Single-pass Tests Research Articles

Highly efficient ZnO photocatalytic foam reactors for micropollutant degradation

The efficient removal of organic micropollutants, pharmaceuticals, pesticides, drugs, and others, remains an unsolved challenge in water treatment. Although photocatalysis has proven highly effective at degrading these substances, its large-scale implementation has been so far hampered by technical and economic concerns. This work describes the development and characterization of novel highly efficient, self-supporting photocatalytic ZnO foams for the degradation of organic micropollutants. A systematic investigation of flow rate, catalyst length and stability under both recirculating and single-pass conditions was conducted using carbamazepine as a UV-recalcitrant model pollutant. Under recirculation, 95 % degradation was achieved with photocatalyst quantum yield of 1.2 × 10−3 and electrical energy per order (EEO) as low as 24 kWh m−3, values outperforming current technology, slurry and immobilised systems. For single-pass tests, complete degradation was achieved in 30 min, with the quantum yield increasing to 6.3 × 10−3, and an EEO of 36 kWh m−3. These values also outperform those for slurries, immobilised and other foam photocatalyst reported in the literature under similar conditions. The low energy consumption of these newly developed photocatalytic foams, combined with their high quantum yield and stability, provides a realistic path towards practical implementation of photocatalytic processes in water treatment, addressing the limitations of existing slurry and immobilised photocatalytic technology.

Tyre Configuration and Axle Load of Front-Wheel Assist and Four-Wheel Drive Tractors Effects on Soil Compaction and Rolling Resistance under No-Tillage

Selecting the appropriate tyre configuration and settings for heavy farm vehicles is important to ensure that soil compaction and power loss in rolling resistance are minimised and traction is optimised. This study investigated the effect of front-wheel assist (FWA, ≈75 kN) and four-wheel drive (4 WD, ≈100 kN) tractors fitted with different tyre configurations (single, dual), tyre sizes and inflation pressures on soil strength (a proxy for soil compaction), and rolling resistance. Single-pass tests were performed on a Typic Argiudoll (≈23% clay, bulk density: 1305 kg m−3) managed under permanent no-tillage. Results showed that average power losses in rolling resistance were 7.5 kN and 5 kN for the 4 WD and FWA tractors, respectively. The average rut depth increased by approximately 1.4 times after a pass of the 4 WD compared with the FWA tractor. The soil cone index (0–600 mm depth) increased from 2023 kPa (before traffic) to 2188 and 2435 kPa after single passes of the FWA and 4WD tractors, respectively (p < 0.05). At the centreline of the tyre rut, dual tyres reduced the soil cone index a little compared with single tyres, but they significantly increased the volume of soil over which soil strength, and therefore soil compaction, was increased. For both tractors (regardless of tyre configuration or settings), soil strength increased to the full measured depth (600 mm), but relative changes before vs. after traffic became progressively smaller with increased soil depth. The power loss in rolling resistance was consistently greater with the heavier tractor, and rut depth was directly related to tyre inflation pressure.

Performance of the graphite felt flow-through electrode in hexavalent chromium reduction using a single-pass mode

Flow-through electrodes generally outcompete traditional parallel-plate electrodes in current efficiency and mass transfer. High-performance electrode materials can be costly and complicated to fabricate, hindering their wide application. In this study, we used commercial graphite felt (GF) as the cathode of a flow-through electrochemical cell to investigate its potential in treating Cr(VI) solution through electroreduction. The flow-through design with the porous GF electrode allowed sufficient contact surface with Cr(VI) and single-pass tests demonstrated a high reduction efficiency (95~100%) [117 mg/L~3 mg/L Cr(VI)] under acidic conditions. Slow flow rate and high current promoted electroreduction of Cr(VI). The presence of other metal ions could further improve Cr(VI) reduction at low flow rates due to enhanced conductivity in dilute solutions and generation of low valent ions as reducing agents. At fast flow rates, competition of these ions for reduction decreased Cr(VI) reduction efficiency. Moreover, an acidic environment prevented the coating of an insoluble layer on the GF surface and promoted durable performance, with a lower energy consumption [0.46 kWh for treating 100 L 117 mg/L Cr(VI) solution per unit area of GF]. This work demonstrated the potential of Cr(VI) detoxification using GF cathodes in flow-through electrochemical cell.

