scholarly journals Hybrid Effect of PVA Fibre and Carbon Nanotube on the Mechanical Properties and Microstructure of Geopolymers

2021 ◽  
Vol 8 ◽  
Author(s):  
Tao Meng ◽  
Xiufen Yang ◽  
Yue Yu ◽  
Hongming Yu ◽  
Miaozhou Huang
Keyword(s):  
Mechanical Properties ◽  
Carbon Nanotubes ◽  
Bending Strength ◽  
Group Analysis ◽  
Strengthening Mechanism ◽  
Magic Angle Spinning ◽  
Nuclear Magnetic Resonance Analysis ◽  
Magic Angle ◽  
Strengthening Effect ◽  
Wide Range

The concept of geopolymers has been widely studied since it was proposed. However, the wide range of applications of geopolymers is affected by brittleness and poor crack resistance. In this study, the mechanical properties of geopolymers with single-doped PVA fibres, single-doped carbon nanotubes, and mixed PVA fibers and carbon nanotubes were studied respectively first. It was found that PVA fibres and carbon nanotubes had a positive effect on improving the mechanical properties of geopolymers, especially bending strength and flexural strength. Moreover, the incorporation of PVA fibre could improve the damage morphology of geopolymers. Additionally, the phase analysis, structural group analysis, and strengthening mechanism were studied via scanning electron microscopy, mercury intrusion porosimetry analysis, X-ray diffraction pattern characterisation, Fourier transform infrared spectroscopy analysis, and magic angle spinning nuclear magnetic resonance analysis. It was found that the strengthening effect of PVA fiber to the geopolymer was primarily a physical strengthening effect, whereas the strengthening effect of carbon nanotubes to the geopolymers was both chemical and physical. Finally, based on the previous study, a multi-scale dual-fibre strengthening mechanism was proposed. Micro-nano fibre composites were used to improve microstructure via physical and chemical effects. This is helpful to improve the performance and application of geopolymers. Furthermore, it lays a preliminary theoretical foundation for engineering applications and technical improvement of geopolymers in the future.

scholarly journals Microstructure and Mechanical Properties of Carbide Reinforced TiC-Based Ultra-High Temperature Ceramics: A Review

Coatings ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1444
Author(s):  
Haobo Mao ◽  
Fuqiang Shen ◽  
Yingyi Zhang ◽  
Jie Wang ◽  
Kunkun Cui ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Carbon Nanotubes ◽  
Solid Solution ◽  
High Temperature ◽  
Bending Strength ◽  
Second Phase ◽  
Strengthening Effect ◽  
Dispersion Strengthening ◽  
The Matrix ◽  
Ultra High Temperature

TiC ceramics have become one of the most potential ultra-high temperature structural materials, because of its high melting point, low density, and low price. However, the poor mechanical properties seriously limit its development and application. In this work, this review follows PRISMA standards, the mechanism of the second phase (particles, whiskers, and carbon nanotubes) reinforced TiC ceramics was reviewed. In addition, the effects of the second phase on the microstructure, phase composition and mechanical properties of TiC ceramics were systematically studied. The addition of carbon black effectively eliminates the residual TiO2 in the matrix, and the bending strength of the matrix is effectively improved by the strengthening bond formed between TiC; SiC particles effectively inhibit the grain growth through pinning, the obvious crack deflection phenomenon is found in the micrograph; The smaller grain size of WC plays a dispersion strengthening role in the matrix and makes the matrix uniformly refined, and the addition of WC forms (Ti, W) C solid solution, WC has a solid solution strengthening effect on the matrix; SiC whiskers effectively improve the fracture toughness of the matrix through bridging and pulling out, the microscopic diagram and mechanism diagram of SiC whisker action process are shown in this paper. The effect of new material carbon nanotubes on the matrix is also discussed; the bridging effect of CNTs can effectively improve the strength of the matrix, during sintering, some CNTs were partially expanded into GNR, in the process of crack bridging and propagation, more fracture energy is consumed by flake GNR. Finally, the existing problems of TiC-based composites are pointed out, and the future development direction is prospected.

