Inhomogeneity correction in calibration of electrical conductivity standards

The method for inhomogeneity investigation of measurement standards for electrical conductivity has been studied in the conductivity range from 2 MS/m to 14 MS/m. For this purpose a planar spiral coil has been developed and characterized. The impedance values of the coil are measured in the air and with a conducting plate above the coil at discrete frequencies from 2 kHz to 70 kHz. By selecting the corresponding operating frequency, relative changes in the conductivity value throughout the sample thicknesses have been measured. It was revealed that inhomogeneity of measurement standards has an effect on further measurements with calibrated conductivity meters. The relative conductivity changes of 0.1% due to inhomogeneity can be detected with the measurement uncertainty (k = 2) of less than 0.3% of the measured value.     

1–15,000 Pa Absolute mode comparisons between the NIST ultrasonic interferometer manometers and non-rotating force-balanced piston gauges

The National Institute of Standards and Technology (NIST) Low Pressure Manometry Project maintains and operates primary standard ultrasonic interferometer manometers (UIMs) over the pressure range of 1 mPa to 360 kPa. Over the past decade a new type of customer gauge, the non-rotating force-balanced piston gauge or FPG (model 8601, DH Instruments, a Fluke Company¹) has been introduced to the standards community that covers the range of ≈1–15,000 Pa and is capable of both absolute and differential measurement modes. Since 2002, NIST customers² have requested that four different FPG units be compared to the NIST primary pressure ultrasonic interferometer manometer standards (UIMs). The results of the comparisons were that all four FPG units were within manufacturers stated uncertainty (0.008 Pa + 30 × 10⁻⁶ × P for absolute mode) when compared against the NIST UIMs at pressures between 10 Pa and 15,000 Pa (absolute mode). At pressures between 5 Pa and 10 Pa, the results were generally within manufacturer’s specifications. Below 5 Pa some of the FPG units were outside of manufacturer’s uncertainty specifications. The use of an isolating capacitance diaphragm gauge (CDG) was necessary during the comparisons to prevent humidified gas from the FPG from entering the NIST 160 kPa mercury UIM primary pressure standard. The results of these four different comparison tests will be discussed in detail, along with test conditions, equipment set-up, and test uncertainty analysis.     

A three-point-probe method for measuring resistivity and the Hall coefficient using Hall devices with minimal design complexity

A novel empirical method for express measurement of resistivity and the Hall coefficient, i.e. the sign, the concentration and the bulk mobility of the majority carriers in semiconductor (silicon) wafers is presented and tested. This approach is based on the parallel-field Hall devices with minimal design complexity containing only three contacts–two input and one (Hall) output. The unique simplicity of this three-point-probe method, the lack of numerical coefficients’ calculation and particular requirements for the geometrical dimensions, probe spacing, wafer form, etc. allows to obtain the necessary information following experimentally clear and technically reproducible steps. The data obtained from non-structured n- and p-type silicon wafers at carrier’s concentration of 10¹⁵ ? n; p ? 10¹⁶ cm⁻³ by appropriate probe arrangements corroborate very well with the results from wafers’ certificates and the results obtained using common measurement techniques. The error does not exceed 5–6% which is about the same as the accuracy of other approaches used for this purpose. The results are especially promising in IC fabrication and complementing the classical Van der Pauw method.     

Implementation of Gold deconvolution for enhanced energy resolution in EEL spectra

Gold’s iterative deconvolution algorithm has been applied to one-dimensional EEL spectra from hexagonal BN. The experimental resolution was varied from 1.1 to 2.25 eV and Gold’s algorithm was able to restore low-loss and core-loss spectra overall well. To estimate the instrument response function, the most convenient method was to extract the zero-loss peak from the low-loss spectrum. By instead using low-loss spectra as kernel, as suggested by Egerton, enhanced energy resolution could also be obtained with plural scattering simultaneously removed. It is further shown how the FWHM of the π^? peak in the boron K-edge of hexagonal BN is reduced from 1.4 to 0.7 eV with almost no noise amplification after 500 iterations while resolving the σ^? doublet. The result was almost identical after a stunning 5000-10,000 iterations, implying that Gold’s method converges and can be stable for a large number of iterations. However, for lower-intensity spectra the number of iterations is limited. The results close to the intense zero-loss peak were uncertain and further testing with better experimental resolution is recommended. It is also found that to improve the resolution and not just sharpen the spectra, a large number of iterations is required.     

