Xiu Hua Chen

Preparation of Porous Silica Microspheres by Polymerization-Induced Colloid Aggregation Method

The UF resin/SiO2 composites microspheres with particle size of 2μm were successfully prepared by polymerization of silica sol from base-catalyzed hydrolysis of tetraethyl orthosilicate, and urea-formaldehyde via the PICA approach, and then calcination in air to remove organic UF resin and yield porous silica microspheres. The samples were characterized by Zetasizer NanoZS Instrument, SEM and Nitrogen adsorption-desorption isotherms. The results showed that the synthesized porous silica microspheres with a BET surface area of 67.01m2/g, a BJH average pore size diameter of 37.32 nm and a total pore volume of 0.69cm3/g, respectively.

Anode-Supported LSGM Films Prepared by Slurry Spin Coating

La0.9Sr0.1Ga0.8Mg0.2O2.85 (LSGM) electrolyte films were successfully prepared by slurry spin coating method on porous La0.7Sr0.3Cr0.5Mn0.5O2.75 (LSCM) anode substrates. Ethyl celluloses content, coating cycles for slurry spin coating on the fabrication LSGM electrolyte films were investigated. The compatibility between LSGM and LSCM powders, microstructures and electricity conductivity of fabricated LSGM films were examined using XRD, SEM and electrochemical workstation. The film with good apparent morphology and electrical conductivity were obtained when the operating parameters were setted as the content of ethyl cellulose 10wt%, and the coating cycles 5.

Preparation of La0.9SR0.1Ga0.8Mg0.2O3-δ Electrolyte Films Deposited by RF Magnetic Sputtering

La0.9Sr0.1Ga0.8Mg0.2O3-d (LSGM) electrolyte materials were synthesized using solid state reactions. The LSGM material film was deposited by radiofrequency magnetic sputtering on La0.7Sr0.3Cr0.5Mn0.5O3-d (LSCM) substrates. The analysis results show the films did not form but formed some “mountains” when deposited for 4 h. While the depositing time extended to 12 h, a dense and uniform film with perovskite phase was obtained, and the element amounts of the film were closed to those of the LSGM materials.

Preparation and Optical Properties Research on Graphene Quantum Dots

In this work, graphene quantum dots were simply and rapidly prepared by thermal decomposition of citric acid. The resulting graphene quantum dots shows good dispersion and high crystallinity, the sizes can be effectively adjusted by controlling the temperature of decomposition. The results indicate that with the increase of temperature, the size of GQDs increased from 2 nm to 12 nm. The effect of the size of graphene quantum dots on the optical properties were carefully studied. Based on the optical properties and electrochemical results, the HOMO and LUMO value of GQDs with different sizes were obtained and the band gap becomes smaller from 3.36 eV to 2.87 eV with the increase of size of GQDs, which provides a potential application in the field of optoelectronic devices.

Nucleation of Multicrystalline Silicon during Directional Solidification

In this work, directional solidification was performed for multicrystalline silicon (mc-Si) ingot casting. The initial nucleation at the bottom of the silicon melt could be controlled by changing the cooling rate from 9 to 20μm/s. Metallographic microscope, X-Ray Diffraction (XRD), Microwave photoconductivity decay meter (μ-PCD) and four-point probe resistivity tester were used to investigate the microstructure, crystal orientation and electrical properties of the mc-Si ingots. The obtained results showed that cooling rate at 17μm/s is the optimum condition for the mc-Si ingots casting, under which the prepared ingot has lower dislocation density of 6×10-3 cm-2, better electrical properties, more uniformer resistivity distribution with an average value of 0.68 Ω×cm and higher minority carrier lifetime with a maximum value of 1.8 μs than that of in the other cooling rate conditions.

