bluuebunny/crossref_metadata_2025 huggingface dataset:
Thickness dependence of the triplet spin-valve effect in superconductor–ferromagnet–ferromagnet heterostructures
Authors: Lenk Daniel , Zdravkov Vladimir I , Kehrle Jan-Michael , Obermeier Günter , Ullrich Aladin , Morari Roman , Krug von Nidda Hans-Albrecht , Müller Claus , Kupriyanov Mikhail Yu , Sidorenko Anatolie S , Horn Siegfried , Deminov Rafael G , Tagirov Lenar R , Tidecks Reinhard
Published: July 2016

Background: In nanoscale layered S/F1/N/F2/AF heterostructures, the generation of a long-range, odd-in-frequency spin-projection one triplet component of superconductivity, arising at non-collinear alignment of the magnetizations of F1 and F2, exhausts the singlet state. This yields the possibility of a global minimum of the superconducting transition temperature Tc, i.e., a superconducting triplet spin-valve effect, around mutually perpendicular alignment.

Results: The superconducting triplet spin valve is realized with S = Nb a singlet superconductor, F1 = Cu41Ni59 and F2 = Co ferromagnetic metals, AF = CoOx an antiferromagnetic oxide, and N = nc-Nb a normal conducting (nc) non-magnetic metal, which serves to decouple F1 and F2. The non-collinear alignment of the magnetizations is obtained by applying an external magnetic field parallel to the layers of the heterostructure and exploiting the intrinsic perpendicular easy-axis of the magnetization of the Cu41Ni59 thin film in conjunction with the exchange bias between CoOx and Co. The magnetic configurations are confirmed by superconducting quantum interference device (SQUID) magnetic moment measurements. The triplet spin-valve effect has been investigated for different layer thicknesses, dF1, of F1 and was found to decay with increasing dF1. The data is described by an empirical model and, moreover, by calculations using the microscopic theory.

Conclusion: The long-range triplet component of superconducting pairing is generated from the singlet component mainly at the N/F2 interface, where the amplitude of the singlet component is suppressed exponentially with increasing distance dF1. The decay length of the empirical model is found to be comparable to twice the electron mean free path of F1 and, thus, to the decay length of the singlet component in F1. Moreover, the obtained data is in qualitative agreement with the microscopic theory, which, however, predicts a (not investigated) breakdown of the triplet spin-valve effect for dF1 smaller than 0.3 to 0.4 times the magnetic coherence length, ξF1.
La modélisation économique mondiale, une technologie de gouvernement à distance ?
Authors: Cornilleau Lise
Published: July 2016

Cet article interroge le rôle de la modélisation économique mondiale dans les programmes de la Révolution Verte en Afrique : dans quelle mesure cette forme de quantification peut-elle être qualifiée de technologie de gouvernement à distance ? Nous présentons le cas du modèle IMPACT de l’International Food Policy Research Institute (IFPRI), un centre international de recherche agronomique dont le siège est à Washington, mais présent en Afrique de l’Est via ses bureaux régionaux et nationaux. Dans un premier temps, nous traçons la généalogie de ce modèle, qui reproblématise la « faim dans le monde » et en définit les solutions par le libre-échange et la technologisation de l’agriculture. Dans un second temps, nous montrons comment ce programme est implicitement voué à être territorialisé en Afrique. Pour cela, nous décrivons les circulations du modèle dans les arènes internationales, et nous analysons comment la modélisation participe également d’une forme de gouvernement à l’échelle nationale. S’inspirant des travaux sur le verrouillage à l’œuvre dans les « paquets technologiques » et financiers de la Révolution Verte, cet article décrit les modalités du lock-in idéologique dont il est le complément.
Savoirs tactiques et expertises
Authors: Viard-Crétat Aurore
Published: July 2016

L’avènement de la notion d’appropriation dans les politiques d’aide au développement s’accompagne de tout un arsenal normatif et de mesures de renforcement de capacités afin d’appuyer et d’encadrer les pratiques. À partir d’une enquête ethnographique sur la candidature du Cameroun au programme forestier Redd+ de la Banque mondiale, l’article analyse la façon dont les enjeux techniques de standardisation et d’apprentissage s’inscrivent dans la tension entre affirmation politique des acteurs nationaux et exigences des partenaires. L’expertise en jeu relève dans une large mesure de savoirs tactiques, de mobilisation de réseaux et d’alliances ponctuelles. Si cette dynamique alimente les capacités d’action des acteurs camerounais, elle prolonge dans un même temps la situation d’extraversion dépendante en confinant celles-ci au cadrage proposé par le programme. Cette étude éclaire finalement certains ressorts du succès politique du dispositif Redd+, et plus largement, des cycles d’engouement/déception qui renouvellent régulièrement les politiques internationales de conservation et de développement autour de nouvelles approches.
La réception des écrits de Max Weber sur le confucianisme au Japon et en Asie du Sud-Est
Authors: Brisson Thomas
Published: July 2016

L’article examine la réception des thèses de la Sociologie des religions de Max Weber au Japon, puis leur déplacement en Asie du Sud-Est entre les années 1930 et 1980. Il s’intéresse en particulier à la manière dont intellectuels asiatiques et spécialistes du Japon ont lu les thèses wébériennes sur le confucianisme. L’article montre comment le rôle central qu’elles ont eu dans le débat sur le capitalisme et la modernité en Asie s’explique moins par leur contenu que par la structure des relations qu’elles organisent. Substantiellement, la thèse wébérienne originale, qui faisait du confucianisme un obstacle au développement du capitalisme, a en effet été progressivement invalidée, le confucianisme devenant un facteur d’explication du succès du capitalisme asiatique. Formellement, cependant, le lien qu’elle établit entre religion et modernité s’est imposé comme un schème d’intellection central de la discussion. En Asie, rejet substantiel et acceptation formelle des thèses wébériennes sont ainsi allés de pair. L’article décrit les différentes étapes de ce processus en faisant fonctionner à la fois une explication internaliste (la plasticité formelle d’une thèse) et une explication externe (tenant aux contextes socio-politiques dans lesquels la thèse s’est transformée).
Physiological and hematological responses of Nile tilapia (Oreochromis Niloticus) to different anesthetics during simulated transport conditions
Authors: Navarro Rodrigo Diana , França Rafael Paiva , Paludo Giane Regina , Bizarro Yvonaldo Wlademir Saldanha , Silva Rodrigo Fortes da , Navarro Fernanda Keley Silva Pereira
Published: July 2016

