Preparation and characterisation of diamond-like carbon films prepared by MW ECR/PACVD process deposited on 41Cr–Al–Mo7 nitrided steel

In the present work, Diamond-Like Carbon (DLC) films were deposited by the Microwave Electron Cyclotron Resonance/Plasma-Assisted Chemical Vapour Deposition process on 41Cr–Al–Mo7 nitrided steel using a benzene–argon gas mixture. The quality of DLC films grown on nitrided steel using different deposit conditions such as benzene flow rate, temperature and time was investigated. Microstructural analysis by Raman spectroscopy showed main G-band peaks are localised between 1564 and 1595?cm^?1, while the D-band peaks are centred at 1297?cm^?1. Fourier Transform Infrared Spectroscopy showed the peaks attributed to C–H bending and stretching vibration modes are in the range of 2600–3100?cm^?1. The microstructure, surface morphology and mechanical properties of the films were examined by X-ray diffraction, atomic force microscopy and use of a Vickers indenter (Zwick). The deposition parameters of the coatings have been studied and optimised to improve mechanical properties. The observed increase in adhesion is related to the formation of (Fe,Cr)₃C, Cr₃C₂ and Cr₂₃C₆ interlayer phases. DLC films showed a better wear resistance, higher hardness and low friction coefficient compared to nitrided layers tested for comparison.     

Impact of interface traps on gate-induced drain leakage current in n-type metal oxide semiconductor field effect transistor

As the features sizes of metal oxide semiconductor field effect transistor (MOSFET) are aggressively scaled into the submicron domain, hot carriers generated by the very large electric fields of drain region create serious reliability problems for the integrated circuit in MOS technology. The charges trapping in the gate oxide and the defects at the Si/SiO₂ interface have also undesirable effects on the degradation and ageing of MOSFET. Among the problems caused by these effects is the band-to-band tunnelling (BBT) of hot carriers in the gate-to-drain overlap region which is the source of the gate-induced drain leakage current I _gidl. The oxide charges shift the flat-band voltage and result in an enhancement of the I _gidl current. On the other hand, the generation of interface traps introduce an additional band-trap-band (BTB) leakage mechanism and lead to a significant increase ?I _gidl in a drain leakage current. In this work we propose a new method to calculate the I _gidl current which takes into account of the BTB leakage mechanism in order to clarify the impact of interface traps located in the gate-to-drain overlap region on the I _gidl current.     

Electrochemical investigation of Ni−P autocatalytic deposition in ammoniacal solutions

The kinetics of Ni–P autocatalytic deposition in ammoniacal solutions was investigated by means of cyclic voltammetry and electrochemical impedance spectroscopy. The effect of the solution constituents (hypophosphite, nickel salt and pH) was examined. Strong interactions between the cathodic and anodic processes occur. The metal discharge is enhanced by the oxidation of hypophosphite, which is the predominant reaction in this process. The nickel deposition also affects the anodic process. With increasing pH the nickel discharge is progressively inhibited due to the change in the nature of the Ni(II) complexes. In contrast, in the presence of Ni(II) species, due to the opposite effect of the two partial processes, the plating rate increases for pH values up to 9 and then decreases for higher pH values.     

Modelisation of Ni-P electroless deposition in ammoniacal solutions

A reaction path for the electroless deposition of Ni-P layers is developed. The steady-state polarisation and impedance responses are calculated. The comparison between the experimental results and the calculation shows the adequacy of the model. The mechanism accounts for most of the experimental features observed for the steady-state and the impedance behaviours and their dependencies with pH, hypophosphite and nickel sulphate concentrations.     

Thermal treatment effect on structural and mechanical properties of Cr–C coatings

In the present study, the effect of thermal treatment on the mechanical and structural properties of chromium carbide coatings with different thicknesses is evaluated. The coatings were deposited by cathodic magnetron sputtering on XC100 steel substrates. Samples were annealed in vacuum, at different temperatures ranging from 700 to 1000°C for 1?h, resulting in the formation of chromium carbides. X-ray diffraction (XRD), microanalysis X/energy-dispersive X-ray spectrometer (EDS), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy analysis were used to characterise the samples. Mechanical properties were evaluated by nano-indentation tests and the residual stress was calculated with the Stoney formula. The XRD analysis suggests the formation of the Cr₇C₃, Cr₂₃C₆ carbides at 900°C. For thin films, they transformed totally to ternary (Cr, Fe)₇C₃ carbides and their partial transformation has been observed in the case of thick films at 1000°C, without the formation of Cr₃C₂. The EDS and XPS showed the diffusion mechanism between the chromium film and the steel substrate for the Cr, Fe, C, O elements during the annealing treatment. The increase of chromium film thickness from 0.5 to 2.64?µm, contributed to the significant enhancement of mechanical properties such as hardness (H) (from 12 to 26.3?GPa) and Young's Modulus (E) (from 250 to 330?GPa), respectively.     

