing trend.

Impact of high Al2O3 content on the microstructure, mechanical properties, and wear behavior Al–Cu–Mg/Al2O3 composites prepared by mechanical milling

Metal matrix composites are increasingly being recognized as new wear-resistant materials. The main purpose of this study is to investigate the microstructure, mechanical properties, and wear resistance of Al–Cu–Mg alloy matrix composites reinforced with high contents of Al2O3 particles. Moreover, the effects of 10, 20, and 40 wt% Al2O3 contents on the microstructure, mechanical properties, and dry wear resistance of the Al–Cu–Mg matrix composites are studied. The results show that the θ (CuAl2) phase ratio increases with increasing Al2O3 contents. The hardness values of the samples also increase with increasing Al2O3 contents. The highest tensile and flexural strengths are measured as 284 and 562.9 MPa, respectively, and these values are obtained for the composite material reinforced with 10 wt% Al2O3 particles. The continuous increase in the hardness of the samples with increasing Al2O3 content may cause the lowest volume loss for the 40 wt% Al2O3-reinforced composite. The friction surfaces show that the wear surfaces comprise adhesion, delamination, and smear layers. Overall, compared to the Al2O3-reinforced composite samples, pure Al–Cu–Mg alloy samples show approximately 2 times more mass gain.

Effect of Al2O3/Ga2O3 ratio on the structure and luminescence properties of Sm3+ doped SrO-Nb2O5-Al2O3-Ga2O3-SiO2 glasses

The Sm3+ doped SrO-Nb2O5-Al2O3-Ga2O3-SiO2 glasses in this work were prepared using the conventional melt quenching method. The effects of Al2O3/Ga2O3 ratio on the structure and orange light emission properties were studied by XRD, Raman spectroscopy, spectrophotometer and J-O theory, respectively. With the increase of Al2O3 content, the absorption coefficient of the glass sample gradually increases, which might be attributed to an increase in non-bridged oxygen bonds caused by a change in the glass network structure. Under 403 nm excitation, the emission spectra show clear peaks at 602 nm and 649 nm, representing the 4G5/2 → 6H7/2, and 4G5/2 → 6H9/2 transitions, respectively. When the Al2O3/Ga2O3 ratio is 0.25, the sample luminescence intensity is the highest, and the emission cross section of A2 glass sample is 4.34 × 10−22 cm2. The CIE color coordinates, color purity, and color temperature values of all samples were determined, and they were all located in the orange-red light region. The experiments results reveal that the prepared silica-aluminum-gallium glasses has a potential application prospect in orange-red LEDs, solid state lasers and other fields.

Effect of Al2O3 and CaO/SiO2 ratio in slag on the cleanliness of bearing steel GCr15

This study investigates the effect of Al2O3 content (ranging from 30% to 38%) and the CaO/SiO2 ratio (ranging from 4 to 7) in LF refining slag at 1600 °C on the cleanliness of bearing steel through laboratory experiments. The driving forces (concentration difference ΔC) of four inclusions (Al2O3, MgO-Al2O3, Mg4Al2O7, and MgO) in the CaO-SiO2-Al2O3-5% MgO slag as well as the slag viscosity (η) at 1600 °C were calculated by Factsage 8.1 software. The relationship between ΔC/η (specifically for MgO·Al2O3 inclusions) and the cleanliness of bearing steel was investigated. The results show that the steel-slag reaction significantly reduces the total oxygen content, inclusion number density, and area fraction within the molten steel, thereby augmenting its cleanliness. With increasing Al2O3 content and CaO/SiO2 ratio in the slag, a notable trend of initial decline followed by subsequent increase is observed in both total oxygen content and total inclusion number density and area fraction within the molten steel. The LF slag composition is suggested to comprise 32% Al2O3, with a CaO/SiO2 ratio of 6. The ΔC/η ratio of MgO·Al2O3 inclusions shows a positive correlation with the apparent rate constant of oxygen removal (ko) while exhibiting a negative correlation with both the number density and area fraction of MgO·Al2O3 inclusions. This indicates that ΔC/η ratio of MgO·Al2O3 inclusions directly affects the removal rate of MgO·Al2O3 inclusions. Moreover, LF refining slag exhibits varying adsorption capacities for the four types of inclusions, ranked as Al2O3 &gt; MgAl2O4 &gt; Mg4Al2O7 &gt; MgO.

