Non-metallic Films Research Articles

High-strength, low infrared-emission nonmetallic films for highly efficient Joule/solar heating, electromagnetic interference shielding and thermal camouflage.

High-strength nonmetallic materials with low infrared (IR) emission are rare in nature, yet highly anticipated especially in military and aerospace fields for thermal camouflage, IR stealth, energy-saving heating. Here, we reported a high-strength (422 MPa) nonmetallic film with very low IR emissivity (12%), realized by constructing alternating multilayered structures consisting of successive MXene functionalized outer layers and continuous GO reinforced inner layers. This nonmetallic film is capable of competing with typical stainless steel (415 MPa, 15.5%), and exhibits remarkable thermal camouflage performance (ΔT = 335 °C), ultrahigh Joule heating capability (350 °C at 2 V), excellent solar-to-thermal conversion efficiency (70.2%), and ultrahigh specific electromagnetic interference shielding effectiveness (83 429 dB cm-1). Impressively, these functionalities can be maintained well after prolonged outdoor aging, and even after undergoing harsh application conditions including strong acid/alkali and boiling water immersion, and cryogenic (-196 °C) temperature.

Deposition of nanoscale metal films with the help of arc discharge

The method of magnetron sputtering using arc discharge is one of the most advanced and high-performance techniques for producing nanoscale films, especially metal films and, in particular, titanium and copper ones. The cathode spots that form during arc discharge are the discharge centers and they provide channels along which current travels from the cathode to the anode in the form of dense plasma jets of the cathode material forming a so-called plasma torch. The ion energy in such plasma torch is higher than in the conventional magnetron sputtering, which ensures a significantly better adhesion of the resulting films. At the same time, nanoscale titanium films are often used to create transition mating sublayers between the substrate and the main working film. Out of non-metallic films, titanium nitride films are of special interest. The main disadvantage of magnetron arc sputtering is the presence of a droplet phase in the plasma torch, which hinders the creation of nanoscale structures by forming condensate on the substrate. The resulting microdroplets are usually electrically neutral, therefore they cannot be removed and neutralized by means of electric or magnetic fields. The arc evaporator needs to be retrofitted so that the droplet phase was eliminated and thin-film coatings (including nanoscale coatings) could be produced. A plasma torch is formed with the help of a focusing coil, in which both ions of the sprayed substance and its droplets are present. A special flap prevents direct-flying droplets from getting in the flow of sprayed substance, and at least one more flap installed in the housing of the focusing coil protects the flow from droplets flying at an angle from the cathode. The flap is designed as a truncated cone made of non-magnetic metal, with the diameter of the larger base of the cone being equal to the inner diameter of the focusing coil, and the smaller diameter of the cone that faces the cooled cathode is equal to twice the diameter of the flap. The flap is coaxial with the cooled cathode of the arc evaporator.

Non-Metallic Films Electroplating on the Low-Conductivity Substrates: The Conscious Selection of Conditions Using Ni(OH)2 Deposition as an Example

Mathematical modelling was used to study the influence of different parameters on the distribution of current density during electrodeposition of low-conductivity films on high-resistance substrates (FTO, ITO etc.). Experimental data were used to model the deposition of non-conductive Ni(OH)2 film onto FTO glass. The influence of substrate resistance, polarization resistance, electrolyte concentration, and other parameters on the current density distribution over the electrode surface was analyzed. The analysis of modelling results revealed that the fundamental differences in the current density distribution during deposition of coatings in electroplating and deposition of low-conductivity films are due to the high resistance of the substrate in the latter case. It was found that the impact on the uniformity of the current density distribution was decreasing in the series “substrate resistivity – polarization resistance – electrolyte conductivity”. The results of the conducted modelling allowed formulating recommendations for electrochemical deposition of low-conductivity films uniformly distributed over the surface of the substrate with low conductivity. In this case, the use of diluted electrolytes was justified. The results of galvanostatic deposition of Ni(OH)2 films onto FTO glass (7.5 Ω/□, 2 × 2 cm) from 1М and 0.01М solutions of Ni(NO3)2 and the subsequent colorization proved the modelling results experimentally. The width of Ni(OH)2 film deposited from 1M solution was less than 1mm, while the coating was absent on the rest of the surface. Deposition from 0.01 solution resulted in a uniform film with complete coverage of the working electrode area.

