Amorphous silicon carbide (a-SiC) thin films have been grown on aluminum nitride (AlN) intermediate layers on (100) Si substrates by RF magnetron sputtering technique. Profilometry, four-point probe method, Rutherford backscattering spectroscopy (RBS) and Fourier transform infrared (FTIR) were employed to characterize the as-deposited SiC thin films. Test structures have been developed to investigate the piezoresistive properties. These structures consist of SiC thin-film resistors on AlN/Si substrates defined by reactive ion etching (RIE) with Ti/Au pads formed by lift-off process. Gauge factor (GF) and temperature coefficient of resistance (TCR) measurements have been performed and demonstrated the potential of these resistors to be used as sensing elements in devices for high temperature application.

High quality single crystal boron-doped diamond films are deposited in a microwave plasma-assisted CVD reactor with feedgas mixtures including hydrogen, methane, diborane, and carbon dioxide at reactor pressures of 160 Torr. The effect of diborane levels and other growth parameters on the incorporated boron levels are investigated, and the doping efficiency is calculated over a wide range of boron concentrations. The boron level is investigated using infrared absorption, and compared to SIMS measurements, and defects are shown to affect the doping uniformity.

We designed and produced pure cubic zirconia (ZrO2) ceramic1coatings by an ion beam assisted deposition (IBAD) with nanostructurescomparable to the size of proteins. Our ceramic coatings exhibit highhardness and a zero contact angle with serum. In contrast to hydroxyapatite(HA), nano-engineered zirconia films possess excellent adhesion to allorthopaedic materials. Cell adhesion and proliferation experiments wereperformed with a bona fide mesenchymal stromal cell line (OMA-AD). Ourexperimental results indicate that the nano-engineered cubic zirconia issuperior in supporting growth, adhesion, and proliferation. Since cellattachment is mediated by adhesive proteins such as fibronectin (FN), toelucidate why cells attach more effectively to our nanostructures, weperformed a comparative analysis of adsorption energies of FN fragment usingquantum mechanical calculations and Monte Carlo (MC) simulation both onsmooth and nanostructured surfaces. We have found that a FN fragment adsorbssignificantly stronger on the nanostructured surface than on the smooth surface2.

Nanoporous gold (np-Au) is a promising nanostructured material with many desirable properties, including large surface area-to-volume ratio, corrosion resistance, high conductivity, and well-studied thiol-based surface chemistry. While np-Au has been used in a variety of applications, from fuel cells to electrochemical sensors, its interface with biology, where many of its exciting applications lie, is surprisingly non-existent. This paper reports on drug delivery from np-Au thin films for modifying cell proliferation in situ. We expect that establishing np-Au as a biomaterial with drug delivery capabilities will create new opportunities for engineering advanced BioMEMS devices that can monitor and modulate biological processes in both in vitro and in vivo settings.

Room temperature magnetic properties of un-doped, as well as 10 at.% Fe-doped ZnO and MgO single-pass layer of ink-jet printed thin films have been investigated to obtain insight into the role of the band gaps and mechanisms for the origin of ferromagnetic order in these materials. It is found that on doping with Fe, the saturation magnetization is enhanced by several-fold in both systems when compared with the respective un-doped thin films. For a “28 nm thick film of Fe-doped ZnO (Diluted Magnetic Semiconductor, DMS) we observe an enhanced moment of 0.465μB /Fe atom while it is around 0.111μB/Fe atom for the doped MgO (Diluted Magnetic Insulator, DMI) film of comparable thickness. Also, the pure ZnO is far more ferromagnetic than pure MgO at comparable low film thicknesses which can be attributed to defect induced magnetism originating from cat-ion vacancies. However, the film thickness dependence of the magnetization and the defect concentrations are found to be significantly different in the two systems so that a comparison of the magnetism becomes more complex for thicker films.

Synthesis of both p-type and n-type oxide semiconductors is required to develop oxide-based electronic devices. Tin monoxide (SnO) recently has received increasing attention as an alternative p-type oxide semiconductor because it is a simple binary compound consisting of abundant elements. Another phase of the tin oxygen system, SnO2, is of great technological interest as transparent electrodes and as heat-reflecting filters. The preparation of tin oxide thin films has been performed by many different procedures. Radio-frequency (RF) ion-thrusters, as designed for propulsion applications, are also qualified for thin film deposition and surface etching, because different gas mixtures, extraction voltages and RF power can be applied. Tin oxide thin films were grown by ion beam sputtering (IBS) using a 3” metallic tin target. Different aspects of the thin film growth and properties of the tin oxide phases were investigated in relation to flux of oxygen fed into the gas discharge in the ion thruster. Results on thin film growth by IBS will be presented, structural, vibrational and optical properties of the films will be discussed.

