An experimental study on the concrete hydration process using Fabry–Perot fiber optic temperature sensors

This paper describes the contribution of Fabry–Perot (FP) fiber optic temperature sensor to investigate the effects of concrete hydration process. The FP temperature sensor was easily fabricated by controllable chemical etching and adjustable fusion splicing. Detailed optical properties of the sensor were theoretically analyzed and temperature calibration experiments were performed. A sensor with a 90 μm cavity length was demonstrated to have a temperature sensitivity of 0.01 nm/°C and the linearity coefficient of 0.99. Furthermore, the FP sensor was embedded in the concrete structure for sensing the temperature change during the early age of hydration. During the concrete hydration experiments, the measured peak temperatures of the concrete specimens with different water-to-cement (w/c) ratios of 0.4, 0.5 and 0.6 were 51.42 °C, 52.88 °C, and 55.08 °C, respectively, corresponding to final setting times of 13.52 h (w/c = 0.4), 14.16 h (w/c = 0.5) and 15.2 h (w/c = 0.6) after concrete casting. Temperature profiles will be used for concrete hydration heat study, which will help us to have a better understanding of cement hydration behavior.     

Accurate conductance measurements of a pinhole orifice using a constant-pressure flowmeter

A pinhole orifice with a known conductance can be used as a secondary flow standard. Commercially available laser-drilled pinhole orifices with diameters ranging from 1.0 μm to 50 μm can have molecular-flow conductances ranging from about 0.1 μL/s to 200 μL/s for N₂ at 23 °C. Gas flows of 10⁻¹¹–10⁻⁶ mol/s can easily be produced by applying an upstream pressure in the range of 1–10⁵ Pa. Accurate measurements of the orifice conductance as a function of pressure are required to use the pinhole orifice as a basis of a flowmeter. We use a constant-pressure flowmeter to make accurate measurements of the conductance of a 20 μm orifice as a function of pressure for gas flows of Ar and N₂ into vacuum. We present results of these conductance measurements for an orifice with a nominal diameter of 20 μm. The N₂ conductance of this orifice ranged from 30 μL/s to 60 μL/s over the range of pressures investigated, and was measured with an uncertainty of better than 0.2% (k = 2) for upstream pressures greater than 10 Pa.     

Fabrication and characterization of ZnO thin film for hydrogen gas sensing prepared by RF-magnetron sputtering

A ZnO thin film-based gas sensor was fabricated using a SiO₂/Si substrate with an integrated platinum comb-like electrode and heating element. The structural characteristics, morphology, and surface roughness of the as-grown ZnO nanostructure were investigated. The optical properties were examined by UV–vis spectrophotometry. The film revealed the presence of a c-axis oriented (0 0 2) phase of 20.8 nm grain size. The sensor response was tested for hydrogen concentrations of 50, 70, 100, 200, 400, and 500 ppm at operating temperatures ranging from 250 °C to 400 °C. The sensitivity toward 50 and 200 ppm of hydrogen at the optimum operating temperature of 350 °C were about 78% and 98%, respectively. The response was linear within the range of 50–200 ppm of hydrogen concentration. Our results demonstrated the potential application of ZnO nanostructure for fabricating cost-effective and high-performance gas sensors.     

INRIM primary standard for microgas-flow measurements with reference to atmospheric pressure

Primary standard flowmeters are developed for the calibration of leak devices used in many applications in which is necessary to detect and quantify gas leakage from a material, a component or a system. At INRIM, a primary standard was designed and realized for the measurement of molar gas flow from 4 × 10⁻¹⁰ mol/s to 2 × 10⁻⁷ mol/s with reference to atmospheric pressure. It is based on the constant-pressure–variable-volume method and is able to work with any tracer gas.     

Behaviour of TEM metal grids during in-situ heating experiments

The stability of Ni, Cu, Mo and Au transmission electron microscope (TEM) grids coated with ultra-thin amorphous carbon (α-C) or silicon monoxide film is examined by in-situ heating up to a temperature in the range 500–850 °C in a transmission electron microscope. It is demonstrated that some grids can generate nano-particles either due to the surface diffusion of metal atoms on amorphous film or due to the metal evaporation/redeposition. The emergence of nano-particles can complicate experimental observations, particularly in in-situ heating studies of dynamic behaviours of nano-materials in TEM. The most widely used Cu grid covered with amorphous carbon is unstable, and numerous Cu nano-particles start to form once the heating temperature reaches 600 °C. In the case of Ni grid covered with α-C film, a large number of Ni nano-crystals occur immediately when the temperature approaches 600 °C, accompanied by the graphitization of amorphous carbon. In contrast, both Mo and Au grids covered with α-C film exhibit good stability at elevated temperature, for instance, up to 680 and 850 °C for Mo and Au, respectively, and any other metal nano-particles are detected. Cu grid covered Si monoxide thin film is stable up to 550 °C, but Si nano-crystals appear under intensive electron beam. The generated nano-particles are well characterized by spectroscopic techniques (EDXS/EELS) and high-resolution TEM. The mechanism of nano-particle formation is addressed based on the interactions between the metal grid and the amorphous carbon film and on the sublimation of metal.     

