Rise Of Sintering Temperature Research Articles

Synthesis and characterization of layered Li(Ni 1/3Mn 1/3Co 1/3)O 2 cathode materials by spray-drying method

Spherical Li(Ni 1/3Mn 1/3Co 1/3)O 2 was prepared via the homogenous precursors produced by solution spray-drying method. The precursors were sintered at different temperatures between 600 and 1 000 °C for 10 h. The impacts of different sintering temperatures on the structure and electrochemical performances of Li(Ni 1/3Mn 1/3Co 1/3)O 2 were compared by means of X-ray diffractometry(XRD), scanning electron microscopy(SEM), and charge/discharge test as cathode materials for lithium ion batteries. The experimental results show that the spherical morphology of the spray-dried powers maintains during the subsequent heat treatment and the specific capacity increases with rising sintering temperature. When the sintering temperature rises up to 900 °C, Li(Ni 1/3Mn 1/3Co 1/3)O 2 attains a reversible capacity of 153 mA-h/g between 3.00 and 4.35 V at 0.2C rate with excellent cyclability.

Electric and mechanical performances of Bi 0.5 Sb 1.5 Te 3 prepared by spark plasma sintering

Thermoelectric (TE) materials are a kind of functional materials which can be used to convert directly heat energy to electricity or reversely. The thermoelectric effects hold great potential for application in power generation and refrigeration. Bi 2Te 3 and its alloys are well known as best TE materials currently available near room temperature. This paper studies respectively the effects of spark plasma sintering (SPS) on electric performance of Bi 0.5Sb 1.5Te 3 thermoelectric materials that are prepared through vacuum melting and ball milling. Through X-ray Diffraction and cold field emission scanning electric microscope s4800, the phase constituent and microstructure of the TE materials samples were analyzed. Electric conductivity and power factor can be improved with the rise of Spark Plasma Sintering temperature (from 300 to 500 °C) and pressure (from 30 to 60 MPa), and the density and mechanical strength of Bi 0.5Sb 1.5Te 3 thermoelectric material increase, too.

Sintering process and grain growth of Mn-Zn ferrite nanoparticles

The density, microstructure and magnetic properties of non-doped Mn-Zn ferrite nanoparticles sintered compacts were investigated. The compacts of non-doped Mn-Zn ferrite nanoparticles were sintered by segmented-sintering process at lower sintering temperature. The density of sintered samples was measured by Archimedes method, and the phase composition and microstructure were examined by XRD and SEM. The sintered Mn-Zn ferrite magnetic measurements were carried out with Vibrating Sample. The results show that the density of sintered compacts increases with the rising of sintering temperature, achieving 4.8245 g·cm −3 when sintered at 900 °C, which is the optimal density of Mn-Zn functional ferrite needed and from the fractured surface of sintered samples, it can be seen that the grain grows well with small grain size and homogeneous distribution.

Phase formation process, microstructure and magnetic properties of Y-type hexagonal ferrite prepared by citrate sol–gel auto-combustion method

Y-type hexagonal ferrites were prepared by citrate sol–gel auto-combustion method (CSAM). The phase formation process, microstructure and magnetic properties were investigated and compared with those of the samples made by conventional solid-state reaction method (SSRM). The selected material system has stoichiometric composition of Ba 2Zn 1.2− x Co x Cu 0.8Fe 12O 22, where x was varied from 0 to 1.2. Phase formation was characterized by powder X-ray diffraction (XRD). The microstructure was observed via scanning electron microscopy (SEM). Frequency spectra of complex permeability were measured via an impedance analyzer. Results reveal auto-combusted powders are about 22 nm and very active. Phase formation temperature and sintering temperature are both 900 °C, much lower than those in SSRM. The sintered samples have fine-grained microstructure. The samples exhibit better magnetic properties in hyper-frequency than those made by SSRM. As zinc content increases, the permeability μ′ is enhanced and the cut-off frequency drops. The magnetic properties are also correlated with the sintering temperature and microstructure. Permeability μ′ increases with the rise of sintering temperature.

