Titanium Adhesion Research Articles

Fabrication of a plasmonic nanocone on top of an AFM cantilever

A novel technique for the nanofabrication of gold nanocones on top of atomic force microscopy cantilever tips is demonstrated. The modified tips are intended as near-field scanning optical microscopy probes. The fabrication process is composed of cutting the probe apex with a focused gallium ion beam to create a platform for the nanocone fabrication. Three thin films are deposited on the cantilever, where gold as the active plasmonic material is sandwiched between a titanium adhesion layer and an Al2O3 thin film. At the top of the cantilever the deposited thin films are partially structured by a ring shaped focused ion beam pattern, leaving behind a cylindrical pillar. Finally, the gold nanocone is produced by argon ion etching with the top thin film on the pillar acting as a hard mask.

Wear behaviour of PVD coated and cryogenically treated tools for Ti-6Al-4V turning

Titanium alloys, mainly because of their poor thermal conductivity, need to be cut at relatively low cutting speeds, with obvious negative consequences on the profitability of machining. An important amount of research has been done in order to increase productivity in titanium machining operations: high performance coatings and innovative technologies to improve insert resistance to wear represent promising solutions. In this work, a highly performing cutting insert (coated with a TiAlN layer obtained by Physical Vapor Deposition (PVD) magnetron sputtering) has been tested against the option of applying a Deep Cryogenic Treatment (DCT), when used for rough turning of aerospace titanium. The effects of the DCT have been experimentally investigated with two different experimental plans at low and high cutting speeds (respectively vc ≤ 50 m/min, vc ≥ 60 m/min). Statistical analyses of the results have been performed. The results show that at low cutting speed, the DCT treatment does not increase the tool life. At higher values of vc, flank wear vs. time curves of coated tools have been determined, with and without DCT, and they clearly show that cryogenically treated tools present better wear resistance at higher cutting speeds. The wear mechanisms on the rake face and the flank for these two TiAlN coated tools have been analysed using a scanning electron microscope. The adhesion of titanium on the tool surface is lower for a DCT treated insert. The results indicate that the hardening of tools induced by the cryogenic treatment improves their useful life in high rate machining of titanium.

Erratum to: The influences of filament temperature on the structure of boron nitride films and its tribological characterization for microforming die application

Boron nitride film was deposited on 〈1 0 0〉-oriented silicon substrate by hot filament assisted chemical vapor deposition. The B[N(CH 3 ) 2 ] 3 (Tris(dimetylamino)borane, TDMAB) was used as the single source precursor both for boron and nitride, and ammonia gas was used as the extra source to increase the N concentration in the films. Elemental composition of the films deposited under different filament temperatures were measured by energy dispersive X-ray (EDX) analysis, and the structure of the films were measured by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). The boron nitride films deposited under lower filament temperature was amorphous, while BN films contain hexagonal structure were deposited at higher filament temperature. To verify whether the films can be applied to the microforming die, a ball on disk test was carried out using pure titanium ball as the counterpart to investigate the interfacial behavior between the films and pure titanium. The results show that the reaction between the films and pure titanium was low as there was no titanium adhesion on the wear track when the film was remained.

The influences of filament temperature on the structure of boron nitride films and its tribological characterization for microforming die application

Boron nitride film was deposited on 〈1 0 0〉-oriented silicon substrate by hot filament assisted chemical vapor deposition. The B[N(CH3)2]3 (Tris(dimetylamino)borane, TDMAB) was used as the single source precursor both for boron and nitride, and ammonia gas was used as the extra source to increase the N concentration in the films. Elemental composition of the films deposited under different filament temperatures were measured by energy dispersive X-ray (EDX) analysis, and the structure of the films were measured by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). The boron nitride films deposited under lower filament temperature was amorphous, while BN films contain hexagonal structure were deposited at higher filament temperature. To verify whether the films can be applied to the microforming die, a ball on disk test was carried out using pure titanium ball as the counterpart to investigate the interfacial behavior between the films and pure titanium. The results show that the reaction between the films and pure titanium was low as there was no titanium adhesion on the wear track when the film was remained.

