Sintering and microstructure of silicon carbide ceramic with Y3Al5O12 added by sol-gel method*

PubMed Central

Guo, Xing-zhong; Yang, Hui

2005-01-01

Silicon carbide (SiC) ceramic with YAG (Y3Al5O12) additive added by sol-gel method was liquid-phase sintered at different sintering temperatures, and the sintering mechanism and microstructural characteristics of resulting silicon carbide ceramics were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and elemental distribution of surface (EDS). YAG (yttrium aluminum garnet) phase formed before the sintering and its uniform distribution in the SiC/YAG composite powder decreased the sintering temperature and improved the densification of SiC ceramic. The suitable sintering temperature was 1860 °C with the specimen sintered at this temperature having superior sintering and mechanical properties, smaller crystal size and fewer microstructure defects. Three characteristics of improved toughness of SiC ceramic with YAG added by sol-gel method were microstructural densification, main-crack deflection and crystal ‘bridging’. PMID:15682507

Effect of temperature on porosity of iron ore sinter with biochar derived from EFB

NASA Astrophysics Data System (ADS)

Purwanto, H.; Rozhan, A. N.; Zakiyuddin, A.; Mohamad, A. S.

2018-01-01

In this research, the replacement of fossil fuel energy (coke) with oil palm empty fruit bunch as a potential energy in sintering of iron ore was investigated. Carbon derived biomass has been produced by using oil palm empty fruit bunch by heat treatment process. In the present investigation, sintering process was carried out by heating the mixed iron ore and biochar at various temperatures. The apparent density and porosity for iron sinter show a significant increase and gradual decrement as the temperature increase, respectively. The porosity of iron sinter shows a gradual decrement from 950 °C to 1050 °C but up to 1150 °C it shows a significant decrement about 44%. Inferring to the micrograph, the agglomeration and assimilation of sinter at high temperature is better compared with low sintering temperature.

Effect of Sintering Temperature on Magnetic Core-Loss Properties of a NiCuZn Ferrite for High-Frequency Power Converters

NASA Astrophysics Data System (ADS)

Yan, Yi; Ngo, Khai D. T.; Hou, Dongbin; Mu, Mingkai; Mei, Yunhui; Lu, Guo-Quan

2015-10-01

In an effort to find a magnetic material for making low-loss magnetic components for high-power-density converters, we investigated the magnetic core-loss characteristics of a commercial NiCuZn ferrite (LSF 50) at 5 MHz as a function of the sintering temperature of the ferrite powder. The ferrite powder was compacted into toroid cores and then sintered at 850°C, 900°C, 950°C, 1000°C, and 1050°C for 2 h. The sintered densities of the cores increased at higher sintering temperatures. The magnetic properties of the sintered cores—complex permeability and core-loss density—were measured. We found that both the real and imaginary parts of the relative permeability increased with sintering temperature. The core-loss results at 5 MHz showed that the cores sintered at 950°C and 1000°C had the lowest core-loss densities, being two to three times lower than that of a commercial NiZn ferrite (4F1) core. Microstructures of the sintered cores were examined by scanning electron microscopy; the grains grew significantly at higher sintering temperatures.

Effect of sintering temperature on flexural properties of alumina fiber-reinforced, alumina-based ceramics prepared by tape casting technique.

PubMed

Tanimoto, Yasuhiro; Nemoto, Kimiya

2006-01-01

The purpose of this study was to investigate the effect of sintering temperature on flexural properties of an alumina fiber-reinforced, alumina-based ceramic (alumina-fiber/alumina composite) prepared by a tape casting technique. The alumina-based ceramic used a matrix consisting of 60 wt% Al(2)O(3) powder and 40 wt% SiO(2)-B(2)O(3) glass powder with the following composition in terms of wt%: 33 SiO(2), 32 B(2)O(3), 20 CaO, and 15 MgO. Prepreg sheets of alumina-fiber/alumina composite in which uniaxial aligned alumina fibers were infiltrated with the alumina-based matrix were fabricated continuously using a tape casting technique employing a doctor blade system. Four sintering temperatures were investigated: 900 degrees C, 1000 degrees C, 1100 degrees C, and 1200 degrees C, all for 4 hours under atmospheric pressure in a furnace. The surface of the alumina-fiber/alumina composite after sintering was observed with a field-emission scanning electron microscope (FE-SEM). A three-point bending test was carried out to measure the flexural strength and modulus of alumina-fiber/alumina composite specimens. In addition, sintered alumina fiber was characterized by X-ray diffraction (XRD). FE-SEM observation showed that alumina-fiber/alumina composite was confirmed to be densely sintered for all sintering temperatures. Three-point bending measurement revealed that alumina-fiber/alumina composite produced at sintering temperatures of 1100 degrees C and 1200 degrees C exhibit flexural strengths lower than those of alumina-fiber/alumina composite produced at sintering temperatures of 900 degrees C and 1000 degrees C; alumina-fiber/alumina composite produced at sintering temperatures of 1100 degrees C and 1200 degrees C exhibit flexural moduli lower than that of alumina-fiber/alumina composite produced at a sintering temperature of 1000 degrees C. Additional XRD pattern of alumina fiber indicated that with increasing sintering temperature, the crystallographic structure of gamma-alumina transformed to mullite. There were significant differences in the flexural properties between the alumina-fiber/alumina composite sintered at the four temperatures. This indicates that the choice of optimum sintering temperature is an important factor for successful dental applications of alumina-fiber/alumina composite developed by the tape casting system.

Effect of sintering temperature on the electrolysis of TiO2

NASA Astrophysics Data System (ADS)

Li, Ze-quan; Ru, Li-yue; Bai, Cheng-guang; Zhang, Na; Wang, Hai-hua

2012-07-01

The effects of sintering temperature on the microstructure and the conductivity of TiO2 cathodes were studied by examining the phase composition, microstructure, and element contents of the sintered cathodes and the cathodic products using X-ray diffraction and scanning electronic microscopy-energy dispersive spectrometry. The oxygen vacancy, conductivity, average pore diameter, and specific surface area of the sintered cathodes were detected by X-ray photoelectron spectroscopy, four-point probe, and ASPA 2010. The results showed that TiO2 phase transformations occurred, and oxygen vacancies formed with the increase of sintering temperature. The cathodic conductivity improved, but the average pore diameter and the effective response area of the TiO2 cathode were reduced when the sintering temperature increased. These phenomena could weaken the contact between reaction ions and electrons and also had the same effect on the cathodes and the molten salt. Moreover, they were disadvantageous to ion migration, so a lower sintering temperature was favorable for the microstructure of electrolysis. Consequently, the cathodic conductivity may be improved, but the microstructure became compact with the increase of sintering temperature. The cathodic products at different temperatures indicated that the cathodic conductivity was more important for electrolysis.

[Influence of compaction pressure and pre-sintering temperature on the machinability of zirconia ceramic].

PubMed

Huang, Huil; Li, Jing; Zhang, Fuqiang; Sun, Jing; Gao, Lian

2011-10-01

In order to make certain the compaction pressure as well as pre-sintering temperature on the machinability of the zirconia ceramic. 3 mol nano-size 3 mol yttria partially stabilized zirconia (3Y-TZP) powder were compacted at different isostatic pressure and sintered at different temperature. The cylindrical surface was traversed using a hard metal tool. Surface and edge quality were checked visually using light stereo microscopy. Pre-sintering temperature had the obviously influence on the machinability of 3Y-TZP. The cutting surface was smooth, and the integrality of edge was better when the pre-sintering temperature was chosen between 800 degrees C to 900 degrees C. Compaction pressure showed only a weak influence on machinability of 3Y-TZP blanks, but the higher compaction pressure result in the poor surface quality. The best machinability of pre-sintered zirconia body was found for 800-900 degrees C pre-sintering temperature, and 200-300 MPa compaction pressure.

Influence of Sintering Temperature on Hardness and Wear Properties of TiN Nano Reinforced SAF 2205

NASA Astrophysics Data System (ADS)

Oke, S. R.; Ige, O. O.; E Falodun, O.; Obadele, B. A.; Mphalele, M. R.; Olubambi, P. A.

2017-12-01

Conventional duplex stainless steel degrade in wear and mechanical properties at high temperature. Attempts have been made by researchers to solve this problems leading to the dispersion of second phase particles into duplex matrix. Powder metallurgy methods have been used to fabricate dispersion strengthened steels with a challenge of obtaining fully dense composite and grain growth. This could be resolved by appropriate selection of sintering parameters especially temperature. In this research, spark plasma sintering was utilized to fabricate nanostructured duplex stainless steel grade SAF 2205 with 5 wt.% nano TiN addition at different temperatures ranging from 1000 °C to 1200 °C. The effect of sintering temperature on the microstructure, density, hardness and wear of the samples was investigated. The results showed that the densities and grain sizes of the sintered nanocomposites increased with increasing the sintering temperature. The microstructures reveal ferrite and austenite grains with fine precipitates within the ferrite grains. The study of the hardness and wear behaviors, of the samples indicated that the optimum properties were obtained for the sintering temperature of 1150 °C.

Sintering Kinetics of Inkjet Printed Conductive Silver Lines on Insulating Plastic Substrate

DOE PAGES

Zhou, Wenchao; List, III, Frederick Alyious; Duty, Chad E; ...

2015-01-24

This paper focuses on sintering kinetics of inkjet printed lines containing silver nanoparticles deposited on a plastic substrate. Upon heat treatment, the change of resistance in the printed lines was measured as a function of time and sintering temperatures from 150 to 200 C. A critical temperature was observed for the sintering process, beyond which there was no further reduction in resistance. Analysis shows the critical temperature correlates to the boiling point of the solvent, which is attributed to a liquid-mediated sintering mechanism. It is demonstrated that the sintering process shuts down after the solvent has completely evaporated.

Mechanical Properties and Plasma Erosion Resistance of ZrO2p(3Y)/BN-SiO2 Ceramic Composites under Different Sintering Temperature

NASA Astrophysics Data System (ADS)

Zhou, Yu; Duan1, Xiaoming; Jia, Dechang; Yang, Zhihua; Meng, Qingchang; Yu, Yang; Yu, Daren; Ding, Yongjie

2011-10-01

ZrO2p(3Y)/BN-SiO2 ceramic composites were hot pressed under different sintering temperature. The ceramic composites were composed by BN, m-ZrO2, t-ZrO2 and SiO2. The relative density, bending strength, elastic modulus and fracture toughness increase with the sintering temperature increasing, the maximum value of which at the sintering temperature of 1800°C are 97.5%, 229.9MPa, 60.8GPa and 3.55MPam1/2, respectively. The erosion resistance ability of ZrO2p(3Y)/BN-SiO2 ceramic composites rise gradually with the sintering temperature increasing, and the erosion rate of the ceramic composite sintered at 1800°C is 8.03×10-3mm/h.

Correlation between structural, electrical and magnetic properties of GdMnO3 bulk ceramics

NASA Astrophysics Data System (ADS)

Samantaray, S.; Mishra, D. K.; Pradhan, S. K.; Mishra, P.; Sekhar, B. R.; Behera, Debdhyan; Rout, P. P.; Das, S. K.; Sahu, D. R.; Roul, B. K.

2013-08-01

This paper reports the effect of sintering temperature on ferroelectric properties of GdMnO3 (GMO) bulk ceramics at room temperature prepared by the conventional solid state reaction route following slow step sintering schedule. Ferroelectric hysteresis loop as well as sharp dielectric anomaly in pure (99.999%) GMO sintered ceramics has been clearly observed. Samples sintered at 1350 °C become orthorhombic with Pbnm space group and showed frequency independent sharp dielectric anomalies at 373 K and a square type of novel ferroelectric hysteresis loop was observed at room temperature. Interestingly, dielectric anomalies and ferroelectric behavior were observed to be dependent upon sintering temperature of GdMnO3. Room temperature dielectric constant (ɛr) value at different frequencies is observed to be abnormally high. The magnetic field and temperature dependent magnetization show antiferromagnetic behavior at 40 K for both 1350 °C and 1700 °C sintered GMO. Present findings showed the possibility of application of GdMnO3 at room temperature as multifunctional materials.

Stress-dislocation interaction mechanism in low-temperature thermo-compression sintering of Ag NPs

NASA Astrophysics Data System (ADS)

Wang, Fuliang; Tang, Zikai; He, Hu

2018-04-01

The sintering of metal nanoparticles (NPs) has been widely studied in the field of nanotechnology, and low-temperature sintering has become the industry standard. In this study, a molecular dynamics (MD) model was established to study the sintering behaviour of silver NPs during low-temperature thermo-compression. Primarily, we studied the sintering process, in which the ratio of neck radius to particle radius (x/r) changes. Under a uniaxial pressure, the maximum ratio in the temperature range 420-425 K was 1. According to the change of x/r, the process can be broken down into three stages: the neck-formation stage, neck-growth stage, and neck-stability stage. In addition, the relationship between potential energy, internal stress, and dislocation density during sintering is discussed. The results showed that cycling internal stress played an important role in sintering. Under the uniaxial pressure, the stress-dislocation interaction was found to be the major mechanism for thermo-compression sintering because the plastic deformation product dislocation intensified the diffusion of atoms. Also, the displacement vector, the mean square displacement, and the changing crystal structure during sintering were studied.

[Influence of manufacture technique on translucency and color of dental porcelain].

PubMed

Xiong, Fang; Chao, Yong-Lie; Zhu, Zhi-Min

2007-12-01

To study the influence of manufacture technique on the translucency and color of dental porcelain. Specimens were made of VITA VMK 95 dentin porcelain and enamel porcelain and divided into 3 groups: Sintering times group (1, 2, 4, 6, 8 and 10 times), sintering temperature group (910, 920, 930, 940 and 950 degrees C), sintering vacuum group (95, 65, 35 and 0 kPa). Transmittance, Y, dominant wavelength and saturation were measured by PR-650 spectra scan spectrocolorimeter. Transmittance of dentin porcelain increased after 6 times repeated sintering. Transmittance of enamel porcelain increased first after the second sintering, and then became decreasing when sintering more than 2 times. Transmittance of enamel porcelain deceased when sintering temperature was lower than standard. Decrease of sintering vacuum caused the transmittance of dentin and enamel porcelain decreased. The changing of value was coordinated with transmittance. Dominant wavelength and saturation had negative correlation with sintering times and temperature, and positive correlation with vacuum. Sintering times, temperature and vacuum all had prominent effects on the translucency and color of dental porcelain. Comparing with dentin porcelain, enamel porcelain was more sensitive with the modification of manufacture technique.

The effect of various sintering temperature on used refractory towards its physical properties

NASA Astrophysics Data System (ADS)

Sudibyo; Wulandari, Y. R.; Amin, M.; Azhar

2018-01-01

The used magnesia refractory from the kiln of cement industry was successfully recycled to new refractory using Kaolin as an adhesive. In this work, the temperatures of sintering were varied from 1000°C to 1500°C. The result shows that the increment temperature effects in sintering process will enhance refractory physical properties such as bulk density, cold crushing strength or pressure strength and thermal conductivity. Meanwhile, the porosity was decreased as the increase of the sintering temperature.

Effect of the Sintering Temperature on the Formation of Ferroelectric Properties of a Lead Zirconate-Titanate Ceramic

NASA Astrophysics Data System (ADS)

Barabanova, E. V.; Topchiev, A. A.; Malyshkina, O. V.

2018-04-01

Effect of the sintering temperature on the formation of the microstructure, the domain structure, and the ferroelectric properties of a lead zirconate-titanate Pb(Ti x Zr1 - x )O3 piezoelectric ceramics has been studied. It is shown that the ferroelectric phase forms at a sintering temperature of 860°C. At higher sintering temperatures, the main effect on the properties is due to a unit cell deformation and free charge carriers.

Method for heat treating and sintering metal oxides with microwave radiation

DOEpatents

Holcombe, Cressie E.; Dykes, Norman L.; Meek, Thomas T.

1989-01-01

A method for microwave sintering materials, primarily metal oxides, is described. Metal oxides do not normally absorb microwave radiation at temperatures ranging from about room temperature to several hundred degrees centrigrade are sintered with microwave radiation without the use of the heretofore required sintering aids. This sintering is achieved by enclosing a compact of the oxide material in a housing or capsule formed of a oxide which has microwave coupling properties at room temprature up to at least the microwave coupling temperature of the oxide material forming the compact. The heating of the housing effects the initial heating of the oxide material forming the compact by heat transference and then functions as a thermal insulator for the encased oxide material after the oxide material reaches a sufficient temperature to adequately absorb or couple with microwave radiation for heating thereof to sintering temperature.

High-temperature mechanical properties of a solid oxide fuel cell glass sealant in sintered forms

NASA Astrophysics Data System (ADS)

Chang, Hsiu-Tao; Lin, Chih-Kuang; Liu, Chien-Kuo; Wu, Szu-Han

High-temperature mechanical properties of a silicate-based glass sealant (GC-9) for planar solid oxide fuel cell have been studied in sintered forms. Ring-on-ring biaxial flexural tests are carried out at room temperature to 800 °C for the sintered GC-9 glass. The results are also compared with those in cast bulk forms. From the force-displacement curves, the glass transition temperature (T g) of the non-aged, sintered GC-9 glass is estimated to be between 700 °C and 750 °C, while that of the aged one is between 750 °C and 800 °C. Due to a crack healing effect of the residual glass at high temperature, the flexural strength of the sintered GC-9 glass at temperature of 650 °C to T g point is greater than that at room temperature. At temperature above T g, the flexural strength and stiffness are considerably reduced to a level lower than the room-temperature one. The sintered GC-9 glass with pores and crystalline phases has a flexural strength lower than the cast bulk one at temperature of 650 °C and below. Due to a greater extent of crystallization, the flexural strength and stiffness of the sintered GC-9 glass are greater than those of the cast bulk one at 700-800 °C.

The effect of impurities elements on titanium alloy (Ti-6Al-4V) MIM sintered part properties

NASA Astrophysics Data System (ADS)

Ahmad, M. Azmirruddin; Jabir, M.; Johari, N.; Ibrahim, R.; Hamidi, N.

2017-12-01

The titanium alloys (Ti-6Al-4V) compact were fabricated by Metal Injection Molding (MIM). However, the real challenge of MIM processing for titanium alloy is its affinity to be contaminated by interstitial light elements such as oxygen and carbon which could degrade the mechanical properties of sintered titanium alloy such as its tensile strength and ductility. The sintering temperature effect on carbon and oxygen content that affects its physical and mechanical properties of the sintered titanium alloy was studied. The titanium MIM brown specimen was sintered at four different sintering temperatures which are 1100 °C, 1150 °C, 1200 °C and 1250 °C for 4 hours under furnace control atmosphere. The experimental result indicated that the specimen which has been made from 100% gas atomized powder have a relative density of 92.2 % - 97.6 %, the range of porosity percent around 2.38 %-3.84 %. Ultimate tensile strength of 873.11 MPa - 1007.19 MPa and ductility percent in range of 1.89 %-3.46 %. The titanium alloy MIM specimen which was sintered at 1150 °C contained 0.145 % of carbon and 0.143 % of oxygen possess the highest value of density and tensile strength, with value of 4.344 gcm-3 and 1007.2 MPa respectively. Meanwhile, the titanium alloy MIM specimen which was sintered at 1200 °C contains 0.130 % of carbon and 0.127 % of oxygen, has the highest percentage of ductility with 3.46 %. The carbon content level increased as the sintering temperature increased due to decomposition of high molecule weight of residue binder system which could not be eliminated during solvent extraction debinding process and sintered at low temperature. Contrarily, the oxygen content level indicates a decrease as the sintering temperature increased. Briefly, the sintering temperature could influence the physical and mechanical properties of titanium alloy MIM sintered specimen as it influences the oxygen and carbon content level in the alloys.

Effect of sintering temperature on micro structural and impedance spectroscopic properties of Ni0.5Zn0.5Fe2O4 nano ferrite

NASA Astrophysics Data System (ADS)

Venkatesh, Davuluri; Ramesh, K. V.; Sastry, C. V. S. S.

2017-07-01

Ni-Zn nanoferrite Ni0.5Zn0.5Fe2O4 is prepared by citrate gel auto combustion method and sintered at various temperatures 800, 900, 1000, 1100 and 1200°C. The room temperature x-ray diffraction conforms that the single phase spinel structure is formed. Crystallite size and density were increased with increasing of sintering temperature. From Raman spectroscopy all sintered samples are single phase with cubic spinel structure belong to Fd3m space group. From surface morphology studies it is clearly observed that the particle size increased with increasing of sintering temperature. Impedance spectroscopy revel that increasing of conductivity is due to grain resistance is decreased with increasing of sintering temperature. Cole-Cole plots are studied from impedance data. The electrical modulus analysis shows that non-Debye nature of Ni0.5Zn0.5Fe2O4 ferrite.

[Effect of two-step sintering method on properties of zirconia ceramic].

PubMed

Huang, Hui; Wei, Bin; Zhang, Fu-Qiang; Sun, Jing; Gao, Lian

2008-04-01

To study the influence of two-step sintering method on the sintering property, mechanical properties and microstructure of zirconia ceramic. The nano-size zirconia powder were compacted and divided into two groups, one group for one-step sintering method, another group for two-step sintering method. All samples sintered at different temperature. The relative density, three-bend strength, HV hardness, fracture toughness and microstructure of sintered block were investigated. Two-step sintering method influenced the sintering property and mechanical properties of zirconia ceramic. The maximal relative density was 98.49% at 900 degrees C/1,450 degrees C sintering temperature. There were significant difference of mechanical properties between one-step sintering and two-step sintering, the three-bend strength and fracture toughness declined, hardness increased at two-step sintering. The three-bend strength, HV hardness and fracture toughness reached to maximum value as 1,059.08 MPa +/- 75.24 MPa, 1,377.00 MPa +/- 16.37 MPa and 5.92 MPa x m1/2 +/- 0.37 MPa x m1/2 at 900 degrees C/1,450 degrees C sintering temperature respectively. Microscopy revealed the relationship between the porosity and shapes of grains was correlated to strength of the zirconia ceramics. Despite of the two-step sintering method influences the properties of zirconia, it also is a promising esthetic all-ceramic dental material.

Fabrication of highly dense SiN4 ceramics without additives by high pressure sintering

NASA Technical Reports Server (NTRS)

Takatori, K.; Shimade, M.; Koizumi, M.

1984-01-01

Silicon nitride (Si3N4) is one of candidate materials for the engineering ceramics which is used at high temperatures. The mechanical strengths of hot pressed or sintered Si2N4 ceramics containing some amount of additives, however, are deteriorated at elevated temperatures. To improve the high temperature strength of Si3N4 ceramics, an attempt to consolidate Si3N4 without additives was made by high pressure sintering technique. Scanning electron micrographs of fracture surfaces of the sintered bodies showed the bodies had finely grained and fully self-bonded sintered bodies were 310N sq m at room temperature and 174N/sq m at 1200 C.

Behavior of Oxide Film at Interface between Particles of Al-Mg Alloy Powder Compacts Prepared by Pulse Electric Current Sintering

NASA Astrophysics Data System (ADS)

Xie, Guoqiang; Ohashi, Osamu; Yamaguchi, Norio; Song, Minghui; Mitsuishi, Kazutaka; Furuya, Kazuo; Noda, Tetsuji

2003-07-01

Al-1.0 mass% Mg alloy powders were sintered using the pulse electric current sintering (PECS) process at various temperatures. The microstructure at the interfaces between powder particles and the effect of sintering temperature on interface characteristics were investigated using transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDS). The precipitates were observed at the interfaces between powder particles of the compacts. The amounts of the precipitates increased and the compositions changed with an increase in sintering temperature: MgO for the compact sintered at 613 K, MgAl2O4+MgO for those at 663 K and 713 K, and MgAl2O4 for those above 763 K. Comparing the results obtained by the PECS process with those of diffusion bonding experiments and thermodynamic calculation, it was suggested that the temperature at the interfaces between the particles was higher than that of the particles sintered by the PECS process.

Influence of sintering temperature on properties of BNKLLT-6 wt% BCTZ binary lead-free piezoelectric ceramic prepared through the solid-state combustion technique

NASA Astrophysics Data System (ADS)

Kornphom, Chittakorn; Laowanidwatana, Artid; Bongkarn, Theerachai

2017-03-01

In this work, a new binary 94 wt%[Bi0.5(Na0.68K0.22Li0.1)0.5TiO3 + 0.10 wt% of La2O3]-6 wt% [(Ba0.85Ca0.15)(Ti0.90Zr0.10)O3] [BNKLLT-6 wt% BCTZ] ceramic was fabricated by the solid-state combustion technique and glycine was used as the fuel. The effect of sintering temperature in the range of 1075-1175 °C for 2 h on phase evolution, microstructure and electrical properties was investigated. The phase formation exhibited a coexistence structure between rhombohedral and tetragonal at low sintering temperature. As the sintering temperature increased, the phase formation changed to pseudo-cubic phase. The average grain size of the ceramics was increased with the increasing sintering temperature. Density, ɛr, ɛSA and TFA of BNKLLT-6 wt% BCTZ ceramics increased while the TSA decreased when the sintering temperature increased up to 1125 °C, while after this temperature the opposite trends occurred. At a sintering temperature of 1125 °C, the BNKLLT-6 wt% BCTZ sample showed the highest theoretical density (95.8%), maximum dielectric constant ɛSA (5278), highest d33 (227 pC/N) and fair ferroelectric properties (Pr = 24.5 µC/cm2 and Ec = 15.45 kV/cm).

Numerical study of the process parameters in spark plasma sintering (sps)

NASA Astrophysics Data System (ADS)

Chowdhury, Redwan Jahid

Spark plasma sintering (SPS) is one of the most widely used sintering techniques that utilizes pulsed direct current together with uniaxial pressure to consolidate a wide variety of materials. The unique mechanisms of SPS enable it to sinter powder compacts at a lower temperature and in a shorter time than the conventional hot pressing, hot isostatic pressing and vacuum sintering process. One of the limitations of SPS is the presence of temperature gradients inside the sample, which could result in non-uniform physical and microstructural properties. Detailed study of the temperature and current distributions inside the sintered sample is necessary to minimize the temperature gradients and achieve desired properties. In the present study, a coupled thermal-electric model was developed using finite element codes in ABAQUS software to investigate the temperature and current distributions inside the conductive and non-conductive samples. An integrated experimental-numerical methodology was implemented to determine the system contact resistances accurately. The developed sintering model was validated by a series of experiments, which showed good agreements with simulation results. The temperature distribution inside the sample depends on some process parameters such as sample and tool geometry, punch and die position, applied current and thermal insulation around the die. The role of these parameters on sample temperature distribution was systematically analyzed. The findings of this research could prove very useful for the reliable production of large size sintered samples with controlled and tailored properties.

Effect of various sintering temperature on resistivity behaviour and magnetoresistance of La{sub 0.67}Ba{sub 0.33}MnO{sub 3}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pratama, R.; Kurniawan, B., E-mail: bkuru07@gmail.com; Manaf, A.

2016-04-19

A detail work was conducted in order to investigate effect of various sintering temperature on resistivity behavior and its relation with the magneto-resistance effect of La{sub 0.67}Ba{sub 0.33}MnO{sub 3} (LBMO). The LBMO samples were synthesized using solid state reaction. Characterization using X-ray diffraction shows that all LBMO samples have a single phase for each variation. Variation of sintering temperature on the LBMO samples affects its lattice parameters. The resistivity measurement in an absence and under applied magnetic field resulted in a highly significant different values. In one of the sintering temperature variation of LBMO, an increasing resistivity had shown atmore » a low temperature and had reached its maximum value at a specific temperature, and then the resistivity decreases to the lowest value near the room temperature. Similar result observed at higher varieties of sintering temperature but with significant lower maximum resistivity.« less

Influence of the sintering temperature on the electrical properties of Ce-doped WO3 ceramics prepared from nano-powders

NASA Astrophysics Data System (ADS)

Dong, Liang; Chen, Han-Jun; Wang, Yu; Li, De-Zhu; Li, Tong-Ye; Zhao, Yong

2007-04-01

Using a nm-level powder fabricated by a wet chemical method as precursor, the CeO2-doped WO3 ceramics were prepared by the conventional solid state reaction at sintering temperatures from 600 to 1100 °C. The x-ray diffraction analysis reveals the coexistence of different WO3 phases in the samples sintered at temperatures below 900 °C, whereas a single phase appears in the samples sintered above 1000 °C. No new Ce-W compound appears. As the sintering temperature increases, the electrical properties of the samples display an interesting transformation from linear to nonlinear behaviour. The measurements of scanning electron microscope, complex impedance and electrical stability indicate that a lot of grain boundary regions in the samples sintered at low temperatures strongly influences the electrical transportation. Therefore, the electrical nonlinearity is due to a basic process controlled by the back-to-back Schottky barriers at grain boundaries with suitable thickness as well as the coexistence of phases.

The influence of sintering temperature on microstructure and mechanical properties of Ni-Al intermetallics fabricated by SPS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thömmes, A., E-mail: thoemmes.alexander@gmail.com; Shevtsova, L. I., E-mail: edeliya2010@mail.ru; Laptev, I. S., E-mail: ilya-laptev-nstu@mail.ru

2015-10-27

In the present study PN85Yu15 was used as elemental powder to produce a sintered compound with Ni3Al as main phase. The Spark Plasma Sintering (SPS) technique is used to compact the powders. The powder was sintered in a temperature range between 1000°C and 1150°C to observe the influence of the sintering temperature on the microstructure and the mechanical properties. The microstructure was observed with optical microscope (OM), the phase composition was characterized by X-ray diffraction (XRD) technique. Density and microhardness were observed and compared the values with the results of other researchers. The compressive-, density- and microhardness tests show asmore » clear result that with increasing the sintering temperature nearly all properties become better and also the microstructure studies show that porous places become less.« less

Study of structural and magnetic properties of cobalt ferrite nanoparticles sintered at different temperature

NASA Astrophysics Data System (ADS)

Kumari, Mukesh; Bhatnagar, Mukesh Chander

2018-05-01

Cobalt ferrite (CFO) has been synthesized in the form of nanoparticles (NPs) through sol-gel auto-combustion method. The prepared NPs of CFO were sintered for four hours at various temperatures from 300°C to 900°C. The physical properties of the sintered samples have been optimized using X-ray diffraction (XRD), Raman spectroscopy and physical properties measurement system (PPMS). The XRD and Raman studies have confirmed the cubic spinel phase formation of CFO NPs. XRD results showed that as we increase the sintering temperature the crystallite size of particles increases. Whereas the magnetic studies revealed that the saturation magnetization (MS) increases while the coercivity (HC) of nanoparticles decreases with increase of sintering temperature.

Influence of sintering temperature on the characteristics of shale brick containing oil well-derived drilling waste.

PubMed

Li, Xiang-Guo; Lv, Yang; Ma, Bao-Guo; Jian, Shou-Wei; Tan, Hong-Bo

2011-11-01

The influence of sintering temperature on the physico-mechanical characteristics (such as water absorption, apparent porosity, bulk density, weight loss on ignition, firing shrinkage, and compressive strength), leachability, and microstructure of shale brick containing oil well-derived drilling waste (DW) was investigated. The experiments were conducted at a temperature ranging from 950°C to 1,050°C with 30% DW addition. The results indicate that increasing the sintering temperature decreases the water absorption and apparent porosity and increases the shrinkage, density, and compressive strength of sintered specimens. Moreover, the physico-mechanical properties of samples sintered at 1,050°C meet the requirements of the MU20 according to GB/T 5101-2003 (in China). The heavy metal concentrations of the leachate are much lower than the current regulatory limits according to GB16889-2008. The results from XRD and SEM show that increasing sintering temperature results in an increase of the high temperature liquid phase, which may have a significant effect on the densification process of the samples.

Low sintering temperature glass waste forms for sequestering radioactive iodine

DOEpatents

Nenoff, Tina M.; Krumhansl, James L.; Garino, Terry J.; Ockwig, Nathan W.

2012-09-11

Materials and methods of making low-sintering-temperature glass waste forms that sequester radioactive iodine in a strong and durable structure. First, the iodine is captured by an adsorbant, which forms an iodine-loaded material, e.g., AgI, AgI-zeolite, AgI-mordenite, Ag-silica aerogel, ZnI.sub.2, CuI, or Bi.sub.5O.sub.7I. Next, particles of the iodine-loaded material are mixed with powdered frits of low-sintering-temperature glasses (comprising various oxides of Si, B, Bi, Pb, and Zn), and then sintered at a relatively low temperature, ranging from 425.degree. C. to 550.degree. C. The sintering converts the mixed powders into a solid block of a glassy waste form, having low iodine leaching rates. The vitrified glassy waste form can contain as much as 60 wt % AgI. A preferred glass, having a sintering temperature of 500.degree. C. (below the silver iodide sublimation temperature of 500.degree. C.) was identified that contains oxides of boron, bismuth, and zinc, while containing essentially no lead or silicon.

Indentation Behavior and Mechanical Properties of Tungsten/Chromium co-Doped Bismuth Titanate Ceramics Sintered at Different Temperatures

PubMed Central

Xu, Jiageng; Chen, Yu; Tan, Zhi; Nie, Rui; Wang, Qingyuan; Zhu, Jianguo

2018-01-01

A sort of tungsten/chromium(W/Cr) co-doped bismuth titanate (BIT) ceramics (Bi4Ti2.95W0.05O12.05 + 0.2 wt % Cr2O3, abbreviate to BTWC) are ordinarily sintered between 1050 and 1150 °C, and the indentation behavior and mechanical properties of ceramics sintered at different temperatures have been investigated by both nanoindentation and microindentation technology. Firstly, more or less Bi2Ti2O7 grains as the second phase were found in BTWC ceramics, and the grain size of ceramics increased with increase of sintering temperatures. A nanoindentation test for BTWC ceramics reveals that the testing hardness of ceramics decreased with increase of sintering temperatures, which could be explained by the Hall–Petch equation, and the true hardness could be calculated according to the pressure-state-response (PSR) model considering the indentation size effect, where the value of hardness depends on the magnitude of load. While, under the application of microsized Vickers, the sample sintered at a lower temperature (1050 °C) gained four linearly propagating cracks, however, they were observed to shorten in the sample sintered at a higher temperature (1125 °C). Moreover, both the crack deflection and the crack branching existed in the latter. The hardness and the fracture toughness of BTWC ceramics presented a contrary variational tendency with increase of sintering temperatures. A high sintering tends to get a lower hardness and a higher fracture toughness, which could be attributed to the easier plastic deformation and the stronger crack inhibition of coarse grains, respectively, as well as the toughening effect coming from the second phase. PMID:29584677

Effects of sintering time and temperature to the characteristics of FeCrAl powder compacts formed at elevated temperature

NASA Astrophysics Data System (ADS)

Rahman, M. M.; Rahman, H. Y.; Awang, M. A. A.; Sopyan, I.

2018-01-01

This paper presents the outcomes of an experimental investigation on the effect of sintering schedule, i.e., holding time and temperature to the final properties of FeCrAl powder compacts prepared through uniaxial die compaction process at above room temperature. The feedstock was prepared by mechanically mixing iron powder ASC 100.29 with chromium (22 wt%) and aluminium (11 wt%) for 30 min at room temperature. A cylindrical shape die was filled with the powder mass and heated for one hour for uniform heating of the die assembly together with the powder mass. Once the temperature reached to the setup temperature, i.e., 150°C, the powder mass was formed by applying an axial pressure of 425 MPa simultaneously from upward and downward directions. The as-pressed green compacts were then cooled to room temperature and subsequently sintered in argon gas fired furnace at a rate of 5°C/min for three different holding times, i.e., 30, 60, and 90 min at three different sintering temperatures, i.e., 800, 900, and 1000°C. The sintered samples were characterized for their density, electrical resistivity, bending strength, and microstructure. The results revealed that the sample sintered at 1000°C for 90 min achieved the better characteristics.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ozturk, Fahrettin; Toros, Serkan; Evis, Zafer

In this study, the diametral strength test of sintered hydroxyapatite was simulated by the finite element software, ABAQUS/Standard. Stress distributions on diametral test sample were determined. The effect of sintering temperature on stress distribution of hydroxyapatite was studied. It was concluded that high sintering temperatures did not reduce the stress on hydroxyapatite. It had a negative effect on stress distribution of hydroxyapatite after 1300 deg. C. In addition to the porosity, other factors (sintering temperature, presence of phases and the degree of crystallinity) affect the diametral strength of the hydroxyapatite.

Effects of sintering temperature on properties of toroid cores using NiZnCu ferrites for power applications at >1 MHz

NASA Astrophysics Data System (ADS)

Liu, Junchang; Mei, Yunhui; Liu, Wen; Li, Xin; Hou, Feng; Lu, Guo-Quan

2018-05-01

The microstructures, magnetic and electronic performance of NiZnCu ferrites have been investigated at temperature from 850 °C to 1000 °C. X-ray diffraction (XRD) patterns showed that only single phase with spinel structure existed. Scanning electron microscopy (SEM) results showed that grain size increased with enhancement of sintering temperature and the most homogeneous, compact microstructure was obtained at 950 °C. Magnetic properties measurements revealed that both complex permeability and saturation magnetization increased with increasing of sintering temperature. The initial permeability was approximately linear within the scope of 850-1000 °C as well as the resonance frequency decreased from 70 MHz to 30 MHz. Power loss density tests demonstrated that the core sintered at 950 °C instead of the one sintered at 1000 °C had the lower power loss density at both 5 mT and 10 mT and the higher inductance under a certain exciting direct current at 1 MHz. Also the inductance of the sample sintered at the higher temperature dropped faster than that at the lower temperature. The results showed that the core sintered at 950 °C had better electrical performance and was suitable for wide usage.

Long-Term Cr Poisoning Effect on LSCF-GDC Composite Cathodes Sintered at Different Temperatures

DOE PAGES

Xiong, Chunyan; Taillon, Joshua A.; Pellegrinelli, Christopher; ...

2016-07-19

Here, the impact of sintering temperature on Cr-poisoning of solid oxide fuel cell (SOFC) cathodes was systematically studied. La 0.6Sr 0.4Fe 0.8Co 0.2O 3-δ - Ce 0.9Gd 0.1O 2-δ symmetric cells were aged at 750°C in synthetic air with the presence of Crofer 22 APU, a common high temperature interconnect, over 200 hours and electrochemical impedance spectroscopy (EIS) was used to determine the degradation process. Both the ohmic resistance (R Ω) and polarization resistance (R P) of LSCF-GDC cells, extracted from EIS spectra, for different sintering temperatures increase as a function of aging time. Furthermore, the Cr-related degradation rate increasesmore » with decreased cathode sintering temperature. The polarization resistance of cathode sintered at lower temperature (950°C) increases dramatically while aging with the presence of Cr and also significantly decreases the oxygen partial pressure dependence after aging. The degradation rate shows a positive correlation to the concentration of Cr. The results indicate that decreased sintering temperature increases the total surface area, leading to more available sites for Sr-Cr-O nucleation and thus greater Cr degradation.« less

Densification behavior, nanocrystallization, and mechanical properties of spark plasma sintered Fe-based bulk amorphous alloys

NASA Astrophysics Data System (ADS)

Singh, Ashish Kumar

Fe-based amorphous alloys are gaining increasing attention due to their exceptional wear and corrosion resistance for potential structural applications. Two major challenges that are hindering the commercialization of these amorphous alloys are difficulty in processing of bulk shapes (diameter > 10 mm) and lack of ductility. Spark plasma sintering (SPS) is evolving as a promising technique for processing bulk shapes of amorphous and nanocrystalline materials. The objective of this work is to investigate densification behavior, nanocrystallization, and mechanical properties of SPS sintered Fe-based amorphous alloys of composition Fe48Cr15Mo14Y2C15B6. SPS processing was performed in three distinct temperature ranges of amorphous alloys: (a) below glass transition temperature (Tg), (b) between Tg and crystallization temperature (Tx), and (c) above Tx. Punch displacement data obtained during SPS sintering was correlated with the SPS processing parameters such as temperature, pressure, and sintering time. Powder rearrangement, plastic deformation below T g, and viscous flow of the material between Tg and Tx were observed as the main densification stages during SPS sintering. Micro-scale temperature distributions at the point of contact and macro-scale temperature distribution throughout the sample during SPS of amorphous alloys were modeled. The bulk amorphous alloys are expected to undergo structural relaxation and nanocrystallization during SPS sintering. X-ray diffraction (XRD), small angle neutron scattering (SANS), and transmission electron microscopy (TEM) was performed to investigate the evolution of nanocrystallites in SPS sintered Fe-based bulk amorphous alloys. The SANS analysis showed significant scattering for the samples sintered in the supercooled region indicating local structural and compositional changes with the profuse nucleation of nano-clusters (~4 nm). Compression tests and microhardness were performed on the samples sintered at different temperatures ranging from 570 °C to 800 °C. Maximum compression strength (1.1+/-0.2 MPa) was obtained for the samples sintered in the supercooled region. Effects of crystallization on tribological behavior of sintered samples were also investigated where crystallization resulted in increase in wear resistance. Laser surface hardening of SPS sintered amorphous samples were performed. Depending on the processing parameters, the laser surface irradiation causes structural relaxation and nanocrystallization, resulting in surface hardening.

Effects of forming temperature and sintering rate to the final properties of FeCuAl powder compacts formed through uniaxial die compaction process

NASA Astrophysics Data System (ADS)

Rahman, M. M.; Ismail, M. A.; Sopyan, I.; Rahman, H. Y.

2018-01-01

This paper presents the outcomes of an experimental investigation on the effects of forming temperature and sintering schedule to the final characteristics of FeCuAl powder mass formed at different temperature and sintered at different schedule. A lab-scale uni-axial die compaction rig was designed and fabricated which enabled the compaction of powder mass at room temperature as well as elevated temperature. Iron (Fe) powder ASC 100.29 was mechanically mixed with other elemental powders, namely copper (Cu), and aluminum (Al) for 60 minutes and compacted at three different temperature, i.e., 30°C, 150°C, and 200°C by applying 425 MPa of simultaneous downward and upward axial loading to generate green compacts. The as-pressed samples were inspected visually and the defect-free green compacts were subsequently sintered in an argon gas fired furnace at 800°C for 60 min at three different heating/cooling rates, i.e., 5, 10, and 15°C/min, respectively. The sintered samples were then characterised for their physical, electrical, and mechanical properties. The microstructures of the sintered samples were also analysed. The results revealed that a forming temperature of 150°C and a sintering rate of 10°C/min could produce a product with better characteristics.

Ultra-low temperature sintering of Cu@Ag core-shell nanoparticle paste by ultrasonic in air for high-temperature power device packaging.

PubMed

Ji, Hongjun; Zhou, Junbo; Liang, Meng; Lu, Huajun; Li, Mingyu

2018-03-01

Sintering of low-cost Cu nanoparticles (NPs) for interconnection of chips to substrate at low temperature and in atmosphere conditions is difficult because they are prone to oxidation, but dramatically required in semiconductor industry. In the present work, we successfully synthesized Cu@Ag NPs paste, and they were successfully applied for joining Cu/Cu@Ag NPs paste/Cu firstly in air by the ultrasonic-assisted sintering (UAS) at a temperature of as low as 160 °C. Their sintered microstructures featuring with dense and crystallized cells are completely different from the traditional thermo-compression sintering (TCS). The optimized shear strength of the joints reached to 54.27 MPa, exhibiting one order of magnitude higher than TCS at the same temperature (180 °C) under the UAS. This ultra-low sintering temperature and high performance of the sintered joints were ascribed to ultrasonic effects. The ultrasonic vibrations have distinct effects on the metallurgical reactions of the joints, resulting in the contact and growth of Cu core and the stripping and connection of Ag shell, which contributes to the high shear strength. Thus, the UAS of Cu@Ag NPs paste has a great potential to be applied for high-temperature power device packaging. Copyright © 2017 Elsevier B.V. All rights reserved.

Effect of surface oxide films on the properties of pulse electric-current sintered metal powders

NASA Astrophysics Data System (ADS)

Xie, Guoqiang; Ohashi, Osamu; Yamaguchi, Norio; Wang, Airu

2003-11-01

Metallic powders with various thermodynamic stability oxide films (Ag, Cu, and Al powders) were sintered using a pulse electric-current sintering (PECS) process. Behavior of oxide films at powder surfaces and their effect on the sintering properties were investigated. The results showed that the sintering properties of metallic powders in the PECS process were subject to the thermodynamic stability of oxide films at particles surfaces. The oxide films at Ag powder surfaces are decomposed during sintering with the contact region between the particles being metal/metal bond. The oxide films at Cu powder surfaces are mainly broken via loading pressure at a low sintering temperature. At a high sintering temperature, they are mainly dissolved in the parent metal, and the contact regions turn into the direct metal/metal bonding. Excellent sintering properties can be received. The oxide films at Al powder surfaces are very stable, and cannot be decomposed and dissolved, but broken by plastic deformation of particles under loading pressure at experimental temperatures. The interface between particles is partially bonded via the direct metal/metal bonding making it difficult to achieve good sintered properties.

On the self-damping nature of densification in photonic sintering of nanoparticles

PubMed Central

MacNeill, William; Choi, Chang-Ho; Chang, Chih-Hung; Malhotra, Rajiv

2015-01-01

Sintering of nanoparticle inks over large area-substrates is a key enabler for scalable fabrication of patterned and continuous films, with multiple emerging applications. The high speed and ambient condition operation of photonic sintering has elicited significant interest for this purpose. In this work, we experimentally characterize the temperature evolution and densification in photonic sintering of silver nanoparticle inks, as a function of nanoparticle size. It is shown that smaller nanoparticles result in faster densification, with lower temperatures during sintering, as compared to larger nanoparticles. Further, high densification can be achieved even without nanoparticle melting. Electromagnetic Finite Element Analysis of photonic heating is coupled to an analytical sintering model, to examine the role of interparticle neck growth in photonic sintering. It is shown that photonic sintering is an inherently self-damping process, i.e., the progress of densification reduces the magnitude of subsequent photonic heating even before full density is reached. By accounting for this phenomenon, the developed coupled model better captures the experimentally observed sintering temperature and densification as compared to conventional photonic sintering models. Further, this model is used to uncover the reason behind the experimentally observed increase in densification with increasing weight ratio of smaller to larger nanoparticles. PMID:26443492

Influence of Hydrogen on Atomized Titanium Powders Sintering

NASA Astrophysics Data System (ADS)

Senkevich, K. S.

2018-07-01

The aim of this work is to study the effect of hydrogen reversible alloying (thermohydrogen processing, THP) on low-temperature sintering of atomized titanium powders. It is stated that alloying with 0.2 to 0.8 wt pct of hydrogen beneficially affects titanium powders sintering. The effect is caused by phase transformations occurring upon hydrogen saturation of powders and dehydrogenation, which substantially intensifies sintering at temperatures from 800 °C to 900 °C. The role of certain THP stages (sintering in hydrogenated state and upon dehydrogenation) on formation of sintered contacts in porous materials is shown.

Influence of Hydrogen on Atomized Titanium Powders Sintering

NASA Astrophysics Data System (ADS)

Senkevich, K. S.

2018-05-01

The aim of this work is to study the effect of hydrogen reversible alloying (thermohydrogen processing, THP) on low-temperature sintering of atomized titanium powders. It is stated that alloying with 0.2 to 0.8 wt pct of hydrogen beneficially affects titanium powders sintering. The effect is caused by phase transformations occurring upon hydrogen saturation of powders and dehydrogenation, which substantially intensifies sintering at temperatures from 800 °C to 900 °C. The role of certain THP stages (sintering in hydrogenated state and upon dehydrogenation) on formation of sintered contacts in porous materials is shown.

Spark plasma sintering of titanium aluminide intermetallics and its composites

NASA Astrophysics Data System (ADS)

Aldoshan, Abdelhakim Ahmed

Titanium aluminide intermetallics are a distinct class of engineering materials having unique properties over conventional titanium alloys. gamma-TiAl compound possesses competitive physical and mechanical properties at elevated temperature applications compared to Ni-based superalloys. gamma-TiAl composite materials exhibit high melting point, low density, high strength and excellent corrosion resistance. Spark plasma sintering (SPS) is one of the powder metallurgy techniques where powder mixture undergoes simultaneous application of uniaxial pressure and pulsed direct current. Unlike other sintering techniques such as hot iso-static pressing and hot pressing, SPS compacts the materials in shorter time (< 10 min) with a lower temperature and leads to highly dense products. Reactive synthesis of titanium aluminide intermetallics is carried out using SPS. Reactive sintering takes place between liquid aluminum and solid titanium. In this work, reactive sintering through SPS was used to fabricate fully densified gamma-TiAl and titanium aluminide composites starting from elemental powders at different sintering temperatures. It was observed that sintering temperature played significant role in the densification of titanium aluminide composites. gamma-TiAl was the predominate phase at different temperatures. The effect of increasing sintering temperature on microhardness, microstructure, yield strength and wear behavior of titanium aluminide was studied. Addition of graphene nanoplatelets to titanium aluminide matrix resulted in change in microhardness. In Ti-Al-graphene composites, a noticeable decrease in coefficient of friction was observed due to the influence of self-lubrication caused by graphene.

Processing Techniques Developed to Fabricate Lanthanum Titanate Piezoceramic Material for High-Temperature Smart Structures

NASA Technical Reports Server (NTRS)

Goldsby, Jon C.; Farmer, Serene C.; Sayir, Ali

2004-01-01

Piezoelectric ceramic materials are potential candidates for use as actuators and sensors in intelligent gas turbine engines. For piezoceramics to be applied in gas turbine engines, they will have to be able to function in temperatures ranging from 1000 to 2500 F. However, the maximum use temperature for state-of-the-art piezoceramic materials is on the order of 300 to 400 F. Research activities have been initiated to develop high-temperature piezoceramic materials for gas turbine engine applications. Lanthanum titanate has been shown to have high-temperature piezoelectric properties with Curie temperatures of T(sub c) = 1500 C and use temperatures greater than 1000 C. However, the fabrication of lanthanum titanate poses serious challenges because of the very high sintering temperatures required for densification. Two different techniques have been developed at the NASA Glenn Research Center to fabricate dense lanthanum titanate piezoceramic material. In one approach, lower sintering temperatures were achieved by adding yttrium oxide to commercially available lanthanum titanate powder. Addition of only 0.1 mol% yttrium oxide lowered the sintering temperature by as much as 300 C, to just 1100 C, and dense lanthanum titanate was produced by pressure-assisted sintering. The second approach utilized the same commercially available powders but used an innovative sintering approach called differential sintering, which did not require any additive.

Apparatus and method for direct measurement of coal ash sintering and fusion properties at elevated temperatures and pressures

DOEpatents

Khan, M. Rashid

1990-01-01

A high-pressure microdilatometer is provided for measuring the sintering and fusion properties of various coal ashes under the influence of elevated pressures and temperatures in various atmospheres. Electrical resistivity measurements across a sample of coal ash provide a measurement of the onset of the sintering and fusion of the ash particulates while the contraction of the sample during sintering is measured with a linear variable displacement transducer for detecting the initiation of sintering. These measurements of sintering in coal ash at different pressures provide a mechanism by which deleterious problems due to the sintering and fusion of ash in various combustion systems can be minimized or obviated.

Influence of spark plasma sintering parameters on magnetic properties of FeCo alloy

NASA Astrophysics Data System (ADS)

Albaaji, Amar J.; Castle, Elinor G.; Reece, Mike J.; Hall, Jeremy P.; Evans, Sam L.

2018-04-01

Equiatomic FeCo alloys with average particle size of 24 μm were sintered using spark plasma sintering (SPS) system at sintering temperatures of 1100, 800, and 850 °C for heating rates 50, 100, 300 °C/min by applying pressure of 50 MPa instantly at room temperature for sintering time of 5 and 15 minutes. The highest saturation induction was achieved at SPS conditions of 50 MPa, 50 °C/min, 1100 °C, without dwelling, of value 2.39 T. The saturation induction was improved with extending sintering time, the coercivity was higher in samples sintered at a fast heating rate in comparison to the slowest heating rate.

3D microenvironment as essential element for osteoinduction by biomaterials.

PubMed

Habibovic, Pamela; Yuan, Huipin; van der Valk, Chantal M; Meijer, Gert; van Blitterswijk, Clemens A; de Groot, Klaas

2005-06-01

In order to unravel the mechanism of osteoinduction by biomaterials, in this study we investigated the influence of the specific surface area on osteoinductive properties of two types of calcium phosphate ceramics. Different surface areas of the ceramics were obtained by varying their sintering temperatures. Hydroxyapatite (HA) ceramic was sintered at 1150 and 1250 degrees C. Biphasic calcium phosphate (BCP) ceramic, consisting of HA and beta-tricalcium phosphate (beta-TCP), was sintered at 1100, 1150 and 1200 degrees C. Changes in sintering temperature did not influence the chemistry of the ceramics; HA remained pure after sintering at different temperatures and the weight ratio of HA and beta-TCP in the BCP was independent of the temperature as well. Similarly, macroporosity of the ceramics was unaffected by the changes of the sintering temperature. However, microporosity (pore diameter <10 microm) significantly decreased with increasing sintering temperature. In addition to the decrease of the microporosity, the crystal size increased with increasing sintering temperature. These two effects resulted in a significant decrease of the specific surface area of the ceramics with increasing sintering temperatures. Samples of HA1150, HA1250, BCP1100, BCP1150 and BCP1200 were implanted in the back muscles of Dutch milk goats and harvested at 6 and 12 weeks post implantation. After explantation, histomorphometrical analysis was performed on all implants. All implanted materials except HA1250 induced bone. However, large variations in the amounts of induced bone were observed between different materials and between individual animals. Histomorphometrical results showed that the presence of micropores within macropore walls is necessary to make a material osteoinductive. We postulate that introduction of microporosity within macropores, and consequent increase of the specific surface area, affects the interface dynamics of the ceramic in such a way that relevant cells are triggered to differentiate into the osteogenic lineage.

Effect of sintering temperature on the microstructure and properties of foamed glass-ceramics prepared from high-titanium blast furnace slag and waste glass

NASA Astrophysics Data System (ADS)

Chen, Chang-hong; Feng, Ke-qin; Zhou, Yu; Zhou, Hong-ling

2017-08-01

Foamed glass-ceramics were prepared via a single-step sintering method using high-titanium blast furnace slag and waste glass as the main raw materials The influence of sintering temperature (900-1060°C) on the microstructure and properties of foamed glass-ceramics was studied. The results show that the crystal shape changed from grainy to rod-shaped and finally turned to multiple shapes as the sintering temperature was increased from 900 to 1060°C. With increasing sintering temperature, the average pore size of the foamed glass-ceramics increased and subsequently decreased. By contrast, the compressive strength and the bulk density decreased and subsequently increased. An excessively high temperature, however, induced the coalescence of pores and decreased the compressive strength. The optimal properties, including the highest compressive strength (16.64 MPa) among the investigated samples and a relatively low bulk density (0.83 g/cm3), were attained in the case of the foamed glass-ceramics sintered at 1000°C.

A comparative study of conventionally sintered and microwave sintered nickel zinc ferrite

NASA Astrophysics Data System (ADS)

Rani, Rekha; Juneja, J. K.; Raina, K. K.; Kotnala, R. K.; Prakash, Chandra

2014-04-01

For the present work, nickel zinc ferrite having compositional formula Ni0.8Zn0.2Fe2O4 was synthesized by conventional solid state method and sintered in conventional and microwave furnaces. Pellets were sintered with very short soaking time of 10 min at 1150 °C in microwave furnace whereas 4 hrs of soaking time was selected for conventional sintering at 1200 °C. Phase formation was confirmed by X-ray diffraction analysis technique. Scanning electron micrographs were taken for microstructural study. Dielectric properties were studied as a function of temperature. To study magnetic behavior, M-H hysteresis loops were recorded for both samples. It is observed that microwave sintered sample could obtain comparable properties to the conventionally sintered one in lesser soaking time at lower sintering temperature.

Effects of pressure and temperature on sintering of Cr-doped Al2O3 by pulsed electric current sintering process

NASA Astrophysics Data System (ADS)

Dang, K. Q.; Nanko, M.

2011-03-01

The aluminium oxide crystal, Al2O3, which contains a small amount of chromium, Cr, is called ruby. Pulsed electric current sintering (PECS) was applied to sinter ruby polycrystals. Cr2O3-Al2O3 powder mixture prepared by drying an aqueous slurry containing amounts of Al2O3 and Cr(NO3)3 was consolidated by PECS process. The PECS process was performed in vacuum at sintering temperature raging from 1100 to 1300°C with heating rate of 2 K/min under applied uniaxial pressure varied from 40 to 100 MPa. This study found that highly densified and transparent Cr-doped Al2O3 can be obtained by the PECS process with the high applied pressure at sintering temperature of 1200°C.

Effect of Process Parameter on Barium Titanate Stannate (BTS) Materials Sintered at Low Sintering

NASA Astrophysics Data System (ADS)

Shukla, Alok; Bajpai, P. K.

2011-11-01

Ba(Ti1-xSnx)O3 solid solutions with (x = 0.15, 0.20, 0.30 and 0.40) are synthesized using conventional solid state reaction method. Formation of solid solutions in the range 0 ≤ x ≤0.40 is confirmed using X-ray diffraction technique. Single phase solid solutions with homogeneous grain distribution are observed at relatively low sintering by controlling process parameters viz. sintering time. Composition at optimized temperature (1150 °C) sintered by varying the sintering time, stabilize in cubic perovskite phase. The % experimental density increase with increasing the time of sintering instead of increasing sintering temperature. The lattice parameter increases by increasing the tin composition in the material. This demonstrates that process parameter optimization can lead to single phase at relatively lower sintering-a major advantage for the materials used as capacitor element in MLCC.

Manufacture of sintered silicon nitrides

NASA Technical Reports Server (NTRS)

Iwai, T.

1985-01-01

Sintered silicon nitrides are manufactured by sintering Si3N powder containing 2 to 15% in wt of a powder mixture composed of nitride powder of lanthanide or Y 100 parts and AIN powder less than 100 parts at 1500 to 1900 deg. temperature under a pressure of less than 200 Kg/sq. cm. The sintered Si3N has high mechanical strength in high temperature. Thus, Si3N4 93.0, Y 5.0 and AlN 2.0% in weight were wet mixed in acetone in N atom, molded and sintered at 1750 deg. and 1000 Kg/sq. cm. to give a sintered body having high hardness.

Improvement of the electrochromic response of a low-temperature sintered dye-modified porous electrode using low-resistivity indium tin oxide nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Watanabe, Yuichi, E-mail: yuichi.watanabe@aist.go.jp; Suemori, Kouji; Hoshino, Satoshi

2016-06-15

An indium tin oxide (ITO) nanoparticle-based porous electrode sintered at low temperatures was investigated as a transparent electrode for electrochromic displays (ECDs). The electrochromic (EC) response of the dye-modified ITO porous electrode sintered at 150 °C, which exhibited a generally low resistivity, was markedly superior to that of a conventional dye-modified TiO{sub 2} porous electrode sintered at the same temperature. Moreover, the EC characteristics of the dye-modified ITO porous electrode sintered at 150 °C were better than those of the high-temperature (450 °C) sintered conventional dye-modified TiO{sub 2} porous electrode. These improvements in the EC characteristics of the dye-modified ITO porous electrode aremore » attributed to its lower resistivity than that of the TiO{sub 2} porous electrodes. In addition to its sufficiently low resistivity attained under the sintering conditions required for flexible ECD applications, the ITO porous film had superior visible-light transparency and dye adsorption capabilities. We conclude that the process temperature, resistivity, optical transmittance, and dye adsorption capability of the ITO porous electrode make it a promising transparent porous electrode for flexible ECD applications.« less

The thermal stability of hydroxyapatite in biphasic calcium phosphate ceramics.

PubMed

Nilen, R W N; Richter, P W

2008-04-01

Biphasic calcium phosphate ceramics (BCP) comprising a mix of non-resorbable hydroxyapatite (HA) and resorbable beta-tricalcium phosphate (beta-TCP) are particularly suitable materials for synthetic bone substitute applications. In this study, HA synthesised by solid state reaction was mechanically mixed with beta-TCP, then sintered to form a suite of BCP materials with a wide range of HA/beta-TCP phase content ratios. The influence of sintering temperature and composition on the HA thermal stability was quantified by X-ray diffraction (XRD). The pre-sinter beta-TCP content was found to strongly affect the post-sinter HA/beta-TCP ratio by promoting the thermal decomposition of HA to beta-TCP, even at sintering temperatures as low as 850 degrees C. For BCP material with pre-sinter HA/beta-TCP = 40/60 wt%, approximately 80% of the HA decomposed to beta-TCP during sintering at 1000 degrees C. Furthermore, the HA content appeared to influence the reverse transformation of alpha-TCP to beta-TCP expected upon gradual cooling from sintering temperatures greater than 1125 degrees C. Because the HA/beta-TCP ratio dominantly determines the rate and extent of BCP resorption in vivo, the possible thermal decomposition of HA during BCP synthesis must be considered, particularly if high temperature treatments are involved.

Low-Temperature Sintering Behavior (≤ 400°C) of Micro-sized Silver Particles Decorated by Silver Nanoparticles Through Surface Iodination

NASA Astrophysics Data System (ADS)

Zhou, Jian; Tang, Hongbo

2018-05-01

This paper introduces a facile and effective route to decorate micro-sized silver particle surfaces with Ag/AgI nanoclusters through a wet chemical reaction at room temperature using iodine and ethanol as reactant and solvent, respectively. Photosensitivity of AgI is utilized in the route, and AgI decomposes into Ag upon contact with sunshine, forming Ag/AgI nanoclusters. The modified micro-sized Ag particles showed sinterability even at 200°C and formed rigid electrical conductive networks at 350°C. Moreover, sintered film containing the modified Ag particles reached the best conductivity, 9.35 mΩ/sq, after sintering at 350°C for 20 min, while the film with untreated control Ag particles obtained its best conductivity at 400°C. The excellent sinterability should be attributed to the nanoclusters which served as a sintering aid during the heating process. However, increase of sintering temperature and time destroyed densification and conductivity of the sintered film containing the modified particles.

One step sintering of homogenized bauxite raw material and kinetic study

NASA Astrophysics Data System (ADS)

Gao, Chang-he; Jiang, Peng; Li, Yong; Sun, Jia-lin; Zhang, Jun-jie; Yang, Huan-ying

2016-10-01

A one-step sintering process of bauxite raw material from direct mining was completed, and the kinetics of this process was analyzed thoroughly. The results show that the sintering kinetics of bauxite raw material exhibits the liquid-phase sintering behavior. A small portion of impurities existed in the raw material act as a liquid phase. After X-ray diffraction analyses, scanning electron microscopy observations, and kinetics calculations, sintering temperature and heating duration were determined as the two major factors contributing to the sintering process and densification of bauxite ore. An elevated heating temperature and longer duration favor the densification process. The major obstacle for the densification of bauxite material is attributed to the formation of the enclosed blowhole during liquid-phase sintering.

Flash sintering of stoichiometric and hyper-stoichiometric urania

DOE PAGES

Valdez, James Anthony; Byler, Darrin David; Kardoulaki, Erofili; ...

2018-03-29

Flash sintering (FS), a novel fabrication technique belonging to the family of field assisted sintering (FAS) techniques, has been utilized in this study to fabricate uranium dioxide (UO 2) pellets. Stoichiometric (UO 2.00) and hyper-stoichiometric (UO 2.16) pellets were flash sintered at 600 °C within a few (2–3) minutes. This is in sharp contrast to conventional sintering where temperatures hundreds of degrees higher are necessary and the sintering time extends to hours. Relating this in terms of the homologous temperature ratio (T H) for both conditions shows that in the case of flash sintering at 600 °C, T H =more » 0.3 versus T H = 0.6 for conventional sintering at 1600 °C. The highest density achieved for a UO 2.00 pellet was 81% theoretical density (TD) when flash sintered at 600 °C for 184 s at a field of 188 V/cm and a current density of 442 mA/mm 2. For the UO 2.16 pellet, the highest achieved density was 92% TD when flash sintered at 600 °C for 140 s at a field of 188 V/cm and a current density of 632 mA/mm 2. X-ray diffraction (XRD) characterization of the sintered pellets showed the final sintered material to be single cubic fluorite phase. Scanning electron microscopy (SEM) of longitudinal sections revealed non-uniform microstructures with regions of high density where the grain size ranged from 1 to 15 μm. Comparisons between conventionally and flash sintered pellets that achieved equivalent shrinkage strains were also conducted. Lastly, in all cases, the flash sintered pellets achieved similar densification to the conventionally sintered pellets at much lower furnace temperatures and shorter times.« less

Flash sintering of stoichiometric and hyper-stoichiometric urania

DOE Office of Scientific and Technical Information (OSTI.GOV)

Valdez, James Anthony; Byler, Darrin David; Kardoulaki, Erofili

Flash sintering (FS), a novel fabrication technique belonging to the family of field assisted sintering (FAS) techniques, has been utilized in this study to fabricate uranium dioxide (UO 2) pellets. Stoichiometric (UO 2.00) and hyper-stoichiometric (UO 2.16) pellets were flash sintered at 600 °C within a few (2–3) minutes. This is in sharp contrast to conventional sintering where temperatures hundreds of degrees higher are necessary and the sintering time extends to hours. Relating this in terms of the homologous temperature ratio (T H) for both conditions shows that in the case of flash sintering at 600 °C, T H =more » 0.3 versus T H = 0.6 for conventional sintering at 1600 °C. The highest density achieved for a UO 2.00 pellet was 81% theoretical density (TD) when flash sintered at 600 °C for 184 s at a field of 188 V/cm and a current density of 442 mA/mm 2. For the UO 2.16 pellet, the highest achieved density was 92% TD when flash sintered at 600 °C for 140 s at a field of 188 V/cm and a current density of 632 mA/mm 2. X-ray diffraction (XRD) characterization of the sintered pellets showed the final sintered material to be single cubic fluorite phase. Scanning electron microscopy (SEM) of longitudinal sections revealed non-uniform microstructures with regions of high density where the grain size ranged from 1 to 15 μm. Comparisons between conventionally and flash sintered pellets that achieved equivalent shrinkage strains were also conducted. Lastly, in all cases, the flash sintered pellets achieved similar densification to the conventionally sintered pellets at much lower furnace temperatures and shorter times.« less

Flash sintering of stoichiometric and hyper-stoichiometric urania

NASA Astrophysics Data System (ADS)

Valdez, J. A.; Byler, D. D.; Kardoulaki, E.; Francis, J. S. C.; McClellan, K. J.

2018-07-01

Flash sintering (FS), a novel fabrication technique belonging to the family of field assisted sintering (FAS) techniques, has been utilized in this study to fabricate uranium dioxide (UO2) pellets. Stoichiometric (UO2.00) and hyper-stoichiometric (UO2.16) pellets were flash sintered at 600 °C within a few (2-3) minutes. This is in sharp contrast to conventional sintering where temperatures hundreds of degrees higher are necessary and the sintering time extends to hours. Relating this in terms of the homologous temperature ratio (TH) for both conditions shows that in the case of flash sintering at 600 °C, TH = 0.3 versus TH = 0.6 for conventional sintering at 1600 °C. The highest density achieved for a UO2.00 pellet was 81% theoretical density (TD) when flash sintered at 600 °C for 185 s at a field of 188 V/cm and a current density of 442 mA/mm2. For the UO2.16 pellet, the highest achieved density was 91% TD when flash sintered at 600 °C for 123 s at a field of 188 V/cm and a current density of 632 mA/mm2. X-ray diffraction (XRD) characterization of the sintered pellets showed the final sintered material to be single cubic fluorite phase. Scanning electron microscopy (SEM) of longitudinal sections revealed non-uniform microstructures with regions of high density where the grain size ranged from 1 to 15 μm. Comparisons between conventionally and flash sintered pellets that achieved equivalent shrinkage strains were also conducted. In all cases, the flash sintered pellets achieved similar densification to the conventionally sintered pellets at much lower furnace temperatures and shorter times.

The effect of sintering temperature on electrical characteristics of Fe2TiO5/Nb2O5 ceramics for NTC thermistor

NASA Astrophysics Data System (ADS)

Wiendartun, Risdiana, Fitrilawati, Siregar, R. E.

2016-02-01

A study on the fabrication of Iron Titanium Oxide (Fe2TiO5) ceramics for negative temperature coefficient (NTC) thermistors has been carried out, in order to know the effect of sintering temperature on the electrical characteristic of 1.0 % mole Nb2O5 doped Fe2TiO5 ceramics.These ceramics were made by mixing commercial powders of Fe2O3, TiO2 and Nb2O5 with proportional composition to produce Fe2TiO5 based ceramic. The raw pellet was sintered at 1000 °C, 1100 °C and 1200 °C temperature for 2 hours in air. Analysis of the microstructure and crystal structure were performed by using a scanning electron microscope (SEM) and x-ray diffraction (XRD) respectively. XRD spectra showed that the crystal structure of all ceramics of Fe2TiO5 made at various sintering temperatures are orthorhombic. The SEM images showed that the grain size of pellet ceramics increase with increasing sintering temperatures. From electrical resistances data that was measured at temperature 30-300 °C, it is found that the value of thermistor constant (B), activation energy (Ea), thermistor sensitivity (α) and room temperature resistance (RRT) decreases with respect to the increasing of sintering temperature. The fabricated Fe2TiO5 ceramics have thermistor constants (B = 6394-6959 K). This can be applied as temperature sensor, and will fulfill the market requirement.

Low temperature sintered giant dielectric permittivity CaCu3Ti4O12 sol-gel synthesized nanoparticle capacitors

NASA Astrophysics Data System (ADS)

Puli, Venkata Sreenivas; Adireddy, Shiva; Kothakonda, Manish; Elupula, Ravinder; Chrisey, Douglas B.

This paper reports on synthesis of polycrystalline complex perovskite CaCu3Ti4O12 (as CCTO) ceramic powders prepared by a sol-gel auto combustion method at different sintering temperatures and sintering times, respectively. The effect of sintering time on the structure, morphology, dielectric and electrical properties of CCTO ceramics is investigated. Tuning the electrical properties via different sintering times is demonstrated for ceramic samples. X-ray diffraction (XRD) studies confirm perovskite-like structure at room temperature. Abnormal grain growth is observed for ceramic samples. Giant dielectric permittivity was realized for CCTO ceramics. High dielectric permittivity was attributed to the internal barrier layer capacitance (IBLC) model associated with the Maxwell-Wagner (MW) polarization mechanism.

Method of forming a ceramic to ceramic joint

DOEpatents

Cutler, Raymond Ashton; Hutchings, Kent Neal; Kleinlein, Brian Paul; Carolan, Michael Francis

2010-04-13

A method of joining at least two sintered bodies to form a composite structure, includes: providing a joint material between joining surfaces of first and second sintered bodies; applying pressure from 1 kP to less than 5 MPa to provide an assembly; heating the assembly to a conforming temperature sufficient to allow the joint material to conform to the joining surfaces; and further heating the assembly to a joining temperature below a minimum sintering temperature of the first and second sintered bodies. The joint material includes organic component(s) and ceramic particles. The ceramic particles constitute 40-75 vol. % of the joint material, and include at least one element of the first and/or second sintered bodies. Composite structures produced by the method are also disclosed.

Grain growth effects on magnetic properties of Ni0.6Zn0.4Fe2O4 material prepared using mechanically alloyed nanoparticles

NASA Astrophysics Data System (ADS)

Syazwan, M. M.; Hapishah, A. N.; Azis, R. S.; Abbas, Z.; Hamidon, M. N.

2018-06-01

The effect of grain growth via sintering temperature on some magnetic properties is reported in this research. Ni0.6Zn0.4Fe2O4 nanoparticles were mechanically alloyed for 6 h and the sintering process starting from 600 to 1200 °C with 25 °C increment with only one sample subjected to all sintering scheme. The resulting change in the material was observed after each sintering. Single phase has been formed at 600 °C and above and the intensity peaks increased with sintering temperature as well as crystallinity increment. The morphological studies showed grain size increment as the sintering temperature increased. Moreover, the density increased while the porosity decreased with increasing sintering temperature. The saturation induction, Bs increased with the increased of grain size. On the other hand, the coercivity-vs-grain size plot reveals the critical single-domain-to-multidomain grain size to be about ∼400 nm. The initial permeability, μi value was increased with grain size enhancement. The microstructural grain growth, as exposed for the first time by this research, is shown as a process of multiple activation energy barriers.

