Characterization Of Alumina Research Articles

Electrochemical and Spectroscopic Characterization of Aluminium(III)-para-methyl-meso-tetraphenylporphyrin Complexes Containing Substituted Salicylates as Axial Ligands

A series of aluminium(III)-p-methyl-meso-tetraphenylporphyrin (p-CH3TPP-Al(III)) containing axially coordinated salicylate anion [p-CH3TPP-Al-X)], where X = salicylate (SA), 4-chlorosalicylate (4-CSA), 5-chlorosalicylate (5-CSA), 5-flourosalicylate (5-FSA), 4-aminosalicylate (4-ASA), 5-aminosalicylate (5-ASA), 5-nitrosalicylate (5-NSA), and 5-sulfosalicylate (5-SSA), have been synthesized and characterized by various spectroscopic techniques including ultraviolet-visible (UV-vis), infrared (IR) spectroscopy, proton nuclear magnetic resonance (1H NMR) spectroscopy,13C NMR, and elemental analysis. A detailed study of electrochemistry of all the synthesized compounds has been done to compare their oxidation and reduction mechanisms and to explain the effect of axial coordination on their redox properties.

Characterization of alumina–alumina/graphite/monel superalloy brazed joints

Active metal brazing of alumina with alumina, graphite and monel 404 superalloy was performed at 910 °C for 5 min using TICUSIL (68.8Ag–26.7Cu–4.5Ti in wt.%) as the braze alloy in vacuum of 5 × 10 −6 mbar. The brazed joints were characterized by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis, nanohardness and Young's modulus measurements by depth sensitive indentation technique. X-ray diffractrometry showed that the Ti-based compounds were formed at the substrate–filler alloy interfaces of the brazed joints as reaction products. The cross sectional microstructures of the brazed joints were observed by scanning electron microscopy. The energy dispersive X-ray analysis determined the elemental compositions at the selective points of the joint cross section, which supported the X-ray diffraction results. The nanohardness and Young's modulus of the substrate–filler alloy interface showed no abrupt change, which suggests reliable joint performance in service.

Synthesis and characterization of aluminum and zinc complexes supported by pyrrole-based ligands and catalysis of the aluminum complexes toward the ring-opening polymerization of ɛ-caprolactone

Reaction of quinolin-8-amine with 1 H-pyrrole-2-carbaldehyde or 5- tert-butyl-1 H-pyrrole-2-carbaldehyde catalyzed by HCO 2H forms N-((1 H-pyrrol-2-yl)methylene)quinolin-8-amine (≡ HL, 3a) or N-((5- tert-butyl-1 H-pyrrol-2-yl)methylene)quinolin-8-amine (≡ HL′, 3b). Treatment of 3a and 3b respectively with AlMe 3 or AlEt 3 in toluene affords corresponding aluminum complexes LAlMe 2 ( 4a), L′AlMe 2 ( 4b) and LAlEt 2 ( 4c). Reaction of 3a and 3b with an equivalent of ZnEt 2 in toluene generates L 2Zn and L′ 2Zn, respectively. A related compound N-((1 H-pyrrol-2-yl)methylene)-2-(3,5-dimethyl-1 H-pyrazol-1-yl)benzenamine (≡ HL″, 7) was prepared by reaction of 2-(3,5-dimethyl-1 H-pyrazol-1-yl)benzenamine with 1 H-pyrrole-2-carbaldehyde in the presence of HCO 2H. Reaction of 7 with AlMe 3 gives L″ 2AlMe ( 8), and with ZnEt 2 yields L″ 2Zn ( 9). All new compounds were characterized by NMR spectroscopy and elemental analysis. The structures of complexes 4b, 5b and 8 were additionally characterized by single crystal X-ray diffraction analyses. Complexes 4a– 4c, and 8 were proved to be active catalysts for the ring-opening polymerization (ROP) of ɛ-caprolactone (ɛ-CL) in the presence of BnOH. The kinetic study of the polymerization reactions catalyzed by 4a and 8 was performed.

