The first hafnium germanate with garnet-type of structure: mild hydrothermal synthesis, crystal structure and new mechanism of hydroxyl inclusion

Sodium hafnium germanate, Na3Hf1.7Ge3O10(OH)1.8, with garnet-type of structure was synthesized as a single phase, nanoparticles (100–600 nm) at mild hydrothermal conditions (230 °C) and autogenous pressure. The structure was solved ab initio from powder X-ray diffraction data and subsequently refined [Rexp: 6.10, Rwp: 7.26, Rp: 5.39, GOF: 1.19, RB: 1.50] by the method of Rietveld. The solid crystallizes in cubic space group Ia-3d (230), with a = 12.6819(2) Å, V = 2039.65(1) Å3 and Z = 8. The structure is built up of rare combination of two tetravalent (Ge4+ and Hf4+) and one monovalent (Na+) cation alternating in form corner-sharing GeO4 tetrahedra and HfO6 octahedra whose negative charge is compensated by Na+ residing in dodecahedral coordination. Unlike the typical tetrahedral site disorder in hydrogarnets (hydrogrossular, hibschite, and katoite) we found that the octahedral position of the heavy Hf4+ cation is partly vacant which reveals alternative mechanism of charge unbalance leading to incorporation of hydroxyl group. Furthermore, the synthesized material is the first hafnium germanate with garnet-type of structure and the second known sodium hafnium germanate.publishe

Interzeolite Transformation from FAU-to-EDI Type of Zeolite

This study reports for the first time the transformation of the pre-made FAU type of zeolite to the EDI type of zeolite. The concentration of the KOH solution controls this interzeolite transformation, which unusually occurs at both room temperature and under hydrothermal conditions. The transformation involves the amorphization and partial dissolution of the parent FAU phase, followed by the crystallization of EDI zeolite. At room temperature, the transformation (11–35 days) provides access to well-shaped nano-sized crystals and hollow hierarchical particles while the hydrothermal synthesis results in faster crystallization (6–27 h). These findings reveal an example of an interzeolite transformation to a potassium zeolite that lacks common composite building units with the parent zeolite phase. Finally, this work also demonstrates the first room-temperature synthesis of EDI zeolite from a gel precursor

A Review on the Green Synthesis of Silver Nanoparticles and Their Morphologies Studied via TEM

Silver has been recognized as a nontoxic, safe inorganic antibacterial/antifungal agent used for centuries. Silver demonstrates a very high potential in a wide range of biological applications, more particularly in the form of nanoparticles. Environmentally friendly synthesis methods are becoming more and more popular in chemistry and chemical technologies and the need for ecological methods of synthesis is increasing; the aim is to reduce polluting reaction by-products. Another important advantage of green synthesis methods lies in its cost-effectiveness and in the abundance of raw materials. During the last five years, many efforts were put into developing new greener and cheaper methods for the synthesis of nanoparticles. The cost decrease and less harmful synthesis methods have been the motivation in comparison to other synthesis techniques where harmful reductive organic species produce hazardous by-products. This environment-friendly aspect has now become a major social issue and is instrumental in combatting environmental pollution through reduction or elimination of hazardous materials. This review describes a brief overview of the research on green synthesis of silver metal nanoparticles and the influence of the method on their size and morphology

¿-Phase nucleation and electrical response of poly(vinylidene fluoride)/microporous titanosilicates composites

Microporous titanosilicates ETS-10, ETS-4 and GTS-1 were applied in the preparation of poly(vinylidene fluoride), PVDF, composites by solvent casting and melt crystallization. The spherulitic microstructure of neat PVDF is maintained but the crystallization phase is altered to the piezoelectric ¿-phase when the sample is melted at temperatures below 200 °C. The crystallinity and the temperature of polymer degradation are hardly influenced by the introduced titanosilicates, however ETS-4 incorporated in the polymer showed improved thermal stability. The dimensional characteristics of the porous framework, different confined mobility of the charge compensating cations and the interfacial polarization led to gradually increased dielectric constant that reached values of 18 at 1 kHz. This behavior was accompanied by increased dielectric losses and a.c. conductivity. The reported PVDF/microporous titanosilicate composites represent a new class of materials with application potential for sensors and actuators.Peer ReviewedPostprint (published version

