bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Novel Technique for the Measurement of the Effective Thermal Conductivity of Thermal Insulating Materials up to 1000°C
Authors: Gao Zenghua , Wang Yang , Zhou Jinshuai , Yuan Tao , Wu Xian 
Published: November 2019

Abstract
A novel large temperature gradient steady-state technique for the measurement of the effective thermal conductivity of thermal insulating materials up to 1000°C has been developed. With the incorporation of a vacuum system, the mean effective thermal conductivity of thermal insulating materials under certain temperature gradient in air and/or inert atmospheres with the gas pressure range of 10−2 Pa to 105 Pa can be measured. A transforming method was proposed to derive the true effective thermal conductivity from the as-measured mean effective thermal conductivity. By evaluating the measurement uncertainty of the constructed testing apparatus as well as comparing experimentally with the guarded hot plate test results, the measurement accuracy of this technique was determined to have an accuracy of less than 8.5%.
Determining Structural Damage of Stone Curtain Walls by Dynamic Method
Authors: Zheng Dezhi , Bao Yiwang , Liu Xiaogen 
Published: November 2019

Abstract
Dry hanging stone curtain wall is widely used in the building envelopes, but it was of ten deemed as a safety risk. The damage of the back anchorage structure may result in the urban disaster accident due to the falling down of the tone panel. There is no yet effective detection method because the damage part is hidden behind the panel. In this paper, a dynamic detection method is presented to monitor the damage degree of the anchorage structure on the back of the panel and to determine the damage location. Experiments indicate that the first three steps of natural frequency of the stone panel declined, with the increase of the damage degree of the anchorage structure. The degradation of the natural frequency can be used to identify the degree of back connection damage. In addition, the relationship between the damage position of the back connection and the modal parameters of the stone was investigated. It was found that the change of the damaged location significantly affected the modal vibration of the stone panel and the relative discriminant method is proposed to determine the damage position.
Fabrication and Properties of 3D Mullite Fiber-Reinforced Al2O3 Matrix Composites Prepared by Sol-Gel Process
Authors: Geng Guangren , Zhou Changling , Zhou Yuanyuan , Wang Kaiyu , Yang Fanghong , Cheng Zhiqiang , Liu Futian 
Published: November 2019

Abstract
Fiber toughening is an effective method to improve the brittleness of ceramic materials. In this paper, three-dimensional mullite fiber reinforced alumina ceramic matrix (3D mullitef/Al2O3) composites were prepared by sol-gel process. Alumina sol was prepared by two ways in the inorganic aluminium salt method, and the alumina sol with good fluidity and high solid content was used as a precursor. The preparation process of alumina sol was studied by XRD and TGA-DSC. The results show that the sol is transformed into Al2O3 at about 1100°C, and the crystal phase is α-Al2O3 phase. The mechanical properties of the sample were analyzed by three-point bending test. The microstructure of the fractures was observed by scanning electron microscopy. The results show that with the increase of the immersion cycles, the density of composites increases continuously, and the toughening mechanism of continuous fiber extraction, interfacial debonding and crack deflection is fully utilized during fracture, which is characterized by ductile fracture behavior and achieved the purpose of toughening.
Processing and Properties of Oxide Fiber Reinforced Alumina Composites
Authors: Yang Rui , Qi Zhe , Gao Ye , Yang Jinhua , Zhou Yiran , Liu Hu , Jiao Jian 
Published: November 2019

Abstract
A simple, low-cost processing method involving slurry infiltration, hot pressing and subsequent densification was developed to manufacture NextelTM 440fiber reinforced alumina (N440/A) composites. The influence of alumina sol on the densification of alumina matrix was investigated through XRD and SEM. Results showed that the introduction of alumina sol into slurry promoted the densification of alumina matrix. Then the effect of sintering temperature from 1100°C to 1300°C on mechanical properties of N440/A composites was investigated. The optimized composite material exhibited a tensile strength > 140MPa and flexural strength > 170MPa.The analysis of the fracture surface suggested that the porous matrix played a vital role in the toughening mechanism of N440/A composites. Numerous matrices attach to pullout fibers of N440/A composites, indicating that matrix cracks propagate through micro-pores in the matrix and deflect at the fiber/matrix interface effectively.
Effect of Microwave Sintering on Morphology and Structure of Porous Al2O3-SiO2 Ceramics
Authors: Yue Xian , Chen Junyong , Li Huaxin , Yu Xianbo , Xiang Junhui 
Published: November 2019

