bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Micro-Sized Alumina Powder on the Hydration Process of Calcium Aluminate Cement
Authors: Xia Zhong Feng , Wang Zhou Fu , Wang Xi Tang , Liu Hao , Ma Yan
Published: August 2018

Micro-sized alumina powder is widely used in low cement high-alumina refractory castables. The hydration of calcium aluminate cement can be affected by adding micro-sized alumina powder. This work addresses the hydration of a commercial cement at 25°C with 50 wt% micro-sized alumina powder added. The hydration heat was measured by isothermal micro-calorimetry. The phase composition and microstructure of the hydration products at the designated times were studied by XRD and SEM, respectively. The results showed that micro-sized alumina powder accelerated the dissolution of CAC. The induction period of the cement hydration reduced from 13h to 4.5h, and the hydration heat within 50hs was increased from 469J/g to 587J/g with the addition of micro-sized alumina powder. The morphology of the hydrates was flocculent amorphous at the beginning, and then transformed to short rods or cubic shape with micro-sized alumina powder added.
Sintering and Crystallization of Al2O3-La2O3-ZrO2 Eutectic Glass
Authors: He Gang , Liu Jia Xi , Lu Nan , Liu Guang Hua , Li Jiang Tao
Published: August 2018

High hardness nanoceramics with a Al2O3-La2O3-ZrO2 eutectic composition were fabricated by sintering and crystallization of glass microspheres. Glass microspheres prepared by the flame spraying-water quenching technique were hot pressing sintered and converted to nanoceramics by controlled crystallization. The sintering densification mechanism of the glass microspheres and the effect of crystallization temperature on microstructure and mechanical properties of the prepared nanoceramics were investigated. The phases of the nanoceramics composed of LaAlO3, ZrO2 and LaAl11O18 at crystallization temperature above 1100°C. It was found that the nanoceramic obtained at 1300°C have a maximum hardness of 18.4 GPa, fracture toughness of 3.3 MPa m1/2.
Cryomilling and Characterization of Ti/Al2O3 Powders
Authors: Wu Jun Yan , Liu Qian , Wang Zhi Hao , Wang Zhi
Published: August 2018

In order to prevent the oxidation of Ti, which ultimately leads to the generation of intermetallic compound Ti3Al, a new method of cryomill in liquid nitrogen was used to deal with the Ti/Al2O3 powders. The size distribution, phase composite and microstructure of the powders were analyzed using laser particle size analyzer, XRD, and TEM, respectively. Then, the performances of Ti/Al2O3 cermet sintered using cryomilled powders and room temperature milled powders were compared. The results show that, with the increase of cryomilling time, the grain size decreases shapely and high reactivitive nanoscale powders are finally obtained. With the cryomilling in liquid nitrogen, the Ti-N bonds are formed, which successfully prevent the oxidation of Ti. Ti/Al2O3 cermet sintered using cryomilled powders shows higher density, better mechanical properties than that using RT milled powders.
Co-Catalyzed Si3N4/Sialon Nanofibers Reinforced SiC Refractories
Authors: Zhang Meng , Huang Jun Tong , Li Xi Bao , Hu Zhi Hui , Liu Ming Qiang , Feng Zhi Jun
Published: August 2018

SiCp matrix refractories reinforced by Si3N4/Sialon nanofibers in-situ catalytic formed were prepared at 1400 °C. The roles of catalyst Co on the structure and properties of as-prepared products were studied. We found that the catalyst Co enhanced the nitridation of Si and/or Al. With the increasing of Co addition (from 0-2.0 wt.%), the apparent porosity of the products decreased first and then increased, while the bending strength and the bulk density were exactly the opposite. The as-prepared Si3N4/Sialon bonded SiC refractories exhibited the highest strength of 61.1 MPa as the Co content was 1.0 wt.%. The addition of Co was beneficial to the formation of Si3N4/Sialon nanofibers and the sintering of Si3N4/Sialon bonded SiC matrix refractories, which effectively improved the strength of the samples.
Characterization of Fiber-Like SiCN Formed during the Nitridation of Silicon
Authors: Qu Ling , Yuan Wen Jie , Zhang Cong , Li Jun
Published: August 2018

Fiber-like SiCN was found in the product from the nitridation of silicon by foaming and reaction sintering. The mixture slurry was comprised of silicon powder and cornstarch as raw material, yttrium oxide as sintering additive and some foams. The casted sample was sintered at 1650oC in nitrogen. The phase composition of the as-prepared sample was determined by X-ray powder diffractometer, and the microstructure of the sample was observed by scanning electron microscope and transmission electron microscope equipped with energy dispersive spectrometer. The results show that fiber-like SiCN with micron scale grown along [100] direction, and the interplanar spacing was 0.655 nm.
Oxidation Behavior of β-Sialon Ultrafine Powders Prepared by the Combined Sol-Gel and Microwave Carbothermal Reduction Nitridation Method
Authors: Li Fa Liang , Fu Fang , Lu Li Lin , Zhang Hai Jun , Zhang Shao Wei
Published: August 2018

Ultrafine powders of β-Sialon were prepared by the combined sol-gel and microwave carbothermal reduction nitridation method, and their oxidation process was studied by a non-isothermal thermogravimetry method. The results indicated that two different mechanism functions respectively corresponded to the initial and final oxidation stages. The reverse Jander equation with activation energy of 240.5 kJ/mol and the Avrami-Erofeev equation with activation energy of 410.7 kJ/mol were respectively identified as the most probable mechanism function for the initial and final oxidation stages in the temperature range of 1423-1623 K.
Joining SiC Ceramics with Ti3SiC2/TixCy Multi-Interlayer by Spark Plasma Sintering
Authors: Wang Zhi Quan , Liu Qiao , Yang An Kang , Zhong Zhi Hong
Published: August 2018

