Electrochemical behaviors of benzoic acid at polyaniline/CuGeO3 nanowire modified glassy carbon electrode

20 wt.% polyaniline/CuGeO₃ nanowires have been used as glassy carbon electrode (GCE) modified materials for electrochemical determination of benzoic acid (BA) in neutral solution. The intensities of the anodic cyclic voltammogram (CV) peaks increase linearly with the increase of BA concentration and scan rate. The linear range is 0.001–2 mM and detection limit is 0.96 μM and 0.47 μM for cvp1 and cvp2, respectively at a signal-to-noise ratio of 3. 20 wt.% polyaniline/CuGeO₃ nanowire modified GCE exhibits good stability and reproducibility. Polyaniline plays an important role in the electrochemical responses of BA at polyaniline/CuGeO₃ nanowire modified GCE. The detection limit decreases to 0.64 μM and 0.28 μM for cvp1 and cvp2, respectively with the polyaniline content increasing to 40 wt.%. Polyaniline/CuGeO₃ nanowire modified GCE exhibit better electrochemical performance than traditional methods.     

Determination of phenyl acetic acid by cyclic voltammetry with electrochemical detection

The phenyl acetic acid (PAA) has been determined by cyclic voltammetry with electrochemical detection using CuGeO₃ nanowires as the glassy carbon electrode (GCE) modified materials. The electrochemical behaviors of the PAA at the CuGeO₃ nanowire modified GCE in neutral solution show that two pairs of electrochemical CV peaks are observed. Two anodic CV peaks are located at 0.31 V and −0.02 V for cv peak 1 and cv peak 2, respectively. The intensities of two anodic peaks vary linearly with the increase of the PAA concentrations from 0.01 to 2 mM. The detection limit is 82.1 μM and 9.1 μM for cv peak 1 and cv peak 2, respectively. The CuGeO₃ nanowire modified GCE exhibits good reproducibility, stability and sensibility.     

Nanowire cutting by an ultrasonically vibrating micro tool

Cutting of a nanoscale workpiece is useful in nano testing and fabrication, and novel cutting methods with little gasification of cut nano samples and simple device structures are needed for practical applications. In this paper, an ultrasonic nanowire cutting strategy is demonstrated, in which the linear and elliptical vibration of the tip of a micro cutting tool and the adhesion force between a substrate and nanowire are employed to cut and fix the nanowire, respectively. With this strategy, cutting of individual silver nanowires with a diameter from 50 nm to 400 nm is implemented, in which the vibration velocity amplitude of the micro cutting tool’s root is from 18 to 220 mm/s, and the working frequency is about 96.9 kHz and 45.2 kHz, respectively. The dependency of the minimum cutting velocity and optimum cutting velocity range’s lower limit on the AgNW diameter is experimentally clarified. Also, the cutting principle is analyzed, which can well explain the incision morphology and cutting characteristics.     

On-site calibration system for trace humidity sensors

A portable device for calibration of trace humidity sensors and an adopted calibration procedure have been developed. The calibration device is based on humidity generation by permeating water through polymeric membrane tubes. Water vapour transmission rates for various polymers were experimentally determined in order to select the most suitable polymeric material. The developed trace humidity generator consists of a gas-flow polymeric hose immersed in a water reservoir thermostated by a sensor-controlled heater. Mole fractions of water vapour between 1 μmol mol⁻¹ and 350 μmol mol⁻¹ (equivalent to frost-point temperatures from −76 °C to −31 °C) were generated by varying either the operating temperature or gas flow. The operating temperature can be varied from 20 °C to 60 °C and kept stable within 0.1 K. Uncertainty analysis indicated that the trace humidity generator produces gas flows of constant humidity amounts with a relative expanded uncertainty less than 3.4% (k = 2) of the generated value.     

Preparation,characterization, electrical conductivity and dielectric studies of Na2SO4 and V2O5 composite solid electrolytes

Composite solid electrolytes (1 − x) Na₂SO₄–(x) V₂O₅ were prepared and characterized by various techniques such as XRD, FT-IR, DTA and SEM. AC impedance spectroscopy revealed that the contribution of grain is strong enough over the grain boundary. Arrhenius plot of the Na₂SO₄ shows a sharp increase in conductivity at 523 K due to the structural phase transition (phase V → I). Composites show the enhanced ionic conductivity than the pristine Na₂SO₄ over the entire temperature range. The maximum conductivity σ = 0.003 S cm⁻¹ at 773 K with the lowest activation energy of 0.28 eV was observed for the x = 0.4 sample. The enhanced value of dielectric constant and dielectric loss in the case of composites was obtained because of increase of conductivity, resulted from the increase of space charge polarization and charge motion.     

