Sintering Temperature Range Research Articles

Microstructure and quality factor of Mg4Nb2O9 ceramics via B-site precursor method

Mg4Nb2O9 ceramics have been prepared by B-site precursor method in this work. Experimental results demonstrate that the uniform particles-size distribution of Mg4Nb2O9 powders can be obtained, which exhibit high reactivity to promote the grain growth of Mg4Nb2O9 ceramics. Moreover, the Mg4Nb2O9 ceramics via B-site precursor method can be sintered at a wide range of sintering temperature from 1275 to 1375 °C with single phase Mg4Nb2O9 composition and high crystallinity. Compared to the conventional solid-state method, the Mg4Nb2O9 ceramics prepared by B-site precursor method exhibit excellent Q × f value by above 168,756 GHz.

Crystal structure, Raman spectra and microwave dielectric properties of novel low-temperature cofired ceramic Li4GeO4

A low-permittivity and low-loss ceramic, Li4GeO4, was fabricated via solid state reaction route. XRD showed that a single orthorhombic Li4GeO4 phase with olivine structure was prepared over the sintering temperature range of 660–740 °C. Dense ceramic sintered at 720 °C revealed excellent microwave properties, with εr ~6.99, Q × f ~47,813 GHz (at 15.5 GHz), and τf ~ − 159.2 ppm/°C. The microwave dielectric performances were analyzed with the intrinsic characteristics of crystal structure by ionic polarizability and Raman spectra. Additionally, the Li4GeO4 ceramic showed good chemical compatibility with Ag sintered at 720 °C. In the low-temperature cofired ceramic (LTCC) application, aforesaid results manifested that Li4GeO4 ceramic was considered as a potential candidate.

The Concurrent Sintering-Crystallization Behavior of Fluoride-Containing Wollastonite Glass-Ceramics.

The fabrication of well densified wollastonite with smooth appearance by direct sintering method is still a challenge due to the competitive behaviors between sintering and crystallization. In this study, the coarser glass frits with a size of 1–4 mm are subjected to heat treatment at different temperatures. An attempt of integrating differential thermal analyzer with a slag melting temperature characteristic tester was exploited to monitor the heat and geometry changes during the heating. The results showed that the addition of CaF2 can significantly promote the crystallization of wollastonite at 940 °C, while hindering the sintering ability. At higher temperature, the increase of CaF2 acts as flux and favors the formation of eutectics, leading to a decline in the precipitation amount of wollastonite. The predominated liquid sintering brought fast shrinkage. It was found out that high content of CaF2 narrows the dense sintering temperature range and results in uneven surfaces. In order to obtain wollastonite glass-ceramics with smooth appearance, the maximum content of CaF2 in sintering glass-ceramics should be limited to 2 wt.%.

High-Performance Giant Dielectric Properties of Cr3+/Ta5+ Co-Doped TiO2 Ceramics.

The effects of the sintering temperature on microstructures, electrical properties, and dielectric response of 1%Cr3+/Ta5+ co-doped TiO2 (CrTTO) ceramics prepared using a solid-state reaction method were studied. The mean grain size increased with an increasing sintering temperature range of 1300–1500 °C. The dielectric permittivity of CrTTO ceramics sintered at 1300 °C was very low (ε′ ∼198). Interestingly, a low loss tangent (tanδ ∼0.03–0.06) and high ε′ (∼1.61–1.9 × 104) with a temperature coefficient less than ≤ ±15% in a temperature range of −60 to 150 °C were obtained. The results demonstrated a higher performance property of the acceptor Cr3+/donor Ta5+ co-doped TiO2 ceramics compared to the Ta5+-doped TiO2 and Cr3+-doped TiO2 ceramics. According to a first-principles study, high-performance giant dielectric properties (HPDPs) did not originate from electron-pinned defect dipoles. By impedance spectroscopy (IS), it was suggested that the giant dielectric response was induced by interfacial polarization at the internal interfaces rather than by the formation of complex defect dipoles. X-ray photoelectron spectroscopy (XPS) results confirmed the existence of Ti3+, resulting in the formation of semiconducting parts in the bulk ceramics. Low tanδ and excellent temperature stability were due to the high resistance of the insulating layers with a very high potential barrier of ∼2.0 eV.

