Solid-state Metathesis Reaction Research Articles

Synthesis of GaN Crystals Through Solid-State Metathesis Reaction Under High Pressure

Well-crystallized gallium nitride (GaN) crystals are prepared through an untraditional solid-state metathesis (SSM) reaction under high pressure between varying phases of lithium metagallate (LiGaO2) and boron nitride (BN). The advantage of the method lies in the potential energy and cost savings over other conventional synthetic routes. Our results also demonstrate that lithium borate (LiBO2) may be a new solution of GaN for large crystal growth. This discovery not only leads to a better understanding of the mechanisms of SSM reactions but also provides a starting point for mass production and growth of large single crystals of GaN from SSM reactions under high pressure.

Crystalline Intermediates during Polycondensation Reactions in the C-N-Cl System - The Paddle-Wheel Molecule N(C6N7Cl2)3

Solid state metathesis reactions between cyanuric chloride and C–N–H or alkali metal–(B–)C–N compounds, respectively, were carried out in the temperature range between 150 °C to 500 °C, studying intermediate stages of reactions and targeting the formation of carbon nitride materials by elimination of HCl or alkali metal chlorides. Although cyanuric chloride was reacted with quite a number of different reaction partners such as melamine, cyanamide, lithium nitride, lithium or sodium carbodiimide, lithium nitridoborate or sodium dicyandiamide, always the same intermediate compounds appeared in the reactions mixtures. Colorless, needle-shaped crystals of the tertiary amine N(C3N3Cl2)3 (1) were obtained at temperatures around 200–250 °C. Temperatures as high as 400 °C yielded yellow, plate-like crystals of the heptazine compound C6N7Cl3 (2). At even higher temperatures, the reaction products were of poorer crystallinity, but evidence of the formation of another crystalline intermediate was given by X-ray powder diffraction and electron diffraction experiments. This third intermediate is assumed to be a tertiary amine, quite similar to 1, however, having heptazine ligands instead of triazine ligands and is assigned with the formula N(C6N7Cl2)3 (3). Theoretical calculations were performed for the structures and the vibrational spectra of 1 and 3. Theoretical calculations and a structure refinement based of X-ray powder diffraction data yielded a plausible structural model for compound 3.

Synthesis and characterization of zirconium diphosphate by microwave assisted metathesis approach

A novel solid-state metathesis (SSM) approach [ZrCl 4 + 2(NH 4) 2HPO 4 → 4NH 4Cl + ZrP 2O 7 + H 2O] has been applied to synthesize technologically important zirconium diphosphate, ZrP 2O 7. The SSM reaction is facilitated by the formation of a high lattice energy by-product such as NH 4Cl, which is the driving force for product formation. The structural, optical, chemical, magnetic and electrochemical properties of the synthesized powders were determined by powder X-ray diffraction, scanning electron microscopy, transmission Fourier transform infrared measurements, X-ray photoelectron spectroscopy, diffused reflectance spectra in the UV–vis range, magnetization measurements, and electrochemical characterization to establish structure–property relationship in the zirconium phosphate materials.

Crystal Structure of Ce3Ni2(BN)2N and Magnetic Behavior of (CeNi(BN))2(CeN)x with x = 0, 1

AbstractThe new compound Ce3Ni2(BN)2N was synthesized by a modified solid state metathesis reaction. The crystal structure of Ce3Ni2(BN)2N was found to be isotypic with the superconducting compound La3Ni2(BN)2N, according to Rietveld refinements performed on X‐ray powder data (I4/mmm, Z = 2, a = 3.5817(1) Å, c = 20.283(1) Å).Corresponding solid state reactions of mixtures composed of CeN/NiB and CeNi/BN yielded CeNi(BN) and a mixture of the two closely related layered structures (CeNi(BN))2(CeN)x with x = 0 and 1.Magnetization experiments on these samples revealed temperature independent paramagnetic behavior for Ce3Ni2(BN)2N and CeNi(BN) without any magnetic ordering down to 5 K.

