Nanoscale Micro Research Articles

Unraveling mudstone compaction at microscale: A combined approach of nanoindentation mapping and machine learning data analysis

Compaction processes within mudstone samples across varying depths (723.5–3213.5 m) in the Vienna Basin were investigated, focusing on porosity changes and the resulting micromechanical response in the clay-rich, fine-grained fraction (“clay matrix”). A novel approach combining nanoindentation mapping with machine learning data analysis was developed to efficiently extract representative micromechanical parameters of the clay matrix. Emphasis was put on capturing the properties of the fine-grained, clay-dominated composite rather than individual mineral phases, enabling the analysis of compaction-induced strength changes at microscale. A significant enhancement in the mechanical strength of the clay matrix with increasing burial depth was observed. Reduced elastic modulus (Er) and hardness (H) increased from 6.8 ± 3.4 to 22.6 ± 7.5 GPa and from 0.2 ± 0.2 to 0.9 ± 0.2 GPa, respectively, over the depth interval of 2490 m. Moreover, a strong correlation between depth and porosity and consequently micromechanical properties of the clay matrix exists. This highlights the substantial influence of intra-clay porosity on mechanical properties, which follow a general compaction trend with depth. Broad ion beam-scanning electron microscopy (BIB-SEM) analysis was used for textural investigations at micro-to nanoscale and indicated that the reduction in porosity predominantly resulted from mechanical compaction rather than mineral diagenesis, which would have been noticeable by signs of significant dissolution or cementation. The correlation coefficient matrix between multiscale porosity measurements and nanoindentation affirmed that the porosity loss was closely linked to the enhanced mechanical properties of the fine-grained composite clay matrix, while other compositional variables like total clay mineral content showed weak correlations. Empirical mathematical equations were derived to describe the mechanical properties as generalized functions of depth and porosity. These may be used as geomechanical input for future basin analysis and geoenergy applications (e.g., seal rock studies in a geological storage context). This study introduces a new approach to unravel compaction processes in fine-grained rocks at microscale, emphasizing the interplay between intra-clay porosity and micromechanical changes during proceeding burial.

A high-precision and efficient adaptive alignment method for Cassegrain dual mirror optical system based on machine learning algorithms

The Cassegrain telescope is widely used in aerospace exploration equipment, characterized by compact structure, complex optical path, and high imaging quality. However, due to the difficulty in establishing an accurate correspondence between the relative pose and imaging quality of a multi mirror group with real machining errors, the current Cassegrain telescope assembly process is very difficult, with blind operation, time-consuming, and low accuracy. This article proposes a high-precision adaptive alignment method for Cassegrain dual mirror optical systems based on machine learning algorisms, and an experimental adaptive alignment system with uncoupled degrees of freedom is developed. Firstly, the overall architecture of the adaptive alignment method is proposed consists of detection, calculation and alignment modules. In the detection module, the Zernike polynomial coefficient of wavefront aberration of the optical system is detected online through the interferometer, meanwhile the pose coordinates of the secondary mirror is accurately fed back through a 6-DOF nanoscale micro mechanism. In the calculation module, machine learning algorithm is applied to build a nonlinear mapping model between the Zernike coefficient and the pose coordinates of the secondary mirror. In the alignment module, the pose coordinates of the secondary mirror can be forced to adjust to the target position. Then, during the real alignment process, the Zernike coefficient test data of the optical system alignment process is monitored in real time, and the nonlinear mapping model is employed to calculate the pose coordinates and then the misalignment of the secondary mirror. Finally, the alignment module is driven to execute the pose correction according to the calculated misalignment value, realizing a high-precision adjustment of the Cassegrain dual mirror optical system. Experimental results shows that the average alignment time cost can be dramatically reduced from around 7 days using the current manual alignment method to just 30 minutes using the proposed adaptive alignment method for achieving a current standard alignment accuracy of wavefront aberration root mean square (RMS) less than 0.1λ, which greatly improves the assembly efficiency. This study proposes a new method for high-precision and efficient alignment of optical systems based on artificial intelligence and contributes to the efficiency improvement for optical assembly.

Hierarchically heterogeneous microstructure enables ultrahigh-strength and good ductility in selective laser melted eutectic high-entropy alloys

Achieving favorable strength-ductility synergy has long been one of the main challenges for developing structural materials. The current work reports a selective laser melted eutectic high-entropy alloy with ultrahigh-strength (yield strength 1446 MPa, ultimate tensile strength 1737 MPa) and good ductility (elongation 11%), achieved by tuning the hierarchically heterogeneous microstructures from micro-to nano-scale. Both of nano-sized B2 and L12 phases effectively hinder the dislocation motion and thus significantly improve the strengths. The cellular face-centered cubic matrix ensures the uniform deformation of the alloy, and the possible brittle failure of the hard B2 phase is alleviated by Cr-rich clusters.

