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Effects of Ball Milling on the Properties of (Ba<sub>1-<i>x</i></sub>Ca<sub>x</sub>)(Ti<sub>0.92</sub>Sn<sub>0.08</sub>)O<sub>3</sub> Lead-Free Ceramics
摘要： The (Ba1-xCax)(Ti0.92Sn0.08)O3 (x = 0 and 0.02) lead-free ceramics were prepared by using different ball-milling method and time (common ball milling 24 h, high energy ball milling 1 and 3 h). The two-step sintering method was used for sintered the samples. The densification, structure, dielectric and piezoelectric properties of the ceramics were investigated. The results showed that Ca addition could reduce sintering temperature effectively and enhanced densification at lower temperature when using the common ball-milling type. The XRD patterns of (Ba1-xCax) (Ti0.92Sn0.08)O3 ceramics revealed the change in crystal symmetries from tetragonal to cubic phase with increasing Ca content from 0 to 0.02. However, the crystal structure did not change due to the effect of ball-milling method. Ca incorporation caused a decrease of the grain size and Curie temperature. Moreover, the largest grain size was found in the x = 0 ceramics with 24 h-common ball-milling, whereas the small size (< 5 μm) was obtained for the x = 0.02 ceramics. The dielectric and piezoelectric properties were also affected to Ca addition and ball-milling. High piezoelectric coefficient of d33 = 173 pC/N, dielectric constant εr ~ 3200 and dissipation factor tanδ ~ 0.05 were obtained for the x = 0 sample with high energy ball-milling for 1 h.
关键词： Ball-milling,Lead-free materials,Two-step sintering
更新于2025-09-09 09:28:46
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Attaining reduced lattice thermal conductivity and enhanced electrical conductivity in as-sintered pure n-type Bi2Te3 alloy
摘要： Undoped n-type Bi2Te3 bulks were prepared via the liquid state manipulation (LSM) with subsequent ball milling and spark plasma sintering processes. The sample with LSM obtains higher carrier concentration and larger effective mass compared with that without LSM, exhibiting favourable electrical transport properties. More importantly, a much reduced lattice thermal conductivity * 0.47 W m-1 K-1 (decreased by 43%) is obtained, due to the enhanced multiscale phonon scattering from hierarchical microstructures, including boundaries, nanograins and lattice dislocations. Additionally, due to the increased carrier concentration and enlarged band gap, the bipolar effect is effectively suppressed in sample BT-LSM. Consequently, zTmax * 0.66 is achieved in the sample with LSM at higher temperature of 475 K, almost 22% improvement compared with that of the contrast.
关键词： spark plasma sintering,thermoelectric,electrical conductivity,thermal conductivity,liquid state manipulation,ball milling,Bi2Te3
更新于2025-09-09 09:28:46
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Synthesis of Li+-ion activated NaYF4: Er3+/Yb3+ phosphors via a modified solid-state process for latent fingerprint detection
摘要： Li+-ion codoped NaYF4: Er3+/Yb3+ phosphors (β-NaYF4) with a hexagonal structure were synthesized via a modified solid-state route. High-speed planetary ball milling and solid-liquid mixing were simultaneously used to overcome the drawbacks of high synthesis temperatures in conventional routes. A pure β-NaYF4 phase was obtained through calcination at 600°C for 3 h. Increases in the codoping content of Li+ ion caused a slight shift in X-ray diffraction peak positions toward high angles owing to the distortion of the local crystal field. Field emission scanning electron microscope images showed agglomerated spherical particles of approximately 0.7 μm with narrow size distribution. The upconversion properties of β-NaYF4 codoped with Li+-ion were explored. Two emission bands in the green regions (520 nm and 545 nm) and one emission band in the red region (615 nm) were observed owing to the 2H11/2→4I15/2, 4S3/2→4I15/2, and 4F9/2→4I15/2 transitions of Er3+, respectively. Codoping with 6 mol% Li+ increased the upconversion intensity by three times, which was explained using the energy level diagram. The present phosphors with improved upconversion properties were utilized for latent fingerprint detection on smooth surfaces of regularly used polymer sheets, glass substrates, and compact discs. Using the present phosphors, the base elements with three-level features, such as sharp ridges, valleys, ridge flow, bifurcation, ridge shapes, and dots, were observed on all hydrophilic and hydrophobic surfaces. The prepared phosphors exhibited promising characteristics to detect the features of fingerprint impression for individual identification in forensic applications.
