Sliding Wear Behavior of TaC‐Containing Ti(CN)‐WC‐Ni/Co Cermets

Four compositions of TiCN‐WC‐Ni/Co cermets with or without TaC were prepared by pressureless sintering of respective powders, and unlubricated sliding wear behavior against bearing grade steel ball was studied at 5, 10, or 20 N load. Maximum hardness and fracture toughness were obtained for Ti(CN)‐5WC‐10Ni‐10Co‐5TaC (in wt%) cermet. With change in the cermet composition and sliding load, coefficient of friction varied from 0.3 to 1.0 and wear rate varied from 3 × 10^?7 to 7 × 10^?7 mm³/Nm. The increased material transfer and formation of iron oxide‐rich tribochemical layer were responsible for the reduction in friction and wear for Ti(CN)‐5WC‐10Ni‐10Co‐5TaC cermet.     

Drop sizes in turbulent liquid–liquid dispersions containing polymeric suspension stabilizers. I. The breakage mechanism

Polymeric suspension stabilizers, when used in sufficient quantities, can stabilize liquid–liquid dispersions against coalescence. Experiments were performed using an in situ photomicrographic technique to determine the critical surface coverage of a hydroxypropyl methylcellulose product. The critical surface coverage was between 2.35 × 10^?7 and 1.2 × 10^?6 g/cm². Noncoalescing dispersions can be prepared by using high concentrations of suspending agents so that the surface coverage is above the critical value. Such noncoalescing dispersions can be used to study the breakage mechanism even at high dispersed phase volume fractions. The study of the breakage mechanism reveals that the volume swept by the turbine impeller is applicable in calculating the power input per unit mass. The new correlation between the Sauter mean diameter and the extent of agitation under turbulent conditions that is found here is in fair agreement with those available in literature.     

Hydrodynamic behaviour and oxygen transfer rate in a pilot plant fermenter: I. Influence of viscosity

The effects of varying impeller speed, aeration rate and viscosity on mixing time, power consumption and oxygen transfer rate were studied in the pilot plant fermenter. The rheological behaviour of erythromycin fermentation broth was simulated by colloidal starch solutions at apparent viscosities of 0.02–0.20 Pa/s. The volumetric oxygen transfer rate coefficient was determined by the sulphite and static method. The experimental results showed that at low viscosities, up to of 0.02 Pa/s, the suitable range of impeller speed is 250–300 min^?1 at aeration rate 0.6–0.8 VVM from the point of view of power input (2.6–2.8 kW/m³) and sufficient coefficient K_La (160–200 h^?1). At viscosities higher than 0.02 Pa/s (with pseudoplastical character) the suitable range of impeller speed is 300–350 min^?1 at the same aeration rate. Then the power input for mixing is 3.0–3.5 kW/m³ and the coefficient K_La ～ 50 h^?1.     

Hydrodynamic behaviour and oxygen transfer rate in a pilot plant fermenter. I. Influence of viscosity

The effects of varying impeller speed, aeration rate and viscosity on mixing time, power consumption and oxygen transfer rate were studied in the pilot plant fermenter. The rheological behaviour of erythromycin fermentation broth was simulated by colloidal starch solutions at apparent viscosities of 0.02–0.20 Pa/s. The volumetric oxygen transfer rate coefficient was determined by the sulphite and static method. The experimental results showed that at low viscosities, up to of 0.02 Pa/s, the suitable range of impeller speed is 250–300 min^?1 at aeration rate 0.6–0.8 VVM from the point of view of power input (2.6–2.8 kW/m³) and sufficient coefficient K_La (160–200 h^?1). At viscosities higher than 0.02 Pa/s (with pseudoplastical character) the suitable range of impeller speed is 300–350 min^?1 at the same aeration rate. Then the power input for mixing is 3.0–3.5 kW/m³ and the coefficient K_La ～ 50 h^?1.     

