Strength Improvement in Transformation Toughened Ceramics using Compressive Residual Surface Stresses

1986 ◽  
Vol 78 ◽  
Author(s):  
R. A. Cutler ◽  
J. J. Hansen ◽  
A. V. Virkar ◽  
D. K. Shetty ◽  
R. C. Winterton
Keyword(s):  
Room Temperature ◽  
Sintering Temperature ◽  
Strain Gages ◽  
X Ray Diffraction ◽  
Stabilized Zirconia ◽  
X Ray ◽  
Apparent Fracture Toughness ◽  
Compressive Stresses ◽  
Flexural Tests ◽  
Strength Improvement

ABSTRACTA1 2 03–15 vol. % ZrO2 bar shaped composite specimens were fabricated by pressing three layers. The two outer layers consisted of Al2O3 and unstabilized ZrO2 (primarily in the monoclinic polymorph), and the inner layer consisted of Al2O3 and partially stabilized zirconia in the tetragonal polymorph. The transformation of ZrO2 from tetragonal to monoclinic, upon cooling from sintering temperature, led to the establishment of residual compressive stresses in the outer layers. Flexural tests at room temperature showed that residual stresses contributed to strength increasing from 450 to 825 MPa. The existence of these stresses was verified by measuring apparent fracture toughness, as well as using strain gages. Strength and toughness data were obtained at 500, 750, and 1000°C. X-ray diffraction was used to explain the elevated temperature data by monitoring the monoclinic to tetragonal transformation upon heating to 1000°C.

scholarly journals Equimolar Yttria-Stabilized Zirconia and Samaria-Doped Ceria Solid Solutions

Ceramics ◽  
2018 ◽  
Vol 1 (2) ◽  
pp. 343-352 ◽  
Author(s):  
Reginaldo Muccillo ◽  
Daniel de Florio ◽  
Eliana Muccillo
Keyword(s):  
Tetragonal Phase ◽  
Room Temperature ◽  
Single Phase ◽  
Rietveld Analysis ◽  
X Ray Diffraction ◽  
Ceramic Powders ◽  
Stabilized Zirconia ◽  
X Ray ◽  
Ceria Solid Solutions ◽  
Attrition Milling

Compositions of (ZrO2)0.92(Y2O3)0.08 (zirconia: 8 mol % yttria—8YSZ) and (CeO2)0.8(Sm2O3)0.2 (ceria: 20 mol % samaria—SDC20) ceramic powders were prepared by attrition milling to form an equimolar powder mixture, followed by uniaxial and isostatic pressing. The pellets were quenched to room temperature from 1200 °C, 1300 °C, 1400 °C and 1500 °C to freeze the defects configuration attained at those temperatures. X-ray diffraction analyses, performed in all quenched pellets, show the evolution of the two (8YSZ and SDC20) cubic fluorite structural phases to a single phase at 1500 °C, identified by Rietveld analysis as a tetragonal phase. Impedance spectroscopy analyses were carried out in pellets either quenched or slowly cooled from 1500 °C. Heating the quenched pellets to 1000 °C decreases the electrical resistivity while it increases in the slowly cooled pellets; the decrease is ascribed to annealing of defects created by lattice micro-tensions during quenching while the increase to partial destabilization of the tetragonal phase.

scholarly journals Improved Flame-Retardant and Ceramifiable Properties of EVA Composites by Combination of Ammonium Polyphosphate and Aluminum Hydroxide

Polymers ◽  
2019 ◽  
Vol 11 (1) ◽  
pp. 125 ◽  
Author(s):  
Feipeng Lou ◽  
Kai Wu ◽  
Quan Wang ◽  
Zhongyu Qian ◽  
Shijuan Li ◽  
...  
Keyword(s):  
Flame Retardant ◽  
Aluminum Hydroxide ◽  
Sintering Temperature ◽  
Ethylene Vinyl Acetate ◽  
Ammonium Polyphosphate ◽  
X Ray Diffraction ◽  
X Ray ◽  
Melt Compounding ◽  
Alumina Trihydrate ◽  
Strength Improvement

