Seed-Assisted Synthesis and Catalytic Performance of Nano-sized ZSM-5 Aggregates in a One-Step Crystallization Process

Hierarchical nano-sized ZSM-5 aggregates were successfully synthesized via a seed-assisted method in the presence of cetyltrimethylammonium bromide(CTAB)through a facile one-step crystallization process.Commercial ZSM-5 zeolites with a SiO2/Al2O3 ratio comparable to that of ZSM-5 products were treated with alkali and used as the seed particles.The influences of crystallization conditions were investigated,and the possible synthesis mechanism was proposed.ZSM-5 zeolites with diff erent amounts of CTAB added were characterized using many techniques and evaluated in toluene alkylation with methanol.The results showed that a trace amount of CTAB signifi cantly promoted the crystallization of ZSM-5 zeolite,with the morphology changing from hexagonal-shape crystals to uniform spherical aggregates.CTAB may act as the structure-directing agent and assemble the primary crystallites to generate hierarchical ZSM-5 aggregates.The ZSM-5 zeolite with the smallest primary particles of 50-80 nm exhibited large specific surface area,abundant mesopores,and the greatest microporosity.The hierarchical nano-sized ZSM-5 aggregate showed higher toluene conversion and a longer lifetime without compromising the selectivity to xylene and p-xylene in toluene alkylation with methanol.

Novel seed-assisted synthesis of indium tin oxide submicro-cubes and their resistivity

Indium tin oxide films,an important n-type semiconductor oxide,show great prospects in optoelectronic device applications.Consequently,as a key raw material of targets for sputtering films,it is important to prepare low-resistivity indium tin oxide powders.Herein,low-resistivity indium tin oxide submicro-cubes are synthesized by a seed-assisted coprecipitation method.The effects of seed content,In^(3+)concentration,aging time,reaction temperature and calcination temperature on resistivity were investigated by single factor and orthogonal experiments.To ensure reliability and reproducibility of data,each experiment was repeated three times and resistivity of each sample was measured three times to obtain average value.The results indicated that optimal sample was matched with cubic phase In_(2)O_(3).The single-crystal indium tin oxide particles exhibited a regular cubic shape with a size of nearly 500 nm and low resistivity of 0.814Ω·cm.Compared with particles prepared by the conventional coprecipitation method,indium tin oxide submicro-cubes showed good dispersion.The presence of seed particles provided nucleation sites with lower energy barriers and promoted formation of submicro-cubes.The face-to-face contact among particles and good dispersion contributed to electron transfer,resulting in lower resistivity.The seed-assisted synthesis provides a novel way to prepare low-resistivity indium tin oxide submicro-cubes.

Progress in Seed-assisted Synthesis of (Silico) Aluminophosphate Molecular Sieves

Aluminophosphate(AlPO)and silicoaluminophosphate(SAPO)molecular sieves are an important class of open-framework crystalline materials with wide applications thanks to their molecular-scale selectivity,moderate/strong acidity and excellent(hydro)thermal stability.In recent decades,the manufacturing of new microporous solids with ordered structures has been widely investigated and many effective methods have been developed,which enriches the material types and broadens their applications beyond the traditional use as catalysts and adsorbents.However,the development on the synthesis of AlPO/SAPO molecular sieves is still insufficient and lags behind the needs of applications.Herein,we summarize the work on the seed-assisted synthesis of AlPO/SAPO molecular sieves compared with the zeolite synthetic system,aiming to prompt the synthesis and application of AlPO/SAPO molecular sieves.

Minority carrier lifetime evaluation of periphery edge region in high-performance multicrystalline ingot produced by seed-assisted directional solidification

A high-performance multicrystalline silicon （mc-Si） ingot was produced by seed-assisted directional solidification, and the minority carrier lifetime of the periphery edge region was evaluated. The defects and impurities in the periphery edge region of the silicon wafers were systematically studied with photoluminescence （PL） imaging, minority carrier lifetime mapping, and Fourier transform infrared （FTIR） spectroscopy. Their relationships with the minority carrier lifetime were investigated. The concentration of substitutional carbon, interstitial oxygen, and dislocation clusters is not directly correlated with the low minority carrier lifetime of the edge zone of the mc-Si ingot. Inhomogeneous grain size distribution and contamination with iron impurities were demonstrated to be the main factors affecting the low minority carrier lifetime. By controlling the impurities and improving the grain size distribution, a modified furnace was designed and a higher-quality mc-Si ingot was manufactured.