A Study of Amorphous Precursors for PbZrO3-PbTiO3 Based Ceramic Materials

Amorphous precursors for PbZrO₃ and PbTiO₃ ceramics were prepared from lead acetate and the transition metaln-propoxide inn-propanol orn-butoxide inn-butanol and hydrolysed with an excess of water. According to GLC and TGA/EGA analyses, the type of alkoxide group influences distinctly the structure of heterometallic precursors, i.e., oxo or acetate bridging, and the amounts of hydroxyl and organic groups bound to the metal network. The local environments of metal atoms in the amorphous precursors were also studied by EXAFS. The analysis reveals that in Pb−Zr precursors alkoxide groups modify the coordination spheres of the zirconium atoms. Conversely, local environments of both lead and titanium atoms within the analysed range of 3.4 A depend weakly on the type of alkoxide used.     

Design of Homogeneous Hybrid Materials through a Careful Control of the Synthetic Procedure

Sols for the synthesis of hybrid organic-inorganic materials have been prepared by mixing zirconium n-propoxide and methacryloxypropyltrimethoxysilane (MPS). The synthesis was done in two steps: a 15 minute hydrolysis of a MPS : H₂O : EtOH 1 : 1 : 2 mixture and then addition of 0.5 molar equivalent of zirconium alkoxide. All the experimental parameters—hydrolysis ratio, pH, dilution, pre-hydrolysis time—have been optimized through a detailed ²⁹ Si and ¹⁷O NMR analysis. Immediately after the addition, 94% of the initial water was consumed for the formation of Si–O–Zr bridges. Cleavage of these bonds, associated with formation of Si–O–Si and Zr–O–Zr bridges are then observed during the aging time.     

EXAFS study of zirconium alkoxides as precursor in the sol-gel process: I. Structure investigation of the pure alkoxides

The properties of materials obtained by sol-gel processing show a certain dependence on the type of metal alkoxide and the solvent. Some authors assumed that these effects are caused by the degree of oligomerization of the metal alkoxides and their solvation. In order to obtain information on the structure and molecular complexity of the metal alkoxide we performed an EXAFS study on primary zirconium alkoxides Zr(OR)₄, with OR = n-propoxide and n-butoxide in solution of their parent alcohol. The EXAFS data for zirconium iso-propoxide have been used as a reference, because its solid state structure is known from X-ray analysis. The Zr-Zr correlations which were observed for all investigated systems provide evidence for an oligomeric structure. Because the analysis of the co-ordination spheres around the central Zr-atom revealed different Zr-O bond lengths, some of the formerly postulated structure models can be ruled out. We propose solvated dimers or trimers or mixtures of both species as possible structures of zirconium propoxide and zirconium butoxide in solution of their parent alcohol.     

Influence of the lead carboxylate on the molecular composition of its solutions with zirconium and titanium isopropoxides or n-butoxides: 2-ethylhexanoate vs acetate, a way to stabilize the first Pb-Zr carboxylatoalkoxides of 1:1 stoichiometry

The reactions between titanium or zirconium alkoxides namely Ti(OR)₄ (R = ⁱ Pr, ⁿ Bu) or Zr₂(O ⁱ Pr)₈(HO ⁱ Pr)₂, Zr(O ⁿ Bu)₄ respectively and lead 2-ethylhexanoate Pb(O₂CC₇H₁₅)₂ were investigated at room temperature (rt) and by heating. The various compounds were characterized by elemental analysis, FT-IR, ¹H and ²⁰⁷Pb NMR. The mixed-metal species obtained at rt were adducts Pb₄Zr₄(μ-O₂CR′)₈(OR)₁₆(OHR)₂ 1 and Pb₂Ti₄(μ-O₂CR′)₄(OR)₁₆ 2 (R′=CHCHEt(CH₂)₂Me, R = ⁱ Pr) independently of the stoichiometry used. The structures of 1 and 2 are based on triangular M₂Pb cores (M = Zr, Ti). with 6-coordinate transition metals -as required for perovskites- and 6- or 7-coordinate lead atoms. Similar observations were made with n-butoxides. Thermal and hydrolytic condensation reactions were investigated. Thermal condensation was more difficult for the n-butoxide derivatives than for the isopropoxide ones. Powders derived from the hydrolysis of the Single Source Precursor 1 in various conditions were characterized by TGA, XRD and SEM for the PZ ceramic.     