Preparation of Alumina-Magnesia Spinel Based High-Porosity Ceramic Materials

The objects of investigation are foam ceramic materials based on aluminum oxide, magnesium oxide, and alumina-magnesia spinel. The results of investigations on the sintering of spinel ceramic using aluminum and magnesium oxides as the initial components are presented. It is shown that the optimal range of the sintering temperatures for obtaining materials with open-cellular pore structure is 1600 – 1700°C. Materials with interconnected porosity up to 85% and strength in compression up to 1.4 MPa were obtained.

A re-investigation: Effect of powder metallurgy parameters on the physical and mechanical properties of aluminium matrix composites

Abstract Aluminium matrix composites are the special class materials used in automobile, aerospace, nuclear, and packing industries. High demand for these materials is due to high electrical conductivity, high thermal conductivity, high strength, high wear resistance, high ductility, and excellent machinability. Stir casting, friction stir processing, and powder metallurgy are common techniques used for the fabrication of Aluminium matrix composites. Some of the advantages of the powder metallurgy technique such as, high material utilization, less power consumption, and less scrap, etc.; are the main reasons for the inclination of researchers towards the use of this technique for the fabrication of Aluminium matrix composites. The Powder metallurgy process parameters, i.e., compaction pressure, sintering temperature, and sintering time, highly influence the physical and mechanical properties of Aluminium matrix composites fabricated by powder metallurgy. The type and weight fraction of reinforcement also have a significant effect on the physical and mechanical properties of Aluminium matrix composites. In the present study, re-investigation has been done on the effect of the above parameters on the physical and mechanical properties of Aluminium matrix composites. During the literature survey, it was observed that, compaction pressure is the most influencing parameter. The Density and porosity can be controlled effectively by controlling the compaction pressure. For Aluminium-based materials fabricated by powder metallurgy, the optimum range of compaction pressure, sintering temperature, and sintering time is 600–700 MPa, 520–600 °C, and 3–4 h, respectively.

Магнитные и радиопоглощающие свойства поликристаллического феррита-шпинели Li-=SUB=-0.33-=/SUB=-Fe-=SUB=-2.29-=/SUB=-Zn-=SUB=-0.21-=/SUB=-Mn-=SUB=-0.17-=/SUB=-0-=SUB=-4-=/SUB=-

Polycrystalline spinel ferrites of the composition Li0.33Fe2.29Zn0.21Mn0.17O4 were synthesized by using the ceramic technology method at sintering temperatures of 950 ° C, 1000 ° C, 1050 ° C, and 1100 ° C. Magnetic hysteresis loops and magnetic permeability of the experimental samples were studied in the range of magnetic fields of -400–400 A/m. In the frequency range of 0.01–7.0 GHz, the behavior of the complex dielectric and complex magnetic permeability, as well as the reflection coefficient on a metal plate, are investigated. It was found that the optimal sintering temperature range for synthesized ferrites is from 1050 ° C to 1100 ° C. It is shown that the spinel ferrite Li0.33Fe2.29Zn0.21Mn0.17O4 intensely absorbs electromagnetic radiation in the frequency range from 0.05 to 7.0 GHz. Possibilities of practical application of the obtained results are discussed.

Preparation, structure and microwave dielectric properties of novel La2MgGeO6 ceramics with hexagonal structure and adjustment of its τf value

A novel La2MgGeO6 ceramic was synthesized through a solid-state reaction process within a sintering temperature range of 1450–1550 °C. By a combination of X-ray diffraction and Rietveld refinement analyses, the ceramics were found to have a pure hexagonal phase structure belonging to space group R3/146. The scanning electron microscopy images revealed that the ceramic grains were closely connected. The effects of internal (lattice energy, valence bond, and fraction packing) and external factors (density) on the microwave properties of ceramics were also studied. The ceramic exhibited excellent microwave dielectric performances, with a relative permittivity (Ɛr) of 21.2, a quality factor (Q × f) of 52 360 GHz, and a temperature coefficient of resonant frequency (τf) of −44.2 ppm/°C, when sintered at 1500 °C for 4 h. The τf value of the La2MgGeO6 ceramic doped with CaTiO3 could be adjusted to zero. Particularly, 0.2La2MgGeO6-0.8CaTiO3 ceramics have good microwave dielectric properties with τf = +2.1 ppm/°C, Q × f = 15 610 GHz, and Ɛr = 40.3.