We have investigated the hexagonal graphene network (GNW) structure for the possible opening of the graphene bandgap. We have fabricated GNW by nanoimprint lithography and compared with previous GNW results based on electron beam (EB) lithography. Hall-bar device with GNW was successfully fabricated using nanoimprint lithography and verified mobility of 1,220 cm2 V-1 s-1 with graphene nanoribbon (GNR) width of 40 nm. The mobility improvement compared with GNW by EB lithography indicates the effectiveness of nanoimprint method for the hexagonal GNW approach.

The effect of phase separation of the donor-acceptor (DA) blend on the dominant recombination mechanism in polymer-fullerene [(poly(3-hexylthiophene) (P3HT) and phenyl-C61-butyric acid methyl ester (PCBM)] based bulk heterojunction (BHJ) cells has been investigated. Coarse (70-150 nm) and fine (20-25 nm) phase separated blends and corresponding devices were prepared using chlorobenzene (CB) and ortho-dichlorobenzene (1,2-DCB) as spin casting solvents respectively. Nanoscale mobility measurements indicated highly unbalanced charge transport in coarse morphology based (CB cast) devices. Linear dependence of short circuit current (Jsc) vs. light intensity (I) suggested first order monomolecular (MR) recombination in the fine phase separated devices (1,2-DCB cast) whereas sub-linearity suggested dominant role of bimolecular (BR) recombination in coarse phase separated devices (CB cast). Improved device efficiency of 1,2-DCB based devices (η ≈ 2.54 %) compared to CB (η ≈ 0.9 %) may be attributed to reduced BR recombination as a result of finer phase separation.

Mesoporous TiO2 nanoparticle assemblies have been synthesized via a surfactant-assisted aggregating process. The products feature a three-dimensional network of interconnected anatase-TiO2 NPs with large internal BET surface area (ca. 142–152 m2g-1) and uniform pores (ca. 7–8 nm). Preliminary catalytic experiments indicated that these mesophases exhibit excellent catalytic activity in UV-visible light oxidation of 1-phenylethanol with molecular oxygen.

In this research we studied the fracture of a cast iron drum for 3.5 ton trucks, and it seeks to determine the causes that led to a series of cracks in different areas of the part of drum brake during the manufacturing process, casting or machining. The work followed the methodology usually used in failure analysis; we used the following analytical techniques: visual inspection, penetrating liquids, fractography, metallography, chemical analysis and mechanical testing of hardness. The analysis of the automotive part surface is divided into four sections which are the flange, track, belt and covers powders which were evaluated by the above techniques to determine the failure of the piece. Metallography analysis in each section of the piece showed different microstructure on gray cast iron; showing that pieces works with different cooling conditions during manufacture, giving a mechanism of failure-prone fragile.

The discovery of carbon nanotubes and subsequently graphene has led to an interest in carbon materials as sensing elements due to their unique properties. Graphene is a 2-dimensional material that has a large surface area (~2630 m2g-1) that can be exposed to surface adsorbates from a target gas. This enables studies on the interaction of gas molecules with the graphene surface and resulting changes in its properties, making graphene an excellent sensing element. We present our graphene based sensor with the focus on designing small, cost effective and reliable sensors with high sensitivity towards the target gas, detailing the assembly of graphene/acrylic based devices, their characterization and investigation of their performance as resistive chemical sensors

Steel quenching from the austenite region is a widely used industrial process to increase strength and hardness through the martensitic transformation. It is well known, however, that it is very likely that macroscopic distortion occurs during the quenching process. This distortion is caused by the rapidly varying internal stress fields, which may change sign between tension and compression several times during quenching. If the maximum internal stress is greater than the yield stress at given processing temperature, plastic deformation will occur and, depending on its magnitude, macroscopic distortion may become apparent.