Experimental evaluation of in-duct electronic air cleaning technologies for the removal of ketones

Reducing volatile organic compounds (VOCs) concentrations in built environments is necessary to achieve acceptable indoor air quality or comply with workplace regulations. Different air cleaning technologies are applied for the removal of VOCs. Unlike conventional adsorption-based technologies like activated carbons, so-called electronic air cleaning (EAC) technologies generate reactive species directly or indirectly to oxidize VOCs. In this study, dynamic single pass tests were conducted in a test rig consisting of four identical test ducts with individual flow control, allowing simultaneous evaluation of four different air purification systems under identical conditions. Three oxidation-based air-cleaning technologies were considered: photocatalytic oxidation (PCO), non-thermal plasma (NTP), and ozonation (O3). A total of 17 different configurations of EAC systems were tested for acetone and/or methyl ethyl ketone (MEK) removal. These include 12 different commercial PCO units, one in-house pilot PCO, two plasma, and two ozonation units. Sixteen of them were tested for the removal of 0.1 ppm MEK and their single pass removal efficiencies varied from 0 to 37%. Eleven of them were examined for the removal of 0.1 and 1 ppm of acetone and the removal efficiencies were between 0 and 23%. Ozonation and PCO-based system using ozone generating vacuum UV lamps generally showed a higher efficiency than PCO-based system with non-ozone generating UVC lamps or plasma units. Formaldehyde, acetaldehyde, and acetone were detected as the oxidation by-products in MEK testing. PCO-based systems tend to generate more by-products.

Cell and Electrode Development for the Hydrogen Peroxide Production Via Partial Oxygen Reduction Reaction

Hydrogen peroxide is an important industrial commodity. For large scale industrial use, the production via the established anthraquinone process is still economical most favourable. However, smaller applications would require substantial logistic efforts for the distribution. For these applications the local production could be more suitable. Electrochemical methods using renewable energy would further support the environmental friendliness. A simple electrochemical way to produce hydrogen peroxide is the partial reduction of oxygen from air according to equation [1]. A limiting factor is the undesired further reduction of hydrogen peroxide to water at the same electrode according to equation [2]. As the reversible potential for this reaction is much higher than that for the oxygen reduction, the reaction is kinetically favoured. Some efforts were made to find catalyst with a low activity for this undesired reaction. One candidate material for an acidic environment are gold catalyst with a small amount of added palladium (1, 2). In own test this was confirmed in RRDE tests (3). In this contribution the transfer into a full cell will be described. As cell a Micro Flow Cell with 10 cm2 electrode area and n Electro MP Cell with 100 cm2 electrode area were used, both ElectroCell A/S, Denmark. Both cells were modified to accommodate house made gas diffusion electrodes. On the cathode side commercial oxygen evolution electrodes by ElectroCell A/S were employed. The gas diffusion electrodes were made from fuel cell type GDLs H23C8 by Freudenberg, Germany. Catalyst layer was either applied by sputter coating or by airbrushing a catalyst ink of carbon supported catalyst. 2 M sulphuric acid was used as electrolyte on both sides. The electrolyte was flown through gaps between the electrode and the separation membrane made from FumaSep F-101020 PK by Fumatech, Germany (cf. Fig. 1). The gap width in 10 cm2 cell was 4 mm on both sides. In the 100 cm2 cell the anodic gap width was increased to 8 mm on the anode side in order to decrease the gap on the cathode side to 1.5 mm. Hydrogen peroxide concentrations were measured using a commercial electrochemical sensor by AMT, Germany downstream of the cell. Tests were either performed by passing a small electrolyte flow through the cathode side once a sampling the product (single pass) or by cycling the electrolyte at a high flow rate till a stable concentration was reached (cycled batch). For the 10 cm2 cell tests with electrodes sputtered with a 50 nm platinum layer were compared to testes with electrodes coated with 20 wt% PdAu/C catalyst with 0.15 mg cm-2 metal loading. In single pass tests with the platinum electrode the highest observed hydrogen peroxide concentration of 0.3 wt% was obtained at an electrolyte flow rate of 0.1 ml min-1 at a current of 250 mA corresponding to a current efficiency of ca. 11% (c.f. Fig. 2). Increasing the flow rate to 0.5 ml min-1 decreased the H2O2 concentration to 0.2% wt% which, however, corresponds to a current efficiency of 37.8%. This can be seen as indication for hydrogen peroxide reduction at longer residence time. Accordingly, no built up in concentration of H2O2 was observed in cycled batch operation. Surprisingly, for the electrode coated with PdAu/C catalyst a much lower hydrogen peroxide concentration of 0.1 wt% was obtained at 0.1 ml min-1 flow rate in spite of a higher current of 550 mA (c.f. Fig. 3), so that the current efficiency was less than 2%. This can only be explained by a long hold back time of hydrogen peroxide in the porous structure of the supported electrode. The strong influence of the local concentration is further supported by the finding that during first tests in the larger cell with smaller gap and thus stronger flow it was possible to obtain hydrogen peroxide concentrations of 0.5 wt% with the sputtered platinum electrode. Here, also an accumulation of hydrogen peroxide during cycled batch operation was possible so that hydrogen peroxide concentrations up to 0.6 wt% were accomplished. In the contribution more details on the tests will be discussed supporting the importance of the cell design for the reaction selectivity. J. S. Jirkovsky, I. Panas, E. Ahlberg, M. Halasa, S. Romani and D. J. Schiffrin, Journal of the American Chemical Society, 133, 19432 (2011).J. S. Jirkovsky, I. Panas, S. Romani, E. Ahlberg and D. J. Schiffrin, Journal of Physical Chemistry Letters, 3, 315 (2012).C. Cremers, B. Kintzel, K. P. Duraisamy, K. Pinkwart and J. Tübke, Meeting s, MA2016-02, 1652 (2016). Figure 1

