Zhang J.,CAS Fujian Institute of Research on the Structure of Matter
Nanoscale | Year: 2010
The crystal growth mechanism, kinetics, and microstructure development play a fundamental role in tailoring the materials with controllable sizes and morphologies. The classical crystal growth kinetics-Ostwald ripening (OR) theory is usually used to explain the diffusion-controlled crystal growth process, in which larger particles grow at the expense of smaller particles. In nanoscale systems, another significant mechanism named "oriented attachment (OA)" was found, where nanoparticles with common crystallographic orientations directly combine together to form larger ones. Comparing with the classical atom/molecular-mediated crystallization pathway, the OA mechanism shows its specific characteristics and roles in the process of nanocrystal growth. In recent years, the OA mechanism has been widely reported in preparing low-dimension nanostructural materials and reveals remarkable effects on directing and mediating the self-assembly of nanocrystals. Currently, the interests are more focused on the investigation of its role rather than the comprehensive insight of the mechanism and kinetics. The inner complicacy of crystal growth and the occurrence of coexisting mechanisms lead to the difficulty and lack of understanding this growth process by the OA mechanism.In this context, we review the progress of the OA mechanism and its impact on materials science, and especially highlight the OA-based growth kinetics aiming to achieve a further understanding of this crystal growth route. To explore the OA-limited growth, the influence of the OR mechanism needs to be eliminated. The introduction of strong surface adsorption was reported as the effective solution to hinder OR from occurring and facilitate the exclusive OA growth stage. A detailed survey of the nanocrystal growth kinetics under the effect of surface adsorption was presented and summarized. Moreover, the development of OA kinetic models was systematically generalized, in which the "molecular-like" kinetic models were built to take the OA nanocrystal growth behavior as the collision and reaction between molecules. The development of OA growth kinetics can provide a sufficient understanding of crystal growth, and the awareness of underlying factors in the growth will offer promising guidance on how to control the size distribution and shape development of nanostructural materials. Source
CAS Fujian Institute of Research on the Structure of Matter | Date: 2014-06-10
The invention belongs to the technical field of preparing oxalate in coal to ethylene glycol, aiming at providing a preparation process for nanocatalysts with (111) crystal facet exposed and a process for vapour-phase CO oxidative coupling to oxalate. The nanocatalysts with (111) crystal facet exposed comprise carrier, active component and promoter on the carrier, wherein, in term of the weight of the carrier, the active component accounts for 0.05-2% of the weight of the carrier, the weight percentage of metal elements in the promoter is 20% or less. The nanocatalysts with (111) crystal facet exposed are prepared by the nanometals in situ supporting process. The preparation process is simple in procedure, has low energy consumption and can precisely control the size and exposed crystal facet of the active component nanoparticles. The obtained nanocatalysts with (111) crystal facet exposed are highly active for vapour-phase CO oxidative coupling to oxalate at a lower loading of noble metal.
CAS Fujian Institute of Research on the Structure of Matter | Date: 2013-05-07
The present invention relates generally to the field of synthetic crystal, and more particularly, this invention relates to doped low-temperature phase barium metaborate single crystal, growth method and frequency-converter. Molten salt method was adopted. The single crystal completely overcome the shortcomings of BBO with strong deliquescence, almost no deliquescence; its frequency doubling effect and optical damage threshold has improved greatly compared with the BBO; its hardness increased significantly, the single crystal with Shore hardness of 101.3 and Mohs hardness of 6, however, BBO with Shore hardness of 71.2 and Mohs hardness of 4. From the UV-Vis region transmittance curves tests, the cut-off wavelength of the single crystal is 190 nm, wavelength of absorption onset is 205 nm. BBSAG is widely applied in the fields of laser and nonlinear optics, and in terms of frequency-converter of ultraviolet and deep-ultraviolet due to its excellent properties better than BBO.
CAS Fujian Institute of Research on the Structure of Matter | Date: 2014-12-09
This disclosure provides a second harmonic generator and an optical parametric oscillator, the second harmonic generator and the optical parametric oscillator comprise one or more nonlinear optical frequency conversion crystal and a pump laser source, the nonlinear optical frequency conversion crystal is a monoclinic Ga
CAS Fujian Institute of Research on the Structure of Matter | Date: 2014-07-18
A GaN based LED epitaxial structure and a method for manufacturing the same. The GaN based LED epitaxial structure may include: a substrate; and a GaN based LED epitaxial structure grown on the substrate, wherein the substrate is a substrate containing a photoluminescence fluorescent material. The photoelectric efficiency of the LED epitaxial structure is enhanced and the amount of heat generated from a device is reduced by utilizing a rare earth element doped Re