CMR La 0.7Ca 0.3MnO 3 and La 0.7Sr 0.3MnO 3 thin films fabricated by sol–gel method

Sol–gel precursors for La 0.7Ca 0.3MnO 3 and La 0.7Sr 0.3MnO 3 were made from La, Ca, Sr and Mn acetates with a mixture of 2-ethylhexanoic acid and 2-methexyethanol in a ratio of 2:1 as solvent. With these precursor solutions, La 0.7Ca 0.3MnO 3 and La 0.7Sr 0.3MnO 3 thin films were deposited on YSZ and MgO substrates, respectively, by spin coating and sintering at different temperatures. X-ray diffraction (XRD) patterns show that these thin films consist of pure La 0.7Ca 0.3MnO 3 and La 0.7Sr 0.3MnO 3 phases. Atomic force microscope images of the thin films show uniformly developed grains and the development of the grains with rising sintering temperature. EDS analysis shows that the composition of grains of La 0.7Ca 0.3MnO 3 thin films is in accordance with the composition of the precursor sol–gel. Magnetization measurements of the fabricated films show typical ferromagnetic order transitions. Conductivity measurements at zero magnetic field show that all the films have typical semiconductor to conductor transitions, and magnetoresistance was demonstrated after a magnetic field was applied.

Frequency dispersion of complex permeability of Y-type hexagonal ferrites

The frequency characteristics of Y-type hexagonal ferrites were studied. The samples were prepared by the conventional ceramics method. X-ray diffraction was used to characterize the phase formation. The microstructure was observed via scanning electron microscopy, and magnetic properties were investigated using vibrating samples magnetometer and impedance analyzer. Experimental results show that composition and processing will determine the magnetization mechanism of Y-type hexagonal ferrites in very high frequency and ultra high frequency. Both domain wall motion and magnetization rotation exist in magnetization processing. There is a double resonance peak with obvious dispersion character for low Co substitution. Co substitution will increase the magnetic anisotropy distinctly. As Co content rises, the increasing magnetic anisotropy leads to the movement of resonance peak towards higher frequency and disappearance of magnetic domain wall resonance; initial permeability decreases at the same time. The rise of sintering temperature will enhance magnetic domain wall resonance remarkably and move resonance peak towards lower frequency.

Yttrium doping behavior in BaTiO 3 ceramics at different sintered temperature

The doping behaviors of Y-doped BaTiO 3 ceramics comparing with that of undoped one at different sintering temperature were studied. Sintering at low temperature, yttrium preferably occupies Ti-site; with the sintering temperature rise, it tends to occupy Ba-site and act as donor. The dense and semiconducting ceramics of Y-doped BaTiO 3 can be obtained when the sintering temperature above 1250 °C. Sintered at 1250 °C results in the sample with the maximum of lattice parameters for the minimum vacancy concentration.

Effects of sintering temperature on structure of hydroxyapatite studied with Rietveld method.

It is obvious that the sintering temperature of hydroxyapatite (HA) ceramics significantly affects their biological responses in vitro or in vivo. The HA ceramics sintered at different temperatures exhibit a wide variation of biological response, but the correlation of this variation with the parameters of HA crystalline structure is not fully investigated. In present study, the crystalline structure of HA powders sintered at different temperatures at 600, 800, 1000, 1200 degrees C, was characterized using X-ray diffraction (XRD), and then refined with Rietveld method. A series of structure parameters, such as, cell lattice parameters (a and c) and bond length, distances of special atoms on surface to nearest atom, a numerical index of distortion for PO(4) tetrahedron, as well as internal energy and density of HA cell, were calculated to characterize the crystalline structure of HA at atom level. The broadening effect of XRD reflections was also separated to calculate the micro-strain/crystalline size, respectively. These parameters of HA crystalline structure and cell demonstrated that with rising of the sintered temperature, the internal energy and micro-strain of HA cell decreased, but the crystalline size increased. The regularity of PO(4) tetrahedron and distance between Ca(1) and O(3) in HA cell showed the same tendency as the internal energy and micro-strain with sintering temperature. All of these parameters indicated that HA became more stable with the rising of sintering temperature.

