Rotors, Caps, and Other Accessories

For those not familiar with Magic Angle Spinning (MAS): A high precision ceramic rotor (sample tube) with plastic caps (usually turbines) on each end of the rotor is spun at extremely high speed on air bearings at the Magic Angle (54.7°). See spinner material information following the links to spinner accessories below.

DI, XC, SuperSonic, High Speed, and Standard accessories are not interchangeable unless specified. (For example, 7 mm “standard” rotors are only about 2/3 the length of our 7 mm XC rotors.) If unsure about type, contact us with the probe DSI-serial number and we can help.

Type	Click Links to Accessories pages (Rotors, Caps and Other Spinner accessories)
For OptiMAS Drop-In (DI) spinner	DI - Rotors, Caps, Cap Pullers and Other
For XC & SuperSonic (SS) MAS 4 mm, 5 mm, and 7 mm	Rotors for XC and SS	Turbine Caps XC and SS
Sealing Cells (for DI and XC)	Sealing cells
For High Speed (HS) MAS 5 mm and 7 mm	High Speed (HS) accessories
For Standard Speed (Std.) MAS 5 mm and 7 mm	Standard Speed (Std.) accessories
For WideLine (WL) probe - sample container & cap accessories	Link to WL- sample container & cap accessories

* Note 1: Non-spinning parts can tolerate different temperatures than caps spinning on rotors.
Note 2: The above chart represents only material characteristics. Check the Probe Specifications

Material Considerations

New Silicon-nitride Rotor Material Identified.

Kyocera has developed a very promising, new grade of Si₃N₄ , SN240, that appears to have better strength and toughness than any previous grade.   We are optimistic that this new material, along with improved processing, will allow us to offer thick-walled rotors rated to higher spinning speeds with greatly reduced chances of failure.    

Improved MAS Turbine Caps.

Glass-fiber-reinforced torlon grade 5030 will now be used on new MAS turbine caps (except for low proton Kel-F caps) for greatly improved VT performance and all-around better reliability and performance. This new material stands out from the rest with respect to isotropic thermal expansion (only 16E-6/0°C), tensile strength at 200°C (120 MPa), and heat distortion temperature (282°C). It also has rather low moisture absorption, high wear resistance, and high impact strength. These caps will be phased in. DI, XC4 and XC5 will be the first probes to use this new turbine cap material.

We have also made changes in 4 and 5 mm XC and SS turbine caps to further improve spinning stability. The XC/SS thick wall Kel-F caps and XC/SS thin wall rotor caps of all materials will have 7 flutes.

Silicon Nitride:  With a density of about 3.18 g/cm³ and a (working) tensile strength of 700 MPa, silicon nitride has the highest strength-to-weight ratio of any ceramic available today.   Its hardness and toughness make it very difficult to grind, but it has the lowest dielectric loss and lowest permittivity of any engineering ceramic, making it the best choice for high frequencies. A HIPed (Hot Isostatic Pressed) variety is available with improved strength and dielectric properties. Its superior electrical properties make it the preferred material for most applications (often, even for silicon and nitrogen), because of silicon's long T₁ and nitrogen's low natural abundance. The color is black. The only additive or impurity greater than 200 ppm in this new material is yttria. Silicon nitride stators, housings, and rotors are available in all sizes. This material is required for fastest spinning. 

Zirconia:  The yttria-stabilized, high-purity material is glossy white and has a density of about 6 g/cm³ and a (working) tensile strength of 700 MPa.   Alumina content can be kept below 100 ppm. Zirconia is less expensive than silicon nitride, but the safe spinning speed for zirconia rotors is lower than that of silicon nitride. 

Macor:  This white, machineable, boro-silicate glass-ceramic is loaded with synthetic mica to inhibit crack propagation.  It is easily machined with conventional tooling.  Macor housings may be provided for carbon and proton studies at temperatures over 160°C in our standard speed MAS probes.  Macor is usable up to 650°C, but it has very poor thermal shock tolerance.  Macor rotors are only available for the high speed and standard spinners.  Macor rotors are made with a thicker wall and are machined with an integral turbine at one end.  Standard speed rotors require a plug-cap at the open end, while high-speed rotors require a rear turbine.  Macor rotors are recommended for wet samples, air sensitive samples, and temperatures from -150°C to 250°C.  Major constituents:  Al, Si, O, B, K, F.

Boron Nitride:  The hexagonal hot-pressed variety, with 6% calcium borate binder, is easily machineable and is used for disposable inserts in the high-temperature ceramic rotors.  The material is soft enough to scratch easily and may absorb up to 1% moisture.

Plastics

Improved MAS Turbine Caps.