Effects of Al2O3 content on the microstructure and performance of Inconel 625-xAl2O3 composite non-skid coatings by plasma enhanced high-velocity arc spraying

The efficient preparation of metal/ceramic composite coatings with excellent performance has been a hot research topic in the field of thermal spraying. In this study, a novel plasma enhanced high-velocity arc spraying (PE-HAS) technique is developed. A series of Inconel 625-xAl2O3 composite non-skid coatings are deposited by PE-HAS with different feeding ratio of alloy wire (1.6 mm in diameter) and ceramic powder (13.5 μm in average particle size). Specifically, the microstructure, mechanical properties, corrosion resistance and tribological performances of the coatings have been comprehensively investigated. Results indicate that all of the composite coatings with different Al2O3 contents are characterized by high densities, low defects (porosity≤3.52 %), strong bonding (≥50 MPa) and high friction coefficient (≤ 1.034). The coatings with low Al2O3 content feature a more homogeneous structure and superior bonding strength. The microhardness and wear resistance of the coatings increases significantly with increasing Al2O3 content, which should be attributed to the formation of many localised enhancement areas composed of different forms of Al2O3 phases. It is worth noting that the unique feedstock feeding method promotes the formation of the in-situ double-layer structure of coatings with high Al2O3 content, which further improves the wear and corrosion resistance. However, the friction coefficient gradually decreases when the Al2O3 content is too high, thus affecting the anti-slip performance of the coating.

Corrosion behaviors and mechanism of AlxCrFeMnCu high-entropy alloys in a 3.5 wt% NaCl solution

This study investigated the corrosion behavior of as-cast AlxCrFeMnCu (x = 0, 0.5, 1.0, 1.5, 2.0) high-entropy alloys (HEAs) in a 3.5 wt% NaCl solution at room temperature. The results indicated that the corrosion resistance of the AlxCrFeMnCu HEAs decreased with increasing Al content. Intergranular corrosion was the primary corrosion type for CrFeMnCu and Al0.5CrFeMnCu HEAs, while Al1.0CrFeMnCu, Al1.5CrFeMnCu, and Al2.0CrFeMnCu HEAs exhibited selective corrosion with enrichment of Al and Cu in the BCC2 phase. The XPS fitting calculations indicated that an increase in the molar ratio of Al led to a decrease in Cr2O3 content and an increase in Al2O3 content, which weakened the stability and protective properties of the passive film.

Preparation and microstructure of Cu-Al2O3 composites by a novel supercritical water liquid phase in-situ reaction method

The high solubility, reactivity and solubility of supercritical water provide a new way for the preparation of advanced metal matrix composites. In this paper, Cu-Al2O3 composites are prepared by supercritical water liquid phase in situ reaction (SW-LIR). In this method, the Cu-Al atomized alloy powder are used as raw material, deionized water as reaction medium, H2O2 as liquid phase oxygen source, and the Cu-Al2O3 composite powder are prepared at 380 ℃ and 22.1 MPa for 10 min. The Cu-Al2O3 composite block is prepared by spark plasma sintering (SPS). The results show that Al2O3 has an average size of 41.8 nm and mainly exists in the form of mixed crystals. The interface with the matrix is coherent or semi-coherent. With the increase of Al2O3 content, the mechanical properties of the composites are obviously improved. When the Al2O3 content is 1.12 wt%, the microhardness is as high as 164.52 HV and the tensile strength is 441 MPA, while still maintaining a high electrical conductivity (75 %IACS). At the same time, it shows quite excellent high temperature performance. It can still retain the characteristics of high strength at 1000℃, which solves the shortcomings of high thermal conductivity but low strength of pure copper. Compared with the traditional method, SW-LIR method has the characteristics of low reaction temperature, fast reaction speed and green environmental protection.