A test rig for analysis of adhesive tapes at 4 K cryogenic temperature

Cryostats and dewar vessels, in particular those used for liquid helium applications, are usually equipped with multi-layer insulation (MLI). Thereby, multiple foils are wrapped around the respective vessels, tubing and components. As standard, different foils are bonded edge to edge using adhesive tapes either based on aluminized non-metallic films or on aluminum foil. There are a number of standard test procedures for adhesive tapes near ambient temperatures (e.g. AFERA 5012/ISO 29863) allowing a standardized characterization of tapes in terms of holding force and long-term reliability. Unfortunately this does not hold true for adhesive tapes to be used at cryogenic temperatures. In this respect, a test rig comprised of a spring-based traction mechanism has been developed by the authors. Combined with a liquid helium dewar, the fabricated test set-up allows a precise and reproducible application of an adjustable tensile load at 4.2 K and measurements of the respective holding time. In the following, the overall set-up including its significant features is described and first experimental results with aluminum tapes are presented.

Free Vibration Analysis of a New Polymer Quartz Piezoelectric Crystal Sensor Applied to Identify Chinese Liquors

This paper deals with the analytical and numerical analysis of free vibration in a new polymer piezoelectric crystal sensor. A quartz piezoelectric crystal here serves as the basal material and nonmetallic polymer thin films with perforative central holes as the surface coating according to the principle of quartz crystal microbalance (QCM), based on the Kirchhoff–Love plate model. A mechanical model of the new sensor was built, and its structure was a quartz piezoelectric sandwich composite circular plate with perforative central holes in the surface layers. The form of the electric potential field in the piezoelectric layer was here assumed to be such that the Maxwell static electricity equation is satisfied. The validation of the mechanical model and its analytic method is conducted by comparing the free vibration frequencies of the piezoelectric sandwich composite circular plate produced by the mechanical model’s analytical and numerical analyses performed using ANSYS software. Results show that the first 100 orders of free vibration frequency values of the mechanical model obtained by two methods, the analytical analysis and the numerical analysis, to be fit. The maximum absolute deviation rate ([Formula: see text] between the analytical solutions ([Formula: see text]) and the numerical solutions ([Formula: see text]) was found to be 6.89%. These results are important reference for the design of the new polymer quartz piezoelectric crystal sensors suitable for the identification of Chinese liquors.

Contactless hybrid sensor for simultaneous detection of light reflectance and eddy currents

We demonstrate a contactless hybrid sensor for the simultaneous detection of light reflectance and eddy currents. The sensor is based on combining an optical system with an RLC self-resonator, wherein the reflected light intensity and resonance frequency are measured. We demonstrate that the hybrid sensor can be used for monitoring metals coated with non-metallic films. Whereas the self-resonator can efficiently distinguish between metals and non-metals, the optical subsystem is sensitive to changes in the reflectance of light. A systematic investigation of the detector response as a function of distance to the material under test is undertaken to characterize its behavior.

Effect of PVD coatings on the strain and low-cycle fatigue resistance of stainless steel and titanium alloys

Introduction. The fracture of structural components is known to be often initiated by the local damage of surface layers of the material. The mechanical properties of the surface layer are built up in manufacturing the structural components and affected in service. The major contributors to the fracture of surface layers are their roughness, stress concentrations, and nonuniform distribution of mechanical properties over the surface and in depth of the material [1]. Experimental investigations, e.g., [2], demonstrated that in a homogeneous stressed state, the yield limit of the surface layer of low-carbon steel was 25% lower than that of the base material. As evidenced by some other findings [3], the yield limit of the thinnest specimens is only 20% of that of the thick ones. Therefore, plastic flow on the surface sets in earlier than in the middle layers. Engineering practice employs different treatments, including the application of metallic and nonmetallic films and coatings, to enhance the strength and protective properties of item surfaces. As early as 1926, Rosko [4] began studying the effect of surface oxide films on the mechanical properties of metals in evaluation of the microhardness of cadmium monocrystals. It was revealed that the oxide film less than 20 atoms thick increased the critical stress of cadmium monocrystals by about 50%. It also interferes with plastic strains in the crystal, which contributes to an increase in the hardness of the surface layer. Investigations [5–9] showed that not only oxide films but also PVD coatings (physical vapor deposition) enhanced the tensile and cyclic load resistance, mainly due to the restriction on plastic strains of the base by a hard surface layer with higher mechanical strength, large residual compression stresses, and good adhesion of the coating material to the base [7–9]. An increase in the tensile and cyclic load resistance is associated with the thickness and hardness of PVD coatings and their nitrogen contents [7, 8, 10].

