Apparatus and method of manufacturing metallic or inorganic strands having a thickness in the micron range by melt spinning

Abstract

Apparatus for producing elongate strands of metal comprises a rotatable wheel having a circumferential surface, at least one nozzle for directing a molten metal onto the circumferential surface and a collection means for collecting solidified strands of metal formed. The solidified strands are formed on the circumferential surface from the molten metal and are separated from the circumferential surface by centrifugal force generated by rotation of the wheel. The circumferential surface has a circumferentially extending structure having circumferentially extending edges and recesses formed between or bounded by the edges, and by an apparatus for controlling a gas pressure applied to the liquid metal which moves the liquid metal through the nozzle opening and delivers it to the circumferential surface of the rotatable wheel. The nozzle has a rectangular cross-section with a width of the nozzle opening in the circumferential direction of rotation of the wheel and a length transverse to the circumferential surface of the wheel which is greater than the width. A method and a wheel adapted for use in the apparatus are also claimed.

Claims

1. An apparatus for producing elongate strands of metal, the apparatus comprising a rotatable wheel having a circumferential surface, the circumferential surface having circumferentially extending edges and recesses formed between or bounded by the edges, each recess of the recesses defining a depth and a width with the depth being greater than 100 μm and the width being greater than 100 μm, a nozzle defining a nozzle opening having a width of between 10 μm to 100 μm for directing a molten metal onto the circumferential surface and to form solidified strands of metal on the circumferential surface from the molten metal, wherein the nozzle has a rectangular cross-section having a width of the nozzle opening in the circumferential direction of rotation of the wheel and a length transverse to the circumferential surface of the wheel which is greater than the width W, and wherein an apparatus is provided for controlling a gas pressure applied to the liquid metal which moves the liquid metal through the nozzle opening and delivers it to the circumferential surface of the rotatable wheel, wherein said wheel is mounted and configured to rotate within a chamber having an atmosphere at a higher pressure than ambient pressure.

2. The apparatus in accordance with claim 1, wherein the circumferential recesses defining the edges have a radial depth greater than 50 μm; and/or wherein the recesses have a cross-sectional shape selected from the group of members consisting of semi-circular, symmetrically v-shaped, asymmetrically v-shaped, rectangular and trapezoidal.

3. The apparatus in accordance with claim 1, there being peripherally extending lands at the circumferential surface of the wheel, each land being disposed between two circumferentially extending recesses.

4. The apparatus in accordance with claim 3, wherein said lands have widths of 1 mm or less.

5. The apparatus in accordance with claim 1, wherein the metal strands have the form of ribbons having a width of 200 μm or less.

6. The apparatus in accordance with claim 1, wherein the metal strands have a thickness of 50 μm or less.

7. The apparatus in accordance with claim 1, wherein the metal strands have at least one transverse dimension of 50 μm or less and a length at least ten times greater than said at least one transverse dimension.

8. The apparatus in accordance with claim 1, wherein the rotatable wheel is temperature controlled.

9. The apparatus in accordance with claim 1, wherein the wheel is made of one of a metal, a metal alloy, a ceramic material and graphite or is a wheel of a base material having a layer or type made of one of a metal, a metal alloy, a ceramic material, graphite and a vapour deposited carbon; and/or wherein said wheel is mounted to rotate within the chamber having the atmosphere, the atmosphere being at least one of air and an inert gas.

10. The apparatus in accordance with claim 1, wherein a deflector is provided upstream of the nozzle in the direction of rotation of the wheel to deflect boundary layer gas from the circumferentially extending surface prior to depositing molten metal on the surface via the nozzle.

11. The apparatus in accordance with claim 1, wherein the gas pressure applied to the molten metal is selected in the range from 50 mbar to 1 bar overpressure relative to a pressure external to the nozzle.

12. The apparatus in accordance with claim 1, wherein a motor is adapted to drive the wheel at a frequency of greater than 85 Hz for a copper wheel having a diameter of 200 mm.