Ceramifiable flame-retardant ethylene-vinyl acetate (EVA) copolymer composites for wire and cable sheathing materials were prepared through melt compounding with ammonium polyphosphate (APP), aluminum hydroxide (ATH) and fluorophlogopite mica as the addition agents. The effects of ammonium polyphosphate, alumina trihydrate, and APP/ATH hybrid on the flame retardant, as well as on the thermal and ceramifiable properties of EVA composites, were investigated. The results demonstrated that the composites with the ratio of APP:ATH = 1:1 displayed the best flame retardancy and the greatest char residues among the various EVA composites. The tensile strength of the composites was 6.8 MPa, and the residue strength sintered at 1000 °C reached 5.2 MPa. The effect of sintering temperature on the ceramifiable properties, microstructures, and crystalline phases of the sintered specimen was subsequently investigated through X-ray diffraction, Fourier transform infrared, and scanning electron microscopy. The XRD and FTIR results demonstrated that the crystal structure of mica was disintegrated, while magnesium orthophosphate (Mg3(PO4)2) was simultaneously produced at an elevated temperature, indicating that the ceramization of EVA composites had occurred. The SEM results demonstrated that a more continuous and compact microstructure was produced with the rise in the sintering temperature. This contributed to the flexural strength improvement of the ceramics.

PHASE STRUCTURE, PIEZOELECTRIC AND MULTIFERRIOC BEHAVIOR OF (K0.48Na0.52)NbO3-Co2O3 PIEZOELECTRIC CERAMICS

2011 ◽  
Vol 04 (03) ◽  
pp. 225-229 ◽  
Author(s):  
WENJUAN WU ◽  
DINGQUAN XIAO ◽  
JIAGANG WU ◽  
JING LI ◽  
JIANGUO ZHU
Keyword(s):  
Room Temperature ◽  
Sintering Temperature ◽  
Magnetic Behavior ◽  
Orthorhombic Phase ◽  
Piezoelectric Ceramics ◽  
X Ray Diffraction ◽  
Two Phase ◽  
X Ray ◽  
Solid State Sintering ◽  
Sintering Method

( K 0.48 Na 0.52) NbO 3-x% Co 2 O 3 (x = 0, 0.03 and 0.05) (KNN-x% Co2O3 ) lead-free piezoelectric ceramics were prepared by the conventional solid-state sintering method. An orthorhombic phase was observed for all KNN-x% Co2O3 ceramics at room temperature, and two phase transitions were confirmed by the high temperature X-ray diffraction and the temperature dependence of the dielectric constant. The Co2O3 greatly improves the density and decreases the sintering temperature of KNN ceramics. The KNN-0.05 mol%Co2O3 ceramic exhibits good properties (d33 = 120 pC/N , k p = 0.41, Q m = 213 and T c = 407°C) and a good age stability. The multiferroic behavior was also observed at room temperature for the KNN-0.05 mol%Co2O3 ceramic, as confirmed by P–E loops and magnetic behavior.

Effect of Sintering Temperature on Structure and Dielectric Properties of BZN Ceramics

2012 ◽  
Vol 512-515 ◽  
pp. 1203-1206
Author(s):  
Yun Hui Xu ◽  
Xiao Hong Zhu ◽  
Qiang Zhang ◽  
Jian Guo Zhu ◽  
Ding Quan Xiao
Keyword(s):  
Dielectric Properties ◽  
Loss Tangent ◽  
Room Temperature ◽  
Sintering Temperature ◽  
Microwave Frequency ◽  
Fabrication Technology ◽  
X Ray Diffraction ◽  
X Ray ◽  
Dielectric Constant And Loss ◽  
Different Temperatures

Bismuth zinc niobate [(Bi1.5Zn0.5)(Nb1.5Zn0.5)O7, abbreviated as BZN] ceramics are receiving increasing attention due to their excellent dielectric properties in the microwave frequency range. This work is aimed at improving the fabrication technology of BZN ceramics. BZN ceramic specimens were prepared using the general electronic ceramic technique including milling, calcining, crushing, pressing, and sintering. Different sintering temperatures in the range of 950-1080°C were used to study how sintering temperature affects the structure and dielectric properties of BZN ceramics. The crystallinity and microstructure of the BZN ceramics, which were measured respectively by X-ray diffraction and scanning electron microscopy, were improved with increasing of the sintering temperature. The frequency dependence of the dielectric constant and loss tangent was measured at room temperature from 1 kHz to 1 MHz. The dielectric properties of the specimen sintered at 1050°C were found to be the best, for which the relative permittivity (εr) and the loss tangent (tanδ) are around 146 and 0.005, respectively. It was also foεund that when the sintering temperature was higher than 1000°C, the εrand the tanδ of BZN ceramics sintered at different temperatures were similar. As a result, 1000°C may be an appropriate sintering temperature for BZN ceramics.

