Titanium nitride

Lithium titanate spinel (Li 4 Ti 5 O 12 , or LTS) is receiving consideration as a nanopowder anode material for use in lithium-ion batteries. LTS has more positive working potential than traditional graphite anodes, and it does not react with electrolyte components. However, the main drawback of LTS powder is its poor interparticle electronic conductance that reduces the high-rate ability of the electrode. To improve this we have coated the surface of the LTS powder with a titanium nitride layer by atomic layer deposition (ALD). In situ infrared spectroscopy studies were conducted to confirm the attachment of the titanium precursor. The nitrogen content of films was measured by total nitrogen content testing. Transmission electron microscopy (TEM) micrographs confirmed the formation of a thin titanium nitride film around LTS particles by ALD. Finally, lithium cells with electrodes made of original and modified LTS nanopowders were assembled and tested.

TiN coatings can be obtained in a relatively wide range of compositions around stoichiometry. Changing the stoichiometry around the 1:1 composition broadens the spectrum of colors and can modify the mechanical properties as compared with those of stoichiometric TiN. In this work, we present the deposition of TiN coatings by using a metallic Ti cathode and varying the nitrogen partial pressure in a cathodic arc evaporation reactive process. The composition, crystalline structure, hardness and color of the different samples are characterized, and the effect of deposition pressure is discussed. The hardest coatings were deposited in the interval of deposition pressures between 5 and 20 Â 10 À3 mbar. From the reflectance spectra in the visible range, a dominant wavelength of 581-582 nm is found for all the TiN samples, very close to that of the pure gold reference spectrum (579 nm) with purity colors that increase with the deposition pressure from 0.67 to 0.84 and approaches the color purity measured for the pure gold reference (0.91).

There is increasing interest in developing novel coatings to enhance the biocompatibility of medical implants. A key issue in biocompatibility research is platelet activation and aggregation on the biomaterials' surface. Stoichiometric and nonstoichiometric titanium nitride (TiN x ) films were developed by sputtering as case study materials, for probing platelet activation behavior onto them. Atomic force microscopy (AFM) facilitates the real-time studies of cells and guarantees cellular viability. In this work a methodology for platelets study by AFM was developed. The morphological, structural, optical, and wettability properties of the TiN x films were obtained by AFM, x-ray diffraction, spectroscopic ellipsometry, and contact angle measurements.The properties of TiN x films were correlated with their thrombogenicity involving platelets' adhesion, activation and protein clustering mechanisms. It was found that the TiN x films stoichiometry and surface roughness affect the platelet response. The stoichiometric and smoother TiN films promote platelets adhesion and activation.

We report about developing high resistivity thin film resistors using titanium oxy-nitride. Titanium nitride films of different thicknesses ranging from 50 to 300 nm were deposited on SiO 2 /Si substrates using the reactive magnetron sputtering method. After deposition, these films were annealed in the air ambient. The structural and electrical properties of the films were examined as a function of annealing temperature. The samples with various thicknesses show TiN(1 1 1) phase. The sheet resistance increases from 150 up to 420 X/h when the film thickness decreases from 300 to 50 nm. Temperature coefficience of resistance (TCR) of the films significantly decreased with decreasing the film thickness. The TCR of 50-nm thick film is quite low, about 49 ppm/K.

Powders used for this study were synthesized by the self-propagating high temperature synthesis (SHS) process. This method allows producing titanium nitride powders in an economic and easy way. Densification of these original powders is carried out by the hot pressing process. Sintering is achieved, under a 50 MPa pressure, at different temperatures (1400°C, 1600°C and 1800°C). At 1600°C properties are optimised and bulk specimen density is superior to 98%. In addition, microhardness reaches the average value of 1790 ± 225 H V and Young modulus measured is 430 ± 10 GPa. A tribological characterization is then carried out with an adapted four balls machine tribometer. Titanium nitride tribological behavior is compared with the one of other hard materials such as 100C6 steel, titanium carbide and two cemented carbides of different compositions. Parameters such as toughness, hardness and wear volume are correlated in order to understand wear mechanisms origins.

This paper outlines the Taguchi optimization methodology, which is applied to optimize cutting parameters in end milling when machining hardened steel AISI H13 with TiN coated P10 carbide insert tool under semi-finishing and finishing conditions of high speed cutting. The milling parameters evaluated are cutting speed, feed rate and depth of cut. An orthogonal array, signal-to-noise (S/N) ratio and Pareto analysis of variance (ANOVA) are employed to analyze the effect of these milling parameters. The analysis of the result shows that the optimal combination for low resultant cutting force and good surface finish are high cutting speed, low feed rate and low depth of cut. Using Taguchi method for design of experiment (DOE), other significant effects such as the interaction among milling parameters are also investigated. The study shows that the Taguchi method is suitable to solve the stated problem with minimum number of trials as compared with a full factorial design. © 2003 Elsevier B.V. All rights reserved.