Controlling grain size via dynamic recrystallization in an advanced polycrystalline nickel base superalloy

Controlling grain size in polycrystalline nickel base superalloy is of paramount importance in optimizing hot-working process and achieving the desirable mechanical properties. Typically, a uniform and fine grain size is required throughout forging process to realize the superplastic deformation. Unfortunately, the forging processing window is very narrow and needs to be synergistically controlled by deformation temperature, strain rate, as well as strain amount, and the failure would lead to the non-uniform grain size, abnormal grain growth and even cracking. During superplastic deformation, dynamic recrystallization (DRX) is the governing mechanism to be adopted to maintain the required grain size. Previous literature have extensively documented the separated effect of deformation parameters using monotonic-pass compression test. Herein, we perform the multi-pass compression experiments to investigate the flow stress behavior and grain size evolution. By conducting multi-pass tests over a range of deformation parameters, it was demonstrated that the flow stress and grain size response differed from that in single-pass tests. The multi-pass compression tests unambiguously uncover the roles of DRX and static recrystallization (SRX) in regulating grain size and affecting flow stress. The experimental results further show, comparing to the monotonic-pass compression, the multi-pass approach can provide versatile routes to attain the desirable grain size distribution by means of utilizing DRX and SRX principles.

Feasibility of Neurapheresis™ as a Therapy for Multidrug Resistant Gram-negative Bacterial Meningitis