Effects of 0.03MF2 – 0.12LiF (M = Ca, Sr, Ba) on the Sintering and Dielectric Properties of SrTiO3 Ceramics

2013 ◽  
Vol 9 ◽  
pp. 1-12
Author(s):  
Laldja Taïbi-Benziada ◽  
Hassiba Kermoun ◽  
Yasmina Belaroussi
Keyword(s):  
Room Temperature ◽  
Single Phase ◽  
Sintering Temperature ◽  
Cubic Phase ◽  
Frequency Range ◽  
X Ray Diffraction ◽  
X Ray ◽  
Frequency Independent ◽  
Cold Pressed ◽  
Piezoelectric Devices

Cold-pressed pellets were prepared from the mixtures SrTiO3- 0.03MF2- 0.12LiF, M = Ca, Sr or Ba, then air-fired at 950 °C for 2 hours. The obtained samples were investigated by X-ray diffraction and scanning electron microscopy. Each ceramic is a perovskite single phase and the relative density reaches 95% for all ceramics. The addition of 3 mol. % of the eutectic composition 1MF2- 4LiF (Tm~ 760 °C) to SrTiO3lowers the sintering temperature of pure strontium titanate from 1400 °C to 950 °C and induces a strong modification in the SrTiO3cubic phase: superlattice reflections are detected and the unit cell symmetry becomes orthorhombic. Dielectric measurements were performed between - 150 °C and 200 °C in the frequency range 20 Hz - 109Hz. The dielectric permittivity εrshowed no maximum in the temperature range investigated and is almost frequency independent. At room temperature, the dielectric losses tanδ are less than 0.1 %. Moreover, the frequency dependence of the complex permittivity exhibits a resonance in the microwave region. These fluorinated ceramics could be of interest in piezoelectric devices and are promising dielectrics for class I capacitors manufactured at low temperature.

The Effect of Milling Time and Sintering Temperature on Synthesis of PbTiO3 by Mechanical Alloying

2015 ◽  
Vol 1123 ◽  
pp. 109-113
Author(s):  
Rindang Fajarin ◽  
Hariyati Purwaningsih ◽  
Febri Nugroho
Keyword(s):  
Mechanical Alloying ◽  
Room Temperature ◽  
Milling Time ◽  
Sintering Temperature ◽  
Milling Process ◽  
X Ray Diffraction ◽  
Test Device ◽  
Test Analysis ◽  
X Ray ◽  
Multilayer Actuator

PbTiO3is one of electroceramic materials which can be applied for electronics and microelectronics due to their dielectric, pyroelectric, and piezoelectric properties. The members of PbTiO3-based ferroelectrics are widely used in multilayer, actuator and sensor capacitor. At room temperature, PbTiO3has a tetragonal perovskite structure. In this research, PbTiO3particles are synthesized by mechanical alloying method with variation of milling time and sintering temperature. The milling time variation is taken for 10, 20 and 30 hours. Sintering temperature variation is performed at 850, 900 and 1000°C. The powders used in the milling process are PbO and TiO2powders. X-Ray Diffraction (XRD) and Scanning Electron Microscopy–Electron Difraction X-ray (SEM-EDX) are performed to analyze the formation of PbTiO3phase. It is found that the synthesized powders contain 100% PbTiO3phase for all sintering temperatures. The PbTiO3particles have agglomeration shape with a broad particle size. The electrical properties of PbTiO3are measured using electrical test device. Electricity test analysis shows that the synthesized PbTiO3behaves as semiconductor-like.

Effect of processing parameters on the characteristics of high-Tc superconductor YBa2Cu3Oy

1988 ◽  
Vol 3 (6) ◽  
pp. 1304-1310 ◽  
Author(s):  
Narottam P. Bansal
Keyword(s):  
Room Temperature ◽  
High Temperature Superconductor ◽  
Sintering Temperature ◽  
Processing Parameters ◽  
Room Temperature Resistivity ◽  
Transition Width ◽  
X Ray Diffraction ◽  
High Tc ◽  
X Ray ◽  
Temperature Resistivity

The influence of sintering temperature, sintering and annealing atmospheres, and quench rate on the properties of the high-temperature superconductor YBa2Cu3Oy has been investigated by electrical resistivity and magnetic susceptibility measurements, thermogravimetric analysis, powder x-ray diffraction, and scanning electron microscopy. Room-temperature resistivity and the transition width decreased, and the fraction of the superconducting material and the bulk density increased with increase in the sintering temperature, but had no effect on the transition temperature (Tc) for samples fired in flowing oxygen. A sample that was rapidly quenched from 930 °C to room temperature after sintering in air had a perovskite structure and Tc (onset) ∼90 K but its resistance did not become zero even at 77 K. A sample sintered in air at 930 °C and furnace cooled had Tc (midpoint) of ∼89.6 K and transition width (10%–90%) of ∼2.6 K. The loss and gain of oxygen occurs reversibly in YBa2Cu3Oy.

