NiCr Layer Research Articles

Effect of Ni-Cr Layer on Adhesion Strength of Flexible Copper Clad Laminate

In this study, the effect of a Ni-Cr layer on the adhesion strength of flexible copper clad laminate (FCCL) was evaluated after thermal treatment. The changes in the chemical composition, morphology, and adhesion properties were characterized by scanning electron microscopy (SEM), x-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and 90 deg peel test. The results showed that both the peel strength and thermal resistance of the FCCL increased with increasing Cr ratio. The thermal treatment of the FCCL increased the proportion of C-N bonds and reduced that of the C-O and carbonyl (C=O) bonds in the polyimide. The roughness of the fracture surface decreased with increasing thermal treatment temperature and holding time. The chemical function and roughness of the fracture surface were affected by the Ni-to-Cr ratio.

Adhesion and interfacial characteristics of metal/PI composite film modified by O 2 ion beam

In this study, the adhesion and interface characteristics of NiCr/Cu metal film on PI film modified by O 2 ion beam were investigated. The surface modification of PI film by O 2 ion beam enabled a significant decrease of contact angles of water from 68° to 4.4° at an ion dose of 1 × 10 18 ions/cm 2, which resulted in an increase of surface energy by a factor of two. The XPS (X-ray Photoelectron Spectroscopy) spectrum showed that the functional groups of C–O and C O bonding on PI surface were increased by the interaction between scissored unstable chains and reactive ions. The peel strength between PI and NiCr/Cu metal film increased with an increase of ion dose and the highest peel strength of 0.70 N/mm was obtained at an ion dose of 1 × 10 18 ions/cm 2. According to the XPS depth profile from NiCr metal layer into modified PI film, the O1s peak was broadened at near-interface region with an increase of depth from NiCr layer, which indicates that the new chemical bonding state was formed. In addition to C–O and C O bonding, the newly formed chemical bonding at the interface between NiCr metal film and PI film was identified as metal-oxide compounds such as NiO, Cr 2O 3, and Cr–O by XPS curve fitting. Consequently, the improvement of adhesion is primarily attributed to the strong chemical bonding caused by the chemical interaction between NiCr and newly formed functional group by O 2 ion beam.

Cyclic oxidation behaviour of Ti 3Al-based alloy with Ni–Cr protective layer

The influence of a thin 80Ni–20Cr (at.%) protective coating on the cyclic oxidation of a Ti–24Al–11Nb (at.%) alloy based on Ti 3Al at 600 and 900 °C in air was investigated using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction analysis (XRD). The results of the oxidation tests showed that deposited Ni–Cr layer provides an improved oxidation resistance due to the formation of protective oxide scale which barriers the outward Ti diffusion into the scale. In some extent surface formation of the nitride layer also prevents diffusion of alloying elements from the matrix. Although oxidation at 900 °C is faster than that at 600 °C, a remarkable reduction in mass gain of the alloy with protective coating was observed. The thickness of oxide scale on the coated samples is approximately two times less than that formed on the uncoated samples treated under the same exposure conditions (120 h).

The structure and field emission enhancement properties of nano-structured flower-like graphitic films

Nano-crystalline graphite films were grown on ceramic substrates by microwave plasma chemical vapor deposition system using Fe–Ni–Cr layer as catalyst deposited by magnetron sputtering method. The microstructure and surface morphology of the nano-crystalline graphite were characterized by X-ray diffraction, Raman spectrum, Scanning electron microscope, and Transmission electron microscope. The measurement results revealed that nano-crystalline graphite film consisted of a series flower-like carbon clusters, which contains a few nano-crystalline graphitic slices. The thickness of the slice is less than 10 nm. The nano-crystalline graphitic film exhibited good field emission properties, which has the turn-on field of 1.26 V/µm, and the current density of 2.1 mA/cm 2 at electric field of 2.2 V/µm. The emission mechanism of nano-crystalline graphitic film was also studied.