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Some of these demonstrations were implemented for wearable applications by exploiting the material's exceptional robustness and flexibility. [5,6] However, there remain major obstacles that hinder the industrial adoption of MoS 2 and other 2D TMDC materials. The most challenging obstacle has been finding an industrially compatible method that enables the production of these materials on a mass scale. We have recently demonstrated that electrodeposition is a potentially viable method for solving this challenge. [7,8] Electrodeposition offers important advantages in 2D material production over other methods such as chemical vapor deposition (CVD), [9,10] sputtering, [11] or atomic layer deposition (ALD). [12] Electrodeposition is not a lineof-sight deposition method as material growth occurs at electrical contacts and is controlled by electrical potential or current. [13] It can hence be utilized to deposit materials over 3D surfaces including patterned nanostructures of high aspect ratios. [14-17] In addition, electrodeposition is usually performed at room temperature, avoiding harsh environments such as plasma or extremely high temperatures, which can damage pre-existing materials on the substrate, such as graphene electrodes. [7] However, there is an important limitation with electrodeposition that needs to be overcome. This method requires an electrically conductive surface from which materials are traditionally grown vertically. [18] Depositing a semiconductor material on a conductor provides a low resistance current path in planar (opto-) electronic devices such as transistors and photodetectors, thus limiting the use of electrodeposition traditionally to certain vertical device structures or metal interconnects (through the dual damascene process). [19] Prior to the work described herein, this limitation has been a drawback, specifically for developing 2D material based devices where planar structures that exploit the unique 2D properties of the material are the "natural" route forward. [20-23] Creating innovative techniques to electrodeposit planar 2D materials over non-conducting surfaces would solve this limitation and open new routes where the insulator base can be utilized, such as in transistor gating. In the early 1990s, Nishizawa et al. described the electrochemical growth of poly(pyrrole)

The process development and characterization of titanium nitride (TiN) as a diffusion barrier for silver (Ag) metallizations were discussed. The structure of Ag/TiN/SiO 2 /Si and Ag/TiN/Si metallizations under N 2 /H 2 thermal annealing at 300-650°C were investigated with sheet resistance measurement, X-ray diffraction (XRD), focused ion beam-scanning electron microscopy (FIB-SEM), atomic force microscope (AFM) and X-ray photoelectron spectroscopy (XPS) and compared to as-deposited multilayers. For 12 nm TiN barrier, no change of sheet resistance was observed after annealing at 600°C, but an abrupt rise appeared at 650°C annealing. FIB-SEM revealed that this is due to the surface morphology change after annealing of the samples at different temperatures and the destruction of the TiN film. Ó 2004 Published by Elsevier B.V.

A full-wafer backside n-ohmic metallization scheme for InP is reported. The contact is formed by a single-step, all-sputter process and has been used successfully in three-inch InP opto-electronic device manufacturing. The metallization is based on the combination of a nickelgermanium -gold ohmic contact followed by a titanium -titanium nitride -titanium -gold metal stack. The titanium nitride layer acts as a barrier to grain boundary diffusion of indium and other material from the substrate to the surface of the top gold layer. The top gold is required for a gold -tin solder die bond process. The sputter process provides better than 5% cross-wafer and wafer-to-wafer thickness uniformity and a contact resistance of 2.5 -8.3 Â 10 À 5 V cm 2 . We report the fabrication process for this metal contact and the results of a full physical characterization by transmission electron microscopy, Auger survey and depth profile analysis and X-ray analysis. D

Several ultrahard materials and coatings of definite interest for tribological applications were tested with respect to their response when irradiated with fs laser pulses. Results on cemented tungsten carbide and on titanium carbonitride are reported for the first time and compared with outcomes of investigations on diamond and titanium nitride. The experiments were carried out in air, in a regime of 5–8 J/cm2 fluences, using the beam of a commercial Ti:sapphire laser. The changes induced in the surface morphology were analysed with a Nomarski optical microscope, and with SEM and AFM techniques. From the experimental data and from the calculated incident energy density distributions, the damage and ablation threshold values were determined. As expected, the diamond showed the highest threshold, while the cemented tungsten carbide exhibited typical values for metallic surfaces. The ablation rates determined (under the above-mentioned experimental conditions) were in the range 0.1–0.2 μm per pulse for all the materials investigated.