Spark plasma sintering (SPS) is a promising method to obtain robust silicon carbide (SiC) joint at a relatively low temperature within a short time. In this work, the joint of SiC ceramics was prepared with TiH2, Si and C mixture powders by SPS from 1150 to 1450 °C for 10 min. The microstructure of SiC joints was observed by scanning electron microscopy (SEM), and the phase composition of the interlayer was determined by x-ray diffraction (XRD) and energy dispersive spectrometer (EDS). The mechanical properties of SiC joints were evaluated by the single lap shear test. The results showed that the microstructure and phase composition of the joints depended on the joining temperature. A dense joint could be obtained above 1250 °C. Ti3SiC2 and TixCy were found in all joints. Also, the decomposition of Ti3SiC2 occurred in the 1450 °C joint. The highest shear strength of 80.5 ± 7.4 MPa was obtained in the 1350 °C joint. The fracture occurred within the joining interlayer and SiC ceramics during shear test, except for the 1150 °C joint, which existed obvious cavities in the joint.
Study on the Microstructure and the Machining Performance of Ti3SiC2-TiB2- TiC Composite Ceramic
Authors: Tang Xiang Jun , Li Jun Shou , Zhao Fang , Qing Li
Published: August 2018

The Ti3SiC2-TiB2-TiC three-phase ceramics are prepared by Spark Plasma Sintering (SPS) method with Self-propagating High-temperature Synthesis (SHS) using Ti, Si, C andB4C powders. The characterization of sintering product’s image and structure is analyzed by XRD and SEM. Most of TiB2’s images are angular cuboid or short bar-shaped and most of TiC phase’s images are irregular spherical particles which are evenly embedded in Ti3SiC2 substrate and have a good combination interface with Ti3SiC2. In the composite ceramic SPS sintering process, sinter sample’s displacement along Z-axis goes through three stages of falling, balance and rising along with the change of heating temperature, which reflects the sample’s change rule between heated expansion force and pressure. Finally its machining performance is analyzed by wire cutting method and machining method. The Ti3SiC2-TiC-TiB2 block composite ceramic proves to have a good machining performance.
Effect of Synthetic Technology on the Properties of Co2O3 Powder
Authors: Xiong Ge , Sun Hui Min , Yang Xue , Li Jin Shi , Chen Mei Hua , Song Jie Guang , Chen Lin , Chen Ai Xia , Yang Chao
Published: August 2018

Ultrafine Co2O3powder was prepared via hydrothermal synthesis. The effect of technology on the performance of the superfine Co2O3powders was investigated, and the hydrothermal parameters in preparing Co2O3were gradually improved. In addition, the morphology and grain size of the Co2O3powder were analyzed by FESEM. Results show that reducing the salt–alkali molar ratio resulted in more uniform Co2O3powder and smaller particles, with average particle size of approximately 40 nm. Reaction time displayed little effect on the Co2O3powder, but the particle size decreased with the reaction time. The concentration of salt solution remarkably affected the morphology of the Co2O3powder. Lower concentration resulted in smaller particle aggregation and particle size.
Thermal Shock Resistance of Yb2SiO5/Si and Yb2Si2O7/Si Coatings Deposited on C/SiC Composites
Authors: Zhong Xin , Niu Ya Ran , Zhu Tao , Li Hong , Zheng Xue Bin , Sun Jin Liang
Published: August 2018

Rare-earth silicates, especially ytterbium silicate (Yb2SiO5and Yb2Si2O7), have been developed for promising environmental barrier coatings (EBCs) for SiC-matrix composites. In this study, double-layer Yb2SiO5/Si and Yb2Si2O7/Si EBC systems were deposited on C/SiC composites by air plasma spray (APS) technique, respectively. Both systems were subjected to thermal shock tests at 1400 °C. The evolution of phase composition and microstructure of those samples before and after thermal shock test were characterized. Results showed that there were penetrating microcracks in the top Yb2SiO5layer and horizontal microcracks at the Yb2SiO5-Si interface after thermal shock test. While extremely few microcracks and no horizontal microcracks were presented in the Yb2Si2O7/Si sample. The EDS analysis also showed that the Si bond layer of the Yb2SiO5/Si sample was oxidized more serious than that of the Yb2Si2O7/Si sample. The different thermal shock behaviors of both systems were clarified based on the thermal expansion behavior, phase composition and microstructure analysis.
Thermal Shock Behavior and Bonding Strength of MoSi2-BaO-Al2O3-SiO2 Gradient Porous Coating with Polymethyl Methacrylate Addition for Porous Fibrous Insulations
Authors: Su Ya Yu , Li Xiao Lei , Tang Hui Jie , Zhao Zhi Hao , He Jian
Published: August 2018

In order to improve the thermal shock behavior of high temperature resistant coating on porous fibrous referactory insulations, the MoSi2-BaO-Al2O3-SiO2(MoSi2-BAS) gradient porous coatings were designed by preparing a dense surface layer and a porous bonding layer with the method of brushing and subsequent sintering at 1773 K. The porous bonding layer was obtained by adding polymethyl methacrylate (PMMA) as pore former. As the content of PMMA increases, the MoSi2-BAS coatings changed from a dense structure into a gradient porous structure. The interface bonding strength and thermal shock resistance of the MoSi2-BAS coatings were investigated. The result shows that the as-prepared coating with gradient porous structure exhibited excellent thermal shock resistance, which remained gradient structure without cracking after thermal cycling 100 times between 1773 K and room temperature. And the interface bonding strength of the gradient porous coating reached 1.5±0.08 Mpa, which was much better than that of the dense coating.
Preparation of Zirconium Sol by Precipitation Method
Authors: Li Lan , Song Yuan Yuan , Geng Guang Ren , Liu Fu Tian
Published: August 2018