Electrodeposition of Ni-Cr alloy on aluminum substrate

Ni-Cr alloys with mass fraction of 1.4%–23.9%Cr, 76.1%–98.6%Ni, and hardness of 70.5–80.5HR were electrodeposited on aluminium substrate from the trivalent chromium sulphate-chloride solution using citric acid as complexing agent. The aluminium was pretreated by means of degreasing and eroding, polishing and twice chemical immersion of zinc. The effects of electrodeposition parameters such as current density, temperature, pH value and bath concentration on the composition and hardness of deposits were investigated. The results show that the Cr content increases with the increase of current density and the decrease of temperature, and that it increases with the increase of pH value to a maximum and then decreases. The increase of Cr content leads to the increase of hardness of the Ni-Cr layers. The deposits with high Cr content are of good corrosion resistance. Good adherence of Ni-Cr deposits to aluminium substrate is obtained. The Ni-Cr alloys are the Ni-Cr solid solution with fcc crystalline structure. The Ni-Cr alloy deposits are fine, bright and smooth and compact.

NiCr coatings on stainless steel by HVOF technique

This paper demonstrates the successful application of NiCr coatings on stainless steel substrates using a high velocity oxy-fuel technique for corrosion applications. We present preliminary results of fabrication and microstructural characterization of NiCr coatings. These coatings were characterized by means of an optical microscope, image analyzer, scanning electron microscope and X-ray diffraction (XRD). A microhardness tester was used in order to determine the mechanical properties of the coating. Microstructural observations pointed out that the NiCr layers possessed porosity, oxidized, unmelted and semimelted particles, and inclusions. XRD results indicated that the outstanding phase of NiCr powder and coating was Ni. It was also found that the microhardness values decreased from the coating to substrate.

OS11(4)-17(OS11W0021) Fatigue Behavior of Thermally Sprayed Materials at High Temperature

High temperature fatigue and thermal cycle damage behavior of SUS304 steel thermally sprayed Al_2O_3/NiCr atmospheric plasma was investigated. Surface deformation behavior was measured using an electronic speckle pattern interferometry (ESPI) system. Cracks and delaminations in the thermally sprayed coatings were observed after high temperature fatigue or thermal cycle testing with SEM. The strain distribution across specimen surface was obtained from ESPI measurements. The relationship between crack generation or delamination and strain distribution was discussed. Surface cracks occurred in the outer Al_2O_3 layer but stopped at the inner NiCr layer after one fatigue cycle when tensile stress was lager than 173MPa at 873K. Surface cracks propagated into the NiCr layer but stopped at the substrate, and local delamination occurred along the interface between the NiCr layer and substrate after N=1×(10)^5 cycles, when the fatigue test was carried out for σ_<max>=173 or 202MPa (R=0) at 873K. No cracks or delamination were observed after N=1×(10)^5 cycles for fatigue condition σ_<max>=115MPa (R=0) at 873K. Short cracks but no delamination were observed for fatigue condition σ_<max>=202MPa (R=0) at 573K. No influence of stress velocities (6.7 or 14Hz) was detected. No damage was observed after thermal cycle testing. The strain value obtained from the ESPI system was confirmed to be approximately the same as that from a strain gauge on an un-sprayed specimen at 293K. The thermal expansion or stress deformation at high temperature was easily measured with the ESPI system. The sprayed specimen surface strain was approximately the same as that of an un-sprayed specimen at 873K, showing that the deformation of the sprayed coating always follows substrate interface deformation at high temperature. Surface strain decreased with N=1×(10)^5 cycle fatigue showing evidence of the hardness effect due to fatigue. Strain values along cracks measured with the ESPI system were larger than those in other areas due to crack opening under the tensile load. In this paper, the larger strain zone is called "the strain concentration zone". Comparing crack location with strain concentration zones, a correspondence was found between the strain distribution obtained from the ESPI system and crack distribution in the thermally sprayed coating. Moreover, strain values decreased or disappeared entirely in the area where delamination in sprayed coating can be detected in situ by analyzing strain concentration or decrease with an ESPI system at high temperature.

