External Jacket Research Articles

Advances in Membrane Suppressors for Ion Chromatography

Narrow bore (400 μm i.d.) thin walled (50 μm thickness) perfluorosulfonate Nation® membrane tubes in helical or knotted filament-filled configurations make low dispersion membrane suppressors of large ion exchange capacity. Such a device, based on a 2-m long membrane tube and utilizing an external cation exchanger bead-packed jacket, can exchange 600 μeq Na+ /min (0.6M NaOH at 1 mL/min) with an induced band dispersion of 60 μL for a 20 μL injected sample at a flow rate of 1 mL/min. With alkali metal hydroxides, the ion exchange capacity decreases, with increasing atomic weight, from Li+ to Na+ to K+.

Transformations of oxypropylmethyl cellulose in suspension polymerization of vinyl chloride

It was shown that at the early stages of suspension polymerization of vinyl chloride the oxypropylmethyl cellulose used as protecting colloid enters graft copolymerization with the monomer. A study was made of the effect of this reaction on mechanisms of polymerization and properties of PVC. An assumption was put forward, according to which the external jacket on particles of suspension PVC is a graft copolymer of oxypropylmethyl cellulose and vinyl chloride.

Fabrication on a laboratory scale and mechanical properties of Cu-Nb-Sn multifilamentary superconducting composite wires produced by cold powder metallurgy processing

Superconducting Cu-Nb-Sn multifilamentary composites are fabricated inexpensively on a laboratory scale. Small (40 μm) particles of Cu and Nb are compacted, placed in a suitable external jacket for containment, then elongated at room temperature to form a multifilamentary circular wire. Processing yields a multifilamentary Cu-Nb-Sn superconductor with high overall critical current densities Jc at high magnetic fields. Measurements of the mechanical properties show no degradation of Jc for strains greater than 1% for composite made with a large areal reduction ratio.

Effect of a lossy jacket on the external field of a coaxial cable with an interrupted shield

An earlier analysis is extended to allow for the influence of ohmic losses in the external dielectric jacket of a coaxial cable that has a circumferential slit in the outer metal shield. It is found that when the loss tangent is greater than zero, the radiation pattern is modified, particularly at angles near the axis of the cable. The external surface wave is then also attenuated.

A sliding thermal tie down suitable for cryogenic temperatures in vacuum

A thermal anchor was designed in the shape of a cage of 20 beryllium-copper wires connecting two copper rings. It can be fitted to any annular space between a supporting tube and an external cylindrical jacket, making it possible to implement cryostat designs with a removable insert containing sample holders, refrigerators or any device requiring thermal tie down. The pressed contact alone shows a thermal conductance of 0.2 W K-1 with solid nitrogen at 48K and 0.4WK-1 with liquid nitrogen, while the whole anchor shows corresponding thermal conductance values of 50 mW K-1 and 65 m W K-1.