Papers by Author: Hai Lin Cao

Abstract: There are shown studies on development of the alkali-activated slag cements and concretes using Chinese raw materials. Such cements and concretes are able to provide high performance characteristics of materials and constructions under exposure of sea climate. The tests had been done for compliance with the requirements set in the national standards of P.R.China and were determined characteristics of strength, wet conditions shrinkage, freeze-thaw resistance, corrosion and weather resistance, biodegradability, water permeability, bond strength between concrete and reinforcement. The obtained positive results of tests allowed to recommend them for a pilot-scale production of the developed materials in sea construction for protection of the sea coastal line in the P.R.China.

Abstract: Less than half a century ago just an idea of presence of free alkalis in a ceramic matrix was considered by ordinary Portland cement people as an absurd one and this was a basic postulate accepted in chemistry of cements. In 1957 a scientist from Ukraine (USSR) Viktor Glukhovsky put forward an assumption which was taken as a base for development and bringing into practice of construction a principally new class of cementitious materials which first appeared in the field under a name of alkaline (now also known under a general name of alkali-activated) cementitious materials. A validity of these ideas was confirmed by more than 50 years of evolutional development and vast experience collected on practical use of new materials in different applications. The paper covers theoretical views on role played by alkali in the formation of an alkali-activated cement matrix with high durability. Examples of compositional build-up of the alkali-activated cementitious materials vs. quantity of added alkali and type of aluminosilicate component are reported together with results of 50-year experience obtained from observation of concrete structures made from these cements.

Abstract: Urchinlike Ni particles with different length and quantity spines were successful synthesized. The microstructures and morphologies of the resulting materials were investigated by X-ray diffraction and scanning electron microscopy. The amount of N2H4H₂O plays an important role in the morphology of urchin. The electromagnetic parameters of these urchinlike Ni were measured with vector network analyzer at 2-18 GHz frequency. The results indicate that the microwave absorbing properties are improved by the urchin structure.

Abstract: Urchinlike Ni particles with different spines were synthesized. The microstructures and morphologies of the resulting materials were investigated by X-ray diffraction and scanning electron microscopy. And the electromagnetic parameters of these urchinlike Ni were measured with vector network analyzer at 2-18 GHz frequency. The results indicate that the electromagnetic parameters are affected by morphologies of materials. The long urchin spines will lead to larger permittivity.