Gas Sensors Based on Locally Heated Multiwall Carbon Nanotubes Decorated with Metal Nanoparticles

We report the design and fabrication of microreactors and sensors based on metal nanoparticle-decorated carbon nanotubes. Titanium adhesion layers and gold films were sputtered onto Si/SiO2substrates for obtaining the electrical contacts. The gold layers were electrochemically thickened until 1 μm and the electrodes were patterned using photolithography and wet chemical etching. Before the dielectrophoretic deposition of the nanotubes, a gap 1 μm wide and 5 μm deep was milled in the middle of the metallic line by focused ion beam, allowing the fabrication of sensors based on suspended nanotubes bridging the electrodes. Subsequently, the sputtering technique was used for decorating the nanotubes with metallic nanoparticles. In order to test the as-obtained sensors, microreactors (100 μL volume) were machined from a single Kovar piece, being equipped with electrical connections and 1/4′′ Swagelok-compatible gas inlet and outlets for controlling the atmosphere in the testing chamber. The sensors, electrically connected to the contact pins by wire-bonding, were tested in the 10−5to 10−2 W working power interval using oxygen as target gas. The small chamber volume allowed the measurement of fast characteristic times (response/recovery), with the sensors showing good sensitivity.

The role of titanium in electromigrated tunnel junctions

A standard route for fabrication of nanoscopic tunnel junctions is via electromigration of lithographically prepared gold nanowires. In the lithography process, a thin adhesion layer, typically titanium, is used to promote the adhesion of the gold nanowires to the substrate. Here, we demonstrate that such an adhesion layer plays a vital role in the electrical transport behavior of electromigrated tunnel junctions. We show that junctions fabricated from gold deposited on top of a titanium adhesion layer are electrically stable at ambient conditions, in contrast to gold junctions without a titanium adhesion layer. We furthermore find that electromigrated junctions fabricated from pure titanium are electrically exceptionally stable. Based on our transport data, we provide evidence that the barrier in gold-on-titanium tunnel devices is formed by the native oxide of titanium.

Surface modification of titanium with thermally treated polydimethylsiloxane coating and the effect on resin to titanium adhesion

In this study, titanium surface modification by a thermal treatment using a polydimethylsiloxane (PDMS) coating was investigated.The surfaces offourtitaniumsamples weresurface treatedbypolishing,sandblasting, andcoatingwitha PDMSwith a thermal treatment at 800 and 1100°C. The titanium surfaces were characterized by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy. The effect of the surface treatments on adhesion of resin to titanium was assessed by shear adhesion strengthtest. XPS analysis showed thatthere was a change ofelemental composition of titaniumsurfacesafter surface treatment. Binding energy shifts for Si2p and O1s were observed after sandblasting and thermally treated PDMS. Therefore, chemical states of Si and O were changed. Atomic force microscopy analysis revealed that the surface topography of the Ti samples was different, and surface roughness was increased after sandblasting and thermal treatment of PDMS coating. Shear adhesion strength test results showed that the adhesion between resin and titanium is affected by the treatment temperature of PDMS coating. The highest adhesion is obtained at 1100°C (14.7±1.57MPa). Copyright © 2014 John Wiley & Sons, Ltd.

Adhesion Investigation Between Metal and Benzocyclobutene (BCB) Polymer Dielectric Materials in 3-D Integration Applications

In this paper, the interfacial adhesion strength between metal layer and benzocyclobutene (BCB) polymer dielectric in 3-D integration applications is investigated. The effects of layer thickness, layer stacking order, and additional adhesion layer of titanium (Ti) layer between copper (Cu) and BCB polymer are investigated. Surprisingly, the conventional titanium adhesion layer commonly used in the semiconductor industry weakens the interfacial adhesion strength between copper and BCB. Additionally, to figure out the interfacial adhesion mechanisms, the interfacial structures probed by sum-frequency-generation vibrational spectroscopy are correlated to the adhesion strengths measured from corresponding sample interfaces. It is found that ordered C-H groups at the metal/BCB interface, such as titanium/BCB or molybdenum/BCB, lead to weak interfacial adhesion strength, whereas disordered interfaces, i.e., copper/BCB, lead to strong interfacial adhesion strength.

