New Multi-Component Alloys
Currently the focus on working with metals from e-waste has been on separation technology, that is selecting single metal elements eg., copper and or gold that can re-enter the bullion supply chain. During EPSRC funded research the idea emerged of working with all the metals from, for example, a single device creating opportunities for new multi-component alloys. This approach would have the benefit of not needing to use different chemical compounds to select different metals and so potentially would also reduce the number of steps involved in the metal recovery process. Through this approach we could also potentially discover new metal alloys with novel aesthetic and mechanical properties.
As a starting point I decided to create an exemplar alloy based on data available to explore what properties such an alloy would have, for example how hard the metal is; can it be easily shaped and formed and what are its aesthetic qualities.
The best source of data available was an article by the BBC from 20161 that details the metals in a typical iPhone.2 Certainly, different manufacturers of mobile devices will use different metals and in different quantities. More recent models will most likely have less gold for example, an iPhone 11 has 0.018g of gold compared to the iPhone 6 in 2016 that contained 0.034g of gold. Apple sold around 2000 million iPhones in 2019 that amounts to 3,600,000 grams of gold in a year. IPhone weights range from the earliest models at 135g to the latest models 240g.4 Approximately 17% of the weight is metal – not including the rare earth metals - elements that are plentiful in the Earth’s crust but extremely difficult to mine and extract economically – including terbium, neodymium, and gadolinium. So, determining the metals in a device and their quantities is a notoriously complex issue with some variation.
Metals in an iPhone - 2016
Percentages Metal Weight in grams
0.08 Gold 0.034
0.84 Silver 0.34
0.04 Palladium 0.015
0.003 Platinum 0.001
61.9 Aluminium 25
37.14 Copper 15
100.003 40.39g
The above table details the metals in a 2016 iPhone and their weights in grams. To achieve an alloy that is sufficient in size to work with and that potentially has the best chance of success the weights have been multiplied by twenty-one. This number was chosen as it is the number of devices in a lifetime that an average person is likely to use given that we replace our phones on average every 3 – 4 years. There is a risk in multiplying the copper by twenty-one that this metal could overwhelm our alloy and so one option would also be to leave the copper out of the calculations. Aluminium is known to create quite a brittle alloy and so I decided it was expedient to exclude this material.
Option 1 - iPhone 2016 weights x 21 but leaving out the copper and aluminium as the quantities of these risk overpowering the alloy or making it too brittle to be worked.
Percentages Metal Weight in grams
8.72 Gold 1.428
87.17 Silver 14.28
3.85 Palladium 0.63
0.26 Platinum 0.042
100 16.38g
This would effectively be a silver alloy – not quite electrum (20% gold 80% silver) a known natural alloy. This alloy is perhaps closer to Doré a named alloy (upto 5% gold, 1% platinum and the rest silver). The term derives from the French meaning gilded. Historically, Doré bars were produced as part of the mining and refining process and sometimes from scrap gold. Doré bars were often mistaken for solid gold. This alloy is rarely sold today and may not have been explored for its aesthetic potential.
Option 2 - IPhone 2016 weights x 21 for the number of devices in a lifetime but leaving the original copper percentage from one device but not including the aluminum.
Percentages Metal Weight in grams Melting point (Celsius)
4.55 Gold 1.428 1100
45.51 Silver 14.28 900 - 1000
2.01 Palladium 0.63 1500
0.13 Platinum 0.042 1550 - 1800
47.80 Copper 15 1085
100 31.38g
Working with the original 15g of copper from one device (rather than multiplying by 21) a potentially workable alloy could be created. The balance of silver and copper is close to a 50/50 shibuichi Japanese alloy. Shibuichi is a traditional copper alloy made up of varying proportions of copper and silver sometimes with a little gold. It will be interesting to see what the addition of the gold, palladium and platinum would do if anything – for hardness, colour etc.
Since the 15th Century Japanese artists and crafts people have developed considerable knowledge and expertise in creating and colouring different metal alloys in particular irogane (copper) alloys. Niiro a traditional Japanese patination solution is made of water, and chemical compounds rokushō and copper sulphate. Shibuichi alloys coloured with niiro demonstrate a variety of shades of grey and shakudo which is 95% copper 5% gold when coloured turns lovely purple and blue hues. So there is also great potential to colour these new multi-component alloys. Copper sulphate one of the key outputs from the hydrometallurgy e-waste process could also be used here maximising the use of metals from e-waste in different states and enhancing the circularity of the process.
First experiment
It was decided to move forward with option 2 first as there was some understanding of how this alloy might behave. It was also decided to create the alloy in two parts. Firstly, mixing the gold, silver and copper together and then mixing the platinum and palladium which have higher melting points. Both mixes would then be combined. A Spir-flame multicell electrolyser torch can achieve the higher melting points (see above) required for platinum and palladium. I created a basic mould/crucible specifically for working with this alloy from a graphite block which had been CNC milled using a digital Rhino3D file in the DJCAD digital makerspace. The silver, copper and gold mixture melted and mixed successfully however the platinum and palladium mix did not. I used the biggest tip to melt the platinum and palladium and while it started to melt it appeared to go so far and then stopped. I subsequently became aware that melting palladium in an open crucible is not recommended as it leaves the alloy free to absorb large quantities of hydrogen.
Spir-flame torch mixing platinum and palladium together in a CNC milled graphite block
Second experiment
With some assistance from Rautomead a local continuous metal casting company based in Dundee I was able to try the melt test again. They created the phase diagram for the iPhone exemplar alloy and melted the complete sample in one operation in a zirconia crucible in a high temperature furnace. From the images below, it appears the sample has not fully mixed as silver veins are visible on the surface compared to the blacker copper on the rear side. This is known as segregation. Whilst the original intention was to have a fully mixed alloy there could perhaps be some benefit in a segregated alloy for colouring and patination effects.
Exemplar IPhone Alloy next to the zirconia crucible in which it was melted
Exemplar iPhone Segregated Alloy
The next stage is to roll down this alloy into sheet / wire to learn more about its working and aesthetic properties. Ultimately, more work is needed to explore the full potential of new multi-component alloys from e-waste. These could have the advantage of novel properties and great aesthetic potential. The reduced costs associated with creating new alloys could also increase the amount of metal recovery from e-waste and contribute towards meeting UN sustainable development goals specifically those related to responsible consumption and production.
This blog post is an excerpt from the book Brick, Bread and Biscuit: The Chemical Recycling of Electronic Waste for Jewellery Design in India.