13. The apparatus in accordance with claim 1, wherein the circumferential surface of the wheel has transversely extending features to control the length of the strands produced.

14. The apparatus in accordance with claim 1, wherein the material of the wheel is selected so that it does not readily bond to the molten metal.

15. A method for producing elongate strands of metal having at least one transverse dimension of 50 μm or less and a length at least ten times greater than said at least one transverse dimension, the method comprising the steps of directing a molten metal through a nozzle having a rectangular cross-section with a width of a nozzle opening in a circumferential direction of rotation of a rotating wheel and a length transverse to a circumferential surface of the rotating wheel which is greater than the width onto the circumferential surface of the rotating wheel, by applying a gas pressure to the molten metal to move it through the nozzle opening and deliver it to the circumferential surface of the rotating wheel, providing the circumferential surface of the rotating wheel with circumferentially extending edges and recesses formed between or bounded by the edges and collecting solidified strands of metal formed on the circumferential surface from the molten metal and separated from the circumferential surface by centrifugal force generated by rotation of the rotating wheel, the method further comprising the steps of controlling the width of the nozzle opening, controlling the gas pressure applied to the molten metal to move it through the nozzle opening and deliver it to the circumferential surface of the rotating wheel and controlling a speed of rotation of the rotating wheel to reduce a flow of molten metal onto the circumferential surface of the rotating wheel to a level at which it is concentrated by the forces that are acting at said circumferentially extending edges and recesses formed between or bounded by the edges and using these edges to concentrate the molten metal at the edges to produce the desired elongate strands of metal, the nozzle opening having a width of between 10 μm to 100 μm and wherein the rotating wheel is mounted and configured to rotate within a chamber having an atmosphere at a higher pressure than ambient pressure.

16. The method in accordance with claim 15, wherein the flow of molten metal is reduced to a level at which the elongated strands have a width of 200 μm to 1 μm.

17. The method in accordance with claim 15, wherein the metal strands have a thickness of 50 μm to 1 μm.

Description

(1) The invention will now be described in further detail and by way of example only with reference to the accompanying drawings and various examples of the method of the invention. In the drawings there are shown:

(2) FIG. 1 a schematic illustration of the basic melt spinning process,

(3) FIG. 2 a front view of the apparatus used for melt spinning equipped with the rotatable wheel of the present invention,

(4) FIG. 3 a detail view of the apparatus of FIG. 2 as seen in a front view with the housing removed,

(5) FIG. 4 a top view of part of the circumferential surface of the spinning wheel of FIGS. 2 and 3 showing a structure applied to the circumferential surface,

(6) FIG. 5 a cross-section through possible structures for the circumferential surface of the wheel of FIGS. 2 and 3,

(7) FIG. 6 a top view of the discharge orifice of the crucible with an explanatory sketch,

(8) FIG. 7 a photograph of a melt spun ribbon of an Fe40Ni40B20 alloy spun on a copper wheel of 200 mm diameter rotating at 30 Hz,

(9) FIG. 8 a view similar to FIG. 5 but with a different structure and quoting dimensions to support the test of Example 1,

(10) FIG. 9 a photograph of the Fe40Ni40B20 ribbon of FIG. 7 as produced in bulk by melt spinning,

(11) FIG. 10 an SEM image showing the partial break-up of the ribbon material in the round groove of FIG. 8,

(12) FIG. 11 a photograph similar to FIG. 9 but showing the Fe40Ni40B20 ribbon formed with the same copper wheel but now rotating at 60 Hz,

(13) FIG. 12 a diagram showing the statistical size distribution of ribbon widths less than 100 μm for a sample of 74 ribbons,

(14) FIG. 13 a diagram illustrating the statistical size variation in width of ribbons produced by means of the invention,

(15) FIG. 14 two diagrams showing the statistical size distribution of ribbons from the sample of FIG. 9 for ribbons less than 500 μm (106 sample ribbons) and less than 150 μm (80 sample ribbons),