Research on LSCMCo-CDC Composites as Improved Anode Material for IT-SOFC

La1-xSrxCr1-yMnyO3-δ(LSCM) has unique advantages over the traditional anodes for it’s stability and high catalytic activity being an anode of solid oxide fuel cell(SOFC). Doped cerium material and Co element are used to improve the conductivity both in oxidative and reductive conditions. La0.7Sr0.3Cr0.5Mn0.5-xCoxO3-δ-Ce0.8Ca0.2O2(LSCMCo-CDC) composite anode materials are synthesized in one-step by glycine nitrate process(GNP). X-ray diffraction patterns(XRD), scanning electron microscopy(SEM) and energy dispersive X-ray spectroscopy(EDS) are used to characterize the powders. The conductivity of LSCMCo-CDC increases with increasing the quantity of Co when the temperature is above 750°C, and the maximum values are 10.5 Scm-1 and 0.7 Scm-1 of LSCMCo0.15-CDC at 800°C in air and H2 atmosphere, respectively. It’s conductivity in intermediate temperature have been promoted obviously comparing to that of LSCM-CDC and LSCMCo. Good chemical compatibility between LSCMCo-CDC and La0.9Sr0.1Ga0.8Mg0.2O3-δ(LSGM) is confirmed by XRD results.

The Effect of Calcination Temperature on Electrochemical Performance of Porous LaMnO3 Catalyst in Al-Air Battery

This study focuses on the development of the pervoskite catalyst for aluminum-air battery. The catalyst powders of porous pervoskite LaMnO3 were prepared by template method with different calcination temperatures. Material characteristics of prepared samples were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and thermalgravimetry (TG). The half-cell polarization curves and cyclic voltammetry curves were found to be strongly depended on the calcination temperature. The result showed the optimized calcination temperature was 650°C. The full-cell discharge test in NaCl solution (3.5 wt%) with a constant discharge current of 10 mA/cm2 was performed at room temperature, and the discharge voltage of sample synthesized under optimized calcination temperature was 0.73 V.

Electroless Deposition of NiMoB Diffusion Barrier Layer Film for ULSI-Cu Metallization

NiMoB alloy films were deposited on silicon substrate by electroless deposition for diffusion barrier application in copper interconnects technology. NiMoB(40nm)/SiO2/Si and NiMoB(20nm)/Cu (40nm)/NiMoB(40nm)/SiO2/Si samples were prepared and annealed at temperatures ranging from 400◦C to 600◦C. Samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Four Point Probes (FPP) and Atomic Force Microscopy (AFM) to investigate the phases, composition, sheet resistance and surface morphology. The results showed that electroless deposited NiMoB film can be used as an effective Cu diffusion barrier layer until 500◦C. And the failure mechanism is that NiMoB crystallized and grains grew after annealing at high temperature, a large number of Cu grains passed through NiMoB film via grain boundaries and then reacted with Si substrate and oxygen, causing the generation of highly resistive Cu4Si and CuO.

Research on Preparation of Porous Silicon Powders from Metallurgical Silicon Material

Stain etching, one step metal assisted chemical etching (1-MACE) and two-step metal assisted chemical etching (2-MACE) were used for preparing porous silicon powders (PSPs) based on metallurgical silicon powder. The influences of different oxidants species and concentrations on the structure of PSP were discussed. The results indicated that the different oxidant species has an important effect on the morphology and structure of PSP. In stain etching, there is still a challenge for fabricating PSP with uniform and controlled pore size structure. In contrast, metal-assisted chemical etching method is easier to prepare PSPs sample with uniform depth and pore size than stain etching, In 1-MACE, the growth rate of the PSPs pore was between 0.05 and 0.10 μm/min, which is far less than that of 2-MACE (about 0.2~0.5 μm/min). Furthermore, 2-MACE showed more advantages than stain etching and 1-MACE in controlling of pore size range and structure.

Electroless CoMoB Diffusion Barrier Layer for ULSI-Cu Metallization

CoMoB film was prepared on Si substrate via electroless deposition as the diffusion barrier for ULSI-Cu metallization. Annealing experiments of CoMoB(30nm) film and CoMoB(10nm)/Cu (40nm)/CoMoB(30nm)/SiO2/Si multi-films were carried out in the temperature range from 400◦C to 700◦C. Failure temperature and mechanism of Cu diffusion in CoMoB film were discussed. The composition, sheet resistance and morphology of the film were investigated by X-Ray Diffractometer (XRD), Four Point Probe (FPP) and Atomic Force Microscopy (AFM), respectively. It can be concluded that the failure temperature of CoMoB film is 600◦C. The main reason of failure is that a large number of Cu particles passed through CoMoB grain boundary and reacted with Si substrate to generate Cu4Si with high resistance.