Abstract
Mesoporous Al2O3-SiO2 ceramics were prepared by one-pot method. In this process, aluminum chloride hexahydrate (AlCl3·6H2O) and tetraethyl orthosilicate (TEOS) acted as the common precursors, and then the composite porous ceramics were obtained by vacuum freeze-drying (FD). Subsequently, the samples were sintered at 800°C, 1000°C and 1200°C by muffle furnace and microwave sintering device (MSD) respectively, and the crystalline transformation process has been characterized by X-ray powder diffraction (XRD). Furthermore, the properties of porous materials were characterized by Fourier transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results indicate that the sintered samples still retain super high specific surface area (over 200m2/g), and microwave sintering can greatly reduce the crystallization temperature of porous alumina ceramics. This rapid sintering method also transforms porous ceramics from leaf-like structure to granular structure, and finally forms nanorod structure. The sintering mechanism was explained from the point of view of crystal growth law.
Effect of Different Crystal Form Nanometre Zirconia on Thermal Shock Resistance of Magnesia Ceramic
Authors: Wu Feng , Xue Zongwei , Li Xinwei , Xu Na , Sheng Kaixun , Luo Xudong 
Published: November 2019

Abstract
The magnesia ceramic specimens were prepared using high purity magnesia powder, monoclinic nanometre zirconia, tetragonal nanometre zirconia, cubic nanometre zirconia as starting materials in order to improve thermal shock resistance of magnesia ceramic. The specimens were sintered at 1550°C for 2 hours under air atmosphere. The thermal shock resistance and sintering property of magnesia ceramics with different crystal nanometre zirconia additives were investigated. The results show that density of the specimens with zirconia is improved due to the dispersal distribution of zirconia in periclase grain boundary. The sintering property of magnesia with zirconia additives are considerably promoted. The thermal shock resistance of the specimens with tetragonal zirconia or cubic zirconia is improved due to second crystalline phase toughening mechanism of zirconia.Thermal shock resistance of specimens with monoclinic zirconia is improved due to phase transformation toughening mechanism and second crystalline phase toughening mechanism of zirconia.
Preparation and Heat Transfer Mechanism of ZrO2 Fiber Flexible Heat-Insulating Materials
Authors: Han Ding , Wang Chunpeng , Sun Xiankai , Zhang Shichao , Sun Haoran , Fang Kai , Chen Yufeng 
Published: November 2019

Abstract
The high temperature insulation material of zirconia fiber and carbon fiber (CZ) was prepared by wet molding process using chopped carbon fiber and zirconia fiber as raw materials. The thermal conductivity of the block was measured by high temperature flat plate thermal conductivity instrument. The effects of content of zirconia fiber, diameter of zirconia fiber and material density on CZ thermal conductivity were studied. The heat transfer mechanism of CZ was also studied. The results showed that the heat conductivity of CZ insulation material could be reduced with the reducing the diameter of zirconia fiber. The heat conductivity of CZ insulation material also could be reduced with increasing the content of zirconia fiber.
The Effect of Particle Size of Silicon Nitride Powder on Properties of Silicon Nitride Ceramic Balls
Authors: Li Honghao , Sun Feng , Dong Tingxai , Xu Xuemin 
Published: November 2019

AbstractThe micron-sized silicon nitride raw powder was ball-milled into submicron powders of different particle sizes, the silicon nitride ceramic balls were prepared by gas pressure sintering with cerium oxide and aluminium oxide as sintering aids. The microstructures and phase composition of the ceramic balls were characterized by SEM and XRD. The effects of particle size of silicon nitride powders on sintering properties and mechanical properties were investigated. The results show that the relative density, hardness and crushing load of silicon nitride ceramic balls increased with the decrease of the particle size of silicon nitride ceramic powder, and the ceramic balls prepared by small particle size have low porosity and uniform grains. The powder with the longest grinding time has a particle size of 0.40 μm, and the density of the silicon nitride ceramic ball is 3.245 g/cm3, the hardness is15.2 GPa, the fracture toughness is 7.6 MPa·m−2, and the crushing load ratio of the steel ball is 51.2%.
Oxidation Behavior of SiC/Si-B-C-N Ceramic Matrix Composites
Authors: Qiu Haipeng , Chen Mingwei , Xie Weijie , Zhang Bingyu , Liu Shanhua , Luo Wendong , Ma Xin 
Published: November 2019

