Effect Of Aluminum Substitution Research Articles

Effect of aluminum substitution on physical–chemical properties of novel iron-sillenite Bi25Fe(1−x)AlxO40 (x = 0.00, 0.20, 0.50)

Effect of aluminum substitution on physical–chemical properties of novel iron-sillenite Bi25Fe(1−x)AlxO40 (x = 0.00, 0.20, 0.50)

Effect of Aluminum Substitution on the Structural, Magnetic, and Magnetothermal Properties of Yttrium Iron Garnet

Effect of Aluminum Substitution on the Structural, Magnetic, and Magnetothermal Properties of Yttrium Iron Garnet

Effect of Aluminium Substitution on Physical Adsorption of Chloride and Sulphate Ions in Cement-Based Materials.

When aluminium-rich phase minerals are added to Portland cement, Al atoms will enter the C-S-H and Al, then a substitution reaction will occur, forming a hydrated silica-calcium aluminate (C-A-S-H), which changes the molecular structure of the cement material. Due to limitations in experimental methods, the research on the bonding effect between corroded ions and Al-substituted structures is still unclear. Here, the mechanism of an Al substitution reaction affecting the adsorption of chloride and sulphate ions was studied using simulation. The C-A-S-H model of aluminium random substitution was built, evaluating the binding effects among the C-A-S-H, and sulphate and chloride ions. The results demonstrated that the C-A-S-H structure generated by the Al substitution reaction increased the physical adsorption capacity of the chloride and sulphate ions. The adsorption capacity of the sulphate ions was 13.26% higher than that before the Al substitution, and the adsorption capacity of chloride ions was 21.32% higher than that before the Al substitution. The addition of high aluminium phase minerals caused the interfacial flocculants C-A-S-H and C-S-H to connect and intertwine in the the interface transition zone (ITZ) structure. The addition of high-alumina phase minerals improves the microstructure of concrete hydration products, improving the physical and mechanical properties and durability of concrete. After the addition of 20% lithium slag, the sulphate ion erosion content and the chloride ion erosion content of the concrete decreased by 13.65% and 15.72%, respectively. This paper provides a deeper understanding of the effect of high-alumina phase admixtures on concrete at the micro-scale.

Effects of aluminum substitution on the microstructure and magnetic properties of cobalt ferrites prepared by the co-precipitation precursor

Effects of aluminum substitution on the microstructure and magnetic properties of cobalt ferrites prepared by the co-precipitation precursor

Effect of aluminum substitution on structural and magnetic properties of nickel ferrites: Raman and 57Fe IFNMR studies

We present the structural and magnetic characteristics of Al substituted nickel ferrites NiFe2-xAlxO4 (x = 0.0–0.3) produced through auto combustion. The phase purity and lattice parameters are determined using X-ray diffraction measurements and rietveld refinement analysis respectively. Magnetic investigations demonstrate that when the Al3+ concentration increases, the saturation magnetization (MS) decreases. Raman investigations revealed that the peaks corresponding to the A and B-site sites intensified as a result of Al3+ replacement. Furthermore, 57Fe Nuclear Magnetic Resonance investigations show that after Al3+ replacement, the centre frequencies corresponding to the A- and B-sites shift to lower frequency levels. The Fe site occupancies at the A and B sites are calculated using the findings of XRD, Raman, and NMR experiments, all of which are concurrent with each other. Based on present findings, Al3+ preferentially occupies the B-site over the A-site in nickel ferrite.

Aluminum Substitution in Ni-Co Based Spinel Ferrite Nanoparticles by Sol–Gel Auto-Combustion Method

In this research work, aluminum substituted Ni-Co ferrite nanoparticles have been produced by a simple and cost-effective method, i.e., sol–gel auto-combustion. Synthesized nanoparticles were annealed in a muffle furnace at 600°C for 3 h before characterization. The x-ray diffraction patterns revealed that the ferrite nanoparticles grew preferentially along the (311) plane and exhibit face centered cubic structure. The crystallite size of nanoparticles (14 to 17 nm) was estimated by Scherrer’s relation. The effect of aluminum substitution on structural parameters of ferrite nanoparticles, such as lattice constant and stacking faults, have been studied. Structural analysis revealed that the lattice constant of the nanoparticles decreases as a function of aluminum content. The Fourier transform infrared spectroscopy confirmed the spinal ferrite crystal structure of synthesized aluminum substituted Ni-Co ferrite nanoparticles. The surface morphology observed through scanning electron microscopy depicts the growth and distribution of nanograins with uniform size with in the samples. Dielectric properties investigated through impedance analyzer spectroscopy revealed that aluminum substituted Ni-Co ferrite nanoparticles demonstrated the high conductivity along with potential dielectric properties. These aluminum substituted Ni-Co ferrite nanoparticles would have possible applications in high storage memory and microwave devices.