Modeling structural metastability of irradiated thin films

The nucleation of crystalline or amorphous phases in irradiated binary metallic, as well as non-metallic compound thin films is interpreted using the atomistic interface migration-charge transfer (IMCT) model. The space and time evolution of dense collision cascades, which form upon ion bombardment of the target, lead to non-equilibrium compositional and electronic density profiles at the interface between each cascade and the surrounding crystalline matrix. This occurs because one of film constituents preferentially migrates to the interface, which becomes enriched in it. Cascade relaxation to metastable equilibrium is simulated by local charge transfer reactions (CTR), each involving a pair of dissimilar atoms of the initial compound, which constitute a dimer of an effective compound. The energy cost to introduce an effective compound dimer into the matrix, the difference of formation enthalpy between effective and initial compound and the local strain suffered by the film as a consequence of ion formation by a CTR are evaluated. Threshold values are found in the above structure stability parameters that allow for a qualitative separation of amorphised from crystalline compounds, both metallic and non-metallic.

Structural stability of irradiated metallic and non-metallic films

The segregation charge transfer model allows the interpretation of the nucleation of either crystalline or vitreous phases in binary non-metallic as well as metallic compounds, ion bombarded under conditions favourable to the formation of dense collision cascades. At the cascade–matrix interface a non-equilibrium electronic density profile forms and it is re-equilibrated by charge transfer reactions (CTRs), each involving a couple of dissimilar atoms, which undergo single ionization. The energy cost associated with a single CTR and the local volume change provoked by CTR products are evaluated. Thresholds in the values taken by the above physical quantities are found for both families of irradiated materials. Those thresholds separate the compounds amorphized from those remaining crystalline under ion bombardment.

High-order optical-harmonic generation in films of nonmetallic crystals

High-order optical-harmonic generation in nonmetallic films interacting with pulses of laser light is examined. The wave functions of the current carriers in a crystal in an external electromagnetic field are chosen in the form of Volkov-Keldysh solutions. An explicit expression for the intensity of the sth harmonic, which depends on the crystal parameters, is derived. A plateau and a cutoff effect, similar to those in the case of harmonic generation on an isolated atom, have been detected. Finally, numerical estimates are made for GaAs films excited by pulses of radiation from a carbon dioxide laser.

DETECTION OF LASER GENERATED LAMB WAVES IN NON-METALS BY CAPACITANCE TRANSDUCERS

Abstract A non-contacting technique has been developed to generate and detect Lamb waves in thin non-metallic polyester films and composites like paper by using a TEA-CO2 laser as generator and a suitably designed electrostatic capacitance transducer as detector. Analysis of these detected waveforms allows an estimation of sheet thickness with a reasonable accuracy in sheets as thin as 19 μm.

Thermal Properties of Non-Metallic Films by Means of Thermal Wave Techniques

AbstractThe propagation of a thermal wave into a thin film or coating depends on the thermal properties of the material. Consequently, thermal wave generation and detection can be used to obtain the heat conductivity of the material. The method is also useful because thermal wave propagation is sensitive to inhomogeneity, porosity, inclusions, voids, and delaminations. The results of two specific applications of the thermal wave technique are presented, the heat resistance of oxide coatings and of diamond films.

Infrared spectroscopic studies of surface oxides

Investigations have recently been performed in our laboratory with the object of developing non-destructive optical techniques for the chemical characterization of non-metallic films on metals. Our initial studies were on oxidized samples of 310 stainless steel with minor titanium additions exposed to low P o2 atmospheres ( P o2 ≈ 10 −15 atm). As the exposure time was increased from 0.5 to 139 h the oxide scale was observed to contain increasing amounts of complex oxide phases such as MnCr 2O 4, FeCr 2O 4 and MnTiO 3. Binary oxides of titanium and chromium were observed at all exposure times. A series of reference spectra were also obtained for comparison with corrosion scale spectra. We consider that Fourier transform IR reflection spectroscopy is an extremely useful tool characterizing non-metallic films. It will be quite valuable in supplementing X-ray diffraction for very thin films and will provide complementary information to data obtained by light scattering and electron spectroscopic techniques.

Characterization of surface oxides by Raman spectroscopy

Raman backscattering spectroscopy is used to characterize thin non-metallic films for applications in materials research. In situ studies of the oxidation and hot salt corrosion of iron- and nickel-based alloys demonstrate the capability of obtaining structural and chemical information from surface films on samples at elevated temperatures (up to 850°C). Studies of the oxidation of SAE 310 stainless steel and similar alloys show that phases of iron, chromium and mixed spinel oxides are identifiable in surface films which are too thin for analysis by X-ray diffractometry. This information is obtained both during and after exposure to high temperature environments. Similar data are obtained from alloys undergoing corrosive attack by a surface coating of molten salt. Both salt chemistry and oxide formation are simultaneously monitored using the Raman technique.