Abstract
Silicon carbide fiber reinforced Si-B-C-N (SiC/Si-B-C-N) ceramic matrix composites were manufactured through polymer impregnation pyrolysis (PIP) process with SiC fiber as disperse phase and Si-B-C-N ceramic as continuous phase. Thermal stability of SiB-C-N ceramic and the high temperature oxidation behavior of SiC/Si-B-C-N ceramic matrix composites were studied. Results showed that the introduction of boron and nitrogen element restrained the growth of SiC grain and the formation of crystalline phase transformation effectively, and could help to keep the amorphous state up to 1400°C. In addition, SiC/Si-B-CN ceramic matrix composites possessed excellent high temperature oxidation resistance with bending strength retention rate of 80.57% after oxidation test at 1200°C for 100 hours due to the formation B2O3 or borosilicate glass from the oxidation of boron element. Liquid B2O3 or borosilicate glass with suitable fluidity could fill the pores and cracks in the interior which acted as a protective layer and lowered oxygen diffusivity according to the morphology and component analysis. Therefore, SiC/Si-B-C-N ceramic matrix composites possessed excellent oxidation resistance for a wide temperature range.
Effect of Boron Carbide Additive on SiC Ceramic Sintered by Solid-Phase Method under Ar Atmosphere
Authors: Zhou Shicong , Chen Changlian , Liang Xin , Ji Jiayou , Huang Zhiliang , Xu Man , Ding Gangqiang , Zhang Hongliang 
Published: November 2019

Abstract
With boron carbide (B4C) as sintering additives, silicon carbide (SiC) ceramics were prepared in 2100°C by solid-phase sintering under argon atmosphere. The change of microstructure, phase composition and density for all sintered samples were studied. The results showed that with the increase of B4C addition, the density of SiC ceramic was significantly increasing between 0-4 wt% of B4C addition and slightly increasing between 4-8 wt%. XRD analysis showed that all the ceramics without B4C were SiC-6H crystal, while those with B4C contained SiC-4H crystal, B4C turned SiC-6H to SiC-4H, and the more B4C added, the more change it made. SiC ceramic particles changed from equiaxial shape without B4C to flake shape with B4C added, and the particle sizes increased significantly with the amount of B4C additive.
Effect of Machining Processes on Mechanical Properties of SiC/SiC Composites
Authors: Xie Weijie , Qiu Haipeng , Guan Hong , Wang Qiming 
Published: November 2019

Abstract
The purpose of this study was to investigate the effects of different machining processes on mechanical properties of SiC fiber reinforced SiC matrix (SiC/SiC) composites. SiC/SiC composites were prepared by polymer impregnation pyrolysis (PIP) progress with polycarbosilane (PCS) as impregnant and SiC fiber as reinforcement. The tensile strength at room temperature and high temperature of the 2.5D braided composites were measured and analyzed after grinding process and laser process. It was found that the tensile strength of the composites with laser cutting was higher than that with grinding cutting, especially at high temperature. While the tensile strength of the composites with laser surface machining was lower than that with grinding surface machining.
The Effect of PyC/SiC Compound Interphase on the Properties of PIP SiC/SiC Composite
Authors: liu Shanhua , Qiu Haipeng , Liu Shijian , Wang Ling , Zhang Bingyu , Chen Mingwei , Xie Weijie , Liang Yanyuan 
Published: November 2019

Abstract
In order to improve the properties of SiC/SiC composite, chemical vapor infiltration (CVI) process was applied for fabricating the PyC/SiC compound interphase. Precursor infiltration and pyrolysis (PIP) process was used to fabricate SiC matrix. Then an investigation was carried out for the effect of PyC/SiC compound interphase thicknesses on the properties of the composites. According to the results, it was found that the mechanical properties of composites with the PyC/SiC compound interphase are much higher than those of composite with only PyC interphase. The flexural strength, flexural modulus, fracture toughness and interlaminar shear strength of the composites increase gradually when the thickness of CVI SiC interphase is lesser than 2 μm. Further increase of the thickness of CVI SiC interphase to 4μm leads to a continuous increase on the modulus of the composites, while a decrease trend occurs on the flexural strength, fracture toughness and interlaminar shear strength of the composites because of the different coefficients of thermal expansion of the CVI SiC interphase and the PIP SiC matrix. SiC/(PyC/SiCx)/SiC composites showed the better properties of oxidation resistance than those of SiC/PyC/SiC composite. It was due to the survived PyC interphase protected by CVI SiC interphase when the oxygen diffuses into the compound PyC/SiCx intherphase.
Preparation of SiCf/SiC Composites with Low Porosity by Liquid Composite Moulding-Pyrolysis Process
Authors: Wang Xiaomeng , Zhang Bingyu , Zhao Yuliang , Wang Ling , Qiu Haipeng 
Published: November 2019