(16) FIGS. 15A to 15C examples of alternative surface structures possible for the wheel of FIGS. 2 and 3,

(17) FIGS. 16A to 16C examples of further melt spun ribbons,

(18) FIG. 17 a table summarizing the results of Examples 5 to 10,

(19) FIG. 18 a series of photographs of the product of Example 5 together with a scale drawing of the cross section of groove profile that is used at the surface of the wheel,

(20) FIG. 19 a series of photographs of the product of Example 6 together with a scale drawing of the cross section of groove profile that is used at the surface of the wheel,

(21) FIG. 20 a series of photographs of the product of Example 7 together with a scale drawing of the cross section of groove profile that is used at the surface of the wheel,

(22) FIG. 21 a series of photographs of the product of Example 8 together with a scale drawing of the cross section of groove profile that is used at the surface of the wheel,

(23) FIG. 22 a series of photographs of the product of Example 9 together with a scale drawing of the cross section of groove profile that is used at the surface of the wheel,

(24) FIG. 23 a series of photographs of the product of Example 10 together with a scale drawing of the cross section of groove profile that is used at the surface of the wheel,

(25) Turning now to the schematic drawing of the melt spinning process shown in FIG. 1 it can be seen that the metal A to be spun is heated in a crucible K by an electrical heating device I. A gas pressure P presses the molten metal through the nozzle N of the crucible K onto the rotating wheel B. The wheel B has a surface structure S (schematically illustrated in FIGS. 4 and 5) which laterally restricts the molten metal incident on the circumferential surface of the wheel before it solidifies and is thrown off by centrifugal force. The nozzle N of the crucible K is likewise structured and can, for example, have a nozzle opening O of rectangular shape as shown in FIG. 6. From FIG. 6 and the schematic diagram of FIG. 4 it can be seen that the length direction L of the nozzle opening is oriented transversely to the circumferential direction C of the groves G in the circumferential surface S of the wheel B and extends over several of these grooves and in a practical example over at least most of the grooves so that the nozzle opening distributes molten metal across the width of the surface structure on the wheel B. The width W of the slot can be chosen within relatively wide limits, e.g. between 1 mm and 10 μm to control the rate of flow of the molten metal from the nozzle N onto the structured surface S of the wheel B. When the width W is relatively large a relatively high flow rate for the molten metal onto the structured surface of the wheel B is obtained and, for a given speed of the wheel, the strands produced are of relatively large cross-section. As the width W is reduced, which is achieved by substituting one crucible K for another one with the desired nozzle width W, the flow rate of the molten metal onto the structured circumferential surface S of the wheel B is reduced and, for the same speed of rotation of the wheel, the strands produced are relatively smaller in cross-section.

(26) The pressure P applied to the molten metal can also be used to change the flow rate. Clearly a relatively large pressure leads to a higher flow rate than a relatively lower pressure. A minimum pressure P is always required in order to force the molten metal through the nozzle N, as gravity alone is not normally sufficient to ensure adequate flow, particularly with a relatively small width W of the nozzle opening. In fact this is advantageous because otherwise some form of valve would be necessary and a valve for regulating the flow of molten metal is technically challenging. It should be noted that the pressure difference ΔP is dependent on the metal used and on the width of the nozzle opening in the circumferential direction. It is also dependent on the length of the nozzle opening in a direction parallel to the axis of rotation of the wheel. The length of the nozzle opening can be varied within wide limits. For laboratory experiments values of 10 to 12 mm have been found useful. In production much greater lengths could be selected in dependence on the axial width of the circumferential surface of the wheel.

(27) FIG. 4 schematically shows a structured peripheral surface S of a wheel B having four grooves or recesses G and a lands L between them. Generally there will be many more circumferentially extending grooves G with circumferentially extending lands L between them, each land L being disposed between two circumferentially extending recesses G. The boundary between each groove G and an adjacent land L defines a circumferentially extending edge or corner.