Thermodynamic Analysis of the Oxidation Behavior of Cerium in High‐Speed Steel during Electroslag Remelting

Cerium loss is difficult to be avoided during the electroslag remelting (ESR) process. To reduce the cerium loss in high‐speed steel during the ESR process, the present study investigates the thermodynamics of cerium oxidation in cerium‐containing high‐speed steel based on the thermodynamic calculation and laboratory‐scale steel–slag reaction experiments. The results show that the reactions between [Ce] and (Al2O3), as well as [Ce] and (MgO) contribute to the cerium loss in the steel. Increasing the contents of CaF2 and MgO in the slag, the activities of Al2O3 and Ce2O3 show a slightly decreasing trend. The addition of CaO and Ce2O3 significantly reduces the Al2O3 activity but enhances the Ce2O3 activity. MgO activity shows an insignificant change with the contents of CaO and Ce2O3, while it decreases with adding Al2O3 and CaF2. Reducing Al2O3 content and enhancing Ce2O3 content in the slag are feasible to increase the cerium yield in the steel. With increasing Al2O3 content from 16.93 to 26.92 wt%, the cerium yield decreases from 8.4% to 6.0%. Increasing Ce2O3 content from 3.98 to 11.01 wt% enhances the cerium yield from 6.0% to 16.9%. The actual soluble Ce content in equilibrium with slag is almost less than 0.001 wt%.

Effect of nano-AlN, Al2O3 on friction and wear properties of copper-steel clad plate immersed in the lubricants

PurposeThis paper aims to investigate the preparation of AlN and Al2O3, as well as the effect of nano-AlN and nano-Al2O3, on friction and wear properties of copper-steel clad plate immersed in the lubricants.Design/methodology/approachNano-AlN or nano-Al2O3 (0.1, 0.2, 0.3, 0.4 and 0.5 Wt.%) functional fluids were prepared. Their tribological properties were tested by an MRS-10A four-ball friction tester and a ball-on-plate configuration, and scanning electron microscope observed the worn surface of the plate.FindingsAn increase in nano-AlN and Al2O3 content enhances the extreme pressure and anti-wear performance of the lubricant. The best performance is achieved at 0.5 Wt.% of nano-AlN and 0.3 Wt.% of nano-Al2O3 with PB of 834 N and 883 N, a coefficient of friction (COF) of approximately 0.07 and 0.06, respectively. Furthermore, the inclusion of nano-AlN and nano-Al2O3 particles in the lubricant enhances its extreme pressure performance and reduces wear, leading to decreased wear spot depth. The lubricating effect of the nano-Al2O3 lubricant on the surface of the copper-steel composite plate is slightly superior to that of the nano-AlN lubricant, with a COF reaching 0.07. Both lubricants effectively fill and lubricate the holes on the surface of the copper-steel composite plate.Originality/valueAlN and Al2O3 as water-based lubricants have excellent lubrication performance and can reduce the COF. It can provide some reference for the practical application of nano-water-based lubricants.Peer reviewThe peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-08-2023-0255/

Dynamic analysis of liquid permeability in the dripping zone of blast furnace and reaction behavior at the slag-coke interface

The dripping zone connects the cohesive zone and the hearth, it is one of the key areas of the blast furnace (BF). This study aims to explore the mechanism of the dripping process in BF. The dripping experiments under different conditions were carried out. Dynamics of liquid permeability in the dripping zone was analyzed, the reaction behavior at the slag-coke interface was investigated, and the consumption of coke in the dripping zone was clarified. The results show that: The retention ratio increases with the increase of Al2O3 content. The increase in retention ratio is related to the viscosity of slag. Once the Al2O3 content in slag increases, Si4+ coordination polymer ions in tetrahedra will be replaced by Al3+ cations, forming a tetrahedral structure of [AlO4]5– tetrahedron. The retention ratio decreases with the increase of FeO content. The dissociation of free oxygen ions (O)2– from FeO increases the concentration of free oxygen ions (O)2– in slag, this reduces the viscosity of slag. The presence of FeO can compensate for the increase in retention ratio caused by Al2O3. The quantitative relationship between retention ratio and Al2O3 content and FeO content in slag is obtained. The reduction reaction of FeO occurs at the slag-coke interface, the molten iron takes on the shape of small iron beads, which is the result of multiple small droplets gathering. The reduction of TiO2 is carried out by a series of reactions, the Ti exhibits a granular embedding state in molten iron, its color is darker than that of molten iron and its particles have distinct edges and corners. In the slag-coke area of retained sample, the reduction reaction occurs between coke and oxides in slag. The carbon will be consumed, resulting in a decrease in particle size. In the iron-coke area of retained sample, the carburization reaction occurs in large quantities due to the carbon content of molten iron in hearth is undersaturated, coke is further consumed.

