Non-hydrothermal Synthesis Research Articles

Stability of amorphous neodymium carbonate and morphology control of neodymium carbonate in non-hydrothermal synthesis

Rare earth carbonates have shown great application value and potential in the process of preparing rare-earth materials. In this work, a non-hydrothermal method of uniform feeding was used to determine the nucleation kinetics of neodymium carbonate. On this basis, the crystallization process and evolution of amorphous phase were studied. For the first time, it is determined the macroscopic crystallization rate of neodymium carbonate follows a zero-order reaction. The primary nucleation activation energy is 36.98 kJ/mol, indicating that the formation of Nd2(CO3)3 is controlled by a mixture of diffusion and chemical reaction. In the initial stage of precipitation, spherical amorphous neodymium carbonate with diameter of 20 nm was formed, with the molecular formula being Nd2(CO3)3·1.87H2O, and subsequently crystallized into tengerite-(Nd) [Nd2(CO3)3·2.5H2O] and lanthanite-(Nd) [Nd2(CO3)3·8H2O]. The stability of the amorphous neodymium carbonate in anhydrous environment and aqueous solution was evaluated, and ion potential was used to judge the stability trend of the rare earth carbonates. During the transition from amorphous phase to crystal, it is found temperature and supersaturation play an important role in the morphology of the final product. The results provide a reference for evaluating the crystallization process and developing large-scale industrial production methods.

Characterization of mesoporous stannosilicates obtained via non-hydrothermal synthesis using Na2SnO3 as the precursor

Abstract This paper describes the synthesis of ordered mesoporous silica MCM-41 and mesoporous stannosilicates Sn-MCM-41, under mild and non-hydrothermal conditions, as well as their characterization. The aim was to explore the influence of the synthesis temperature (25 and 80 °C) on the properties of the mesostructured material. A short synthesis time (30 min) and a sol-gel method were employed, with an Si/Sn ratio of 10, using tetraethyl orthosilicate (TEOS) as a source of silica and cetyltrimethyl ammonium bromide (CTAB) as a structure-template. To the best of our knowledge, this is the first time that sodium stannate (Na2SnO3) has been employed as an Sn(IV) source in MCM-41 synthesis. The characterization of the materials was performed via several techniques and the results revealed the formation of MCM-41 and Sn-MCM-41 with a high specific surface area and narrow pore size distribution, and there are strong indications that Sn(IV) is inserted in the MCM-41 lattice. This approach represents a significant advance compared to the materials commonly obtained via hydrothermal synthesis with time-consuming procedures and could be easily applied to large-scale production.

A mild conditions synthesis route to produce hydrosodalite from kaolinite, compatible with extrusion processing

Hydrosodalites are a family of zeolitic materials which have a diverse range of possible applications such as water desalination. Typical synthesis methods are relatively complex, using hydrothermal production and pre-processing and it is desirable to use lower energy and more cost-effective processing routes. For the first time, a low temperature, non-hydrothermal synthesis procedure for hydrosodalites, compatible with extrusion processing, is demonstrated. Kaolinite precursor, without calcination, was activated with a sodium hydroxide solution and formed at a workability consistent with extrusion. The cured samples were characterised using a range of advanced analytical techniques including PXRD, SEM, TGA, 27Al and 29Si-MAS-NMR, and FTIR to confirm and quantify conversion of the precursor to product phases. The synthesis consistently formed a 8:2:2 basic hydroxysodalite phase and the reaction was shown to follow a largely linear relationship with Na:Al until full conversion to the hydrosodalite phase was approached. The hydrosodalite became more ordered for Na:Al ≥ 1. There is good agreement between quantitative measurements made using PXRD, TGA and 29Si-MAS-NMR methods, providing confidence in the results. It has been shown that it is possible to synthesise hydrosodalite materials in a consistent and predictable manner, using non-hydrothermal methods, at the viscosity used for extrusion processing. This novel processing route could reduce production costs, production impacts and open up new applications for this important family of materials.