(28) The grooves or recesses G can have a cross-sectional shape selected from the group comprising semi-circular, symmetrically v-shaped, asymmetrically v-shaped, rectangular and trapezoidal and grooves G of this kind are shown in FIGS. 5, 8 and 15A to 15C as well as in FIGS. 17 to 23. It will be appreciated that further circumferentially extending edges or corners are formed at the base of the grooves G and can also form positions at which molten metal preferentially collects. Strictly speaking it is not necessary for lands to be present at all, the grooves or recesses G could have a cross-sectional shape corresponding to a v-shaped machine thread (as shown in FIGS. 15B and 15C and indeed such grooves G could either extend strictly circumferentially around the circumferential surface of the wheel B or could take the form of a screw thread having a pitch, For a relatively fine thread a correspondingly small pitch is appropriate.

(29) When lands are provided they generally have widths of 1 mm or less.

(30) As can be seen from FIG. 4 the grooves G can have a width x and the lands L a width y. These dimensions provide flexibility in tailoring the process to produce relatively uniform strands of selected dimensions. As the nozzle opening O extends over a plurality of grooves G the volume of the grooves, which is related to their width x acts to collect molten metal and has an influence on the size of the strands. Generally speaking the narrower x is the smaller is the volume of the groove G and the smaller is the cross section of the strands that are produced. The width y of the lands L affects the heat removal from the molten metal and also has an influence on the cross-sectional shape of the strands and the length thereof.

(31) The overall aim of the tests carried out to date is to investigate whether the melt spinning process can produce thin fibers with diameters in the micron range, for industrial applications such as light weight, mechanically strengthened textiles (textiles reinforced by the metal strands), filters and catalytically active materials. The actual apparatus used is shown in FIGS. 2 and 3. Apart from the design of the wheel B the apparatus shown in FIGS. 2 and 3 is a commercially available melt spinner obtainable from the company Edmund Buehler GmbH, Hechingen, Germany. It consists of a metallic chamber 10 having a cylindrical portion 12 and a tangentially extending collection tube 14 with a closable port 16 at the end remote from the cylindrical portion 12. Above the cylindrical portion 12 the crucible K with the electrical heating system I and the gas pressure supply P are mounted within a short cylindrical extension 18 of the chamber 10 and provided with the necessary supply lines for a pressurized gas such as argon, for electrical power and control of the gas flow valve determining the pressure P, for the power of the heating system I and for the monitoring of parameters such as gas pressure and temperature of the melt. The wheel B is mounted on the inside of and concentric to the cylindrical portion 12 and is supported by bearings (not shown) on an axle 20 driven by an electric motor 22 flanged to the rear of the cylindrical portion 12 (see FIG. 3). The front side 24 of the cylindrical portion, i.e. the side 26 opposite the drive motor 22 is made of glass so that the spinning process can be observed and filmed by a high speed camera. The chamber 10 can be evacuated by a vacuum pump via an evacuation stub 28 and can be supplied with a flow of an inert or reactive gas via a further feed stub 30. Thus a desired atmosphere at a desired temperature and pressure can be provided within the chamber 10.

(32) The cover for closing the port 16 can be a hinged or removable glass cover permitting the material collected in the cylindrical extension 18 to be observed, removed and filmed as required.

(33) The following experiments were conducted:

COMPARATIVE EXAMPLE 1

(34) In the first experiment melt spun ribbons were generated on a standard copper wheel B with a diameter of 200 mm and a smooth circumferential surface 32 (indicated in FIG. 4) having the shape of a right cylinder. A melt of Fe 40Ni40B20 is formed by the heating system I within the boron nitride crucible K. The crucible K has a slit orifice with nominal dimensions, length L=10 mm and width W=0.4 mm. Once the metal has melted gas pressure is applied to the molten gas by the pressure source P to expel the molten metal through the orifice and onto the copper wheel B. The copper wheel B was rotated by the drive motor at a wheel drive frequency of 30 Hz. The mass of the metal sample was ca. 10 g. As shown in FIG. 7, a single continuous ribbon was generated, which had a length of >1 m, a typical width of 9.3+1−0.1 mm, and a typical thickness of 42+1−2 microns. FIG. 7 shows that the ribbons manufactured in this way are of good quality.