Effect of aluminium substitution in magnetically affluent inverse spinel ferrites studied via 57Fe-Internal field NMR

Ferro/ferrimagnetic materials are of fundamental interest due to their variety of applications. The structural and magnetic properties change significantly with different synthesis procedures. Here, we report the synthesis, X-Ray Diffraction (XRD), Vibrating Sample Magnetometry (VSM), and Nuclear Magnetic Resonance (NMR) studies of spinel nickel ferrites doped with non-magnetic cations like cadmium and aluminium. The spinel ferrites like Ni0.7Cd0.3Fe2-xAlxO4 (x = 0, 0.1, 0.2) are synthesized using one step auto combustion technique. The X-ray diffraction measurements confirm the formation of these systems in pure phase. In the present study we have used the modified home-built NMR spectrometer to study 57Fe NMR in these ferro magnetic materials. The difference in the Fe3+ bonding at the octahedral (B-site) and the tetrahedral (A-site) sites result in the different hyperfine fields yielding Internal Field (IF) NMR frequencies at two different frequencies. The substitution of the non-magnetic Al3+ results in increasing in the line width of the NMR spectra corresponding to the octahedral site (B-site). Further, the NMR spectra corresponding to A-site decreases (both in terms of line width and area) due to the decrease in the ferrimagnetic contribution at that site. Change in the local environment around Fe3+ ion present at B-site is very well observed using 57Fe NMR technique.

Effects of aluminum substitution on the surface charge of colloidal goethite particles: experiments and MUSIC modeling.

Proton adsorption behavior on the surface of Al-substituted goethites as a function of pH and ionic strength was investigated and simulated with the multisite surface complexation (MUSIC) model. In addition, X-ray diffraction, X-ray photoelectron spectroscopy, and field emission scanning electron microscope were used to characterize the crystal structure, chemical composition, micromorphology, and surface properties of the Al-substituted goethite. Al substitution was found to affect the crystal structure and micromorphology of goethite. The morphological differences did not result in significant differences in PZC value but largely affected the surface charge values. Goethite surface charge capacity increased progressively with increasing amount of Al substitution, which was attributed to increases in the density of surface coordinated sites due to the increase in (021)/(110) face ratio. The optimization calculations enabled a satisfactory fitting of the titration data of both pure goethite and Al-substituted goethite, and the MUSIC model facilitated a more specific understanding of the charging behavior of Al-substituted goethite. The singly (≡FeOH-0.5 + ≡AlOH-0.5) and triply coordinated (≡Fe3O-0.5 + ≡AlFe2O-0.5) surface groups were most likely responsible for the basic charging behavior of goethite in the pH range of 4-10. All results indicate that the MUSIC model has excellent performance in characterizing Al-substituted goethite, and the model has promising application prospect in other substituted metal (hydr)oxides.

Magnetic Properties of La0.7Ba0.3Mn1−xAlxO3 (0 ≤ × ≤ 0.15) Perovskites

The effects of aluminum substitution on the magnetic properties of perovskite type La0.7Ba0.3Mn1−xAlxO3 (0.05 ≤ × ≤ 0.15) compounds have been studied. The phase purity of the samples has been determined with X-ray powder diffraction. Comparison among various structural parameters has been performed to understand the effect of Al3+ substitution at Mn3+ site. The DC magnetization study includes the thermo-magnetic measurements in zero field cooled (ZFC) mode within the temperature range of 100 to 300 K and the isothermal M-H curve at 100 K. It has been observed that incorporation of Al3+ ion at the Mn3+ site significantly affects the exchange interaction processes and hence results in suppressed magnetic moments. It has been observed that the uniform distribution of Al3+ at Mn3+ sites results in weakening of long-range ferromagnetic (FM) ordering in the parent compound. The inclusion of 10–15% of Al3+ significantly affects the double-exchange (DE)-interactions, thereby promotes a non-magnetic phase along with separated short-range FM clusters. The presence of non-magnetic phase and non-spontaneous magnetization among FM clusters has been observed for samples with 10–15% of aluminum substitution.