Wettability of eutectic NaLiCO3 salt on magnesium oxide substrates at 778 K

NASA Astrophysics Data System (ADS)

Li, Chuan; Li, Qi; Cao, Hui; Leng, Guanghui; Li, Yongliang; Wang, Li; Zheng, Lifang; Ding, Yulong

2018-06-01

We investigated the wetting behavior of a eutectic carbonate salt of NaLiCO3 on MgO substrates at an elevated temperature of 778 K by measuring contact angle with a sessile drop method. Both sintered and non-sintered MgO were prepared and used as the substrates. The sintered substrates were obtained by sintering compacted MgO powders at 500-1300 °C. For comparison purposes, a single crystal MgO substrate was also used in the work. The different sintering temperatures provided MgO substrates with different structures, allowing their effects on salt penetration and hence wettability and surface energy to be investigated. A scanning electron microscope equipped with energy dispersive spectrometry and an atomic force microscope were used to observe the morphology and structures of the MgO substrates as well as the salt penetration. The results showed a good wettability of the carbonate salt on both the sintered and non-sintered MgO substrates and the wettability depended strongly on the structure of the substrates. The non-sintered MgO substrate has a loose surface particle packing with large pores and crevices, leading to significant salt infiltration, and the corresponding contact angle was measured to be ∼25°. The contact angle of the salt on the sintered MgO substrates increased with an increase in the sintering temperature of the MgO substrate, and the contact angle of the salt on the single crystal substrate was the highest at ∼40°. The effect of the sintering temperature for making the MgO substrate could be linked to the surface energy, and the linkage is validated by the AFM measurements of the adhesion forces of the MgO substrates.

Method of forming a joint

DOEpatents

Butt, Darryl Paul; Cutler, Raymond Ashton; Rynders, Steven Walton; Carolan, Michael Francis

2006-08-22

A method of joining at least two sintered bodies to form a composite structure, including providing a first multicomponent metallic oxide having a perovskitic or fluorite crystal structure; providing a second sintered body including a second multicomponent metallic oxide having a crystal structure of the same type as the first; and providing at an interface a joint material containing at least one metal oxide containing at least one metal identically contained in at least one of the first and second multicomponent metallic oxides. The joint material is free of cations of Si, Ge, Sn, Pb, P and Te and has a melting point below the sintering temperatures of both sintered bodies. The joint material is heated to a temperature above the melting point of the metal oxide(s) and below the sintering temperatures of the sintered bodies to form the joint. Structures containing such joints are also disclosed.

Development of Sintered Si3N4 for High Performance Thermomechanical Applications.

DTIC Science & Technology

1984-01-01

noted( 17) that final grain size of sintered Si3 N4 is quite sensitive to both temperature and time at temperature. The sintering of Si NI containing...Characterization of Ube-SN-E0 Si3 N4 Chemical Analysis Lot A-10 Lot A-18 N (alkali fusion) wt . % 38 38 0 (inert gas fusion) wt . % 1.2 1.4 C (inert gas fusion) wt ...temperature stutral applications except for the high creep rate, Which is of the ame order a NC-13. The sintering of -qfiN4ontaning 5 wt % LiAIq0 1and

Effect of Sintering Temperature on Structural, Dielectric, and Magnetic Properties of Multiferroic YFeO₃ Ceramics Fabricated by Spark Plasma Sintering.

PubMed

Wang, Meng; Wang, Ting; Song, Shenhua; Ma, Qing; Liu, Renchen

2017-03-07

Based on precursor powders with a size of 200-300 nm prepared by the low-temperature solid reaction method, phase-pure YFeO₃ ceramics are fabricated using spark plasma sintering (SPS) at different temperatures. X-ray diffraction (XRD) and scanning electron microscopy (SEM) reveal that the high-purity YFeO₃ ceramics can be prepared using SPS, while the results from X-ray photoelectron spectroscopy (XPS) show that the concentration of oxygen vacancies resulting from transformation from Fe 3+ to Fe 2+ is low. The relative density of the 1000 °C-sintered sample is as high as 97.7%, which is much higher than those of the samples sintered at other temperatures. The present dielectric and magnetic properties are much better than those of the samples fabricated by conventional methods. These findings indicate that the YFeO₃ ceramics prepared by the low temperature solid reaction and SPS methods possess excellent dielectric and magnetic properties, making them suitable for potential applications involving magnetic storage.

Effects of sintering atmosphere and temperature on structural and magnetic properties of Ni-Cu-Zn ferrite nano-particles: Magnetic enhancement by a reducing atmosphere

NASA Astrophysics Data System (ADS)

Gholizadeh, Ahmad; Jafari, Elahe

2017-01-01

In this work, effects of sintering atmosphere and temperature on structural and magnetic properties of Ni0.3Cu0.2Zn0.5Fe2O4 nanoparticles prepared by citrate precursor method have been studied. The structural characterization of the samples by X-ray powder diffraction and FT-IR spectroscopy is evidence for formation of a cubic structure with no presence of impurity phase. Calculated values of crystallite size and unit cell parameter show an increase with sintering temperature under different atmospheres. Variation of saturation magnetization with sintering temperature and atmosphere can be attributed to change of three factors: magnetic core size, inversion parameter and the change of Fe3+-ion concentration due to the presence of Fe4+ and Fe2+ ions. The saturation magnetization gradually grows with sintering temperature due to increase of magnetic core size and a maximum 63 emu/g was achieved at 600 °C under carbon monoxide-ambient atmosphere.

Effect of sintering temperature on the microstructure, electrical and magnetic properties of Zn0.98 Mn0.02O material

NASA Astrophysics Data System (ADS)

Sebayang, K.; Aryanto, D.; Simbolon, S.; Kurniawan, C.; Hulu, S. F.; Sudiro, T.; Ginting, M.; Sebayang, P.

2018-02-01

Zn0.98Mn0.02O material was synthesized from ZnO and MnO2 powders using solid state reaction method. The microstructure, electrical and magnetic properties of Zn0.98Mn0.02O were studied as a function of sintering temperature. The X-ray diffraction analysis indicates that the main phase of synthesized sample is composed of hexagonal wurtzite ZnO phase. While the secondary phase of ZnMnO3 were found at the sintering temperature of 700°C and 900°C. The electrical properties measurement of Zn0.98Mn0.02O sample revealed that the resistivity and the dielectric constant of samples increase with the increase of sintering temperature. The ferromagnetic properties at room temperature were observed in the Zn0.98Mn0.02O samples sintered at 500°C and 700°C. It also found that the increase in sintering temperature leads to a tendency toward the changes in the magnetic properties into paramagnetic. The presence of ZnMnO3 secondary phases in Zn0.98Mn0.02O system is believed to be a factor that affects the decrease of the electrical and magnetic properties of the sample.

Effect of sintering temperatures on the in vitro bioactivity, molecular structure and mechanical properties of titanium/carbonated hydroxyapatite nanobiocomposites

NASA Astrophysics Data System (ADS)

Youness, Rasha A.; Taha, Mohammed A.; Ibrahim, Medhat A.

2017-12-01

Titanium-containing carbonated hydroxyapatite (Ti-CHA) nanocomposite powders, with different CHA contents, have been prepared using high-energy ball milling method. The effect of sintering temperatures, 900, 1100 and 1300 °C on molecular structure and microstructure of these samples were examined by XRD; Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM), respectively. Furthermore, their mechanical properties including hardness, longitudinal modulus, Young's modulus, shear modulus, bulk modulus and Poisson's ratio were measured by ultrasonic non-destructive technique. Moreover, bioactivity of sintered samples at different firing temperatures was assessed by immersing them in simulated body fluid at 37 ± 0.5 °C for 7 days and then, analyzed by FTIR spectroscopy. The results pointed out that increasing sintering temperature up to 1100 °C caused significant increases in densities and mechanical properties of these nanocomposite samples. However, further increase of firing temperature to 1300 °C was responsible for complete CHA decomposition and the resultant α-tricalcium (α-TCP) phase greatly affected these properties. On the contrary, better bioactivity was observed for sintered samples at 900 °C only. However, increase of sintering temperature of these samples up to 1300 °C led to severe decrease in their bioactivity due to the formation of highly soluble α-TCP phase.

Al2O3-TiC Composite Prepared by Spark Plasma Sintering Process: Evaluation of Mechanical and Tribological Properties

NASA Astrophysics Data System (ADS)

Kumar, Rohit; Chaubey, A. K.; Bathula, Sivaiah; Prashanth, K. G.; Dhar, Ajay

2018-03-01

Al2O3-10TiC composites were synthesized by spark plasma sintering (SPS) process. Microstructural and mechanical properties of the composite reveal homogeneous distribution of the fine TiC particles in the matrix. The samples were produced with different sintering temperature, and it shows that the hardness and density gradually increases with increasing sintering temperature. Abrasion wear test result reveals that the composite sintered at 1500 °C shows high abrasion resistance (wt. loss 0.016 g) and the lowest abrasion resistance was observed for the composite sample sintered at 1100 °C (wt. loss 1.459 g). The profilometry surface roughness study shows that sample sintered at 1100 °C shows maximum roughness ( R a = 6.53 µm) compared to the sample sintered at 1500 °C ( R a = 0.66 µm) corroborating the abrasion wear test results.

Temperature variation in metal ceramic technology analyzed using time domain optical coherence tomography

NASA Astrophysics Data System (ADS)

Sinescu, Cosmin; Topala, Florin I.; Negrutiu, Meda Lavinia; Duma, Virgil-Florin; Podoleanu, Adrian G.

2014-01-01

The quality of dental prostheses is essential in providing good quality medical services. The metal ceramic technology applied in dentistry implies ceramic sintering inside the dental oven. Every ceramic material requires a special sintering chart which is recommended by the producer. For a regular dental technician it is very difficult to evaluate if the temperature inside the oven remains the same as it is programmed on the sintering chart. Also, maintaining the calibration in time is an issue for the practitioners. Metal ceramic crowns develop a very accurate pattern for the ceramic layers depending on the temperature variation inside the oven where they are processed. Different patterns were identified in the present study for the samples processed with a variation in temperature of +30 °C to +50 °C, respectively - 30 0°C to -50 °C. The OCT imagistic evaluations performed for the normal samples present a uniform spread of the ceramic granulation inside the ceramic materials. For the samples sintered at a higher temperature an alternation between white and darker areas between the enamel and opaque layers appear. For the samples sintered at a lower temperature a decrease in the ceramic granulation from the enamel towards the opaque layer is concluded. The TD-OCT methods can therefore be used efficiently for the detection of the temperature variation due to the ceramic sintering inside the ceramic oven.

Pressure-assisted low-temperature sintering for paper-based writing electronics.

PubMed

Xu, L Y; Yang, G Y; Jing, H Y; Wei, J; Han, Y D

2013-09-06

With the aim of preparing paper-based writing electronics, a kind of conductive pen was made with nano-silver ink as the conductive component and a rollerball pen as the writing implement. This was used to direct-write conductive patterns on Epson photo paper. In order to decrease the sintering temperature, pressure was introduced to enhance the driving forces for sintering. Compared with hot sintering without pressure, hot-pressure can effectively improve the conductivity of silver coatings, reduce the sintering time and thus improve productivity. Importantly, pressure can achieve a more uniform and denser microstructure, which increases the connection strength of the silver coating. At the optimum hot-pressure condition (sintering temperature 120 ° C/sintering pressure 25 MPa/sintering time 15 min), a typical measured resistivity value was 1.43 × 10⁻⁷ Ω m, nine greater than that of bulk silver. This heat treatment process is compatible with paper and does not cause any damage to the paper substrates. Even after several thousand bending cycles, the resistivity values of writing tracks by hot-pressure sintering stay almost the same (from 1.43 × 10⁻⁷ to 1.57 × 10⁻⁷ Ω m). The stability and flexibility of the writing circuits are good, which demonstrates the promising future of writing electronics.

Cryomilled and spark plasma sintered titanium: the evolution of microstructure

NASA Astrophysics Data System (ADS)

Kozlík, Jiří; Becker, Hanka; Harcuba, Petr; Stráský, Josef; Janeček, Milos

2017-05-01

Bulk ultra-fine grained (UFG) commercially pure Ti was prepared by cryogenic milling in liquid argon and subsequent spark plasma sintering (SPS). During cryogenic milling, individual powder particles are repetitively severely deformed by attrition forces. Powder particles were not significantly refined, but due to severe repetitive plastic deformation, ultra-fine grained microstructure emerges within each powder particle. Cryogenic milling can be therefore considered as a specific severe plastic deformation (SPD) method. Compactization of cryomilled powder by SPS technique (also referred to as field assisted sintering technique - FAST) requires significantly lower sintering temperatures and shorter sintering times for successful compaction when compared to any other sintering technique. This is crucial for maintaining the UFG microstructure due to its limited thermal stability. Several specimens were prepared by varying processing parameters, in particular the sintering temperature. The microstructure of powders and compacted samples was observed by scanning electron microscopy (SEM). Increased sintering temperature results in recrystallization and grain growth. A trade-off relationship between the density of compacted material and grain size was identified. Microhardness of the material was found to depend on residual porosity rather than grain size. This contribution presents cryogenic milling and spark plasma sintering as a viable alternative for achieving UFG microstructure in commercially pure Ti.

[Effect of sintering temperature on mechanical properties of dental zirconia toughened alumina ceramics].

PubMed

Fan, Jiang-Yuan; Lin, Ting-Ting; Hu, Fang-Xuan; Zheng, Rui-Bin; Fan, Fan; Ma, Jian-Feng

2017-04-01

To investigate the effect of sintering temperature on mechanical properties of dental zirconia toughened alumina (ZTA) ceramics prepared by gel-casting technique. The samples prepared by gel-casting were sintered at 1100, 1200, 1250, 1300 and 1400degrees centigrade for each group. The flexural strength, fracture toughness, Vickers hardness and brittleness index were obtained and microscopic morphology of each group was observed under scanning electron microscope (SEM). The data were statistically analyzed using SPSS 19.0 software package. The flexural strength, fracture toughness and Vickers hardness increased with the increasing sintering temperature during 1100~1400degrees centigrade. The lowest brittleness index (0.74±0.16) μm -1/2 was observed in group sintered at 1200degrees centigrade and the highest (2.76±0.14) μm -1/2 was at 1400degrees centigrade (P<0.05), while the flexural strength of these two groups was (46.89±3.24) MPa and (349.64±54.72) MPa, respectively. The ZTA dental ceramics exhibit good machinability with proper sintering temperature (1200degrees centigrade) and the strength meets the requirement of clinical application.

Room-Temperature Chemical Welding and Sintering of Metallic Nanostructures by Capillary Condensation.

PubMed

Yoon, Sung-Soo; Khang, Dahl-Young

2016-06-08

Room-temperature welding and sintering of metal nanostructures, nanoparticles and nanowires, by capillary condensation of chemical vapors have successfully been demonstrated. Nanoscale gaps or capillaries that are abundant in layers of metal nanostructures have been found to be the preferred sites for the condensation of chemically oxidizing vapor, H2O2 in this work. The partial dissolution and resolidification at such nanogaps completes the welding/sintering of metal nanostructures within ∼10 min at room-temperature, while other parts of nanostructures remain almost intact due to negligible amount of condensation on there. The welded networks of Ag nanowires have shown much improved performances, such as high electrical conductivity, mechanical flexibility, optical transparency, and chemical stability. Chemically sintered layers of metal nanoparticles, such as Ag, Cu, Fe, Ni, and Co, have also shown orders of magnitude increase in electrical conductivity and improved environmental stability, compared to nontreated ones. Pertinent mechanisms involved in the chemical welding/sintering process have been discussed. Room-temperature welding and sintering of metal nanostructures demonstrated here may find widespread application in diverse fields, such as displays, deformable electronics, wearable heaters, and so forth.

Dry-spray deposition of TiO2 for a flexible dye-sensitized solar cell (DSSC) using a nanoparticle deposition system (NPDS).

PubMed

Kim, Min-Saeng; Chun, Doo-Man; Choi, Jung-Oh; Lee, Jong-Cheon; Kim, Yang Hee; Kim, Kwang-Su; Lee, Caroline Sunyong; Ahn, Sung-Hoon

2012-04-01

TiO2 powders were deposited on indium tin oxide (ITO) coated polyethylene terephthalate (PET) substrates for application to the photoelectrode of a dye-sensitized solar cell (DSSC). In the conventional DSSC manufacturing process, a semiconductor oxide such as TiO2 powder requires a sintering process at higher temperature than the glass transition temperature (T(g)) of polymers, and thus utilization of flexible polymer substrates in DSSC research has been constrained. To overcome this restriction related to sintering, we used a nanoparticle deposition system (NPDS) that could produce a thin coating layer through a dry-spray method under atmospheric pressure at room temperature. The powder was sprayed through a slit-type nozzle having a 0.4 x 10 mm2 rectangular outlet. In order to determine the deposited TiO2 thickness, five kinds of TiO2 layered specimens were prepared, where the specimens have single and double layer structures. Deposited powders on the ITO coated PET substrates were observed using FE-SEM and a scan profiler The thicker TiO2 photoelectrode with a DSSC having a double layer structure showed higher energy efficiency than the single layer case. The highest fabricated flexible DSSC displayed a short circuit current density J(sc) = 1.99 mA cm(-2), open circuit voltage V(oc) = 0.71 V, and energy efficiency eta = 0.94%. These results demonstrate the possibility of utilizing the dry-spray method to fabricate a TiO2 layer on flexible polymer substrates at room temperature under atmospheric pressure.

Pressure- and Additive-Mediated Sintering of B4C at Relatively Low Temperatures

NASA Astrophysics Data System (ADS)

Goswami, Ramasis; Qadri, Syed B.; Wollmershauser, James; Kolel-Veetil, Manoj K.; Feygelson, Boris

2017-03-01

A significant improvement in sinterability of B4C was achieved at a relatively low temperature by applying high pressure (2 GPa) and adding a small amount (5 wt pct) of Ni. The sintered B4C and Ni powder mixture showed improved hardness in the range of 21 to 32 GPa and improved modulus as compared to the sintered B4C powder without additive. This is mostly attributed to the formation of Ni4B3, as characterized by Reitveld refinement method and transmission electron microscopy (TEM), which enhances the bonding between B4C particles. These results provide a new avenue toward the development of sintering of B4C at relatively low temperatures (<0.5 T m of B4C).

Structural and mechanical characterization of boron doped biphasic calcium phosphate produced by wet chemical method and subsequent thermal treatment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Albayrak, Onder, E-mail: albayrakonder@mersin.edu.tr

In the current study, boron doped biphasic calcium phosphate bioceramics consisting of a mixture of boron doped hydroxyapatite (BHA) and beta tricalcium phosphate (β-TCP) of varying BHA/β-TCP ratios were obtained after sintering stage. The effects of varying boron contents and different sintering temperatures on the BHA/β-TCP ratios and on the sinterability of the final products were investigated. Particle sizes and morphologies of the obtained precipitates were determined using SEM. XRD and FTIR investigation were conducted to detect the boron formation in the structure of HA and quantitative analysis was performed to determine the BHA/β-TCP ratio before and after sintering stage.more » In order to determine the sinterability of the obtained powders, pellets were prepared and sintered; the rates of densification were calculated and obtained results were correlated by SEM images. Also Vickers microhardness values of the sintered samples were determined. The experimental results verified that boron doped hydroxyapatite powders were obtained after sintering stage and the structure consists of a mixture of BHA and β-TCP. As the boron content used in the precipitation stage increases, β-TCP content of the BHA/β-TCP ratio increases but sinterability, density and microhardness deteriorate. As the sintering temperature increases, β-TCP content, density and microhardness of the samples increase and sinterability improves. - Highlights: • This is the first paper about boron doped biphasic calcium phosphate bioceramics. • Boron doping affects the structural and mechanical properties. • BHA/β-TCP ratio can be adjustable with boron content and sintering temperature.« less

Behavior of oxide film at the interface between particles in sintered Al powders by pulse electric-current sintering

NASA Astrophysics Data System (ADS)

Xie, Guoqiang; Ohashi, Osamu; Song, Minghui; Furuya, Kazuo; Noda, Tetsuji

2003-03-01

The microstructure of the bonding interfaces between particles in aluminum (Al) powder sintered specimens by the pulse electric-current sintering (PECS) process was observed, using conventional transmission electron microscopy (CTEM) and high-resolution transmission electron microscopy (HRTEM). The behavior of oxide film at the interface between Al particles and its effect on properties of the sintered specimens were investigated. The results showed there were two kinds of bonding interfaces in the sintered specimens, namely, the direct metal/metal bonding and the metal/oxide film layer/metal bonding interface. By increasing the fraction of the direct metal/metal bonding interfaces, the tensile strength of the sintered specimens increased, and the electrical resistivity decreased. By increasing the loading pressure at higher sintering temperatures or increasing the sintering temperature under loading pressure, the breakdown of oxide film was promoted. The broken oxide film debris was dispersed in aluminum metal near the bonding interfaces between particles.

[Effect of compaction pressure on the properties of dental machinable zirconia ceramic].

PubMed

Huang, Hui; Wei, Bin; Zhang, Fu-qiang; Sun, Jing; Gao, Lian

2010-10-01

To investigate the effect of compaction pressure on the linear shrinkage, sintering property and machinability of the dental zirconia ceramic. The nano-size zirconia powder was compacted at different isostatic pressure and sintered at different temperature. The linear shrinkage of sintered body was measured and the relative density was tested using the Archimedes method. The cylindrical surface of pre-sintering blanks was traversed using a hard metal tool. Surface and edge quality were checked visually using light stereo microscopy. The sintering behaviour depended on the compaction pressure. Increasing compaction pressure led to higher sintering rate and lower sintering temperature. Increasing compaction pressure also led to decreasing linear shrinkage of the sintered bodies, from 24.54% of 50 MPa to 20.9% of 400 MPa. Compaction pressure showed only a weak influence on machinability of zirconia blanks, but the higher compaction pressure resulted in the poor surface quality. The better sintering property and machinability of dental zirconia ceramic is found for 200-300 MPa compaction pressure.

Effect of Sintering Temperature on Dielectric Properties of Iron Deficient Nickel-Ferrite

NASA Astrophysics Data System (ADS)

Rani, Renu; Singh, Sangeeta; Juneja, J. K.; Prakash, Chandra; Raina, K. K.

2011-11-01

Nickel Ferrite among all the magneto ceramic materials have been studied very much due to its large number of applications. But there is a large scope of modification of its properties. Thus people still working on it for improvisation of its properties via compositional and structural modifications. Present paper reporting the preparation and characterization of iron deficient Nickel ferrite for different sintering temperature. Ferrite samples having the general formula NiFe1.98O4 were prepared using the standard ceramic method. The phase formation was confirmed by X-ray diffraction technique. The effect of sintering temperature on the electrical properties and resistivity was studied. The data shows that dielectric properties are highly dependent on the sintering temperature.

[Translucency of dental zirconia ceramics sintered in conventional and microwave ovens].

PubMed

Yuemei, Jiang; Ying, Yang; Wenhui, Zhan; Guoxin, Hu; Qiuxia, Yang

2015-12-01

To evaluate the effect of microwave sintering on the translucency of zirconia and to compare these effect with those of conventional sintering. The relationship between the microstructure of specimens and translucency was investigated. A total of 10 disc-shaped specimens were fabricated from 2 commercial brands of zirconia, namely, Zenostar and Lava. Each group included 5 discs. Conventional sintering was performed according to the manufacturers' specifications. The maximum temperature for Zenostar was 1,490 °C, whereas that for Lava was 1,500 °C. The dwelling time was 2 h. The sintering temperature for microwave sintering was 1,420 °C, heating rate was 15 °C · min⁻¹, and dwelling time was 30 min. After sintering, the translucency parameter (TP) of the specimens were measured with ShadeEye NCC. The sintered density of the specimens was determined by Archimedes' method. The grain size and microstructure of the specimens were investigated by scanning electron microscopy. Density and translucency slightly increased by microwave sintering, but no significant difference was found between microwave and conventional sintering (P > 0.05). Small and uniform microstructure were obtained from microwave sintering. The mean TP of Lava was significantly higher than that of Zenostar (P < 0.001). The translucency of zirconia sintered by microwave sintering is similar to that of the zirconia sintered by conventional sintering.

Pressureless sintered beta prime-Si3N4 solid solution: Fabrication, microstructure, and strength

NASA Technical Reports Server (NTRS)

Dutta, S.

1977-01-01

Si3N4, AlN, and Al2O3 were used as basic constituents in a study of the pressureless sintering of beta prime-Si3N4 solid solution as a function of temperature. Y2O3-SiO2 additions were used to promote liquid-phase sintering. The sintered specimens were characterized with respect to density, microstructure, strength, oxidation, and thermal shock resistance. Density greater than 98 percent of theoretical was achieved by pressureless sintering at 1750 C. The microstructure consisted essentially of fine-grained beta prime-Si3N4 solid solution as the major phase. Modulus of rupture strengths up to 483 MPa were achieved at moderate temperature (1000 C), but decreased to 228 MPa at 1380 C. This substantial strength loss was attributed to a glassy grain boundary phase formed during cooling from the sintering temperature. The best oxidation resistance was exhibited by a composition containing 3 mol % Y2O3-SiO2 additives. Water quench thermal shock resistance was equivalent to that of reaction sintered silicon nitride but lower than hot-pressed silicon nitride.

Effect of Bed Temperature on the Laser Energy Required to Sinter Copper Nanoparticles

NASA Astrophysics Data System (ADS)

Roy, N. K.; Dibua, O. G.; Cullinan, M. A.

2018-03-01

Copper nanoparticles (NPs), due to their high electrical conductivity, low cost, and easy availability, provide an excellent alternative to other metal NPs such as gold, silver, and aluminum in applications ranging from direct printing of conductive patterns on metal and flexible substrates for printed electronics applications to making three-dimensional freeform structures for interconnect fabrication for chip-packaging applications. Lack of research on identification of optimum sintering parameters such as fluence/irradiance requirements for sintering of Cu NPs serves as the primary motivation for this study. This article focuses on the identification of a good sintering irradiance window for Cu NPs on an aluminum substrate using a continuous wave (CW) laser. The study also includes the comparison of CW laser sintering irradiance windows obtained with substrates at different initial temperatures. The irradiance requirements for sintering of Cu NPs with the substrate at 150-200°C were found to be 5-17 times smaller than the irradiance requirements for sintering with the substrate at room temperature. These findings were also compared against the results obtained with a nanosecond (ns) laser and a femtosecond (fs) laser.

Method to synthesize bulk iron nitride

DOE Office of Scientific and Technical Information (OSTI.GOV)

Monson, Todd; Lavernia, Enrique J.; Zheng, Baolong

Bulk iron nitride can be synthesized from iron nitride powder by spark plasma sintering. The iron nitride can be spark plasma sintered at a temperature of less than 600°C. and a pressure of less than 600 MPa, with 400 MPa or less most often being sufficient. High pressure SPS can consolidate dense iron nitrides at a lower temperature to avoid decomposition. The higher pressure and lower temperature of spark discharge sintering avoids decomposition and limits grain growth, enabling enhanced magnetic properties. The method can further comprise synthesis of nanocrystalline iron nitride powders using two-step reactive milling prior to high-pressure sparkmore » discharge sintering.« less

SINTERED REFRACTORY MASS

DOEpatents

Williams, A.E.

1955-09-01

A method is given for joining sintered masses of refractory compounds. It consists in maintaining the masses in contact with each other by application of a moderate pressure, while they are at sintering temperature. The sintered masses are subjected to am applied pressure of about 1/2 to 1 ton per square inch of the surface in contact for about 10 minutes, and the temperature employed may be fropn about 1400 deg C to 2000 deg C. Refractory oxides to which the invention may be applied are beryllia, alumina, thoria, and magnesia.

A new in vivo screening model for posterior spinal bone formation: comparison of ten calcium phosphate ceramic material treatments.

PubMed

Wilson, Clayton E; Kruyt, Moyo C; de Bruijn, Joost D; van Blitterswijk, Clemens A; Oner, F Cumhur; Verbout, Abraham J; Dhert, Wouter J A

2006-01-01

This study presents a new screening model for evaluating the influence of multiple conditions on the initial process of bone formation in the posterior lumbar spine of a large animal. This model uses cages designed for placement on the decorticated transverse process of the goat lumbar spine. Five conduction channels per cage, each be defined by a different material treatment, are open to both the underlying bone and overlying soft tissue. The model was validated in ten adult Dutch milk goats, with each animal implanted with two cages containing a total of ten calcium phosphate material treatments according to a randomized complete block design. The ten calcium phosphate ceramic materials were created through a combination of material chemistry (BCP, TCP, HA), sintering temperature (low, medium, high), calcination and surface roughness treatments. To monitor the bone formation over time, fluorochrome markers were administered at 3, 5 and 7 weeks and the animals were sacrificed at 9 weeks after implantation. Bone formation in the conduction channels was investigated by histology and histomorphometry of non-decalcified sections using traditional light and epifluorescent microscopy. According to both observed and measured bone formation parameters, materials were ranked in order of increasing magnitude as follows: low sintering temperature BCP (rough and smooth) approximately medium sintering temperature BCP approximately = TCP > calcined low sintering temperature HA > non-calcined low sintering temperature HA > high sintering temperature BCP (rough and smooth) > high sintering temperature HA (calcined and non-calcined). These results agree closely with those obtained in previous studies of osteoconduction and bioactivity of ceramics thereby validating the screening model presented in this study.

Modeling the mechanical behavior of ceramic and heterophase structures manufactured using selective laser sintering and spark plasma sintering

NASA Astrophysics Data System (ADS)

Skripnyak, Vladimir A.; Skripnyak, Evgeniya G.; Skripnyak, Vladimir V.; Vaganova, Irina K.

A model for predicting mechanical properties of ultra-high temperature ceramics and composites manufactured by selective laser sintering (SLS) and spark plasma sintering (SPS) under shock loading is presented. The model takes into account the porous structure, the specific volume and average sizes of phases, and the temperature of sintering. Residual stresses in ceramic composites reinforced with particles of refractory borides, carbides and nitrides after SLS or SPS were calculated. It is shown that the spall strength of diboride-zirconium matrix composites can be increased by the decreasing of porosity and the introduction of inclusions of specially selected refractory strengthening phases.

Fabrication of porous titanium implants by three-dimensional printing and sintering at different temperatures.

PubMed

Xiong, Yaoyang; Qian, Chao; Sun, Jian

2012-01-01

This study evaluated the feasibility of using three-dimensional printing (3DP) to fabricate porous titanium implants. Titanium powder was blended with a water-soluble binder material. Green, porous, titanium implants fabricated by 3DP were sintered under protective argon atmosphere at 1,200, 1,300, or 1,400°C. Sintered implant prototypes had uniform shrinkage and no obvious shape distortion after sintering. Evaluation of their mechanical properties revealed that titanium prototypes sintered at different temperatures had elastic modulus of 5.9-34.8 GPa, porosity of 41.06-65.01%, hardness of 115.2-182.8 VHN, and compressive strength of 81.3-218.6 MPa. There were significant differences in each type of these data among the different sintering temperatures (p<0.01). Results of this study confirmed the feasibility of fabricating porous titanium implants by 3DP: pore size and pore interconnectivity were conducive to bone cell ingrowth for implant stabilization, and the mechanical properties matched well with those of the human bone.

Structure and properties of sintered MM-Fe-B magnets

NASA Astrophysics Data System (ADS)

Shang, R. X.; Xiong, J. F.; Li, R.; Zuo, W. L.; Zhang, J.; Zhao, T. Y.; Chen, R. J.; Sun, J. R.; Shen, B. G.

2017-05-01

MM14Fe79.9B6.1 magnets were prepared by conventional sintering method. The Curie temperature of the sintered MM2Fe14B magnet was about 210 °C. When the sintering temperature increased from 1010 °C to 1030 °C, the density of the magnet increased from 6.85 g/cm3 to 7.52 g/cm3. After the first stage tempering at 900 °C, the (BH)max and Hcj had a slight increase. The maximum value of (BH)max = 7.6 MGOe and Hcj = 1080 Oe was obtained when sintered at 1010 °C and tempering at 900 °C, respectively. The grain size grew very large when the sintering temperature increased to 1050 °C, and the magnetic properties deteriorated rapidly. La reduced by ˜ 7.5 at. % in grains, which is almost equal to the increased percentage of Nd. That is mainly because La-Fe-B is very difficult to form the 2: 14: 1 phase.

Powder Metallurgy Fabrication of Porous 51(at.%)Ni-Ti Shape Memory Alloys for Biomedical Applications

NASA Astrophysics Data System (ADS)

Ibrahim, Mustafa K.; Hamzah, E.; Saud, Safaa N.; Nazim, E. M.

2018-05-01

The effect of time and temperature on the microwave sintering of 51(at.%)Ni-Ti shape memory alloys (SMAs) was investigated in the current research. Furthermore, the microstructure, mechanical properties, and bio-corrosion properties were analyzed based on the sintering conditions. The results revealed that the sintering condition of 700 °C for 15 min produced a part with coherent surface survey that does not exhibit gross defects. Increasing the sintering time and temperature created defects on the outer surface, while reducing the temperature to 550 °C severely affected the mechanical properties. The microstructure of these samples showed two regions of Ni-rich region and Ti-rich region between them Ti2Ni, NiTi, and Ni3Ti phases. The differential scanning calorimeter (DSC) curves of Ni-Ti samples exhibited a multi-step phase transformation B19'-R-B2 during heating and cooling. An increase in the sintering temperature from 550 to 700 °C was found to increase the fracture strength significantly and decreased the fracture strain slightly. Reducing the sintering temperature from 700 to 550 °C severely affected the corrosion behaviors of 51%Ni-Ti SMAs. This research aims to select the optimum parameters to produce Ni-Ti alloys with desired microstructure, mechanical properties, and corrosion behaviors for biomedical applications.

Effect of Sintering Temperature on Structural, Dielectric, and Magnetic Properties of Multiferroic YFeO3 Ceramics Fabricated by Spark Plasma Sintering

PubMed Central

Wang, Meng; Wang, Ting; Song, Shenhua; Ma, Qing; Liu, Renchen

2017-01-01

Based on precursor powders with a size of 200–300 nm prepared by the low-temperature solid reaction method, phase-pure YFeO3 ceramics are fabricated using spark plasma sintering (SPS) at different temperatures. X-ray diffraction (XRD) and scanning electron microscopy (SEM) reveal that the high-purity YFeO3 ceramics can be prepared using SPS, while the results from X-ray photoelectron spectroscopy (XPS) show that the concentration of oxygen vacancies resulting from transformation from Fe3+ to Fe2+ is low. The relative density of the 1000 °C-sintered sample is as high as 97.7%, which is much higher than those of the samples sintered at other temperatures. The present dielectric and magnetic properties are much better than those of the samples fabricated by conventional methods. These findings indicate that the YFeO3 ceramics prepared by the low temperature solid reaction and SPS methods possess excellent dielectric and magnetic properties, making them suitable for potential applications involving magnetic storage. PMID:28772626

Estimation of Sintering Kinetics of Oxidized Magnetite Pellet Using Optical Dilatometer

NASA Astrophysics Data System (ADS)

Sandeep Kumar, T. K.; Viswanathan, Neelakantan Nurni; Ahmed, Hesham M.; Andersson, Charlotte; Björkman, Bo

2015-04-01

The quality of magnetite pellet is primarily determined by the physico-chemical changes the pellet undergoes as it makes excursion through the gaseous and thermal environment in the induration furnace. Among these physico-chemical processes, the oxidation of magnetite phase and the sintering of oxidized magnetite (hematite) and magnetite (non-oxidized) phases are vital. Rates of these processes not only depend on the thermal and gaseous environment the pellet gets exposed in the induration reactor but also interdependent on each other. Therefore, a systematic study should involve understanding these processes in isolation to the extent possible and quantify them seeking the physics. With this motivation, the present paper focusses on investigating the sintering kinetics of oxidized magnetite pellet. For the current investigation, sintering experiments were carried out on pellets containing more than 95 pct magnetite concentrate from LKAB's mine, dried and oxidized to completion at sufficiently low temperature to avoid sintering. The sintering behavior of this oxidized pellet is quantified through shrinkage captured by Optical Dilatometer. The extent of sintering characterized by sintering ratio found to follow a power law with time i.e., Kt n . The rate constant K for sintering was determined for different temperatures from isothermal experiments. The rate constant, K, varies with temperature as and the activation energy ( Q) and reaction rate constant ( K') are estimated. Further, the sintering kinetic equation was also extended to a non-isothermal environment and validated using laboratory experiments.

Flash sintering of ceramic materials

NASA Astrophysics Data System (ADS)

Dancer, C. E. J.

2016-10-01

During flash sintering, ceramic materials can sinter to high density in a matter of seconds while subjected to electric field and elevated temperature. This process, which occurs at lower furnace temperatures and in shorter times than both conventional ceramic sintering and field-assisted methods such as spark plasma sintering, has the potential to radically reduce the power consumption required for the densification of ceramic materials. This paper reviews the experimental work on flash sintering methods carried out to date, and compares the properties of the materials obtained to those produced by conventional sintering. The flash sintering process is described for oxides of zirconium, yttrium, aluminium, tin, zinc, and titanium; silicon and boron carbide, zirconium diboride, materials for solid oxide fuel applications, ferroelectric materials, and composite materials. While experimental observations have been made on a wide range of materials, understanding of the underlying mechanisms responsible for the onset and latter stages of flash sintering is still elusive. Elements of the proposed theories to explain the observed behaviour include extensive Joule heating throughout the material causing thermal runaway, arrested by the current limitation in the power supply, and the formation of defect avalanches which rapidly and dramatically increase the sample conductivity. Undoubtedly, the flash sintering process is affected by the electric field strength, furnace temperature and current density limit, but also by microstructural features such as the presence of second phase particles or dopants and the particle size in the starting material. While further experimental work and modelling is still required to attain a full understanding capable of predicting the success of the flash sintering process in different materials, the technique non-etheless holds great potential for exceptional control of the ceramic sintering process.

Low-Temperature Sintering of AlN Ceramics by Sm2O3-Y2O3-CaO Sintering Additives Formed via Decomposition of Nitrate Solutions

NASA Astrophysics Data System (ADS)

Zhan, Jun; Cao, Ye; Zhang, Hao; Guo, Jun; Zhang, Jianhua; Geng, Chunlei; Shi, Changdong; Cui, Song; Tang, Wenming

2017-01-01

The Sm, Y and Ca anhydrous nitrates were mixed with the AlN powder in ethanol and then decomposed into the Sm2O3-Y2O3-CaO sintering additives via calcining. Low-temperature sintering of the AlN ceramics was carried out at temperature range from 1675 to 1750 °C. Effects of the composition and adding amount of the sintering additives on the phases, microstructures and properties of the AlN ceramics were investigated. During sintering the AlN ceramics, main secondary phases of CaYAl3O7 and CaSmAl3O7 form. The relative density, bending strength and thermal conductivity of the AlN ceramics increase with the increase in the rare-earth oxides in them. The thermal conductivity of the sintered AlN ceramics is also greatly affected by the distribution of the secondary phases. As sintered at 1750 °C, the AlN ceramics by adding the sintering additives of 2 wt.% Sm2O3, 2 wt.% Y2O3 and 1 wt.% CaO formed via decomposition of their nitrates is fully dense and have the optimal bending strength and thermal conductivity of 402.1 MPa and 153.7 W/(m K), respectively.

Influence of temperature and aging time on HA synthesized by the hydrothermal method.

PubMed

Kothapalli, C R; Wei, M; Legeros, R Z; Shaw, M T

2005-05-01

The influence of temperature and aging time on the morphology and mechanical properties of nano-sized hydroxyapatite (HA) synthesized by a hydrothermal method is reported here. The pre-mixed reactants were poured into a stirred autoclave and reacted at temperatures between 25-250 degrees C for 2-10 h. HA powders thus obtained were examined using X-ray diffraction (XRD), high-resolution field emission scanning electron microscopy (FESEM) and a particle size analyzer. It was found that the aspect ratio of the particles increased with the reaction temperature. The length of the HA particles increased with the reaction temperature below 170 degrees C, but it decreased when the temperature was raised above 170 degrees C. The agglomerates of HA particles were formed during synthesis, and their sizes were strongly dependent on reaction temperatures. As the reaction temperature increased, the agglomerate size decreased (p = 0.008). The density of the discs pressed from these samples reached 85-90% of the theoretical density after sintering at 1200 degrees C for 1 h. No decomposition to other calcium phosphates was detected at this sintering temperature. A correlation existed (p = 0.05) between the agglomerate sizes of HA particles synthesized at various conditions and their sintered densities. With the increase of the agglomerate size, the sintered density of the HA compact decreased. It was found that both the sintered density and flexural strength increased with increasing aging time and reaction temperature. A maximum flexural strength of 78 MPa was observed for the samples synthesized at 170 degrees C for 5 h with the predicted average at these conditions being 65 MPa. These samples attained an average sintered density of 88%.

Electric field-assisted sintering of nanocrystalline hydroxyapatite for biomedical applications

NASA Astrophysics Data System (ADS)

Tran, Tien Bich

As the main inorganic component of bone, hydroxyapatite (HA, Ca 10(PO4)6(OH)2) should be an ideal candidate in biomaterials selection. When grain sizes are in the nanometric regime, protein adsorption and cell adhesion are enhanced, while strength, hardness, and wear resistance are improved. Unfortunately, low phase stability, poor sinterability, and a tendency towards exaggerated grain coarsening challenge full densification of nanocrystalline hydroxyapatite by conventional sintering methods. The field-assisted sintering technique (FAST) has successfully consolidated a variety of nanocrystalline metals and ceramics in dramatically reduced times. The sintering enhancements observed during FAST can be attributed to thermal and athermal effects. The rapid heating rates (up to ˜1000ºC/min) afforded by FAST contribute a significant thermal effect. Since fast heating rates reduce powder exposure to sub-sintering temperatures, non-densifying surface diffusion is limited. The athermal effects of FAST are less well understood and can include plasma generation, dielectric breakdown, particle surface cleaning, grain boundary pinning, and space charge effects. Applying the field-assisted sintering technique to nanocrystalline hydroxyapatite yielded surprising results. Deviations from conventional densification behavior were observed, with dehydroxylation identified as the most deleterious process to densification as well as mechanical and biological performance. Since hydroxyapatite is not a stable phase at high temperatures and low water partial pressure atmospheres, desintering due to dehydroxylation-related pore formation became apparent during Stage III sintering. In fact, the degree of desintering and pore formation increased with the extent of Stage III sintering and grain growth. The atomic rearrangements taking place during grain boundary migration are believed to favor the formation of more-stable oxyapatite through hydroxyapatite dehydroxylation. This behavior was consistent during varied heating rate (50--400ºC/min) and varied pressure application (25--90 MPa) studies. While in vitro cytocompatibility studies using MG63 osteoblast-like cells demonstrated the biocompatibility of the FAST-processed specimens, bioactivity was sensitive to processing parameters. Since extensive dehydroxylation reduces the surface charge of the sintered materials, apatite deposition during simulated body fluid immersion only occurred when dehydroxylation was mild---i.e., on specimens sintered at low temperatures (800--900ºC) or for short periods. Microstructural investigations revealed that HA sintered at temperatures above 900ºC under an applied electric field contained nanometric residual pores in grain interiors, as well as micron-sized dehydroxylation-related pores at grain boundaries and grain boundary junctions. These larger pores were responsible for the increasing embrittlement of specimens sintered at higher temperatures. Although grain size dependence could not be found in the 60--100 nm grain size range, fracture toughness (KIC = 1.92 MPa√m, maximum) increased with decreasing sintering temperature. Results from the suite of investigations conducted demonstrate that biocompatible and bioactive nanocrystalline hydroxyapatite with enhanced mechanical properties can be efficiently manufactured by field-assisted sintering under controlled processing conditions.

Effect of addition of nanoparticle TiO 2/SiO 2 on the superconducting properties of MgB 2

NASA Astrophysics Data System (ADS)

Zhang, Y.; Zhou, S. H.; Wang, X. L.; Dou, S. X.

2008-09-01

In this paper, bulk MgB 2 was prepared by doping with nanoparticle TiO 2 surface-modified by 5-10% SiO 2. The doping ratio of TiO 2/SiO 2 to MgB 2 was 0, 5, 10, and 15 wt%. The sintering temperature varied from 650 °C to 950 °C. Quantitative X-ray diffraction (XRD) analysis was performed to obtain the lattice constants and the weight fraction of impurities using the Rietveld method. It was found that the critical temperature ( Tc) increases with the lattice constants. The critical current density ( Jc) is affected by the doping ratio and the sintering temperature. The Jc exhibited the highest value at the doping ratio of 10 wt% for 5 K and 20 K and at the doping ratio of 5 wt% for 30 K, when the sintering temperature was fixed at 750 °C. When the doping ratio was fixed at 5 wt%, the samples with the sintering temperature of 750 °C had the best Jc for 5 K and 20 K, while the sample with the sintering temperature of 850 °C exhibited the highest Jc at 30 K.

Accelerated sintering in phase-separating nanostructured alloys

PubMed Central

Park, Mansoo; Schuh, Christopher A.

2015-01-01

Sintering of powders is a common means of producing bulk materials when melt casting is impossible or does not achieve a desired microstructure, and has long been pursued for nanocrystalline materials in particular. Acceleration of sintering is desirable to lower processing temperatures and times, and thus to limit undesirable microstructure evolution. Here we show that markedly enhanced sintering is possible in some nanocrystalline alloys. In a nanostructured W–Cr alloy, sintering sets on at a very low temperature that is commensurate with phase separation to form a Cr-rich phase with a nanoscale arrangement that supports rapid diffusional transport. The method permits bulk full density specimens with nanoscale grains, produced during a sintering cycle involving no applied stress. We further show that such accelerated sintering can be evoked by design in other nanocrystalline alloys, opening the door to a variety of nanostructured bulk materials processed in arbitrary shapes from powder inputs. PMID:25901420

Debinding and Sintering of an Injection-Moulded Hypereutectic Al⁻Si Alloy.

PubMed

Ni, Jiaqi; Yu, Muhuo; Han, Keqing

2018-05-16

Hypereutectic Al⁻Si (20 wt.%) alloy parts were fabricated by employing a powder injection moulding (PIM) technique with a developed multi-component binder system composed of high-density polyethylene (35 wt.%), carnauba wax (62 wt.%) and stearic acid (3 wt.%). The feedstocks contained 83 wt.% metal powders. The debinding process was carried out by a combination of solvent extraction and thermal decomposition. The effects of solvent debinding variables such as kind of solvents, debinding temperatures and time, and the bulk surface area to volume ratios on the debinding process were investigated. Thermal debinding and the subsequent sintering process were carried out in a heating sequence under a nitrogen atmosphere. The influences of sintering temperature and sintering time on the mechanical properties and structure were considered. Under the optimal sintering condition, sintering at 550 °C for 3 h, the final sintering parts were free of distortion and exhibited good mechanical properties. Relative sintered density, Brinell hardness, and tensile strength were ~95.5%, 58 HBW and ~154, respectively.

Borax as flux on sintering of iron Ancor Steel 1000® under glow discharge

NASA Astrophysics Data System (ADS)

Ariza Suarez, H. G.; Sarmiento Santos, A.; Ortiz Otálora, C. A.

2016-02-01

This work studies the flux effect of borax (di sodium tetraborate decahydrate) on sintering of iron Ancor Steel 1000® in abnormal glow discharge. The incidence of the percentage by weight of borax and the sintering temperature in the process were observed. Samples of powder metallurgical iron were prepared with proportions of 0.50%, 2.0%, 4.0% and 6.0% by weight of borax using the procedures of powder metallurgy. The samples were sintered at 800 and 1100°C for 30min, by glow discharge at low pressure in a reducing atmosphere composed of 20% H2+80% Ar. The samples in compact green-state were analyzed by TGA-DSC to determine the fusion process and mass loss during sintering. The analysis of microhardness and density, shows that at a sintering temperature of 800°C the sample density decreases and the sample microhardness increases with respect to sintered samples without borax. Sintered samples were analysed by DRX showing the absence of precipitates.

The Effects of Atmosphere on the Sintering of Ultrafine-Grained Tungsten with Ti

NASA Astrophysics Data System (ADS)

Ren, Chai; Koopman, Mark; Fang, Z. Zak; Zhang, Huan

2016-11-01

Tungsten (W) is a brittle material at room temperature making it very difficult to fabricate. Although the lack of ductility remains a difficult challenge, nano-sized and ultrafine-grained (UFG) structures offer the potential to overcome tungsten's room-temperature brittleness. One way to manufacture UFG W is to compact and sinter nano-sized W powder. It is challenging, however, to control grain growth during sintering. As one method to inhibit grain growth, the effect of Ti-based additives on the densification and grain growth of nano-W powders was investigated in this study. Addition of 1% Ti into tungsten led to more than a 63% decrease in average grain size of sintered samples at comparable density levels. It was found that sintering in Ar yielded a finer grain size than sintering in H2 at similar densities. The active diffusion mechanisms during sintering were different for W-1% Ti nano powders sintered in Ar and H2.

METHOD OF JOINING CARBIDES TO BASE METALS

DOEpatents

Krikorian, N.H.; Farr, J.D.; Witteman, W.G.

1962-02-13

A method is described for joining a refractory metal carbide such as UC or ZrC to a refractory metal base such as Ta or Nb. The method comprises carburizing the surface of the metal base and then sintering the base and carbide at temperatures of about 2000 deg C in a non-oxidizing atmosphere, the base and carbide being held in contact during the sintering step. To reduce the sintering temperature and time, a sintering aid such as iron, nickel, or cobait is added to the carbide, not to exceed 5 wt%. (AEC)

Study of sintering temperature on the structure of silicon carbide membrane

NASA Astrophysics Data System (ADS)

Sadighzadeh, A.; Mashayekhan, Sh.; Nedaie, B.; Ghorashi, A. H.

2014-09-01

Study of the microstructure of silicon carbide (SiC) membrane as a function of sintering temperature and the percentage amount of additive kaolin is the outcome of the experimental fabrications presented in this paper. The SEM micrographs are used to investigate the impact of above parameters on the porosity of membrane. The experimental results show that the rise in the temperature causes more sintering of powder particles, growing granules, augmentation of the number of pores and consequently increasing the total porosity of membrane. Using XRD analyses, it is found that SiC amorphous phase is highly sensitive to the temperature and its crystallization physically grows with temperature increase.

Exothermic low temperature sintering of Cu nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mittal, Jagjiwan; Lin, Kwang-Lung, E-mail: matkllin@mail.ncku.edu.tw

2015-11-15

Sintering of the Cu nanoparticle at low temperatures resulted in exothermic behavior after its initiation. The calorimetry study of the heating of a 20 nm copper nanoparticles agglomerate revealed the evolution of 41.17 J/g of heat between 170 °C and 270 °C. High resolution transmission electron microscopy (HRTEM) images indicated that the heat generation was accompanied by sintering. The surface energy of the 20 nm copper nanoparticles was estimated to be 1.23 × 10{sup 3} erg/cm{sup 2} based on the heat released during sintering. The in situ high resolution transmission electron microscope (HRTEM) investigation showed that vigorous sintering occurred betweenmore » 217 and 234 °C, which took place through the dislocation sintering mechanism. - Highlights: • Calorimetry showed exothermic behavior during heating of Cu nanoparticles between 170 and 270 °C. • Heat released due to the sintering of Cu nanoparticles was demonstrated by HRTEM. • Surface energy of 20 nm copper nanoparticles was estimated to be 1.23 × 10{sup 3} erg/cm{sup 2} during sintering. • Growth in crystallite sizes during sintering is disclosed by X-ray diffraction. • In situ HRTEM heating study showed occurrence of sintering through dislocation mechanism.« less

Enhanced thermal conductivity of uranium dioxide-silicon carbide composite fuel pellets prepared by Spark Plasma Sintering (SPS)

NASA Astrophysics Data System (ADS)

Yeo, S.; Mckenna, E.; Baney, R.; Subhash, G.; Tulenko, J.

2013-02-01

Uranium dioxide (UO2)-10 vol% silicon carbide (SiC) composite fuel pellets were produced by oxidative sintering and Spark Plasma Sintering (SPS) at a range of temperatures from 1400 to 1600 °C. Both SiC whiskers and SiC powder particles were utilized. Oxidative sintering was employed over 4 h and the SPS sintering was employed only for 5 min at the highest hold temperature. It was noted that composite pellets sintered by SPS process revealed smaller grain size, reduced formation of chemical products, higher density, and enhanced interfacial contact compared to the pellets made by oxidative sintering. For given volume of SiC, the pellets with powder particles yielded a smaller grain size than pellets with SiC whiskers. Finally thermal conductivity measurements at 100 °C, 500 °C, and 900 °C revealed that SPS sintered UO2-SiC composites exhibited an increase of up to 62% in thermal conductivity compared to UO2 pellets, while the oxidative sintered composite pellets revealed significantly inferior thermal conductivity values. The current study points to the improved processing capabilities of SPS compared to oxidative sintering of UO2-SiC composites.

Optimization of sintering conditions for cerium-doped yttrium aluminum garnet

NASA Astrophysics Data System (ADS)

Cranston, Robert Wesley McEachern

YAG:Ce phosphors have become widely used as blue/yellow light converters in camera projectors, white light emitting diodes (WLEDs) and general lighting applications. Many studies have been published on the production, characterization, and analysis of this optical ceramic but few have been done on determining optimal synthesis conditions. In this work, YAG:Ce phosphors were synthesized through solid state mixing and sintering. The synthesized powders and the highest quality commercially available powders were pressed and sintered to high densities and their photoluminescence (PL) intensity measured. The optimization process involved the sintering temperature, sintering time, annealing temperature and the level of Ce concentration. In addition to the PL intensity, samples were also characterized using particle size analysis, X-ray diffraction (XRD), and scanning electron microscopy (SEM). The PL data was compared with data produced from a YAG:Ce phosphor sample provided by Christie Digital. The peak intensities of the samples were converted to a relative percentage of this industry product. The highest value for the intensity of the commercial powder was measured for a Ce concentration of 0.3 mole% with a sintering temperature of 1540°C and a sintering dwell time of 7 hours. The optimal processing parameters for the in-house synthesized powder were slightly different from those of commercial powders. The optimal Ce concentration was 0.4 mole% Ce, sintering temperature was 1560°C and sintering dwell time was 10 hours. These optimal conditions produced a relative intensity of 94.20% and 95.28% for the in-house and commercial powders respectively. Polishing of these samples resulted in an increase of 5% in the PL intensity.

Morphology and phase identification of micron to nanosized manganese oxide (MnO) with variations in sintering time

NASA Astrophysics Data System (ADS)

Sasongko, Muhammad Ilman Nur; Puspitasari, Poppy; Yazirin, Cepi; Tsamroh, Dewi Izzatus; Risdanareni, Puput

2017-09-01

Manganese oxide (MnO) occurs in many rock types and may take the form of minerals. MnO has its drawbacks, namely highly reactive oxidizing species classified as dangerous and explosive at temperatures above 55 °C. Despite this,MnO has excellent magnetic, electrochemical, and conductivity properties, which should be reduced to nano-size to maximize their use and improve the properties of MnO. Phase and morphology characterization of powder this research aims to reduce the grain size of the MnO from micro to nano using the sol-gel method with various sintering times. Sol-gel is a simple synthesis method that has been proven capable of synthesizing a wide variety of micro-sized oxide materials into nano. Sintering time is a technique performed in the synthesis process to dry the material to a temperature above the normal temperature. The temperature used for sintering starting from 600 °C to 1000 °C. Characterizations were done using XRD, SEM, EDX, and FTIR machines. The sintering processes in this study used a temperature of 600 °C with different sintering periods of 30, 60 and 90 minutes. The XRD characterization with a 30-minute sintering time resulted in the smallest MnO in the form crystalline powder of 47.3 nm. The highest intensity (degree of crystallinity) found in MnO sintered for 90 minutes. The results of the morphological characterization of SEM showed a morphological change in MnO from micro-sized triangular to nano-sized spherical shape. The EDX characterization results indicated that the 30-minute sintering caused the lowest change in Mn and the highest change in O. The results of FTIR characterization showed a shift in C-H and Mn-O followed by an increase in the group of N-H, C=O and Mn-O.

Development of high Tc (greater than 110K) Bi, Tl and Y-based materials as superconducting circuit elements

NASA Technical Reports Server (NTRS)

Haertling, Gene H.; Lee, Burtrand; Grabert, Gregory; Gilmour, Phillip

1991-01-01

This report is presented in two parts. Part 1 deals primarily with Bi-based materials and a small amount of work on a Y-based composition while Part 2 covers work on Tl-based materials. In Part 1, a reliable and reproducible process for producing bulk bismuth-based superconductors has been developed. It is noted however, that a percentage of the tapecast material experiences curling and fracturing after a 30 hour sintering period and is thus in need of further examination. The Bi-Sr-Ca-Cu-O (BSCCO) material has been characterized by critical temperature data, X-ray diffraction data, and surface morphology. In the case of T sub c, it is not critical to anneal the material. It appears that the BSCCO material has the possibility of producing a better grounding strap than that of the 123 material. Attempts to reproduce near room temperature superconductors in the Y-Ba-Cu-O system were unsuccessful. In Part 2, several methods of processing the high temperature superconductor Tl2Ba2Ca2Cu3O10 were investigated; i.e., different precursor compositions were sintered at various sintering times and temperatures. The highest superconductig temperature was found to be 117.8K when fired at 900 C for three hours. Higher sintering temperatures produced a melted sample which was nonsuperconducting at liquid nitrogen temperature. Also, a preliminary study found Li2O substitutions for copper appeared to increase the transition temperature and create fluxing action upon sintering. It was suggested that lower sintering temperatures might be obtained with lithium additions to produce reliable Tl2Ba2Ca2Cu3O10 processing methods.

Microstructures and mechanical properties of powder injection molded Ti-6Al-4V/HA powder.

PubMed

Thian, E S; Loh, N H; Khor, K A; Tor, S B

2002-07-01

Taguchi method with an L9 orthogonal array was employed to investigate the sintered properties of Ti-6Al-4V/HA tensile bars produced by powder injection molding. The effects of sintering factors at the 90% significance level: sintering temperature (1050 degrees C, 1100 degrees C and 1150 degrees C), heating rate (5 degrees C/min, 7.5 degrees C/min and 10 degrees C/min), holding time (30, 45 and 60 min) and cooling rate (5 degrees C/min, 20 degrees C/min and 40 degrees C/min) were investigated. Results showed that sintering temperature, heating rate and cooling rate have significant effects on sintered properties, whereas the influence of holding time was insignificant. It was found that a sintering temperature of 1100 degrees C, a heating rate of 7.5 degrees C/min and a cooling rate of 5 degrees C/min increased the relative density, Vicker's microhardness, flexural strength and flexural modulus. However, a further increment of sintering temperature to 1150 degrees C did not show any discernable improvement in the relative density and Vicker's microhardness, but there was a slight increase of 0.6% and 0.9% in the flexural strength and flexural modulus, respectively. Mechanically strong Ti-6Al-4V/HA parts with an open porosity of around 50% were developed.

Analysis of key factors influencing the evaporation performances of an oriented linear cutting copper fiber sintered felt

NASA Astrophysics Data System (ADS)

Pan, Minqiang; Zhong, Yujian

2018-01-01

Porous structure can effectively enhance the heat transfer efficiency. A kind of micro vaporizer using the oriented linear cutting copper fiber sintered felt is proposed in this work. Multiple long cutting copper fibers are firstly fabricated with a multi-tooth tool and then sintered together in parallel to form uniform thickness metal fiber sintered felts that provided a characteristic of oriented microchannels. The temperature rise response and thermal conversion efficiency are experimentally investigated to evaluate the influences of porosity, surface structure, feed flow rate and input power on the evaporation characteristics. It is indicated that the temperature rise response of water is mainly affected by input power and feed flow rate. High input power and low feed flow rate present better temperature rise response of water. Porosity rather than surface structure plays an important role in the temperature rise response of water at a relatively high input power. The thermal conversion efficiency is dominated by the input power and surface structure. The oriented linear cutting copper fiber sintered felts for three kinds of porosities show better thermal conversion efficiency than that of the oriented linear copper wire sintered felt when the input power is less than 115 W. All the sintered felts have almost the same performance of thermal conversion at a high input power.

Method of joining ITM materials using a partially or fully-transient liquid phase

DOEpatents

Butt, Darryl Paul; Cutler, Raymond Ashton; Rynders, Steven Walton; Carolan, Michael Francis

2006-03-14

A method of forming a composite structure includes: (1) providing first and second sintered bodies containing first and second multicomponent metallic oxides having first and second identical crystal structures that are perovskitic or fluoritic; (2) providing a joint material containing at least one metal oxide: (a) containing (i) at least one metal of an identical IUPAC Group as at least one sintered body metal in one of the multicomponent metallic oxides, (ii) a first row D-Block transition metal not contained in the multicomponent metallic oxides, and/or (iii) a lanthanide not contained in the multicomponent metallic oxides; (b) free of metals contained in the multicomponent metallic oxides; (c) free of cations of boron, silicon, germanium, tin, lead, arsenic, antimony, phosphorus and tellurium; and (d) having a melting point below the sintering temperatures of the sintered bodies; and (3) heating to a joining temperature above the melting point and below the sintering temperatures.

Raman analysis of non stoichiometric Ni1-δO

NASA Astrophysics Data System (ADS)

Dubey, Paras; Choudhary, K. K.; Kaurav, Netram

2018-04-01

Thermal decomposition method was used to synthesize non-stoichiometric nickel oxide at different sintering temperatures upto 1100 °C. The structure of synthesized compounds were analyzed by X ray diffraction analysis (XRD) and magnetic ordering was studied with the help of Raman scattering spectroscopy for the samples sintered at different temperature. It was found that due to change in sintering temperature the stoichiometry of the sample changes and hence intensity of two magnon band changes. These results were interpreted as the decomposition temperature increases, which heals the defects present in the non-stoichiometric nickel oxide and antiferromagnetic spin correlation changes accordingly.

Enhanced Sintering of TiNi Shape Memory Foams under Mg Vapor Atmosphere

NASA Astrophysics Data System (ADS)

Aydoğmuş, Tarik; Bor, Şakir

2012-12-01

TiNi alloy foams are promising candidates for biomaterials to be used as artificial orthopedic implant materials for bone replacement applications in biomedical sector. However, certain problems exist in their processing routes, such as formation of unwanted secondary intermetallic phases leading to brittleness and deterioration of shape memory and superelasticity characteristics; and the contamination during processing resulting in oxides and carbonitrides which affect mechanical properties negatively. Moreover, the eutectic reaction present in Ti-Ni binary system at 1391 K (1118 °C) prevents employment of higher sintering temperatures (and higher mechanical properties) even when equiatomic prealloyed powders are used because of Ni enrichment of TiNi matrix as a result of oxidation. It is essential to prevent oxidation of TiNi powders during processing for high-temperature (>1391 K i.e., 1118 °C) sintering practices. In the current study, magnesium powders were used as space holder material to produce TiNi foams with the porosities in the range of 40 to 65 pct. It has been found that magnesium prevents secondary phase formation and contamination. It also prevents liquid phase formation while enabling employment of higher sintering temperatures by two-step sintering processing: holding the sample at 1373 K (1100 °C) for 30 minutes, and subsequently sintering at temperatures higher than the eutectic temperature, 1391 K (1118 °C). By this procedure, magnesium may allow sintering up to temperatures close to the melting point of TiNi. TiNi foams produced with porosities in the range of 40 to 55 pct were found to be acceptable as implant materials in the light of their favorable mechanical properties.

Interfacial reactions and wetting in Al-Mg sintered by powder metallurgy process

DOE Office of Scientific and Technical Information (OSTI.GOV)

Faisal, Heny, E-mail: faisal@physics.its.ac.id; Darminto,; Triwikantoro,

2016-04-19

Was conducted to analyze the effect of temperature variation on the bonding interface sintered composite Al-Mg and analyze the effect of variations of the density and hardness sinter. Research carried out by the base material powders of Al, Mg powder and solvent n-butanol. The method used in this study is a powder metallurgy, with a composition of 60% volume fraction of Al - 40% Mg. Al-Mg mixing with n-butanol for 1 hour at 500 rpm. Then the emphasis (cold comression) with a size of 1.4 cm in diameter dies and height of 2.8 cm, is pressed with a force of 20 MPa and heldmore » for 15 minutes. After the sample into pellets, then sintered at various temperatures 300 °C, 350 °C, 400 °C and 450 °C. Characterization is done by using the testing green density, sintered density, X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), vickers microhardness, and press test. XRD data analysis done by using X’Pert High Score Plus (HSP) to determine whether there is a new phase is formed. Test results show that the sintered density increasing sintering temperature, the resulting density is also increasing (shrinkage). However, at a temperature of 450 °C decreased (swelling). With the increased sinter density, interfacial bonding getting Kuta and more compact so that its hardness is also increased. From the test results of SEM / EDX, there Mg into Al in the border area. At temperatures of 300 °C, 350 °C, 400 °C, the phase formed is Al, Mg and MgO. While phase is formed at a temperature of 450 °C is aluminum magnesium (Al{sub 3}Mg{sub 2}), Aluminum Magnesium Zinc (AlMg{sub 2}Zn).« less

[Application of sintered Ti powder to dental prostheses].

PubMed

Hikosaka, Tatsuya; Tanaka, Yoshinobu; Hoshiai, Kazumoto; Kanazawa, Takeshi; Nakamura, Yoshinori; Tsuda, Kenji; Ohasi, Hideya

2005-04-01

Powder metallurgy is a metal processing technology. Porous titanium produced from powder is widely used. The method is applied to titanium, which is not easy to cast as it sinters under melting point. In prosthetic dentistry, powder metallurgy can be applied to high fusing metal that is biocompatible. In this study, we examined the mechanical characteristics of the Ti sheet produced by sintering and discussed its application to dental prosthesis manufacturing. Ti sheets of 1-mm thickness, in which a binder was added to spherical Ti powder, were produced with the Doctor Blade Method. The sintering was carried out between 900-1150 degrees C at 6 temperatures. The sintered compact was evaluated by dimensional change rate, hardness test, bending strength, tensile strength and SEM observation. Another compact was sintered on the refractory cast. Mechanical strength significantly increased with sintering temperature. In addition, excellent mechanical strength was acquired by adding crushed powder and performing the de-binder process. In the sintering on the refractory cast, pre-baking for more than 100 minutes and sintering at over 1050 degrees C was needed for practical application. It thus seems possible to apply sintered titanium to dental prostheses. However, it will be necessary to examine the control of the shrinkage of the sintered compact in the future too.

Pulsed Laser Deposition of High Temperature Protonic Films

NASA Technical Reports Server (NTRS)

Dynys, Fred W.; Berger, M. H.; Sayir, Ali

2006-01-01

Pulsed laser deposition has been used to fabricate nanostructured BaCe(0.85)Y(0.15)O3- sigma) films. Protonic conduction of fabricated BaCe(0.85)Y(0.15)O(3-sigma) films was compared to sintered BaCe(0.85)Y(0.15)O(3-sigma). Sintered samples and laser targets were prepared by sintering BaCe(0.85)Y(0.15)O(3-sigma) powders derived by solid state synthesis. Films 1 to 8 micron thick were deposited by KrF excimer laser on porous Al2O3 substrates. Thin films were fabricated at deposition temperatures of 700 to 950 C at O2 pressures up to 200 mTorr using laser pulse energies of 0.45 - 0.95 J. Fabricated films were characterized by X-ray diffraction, electron microscopy and electrical impedance spectroscopy. Single phase BaCe(0.85)Y(0.15)O(3-sigma) films with a columnar growth morphology are observed with preferred crystal growth along the [100] or [001] direction. Results indicate [100] growth dependence upon laser pulse energy. Electrical conductivity of bulk samples produced by solid state sintering and thin film samples were measured over a temperature range of 100 C to 900 C. Electrical conduction behavior was dependent upon film deposition temperature. Maximum conductivity occurs at deposition temperature of 900 oC; the electrical conductivity exceeds the sintered specimen. All other deposited films exhibit a lower electrical conductivity than the sintered specimen. Activation energy for electrical conduction showed dependence upon deposition temperature, it varied

Physical properties and microstructure study of 316L SS fabricated by metal injection moulding process

NASA Astrophysics Data System (ADS)

Dandang, Nur Aidah Nabihah; Harun, Wan Sharuzi Wan; Khalil, Nur Zalikha; Ismail, Muhammad Hussain; Ibrahim, Rosdi

2017-12-01

Metal injection moulding (MIM) has been practised to process alloy powders to become components with significant physical and mechanical properties. Dissimilar than other methods, MIM focuses on the production of high volume, a small, and complex shape of products. The performance of the compacts depends on the suitable sintering parameters that governs their strengths in the final phase which determines the excellent properties of the sintered compacts. Three different sintering temperatures were utilised; 1100, 1200, and 1300 °C with two different soaking times; 1 and 3 hours at 10 °C/min heating rate to study their effect on the physical properties and microstructure analysis of 316L SS alloy compacts. The shrinkage measurement, surface roughness, and density measurement had been conducted for physical properties study. Different sintering temperatures give an effect to the physical properties of the sintered compacts. The shrinkage measurement at 1300 °C and 3-hour sintering condition demonstrated the highest percentage reading which was 10.1 % compared to the lowest percentage reading of 6.4 % at 1100 °C and 1-hour sintering conditions. Whereas, the minimum percentage of density measurement can be found at sintering conditions of 1100 °C and 1-hour which is 83.9 % and the highest percentage is at 1300 °C and 3-hour sintering condition which is about 89.51 %. Therefore, it has been determined that there could be a significant relationship between sintering temperature and physical properties in which it can be found from the porosity of the compact based on the microstructure studies.

Developing Cost-Effective Dense Continuous SDC Barrier Layers for SOFCs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nguyen, Hoang Viet P.; Hardy, John S.; Coyle, Christopher A.

Significantly improved performance during electrochemical testing of a cell with a dense continuous pulsed laser deposited (PLD) samarium doped ceria (SDC) layer spurred investigations into the fabrication of dense continuous SDC barrier layers by means of cost-effective deposition using screen printing which is amenable to industrial production of SOFCs. Many approaches to improve the SDC density have been explored including the use of powder with reduced particle sizes, inks with increased solids loading, and doping with sintering aids (1). In terms of sintering aids, dopants like Mo or binary systems of Mo+Cu or Fe+Co greatly enhance SDC sinterability. In fact,more » adding dopants to a screen printed, prefired, porous SDC layer made it possible to achieve a dense continuous barrier layer atop the YSZ electrolyte without sintering above 1200°C. Although the objective of fabricating a dense continuous layer was achieved, additional studies have been initiated to improve the cell performance. Underlying issues with constrained sintering and dopant-enhanced ceria-zirconia solid solubility are also addressed in this paper.« less

Effects of particle size and forming pressure on pore properties of Fe-Cr-Al porous metal by pressureless sintering

NASA Astrophysics Data System (ADS)

Koo, Bon-Uk; Yi, Yujeong; Lee, Minjeong; Kim, Byoung-Kee

2017-03-01

With increased hydrogen consumption in ammonia production, refining and synthesis, fuel cells and vehicle industries, development of the material components related to hydrogen production is becoming an important factor in industry growth. Porous metals for fabrication of hydrogen are commonly known for their relative excellence in terms of large area, lightness, lower heat capacity, high toughness, and permeability. Fe-Cr-Al alloys not only have high corrosion resistance, heat resistance, and chemical stability but also ductility, excellent mechanical properties. In order to control powder size and sintering temperature effects of Fe-Cr-Al porous metal fabrication, Fe-Cr-Al powder was classified into 25-35 μm, 35-45 μm, 45-75 μm using an auto shaking sieve machine and then classified Fe-Cr-Al powders were pressed into disk shapes using a uniaxial press machine and CIP. The pelletized Fe-Cr-Al specimens were sintered at various temperatures in high vacuum. Properties such as pore size, porosity, and air permeability were evaluated using perm-porosimetry. Microstructure and phase changes were observed with SEM and XRD. Porosity and relative density were proportionated to increasing sintering temperature. With sufficient sintering at increasing temperatures, the pore size is expected to be gradually reduced. Porosity decreased with increasing sintering temperature and gradually increased necking of the powder.