(35) The specific parameters used were as follows:

(36) TABLE-US-00001 Weight of metal sample 10 g Length L of nozzle opening 10 mm Width W of nozzle opening 0.4 mm Temp. of wheel RT Gas in chamber Argon Pressure in chamber 12 400 mbar Temp. of gas in chamber 12. RT Temperature of molten metal 1350° C. Pressure applied to molten metal 200 mbar (overpressure) Speed of wheel 30 Hz Diameter of wheel 200 mm Distance between wheel and orifice 0.2 mm

ILLUSTRATIVE EXAMPLE 1

(37) Using the same apparatus as in FIGS. 2 and 3 the smooth copper wheel was then replaced by a copper wheel of the same size, but having the structure shown in FIG. 8 at its right cylindrical surface. The melt spinning process was then repeated using the same parameters as in comparative example 1. The drawing of the wheel structure shown in FIG. 8 comprises 7 grooves of semicircular cross-section with a diameter of 1 mm, with a 1 mm spacing or land between adjacent pairs of grooves. As can be seen in FIG. 9, the resultant strands took the form of ribbons molded according to the surface structure of the wheel. They had a typical length of only a few cm, and widths varying from .sup.˜2 to .sup.˜9 mm. Thicknesses of around 200 micron were measured using a thickness gauge, however an accurate measurement was hindered by the curvature of the ribbons and their brittleness. The brittleness of the ribbons is thought to be caused by their crystalline structures, which may be in turn effected by the insufficient thermal coupling between the wheel and the ribbons. The ribbons produced by the use of the structured wheel of FIG. 8 are shown in the photograph of FIG. 9.

(38) To investigate the microstructure of the melt-spun ribbons shown in FIG. 9 SEM images were acquired at a low magnification. A typical example is shown in FIG. 10 which revealed the partial break-up of the ribbon in the groove (and not in the material in the webs between the grooves). The ribbons resulting from the inventive example 1 have significant uniformity, meaning that the collection of strands has a preferred orientation in which the lengths of the individual strands are substantially in parallel to one another and have a substantially similar length.

INVENTIVE EXAMPLE 1

(39) For this example the aim was to make the single ribbons finer by promoting the break-up of the liquid melt on the copper wheel by reducing the volume of the liquid pool forming on the wheel between the wheel surface and the orifice of the crucible K. This concept was based on the recognition that single ribbons with 1 mm widths would have been generated on the flat surfaces in between the semicircular grooves, if the breakup of the ribbon material could be promoted to reach completion. In this example, this was achieved using the same structured surface as in Illustrative Example 1, and the same set of parameters as in Comparative Example 1 but by increasing the speed of rotation of the wheel B to 60 Hz corresponding to a surface speed of the wheel of 37.5 m/s. The resultant ribbons are shown in FIG. 11. As can be seen in this figure, narrow ribbons were obtained from this experiment. They had lengths of around 10 cm, a typical width of 1.3+/−0.5 mm, and a typical thickness of 31+/−8 microns. About 30% of the initial mass was found to be transformed into the .sup.˜1 mm wide ribbons. The remaining product comprised flakes of the material (Fe40Ni40B20) and crumbling ribbon material with a typical length of about 1 cm, not shown in FIG. 11.

(40) The mass and size distribution of the strands shown in the photograph of FIG. 11 resulted in the following result illustrated in FIG. 12:

(41) Total mass=9.70 g (100%)

(42) Mass of agglomerated strands=2.83 g (29%);

(43) Length of the strands: plural centimetres (10 cm);

(44) Typical width: ca. 1.3 mm

(45) Mass of remaining material: 6.73 g (69%) Mass of material lost; =0.14 g (1%).