Zirconium sol was prepared using precipitation method. In the process, ZrO(OH)2precipitate was firstly obtained through the addition of strong base into the zirconium ions, and then was washed to remove the chloride ion. Lastly, the obtained ZrO(OH)2precipitate was dissolved in nitric acid solution to obtain the white mixed solution. The clear and transparent zirconium sol can be obtained after heated the white mixed solution in a water bath. In this study, the effects of three precipitating agents on the properties of zirconium sol were studied. Zirconium sol prepared by using ammonia as precipitating agent is easy to peptize, while its viscosity is very high. On the other hand, zirconium sol prepared by using urea as precipitating agent exhibits low solid content. Notably, the performance of zirconium sol prepared using ammonia and NH4Cl solution as precipitating agent is best due to its low viscosity and high solid content. In addition, zirconium sol, xerogel and zirconium dioxide powder prepared using ammonia and NH4Cl solution as precipitating agent were systematically characterized by SEM, viscometer, XRD, FTIR. The optimal zirconium sol was synthesized using a peptizing time of 8 h under a peptizing temperature was 80 °C, and the dried amorphous xerogel was converted to tetragonal ZrO2after calcined at 600 °C, while monoclinic at 1000 °C.
Microstructure and Erosion Properties of HVOF Sprayed Cermet Coatings via Different Feedstock Powders
Authors: Fu Wei , Chen Qing Yu , Chen Xiao , Bai Xiao Bo , Wang Hong Tao , Yang Chao , Ji Gang Chang , Yao Hai Long
Published: August 2018

In the present study, Cr3C2-NiCr and WC-Co coatings have been deposited using high velocity oxygen-fuel (HVOF) spray technology from five available powders with various bonding phase content or manufacturing process. The microstructure of coatings was observed by scanning electron microscopy (SEM). Microhardness and erosion performance of the coatings were studied. The influence of powder characteristics on the microstructure and erosion performance of coatings was also investigated. The results indicated that an independent bonding phase distributed in the feedstock powder can effectively improve the erosion resistance of Cr3C2-NiCr coatings although the microhardness of the coatings may be lower. Deformation of the free NiCr binder layer in the coating is probably to prevent nucleation and propagation of cracks, which may result in improving the erosion resistance of the coating. Nano WC-Co coatings reached lower erosion resistance than micro WC-Co coatings due to the higher porosity and lower microhardness of nano WC-Co coatings.
Using Superhydrophobic SU-8 Film as the Dielectric for Electrowetting-on-Dielectric
Authors: Piao Yu Hao , Wang Wei Qiang
Published: August 2018

In this paper, we study the electrowetting effect of superhydrophobic SU-8 film as the dielectric for Electrowetting-on-Dielectric (EWOD). The change of apparent contact angle (APCA) on superhydrophobic surface in electrowetting systems was measured and analyzed using a modified Lippmann-Yong equation. The variation of APCA between droplet and device surface under various DC voltage and AC voltage of different frequencies was fully experimented. The experimental results were in good agreement with the theoretical predictions. This study shows the potential of using superhydrophobic SU-8 film as the dielectric layer in high-performance EWOD devices.
Effect of Sintering Process on Microstructures and Dielectric Properties of Nb-Doped BaTiO3-(Bi0.5Na0.5)TiO3 Ceramics for X9R MLCC Applications
Authors: Chen Ling Ling , Shen Zheng Bo , Zhao Qian Cheng , Cai Zi Ming , Wang Xiao Hui , Li Long Tu
Published: August 2018

Multilayer ceramic capacitor (MLCC) chips have been successfully prepared through tape-casting and screen-printing. Conventional sintering method and two-step sintering method with different sintering temperature and holding time are used to obtain the MLCC chips. The scanning electron microscopes show that MLCC chips sintered by two-step sintering at T1=1200°C and T2=1130°C for 3h have a highly dense dielectric layer. The temperature coefficient of capacitance (TCC) of the MLCC chip is less than ±15% from-60°C to 235 °C that satisfactorily meets the requirement of X9R. The average capacitance and the dielectric loss of the MLCC chip are 88nF and 1.8% at the room temperature, respectively.
Preparation of Spherical Silica with Controllable Size
Authors: Wang Shu Lin , Wang Zhao , Li Bing Hao , Xu Man
Published: August 2018

The spherical silica particles were prepared by sol-gel method with TEOS as precursor, ethanol as solvent in the presence of ammonia. The effects of reaction temperature and the amount of ammonia and TEOS on the size and morphology of silica particles were investigated. The hydrolysis temperature , alkali and TEOS content does not affect the morphology of silica, the silica particles were spherical; With the increase of hydrolysis temperature, particle size of silica showed first increased and then decreased, when the hydrolysis temperature is 30 °C, the silica particle size up to 0.6 μm, when the hydrolysis temperature is 60 °C, the silica particle size is 0.15 μm; With the increase of the content of alkali, silica particle size showed first increased and then decreased, when the alkali content is 20 ml, the silica particle size up to 0.6 μm and when the alkali content is 10 ml, the silica particle size is 0.2 μm; With the increase of TEOS dosage, the amount of spherical silica increased and the particle size of silica spherical particles first increased and then decreased.
Effect of the Adjuvants on the Properties of Superfine SnO2 Powders
Authors: Song Jie Guang , Chen Lin , Zhou Xian Jie , Yang Xue , Lou Xin Peng , Chen Mei Hua , Lai Xiao Hui , Yang Chao , Chen Ai Xia
Published: August 2018