Accelerated nano-fretting testing of Si(1 0 0)

A nano-fretting test technique has been recently developed to enable the in situ study of wear at the micro- and nano-scale. It has been used to study the small scale wear of Si(1 0 0) using a 4.6 μm spheroconical indenter as test probe over the applied load range 30-300 mN. Contact damage assessment by in situ measurements of probe displacement were supplemented by post-test SEM imaging and wear scar analysis by confocal microscopy. The wear behaviour was dependent on the rate of initial loading. When the load was applied abruptly (<0.3 s), radial and lateral cracking and material removal was observed and large displacement jumps (pop-ins) were observed during the subsequent 1000 s constant load nano-fretting test. The crack morphology was very similar to that in repetitive nano-impact tests and conventional nanoindentation at higher applied load with the same probe. In contrast, when the load was applied more slowly (10 s) radial cracking was not observed and there was a distinct threshold load (∼100 mN) marking the transition to a more severe wear mode with extensive lateral cracking and material removal.     

The measurement of thermal conductivity variation with temperature for solid materials

An apparatus was designed to routinely measure the thermal conductivity variation with temperature for solid materials. The apparatus was calibrated by measuring the thermal conductivity variations with temperature for aluminum, zinc, tin and indium metals. The variations of thermal conductivity with temperature for the Zn-[x] wt.% Sb alloys (x = 10, 20, 30 and 40) were then measured by using the linear heat flow apparatus designed in present work. From experimental results it can be concluded that the linear heat flow apparatus can be used to measure thermal conductivity variation with temperature for multi component metallic alloys as well as pure metallic materials and for any kind of alloys. Variations of electrical conductivity with temperature for the Zn-[x] wt.% Sb alloys were determined from the Wiedemann–Franz (W–F) equation by using the measured values of thermal conductivity. Dependencies of the thermal and electrical conductivities on composition of Sb in the Zn–Sb alloys were also investigated. According to present experimental results, the thermal conductivity and electrical conductivity for the Zn-[x] wt.% Sb alloys decrease with increasing the temperature and the composition of Sb.     

Analysis of composition dependence of some thermal transport properties in glassy Se80−xTe20Snx (0 ⩽ x ⩽ 10) alloys using transient plane source measurements

In the present work, we have studied simultaneous measurements of thermal transport properties (effective thermal conductivity, diffusivity, specific heat per unit volume, thermal inertia I_T) of glassy Se_80−xTe₂₀Sn_x (0 ? x ? 10) system using their twin pellets. The glassy system is prepared under a load of 5 tons and measurements have been made at room temperature using Transient Plane Source (TPS) technique. The composition dependence of the thermal transport properties of given glassy system is also discussed.     

Energy resolution of an Omega-type monochromator and imaging properties of the MANDOLINE filter

We report on the energy resolution properties of an Omega-type monochromator. In a TEM/STEM setup with a MANDOLINE filter and extreme stability of the high voltage and the filter current, an energy resolution of 43 meV for 0.1 s exposure time and 87 meV for 100 s exposure time was measured at 200 kV with 40 meV monochromator slit width. The monochromized zero-loss peaks are additionally characterized by their edge steepness. Moreover a drop in the monochromized zero-loss peak by 10³ after 260 meV can be obtained even without deconvolution. For small fields of view, the energy resolution mostly does not depend on the MANDOLINE filter. With the Corrected OMEGA filter an energy resolution of 41 meV was measured for 0.03 s exposure time at 200 kV with 30 meV monochromator slit width and 77 meV for 50 s exposure time at 80 kV with 40 meV monochromator slit width. Furthermore, the MANDOLINE filter’s setup and imaging properties are presented such as isochromaticity (<5 meV) and transmissivity (T_(1 eV)=17,400 nm²), which set a new standard for imaging energy filters and allow EFTEM spectrum imaging with energy windows ≤200 meV and reasonable fields of view.     