(46) The diagrams of FIG. 12 show that the useful strands of material had a size distribution with the majority of strands having widths in the range from 200 μm to 500 μm.

INVENTIVE EXAMPLE 2

(47) In this example the same basic set-up was retained as for Inventive Example 1 but the pressure on the melt was reduced to 100 mbar in order to reduce the deposition rate of the melt onto the spinning wheel. This resulted in two types of metal strands:

(48) Metallic strands in the form of agglomerations of similar strands with homogenous diameters and of several cm's length and strands in the form of a fiber mix including all the remaining fiber products.

(49) The following results were obtained:

(50) Total mass 6.06 g (100%),

(51) Mass of agglomerated strands 4.18 g (69%)

(52) Average width 389 μm+/−167 μm

(53) Average thickness 28 μm+/−7 μm

(54) Length of strands ca 10 cm

(55) Residual mix 1.66 g (27%)

(56) Length several mm's,

(57) Average width of ca. 20 μm

(58) Material loss 0.22 g (4%)

(59) FIG. 11 shows the Fe4ONi4OB2O ribbons generated using the structured wheel and slit orifice of Inventive example 2 and FIG. 12 shows the narrow distribution of sizes of the useful metal strands forming 60% of the resulting material.

(60) FIG. 13 shows another characterization of the metal mix, i.e. the useful strands of Inventive Example 3. FIG. 14 shows the distribution of strands having widths less than 500 μm. As can be seen a large proportion of the strands has a width in the range of 1 to 50 μm. The second diagram of FIG. 14 shows the distribution of strands for widths in the range of 1 to 150 μm, it can be seen that a large proportion of strands have widths in the range from 4 to 40 μm.

INVENTIVE EXAMPLE 3

(61) In this case the parameters used were as follows:

(62) Material lead (Pb)

(63) Surface structure, size and speed of rotation of copper wheel as in inventive example 1

(64) TABLE-US-00002 Weight of metal sample 9.04 g Nominal length of nozzle opening 10 mm Nominal width of nozzle opening 0.4 mm Temp of wheel RT (~23° C.) Gas in chamber Argon Pressure in chamber 12 400 mbar Temp. of gas in chamber 12 RT Ejection temperature 400° C. < T.sub.ejection < 700° C. Ejection pressure 100 mbar Speed of wheel 60 Hz Diameter of wheel 200 mm Distance between nozzle and wheel 0.3 mm Average width of the resultant ribbon 0.7 +/− 0.05 mm Average thickness of the resultant ribbon 59 μm +/− 23 μm

(65) The ribbons produced in this way are shown in FIG. 16A.

INVENTIVE EXAMPLE 4

(66) In this case the parameters used were as follows:

(67) Material Aluminium (Al)

(68) TABLE-US-00003 Weight of metal sample 4.85 g Nominal length of nozzle opening 10 mm Nominal width of nozzle opening 0.4 mm Temp of wheel RT (~25° C.) Gas in chamber Argon Pressure in chamber 12 400 mbar Temp. of gas in chamber 12 RT Ejection temperature 900° C. Ejection pressure 200 mbar Speed of wheel 60 Hz Diameter of wheel 200 mm Distance between nozzle and wheel 0.3 mm Average width of the resultant ribbon 2.0 +/− 0.3 mm Average thickness of the resultant ribbon 46 μm +/− 10 μm

(69) In the following further examples will be given of fibres produced using different parameters of the melt spinning process using a structured wheel. In all the following examples the wheel is a copper wheel having various groove configurations which are illustrated in the summary of FIG. 17 together with an indication of how the topography of the grooves is wetted by the melt;

EXAMPLE 5

(70) TABLE-US-00004 Material: Fe40Ni40B20 Experiment MS03 Nominal length of nozzle opening 10 mm Nominal width of nozzle opening 400 μm Temp of wheel RT (~23° C.) Gas in chamber Argon Pressure in chamber 12 400 mbar Temp. of gas in chamber 12 RT Ejection temperature 1350° C. Ejection pressure 200 mbar Speed of wheel 30 Hz Diameter of wheel 200 mm Distance between nozzle and wheel 0.3 mm Average width of the resultant ribbon Textured ribbon, lamella with the profile of the grooved structure, see FIG. 17 Average thickness of the resultant ribbon Experiment failed