Silica-Zirconia Sol–Gel Coatings Obtained by Different Synthesis Routes

Homogeneous xSiO₂-(1−x)ZrO₂ coatings have been prepared onto glass-slides, monocrystalline Si and stainless steel (AISI 304) using sols prepared via acid and basic catalysis. Zirconium tetrabutoxide (TBOZr), zirconium n-propoxide (TPZ), tetraethoxysilane (TEOS) and methyltriethoxysilane (MTES) were used as precursors of zirconia and silica, respectively. The different parameters involved in the synthesis procedure, as molar ratios H₂O/alkoxides, NaOH/alkoxides, and sintering temperature have been analysed, correlating the stability and rheological properties of the sols. The evolution and structure of the sols and coatings have been studied by FTIR. Coatings have been prepared by dipping from acid and basic sols. Electrophoretic Deposition (EPD) technique has also been used to prepare coatings onto stainless steel from basic particulate sols in order to increase the critical thickness. A maximum thickness of 0.5 μ m was reached by both dipping and EPD process for 75SiO₂: 25 ZrO₂ composition. The critical thickness decreases with ZrO₂ amount depending strongly of the drying conditions. Si–O–Zr bonds have been identified by FTIR, indicating the existence of mixed network Si–O–Zr in the coatings obtained by the different routes. Crystallisation of ZrO₂(t) was only observed at high sintering temperature (900^∘C) by FTIR and confirmed by DRX.     

Effect of Zirconia Precursor on the Properties of ZrO2-SiO2 Sol-Gel Oxides

Sol-gel zirconia-silica oxides were synthesized with two zirconium precursors, zirconium n-butoxide and zirconium acetylacetonate, and two different hydrolysis catalysts, HCl and H₂SO₄. The samples prepared with HCl were additionally sulfated with a 1 M solution of H₂SO₄. Characterization was performed with FTIR and ²⁹Si-MAS-NMR spectroscopy, as well as with nitrogen adsorption. Because zirconium and silicon alkoxides have different hydrolysis rates, it was necessary to perform a pre-hydrolysis of the silicon alkoxide before mixing. The atom distribution in the ZrO₂-SiO₂ system depended on the zirconium precursor, which also determined the zirconium incorporation in the silica lattice, which was greater for zirconium acetylacetonate. The zirconium precursor also was responsible for the silanol concentration, which increases when samples were sulfated. Sulfating stabilizes the specific surface area. On sulfate samples calcined at 800°C BET areas larger than 500 m²/g were obtained.     

Coordination of mono- and diamines to titanium and zirconium alkoxides

The structural chemistry of crystalline adducts M₂(OR)₈(amine)₂ (M = Ti: OR = OⁱPr, amine = NH₂CH₂Ph, NH₂Bu; M = Ti: OR = OEt, amine = piperidine; M = Zr: OR = OⁱPr, amine = NH₂CH₂Ph, NH₂C₆H₁₁) is discussed. The adducts were obtained by reaction of Ti(OEt)₄ or M(OⁱPr)₄ with primary or secondary amines. The monoamine adducts are centrosymmetric dimers in which the amines are coordinated axially to the M₂μ-OR)₂ ring and hydrogen-bonded to neighboring alkoxo ligands. The adducts are sufficiently stable if the hydrogen bond is strong. ¹⁵N NMR studies revealed that the amines are also coordinated in solution. Coordination polymers were obtained when diamines with two terminal NH₂ groups are reacted with Ti(OⁱPr)₄. The general structure is the same as that of Ti₂(OⁱPr)₈(RNH₂)₂. However, the diamines bridge the Ti₂(OⁱPr)₈ units. When Zr(OⁱPr)₄ was reacted with NH₂CH₂CH₂NHMe, the adduct Zr₂(OⁱPr)₈[NH₂CH₂CH₂NHMe]₂ was obtained where only the NH₂ group is coordinated.     

