Acoustic Microscopy Technique Research Articles

Thickness-Dependent Nanoscale Elastic Stiffening of Chemical Vapor Deposited Atomically Thin 2H-MoS2 Films.

Understanding the nanoscale elastic-size-effects of atomically thin transition-metal dichalcogenides (TMDs) as a function of thickness underpins the avenue of flexible 2D electronics. In this work, we employed the atomic force acoustic microscopy (AFAM) technique to investigate the thickness-dependent elastic properties of CVD grown 2H-MoS2 films. The monolayer MoS2 exhibited a Young's modulus of 273 ± 27 GPa. Our systematic analysis from bulk to monolayer suggests that the 2H-MoS2 phase exhibits nanoscale elastic-stiffening behavior with decreasing number of layers (thickness). The Young's modulus increased by a factor of ∼2.7 for monolayer MoS2 when compared with the bulk. First-principle DFT calculations affirm the nanoscale elastic-stiffening behavior of MoS2 with decreasing number of layers. Our findings suggest that the observed elastic stiffening is due to the interlayer sliding, which may be facilitated by defects in MoS2 layers. The observed elastic stiffening may be of potential importance for understanding TMD based nanomechanical devices.

Analytical study to effects on reflection coefficient of Ti–Mn alloys at increasing concentration Mn element in the dental implants application

Manganese (Mn) is one of the trace elements in the human body, The titanium-manganese (TiMn) alloys have been used in some applications as well. The TiMn alloys with various manganese contents ranging from 2 to 12 wt % were prepared by using mechanical alloying and spark plasma sintering (SPS) techniques (Sibum, 2003). This paper investigated the effects of increasing manganese content in the Ti. Concentrations of Mn (2 wt % to 12 wt %) in titanium influence the reflection coefficients and acoustic signatures of Ti–Mn alloys by Scanning Acoustic Microscopy (SAM) technique, was determined by The oscillatory behavior, The spectral treatment of these signatures, via fast Fourier transform. Correspond to longitudinal and Rayleigh relations depend on Mn Concentrations, was Concluded that Mn Concentrations (from 2 wt % To 12 wt %) increase with increasing Bulk physical properties and Acoustic wave velocities (AWV) as Young's Modulus, Shear Modulus, Bulk modulus, Longitudinal Velocity, Transverse Velocity, and Rayleigh Velocity were (from 105 To 122)Gpa, (from 39.6 To 45.9)Gpa, (from 103 To 119.6)Gpa, (from 4862 To 6183) ms1, (from 2450 To 3115)ms−1and (from 1658 To 2064)ms−1 respectively.

Intelligent diagnosis of flip chip solder joints with resolution enhanced SAM image

Scanning acoustic microscopy (SAM) technique has been applied to defect inspection in electronic devices. With the increase of packaging density, detection of the micro-defects in high density devices becomes more and more challenging. The SAM test is suffering from sacrificing the spatial resolution to reach a certain penetration depth of the ultrasonic waves. So it is necessary to enhance the resolution level of the SAM image. In this paper, a wavelet based resolution enhancement technique was investigated to reconstruct a high quality image for SAM test of the flip chip packages. The stationary wavelet transform was adopted to decompose the captured SAM image into four frequency subbands, and the high frequency subbands were enhanced by adding the difference matrix in the intermediate stage, and a super resolution SAM image was derived from combining all the subbands by using the Inverse Discrete Wavelet Transform. Then the solder joints segmented from the SR-SAM image were classified by using the SVM algorithm. The results validated that the proposed technique is effective to improve the detection accuracy of SAM test.