Elastic-plastic characterization of a high strength bainitic roller bearing steel—experiments and modelling

Monotonic and cyclic deformations were studied for a high strength bainitic roller bearing steel. The temperature of 75 °C corresponded to normal roller bearing conditions. The materials showed hydrostatic influence on yielding, but no or marginal influence of plastic deformation on density change. Therefore, a linear elastic constitutive model with pressure dependent yielding, non-associated flow rule, combined non-linear kinematic and isotropic hardening was necessary to characterize the cyclic behaviour. A stepwise process is detailed for determining the material parameters of the pressure dependent model, where particular attention was placed on the hardening parameters. One set of parameters was sufficient to describe all tested load ranges including compressive ratchetting. Some comparative tests were performed at room temperature, 150 °C and on martensitic specimens at 75 °C. The temperature influence was limited to the isotropic hardening parameters.     

Measuring temperature dependence of photoelectric conversion efficiency with dye-sensitized solar cells

It’s well known that the drift velocity of electrons in conductors depends on temperature in accordance with thermodynamics, which influences also photoelectric conversion efficiency of solar cells. The article presents experimental data for studying temperature influence of photoelectric conversion efficiency with dye-sensitized solar cells (DSSCs). The measured DSSCs were built in three layers, the photoelectrode, the electrolyte, and the counter electrode, which were made in the CCT laboratory, National Taipei University of Technology, Taiwan. The photoelectrode is coated by using ? = 21 nm nano TiO₂ and dye as well as the counter electrode using ? = 5 nm nano carbon black on their individual ITO glass. The fluidic electrolyte is used in this work due to its good ionic drift property. In process, the DSSC was waterproof and immersed in the constant temperature water tank for temperature adjusting. The measured temperature range was from ca. 5 °C to 80 °C at an interval of ca. 10 °C. The results show the higher temperature, the lower photoelectric conversion efficiency of DSSCs.     

Effect of pre-readout annealing treatments on TL mechanism in tellurite glasses at therapeutic radiation doses level

The higher sensitization for thermal annealing on TL mechanism in the region 550–600 °C for 80(TeO₂)–5(TiO₂)–(15 − x) (WO₃)–(x) A_nO_m where A_nO_m = Nb₂O₅, Nd₂O₃, Er₂O₃ and x = 5 mol% has been measured. The behavior of trap centers and luminescence centers has been investigated for tellurite glasses doped with rare earth oxides irradiated at 0.5 up to 2 Gy and annealed at different temperatures in the range 350–700 °C. The behavior of the three types of tellurite glasses is analyzed regarding to their kinetic parameters and luminescence emission which enhance the claim of tellurite glasses for use as TLD material at therapeutic radiation doses.     

Design and performance of an advanced metrology building for MIKES

Fundamental metrology is closely linked to the development of science and needs good facilities to achieve low measurement uncertainty in demanding experiments. The laboratories must have good temperature stability, low vibration level, good electromagnetic shielding, clean room air, and humidity control. This paper outlines specification and design principles of a compact laboratory building that brings most of the activities of MIKES under one roof, thus attaining the performance of the most demanding laboratories. The most demanding specifications of temperature and vibration were set for the length and mass laboratories. The tightest room temperature specification was (20 ± 0.05) °C. The vibration level was specified at the tightest level to 1 μm/s at frequencies of 0.1-5 Hz. Electromagnetic shielding was specified at best to 100 dB for plane waves up to 20 GHz. Relative humidity was specified (48 ± 2)% at 20 °C. The specifications were clearly achieved and state of the art metrology laboratories implemented.     

