Fabrication of novel glasses and glass micro-spheres by acoustic levitation and laser heating.

Lead Research Organisation: University of Bristol
Department Name: Physics

Abstract

Oxide glasses have been important materials for millennia. Their transparency at optical wavelengths makes them ubiquitous in windows for houses and cars and their use in lenses for microscopes and telescopes has been key to much scientific development. Today they remain key technological materials with additional applications in, for example, the hard glasses used in mobile phone screens, the fibre optics that underpin current high-speed communications and as laser host materials to name a few.

The process of making a typical oxide glass involves melting the material and allowing it to cool (quench) into a form in which the atoms have a disordered, non-crystalline arrangement. In practice, this non-crystalline form is difficult to achieve for most materials, apart from those that contain significant quantities of silicon dioxide, boron oxide or phosphorus oxide. In order to produce glasses with improved properties (e.g. refractive index, infrared transmission, rare-earth ion content ...) these components need to be avoided which has a significant impact on their glass forming ability. Hence, new methods for glass fabrication are required.

The ability of a material to form a glass reliably depends on how fast it can be cooled (the quench rate), the container it is in and the presence of any solid impurities (that promote crystallization). The rate at which a very hot material will cool freely in air by radiation depends on its size. Hence to improve the quench rate for a given material we need to make it as small as possible. To avoid crystallization due to a container we need to use either, a very smooth container, or no container at all. Hence to discover and produce new glassy materials it is ideal to work with small samples under containerless conditions.

In this project we will develop acoustic levitation methods to allow us to process materials at high temperatures without the need for a container. In this project we will exploit new techniques that have been developed recently in Bristol. In particular, we will develop further the 'TinyLev' device that allows routine levitation of materials with moderate density (up to 5 g. cm-3) and auto-tuning Langevin Horn based devices for use with high density materials (in excess of 12 g. cm-3).

To achieve high melt temperatures we will use an aligned carbon dioxide laser system to heat the samples to temperatures in excess of 2500K. The use of a laser heating system means that the samples may be heated and melted in a matter of seconds with small thermal gradients. As a heat source the lasers may be switched off instantaneously so that the sample will be free cooled at its maximum rate so that for a size of less than 1mm diameter, quench rates of the order of 10,000 Kelvin/second will be achieved. The system will be very suitable for rapid processing/prototyping of new glass materials.

The acoustic levitation and laser heating systems will be used to study the structure of novel silica-free glass forming systems, based on aluminium oxide, titanium oxide and gallium oxide, by X-ray and neutron diffraction. In particular, we will use the system to follow, in situ, the evolution of the liquid structure as it is rapidly cooled, to form either a glass or to observe the processes giving rise to crystal nucleation. The experiments will be coupled with state-of-the-art computer simulations to give new insight into the glass forming process.

There is increasing interest in the use of high quality glass spheres with sizes of the order 10-100 microns diameter for applications in Whispering Gallery Mode (WGM) devices such as biosensors, temperature sensors and lasers. This acoustic levitation and laser heating system will be ideal to produce these spheres and the final part of this project will be to explore and evaluate this method for producing WGM spheres for these applications.

Planned Impact

The containerless processing system based on acoustic levitation proposed here has the potential to open up a new and wider range of glass compositions than can be developed for new applications of photonic, laser and solar voltaic glasses.
We have identified with Johnson Matthey PLC that these methods could be used, not only for fabrication of new materials but also as a method for rapidly surveying materials in order to reduce materials costs (only tiny samples are used) and the timescales of investigations compared to traditional methods.

We will continue to explore opportunities for exploitation of these methods as the project progresses by directly contacting and working with possible beneficiaries, such as NSG Group Limited (Pilkington), Corning Inc. via the Corning European Technology Centre, and Schott AG who offer custom-tailored components and innovative products based on advances in materials and processing.

Development and progress in the fabrication of whispering gallery mode applications from microspheres will be managed through our collaboration with Prof. Barker and Dr Li at UCL and their partners (DSTL and Harris Aerospace for optomechanical applications).

In future any relevant project outputs will be developed further in conjunction with industrial partners via case awards, collaborations and knowledge transfer partnerships through UKRI or the Innovate UK Knowledge Transfer Network, which has relevant interests in Energy, Materials, and Manufacturing.

Any work that leads directly to applications on the timescale of the award will be exploited through licence deals via the Research and Enterprise Development (RED) team at the University of Bristol (UOB) who are responsible for technology transfer, licensing and commercialization of research output.

Since its development we have used TinyLev for a large number of public demonstrations and open days. There is no doubt about the fascination and interest from the general public when they see it in operation. We will us this public facing side of our research to promote interest in science and technology and to encourage school pupils to consider pursuing careers in science and engineering. It will also be used to promote awareness of materials, our limited planetary resources and the importance for considering the complete life re-cycling (circular economy) of all materials.