Characteristics of MSM photodetector fabricated on porous In0.08Ga0.92N

In this study, nanoporous structures of In_0.08Ga_0.92N thin films were synthesized using anodic etching at various etching durations. The metal–semiconductor–metal photodetectors subsequentaly have been fabricated by depositing a high work function metal (Pt) on the thin films. Results show that the responsivity of the detector increased with increasing the etching duration to reach to the maximum value at 15 min. Moreover, the rise and recovery times of the device were investigated at 390 nm chopped light.     

Thermal optimization and supercapacitive application of electrodeposited Fe2O3 thin films

In the present work, thin films of Fe₂O₃ were deposited onto stainless steel substrates by electrodeposition method. All deposited electrodes were annealed for 1 h within the temperature range of 423–673 K with an interval of 50 K. These were further characterized for their structural and morphological measurements by means of X-ray diffraction and scanning electron microscopy techniques, respectively. The supercapacitive characteristics of as-deposited and annealed electrodes were carried out in 1 M KOH electrolyte to confirm the variation in specific capacitance, specific energy, specific power and columbic efficiency, etc., with annealing temperatures.     

Friction of molybdenum disulfide–titanium films under cryogenic vacuum conditions

The tribological behavior of steel and sapphire sliding on a sputtered MoS₂+Ti coating was studied in ultra-high vacuum as a function of temperature over the range of 4–300 K. The coefficient of kinetic friction for the steel/moly interface was determined to be approximately 0.05 from room temperature to 240 K, and increased monotonically to 0.125 at 4 K. The sapphire/moly friction coefficient was measured to be 0.15±0.05 at room temperature and increased monotonically to 0.25 at 4 K. We also analyze in detail the flash temperature due to frictional heating at the sliding contacts. Flash heating is a particularly strong effect at cryogenic temperatures.     

Simple apparatus to measure Seebeck coefficient up to 900 K

An apparatus for measuring Seebeck coefficient (S) has been designed that allows measurement of S from room temperature to 900 K. It is constructed from readily available equipment and instrumentation with parts that can be easily fabricated. The details of instrument fabrication, sources of errors, method of calibration, typical measurement in test sample are described. We report the Seebeck coefficient measurement of Ca-cobaltite (Ca₃Co₄O₉) a p-type thermoelectric material. The obtained results from the fabricated setup are well matched with the reported and standard instrument data with standard deviation of ±3%.     

Tribological properties of Ni3Al produced by pressure-assisted volume combustion synthesis

The production of Ni₃Al was performed under an uniaxial pressure of 150 MPa at 1050 °C for 1 h. The formation temperature of Ni₃Al was determined to be 655 °C. The presence of Ni₃Al was confirmed by XRD analysis. SEM analysis revealed that the Ni₃Al phase has very low porosity. The relative density and microhardness of test materials were 97.8% and about 359±31 HV_1.0, respectively. The specific wear rate of Ni₃Al was 0.029 mm³/N m for 2 N, 0.017 mm³/N m for 5 N and 0.011 mm³/N m for 10 N, respectively. The distribution of alloying elements was determined by energy-dispersive spectroscopy (EDS).     

Mechanical and tribological properties of NiCr–Al2O3 composites at elevated temperatures

The effect of Al₂O₃ content on the mechanical and tribological properties of Ni–Cr alloy was investigated from room temperature to 1000 °C. The results indicated that NiCr–40 wt% Al₂O₃ composite exhibited good wear resistance and its compressive strength remained 540 MPa even at 1000 °C. The values obtained for flexural strength and fracture toughness at room temperature were 771 MPa, 15.2 MPa m^1/2, respectively. Between 800 °C and 1000 °C, the adhesive and plastic oxide layer on the worn surface of the composite was claimed to be responsible for low friction coefficient and wear rate.     