Alternating current diagnostics of poorly conducting thin films

The measurements of the dependence of direct current in non-metallic films on the value of the electric field and temperature provide information about the nature of the prevailing conduction mechanisms. It is difficult to know, however, to what extent these measurements reflect the properties of the bulk material and to what extent they are affected by interfacial barriers at contact or in the inhomogeneous bulk material. Alternating current response as a function of frequency offers valuable additional information about the dynamic response of the system and makes it possible to distinguish between bulk and interfacial phenomena. A review is given of the most important bulk and interfacial responses, in particular the dipolar and hopping charge contributions and the effects of depletion and injection barriers, with examples from a range of measurements on SiO, chalcogenide films, stearic acid, electrolytic capacitors and ceramics. It is shown that the bulk properties may be characterized by two types of dielectric response: Debye-like, giving relatively sharp loss peaks in frequency, and a much broader response which is called the “universal dielectric response” and is to be found in a very wide range of materials regardless of their physical and chemical nature. It is shown that both the Debye and the “universal” responses may be caused by either dipolar or hopping charge phenomena. In the presence of barriers the admittance or impedance plots in the complex plane often give skewed semicircles. This is illustrated with an example of chalcogenide glass and is interpreted as a manifestation of the universal dielectric behaviour.

The use of RF voltage in quartz crystal microbalance measurements: application to nonmetallic films

The applications of the piezoelectrical quartz crystal microbalance are extended by measuring the RF voltage simultaneously with the frequency. The RF voltage decreases linearly with the added mass and is sensitive to a mass change (dU/dm= sigma v) of the same order of magnitude as the frequency. The sensitivity sigma v depends on the mechanical rigidity of the deposited films, i.e. on the interaction forces within the films.

Studies of Epitaxial Growth of Metallic and Nonmetallic Films by Means of High-Resolution Ciné and Still-Electron Microscopy

Growth processes of metallic vacuum deposits, Ag and Au, and nonmetallic deposits, PbS and PbSe, on MgO and MoS2 substrates have been studied by means of direct cine recording of electron micrographs resolvable down to 17 A moire spacing. The detailed kinetics of the film growth as revealed by the moire fringes are discussed in the light of growth mechanisms. The main differences between the metallic and nonmetallic film growths are the absence, in the cases of nonmetallic film growth, of “liquid-like” behavior during coalescence, and lack of the secondary nucleation, which are known to be very important in metallic film growth. Growth processes of so-called multiply-twinned particles and twin formation and release in the metallic film growth have also been studied. The direct observation of formation of pseudomorphic interfacial dislocations was carried out in the case of PbSe on PbS. The lattice spacing anomalies in pseudomorphic overgrowth have been examined by means of high-resolution still-electron m...

The Physics of Track Registration in Solids

During the last ten years many observations of charged particle tracks in solids have been reported, and the utilization of this phenomenon in several fields of physics has grown apace. For example, Fleischer, Price, Walker, and their many collaborators have demonstrated the usefulness of track formation as a tool in nuclear physics, radiation dosimetry, geochronology and cosmic-ray physics. All the more reason, then, that one should endeavour to understand the basic mechanisms of track production in different kinds of solids. To do this, one must investigate the relationship between stopping power and track formation, the nature of the damaged region comprising a track, and the annealing behavior of the tracks. The electron microscope can furnish much of the necessary information provided that one is able to interpret the diffraction-contrast image of the tracks.Linear damage regions have been found both in thin films and in bulk samples. While tracks appear in metallic and nonmetallic thin films they have only been found in nonmetallic bulk solids. The latter include a wide variety of plastics, glasses and minerals.

1967 Thin Films Conference Resistive and dielectric properties of thin films Nottingham, April 1967

The conference was a three-day meeting sponsored jointly by the Electronics Group, the Electron Microscopy and Analysis Group, and the Vacuum Physics Group of The Institute of Physics and The Physical Society. It follows conferences on electrical and magnetic properties of thin films at Imperial College in 1964 and on non-metallic films at Chelsea in 1965 and is intended to be the first of a series of annual Spring conferences on the physics of thin films. There were 228 participants, including 43 from overseas.

903. Field emission of electrons from metals with non-metallic films: N V Mileshkina and I L Sokol'skaya,Fiz Tverd Tela, 8, (11) Nov 1966, 3163–3166 ( in Russian)

903. Field emission of electrons from metals with non-metallic films: N V Mileshkina and I L Sokol'skaya,Fiz Tverd Tela, 8, (11) Nov 1966, 3163–3166 ( in Russian)