Qi Bin Liu

Microstructure and Properties of MoFeCrTiW High-Entropy Alloy Coating Prepared by Laser Cladding

To obtain high-entropy alloys (HEAS) coating with excellent properties on Q235 steel, a kind of HEAS powders was designed. The HEAS coating was prepared uniformly on Q235 steel by laser cladding. By means of OM, XRD and microhardness tester, the microstructure and properties of the high-entropy alloy layer were investigated. The experimental results indicate that the phases in the high-entropy alloy coating is mainly MoFeCrTiW with simple BCC, whose lattice parameter is a-3.1256Å. The microstructure in the coating is mainly cellular crystal, on which dispersion precipitates exist. And in the near bottom of the coating, there is few precipitates, in the middle part of coating, the precipitates are larger than that of bottom coating, while in near top of coating, dispersion precipitates become largest. The maximum microhardness value of coating reaches 800HV0.98.

Effect of Sintering Temperature on Microstructure and Electrical Properties of (1-x)BCZT-xBY Lead-Free Ceramics

Lead-free 0.996(Ba0.85Ca0.15)(Zr0.1Ti0.9)O3-0.004BiYO3 [BCZT-BY] ceramics were prepared by the conventional solid-state sintering method. By means of XRD, SEM, and quasi-static d33 meter etc., the effect of sintering temperature on the microstructure, piezoelectric and dielectric properties of BCZT-BY ceramics were investigated. All the ceramics possess a pure perovskite structure, indicating that Bi3+ and Y3+ are incorporated into Ba0.85Ca0.15Ti0.9Zr0.1O3 lattices to form a solid solution. The results show that the ceramics sintered at 1420°C exhibit the optimum electrical properties: d33 = 130 pC/N, kp = 18.2 %, εr = 4225, and tan δ = 1.95%, respectively.

Effect of Sintering Temperature on Microstructure and Electrical Properties of (Mn, Nb)-Doped BZT-BCT Ceramics

To obtain lead-free 0.5Ba (Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 ceramics with excellent microstructure and electrical properties, BZT-BCT ceramics doping Mn4+ and Nb5+ was synthesized follow a conventional solid state reaction route. By means of SEM, XRD, quasi-static d33 meter, the influence of sintering temperature on microstructure, piezoelectric and dielectric properties of BZT-BCT-Mn-Nb ceramics was discussed. The results show that grain size and the dielectric loss of BZT-BCT-Mn-Nb ceramics increase as raising the sintering temperature. When BZT-BCT-Mn-Nb ceramics is sintered at 1380°C, the optimum piezoelectric coefficient and dielectric constant are 264pC/N and 4142, respectively.

Effect of Technological Parameters on the Microstructure and Electrical Properties of ZnO Varistors

To improve voltage-gradient and to reduce the sintering temperature of ZnO varistors, high voltage-gradient ZnO varistors were synthesized with a conventional solid state reaction route. By means of SEM and DC parameter instrument for varistor, the influence of different technological parameters on microstructure, voltage-gradient and leakage current of ZnO varistors was investigated. The experimental results show that by using the process that presintering the additives at 850°C, the density is improved, the voltage-gradient is increased, and the leakage current is decreased. The optimum voltage-gradient and leakage current are 371V/mm and 3μA, respectively.

The Bioactivity of Gradient Composite Bioceramic Coating with La2O3 Fabricated by Wide Band Laser Cladding

To improve the quality of bioceramic gradient coatings, wide band laser cladding technique was adopted to produce a kind of gradient composite bioceramic coating, which combines the good biocompatibility of HA and β-TCP with good toughness and strength of TC4 alloy. The rare earths oxide La2O3 was added to improve the properties of the bioceramic coating. The results indicate that when the adding of La2O3 is 0.6wt%, the ceramics coating is of the largest amount of HA and β-TCP catalyzed, and the number of cells proliferated and the ALP secreted on coatings is the biggest, which indicates that the biocompatibility and bioactivity of gradient bioceramic coating is the best. The biocompatibility and bioactivity are closely related to the amount of HA and β-TCP catalyzed by La2O3.