A gas mixture of tungsten hexafluoride (WF 6 ) and silane (SiH 4 ) is generally used to form the initial layer of tungsten (W) on titanium nitride (TiN). However, the nucleation mechanism is still not clear, thus making it difficult to optimize such processes for complete filling of via holes. Therefore, in this study, we examined the nucleation process by laser-reflection measurements, scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). These measurements indicate that W nucleation has two stages: monolayer formation followed by nucleation of three-dimensional (3D) islands. The monolayer formation can be expressed as Langmuir-type adsorption, and proceeds with the reduction of WF 6 by Ti on TiN substrates. After monolayer formation, nucleation of 3D islands occurs and islands rapidly grow. These processes were quantitatively modeled using a simple rate equation. The results of our model agree well with our measurements of the deposited amount and coverage of islands.

We discuss options for metal-oxide-semiconductor field-effect transistor (MOSFET) gate stack scaling with thin titanium nitride metal gate electrodes and high-permittivity ('high-k') gate dielectrics, aimed at gate-first integration schemes. Both options are based on further increasing permittivity of the dielectric stack. First, we show that hafnium-based stacks such as TiN/HfO 2 can be scaled to capacitance equivalent thickness in inversion (T inv ) of 10 Å and equivalent oxide thickness (EOT) of 6 Å by using silicon nitride instead of silicon oxide as a high-k/channel interfacial layer. This is based on the higher dielectric constant of Si 3 N 4 and on its resistance to oxidation. Although the nitrogen introduces positive fixed charges, carrier mobility is not degraded. Secondly, we investigate whether Ti-based 'higher-k' dielectrics have the potential to ultimately replace Hf. We discuss oxygen loss from TiO 2 as a main challenge, and identify two migration pathways for such oxygen atoms: In addition to well-known down-diffusion and channel Si oxidation, we have newly observed oxygen up-diffusion through the TiN metal gate, forming SiO 2 at the poly-Si contact. We further address the performance of Si 3 N 4 and HfO 2 as oxygen barrier layers.

The problem of removing macroparticle contamination from cathodic arc deposition technology has been addressed by several techniques. These techniques have been sufficiently successful that in recent years improved coatings have been developed and advanced applications are starting to appear. The present paper is a review of these advances and the properties of new materials synthesised using different filtered cathodic arc configurations. ᮊ 2001 Elsevier Science B.V. All rights reserved. Keywords: Filtered cathodic vacuum arc; Tetrahedral amorphous carbon; Titanium nitride 0040-6090r01r$ -see front matter ᮊ 2001 Elsevier Science B.V. All rights reserved. Ž . PII: S 0 0 4 0 -6 0 9 0 0 1 0 1 1 6 9 -5 ( ) P.J. Martin, A. Benda¨id r Thin Solid Films 394 2001 1᎐15 2

The scanning probe microscopy (SPM) technique has been used in its atomic force microscopy (AFM) and lateral force microscopy (LFM) modes, in order to characterize morphologically and to determine the friction coefficient, respectively, for coatings of TiN and ZrN thin films. The measure on the friction coefficient shows that although these films have similar physical and chemical properties, they present a difference in their friction coefficient, showing that TiN presents a higher friction coefficient than ZrN. Using X-ray diffraction (XRD), the coatings were characterized structurally. Chemical states of the TiN and ZrN films were determined by X-ray photoelectron spectroscopy (XPS).

Two kinds of reactively evaporated titanium nitride films with columnar (t30 films) and fine-grained (/3+ films) film structures, respectively, have been examined as diffusion barriers for preventing aluminium diffusion. The aluminium diffusion profiles have been investigated by 2 MeV 4He+ Rutherford backscattering spectrometry (RBS) at temperatures up to 550 ° C. The diffusivity from 300°C to 550°C is: D[m2s -x] = 3 x lO-18exp[-30/(RT)] in/30 layers and D[mZs -1] = 1.4 x 10 -16 exp[-48/(RT)] in/3+

The initial stages of titanium nitride atomic layer deposition using sequential additions of TiCl 4 and NH 3 on fumed silica powder were investigated using in situ Fourier transform infrared spectroscopy techniques. After the first stage, the primary active surface species for the formation of TiN were determined to be TiCl x and Ti 2 NH. After six complete atomic layer deposition cycles the infrared spectrum indicated a strong TiN band that was verified by diffuse reflectance infrared spectroscopy recorded on pure TiN powder. Incomplete surface reactions were also observed.

A tribological analysis of deformations and stresses generated and their influence on crack generation and surface fracture in a coated surface loaded by a sliding sphere in dry conditions is presented. A three-dimensional finite element method (3D FEM) model has been developed for calculating the first principal stress distribution in the scratch tester contact of a diamond spherical tip with 200 mm radius sliding with increasing load on a 2 mm thick titanium nitride coated steel surface. The model is comprehensive in that sense that it considers elastic, plastic and fracture behaviour of the surfaces. The hard coating will be stretched and accumulates high tensile stresses. At the same time, it is carrying part of the load and thus reducing the compressional stresses in the substrate under the sliding tip. The first crack is initiated at the top of the coating from bending and pulling actions and it grows down through the coating. The fracture toughness of the coating is calculated by identifying from a scratch test experiment the location of the first cracks and the crack density and using this as input data. q

Although single-layer coatings are finding a range of applications in many sectors of engineering, there are an increasing number of applications where the properties of a single material are not sufficient. One way to surmount this problem is to use a multilayer coating that combines the attractive properties of several materials, each chosen to solve a problem in the application.

