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 of Cu cathode was alloyed by several elements, including pure Ni , Fe , Ag and pyrolytic graphite, during electric spark processing technology (ESP). The energy, gap between the electrode and matrix, and the total fabricating time of ESP are 0.9 J, 0.5 mm, and 30 s, respectively. The ESP was performed under a constant magnetic field (CMF) of 630 kA/m. The atom distribution profiles along the depth were measured by a serial sectioning and autoradiography. The lattice constants were studied by an X-ray diffractometer. The results show that there is one or several concentration peaks in the subsurface of Cu . When the depth is beyond the location corresponding to the concentration peaks, the concentration distribution in the matrix can be described by an exponential function. Fe and C atoms can homogeneously diffuse into the Cu lattice, accompanied by mechanical mixtures, and no traces of diffusion along the grain boundaries can be found. Comparing with the condition without a CMF, the diffusion coefficient decreases when the magnetic field is parallel to the surface, whereas the diffusion coefficient is the smallest when the magnetic field is perpendicular to the surface. The lattice constant of Cu becomes smaller after the ESP.

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.

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