Sintering Preparation of 15 wt% Cr Cast Iron as well as Its Mechanical Properties and Impact Abrasive Wear

15 wt% Cr sintered High Chromium Cast Iron (HCCI) with full density was successfully prepared by Super-solidus Liquid Phase Sintering (SPLS) technique, with water atomized 15 wt% Cr high chromium cast iron powder as initial materials. Its densification behavior and microstructure evolution in SPLS process and mechanical properties were investigated systematically. Additionally, the impact abrasive wear resistance under different impact energies were also analyzed and compared with another sintered HCCI with 20 wt% Cr. The results indicated that sintering temperature has a strong influence on the sintered alloy’s density, hardness, impact toughness and bending strength. The M7C3 type (M is Cr and Fe) carbides were obviously coarsened as temperature increased and their rod-shaped branches were fully developed at the same time, thereby resulting in carbide network formation in the matrix. The reasonable sintering temperature range was 1195–1205 °C, and the optimum mechanical properties had the hardness of 63.9 HRC, bending strength of 2112.65 MPa and impact toughness of 7.92 J/cm2. What is more important impact abrasive wear test results indicated 15 wt% Cr sintered HCCI’s wear resistance could be comparable to 20 wt% Cr sintered HCCI under impact energy 1~3 J/cm2, and it is more cost effective.

Mg or Zn for Ca substitution improves the sintering of bioglass 45S5

Bioglass 45S5 is well-known for its bioactivity, but it possesses poor sintering behaviour owing to viscous flow being inhibited by the crystallisation of sodium calcium silicate phases. Mg or Zn were partially (0, 25, 50, 75%) or fully (100%) substituted for Ca on a molar base, and thermal properties (differential scanning calorimetry, dilatometry) and sintering (heating microscopy, SEM and X-ray diffraction) were investigated. Here we show that sintering can be improved significantly by partial or complete substitution of Mg or Zn for Ca, owing to a pronounced decrease in crystallisation tendency. Glass transition temperature and dilatometric softening point went through minima for mixed compositions, with random mixing of Mg/Ca or Zn/Ca ions in the glass structure and the resulting effect on configurational entropy being a likely explanation. As the onset of crystallisation did not vary much with substitution, substituted glasses possessed a wider temperature range for sintering, resulting in up to 57% and 27% sample height reduction for Mg and Zn substituted glasses, respectively, compared to only 3% height reduction for Bioglass 45S5. Taken together, these results suggest that using a combination of modifiers, particularly alkaline earths or zinc, may be a promising approach for improving the sintering of Bioglass 45S5.

Sintering characteristics and microwave dielectric properties of a new temperature-stable ceramic of Ce0.5Sm0.5O1.75

The novel temperature-stable microwave dielectric ceramics of Ce0.5Sm0.5O1.75 were fabricated via the mixed oxide reaction method, with the detail information including crystal phase, microstructure, sintering behavior and microwave dielectric properties being systematically investigated. For crystal phase, all the diffraction patterns were indexed as cubic fluorite-type structure with Fm-3m (225) space group and exhibited a single phase with no obvious peak position shift. The grain growth was analyzed by density and average grain size. For microwave dielectric properties of Ce0.5Sm0.5O1.75 ceramics, the dielectric constant value (er) was dependent on density. The quality factors (Q × f values) were investigated considered with average grain size. And the temperature coefficient of resonant frequency (τf value) had no significant change during the sintering temperature range, which was found consistent with the trend of the dielectric constant value. The Ce0.5Sm0.5O1.75 ceramics sintered at 1475 °C for 4 h exhibited good microwave dielectric performances with er = 18.21, Q × f = 70,500 GHz, and τf = − 16.4 ppm/°C.

