Papers by Keyword: Film

Abstract: TiO₂ thin films with a thickness of about 150 nm were deposited by spin coating method on sapphire substrate from a sol-gel system. The hydrogen sensing properties of TiO₂ films annealed at various temperatures were studied and correlated with their structure, optical and electrical properties. The annealing temperatures in the range of 600 800 °C lead to anatase films with a roughness in the range of 0.6 0.9 nm. Their sensitivity towards hydrogen is low. The thin films annealed at temperatures in the range 900 1000 °C consist of rutile phase and their roughness increased to 11.7 13.5 nm. They showed good hydrogen sensitivity with optimal operating temperature 200 250 °C. The structure and sensing properties of the prepared films are compared with those synthesized with magnetron sputtering. The maximum of sensitivity was measured on the thin films with diameter of the grains about 100 nm in both cases, i.e. on thin films prepared by sol-gel method as well as on thin films prepared by magnetron sputtering. The maximum sensitivity correlates with the diameter of the grains and dont depend on the allotropy of the titanium dioxide anatase or rutile.

Abstract: Hydroxyapatite (HA) is a leading biocompatible material extensively used for bone implants as a porous ceramic graft and as a bioactive coating. Electrical characteristics of HA can be employed in implantable devices for real-time in vivo pressure sensor applications such as in knee or hip prosthesis. In particular, high piezo and pyroelectricity of HA, its polarisation by electron beam and selective adsorption of proteins on polarised domains indicate the potential for real-time biosensing applications of HA. For this purpose, a comprehensive understanding of the dielectric behaviour of different forms of HA over a frequency range relevant for biomedical sensing is critical. Such information for HA, especially its frequency dependent dielectric behaviour over the GHz range, is rare. To this end, we report on novel investigations of properties of HA in powder and film forms in the GHz frequency range.

Abstract: The effects of isothermal aging and the thermal cycling loading on the shear toughness of different solder materials and ball sizes have been explored. The difference between shear toughness values of traditional Sn/37Pb eutectic solder ball joints and the lead free Sn/3.0Ag/0.5Cu solders are chosen for discussion. The experiment measurements under the ball shear test (BST) have been compared and studied for both solder joints. The fracture behaviors of the solder joints under the high temperature aging and thermal cycling testing are examined by scanning electron microscope (SEM). The variation of shear toughness of different ball joints reveals that the high temperature aging and thermal cyclic loading reduce the shear toughness significantly. The measured shear toughness values indicate that the Sn/3.0Ag/0.5Cu solder joints have better ductility for the joints undergoing the high temperature aging and the thermal cycle loadings. Based on the measured results, the better reliability for the Sn/3.0Ag/0.5Cu ball joints is expected, due to the aging and cycling load testing.

Abstract: To study the effects of substrate materials on the photocatalytic activity, TiO₂ films were immobilized on the inner wall surface of ceramic, glass and stainless steel tubes by sol-gel method. X-ray diffraction (XRD) results indicated that the crystal form of TiO₂ were all anatase type with theoretical particle size of 15 nm. According to the X-ray photoelectron spectroscopy (XPS) results, appearance of the element Na was observed which would decrease the photocatalytic activity. Scanning electron microscope (SEM) photos showed that the film coating on the ceramic and glass were even and uniform with thickness of about 300 nm and practical particle size of 20 nm to 100 nm. However, the film coating on stainless steel was hackly which would lead to diffraction of lights. The degradation rate constants of methylene blue (MB) with initial concentration of 5 mg.L^-1 were 0.049 min^-1、0.029 min^-1 and 0.023 min^-1 with films coating on ceramic, stainless steel and glass tubes respectively. Degraded with TiO² film coating on ceramic tube, the according rate constants of phenol were 0.37, 0.14, 0.04 and 0.02 min^-1 for initial concentration of 2, 10, 50 and 100 mg.L^-1 respectively.