Effect of aluminium substitution on low energy electrodynamics of barium-lead M-type hexagonal ferrites

We present the first detailed study of the terahertz-infrared dielectric response of single crystalline lead-substituted M-type barium hexaferrites doped with Al3+. The broadband spectra of complex dielectric permittivity ε*(v)=ε’(v)+iε"(v) of Ba0.8Pb0.2AlxFe12-xO19 with concentrations of the dopant x(Al)=1.2, 3, 3.3 are obtained for two principle polarizations using Fourier-transform infrared spectroscopy and terahertz time-domain spectroscopy in the temperature range from 4 to 300 K and at frequencies from 10 cm−1 up to 8000 cm−1. We observe a rich set of excitations and assign them to the electronic transitions within the ground state 5E of the 4-fold coordinated divalent iron and to phonon resonances. Effect of Al3+ cation substitution on low energy (terahertz) dielectric response and infrared phonon spectra of barium-lead M-type hexaferrites is analysed and discussed.

Effects of aluminum substitution by potassium in the P2O5–Al2O3–Na2O–K2O phosphate glasses

P2O5–Al2O3–Na2O–K2O phosphate glasses with various K2O/Al2O3 ratios were synthesized using the melt quenching technique. Raman and absorption spectra were measured to investigate the effects of these ratios on the structures and spectroscopic properties of the glasses. As the K2O/Al2O3 ratio increases, the Raman spectra show shifts of some of the scattering bands to lower wavenumbers, the broadening of some bands and the tendency of decreasing the overlap between them, especially in the regions 400-700 cm−1 and 850-1300 cm−1. On the other hand, the absorption spectra of these phosphate glasses showed no marked changes in the optical band gap energy. Also, optical and thermal properties were measured to evaluate their potential for athermalization. As the ratio K2O/Al2O3 increases, the refractive index and glass transition temperature decrease, while the thermal expansion coefficient (α) increases. The existence of a negative thermo-optic coefficient (dn/dT) is important to obtain the temperature coefficient of the optical path (ds/dT) equal to −0.06·10−6/K for PAN10K glass. The results showed that increasing the K2O/Al2O3 ratio in phosphate glasses can control the value of ds/dT to achieve the athermalization.

Mechanochemically aided sintering process for the synthesis of barium ferrite: Effect of aluminum substitution on microstructure, magnetic properties and microwave absorption

Abstract This work reported a mechanochemically aided sintering process for the synthesis of BaFe 12−x Al x O 19 (x = 0.0, 0.5, 1.0, 1.5, 2.0) hexaferrite ceramic. A brief analysis was conducted on the synthesis mechanism of the pure barium ferrite, its morphology, and magnetic properties. By substitution of Al 3+ ions into BaFe 12 O 19 lattice, the size of the grains decreased and their hexagonal-plate shape tended toward a rod-like shape. These events led to a single domain nature in the grains and also an increase in their magneto-crystalline anisotropy. Single domain nature obtained a barrier against the movement of the domain walls, which led to an increase in coercivity. On the other hand, the increase of anisotropy led to the enhancement of coercivity, according to the Stoner–Wohlfarth model. The substitution of Al 3+ ions also led to the decrease of the saturation magnetization, which was because of the lower magnetic moment of Al 3+ ions (0 μB) compared to that of Fe 3+ ions (+5 μB). As a result of substituting Al 3+ ions with a value of x = 2, a maximum reflection loss of −43 dB was obtained at a frequency of 15.7 GHz.

Microstructure and characterization of hydrothermal synthesis of Al-substituted tobermorite

Tobermorite is an important mineral analog of calcium silicate hydrate (C-S-H), the main phase formed by hydration of Portland cement, due to the structural similarity. As part of a broader study on the effect of aluminum substitution C-S-H, the synthesis and characterization of tobermorite with and without aluminum were conducted. The X-ray diffraction pattern indicated that a suitable synthesis time for tobermorite with or without aluminum was 5 h in an autoclave at 180°C and saturated steam pressure around 1MPa. In both samples the mineral is 11Å-tobermorite. X-ray fluorescence showed that the sample with aluminum had a higher molar ratio of Ca/(Si+Al). Thermogravimetry-differential scanning calorimetry showed the same general changes, loss of free water at 55°C, loss of interlayer water at 187°C, dehydroxylation at 664°C, and conversion to wollastonite at 841°C. With the incorporation of aluminum, 29Si and 27Al magic angle spinning-nuclear magnetic resonance spectra showed aluminum addition increases the mean chain length, Al mainly occupies Q2 bridging and Q3 branching sites. Scanning electron micrographs indicated that tobermorite crystals are larger than those of sample without alumina. This work is beneficial for understanding the implication of the use of admixtures containing aluminum in concrete on its micro- and atomic-scale properties.

