Increasing Al2O3 Content Research Articles

Effect of CaO/SiO2and Al2O3on Viscous Behaviors of the Titanium-Bearing Blast Furnace Slag

In the Blast Furnace (BF) process, the viscous behaviors of molten slags are essential to the efficiency and the productivity of operations. In this work, the effects of CaO/SiO2 and Al2O3 on the viscosity, activation energy for viscous flow, and break point temperature of titanium-bearing BF slags are analyzed. To connect the viscosity and the slag structure, Fourier transform infrared spectroscopy (FTIR) is performed on the as-quenched slags. It is found that the viscosity and the activation energy for viscous flow of slags decrease as the CaO/SiO2 content increases from 1.00 to 1.20 and increase with increasing the Al2O3 content from 11.00 to 15.00 wt%. As for the break point temperature, it raises when the CaO/SiO2 and the Al2O3 content increases. FTIR results reveal that the polymerization degree of complex viscous units in the slag decreases as the CaO/SiO2 increases. However, it is opposite when the Al2O3 content increases. The variation of viscosity and activation energy for viscous flow for the different CaO/SiO2 and Al2O3 content slags are explained.

Dielectric and microwave absorption properties of TiAlCo ceramic fabricated by atmospheric plasma spraying

Composite TiAlCo powders (TiO2, Co3O4 and Al2O3) were synthesized by spray–drying technology. The phase composition and morphology of synthesized powders were characterized by X-ray diffraction and scanning electron microscopy, respectively. Using above synthesized powders as starting materials, TiAlCo ceramic were successfully prepared by atmospheric plasma spraying (APS) with an internally fed powder torch. Electromagnetic parameters and microwave absorption properties of the prepared ceramic coatings were investigated in the frequency range from 8.2 to 12.4GHz (X-band). It was found that both the real part and imaginary part of dielectric constant decreases with increasing Al2O3 content in the whole measured frequency region. Dielectric properties are closely related to the relaxation polarization and interfacial polarization and electric conductivity. Furthermore, by combination of the frequency selective surfaces (FSS) and prepared coatings, a double absorption band of the reflection loss spectra had been observed in X-band. The optimized reflection loss values exceeding −10dB can be obtained in the frequency range of X-band when the coating thickness is only 1.8mm, and the reflection loss is insensitive to incident angle from 0° to 45° for both transverse electromagnetic (TE) and transverse magnetic (TM) polarizations.

Influence of MgO, Al2O3 and CaO/SiO2 on the viscosity of blast furnace type slag with high Al2O3 and 5 wt-% TiO2

The effect of MgO, Al2O3 and CaO/SiO2 on the viscosity of CaO–SiO2–Al2O3–MgO–5 wt-% TiO2 slag was studied in the temperature range of 1673–1773 K. At a fixed CaO/SiO2 ratio of 1·17 and 12 wt-% Al2O3, the viscosity of the slag decreased with increasing MgO content because of depolymerisation of the silicate structures. At a fixed CaO/SiO2 ratio of 1·17 and 8 wt-% MgO, the viscosity of the slag increased with increasing Al2O3 content. At 8 wt-% MgO and 12 wt-% Al2O3 wt-%, increasing the CaO/SiO2 ratio from 1·07 to 1·50 resulted in lower slag viscosity. The temperature dependencies of the viscosity on MgO addition, Al2O3 addition, and CaO/SiO2 ratio were analyzed, and the apparent activation energies of each system were found to be between 178 and 232 kJ/mol, 273 and 360 kJ/mol, and 204 and 233 kJ/mol, respectively. Five different viscosity models were employed to predict slag viscosity, and the Riboud model was found to be the best for predicting this parameter.