When an energy-carrying beam strikes a solid surface, the surface is sputtered and many effects on the atomic, microscopic and macroscopic scale can be observed. The morphological changes induced on solid surfaces, the shape and size of damaged area depend on the beam and target characteristics. Laser beams are frequently used in modern technology to obtain materials with certain bulk properties and different surface properties. During the last years, there has been an interest for advanced technology application of implemented ceramic thin filmsrcoatings deposited by various methods. In Ž . this work the microscopic changes induced by laser beam on TiN and Ti,Al N coatings deposited on steel were studied. For Ž . this purpose we used pulsed, Transversely Excited Atmospheric TEA CO laser, operating with typical and non-typical gas

The Spallation Neutron Source (SNS) ring is designed to accumulate high intensity protons. Ultrahigh vacuum of 10 -9 Torr is required in the accumulator ring to minimize beam-residual gas ionization. To reduce the secondary electron yield (SEY) and the associated electron cloud instability, the ring vacuum chambers are coated with titanium nitride (TiN). This paper describes the design, fabrication, assembly and vacuum processing of the ring and beam transport line vacuum chambers as well as the associated instrumentation

Titanium nitride films were prepared by low pressure chemical vapor deposition from TiCl4 and NH3 at 630°C. Metallic Ti films were deposited from TiCl4 and H2 using plasma-enhanced chemical vapor deposition at 570 and 590°C. A layer of TiSi2 was formed on the silicon surface. TiSi2 thickness depends on deposition temperature and deposition time. All the films have chlorine concentrations

Nickel-base superalloy Inconel 718 is a high-strength, thermal-resistant. Because of its excellent mechanical properties, it plays an important part in recent years in aerospace, petroleum and nuclear energy industries. Due to the extreme toughness and work hardening characteristic of the alloy, the problem of machining Inconel 718 is one of ever-increasing magnitude. This investigation optimized the machining characteristics of Inconel 718 bars using tungsten carbide and cermet cutting tools. The approach is based on Taguchi method, the signal-to-noise (S/N) ratio and the analysis of variance (ANOVA) are employed to study the performance characteristics in turning operations. The roundness and flank wear of the ultrasonically and conventionally machined workpieces were measured and compared.

Ti-doped diamond like carbon films were deposited on both untreated and plasma nitrided Ti6Al4V alloy using Closed Field Unbalanced Magnetron Sputtering (CFUMBS) method and their tribological properties were evaluated by conducting sliding wear conditions. The influence of the nitrided layer on tribological behavior of Ti-DLC films was studied by means of XRD, SEM, scratch tester, microhardness tester and pin-ondisc tribotester. The microhardness results pointed out that the duplex treatment dramatically increased the surface hardness and reduced the plastic deformation of the alloy. Wear tests showed that Ti-DLC coatings on both untreated and nitrided surfaces caused a reduction in the coefficient of friction. The reason of the reduction in the coefficient of friction was found to be the formation of transfer film between the sliding surfaces. Wear rates demonstrated that wear resistance of duplex treated (Ti-DLC coating after nitriding) Ti6Al4V alloy was significantly improved.

The machining process is essential in the manufacturing industry. Among the all
machining process, turning is the broadest techniques used to remove the metal. In
this machining process, metal removal rate was influenced by the sharpness of the
cutting tools. Due to the friction between the workpiece and the tool insert, tool wear
occurs. After the wear takes place, the efficiency of the machine will be reduced and
metal removal time will be increased. Hence, it is essential to investigate the
behaviour of the tool wear under the machining. This investigation is to analyse the
wear characteristics of the tool inserts. The machining of the EN8 was examined in
this research using silicon carbide tool inserts and Titanium nitride coated tool
inserts. This research was investigated the wear behaviour of the silicon carbide tool
insert, and titanium nitride tool insert in machining of EN8 steel using a horizontal
machining centre. The wear of the inserts was measured using toolmakers
microscope. The flank wear and crater wear was considered in the tool wear
measurement.