Investigation of the effect of BaO-Al2O3 variations for BAS glass-ceramic glaze: Insights into thermal, phase, microstructural and surface features

This study aims to investigate the phase transformation, thermal behavior, microstructure evaluation and surface feature of the barium aluminosilicate (BAS) glass-ceramic glaze by changing barium oxide (BaO) and aluminium oxide (Al2O3) amounts. Differential thermal analysis (DTA) analysis showed that the first crystallization occurred at 800 °C and referred to the celsian formation, and crystallization temperature increased as Al2O3 content increased. Characteristic temperature and high thermal viscosity behavior was examined by hot-stage microscope analysis and the Vogel–Fulcher–Tammann (VFT) equation. X-ray diffraction (XRD) analysis showed that replacing Al2O3 with BaO resulted in an enhanced celsian (Ba0.8Al1.6Si2.4O8) phase. On the other hand, increasing Al2O3 content promoted the corundum (α-Al2O3) phase. The glassy and crystalline phase amount was determined by using Rietveld method. Field Emission Scanning Electron Microscope (FESEM) observations showed rectangular, strip-like celsian crystals, unshaped corundum crystals and porous microstructure. Surface roughness and the height distribution of surfaces were supported by 3D topographic mapping and determined according to ISO 4287. The highest BaO-contained R1 exhibits lower peaks with 190 µm and valleys with 80 µm, on the contrary, the highest Al2O3-contained R5 has high peaks with 252.7 µm, and deep valleys with 150 µm. Finer celsian crystals and lowest surface roughness ensured the cleanability of the surface and resulted in Class 5 according to ISO 10545-14. When Al2O3 content increased by 30 wt% and above, cleanability began to weaken, resulting in Class 1 and Class 2. The surface has become opaque with an increase in the Al2O3 content.

Thermodynamic evaluation of viscosity behavior for CaO–SiO2–Al2O3–MgO slag systems examined at the temperatures range from 1500 to 1700 °C

This work showed an application of computational tools to understand systematically the behavior of viscosity on CSAM systems relevant to industrial uses. Consequently in this study, the viscosity experimental data obtained from the literature were compared with the thermodynamic calculated results via the software FactSage v.7.3 for melts in CaO–SiO2–Al2O3–MgO slag system with the range of compositions slags cover 0–100 wt% CaO, 0–100 wt% SiO2, 0–100 wt% Al2O3 and 0–15 wt% MgO at temperature ranges of 1500–1700 °C. Using open-source software in Python, the results of viscosity, liquid, and solid fraction of the slag, as a function of composition and temperature, are represented by multiple color maps and by iso-viscosity contours. The results of the viscosity values indicated that the effect of all the oxides in the CSAM slag system follows the well-known behavior trend observed in the literature. Viscosities of the slag were found to increase with increasing SiO2 contents and decrease with increasing basicities (high CaO). The increase in Al2O3 content increases the viscosity values. An increase of 0–15% MgO depolymerized the slag melt and decreases the viscosity. However, above 5% MgO content occur a decrease in the liquid zone (single phase) and a liquid fraction (two-phase region) of the slag. For a constant MgO concentration, the increase in temperature generates an expansion of low-viscosity zones associated with an increase in the liquid phase of the slag. From the comparison between the calculated and experimental viscosities data keeps up within 30% average relative deviation (Δ), the predictions are considered acceptable for viscosity in the CSAM slag system at high temperatures.