Towards acoustic microscopy at the nanoscale by coupling atomic force microscopy with picosecond ultrasonics

Acoustic imaging techniques are powerful, nondestructive tools used to perform elastic imaging of systems. Acoustic imaging techniques have a large variety of applications in both industrial and fundamental research. Acoustic wave generation in the GHz range using picosecond acoustics has enabled the development of elastic images with nanometric in-depth resolution. However, the spatial lateral resolution for this imaging technique is limited by the laser spot size, which cannot be reduced below a couple hundred nanometers due to light diffraction. In this paper, we report the results from an approach in which we couple time-resolved pump-probe spectroscopy and atomic force microscopy. We generate GHz waves directly into an AFM probe from the top of the probe. Acoustic transmission from the probe to the sample is also achieved, which paves the way to perform subsurface imaging. Due to the nanometric radius size of the commercial tip, acoustic imaging with an improved lateral resolution could be achieved. These results are an encouraging step toward the development of a new acoustic microscopy technique.

Application of deuterium oxide (D2O) isotope tracing technique for encapsulated QFN failure analysis

Polymer encapsulated components are universally used in consumable applications. However, polymer encapsulants for packages commonly are non-hermetic. The polymer encapsulants can absorb moisture from atmosphere which will post a risk to the package reliability. In this study, a type of polymer encapsulated Quad Flat No-Lead (QFN) package encountered electricity leakage after Highly Accelerated Stress Tests (HAST) 96 h. Although it is suspected that penetration of moisture into the encapsulated package caused electrical leakage failure, there is no direct evidence to prove this assumption. Traditional X-ray and Scanning Acoustic Microscopy (C-SAM) techniques cannot detect any defect of the package due to their detection limit.To solve above issues, this study employed a new deuterium oxide (D2O) isotope tracing method. The encapsulated package underwent highly Accelerated Stress Tests (HAST) with D2O, and D signal of the sample was analysed by Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS). The results showed that D localized at the failure area where leakage occurred. It is direct evidence to show it is a moisture-induced leakage.

Evaluation of Acoustic Waves in Acousto-Optical Devices by Ultrasonic Imaging.

The structure of the acoustic field defines the key parameters of acousto-optical (AO) devices. To confirm their compliance with the expected values in the presence of multiple real factors, AO crystalline cells require accurate experimental investigation of the acoustic field after being totally assembled. For this purpose, we propose to detect and quantify all the acoustic waves propagating in AO cells using an impulse acoustic microscopy technique. To validate this approach, we have analyzed both theoretically and experimentally the modes, amplitudes, propagation trajectories, and other features of the ultrasonic waves generated inside an AO modulator made of fused quartz. Good correspondence between theoretical and experimental data confirms the effectiveness of the proposed technique.

Effects of Al Content on Elastic Parameters of AlxGa1-xAs (0 ≤ x ≤ 1) Alloys

Elastic parameters of AlxGa1-xAs (0 ≤ x ≤ 1) alloys are numerically determined and analyzed on the basis of scanning acoustic microscopy technique. Thus, the dependence of Al concentrations, x, on all features of reflection coefficient and acoustic materials signatures (critical angles of reflected modes, spatial periods, peaks of FFT spectra and their corresponding wave velocities) has been considered, analyzed and discussed. It is found that as Al content increases several behaviors are obtained: (i) all critical angles of longitudinal, transverse and Rayleigh waves, decrease, (ii) all spatial periods increase and (ii) both Rayleigh and longitudinal wave velocities increase. Moreover, the variations of these parameters, P, were quantified and semi-empirical formulas were found to be of the form: P = c + ax + bx2; from these formulas, valuable information can be derived and may be useful for AlxGa1-xAs compositional characterization.

On the Bandwidth and Beam Profile Characteristics of a Simple Low-Frequency Collimated Ultrasound Beam Source

Abstract We numerically investigate the bandwidth and collimation characteristics of ultrasound beams generated by a simple collimated ultrasound beam source that consists of a piezoelectric disk operated near its radial mode resonances. We simulate the ultrasound beam generated in a fluid medium as a function of the excitation frequency for two cases: (1) free piezoelectric disk that corresponds to zero-traction along the lateral edge and (2) fixed piezoelectric disk that corresponds to zero-displacement along the lateral edge. We present and discuss the physical mechanism underpinning the frequency-dependent collimation and bandwidth properties of the ultrasound beams. We observe that the collimated beam generated by the free disk repeatedly lengthens/shortens and also extends/retracts sidelobes with increasing frequency. Alternatively, fixing the piezoelectric disk results in a consistent beam profile shape across a broad range of frequencies. This facilitates generating broadband signals such as a Gaussian pulse or chirp, which are common in ultrasound imaging. Thus, the fixed piezoelectric disk finds application as a collimated ultrasound beam source in a wide range of applications including medical ultrasound imaging, scanning acoustic microscopy, sonar detection, and other nondestructive ultrasound inspection techniques.