AbstractTraditionally, Polymer infiltration and pyrolysis (PIP), chemical vapor infiltration (CVI) and melt infiltration (MI) are main processes to fabricate continuous silicon carbide fiber reinforced silicon carbide matrix (SiCf/SiC) composites, one of attractive potential high temperature structural materials. However, long preparation period and high porosity are still problems for further applications. Especially, porosity is crucial to the mechanical properties. Liquid composite moulding-pyrolysis (LCMP) used liquid SiC precursor to decrease the open porosity to 5% with no more than 11 cycles of infiltration and pyrolysis. Mechanical properties like bending strength was investigated with different thickness of pyrolitic carbon (PyC) interface and pyrolysis cycles. The bending strength reached 585 MPa with 200 nm PyC interface under 1200°C pyrolysis temperature. Thus, LCMP process offers exciting opportunities to improve performance of SiCf/SiC composites.
Effect of Si Content on Melt Infiltration Method of SiCf/SiC-Ti3SiC2
Authors: Zhou Y R , Jiao J , Jiang Z Y , Lv X X , Yang R , Qi Z 
Published: November 2019

Abstract
SiCf/SiC composites have attracted wide attention as thermo-structural materials owing to its extraordinary properties at elevated temperature. To further improve the toughness of SiCf/SiC, Ti3SiC2 is used as the reinforcement of SiC matrix. In this study, the effect of Si content on the formation of Ti3SiC2 was discussed. The melt Si infiltration method was used to prepare the SiC matrix, whichTi3SiC2phase was in-situ formed from the reaction between TiC, C and Si during the infiltration process. X-ray diffractometry (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were determined to characterize the phase constitution and microstructure of the matrix. The results demonstrate that the synthesis of Ti3SiC2 was depended on the amount of Si during the molten Si infiltration. The small amount of Si could resulted in the incomplete infiltration reaction. TiSi2 was obtained at the presence of excessive Si. Thus appropriate amount of Si promotes the formation of Ti3SiC2 and improves the purity.
BN/SiC Coating on SiC Tows Prepared by Chemical Vapor Infiltration
Authors: Qi Zhe , Lv Xiaoxu , Zhao Wenqing , Zhu Shizhen , Jiao Jian 
Published: November 2019

Abstract
Boron nitride (BN) and silicon carbide (SiC) coatings were prepared in sequence on desized SiC tows by chemical vapor infiltration (CVI) at the temperature of 950°C. BN was synthesized by the reaction between boron trichloride (BCl3) and ammonia (NH3) while SiC was from the thermal decomposition of methyl trichlorosilane (MTS). The thickness of the coatings was uniform on a certain cross section of a monofilament, and the thickest/thinnest ratio is less than ∼2 across the whole SiC tows for both SiC and BN coatings, as observed by scanning electron microscopy (SEM). Distinct β-SiC powder X-ray diffraction (XRD) pattern was obtained for as-prepared CVI SiC while as-prepared BN coating only showed a bump and a tiny peak corresponding to hexagonal BN (h-BN). This result was verified by transmission electron microscopy (TEM) images, in which CVI BN only had curved diffraction fringes within small pockets, known as turbostractic structures(t-BN). However, t-BN possesses similar short-range structure to h-BN as demonstrated by 11B solid-state NMR spectrum. SiCf/SiC minicomposites using the interphase coating mentioned above is currently under investigation.
Influence of the content of ZrxAlyCz on properties of ZrB2-ZrxAlyCz Composite Ceramics Fabricated by Spark Plasma Sintering
Authors: Guo Qilong , Pang Jianli , Gan Jizhong , Junguo LI , Zhang Lianmeng 
Published: November 2019

Abstract
ZrB2/ZrxAlyCz composite ceramics with different volume contents of ZrxAlyCz were fabricated by the spark plasma sintering. The sintering behavior, microstructure, mechanical properties and oxidation resistance were studied. The results indicated that sinterability of the composites was remarkably improved by addition of ZrxAlyCz compared to the single-phase ZrB2 ceramic. As the content of ZrxAlyCz increased, both the Vickers hardness and Young’s modulus of the composites first increased and then decreased. The fracture toughness of the ZrB2-40vol% ZrxAlyCz composite was 3.56 MPa·m1/2, which increased by approximately 70% compared to the monolithic ZrB2 ceramic. As increasing the content of ZrxAlyCz, the oxidation resistance of composite ceramics was obviously enhanced. The oxidation-resulted increase in weight of composite ceramic with 20vol% ZrxAlyCz was the best performance in oxidation resistance at 1500 °C. The high-temperature oxidation resulted in dense and stable Al-B-O glass due to adding ZrxAlyCz into the composite ceramics, those resulting products effectively blocked the oxygen atoms entering into the ceramic matrix.
Effect of Oxidation Exposure on Flexural Strength of Hot-Pressed ZrB2-SiC Composites with Cr3C2 Additives
Authors: Guo Shuqi 
Published: November 2019

