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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