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.     

Multiscale characteristic lengths of abraded surfaces: Three stages of the grit-size effect

The abrasion mechanisms in polishing titanium-alloy samples with different grades of silicon carbide-coated abrasives were characterized using a novel multiscale analysis of the extreme amplitudes of the peaks and valleys (EAPV) of surface roughness. Two stages of roughness were found: a fractal stage (l∈10-160 μm), where EAPV values versus the observation length l were linked to the fractal dimension D (EAPV∝l^2−D), and a stochastic stage (l>160 μm), where EAPV was modeled by the extreme-value theory, allowing the prediction of EAPV values versus observation length. Three regimes of abrasion were found: for grit particles of diameter d>100 μm, EAPV values did not depend on the observation scale and were consistent with Archard’s model. For particle sizes 10 μm<d<100 μm, the EAPV diminished with d regardless of scale, representing the “grit-size effect”. For particles of diameter d<10 μm, the EAPV dramatically decreased at all scales and was independent of d because of adhesive wear. We show that Regimes one and three were dominated by the valleys due to cutting and adhesive wear, respectively, whereas Regime two (the grit-size effect) was dominated by wear peaks due to clogging and deterioration of the abrasive surface, which led to a lower indentation of the abrasive. This contribution proves that the bifractal characteristic previously observed in abrasion can be explained by a single fractal power law and, above a threshold of l>160 μm, by a cumulative-damage model, with a probability proportional to the length of the sample but always uncorrelated with scale.     

An experimental analysis and measurement of process performances in machining of nimonic C-263 super alloy

Nimonic C-263 alloy is extensively used in the fields of aerospace, gas turbine blades, power generators and heat exchangers because of its unique properties. However, the machining of this alloy is difficult due to low thermal conductivity and work hardening characteristics. This paper presents the experimental investigation and analysis of the machining parameters while turning the nimonic C-263 alloy, using whisker reinforced ceramic inserts. The experiments were designed using Taguchi’s experimental design. The parameters considered for the experiments are cutting speed, feed rate and depth of cut. Process performance indicators, viz., the cutting force, tool wear and surface finish were measured. An empirical model has been created for predicting the cutting force, flank wear and surface roughness through response surface methodology (RSM). The desirability function approach has been used for multi response optimization. The influence of the different parameters and their interactions on the cutting force, flank wear and surface roughness are also studied in detail and presented in this study. Based on the cutting force, flank wear and surface roughness, optimized machining conditions were observed in the region of 210 m/min cutting speed and 0.05 mm/rev feed rate and 0.50 mm depth of cut. The results were confirmed by conducting further confirmation tests.     

Optimization of multilayer cylindrical coils in a wireless localization system to track a capsule-shaped micro-device

A wireless electromagnetic localization method has been presented to track capsule-shaped micro-devices in the gastrointestinal tract. And a prototype for the novel localization system has been developed. In the localization method, cylindrical coils placed on the patient’s abdomen generate alternating electromagnetic fields one by one. The system of equations from the localization model has been established and then transformed into a nonlinear optimization problem. The localization method presents excellent anti-interference ability and high stability. In order to solve the magnetic inverse problem in the localization model, an analytical expression between the magnetic flux density and the position & orientation should be derived by superposition of the fields generated by the coil turns, which causes systematic errors. As a result, the geometry of the cylindrical coils is optimized to reduce the errors. A full factorial experiment with two factors has been carried out. The experiment shows that the optimal L/Dout ratio and Din/Dout ratio are 0.4 and 0.8, respectively. In this case, the mean error and the standard deviation are reduced to 0.89% and 0.77%, respectively, where the distance along the axis of the cylindrical coil from the coil’s center to a measured point is 30 mm. Furthermore, the experimental results also show that the imitation error decreases significantly with increased distance from the coil. The accuracy of the localization model can be further improved using the optimized coil.     