High Temperature Fatigue Deformation Measurement of Ceramics Thermally Sprayed SUS304 Steel Using an ESPI System

Surface strains of Al2O3/NiCr thermally sprayed SUS304 steel specimens during the fatigue test (σmax=173MPa, R=0, T=873K) were measured using an electronic speckle pattern interferometry (ESPI) system. The relationships between surface strain and crack initiation/delamination behavior are discussed.The strain values obtained from the ESPI system were confirmed to be almost the same as those from strain gauges on un-sprayed specimens when tensile stresses were loaded at 293K. Thermal expansion deformation and stress deformation at high temperatures were easily measured with the ESPI system. The presence of cracks and delamination on the sprayed coatings can be nondestructively detected by analyzing the strain concentration or decrease. The surface strains of sprayed specimens were almost the same as those of un-sprayed specimens at 873K, indicating that the deformation of the sprayed coatings are always associated with that of the substrate surfaces at high temperature. The maximum surface strain after 1×105 cycles test was a little lower than after 2 cycles test. Surface cracks occurred but stopped at the inner NiCr layer after 2 cycles test at 873K. Many surface cracks and delamination along the interface between the NiCr layer and substrate inte face were confirmed after 1×105 cycles test.

ＥＳＰＩ法を用いたセラミックス溶射材の高温疲労変形の測定

In this paper, the surface strain of an Al2O3/Ni-Cr atmospheric plasma thermally sprayed SUS304 steel specimen during the fatigue test (σmax=173MPa, R=0, 873K) was measured with an electronic speckle pattern interferometry (ESPI) system. The relationship between surface strain and crack initiation/delamination behavior was discussed.The strain value obtained from the ESPI system was confirmed to be almost the same as that obtained from a strain gauge on an un-sprayed specimen when tensile stress was loaded at 293K. Thermal expansion deformation and stress deformation at high temperatures were easily measured with the ESPI system. The presence of cracks and delamination on a sprayed coating can be detected in situ and the strain concentration or disappearing can be detected without damage. The sprayed specimen surface strain was almost the same as the un-sprayed specimen at 873K, which indicates that deformation of the sprayed coating is always associated with substrate surface deformation at high temperature. The maximum surface strain was lower after 1×105 cycles fatigue than after 2 cycles fatigue. Surface cracks occurred but stopped at the inner Ni-Cr layer after 2 fatigue cycles at 873K. Many surface cracks and delaminations along the interface between the Ni-Cr layer, and substrate were confirmed after 1×105 fatigue cycles.

Preparation of 3D 256 Element PCLT/P (VDF-TrFE) Infrared Array

A 256(16 2 16) element infrared array was integrated by 3-dimensional CMOS technology. 0-3 nanocomposite thin film consisting of nanosized calcium and lanthanum doped lead titanate (PCLT) powder dispersed in a vinylidene fluoride-trifluoroethylene [P(VDF-TrFE)] matrix with 0.16 volume fraction of PCLT was used as the sensing element. PMOSFETs and two 16-bits shift registers were used as the impedance converter and address selection of the elements, respectively. The thermal insulation layer was a 6 w m polyimide film and the absorption layer was a 40 nm Ni-Cr layer. The specific detectivity was 2.6E7cmHz 1/ 2W m 1 as tested by using a black body infrared source.