Glass-Fiber-reinforced Torlon (GFT) grade 5030 will be used for some MAS turbine caps for greatly improved VT performance and all-round better reliability and performance.   This new material stands out from the rest with respect to isotropic thermal expansion (only 16E-6/°C), tensile strength at 200°C (120 MPa), and heat distortion temperature (282°C). It also has rather low moisture absorption, high wear resistance, and high impact strength. These caps are the most wear resistant and have the widest temperature range. GFT is not recommended for proton studies, or for some silicon and some carbon studies. Caps may be used from -120°C to 160°C repeatedly (or when glued in with epoxy from -170°C to 250°C). GFT caps are being phased in. DI probes, XC4 and XC5 are the first probes to use this turbine cap material. Note: For the present, customers will receive either Aurum, torlon, or glass-fiber-reinforced Torlon (determined by stock).

Kel-F:  This is our standard housing material for Standard and High Speed probes.  A translucent white plastic, Kel-F is background free for all nuclei except F, Cl, and C.   Kel-F is also excellent for carbon studies since the strong fluorine coupling effectively broadens the Kel-F carbon signal, and there are no protons to cross polarize. Unfortunately, Kel-F is not as strong as the other cap materials and is thus restricted to lower spinning speeds. Kel-F turbine caps are used with silicon nitride and zirconia rotors.  The turbine caps can be used at temperatures from -20°C to 70°C. (In parts of the spinner assembly that do not spin, the usuable temperature range is -100°C to 150°C.)

Torlon:   Torlon, a green thermoplastic polyamide-imide, has exceptional chemical resistance and is one of the toughest plastics available. Torlon can also be used for low silicon applications. Torlon is not recommended for proton studies or some carbon studies. Caps may be used at temperatures from -30°C to 80°C repeatedly with silicon nitride and zirconia rotors. (The caps may be used once to higher temperatures but they will be too loose after that.) As above, the useable temperature range of the spinning caps is more limited than the range of non-spinning spinner assembly parts. In non-spinning parts of the spinner assembly, the upper temperature limit is 260°C.

Aurum:  This dark brown to black thermoplastic polyimide has excellent dielectric properties similar to Torlon. Aurum can be used for low silicon applications when fast spinning is desired. Aurum may be supplied for some turbine caps and spinner parts on probes designed for fluorine studies and other applications where carbon is not a problem. Turbine caps may be used from -30°C to 80°C repeatedly. (In non-spinning parts of the spinner assembly, the upper temperature limit is 240°C.)
 Aurum or Torlon may be supplied, depending on the availability of materials.

• Kel-F Turbine Caps:      .............. Temperature range:   -20°C to 70°C.

• Torlon Turbine Caps:     ............. Temperature range:   -30°C to 80°C.

• Aurum Turbine Caps:     ............ Temperature range:   -30°C to 80°C.

  O-Ring Caps

For wet samples, air sensitive samples, and variable temperatures

O-ring Caps:  Turbines and plug caps with dual Viton o-ring seals are available for Macor, silicon nitride, and zirconia rotors.  Macor rotors, (available only for standard and high speed probes) are recommended for wet samples, air sensitive samples, and temperatures from -60°C to 250°C.  A single (rear) cap with o-rings is used with a Macor rotor.  However, if faster spinning is critical, VT and air-sensitive experiments can be done in silicon nitride or zirconia rotors using o-ring-sealed cap pairs.

O-ring turbine caps are normally inserted and removed by hand.  Turbines with threaded holes can be ordered (with a threaded insertion tool) for use when loading samples in a glove box.  (A threaded insertion tool is always required to insert and remove the plug cap of standard speed cap pairs.)  Caps can be ordered with axial holes for out-gassing during higher temperature work or to remove air bubbles from wet samples.     

•  Kel-F O-ring Caps:   ................. Temperature range with o-rings:  -45°C to 80°C.

•  Torlon or Aurum O-ring Caps: ...Temperature range with o-rings:  -45°C to 120°C.

•  Note:   Although the supersonic o-ring caps can be used for air sensitive samples in XC5 and XC7 probes, XC sealing cells are usually prefered.  

Extended Temperature Caps

DI, XC4 and XC5 probes (and some supersonic) use Glass-fiber-reinforced Torlon (GFT) - glued in. GFT - if glued in:....... Temperature range:  -170°C to 250°C.

XC7, SuperSonic, High Speed, and Standard Extended VT caps have included a small screw along the axis of the rotor to retain the caps. A tamp with a central hole in the middle is required for sample packing.

Kel-F Extended VT Caps with axial screw:   ....... Temperature range: -270° to 80°C.

Vespel Extended VT Caps with axial screw:   ..... Temperature range: -270° to 240°C.

Notes:
• O-ring caps are easier to pack than VT axial screw caps.
• Extended VT caps with axial screws and o-ring caps are made only for thin wall rotors.
• XC, SuperSonic, and high-speed rotors require a front turbine and a rear turbine.
• Standard speed rotors require a front turbine and a plug.

Click here for Spinning Speeds information

Please contact accessories@dotynmr.com with questions.