Non-contact temperature measurement of silicon wafers based on the combined use of transmittance and radiance

We propose a non-contact temperature measurement method that combines the temperature dependence of transmittance below 600 °C and radiation thermometry above 600 °C. The combined method uses a polarization technique and the Brewster angle between air and a dielectric film such as SiO₂ or Si₃N₄ grown on silicon wafers. A prominent feature of this method is that both measurements of transmittance and radiance are performed with the same geometrical arrangement.For a semitransparent wafer, the measurement of p-polarized transmittance at the wavelengths of 1.1, 1.2 and 1.3 μm enables temperature measurement in the range from room temperature to 600 °C. For an opaque wafer above 600 °C, the p-polarized radiation thermometry at the wavelength of 4.5 μm allows the temperature measurement without the emissivity problem. The combined method with the use of transmittance and radiance is valid in the entire temperature range irrespective of variations of film thickness and resistivity.     

Parallel-kinematics XYZ MEMS part 2: Fabrication and experimental characterization

This paper, the second of a set of two papers addressing parallel-kinematics MEMS stages for spatial translation, deals with fabrication, characterization and control of such devices. Double device layer SOI (silicon-on-insulator) substrates are used, providing three layers (two device layers and the handle) into which the elements of the stage can be mapped. Using the mechanism concept, realization scheme, and kinematic and dynamic models developed in the first paper of this set, this paper provides a detailed approach to fabricating these devices. The stages fabricated have a workspace cube of roughly 20 μm on the side, an in-plane stiffness of 96 N/m, and an out-of-plane stiffness of 166 N/m. Further, it characterizes the performance of the individual actuating and sensing elements, configures feedback controllers for each actuated joint, and assesses and verifies the stage’s designed performance. Finally, it demonstrates full 3-axis, closed-loop positioning of a MEMS stage.     

Design and Analysis of MEMS Comb Drive Capacitive Accelerometer for SHM and Seismic Applications

This work presents the design of a MEMS accelerometer that is specifically intended for Structural Health Monitoring (SHM) applications where sensing low frequency low amplitude accelerations with high resolution is essential. The surface micromachined comb drive capacitance accelerometer structure has been considered in this design. The simulation experiments conducted on these devices using IntelliSuite MEMS design tool show that it has excellent displacement sensitivity of 21.39 μm/g, a capacitive sensitivity of 1.22 pF/g and voltage sensitivity of 1783 mV/g/V when it is designed to measure 0–0.1 g. Further, it is seen that it has a very low noise floor of 1.32 μg/√Hz and therefore high resolution. Since the accelerations can be as low as 0.04 g in SHM applications, excellent resolution is the primary goal in this design. Further, one more sensor specifically meant for strong motion seismic application has also been reported. This device has a bandwidth of 0–250 Hz and a noise floor of 5.612 μg/√Hz in addition to a sensor level voltage sensitivity of 97.9 mV/g/V. Finally, the comparison of these results with other similar devices reported in the past clearly illustrates the comparable performance of the present devices. Further, these devices, unlike the commercial low frequency accelerometers and other similar devices reported in the past can be fabricated by surface micromachining and CMOS compatible processes.     

Wear characteristics of Cr3C2–NiCr and WC–Co coatings deposited by LPG fueled HVOF

Wear behavior of the HVOF deposited Cr₃C₂–NiCr and WC–Co coatings on Fe-base steels were evaluated by the pin-on-disc mechanism. The constant normal load applied to the pin was 49 N and sliding distance was 4500 m with velocity of 1 m/s, at ambient temperature and humidity. The specific wear rate of WC–Co coating was 3 mm³/N m and Cr₃C₂–NiCr coating was 5.3 mm³/N m. SEM/EDAX and XRD techniques were used to analyze the worn out surface and wear debris. The Fe₂O₃ was identified as the major phase in the wear debris. The wear mechanism is mild adhesive wear in nature.     

Effect of CuO as a dopant in TiO2 on ammonia and hydrogen sulphide sensing at room temperature

The heterogeneous nanocomposites of CuO doped TiO₂ nanoparticles were synthesized using sol gel method by varying the concentration of CuO as 0.1, 0.5 and 1 mol% for the sensing of ammonia and hydrogen sulphide. The substitutional doping of CuO in TiO₂ matrix was confirmed by the X-ray diffraction. Average crystallite size of the doped nanocomposites was found to reduce with increase in concentration of CuO. The 0.1 mol% CuO doped TiO₂ nanocomposites showed highest sensitivity to ammonia (97%) with response time of 2 s, while 1 mol% was selective to H₂S gas (77%) with response time of 45 s for 50 ppm of each gas at room temperature.     

