bluuebunny/crossref_metadata_2025 huggingface dataset:
Le rôle de la pause dans l’acquisition de la première syntaxe en français
Authors: Dodane Christelle , Martel Karine , Nunes De Vasconcelos Angelina
Published: August 2018

Pour mieux comprendre le rôle de la pause dans l’émergence de la syntaxe dans l’acquisition du français, nous avons analysé les premières combinaisons de deux mots dans une étude longitudinale de deux enfants monolingues français, filmés, entre 15 et 25 mois, en interaction avec leurs parents. Les résultats montrent que le critère de la pause est très important dans la construction de la première syntaxe mais qu’il doit être étudié en association avec d’autres indices prosodiques tels que l’allongement de la dernière syllabe de chaque mot et le contour d’intonation. En l’absence de mots grammaticaux, ce sont ces différents indices qui contribuent à rapprocher et renforcer la cohésion sémantique au sein de l’énoncé. Les données confirment l’existence d’une période de transition consistant à produire des SSWUs (Successive Single-Word Utterances) avant de produire une majorité d’énoncés typiques de deux mots.
Le morphème, une unité de traitement dans l’acquisition de la litéracie
Authors: Casalis Séverine , Colé Pascale
Published: August 2018

L’article présente une synthèse des travaux menés en langue française évaluant l’impact de la morphologie dans l’acquisition de la litéracie. Les études ont mis en évidence le lien entre la conscience morphologique et le niveau de réussite en lecture, indépendamment de la conscience phonologique. L’analyse des mécanismes de reconnaissance de mots montre non seulement une sensibilité des enfants dès la 2 e ou 3 e  année de primaire aux unités morphologiques, mais également des capacités de décomposition automatique des mots écrits. Dans le domaine de l’orthographe, il est également montré que l’information morphologique est prise en compte et contribue au niveau de performance. Enfin, un exemple d’enseignement de la morphologie dès la première année d’apprentissage de la lecture/écriture est présenté.
L’autobiographie au féminin, ou les codes de la distinction
Authors: Hanin Laetitia
Published: August 2018

Partant du constat de la forte sociabilité des autobiographies féminines et de leur rayonnement culturel – grand nombre d’écrivaines étant connues aujourd’hui par leurs amis, époux ou amants –, cet article se saisit de quelques autobiographies de femmes pour interroger les conditions sociales et les processus identitaires qui déterminent le devenir-écrivain des femmes aux xix e et xx e siècles. Pour ce faire, il passe en revue les diverses modalités de filiation et montre comment la relation aux modèles féminins se dé-complexifie d’un siècle à l’autre.
« Vous êtes descendue d'un piédestal » : une appropriation collective des Mémoires de Simone de Beauvoir par ses lectrices (1958-1964)
Authors: Rouch Marine
Published: August 2018

À partir des lettres encore inédites reçues par Simone de Beauvoir de la part de ses lectrices entre 1949 et 1963, l’article traite d’abord de la manière dont Beauvoir a été, grâce au Deuxième Sexe puis aux deux premiers volumes autobiographiques, investie comme modèle et représentante des femmes. Bien que La Force des choses et sa clausule, « j’ai été flouée », sont loin d’avoir fait l’unanimité dans la presse, il s’agit ensuite de montrer que ce troisième volume a paradoxalement renforcé et consolidé l’appropriation de l’écrivaine et de son œuvre par les femmes.
Annie Ernaux et Didier Éribon : retour(s) à Beauvoir
Authors: Fort Pierre-Louis
Published: August 2018

On a souvent rapproché Annie Ernaux et Didier Éribon pour de multiples raisons (leurs trajectoires de transfuges de classe ou la dimension auto-socio-biographique d’une partie de leurs écrits) : cela vaut également pour rôle que Beauvoir a joué dans leur vie. L’un comme l’autre ont en effet affirmé qu’elle les avait transformés. Au-delà de cette communauté d’attitude, Ernaux et Éribon sont-ils attachés aux mêmes œuvres ? Plus précisément : eux qui se rejoignent pour avoir placé certaines de leurs œuvres sous le signe du retour et de l’écriture à la première personne, que retiennent-ils de Beauvoir mémorialiste ?
Mode de vie : de quoi parle-t-on ? Peut-on le transformer ?
Authors: Maresca Bruno
Published: August 2018

Le mode de vie est une prénotion sociologique fortement mobilisée du fait des mutations technologiques et économiques et des débats sur la transition écologique. Sa transformation est-elle un enjeu collectif ou plutôt une responsabilité individuelle ? On éclaire cette question par une mise à plat de la polysémie des termes « genre de vie », « mode de vie », « style de vie », et l’on remonte leur généalogie pour clarifier ce concept. Le mode de vie est un système structurant et différenciant à l’intérieur duquel les styles de vie sont une dynamique de renouvellement des manières d’être. La transition écologique ne prendra un tournant décisif que si le changement se trouve engagé au cœur de la structure du mode de vie par une révolution de l’architecture du vivre-ensemble.
Patient Perceptions of Home Health Care Services After Total Joint Replacement
Authors: Adelani Muyibat A. , Nunley Ryan M. , Clohisy John C. , Barrack Robert L.
Published: August 2018

