CsPbBr3 NCs can be prepared by high energy ball milling in one-step.NCs exhibit excellent optical properties and the synthesis mechanism is explained.As-prepared CsPbBr3 NCs show good stability in ethanol and living conditions.CsPb2Br5 NCs (PLQY up to 92%) can be prepared by dispersing CsPbBr3 NCs in water.
All-inorganic halide perovskite nanocrystals (NCs) are generally prepared by liquid phase method with the help of volatile organic solvents, inert gas protection and complex organometallic precursors. Herein, a simple, efficient and green method based on all-solid-state mechanochemical synthesis is proposed to prepare CsPbBr3 NCs. NCs with excellent performance can be prepared by grinding raw materials CsBr and PbBr2 through high energy ball milling, and prepared NCs show good stability in ethanol and living conditions. Interestingly, CsPbBr3 NCs prepared by ball milling have a sudden increase in their fluorescence intensity dispersed in water. After soaking for 8h, CsPbBr3 NCs have been almost entirely transformed into CsPb2Br5 NCs. The fluorescence intensity of samples is 80 times of that before soaking, and absolute PL quantum yield (PLQY) of samples increases significantly by up to 92%. These results provide a strong evidence for the current debate about whether CsPb2Br5 emits light and propose a deeper understanding about structural transition from orthorhombic CsPbBr3 to tetragonal CsPb2Br5, which is of great significance to the application of CsPb2Br5 in optoelectronic devices. This will provide a new idea for the synthesis and transformation of halide perovskites.
A rational design of TiO2 catalyst supports by high-energy ball milling is presented.Mixtures of titania phases were obtained due to polymorphic transformation.Milling process increases oxygen vacancies, reducibility and oxygen mobility.Unusual TiO2 (II) phase remains stable even under extreme conditions.Materials with improved properties for catalyst support application are proposed.
We carried out a rational design of catalyst supports by high-energy ball milling. Tailored mixtures of TiO2 crystalline phases were obtained using rotational speed and milling time as variable parameters. Polymorphic transformation from anatase to rutile through high-pressure TiO2 (II) as intermediate was confirmed by X-ray Diffraction (XRD), Raman Spectroscopy and Transmission Electron Microscopy (TEM). Also, starting material doubled its specific surface area due to particle fragmentation, as confirmed by surface area of Brunauer-Emmet-Teller (SBET) and Scanning Electron Microscopy (SEM). Defects introduced during milling process generated oxygen vacancies in the surface and bulk of supports, as evidenced by X-ray Photoelectron Spectroscopy (XPS) and Electron Paramagnetic Resonance (EPR). Furthermore, longer milling time increased reducibility and oxygen mobility of supports, as observed by H2 Temperature Programmed Reduction (H2-TPR) and O2 Temperature Programmed Desorption (O2-TPD). Phase composition remained unchanged even under extreme conditions, highlighting the stability of unusual TiO2 (II) phase. Properties achieved in present materials could benefit metal-support interactions and play a major role in supported catalysts.
AA6005A/n-TiC nanocomposite powders were successfully developed via mechanical alloying.A fine homogeneous dispersion of the reinforcement phase in the whole particle was obtained.Evolution of morphology and microstructure of the reinforced powders vs. milling time is affected by the reinforcement amounts.The effect of milling process in the hardness is greater than that of the reinforcement.The higher the volume fraction of reinforcement, the higher the hardness obtained.
Micron-sized aluminium powder alloy AA 6005A was reinforced with different volume fractions, from 1.5, 3 and 6vol.%, of 2030nm diameter nano-sized TiC particles (n-TiC). The nanocomposite powders were synthesized by applying high energy ball milling for different milling times, in the range from 1 to 10h. It was evident that the presence of n-TiC particles had a marked influence on the powder morphology, average particle size and microstructure of the matrix during the milling process. Also, a fine homogeneous dispersion of the reinforcement phase into the Al alloy powder was obtained after ball milling. No intermetallic compounds were observed during high energy ball milling nor was iron contamination present due to ball and vial media after 10h milling. The correlations between the morphological and microstructural evolution of the matrix powder particles and the milling time were investigated for each n-TiC volume fraction. The results of this work suggest that the higher reinforcement content produces finer and narrower size distribution of matrix particles at shorter milling times and could be associated with the presence of n-TiC particles, which can favour the refining of matrix particles. The evolution of the crystallite size of the matrix powder particles with the milling time of the three nanocomposite powders is similar to the unreinforced alloy powder, and an increase in the amount of n-TiC particles in the soft matrix didn't result in a finer crystallite size. Furthermore, micro-hardness results of the nanocomposite powder samples showed that their hardness values increased with increasing milling time and reinforcement content and that the contribution of milling process is greater than that of the reinforcement.
High-purity disperse -Al2O3 nanoparticles prepared by direct ball-milling.-Al2O3 nanoparticles have an average size of 8nm and a purity of 99.96%.Formation mechanism of disperse fine equiaxed -Al2O3 nanoparticles discussed.Al2O3 nanocrystalline ceramic with a 99.8% density and a grain size of 34nm sintered.
