Inverse precipitation synthesis of ZrO2 nanopowder and in-situ coating on MWCNTs

ZrO₂-multiwall carbon nanotubes composite was successfully prepared by simple inverse precipitation method. The effects of initial ZrOCl₂·H₂O concentration (0.5 and 1?g) and stirring speeds (400, 800 and 1200?rpm) on the phase formation, texture, surface characterization and microstructural evolutions were studied. Results from XRD showed that almost all of the synthesis ZrO₂ exists in tetragonal phase; however, depending on ZrOCl₂·8H₂O concentration and stirring speed, some peaks of monoclinic phase existed in the composites. Texture studies illustrated the (111) plane preferred growth for tetragonal phases. The FTIR results confirmed the formation of different oxide groups in the surface of the CNTs. In addition, formation of the tetragonal ZrO₂ on the surface of CNTs was proved by Raman spectroscopic analyses. The results from microscopic images showed that the size of the ZrO₂ nanoparticles significantly decreased (30?nm) with an increase in the initial ZrOCl₂·8H₂O concentration to 1?g.     

Zr K-edge XAS study on ZrO<Subscript>2</Subscript>-pillared aluminosilicate

The ZrO₂-pillared clay with high acidic property has been prepared by reacting 1 wt% colloidal suspension of Na⁺-montmorillonite with 1 N aqueous solution of ZrOCl₂·8H₂O and by subsequent heating. The evolution of local structure around zirconium of the intercalant stabilized in-between aluminosilicate layers upon intercalating, drying, and pillaring condition has been systematically studied by X-ray absorption spectroscopy, and compared to those of reference compounds such as ZrO₂, and ZrOCl₂ · 8H₂O and its 1 N aqueous solution. The intercalated zirconium species was identified as the Zr-tetramer, [Zr₄(OH)₁₄(H₂O)₁₀]²⁺, with an average molecular volume of 10 × 10 Å² and a thickness of 4.5 Å. Also it becomes more condensed upon drying and eventually transforms to a zirconium oxide pillar upon calcination.     

ZrCl4/NaI and ZrOCl2 · 8H2O/NaI as effective systems for reductive coupling of sulfonyl chlorides and chemoselective deoxygenation of sulfoxides

Zirconium tetrachloride/sodium iodide (ZrCl₄/NaI) and ZrOCl₂ · 8H₂O/NaI conduct effective reductive coupling of sulfonyl chlorides to their corresponding disulfides and chemoselective reduction of sulfoxides to their thioethers in high yields.     

ZrOCl2·8H2O as an environmentally friendly and recyclable catalyst for the chemoselective synthesis of 2-aryloxazolines and bis-oxazolines under thermal conditions and microwave irradiation

The reactions of arylnitriles with β-aminoalcohols to prepare 2-aryloxazolines has been efficiently carried out in the presence of catalytic amounts of ZrOCl₂·8H₂O using heat or microwave irradiation. Synthesis of mono- and bis-oxazolines from dicyanobenzenes was accomplished with high selectivity using this catalyst. Chemoselective conversion of arylnitriles to their corresponding 2-oxazolines in the presence of alkylnitriles was also achieved by this method. The use of ZrOCl₂·8H₂O catalyst is feasible because of its easy availability, easy handling, stability, easy recovery, reusability, good activity and eco-friendly.     

Potential of integrating Na2SO4 · 10H2O pellets in solar drying system

In the current study, evolution of thermophysical properties of red chilli dried in a mixed mode solar dryer that integrates sodium sulfate decahydrate (Na₂SO₄?·?10H₂O) and sodium chloride (NaCl) as thermal storage were presented. Solar drying with Na₂SO₄?·?10H₂O reduced the drying time by 26.7 and 39%, compared to the drying time with or without NaCl. Dimensional shrinkage was gradual with a nonlinear exponential shape for the whole drying conditions. The evolution of the bulk and particle densities decreased while the porosity of the seed increased with time. The coefficient of heat and mass transfer varied from 0.0036???0.035?W/m²?K to 6.09?×?10^?9???6.2?×?10^?8?m/s, respectively. The thermal conductivity, specific heat capacity, and thermal diffusivity ranged from 0.0568 to 0.1093?W/m?K, 1,072 to 2218.7?J/kg?K, and 4.7?×?10^?5 to 5.13?×?10^?5?m²/s, respectively.     