Value-based payment programs have incentivized the reduction of many post-acute care services, including home health care. Patient perceptions of home health care services are currently unknown. The objectives of this study were to determine the value that patients place on home health care after joint replacement surgery and to assess their impression of Medicare reimbursement for these services. Patients with traditional Medicare insurance who underwent primary total hip or knee arthroplasty between January 2016 and July 2017 were given a questionnaire in which they were asked to quantify their satisfaction with home health care, estimate Medicare reimbursement for these services, and give their impression of actual reimbursement. One hundred sixtythree patients completed the questionnaire. Patients were generally satisfied with the services received, giving an overall mean ranking of 9.3 (range, 1–10). Respondent estimates of the cost of home health care services ranged from $0 to $300,000 (average, $8067). Ninety-three percent of patients would choose home health care again if they were to undergo another joint replacement. Patients in this study placed significant value on home health care services after total hip and knee replacement surgery. Further consideration of patient satisfaction may be warranted prior to eliminating home health care services following total joint arthroplasty. [
Orthopedics
. 2018; 41(5):e713–e717.]
Early Clinical Outcomes of a New Cementless Total Knee Arthroplasty Design
Authors: Cohen Russell G. , Sherman Nathan C. , James Sheridan L.
Published: August 2018

Cementless fixation design failures led to low use of this alternative technology. A cementless total knee arthroplasty addressed these design flaws. The single radius knee design incorporated additive manufacturing to produce the tibial and patellar implants. Both implants have enhanced porous substrates, optimizing initial bony ingrowth. A nonrandomized prospective review was conducted of 72 cementless knees followed for a minimum of 2 years (mean, 37 months). Surgical time, estimated blood loss, and range of motion at 6 weeks were compared with those of a matched cohort of 70 cemented knees performed by the same surgeon. Knee Society Score and Oxford Knee Score were recorded for the cementless group. Radiographs were evaluated for change in implant position, subsidence, and radiolucent and sclerotic lines. Operative time was statistically shorter in the cementless group (40 vs 45 minutes), but there was no significant difference in postoperative estimated blood loss (557 vs 355 mL). Range of motion at 6 weeks averaged 118° in the cementless group vs 114° in the cemented group. Knee Society Score improved from 53.9 preoperatively to 85.0 at 6 weeks and 91.6 at most recent follow-up. Oxford Knee Score improved from 23.9 preoperatively to 31.7 at 6 weeks and 43.4 at most recent follow-up. No implants aseptically loosened or migrated. There were 2 early infections in the cemented group requiring revision. This cementless total knee arthroplasty revealed excellent clinical results at 3-year follow-up and resulted in shortened operative times. Biologic fixation was achieved in 100% of patients with improved functional and objective scores. Early results are encouraging, and this cementless total knee arthroplasty appears to provide an excellent alternative to cemented total knee arthroplasty. [
Orthopedics
. 2018; 41(6):e765–e771.]
Orientation et parcours des filles et des garçons dans l'enseignement supérieur
Authors: Fontanini Christine
Published: August 2018

Deux grands bouleversements ont traversé la deuxième moitié du XXe siècle en France : la massification des étudiant(e)s et l'évolution spectaculaire de la scolarité des filles, notamment dans l'enseignement supérieur.

L'enseignement supérieur a encore été très peu exploré pour ce qui concerne les choix d'orientation des filles et des garçons et, en France, il existe peu de recherches portant sur les raisons pour lesquelles certaines filières de l'enseignement supérieur se féminisent fortement ces trente dernières années et d'autres beaucoup moins. Les études sur les choix d'orientation des garçons dans l'enseignement supérieur sont encore plus rares. Or, la division sexuée de l'orientation est tout autant le produit des choix des garçons que celui des filles ; il faut donc analyser les mécanismes du processus d'orientation conjointement, du point de vue des deux sexes. Ce livre a pour objectif de présenter une synthèse des diverses recherches sur l'évolution des choix d'orientation des filles et des garçons dans l'enseignement supérieur depuis une trentaine d'années. Quels sont les facteurs explicatifs de l'attrait des filles pour certaines professions et formations supérieures, mais aussi pourquoi certaines filières les attirent encore peu ? Quelles sont les mutations des choix d'orientation post-baccalauréat des garçons ?
La construction sexuée du parcours d’insertion professionnelle des diplômés chinois en France
Authors: Li Yong
Published: August 2018

Depuis la fin des années 1990, l’immigration étudiante chinoise vers la France a augmenté considérablement en même temps qu’elle s’est féminisée. Aujourd’hui, les étudiantes sont majoritaires dans la population étudiante chinoise à l’université française (57 % des effectifs totaux). La présence massive des filles chinoises dans la migration pour études semble s’expliquer par l’égalisation des sexes en marche face aux études supérieures dans la société chinoise contemporaine. Néanmoins, un certain nombre d’indices nous laissent penser que le genre, à côté des autres déterminants sociaux, reste une variable significative pour rendre compte des formations différentielles des biographies des filles et des garçons en mobilité et de leurs expériences subjectives. De plus, la situation d’immigration tend à reproduire, voire à renforcer les identités sexuées des migrants. Notre hypothèse considère que la migration pour études, plus qu’un simple investissement dans le capital humain, représente un enjeu émancipateur particulièrement important pour les filles chinoises de couches moyennes urbaines.
The Investigation of Structural and Magnetic Properties at High-Temperature of Nanostructured Fe90-Mg10 Alloys Produced by Mechanical Alloying
Authors: El Mohri A. , Zergoug M. , Taibi K. , Azzaz M.
Published: August 2018

Nanocrystalline Fe90Mg10 alloy samples were prepared by mechanical alloying process using planetary high energy ball mill. The prepared powders were characterized using differential thermal analysis (DTA), X-ray diffraction technique (XRD) at high temperature, transmission electron microscopy (TEM), and the vibrating sample magnetometer (VSM). Obtained results are discussed according to milling time. XRD at high temperature results also indicated that when the milling time increases, the lattice parameter and the mean level of grain size increase, whereas the microstrains decrease. The result of the observation by the TEM of the Fe-Mg powders prepared in different milling time, coercive fields derived and Saturation magnetization derived from the hysteresis curves in high temperature are discussed as a function of milling time.
Research Progress of Preparation Technology of Nano Copper Powder for 3D Printing
Authors: Shi Jing Min , Wang Jian Wei , Xiao Wei
Published: August 2018

