MODIFIED CAST METAL OBJECT

Abstract

The invention relates to a device, specifically a cast metal object, composed of one or more metals with an additive, such as an aluminate, silicate, or aluminosilicate, dispersed throughout. The additive may be a halloysite nanotube or kaolinite, and may be present in amounts between 0.1 to 10 wt. % relative to the object's total weight. The metal may vary, with options including copper, iron, steel, and their respective alloys. Additionally, a method for generating the cast metal object is provided. The method may provide for preparing a molten material with the metal and additive, pouring this into a casting mold, and cooling it to form the object. The resulting device may be utilized to decrease the transmission of diseases by reducing microbial contamination on touch surfaces. The method may applicable to communicable diseases resulting from viral or bacterial infections, such as coronaviruses or antibiotic-resistant bacteria.

Claims

1. A cast metal object comprising one or more metals having dispersed throughout an additive selected from an aluminate, silicate or aluminosilicate material.

2. The cast metal object according to claim 1, wherein said additive is a halloysite nanotube of formula (Al.sub.2Si.sub.2).sub.5(OH).sub.4.Math.nH.sub.2O) where n is 0-2.

3. The cast metal object according to claim 1, wherein said additive is a kaolinite of formula Al.sub.2Si.sub.2O.sub.5(OH.sub.4).

4. The cast metal object according to claim 1, wherein said additive is present in an amount from about 0.1 to 10 wt. % with respect to a total weight of said metal object.

5. The cast metal object according to claim 1, wherein said metal is selected from the group consisting of copper, iron, steel, mild steel, zinc, silver, gold, platinum, tin, aluminum and alloys thereof.

6. The cast metal object according to claim 5, wherein said metal is steel, silver or copper alloy and wherein said alloy further comprises one or more metal selected from the group consisting of copper, magnesium, manganese, silicon, tin, nickel, silver, gold, germanium and zinc.

7. The cast metal object according to claim 1, wherein said object is at least 1 mm thick.

8. A process for manufacturing the cast metal object according to claim 1, wherein said process comprising steps: i) preparing a molten material comprising said one or more metals; ii) dispersing said additive within said molten material to produce a precursor liquid; iii) pouring said precursor liquid into a casting mold; iv) solidifying the precursor liquid in the casting mold by cooling to prepare a cast metal object; and v) removing said cast metal object from said casting mold.

9. The process according to claim 8, wherein step ii) and/or step iii) further comprises stirring or agitating said precursor liquid.

10. A cast metal object prepared according to claim 8.

11. A method for inhibiting a transmission of communicable diseases by microbial contamination of touch surfaces, said method comprising forming said touch surfaces from a cast metal object according to claim 1.

12. The method according to claim 11, wherein: i) said communicable disease is caused by a viral infection; or ii) said communicable disease is caused by a bacterial infection.

13. A method for inhibiting a transmission of communicable diseases by microbial contamination of a cast metal touch surface comprising an aluminate, silicate or aluminosilicate material as an additive within said touch surface.

14. The method according to claim 13, wherein: i) said communicable disease or disorder is caused by a viral infection; or ii) said communicable disease or disorder is caused by a bacterial infection.

15. The method according to claim 13, wherein said additive is a halloysite nanotube of formula (Al.sub.2Si.sub.2).sub.5(OH).sub.4.Math.nH.sub.2O) where n is 0-2.

16. The method according to claim 13, wherein said additive is a kaolinite of formula Al.sub.2Si.sub.2O.sub.5(OH.sub.4).

17. The method according to claim 13, wherein said additive is present in an amount from about 0.1 to 10 wt. % with respect to a total weight of said cast metal.

18. The method according to claim 13, wherein said metal is selected from the group consisting of copper, iron, steel, mild steel, zinc, silver, gold, platinum, tin, aluminum and alloys thereof.

19. The method according to claim 18, wherein said metal is a steel, silver, copper or aluminum alloy and wherein said alloy further comprises one or more metal selected from the group consisting of copper, magnesium, manganese, silicon, tin, nickel, silver, gold, germanium and zinc.

20. The method according to claim 12, wherein said communicable disease is a coronavirus.

21. The method according to claim 12, wherein said communicable disease is caused by an antibiotic resistant bacterial infection.

22. The method according to claim 14, wherein said communicable disease or disorder is caused by a coronavirus infection.

