Varian Solid-State NMR - Rotor Characteristics and Composition

2.2 Rotor Characteristics and Composition
01-999162-00 C0402 VNMR 6.1C User Guide: Solid-State NMR 20
2.2 Rotor Characteristics and Composition
Varian high-speed rotors (with and without vent holes) are composed of zirconia or of
silicon nitride (Si
3
N
4
) with pMMA, Kel-f, or Torlon end caps. The cap twist-fits into the
rotor body and is held with two O-rings. Always check the maximum spin rate specification
for Varian rotors and end caps as listed Table 1.
Current Si
3
N
4
rotors are of two-piece construction. If the rotor plug breaks loose from the
rotor body, reinsert the plug and secure it with cyanoacrylate.
Tachometer sensing on high-speed rotors is on the rotor bottom. Zirconia rotors are marked
with a permanent black marking pen or black enamel paint so that 50% of the bottom of
surface area is shaded black; silicon nitride (Si
3
N
4
) rotors are marked with white enamel
paint in the same fashion. Centrifugal force and rotor crashes cause the black and white
markings to flake off around the edges resulting in inaccurate tachometer readings. Reapply
the black or white half circle. Make the diameter marking straight.
Below -100
°C, a potential for slipping due to differential contraction with the ceramic rotor
exists. Kel-F end caps (colorless-opaque) have a VT upper limit of about +70
°C and should
not be spun faster than 6500 Hz at any temperature. Use pMMA (colorless-clear) end caps
only at room temperature and below. Visually distinguishing between Kel-F and pMMA
end caps can be difficult, so you may want to mark them appropriately.
Table 1. Characteristics of Varian Rotors and End Caps
Item Material Color
Recommended
Temperature
Range (C)
Max Spin Rate
Ambient
(Hz)
Max Spin
Rate VT
(Hz)
Varian Part No.
Rotor,
7 mm
Zirconia white or
off-white
— 7200 — 00-991036-00
Rotor,
7 mm
Silicon
nitride
gray –125° to +125° 9500 9000 00-990874-00
Rotor,
5 mm
Silicon
nitride
gray –125° to +125° 15000 13000 00-992521-00
Rotor,
5 mm
Silicon
nitride
gray
(CRAMPS)
–125° to +125° 15000 13000 00-993263-00
Cap,
7 mm
Torlon green –125° to +125° 9500 9000 00-991646-01
Cap,
7 mm
Torlon,
vented
green –125° to +125° 5000 — 00-991647-00
Cap,
5 mm
Torlon green –125° to +125° 15000 9000 00-992519-00
Cap,
5 mm
Torlon,
vented
green — 5000 — 00-992524-00
Cap,
7 mm
pMMA colorless-
clear
–125° to
ambient
9500 9000 00-991038-00
Cap,
5 mm
Kel-F,
vented
colorless-
opaque
–125° to
+ 80°
5000 5000 01-902171-00
Cap,
7 mm
Kel-F colorless-
opaque
–125° to
+ 80°
7000 7000 00-992558-00
Cap,
5 mm
Kel-F colorless-
opaque
–125° to
+ 80°
7000 7000 00-993228-00
Cap,
5 mm
Kel-F colorless-
opaque
–125° to
+ 80°
7000 7000 00-993262-00