Ping Feng

The dielectric and tunable properties of Mn doped (Ba0.6Sr0.4)0.925K0.075TiO3 thin films fabricated by sol-gel method

(Ba0.6Sr0.4)92.5%K7.5%TiO3 (BSKT) thin films doped by Mn from 0 to 6 mol % were fabricated by the sol-gel method on a Pt/TiO2/SiO2/Si substrate. The structure and surface morphology of Mn-doped BSKT thin films were investigated as a function of Mn concentration by x-ray diffraction and scanning electron microscopy. The dielectric measurements were conducted on metal-insulator-metal capacitors at the frequency from 100 Hz to 1 MHz at room temperature. It was found that the Mn concentration in Mn doped BSKT thin films has a strong influence on material properties including surface morphology and dielectric and tunable properties. Increasing Mn content leads to simultaneous decreasing of surface roughness, dielectric constant, and tunability of Mn doped BSKT films. However the dielectric loss of Mn doped BSKT decreases first and then increases with the increase in Mn dopant. The effects of Mn doping on the microstructure and dielectric and tunable properties of Mn doped BSKT thin films were analyzed. (Ba0.6S...

Effect of TiN Addition on the Microstructure and Mechanical Properties of Ti(C, N)-Based Cermets

The effect of titanium nitride addition on the microstructure, porosity and mechanical properties of Ti(C, N)-based cermets were investigated in this work. Results show that cermets have typical core-rim microstructure, the grain size of hard phase refines and the porosity increases with the addition of titanium nitride content. The transverse rupture strength reaches maximum at about 15wt.% titanium nitride. The hardness declines with the incremental titanium nitride content.

Tribological Behavior of Ti(C, N)-Based and Functionally Gradient Ti(C, N)-Based Cermets

Ti(C, N)-based cermet and functionally gradient Ti(C, N)-based cermet were prepared by vacuum sintering and post surface heat-treatment in nitrogen, respectively. Tribological behaviors of obtained cermets were comparatively studied. Dry sliding wear and cutting test were conducted against quenched medium carbon steel. It was found that a graded structure formed and the surface hardness of functionally gradient Ti(C, N)-based cermet was improved. Friction coefficients of both cermets decreased with the increase of the sliding speed. The friction coefficient of Ti(C, N)-based cermet was lower than that of functionally gradient Ti(C, N)-based cermet at the conditions of higher sliding speed and higher load. The cutting test demonstrated that Ti(C, N)-based cermet exhibited better cutting performance and higher wear resistance than the cemented carbide YT15, cermet TN20 and functionally gradient Ti(C, N)-based cermet, while the functionally gradient Ti(C, N)-based cermet exhibited a similar performance as YT15 and TN20.

Research on Effect of Cr3C2 Addition on Microstructure and Mechanical Properties of Ti(C,N)-Based Cermets

Four Ti (C,N)-based cermets with Cr3C2 content of 0.3%, 0.6%, 0.9% and 1.2 % in mass ratio were sintered in vacuum at 1430oC, 1450oC, 1465oC and 1480oC. The mechanical properties of the specimens were determinted and microstructures were observed using the scanning electron microscope (SEM) to study the effect of Cr3C2 content on mechanical properties and microstructure. The results show that the four Ti (C,N)-based cermets sintered at 1465oC have the best overall mechanical properties; and among them, the cermet with 0.6% Cr3C2 has the best overall mechanical properties, i.e. transverse rupture strength (TRS) 1967MPa, hardness 1556HV and fracture toughness (KIC) 9.5MPa.m1/2. With the increase of Cr3C2 content, the black core volume fraction firstly increases and then decreases, the white core decreases in a progressive and continuous manner, the rim phase firstly increases and then decreases, the binder phase firstly decreases and then increases.

Effect of Carbon Content on Microstructure, Mechanical Properties and Wear Resistance of Ti(C,N)-Based Cermets

Ti(C,N)-based cermets with three carbon contents are prepared by sintering in vacuum. The effects of carbon content on the microstructure, mechanical properties and wear resistance of Ti(C,N)-based cermets were investigated. The results show that the grains refine gradually and the hard phase core becomes smaller when the carbon contents increases. The mechanical properties closely relates to the carbon content. With the increase of carbon content, the furrows created by grains cutting are getting narrower and more intensive. When the carbon content reaches 0.8%, a large quantity of wear debris bonding blocks are attached on the wearing surface. In this condition, the Ti(C,N)-based cermets are of the minimum wear weight loss and the best comprehensive mechanical property.