Tribological and corrosion behaviors of fluorocarbon coating reinforced with sodium iron titanate platelets and whiskers

A series of sodium iron titanate (NFTO)–fluorocarbon composite coatings have been prepared with the liquid-phase blending method. The effects of two types of NFTO, NFTO platelets, and NFTO whiskers, on the tribological and corrosion behaviors of the composite coatings, are systematically studied. The results show that the addition of NFTO can significantly enhance the friction-reducing and wear resistance performances of the fluorocarbon coating. Under dry sliding, the minimum specific wear rate is 1.67 × 10⁻⁴ mm³/Nm for the platelet-filled composite coatings and 1.15 × 10⁻⁴ mm³/Nm for the whisker-filled composite coatings, respectively, showing a decrease of 83.5 and 88.6% than that of pure coating. Under a simulated seawater environment, the minimum specific wear rate is 5.44 × 10⁻⁵ mm³/Nm for the platelet-filled composite coatings and 0.84 × 10⁻⁵ mm³/Nm for the whisker-filled composite coatings, respectively, showing a decrease of 90.5 and 98.5% than that of pure coating. The morphologies of worn surfaces, wear debris, and transfer films are analyzed, and the corresponding wear resistance mechanisms are discussed. The electrochemical impedance spectroscopy certifies a remarkably improved corrosion resistance of the composite coatings which have been immersed in 3.5 wt % NaCl solution for 30 days. The composite coating reinforced with 7.5 wt % platelets shows the highest resistance of 256.3 × 10⁶ Ω·cm², approximately two orders of magnitude higher than that of pure coating. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48936.     

Wear behavior of plasma sprayed hydroxyapatite bioceramic coating in simulated body fluid

To investigate the wear behavior of bioceramic coating, two-body abrasive wear of air-plasma sprayed (APS) hydroxyapatite (HA) coating was studied in different conditions including: i) in simulated body fluid (SBF) and in dry conditions, and ii) sliding on Al₂O₃ abrasive paper, HA, polycarbonate (PC) and polyurethane (PU), as well as iii) on different applied loads. Cross-sectional microstructures and worn surface morphologies of the coating were examined by scanning electron microscopy (SEM). Phase constitutions were analyzed by X-Ray diffraction (XRD). Microhardness, elastic modulus, fracture toughness and bond strength of the coating were investigated. It was revealed that, under the load of 20?N and sling on different counterpart materials, the wear rates of the coating varied from 24.09?×?10^?2to 0.25?×?10^?2 mg/Nm in SBF and varied from 13.54?×?10^?2 to 0.05?×?10^?2 mg/Nm in dry condition, respectively. The accumulated weight loss of the coating sliding on HA in SBF increased from 3.1 to 7.9?mg as the applied load increased from 5?N to 20?N. As sliding on Al₂O₃ in dry condition and/or under high load, the abrasive wear of the coating dominantly occurred in the form of ploughing and peeling off of splats. As sliding on PC, PU and HA in SBF, the adhesive wear of the coating mainly occurred in the form of exfoliation.     

Mass transfer into simulated fermentation media

The rates of oxygen mass transfer into a simulated fermentation medium, made up of 16 kg of paper pulp per m³ of aqueous sodium sulphite solution with a cupric ion catalyst, were determined in vessels of 0·187, 0·291 and 0·451 m dia., using flat-bladed turbine impellers, and the effect of varying impeller dimensions and operating speed were investigated. Above a critical impeller tip speed the volumetric mass transfer coefficients obtained at the same speed with different power inputs (produced by variations in the impeller blade dimensions) could be represented by the sum of two terms, one depending on the impeller speed, the diameters of the impeller and vessel, and the height of pulp suspension in the vessel, and the other function of the power input per unit volume and the air velocity through the vessel. At each impeller speed the increase in the volumetric mass transfer coefficient with power input was found to be greater below a certain power input per unit volume, and a correlation for this power per unit volume was based on it corresponding to a change in the rate of air recirculation through the impeller. The expression for the mass transfer coefficient provides a more accurate basis for scale-up than the use of simple rules, such as constant power per unit volume.     