Molecular dynamics simulations of the structural properties of Al2O3-based binary systems

In order to aid the research and development of Al2O3-based mold fluxes, a comprehensive study of the structural properties of Al2O3-based binary systems was carried out via molecular dynamics simulations. The simulation results demonstrated that the structural properties of Al2O3-based binary systems varied with both the Al3+ content and the type of metal cation. The aluminate network becomes more complex with increasing Al2O3 content, and for a given Al2O3 content in different systems, both the Al–O structural disorder and the polymerization degree of the network structure increase as the metal cations become more electronegative. For a given Al2O3 content, the effects of the components on stabilizing the Al–O network is sequenced as K2O>Na2O>CaO>MgO, and the polymerization degree of the structure in different systems follows the order K2O–Al2O3<Na2O–Al2O3<CaO–Al2O3<MgO–Al2O3. In addition, both the metal cations and the oxygen triclusters play a role in the charge compensation of the AlO4 tetrahedron.

Study on Control of Inclusion Compositions in Tire Cord Steel by Low Basicity Top Slag

AbstractTop slag melting experiment was conducted in a silicon molybdenum furnace with tire cord steel billet. The influence of top slag composition on the plasticity of CaO–Al2O3–SiO2–MgO inclusion and inclusion plasticization conditions was calculated by thermodynamic software FactSage. Use the thermodynamic calculation to guide the laboratory experiments to study slag compositions influence inclusions composition. Then industrial experiments were conducted based on the theoretical calculation and results of laboratory experiments. Scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) were used to determine the morphology and composition of inclusions in steel. All studies show that in the CaO–Al2O3–SiO2–10% MgO diagram, when CaO = 8–48%, SiO2 = 35–75%, Al2O3 = 0–32%, inclusions are in the plastic area. When basicity of top slag is certain, Al2O3 content in inclusions increases with the increase of Al2O3 content in the slag, and the distribution of inclusions becomes scattered with the increase of Al2O3 content in slag. Inclusion plasticization can be achieved when the binary basicities of top slag are 0.6, 0.8–1.2, 1.4 and corresponding w(Al2O3)s are 2–15%, 2–10%, &lt;2%. According to industrial experimental results, when top slag basicity decreases from 1.5 to 0.67–0.9 and Al2O3 content decreases below 10 wt%, the inclusion falls into plastic area. It is feasible in practice to control the CaO–Al2O3–SiO2–MgO inclusions plastic through adjusting Al2O3 content in slag.

Effect of Basicity, Al2O3and MgO content on the softening and melting properties of the CaO-MgO-SiO2-Al2O3high alumina quaternary slag system

The flow characteristic temperatures of the selected quaternary CaO-MgO-SiO2 -Al2 O3 slags have been experimentally measured by performing softening and melting tests using a high temperature microscope in accordance with German standard 51730. An effective statistical model is developed through constructing empirical equations by regression analysis method to predict Softening temperature (ST), Hemispherical temperature (HT), and Flow temperature (FT) based on Al2 O3 (25%–30%) content, CaO/SiO2 (C/S ratio: 0.9–1.4), and MgO (4%–12%) content. The effect of basicity, MgO and Al2 O3 content on characteristic temperature are also studied. FactSage 6.4 data base is used to calculate liquidus temperature of the above quaternary slags and compared with the experimental and regression results. The experimental results show that, increase in Al2 O3 content increases ST and HT while decreases FT of the slags. The ST, HT and FT increase with increase in C/S ratio. Increase in MgO content decreases both ST and HT while increases FT of the slags. The liquidus temperature obtained from FactSage 6.4 are found to correspond well with the experimental and regression data. Under the range of composition examined, a high Al2 O3 (30%) and high C/S ratio (1.4) coupled with low MgO (4%) content is beneficial for the blast furnaces running with high Alumina slags, as it ensures the formation of a short slag.

Development of Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt;-Bi&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt;-B&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; Glasses for Neutron Shielding Material

A glass system with chemical formula xB2O3:20Bi2O3:(100-x) Al2O3 (x = 55, 60, 65, 70, 75 and 80 mol%) is prepared by melt quenching technique and were investigated the physical and neutron shielding properties. The physical properties were investigated by density, molar volume and discussed with different Al2O3 contents. The neutron shielding property was investigated by Monte Carlo techniques (FLUKA and GEANT4 codes) and neutron equivalent dose rate measurements. As a result, neutron shielding capacity of glass samples decrease with increased Al2O3 content, so increased B2O3 content is a result of positive effects on neutron shielding.