Novel microwave initiated synthesis of Zn2SiO4 and MCrO4 (M=Ca, Sr, Ba, Pb)

Abstract A novel microwave initiated solid-state metathesis synthesis of metal chromates and zinc silicate has been investigated. The high lattice energy of NaCl drives the solid-state metathesis reaction (CaCl 2 ·2H 2 O + Na 2 CrO 4 ·4H 2 O → NaCl + CaCrO 4 + 6H 2 O↑) in the forward direction to obtain the products. The structural, optical, and chemical properties of synthesized compounds are determined by powder X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, and diffused reflectance spectroscopy in the UV–vis range.

Novel microwave initiated solid-state metathesis synthesis and characterization of lanthanide phosphates and vanadates, LMO 4 (L = Y, La and M = V, P)

A novel solid-state metathesis (SSM) approach represented by the reaction (LCl 3 + Na 3VO 4 → LVO 4 + NaCl) (L = Y, La) is proposed to synthesize technologically important rare-earth phosphates and vanadates. The SSM reaction, driven in the forward direction is facilitated by the formation of high lattice energy by-product like NaCl. The structural, thermal, optical, and chemical properties of synthesized powders are determined by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), differential scanning calorimetry (DSC), and diffused reflectance (DR) spectra in the UV–vis range. The direct band gap of the synthesized materials was found out to be ∼3.5 eV for LaVO 4, YVO 4, YPO 4 and ∼2.6 eV for LaPO 4.

Rapid and exothermic solid-state synthesis of metal oxyhalides and their solid solutions via energetic metathesis reactions

Rapid solid-state metathesis reaction chemistry has been extended to the production of layered metal oxyhalide systems. This article describes the successful synthesis of crystalline BiO X ( X=Cl, I), and lanthanide oxychlorides ( LnOCl, Ln=La, Sm, Gd) from metal trihalides and Na 2O 2 in seconds. These known materials contain halide double layers separating M–O layers. Powder X-ray diffraction results on the metathesis metal oxyhalide products agree with prior literature reports. The morphological and compositional properties of the metal oxyhalide products are described. The rapid production of well-mixed paramagnetic Gd x Sm 1− x OCl solid-solution materials was achieved using physical mixtures of SmCl 3 and GdCl 3 precursors reacted with Na 2O 2. The room-temperature magnetic properties of these materials with varying compositions are also described. As expected, magnetism, unit cell parameters, and M–O vibrational bands are all dependent on metal composition in the solid-solution products and vary in an approximately linear Vegard's law fashion.

Solid-state metasynthesis and characterization of AlN nanocrystals

Abstract Hexagonal AlN nanocrystals were synthesized successfully from solid-state metathesis reactions by using Mg3N2 as the nitriding sources at the temperature of 500 °C. The samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), selected area electron diffractions, Fourier transformation infrared (FT-IR) spectroscopy and Raman spectroscopy respectively. The results show that the obtained samples are pure hexagonal AlN with a grain size less than 10 nm.

Phase formation and electrochemical properties of cryochemically processed Li1+xV3O8 materials

Abstract Li 1+ x V 3 O 8 cathode materials for secondary Li batteries are prepared by freeze drying (FD) synthesis from aqueous solutions of NH 4 VO 3 and various Li salts at different pH values. The polyanionic forms of vanadates in the FD products are significantly different from the ones existing in the starting solutions. The degree of VO 3 − polymerization is influenced both by co-existing anion and by pH value of the starting solution. The appearance of NH 4 V 3 O 8 among FD products promotes a faster formation of the crystallochemically similar LiV 3 O 8 during the following solid state metathesis reaction. LiV 3 O 8 powders obtained by the thermal decomposition of various FD precursors at 300–400 °C demonstrate rather different micromorphologies and drastically dissimilar electrochemical properties. The best electrochemical performance is exhibited by poorly crystalline but faceted fine particles obtained by the thermal decomposition of nitrate-containing precursor.

