Advanced Materials Research Vols. 476-478

Abstract: This document introduce commonly used to control the centrifugal water pump flow, The valve export opens degree, control pump turning speed , working principle and characteristics of the Two kinds methods, the structure of the three-phase Frequency Conversion, the Frequency Conversion external connection, point out the effect that frequency conversion timing to Adjust the flow of the pump.

Abstract: The main scope of this article is to simulate a cracked pipeline embedded with piezoelectric sensors and actuators utilizing bond graph approach. Piezoelectric sensors/actuators are becoming very popular in various applications such as health monitoring, active vibration control or noise reduction, and as a part of the systems called smart structures. The proposed bond graph structure in this study, graphically illustrates the power flow between the electrical and mechanical frameworks included in the system. In addition, the proposed framework makes it possible to utilize a modular structure for separately representing the electrical polarization of the material and its macroscopic electrical and mechanical effects. Simulation results illustrate that at the location of the crack the equivalent impedance is increased and the capacitance is decreased in comparison with the intact region.

Abstract: Magnetotactic bacteria are the bacteria which synthesize nano-sized magnetic particles within their cell body. In the present study, the cells of a magnetotactic bacteria M. magnetotacticum MS-1 was fractionated and the iron amount of the cell fractions were measured. In order to study the relationship between the process of the biosynthesis of magnetosome and the intracellular transport of iron, MS-1 cells were cultured under iron limited culture conditions and the amount of iron in the cell fractions were compared with those under optimal culture conditions. The whole amount of iron was measured colorimetrically. To estimate the number of ferric ion, the number of spin was determined from the ESR spectrum. The cell fractions obtained after removing magnetosome (non-magnetic fractions) contained 30-40 % of the total iron in the intact cells. There was a good correlation between the number of spin and the iron amount of non-magnetic fractions under optimal culture conditions. Under iron limited conditions, the iron amount decreased not only in the fraction containing magnetosome but also in the non-magnetic fractions. The number of spin in the soluble fraction decreased remarkably. So, the correlation between the number of spin and the amount of iron was not observed under iron limited conditions. These results imply that the ratio of ferrous ion to whole amount of iron increased in the non-magnetic fractions under iron limited conditions as compared with that under optimal conditions.

Abstract: A key factor of preparing different morphologies of nanometer calcium sulfate (CaSO4) is to select proper surfactants for forming compounding reverse micelle microemulsion, which makes calcium sulfate crystals grow with an optimal template effect of reverse micelle. It was found that flake-like, rod-like and sphere-like nanometer calcium sulfates were obtained in reverse microemulsion systems of OP-10 / cyclohexane / n-pentanol / water, AEO / cyclohexane / n-pentanol / water and AOT+OP-10 / cyclohexane / n-pentanol / water, respectively. The morphology and particle size were characterized by scanning electron microscope (SEM). The morphology of nanometer calcium sulfate by some other surfactants of reverse micelle microemulsion systems was briefly introduced. Furthermore, how the critical packing parameter (P) of different surfactant molecules influence the morphology of nanometer calcium sulfate was also analyzed.

Abstract: Al₂O₃-TiC-ZrO₂ ceramic composites (ATZ) were fabricated by hot-pressed sintering. The phases and microstructure of the composites were studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The relative density and mechanical properties (flexural strength, fracture toughness and Vicker’s hardness) of the composites were tested. The results show that the microstructure of the composites was the gray core-white rim. With the increase of sintering temperature, the relative density and mechanical properties of the composites increased first and then decreased. The composite sintered at 1705°C has the highest synthetical properties, and its relative density, flexural strength, fracture toughness and Vickers hardness are 98.3%,970MPa,6.0 MPa•m^1/2 and 20.5GPa, respectively.

Abstract: Grinding is the mostly leading machining technology for engineering ceramics. The quality of ground surface can be evaluated by various roughness parameters. And a textural analysis method based on Gray Level Co-occurrence Matrix was employed in researching the roughness of ground ceramics. The relationship between texture features and roughness was investigated through a series of surface images of engineering ceramics collected by a digital microscope. The sampling offset and total gray levels of surface images were determined firstly. Then 4 GLCMs were built up to calculate the average of texture features. And 6 parameters were fixed as main texture parameters. Furthermore, the multiple nonlinear regression theory was used to assess the relation between the texture features and roughness Ra. By statistic test and comparison, the deviation of calculated Ra and actual Ra is less than 0.25. It is shown that this relation is much satisfactory and the method may be suitable for quickly measuring the roughness of ground ceramics.

Abstract: Considered in this paper is a semi-infinite cellular ceramic solid containing an edge crack. The solid is subjected to a sudden cooling on its surface. The temperature field and associated thermal stress field for the uncracked solid are calculated. The stress for uncracked medium is used as the crack surface stress with opposite sign to formulate the mixed boundary value problem. The stress intensity factors as the function of crack length, time and relative density are calculated. It is found that the presence of porosity in the ceramic is generally beneficial to increasing the thermal shock strength of the ceramics if the failure is dominated by a pre-existing crack. The paper may be helpful for the design and manufacturing of advanced thermal shock resistive cellular ceramics.

Abstract: (1-x)KNbO3-xBaGeO3 based PTCR ceramic materials are prepared using high purity K2CO3, Nb2O5, GeO2, Al2O3 and BaCO3 powders as starting materials, and the structural and electrical properties have been investigated. The results indicated that the samples doped with minute Ba as donor show excellent PTCR effect above the temperature of about 36°C. For the 0.40at% Ba-doped sample, the minimum resistance of 4.2×104Ω·cm, temperature coefficient (αk) of 24.37%/°C, PTCR anomaly lg(Rmax/Rmin) of 3.82 and transition temperature (Tmin) of 36°C are obtained.

Abstract: Preparation of aqueous ceramics slurry with high solid volume and low viscosity is premise and key step of gelcasting, and dispersant play important role in slurry preparation. In this paper, triammonium citrate (TAC) was used as dispersant of PMN-PZT piezoelectric ceramics slurry, the effects of TAC on slurry stability and rheological properties and dispersion mechanism of TAC were investigated by sedimentation test, viscosity, scanning electron microscopy (SEM) and FTIR analysis. The SEM results indicated that TAC could reduce the agglomeration of powder particles and make ceramic particles well-dispersed. FTIR indicated that strong chemical absorption occurred between TAC and PMN-PZT powder, and slurry stability and rheological properties of PMN-PZT slurry were improved through electrostatic interaction of TAC. The effects of TAC on sedimentation volume and viscosity have similar tendency. When TAC content was 7.5vol% and pH of slurry was about10, PMN-PZT slurry suitable for gel-casting could be acquired.

Abstract: The corrosion behavior of six refractory materials in molten salts for magnesium electrolysis was studied. Experimental results showed that porous clay brick was the most suitable lining material for magnesium electrolytic cell.