Synthesis of enaminones and enamino esters catalysed by ZrOCl2 · 8H2O

A simple, fast and efficient procedure has been developed for the synthesis of β-enaminones and β-enamino esters catalysed by zirconyl chloride octahydrate (ZrOCl₂ · 8H₂O). The reaction of β-diketones and β-ketoesters with primary amines was carried out efficiently under solvent-free conditions at room temperature and led to chemo- and regio-selective formations of enamine derivatives in high to excellent yields.     

Preparation of Nano-ZrO2 powder via a microwave-assisted hydrothermal method

ZrO₂ nanocrystals were synthesised by a microwave-assisted hydrothermal method using zirconium oxychloride (ZrOCl₂·8H₂O), yttrium chloride (YCl₃·6H₂O), and liquor ammonia (NH₃·H₂O) as raw materials, triethanolamine (TEOA) as mineraliser, and polyethylene glycol (PEG) as dispersant. The obtained products were characterised with thermogravimetry-differential scanning calorimetry (TG-DSC), Fourier transform-infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The results show that the concentration of ZrOCl₂·8H₂O had little effect on the material properties, whereas the PEG molecular weight, microwave hydrothermal time and temperature, and the concentration of TEOA greatly influenced the dispersibility of the nano-sized zirconia powders. XRD and FT-IR analyses indicated that the ZrO₂ nanocrystals synthesised by the microwave hydrothermal method had a tetragonal phase without any trace of monoclinic or cubic phases. The optimal parameters for preparing nano-zirconia powders with appreciable crystallinity and crystal forms included the use of PEG1000/PEG2000/PEG4000 dispersants, a microwave hydrothermal time of 30–50 min and a temperature of 200–240 °C, and a TEOA concentration of 0.3–0.5 M. Nano-ZrO₂ powder prepared via our optimised microwave hydrothermal method contained mostly tetrahedral, spherically shaped, highly homogeneous, and well-dispersed 20–30 nm particles.     

ZrOCl2·8H2O as an efficient,environmentally friendly and reusable catalyst for synthesis of benzoxazoles,benzothiazoles, benzimidazoles and oxazolo[4,5-b]pyridines under solvent-free conditions

A new and efficient method for the preparation of benzoxazoles, benzothiazoles, benzimidazoles and oxazolo[4,5-b]pyridines from reactions of orthoesters with o-substituted aminoaromatics and 2-amino-3-hydroxypyridine in the presence of catalytic amounts of the moisture stable, inexpensive ZrOCl₂·8H₂O under solvent-free conditions is presented. This new protocol has the advantages of easy availability, easy handling, stability, reusability and eco-friendly of the catalyst, high yields, very short reaction times, solvent-free reaction conditions, simple experimental and work-up procedure.     

Synthesis and growth behavior of micron-sized rod-like ZrB2 powders

Using ZrOCl₂·8H₂O, Na₂B₄O₇·10H₂O and C₁₂H₂₂O₁₁ as raw materials, micron-sized rod-like ZrB₂ powders were prepared via a molten-salt-mediated carbothermal reduction from chemically homogenous precursors obtained by sol-gel method. The effects of Zr/B/C molar ratio, firing temperature, holding time and molten salt on the composition of products have been investigated, respectively. Pure micron-sized ZrB₂ powders with controllable rod-like morphology were obtained at 1400 °C for 4 h holding with Zr/B/C of 1/5/5 in presence of molten salt, which has a diameter of 1–2 µm and aspect ratios of 3–10. The investigation of growth behavior showed that at the first stage, nano-size ZrB₂ columns grew along the c-axis with ZrC_x thin film on their top as “active-site”. Then, with consuming ‘active sites’, ZrB₂ columns started to grow in diameter direction, and finally small columns merged into a larger rod.     

Efficient degradation of methylene blue dye by catalytic oxidation using the Na8Nb6O19·13H2O/H2O2 system

Na₈Nb₆O₁₉·13H₂O particles were synthesized by a simple hydrothermal method. The catalysts were characterized by X-ray diffraction (XRD), scanning electronic microscopy (SEM) and thermogravimetric and differential scanning (TG-DSC). The XRD and TG-DSC analyses indicated that Na₈Nb₆O₁₉·13H₂O was an intermediate hexaniobate during the preparation of NaNbO₃ powders. Methylene blue (MB) dye degradation using Na₈Nb₆O₁₉·13H₂O/H₂O₂, Nb₂O₅/H₂O₂ and NaNbO₃/H₂O₂ systems were investigated, respectively. Among the catalytic oxidation systems, Na₈Nb₆O₁₉· 13H₂O showed the highest activity for degradation of MB in the presence of H₂O₂. The results indicated that the dye degradation efficiency could be 93.5% at 30 °C after 60 min in the presence of the Na₈Nb₆O₁₉·13H₂O/H₂O₂ system. It was also found that the degradation of MB over the catalytic systems followed pseudo-first-order kinetics, and the degradation rate was 0.02376 min⁻¹ in the Na₈Nb₆O₁₉·13H₂O/H₂O₂ system, which was higher than that in the Nb₂O₅/H₂O₂ and NaNbO₃/H₂O₂ systems. A possible mechanism for MB catalytic oxidation degradation using the Na₈Nb₆O₁₉·13H₂O/H₂O₂ system was proposed.     