Minimization of stress during the transportation of live fish is essential in maintaining the welfare and performance of the animals. In order to test the hypothesis that stress during transport of fingerlings of Nile tilapia (Oreochromis niloticus) can be reduced with the aid of the anesthetics menthol, eugenol or benzocaine, we have assessed the effects of these agents at various concentrations on the physiological parameters and survival rates of fish subjected to conditions simulating those normally used in transportation. Fingerlings (N = 1200) were fasted for 24 hours and distributed in 20 L polyethylene bags (N = 50 per bag) containing 5 L of water and an anesthetic at the appropriate concentration. Fingerlings treated with menthol at 75 mg L-1, or eugenol or benzocaine at 20 mg L-1, maintained levels of plasma cortisol and glucose that were lower than those of the stressed but untreated controls and within the physiological limits of the baseline values for this species. Under these conditions, the survival rate was 100%, suggesting that stress was substantially reduced despite dense consignment. Treatments involving higher doses of the studied agents induced significant anesthetic toxicity.
Polysilane as SiC Precursor: Preparation, Catalytic Cure and Pyrolysis
Authors: Huang Chuan Jin , Wang Zhe Hui , Wang Ming Cun
Published: July 2016

Liquid polysilane (methyl-terminated vinyl-containing oligomethylsilane, PSI) was prepared by lithium condensation and used as SiC precursor. With the increase of catalyst Ni(acac)2, the thermal cure exotherm shifted to lower temperatures gradually, and the ceramic yield was gradually increased. The crystallinity was promoted by catalyst addition, meanwhile the elements in the pyrolyzed β-SiC were distributed uniformly.
Preparation of Ti2AlN Porous Ceramics by Organic Foam Impregnation Process
Authors: Shang Shan Shan , He Xiong , Yang Yi , Yan Ming
Published: July 2016

In this work, Ti2AlN porous ceramics was made by the organic foam impregnation. High-purity Ti2AlN powder was sintered at 1300 °C for 2 h of Ti/1.1Al/TiN in stoichiometric proportion. The slurry solids of organic foam impregnation method was 60 %, using 2 % polyacrylamide as dispersant, 0.5 % polyvinyl alcohol as a binder and 0.5 % ethanol as defoaming. The polyurethane sponge was pre-treatment for 6 h with 15 % NaOH solution and soak for 24 h with 4 % of carboxymethyl cellulose (CMC) solution. Through the pre-treatment, the polyurethane sponge hangs pulp quantity is higher, and the percentage of plugged hole is the lowest. The Ti2AlN porous ceramics is relatively uniform open holes with three-dimensional skeleton structure. This study can generate to the studies of the preparation of the mesh structure products and the preparation of ceramic matrix composites by pressureless infiltration process.
Densification Behaviors in the Early Stage of Spark Plasma Sintering of 3Y-TZP Nanoceramics
Authors: Xiong Yan , Wang Ling , Liu Chong
Published: July 2016

The early-stage sintering behaviours of 3 mol% yttria-stabilized tetragonal zirconia polycrystal (3Y-TZP) ceramics during spark plasma sintering (SPS) was investigated using different pressure and heating regimes.It was found that dependent neither on pressure value (20~100 MPa) nor heating rates higher than 50 °C/min, the maximum densification rate had always been observed at rather similar ~78% of theoretical density (TD), where the grain growth was rather moderate. A novel intensive-particle-rearrangement mechanism was proposed to dominate the rapid densification of early-stage SPS process, by which yielded the considerable faster densification rate than those achievable by diffusion-related processes.Present findings showed the possibility of particle rearrangement in high density compacts and the effects of classic particle rearrangement should be re-evaluated in nanoceramic sintering.
Sintering of High Quality Titanium-Doped Zinc Oxide Ceramic Sputtering Target
Authors: Pi Chen Bing , Cai Xue Xian , Xiao Chao , Yang Hai Peng , Gao Ji Hua , Gao Ling , Yang Hai Tao
Published: July 2016

The ultrahigh density zinc oxide doped with 1wt% TiO2 (ZTO) ceramic targets were prepared by pressureless sintering. Scanning electron microscopy and X-ray diffraction analysis were used to characterize the morphologies and structure of the sintered ZTO targets. The effects of the sintering temperatures on the microstructure, densification behavior, mechanical and electrical properties were discussed and the optimal sintering condition was obtained. The ZTO targets sintered at 1350°C for 3 hours achieved a relative density of 99.7%, a bending strength of 115MPa, a Vickers hardness of 222.16HV and a a electrical resistivity of 1Ω·cm, which was excellent as a high-quality sputtering target to deposit ZnO-based transparent conductive films.
Preparation and Characterization of Bi2Ti2O7 Microwave Dielectric Ceramics by Citrate Sol-Gel Method
Authors: Zhang Yun , Zhang Ying Chun , Su Xiao Li , Xiang Mao Qiao
Published: July 2016

Bi2Ti2O7 microwave dielectric ceramics were synthesized by a modified sol-gel method using citric acid as metal chelating agent. The thermal decomposition behavior of the as-prepared precursor was characterized by XRD technique. The effects of the amount of citric acid and the molar ratio of bismuth nitrate to tetrabutyl titanate on the crystal structure of Bi2Ti2O7 were also investigated. XRD results showed that well-crystallized Bi2Ti2O7 powders could be synthesized by calcining the precursor at 550 °C as the molar ratio of CA to Bi was 1:1. Moreover, non-stoichiometric ratio of Bi to Ti was required to form the pure Bi2Ti2O7 phase. However, Bi4Ti3O12 and Bi2Ti4O11 second phases were formed after sintering process. At 1150 °C, only the sample doped with 3 wt% Ho3+ showed a single pyrochlore structure, which exhibited good microwave dielectric properties with a high εr of 115.02, a Q × f of 1,515 GHz, and a τf of 30 ppm/°C.
Using Ferroelectric Thin Film as the Dielectric for Electrowetting-on-Dielectric
Authors: Niu Jia Qi , Xie Zhen Kun , Yue Zhen Xing , Wang Wei Qiang
Published: July 2016

