Effects of Interlayer Composition on Bond Strength and Interfacial Microstructure of Green Joined CePO_4-ZrO_2 Ceramics

Effects of interlayer composition on bonding strength and interfacial microstructure of green joined CePO_4-ZrO_2 ceramics were studied. Green bodies of 25%CePO_4/ZrO_2 and ZrO_2 ceramics were joined by using interlayer composed of CePO_4 and ZrO_2 at 1450 ℃ for 120 min without applied pressure.The effects of CePO_4/(CePO_4+ZrO_2) ratio on the bond strength of the joints were investigated. Under the experimental conditions, the grain size of the particles grown in the joint is smaller than those in joined ceramics. The microstructure of the joint is more homogeneous than that of the matrix and without obvious cracks, pores and other defects.

Dual-enhancement of chromaticity and thermal stability:In-situ synthesis of core-shell γ-Ce_(2)S_(3) @CePO_(4) configuration

Non-toxic rare earth(RE) composite materials are promising and active in optoelectronic fields,such as pigment.In this work,Na ions doped γ-Ce_(2) S_(3) pigments were synthesized by solid-phase vulcanization and followed by in-situ synthesis to prepare an outer layer of CePO_(4) film.The characterizations of X-ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM),X-ray photoelectron spectroscopy(XPS),solid state nuclear magnetic resonance(NMR) indicate that Na-dopedγ-Ce_(2) S_(3) and CePO_(4) uniformly and tightly coated core-shell structure was successfully synthesized.The thermogravimetric analysis(TG) and reflection spectrum(RS) reveal that the CePO_(4) coating significantly improves the colorant and thermal stability performance of γ-Ce_(2) S_(3) .The excellent color quality of γ-Ce_(2) S_(3) @CePO_(4)(L*=45.16,a*=55.94.b*=44.53) is achieved and the red color(L*=43.82,a*=49.79,b*=38.04) is still retained even if the sample is heated in air at 400℃ for 30 min.

Machinability evaluation of machinable ceramics with fuzzy theory

The property parameters and machining output parameters were selected for machinability evaluation of machinable ceramics. Based on fuzzy evaluation theory, two-stage fuzzy evaluation approach was applied to consider these parameters. Two-stage fuzzy comprehensive evaluation model was proposed to evaluate machinability of machinable ceramic materials. Ce-ZrO2/CePO4 composites were fabricated and machined for evaluation of machinable ceramics. Material removal rates and specific normal grinding forces were measured. The parameters concerned with machinability were selected as alternative set. Five grades were chosen for the machinability evaluation of machnable ceramics. Machinability grades of machinable ceramics were determined through fuzzy operation. Ductile marks are observed on Ce-ZrO2/CePO4 machined surface. Five prepared Ce-ZrO2/CePO4 composites are classified as three machinability grades according to the fuzzy comprehensive evaluation results. The machinability grades of Ce-ZrO2/CePO4 composites are concerned with CePO4 content.

Phosphorus fixation capacity of CaO-SiO_(2)-Al_(2)O_(3)-MnO-Ce_(2)O_(3) slag based on structural considerations

The phosphorus fixation capacity of some slag systems,such as Ce_(2)O_(3)-containing slag,has hardly been investigated from a thermodynamics view due to the lack of relevant thermodynamic data.Since the macroscopic properties are primarily determined by the microscopic structure,the correlation between phosphorus fixation capacity and slag structure was explored by spectroscopy(XPS),Raman spectroscopy,and ferromanganese dephosphorization experiments.The results show that the predominant species of P^(5+)are Q_(P)^(0)(PO_(4)^(3-))and Q_(P)^(1)(P_(2)O_(7)^(4-))units in the CaO^(-)SiO_(2)-Al_(2)O_(3)-MnO^(-)Ce_(2)O_(3)-P_(2)O_(5)quenched slag,and the phosphorus fixation capacity increases with the Q_(P)^(1)(P_(2)O_(7)^(4-))unit to Q_(P)^(0)(PO_(4)^(3-))unit transformation(the P-O^(0) bond to P-O^(-)bond transformation)since the electron cloud density between P and O atoms increases and the average radius of P-O bonds decreases.Especially,CaO or Ce_(2)O_(3) as a network modifier can release the O_(2)-and promote the P-O^(0) bond to P-O^(-)bond(connected to Ca^(2+),/Ce^(3+))transformation in the quenched slag.Furthermore,the phosphorus enrichment phases in the slow cooling slag are confirmed as nCa_(2)SiO_(3)-Ca_(3)P_(2)O_(8)(nC_(2)S-C3P)and CePO_(4) solid solutions by the scan electron microscopy(SEM),transmission electron microscopy(TEM),and energy-dispersive spectrometer(EDS)methods.The re sults show Ce_(2)O_(3) can depolymerize the polyphosphate structure partially replacing CaO after introducing Ce_(2)O_(3) into CaO based slag because of its strong ability to donate electrons.The above results not only help to understand the dependence of phosphorus fixation capacity on slag composition from a structural view,but also provide the theoretical guidance for optimizing the composition of Ce_(2)O_(3)-containing dephosphorization slag.

Effect of different acid anions on highly efficient Ce-based catalysts for selective catalytic reduction of NO with NH_(3)

Three kinds of Ce-based catalysts(CePO_(4),CeVO_(4),Ce_(2)(SO_(4))_(3))were synthesized and used for the selective catalytic reduction(SCR)of NO by NH_(3).NH_(3)-SCR performances were conducted in the temperature range of 80 to 400°C.The catalytic efficiencies of the three catalysts are as follow:CePO_(4)>CeVO_(4)>Ce_(2)(SO_(4))_(3),which is in agreement with their abilities of NH_(3)adsorption capacities.The highest NO conversion rate of CePO_(4)could reach about 95%,and the catalyst had more than 90%NO conversion rate between 260 and 320°C.The effect of PO_(4)^(3–),VO_(4)^(3–)and SO_(4)^(2–)on NH_(3)-SCR performances of Ce-based catalysts was systematically investigated by the X-ray photoelectron spectroscopy analysis,NH_(3)temperature programmed desorption,H2 temperature programmed reduction and field emission scanning electron microscopy tests.The key factors that can enhance the SCR are the existence of Ce4+,large NH_(3)adsorption capacity,high and early H2 consumptions,and suitable microstructures for gas adsorption.Finally,CePO_(4)and CeVO_(4)catalysts also exhibited relatively strong tolerance of SO2,and the upward trend about 8%was detected due to the sulfation enhancement by SO2 for Ce_(2)(SO_(4))3.