Removal of cadmium and production of cadmium powder using a continuous undivided electrochemical reactor with a rotating cylinder electrode

The behaviour of a continuous undivided electrochemical reactor with a rotating cylinder electrode under potentiostatic control is examined for the abatement of cadmium from synthetic sodium sulfate solutions with Cd(II) concentrations lower than 500 mg dm^?3 at a reactor inlet pH ? 7. The process was designed to convert the metal ions in solution to metal powder, which settles to the conical of the reactor and may be removed at intervals as a sludge by opening a drop valve. The effect of applied potential, inlet cadmium concentration, rotation speed and hydrogen evolution as side cathodic reaction on the ‘figures of merit’ of the reactor are analysed. The best results were obtained for cathode potentials in the range from ?0.9 V to ?1.0 V against the saturated calomel electrode. Therefore, when the rotation speed was 1000 rpm the space time yield and the normalized space velocity were 0.64 ×10^?2 mol m^?3 s^?1 and 0.89 h^?1 respectively, while the fractional conversion per pass was 35% with a current efficiency higher than 74%. The surface morphology of the deposits as a function of the process variables is also reported. © 2002 Society of Chemical Industry     

Some Characteristics of Stirred Vessel Flows of Dilute Polymer Solutions Powered by a Hyperboloid Impeller

Measurements of the power consumption and mean and turbulent velocities in the wall jet of a stirred vessel flow, powered by a hyperboloid impeller, were carried out. The fluids were aqueous solutions of tylose, CMC and xanthan gum (XG), at weight concentrations ranging from 0.1% to 0.6%, which exhibited varying degrees of shear‐thinning and viscoelasticity. The hyperboloid impeller parameter k of Metzner and Otto (1957) was found to be equal to 27.2 ±4. In the Reynolds number range of 10³ to 3 × 10⁴ the mixing power was reduced for all non‐Newtonian fluids, but never by more than 13%. The flows of the 0.2% CMC and 0.2% XG solutions were found to be less turbulent than those of water, especially for the latter fluid where a reduction in axial rms in excess of 50% was found in the wall jet. This was attributed to elasticity effects and especially to the high zero shear viscosity of the latter fluid.     

Atomic force microscopy analysis of cathodic arc ion-plated CrN and CrC coatings

Coatings of CrN and CrC were deposited on a YT14 cemented carbide cutting tool using cathodic arc ion plating (CAIP). The surface and interface morphologies of the as-obtained CrN and CrC coatings were analyzed using a field emission scanning electron microscope. The heights, particle diameters and power spectral densities of CrN and CrC coatings were analyzed using atomic force microscopy and the correlated parameters of roughness were obtained. The results show that the roughness of the CrN and CrC coatings is 81.7 × 10^?3 and 70.2 × 10^?3 nm, respectively, and CAIP has little effect on the CrN and CrC coating roughness. The height of the peak values of CrN and CrC coatings is 0.498 and 0.502 nm, respectively, and the reduction friction of the CrN coating was slightly better than that of the CrC coating. The average particle diameter of the CrN and CrC coatings is 6.575 × 10² and 7.678 × 10² nm, respectively, and the particles are uniformly distributed with no large-scale fluctuations. The power between the cursors of the CrN and CrC coatings is 1.44 × 10^?2 and 9 × 10^?3 nm², respectively, with the power spectral density of the CrN coating being the dominant frequency.     

Effect of Convective Air Attributes with Microwave Drying of Soybean: Model Prediction and Experimental Validation

The heat and mass transfer that occurred during drying of soybeans by a combined process using microwave (MW) and convective hot air was studied. A coupled mathematical model was developed to simulate this phenomenon. The soybean samples were re-wetted to 20% wet basis, the selected level of initial moisture content (IMC), and then dried in a domestic microwave oven under various MW power levels from 300 to 390 W, using inlet air with relative humidity of 35, 55, 75, and 95%. The simulated moisture loss profiles obtained from the coupled model compared well with those obtained in the experiments. Results showed that the drying rate decreased from 6.235 × 10^?5 to 6.192 × 10^?5 kg water/(kg wb s) as the inlet air temperature increased from 30 to 60°C. Furthermore, the drying rate was observed to increase from 6.192 × 10^?5 to 6.211 × 10^?5 kg water/(kg wb s) as the relative humidity (RH) increased from 35 to 95%.     