In this paper, the dielectric and electrowetting properties of Pb (Zr0.4Ti0.6)O3 (PZT) ferroelectric thin film are studied as the dielectric layer in electrowetting-on-dielectric (EWOD) device. The PZT thin film is formed by spin-coating, pyrolysis and annealing. The characterization results show that PZT thin film can serve as the dielectric of EWOD with a high dielectric constant and a great electrowetting performance when used in silicon oil bath environment. To test the electrowetting effect, a EWOD device with 200nm thick PZT ferroelectric thin film dielectric layer is fabricated. The variation of contact angle between droplet and device surface achieved with DC voltage, AC voltage and AC frequency change of electrowetting on PZT are fully experimented. The EWOD device with PZT dielectric layer can manipulate water droplet at low driving voltages. This study shows the potential of using ferroelectric ceramic material as the dielectric layer in high-performance EWOD devices.
Influence of (Bi0.5M0.5)TiO3 (M=Li, Na, K, Rb) Addition on the Curie Temperature and PTC Effect of BaTiO3-Based Ceramics
Authors: Yang Meng Meng , Peng Zhi Jian , Wang Cheng Biao , Fu Xiu Li
Published: July 2016

In order to investigate the influence of (Bi0.5M0.5)TiO3 (M=Li, Na, K, Rb) addition on the Curie temperature (Tc) and positive temperature coefficient (PTC) effect of BaTiO3-based ceramics, BaTiO3-(Bi0.5M0.5)TiO3 (M=Li, Na, K, Rb) solid solutions were prepared by a conventional solid sintering reaction using high-purity reagents. It was found that the Tc of the samples would vary with (Bi0.5M0.5)TiO3 of different alkali ions, in which BT-BKT ceramics had the highest value (about 148 °C). Moreover, the incorporation of alkali ions would influence the PTC effect of the sample, which can be defined by the resistivity jump with the ratio of maximum to minimum resistivity (ρmax/ρmin). Under the present conditions, the ρmax/ρmin of BT-BRT and BT-BLT ceramics were almost equal and higher than those of BT-BNT and BT-BKT ceramics.
Effect of Defect Characteristics on the Color of BaTiO3-Based PTC Ceramic
Authors: Yang Ai Mei , Deng Jian Ming , Su Cong Xue , Jia Wen Hao , Liu Lai Jun
Published: July 2016

The barium titanium based PTC ceramic with two kind of colors, light blue and yellow, were obtained by changing sintering processing. In order to reveal the relationship between color and electrical properties of the ceramics. The phase structure and microstructure of as synthesized samples were investigated by powder X-ray diffraction (XRD) and scanning electron microscopic (SEM) analysis. The micro area elements were characterized by electron probe micro-analyzer (EPMA) and x-ray photoelectron spectrometer (XPS). The thermo-sensitive properties were studied by resistance-temperature measurement system. The results reveal that two kinds of PTC ceramics have the same structure, similar elements, but different microstructure and valence concentration of titanium. It is suggested that difference of color of the PTC ceramics are originated from the defect concentration of titanium.
Densification Behavior and Dielectric Properties of CaO-B2O3-SiO2 System Glass-Ceramics Containing ZrO2
Authors: Liu Jin Zhuang , Yao Zhong Hua , Xu Nuo Xin , Zhang Qi Long , Yang Hui
Published: July 2016

CaO–B2O3–SiO2 (CBS) glass-ceramics containing ZrO2 were prepared by conventional melting and heat treated crystallization method. The effects of ZrO2 on the crystallization behavior, sintering characterization and dielectric properties of the glass-ceramics were analyzed respectively. The results indicated that ZrO2 addition can improve the crystallization and densification of CBS glass-ceramics. The major crystallized phase of sample with≥7wt% ZrO2 was cyclowollastonite (α-CaSiO3).It is found that the optimal sintering condition for the glass-ceramics is 770 oC for 30min. CBS glass ceramics sample with 7wt% ZrO2 shows the best sintering characterization and dielectric properties (ρ= 2.71g/cm3, εr ≈8.8,tan δ=2.36×10-3 at 1 MHz), which is supposed to be suitable for LTCC application.
Phase Evolution and Properties of Li2O-Al2O3-SiO2-Based Glass-Ceramic for LTCC Applications
Authors: Qing Zhen Jun , Li Bo , Duan Din An , Li Hao , Li Ying Xiang , Zhang Shu Ren
Published: July 2016

In this paper, the influences of sintering conditions on the phase transformation, microstructure, bulk density, bending strength, coefficient of thermal expansion, and dielectric properties of Li2O-Al2O3-SiO2 glass-ceramic were investigated. Conventional melt-quenching method was used to synthesize this glass-ceramic. Scanning electron microscopy, X-ray diffractometer and differential thermal analysis were employed to study this material. The XRD data show that Li2OAl2O37.5SiO2 is the main crystalline phase of this glass-ceramic. ZrO2 and CaMgSi2O6 are the two other phases in this glass-ceramic. The increasing sintering temperature and soaking time affect the phase composition obviously, which lead to the obvious variations of microstructure, mechanical, dielectric and thermal properties of this glass-ceramic. Sintering temperature and time play a key role in the sintering of Li2O-Al2O3-SiO2 glass-ceramic. The sample sintered at 800 °C for 30 min showed good microstructure, low sintering temperature of 800 °C, high density of ~2.6 g/cm3, excellent dielectric properties (εr: ~6.9, tan δ: ~2*10-3), good bending strength of 143 MPa and adjustable CTE from 1.1 to 2.7 *10-6 K-1 close that of silicon. These results mean that the obtained LAS glass-ceramic can be used in the application of LTCC substrate, especially, the manufacture of the substrate of silicon.
Influence of CeO2-Doping on the Electrical Properties of ZnO-Bi2O3-Based Varistor Ceramics
Authors: Cao Zhan Chuan , Zheng Liao Ying , Cheng Li Hong , Tian Tian , Li Guo Rong
Published: July 2016