关键词： fingerprint detection,solid-liquid mixing,upconversion,ball milling,Li+-ion codoping
更新于2025-09-09 09:28:46
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Preparation of Si-SiOx nanoparticles from volatile residue produced by refining of silicon
摘要： Residual Si was produced on a furnace wall when upgraded metallurgical grade Si was re?ned by electron beam melting. It was then recycled to prepare Si-SiOx nanoparticles with an average size of 100 nm by planetary ball milling. The obtained Si-SiOx nanoparticles mainly consist of amorphous Si, crystalline Si and amorphous SiOx, which was con?rmed by XRD, FTIR, XPS and TEM. SiOx is mainly composed of SiO2 and SiO1.35. Distilled water used as a grinding aid not only enhances milling ef?ciency, but also plays a key role in obtaining SiOx. During re?ning of upgraded metallurgical grade Si, the deposition pattern of residual Si on furnace wall agrees with model of three-dimension growth. Growth of Si-SiOx nanoparticles is the mutual effect of distilled water and ball milling. Si-SiOx nanoparticles were doped into phenolic resin pyrolysis carbon as anode materials for lithium ion batteries, and 10% doping was observed to improve the speci?c capacity. After 500 cycles, speci?c capacity of delithiation remained around 550 mA h/g. It suggests the residual Si is a value-added by-product, and it can be recycled as anode materials for lithium ion batteries.
关键词： Residual Si,Si-carbon anode,Si-SiOx nanoparticles,Planetary ball milling,Electron beam melting
更新于2025-09-04 15:30:14
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Robust active control based milling chatter suppression with perturbation model via piezoelectric stack actuators
摘要： Milling, as the most widely used processing method, plays an important role in advanced manufacturing. However, milling chatter has severely restricted the development of advanced manufacturing industry. Therefore, it is of great theoretical significance and application value to study the active control of milling chatter. This paper focuses on the design of robust controller for chatter suppression. At first, the milling dynamic equations with active control force are established and simplified with the approximate linear time-invariant model for robust controller design. Then, the perturbation modeling of modal parameters and milling parameters are built and analyzed. Based on the perturbation models, the control algorithm is designed. The numerical simulation in milling process verifies the effectiveness of the designed controller. In order to validate the practical effect, the flank milling and end milling tests are implemented, respectively. The experimental results show that the designed algorithm is able to suppress chatter greatly and lead to the better workpiece surface, which prove the effectiveness and robustness of the designed controller.
关键词： Milling chatter suppression,Piezoelectric stack,Zero order Fourier expansion,Robust active control,Pade approximation,Parameters perturbation
更新于2025-09-04 15:30:14
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[Micro/Nano Technologies] Micro and Nano Fabrication Technology Volume 1 || Micro Milling for Functional Surface
摘要： Micro manufacturing has recently increased in the several ?elds that include optics, electronics, medicine, biotechnology, and communications. Then, drastic progresses have been seen in the micro milling with the technologies in micro/nano-scale measurement, control, and tooling. This chapter describes the micro milling for manufacturing of the functional surfaces, which control material behavior with the surface topography. In the introduction, the current technical status in the functional surfaces is reviewed with the micro fabrication processes, and some issues in the micro milling are described to achieve high qualities of the micro elements and structures on the surfaces. Then, the typical micro milling process is discussed in terms of the operations and the removal process. Regarding material behavior, the effect of crystal grain size and orientation on the removal process becomes relatively large. When the grain size reduces, the dynamic components in the cutting force, burr formation, and affected layer can be controlled in micro cutting. Micro milling is applied to manufacture the functional surfaces with the micro dimples at high machining rates. The micro dimples are machined in milling with the inclined spindle at 45(cid:1). The milling with the cutter axis inclination is also applied to machine the micro dimples on the cylinder surfaces. A mechanistic model is applied to control the dimple shape for the cutting parameters, the feed direction, and the tool geometry. The surfaces with the micro dimples are applied to control the surface functions such as optical re?ection and wettability.
关键词： Surface function,Micro milling,Micro dimple,Wettability,Mechanistic model,Fine grained steel,Optical control
更新于2025-09-04 15:30:14