Effects of Li2CO3 and CuO as Composite Sintering Aids on the Structure, Piezoelectric Properties, and Temperature Stability of BiFeO3-BaTiO3 Ceramics

In order to reduce the sintering temperature of ceramics, the effects of binary composite sintering aids, Li2CO3 and CuO, on the sintering temperature and properties of 0.7BiFeO3-0.3BaTiO3-0.0035MnCO3 + 0.002Li2CO3 + xCuO (BF-BT-LC + xCuO) ceramics were studied by traditional solid-state sintering. The results show that the sintering liquid phase can effectively promote the sintering of BF-BT-LC + xCuO ceramics by adding a certain amount of Li2CO3 and changing the amount of CuO. The samples sintered at 930°C/2 h with 0.4 mol.% CuO get a piezoelectric constant d33 = 168 pC/N, an electromechanical coupling coefficient kp = 0.302, and a mechanical quality factor Qm = 31.207. The addition of CuO was conducive to obtaining stable BF-BT-LC + xCuO piezoelectric ceramics. We conclude that the composite sintering aids, Li2CO3 and CuO, can effectively promote the sintering of BF-BT-LC + xCuO, which is beneficial to obtain BF-BT-LC + xCuO ceramics with a wide sintering temperature range and stable properties.

Sintering Temperature Effect on the Luminescence Properties of Y2O3:Tb3+ Phosphors Synthesized using a Liquid-Phase Reaction

The photoluminescence properties of crystalline Y2O3:Tb3+ nanoparticles fabricated using a liquid-phase reaction have been examined over a certain sintering temperature range for dopant activation. X-Ray diffraction (XRD) and transmission electron microscopy (TEM) were used to examine the size and the morphology of Y2O3:Tb3+ particles and disclosed the cubic Bragg peaks of the Y2O3:Tb3+ particles regardless of the sintering temperature with no substantial peak shift. The maximum photoluminescence (PL) emission intensity was observed from the Y2O3:Tb3+ phosphors sintered at 400 °C. The photoluminescence excitation (PLE) spectra of the Y2O3:Tb3+ phosphors are composed of broad bands at ∼260 nm (∼4.7 eV) and shoulder bands at ∼306 nm (∼4.05 eV). The experimental results revealed that the particle size and the crystallinity of the Y2O3:Tb3+ phosphors played a critical role in the luminescence. Over the entire range of sintering temperatures, the room-temperature decay time was found to be ∼2.81 ms.

Low temperature synthesis of highly pure cordierite materials by spark plasma sintering nano-oxide powders

The development of cordierite ceramics, using traditional materials and conventional methods, remains a key challenge because of the high and narrow sintering temperature range. In this work, single-phase cordierite ceramics were produced by spark plasma sintering nano-oxide powders, at low temperatures. A starting mixture of Al2O3, SiO2, and MgO nano-powders with the composition of stoichiometric cordierite was first sonicated, then, sintered in the temperature range 900–1200 °C. The raw powders, sonicated powder mixture, phase transformations, and fracture surface of sintered specimens were characterized by using an x-ray diffractometer and a field emission scanning electron microscope (FE-SEM). The hardness and fracture toughness were measured using the indentation technique. The influence of testing conditions, process parameters, characterization technique, and calculation method on hardness and fracture toughness was investigated. The FE-SEM images, x-ray maps, and EDS results revealed the homogeneity and stoichiometry of the sonicated powder and sintered samples. Highly pure α-cordierite was formed at 1150 °C. Samples that were sintered at 1150 and 1200 °C had bulk density of 2.58 g/cm3 (relative density of 100%), and maintained low average grain sizes of 28.68 and 34.95 nm, respectively. With the decrease in the temperature from 1200 to 1150 °C, the hardness of cordierite was slightly increased from 8.25 ± 0.158 to 8.46 ± 0.188 GPa, the fracture toughness was marginally improved from 2.2 ± 0.158 to 2.25 ± 0.238 MPa mm1/2, and the critical strain energy release rate was raised from 32.46 to 33.95 J/m2.