The microstructure and electrical properties of CeO2-doped ZnO-Bi2O3-based varistors were investigated for different amounts of the dopant. The phase composition of CeO2-doped samples was similar to the undoped samples. Ce mainly segregated at the grain boundaries within the EDS detection limit. The average grain size decreased from 7.3 to 6.7 μm and the breakdown voltage increased from 438 to 501 V/mm when the content of CeO2 ranged from 0 to 0.2 mol%. The nonlinear coefficient increased from 38 to 51 when the content of CeO2 increased from 0 to 0.1 mol%., but the further doping caused it to decrease up to 44 at 0.2mol%. The leakage current decreased from 1 to 0.4 μA/cm2 when the content of CeO2 ranged from 0 to 0.1 mol%. Then it increased to 0.7 μA/cm2 at 0.2 mol%. The density of interface states, the barrier height and the donor concentration increased when the content of CeO2 ranged from 0 to 0.1 mol%, but decreased at 0.2 mol%. Hence, when the content ranges from 0 to 0.1 mol%, CeO2 acts as a donor and can improve the electrical properties.
Performance of (Y2O3,V2O5) Co-Doping TiO2 Ceramics
Authors: Jiang Gui Min , Yan Ji Kang , Yang Gang , Duan Zhi Cao , Kang Kun Yong , Du Jing Hong , Gan Guo You , Yi Jian Hong
Published: July 2016

The present study investigated the effect of the sintering temperature and (Y2O3, V2O5) co-doping on the performance of TiO2 varistor ceramic which has lower varistor voltage and high nonlinear coefficient. The results showed that the TiO2-based varistor ceramic which doped with 0.35% mol and 0.25% mol of Y2O3 and V2O5 has good comprehensive electrical performance and excellent dielectric constant sintered at 1200°C. Its varistor voltage V1mA is 38.1V, nonlinear coefficient is 4.6.
V2O5-WO3/TiO2 Catalysts for Low Temperature NH3 SCR: Catalytic Activity and Characterization
Authors: Deng Yu Xin , Chen Xin , Shao Rong , Hu Li Ming , Tang Jie , Wang Chong Qing
Published: July 2016

A systematic investigation of the effect of WO3 loading over V2O5/TiO2 catalysts was carried out for the selective catalytic reduction of NO by NH3. The characteristics were examined use BET surface area , X-ray diffractometry (XRD) , Temperature programmed desorption (TPD) of NH3 . It was fund that the WO3 species could interact with the TiO2 anatase phase to exhibits a high activity. With increasing WO3 content ,the activity of V-W/TiO2 for the selective catalytic reduction of NO by NH3 was improved at low temperatures in the range of 3～7%. The results showed that the adding of WO3 to V2O5/TiO2 could result in exposing acid sites of catalysts doped WO3 at low temperature. Furthermore, especially the catalytic activity of VW7Ti showed higher than 80% at 180 °C. However, the catalytic BET surface area and the mass of acid sites not play a leading role for improving low-temperature activity of VWTi in this paper.
Preparation and Mechanical Properties of BiFeO3 Ceramics
Authors: Zhang Xiao Yang , Qi Xi Wei , Yang Zhi Yuan , Bao Li , Zhang Min
Published: July 2016

Hydrothermal method and sol-gel process were used to synthesize multiferroic BiFeO3 ceramics. X-ray diffraction, scanning electron microscopy, vickers diamond indenter and three-point bending method were used to investigate the effects of methods on the phase structure, microstructures and mechanical properties. Cold isostatic pressing on the ceramics with two different loads (10 MPa, 200 MPa) was used to illustrate the influence of pressure in mechanical properties. The results show that all samples are crystallized in the perovskite phase. A few small traces of impurity are observed at a 2θ of ~28 o, which are found to be those of Bi2Fe4O9. The SEM images depict that samples prepared by sol-gel process are more uniform and the grain size is slightly larger than that of hydrothermal processed samples. The investigations on the hardness and flexural strength demonstrate the ceramics prepared by hydrothermal method have better mechanical properties than that of sol-gel process, and the mechanical properties can be obviously enhanced by increasing pressure.
Preparation and Magnetic Properties of Fe80Co20, Fe80Pt20 and Fe80Co20/Fe80Pt20 Bilayer Films
Authors: Pan Rui Kun , Zhou Chao , Zhou Feng Li , Chao Wan Qiang
Published: July 2016

Fe80Co20, Fe80Pt20 and Fe80Co20/Fe80Pt20 bilayer thin films were prepared on glass substrates by the magnetron sputtering method. The magnetic properties of these films were monitored with a SQUID magnetometer using both an in-plane and an out-of-plane magnetic field. Several-nanometer-thick Fe80Co20 and Fe80Pt20 films show different in-plane and out-of-plane saturation magnetizations (Ms) with very small coercive force (Hc). Due to the lattice misfit between two layers of Fe80Co20/Fe80Pt20 or presence of stress from the glass substrates during cooling, an intrinsic stress causes perpendicular magnetic anisotropy and magnetization in these thin films under magnetic field. Analysis indicates that Fe80Co20 and Fe80Pt20 ultra-thin films are great potential in the application of the high density magnetic recording media.
The Role of Aluminium Source (Al2O3/AlN) in the Synthesis of the Ca-α-SiAlON:Eu2+ Phosphor
Authors: Pawlik Tomasz , Michalik Daniel , Sopicka-Lizer Małgorzata , Miczek Aleksandra , Krzywda Paweł , Lisiecki Radosław
Published: July 2016