Heteroleptic Complexes of Zirconium Acetylacetonates: Better Precursors for the Preparation of Zirconia. Structural Characterization of [(acac)2Zr{ONC(Me)py‐2}2]

The reactions of the heteroleptic zirconium diisopropoxide bis(acetylacetonate) in benzene solution with two equivalents of oximes, alkoxyalkanols, triphenylsilanol and trimethylsilyl acetate yield products with the formula [{MeC(O)CHC(O)Me}₂ZrL₂] with L = —ONC(Me)C₅H₄N‐2, —ONC(Me)C₄H₃O‐2, —OCH₂CH₂OR (R = Me, Et, Buⁿ; py = pyridine, fu = furan), —OSiPh₃ and —OSiMe₃. Most of these derivatives are solids, but the [(acac)₂Zr(OSiMe₃)₂] is a viscous oil. They could be purified either by recrystallization or by vacuum distillation; all of these are monomeric in boiling benzene. Their elemental analyses, molecular weight measurements and IR as well as NMR spectra were measured. The oximato complex [(acac)₂Zr{ONC(Me)py‐2}₂] has been shown by single crystal X‐ray crystallography to be monoclinic and mononuclear in the solid state, where zirconium has the coordination number 8; all the ligands are situated in cis‐ position and the oximato ligand binds via N and O in a dihapto (η²‐N, O) manner.     

Conversion of lactides into ethyl lactates and value-added products

This Letter describes an attractive and efficient method for Mg(OR)₂-mediated lactide alcoholysis. The catalysts were generated in situ from di-n-butylmagnesium and ROH to prevent aggregation of Mg(OR)₂. The reaction of ROH [R = Me, Et, RCO₂(Me)CH] with lactide initially yielded the ring-opened product HO[CH(CH₃)CO]_nOR (n = 2 or 3). The complete consumption of lactide caused the reaction to proceed further, giving environmentally friendly lactic acid esters in excellent yields under ambient conditions.     

Structure evolution in the PbO-ZrO2-TiO2 sol-gel system: Part I — Characterization of prehydrolyzed precursors

In this investigation, several spectroscopic and analytical techniques were used to determine the chemical compositions and structures of the lead, zirconium, titanium, and Pb-(Zr, Ti) alkoxides involved in the sol-gel synthesis of PZT thin films. These techniques included ¹H, ¹³C, and ²⁰⁷Pb NMR; FT-IR; gas chromatography; Karl Fischer titration; and number-average molecular weights (M _n ) determined by cryoscopy. It was found that the titanium precursor had a M _n of 548 and a formula of [Ti(OCH₂CH₂OCH₃)₄]_1.6; the zirconium precursor had a M _n of 1015 and a formula of [Zr(OCH₂CH₂OCH₃)₄]_2.6; and the lead precursor had a formula Pb₆(OOCCH₃)₅(OCH₂CH₂OCH₃)₇. 4 H₂O and a molecular weight of 2131 (M _n =2113). It was observed that residual water from the incomplete dehydration of lead acetate trihydrate coupled with released water due to the esterification of acetic acid caused M-O-M (M=Pb, Zr, Ti) bonds in the Pb-(Zr, Ti) alkoxide. Two possible isomeric structures of the Pb-(Zr, Ti) alkoxide have been proposed. They are both cyclic and have a formula of Pb₂MMO₂(OR)₈(ROH)₂, (MM=Zr and/or Ti) and a molecular weight of 1336 (M _n =1386).     