Elaboration and characterization of alumina - fluorapatite composites

Alumina and fluorapatite powder were mixed in a wet medium in order to elaborate biphasic ceramics composites. The effect of fluorapatite addition (26.5 wt%) in the densification and the mechanical properties of the alumina matrix were measured. The phase developments have been systematically analysed by scanning electronic microscopy, X-ray diffraction, Infrared spectroscopy and 31P and 27Al magic angle scanning nuclear magnetic resonance. The Brazilian test was used to measure the mechanical resistance of alumina - 26.5 wt% fluorapatite composites. The densification and strength rupture of composites increase versus sintering temperature and holding time. At 1600°C, the composites densities reached 85% and the rupture strength was about 22 MPa. Also, the composites sintering at 1500°C for 5 hours provides samples with similar density and having higher mechanical resistance, above 26 MPa. For longer holding times, the mechanical properties were hindered by the exaggerated grain growth and the formation of intragranular porosity. From 1400°C, the characterization of the alumina - 26.5 wt% fluorapatite composites indicates the formation of calcium aluminates.

Synthesis and characterisation of aluminium(iii) and tin(ii) complexes bearing quinoline-based N,N,O-tridentate ligands and their catalysis in the ring-opening polymerisation of ε-caprolactone

The synthesis and catalysis in the ring-opening polymerisation (ROP) of ε-caprolactone (ε-CL) of aluminium(iii) and tin(ii) complexes supported by quinoline-based N,N,O-tridentate ligands are reported. Reaction of 8-{RC(O)CH(2)P(Ph(2)) = N}C(9)H(6)N (R = Bu(t), 2; R = Ph, 3) with AlMe(3) gave [Al(Me(2)){OCR = CHP(Ph(2)) = N(8-C(9)H(6)N)}] (R = Bu(t), 4; R = Ph, 5). Treatment of 2 and 3 with Sn[N(SiMe(3))(2)](2) generated tin(ii) complexes [Sn{OC(R) = CHP(Ph(2)) = N(8-C(9)H(6)N)}{N(SiMe(3))(2)}] (R = Bu(t), 6; R = Ph, 7). A similar reaction of AlMe(3) with 8-{MeC(O)CH(2)C(Me) = N}C(9)H(6)N gave [Al(Me(2)){OC(Me) = CHC(Me) = NC(9)H(6)N}] (9). Compounds 2-9 were characterised by NMR spectroscopy and elemental analysis. The molecular structures of complexes 4, 6 and 9 were determined by single crystal X-ray diffraction techniques. Investigation of catalysis of complexes 4-7 and 9 in the ROP of ε-CL revealed that the aluminium complexes, 4, 5 and 9, are much more active than the tin(ii) complexes. The kinetic studies for the polymerisation of ε-CL catalysed by complexes 4, 5 and 9 in the presence of benzyl alcohol (BnOH) indicated that the polymerisations proceed with the first-order dependence on monomer concentration. The polymerisation was well controlled and gave a polymer with narrow molecular weight distribution.

Synthesis and characterization of aluminum and Al/REE pillared clays and supported palladium catalysts for benzene oxidation

Volatile organic compounds (VOCs) are considered as a major pollutant in indoor and outdoor air. More stringent environmental regulations have been implemented in order to reduce the VOC emissions. One of the techniques available for destructive removal of VOCs is catalytic oxidation. In the present work, Al/Rare Earths (REE: Y, Ce, La, Pr and Nd) pillared clays (PILCs) were used to support 0.2 wt.% of palladium for the complete oxidation of low concentration of benzene. The supports and catalysts were characterized by XRD, N 2 adsorption/desorption, FTIR spectroscopy, HRTEM and H 2-TPR techniques. The results indicated that after Al and Al/REE pillaring, the basal spacing, S BET, A mic and V mic of Al and AlREE-PILC had a considerable increase compared with those of Na-mmt. Activity tests of deep oxidation of benzene showed that the catalytic activity of Pd catalysts supported on Al and AlREE-PILC were much higher than that on initial clays, which was due to the fact that optimized structure of PILCs, such as large basal spacing, high S BET and porosity, improved Pd dispersion and increased the active sites of Pd. Especially for Pd/AlCe-PILC, the temperature of complete oxidation was about 280 °C, exhibiting the highest catalytic activity.