Decomposition Rate of Si3N4 during Microwave Sintering

A densification temperature of a ceramic material by microwave sintering is quite lower than the temperature by conventional sintering. However, the ceramic material is self-heated by electromagnetic energy during the microwave sintering processing, so that possibility of temperature measuring error is considerably high. Then it is difficult to prove that the densification temperature by microwave sintering is lower than the temperature by conventional sintering.There is a problem of sintering Si3N4 that sintering temperature is higher than decomposition temperature in atmospheric pressure of N2 gas, and a specimen can not be high density if a powder bed is not used. The decomposition rate becomes fast at the densification temperature. Furthermore, sintering density is lowered with the rise of sintering temperature since the decomposition rate becomes faster. Because of that, Si3N4 is sintered in high pressure N2 gas, or in atmospheric pressure of N2 gas with powder bed.When a Si3N4 specimen which included 5 w% Al2O3 and 5 w% Y2O3 as sintering aids, was sintered at 1700°C by conventional heating in atmospheric pressure of N2 gas without powder bed, sintering density reached 88%. And the density is lowered when the heating temperature was higher than 1700°C. The density more than 88% was not obtained even the sintering temperature was higher.On the other hand, when the specimen was sintered by microwave treating in atmospheric pressure of N2 gas at 1600V without powder bed, the sintering density was 98.1% and 98.7% at 1650°C and reached 99.0% at 1700°C.This shows clearly that the densification temperature by microwave sintering is lower than decomposition temperature. In other words, this shows that the densification temperature by microwave sintering is lower than the temperature by conventional sintering.

Sintering of Nanopowders of Amorphous Silicon Nitride Under Ultrahigh Pressure

Nanopowders of amorphous silicon nitride were densified and sintered without additives under ultrahigh pressure (1.0–5.0 GPa) between room temperature and 1600 °C. The powders had a mean diameter of 18 nm and contained ∼5.0 wt% oxygen that came from air-exposure oxidation. Sintering results at different temperatures were characterized in terms of sintering density, hardness, phase structure, and grain size. It was observed that the nanopowders can be pressed to a high density (87%) even at room temperature under the high pressure. Bulk Si3N4 amorphous and crystalline ceramics (relative density: 95–98%) were obtained at temperatures slightly below the onset of crystallization (1000–1100 °C) and above 1420 °C, respectively. Rapid grain growth occurred during the crystallization leading to a grain size (>160 nm) almost 1 order of magnitude greater than the starting particulate diameters. With the rise of sintering temperature, a final density was reached between 1350 and 1420 °C, which seemed to be independent of the pressure applied (1.0–5.0 GPa). The densification temperature observed under the high pressure is lower by 580 °C than that by hot isostatic pressing sintering, suggesting a significantly enhanced low-temperature sintering of the nanopowders under a high external pressure.

Photoacoustic spectroscopy of ceramic ZnO doped with Bi 2O 3

Photoacoustic (PA) spectroscopy is applied to study the heat generation by nonradiative processes of ceramic ZnO containing 1 mol.% Bi 2O 3 for the different sintering temperatures (700–1100°C) in the wavelength range of 320–800 nm with a modulation frequency of 33 Hz. PA spectroscopy provides optical absorption spectra for opaque samples such as ceramics. PA signal intensities increase above a photon energy of 2.3 eV. It is found that the PA signal intensities plotted semilogarithmically vary linearly below a photon energy of 3.0 eV in the two regions (A: 3.0–2.8 eV; B: 2.6–2.4 eV). The steepness factor of region A, which characterizes the slope of exponential optical absorption, decreases with rising sintering temperature, indicating the increase of segregation of Bi at particle surfaces and grain boundaries. That of region B increases rapidly with rising sintering temperature, indicating the structural ordering by sintering processes. Thus, PA method has a potential for characterizing the electronic states and structural disorder of ceramic materials.