Sol–Gel Approach to Sr<Subscript>2</Subscript>CeO<Subscript>4</Subscript> Phosphor from Single Alkoxide Precursors

Syntheses and characterizations of sol–gel precursors of Sr₂CeO₄ were carried out. Each molecular precursor, [Sr₂Ce(OCH₂CH₂OCH₃)₈] (1), [Sr₂Ce(OⁱPr)₈] (2) and [Sr₂Ce₂(OⁱPr)₁₂(ⁱPrOH)₄] (3) was prepared from mixtures of Sr complexes and cerium(IV) alkoxides. The molecular structure of 3 showed that [CeO₆] octahedra are connected with distorted [SrO₆] octahedra by sharing edges with oxo bridges. X-ray powder diffraction patterns and spectrofluorometry were used to determine the evolution of structure from the precursor molecules to the luminescent oxides. The luminescent strontium cerium oxides were derived at relatively mild reaction conditions (700 °C for 1 h), and complete conversion was observed at 1000 °C for 1 h from these precursors. Comparing the spectra of the oxides derived from 2 and 3, the emission intensity of the oxide derived from 2 is much stronger.     

Mechanism of Formation of Nanocrystalline ZnO Particles through the Reaction of [Zn(acac)2] with NaOH in EtOH

The mechanism of formation of nanocrystalline ZnO particles from the reaction of zinc acetylacetonate ([Zn(acac)₂]) with 2-equivalent NaOH in boiling EtOH was investigated by characterizing the particles and following the transformation of acac moieties. The reaction was found to proceed via hydrolysis of zinc ethoxide derivatives, followed by dehydration–condensation reactions. High-resolution solid-state CP-MAS¹³C NMR measurements indicate that the ZnO particles are produced through Zn (acac)(OZn)_n(acac) (3). Furthermore, it was suggested that acac⁻ligands play an important role in the generation of nanocrystalline ZnO particles by suppressing the hydrolysis–condensation of Zn(acac)(OZn)_n(acac).     

TADDOLate as Ligand in Zirconium and Hafnium Chemistry

The enantiomeric pure TADDOLate complexes of the heavier group 4 metals [(η⁵‐C₅H₅)₂M{(S,S)‐TADDOLate}] (M = Zr, Hf) were prepared by treatment of (S,S)‐TADDOL with 2.5 equivalents of n‐butyl lithium followed by reaction with zirconocene and hafnocene dichloride, respectively. The new complexes have been characterized by standard analytical/spectroscopic techniques and the solid‐state structures of both compounds were established by single crystal X‐ray diffraction. The title compounds are the first fully characterized TADDOLate complexes of zirconium and hafnium.     

Zirconium Dioxide Solubility in High Temperature Aqueous Solutions

The heat transport purification system of CANDU nuclear reactors is used to remove particulates and dissolved impurities from the heat transport coolant. Zirconium dioxide shows some potential as a high-temperature ion-exchange medium for cationic and anionic impurities found in the CANDU heat transport system (HTS). Zirconium in the reactor core can be neutron activated, and potentially can be dissolved and transported to out-of-core locations in the HTS. However, the solubility of zirconium dioxide in high-temperature aqueous solutions has rarely been reported. This paper reports the solubility of zirconium dioxide in 10⁻⁴ mol⋅kg⁻¹ LiOH solution, determined between 298 and 573 K, using a static autoclave. Over this temperature range, the measured solubility of zirconium dioxide is between 0.9 and 12×10⁻⁸ mol⋅kg⁻¹, with a minimum solubility around 523 K. This low solubility suggests that its use as a high-temperature ion-exchanger would not introduce significant concentrations of contaminants into the system. A thermodynamic analysis of the solubility data suggests that Zr(OH)₄⁰ likely is the dominant species over a wide pH region at elevated temperatures. The calculated Gibbs energies of formation of Zr(OH)₄⁰(aq) and Zr(OH)₄(am) at 298.15 K are −1472.6 kJ⋅mol⁻¹ and −1514.2 kJ⋅mol⁻¹, respectively. The enthalpy of formation of Zr(OH)₄⁰ has a value of −1695±11 kJ⋅mol⁻¹ at 298.15 K.     

EXAFS study of zirconium alkoxides as precursors in the sol-gel process: II. The influence of the chemical modification

EXAFS studies of primary zirconium alkoxides Zr(OR)₄ with OR = n-propoxide and n-butoxide, dissolved in their corresponding alcohols and chemically modified with acetylacetone (Hacac) and acetic acid (HOAc) in different molal ratios, are presented. The EXAFS-spectroscopic results, supported by FT-IR-studies, indicate a different chemical behavior of the complexing agents. In contrast to acetylacetone, the addition of acetic acid does not change the oligomeric structure of the zirconium alkoxides. Amazingly, the modification with acetic acid leads, in comparison to the pure compounds, to a shortened metal centre distance, whereas in the reaction with acetylacetone the Zr-Zr distance is not changed. With the determined distances and a rough quantitative inclusion of the coordination numbers it was possible to deduce detailed structure models.     