Structural and magnetic properties of Ga-substituted Co 2 ‑W hexaferrites

NASA Astrophysics Data System (ADS)

Mahmood, Sami H.; Al Sheyab, Qusai; Bsoul, Ibrahim; Mohsen, Osama; Awadallah, Ahmad

2018-05-01

Precursor powders of BaMg2-xCoxFe16O27 with (x = 0.0, 1.0, and 2.0) were prepared using high-energy ball milling, and the effects of chemical composition and sintering temperature on the structural and magnetic properties were investigated using x-ray diffractometer (XRD), scanning electron microscopy (SEM), and vibrating sample magnetometry (VSM). XRD patterns of the prepared samples indicated that crystallization of pure BaW hexaferrite phase was achieved at sintering temperature of 1300{\\deg} C, while BaM and cubic spinel phase intermediate phases were obtained at lower sintering temperatures of 1100{\\deg} C and 1200{\\deg} C. SEM images revealed improvement of the crystallization of the structural phases, and growth of the particle size with increasing the sintering temperature. The magnetic data of the samples sintered at 1300{\\deg} C revealed an increase of the saturation magnetization from 59.44 emu/g to 72.56 emu/g with increasing Co concentration (x) from 0.0 to 2.0. The coercive field Hc decreased from 0.07 kOe at x = 0.0, to 0.03 kOe at x = 1.0, and then increases to 0.09 kOe at x = 2.0. The thermomagnetic curves of the samples sintered at 1300{\\deg} C confirmed the existence of the W-type phase, and revealed spin reorientation transitions above room temperature.

A comparative study of the physical properties of Cu-Zn ferrites annealed under different atmospheres and temperatures: Magnetic enhancement of Cu0.5Zn0.5Fe2O4 nanoparticles by a reducing atmosphere

NASA Astrophysics Data System (ADS)

Gholizadeh, Ahmad

2018-04-01

In the present work, the influence of different sintering atmospheres and temperatures on physical properties of the Cu0.5Zn0.5Fe2O4 nanoparticles including the redistribution of Zn2+ and Fe3+ ions, the oxidation of Fe atoms in the lattice, crystallite sizes, IR bands, saturation magnetization and magnetic core sizes have been investigated. The fitting of XRD patterns by using Fullprof program and also FT-IR measurement show the formation of a cubic structure with no presence of impurity phase for all the samples. The unit cell parameter of the samples sintered at the air- and inert-ambient atmospheres trend to decrease with sintering temperature, but for the samples sintered under carbon monoxide-ambient atmosphere increase. The magnetization curves versus the applied magnetic field, indicate different behaviour for the samples sintered at 700 °C with the respect to the samples sintered at 300 °C. Also, the saturation magnetization increases with the sintering temperature and reach a maximum 61.68 emu/g in the sample sintered under reducing atmosphere at 600 °C. The magnetic particle size distributions of samples have been calculated by fitting the M-H curves with the size distributed Langevin function. The results obtained from the XRD and FTIR measurements suggest that the magnetic core size has the dominant effect in variation of the saturation magnetization of the samples.

Behavior of New Zealand Ironsand During Iron Ore Sintering

NASA Astrophysics Data System (ADS)

Wang, Zhe; Pinson, David; Chew, Sheng; Rogers, Harold; Monaghan, Brian J.; Pownceby, Mark I.; Webster, Nathan A. S.; Zhang, Guangqing

2016-02-01

A New Zealand ironsand sample was characterized by scanning electron microscopy (SEM), X-ray fluorescence spectroscopy, qualitative and quantitative X-ray diffraction, and electron probe microanalysis. The titanomagnetite-rich ironsand was added into an industrial sinter blend in the proportion of 5 wt pct, and the mixture was uniaxially pressed into cylindrical tablets and sintered in a tube furnace under flowing gas with various oxygen potentials and temperatures to develop knowledge and understanding of the behavior of titanium during sintering. An industrial sinter with the addition of 3 wt pct ironsand was also examined. Both the laboratory and industrial sinters were characterized by optical and SEM. Various morphologies of relict ironsand particles were present in the industrial sinter due to the heterogeneity of sintering conditions, which could be well simulated by the bench-scale sintering experiments. The assimilation of ironsand during sintering in a reducing atmosphere started with the diffusion of calcium into the lattice of the ironsand matrix, and a reaction zone was formed near the boundary within individual ironsand particles where a perovskite phase was generated. With increasing sintering temperature, in a reducing atmosphere, ironsand particles underwent further assimilation and most of the titanium moved from the ironsand particles into a glass phase. In comparison, more titanium remained in the original ironsand particles when sintered in air. Ironsand particles are more resistant to assimilation in an oxidizing atmosphere.

Effect of two-stage sintering on dielectric properties of BaTi0.9Zr0.1O3 ceramics

NASA Astrophysics Data System (ADS)

Rani, Rekha; Rani, Renu; Kumar, Parveen; Juneja, J. K.; Raina, K. K.; Prakash, Chandra

2011-09-01

The effect of two-stage sintering on the dielectric properties of BaTi0.9Zr0.1O3 ceramics prepared by solid state route was investigated and is presented here. It has been found that under suitable two-stage sintering conditions, dense BaTi0.9Zr0.1O3 ceramics with improved electrical properties can be synthesized. The density was found to have a value of 5.49 g cc-1 for normally sintered samples, whereas in the case of the two-stage sintered sample it was 5.85 g cc-1. Dielectric measurements were done as a function of frequency and temperature. A small decrease in the Curie temperature was observed with modification in dielectric loss for two-stage sintered ceramic samples.

Effect of sintering conditions on the electrical-transport properties of the SrZrO3-based protonic ceramic electrolyser membrane

NASA Astrophysics Data System (ADS)

Heras-Juaristi, Gemma; Pérez-Coll, Domingo; Mather, Glenn C.

2016-11-01

The effects of sintering temperature and addition of 4 mol.% ZnO as sintering additive on the crystal structure, microstructure and electrical properties of SrZr0.9Y0.1O3-δ are reported. The presence of ZnO as sintering aid brings about high densification at 1300 °C (relative density ∼97%); gas-tightness is not achieved for ZnO-free samples sintered below 1600 °C. Bulk conductivity (σB) is considerably higher in wet and dry O2 on doping with ZnO, but only slight variations of σB with sintering temperature are observed for the Zn-containing phases. Similarly, the apparent grain-boundary conductivities are much greater for the Zn-doped samples. The grain-boundary volume and accompanying resistances are much reduced on sintering at 1500 °C with ZnO addition in comparison to Zn-modified samples sintered below 1500 °C, with only minor changes in grain-boundary relaxation frequency observed. Conversely, in comparison to the undoped sample with sintering temperature of 1600 °C, there is an enormous improvement in the specific grain-boundary conductivity of two orders of magnitude for the ZnO-containing samples. Analysis on the basis of the core space-charge-layer model relates the enhancement of the grain-boundary transport to a higher concentration of charge carriers in the space-charge layer and associated lower potential barrier heights.

Thermomechanical Performance of Si-Ti-C-O and Sintered SiC Fiber-Bonded Ceramics at High Temperatures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Matsunaga, Tadashi; Lin, Hua-Tay; Singh, Mrityunjay

2011-01-01

The stress-temperature-lifetime response of Si-Ti-C-O fiber-bonded ceramic (Tyrannohex ) and sintered SiC fiber-bonded ceramic (SA-Tyrannohex ) materials were investigated in air from 500 to 1150 C and 500 to 1400 C, respectively. The apparent threshold stress of Si-Ti-C-O fiber-bonded ceramic was about 175 MPa in the 500-1150 C temperature range. When the applied stress of the sintered SiC fiber-bonded ceramic was below an apparent threshold stress (e.g., ~225MPa) for tests conducted 1150 C, no failures were observed for lifetimes up to 1000h. In the case of sintered SiC fiber-bonded ceramic, at the temperature of 1300 C, the apparent threshold stressmore » decreased to 175 MPa. The decrease in strength seemed to be caused by grain growth which was confirmed from the SEM fractography. Both fiber-bonded ceramics exhibited much higher durability than a commercial SiC/SiC composite at temperatures above 500 C. In addition, results suggested that the sintered SiC fiber-bonded ceramic (SA-Tyrannohex) is more stable than a Hi-Nicalon/MI SiC composite with BN/SiC fiber coating at temperatures above 1300 C.« less

A strategy to optimize the thermoelectric performance in a spark plasma sintering process

PubMed Central

Chiu, Wan-Ting; Chen, Cheng-Lung; Chen, Yang-Yuan

2016-01-01

Spark plasma sintering (SPS) is currently widely applied to existing alloys as a means of further enhancing the alloys’ figure of merit. However, the determination of the optimal sintering condition is challenging in the SPS process. This report demonstrates a systematic way to independently optimize the Seebeck coefficient S and the ratio of electrical to thermal conductivity (σ/κ) and thus achieve the maximum figure of merit zT = S2(σ/κ)T. Sb2−xInxTe3 (x = 0–0.2) were chosen as examples to validate the method. Although high sintering temperature and pressure are helpful in enhancing the compactness and electrical conductivity of pressed samples, the resultant deteriorated Seebeck coefficient and increasing thermal conductivity eventually offset the benefit. We found that the optimal sintering temperature coincides with temperatures at which the maximum Seebeck coefficient begins to degrade, whereas the optimal sintering pressure coincided with the pressure at which the σ/κ ratio reaches a maximum. Based on this principle, the optimized sintering conditions were determined, and the zT of Sb1.9In0.1Te3 is raised to 0.92 at 600 K, showing an approximately 84% enhancement. This work develops a facile strategy for selecting the optimal SPS sintering condition to further enhance the zT of bulk specimens. PMID:26975209

Sintering of MSW fly ash for reuse as a concrete aggregate.

PubMed

Mangialardi, T

2001-10-12

The sintering process of municipal solid waste (MSW) fly ash was investigated in order to manufacture sintered products for reuse as concrete aggregates. Four types of fly ash resulting from different Italian MSW incineration plants were tested in this study. A modification of the chemical composition of MSW fly ash--through a preliminary four-stage washing treatment of this material with water--was attempted to improve the chemical and mechanical characteristics of sintered products.The sintering treatment of untreated or washed fly ash was performed on cylindrical compact specimens (15 mm in diameter and 20mm in height) at different compact pressures, sintering temperatures and times.The sintering process of untreated MSW fly ashes proved to be ineffective for manufacturing sintered products for reuse as a construction material, because of the adverse chemical characteristics of these fly ashes in terms of sulfate, chloride, and vitrifying oxide contents.A preliminary washing treatment of MSW fly ash with water greatly improved the chemical and mechanical characteristics of sintered products and, for all the types of fly ash tested, the sintered products satisfied the Italian requirements for normal weight aggregates for use in concretes having a specified strength not greater than 12 and 15N/mm(2), when measured on cylindrical and cubic specimens, respectively.A compact pressure of 28 N/mm(2), a sintering temperature of 1140 degrees C, and a sintering time of 60 min were the best operating conditions for manufacturing sintered products of washed MSW fly ash.

Optimisation of Copper Oxide Impregnation on Carbonised Oil Palm Empty Fruit Bunch for Nitric Oxide Removal using Response Surface Methodology

NASA Astrophysics Data System (ADS)

Ahmad, Norhidayah; Yong, Sing Hung; Ibrahim, Naimah; Ali, Umi Fazara Md; Ridwan, Fahmi Muhammad; Ahmad, Razi

2018-03-01

Oil palm empty fruit bunch (EFB) was successfully modified with phosphoric acid hydration followed by impregnation with copper oxide (CuO) to synthesize CuO modified catalytic carbon (CuO/EFBC) for low-temperature removal of nitric oxide (NO) from gas streams. CuO impregnation was optimised through response surface methodology (RSM) using Box-Behnken Design (BBD) in terms of metal loading (5-20%), sintering temperature (200-800˚C) and sintering time (2-6 hours). The model response for the variables was NO adsorption capacity, which was obtained from an up-flow column adsorption experiment with 100 mL/min flow of 500 ppm NO/He at different operating conditions. The optimum operating variables suggested by the model were 20% metal loading, 200˚C sintering temperature and 6 hours sintering time. A good agreement (R2 = 0.9625) was achieved between the experimental data and model prediction. ANOVA analysis indicated that the model terms (metal loading and sintering temperature) are significant (Prob.>F less than 0.05).

Novel Routes for Sintering of Ultra-high Temperature Ceramics and their Properties

DTIC Science & Technology

2014-10-31

UHTCs charge (zirconium and hafnium borides , SiC) with additives (chromium carbide, nickel, chromium, etc.), which activate sintering process, is...temperature phases in a form of carboborides of zirconium and bi borides of zirconium or chromium. Elevation of densification rate of sintered borides is...superplasticity under the slip mechanism of zirconium boride and silica carbide grains on grain boundary interlayers with nanocrystalline grains of carbon

Yttria catalyzed microstructural modifications in oxide dispersion strengthened V-4Cr-4Ti alloys synthesized by field assisted sintering technique

NASA Astrophysics Data System (ADS)

Krishnan, Vinoadh Kumar; Sinnaeruvadi, Kumaran; Verma, Shailendra Kumar; Dash, Biswaranjan; Agrawal, Priyanka; Subramanian, Karthikeyan

2017-08-01

The present work deals with synthesis, characterisation and elevated temperature mechanical property evaluation of V-4Cr-4Ti and oxide (yttria = 0.3, 0.6 and 0.9 at%) dispersion strengthened V-4Cr-4Ti alloy processed by mechanical alloying and field-assisted sintering, under optimal conditions. Microstructural parameters of both powder and sintered samples were deduced by X-ray diffraction (XRD) and further confirmed with high resolution transmission electron microscopy. Powder diffraction and electron microscopy study show that ball milling of starting elemental powders (V-4Cr-4Ti) with and without yttria addition has resulted in single phase α-V (V-4Cr-4Ti) alloy. Wherein, XRD and electron microscopy images of sintered samples have revealed phase separation (viz., Cr-V and Ti-V) and domain size reduction, with yttria addition. The reasons behind phase separation and domain size reduction with yttria addition during sintering are extensively discussed. Microhardness and high temperature compression tests were done on sintered samples. Yttria addition (0.3 and 0.6 at.%) increases the elevated temperature compressive strength and strain hardening exponent of α-V alloys. High temperature compression test of 0.9 at% yttria dispersed α-V alloy reveals a glassy behaviour.

Microwave sintering of single plate-shaped articles

DOEpatents

Katz, Joel D.; Blake, Rodger D.

1995-01-01

Apparatus and method for high temperature sintering of plate-shaped articles of alumina, magnesia, silica, yttria, zirconia, and mixtures thereof using microwave radiation. An article is placed within a sintering structure located within a sintering container which is placed in a microwave cavity for heating. The rates at which heating and cooling take place is controlled.

Evaluation of Sintering Behaviors of Saprolitic Nickeliferous Laterite Based on Quaternary Basicity

NASA Astrophysics Data System (ADS)

Luo, Jun; Li, Guanghui; Rao, Mingjun; Zhang, Yuanbo; Peng, Zhiwei; Zhi, Qian; Jiang, Tao

2015-09-01

The sintering behaviors of saprolitic nickeliferous laterite with various quaternary basicities [(CaO + MgO)/(SiO2 + Al2O3) mass ratio] in a reductive atmosphere are investigated by simulative sintering and validated by sintering pot tests. The simulative sintering results show that the generation of diopside (CaMgSi2O6) with low melting point is the key reason for the decrease in characteristic fusion temperatures when the quaternary basicity increases from 0.5 to 0.8-1.0. Continuous increase of basicity leads to transformation of diopside (CaMgSi2O6) into akermanite (Ca2MgSi2O7), which adversely increases the characteristic fusion temperatures. These findings are confirmed by the sinter pot tests, which demonstrate that the sintering indexes including vertical sintering velocity (VSV), yield ( Y), and productivity ( P), can be improved by optimizing quaternary basicity. At basicity of 1.0, the VSV, Y, P, and ISO tumbling index reach 49.2 mm/min, 80.5%, 1.0 t/(h m2), and 66.5%, respectively.

Sintering Behavior of Spark Plasma Sintered SiC with Si-SiC Composite Nanoparticles Prepared by Thermal DC Plasma Process

NASA Astrophysics Data System (ADS)

Yu, Yeon-Tae; Naik, Gautam Kumar; Lim, Young-Bin; Yoon, Jeong-Mo

2017-11-01

The Si-coated SiC (Si-SiC) composite nanoparticle was prepared by non-transferred arc thermal plasma processing of solid-state synthesized SiC powder and was used as a sintering additive for SiC ceramic formation. Sintered SiC pellet was prepared by spark plasma sintering (SPS) process, and the effect of nano-sized Si-SiC composite particles on the sintering behavior of micron-sized SiC powder was investigated. The mixing ratio of Si-SiC composite nanoparticle to micron-sized SiC was optimized to 10 wt%. Vicker's hardness and relative density was increased with increasing sintering temperature and holding time. The relative density and Vicker's hardness was further increased by reaction bonding using additional activated carbon to the mixture of micron-sized SiC and nano-sized Si-SiC. The maximum relative density (97.1%) and Vicker's hardness (31.4 GPa) were recorded at 1800 °C sintering temperature for 1 min holding time, when 0.2 wt% additional activated carbon was added to the mixture of SiC/Si-SiC.

Manufacture of dense sintered bodies containing silicon nitride

NASA Technical Reports Server (NTRS)

Hirota, K.; Hasegawa, Y.; Ogura, K.; Yashima, Y.

1985-01-01

Sintered bodies containing 1-32.5 Si oxide and 1.5 wt.% SiC (Si oxide/SiC wt. ratio 3/2) are prepared and kept in a 10-3000 kg/2 sq. cm. N (g) atmosphere at 1500-2300 degrees, while simultaneously maintaining the CO (g) partial pressure around the body lower than the nitrogenation equil. pressure to give a dense sintered body. The prepared dense sintered body has high strength at high temperatures. Thus, SiC 40, oxide 30 and Si3N4 30 wt% were fired to a body which was kept in 1500 kg/sq. cm. N (g) for 20 h at 2000 degrees to give a dense sintered body having high bending strength at high temperatures.

Onset conditions for flash sintering of UO 2

DOE PAGES

Raftery, Alicia M.; Pereira da Silva, João Gustavo; Byler, Darrin D.; ...

2017-06-22

In this paper, flash sintering was demonstrated on stoichiometric and non-stoichiometric uranium dioxide pellets at temperatures ranging from room temperature (26°C) up to 600°C. The onset conditions for flash sintering were determined for three stoichiometries (UO 2.00, UO 2.08, and UO 2.16) and analyzed against an established thermal runaway model. The presence of excess oxygen was found to enhance the flash sintering onset behavior of uranium dioxide, lowering the field required to flash and shortening the time required for a flash to occur. Finally, the results from this study highlight the effect of stoichiometry on the flash sintering behavior ofmore » uranium dioxide and will serve as the foundation for future studies on this material.« less

Onset conditions for flash sintering of UO2

NASA Astrophysics Data System (ADS)

Raftery, Alicia M.; Pereira da Silva, João Gustavo; Byler, Darrin D.; Andersson, David A.; Uberuaga, Blas P.; Stanek, Christopher R.; McClellan, Kenneth J.

2017-09-01

In this work, flash sintering was demonstrated on stoichiometric and non-stoichiometric uranium dioxide pellets at temperatures ranging from room temperature (26 °C) up to 600 °C . The onset conditions for flash sintering were determined for three stoichiometries (UO2.00, UO2.08, and UO2.16) and analyzed against an established thermal runaway model. The presence of excess oxygen was found to enhance the flash sintering onset behavior of uranium dioxide, lowering the field required to flash and shortening the time required for a flash to occur. The results from this study highlight the effect of stoichiometry on the flash sintering behavior of uranium dioxide and will serve as the foundation for future studies on this material.

Solvent/non-solvent sintering: a novel route to create porous microsphere scaffolds for tissue regeneration.

PubMed

Brown, Justin L; Nair, Lakshmi S; Laurencin, Cato T

2008-08-01

Solvent/non-solvent sintering creates porous polymeric microsphere scaffolds suitable for tissue engineering purposes with control over the resulting porosity, average pore diameter, and mechanical properties. Five different biodegradable biocompatible polyphosphazenes exhibiting glass transition temperatures from -8 to 41 degrees C and poly (lactide-co-glycolide), (PLAGA) a degradable polymer used in a number of biomedical settings, were examined to study the versatility of the process and benchmark the process to heat sintering. Parameters such as: solvent/non-solvent sintering solution composition and submersion time effect the sintering process. PLAGA microsphere scaffolds fabricated with solvent/non-solvent sintering exhibited an interconnected porosity and pore size of 31.9% and 179.1 mum, respectively which was analogous to that of conventional heat sintered PLAGA microsphere scaffolds. Biodegradable polyphosphazene microsphere scaffolds exhibited a maximum interconnected porosity of 37.6% and a maximum compressive modulus of 94.3 MPa. Solvent/non-solvent sintering is an effective strategy for sintering polymeric microspheres, with a broad spectrum of glass transition temperatures, under ambient conditions making it an excellent fabrication route for developing tissue engineering scaffolds and drug delivery vehicles. (c) 2007 Wiley Periodicals, Inc.

Solvent/Non-Solvent Sintering: A Novel Route to Create Porous Microsphere Scaffolds For Tissue Regeneration

PubMed Central

Brown, Justin L.; Nair, Lakshmi S.; Laurencin, Cato T.

2009-01-01

Solvent/non-solvent sintering creates porous polymeric microsphere scaffolds suitable for tissue engineering purposes with control over the resulting porosity, average pore diameter and mechanical properties. Five different biodegradable biocompatible polyphosphazenes exhibiting glass transition temperatures from −8°C to 41oC and poly(lactide-co-glycolide), (PLAGA) a degradable polymer used in a number of biomedical settings, were examined to study the versatility of the process and benchmark the process to heat sintering. Parameters such as: solvent/non-solvent sintering solution composition and submersion time effect the sintering process. PLAGA microsphere scaffolds fabricated with solvent/non-solvent sintering exhibited an interconnected porosity and pore size of 31.9% and 179.1µm respectively which was analogous to that of conventional heat sintered PLAGA microsphere scaffolds. Biodegradable polyphosphazene microsphere scaffolds exhibited a maximum interconnected porosity of 37.6% and a maximum compressive modulus of 94.3MPa. Solvent/non-solvent sintering is an effective strategy for sintering polymeric microspheres, with a broad spectrum of glass transition temperatures, under ambient conditions making it an excellent fabrication route for developing tissue engineering scaffolds and drug delivery vehicles. PMID:18161819

Characterization of Multiwalled Carbon Nanotube-Reinforced Hydroxyapatite Composites Consolidated by Spark Plasma Sintering

PubMed Central

Kim, Duk-Yeon; Han, Young-Hwan; Lee, Jun Hee; Kang, Inn-Kyu; Jang, Byung-Koog; Kim, Sukyoung

2014-01-01

Pure HA and 1, 3, 5, and 10 vol% multiwalled carbon nanotube- (MWNT-) reinforced hydroxyapatite (HA) were consolidated using a spark plasma sintering (SPS) technique. The relative density of pure HA increased with increasing sintering temperature, but that of the MWNT/HA composite reached almost full density at 900°C, and then decreased with further increases in sintering temperature. The relative density of the MWNT/HA composites increased with increasing MWNT content due to the excellent thermal conductivity of MWNTs. The grain size of MWNT/HA composites decreased with increasing MWNT content and increased with increasing sintering temperature. Pull-out toughening of the MWNTs of the MWNT/HA composites was observed in the fractured surface, which can be used to predict the improvement of the mechanical properties. On the other hand, the existence of undispersed or agglomerate MWNTs in the MWNT/HA composites accompanied large pores. The formation of large pores increased with increasing sintering temperature and MWNT content. The addition of MWNT in HA increased the hardness and fracture toughness by approximately 3~4 times, despite the presence of large pores produced by un-dispersed MWNTs. This provides strong evidence as to why the MWNTs are good candidates as reinforcements for strengthening the ceramic matrix. The MWNT/HA composites did not decompose during SPS sintering. The MWNT-reinforced HA composites were non-toxic and showed a good cell affinity and morphology in vitro for 1 day. PMID:24724100

Advanced Ceramic Technology for Space Applications at NASA MSFC

NASA Technical Reports Server (NTRS)

Alim, Mohammad A.

2003-01-01

The ceramic processing technology using conventional methods is applied to the making of the state-of-the-art ceramics known as smart ceramics or intelligent ceramics or electroceramics. The sol-gel and wet chemical processing routes are excluded in this investigation considering economic aspect and proportionate benefit of the resulting product. The use of ceramic ingredients in making coatings or devices employing vacuum coating unit is also excluded in this investigation. Based on the present information it is anticipated that the conventional processing methods provide identical performing ceramics when compared to that processed by the chemical routes. This is possible when sintering temperature, heating and cooling ramps, peak temperature (sintering temperature), soak-time (hold-time), etc. are considered as variable parameters. In addition, optional calcination step prior to the sintering operation remains as a vital variable parameter. These variable parameters constitute a sintering profile to obtain a sintered product. Also it is possible to obtain identical products for more than one sintering profile attributing to the calcination step in conjunction with the variables of the sintering profile. Overall, the state-of-the-art ceramic technology is evaluated for potential thermal and electrical insulation coatings, microelectronics and integrated circuits, discrete and integrated devices, etc. applications in the space program.

Sintering Behavior of Hypereutectic Aluminum-Silicon Metal Matrix Composites Powder

NASA Astrophysics Data System (ADS)

Rudianto, Haris; Sun, Yang Sang; Jin, Kim Yong; Woo, Nam Ki

Lightweight materials of Aluminum-Silicon P/M alloys offer the advantage of high-wear resistance, high strength, good temperature resistance, and a low coefficient of thermal expansion. An A359 MMC alloy was mixed together with Alumix 231 in this research. Powders were compacted with compaction pressure up to 700 MPa. Particle size and compaction pressure influenced green density. Compacted powders were sintered in a tube furnace under a flowing nitrogen gas. Sintering temperature, heating rate and sintering time were verified to determine best sintering conditions of the alloys. Chemical composition also contributed to gain higher sintered density. Precipitation strengthening method was used to improve mechanical properties of this materials.T6 heat treatment was carried out to produce fine precipitates to impede movement of dislocation. The chemical composition of this materials allow for the potential formation of several strengthening precipitates including θ (Al2Cu) and β (Mg2Si).

Structural and Magnetic Studies of Thermally Treated NiFe2O4 Nanoparticles

NASA Astrophysics Data System (ADS)

Ghosh, Surajit; Patel, Prayas Chandra; Gangopadhyay, Debraj; Sharma, Poornima; Singh, Ranjan K.; Srivastava, P. C.

2017-12-01

The heat treatment of nanoparticles can have a direct effect on their particle sizes, which, in turn, can influence many of their structural and magnetic properties. Here, we report the effect of sintering temperature on the chemically synthesized high-quality NiFe2O4 nanoparticles. The structural studies show the formation of pure NiFe2O4 nanoparticles with the space group Fd{\\bar{3}}m . The inverse spinel structure was also confirmed from the lattice vibrations analyzed from Raman and Fourier transform infrared spectroscopy (FTIR) spectra. The presence of strong exchange interactions was detected from the temperature-dependent magnetization study. Moreover, at higher sintering temperatures, the grain growth due to fusion of several smaller particles by coalescing their surfaces enhances the crystallinity and its magnetocrystalline anisotropy. Coercivity and saturation magnetization were found to depend significantly on the sintering temperature, which was understood in the realm of the formation of single-domain-like structure and change in magnetocrystalline anisotropy at higher sintering temperatures.

Development of a sintering process for recycling oil shale fly ash and municipal solid waste incineration bottom ash into glass ceramic composite.

PubMed

Zhang, Zhikun; Zhang, Lei; Li, Aimin

2015-04-01

Oil shale fly ash and municipal solid waste incineration bottom ash are industrial and municipal by-products that require further treatment before disposal to avoid polluting the environment. In the study, they were mixed and vitrified into the slag by the melt-quench process. The obtained vitrified slag was then mixed with various percentages of oil shale fly ash and converted into glass ceramic composites by the subsequent sintering process. Differential thermal analysis was used to study the thermal characteristics and determine the sintering temperatures. X-ray diffraction analysis was used to analyze the crystalline phase compositions. Sintering shrinkage, weight loss on ignition, density and compressive strength were tested to determine the optimum preparation condition and study the co-sintering mechanism of vitrified amorphous slag and oil shale fly ash. The results showed the product performances increased with the increase of sintering temperatures and the proportion of vitrified slag to oil shale fly ash. Glass ceramic composite (vitrified slag content of 80%, oil shale fly ash content of 20%, sintering temperature of 1000 °C and sintering time of 2h) showed the properties of density of 1.92 ± 0.05 g/cm(3), weight loss on ignition of 6.14 ± 0.18%, sintering shrinkage of 22.06 ± 0.6% and compressive strength of 67 ± 14 MPa. The results indicated that it was a comparable waste-based material compared to previous researches. In particular, the energy consumption in the production process was reduced compared to conventional vitrification and sintering method. Chemical resistance and heavy metals leaching results of glass ceramic composites further confirmed the possibility of its engineering applications. Copyright © 2015 Elsevier Ltd. All rights reserved.

Gas response properties of citrate gel synthesized nanocrystalline MgFe{sub 2}O{sub 4}: Effect of sintering temperature

DOE Office of Scientific and Technical Information (OSTI.GOV)

Patil, J.Y.; Mulla, I.S.; Suryavanshi, S.S., E-mail: sssuryavanshi@rediffmail.com

2013-02-15

Graphical abstract: Display Omitted Highlights: ► Synthesis of nanocrystalline MgFe{sub 2}O{sub 4} by economical citrate gel combustion method. ► Structural, morphological, and gas response properties of MgFe{sub 2}O{sub 4}. ► Enhancement in selectivity of MgFe{sub 2}O{sub 4} towards LPG with sintering temperature. ► Use of MgFe{sub 2}O{sub 4} to detect different gases at different operating temperatures. -- Abstract: Spinel type MgFe{sub 2}O{sub 4} material was synthesized by citrate gel combustion method. The effect of sintering temperature on structural, morphological, and gas response properties was studied. The powder X-ray diffraction pattern and transmission electron microscope study confirms nanocrystalline spinel structure ofmore » the synthesized powder. The material was tested for response properties to various reducing gases like liquid petroleum gas (LPG), acetone, ethanol, and ammonia. The results demonstrated n-type semiconducting behavior of MgFe{sub 2}O{sub 4} material. It was revealed that MgFe{sub 2}O{sub 4} sintered at 973 K was most sensitive to LPG at 648 K and to acetone at 498 K. However MgFe{sub 2}O{sub 4} sintered at 1173 K exhibited higher response and selectivity to LPG with marginal increase in the operating temperature. Furthermore, the sensor exhibited a fast response and a good recovery. It was observed that the particles size, porosity, and surface activity of the sensor material is affected by the sintering temperature.« less

Synthesis and characterization of a model dual-phase system using the spark plasma sintering technique

NASA Astrophysics Data System (ADS)

Teimouri, M.; Godfrey, A.

2017-07-01

Samples of a model dual-phase system, consisting of copper and AISI-420 martensitic steel have been synthesized using spark plasma sintering, with the objective of developing a microstructural analogue for dual-phase steels, in which the volume fraction and size of each phase can be controlled independently. Microstructural investigation of the samples, including fractography of samples deformed in tension until failure, show that densification is strongly temperature dependent. Samples sintered at temperatures of 900 °C or above at a pressure of 60 MPa show a density of more than 98%. The best mechanical properties, in terms of ultimate tensile strength and ductility is found in samples sintered at a temperature of 1000 °C, where a density of nearly 99% is achieved.

Thermal and Electrical Characterization of Alumina Substrate for Microelectronic Applications

NASA Astrophysics Data System (ADS)

Ahmad, S.; Ibrahim, A.; Alias, R.; Shapee, S. M.; Ambak, Z.; Zakaria, S. Z.; Yahya, M. R.; Mat, A. F. A.

2010-03-01

This paper reports the effect of sintering temperature on thermal and electrical properties of alumina material as substrate for microelectronic devices. Alumina materials in the form of green sheet with 1 mm thickness were sintered at 1100° C, 1300° C and 1500° C for about 20 hours using heating and cooling rates of 2° C/min. The densities were measured using densitometer and the microstructures of the samples were analyzed using SEM micrographs. Meanwhile thermal and electrical properties of the samples were measured using flash method and impedance analyzer respectively. It was found that thermal conductivity and thermal diffusivity of the substrate increases as sintering temperature increases. It was found also that the dielectric constant of alumina substrate increases as the sintering temperature increases.

SINTERING METHOD

DOEpatents

Googin, J.M.

1963-11-01

Methods of making articles by powder metallurgy techniques are presented. An article is made by packing a metal powder into a desired shape, raising the temperature of the powder compact to a sintering temperature in the presence of a reducing gas, and alternately increasing and decreasing the pressure of the gas while the temperatume is being raised. The product has a greater density than can be achieved by sintering for the same length of time at a constant gas pressure. (AEC)

Field assisted sintering of refractory carbide ceramics and fiber reinforced ceramic matrix composites

NASA Astrophysics Data System (ADS)

Gephart, Sean

The sintering behaviors of silicon carbide (SiC) and boron carbide (B4C) based materials were investigated using an emerging sintering technology known as field assisted sintering technology (FAST), also known as spark plasma sintering (SPS) and pulse electric current sintering (PECS). Sintering by FAST utilizes high density electric current, uniaxial pressure, and relatively high heating rate compared to conventional sintering techniques. This effort investigated issues of scaling from laboratory FAST system (25 ton capacity) to industrial FAST system (250 ton capacity), as well as exploring the difference in sintering behavior of single phase B4C and SiC using FAST and conventional sintering techniques including hot-pressing (HP) and pressure-less sintering (PL). Materials were analyzed for mechanical and bulk properties, including characterization of density, hardness, fracture toughness, fracture (bend) strength, elastic modulus and microstructure. A parallel investigation was conducted in the development of ceramic matrix composites (CMC) using SiC powder impregnation of fiber compacts followed by FAST sintering. The FAST technique was used to sinter several B4C and SiC materials to near theoretical density. Preliminary efforts established optimized sintering temperatures using the smaller 25 ton laboratory unit, targeting a sample size of 40 mm diameter and 8 mm thickness. Then the same B4C and SiC materials were sintered by the larger 250 ton industrial FAST system, a HP system, and PL sintering system with a targeted dense material geometry of 4 x 4 x 0.315 inches3 (101.6 x 101.6 x 8 mm3). The resulting samples were studied to determine if the sintering dynamics and/or the resulting material properties were influenced by the sintering technique employed. This study determined that FAST sintered ceramic materials resulted in consistently higher averaged values for mechanical properties as well as smaller grain size when compared to conventionally sintered materials. While FAST sintered materials showed higher average values, in general they also showed consistently larger variation in the scattered data and consequently larger standard deviation for the resulting material properties. In addition, dynamic impact testing (V50 test) was conducted on the resulting materials and it was determined that there was no discernable correlation between observed mechanical properties of the ceramic materials and the resulting dynamic testing. Another study was conducted on the sintering of SiC and carbon fiber reinforced SiC ceramic matrix composites (CMC) using FAST. There has been much interest recently in fabricating high strength, low porosity SiC CMC.s for high temperature structural applications, but the current methods of production, namely chemical vapor infiltration (CVI), melt infiltration (MI), and polymer infiltration and pyrolysis (PIP), are considered time consuming and involve material related shortcomings associated with their respective methodologies. In this study, SiC CMC.s were produced using the 25 ton laboratory unit with a target sample size of 40 mm diameter and 3 mm thickness, as well as on the larger 250 ton industrial FAST system targeting a sample size of 101.6 x 101.6 x 3 mm3 to investigate issues associated with scaling. Several sintering conditions were explored including: pressure of 35-65 MPa, temperature of 1700-1900°C, and heating rates between 50-400°C/min. The SiC fibers used in this study were coated using chemical vapor deposition (CVD) with boron nitride (BN) and pyrolytic carbon to act as a barrier layer and preserve the integrity of the fibers during sintering. Then the barrier coating was coated by an outer layer of SiC to enhance the bonding between the fibers and the SiC matrix. Microstructures of the sintered samples were examined by FE-SEM. Mechanical properties including flexural strength-deflection and stress-strain were characterized using 4-point bend testing. Tensile testing was performed on the larger 101.6 x 101.6 x 3 mm samples. The microstructures of samples sintered using the 25 ton laboratory FAST system showed a reduction in porosity and good adhesion between the fiber-fiber and fiber-matrix interface. The microstructures of samples sintered on the 250 ton industrial FAST system showed a reduction in porosity, but there was visible reaction of the fiber and fiber coatings with the surrounding matrix. Additionally, there was significant radial cracking of the fibers visible in the microstructures. There is gap in the understanding of sintering behavior between laboratory and industrial scale FAST systems. The vast majority of publications on FAST sintering have been primarily focused on small sample geometries (20 mm diameter, less than 3 mm thick). A study was coordinated to investigate the thermal properties during heating and cooling using a 250 ton industrial FAST system at 900°C using B4C and SiC materials inside the graphite die assembly. The thermal properties were then compared to the resulting material properties of the identically sintered B4C and SiC to approximately 94% relative density, at a temperature of 1950°C, pressure of 45 MPa, 10 minute hold, and heated at a rate of 100°C/min. The study determined that at 900°C there were significant thermal gradients within the system for the examined materials, and that these gradients correlated well with the material property difference of the samples sintered at higher temperatures where the gradients are presumably larger due to an increase in radiative heat loss. The observed temperatures throughout the graphite were significantly different between B4C and SiC. These temperatures also correlated well with the material properties of the sintered products which showed more substantial variation for B4C when compared to SiC which was overall less affected by thermal gradients. This was attributed to the intrinsic thermal conductivity difference between the two subject materials which was manifested as thermal gradients throughout the material and graphite die assembly. Additionally, both the observed temperature gradients throughout the graphite die assembly and the difference in temperature reading between the optical pyrometer and thermocouples were significantly larger for the 250 ton FAST system than previous publications have demonstrated experimentally or via modeling of smaller laboratory scale systems. The findings from this work showed that relative to conventional sintering methods, the FAST process demonstrated comparable or improved material and mechanical properties with a significantly shorter processing cycle. However, the results demonstrated on the 25 ton laboratory scale unit were significantly different compared to results for the same materials sintered using the 250 ton industrial scale unit. The temperature gradients observed on the 250 ton FAST unit were significantly larger than previous reports on smaller FAST units. This result showed future efforts to scale up the FAST sintering process while maintaining similar results will require careful attention to minimizing temperature gradients. This could potentially be achieved by reducing radiative heat loss during processing and/or optimizing the graphite die design and implementing heat spreaders in specific locations dependent on the host material.s thermal and electrical properties as well as the sample geometry.

Microwave sintering of single plate-shaped articles

DOEpatents

Katz, J.D.; Blake, R.D.

1995-07-11

Apparatus and method are disclosed for high temperature sintering of plate-shaped articles of alumina, magnesia, silica, yttria, zirconia, and mixtures thereof using microwave radiation. An article is placed within a sintering structure located within a sintering container which is placed in a microwave cavity for heating. The rates at which heating and cooling take place is controlled. 2 figs.

Conventional and two step sintering of PZT-PCN ceramics

NASA Astrophysics Data System (ADS)

Keshavarzi, Mostafa; Rahmani, Hooman; Nemati, Ali; Hashemi, Mahdieh

2018-02-01

In this study, PZT-PCN ceramic was made via sol-gel seeding method and effects of conventional sintering (CS) as well as two-step sintering (TSS) were investigated on microstructure, phase formation, density, dielectric and piezoelectric properties. First, high quality powder was achieved by seeding method in which the mixture of Co3O4 and Nb2O5 powder was added to the prepared PZT sol to form PZT-PCN gel. After drying and calcination, pyrochlore free PZT-PCN powder was synthesized. Second, CS and TSS were applied to achieve dense ceramic. The optimum temperature used for 2 h of conventional sintering was obtained at 1150 °C; finally, undesired ZrO2 phase formed in CS procedure was removed successfully with TSS procedure and dielectric and piezoelectric properties were improved compared to the CS procedure. The best electrical properties obtained for the sample sintered by TSS in the initial temperature of T 1 = 1200 °C and secondary temperature of T 2 = 1000 °C for 12 h.

Application of Box-Behnken Design and Response Surface Methodology for Surface Roughness Prediction Model of CP-Ti Powder Metallurgy Components Through WEDM

NASA Astrophysics Data System (ADS)

Das, Arunangsu; Sarkar, Susenjit; Karanjai, Malobika; Sutradhar, Goutam

2018-04-01

The present work was undertaken to investigate and characterize the machining parameters (such as surface roughness, etc.) of uni-axially pressed commercially pure titanium sintered powder metallurgy components. Powder was uni-axially pressed at designated pressure of 840 MPa to form cylindrical samples and the green compacts were sintered at 0.001 mbar for about 4 h with sintering temperature varying from 1350 to 1450 °C. The influence of the sintering temperature, pulse-on and pulse-off time at wire-EDM on the surface roughness of the preforms has been investigated thoroughly. Experiments were conducted under different machining parameters in a CNC operated wire-cut EDM. The surface roughness of the machined surface was measured and critically analysed. The optimum surface roughness was achieved under the conditions of 6 μs pulse-on time, 9 μs pulse-off time and at sintering temperature of 1450 °C.

Processing and Characterization of Porous Ti2AlC with Controlled Porosity and Pore Size

DTIC Science & Technology

2012-09-11

fabricated by spark plasma sintering , were also characterized. The effects of porosity and/or pore size on the room temperature elastic moduli...pressureless- sintered without NaCl pore former, or fabricated by spark plasma sintering , were also characterized. The effects of porosity and/or pore size...as well as several samples sintered using spark plasma sintering (SPS). Furthermore, we demon- strate that the developed methodology can be implemented

Lowering the synthesis temperature of Y3Fe5O12 by surfactant assisted solid state reaction

NASA Astrophysics Data System (ADS)

Xue, Fenghua; Huang, Ju; Li, Tianrui; Wang, Zifan; Zhou, Xiaochao; Wei, Lujun; Gao, Baizhi; Zhai, Ya; Li, Qi; Xu, Qingyu; Du, Jun

2018-01-01

There is an urgent technical requirement of lowering the sintering temperature of Y3Fe5O12 (YIG) for its practical applications. In this paper, a modified solid state reaction method is reported by adding the surfactant of cetyltrimethylammonium bromide (CTAB). A high sintering temperature of 1200 °C is required for the formation of YIG phase without adding CTAB, which is effectively decreased to 1050 °C by adding CTAB. The morphology studies show that the sintering temperature plays the main role in the crystal growth and excludes the possible contribution of CTAB. The prepared YIG ceramic samples show soft ferromagnetic properties, with coercivity of only 21.2 Oe for the sample prepared with CTAB at 1050 °C, which decreases with increasing sintering temperature. The main role of adding CTAB is preventing the agglomeration of ball milled ultrafine source particles, which may facilitate the interdiffusion among them and promote the reaction at lower temperatures. Furthermore, the Gilbert damping constant is significantly reduced for YIG prepared by adding CTAB, which is one order smaller than that without CTAB.

The Influence of Sintering Temperature on the Microstructure and Thermoelectric Properties of n-Type Bi2Te3- x Se x Nanomaterials

NASA Astrophysics Data System (ADS)

Du, Y.; Cai, K. F.; Li, H.; An, B. J.

2011-05-01

Pure Bi2Te3 and Bi2Se3 nanopowders were hydrothermally synthesized, and n-type Bi2Te3- x Se x bulk samples were prepared by hot pressing a mixture of Bi2Te3 and Bi2Se3 nanopowders at 623 K, 648 K or 673 K and 80 MPa in vacuum. The phase composition of the powders and bulk samples were characterized by x-ray diffraction. The morphology of the powders was examined by transmission electron microscopy. The microstructure and composition of the bulk samples were characterized by field-emission scanning electron microscopy and energy-dispersive x-ray spectroscopy, respectively. The density of the samples increased with sintering temperature. The samples were somewhat oxidized, and the amount of oxide (Bi2TeO5) present increased with sintering temperature. The samples consisted of sheet-like grains with a thickness less than 100 nm. Seebeck coefficient, electrical conductivity, and thermal conductivity of the samples were measured from room temperature up to 573 K. Throughout the temperature range investigated, the sample sintered at 623 K had a higher power factor than the samples sintered at 648 K or 673 K.

Effect of sintering temperature of Ce3+-doped Lu3Al5O12 phosphors on light emission and properties of crystal structure for white-light-emitting diodes

NASA Astrophysics Data System (ADS)

Koizumi, Hiroshi; Watabe, Junya; Sugiyama, Shin; Hirabayashi, Hideaki; Homma, Tetsuya

2018-06-01

The effect of the sintering temperature of Ce3+-doped Lu3Al5O12 (Ce-LuAG) phosphors on the emission and properties of the crystal structure was studied. A cathodoluminescence peak at 317 nm, which was assigned to lattice defects, was exhibited in addition to emission peaks at 508 and 540 nm for the Ce-LuAG phosphors. The intensities of the 317 nm emission peak for the phosphors with mean particle diameters of 5.0 and 10.0 µm formed at a low sintering temperature of 1430 °C were higher than those for the phosphors with mean particle diameters of 18.0 and 20.5 µm formed at a high sintering temperature of 1550 °C. In contrast, the electroluminescence spectra for fabricated white-light-emitting diodes (LEDs) using the phosphors revealed that the intensity of the peak at 540 nm was strong for the mean particle diameters of 18.0 and 20.5 µm. The intensity of the 540 nm peak, which is attributed to the 4f→5d transition of the Ce3+ activator, showed a dependence on the sintering temperature. The relationship between the optical properties and the lattice defects is discussed.

Effect of sintering on structure and magnetic properties of Mn-doped Zn ferrite

NASA Astrophysics Data System (ADS)

Farheen, Atiya; Singh, Rajender

2018-05-01

The Mn-doped zinc ferrites, MnxZn1-xFe2O4 (x= 0 and 0.1) were prepared using co-precipitation method. The as-prepared samples were sintered at different temperatures. The x-ray diffraction pattern for all the samples confirms single phase spinel structure with Fd-3m space group. The lattice parameters have been estimated using Rietveld fitting. The magnetic moment is found to increase with Mn-doping. The magnetization increases as the sintering temperature increases up to 1200°C. The as-prepared samples are super paramagnetic, while the sintered samples are ferrimagnetic in nature.

Low-temperature sintering and electrical properties of strontium- and magnesium-doped lanthanum gallate with V2O5 additive

NASA Astrophysics Data System (ADS)

Ha, Sang Bu; Cho, Yoon Ho; Ji, Ho-Il; Lee, Jong-Ho; Kang, Yun Chan; Lee, Jong-Heun

2011-03-01

The effects of a V2O5 additive on the low-temperature sintering and ionic conductivity of strontium- and magnesium-doped lanthanum gallate (LSGM: La0.8Sr0.2Ga0.8Mg0.2O2.8) are studied. The LSGM powders prepared by the glycine nitrate method are mixed with 0.5-2 at.% of VO5/2 and then sintered at 1100-1400 °C in air for 4 h. The apparent density and phase purity of the LSGM specimens are increased with increasing sintering temperature and VO5/2 concentration due to the enhanced sintering and mass transfer via the intergranular liquid phase. The 1 at.% VO5/2-doped LSGM specimen sintered at 1300 °C exhibits a high oxide ion conductivity of ∼0.027 S cm-1 at 700 °C over a wide range of oxygen partial pressure (PO2 =10-27 - 1 atm), thereby demonstrating its potential as a useful electrolyte for anode-supported solid oxide fuel cells (SOFCs) without the requirement for any buffer layer between the electrolyte and anode.

Mechanical behaviour of pressed and sintered CP Ti and Ti-6Al-7Nb alloy obtained from master alloy addition powder.

PubMed

Bolzoni, L; Weissgaerber, T; Kieback, B; Ruiz-Navas, E M; Gordo, E

2013-04-01

The Ti-6Al-7Nb alloy was obtained using the blending elemental approach with a master alloy and elemental titanium powders. Both the elemental titanium and the Ti-6Al-7Nb powders were characterised using X-ray diffraction, differential thermal analysis and dilatometry. The powders were processed using the conventional powder metallurgy route that includes uniaxial pressing and sintering. The trend of the relative density with the sintering temperature and the microstructural evolution of the materials sintered at different temperatures were analysed using scanning electron microscopy and X-ray diffraction. A minimum sintering temperature of 1200°C has to be used to ensure the homogenisation of the alloying elements and to obtain a pore structure composed of spherical pores. The sintered samples achieve relative density values that are typical for powder metallurgy titanium and no intermetallic phases were detected. Mechanical properties comparable to those specified for wrought Ti-6Al-7Nb medical devices are normally obtained. Therefore, the produced materials are promising candidates for load bearing applications as implant materials. Copyright © 2013 Elsevier Ltd. All rights reserved.

Effects of chromium addition on the metallurgy and P/M processing response of Alumix 431D

NASA Astrophysics Data System (ADS)

Mosher, Michael Patrick

The ever growing industry of Powder Metallurgy (P/M) is developing to include new alloys and improve those currently available. This project relates to the optimization of a commercially available Al-Zn-Mg-Cu based alloy (Alumix 431D). This alloy is the P/M equivalent of the wrought 7075 alloy, and yields some of the top performance found in any available aluminum alloy. Optimization of the alloy has been conducted with a focus on sintering conditions; in particular the effect of sintering temperature and post-sintering cooling. Five sintering temperatures were investigated and the optimal temperature was found to be 605°C. Cr was added in trace amounts as per literature recommendations in an attempt to improve corrosion resistance. Both the Cr-free and Cr-containing alloys were then assessed for post-sinter cooling effects. The Alumix 431D w/Cr compacted and sintered to a higher density which further resulted in improved hardness over the Cr-free counterpart. The cooling profile was modified to include an increasingly larger post-sinter furnace-cooling section, before gas quenching. Seven quenching temperatures were chosen to investigate ranging from the sintering temperature (605°C) down to 480°C. This furnace cooling allowed the alloy-rich liquid phase to dwell for an extended time at elevated temperature and thereby diffuse into the matrix grains increasing the alloy content. This was confirmed through EPMA and correlated with an increase in mechanical properties. For both alloys peak hardness was produced by specimens cooled to 520°C before quenching. Tensile strength also increased by as much as 12% when furnace cooled to 540°C. The heat treatment parameters were determined to yield an optimal T6 temper. Specimens of both alloys processed under all conditions were then subjected to this heat treatment and further characterized. Many of the improvements offered by furnace cooling that were obvious in the T1 'as-sintered' product, became less pronounced after heat treatment. Corrosion resistance was also studied and compared to the wrought 7075 equivalent. For 'as-sintered' P/M components the Tafel extrapolation was less effective in accurately determining corrosion rate due to the effect of porosity on surface area. To remedy this, samples were hot worked to near full density (>99.5% theoretical), heat treated and tested. The hot worked P/M samples performed up to 2x better than the wrought 7075 with respect to corrosion current densities.

Process Developed for Generating Ceramic Interconnects With Low Sintering Temperatures for Solid Oxide Fuel Cells

NASA Technical Reports Server (NTRS)

Zhong, Zhi-Min; Goldsby, Jon C.

2005-01-01

Solid oxide fuel cells (SOFCs) have been considered as premium future power generation devices because they have demonstrated high energy-conversion efficiency, high power density, and extremely low pollution, and have the flexibility of using hydrocarbon fuel. The Solid-State Energy Conversion Alliance (SECA) initiative, supported by the U.S. Department of Energy and private industries, is leading the development and commercialization of SOFCs for low-cost stationary and automotive markets. The targeted power density for the initiative is rather low, so that the SECA SOFC can be operated at a relatively low temperature (approx. 700 C) and inexpensive metallic interconnects can be utilized in the SOFC stack. As only NASA can, the agency is investigating SOFCs for aerospace applications. Considerable high power density is required for the applications. As a result, the NASA SOFC will be operated at a high temperature (approx. 900 C) and ceramic interconnects will be employed. Lanthanum chromite-based materials have emerged as a leading candidate for the ceramic interconnects. The interconnects are expected to co-sinter with zirconia electrolyte to mitigate the interface electric resistance and to simplify the processing procedure. Lanthanum chromites made by the traditional method are sintered at 1500 C or above. They react with zirconia electrolytes (which typically sinter between 1300 and 1400 C) at the sintering temperature of lanthanum chromites. It has been envisioned that lanthanum chromites with lower sintering temperatures can be co-fired with zirconia electrolyte. Nonstoichiometric lanthanum chromites can be sintered at lower temperatures, but they are unstable and react with zirconia electrolyte during co-sintering. NASA Glenn Research Center s Ceramics Branch investigated a glycine nitrate process to generate fine powder of the lanthanum-chromite-based materials. By simultaneously doping calcium on the lanthanum site, and cobalt and aluminum on the chromium site, we could sinter the materials below 1400 C. The doping concentrations were adjusted so that the thermal expansion coefficient matched that of the zirconia electrolyte. Also, the investigation was focused on stoichiometric compositions so that the materials would have better stability. Co-sintering and chemical compatibility with zirconia electrolyte were examined by X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy (line scanning and dot map). The results showed that the materials bond well, but do not react, with zirconia electrolyte. The electric conductivity of the materials measured at 900 C in air was about 20 S/cm.

Synthesis of Nano-Scale Fast Ion Conducting Cubic Li7La3Zr2O12

DTIC Science & Technology

2013-09-25

offer the flexibility to make nano-dimensional particles with high sinterability nor the ability to coat/protect electrode powders. By developing a...sintering temperature are needed. One possible approach is to use small particles , such as nano-scale particles , that can be sintered at lower temperatures...matrix to suppress Li dendrite penetration. By developing a sol–gel process, the LLZO particle size can be precisely tuned, from the nanometer to the

Effects of flux concentrations and sintering temperature on dental porcelain

NASA Astrophysics Data System (ADS)

Ghose, Polash; Gafur, Md. Abdul; Das, Sujan Kumar; Ranjan Chakraborty, Shyamal; Mohsin, Md.; Deb, Arun Kumar; Rakibul Qadir, Md.

2014-02-01

In this study, samples of dental porcelain bodies have been made by using the materials collected from selected deposits employing different mixing proportions of clay, quartz and feldspar. Dental porcelain ceramics have been successfully fabricated by using the sintering technique together with some Na2CO3 additive. The dental porcelain powder has been pressed into pellets at first and subsequently sintered at 700, 800, 900, 1000 and 1100 °C for 2 h. The physical and mechanical properties of the prepared samples have been investigated. The sintering behavior of the fired samples has been evaluated by bulk density, linear shrinkage, water absorption and apparent porosity measurements. This study includes the evaluation of the Vickers's microhardness by microhardness tester. Phase analysis and microstructural study have been performed by XRD and optical microscope respectively. Optical properties have been investigated using UV-visible spectroscopy. Influence of firing conditions on leucite formation, densification and microstructural development of the sintered samples has been investigated. It has been found that the choice of sintering temperature is one of the key factors in controlling leucite crystallization in dental porcelain ceramics. It has also been found that the flux concentration of material and the effect of temperature on preparation of dental porcelain contribute to the firing shrinkage and hardness, which has been found to increase with the increase of treatment temperature.

Study of sintering behavior of vapor forms of 1-octanethiol coated copper nanoparticles for application to ink-jet printing technology.

PubMed

Kwon, Jinhyeong; Park, Shinyoung; Haque, Md Mominul; Kim, Young-Seok; Lee, Caroline Sunyong

2012-04-01

Sub-50 nm copper nanoparticles coated with sub-5 nm 1-octanethiol layer for oxidation inhibition were examined to confirm the 1-octanethiol removal temperature as the sub-50 nm copper nanoparticles are sintered. As a result, 1-octanethiol Self-Assembled Multi-layers (SAMs) on sub-50 nm copper nanoparticles were successfully removed before sintering of copper nanoparticles so that a high density of copper line could be obtained. Finally, the line resistivity was measured and compared to verify the effect of sintering in different atmospheres. As a result, electrical resistivity of the copper pattern sintered in hydrogen atmosphere was measured at 6.96 x 10(-6) ohm-cm whereas that of the copper pattern sintered in mixed gas atmosphere was measured at 2.62 x 10(-5) ohm-cm. Thus, sintering of copper patterns was successfully done to show low electrical resistivity values. Moreover, removal of 1-octanethiol coating after sintering process was confirmed using X-ray photoelectron spectroscopy (XPS) analysis. By showing no sulfur content, XPS results indicate that 1-octanethiol is completely removed. Therefore, the vapor form of 1-octanethiol coating layers can be safely used as an oxidation inhibition layer for low temperature sintering processes and ink-jet applications.

Flash (Ultra-Rapid) Spark-Plasma Sintering of Silicon Carbide

PubMed Central

Olevsky, Eugene A.; Rolfing, Stephen M.; Maximenko, Andrey L.

2016-01-01

A new ultra-rapid process of flash spark plasma sintering is developed. The idea of flash spark plasma sintering (or flash hot pressing - FHP) stems from the conducted theoretical analysis of the role of thermal runaway phenomena for material processing by flash sintering. The major purpose of the present study is to theoretically analyze the thermal runaway nature of flash sintering and to experimentally address the challenge of uncontrollable thermal conditions by the stabilization of the flash sintering process through the application of the external pressure. The effectiveness of the developed FHP technique is demonstrated by the few seconds–long consolidation of SiC powder in an industrial spark plasma sintering device. Specially designed sacrificial dies heat the pre-compacted SiC powder specimens to a critical temperature before applying any voltage to the powder volume and allowing the electrode-punches of the SPS device setup to contact the specimens and pass electric current through them under elevated temperatures. The experimental results demonstrate that flash sintering phenomena can be realized using conventional SPS devices. The usage of hybrid heating SPS devices is pointed out as the mainstream direction for the future studies and utilization of the new flash hot pressing (ultra-rapid spark plasma sintering) technique. PMID:27624641

Flash (Ultra-Rapid) Spark-Plasma Sintering of Silicon Carbide

DOE PAGES

Olevsky, Eugene A.; Rolfing, Stephen M.; Maximenko, Andrey L.

2016-09-14

A new ultra-rapid process of flash spark plasma sintering is developed. The idea of flash spark plasma sintering (or flash hot pressing - FHP) stems from the conducted theoretical analysis of the role of thermal runaway phenomena for material processing by flash sintering. The major purpose of the present study is to theoretically analyze the thermal runaway nature of flash sintering and to experimentally address the challenge of uncontrollable thermal conditions by the stabilization of the flash sintering process through the application of the external pressure. The effectiveness of the developed FHP technique is demonstrated by the few seconds–long consolidationmore » of SiC powder in an industrial spark plasma sintering device. Specially designed sacrificial dies heat the pre-compacted SiC powder specimens to a critical temperature before applying any voltage to the powder volume and allowing the electrode-punches of the SPS device setup to contact the specimens and pass electric current through them under elevated temperatures. The experimental results demonstrate that flash sintering phenomena can be realized using conventional SPS devices. The usage of hybrid heating SPS devices is pointed out as the mainstream direction for the future studies and utilization of the new flash hot pressing (ultra-rapid spark plasma sintering) technique.« less

SEM and TEM characterization of microstructure of stainless steel composites reinforced with TiB{sub 2}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sulima, Iwona, E-mail: isulima@up.krakow.pl

Steel-8TiB{sub 2} composites were produced by two new sintering techniques, i.e. Spark Plasma Sintering (SPS) and High Pressure-High Temperature (HP-HT) sintering. This study discusses the impact of these sintering methods on the microstructure of steel composites reinforced with TiB{sub 2} particles. Scanning electron microscopy (SEM), wavelength dispersive spectroscopy (WDS), X-ray diffraction, electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) were used to analyze the microstructure evolution in steel matrix composites. The results of microscopic examinations revealed a close relationship between the composite microstructure and the methods and conditions of sintering. Substantial differences were observed in the grain size ofmore » materials sintered by HP-HT and SPS. It has been demonstrated that the composites sintered by HP-HT tend to form a chromium-iron-nickel phase in the steel matrix. In contrast, the microstructure of the composites sintered by SPS is characterized by the presence of complex borides and chromium-iron phase. - Highlights: •The steel-8TiB{sub 2} composites were fabricated by Spark Plasma Sintering (SPS) and High Pressure-High Temperature (HP-HT). •Sintering techniques has an important effect on changes in the microstructure of steel-8TiB{sub 2} composites. •New phases of different size and morphology were identified.« less

Sintering of Lead-Free Piezoelectric Sodium Potassium Niobate Ceramics

PubMed Central

Malič, Barbara; Koruza, Jurij; Hreščak, Jitka; Bernard, Janez; Wang, Ke; Fisher, John G.; Benčan, Andreja

2015-01-01

The potassium sodium niobate, K0.5Na0.5NbO3, solid solution (KNN) is considered as one of the most promising, environment-friendly, lead-free candidates to replace highly efficient, lead-based piezoelectrics. Since the first reports of KNN, it has been recognized that obtaining phase-pure materials with a high density and a uniform, fine-grained microstructure is a major challenge. For this reason the present paper reviews the different methods for consolidating KNN ceramics. The difficulties involved in the solid-state synthesis of KNN powder, i.e., obtaining phase purity, the stoichiometry of the perovskite phase, and the chemical homogeneity, are discussed. The solid-state sintering of stoichiometric KNN is characterized by poor densification and an extremely narrow sintering-temperature range, which is close to the solidus temperature. A study of the initial sintering stage revealed that coarsening of the microstructure without densification contributes to a reduction of the driving force for sintering. The influences of the (K + Na)/Nb molar ratio, the presence of a liquid phase, chemical modifications (doping, complex solid solutions) and different atmospheres (i.e., defect chemistry) on the sintering are discussed. Special sintering techniques, such as pressure-assisted sintering and spark-plasma sintering, can be effective methods for enhancing the density of KNN ceramics. The sintering behavior of KNN is compared to that of a representative piezoelectric lead zirconate titanate (PZT). PMID:28793702

Sintering Behavior of Spark Plasma Sintered SiC with Si-SiC Composite Nanoparticles Prepared by Thermal DC Plasma Process.

PubMed

Yu, Yeon-Tae; Naik, Gautam Kumar; Lim, Young-Bin; Yoon, Jeong-Mo

2017-11-25

The Si-coated SiC (Si-SiC) composite nanoparticle was prepared by non-transferred arc thermal plasma processing of solid-state synthesized SiC powder and was used as a sintering additive for SiC ceramic formation. Sintered SiC pellet was prepared by spark plasma sintering (SPS) process, and the effect of nano-sized Si-SiC composite particles on the sintering behavior of micron-sized SiC powder was investigated. The mixing ratio of Si-SiC composite nanoparticle to micron-sized SiC was optimized to 10 wt%. Vicker's hardness and relative density was increased with increasing sintering temperature and holding time. The relative density and Vicker's hardness was further increased by reaction bonding using additional activated carbon to the mixture of micron-sized SiC and nano-sized Si-SiC. The maximum relative density (97.1%) and Vicker's hardness (31.4 GPa) were recorded at 1800 °C sintering temperature for 1 min holding time, when 0.2 wt% additional activated carbon was added to the mixture of SiC/Si-SiC.

Optimization of the sintering atmosphere for high-density hydroxyapatite–carbon nanotube composites

PubMed Central

White, Ashley A.; Kinloch, Ian A.; Windle, Alan H.; Best, Serena M.

2010-01-01

Hydroxyapatite–carbon nanotube (HA–CNT) composites have the potential for improved mechanical properties over HA for use in bone graft applications. Finding an appropriate sintering atmosphere for this composite presents a dilemma, as HA requires water in the sintering atmosphere to remain phase pure and well hydroxylated, yet CNTs oxidize at the high temperatures required for sintering. The purpose of this study was to optimize the atmosphere for sintering these composites. While the reaction between carbon and water to form carbon monoxide and hydrogen at high temperatures (known as the ‘water–gas reaction’) would seem to present a problem for sintering these composites, Le Chatelier's principle suggests this reaction can be suppressed by increasing the concentration of carbon monoxide and hydrogen relative to the concentration of carbon and water, so as to retain the CNTs and keep the HA's structure intact. Eight sintering atmospheres were investigated, including standard atmospheres (such as air and wet Ar), as well as atmospheres based on the water–gas reaction. It was found that sintering in an atmosphere of carbon monoxide and hydrogen, with a small amount of water added, resulted in an optimal combination of phase purity, hydroxylation, CNT retention and density. PMID:20573629

Temperature dependences of the electromechanical and electrocaloric properties of Ba(Zr,Ti)O3 and (Ba,Sr)TiO3 ceramics

NASA Astrophysics Data System (ADS)

Maiwa, Hiroshi

2017-10-01

The electrocaloric properties of Ba(Zr,Ti)O3 and (Ba,Sr)TiO3 ceramics (BZT and BST, respectively) were investigated by the indirect estimation and direct measurement of temperature-electric field (T-E) hysteresis loops. The measured T-E loops had shapes similar to those of the strain-electric field (s-E) loops. The measured temperature changes (ΔTs) at around 30 °C of the BZT ceramics sintered at 1450 °C and BST ceramics sintered at 1600 °C upon the release of the electric field from 30 kV/cm to 0 were 0.34 and 0.57 K, respectively. The temperature dependences of the electromechanical and electrocaloric properties were investigated. The BZT ceramics sintered at 1450 °C exhibited the largest electromechanical and electrocaloric properties at around 30 °C, which corresponds to the phase transition temperature. BST is more temperature dependent than BZT. BST ceramics sintered at 1600 °C exhibited the largest electromechanical and electrocaloric properties at around 29 °C, which is about 10 °C higher than the phase transition temperature.

Effects of sintering process on wear and mechanical behavior properties of titanium carbide/hexagonal boron nitrid/steel 316L base nanocomposites

NASA Astrophysics Data System (ADS)

Sadooghi, Ali; Payganeh, Gholamhassan

2018-02-01

Powder metallurgy process is one of the approaches to manufacture nanocomposite samples, in which the product quality depends upon the pressure, temperature, and sintering time. In this manuscript, steel is selected as the base material together with 2% carbon-based reinforcing TiC particles, and 2% hBN particles as the self-lubricant material. The powders were mixed for 5 h in high ball milling, and compacted with two pressures of 350 and 450 MPa, sintered in the furnace for 2 and 4 h, and sintering temperatures of 1350 and 1450 °C were utilized. SEM, XRD, and EDX tests are performed to identify the nanocomposite structure, and DTA tests are carried out to specify the temperature graph of the material. Finally, hardness, wear, and bending tests are done to find the corresponding mechanical properties of the samples. As a result, the optimum process parameters, including pressure, temperature and sintering duration is achieved. Results show that adding the reinforcing particles into a steel matrix increase the hardness, as well as flexural strength of the nanocomposite product. Also, coefficient of friction shows a decreases.

Thermoelectric properties of Ca0.8Dy0.2MnO3 synthesized by solution combustion process

NASA Astrophysics Data System (ADS)

Park, Kyeongsoon; Lee, Ga Won

2011-10-01

High-quality Ca0.8Dy0.2MnO3 nano-powders were synthesized by the solution combustion process. The size of the synthesized Ca0.8Dy0.2MnO3 powders was approximately 23 nm. The green pellets were sintered at 1150-1300°C at a step size of 50°C. Sintered Ca0.8Dy0.2MnO3 bodies crystallized in the perovskite structure with an orthorhombic symmetry. The sintering temperature did not affect the Seebeck coefficient, but significantly affected the electrical conductivity. The electrical conductivity of Ca0.8Dy0.2MnO3 increased with increasing temperature, indicating a semiconducting behavior. The absolute value of the Seebeck coefficient gradually increased with an increase in temperature. The highest power factor (3.7 × 10-5 Wm-1 K-2 at 800°C) was obtained for Ca0.8Dy0.2MnO3 sintered at 1,250°C. In this study, we investigated the microstructure and thermoelectric properties of Ca0.8Dy0.2MnO3, depending on sintering temperature.

Thermoelectric properties of Ca0.8Dy0.2MnO3 synthesized by solution combustion process

PubMed Central

2011-01-01

High-quality Ca0.8Dy0.2MnO3 nano-powders were synthesized by the solution combustion process. The size of the synthesized Ca0.8Dy0.2MnO3 powders was approximately 23 nm. The green pellets were sintered at 1150-1300°C at a step size of 50°C. Sintered Ca0.8Dy0.2MnO3 bodies crystallized in the perovskite structure with an orthorhombic symmetry. The sintering temperature did not affect the Seebeck coefficient, but significantly affected the electrical conductivity. The electrical conductivity of Ca0.8Dy0.2MnO3 increased with increasing temperature, indicating a semiconducting behavior. The absolute value of the Seebeck coefficient gradually increased with an increase in temperature. The highest power factor (3.7 × 10-5 Wm-1 K-2 at 800°C) was obtained for Ca0.8Dy0.2MnO3 sintered at 1,250°C. In this study, we investigated the microstructure and thermoelectric properties of Ca0.8Dy0.2MnO3, depending on sintering temperature. PMID:21974984

Thermoelectric properties of Ca0.8Dy0.2MnO3 synthesized by solution combustion process.

PubMed

Park, Kyeongsoon; Lee, Ga Won

2011-10-05

High-quality Ca0.8Dy0.2MnO3 nano-powders were synthesized by the solution combustion process. The size of the synthesized Ca0.8Dy0.2MnO3 powders was approximately 23 nm. The green pellets were sintered at 1150-1300°C at a step size of 50°C. Sintered Ca0.8Dy0.2MnO3 bodies crystallized in the perovskite structure with an orthorhombic symmetry. The sintering temperature did not affect the Seebeck coefficient, but significantly affected the electrical conductivity. The electrical conductivity of Ca0.8Dy0.2MnO3 increased with increasing temperature, indicating a semiconducting behavior. The absolute value of the Seebeck coefficient gradually increased with an increase in temperature. The highest power factor (3.7 × 10-5 Wm-1 K-2 at 800°C) was obtained for Ca0.8Dy0.2MnO3 sintered at 1,250°C. In this study, we investigated the microstructure and thermoelectric properties of Ca0.8Dy0.2MnO3, depending on sintering temperature.

Monolithic Pellets, Composites and Thick Films of Hydroxyapatite: Correlation of Mechanical Properties with Microstructure.