23. The method according to claim 14, wherein said communicable disease or disorder is caused by an antibiotic resistant bacterial infection.

Description

EXAMPLES

Example 1: Preparation of Cast Metal Samples

Materials

[0051] Aluminosilicate (halloysite) additive was purchased from Sigma Aldrich Ltd.

Methods

[0052] Additive free and aluminosilicate containing cast silver and steel ingots were prepared by conventional vacuum induced melting (VIM) at the Steel and Metals Institute at Swansea University. In summary, bulk metal and, where required, halloysite additive (1 wt. %., based on the total weight of the bulk metal), are placed in in a core-less induction furnace (100 mm wide by 500 mm high, leaving around 60-80 mm void space at top of the furnace), wherein eddy currents are induced within the furnace to melt the bulk metal under vacuum pressure. In addition to melting the bulk metal, induced eddy currents also provide an agitating effect, and so ensure an even dispersal of halloysite additive throughout the molten bulk metal prior to ingot formation upon cooling. The ingot solidification process occurs following pouring of the molten material, by initially cooling for 40-50 mins prior to releasing the vacuum and leaving to cool for a further 3 to 4 hours before the cast metal ingot is removed.

[0053] Each steel ingot was formed from 28 kg of bulk metal and, for additive containing samples, 280 g of aluminosilicate (halloysite nanotube) was added (1 wt. %), based on bulk metal weight.

[0054] Table 1 outlines the specimens produced.

TABLE-US-00001 TABLE 1 Specimen Substrate Additive (1 wt. %) 1 Steel None 2 Steel Halloysite 3 Silver None 4 Silver Halloysite

Results

[0055] In all cases, a bright and uniform metal ingot was produced, demonstrating that aluminosilicate additives can be incorporated throughout bulk metal castings without negatively influencing the appearance of the casting.

Example 2: Antimicrobial Efficacy Testing

[0056] The antimicrobial efficacy of cast metals comprising aluminosilicate additives was assessed by measuring the viral persistence levels on metal ingots of specimens 1 to 4 prepared in Example 1 above 1 or 4 hours after contact with a known titration (approximately 1?10.sup.7 PFU/100 ?l) of SARS-CoV-2, the causative infectious agent of Covid-19.

Methods

Sars-CoV-2 Plaque Assay

[0057] As the skilled reader would readily appreciate, a plaque assay represents a standard method to determine virus concentration in terms of infectious doses. In particular, viral plaque assays determine the number of plaque forming units (PFU) in a virus sample, which is a measure of virus quantity. A standard SARS-CoV-2 plaque assay used to quantify SARS-CoV-2 levels is as follows: [0058] i. VeroE6-ACE2-TMPRSS cells are seeded into 12-well plates at 2?10.sup.5/well, in 10% Dulbecco's Modified Eagle Medium (DMEM); [0059] ii. SARS-CoV2 logarithmic dilutions are prepared; ii. [0060] iii. Media is removed, and 50 ?l of 2% DMEM is then added to each well. 100 ?l/well of virus inoculum is then added to each well before incubation for 1 hour at 37? C. with rocking to allow virus adsorption. [0061] iv. An overlay medium is then prepared by mixing Avicel? binder with 2? Minimal Essential Medium?/4% foetal Calf Serum at ratio 1:1; [0062] v. After 1 hour virus adsorption, inoculum is removed and replaced with 1 ml of overlay medium per well and the plate is then incubated for 3 days at 37? C.; [0063] vi. Overlay medium is removed, and well is washed once in phosphate buffered saline; [0064] vii. 2 ml ice cold methanol is added for 5 min to fix; [0065] viii. 1 ml crystal violet stain is added and left for 5 min before removal and washing with water; and [0066] ix. Plaques are manually counted to calculate, in combination with the required dilution factor, PFU/sample volume.