Small-Scale Mechanical Characterization of Aluminum and Titanium Alloys

Abstract A Small Punch Test method with 3 mm diameter and 0.5 mm thick specimens was utilized to characterize 3003-H14 aluminum, 2618-T61 aluminum, and Ti-6Al-4V alloys. The method was found to be repeatable and the effect of surface roughness negligible within the range of 0.450–3.011 μm. In addition, the titanium has shown higher strength and elastic modulus than the aluminum specimens. The addition of iron, copper, and nickel elements to Al makes the alloy stronger and more ductile. The research shows that the Small Punch Test can be used to qualitatively compare such mechanical properties as surface hardness, ductility, toughness, yield strength, and ultimate tensile strength of small volume test specimens in aluminum and titanium alloys. The advantage of such a method is its ability to obtain consistent evaluation of mechanical properties from small specimen volumes effectively.

Characterization of alumina- and niobia-supported gold catalysts used for oxidation of glycerol

Gold catalysts supported on niobia and alumina are active in glycerol oxidation performed in liquid basic solution in the presence of oxygen. Niobia-supported gold is only slightly less active than commercial Au/TiO 2 catalyst. XPS data allow to characterize gold nanoparticles on both supports. IR studies show that CO adsorbs on gold particles loaded on niobia producing well characterized terminal carbonyls whose C–O stretching frequency shifts up by decreasing CO coverage, an usual behaviour for gold carbonyls. Two families of gold nanoparticles on niobia are characterized by CO stretching frequencies of adsorbed CO at 2098–2112 cm −1 after reduction at 573 K and at 2108–2120 and 2125–2135 cm −1 after reduction at 773 K. However, after both reduction pretreatments such gold metal particles coexist with strongly oxidizing gold species which are able to convert CO into CO 2 at 153–193 K. Based on IR and XPS experiments, the lower activity of alumina-supported gold may be due to a lower density of corner and edge sites on Au nanoparticles, associated to the minor dispersing ability of alumina for gold.

The synthesis and characterization of aluminum, gallium and zinc formamidinates

Reactions of the formamidinate ligand, RN(H)C(H)NR, L H, (R = 2,6-diisopropylphenyl), with AlMe 3, AlMe 2Cl, GaMe 3 and ZnEt 2 were investigated to examine potential coordination modes of the ligand and the effect of hydrolysis on the products. Nine new complexes have been fully characterized by X-ray crystallography and other spectroscopic techniques and highlight the diverse coordination modes of the formamidinate ligand.

Synthesis and characterization of alumina flakes/polymer composites

AbstractAlumina flakes were prepared by solution combustion method and milled to provide powder. XRD and SEM data exhibited microsized flakes with 100 nm thickness and nanosized grains. Then the powders were dispersed in polystyrene (PS) and poly methyl methacrylate (PMMA) matrixes and thin sheets of composites were produced by solution method. Mechanical properties of the composites were characterized using tensile test and their fracture surfaces, elemental composition and hydrophobic property were tested by SEM, EDX and contact angle techniques, respectively. The results exhibited better mechanical properties compared to pure polymer samples i.e. the elastic modulus in PMMA and PS composites, were increased about 107 and 109%, respectively. In addition the composite surfaces became more hydrophobic than pure polymer systems. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Synthesis and characterization of aluminium containing CIT-1 and their structure–property relationship to hydrocarbon trap performance