NASA Astrophysics Data System (ADS)

Wang, Pauchiu Either

Hydroxyapatite Ca_{10}(PO _4)_6(OH)_2 (abbreviated as HA) has great biocompatibility. Poor mechanical properties of HA implants and decomposition of HA during processing are the major obstacles for widespread uses of HA. In the present thesis we have attempted to understand the sintering behavior of monolithic HA and metal-reinforced HA-matrix composites, and the mechanism of formation of HA coating in the solutions at the normal temperature. The powders of two calcium phosphates, namely hydroxyapatite and dicalcium phosphate (DCP: chemical formula Ca_2P_2O_7), were sintered at various temperatures and in various environments. The density, flexural strength and knoop hardness of both phosphates sintered in air for 4 h initially increased with the sintering temperature, reaching maxima at around 1000-1150 ^circC, and then decreased due to decomposition. To reduce dehydroxylation, HA powder was sintered in moisture at various temperatures up to 1350^circ C and X-ray diffraction study did not indicate any decomposition at the highest sintering temperature. It is seen that dehydroxylation did not hinder sintering, but decomposition obstructed sintering of both HA and DCP. Ductile-phase reinforcement of hydroxyapatite was achieved by addition of silver particulates (5-30 vol.%) in HA powder compacts. A composite made by sintering 10 vol.% Ag and balance HA at 1200^circ C for 1 h in air had flexural strength of 75 +/- 7 MPa, which was almost double that of pure HA sintered under an identical condition. Silver in the composite melted during sintering, but due to poor wetting, did not spread in between HA particles. The increase in the flexural strength of the composites was thought to be due to crack-bridging and crack-arrest by silver inclusions. Thick films (several μm) of hydroxyapatite were deposited on silicon single crystal placed in close proximity to a plate of apatite- and wollastonite -containing glass and dipped into a simulated body fluid (SBF) at 36^circC. Amorphous calcium phosphate phase present in the glass leached into the SBF, causing supersaturation of Ca^ {2+} and (PO_4)^ {3-} ions. HA films grown on Si(111) showed strong (102) texture. As a contrast hardly any HA film could be grown on Si(100) surface. Our results suggest that the driving force for formation of apatite films arises from lowering of free energy of the supersatured solution by deposition of ions in certain crystallographic arrangements on suitable substrates with low interface energies.

Preparation of high-permeability NiCuZn ferrite.

PubMed

Hu, Jun; Yan, Mi

2005-06-01

Appropriate addition of CuO/V2O5 and the reduction of the granularity of the raw materials particle decrease the sintering temperature of NiZn ferrite from 1200 degrees C to 930 degrees C. Furthermore, the magnetic properties of the NiZn ferrite prepared at low temperature of 930 degrees C is superior to that of the NiZn ferrite prepared by sintering at high temperature of 1200 degrees C because the microstructure of the NiZn ferrite sintered at 930 degrees C is more uniform and compact than that of the NiZn ferrite sintered at 1200 degrees C. The high permeability of 1700 and relative loss coefficient tandelta/mu(i) of 9.0x10(-6) at 100 kHz was achieved in the (Ni0.17Zn0.63Cu0.20)Fe1.915O4 ferrite.

Research On Bi-Based High-Temperature Superconductors

NASA Technical Reports Server (NTRS)

Banks, Curtis; Doane, George B., III; Golben, John

1993-01-01

Brief report describes effects of melt sintering on Bi-based high-temperature superconductor system, as well as use of vibrating-sample magnetometer to determine hysteresis curves at 77 K for partially melt-sintered samples. Also discussed is production of high-temperature superconducting thin films by laser ablation: such films potentially useful in detection of signals of very low power.

Microwave sintering of sol-gel derived abrasive grain

DOEpatents

Plovnick, Ross; Celikkaya, Ahmet; Blake, Rodger D.

1997-01-01

A method is provided for making microwave-sintered, free flowing alpha alumina-based ceramic abrasive grain, under conditions effective to couple microwaves with calcined alpha alumina-based abrasive gain precursor and sinter it at a temperature of at least about 1150.degree. C.

Mechanism research on arsenic removal from arsenopyrite ore during a sintering process

NASA Astrophysics Data System (ADS)

Cheng, Ri-jin; Ni, Hong-wei; Zhang, Hua; Zhang, Xiao-kun; Bai, Si-cheng

2017-04-01

The mechanism of arsenic removal during a sintering process was investigated through experiments with a sintering pot and arsenic-bearing iron ore containing arsenopyrite; the corresponding chemical properties of the sinter were determined by inductively coupled plasma atomic emission spectrometry (ICP-AES), X-ray diffraction (XRD), and scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDS). The experimental results revealed that the reaction of arsenic removal is mainly related to the oxygen atmosphere and temperature. During the sintering process, arsenic could be removed in the ignition layer, the sinter layer, and the combustion zone. A portion of FeAsS reacted with excess oxygen to generate FeAsO4, and the rest of the FeAsS reacted with oxygen to generate As2O3(g) and SO2(g). A portion of As2O3(g) mixed with Al2O3 or CaO, which resulted in the formation of arsenates such as AlAsO4 and Ca3(AsO4)2, leading to arsenic residues in sintering products. The FeAsS component in the blending ore was difficult to decompose in the preliminary heating zone, the dry zone, or the bottom layer because of the relatively low temperatures; however, As2O3(g) that originated from the high-temperature zone could react with metal oxides, resulting in the formation of arsenate residues.

Effect of boron addition on injection molded 316L stainless steel: mechanical, corrosion properties and in vitro bioactivity.

PubMed

Bayraktaroglu, Esra; Gulsoy, H Ozkan; Gulsoy, Nagihan; Er, Ozay; Kilic, Hasan

2012-01-01

The research was investigated the effect of boron additions on sintering characteristics, mechanical, corrosion properties and biocompatibility of injection molded austenitic grade 316L stainless steel. Addition of boron is promoted to get high density of sintered 316L stainless steels. The amount of boron plays a role in determining the sintered microstructure and all properties. In this study, 316L stainless steel powders have been used with the elemental NiB powders. A feedstock containing 62.5 wt% powders loading was molded at different injection molded temperature. The binders were completely removed from molded components by solvent and thermal debinding at different temperature. The debinded samples were sintered at different temperature for 60 min. Mechanical property, microstructural characterization and electrochemical property of the sintered samples were performed using tensile testing, hardness, optical, scanning electron microscopy and electrochemical corrosion experiments. Sintered samples were immersed in a simulated body fluid (SBF) with elemental concentrations that were comparable to those of human blood plasma for a total period of 15 days. Both materials were implanted in fibroblast culture for biocompatibility evaluations were carried out. Results of study showed that sintered 316L and 316L with NiB addition samples exhibited high mechanical and corrosion properties in a physiological environment. Especially, 316L with NiB addition can be used in some bioapplications.

Low temperature sintering of fluorapatite glass-ceramics.

PubMed

Denry, Isabelle; Holloway, Julie A

2014-02-01

Fluorapatite glass-ceramics have been shown to be excellent candidates as scaffold materials for bone grafts, however, scaffold production by sintering is hindered by concurrent crystallization of the glass. Objective, our goal was to investigate the effect of Ca/Al ratio on the sintering behavior of Nb-doped fluorapatite-based glasses in the SiO2-Al2O3-P2O5-MgO-Na2O-K2O-CaO-CaF2 system. Methods, glass compositions with Ca/Al ratio of 1 (A), 2 (B), 4 (C) and 19 (D) were prepared by twice melting at 1525°C for 3h. Glasses were either cast as cylindrical ingots or ground into powders. Disk-shaped specimens were prepared by either sectioning from the ingots or powder-compacting in a mold, followed by heat treatment at temperatures ranging between 700 and 1050°C for 1h. The density was measured on both sintered specimens and heat treated discs as controls. The degree of sintering was determined from these measurements. Results and Significance XRD showed that fluorapatite crystallized in all glass-ceramics. A high degree of sintering was achieved at 775°C for glass-ceramic D (98.99±0.04%), and 900°C for glass-ceramic C (91.31±0.10). Glass-ceramics A or B were only partially sintered at 1000°C (63.6±0.8% and 74.1±1.5%, respectively). SEM revealed a unique microstructure of micron-sized spherulitic fluorapatite crystals in glass-ceramics C and D. Increasing the Ca/Al ratio promoted low temperature sintering of fluorapatite glass-ceramics, which are traditionally difficult to sinter. Copyright © 2013 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Sintering polycrystalline olivine and polycrystalline clinopyroxene containing trace amount of graphite from natural crystals

NASA Astrophysics Data System (ADS)

Tsubokawa, Yumiko; Ishikawa, Masahiro

2017-09-01

Graphite-bearing polycrystalline olivine and polycrystalline clinopyroxene with submicron to micron grain size were successfully sintered from a single crystal of naturally occurring olivine (Fo88-92Fa12-8: Mg1.76-1.84Fe0.16-0.24SiO4) and a single crystal of naturally occurring clinopyroxene (Di99Hed1: Ca0.92Na0.07Mn0.01Mg0.93Fe0.01Al0.06Si2O6). The milled powders of both these crystals were sintered under argon gas flow at temperatures ranging from 1130 to 1350 °C for 2 h. As the sintering temperature increased, the average grain size of olivine increased from 0.2 to 1.4 µm and that of clinopyroxene increased from 0.1 to 2.4 µm. The porosity of sintered samples remained at an almost-constant volume of 2-5% for olivine and 3-4% for clinopyroxene. The samples sintered from powders milled with ethanol exhibited trace amount of graphite, identified via Raman spectroscopy analysis. As the sintering temperature increased, the intensity of the graphite Raman peak decreased, compared with both olivine and clinopyroxene peaks. The carbon content of the sintered samples was estimated to be a few hundred ppm. The in-plane size ( L a ) of graphite in the sintered olivine was estimated to be <15 nm. Our experiments demonstrate new possibilities for preparing graphite-bearing silicate-mantle mineral rocks, and this method might be useful in understanding the influence of the physical properties of graphite on grain-size-sensitive rheology or the seismic velocity of the Earth's mantle.[Figure not available: see fulltext.

Low temperature sintering of fluorapatite glass-ceramics

PubMed Central

Denry, Isabelle; Holloway, Julie A.

2014-01-01

Fluorapatite glass-ceramics have been shown to be excellent candidates as scaffold materials for bone grafts, however, scaffold production by sintering is hindered by concurrent crystallization of the glass. Our goal was to investigate the effect of Ca/Al ratio on the sintering behavior of Nb-doped fluorapatite-based glasses in the SiO2-Al2O3-P2O5-MgO-Na2O-K2O-CaO-CaF2 system. Glass compositions with Ca/Al ratio of 1 (A), 2 (B), 4 (C) and 19 (D) were prepared by twice melting at 1525°C for 3h. Glasses were either cast as cylindrical ingots or ground into powders. Disc-shaped specimens were prepared by either sectioning from the ingots or powder-compacting in a mold, followed by heat treatment at temperatures ranging between 700 and 1050°C for 1h. The density was measured on both sintered specimens and heat treated discs as controls. The degree of sintering was determined from these measurements. XRD showed that fluorapatite crystallized in all glass-ceramics. A high degree of sintering was achieved at 775°C for glass-ceramic D (98.99±0.04%), and 900°C for glass-ceramic C (91.31±0.10). Glass-ceramics A or B were only partially sintered at 1000°C (63.6±0.8% and 74.1±1.5%, respectively). SEM revealed a unique microstructure of micron-sized spherulitic fluorapatite crystals in glass-ceramics C and D. Increasing the Ca/Al ratio promoted low temperature sintering of fluorapatite glass-ceramics, which are traditionally difficult to sinter. PMID:24252652

Sintering in Ceramics and Solid Oxide Fuel Cells

NASA Astrophysics Data System (ADS)

Hunt, Clay Dale

Nature's propensity to minimize energy, and the change in energy with respect to position, drives diffusion. Diffusion is a means by which mass transport resulting in the bonding of the particles of a powder compact can be achieved without melting. This phenomenon occurs in powdered materials near their melting temperature, and is referred to as "sintering". Because of the extreme melting temperature of some materials, sintering might be the only practical means of processing. The complexity and subtlety of sintering ceramics motivated the evaluation of empirical data and existing sintering models. This project examined polycrystalline cubic-zirconia sintering with and without transition-metal oxide additions that change sintering behavior. This study was undertaken to determine how sintering aids affect the driving force, and activation energy, the energy barrier that must be overcome in order for an atom or ion to diffuse, of the densification occurring during sintering. Examination of commercially-available cubic-zirconia powder sintering behavior was undertaken with dilatometry, which allows monitoring of the length change a material undergoes as it sinters, and with scanning electron microscopy, which facilitates the study of sintered-sample microstructure. MATLAB algorithms quantifying sintering results were developed. Results from this work include proposed definitions of a 26-year-old undefined function of density factor in a well-accepted mathematical model of sintering. These findings suggest activation energy is not changing with density, as is suggested by recent published results. The first numerical integration of the studied sintering model has been performed. With these tools, a measure of the activation energy of densification of cubic-zirconia with and without the addition of cobalt-oxide as a sintering aid has been performed. The resulting MATLAB algorithms can be used in future sintering studies. It is concluded that sintering enhancement achieved with cobalt-oxide addition comes from reduction in activation energy of densification of cubic-zirconia. Further, it is suggested that the activation energy of densification does not change with material density. This conclusion is supported by the sensitivity of the numerical integration of the aforementioned sintering model to changes in activation energy.

Effect of Starch on Sintering Behavior for Fabricating Porous Cordierite Ceramic

NASA Astrophysics Data System (ADS)

Li, Ye; Cao, Wei; Gong, Lunlun; Zhang, Ruifang; Cheng, Xudong

2016-10-01

Porous cordierite ceramics were prepared with starch as pore-forming agent by solid-state method. The green bodies were sintered at 1,100-1,400 °C for 2 h. The characterization was focused on thermal analysis, phase evolution, sintering behavior, porosity and micro-structural changes. The results show that cordierite becomes the main crystallization phase at 1,200 °C. The shrinkage behavior shows the most obvious dependence on the sintering temperature and starch content, and it can be divided into three stages. Moreover, the open porosity increases with the increase of starch content, but the pore-forming effectivity decreases. Nevertheless, compared with the open porosity curves, the bulk density curves are more in line with the linear rule. The microphotographs show the densification process with the sintering temperature and the variation of pore connectivity with the starch content.

The impact of sintering temperature on structural, morphological and thermoelectric properties of zinc titanate nanocrystals

NASA Astrophysics Data System (ADS)

Chandrasekaran, P.; Murugu thiruvalluvan, T. M. V.; Arivanandhan, M.; Jayakumari, T.; Anandan, P.

2017-07-01

The effect of sintering temperature and Ti:Zn ratio of precursor solutions on the structural, morphological and thermoelectric properties of Zinc titanate (TZO) nanocrystals have been investigated. TZO nanocrystals were synthesized by changing the molar ratio of precursors of Zn and Ti sources by sol-gel method. The synthesized materials were sintered at different temperatures and the formation of multi phases of TZO were analysed by x-ray diffraction studies. The morphological properties and composition of TZO samples were studied by FESEM, TEM and XPS analysis. The thermoelectric properties of the TZO have been studied by measuring the Seebeck coefficient of the materials at various temperature. It was observed that the Seebeck coefficient of TZO sample increases with increasing Zn content in the sample especially at high temperature.

Microstructure and microwave magnetic properties of Low-Firing Li0.42Zn0.27Ti0.11Mn0.1Fe2.1O4 ferrite

NASA Astrophysics Data System (ADS)

Xie, Fei; Jia, Lijun; Shen, Qihang; Qiu, Hua; Zhang, Huaiwu

2018-03-01

Low firing temperature and excellent gyromagnetic properties such as high remanence square ratio and narrow ferromagnetic resonance line width are required for the application in nonreciprocal microwave ferrite devices based on low temperature cofired ceramics (LTCC) technology. In this research, Bi2O3-Li2CO3 mixture was introduced as the sintering agent to lower the sintering temperature of Li0.42Zn0.27Ti0.11Mn0.1Fe2.1O4 ferrite. The influence of Bi2O3-Li2CO3 mixture upon the phase composition, composite microstructures and gyromagnetic properties of LiZnTiMn ferrite sintered at low temperature has been investigated for LTCC integration applications. With a proper amount of Bi2O3-Li2CO3 mixture, the sintering temperature of LiZnTiMn ferrite successfully reduced to below 900°C from 1100°C without degradation of magnetic properties, meanwhile, both of saturation flux density and remanence square ratio were increased.

Thermoelectric Coolers with Sintered Silver Interconnects

NASA Astrophysics Data System (ADS)

Kähler, Julian; Stranz, Andrej; Waag, Andreas; Peiner, Erwin

2014-06-01

The fabrication and performance of a sintered Peltier cooler (SPC) based on bismuth telluride with sintered silver interconnects are described. Miniature SPC modules with a footprint of 20 mm2 were assembled using pick-and-place pressure-assisted silver sintering at low pressure (5.5 N/mm2) and moderate temperature (250°C to 270°C). A modified flip-chip bonder combined with screen/stencil printing for paste transfer was used for the pick-and-place process, enabling high positioning accuracy, easy handling of the tiny bismuth telluride pellets, and immediate visual process control. A specific contact resistance of (1.4 ± 0.1) × 10-5 Ω cm2 was found, which is in the range of values reported for high-temperature solder interconnects of bismuth telluride pellets. The realized SPCs were evaluated from room temperature to 300°C, considerably outperforming the operating temperature range of standard commercial Peltier coolers. Temperature cycling capability was investigated from 100°C to 235°C over more than 200 h, i.e., 850 cycles, during which no degradation of module resistance or cooling performance occurred.

SINTERING AND SULFATION OF CALCIUM SILICATE-ALUMINATE

EPA Science Inventory

The effect of sintering on the reactivity of solids at high temperature was studied. The nature of the interaction was studied with calcium silicate-aluminate reacting with SO2 between 665 and 800 C. The kinetics of the sintering and sulfation processes were measured independentl...

Nano-Hydroxyapatite/Fluoridated and Unfluoridated Bioactive Glass Composites: Structural Analysis and Bioactivity Evaluation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Batra, Uma; Kapoor, Seema; Sharma, J. D.

2011-12-12

Biphasic bioceramic composites containing nano-hydroxyapatite (HAP) and nanosized bioactive glasses have been prepared in the form of pellets and have been examined for the effects of bioglass concentrations and sintering temperature on the structural transformations and bioactivity behavior. Pure stoichiometric nano-HAP was synthesized using sol-gel technique. Two bioglasses synthesized in this work--fluoridated bioglass (Cao-P{sub 2}O{sub 5}-Na{sub 2}O{sub 3}-CaF{sub 2}) and unfluoridated bioglass (Cao-P{sub 2}O{sub 5}-Na{sub 2}O{sub 3}) designated as FBG and UFBG respectively, were added to nano-HAP with concentrations of 5, 10, 12 and 15%. The average particle sizes of synthesized HAP and bioglasses were 23 nm and 35 nm,more » respectively. The pellets were sintered at four different temperatures i.e. 1000 deg. C, 1150 deg. C, 1250 deg. C and 1350 deg. C. The investigations involved study of structural and bioactivity behavior of green and sintered pellets and their deviations from original materials i.e. HAP, FBG and UFBG, using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The phase composition of the sintered pellets was found to be non-stoichiometric HAP with {alpha}-TCP (tricalcium phosphate) and {beta}-TCP. It was revealed from SEM images that bonding mechanism was mainly solid state sintering for all pellets sintered at 1000 deg. C and 1150 deg. C and also for pellets with lower concentrations of bioglass i.e. 5% and 10% sintered at 1250 deg. C. Partly liquid phase sintering was observed for pellets with higher bioglass concentrations of 12% and 15% sintered at 1250 deg. C and same behaviour was noted for pellets at all concentrations of bioglasses at 1350 deg. C. The sintered density, hardness and compression strength of pellets have been influenced both by the concentration of the bioglasses and sintering temperature. It was observed that the biological HAP layer formation was faster on the green pellets surface than on pure HAP and sintered pellets, showing higher bioactivity in the green pellets.« less

Corrosion Behavior of Magnesium Based Foam Structure in Hank’s Solution

NASA Astrophysics Data System (ADS)

Franciska, P. L.; Erryani, A.; Annur, D.; Kartika, I.

2017-05-01

Metal foam is a new class of materials with promising applications and a unique combination of physical, chemical, and mechanical properties. The purpose of biodegradable implants is to support tissue regeneration and healing in a particular application by material degradation and implant replacement through the surrounding tissue. Magnesium alloys are expected to be degraded in the body and its corrosion products not deleterious to the surrounding tissue. In the present study, the foam metal was manufactured via powder metallurgy with a different variation of sintering temperature and TiH2 used as a foaming agent which are added to Mg-1Ca-3Zn alloy as much 3% wt TiH2. The sintering temperatures were 500, 550 and 600 °C with a constant holding time of 5 hours. It’s critical that the sintering temperature is carefully selected in consideration of their corrosion behavior. This paper reports the study of the behavior of the Mg-Ca-Zn alloy metal foam which evaluated by SEM, EDX, and electrochemical corrosion test in Hank’s solutions. After exposure, the SEM result of Mg-Ca-Zn-3TiH2 to Hank’s solution, a volcano-like structure is formed. The streams of H2 bubbles form at local sites on the Mg alloy surface where electrochemical reactions are taking place, leading to the particular structure with around shape and often with a hole in the center. The corresponding EDS result maps reveal enrichment of O, Ca, P and Mg as corrosion product. Potentiodynamic polarization experiments conducted at 37 °C and pH 7.4 indicated the increased biodegradation rates resulted from porous structure of foam samples. Corrosion rate in 500oC sintering temperature were 1.99 millimiles per year (mmpy) with corrosion current density (I corr ) 87.3.10-6 A/cm2, corrosion rate in 550 °C sintering temperature were 2,16 mmpy with I corr 94.4.10-6 A/cm2 and rate in 600 °C sintering temperature were 2.41 mmpy with I corr 105.10-6 A/cm2. The results showed that the increasing of sintering temperature could influence the corrosion resistance of Mg alloy.

Computer simulation of low-temperature composites sintering processes for additive technologies

NASA Astrophysics Data System (ADS)

Tovpinets, A. O.; Leytsin, V. N.; Dmitrieva, M. A.

2017-12-01

This is impact research of mixture raw components characteristics on the low-temperature composites structure formation during the sintering process. The obtained results showed that the structure determination of initial compacts obtained after thermal destruction of the polymer binder lets quantify the concentrations of main components and the refractory crystalline product of thermal destruction. Accounting for the distribution of thermal destruction refractory product allows us to refine the forecast of thermal stresses in the matrix of sintered composite. The presented results can be considered as a basis for optimization of initial compositions of multilayer low-temperature composites obtained by additive technologies.

DC and AC conductivity properties of bovine dentine hydroxyapatite (BDHA)

NASA Astrophysics Data System (ADS)

Dumludag, F.; Gunduz, O.; Kılıc, O.; Ekren, N.; Kalkandelen, C.; Ozbek, B.; Oktar, F. N.

2017-12-01

Bovine dentine bio-waste may be used as a potential natural source of hydroxyapatite (BDHA), thus extraction of bovine dentin hydroxyapatite (BDHA) from bio-waste is significantly important to fabricate in a simple, economically and environmentally preferable. DC and AC conductivity properties of BDHA were investigated depending on sintering temperature (1000ºC - 1300°C) in air and vacuum (<10-2 mbar) ambient at room temperature. DC conductivity measurements performed between -1 and 1 V. AC conductivity measurements performed in the frequency range of 40 Hz - 100 kHz. DC conductivity results showed that dc conductivity values of the BDHA decrease with increasing sintering temperature in air ambient. It is not observed remarkable/systematic behavior for ac conductivity depending on sintering temperature.

[Studies on sintering of dental porcelain. (Part 1) Binary system sintering of alumina and low fusing frit (author's transl)].

PubMed

Kuwayama, N; Kon, M

1981-04-01

Dental porcelains were made from frit and glass powder with electro fused alumina powder addition in the range from 20 to 60 wt% using sintering method at the temperature from 500 degree C to 1 000 degree C, and the effects of alumina content and firing temperature on firing processes of sintered composite were investigated. Shrinkage curves of the powder compacts varied with kind of frit and content of alumina. Particulary, powder compact with alumina addition in the range from 50 to 55% was found to have a remarkable influence for extention of firing temperature range. The densification of the powder compacts was considered to be accelerated by the dissolution of a small a mount of alumina particle into the frit and glass above 900 degree C. Expansion coefficient value of sintered composite of alumina and Pyrex glass powder gradually increased with increase of alumina content. Inversely, expansion coefficient of soda-lime-silica glass showed the minimum value at 40 wt% alumina content and then had a tendency of slight increases with increase of alumina content.

[Preparing of Al2O3/ZrO2 composite dental ceramics through isostatic pressing technology].

PubMed

Liang, Xiao-Feng; Yin, Guang-Fu; Yang, Shi-Yuan; Wang, Jun-Xia

2006-08-01

To find out how to prepare high-density dental ceramics through isostatic pressing so that sintering shrinkage will be reduced. To prepare Al2O3/ZrO2 composite powder first, then to mold through dry-pressing, and to shape the green-body through isostatic pressing. The green-bodies were sintered at the temperature of 1 400 degrees C and kept at the temperature for different period of time (2 h, 3 h, 4 h). After that, the density and fracture strength were measured and the microstructure observed by scanning electron microscope (SEM). The sample product's density, line-shrinkage, and fracture strength of ceramics was rising with the sintering time lengthened. The sample product kept under the temperature of 1 400 degrees C for 4 hours, the fracture strength was (497.27 +/- 78.45) MPa and glass phase distributed evenly in the ceramics and the grains were integrated owing to the glass phase. The longer the sintering time, the more even the microstructure was. The sintering quality and the efficiency were improved through isostatic pressing.

Method of sintering materials with microwave radiation

DOEpatents

Kimrey, Jr., Harold D.; Holcombe, Jr., Cressie E.; Dykes, Norman L.

1994-01-01

A method of sintering ceramic materials following: A compacted article comprising inorganic particles coated with carbon is provided, the carbon providing improved microwave coupling. The compacted article is then heated by microwave radiation to a temperature and for a period of time sufficient to sinter the compacted article.

Effect of sintering temperature on physical, structural and optical properties of wollastonite based glass-ceramic derived from waste soda lime silica glasses

NASA Astrophysics Data System (ADS)

Almasri, Karima Amer; Sidek, Hj. Ab Aziz; Matori, Khamirul Amin; Zaid, Mohd Hafiz Mohd

The impact of different sintering temperatures on physical, optical and structural properties of wollastonite (CaSiO3) based glass-ceramics were investigated for its potential application as a building material. Wollastonite based glass-ceramics was provided by a conventional melt-quenching method and followed by a controlled sintering process. In this work, soda lime silica glass waste was utilized as a source of silicon. The chemical composition and physical properties of glass were characterized by using Energy Dispersive X-ray Fluorescence (EDXRF) and Archimedes principle. The Archimedes measurement results show that the density increased with the increasing of sintering temperature. The generation of CaSiO3, morphology, size and crystal phase with increasing the heat-treatment temperature were examined by field emission scanning electron microscopy (FESEM), Fourier transforms infrared reflection spectroscopy (FTIR), and X-ray diffraction (XRD). The average calculated crystal size gained from XRD was found to be in the range 60 nm. The FESEM results show a uniform distribution of particles and the morphology of the wollastonite crystal is in relict shapes. The appearance of CaO, SiO2, and Ca-O-Si bands disclosed from FTIR which showed the formation of CaSiO3 crystal phase. In addition to the calculation of the energy band gap which found to be increased with increasing sintering temperature.

Structural, optical and dielectric properties of Ce0.9Nd0.1O1.95 nanocrystalline oxygen ion conductors: Effect of sintering temperature

NASA Astrophysics Data System (ADS)

Anirban, Sk.; Dutta, A.

2015-01-01

Neodymium doped nanocrystalline ceria [Ce0.9Nd0.1O1.95] was prepared through citrate auto-ignition method. The prepared samples were sintered at five different temperatures starting from 400 °C up to 1200 °C. Rietveld's powder structure refinement analysis of XRD data confirmed the single phase cubic fluorite structure of the prepared samples with space group Fm 3 barm and the obtained particle size and lattice parameter values were found to vary with sintering temperature from 6.68 nm to 39.51 nm and from 5.39077 Å to 5.42317 Å respectively. The optical properties were studied using FT-IR and UV-vis absorption spectra. The FT-IR spectra confirm the presence of functional groups and chemical bonding in the material. The optical band gap was calculated from UV-vis spectra and its value was found to decrease from 3.70 eV to 2.46 eV with increase in sintering temperature. The dc conductivity was found to be thermally activated and decreased with increase in sintering temperature. The nature of impedance spectra reveals the presence of both grain and grain boundary effect. The tangent loss exhibited the presence of relaxation peaks due to the presence of defect pair in the synthesized samples.

Preparation of high-permeability NiCuZn ferrite*

PubMed Central

Hu, Jun; Yan, Mi

2005-01-01

Appropriate addition of CuO/V2O5 and the reduction of the granularity of the raw materials particle decrease the sintering temperature of NiZn ferrite from 1200 °C to 930 °C. Furthermore, the magnetic properties of the NiZn ferrite prepared at low temperature of 930 °C is superior to that of the NiZn ferrite prepared by sintering at high temperature of 1200 °C because the microstructure of the NiZn ferrite sintered at 930 °C is more uniform and compact than that of the NiZn ferrite sintered at 1200 °C. The high permeability of 1700 and relative loss coefficient tanδ/μi of 9.0×10−6 at 100 kHz was achieved in the (Ni0.17Zn0.63Cu0.20)Fe1.915O4 ferrite. PMID:15909348

Silicon nitride-aluminum oxide solid solution (SiAION) formation and densification by pressure sintering

NASA Technical Reports Server (NTRS)

Yeh, H. C.; Sanders, W. A.; Fiyalko, J. L.

1975-01-01

Stirred-ball-mill-blended Si3N4 and Al2O3 powders were pressure sintered in order to investigate the mechanism of solid solution formation and densification in the Si3N4-Al2O3 system. Powder blends with Si3N4:Al2O3 mole ratios of 4:1, 3:2, and 2:3 were pressure sintered at 27.6-MN/sq m pressure at temperatures to 17000 C (3090 F). The compaction behavior of the powder blends during pressure sintering was determined by observing the density of the powder compact as a function of temperature and time starting from room temperature. This information, combined with the results of X-ray diffraction and metallographic analyses regarding solutioning and phase transformation phenomena in the Si3N4-Al2O3 system, was used to describe the densification behavior.

Effect of the quantity of carbonate components and sintering parameters on the quality of hydrothermally synthesized carbonate hydroxyapatite

NASA Astrophysics Data System (ADS)

Ruddyard, A. A.; Soejoko, D. S.; Nurlely

2017-07-01

Carbonated hydroxyapatite is a biomaterial with high biocompatibility with human bone, moreso than regular hydroxyapatite, making it an acceptable synthetic bone graft material. The purpose of this research is to study the effect of sintering temperature and time on carbonated hydroxyapatite samples synthesized using a hydrothermal method with CaCO3 as one of its components. The samples are then characterized using Fourier-Transform Infrared Spectroscopy, X-Ray Diffraction, and Scanning Electron Microscope. Infrared (IR) spectra showed that the CO3 content in each sample is proportional to the amount of CaCO3 used during synthesis. X-Ray Diffraction (XRD) patterns showed an increase in apatite content and a decrease in calcite content as sintering temperature and time increases, with temperature increases having a stronger effect on the samples than time increases. Calcite disappears completely after sintering at 900 °C for 2 hours.

Raman and dielectric studies of GdMnO3 bulk ceramics synthesized from nano powders

NASA Astrophysics Data System (ADS)

Samantaray, S.; Mishra, D. K.; Roul, B. K.

2017-05-01

Nanocrystalline GdMnO3 (GMO) powders has been synthesized by a simple chemical route i. e. pyrophoric reaction technique and then sintered in the form of bulk pellet at 850°C for 24 hours by adopting slow step sintering schedule. It is observed that by reducing the particles size, chemical route enhances the mixing process as well as decreasing the sintering temperature to get single phase material system in compared to the polycrystalline sample prepared directly from the micron sized commercial powder. Raman spectroscopic studies confirm that the sample is in single phase without any detectable impurity. Frequency dependent dielectric properties i.e., dielectric constant (K) and dielectric loss (tanδ) of GMO ceramics sintered at 850°C for 24 hours were studied at room temperature. The sample showed high K value (˜2736) in the frequency of 100 Hz at room temperature.

Thermoelectric properties of a doped LaNiO3 perovskite system prepared using a spark-plasma sintering process

NASA Astrophysics Data System (ADS)

Tak, Jang-Yeul; Choi, Soon-Mok; Seo, Won-Seon; Cho, Hyung Koun

2013-07-01

Both perovskites LaNiO3 and LaCuO3 have a limitation associated with phase transitions for high-temperature thermoelectric applications. The optimized conditions were investigated to obtain the LaNi1- x Cu x O3- δ perovskite single phase showing a Cu-doping effect into Ni sites against unintended deoxidized phases. Three advantages of synergetic effects due to the simultaneous presence of nickel and copper were investigated: a low melting temperature of CuO as compared to that of NiO, the absence of intermediated deoxidized phases in the LaCuO3 system, and the Cu doping effect, which suppresses the formation of intermediate secondary phases. A solid solution was also fabricated using a spark-plasma sintering (SPS) process for the purpose of sintering LaNi1- x Cu x O3- δ compositions at a low sintering temperature.

A device for microwave sintering large ceramic articles

DOEpatents

Kimrey, H.D. Jr.

1987-07-24

A microwave sintering system is provided for uniform sintering of large and/or irregular shapes ceramic articles at microwave frequencies of at least 28 GHz in the hundreds of kilowatts power range in an untuned cavity. A 28 GHz, 200 kw gyrotron with variable power output is used as the microwave source connected to an untuned microwave cavity formed of an electrically conductive housing. The part to be sintered is placed in the cavity and supported on a removable high temperature table in a central location within the cavity. The part is surrounded by a microwave transparent bulk insulating material to reduce thermal heat loss at the part surfaces and maintain more uniform temperature. The cavity may be operated at a high vacuum to aid in preventing arcing. The system allows controlled increased heating rates of greater than 200/degree/C/min to provide rapid heating of a ceramic part to a selected sintering temperature where it is maintained by regulating the microwave power applied to the part. As a result of rapid heating, the extent on non-isothermal processes such as segregation of impurities to the grain boundaries are minimized and exaggerated grain growth is reduced, thereby strengthening the mechanical properties of the ceramic part being sintered. 1 fig.

Ni-SDC cermet anode for medium-temperature solid oxide fuel cell with lanthanum gallate electrolyte

NASA Astrophysics Data System (ADS)

Zhang, Xinge; Ohara, Satoshi; Maric, Radenka; Mukai, Kazuo; Fukui, Takehisa; Yoshida, Hiroyuki; Nishimura, Masayoshi; Inagaki, Toru; Miura, Kazuhiro

The polarization properties and microstructure of Ni-SDC (samaria-doped ceria) cermet anodes prepared from spray pyrolysis (SP) composite powder, and element interface diffusion between the anode and a La 0.9Sr 0.1Ga 0.8Mg 0.2O 3- δ (LSGM) electrolyte are investigated as a function of anode sintering temperature. The anode sintered at 1250°C displays minimum anode polarization (with anode ohmic loss), while the anode prepared at 1300°C has the best electrochemical overpotential, viz., 27 mV at 300 mA cm -2 operating at 800°C. The anode ohmic loss gradually increases with increase in the sintering temperature at levels below 1300°C, and sharply increases at 1350°C. Electron micrographs show a clear grain growth at sintering temperatures higher than 1300°C. The anode microstructure appears to be optimized at 1300°C, in which nickel particles form a network with well-connected SDC particles finely distributed over the surfaces of the nickel particles. The anode sintered at 1350°C has severe grain growth and an apparent interface diffusion of nickel from the anode to the electrolyte. The nickel interface diffusion is assumed to be the main reason for the increment in ohmic loss, and the resulting loss in anode performance. The findings suggest that sintering Ni-SDC composite powder near 1250°C is the best method to prepare the anode on a LSGM electrolyte.

Phase evolution, mechanical and corrosion behavior of Fe(100-x) Ni(x) alloys synthesized by powder metallurgy

NASA Astrophysics Data System (ADS)

Singh, Neera; Parkash, Om; Kumar, Devendra

2018-03-01

In the present investigation, Fe(100-x) Ni(x) alloys (x = 10, 20, 30, 40 and 50 wt%) were synthesized through the evolution of γ-taenite and α-kamacite phases by powder metallurgy route using commercially available Fe and Ni powders. Mechanically mixed powders of Fe and Ni were compacted at room temperature and sintered at three different temperatures 1000, 1200 and 1250 °C for 1 h. Both Ni concentration and sintering temperature have shown a strong impact on the phase formation, tribological and electrochemical behavior. Micro structural study has shown the formation of taenite (γ-Fe,Ni) and kamacite (α-Fe,Ni) phases in the sintered specimens. An increase in Ni fraction resulted in formation of more taenite which reduces hardness and wear resistance of specimens. Increasing the sintering temperature decreased the defect concentration with enhanced taenite formation, aiding to higher densification. Taenite formed completely in Fe50Ni50 after sintering at 1250 °C. Tribological test revealed the maximum wear resistance for Fe70Ni30 specimen due to the presence of both kamacite and taenite in significant proportions. The formation of taenite as well as the decrease in defect concentration improves the corrosion resistance of the specimens significantly in 1M HCl solution. A maximum corrosion protection efficiency of around ∼87% was achieved in acidic medium for Fe50Ni50, sintered at 1250 °C.

Investigation of Sintering Temperature on Attrition Resistance of Highly Porous Diatomite Based Material

DOE Office of Scientific and Technical Information (OSTI.GOV)

Garderen, Noemie van; Clemens, Frank J.; Scharf, Dagobert

2010-05-30

Highly porous diatomite based granulates with a diameter of 500 mum have been produced by an extrusion method. In order to investigate the relation between microstructure, phase composition and attrition resistance of the final product, the granulates were sintered between 800 and 1300 deg. C. Mean pore size of the granulates was evaluated by Hg-porosimetry. An increase of the pore size is observed in the range of 3.6 nm to 40 mum with increasing sintering temperature. Higher mean pore radii of 1.6 mum and 5.7 mum obtained by sintering at 800 and 1300 deg. C respectively. X-ray diffraction shows thatmore » mullite phase appears at 1100 deg. C due to the presence of clay. At 1100 deg. C diatomite (amorphous silicate) started to transform into alpha-cristobalite. Attrition resistance was determined by evaluating the amount of ground material passed through a sieve with a predefined mesh size. It was observed that a material sintered at high temperature leads to an increase of attrition resistance due to the decrease of total porosities and phase transformation. Due to the reason that attrition resistance significantly increased by sintering the granulates at higher temperature, a so called attrition resistance index was determined in order to compare all the different attrition resistance values. This attrition resistance index was determined by using the exponential component of the equation obtained from attrition resistance curves. It permits comparison of the attrition behaviour without a time influence.« less

Thermal boundary resistance between liquid helium and silver sinter at low temperatures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Voncken, A.P.J.; Koenig, R.; Pobell, F.

1996-10-01

The authors present measurements of the thermal coupling between Ag sinter (nominal grain size {approx} 700{angstrom}) and superfluid {sup 3}He-B at p=0.3, 10, and 20 bar as well as a phase-separated {sup 3}He-{sup 4}He mixture at p=0.5 bar in the submillikelvin regime. In order to analyze the data of the pure {sup 3}He-B sample with respect to different contributions to the thermal resistance, a one-dimensional model for the heat flow in the sinter is presented. As a result it is shown that the thermal conductivity of the liquid in the sinter has to be taken into account to extract themore » temperature and pressure dependence of the boundary resistance in the confining geometry of the sinter. Depending on the value of this thermal conductivity, a boundary resistance proportional to T{sup {minus}2} or T{sup {minus}3} is found. Moreover, it is shown that a pressure dependence of the boundary resistance might be explained by a pressure dependence of the thermal conductivity of the liquid in the sinter. The data on the phase-separated mixture are equally well described by a T{sup {minus}2}- and a T{sup {minus}3}-dependence of the boundary resistance. The authors point out that a common problem in most measurements of the Kapitza resistance performed so far is the small temperature interval investigated, which usually does not allow a definite conclusion concerning the temperature dependence.« less

The effects of annealing temperature on the in-field Jc and surface pinning in silicone oil doped MgB2 bulks and wires

NASA Astrophysics Data System (ADS)

Hossain, M. S. A.; Motaman, A.; Çiçek, Ö.; Ağıl, H.; Ertekin, E.; Gencer, A.; Wang, X. L.; Dou, S. X.

2012-12-01

The effects of sintering temperature on the lattice parameters, full width at half maximum (FWHM), strain, critical temperature (Tc), critical current density (Jc), irreversibility field (Hirr), upper critical field (Hc2), and resistivity (ρ) of 10 wt.% silicone oil doped MgB2 bulk and wire samples are investigated in state of the art by this article. The a-lattice parameter of the silicone oil doped samples which were sintered at different temperatures was drastically reduced from 3.0864 Å to 3.0745 Å, compared to the un-doped samples, which indicates the substitution of the carbon (C) into the boron sites. It was found that sintered samples at the low temperature of 600 °C shows more lattice distortion by more C-substitution and higher strain, lower Tc, higher impurity scattering, and enhancement of both magnetic Jc and Hc2, compared to those sintered samples at high temperatures. The flux pinning mechanism has been analyzed based on the extended normalized pinning force density fp = Fp/Fp,max scaled with b = B/Bmax. Results show that surface pinning is the dominant pinning mechanism for the doped sample sintered at the low temperature of 600 °C, while point pinning is dominant for the un-doped sample. The powder in tube (PIT) MgB2 wire was also fabricated by using of this liquid doping and found that both transport Jc and n-factor increased which proves this cheap and abundant silicone oil doping can be a good candidate for industrial application.

The Effect of MnO2 Content and Sintering Atmosphere on The Electrical Properties of Iron Titanium Oxide NTC Thermistors using Yarosite

NASA Astrophysics Data System (ADS)

Wiendartun; Gustaman Syarif, Dani

2017-02-01

The effect of MnO2 content and sintering atmosphere on the characteristics of Fe2TiO5 ceramics for Negative Thermal Coefficient (NTC) thermistors by using Fe2O3 derived from yarosite has been studied. The ceramics were produced by pressing a homogeneous mixture of Fe2O3, TiO2 and MnO2 (0-2.0 w/o) powders in appropriate proportions to produce Fe2TiO5 based ceramics and sintering the pressed powder at 1100-1200°C for 3 hours in air, O2 and N2 gas. Electrical characterization was done by measuring electrical resistivity of the sintered ceramics at various temperatures from 30°C to 200°C. Microstructure and structural analyses were also carried out by using an scanning electron microscope (SEM) and x-ray diffraction (XRD). The XRD data showed that the pellets crystallize in orthorhombic. The presence of second phase could not be identified from the XRD analyses. The SEM images showed that the grain size of pellet ceramics increase with increasing of MnO2 addition, and the grains size of the ceramic sintered in oxygen gas is smaller than sintered in nitrogen gas. Electrical data showed that the value of room temperature resistance (RRT) tend to decrease with respect to the increasing of MnO2 addition and the pellet ceramics sintered in oxygen gas had the largest thermistor constant (B), activation energy (Ea), sensitivity (α) and room temperature resistance (RRT), compared to the sintered in nitrogen gas. From the electrical characteristics data, it was known that the electrical characteristics of the Fe2TiO5 pellet ceramics followed the NTC characteristic. The fabricated Fe2TiO5 ceramics have thermistor constants (B = 2207-7145K). This can be applied as temperature sensor, and will fulfill the market requirement.

Electric-Loading Enhanced Kinetics in Oxide Ceramics: Pore Migration, Sintering and Grain Growth: Final Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, I-Wei

Solid oxide fuel cells and solid oxide electrolysis cells rely on solid electrolytes in which a large ionic current dominates. This project was initiated to investigate microstructural changes in such devices under electrochemical forces, because nominally insignificant processes may couple to the large ionic current to yield non-equilibrium phenomena that alter the microstructure. Our studies had focused on yttria-stabilized cubic zirconia (YSZ) widely used in these devices. The experiments have revealed enhanced grain growth at higher temperatures, pore and gas bubble migration at all temperatures, and the latter also lead to enhanced sintering of highly porous ceramics into fully densemore » ceramics at unprecedentedly low temperatures. These results have shed light on kinetic processes that fall completely outside the realm of classical ceramic processing. Other fast-oxygen oxide ceramics closely related to, and often used in conjunction with zirconia ceramics, have also be investigated, as are closely related scientific problems in zirconia ceramics. These include crystal structures, defects, diffusion kinetics, oxygen potentials, low temperature sintering, flash sintering, and coarsening theory, and all have resulted in greater clarity in scientific understanding. The knowledge is leveraged to provide new insight to electrode kinetics and near-electrode mixed conductivity and to new materials. In the following areas, our research has resulted in completely new knowledge that defines the state-of-the-art of the field. (a) Electrical current driven non-equilibrium phenomena, (b) Enhanced grain growth under electrochemically reducing conditions, (c) Development of oxygen potential polarization in electrically loaded electrolyte, (d) Low temperature sintering and grain growth, and (e) Structure, defects and cation kinetics of fluorite-structured oxides. Our research has also contributed to synthesis of new energy-relevant electrochemical materials and new understanding of flash sintering, which is a rapid sintering process initiated by a large electrical loading.« less

Microwave sintering of multiple articles

DOEpatents

Blake, Rodger D.; Katz, Joel D.

1993-01-01

Apparatus and method for producing articles of alumina and of alumina and silicon carbide in which the articles are sintered at high temperatures using microwave radiation. The articles are placed in a sintering container which is placed in a microwave cavity for heating. The rates at which heating and cooling take place is controlled.

Method of sintering materials with microwave radiation

DOEpatents

Kimrey, H.D. Jr.; Holcombe, C.E. Jr.; Dykes, N.L.

1994-06-14

Disclosed is a method of sintering ceramic materials. A compacted article comprising inorganic particles coated with carbon is provided, the carbon providing improved microwave coupling. The compacted article is then heated by microwave radiation to a temperature and for a period of time sufficient to sinter the compacted article. No Drawings

Low-Temperature Oxidation-Free Selective Laser Sintering of Cu Nanoparticle Paste on a Polymer Substrate for the Flexible Touch Panel Applications.

PubMed

Kwon, Jinhyeong; Cho, Hyunmin; Eom, Hyeonjin; Lee, Habeom; Suh, Young Duk; Moon, Hyunjin; Shin, Jaeho; Hong, Sukjoon; Ko, Seung Hwan

2016-05-11

Copper nanomaterials suffer from severe oxidation problem despite the huge cost effectiveness. The effect of two different processes for conventional tube furnace heating and selective laser sintering on copper nanoparticle paste is compared in the aspects of chemical, electrical and surface morphology. The thermal behavior of the copper thin films by furnace and laser is compared by SEM, XRD, FT-IR, and XPS analysis. The selective laser sintering process ensures low annealing temperature, fast processing speed with remarkable oxidation suppression even in air environment while conventional tube furnace heating experiences moderate oxidation even in Ar environment. Moreover, the laser-sintered copper nanoparticle thin film shows good electrical property and reduced oxidation than conventional thermal heating process. Consequently, the proposed selective laser sintering process can be compatible with plastic substrate for copper based flexible electronics applications.

Fabrication and thermoelectric properties of n-type (Sr0.9Gd0.1)TiO3 oxides

NASA Astrophysics Data System (ADS)

Li, Liangliang; Qin, Xiaoying; Liu, Yongfei; Xin, Hongxing; Zhang, Jian; Li, Di; Song, Chunjun; Guo, Guanglei; Dou, Yunchen; Zou, Tianhua

2014-02-01

The n-type oxides (Sr0.9Gd0.1)TiO3 (SGTO) have been successfully prepared via a sol-gel process followed by solid-state sintering. The effects of sintering temperature on the thermoelectric (TE) properties of the SGTO samples have been investigated. The Seebeck coefficient showed no obvious difference, while the electrical conductivity increased with increasing sintering temperature, benefiting from an enhancement of densification. The maximum power factor (PF) value, 20.5μW/K2cm at 370 K in the metallic region, was observed for the sample sintered at 1748 K. As a result, the peak figure of merit (ZT) values for the samples sintered at higher than 1673 K were in the range of 0.28-0.30. All the results indicate that such synthetic method provides a simple and effective way to prepare TE oxides.

Examination of the sintering process-dependent properties of TiO2 on glass and textile substrates

NASA Astrophysics Data System (ADS)

Junger, Irén Juhász; Homburg, Sarah Vanessa; Grethe, Thomas; Herrmann, Andreas; Fiedler, Johannes; Schwarz-Pfeiffer, Anne; Blachowicz, Tomasz; Ehrmann, Andrea

2017-01-01

In recent years, the development of smart textiles has attracted great attention. Such textiles can contain small electrical devices, which need a power supply. Dye-sensitized solar cells, which can be produced from nontoxic, cheap, low-purity materials, could fill this purpose. However, to reach reasonable cell properties, sintering the TiO2 layer on the substrate is necessary. Unfortunately, only a few textile materials can withstand a sintering process at high temperatures. Therefore, it is important to find an optimal temperature leading to a reasonable improvement of the cell characteristics without damaging the textile substrate. The influence of the sintering temperature on different properties is investigated. For this, the surface properties of the TiO2 coating, such as adhesion to the substrate, dye adsorption characteristic, and film stability, are investigated on different substrates, i.e., a glass plate, a stainless steel nonwoven fabric, and a carbon woven fabric. Two commercially available TiO2 sources are used: a TiO2 dispersion obtained from Man Solar and a water-based solution of TiO2 particles purchased from Kronos. The influence of the sintering temperature on short-circuit current and open-circuit voltage of solar cells on the aforementioned substrates is also examined.

Chemical sintering of direct-written silver nanowire flexible electrodes under room temperature.

PubMed

Hui, Zhuang; Liu, Yangai; Guo, Wei; Li, Lihang; Mu, Nan; Jin, Chao; Zhu, Ying; Peng, Peng

2017-07-14

Transparent and flexible electrodes on cost effective plastic substrates for wearable electronics have attract great attention recently. Due to the conductivity and flexibility in network form, metal nanowire is regarded as one of the most promising candidates for flexible electrode fabrication. Prior to application, low temperature joining of nanowire processes are required to reduce the resistance of electrodes and simultaneously maintain the dimensionality and uniformity of those nanowires. In the present work, we presented an innovative, robust and cost effective method to minimize the heat effect to plastic substrate and silver nanowires which allows silver nanowire electrodes been directly written on polycarbonate substrate and sintered by different electrolyte solutions at room temperature or near. It has been rigorously demonstrated that the resistance of silver nanowire electrodes has been reduced by 90% after chemical sintering at room temperature due to the joining of silver nanowires at junction areas. After ∼1000 bending cycles, the measured resistance of silver nanowire electrode was stable during both up-bending and down-bending states. The changes of silver nanowires after sintering were characterized using x-ray photoelectron spectroscopy and transmission electron microscopy and a sintering mechanism was proposed and validated. This direct-written silver nanowire electrode with good performance has broad applications in flexible electronics fabrication and packaging.

Characterizing Sintered Nano-Hydroxyapatite Sol-Gel Coating Deposited on a Biomedical Ti-Zr-Nb Alloy

NASA Astrophysics Data System (ADS)

Jafari, Hassan; Hessam, Hamid; Shahri, Seyed Morteza Ghaffari; Assadian, Mahtab; Shairazifard, Shahin Hamtaie Pour; Idris, Mohd Hasbullah

2016-03-01

In this study, sol-gel dip-coating method was used to coat nano-hydroxyapatite on specimens of Ti-14Zr-13Nb alloy for orthopedic applications. The coated specimens were sintered at three different temperatures and time spans to evaluate the impact of sintering process on microstructure, mechanical, bio-corrosion, and bioactivity properties of the coating. Field-emission scanning electron microscopy and x-ray diffraction were used to analyze the coating microstructure. Coating adhesion and mechanical performance were also investigated by scratch testing. Besides, electrochemical corrosion and immersion tests were performed in simulated body fluid to examine the sintering effect on corrosion performance and bioactivity of the coatings, respectively. The evaluations of coated specimens displayed that sintering at elevated temperatures leads to higher surface integrity and improves crystallinity of the nano-hydroxyapatite to approximately 89% which brings about distinctively enhanced mechanical properties. Similarly, it improved the corrosion rate for about 17 times through sintering at 700 °C. Immersion test proved that the coating increased the bioactivity resulted from the dissolution of calcium phosphates into the corresponding environment. It is noticeable that sintering the dip-coated specimens in the nano-hydroxyapatite improves corrosion performance and maintains bioactive behaviors as well.

Reaction-sintered porous mineral-based mullite ceramic membrane supports made from recycled materials.

PubMed

Dong, Yingchao; Zhou, Jian-Er; Lin, Bin; Wang, Yongqing; Wang, Songlin; Miao, Lifeng; Lang, Ying; Liu, Xingqin; Meng, Guangyao

2009-12-15

Bulk porous mullite supports for ceramic membranes were prepared directly using a mixture of industrial waste fly ash and bauxite by dry-pressing, followed by sintering between 1200 and 1550 degrees C. The effects of sintering temperature on the phase composition and shrinkage percent of porous mullite were studied. The XRD results indicate that secondary mullitization reaction took place above 1200 degrees C, and completed at 1450 degrees C. During sintering, the mixture samples first shrunk, then expanded abnormally between 1326 and 1477 degrees C, and finally shrunk again above 1477 degrees C. This unique volume self-expansion is ascribed to the secondary mullitization reaction between bauxite and fly ash. More especially, the micro-structural variations induced by this self-expansion sintering were verified by SEM, porosity, pore size distribution and nitrogen gas permeation flux. During self-expansion sintering, with increasing temperature, an abnormal increase in both open porosity and pore size is observed, which also results in the increase of nitrogen gas flux. The mineral-based mullite supports with increased open porosity were obtained. Furthermore, the sintered porous mullite membrane supports were characterized in terms of thermal expansion co-efficient and mechanical strength.

Microwave sintering of Ag-nanoparticle thin films on a polyimide substrate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fujii, S., E-mail: fujii.s.ap@m.titech.ac.jp; Department of Information and Communication System Engineering, National Institute of Technology, Okinawa College, Nago, Okinawa 905-2192; Kawamura, S.

2015-12-15

Ag-nanoparticle thin films on a polyimide substrate were subjected to microwave sintering by use of a single-mode waveguide applicator. A two-step sintering process was employed. First, at low conductivities of the film, the film sample was placed at the site of the maximum electric field and subjected to microwave irradiation. Second, when the conductivity of the film increased, the film sample was placed at the site of the maximum magnetic field and again subjected to microwave irradiation. The microwave sintering process was completed within 1.5 min, which is significantly lower than the time required for the oven heating process. Themore » resulting conductivity of the film, albeit only 30% of that of the bulk material, was seven times that of a film annealed at the same temperature in a furnace. Scanning electron microscopy images revealed that the nanoparticles underwent both grain necking and grain growth during microwave sintering. In addition, this sintering process was equivalent to the oven heating process performed at a 50 °C higher annealing temperature. An electromagnetic wave simulation and a heat transfer simulation of the microwave sintering process were performed to gain a thorough understanding of the process.« less

Investigation on the effect of sintering temperature on kaolin hollow fibre membrane for dye filtration.

PubMed

Mohtor, Nur Hamizah; Othman, Mohd Hafiz Dzarfan; Ismail, Ahmad Fauzi; Rahman, Mukhlis A; Jaafar, Juhana; Hashim, Nur Awanis

2017-07-01

Despite its extraordinary price, ceramic membrane can still be able to surpass polymeric membrane in the applications that require high temperature and pressure conditions, as well as harsh chemical environment. In order to alleviate the high cost of ceramic material that still becomes one of the major factors that contributes to the high production cost of ceramic membrane, various attempts have been made to use low cost ceramic materials as alternatives to well-known expensive ceramic materials such as alumina, silica, and zirconia in the fabrication of ceramic membrane. Thus, local Malaysian kaolin has been chosen as the ceramic material in this study for the preparation of kaolin hollow fibre membrane since it is inexpensive and naturally abundant in Malaysia. Due to the fact that the sintering process plays a prominent role in obtaining the desired morphology, properties, and performances of prepared ceramic membrane, the aim of this work was to study the effect of different sintering temperatures applied (ranging from 1200 to 1500 °C) in the preparation of kaolin hollow fibre membrane via dry/wet phase inversion-based spinning technique and sintering process. The morphology and properties of membrane were then characterised by SEM, AFM, FTIR, XRD, and three-point bending test, while the performances of membrane were investigated by conducting water permeation and Reactive Black 5 (RB5) dye rejection tests. From the experimental results obtained, the sintering temperature of 1400 °C could be selected as the optimum sintering temperature in preparing the kaolin hollow fibre membrane with the dense sponge-like structure of separation layer that resulted in the good mechanical strength of 70 MPa with the appreciable water permeation of 75 L/h m 2  bar and RB5 rejection of 68%.

Ice sintering timescales at the surface of Europa and implications for surface properties

NASA Astrophysics Data System (ADS)

Phillips, C. B.; Molaro, J.; Meirion-Griffith, G.

2017-12-01

The planned exploration of Europa by NASA's Europa Clipper Mission and the possibility of a future Europa lander have driven the need to characterize its surface strength, roughness, porosity, thermal conductivity, and regolith depth in order to accurately interpret remote sensing data and develop appropriate spacecraft landing systems. Many processes contribute to Europa's landscape evolution, such as sputtering, mass wasting, thermal segregation, and impact gardening, driving the creation and distribution of icy regolith across the surface. While the efficacy of these processes are not well constrained, any amount of regolith emplaced at the surface will undergo subsequent processing due to sintering. Ice sintering is a form of frost metamorphism whereby contacting ice grains experience the diffusion of material into their contact region, forming a "neck" between them and densifying over time. Over long enough timescales, ice aggregates will sinter into solid material, which may contribute to the incorporation of non-ice material into Europa's subsurface and help to drive subsurface chemistry. Sintering also interacts with other processes, adding to the complexity of icy surface evolution. For example, sputtering preferentially removes larger grains and may enhance sintering rates, and changes in ice porosity may affect the response of the surface to micrometeorite impacts. Quantifying the effects of ice sintering will allow us to predict the microstructural properties of Europa's surface at spacecraft scales. To this end, we have modeled pressure-less (no overburden) sintering of spherical water-ice grains and validated the results with a laboratory experiment. We also modeled ice at the surface of Europa to obtain a first-order approximation of the sintering timescale and surface properties. Preliminary results indicate that ice grains will experience neck growth but not significant densification over Europa's surface age, suggesting that loose surface ice forms a weak and porous crust. Furthermore, our results suggest that existing models do not accurately quantify all stages of the sintering process for ice, emphasizing the need for more laboratory studies on this topic.

Experimental sintering of ash at conduit conditions and implications for the longevity of tuffisites

NASA Astrophysics Data System (ADS)

Gardner, James E.; Wadsworth, Fabian B.; Llewellin, Edward W.; Watkins, James M.; Coumans, Jason P.

2018-03-01

Escape of gas from magma in the conduit plays a crucial role in mitigating explosivity. Tuffisite veins—ash-filled cracks that form in and around volcanic conduits—represent important gas escape pathways. Sintering of the ash infill decreases its porosity, eventually forming dense glass that is impermeable to gas. We present an experimental investigation of surface tension-driven sintering and associated densification of rhyolitic ash under shallow conduit conditions. Suites of isothermal (700-800 °C) and isobaric H2O pressure (20 and 40 MPa) experiments were run for durations of 5-90 min. Obsidian powders with two different size distributions were used: 1-1600 μm (mean size = 89 μm), and 63-400 μm (mean size = 185 μm). All samples evolved similarly through four textural phases: phase 1—loose and cohesion-less particles; phase 2—particles sintered at contacts and surrounded by fully connected tortuous pore space of up to 40% porosity; phase 3—continuous matrix of partially coalesced particles that contain both isolated spherical vesicles and connected networks of larger, contorted vesicles; phase 4—dense glass with 2-5% fully isolated vesicles that are mainly spherical. Textures evolve faster at higher temperature and higher H2O pressure. Coarse samples sinter more slowly and contain fewer, larger vesicles when fully sintered. We quantify the sintering progress by measuring porosity as a function of experimental run-time, and find an excellent collapse of data when run-time is normalized by the sintering timescale {λ}_s=η \\overline{R}/σ , where η is melt viscosity, \\overline{R} is mean particle radius, and σ is melt-gas surface tension. Because timescales of diffusive H2O equilibration are generally fast compared to those of sintering, the relevant melt viscosity is calculated from the solubility H2O content at experimental temperature and pressure. We use our results to develop a framework for estimating ash sintering rates under shallow conduit conditions, and predict that sintering of ash to dense glass can seal tuffisites in minutes to hours, depending on pressure (i.e., depth), temperature, and ash size.

Development of a sintering process for recycling oil shale fly ash and municipal solid waste incineration bottom ash into glass ceramic composite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Zhikun; Zhang, Lei; Li, Aimin, E-mail: leeam@dlut.edu.cn

Highlights: • Glass ceramic composite is prepared from oil shale fly ash and MSWI bottom ash. • A novel method for the production of glass ceramic composite is presented. • It provides simple route and lower energy consumption in terms of recycling waste. • The vitrified slag can promote the sintering densification process of glass ceramic. • The performances of products decrease with the increase of oil shale fly ash content. - Abstract: Oil shale fly ash and municipal solid waste incineration bottom ash are industrial and municipal by-products that require further treatment before disposal to avoid polluting the environment.more » In the study, they were mixed and vitrified into the slag by the melt-quench process. The obtained vitrified slag was then mixed with various percentages of oil shale fly ash and converted into glass ceramic composites by the subsequent sintering process. Differential thermal analysis was used to study the thermal characteristics and determine the sintering temperatures. X-ray diffraction analysis was used to analyze the crystalline phase compositions. Sintering shrinkage, weight loss on ignition, density and compressive strength were tested to determine the optimum preparation condition and study the co-sintering mechanism of vitrified amorphous slag and oil shale fly ash. The results showed the product performances increased with the increase of sintering temperatures and the proportion of vitrified slag to oil shale fly ash. Glass ceramic composite (vitrified slag content of 80%, oil shale fly ash content of 20%, sintering temperature of 1000 °C and sintering time of 2 h) showed the properties of density of 1.92 ± 0.05 g/cm{sup 3}, weight loss on ignition of 6.14 ± 0.18%, sintering shrinkage of 22.06 ± 0.6% and compressive strength of 67 ± 14 MPa. The results indicated that it was a comparable waste-based material compared to previous researches. In particular, the energy consumption in the production process was reduced compared to conventional vitrification and sintering method. Chemical resistance and heavy metals leaching results of glass ceramic composites further confirmed the possibility of its engineering applications.« less

Spark plasma sintering of pure and doped tungsten as plasma facing material

NASA Astrophysics Data System (ADS)

Autissier, E.; Richou, M.; Minier, L.; Naimi, F.; Pintsuk, G.; Bernard, F.

2014-04-01

In the current water cooled divertor concept, tungsten is an armour material and CuCrZr is a structural material. In this work, a fabrication route via a powder metallurgy process such as spark plasma sintering is proposed to fully control the microstructure of W and W composites. The effect of chemical composition (additives) and the powder grain size was investigated. To reduce the sintering temperature, W powders doped with a nano-oxide dispersion of Y2O3 are used. Consequently, the sintering temperature for W-oxide dispersed strengthened (1800 °C) is lower than for pure W powder. Edge localized mode tests were performed on pure W and compared to other preparation techniques and showed promising results.

Temperature Field Simulation of Powder Sintering Process with ANSYS

NASA Astrophysics Data System (ADS)

He, Hongxiu; Wang, Jun; Li, Shuting; Chen, Zhilong; Sun, Jinfeng; You, Ying

2018-03-01

Aiming at the “spheroidization phenomenon” in the laser sintering of metal powder and other quality problems of the forming parts due to the thermal effect, the finite element model of the three-dimensional transient metal powder was established by using the atomized iron powder as the research object. The simulation of the mobile heat source was realized by means of parametric design. The distribution of the temperature field during the sintering process under different laser power and different spot sizes was simulated by ANSYS software under the condition of fully considering the influence of heat conduction, thermal convection, thermal radiation and thermophysical parameters. The influence of these factors on the actual sintering process was also analyzed, which provides an effective way for forming quality control.

Comparison of aged polyamide powders for selective laser sintering

NASA Astrophysics Data System (ADS)

Martínez, A.; Ibáñez, A.; Sánchez, A.; León, M. A.

2012-04-01

Selective Laser Sintering (SLS) is an additive manufacturing technology in which a three-dimensional object is manufactured layer by layer by melting powder materials with heat generated from a CO2 laser. However, a disadvantage of sintered materials is that the unsintered powder material during the process can be reused only a limited number of cycles, as during the heating phase in the sintering chamber the material remains at a temperature near the fusion point for a certain period of time and lose properties. This work shows the study of two polyamides (PA12)-based powders used in SLS with the aim of understanding the modification of their properties mainly with the temperature and the time at which they are exposed during the processing.

Improved performance of silicon nitride-based high temperature ceramics

NASA Technical Reports Server (NTRS)

Ashbrook, R. L.

1977-01-01

Recent progress in the production of Si3N4 based ceramics is reviewed: (1) high temperature strength and toughness of hot pressed Si3N4 were improved by using high purity powder and a stabilized ZrO2 additive, (2) impact resistance of hot pressed Si3N4 was increased by the use of a crushable energy absorbing layer, (3) the oxidation resistance and strength of reaction sintered Si3N4 were increased by impregnating reaction sintered silicon nitride with solutions that oxidize to Al2O3 or ZrO2, (4) beta prime SiA1ON compositions and sintering aids were developed for improved oxidation resistance or improved high temperature strength.

Structural, microstructural, dielectric and ferroelectric properties of lead free Ba0.85Ca0.15Zr0.1Ti0.9O3 ceramic

NASA Astrophysics Data System (ADS)

Sharma, Sarita; Sharma, Hakikat; Negi, N. S.

2018-05-01

Lead free Ba0.85Ca0.15Zr0.1Ti0.9O3(BCTZ) ceramic has been synthesized by sol-gel method. Properties of material are studied at different sintering temperatures for 5 hours. Structural and microstructural properties are analyzed by using X-ray diffractrometer (XRD) and scanning electron microscopy (SEM) at annealing temperature of 850°C and 1050°C XRD pattern confirm the perovskite structure of the material without any unwanted phases crystalinity increased with increase of sintering temperature so as roughness and porosity is decreased as shown by SEM micrographs. There is large improvement in density with rise of sintering temperature which also leads to drastic change in ferroelectric and dielectric properties.

Structural, magnetic, elastic, dielectric and electrical properties of hot-press sintered Co1-xZnxFe2O4 (x = 0.0, 0.5) spinel ferrite nanoparticles

NASA Astrophysics Data System (ADS)

Singh Yadav, Raghvendra; Kuřitka, Ivo; Havlica, Jaromir; Hnatko, Miroslav; Alexander, Cigáň; Masilko, Jiri; Kalina, Lukas; Hajdúchová, Miroslava; Rusnak, Jaroslav; Enev, Vojtěch

2018-02-01

In this article, Co1-xZnxFe2O4 (x = 0.0 and 0.5) disc-shaped pellets were formed by hot-press sintering of nanoparticles at temperature 925 °C for 10 min in vacuum atmosphere under 30 MPa mechanical pressure. X-ray diffraction study confirmed the formation of spinel cubic ferrite structure of hot-press sintered spinel ferrite Co1-xZnxFe2O4 (x = 0.0 and 0.5) samples. The scanning electron microscopy image indicated that the growth and densification of smaller ferrite nanoparticles were higher than larger ferrite nanoparticles. Magnetic properties of sintered samples were investigated by the superconducting quantum interface device (SQUID) magnetometer at room temperature. The hot press sintered Co1-xZnxFe2O4 (x = 0.0 and 0.5) pellet samples exhibited magnetic properties dependent on the grain size of spinel ferrite particles. The maximum saturation magnetization 82.47 emu/g was obtained for Co0.5Zn0.5Fe2O4 hot press sintered sample of ball-milled ferrite particles. Further, the impact of grain size and density of sample on hardness, dielectric property and ac conductivity of hot-press sintered samples was investigated. In addition, the longitudinal wave velocity (Vl), transverse wave velocity (Vt), mean elastic wave velocity (Vm), bulk modulus (B), rigidity modulus (G), Young's modulus (E), Poisson ratio (σ) and Debye temperature (θD) were calculated. The elastic moduli of hot press sintered ferrite samples were corrected to zero porosity using Hosselman and Fulrath model.

CALCIUM OXIDE SINTERING IN ATMOSPHERES CONTAINING WATER AND CARBON DIOXIDE

EPA Science Inventory

The paper gives results of measurements of the effects of water vapor and CO2 on the sintering rate of nascent CaO, as a function of partial pressure and temperature using CaO prepared by rapid decomposition of CaCO3 and CA(OH)2. Each gas strongly catalyzed the sintering process ...

The influence of Ca/P ratio on the properties of hydroxyapatite bioceramics

NASA Astrophysics Data System (ADS)

Ramesh, S.; Tan, C. Y.; Hamdi, M.; Sopyan, I.; Teng, W. D.

2007-07-01

The paper reports on the effect of Ca/P ratio (1.57, 1.67 and 1.87) on the densification behaviour of nanocrystalline hydroxyapatite (HA) prepared by a chemical precipitation method. Green compacts were prepared and sintered at temperatures ranging from 1000°C to 1350°C. The sintered samples were characterized to determine the HA phase stability, bulk density, hardness, fracture toughness and Young's modulus. XRD analysis revealed that the phase stability was not disrupted throughout the sintering regime employed for HA having Ca/P ratio of 1.57 and 1.67. However, secondary phases were observed for HA having a Ca/P ratio of 1.87 when sintered at high temperatures. In general, regardless of Ca/P ratio, the HA bodies achieved > 95% relative density when sintered at 1100°C-1250°C. The results indicated that the stoichiometric HA (Ca/P ratio = 1.67) exhibited the overall best properties, with the highest hardness of 7.23 GPa and fracture toughness of 1.28 MPam1/2 being attained when sintered at 1000°C-1050°C.

Effect of sintering temperatures and screen printing types on TiO2 layers in DSSC applications

NASA Astrophysics Data System (ADS)

Supriyanto, Agus; Furqoni, Lutfi; Nurosyid, Fahru; Hidayat, Jojo; Suryana, Risa

2016-03-01

Dye-Sensitized Solar Cell (DSSC) is a candidate solar cell, which has a big potential in the future due to its eco-friendly material. This research is conducted to study the effect of sintering temperature and the type of screen-printing toward the characteristics of TiO2 layer as a working electrode in DSSC. TiO2 layers were fabricated using a screen-printing method with a mesh size of T-49, T-55, and T-61. TiO2 layers were sintered at temperatures of 600°C and 650°C for 60 min. DSSC structure was composed of TiO2 as semiconductors, ruthenium complex as dyes, and carbon as counter electrodes. The morphology of TiO2 layer was observed by using Nikon E2 Digital Camera Microscopy. The efficiencies of DSSC were calculated from the I-V curves. The highest efficiency is 0.015% at TiO2 layer fabricated with screen type T-61 and at a sintering temperature of 650°C.

Effect of Aging Temperature on Corrosion Behavior of Sintered 17-4 PH Stainless Steel in Dilute Sulfuric Acid Solution

NASA Astrophysics Data System (ADS)

Szewczyk-Nykiel, Aneta; Kazior, Jan

2017-07-01

The general corrosion behavior of sintered 17-4 PH stainless steel processed under different processing conditions in dilute sulfuric acid solution at 25 °C was studied by open-circuit potential measurement and potentiodynamic polarization technique. The corrosion resistance was evaluated based on electrochemical parameters, such as polarization resistance, corrosion potential, corrosion current density as well as corrosion rate. The results showed that the precipitation-hardening treatment could significantly improve the corrosion resistance of the sintered 17-4 PH stainless steel in studied environment. As far as the influence of aging temperature on corrosion behavior of the sintered 17-4 PH stainless steel is concerned, polarization resistance and corrosion rate are reduced with increasing aging temperature from 480 up to 500 °C regardless of the temperature of solution treatment. It can be concluded that the highest corrosion resistance in 0.5 M H2SO4 solution exhibits 17-4 PH after solution treatment at 1040 °C followed by aging at 480 °C.

Enhancement of structural and magnetic properties of M-type hexaferrite permanent magnet based on synthesis temperature

NASA Astrophysics Data System (ADS)

Anjum, Safia; Sehar, Fatima; Mustafa, Zeeshan; Awan, M. S.