Experimental investigation on the compressibility of Al/Al&lt;SUB align="right"&gt;2O&lt;SUB align="right"&gt;3 nanocomposites

The scientific importance of nanocomposites is being increased due to their improved properties. This paper introduces an experimental investigation on the relationship between the reinforcement weight fraction and compressibility of Al/Al2O3 during high energy ball milling. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to characterise the produced powder. The results showed that the grain size of milled powders was about 43 nm with a noticeable presence of agglomerates at 10 wt.% of Al2O3. By increasing Al2O3 weight fraction to 12% the decrease in grain size was very. With up to 12 wt.% of Al2O3, microhardness increases from 62 to 150 HV due to the decrease of the crystallite size. The compressibility behaviour of the nanocomposite powder was decreased slowly by increasing Al2O3 content due to work hardening on the matrix powder.

Characteristics of clay minerals in soil particles of two Alfisols in China

The composition, structure and transformation characteristics of clay minerals in various size particles (<2000, 450–2000, 100–450 and 25–100nm) of two Alfisols (Haplustalf and Hapludalf) in China were investigated by elemental analysis, X-ray diffraction (XRD), Fourier-Transform Infrared Spectroscopy (FT-IR) and 27Al and 29Si Magic-angle Spinning Nuclear Magnetic Resonance (MAS NMR). The clay minerals in <2000, 450–2000 and 100–450nm size particles of the two soils were illite, vermiculite, smectite, kaolinite and kaolinite interstratified minerals. In Haplustalf, vermiculite was dominant clay mineral in 450–2000nm particles and illite was dominant clay mineral in 100–450nm particles. In Hapludalf, kaolinite (and kaolinite interstratified minerals) predominated in all size particles. With decreasing particle sizes, the two clays showed a decrease in K2O, Na2O, MgO and SiO2 contents and an increase in Al2O3 content, with the minimum molar ratio of SiO2 to Al2O3 observed in nanoparticles (25–100nm). Meanwhile, the smectite and vermiculite contents decreased or disappeared, leaving illite and kaolinite (and kaolinite interstratified minerals) as the main clay minerals in the two soil nanoparticles. Additionally, with decreasing particle sizes, the clay mineral structures were transformed from well crystalline to poor crystalline, with illite being the poor crystalline in nanoparticles of the soils. The hydroxyl groups between the tetrahedral and octahedral structures of the 2:1 clay minerals and the surface of kaolinite gradually broke down, and IVAl of the tetrahedral structure gradually reduced. In nanoparticles, Al mainly appeared in the octahedral structure as VIAl, and Si in the structure of Q3 (Si linked to three other Si atoms via oxygen). The composition and structure of clay minerals in different size particles showed that the clay minerals weathered from larger particles (>100nm) were an important mineral source of nanoparticles, and the 1:1 clay minerals were mainly inherited from the minerals in larger particles and transformed from 2:1 clay minerals into nanoparticles.

Experimental Investigation on Viscosity of CaO-MgO(-Al2O3)-SiO2 Slags and Solid-liquid Mixtures

The viscosities for the selected CaO-MgO-SiO2 and CaO-MgO-Al2O3-SiO2 slags were measured by rotating cylinder method in a wide temperature range from 1608 K to 1823 K. The effects of temperature, slag basicity and Al2O3 content were studied. The results indicated that the viscosity decreased with increasing the slag basicity at the same temperature. And the viscosities of the slag initially increased linearly with increasing Al2O3 content in the slags and then decreased as the Al2O3 content in the slags continued to increase. Al2O3 addition has a more significant effect on the viscosity than slag basicity in the selected slags. Based on the experimental data and the fraction of solid phases calculated by the thermodynamic software, the effect of solid phases on slag viscosity was evaluated. The results indicated that the relationship between the relative viscosity and the volume fraction of solid phases estimated from the slag composition can be reasonable by allowing the inverse maximum fraction of solid particles to vary.