Identifying the source of gold geochemical anomalies in Jiaodong, eastern China: Tracking the occurrence of gold nanoparticles in a metallogenic system

The gold particles induced geochemical anomaly shows good potential for the prospecting of gold deposits all around world. Most of the discovered gold resources are located at geochemical related anomaly area in Jiaodong, which are associated with Micro-to nanoscale particle matter. However, it has been known little about the relationship between the occurrence of gold nanoparticles and their geochemical anomaly in multimedia accommodating to the detailed process of gold mineralization system and geochemical exploration. Micro-to nanoscale gold as nanoparticles are related to the hydrothermal fluid flows and precipitation among elemental migration. This paper presents gold nanoparticles in ore, constructed the fundamental link to geochemical anomaly distribution maps of gold in drainage sediments, wall rocks, and ore, aimed to identify the source of primary and secondary geochemical anomalies according to careful observation at nanoscale gold and revealed the genesis of gold mineralization and their potential in Jiaodong. A potential model of migration pathway of gold nanoparticle was built to understand the process of massive gold accumulation and the further prospecting in the Jiaodong Peninsula.

Tribological study of TaTiN/TaTi multilayer films with hierarchical arrangement

The tribological performance of the coatings depends on their properties like material, morphology, structure, among others. This work compares the tribological performance of two multilayers films of ceramic/metallic (TaTiN/TaTi) combination with a hierarchical morphology arrangement using DC-magnetron co-sputtering with Ta and Ti metallic targets controlling the sizes of their ceramic-layer thickness on the Ti substrate. These films had the configuration of the nano to microscales (NML) and micro to nanoscale (MNL) layers. The films had the structure combination of c-TaTiN, c-TiN, and α”-TaTi, with higher Nitrogen in the MNL coatings and higher intensity of LA vibrational mode in their Raman spectra. The XPS study showed that the MNL coating presented a higher metallic composition in the top layer than NML. Nevertheless, MNL film had a higher H and lower E* than NML coating due to the stress distribution by the multilayer arrangement. The MNL coatings showed higher elastoplastic deformation and reduced the presence of cracks and fractures of the layers. The Raman spectra of MNL coating presented a higher presence of Ta2O5 vibrational modes than the MNL film due to a tribolayer formed by debris accumulation.

Preparation of cellulose nanofibers from cassava pulp residue by mechanical defibrillation

Cassava pulp residue (CPR) is one of the most interesting renewable materials that is widely used as active precursors for many applications. Based on its characteristic, cellulose is a typical component locally found in CPR in which it plays an important role in various potential fileds such as reinforcing fillers, stabilizing agents, and dietary fibers. To prepare cellulose nanofibers (CNFs), mechanical defibrillation by microfluidizer is an effective method commonly employed to reduce the size of cellulose from micro-to nanoscale. In this work, CNFs were successfully prepared from CPR by alkaline treatment, hydrogen peroxide bleaching, and mechanical defibrillation at different times. Physical, thermal, and morphological properties of the resulting fibers were comparatively demonstrated. The results showed that most of the impurities in CPR including residual starch granules, lignin, and hemicellulose were removed significantly after chemical treatments. Additionally, thermal degradation temperatures of the obtained fibers were improved remarkably, while the degree of crystallinity with cellulose type I structure was also increased when comparing to CPR. As observed by FE-SEM analysis, the CNFs revealed a fibrous network structure having a mean diameter in the range of 10-30 nm. The produced CNFs could be utilized as reinforcing fillers, food packaging, and biomedical fields.

Micro Defects on Diamond Tool Cutting Edge Affecting the Ductile-Mode Machining of KDP Crystal.

As a soft-brittle material, the machined surface quality of potassium dihydrogen phosphate (KDP) crystal is heavily affected by the edge quality of the diamond cutting tool. However, nanoscale micro defects inevitably occur on the freshly sharpened tool edge, and the machining mechanism for KDP crystal remains unclear. Therefore, in this work, three types of tool-edge micro defects are classified according to their cross-sections, including the blunt-edge, crescent-edge, and flat-edge micro defects. Moreover, the smoothed particle hydrodynamics (SPH) method is employed to reveal the material removal mechanism of KDP crystal with consideration of different tool-edge micro defects, and the flat-edge micro defects are subdivided into flat edge A (similar to flank wear) and flat edge B (similar to chamfered edge) on the basis of their effects in machining. The simulation results indicate that the surfaces machined by crescent edge and flat edge A are unsmooth with large-size defects due to the disappearance of hydrostatic pressure beneath the cutting edge. As for the blunt edge and flat edge B, the machined surfaces are smooth with a favorable increment of hydrostatic pressure for processing brittle materials, which indicates that a solution to eliminate the tool-edge micro defects is necessary, e.g., the passivation method. For keeping the cutting edge as sharp as possible in removing the tool-edge micro defects completely by passivation, the effect of tool shank depression angles on the geometries of the passivated cutting edge is investigated, and a high-quality cutting edge with a micro chamfered edge is obtained after passivation at a depression angle of 60° and re-sharpening of the rake face. Finally, the tool cutting performance after passivation is validated through fly-cutting experiments of KDP crystal. The chamfered edge can produce the best defect-free surface with the minimum surface roughness.