(71) The textured ribbon produced in this experiment is shown in photographs with different magnifications in FIG. 18 together with an enlarged cross sectional profile of the grooves used for this Example 5 and showing the groove width. The profile of the grooves is shown to scale. In the photograph at the top left the scale bar is 50 mm and in the photograph at the top right 5 mm. The scale bar in the profile diagram indicates 1 mm in length. In the profile diagram for the wheel, which is the same as the corresponding profile diagram in FIG. 17 for the Experiment MS03, it can be seen that the metal film forms a layer over the whole profiled surface of the roll.

EXAMPLE 6

(72) TABLE-US-00005 Material: Fe40Ni40B20 Experiment MS23 Nominal length of nozzle opening 10 mm Nominal width of nozzle opening 400 μm Temp of wheel RT (~23° C.) Gas in chamber Argon Pressure in chamber 12 400 mbar Temp. of gas in chamber 12 RT Ejection temperature 1350° C. Ejection pressure 200 mbar Speed of wheel 85 Hz Diameter of wheel 200 mm Distance between nozzle and wheel 0.3 mm Average width of the resultant ribbon Textured ribbon, the lamella breaks up and no longer follows the shape of the groove Average thickness of the resultant ribbon Experiment failed

(73) The textured ribbon produced in this experiment is shown in photographs with different magnifications in FIG. 19 together with an enlarged cross sectional profile of the grooves used for this Example 6 and showing the groove width. The profile of the grooves is shown to scale. In the photograph at the top left the scale bar indicates 10 mm and in the photograph at the top right 1 mm. The scale bar in the profile diagram indicates 1 mm in length. In the profile diagram for the wheel, which is the same as the corresponding profile diagram in FIG. 17 for the Experiment MS23, it can be seen that the metal film forms layers of irregular width over parts of profiled surface of the roll.

EXAMPLE 7

(74) TABLE-US-00006 Material: Fe40Ni40B20 Experiment MS34 Nominal length of nozzle opening 10 mm Nominal width of nozzle opening 100 μm Temp of wheel RT (~23° C.) Gas in chamber Argon Pressure in chamber 12 400 mbar Temp. of gas in chamber 12 RT Ejection temperature 1350° C. Ejection pressure 400 mbar Speed of wheel 85 Hz Diameter of wheel 200 mm Distance between nozzle and wheel 0.3 mm Width of the resultant ribbons Max 171.4 μm, min 10.4 μm Thickness of the resultant ribbon <5 μm

(75) The fibres produced in this experiment are shown in photographs with different magnifications in FIG. 20 together with an enlarged cross sectional profile of the grooves used for this Example 7 and showing the groove width. The profile of the grooves is shown to scale. In the photograph at the top the scale bar indicates 10 mm. The scale bar in the profile diagram indicates 1 mm in length. In the profile diagram for the wheel, which is the same as the corresponding profile diagram in FIG. 17 for the Experiment MS34, it can be seen that the metal film has been split up and is concentrated at the edges of the recesses or grooves adjacent the lands.

EXAMPLE 8

(76) TABLE-US-00007 Material: Fe40Ni40B20 Experiment MS031 Nominal length of nozzle opening 10 mm Nominal width of nozzle opening 100 μm Temp of wheel RT (~23° C.) Gas in chamber Argon Pressure in chamber 12 400 mbar Temp. of gas in chamber 12 RT Ejection temperature 1350° C. Ejection pressure 400 mbar Speed of wheel 85 Hz Diameter of wheel 200 mm Distance between nozzle and wheel 0.3 mm Average width of the resultant ribbons Max 146.2 μm, min8.4 μm Thickness of the resultant ribbons <5 μm

(77) The fibres produced in this experiment are shown in photographs with different magnifications in FIG. 21 together with an enlarged cross sectional profile of the grooves used for this Example 8 and showing the groove width. The profile of the grooves is shown to scale The scale bar in the drawing of the profile indicates 250 μm. In the photograph at the top the scale bar indicates 10 mm. In the profile diagram for the wheel, which is the same as the corresponding profile diagram in FIG. 17 for the Experiment MS31, it can be seen that the metal film has been split up and is concentrated at the edges of the recesses or grooves adjacent the lands.