TiO2-(Zn1/3Nb2/3)O2-ZrO2 microwave dielectric ceramics with near-zero temperature coefficient of resonant frequency

(56.33-x)TiO2-x(Zn1/3Nb2/3)O2-43.67ZrO2 (x = 2.60-37.66) ceramics with 0.5%wt CuO addition were prepared by the mixed metal oxide route. Effects of sintering temperature were investigated on the sintering behavior and microwave dielectric properties of ceramics. For all ceramics with x = 2.60-37.66, the optimal sintering temperature range was determined to be around 1280 °C. XRD analysis showed that the main crystalline phase of ceramics sintered at 1280 °C changed from ZrTiO4 type at x = 2.60-30.20 to ZrTi2O6 type at x = 30.20-37.66. In addition to the main crystalline phase, trace amounts of secondary phases ZrO2 and ZnCuTiO4 were also observed from SEM and EDS analysis for all ceramics. The permittivity decreased with the increasing x in the range of x = 2.60-30.20 and then remained stable at x = 30.20-37.66, corresponding to the density and covalency bond due to the substitution of (Zn1/3Nb2/3)4+ for Ti4+ and phase transition at x = 30.20. Furthermore, it was surprisingly found that the temperature coefficient of resonant frequency was near-zero (τf = -9.2 to +9.9 ppm/°C) in a very wide range of x = 10.80-30.20.

Evaluation of the Microstructure and the Electrochemical Properties of Ce0.8(1−x)Gd0.2(1−x)CuxO[1.9(1−x)+x] Electrolytes for IT-SOFCs

The influence of copper addition (0.5–2 mol%) on the crystal structure, densification microstructure, and electrochemical properties of Ce0.8Gd0.2O1.9 synthesized in a one-step sol–gel combustion synthesis route has been studied. It has been found that Cu is very active as sintering aids, with a significative reduction of GDC firing temperature. A reduction of 500 °C with a small amount of copper (0.5 mol%) was observed achieving dense bodies with considerable ionic conductivities. Rietveld refined was used to investigate the crystal structure while relative density and microstructural examination were performed in the sintering temperature range of 1000–1200 °C after dilatometer analysis. High dense bodies were fabricated at the lowest sintering temperature, which promotes the formation of Ce0.8(1−x)Gd0.2(1−x)CuxO[1.9(1−x)+x] solid solution and the absence of secondary phase Cu-rich or the segregation or copper at the grain boundary. As compared to the pure GDC an improvement of total conductivity was achieved with a maximum for the highest copper content of 2.23·10−3–9.19·10−2 S cm−1 in the temperature range of 200–800 °C.

Assembling an All-Solid-State Ceramic Battery: Assessment of Chemical and Thermal Compatibility of Solid Ceramic Electrolytes and Active Material Using High Temperature X-Ray Diffraction

Lithium ion batteries (LIBs) are the most known and used batteries for portable energy storage because of their high energy densities, long cycle life and relatively low price. However, they still fall short for the development of long range electric vehicles and stationary applications due to organic liquid electrolytes that are currently electrochemically limited and present safety issues (fire or explosion in case of short-cut or overcharging). Solid oxide electrolytes appear to be one of the solutions because of their non-flammability and wide potential window. Inorganic oxide electrolytes have reasonable ionic conductivities (10-5-10-3 S/cm at ambient temperature), high mechanical strength, and high chemical stability.Assembling an all ceramic solid-state battery with inorganic oxide electrolyte is challenging as it requires a deep knowledge of the thermal, chemical and electrochemical behavior of each component of the cell. The battery must be a continuous monolithic block with a thin dense electrolyte separator, in order to minimize the polarization. In addition, optimized interfaces between active material and electrolytes must be ensured in the composite electrodes. This is often achieved with oxide-based materials by using high temperature processing.Thermal expansion occurring during this step can lead to cracks, which will affect the performance and cyclability of the device. The primary driving force of a crack during the fabrication of hybrid ceramic is the stress due to mismatch in the coefficient of thermal expansion (TEC) of the various layers/materials. Moreover, it must be certain that no reaction occurs between active material and electrolytes in the sintering temperature range. These are then two key parameters to address for the development of all ceramic solid-state batteries.In this work, in situ-XRD has been used to determine the TEC and the thermal stability of various well-known oxide active materials and solid electrolytes. The aim of this presentation is to discuss about the best selection of compatible oxide-based materials to avoid unwanted cracks or reaction during the sintering processing of ceramic solid-state batteries.

A Review of Geopolymer Based Metakaolin Membrane as an Effective Adsorbent for Waste Water Treatment.