An algebraic–analytic framework for measurement theory

The goal of this paper is to present an algebraic–analytic framework for (static and dynamic) deterministic measurement theory, which we find to be fully adequate in engineering and natural science applications. The starting point of this paradigm is the notion of a quantity algebra of a measured system and that of a measuring instrument, underlying the causal linkages in classical ‘system + instrument’ interactions. This approach is then further enriched by providing a superimposed data lattice of measurement outcomes, intended to handle the information flow from the measured system to its measurand’s instrument. The original motivation for this algebraic–analytic setting for measurement was the authors’ earlier work (including Batitsky (1998) [1], Domotor (1992) [10], Domotor and Batitsky (2008) [11]), in which they express various concerns about the foundational adequacy of the well-known representational theory of measurement, henceforth acronymed RTM for short. There is a growing body of arguments and evidence, showing that, by and large, real-world measurements in the natural sciences and technology do not conform to the philosophical and mathematical assumptions of RTM. To make precise what we mean by all this, we begin by recalling the gist of our previous discussions of the philosophical rights and wrongs of the representational view of measurement. Then we move on to present an alternative algebraic–analytic measurement theory which, we believe, offers a natural account of classical deterministic measurement.     

Metrological characterization of the new 1 MN force standard machine of NPL India

Since November 2010, NPL India’s force scale has been complemented in the range from 10 kN to 1 MN by a further force standard machine. This automatically working 1 MN force standard machine utilizes a lever amplification of a 100 kN mass stack and enables low relative expanded uncertainties of smaller than 9 × 10⁻⁵ on the lever, and 2 × 10⁻⁵ on the deadweight side. In this paper, the constructional design of the machine is described. According to the new EURAMET Calibration Guide, a model for the uncertainties is developed.Supplementary to this, results from comparison measurements of the new NPL India machine with PTB´s force standard machines are presented.     

Development of electrically controlled polishing with dispersion type ER fluid under AC electric field

This paper shows that a dispersion type functional fluid and AC electric field may be used to control the distribution of abrasives in free-abrasive polishing and to improve surface roughness and finishing time. In the case of polishing conductive materials, such as cemented carbide, an AC electric field created by a mono-pole electrode has concentrated abrasives in the polishing area. To obtain a minimum surface roughness, a peak-to-valley voltage of 2 kV at a frequency of 0.8 Hz has been applied. Then the surface roughness of a cemented carbide plate was reduced from 0.65 μm Ra to 0.02 μm Ra in 5 min. But to polish non-conductive materials, such as glass and semiconductors, a multi-layered concentric electrode must be introduced. The surface roughness of borosilicate glass plates has been reduced from 13.5 nm Ra to 7.5 nm Ra in 3 min under the optimum AC electric field gradient of 2 kV/mm and 0.8 Hz frequency.     

Magneto-transport properties of Fe-doped LSMO manganites

Magneto-transport measurements have been performed on La_0.67Sr_0.33Mn_1−xFe_xO₃ (x = 0.0, 0.05 and 0.07) manganites synthesized by solid state route. The overall nature of AC susceptibility is found to be frequency independent. With the substitution of Mn by Fe, the transport properties dramatically change suppressing the double-exchange interaction. This in turn weakens the ferromagnetism and consequently decreases the paramagnetic to ferromagnetic transition temperature (T_c). However, DC electrical resistivity of the samples show board hump at metal-insulator transition temperature (T_MI) in contrary with sharp transition at T_c and T_MI < T_c indicating decoupling of electrical and magnetic properties. Resistivity behavior of these samples can be well explained by the consideration of bond percolation model which is basically developed from effective approximation method.     

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.     