The Bioactivity of Gradient Composite Bioceramic Coating with Different Contents of Multiple Rare Earth Deoxide Fabricated by Wide Band Laser Cladding

To improve bonding strength between titanium alloy and coating and to eliminate thermal stress during laser cladding, a gradient coating materials is designed. And the gradient coating with different contents of multiple rare earth deoxide was produced by wide band laser cladding technique. The experimental results indicate that when addition of Sm2O3 is fixed to 0.3wt.%, as addition of Y2O3 increases, the microstructure of bioceramic is different. When addition of Y2O3 reaches 0.4wt.%, the amount of Ca-P based bioactive phases such as HA, α-TCP as well as β-TCP becomes biggest. After soaking the coating with 0.3wt.% Sm2O3 and 0.4wt.% Y2O3 in SBF for 14 days, a large amount of Ca-P white spherical particles can be observed on coating, which demonstrates the bioceramic coating is of best bioactivity.

Effect of Sintering Temperature on Electrical Properties of ZnO Varistor Ceramics

To obtain ZnO varistors with high voltage gradient, ZnO varistors were fabricated by traditional ceramic sintering technique, the effect of different sintering temperature (1135～1155 °C) on electrical properties of ZnO varistors were investigated. The experimental results show that with increasement of sintering temperature, the grain size of ZnO varistor ceramic becomes bigger, the voltage gradient of varistor decreases and the density is improved. When the sintering temperature is at 1135 °C, the voltage gradient of varistor is up to 329V/mm, the leakage current is 8μA and the density is 96.4%. When the sintering temperature is at 1140 °C, the voltage gradient of varistor is 301V/mm, the leakage current is 4μA and the density is 96.6%. Compared the results at 1135 °C with 1140 °C , it is found that the comprehensive electrical properties of ZnO varistors reach maximum at 1140 °C.

Effect of Y2O3 on Room Resistivity of Honeycomb Ceramics

To improve the room resistivity, 96MgAl2O4-2SiO2-2TiO2 honeycomb ceramic doped with different Y2O3 contents was fabricated by technique of raditional solid phase sintering. The microstructure and room resistivity of the samples were nvestigated by SEM and portable pH/Cond 3400i resistivity tester. The results show that as the amount of the Y2O3 increases, room resistivity of the samples decreases gradually. When Y2O3 content is up to 0.06mol%, the resistivity becomes minimum with 5.5×101Ω•m. When Y2O3 content is up to 0.10mol%, the resistivity conversely increases.

Electrical Degradation Induced Formations of Current Transients in Lead Zirconate Titanate

Nowadays, the piezoelectric materials are widely used in many areas. The piezoelectric materials will undergo an electrical degradation process during working causes the piezoelectricity and resistance of the piezoelectric materials degrade. The existence of the electrical degradation phenomenon severely limits the applications of the piezoelectric products. During the electrical degradation process, electrical breakdown often occurs and this electrical breakdown has been proposed [1, 2] induces the resistance decrease and local phase changing. In this paper, the electrical breakdown induced current transients are detailed investigated. Three types of current transients are presented and the time durations of current transients are suggested not constant and corresponding to the time duration of the local burn-out process, which is caused by the heat released from the electrical breakdown process.

Study on Microstructure and Electrical Properties of ZnO Varistor Ceramics

To obtain ZnO varistors with high voltage gradient, ZnO varistors were fabricated by traditional ceramic sintering technique, which were sintered from 1135 to 1155 °C, the microstructure and properties of varistors were characterized by SEM, X-rays diffraction and DC parameter instrument for varistors. The experimental results show that the spinel phase Zn7Sb2O12 generated during sintering process, very thin amorphous Bi rich films are formed between the ZnO/ZnO grain boundaries, with increasement of sintering temperature, the grain size of ZnO varistor ceramic becomes bigger, the voltage gradient of varistor decreases and the density is improved. The optimized parameters are that when the sintering temperature is at 1140 °C, the voltage gradient of varistor is 301V/mm, the leakage current is 4μA and the density is 96.6%, the comprehensive electrical properties of ZnO varistors reach maximum.