Nanocopper has become one of the research hotspots of metal powder for 3D printing, due to its excellent properties. In this paper, technical methods, process flow and research progress were systematically introduced of nanocopper powder for 3D printing. Preparation of nano-copper powder for 3D printing are mainly physical and chemical methods. Physical methods include atomization method, physical vapor deposition method, grinding method, electric explosion method. Chemical methods include sol-gel method, radiation chemistry, plasma, microemulsion, hydrothermal, liquid reduction and so on. The advantages and disadvantages of these methods were compared in detail, and the future development direction of nano-copper powder for 3D printing was look forward to.
Synthesis of Nano-Sized Materials Using Novel Water Assisted Solid State Reaction Method
Authors: Toda Kenji , Kaneko Tatsuro , Hasegawa Takuya , Watanabe Mizuki , Abe Yusuke , Kuroi Takeshi , Sato Mineo , Uematsu Kazuyoshi , Kim Sun Woog , Kudo Yoshiaki , Masaki Takaki , Yoon Dae Ho
Published: August 2018

We report synthesis of nanosized oxide materials using a novel water assisted solid state reaction (WASSR) method. This novel soft chemical synthesis method is very simple and can synthesize nanoparticle materials just by storing or mixing raw materials added a small amount (typically 10wt%) of water in a reactor at low temperature below 373 K. Combinations of raw materials have a significant influence on the reaction rate.
Structural-Phase Changes of Graphite during Mechanochemical Treatment
Authors: Chaika Victoriia A. , Savin V.V. , Savina L.A. , Osadchy A. V. , Zherebcov I.S.
Published: August 2018

Studied the structure and phase changes in graphite MPG-7 depending on time of mechanochemical treatment (MCT) in high-speed ball mill at different rotation frequencies. The formation of the carbon material with amorphous and diamond-like component shows. Note the spontaneous combustion of the carbon powder after 8 hours of the MCT at 1500 rpm.
Alkaline Stability of Polyaniline Synthesized Using Pulsed Inductively Coupled Plasma Device
Authors: Suwanprateep Sasikan , Pimpan Vimolvan , Mongkolnavin Rattachat
Published: August 2018

The stability of polyaniline synthesized using pulsed inductively coupled plasma device was studied in alkaline media. Polyaniline was exposed to potassium hydroxide at 25°C and 90°C for various time intervals up to 4 months. An increase in %mass loss, the decreases in the absorbance intensities of polyaniline characteristic bands in FT-IR and UV-Visible spectra and the reduction of the conductivity with increasing exposure time to alkaline solution and/or temperature indicated the increases in the conversion of polyaniline into its base form and the degradation of its structure. The results also suggested that the temperature was the main factor affecting its conductivity in alkaline stability since exposing at 25°C and 90°C caused the conductivity to decrease from 4.53x10-8 S.cm-1 to 1.74x10-8 S.cm-1 and 8.15x10-9 S.cm-1 in 4 months, respectively. Therefore, this polyaniline synthesized via this system may be suitable for the applications at room temperature where alkaline stability is needed.
Preparation of Activated Carbon-Based Catalyst from Candlenut Shell Impregnated with KOH for Biodiesel Production
Authors: Taslim  , Bani Octa , Iriany  , Aryani Novi , Kaban Gapenda Sari
Published: August 2018

Candlenut shell is an agricultural waste which can be processed into low-cost active carbon. Activated carbon cannot be used directly as a heterogeneous catalyst in transesterification of biodiesel because of its low alkalinity, thus treatment is required. In this study, the carbonization of candlenut shells was conducted at 500°C for 4 h. The activated carbon obtained was modified by impregnation with potassium hydroxide (KOH) solution. KOH concentration used was 50g/150 ml aqua des and impregnation time was 24 h. The impregnated activated carbon was characterized by Scanning Electron Microscopy - energy dispersive spectroscopy (SEM-EDS), Fourier Transform Infrared (FTIR) spectroscopy, and was further tested as a heterogeneous catalyst for biodiesel production.
Effects of Processing Parameters on Microstructure and Properties of Aluminum-Silicon Alloy ADC12
Authors: Charoenrut Kasem , Banjongprasert Chaiyasit
Published: August 2018

Aluminum-Silicon Alloy, ADC12 is one of the most popular alloys for pressure die casting due to its high castability and high productivity. ADC12 is a hypoeutectic aluminum-silicon alloy that contains 10-12wt% of Si and has an occasional problem for a mechanical properties failure such as crack and shrinkage porosity. This study presents the investigation of the microstructure of ADC12 parts produced by pressured die casting with different process parameters and chemical compositions. The microstructure was observed using optical microscopy (OM) and scanning electron microscopy (SEM) with energy – dispersive X-ray (EDX) and electron backscatter diffraction (EBSD) to determine phases, grain, and crystallographic information in order to understand the microstructural evolution after die casting with different process conditions. Changes in casting pressure and a reduction of iron content contributed to enhanced mechanical properties and less shrinkage porosity. This was due to different processing parameters, mainly casting pressure. The average grain size of aluminum matrix was also reduced due to a higher pressure during casting with a moderately fast cooling rate.
Effect of Welding Consumables on Dissimilar AISI304/AISI1015 Steels Butt Joint Properties
Authors: Triwanapong Surat , Kimapong Kittipong
Published: August 2018