Non-hydrothermal synthesis of (NH4)2V3O8 hierarchical flowers and their conversion into V2O5 for lithium ion battery

(NH4)2V3O8 microflowers were synthesized through a non-hydrothermal/solvothermal method. And 3D hierarchical (NH4)2V3O8 as precursor could be easily transformed into V2O5 with preserved microstructure via subsequent calcination. The thickness of nanosheets (petals) can be controlled by varying the ratio of ethanol/water in the deposition system. 3D hierarchical V2O5 flowers demonstrate a very high capacity (289mAhg−1) and good cyclic stability.

Non-hydrothermal synthesis, structural characterization and thermochemistry of water soluble and neutral coordination polymers of Zn(ii) and Cd(ii): precursors for the submicron-sized crystalline ZnO/CdO

Eight new water soluble and neutral coordination polymers of Zn(ii) and Cd(ii) with flexible tridentate ancillary ligands and the acetylene dicarboxylate linker are reported.

Facile non-hydrothermal synthesis of oligosaccharides coated sub-5 nm magnetic iron oxide nanoparticles with dual MRI contrast enhancement effect.

Ultrafine sub-5 nm magnetic iron oxide nanoparticles coated with oligosaccharides (SIO) with dual T1-T2 weighted contrast enhancing effect and fast clearance has been developed as magnetic resonance imaging (MRI) contrast agent. Excellent water solubility, biocompatibility and high stability of such sub-5 nm SIO nanoparticles were achieved by using the "in-situ polymerization" coating method, which enables glucose forming oligosaccharides directly on the surface of hydrophobic iron oxide nanocrystals. Reported ultrafine SIO nanoparticles exhibit a longitudinal relaxivity (r1) of 4.1 mM-1s-1 and a r1/r2 ratio of 0.25 at 3 T (clinical field strength), rendering improved T1 or "brighter" contrast enhancement in T1-weighted MRI in addition to typical T2 or "darkening" contrast of conventional iron oxide nanoparticles. Such dual contrast effect can be demonstrated in liver imaging with T2 "darkening" contrast in the liver parenchyma but T1 "bright" contrast in the hepatic vasculature. More importantly, this new class of ultrafine sub-5 nm iron oxide nanoparticles showed much faster body clearance than those with larger sizes, promising better safety for clinical applications.

Template-free and non-hydrothermal synthesis of CeO2nanosheets via a facile aqueous-phase precipitation route with catalytic oxidation properties

Petal and belt-like CeO2nanosheets are synthesized using an aqueous phase precipitation method under template-free and non-hydrothermal conditions and exhibit excellent catalytic oxidation performance.

Non-hydrothermal synthesis and characterization of MCM-41 mesoporous materials from iron ore tailing

This study reported a facile synthetic method for MCM-41 mesoporous material at room temperature using iron ore tailing and cetyltrimethylammonium bromide (CTAB) as a silicon source and a structure-directing agent, respectively. The obtained product was systematically characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and nitrogen absorption–desorption measurement. It was confirmed that the as-synthesized material exhibited a well-ordered mesostructure with high surface area of ca. 634m2/g, large pore volume of 0.61cm3/g, and average pore diameter of 3.8nm. The removal efficiency towards model pollutant methylene blue (MB) was performed through produced MCM-41 and 111mg/g of MB could be eliminated under an optimal condition. Therefore, the material could be potentially used as a low-cost and efficient adsorbent candidate to treat organic contaminates in wastewater or other fields.