Ultrafine SnO2 is a new type of material, in the field of solar cells and semiconductors have a lot of use. To get different morphology and different properties of tin oxide powder material, making more applications in the field, the effect of the adjuvants on the properties of superfine SnO2 powders were distigated. Through the analysis of experimental results, the conclusions are shown the stronger the alkalinity of the auxiliary agent, the larger the grain size of the obtained particles and the more uniform the particles. When the molar ratio of salt to alkali is more than 1: 4, the amount of alkali is gradually reduced, the particle size is small, the morphology is not uniform and easy to agglomerate. When the molar ratio of salt to alkali is 1: 4, the smaller particle size is shown, the appearance morphology is uneven. The longer the reaction time, the more complete the grain, the more uniform the morphology. Under the condition of SnCl4 concentration of 0.05mol/L, reaction time is 4 days, salt and alkali molar ratio is 1: 4, holding temperature is 200°C, the auxiliary agent is NaOH, the size, shape and performance of synthesized SnO2 are the better.
Preparation and Properties of Cr,Nd:YAG Transparent Ceramics by Slip Casting
Authors: Wan Xiu Juan , Zhang Ying Chun , Wang Man , Liu Yang , Li Yu Sha
Published: August 2018

In this paper transparent chromium and neodymium co-doped YAG ceramics were prepared by slip casting and vacuum sintering using high purity Al2O3, Y2O3, Nd2O3 and Cr2O3 powders. After mixing the high purity Al2O3, Y2O3, Nd2O3 and Cr2O3 powders under the appropriate percentages, pure phase Cr-Nd-doped YAG powders were preparated via calcining at 1300°C for 2 hours. The slurry with the solid content of 40% was casted by self-pressure slip casting under 25°C and 60% humidity to obtain green body. The green body was dried for 96 hours at 33 °C and 75% humidity and then sintered at 1800 °C for 10 hours in vacuum to obtain Cr,Nd:YAG ceramics finally. The transmittance of 1.0 at.%Cr,1.0 at.% Nd:YAG is nearly 80% at 1064nm, and two absorption peaks of Nd3+ can be seen near 760 nm and 808 nm.
Synthesis and Characterization of Novel Multipods-Branched Cd-Se-S Micro-/Nano-Structures
Authors: Li Hong , Zhang Yu , Wang Cheng Biao , Peng Zhi Jian , Fu Xiu Li
Published: August 2018

Novel multipods-branched Cd-Se-S micro-/nanostructures (MNSs) were successfully prepared in a tube furnace by thermal evaporation under atmospheric pressure through using high-purity CdS and CdSe mixture powder with a molar ratio of 1:1 as evaporation source, high-purity Ar gas as carrier and protective gas, and mica wafer as substrate. Under the optimum condition, the evaporation temperature was 1100 °C, Ar gas flow rate was 200 sccm, and the distance between the evaporation source and substrate was 22 cm. The microstructure examination revealed that the length of the obtained branches was up to tens of microns and the diameter of the branches was of a few microns. The composition and crystal structure analyses indicated that, the chemical composition of the multipods-branched Cd-Se-S MNSs was CdSe0.86S0.14, which had a hexagonal structure and good crystallinity. The photoluminescence spectrum at room temperature displays an intrinsic emission peak around 620 nm. In addition, their growth might be controlled by a vapor-solid mechanism.
Effect of Anionic Surfactant on Adsorption Properties of Nano Calcium Carbonate
Authors: Ren Qing Li , Luo Qiang , Wang Feng Lei
Published: August 2018

Because of its superior surface properties, nanocalcium carbonate can be applied to the adsorption of heavy metals in wastewater. However, because of the easy aggregation of nanocalcium carbonate, high surface energy and poor dispersibility in water, it is not conducive to the process of adsorption. Therefore, surface modification of nanocalcium carbonate is needed. In this paper, nanocalcium carbonate was prepared by liquid phase method. And the nanocalcium carbonate was surface modified by sodium dodecyl sulfate. The effects of modifier amount, modification temperature, and modification time on the activation and absorbance of nanocalcium carbonate were investigated. And the morphology and particle size of modified nanocalcium carbonate were tested by SEM and XRD patterns.The results show that the dispersion and surface activity of the modified nanocalcium carbonate have been improved remarkably. Moreover, the Cu2+ was adsorbed by sodium dodecyl sulfate modified nanocalcium carbonate and unmodified nanocalcium carbonate under the optimum modification conditions. And the effects of nanocalcium carbonate initial concentration on the adsorption performance were studied. The results show that the adsorption performance of modified calcium carbonate is better than that of the unmodified. Moreover, the adsorption process is studied by adsorption isotherm. By drawing the adsorption isotherms lines and by comparing the fitting result of the experimental data based on the Langmuir model and that of Freundlich model, it is found that the adsorption of Cu2+ by modified nanocalcium carbonate meets the Langmuir model.
Zn-Cr Layered Double Hydroxides Composites for Methyl Orange (MO) Absorption
Authors: Zhou Tao , Ai Jian Ping , Liao Wei Xiu , Cheng Li Hong , Zhang Yue , Jiang Rui , Chen Zhi Qin , Li Wen Kui
Published: August 2018