Experimental failure analysis and mechanical performance evaluation of fiber-metal sandwich laminates interleaved with polyamide-6,6 interlayers through the combined usage of acoustic emission, thermography and microscopy techniques

Fiber-metal laminates are hybrid sandwich composite structures made of thin metallic sheets and layers of fiber-reinforced plastics. In this study, for the first time, the effects of polyamide 66 nonwoven interlayers on the tensile, three-point bending, interlaminar shear strength, and low velocity impact responses of fiber-metal laminates are investigated by coupling acoustic emission, thermography, and microscopy techniques. The fiber-metal laminates are interleaved with polyamide 66 nonwoven fabrics at two different areal weight density, namely, 17 gsm (grams per square meter) and 50 gsm. The tensile, bending, interlaminar shear strength, and low velocity impact tests are carried out in accordance with the ASTM standards. During the tensile and flexural tests, acoustic emission data are collected to understand damage types occurring under various loading conditions and, in turn, clearly shed light on the performance of polyamide 66 for interfacial strengthening in fiber-metal laminates. The results of acoustic emission investigation are correlated with the optical and scanning electron microscope-based microscopic analysis. It is shown that the interlaminar shear strength of fiber-metal laminates can be increased significantly (about 42%) by using polyamide 66 nonwoven interlayers. The impacted fiber-metal laminate specimens are examined to determine damage area and length using the lock-in thermography method. It is found that the polyamide 66 interlayers decrease the debonded length and damaged area up to 39 and 32%, respectively. The tensile and flexural strength and modulus of the fiber-metal laminate are not significantly affected by the presence of polyamide 66 interlayers, except a negligible drop in the value of tensile and flexural strength by 6 and 4%, respectively. The polyamide 66 interlayers are proved to be very successful in enhancing plastic deformation ability of the matrix and bonding efficiency between aluminum and composite sections.

Noninvasive high-frequency acoustic microscopy for 3D visualization of microstructure and estimation of elastic properties during hydrolytic degradation of lactide and ε-caprolactone polymers

The monitoring of degradation processes' kinetics in polymers is one of the attractive possibilities of ultrasound technique applications that provide non-destructive imaging of polymers' internal microstructure and measurements of elastic properties. In this work, biodegradable polymers and copolymers based on L,L-lactide, D,L-lactide and ε-caprolactone have been studied at different stages of hydrolysis at 37 °C by high-frequency (100 and 200 MHz) ultrasound. The acoustic microscopy technique has been developed to reveal changes in the internal microstructure and bulk sound speed in polymer samples over a hydrolysis period of 25 weeks. Ultrasound imaging provides visualization of amorphous and crystalline phases, internal imperfections, variation in packing density, and other microstructural features. Acoustic images demonstrate nucleation, growth, and the changes in internal inhomogeneities in polymers during degradation accompanied by a decrease in the polymers' molecular weight. We associate the changes in the elastic properties (the speed of a longitudinal wave) with crystallinity variations in polymers during hydrothermal aging. The results of the ultrasound investigations are supplemented by gel permeation chromatography, differential scanning calorimetry, and wide-angle X-ray spectroscopy. Statement of SignificanceMonitoring the kinetics of degradation processes in polymers is one of the attractive possibilities of applying ultrasound techniques that provide non-destructive imaging of the polymers' internal microstructure and measurements of elastic properties. In this work, visualization of nucleation, growth, and evolution of internal inhomogeneities in the volume of polymers and variation of values of speed of longitudinal and transverse sound waves during hydrolysis are compared with measurements of molecular weight, density, data of DSC curves, and X-ray scattering analysis. We discuss several common phenomena that occur in the volume of poly(L-lactide) and poly(D,L-lactide) over the degradation process as well as improvement of elastic properties of the poly(ε -caprolactone) and poly(L-lactide-co-caprolactone) during hydrothermal aging.

