No abstract

No abstract

Single crystals of LnM x Ga 3 (Ln = Ho, Er; M = Fe, Co; x < 0.2) were grown from a Ga self-flux. The compounds crystallize in a "stuffed" variant of the AuCu 3 -structure type where Fe or Co partially occupies the body-centered position of the unit cell surrounded by six Ga atoms. The insertion of Fe or Co guest atoms into the AuCu 3 -structure type causes a structural change in the host material where chemical pressure is exerted on Ga-Ga contacts surrounding the filled octahedra. This in turn affects the stability of the AuCu 3 -structure type and the intrinsic properties of the materials. With increasing Ho−Ho distances of 4.2355(5), 4.2377(5), and 4.2441(3) Å, HoCo 0.16(2) Ga 3 , HoFe 0.11(1) Ga 3 , and HoFe 0.16(2) Ga 3 order antiferromagnetically with decreasing Néel temperatures of T N = 10.2, 7.2, and 6.5 K, respectively. ErCo 0.06(2) Ga 3 , ErFe 0.06(1) Ga 3 , and ErFe 0.11(2) Ga 3 order antiferromagnetically with Néel temperatures of T N = 3.3, 5.2, and 6.2 K. The magnetic properties are attributed to changes in the coupling strength of local magnetic moment with conduction electrons as a function of transition metal and rare earth.

Single crystals of CeCo(2-x)M(x)Al(8) (M = Mn, Fe, Ni; 0 ≤ x < 1) were grown and characterized by X-ray diffraction and magnetic susceptibility. The unit cell volumes of Mn-doped compounds increase and those of Ni-doped compounds decrease with increasing dopant concentration. All samples display a magnetic ordering near 6 K with magnetic moments of the analogues ranging from 2.61 to 2.81 μ(B)/mol Ce and slightly higher than Ce(3+) only magnetic moment. The unit cell volumes of Fe-doped compounds also increase with increasing Fe concentration. However, the cell volume of CeCo(2-x)Fe(x)Al(8) decreases for x = 1.00 and is not Curie-Weiss possibly because of valence fluctuation.

The use of microwave irradiation for the synthesis of inorganic nanomaterials has recently become a widespread area of research that continues to expand in scope and specialization. The growing demand for nanoscale materials with composition and morphology tailored to specific applications requires the development of facile, repeatable, and scalable synthetic routes that offer a high degree of control over the reaction environment. Microwave irradiation provides unique advantages for developing such routes through its direct interaction with active reaction species, which promotes homogeneous heat distribution, increased reaction rates, greater product quality and yield, and use of mild reaction conditions. Many catalytic nanomaterials such as noble metal nanoparticles and intricate nanocomposites have very limited synthetic routes due to their extreme temperature sensitivity and difficulty achieving homogeneous growth. This work presents recent advances in the use of MW irradiation methods to produce high-quality nanoscale composites with controlled size, morphology, and architecture.

No abstract

No abstract

The impact on the morphology nanoceramic materials generated from group 4 metal alkoxides ([M(OR)]) and the same precursors modified by 6,6'-(((2-hydroxyethyl)azanediyl)bis(methylene))bis(2,4-di- tert-butylphenol) (referred to as H-AM-DBP (1)) was explored. The products isolated from the 1:1 stoichiometric reaction of a series of [M(OR)] where M = Ti, Zr, or Hf; OR = OCH(CH)(OPr ); OC(CH)(OBu ); OCHC(CH)(ONep) with H-AM-DBP proved, by single crystal X-ray diffraction, to be [(ONep)Ti( k( O,O',O'',N)-AM-DBP)] (2), [(OR)M(μ( O)- k( O',O'',N)-AM-DBP)] [M = Zr: OR = OPr , 3·tol; OBu, 4·tol; ONep, 5·tol; M = Hf: OR = OBu , 6·tol; ONep, 7·tol]. The product from each system led to a tetradentate AM-DBP ligand and retention of a parent alkoxide ligand. For the monomeric Ti derivative (2), the metal was solved in a trigonal bipyramidal geometry, whereas for the Zr (3-5) and Hf (6, 7) derivatives a symmetric dinuclear complex was formed where the ethoxide moiety of the AM-DBP ligand bridges to the other metal center, generating an octahedral geometry. High quality density functional theory level gas-phase electronic structure calculations on compounds 2-7 using Gaussian 09 were used for meaningful time dependent density functional theory calculations in the interpretation of the UV-vis absorbance spectral data on 2-7. Nanoparticles generated from the solvothermal treatment of the ONep/AM-DBP modified compounds (2, 5, 7) in comparison to their parent [M(ONep)] were larger and had improved regularity and dispersion of the final ceramic nanomaterials.