Nanocrystalline hydroxyapatite doped with aluminium: A potential carrier for biomedical applications

Biocompatible materials based on hydroxyapatite are potentially attractive for a wide range of medical applications. The effect of aluminium substitution on the biocompatibility of hydroxyapatite (HA) under the physiochemical conditions has been investigated. Various samples of aluminium doped hydroxyapatite (Al-HA) with different concentration (0, 0.5, 1.0, 1.5, 2.0, 2.5mol%) were successfully synthesised by solution combustion method and characterized by X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM), and Scanning Electron Microscopy (SEM), and thermal analysis technique. XRD and TEM results reveal uniform and crystalline nature of Al-HA nanoparticles. The biocompatibility of the Al-HA nanoparticles was studied using L929 cell lines by MTT assays up to 24h. These Al-HA nanoparticles are biocompatible on cell lines L929 and do not have toxic effects for further possible in vivo applications. The results of these studies confirmed the biocompatibility of Al-HA and demonstrated the suitability for biomedical applications. The present work reveals the importance of structural, morphological, biocompatible properties of Al-HA nanoparticles and predicts the suitability for biomedical applications.

Effects of aluminum substitution on the structure and electric properties of langasite family crystals

The effects of aluminum substitution on the structure and electric properties of langasite (La3Ga5SiO14) family crystals are reported. The maximum Al content x of La3Ga5-xAlxSiO14 (LGAS), La3Nb0.5Ga5.5-xAlxO14 (LNGA), and La3Ta0.5Ga5.5-xAlxO14 (LTGA) crystals grown by the conventional Czochralski technique are x = 0.9, 0.2, and 0.5, respectively. Single-crystal X-ray structural analysis reveals that Al atoms are distributed in all cation sites except for the decahedral one occupied by La, rather than favoring the smallest tetrahedral sites. The electrical properties of the Al-substituted crystals were also compared with those of pure ones. Al substitution was found to affect the piezoelectric constant d14, but not d11. The LGAS and LTGA crystals exhibit higher electric resistivity ρ as a result of Al substitution. Among the Al-substituted and pure crystals, the LTGA crystal featured the lowest temperature dependence of d11 and highest ρ, making it the most suitable of the group for high-temperature piezoelectric applications.

Thermal expansion in the garnet-type solid electrolyte (Li7−xAlx/3)La3Zr2O12 as a function of Al content

The thermal expansion (TE) coefficients of the lithium-stable lithium-ion conducting garnet lithium lanthanum zirconium oxide (LLZ) and the effect of aluminum substitution were measured from room temperature up to 700°C by a synchrotron-based X-ray diffraction. The typical TE value measured for the most reported composition (LLZ doped with 0.3wt.% or 0.093mol% aluminum) was 15.498×10−6K−1, which is approximately twice the value reported for other garnet-type structures. As the Al(III) concentration has been observed to strongly affect the structure observed and the ionic conductivity, we also assessed its role on thermal expansion and noted only a small variation with increasing dopant concentration. The materials implications for using LLZ in a solid state battery are discussed.

Effects of aluminum substitution on the crystal structure and magnetic properties in Zn2Y-type hexaferrites