Reactivity investigations of some chosen peroxo-vanadium(V), manganese(III) and chromium(VI) compounds

An interpretative account of the results of reactions in aqueous medium of a highly peroxygenated vanadium(V) complex, K [V(O_{2 3}]·3H₂O, with different organic and inorganic substrates is presented. The reactions were monitored by solution EPR spectroscopy and isolation of products at different stages of the reactions. Redox reactions between diperoxide, K[VO(O₂)₂(H₂O)] and VOSO₄ were conducted. The results of the investigation suggest that secondary oxygen exchange-reaction occurs which not only depends on but also utilises the intermediates in the primary reaction during diperoxovanadate-dependent oxidation of VOSO₄. In an interesting reactiontris(acetylacetonato)-manganese(III), Mn(acac)₃, on being reacted with a hydrogen peroxide adduct, KF·H₂O₂, and bpy and phen afforded crystalline [Mn(acac)₂(bpy)] and [Mn(acac)₂(phen)], respectively. The X-ray structural analysis of [Mn(acac)₂(phen)] showed that the compound crystallised in orthorhombic space groupPbcn. The structure consists of a pseudooctahedral Mn(II) ion being bound to two acac⁻(C₅H₅O ₂ ⁻ ) and a phen ligand with the molecule lying on two-fold axis. Reactivity profiles of two new chromium(VI) reagents viz., pyridinium fluorochromate, C₅H₅NH[CrO₃F] (PFC), and quinolinium fluorochromate C₉H₇NH [CrO₃F] (QFC), have been presented. The compounds are capable of acting as both electron-transfer and oxygen-atom-transfer agents. The X-ray analysis of PFC crystals reveals that the compound crystallises in the orthorhombic space group CmcZ₁. The structure consists of discrete pyridinium cations and CrO₃ F anions with no significant hydrogen bonding. This results in total disorder of the pyridinium cation. The tetrahedral [CrO₃ F]⁻ ion lies on a crystallographic mirror plane.     

Phthalocyaninate und Tetraphenylporphyrinate von hochkoordiniertem ZrIV/HfIV mit Hydroxo‐, Chloro‐, (Di)Phenolato‐, (Hydrogen)Carbonato‐ sowie (Amino)Carboxylato‐Liganden