Hydrodynamic characteristics of cold-bed circulating fluidized beds for the methanol to olefins process

The effects of the riser inlet velocity (2.2–3.9 m/s), seal-pot inlet velocity (2.4–7.1 U _mf ), aeration flow rate (2.5×10^?7–3.7×10^?6 m³/s) in seal-pot, and solid inventory (0.15–0.2 kg) on the hydrodynamic characteristics of a 9 mm-ID×1.9 m-high cold-bed circulating fluidized bed for methanol to olefins (MTO) process were investigated. FCC (Engelhard; 82.4 μm) particles were used as bed particles. Most of the experimental flow regimes were observed in fast fluidization and pneumatic transport regimes. The axial solid holdup in a riser increased with increasing solid mass flux and solid inventory. Solid mass flux increased proportionally until reaching a maximum value and then decreased with increasing seal-pot inlet velocity. The obtained hydrodynamic characteristics in the cold-bed circulating fluidized beds were compared with previous results.     

Numerical investigation of granular mixing in an intensive mixer:Effect of process and structural parameters on mixing performance and power consumption

Discrete element method (DEM) simulations of particle mixing process in an intensive mixer were con-ducted to study the influence of structural and process parameters on the mixing performance and power consumption. The DEM model was verified by comparing the impeller torque obtained from simulation with that from experiment. Impeller and vessel torque, coordination number (CN) and mixing index (Relative standard deviation) were adopted to qualify the particle dynamics and mixing performance with different parameters. A method based on cubic polynomial fitting was proposed to determine the critical mixing time and critical specific input work during the mixing process. It is found that the mixing performance and energy efficiency increases with the decrease of impeller offset. The mixing perfor-mance is improved slightly with the increase of blade number and the impeller with 3 blades has the highest energy efficiency due to its low input torque. Results indicate that the energy efficiency and the mixing performance increase with the decrease of filling level when the height of granular bed is higher than that of blade.     

Influence of agitation on the creation of coagulum during the emulsion polymerization of the system styrene–butylacrylate–acrylic acid

This paper gives the results of the estimated coagulum content in the final sample of a dispersion based on styrene–butylacrylate–acrylic acid, prepared by semicontinuous emulsion polymerization. The results were gained from experiments on 25 L and 5 m³ reactors. The dependence of the amount of coagulum on the agitation intensity was studied. It was found that it is necessary to divide the results into two regions: (a) for specific power input smaller than 80 W/m³; (b) for specific power input greater than 80 W/m³. It was found that polymerization scaling up from the point of constant coagulum content in the system studied is possible under the conditions of constant specific power input. The specific power input varied in the range from 5 to 3000 W/m². For the first region was gained the empiric correlation Y = 2.16(?_V)^?1 and for the second region the equation Y = 3.5 × 10^?5(?_V)^1.5, where Y is the amount of coagulum (wt %). For the existence of two regions we propose the following hypothesis according to which increasing mixing intensity improves the temperature and concentration nonuniformity which results in the decrease of coagulum content. From the certain value of specific power input, which is specific for each system, the amount of coagulum starts to increase due to increasing shear stress.     

Electrochemical,spectroscopic and molecular docking studies of 4-methyl-5-((phenylimino)methyl)-3H- and 5-(4-fluorophenyl)-3H-1,2-dithiole-3-thione interacting with DNA

