Papers by Author: Li Guang Xiao

Abstract: Iron tailings are mineral wastes obtained from industrial processing and magnetic separation of iron ore. Foam concrete with iron tailings can be made with iron tailings, cement, fly ash, silica fume, polypropylene fiber, superplasticizer, early strength agent, accelerating agent and foaming agent. The influences of polypropylene fiber on the crack resistance and frost resistance of foam concrete have been investigated in this study. Further, the microstructure of foam concrete was observed. This result demonstrates that polypropylene fiber has greatly increased the crack resistance and frost resistance of foam concrete. The pore structure of foam concrete is improved obviously by polypropylene fiber. Due to the uniformly distributed pores, high porosity and rather complete pore wall, the mechanical properties and thermal properties of foam concrete are excellent. The foam concrete with high-strength and excellent thermal insulation property develops a new route for the comprehensive utilization of iron tailings.

Abstract: A 1-D chain-like POM - based organic-inorganic hybrid compound with the chemical formula of [Ni (en)₂]{[Ni (en)₂]₂[Mo₈V₈O₄₀(VO₄)]}[(NH₂)₂(C₂H₄)₂NH]₂·2H₂O (en = ethylenediamine) (1) has been hydrothermally synthesized and structurally characterized by the elemental analysis, and single crystal X-ray diffraction. Compound 1 consists of the bi-supported tetra-capped Keggin-type {[Ni (en)₂]₂[Mo₈V₈O₄₀(VO₄)]}^2- building blocks and [Ni (en)₂]²⁺ metal organic cationic moieties are connected together to form 1-D chain through covelent-bonding interactions, which is further linked into 3-D supramolecular networks . The degradation of methylene blue (MB) under UV irradiation with 1 as the heterogeneous photocatalyst has been investigated, showing a good photocatalytic property of 1 for MB degradation.

Abstract: A new bi-capped Keggin heteropoly molybdovanadated derivative, [Co (en)₃]₂[SiMo₈V₆O₄₂]∙6H₂O (1) (en = ethylendiamine) has been hydrothermally synthesized and structurally characterized by the elemental analysis, IR, XPS and single crystal X-ray diffraction. The crystal structure analysis reveals that compound 1 consists of [Co (en)₃]²⁺ transition metal coordination fragment and the [SiMo₈V₆O₄₂]^4- building blocks, which are linked together via hydrogen-bonding interactions to form a new 3-D supramolecular networks.

Abstract: The thermal insulation mortar with cinders and phase change materials which is made from expanded perlites adsorbing composite phase change material, cinders and vitrified small ball as lightweight aggregate has the characteristics of both energy storage and thermal insulation. In this paper,we studied the effect of redispersible emulsion powder, methyl cellulose ether, organic fiber and water-reducing agent on the performance of thermal insulation mortar with cinders and phase change materials. The result showed that all the performance met the national standards of the thermal insulation mortar.

Abstract: In this study, a kind of water reducing agent based on Isoamyl enol polyoxyethylene ether were synthesized in water solution by radical copolymerization. The influence of copolymerization conditions on dispersing performance of the water reducing agent in the cement was investigated. The molecular structure of the copolymer was tested by NMR, and GPC was used to determine the molecular weight of copolymer and the big monomer percent conversion, also, testing the adaptability of the water reducing agent in different types of cement. The testing results show that the water reducing agent has the good performance on concrete. When the dosage of water reducing agent was 0.2%, the (Deer ding card, P.O42.5) slurry flow degree of the cement was 270mm, and the water reducing ratio reached 19.6%. When the dosage of water reducing agent was 0.3% and 0.4%, the water reducing ratio reached to 28.6% and 31.9% respectively. Comparing the adaptability of the water reducing agent on all kinds of cement, the water reducing agent performed the worst in the P.C cement and better in the P.O cement, its adaptability in the standard cement and P.S cement was the best. When the dosage of water reducing agent was 0.2%-0.4%, the water reducing ratio was nearly the same, When the dosage of water reducing agent was 0.4%-0.6%, the water reducing ratio in the standard cement was higher than in the P.S cement.