Synthesis and Characterization of Nickel Manganite Ceramics by Polymeric Precursors Method

2016 ◽  
Vol 881 ◽  
pp. 123-127 ◽  
Author(s):  
A.C.B. de Oliveira ◽  
D.M.S. Ribeiro ◽  
C.G.P. Moraes ◽  
R.S. Silva ◽  
Nilson Santos Ferreira ◽  
...  
Keyword(s):  
Room Temperature ◽  
Sintering Temperature ◽  
Synthesis And Characterization ◽  
X Ray Diffraction ◽  
Temperature Dependent ◽  
Precursor Method ◽  
Spinel Type ◽  
X Ray ◽  
Lower Resistivity

This work presents the synthesis and characterization of NTC ceramic (Negative coefficient Temperature) based on nickel manganite (NiMn2O4) produced by the polymeric precursor method. NiMn2O4 were sintered at 900-1200 °C during 3h to produce the ceramics samples. The effect of sintering temperature on microstructure and electric properties of the NiMn2O4 ceramics was studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and temperature dependent resistance R(T) measurements. The XRD measurement indicated formation of cubic spinel-type structure of NiMn2O4. The crystallite size (as confirmed by XRD) and the particle size (as confirmed by SEM) increased as the sintering temperature increased from around 18nm (900 °C) to 100nm (1200 °C). All samples showed NTC behavior and, among the studied ceramics, that one sintered at 1200 °C showed lower resistivity value (~103Ω.cm) at room temperature.

Study of the Sintering Dental Ceramic Waste from ZrO2-Y2O3 System

2016 ◽  
Vol 881 ◽  
pp. 392-397 ◽  
Author(s):  
L.B. Silva ◽  
Wilson Acchar ◽  
Vamberto Monteiro Silva
Keyword(s):  
Sintering Temperature ◽  
High Strength ◽  
Raw Material ◽  
X Ray Diffraction ◽  
Stabilized Zirconia ◽  
Cost Of Treatment ◽  
X Ray ◽  
Zirconia Nanoparticle ◽  
Materials Used ◽  
Financial Losses

During processing of zirconia blocks, where they are used for different dental implants type, most of the loosed material as a powder is subsequently discarded. Besides damage to the environment, waste of material results in financial losses, resulting in higher final cost of treatment. The yttria stabilized zirconia (Y-TZP) has a variety of applications due to it is combination of high strength and fracture toughness. The objective was to reuse zirconia waste analyzing the effects of sintering temperature. The starting materials used in this study were two different powders of ceramic system ZrO3-Y2O3: commercial zirconia nanoparticle and microparticle zirconia waste. The raw material was shaped by uniaxial and isostatic pressing and then sintered at 1500, 1550 and 1600 ° C over 1 hour. The X-ray diffraction (XRD) and dilatometry were used to powder characterization. After sintering density / porosity, flexural strength, and scanning electron microscopy (SEM) were realized .The waste showed similar values of density, and grain size to commercial material studied, confirming that it can be reused.

scholarly journals Preparation, Microstructure and Electrical Conductivity of LATP/LB Glass Ceramic Solid Electrolytes

2021 ◽  
Vol 2101 (1) ◽  
pp. 012081
Author(s):  
Jiajia Luo ◽  
Yang Zhong ◽  
Guohua Chen
Keyword(s):  
Glass Ceramic ◽  
Solid Electrolytes ◽  
Room Temperature ◽  
Sintering Temperature ◽  
Glass Ceramics ◽  
Lithium Ion ◽  
X Ray Diffraction ◽  
Ac Impedance Spectroscopy ◽  
X Ray ◽  
Grain Sizes

Abstract The Li2O-Al2O3-TiO2-P2O5 system glass ceramic solid electrolytes were prepared by adding Li3BO3 (LB) frits. The phase composition, microstructure and electrical properties of glass ceramics were investigated by using X-ray diffraction, scanning electron microscopy and AC impedance spectroscopy. The results show that the principal crystalline phase of all glass ceramic samples was LiTi2(PO4)3. The grain sizes of glass ceramic sample increase with the increase of sintering temperature. When the additive amount of LB is 1wt %, the glass ceramic solid electrolyte sintered at 950 oC shows the highest room-temperature ionic conductivity of 1.9×10−4 S.cm−1, which can be expected to be used in solid-state lithium-ion batteries.

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