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Materials in extreme environments are the unsung heroes in our everyday lives.  Materials used in rocket, jet and automotive engines, nuclear reactors, space satellites, submarines, aircraft structures, and other extreme environments are exposed to unusually harsh environments that challenge their own existence! As a result, such materials develop high temperature, tremendous stress, and extreme strain rate that lead to the formation of cracks and other defects,  eventually causing their demise. UCLA MAE Professor Nasr Ghoniem’s research is focused on understanding the physics and mechanics of materials in extreme environments, finding ways to make them stronger, longer-lasting, and easier to manufacture, while also inventing practical applications of more resilient materials.

The need to generate energy for propulsion, storage, and transmission requires materials that operate at extreme heat flux. Such materials must be designed for maximum lifetime, measured in units of kW.hr/cm2, as shown here.

What was your attraction to working with materials in extreme environments?

When I started choosing my research path as a nuclear engineer, I had two choices: one was more mathematically elegant to neutron transport; and the other was to do research on  radiation effects on materials. I chose the second because I realized that materials are very complex, and that much was less understood. I just thought that since less is understood, I might have a chance to make some new contributions. For my Ph.D., I developed theoretical and computational methods to determine changes in the properties of structural materials in nuclear reactors.

Microscopic nature of plastic deformation in metals, where massive avalanche-like behavior of dislocations control macroscopic strain and failure.

For example, the properties of the cladding material of nuclear fuels, or the pressure vessel of the nuclear reactor itself change drastically after operation for a few months or even years. Some materials swell, they become much bulkier and hard to fit as assembled. Thus, there is great impact on the design and safety of nuclear reactors because of changes in the dimensions and properties of structural materials because of irradiation. I focused my effort in understanding how defects evolve in materials when irradiation penetrates a structure. For example, if you have a neutron, it doesn’t have a charge, and therefore it doesn’t “see” any of the atoms; it just goes very deep through the structure. All of a sudden, it collides with an atom generating an atomic cascade, just like in a billiard ball game.  As the cascade spreads further, many defects are generated in the material making them weaker and more prone to failure.

The first period of my research focused on the physics of radiation interaction with materials. As we know, radiation sources include neutrons, ions, electrons, and photons.  Applications of this knowledge are very broad, encompassing material processing with ion and plasma beams, space radiation effects on microelectronics, fabrication of computer chips by ion implantation, and the mitigation of material degradation in nuclear environments.  One of the most important challenges in our lifetime is the development of fusion energy. Nuclear fusion of hydrogen isotopes occurs in every star, including our sun, and powers the universe. Fusion energy is clean and inexhaustible and may well be the ultimate salvation of human existence when all other sources of energy are exhausted or depleted.  Here, the environment that materials see in a fusion reactor is very hostile and requires a great degree of physical understanding for an engineering design of a commercial fusion power plant.  Fusion energy is also sought after to power deep space missions, such as those to Mars and beyond.

Have you been able to apply your fundamental research into building fusion reactors?

Inside a Tokamak.

Yes. In the core of the fusion reactor, the fuel is an electrified gas that has electrons and ions (the plasma, which is the fourth state of matter). The gas is extremely hot, like the surface of the sun, with temperature in excess of 10,000 degrees. If this gas hits a surrounding wall, it will immediately vaporize it. This is why we use very strong magnets to exert an electromagnetic force (the Lorenz force) to “fuse” ions together and to confine the hot plasma away from the surrounding walls. The most common reactor system is called the Tokamak, which has a donut-shape surrounded by magnets that look like rings and that can squeeze the plasma. My interest is in the development and design of the structural materials that are used to surround the plasma and contain it. The radiation emanating from the plasma penetrates the walls of the surrounding vessel and causes significant damage and degradation of structural properties, thus limiting the lifetime. In addition to radiation, the surrounding material also experiences excessive heat flux that goes up and down in magnitude, resulting in plastic deformation, creep and fracture.

How has your research emphasis changed over the years?

My current research has become much broader than just the subject of radiation effects on materials. During the last two decades, I realized that the excessive heat and radiation environments are more common in many other applications.  These encompass all types of materials used in space systems, defense and the military, and especially in modern jet engines.  In some of these applications, the radiation field is absent, but the key challenge is in the high thermal and mechanical loads that materials experience.  Even understanding how to design crash-resistant materials for automotive applications requires good knowledge in material physics of high speed deformation. This breadth led me to a successful career and the ability to attract research funding from many sources: the Air Force, National Science Foundation, the Department of Energy, and the private sector.

When was the first time you set eyes on Los Angeles?

I remember it very vividly. The day was February 5, 1976. I was doing my Ph.D. at the University of Wisconsin, and 1976 was one of the coldest years on record in Wisconsin. We had the full month of January with temperatures below zero. I grew up in Alexandria, Egypt, where the weather is warm and very similar to Los Angeles. I was missing that weather where I lived in the Midwest for a few years. When the plane landed in Los Angeles, I was amazed at how everything was still green compared to Wisconsin. This had a big impression on me, as I still remember that day.

