Apple explores the use of Titanium, Titanium Alloys and Hybrid Plastics for Future Devices
As always, Apple is exploring the use of new materials for future editions of their key products and three patent flings this week confirmed that Apple is looking into using titanium, titanium alloys and hybrid plastics.
In the 'patent background' found in the first of two patent filings published this week by the U.S. Patent Office regarding titanium, Apple notes that " It is often desirable to form strong, cost-effective metallic surfaces with a dark grey or black color. Conventional dark metallic materials can be produced using pure zirconium, or zirconium alloys. Such materials are expensive, heavy, and difficult to machine.
Titanium alloys are strong, lower weight alloys. Titanium alloys can be surface finished by conventional methods such as anodizing or surface coating treatments. However, such conventional oxidized or anodized surfaces typically have an average thickness on the order of nanometers.
Cosmetic finishing can be accomplished by physical vapor deposition (PVD) coating or plating to achieve a given color or finish. For example, dark parts can be made directly by applying a PVD chromium carbide coating on a steel or titanium substrate. However, there have been no efforts at preparing a native oxide on a compositionally modified titanium surface.
There is a need for alloys having the strength and cost-effectiveness of titanium, at a grey or black color
Dark Surface Finishes on Titanium Alloys
Apple's invention, found in their filing titled "Dark Surface finishes on Titanium Alloys," relates to a coated titanium alloy. The alloy has an oxidized coating disposed on a titanium substrate. The coating has a dark surface color. In various embodiments, the coating can have an average depth of at least one micron.
Titanium alloys have high tensile strength and toughness. By creating an oxidized surface coating (i.e., native oxide) or oxide-interdiffused coating at the titanium substrate surface, the resulting treated titanium alloy may have a dark color (e.g., grey to black).
In various embodiments, the oxidized coated titanium substrate or oxide-interdiffused coated titanium substrate has a grey to black color. In some variations, the oxidized coated titanium alloy can have an interdiffused portion of unoxidized surface coating
In one aspect, methods for creating a dark surface on a titanium alloy are provided. With reference to patent FIG. 1 noted below, a titanium alloy may be prepared, e.g., a titanium alloy may be machined to a desired form, optionally surfaced finished, and cleaned.
An oxidizable surface coating is deposited on the titanium substrate, and then oxidized by heat treatment. In certain embodiments, the oxidizable surface coating may be oxidized in air or under a pressure controlled environment. In certain embodiments, the oxidizable surface coating may be heat treated in a pressure controlled environment, e.g., under vacuum, to interdiffuse the oxidizable coating into the titanium alloy, prior to oxidation.
In certain embodiments, the oxidizable surface coating may interdiffuse into the titanium alloy during oxidation. The resulting oxidized coated titanium alloy may have a dark color or hue. The titanium alloy can be titanium metal, or any titanium alloy known in the art.
Apple's patent application 20170088927 filed in September 2016 is highly technical and one that only other engineers would actually enjoy exploring. But of course anyone can check out the details of this invention here.
Apple notes that use of titanium or titanium alloy could be used in future Apple products as noted in the patent figure above: iPhone, iPad, Apple Watch and MacBook. Of course Apple lists other products that you could find in the patent such as Apple TV, iPods, remotes and more.
Durable Cosmetic Finishes for Titanium Surfaces
A second patent on titanium was published by USPTO on Thursday titled "Durable Cosmetic Finishes for Titanium Surfaces."
Apple's patent abstract states that "A method for providing a surface finish to a metal part includes both diffusion hardening a metal surface to form a diffusion-hardened layer, and oxidizing the diffusion-hardened layer to create an oxide coating thereon. The diffusion-hardened layer can be harder than an internal region of the metal part and might be ceramic, and the oxide coating can have a color that is different from the metal or ceramic, the color being unachievable only by diffusion hardening or only by oxidizing.
The metal can be titanium or titanium alloy, the diffusion hardening can include carburizing or nitriding, and the oxidizing can include electrochemical oxidization. The oxide layer thickness can be controlled via the amount of voltage applied during oxidation, with the oxide coating color being a function of thickness. An enhanced hardness profile can extend to a depth of at least 20 microns below the top of the oxide coating."
Apple's patent application 20170088931 that was filed in December 2015 could be reviewed in full for details here.
Device Structures Formed from Porous Metal Bonded to Plastic
Apple's invention generally relates to bonding a plastic to a metal, and more particularly to filling pores or other apertures in the metal with a material that bonds more strongly with the plastic than does the metal alone. Typically, the material filling the pores may create a chemical or mechanical bond having higher bond energy than a metal-plastic bond. The material may be an adhesive, such as a heat-curable adhesive, in certain embodiments.
Pores may be formed in the metal substrate by chemically etching the metal, using nano-molding technology to create pits or other apertures in the metal, blasting the metal, abrading them metal, and so on. The resulting pores (or other apertures) may accept the adhesive, which may fully or partially fill the pores. The adhesive may be sprayed or brushed on, or otherwise deposited. In some embodiments, the metal may be dipped in the adhesive.
Waterproofing Impact Resistant Advantages
One advantage to this process of plastic on metal is to provide waterproofing as well as decorative and aesthetically pleasing surfaces on the device. Waterproof thermoplastic surfaces do not rust or corrode and thus are preferred over some metal surfaces which may not be as resistant to these elements. In addition, in order to protect the metal surface and certain electronic components, a watertight seal may be desirable between the thermoplastic material layer and the metal housing of the device.
In patent point #36 they further note that "In addition to providing a waterproof or other liquid-proof bond, the strength of the bonds between the materials may provide some degree of impact resistance to the electronic device. The increased bond strength thus results in a sturdier, more durable product.
Apple's patent FIG. 2 noted above particularly illustrates the plastic cover surface #130 and the metal body #120 in cross-section, showing a sample seam or joint between the two. Apple further notes in their filing that "The plastic section #130 may be transparent in certain embodiments and may form a cover surface," illustrated as a MacBook cover in FIG. 4. Patent FIG. 3 is an exaggerated view of the FIG.2 where the metal and the plastic meet.
Apple's patent application 20170094824 was filed in September 2016. Considering that this is a patent application, the timing of such a product to market is unknown at this time.
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