Cyclic voltammetry (CV) and UV–Visible spectroscopy (UV–Vis) techniques were used to calculate binding parameters of 4-methyl-5-((phenylimino)methyl)-3H-1,2-dithiole-3-thione (MPDT) and 5-(4-fluorophenyl)-3H-1,2-dithiole-3-thione (FPDT) with DNA. The results obtained from both techniques were confirmed by computational molecular docking using AutoDock molecular docking software. The anodic peak potential shift in CV indicated an intercalative mode of binding. The binding constants (M^?1) of the adducts MPDT-DNA and FPDT-DNA obtained from voltammetric measurements were found to be 8.0?×?10⁴ and 2.4?×?10⁴, respectively, with binding free energy being ?27.99 and ?25.01?KJ?mol^?1, respectively. These results are in good agreement with those obtained from UV–Visible spectroscopic studies. The diffusion coefficients of MPDT and FPDT (2.06?×?10^?10 and 2.42?×?10^?9, respectively) were found to be higher than those of DNA-bound compounds (1.27?×?10^?10 and 1.65?×?10^?9?cm²/s, respectively). The binding free energy of MPDT and FPDT to DNA was also calculated by molecular docking study. The docking study gave excellent approximation with experimental results, shedding light on the sites of binding.     

Microstructural,mechanical and marine water tribological properties of plasma-sprayed graphene nanoplatelets reinforced Al2O3- 40 wt% TiO2 coating

Graphene nanoplatelets (GNPs) as reinforcement in the ceramic matrix is rising continuously due to their outstanding mechanical and lubricative properties. Herein, different compositions of GNPs (0.5–2 wt%) reinforced alumina-titania coatings were prepared using atmospheric plasma spraying. The relative density of AT coating increased from 83% to 94% with just (1.5 wt%) addition of GNP. Consequently, mechanical properties i.e. hardness and elastic modulus were improved by ~77% and ~69% respectively. Fracture toughness also increased from 2.65 ± 0.95 MPa.m^1/2 to 5.85 ± 1.07 MPa.m^1/2. Furthermore, the seawater wear test, using a ball-on-disc tribometer revealed that the wear rate of AT coating decreased from ~11 × 10^?14 m³/Nm to ~4 × 10^?14 m³/Nm, whereas the coefficient of friction reduced from 0.33 ± 0.05–0.16 ± 0.03. The mechanisms involved to improve these properties, viz. GNP sandwiching, crack bridging, crack arrest, etc. GNP’s multi-layers facilitated long-term lubricity and enhanced the wear resistance properties of the coatings.     

Sulfonated copoly(norbornene)s bearing sultone pendant groups and application as proton exchange membranes candidates

Novel copolynorbornenes bearing pendant sultone groups (designated as P(BN/SulNBOH) and P(BN/SulNBOMe)) have been successfully synthesized via copolymerization of functionalized norbornenes bearing sultones (designated as SulNBOH and SulNBOMe) with 2-butoxymethylene norbornene (BN). The catalyst system showed high catalyst activity (10⁴ g_polymer/mol_Ni·h) and the obtained copolymers have high molecular weight and a narrow molecular weight distribution. Furthermore, the achieved copolymers P(BN/SulNBOH) and P(BN/SulNBOMe) were converted into sulfonated copolymers sP(BN/NBOH) and sP(BN/NBOMe). Both sP(BN/NBOH) and sP(BN/NBOMe) membranes displayed low water uptake, high thermal properties, good mechanical properties, and better proton exchange membranes properties. The proton conductivities measured in the hydrated state at 80?°C ranged from 10^?5 to 7.19?×?10^?3?S·cm^?1.

A comparison of cavern development in mixing a yield stress fluid by rushton and intermig impellers

Intermig impellers have been postulated as very efficient for mixing highly viscous non-Newtonian fluids (such as xanthan and mycelial broths). However, no formal characterisation has been published and no fair comparisons have been made, based on accurate power drawn measurements and using equal number of impeller stages and equal diameter, if compared (for example) with the performance of Rushton turbines. Characterisation of the shape, size, and evolution of the well-mixed zones or “caverns” were correlated with power drawn, for single and dual Rushton turbines and for one- as well as two-stage Intermig unslotted impellers. Cavern evolution studies were carried out in a mixing tank (diameter=0.205 m, H/T=1.6) equipped with an accurate air bearing dynamometer. Carbopol 940 (0.25 wt.-%) was used as a model, transparent fluid. Impeller to tank diameter ratio was 0.53 for both impellers. Caverns were visualised by injecting methylene blue in the well-mixed zones. A single Rushton turbine developed larger caverns if compared with one-stage Intermig of the same diameter under power drawn below 1.5 kW m^?3. At higher power drawn, both impellers behaved very similarly, reaching a limit in cavern volume of about 40% of the total liquid volume, even at very high (20 kW m⁰³) power drawn. A similar trend characterised dual combinations: below 3 kW m^?3, dual Rushtons gave larger cavern volume if compared with the performance of two-stage Intermigs. In either case, power drawn higher than 3 kW m⁰³ was sufficient to mix more than 90% of the liquid volume. The presence or absence of the slot in the Intermig did not influence cavern development. Experiments with a smaller if compared with those obtained with the larger Intermig (D/T = 0.53).     