A modified pin-on-disc machine was used for the tribological investigation of ultrahigh molecular weight polyethylene (UHMWPE) sliding on stainless steel or stainless steel coated with diamond-like carbon, titanium nitride or Micronite. Micronite is a new type of coating applied by a physical vapour deposition technique combined with a very low friction coating material giving improved tribological properties. The tribological parameters used were chosen to mimic the conditions prevailing in the human body. The wear debris and the counter-surfaces were analysed. The surface analysis showed that the coating changed the roughness of the counter-surfaces. The diamond-like carbon and Micronite coatings had a much higher surface roughness than the titanium nitride coating. The results indicated that the enhanced tribological behaviour of the Micronite/UHMWPE sliding pair might be used as a material combination in artificial joints. Further studies are however required in order to support this.

Sintered NdFeB magnets have poor corrosion resistance that renders them susceptible to corrosion in industrial and marine environments. This paper evaluates the properties of cathodic arc physical vapour deposited (CAPVD) titanium nitride coating for corrosion protection of sintered NdFeB permanent magnets. The performance of titanium nitride coating has been compared to the electrodeposited nickel-copper-nickel multilayer coating. The rates of coatings degradation in simulated marine environment were estimated with electrochemical impedance spectroscopy (EIS). Cyclic polarization was carried out to assess the pitting potential. The surface chemistry and coating morphologies were studied with scanning electron microscope (SEM). X-ray diffraction (XRD) was used for qualitative phase analyses of coatings and the substrate. It was figured out that the charge transfer resistance of CAPVD titanium nitride coating increased with exposure time. The negative rate of Rpdegradation for titanium nitride coating compared to the nickel-copper-nickel multilayer for equivalent exposure time is a unique and valuable result. Polarization results showed that 'pits re-passivation' of titanium nitride coating could be responsible for the extended corrosion protection of the NdFeB substrate. The magnetic properties remained comparable for both types of coatings.

Many applications of neural stimulation demand a high current density from the electrodes used for stimulus delivery. New materials have been searched that can provide such large current and charge densities where the traditional noble metal and capacitor electrodes are inadequate. Titanium nitride, which has been used in cardiac pacemaker leads for many years, is one of these materials recently considered for neural stimulation. In this short report, we investigated the charge injection capacity of TiN electrodes for an extended range of cathodic voltages. The injected charge increased first slowly as a function of the electrode voltage, and then at a faster rate beyond −1.6 V. The maximum charge was 4.45 mC/cm 2 (n=6) for a cathodic voltage peak of −3.0 V and a bias voltage of −0.8 V. There was no evidence of bubble generation under microscopic observation. The unrecoverable charges remained under 7% of the total injected charge for the largest cathodic voltage tested. These large values of charge injection capacity and relatively small unrecoverable charges warrant further investigation of the charge injection mechanism in TiN interfaces at this extended range of electrode voltages.

Monolithic coatings of chromium nitride, titanium nitride and multilayer titaniumychromium nitride coatings were produced by r.f. and d.c. reactive magnetron sputtering in order to determine their potential to be used as protective coatings for machinery parts of plastic injection moulding or extruding machines. The tribological and mechanical behaviour of these coatings were studied. Monolithic coatings showed lower wear rates, measured by pin-on-disc experiments, when compared with multilayer coatings. The oxidation of the surface was also lower in monolithic coatings. The performance of the coatings during plastic processing was tested in a dye fitted to an injection moulding machine and using glass reinforced thermoplastic. The wear rates of the nitride-based coatings during plastic processing was more than two orders of magnitude better then some traditional methods of protecting the surfaces such as hardening the steel by heat treatment, electrodepositing hard chromium or nitriding the steel surface. The physical vapour deposition coatings also showed higher corrosion protection during plastic processing tests. ᮊ

Adhesion and other mechanical behaviour of coatings is at present routinely tested in industry and research organisations using the scratch test. The test has been the subject of a European Standard prEN 1071-3:2000 established by the European Standards Committee CEN TC184 WG5. A previous European project on the development and validation of test methods for thin hard coatings-FASTE-revealed that uncertainties in the Rockwell C stylus tip shape represent a major source of error for the scratchtest method. Therefore a follow-up project-REMAST-was started to develop and certify a reference material as a quality control tool for the testing and qualification of scratch-test instruments. In addition, a considerable effort was devoted to improve the scratch stylus manufacturing process. This paper presents the results of the REMAST project. During a feasibility study, two candidate materials-titanium nitride (TiN) and diamond-like carbon (DLC) coatings both on high speed steel substrates-were evaluated. Because of the lower sensitivity to styli tip shape variations and higher data scatter observed for the TiN coating, DLC was chosen as the reference material to be certified. One thousand samples were produced, as well as qualified styli to carry out the certification campaign, including homogeneity and stability testing. Nine independent laboratories were involved in the certification exercise, and the data were statistically analysed to obtain the certified critical load values and their uncertainty ranges. A certified reference material BCR-692 is available for verification purposes. This presents three repeatable failure events at certified critical load intervals and can provide a good indication of overall scratch-test instrument performance, including stylus condition and calibration. It is also useful as a diagnostic tool, providing a means of sensitive monitoring of machine and stylus performance over extended periods. Considerable improvement of the quality of scratch styli was achieved by the strict control of all manufacturing steps.