Synthesis of a soluble preceramic polymer for ZrC using 2-hydroxybenzyl alcohol as carbon source

A preceramic polymer for ZrC was successfully synthesised by chemical reaction between zirconium oxychloride (ZrOCl₂·8H₂O) and 2-Hydroxybenzyl alcohol via a one-pot route. The molecular structure, thermal properties and pyrolysis behaviour of the precursor were investigated. The results indicated that the precursor might be Zr–O–Zr chain polymer with 2-Hydroxybenzyl alcohol as ligand. The precursor was air-stable and exhibited excellent solubility in common organic solvents. The conversions from precursor to ZrC powders were investigated by TG-DTA, X-ray diffraction, Scanning electron microscope, TEM and Raman spectrum. The precursor underwent a thermal decomposition in four steps, and ZrC powders were formed at 1300°C via carbothermal reduction reaction of ZrO₂ and carbon in argon with ceramic yield of 63.0%. The ZrC particles were fine and exhibited irregular polyhedron morphology with average size in the range of 100–300?nm.     

The transformation: Brushite → calcium monofluorophosphate under aqueous conditions

The reaction between CaHPO₄. 2H₂O and 10^?1 M solution of Na₂PO₃F have been studied in the pH range 7 to 5 at 25 °C. The formation of CaPO₃F · 2H₂O, rather than CaF₂ or Ca₅F (PO₄)₃ by initial hydrolysis and subsequent reaction with the F^? formed, appeared to occur. The value of ΔG for CaPO₃F · 2H₂O has been calculated as – 530.9 kcal mol^?1. A comparison is drawn to the exchange reactions reported here, and to the similar reactions reported to occur in calcium deficient apatite.     

Preparation of Co3O4/ZrO2(Y2O3) Catalyst and its Enhanced Catalytic Oxidation of CO

Yttria-stabilized zirconia powders were prepared by the sol–gel method coupled with supercritical CO₂ fluid-drying technology, using ZrOCl₂·8H₂O as the precursor, urea as the precipitant, and yttria as the stabilizer. The particles were characterized by X-ray diffraction, TEM and BET. The Co₃O₄/ZrO₂(Y₂O₃) catalysts were prepared by the impregnation method. The content of cobalt was varied from 5 to 12 wt%. The prepared catalysts were calcined at 200–500 °C and the pretreating temperature was varied from 200–400 °C. The performance of CO catalytic oxidation was tested and the catalyst with 8% Co loading, calcined at 200 °C, and with a pretreating temperature of 300 °C, showed the highest catalytic activity. The temperature for 95% CO conversion was as low as 113 °C; and, the catalyst showed both good cycling stability and excellent long-term stability.     

An expeditious synthesis of benzimidazole derivatives catalyzed by Lewis acids

An expeditious and efficient route for the synthesis of benzimidazole derivatives by the reaction of o-phenylenediamines with orthoesters in the presence of Lewis acids was described. ZrCl₄, SnCl₄ · 5H₂O, TiCl₄, BF₃ · Et₂O, ZrOCl₂ · 8H₂O and HfCl₄ exhibited high catalytic activity for this transformation.     

Microwave assisted solvent-free synthesis of dihydropyrimidinones by Biginelli reaction over Si-MCM-41 supported FeCl3 catalyst

Among the Si-MCM-41 or montmorillonite K 10 clay supported ZnCl₂, AlCl₃, GaCl₃, InCl₃ and FeCl₃ catalysts, FeCl₃/Si-MCM-41 shows best performance for the microwave-assisted synthesis of dihydropyrimidinones by the Biginelli reaction involving multicomponent condensation of aromatic aldehyde, ethyl acetoacetate and urea in the absence of any solvent. It is a promising catalyst for the microwave-assisted reaction providing high product yield in a short period (3.0–5.0 min).     