Phthalocyaninates and Tetraphenylporphyrinates of High Co‐ordinated Zr^IV/Hf^IV with Hydroxo, Chloro, (Di)Phenolato, (Hydrogen)Carbonato, and (Amino)Carboxylato Ligands Crystals of tetra(n‐butyl)ammonium cis‐tri(phenolato)phthalocyaninato(2‐)zirconate(IV) ( 2 ) and ‐hafnate(IV) ( 1 ), di(tetra(n‐butyl)ammonium) cis‐di(tetrachlorocatecholato(O, O')phthalocyaninato(2‐)zirconate(IV) ( 3 ), and cis‐(di(μ‐alaninato(O, O')di(μ‐hydroxo))di(phthalocyaninato(2‐)zirconium(IV)) ( 12 ) have been isolated from tetra(n‐butyl)ammonium hydroxide solutions of cis‐di(chloro)phthalocyaninato(2‐)zirconium(IV) and ‐hafnium(IV), respectively, and the corresponding acid in polar organic solvents. Similarly, with cis‐di(chloro)tetraphenylporphyrinato(2‐)zirconium(IV), ^cis[Zr(Cl)₂tpp] as precursor crystalline tetra(n‐butyl)ammoniumcis‐tetrachlorocatecholato(O, O')hydrogentetrachlorocatecholato(O)tetraphenylporphyrinato(2‐)zirconate(IV) ( 4 ), cis‐hydrogencarbonato(O, O')phenolatotetraphenylporphyrinato(2‐)zirconium(IV) ( 6 ), cis‐di(benzoato(O, O'))tetraphenylporphyrinato(2‐)zirconium(IV) ( 11 ), and cis‐tetra(μ‐hydroxo)di(tetraphenylporphyrinato(2‐)zirconium(IV)) ( 13 ) with a cis‐arrangement of the symmetry equivalent μ‐hydroxo ligands, and from di(acetato)tetraphenylporphyrinato(2‐)zirconium(IV) the corresponding trans‐isomer ( 14 ) have been prepared. The endothermic dehydration at 215 °C of 13/14 yields μ‐oxodi(μ‐hydroxo)di(tetraphenylporphyrinato(2‐)zirconium(IV)) ( 15 ). 15 also precipitates on dilution of a solution of ^cis[Zr(X)₂tpp] (X = Cl, OAc) in dmf/(ⁿBu₄N)OH with water, while on prolonged standing of this solution on air tri(tetra(n‐butyl)ammonium) cis‐(^nido〈di(carbonato(O, O'))undecaaquamethoxide〉tetraphenylporphyrinato(2‐)zirconate(IV) ( 7 ) crystallizes, in which Zr^IV coordinates a supramolecular nestlike ^nido〈(O₂CO)₂(H₂O)₁₁OCH₃〉^5— cluster anion stabilised by hydrogen bonding in a nanocage of surrounding (ⁿBu₄N)⁺ cations. On the other hand, ^cis[Zr(Cl)₂pc] forms with (Et₄N)₂CO₃ in dichloromethane di(tetraethylammonium) cis‐di(carbonato(O, O')phthalocyaninato(2‐)zirconate(IV) ( 5 ). ^cis[Zr(Cl)₂tpp] dissolves in various O‐donor solvents, from which cis‐di(chloro)dimethylformamidetetraphenylporphyrinato(2‐)zirconium(IV) ( 8 ), cis‐di(chloro)dimethylsulfoxidetetraphenylporphyrinato(2‐)zirconium(IV) ( 9 ), and a 1:1 mixture ( 10 ) of cis‐di(chloro)dimethylsulfoxidetetraphenylporphyrinato(2‐)zirconium(IV) ( 10a ) and cis‐chlorodi(dimethylsulfoxide)tetraphenylporphyrinato(2‐)zirconium(IV) chloride ( 10b ) crystallize. All complexes contain solvate molecules in the solid state, except 3 . Zr^IV/Hf^IV is directed by ∼1Å out of the plane of the tetrapyrrolic ligand (pc, tpp) towards the mutually cis‐coordinated axial ligands. In the more concavely distorted phthalocyaninates, Zr^IV is mainly eight‐coordinated and in the tetraphenylporphyrinates seven‐coordinated. The octa‐coordinated Zr atom is in a distorted quadratic antiprism, and the hepta‐coordinated one is in a square‐base‐trigonal‐cap cooordination polyhedron. In most tpp complexes, the Zr atom is displaced by up to 0.3Å out of the centre of the coordination polyhedron towards the tetrapyrrolic ligand. In 13/14 , both antiprisms are face shared by an O₄ plane, and in 12 they are shared by an O₂ edge and the O atoms of the bridging aminocarboxylates, the dihedral angle between the O₄ planes of both antiprisms being 50.1(1)°. The mean Zr‐N_p distance is 0.05Å longer in the pc complexes than in the tpp complexes (d(Zr‐N_p)_pc = 2.31Å). In the monophenolato complexes, the mean Zr‐O distance (∼2.00Å) is shorter than in the complexes with other O‐donor ligands (d(Zr‐O)_pc = 2.18Å; d(Zr‐O)_tpp = 2.21Å); the Zr‐Cl distances vary between 2.473(1) and 2.559(2)Å (d(Zr‐Cl)_tpp = 2.51Å). d(C‐O_exo) = 1.494(4)Å in the bidentate hydrogencarbonato ligand in 6 is 0.26Å longer than in the bidentate carbonato ligands in 5 and 7 . 9 and 10a are rotamers slightly differing by the orientation of the axial ligands with respect to the tpp ligand. In 1—4, 6 , and 11 the phenolato, catecholato, and benzoato ligands, respectively, are in syn‐ and/or anti‐conformations with respect to the plane of the macrocycle. π‐Dimers with modest overlap of the neighbouring macrocyclic rings are observed in 5, 6, 8, 9, 10b, 12 , and 14 . The common UV/Vis spectroscopical and vibrational properties of the new phthalocyaninates and tetraphenylporphyrinates scarcely reflect their rich structural diversity.     

