Synthesis and thermal solid-phase transformations of cellulose-iron(II,III) oxide composite

Possibility of obtaining cellulose-iron(II, III) oxide composites with various component ratios was studied. The specific magnetization of the material was determined in relation to the mass fraction of the magnetic component in the composite.     

Crystal structures of Ti(NH<Subscript>4</Subscript>)<Subscript>2</Subscript>P<Subscript>4</Subscript>O<Subscript>13</Subscript> and Sn(NH<Subscript>4</Subscript>)<Subscript>2</Subscript>P<Subscript>4</Subscript>O<Subscript>13</Subscript>

The characteristics of crystal structures of the titanium(IV) diammonium (Ti(NH₄)₂P₄O₁₃) and tin(IV) diammonium (Sn(NH₄)₂P₄O₁₃) tetraphosphates, which are isostructural with similar silicon(IV) and germanium(IV) salts, have been obtained by the Rietveld method using X-ray powder diffraction data. The compounds crystallize in the triclinic system, space group P \(\overline 1 \), Z = 2, a = 15.0291(7) Å, b = 7.9236(4) Å, c = 5.0754(3) Å, α = 99.168(3)°, β = 97.059(3)°, γ = 83.459(3)° for Ti(NH₄)₂P₄O₁₃ and a = 15.1454(7) Å, b = 8.0103(5) Å, c = 5.1053(3) Å, α = 99.898(6)°, β = 96.806(3)°, γ = 83.881(4)° for Sn(NH₄)₂P₄O₁₃. The structure is refined in the isotropic approximation using the pseudo-Voigt function: R _p = 0.077, R _Bragg = 0.045, R _F = 0.057 for Ti(NH₄)₂P₄O₁₃; R _p = 0.082, R _Bragg = 0.044, R _F = 0.046 for Sn(NH₄)₂P₄O₁₃. The hydrogen atoms of the ammonium cations are placed in the calculated positions. A comparative analysis of the structures of the compounds of the M^IV(NH₄)₂P₄O₁₃ (M^IV = Si, Ge, Ti, Sn) series has been carried out.     

Crystal structures of CrH2P3O10 and InH2P3O10

The crystal structures of chromium and indium dihydrogen triphosphates, CrH₂P₃O₁₀ and InH₂P₃O₁₀, in modification II are refined by the Rietveld method using X-ray powder diffraction data. The compounds crystallize in the monoclinic crystal system, space group P21/n. Z = 4, a = 7.3225(4)Å, b = 8.6835(6)Å, c = 11.6599(7) Å, and b = 102.388(3)° for CrH₂P₃O₁₀, and a = 7.5332(1)Å, b = 9.0841(1)Å, c = 11.8600(1) Å, and b = 103.9596(7)° for InH₂P₃O₁₀. The structures are refined in the isotropic approximation (pseudo-Voigt profile function): R_p = 4.8%, R_wp = 6.9%, R_Bragg = 7.5%, R_F = 9.9% for CrH₂P₃O₁₀; R_p = 6.3%, R_wp = 8.3%, R_Bragg = 6.2%, R_F = 4.1% for InH₂P₃O₁₀. The crystal structures of compounds in the isostructural series M^IIIH₂P₃O₁₀-II, where M^III = Al, Ga, Cr, V, Fe, and In, are examined and compared.     

Crystal structure of Iron(III) hydrogen diphosphate FeHP<Subscript>2</Subscript>O<Subscript>7</Subscript>

The crystal structure of the β modification of iron(III) hydrogen diphosphate FeHP₂O₇ has been refined by the Rietveld method using powder X-ray diffraction data. The compound crystallizes in the monoclinic system, space group P2₁/n, Z = 4, a = 7.9756(1) Å, b = 12.8260(2) Å, c = 4.8664(6) Å, β = 98.6404(8)°, V = 492.16(1) ų. The structure was refined in the isotropic approximation (pseudo-Voigt function), R _p = 0.024, R _wp = 0.033, R _Bragg = 0.091, R _F = 0.067, and compared with the structures of other compounds M^IIIHP₂O₇ (M^III is a trivalent metal).     

Preparation and thermal degradation of methyl methacrylate-methacrylic acid copolymers

Copolymers of methyl methacrylate with methacrylic acid, with the mole fraction of methacrylic acid units from 0.21 to 0.73, were prepared by radical copolymerization in the bulk. The influence of the composition of the copolymers on the features of their thermal degradation was examined by combined thermal analysis involving differential scanning calorimetry and thermogravimetry.