Effect of nano-Al2O3 addition on microstructure and mechanical properties of Ti2AlNb-based composites prepared by powder metallurgy

To meet the commercial application, the mechanical properties of Ti2AlNb-based alloys must be improved. However, the strengthening mechanism of the Ti2AlNb-based composites with Al2O3 particles needs further to investigate. Nano-Al2O3/Ti‐22Al‐25Nb composites are prepared by mechanical alloying (MA), high-energy ball milling (HEBM), and hot pressing (HP). The purpose of this study is to identify the effect of Al2O3 content on the microstructure and mechanical properties of the composites. The results show that the grain size decreases, and phase transformation occurs with an increase in the Al2O3 content. With the increase of Al2O3 content from 2 wt.% to 6 wt.%, the microstructure of Ti2AlNb-based composites transformed from the ultrafine acicular O phase to the uniform equiaxed O phase. The hardness and ultimate compressive strength of the Ti2AlNb-based composites first increase and then decrease. The hardness of the composite is up to 8.6 GPa when the Al2O3 content is 6 wt.%, almost twice that of Ti‐22Al‐25Nb alloy. The hardening effect is the result of a higher volume fraction of the O phase and grain refinement with addition of Al2O3 particles. The optimal combination of hardness, ultimate compressive strength, and strain-to-failure of the composite with 2 wt.% Al2O3 is 5.9 GPa, 2190 MPa, and 8.1%, respectively. The strengthening mechanisms of Al2O3 phase dispersion and ultrafine acicular O phase precipitation are proposed and confirmed. This research offers a new idea for the wider application of Ti2AlNb-based composites.

Performance enhancement of free CaO containing magnesia by in situ intergranular CaAl2O4 and MgAl2O4

Magnesia refractory raw material with free CaO has inherent weaknesses of low resistance to hydration, thermal shock and slag penetration. In this work, micro-sized Al2O3 powder was added into such magnesia with the purpose of improving its comprehensive performances. The results showed that with increasing Al2O3 content, CaAl2O4 and MgAl2O4 phases were sequentially formed at the MgO grain boundaries, which enlarged the MgO grains and reduced the apparent porosity. Owing to the transformation of free CaO to CaAl2O4, reduction of apparent porosity and covering of intergranular MgAl2O4 on MgO grains, hydration of the specimens was inhibited effectively by introducing the Al2O3 addition. The formed CaAl2O4 and MgAl2O4 phases lowered the thermal expansion coefficient and induced crack deflection, and therefore residual flexural strength ratio after thermal shock tests increased remarkably from 15.1% to 33.2% with increasing Al2O3 addition from 0 wt% to 7 wt%. Moreover, slag penetration resistance of the specimens was improved effectively with raising the Al2O3 content to 3 wt%, attributing to the increase in MgO grain size, decrease in apparent porosity and formation of high stable intergranular CaAl2O4 phase. However, further increasing Al2O3 content would dramatically accelerate the slag penetration owing to the decrease in grain size and formation of more unstable intergranular MgAl2O4 phase.

Dissolution behavior of AlN in CaO–Al2O3–BaO–CaF2–Li2O system mold fluxes

The dissolution behavior of AlN in three CaO–Al2O3–BaO–CaF2–Li2O non-reactive mold fluxes which were designated as N1 (low break temperature), N2 (good lubrication performance), N3 (high break temperature) for high-Al steel with different requirements was explored by static method. The sizes of AlN rods after dissolving in three slags decreased to 8.35 mm, 7.90 mm, and 9.10 mm, from the initial 10 mm, resulting in 0.59 wt.%, 1.78 wt.%, 0.01 wt.% decrease in Li2O content and 1.60 wt.%, 4.33 wt.%, 0.26 wt.% increase in Al2O3 content in the slags which were in contact with AlN, respectively. The interfaces between slags and AlN rods was investigated by field emission scanning electron microscopy. The results confirmed that the widths of the element transition layer were 6.3 μm, 8.0 μm and 5.3 μm for slags N1, N2, and N3 which were in contact with AlN, respectively. Furthermore, the product at the interface close to the slag sides were Al2O3–CaO–BaO–CaF2 complexes, while close to the AlN rod sides, individual Al2O3 and AlN–Al2O3 complexes were found. The thermodynamic calculation showed that only Li2O in molten slag reacted with AlN to form Al2O3. Thus, the dissolution behavior of AlN in three slags was that AlN reacted with Li2O to form Al2O3, which then diffused into the slags and was absorbed by the slags. In addition, the slags N1 and N2 with lower initial Al2O3 content had a stronger reactivity with AlN, they have a more superior ability to dissolve AlN inclusion.