2018-01-01

The main purpose of this research work is to develop the single domain magnetic particles of M-type barium hexaferrite (BaFe12O19) using oxide precursors employing conventional powder metallurgy technique. The phase formation and magnetic performance of the powders and magnets will be optimized by adjusting calcination and sintering temperatures. The synthesis of M-type barium hexaferrite was carried out in two sections. A series of four samples have been prepared by initial wet mixed powders calcined at different temperatures, i.e., 750, 850, 950 and 1050 °C. On the basis of structural analysis, the sample calcined at 950 °C has been selected and further divided into four parts to sintered them at 1100, 1150, 1200 and 1250 °C. The structural measurements depict the confirmation of M-type barium hexaferrite structure. SEM micrographs show the hexagonal-shaped grains. The abrupt decrease in coercivity for the sample sintered at 1250 °C has been seen which may be due to high sintering temperature, at which the particles have multi-domain properties.

Effect of sintering temperature rise from 870 to 920°C on physicomechanical and biological quality of nano-hydroxyapatite: An explorative multi-phase experimental in vitro/vivo study.

PubMed

Khoshzaban, Ahad; Rakhshan, Vahid; Najafi, Farhood; Aghajanpour, Leila; Hashemian, Seyed Jafar; Keshel, Saeed Heidari; Watanabe, Ikuya; Valanezhad, Alireza; Jafarzadeh Kashi, Tahereh Sadat

2017-08-01

Hydroxyapatite (HA) is a proper scaffold for bone repair, however, it is not of excellent mechanical properties. Most previous studies on the effect of temperature increases were in vitro and had assessed merely improvements of HA's physicomechanical quality. This in vitro/vivo study investigated the effect of temperature increases from 870 to 920°C on physicomechanical and biological quality of Nano-HA. Forty experimentally produced HA disks sintered at 870 to 920°C were prepared (n=20×2). Disks were subjected to Vickers microindentation test (1 disk from each group divided into 4 quarters), Fourier transform infrared spectroscopy (1 disk), X-ray diffraction (XRD) [1 disk together with non-sintered HA], field emission scanning electron microscopy (FSEM, 1 disk from each group together with non-sintered HA), cell seeding and SEM assessment (2 disks), MTT assay over 4 different time periods (16 quadrants of 4 disks from each group), 6 one-thirds of 2 disks from each group for immunocytochemical (ICC) assay, and 8 disks from each group [as well as non-sintered HA] for the animal study (implantation in 4 sockets in 8 rabbits [32 specimens], histomorphometry, and computerized tomography) over two time periods. Quantitative data were analyzed statistically (α=0.05). Vickers microhardness increased from 63.7±11.9 in the 870 group to 153.4±104.7 in the 920 group (P=0.057). XRD indicated more regular crystal patterns in sintered groups compared to non-sintered nanoHA. FSEM showed larger crystals in the 920 group compared to 870 and non-sintered nanoHA. Expression of osteocalcin, osteonectin, and RUNX2 genes were more visible in ICC samples of the 920HA group. In MTT, cell numbers increased in all groups significantly (P=0.000), with no between-group differences (P>0.3). In rabbit experiments, the extent of 'newly formed bone' increased significantly over time (two-way ANOVA, P=0.000), reaching 39.5%, 46.4%, and 77.5% in the groups non-sintered HA, 870, and 920, respectively. The 920°C-sintered nanoHA induced the highest bone formation (P=0.000). Increasing the temperature of nanoHA sintering from 870 to 920°C can improve its physicomechanical properties and bone formation potential. Copyright © 2017 Elsevier B.V. All rights reserved.

Infiltration sintering properties of Ni-4B-4Si(wt.%) alloy powders

NASA Astrophysics Data System (ADS)

Yang, Q.; Zhang, X. C.; Wang, F. L.; Zou, J. T.

2018-01-01

The Ni-4B-4Si(wt.%) alloy powders were infiltrated into the nickel skeletons, the effects of sintering temperatures (1050-1150 °C) and skeletons (loose and compact nickel powders) on the microstructures and hardness of the sintered alloys were investigated. The Ni-B-Si alloy sintered at 1100 °C consisted of γ-Ni and Ni3B, and Si mainly solid soluted in the γ-Ni. The loose nickel powders favored to the infiltration of Ni-B-Si liquid alloy into the nickel skeletons, the sintered alloys exhibited dense microstructures and good interfacial bonding with Ni substrates. The interfacial hardness was equal to that of the sintered alloys and Ni substrates. Loose nickel powders ensured the density and interfacial bonding of the sintered alloys, the infiltration sintering process can be simplified and easily applied to practice.

Ni-base superalloy powder-processed porous layer for gas cooling in extreme environments

DOE PAGES

White, Emma M. H.; Heidloff, Andrew J.; Byrd, David J.; ...

2016-05-26

Extreme high temperature conditions demand novel solutions for hot gas filters and coolant access architectures, i.e., porous layers on exposed components. These high temperatures, for example in current turbine engines, are at or exceeding current material limits for high temperature oxidation/corrosion, creep resistance, and, even, melting temperature. Thus novel blade designs allowing greater heat removal are required to maintain airfoil temperatures below melting and/ or rapid creep deformation limits. Gas atomized Ni-base superalloy powders were partially sintered into porous layers to allow full-surface, transpirational cooling of the surface of airfoils. Furthermore, these powder-processed porous layers were fully characterized for surface,more » morphology, cross-sectional microstructure, and mechanical strength characteristics. A sintering model based on pure Ni surface diffusion correlated well with the experimental results and allowed reasonable control over the partial sintering process to obtain a specified level of porosity within the porous layer.« less

Ni-base superalloy powder-processed porous layer for gas cooling in extreme environments

DOE Office of Scientific and Technical Information (OSTI.GOV)

White, Emma M. H.; Heidloff, Andrew J.; Byrd, David J.

Extreme high temperature conditions demand novel solutions for hot gas filters and coolant access architectures, i.e., porous layers on exposed components. These high temperatures, for example in current turbine engines, are at or exceeding current material limits for high temperature oxidation/corrosion, creep resistance, and, even, melting temperature. Thus novel blade designs allowing greater heat removal are required to maintain airfoil temperatures below melting and/ or rapid creep deformation limits. Gas atomized Ni-base superalloy powders were partially sintered into porous layers to allow full-surface, transpirational cooling of the surface of airfoils. Furthermore, these powder-processed porous layers were fully characterized for surface,more » morphology, cross-sectional microstructure, and mechanical strength characteristics. A sintering model based on pure Ni surface diffusion correlated well with the experimental results and allowed reasonable control over the partial sintering process to obtain a specified level of porosity within the porous layer.« less

Influence of sintering temperature on the phases and photoelectric characteristics of BiOCl/ZnO composite powders

NASA Astrophysics Data System (ADS)

Chen, Song; Zhu, De-gui

2017-12-01

Zinc oxide is a typical functional oxide that has been widely researched for various industry applications due to its peculiar physical characteristics. However, to achieve its potential in promising applications, much work has been diligently performed to improve the physical properties of ZnO. In this work, an aqueous suspension route was used to prepare BiOCl/ZnO composite powders, and sintering processes were applied to investigate the influence of sintering temperature on the phase evolutions, microstructures, and photoelectric characteristics of BiOCl/ZnO composite powders. The results indicated that the photoelectric properties mainly depend on the relevant content of BiOCl in the composite powders and the sintering temperature. The photoelectric measurements in K2SO4 solutions show that the photoelectric properties of the samples with the appropriate BiOCl content (0.3mol% and 2.0mol%) are better than those of ZnO and commercial TiO2 (P25) powders, but the photoelectric measurements in NaOH solutions indicate that the photoelectric characteristics of the as-sintered samples are only better than those of P25.

Fabrication of lanthanum-doped thorium dioxide by high-energy ball milling and spark plasma sintering

NASA Astrophysics Data System (ADS)

Scott, Spencer M.; Yao, Tiankai; Lu, Fengyuan; Xin, Guoqing; Zhu, Weiguang; Lian, Jie

2017-03-01

High-energy ball milling was used to synthesize Th1-xLaxO2-0.5x (x = 0.09, 0.23) solid solutions, as well as improve the sinterability of ThO2 powders. Dense La-doped ThO2 pellets with theoretical density above 94% were consolidated by spark plasma sintering at temperatures above 1400 °C for 20 min, and the densification behavior and the non-equilibrium effects on phase and structure were investigated. A lattice contraction of the SPS-densified pellets occurred with increasing ball milling duration, and a secondary phase with increased La-content was observed in La-doped pellets. A dependence on the La-content and sintering duration for the onset of localized phase segregation has been proposed. The effects of high-energy ball milling, La-content, and phase formation on the thermal diffusivity were also studied for La-doped ThO2 pellets by laser flash measurement. Increasing La-content and high energy ball milling time decreases thermal diffusivity; while the sintering peak temperature and holding time beyond 1600 °C dramatically altered the temperature dependence of the thermal diffusivity beyond 600 °C.

Method and device for microwave sintering large ceramic articles

DOEpatents

Kimrey, Jr., Harold D.

1990-01-01

A microwave sintering system and method are provided for extremely uniform sintering of large and/or irregular shaped ceramic articles at microwave frequencies of at least 28 GHz in the hundreds of kilowatts power range in an untuned cavity. A 28 GHz, 200 kw gyrotron with variable power output is used as the microwave source connected to an untuned microwave cavity formed of an electrically conductive housing through an overmoded waveguide arrangement which acts in conjunction with a mode promoter within the cavity to achieve unexpected field uniformity. The part to be sintered is placed in the cavity and supported on a removable high temperature table in a central location within the cavity. The part is surrounded by a microwave transparent bulk insulating material to reduce thermal heat loss at the part surfaces and maintain more uniform temperature. The cavity may be operated at a high vacuum to aid in preventing arcing. The system allows controlled increased heating rates of greater than 200.degree. C./min to provide rapid heating of a ceramic part to a selected sintering temperature where it is maintained by regulating the microwave power applied to the part. As a result of rapid heating, the extent of non-isothermal processes such as segregation of impurities to the grain boundaries are minimized and exaggerated grain growth is reduced, thereby strengthening the mechanical properties of the ceramic part being sintered.

Preparation of Ti3Al intermetallic compound by spark plasma sintering

NASA Astrophysics Data System (ADS)

Ito, Tsutomu; Fukui, Takahiro

2018-04-01

Sintered compacts of single phase Ti3Al intermetallic compound, which have excellent potential as refractory materials, were prepared by spark plasma sintering (SPS). A raw powder of Ti3Al intermetallic compound with an average powder diameter of 176 ± 56 μm was used in this study; this large powder diameter is disadvantageous for sintering because of the small surface area. The samples were prepared at sintering temperatures (Ts) of 1088, 1203, and 1323 K, sintering stresses (σs) of 16, 32, and 48 MPa, and a sintering time (ts) of 10 min. The calculated relative densities based on the apparent density of Ti3Al provided by the supplier were approximately 100% under all sintering conditions. From the experimental results, it was evident that SPS is an effective technique for dense sintering of Ti3Al intermetallic compounds in a short time interval. In this report, the sintering characteristics of Ti3Al intermetallic compacts are briefly discussed and compared with those of pure titanium compacts.

Constrains on the Rheology of the Lithosphere Inferred from Nano-Forsterite Deformation Experiments

NASA Astrophysics Data System (ADS)

Gasc, J.; Demouchy, S. A.; Barou, F.; Koizumi, S.

2017-12-01

The rheology of the lithospheric mantle is usually inferred from experiments performed at temperatures and strain rates greater than in the Earth. In these conditions, deformation occurs via dislocation creep and the flow laws obtained experimentally are then extrapolated to natural conditions. Despite the difficulty of achieving steady-state flow at low temperatures (<1200°C), recent studies have shown that low-temperature deformation of olivine implies different deformation mechanisms and that rotational defects, i.e. disclinations, might be involved in the low-temperature rheology of the mantle. To help constrain the rheology of the upper mantle and address the role of the various defects at play at the microscopic scale, we used a high-pressure high-temperature gas medium deformation apparatus (aka. Paterson press) to deform pre-sintered nano-forsterite aggregates. The fine-grained nature of the samples allows us to probe the deformation mechanisms at play when dislocation creep is limited. Experiments were performed at 300 MPa, 900-1200°C, and constant displacement yielding strain rates around 10-5 s-1. The samples were analyzed using state-of-the-art microscopy techniques. EBSD analysis did not reveal crystal preferred orientation. However, grain plasticity was evidenced and takes place almost exclusively via subgrain formation with rotation around the c-axis, a condition that does not allow sustainable plastic flow. Further investigations are ongoing to identify if other defects, such as disclinations are present. Grain rotation was also evidenced by a shape preferred orientation. Regardless of the mechanisms involved, rheology data show that the samples are stronger (from 0.5-2 GPa) than their iron-bearing olivine counterparts, due to a combined effect of grain size and composition (Fe has a softening effect on olivine). The temperature dependence is weaker than predicted by high temperature data in the dislocation creep regime, but remains greater than reported from experiments and models in the same conditions for olivine, which has important implications regarding the strength of the lithospheric mantle.

Effects of sintering temperature on the microstructural evolution and wear behavior of WCp reinforced Ni-based coatings

NASA Astrophysics Data System (ADS)

Chen, Chuan-hui; Bai, Yang; Ye, Xu-chu

2014-12-01

This article focuses on the microstructural evolution and wear behavior of 50wt%WC reinforced Ni-based composites prepared onto 304 stainless steel substrates by vacuum sintering at different sintering temperatures. The microstructure and chemical composition of the coatings were investigated by X-ray diffraction (XRD), differential thermal analysis (DTA), scanning and transmission electron microscopy (SEM and TEM) equipped with energy-dispersive X-ray spectroscopy (EDS). The wear resistance of the coatings was tested by thrust washer testing. The mechanisms of the decomposition, dissolution, and precipitation of primary carbides, and their influences on the wear resistance have been discussed. The results indicate that the coating sintered at 1175°C is composed of fine WC particles, coarse M6C (M=Ni, Fe, Co, etc.) carbides, and discrete borides dispersed in solid solution. Upon increasing the sintering temperature to 1225°C, the microstructure reveals few incompletely dissolved WC particles trapped in larger M6C, Cr-rich lamellar M23C6, and M3C2 in the austenite matrix. M23C6 and M3C2 precipitates are formed in both the γ/M6C grain boundary and the matrix. These large-sized and lamellar brittle phases tend to weaken the wear resistance of the composite coatings. The wear behavior is controlled simultaneously by both abrasive wear and adhesive wear. Among them, abrasive wear plays a major role in the wear process of the coating sintered at 1175°C, while the effect of adhesive wear is predominant in the coating sintered at 1225°C.

Powder metallurgy: Solid and liquid phase sintering of copper

NASA Technical Reports Server (NTRS)

Sheldon, Rex; Weiser, Martin W.

1993-01-01

Basic powder metallurgy (P/M) principles and techniques are presented in this laboratory experiment. A copper based system is used since it is relatively easy to work with and is commercially important. In addition to standard solid state sintering, small quantities of low melting metals such as tin, zinc, lead, and aluminum can be added to demonstrate liquid phase sintering and alloy formation. The Taguchi Method of experimental design was used to study the effect of particle size, pressing force, sintering temperature, and sintering time. These parameters can be easily changed to incorporate liquid phase sintering effects and some guidelines for such substitutions are presented. The experiment is typically carried out over a period of three weeks.

Fabrication of Ce3+ doped Gd3Ga3Al2O12 ceramics by reactive sintering method

NASA Astrophysics Data System (ADS)

Ye, Yong; Liu, Peng; Yan, Dongyue; Xu, Xiaodong; Zhang, Jian

2017-09-01

Ce3+ doped Gd3Ga3Al2O12 (Ce:GGAG) ceramics were fabricated by solid state reactive sintering method in this study. The ceramics were pre-sintered in normal muffle furnace in air at various temperature range from 1410 °C to 1550 °C for 10 h and post-treated by hot isostatic press at 1400 °C/2 h in 200 MPa Ar. The phase and microstructure evolution of Ce: GGAG samples during the densification process were investigated by X-ray diffraction and scanning electron microscope. Pure GGAG phase appeared with the temperature increased to 1200 °C. The fully dense and translucent GGAG ceramics were fabricated by pre-sintering at 1450 °C and followed by HIP treatment.

The Influence of Sintering Method on Kaolin-Based Geopolymer Ceramics with Addition of Ultra High Molecular Weight Polyethylene as Binder

NASA Astrophysics Data System (ADS)

Romisuhani, A.; AlBakri, M. M.; Kamarudin, H.; Andrei, S. V.

2017-11-01

The influence of sintering method on kaolin-based geopolymer ceramics with addition of Ultra High Molecular Weight Polyethylene as binder were studied. Geopolymer were formed at room temperature from kaolin and sodium silicate in a highly alkaline medium, followed by curing and drying at 80 °C. 12 M of sodium hydroxide solution were mixed with sodium silicate at a ratio of 0.24 to form alkaline activator. Powder metallurgy technique were used in order to produce kaolin geopolymer ceramics with addition of Ultra High Molecular Weight Polyethylene. The samples were heated at temperature of 1200 °C with two different sintering method which are conventional method and two-step sintering method. The strength and density were tested.

Improved Properties of Pb Based BLZT Ferroelectric Ceramics

NASA Astrophysics Data System (ADS)

Kumar, Parveen; Singh, Sangeeta; Juneja, J. K.; Raina, K. K.; Prakash, Chandra

2011-11-01

Present report is concerning with investigation of effect of different sintering profiles on Pb based BLZT ceramics. The material powder of selected composition (Ba0.795La0.005Pb0.20Ti0.90Zr0.10O3) was prepared by solid state reaction route and then powder was compacted in the form of circular discs. The discs were then sintered at different temperatures (1325 °C for 4h, 1325 °C for 15min+1200 °C for 4h). Improved dielectric and ferroelectric properties were observed for samples sintered at 1200 °C. Shifting in Tc to higher temperature could be related to enhanced tetragonality, which was further confirmed by X-ray diffraction analysis. All these improvements evidences that there is less Pb loss in case of modified sintering profile.

Effects of PbO-B2O3 Glass Doping on the Sintering Temperature and Piezoelectric Properties of 0.35Pb (Ni1/3Nb2/3)O3-0.65Pb(Zr0.41Ti0.59)O3 Ceramics

NASA Astrophysics Data System (ADS)

Yi, Jinqiao; Shen, Meng; Liu, Sisi; Jiang, Shenglin

2015-12-01

0.35Pb(Ni1/3Nb2/3)O3-0.65Pb(Zr0.41Ti0.59)O3 (PNN-PZT) ceramics doped with 0.5PbO-0.5B2O3 glass have been synthesized by the conventional solid-state sintering technique. The effects of 0.5PbO-0.5B2O3 glass on the sintering temperature and piezoelectric properties of PNN-PZT ceramics were studied. The results indicated that the sintering temperature of PNN-PZT was significantly reduced due to the incorporation of 0.5PbO-0.5B2O3 glass dopant. When the content of 0.5PbO-0.5B2O3 glass was 0.5 wt.%, the sintering temperature of PNN-PZT was observed to reduce from above 1200°C to 920°C while the samples maintained high density (7.91 g/cm3), excellent piezoelectric constant ( d 33 = 479 pC/N), large electromechanical coupling coefficient ( K p = 0.55), and relatively low electromechanical quality factor ( Q m = 79). Moreover, large dielectric constant ( ɛ 33 T / ɛ 0 = 2904) and low dielectric loss (tan δ = 0.0166) were obtained in this work.

Characteristics of B2O3 and Fe added into BaFe12O19 permanent magnets prepared at different milling time and sintering temperature

NASA Astrophysics Data System (ADS)

Sebayang, Perdamean; Sari, Ayu Yuswita; Ginting, Delovita; Allan, Yola; Nasruddin M., N.; Sebayang, Kerista

2016-02-01

The objective of present work is to investigate the characteristic of BaFe12O19, B2O3-BaFe12O19 and Fe-BaFe12O19 magnets fabricated at different milling time and sintering temperature. The characteristic of perrmanen magnet BaFe12O19 with different content of B2O3 and Fe which was fabricated at different milling time and sintering temperature were investigated. The powder mixtures were prepared by dry and wet milling at various milling time. The powder were mixtured and prepared by dry and wet milling at various milling time. The mixture powder was then compacted by anisotropic with compressive pressure of 50 N/cm2. The green bodies were sinter at 1050, 1100, 1150 and 1200°C and hold for 1 h, separately. The density, magnetic flux density and B-H curve were measured by Archimedes principle, Gauss meter and Permagraph, respectively. The microstructure and phase composition characterization were performed by SEM and XRD. The results of this study are presented in this paper. It shows that addition of Fe (in wet milling) and B2O3 (in dry milling) respectively give a potential benefit to reduce the sintering temperature and improve the magnetic flux density of barium hexaferrite.

Development of Al2O3 electrospun fibers prepared by conventional sintering method or plasma assisted surface calcination

NASA Astrophysics Data System (ADS)

Mudra, E.; Streckova, M.; Pavlinak, D.; Medvecka, V.; Kovacik, D.; Kovalcikova, A.; Zubko, P.; Girman, V.; Dankova, Z.; Koval, V.; Duzsa, J.

2017-09-01

In this paper, the electrospinning method was used for preparation of α-Al2O3 microfibers from PAN/Al(NO3)3 precursor solution. The precursor fibers were thermally treated by conventional method in furnace or low-temperature plasma induced surface sintering method in ambient air. The four different temperatures of PAN/Al(NO3)3 precursors were chosen for formation of α-Al2O3 phase by conventional sintering way according to the transition features observed in the TG/DSC analysis. In comparison, the low-temperature plasma treatment at atmospheric pressure was used as an alternative sintering method at the exposure times of 5, 10 and 30 min. FTIR analysis was used for evaluation of residual polymer after plasma induced calcination and for studying the mechanism of polymer degradation. The polycrystalline alumina fibers arranged with the nanoparticles was created continuously throughout the whole volume of the sample. On the other side the low temperature approach, high density of reactive species and high power density of plasma generated at atmospheric pressure by used plasma source allowed rapid removal of polymer in preference from the surface of fibers leading to the formation of composite ceramic/polymer fibers. This plasma induced sintering of PAN/Al(NO3)3 can have obvious importance in industrial applications where the ceramic character of surface with higher toughness of the fibers are required.

Co-melting technology in resource recycling of sludge derived from stone processing.

PubMed

Hu, Shao-Hua; Hu, Shen-Chih; Fu, Yen-Pei

2012-12-01

Stone processing sludge (SPS) is a by-product of stone-processing wastewater treatment; it is suitable for use as a raw material for making artificial lightweight aggregates (ALWAs). In this study, boric acid was utilized as a flux to lower sintering temperature. The formation of the viscous glassy phase was observed by DTA curve and changes in XRD patterns. Experiments were conducted to find the optimal combination of sintering temperature, sintering time, and boric acid dosage to produce an ALWA of favorable characteristics in terms of water absorption, bulk density, apparent porosity, compressive strength and weight loss to satisfy Taiwan's regulatory requirements for construction and insulation materials. Optimal results gave a sintering temperature of 850 degrees C for 15 min at a boric acid dosage of 15% by weight of SPS. Results for ALWA favorable characteristics were: 0.21% (water absorption), 0.35% (apparent porosity), 1.67 g/cm3 (bulk density), 66.94 MPa (compressive strength), and less than 0.1% (weight loss).

Co-melting technology in resource recycling of sludge derived from stone processing.

PubMed

Hu, Shao-Hua; Hu, Shen-Chih; Fu, Yen-Pei

2012-12-01

Stone processing sludge (SPS) is a by-product of stone-processing wastewater treatment; it is suitable for use as a raw material for making artificial lightweight aggregates (ALWAs). In this study, boric acid was utilized as a flux to lower sintering temperature. The formation of the viscous glassy phase was observed by DTA curve and changes in XRD patterns. Experiments were conducted to find the optimal combination of sintering temperature, sintering time, and boric acid dosage to produce an ALWA of favorable characteristics in terms of water absorption, bulk density, apparent porosity, compressive strength and weight loss to satisfy Taiwan's regulatory requirements for construction and insulation materials. Optimal results gave a sintering temperature of 850 °C for 15 min at a boric acid dosage of 15 % by weight of SPS. Results for ALWA favorable characteristics were: 0.21 % (water absorption), 0.35 %(apparent porosity), 1.67 g/cm3 (bulk density), 66.94 MPa (compressive strength), and less than 0.1% (weight loss). [Box: see text].

Mechanical strength and thermophysical properties of PM212: A high temperature self-lubricating powder metallurgy composite

NASA Technical Reports Server (NTRS)

Edwards, Phillip M.; Sliney, Harold E.; Dellacorte, Christopher; Whittenberger, J. Daniel; Martineau, Robert R.

1990-01-01

A powder metallurgy composite, PM212, composed of metal bonded chromium carbide and solid lubricants is shown to be self-lubricating to a maximum application temperature of 900 C. The high temperature compressive strength, tensile strength, thermal expansion and thermal conductivity data needed to design PM212 sliding contact bearings and seals are reported for sintered and isostatically pressed (HIPed) versions of PM212. Other properties presented are room temperature density, hardness, and elastic modulus. In general, both versions appear to have adequate strength to be considered as sliding contact bearing materials, but the HIPed version, which is fully dense, is much stronger than the sintered version which contains about 20 percent pore volume. The sintered material is less costly to make, but the HIPed version is better where high compressive strength is important.

Silver Oxalate Ink with Low Sintering Temperature and Good Electrical Property

NASA Astrophysics Data System (ADS)

Yang, Wendong; Wang, Changhai; Arrighi, Valeria

2018-02-01

Favorable conductivity at low temperature is desirable for flexible electronics technology, where formulation of a suitable ink material is very critical. In this paper, a type of silver organic decomposable ink (10 wt.% silver content) was formulated by using as-prepared silver oxalate and butylamine, producing silver films with good uniformity and conductivity on a polyimide substrate after sintering below 130°C (15.72 μΩ cm) and even at 100°C (36.29 μΩ cm). Silver oxalate powder with good properties and an appropriate solid amine complex with lower decomposition temperature were synthesized, both differing from those reported in the literature. The influence of the factors on the electrical properties of the produced silver films such as sintering temperature and time was studied in detail and the relationship between them was demonstrated.

Ammonia formation caused by the presence of water in the wet grinding of silicon nitride powder

NASA Technical Reports Server (NTRS)

Kanno, Y.; Suzuki, K.; Kuwahara, Y.

1984-01-01

Si3 N4 powder (amorphous, alpha-, and beta-Si3 N4) was mixed with MeOH containing 8.87 mol. % H2O and ground. The NH3 generation rapidly increased after a grinding time of 100 hours. Silicon nitride sintered material was chosen as one of the high temperature, high strength structural materials and studies of the control of the raw material powder, preparation of the sintered body (finding the right assistant, hot press, high pressure sintering, fracture toughness and oxidation at high temperature were performed.

Effect of Bi doping on morphotropic phase boundary and dielectric properties of PZT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Joshi, Shraddha; Acharya, Smita, E-mail: saha275@yahoo.com

2016-05-23

In our present attempt, Pb{sub (1-x)}Bi{sub x}Zr{sub 0.52}Ti{sub 0.48}O{sub 3} [PBZT] {where x = 0, 0.05, 0.1} is synthesized by sol-gel route. Effect of Bi addition on structure, sinterability and dielectric properties are observed. The presence of morphotropic phase boundary (coexistence of tetragonal and rhombohedral symmetry) is confirmed by X-ray diffraction. Enhancement of sinterability after Bi doping is observed through a systematic sintering program. Frequency and temperature dependent dielectric constant are studied. Bi doping in PZT is found to enhance room temperature dielectric constant. However, at high temperature the dielectric constant of pure PZT is more than that of dopedmore » PZT.« less

Sintering effects on dielectric properties of Zn-doped CaCu3Ti4O12 ceramic synthesized by modified sol-gel route

NASA Astrophysics Data System (ADS)

Singh, Laxman; Rai, U. S.; Rai, Alok Kumar; Mandal, K. D.

2013-01-01

CaCu2.90Zn0.10Ti4O12 ceramic was synthesized by a novel semi-wet route and calcined at 800°C in air for 8 h. The obtained powder was divided into three parts and sintered in air at 950°C for 6 h, 8 h, and 12 h, separately. XRD results confirmed the single phase formation of all the sintered samples with similar cubic structure of CaCu3Ti4O12 (CCTO). Scanning electron micrographs of the CaCu2.9Zn0.1Ti4O12 ceramic sintered for 6 h shows bimodal grain size distribution. Increasing the sintering time significantly promotes the grain growth and microstructural densification. The sintering duration was found to have tremendous influence on microstructure and dielectric properties of CaCu2.90Zn0.10Ti4O12 ceramic. The CaCu2.9Zn0.1Ti4O12 ceramic sintered for 12 h exhibited high dielectric constant ɛ r ˜ 5971 at 1 kHz and room temperature. It is found that ɛ r is independent at high frequency and weakly dependent on temperature.

Recent Trends in Newly Developed Plasma-Sprayed and Sintered Coatings for Implant Applications

NASA Astrophysics Data System (ADS)

Bsat, Suzan; Speirs, Andrew; Huang, Xiao

2016-08-01

The current paper aims to review recent trends (2011 to 2015) in newly developed plasma-sprayed and sintered coatings for implant applications. Recent developments in plasma-sprayed and sintered coatings have focused on improving biological performance, bacterial growth resistance, and mechanical properties, predominantly of HA and glass ceramics. The majority of these improvements are attributed to the addition of dopants. To improve biological performance, trace elements, such as Zn and Mg, both of which are found in bone, were added to replicate the functions they provide for the skeletal system. Though bacterial growth resistance is traditionally improved by Ag dopant, the addition of new dopants such as CeO2 and Zn were explored as well. Great effort has also been made to improve coating adherence and reduce stresses by minimizing coefficient of thermal expansion mismatch between the coating and substrate through the addition of elements such as Zn and Mg or the inclusion of a buffer layer. For sintering process in particular, there was an emphasis on reducing sintering temperature through modification of 45S5 Bioglass. New plasma spray and sintering technologies aimed at reducing high-temperature exposure are briefly introduced as well. These include microplasma spray and spark plasma sintering.

Mechanical behaviour of pressed and sintered titanium alloys obtained from prealloyed and blended elemental powders.

PubMed

Bolzoni, L; Esteban, P G; Ruiz-Navas, E M; Gordo, E

2012-10-01

The applicability of irregular prealloyed Ti-6Al-4V powder for the fabrication of titanium products by pressing and sintering and its employment as a master alloy to obtain the Ti-3Al-2.5V alloy was studied. To this end, the starting powders were characterised by dilatometry, differential thermal analysis and XRD. Green samples were obtained by cold uniaxial pressing, and the evolution of the microstructure over the sintering temperature range 900-1400°C was studied. The variation of the final density and mechanical properties with the sintering temperature was considered. Based on the study carried out, it can be stated that more reliable powders are needed to open the titanium market to new applications. A relative density of 95% and diverse microstructural features and mechanical properties equivalent to those of biomedical devices can be obtained by the pressing and sintering route. Copyright © 2012 Elsevier Ltd. All rights reserved.

Lower sintering temperature of nanostructured dense ceramics compacted from dry nanopowders using powerful ultrasonic action

NASA Astrophysics Data System (ADS)

Khasanov, O.; Reichel, U.; Dvilis, E.; Khasanov, A.

2011-10-01

Nanostructured high dense zirconia ceramics have been sintered from dry nanopowders compacted by uniaxial pressing with simultaneous powerful ultrasonic action (PUA). Powerful ultrasound with frequency of 21 kHz was supplied from ultrasonic generator to the mold, which was the ultrasonic wave-guide. Previously the mold was filled by non-agglomerated zirconia nanopowder having average particle size of 40 nm. Any binders or plasticizers were excluded at nanopowder processing. Compaction pressure was 240 MPa, power of ultrasonic generator at PUA was 1 kW and 3 kW. The fully dense zirconia ceramics has been sintered at 1345°C and high-dense ceramics with a density of 99.1%, the most grains of which had the sizes Dgr <= 200 nm, has been sintered at low sintering temperature (1325°C). Applied approach prevents essential grain growth owing to uniform packing of nanoparticles under vibrating PU-action at pressing, which provides the friction forces control during dry nanopowder compaction without contaminating binders or plasticizers.

Effects of High-Pressure High-Temperature Sintering on the Band Gap and Thermoelectric Properties of PbSe

NASA Astrophysics Data System (ADS)

Chen, Bo; Li, Yi; Sun, Zhen-Ya

2018-06-01

In this study, PbSe bulk samples were prepared by a high-pressure high-temperature (HPHT) sintering technique, and the phase compositions, band gaps and thermoelectric properties of the samples were systematically investigated. The sintering pressure exerts a significant influence on the preferential orientation, band gap and thermoelectric properties of PbSe. With increasing pressure, the preferential orientation decreases, mainly due to the decreased crystallinity, while the band gap first decreases and then increases. The electrical conductivity and power factor decrease gradually with increasing pressure, mainly attributed to the decreased carrier concentration and mobility. Consequently, the sample prepared by 2 GPa shows the highest thermoelectric figure-of-merit, ZT, of 0.55 at ˜ 475 K. The ZT of the HPHT-sintered PbSe could be further improved by properly doping or optimizing the HPHT parameters. This study further demonstrates that the sintering pressure could be another degree of freedom to manipulate the band structure and thermoelectric properties of materials.

An application of powder metallurgy to dentistry.

PubMed

Oda, Y; Ueno, S; Kudoh, Y

1995-11-01

Generally, the dental casting method is used to fabricate dental prostheses made with metal. The method of fabricating dental prostheses from sintered titanium alloy has certain advantages: the elimination of casting defects, a sintering temperature that is lower than the melting point, and a shorter processing time. By examining (1) the properties of green, sintered compacts of titanium powder, (2) the effects of adding aluminum powder on the properties of green, sintered compacts of Ti-Al compound, and (3) the effects of adding copper powder on the properties of green, sintered compacts of Ti-Al-Cu compound, the authors developed a sintered titanium alloy on a trial basis. Because the properties satisfied the requirements of dental restorations, a powder metallurgical method of making dental restorations from this sintered titanium alloy was devised. Applications of such sintered titanium alloys for the metal coping of metal-ceramic crowns and denture base plates were discussed.

Structural comparison of sintering products made of "TiC + Ti" composite powders and "Ti + C" powder mixtures

NASA Astrophysics Data System (ADS)

Krinitcyn, Maksim G.; Pribytkov, Gennadii A.; Korosteleva, Elena N.; Firsina, Irina A.; Baranovskii, Anton V.

2017-12-01

In this study, powder composite materials comprised of TiC and Ti with different ratios are processed by sintering of Ti and C powder mixtures and self-propagating high-temperature synthesis (SHS) in "Ti+C" system followed by sintering. The microstructure and porosity of obtained composites are investigated and discussed. The dependence of porosity on sintering time is explained theoretically. Optimal regimes that enable to obtain the most homogeneous structure with the least porosity are described.

Fabrication of turbine components and properties of sintered silicon nitride

NASA Technical Reports Server (NTRS)

Neil, J. T.; French, K. W.; Quackenbush, C. L.; Smith, J. T.

1982-01-01

This paper presents a status report on the injection molding of sinterable silicon nitride at GTE Laboratories. The effort involves fabrication of single axial turbine blades and monolithic radial turbine rotors. The injection molding process is reviewed and the fabrication of the turbine components discussed. Oxidation resistance and strength results of current injection molded sintered silicon nitride as well as dimensional checks on sintered turbine blades demonstrate that this material is a viable candidate for high temperature structural applications.

Thermal barrier coating resistant to sintering

DOEpatents

Subramanian, Ramesh; Sabol, Stephen M.

2001-01-01

A device (10) having a ceramic thermal barrier coating layer (16) characterized by a microstructure having gaps (18) with a sintering inhibiting material (22) disposed on the columns (20) within the gaps (18). The sintering resistant material (22) is stable over the range of operating temperatures of the device (10) and is not soluble with the underlying ceramic layer (16). For a YSZ ceramic layer (16) the sintering resistant layer (22) may preferably be aluminum oxide or yttrium aluminum oxide, deposited as a continuous layer or as nodules.

Monoclinic β-Li2TiO3 nanocrystalline particles employing novel urea assisted solid state route: Synthesis, characterization and sintering behavior

NASA Astrophysics Data System (ADS)

Tripathi, Biranchi M.; Mohanty, Trupti; Prakash, Deep; Tyagi, A. K.; Sinha, P. K.

2017-07-01

Pure phase monoclinic nano-crystalline Li2TiO3 powder was synthesized by a novel urea assisted solid state synthesis method using readily available and economical precursors. A single phase and well crystalline Li2TiO3 powder has been obtained at slightly lower temperature (600-700 °C) and shorter duration (2 h) as compared to the conventional solid state method. The proposed method has significant advantages in comparison to other viable methods mainly in terms of phase purity, powder properties and sinterability. Analysis of chemical composition using inductively coupled plasma atomic emission spectroscopy (ICP-AES) shows no loss of lithium from Li2TiO3 in the proposed method. The emergence of monoclinic Li2TiO3 phase was confirmed by X-ray diffraction (XRD) pattern of as-synthesized powder. The crystallite size of Li2TiO3 powder was calculated to be in the range of 15-80 nm, which varied as a function of urea composition and temperature. The morphology of as-prepared Li2TiO3 powders was examined by scanning electron microscope (SEM). The effect of urea composition on phase and morphology was investigated so as to delineate the role of urea. Upon sintering at < 1000 °C temperature, the Li2TiO3 powder compact attained about 98% of the theoretical density with fine grained (grain size: 2-3 μm) microstructure. It indicates excellent sinter-ability of Li2TiO3 powder synthesized by the proposed method. The fine grained structure is desirable for better tritium breeding performance of Li2TiO3. Electrochemical impedance spectroscopy at variable temperature showed good electrical properties of Li2TiO3. The proposed method is simple, anticipated to be cost effective and convenient to realise for large scale production of phase pure nanocrystalline and having significantly enhanced sinter-ability Li2TiO3 powder.

Mechanisms and mechanics of shape loss during supersolidus liquid-phase sintering

NASA Astrophysics Data System (ADS)

Lal, Anand

Rapid sinter densification of relatively coarse prealloyed powders is possible by exceeding the solidus temperature in an approach termed supersolidus liquid phase sintering (SLPS). However, narrow processing windows for densification without distortion often limit this process. The liquid films at the grain boundaries that are responsible for densification also reduce the structural rigidity of components. Hence, components tend to slump under their own weight. Thus, the present study investigates shape loss during SLPS and rationalizes the processing and material factors with regard to separating densification from distortion. Experiments are performed on various prealloyed powders, including bronze, 316L stainless steel, and T15 tool steel. Differential thermal analysis, dilatometry, and in situ video imaging of sintering compacts are used to follow melting, densification, and distortion, respectively. Further, density and dimensional measurements are performed on sintered compacts. Results indicate a dependence of distortion on the sintering temperature and time, compact size, and melting behavior of the alloy. It is shown that the sintering temperature window, where high-density, precise components are obtained, can be widened for 316L stainless steel by boron addition. For the first time, a beam bending technique is used to measure the macroscopic apparent viscosity of semisolid bronze. The viscosity drops with temperature above the solidus and lies in the range of 108 to 106 Pa-s. Additionally, the in situ transverse rupture strength of bronze is measured to demonstrate the softening above the solidus temperature. Further, microstructural measurements are performed to enable correlation with the slumping behavior and viscosity. A model combining the deformation mechanisms, driving forces, and microstructural characteristics is developed to predict the conditions for densification and distortion onset. The microstructure is also correlated with the magnitude of shape loss and viscosity of a semisolid aggregate. A mechanistic model, based on the semisolid rheological characteristics, is developed to predict the magnitude and nature of shape loss. The model shows good correlation with experimental data for bronze. This study offers critical insight into SLPS and provides processing strategies for fabrication of high-density components without shape loss.

Effect of sintering temperature variations on fabrication of 45S5 bioactive glass-ceramics using rice husk as a source for silica.

PubMed

Leenakul, Wilaiwan; Tunkasiri, Tawee; Tongsiri, Natee; Pengpat, Kamonpan; Ruangsuriya, Jetsada

2016-04-01

45S5 bioactive glass is a highly bioactive substance that has the ability to promote stem cell differentiation into osteoblasts--the cells that create bone matrix. The aim of this work is to analyze physical and mechanical properties of 45S5 bioactive glass fabricated by using rice husk ash as its silica source. The 45S5 bioactive glass was prepared by melting the batch at 1300 °C for 3h. The samples were sintered at different temperatures ranging from 900 to 1050 °C with a fixed dwell-time of 2h. The phase transitions, density, porosity and microhardness values were investigated and reported. DTA analysis was used to examine the crystallization temperatures of the glasses prepared. We found that the sintering temperature had a significant effect on the mechanical and physical properties of the bioactive glass. The XRD showed that when the sintering temperature was above 650 °C, crystallization occurred and bioactive glass-ceramics with Na2Ca2Si3O9, Na2Ca4(PO4)2SiO4 and Ca3Si2O7 were formed. The optimum sintering temperature resulting in maximum mechanical values was around 1050 °C, with a high density of 2.27 g/cm(3), 16.96% porosity and the vicker microhardness value of 364HV. Additionally, in vitro assay was used to examine biological activities in stimulated body fluid (SBF). After incubation in SBF for 7 days, all of the samples showed formations of apatite layers indicating that the 45S5 bioactive glasses using rice husk as a raw material were also bioactive. Copyright © 2015 Elsevier B.V. All rights reserved.

Vacuum-sintered body of a novel apatite for artificial bone

NASA Astrophysics Data System (ADS)

Tamura, Kenichi; Fujita, Tatsushi; Morisaki, Yuriko

2013-12-01

We produced regenerative artificial bone material and bone parts using vacuum-sintered bodies of a novel apatite called "Titanium medical apatite (TMA®)" for biomedical applications. TMA was formed by chemically connecting a Ti oxide molecule with the reactive [Ca10(PO4)6] group of Hydroxyapatite (HAp). The TMA powders were kneaded with distilled water, and solid cylinders of compacted TMA were made by compression molding at 10 MPa using a stainless-steel vessel. The TMA compacts were dried and then sintered in vacuum (about 10-3 Pa) or in air using a resistance heating furnace in the temperature range 1073-1773 K. TMA compacts were sintered at temperatures greater than 1073 K, thus resulting in recrystallization. The TMA compact bodies sintered in the range 1273-1773 K were converted into mixtures composed of three crystalline materials: α-TCP (tricalcium phosphate), β-TCP, and Perovskite-CaTiO3. The Perovskite crystals were stable and hard. In vacuum-sintering, the Perovskite crystals were transformed into fibers (approximately 1 µm in diameter × 8 µm in length), and the fiber distribution was uniform in various directions. We refer to the TMA vacuum-sintered bodies as a "reinforced composite material with Perovskite crystal fibers." However, in atmospheric sintering, the Perovskite crystals were of various sizes and were irregularly distributed as a result of the effect of oxygen. After sintering temperature at 1573 K, the following results were obtained: the obtained TMA vacuum-sintered bodies (1) were white, (2) had a density of approximately 2300 kg/m3 (corresponding to that of a compact bone or a tooth), and had a thermal conductivity of approximately 31.3 W/(m·K) (corresponding to those of metal or ceramic implants). Further, it was possible to cut the TMA bodies into various forms with a cutting machine. An implant made of TMA and inserted into a rabbit jaw bone was covered by new bone tissues after just one month because of the high biocompatibility of the TMA implant. TMA vacuum-sintered bodies are promising biomaterials for use as artificial bone materials to regenerate bone parts and produce bone reinforcement structures that are used for bone junctions in dental and orthopedic surgery.

Sintering of Lunar and Simulant Glass

NASA Technical Reports Server (NTRS)

Cooper, Bonnie L.

2007-01-01

Most oxygen-extraction techniques are temperature-dependent, with higher temperatures resulting in higher oxygen yield. An example is hydrogen reduction, in which the optimum process temperature is 1050 C. However, glass-rich lunar soil begins to show the effects of sintering at temperatures of 900 C or lower. Sintering welds particles together due to viscous relaxation of the glass in the sample. One approach to avoid problems related to sintering, such as difficulty in removing waste material from the reactor, is to keep the soil in motion. One of several methods being studied to accomplish this is fluidized-bed processing techniques, in which the grains are kept in motion by the action of flowing reductant gas. The spent material can be removed from the chamber while still fluidized, or the fluidizing motion can continue until the material has cooled below approx. 500 C. Until end-to-end prototypes are built that can remove the heated soil, the most practical option is to keep the bed fluidized while cooling the waste material. As ISRU technology advances, another option will become valuable, which is to intentionally sinter the material to a great enough extent that it becomes a brick. The free iron in lunar soil is magnetic, and ferromagnetic bricks can be manipulated by robotic systems using electromagnetic end effectors. Finally, if an electromagnetic field is applied to the soil while the brick is being formed, the brick itself will become a magnet. This property can be used to create self-aligning bricks or other building materials that do not require fasteners. Although sintering creates a challenge for early lunar surface systems, knowledge gained during prototype development will be valuable for the advanced lunar outpost.

Microwave processed NiMg ferrite: Studies on structural and magnetic properties

NASA Astrophysics Data System (ADS)

Chandra Babu Naidu, K.; Madhuri, W.

2016-12-01

Ferrites are magnetic semiconductors realizing an important role in electrical and electronic circuits where electrical and magnetic property coupling is required. Though ferrite materials are known for a long time, there is a large scope in the improvement of their properties (vice sintering and frequency dependence of electrical and magnetic properties) with the current technological trends. Forth coming technology is aimed at miniaturization and smart gadgets, electrical components like inductors and transformers cannot be included in integrated circuits. These components are incorporated into the circuit as surface mount devices whose fabrication involves low temperature co-firing of ceramics and microwave monolithic integrated circuits technologies. These technologies demand low temperature sinter-ability of ferrites. This article presents low temperature microwave sintered Ni-Mg ferrites of general chemical formula Ni1-xMgxFe2O4 (x=0, 0.2, 0.4, 0.5, 0.6, 0.8, 1) for potential applications as transformer core materials. The series of ferrites are characterized using X-ray diffractometer, scanning electron microscopy, Fourier transform infrared and vibrating sample magnetometer for investigating structural, morphological and magnetic properties respectively. The initial permeability is studied with magnesium content, temperature and frequency in the temperature range of 308 K-873 K and 42 Hz-5 MHz.

Relating adatom emission to improved durability of Pt-Pd diesel oxidation catalysts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johns, Tyne Richele; Goeke, Ronald S.; Ashbacher, Valerie

Sintering of nanoparticles is an important contributor to loss of activity in heterogeneous catalysts, such as those used for controlling harmful emissions from automobiles. But mechanistic details, such as the rates of atom emission or the nature of the mobile species, remain poorly understood. Herein we report a novel approach that allows direct measurement of atom emission from nanoparticles. We use model catalyst samples and a novel reactor that allows the same region of the sample to be observed after short-term heat treatments (seconds) under conditions relevant to diesel oxidation catalysts (DOCs). Monometallic Pd is very stable and does notmore » sinter when heated in air (T ≤ 800 °C). Pt sinters readily in air, and at high temperatures (≥800 °C) mobile Pt species emitted to the vapor phase cause the formation of large, faceted particles. In Pt–Pd nanoparticles, Pd slows the rate of emission of atoms to the vapor phase due to the formation of an alloy. However, the role of Pd in Pt DOCs in air is quite complex: at low temperatures, Pt enhances the rate of Pd sintering (which otherwise would be stable as an oxide), while at higher temperature Pd helps to slow the rate of Pt sintering. DFT calculations show that the barrier for atom emission to the vapor phase is much greater than the barrier for emitting atoms to the support. Thus, vapor-phase transport becomes significant only at high temperatures while diffusion of adatoms on the support dominates at lower temperatures.« less

Relating adatom emission to improved durability of Pt-Pd diesel oxidation catalysts

DOE PAGES

Johns, Tyne Richele; Goeke, Ronald S.; Ashbacher, Valerie; ...

2015-06-05

Sintering of nanoparticles is an important contributor to loss of activity in heterogeneous catalysts, such as those used for controlling harmful emissions from automobiles. But mechanistic details, such as the rates of atom emission or the nature of the mobile species, remain poorly understood. Herein we report a novel approach that allows direct measurement of atom emission from nanoparticles. We use model catalyst samples and a novel reactor that allows the same region of the sample to be observed after short-term heat treatments (seconds) under conditions relevant to diesel oxidation catalysts (DOCs). Monometallic Pd is very stable and does notmore » sinter when heated in air (T ≤ 800 °C). Pt sinters readily in air, and at high temperatures (≥800 °C) mobile Pt species emitted to the vapor phase cause the formation of large, faceted particles. In Pt–Pd nanoparticles, Pd slows the rate of emission of atoms to the vapor phase due to the formation of an alloy. However, the role of Pd in Pt DOCs in air is quite complex: at low temperatures, Pt enhances the rate of Pd sintering (which otherwise would be stable as an oxide), while at higher temperature Pd helps to slow the rate of Pt sintering. DFT calculations show that the barrier for atom emission to the vapor phase is much greater than the barrier for emitting atoms to the support. Thus, vapor-phase transport becomes significant only at high temperatures while diffusion of adatoms on the support dominates at lower temperatures.« less

Ceramic synthesis of 0.08BiGaO3-0.90BaTiO3-0.02LiNbO3 under high pressure and high temperature

NASA Astrophysics Data System (ADS)

Hui, Jin; Yong, Li; Mou-Sheng, Song; Lin, Chen; Xiao-Peng, Jia; Hong-An, Ma

2016-07-01

In this paper, the preparation of 0.08BiGaO3-0.90BaTiO3-0.02LiNbO3 is investigated at pressure 3.8 GPa and temperature 1100-1200 °C. Experimental results indicate that not only is the sintered rate more effective, but also the sintered temperature is lower under high pressure and high temperature than those of under normal pressure. It is thought that the adscititious pressure plays the key role in this process, which is discussed in detail. The composition and the structure of the as-prepared samples are recorded by XRD patterns. The result shows that the phases of BaTiO3, BaBiO2.77, and Ba2Bi4Ti5O18 with piezoelectric ceramic performance generate in the sintered samples. Furthermore, the surface morphology characteristics of the typical samples are also investigated using a scanning electron microscope. It indicates that the grain size and surface structure of the samples are closely related to the sintering temperature and sintering time. It is hoped that this study can provide a new train of thought for the preparation of lead-free piezoelectric ceramics with excellent performance. Project supported by the National Natural Science Foundation of China (Grant No. 51172089), the Natural Science Foundation of Education Department of Guizhou Province, China (Grant Nos. KY [2013]183 and LH [2015]7232), and the Research Fund for the Doctoral Program of Tongren University, China (Grant No. DS1302).

Microstructures and Properties of W-Ti Alloys Prepared Under Different Cooling Conditions

NASA Astrophysics Data System (ADS)

Dai, Weili; Liang, Shuhua; Yang, Qing; Zou, Juntao; Zhuo, Longchao

2016-07-01

W-(10 to 15) wt.% Ti alloys were sintered at 1400 or 1500 °C and cooled under different cooling conditions. The microstructures and properties of W-Ti alloys were affected by the cooling conditions. XRD, SEM, EBSD, and TEM were carried out to investigate the effects of cooling conditions and sintering temperature on the microstructures of W-Ti alloys. The nanohardness and elastic modulus of the alloys were also investigated. The results showed that when the temperature was 1500 °C, the content of Ti-rich phase in W-(10 to 15) wt.% Ti alloys decreased obviously with the increase of cooling rate (the average cooling rate of furnace cooling, air cooling and water cooling was 0.2, 10, and 280 °C/s, respectively). For the W-10 wt.% Ti alloy, the content decreased from 20.5 to 9.7%, and the grain size decreased from 2.33 to 0.67 μm. When the temperature decreased to 1400 °C, the grain size was also decreased sharply with the increase of cooling rate, but there was a little change in the microstructure. Meanwhile, the grain sizes were smaller than those of the alloys sintered at 1500 °C. The nanohardness and elastic modulus increased with the increase of cooling rate, and the alloys sintered at different temperatures had different nanohardness and elastic modulus which depended on the cooling conditions. Sintering at a proper temperature and then cooling at a certain cooling condition was a useful method to fabricate alloy with less Ti-rich phase and high properties.

Preparation and flash sintering of MgTiO3 nanopowders obtained by the polyacrylamide gel method

NASA Astrophysics Data System (ADS)

Su, Xinghua; Bai, Ge; Zhang, Jing; Zhou, Jie; Jia, Yongjie

2018-06-01

Using a polyacrylamide gel method, phase pure and well-dispersed MgTiO3 nanopowders were prepared at 800 °C for 2 h. It was found that a high mole ratio of monomers to precursors resulted in low formation temperature of MgTiO3, due to the highly mixing homogeneity and smaller particle sizes of precursors. Sintering behaviors of MgTiO3 nanopowders under DC electric field from 500 to 800 V/cm were investigated. Nearly full dense MgTiO3 ceramics can be prepared in 30 s. An abrupt and simultaneous increase in current density and power dissipation were observed in sintering process, which are characteristics of flash sintering. The power dissipation for the flash sintering was found to be 82 mW/mm3. The densities and average grain sizes of samples increase with the increase of the electrical field strength. It was suggested that Joule heating was the main mechanism of flash sintering of MgTiO3 ceramics. Our work provides a useful route for the fabrication of dense MgTiO3 ceramics at low temperature in short time.

Microwave sintering of nanopowder ZnNb2O6: Densification, microstructure and microwave dielectric properties

NASA Astrophysics Data System (ADS)

Bafrooei, H. Barzegar; Nassaj, E. Taheri; Hu, C. F.; Huang, Q.; Ebadzadeh, T.

2014-12-01

High density ZnNb2O6 ceramics were successfully fabricated by microwave sintering of ZnO-Nb2O5 and ZnNb2O6 nanopowders. Phase formation, microstructure and microwave electrical properties of the microwave sintered (MS) and microwave reaction sintered (MRS) specimens were examined using X-ray diffraction, field emission scanning electron microscopy and microwave dielectric properties measurement. Specimens were sintered in a temperature range from 950 to 1075 °C for 30 min at an interval of 25 °C using a microwave furnace operated at 2.45 GHz frequency, 3 kW power. XRD pattern revealed the formation of pure columbite phase of ZnNb2O6. The SEM micrographs show grain growth and reduction in porosity of specimens with the increase in sintering temperature. Good combination of microwave dielectric properties (εr~23.6, Qf~64,300 GHz and τf~-66 ppm/°C and εr~24, Qf~75,800 GHz and τf~-64 ppm/°C) was obtained for MS- and MRS-prepared samples at 1000 °C and 1050 °C for 30 min, respectively.

The physical chemistry and materials science behind sinter-resistant catalysts.

PubMed

Dai, Yunqian; Lu, Ping; Cao, Zhenming; Campbell, Charles T; Xia, Younan

2018-06-18

Catalyst sintering, a main cause of the loss of catalytic activity and/or selectivity at high reaction temperatures, is a major concern and grand challenge in the general area of heterogeneous catalysis. Although all heterogeneous catalysts are inevitably subjected to sintering during their operation, the immediate and drastic consequences can be mitigated by carefully engineering the catalytic particles and their interactions with the supports. In this tutorial review, we highlight recent progress in understanding the physical chemistry and materials science involved in sintering, including the discussion of advanced techniques, such as in situ microscopy and spectroscopy, for investigating the sintering process and its rate. We also discuss strategies for the design and rational fabrication of sinter-resistant catalysts. Finally, we showcase recent success in improving the thermal stability and thus sinter resistance of supported catalytic systems.

Lanthanide (Nd, Gd) compounds with garnet and monazite structures. Powders synthesis by "wet" chemistry to sintering ceramics by Spark Plasma Sintering

NASA Astrophysics Data System (ADS)

Potanina, Ekaterina; Golovkina, Ludmila; Orlova, Albina; Nokhrin, Aleksey; Boldin, Maksim; Sakharov, Nikita

2016-05-01

Complex oxide Y2.5Nd0.5Al5O12 with garnet structure and phosphates NdPO4 and GdPO4 with monazite structure were obtained by using precipitation methods. Ceramics Y2.5Nd0.5Al5O12 and NdPO4 were processed by Spark Plasma Sintering (SPS). Relative density more 98%, sintering time did not exceed 8 min, sintering temperature 1330-1390 °C. Leaching rates of elements from ceramics were 10-6-10-7 g/(cm2 d). The process of ceramics sintering has two-stage character: the first step of sintering-compaction process is related to the plastic flow of the material, the second step-to the process of grain boundary diffusion and grain growth.

Process for fabrication of large titanium diboride ceramic bodies

DOEpatents

Moorhead, Arthur J.; Bomar, E. S.; Becher, Paul F.

1989-01-01

A process for manufacturing large, fully dense, high purity TiB.sub.2 articles by pressing powders with a sintering aid at relatively low temperatures to reduce grain growth. The process requires stringent temperature and pressure applications in the hot-pressing step to ensure maximum removal of sintering aid and to avoid damage to the fabricated article or the die.

Al{sub 2}O{sub 3} - TiO{sub 2}-A simple sol-gel strategy to the synthesis of low temperature sintered alumina-aluminium titanate composites through a core-shell approach

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jayasankar, M.; Ananthakumar, S.; Mukundan, P.

A simple sol-gel based core-shell approach for the synthesis of alumina-aluminium titanate composite is reported. Alumina is the core and titania is the shell. The coating of titania has been performed in aqueous medium on alumina particle by means of heterocoagulation of titanyl chloride. Further heat treatment results in low temperature formation of aluminium titanate as well as low temperature sintering of alumina-aluminium titanate composites. The lowering of the reaction temperature can be attributed to the maximisation of the contact surface between the reactants due to the core-shell approach involving nanoparticles. The mechanism of formation of aluminium titanate and themore » observations on densification features in the present process are compared with that of mixture of oxides under identical conditions. The sintered alumina-aluminium titanate composite has an average grain size of 2 {mu}m. - Graphical abstract: The article presents a simple sol-gel process through core-shell approach to the synthesis of low temperature sintered alumina-aluminium titanate. The lowering of the reaction temperature can be attributed to the maximisation of the contact surface between the reactant due to the core-shell approach. This material showed the better microstructure control compared to the standard solid-state mixing route.« less

High-Pressure Spark Plasma Sintering (HP SPS): A Promising and Reliable Method for Preparing Ti-Al-Si Alloys.

PubMed

Knaislová, Anna; Novák, Pavel; Cygan, Sławomir; Jaworska, Lucyna; Cabibbo, Marcello

2017-04-27

Ti-Al-Si alloys are prospective material for high-temperature applications. Due to low density, good mechanical properties, and oxidation resistance, these intermetallic alloys can be used in the aerospace and automobile industries. Ti-Al-Si alloys were prepared by powder metallurgy using reactive sintering, milling, and spark plasma sintering. One of the novel SPS techniques is high-pressure spark plasma sintering (HP SPS), which was tested in this work and applied to a Ti-10Al-20Si intermetallic alloy using a pressure of 6 GPa and temperatures ranging from 1318 K (1045 °C) to 1597 K (1324 °C). The low-porosity consolidated samples consist of Ti₅Si₃ silicides in an aluminide (TiAl) matrix. The hardness varied between 720 and 892 HV 5.

High-Pressure Spark Plasma Sintering (HP SPS): A Promising and Reliable Method for Preparing Ti–Al–Si Alloys

PubMed Central

Knaislová, Anna; Novák, Pavel; Cygan, Sławomir; Jaworska, Lucyna; Cabibbo, Marcello

2017-01-01

Ti–Al–Si alloys are prospective material for high-temperature applications. Due to low density, good mechanical properties, and oxidation resistance, these intermetallic alloys can be used in the aerospace and automobile industries. Ti–Al–Si alloys were prepared by powder metallurgy using reactive sintering, milling, and spark plasma sintering. One of the novel SPS techniques is high-pressure spark plasma sintering (HP SPS), which was tested in this work and applied to a Ti–10Al–20Si intermetallic alloy using a pressure of 6 GPa and temperatures ranging from 1318 K (1045 °C) to 1597 K (1324 °C). The low-porosity consolidated samples consist of Ti5Si3 silicides in an aluminide (TiAl) matrix. The hardness varied between 720 and 892 HV 5. PMID:28772824

Sintering Characteristics of Multilayered Thermal Barrier Coatings Under Thermal Gradient and Isothermal High Temperature Annealing Conditions

NASA Technical Reports Server (NTRS)

Rai, Amarendra K.; Schmitt, Michael P.; Bhattacharya, Rabi; Zhu, Dongming; Wolfe, Douglas E.

2014-01-01

Pyrochlore oxides have most of the relevant attributes for use as next generation thermal barrier coatings such as phase stability, low sintering kinetics and low thermal conductivity. One of the issues with the pyrochlore oxides is their lower toughness and therefore higher erosion rate compared to the current state-of-the-art TBC material, yttria (6 to 8 wt%) stabilized zirconia (YSZ). In this work, sintering characteristics were investigated for novel multilayered coating consisted of alternating layers of pyrochlore oxide viz Gd2Zr2O7 and t' low k (rare earth oxide doped YSZ). Thermal gradient and isothermal high temperature (1316 C) annealing conditions were used to investigate sintering and cracking in these coatings. The results are then compared with that of relevant monolayered coatings and a baseline YSZ coating.

Controlled metal-semiconductor sintering/alloying by one-directional reverse illumination

DOEpatents

Sopori, Bhushan L.

1993-01-01

Metal strips deposited on a top surface of a semiconductor substrate are sintered at one temperature simultaneously with alloying a metal layer on the bottom surface at a second, higher temperature. This simultaneous sintering of metal strips and alloying a metal layer on opposite surfaces of the substrate at different temperatures is accomplished by directing infrared radiation through the top surface to the interface of the bottom surface with the metal layer where the radiation is absorbed to create a primary hot zone with a temperature high enough to melt and alloy the metal layer with the bottom surface of the substrate. Secondary heat effects, including heat conducted through the substrate from the primary hot zone and heat created by infrared radiation reflected from the metal layer to the metal strips, as well as heat created from some primary absorption by the metal strips, combine to create secondary hot zones at the interfaces of the metal strips with the top surface of the substrate. These secondary hot zones are not as hot as the primary hot zone, but they are hot enough to sinter the metal strips to the substrate.

Effect of sintering temperatures and screen printing types on TiO{sub 2} layers in DSSC applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Supriyanto, Agus; Furqoni, Lutfi; Nurosyid, Fahru, E-mail: nurosyid@yahoo.com

2016-03-29

Dye-Sensitized Solar Cell (DSSC) is a candidate solar cell, which has a big potential in the future due to its eco-friendly material. This research is conducted to study the effect of sintering temperature and the type of screen-printing toward the characteristics of TiO{sub 2} layer as a working electrode in DSSC. TiO{sub 2} layers were fabricated using a screen-printing method with a mesh size of T-49, T-55, and T-61. TiO{sub 2} layers were sintered at temperatures of 600°C and 650°C for 60 min. DSSC structure was composed of TiO{sub 2} as semiconductors, ruthenium complex as dyes, and carbon as counter electrodes.more » The morphology of TiO{sub 2} layer was observed by using Nikon E2 Digital Camera Microscopy. The efficiencies of DSSC were calculated from the I-V curves. The highest efficiency is 0.015% at TiO{sub 2} layer fabricated with screen type T-61 and at a sintering temperature of 650°C.« less

Evaluation and ranking of candidate ceramic wafer engine seal materials

NASA Technical Reports Server (NTRS)

Steinetz, Bruce M.

1991-01-01

Modern engineered ceramics offer high temperature capabilities not found in even the best superalloy metals. The high temperature properties of several selected ceramics including aluminum oxide, silicon carbide, and silicon nitride are reviewed as they apply to hypersonic engine seal design. A ranking procedure is employed to objectively differentiate among four different monolithic ceramic materials considered, including: a cold-pressed and sintered aluminum oxide; a sintered alpha-phase silicon carbide; a hot-isostatically pressed silicon nitride; and a cold-pressed and sintered silicon nitride. This procedure is used to narrow the wide range of potential ceramics considered to an acceptable number for future detailed and costly analyses and tests. The materials are numerically scored according to their high temperature flexural strength; high temperature thermal conductivity; resistance to crack growth; resistance to high heating rates; fracture toughness; Weibull modulus; and finally according to their resistance to leakage flow, where materials having coefficients of thermal expansion closely matching the engine panel material resist leakage flow best. The cold-pressed and sintered material (Kyocera SN-251) ranked the highest in the overall ranking especially when implemented in engine panels made of low expansion rate materials being considered for the engine, including Incoloy and titanium alloys.

Lightweight Aggregate Made from Dredged Material in Green Roof Construction for Stormwater Management.

PubMed

Liu, Rui; Coffman, Reid

2016-07-23

More than 1.15 million cubic meters (1.5 million cubic yards) of sediment require annual removal from harbors and ports along Ohio's Lake Erie coast. Disposing of these materials into landfills depletes land resources, while open water placement of these materials deteriorates water quality. There are more than 14,000 acres of revitalizing brownfields in Cleveland, U.S., many containing up to 90% impervious surface, which does not allow "infiltration" based stormwater practices required by contemporary site-based stormwater regulation. This study investigates the potential of sintering the dredged material from the Harbor of Cleveland in Lake Erie to produce lightweight aggregate (LWA), and apply the LWA to green roof construction. Chemical and thermal analyses revealed the sintered material can serve for LWA production when preheated at 550 °C and sintered at a higher temperature. Through dewatering, drying, sieving, pellet making, preheating, and sintering with varying temperatures (900-1100 °C), LWAs with porous microstructures are produced with specific gravities ranging from 1.46 to 1.74, and water absorption capacities ranging from 11% to 23%. The water absorption capacity of the aggregate decreases as sintering temperature increases. The LWA was incorporated into the growing media of a green roof plot, which has higher water retention capacity than the conventional green roof system.

Sintering characteristic and microwave dielectric properties of 0.45Ca0.6Nd0.267TiO3-0.55Li0.5Nd0.5TiO3 ceramics with La2O3-B2O3-ZnO additive

NASA Astrophysics Data System (ADS)

Chen, Yawei; Zhang, Shuren; Li, Enzhu; Niu, Na; Yang, Hongcheng

2018-02-01

The La2O3-B2O3-ZnO (LBZ) glass was proved to be an effective sintering aid of the 0.45Ca0.6Nd0.26TiO3-0.55Li0.5Nd0.5TiO3 (CNT-LNT) ceramics. The influence of LBZ glass on the phase composition, low temperature sintering process, microstructure, activation energy, and dielectric properties of CNT-LNT ceramics was investigated in detail. The LBZ glass induced an obvious decrease of the CNT-LNT ceramics sintering temperature from 1350 to 1000 °C due to the liquid phase formation, which reduced the activation energy ( E a) of the CNT-LNT ceramics. In addition, the near zero temperature coefficient of resonant frequency (τƒ) value was obtained by adding moderate quantity of LBZ glass. CNT-LNT + 5 wt% LBZ (CNT-LNT + 5L) ceramics sintered at 1000°C/4 h displayed good microwave dielectric properties of: ɛ r = 101.7, Q × f = 1560 GHz ( f = 3.25 GHz) and τ ƒ = 2.3 ppm °C-1.

Sintering and Microstructure of BaTiO3 Nano Particles Synthesized by Molten Salt Method.

PubMed

Lee, Chang-Hyun; Shin, Hyo-Soon; Yeo, Dong-Hun; Ha, Gook-Hyun; Nahm, Sahn

2016-05-01

In order to establish thinner dielectric layers in thick film electronic components such as MLCC (Multilayer ceramic capacitor), BaTiO3 nanoparticles have been utilized. However, studies on the synthesis of nanoparticles smaller than 20 nm, the characteristics of the BaTiO3 powder, and the powder's sintering are lacking. Therefore, this paper aims to synthesize BaTiO3 particles smaller than 20 nm by using the molten salt method and evaluate the microstructure and dielectric properties by varying the sintering temperature from 750 degrees C to 1200 degrees C. Through the molten salt method and by using KOH-KCl mixed salt, 20 nm BaTiO3 powder was synthesized at a low temperature of 150 degrees C. Sintering the pellets formed from the synthesized 20 nm BaTiO3 nano powder led to the observation of an unusual phenomenon where the particles grew to approximate sizes below 850 degrees C where densification progressed. At sintering temperatures above 950 degrees C, particles that expanded into rod shapes were observed and these particles were identified to be unreacted TiO2 based on the results of the EDX (Energy Dispersive X-ray Spectroscopy) analysis and phase analysis results.

Influences of spark plasma sintering temperature on the microstructures and thermoelectric properties of (Sr0.95Gd0.05)TiO3 ceramics

NASA Astrophysics Data System (ADS)

Li, Liang-Liang; Qin, Xiao-Ying; Liu, Yong-Fei; Liu, Quan-Zhen

2015-06-01

(Sr0.95Gd0.05)TiO3 (SGTO) ceramics are successfully prepared via spark plasma sintering (SPS) respectively at 1548, 1648, and 1748 K by using submicron-sized SGTO powders synthesized from a sol-gel method. The densities, microstructures, and thermoelectric properties of the SGTO ceramics are studied. Though the Seebeck coefficient shows no obvious difference in the case that SPS temperatures range from 1548 K to 1648 K, the electrical conductivity and the thermal conductivity increase remarkably due to the increase in grain size and density. The sample has a density higher than 98% theoretical density as the sintering temperature increases up to 1648 K and shows average grain sizes increasing from ˜ 0.7 μm to 7 μm until 1748 K. As a result, the maximum of the dimensionless figure of merit of ˜ 0.24 is achieved at ˜ 1000 K for the samples sintered at 1648 K and 1748 K, which was ˜ 71% larger than that (0.14 at ˜ 1000 K) for the sample sintered at 1548 K due to the enhancement of the power factor. Project supported by the National Natural Science Foundation of China (Grant Nos. 11174292, 51101150, and 11374306).

Improvements to Zirconia Thick-Film Oxygen Sensors

NASA Astrophysics Data System (ADS)

Maskell, William C.; Brett, Daniel J. L.; Brandon, Nigel P.

2013-06-01

Thick-film zirconia gas sensors are normally screen-printed onto a planar substrate. A sandwich of electrode-electrolyte-electrode is fired at a temperature sufficient to instigate sintering of the zirconia electrolyte. The resulting porous zirconia film acts as both the electrolyte and as the diffusion barrier through which oxygen diffuses. The high sintering temperature results in de-activation of the electrodes so that sensors must be operated at around 800 °C for measurements in the percentage range of oxygen concentration. This work shows that the use of cobalt oxide as a sintering aid allows reduction of the sensor operating temperature by 100-200 °C with clear benefits. Furthermore, an interesting and new technique is presented for the investigation of the influence of dopants and of the through-porosity of ionically-conducting materials.

