In 1996, while looking at how tiny particles are produced in coal combustion, Shel discovered that one of the biggest unknowns was the behavior of particles composed of about 100 or 1000 molecules. The particles that people had been concerned with were much bigger than that, composed of millions of molecules. Shel’s group worked on the generation of titanium particles and found that they band together to form chains. Further, they showed that these chains could be stretched and would retract upon stress release. This discovery suggested that such particle chains could be used to produce ceramic materials with some of the properties of rubber. The dynamics of strained nanoparticle chain aggregates developed into a new field of great potential importance to the synthesis of high-performance nanocomposite materials.
Throughout his career, he received numerous distinctions for his seminal contributions and pioneering work in the field of aerosol science and technology, including a Fulbright Scholarship (1960), a Guggenheim Fellowship (1969), the Colburn Award (1959), the Alpha Chi Sigma Award (1974), the Walker Award (1979), the Fuchs Memorial Award (1990), the Lawrence K. Cecil Award (1995), the Christian Junge Award (2000), the Lifetime Achievement Award of the AIChE Particle Technology Forum (2001), and the Aurel Stodola Medal (ETH Zurich, 2004), as well as many honorary lectureships. He was elected to the National Academy of Engineering in 1975 in recognition of his work on the origins and control of particulate pollution.