In this study, The Zn-Cr nanocomposite was synthesized using the hydrothermal method show good adsorption property. The as-prepared LDHs absorbent were characterized by Powder X-ray Diffraction (XRD), field emission scanning electron microscopy (FESEM), Fourier Transform Infrared (FT-IR), BET surface area, and simultaneously UV-visible spectrophotometer. The nanocomposites of Zn-Cr layered double hydroxides, the strong adsorptive adsorbents for anions. Zn-Cr LDHs with various Zn/Cr molar ratios for 2, 3, 4. The nanocomposites quickly adsorbed the anionic dyes such as methyl orange (MO) without the light illumination. The effects of Zn/Cr molar ratio on the adsorption performance of Zn-Cr LDHs were investigated.
Synthesis of La2NiO4+δ Nanofibers by Electrospinning Method and their Application
Authors: Xing Yan , Zhang Meng Fei , Li Tian Jun , Pan Wei
Published: August 2018

La2NiO4+σ nanofibers exhibiting typical Ruddlesden–Popper structure (K2NiO4) were fabricated by a facile electrospinning method. X-ray diffraction, scanning electron microscopy and transmission electron microscopy were used to analyze the structure, morphology and crystal process of the La2NiO4+σ nanofibers. For electrical properties measurement, uniaxially aligned nanofibers were directly collected and assembled into electrode. In our research, La2NiO4+σ phase forms above 873K with no impurity phase emerges during the thermal treatments. The nanofibers are smooth and uniform throughout the entire length and the grain is growing as calcination temperature increases. Furthmore, the La2NiO4+σ nanofibers own high mixed conductivity at 773K, laying good foundation for intermediate temperature solid oxide fuel cells application.
Preparation and Optical Properties of ZnO Nanocrystals by Chemical Bath Deposition
Authors: Zhong Rui Fang , Liu Zhao , Zhang Ling , Liu Ting Zhi , Duo Shu Wang
Published: August 2018

ZnO nanocrystals were prepared using three different salts of ZnSO4, Zn (CH3COO)2and Zn (NO3)2by chemical bath deposition. The samples were characterized by XRD, SEM, PL, and FTIR spectroscopy. The XRD results showed that all the samples exhibit the hexagonal wurtzite standard crystal of ZnO. When the zinc precursor is ZnSO4and Zn (CH3COO)2, B1 and A2 possess the best crystallinity. The FESEM results showed all the samples have flower-like ZnO structures with difference grain size distributions, diameters and tips of the ZnO nanoneedles or nanorods. In the photoluminescence spectrum, we can observe that, all the samples have a very strong at the wavelengths from 475 to 650 nm, corresponding to relatively broad visible emission peak attributed to the oxygen defects. The experimental results of the sample prepared by ZnSO4exhibit the highest visible luminescent performance. In the infrared absorption spectrum, the band of all the ZnO powders was located at about 500 cm-1, which was the characteristic absorption peak of Zn-O bond. The stretching vibration peak of C=O can be observed at about 1700 cm-1. Meanwhile, there is a strong absorption of the hydroxyl groups in/on Zn (OH)2at around 3450 cm-1, which were from the water molecules.
Effect of Alkali Activator on Preparation, and Mechanical and Thermal Properties of Iron Mine Tailing-Based Lightweight Materials
Authors: Ge Sheng Tao , Bi Yu Bao , Wang Jun Kai , Li Sai Sai , Zhang Gen , Zhang Hai Jun
Published: August 2018

Lightweight materials applied in construction field were prepared using waste iron mine tailings (WIMT) as raw materials, the commercial silicate cement (CSC) as cementing agent, NaOH as the alkali activator, and triethanolamine lauryl sulfate (TLS) as foaming agent via foam-gelcasting method. The effects of water/cement (W/C) mass ratio (0.6-1.0), addition of NaOH (0-0.15wt%) and foaming agent (0-0.3vol%) on the porosity, bulk density, and mechanical properties of the iron mine tailing-based lightweight materials were studied. The results showed that the mechanical properties of iron mine tailing-based lightweight materials were improved by adding NaOH, the as-prepared materials had a 7-day compressive strength of 5.18 MPa, porosity of 51.40%, bulk density of 1.73 g/cm3and thermal conductivity of 0.193 W・(m-1K-1) when the W/C ratio was 0.8, the mass ratio of WIMT/CSC/NaOH 1.85:1:0.15, and foaming agent content 0.3vol%.
Low Temperature SiGe Steam Oxide - Aqueous Hf and NH3/NF3 Remote Plasma Etching and its Implementation as Si GAA Inner Spacer
Authors: Wostyn Kurt , Kenis Karine , Mertens Hans , Vaisman Chasin Adrian , Hikavyy Andriy , Holsteyns Frank , Horiguchi Naoto
Published: August 2018

For horizontally stacked nanowires or-sheets to compete with finFET, the development of a robust inner spacer module is essential. These inner spacers are required to reduce the parasitic capacitance due to the overlap between the source/drain and gate regions. Here we propose an inner spacer integration scheme for Si gate-all-around (GAA) taking advantage of the selective oxidation and oxide removal of SiGe versus Si. Compared to thermal oxide, we found a very high SiGe-oxide etch rate in aqueous HF solutions. When using an NH3/NF3remote plasma, a reduction in etch rate was found for SiGe-oxide versus thermal oxide. We show Si0.75Ge0.25-oxide meets inner spacer requirements for leakage current and electrical breakdown field and finally demonstrate the proposed inner spacer integration scheme using a fin-shaped SiGe/Si multilayer topological-test-structure.
RMG Patterning by Digital Wet Etching of Polycrystalline Metal Films
Authors: Oniki Yusuke , Vereecke Guy , Dentoni Litta Eugenio , Ragnarsson Lars-Ake , Dekkers Harold , Schram Tom , Holsteyns Frank , Horiguchi Naoto
Published: August 2018