Ion implantation induced nanotopography on titanium and bone cell adhesion

Abstract Permanent endo-osseous implants require a fast, reliable and consistent osseointegration, i.e. intimate bonding between bone and implant, so biomechanical loads can be safely transferred. Among the parameters that affect this process, it is widely admitted that implant surface topography, surface energy and composition play an important role. Most surface treatments to improve osseointegration focus on micro-scale features, as few can effectively control the effects of the treatment at nanoscale. On the other hand, ion implantation allows controlling such nanofeatures. This study has investigated the nanotopography of titanium, as induced by different ion implantation surface treatments, its similarity with human bone tissue structure and its effect on human bone cell adhesion, as a first step in the process of osseointegration. The effect of ion implantation treatment parameters such as energy (40–80 keV), fluence (1–2 e17 ion/cm 2 ) and ion species (Kr, Ar, Ne and Xe) on the nanotopography of medical grade titanium has been measured and assessed by AFM and contact angle. Then, in vitro tests have been performed to assess the effect of these nanotopographies on osteoblast adhesion. The results have shown that the nanostructure of bone and the studied ion implanted surfaces, without surface chemistry modification, are in the same range and that such modifications, in certain conditions, do have a statistically significant effect on bone tissue forming cell adhesion.

Tribological Characterization of Boron Nitride Films against Pure-titanium for Microforming die Application

Boron nitride films were deposited onto Si substrates by hot filament chemical vapor deposition. The Tris(dimetylamino)borane (B[N(CH3)2]3) was used as source precursor, and the ammonia gas was used as the extra nitrogen source to increase the N concentration in the films. The bias was applied on the substrate stage to obtain the cubic phase of boron nitride. Structures and compositions of the films were investigated by energy dispersive X-ray (EDX) analysis and Raman spectroscopy. BN films contain hexagonal structures were deposited. To verify whether the films can be applied to the microforming die for forming pure titanium, the ball-on-disk test was carried out with pure titanium as the counterpart. The interfacial behavior between the films and pure titanium was also investigated by observe the wear track after the ball-on-disk test. The result shows that there was no titanium adhesion on the wear track when BN films were remained.

The Performance of Diamond-Like Carbon Coated Drills in Thermally Assisted Drilling of Ti-6Al-4V

Drilling performances of diamond-like carbon coatings incorporating W (W-DLC) deposited on high-speed steel tools were evaluated when drilling Ti-6Al-4V at 25 °C and under thermally assisted machining (TAM) conditions at 400 °C. Dry drilling using W-DLC coated drills caused immediate tool failure as a result of titanium adhesion. The tool lives improved for TAM drilling using W-DLC when the Ti-6Al-4V was placed (with dry surface) in a cooling bath at −80 °C and resulted in low and uniform drilling torques as well as good surface finish. The low coefficient of friction (COF) of W-DLC against Ti-6Al-4V observed under TAM conditions was attributed to the formation of W oxide layers at the tool surface, as determined by Raman spectroscopy. Introducing a cooling bath was necessary in order to restrict the temperature rise in the workpiece that caused rapid tool wear above 500 °C during drilling operations and also to prevent adhesion with minimal built-up edge (BUE) formation during drilling. The TAM performance of W-DLC coated drills was shown to be similar to that of WC-Co drills used in conventional flooded drilling.

High temperature tribological behavior of W containing diamond-like carbon (DLC) coating against titanium alloys

The current study has been undertaken to determine friction, adhesion and wear mechanisms of tribological coatings for elevated temperature applications of Ti–6Al–4V alloy. Sliding wear characteristics of diamond-like carbon (DLC) coatings and polycrystalline diamond (PCD) was studied and compared with those of conventional N-based coatings, which exhibited a high coefficient of friction (COF) due to titanium adhesion to the coating surface. Hydrogenated DLC (H-DLC) and W containing DLC (W-DLC) coatings offered low and stable COF values of 0.11–012 at 25°C while the PCD had the lowest COF of 0.05 at 25°C. At temperatures >200°C H-DLC's COF increased rapidly accompanied by high coating wear. At 100°C W-DLC had a COF of 0.06 which increased to 0.46–0.54 between 200°C and 300°C similar to that of H-DLC. However, at 400°C W-DLC's COF decreased to 0.07, and a low COF of 0.08 persisted at temperatures as high as 500°C. The governing mechanisms of the low friction of W-DLC observed at elevated temperatures were revealed by studying the compositions of the coating surfaces and the transfer layers formed on Ti–6Al–4V. Raman spectroscopy indicated that at 25°C the transfer layers were rich in carbon, whereas at 500°C they consisted mainly of tungsten trioxide (WO3) that formed on W-DLC's surface.