Non-hydrothermal synthesis and optical limiting properties of one-dimensional Se/C, Te/C and Se–Te/C core–shell nanostructures

A single step, nontoxic, non-hydrothermal, low temperature and reproducible method for the preparation of carbon-coated selenium and tellurium nanowires (Se/C and Te/C, respectively), and selenium–telluride (Se–Te/C) nanorods, is presented. Sodium dodecyl sulfate is used as the surfactant, and glucose is employed as the reducing and carbonizing agent. Uncoated nanowires of trigonal Se and Te without the carbon shell are obtained as products, at lower glucose concentrations, whereas at higher glucose concentrations carbon-coated nanowires of trigonal Se and Te are formed. Structural, morphological and compositional properties of the prepared products are examined using X-ray diffraction, scanning electron microscopy, high resolution transmission electron microscopy, and energy dispersive X-ray spectroscopy, respectively. The formation of amorphous carbon shell and the model depicting the growth of core–shell nanowires and nanorods are discussed on the basis of the experimental results. Nonlinear optical transmission of the samples is studied at 532nm using the open-aperture Z-scan technique employing 5ns laser pulses. Results show that the samples are efficient optical limiters, and that a three-to-four-fold enhancement in the value of the effective two-photon absorption coefficient (β) can be achieved by coating the nanowires and nanorods with carbon.

Non-hydrothermal synthesis of mesoporous materials using sodium silicate from coal fly ash

Siliceous mesoporous materials with pores of ordered 2-D hexagonal structure were successfully prepared without hydrothermal treatment from condensation–polymerization of various concentration of quaternary ammonium salt as structure directing agents and silica precursor from the supernatant of coal fly ash (CFA) in the presence of catalyst. The synthesized materials had high surface area of ca. 740 m 2 g −1 and pore volume of ca. 0.42 mL g −1. The synthesized material exhibited a narrow size pore distribution and the mean pore diameter as measured by Dollimore–Heal method was about 2.3 nm. The formation of ammonium salt that act as precipitant during the synthesis enable the hydrolysis and co-condensation of the sodium silicate at room temperature.

Synthesis and characterization of saponite clays

A new procedure has been developed for a fast preparation of saponite clays under the non-hydrothermal synthesis conditions of 90 degrees Celsius and 1 atmosphere. Saponites were synthesised from a stoichiometric mixture containing Si/Al3+ gel, M2+-nitrate (M2+ = Mg, Zn, Ni, Co, or Cu), urea and water within a few hours. The synthesis products were characterised with XRD, IR, TEM, XRF, N2-physisorption, Al-EXAFS, and 27Al- and 29Si-MASNMR Incorporation of Mg, Zn, Co, Ni, or a combination of these cations in the octahedral sheet, as well as controlling the Si/Al ratio in the tetrahedral sheet in the range between 5.67 and 39.0 could easily be established. Pure Cu-saponite could not be synthesised due to the preferred formation of chrysocolla, but a combination of Mg2+ and Cu2+ resulted in saponite formation. The chemical composition strongly influences the textural properties of the saponites. It is possible to prepare saponite samples of a specific surface area and pore volume of 100 to 750 m2/g and 0.15 to 1.05 ml/g, respectively. The lateral size and the amount of stacking of the saponite platelets could be influenced by the composition, synthesis duration and amount of urea. The new synthesis procedure provides an easy way to prepare high quantities of saponites with far-reaching control on the texture as well as the composition.

Molten Salt Synthesis of Tin Oxide Nanorods: Morphological and Electrochemical Features

This article reports the nonhydrothermal synthesis of SnO2 nanorods at moderate temperatures (320 or 700 °C), and the application of these nanorods as a Li storage compound for Li-ion batteries. The 15 nm diameter high aspect ratio (∼50−100) SnO2 nanorods prepared at 700 °C were fabricated as Li-ion battery anodes and tested. They exhibited good capacity (∼700 mAh/g nominal in the 5 mV to 1 V range) and extended cyclability for a tin-based anode. More interestingly was the observation of a capacity of ∼1100 mAh/g in the 5 mV to 2 V window that exceeds the theoretical capacity of SnO2. SEM and TEM characterizations revealed substantial morphological changes in the nanorods during cycling. A few possible reasons for the high capacity and the morphological changes are provided.