Publications

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Pozdnyakova I (2021) Structure of levitated Si-Ge melts studied by high-energy x-ray diffraction in combination with reverse Monte Carlo simulations. in Journal of physics. Condensed matter : an Institute of Physics journal

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Drewitt JWE (2021) Liquid structure under extreme conditions: high-pressure x-ray diffraction studies. in Journal of physics. Condensed matter : an Institute of Physics journal

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Drewitt JWE (2023) Iron coordination in liquid FeAl2O4. in Philosophical transactions. Series A, Mathematical, physical, and engineering sciences

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Heinen B (2022) LiquidDiffract: software for liquid total scattering analysis in Physics and Chemistry of Minerals

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Drewitt J (2022) From Short to Medium Range Order in Glasses and Melts by Diffraction and Raman Spectroscopy in Reviews in Mineralogy and Geochemistry

 
Description The particular goal that we are trying to achieve in this funded programme is to produce and study liquid and glassy materials under containerless conditions using acoustic levitation. The principle has been established in previous work through the design and construction of the so-called 'TinyLev' system. This system demonstrated stable acoustic levitation for samples with densities of the order of ~3 g.cm-3 (or typically that of window glass). In the current work we have extended the capability of acoustic levitation to allow for routine stable levitation of materials with densities in excess of lead ( ~11 g.cm-3). These are the kind of densities that we will need to levitate for the materials of interest to this programme. In addition, we have constructed a laser heating system (2 60W CO2 lasers) capable of heating levitated samples to temperatures in excess of 3000K. As expected, we see instabilities in the levitated samples as we are heating and this can lead to the sample falling from the acoustic trap. Our current focus, is to determine methods by which we can reduce these instabilities while maintaining levitation through the heating process. We are approaching this, experimentally by observing the conditions when the instability sets in, comparing this with simulation and theoretical understanding of the instabilities and by direct imaging of the distortion of the acoustic field through heating by schielren imaging.
Exploitation Route Since the development of the original levitation system (TinyLEv) there has been a widespread adoption of the method in many scientific areas, from study of COVID transmission , to protein crystallography to materials processing. We envisage that the extension of the technique to allow heating and cooling of samples will extend these applications further.

The improvements we have made to the TinyLev device has lead to a successful EPSRC Impact Acceleration Award to Dr. Drewitt, "Elevating innovation in biotechnology: development of a containerless reagent mixing prototype for engagement with instrument manufacturers.
Sectors Aerospace

Defence and Marine

Digital/Communication/Information Technologies (including Software)

Electronics

Energy

Healthcare

Manufacturing

including Industrial Biotechology

Pharmaceuticals and Medical Biotechnology

 
Description The demonstration of acoustic levitation is visually attractive and intriguing for the non-specialist and especially school age children. We have developed a simple to operate levitation system (plug and play) that we have used successfully in University open days and other events to encourage students to consider physics as a career option. We are currently developing a new system that will not only demonstrate levitation but also the containerless manipulation of levitated materials.
First Year Of Impact 2022
Sector Education
 
Title Data from Drewitt et al RSTA 2023 
Description This deposit contains neutron diffraction with isotopic substitution (NDIS) data and associated molecular dynamics simulation results from the paper by Drewitt et al. (2023) "Iron coordination in liquid FeAl2O4" in Philisophical Transactions of the Royal Society A (https://doi.org/10.1098/rsta.2022.0351) 
Type Of Material Database/Collection of data 
Year Produced 2023 
Provided To Others? Yes  
URL https://data.bris.ac.uk/data/dataset/w9d5ypz91ltv2wksargnm510s/
 
Description Laser heating under extreme conditions in pressure cell 
Organisation University of Bristol
Country United Kingdom 
Sector Academic/University 
PI Contribution The laser heating system that we have developed for the acoustic levitation experiments is very versatile (as it includes defined laser paths with a fully safety interlocked enclosure). We have used this system to test the feasibility of using our equipment for this type of experiment in the future.
Collaborator Contribution Pressure cells and about £2000 of optical equipment for fine focus of the CO2 lasers used for heating.
Impact Not yet but it will be part of future research studies in Earth Sciences in Bristol. It needs some refinement of the optics.
Start Year 2023
 
Description We have been actively engaged with Dr. Peter Docker at the DIAMOND light source in the development of acoustic levitation for actively studying protein crystallization and related topics for in-situ X-ray scattering 
Organisation Diamond Light Source
Country United Kingdom 
Sector Private 
PI Contribution This collaboration is currently in the early stages. Dr Docker at DIAMOND has used our acoustic levitator at DIAMOND in a previous study. He is particular interested to work with us on improving the levitation stability and in the active manipulation of samples in the X-ray beam. We have been giving advice, practical help and generating new schemes for improving the levitation. In particular, the design and construction of a levitator that uss He gas wouldbe particularly advantageous for X-ray measurements.
Collaborator Contribution We have been advising on the design and construction of a new levitation system and in particular a design for a prototype He gas acoustic levitator. We have also been giving practical advice on the electronics and software needed to improve the capabilities of our current levitator.
Impact It is too early for an publishable outcomes.
Start Year 2022
 
Description Demonstration of acoustic levitation 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Schools
Results and Impact We have an acoustic levitator that we use on University Open days and other outreach activities in the school. This is seen typically by over 100 people each open day. It is always attracts many questions about the principle of acoustic levitation and is popular, even among the parents.
Year(s) Of Engagement Activity 2021,2022,2023,2024
 
Description Youtube videos demonstrating acoustic levitation and laser heating 
Form Of Engagement Activity Engagement focused website, blog or social media channel
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact We produced 4 videos on youtube demonstrating acoustic levitation and laser heating. To date these have received in excess of 1000 views in total and over 500 for "Acoustic levitation of dense solids". This has been to a wide international audience.
Year(s) Of Engagement Activity 2022,2023,2024
URL https://www.youtube.com/watch?v=QoKwdMMXhRA