The present work focuses on the synthesis of Al-CIT-1 by various post-modification procedures of B-CIT-1 and their structure–property relation to hydrocarbon trap performance. Al substitution in B-CIT-1 was carried out by three different post-modification procedures, viz., direct exchange (Al-CIT-1_DEX), insertion (Al-CIT-1_INS), and impregnation (Al-CIT-1_IMP), and characterized in detail by various physico-chemical techniques such as XRD, N 2 adsorption, SEM, NH 3-TPD, XPS, and solid state 27Al and 29Si MAS NMR. The Al-CIT-1 samples were tested for their adsorption–desorption characteristics of toluene, and 2,2,4-trimethylpentane (2,2,4-TMP) to understand the Al distribution in CIT-1 as well as the efficacy of these materials as hydrocarbon traps. The Al distribution in Al-CIT-1 plays a critical role in the adsorption–desorption characteristics of toluene and 2,2,4-TMP. Al-CIT-1 with high relative proportion of framework Al and less extraframework Al (Al-CIT-1_DEX) showed maximum toluene and 2,2,4-TMP adsorption capacity. The presence of finely distributed extraframework Al 2O 3 species in Al-CIT-1_INS modify the pores and causes a slow release of toluene during desorption. Al-CIT-1_IMP with less Al content and acidity showed the lowest toluene desorption temperature. Large amount of surface Al species hinder a relatively bulky molecule 2,2,4-TMP to access the available active sites of tetrahedral Al and the associated Brϕnsted sites in the zeolite, and as a result, Al-CIT-1_INS showed hardly any adsorption towards 2,2,4-TMP. Thus, by varying the post-modification method and treatment condition, it is possible to tune the performance of Al incorporated CIT-1 as a useful material for hydrocarbon trap.

Characterization of Aluminum in Cation-Exchanged NH4NaY and USY Zeolites by 27Al MAS NMR Spectroscopy

The effects of cations on the local electromagnetic environments of catalytic sites in Y-zeolites are studied as a function of cation type and concentration. Quadrupolar coupling parameters measurable using 27Al MAS NMR at multiple field strengths, provide a window to study aluminum’s local electronic structure. Quadrupolar parameters calculated for framework tetrahedral aluminum are related to cation concentration and Bronsted acidity for potassium-, zinc-, and lanthanum-exchanged NH4NaY and USY zeolites.

Preparation and characterization of Ru/MgO-Al 2O 3 catalysts for methane steam reforming

The preparation and characterization of aluminum and magnesium oxides-supported ruthenium were described in this work, aiming to compare different supports to methane steam reforming catalysts for producing hydrogen. Gama-alumina-supported ruthenium and periclase-supported ruthenium were produced. The addition of small amounts of magnesium to alumina-supported ruthenium in the range of Mg/Al (molar) = 0.2–0.5 did not change the gama-alumina structure while high amounts (Mg/Al (molar) = 5) led to the production of periclase. Magnesium caused a decrease of specific surface area of alumina-supported ruthenium catalysts and this effect increased with the amount of the metal in solids. Magnesium also decreased the acidity of alumina-supported ruthenium and generated electron deficient ruthenium species, besides increasing their interaction with the support. The addition of magnesium increased the ruthenium dispersion but did not increase the methane conversion, suggesting that it negatively changed the electron properties of ruthenium towards methane conversion. However, it avoided deactivation during reaction and changed the activity for the water gas shift reaction, allowing tailoring the hydrogen to carbon monoxide molar ratio. The catalysts showed activity close or higher than a commercial sample, indicating that they are promising for the reaction, with the advantage that it can be tailored for several applications.

Synthesis and Mechanical Characterization of Aluminum Based Composites Prepared by Powder Metallurgy

ABSTRACTAluminum-based composites prepared from pure Al powder and previously Cu metallized graphite are fabricated by a solid state route and are characterized by X-ray diffraction and scanning electron microscopy in order to follow their microstructural evolution. Composites are processed using powder metallurgy technique in order to obtain cylindrical samples to carry out mechanical testing. Microstructural and mechanical characterizations reveal that, by milling, a homogeneous dispersion of insoluble particles into the Al matrix is obtained; this produces an important improvement in hardness and strength with respect to an un-milled sample. Milling intensity and particle concentration have an important effect on the mechanical properties of the synthesized composites.

Fabrication and Characterization of Aluminum Nitride/Boron Nitride Nanocomposites by Carbothermal Reduction and Nitridation of Aluminum Borate Powders

In order to fabricate aluminum nitride/boron nitride (AIN/BN) nanocomposites by pressureless sintering, the present study investigated the synthesis of AIN-BN nanocomposite powders by carbothermal reduction and nitridation of aluminum borate powders. Homogeneous mixtures of alumina (Al2O3), boric acid (H3BO3), and carbon powder were used to synthesize AIN/BN nanocomposite powders containing 10 and 20 vol% BN. Aluminum borate was produced by reacting Al2O3 and B2O3 above 800 degrees C, and AIN and turbostratic BN (t-BN) were produced by reacting aluminum borate with carbon powder and nitrogen gas at 1500 degrees C. Carbothermal reduction followed by nitridation yielded an AIN/BN nanocomposite powder composed of nanosized AIN and t-BN. By pressureless sintering nanocomposite AIN/BN powders containing 5 wt% Y22O3, AIN/BN nanocomposites were obtained without compromising the high thermal conductivity and high hardness.