Thermal sensors based on p-Pb0.925Yb0.075Te:Te and n-Pb0.925Yb0.075Se0.2Te0.8 thin films grown using thermal evaporation method

We utilize p-Pb_0.925Yb_0.075Te:Te and n-Pb_0.925Yb_0.075Se_0.2Te_0.8 ingots in a standard solid-state microwave synthesis route to fabricate thermally evaporated thin films. The nanostructure and composition of the films were studied through X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and energy dispersive X-ray spectroscopy (EDX). The Seebeck coefficient and electrical conductivity were measured at a temperature range of 298–523 K. The micro-thermoelectric devices were composed of 20 pairs and 10 pairs of p-Pb_0.925Yb_0.075Te:Te and n-Pb_0.925Yb_0.075Se_0.2Te_0.8 thin films on glass substrates, respectively. The dimensions of the thin films thermoelectric generators which comprised of 10-pair were 12 mm × 10 mm, whereas, 20-pair were 23 mm × 20 mm, respectively of legs connected through aluminum electrodes. The serial 20-pair p–n thermocouples generated a maximum output open-circuit voltage of 275.3 mV and a maximum output power of 54.37 nW at a temperature difference of ΔT = 162 K; the values are 109.4 mV and 16.68 nW at ΔT = 162 K for the 10-pair thermocouples, respectively.     

FEA calculation of pressure distortion coefficients of gas-operated pressure balances – EURAMET project 1039

Finite element analysis methods were developed and applied to gas piston–cylinder units (PCUs) of piston- and cylinder-floating configuration (2, 5, 10 and 20) cm² nominal effective area, operated in gauge and absolute mode at pressures (0.06–7.5) MPa to determine their zero pressure and pressure-dependent effective areas, as well as pressure distortion coefficients (λ) with associated uncertainties. Real dimensional properties of the PCUs were used. λ were found to be independent of gas (ideal, N₂, He) within the viscous flow model, but strongly dependent on the gap shape, operation mode and elastic properties. Results demonstrate good agreement for λ, with its uncertainty for different PCUs varying between (0.03 and 0.21) × 10⁻⁶ MPa⁻¹ corresponding to maximum relative uncertainties in pressure of (0.07–0.34) × 10⁻⁶.     

Miniature low-power IR monitor for methane detection

A portable methane gas monitor based on an infrared spectrum absorption principle has been developed using a dual-channel and dual-wavelength pyroelectric infrared detector, active filters around the overtone absorption lines of methane at 3.31 μm, reference filters around the non-absorption lines of methane at 3.93 μm, mid-IR LEDs, a miniature gold-filled cell structure, temperature sensors for gas concentration calibration and compensation, an electrical modulation source, and a highly integrated intelligent controller. A detailed investigation has been carried out to design a low-cost portable IR optical sensor for methane detection that can operate in harsh environments with temperature variations between −10 °C and 40 °C. The infrared detection optics principle used in developing this system is mainly analyzed. A prototype based on this design showed an accuracy of ±0.05%, which meets the technology requirements of lower-power consumption, reduced volume, and wide measurement range.     

Use of a higher order Heydemann–Welch model to characterize a controlled clearance piston gauge

We present a new method for characterizing a controlled-clearance piston gauge as a primary pressure standard. This method requires operating the piston gauge to jacket pressures of over 80% of the system pressure. We present measurements on a hydraulic piston gauge with a 290 MPa maximum pressure and a nominal piston diameter of 3.27 mm. Measurements showed that the cylinder becomes stiffer as the jacket pressure increases, and that non-linear models of the Heydemann–Welch parameters improve the determination of the effective area. The relative standard uncertainty in the effective area of the piston gauge ranges from 16.0 × 10⁻⁶ to 17.6 × 10⁻⁶, and the agreement to the present NIST pressure scale is within the standard uncertainty.     

Design and development of a high precision thermocouple based smart industrial thermometer with on line linearisation and data logging feature

Design and development of a high precision thermometer for industrial application is described in this paper. A class-1 grade K-type Thermocouple is considered for this purpose. The conditioned signal is linearised using a 9th order polynomial based on National Institute of Standards and Technology (NIST) data with the help of a 12-bit analog-to-digital converter and a 8-bit microcontroller. The cold junction compensation is achieved using a serial synchronous temperature to digital converter. The linearised data is transmitted for remote monitoring and logging via RS232C. The system is calibrated with 20 calibration point from 0 °C to 200 °C with a low cost calibration setup. The precision index of the system is also calculated.     

A humidity generator with a test chamber system

For the calibration of relative humidity hygrometers and dew-point hygrometers with an open sensor, a test chamber system was constructed and connected to a dew-point generator. The system includes several small chambers connected in series. By reversing the flow direction, humidity and temperature gradients in the test chamber system are monitored during calibration measurements. This paper reports the construction of the test chamber system and the improvements in the construction and the analysis of the dew-point generator. A full uncertainty analysis is presented. The expanded uncertainty of the dew-point temperature and the relative humidity with the coverage factor k=2 are from ±0.05°C to ±0.08°C and from ±0.1%rh to ±1.0%rh, respectively. Although the dew-point temperature range is from −40°C to +77°C, the limits for the temperature range of the test chamber system are −20°C and +60°C. The system was not tested with relative humidity values lower than 10% or higher than 95%.     