Syntheses and Structural Properties of Rare Earth Carbodiimides

Crystalline samples of rare earth carbodiimides were synthesized by solid-state metathesis reactions of rare earth trichlorides with lithium cyanamide in sealed silica ampules. Two distinct structures were determined by single-crystal X-ray diffraction. The structure determined for Sm2(CN2)3 [C2/m, Z = 2, a = 14.534(2) A, b = 3.8880(8) A, c = 5.2691(9) A, beta = 95.96(2) degrees , R1 = 0.0267, and wR2 = 0.0667] was assigned for RE2(CN2)3 compounds with RE = Y, Pr, Nd, Sm, Gd, Tb, Dy, Ho, and Er, and the structure determined for Lu2(CN2)3 [R32, Z = 3, a = 6.2732(8) A, c = 14.681(2) A, R1 = 0.0208, and wR2 = 0.0526] was assigned for the smallest rare earth ions with RE = Tm, Yb, and Lu by powder X-ray diffraction. Both types of crystal structures are characterized by layers of [NCN](2-) ions whose arrangements can be derived from the motif of a closest packed layer of sticks. These layers alternate with layers of rare earth ions in a one-by-one sequence. Different tilting arrangements of the N-C-N-axes relative to the stacking directions (c) and different arrangements of RE3+ ions within metal atom layers account for the two distinct structures in which Sm3+ and Lu3+ ions adopt the coordination numbers 7 and 6, respectively.

Enhanced Solid-State Metathesis Routes to Carbon Nanotubes

Ignition of three solids creates multiwalled carbon nanotubes in seconds. A solid-state metathesis (exchange) reaction between hexachloroethane (C2Cl6) and lithium acetylide (Li2C2) with 5% cobalt dichloride (CoCl2) added as an initiator produces up to 7% carbon nanotubes, as observed via transmission electron microscopy. Using the concept that sulfur can promote nanotube growth, the reaction yield can be increased to 15% by switching to CoS as the initiator. The more readily available, inexpensive calcium carbide (CaC2) can be substituted for lithium acetylide while maintaining comparable yields. Switching initiators to FeS can be used to further enhance the yield. A systematic study of the C2Cl6/CaC2 reaction system indicates that a yield up to 25% can be realized by using 6% FeS as the initiator. Reaction temperatures for the C(2)Cl6/CaC2 system of up to 3550 degrees C are calculated using thermodynamic data assuming quantitative yield and adiabatic conditions.

Mechanochemically assisted room temperature solid state metathesis reaction for the synthesis of MMoO4 (M = Ca, Sr and Ba)

This communication reports a novel mechanochemically assisted room temperature solid state metathesis reaction for the synthesis of submicron-size alkaline-earth molybdates crystallizing in a tetragonal Scheelite structure. The solids were characterized by powder XRD, FTIR, TGA, DTA, SEM, EDAX and TEM to ascertain their composition, phase homogeneity and morphology.

Synthesis of Nanocrystalline TiO2 and Reduced Titanium Oxides via Rapid and Exothermic Metathesis Reactions

Nanocrystalline titanium dioxide is conventionally produced by aqueous precipitation reactions, followed by annealing post-treatment, which can also cause structural conversions from the photocatalytically active anatase to rutile phases. Solvent-free exothermic solid-state metathesis (SSM) reactions have shown wide utility in the synthesis of binary solids. This paper describes the application and chemical flexibility of the SSM method for the synthesis of TiO2 from TiCl3 and Na2O2. The use of an insulating crucible and addition of a NaCl heat sink to this rapid and exothermic SSM led to improved product crystallinity and increases in anatase to rutile TiO2 phase content. Small particle size products were synthesized at high salt dilution levels. The photocatalytic activity of SSM synthesized TiO2 powders containing some anatase TiO2 were comparable to a commercial TiO2 standard, even though the SSM powders had 30−50% lower surface areas. By changing the Na2O2 reagent to a more oxygen deficient one, Na2O, reduced titanium phases, primarily Ti2O3, were synthesized along with Na−Ti−O structures.

Route to GaN and VN Assisted by Carbothermal Reduction Process

A route to prepare nitrides, such as GaN, VN, and other nitrides, is reported. The reaction pathway involves a two-step process by using the as-synthesized a-C3N3.69 as precursor. The route is so potent that a series of nitrides can be directly synthesized from their oxides at moderate temperatures. A striking feature of this method lies in that a-C3N3.69 is found to play double roles as both carbonizing and nitridizing agent in these reactions. These results will greatly deepen our understandings of the mechanism for solid-state metathesis reactions.

