Search

Copyright of Journal of Materials Engineering / Cailiao Gongcheng is the property of Journal of Materials Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

C/C-SiC composites were prepared by chemical vapor infiltration （CVI） and reactive melt infiltration （RMI） using carbon fiber preforms with stitched and needle-punched structures. The microstructure and pore characteristics of C/C porous composites obtained from the two structural preforms， as well as the microstructure and flexural properties of C/C-SiC composites， were systematically studied. Results show that the pore size of stitched C/C porous composite is multimodal distribution， and the pores are mostly inter-bundle pores. The pore size of needle-punched C/C porous composite is unimodal distribution. Due to the addition of mesh， some inter-bundle pores are transformed into connected small pore networks. The simulated absolute permeability in the Z direction of the latter is slightly greater than that of the former， which is conducive to the subsequent RMI densification process of the latter （high density， low open-porosity and low residual metal）. The average flexural strength of stitched C/C-SiC composites is higher than that of needle-punched C/C-SiC composites， both of which exhibit a “pseudo plastic” fracture mode. The needle-punched C/C-SiC composite has a higher density and lower residual Si content， but its fiber volume content is lower， and the integrity of long straight fibers is poor， resulting in lower load-bearing property of the composite.

The exploration of unleaded free-cutting Cu40Zn brass with excellent mechanical and tribological properties has always drawn the attention of researchers. Due to its attractive properties combining metals and ceramics, Ti3AlC2 was added to Cu40Zn brass using high-energy milling and hot-pressing sintering. The effects of Ti3AlC2 on the microstructure, mechanical and tribological properties of Cu40Zn-Ti3AlC2 composites were studied. The results showed that Ti3AlC2 could suppress the formation of ZnO by adsorbing oxygen impurity and promote the formation of the β phase by releasing the β-forming element Al to the substrate. The hardness and wear resistance of Cu40Zn-Ti3AlC2 composites increased with increasing Ti3AlC2 content from 0 to 5 wt.%. The proper Ti3AlC2 additive was beneficial to both the strength and plasticity of the composites. The underlying mechanisms were discussed. [ABSTRACT FROM AUTHOR]

Based on the self-made Zr0.5Hf0.5C precursor and commercial liquid polycarbosilane, C/Zr0.5Hf0.5C-SiC composite was successfully prepared by the precursor impregnation and pyrolysis(PIP) process. The influence of the thickness of pyrolytic C coating on the structure and bending properties of composite materials was studied. The results show that the self-made Zr0.5Hf0.5C precursor can be converted into Zr0.5Hf0.5C solid solution at a relatively low temperature of 1400 ℃. Because of its good permeability, the transformed Zr0.5Hf0.5C matrix exists in both the inter-bundle and intra-bundle regions of the C/Zr0.5Hf0.5C-SiC composite, which presents as a layered structure on SiC matrix. The phase composition of C/Zr0.5Hf0.5C-SiC composite mainly includes C, SiC and Zr0.5Hf0.5C. The densities of three groups of composites with different thicknesses of pyrolytic C coating (0.67, 0.84, 1.36 μm) are 2.07, 1.99, 1.98 g/cm3, respectively. SiC content in the composite decreases with the increase of the thickness of pyrolytic C coating. The three groups of composites with different thicknesses show pseudoplastic fracture mode during bending loading tests, bending strength, bending modulus and fracture toughness are above 410 MPa, 60 GPa and 15.6 MPa·m1/2, respectively. Good interface bonding and pre-introduced SiC matrix are the keys to obtaining excellent bending properties of C/Zr0.5Hf0.5C-SiC composites.

Copyright of Journal of Materials Engineering / Cailiao Gongcheng is the property of Journal of Materials Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Harbin Institute of Technology. Social Sciences Edition / Haerbin Gongye Daxue Xuebao. Shehui Kexue Ban is the property of Harbin Institute of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract Ternary-layered compound Ti 2 AlN reinforced TiAl matrix composites with a novel network structure were successfully fabricated through hot-press sintering technique. The microstructure and flexural performance at elevated temperatures were systematically investigated. The results manifest that the in situ synthesized Ti 2 AlN distributes around the lamellar TiAl matrix to form the network structure, which transforms from the particle with a size of 1–3 µm to the larger block as the volume fraction extends from 15% to 20%. Besides, the unique structure contributes to the significant refinement of the TiAl matrix. As the volume fraction of Ti 2 AlN gradually increases to 20%, the high-temperature flexural performance is first strengthened and then deteriorated. 15 vol%Ti 2 AlN/TiAl displays the optimum flexural property with the strength of 791.6, 767.2 and 590.9 MPa at 700, 800 and 900 ℃, which is improved by 28.0%, 35.9% and 25.7% in contrast with that of TiAl alloy. As specifically elucidated through the fracture morphologies, the enhanced flexural property originates from the effective inhibition of Ti 2 AlN particle to the crack propagation, the extended path caused by the crack deflection, as well as the refinement of the TiAl matrix. [ABSTRACT FROM AUTHOR]