Translucent titanium coating altered the composition of focal adhesions and promoted migration of osteoblast‐like MG‐63 cells on glass

"TiGlass" was designed and was known to promote initial adhesion and increase migration of rat calvarial osteoblats. In this article, migration study and a series of epifluorescence microscopic studies were conducted to find out the composition of focal adhesion on titanium surface. The translucent titanium surface was applied in random migration analysis and immunofluorescence cell staining. In the immunofluorescent double staining, phosphorylated focal adhesion kinase was tested with vinculin. Various integrin subunits were then tested with vinculin to study the composition of activated focal adhesions. Integrin subunit α5 and αV were tested against β3; integrin subunits α5, αV, β3, and αVβ3 were tested with F-actin, respectively. The MG-63 cells began migration earlier and migrated faster on "TiGlass." Immunofluorescent double staining revealed that all focal adhesion kinase in the focal adhesions were activated on both the surfaces. The osteoblast was inferred to made adhesion to titanium and glass through integrins. The focal adhesions on glass were found to be composed of integrin subunits αV and β3. However, on "TiGlass," integrin subunits α5 might have supplemented the adhesion to titanium. Results from double staining of integrin subunits α5, αV, β3, and αVβ3 with F-actin also supported integrin subunits α5 might have involved in adhesion of titanium.

Fatigue property improvements of Ti–6Al–4V by thin film coatings of metallic glass and TiN: a comparison study

Thin film metallic glasses (TFMGs) with unique physical and mechanical properties have attracted interest in the past decade. With the aim of taking their advantages to their applications, a 200-nm-thick TFMG (Zr50Cu27Al16Ni7) film with a 10nm titanium adhesion layer and a hard coating TiN film were coated on a substrate. Effects of these two types of films on the four-point fatigue property improvements of Ti–6Al–4V substrate were investigated. The fatigue life improved from 2.2×105cycles of uncoated sample to 3.7×106cycles, ~17 times, and 1.0×106 cycles, ~4.5 times, by TFMGs and TiN coatings, respectively, all under a stress of 675MPa. It is demonstrated that both TFMG and TiN films with high strength retarded the cracks propagated during fatigue cycles, resulting in increased fatigue life. The especially significant improvement from TFMGs was largely attributable to improved ductility and flexibility and to increased adhesion strength from the titanium adhesion layer.

Comparison of the influence of titanium and chromium adhesion layers on the properties of sol–gel derived NKN thin films

Lead-free (Na0.5K0.5)NbO3 (NKN) thin films were prepared on Pt/X/SiO2/Si substrates (with the adhesion promoters X = Ti, Cr) by a sol–gel process with and without post-annealing treatment. The effect of the diffusion of the adhesion layer elements Ti and Cr into the NKN film was analysed by secondary ion mass spectrometry, scanning electron microscopy pictures, X-ray diffraction (XRD), and leakage current measurements. It turned out that Cr diffuses into the films to a higher extent than Ti. The high amount of Cr diffusion led to the formation of a secondary phase, as seen in the XRD pattern, and to pore formation on the surface of the NKN films. In contrast, the films with Ti adhesion layer were single phase NKN without pore formation. Also, the leakage current measurements showed a strong influence of the Cr diffusion. The leakage current of the films with Cr adhesion layer was about four orders of magnitude higher than that of the films with Ti adhesion layer. The study shows the strong influence of the adhesion layer of the substrate on the properties of NKN films.

Decoupling Diameter and Pitch in Silicon Nanowire Arrays Made by Metal‐Assisted Chemical Etching

The fabrication of well‐separated, narrow, and relatively smooth silicon nanowires with good periodicity is demonstrated, using non‐close‐packed arrays of nanospheres with precisely controlled diameters, pitch, and roughness. Controlled reactive ion etching in an inductively coupled plasma reduces the self‐assembled nanospheres to approximately a tenth of their original diameter, while retaining their surface smoothness and periodic placement. A titanium adhesion layer between the silicon substrate and gold film allows much thinner catalyst layers to be continuous, facilitating the film liftoff and formation of the perforated pattern without influencing catalyzed etching of silicon. Using these methods, a periodic array of silicon nanowires with a large pitch and small diameter (e.g., a 490 nm pitch and 55 nm diameter) is created, a combination not typically found in the open literature. This approach extends the types and quality of silicon nanostructures that can be fabricated using the combined nanosphere lithography and metal‐assisted chemical etching techniques.