The purpose of the presented research was to compare the effect of changing the aluminium source in the mixture of initial powders on the properties of the final phosphor powder of Ca – α-SiAlON doped with Eu2+. The phosphor composition was designed as Eu0,048Ca0,752Si9,6Al2,4O0,8N15,2 and it was prepared by the solid state reaction in a temperature range of 1450-1650 °C. AlN and/or η-Al2O3 powders were used as a source of aluminium. It has been found that presence of aluminium nitride or oxide in the mixture of initial materials significantly changed the course of α-sialon formation, chemical composition of that solid solution and the resultant photoluminescence properties. It has been established that a small amount of η-Al2O3 with a suitable carbon addition was profitable for liquid formation and enhanced crystallization of Ca,Eu-α-sialon. The excessive oxide-rich liquid at reaction temperature led to sintering of phosphor particles and decreased emission intensity while lack of sufficient amount of liquid (nitrogen-rich starting composition) resulted in AlN presence and considerably reduced emission intensity of this phosphor.
Phase and Morphology Evolution of Manganese Oxides during Thermal Treatment
Authors: Zhao Yu Cheng , Li Sa , Wang Chang An
Published: July 2016

Core-shell structure with inner carbon spheres and outer MnO2 layer was successfully prepared in this study. Thermal treatment was further conducted to remove the carbon cores to get hollow MnO2 sphere. However, it was surprisingly found that the original MnO2 particles turn nanorods. Moreover, it is believed that the appearance of such one-dimensional morphology attributes to the fact that the original irregularly shaped particles of amorphous MnO2 change to mainly Mn3O4 fibers as a result of exposure to open air at room temperature and the fibers would convert to pyrolusite MnO2 with heat treatment. Continuous heating would induce phase transformation from MnO2 to Mn3O4 takes place at 900°C. Based on the XRD, SEM, TEM and TG-DSC analysis, we believe that the K+ intercalated into the MnO2 tunnels stabilizes the nanorods structure and prevents the tunnels from collapse.
Microstructure and Mechanical Properties of Multiscale Zirconia Ceramics Prepared by Field Assisted Sintering Technique
Authors: Eltayeb Khalid , Jin Dong Qin , Han Young Hwan , Chen Fei , Shen Qiang , Zhang Lian Meng
Published: July 2016

Two kinds of powders of 3 mol. % yttria stabilized zirconia (3Y–TZP) with different particles sizes; one was 20 nm denoted by N whereas the other was 0.5 µm denoted by M, were mechanically mixed via ball milling machine using different amounts of N wt. % to obtain multiscale zirconia composite powder. Then the mixed powders were sintered by field assisted sintering technique (FAST). The effect of N content on the microstructure as well as on mechanical properties of zirconia is investigated. Results show that the microstructure of M completely surrounded by N emerged in zirconia composites, and tetragonal phase is presented in all the sintered samples. The obtained zirconia ceramics with 15 wt. % N own a highly dense structure (~ 99.9 % relative density) and high flexural strength of 813.59 MPa wherein a 15 % increase in flexural strength compared to zirconia ceramics without adding N, but the fracture toughness of the composites just lightly decreases. The improved flexural strength of the composites is caused by the multiscale effect.
Preparation of Small Size Ceria Stabilized Zirconia Microspheres by External Gelation: Effect of Vibration Frequency
Authors: Wang Guo Gao , Ma Jing Tao , Gao Yong , Zhao Xing Yu , Hao Shao Chang , Deng Chang Sheng
Published: July 2016

Ceria stabilized zirconia microspheres of about 150 microns were prepared by external gelation. The effect of vibration frequency on jet droplet dispersion and size uniformity was investigated. The diameter variances of microspheres prepared at frequency range of 1300 to 2300 Hz were calculated. The optimal frequency was found to be in good accordance with Raleigh’s theory. The obtained microspheres under optimal frequency were characterized by optical microscopy, scanning electron microscopy (SEM) and X-ray diffraction (XRD). The data showed their good size uniformity, smooth surface, compactness, and good CSZ phase.
Effect of the Cooling Ways on the Properties and Microstructure of ZrO2/ZrW2O8 Ceramic Composites
Authors: Li Jin Ping , Yang Cheng , Meng Song He , Yi Fa Jun , Li Yu Han
Published: July 2016

ZrO2 has been widely used due to its good physical and chemical properties and the ZrO2/ZrW2O8 ceramic composites with adjustable thermal expansion coefficient can be prepared by mixing and sintering the ZrO2 and ZrW2O8 powders. In this paper, the ZrO2/ZrW2O8 ceramic composites have been prepared by mixing, cold isostatic pressing and atmospheric sintering, and then being cooled in air or in water. We focus on the effect of the cooling ways on the properties and microstructure of the ZrO2/ZrW2O8 ceramic composites. The results show that the relative density of all samples is more than 98%. For the in-situ method, the density and flexural strength of the samples cooled in air and in water are 98.1% and 98.4%, 112.96MPa and 45.23MPa, respectively. The ZrW2O8 content and thermal expansion coefficient of the samples cooled in the air are less and higher than those in the water, respectively. For the direct mixture method, the density and flexural strength of the samples cooled in air and in water are 98.9% and 99.3%, 195.99MPa and 58.71MPa, respectively. For the four groups of the composite samples, they behave better mechanical properties after cooled in air, and lower thermal expansion coefficients after cooled in water.
Effect of Preparation Technology on Properties of Quartz Pore Gradient Materials Using Low-Grade Quartz Sand
Authors: Wang Fang , Song Jie Guang , Xu Ming Han , Li Shi Bin , Li Yao Qiu , Yu Si Yuan , Li Xin , Cao Gui Lian , Dong Shuang , Liu Rong Jin
Published: July 2016