Epidemiological and clinical profile of superficial mycoses in the Monastir region (Tunisia). Retrospective study (1991-1994) of 3578 cases

Despite of socio-economical improvement in our population and the efficacy of available antifungal treatment, superficial mycoses remain a common condition in dermatologic practice. To determine the epidemio-clinical pattern of superficial mycoses in our region, a retrospective study of 3578 cases have been carried out in the Department of Dermatology of the University Hospital of Monastir during a 4 year-period. The mean age of patients was 33 years (range: 6 months-91 years). The male to female sex-ratio was 0.82. Rural origin, history of previous mycoses, diabetes, topic or systemic corticosteroids and the presence of animals in surroundings were the most predisposing factors. The most frequent clinical patterns were: tinea corcoris and pedis (40.3%), Tinea versicolor (21.6%), Tinea capitis (9.7%) dermatophytosis of hairless skin (9.6%) and onychomycosis (8.6%). Dermatophyte was the most frequent (55.5%). The occurrence of superficial mycose especially if it affects diffuse area of the body, or if it is relapsing and resistant to treatment, requires looking for predisposing factors.     

Study of phosphonate addition and hydrodynamic conditions on ordinary steel corrosion inhibition in simulated cooling water

The effect of phosphonate anion (PHOS) on the corrosion of ordinary steel in simulated cooling water has been studied using weight loss, polarization curves and electrochemical impedance spectroscopy measurements. PHOS was studied in the concentration range from 7.5 × 10⁻⁵ to 10⁻³ M. The results obtained reveal that PHOS perform excellently as corrosion inhibitor for ordinary steel in simulated cooling water. The inhibition efficiency of PHOS was increased with increasing both its concentration and water circulation velocity. These two factors seem to promote the adsorption of phosphorus and oxygen ions on the metal surface, leading to the formation of a protective layer with a greater charge transfer resistance and lower permeability.     

Synchronous machine parameter identification by various excitation signals

This paper presents the results of a time-domain identification procedure to estimate the linear parameters of a salient-pole synchronous machine at standstill. In this study, several input signals are used to identify the model structure and parameters of a salient-pole synchronous machine. The procedure consists to define, to conduct the standstill tests and also to identify the model structure. The signals used for identification are the different excitation voltages at standstill and the flowing current in different windings. We identify the parameters of operational impedances, in other words the reactances and time constants. The tests were carried out on synchronous machine of 1.5 kVA/380 V/1500 rpm.     

Effects of milking interval and cisternal udder evaluation in Tunisian Maghrebi dairy dromedaries (Camelus dromedarius L.)

Effects of 4 different milking intervals (8, 12, 16, and 24 h) on milk yield and milk composition were studied in Tunisian Maghrebi dairy dromedaries (n = 6) at late lactation [240 ± 14 days in milk (DIM), 5.84 ± 1.62 L/d]. Camel-cows suckled their calves for 2 mo, were hand milked while suckling until mo 4 of lactation (calf weaning) and machine milked thereafter. Intravenous injection of oxytocin was administered before machine milking at each experimental milking to induce complete milk ejection and to avoid carryover effects of milking intervals. Cisternal and alveolar milk were measured at 380 ± 16 DIM for a 24-h milking interval. Milk accumulated logarithmically (R² = 0.95) in the udder from 8- to 24-h milking interval without reaching a plateau. Consequently, milk secretion rate decreased exponentially (R² = 0.93) according to milking interval. Compared with 12-h milking interval (6.1 L/d), estimated daily milk yield was 113, 87, and 70% for 8-, 16-, and 24-h intervals, respectively. Total milk solids, milk fat content, and milk pH decreased with increasing milking interval, showing the greatest value at 8-h intervals (14.1 ± 0.4%, 4.6 ± 0.5%, and 6.66 ± 0.05, respectively) and the lowest at 24-h intervals (12.3 ± 0.9%, 2.9 ± 0.6%, and 6.54 ± 0.02, respectively). Milk protein (3.9 ± 0.1%), lactose (4.5 ± 0.2%), ash (0.84 ± 0.01%) and density (1.028 ± 0.01) remained constant for all milking intervals. Milk K, Ca, and Mg contents increased as milking interval increased, but Na content did not change (0.06 ± 0.01%, on average). Milk Na:K ratio tended to decrease from 0.35 (1:2.9) to 0.22 (1:4.5) for the extreme milking intervals. Plasma lactose concentration steadied from 8- to 16-h (67 ± 32 μmol) but increased dramatically at 24-h intervals (338 ± 118 μmol), indicating that mammary tight junctions became permeable after 24 h of milk accumulation. Camel udders showed small cisterns (19.3% of total milk in the udder at 24 h) when compared with other dairy animals; we recommend the use of prestimulation for machine milking and selection for larger udder cisterns. Alveolar milk contained more fat (5.16 vs. 1.75%; SEM, 0.39%) and protein (3.23 vs. 2.73%; SEM, 0.15%) than cisternal milk. Despite the increase of plasma lactose during tight junction leakiness, the tendency for the Na:K ratio to decrease may be indicative of a camel's specific regulatory mechanism for controlling Na and K concentrations in milk and delaying the inhibitory effect of milk stasis on milk secretion rate. In conclusion, this short-term study proved the low storage capacity of the Tunisian Maghrebi camel udder but also showed their moderate ability to adapt to extended milking intervals at late lactation.