Colloidal nanoparticles are being intensely pursued in current nanoscience research. Nanochemists are often frustrated by the well-known fact that no two nanoparticles are the same, which precludes the deep understanding of many fundamental properties of colloidal nanoparticles in which the total structures (core plus surface) must be known. Therefore, controlling nanoparticles with atomic precision and solving their total structures have long been major dreams for nanochemists. Recently, these goals are partially fulfilled in the case of gold nanoparticles, at least in the ultrasmall size regime (1–3 nm in diameter, often called nanoclusters). This review summarizes the major progress in the field, including the principles that permit atomically precise synthesis, new types of atomic structures, and unique physical and chemical properties of atomically precise nanoparticles, as well as exciting opportunities for nanochemists to understand very fundamental science of colloidal nanoparticles (such as the s...

Atomically Precise Colloidal Metal Nanoclusters and Nanoparticles: Fundamentals and Opportunities

Semiconductor nanowires (NWs) have been studied extensively for over two decades for their novel electronic, photonic, thermal, electrochemical and mechanical properties. This comprehensive review article summarizes major advances in the synthesis, characterization, and application of these materials in the past decade. Developments in the understanding of the fundamental principles of "bottom-up" growth mechanisms are presented, with an emphasis on rational control of the morphology, stoichiometry, and crystal structure of the materials. This is followed by a discussion of the application of nanowires in i) electronic, ii) sensor, iii) photonic, iv) thermoelectric, v) photovoltaic, vi) photoelectrochemical, vii) battery, viii) mechanical, and ix) biological applications. Throughout the discussion, a detailed explanation of the unique properties associated with the one-dimensional nanowire geometry will be presented, and the benefits of these properties for the various applications will be highlighted. The review concludes with a brief perspective on future research directions, and remaining barriers which must be overcome for the successful commercial application of these technologies.

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25th Anniversary Article: Semiconductor Nanowires – Synthesis, Characterization, and Applications

Sustainable Industry 4.0 framework: A systematic literature review identifying the current trends and future perspectives

Ultraviolet (UV) photodetection has drawn a great deal of attention in recent years due to a wide range of civil and military applications. Because of its wide band gap, low cost, strong radiation hardness and high chemical stability, ZnO are regarded as one of the most promising candidates for UV photodetectors. Additionally, doping in ZnO with Mg elements can adjust the bandgap largely and make it feasible to prepare UV photodetectors with different cut-off wavelengths. ZnO-based photoconductors, Schottky photodiodes, metal–semiconductor–metal photodiodes and p–n junction photodetectors have been developed. In this work, it mainly focuses on the ZnO and ZnMgO films photodetectors. We analyze the performance of ZnO-based photodetectors, discussing recent achievements, and comparing the characteristics of the various photodetector structures developed to date.

https://www.mdpi.com/1424-8220/10/9/8604/pdf

ZnO-Based Ultraviolet Photodetectors

Piezo-actuated stages have become more and more promising in nanopositioning applications due to the excellent advantages of the fast response time, large mechanical force, and extremely fine resolution. Modeling and control are critical to achieve objectives for high-precision motion. However, piezo-actuated stages themselves suffer from the inherent drawbacks produced by the inherent creep and hysteresis nonlinearities and vibration caused by the lightly damped resonant dynamics, which make modeling and control of such systems challenging. To address these challenges, various techniques have been reported in the literature. This paper surveys and discusses the progresses of different modeling and control approaches for piezo-actuated nanopositioning stages and highlights new opportunities for the extended studies.

Modeling and Control of Piezo-Actuated Nanopositioning Stages: A Survey

A new spindle error measurement system is described. It employs a specially designed rotational fixture with a corner cube to replace the precision reference master ball used in the traditional method. A two-dimensional position-sensitive detector (PSD) is used to replace the noncontact sensor for measuring the motion error of the rotating spindle. The rotational fixture is held on the tool holder, and the PSD is mounted on an adjustable holder to detect the position of an incident laser beam reflected from the corner cube. When the spindle rotates, the spindle error changes the direction of the reflective beam and also the positions of the spots on the PSD. Thus, the radial runout of the spindle can be obtained via the PSD outputs. The theoretical analysis to eliminate the setup error and eccentricity-induced error, as well as the error analysis, is given. This system is proposed as a new instrument and method for spindle metrology.