Nonhydrothermal Synthesis and Properties of Saponite-Like Materials

Main features of nonhydrothermal synthesis of saponite-like materials containing Zn(II) and Mg(II) cations in octahedral networks were studied. Optimal conditions for the synthesis were determined. The influence exerted by the double-charged structure-forming cation on the rate of structure formation in the synthesized materials and also on their pore structure and thermal stability was studied.

Copper ions distribution in synthetic copper-zinc hydrosilicate

Copper ions distribution in the structure of synthetic copper-zinc hydrosilicate of zincsilite structure, obtained non-hydrothermal synthesis have been studied. Zinesilite is referred to the layered silicates of smectite group and is described by the formula Znx (Zn3-x □x) [Si4O10](OH)2.nH2O, where Zn3-x—are the ions located in the octahedral positions of layers, formed by two sheets of [Si4O10] tetrahedrons; Znx are zinc ions in the interlayer; □x are the cation vacancies. Two types of copper ions were distinguished in accordance with the character of their interaction with hydrogen: (1)—substituting zinc ions in the octahedral positions of layers; (2)—substituting zinc ions in the interlayer. These two types of copper ions display the following properties when reacting with hydrogen: (1)—copper ions in octahedral positions start to be reduced at temperatures 553–573 K, and at 723 K reduction degree is 50%; (2)—copper ions from interlayer start to be reduced at 503–533 K with a constant energy of activation, and their reduction may be complete at this temperature.

Non-hydrothermal synthesis of copper-, zinc- and copper-zinc hydrosilicates

Cu/SiO2, Zn/SiO2 and Cu-Zn/SiO2 samples have been prepared by the homogeneous deposition-precipitation method. The samples were analyzed by thermal analysis, X-ray diffraction and infrared spectroscopy after various heat treatments and compared with data obtained for several minerals. It has been shown that interaction between the components occurs through formation of hydrosilicates. Copper-silica system at a Cu:Si ratio ≤ 1, gives rise to a hydrosilicate stable up to a calcination temperature of 930 K resembling the mineral Chrisocolla; at higher ratios a hydroxonitrate (gerhardite type) is also formed. Zinc-silica interaction produces two hydrosilicates such as a well crystallized Hemimorphite at Zn:Si = 2 and highly dispersed Zincsilite at Zn:Si ≤ 0.75, both stable up to 1073 K. The Zincsilite structure consists of three layered sheets (an octahedral layer sandwiched by two tetrahedral ones) like the Stevensite mineral group. For the copper-zinc-silica system no copper hydrosilicate is formed. Copper merely enters the Zincsilite structure independenly of the applied (Cu + Zn):Si ratio. Resulting layered copper-zinc hydrosilicate may be described by formula Znx-yCuy(Zn3-x-zCuz-y□x)[Si4O10](0H)2.nH2O, where Zn3-x-zCuz-y—ions are located in octahedral sites, Znx-yCuy-ions in the interlayer; □x are vacancies in the layers. Copper and zinc in excess of the Zincsilite ratio of Me:Si = 0.75, gives rise to copper and copper-zinc hydroxonitrates.

Hydrothermal versus Nonhydrothermal Synthesis for the Preparation of Organic−Inorganic Solids: The Example of Cobalt(II) Succinate

Hydrothermal technique was used together with a room-temperature process for the synthesis of cobalt−succinate compounds. Four structures are described for two new compounds: K2Co(C4H4O4)2 and Co(H2O)4(C4H4O4). Whatever the solution conditions, carboxylate ligands, which possess a strong nucleophilic character, coordinate each metal ion. However, the coordination ability of carboxylate under hydrothermal conditions is different from that under mild ones. For high-temperature phases, carboxylic groups are multidentate and the organic acts as a “template” during the condensation of the oxygen−metal networks, whereas under room temperature conditions, they are unidentate and infinite structures are obtained via the bridging role of the ligand.