BackgroundThe World Health Organization has identified Pseudomonas, Acinetobacter and Klebsiella (PAK) as three multidrug resistant (MDR) gram-negative pathogens that pose a threat to human health. The greatest threat lies in hospitals, nursing homes, and patients with devices such as intravenous catheters and ventilators. Gram-negative bacterial meningitis (GBM) manifests when these bacteria invade the central nervous system. Due to the threat of increasing antibiotic resistance and the high mortality associated with MDR GBM, we have tested a closed-loop, extracorporeal cerebrospinal fluid (CSF) filtration system (NeurapheresisTM) for its applicability in this context. Here we demonstrate feasibility of Neurapheresis for MDR GBM and characterize system parameters for bacterial clearance.Methods PAK cultures were grown and diluted to 1 × 107 cells/mL in artificial CSF or Luria-Miller broth. Both single pass and closed loop filtration were performed with various tangential flow filtration (TFF) and dead-end filter paradigms. Samples were taken either immediately post-filter or after every full CSF volume cycle (150 mL) during a long-term closed loop experiment. Bacterial load, endotoxin and cytokines were quantified.ResultsIn single pass tests, 5kDa and 100kDa TFF filters and 0.2µm and 0.45µm dead-end filters excluded all PAK organisms completely. The 100kDa and 5kDa TFF filters significantly reduced endotoxin concentration by >95% and >99% of baseline, respectively. The 5 kDa TFF filters produced a 2-log (>99%) reduction in cytokines (IL-1ra, IL-6, TNF, CRP, and CXCL10). In closed-loop experiments, both TFF filters demonstrated a 1–2 Log CFU (90–99%) reduction of all PAK organisms over 4 filtration cycles.ConclusionNeurapheresis shows potential to be an efficient multi-modal tool for controlling and treating MDR GBM in this in vitro model. Extending closed loop filtration over time demonstrates capability for rapid sterilization of the CSF. Future iterations may include adjunctive intrathecal drug delivery to further accelerate elimination of bacteria. Reduction of both endotoxin and cytokines by Neurapheresis may have significant implications for controlling the damaging neuro-inflammatory response during MDR GBM.Disclosures B. Hedstrom, Minnetronix, Inc.: Employee, Salary; L. Zitella Verbick, Minnetronix, Inc.: Employee, Salary; A. Mccabe, Minnetronix, Inc.: Employee, Salary; S. P. Lad, Minnetronix, Inc.: Collaborator and Scientific Advisor, Licensing agreement or royalty, Research grant and Research support; V. Fowler Jr., Pfizer, Novartis, Galderma, Novadigm, Durata, Debiopharm, Genentech, Achaogen, Affinium, Medicines Co., Cerexa, Tetraphase, Trius, MedImmune, Bayer, Theravance, Cubist, Basilea, Affinergy, Janssen, xBiotech, Contrafect: Consultant, Consulting fee; NIH, MedImmune, Cerexa/Forest/Actavis/Allergan, Pfizer, Advanced Liquid Logics, Theravance, Novartis, Cubist/Merck; Medical Biosurfaces; Locus; Affinergy; Contrafect; Karius: Grant Investigator, Grant recipient; Green Cross, Cubist, Cerexa, Durata, Theravance; Debiopharm: Consultant, Consulting fee; UpToDate: Royalties, Royalties

The effects of thermomechanical history on the microstructure of a nickel-base superalloy during forging

The effect of thermo-mechanical history on hot compression behaviour and resulting microstructures of a nickel base superalloy is presented. Hot compression tests were carried out on HAYNES® 282® specimens to varying strains from 0.1 to 0.8. Both single pass and multi-pass tests were completed. 60min inter-pass times were utilized to accurately replicate industrial forging practices. The effect of dynamic, metadynamic and static recrystallization during inter-pass times on flow stress was investigated. The resulting microstructures were analysed using scanning electron, optical microscopy and EBSD to relate grain size and homogeneity with flow stress data. The study showed a negligible difference between multi-pass and single pass tests for strain increments above 0.2. Therefore, when modelling similar low strain and strain rate forging processes in HAYNES® 282®, previous forging steps can be ignored.