Titanium nitride (TiN) widely used as hard coating material, was coated on tool steels, namely on high-speed steel (HSS) and D2 tool steel by physical vapor deposition method. The study concentrated on cathodic arc physical vapor deposition (CAPVD), a technique used for the deposition of hard coatings for tooling applications, and which has many advantages. The main drawback of this technique, however, is the formation of macrodroplets (MDs) during deposition, resulting in films with rougher morphology. Various standard characterization techniques and equipment, such as electron microscopy, atomic force microscopy, hardness testing machine, scratch tester, and pin-on-disc machine, were used to analyze and quantify the following properties and parameters: surface morphology, thickness, hardness, adhesion, and coefficient of friction (COF) of the deposited coatings. Surface morphology revealed that the MDs produced during the etching stage, protruded through the TiN film, resulting in film with deteriorated surface features. Both coating thickness and indentation loads influenced the hardness of the deposited coatings. The coatings deposited on HSS exhibit better adhesion compared to those on D2 tool steel. Standard deviation indicates that the coating deposited with thickness around 6.7 µm showed the most stable trend of COF versus sliding distance.

Cathodic arc evaporation (CAE) is a widely used technique for generating highly ionised plasma from which hard, wearresistant PVD coatings can be deposited. A major drawback of this technique is the emission of micrometer-sized droplets of cathode material from the arc spot, which are commonly referred to as 'macroparticles'. In this study, the effect of cathode poisoning was investigated as a method to reduce the number of macroparticles in PVD coatings. While the study focuses on the reduction of macroparticles in titanium nitride coatings, the outcomes and key findings can be broadly applied to the cathodic arc process, in particular, for the reduction of macroparticles in more advanced CAE coatings. The results support earlier findings that have shown that poisoning of the cathode can reduce the number of macroparticles emitted from the arc spot. The results of glow discharge optical emission spectroscopy (GD-OES) showed that the titanium content of the coatings varied little between the respective coatings despite changes in the deposition pressure from 0.1 to 1.2 Pa. The GD-OES results also showed the presence of oxide contamination at the surface of the coatings, which was significantly reduced with increasing deposition pressure. The coatings were also deposited onto high-speed steel twist drills to compare the metal-cutting performance when dry drilling a workpiece of cast iron. The results of the drill tests showed that tool life increased with a reduction in the number of macroparticles. ᮊ

A low electrode-electrolyte impedance interface is critical in the design of electrodes for biomedical applications. To design low-impedance interfaces a complete understanding of the physical processes contributing to the impedance is required. In this work a model describing these physical processes is validated and extended to quantify the effect of organic coatings and incubation time. Electrochemical impedance spectroscopy has been used to electrically characterize the interface for various electrode materials: platinum, platinum black, and titanium nitride; and varying electrode sizes: 1 cm 2 , and 900 m 2 . An equivalent circuit model comprising an interface capacitance, shunted by a charge transfer resistance, in series with the solution resistance has been fitted to the experimental results. Theoretical equations have been used to calculate the interface capacitance impedance and the solution resistance, yielding results that correspond well with the fitted parameter values, thereby confirming the validity of the equations. The effect of incubation time, and two organic cell-adhesion promoting coatings, poly-L-lysine and laminin, on the interface impedance has been quantified using the model. This demonstrates the benefits of using this model in developing a better understanding of the physical processes occurring at the interface in more complex, biomedically relevant situations.

Dry etching processes for bulk-single crystal zinc oxide ͑ZnO͒ and molecular beam epitaxy ͑MBE͒ grown ZnO have been investigated using inductively coupled plasma ͑ICP͒ of CH 4 and SiCl 4 based plasma chemistry. The CH 4 -based chemistry showed a higher etch rate than the SiCl 4 based chemistry, presumably due to the formation of highly volatile metal organic zinc compound. The influence of base pressure, radio frequency table power, and ICP power on etch rate was studied. Auger electron spectroscopy has been employed to examine the surface stoichiometry of etched ZnO using both plasma chemistries. Furthermore, with optimized process parameters, the effect of plasma etching on the optical properties of MBE grown ZnO film is studied. An enhancement of the band edge luminescence along with almost complete suppression of defect level luminescence in hydrogen-containing plasma treated ZnO film has been observed.