Significance of size dependent and material structure coupling on the characteristics and performance of nanocrystalline micro/nano gyroscopes

Capacitive-based sensing microelectromechanical (MEMS) and nanoelectromechanical (NEMS) gyroscopes have significant advantages over conventional gyroscopes, such as low power consumption, batch fabrication, and possible integration with electronic circuits. However, inadequacies in the modeling of these inertial sensors have presented issues of reliability and functionality of micro-/nano-scale gyroscopes. In this work, a micromechanical model is developed to represent the unique microstructure of nanocrystalline materials and simulate the response of micro-/nano-gyroscope comprising an electrostatically-actuated cantilever beam with a tip mass at the free end. Couple stress and surface elasticity theories are integrated into the classical Euler-Bernoulli beam model in order to derive a size-dependent model. This model is then used to investigate the influence of size-dependent effects on the static pull-in instability, the natural frequencies and the performance output of gyroscopes as the scale decreases from micro-to nano-scale. The simulation results show significant changes in the static pull-in voltage and the natural frequency as the scale of the system is decreased. However, the differential frequency between the two vibration modes of the gyroscope is observed to drastically decrease as the size of the gyroscope is reduced. As such, the frequency-based operation mode may not be an efficient strategy for nano-gyroscopes. The results show that a strong coupling between the surface elasticity and material structure takes place when smaller grain sizes and higher void percentages are considered.

Reservoir spaces in tight sandstones: Classification, fractal characters, and heterogeneity

Evaluation of tight sandstone reservoir, including space types, storage capacity, and heterogeneity, provides a basis for the selection of favorable areas for tight gas and oil. Therefore, a variety of research methods, such as rate-controlled mercury injection, fractal theory, and observation of thin sections and SEM (scanning electron microscope) images, were integrated to explore these parameters.With the decrease of porosity and permeability, tight sandstones can be classified into three types: pore-dominated, pore-throat, and throat-dominated. The reservoir spaces of the three types of tight sandstones gradually evolve from micro-to nano-scale. The micro-scale spaces in pore-dominated and pore-throat type samples are primarily made up of intergranular and mixed pores and are characterized by a two-segment fractal feature, while the throat-dominated samples are mainly composed of intergranular pores with a one-segment fractal feature. The nano-scale reservoir spaces in the three types of tight sandstones also display similar two- and one-segment fractal characteristics, and are mainly composed of intragranular honeycombed dissolution pores, authigenic mineral intercrystalline pores, and throats in pore-dominated and pore-throat tight sandstones. However, the authigenic mineral intercrystalline pores constitute the main nano-scale spaces in throat-dominated tight sandstones. With the tight sandstones from pore-dominated through pore-throat to throat-dominated types, the fractal dimensions of micro-scale spaces increase gradually, but in nano-scale spaces the fractal dimensions decrease, which indicating that the heterogeneity of micro-scale spaces is gradually enhanced whereas that of the nano-scale spaces is gradually weakened.Because of differences in reservoir space types and heterogeneity, the enrichment and distribution of tight gas and oil changes with the distance between the reservoir layers and the source rocks. The tight reservoirs dominated by nano-scale spaces are also incorporated into the exploration and development goals in areas adjacent to source rocks. However, in areas located far from source rocks, the tight reservoirs dominated by micro-scale spaces should be the preferred targets for tight gas and oil.

Improving the Wear Resistance of Aluminum Fly Ash Composites by Multipass Friction Stir Processing

In this study, the multi-pass friction stir processing (MP-FSP) technique was performed on ADC6 aluminum alloy + 5 wt% fly ash composite (A5FC) castings to increase their surface area. The dry sliding wear behaviors of the ADC6 alloy, A5FCs, and MP-FSPed A5FCs were evaluated. Dry sliding wear tests were performed using a ring-on-washer machine at a constant rotation speed of 100 rpm for 60 min, and the normal load was 10, 20, 30, and 40 N. The results showed that the MP-FSPed A5FCs had the lowest wear rates in the load range from 10 to 40 N, and adhesive wear was the major wear mechanism in these tests. The increased wear resistance was mainly due to grain refinement and elimination of casting defects after subjecting the ash composite to MP-FSP. The microstructure of the MP-FSPed A5FCs reveals that the sizes of the added raw fly ash particles decreased from micro-to nanoscale levels, and the nanoscale fly ash was uniformly dispersed in the aluminum matrix.