The butt joint of dissimilar AISI304/AISI1015 steels was produced by a Shielded Metal Arc Welding (SMAW) with 3 types of the covered electrodes and the welding current of 80-120 A. The investigation of joint properties for the impact strength, the hardness, and the microstructure, was performed. The SMAW butt joint that was welded by the E312 covered electrode and 100A welding current showed the highest impact strength of 112 J. The chromium was the important reinforced element affected to increase in the hardness and the impact strength of the joint by forming and dispersing the chromium carbide in the weld metals. Interface structure of the carbon steel/the weld metal clearly showed a small combined area of the metals in opposition to the interface structure of the stainless steel/ the weld metal which had a large combined area of the metals.
Material Characteristic for Capability Analysis of Solid Tire by Finite Element Method
Authors: Phromjan Juthanee , Suvanjumrat Chakrit
Published: August 2018

The natural rubber compound of each layer of solid tire had determined the mechanical properties in tension. It was found that the stress-strain relation of each material tire layer was fitted very well with the Ogden constitutive model. The R2 which was 0.986, 0.996 and 0.985 represented the certain curve fitting on the internal, middle and tread layer of solid tire, respectively. Subsequently, the Ogden model was implemented in the finite element model of the rubber specimen and solid tire. The finite element analysis results obtained an average error of 18.00% and 14.63% for the specimen and solid tire model by comparing to the physical experiment, respectively. Particularly, the mechanical properties of the natural compounds could be used to predict the ultimate compression load for the solid tire failure.
Fabrication and Testing of Glass/Banana Hybridized Epoxy Mono Composite Leaf Spring under Static Loading
Authors: Heckadka Srinivas Shenoy , Nayak Suhas Yeshwant , Krishna Vernekar Navaneeth
Published: August 2018

This study makes use of E glass fiber and Banana fiber woven mats for the development of the hybrid composite mono leaf spring. Six composite laminates for selecting the optimum stack sequence were fabricated, four hybrids and two standalone using epoxy as matrix. From the flexural tests, two hybrid combinations were selected for fabricating the mono leaf spring. Among the hybrid composites, the one with three layers of glass fabric on the outside displayed maximum bending strength of 99.6 MPa. Composite mono leaf spring with three layers of glass fabric on the outside exhibited lower deflection when compared to conventional leaf spring. Results indicate that mono composite leaf spring has the potential to be used as an alternative to conventional leaf spring with continual research.
Minimally Invasive Detection Technologies for the Defects in Ancient Timber Structural Building
Authors: Wang Pei Xuan , Zhang Wei , Li Sheng Cai , Hu Chang Yong , Macchioni Nicola , Yuan Jian Li , Zhao You Jun
Published: August 2018

How to examine and describe the defects in timber is vital for assessing the performance of an ancient timber structural building. This paper mainly elaborates the methodology of detecting the defects in ancient timber structures. The detection method includes preliminary condition survey, stress-wave tomography test, and correction with resistographic drilling. By means of above detection, the defects inside a timber structural building could be described more accurately.
Dynamic Mechanical Behavior of Aluminum Alloy Mortise-and-Tenon T-Joints
Authors: Xiong Hui Yuan , Luo Zhi Peng
Published: August 2018

An experimental investigation was conducted on aluminum alloy mortise-and-tenon T-joints (MT-joints) under dynamic cyclic loading. The MT-joints strengths, stiffness, failure characteristics, hysteresis curves, skeleton curves, restoring force models and energy dissipation curves of the joints have been reported. It’s shown from the experiment that main failure modes of the MT-joints are plastic deformation of squeezing area and tenon divorced from joint. And MT-joints structure is a typical semi-rigid connection that can withstand both rotation and bending moment.
Testing and Characterization of Simply Supported Pultruded FRP Angle Beams Using Bending Tests
Authors: Thumrongvut Jaksada
Published: August 2018

Structural performance and buckling behaviors of pultruded fiber-reinforced polymer (PFRP) angle profile beams under three-point bending tests are presented in this paper. The angle specimens were evaluated to investigate the effect of unbraced length of the beams on the buckling responses and critical buckling loads. In total, sixteen specimens, including eight span-to-width ratios (L/b) were tested. The dimension of the angle profile was commercially available 76x6.4 mm. The span-to-width ratios of the specimens were in the range of approximately 13 to 59. The constituent materials used for the angle profiles consist of unidirectional E-glass fibers and polyester resin. From the bending tests, the load-deformation relationships and failure modes of angle beams were reported. The experimental results indicated that the critical buckling load decreases as the span-to-width ratio increases. The degree of flexural-torsional buckling is directly related to span-to-width ratio. Furthermore, the comparison between the critical buckling loads obtained from experimental study and prediction using methods provided in AISC-LRFD design equation for PFRP angle profile beams showed an unsatisfactory correlation of the critical buckling loads.
The Effect of High Salinity Water to the Compressive Strength of Mine Backfill Material
Authors: Dang Vu Hai , Masniyom Manoon
Published: August 2018

The effect of the high salinity water on the compressive strength of mine backfill was studied. Two types of salinity water: saturated and unsaturated brines were employed to mix with mine backfill materials, and the results were compared. The one with saturated brine had high salt content of 400 g/l while the other had 200 g/l. The results showed that compressive strength decreased with increasing salt content. The mine backfill with high salt content (saturated brine) exhibited the poorest compressive strength in which its strength decreased to approximately 50-70 % of the original strength gained from the backfill samples based on water without salt. Additionally, the optimal saline water solid ratio was 0.2.
Effects of Sintering Temperatures on Structural, Electrical and Mechanical Properties of BNKT Piezoelectric Ceramics
Authors: Manotham Supalak , Butnoi Pichitchai , Lertcumfu Narumon , Jaita Pharatree
Published: August 2018