The preparation of disperse fine equiaxed -Al2O3 nanoparticles with narrow size distribution, high purity, and high yield is essential for producing Al2O3 nanocrystalline ceramic of fine grains which may exhibit a good toughness. In this work, micron-sized -Al2O3 particles were directly ball-milled and subsequently washed with hydrochloric acid at room temperature. Fracture of large -Al2O3 particles and cold welding of fine -Al2O3 nanoparticles occur simultaneously during ball milling. It leads to the reduction of particle size with increasing milling duration below 80h and reaches to a dynamic equilibrium with a minimal average particle size of 6.4nm for milling durations over 80h. Using the optimized high-energy ball milling parameters, we prepared high-purity disperse equiaxed -Al2O3 nanoparticles with an average particle size of 8nm and a purity of 99.96% (mass percent) in a high yield. After fractionated coagulation separations, disperse fine equiaxed -Al2O3 nanoparticles with narrow size distribution were obtained. Finally, Al2O3 nanocrystalline ceramic with a relative density of 99.8% and an average grain size of 34nm was sintered from the disperse fine equiaxed -Al2O3 nanoparticles with an average particle size of 4.8nm and a size distribution of 210nm by pressureless two-step sintering.
Amorphous silicon/titanium carbide/graphite (a-Si/TiC/G) composite anodes were successfully prepared by multi-step high-energy ball-milling. x-ray diffraction and high-resolution transmission electron microscopy analyses demonstrated that the Si was completely transformed into an amorphous phase mixed with TiC after prolonged milling. TiC was gradually converted into nanocrystalline grains that were distributed on the surface of the amorphous silicon as a network of nanosized conductive channels. Cycle performance tests showed that the anode delivered a specific capacity of 835.4 mAhg1 with a capacity retention of 71.5% after 100 cycles at 0.2C. Electrochemical impedance spectroscopy showed that TiC plays the role of electronic transmission channels that significantly decreased the transfer resistance of the anode. This work provided a scalable preparation method of high-performance Si/TiC/G anode material.
X.H. Liu, J.W. Wang, S. Huang, F. Fan, X. Huang, Y. Liu, S. Krylyuk, J. Yoo, S.A. Dayeh, A.V. Davydov, S.X. Mao, S.T. Picraux, S. Zhang, J. Li, T. Zhu, and J.Y. Huang, Nat. Nanotechnol., 7, 749 (2012).
Pan, W., Cai, X., Yang, C. et al. Amorphous Si/TiC/Graphite Composite Fabricated by High-Energy Ball-Milling as an Anode for Lithium-Ion Batteries. Journal of Elec Materi 50, 25842593 (2021). https://doi.org/10.1007/s11664-021-08767-1
In this investigation, the chemical and structural characteristics of Fe nanoparticles synthesized by high-energy ball milling have been explored. After the milling process the nanoparticles were collected using a magnetic field. The structure, morphology and composition of the powders were obtained using high-resolution electron microscopy. HREM images confirmed the nanoparticles presence with approximately 24nm in size. It was found that using this method allowed the formation of nanoparticles in a smaller size range than other synthesis methods. Also, it was confirmed by HREM images that the obtained nanoparticles were mainly of the fcc nature and some of them of the MTP type.
Ziolo RF, Giannelis EP, Weinstein BA, OHoro MP, Anguly BN, Mehrotra V, Russell MW, Hufman DR (1992) Matrix-mediated synthesis of nanocrystalline -Fe2O3: a new optically transparent magnetic material. Science 257:219223
In this paper, we report the impact of mechanical activation on structural, microstructural, thermal, and optical properties of Mg2TiO4 (MTO) nanoparticles prepared by high-energy ball milling. WilliamsonHall (WH) method was carried out in order to understand the origin of the broadening in the X-ray diffraction (XRD) peaks and for the estimation of crystallite size of MTO nanocrystalline powder. It is revealed that the peak broadening is not only due to reduced coherently diffracting domain size but also due to a significant strain distribution. The calculated strain was 9.0103 and the average crystallite sizes are 4060nm for 35-h milled powder and this result is consistent with transmission electron microscopy (TEM) analysis. To examine the nature of lattice fringes for the 35-h milled samples, high-resolution TEM study was carried out. It revealed that the as-prepared samples are highly crystalline in nature. The surface morphological studies were carried out by using scanning electron microscopy (SEM) and atomic force microscopy (AFM). Further, MTO nanoparticles showed a strong absorption at ~356nm, and the bandgap values ranged between 3.26 and 3.78eV with an increase of milling time from 0 to 35h. The photoluminescence (PL) spectrum measured at room temperature showed the bands which are belong to the near band edge emission at 357nm. The MTO nanoparticles prepared by mechanical alloying method exhibited promising optical properties which are suitable for commercial optoelectronic applications.
The author RKB acknowledges the financial assistance from DRDO. The authors acknowledge Prof. Piyus Ranjan Das, Department of Physics, VSSUT Burla and Dr. Banarji Behera, Department of Physics, Sambalpur University for their kind cooperation and discussion for the betterment of the manuscript.
Bhuyan, R.K., Mohapatra, R.K., Nath, G. et al. Influence of high-energy ball milling on structural, microstructural, and optical properties of Mg2TiO4 nanoparticles. J Mater Sci: Mater Electron 31, 628636 (2020). https://doi.org/10.1007/s10854-019-02568-3