Effect of processing conditions on microstructural features in Mn–Si sintered steels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oro, Raquel, E-mail: raqueld@chalmers.se; Hryha, Eduard, E-mail: hryha@chalmers.se; Campos, Mónica, E-mail: campos@ing.uc3m.es

2014-09-15

Sintering of steels containing oxidation sensitive elements is possible if such elements are alloyed with others which present lower affinity for oxygen. In this work, a master alloy powder containing Fe–Mn–Si–C, specifically designed to create a liquid phase during sintering, has been used for such purpose. The effect of processing conditions such as sintering temperature and atmosphere was studied with the aim of describing the microstructural evolution as well as the morphology and distribution of oxides in the sintered material, evaluating the potential detrimental effect of such oxides on mechanical properties. Chemical analyses, metallography and fractography studies combined with X-raymore » photoelectron spectroscopy analyses on the fracture surfaces were used to reveal the main mechanism of fracture and their correlation with the chemical composition of the different fracture surfaces. The results indicate that the main mechanism of failure in these steels is brittle fracture in the surrounding of the original master alloy particles due to degradation of grain boundaries by the presence of oxide inclusions. Mn–Si oxide inclusions were observed on intergranular decohesive facets. The use of reducing atmospheres and high sintering temperatures reduces the amount and size of such oxide inclusions. Besides, high heating and cooling rates reduce significantly the final oxygen content in the sintered material. A model for microstructure development and oxide evolution during different stages of sintering is proposed, considering the fact that when the master alloy melts, the liquid formed can dissolve some of the oxides as well as the surface of the surrounding iron base particles. - Highlights: • Oxide distribution in steels containing oxidation-sensitive elements • Mn, Si introduced in a master alloy powder, mixed with a base iron powder • Selective oxidation of Mn and Si on iron grain boundaries • Decohesive fracture caused by degradation of grain boundaries by oxide inclusions • Reducing agents efficient at low temperatures critical for avoiding oxide inclusions.« less

Ice sintering timescales at the surface of Europa and implications for surface properties

NASA Astrophysics Data System (ADS)

Molaro, Jamie; Phillips, Cynthia B.; Meirion-Griffith, Gareth

2017-10-01

The planned exploration of Europa by NASA’s Europa Clipper Mission and the possibility of a future Europa lander have driven the need to characterize its surface strength, roughness, porosity, thermal conductivity, and regolith depth in order to accurately interpret remote sensing data and develop appropriate spacecraft landing systems. Many processes contribute to Europa’s landscape evolution, such as sputtering, mass wasting, thermal segregation, and impact gardening, driving the creation and distribution of icy regolith across the surface. While the efficacy of these processes are not well constrained, any amount of regolith emplaced at the surface will undergo subsequent processing due to sintering. Ice sintering is a form of frost metamorphism whereby contacting ice grains experience the diffusion of material into their contact region, forming a “neck” between them and densifying over time. Over long enough timescales, ice aggregates will sinter into solid material, which may contribute to the incorporation of non-ice material into Europa’s subsurface and help to drive subsurface chemistry. Sintering also interacts with other processes, adding to the complexity of icy surface evolution. For example, sputtering preferentially removes larger grains and may enhance sintering rates, and changes in ice porosity may affect the response of the surface to micrometeorite impacts.Quantifying the effects of ice sintering will allow us to predict the microstructural properties of Europa’s surface at spacecraft scales. To this end, we have modeled pressure-less (no overburden) sintering of spherical water-ice grains and validated the results with a laboratory experiment. We also modeled ice at the surface of Europa to obtain a first-order approximation of the sintering timescale and surface properties. Preliminary results indicate that ice grains will experience neck growth but not significant densification over Europa’s surface age, suggesting that loose surface ice forms a weak and porous crust. Furthermore, our results suggest that existing models do not accurately quantify all stages of the sintering process for ice, emphasizing the need for more laboratory studies on this topic.

Enhanced High Temperature Piezoelectrics Based on BiScO3-PbTiO3 Ceramics

NASA Technical Reports Server (NTRS)

Sehirlioglu, Alp; Sayir, Ali; Dynys, Fred

2009-01-01

High-temperature piezoelectrics are a key technology for aeronautics and aerospace applications such as fuel modulation to increase the engine efficiency and decrease emissions. The principal challenge for the insertion of piezoelectric materials is the limitation on upper use temperature which is due to low Curie-Temperature (TC) and increasing electrical conductivity. BiScO3-PbTiO3 (BS-PT) system is a promising candidate for improving the operating temperature for piezoelectric actuators due to its high TC (greater than 400 C). Bi2O3 was shown to be a good sintering aid for liquid phase sintering resulting in reduced grain size and increased resistivity. Zr doped and liquid phase sintered BS-PT ceramics exhibited saturated and square hysteresis loops with enhanced remenant polarization (37 microC per square centimeter) and coercive field (14 kV/cm). BS-PT doped with Mn showed enhanced field induced strain (0.27% at 50kV/cm). All the numbers indicated in parenthesis were collected at 100 C.

Low-Thermal-Conductivity Pyrochlore Oxide Materials Developed for Advanced Thermal Barrier Coatings

NASA Technical Reports Server (NTRS)

Bansal, Narottam P.; Zhu, Dong-Ming

2005-01-01

When turbine engines operate at higher temperatures, they consume less fuel, have higher efficiencies, and have lower emissions. The upper-use temperatures of the base materials (superalloys, silicon-based ceramics, etc.) used for the hot-section components of turbine engines are limited by the physical, mechanical, and corrosion characteristics of these materials. Thermal barrier coatings (TBCs) are applied as thin layers on the surfaces of these materials to further increase the operating temperatures. The current state-of-the-art TBC material in commercial use is partially yttria-stabilized zirconia (YSZ), which is applied on engine components by plasma spraying or by electron-beam physical vapor deposition. At temperatures higher than 1000 C, YSZ layers are prone to sintering, which increases thermal conductivity and makes them less effective. The sintered and densified coatings can also reduce thermal stress and strain tolerance, which can reduce the coating s durability significantly. Alternate TBC materials with lower thermal conductivity and better sintering resistance are needed to further increase the operating temperature of turbine engines.

Reaction of Unalloyed and Cr-Mo Alloyed Steels with Nitrogen from the Sintering Atmosphere

NASA Astrophysics Data System (ADS)

Dlapka, Magdalena; Gierl-Mayer, Christian; Calderon, Raquel de Oro; Danninger, Herbert; Bengtsson, Sven; Dudrova, Eva

2016-12-01

Nitrogen is usually regarded as an inert sintering atmosphere for PM steels; however, this cannot be taken for granted in particular for steels alloyed with nitride forming elements. Among those elements, chromium has become more and more important as an alloying element in sintered low alloy structural steels in the last decade due to the moderate alloying cost and the excellent mechanical properties obtainable, in particular when sinter hardening is applied. The high affinity of Cr to oxygen and the possible ways to overcome related problems have been the subject of numerous studies, while the fact that chromium is also a fairly strong nitride forming element has largely been neglected at least for low alloy steel grades, although frequently used materials like steels from Cr and Cr-Mo prealloyed powders are commonly sintered in atmospheres consisting mainly of nitrogen. In the present study, nitrogen pickup during sintering at different temperatures and for varying times has been studied for Cr-Mo prealloyed steel grades as well as for unalloyed carbon steel. Also the effect of the cooling rate and its influence on the properties, of the microstructure and the composition have been investigated. It showed that the main nitrogen uptake occurs not during isothermal sintering but rather during cooling. It could be demonstrated that a critical temperature range exists within which the investigated CrM-based steel is particularly sensitive to nitrogen pickup.

New materials through a variety of sintering methods

NASA Astrophysics Data System (ADS)

Jaworska, L.; Cyboroń, J.; Cygan, S.; Laszkiewicz-Łukasik, J.; Podsiadło, M.; Novak, P.; Holovenko, Y.

2018-03-01

New sintering techniques make it possible to obtain materials with special properties that are impossible to obtain by conventional sintering techniques. This issue is especially important for ceramic materials for application under extreme conditions. Following the tendency to limit critical materials in manufacturing processes, the use of W, Si, B, Co, Cr should be limited, also. One of the cheapest and widely available materials is aluminum oxide, which shows differences in phase composition, grain size, hardness, strain and fracture toughness of the same type of powder, sintered via various methods. In this paper the alumina was sintered using the conventional free sintering process, microwave sintering, Spark Plasma Sintering (SPS), high pressure-high temperature method (HP-HT) and High Pressure Spark Plasma Sintering (HP SPS). Phase composition analysis, by X-ray diffraction of the alumina materials sintered using various methods, was carried out. For the conventional sintering method, compacts are composed of α-Al2O3 and θ-Al2O3. For compacts sintered using SPS, microwave and HP-HT methods, χ-Al2O3 and γ-Al2O3 phases were additionally present. Mechanical and physical properties of the obtained materials were compared between the methods of sintering. On the basis of images from scanning electron microscope quantitative analysis was performed to determine the degree of grain growth of alumina after sintering.

Process for the production of metal nitride sintered bodies and resultant silicon nitride and aluminum nitride sintered bodies

NASA Technical Reports Server (NTRS)

Yajima, S.; Omori, M.; Hayashi, J.; Kayano, H.; Hamano, M.

1983-01-01

A process for the manufacture of metal nitride sintered bodies, in particular, a process in which a mixture of metal nitrite powders is shaped and heated together with a binding agent is described. Of the metal nitrides Si3N4 and AIN were used especially frequently because of their excellent properties at high temperatures. The goal is to produce a process for metal nitride sintered bodies with high strength, high corrosion resistance, thermal shock resistance, thermal shock resistance, and avoidance of previously known faults.

Development of SiAlON materials

NASA Technical Reports Server (NTRS)

Layden, G. K.

1977-01-01

Cold pressing and sintering techniques were used to produce ceramic bodies in which the major phase was beta prime Si3-Al-O-N4 solid solution. A variety of foreign oxides were used to promote liquid phase sintering, and this resulted in the incorporation of additional solid phases in the ceramic bodies which controlled elevated temperature properties. None of the bodies studied to date exhibited both adequate high temperature mechanical properties and oxidation resistance. Criteria are suggested to guide the formulation of bodies with improved high temperature properties.

Development of Economical Improved Thick Film Solar Cell Contact

NASA Technical Reports Server (NTRS)

Ross, B.

1979-01-01

Materials were surveyed to provide candidates for an all metal electrode paste system. These consisted of a major constituent metal powder, a low melting metal powder suitable for a liquid phase sintering medium, and a powder material suitable as an etchant for silicon dioxide at sintering temperatures. By means of thermal gravimetric analysis a suitable binder was identified for low temperature fired inks.

Room Temperature Electrochemical Sintering of Zn Microparticles and Its Use in Printable Conducting Inks for Bioresorbable Electronics.

PubMed

Lee, Yoon Kyeung; Kim, Jeonghyun; Kim, Yerim; Kwak, Jean Won; Yoon, Younghee; Rogers, John A

2017-10-01

This study describes a conductive ink formulation that exploits electrochemical sintering of Zn microparticles in aqueous solutions at room temperature. This material system has relevance to emerging classes of biologically and environmentally degradable electronic devices. The sintering process involves dissolution of a surface passivation layer of zinc oxide in CH 3 COOH/H 2 O and subsequent self-exchange of Zn and Zn 2+ at the Zn/H 2 O interface. The chemical specificity associated with the Zn metal and the CH 3 COOH/H 2 O solution is critically important, as revealed by studies of other material combinations. The resulting electrochemistry establishes the basis for a remarkably simple procedure for printing highly conductive (3 × 10 5 S m -1 ) features in degradable materials at ambient conditions over large areas, with key advantages over strategies based on liquid phase (fusion) sintering that requires both oxide-free metal surfaces and high temperature conditions. Demonstrations include printed magnetic loop antennas for near-field communication devices. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effect of electrode material on characteristics of non-volatile resistive memory consisting of Ag{sub 2}S nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jang, Jaewon, E-mail: j1jang@knu.ac.kr

2016-07-15

In this study, Ag{sub 2}S nanoparticles are synthesized and used as the active material for two-terminal resistance switching memory devices. Sintered Ag{sub 2}S films are successfully crystallized on plastic substrates with synthesized Ag{sub 2}S nanoparticles, after a relatively low-temperature sintering process (200 °C). After the sintering process, the crystallite size is increased from 6.8 nm to 80.3 nm. The high ratio of surface atoms to inner atoms of nanoparticles reduces the melting point temperature, deciding the sintering process temperature. In order to investigate the resistance switching characteristics, metal/Ag{sub 2}S/metal structures are fabricated and tested. The effect of the electrode materialmore » on the non-volatile resistive memory characteristics is studied. The bottom electrochemically inert materials, such as Au and Pt, were critical for maintaining stable memory characteristics. By using Au and Pt inert bottom electrodes, we are able to significantly improve the memory endurance and retention to more than 10{sup 3} cycles and 10{sup 4} sec, respectively.« less

Compaction and sintering behaviors of a Nd-Fe-B permanent magnet alloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chin, T.; Hung, M.; Tsai, D.

1988-11-15

Extensive x-ray diffraction (XRD) and magnetic measurements were done on Nd/sub 15/ Fe/sub 77/ B/sub 8/ magnet alloy green compacts after cold isostatic pressing following a pulsed 2-T field (CIP) and die-pressing under a static 1.2-T perpendicular field (DP1) or parallel field (DP2), and on those after sintering. An alignment factor F, through the calculation of the integrated diffraction intensity ratio of the XRD patterns, was adopted as the effectiveness of magnetic alignment. At the green compact state, DP1 has the best alignment while CIP the worst. However, after sintering the alignment factor was such that CIP>DPI>DP2, the same ordermore » as the magnetic properties. Three mechanisms were proposed for the evolution of the alignment factor at different stages of sintering, i.e., that both the appearance of a liquid phase at low temperatures and preferred grain growth at high temperatures enhance F, while recrystallization at intermediate temperatures deteriorates F. CIP results in less-defect green compact, hence less recrystallization, leading to better resultant alignment« less

Densification of LSGM electrolytes using activated microwave sintering

NASA Astrophysics Data System (ADS)

Kesapragada, S. V.; Bhaduri, S. B.; Bhaduri, S.; Singh, P.

Lanthanum gallate doped with alkaline rare earths (LSGM) powders were densified using an activated microwave sintering process for developing a dense stable electrolyte layer for applications in intermediate temperature-solid oxide fuel cells (IT-SOFCs). Due to heat generation in situ, the process of sintering gets activated with faster kinetics compared to a conventional sintering process. The effect of various microwave process parameters on the microstructure and phase formation was studied. The sintered pellets were characterized using scanning electron microscopy-energy dispersive analysis (SEM-EDAX), and X-ray diffraction (XRD). The density of LSGM pellets microwave sintered at 1350 °C for 20 min is greater than 95% theoretical density with a fine grained microstructure (˜2-3 μm) and without the presence of other phase(s).

Influence of processing parameters on microstructure and biocompatibility of surface laser sintered hydroxyapatite-SiO2 composites.

PubMed

Kivitz, E; Görke, R; Schilling, A F; Zhang, J; Heinrich, J G

2013-05-01

Silica-doped hydroxyapatite (HA) is a promising material concerning biocompatibility to natural bone, bioactivity and osteoconductive characteristics. HA exhibits phase transformations during sintering which are attendant to the change in volume and thermal strain. To avoid cracks during sintering, the exact knowledge of the phase transition temperatures is necessary. The sintering behavior of HA can be improved by adding amorphous silica with a low coefficient of thermal expansion. Therefore, the phase transformations in the system HA-SiO2 were analyzed by using differential scanning calorimetry followed by quantitative phase analysis by X-ray diffraction with the Riedveld method. The maximum sintering temperature without reversible phase transformation was defined as 1265°C. In laser surface sintered (LSS) samples, amorphous SiO2 , HA, and Si-α-TCP (or α-TCP) were detected. By comparison, only crystalline phases, such as cristobalite, HA, β-TCP, and Si-α-TCP (or α-TCP), were determined after furnace sintering. Scanning electron microscopy micrographs of furnace sintered and LSS samples show the differences in the resulting microstructures. Biocompatibility was determined by measuring cell activity of osteoblasts cultivated on four laser-sintered materials in the HA-SiO2 system in comparison to normal cell culture plastic. Cell proliferation was similar on all surfaces. The level of the cell activity on day 8 varied depending on the composition of the material and increased linearly as the amorphous SiO2 content rose. Taken together a laser-based method to develop novel biocompatible HA-SiO2 ceramics with adjustable properties and possible applications as orthopedic bioceramics are discussed. Copyright © 2012 Wiley Periodicals, Inc.

EFFECT OF MICROWAVE SINTERING ON THE STRUCTURAL AND ELECTRICAL PROPERTIES OF Li0.51Zn0.2Ti0.2V0.01Fe2.08O4 FERRITE

NASA Astrophysics Data System (ADS)

Maisnam, Mamata; Phanjoubam, Sumitra

2013-07-01

Effect of microwave sintering on the structural and electrical properties of Li+0.51Zn2+0.2Ti4+0.2V5+0.01Fe3+2.08O2-4 is studied in comparison with that of conventionally sintered one. The technique is advantageous in terms of significantly reduced size of microwave kilns and rapid heating compared to the cumbersome and slow heating of conventional sintering technology. Microwave sintering produced enhanced densification and much finer microstructures. The DC resistivity is markedly increased. Microwave sintering reduces chances of evaporation of lithium and oxygen during sintering of lithium based ferrites resulting in formation of lesser ferrous ions. This has profound effect on the electrical properties of microwave sintered ferrites. The dielectric constant is significantly reduced possibly due to reduced space charge polarization and the temperature dependence of the dielectric properties are also studied.

Preparation and characterization of a novel willemite bioceramic.

PubMed

Zhang, Meili; Zhai, Wanyin; Chang, Jiang

2010-04-01

Willemite (Zn(2)SiO(4)) ceramics were prepared by sintering the willemite green compacts. The effects of sintering temperature on the linear shrinkage, porosity and mechanical strength of the ceramics were examined. With the sintering temperature increased, the linear shrinkage of the ceramics increased and the porosity decreased. When sintered at 1,300 degrees C, willemite ceramics showed mechanical properties of the same order of magnitude as values for human cortical bone, as measured by bending strength (91.2 +/- 4.2 MPa) and Young's modulus (37.5 +/- 1.5 GPa). In addition, the adhesion and proliferation of rabbit bone marrow stromal cells (BMSCs) on willemite ceramics was investigated. The results showed that the ceramics supported cell adhesion and stimulated the proliferation. All these findings suggest that willemite ceramics possess suitable mechanical properties and favorable biocompatibility and might be a promising biomaterial for bone implant applications.

Fabrication of Fe1.1Se0.5Te0.5 bulk by a high energy ball milling technique

NASA Astrophysics Data System (ADS)

Liu, Jixing; Li, Chengshan; Zhang, Shengnan; Feng, Jianqing; Zhang, Pingxiang; Zhou, Lian

2017-11-01

Fe1.1Se0.5Te0.5 superconducting bulks were successfully synthesized by a high energy ball milling (HEBM) aided sintering technique. Two advantages of this new technique have been revealed compared with traditional solid state sintering method. One is greatly increased the density of sintered bulks. It is because the precursor powders with β-Fe(Se, Te) and δ-Fe(Se, Te) were obtained directly by the HEBM process and without formation of liquid Se (and Te), which could avoid the huge volume expansion. The other is the obvious decrease of sintering temperature and dwell time due to the effective shortened length of diffusion paths. The superconducting critical temperature Tc of 14.2 K in our sample is comparable with those in previous reports, and further optimization of chemical composition is on the way.

Preparation of Cu and Fly Ash Composite by Powder Metallurgy Technique

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chew, P. Y.; Lim, P. S.; Ng, M. C.

2011-03-30

Cu and Fly Ash (FA) mixtures with different weight percentages were prepared. Pellets of the mixture powder were produced with the dimension of 17.7 mm in diameter and 10-15 mm in height. These different composites were compacted at a constant pressure of 280 MPa. One of the selected weight percentages was then compacted to form into pellet and sintered at different temperatures which were at 900, 950 and 1000 deg. C respectively for 2 hours. Density of green pellet was measured before sintered in furnace. After sintering, all the pellets with different temperatures were re-weighed and sintered density were calculated.more » The densification of the green and sintered pellets was required to be measured as one of the parameter in selection of the best material properties. Porosity of the pellet shall not be ignored in order to analyze the close-packed particles stacking in the pellet. SEM micrograph had been captured to observe the presence of pores and agglomeration of particles in the sample produced.« less

Effect of Zr, Nb and Ti addition on injection molded 316L stainless steel for bio-applications: Mechanical, electrochemical and biocompatibility properties.

PubMed

Gulsoy, H Ozkan; Pazarlioglu, Serdar; Gulsoy, Nagihan; Gundede, Busra; Mutlu, Ozal

2015-11-01

The research investigated the effect of Zr, Nb and Ti additions on mechanical, electrochemical properties and biocompatibility of injection molded 316L stainless steel. Addition of elemental powder is promoted to get high performance of sintered 316L stainless steels. The amount of additive powder plays a role in determining the sintered microstructure and all properties. In this study, 316L stainless steel powders used with the elemental Zr, Nb and Ti powders. A feedstock containing 62.5 wt% powders loading was molded at different injection molded temperature. The binders were completely removed from molded components by solvent and thermal debinding at different temperatures. The debinded samples were sintered at 1350°C for 60 min. Mechanical, electrochemical property and biocompatibility of the sintered samples were performed mechanical, electrochemical, SBF immersion tests and cell culture experiments. Results of study showed that sintered 316L and 316L with additives samples exhibited high corrosion properties and biocompatibility in a physiological environment. Copyright © 2015 Elsevier Ltd. All rights reserved.

Effect of microwave-assisted sintering on dielectric properties of CaCu3Ti4O12 ceramic

NASA Astrophysics Data System (ADS)

Rani, Suman; Ahlawat, Neetu; Punia, R.; Kundu, R. S.; Ahlawat, N.

2016-05-01

In this present work, CaCu3Ti4O12 (CCTO) was synthesized by conventional solid-state reaction technique. The synthesis process was carried out in two phases; by conventional process (calcination and sintering at 1080°C for 10 hours) and phase II involves the micro assisted pre sintering of conventionally calcined CCTO for very short soaking time of 30 min at 1080°C in a microwave furnace followed by sintering at 1080°C for 10 hours in conventional furnace. X-ray diffraction (XRD) patterns confirmed the formation of single phase ceramic. Dielectric properties were studied over the frequency range from 50Hz -5MHz at temperatures (273K-343K). It was observed that pre- microwave sintering enhance the dielectric constant values from 10900 to 11893 and respectively reduces the dielectric loss values from 0.49 to 0.34 at room temperature(1 KHz). CCTO ceramics which are found desirable for many technological applications. The effect is more pronounced at low frequencies of applied electric field.

Isothermal reduction kinetics and mineral phase of chromium-bearing vanadium-titanium sinter reduced with CO gas at 873-1273 K

NASA Astrophysics Data System (ADS)

Yang, Song-tao; Zhou, Mi; Jiang, Tao; Xue, Xiang-xin

2018-02-01

Reduction of chromium-bearing vanadium-titanium sinter (CVTS) was studied under simulated conditions of a blast furnace, and thermodynamics and kinetics were theoretically analyzed. Reduction kinetics of CVTS at different temperatures was evaluated using a shrinking unreacted core model. The microstructure, mineral phase, and variation of the sinter during reduction were observed by X-ray diffraction, scanning electron microscopy, and metallographic microscopy. Results indicate that porosity of CVTS increased with temperature. Meanwhile, the reduction degree of the sinter improved with the reduction rate. Reduction of the sinter was controlled by a chemical reaction at the initial stage and inner diffusion at the final stage. Activation energies measured 29.22-99.69 kJ/mol. Phase transformations in CVTS reduction are as follows: Fe2O3→Fe3O4→FeO→Fe; Fe2TiO5→Fe2TiO4→FeTiO3; FeO·V2O3→V2O3; FeO·Cr2O3→Cr2O3.

The fracture strength of cryomilled 99.7 Al nanopowders consolidated by high frequency induction sintering

NASA Astrophysics Data System (ADS)

El-Danaf, Ehab A.; Baig, Muneer; Almajid, Abdulhakim A.; Soliman, Mahmoud S.

2014-08-01

Mechanical Attrition of metallic powders induces severe plastic deformation and consequently reduces the average grain size. Powders of 99.7 Al (45μm particle size), cryomilled for 7 hrs having a crystal size of ~ 20 nm, were consolidated by high frequency induction sintering under a constant pressure of 50 MPa and at two temperatures of 500 and 550 °C for two sintering dwell times of 1 and 3 minutes at a constant heating rate of 400 °C/min. The bright field TEM image and X-ray line broadening technique, for the cryomilled powders, were used to measure-the crystallite size. Simple compression at an initial strain rate of 10-4 s-1 was conducted at room temperature, 373 and 473 K, and the yield strength was documented and correlated with the sintering parameters. The as-received 99.7 Al powders-consolidated using one of the sintering parameters was used as a reference material to compare the mechanical properties. Hardness, density and crystal size of the consolidated sample, that gave the highest yield and fracture strength, were measured.

Enhanced Multiferroic Properties of YMnO3 Ceramics Fabricated by Spark Plasma Sintering Along with Low-Temperature Solid-State Reaction

PubMed Central

Wang, Meng; Wang, Ting; Song, Shenhua; Ravi, Muchakayala; Liu, Renchen; Ji, Shishan

2017-01-01

Based on precursor powders with a size of 200–300 nm prepared by the low-temperature solid-state reaction method, phase-pure YMnO3 ceramics are fabricated using spark plasma sintering (SPS). X-ray diffraction (XRD) and scanning electron microscopy (SEM) reveal that the high-purity YMnO3 ceramics can be prepared by SPS at 1000 °C for 5 minutes with annealing at 800 °C for 2 h. The relative density of the sample is as high as 97%, which is much higher than those of the samples sintered by other methods. The present dielectric and magnetic properties are much better than those of the samples fabricated by conventional methods and SPS with ball-milling precursors, and the ferroelectric loops at room temperature can be detected. These findings indicate that the YMnO3 ceramics prepared by the low temperature solid reaction method and SPS possess excellent dielectric lossy ferroelectric properties at room temperature, and magnetic properties at low temperature (10 K), making them suitable for potential multiferroic applications. PMID:28772832

Thermal barrier coating resistant to sintering

DOEpatents

Subramanian, Ramesh; Seth, Brig B.

2005-08-23

A device (10) is made, having a ceramic thermal barrier coating layer (16) characterized by a microstructure having gaps (18) with a sintering inhibiting material (22) disposed on the columns (20) within the gaps (18). The sintering resistant material (22) is stable over the range of operating temperatures of the device (10), is not soluble with the underlying ceramic layer (16) and is applied by a process that is not an electron beam physical vapor deposition process. The sintering inhibiting material (22) has a morphology adapted to improve the functionality of the sintering inhibiting material (22), characterized as continuous, nodule, rivulet, grain, crack, flake and combinations thereof and being disposed within at least some of the vertical and horizontal gaps.

[Effect of staining method and sintering temperature on the color of porcelain-fused-to-metal restorations].

PubMed

Wang, Yan; Yan, Wei-hao; Zhang, Xin-chun; Huang, Yue; Shen, Lin-han

2004-12-01

To investigate the effect of staining method and sintering temperature on the color of porcelain-fused-metal restorations. 40 cylindrical stained porcelain-metal specimens of 15 mm in diameter and 6 mm in height were fabricated with customized mould, consisting of 2 mm Ni-Cr metal, 1 mm opaque porcelain, 2 mm dentine porcelain and 1 mm enamel porcelain. The specimens were prepared by 5 techniques, 8 for each group. Group A: internal staining, Group B: external staining, 900 degrees centigrade sintering temperature was used in both A and B group; Group C to E: external staining, with the sintering temperature of 880 degrees centigrade, 900 degrees centigrade and 920 degrees centigrade respectively. Sofu A2 porcelain and Sofu 44 stain system were used for the study. Using standard white plate as a reference, colors (L*,a*,b* coordinates) of the specimens were measured with a computerized colorimeter. Student's t test and one way ANOVA were used to analyze the data. DeltaE, b* and Delta C(ab)* of Group B (external staining) and group A (internal staining) were 43.72 +/- 2.99/26.51 +/- 1.64/31.31 +/- 2.48 and 39.71 +/- 1.78/23.69 +/- 0.36/26.55 +/- 2.16, respectively. The values of the former group were significantly higher than that of the latter (P < 0.05); For Group C to E, there were no significant differences in all the color parameters. Staining method has a significant effect on the color parameters of porcelain-fused-to-metal restorations; For external staining, within the clinically-used range, changing the sintering temperature does not have an obvious effect on the color.

Development of a double-stage DDIA apparatus and its application to in-situ melting experiments at high pressures

NASA Astrophysics Data System (ADS)

Jing, Z.; Wang, Y.; Tange, Y.; Hilairet, N.; Yu, T.; Sakamaki, T.

2010-12-01

Melting experiments at high pressures are critical to our studies on the chemical evolution and dynamics of Earth and other terrestrial planets. A large volume press can generate a homogeneous and stable high-temperature environment, which is the key to melting experiments. However, previous in-situ melting experiments using a large volume press were often restricted to relatively low pressures. In order to expand the P-T conditions, a double-stage 6-8 configuration (6 first-stage anvils and 8 second stage-anvils) has been developed in a DDIA apparatus (DDIA-30), recently installed at the GSECARS Beamline 13-ID-D at the Advanced Photon Source. 27 mm DIA-type first-stage anvils and 14 mm second-stage anvils with the truncation edge length (TEL) of 1.5 mm are employed. A cell assembly that is suitable for synchrotron X-ray studies developed by Tange et al. (2008) has been adopted for melting experiments. High pressure and temperature conditions are generated up to 27 GPa and 2473 K by using tungsten carbide anvils, and up to 35 GPa and 1773 K by using sintered diamond anvils. Both LaCrO3 and TiB2 heater materials have been successfully applied for high-temperature generation. Although TiB2 shows a decrease of resistance at temperatures higher than 2000 K at 20 GPa, we are able to achieve 2473 K with temperature fluctuations in the range of ±30 K. Using tungsten carbide anvils and TiB2 heaters, we have determined the melting curve of gold up to 20 GPa. We constrain the melting temperature based on the disappearance of the gold peaks in energy dispersive X-ray diffraction patterns and the change of sample shape in the radiographic images. The combination of these two observations can reduce the uncertainties in melting temperatures to within 100 K. The measured melting temperatures of gold at 8, 13, and 20 GPa are consistent with the low-pressure results (up to 6 GPa) such as Mirwald and Kennedy (1979). Melting experiments with sintered diamond anvils are currently under development. This will enable us to conduct melting experiments up to 50 GPa on Fe alloys and silicates.

Method of producing amorphous thin films

DOEpatents

Brusasco, Raymond M.

1992-01-01

Disclosed is a method of producing thin films by sintering which comprises: a. coating a substrate with a thin film of an inorganic glass forming parulate material possessing the capability of being sintered, and b. irridiating said thin film of said particulate material with a laser beam of sufficient power to cause sintering of said material below the temperature of liquidus thereof. Also disclosed is the article produced by the method claimed.

Method of producing amorphous thin films

DOEpatents

Brusasco, R.M.

1992-09-01

Disclosed is a method of producing thin films by sintering which comprises: (a) coating a substrate with a thin film of an inorganic glass forming material possessing the capability of being sintered; and (b) irradiating said thin film of said particulate material with a laser beam of sufficient power to cause sintering of said material below the temperature of liquidus thereof. Also disclosed is the article produced by the method claimed. 4 figs.

Synthesis of Ti-6Al-4V alloy with nano-TiN microstructure via spark plasma sintering technique

NASA Astrophysics Data System (ADS)

E Falodun, O.; Obadele, B. A.; Oke, S. R.; E Maja, M.; Olubambi, P. A.

2017-12-01

The effect of nano-TiN dispersion strengthened Ti-6Al-4V via spark plasma sintering method has been investigated. Ti-6Al-4V with 4 vol. percent of nano-TiN were mixed in a Turbula shaker mixer for 8 h at a speed of 49 rpm and the admixed powders were sintered at sintering temperature range of 1000 - 1100 °C, holding time of 10-30 mins, heating rate of 100 °C/min under an applied pressure of 50 MPa. The morphology of the as-received and sintered compacts was examined by scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDS) and phase analysis was done by X-ray diffractometry (XRD). The sintered compacts without nano-TiN reveal lamellar structure while reinforced Ti-6Al-4V with nano-TiN shows a bimodal structure and titanium nitride has a great influence on a grain growth at high temperature. Furthermore, the microstructural formation mechanism was investigated. With the addition of the content of Ti-6Al-4V with 4 vol.% of nano-TiN, the micro-hardness also improved and this was due to homogenous distribution of TiN in Ti-6Al-4V matrix.

Effect of Alloying Type and Lean Sintering Atmosphere on the Performance of PM Components

NASA Astrophysics Data System (ADS)

Sundaram, M. Vattur; Shvab, R.; Millot, S.; Hryha, E.; Nyborg, L.

2017-12-01

In order to be cost effective and to meet increasing performance demands, powder metallurgy steel components require continuous improvement in terms of materials and process development. This study demonstrates the feasibility of manufacturing structural components using two different alloys systems, i.e. lean Cr-prealloyed and diffusion bonded water atomised powders with different processing conditions. The components were sintered at two different temperatures, i.e. 1120 and 1250 °C for 30 minutes in three different atmospheres: vacuum, N2- 10%H2 atmosphere as well as lean N2-5%H2-0.5%CO-(0.1-0.4)%CH4 sintering atmosphere. Components after sintering were further processed by either low pressure carburizing, sinterhardening or case hardening. All trials were performed in the industrial furnaces to simulate the actual production of the components. Microstructure, fractography, apparent and micro hardness analyses were performed close to the surface and in the middle of the sample to characterize the degree of sintering (temperature and atmosphere) and the effect of heat treatment. In all cases, components possess mostly martensitic microstructure with a few bainitic regions. The fracture surface shows well developed sinter necks. Inter- and trans-granular ductile and cleavage fracture modes are dominant and their fraction is determined by the alloy and processing route.

The development of manganese oxide coated ceramic membranes for combined catalytic ozonation and ultrafiltration of drinking water

NASA Astrophysics Data System (ADS)

Corneal, Lindsay Marie

A novel method for the preparation of hydrated MnO2 by the ozonation of MnCl2 in water is described. The hydrated MnO 2 was used to coat titania water filtration membranes using a layer-by-layer technique. The coated membranes were then sintered in air at 500°C for 45 minutes. Upon sintering, the MnO2 is converted to alpha-Mn 2O3 (as characterized by x-ray and electron diffraction). Atomic force microscopy (AFM) imaging showed no significant change in the roughness or height of the surface features of coated membranes, while scanning electron microscopy (SEM) imaging showed an increase in grain size with increasing number of coating layers. Energy dispersive x-ray spectroscopy (EDS) mapping and line scans revealed manganese present throughout the membrane, indicating that manganese dispersed into the porous membrane during the coating process and diffused into the titania grains during sintering. Selected area diffraction (SAD) of the coated and sintered membrane was used to index the surface layer as alpha-Mn2O3. The surface layer was uneven, although there was a trend of increasing thickness with increasing coating layers. The coating acts as a catalyst for the oxidation of organic matter when coated membranes are used in a hybrid ozonation-membrane filtration system. A trend of decreasing total organic carbon (TOC) in the permeate water was observed with increasing number of coating layers. The catalytic activity also manifests itself as improved recovery of the water flux due to oxidation of foulants on the membrane surface. Ceramic nanoparticle coatings on ceramic water filtration membranes must undergo high temperature sintering. However, this means that the underlying membrane, which has been engineered for a given molecular weight cut-off (MWCO), also undergoes a high temperature heat treatment that serves to increase pore size that have resulted in increases in permeability of titania membranes. Coating the titania membrane with manganese oxide followed by sintering in air at 500°C maintains the MWCO of the membranes, with high DI water permeability, which may be favorable in terms of membrane use. SEM micrographs of titania membrane samples sintered between 500°C to 900°C were analyzed to identify a statistically significant increase in grain size with increasing sintering temperature. The grains however, generally retain a uniform shape until the 900°C sintering temperature, where large, irregularly shaped grains were observed. AFM analysis showed a corresponding increase in the surface roughness of the membrane for the sample sintered at 900°C.

Fabrication, Structural Characterization and Uniaxial Tensile Properties of Novel Sintered Multi-Layer Wire Mesh Porous Plates

PubMed Central

Duan, Liuyang; Zhou, Zhaoyao; Yao, Bibo

2018-01-01

There is an increasing interest in developing porous metals or metallic foams for functional and structural applications. The study of the physical and mechanical properties of porous metals is very important and helpful for their application. In this paper, a novel sintered multilayer wire mesh porous plate material (WMPPs) with a thickness of 0.5 mm–3 mm and a porosity of 10–35% was prepared by winding, pressing, rolling, and subsequently vacuum sintering them. The pore size and total size distribution in the as-prepared samples were investigated using the bubble point method. The uniaxial tensile behavior of the WMPPs was investigated in terms of the sintering temperature, porosity, wire diameter, and manufacturing technology. The deformation process and the failure mechanism under the tensile press was also discussed based on the appearance of the fractures (SEM figures). The results indicated that the pore size and total size distribution were closely related to the raw material used and the sintering temperature. For the WMPPs prepared by the wire mesh, the pore structures were inerratic and the vast majority of pore size was less than 10 μm. On the other hand, for the WMPPs that were prepared by wire mesh and powder, the pore structures were irregular and the pore size ranged from 0 μm–50 μm. The experimental data showed that the tensile strength of WMPPs is much higher than any other porous metals or metallic foams. Higher sintering temperatures led to coarser joints between wires and resulted in higher tensile strength. The sintering temperature decreased from 1330 °C to 1130 °C and the tensile strength decreased from 296 MPa to 164 MPa. Lower porosity means that there are more metallurgical joints and metallic frameworks resisting deformation per unit volume. Therefore, lower porosities exhibit higher tensile strength. An increase of porosity from 17.14% to 32.5% led to the decrease of the tensile strength by 90 MPa. The coarser wires led to a bigger contact area between the interconnecting wires, resulting in a stronger sintering neck that exhibited higher tensile strength. The wire diameter increased from 81 μm to 122 μm and the tensile strength increased from 296 MPa to 362 MPa. The fracture morphology showed that the wires experience necking deformation and ductile fracture. PMID:29342129

Fabrication, Structural Characterization and Uniaxial Tensile Properties of Novel Sintered Multi-Layer Wire Mesh Porous Plates.

PubMed

Duan, Liuyang; Zhou, Zhaoyao; Yao, Bibo

2018-01-17

There is an increasing interest in developing porous metals or metallic foams for functional and structural applications. The study of the physical and mechanical properties of porous metals is very important and helpful for their application. In this paper, a novel sintered multilayer wire mesh porous plate material (WMPPs) with a thickness of 0.5 mm-3 mm and a porosity of 10-35% was prepared by winding, pressing, rolling, and subsequently vacuum sintering them. The pore size and total size distribution in the as-prepared samples were investigated using the bubble point method. The uniaxial tensile behavior of the WMPPs was investigated in terms of the sintering temperature, porosity, wire diameter, and manufacturing technology. The deformation process and the failure mechanism under the tensile press was also discussed based on the appearance of the fractures (SEM figures). The results indicated that the pore size and total size distribution were closely related to the raw material used and the sintering temperature. For the WMPPs prepared by the wire mesh, the pore structures were inerratic and the vast majority of pore size was less than 10 μm. On the other hand, for the WMPPs that were prepared by wire mesh and powder, the pore structures were irregular and the pore size ranged from 0 μm-50 μm. The experimental data showed that the tensile strength of WMPPs is much higher than any other porous metals or metallic foams. Higher sintering temperatures led to coarser joints between wires and resulted in higher tensile strength. The sintering temperature decreased from 1330 °C to 1130 °C and the tensile strength decreased from 296 MPa to 164 MPa. Lower porosity means that there are more metallurgical joints and metallic frameworks resisting deformation per unit volume. Therefore, lower porosities exhibit higher tensile strength. An increase of porosity from 17.14% to 32.5% led to the decrease of the tensile strength by 90 MPa. The coarser wires led to a bigger contact area between the interconnecting wires, resulting in a stronger sintering neck that exhibited higher tensile strength. The wire diameter increased from 81 μm to 122 μm and the tensile strength increased from 296 MPa to 362 MPa. The fracture morphology showed that the wires experience necking deformation and ductile fracture.

Densification of Zirconia with Borates.

DTIC Science & Technology

1980-01-24

solid electrolytes for fuel cell and oxygen sensor applications.1 ’ 2 The sintering temperatures for commercial quality stabilized zirconia powders are...in the temperature range 1450-1500C). A few studies were also made using a much coarser particle size (- 1-2 pm ave.) cubic stabilized zirconia ... powder , "Zircoa B" [Zirconia Corp. of America]. The additives used as sintering aids were reagent grade horic anhydride, calcium metaborate and calcium

Sintering of highly porous silica-particle samples: analogues of early Solar-System aggregates

NASA Astrophysics Data System (ADS)

Poppe, T.

2003-07-01

I describe a new method to make particle layers which consist of SiO 2 spheres with 0.78 μm radius. The layers were produced by sedimentation of aggregates which had grown in ballistic particle collisions, and the layers had a porosity of 0.95. They were used for experiments on sintering, i.e., the samples were heated in an oven at varying temperatures and heating durations, and the samples were analyzed by scanning electron microscopy. Based on the change of particle diameter, surface diffusion sintering and viscous flow are identified as important transformation mechanisms. The first effect dominated at the start of restructuring and the latter at higher temperatures. The neck growth of adjacent particles was fitted to a surface diffusion sintering model and predicts neck radii as a heating temperature and duration function. Between the temperature range of neck formation and of melting, further restructuring occurred which lead to dissolution of particulate structure and to densification and which resulted in a porous object consisting of straight elongated substructures which connected kinks of higher material density. The thermal transformation is important for the change of strength, collisional behavior, light-scattering properties, and thermal conductivity with relevance to dust aggregates, planetesimals, comets, interplanetary dust particles, and regolith-covered celestial bodies.

Sintering temperature effect of divalent europium ion doped tetra-calcium phosphate phosphors for latent fingerprint detection

NASA Astrophysics Data System (ADS)

Hong, Woo Tae; Park, Jin Young; Je, Jae-Yong; Yang, Hyun Kyoung

2018-07-01

Ca4(PO4)2O:Eu2+ (CPO:Eu2+) phosphors were successfully synthesized by high-energy ball milling. In order to study the effect of sintering temperature, the phosphors were synthesized at various sintering temperatures. The crystal structure of CPO:Eu2+ was determined to be monoclinic P21. Owing to the f-d transitions of the Eu2+ ions in the CPO:Eu2+ phosphors, the PL spectra of the phosphors showed an intense red emission centered at 635 nm with 418 nm excitation. Using high-energy ball milling, a more intense emission (compared to that reported from other research) can be visually observed with human eyes in the form of orange-red light, which is helpful in latent fingerprint detection. In addition, high-temperature sintering results in an increase of the PL intensity owing to the larger particle size and lower levels of impurities in the CPO:Eu2+ phosphors. The latent fingerprint image obtained by using CPO:Eu2+ phosphors reveals a high contrast for various substrate materials, because the phosphors exhibit strong red emission and adhere to the residue of the fingerprint after flowing. On the basis of these results, red-emitting CPO:Eu2+ phosphors can be used for the detection of latent fingerprints in solving criminal cases.

Effects of oxide additions and temperature on sinterability of milled silicon nitride

NASA Technical Reports Server (NTRS)

Arias, A.

1980-01-01

Specimens of milled alpha-Si3N4 with 0 to 5.07 equivalent percent of oxide additions were pressureless sintered at 1650 to 1820 C for 4 hours in nitrogen while covered with powdered Si3N4 + SiO2. Densities of less than or equal to 97.5 percent resulted with approximately 2.5 equivalent percent of MgO, CeO2, Y2O3, and three mixtures involving these oxides. Densities of greater than or equal to 94 percent were obtained with approximately 0.62 equivalent percent of the same additives. At most temperatures, best sinterability (density maxima) was obtained with 1.2 to 2.5 equivalent percent additive.

Sintering of wax for controlling release from pellets.

PubMed

Singh, Reena; Poddar, S S; Chivate, Amit

2007-09-14

The purpose of the present study was to investigate incorporation of hydrophobic (ie, waxy) material into pellets using a thermal sintering technique and to evaluate the pellets in vitro for controlled release. Pellets prepared by extrusion-spheronization technology were formulated with a water-soluble drug, microcrystalline cellulose, and carnauba wax. Powdered carnauba wax (4%-20%) prepared by grinding or by emulsification was studied with an attempt to retard the drug release. The inclusion of ground or emulsified carnauba wax did not sustain the release of theophylline for more than 3 hours. Matrix pellets of theophylline prepared with various concentrations of carnauba wax were sintered thermally at various times and temperatures. In vitro drug release profiles indicated an increase in drug release retardation with increasing carnauba wax concentration. Pellets prepared with ground wax showed a higher standard deviation than did those prepared with emulsified wax. There was incomplete release at the end of 12 hours for pellets prepared with 20% ground or emulsified wax. The sintering temperature and duration were optimized to allow for a sustained release lasting at least 12 hours. The optimized temperature and duration were found to be 100 degrees C and 140 seconds, respectively. The sintered pellets had a higher hydrophobicity than did the unsintered pellets. Scanning electron micrographs indicated that the carnauba wax moved internally, thereby increasing the surface area of wax within the pellets.

Bonding of TRIP-Steel/Al2O3-(3Y)-TZP Composites and (3Y)-TZP Ceramic by a Spark Plasma Sintering (SPS) Apparatus

PubMed Central

Miriyev, Aslan; Grützner, Steffen; Krüger, Lutz; Kalabukhov, Sergey; Frage, Nachum

2016-01-01

A combination of the high damage tolerance of TRIP-steel and the extremely low thermal conductivity of partially stabilized zirconia (PSZ) can provide controlled thermal-mechanical properties to sandwich-shaped composite specimens comprising these materials. Sintering the (TRIP-steel-PSZ)/PSZ sandwich in a single step is very difficult due to differences in the sintering temperature and densification kinetics of the composite and the ceramic powders. In the present study, we successfully applied a two-step approach involving separate SPS consolidation of pure (3Y)-TZP and composites containing 20 vol % TRIP-steel, 40 vol % Al2O3 and 40 vol % (3Y)-TZP ceramic phase, and subsequent diffusion joining of both sintered components in an SPS apparatus. The microstructure and properties of the sintered and bonded specimens were characterized. No defects at the interface between the TZP and the composite after joining in the 1050–1150 °C temperature range were observed. Only limited grain growth occurred during joining, while crystallite size, hardness, shear strength and the fraction of the monoclinic phase in the TZP ceramic virtually did not change. The slight increase of the TZP layer’s fracture toughness with the joining temperature was attributed to the effect of grain size on transformation toughening. PMID:28773680

Lightweight Aggregate Made from Dredged Material in Green Roof Construction for Stormwater Management

PubMed Central

Liu, Rui; Coffman, Reid

2016-01-01

More than 1.15 million cubic meters (1.5 million cubic yards) of sediment require annual removal from harbors and ports along Ohio’s Lake Erie coast. Disposing of these materials into landfills depletes land resources, while open water placement of these materials deteriorates water quality. There are more than 14,000 acres of revitalizing brownfields in Cleveland, U.S., many containing up to 90% impervious surface, which does not allow “infiltration” based stormwater practices required by contemporary site-based stormwater regulation. This study investigates the potential of sintering the dredged material from the Harbor of Cleveland in Lake Erie to produce lightweight aggregate (LWA), and apply the LWA to green roof construction. Chemical and thermal analyses revealed the sintered material can serve for LWA production when preheated at 550 °C and sintered at a higher temperature. Through dewatering, drying, sieving, pellet making, preheating, and sintering with varying temperatures (900–1100 °C), LWAs with porous microstructures are produced with specific gravities ranging from 1.46 to 1.74, and water absorption capacities ranging from 11% to 23%. The water absorption capacity of the aggregate decreases as sintering temperature increases. The LWA was incorporated into the growing media of a green roof plot, which has higher water retention capacity than the conventional green roof system. PMID:28773734

Effect of Sintering Temperature to Physical, Magnetic Properties and Crystal Structure on Permanent Magnet BaFe12O19 Prepared From Mill Scale

NASA Astrophysics Data System (ADS)

Ramlan; Muljadi; Sardjono, Priyo; Gulo, Fakhili; Setiabudidaya, Dedi

2017-07-01

Permanent magnet of Barium hexa Ferrite with formula BaFe12O19 has been made by metallurgy powder method from raw materials : Barium carbonate (BaCO3 E-merck) and Iron Oxide (Fe2O3 from mill scale). Both of raw materials have been mixed with stoichiometry composition by using a ball mill for 24 hours. The fine powder obtained from milling process was formed by using a hydraulic press at pressure 50 MPa and continued with sintering process. The sintering temperature was varied : 1150°C, 1200°C, 1250°C and 1300°C with holding time for 1 hour. The sintered samples were characterized such as : physical properties (bulk density, porosity and shrinkage), magnetic properties (flux density, remanence, coercivity and magnetic saturation) by using VSM and crystal structure by using XRD. According characterization results show that the crystal structure of BaFe12O19 does not change after sintering process, but the grain size tends to increase. The optimum condition is achieved at temperature 1250°C, and at this condition, the sample has characterization such as : bulk density = 4.35 g/cm3, porosity = 1.03% and firing shrinkage = 11.63%, flux density = 681.1 Gauss, remanence (σr) = 20.78 emu/g, coercivity (Hc) = 2058 Oe and magnetic saturation (σs) 45.16 emu/g.

Sintering mechanism of the CaF2 on hydroxyapatite by a 10.6-l microm CO2 laser.

PubMed

Wu, Cheng-Chei; Roan, Rong-Tai; Chen, Jeng-Huey

2002-01-01

Laser has been reported as a heat source for melting and re-crystallization. Occurring at about 1100 degrees C, the melting of surface dental enamel along with re-crystallization might have an assistant role in the therapy of hypersensitive tooth, apical sealing of endodontic surgery in dentistry, preventive dentistry for pit and fissure sealing, and fluoridation. For laser to be accepted in clinical applications, it is desired that, studies must show the incorporation of CaF(2) into hydroxyapatite could reduce the sintering temperature for the sake of safety. In this study, the Sharplan 20XJ CO(2) laser with 10.6- microm wavelength was set under the following parameters: power, 5 W; repetitive mode, 0.1 second; beam, focused. Fluorite was added to hydroxyapatite as a synthetic compound to lower the sintering temperature. Human dental enamel without caries was used for in vitro sintering test. Scanning electron microscopy (SEM), X-ray diffractometer (XRD), Fourier transforming infrared spectroscopy (FTIR), and differential thermal analysis/thermogravimetric analysis (DAT/TGA) were used for the investigation of sintering mechanism of CaF(2). Fusion between hexagonal shape crystals and cubic shape crystals (CaF(2)) were observed under SEM study. Hexagonal shape crystals indicated the formation of fluorapatite under XRD analysis. Under FTIR study, we examined reductions of water (3445 cm(-1)) and hydroxyl bands (3567 and 627 cm(-1)) in irradiated compounds. From the DTA pattern of synthetic compound, it showed the endothermic reaction reaching its peak point around 1180 +/- 20 degrees C. It was attributed to the phase transformation and/or initial melting. In this study, we proposed the interrelationship of the eutectics between initiator (CaF(2)) and the reaction product (calcium hydroxide) that reduced the sintering temperature. It appeared that the co-eutectics interacted to reduce the sintering temperature of hydroxyapatite below 800 degrees C and that the key eutectic was calcium hydroxide. The clinical feasibility of the melting and re-crystallization of hydroxyapatite under 10.6-microm CO(2) laser would be therefore enhanced. Copyright 2002 Wiley-Liss, Inc.

Surface-selective laser sintering of thermolabile polymer particles using water as heating sensitizer

NASA Astrophysics Data System (ADS)

Antonov, E. N.; Krotova, L. I.; Minaev, N. V.; Minaeva, S. A.; Mironov, A. V.; Popov, V. K.; Bagratashvili, V. N.

2015-11-01

We report the implementation of a novel scheme for surface-selective laser sintering (SSLS) of polymer particles, based on using water as a sensitizer of laser heating and sintering of particles as well as laser radiation at a wavelength of 1.94 μm, corresponding to the strong absorption band of water. A method of sintering powders of poly(lactide-co-glycolide), a hydrophobic bioresorbable polymer, after modifying its surface with an aqueous solution of hyaluronic acid is developed. The sintering thresholds for wetted polymer are by 3 - 4 times lower than those for sintering in air. The presence of water restricts the temperature of the heated polymer, preventing its thermal destruction. Polymer matrices with a developed porous structure are obtained. The proposed SSLS method can be applied to produce bioresorbable polymer matrices for tissue engineering.

Influence of pH Adjustment Parameter for Sol-Gel Modification on Structural, Microstructure, and Magnetic Properties of Nanocrystalline Strontium Ferrite

NASA Astrophysics Data System (ADS)

Azis, Raba'ah Syahidah; Sulaiman, Sakinah; Ibrahim, Idza Riati; Zakaria, Azmi; Hassan, Jumiah; Muda, Nor Nadhirah Che; Nazlan, Rodziah; Saiden, Norlaily M.; Fen, Yap Wing; Mustaffa, Muhammad Syazwan; Matori, Khamirul Amin

2018-05-01

Synthesis of nanocrystalline strontium ferrite (SrFe12O19) via sol-gel is sensitive to its modification parameters. Therefore, in this study, an attempt of regulating the pH as a sol-gel modification parameter during preparation of SrFe12O19 nanoparticles sintered at a low sintering temperature of 900 °C has been presented. The relationship of varying pH (pH 0 to 8) on structural, microstructures, and magnetic behaviors of SrFe12O19 nanoparticles were characterized by X-ray diffraction (XRD), field emission scanning microscope (FESEM), and vibrating sample magnetometer (VSM). Varying the pH of precursor exhibited a strong effect on the sintered density, crystal structure and magnetic properties of the SrFe12O19 nanoparticles. As the pH is 0, the SrFe12O19 produced relatively largest density, saturation magnetization, M s, and coercivity, H c, at a low sintering temperature of 900 °C. The grain size of SrFe12O19 is obtained in the range of 73.6 to 133.3 nm. The porosity of the sample affected the density and the magnetic properties of the SrFe12O19 ferrite. It is suggested that the low-temperature sintered SrFe12O19 at pH 0 displayed M s of 44.19 emu/g and H c of 6403.6 Oe, possessing a significant potential for applying in low-temperature co-fired ceramic permanent magnet.

Effects of Heat Treatment on the Microstructures and High Temperature Mechanical Properties of Hypereutectic Al-14Si-Cu-Mg Alloy Manufactured by Liquid Phase Sintering Process

NASA Astrophysics Data System (ADS)

Heo, Joon-Young; Gwon, Jin-Han; Park, Jong-Kwan; Lee, Kee-Ahn

2018-05-01

Hypereutectic Al-Si alloy is an aluminum alloy containing at least 12.6 wt.% Si. It is necessary to evenly control the primary Si particle size and distribution in hypereutectic Al-Si alloy. In order to achieve this, there have been attempts to manufacture hypereutectic Al-Si alloy through a liquid phase sintering. This study investigated the microstructures and high temperature mechanical properties of hypereutectic Al-14Si-Cu-Mg alloy manufactured by liquid phase sintering process and changes in them after T6 heat treatment. Microstructural observation identified large amounts of small primary Si particles evenly distributed in the matrix, and small amounts of various precipitation phases were found in grain interiors and grain boundaries. After T6 heat treatment, the primary Si particle size and shape did not change significantly, but the size and distribution of CuAl2 ( θ) and AlCuMgSi ( Q) changed. Hardness tests measured 97.36 HV after sintering and 142.5 HV after heat treatment. Compression tests were performed from room temperature to 300 °C. The results represented that yield strength was greater after heat treatment (RT 300 °C: 351 93 MPa) than after sintering (RT 300 °C: 210 89 MPa). Fracture surface analysis identified cracks developing mostly along the interface between the primary Si particles and the matrix with some differences among temperature conditions. In addition, brittle fracture mode was found after T6 heat treatment.

Effects of Ceramic Density and Sintering Temperature on the Mechanical Properties of a Novel Polymer-Infiltrated Ceramic-Network Zirconia Dental Restorative (Filling) Material.

PubMed

Li, Weiyan; Sun, Jian

2018-05-10

BACKGROUND Polymer-infiltrated ceramic-network (PICN) dental material is a new and practical development in orthodontics. Sintering is the process of forming a stable solid mass from a powder by heating without melting. The aim of this study was to evaluate the effects of sintering temperature on the mechanical properties of a PICN zirconia dental material. MATERIAL AND METHODS A dense zirconia ceramic and four PICN zirconia dental materials, with varying porosities, were sintered at three different temperatures; 12 PICN zirconia dental materials based on these porous ceramics were prepared, as well as a pure polymer. After the specimen preparation, flexural strength and elastic modulus values were measured using the three-point bending test, and fracture toughness were determined by the single-edge notched beam (SENB) method. The Vickers hardness test method was used with an indentation strength (IS) test. Scanning electron microscopy (SEM) was used to examine the microstructure of the ceramic surface and the fracture surface. RESULTS Mechanical properties of the PICN dental materials, including flexural strength, elastic modulus, fracture toughness, and hardness, were more similar to the properties of natural teeth when compared with traditional dental ceramic materials, and were affected by the density and sintering temperature. SEM showed that the porous ceramic network became cohesive and that the length of cracks in the PICN dental material was reduced. CONCLUSIONS PICN zirconia dental materials were characterized by similar mechanical properties to natural dental tissues, but further studies are required continue to improve the similarities with natural human enamel and dentin.

Effects of Ceramic Density and Sintering Temperature on the Mechanical Properties of a Novel Polymer-Infiltrated Ceramic-Network Zirconia Dental Restorative (Filling) Material

PubMed Central

Li, Weiyan

2018-01-01

Background Polymer-infiltrated ceramic-network (PICN) dental material is a new and practical development in orthodontics. Sintering is the process of forming a stable solid mass from a powder by heating without melting. The aim of this study was to evaluate the effects of sintering temperature on the mechanical properties of a PICN zirconia dental material. Material/Methods A dense zirconia ceramic and four PICN zirconia dental materials, with varying porosities, were sintered at three different temperatures; 12 PICN zirconia dental materials based on these porous ceramics were prepared, as well as a pure polymer. After the specimen preparation, flexural strength and elastic modulus values were measured using the three-point bending test, and fracture toughness were determined by the single-edge notched beam (SENB) method. The Vickers hardness test method was used with an indentation strength (IS) test. Scanning electron microscopy (SEM) was used to examine the microstructure of the ceramic surface and the fracture surface. Results Mechanical properties of the PICN dental materials, including flexural strength, elastic modulus, fracture toughness, and hardness, were more similar to the properties of natural teeth when compared with traditional dental ceramic materials, and were affected by the density and sintering temperature. SEM showed that the porous ceramic network became cohesive and that the length of cracks in the PICN dental material was reduced. Conclusions PICN zirconia dental materials were characterized by similar mechanical properties to natural dental tissues, but further studies are required continue to improve the similarities with natural human enamel and dentin. PMID:29746449

Sintering of catalytic nanoparticles: particle migration or Ostwald ripening?

PubMed

Hansen, Thomas W; Delariva, Andrew T; Challa, Sivakumar R; Datye, Abhaya K

2013-08-20

Metal nanoparticles contain the active sites in heterogeneous catalysts, which are important for many industrial applications including the production of clean fuels, chemicals and pharmaceuticals, and the cleanup of exhaust from automobiles and stationary power plants. Sintering, or thermal deactivation, is an important mechanism for the loss of catalyst activity. This is especially true for high temperature catalytic processes, such as steam reforming, automotive exhaust treatment, or catalytic combustion. With dwindling supplies of precious metals and increasing demand, fundamental understanding of catalyst sintering is very important for achieving clean energy and a clean environment, and for efficient chemical conversion processes with atom selectivity. Scientists have proposed two mechanisms for sintering of nanoparticles: particle migration and coalescence (PMC) and Ostwald ripening (OR). PMC involves the mobility of particles in a Brownian-like motion on the support surface, with subsequent coalescence leading to nanoparticle growth. In contrast, OR involves the migration of adatoms or mobile molecular species, driven by differences in free energy and local adatom concentrations on the support surface. In this Account, we divide the process of sintering into three phases. Phase I involves rapid loss in catalyst activity (or surface area), phase II is where sintering slows down, and phase III is where the catalyst may reach a stable performance. Much of the previous work is based on inferences from catalysts that were observed before and after long term treatments. While the general phenomena can be captured correctly, the mechanisms cannot be determined. Advancements in the techniques of in situ TEM allow us to observe catalysts at elevated temperatures under working conditions. We review recent evidence obtained via in situ methods to determine the relative importance of PMC and OR in each of these phases of catalyst sintering. The evidence suggests that, in phase I, OR is responsible for the rapid loss of activity that occurs when particles are very small. Surprisingly, very little PMC is observed in this phase. Instead, the rapid loss of activity is caused by the disappearance of the smallest particles. These findings are in good agreement with representative atomistic simulations of sintering. In phase II, sintering slows down since the smallest particles have disappeared. We now see a combination of PMC and OR, but do not fully understand the relative contribution of each of these processes to the overall rates of sintering. In phase III, the particles have grown large and other parasitic phenomena, such as support restructuring, can become important, especially at high temperatures. Examining the evolution of particle size and surface area with time, we do not see a stable or equilibrium state, especially for catalysts operating at elevated temperatures. In conclusion, the recent literature, especially on in situ studies, shows that OR is the dominant process causing the growth of nanoparticle size. Consequently, this leads to the loss of surface area and activity. While particle migration could be controlled through suitable structuring of catalyst supports, it is more difficult to control the mobility of atomically dispersed species. These insights into the mechanisms of sintering could help to develop sinter-resistant catalysts, with the ultimate goal of designing catalysts that are self-healing.

Improved silicon carbide for advanced heat engines. II - Pressureless sintering and mechanical properties of injection molded silicon carbide

NASA Technical Reports Server (NTRS)

Whalen, Thomas J.; Baer, J. R.

1989-01-01

The influence on density and strength of pressureless sintering in vacuum and argon environments has been evaluated with injection molded SiC materials. Main effects and two factor interactions of sintering (cycle variables temperature, time, heating rate, and atmosphere) were assessed. An improved understanding of the influence of the processing flaws and sintering conditions has been obtained. Strength and density have improved from a baseline level of 299 MPa (43.3 Ksi) and 94 pct of theoretical density to values greater than 483 MPa (70 Ksi) and 97 pct.

Report on in-situ studies of flash sintering of uranium dioxide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Raftery, Alicia Marie

Flash sintering is a novel type of field assisted sintering that uses an electric field and current to provide densification of materials on very short time scales. The potential for field assisted sintering techniques to be used in producing nuclear fuel is gaining recognition due to the potential economic benefits and improvements in material properties. The flash sintering behavior has so far been linked to applied and material parameters, but the underlying mechanisms active during flash sintering have yet to be identified. This report summarizes the efforts to investigate flash sintering of uranium dioxide using dilatometer studies at Los Alamosmore » National Laboratory and two separate sets of in-situ studies at Brookhaven National Laboratory’s NSLS-II XPD-1 beamline. The purpose of the dilatometer studies was to understand individual parameter (applied and material) effects on the flash behavior and the purpose of the in-situ studies was to better understand the mechanisms active during flash sintering. As far as applied parameters, it was found that stoichiometry, or oxygen-to-metal ratio, has a significant effect on the flash behavior (time to flash and speed of flash). Composite systems were found to have degraded sintering behavior relative to pure UO 2. The critical field studies are complete for UO 2.00 and will be analyzed against an existing model for comparison. The in-situ studies showed that the strength of the field and current are directly related to the sample temperature, with temperature-driven phase changes occurring at high values. The existence of an ‘incubation time’ has been questioned, due to a continuous change in lattice parameter values from the moment that the field is applied. Some results from the in-situ experiments, which should provide evidence regarding ion migration, are still being analyzed. Some preliminary conclusions can be made from these results with regard to using field assisted sintering to fabricate nuclear fuel. First, the pure UO 2-based system shows promising behavior with flash sintering, but composite systems are likely to show better sintering behavior with spark plasma sintering. Efforts to develop these methods should therefore be tailored towards the likelihood of success. Additionally, modeling is a rapidly developing aspect of current flash sintering research and should be used in parallel with experiments. Ultimately, ongoing flash sintering studies on various materials, like those summarized in this report, are rapidly contributing to the feasibility of controlling this method for use in the future.« less

The effect of precipitation and calcination parameters on oxalate derived ThO2 pellets

NASA Astrophysics Data System (ADS)

Wangle, Tadeas; Tyrpekl, Vaclav; Cagno, Simone; Delloye, Thierry; Larcher, Olivier; Cardinaels, Thomas; Vleugels, Jozef; Verwerft, Marc

2017-11-01

Thorium oxalate is easy to prepare, but the derived oxide powders retain the platelet morphology of the primary oxalate. This negatively impacts packing and sintering. If powder milling is to be avoided, powder synthesis needs to be optimized. That is the goal of this paper, where different precipitation strategies were used and their effect on powder characteristics and pellet synthesis was investigated. Oxalates prepared by adding a thorium nitrate solution to an oxalic acid solution proved most promising. Further optimizing of the calcination temperature revealed that with increasing calcination temperature the packing density improved significantly. This came at the cost of decreased early stage sintering and a higher frequency of end-capping during compaction. The calcination temperature at which the highest final density can be reached was dependent on the sintering cycle. Furthermore, the ThO2 powders had less surface area and thus adsorbed less gases during storage when calcined at higher temperatures.

Phenomenological analysis of densification mechanism during spark plasma sintering of MgAl2O4

NASA Astrophysics Data System (ADS)

Bernard-Granger, Guillaume; Benameur, Nassira; Addad, Ahmed; Nygren, Mats; Guizard, Christian; Deville, Sylvain

2009-05-01

Spark plasma sintering (SPS) of MgAl2O4 powder was investigated at temperatures between 1200 and 1300{\\deg}C. A significant grain growth was observed during densification. The densification rate always exhibits at least one strong minimum, and resumes after an incubation period. Transmission electron microscopy investigations performed on sintered samples never revealed extensive dislocation activity in the elemental grains. The densification mechanism involved during SPS was determined by anisothermal (investigation of the heating stage of a SPS run) and isothermal methods (investigation at given soak temperatures). Grain-boundary sliding, accommodated by an in-series {interface-reaction/lattice diffusion of the O$^2$-anions} mechanism controlled by the interface-reaction step, governs densification. The zero-densification-rate period, detected for all soak temperatures, arise from the difficulty of annealing vacancies, necessary for the densification to proceed. The detection of atomic ledges at grain boundaries and the modification of the stoichiometry of spinel during SPS could be related to the difficulty to anneal vacancies at temperature soaks.

Mechanical and electrical properties of low temperature phase MnBi

NASA Astrophysics Data System (ADS)

Jiang, Xiujuan; Roosendaal, Timothy; Lu, Xiaochuan; Palasyuk, Olena; Dennis, Kevin W.; Dahl, Michael; Choi, Jung-Pyung; Polikarpov, Evgueni; Marinescu, Melania; Cui, Jun

2016-01-01

Low temperature phase (LTP) manganese bismuth (MnBi) is a promising rare-earth-free permanent magnet material due to its high intrinsic coercivity and large positive temperature coefficient. While scientists are making progress on fabricating bulk MnBi magnets, engineers have begun considering MnBi magnets for motor applications. Physical properties other than magnetic ones could significantly affect motor design. Here, we report results of our investigation on the mechanical and electrical properties of bulk LTP MnBi and their temperature dependence. A MnBi ingot was prepared using an arc melting technique and subsequently underwent grinding, sieving, heat treatment, and cryomilling. The resultant powders with a particle size of ˜5 μm were magnetically aligned, cold pressed, and sintered at a predefined temperature. Micro-hardness testing was performed on a part of original ingot and we found that the hardness of MnBi was 109 ± 15 HV. The sintered magnets were subjected to compressive testing at different temperatures and it was observed that a sintered MnBi magnet fractured when the compressive stress exceeded 193 MPa at room temperature. Impedance spectra were obtained using electrochemical impedance spectroscopy at various temperatures and we found that the electrical resistance of MnBi at room temperature was about 6.85 μΩ m.

Performance and Reliability of Bonded Interfaces for High-temperature Packaging: Annual Progress Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

DeVoto, Douglas J.

2017-10-19

As maximum device temperatures approach 200 °Celsius, continuous operation, sintered silver materials promise to maintain bonds at these high temperatures without excessive degradation rates. A detailed characterization of the thermal performance and reliability of sintered silver materials and processes has been initiated for the next year. Future steps in crack modeling include efforts to simulate crack propagation directly using the extended finite element method (X-FEM), a numerical technique that uses the partition of unity method for modeling discontinuities such as cracks in a system.

Hydrothermal Cold Sintering

NASA Astrophysics Data System (ADS)

Kang, Xiaoyu

Solid state sintering transforms particle compact to a physically robust and dense polycrystalline monolith driven by reduction of surface energy and curvature. Since bulk diffusion is required for neck formation and pore elimination, sintering temperature about 2/3 of melting point is needed. It thus places limitations for materials synthesis and integration, and contributes to significant energy consumption in ceramic processing. Furthermore, since surface transport requires lower temperature than bulk processes, grain growth is often rapid and can be undesired for physical properties. For these reasons, several techniques have been developed including Liquid Phase Sintering (LPS), Hot Pressing (HP) and Field Assisted Sintering Technique (FAST), which introduce either viscous melt, external pressure or electric field to speed up densification rates at lower temperature. However, because of their inherent reliability on bulk diffusion, temperatures required are often too high for integrating polymers and non-noble metals. Reduction of sintering temperature below 400 °C would require a different densification mechanism that is based on surface transport with external forces to drive volume shrinkage. Densification method combining uniaxial pressure and solution under hydrothermal condition was first demonstrated by Kanahara's group at Kochi University in 1986 and was brought to our attention by the work of Kahari, etc, from University of Oulu on densification of Li2MoO 4 in 2015. This relatively new process showed promising ultra-low densification temperature below 300 °C, however little was known about its fundamental mechanism and scope of applications, which became the main focus of this dissertation. In this work, a uniaxial hydraulic press, a standard stainless steel 1/2 inch diameter die with heating band were utilized in densifying metal oxides. Applied pressure and sintering temperature were between 100 MPa and 700 MPa and from room temperature to 300 °C, respectively. Process variables were defined and effects of individual parameters were studied systematically through control variable method with Li2MoO4-water system. Crystalline structure, fractured surface morphology and chemical bonding information of the cold sintered pellets were studied with X-ray diffraction (XRD), field effect scanning electron microscopy (FE-SEM) and Raman spectroscopy, etc. Densification mechanism studies were conducted on ZnO. Through comparison experiments, it was found that the Zn2+ concentration in the solution is critical for densification, while dissolution of grains only serves as a means to the former. Through pressure dependent studies, a critical value was found, which correlated well with the hydrostatic pressure keeping liquid water from thermal expansion. These results confirmed establishment of hydrothermal condition that would be important for mass transport in densification. Densification rate variations with process time was estimated and similar time dependence to Kingery's model was found. The densification process was proposed to be consist of three consecutive stages, which are quick initial compaction, grain rearrangement and dissolution-reprecipitation events. Binary metal oxides with different acidities were subjected to cold sintering with various aqueous solutions in establishing a criteria for material selection. It was found that in general materials with high solubility at around neutral pH, high dissolution kinetics and similar free energy to their hydroxides or hydrates at ambient would be more likely for full densification with high phase purity. The anions in solution should also be wisely selected to avoid stable compound or complex formation. To extend the applicable material list for full densification, non-aqueous solvent of dimethyl sulfoxide (DMSO) based solution was studied for cold sintering. Both improvement of pellet density and suppression of hydroxide formation were achieved for MnO by using DMSO-HOAc solution. With this strategy, densification of other metal oxides with strong hydroxide formation may also be improved, for example oxides of alkaline earth and many transition metals. Finally, the author's previous work on Zn1-xMg xO thin films is included in Chapter 7.

Silicon nitride: A ceramic material with outstanding resistance to thermal shock and corrosion

NASA Technical Reports Server (NTRS)

Huebner, K. H.; Saure, F.

1983-01-01

The known physical, mechanical and chemical properties of reaction-sintered silicon nitride are summarized. This material deserves interest especially because of its unusually good resistance to thermal shock and corrosion at high temperatures. Two types are distinguished: reaction-sintered (porous) and hot-pressed (dense) Si3N4. Only the reaction-sintered material which is being produced today in large scale as crucibles, pipes, nozzles and tiles is considered.

Thermal barrier coating resistant to sintering

DOEpatents

Subramanian, Ramesh; Seth, Brij B.

