Li Fanghua
Li Fanghua | |
|---|---|
| Born | 1932-01-06 Hong Kong |
| Died | 2020-01-24 |
| Nationality | Chinese |
| Occupation(s) | Physicist, crystallographer |
| Known for | High-resolution electron microscopy, electronic crystallography, crystal structure analysis |
| Notable work | Electronic Crystallography and Image Processing (2009) |
Li Fanghua (; 6 January 1932 – 24 January 2020) was a physicist born in Hong Kong with Chinese nationality. She held memberships in the Chinese Academy of Sciences, The World Academy of Sciences, and the International Union of Crystallography. Li also took on leadership roles as director of both the Chinese Society of Physics and the China Union of Crystallography. Additionally, she contributed as an editor to several journals, including the Journal of Chinese Electron Microscopy Society, J. Electron Microscopy, Chinese Physics Letter, and Chinese Journal of Physics.
In 2003, Li was honored with the L'Oréal-UNESCO Awards for Women in Science. She was proficient in multiple languages: English, French, German, Japanese, and Russian.
Early years
Born in Hong Kong in 1932, Li Fanghua’s father, Li Jiong, was a former major general in the Fourth Army of the National Revolutionary Army and had participated in the 1911 Revolution. He also managed business ventures in Hong Kong.
- Following the Lugouqiao Incident in 1937, her family moved to Deqing County, Guangdong to escape the advancing Japanese forces.
- In 1938, her mother returned to Hong Kong with Li and her siblings to continue their education. The family later relocated first to Shanghai and then to Beijing, where Li attended Beijing No. 56 Middle School.
- By 1947, Li had moved back to Guangzhou with her mother and enrolled at Peidao Girls’ High School through her father’s arrangements.
Studies and research
Li Fanghua began her higher education in 1949 at the Department of Physics at Lingnan University, while also gaining admission to the Department of Astronomy at Sun Yat-sen University. Due to frequent class interruptions and political unrest at Sun Yat-sen University, she sought a more stable academic setting.
- In 1950, she transferred to the Department of Physics at Wuhan University.
- In 1952, selected by government authorities for study abroad, she first attended the Preparatory Department at Beijing Russian Language School before enrolling at Leningrad University's Department of Physics in the Soviet Union. She advanced directly into her second year to reduce study duration.
- Under mentors Mi. Asia and Rums (М.Α.Яумшь), she completed a graduation thesis titled "Electron Diffraction of In-situ Evaporated Bismuth Metal Thin Films".
- She graduated from Leningrad University’s Department of Physics in 1956.
- In 1960, under the arrangement of Shi Ruwei from the Chinese Academy of Sciences, Li spearheaded independent electron diffraction studies aimed at applying Soviet scientific techniques domestically, concentrating on "Single crystal electron diffraction" for structural investigations.
- Between October 1982 and May 1983, she served as a visiting scholar at Osaka University's Department of Applied Physics, introducing new mineral specimens from China for advanced electron microscopy examinations.
Honors and awards
- 1984: Awarded second prize by the Chinese Academy of Sciences Scientific and Technological Achievement Award for work on "The establishment of lattice image and direct observation of crystal structure".
- 1991: Received the Ye Qisun Physics Prize from the Chinese Physical Society.
- 1992: Honored with the Hashimoto First Jiro Award by the Chinese Society of Electron Microscopy.
- 1993: Became an academician of the Chinese Academy of Sciences.
- 1996–2000: Served as chairman of the Chinese Society of Electron Microscopy.
- 1998: Elected as an academician of The World Academy of Sciences.
- 2002: The journal Ultramicroscopy dedicated a special issue to commemorate her 70th birthday.
- 2003: Recognized as the first Chinese laureate of the L'Oréal-UNESCO For Women in Science Awards.
- 2009: Received the He Liang He Li Foundation Science and Technology Progress Award; also published her monograph titled Electronic Crystallography and Image Processing.
Personal life
Li was married to physicist Fan Haifu.
Main achievements
In 1985, Li Fanghua introduced a practical approximate analytical formula for high-resolution image intensity, formulated a theory of image contrast, and resolved the theoretical foundation for electronic crystallographic image analysis. Her contributions propelled advancements in related fields and supplied essential crystal structure information for novel materials, facilitating deeper insights into their properties, structures, and technological applications. Her research highlights include:
High-resolution electron microscopy and electronic crystallography
During the early 1960s, Li was a pioneer in electron diffraction techniques within China to analyze single crystal structures, achieving the nation's first determination of hydrogen atom locations in crystals. This pioneering work continues to be widely referenced internationally.
In the 1970s, in collaboration with Fan Haifu, she integrated diffraction approaches with high-resolution electron microscopy, establishing innovative theories and technologies for image processing. Subsequently, she and her students developed an unwinding processing method based on maximum entropy principles, allowing for accurate crystal structure determination in materials such as high-temperature superconductors.
While working in Japan during the 1980s, Li devised new experimental guidelines and techniques for identifying light atoms. Upon returning to China, she introduced the "pseudo-weak phase object approximation" theory of image contrast, elucidating the connection between image intensity and crystal thickness. This theory became foundational for advanced image processing methods and facilitated the first experimental detection of lithium atoms in crystals. Additionally, she contributed to early high-resolution electron microscopy investigations of high-temperature superconductors and was among the first worldwide to report modulation structures in bismuth-based superconductors.
Quasi-crystal
Li's research group was the first to discover and theoretically interpret the nearly continuous transformation between quasicrystals and conventional crystals. By employing phase sub-strain fields, she derived formulas that link quasicrystalline and crystalline structures and introduced novel approaches to determine quasicrystal configurations and local phase sub-strain fields. These techniques were effectively applied to Al-Cu-Li and Al-Mn-Si quasicrystals.
Crystal defects
In the advancement of field emission electron microscopy, Li Fanghua led efforts in atomic-scale characterization of crystal defects. She successfully identified a 60-degree dislocation at the interface of SiGe/Si epitaxial films as comprising two partial dislocations of 90 and 30 degrees separated by a stacking fault. This represented the first atomic-resolution identification of defects at the SiGe/Si epitaxial interface.