This research investigated the effects of sintering temperatures on the structural, dielectric, ferroelectric, piezoelectric and mechanical properties of lead-free Bismuth Sodium Potassium Titanate (BNKT) piezoelectric ceramics. The BNKT ceramics were prepared by solid-state mixed oxide method and sintering at temperature ranging from 1100 to 1150°C for 2 h. All ceramics sample showed highly density and reach a maximum at sintering temperature 1125°C of 5.81 g/cm3. X-ray diffraction patterns exhibited pure perovskite structure with coexisting of rhombohedral-tetragonal phases for all compositions. The microstructure was characterized by Scanning Electron Microscope (SEM), from SEM image the ceramics showed cubic-like grain shape. The average grain size increased with increasing sintering temperature. The dielectric permittivity showed the optimum sintering at 1125°C with reach a maximum dielectric constant of 4,194. Furthermore, at sintering temperature 1125°C present highest strain (Smax = 0.14%) with a large normalized strain coefficient (d*33 = Smax/Emax) of 233 pm/V.
Effect of Nano-Al2O3 Particles Addition on Thermal Shock Resistance of ZTA/Cordierite Composites
Authors: Chen Hai Tao , Zhang Zi Jie , Zhang Ling , Lu Hong Xia , Gao Kai , Wang Hai Long , Zhang Rui
Published: August 2018

ZTA/cordierite composites were prepared using ZrO2, Micro-Al2O3/Nano-Al2O3 and cordierite as raw materials by pressureless sintering. The influence of Nano-Al2O3 particles content on phase composition, microstructure and thermal shock resistance of ZTA/cordierite were investigated. The results show that m-ZrO2, t-ZrO2 and Al2O3 existed in the matrix and t-ZrO2 content increased with the increase of Nano-Al2O3 powders content. By adding Nano-Al2O3 powders and ultrasonic dispersion, which can refine grain and promote sintering, the grain size is uniform, the porosity is less and some grains were pulled out, the fracture mode changes from intergranular fracture to intergranular fracture and transgranular fracture. The thermal shock test was carried out at 300°C-1000°C, the critical thermal shock temperature of ZTA ceramic without adding cordierite and Nano-Al2O3 particles is 800°C and the residual strength retention rate of the material is only 32.4%. But by adding Nano-Al2O3 powers and ultrasonic dispersion 30 min,the residual strength retention rate, relative density, flexural strength and fracture toughness of ZTA/cordierite sintered at 1550°C for 4 h increased greatly and were up to 73.6%, 97.2%, 436 MPa and 4.6 MPa.m1/2, respectively.
Effect of Sintering Aids Sorts on Properties of Prepared Al2O3-Al Cermet
Authors: Wang Rui Hua , Bai Xiao Bo , Jiang Xiao Dong , Yi Deng Liang , Wang Fang , Chen Ai Xia , Song Jie Guang , Chen Lin
Published: August 2018

Cermet while maintaining the excellent properties of ceramic materials, but also have the advantages of a metal material, is an important new engineering materials. In this paper, Al-Al2O3 cermet is prepared adding different sintering aids via the powder metallurgy method to study the properties of Al-Al2O3 cermet. The conclusions are shown the adding sintering aids can significantly improve the sintered density of Al-Al2O3 cermet. The sintering aiding effect of adding MgO is better than that of SiO2 and Y2O3, and the hardness and the strength of the sample are higher than those of samples with SiO2 and Y2O3, and the densification degree of Al-Al2O3 metal ceramic material is the best, the relative density is 94.8%, the surface hardness is 824HV. The flatness of the surface of the sample adding MgO shows that the bonding strength between aluminum powder and alumina powder is high. The prepared Al-Al2O3 cermet adding different sintering aids have higher density and fewer pores in the microstructure the prepared Al-Al2O3 cermet adding sintering aids has a package structure.
A Mechanically-Alloyed Amorphous 2Si-B-3C-N Ceramic with a Crystallization Temperature up to 1800°C
Authors: Zhang Peng Fei , Jia De Chang , Yang Bin , Wang Guang Xin
Published: August 2018

A mixture of cubic silicon powder, hexagonal boron nitride powder and graphite powder was mechanically alloyed for 30 hrs in argon. The as-milled 2Si-B-3C-N composite powder was heated up to 1900 °C in nitrogen, with a heating rate of 25 °C/min and under a pressure of 80 MPa. XRD and HRTEM results show that the as-milled 2Si-B-3C-N composite powder has a well amorphous structure. Under the current hot-pressing circumstances, the amorphous ceramic starts to crystallize at a temperature between 1800 °C and 1900 °C. Once the temperature is higher than crystallization temperature, crystallites appear in the amorphous matrix with a great nucleation rate, but a small growth rate. Hot pressed at 1900 °C for 0 mins or 10 mins, the prepared 2Si-B-3C-N bulk ceramic has an average grain size of 8.7 nanometers and 22.3 nanometers, respectively. After an intensive literature search, we believe the present work is the first one to make clear that it is possible to use the mechanical alloying route to prepare amorphous Si-B-C-N ceramic with such a high crystallization temperature.
Characterization of Cf/SiC Composite Fiber Bundle Surface Based on an Optical System
Authors: Wei Jin Hua , Wang Hao Ji , Lin Bin
Published: August 2018

