Encapsulation of different guest-species such as molecules and ions inside carbon nanotubes (CNTs) has been reported in the literatures during the last 15 years and represents an exciting development of nanoengineering of novel materials and composites. The reported nanocomposite materials show the semi-conducting properties with potential applications in nanosensors, nanounits and nanocircuits as well as advanced energy transfer and storage properties, and encompass manufacturing for novel nanowires, nanoelectronic devices with properties designed with optoelectronic, spintronic and nanomagnetic qualities. This review reports on a wide range of encapsulation references with particular focus on single molecules, atomic chains, metal halides and polymers encapsulated inside CNTs. The encapsulation methods and the chemical and physical qualities of these novel materials are crucial for the future manufacturing of novel innovations in nanotechnology, and represent therefore the current state-of-the-art of encapsulation methods in advanced manufacturing.
This paper considers the copper electrodeposition processes in microvias and investigates whether the quality of the electroplating process can be improved by acoustic streaming using megasonic transducers placed into a plating cell. The theoretical results show that acoustic streaming does not take place within the micro-via (either through or blind-via’s), however it does help improve cupric ion transport in the area close to the mouth of a via. This replenishment of cupric ions at the mouth of micro-via leads to better quality filling of the micro-via through diffusion compared to basic conditions. Experiments showing the improved quality of the filling of vias are also presented.
The integration of nanomaterials such as carbon nanotubes (CNTs) into microsystems is highly desirable, in order to make use of the unique nanomaterial properties in real devices. However, the CNT-to-microsystem integration is challenging to implement in a manufacturable, cost-effective industrial process. This paper presents our work towards a process for making complete, integrated CMOS / MEMS systems with integrated CNT. We demonstrate the feasibility of the process, using room-temperature processing, low-cost equipment and consumables, and electrical control with automation possibilities. CNTs are directly integrated at the desired positions in the Si microsystem, forming closed Si / CNT / Si circuits. We explore different designs with the aim to obtain uniform and well-defined CNT synthesis conditions, and show that simplified designs can perform comparably to more complex ones. The Si / CNT / Si circuits obtained can show rectifying (Schottky-like) or near-ohmic behavior. Gas sensing possibilities are demonstrated, indicating the possibility of monitoring aging/ fermenting of food. Functionalization of CNTs is demonstrated, using thermal evaporation of Sn and Pd, opening for selective and sensitive sensors for various gases and analytes. Detailed microscopic characterization of the obtained CNTs are presented.
Hermetic packaging is often an essential requirement to enable proper functionality throughout the device’s lifetime and ensure the optimal performance of a micro electronic mechanical system (MEMS) device. Solid-liquid interdiffusion (SLID) bonding is a novel and attractive way to encapsulate MEMS devices at a wafer level. SLID bonding utilizes a low-melting-point metal to reduce the bonding process temperature; and metallic seal rings take out less of the valuable surface area and have a lower gas permeability compared to polymer or glass-based sealing materials. In addition, ductile metals can adopt mechanical and thermo-mechanical stresses during their service lifetime, which improves their reliability. In this study, the principles of Au-Sn and Cu-Sn SLID bonding are presented, which are meant to be used for wafer-level hermetic sealing of MEMS resonators. Seal rings in 15.24 cm silicon wafers were bonded at a width of 60 μm, electroplated, and used with Au-Sn and Cu-Sn layer structures. The wafer bonding temperature varied between 300 °C and 350 °C, and the bonding force was 3.5 kN under the ambient pressure, that is, it was less than 0.1 Pa. A shear test was used to compare the mechanical properties of the interconnections between both material systems. In addition, important factors pertaining to bond ring design are discussed according to their effects on the failure mechanisms. The results show that the design of metal structures can significantly affect the reliability of bond rings.
Due to their unique thermal, electronic and mechanical properties, carbon nanotubes (CNTs) have aroused various attentions of many researchers. Among all the techniques to fabricate CNTs, plasma enhanced chemical vapor deposition (PECVD) has been extensively developed as one growth technique to produce vertically-aligned carbon nanotubes (VACNTs). Though CNTs show a trend to be integrated into nanoelectromechanical system (NEMS), CNT growth still remains a mysterious technology. This paper attempts to reveal the effects of substrates and underlayers to CNT synthesis. We tried five different substrates by substituting intrinsic Si with high resistivity ones and by increasing the thickness of SiO2 insulativity layer. And also, we demonstrated an innovative way of adjusting CNT density by changing the thickness of Cu underlayer.
The reconfigurable manufacturing system (RMS) is the next step in manufacturing, allowing the production of any quantity of highly customized and complex parts together with the benefits of mass production. In RMSs, parts are grouped into families, each of which requires a specific system configuration. Initially system is configured to produce the first family of parts. Once it is finished, the system will be reconfigured in order to produce the second family, and so forth. The effectiveness of a RMS depends on the formation of the optimum set of part families addressing various reconfigurability issues. The aim of this work is to establish a methodology for grouping parts into families for effective working of RMS. The methodology carried out in two phases. In the first phase, the correlation matrix is used as similarity coefficient matrix. In the second phase, agglomerative hierarchical K-means algorithm is used for the parts family formation resulting in an optimum set of part families for reconfigurable manufacturing system.