Optically Detecting Acoustic Oscillations at the Nanoscale: Exploring Techniques Suitable for Studying Elastic Wave Propagation

Nanoacoustics is the study of acoustic wave propagation on a submicron scale. Research in this area is motivated by fundamental [1] and technological interests [2]. On the fundamental side, nanoscale objects can provide information about the impact of size, geometry, and surface conditions on elastic properties, elastic energy dissipation, and the validity of continuum mechanics models close to the atomic scale. On the technological side, high-frequency (MHz-THz) nanomechanical oscillators and nanoelectromechanical systems are promising tools for electromechanical computers and information storage, sensors for ultraweak chemicals and biological agents and ultralow forces and masses, radio frequency mobile phone f ilters, and artificial brains for self-aware autonomous vehicles. Furthermore, acoustic microscopy techniques [3]-[6] that rely on elastic waves with nanoscale wavelengths have great potential for materials characterization, failure analysis, and nondestructive imaging of 3D integrated structures with nanoscale scale spatial resolution. Surface acoustic waves (SAWs), which propagate in the near surface of a material with mechanical oscillations confined to a fraction of their wavelength from the surface, have nanoscale wavelengths at frequencies in the hundreds-of-GHz range. The nanoscale confinement of these elastic waves can facilitate studies of ultrasonic properties of individual grain boundaries in nanocrystalline materials [7], applicable to material fracture and nanoscale thermal transport [8].

Application of acoustic microscopy technique for the bulk visualization and elasticity measurement of nanocomposites

The impulse acoustic microscopy (AM) has been applied to study 3D microstructure and local mechanical properties of carbon nanocomposites. The particles of exfoliated graphite, graphite nanoplatelets, carbon nanoflakes, and carbon nanotubes have been used as a nanofiller. The AM technique shows the tendency of carbon nanoparticles to clusterization and formation of fractal micron-sized structures. Nanoparticle aggregates are visible on acoustic images for all types of carbon nanocomposites at arbitrary depth of their bulk. The elastic measurement demonstrates a weak dependence on type and content of carbon nanofiller. The impulse AM is the technique that provides direct data on bulk structure of a composite matter; it is characterized by combination of high efficiency and availability.

Preliminary Design of a High-Frequency Phased-Array Acoustic Microscope Probe for Nondestructive Evaluation of Pressure Vessel and Piping Materials

In pressure vessel and pipe inspection, ultrasonic nondestructive evaluation plays a pivotal role in both in-situ and laboratory examinations. Scanning acoustic microscopy (SAM) has been a well-recognized laboratory tool for both visualization and quantitative evaluation of pressure vessel and piping materials at the microscale since its invention in 1974. While there have been multiple advances in SAM over the past four decades, some issues still remain to be addressed. First, the measurement speed is limited by the mechanical movement of the acoustic lens and the sample stage. Second, a single-element transducer with an acoustic lens forms a predetermined beam pattern for a fixed focal length and incident angle, thereby limiting control of the inspection beam. Here, we propose to develop a phased-array probe as an alternative to overcome these issues. Preliminary studies to design a practical high-frequency phased-array acoustic microscope probe were explored. A linear phased-array, comprising 32 elements and operating at 5 MHz, was modeled using PZFlex, a finite element method software. This phased-array system was characterized in terms of electrical input impedance response, pulse-echo and impulse response, surface displacement profiles, mode shapes, and beam profiles. Details of the construction of the model and the results are presented in this paper. Development of a phased-array acoustic microscope probe will significantly enhance scanning acoustic microscopy techniques for detecting surface and subsurface defects and microstructural changes in laboratory samples of pressure vessel and piping materials.