EXAMPLE 9

(78) TABLE-US-00008 Matterial: Fe40Ni40B20 Experiment MS37 Nominal length of nozzle opening 10 mm Nominal width of nozzle opening 50 μm Temp of wheel RT (~23° C.) Gas in chamber Argon Pressure in chamber 12 400 mbar Temp. of gas in chamber 12 RT Ejection temperature 1350° C. Ejection pressure 1000 mbar Speed of wheel 85 Hz Diameter of wheel 200 mm Distance between nozzle and wheel 0.3 mm Width of the resultant ribbons Max 48.4 μm, min 9.3 μm Thickness of the resultant ribbon <5 μm

(79) The fibres produced in this experiment are shown in photographs with different magnifications in FIG. 22 together with an enlarged cross sectional profile of the grooves used for this Example 9 and showing the groove width. The profile of the grooves is shown to scale. In the photograph at the top the scale bar indicates 10 mm. The scale bar in the profile diagram indicates 1 mm in length. In the profile diagram for the wheel, which is the same as the corresponding profile diagram in FIG. 17 for the Experiment MS37, it can be seen that the metal film has been split up and is concentrated at the edges of the recesses or grooves adjacent the lands.

EXAMPLE 10

(80) TABLE-US-00009 Material: Fe40Ni40B20 Experiment MS33 Nominal length of nozzle opening 10 mm Nominal width of nozzle opening 100 μm Temp of wheel RT (~23° C.) Gas in chamber Argon Pressure in chamber 12 400 mbar Temp. of gas in chamber 12 RT Ejection temperature 1350° C. Ejection pressure 400 mbar Speed of wheel 60 Hz Diameter of wheel 200 mm Distance between nozzle and wheel 0.3 mm Width of the resultant fobres Max 75.1 μm, min 2.8 μm Thickness of the resultant fibres <5 μm

(81) The fibres produced in this experiment are shown in photographs with different magnifications in FIG. 23 together with an enlarged cross sectional profile of the grooves used for this Example 10 and showing the groove width. The profile of the grooves is shown to scale. In the photograph at the top left the scale bar indicates 10 mm, in the photograph at the top right the scale bar indicates 200 μm and in the photograph art the bottom left the scale bar indicates 1000 μm. The scale bar in the profile diagram indicates 250 μm in length. In the profile diagram for the wheel, which is the same as the corresponding profile diagram in FIG. 17 for the Experiment MS33, it can be seen that the metal film has been split up and is concentrated at the apices, i.e. at the edges of the recesses or grooves.

EXAMPLE 11

(82) TABLE-US-00010 Material: Stainless steel V2A Experiment MS058 Nominal length of nozzle opening 10 mm Nominal width of nozzle opening 75 μm Temp of wheel RT (~23° C.) Gas in chamber Argon Pressure in chamber 12 400 mbar Temp. of gas in chamber 12 RT Ejection temperature 1550° C. Ejection pressure 800 mbar Speed of wheel 95 Hz Diameter of wheel 200 mm Distance between nozzle and wheel 0.3 mm Width of the resultant fibres Max 144 μm, min 2.3 μm Thickness of the resultant fibres <5 μm

(83) The values of all the examples 5 to 11 are summarized—together with other relevant values—in the Table of FIG. 17 classified by the experiment number and FIG. 17 includes sketches illustrating the profile of the grooved surface of the wheel used for each experiment.