Professor Ajayan earned his B. Tech in metallurgical engineering from Banaras Hindu University in 1985 and Ph.D. in materials science and engineering from Northwestern University in 1989. After three years of post-doctoral experience at NEC Corporation in Japan, he spent two years as a research scientist at the Laboratoire de Physique des Solides, Orsay in France and nearly a year and a half as an Alexander von Humboldt fellow at the Max-Planck-Institut fur Metallforschung, Stuttgart in Germany. In 1997, he joined the materials science and engineering faculty at Rensselaer Polytechnic Institute (RPI) as an Assistant Professor and was the Henri Burlage chair Professor in Engineering until he left RPI in 2007. He joined the mechanical engineering and materials science department of Rice University, as the Benjamin M. and Mary Greenwood Anderson Professor in Engineering from July 2007. From 2014, he is the founding chair of the new department of Materials Science and NanoEngineering at Rice University.

Professor Ajayan's research interests include synthesis and structure-property relations of nanostructures and nanocomposites, materials science and applications of nanomaterials, energy storage, and phase stability in nanoscale systems. He is one of the pioneers in the field of carbon nanotubes and was involved in the early work on the topic along with the NEC group. He has published one book and 1300 journal papers with nearly 218294 citations and an h-index of 226, based on ISI database. He has given more than 400 invited talks including several named lectures, keynote and plenary lectures in several countries and at several international conferences.

Ajayan has received several awards including the Spiers Memorial Award by the Royal Society of Chemistry (UK), Senior Humboldt Prize, MRS medal, Scientific American 50 recognition, RPI senior research award, the Burton award from the microscopic society of America and the Hadfield medal for the outstanding student metallurgist in India. He has been elected as a fellow of the Royal Society of Chemistry (UK), AAAS, foreign fellow of the Mexican Academy of Sciences and National Academy of Sciences (India), and has been elected honorary member of Materials Research Society of India and the Indian Institute of Metals. He also received the distinguished alumnus award from the department of Materials Science and Engineering at Northwestern University and from Banaras Hindu University. He has held distinguished guest Professorships in the school of Materials Sciences at University of Louis Pasteaur at Strasbourg and ISIS (France), Tsinghua University (China), Shandong University (China) and Shinshu University (Japan), Indian Institute of Science Bangalore (India), Indian Institute of Technology Chennai (India), Nanyang Technological University (Singapore). He received the Docteur Honoris Causa Université Catholique de Louvain (Belgium) in 2014. In 2023, he has been elected a foreign fellow of the Indian National Science Academy (INSA) for his “pioneering work on nanocomposites, starting with carbon nanotube polymer composites, providing insights into multifunctional nanocomposite materials.”. He is on the advisory editorial board of several materials science and nanotechnology journals and on the boards of several nanotech companies. He has been part of two Guiness Book of World records, one for the creation of the smallest brush and the other for creating the darkest material.