Inviscid melt spinning processes

One inviscid melt spinning process, the containerless laser heated melt process (Chapter 4.4.4) is believed to facilitate the formation of fibers by increasing the viscosity of the inviscid melt (and jet lifetime) at a normal quench rate of IC K/s, i.e., without increasing the quench rate to -10 K/s. 

In the inviscid melt spinning process [10] [51], steel wires are formed by the same mechanism as glass fibers. In this case, the process shown in Figure 14 depends on the presence of silicon in the steel formulation and on the presence of carbon dioxide in the process environment. 

Figure 14. Inviscid melt spinning process (schematic drawing). Redrawn from F. T. Wallenbeiger, N. E. Weston and S. A. Dunn, Inviscid melt spinning as-spun amorphous alumina fibers. Materials Letters, 2 [4] 121-127 (1990).

A viable process for the formation of continuous, self-supporting fibers such as hydrogen from liquefied gases has emerged over the past two decades [74]. Like all prior process iterations [74], it appears to be an inviscid melt spinning process (IMS) and not a rapid solidification (RS) process. 

Melts of metals as well as crystalline ceramic oxides have low viscosities. All solidify at a sharp melting point and their viscosity above the melting point increases rapidly and then reaches a viscosity comparable to that of motor oil at room temperature, i.e., log <0.2 poise. Yet, fiber formation from the liquid phase requires a viscosity of log 2.5 to log 3.0 poise. Only liquid droplets are formed if a low viscosity liquid is extruded at a normal quench rate of -10" K/s through an orifice, spinneret hole or bushing tip. To facilitate fiber formation, the viscosity must be raised from log <0.2 poise to log 2.5 to log 3.0 poise. This can be achieved by one of two generic routes, i.e., by a rapid solidification (RS) or an inviscid melt spinning (IMS) process. 

Commercial wire drawing processes produce metal wires with round cross sections but they are highly energy and labor intensive. Wire drawing falls outside the scope of this book. Commercial rapid solidification processes yield amorphous metallic ribbons. Inviscid melt spinning yields metal fibers by a chemically assisted jet stabilization process. 

Inviscid melt spinning is considered to be a potentially viable alternative to wire drawing [51] for making steel wires for radial automobile tires, but a prior product development did not reach beyond the pilot plant level. Using silica steels, the complex chemistry (Equations 4-6) produce also minute amounts of iron oxides which were detected by ESCA [51], and are a potentially undesirable trace byproduct. The challenge [4] remains to fine tune the chemistry of this process before commercial development. 

Continuous binary calcium aluminate glass fibers can also be formed by inviscid melt spinning. In this case, carbon particles which are formed by the decomposition of propane enter into the surface of the molten jet and raise its surface viscosity, a process that lengthens the lifetime of the jet and prevents its breakup. 

Inviscid melt spinning A process which allows low viscosity molten material to be spun into fibers. The low viscosity jet is chemically stabilized rather than rapidly solidified. 

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