Development of a novel optical measurement system for the error verification of a rotating spindle

In this paper a method is developed for straightness measurement of a linear guide by using a straightness self-compensating stage with an optical straightness measuring system, an eddy current sensor, and a cross-roller type compensation stage. Both the compensation stage and the optical straightness system were set up on a scanning stage to measure the straightness error of the scanning stage. The measured straightness error was fed back to the control system to compensate directly in real time. Thus, straightness of a linear guide without the added straightness error of the scanning stage could be measured. The Hewlett Packard laser straightness calibration system was used to verify the real-time compensated results. Straightness error of the scanning stage was compensated from the worst straightness error of 20 μm/150 mm to 0.9 μm/150 mm. The eddy current sensor measured straightness of the linear guide and the measured result matched the result obtained by the coordinate measuring machine.

Automatic straightness measurement of a linear guide using a real-time straightness self-compensating scanning stage:

The accuracy of machine tools restricts the dimensional accuracy of parts processed thereon. It is, therefore, necessary to monitor the errors of machine tools constantly. Normally, it takes a long set-up time before one can observe the machine tool and monitor its errors. The cost of such delays is inevitably high. As for CNC, the conventional measurement system is capable of measuring one-dimensional signals, as a laser interferometer does, and two-dimensional signals, as a grid encoder does. Three-dimensional measurement techniques, however, are far from being well developed and are not yet well known. This paper proposes a triangulation method incorporating three built-in linear-scale ball bars that requires less set-up time and lower costs than the laser ball bar system, and is capable of acquiring three-dimensional signals with greater accuracy with the extension bars, so that large volumes can be checked.

The Development of a Triple Ball Bar System for Calibration of CNC Machine Tools

The nanoforging process and mechanism of pure aluminum samples is studied using molecular dynamics (MD) simulations based on embedded atom method (EAM) potential function. The effects of the forging temperature and the forging velocity are evaluated in terms of molecular trajectories, internal energy, and a radial distribution function. The simulation results clearly show that the internal energy of the workpiece exerted on it during the forging process have high energy with decreasing forging temperature ; however, with increasing forging velocity, the internal energy have higher energy. During the forging process, a special atomic structure in (011) and (0) slip planes was observed, and that represents the site of generation of dislocation and growth nucleation. When severe plastic deformation occurs, the density of the workpiece varied. The forged workpiece has similar distributions of atomic density after the loading for various forging temperatures and forging velocities.

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Analysis and Nanomold Design for Aluminum Nanoimprinting

This paper presents a real-time straightness measurement and compensation system with an optical straightness measurement system and a single-axis flexure-hinge type lead zirconate titanate (PZT)-based compensation stage. The optical straightness measurement system consists of a He–Ne laser, a quadrant photodiode detector, and five right-angle reflectors. Multiple laser beam reflections between the right-angle reflectors increase the sensitivity of the straightness measurement by a factor of 6. The right-angle reflectors can be moved by the flexure-hinge type PZT-based compensation stage that is actuated by a PZT actuator to ensure that the laser beam is always projected onto the center of the quadrant detector. These two systems are integrated and fixed on a scanning stage. The resolution of the straightness measurement system is 0.1 μm. Using the real-time straightness compensation system, the straightness error of the scanning stage is fed back to the control system. The compensated straightness error ...

Development of a straightness measurement and compensation system with multiple right-angle reflectors and a lead zirconate titanate-based compensation stage

Chien-Hung Liu

Papers

Development of a novel optical measurement system for the error verification of a rotating spindle

Automatic straightness measurement of a linear guide using a real-time straightness self-compensating scanning stage:

The Development of a Triple Ball Bar System for Calibration of CNC Machine Tools

Analysis and Nanomold Design for Aluminum Nanoimprinting

Development of a straightness measurement and compensation system with multiple right-angle reflectors and a lead zirconate titanate-based compensation stage