Experimental study on flow properties of blast furnace slag with different alumina contents based on the image measurement method

This paper established a novel visualization method for measuring blast furnace slag(BFS) flow properties and investigated the effect of alumina content on the CaO–SiO2–Al2O3–MgO BFS system. The outcomes indicate that elevating Al2O3 concentration in the BFS mixture from 14% to 26% results in a rise of critical flow temperature Tc from 1332.5 °C to 1384.1 °C, leading to a deterioration of BFS flow properties. However, the critical flow velocity Vc of BFS rises from 1.82 mm/min to 2.91 mm/min, representing a 60% increment. BFS with high Al2O3 content was found to be more likely to form high melting point crystals, such as gehlenite, with better crystallization, which is one of the main reasons for the deterioration of BFS flow properties. Fourier Transform Infrared Spectrometer (FTIR) and Raman spectra analysis indicate that the proportional content of simple silicate structures denoted as QSi0([SiO4]4−),QSi1([Si2O7]6−) decreased with increasing Al2O3 content, while those of complex silicate structures, QSi2([Si3O10]8−),QSi3([Si3O9]6−) increased. Furthermore, the Si–O–Al structural unit concentration progressively increased, indicating that the escalation in bridging oxygen within the BFS system raised the polymerization degree of the BFS, leading to a more complex aluminosilicate structure. Notably, the [AlO4]5- tetrahedra content within the BFS has reached saturation at roughly 21%. Further increases in Al2O3 content induced an excess of [AlO6]9−octahedra formation, which generally acts as a network modifier to lower the polymerization degree of the BFS system. However, this effect was not noticeable in this study, which may be attributable to the low basicity (CaO/SiO2 = 0.99) and MgO content (MgO/Al2O3 = 0.21–0.34) of the BFS samples in this study.

Crystallization and microwave dielectric properties of novel CaO-Al2O3-B2O3 glass-ceramics with different Al2O3 content

CaO-Al2O3-B2O3 (CAB) glass-ceramics with varying Al2O3 content were fabricated using the melting method including melting and quenching of mixture of raw materials. The obtained glass powder was pressed into the desired shape and sintered for measurement. At 900 °C, the crystallinity initially increased and then decreased with increasing Al2O3 content. The highest crystallinity of 62.29 % was obtained when the Al2O3 content was 0.5 mol%, and exhibited excellent dielectric properties: εr = 4.35, Q × f = 53,085 GHz, and τf = –33.95 ppm/°C. The variation of dielectric properties with increasing Al2O3 content is attributed to the crystallinity process. The crystallization process of CAB system was determined by crystallization activation energy, the lowest value of 302.085 kJ/mol corresponds to the highest crystallinity. The crystallization, dielectric properties and sintering behavior of CAB system indicate that CAB system prepared by melting method have promising prospect as new LTCC glass-ceramics.

Preparing and Wear-Resisting Property of Al2O3/Cu Composite Material Enhanced Using Novel In Situ Generated Al2O3 Nanoparticles.

Al2O3/Cu composite material (ACCM) are highly suitable for various advanced applications owing to its excellent properties. In the present work, a combination of the solution combustion synthesis and hydrogen reduction method was first employed to prepare Al2O3/Cu composite powder (ACCP), and subsequently ACCM was prepared by employing spark plasma sintering (SPS) technique. The effect of Al2O3 contents and SPS temperatures on the properties (relative density, hardness, friction coefficient, and electrical conductivity, et al.) of ACCM were investigated in detail. The results indicated that ACCM was very dense, and microstructure was consisted of fine Al2O3 particles evenly distributed in the Cu matrix. With the increase of SPS temperature, the relative density and hardness of ACCM had first increased and then decreased. At 775 °C, the relative density and hardness had attained the maximum values of 98.19% and 121.4 HV, respectively. With the increase of Al2O3 content, although the relative density of ACCM had gradually decreased, nevertheless, its friction coefficient had increased. Moreover, with the increase of Al2O3 contents, the hardness of ACCM first increased and then decreased, and reached the maximum value (121.4 HV) with 3 wt.% addition. On the contrary, the wear rate of ACCM had first decreased and then increased with the increase of Al2O3 contents, and attained the minimum (2.32 × 10-5 mm3/(N.m)) with 3 wt.% addition.