2004-06-29

A device (10) is made, having a ceramic thermal barrier coating layer (16) characterized by a microstructure having gaps (18) with a sintering inhibiting material (22) disposed on the columns (20) within the gaps (18). The sintering resistant material (22) is stable over the range of operating temperatures of the device (10), is not soluble with the underlying ceramic layer (16) and is applied by a process that is not an electron beam physical vapor deposition process.

Method of making a composite refractory material

DOEpatents

Morrow, Marvin S.; Holcombe, Cressie E.

1995-01-01

A composite refractory material is prepared by combining boron carbide with furan resin to form a mixture containing about 8 wt. % furan resin. The mixture is formed into a pellet which is placed into a grit pack comprising an oxide of an element such as yttrium to form a sinterable body. The sinterable body is sintered under vacuum with microwave energy at a temperature no greater than 2000.degree. C. to form a composite refractory material.

Method of making a composite refractory material

DOEpatents

Morrow, M.S.; Holcombe, C.E.

1995-09-26

A composite refractory material is prepared by combining boron carbide with furan resin to form a mixture containing about 8 wt. % furan resin. The mixture is formed into a pellet which is placed into a grit pack comprising an oxide of an element such as yttrium to form a sinterable body. The sinterable body is sintered under vacuum with microwave energy at a temperature no greater than 2000 C to form a composite refractory material.

Synthesis of Nanocrystalline CaWO4 as Low-Temperature Co-fired Ceramic Material: Processing, Structural and Physical Properties

NASA Astrophysics Data System (ADS)

Vidya, S.; Solomon, Sam; Thomas, J. K.

2013-01-01

Nanocrystalline scheelite CaWO4, a promising material for low-temperature co-fired ceramic (LTCC) applications, has been successfully synthesized through a single-step autoignition combustion route. Structural analysis of the sample was performed by powder x-ray diffraction (XRD), Fourier-transform infrared spectroscopy, and Raman spectroscopy. The XRD analysis revealed that the as-prepared sample was single phase with scheelite tetragonal structure. The basic optical properties and optical constants of the CaWO4 nanopowder were studied using ultraviolet (UV)-visible absorption spectroscopy, which showed that the material was a wide-bandgap semiconductor with bandgap of 4.7 eV at room temperature. The sample showed poor transmittance in the ultraviolet region but maximum transmission in the visible/near-infrared regions. The photoluminescence spectra recorded at different temperatures showed intense emission in the green region. The particle size estimated from transmission electron microscopy was 23 nm. The feasibility of CaWO4 for LTCC applications was studied from its sintering behavior. The sample was sintered at a relatively low temperature of 810°C to high density, without using any sintering aid. The surface morphology of the sintered sample was analyzed by scanning electron microscopy. The dielectric constant and loss factor of the sample measured at 5 MHz were found to be 10.50 and 1.56 × 10-3 at room temperature. The temperature coefficient of the dielectric constant was -88.71 ppm/°C. The experimental results obtained in this work demonstrate the potential of nano-CaWO4 as a low-temperature co-fired ceramic as well as an excellent luminescent material.

Sintered bentonite ceramics for the immobilization of cesium- and strontium-bearing radioactive waste

NASA Astrophysics Data System (ADS)

Ortega, Luis Humberto

The Advanced Fuel Cycle Initiative (AFCI) is a Department of Energy (DOE) program, that has been investigating technologies to improve fuel cycle sustainability and proliferation resistance. One of the program's goals is to reduce the amount of radioactive waste requiring repository disposal. Cesium and strontium are two primary heat sources during the first 300 years of spent nuclear fuel's decay, specifically isotopes Cs-137 and Sr-90. Removal of these isotopes from spent nuclear fuel will reduce the activity of the bulk spent fuel, reducing the heat given off by the waste. Once the cesium and strontium are separated from the bulk of the spent nuclear fuel, the isotopes must be immobilized. This study is focused on a method to immobilize a cesium- and strontium-bearing radioactive liquid waste stream. While there are various schemes to remove these isotopes from spent fuel, this study has focused on a nitric acid based liquid waste. The waste liquid was mixed with the bentonite, dried then sintered. To be effective sintering temperatures from 1100 to 1200°C were required, and waste concentrations must be at least 25 wt%. The product is a leach resistant ceramic solid with the waste elements embedded within alumino-silicates and a silicon rich phase. The cesium is primarily incorporated into pollucite and the strontium into a monoclinic feldspar. The simulated waste was prepared from nitrate salts of stable ions. These ions were limited to cesium, strontium, barium and rubidium. Barium and rubidium will be co-extracted during separation due to similar chemical properties to cesium and strontium. The waste liquid was added to the bentonite clay incrementally with drying steps between each addition. The dry powder was pressed and then sintered at various temperatures. The maximum loading tested is 32 wt. percent waste, which refers to 13.9 wt. percent cesium, 12.2 wt. percent barium, 4.1 wt. percent strontium, and 2.0 wt. percent rubidium. Lower loadings of waste were also tested. The final solid product was a hard dense ceramic with a density that varied from 2.12 g/cm3 for a 19% waste loading with a 1200°C sintering temperature to 3.03 g/cm 3 with a 29% waste loading and sintered at 1100°C. Differential Scanning Calorimetry and Thermal Gravimetric Analysis (DSC-TGA) of the loaded bentonite displayed mass loss steps which were consistent with water losses in pure bentonite. Water losses were complete after dehydroxylation at ˜650°C. No mass losses were evident beyond the dehydroxylation. The ceramic melts at temperatures greater than 1300°C. Light flash analysis found heat capacities of the ceramic to be comparable to those of strontium and barium feldspars as well as pollucite. Thermal conductivity improved with higher sintering temperatures, attributed to lower porosity. Porosity was minimized in 1200°C sinterings. Ceramics with waste loadings less than 25 wt% displayed slump, the lowest waste loading, 15 wt% bloated at a 1200°C sintering. Waste loading above 25 wt% produced smooth uniform ceramics when sintered >1100°C. Sintered bentonite may provide a simple alternative to vitrification and other engineered radioactive waste-forms.

Producing Zirconium Diboride Components with Complex, Near-Net Shape Geometries by Aqueous Room-Temperature Injection Molding

NASA Technical Reports Server (NTRS)

Wiesner, Valerie L.; Youngblood, Jeffrey; Trice, Rodney

2014-01-01

Room-temperature injection molding is proposed as a novel, low-cost and more energy efficient manufacturing process capable of forming complex-shaped zirconium diboride (ZrB2) parts. This innovative processing method utilized aqueous suspensions with high powder loading and a minimal amount (5 vol.) of water-soluble polyvinylpyrrolidone (PVP), which was used as a viscosity modifier. Rheological characterization was performed to evaluate the room-temperature flow properties of ZrB2-PVP suspensions. ZrB2 specimens were fabricated with high green body strength and were machinable prior to binder removal despite their low polymer content. After binder burnout and pressureless sintering, the bulk density and microstructure of specimens were characterized using Archimedes technique and scanning electron microscopy. X-Ray Diffraction was used to determine the phase compositions present in sintered specimens. Ultimate strength of sintered specimens will be determined using ASTM C1323-10 compressive C-ring test.

Structural properties and gas sensing behavior of sol-gel grown nanostructured zinc oxide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rajyaguru, Bhargav; Gadani, Keval; Kansara, S. B.

2016-05-06

In this communication, we report the results of the studies on structural properties and gas sensing behavior of nanostructured ZnO grown using acetone precursor based modified sol-gel technique. Final product of ZnO was sintered at different temperatures to vary the crystallite size while their structural properties have been studied using X-ray diffraction (XRD) measurement performed at room temperature. XRD results suggest the single phasic nature of all the samples and crystallite size increases from 11.53 to 20.96 nm with increase in sintering temperature. Gas sensing behavior has been studied for acetone gas which indicates that lower sintered samples are moremore » capable to sense the acetone gas and related mechanism has been discussed in the light of crystallite size, crystal boundary density, defect mechanism and possible chemical reaction between gas traces and various oxygen species.« less

Microstructural and crystallographic imperfections of MgB2 superconducting wire and their correlation with the critical current density

NASA Astrophysics Data System (ADS)

Shahabuddin, Mohammed; Alzayed, Nasser S.; Oh, Sangjun; Choi, Seyong; Maeda, Minoru; Hata, Satoshi; Shimada, Yusuke; Hossain, Md Shahriar Al; Kim, Jung Ho

2014-01-01

A comprehensive study of the effects of structural imperfections in MgB2 superconducting wire has been conducted. As the sintering temperature becomes lower, the structural imperfections of the MgB2 material are increased, as reflected by detailed X-ray refinement and the normal state resistivity. The crystalline imperfections, caused by lattice disorder, directly affect the impurity scattering between the π and σ bands of MgB2, resulting in a larger upper critical field. In addition, low sintering temperature keeps the grain size small, which leads to a strong enhancement of pinning, and thereby, enhanced critical current density. Owing to both the impurity scattering and the grain boundary pinning, the critical current density, irreversibility field, and upper critical field are enhanced. Residual voids or porosities obviously remain in the MgB2, however, even at low sintering temperature, and thus block current transport paths.

Effect of decomposition and organic residues on resistivity of copper films fabricated via low-temperature sintering of complex particle mixed dispersions

NASA Astrophysics Data System (ADS)

Yong, Yingqiong; Nguyen, Mai Thanh; Tsukamoto, Hiroki; Matsubara, Masaki; Liao, Ying-Chih; Yonezawa, Tetsu

2017-03-01

Mixtures of a copper complex and copper fine particles as copper-based metal-organic decomposition (MOD) dispersions have been demonstrated to be effective for low-temperature sintering of conductive copper film. However, the copper particle size effect on decomposition process of the dispersion during heating and the effect of organic residues on the resistivity have not been studied. In this study, the decomposition process of dispersions containing mixtures of a copper complex and copper particles with various sizes was studied. The effect of organic residues on the resistivity was also studied using thermogravimetric analysis. In addition, the choice of copper salts in the copper complex was also discussed. In this work, a low-resistivity sintered copper film (7 × 10-6 Ω·m) at a temperature as low as 100 °C was achieved without using any reductive gas.

The Effect of Sintering Temperature on Linear and Nonlinear Optical Properties of YAG Nanoceramics

NASA Astrophysics Data System (ADS)

Gayvoronsky, V. Ya.; Popov, A. S.; Brodyn, M. S.; Uklein, A. V.; Multian, V. V.; Shul'zhenko, O. O.

Recent improvements in powder synthesis and ceramics sintering made it possible to fabricate high-quality optical materials. The work is devoted to the structural and optical characterization of the ({Y_3}{Al_5}{O_{12}}, YAG) ceramics prepared by high-pressure low-temperature technique. The structural properties of the studied ceramic samples was obtained by X-ray diffraction. The studies of the total and in-line transmittance as well as optical scattering indicatrices were performed in visible and NIR ranges. The scatterer size ˜200 nm was estimated by Rayleigh-Gans-Debye model. It was shown that the studied samples demonstrate high transparency at 1064 nm. The nonlinear optical characterization of the samples was done by the self-action of the picosecond laser pulses at 1064 nm. The measured nonlinear optical response (χ^(3)) ˜ 10^{-11} esu) showed significant dependence on the sintering temperature variation.

Effects of sintering atmosphere on the physical and mechanical properties of modified BOF slag glass

NASA Astrophysics Data System (ADS)

Dai, Wen-bin; Li, Yu; Cang, Da-qiang; Zhou, Yuan-yuan; Fan, Yong

2014-05-01

This study proposes an efficient way to utilize all the chemical components of the basic oxygen furnace (BOF) slag to prepare high value-added glass-ceramics. A molten modified BOF slag was converted from the melting BOF slag by reducing it and separating out iron component in it, and the modified BOF slag was then quenched in water to form glasses with different basicities. The glasses were subsequently sintered in the temperature range of 600-1000°C in air or nitrogen atmosphere for 1 h. The effects of different atmospheres on the physical and mechanical properties of sintered samples were studied by using differential scanning calorimetry (DSC), X-ray diffraction (XRD) and scanning electron microscopy (SEM) and by conducting experiment on evaluating the sintering shrinkage, water absorption and bulk density. It is found that the kinetics of the sintering process is significantly affected by sintering atmosphere. In particular, compared with sintering in air atmosphere, sintering in N2 atmosphere promotes the synergistic growth of pyroxene and melilite crystalline phases, which can contribute to better mechanical properties and denser microstructure.

Application of the Zero-Order Reaction Rate Model and Transition State Theory to predict porous Ti6Al4V bending strength.

PubMed

Reig, L; Amigó, V; Busquets, D; Calero, J A; Ortiz, J L

2012-08-01

Porous Ti6Al4V samples were produced by microsphere sintering. The Zero-Order Reaction Rate Model and Transition State Theory were used to model the sintering process and to estimate the bending strength of the porous samples developed. The evolution of the surface area during the sintering process was used to obtain sintering parameters (sintering constant, activation energy, frequency factor, constant of activation and Gibbs energy of activation). These were then correlated with the bending strength in order to obtain a simple model with which to estimate the evolution of the bending strength of the samples when the sintering temperature and time are modified: σY=P+B·[lnT·t-ΔGa/R·T]. Although the sintering parameters were obtained only for the microsphere sizes analysed here, the strength of intermediate sizes could easily be estimated following this model. Copyright © 2012 Elsevier B.V. All rights reserved.

Fabrication of thermoelectric modules with Mg2Si and SrRuO3 by the spark plasma sintering method

NASA Astrophysics Data System (ADS)

Nishio, Keishi; Sawada, Yukie; Arai, Koya; Sakamoto, Tatsuya; Kogo, Yasuo; Iida, Tsutomu

2012-06-01

Thermoelectric (TE) modules with a π structure were fabricated by the spark plasma sintering method. The modules were composed of SrRuO3 for the p-type semiconductor, Mg2Si for the n-type semiconductor, and Ni for the electrodes. The SrRuO3 powder was synthesized using the metal-citric-acid complex decomposition method. Mg2Si bulk prepared by meltquenching was ground into powder and sieved to a particle size of 75 μm or less. To obtain the sintered body of SrRuO3, the powder was sintered using spark plasma sintering (SPS). For SPS, the precursor powder was placed in a graphite die and kept at that temperature under a uni-axial pressure of 50 MPa and in vacuum conditions (less than 7 Pa). After sintering by SPS, the ceramic sample was annealed at 1573K in air because the SrRuO3 was slightly reduced during the SPS process in the graphite die. These TE sintered bodies were cut and polished. The dimensions of the samples used for fabrication of the p-type parts of the TE modules were 4.50×9.50×7.45 mm3 and those for the n-type parts were 5.50×11.45×7.45 mm3. Pressed Ni powder was put between these TE materials and the Ni electrodes in order to connect them together, and electrical power was passed through the electrodes from the SPS equipment. The output power under temperature differences ΔT ranging from 100 to 500 K was measured. The open-circuit voltage, maximum output current and maximum output power increased with increasing temperature difference ΔT. The open-circuit voltage of the single module was 91.0 mV, and the maximum output current and maximum output power were 5000 mA and 110 mW at ΔT=500 K, respectively.

Processing of uranium dioxide nuclear fuel pellets using spark plasma sintering

NASA Astrophysics Data System (ADS)

Ge, Lihao

Uranium dioxide (UO2), one of the most common nuclear fuels, has been applied in most of the nuclear plant these days for electricity generation. The main objective of this research is to introduce a novel method for UO 2 processing using spark plasma sintering technique (SPS). Firstly, an investigation into the influence of processing parameters on densification of UO2 powder during SPS is presented. A broad range of sintering temperatures, hold time and heating rates have been systematically varied to investigate their influence on the sintered pellet densification process. The results revealed that up to 96% theoretical density (TD) pellets can be obtained at a sintering temperature of 1050 °C for 30s hold time and a total run time of only 10 minutes. A systematic study is performed by varying the sintering temperature between 750°C to 1450°C and hold time between 0.5 min to 20 min to obtain UO2 pellets with a range of densities and grain sizes. The microstructure development in terms of grain size, density and porosity distribution is investigated. The Oxygen/Uranium (O/U) ratio of the resulting pellets is found to decrease after SPS. The mechanical and thermal properties of UO2 are evaluated. For comparable density and grain size, Vickers hardness and Young's modulus are in agreement with the literature value. The thermal conductivity of UO2 increases with the density but the grain size in the investigated range has no significant influence. Overall, the mechanical and thermal properties of UO2 are comparable with the one made using conventional sintering methods. Lastly, the influence of chromium dioxide (Cr2O3) and zirconium diboride (ZrB2) on the grain size of doped UO 2 fuel pellet is performed to investigate the feasibility of producing large-grain-size nuclear fuel using SPS. The benefits of using SPS over the conventional sintering of UO2 are summarized. The future work of designing macro-porous UO2 pellet and thorium dioxide (ThO 2) cored UO2 pellet is also proposed.

The effect of processing parameters and solid concentration on the mechanical and microstructural properties of freeze-casted macroporous hydroxyapatite scaffolds.

PubMed

Farhangdoust, S; Zamanian, A; Yasaei, M; Khorami, M

2013-01-01

The design and fabrication of macroporous hydroxyapatite scaffolds, which could overcome current bone tissue engineering limitations, have been considered in recent years. In the current study, controlled unidirectional freeze-casting at different cooling rates was investigated. In the first step, different slurries with initial hydroxyapatite concentrations of 7-37.5 vol.% were prepared. In the next step, different cooling rates from 2 to 14 °C/min were applied to synthesize the porous scaffold. Additionally, a sintering temperature of 1350 °C was chosen as an optimum temperature. Finally, the phase composition (by XRD), microstructure (by SEM), mechanical characteristics, and the porosity of sintered samples were assessed. The porosity of the sintered samples was in a range of 45-87% and the compressive strengths varied from 0.4 MPa to 60 MPa. The mechanical strength of the scaffolds increased as a function of initial concentration, cooling rate, and sintering temperature. With regards to mechanical strength and pore size, the samples with the initial concentration and the cooling rate of 15 vol.% and 5 °C/min, respectively, showed better results. Copyright © 2012 Elsevier B.V. All rights reserved.

Ga2O3 doping and vacancy effect in KNN—LT lead-free piezoceramics

NASA Astrophysics Data System (ADS)

Tan, Zhi; Xing, Jie; Jiang, Laiming; Zhu, Jianguo; Wu, Bo

2017-12-01

Ga2O3 was doped into 0.95(K0.48Na0.52)NbO3—0.05LiTaO3 (KNN—LT) ceramics and its influences on the sintering behavior, phase structure and electrical properties of ceramics were studied. Firstly, SEM observation exhibits that more and more glass phase appears in ceramics with the gradual addition of Ga2O3, which determines the continuous decrease in sintering temperatures. And the addition of Ga2O3 is also found to increase the orthorhombic—tetragonal transition temperature ( T O—T) of system to a higher level. Secondly, both the density and the coercive field ( E C) of ceramics increase firstly and then decrease with increasing the Ga2O3 content, and the KNN—LT— xGa sample at x = 0.004 shows a pinched P— E hysteresis loop. Finally, the impedance characteristics of KNN—LT— xGa ceramics were investigated at different temperatures, revealing a typical vacancy related conduction mechanism. This work demonstrates that Ga2O3 is a good sintering aid for KNN-based ceramics, and the vacancy plays an important role in the sintering and electrical behaviors of ceramics.

Low-Temperature Sintering Li3Mg1.8Ca0.2NbO6 Microwave Dielectric Ceramics with LMZBS Glass

NASA Astrophysics Data System (ADS)

Wang, Gang; Zhang, Huaiwu; Liu, Cheng; Su, Hua; Jia, Lijun; Li, Jie; Huang, Xin; Gan, Gongwen

2018-05-01

Li3Mg1.8Ca0.2NbO6 ceramics doped with Li2O-MgO-ZnO-B2O3-SiO2 glass (LMZBS) were prepared via a solid-state route. The LMZBS glass effectively reduced the sintering temperature of Li3Mg1.8Ca0.2NbO6 ceramics to 950°C. The effects of the LMZBS glass on the sintering behavior, microstructures and microwave dielectric properties of Li3Mg1.8Ca0.2NbO6 ceramics are discussed in detail. Among all the LMZBS doped Li3Mg1.8Ca0.2NbO6 ceramics, the sample with 1 wt.% of LMZBS glass sintered at 950°C for 4 h exhibited good dielectric properties: ɛ r = 16.7, Q × f = 31,000 GHz (9.92 GHz), τ f = - 1.3 ppm/°C. The Li3Mg1.8Ca0.2NbO6 ceramics possessed excellent chemical compatibility with Ag electrodes, and could be applied in low temperature co-fired ceramics (LTCC) applications.

Interfacial characterization in carbon nanotube reinforced aluminum matrix composites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Housaer, F., E-mail: francois.housaer@ed.univ-lille1.fr; Beclin, F., E-mail: franck.beclin@univ-lille1.fr; Touzin, M., E-mail: matthieu.touzin@univ-lille1.fr

2015-12-15

In this work, the effects of the sintering parameters, such as temperature and the techniques used (HP and SPS), on CNT/Al composite interfaces are studied. The major role of the native aluminum oxide (Al{sub 2}O{sub 3}) layer covering the aluminum grains is highlighted. It is shown that, for a sintering temperature below 620 °C, the amorphous Al{sub 2}O{sub 3} layer prevents the reaction between aluminum and carbon. For greater sintering temperatures, the breaking of the oxide layer due to its crystallization leads to the formation of aluminum carbide (Al{sub 4}C{sub 3}) by reaction between aluminum and the CNT. The Al{submore » 4}C{sub 3} crystals grow perpendicularly to the matrix grain boundaries by thermally activated diffusion of the carbon atoms coming from the CNT. It is also demonstrated that, by limiting the sintering time, which is the case in SPS, it is possible to limit the growth of the Al{sub 4}C{sub 3} crystals and thus to preserve the CNT. - Highlights: • The high reactivity between CNT and Al matrix, resulting Al{sub 4}C{sub 3} formation during the sintering process is highlighted. • We demonstrate, thanks to in-situ TEM observations, that Al{sub 4}C{sub 3} crystals grow into aluminum grains by carbon diffusion. • The native aluminum oxide around the aluminum particles prevents the diffusion of carbon into the aluminum grains. • We show that the protective layer can be broken because of its crystallization, leading to the formation of Al{sub 4}C{sub 3}. • SPS, by limiting the sintering duration, is an interesting way for preparing CNT/Al composites without carbide formation.« less

Improvement microstructural and damage characterization of ceramic composites Y{sub 2}O{sub 3} – V{sub 2}O{sub 5} with MgO nano particles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Issa, T. T., E-mail: alazbrh@yahoo.com; Hasan, J. M.; Abdullah, E. T.

2016-04-21

Compacted samples of Y{sub 2}O{sub 3}-V{sub 2}O{sub 5} – MgO Nano – particles wt. % sintered at different sintering temperature (700, 900, 1100, 1300) ) C° for 2 hours under static air were investigated by x-ray diffraction and differential thermal analysis(DTA), to identify the phase present .Microstructure examination achieved by scanning electron microscopy .Sintered density and porosity were measured for all sintered samples .Compression was tested too and the Brake down voltage and dielectric strength were measure for all sintered samples .The clear improvement were noticed in both microstructure and damage characterization respectively after existing the MgO Nano-particles, by increasingmore » in about 30% in sintered density and 25% for the compressive strength .The improvement also noticed on both brake down voltage and dielectric strength.« less

Mechanical and microstructural characterization of W–Cu FGM fabricated by one-step sintering method through PM route

NASA Astrophysics Data System (ADS)

Gupta, Rajat; Kumar, Rohit; Chaubey, A. K.; Kanpara, Shailesh; Khirwadkar, S. S.

2018-03-01

Five layer W-Cu functionally graded material (FGM) for components in nuclear fusion application was fabricated by a one-step resistance sintering process, known as spark plasma sintering (SPS). In this study effect of sintering temperature (Ts) on physical, mechanical and surface property was investigated. Detailed microstructural study revealed that the graded structure of the composite layers with varying composition from 0 to 100 wt% W and Cu in opposite directions could be well densified after the SPS process. It also indicates that the fine microstructure within functionally graded layers can be maintained because of short sintering time. The sample sintered at 1050°C shows more than 90% theoretical density, hardness greater than 239±5 Hv and excellent surface scratch resistance. The result demonstrates that SPS is promising and more suitable process for fabrication of W-Cu FGM.

Influence factors of the inter-nanowire thermal contact resistance in the stacked nanowires

NASA Astrophysics Data System (ADS)

Wu, Dongxu; Huang, Congliang; Zhong, Jinxin; Lin, Zizhen

2018-05-01

The inter-nanowire thermal contact resistance is important for tuning the thermal conductivity of a nanocomposite for thermoelectric applications. In this paper, the stacked copper nanowires are applied for studying the thermal contact resistance. The stacked copper nanowires are firstly made by the cold-pressing method, and then the nanowire stacks are treated by sintering treatment. With the effect of the volumetric fraction of nanowires in the stack and the influence of the sintering-temperature on the thermal contact resistance discussed, results show that: The thermal conductivity of the 150-nm copper nanowires can be enlarged almost 2 times with the volumetric fraction increased from 32 to 56% because of the enlarged contact-area and contact number of a copper nanowire. When the sintering temperature increases from 293 to 673 K, the thermal conductivity of the stacked 300-nm nanowires could be enlarged almost 2.5 times by the sintering treatment, because of the improved lattice property of the contact zone. In conclusion, application of a high volumetric fraction or/and a sintering-treatment are effectivity to tune the inter-nanowire thermal contact resistance, and thus to tailor the thermal conductivity of a nanowire network or stack.

Effect of microwave-assisted sintering on dielectric properties of CaCu{sub 3}Ti{sub 4}O{sub 12} ceramic

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rani, Suman, E-mail: sumanranigju@gmail.com; Ahlawat, Neetu; Punia, R.

2016-05-23

In this present work, CaCu{sub 3}Ti{sub 4}O{sub 12} (CCTO) was synthesized by conventional solid-state reaction technique. The synthesis process was carried out in two phases; by conventional process (calcination and sintering at 1080°C for 10 hours) and phase II involves the micro assisted pre sintering of conventionally calcined CCTO for very short soaking time of 30 min at 1080°C in a microwave furnace followed by sintering at 1080°C for 10 hours in conventional furnace. X-ray diffraction (XRD) patterns confirmed the formation of single phase ceramic. Dielectric properties were studied over the frequency range from 50Hz -5MHz at temperatures (273K-343K). It wasmore » observed that pre- microwave sintering enhance the dielectric constant values from 10900 to 11893 and respectively reduces the dielectric loss values from 0.49 to 0.34 at room temperature(1 KHz). CCTO ceramics which are found desirable for many technological applications. The effect is more pronounced at low frequencies of applied electric field.« less

Study of sintering on Mg-Zn-Ca alloy system

NASA Astrophysics Data System (ADS)

Annur, Dhyah; Lestari, Franciska P.; Erryani, Aprilia; Kartika, Ika

2018-05-01

Magnesium and its alloy have gained a lot of interest to be used in biomedical application due to its biodegradable and biocompatible properties. In this study, sintering process in powder metallurgy was chosen to fabricatenonporous Mg-6Zn-1Ca (in wt%) alloy and porous Mg-6Zn-1Ca-10 Carbamide alloy. For creating porous alloy, carbamide (CO(NH2)2 was added to alloy system as the space holder to create porous structure material. Effect of the space holder addition and sintering temperature on porosity, phase formation, mechanical properties, and corrosion properties was observed. Sintering process was done in a tube furnace under Argon atmosphere in for 5 hours. The heat treatment was done in two steps; heated up at 250 °C for 4 hours to decompose spacer particle, followed by heated up at 580 °C or 630 °C for 5 hours. The porous structure of the resulted alloys was examined using Scanning Electron Microscope (SEM), while the phase formation was characterized by X-ray diffraction (XRD) analysis. Mechanical properties were examined using compression testing. From this study, increasing sintering temperature up to 630 °C reduced the mechanical properties of Mg-Zn-Ca alloy.

Method for fabricating prescribed flaws in the interior of metals

DOEpatents

Hsu, David K.; Thompson, Donald O.

1989-03-07

The method for fabricating a metal body having a flaw of predetermined size and shape located therein comprises placing half of the metal powder required to make the metal body in the die of a press and pressing it to create a flat upper surface thereon. A piece of copper foil is cut to the size and shape of the desired interior crack and placed on the upper surface of the powder and centered in position. The remaining powder is then placed in the die to cover the copper foil. The powder is first cold pressed and removed from the press. The powder metal piece is then sintered in a furnace at a temperature above the melting point of the copper and below the melting point of the metal. It is then removed from the furnace, cooled to room temperature, and placed back in the die and pressed further. This procedure results in an interior flaw or crack. Modified forms of the method involve using a press-sinter-press-sinter cycle with the first sinter being below the melting point of the copper and the second sinter being above the melting point of the copper and below the melting point of the metal.

SPS Fabrication of Tungsten-Rhenium Alloys in Support of NTR Fuels Development

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jonathan A. Webb; Indrajit Charit; Cory Sparks

Abstract. Tungsten metal slugs were fabricated via Spark Plasma Sintering (SPS) of powdered metals at temperatures ranging from 1575 K to 1975 K and hold times of 5 minutes to 30 minutes, using powders with an average diameter of 7.8 ?m. Sintered tungsten specimens were found to have relative densities ranging from 83 % to 94 % of the theoretical density for tungsten. Consolidated specimens were also tested for their Vickers Hardness Number (VHN), which was fitted as a function of relative density; the fully consolidated VHN was extrapolated to be 381.45 kg/mm2. Concurrently, tungsten and rhenium powders with averagemore » respective diameters of 0.5 ?m and 13.3 ?m were pre-processed either by High-Energy-Ball-Milling (HEBM) or by homogeneous mixing to yield W-25at.%Re mixtures. The powder batches were sintered at temperatures of 1975 K and 2175 K for hold times ranging from 0 minutes to 60 minutes yielding relative densities ranging from 94% to 97%. The combination of HEBM and sintering showed a significant decrease in the inter-metallic phases compared to that of the homogenous mixing and sintering.« less

Superconductivity in BiPbCaSrCuO thin films

NASA Astrophysics Data System (ADS)

Fu, S. M.; Yang, H. C.; Chen, F. C.; Horng, H. E.; Jao, J. C.

1989-12-01

Thin films of BiPbCaSrCuO sample were prepared by RF sputtering from sintered ceramic targets. Single crystal of MgO(100) was selected as substrate. The sputtering was held at room temperature. Different annealing conditions were carried out to obtain optimum conditions. High temperature resistivity was measured in air to study the thermodynamic reaction of the sintered films. An resistivity anomaly was found in the first heating cycle which suggests a thermodynamic reaction. A temperature dependence of I c was measured to study the coupling of grains in the granular films in different temperature ranges and the results will be discussed.

Influence of the particle size and intrinsic magnetic characteristics on the coercivity of sintered magnets

NASA Astrophysics Data System (ADS)

Turilli, G.; Paoluzi, A.; Lucenti, M.; Pareti, L.

1992-02-01

Using sintered specimens of Ba-hexaferrite powders as a model system, a study was made of the dependence of coercivity on the particle dimensions and on the temperature from RT up to the Curie temperature. The temperature behaviour of the coercive and anisotropy field are the same in single-domain particle specimens while they are rather different in polydomain particle specimens. However, the coercivity behaviour of both systems can be fitted well up to 350°C using a simple relation between Hc, HA, and Ms. Further contributions to the coercivity have to be taken into account at higher temperatures.

High temperature resistant cermet and ceramic compositions

NASA Technical Reports Server (NTRS)

Phillips, W. M. (Inventor)

1978-01-01

Cermet compositions having high temperature oxidation resistance, high hardness and high abrasion and wear resistance, and particularly adapted for production of high temperature resistant cermet insulator bodies are presented. The compositions are comprised of a sintered body of particles of a high temperature resistant metal or metal alloy, preferably molybdenum or tungsten particles, dispersed in and bonded to a solid solution formed of aluminum oxide and silicon nitride, and particularly a ternary solid solution formed of a mixture of aluminum oxide, silicon nitride and aluminum nitride. Also disclosed are novel ceramic compositions comprising a sintered solid solution of aluminum oxide, silicon nitride and aluminum nitride.

Mechanical characterization of injection-molded macro porous bioceramic bone scaffolds.

PubMed

Vivanco, Juan; Aiyangar, Ameet; Araneda, Aldo; Ploeg, Heidi-Lynn

2012-05-01

Bioactive ceramic materials like tricalcium phosphate (TCP) have been emerging as viable material alternatives to the current therapies of bone scaffolding to target fracture healing and osteoporosis. Both material and architectural characteristics play a critical role in the osteoconductive capacity and strength of bone scaffolds. Thus, the objective of this research was to investigate the sintering temperature effect of a cost-effective manufacturing process on the architecture and mechanical properties of a controlled macro porous bioceramic bone scaffold. In this study the physical and mechanical properties of β-TCP bioceramic scaffolds were investigated as a function of the sintering temperature in the range of 950-1150 °C. Physical properties investigated included bulk dimensions, pore size, and strut thickness; and, compressive mechanical properties were evaluated in air at room temperature and in saline solution at body temperature. Statistically significant increases in apparent elastic modulus were measured for scaffolds sintered at higher temperatures. Structural stiffness for all the specimens was significantly reduced when tested at body temperature in saline solution. These findings support the development of clinically successful bioceramic scaffolds that may stimulate bone regeneration and scaffold integration while providing structural integrity. Copyright © 2012 Elsevier Ltd. All rights reserved.

Possible observation of Griffith phase over large temperature range in plasma sintered La0.67Ca0.33MnO3

NASA Astrophysics Data System (ADS)

Mishra, D. K.; Roul, B. K.; Singh, S. K.; Srinivasu, V. V.

2018-02-01

We report on the possible observation of Griffith phase in a wide range of temperature (>272-378 K) in the 2.5 min plasma sintered La0.67Ca0.33MnO3 (LCMO) as deduced from careful electron spin resonance studies. This is 106 K higher than the paramagnetic to ferromagnetic transition (Curie transition ∼272 K) temperature. The indication of Griffith phase in such a wide range is not reported earlier by any group. We purposefully prepared LCMO samples by plasma sintering technique so as to create a disordered structure by rapid quenching which we believe, is the prime reason for the observation of Griffith Phase above the Curie transition temperature. The inverse susceptibility curve represents the existence of ferromagnetic cluster in paramagnetic region. The large resonance peak width (40-60 mT) within the temperature range 330-378 K confirms the sample magnetically inhomogeneity which is also established from our electron probe microstructure analysis (EPMA). EPMA establishes the presence of higher percentage of Mn3+ cluster in comparison to Mn4+. This is the reason for which Griffith state is enhanced largely to a higher range of temperature.

Reactive sintering of ceramic lithium ion electrolyte membranes

DOEpatents

Badding, Michael Edward; Dutta, Indrajit; Iyer, Sriram Rangarajan; Kent, Brian Alan; Lonnroth, Nadja Teresia

2017-06-06

Disclosed herein are methods for making a solid lithium ion electrolyte membrane, the methods comprising combining a first reactant chosen from amorphous, glassy, or low melting temperature solid reactants with a second reactant chosen from refractory oxides to form a mixture; heating the mixture to a first temperature to form a homogenized composite, wherein the first temperature is between a glass transition temperature of the first reactant and a crystallization onset temperature of the mixture; milling the homogenized composite to form homogenized particles; casting the homogenized particles to form a green body; and sintering the green body at a second temperature to form a solid membrane. Solid lithium ion electrolyte membranes manufactured according to these methods are also disclosed herein.

Method of sintering ceramic materials

DOEpatents

Holcombe, Cressie E.; Dykes, Norman L.

1992-01-01

A method for sintering ceramic materials is described. A ceramic article is coated with layers of protective coatings such as boron nitride, graphite foil, and niobium. The coated ceramic article is embedded in a container containing refractory metal oxide granules and placed within a microwave oven. The ceramic article is heated by microwave energy to a temperature sufficient to sinter the ceramic article to form a densified ceramic article having a density equal to or greater than 90% of theoretical density.

The Development of a Ti-6Al-4V Alloy via Oxygen Solid Solution Strengthening for Aerospace and Defense Applications

DTIC Science & Technology

2013-03-01

latter strategy. Mixtures of titanium powders and TiO2 particles were employed as starting materials and consolidated by spark - plasma sintering and...were consolidated in a carbon container installed in the spark - plasma sintering (SPS) equipment under vacuum condition (ɞ Pa) at a temperature of...evaluation of tensile properties of the wrought pure titanium materials consolidated by sintering and hot extrusion process, a theoretical approach using

Process for the recovery of alumina from fly ash

DOEpatents

Murtha, M.J.

1983-08-09

An improvement in the lime-sinter process for recovering alumina from pulverized coal fly ash is disclosed. The addition of from 2 to 10 weight percent carbon and sulfur to the fly ash-calcium carbonate mixture increase alumina recovery at lower sintering temperatures.

A novel in situ synthesis of SiBCN-Zr composites prepared by a sol-gel process and spark plasma sintering.

PubMed

Miao, Yang; Yang, Zhihua; Liang, Bin; Li, Quan; Chen, Qingqing; Jia, Dechang; Cheng, Yi-Bing; Zhou, Yu

2016-08-09

In the work reported here, SiBCN amorphous powders were first prepared by a mechanical alloying technique, employing cubic silicon, graphite and hexagonal boron nitride powders as raw materials. Zirconia was then introduced via sol-gel methods. The resulting powder composite was then consolidated via SPS sintering. The SPS sintering sample was evaluated using XRD, SEM and TEM. XRD reveals a chemical transformation wherein amorphous BN(C) and ZrO2 form the primary ZrC and ZrB2 phases after SPS processing along with SiC and BN(C). Thereafter ZrC reacts with BN(C) completely to form ZrB2. The reaction starts at the temperature of 1500 °C and is complete at the temperature of 1900 °C. The fracture toughness of the sintered composites reaches 4.9 ± 0.2 MPa m(1/2) due to the presence of the laminated structure of the BN(C) phase.

Correlation between porosity and space holder content at different sintering temperatures of aluminum foam

NASA Astrophysics Data System (ADS)

Rushdi, N. M. F. M.; Jamaludin, S. B.; Mazlee, M. N.; Jamal, Z. A. Z.

2016-07-01

Aluminum foam is the most popular metal foam that can be used as energy absorbers, heat exchangers, air-oil separators and structure core of fuel cells. Melt-foaming agent, melt-gas injection, investment casting and powder-foaming agent techniques can be used to manufacture aluminum foam, but these techniques are too expensive. In this study, the aluminum foam was manufactured via a sintering dissolution process (SDP). Powders of aluminum and sodium chloride as space holder (25, 40, 50 wt. %) were mixed together to produce a homogeneous mixture. The mixture was compacted at 200 MPa followed by sintering at 500, 550 and 600˚C for 2 hours. A warm running water stream was used to dissolve the space holder that was embedded in the aluminum. The result showed that, the space holder content performed a significant role to control the total porosity to a value between 18 and 40%, and the porosity increased with increasing content of space holder and sintering temperature.

Copper-polydopamine composite derived from bioinspired polymer coating

DOE PAGES

Zhao, Yao; Wang, Hsin; Qian, Bosen; ...

2018-04-01

Metal matrix composites with nanocarbon phases, such carbon nanotube (CNT) and graphene, have shown potentials to achieve improved mechanical, thermal, and electrical properties. However, incorporation of these nanocarbons into the metal matrix usually involves complicated processes. Here, this study explored a new processing method to fabricate copper (Cu) matrix composite by coating Cu powder particles with nanometer-thick polydopamine (PDA) thin films and sintering of the powder compacts. For sintering temperatures between 300°C and 750°C, the Cu-PDA composite samples showed higher electrical conductivity and thermal conductivity than the uncoated Cu samples, which is likely related to the higher mass densities ofmore » the composite samples. After being sintered at 950°C, the thermal conductivity of the Cu-PDA sample was approximately 12% higher than the Cu sample, while the electrical conductivity did not show significant difference. On the other hand, Knoop micro-hardness values were comparable between the Cu-PDA and Cu samples sintered at the same temperatures.« less

Improved silicon nitride for advanced heat engines

NASA Technical Reports Server (NTRS)

Yeh, H. C.; Wimmer, J. M.; Huang, H. H.; Rorabaugh, M. E.; Schienle, J.; Styhr, K. H.

1985-01-01

The AiResearch Casting Company baseline silicon nitride (92 percent GTE SN-502 Si sub 3 N sub 4 plus 6 percent Y sub 2 O sub 3 plus 2 percent Al sub 2 O sub 3) was characterized with methods that included chemical analysis, oxygen content determination, electrophoresis, particle size distribution analysis, surface area determination, and analysis of the degree of agglomeration and maximum particle size of elutriated powder. Test bars were injection molded and processed through sintering at 0.68 MPa (100 psi) of nitrogen. The as-sintered test bars were evaluated by X-ray phase analysis, room and elevated temperature modulus of rupture strength, Weibull modulus, stress rupture, strength after oxidation, fracture origins, microstructure, and density from quantities of samples sufficiently large to generate statistically valid results. A series of small test matrices were conducted to study the effects and interactions of processing parameters which included raw materials, binder systems, binder removal cycles, injection molding temperatures, particle size distribution, sintering additives, and sintering cycle parameters.

Effects of Sintering and Extrusion on the Microstructures and Mechanical Properties of a SiC/Al-Cu Composite

NASA Astrophysics Data System (ADS)

Sun, Chao; Shen, Rujuan; Song, Min

2012-03-01

This article studied the effects of sintering and extrusion on the microstructures and mechanical properties of SiC particle reinforced Al-Cu alloy composite produced by powder metallurgy method. It has been shown that both extrusion and increasing sintering temperature can significantly improve the strength and plasticity of the composite. The extrusion and increase of the sintering temperature can break up the oxide coating on the matrix powder surfaces, decrease the number of pores, accelerate the elements' diffusion and increase the density and particle interfacial bonding strength, thus significantly improve the mechanical properties of the composite. The strength and hardness of the composite increase and the elongation decreases with increasing the aging time at under-aged stage, while the strength and hardness start to decrease and the elongation starts to increase with increasing the aging time at over-aged stage due to the formation and growth of the secondary strengthening precipitates in the Al-Cu matrix.

Hot-pressed silicon nitride with various lanthanide oxides as sintering additives

NASA Technical Reports Server (NTRS)

Ueno, K.; Toibana, Y.

1984-01-01

The effects of addition of various lanthanide oxides and their mixture with Y2O3 on the sintering of Si3N4 were investigated. The addition of simple and mixed lanthanide oxides promoted the densification of Si3N4 in hot-pressing at 1800 C under 300-400kg/ centimeters squared for 60 min. The crystallization of yttrium and lanthanide-silicon oxynitrides which was observed inn the sintered body containing yttrium-lanthanide mixed oxides as additives led to the formation of a highly refractory Si3N4 ceramic having a bending strength of 82 and 84 kg/millimeters squared at room temperature and 1300 C respectively. In a Y2O3+La2O3 system, a higher molar ratio of La2O3 to Y2O3 gave a higher hardness and strength at high temperatures. It was found that 90 min was an optimum sintering time for the highest strength.

Copper-polydopamine composite derived from bioinspired polymer coating

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, Yao; Wang, Hsin; Qian, Bosen

Metal matrix composites with nanocarbon phases, such carbon nanotube (CNT) and graphene, have shown potentials to achieve improved mechanical, thermal, and electrical properties. However, incorporation of these nanocarbons into the metal matrix usually involves complicated processes. Here, this study explored a new processing method to fabricate copper (Cu) matrix composite by coating Cu powder particles with nanometer-thick polydopamine (PDA) thin films and sintering of the powder compacts. For sintering temperatures between 300°C and 750°C, the Cu-PDA composite samples showed higher electrical conductivity and thermal conductivity than the uncoated Cu samples, which is likely related to the higher mass densities ofmore » the composite samples. After being sintered at 950°C, the thermal conductivity of the Cu-PDA sample was approximately 12% higher than the Cu sample, while the electrical conductivity did not show significant difference. On the other hand, Knoop micro-hardness values were comparable between the Cu-PDA and Cu samples sintered at the same temperatures.« less

Synthesis and Characterization of Hydroxyapatite Powder by Wet Precipitation Method

NASA Astrophysics Data System (ADS)

Cahyaningrum, S. E.; Herdyastuty, N.; Devina, B.; Supangat, D.

2018-01-01

Hydroxyapatite is main inorganic component of the bone with formula Ca10(PO4)6(OH)2. Hydroxyapatite can be used as substituted bone biomaterial because biocompatible, non toxic, and osteoconductive. In this study, hydroxyapatite is synthesized using wet precipitation method from egg shell. The product was sintered at different temperatures of 800°C to 1000°C to improve its crystallinity. The hydroxyapatite was characterized by X-ray analysis, Scanning Electron Microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FTIR) to reveal its phase content, morphology and types of bond present within it. The analytical results showed hydroxyapatite had range in crystallinity from 85.527 to 98.753%. The analytical functional groups showed that presence of functional groups such as OH, (PO4)3 2-, and CO3 2- that indicated as hydroxyapatite. The result of characterization SEM indicated that hydroxyapatite without sintering and HAp sintering at 800 °C were irregular shape without pore. The best hydroxyapatite with temperature sintering at 900 °C showed oval shaped with pores without agglomerated.

Effects of La2O3-B2O3-ZnO additions on the low temperature sintering and microwave dielectric properties of (Ca0.61La0.26) TiO3 ceramics

NASA Astrophysics Data System (ADS)

Chen, Y. W.; Li, E. Z.; Niu, N.; Zou, M. Y.; Duan, S. X.; Zhang, S. R.

2017-02-01

The influence of La2O3-B2O3-ZnO (LBZ) additions on the sintering behavior, microstructure, phase composition, and the microwave dielectric properties of (Ca0.61La0.26) TiO3 (CLT) ceramics have been investigated. The results indicate that the LBZ additions could efficiently lower the sintering temperature of the CLT ceramics from 1400°C to 950°C, and excellent microwave properties remain. Small amount of LBZ glass promotes the densification of the CLT ceramics and enhances the microwave dielectric properties. However, excess amount of LBZ glass deteriorates the dielectric properties because of the increasing glass phase. The CLT ceramic with 3 wt. % LBZ additions, sintered at 950°C, exhibit excellent properties: εr= 103.12, Q× f = 8826 GHz(f=3.312 GHz) and τƒ=299.52 ppm/°C.

Microwave sintering of nanophase ceramics without concomitant grain growth

DOEpatents

Eastman, Jeffrey A.; Sickafus, Kurt E.; Katz, Joel D.

1993-01-01

A method of sintering nanocrystalline material is disclosed wherein the nanocrystalline material is microwaved to heat the material to a temperature less than about 70% of the melting point of the nanocrystalline material expressed in degrees K. This method produces sintered nanocrystalline material having a density greater than about 95% of theoretical and an average grain size not more than about 3 times the average grain size of the nanocrystalline material before sintering. Rutile TiO.sub.2 as well as various other ceramics have been prepared. Grain growth of as little as 1.67 times has resulted with densities of about 90% of theoretical.

Densification and Electrical Properties of Zinc Oxide Varistors Microwave-Sintered Under Different Oxygen Partial Pressures

NASA Astrophysics Data System (ADS)

Lin, Cong; Wang, Bo; Xu, Zheng; Peng, Hu

2012-11-01

ZnO varistors were prepared by microwave sintering under different oxygen partial pressures. The temperature profile and the densification behavior in different atmospheres were investigated. It was found that the density of ZnO varistors during sintering was the key factor affecting the absorption of microwave energy. The electrical properties, including the nonlinear properties and capacitance-voltage ( C- V) characteristics, were also carefully studied. The results showed that the oxygen partial pressure has significant effects on the electrical properties of ZnO varistors by changing the concentration of defects through a series of reactions involving oxygen during sintering.

Liquid phase sintering of silicon carbide

DOEpatents

Cutler, R.A.; Virkar, A.V.; Hurford, A.C.

1989-05-09

Liquid phase sintering is used to densify silicon carbide based ceramics using a compound comprising a rare earth oxide and aluminum oxide to form liquids at temperatures in excess of 1,600 C. The resulting sintered ceramic body has a density greater than 95% of its theoretical density and hardness in excess of 23 GPa. Boron and carbon are not needed to promote densification and silicon carbide powder with an average particle size of greater than one micron can be densified via the liquid phase process. The sintered ceramic bodies made by the present invention are fine grained and have secondary phases resulting from the liquid phase. 4 figs.

Liquid phase sintering of silicon carbide

DOEpatents

Cutler, Raymond A.; Virkar, Anil V.; Hurford, Andrew C.

1989-01-01

Liquid phase sintering is used to densify silicon carbide based ceramics using a compound comprising a rare earth oxide and aluminum oxide to form liquids at temperatures in excess of 1600.degree. C. The resulting sintered ceramic body has a density greater than 95% of its theoretical density and hardness in excess of 23 GPa. Boron and carbon are not needed to promote densification and silicon carbide powder with an average particle size of greater than one micron can be densified via the liquid phase process. The sintered ceramic bodies made by the present invention are fine grained and have secondary phases resulting from the liquid phase.

Nuclear Rocket Ceramic Metal Fuel Fabrication Using Tungsten Powder Coating and Spark Plasma Sintering

NASA Technical Reports Server (NTRS)

Barnes, M. W.; Tucker, D. S.; Hone, L.; Cook, S.

2017-01-01

Nuclear thermal propulsion is an enabling technology for crewed Mars missions. An investigation was conducted to evaluate spark plasma sintering (SPS) as a method to produce tungsten-depleted uranium dioxide (W-dUO2) fuel material when employing fuel particles that were tungsten powder coated. Ceramic metal fuel wafers were produced from a blend of W-60vol% dUO2 powder that was sintered via SPS. The maximum sintering temperatures were varied from 1,600 to 1,850 C while applying a 50-MPa axial load. Wafers exhibited high density (>95% of theoretical) and a uniform microstructure (fuel particles uniformly dispersed throughout tungsten matrix).

Evolving microstructure, magnetic properties and phase transition in a mechanically alloyed Ni0.5Zn0.5Fe2O4 single sample

NASA Astrophysics Data System (ADS)

Ismail, Ismayadi; Hashim, Mansor; Kanagesan, Samikannu; Ibrahim, Idza Riati; Nazlan, Rodziah; Wan Ab Rahman, Wan Norailiana; Abdullah, Nor Hapishah; Mohd Idris, Fadzidah; Bahmanrokh, Ghazaleh; Shafie, Mohd Shamsul Ezzad; Manap, Masni

2014-02-01

We report on an investigation to unravel the dependence of magnetic properties on microstructure while they evolve in parallel under the influence of sintering temperature of a single sample of Ni0.5Zn0.5Fe2O4 synthesized via mechanical alloying. A single sample, instead of the normally practiced approach of using multiple samples, was sintered at various sintering temperatures from 500 °C to 1400 °C. The morphology of the samples was studied by means of scanning electron microscopy (SEM) equipped with EDX; density measurement was conducted using the Archimedes principle; and hysteresis measurement was carried out using a B-H hysteresisgraph system. XRD data showed that the first appearance of a single phase was at 800 °C and an amorphous phase was traced at lower sintering temperatures. We correlated the microstructure and the magnetic properties and showed that the important grain-size threshold for the appearance of significant ordered magnetism (mainly ferromagnetism) was about ≥0.3 µm. We found that there were three stages of magnetic phase evolution produced via the sintering process with increasing temperatures. The first stage was dominated by paramagnetic states with some superparamagnetic behavior; the second stage was influenced by moderately ferromagnetic states and some paramagnetic states; and the third stage consisted of strongly ferromagnetic states with negligible paramagnetic states. We found that three factors sensitively influenced the sample's content of ordered magnetism—the ferrite-phase crystallinity degree, the number of grains above the critical grain size and the number of large enough grains for domain wall accommodation.

Cu ion ink for a flexible substrate and highly conductive patterning by intensive pulsed light sintering.

PubMed

Wang, Byung-Yong; Yoo, Tae-Hee; Song, Yong-Won; Lim, Dae-Soon; Oh, Young-Jei

2013-05-22

Direct printing techniques that utilize nanoparticles to mitigate environmental pollution and reduce the processing time of the routing and formation of electrodes have received much attention lately. In particular, copper (Cu) nanoink using Cu nanoparticles offers high conductivity and can be prepared at low cost. However, it is difficult to produce homogeneous nanoparticles and ensure good dispersion within the ink. Moreover, Cu particles require a sintering process over an extended time at a high temperature due to high melting temperature of Cu. During this process, the nanoparticles oxidize quickly in air. To address these problems, the authors developed a Cu ion ink that is free of Cu particles or any other impurities. It consequently does not require separate dispersion stability. In addition, the developed ink is environmentally friendly and can be sintered even at low temperatures. The Cu ion ink was sintered on a flexible substrate using intense pulsed light (IPL), which facilitates large-area, high-speed calcination at room temperature and at atmospheric pressures. As the applied light energy increases, the Cu2O phase diminishes, leaving only the Cu phase. This is attributed to the influence of formic acid (HCOOH) on the Cu ion ink. Only the Cu phase was observed above 40 J cm(-2). The Cu-patterned film after sintering showed outstanding electrical resistivity in a range of 3.21-5.27 μΩ·cm at an IPL energy of 40-60 J cm(-2). A spiral-type micropattern with a line width of 160 μm on a PI substrate was formed without line bulges or coffee ring effects. The electrical resistivity was 5.27 μΩ·cm at an energy level of 40.6 J cm(-2).

Effect of LiF as Sintering Agent on the Densification and Phase Formation in Al2O3-4 Wt Pct Nb2O5 Ceramic Compound

NASA Astrophysics Data System (ADS)

Santos, J. L.; Marçal, R. L. S. B.; Jesus, P. R. R.; Gomes, A. V.; Lima, E. P.; Monteiro, S. N.; de Campos, J. B.; Louro, L. H. L.

2017-10-01

Different amounts of LiF were added to an Al2O3-4 pct Nb2O5 basic ceramic, as sintering agent. Improved new ceramics were obtained with LiF concentrations varying from 0.25 to 1.50 wt pct and three sintering temperatures of 1573 K, 1623 K, and 1673 K (1300 °C, 1350 °C, and 1400 °C). The addition of 0.5 wt pct LiF yielded the highest densification, 94 pct of the theoretical density, in association with a sintering temperature of 1673 K (1400 °C). Based on X-ray diffraction (XRD), this improvement was due not only to the presence of transformed phases, more precisely Nb3O7F, but also to the absence of LiAl5O8. The preferential interaction of LiF with Nb2O5, instead of Al2O3, contributed to increase the alumina sintering ability by liquid phase formation. Scanning electron microscopy (SEM) results revealed well-connected grains and isolated pores, whereas the chemical composition analysis by energy dispersive energy (EDX) indicated a preferential interaction of fluorine with niobium, in agreement with the results of XRD. It was also observed from thermal analysis that the polyethylene glycol binder burnout temperature increased for all LiF concentrations. This may be related to the formation of hydrogen bridge bonds.

Making High-Temperature Superconductors By Melt Sintering

NASA Technical Reports Server (NTRS)

Golben, John P.

1992-01-01

Melt-sintering technique applied to YBa2Cu3O7-x system and to Bi/Ca/Sr/Cu-oxide system to produce highly oriented bulk high-temperature-superconductor materials extending to macroscopically usable dimensions. Processing requires relatively inexpensive and simple equipment. Because critical current two orders of magnitude greater in crystal ab plane than in crystal c direction, high degree of orientation greatly enhances critical current in these bulk materials, making them more suitable for many proposed applications.

[Influences of R2O-Al2O3-B2O3-SiO2 system glass and superfine alpha-Al2O3 on the sintering and phase transition of hydroxyapatite ceramics].

PubMed

Wang, Zhiqiang; Chen, Xiaoxu; Cai, Yingji; Lü, Bingling

2003-06-01

The effects of R2O-Al2O3-B2O3-SiO2 system glass and superfine alpha-Al2O3 on the sintering and phase transition of hydroxyapatite (HAP) ceramics were assessed. The results showed that alpha-Al2O3 impeded the sintering of HAP and raised the sintering temperature. When glass and alpha-Al2O3 were used together to reinforce HAP ceramics, better results could be obtained; the bending strength of multiphase HAP ceramics approached 106 MPa when 10% (wt) alpha-Al2O3 and 20%(wt) glass were used and sintered at 1200 for 1 h.

Influence of microstructure and AlPO4 secondary-phase on the ionic conductivity of Li1.3Al0.3Ti1.7(PO4)3 solid-state electrolyte

NASA Astrophysics Data System (ADS)

Yu, Shicheng; Mertens, Andreas; Gao, Xin; Gunduz, Deniz Cihan; Schierholz, Roland; Benning, Svenja; Hausen, Florian; Mertens, Josef; Kungl, Hans; Tempel, Hermann; Eichel, Rüdiger-A.

2016-09-01

A ceramic solid-state electrolyte of lithium aluminum titanium phosphate with the composition of Li1.3Al0.3Ti1.7(PO4)3 (LATP) was synthesized by a sol-gel method using a pre-dissolved Ti-source. The annealed LATP powders were subsequently processed in a binder-free dry forming method and sintered under air for the pellet preparation. Phase purity, density, microstructure as well as ionic conductivity of the specimen were characterized. The highest density (2.77gṡcm-3) with an ionic conductivity of 1.88×10-4 Sṡcm-1 (at 30∘C) was reached at a sintering temperature of 1100∘C. Conductivity of LATP ceramic electrolyte is believed to be significantly affected by both, the AlPO4 secondary phase content and the ceramic electrolyte microstructure. It has been found that with increasing sintering temperature, the secondary-phase content of AlPO4 increased. For sintering temperatures above 1000∘C, the secondary phase has only a minor impact, and the ionic conductivity is predominantly determined by the microstructure of the pellet, i.e. the correlation between density, porosity and particle size. In that respect, it has been demonstrated, that the conductivity increases with increasing particle size in this temperature range and density.

Phase composition and in vitro bioactivity of porous implants made of bioactive glass S53P4.

PubMed

Fagerlund, S; Massera, J; Moritz, N; Hupa, L; Hupa, M

2012-07-01

This work studied the influence of sintering temperature on the phase composition, compression strength and in vitro properties of implants made of bioactive glass S53P4. The implants were sintered within the temperature range 600-1000°C. Over the whole temperature range studied, consolidation took place mainly via viscous flow sintering, even though there was partial surface crystallization. The mechanical strength of the implants was low but increased with the sintering temperature, from 0.7 MPa at 635°C to 10 MPa at 1000°C. Changes in the composition of simulated body fluid (SBF), the immersion solution, were evaluated by pH measurements and ion analysis using inductively coupled plasma optical emission spectrometry. The development of a calcium phosphate layer on the implant surfaces was verified using scanning electron microscopy-electron-dispersive X-ray analysis. When immersed in SBF, a calcium phosphate layer formed on all the samples, but the structure of this layer was affected by the surface crystalline phases. Hydroxyapatite formed more readily on amorphous and partially crystalline implants containing both primary Na(2)O·CaO·2SiO(2) and secondary Na(2)Ca(4)(PO(4))(2)SiO(4) crystals than on implants containing only primary crystals. Copyright © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Synthesis of Highly Uniform and Compact Lithium Zinc Ferrite Ceramics via an Efficient Low Temperature Approach.

PubMed

Xu, Fang; Liao, Yulong; Zhang, Dainan; Zhou, Tingchuan; Li, Jie; Gan, Gongwen; Zhang, Huaiwu

2017-04-17

LiZn ferrite ceramics with high saturation magnetization (4πM s ) and low ferromagnetic resonance line widths (ΔH) represent a very critical class of material for microwave ferrite devices. Many existing approaches emphasize promotion of the grain growth (average size is 10-50 μm) of ferrite ceramics to improve the gyromagnetic properties at relatively low sintering temperatures. This paper describes a new strategy for obtaining uniform and compact LiZn ferrite ceramics (average grains size is ∼2 μm) with enhanced magnetic performance by suppressing grain growth in great detail. The LiZn ferrites with a formula of Li 0.415 Zn 0.27 Mn 0.06 Ti 0.1 Fe 2.155 O 4 were prepared by solid reaction routes with two new sintering strategies. Interestingly, results show that uniform, compact, and pure spinel ferrite ceramics were synthesized at a low temperature (∼850 °C) without obvious grain growth. We also find that a fast second sintering treatment (FSST) can further improve their gyromagnetic properties, such as higher 4πM s and lower ΔH. The two new strategies are facile and efficient for densification of LiZn ferrite ceramics via suppressing grain growth at low temperatures. The sintering strategy reported in this study also provides a referential experience for other ceramics, such as soft magnetism ferrite ceramics or dielectric ceramics.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sudiana, I. Nyoman, E-mail: sudiana75@yahoo.com; Ngkoimani, La Ode; Usman, Ida

Microwave sintering of materials has attracted much research interest because of its significant advantages (e.g. reduced sintering temperatures and soaking times) over the conventional heating. Most researchers compared processes that occurred during the microwave and conventional heating at the same temperature and time. The enhancements found in the former method are indicated as a 'non-thermal effect' which is usually used for explaining the phenomena in microwave processing. Numerous recent studies have been focused on the effect to elucidate the microwave interaction mechanism with materials. Moreover, recent progress on microwave sources such as gyrotrons has opened the possibility for processing materialsmore » by using a higher microwave frequency. Therefore, the technology is expected to exhibit a stronger non-thermal effect. This paper presents results from a series of experiments to study the non-thermal effect on microwave sintered alumina. Sintering by using a wide rage of microwave frequencies up to 300 GHz as well as a conventional furnace was carried out. The linear shrinkages of samples for each sintering method were measured. Pores and grains taken from scanning electron microstructure (SEM) images of cut surfaces were also examined. The results of a comparative study of the shrinkages and microstructure evolutions of the sintered samples under annealing in microwave heating systems and in an electric furnace were analyzed. A notably different behavior of the shrinkages and microstructures of alumina after being annealed was found. The results suggested that microwave radiations provided an additional force for mass transports. The results also indicated that the sintering process depended on microwave frequencies.« less

Process for making dense thin films

DOEpatents

Jacobson, Craig P.; Visco, Steven J.; DeJonghe, Lutgard C.

2005-07-26

Provided are low-cost, mechanically strong, highly electronically conductive porous substrates and associated structures for solid-state electrochemical devices, techniques for forming these structures, and devices incorporating the structures. The invention provides solid state electrochemical device substrates of novel composition and techniques for forming thin electrode/membrane/electrolyte coatings on the novel or more conventional substrates. In particular, in one embodiment the invention provides techniques for firing of device substrate to form densified electrolyte/membrane films 5 to 20 microns thick. In another embodiment, densified electrolyte/membrane films 5 to 20 microns thick may be formed on a pre-sintered substrate by a constrained sintering process. In some cases, the substrate may be a porous metal, alloy, or non-nickel cermet incorporating one or more of the transition metals Cr, Fe, Cu and Ag, or alloys thereof.

Sintering characteristics and properties of PuS and PuP are determined

NASA Technical Reports Server (NTRS)

Kruger, O. L.; Moser, J. B.

1969-01-01

Report on the preparation of plutonium monosulphide and plutonium monophosphide includes a description of the sintering characteristics and properties of these high-temperature compounds. data on weight loss, microstructure, density, melting point, thermal expansion, microhardness, Seebeck coefficient, and thermal diffusion are included.

PREPARATION OF COMPACTS MADE FROM URANIUM AND BERYLLIUM BY SINTERING

DOEpatents

Angier, R.P.

1961-04-11

A powder metallurgical method for making high-density compacts of uranium and beryllium is reported. Powdered UBe/sub 9/ and powdered Be are blended, compacted, and then sintered by rapidly heating to a temperature of approximately 1220 to 1280 deg C in an inert atmosphere.

Determination of the Darcy permeability of porous media including sintered metal plugs

NASA Technical Reports Server (NTRS)

Frederking, T. H. K.; Hepler, W. A.; Yuan, S. W. K.; Feng, W. F.

1986-01-01

Sintered-metal porous plugs with a normal size of the order of 1-10 microns are used to evaluate the Darcy permeability of laminar flow at very small velocities in laminar fluids. Porous media experiment results and data adduced from the literature are noted to support the Darcy law analog for normal fluid convection in the laminar regime. Low temperature results suggest the importance of collecting room temperature data prior to runs at liquid He(4) temperatures. The characteristic length diagram gives a useful picture of the tolerance range encountered with a particular class of porous media.

Phase equilibrium and preparation, crystallization and viscous sintering of glass in the alumina-silica-lanthanum phosphate system

NASA Astrophysics Data System (ADS)

He, Feng

The phase equilibrium, viscosity of melt-quenched glasses, and processing of sol-gel glasses of the alumina-silica-lanthanum phosphate system were studied. These investigations were directed towards serving the objective of synthesizing nano-structured ceramic-matrix-composites via controlled crystallization of glass precursors. The thermal stability, phase equilibrium, and liquidus temperatures of the alumina- and mullite-lanthanum phosphate systems are determined. An iridium wire heater was constructed to anneal samples up to 2200°C. Phosphorus evaporation losses were significant at high temperatures, especially over 1800°C. The tentative phase diagrams of the two quasi-binary systems were presented. The viscosity of the melt-quenched mullite-lanthanum phosphate glasses was measured by three different methods, including viscous sintering of glass powder compacts, neck formation between two Frenkel glass beads, and thermal analysis of the glass transition. Improved methodologies were developed for applying the interpretative mathematical models to the results of the sintered powder and thermal analytical experiments. Good agreement was found between all three methods for both absolute values and temperature dependence. A sol-gel process was developed as a low temperature route to producing glasses. A unique, single phase mullite gel capable of low temperature (575°C) mullitization was made from tetraethoxysilane and aluminum isopropoxide at room temperature in three days. Low temperature crystallization was attributed to the avoidance of phase segregation during gel formation and annealing. This was greatly enhanced by a combination of low temperature preheating in the amorphous state, a high heating rate during crystallization and low water content. The Al2O3 content in mullite (61-68 mol%) depended on the highest annealing temperature. Two mullite-lanthanum phosphate gels were made based upon modifying the chemical procedures used for the homogeneous single phase and heterogeneous diphasic mullite gels from same starting chemicals. Amorphous powders were obtained after optimized calcinations. Their different crystallization routes and sintering behavior were investigated and correlated with the different homogeneities of precursor gels. Structurally stable open, porous ceramics (up to 80% porosity) were produced from the single-phase gel derived powder, where gases exsolved during calcination caused foaming coincident with sintering. Translucent, dense glass ceramic was made from the calcined diphasic gel by hot-pressing.

Method of sintering ceramic materials

DOEpatents

Holcombe, C.E.; Dykes, N.L.

1992-11-17

A method for sintering ceramic materials is described. A ceramic article is coated with layers of protective coatings such as boron nitride, graphite foil, and niobium. The coated ceramic article is embedded in a container containing refractory metal oxide granules and placed within a microwave oven. The ceramic article is heated by microwave energy to a temperature sufficient to sinter the ceramic article to form a densified ceramic article having a density equal to or greater than 90% of theoretical density. 2 figs.

Vacuum Pressureless Sintering of Ti-6Al-4V Alloy with Full Densification and Forged-Like Mechanical Properties

NASA Astrophysics Data System (ADS)

Zhang, Ce; Lu, Boxin; Wang, Haiying; Guo, Zhimeng; Paley, Vladislav; Volinsky, Alex A.

2018-01-01

Ti-6Al-4V ingots with a nearly 100% density, fine and homogeneous basket-weave microstructure, and better comprehensive mechanical properties (UTS = 935 MPa, Y.S. = 865 MPa, El. = 15.8%), have been manufactured by vacuum pressureless sintering of blended elemental powders. Coarse TiH2 powder, Al powder (2, 20 μm), V powder, and Al-V master alloy powder were used as raw materials to produce different powder mixtures ( D 50 = 10 μm). Then, the compacts made by cold isostatic pressing were consolidated by different sintering curves. A detailed investigation of different as-sintered samples revealed that a higher density can be obtained by generating transient molten Al in the sintering process. Coarse Al powder and a rapid heating rate under the melting point of Al contribute to molten Al formation. The presence of temporary liquid phase changes the sintering mechanism, accelerating the sintering neck formation, improving sinterability of the powder mixtures. Density of 99.5% was achieved at 1150 °C, which is markedly lower than the sintering temperatures reported for conventional blended elemental powder metallurgy routes. In addition, low interstitial content, especially for oxygen (0.17 wt.%), is obtained by strict process control.

Preparation of Porous Stainless Steel Hollow-Fibers through Multi-Modal Particle Size Sintering towards Pore Engineering

PubMed Central

Allioux, Francois-Marie; Etxeberria Benavides, Miren

2017-01-01

The sintering of metal powders is an efficient and versatile technique to fabricate porous metal elements such as filters, diffusers, and membranes. Neck formation between particles is, however, critical to tune the porosity and optimize mass transfer in order to minimize the densification process. In this work, macro-porous stainless steel (SS) hollow-fibers (HFs) were fabricated by the extrusion and sintering of a dope comprised, for the first time, of a bimodal mixture of SS powders. The SS particles of different sizes and shapes were mixed to increase the neck formation between the particles and control the densification process of the structure during sintering. The sintered HFs from particles of two different sizes were shown to be more mechanically stable at lower sintering temperature due to the increased neck area of the small particles sintered to the large ones. In addition, the sintered HFs made from particles of 10 and 44 μm showed a smaller average pore size (<1 μm) as compared to the micron-size pores of sintered HFs made from particles of 10 μm only and those of 10 and 20 μm. The novel HFs could be used in a range of applications, from filtration modules to electrochemical membrane reactors. PMID:28777352

Sintering Effects on Morphology, Thermal Stability and Surface Area of Sol-Gel Derived Nano-Hydroxyapatite Powder

NASA Astrophysics Data System (ADS)

Kapoor, Seema; Batra, Uma; Kohli, Suchita

2011-12-01

Hydroxyapatite (HAP) ceramics have been recognized as substitute materials for bone and teeth in orthopedic and dentistry field due to their chemical and biological similarity to human hard tissue. The nanosized and nanocrystalline forms of HAP have great potential to revolutionize the hard tissue-engineering field, starting from bone repair and augmentation to controlled drug delivery systems. This paper reports the synthesis of biomimetic nano-hydroxyapatite (HAP) by sol-gel method using calcium nitrate tetrahydrate (CNT) and potassium dihydrogen phosphate (KDP) as calcium and phosphorus precursors, respectively to obtain a desired Ca/P ratio of 1.67. Deionized water was used as a diluting media for HAP sol preparation and ammonia was used to adjust the pH to 11. After aging, the HAP gel was dried at 55 °C and sintered to different temperatures (200 °C, 400 °C, 600 °C, 800 °C, 1000 °C and 1200 °C). The dried and sintered powders were characterized for phase composition using Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD). The particle size and morphology was studied using transmission electron microscopy (TEM). The thermal behavior of the dried HAP nanopowder was studied in the temperature range of 55 °C to 1000 °C using thermal gravimetric analyser (TGA). The BET surface area of absorbance was determined by Nitrogen adsorption using Brunauer-Emmett-Teller (BET) method. The presence of characteristic peaks of the phosphate and OH groups in FTIR spectrums confirmed the formation of pure HAP in dried as well as sintered powders. XRD results also confirmed the formation of stoichiometric nano-HAP. Sintering revealed that with increase in temperature, both the crystallinity and crystallite size of nano-HAP particles increased. The synthesized nano-HAP powder was found to be stable upto 1000 °C without any additional phase other than HAP, whereas peak of β-TCP (tricalcium phosphate) was observed at 1200 °C. Photomicrograph of TEM showed that the nanopowder sintered at 600 °C is composed of hydroxyapatite nanoparticles (26.0-45.6 nm), which is well in agreement with the crystallite size calculated using XRD data. TGA study showed the thermal stability of the synthesized nano-HAP powder. The BET surface area decreased with increase in sintering temperature.