Synthesis and Characterization of Alumina–Zirconia Nanopowders via an Oxalate Route

Nanocrystalline Al2O3–ZrO2 powder was synthesized by a simple method using oxalic acid as a chelating agent. The formation temperature of α - Al2O3 was investigated by differential thermal analysis. X-ray diffraction (XRD) analysis shows that t-ZrO2 was stabilized in alumina matrix with oxalic acid content 0.5 M and 1 M, respectively. In addition, the data from XRD showed α-Al2O3 and t-ZrO2 phase can be formed at 1100°C with 1 M oxalic acid content. Transmission electron microscope (TEM) micrograph of calcined powders revealed as the oxalic acid content in the precursor solutions is increased from 0.25 M to 0.5 M concentration. The obtained materials could be modified from segregated nanoparticles to agglomerated nanoparticles and finally to large agglomerate with 1 M concentration of oxalic acid. The Fourier transform infrared spectra (FTIR) confirms the formation of α-Al2O3 in corroboration with X-ray studies.

Synthesis and Characterization of Aluminum- and Gallium-Bridged [1.1]Chromarenophanes and [1.1]Molybdarenophanes

The synthesis and structural characterization of the first [1.1]chromarenophanes and the first [1.1]molybdarenophanes are described. A salt-metathesis reaction of [2-(Me 2NCH 2)C 6H 4]AlCl 2 with freshly prepared [Cr(LiC 6H 5) 2].TMEDA (TMEDA = N, N, N', N'-tetramethylethylenediamine) resulted in the dialumina[1.1]chromarenophane [{2-(Me 2NCH 2)C 6H 4}Al(eta (6)-C 6H 5) 2Cr] 2 ( 2a). The poor solubility of 2a in organic solvents prompted us to synthesize the new intramolecularly coordinated aluminum- and gallium dichlorides [5- tBu-2-(Me 2NCH 2)C 6H 3]ECl 2 [E = Al ( 3a), Ga ( 3b)] in which the phenyl group was equipped with a tert-butyl group. Salt-metathesis reactions of 3a and 3b, respectively, with freshly prepared [M(LiC 6H 5) 2].TMEDA (M = Cr, Mo) resulted in four new [1.1]metallarenophanes of the general type [{5- tBu-2-(Me 2NCH 2)C 6H 3}E(eta (6)-C 6H 5) 2M] 2 [E = Al, M = Cr ( 4a); E = Ga, M = Cr ( 4b); E = Al, M = Mo ( 5a); E = Ga, M = Mo ( 5b)]. 2a, 4a, b, and 5a, b have been structurally characterized by single-crystal analysis [ 2a.1/2C 6H 12: C 48H 56Al 2Cr 2N 2, monoclinic, P2 1/ c, a = 9.9117(9) A, b = 19.9361(16) A, c = 10.638(2) A, alpha = 90 degrees , beta = 112.322(5) degrees , gamma = 90 degrees , Z = 2; 4a.2C 6H 6: C 62H 72Al 2Cr 2N 2, monoclinic, P2 1/ c, a = 10.9626(9) A, b = 19.3350(18) A, c = 12.4626(9) A, alpha = 90 degrees , beta = 100.756(5) degrees , gamma = 90 degrees , Z = 2; 4b.2C 6H 6: C 62H 72Cr 2Ga 2N 2, monoclinic, P2 1/ c, a = 10.8428(2) A, b = 19.4844(4) A, c = 12.4958(2) A, alpha = 90 degrees , beta = 100.6187 degrees , gamma = 90 degrees , Z = 2; 5a.2C 6H 6: C 62H 72Al 2Mo 2N 2, triclinic, P1, a = 10.4377(4) A, b = 11.6510(4) A, c = 11.6514(4) A, alpha = 73.545(3) degrees , beta = 89.318(2) degrees , gamma = 76.120(2) degrees , Z = 1; 5b.2C 6H 6: C 62H 72Ga 2Mo 2N 2, triclinic, P1, a = 10.3451(5) A, b = 11.6752(6) A, c = 11.6900(5) A, alpha = 73.917(3) degrees , beta = 89.550(3) degrees , gamma = 76.774(2) degrees , Z = 1]. All five [1.1]metallarenophanes 2a, 4a, b, and 5a, b crystallize as anti isomers with both Me 2N donor groups in exo positions ( C i point group symmetry). The new [1.1]metallarenophanes show NMR spectra that can be interpreted as being caused by time-averaged C 2 h symmetrical species, which is consistent with the findings of their molecular structures in the solid state. Variable-temperature (1)H NMR measurements for 4a, b and 5a, b (500 MHz; -90 to 90 degrees C) revealed only peak broadening in the lower temperature range of -70 to -90 degrees C. (1)H NMR saturation transfer difference experiments did not show an expected anti-to-anti isomerization, rendering the new [1.1]metallacyclophanes rigid on the NMR time scale. Electrochemical measurements were performed for 4a, b and 5a, b. However, reproducible cyclic voltammograms could only be obtained for the two gallium species 4b and 5b, revealing the expected weak communication between the two transition-metal atoms in both compounds (class II).