Complex chemical bond theory, Raman spectra and microwave dielectric properties of low loss ceramics NdNbO4–xAl2O3

In this work, low loss microwave dielectric materials of NdNbO4–x wt% Al2O3 ceramics were prepared via a solid-state reaction method. The complex chemical bond theory, phase composition, standard deviation (σ) of the bond angles, microstructures, microwave dielectric properties and vibrational phonon modes were investigated. Microscopic analysis showed that sintered specimens presented single monoclinic fergusonite phase. The Rietveld refinements and Raman spectra were used to evaluate the correlation between the complex chemical bond theory and the microwave dielectric properties. With an increase of Al2O3 content, the Raman shift of Ag (331 and 808 cm−1) toward to the bigger value direction and the FWHM of Ag (331 and 808 cm−1) decrease, which lead to a decrease in bond ionicity and increase in lattice energy. The microwave dielectric properties of NdNbO4–x wt% Al2O3 exhibit closely relationship with the complex chemical bond theory. The variation trend of dielectric constant was accordance with the bond ionicity. The Q × f value and τ f value were mainly dependence on the lattice energy and bond energy, respectively. Fine microwave dielectric properties for NdNbO4–3 wt% Al2O3 ceramic was obtained with er = 18.1, Q × f = 54,700 GHz (9.1 GHz), τ f = −0.51 ppm/°C sintered at 1150 °C for 4 h.

Optimization of Slag Chemistry Toward Inclusion Control for 28CrMo47 Drill Pipe Steel Based on Viscosity and Equilibration Studies

During the refining of 28CrMo47 drill pipe steel, it is found that the product often has internal defects and cracks. The present work is initiated with a view to examine if these problems could be solved by optimizing the slag chemistry of the refining slag. Three series of slags, namely, slag A (57.09%CaO–15.74%SiO2–16.35%Al2O3–5.35%MgO, original slag in the steel plant), slag B (55%CaO–21%SiO2–12%Al2O3–7%MgO–5%CaF2), and slag C (51%CaO–17%SiO2–25%Al2O3–7%MgO) are designed and their viscosities are measured. The effect of Al2O3 content on viscosity of the slag C is also investigated as part of the slag optimization. Slag–steel equilibrium experiments are subsequently carried out in order to understand the effect of the slag chemistry, especially the variation in the Al2O3 content in the same on the inclusions in drill pipe steel. It is concluded that both increasing Al2O3 content of the slag used in the refining unit in the plant and addition of CaF2 could decrease effectively the slag viscosity. Inclusions in steel equilibrated with slag C1, corresponding to 51%CaO–7%MgO–25%Al2O3–17SiO2, consisted mainly of low melting point CaO–Al2O3 complex, which did not have any negative effect on the steel quality.

Preparation and characterization of Mo/Al2O3 composites

In order to improve the performance of molybdenum, the Mo/Al2O3 composites were prepared by using a hydrothermal method for the synthesis of the precursor powders and subsequent powder metallurgical processing. The morphologies of the composite powders and the microstructures and properties of the composites were investigated. Compared with the pure Mo powder, the grains of composite powders are smaller because of the existence of the fine Al2O3 particles. The results from the sintered composites show that the fine Al2O3 particles are evenly distributed in the Mo matrix and well bonded with the Mo matrix. With increasing Al2O3 content, all the values of the micro-hardness, compressive strength and flow stress at 0.08 strain are increased. The strengthening effect is more remarkable at elevated temperatures. At room temperature, the compressive strength and the flow stress at 0.08 strain of the composite with 40vol.% Al2O3 are 1.67 and 2.01 times greater than those of pure molybdenum, respectively, while the values are up to 2.02 and 2.52 at 1100°C.