Colloidal Dispersion of High Solid Loading ZnO Powders with 2 wt% Al2O3 Stabilized with Polyelectrolyte

The high solid loading slurries with ZnO-Al2O3 powders stabilized with polyelectrolytes have been studied. The influence of Sodium poly(acrylate) (PA 30) on the fluidity and stablility of the slurries was investigated. Morphological features of ZnO-Al2O3 powders in suspension and fracture surface of green compact were observed using TEM and SEM. The slurries with pH 9 were prepared after milled using ZnO mixed powders and the PA 30 solution of pH 8. As 0.2 wt% PA 30 added, the lowest viscosity and the highest sediment were obtained. ZnO and Al2O3 particles had been homogeneous dispersed. The maximum density (66.7 %TD) of green compact was obtained.

The Maximum Solid Loading and Viscosity Estimation of Ultra-Fine ZnO-Al2O3 Mixed Powders Aqueous Suspensions

The rheological behavior of sub-micron zinc oxide and alumina mixture powders aqueous suspension has been investigated over a wide range of volumetric solids loading (Ø = 0.2–0.55), in which polyacrylic acid (PAA) was used as a dispersant. The dependence of relative viscosity (ηr)–solids loading (Ø) determined experimentally was compared with models. The experimental results showed that the suspension apparent viscosity (η) reached a minimum as the dispersant addition reached 0.2 wt%, the viscosity increased with the solids loading and the rheological behavior of the suspension was content basically with the model proposed by Liu. From ηr–Ø relationship the maximum solid loading (Øm) was estimated to be 0.55, which was in accord with our experimental results.

Effect of Pressure of Nitrogen Atmosphere on Microstructure and Mechanical Properties of Ti(C, N)–12WC–16Ni–4Mo2C Cermet

The effect of sintering atmosphere and nitrogen pressure on microstructure of Ti(C, N)–12WC–16Ni–4Mo2C cermet were investigated by scanning electron microscopy (SEM) and optical microscopy (OM), the transverse rupture strength (TRS), porosities, volume fractions of phases and grain sizes were determined. Results show that nitrogen pressure has a significant impact on TRS, appropriate nitrogen pressure could improve TRS. Vacuum sintering promotes the densification of sintered body, however, nitrogen atmosphere sintering could gain maximal TRS. Nitrogen atmosphere sintering facilitates the formation of inner rim phase and reduces the dissolution of TiC and TiN, small grain size is gained.

Effect of Mo2C Content on Microstructure and Composition of Ti(C,N)-Based Cermets Mixing in Water

Element Mo plays a significant role in Ti(C,N)-based cermets. In this work, mixing was carried out in water and cermets with high mechanical properties were fabricated. The effect of Mo2C content on microstructure and composition was investigated by field emission scanning electron microscope (FSEM) and energy dispersive spectrometer (EDS). Results showed that microstructure becomes uniformly distributed, binder distribution becomes symmetrical and the particle size becomes small with increase of Mo2C content. The volume fraction of (outer + inner) rim structure increases, the volume fractions of core structure and binder phase decrease instead. It was found that Mo2C content in raw material affects compositions in phases. With the level of Mo2C content rising, the concentration of element Mo in rim structure increases, the concentration of element Ti in binder decreases.

Dispersibility of Nano TiN Powder in Ethanol Liquid

Effect of pH value and dispersant of polyethylene imine (PEI) on dispersion of nano TiN in ethanol liquid was investigated by sedimentation volume and viscosity, surface electric characteristic of particles was measured by Zeta potential. Results showed that pH value and PEI concentration had an important effect on dispersion of nano TiN. Excellent dispersibility was obtained through adjusting PEI amount and pH value. It was found that PEI was an efficient dispersant for nano TiN to disperse in ethanol liquid. The dispersibility follows by electrostatic and space steric stability mechanism.