Effect of SiC particles on the friction and wear behavior of Ti3Si(Al)C2-based composites

The non-lubricated, sliding friction and wear behavior of Ti₃Si(Al)C₂ and SiC-reinforced Ti₃Si(Al)C₂ composites against AISI 52100 bearing steel ball were investigated using a ball-on-flat, reciprocating tribometer at room temperature. The contact load was varied from 5 to 20 N. For monolithic Ti₃Si(Al)C₂, high friction coefficients between 0.61 and 0.90 and wear rates between 1.79 × 10⁻³ and 2.68 × 10⁻³ mm³ (N m)⁻¹ were measured. With increasing SiC content in the composites, both the friction coefficients and the wear rates were significantly decreased. The friction coefficients reduced to a value between 0.38 and 0.50, and the wear rates to between 2.64 × 10⁻⁴ and 1.93 × 10⁻⁵ mm³ (N m)⁻¹ when the SiC content ranged from 10 to 30 vol.%. The enhanced wear resistance of Ti₃Si(Al)C₂ is mainly attributed to the facts that the hard SiC particles inhibit the plastic deformation and fracture of the soft matrix, the oxide debris lubricate the counterpair, and the wear mode converts from adhesive wear to abrasive wear during dry sliding.     

WC–ZrO2 composites: processing and unlubricated tribological properties

In the present work, we report the processing and properties of WC–6 wt.% ZrO₂ composites, densified using the pressureless sintering route. The densification of the WC–ZrO₂ composites was carried out in the temperature range of 1500–1700 °C with varying time (1–3 h) in vacuum. The experimental results indicate that significantly high hardness of 22–23 GPa and moderate fracture toughness of ∼5 MPa m^1/2 can be obtained with 2 mol% Y-stabilized ZrO₂ sinter-additive, sintered at 1600 °C for 3 h. Furthermore, the friction and wear behavior of optimized WC–ZrO₂ composite is investigated on a fretting mode I wear tester. The tribological results reveal that a moderate coefficient of friction in the range from 0.15 to 0.5 can be achieved with the optimised composite. An important observation is that a transition in friction and wear with load is noted. The dominant mechanisms of material removal appear to be tribochemical wear and spalling of tribolayer.     

Feasibility assessment of magnetic resonance-thermometry on pancreas undergoing laser ablation: Sensitivity analysis of three sequences

Laser ablation (LA) is a minimally invasive technique for the treatment of tumors as an alternative to surgical resection. The light absorbed by tissue is converted into heat, and causes irreversible cell damage when temperatures higher than 60 °C are reached. The knowledge in real time of temperature may be particularly beneficial for adjusting laser settings applied during treatment and to be notified in real time about its end-point. As a consequence, several techniques for temperature monitoring within the tissue have been investigated along the last decades. In the field of LA, particularly attractive are non-invasive methods. Among these techniques, thermometry based on the analysis of Magnetic Resonance Imaging (MR-thermometry) has gaining large acceptance in this field. MR-thermometry allows estimating the temperature variation thanks to the thermal dependence of several MRI parameters, among others the most promising are T₁ relaxation time, and proton resonance frequency shift.The aim of this study is to assess the sensitivity of MRI thermometry using three T₁-weighted sequences (i.e., Inversion Recovery Turbo-FLASH, IRTF, Saturation Recovery Turbo-FLASH, SRTF, and FLASH) using an 1.5-T MR scanner on healthy swine pancreases undergoing LA. The reference temperature was measured by MRI-compatible fiber optic sensors (fiber Bragg grating sensors). The sensitivity of the proposed techniques was estimated and compared. The thermal sensitivity of the three sequences was −1.47 ± 0.08 °C⁻¹, −0.95 ± 0.05 °C⁻¹, and −0.56 ± 0.04 °C⁻¹ for IRTF, SRTF and FLASH, respectively. Results show that the proposed technique may be adequate for temperature monitoring during LA.