The technology of quartz pore gradient ceramics were researched with the low grade quartz sand along the Yangtze River via the vacuum sintering method in this paper, which lay technology foundation for exploiting new heat insulating materials. The research results are shown as following, when the ratio of water to raw materials is 1, the shape and pore distribution of pore gradient ceramics is better. The porosity are first increased and then decreased with an increasing the sintering temperature. The suitable sintering temperature is decided at 1100°Cæ, the density is 1.343g/cm3, the porosity is 48.7%, the compressive strength is 7.071MPa, and the pore gradient structure is homogeneous transition zone.
The Effect of Particle Size of Expandable Graphite on the Properties of an Expandable Thermal Insulation Material
Authors: Fang Kai , Chen Yu Feng , Zhang Shi Chao , Sun Hao Ran , Wang Guang Hai , Sun Xian Kai
Published: July 2016

An expandable thermal insulation material was prepared which can expand the volume at high temperature. The paper is aimed to study the effect of the particle size of expandable graphite for this material, through comparing properties including expansion rate, compression strength and heat conductivity coefficient. The material with 200 mesh has the lowest expansion rate, but compression strength is the maximum 0.901MPa at 800°C while the lowest heat conductivity coefficients 0.118W/m·k at 1100°C which has a 25% reduction in the 50 mesh.
Effect of Moisture Absorption on High Temperature Thermal Insulation Performance of Fiber Insulation Materials
Authors: Sun Hao Ran , Zhang Si Chao , Chen Shu Guang , Wang Guang Hai , Tao Liu Shi , Chen Yu Feng
Published: July 2016

In this paper, effect of moisture absorption on high temperature thermal insulation performance of fiber insulation material is studied. Fiber material is stored in 40°C through a long period of time, then spontaneous moisture absorption of fiber material is measured. According this test result, 20% and 40% moisture absorption content gradient are determined. Pore distribution and high temperature thermal insulation property of samples of 20% and 40% moisture absorption and the dry samples are all tested in this study. The internal pore size distribution of fiber insulation material after moisture absorbing has a certain coarsening. Fiber material after moisture absorbing will make its pore size become large. And oxygen acetylene test results showed that: the larger moisture absorption, the more slowly the initial temperature rises. Fiber material after moisture absorbing will make its low temperature thermal insulation performance reduce, but it has little impact of its high temperature thermal insulation performance.
Optimized Design of Multilayer Thermal Insulations for Hypersonic Vehicles
Authors: Wang Guang Hai , Zhang Feng , Sun Xian Kai , Sun Hao Ran , Huo Yan Li , Zhang Shi Chao , Chen Yu Feng
Published: July 2016

In this paper, high temperature multilayer thermal insulations were to investigate in thermal protection systems for hypersonic vehicles. The thermal response and thermal property of the multilayer insulations were simulated and analyzed by using Ansys software. The calculation results were analyzed and the effects of parameters such as layer thermal conductivity, layer thickness, layer density, and numbers of layer are clarified. Thermal property of multilayer insulations was optimized. The results are helpful to the optimum design of the multilayer insulation system.
Preparation and Properties of Si3N4-SiC Radar Wave-Absorbing Nanocomposites
Authors: Zhang Ping Ping , Wang Hong Sheng , Li Ling , Lv Lai , Zhang Qing Li
Published: July 2016

The vacuum-sintering technology was adopted to prepared Si3N4-SiC composite ceramic, a type of Radar Wave-Absorbing materials (RAW). The mechanical performances of the composite materials were tested and the influences of SiC powers on the mechanics performances and microstructure of Si3N4 ceramics were investigated. The results show that the sintering density, the content of size ofβ-Si3N4 and the strength of Si3N4-SiC all decrease along with the increase of SiC powers in sample, compared with the pure matrix Si3N4 .Meanwhile, Relationship between SiC content and relative permittivity of Si3N4-SiC within the frequency range of 8.2–12.4 GHz (X-band) was studied. The average of relative permittivityεof Si3N4-SiC increased from 7.878 to 13.88 and the average of dielectric loss tanδincreased from 5.6×10-3 to 0.7869 when the content of SiC increased from 0 to 15 wt.%. The excellent microwave absorbing abilities of Si3N4–SiC ceramic were attributed to the interfacial polarization at interface between Si3N4 and SiC and at grain boundary between SiC nanocrystals.
Preparation and Properties of SiC/Si-B-C-N Ceramic Composites
Authors: Chen Ming Wei , Qiu Hai Peng , Xie Wei Jie
Published: July 2016

Abstract：SiC/Si-B-C-N and SiC/SiC ceramic matrix composites were prepared through a combination of chemical vapor infiltration (CVI) and polymer impregnation pyrolysis process(PIP). The microscopic morphology and solid phase structure of the SiC/Si-B-C-N and SiC/SiC composites were investigated by SEM and XRD respectively. Moreover,the flexural strength and fracture toughness were measured using three point bending and single-edge notched beam test. Results showed that the formation of crystalline phases transformation was restrained by introduce BN into matrix phase, which might improve the stability of ceramic matrix composites. Furthermore, the flexural strength and fracture toughness of ceramic matrix composites increased to a maximum of 367 MPa and 26.81 MPa·m1/2 with the 30% PBN weight ratios which might be mainly caused by crack arresting, crack deflecting, micro cracks and fiber pullout.
Preparation of B4C-ZrB2  Laminated Composites by Non-Aqueous Tape Casting and Hot-Press Sintering
Authors: Liu Wei Liang , Shi Zhong Tao , Li Yang Cheng , Xu Zhao Liang
Published: July 2016

B4C and ZrB2 ceramic tapes were prepared by non-aqueous tape casting with B4C and ZrB2 as main materials, xylene and n-butanol as binary solvent, castor oil as dispersant, polyvinyl butyral (PVB) as binder and dioctyl phthalate (DOP) as plasticizer. B4C-ZrB2 laminated composites were prepared by cutting, laminating, dumping and hot-press sintering. The experiment results indicated that ZrB2 ceramic tapes with high solid content of 48 wt.% could be prepared with 0.8 wt.% castor oil, 3.4 wt.% PVB and 6.8 wt.% DOP. Ceramic tapes have smooth surface, no crack and good ductility. B4C-ZrB2 laminated composites with high relative density of 97.8% were prepared by hot-press sintering under 2020°C sintering temperature, 30MPa pressure, 35 min hold temperature and pressure time. Their bending strength and fracture toughness were 488.6 MPa and 5.85 MPa·m1/2 respectively.
Influence of SiC on the Properties of PcBN Cutting Tools Fabricated by High Pressure and High Temperature Sintering
Authors: Zhang Shi Xun , Li Jian , Ma Yao , Wang Hai Long , Zhang Rui
Published: July 2016