The traditional contact devices measure material's surface roughness by scratching its surface, which may cause surface damage and sampling error. In order to avoid these troubles, an optical measurement system is used in this paper. Considering the anisotropic and inhomogeneous surface structure of Cf/SiC composite, a multi-scale measure system must be established. Fiber bundle is the first scale to be studied, whose appropriate measurement parameters are studied here. When sampling area is 150μm×150μm and sampling step is from 0.1μm to 0.5μm, the values of 3D surface parameters Sa, Sq, Ssk and Sku are steady and their relative changes are small. 2D surface roughness Ra is adopted to select the proper sampling length. The results show that as long as the sampling length is more than 112μm, the mean value of 2D surface roughness Ra are relatively stable. The critical sampling length is about 1/7 of the standard minimum sampling length in ISO 468-1982. According to the results obtained, the research provides a useful guideline for determination on the appropriate sampling conditions of Cf/SiC composite fiber bundle surface measurement.
The Microstructure and Shear Properties of SiC/SiC Composite Pins with Designed SiC Fiber Preform
Authors: Liu Shan Hua , Qiu Hai Peng , Wang Ling , Zhang Bing Yu , Chen Ming Wei , Xie Wei Jie , Liang Yan Yuan
Published: August 2018

In order to obtain the near net shaped SiC/SiC composite pins without the processing cost, four kinds of SiC fiber pin preforms including the knitting yarn and core yarn with two dimension braided structure were designed. The SiC/SiC composite pins were fabricated by precursor infiltration pyrolysis (PIP) process used a liquid SiC ceramic precursor. The results showed that, the near net shaped SiC/SiC composite pins could be obtained by using the designed SiC fiber preform and the graphite mould with curved groove. The macrostructure and microstructure of the SiC/SiC composite pins were observed by scanning electron microscope. Both the single shear stress-displacement curves and the double shear stress-displacement curves of the different kinds of SiC/SiC composite pins showed the saddle-shaped, which indicated the fracture model of the SiC/SiC composites pins was non-catastrophic, and the SiC/SiC composite pins in this paper possessed the secondary bearing capacity. This paper may provide some new ideas for fiber reinforced SiC ceramic matrix composites components designers.
Preparation and Performance of C/C-SiC Ceramic Matrix Composites
Authors: Yang Fang Hong , Wang Yan Yan , Liu Rui Xiang , Zhou Chang Ling , Yang Lu Ping , Jiang Kai
Published: August 2018

Carbon/carbon composite of various density were synthesized via chemical vapor infiltration process, and the sedimentary process of pyrolytic carbon were also researched. The density of the sample increased with the extension of growth time. Density change rate of the samples were various at different stages of the growth process, namely pyrolytic carbon of different densities formed at the different stages. It was found that pyrolytic carbon filled the pores of carbon fiber preform, which can help to relieve the interface stress between the fiber and the ceramic substrate. In order to improve the performance of the composite, SiC and ZrC ceramics were introduced into the carbon/carbon composite via polymer infiltration and pyrolysis (PIP) process. The ability of high temperature resistance and oxidation resistance of the composite were strengthened by the PIP process. The bending strength, tensile strength and compressive strength were also increased with the extension of PIP cycle. The C/C-SiC-ZrC composites were obtain through this process, which are useful in various areas.
Processing and Properties of (Zr,Hf)B2-SiC Ceramic Composites
Authors: Zhao Xiao Tong , Wang Hai Long , Shao Gang , Fan Bing Bing , Lu Hong Xia , Xu Hong Liang , Chen De Liang , Zhang Rui
Published: August 2018

Different molar ratio of HfB2and ZrB2had been mixed, and 30 vol.% SiC was selected as sintering additives. The mixing powders were sintered by hot pressing at 1900 °C for 1 h under a pressure of 20 MPa in Ar atmosphere. X-ray diffraction, scanning microscopy and Archimedes’s method were used to characterize the phase, microstructure and density of the sintered composites. Meanwhile, the hardness, the fracture toughness and flexural strength of the obtained composites were considered too. It can be found that the (Zr,Hf)B2solid solutions were formed by HfB2and ZrB2during the sintering. The flexural strength of (Zr,Hf)B2-SiC composites increased with the amount of HfB2increasing, which reached (332±40) MPa for the composites content of 70% HfB2. Which fracture toughness was (2.22±0.25) MPa·m1/2. The highest Vickers’ harness of was (24.8±3.4) GPa for the composites content of 50% HfB2.
Preparation of Dense Al2O3 Film on 8YSZ Coating by Sol-Gel Method
Authors: Wang Min , Wang Zi Yuan , Yuan Ya Jie , Pan Wei
Published: August 2018

The 8 wt.% yttria-stabilized zirconia (8YSZ) thermal barrier coatings (TBCs) are widely used to protect hot superalloy components of gas turbine and jet engine. However, Cracks and pores in the 8YSZ coating would accelerate the oxidation of the bondcoat alloy and the corrosion of 8YSZ topcoat by molten salts and finally result in permanent failure of the TBCs. Hence, in this work, a sol-gel spin-coating method was employed to prepare a dense α-Al2O3 film on the surface of air-plasma-sprayed 8YSZ coatings, in order to block the paths of cracks and pores while keeping the stress tolerance of 8YSZ coatings. The influences of the polyvinylpyrrolidone (PVP) and alumina content of the sol on the microstructure of the α-Al2O3 film were investigated. It is found that a sol with PVP addition amount of 50 mg/mL and alumina solid content of 10% let to the achievement of a compact α-Al2O3 film. The positive results in this work would inspire more efforts to prepare dense films on TBCs and therefore improve their performance under service conditions.
Synthesis of Boron Nitride Coating on Graphene
Authors: Sun Guo Xun , Bi Jian Qiang , Wang Wei Li , Hao Xu Xia , Gao Xi Cheng , Yan Wei Kang , Wang Lu
Published: August 2018

