Zhong-Tao Jiang

Synthesis and characterisation of nanohydroxyapatite using an ultrasound assisted method.

Nanostructured hydroxyapatite (HAP) was prepared by a wet precipitation method using Ca(NO(3)) and KH(2)PO(4) as the main material and NH(3) as the precipitator under ultrasonic irradiation. The Ca/P ratio was set at 1.67 and the pH maintained at a minimum of 9. The temperature conditions and ultrasound influences were investigated using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and Fourier transform infrared spectroscopy (FT-IR). The results showed that Nano-HAP can be obtained by this method and the particles were achieved to around 30 nm.

Measurement and calculation of optical band gap of chromium aluminum oxide films

The optical band gap is a basic property of optical materials. The measured band gap depends not only on the material but also on its characteristics such as crystallinity and stoichiometry. The optical band gap of chromium aluminum oxide films was measured and calculated by three different methods. Firstly, we used the conventional experimental-graphical method, which is commonly used. However, this method is applicable only to an all-crystalline phase or an all-amorphous phase. The second one was an experimental-calculation method applicable to films composed of both crystalline and amorphous phases. We calculated the optical band gap between the highest occupied molecular orbital of O2p and the lowest unoccupied molecular orbital of Cr3d in Cr1.71Al0.29O3 films composed of both amorphous and crystalline phases. Also, a band gap for the d–d transition was obtained. Finally, the measured value was compared with the theoretical optical band gap calculated by the discrete variational-Xα (DV-Xα) method.

Investigation of the drying temperature dependence of the orientation in sol–gel processed PZT thin films

The crystal orientations of lead zirconate titanate (PZT) thin films have been investigated by using various drying temperatures in the sol–gel process. The films were dried at different temperatures between 310 and 350°C for pyrolysis and then were heat treated at 650°C using rapid thermal annealing (RTA). TG/DTA and FTIR spectroscopy were used to detect the remnants of organic materials in the thin films prior to the final heat treatment. In order to examine the relationship between the film orientation and the remaining organic materials for the prior and final heat treatment, the films were fabricated with different coating cycles and dried for different holding times and then annealed at 650°C. The preferred orientations were investigated using X-ray diffraction.

An In Situ Synchrotron Radiation Grazing Incidence X-Ray Diffraction Study of Carbon Dioxide Corrosion

An in situ surface study of the carbon dioxide corrosion of mild steel has been undertaken using the tandem technique of mixed potential/synchrotron radiation-grazing incidence X-ray diffraction (SR-GIXRD). Long-term monitoring of the mixed potential showed there was an initial shift toward cathodic potentials attributable to preferential suppression of the cathodic half-reaction (viz., the reduction of carbonic acid), probably due to the formation of an adlayer of corrosion product physically blocking the cathodic reaction sites during the uniform corrosion of mild steel. Subsequently, the mixed potential displayed a gradual shift to anodic potentials, symbolizing the preferential suppression of the anodic half-reaction as the primary corrosion products [viz., Fe2(OH)2CO3, Fe2O2(CO3), Fe6(OH)12(CO3), and Fe6(OH)12(CO3)·2H2O] acquired a sufficient thickness to physically block the interface against further corrosion. Nevertheless, the corrosion product continues to grow over time, indicating that the corrosion product is discontinuous and porous, allowing the ingression of electrolyte to enable the further corrosion of the mild steel. This research has important ramifications for the field of corrosion research; it should enable researchers to develop improved methods of chemical inhibition by using compounds that can actually bind to the newly postulated corrosion products on mild steel.

Effect of dilute gelatine on the ultrasonic thermally assisted synthesis of nano hydroxyapatite.

A series of nano hydroxyapatite-gelatine composites with different dilute solutions of gelatine concentrations were synthesized by a thermally assisted low-power ultrasonic irradiation method. The gelatine hydroxyapatite, (Gel-HAP) nanoparticles were prepared using Ca(NO(3))(2) and KH(2)PO(4) in the presence of gelatine in an aqueous solution. The synthesised products were heat treated between 100 and 400°C. The effect of the addition of gelatine on the nucleation and growth of synthesised nano HAP was investigated. Characterisation was performed using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and Fourier transform infrared spectroscopy (FT-IR). The characterisation results indicate that gelatine has been appended to the nano HAP forming regular spherical shaped crystals of nano sized Gel-HAP.

A critical role for Al in regulating the corrosion resistance of nanocrystalline Mo(Si1−xAlx)2 films

Novel nanocrystalline Mo(Si1−xAlx)2 films, with differing Al contents were synthesized by double cathode glow discharge. The films exhibited a compact columnar microstructure having a pronounced (111) preferred orientation. The corrosion behaviour of these films were characterized by using various electrochemical techniques including open circuit potential (OCP), potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS) in 3.5 wt% NaCl solution. The corrosion resistance of the films increased with increasing Al content in the as-synthesized films. The composition and chemical state of the passive layers formed on the films were investigated by X-ray photoelectron spectroscopy (XPS). It was demonstrated that the passive layer formed on the binary MoSi2 film was highly enriched in SiO2 with minor amounts of MoO42−, MoO2 and SiOx. With the increase of Al content in the films, Al2O3 was generated and incorporated into the passive layers, enhancing the corrosion resistance of the films by inhibiting the dissolution of Mo. Built upon the experimental results, the first-principles density-functional theory was applied to calculate the inter-atomic bonding strength in Mo(Si1−xAlx)2 and elucidate the role of Al in controlling the corrosion resistance of the films. The new findings lay a solid basis for the development and application of MoSi2 based corrosion-resistant films.