Effects of thickness coating on the electrochemical behaviour of thermal spray Cr 3C 2–NiCr coatings

Thermally sprayed HVOF coatings are increasingly being used in industrial applications where high wear and corrosion resistance are needed [1,2]. In this paper, electrochemical ac and dc experiments were used in order to obtain the corrosion resistance of coated steel with different numbers of Cr 3C 2–NiCr layers. This work has been performed in order to determine the role of coating thickness in the corrosion behaviour of a steel protected with cermet thermally sprayed coatings. It is known that a thicker layer protects better against corrosion when a metallic coating is evaluated. But cermet coatings, such as Cr 3C 2–NiCr, contain higher levels of porosity and residual stresses than metallic coatings, which really could influence the corrosion resistance of the deposited layer. Electrochemical measurements, such as Open-Circuit Potential ( E OC), Polarisation Resistance ( R p) and Cyclic Voltammetry (CV), were performed in an aerated 3.4 NaCl media (%wt.). Electrochemical Impedance Measurements (EIS) were also done in order to obtain a mechanism that explains the corrosion process. Structural Characterisation was carried out by means of Optical and Scanning Electron Microscopes (OM, SEM) with an Energy Dispersive Spectrometry analyser (EDS). Results show that the corrosion resistance of the complete system is mainly influenced by the substrate behaviour. The application of a higher number of deposited layers did not substantially increase their anticorrosive properties. Stress generation during the spraying deposition process plays an important role in the behaviour of the coated steel against corrosion phenomena.

Magnetic characteristics of new cyano-bridged two-dimensional honeycomb-like bimetallic assemblies containing Ni(II)-N[triple bond]C-Cr(III) or Ni(II)-N[triple bond]C-Cr(I) linkages.

Three cyano-bridged bimetallic assemblies, [NiL(1)](3)[Cr(CN)(6)](2).7H(2)O (1), [NiL(2)](3)[Cr(CN)(6)](2).9H(2)O (2), and [NiL(2)](3)[Cr(CN)(5)(NO)](2).9H(2)O (3) (L(1) = 3,10-dimethyl-1,3,5,8,10,12-hexaazacycloctadecane and L(2) = 3,10-diethyl-1,3,5,8,10,12-hexaazacycloctadecane), have been prepared and characterized structurally and magnetically. Complex 1 crystallizes in the monoclinic space group of C2/c with a = 25.929 A, b = 15.442(3) A, c = 19.553(4) A, beta = 106.21(3) degrees, and Z = 4, while 2 and 3 are in the trigonal space group P3 with a = b = 14.919(2) A, c = 9.5246(19) A, gamma = 120 degrees, and Z = 1 for 2 and a = b = 14.863(2) A, c = 9.3134(19) A, gamma = 120 degrees, and Z = 1 for 3. The structures of 1-3 are similar and consist of cyano-bridged two-dimensional (2D) honeycomb-like neutral Ni(3)Cr(2) layers. In each complex, [Cr(CN)(6)](3-) or [Cr(CN)(5)(NO)](3-) coordinates to three trans-[Ni(macrocycle)](2+) groups using three fac-CN(-) ligands, providing a 2D layered network. The NO group in [Cr(CN)(5)(NO)](3-) remains monodentate. Magnetic studies show the existence of a short-range ferromagnetic interaction in all of the complexes. Complexes 1 and 2 exhibit long-range antiferromagnetic ordering at 13.0 and 11.9 K, respectively, and a metamagnetic transition with critical field of ca. 1.6 kOe for 1 and 1.5 kOe for 2 at 1.8 K. Complex 3 exhibits long-range ferromagnetic ordering below 4.3 K.

Development and tests of B 4C-covered heat shields for TJ-II

The Neutral Beam Injection System for the Spanish Stellarator will start in 2001. This heating system consists of two beam lines and will inject about 2 MW into the plasma. The ‘groove region’ of the vacuum vessel (Proc. 18th Symp. On Fusion Technol. (1994) 771) will be exposed to thermal loads as high as 5 MW/m 2 (Fus. Technol. Vol. 35, (1999)). A heat resistant material must cover the present stainless steel groove protection plates. Plasma-sprayed boron carbide (B 4C) seems to fulfil all the requirements, in addition needs little room and therefore does not reduce the size of the plasma. The development of the B 4C-covered plates was done in two steps. In the first one, stainless steel plates with simplified geometry were covered with B 4C and tested at the JET Neutral Beam Test Bed. To analyse damages after the tests, surface analysis by means of SEM, ESCA and Auger techniques have been done at Ciemat. The second step comprises the plasma spraying of stainless steel plates with the real geometry. In order to achieve a sufficiently good adhesion of the B 4C-layer an intermediate layer of NiCr was sprayed. Standard tests of these plates at the manufacturer have successfully been terminated. The heat load cycling remains to be done in the near future.