The crystallization process of Fe78Zr7B15 (at%) amorphous ribbon was investigated by X-ray diffraction (XRD), differential scanning calorimetry and scanning electron microscopy (SEM). The fully amorphous structure of as-quenched (Aq) ribbons was confirmed by XRD pattern. The saturation magnetization (M s) and Curie temperature of the Aq ribbon were measured as 124.3 (A·m2)/kg and 305 °C with vibrating sample magnetometer (VSM), respectively. When the ribbons was annealed at 550 °C near the first onset temperature (T x1 = 564.9 °C), the M s was increased by 17 %, which was caused by the formation of a dual phase structure. The isothermal crystallization kinetics and crystallization mechanism of primary α-Fe phase in the dual phase structure were studied by Arrhenius and Johnson-Mehl-Avrami-Kolmogorov equations respectively. The results showed that the crystallization of α-Fe phase was a diffusion-controlled surface nucleation growth process, and the nucleation rate decreased with longer crystallization time.
Conventionally, image object recognition and pose estimation are two independent components in machine vision. This paper presented a simple but effective method KNN-SNG, which tightly couples these two components within a single algorithm framework. The basic idea of this method came from the bionic pattern recognition and the manifold ways of perception. Firstly, the shortest neighborhood graphs (SNG) are established for each registered object. SNG can be regarded as a covering and triangulation for a hypersurface on which the training data are distributed. Then for recognition task, the determined test image lies on which SNG by employing the parameter “k”, which could be calculated adaptively. Finally, the local linear approximation method was adopted to build a local map between high-dimensional image space and low-dimensional manifold for pose estimation. The projective coordinates on manifold can depict the pose of object. Experiment results manifested the effectiveness of the method.
The compliance of an integrated approach, principal component analysis (PCA), coupled with Taguchi’s robust theory for simultaneous optimization of correlated multiple responses of wire electrical discharge machining (WEDM) process for machining SiCP reinforced ZC63 metal matrix composites (MMCs) is investigated in this work. The WEDM is proven better for its efficiency to machine MMCs among others, while the particulate size and volume percentage of SiCp with the composite are the utmost important factors. These improve the mechanical properties enormously, however reduce the machining performance. Hence the WEDM experiments are conducted by varying the particulate size, volume fraction, pulse-on time, pulse-off time and wire tension. In the view of quality cut, the most important performance indicators of WEDM as surface roughness (R a), metal removal rate (MRR), wire wear ratio (WWR), kerf (K w) and white layer thickness (WLT) are measured as responses. PCA is used as multi-response optimization technique to derive the composite principal component (CPC) which acts as the overall quality index in the process. Consequently, Taguchi’s S/N ratio analysis is applied to optimize the CPC. The derived optimal process responses are confirmed by the experimental validation tests results. The analysis of variance is conducted to find the effects of choosing process variables on the overall quality of the machined component. The practical possibility of the derived optimal process conditions is also presented using SEM.
To investigate the application of reformed coke oven gas (COG) in producing the direct reduction iron (DRI), we simulated a countercurrent gas solid moving bed reactor in which the iron ore pellet was reduced by reformed COG. An ordinary differential equation (ODE) was set based on the unreacted shrinking core model considering both mass and energy balances of the reactor. The concentration and temperature profiles of all species within the reactor were obtained by solving the ODE system. The solid conversion and gas utilization were studied by changing gas flow rate, solid flow rate, reactor length, and the ratio of O/CH4 to guide the practical application of COG in DRI production. Model results showed that COG was suitable for the DRI production. In order to meet the requirement of the industrial production, the minimum gas flow rate was set as 130,000 Nm3/h, and the maximum production was 90 t/h. The reactor length and the mole ratio x(O): x(CH4) were depended on the actual industrial situations.
In order to supply better accordance for modeling and simulation of complex networks, a new degree dependence entropy (DDE) descriptor is proposed to describe the degree dependence relationship and corresponding characteristic in this paper. First of all, degrees of vertices and the shortest path lengths between all pairs of vertices are computed. Then the degree dependence matrices under different shortest path lengths are constructed. At last the DDEs are extracted from the degree dependence matrices. Simulation results show that the DDE descriptor can reflect the complexity of degree dependence relationship in complex networks; high DDE indicates complex degree dependence relationship; low DDE indicates the opposite one. The DDE can be seen as a quantitative statistical characteristic, which is meaningful for networked modeling and simulation.
This paper presents a wave-based bilateral teleoperation structure to reduce the wave reflection and enhance the force and speed tracking performance through adjusting the relative parameters. A time domain passive approach is also applied to deal with the passivity of whole system even with non passive environment. The efficiency of the proposed method is confirmed by some experimental results.