Here is what I have found in English. The most information is concentrated in a Wikipedia article on Fan Zhen.
On Food for Thought, a web site of heretical quotations, this one can be found:
The spirit is to the body what the sharpness is to the knife. We have never heard that after the knife has been destroyed the sharpness can persist.
Fan Chen (c.450-c.515)Fan Zhen gets singled out in John C. Plott's Global History of Philosophy: The Patristic-Sutra Period, Volume 3. He gets two sentences in Rom Harré's One Thousand Years of Philosophy: From Rāmānuja to Wittgenstein.
Thung Chien Kang Mu, Chapter 28
Translated by Leon Wieger (1856-1933)
Textes Historiques, 1905
Fan Zhen is best known for his opposition to Buddhism and his denial of the immortality of the soul, in effect a materialism denying the separate existence of the soul. According to the Wikipedia article, he got in big trouble for this.
I first learned of Fan Zhen via Esperanto: Ateisto Fan Ĝen, a chapter in Antikvaj Filozofoj de Ĉinio [Ancient Philosophers of China] by Hoŭ Ĝjŭeljang, translated from the Chinese. Fan Zhen is labeled an atheist. He also opposed the putative law of karma and its justification for the existence of rich and poor. There is some detail in this short chapter of the Fan Zhen's ideas of the material basis of the "soul". Perhaps one day, in lieu of further sources in English, I will translate this chapter.
In the meantime, we can thank Esperanto as a bridge language from Chinese culture, and we can enroll Fan Zhen as a hero in the annals of freethought.