Measurement of the elastic constants of pressure balance materials using resonance ultrasound spectroscopy

To minimise the uncertainty in pressure measured with a pressure balance its pressure distortion coefficient should be determined with a sufficiently low uncertainty. The elastic constants of piston–cylinder assembly (PCA) materials are used in the calculation of the pressure distortion coefficient and thus are one of the uncertainty sources. In this work, the resonant ultrasound spectroscopy (RUS) is applied to determine the elastic constants of PCAs’ tungsten carbide (WC) materials. A validation of the RUS technique has been carried out by measurements on rectangular parallelepiped and cylindrical samples of fused quartz, steel D22S (30CrNiMo8) and a well-known WC material. The WC materials which are used in new 7 MPa absolute pressure balances aimed at a redetermination of the Boltzmann constant have been studied. The measurements demonstrate RUS to be suitable for determining the Young modulus (E) and the Poisson ratio (μ) with standard uncertainties as low as 0.03% and 0.05%, respectively. They show variations in E and μ of up to 4% and 2%, respectively, for different batches of nominally the same material. In a few cases, even for samples cut out of the same WC piece, material inhomogeneities have been observed in both RUS and the density measurements with variations in E and μ of up to 0.8% and 0.5%, respectively.     

Investigations on the friction force anisotropy of the silicon lattice

State of the art thin film technologies allow silicon, the material of choice in semiconductor applications, to be used for micro-electro-mechanical systems (MEMS) type microactuators. To investigate the suitability of silicon for these applications, friction force tests for a silicon-silicon interface were performed. For microactuators using friction bearings there is a great need for a general understanding of friction and wear phenomena. Since silicon wafers in general exhibit a single crystalline structure, the investigations included activities regarding the influence of the single crystal silicon’s orientation. The test result shows a periodic change in the coefficient of friction depending on the slider’s rotational position. For instance, a single crystal silicon disk with a {1 1 1} surface crystal orientation exhibits six recurring maxima of the friction force per rotation when tested against a specimen with the same crystal orientation. The contact between wafer and specimen results in a coefficient of friction μ reaching its maximal value of 0.5 every 60° of rotation. To find the root cause for this repetitive behavior, the sliding directions for maximal friction values were compared to the wafer’s respective crystal orientation. For a {1 1 1} silicon wafer, the atoms at the surface are arranged in equilateral triangles. The angle of 60° between the atoms in these triangles corresponds with the periodicity of the friction force. It therefore may be concluded that the coefficient of friction follows the crystal structure. Depending on the lattice orientation, the friction force varies by more than 50%. This information is crucial for designing a micro-slide bearing as well as choosing a combination of lattice orientations that yield minimal friction.     

Analysis of computational EELS modelling results for MgO-based systems

The ab-initio density functional theory (DFT) code CASTEP was used to model oxygen K edges in various magnesium oxide systems. Firstly, for the bulk material the process of geometry optimisation was carried out. Predicted oxygen K edges were found for a single cell with experimental lattice parameters, and parameters obtained after geometry optimisation, both with single electron core-holes in place. After geometry optimisation, a different predicted result was obtained, although it was qualitatively similar to the result for experimental lattice parameters in some respects. For example, approximately the same sets of peaks are observed, though in different energy positions, and with different relative peak intensities within those sets. Ultimately for the single cell results the experimental lattice parameters generated the predicted result that was in the closest agreement with experiment. It was further observed that a large supercell result (based on the experimental lattice parameters, utilising a core-hole) led to a slightly improved comparison with experiment as compared to the corresponding single cell result, although the latter result, and indeed a ground state calculation also give reasonable agreement with experiment. To rationalise these observations it was necessary to investigate the density of states (DOS) for the MgO cell and its constituent atoms, and it was observed that the conduction bands were of predominantly magnesium character. Furthermore, the core-hole’s introduction had relatively little overall effect on the p DOS prediction for oxygen, though there is a significant localised change close to the Fermi level. This work also considers interface and surface results. The principal aim of the study was to explore the interface of Fe (0 0 1)/MgO (0 0 1), crucial in certain classes of magnetic tunnel junctions (MTJs), which have significant technological applications. An initial step was to consider a MgO (0 0 1) surface. It was verified that a surface could be constructed such that within that surface a theoretical result could be found that matched the bulk result. It was then valid to use this surface as part of an interface with iron. Theoretical results obtained at that interface compare well with experimental results from an epitaxially grown MTJ, and various conclusions are drawn with regard to the nature of the interface.