Lock-In-Thermography, Photoemission, and Time-Resolved GHz Acoustic Microscopy Techniques for Nondestructive Defect Localization in TSV

Through silicon via (TSV) is the most promising technology for vertical system integration and novel 3-D chip architectures. Reliability and quality assessment necessary for process development, root-cause analysis, and manufacturing require appropriate nondestructive testing techniques to achieve high processing yield and reliability. This paper presents two advanced approaches for nondestructive localization of defects in TSVs. The first method investigated here was lock-in thermal imaging by thermography and photoemission microscopy to inspect and localize electrical shorts within the 3-D geometry of the TSV insulation liner. In addition, filling defects in the TSVs have been inspected using acoustic microscopy in the gigahertz frequency band in time and spectral domains.

Cluster microstructure and local elasticity of carbon‐epoxy nanocomposites studied by impulse acoustic microscopy

The impulse acoustic microscopy method was applied to observe the bulk microstructure and to measure sonic velocities and elastic moduli in the carbon nanocomposite specimens prepared by a traditional method and with the use of a vacuum mixer. It is shown that carbon nanoparticles tend to cluster and form micron‐sized aggregates. The impulse acoustic microscopy technique makes it possible to visualize a non‐uniform distribution of carbon nanofillers over the specimen bulk. Both nanotube and nanoplatelets conglomerates are visible most likely due to the air containing. Results of the elastic measurements demonstrate homogeneity of elastic properties over the material bulk and a weak dependence of sonic velocities and elastic moduli on the filler content. Reduction of the air content and enhancement of elastic properties are observed when increasing the nanofiller content and employing the vacuum mixing technology in nanocomposite fabrication. POLYM. ENG. SCI., 57:697–702, 2017. © 2017 Society of Plastics Engineers

EVALUATION OF BIOPHYSICAL PROPERTIES OF THE BONE TISSUE FOR BIOMEDICAL APPLICATIONS

Background and aim: The volume of reconstructive surgery in traumatology in recent decades has increased significantly due to an increase in traumas, numbers of affected in local military conflicts, and environmental deterioration. This has led to an increase in demand for plastic materials, and the need to create modern high technologies to meet this need, including alternative sources of bone implants. Any solution to this problem would involve an in-depth study of bone biophysical properties with innovative techniques to develop requirements to elaboration of new effective implants based on natural bone, as well as on natural or synthetic analogues. This study aimed exactly at these aspects. Materials and methods: We studied human bone samples taken from various parts of the skeleton aged from 3 to 89 years and animal (bovine) bone samples aged from 1.5 to 2 years. Biophysical characteristics of the studied materials were assessed at the stage of sample preparation with original author's methods of physical and mechanical processing, in the process of analysis of patterns of normal changes in the bone structure and function, as well as during changes in its composition with age, anisotropy of the material and the level of structural organization. Structure patterns were studied by classical (light, scanning electron microscopy) and advanced (acoustic microscopy) techniques. Methods of engineering biomechanics were used to assess functional changes in macro and micro volumes of bone samples. Results: The main study results involve the development of innovative methods of sample preparation and structural and functional analysis. First of all, these are the methods of mechanical processing of bone fragments based on the use of hollow cylindrical milling cutters in the environment of limited amounts of mineralized biological tissues, as well as on the application of hydrodynamic cutting ensuring a delicate and highly efficient bone cut. Another distinctive feature of the study is the elaborated methodology for morphological and mechanical analysis of bone samples at the macro and micro levels, with consideration of real physical and chemical condition of samples. To ensure sample sterility, the authors proposed innovative techniques using of ozone-oxygen mixtures. The study results gave a complex of quantitative characteristics describing age-related compositional changes of the human bone, anisotropy of its physical and mechanical characteristics, osteon parameters and physical and mechanical characteristics of bone tissue depending on its composition. Conclusion: The use of the proposed methodology allowed for obtaining of new data on biophysical properties of bone tissue that are of interest for bioimplantology, biomaterial science and expands basic information on the bone as a natural biocomposite. They can be the basis for development of practical guidelines on optimization of the choice of bone fragments for manufacture of implants based on the detected patterns of changes in macro- and microstructure, physical and mechanical characteristics and bone composition in the studied age range.