SiC-Al3BC3-cBN composites with different contents of cBN were fabricated by high pressure and high temperature sintering (HPHT) at 1450 °C for 3 min under a pressure of 5.0 GPa using SiC, Al, B4C and C as additives. The effect of SiC content on the density and mechanical properties of SiC-Al3BC3-cBN composites was investigated. X-ray diffraction (XRD) and Scanning electron microscope (SEM) were used to analyze phases and micro-structure of the sintered samples. The hardness of SiC-Al3BC3-cBN composites decreased with the increasing of SiC content, However, the fracture strength of SiC-Al3BC3-cBN composites increased with the increasing of SiC content.
Microstructure and Ablation Property of TaC-SiC Composite Coatings
Authors: Niu Ya Ran , Pu Hui , Huang Li Ping , Zhao Jun , Zheng Xue Bin
Published: July 2016

TaC-based composite coatings containing different contents of SiC (5 vol.%, 10 vol.% and 15 vol.%, respectively) were fabricated by low pressure plasma spray (LPPS) technique. The phase composition and microstructure of the coatings were characterized. The ablation property of the TaC-SiC composite coatings was evaluated by a plasma flame over 2000 oC. The results showed that SiC was uniformly distributed in the composite coatings. The addition of SiC was good for the ablation-resistance of the composite coatings. The mass loss of the composite coatings decreased with increasing the amount of SiC. The mass loss of the TaC-15vol.%SiC composite coating was about 0.15 % after ablation for 60 s, which exhibited the best ablation-resistance among the three kinds of coatings. It was thought that the formed Ta2O5-SiO2 mixed layer on the coating surface contributed to the improved ablation resistance.
Phase Equilibria in the BaO-SiO2-Al2O3 Ternary System at 1500 °C
Authors: Zhang Rui , Taskinen Pekka
Published: July 2016

Phase equilibria of the BaO-SiO2-Al2O3 ternary system was experimentally investigated using a quenching technique and analyzed by Scanning Electron Microscopy (SEM) equipped with Energy Dispersive Analysis (EDS) and X-ray Powder Diffraction (XRD). A ternary compound was confirmed in the present work. The liquidus composition in equilibrium with the ternary compound at 1500 °C were quantified. The isothermal sections of the BaO-SiO2-Al2O3 ternary system at 1400 °C, 1500 °C, 1600 °C, and 1700 °C were calculated. Based on the data acquired, the isothermal section at 1500 °C was constructed.
Influence of Contents of Pre-Synthesized Spinel on the Microstructures and Mechanical Properties of the Lightweight Corundum-Spinel Refractory Castables
Authors: Chen Qing Jie , Yan Wen , Li Nan , Lin Xiao Li , Zhou Wen Ying , Wang Luo
Published: July 2016

Five kinds of lightweight refractory castables were prepared by using lightweight corundum-spinel aggregates (LCSA), pre-synthesized spinel (PSS), magnesia and corundum powders as raw materials. Effects of the PSS contents on the microstructures and mechanical properties of the refractory castables were studied by means of X-ray diffractometer (XRD), elastic modulus tester and scanning electron microscopy (SEM), etc. It is found that with the PPS content increase from 0 to 15.3 wt %, the permanent linear change (PLC) of castables sintered at 1600 °C decreases from 1.02% to -0.56%; the bulk density (BD) and apparent porosity (AP) are in the range of 29.6 %~27.8 % and 2.71~2.79 g/cm3, respectively, changing a little; the cold compressive strength (CCS) decreases from 106.0 MPa to 94.4 MPa; the thermal shock resistance improves; the hot modulus of rupture (HMOR) decreases from 6.7 MPa to 4.3 MPa. Considering these aspects, sample with 7.6 wt% PPS (LA7.6) has the best performance.
Influence of Voltage on Microstructure of Micro-Arc Oxide Films on TC4 Titanium Alloy
Authors: Teng Yuan , Tang Wan Xia , Ni Er Xin , Wu Yun Feng , Sun Yan Hua , Fang Shu Ming , Shi Zhe , Yang Gang , Yan Ji Kang
Published: July 2016

The porous ceramic biologic films were prepared on the surface of Ti6Al4V (TC4) with micro-arc oxidation technology (MAO). The phase composition, microstructure and cross section morphology, surface elements composition and valence state of micro-arc oxide films were studied. Results show that with increasing of the micro-arc oxidation voltage, the better biocompatible hydroxyapatite appears on the surface of titanium alloy (TC4). The high voltage promotes the surface pore size enlarge.
Analysis on Low Cycle Fatigue Life and Fatigue Fracture Surface Morphology of TC25 Titanium Alloy
Authors: Zhao Rong Guo , Yan Yi , Jiang Yong Zhou , Luo Xi Yan , Li Qi Bang , Liu Ya Feng , Cai Peng , Chen Yue
Published: July 2016