In this paper, acrylonitrile-butadiene-styrene (ABS) nanocomposite foams are produced using carbon dioxide through the solid-state batch process. Microcellular closed-cell foams are produced with the relative density ranging from 0.38 to 0.97. The effects of the processing conditions on the density, morphology, and flexural properties of ABS and its nanocomposite foams are studied. It is found that nano-clay particles, as nucleating sites, play an important role in reducing the size of cells and increasing their number in the unit volume of foamed polymer, as well as increasing the flexural modulus of foam through reinforcing its matrix. [ABSTRACT FROM AUTHOR]

Abstract: Carbon nanotubes (CNTs) were in-situ grown in carbon felts using ferric chloride as catalyst and natural gas as carbon precursor via thermal gradient chemical vapor infiltration (TGCVI). Subsequently, the carbon felts were densified to obtain CNT reinforced carbon/carbon (C/C) composites in the same furnace. Effects of CNTs on the microstructure and flexural property of C/C composites were investigated by polarized light microscopy, Raman spectroscopy, scanning electron microscopy and universal mechanical testing machine. The results of PLM observation and Raman analysis showed that CNTs have two-sided effects on the microstructure of pyrocarbon: the pyrocarbons in the region without CNTs show medium texture; while, in the region full of CNTs, the microstructure was low-textured or even isotropic though the TGCVD conditions would lead to the deposition of pure low texture pyrocarbons. Analysis based on stress–strain curves demonstrated that the flexural strength increased first and then decreased with the CNT content increasing. When the CNT content was 5.23wt%, the flexural strength was maximum and had a nearly 35% improvement compared with pure C/C composite. Besides, after adding CNTs, the flexural modulus of the composites decreased and the ductility increased obviously, indicating CNTs can toughen C/C composites. [Copyright &y& Elsevier]

In this study, maize stalk tegument separated from the maize pith was crushed to obtain the fiber. The cross-linking maize starch adhesives considering four main factors (water content, gelatinization temperature, NaOH as gelatinization agent and Na2B4O7 10H2O as cross-linking agent) with three levels were prepared based on an orthogonal test scheme L9(34) in order to increase the water-resisting property and the bonding strength of the common maize starch adhesives. The bonding properties of maize starch adhesives were characterized using shearing strength under compression loading. Physical models of fiber reinforced composites were established according to the microstructure analysis of the four species of insects' elytra including Protaetia orentalis, Copris ochus Motschulsky, Anoplophora chinensis and Cytister bengalensis Aube, which will provide the biomimetic models for the biomimetic laminated boards. The maize stalk fiber biomimetic laminated boards were prepared based on the structural models of the elytra material. The flexural strength and flexural elastic modulus of the biomimetic boards were examined. The results showed that the fiexural strengths of the single layer jute fiber, -reinforced maize stalk fiber boards and the dual layer jute fiber reinforced maize stalk fiber boards are higher than those of the common maize stalk fiber boards and the other three groups of jute fiber hybrid reinforced stalk fiber boards because of the biomimetic laminated design. [ABSTRACT FROM AUTHOR]

• The fiber dispersion characteristics are determined by backscattering technique. • The flexural and uniaxial compression properties of CW-SPFRCC are studied. • The compression constitutive models for CW-SPFRCC are established. • Microstructure analysis reveals the modified mechanism of CW in SPFRCC. Calcium carbonate whisker (CW) is used to modify the steel-PVA hybrid fibers reinforced cementitious composites (SPFRCC). The addition of CW result in excellent mechanical properties and considerable economic benefit owing to its microscopic reinforcement effect and low cost. In this study, the flexural behavior, fiber distribution characteristics and compression response of CW modified steel-PVA hybrid fibers reinforced cementitious composites (CW-SPFRCC) are investigated by three-point bending test, image processing technique and uniaxial compression test, respectively. The results indicate that the addition of CW can effectively improve the flexural properties of SPFRCC because of the crack resistance and filling effect at microscale. The best fiber distribution characteristics are observed in CW10-S15P05 due to the presence of CW that modify the adhesion and flowability of cement matrix. The uniaxial compression strength, peak strain, elastic modulus and Poisson's ratio of CW-SPFRCC are increased by 37.1%, 40.2%, 3.7% and 30.7%, respectively. Meanwhile, the uniaxial compression constitutive model is proposed to describe the compression stress–strain relationship of CW-SPFRCC based on the experimental results. Moreover, the microstructure analysis demonstrates that the modification mechanism of CW in SPFRCC is attributed to the interface improvement, CW pull-out, CW slippage, and CW rupture. [ABSTRACT FROM AUTHOR]