A self-limiting wet etching of metal thin films has been developed for the replacement metal gate patterning in advanced logic devices, which will have aggressively scaled gate length and fin pitches. A uniform and highly selective wet etching of polycrystalline TiN films is demonstrated by a diffusion-limiting oxide growth on the metal surfaces as well as a subsequent highly selective oxide removal.
Is Highly Selective Si3N4/SiO2 Etching Feasible without Phosphoric Acid?
Authors: Son Chang Jin , Kim Taeh Yeon , Park Tae Gun , Lim Sang Woo
Published: August 2018

Si3N4 film could be selectively removed by a special H3PO4-free etchant. In order to increase Si3N4 etching rate and Si3N4/SiO2 etch selectivity, various additives were added to H3PO4-free etchant. The optimization of additives into H3PO4-free solution, a comparable Si3N4 etching rate with 50 times increased Si3N4/SiO2 etch selectivity was obtained as compared to the conventional H3PO4 process.
Self-Aligned Contacting Processes for the 80 nm p-MTJ Device Fabrication by Wet Approach
Authors: Cui Hu Shan , Cao Kai Hua , Zhang You Guang , Xiong Hua Gang , Wei Jia Qi , Li Jun Jie , Bai Guo Bin , Li Jun Feng , Zhao Chao , Zhao Wei Sheng
Published: August 2018

In this work, a novel process integration scheme for p-MTJ devices’ passivation and contacting was proposed. The method can efficiently protect the ferromagnetic metals and the magnesium oxide which are the key building block of p-MTJs, and effectively make electrical contact with the interconnect metals for p-MTJs. The scheme consists of passivation of p-MTJs with dual dielectrics - silicon nitride and silicon oxide, followed by planarization and selective wet etch. The proposed integration scheme was successfully demonstrated with 80 nm size p-MTJ devices.
Fixed Charge Control of Silylated Surface for Stiction-Free Drying with Surface Energy Reduction Process
Authors: Koide Tatsuhiko , Kimura Shinsuke , Kobayashi Takashi , Iimori Hiroyasu , Tomohiko Sugita , Sato Katsuhiro , Ogawa Yoshihiro
Published: August 2018

Recently, a surface energy reduction process (SERP) for stiction-free drying is used for a high aspect pattern structure like shallow trench isolation (STI). The key technology of SERP is trimethylsilyl (TMS) groups termination of the device surface. To explain the electrical influence of TMS groups was found acceptable by measuring the planar capacitor flat-band voltage shift, and the threshold voltage characteristics of 1x-nm node MOS transistors.
Factors Influencing Drying Induced Pattern Collapse
Authors: Mui David S.L. , Musselwhite Nathan , Kawaguchi Mark
Published: August 2018

The collapse of high aspect ratio features is a daunting challenge facing the semiconductor industry. The complex physics and dynamics that govern this process are not entirely understood. Through the use of optical video imaging we have observed pattern collapse in real time. It was found that the liquid meniscus reconfigures itself laterally along the length of the structure as opposed to the expected top-to-bottom drying. Herein, we report on our observations and the physics of drying high aspect ratio structures.
300 mm Wafer Development for Pattern Collapse Evaluations
Authors: Xu Xiu Mei , Zheng Tao , Saib Mohamed , Sebaai Farid , van de Kerkhove Jeroen , Vrancken Nandi , Vereecke Guy , Holsteyns Frank
Published: August 2018

Over the past decade, many advanced drying techniques have been developed to reduce and prevent pattern collapse of high aspect ratio (HAR) structures after wet processing. However, different dimensions, profiles and materials of HAR structures used in literature make it difficult to compare the efficiency of different drying processes. In this work, standard 300 mm wafer test structures, characterization and analysis techniques have been developed for quantitative analysis of pattern collapse rate as a function of the intrinsic mechanical property of HAR structures. Such standardized single wafer evaluations are important for benchmarking different drying techniques.
Corrosion of Co in BEOL interconnects in dilute HF solution
Authors: Akanishi Yuya , Kesters Els , Le Quoc Toan , Holsteyns Frank
Published: August 2018

The impact of dissolved oxygen (O2) on cobalt (Co) corrosion in dilute HF (dHF) solution was studied. It was confirmed that Co etch rate was enhanced as the amount of dissolved O2 in the HF solution increased. The Co etch rate was also found to increase radially outward when performed on a single-wafer spin process in atmospheric air due to the uptake of O2 during the dispense process. The galvanic corrosion of Co was investigated with two types of structures with a Co/Cu interface in different dissolved O2 concentrations, i.e. (1) Co bump structures on Cu and (2) Cu lines with a Co/TaN liner/barrier structure. By controlling both the dissolved and the atmospheric O2 levels, galvanic corrosion prevention at the Co/Cu interface was achieved.
Optimization of Post Etch Cobalt Compatible Clean by pH and Oxidizer
Authors: Iino Hideaki , Ogawa Yuichi , Masaoka Toru , Le Quoc Toan , Kesters Els , Rip Jens , Oniki Yusuke , Akanishi Yuya , Iwasaki Akihisa , Holsteyns Frank
Published: August 2018

The introduction of Co into MOL and BEOL requires a robust wet clean, especially the optimization of the Co rinsing step seems to be critical. The wafer rinsing solutions with a precisely controlled pH and oxidizing additive have been developed to suppress the Co corrosion. In addition, the mechanism of passivation and corrosion of the cobalt surface as well as the passivation stability is discussed.
Developing Integrated Solutions and Wet Cleans to Eliminate Tungsten Contact Attack in Sub 0x nm Nodes
Authors: Sehgal Akshey , DeVre Michael , Balu Elango
Published: August 2018

