ABSTRACT:In this article, high-sulfonated melamine-formaldehyde (HSMF) resins were prepared with a sulfite/melamine (S/M1.5) molar ratio. During the sulfonation process, the reaction temperature and the added velocity of sodium bisulfite affecting the properties of the resin were studied. In the condensation stage, where the pH range is 6.0 and the temperature is about 25°C, the condensation time was prolonged above 24 h. The stability and water solubility of the resin was improved greatly. It is an effective superplasticizer at small dosages of admixture.
The surface energy quantifies the disruption of intermolecular bond that occurs when a surface is created. The paper discusses critical size dc of mono-dispersed nanometer particle by analyzing the change of interfacial surface energy. The traditional theory neglects that the mono-dispersed nanometer particle has quantum standing wave in its internal structure with a size below critical dc. During the preparation of mono-dispersed nanometer powder, the large surface energy is formed ont only by cutting surface bond but also by forming quantum standing wave that opposites to interfacial edge unsaturated bond on the nanometer partcile surface atom. The preparation process of nanometer material needs more energy than the size surpass dc material. The new theory can explain why the melting point of nanometer powder decreases and other phenomina of nanometer material.
Graphene oxide (GO) was prepared using the improved Hummer method, and mono-dispersed manganese cobalt nickel oxide (MCN) semiconductor nanometer particles were synthesized and coated with GO. Under 980-nm infrared laser excitation, this novel hybrid material demonstrated nanometer-scale surface plasmon resonance. The same mechanism has previously only been reported in good conductors. Although the MCN semiconductor is a negative temperature coefficient material, it can realize the same effect as a good conductor. The experimental data indicated that the hybrid material absorbed infrared laser photothermal energy with a transformation efficiency more than fourfold larger than that of pure mono-disperse MCN semiconductor nanopowder. The chain heat conductivity velocity of the hybrid material compares favorably with that of metal in that it alters the laser radiation energy heat transfer method on the surface. The hybrid material is one new kind of photothermal energy transfer material by new chain nanoscale surface plasmon mechanical, it can absorb sunlight and ultra-red light totally, and is one excellent energy transform and absorb material for sunlight.
We report a novel Mn-Co-Ni-O (MCN) nanocomposite in which the p-type semiconductivity of Mn-Co-Ni-O can be manipulated by addition of graphene. With an increase of graphene content, the semiconductivity of the nanocomposite can be tuned from p-type through electrically neutral to n-type. The very low effective mass of electrons in graphene facilitates electron tunneling into the MCN, neutralizing holes in the MCN nanoparticles. XPS analysis shows that the multivalent manganese ions in the MCN nanoparticles are chemically reduced by the graphene electrons to lower-valent states. Unlike traditional semiconductor devices, electrons are excited from the filled graphite band into the empty band at the Dirac points from where they move freely in the graphene and tunnel into the MCN. The new composite film demonstrates inherent flexibility, high mobility, short carrier lifetime, and high carrier concentration. This work is useful not only in manufacturing flexible transistors, FETs, and thermosensitive and thermoelectric devices with unique properties but also in providing a new method for future development of 2D-based semiconductors.
A thorough review on the patents in the applications of nano-powder technology shows that research work in this technical field is growing stronger, as indicated by a rapid increase in the number of independent patents in relevant topics. This also indicates ever increasing and continuous interests on the nano-powder technology even after 15 years of dynamic global nanotechnology development. The review on the patents in the nano-powder area shows that the use of specialized databanks is recommendable and beneficial in providing the researchers in this technical community an updated, systematic and rapid reference in furthering new development and expansion of this vital nanotechnology field.
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