A method to synthesize boron nitride (BN) coating on the surface of graphene has been developed. BN coating was synthesized by the direct reaction of sodium borohydride and ammonium chloride at a relatively low temperature of 600 °C. Synthesized sample was characterized by RAM, XRD, FESEM, TEM and XPS. It is revealed that the BN coating combines with graphene through van der Waals interactions, and the elements B and N distribute homogeneously on the surface of graphene. Thermogravimetric analysis showed that the oxidation resistance of the graphene was improved after being coated with BN.
Effects of Bias Voltage on Microstructure, Hardness and Bonding Strength of TiN Coating Deposited by High Power Pulsed Magnetron Sputtering
Authors: Chang Wei Jie , Zhang Hao , Xue Xue , Liu Shuang , Yang Jian Feng , Zhang Xue , Long Lin , Duo Shu Wang
Published: August 2018

Generally, bias voltage exercises a great influence on micro-properties (morphology, preferred orientation, mechanical properties, and so on) of the coatings in the process of coating deposited. In order to more systematically explore the influence of bias voltage on microstructure, hardness and adhesion of TiN coatings, TiN coatings were deposited successfully on the surface of 316 stainless steel by high power pulsed magnetron sputtering (HPPMS). A field emission scanning electron microscopy equipped with energy dispersive spectrometer (FESEM/EDS) and an X-ray diffractometer were employed to analyze the surface morphology, chemical composition and phase structure of coatings, respectively. And a nanoindentation and scratch tester was used to investigate the hardness, elastic modulus and adhesion of TiN coatings. Results showed that bias voltage has a great influence on surface morphology of TiN coatings. Moreover, bias voltage can promote preferential orientation and the phase in TiN coating is mainly TiN with a small amount of Ti2N. The influence of bias voltage on the hardness and modulus of TiN coating is not obvious, however, the binding force increases fast first and then decreases slow with the increase of bias voltage. TiN coating has excellent performance when bias voltage is-100V.
Preparation, Performances and Reaction Process of NiZrNb2O8 Microwave Dielectric Ceramics
Authors: Wu Meng Juan , Zhang Ying Chun , Chen Jun Dan , Zhang Yun
Published: August 2018

Microwave dielectric ceramics have great potential applications in the fields of modern communication technology. However, the effects of processing of solid reaction on the crystal structure and properties of NiZrNb2O8 has not been reported. In this paper, the NiZrNb2O8 ceramic was prepared using different raw materials. The solid state reaction process, crystal structure, and dielectric properties of the NiZrNb2O8 ceramics were investigated. The X-ray diffractometer (XRD) results showed that the solid state reaction of NiZrNb2O8 could be divided into two steps using NiO, ZrO2 and Nb2O6 as raw materials. Scanning electron microscope (SEM) analysis results showed that the surface of NiZrNb2O8 prepared from NiNb2O6 and ZrO2 was more compact. The optimal density of the samples reached 99.28% of the theoretical value. And the dielectric constant (εr), quality factor (Q×f), temperature coefficient of resonant (τf) reached 23.6, 37237 GHz, -7.796 ppm/°C, respectively.
Polarity Effect and Dielectric Breakdown of Composite Ferroelectric Films as the Dielectric for Electrowetting Systems
Authors: Wang Wei Qiang , Su Yan
Published: August 2018

In this paper, we study the electrical properties and breakdown phenomena of BaTiO3/Teflon composite ferroelectric thin film in electrowetting systems. The experimental results showed that the electrowetting effect and the breakdown voltage depend on DC voltage polarity, and this polarity dependence is closely related to the thickness of the ferroelectric film. Under AC voltages, the breakdown voltage increased directly with voltage frequency. These results are useful for designing reliable EWOD devices with low operation voltages and high robustness.
BaTiO3/ Teflon Nanocomposite Ferroelectric Thin Films for Low Voltage Electrowetting Systems
Authors: Wang Wei Qiang , Niu Jia Qi , Su Yan
Published: August 2018

We present a simple and cost effective method for the design and fabrication of electrowetting devices using a nanocomposite thin film of BaTiO3 and Teflon-AF as the dielectric layer to achieve low voltage operation. The nanocomposite film is prepared by using Teflon-AF as matrix and BaTiO3 nanoparticles as the filler material. The solution is spin coated to deposit thin film on metal electrodes. The characterization results show that the nanocomposite thin film can serve as the dielectric for EWOD with a high dielectric constant and a crack free hydrophobic film. To test the electrowetting effect, the variation of droplet contact angle achieved with DC voltage, AC voltage and AC frequency change are fully experimented. The EWOD device with nanocomposite dielectric layer also manipulates water droplet at low driving voltages. This study shows the potential of using ferroelectric nanocomposite film as the dielectric layer in high-performance EWOD devices.
Topochemical Synthesis of High-Aspect-Ratio Lead-Free (K, Na)NbO3 Plate-Like Structures
Authors: Cheng Li Qian , Feng Mei , Chen Kai
Published: August 2018