The complex interaction between thermal contraction and the expansion resulting from the martensitic transformation is behind the sign changes in the internal stress fields. Variations in the steel composition and cooling rate will result in a number of different paths, which the internal stresses will follow during processing. Depending on the route followed, the martensitic transformation may hinder the thermal stresses evolution to the point where the stress fields throughout the component may actually be reverted. A different path may support the thermal stresses evolution further increasing their magnitude. The cross-sectional area also affects the internal stresses magnitude, since smaller areas will have further trouble to accommodate stress, thus increasing the distortion. Additionally, the bainitic transformation occurring during relatively slow cooling rates may have an important effect in the final stress field state.

A finite-element (FE) model of steel quenching has been developed in the DEFORM 3D simulation environment. This model has taken into account the kinetics of both austenite-bainite and austenite-martensite transformations in a simplified leaf spring geometry. The results are discussed in terms of the optimal processing parameters obtained by the simulation against the limitations in current industrial practice.

Currently, ceramics are being used under increasingly demanding environments. These materials have to exhibit phase stability and resist chemical attack during service. This research involves the study of the high-temperature stability of ceramic materials in gas turbines. SiC/SiC ceramic matrix composites (CMCs) are being increasingly used in the hot-sections of gas turbines, especially for aerospace applications. These CMCs are prone to recession of their surface if exposed to a flow of high-velocity water vapor, and to hot-corrosion when exposed to molten alkali salts. The objective of this investigation was the development of a hybrid system containing an environmental barrier coating (EBC) for protection of the CMC from chemical attack and a thermal barrier coating (TBC) that allows a steep temperature gradient across it to lower the temperature of the CMC for increased lifetimes. The EBC used was a functionally graded mullite (3Al2O3∙2SiO2) coating deposited by chemical vapor deposition (CVD), while the TBC layer was yttria-stabilized zirconia (YSZ) deposited by air plasma spray (APS). The stability of this system was investigated, via adhesion between the two coating layers and the substrate, the physical and chemical stability of each layer at high temperature, and the performance under severe thermal shock and exposure to hot corrosion.

Stone coal is an important vanadium-bearing resource in China. Most vanadium exists in stone coal as V(III), which is stable and not easily to be extracted. The V(III) should be oxidized to V(IV) and/or V(V) by roasting with additives at high temperature and then extracted by acid leaching and/or water leaching. Hence, the vanadium valency in roasted stone coal can reflect the roasting efficiency and leaching rate. In traditional digestion process, the V(V) can oxidize V(III) in solution and this causes great error to the determination of vanadium valency. In this study, the V(IV) and V(V) in roasted stone coal is dissolved firstly in 5% of hydrochloric acid at room temperature for 1h because the V(III) embedded in crystal lattice can not dissolve in dilute acid. The acid solution containing V(IV) and V(V) is titrated by 0.02 M ammonium ferrous sulfate (AFS), and the jump in titration curve indicates the reducing of V(V) to V(IV) by ferrous ion. The volume of V(V) can be calculated according to the consumption of AFS. The total volume of vanadium can be determined by potassium permanganate oxidation-ammonium ferrous sulfate titrimetric method. Hence, the volume of V(IV) can be obtained by deducting the quantity of V(V) from the total vanadium. Secondly, the undissolved residue is digested in Teflon vessel by phosphoric acid and hydrofluoric acid at 90 °C for 2h. The digestion solution is also titrated by AFS under nitrogen atmosphere, and the jump in titration curve denotes the reducing of V(IV) to V(III) by ferrous ion in phosphoric acid medium. So, the volume of V(III) and V(IV) can be obtained in the same way. This method is characterized by high measuring accuracy and excellent reproducibility.

Highly mesoporous TiO2 nanoparticles (NPs) were synthesized by an aero-sol-gel process in this approach. By varying the mass fraction of inorganic templates, the formation of mesoporous TiO2 NPs with optimized surface area and pore volume distributions was examined. Then, the photovoltaic properties of the resulting mesoporous TiO2 NPs were systematically investigated by applying them into the photoanode of dye-sensitized solar cells (DSSCs). The mesoporous TiO2 NP-based DSSCs fabricated in this study showed an improved short circuit current density and power conversion efficiency compared with solid TiO2 NP-based DSSCs due to the increase of the amount of inorganic dye (N719) adsorption in the mesoporous TiO2 NPs. These mesoporous TiO2 NPs fabricated have a strong potential as an effective dye supporting and electron transfer medium to improve the photovoltaic performance of DSSCs.

