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Zhong S.,Tongji University | Li J.,Tongji University | Li J.,Sinoma International Engineering Co. | Ni K.,Tongji University | And 2 more authors.
Construction and Building Materials | Year: 2013

In order to understand why polymer-modified mortars (PMMs) with hydroxypropylmethyl cellulose (HPMC) often show better properties than that without HPMC, the influence of HPMC on the adsorption of styrene-acrylic ester (SAE) latex particles on cement grains was studied through the particle size distribution and the zeta potential of latex modified cement paste (LMCP) with and without HPMC keep the latex/cement ratio (L/C) to 10%. The differences between the calculated and measured particle size distribution curves of LMCP indicate strong interactions between latex particles and cement grains in fresh cement pastes. The particle size distribution results show that the adsorbed rate of SAE on cement is 75.24% in LMCP, while the adsorbed rate of SAE latex particles in LMCP with HPMC is 4% lower than that in LMCP without HPMC. The zeta potential results show that the zeta potential of LMCP is negative, the equilibrium zeta potential of LMCP with HPMC is more negative than that of LMCP without HPMC and decreases with the increase of the HPMC to cement ratio (HPMC/C). The microstructures of hardened LMCP with and without HPMC were observed using scanning electronic microscopy (SEM). Without etching of LMCP with or without HPMC, the polymer films are more easily seen in pores while hard to found at the cement matrix. After etching the specimen in diluted hydrochloric acid (HCl), coherent polymer films were observed. The differences of the polymer films in samples prepared with different procedures, that is the specimens stored in absolute alcohol or not, show that they are composite films of SAE latex and HPMC in LMCP with HPMC. Higher the HPMC/C is, bigger the covered area of the polymer films is on the surface of pores, and more rigid the polymer films are, what can be confirmed from the tensile test results of films made from the HPMC and SAE latex mixture that show decreased elongation at break and increased tensile strength with the increase of HPMC to latex ratio (HPMC/L). © 2012 Elsevier Ltd. All rights reserved.

Zhang Q.,Tianjin University | Yang X.,Tianjin University | Liu T.,Tianjin University | Liu Y.,Tianjin University | Yan H.,Sinoma International Engineering Co.
Chinese Journal of Sensors and Actuators | Year: 2013

A design of a smart digital visual sensor for inline visual inspection system for the white body of cars is reported. Based on ARM 6410 processor, the system integrates the functionalities of data collection, 2D pixel-level locating, communication as well as controlling, and it aims at solving the problem of poor signal processing capability and bad immunity to interference in traditional visual sensors. A fast and stable pixel-level template matching algorithm based on Linux system is designed, which uses NNPROD as similarity measurement and adopts a multi-resolution strategy. In the matching algorithm, a new 2D summation method called "Running Sum with Complementing Lost Pixels" is proposed, which optimizes the calculation of the cross-correlation coefficient. With a comprehensive fault-tolerant mechanism in addition to the matching algorithm, the visual sensor has been proved experimentally to run the pixel-level locating function with high speed, high precision and high robustness, and to fulfill the task of front-end data collecting and processing in the inspection system.

Zhong S.-Y.,Tongji University | Li J.-M.,Tongji University | Li J.-M.,Sinoma International Engineering Co. | Han D.-D.,Tongji University | And 2 more authors.
Jianzhu Cailiao Xuebao/Journal of Building Materials | Year: 2013

Because of less thorough study on the properties of cement pastes with superplasticizers and latex mixed together, the influence of different mixing procedures of superplasticizers and latex on the ζ potential of cement pastes(fresh) were analyzed using the ZetaProbe instrument. The experimental results show that with adding different use level(by mass) of polycarboxylic superplasticizer(PC), the cement pastes with both PC and latex added have negative or positive ζ potential. However, the ζ potential of cement pastes with both naphthalene formaldehyde condensate superplasticizer(NF) and latex added is lower than that of cement pastes with NF added but higher than that of cement pastes with latex added. Adding NF into cement pastes with latex added, the absolute value of equilibrium ζ potential of the cement pastes is lower than that of cement pastes with NF added, cement pastes with latex added and cement pastes with both NF and latex added. Adding PC into cement pastes with latex added, the ζ potential of the cement pastes can even reach the equilibrium ζ potential of cement paste with latex added. When latex is added in, the ζ potential of cement paste with 1.0% PC added doesn't change, but the ζ potential of cement paste with 0.1% PC added decreases greatly to a certain value. The ζ potential of cement paste with NF added increases from -10 mV to -6 mV when latex is added in, and then increases slowly with the increase of use level of latex. By adding superplasticizer(NF or PC) and latex into cement pastes simultaneously or adding latex into cement pastes with superplasticizer(NF or PC) added, the adsorbed proportion of polymer particles on cement grains can be decreased.

Zhong S.,Tongji University | Han D.,Tongji University | Li J.,Sinoma International Engineering Co.
Advanced Materials Research | Year: 2013

Whether and how many polymer particles will be adsorbed on the cement grain in the polymer-modified cement composites (PCC) is still a question. In this paper the possibility and the test method of adsorption of polymer particles on the cement grain were reviewed. A theoretical analysis on the principle of adsorption was discussed. It was then summarized that polymer particles will be adsorbed by the cement mainly due to electrostatic attract and the entropy effect. The zeta potential measurement based on the electroacoustic principle is a useful tool to study the adsorption of polymer, in combination with sedimentation of the polymer latex-modified cement with high water/cement (W/C) ratio quantitative evaluation of the adsorption is possible. © (2013) Trans Tech Publications, Switzerland.

Zhang L.,Nanjing University of Technology | Lu Z.,Nanjing University of Technology | Han P.,Nanjing University of Technology | Lu J.,Sinoma International Engineering Co. | And 3 more authors.
Journal of the American Ceramic Society | Year: 2012

Two different Sr2SiO4:Dy3+ phosphors were successfully synthesized at 1000°C for 4 h using NH4Cl or SrCl2 as the flux, respectively. The luminescence intensity of Sr2SiO4:Dy3+ was enhanced 60 times by the addition of 5 wt% NH4Cl. The phase evolution and photoluminescence (PL) properties of the phosphors were investigated by the calculation of phase equilibrium and the analysis of TG/DSC, XRD, SEM, and PL. The role of NH 4Cl was proved to be attributed to the formation of SrCl2 at ~300°C. The flux NH4Cl or SrCl2 lowered the decomposition temperature of carbonate and promoted the preferential formation of α' phase in the solid-state reaction through accelerating the kinetics of the formation of Sr2SiO4 by enhancing diffusion with more liquid phase. © 2012 The American Ceramic Society.

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