Influence of Al3+doping on the energy levels and thermal property of the 3.5MgO·0.5MgF2·GeO2:Mn4+ red-emitting phosphor**Project supported by the National High Technology Research and Development Program of China (Grant No. 2013AA014201), the Natural Science Foundation of Tianjin City, China (Grant Nos. 11JCYBJC00300 and 14JCZDJC31200), and the National Key Foundation for Exploring Scientific Instrument of China (Grant No. 2014YQ120351).

A series of Al3+ -doped 3.5MgO·0.5MgF2·GeO2:Mn4+ red-emitting phosphors is synthesized by high temperature solid-state reaction. The broad excitation band at 300 nm–380 nm, resulting from the 4A2 → 4T1 transition of Mn4+, exhibits a blue shift with the increase of Al2O3 content. The observation of the decreased Mn4+O2 − distance is explained by the crystal field theory. The temperature-dependent photoluminescence spectra with various amounts of Al2O3 content are comparatively measured and the calculation shows that the activation energy increases up to 0.41 eV at the Al2O3 content of 0.1 mol. The maximum phonon densities of state for these samples are calculated from Raman spectra and they are correlated with the thermal properties.

Selective Crystallization Behavior of CaO-SiO2-Al2O3-MgO-FetO-P2O5 Steelmaking Slags Modified through P2O5 and Al2O3

In this study, the selective crystallization behavior of synthetic FetO-rich steelmaking slags modified by P2O5 and Al2O3 additions was explored using non-isothermal differential scanning calorimetry, X-ray diffraction, and field emission scanning electron microscopy techniques. Continuous cooling transformation diagrams of Fe-enriched and P-enriched phases were constructed. It was found that P2O5 addition can suppress the crystallization due to the increasing viscosity caused by increasing degree of polymerization; however, an increase of Al2O3 content accelerated the precipitation of dystectic MgFeAlO4, copolymerized by [AlO4]-tetrahedra and [FeO4]-tetrahedra units. It was also noted that the content of phosphorus in P-enriched phase can reach a high value as 28.71 wt pct for the slags modified by 15.17 wt pct Al2O3. The non-isothermal crystallization kinetics derived from activation energy and the structure of the slags explained by Raman spectra were further analyzed, which was well in accordance with the above analysis.

Synthesis and properties of Mn1.05−yCo1.95−x−z−wNixMgyAlzFewO4 NTC ceramic by co-precipitation method

Mn1.05−yCo1.95−x−z−wNixMgyAlzFewO4 negative temperature coefficient (NTC) material was synthesized by double precipitation reacting method. The synthesis condition was optimized. Fourier infrared (FI) spectrometer indicated that the precursor was consisted of oxalate and hydroxide. The powder was studied by X–ray diffraction (XRD) to obtain the optimum calcination temperature of 800 °C. The ceramics were mainly in the cubic spinel structure except for the minority of cubic cobalt oxide. Scanning electron microscope (SEM) image showed that the grain size decreased with the increase of Al2O3 content in the ceramic. While the room temperature resistivity ρ25 increased from 3027 Ω cm to 16,911 Ω cm with increasing Al2O3 content. The material constants B25/85 and activity energies were in the range of 3592–3977 K and 0.3112–0.3330 eV, respectively. Complex impedance analysis indicated that the grain boundary resistivity increased with increasing Al2O3 content, whereas, the grain resistance remains virtually unchanged.

Effect of Al2O3, MgO, and CaO/SiO2on Viscosity of High Alumina Blast Furnace Slag

The effects of Al2O3, MgO, and binary basicity on the viscosity of high alumina blast furnace slag are studied systematically at the temperatures of 1773 K and below using the orthogonal experimental design method. The results show that, at fixed binary basicity (CaO/SiO2) between 1.1 and 1.2, higher Al2O3 content increase the slag viscosity due to the polymerization of the aluminate structures. At fixed Al2O3 content between 15 and 20%, increasing the CaO/SiO2 from 1.1 to 1.2 lead to lower viscosity due to the depolymerization of the aluminate structures. At fixed MgO between 9 and 11%, both increasing Al2O3 content and CaO/SiO2 can make the melting temperature increase. In addition, the viscosity data of high alumina blast furnace slag was in accordance with the estimated values of viscosity by Riboud model. Understanding the mechanism of Al2O3, MgO, and binary basicity on the viscosity of blast furnace slag can provide a promising method for optimizing its viscosity value and improving the blast furnace operation.