Abstract: Iron tailing is a kind of mineral waste from industrial processing and magnetic separation of iron ore, which severely pollute the air, soil property and the source of water. For large scale tailing ponds (dam height >100 m), the accident could cause a substantial damage. Therefore, it is significant to appropriately utilize the tailings. The present paper systematically studies the possibility of complete replacement of quartz sand with the iron tailings in polymer modified cement mortar used in external wall insulation plaster. The effects of redispersible polymer powers, cellulose ether, water reducing agent, lignin and polypropylene fiber on the performance of polymer modified cement mortar have been discussed. The results show that the performance of polymer-modified cement mortar composed of iron tailings has reached the national standard of external wall insulation system in China.

Abstract: As a new self-Insulation wall material, the autoclaved aerated concrete block has many advantages such as lightweight, thermal insulation, waste recycling, low energy consumption, friendly to environment, etc. It is gaining favors in the construction market day by day, and has been more and more widely used in construction engineering program. However, aerated concrete block faces disadvantages, e.g. large volume deformation coefficient, high water absorption, low strength, brittle character, etc. When aerated concrete block is used in combination with plain mortar, many problems may appear due to the incompatibility between them, for example crevices on the wall, large cracking, hollowing and exfoliation on the plaster layer, which become more serious on the north-facing wall in the cold region. These problems greatly hinder the wide application of aerated concrete block. Therfore, it is critical to develop a special plaster mortar that is compatible with the aerated concrete block. This paper concentrates on the chemical admixtures such as polymer and fiber, and studies their influences on the performance of the special plaster mortar. The experimental results show that polymer powder can significantly improve the properties of plaster mortar such as bonding strength, absorption performance and cohesive quality. Also, it prevents the bleeding and segregation of the paste, prevents the hollowing and exfoliation of plaster mortar layer on aerated concrete block wall. Polypropylene fiber has been revealed to increase the fracture toughness and cracking resistance of plaster mortar, thus preventing the cracking of plaster mortar layer on aerated concrete block wall. Additionally, this paper presents the microstructure of plaster mortar and discusses the working mechanism of admixtures in the mortar.

Abstract: High polymer active functional groups can be grafted on the surface of carbon fibers so as to adjust the interface effect between fibers in the composite material and resin and improve the performance of composite material, by controlling the structure of grafted high polymer, the interface layer with intended performance can be well designed. The surface of carbon fiber has great influence on the nylon generated through in situ polymerization and modified nylon crystallization, and little transcrystallization on the surface will be formed when the fiber carbon without grafting; after grating of carbon fiber, large quantity of crystalline texture can be seen near the fiber, and the crystal with high density is helpful for the improvement of material performance.

Abstract: High polymer active functional groups can be grafted on the surface of carbon fibers so as to adjust the interface effect between fibers in the composite material and resin and improve the performance of composite material, by controlling the structure of grafted high polymer, the interface layer with intended performance can be well designed. Heat treatment does not affect the fiber strength, the content of functional groups on the surface of the fibers reaches the max. value around 1h. There are no macromolecules polymerized and grafted on the surface of carbon fibers not subjected to isocyanate grafting treatment. Through isocyanate treatment after heat treatment, it can be obviously seen that the nylon molecules are grafted on the fiber surface. When no activating agent is added in the polymerized monomers, the resin grafting percent of fiber surface can reach 18.8%; when 0.003 activating agent (mole ratio of it to monomers) is added in the monomers, the grafting percent of PA6 on surface of carbon fibers is only 7.65%, this is the result of reactive competition on the interface between monomer matrix and fibers.

Abstract: The thermoplastic composite material with general plastics and high-performance engineering plastics as the matrix has become the hot spot of current research, because of big viscosity of thermoplastic resin melt, the focal point of research has been long concentrated on the aspect of impregnation technology, therefore, it is of particular importance to theoretically build the percolation model for fibers impregnated with thermoplastic resin. In this paper a theoretical model for fibers impregnated with thermoplastic resin melt through percolation is established, this model characterizes the influential laws of process parameters, melt viscosity and fiber structure on impregnation time. The model shows that theoretical volume fraction of fibers of the molten nylon resin composite material is hard to reach over 70%; for the nylon resin melt after viscosity reduction treatment, the time for complete impregnation is still very long, and raising temperature or increasing pressure can only improve the impregnation effect to a certain degree.