ABSTRACT Diffusion barrier materials, such as TiN, WxN, WNxCy and their nanolaminates were deposited by atomic layer deposition method. TiN film exhibited excellent properties, but WxN film exhibited high resistivity despite the low residue concentration. Both TiN and WxN films suffered from serious incompatibility with the copper metal. WNxCy film was deposited by introducing triethylboron as a reducing agent for tungsten. Excellent film properties were obtained, including very good compatibility with the copper metal, evident as strong adhesion and no pitting on the copper surface. Nanolaminate barrier stacks of WxN/TiN and WNxCy/TiN were successfully deposited. TiN deposition did not cause copper pitting when thin WNxCy film was deposited underneath.

In order to improve the performance of thermal solar collectors, the development of good, durable and reproducible spectrally selective solar absorber surfaces for photothermal conversion is of greatest importance. Spectrally selective cermet coatings were produced by DC magnetron sputtering using metallic chromium and titanium targets at constant target current, substrate bias and substrate temperature. These coatings are graded cermets with a metal concentration decreasing from the substrate to the coating surface. Basically, these coatings are formed with a layer structure consisting of a cermet layer enriched in metal, one or more cermet layers with less metal than the first one, and on top a pure ceramic layer as an antireflection layer. The metal layer was deposited by non-reactive DC sputtering, while the ceramic layers were deposited by DC reactive sputtering in argon-nitrogen or argon-oxygen atmosphere. The metallic and ceramic layers were deposited as a sub-layer system, consisting of alternating metallic and nitride or oxide sub-layers. The effect of the optical properties in dependence on the metallic fraction in the layers and the number of sub-layers in the film is discussed. For coatings based on chromium, the optimum selectivity achieved was a solar absorptance of 94% and a thermal emittance of 6% at 82 8C. For titanium oxynitride based coatings, the best selectivity achieved was a solar absorptance of 91% and a thermal emittance of 4%. The microstructure and thickness were studied by scanning electron microscopy (SEM). The surface microtopography was analysed by atomic force microscopy (AFM) and the metal concentration profile by Rutherford backscattering spectrometry (RBS).

Nickel-base superalloy Inconel 718 is a high-strength, thermal-resistant. Because of its excellent mechanical properties, it plays an important part in recent years in aerospace, petroleum and nuclear energy industries. Due to the extreme toughness and work hardening characteristic of the alloy, the problem of machining Inconel 718 is one of ever-increasing magnitude. This investigation optimized the machining characteristics of Inconel 718 bars using tungsten carbide and cermet cutting tools. The approach is based on Taguchi method, the signal-to-noise (S/N) ratio and the analysis of variance (ANOVA) are employed to study the performance characteristics in turning operations. The roundness and flank wear of the ultrasonically and conventionally machined workpieces were measured and compared.

The aging behavior of type 308 stainless steel and type 308 stainless steel with controlled residual elements (308CRE) was studied. The alloys were initially homogenized, resulting in a fully austenitic structure in the type 308 alloy and a duplex, austenite plus ferrite structure in the type 308CRE alloy. The materials were subsequently aged at 550, 650, 750, and 850 ~ for times up to 10,000 hours. Aging of the type 308 steel resulted in precipitation of chromium-rich M23C6, primarily along grain boundaries, followed by sigma-phase formation after long aging times (->5000 hours). The aging response of the duplex type 308CRE steel was somewhat more complicated. Although the titaniumrich carbides, nitrides, and sulfides produced during homogenization remained stable during subsequent aging, some additional precipitation was found. G-phase formed within the residual ferrite but eventually redissolved. The ferrite partially dissolved during early aging and later transformed to sigma phase. The sigma-phase formed significantly faster in the aged type 308CRE alloy. The results are summarized in the form of TTT diagrams. A comparison is made with a similar aging study on the same alloys but starting with the as-welded condition.

Thin TiN films were grown on SiO 2 by reactive high power impulse magnetron sputtering (HiPIMS) at a range of temperatures from 45 to 600°C. The film properties were compared to films grown by conventional dc magnetron sputtering (dcMS) at similar conditions. Structural characterization was carried out using X-ray diffraction and reflection methods. The HiPIMS process produces denser films at lower growth temperature than does dcMS. Furthermore, the surface is much smoother for films grown by the HiPIMS process. The [200] grain size increases monotonically with increased growth temperature, whereas the size of the [111] oriented grains decreases to a minimum for a growth temperature of 400°C after which it starts to increase with growth temperature. The [200] crystallites are smaller than the [111] crystallites for all growth temperatures. The grain sizes of both orientations are smaller in HiPIMS grown films than in dcMS grown films.

