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CdI2 is trigonal omega-like structured and crystallizes in the trigonal P3m1 space group. The structure is two-dimensional and consists of twenty-five CdI2 sheets oriented in the (0, 0, 1) direction. Cd2+ is bonded to six equivalent I1- atoms to form edge-sharing CdI6 octahedra. All Cd–I bond lengths are 3.04 Å. I1- is bonded in a distorted T-shaped geometry to three equivalent Cd2+ atoms.
CdI2 is trigonal omega-like structured and crystallizes in the trigonal P3m1 space group. The structure is two-dimensional and consists of twenty-two CdI2 sheets oriented in the (0, 0, 1) direction. Cd2+ is bonded to six equivalent I1- atoms to form edge-sharing CdI6 octahedra. All Cd–I bond lengths are 3.04 Å. I1- is bonded in a distorted T-shaped geometry to three equivalent Cd2+ atoms.
CdI2 is trigonal omega-like structured and crystallizes in the trigonal P3m1 space group. The structure is two-dimensional and consists of fourteen CdI2 sheets oriented in the (0, 0, 1) direction. Cd2+ is bonded to six equivalent I1- atoms to form edge-sharing CdI6 octahedra. All Cd–I bond lengths are 3.04 Å. I1- is bonded in a distorted T-shaped geometry to three equivalent Cd2+ atoms.
(CdI2)13(I)2 is trigonal omega-like structured and crystallizes in the trigonal P3m1 space group. The structure is two-dimensional and consists of thirteen CdI2 sheets oriented in the (0, 0, 1) direction and one I sheet oriented in the (0, 0, 1) direction. In each CdI2 sheet, Cd is bonded to six I atoms to form edge-sharing CdI6 octahedra. All Cd–I bond lengths are 3.04 Å. There are two inequivalent I sites. In the first I site, I is bonded in a distorted T-shaped geometry to three equivalent Cd atoms. In the second I site, I is bonded in a distorted T-shaped geometry to three equivalent Cd atoms. In the I sheet, I is bonded in a 3-coordinate geometry to three equivalent I atoms. All I–I bond lengths are 3.47 Å.
CdI2IN2 crystallizes in the orthorhombic Pmc2_1 space group. The structure is one-dimensional and consists of four IN2 clusters and two CdI2 ribbons oriented in the (0, 1, 0) direction. In each IN2 cluster, N+0.50+ is bonded in a single-bond geometry to one I1- atom. The N–I bond length is 1.90 Å. I1- is bonded in a water-like geometry to two equivalent N+0.50+ atoms. In each CdI2 ribbon, there are two inequivalent Cd2+ sites. In the first Cd2+ site, Cd2+ is bonded in a distorted trigonal planar geometry to three I1- atoms. There are one shorter (2.72 Å) and two longer (2.74 Å) Cd–I bond lengths. In the second Cd2+ site, Cd2+ is bonded in a 3-coordinate geometry to three I1- atoms. There are one shorter (2.76 Å) and two longer (3.16 Å) Cd–I bond lengths. There are three inequivalent I1- sites. In the first I1- site, I1- is bonded in a distorted single-bond geometry to one Cd2+ atom. In the second I1- site, I1- is bonded in a single-bond geometry to one Cd2+ atom. In the third I1- site, I1- is bonded in a distorted water-like geometry to two Cd2+ atoms.
The friction and wear rate characteristics of 50/50 (weight per cent) graphite fiber-polyimide composites were studied by sliding metallic hemispherically tipped riders against disks made from the composites. Two different polyimides and two different graphite fibers were evaluated. Also studied were such variables as the effect of adding 10 per cent weight additions of powdered (CF-1.1)n, CdI2, or CdO, the effect of moisture in an air atmosphere, the effect of temperature, and the effect of different sliding speeds. In general, wear to the metallic riders was negligible and composite wear increased at a constant rate as a function of number of sliding cycles.
Oscillating, plain spherical bearings with graphite-fiber-reinforced polyimide (GFRPI) liners were tested for friction and wear from 25 to 315 C. A condensation polymer was compared with an addition polymer, and a high-modulus fiber was compared with a lower cost, low-modulus fiber. All polymer-fiber combinations gave friction coefficients from 0.05 to 0.18 and low wear. Adding CdO and CdI2 reduced the wear of degassed bearings in dry air. These additives were not needed when the bearing liners contained adsorbed moisture. Although, at 25 C, MoS2 reduced the friction and wear of the base composite at unit loads above 70,000,000 N/m squared (10,000 psi), it had no beneficial effect at lighter loads.
Composites made of graphite-fiber-reinforced polyimide (GFRPI) with a fiber-resin ratio (by weight) of about 1 were evaluated as molded outer-race liners in plain spherical bearings. Several compositions were examined: two types of polyimide (addition and condensation polymers), two types of graphite fiber (high and low modulus) and four powder additives (CdO, CdI2, (CF1.1)n, and MoS2). Friction and wear were measured during oscillation at 25, 200, and 315 C. It is shown that all compositions provided good lubrication in dry air, that neither type of polyimide or graphite fiber nor the additives gave a clear advantage, and that wear rates were always higher during run-in, before conditions stabilized. It is concluded that GFRPI composites are self-lubricating under all but the most extreme moisture-free conditions at 25 C. The additives are helpful only with very high loads or extremely dry environments.