Oxidation, Diffusion and Segregation in CuNi(Mn) Films Studied by AES

The surface and in-depth compositions of sputter-deposited Cu0.57Ni0.42Mn0.01 thin films were studied by Auger electron depth profiling after thermal treatment. The samples were thermally cycled to maximum temperatures of 300 °C to 550 °C in air, argon and forming gas (N2, 5 vol. % H2). Linear least-squares fit to standard spectra and factor analysis were applied to separate the overlapping Auger transitions of Cu and Ni. Under bombardment by 4 keV argon ions, CuNi(Mn) layers display bombardment-induced surface enrichment of Ni in the same extent as binary CuNi alloys. At sufficiently high oxygen partial pressures, a duplex oxide layer is formed and a thick surface copper oxide overgrows the initial nickel oxide. In reducing atmosphere selective oxidation of manganese takes place. A capping NiCr layer prevents CuNi(Mn) from being oxidized, but the film configuration is degraded with increasing annealing temperature due to formation of a surface chromium oxide and diffusion of Ni from the CuNi(Mn) layer into the NiCr/CuNi(Mn) interface.

Comparative Analysis of a Solar Control Coating on Glass by AES, EPMA, SNMS and SIMS

A solar control coating was analysed by different methods of surface analysis with respect to the layer sequence and the composition and thickness of each sublayer. The methods used for depth profiling were Auger electron spectroscopy, electron probe microanalysis, secondary neutral mass spectroscopy and secondary ion mass spectroscopy based on MCs+. The structure of the coating was unknown at first. All methods found a system of two metallic Ag layers, embedded between dielectric SnOX layers. Additionally, thin Ni-Cr layers of 1–2 nm were detected on top of the Ag layers. Thus the detected layer sequence is SnOX/Ni-Cr/Ag/SnOX/Ni-Cr/Ag/SnOX/glass. The Ni:Cr ratio in the nm-thin layers could be quantified by every method, the Cr fraction corresponding to less than one monolayer. We compare the capabilities and limitations of each method in routinely investigating this solar control coating. Importance was attached to an effective investigation. Nevertheless, by combining all methods, measuring artefacts could be uncovered and a comprehensive characterisation of the system was obtained.

Characterization of a heat-insulating coating on floatglass by sputter-assisted EPMA

Heat-insulating coatings on window glass consist of thin metallic films embedded in thin dielectric films. Such multilayer systems are produced commercially by physical vapour deposition in a continuous technique. For process control as well as for the development of new types of multilayer systems, surface-sensitive methods of analysis are essential to characterize the structure of the coatings in terms of the thickness and chemical composition of each layer. The present work reports on the first application of electron probe microanalysis (EPMA) in depth profiling of a complex heat-insulating coating on floatglass. It is well known that conventional EPMA is a powerful tool in microbeam analysis to quantify chemical compositions with high accuracy and to detect rather low concentrations even for light elements (B-F). However, the large information depth of x-rays (∼0.1-1 μm) limits the applicability to depth profiling. A great step forward in depth profiling in the submicrometre range was achieved by combining EPMA with surface removal by a sputtering procedure. Two various techniques can be applied: measurement of the emitted x-rays by scanning the electron beam across a sputter crater edge; or sputtering the material in situ with an integrated ion gun. In this work we succeeded in quantifying the film thickness (mass coverage) and chemical composition of each single component of the heat-insulating structure. The great advantage of the new method is its ability to determine the depth scale, as well as its remarkable detection limit. For example, in a depth of 100 nm a thin NiCr layer ∼1 nm thick could be detected. The Ni/Cr ratio of the layer was determined reproducibly to be 85: 15. The minimal thickness that could have been detected was estimated to be 0.15 nm.