Having successfully developed high volume manufacturing (HVM) processes for the 0x nm node, the semiconductor industry is now engaged in developing the next advanced node. This 0xnm node development is being accomplished by a combination of shrinking 0x nm dimensions, introducing new materials and films and consequently new lithography, dry etch and wet clean processes for the new node. One of the major challenges is developing processes, including BEOL Cleans Steps, to successfully and reliably expose the MOL metal contact during the first metal line formation without degrading the contact itself. One such compatible method/clean is discussed in this study.
Post-CMP Cleaners for Tungsten Advanced Nodes: 10nm and 7nm
Authors: Lieten Ruben R. , White Daniela , Parson Thomas , White Michael
Published: August 2018

Chemical Mechanical Planarization (CMP) is a key process for IC manufacturers. Tungsten (W) is an important material for connecting logic elements and for connecting memory elements, thanks to its excellent planarization, filling, mechanical and electromigration properties. W slurries are developed to remove high amounts of W via an abrasive, in conjunction with an oxidizer. After the polishing process, the planarized surface is contaminated with abrasive particles, organic residue, pad debris and metal cations through covalent or hydrogen-bonding, electrostatic and Van der Waals attractions. Post-CMP cleaning is required to remove all these contaminants while exhibiting low galvanic and chemical corrosion. Formulated cleans are needed to meet all these requirements. The performance of formulated W/TiN post-CMP cleaners for N10 and N7 has been evaluated. The newly developed formulations show a factor 4 reduction in metal surface contamination (from ~2 x 1012atoms/cm2to ~ 5 x 1011atoms/cm2), which is important to prevent dielectric breakdown. Very low particulate and organic residue defectivity was additionally confirmed by different surface characterization techniques: XPS, FTIR, contact angle/surface energy.
Electrostatic Discharge Control and Visualization in Spray Nozzle
Authors: Cha Ji Hoon , Kim Tae Hong , Kim Young Hoo , Lee Kun Tack , Koh Yong Sun
Published: August 2018

The general method to remove contaminated particles in the non-pattern cleaning such as pre-photo cleaning, post-deposition cleaning, and post-CMP cleaning is to physically remove particles using spray nozzle. However, high-speed fluids for increasing particle removal efficiency cause static electricity due to friction between liquid and nozzle surfaces, resulting in unexpected charge defects. In this study, we propose a method to reduce static electricity by changing the material of nozzle and grounding by visualizing static electricity according to electric voltage.
The light at the end of the tunnel: photosensitivity in larvae of the mountain pine beetle (Coleoptera: Curculionidae: Scolytinae)
Authors: Wertman Debra L. , Bleiker Katherine P. , Perlman Steve J.
Published: August 2018

Investigations of light sensitivity and its physiological effects on insects developing within subcortical tree tissues are limited, presumably due to the assumption that cryptic microhabitats are completely devoid of light. In this study, we documented light-mediated behaviour and opsin gene expression in larvae of the mountain pine beetle, Dendroctonus ponderosae Hopkins (Coleoptera: Curculionidae: Scolytinae), an extremely important forest insect that is well adapted for development beneath the bark of pine (Pinus Linnaeus; Pinaceae) trees and is eyeless in the larval stage. Larvae were negatively phototactic, as they selected dark over light microhabitats in phototaxis assays. We recovered long-wavelength opsin transcripts from all life stages, including eggs and larvae, suggesting that D. ponderosae is photosensitive throughout its entire life cycle. Our results imply that photosensitivity contributes to immature D. ponderosae survival and that extraocular photoreception could be common among bark beetle larvae.
Leveraging Virtual Worlds Foreign Language Teacher Preparation
Authors: Moser Kelly , Miller Nicole C , Chambless Krista
Published: August 2018

Recently in the field of teacher education, there has been a call for a more practice-based approach to teacher education. Best practices for developing any skill set is live practice and coaching. However, due to the many ethical considerations and the obstacles presented to the learning-to-teach process, it is neither practical nor best practice, to have teacher candidates conduct live practice lessons in real classrooms with constant interruptions by expert teachers. In contrast, virtual worlds such as Second Life (SL) can potentially assist teacher educators in overcoming these obstacles. This article presents the findings of a research study using SL in an inter-university Foreign Language (FL) methods course to provide teacher candidates with opportunities to teach (practice skills) while receiving continuous live feedback (coaching) from their methods instructors. The virtual experience and immediate feedback impacted candidate confidence as well as pedagogical practice and forced candidates to engage in reflective practice regarding content and pedagogical knowledge. The complexity of teaching, the role of feedback, and simulation within SL in FL teacher candidate learning are also discussed.
Virtual worlds, real consequences: Negative opinions about online dating and video gaming among non-participants
Authors: Jain Abhijit
Published: August 2018

This is an exploratory analysis conducted on data from a large scale representative survey related to opinions about online dating and video gaming in the U.S. The goal of this research is to understand the characteristics of individuals who have never participated in online dating or in playing video games, and yet have negative opinions about these activities. When individuals harbor negative opinions about an activity without having participated in it, one of the sources for these opinions is their (individuals’) context. Eighty five percent of respondents have never participated in online dating, and fifty percent have never participated in playing video games. Using the sociotechnical perspective to uncover the demographic context of non-participants’ negative opinions, this research finds that among those who have never participated in online dating, more negative opinions about online dating are associated with a higher frequency of internet usage, a lower education level, a more conservative political orientation and a lower income level. With respect to video gaming, among those who have never participated in video gaming, more negative opinions about video gaming are associated with a higher age and a more conservative political orientation. Additionally, for non-participants, a belief that people who play violent video games are more likely to be violent themselves is associated with higher age, lower income level, and being female.Shopping from home for a relationship via online dating and immersing oneself in augmented, mixed environments via video games are common activities in the present era. Yet, there is scarce research on non-participants in these activities even though these non-participants comprise at least half the population. By paying attention to these ignored groups, this study advances broader understanding of the individual and societal contexts under which individuals choose to not participate in these activities. Non-participation is related to technophobia and the findings from this study will help broaden understanding of that phenomenon.
Avatars and Security Clearances: How can we reconcile the two?
Authors: Cummins Michael P
Published: August 2018