Did it become a goal then to want to work at UCLA?

When I interviewed at UCLA I hadn’t finished my Ph.D. yet. It was just six months before I finished, and there was a very active research group in nuclear safety at UCLA; a very famous group. After my interview, I was very impressed with the quality of the professors, their collegiality and their knowledge. The leader of this group, Prof. Okrent, was very well-known outside of UCLA. I was hoping to get an offer, and once I got the offer, I did not look any further. In fact, I had many opportunities later in life with offers from other universities, but I decided to stay at UCLA for all these years.

You’ve been teaching at UCLA for more than 40 years!

Yes, indeed. I finished my Ph.D.  in September 1977, was offered an assistant professor job before I finished, and started here on October 1st or 2nd 1977, it’s been over 41 years now.

How have you and the MAE Department evolved together?

When I joined UCLA, the MAE department did not exist. There was a different structure of the School of engineering. The founder of the School, Prof. Boelter, had the vision of an integrated engineering curriculum, where people learned all kinds of disciplines across fields. Later on, traditional departments started to emerge within the School of Engineering and Applied Science. The department that I joined was called Chemical, Nuclear, and Thermal Engineering, where three subjects coalesced together. In the mid-80s, more classical disciplines emerged, and we became the Department of Mechanical, Aerospace, and Nuclear Engineering. In the early nineties, nuclear engineering was dropped because of changes in the job market, and we ended up with the current configuration of Mechanical and Aerospace Engineering (MAE)

You were here at the birth of the MAE department.

Yes!

That’s very impressive!

Yeah, it’s been a long trip! In the initial phase, I interacted quite a bit with chemical engineers and thermal engineers. Prof. Vijay Dhir, the former Dean, was also in the same department. Prof. Catton was in the same department. There was a lot of emphasis on energy-related research at that time, and thermal engineering was a big part of it. Back then, my interest was more in the structures that are used in energy applications, and thus I ended up in the structures group, even though I was trained as a materials physicist!

Which technological changes are coming soonest in the next 40 years?

During my 40-year journey, many changes took place at an ever-increasing pace. I believe that the pace of change will accelerate even more because of the ease at which knowledge spreads, the exponential increase in the number of learners worldwide, and the availability of a great technological infrastructure. Having said that, it is hard to imagine what may happen, but it is fun, nevertheless. I can immediately see that self-driving vehicles will be common place, for example in transportation, trucking, mining operations, etc.  There’s a lot of research now on artificial intelligence, and its inclusion into machinery (robotics).  Energy research and applications will probably realize commercial fusion energy, fusion and plasma-driven propulsion of space craft, high-speed transport, and so on.

How soon until half the cars on the road are driving themselves?

It’s hard to put a timeline, but it probably would be introduced gradually in certain applications before we see most cars self-driving on the roads.  For example, in mining operations, you need gigantic trucks and machinery to excavate and mine rocks with many human operators.  Self-driving excavators and transport trucks will be used more efficiently because of the small impact on public safety. The trucking industry in certain locations (such as in harbors) will be automated sooner.  In the public transportation arena, self-driving cars will first be in drive-assistance mode (as is now with some cars), and perhaps within 10 to 15 years, we may see a good fraction of self-driving cars on the roads.

A simulation of porous material with interconnected microchannels in response to transient laser heating and fluid flow.

You said in your Egyptian-American Organization (EAO) presentation that physics is a search for truth. What did you mean?

This is really what motivated me to spend my lifetime studying science. The attractiveness of physics is that it is a study of the laws of nature. These are very precise, and they govern the behavior of everything that surrounds us. The study of physics is thus to seek the absolute truth without personal opinions. In many other areas (political, societal, medicine, etc.) the laws are not so precise or well-understood. Thus, opinions matter and can be very confusing and unsettling. By contrast, in physics, once you apply the same laws as everyone else, and discover a new phenomenon, you have a sense of happiness that you found the truth.

In my case, for example, the formation of patterns and self-organization in materials science intrigued me. I did not know why patterns form, and what motivates inanimate materials to organize themselves as if they have a soul.  I wanted to understand how materials organize themselves without any body telling them what to do!. This is also like what happens in fluids, for example, the formation of waves or patterns in a swimming pool or on the ocean surface. In materials science, patterns happen to form  in every aspect of the microstructure. Pattern formation is thus a puzzle that can keep you thinking for a long time.  I co-authored a two-volume book with a Belgian scientist (Professor Daniel Walgraef) of over 1100 pages in an attempt to solve this puzzle. In our two-volume book, you see a lot of math and physics of non-linear systems, and weird behavior that comes about from the application of firm physical principles and advanced mathematics. Again, Daniel Walgraef and I had a collaboration extending over 20 years to study the truth behind the physics of pattern formation. However, I am still amazed by the emergence of simple order out of chaos in solid inanimate materials!

Article by Alex Duffy


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