Phase formation in fabrication of a refractory material from nonstabilized Zro2

Results of a study of fabrication of heat-insulating binary powders from nonstabilized ZrO₂ are presented. The strength of grains of monoclinic ZrO₂ is enhanced due to formation of a binder of tetragonal ZrO₂ after introduction of ZrOCl₂ · 8H₂O into the charge or firing of monoclinic ZrO₂ in MgO vapor.     

A photoluminescent 3D silver(I) polymer with mixed 2-naphthol-5-carboxylate and hexamethylenetetramine ligands,showing an unusual (3,4)-connected (6·7·8)2(4·6·7)2(4·7·8)2(72·8)2(62·7·83)(62·72·8·10) topology

The reaction of AgClO₄ with 2-naphthol-5-carboxylic acid (HL) and hexamethylenetetramine (hmt) in the presence of 2,6-dimethylpyridine afforded a photoluminescent three-dimensional (3D) Ag^I polymer {[Ag₆(L)(μ₃-hmt)₂(μ₄-hmt)₂(ClO₄)](ClO₄)₄(H₂O)}_∞ (1), which exhibited an unusual (3,4)-connected (6·7·8)₂(4·6·7)₂(4·7·8)₂(7²·8)₂(6²·7·8³)(6²·7²·8·10) topological network (L = 2-naphthol-5-carboxylate). Moreover, the luminescent properties of 1 have been briefly investigated.     

Two highly connected frameworks and one polythreading architecture based on multidentate N-donor ligands: Syntheses,structures, characterizations and photoluminescent properties

Three coordination polymers based on multidentate N-donor ligands and polycarboxylate anions, namely, [Co₃(4,4′-tmbpt)₄(btc)₂]·9.5H₂O (1), [Ag₄(4,4′-tmbpt)(btec)(H₂O)₂]·H₂O (2) and [Zn(4,4′-tmbpt)(btec)_0.5(H₂O)]·0.5H₂O (3) (4,4′-tmbpt = 1-((1H-1,2,4-triazol-1-yl)methyl)-3,5-bis(4-pyridyl)-1,2,4-triazole, H₃btc = 1,3,5-benzenetricarboxylic acid, and H₄btec = 1,2,4,5-benzenetetracarboxylic acid) have been prepared under hydrothermal condition. Compound 1 displays a 3D (3,6,8)-connected framework with (4·6²)(4⁴·6¹⁰·8)(4¹⁴·6¹²·8²) topology. Compound 2 is a 3D (4,5,8)-connected framework with (4³·6²·8)(4³·6⁵·8²)(4⁸·6²)(4¹⁰·6¹⁰·8⁸) topology. Compound 3 exhibits a 2D → 3D polythreading architecture. The photoluminescent spectra indicate that at room temperature, compounds 2 and 3 emit green and blue luminescence, respectively.     

Intermediate temperature electrical properties in 4 mol% ZnO-doped Zr0.92Y0.08O2-α/NaCl-KCl composite electrolyte

In this paper, 4?mol% ZnO-doped Zr_0.92Y_0.08O_2-α (8YSZ) and its 8YSZ+4ZnO/NaCl-KCl composite electrolyte were synthesized by a solid-state reaction. The X–ray diffraction (XRD) analysis indicates that 8YSZ+4ZnO and inorganic chlorides phases can coexist. The inorganic chlorides decrease the synthesis temperature of 8YSZ+4ZnO. The highest conductivities of 8YSZ+4ZnO and 8YSZ+4ZnO-NK are 7.0?×?10^?3 S?cm^?1 and 7.7?×?10^?2 S?cm^?1 at 700?°C, respectively. The oxygen concentration discharge cell shows that 8YSZ+4ZnO and 8YSZ+4ZnO-NK are good oxide ionic conductors under an oxygen-containing atmosphere. Finally, an H₂/O₂ fuel cell based on the 8YSZ+4ZnO-NK electrolyte reached the maximum power density (P_max) of 315.5?mW?cm^?2 at 700?°C.     

ZrOCl2.8H2O/SiO2: An efficient and recyclable catalyst for the preparation of coumarin derivatives by Pechmann condensation reaction

Silica gel supported zirconyl chloride octahydrate was found to be an efficient and recyclable catalyst for the synthesis of a series of biologically important molecules in high turnover numbers and rates. Several substituted coumarins can be prepared in high yield and purity by direct reaction of β-keto esters and phenol derivatives in the presence of a catalytic amount of ZrOCl₂.8H₂O/SiO₂ as Lewis acid and at ambient temperature under solvent-free conditions. This method which is called Pechmann condensation is a very easy and a rapid reaction for the synthesis of coumarin derivatives.