Nanosized objects in equilibrium supercritical fluids

Supercritical fluids (SCF) now attract a large attention of both practitioners and researchers. They open new possibilities for dry cleaning, processing of chemical and nuclear wastes, residuum oil supercritical extraction and selective extraction of useful substances from biomasses and mineral ores [1-3]. From a scientific point of view they present a new state of matter, intermediate between gases and liquids. The growing utilization of SCF in modern chemical technologies is based on the remarkable mixture of solvent power, characteristic to liquids, and transport properties, specific for gases. This mixture of features specific for liquids and gases in SCF is due to their high heterogeneity resulting from the plurality of nanosized clusters in the gas-like zone of the fluid and nanosized pores in the liquid-like zone. Supercritical fluids near their critical density possess huge density fluctuations. The well known and seen by eyes critical opalescence results from heterogeneities in fluids near the critical point with dimensions measured in microns [4]. But the visible transparency of the supercritical fluid over the critical point does not mean that the heterogeneities have disappeared. Their dimensions simply moved from the microto nanoscale [5]. Dr. K. Nishikawa and her group by X-rays scattering have discovered the peak line of the density fluctuations in SCF [6-8]. They named the peak line on the (T, P) diagram as the ridge. This line may be traced also by peaks of some other thermophysical properties, especially, the constant pressure heat capacity [9, 10]. In many works this peak line is named as the Widom line [11, 12]. This line divides the supercritical zone into two regions that “can be identified by different dynamical regimes: gas-like and liquid-like” [12]. The ridge or the Widom line looks like the extension of the saturation curve in the supercritical zone. The aim of this report is the investigation of the nanosized clusters and their characteristics near the ridge line in the gas-like SCF. The investigation is performed by the computer aided analysis of precise equilibrium thermophysical data for several pure van der Waals and polar fluids. The source of data is the NIST database [13], generalizing experimental results of many scientific groups from all over the World. The knowledge of the clusters’ characteristics may be useful for practical applications and better understanding of the supercritical fluids’ nature.

Nanowire Mechanical Switch with a Built‐In Diode

Figure 1. Schematic diagramof a cross-point switch (a), which consists of a Cartesian matrix of orthogonal wires with an air gap at each intersection. The switch at each intersection can be turned on and off by The main driving engine of the IT revolution has been geometry miniaturization of transistors. This has been accomplished with a striking development in microfabrication technology, referred to as ‘‘Moore’s law;’’: the number of transistors on an integrated circuit (IC) doubles every 2 years, and industrial guidelines enable multiple devices to be integrated within a given chip area. However, as the gate insulator thickness shrinks below 2 nm and the distance between the source and drain is reduced below 50 nm, gate leakage and subthreshold leakage current flow even though the transistor is supposed to be off. Standby power when devices are supposed to be in the off state therefore occupies a significant portion of total power consumption. In addition, this situation has pushed the metal–oxide–semiconductor (MOS) transistor to the end-point of the international technology roadmap for semiconductors (ITRS). Thus, the development of a new device that consumes low power is an important undertaking. In the mechanical switch, since two electrodes are physically separated in the off state, the power consumption in the off state is ideally zero. In particular, as the accumulated heritage from semiconductor fabrication technology enables device sizes from the microto nanoscale regime, realization of a mechanical switch on the nanoscale will become more feasible. In the previously proposed approach, two terminal mechanical switches are arranged in a cross-point structure (Figure 1a). A bistable property of the cross-point structure also leads to a basis of binary digits, where information is detected by measuring the contact resistance at the cross-point: high contact resistance at the switch-off state (Figure 1b) or low contact resistance at the switch-on state (Figure 1c). These cross-point devices have been explored by the bottom-up assembly of various materials, such as carbon nanotubes, silicon–

Design and simulation of a nano-scale micro positioning stage

Micro positioning stage is a commonly used platform for MEMS. In this article, we present a new micro positioning stage including its design, simulation and optimisation. The new micro positioning stage is made of four sets of two leaf springs. The geometric dimensions are determined by optimisation. Its performance, including stress and displacement, is evaluated using finite element analysis by ANSYS. The simulation results indicated that the new design can reliably achieve nano position accuracy.

Sensitivity of structural models of composite material to structural length scales

It is shown that there are models in the micromechanics of composite materials (so-called structural models of the second order) that are sensitive to structural change from micro-to nanoscale, whereas the model of effective constants (structural model of the first order) in the mechanics of composites does not have such a property. The structural model of elastic mixture is used as an example to reveal a distinction between the descriptions of the dispersion of plane waves propagating in fibrous micro-and nanocomposites of similar structure