焼結Ｆｅ－１８Ｃｒ－２Ｍｏ磁性合金の直流および交流時最大磁束密度に及ぼすＳｉ成分の影響

Influence of the silicon content on the maximum magnetic flux density was studied on the sintered Fe-18Cr-2Mo alloy at applied magnetic field in three Oersted. The highest maximum magnetic flux densities in DC and AC magnetic field were attained at the content of two-percent silicon. The lower magnetic properties was observed for the three-percent silicon or more. The sintered density and the DC maximum magnetic flux density consequently were improved with the rise of sintering temperature. On the other hand the AC maximum magnetic flux density indicated the change of a decrease after an increase. An excess sintering temperature rather causes a lowering of AC maximum magnetic flux density. An increase of the resistivity contributes to an improvement of AC maximum magnetic flux density on the whole, but for the lower sintered density, tends to cause the deteriorating of AC maximum magnetic flux density. The comparison of measured and calculated value for the frequency dependence

酸化物超伝導体の合成と特性 シリコンを含むＰ／Ｍ二相ステンレス鋼の機械的性質と耐食性

Influence of the addition of silicon on mechanical properties and corrosion resistances of P/M austenitic stainless steels was investigated by means of microstructual examinations, calorimetric analysis and X-ray analysis. Silicon addition to P/M austenitic stainless steels makes the sintering in the duplex structure of austenite(γ) and ferrite(α) possible by the liquid phase sintering with a eutectic liquid. For example, addition of 4mass% Si results in the formation of about 40vol% of ferrite. Tensile strength of sintered steels increases with increased silicon content, and the maximum strength (940MPa) was obtained in the steel with 4mass%Si which was sintered for 3.6ks at 1623K. On the other hand, elongation of sintered steels tends to increase with rising sintering temperature. The maximum elongation (47.5%) was obtained in the steel with 2mass%Si which was sintered for 3.6ks at 1673K. The sintered steel with 2mass%Si was found to have excellent corrosion resistance in a boiling solution of 65% HNO3 : The corrosion rate of the steel was very small in comparison with the sintered SUS304L steel, but it was three times larger than that of a SUS304L steel produced by ingot metallurgy. However, further addition of silicon causes a decline in corrosion resistance probably due to a decrease in the green density.

Sintering temperature dependence of the photothermal spectra in ceramic CdS

Photothermal spectroscopy using a thermistor is applied to study the heat generation by nonradiative processes in ceramic CdS. It is found that photothermal spectra of ceramic CdS depend on the sintering temperature ; i. e. the absorption edge of the spectrum shifts towards higher energies and the slope increases with rising sintering temperature (600°C to 800°C). However, the spectrum shifts towards lower energies region above 800°C sintering temperature and the slope decreases.

金型成形-普通焼結法による高密度TiAl焼結材の製造

In order to develop highly densified TiAl by die compaction-sintering method, the sintering behavior of Ti(or TiH2)+TiAl3 mixed powders, promising as a starting powder, was investigated.The mixed powders were consolidated by cold pressing and sintered in vacuum without extermal pressure. In the sintering behavior, the densification characteristics of mixed powders were examined as a function of particle size and composition, and the microstructure and oxygen content of the sintered TiAl were also examined.The results were as follows:(1) The densification behavior of the Ti+TiAl3 mixed powders was influenced by the particle size of constituent powders, especially the size of Ti powder. With refining Ti powder, a greater densification over 95% relative density took place.(2) The densification behavior of the mixed powders was also inflienced by their composition. Although Al-rich TiAl of 55 at%Al showed a small densification irrespective of a proper adjustment of particle size, TiAl containing 40∼50 at%Al showed excellent sinterability. This is mainly due to the α-Ti phase which appears during sintering.(3) The microstructure of sintered TiAl of 55 at%Al consisted of a single γ-phase, while those of 40∼50 at%Al were composed of equiaxis γ-phase and γ⁄α2-lamellar structure. In the mixed structures, the amount of the lamellar structure increased with a rise of sintering temperature and decreased with an increase of Al content.(4) The oxygen content of sintered TiAl was dependent on the oxygen content of starting powders, de-waxing conditions, the amount of interconnected pores and so forth. It was found that the oxygen content of the highly densified TiAl obtained by this die compaction-sintering method was 0.45∼0.55% and an appropriate handling of starting powders made it possible to reduce them less than 0.4%.

