Zhi-Quan Liu

Micro-sized and Nano-sized Fe3O4 Particles as Anode Materials for Lithium-ion Batteries

Micro-sized (1030.3 +/- 178.4 nm) and nano-sized (50.4 +/- 8.0 nm) Fe(3)O(4) particles have been fabricated through hydrogen thermal reduction of alpha-Fe(2)O(3) particles synthesized by means of a hydrothermal process. The morphology and microstructure of the micro-sized and the nano-sized Fe(3)O(4) particles were characterized by X-ray diffraction, field-emission gun scanning electron microscopy, transmission electron microscopy and high-resolution electron microscopy. The micro-sized Fe(3)O(4) particles exhibit porous structure, while the nano-sized Fe(3)O(4) particles are solid structure. Their electrochemical performance was also evaluated. The nano-sized solid Fe(3)O(4) particles exhibit gradual capacity fading with initial discharge capacity of 1083.1 mAhg(-1) and reversible capacity retention of 32.6% over 50 cycles. Interestingly, the micro-sized porous Fe(3)O(4) particles display very stable capacity-cycling behavior, with initial discharge capacity of 887.5 mAhg(-1) and charge capacity of 684.4 mAhg(-1) at the 50th cycle. Therefore, 77.1% of the reversible capacity can be maintained over 50 cycles. The micro-sized porous Fe(3)O(4) particles with facile synthesis, good cycling performance and high capacity retention are promising candidate as anode materials for high energy-density lithium-ion batteries.

Memory antibacterial effect from photoelectron transfer between nanoparticles and visible light photocatalyst

A novel visible light photocatalyst system was developed, consisting of palladium oxide (PdO) nanoparticles well dispersed on a nitrogen-doped titanium oxide (TiON) matrix. Clear evidence of photoelectron transfer between PdO nanoparticles and the TiON matrix was obtained for the first time. The optoelectronic coupling between PdO and TiON introduces enhanced photocatalytic bacterial disinfection under visible light illumination by electron trapping on a PdO nanoparticle, and a unique catalytic memory effect on bacterial disinfection due to the discharging of trapped electrons on PdO nanoparticles in the dark when the illumination is switched off. Thus, a unique robust catalytic disinfection system is created, which is driven by solar/visible light illumination, enables the continuous operation in day and night, and could be adapted to a broad range of environmental applications.

Low Temperature Sintering Cu6Sn5 Nanoparticles for Superplastic and Super‐uniform High Temperature Circuit Interconnections

Brittle intermetallics such as Cu6 Sn5 can be transformed into low cost, nonbrittle, superplastic and high temperature-resistant interconnection materials by sintering at temperatures more than 200 °C lower than its bulk melting point. Confirmed via in situ TEM heating, the sintered structure is pore-free with nanograins, and the interface is super-uniform.

Synthesis of Single-Crystal TiO2 Nanowire Using Titanium Monoxide Powder by Thermal Evaporation

TiO2 nanowires were synthesized successfully in a large quantity by thermal evaporation using titanium monoxide powder as precursor. X-ray diffraction results showed that all the products were pure rutile phase of TiO2. According to microstructural observations, the nanowires have two typical morphologies, a long straight type and a short tortuous type. The straight nanowires were obtained at a wide temperature range of 900-1050 degrees C, while the tortuous ones were formed below 900 degrees C. Transmission electron microscopy characterization revealed that both the straight and the tortuous nanowires are single-crystal rutile TiO2. The preferential growth direction of the nanowires was determined as [110] orientation according to electron diffraction and high-resolution image analyses. The morphological change of TiO2 nanowires was discussed by considering the different atomic diffusion rates of Ti atoms caused by the phase transformation in Ti substrate at around 900 degrees C.

Microstructure and Phase Stability Studies on Heusler Phase Ni2AlHf and G-phase Ni16Hf6Si7 in Directionally Solidified NiAl–Cr(Mo) Eutectic Alloyed with Hf