Gassed and ungassed power draw in a pilot scale 550 litre fermentor retrofitted with up-pumping hydrofoil B2 impellers in media of different viscosity and with very high power draw

A number of modern impellers have been designed in the pursuit of an alternative to the traditional Rushton turbine, which has a number of well recognized deficiencies. A dual up-pumping combination of the Hayward Tyler B2 (former APV-B2 or simply B2), a high solidity ratio hydrofoil impeller, was retrofitted using traditional methods to a pilot scale fermentor based on cited reference studies of the impeller performance. Using water as a media and comparatively low power draws, the B2 impeller has previously been shown to have good gas handling properties and a low ungassed power number allowing for use at high impeller-to-tank diameter ratio. In the present study a power characterization of the B2 impeller was undertaken in order to extend the available data to viscous media resembling fermentation broths and to very high power draws. Power characterizations were carried out with specific energy input rates up to 12.9 kW/m³ using different shear-thinning media.The ungassed power number of the B2 impeller was determined (3.3 for power draws in the range 0-11.6 kW/m³) and our findings confirm those of previous studies and extend the trends to media of high viscosity. Upon aeration the B2 impellers loose little power compared to the traditional impeller even when applying a very high power draw (10-20% power loss at 450 rpm and 1.28 vvm corresponding to 11.6 kW/m³). Torque fluctuations are found to be small (<5%) for this impeller at high power draw and high viscosity media. Finally it is shown that the B2 impeller can be retrofitted to pilot scale fermentors using traditional methods with a high degree of confidence.     

Wear resistance and hardness properties of TiB2– Fe coating developed on AISI 1020 steel by tungsten inert gas (TIG) cladding

The present work is attempted to improve the microhardness and wear properties of AISI 1020 steel by depositing TiB₂–Fe composite coating using tungsten inert gas (TIG) cladding. In this study, different compositions of TiB₂–Fe paste form were preplaced on the substrate plates and then TIG heat input was applied to deposit hard composite coating layer. The main objective of the present work was to explore the influence of TIG input current as well as iron content on the microstructure and surface properties of deposited coatings. Microhardness, microstructural and phase characterization of the coating have been done by the Vickers microhardness tester, scanning electron microscope (SEM), Energy dispersive spectroscopy (EDS) and X-ray diffractrometer (XRD). The results showed that the microhardness of the TiB₂–Fe coating was strongly influenced by the composition of the coating materials as well as the TIG processing current. The microhardness increases with decreasing Fe contents in the coating materials with constant processing current (90 A) as well as it also increases with decreasing processing current with the fixed composition of coating materials (80TiB₂–20Fe). The maximum average microhardness found was 3082 HV_0.1 for the coating of 100TiB₂–0Fe composition ratio and 90 A processing current which was about 18 times higher than that of the substrate average microhardness value (163 HV_0.1). Average wear rate evaluated by considering weight loss of the TIG cladded samples using pin on disc tribometer by the sliding distance of 864 m and 20 N normal loads. The wear results also showed that the coating contains 100 wt% of TiB₂ (0 wt% of Fe) exhibited lower rate of wear 6.74 × 10^?8 g/Nm which is about 24 times lower as compared to AISI 1020 mild steel wear rate (166.31 × 10^?8 g/Nm).