Spectroscopic mapping ellipsometry measurements in the visible spectrum (1.25 to 5.35 eV) are performed to determine the lateral variations of epitaxial graphene properties as grown on 3C SiC. Data taken in the visible spectrum is sensitive to both the Drude absorption of free charge carriers and the characteristic exciton enhanced van Hove singularity at 5 eV. Subsequent analysis with simple oscillator models allows the determination of physical parameters such as free charge carrier scattering time and local graphene thickness with a lateral resolution of 50 microns.

We have successfully formed high-quality nanoporous NiO films by the hydrothermal technique and observed intense ultraviolet (UV) luminescence at room temperature. The SEM image reveals nanoporous NiO films with pore diameters from 70 to 500 nm. The results of XRD, Micro Raman and FTIR characterizations confirm the cubic structure of NiO. The optical band gaps estimated from the absorption spectrum are found to be 3.86 and 4.51 eV. The former is similar to that of bulk NiO, while the latter is much higher than that of bulk NiO. The increased band gap was attributed to the quantum confinement in the NiO nanocrystals, which may be present in the nanoporous NiO film. The room-temperature photoluminescence (PL) spectrum shows a peak of intense luminescence at 3.70 eV and several other peaks in the UV and near-UVwavelength regions. The intense UV luminescence at 3.70 eV was associated with the near band-edge emission and the others with defect-related emission. The high-quality wall of nanoporous NiO with a large surface-to-volume ratio provided the intense UV emission.

Synthesis of wurtzite-type ZnS nanoparticles by an electric discharge submerged in molten sulfur is reported. By the pulsed plasma between two zinc electrodes of 5 mm diameter in molten sulfur, we have synthesized high-temperature phase (wurtzite-type) ZnS nanocrystals with an average size of about 20 nm. Refined lattice parameters of the synthesized wurtzite-type ZnS nanoparticles were found to be larger than those of the reported ZnS (JCPDS 36-1450). UV-Visible absorption spectroscopy analysis showed that the absorption peak of the as-prepared ZnS sample (319 nm) displays a blue-shift comparing to the bulk ZnS (335 nm). Photoluminescence spectra of the samples revealed peaks at 340, 397, 423, 455 and 471 nm, which were related to excitonic emission and stoichiometric defects. Synthesis of ZnMgS (solid solution of ZnS and MgS) was achieved by using ZnMg alloys as both cathode and anode electrodes. Also, rocksalt structure MgS was synthesized by using magnesium rods as both cathode and anode electrodes.

Homoepitaxial growth on 4H-SiC Si-face substrates with sizes corresponding to 150 mm was carried out. The influence of growth conditions for uniformity and epitaxial defect density was investigated. A 150 mm size was realized by using two 76.2 mm wafers lined up in a radial direction. C/Si ratio is found to be a major parameter for controlling triangular defect density and the generation of step bunching. As a result, the surface morphology without bunched step structure and the triangular defect density with 0.5 cm−2 were obtained by decreasing C/Si ratio to 1.0 on the size corresponding to 150 mm. Under this condition, good carrier concentration and thickness uniformity of σ/mean =15.2 % and 1.7 % could be obtained.

Higher silicon solar efficiencies are possible if metal contact is made to the cell though openings in a well-passivated surface. Patterning for rear point-contact schemes has typically been achieved using deterministic patterning methods involving either the use of photolithography, laser or inkjet patterning. However, with these approaches it is difficult to achieve cost-effective, high-throughput and robust processing if very small and closely-spaced openings are required. In this paper we review recent progress in the use of self-patterning anodised aluminium oxide layers to both passivate and enable point metal contacts to the rear surface of silicon solar cells. We describe a wet chemical method for anodising aluminium layers thermally-evaporated on the rear surfaces of silicon solar cells, and demonstrate that the layers can result in excellent passivation of the underlying silicon and also enable metal contact to the solar cell. Additionally, we describe how patterning of either the anodic aluminium oxide layer or the source aluminium layer can result in patterns of metallic and dielectric regions on a surface, and how currently-available solar cell electroplating tools can be adapted to achieve anodisation of solar cells at commercial processing throughput rates.