Sars-CoV-2 Persistence on Additive Containing and Additive Free Cast Metal Objects

[0067] Viral persistence on additive containing and additive fee cast metal objects was monitored by simple adaptation of the plaque assay detailed above. In particular, the following standard process was followed: [0068] i. A small test piece of the test materials, i.e. additive containing or additive free bulk metal specimens 1-4 are placed into the bottom of a 6-well dish (well diameter 34.6 mm); [0069] ii. A specific volume (100 ?l) of a known concentration (approx. 10.sup.7 CFU/ml) of Sars-CoV-2 is then added to the surface of each test sample. If the liquid does not bead, then a cell spreader is used to create a thinner film; [0070] iii. Wait for an appropriate test contact period (1 hour or 4 hour) before adding 1 ml of 10% DMEM to each well and gently pipetting the liquid against the surface of the test substrates to recover virus; and [0071] iv. Collect the 10% DMEM samples and perform a series of logarithmic dilutions for use in step (ii) of above plaque assay to calculate, in combination with the required dilution factor, PFU/test sample.

Results

[0072] As expected, significant levels of SARS-CoV-2 persist on the surface of the additive free cast steel test samples (Table 1, Specimen 1). However, the dispersal of an aluminosilicate additive, in this case a halloysite, throughout the bulk steel casting (Table 1, Specimen 2) can reduce the duration of viral persistence on the steel surface. Therefore, aluminosilicate additive(s) may be included within steel castings to reduce the risk of infection by indirect contact transmission from cast steel objects.

[0073] A similar decrease in viral persistence can be observed for cast silver specimens upon dispersal of an aluminosilicate throughout the bulk silver casting (Table 1, Specimens 3 and 4). Therefore, aluminosilicate additive(s) may also be included within silver castings to reduce the risk of infection by indirect contact transmission from cast silver objects. It is expected that this increased antimicrobial activity will extend to other aluminosilicate additive containing bulk metal castings.

Example 3: Corrosion Testing

Methods

[0074] The resistance to corrosion was assessed using small test pieces removed from four test specimensadditive free cast steel [Table 1, Specimen 1], aluminosilicate containing cast steel [Table 1, Specimen 2], additive free cast silver [Table 1, Specimen 3], and aluminosilicate containing cast silver [Table 1, Specimen 4].

[0075] Each of the cast steel and silver test specimens were subjected to humidity testing which involved enclosing the specimens in a holding space with relative humidity of 95% at 40? ? C. for extended duration tests.

[0076] In addition, the tarnish/corrosion resistance of each of the test specimens were assessed using the International Standard Thioacetamide corrosion Test (TAA testISO 4538-1978). In summary, said testing involved exposure of the test specimens to vapours emitted by thioacetamide in an atmosphere having a relative humidity of 75%, maintained by the presence of a saturated solution of sodium acetate.

Results

[0077] As expected, significant corrosion/tarnishing was observed on the surface of the additive free cast steel test samples (Table 1, Specimen 1) following completion of humidity test and/or the TAA test. However, the dispersal of an aluminosilicate additive, in this case a halloysite, throughout the bulk steel casting (Table 1, Specimen 2) can significantly reduce the rate of observed corrosion/tarnish. Therefore, aluminosilicate additive(s) may be included within steel castings to provide corrosion resistant cast steel objects.

[0078] A similar surprising decrease in tarnishing can be observed for cast silver specimens, upon dispersal of an aluminosilicate throughout the bulk silver casting (Table 1, Specimens 3 and 4). Therefore, aluminosilicate additive(s) may also be included within silver castings to provide tarnish resistant cast silver objects.

[0079] It is expected that such corrosion/tarnish resistance will extend to other aluminosilicate additive containing bulk metal castings.

Example 4: Mechanical Testing

Methods

[0080] The mechanical properties of cast metals comprising aluminosilicate additives was assessed and compared to additive free cast metals by comparing one or more of fatigue strength, impact resistance, hardness and (tensile) strength for (i) a test piece obtained from an additive free steel ingot (Table 1, Specimen 1) with a test piece obtained from an aluminosilicate containing steel ingot (Table 1, Specimen 2); or (ii) a test piece obtained from an additive free silver ingot (Table 1, Specimen 3) with a test piece obtained from an aluminosilicate containing silver ingot (Table 1, Specimen 4).

Results

[0081] It is expected that the dispersal of aluminosilicate additive throughout the bulk metal casting will enhance one or more of the abovementioned mechanical properties, both for steel and silver castings.

REFERENCES

[0082] 1. Gerhardus H. Koch M P H, Brongers and NGTYPVJHP. Corrosion costs and preventive strategies in the United States. Summ Shute Inst [Internet]. 2002; 1-12. Available from: papers2://publication/uuid/4D469A9D-07D6-4543-B217-3A15873793CF