At room temperature, the low cycle fatigue tests for smooth specimens of TC25 titanium alloy under various stress ranges are operated at a CSS280I-20w Electro Hydraulic Servo Universal Testing Machine with a microscopic observation system, and the low cycle fatigue lifetimes are measured. Based upon the analysis of stress-strain hysteresis loop of low cycle fatigue of TC25 titanium alloy, a simplified Manson-Coffin formula is derived according to both the experimental characteristics and the stress-strain constitutive model, the fatigue lifetimes are plotted against stress ranges, and a stress-fatigue life curve for TC25 titanium alloy is obtained by the linear regression analysis method. Finally, the fracture surface morphologies of TC25 specimens are investigated using a JSM-6360 Scanning Electron Microscopy, and the fatigue fracture mechanisms of low cycle fatigue are studied. It shows that the plastic deformations are mainly formed at the accelerated fracture stage, and various shear lips can be observed on the fracture surfaces, which demonstrates that the shear stress results in the final rupture of TC25 titanium alloy. During the fracture of low cycle fatigue, the cleavage nucleation leads to the formation of fatigue crack initiation region, the fatigue crack growth exhibits a mixed transgranular and intergranular crack growth mode, and in the final rupture region, the fracture surface of low cycle fatigue of TC25 titanium alloy appears as a typical semi-brittle fracture mode.
Synthesis and Antibacterial Activities of Ag/ZnO Nanoparticles
Authors: Hu Ya Wei , He Hui Rong , Kong Xia , Ma Yang Min
Published: July 2016

Ag/ZnO nanoparticles with different Ag concentrations were fabricated through sol-gel method under 500 °C for 60 min with a heating rate 5 °C·min-1. The phase, the crystallographic structure and the surface topography of the Ag/ZnO nanoparticles were charactered by XRD and SEM. The antibacterial activities of the Ag/ZnO nanoparticles were performed by disc diffusion method. The results indicate that the as-prepared Ag/ZnO nanoparticles display great antibacterial activity than ZnO nanoparticle without Ag doping. And Ag/ZnO nanoparticles with 5 mol% Ag concentration show more excellent antibacterial activity toward S.aureus, B. subtilis, E. coli and P. aeruginosa with diameters zones of inhibition 21.7, 18.5, 18.4 and 17.8 mm than other Ag/ZnO nanoparticles. And the mechanism of ZnO antibacterial activity is discussed.
Microwave Assisted Preparation of YAG and Yb:YAG Transparent Ceramic Nanopowders for Laser Crystal
Authors: Si Wei , Xiong Cang , Jiang Yi Wen , Xing Zhi Feng , Pan Wei
Published: July 2016

YAG and Yb:YAG transparent ceramic nanopowders for laser crystal were synthesized by microwave-assisted alkoxide hydrolysis precipitation method. The YAG and Yb:YAG nanopowders were characterized by differential thermal analysis and thermo gravimetric analysis (DTA-TG), infrared spectrum (IR), X-ray diffraction (XRD), field emission scanning electron microscope (FESEM) and photoluminescence (PL) spectrum. The results show that the crystallizing temperature of the precursor of YAG and Yb:YAG is about 930 °C. The pure phase YAG and Yb:YAG nanopowders can be obtained at microwave radiation power of 385 W, microwave radiation time of 30 min and sintering temperature of 1100 °C. The average particle size of YAG is about 120 nm. Yb:YAG is uniform sphere and the average sizes is about 100 nm. The intensity of luminescence of Yb:YAG nanopowders decreased with the increasing of microware time. The maximum luminous intensity of the Yb:YAG nanopowders can be obtained when the microwave radiation is 30 min.
Sintering of SiC Coating Layer on Graphite Spheres Prepared by Pack Cementation
Authors: Zhou Ping , Li Zi Qiang , Zhao Hong Sheng , Zhang Kai Hong , Liu Xiao Xue , Liu Bing
Published: July 2016

Pack cementation is an effective method in the manufacture of SiC coating on carbon material substrate surface, which is a controllable and simple process. Meanwhile, due to the reactive infiltration process of powder mixture into the substrate, a gradient transition structure layer is formed between the substrate and outer layer. In this paper, SiC was coated on the spherical substrates taken from the matrix graphite pebbles of high temperature gas-cooled reactor (HTR) fuel element. Relations between the Si/C content ratio of the pack mixture and the thickness of SiC layer were studied. Analysis found that Si/C content ratio, powder size and sintering time are factors influenced the thickness of the coating layers. When the Si/C content ratio was higher than 3:1, a uniform thickness coating bonded well with the substrate was obtained. The composition phases and thickness of coating layer etc. also had obvious changes along with the change of the Si/C content ratio in this research.Results also show that sintering atmosphere and particle size of powders are important factors affecting coating microstructure, while a vacuum atmosphere can smaller powder size can help to get a dense structure.
Preparation of Li4SiO4 Ceramic Pebbles by Agar Method Using Li2SiO3 and Li2CO3 as Raw Materials
Authors: Xiang Mao Qiao , Zhang Ying Chun , Zhang Yun , Wang Chao Fu , Yu Yong Hong
Published: July 2016

Lithium-containing ceramic pebbles, the likeliest tritium breeders in the future, are needed in the fusion reactor blankets. Currently, lithium orthosilicate (Li4SiO4) has been widely studied for tritium breeding pebble as it has 1250 °C melting temperature, 0.54 g/cm3 lithium concentration, and excellent tritium release performance. For simplifying reaction mechanism and the preparation technology to tailor the properties, the Li4SiO4 breeders were produced with an agar-gel technology using stable and cheap lithium metasilicate and lithium carbonate as starting materials. In addition, the solid (the prepared powder and ager) and liquid (deionized water) weight ration of the green pebble was also evaluated. The crush load, density, and open porosity achieved 36 N, 89.3% TD, and 4.5 %, respectively.
Magnetocaloric Properties of Perovskite-Type Manganite La0.65Sr0.2Na0.15MnO3
Authors: Ji Qing Ling , Zou Zheng Guang , Long Fei , Wu Yi
Published: July 2016

Polycrystalline perovskite-type manganite La0.65Sr0.2Na0.15MnO3 was prepared by sol-gel method. An X-ray diffraction measurement showed that the sample was a single phase. The Curie temperature of the sample was determined to be 350K. The maximum magnetic entropy change |ΔSM| corresponding to a 1T magnetic field variation was found to be 1.08 J/kg K and about 40.6 J/kg of relative cooling power was obtained near the Curie temperature. The first-order or the second-order on the phase transition of the manganite was distinguished by Banerjee criteria.