LUBBOCK, Texas — A young college student from Saudi Arabia who studied chemical engineering in Texas purchased explosive chemicals over the Internet as part of a plan to hide bomb materials inside dolls and baby carriages to blow up dams, nuclear plants or the Dallas home of former President George W. Bush, the Justice Department said today.

“After mastering the English language, learning how to build explosives and continuous planning to target the infidel Americans, it is time for jihad,” the student wrote in his private journal, according to court documents. He said he was influenced by speeches from Osama bin Laden and despaired the plight of Muslims.

One of the chemical companies, Carolina Biological Supply of Burlington, N.C., reported suspicious purchases by Khalid Ali-M Aldawsari, 20, of Lubbock, Texas, to the FBI on Feb. 1. Within weeks, federal agents had traced his other online purchases, discovered extremist posts he made on the Internet and secretly searched his off-campus apartment, computer and e-mail accounts and read his diary, according to court records.

TNP, the chemical explosive that Aldawsari was allegedly trying to obtain, has about the same destructive power as TNT. FBI bomb experts said the amounts in the Aldawsari case would have yielded almost 15 pounds of explosive. That’s about the same amount used per bomb in the July 2005 London subway attacks, which killed scores of people.

Aldawsari, who was legally in the U.S. on a student visa, is expected to appear in federal court on Friday. He was charged today with attempted use of a weapon of mass destruction.