The cluster architecture of carbon in polymer nanocomposites observed by impulse acoustic microscopy

The high‐resolution ultrasonic technique (impulse acoustic microscopy) was applied for observing the bulk microstructure of nanocomposites with various types of carbon nanoparticles as filler. It was shown that ultrasonic methods are excellent tools for studying nanoparticle distribution over the material bulk and for revealing probable nonuniformity. The acoustic microscopy technique allows for looking through the bulk microstructure of objects by means of layer‐by‐layer visualization and object cross‐sectional imaging. In composites based on dispersed micrometer‐sized particles of exfoliated graphite, the particle distribution over the composite material bulk was observed. In nanocomposites with various kinds of low‐dimensional carbon nanofillers, i.e., nanoflakes, nanoplatelets, and nanotubes, the technique allowed the cluster architecture of the nanoparticle distribution to be revealed. Contact conjugation of low‐dimensionality nanoparticles led to fractal clusters despite significant technological efforts for providing homogeneity to the nanocomposite materials and uniformity to their properties. A pronounced tendency to form micrometer‐sized fractal agglomerates was found for 2D carbon nanoparticles: nanoflakes and nanoplatelets. The impulse acoustic microscopy technique provides visualization of the agglomerate distribution over the nanocomposite material bulk. Another kind of nanoparticle distribution was observed with carbon nanotubes (CNTs). The latter formed CNT packings having different densities. Such regions were seen in acoustical images as small‐sized areas of various brightness.

Characterization of the geometry of microscale periodic structures using acoustic microscopy

Periodic structures are very common in both scientific investigations and engineering applications. The geometry of the periodic structure is important for its designed functionality. Although the techniques such as optical and electron microscopy are capable of measuring the periodicity of microscale periodically-corrugated structures, they cannot be used to measure the height or depth of the corrugation. The technique of acoustic microscopy has been developed rapidly and it has been applied in the studies of steel integrated structures, ferro-elastic ceramics, human retina, semiconductors, composites, etc. In acoustic microscopy, V(z) curves have been used to investigate the visco-elastic parameters of thin sliced samples of composites, animal tissue, etc., while in this work it is applied in characterizing the geometry of periodically corrugated structures. The measurements of the geometry of periodic structures obtained using acoustic microscopy are compared with those obtained using optical microscopy, and the reliability of this acoustic technique is also examined.

Microstructure, elastic and electromagnetic properties of epoxy-graphite composites

A set of epoxy resin-based composites filled with 0.25 – 2.0 wt.% of commercially available exfoliated graphite (EG) and thick graphene (TG), prepared by suspending EG particles in cyclohexane, and submitting the suspension to a series of grinding and ultrasonic dispersion steps, was produced. The microstructure of such epoxy-graphite composites has been studied by the impulse acoustic microscopy technique. According to acoustic microscopy data, exfoliated graphite microparticles have been well dispersed in the epoxy matrix. TG nanoflakes demonstrated persistent tendency to clustering and formation of agglomerates. The addition of graphite particles in small amount (0.25 – 2.0 wt.%) did not influence the bulk elastic properties of epoxy-graphite composite materials. Being extremely lightweight, 0.003 g cm−3, EG had a lower percolation threshold than TG, at the level of 1-1.5 wt.% against 2.1-3.2 wt.%, respectively. As a result, epoxy composites filled with 1.0-2.0 wt.% EG provided high electromagnetic (EM) interference shielding both at microwave and THz frequencies. In contrast, no significant influence of TG loading was observed at low weight fraction (up to 2 wt.%) on the EM performance of epoxy composites.

Acoustic Microscopy for Visualization and Evaluation of Ceramic-ceramic Contact Zone

Impulse acoustic microscopy technique has been applied for investigation of features of ceramic-ceramic contact zone. At the interface the method allows to identified and localized detachment and extended partial contact area (kissing contact), shown distribution of the thickness of the interlayer and its homogeneity.