The potential of an alkaliphilic bacterium Klebsiella sp. strain RJ-03, to utilize different carbon sources for the production of an extracellular biosurfactant was evaluated. Among the several carbon substrates tested, production of the crude biosurfactant was found to be the highest with starch (10.1 ± 0.11 g/L) followed by sucrose (5.1 ± 0.11 g/L), xylose (3.25 ± 0.08 g/L), galactose (3.1 ± 0.16 g/L) glucose (2.75 ± 0.11 g/L) and fructose (2.62 ± 0.07 g/L). The crude biosurfactant production was done using starch, sucrose, xylose, galactose and glucose containing medium, that exhibited significantly high viscosity, emulsification activity and maximum reduction in surface tension as compared to those obtained from fructose and maltose. The carbon source has significant effect on the quantity as well as the quality of biosurfactant production. The chemical characteristics of purified biosurfactant was compared by NMR, FT-IR, SEM, GPC, MALDI TOF-TOF MS, GC-MS, TG and DSC analysis, indicating variation in the functional groups, bonds, elements, monosaccharide composition, molecular mass and thermo stability.

The production of biosurfactant by Bacillus subtilis LSFM-05 was carried out using raw glycerol, obtained from a vegetable oil biodiesel plant in Brazil, as the sole carbon source. Production of the biosurfactant was carried out in a 15-L bench-top fermentor and the surfactant was obtained from the foam produced. The crude surfactant was purified by silica gel column chromatography with a yield of 230 mg of the purified biosurfactant per liter of foam. TLC, IR spectroscopy, 1 H and 13 C NMR and Fourier transform ion cyclotron resonance mass spectrometry with electrospray ionization (ESI-FTMS) were used to characterize the purified surfactant. The isolated surfactant was identified as a surfactin lipopeptide. MS/MS data identified the amino acid sequence as GluOMe-Leu-Leu-Asp-Val-Leu-Leu and showed that the fatty acid moiety contained 14 carbons in iso, anteiso or normal configurations. The critical micelle concentration of the C 14 /Leu 7 surfactin was 70 M, with emulsification efficiency after 24 h (E 24 ) of 67.6% against crude oil. Raw glycerol represents an abundant and renewable carbon source and provides an opportunity for reducing the cost of biosurfactant production and may add value to biodiesel production by creating new commercial applications for this by-product.

Due to the influence of the substrate, direct measurement of the hardness of thin films by standard micro-indentation tests is not always possible. In such situation, determination of the intrinsic film hardness requires the analysis of a set of experimental apparent hardness values obtained for different indentation loads. A number of mathematical equations based on various assumptions were proposed in literature for that purpose.

In this work, we have studied the influence of the coating design and composition on the oxidation behavior of Al x Cr 1−x N (x = 0.70) coatings. In particular, we have studied the effect brought about by the deposition of an additional subsurface titanium nitride barrier layer as well as by the doping of the AlCrN-based coatings by tungsten, boron and silicon. The coatings studied have been deposited using the cathodic arc vacuum (CAV) technique. The multilayered AlCrN/TiN coatings with TiN sublayer were oxidized in air at 900°C over 3 h and then analyzed by Glow Discharge Optical Emission Spectroscopy (GDOES) and X-ray photoelectron spectroscopy (XPS). Oxidation tests were performed in air at 900 and 1100°C for the AlCrN and AlCrWN, AlCrSiN, and AlCrBN coatings. In each case weight gain was measured and the surface morphology of the oxidized samples were studied using Secondary Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). The results obtained showed that the oxidation behavior of the aluminum rich AlCrN-based coatings could be improved in two ways: (1) by controlling the chromium outward diffusion rate in multi-layered coatings and (2) by alloying the AlCrN-based coatings with Si. Both improvements are related to the enhancement of the protective oxide film formation.

The room temperature oxidation process of thin TiN x ®lms, grown by DC reactive magnetron sputtering, was studied by in-situ and real time spectroscopic ellipsometry, X-ray re¯ectivity, Auger electron spectroscopy, X-ray photoelectron spectroscopy and stress measurements. The ®lms were deposited at various negative bias voltages (V b) in order to vary the TiN x stoichiometry and then exposed to several gases and to air at room temperature. The oxidation rate was found to depend strongly on V b and thus on ®lm stoichiometry. Fast oxidation was observed in ®lms deposited at low uV b u, that contain nitrogen which is weakly bonded to Ti and can be easily replaced by oxygen. At high uV b u values (above 2 80 V) stoichiometric TiN ®lms were developed, that were stable and not prone to oxidation. The results showed that oxidation takes place in the bulk of the ®lm and can proceed up to about 10% transformation of titanium nitride into titanium oxide. The fastest step in the ®lm oxidation mechanism is diffusion of oxygen along the columnar grain boundary structure, followed by the reaction of oxygen with the weakly bonded TiN. The results suggest that the oxidation process proceeds with different stages involving formation of TiON, followed by a slow stage of TiO 2 formation. These microstructural changes are consistent with the evolution of compressive stresses in the ®lms and the increase in ®lm density and thickness and the decrease in surface roughness as determined by X-ray re¯ectivity.