Geopolymer-based products help eco-accommodating sources of materials such as metakaolin, slag or fly ash. This review explores the blend configuration to generate geopolymer-based metakaolin membrane metakaolin and to evaluate the impact of a range of geopolymer-based metakaolin sintering temperatures at a temperature of 50 °C, 60 °C, 70 °C and 80 °C. As the quick development of a modern culture contributes to a large increase in interest in water, adsorption is taken closer to examined waste water extraction of the adsorption and repulsion of a metakaolin membrane geopolymer. Membrane waste water treatment is chosen to explore simple and inorganic membrane preparation techniques that have long help lives and low production costs. Reviews for geopolymer-based metakaolin membrane were therefore synthesized via a suspension that depends on the quick solidification method of high temperature suspension geopolymer slurries that were used as an adsorbent for treating waste water. Porous geopolymeric spheres have developed a homogenous structure with the aid of electron microscopy and Brunauer Emmett Teller (BET) investigations.Since permeable materials are regularly adsorbents, this examination has analyzed the adsorption by membrane geopolymers of heavy metals. This finding will advance the formation of improved wastewater treatment systems and along these lines give an elective answer for ecological harm brought about by substantial metal contaminations. Along these lines, molar (SiO2/Na2O) ratio of metakaolin and sodium silicate are fundamental in assembling a sort of geopolymer-based inorganic membrane which does not require a high temperature sintering process. Adsorption and dismissal consolidated can be utilized for wastewater auxiliary electrical plating forms not exclusively to proficiently wipe out center and low groupings of overwhelming metals in wastewater yet in addition to wipe out little sub-atomic contaminants in wastewater.

Modification of barium aluminosilicate glass-ceramics with zirconium oxide additives

Barium aluminosilicate glass-ceramics modified with zirconium oxide (ZrO2) in the presence and without of stabilizing yttrium oxide was synthesized by the sol-gel method. The influence of the concentration of zirconium oxide on gelation, phase formation and sintering of materials were investigated. It was found that modification with zirconium oxide leads to a reduction in the gelation time of the initial solutions. It was shown that the introduction of ZrO2 in an amount of up to 10 wt.% leads to the intensification of sintering of glass-ceramics. However, with a further increase in the ZrO2 content to 15 wt.%, it is necessary to increase the sintering temperature to 1600°C. But this is not permissible, since it leads to not a desired metastable phase – hexacylsian becoming predominant in all samples. Only glass-ceramics modified with 10 wt.% ZrO2 contains only the monocelsian phase in the entire sintering temperature range. The use of the sol-gel method made it possible to synthesize glass-ceramics with a fine-crystalline structure and a uniform volume distribution of ZrO2 grains.

Properties and pore-forming mechanism of silica sand tailing-steel slag-coal gangue based permeable ceramics

In order to promote the construction of “sponge city”, fully utilize industrial solid waste, an eco-friendly permeable ceramic was successfully prepared by using silica sand tailing, steel slag and coal gangue. Through systematic investigation of water permeability, density, compressive strength, bending strength and chemical stability to study the effects of composition and sintering temperature changes on its properties. Its pore-forming mechanism was mainly researched by XRD, SEM and phase diagram analysis. Research indicates: As the content of silica sand tailing increases, the permeable ceramic structure becomes denser and the pores decrease. The best composition formula is silica sand tailing 55 wt%-steel slag 20 wt%-coal gangue 25 wt% (water permeability 4.68 × 10−2 cm/s, compressive strength 42.83 MPa, bending strength 6.87 MPa); with sintering temperature increasing, the permeable ceramic structure becomes porous, the optimum sintering temperature range is 1150 °C–1170 °C (water permeability 4.11 × 10−2 cm/s–4.96 × 10−2 cm/s, compressive strength 40.15 MPa–45.41 MPa, bending strength 6.26 MPa–7.88 MPa). Maintaining good chemical stability in both composition and sintering temperature change, and their permeability is far beyond the Chinese standard (1 × 10−2 cm/s). The pore formation is mainly attributed to the fact that the O2 released by the decomposition of Fe2O3 is coated by the formed glass liquid phase (Ca-Fe-Si-Mg-Al-O system) and flowing, then ruptures everywhere in the sample. This work maximizes the introduction of solid waste (100%), which not only protects the environment but also creates good economic benefits.