Sintering of micro-trusses created by extrusion-3D-printing of lunar regolith inks

NASA Astrophysics Data System (ADS)

Taylor, Shannon L.; Jakus, Adam E.; Koube, Katie D.; Ibeh, Amaka J.; Geisendorfer, Nicholas R.; Shah, Ramille N.; Dunand, David C.

2018-02-01

The development of in situ fabrication methods for the infrastructure required to support human life on the Moon is necessary due to the prohibitive cost of transporting large quantities of materials from the Earth. Cellular structures, consisting of a regular network (truss) of micro-struts with ∼500 μm diameters, suitable for bricks, blocks, panels, and other load-bearing structural elements for habitats and other infrastructure are created by direct-extrusion 3D-printing of liquid inks containing JSC-1A lunar regolith simulant powders, followed by sintering. The effects of sintering time, temperature, and atmosphere (air or hydrogen) on the microstructures, mechanical properties, and magnetic properties of the sintered lunar regolith micro-trusses are investigated. The air-sintered micro-trusses have higher relative densities, linear shrinkages, and peak compressive strengths, due to the improved sintering of the struts within the micro-trusses achieved by a liquid or glassy phase. Whereas the hydrogen-sintered micro-trusses show no liquid-phase sintering or glassy phase, they contain metallic iron 0.1-2 μm particles from the reduction of ilmenite, which allows them to be lifted with magnets.

Studying hardness, workability and minimum bending radius in selectively laser-sintered Ti–6Al–4V alloy samples

NASA Astrophysics Data System (ADS)

Galkina, N. V.; Nosova, Y. A.; Balyakin, A. V.

2018-03-01

This research is relevant as it tries to improve the mechanical and service performance of the Ti–6Al–4V titanium alloy obtained by selective laser sintering. For that purpose, sintered samples were annealed at 750 and 850°C for an hour. Sintered and annealed samples were tested for hardness, workability and microstructure. It was found that incomplete annealing of selectively laser-sintered Ti–6Al–4V samples results in an insignificant reduction in hardness and ductility. Sintered and incompletely annealed samples had a hardness of 32..33 HRC, which is lower than the value of annealed parts specified in standards. Complete annealing at temperature 850°C reduces the hardness to 25 HRC and ductility by 15...20%. Incomplete annealing lowers the ductility factor from 0.08 to 0.06. Complete annealing lowers that value to 0.025. Complete annealing probably results in the embrittlement of sintered samples, perhaps due to their oxidation and hydrogenation in the air. Optical metallography showed lateral fractures in both sintered and annealed samples, which might be the reason why they had lower hardness and ductility.

An Arrhenius-type viscosity function to model sintering using the Skorohod Olevsky viscous sintering model within a finite element code.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ewsuk, Kevin Gregory; Arguello, Jose Guadalupe, Jr.; Reiterer, Markus W.

2006-02-01

The ease and ability to predict sintering shrinkage and densification with the Skorohod-Olevsky viscous sintering (SOVS) model within a finite-element (FE) code have been improved with the use of an Arrhenius-type viscosity function. The need for a better viscosity function was identified by evaluating SOVS model predictions made using a previously published polynomial viscosity function. Predictions made using the original, polynomial viscosity function do not accurately reflect experimentally observed sintering behavior. To more easily and better predict sintering behavior using FE simulations, a thermally activated viscosity function based on creep theory was used with the SOVS model. In comparison withmore » the polynomial viscosity function, SOVS model predictions made using the Arrhenius-type viscosity function are more representative of experimentally observed viscosity and sintering behavior. Additionally, the effects of changes in heating rate on densification can easily be predicted with the Arrhenius-type viscosity function. Another attribute of the Arrhenius-type viscosity function is that it provides the potential to link different sintering models. For example, the apparent activation energy, Q, for densification used in the construction of the master sintering curve for a low-temperature cofire ceramic dielectric has been used as the apparent activation energy for material flow in the Arrhenius-type viscosity function to predict heating rate-dependent sintering behavior using the SOVS model.« less

SINTERING OF NASCENT CALCIUM OXIDE

EPA Science Inventory

The paper discusses the measurement of the sintering rate of CaO in a nitrogen atmosphere at temperatures of 700-1100 C. CaO prepared from ultrapure CaCO3 was compared with an impure CaO derived from limestone. Both materials yielded an initial surface area of 104 sq m/g. The rat...

Strength evaluation test of pressureless-sintered silicon nitride at room temperature

NASA Technical Reports Server (NTRS)

Matsusue, K.; Takahara, K.; Hashimoto, R.

1984-01-01

In order to study strength characteristics at room temperature and the strength evaluating method of ceramic materials, the following tests were conducted on pressureless sintered silicon nitride specimens: bending tests, the three tensile tests of rectangular plates, holed plates, and notched plates, and spin tests of centrally holed disks. The relationship between the mean strength of specimens and the effective volume of specimens are examined using Weibull's theory. The effect of surface grinding on the strength of specimens is discussed.

Impedance response and dielectric relaxation in co-precipitation derived ferrite (Ni,Zn)Fe{sub 2}O{sub 4} ceramics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, D. G.; Tang, X. G.; Liu, Q. X.

2013-06-07

Dielectric spectra and magnetization hysteresis loops were used to investigate the grain size effect with temperature on the electrical and magnetic response of co-precipitation derived spinel (Ni{sub 0.5}Zn{sub 0.5})Fe{sub 2}O{sub 4} (NZFO) ceramics. Remarkable dielectric relaxation phenomena of non-Debye type have been observed in each NZFO ceramics as confirmed by two kinds of Cole-Cole plots of the 1100 Degree-Sign C sintered samples, mainly due to the electron-hopping mechanism between n-type and p-type carriers and interfacial ion effect when applied an increase of temperature. The high and low response of grain and grain-boundary regions were determined by modeling the impedance experimentalmore » results on two equivalent RC circuits taking into account grain deep trap states. By employing the modified Arrhenius equation, activation energy values of different sintering temperatures were calculated and analyzed in combination with oxygen vacancy. In addition, the magnetization of various sintering temperature samples is dominated by cation distribution and surface effect in different particle ranges.« less

110K Bi-Sr-Ca-Cu-O superconductor oxide and method for making same

DOEpatents

Veal, B.W.; Downey, J.W.; Lam, D.J.; Paulikas, A.P.

1992-12-22

A superconductor is disclosed consisting of a sufficiently pure phase of the oxides of Bi, Sr, Ca, and Cu to exhibit a resistive zero near 110K resulting from the process of forming a mixture of Bi[sub 2]O[sub 3], SrCO[sub 3], CaCO[sub 3] and CuO into a particulate compact wherein the atom ratios are Bi[sub 2], Sr[sub 1.2-2.2], Ca[sub 1.8-2.4], Cu[sub 3]. Thereafter, heating the particulate compact rapidly in the presence of oxygen to an elevated temperature near the melting point of the oxides to form a sintered compact, and then maintaining the sintered compact at the elevated temperature for a prolonged period of time. The sintered compact is cooled and reground. Thereafter, the reground particulate material is compacted and heated in the presence of oxygen to an elevated temperature near the melting point of the oxide and maintained at the elevated temperature for a time sufficient to provide a sufficiently pure phase to exhibit a resistive zero near 110K. 7 figs.

110K Bi-Sr-Ca-Cu-O superconductor oxide and method for making same

DOEpatents

Veal, Boyd W.; Downey, John W.; Lam, Daniel J.; Paulikas, Arvydas P.

1992-01-01

A superconductor consisting of a sufficiently pure phase of the oxides of Bi, Sr, Ca, and Cu to exhibit a resistive zero near 110K resulting from the process of forming a mixture of Bi.sub.2 O.sub.3, SrCO.sub.3, CaCO.sub.3 and CuO into aparticulate compact wherein the atom ratios are Bi.sub.2, Sr.sub.1.2-2.2, Ca.sub.1.8-2.4, Cu.sub.3. Thereafter, heating the particulate compact rapidly in the presence of oxygen to an elevated temperature near the melting point of the oxides to form a sintered compact, and then maintaining the sintered compact at the elevated temperature for a prolonged period of time. The sintered compact is cooled and reground. Thereafter, the reground particulate material is compacted and heated in the presence of oxygen to an elevated temperature near the melting point of the oxide and maintained at the elevated temperature for a time sufficient to provide a sufficiently pure phase to exhibit a resistive zero near 110K.

High temperature resistant cermet and ceramic compositions. [for thermal resistant insulators and refractory coatings

NASA Technical Reports Server (NTRS)

Phillips, W. M. (Inventor)

1978-01-01

High temperature oxidation resistance, high hardness and high abrasion and wear resistance are properties of cermet compositions particularly to provide high temperature resistant refractory coatings on metal substrates, for use as electrical insulation seals for thermionic converters. The compositions comprise a sintered body of particles of a high temperature resistant metal or metal alloy, preferably molybdenum or tungsten particles, dispersed in and bonded to a solid solution formed of aluminum oxide and silicon nitride, and particularly a ternary solid solution formed of a mixture of aluminum oxide, silicon nitride and aluminum nitride. Ceramic compositions comprising a sintered solid solution of aluminum oxide, silicon nitride and aluminum nitride are also described.

Effect of sintering on transparent TiO2 18NR-T type thin films as the working electrode for transparent solar cells

NASA Astrophysics Data System (ADS)

Supriyanto, A.; Nandani; Wahyuningsih, S.; Ramelan, A. H.

2018-03-01

The working electrode based on semiconductor transparent TiO2 type 18NR-T for transparent solar cells have been grown by screen printing method. This study aim is to determine the effect of sintering on TiO2 thin films transparent as the working electrode of transparent solar cells. TiO2 films will be sintered at temperature 450°C, 500°C, 550°C and 600°C. TiO2 films optical properties were characterized using UV-Vis spectrophotometer, electrical properties were characterized using 4 point probemethods and the crystallization was characterized by X-Ray Diffraction (XRD). The lowest transmittance due to the treatment of annealing temperature variations is 550°C because the 550°C TiO2 layer is more absorbing. The peaks resulted from the annealing temperature treatment show that the high temperature the more anatase peaks. Characterization using four-point probe showed that the highest conductivity of TiO2 18NR-T thin film was 2.42 x 102 Ω-1m-1 at annealing temperature 550°C.

Effect of heating parameters on sintering behaviors and properties of mullite whisker frameworks

NASA Astrophysics Data System (ADS)

Zhang, Y. M.; Zeng, D. J.; Wang, B.; Yang, J. F.

2018-04-01

Mullite whisker frameworks were fabricated by vapor-solid reaction with SiO2, Al2O3 and AlF3 powders as the whisker forming agent at high temperatures. The effects of heating temperature and soaking time on the weight loss, liner shrinkage, porosity, microstructure and compressive strength were investigated. The results showed that with the increasing of the sintering temperature and soaking time, the weight loss and liner shrinkage of the samples increased and the porosities decreased due to the accelerated vapor-solid reaction, resulting in strong bonding and grain growth of the mullite frameworks. The compressive strength of the samples increased with increasing the sintering temperature from 1500 to 1650 °C, and decreased with the soaking time extended to more than 5 h for 1500 °C and 2 h for 1650 °C. A maximum compressive strength of 142 MPa at a porosity of 62.3% was obtained for the mullite whisker framework heated at 1500 °C for 5 h. The enhanced strength was attributed to the strong bonding strength and fine mullite grains resulting from a relative lower heating temperature and a modest soaking time.

Physical, mechanical and electrochemical characterization of all-perovskite intermediate temperature solid oxide fuel cells

NASA Astrophysics Data System (ADS)

Mohammadi, Alidad

Strontium- and magnesium-doped lanthanum gallate (LSGM) has been considered as a promising electrolyte for solid oxide fuel cell (SOFC) systems in recent years due to its high ionic conductivity and chemical stability over a wide range of oxygen partial pressures and temperatures. This research describes synthesis, physical and mechanical behavior, electrochemical properties, phase evolution, and microstructure of components of an all-perovskite anode-supported intermediate temperature solid oxide fuel cell (ITSOFC), based on porous La 0.75Sr0.25Cr0.5Mn0.5O3 (LSCM) anode, La0.8Sr0.2Ga0.8Mg0.2O 2.8 (LSGM) electrolyte, and porous La0.6Sr0.4Fe 0.8Co0.2O3 (LSCF) cathode. The phase evolution of synthesized LSGM and LSCM powders has been investigated, and it has been confirmed that there is no reaction between LSGM and LSCM at sintering temperature. Using different amounts of poreformers and binders as well as controlling firing temperature, porosity of the anode was optimized while still retaining good mechanical integrity. The effect of cell operation conditions under dry hydrogen fuel on the SOFC open circuit voltage (OCV) and cell performance were also investigated. Characterization study of the synthesized LSGM indicates that sintering at 1500°C obtains higher electrical conductivity compared to the currently published results, while conductivity of pellets sintered at 1400°C and 1450°C would be slightly lower. The effect of sintering temperature on bulk and grain boundary resistivities was also discussed. The mechanical properties, such as hardness, Young's modulus, fracture toughness and modulus of rupture of the electrolyte were determined and correlated with scanning electron microscopy (SEM) morphological characterization. Linear thermal expansion and thermal expansion coefficient of LSGM were also measured.

[Raman studies of nanocrystalline BaTiO3 ceramics].

PubMed

Xiao, Chang-jiang; Jin, Chang-qing; Wang, Xiao-hui

2008-12-01

High pressure can significantly increase the densification. Further, during the high pressure assisted sintering, the nucleation rate is increased due to reduced energy barrier and the growth rate is suppressed due to the decreased diffusivity. Thus high pressure enables the specimen to be fabricated with relatively lower temperature and shorter sintering period that assures to obtain dense nanocrystalline ceramics. Dense nanocrystalline BaTiO3 ceramics with uniform grain sizes of 60 and 30 nm, respectively, were obtained by pressure assisted sintering. The crystal structure and phase transitions were investigated by Raman scattering at temperatures ranging from -190 to 200 degrees C. The Raman results indicated that the evolution of Raman spectrum with grain size is characterized by an intensity decrease, a broadening of the line width, a frequency shift, and the disappearance of the Raman mode. With increasing temperature, similar to 3 mm BaTiO3 normal ceramics, the successive phase transitions from rhombohedral to orthorhombic, orthorhombic to tetragonal, and tetragonal to cubic were also observed in nanocrystalline BaTiO3 ceramics. In addition, when particle size is reduced to the nanoscale, one will find some unusual physical properties in nanocrystalline ceramics, compared with those of coarse-grained BaTiO3 ceramics. The different coexistences of multiphase were found at different temperature. Especially, the ferroelectric tetragonal and orthorhombic phase can coexist at room temperature in nanocrystalline BaTiO3 ceramics. The phenomenon can be explained by the internal stress. The coexistences of different ferroelectric phases at room temperature indicate that the critical grain size for the disappearance of ferroelectricity in nanocrystalline BaTiO3 ceramics fabricated by pressure assisted sintering is below 30 nm.

Strain Hardening Behaviour and Its Effect on Properties of ZrB2 Reinforced Al Composite Prepared by Powder Metallurgy Technique

NASA Astrophysics Data System (ADS)

Kaku, Sai Mahesh Yadav; Khanra, Asit Kumar; Davidson, M. J.

2018-04-01

Strain hardening behaviour has significant effect on altering the properties of materials. In the present study, Al-ZrB2 metal matrix composites are made through powder metallurgy route. Incremental weight percentage (wt%) of ZrB2 (0, 2, 4 and 6 wt%) are added to Aluminium matrix to produce different composites. The homogenous powder mixture is compacted and pressurelessly sintered. Sintering of composites is performed over a range of 450-575 °C. The optimized sintered condition is observed at 550 °C for 1 h in controlled atmosphere (argon gas flow). The sintered compacts are strained in incremental steps in different levels up to failure. A visible crack on the bulge of the powder preform is considered as the failure. Composites are strain hardened up to failure. To evaluate the effect of temperature on strain hardening, strain hardening is carried out at different temperatures. Composites are densified with the extent of straining and hardness increases with the increase of strain. Hardness increase with the increase in temperature is maintained during strain hardening. To evaluate the corrosion behaviour of Al-ZrB2 composite, potentiodynamic polarization study are performed on the strained composites. Corrosion rate decrease with the extent of straining.

The effects of salinity and temperature on phase transformation of copper-laden sludge.

PubMed

Hsieh, Ching-Hong; Shih, Kaimin; Hu, Ching-Yao; Lo, Shang-Lien; Li, Nien-Hsun; Cheng, Yi-Ting

2013-01-15

To stabilize the copper and aluminum ions in simulated sludge, a series of sintering processes were conducted to transform Cu/Al precipitation into spinel structure, CuAl(2)O(4). The results indicated that the large amount of salt content in the simulated sludge would hinder the formation of crystalline CuAl(2)O(4) generated from the incorporation of CuO and Al(2)O(3), even after the sintering process at 1200 °C. Opposite to the amorphous CuAl(2)O(4), the crystalline CuAl(2)O(4) can be formed in the sintering process at 700-1100 °C for 3 h with the desalinating procedure. According to the theory of free energy, the experimental data and references, the best formation temperature of CuAl(2)O(4) was determined at 900-1000 °C. As the temperature rose to 1200 °C, CuAlO(2) was formed with the dissociation of CuAl(2)O(4). The XPS analysis also showed that the binding energy of copper species in the simulated sludge was switched from 933.8 eV for Cu(II) to 932.8 eV for Cu(I) with the variation of temperature. In this system, the leaching concentration of copper and aluminum ions from sintered simulated sludge was decreased with ascending temperature and reached the lowest level at 1000 °C. Furthermore, the descending tendency coincided with the formation tendency of spinel structure and the diminishing of copper oxide. Copyright © 2012 Elsevier B.V. All rights reserved.

Reduction mechanism of surface oxide films and characterization of formations on pulse electric-current sintered Al Mg alloy powders

NASA Astrophysics Data System (ADS)

Xie, Guoqiang; Ohashi, Osamu; Song, Minghui; Mitsuishi, Kazutaka; Furuya, Kazuo

2005-02-01

The microstructure of interfaces between powder particles in Al-Mg alloy specimens sintered by pulse electric-current sintering (PECS) process was characterized using high resolution transmission electron microscopy (HRTEM) and energy dispersive X-ray spectroscopy (EDS). The crystalline precipitates with nano-size in the interface were observed in all of Al-Mg alloy specimens. The composition was determined to be MgAl 2O 4 or MgO, or both of them, which depended on Mg content in alloy powder and sintering temperature. The precipitates were suggested to contribute to reduction reaction of Mg with oxide films originally covered at powder particles surface.

Effect on the grain size of single-mode microwave sintered NiCuZn ferrite and zinc titanate dielectric resonator ceramics.

PubMed

Sirugudu, Roopas Kiran; Vemuri, Rama Krishna Murthy; Venkatachalam, Subramanian; Gopalakrishnan, Anisha; Budaraju, Srinivasa Murty

2011-01-01

Microwave sintering of materials significantly depends on dielectric, magnetic and conductive Losses. Samples with high dielectric and magnetic loss such as ferrites could be sintered easily. But low dielectric loss material such as dielectric resonators (paraelectrics) finds difficulty in generation of heat during microwave interaction. Microwave sintering of materials of these two classes helps in understanding the variation in dielectric and magnetic characteristics with respect to the change in grain size. High-energy ball milled Ni0.6Cu0.2Zn0.2Fe1.98O4-delta and ZnTiO3 are sintered in conventional and microwave methods and characterized for respective dielectric and magnetic characteristics. The grain size variation with higher copper content is also observed with conventional and microwave sintering. The grain size in microwave sintered Ni0.6Cu0.2Zn0.2Fe1.98O4-delta is found to be much small and uniform in comparison with conventional sintered sample. However, the grain size of microwave sintered sample is almost equal to that of conventional sintered sample of Ni0.3Cu0.5Zn0.2Fe1.98O4-delta. In contrast to these high dielectric and magnetic loss ferrites, the paraelectric materials are observed to sinter in presence of microwaves. Although microwave sintered zinc titanate sample showed finer and uniform grains with respect to conventional samples, the dielectric characteristics of microwave sintered sample are found to be less than that of conventional sample. Low dielectric constant is attributed to the low density. Smaller grain size is found to be responsible for low quality factor and the presence of small percentage of TiO2 is observed to achieve the temperature stable resonant frequency.

Fermi Surface Studies and Temperature Dependence of the Electron-Positron Momentum Density in the High Critical Temperature Superconducting Yttrium BARIUM(2) COPPER(3) OXYGEN(7-X) System by Two-Dimensional Acar

NASA Astrophysics Data System (ADS)

von Stetten, Eric Carl

The electron-positron momentum density has been measured by the two dimensional angular correlation of annihilation radiation (2D ACAR) technique for single crystal and polycrystalline (sintered powder) YBa_2 Cu_3O_{7-x} samples. For sintered superconducting and nonsuperconducting samples, the shape and temperature variation of the momentum density was investigated using the high sensitivity 2D ACAR technique. The possible existence of Fermi surfaces (FS's) in the YBa_2Cu _3O_{7-x} system was investigated in high precision 2D ACAR experiments on an oriented (twinned) single crystal superconducting YBa_2Cu _3O_{7-x} (x ~ 0.1) sample, at temperatures above and below the superconducting transition temperature (~85 K). These experiments were performed in the c-axis projection, in order to observe the theoretically predicted cylindrical FS's (if they exist) in a single experiment, without a full reconstruction of the three dimensional momentum density. Large differences were observed between the room temperature 2D ACAR spectra for superconducting and nonsuperconducting sintered powder samples, and smaller differences were observed between the spectra for similarly prepared superconducting samples. For sintered superconducting samples, complex sample dependent temperature variations of the momentum density were observed, in contrast to the small linear temperature variation observed for a sintered powder nonsuperconducting sample. These results are interpreted as manifestations of the theoretically predicted preferential sampling of the linear Cu-O chain region by the positron in the YBa _2Cu_3O _{7-x} system. High precision experiments on the single crystal superconducting sample revealed a nearly isotropic 2D ACAR spectrum, with only four small (~3% of the height at p_{x} = p _{y} = 0) peaks centered along the (110) symmetry lines. A small narrowing of the 2D ACAR spectrum was observed above T_{c}. The Brillouin-zone-reduced momentum density was formed using the "Lock-Crisp-West folding" technique, in order to identify possible FS signatures; several small features were observed that could possibly be due to FS's. A computer study of statistical noise propagation in 2D ACAR data, however, found that the possible FS signatures in the experimental data are similar in shape and magnitude to noise produced features.

Leachability of Heavy Metals from Lightweight Aggregates Made with Sewage Sludge and Municipal Solid Waste Incineration Fly Ash

PubMed Central

Wei, Na

2015-01-01

Lightweight aggregate (LWA) production with sewage sludge and municipal solid waste incineration (MSWI) fly ash is an effective approach for waste disposal. This study investigated the stability of heavy metals in LWA made from sewage sludge and MSWI fly ash. Leaching tests were conducted to find out the effects of MSWI fly ash/sewage sludge (MSWI FA/SS) ratio, sintering temperature and sintering time. It was found that with the increase of MSWI FA/SS ratio, leaching rates of all heavy metals firstly decreased and then increased, indicating the optimal ratio of MSWI fly ash/sewage sludge was 2:8. With the increase of sintering temperature and sintering time, the heavy metal solidifying efficiencies were strongly enhanced by crystallization and chemical incorporations within the aluminosilicate or silicate frameworks during the sintering process. However, taking cost-savings and lower energy consumption into account, 1100 °C and 8 min were selected as the optimal parameters for LWA sample- containing sludge production. Furthermore, heavy metal leaching concentrations under these optimal LWA production parameters were found to be in the range of China’s regulatory requirements. It is concluded that heavy metals can be properly stabilized in LWA samples containing sludge and cannot be easily released into the environment again to cause secondary pollution. PMID:25961800

Electrical and dielectric properties of Na1/2La1/2Cu3Ti4O12 ceramics prepared by high energy ball-milling and conventional sintering

NASA Astrophysics Data System (ADS)

Mahfoz Kotb, H.; Ahmad, Mohamad M.

2016-12-01

We report on the measurements of the electrical and dielectric properties of Na1/2La1/2Cu3Ti4O12 (NLCTO) ceramics prepared by high energy ball-milling and conventional sintering without any calcination steps. The x-ray powder diffraction analysis shows that pure perovskite-like CCTO phase is obtained after sintering at 1025 °C-1075 °C. Higher sintering temperatures result in multi-phase ceramics due to thermal decomposition. Scanning electron microscope observations reveal that the grain size is in a range of ˜3 μm-5μm for these ceramics. Impedance spectroscopy measurements performed in a wide frequency range (1 Hz-10 MHz) and at various temperatures (120 K-470 K) are used to study the dielectric and electrical properties of NLCTO ceramics. A good compromise between high ɛ‧ (5.7 × 103 and 4.1 × 103 at 1.1 kHz and 96 kHz, respectively) and low tan δ (0.161 and 0.126 at 1.1 kHz and 96 kHz, respectively) is obtained for the ceramic sintered at 1050 °C. The observed high dielectric constant behavior is explained in terms of the internal barrier layer capacitance effect.

Influence of Sintering Temperature on Mechanical and Physical properties of Mill Scale based Bipolar Plates for PEMFC

NASA Astrophysics Data System (ADS)

Khaerudini, Deni S.; Berliana, Rina; Prakoso, Gatra B.; Insiyanda, Dita R.; Alva, Sagir

2018-03-01

This work concerns the utilization of mill scale, a by-product of iron and steel formed during the hot rolling of steel, as a potential material for use as bipolar plates in proton exchange membrane fuel cells (PEMFCs). On the other hand, mill scale is considered a very rich in iron source having characteristic required such as for current collector in bipolar plate and would significantly contribute to lower the overall cost of PEMFC based fuel cell systems. In this study, the iron reach source of mill scale powder, after sieving of 150 mesh, was mechanically alloyed with the aluminium source containing 30 wt.% using a shaker mill for 3 h. The mixed powders were then pressed at 300 MPa and sintered at various temperatures of 400, 450 and 500 °C for 1 h under inert gas atmosphere. The structural changes of powder particles during mechanical alloying and after sintering were studied by x-ray diffractometry, scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDX), microhardness measurement, and density - porosity analysis. The details of the performance variation of three different sintering conditions can be preliminary explained by the metallographic and crystallographic structure and phase analysis as well as sufficient mechanical strength of the sintered materials was presented in this report.

Leachability of heavy metals from lightweight aggregates made with sewage sludge and municipal solid waste incineration fly ash.

PubMed

Wei, Na

2015-05-07

Lightweight aggregate (LWA) production with sewage sludge and municipal solid waste incineration (MSWI) fly ash is an effective approach for waste disposal. This study investigated the stability of heavy metals in LWA made from sewage sludge and MSWI fly ash. Leaching tests were conducted to find out the effects of MSWI fly ash/sewage sludge (MSWI FA/SS) ratio, sintering temperature and sintering time. It was found that with the increase of MSWI FA/SS ratio, leaching rates of all heavy metals firstly decreased and then increased, indicating the optimal ratio of MSWI fly ash/sewage sludge was 2:8. With the increase of sintering temperature and sintering time, the heavy metal solidifying efficiencies were strongly enhanced by crystallization and chemical incorporations within the aluminosilicate or silicate frameworks during the sintering process. However, taking cost-savings and lower energy consumption into account, 1100 °C and 8 min were selected as the optimal parameters for LWA sample- containing sludge production. Furthermore, heavy metal leaching concentrations under these optimal LWA production parameters were found to be in the range of China's regulatory requirements. It is concluded that heavy metals can be properly stabilized in LWA samples containing sludge and cannot be easily released into the environment again to cause secondary pollution.

New potassium-sodium niobate lead-free piezoceramic: Giant-d33 vs. sintering temperature

NASA Astrophysics Data System (ADS)

Wu, Jiagang; Wang, Xiaopeng; Cheng, Xiaojing; Zheng, Ting; Zhang, Binyu; Xiao, Dingquan; Zhu, Jianguo; Lou, Xiaojie

2014-03-01

The objective of this work is to achieve a giant piezoelectric constant in (K,Na)NbO3-based lead-free ceramics, and then 0.96K0.46Na0.54Nb0.95Sb0.05O3-0.04Bi0.5(Na0.82K0.18)0.5ZrO3 lead-free piezoceramics were designed and prepared by optimizing the sintering temperature (TS). The rhombohedral-tetragonal phase boundary is found in the ceramics sintered at 1070 ˜ 1105 °C and is suppressed when sintered at low TS of 1060 ˜ 1065 °C. The threshold for TS is 1070 °C in terms of their ferroelectric and piezoelectric properties owing to the difference in the phase boundary and the microstructure, and a large d33 of 388 ˜ 465 pC/N could be attained in a wide TS range of 1070 ˜ 1105 °C, benefiting their practical applications because of broad TS. More interestingly, the ceramic sintered at 1075 °C has a giant d33 of ˜465 pC/N. We think that such a giant d33 of this material system can benefit the development of (K,Na)NbO3-based piezoceramics.

Cold sintering and electrical characterization of lead zirconate titanate piezoelectric ceramics

NASA Astrophysics Data System (ADS)

Wang, Dixiong; Guo, Hanzheng; Morandi, Carl S.; Randall, Clive A.; Trolier-McKinstry, Susan

2018-01-01

This paper describes a cold sintering process for Pb(Zr,Ti)O3 ceramics and the associated processing-property relations. Pb(Zr,Ti)O3 has a very small, incongruent solubility that is a challenge during cold sintering. To circumvent this, a Pb(NO3)2 solution was used as the transient liquid phase. A bimodal lead zirconate titanate powder was densified to a relative density of 89% by cold sintering at 300 °C and 500 MPa. After the cold sintering step, the permittivity was 200, and the dielectric loss was 2.0%. A second heat-treatment involving a 3 h anneal at 900 °C increased the relative density to 99%; the resulting relative dielectric permittivity was 1300 at room temperature and 100 kHz. The samples showed well-defined ferroelectric hysteresis loops, having a remanent polarization of 28 μC/cm2. On poling, the piezoelectric coefficient d33 was ˜200 pC/N. With a 700 °C 3 h post-annealing, samples show a lower room temperature relative permittivity (950 at 100 kHz), but a 24 h hold time at 700 °C produces ceramics where there is an improved relative dielectric constant (1050 at 100 kHz).

Low-cost optical fabrication of flexible copper electrode via laser-induced reductive sintering and adhesive transfer

NASA Astrophysics Data System (ADS)

Back, Seunghyun; Kang, Bongchul

2018-02-01

Fabricating copper electrodes on heat-sensitive polymer films in air is highly challenging owing to the need of expensive copper nanoparticles, rapid oxidation of precursor during sintering, and limitation of sintering temperature to prevent the thermal damage of the polymer film. A laser-induced hybrid process of reductive sintering and adhesive transfer is demonstrated to cost-effectively fabricate copper electrode on a polyethylene film with a thermal resistance below 100 °C. A laser-induced reductive sintering process directly fabricates a high-conductive copper electrode onto a glass donor from copper oxide nanoparticle solution via photo-thermochemical reduction and agglomeration of copper oxide nanoparticles. The sintered copper patterns were transferred in parallel to a heat-sensitive polyethylene film through self-selective surface adhesion of the film, which was generated by the selective laser absorption of the copper pattern. The method reported here could become one of the most important manufacturing technologies for fabricating low-cost wearable and disposable electronics.

Fabrication and Analysis of the Wear Properties of Hot-Pressed Al-Si/SiCp + Al-Si-Cu-Mg Metal Matrix Composite

NASA Astrophysics Data System (ADS)

Bang, Jeongil; Oak, Jeong-Jung; Park, Yong Ho

2016-01-01

The aim of this study was to characterize microstructures and mechanical properties of aluminum metal matrix composites (MMC's) prepared by powder metallurgy method. Consolidation of mixed powder with gas atomized Al-Si/SiCp powder and Al-14Si-2.5Cu-0.5Mg powder by hot pressing was classified according to sintering temperature and sintering time. Sintering condition was optimized using tensile properties of sintered specimens. Ultimate tensile strength of the optimized sintered specimen was 228 MPa with an elongation of 5.3% in longitudinal direction. In addition, wear properties and behaviors of the sintered aluminum-based MMC's were analyzed in accordance with vertical load and linear speed. As the linear speed and vertical load of the wear increased, change of the wear behavior occurred in order of oxidation of Al-Si matrix, formation of C-rich layer, Fe-alloying to matrix, and melting of the specimen

Implementation of a spark plasma sintering facility in a hermetic glovebox for compaction of toxic, radiotoxic, and air sensitive materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tyrpekl, V., E-mail: vaclav.tyrpekl@ec.europa.eu, E-mail: vaclav.tyrpekl@gmail.com; Berkmann, C.; Holzhäuser, M.

Spark plasma sintering (SPS) is a rapidly developing method for densification of powders into compacts. It belongs to the so-called “field assisted sintering techniques” that enable rapid sintering at much lower temperatures than the classical approaches of pressureless sintering of green pellets or hot isostatic pressing. In this paper, we report the successful integration of a SPS device into a hermetic glovebox for the handling of highly radioactive material containing radioisotopes of U, Th, Pu, Np, and Am. The glovebox implantation has been facilitated by the replacement of the hydraulic system to apply pressure with a compact electromechanical unit. Themore » facility has been successfully tested using UO{sub 2} powder. Pellets with 97% of the theoretical density were obtained at 1000 °C for 5 min, significantly lower than the ∼1600 °C for 5-10 h used in conventional pellet sintering.« less

Development and Investigation of Tungsten Copper Sintered Parts for Using in Medium and High Voltage Switching Devices

NASA Astrophysics Data System (ADS)

Lungu, M. V.; Lucaci, M.; Tsakiris, V.; Brătulescu, A.; Cîrstea, C. D.; Marin, M.; Pătroi, D.; Mitrea, S.; Marinescu, V.; Grigore, F.; Tălpeanu, D.; Stancu, N.; Godeanu, P.; Melnic, C.

2017-06-01

Abstract Tungsten-copper (W-Cu) sintered parts with 75 wt.% W, 24 wt.% Cu and 1 wt.% Ni for using as arcing contacts in medium and high voltage switching devices were developed successfully by powder metallurgy (PM) techniques. Sintered parts with diameter of 50±0.5 mm and height of 6±0.5 mm were manufactured by pressing-sintering-infiltration (P-S-I) and spark plasma sintering (SPS) at sintering temperature of 1150°C, and 1050°C, respectively. Physical, chemical, electrical, thermal and mechanical properties of the samples were investigated. Microstructure was analyzed by optical microscopy and scanning electron microscopy. Material properties were influenced by the consolidation processes. The best results were achieved by SPS process. The relative density was more than 95 %, Vickers hardness HV1/15 was over 227, elastic modulus was over 143 GPa, and homogeneous microstructure was revealed. These good properties can contribute to higher lifetime of arcing contacts under severe working conditions.

Effect of sintering time on the performance of turmeric dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Basuki, Hidajat, R. Lullus Lambang G.; Suyitno, Kristiawan, Budi; Rachmanto, Rendy Adhi

2017-01-01

This study reports the effect of sintering time on the performance of the dye-sensitized solar cells with turmeric dyes as sensitizers. Sintering TiO2 semiconductors were conducted at a temperature of 450°C for 30, 50, 90, 120, 150, and 180 minutes. The natural dye was extracted from dried turmeric powders with ethanol solvent. The results show that size of grains and the opening area of TiO2 semiconductor depended on the sintering time. The improvement of the properties of TiO2 semiconductor allowed more turmeric dyes were adsorbed by the semiconductors and then improved the performance of solar cells. The sintering time of 150 minutes produced large grains with an average diameter of 68.87 nm, and a porosity area of 26.51% caused the performance of DSSCs was the highest among other sintering time. The Voc, Jsc, and efficiency of DSSCs with turmeric-based natural dyes 0.64 V, 0.47 mA/cm2, and 0.2%, respectively.

Low temperature synthesis and sintering of d-UO2 nanoparticles.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nenoff, Tina Maria; Ferreira, Summer Rhodes; Robinson, David B.

We report on the novel room temperature method of synthesizing advanced nuclear fuels; a method that virtually eliminates any volatility of components. This process uses radiolysis to form stable nanoparticle (NP) nuclear transuranic (TRU) fuel surrogates and in-situ heated stage TEM to sinter the NPs. The radiolysis is performed at Sandia's Gamma Irradiation Facility (GIF) 60Co source (3 x 10{sup 6} rad/hr). Using this method, sufficient quantities of fuels for research purposes can be produced for accelerated advanced nuclear fuel development. We are focused on both metallic and oxide alloy nanoparticles of varying compositions, in particular d-U, d-U/La alloys andmore » d-UO2 NPs. We present detailed descriptions of the synthesis procedures, the characterization of the NPs, the sintering of the NPs, and their stability with temperature. We have employed UV-vis, HRTEM, HAADF-STEM imaging, single particle EDX and EFTEM mapping characterization techniques to confirm the composition and alloying of these NPs.« less

Can the use of pulsed direct current induce oscillation in the applied pressure during spark plasma sintering?

PubMed Central

Salamon, David; Eriksson, Mirva; Nygren, Mats; Shen, Zhijian

2012-01-01

The spark plasma sintering (SPS) process is known for its rapid densification of metals and ceramics. The mechanism behind this rapid densification has been discussed during the last few decades and is yet uncertain. During our SPS experiments we noticed oscillations in the applied pressure, related to a change in electric current. In this study, we investigated the effect of pulsed electrical current on the applied mechanical pressure and related changes in temperature. We eliminated the effect of sample shrinkage in the SPS setup and used a transparent quartz die allowing direct observation of the sample. We found that the use of pulsed direct electric current in our apparatus induces pressure oscillations with the amplitude depending on the current density. While sintering Ti samples we observed temperature oscillations resulting from pressure oscillations, which we attribute to magnetic forces generated within the SPS apparatus. The described current–pressure–temperature relations might increase understanding of the SPS process. PMID:27877472

[The influence of different opaque thickness on the bond strength of porcelain-fused-to metal restoration].

PubMed

Xu, Kan; He, Fan; Geng, Yi

2009-12-01

To study the influence of different opaque thickness on the bond strength of porcelain-fused-to metal (PFM) restorations. The testing sheets were made as the samples of ISO9693. With different sintering temperature and different opaque thickness on the bond strength of PFM restorations, the primary pressure of porcelain crack was measured by using three-points-bending test. Statistical analysis was carried out using a SPSS 10.0 software package. A post hoc multiple comparison test (Student-Newman-Keuls) was performed to evaluate the differences between the individual groups. In low sintering temperature group, the thin layer of opaque significantly improved the bond strength compared with thick layer of opaque (P<0.05). In high sintering temperature group, the thickness of opaque has no significant influence on the PFM bonding strength. Using the opaque, the bonding strength was better than those without opaque. The thickness of opaque has a little influence on the PFM bonding strength.

Influence of grain size and sintering temperature grain size on the critical behavior near the paramagnetic to ferromagnetic phase transition temperature in La0.67Sr0.33MnO3 nanoparticles

NASA Astrophysics Data System (ADS)

Baaziz, H.; Tozri, A.; Dhahri, E.; Hlil, E. K.

2018-03-01

We have undertaken a systematic study of critical behavior in La0.67Sr0.33MnO3 nanoparticles, sintered at different temperatures (L6, L8, L10 and L12 sintered at 600 °C, 800 °C, 1000 °C, 1200 °C respectively), by magnetization measurements. The critical exponents are estimated by various techniques such as the Modified Arrott plot, Kouvel-Fisher plot and critical isotherm technique. Compared to standard models, the critical exponents are close to those expected by the Mean-field model (with β = 0.5 γ = 1, and δ = 3) for (L6, L8, and L10) samples and by the (3D) Heisenberg model (β = 0.365, γ = 1.336 and δ = 4.80) for L12 sample. We conclude that the reduction of grain size strongly influences the universality class.

Lithofacies and biofacies of mid-Paleozoic thermal spring deposits in the Drummond Basin, Queensland, Australia

NASA Technical Reports Server (NTRS)

Walter, M. R.; Desmarais, D.; Farmer, J. D.; Hinman, N. W.

1996-01-01

The Devonian to Carboniferous sinters of the Drummond Basin, Australia, are among the oldest well established examples of fossil subaerial hot springs. Numerous subaerial and subaqueous spring deposits are known from the geological record as a result of the occurrence of economic mineral deposits in many of them. Some are reported to contain fossils, but very few have been studied by paleobiologists; they represent an untapped source of paleobiological information on the history of hydrothermal ecosystems. Such systems are of special interest, given the molecular biological evidence that thermophilic bacteria lie near the root of the tree of extant life. The Drummond Basin sinters are very closely comparable with modern examples in Yellowstone National Park and elsewhere. Thirteen microfacies are recognisable in the field, ranging from high temperature apparently abiotic geyserite through various forms of stromatolitic sinter probably of cyanobacterial origin to ambient temperature marsh deposits. Microfossils in the stromatolites are interpreted as cyanobacterial sheaths. Herbaceous lycopsids occur in the lower temperature deposits.

Effects of intergranular phase on the coercivity for MnBi magnets prepared by spark plasma sintering

NASA Astrophysics Data System (ADS)

Cao, J.; Huang, Y. L.; Hou, Y. H.; Zhang, G. Q.; Shi, Z. Q.; Zhong, Z. C.; Liu, Z. W.

2018-05-01

MnBi magnets with a high content of low temperature phase (LTP) and excellent magnetic properties were prepared by spark plasma sintering (SPS) using ball milling powders as precursors without magnetic purification. A complicated intergranular phase, which contains Mn phase, Bi phase, MnO phase, and even amorphous phase in MnBi magnets, was characterized and reported systematically. It was found that the formation of intergranular phase which was contributed by ball milling precursors and sintering mechanism, jointly, had important influence on the magnetic properties. The appropriate content of intergranular phase was beneficial in improving the coercivity due to the strong magnetic isolation effects. The optimum magnetic properties with Mr=26.0 emu/g, Hci= 7.11 kOe and (BH)max=1.53 MGOe at room temperature, and a maximum value Hci= 25.37 kOe at 550 K can be obtained. Strongly favorable magnetic properties make SPSed MnBi magnets an attractive candidate material for small permanent magnets used in high-temperature applications.

Structural, dielectric and magnetic properties of NiFe2O4 prepared via sol-gel auto-combustion method

NASA Astrophysics Data System (ADS)

Sun, Li; Zhang, Ru; Wang, Zhenduo; Ju, Lin; Cao, Ensi; Zhang, Yongjia

2017-01-01

Nickelferrite (NiFe2O4)powders were synthesized via sol-gel auto-combustion method and the corresponding temperature dependence of microstructure, dielectric and magnetic properties have been investigated. Results of XRD and SEM indicate that the NiFe2O4 samples exhibit a typical single phase spinel structure and a uniform particle distribution. The dielectric constant and dielectric loss measurements show strong frequency dependence of all the samples. The peak observed in frequency dependence of dielectric loss measurements shifts to higher frequency with the increasing sintering temperature, indicating a Debye-like dielectric relaxation. The remanent magnetization increases with the increasing grain size while the coercivity is just the opposite. The saturation magnetization can achieve 50 emu/g when the sintering temperature is more than 1000 °C, and the lowest coercivity (159.49 Oe) was observed in the NFO sample sintered at 1300 °C for 2 h.

Correlation of processing and sintering variables with the strength and radiography of silicon nitride

NASA Technical Reports Server (NTRS)

Sanders, W. A.; Baaklini, G. Y.

1986-01-01

A sintered Si3N4-SiO2-Y2O3 composition, NASA 6Y, was developed that reached four-point flexural average strength/standard deviation values of 857/36, 544/33, and 462/59 MPa at room temperature, 1200 and 1370 C respectively. These strengths represented improvements of 56, 38, and 21 percent over baseline properties at the three test temperatures. At room temperature the standard deviation was reduced by over a factor of three. These accomplishments were realized by the iterative utilization of conventional x-radiography to characterize structural (density) uniformity as affected by systematic changes in powder processing and sintering parameters. Accompanying the improvement in mechanical properties was a change in the type of flaw causing failure from a pore to a large columnar beta- Si3N4 grain typically 40 to 80 microns long, 10 to 30 microns wide, and with an aspect ratio of 5:1.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhan, Wangcheng; He, Qian; Liu, Xiaofei

Supported gold (Au) nanocatalysts hold great promise for heterogeneous catalysis; however, their practical application is greatly hampered by poor thermodynamic stability. Herein, a general synthetic strategy is reported where discrete metal nanoparticles are made resistant to sintering, preserving their catalytic activities in high-temperature oxidation processes. Taking advantage of the unique coating chemistry of dopamine, sacrificial carbon layers are constructed on the material surface, stabilizing the supported catalyst. Upon annealing at high temperature under an inert atmosphere, the interactions between support and metal nanoparticle are dramatically enhanced, while the sacrificial carbon layers can be subsequently removed through oxidative calcination in air.more » Owing to the improved metal-support contact and strengthened electronic interactions, the resulting Au nanocatalysts are resistant to sintering and exhibit excellent durability for catalytic combustion of propylene at elevated temperatures. Moreover, the facile synthetic strategy can be extended to the stabilization of other supported catalysts on a broad range of supports, providing a general approach to enhancing the thermal stability and sintering resistance of supported nanocatalysts.« less

Powder metallurgy inspired low-temperature fabrication of high-performance stereocomplexed polylactide products with good optical transparency

PubMed Central

Bai, Dongyu; Liu, Huili; Bai, Hongwei; Zhang, Qin; Fu, Qiang

2016-01-01

Stereocomplexation between enantiomeric poly(l-lactide) (PLLA) and poly(d-lactide) (PDLA) provides an avenue to greatly enhance performance of eco-friendly polylactide (PLA). Unfortunately, although the manufacturing of semicrystalline polymers generally involves melt processing, it is still hugely challenging to create high-performance stereocomplexed polylactide (sc-PLA) products from melt-processed high-molecular-weight PLLA/PDLA blends due to the weak crystallization memory effect of stereocomplex (sc) crystallites after complete melting as well as the substantial degradation of PLA chains at elevated melt-processing temperatures of ca. 240–260 °C. Inspired by the concept of powder metallurgy, here we report a new facile route to address these obstacles by sintering of sc-PLA powder at temperatures as low as 180–210 °C, which is distinctly different from traditional sintering of polymer powders performed at temperatures far exceeding their melting temperatures. The enantiomeric PLA chain segments from adjacent powder particles can interdiffuse across particle interfaces and co-crystallize into new sc crystallites capable of tightly welding the interfaces during the low-temperature sintering process, and thus highly transparent sc-PLA products with outstanding heat resistance, mechanical strength, and hydrolytic stability have been successfully fabricated for the first time. PMID:26837848

Powder metallurgy inspired low-temperature fabrication of high-performance stereocomplexed polylactide products with good optical transparency

NASA Astrophysics Data System (ADS)

Bai, Dongyu; Liu, Huili; Bai, Hongwei; Zhang, Qin; Fu, Qiang

2016-02-01

Stereocomplexation between enantiomeric poly(L-lactide) (PLLA) and poly(D-lactide) (PDLA) provides an avenue to greatly enhance performance of eco-friendly polylactide (PLA). Unfortunately, although the manufacturing of semicrystalline polymers generally involves melt processing, it is still hugely challenging to create high-performance stereocomplexed polylactide (sc-PLA) products from melt-processed high-molecular-weight PLLA/PDLA blends due to the weak crystallization memory effect of stereocomplex (sc) crystallites after complete melting as well as the substantial degradation of PLA chains at elevated melt-processing temperatures of ca. 240-260 °C. Inspired by the concept of powder metallurgy, here we report a new facile route to address these obstacles by sintering of sc-PLA powder at temperatures as low as 180-210 °C, which is distinctly different from traditional sintering of polymer powders performed at temperatures far exceeding their melting temperatures. The enantiomeric PLA chain segments from adjacent powder particles can interdiffuse across particle interfaces and co-crystallize into new sc crystallites capable of tightly welding the interfaces during the low-temperature sintering process, and thus highly transparent sc-PLA products with outstanding heat resistance, mechanical strength, and hydrolytic stability have been successfully fabricated for the first time.

Powder metallurgy inspired low-temperature fabrication of high-performance stereocomplexed polylactide products with good optical transparency.

PubMed

Bai, Dongyu; Liu, Huili; Bai, Hongwei; Zhang, Qin; Fu, Qiang

2016-02-03

Stereocomplexation between enantiomeric poly(l-lactide) (PLLA) and poly(d-lactide) (PDLA) provides an avenue to greatly enhance performance of eco-friendly polylactide (PLA). Unfortunately, although the manufacturing of semicrystalline polymers generally involves melt processing, it is still hugely challenging to create high-performance stereocomplexed polylactide (sc-PLA) products from melt-processed high-molecular-weight PLLA/PDLA blends due to the weak crystallization memory effect of stereocomplex (sc) crystallites after complete melting as well as the substantial degradation of PLA chains at elevated melt-processing temperatures of ca. 240-260 °C. Inspired by the concept of powder metallurgy, here we report a new facile route to address these obstacles by sintering of sc-PLA powder at temperatures as low as 180-210 °C, which is distinctly different from traditional sintering of polymer powders performed at temperatures far exceeding their melting temperatures. The enantiomeric PLA chain segments from adjacent powder particles can interdiffuse across particle interfaces and co-crystallize into new sc crystallites capable of tightly welding the interfaces during the low-temperature sintering process, and thus highly transparent sc-PLA products with outstanding heat resistance, mechanical strength, and hydrolytic stability have been successfully fabricated for the first time.

Spark plasma sintering of highly dense fine-grained mineral aggregates

NASA Astrophysics Data System (ADS)

Koizumi, S.; Suzuki, T. S.; Sakka, Y.; Hiraga, T.

2017-12-01

To obtain highly dense and fine-grained mineral aggregates, which are suitable for laboratory measurements of their physical and chemical properties, we applied spark plasma sintering (SPS) to synthetic mineral powders and powders originated from naturally derived crystals. SPS is an emerging consolidation technique which has been applied to various metals and ceramics and rarely to geomaterials (e.g., Guignard et al., 2011). The technique uses spark plasma created by a pulse direct current during heat treatment of powders in a graphite die. It has been found that the technique provides better densification with little grain growth during sintering compared to a conventional sintering technique in many materials. To obtain ideal highly dense fine-grained materials, it is essential to prepare starting powders suitable for the sintering and also to find appropriate sintering conditions of applied uniaxial pressures, pulsed current patterns and heating rates. We prepared synthetic mineral powers through solid state reaction of source powders at high temperature well developed by our group (Koizumi et al. 2010). We also used jet milling at wet condition and subsequent elutriation to prepare olivine powders with sub-micron particle size and equiaxed particle shape. At heating rate of ≦10°C/min and an achievement of highest temperature of 1150°C, Fe-free olivine aggregate with average grain size of 200 nm with porosity of 0.003% was obtained. We also could obtain olivine aggregate, which was sintered from powders of Horoman peridotite, with average grain size of 500 nm and porosity of 0.2%. We will show results of other minerals including major rock forming minerals of the Earth's crust.

Fabrication of β-tricalcium phosphate composite ceramic sphere-based scaffolds with hierarchical pore structure for bone regeneration.

PubMed

He, Fupo; Qian, Guowen; Ren, Weiwei; Li, Jiyan; Fan, Peirong; Shi, Haishan; Shi, Xuetao; Deng, Xin; Wu, Shanghua; Ye, Jiandong

2017-04-24

Polymer sphere-based scaffolds, which are prepared by bonding the adjacent spheres via sintering the randomly packed spheres, feature uniform pore structure, full three-dimensional (3D) interconnection, and considerable mechanical strength. However, bioceramic sphere-based scaffolds fabricated by this method have never been reported. Due to high melting temperature of bioceramic, only limited diffusion rate can be achieved when sintering the bioceramic spheres, which is far from enough to form robust bonding between spheres. In the present study, for the first time we fabricated 3D interconnected β-tricalcium phosphate ceramic sphere-based (PG/TCP) scaffolds by introducing phosphate-based glass (PG) as sintering additive and placing uniaxial pressure during the sintering process. The sintering mechanism of PG/TCP scaffolds was unveiled. The PG/TCP scaffolds had hierarchical pore structure, which was composed by interconnected macropores (>200 μm) among spheres, pores (20–120 μm) in the interior of spheres, and micropores (1–3 μm) among the grains. During the sintering process, partial PG reacted with β-TCP, forming β-Ca2P2O7; metal ions from PG substituted to Ca2+ sites of β-TCP. The mechanical properties (compressive strength 2.8–10.6 MPa; compressive modulus 190–620 MPa) and porosity (30%–50%) of scaffolds could be tailored by manipulating the sintering temperatures. The introduction of PG accelerated in vitro degradation of scaffolds, and the PG/TCP scaffolds showed good cytocompatibility. This work may offer a new strategy to prepare bioceramic scaffolds with satisfactory physicochemical properties for application in bone regeneration.

METHOD FOR PREPARATION OF SINTERABLE BERYLLIUM OXIDE

DOEpatents

Sturm, B.J.

1963-08-13

High-purity beryllium oxide for nuclear reactor applications can be prepared by precipitation of beryllium oxalate monohydrate from aqueous solution at a temperature above 50 deg C and subsequent calcination of the precipitate. Improved purification with respect to metallic impurities is obtained, and the product beryllium oxide sinters reproducibly to a high density. (AEC)

Production Process for Strong, Light Ceramic Tiles

NASA Technical Reports Server (NTRS)

Holmquist, G. R.; Cordia, E. R.; Tomer, R. S.

1985-01-01

Proportions of ingredients and sintering time/temperature schedule changed. Production process for lightweight, high-strength ceramic insulating tiles for Space Shuttle more than just scaled-up version of laboratory process for making small tiles. Boron in aluminum borosilicate fibers allows fusion at points where fibers contact each other during sintering, thereby greatly strengthening tiles structure.

Mixed uranium dicarbide and uranium dioxide microspheres and process of making same

DOEpatents

Stinton, David P.

1983-01-01

Nuclear fuel microspheres are made by sintering microspheres containing uranium dioxide and uncombined carbon in a 1 mole percent carbon monoxide/99 mole percent argon atmosphere at 1550.degree. C. and then sintering the microspheres in a 3 mole percent carbon monoxide/97 mole percent argon atmosphere at the same temperature.

Development of dense glass-ceramic from recycled soda-lime-silicate glass and fly ash for tiling

NASA Astrophysics Data System (ADS)

Mustaffar, Mohd Idham; Mahmud, Mohamad Haniza; Hassan, Mahadi Abu

2017-12-01

Dense glass-ceramics were prepared by sinter-crystallization process from a combination of soda-lime-silicate glass waste and fly ash. Bentonite clay that acted as a binder was also added in a prepared formulation. The powder mixture of soda-lime glass, fly ash and bentonite clay were compacted by using uniaxial hydraulic press machine and sintered at six (6) various temperatures namely 750, 800, 850, 900, 950 and 1000 °C. The heating rate and sintering time were set at 5 °C/min and 30 minutes respectively. The results revealed that modulus of rupture (MOR), density and linear shrinkage increase first from 750 to 800 °C but decrease later after 800 to 1000 °C. In the meantime, water absorption was showing completely an opposite trend. The glass-ceramic sintered at 800 °C was found to have the best combination of physical-mechanical properties and has the potential to be applied in the construction industry particularly as floor and wall tiles because of the simple manufacturing process at low temperature.

Evaluation of the mechanical properties of powder metallurgy Ti-6Al-7Nb alloy.

PubMed

Bolzoni, L; Ruiz-Navas, E M; Gordo, E

2017-03-01

Titanium and its alloys are common biomedical materials owing to their combination of mechanical properties, corrosion resistance and biocompatibility. Powder metallurgy (PM) techniques can be used to fabricate biomaterials with tailored properties because changing the processing parameters, such as the sintering temperature, products with different level of porosity and mechanical performances can be obtained. This study addresses the production of the biomedical Ti-6Al-7Nb alloy by means of the master alloy addition variant of the PM blending elemental approach. The sintering parameters investigated guarantee that the complete diffusion of the alloying elements and the homogenization of the microstructure is achieved. The sintering of the Ti-6Al-7Nb alloy induces a total shrinkage between 7.4% and 10.7% and the level of porosity decreases from 6.2% to 4.7% with the increment of the sintering temperature. Vickers hardness (280-300 HV30) and tensile properties (different combination of strength and elongation around 900MPa and 3%) are achieved. Copyright © 2016 Elsevier Ltd. All rights reserved.

Extrinsic contributions to the dielectric response in sintered BaTiO3 nanostructures in paraelectric and ferroelectric regimes

NASA Astrophysics Data System (ADS)

Jaffari, G. Hassnain; Rehman, Atiq ur; Iqbal, Asad M.; Awan, M. S.; Saleemi, Mohsin

2017-11-01

Post sintering studies of BaTiO3 (BTO) nanoparticles are presented in detail. Bulk nanostructures were prepared via three different compaction processes, namely, uniaxial cold pressing (UCP), Cold Isostatic Pressing (CIP) and Spark Plasma Sintering (SPS). Effect of compaction technique on microstructures have been investigated and correlated with electrical response for each sample. In addition to the transport properties, temperature and frequency dependent dielectric response of variously sintered samples and bulk counterpart was recorded. Several aspects have been identified that are essential to be taken into account in order to completely understand physical processes. Drastically distinct features were observed in paraelectric (PE) regime well above ferroelectric (FE)-PE transition temperature. These features include intra grain conduction with a reduction in the magnitude of PE to FE peak dielectric constant magnitude. Role of strain, grain boundary conduction associated with observation of Maxwell Wagner relaxation and hopping conduction in dielectric and ferroelectric response have been observed and discussed. Densification with presence of oxygen vacancies, significantly enhances conductivity associated with the hopping of the carriers, in turn deteriorated ferroelectric response.

Investigation of consolidation kinetics and microstructure evolution of Al alloys in direct metal laser sintering using phase field simulation

NASA Astrophysics Data System (ADS)

Bimal Satpathy, Bubloom; Nandy, Jyotirmoy; Sahoo, Seshadev

2018-03-01

Direct metal laser sintering is one of the very efficient processes which comes under the field of additive manufacturing and is capable of producing products of good mechanical and physical properties. The process parameters affect the physical and mechanical properties of the final products. Rapid solidification plays an important role in the consolidation kinetics as the powdered material sinters and forms a polycrystalline structure. In the recent times, the enormous use of computational modeling has helped in examining the utility of final products in a wide range of applications. In this study, a phase field model has been implemented to foresee the consolidation kinetics during the liquid state sintering. Temperature profiles have been used to study the densification behavior and neck growth which is caused by the surface diffusion of particles at initial stage. Later, importance of grain boundary and the volume diffusion during densification process is analyzed. It is also found that with rise in temperature, neck growth also increases rapidly due to the interaction of adjacent grains through grain boundary diffusion and stabilization of grain growth.

Application of spark plasma sintering for fabricating Nd-Fe-B composite

NASA Astrophysics Data System (ADS)

Sivkov, A. A.; Ivashutenko, A. S.; Lomakina, A. A.

2015-10-01

Constant magnets are applied in such fields as electric equipment and electric generators with fixed rotor. Rare earth metal neodymium is well known as promising material. Production of magnets by sintering three elements (neodymium, iron and boron) is one the most promising methods. But there are difficulties in choosing the right temperature for sintering and further processing. Structure and properties of the product, consisted of rare earth metals, was analyzed. X-ray analysis of the resulting product and the finished constant magnet was performed. Vickers microhardness was obtained.

Structures and fabrication techniques for solid state electrochemical devices

DOEpatents

Visco, Steven J.; Jacobson, Craig P.; DeJonghe, Lutgard C.

2006-10-10

Low-cost, mechanically strong, highly electronically conductive porous substrates and associated structures for solid-state electrochemical devices, techniques for forming these structures, and devices incorporating the structures provide solid state electrochemical device substrates of novel composition and techniques for forming thin electrode/membrane/electrolyte coatings on the novel or more conventional substrates. In particular, in one aspect the invention provides techniques for co-firing of device substrate (often an electrode) with an electrolyte or membrane layer to form densified electrolyte/membrane films 5 to 20 microns thick. In another aspect, densified electrolyte/membrane films 5 to 20 microns thick may be formed on a pre-sintered substrate by a constrained sintering process. In some cases, the substrate may be a porous metal, alloy, or non-nickel cermet incorporating one or more of the transition metals Cr, Fe and Cu, or alloys thereof.

Tensile test of pressureless-sintered silicon nitride at elevated temperature

NASA Technical Reports Server (NTRS)

Matsusue, K.; Fujisawa, Y.; Takahara, K.

1985-01-01

Uniaxial tensile strength tests of pressureless sintered silicon nitride were carried out in air at temperatures ranging from room temperature up to 1600 C. Silicon nitrides containing Y2O3, Al2O3, Al2O3-MgO, or MgO-CeO2 additives were tested. The results show that the composition of the additive used influences the strength characteristics of the silicon nitride. The tensile strength rapidly decreased at temperatures above 1000 C for the materials containing MgO as the additive and above 1000 C for the material with Y2O3. When the temperature increased to as high as 1300 C, the strength decreased to about 10 percent of the room temperature strength in each case. Observations of the fracture origin and of the crack propagation on the fracture surfaces are discussed.

Development of nano-structured duplex and ferritic stainless steels by pulverisette planetary milling followed by pressureless sintering

DOE Office of Scientific and Technical Information (OSTI.GOV)

R, Shashanka, E-mail: shashankaic@gmail.com; Chaira, D., E-mail: chaira.debasis@gmail.com

Nano-structured duplex and ferritic stainless steel powders are prepared by planetary milling of elemental Fe, Cr and Ni powder for 40 h and then consolidated by conventional pressureless sintering. The progress of milling and the continuous refinement of stainless steel powders have been confirmed by means of X-ray diffraction and scanning electron microscopy. Activation energy for the formation of duplex and ferritic stainless steels is calculated by Kissinger method using differential scanning calorimetry and is found to be 159.24 and 90.17 KJ/mol respectively. Both duplex and ferritic stainless steel powders are consolidated at 1000, 1200 and 1400 °C in argonmore » atmosphere to study microstructure, density and hardness. Maximum sintered density of 90% and Vickers microhardness of 550 HV are achieved for duplex stainless steel sintered at 1400 °C for 1 h. Similarly, 92% sintered density and 263 HV microhardness are achieved for ferritic stainless steel sintered at 1400 °C. - Highlights: • Synthesized duplex and ferritic stainless steels by pulverisette planetary milling • Calculated activation energy for the formation of duplex and ferritic stainless steels • Studied the effect of sintering temperature on density, hardness and microstructure • Duplex stainless steel exhibits 90% sintered density and microhardness of 550 HV. • Ferritic stainless steel shows 92% sintered density and 263 HV microhardness.« less

Implementation Challenges for Sintered Silicon Carbide Fiber Bonded Ceramic Materials for High Temperature Applications

NASA Technical Reports Server (NTRS)

Singh, M.

2011-01-01

During the last decades, a number of fiber reinforced ceramic composites have been developed and tested for various aerospace and ground based applications. However, a number of challenges still remain slowing the wide scale implementation of these materials. In addition to continuous fiber reinforced composites, other innovative materials have been developed including the fibrous monoliths and sintered fiber bonded ceramics. The sintered silicon carbide fiber bonded ceramics have been fabricated by the hot pressing and sintering of silicon carbide fibers. However, in this system reliable property database as well as various issues related to thermomechanical performance, integration, and fabrication of large and complex shape components has yet to be addressed. In this presentation, thermomechanical properties of sintered silicon carbide fiber bonded ceramics (as fabricated and joined) will be presented. In addition, critical need for manufacturing and integration technologies in successful implementation of these materials will be discussed.

Magnetic properties of ball-milled SrFe12O19 particles consolidated by Spark-Plasma Sintering

PubMed Central

Stingaciu, Marian; Topole, Martin; McGuiness, Paul; Christensen, Mogens

2015-01-01

The room-temperature magnetic properties of ball-milled strontium hexaferrite particles consolidated by spark-plasma sintering are strongly influenced by the milling time. Scanning electron microscopy revealed the ball-milled SrFe12O19 particles to have sizes varying over several hundred nanometers. X-Ray powder-diffraction studies performed on the ball-milled particles before sintering clearly demonstrate the occurrence of a pronounced amorphization process. During sintering at 950 oC, re-crystallization takes place, even for short sintering times of only 2 minutes and transformation of the amorphous phase into a secondary phase is unavoidable. The concentration of this secondary phase increases with increasing ball-milling time. The remanence and maximum magnetization values at 1T are weakly influenced, while the coercivity drops dramatically from 2340 Oe to 1100 Oe for the consolidated sample containing the largest amount of secondary phase. PMID:26369360

Structure and characteristics of functional powder composite materials obtained by spark plasma sintering

NASA Astrophysics Data System (ADS)

Oglezneva, S. A.; Kachenyuk, M. N.; Kulmeteva, V. B.; Ogleznev, N. B.

2017-07-01

The article describes the results of spark plasma sintering of ceramic materials based on titanium carbide, titanium carbosilicide, ceramic composite materials based on zirconium oxide, strengthened by carbon nanostructures and composite materials of electrotechnical purpose based on copper with addition of carbon structures and titanium carbosilicide. The research shows that the spark plasma sintering can achieve relative density of the material up to 98%. The effect of sintering temperature on the phase composition, density and porosity of the final product has been studied. It was found that with addition of carbon nanostructures the relative density and hardness decrease, but the fracture strength of ZrO2 increases up to times 2. The relative erosion resistance of the electrodes made of composite copper-based powder materials, obtained by spark plasma sintering during electroerosion treatment of tool steel exceeds that parameter of pure copper up to times 15.

Sub-second carbon-nanotube-mediated microwave sintering for high-conductivity silver patterns on plastic substrates

NASA Astrophysics Data System (ADS)

Jung, Sunshin; Chun, Su Jin; Han, Joong Tark; Woo, Jong Seok; Shon, Cha-Hwa; Lee, Geon-Woong

2016-02-01

A method of microwave sintering that is mediated by carbon nanotubes (CNTs) has been developed to obtain high-conductivity Ag patterns on the top of heat-sensitive plastic substrates within a short time. The Ag patterns are printed on CNTs formed on plastic substrates and rapidly heated to a great extent by the heat transferred from the microwave-heated CNTs. The conductivity of the microwave-sintered Ag patterns reaches ~39% that of bulk Ag within 1 s without substrate deformation. Furthermore, microwave sintering enhances the adhesion of Ag patterns to the thermoplastic substrates because the sintering causes interfacial fusion between the Ag patterns and the substrates, and CNTs physically connect the patterns with the substrates.A method of microwave sintering that is mediated by carbon nanotubes (CNTs) has been developed to obtain high-conductivity Ag patterns on the top of heat-sensitive plastic substrates within a short time. The Ag patterns are printed on CNTs formed on plastic substrates and rapidly heated to a great extent by the heat transferred from the microwave-heated CNTs. The conductivity of the microwave-sintered Ag patterns reaches ~39% that of bulk Ag within 1 s without substrate deformation. Furthermore, microwave sintering enhances the adhesion of Ag patterns to the thermoplastic substrates because the sintering causes interfacial fusion between the Ag patterns and the substrates, and CNTs physically connect the patterns with the substrates. Electronic supplementary information (ESI) available: Temperature difference in Ag/CNT/PC samples; the carbon content and electrical performance after microwave sintering; microwave sintering of Ag/CNT patterns; physical connection between the substrate and sintered Ag lines; touch-piano (figure and movie). See DOI: 10.1039/c5nr08082g

Clean recycle and utilization of hazardous iron-bearing waste in iron ore sintering process.

PubMed

Gan, Min; Ji, Zhiyun; Fan, Xiaohui; Chen, Xuling; Zhou, Yang; Wang, Guojing; Tian, Ye; Jiang, Tao

2018-04-18

Applying recycled iron-bearing waste materials (RIM) into iron ore sintering process is the general disposal approach worldwide, while its use is still a thorny problem. Results showed that adding RIM increased contents of hazardous elements (K, Na, Pb, Zn, and Cl) in sinter product, and also enhanced emission concentration of PM 2.5 in flue gas; increasing reaction temperature, and contents of CaO & coke breeze in raw mixtures improved hazardous elements removal. Based on these features, a novel method through granulating natural iron ores and RIM separately and distributing granulated RIM in bottom sintering layers was proposed for clean RIM cycle. When recycling 5% RIM, granulating RIM separately with higher contents of CaO and coke breeze removed hazardous elements effectively, the contents of which in sinter were reduced to comparable level of the case without RIM. Moreover, distributing RIM in bottom sintering layer reached intensive release of hazardous elements and PM 2.5 during sintering, which reduced the flue gas volume needing purification by about 2/3. Through activated carbon purification, about 60% of PM 2.5 comprised high contents of hazardous elements was removed. Novel technique eliminated the negative impact of RIM and has the prospect to reach clean recycle in sinter-making plants. Copyright © 2018. Published by Elsevier B.V.

Proportional integral derivative, modeling and ways of stabilization for the spark plasma sintering process

DOE Office of Scientific and Technical Information (OSTI.GOV)

Manière, Charles; Lee, Geuntak; Olevsky, Eugene A.

The stability of the proportional–integral–derivative (PID) control of temperature in the spark plasma sintering (SPS) process is investigated. The PID regulations of this process are tested for different SPS tooling dimensions, physical parameters conditions, and areas of temperature control. It is shown that the PID regulation quality strongly depends on the heating time lag between the area of heat generation and the area of the temperature control. Tooling temperature rate maps are studied to reveal potential areas for highly efficient PID control. The convergence of the model and experiment indicates that even with non-optimal initial PID coefficients, it is possiblemore » to reduce the temperature regulation inaccuracy to less than 4 K by positioning the temperature control location in highly responsive areas revealed by the finite-element calculations of the temperature spatial distribution.« less

Proportional integral derivative, modeling and ways of stabilization for the spark plasma sintering process

DOE PAGES

Manière, Charles; Lee, Geuntak; Olevsky, Eugene A.

2017-04-21

The stability of the proportional–integral–derivative (PID) control of temperature in the spark plasma sintering (SPS) process is investigated. The PID regulations of this process are tested for different SPS tooling dimensions, physical parameters conditions, and areas of temperature control. It is shown that the PID regulation quality strongly depends on the heating time lag between the area of heat generation and the area of the temperature control. Tooling temperature rate maps are studied to reveal potential areas for highly efficient PID control. The convergence of the model and experiment indicates that even with non-optimal initial PID coefficients, it is possiblemore » to reduce the temperature regulation inaccuracy to less than 4 K by positioning the temperature control location in highly responsive areas revealed by the finite-element calculations of the temperature spatial distribution.« less

Spark plasma sintering of ceramic matrix composite based on alumina, reinforced by carbon nanotubes

NASA Astrophysics Data System (ADS)

Leonov, A. A.; Khasanov, A. O.; Danchenko, V. A.; Khasanov, O. L.

2017-12-01

Alumina composites reinforced with 3 vol.% multi-walled carbon nanotubes (MWCNTs) were prepared by spark plasma sintering (SPS). The influence of sintering temperature (1400-1600 °C) on the composites microstructure and mechanical properties was investigated. Microstructure observations of the composite shows that some CNTs site along alumina grains boundary, while others embed into the alumina grains and shows that CNTs bonded strongly with the alumina matrix contributing to fracture toughness and microhardness increase. MWCNTs reinforcing mechanisms including CNT pull-out and crack deflection were directly observed by scanning electron microscope (SEM). For Al2O3/CNT composite sintered at 1600 °C, fracture toughness and microhardness are 4.93 MPa·m1/2 and 23.26 GPa respectively.

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

NASA Technical Reports Server (NTRS)

Bansal, Narottam P.

1988-01-01

SEM, thermogravimetric analysis, powder X-ray diffraction,and measurements of electrical resistivity and magnetic susceptibility, are presently used to characterize the influence of sintering temperature, sintering and annealing atmospheres, and quench-rate on the properties of the YBa2Cu3Oy superconducting oxide. It is established that annealing in oxygen, together with slow cooling rates, are required for preparation of high-Tc superconductors with sharp transitions; rapid quenching from high temperature does not yield good superconductors, due to low oxygen content.