Crystal structure of cobalt molybdate hydrate CoMoO4·nH2O

We have determined the crystal structure of the title compound, which has a triclinic cell with cell parameters of , , , α=76.617°, β=84.188°, γ=74.510° and space group . The crystal structure suggests the chemical formula CoMoO₄·3/4H₂O. The structure consists of MoO₄ tetrahedra and CoO₆ octahedra, confirming the earlier X-ray absorption near-edge spectroscopic (XANES) investigation on the hydrate. The comparison of the crystal structures of the hydrate and the α-,β-, and hp-phases shows that the hydrate exhibits metal cation coordinations similar to those of the β-phase, but had arrangements of CoO₆ and MoO_n polyhedra similar to those of the hp-phase.     

Room Temperature Solid State Reaction Involving Structural Transformation of Covalent Oxide Network

An interesting structural transformation from a two dimensional (2d) covalent oxide network with a layered structure to a three-dimensional (3d) network with a tunnel structure was found at room temperature in the mixture of hydrated alkali-metal molybdenum bronze and amorphous alkali-metal molybdate. From various experimental results it was concluded that the transformation was due to a room temperature solid state reaction.     

Hydrothermal Synthesis of the Blue Potassium Molybdenum Bronze, K0.28MoO3

Blue potassium molybdenum bronze, K_0.28MoO₃, was prepared by hydrothermal heating hydrogen molybdenum bronze in KCl solution at 431 K. Hydrated molybdenum bronze was found formed as an intermediate during the conversion from hydrogen molybdenum bronze to blue bronze. The hydrothermal method proved itself an easy and effective for synthesis of mixed-valence compounds.     

Rubber elasticity in the introductory thermodynamics course

An experimental set-up is described in which the temperature of a piece of rubber is measured with thin wire thermocouples. It measures and records the temperature change of the rubber as it heats and cools in response to elongation and contraction. This mechano-caloric effect arising from the entropy elasticity of rubber represents a reversible thermal process in clear distinction from most of other heat effects encountered in our daily experience where the irreversibility is inevitably involved. The demonstration experiment has been proved useful in elementary thermodynamic courses for introducing the entropy concept. This revised version was published online in August 2006 with corrections to the Cover Date.     

Reactive silica, XIV. Sorption and polymerization of ethylene oxide on reactive silica

Ethylene oxide vapor was exposed to reactive silica (RS). It chemisorbed immediately on a pair of silicon radicals as –O–CH₂–CH₂–, and the adsorbed species polymerized. It is assumed that polymerization is not an ionic but a radical type reaction.

---

. –O–CH₂–CH₂– . , , .

---

---

Part XIII: Ref. 15     

Effect of surface morphology on membrane fouling by humic acid with the use of cellulose acetate butyrate hollow fiber membranes

A serious problem faced during the application of membrane filtration in water treatment is membrane fouling by natural organic matter (NOM). The hydrophilicity, zeta potential and morphology of membrane surface mainly influence membrane fouling. The aim of the present study is to reveal the correlation between membrane surface morphology and membrane fouling by use of humic acid solution and to investigate the efficiency of backwashing by water, which is applied to restore membrane flux. Cellulose acetate butyrate (CAB) hollow fiber membranes were used in the present study. To obtain the membranes with various surface structures, membranes were prepared via both thermally induced phase separation (TIPS) and nonsolvent-induced phase separation (NIPS) by changing the preparation conditions such as polymer concentration, air gap distance and coagulation bath composition. Since the membrane material is the same, the effects of hydrophilicity and zeta potential on membrane fouling can be ignored. More significant flux decline was observed in the membrane with lower humic acid rejection. For the membranes with similar water permeability, the lower the porosity at the outer surface, the more serious the membrane fouling. Furthermore, the effect of the membrane morphology on backwashing performance was discussed.     

Structure-inheriting solid-state reactions under hydrothermal conditions

We have explored several structure-inheriting solid-state reactions (SISSRs) under hydrothermal conditions for syntheses in the Co-Mo-O system. And we found an interesting hydrothermal SISSR from CoMoO₄·3/4H₂O to high-pressure (hp-) phase of CoMoO₄, which enabled us to considerably reduce the severe conditions for the synthesis of hp-CoMoO₄. As similar hydrothermal SISSRs are expected to be useful tools for material syntheses, we also briefly discuss them as a means of developing novel material syntheses and designs.     

Transition metal tetramolybdate dihydrates MMo4O13·2H2O (M=Co,Ni) having a novel pillared layer structure

Hydrothermal synthesis in the M/Mo/O (M=Co,Ni) system was investigated. Novel transition metal tetramolybdate dihydrates MMo₄O₁₃·2H₂O (M=Co,Ni), having an interesting pillared layer structure, were found. The molybdates crystallize in the triclinic system with space group P−1, Z=1 with unit cell parameters of a=5.525(3) Å, b=7.058(4) Å, c=7.551(5) Å, α=90.019(10)°, β=105.230(10)°, γ=90.286(10)° for CoMo₄O₁₃·2H₂O, and a=5.508(2) Å, b=7.017(3) Å, c=7.533(3) Å, α=90.152(6)°, β=105.216(6)°, γ=90.161(6)° for NiMo₄O₁₃·2H₂O The structure is composed of two-dimensional molybdenum-oxide (2D Mo-O) sheets pillared with CoO₆ octahedra. The 2D Mo-O sheet is made up of infinite straight ribbons built up by corner-sharing of four molybdenum octahedra (two MoO₆ and two MoO₅OH₂) sharing edges. These infinite ribbons are similar to the straight ones in triclinic-K₂Mo₄O₁₃ having 1D chain structure, but are linked one after another by corner-sharing to form a 2D sheet structure, like the twisted ribbons in BaMo₄O₁₃·2H₂O (or in orthorhombic-K₂Mo₄O₁₃) are.     

Decomposition of hydrogen molybdenum bronze, H0.30MoO3, upon increasing temperature in various gases

When H_0.30MoO₃ was heated at increasing temperature in H₂, N₂, H₂O, and in vacuum, the total weight loss just corresponded to the weight of 0.15 H₂O in H_0.30MoO₃. On the other hand, when the bronze was heated in CH₃OH vapor, one of the lattice oxygens was removed and the bronze was partly reduced to MoO₂.

---

H_0,30MoO₃ H₂, N₂, H₂O , 0,15H₂O H_0,30MoO₃. , CH₃OH, MoO₂.