Ａｌ２Ｏ３／Ｍｏナノ複合材料の微構造と機械的特性

The Al2O3/5-20vol%Mo composites were fabricated by hot-pressing a mixture of a-Al2O3 and fine Mo powders under a vacuum. In these composites, nanometer size Mo particles were dispersed within theAl2O3 grains and relatively large Mo particles, above 1μm, were located at the grain boundaries. Thus, it was confirmed that ceramic/metal nanocomposites could be successfully fabricated with a conventional powder metallurgical process. The addition of Mo particles resulted in the grain growth inhibition of the Al2O3 matrix. A significant improvement in fracture strength and toughness was observed, but they could not be achieved simultaneously. A fracture strength of 884MPa for the Al2O3/7.5vol%Mo composite sintered at 1400°C was obtained. The fracture toughness was improved with increasing Mo content and rising sintering temperature. It obtained a value of 7.21MPa⋅1/2 for the Al2O3/20vol%Mo composite sintered at 1700°C.

ＹＢａ２Ｃｕ３Ｏｙの超電導特性におよぼす長時間焼結の影響

Y Ba 2Cu3Oy powders obtained by pulverizing the mixed powder aggregate fired at 1173K for 86.4ks were cold pressed at 98MPa and sintered at various temperatures for 86.4-1036.8ks, and the relation between the sintering behavior and superconducting properties was investigated.The abrupt increment of sintered density ratio was observed by the sintering at 1198K after gradual increment with rising sintering temperature up to 1173K, and it remained constant in the higher sintering temperature range than 1198K. Though the sintered density ratio was about 72% even after sintering at 1173K for 1036.8ks, it exceeds 90% in the case of sintering at 1223K for 1036.8ks. The marked degradation of superconducting properties was recognized in the specimen sintered at 1223K for 759.6ks, where the lamella structure along the grain boundary due to the liquid phase formed during sintering was observed.

Dilatometric investigation of the sintering of compacts from titanium and iron powder mixtures

The sintering of mixtures of titanium and iron powders at temperatures above the eutectic point is accompanied by a strong reaction between the metals in contact, which manifests itself in a stepwise change in the dimensions of the compact being sintered. The rate of the growth in specimen volume due to the formation of an intermetallic compound during sintering at temperatures above the eutectic point increases with increasing fineness of the powders used and with rising sintering temperature.

Improvement in Ductility of Sintered Iron-Copper Alloys

In the conventional way for increasing ductility of iron-copper compacts, emphasis has been layed on obtaining their homogeneous structures by sintering above the melting point of copper. Also in our experiments which were carried out according to the above method, both the tensile strength and the elongation of sintered iron-copper compacts increased with compacting and repressing pressures. But it was observed that the elongation decreased with rising sintering temperature and extending sintering time, while the tensile strength increased.The authors assumed that both the elongation and the strength might increase by means of two-stage sintering, thus effectuating tight bonding of iron particles in the primary sintering under the melting point of copper and subsequent partial diffusion of copper into the iron skeleton above the melting point of copper. And it has been proved experimentally that the elongation of sintered iron-copper compacts was improved by this process without significant decrease in the tensile strength. The results were confirmed with the aid of photomicrography and electron microanalyser analysis.

Study on Manufacture of S.A.P. from Al-Paste

Al-paste de-oiled by soap-suds or trichlor ethylene can be used as raw materials for S.A.P.. Al-paste de-oiled by soap-suds contain 4-5% Al2O3, and ones de-oiled by trichlor ethylene contain about 1% Al2O3. Al2O3 content of de-oiled Al-pastes can de adjusted by soaking in water for moderate duration.Aluminium powders made from Al-paste are compacted and sintered. Physical and mechanical properties of material increase with the rise of sintering temperature and the prolongation of sintering time. And, the longer the hot-pressing time, the better the properties of material.By "composite powder method", aluminium powders are coated by copper. Effects of copper on the properties of S.A.P. are examined by using-Cu-coated Al-powders.