A depth filtration model of straining within the void networks of stainless steel filters

AbstractA depth filtration model has been developed, based on the three‐dimensional void network model Pore‐Cor. The geometry of the void network is fitted, by means of an eight‐dimensional Boltzmann annealed amoeboid simplex, to the porosity and percolation characteristics of stainless steel sintered filters measured by mercury porosimetry. Preferential and critical flow paths through the network are calculated. Particles from an experimental size distribution are fed along these flow‐biased paths, and when straining occurs, the flow paths are re‐calculated. We show that the model usefully reproduces experimental filtration efficiencies as a function of pressure drop, measured by single pass tests. We also offer a critique of current measurements of filtration efficiency, suggesting the use of a new “alpha efficiency” rather than the standard beta efficiency. The model is currently being adapted to accept porometry as well as porosimetry data, hence avoiding the use of mercury. © 2009 American Institute of Chemical Engineers AIChE J, 2009

Rejection of organic micropollutants by high pressure membranes: comparison of bench-scale versus single element tests

There has been considerable information reported on rejection of trace organic compounds from pilot-scale and full-scale experiments with reverse osmosis (RO) and nanofiltration (NF), but this information has limited value in predicting the rejection of these compounds by high-pressure membranes. The goal of this research is to define relationships between compound properties, membrane properties, and operational conditions, e.g. pressure, recovery, affecting trace organic compound rejection, comparing bench-scale recirculation tests and bench-scale single-pass tests. In addition, bench-scale results are compared against single element tests to ascertain scale-up effects.

Middle molecule removal in low‐flux polysulfone dialyzers: Impact of flows and surface area on whole‐body and dialyzer clearances

Some studies found that the removal of middle molecules has a long-term effect on mortality and, even more, is enhanced by high-flux dialysis. In order to enhance middle molecule removal in a low-flux dialyzer, the present study aimed at investigating the combined impact of dialyzer flows and membrane surface area. Blood and dialysate flows were varied within the clinical range 300-500 and 500-800 mL/min, respectively, while the ultrafiltration rate was kept constant at 0.1 L/hr. Single-pass tests were performed in vitro in a single Fresenius F6HPS dialyzer (3 tests) and serially (5 tests) and parallel (3 tests) connected dialyzers. The blood substitution fluid consisted of dialysis fluid in which radioactive-labeled vitamin B12 (molecular weight 1355 Da) was dissolved. Dialyzer clearance as well as whole-body clearance was calculated from radioactivity concentrations of samples taken from the inlet and outlet bloodline. Adding a second dialyzer in series or parallel ameliorated the overall dialyzer and whole-body clearance significantly, except for the highest applied blood flows of 500 mL/min. Better solute removal was also obtained with higher dialysate flows, while the use of higher blood flows seemed advantageous only when using a single dialyzer. Analysis of the ultrafiltration profiles in the different configurations illustrated that enhancing the internal filtration rate ameliorates convective transport of middle molecules. Adequate solute removal results from a number of interactions, as there are blood and dialysate flows, membrane surface area, filtration profile and concentration profiles in the blood and dialysate compartment.

Impact of flow and surface area on middle molecule clearance

Urea is still clinically applied as standard marker to quantify dialysis adequacy. The removal of middle molecules has however been proven in some studies to have a long‐term effect on mortality. Therefore, the present study is aimed at investigating the impact of blood and dialysate flow, and membrane surface area on middle molecule removal in low flux Fresenius F6HPS dialyzers. Blood and dialysate flows were varied within the clinical range of 300–500 mL/min and 500–800 mL/min, respectively, while ultrafiltration rate was kept constant at 0.1 L/h. Single pass tests were performed in vitro in a single dialyzer (3 tests) and in serially (5 tests) and parallel (3 tests) connected dialyzers. The blood substitution fluid consisted of bicarbonate dialysate in which radioactive labeled vitamin B12 (MW1355) was dissolved. Middle molecule concentrations of samples taken at the inlet and outlet blood line were derived from radioactivity measurements and were applied to calculate the dialyzer clearance as well as the reduction ratio. For the latter, the surrogate middle molecule vitamin B12 was assumed as distributed according to a two‐pool kinetic model. Adding a second dialyzer in series or parallel ameliorates significantly overall dialyzer clearance and reduction ratio, except for the highest applied blood flow rate of 500 mL/min. Better solute removal is also obtained with higher dialysate flows, while the use of higher blood flows seemed only advantageous when using a single dialyzer. Analysis of the ultrafiltration profiles in the different configurations illustrated that enhancing the internal filtration rate ameliorates the convective transport of middle molecules. In conclusion, adequate solute removal results from a number of interactions, as there are, blood and dialysate flow rates, membrane surface area, filtration profile, and concentration profiles in the blood and dialysate compartment.

