Лако-красочные материалы — производство

The following are the most common crystal classes:

1. Cubic: zinc blend lattice (e. g., precipitated CdS), spinel lattice (e. g., Fe3O4, CoAl2O4)

2. Tetragonal: rutile lattice (e. g., TiO2, SnO2)

3. Rhombic: goethite lattice (e. g., a-FeOOH)

4. Hexagonal: corundum lattice (e. g., a-Fe2O3, a-Cr2O3)

5. Monoclinic: monazite lattice (e. g., PbCrO4)

In ideal solid ionic compounds, the absorption spectrum is composed of the spec­tra of the individual ions, as is the case in ionic solutions. For metal ions with filled s, p, or d orbitals, the first excited energy level is so high that only ultraviolet light can be absorbed. Thus, when the ligands are oxygen or fluorine, white inorganic com­pounds result. The absorption spectra of the chalcogenides of transition elements with incompletely filled d and f orbitals are mainly determined by the charge-transfer spectrum of the chalcogenide ion, which has a noble gas structure. For the transition metals, lanthanides, and actinides, the energy difference between the ground state and the first excited state is so small that wavelength-dependent excitations take place on absorption of visible light, leading to colored compounds [1.11].

X-ray investigation ofinorganic pigments yields information on the structure, fine structure, state of stress, and lattice defects of the smallest coherent regions that are capable of existence (i. e. crystallites) and on their size. This information cannot be obtained in any other way. Crystallite size need not be identical with particle size as measured by the electron microscope, and can, for example, be closely related to the magnetic properties of the pigment.