UV-light assisted synthesis of high silica faujasite-type of zeolites

Currently, the direct synthesis of faujasite-type (FAU) zeolites with Si/Al ratios greater than 3 depends on organic or inorganic additives. Here, we report the first additive-free synthesis of faujasite with Si/Al ratios greater than 3 using ultraviolet (UV) light assistance. The obtained zeolite shows excellent catalytic performance comparable to the commercial zeolite Y.publishe

Infuence of zeolite structure and chemistry on the electrical response and crystallization phase of poly(vinylidene fluoride)

Zeolites with framework types LTL, LTA, FAU, and MFI were synthesized and used as fillers to prepare PVDF/zeolite composites. The obtained composites showed structural and electrical dependence on the pore system and chemical content of the inorganic host. The larger polymer-zeolite electrostatic interactions of the Y and A zeolites lead the polymer to crystallize in the electroactive ¿-phase, which in the case of the L zeolite is prevented due to the reduced interaction area. The solvent and water encapsulation ability of the zeolite as well as improve of the dielectric response of the composite is directly related to the Si/Al ratio, leading zeolites with lower Si/Al ratios to larger dielectric responses and encapsulation efficiencies in the composites. These effects show also some dependency on the dimensionality of the pore system; the zeolite L-containing 1D channels showing superior dielectric performance than the 3D pore system of zeolite Y.Peer Reviewe

Hydrothermal Synthesis of Copper Zirconium Phosphate Hydrate [Cu(OH)(2)Zr(HPO4)(2)center dot 2H(2)O] and an Investigation of its Lubrication Properties in Grease

Copper zirconium phosphate hydrate (Cu(OH)(2)Zr(HPO4)2 center dot 2H(2)O, hereafter referred to as Cu-alpha-ZrP) with high crystallinity was directly synthesized in a NaF-CuO-ZrO-P2O5-H2O system under hydrothermal conditions. The copper ion was confirmed to be an exchangeable cation in the Cu-alpha-ZrP through elemental analysis and a proton ion exchange process. The crystal structure of the Cu-alpha-ZrP was determined ab initio by using X-ray powder diffraction data. In the structure, the CuO6 octahedron would be located in an exchangeable atom position. Moreover, Cu-alpha-ZrP was evaluated as an additive in grease in a four ball test. The maximum nonseizure load (P-B, representing the load-carrying capacity) of the base grease containing Cu-alpha-ZrP was increased from 353 to 1235 N. The excellent load-carrying capacity may be explained by the easier adherence of the material to the worn surface forming a tight protective film

¿-Phase nucleation and electrical response of poly(vinylidene fluoride)/microporous titanosilicates composites

Microporous titanosilicates ETS-10, ETS-4 and GTS-1 were applied in the preparation of poly(vinylidene fluoride), PVDF, composites by solvent casting and melt crystallization. The spherulitic microstructure of neat PVDF is maintained but the crystallization phase is altered to the piezoelectric ¿-phase when the sample is melted at temperatures below 200 °C. The crystallinity and the temperature of polymer degradation are hardly influenced by the introduced titanosilicates, however ETS-4 incorporated in the polymer showed improved thermal stability. The dimensional characteristics of the porous framework, different confined mobility of the charge compensating cations and the interfacial polarization led to gradually increased dielectric constant that reached values of 18 at 1 kHz. This behavior was accompanied by increased dielectric losses and a.c. conductivity. The reported PVDF/microporous titanosilicate composites represent a new class of materials with application potential for sensors and actuators.Peer Reviewe