Abstract
In this study, the effect of oxidation exposure on room temperature flexural strength was examined in 3 and 5 wt% Cr3C2-containing ZrB2-20 vol% SiC composites exposed to air at different temperatures between 1100°C and 1300°C, for up to 100 h. The oxidation products determined by X-ray diffraction consisted of ZrO2, SiO2, Cr2O3 and ZrSiO4. After 100 h of oxidation, the flexural strength of the two compositions was evaluated at room temperature by four-point bending test. The results show that the strength retention displayed by the two compositions depended on the amount of Cr3C2 additives. For 3 wt% Cr3C2composition, the flexural strength slightly increased after 100 h of oxidation at 1100°C, however, the strength substantially degraded after 100 h oxidation at 1200°Cand 1300°C. For 5 wt% Cr3C2 composition, on the other hand, the flexural strength decreased after 100 h of oxidation between 1100°Cand 1300°C. Additionally, the flexural strength was higher for 3 wt%Cr3C2 composition than for 5 wt%Cr3C2one in the oxidation temperature range 1100°C to 1300°C. The strength decrease was associated with the formation and coarsening of defects in the oxidized layer and the delamination of the outermost thinner dense oxide layer.
Processing and Properties of Laminated ZrB2-Mo5SiB2 Ceramic Composites Fabricated by Tape Casting and Hot Pressing Sintering
Authors: Zhao Pengbo , Zhao Xiaotong , Wang Hailong 
Published: November 2019

Abstract
The slurry of ZrB2-Mo-Si-B have been prepared using the polyethylene glycol-800 (PEG800) and polyvinyl butyral (PVB) as dispersant and binder respectively. The effects of different additive concentration on the fluidity of the slurry were studied. When the amount of dispersant and binder were 0.2wt%, 4wt% and R value were 1.0, the slurry was most suitable for casting, and the green tape were smooth and flexible. ZrB2-Mo-Si-Blaminated structure ceramics have been successfully prepared by tape casting and hot-pressure sintering at 1900°C for 1h under a pressure of 30 MPa in argon gas. The highest flexural strength and fracture toughness of sintered samples at room temperature were 490±10 MPa and 7.73 ± 0.56 MPa·m1/2, respectively.
Effect of SiC Content on the Microstructure and Properties of Zr2Al4C5/SiC Composites in situ Fabricated by Spark Plasma Sintering
Authors: Guo Qilong , Wang Jing , Pei Junjun , Li Junguo , Zhang Lianmeng 
Published: November 2019

Abstract
Zr2Al4C5/SiC composite ceramics were successfully fabricated from the powder mixture of Zr, Al, C and SiC by spark plasma sintering method. The composition-dependent densification, phase evolution, microstructure and mechanical properties of the composite ceramics were studied. With increasing the SiC content in the starting powder mixture, the densification behavior of sintered samples was promoted. It is found that the as-sintered products are mainly composed of Zr2Al4C5 matrix and SiC reinforcement, and the fine SiC particles tend to disperse on the matrix grain boundaries. Besides, the addition of SiC particles can evidently hinder the coarsening of Zr2Al4C5 grains. Both the Vickers hardness and Young’s modulus of composites ceramics gradually increase as increasing the SiC content. The fracture toughness of the composites decreases first then increases with the increase in the SiC and the Zr2Al4C5/30vol%SiC sample possesses the maximum value of 4.4MPa·m1/2.
Effect of He2+ Ion Irradiation on the Crystal Structure of Non-stoichiometric Sm2+xZr2-xO7-x/2 (x = 0, 0.2, 0.4, 0.6)
Authors: Feng Hanghang , Qu Zhixue , Sun Yuan , Ji Yarou 
Published: November 2019

Abstract
In this paper, a series of non-stoichiometric Sm2+xZr2-xO7-x/2 (x=0, 0.2, 0.4, 0.6) were synthesized by chemical co-precipitation method. He2+ ion irradiation experiments were carried out with irradiation energy of 500 KeV and irradiation flux of 5×1016 ions/cm2. Effect of He2+ ion irradiation on the crystal structure was characterized by XRD, GIXRD, and Raman spectroscopy. The XRD patterns show that all the peaks shift to lower diffraction angles and the characteristic peaks of pyrochlore structure weaken after irradiation, which suggests an expansion of the lattice and the degeneration of pyrochlore structure. Moreover, the GIXRD patterns reveal the existence of an irradiated layer on the surface of the sample.