Effects of composition and sintering temperature on the structure and compressive property of the lamellar Al2O3–ZrO2 scaffolds prepared by freeze casting

Using 3 wt% TiO2 nanopowders as sintering aid, we prepared porous lamellar Al2O3–ZrO2 composites with an initial solid loading of 30 vol% and the Al2O3/ZrO2 weight ratios of 1:9, 3:7, 5:5, 7:3, and 9:1 by freeze casting. The viscosity of water-based slurries decreased with increasing Al2O3 content while the porosity and the wavelength of the lamellae in the sintered scaffolds showed first an increase and then decrease with maximum values appearing at Al2O3:ZrO2 = 5:5. A relatively large amount of tetragonal (t) ZrO2 transformed to monoclinic (m) ZrO2 with the increase in the Al2O3 content and sintering temperature, thus reducing stress-induced phase transformation effect during loading. The compressive strength of the sintered scaffolds depended on sintering temperature, porosity, and the phase composition in the composites. A maximum value of 105 ± 10 MPa was achieved in the scaffolds with a composition of Al2O3:ZrO2 = 3:7 after sintering at 1450 °C for 2 h.

Effect of Al2O3 on the Crystallization of Mold Flux for Casting High Al Steel

In order to lower the weight of automotive bodies for better fuel-efficiency and occupant safety, the demand for high Al-containing advanced high strength steel, such as transformation-induced plasticity and twinning-induced plasticity steel, is increasing. However, high aluminum content in steels would tend to significantly affect the properties of mold flux during the continuous casting process. In this paper, a kinetic study of the effect of Al2O3 content on the crystallization behavior of mold flux was conducted by using the single hot thermocouple technique and the Johnson–Mehl–Avrami model combined with the Arrhenius Equation. The results suggested that Al2O3 behaves as an amphoteric oxide in the crystallization process of mold flux. The precipitated phases of mold flux change from cuspidine (Ca4Si2O7F2) into nepheline (NaAlSiO4) and CaF2, and then into gehlenite (Ca2Al2SiO7) with the increase of Al2O3 content. The kinetics study of the isothermal crystallization process indicated that the effective crystallization rate (k) and Avrami exponent (n) also first increased and then decreased with the increase of Al2O3 content. The values for the crystallization activation energy of mold flux with different Al2O3 contents were E R0.8A7 = 150.76 ± 17.89 kJ/mol, E R0.8A20 = 136.43 ± 6.48 kJ/mol, E R0.8A30 = 108.63 ± 12.25 kJ/mol and E R0.8A40 = 116.15 ± 8.17 kJ/mol.

Influence of MgO/Al2O3 Ratio on Viscosity of Blast Furnace Slag With High Al2O3 Content

The viscosity of SiO2−CaO−MgO−Al2O3−TiO2−FeO blast furnace (BF) slag system with high Al2O3 content is studied by using a rotating cylinder viscometer. The effect of the MgO/Al2O3 ratio on the viscosity, the stability, and break point temperature of BF slag are investigated. As a result, an increase in the Al2O3 content and a decrease of temperature tended to make the stability of slag become worse gradually due to an increase in the degree of the polymerization of the slag. In addition, increasing Al2O3 content results in an increase in viscosity at a fixed temperature. The MgO/Al2O3 ratio of the slag have obvious effect on the influence of the temperature of the BF slag on viscosity of the slag; the proper use of the MgO/Al2O3 ratio can obviously improve the stability and the fluidity of the slag, and the suitable value of the MgO/Al2O3 ratio decrease with increasing the Al2O3 content in the BF slag. In order to maintain a good stability and fluidity of the slag, the Al2O3 content in the slag should be 18&amp;#x0025 not exceed 19&amp;#x0025 and the ration of MgO/Al2O3 in a range of 0.6–0.7.