Synthesis of nano-sized alkaline-earth hydroxyapatites through microwave assisted metathesis route

In this paper, we report a microwave assisted solid state metathesis reaction to obtain nano-sized particles of alkaline-earth hydroxyapatites, A 10(PO 4) 6(OH) 2 where A = Sr and Ba. The solids were characterized by powder XRD, FTIR, TGA, DTA, particle size measurements, SEM, EDAX and TEM to ascertain their phase homogeneity and particle size distribution.

A Solid‐State Metathesis Route to MgSiN2.

AbstractFor Abstract see ChemInform Abstract in Full Text.

A Solid-State Metathesis Route to MgSiN2

Nitrides, such as magnesium silicon nitride, hold promise for applications requiring materials with high thermal conductivity. The synthesis of the ternary nitride MgSiN2 is accomplished using SiO2 and Mg3N2 as reactants in a solid-state metathesis (exchange) reaction. This self-propagating reaction is readily initiated when a flame with a temperature ≥1100 °C is brought into contact with a pressed SiO2/Mg3N2 pellet. By using Mg3N2 in ≥1 M excess, X-ray-pure MgSiN2 can be produced. With lower ratios, elemental silicon forms as an impurity. Increasing the flame initiation temperature to ≥2500 °C can also be used to eliminate silicon impurities with the benefit of increasing the crystallinity of the product. The use of other forms of silica as a silicon source provides an inexpensive alternative to produce MgSiN2. A variety of silica sources are examined, including fumed silica, sand, ground quartz, bottle glass, and rice hull ash. Since rice hull ash is an industrial waste product from rice processing, new...

A Soft Solution Process to Synthesize Nanocrystalline Barium Zirconate via Reactive Solid State Precursors

Barium zirconate, a perovskite oxide has been synthesized by a new procedure using solid state metathesis reaction precursors subjected to sonication. We report the lowest temperature of synthesis with particle size ranging from 20 to 30 nm. The initial stage involves formation of composite hydroxide nanoparticles by the solid state reaction of precursor salts with KOH at ambient temperature followed by sonication. BaZrO3 formation as a consequence of ultrasonicator output power variation and ultrasonic time variation has been studied. Results indicate that the process is convenient, low energy, environmentally benign and having narrow particle size distribution of BaZrO3.

Transforming n=1 members of the Ruddlesden–Popper phases to a n=3 member through metathesis: synthesis of a new layered perovskite, Ca 2La 2CuTi 2O 10

We report the formation of a new n=3 Ruddlesden–Popper (R–P) layered perovskite oxide, Ca 2La 2CuTi 2O 10 ( I), in the metathesis reaction between NaLaTiO 4 and Ca 2CuO 2Cl 2 ( n=1 R–P phases) at 700°C in air. Rietveld refinement of powder XRD data shows that I is isostructural with Sr 4Ti 3O 10 (space group I4/ mmm; a=3.8837(5), c=27.727(6) Å), consisting of triple perovskite CuTi 2O 10 sheets wherein Cu and Ti are ordered at the central and terminal octahedral sites, respectively. Magnetization data provide support for the presence of strong antiferromagnetically coupled CuO 2 sheets in the structure. I is metastable decomposing at higher temperatures (∼950°C) to a mixture of perovskite-like CaLa 2CuTi 2O 9 and CaO. Interestingly, the reaction between NaLaTiO 4 and Sr 2CuO 2Cl 2 follows a different metathesis route, 2NaLaTiO 4+Sr 2CuO 2Cl 2→La 2CuO 4+2SrTiO 3+2NaCl, revealing multiplicity of reaction pathways for solid-state metathesis reactions.

2D—3D Transformation of Layered Perovskites Through Metathesis: Synthesis of New Quadruple Perovskites A2La2CuTi3O12 (A: Sr, Ca).

AbstractFor Abstract see ChemInform Abstract in Full Text.