Diffusive clearance of small and middle-sized molecules in combined dialyzer flow configurations.

Clearance of low (LMW) and middle molecular weight (MMW) solutes was investigated in vitro for different dialyzer configurations and mutual flow directions. Single pass tests were performed with two low flux Fresenius F6HPS hemodialyzers placed in series (12 tests) and in parallel (6 tests), and results were compared with those for one single dialyzer (2 tests). Either high concentrated (45mS/cm) bicarbonate dialysis fluid (surrogate LMW) or trisodiumphosphate (surrogate MMW) concentration (31mS/cm) was used as blood substitution fluid. Standard blood and dialysate flows of 250 and 500ml/min, respectively, were prescribed. Clearance was derived from conductivity measurements in blood and dialysate compartment, correcting for the overall ultrafiltration rate of 0.1-0.5l/h. In a single dialyzer, changing the counter current flow to co-current deteriorates diffusive clearance by 14% (LMW) and 18% (MMW). Compared to one single dialyzer using counter current flow, clearance increases by 3 to 8% (LMW) and by 15 to 18% (MMW) using two dialyzers in parallel and in series, respectively. As a consequence, the benefit by using a second dialyzer is more prominent for larger molecules. Moreover, pressure profiles drawn for the different configurations show the impact of limited convection on diffusive clearance.

CLEARANCE OF SMALL AND MIDDLE-SIZED MOLECULES IN COMBINED DIALYZER SYSTEMS

To overcome problems of insufficient clearance in obese patients, multiple dialyzers may be placed in series or in parallel. We studied ex vivo the influence on the overall clearance of different dialyzer configurations in which mutual flow directions are changed. The kinetics of low (LMW) as well as middle molecular weight (MMW) molecules is investigated. Single pass tests are performed with F6HPS hemodialyzers placed in series (8 tests), in parallel (3) and in single use (2), using either high concentrated (45mS) bicarbonate dialysate (LMW) or trisodiumphosphate (MMW) concentration (30mS) with standard blood and dialysate flows of 250 and 500ml/min, respectively. Clearance is derived from conductivity measurements (WTW LF340) in both compartments, correcting for the overall ultrafiltration rate of 0.1-0.51/h. Compared to one single dialyzer in countercurrent flow, clearance increases by 3 and 7% using two dialyzers in parallel and in series, respectively. With cocurrent flows, clearance deteriorates (2%) using a parallel dialyzer configuration, while molecules are better removed for dialyzers in series, depending on whether both fluid inlets are in the same dialyzer (4%) or not (21%). Changing subsequently the counter-current flows to cocurrent in one and both dialyzers in series, the overall clearance decreases by 2 to 7%, respectively, for LMW, and by 6 to 15% for MMW molecules. With respect to the parallel set up, the removal of both molecule types is declined by 10 to 20%, respectively. To obtain a better clearance, two dialyzers in series with countercurrent flows should be considered.

Wear transition of a lubricated sliding steel contact as a function of surface texture anisotropy and formation of boundary layers

This article presents an experimental study of how the transition from mild to severe running conditions of a lubricated sliding steel contact depends on surface texture anisotropy and boundary layers formation. An experimental series was performed on a lubricated sliding ball-on-disc test machine with the capability to make quick but controlled transient single-pass tests. The test discs were finely ground with a strongly anisotropic surface texture. The transition tests were performed at 18 different sliding velocities between 0.038 and 1.19 m/s. For each sliding velocity, the applied load was increased with a constant load rate from zero to a pre-defined load level before the disc had rotated one turn. The first contact between the disc and the ball was arbitrary in relation to the topography orientation for the different tests. Four different states of the test discs were studied: as machined; oxidised by increased temperature in air; pre-treated by immersion in the lubricant and then heating; and pre-treated by applying the lubricant on heated discs. The lubricant was an ISO VG 150 paraffinic mineral oil with triphenylphosphorothionate (TPPT) and phosphorous–nitrogen (PN) additives. The test results show that the load level at which the graduate development from local to complete failure strongly depends on the surface texture orientation relative the sliding direction. The results also show that pre-formed boundary layers decrease the risk of wear transition.