Abstract: Bi0.9Nd0.1FeO3 (BNFO) films were deposited on Si (100) and (La,Sr)(Al,Ta)O3 (100) (LAST) substrate by radio frequency (RF) magnetron sputtering method respectively. The structure，morphology and magnetic properties were studied. X-ray diffraction (XRD) result indicates that the BNFO films on different substrate adopted different orientation. Cross-section scanning electron microscopy shows that the film thickness is 145 nm．Magnetic properties measurement shows that the film on Si(100) substrate has the larger saturation magnetization (Ms) of 3 686 emu/cm3, while the Ms value of the BNFO films on LSAT(100) substrate is only 1 213 emu/cm3.

Abstract: A new kind of two phase ammonium dihydrogen phosphate (NH₄H₂PO₄ or ADP)/polyvinyl alcohol (PVA) composite films have been prepared by solution cast technique. Significant enhancement of dielectric permittivity (~442) of ADP/PVA composites are observed at low ADP concentration (f_ADP f_C ~5 wt %) which is the percolation threshold value estimated from the concentration dependent transport and dielectric data. Nearly 85 times increase in dielectric permittivity compared to that of the bare PVA film in the composite film around f_C with low loss (~0.14) at 1 kHz and room temperature is observed. The present ADP based PVA composite material might be processed for application in devices.

Abstract: The nucleation and growth model of Bi₂Te_3-ySe_y film on indium tin oxide-coated glass substrates from an aqueous acidic electrolyte at room temperature were studied using cyclic voltammetry, chronopotentiometry and field emission scanning electron microscope. The electrodeposition process was irreversible and controlled by diffusion, with a limiting current density of 1.78 mA/cm². When the deposition current density was lower than the value or above the value but with agitation, the formation and growth of the film were controlled by instantaneous nucleation and gradually growth process, and homogeneous film was formed. While when the current density was larger than the value without agitation, flocculent film was obtained. Bi₂Te_3-ySe_y film deposited at 4 mA/cm² with agitation showed smoother morphology compared with the film deposited at 1 mA/cm². The electrical conductivity and Seebeck coefcient of the two Bi₂Te_3-ySe_y films were measured after being transferred onto a non-conductive rubberized fabric support. Both the films showed n-type conduction, and the former showed higher electrical conductivity and power factor.

Abstract: The thermal stability of polypropylene (PP) based cellular electromechanical films was improved by compounding PP with thermally more durable cyclo olefin copolymer (COC) and polyhedral oligomeric silsesquioxane (POSS) nanochemical. The cast films were biaxially oriented in laboratory scale and then expanded by a gas diffusion expansion method, which increased the pore size inside the cellular film structure and the thickness of the film. The cellular films were then electrostatically charged by a contact charging method and metallized by gold sputtering. The samples were aged at 85°C showing that the d33 signal decreased from the original value, but remained at high level; more than 120 pC/N even after two weeks of ageing.

Abstract: Tourmaline has characteristics of repeatedly producing electric dipole polarity transformation. Using FTO glass substrate coated with conductive films as raw materials, the research aims to prepare functional glass materials, which have spontaneous polarization effect, absorption of wideband electromagnetic radiation and high visible light transmittance. This paper applied Magnetron Sputtering deposition technique, studying on tourmaline as target, sputtering on conductive FTO glass, using multiple means to measure and analyze the surface morphology, component, structure, electrical and magnetic properties. And the functions of tourmaline as composite electromagnetic shielding films are also discussed in the paper.

Abstract: Er₂O₃-doped bismuth titanate (Bi_4-xEr_xTi₃O₁₂, BET) and pure Bi4Ti3O12 (BIT) thin films with random orientation were fabricated on Pt/Ti/SiO₂/Si substrates by rf magnetron sputtering technique. These samples had polycrystalline Bi-layered perovskite structure without preferred orientation, and consisted of well developed rod-like grains with random orientation. Er-doping into BIT caused a large shift of the Curie temperature ( TC ) from 675°C to lower temperature and a improvement in dielectric property. The experimental results indicated that Er doping into BIT also result in a remarkable improvement in ferroelectric property. The Pr and the Ec values of the BET film with x=0.75 were 21 μC/cm² and 80 kV/cm, respectively.