Small additions of Hf to directionally solidified NiAl-Cr(Mo) eutectic resulted in precipitation of a high density of Heusler phase Ni2AlHf along with fine G-phase Ni16Hf6Si7. The Heusler phase was mainly located on the grain boundary region. The fine G-phase formed in the presence of Si, which was a contamination resulting from contact with ceramic shell molds during directional solidification of the alloy. These fine G-phases were cuboidal in shape and coherent with the NiAl matrix. After hot isostatic pressing and aging treatment, the fine G-phases completely disappeared. The density of the Heusler phase was partially reduced, and the Heusler particles precipitated preferentially on the NiAl/Cr(Mo) interfaces and grain boundaries of the NiAl matrix. Some Heusler particles precipitated locally within the NiAl matrix, and small amounts of them precipitated within the Cr(Mo) phase. The structures of the NiAl/Ni2AlHf and NiAl/Ni16Hf6Si7 interfaces were investigated by high-resolution electron microscopy. The habit plane of the fine G-phase was {001}(NiAl). This result was in good agreement with calculation based on the linear elastic theory. The misfit dislocation network on the NiAl/Ni2AlHf ((1) over bar 10) interface was calculated from the O-lattice model and compared with the observation, which showed good agreement.

A dynamic Monte Carlo study of the in situ growth of a substance deposited using electron-beam-induced deposition

The in situ growth of a deposit in electron-beam-induced deposition (EBID) was studied by dynamic Monte Carlo simulation, showing first the preferential growth of deposit along the incident direction of the electron beam. The effects of electron energy, probe size, substrate thickness, and deposit (or substrate) composition on EBID were investigated and discussed, considering the electron scattering of not only secondary electrons but also primary and backscattered electrons in solids. By including the depositions at not only the top but also the bottom surfaces of the substrate, the growth model of the deposit in EBID was modified. Concerning the resolution of EBID, a small lateral size can be achieved on the deposit (or substrate) containing light atoms using a high-energy electron beam with a fine probe size.

Intermetallic compound identification and Kirkendall void formation in eutectic SnIn/Cu solder joint during solid-state aging

Microstructural investigations were performed on the interfacial reactions between eutectic SnIn solder and Cu substrate during reflowing at 433 K and solid-state aging at 373 K. Cu2(In,Sn) was identified as the only intermetallic compound (IMC) at the interface, which consists of two sublayers with different morphology, a fine-grained sublayer at the Cu side and a coarse-grained sublayer at the solder side. During solid-state aging, voids were found between these two Cu2(In,Sn) sublayers but not at the substrate interface, which is also attributed to the Kirkendall effect considering the different diffusion fluxes of Sn or In and Cu atoms in different sublayers.

Fabrication and characterization of cellular iron nanocrystalline film

Cellular iron nanocrystalline film was fabricated on carbon substrate by electron beam chemical vapor deposition (EB-CVD). The film was made up of single alpha-iron cubes with {100} facets ranging from several tens to 200 nm. The thickness and distribution of the film could be controlled by adjusting the irradiation position and duration of the electron beam. The integration of well-faceted nanocrystals enables the film to have a high ratio of free surfaces, which are essential for applications in chemical catalysis and energy absorption. The application of this film as a substrate for further nanofabrication was demonstrated.

Fabrication and Investigation of Tungsten Deposit on Top and Bottom Surfaces of Thin Film Substrate

Electrons with energies of 20, 200, and 400 keV were used in electron-beam-induced deposition (EBID) to investigate deposition on both the top and bottom surfaces of a film substrate when an electron beam is injected into the top surface. Tungsten tips were successfully fabricated on the-bottom surface of the film substrate using 200 and 400 keV electrons. The microstructure as-deposited at a different electron energy,is a mixture of nanocrystallites and amorphous materials. The nanocrystallites of the structure deposited using 20 keV electrons (1-2 nm) were smaller than those of the structures deposited using 200 keV (2-4 nm) and 400 keV electrons (3-5 nm). The proportion of amorphous materials in the as-deposited structure was reduced using high-energy electrons. There was no difference in microstructure between the top and bottom tips simultaneously deposited on the film substrate using high-energy electrons.

First-principles Investigation of Bi Segregation at the Solder Interface of Cu/Cu3Sn(010)

in Cu3Sn slab was found to be the most energy-favored at an adhesion energy of 1.96 J/m 2 . Based on this construction, flve possible segregation sites were examined, and the most likely segregation site was determined with adhesion energy as low as 1.06 J/m 2 , which was almost half of the initial one. Comparing with other sites 0 adhesion energies, it was concluded that size efiect took a large part in embrittlement. The analyses of atomic structure and electronic density revealed that the slabs shifted away from interfaces due to bismuth segregation, and the atoms around Bi atom were pressed away. This calculated work agreed qualitatively with reported experimental results.