Single crystalline lead-free (K, Na)NbO3 (KNN) nanostructures have attracted much attention for the high piezoelectricity and environmental compatibility. Especially, the plate-like KNN structures are supposed to be utilized in the synthesis of textured KNN-based ceramics. The KNN plate-like templates were prepared by a two-step molten salt reaction. The layered-perovskite Bi2.5Na3.5Nb5O18 (BNN5) was first prepared by using Bi2O3, Nb2O5, Na2CO3, NaCl as raw materials. The BNN5 precursors possess high aspect ratio with an average size of 15 - 20 μm in width and 0.5 - 1 μm in thickness. Then Bi element in the BNN5 was replaced by Na/K through topochemical reaction, and KNN plate-like products which have anisotropic crystal structure were fabricated. It should be emphasized that piezoresponse force microscopy (PFM) was used to confirm three-dimensional (3-D) morphology, while piezoelectric properties of single crystalline KNN platelets were acquired simultaneously. The as-synthesized KNN structures are expected to play an important role in the study of textured KNN ceramics. Meanwhile, the methodology investigated in this paper can also be applied for further fundamental studies on KNN system as well as other lead-free piezoelectric materials.
A Facile Co-Precipitation Synthesis and Luminescence Properties of Red-Emitting La2O2SO4: x%Eu3+ Nanophosphors
Authors: Liu Fan , Lian Jing Bao , Xu Guang Xi , Wu Nian Chu
Published: August 2018

A series of Eu3+ ions activated La2O2SO4 nanophosphors had been prepared successfully by a facial co-precipitation route followed by a subsequent calcination treatment. The commercial Eu2O3, La2O3, HNO3, (NH4)2SO4 and NH3·H2O were used as the raw materials. The structural analyses and luminescence properties of as-prepared products were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM) and photoluminescence (PL) spectra. Pure La2O2SO4 quasi-sphere nanoparticles with an average diameter of 40 nm were successfully prepared by calcining the precursor at 800 °C for 2 h in air. PL results reveal that the strongest red emission peak is centred at 617 nm upon 393 nm light excitation, corresponding to the 5D0→7F2 transition of Eu3+ ions. Its quenching concentration is 9 mol%, which can be attributed to the exchange interaction among Eu3+ ions and the corresponding decay process shows a double exponential decay behavior, with 0.310 μs for t1 and 1.419 μs for t2.
Enhanced Ionic Conductivity in Ce0.8Gd0.2O2-δ Nanofiber: Effect of the Crystallite Size
Authors: Zhang Meng Fei , Li Tian Jun , Zhao Xiao Hui , Zhou Hua Jian , Pan Wei
Published: August 2018

The relationship between the microstructure and the conductivity of nanocrystallized oxygen ionic electrolytes has been received great interest since it provides guidelines for designing electrolytes with high performances which might ﬁnd applications in fuel cells and oxygen sensors. Here, we present a strategy for controlling the calcination temperature to tune the crystallite size and ionic transport properties of solid electrolyte. Different crystallite sizes of Ce0.8Gd0.2O2-δ (CGO) nanofiber electrolytes were prepared. As the average crystallite size decreased from 27 nm to 8 nm, the conductivity of the nanoﬁbers increased by more than five times. An exceptionally high oxide ion conductivity of 0.023 S∙cm-1 for the nanoﬁbers was observed at 550°C. These insights into the eﬀect of the crystallite size on the structure and the conductivity allow a better control of the electrical properties of solid electrolytes, which might foster their applications in electrochemical devices operable at lower temperatures.
Preparation and Lithium Storage Performances of Porous Co3O4 Nanorods
Authors: Li Li , Wang Zhi Hao , Jiang Gao Xue
Published: August 2018

We report on the porous Co3O4 nanorods synthesized by hydrothermal reaction and applied as an anode material for reversible lithium storage. The Co3O4 with porous nanorods structure increases the contact surface, shortens the diffusion path of ion/electron, and improves its structure stability and collaborative electronic transmission. Due to the nanoparticle subunits, the electrodes exhibit high electrochemical performance. Impressively, a high reversible discharge specific capacity of 1105 mAh g-1 is obtained at 200 mA g-1 after 50 cycles. This indicates the excellent potential of porous Co3O4 nanorods as an anode material for lithium ion batteries. Thus, the porous Co3O4 nanorods might open an insight for transition-metal oxides as energy storage materials.
The Synthesis, Characterization and Visible-Light Photodegradation Performance of Graphitic Carbon Nitride Coupling with CoAPO-5
Authors: Zhou Zhi Wei , Qiu Ling Fang , Qiu Xiao Bin , Duo Shu Wang
Published: August 2018

In order to enhance hole/electron separation and charge transfer in photocatalysts, the heterostructured g-C3N4/CoAPO-5 hybrids materials were synthesized via a simple grinding method and were investigated using X-ray diffraction (XRD), fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). The optical properties of g-C3N4/CoAPO-5 hybrids materials were measured by ultraviolet-visible diffuse-reflectance spectroscopy (DRS), photoluminescence (PL) spectra and ultraviolet-visible absorption (UV-Vis) spectra. Under visible-light illumination, this work shows the heterogeneous g-C3N4/CoAPO-5 hybrids present a superior photocatalytic activity.
The Effect of Dispersion Method on the Mechanical Properties of Graphene Reinforced Alumina Composites
Authors: Wang Lu , Bi Jian Qiang , Wang Wei Li , Hao Xu Xia , Gao Xi Cheng , Yan Wei Kang
Published: August 2018

Due to the remarkable physical and mechanical properties of graphene, it is considered to be one of the most promising reinforcements for structural ceramics. In this paper, the composite material is compacted by hot pressing and the effects of mechanical stirring and ultrasonic on dispersion of graphene in alumina matrix were investigated, which was believed to have a great influence on the mechanical properties of the hot-pressed composites. It is found that from Scanning electron microscopy (SEM) observation. Compared with ultrasonic, the composite, in which graphene was dispersed by mechanical stirring, showed higher bending strength (555.1MPaVS432.3MPa) and fracture toughness (4.4MPa·m1/2VS 4.1MPa·m1/2). The result is much more promising to be employed in the designing and processing of graphene composites.