Government and military personnel in positions of trust are required to obtain and retain security clearances as part of conducting their duties within those positions. Part of obtaining a clearance requires personnel to report on any foreign contacts or business interests they may have. During the time that they hold such a position, personnel must report any significant contact with citizens of various countries to ensure they have not been targeted as part of a foreign intelligence collection effort. As more cleared personnel begin actively participating in virtual worlds, and as more personnel already active in virtual worlds begin applying for positions of trust, how will vetting agencies reconcile the borderless nature of virtual worlds with the requirements set forth for establishing and maintaining security clearances?Legislation has historically not kept pace with rapidly developing community technologies, and bureaucracies may make a choice between taking online relationships too seriously, and not taking them seriously enough. In the past, foreign relationships were easily defined, with physical travel, face-to-face contact, phone, and postal connections being the norm. Today, the global nature of online gaming and virtual environments make these definitions less clear. In order to ensure personnel continue to be effectively screened, virtual worlds and relationships, however benign, may need to be taken into account as part of the vetting process. If so, they will need to be properly understood by the investigating agencies. This paper proposes to outline some of the relevant issues involved in a rapidly evolving online community.
Transcending the Digital Divide: Video Use Communication Models for the English Language Learning Classroom
Authors: Reid McLain Terrill
Published: August 2018

With the development of web 2.0 tools, many companies are rushing to meet the demand and create attractive and useful Educational Technology (EdTech) that appeal to instructors to implement in their classes. Many of these tools include video services that are available to everyone with a connected device. ESL Instructors also look for new and engaging activities and techniques to help their students L2 confidence and language practice. Research shows that video is a powerful and useful tool for educators to boost language learning in the classroom. When deciding to implement video in the classroom, it is essential to understand the different attributes that students experience surrounding the consumption, the creation, and interaction with video. To effectively implement video in the English class it is also necessary to understand how videos replicate elements of the communication process to determine what kind of—if any—interaction will take place. Once the attributes are understood, and the communication model is chosen, teachers can select a tool that fits their pedagogical practice and logistical situation. This paper explores the justification and use categories of video in the context of English language learning, introduces the idea of Video Use Communication Models to help instructors choose a tool that will align with their pedagogical goals, and advocate the promotion of video solutions that allow affordable and available access for an English teacher who wants to use video.
Trinta anos esta noite: busca por segurança e medidas autoritárias na Constituição federal de 1988
Authors: Augusto Acácio
Published: August 2018

Este texto é um breve ensaio que aponta algumas leituras críticas sobre a permanência do elemento autoritário e militar no texto constitucional de 1988. Apresenta situações atuais que demonstram como esse autoritarismo de Estado segue sendo praticado. Afirma a urgência em romper com essa configuração institucional da democracia securitária legada do período ditatorial e recusa a paralisia político-social diante dela.
Direito internacional privado e poder local: a necessária valorização de soluções regionais para conflitos globais
Authors: Rigo Santin Janaína , Leidens Letícia
Published: August 2018

O presente artigo, pelo método dialético, problematiza a questão da aplicação do direito internacional privado a conflitos entre cidadãos de países diversos, questionando quais os órgãos de jurisdição internacional cabíveis para a solução desses casos. Entende-se que, em função de sua localização mais próxima aos cidadãos, a Organização dos Estados Americanos pode se mostrar um importante espaço de decisões envolvendo cidadãos latino-americanos, eis que composta por um reduzido número de países que comungam de aspectos identitários comuns, os quais por certo têm melhores condições de conhecer e entender as necessidades locais, as identidades e a cultura dos cidadãos dos países signatários envolvidos no conflito. Quando se trata de direito internacional e órgãos de jurisdição supranacional, entende-se que é preciso valorizar o poder local e as soluções adotadas por órgãos mais próximos dos cidadãos e das nações envolvidas, pois assim estarão sendo valorizadas a cultura, a identidade e a forma de organização regionais, em detrimento de soluções de caráter uniformizador em âmbito global.
O tecido social da universidade brasileira e a expressão cultural de uma crise
Authors: Pires Cecilia
Published: August 2018

A universidade brasileira traz em sua história o vestígio da situação colonial vivida no país, produzida pelos colonizadores portugueses. As relações sociais, políticas, culturais e econômicas encontradas na sociedade civil, em sua relação com o Estado, estão expressas na vida universitária. Nos episódios de duas ditaduras marcantes, o período do Estado Novo, na era Vargas, e o golpe civil-militar de 1964, a universidade sofreu o impacto de reformas que estabeleceram estruturas de ensino com viés autoritário, próprio desses regimes. Especialmente, as reformas de base do período de João Goulart foram abortadas, e o regime ditatorial produziu a reforma modernizadora de 1968, que traduz a submissão dos governantes militares às decisões de organismos norte-americanos. Muito intelectuais denunciaram e lutaram por uma universidade pública, democrática e de qualidade e deixaram suas contribuições. Anseia-se e luta-se ainda hoje para que a universidade brasileira se torne um lugar de debate democrático, com avanços sociais fundamentados em valores éticos.