Current Search: Qiu, Shen-Li (x)
View All Items
(1 - 4 of 4)
- Title
- Characterization of some iron rich nickel-iron alloys.
- Creator
- Wang, Wei, Florida Atlantic University, Qiu, Shen-Li
- Abstract/Description
-
Characterization investigations were carried out for Ni-Fe alloys for three different concentrations of iron. The starting and ending temperatures of the fcc-bcc phase transformation both on heating and on cooling were obtained by measuring the resistance as a function of temperature; the results agree with previous work. We also measured the lattice constants of both structures by using a modified Debye-Scherrer method. For the fcc structure a is 3.5837 A, for the bcc structure a is 2.875 A,...
Show moreCharacterization investigations were carried out for Ni-Fe alloys for three different concentrations of iron. The starting and ending temperatures of the fcc-bcc phase transformation both on heating and on cooling were obtained by measuring the resistance as a function of temperature; the results agree with previous work. We also measured the lattice constants of both structures by using a modified Debye-Scherrer method. For the fcc structure a is 3.5837 A, for the bcc structure a is 2.875 A, and we noticed a decrease of the lattice constant as the iron concentration is increased. Auger electron spectroscopy was carried out for the purpose of studying the surface segregation and a concentration analysis was attempted. The results show that Ni is preferentially sputtered but an annealing process can overcome this segregation. Magnetic measurements show a change of magnetization with temperature though the data is insufficient to obtain the average moment.
Show less - Date Issued
- 1994
- PURL
- http://purl.flvc.org/fcla/dt/14996
- Subject Headings
- Ferromagnitism, Ferromagnetic materials, Alloys--Thermal properties
- Format
- Document (PDF)
- Title
- Photoemission studies of FeRh.
- Creator
- Zhao, Biao, Florida Atlantic University, Qiu, Shen-Li
- Abstract/Description
-
Characterization and photoemission investigations were carried on an equiatomic FeRh alloy. The starting and ending temperatures of the phase transition were obtained by resistivity measurements; the results agree with previous work. We also measured the lattice constant of FeRh using a diffractometer and a Debye-Scherrer camera. The results of both methods are the same. Auger electron spectroscopy was carried out to study the surface of the sample and a composition analysis was conducted....
Show moreCharacterization and photoemission investigations were carried on an equiatomic FeRh alloy. The starting and ending temperatures of the phase transition were obtained by resistivity measurements; the results agree with previous work. We also measured the lattice constant of FeRh using a diffractometer and a Debye-Scherrer camera. The results of both methods are the same. Auger electron spectroscopy was carried out to study the surface of the sample and a composition analysis was conducted. Synchrotron-based photoemission and XPS have been used to investigate the electronic structure in FeRh. The Fe 3s and Rh 4s core level spectra show that the local moments on both Fe and Rh sites in FeRh alloy remain unchanged upon the phase transition from the antiferromagnetic (AF) to ferromagnetic (FM) states. The shifts of Fe 3s and Fe 3p core levels are large, while shifts of Rh 4s and Rh 4p core levels are very small. We discuss four possibilities why we do not observe the expected line-shape change of the Rh 4s core level.
Show less - Date Issued
- 1997
- PURL
- http://purl.flvc.org/fcla/dt/15428
- Subject Headings
- Iron-rhodium alloys, Photoemission
- Format
- Document (PDF)
- Title
- An experimental study of LEED and UPS on bombarded and vacuum cleaved zinc(0001) surfaces.
- Creator
- Liu, Yu, Florida Atlantic University, Jordan, Robin G., Qiu, Shen-Li
- Abstract/Description
-
Several Zn single crystals were grown by the Bridgman method and their orientations were determined by the Laue X-ray back-reflection method. Zn(0001) surfaces were prepared by vacuum cleaving and by Ar+ bombardment with annealing. LEED patterns and UPS spectra were taken on both the cleaved and bombarded Zn(0001) surfaces. The LEED patterns from cleaved surfaces showed 6-fold symmetry whereas those from bombarded surfaces showed a hexagonal array but with some differences: the spots with the...
Show moreSeveral Zn single crystals were grown by the Bridgman method and their orientations were determined by the Laue X-ray back-reflection method. Zn(0001) surfaces were prepared by vacuum cleaving and by Ar+ bombardment with annealing. LEED patterns and UPS spectra were taken on both the cleaved and bombarded Zn(0001) surfaces. The LEED patterns from cleaved surfaces showed 6-fold symmetry whereas those from bombarded surfaces showed a hexagonal array but with some differences: the spots with the same distances from the center of LEED pattern had different intensities and they were dimmer and more blurry compared to those from the cleaved surface. A value of 2.64+-0.07 A for the nearest neighbor spacing was determined from the LEED patterns. The UPS spectra showed that for both types of surfaces the 3d peak is at 9.8 eV with a spin splitting of 0.7 eV, which are in agreement with previous experimental and theoretical results. Differences in spectra between the two types of surfaces were found in the ratios of signal/background and in the ratios of the 3d doublet.
Show less - Date Issued
- 1996
- PURL
- http://purl.flvc.org/fcla/dt/15304
- Subject Headings
- Metal crystals, Engineering, Materials Science, Low energy electron diffraction, Photoelectron spectroscopy
- Format
- Document (PDF)
- Title
- The copper local density of states in equi-atomic copper-gold.
- Creator
- Dorsey, Anthony Travis., Florida Atlantic University, Jordan, Robin G., Qiu, Shen-Li
- Abstract/Description
-
We attempted to isolate the individual Cu and Au contributions to the local density of states in equi-atomic CuAu using photoemission measurements with synchrotron radiation over the range 21 to 160eV. We compared our experimentally measured Au-5d/Cu-3d photoemission cross sections ratio with those of Yeh and Lindau (Atomic Data Nucl. Data Tables 32, 1, (1985)) and of Shirley et al (Physica Scripta 16, 398, (1977)) and found agreement with the former, suggesting difficulty in extracting the...
Show moreWe attempted to isolate the individual Cu and Au contributions to the local density of states in equi-atomic CuAu using photoemission measurements with synchrotron radiation over the range 21 to 160eV. We compared our experimentally measured Au-5d/Cu-3d photoemission cross sections ratio with those of Yeh and Lindau (Atomic Data Nucl. Data Tables 32, 1, (1985)) and of Shirley et al (Physica Scripta 16, 398, (1977)) and found agreement with the former, suggesting difficulty in extracting the Au local density of states. Hence, while others have suggested it is possible to isolate the Au local density of states at 50eV using similar methods, we found we could not. The density of states calculation and the photocurrent calculations at 50eV confirmed this by showing significant overlap of the Au and Cu states. Since the Au-5d states experience a Cooper minimum around 160eV, the experimental spectrum of CuAu at this photon energy contains very little Au contribution, thus allowing us to "experimentally determine" the Cu local density of states. The photocurrent calculations at 160eV confirmed the lack of Au contribution and comparison of experimental spectra with the photocurrent calculations at 160eV showed good agreement.
Show less - Date Issued
- 1993
- PURL
- http://purl.flvc.org/fcla/dt/14960
- Subject Headings
- Photoemission, Order-disorder in alloys
- Format
- Document (PDF)