Characteristics of a free-standing superconducting nanobridge with an integrated heater fabricated using a self-aligned technique

We report on a novel method of controlling the supercurrent flow in a superconducting weaklink. We have fabricated a free-standing superconducting nanobridge with an integrated NiCr heater. This NiCr layer acts as a self-aligned mask for reactive ion etching and also as the normal metal heating element of the nanobridge. The heater is used to control the critical current of the superconducting weaklink part of the nanobridge; the free-standing nature of the nanobridge reduces the heater power required. We discuss the dependence of the current–voltage characteristics of the superconducting weaklink on heater current. This device has advantages over existing controllable weaklink devices.

Auger electron spectroscopy study of interdiffusion, oxidation and segregation during thermal treatment of NiCr/CuNi(Mn)/NiCr thin films

The effect of annealing on sputter deposited thin-films NiCr/CuNi(Mn)/NiCr is studied by Auger electron depth profiling. The samples were annealed to maximum temperatures of 300°C to 550°C and investigated at ambient temperature. Auger transitions of Cu and Ni are separated by target factor analysis, principal component analysis and linear least squares fit to standard spectra. For the CuNi(Mn) layer in the as-received state AES results shows a Cu depletion caused by bombardment induced segregation. After annealing the measured Cu concentration has increased due to Ni diffusion to the interfaces. The NiCr layer is degraded with increasing annealing temperature due to formation of a chromium oxide and diffusion of Ni from the CuNi(Mn) layer. A sequence with nominal compositions near Cr 2Ni, CrNi and CrNi 2 is found. At the NiCr/CuNi(Mn) interface an interdiffusion zone phase Ni 0.6Cr 0.2Cu 0.2 is formed.

Influence of the thickness and area of NiCr/Ag electrodes on the characteristics of BaTiO3- ceramic based positive-temperature-coefficient thermistors

The electrical behaviour of commercial BaTiO3-based positive-temperature-coefficient (PTC) thermistors with NiCr/Ag electrodes was investigated by impedance analysis in the frequency domain. The contact resistance and thus the total resistance of the PTC increases with decreasing thickness as well as with decreasing area of the NiCr layer at constant Ag top layer. The increase in the total resistance in both cases is explained by the increase in the contact area of the Ag layer to the ceramic which is represented by a model. The Ag forms a blocking contact to the ceramic in contrast to the NiCr which shows an ohmic behaviour. Using our model, the electrode impedance contribution of very thin NiCr layers can be interpreted in terms of incomplete wetting of the ceramic surface by the NiCr metal during the deposition. Supplementary scanning electron microscopy and high-resolution transmission electron microscopy analyses have been used to study the structure of the electrode interface and the structure of the layers. © 1998 Kluwer Academic Publishers

Silver-based low-emissivity coatings for architectural windows: Optical and structural properties

Spectrally selective coatings are, nowadays, deposited onto architectural windows to be employed in commercial and residential buildings for the purpose of saving energy. In this work, the fundamental optical and structural properties of two types of low-emissivity silver-based coatings deposited onto glass, Ag and SnO 2/Ni-Cr/Ag/Ni-Cr/SnO 2 (Vitrage à couches avec une forte reflexion des rayonnements thermiques, European Patent EP 0 506 507 B1) are analyzed. It has been demonstrated that the silver-based multilayer coatings give an efficient heat isolation due to their low emissivity values, thus not deteriorating the optical properties in the visible range given by the glass substrate. From Atomic Force Microscopy measurements it has been determined that the Ag layer has a more homogeneous grain size when is deposited onto the Ni-Cr layer than when is deposited onto glass.