Synthesis and characterization of Fe2O3/SiO2 nanocomposites

Fe₂O₃/SiO₂ nanocomposites based on fumed silica A-300 (S_BET = 337 m²/g) with iron oxide deposits at different content were synthesized using Fe(III) acetylacetonate (Fe(acac)₃) dissolved in isopropyl alcohol or carbon tetrachloride for impregnation of the nanosilica powder at different amounts of Fe(acac)₃ then oxidized in air at 400–900 °C. Samples with Fe(acac)₃ adsorbed onto nanosilica and samples with Fe₂O₃/SiO₂ including 6–17 wt% of Fe₂O₃ were investigated using XRD, XPS, TG/DTA, TPD MS, FTIR, AFM, nitrogen adsorption, Mössbauer spectroscopy, and quantum chemistry methods. The structural characteristics and phase composition of Fe₂O₃ deposits depend on reaction conditions, solvent type, content of grafted iron oxide, and post-reaction treatments. The iron oxide deposits on A-300 (impregnated by the Fe(acac)₃ solution in isopropanol) treated at 500–600 °C include several phases characterized by different nanoparticle size distributions; however, in the case of impregnation of A-300 by the Fe(acac)₃ solution in carbon tetrachloride only α-Fe₂O₃ phase is formed in addition to amorphous Fe₂O₃. The Fe₂O₃/SiO₂ materials remain loose (similar to the A-300 matrix) at the bulk density of 0.12–0.15 g/cm³ and S_BET = 265–310 m²/g.     

The role of complexing ligands in the formation of non-aggregated nanoparticles of zirconia

The hydrolysis and condensation of zirconium n-propoxide in n-propanol have been chemically controlled via the complexation of the zirconium precursor with acetylacetone. The size of the zirconium oxide-based particles is mainly controlled by the complexation ratio x=[acac]/[Zr]. the mean size increases from nanometric to submicronic range when x decreases from 1 to 0.1. Amorphous colloidal particles are obtained at room temperature. They result from a competitive growth/termination mechanism of zirconium-oxo species in the presence of acac surface capping agents. However non-aggregated nanocrystalline particles of tetragonal zirconia, about 2 nm in diameter are formed upon aging at 60°C when hydrolysis is performed in the presence of paratoluene sulfonic acid (PTSA).     

Zirconium(IV) complexes ofSchiff bases

Zirconium(IV)Schiff base derivatives have been synthesised by reacting zirconium isopropoxide with monofunctional bidentateSchiff bases in different stoichiometric ratios. The resulting derivatives of the type Zr(O-Isopr)₃(SB) and Zr(O-Isopr)₂(SB)₂, whereSB ^– is the anion of the correspondingSchiff baseSBH, have been isolated in almost quantitative yields. Their molecular weights have been determined ebullioscopically and their ir spectra recorded.

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Zirkonium(IV)-Komplexe von Schiff-Basen

Zusammenfassung Es wurden Zirkonium(IV)-Schiff-Basen-Derivate in verschiedenen stöchiometrischen Zusammensetzungen über die Reaktion von Zirkoniumisopropoxid mit monofunktionellen zweizähnigenSchiff-Basen synthetisiert. Die Komplexe vom Typ Zr(O-Isopr)₃(SB) und Zr(O-Isopr)₂(SB)₂ [SB ^– als Anion derSchiff-BaseSBH] wurden in fast quantitativer Ausbeute erhalten. Es werden Strukturen vorgeschlagen, die auf ebullioskopisch bestimmten Molekulargewichten und den IR-Spektren basieren.