Possibility of Simultaneous Monitoring of Temperature and Surface Layer Thickness of Si Substrate by In Situ Spectroscopic Ellipsometry

The possibility of simultaneous monitoring of the temperature and the thickness of the surface layer of a crystalline silicon (c-Si) substrate by in situ spectroscopic ellipsometry (SE) is demonstrated using a surface adsorption layer (SAL) as an example. The model dielectric function (MDF) developed by Adachi and the tabular data of the dielectric function of fused silica were applied to a Si wafer and SAL, respectively. The best-fit curve has been obtained by fitting the measured \varPsi and Δ spectra simultaneously by adjusting the 12 MDF parameters and the thickness of SAL over the temperature range of 293–803 K. The best-fit MDF parameters indicate that the SAL thickness has almost no influence on the best-fit values of the MDF parameters. This fact can be used to monitor the temperature of a c-Si wafer independent of the thickness of surface layer by checking the shift of MDF parameters (e.g., E2) using the SE and the MDF. The measurement errors in thickness and temperature are roughly estimated to be 0.1 nm and less than 10 K, respectively.

Titanium oxide film for the bottom antireflective layer in deep ultraviolet lithography

Titanium oxide thin film, fabricated with tetraisopropyltitanate and oxygen by electron cyclotron resonance-plasma-enhanced chemical vapor deposition, is investigated as a potential candidate for the antireflective layer in KrF excimer laser (248-nm) lithography. The oxygen flow-rate dependence of the optical properties such as the refractive index (n) and the extinction coefficient (k) of the film at the 248-nm wavelength has been characterized, and the films with the expected combinations of n and k values for the antireflective layer have been deposited. Simulation results indicate that reflectance values of less than 4% and as low as 1.2% can be reached at the interface between the photoresist and the film postulating the structures of the photoresist/300-A TiO(x) film/c-Si substrate and the W-Si substrate, respectively, by selected proper combinations of n and k values. Moreover the reflectance can be further reduced to almost zero by changing the film thickness. Thus it is found that titanium oxide thin films can be used as the bottom antireflective layer in KrF excimer laser lithography.

Thermal Recycling of Brominated Flame Retardants with Fe2O3

Plastics containing brominated flame retardants (BFRs) constitute the major fraction of nonmetallic content in e-waste. Co-pyrolysis of BFRs with hematite (Fe2O3) represents a viable option for the thermal recycling of BFRs. Consensus of experimental findings confirms the excellent bromine fixation ability of Fe2O3 and the subsequent formation of iron bromides. This contribution provides a comprehensive mechanistic account of the primary reactions between a cluster model of Fe2O3 and major bromine-bearing products from the decomposition of tetrabromobisphenol A (TBBA), the most commonly deployed BFR. We estimate the thermo-kinetic parameters for interactions of Fe2O3 with HBr, brominated alkanes and alkenes, bromobenzene, and bromophenol. Dissociative addition of HBr at a Fe-O bond proceeds through a trivial barrier of 8.2 kcal/mol with fitted parameters in the Arrhenius equation of k(T) = 7.96 × 10(11) exp(-6400/RT) s(-1). The facile and irreversible nature for HBr addition to Fe2O3 accords with the experimentally reported 90% reduction in HBr emission when Fe2O3 interacts with TBBA pyrolysates. A detailed kinetic analysis indicates that, transformation of Fe2O3 into iron bromides and oxybromides occurs via successive addition of HBr to Fe(Br)-O(H) entities. Elimination of a water molecule proceeds through an intramolecular H transfer. A direct elimination one-step mechanism operates in the dehydrohalogenation of bromoethane into ethene over Fe2O3. Dissociative decomposition and direct elimination channels assume comparable reaction rates in formation of acetylene from vinyl bromide. Results from this study provide an atomic-based insight into a promising thermal recycling route of e-waste.

The Ag M5N45N45 Auger photoelectron coincidence spectra of disordered Ag0.5Pd0.5 alloy

An effect of disorder broadening (DB) on the Ag M5N45N45 Auger spectra in the random substituted Ag0.5Pd0.5 has been investigated by Auger photoelectron coincidence spectroscopy (APECS). Data were collected for the Ag M5N45N45 Auger line coincident with the Ag 3d5/2 photoelectron line (and its higher and lower binding energy sides). It is shown that the broadening of the Ag M5N45N45 line is directly associated with the presence of disorder broadening of the Ag 3d5/2 photoelectron line. The APECS experiment is used to demonstrate the broadening in a novel way.