Polypyrrole-NiO hybrid nanocomposite: Structural,morphological, optical and electrical transport studies

Polypyrrole (PPy)-nickel oxide (NiO) hybrid nanocomposite thin films have been prepared by spin coating method. The PPy–NiO hybrid nanocomposites were characterized for structural, morphological, optical and electrical analysis, and the results were compared with the pure PPy films. The structural and optoelectronic properties of PPy–NiO hybrid nanocomposites are quite different from those of pure PPy and NiO nanoparticles, which were attributed to the strong interaction between the PPy and NiO nanoparticles. The XRD pattern shows that broad peak of PPy becoming weaker on increasing the content of NiO nanoparticles in the PPy–NiO hybrid nanocomposites. Also the diffraction peaks of NiO nanoparticles in PPy–NiO (10–50 wt%) nanocomposites were found to shift to lower 2θ values. The morphological studies revealed that the transformation of granular morphology of PPy to the nanospheres and clusters in the PPy–NiO hybrid nanocomposites. FTIR spectra of PPy–NiO hybrid nanocomposites, revealed that the main absorption at 1204 cm⁻¹ and 1559 cm⁻¹ are affected by the presence of NiO nanoparticle in pure PPy and get shifted to 1216 cm⁻¹ and 1570 cm⁻¹ respectively indicates, insertion of NiO nanoparticles in the PPy–NiO hybrid nanocomposite. UV–vis absorption spectrum of PPy corresponding to λ_max = 442 nm is blue shifted to λ_max = 375 nm in the PPy–NiO hybrid nanocomposites, reveals strong interaction between PPy and NiO nanoparticles. The room temperature dc electrical conductivity is increased from 8.66 × 10⁻⁹ to 4.08 × 10⁻⁷ (Ω/cm)⁻¹ as the content of NiO nanoparticles increased from 10 to 50 in wt% in the PPy–NiO hybrid nanocomposites.     

A large deflection and high payload flexure-based parallel manipulator for UV nanoimprint lithography: Part I. Modeling and analyses

This paper presents a flexure-based parallel manipulator (FPM) that delivers nanometric co-planar alignment and direct-force imprinting capabilities to automate an ultra-violet nanoimprint lithography (UV-NIL) process. The FPM is articulated from a novel 3-legged prismatic-prismatic-spherical (3PPS) parallel-kinematic configuration to deliver a θ_x–θ_y–Z motion. The developed FPM achieves a positioning and orientation resolution of ±10 nm and 0 . 05″ respectively, and a continuous output force of 150 N/Amp throughout a large workspace of 5°×5°×5 mm. Part I mainly focuses on a new theoretical model that is used to analyze the stiffness characteristics of the compliant joint modules that formed the FPM, and experimental evaluations of each compliant joint module. Part II presents the stiffness modeling of the FPM, the performance evaluations of the developed prototype, and the preliminary results of the UV-NIL process.     

Determination of protein with Thioguanine (6-TG) as a probe by synchronous fluorescence technique

The synchronous fluorescence technique was developed for the determination of human serum albumin (HSA) in human body fluids with Thioguanine (6-TG) as a molecular probe. Under the optimal experimental conditions, the synchronous fluorescence peak of HSA–6-TG system is located at about 301 nm and the enhancement synchronous intensity was proportion to the concentration of HSA. The calibration graphs are linear over the range of 0.69–552.0 μg mL⁻¹ with a correlation coefficient (R) of 0.9994. The detection limit was 0.133 μg mL⁻¹. It was successfully applied to determine the protein in human body fluids including serum, urine and saliva samples with 6-TG as probe with a satisfying result. In the analysis of human body liquids samples, the relative standard deviations (RSDs) were 0.55–3.31%, which obtained from 6 replicate determinations and recoveries were in the range of 97.0–104.1%.     

Studies of high temperature sliding wear of metallic dissimilar interfaces III: Incoloy MA956 versus Incoloy 800HT

Wear variations of Incoloy MA956 slid against Incoloy 800HT between room temperature and 750 °C, and sliding speeds of 0.314, 0.654 and 0.905 m s⁻¹ were investigated using a ‘reciprocating block-on-cylinder’ (low debris retention) configuration.Three forms of wear depending largely on sliding temperature were observed: ‘severe wear’ with high transfer between room temperature and 270 °C, ‘severe wear’ with low transfer between 390 and 570 °C and ‘glaze formation’ (retarded by increased sliding speed) at 630 °C and above. The differences in wear behaviour are discussed, with wear behaviour mapped and wear surfaces at 750 °C (0.314 and 0.905 m s⁻¹) cross-sectioned and profiled.