Titanium nitride thin film as an adhesion layer for surface plasmon resonance sensor chips

Optical properties, surface plasmon resonance (SPR) response characteristics, and the adhesion properties of the plasmonic stacks with titanium nitride (TiNx) adhesion layers were analyzed and compared with those of the Au single stack and the plasmonic stacks with conventional titanium adhesion layer. All the films were deposited by radio frequency magnetron sputtering. TiNx single layer exhibited higher electrical conductivity and reflectance in long wavelength range than Ti single layer of similar thickness. When compared with the plasmonic stacks with Ti adhesion layer, the plasmonic stacks with TiNx adhesion layer showed higher peak transmittance and less absorption loss in wavelength range longer than 500nm. Examination of the SPR response curves revealed that much improved SPR characteristics could be attained if conventional Ti adhesion layer were replaced by TiNx layer, and it was attributed to the lower damping of TiNx film than Ti film at corresponding thickness. Also, it was proved that TiNx layer could provide sufficient adhesion strength at the glass/TiNx and TiNx/Au interfaces, which is comparable with that of Ti layer.

Effects of plasma nitriding and multiple arc ion plating TiN coating on bacterial adhesion of commercial pure titanium via in vitro investigations

The invalidation of dental implant is mainly caused by periimplantitis, which is closely related to the bacterial adhesion on the surface of material. In order to prevent it from bacteria adhesion, two kinds of nitride modification coatings were synthesized on the dental implant materials of commercial pure titanium via plasma nitriding and multiple arc ion plating techniques, respectively. The effects of plasma nitriding and TiN coating plating on bacterial adhesion of commercial pure titanium were assessed by using in vitro investigations. The results showed that there were a large amount of bacteria attached on the commercial pure titanium surface, while few bacteria adhered to the surfaces of two modification coatings. The nitriding coating accounted for about 57.40% and the TiN coating made up nearly 62.45% of the bacterial adhesion amount on that of commercial pure titanium. Modification coatings obtained by plasma nitriding and multiple arc ion plating TiN significantly reduced the bacterial adhesion. Both the nitriding coating and TiN coating possessed certain properties of antibacterial adhesion. There is no significant difference between the two modification coatings on the resistance of bacterial adhesion from a statistical point of view.

Wear characteristic on BAM coated carbide tool in drilling of composite/titanium stack

This paper studied characteristics on a BAM coated carbide, which comes from a ceramic alloy of boron, aluminum, magnesium, etc., in drilling of CFRP and titanium (Ti) stacks. A series of drilling test was performed starting from drilling of CFRP (top) to Ti (bottom) in the stacks using uncoated tungsten carbide (WC) and BAM coated WC. The BAM coating, which is known for one of the hardest and slipperiest materials. In this regard, BAM coating can be used for cutting tool by reducing the adhesion of work material and interfacial friction. Tool surfaces were periodically measured during the drilling tests using scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS) and confocal laser scanning microscope (CLSM) in order to analyze the tool wear evolution and metallurgical changes on the tool surface. From the experiment, it was observed that no major wear occurred on rake surface and center of the tool while flank wear was significant. The wear mechanisms on flank surface were abrasion and titanium adhesion. The abrasion wear took place by the hard carbon fibers in CFRP and the hard inclusions in titanium. On the other hand, the adhesive wear occurred by pulling out the carbide grains when the adhered titanium layers detached from the tool surface. BAM coated carbide tool showed substantially reduced Ti adhesion especially at high cutting speed. In addition, the lower flank wear was observed for BAM coated tool compared with for uncoated carbide tool.

Metallic Adhesion Layer Induced Plasmon Damping and Molecular Linker as a Nondamping Alternative

Drastic chemical interface plasmon damping is induced by the ultrathin (∼2 nm) titanium (Ti) adhesion layer; alternatively, molecular adhesion is implemented for lithographic fabrication of plasmonic nanostructures without significant distortion of the plasmonic characteristics. As determined from the homogeneous linewidth of the resonance scattering spectrum of individual gold nanorods, an ultrathin Ti layer reduces the plasmon dephasing time significantly, and it reduces the plasmon scattering amplitude drastically. The increased damping rate and decreased plasmon amplitude are due to the dissipative dielectric function of Ti and the chemical interface plasmon damping where the conduction electrons are transferred across the metal-metal interface. In addition, a pronounced red shift due to the Ti adhesion layer, more than predicted using electromagnetic simulation, suggests the prevalence of interfacial reactions. By extending the experiment to conductively coupled ring-rod nanostructures, it is shown that a sharp Fano-like resonance feature is smeared out due to the Ti layer. Alternatively, vapor deposition of (3-mercaptopropyl)trimethoxysilane on gently cleaned and activated lithographic patterns functionalizes the glass surface sufficiently to link the gold nanostructures to the surface by sulfur-gold chemical bonds without observable plasmon damping effects.