Crystal structure and magnetic properties of multiferroic Y-type hexaferrites Ba0.5Sr1.5Zn2(Fe1−xAlx)12O22 (x = 0, 0.04, 0.08, and 0.12) were investigated. The Z- and M-type impurity phases decrease with increasing Al content, and the pure phase samples can be obtained by modulating Al-doping. Lattice distortion exists in Al-doped samples due to the different radius of Al ion (0.535 Å) and Fe ion (0.645 Å). The microstructural morphologies show that the hexagonal shape grains can be observed in all the samples, and grain size decreases with increasing Al content. As for magnetic properties of Ba0.5Sr1.5Zn2(Fe1−xAlx)12O22, there exist rich thermal- and field-driven magnetic phase transitions. Temperature dependence of zero-field cooling magnetization curves from 5 K to 800 K exhibit three magnetic phase transitions involving conical spin phase, proper-screw spin phase, ferromagnetic phase, and paramagnetic phase, which can be found in all the samples. Furthermore, the phase-transition temperatures can be modulated by varying Al content. In addition, four kinds of typical hysteresis loops are observed in pure phase sample at different temperatures, which reveal different magnetization processes of above-motioned magnetic spin structures. Typically, triple hysteresis loops in low magnetic field range from 0 to 0.5 T can be observed at 5 K, which suggests low-field driven magnetic phase transitions from conical spin order to proper-screw spin order and further to ferrimagnetic spin order occur. Furthermore, the coercive field (HC) and the saturation magnetization (MS) enhance with increasing Al content from x = 0 to 0.08, and drop rapidly at x = 0.12, which could be attribute to that in initial Al-doped process the pitch of spin helix increases and therefore magnetization enhances, but conical spin phase eventually collapses in higher-concentration Al-doping.

Magnetic behavior and dielectric properties of aluminum substituted M-type barium hexaferrite

Various parameters in the structural features of the aluminum substituted barium hexagonal ferrite particles BaAlxFe12−xO19 with 0≤x≤3.5 which were prepared by the solid state reaction method have been studied. The infrared transmission spectrum was measured in the wave number region 5000–200cm−1 at room temperature. The results were interpreted in terms of the vibrations of the isolated molecular units in such a way to preserve the tetrahedral and octahedral clusters of metal oxides in the barium aluminum hexagonal ferrites. The infrared features are assigned to Fe–O and Ba–O bonds in M-type hexagonal ferrite (BaFe12O19) molecules. Also, the results explain the structural model, based on the effect of aluminum substitution “Al–O bond”. On the other hand, the magnetic behavior of the samples was studied using the vibrating sample magnetometer technique. The saturation magnetization (Ms) and magneton number (nB) decrease with increasing Al3+ substitution from 61.2 to 28.9emu/g and from 12.2 to 5.3µB respectively. Also, all samples were characterized using X-ray diffraction and the values of grain size, microstrain and dislocation density of all samples were calculated. The dielectric parameters and ac conductivity measurements were performed within a temperature range 293–493K. The ac conductivity showed a linear relation with the frequency power law with an exponent s≈0.69–0.14 for BaFe12O19. It decreases with increasing temperature, indicating that the heterogeneous structures increase. While the dielectric constant (ε′) and the dielectric loss (ε″) decrease with increasing Al substitution.

The effect of aluminum substitution on the mechanically induced self-sustaining reaction of molybdenum-silicon powders

The effect of Al concentration on the ignition of mechanically-induced self-sustaining reaction (MSR) in Mo + (2 − x)Si + 2xAl powder mixtures has been investigated. When MoSi2 is prepared by SHS method, Al addition results in the formation of Si-Al eutectic and consequently lowers the ignition temperature. In the case of MSR, replacing brittle Si with ductile Al also affects the activation process. The ignition of MSR was investigated as a function of the Al content in a SPEX 8000 Mixer Mill. The ignition time decreased by 30% between x = 0 and 0.08. At the same time, the grain size increased by about 50% according to XRD linewidth measurements. Comparison of SEM images suggests that Al substitution promotes the formation of agglomerates and lamellar structures, although the differences between the binary Mo-Si and Alcontaining samples are very small. Al substitution encourages the formation of hexagonal Mo(SiAl)2 over the tetragonal form of MoSi2. It also promotes more complete conversion during MSR.

Kinetic study of goethite dehydration and the effect of aluminium substitution on the dehydrate

Goethite and Al-substituted goethite were synthesized and were characterized using XRD and XRF. The kinetic study of goethite dehydrate was investigated by TG and DTG at different heating rates (2, 5, 10, 15, 20°C/min) and the effect of Al substitution for Fe on dehydrate was studied. The results showed that two types of absorbed water with the same Ed values of 3.4, 6.2kJ/mol were confirmed on goethite and Al-substituted goethite. Three types of hydroxyl units were proved, one being on the surface and the other two being in the structure of goethite. The substitution of Al for Fe in the structure of goethite decreases the desorption rate of hydroxyl, increases the dehydroxylation temperature, broadens the desorption peaks in DTG curves, and improves the Ed values from 19.4, 20.4, 26.1kJ/mol to 21.6, 30, 33.6kJ/mol when Al substitution comes to 9.1%.