Synthesis and characterization of aluminum or copper tungstophosphate and tungstosilicate immobilized in a polymeric blend

Aluminum or copper tungstophosphates and tungstosilicates were synthesized and immobilized in a polymeric blend formed by polyvinyl alcohol and polyethylene glycol using the freeze-thawing method. The salts retained the Keggin structure of the heteropolyanions during their synthesis and immobilization. Materials with spherical shape and a mean size of 2mm were obtained, with an almost constant distribution of the salts along the sphere width. Besides, the immobilized salts presented very strong acid sites and good thermal stability. The synthesized hybrid materials present suitable properties to be used as heterogeneous acid catalysts which are very attractive for many processes as replacement of conventional liquid ones.

Hydrothermal synthesis and characterization of aluminium and sulfate substituted 1.1nm tobermorites

Substitutions of sulfate and aluminum ions in calcium silicate hydrate (tobermorite) were investigated at 175 °C under saturated steam pressure. Structure and morphology of different tobermorite samples were investigated using XRD, FTIR and SEM. A sample of pure xonotlite was prepared to assist in FTIR band assignment of different tobermorites. Al 3+ decreases the degree of crystallinity at short curing time and increases crystallinity at longer curing times, with a sort of stabilization of small crystals. Al 3+ changes the morphology of tobermorite from platy-shape to lath-shape. Sulfate ion increases imperfection of tobermorite crystal structure and the morphology of tobermorite change magnificently to leafy shape. The FTIR spectra of all 1.1 nm tobermorite samples are nearly similar. All tobermorite samples have a significant concentration of Q 3 Si sites, which indicates cross-linking of the chains. Sulfate substitution for silicate in tobermorite structure is associated with the appearance of the bands at 1610 and 631 cm −1 which indicates the incorporation of CaO–H group in tobermorite structure. This indicated the charge compensation mechanism; SiO 4 4− is substituted by SO 4 2− and 2OH − .

Synthesis and characterization of alumina- and zirconia-based powders obtained by the ultrasonic spray pyrolysis

The ultrasonic spray pyrolysis (USP) technique was used for synthesis of alumina- and zirconia-based powders. The starting agents were aqueous solutions, atomized by the ultrasonic spray generator and pyrolized in the furnace under the open-air conditions. The powders prepared by USP were in the form of solid and hollow aggregates (spheres) consisted of nanosize amorphous grains as determined by the microscopy and the X-ray diffraction techniques. The alumina-based powders were consolidated by the pulse plasma sintering resulting in single-phase materials. Different behavior of solid and hollow particles during the isostatic sintering is found; a higher degree of deformation of spheres is observed in the second case.