RAMIFICATIONS OF METHOD OF SELECTING EFFECTIVE SWATH WIDTH

<!--**************************************************************** ** DIR: asae\data\abstracts ** FILE NAME: pm2795.htm ** Function: display abstract of xml ** Created ON: 08/22/01 ** Created BY: Lisa Rupp ** Revision History ****************** ** REVISION DATE: BY: ** REVISION DESCRIPTION: ** ********************************************************************--> RAMIFICATIONS OF METHOD OF SELECTING EFFECTIVE SWATH WIDTH RAMIFICATIONS OF METHOD OF SELECTING EFFECTIVE SWATH WIDTH/h1> Spreader pattern and width determinations are sometimes made from single-pass tests and sometimes from multiple-pass tests. Recent work in New Zealand showed that data from multiple-pass tests resulted in overstating swath width compared with data from single-pass tests. Results presented here demonstrate that the effect of multiple-pass tests on the determination of swath width is dependent upon the method used to determine effective swath width. If the effective swath width is determined by selecting the greatest swath width that will not exceed a selected coefficient of variation (CV) value, then the use of multiple-pass testing can affect the selection of swath width. If, however, effective swath width is determined from minimum points in the CV:width function, then it is much less likely that the use of multiple-pass testing will affect swath width, and the use of multiple-pass testing will provide more consistent data or the same consistency with less effort than single-pass testing.

The influence of microstructure on tribological properties of WO 3 thin films

The influence of the microstructure of WO 3 thin films upon friction and wear during sliding contact was studied using two different tribometers. The tungsten trioxide (WO 3) thin films of controlled microstructure were grown on R-plane sapphire substrates using electron cyclotron resonance (ECR) oxygen-plasma-assisted electron beam evaporation of WO 3 pellets. The WO 3 films were fabricated to consist of amorphous, polycrystalline or epitaxial microstructure, depending on the deposition temperature, as indicated by in situ RHEED analysis. Pin-on-disk testing of the WO 3 films was performed using 10 mm diameter sapphire and 440C stainless steel sliders and 1 N normal force. Epitaxial crystalline WO 3 films showed lowest friction ( μ∼0.3 for both sapphire and steel spheres) and greatest production of debris, while amorphous WO 3 films exhibited higher friction coefficients (up to μ∼0.6 for sapphire spheres and μ∼1.1 for steel spheres), less debris production, and more slider wear. Epitaxial WO 3 films exhibited low friction ( μ∼0.16) in single pass tests with sapphire and steel sliders (1 mm stroke, 0.1 mm/s, 0.1 N load,), whereas amorphous and polycrystalline WO 3 films showed transitions to much higher friction (up to μ∼0.7). Lower friction and wear of WO 3 films with epitaxial structure compared to amorphous structure appears to be due to a lubricious WO 3 layer transferred to the slider from the epitaxial film.

Frictional deformation and fracture in polycrystalline SiC and Si 3N 4

Electron optical microscopy was employed to study the friction and wear of commercial polycrystalline varieties of SiC and Si 3N 4 in air at ambient temperature. Friction and wear tests were conducted in a reciprocating configuration with conical riders (both diamond and ceramic) sliding on a flat ceramic substrate. Worn surfaces were examined by both scanning electron microscopy and transmission electron microscopy. In general, friction and wear in the diamond-ceramic couples were severe. Friction with ceramic-ceramic couples was low, with friction coefficients between 0.1 and 0.4, wear being absent in single-pass tests. With ceramic-ceramic couple multipass systems, wear of Si 3N 4 occurs by plastic deformation which increases in severity with sliding distance accompanied by a corresponding increase in friction coefficient. With SiC, wear occurs by a mixture of intergranular fracture due to grain boundary weakness and plastic deformation.