Microstructure and Properties of Microwave Sintered 40 wt. % WC Steel-Bonded Carbides

2011 ◽  
Vol 335-336 ◽  
pp. 836-840 ◽  
Author(s):  
Jun Ming Luo ◽  
Zheng Wei ◽  
Ji Lin Xu ◽  
Li Ping Deng
Keyword(s):  
Mechanical Properties ◽  
Phase Transition ◽  
Bending Strength ◽  
Microwave Sintering ◽  
Strengthening Mechanism ◽  
Sintering Behavior ◽  
Transgranular Fracture ◽  
Strengthening Effect ◽  
Steel Matrix ◽  
Conventional Sintering

40 wt. %WC steel-bonded carbides were prepared by microwave sintering. The sintering behavior and mechanical properties of 40 wt. %WC-Fe were investigated in comparison with 0 wt. %WC-Fe. The green compact of 40 wt. %WC-Fe sintered at 1280 °C, the phase transition between WC and Fe is observed, generating new Fe2W2C phase. The phase transition promotes the densification of the sample, which plays a strengthening effect on the material. Microwave sintering possesses even quicker densification than conventional sintering, as well as substantially higher mechanical properties. The microhardness and bending strength of steel-bonded carbides prepared by microwave sintering are 10% ~ 20% higher than the conventional sintering. The microhardness of 40 wt. %WC-Fe is up to 544 HV, eight times higher than that of 0 wt. %WC-Fe and the bending strength of 40 wt. %WC-Fe is three times higher than that of 0 wt. %WC-Fe. Strengthening mechanism of 40 wt. %WC-Fe samples is that the Fe2W2C rigid phase dispersed over the steel matrix is not deformation, and plays the effect of hindering dislocation motion. The fracture mode is mixed intergranular fracture and transgranular fracture, belonging to brittle fracture.

Structure and properties of compact articles from high-alloyed iron powder with adding of boron nitride

2020 ◽  
pp. 39-48
Author(s):  
B. O. Bolshakov ◽  
◽  
R. F. Galiakbarov ◽  
A. M. Smyslov ◽  
◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Boron Nitride ◽  
Grain Boundary ◽  
Bending Strength ◽  
Physical And Mechanical Properties ◽  
Operating Conditions ◽  
Structure And Properties ◽  
Steam Turbines ◽  
Friction Forces ◽  
Wide Range

The results of the research of structure and properties of a composite compact from 13 Cr – 2 Мо and BN powders depending on the concentration of boron nitride are provided. It is shown that adding boron nitride in an amount of more than 2% by weight of the charge mixture leads to the formation of extended grain boundary porosity and finely dispersed BN layers in the structure, which provides a high level of wearing properties of the material. The effect of boron nitride concentration on physical and mechanical properties is determined. It was found that the introduction of a small amount of BN (up to 2 % by weight) into the compacts leads to an increase in plasticity, bending strength, and toughness by reducing the friction forces between the metal powder particles during pressing and a more complete grain boundary diffusion process during sintering. The formation of a regulated structure-phase composition of powder compacts of 13 Cr – 2 Mо – BN when the content of boron nitride changes in them allows us to provide the specified physical and mechanical properties in a wide range. The obtained results of studies of the physical and mechanical characteristics of the developed material allow us to reasonably choose the necessary composition of the powder compact for sealing structures of the flow part of steam turbines, depending on their operating conditions.

Leucite-pollucite structure-type variability and the structure of a synthetic end-member calcium wairakite (CaAl2Si4O12·2H2O)

1998 ◽  
Vol 62 (2) ◽  
pp. 165-178 ◽  
Author(s):  
C. M. B. Henderson ◽  
A. M. T. Bell ◽  
S. C. Kohn ◽  
C. S. Page
Keyword(s):  
Rietveld Analysis ◽  
Structure Type ◽  
Magic Angle Spinning ◽  
Resonance Spectroscopy ◽  
Magic Angle ◽  
Synthetic Sample ◽  
Cation Site ◽  
Wide Range ◽  
Angle Spinning ◽  
Cation Sites

AbstractThe structure of a synthetic end-member wairakite (CaAl2Si4O12·2H2O) has been determined using Rietveld analysis of high-resolution, synchrotron X-ray powder diffraction data, and 29Si and 27Al magic angle spinning nuclear magnetic resonance spectroscopy. The framework in the synthetic sample is more disordered than that in natural wairakite. Ca is distributed over the cavity cation sites M2, M12A, M12B in the approximate proportions 0.8:0.1:0.1, respectively, with M11 being vacant. 29Si MAS NMR data are consistent with about 80% of the Si occupying tetrahedral T11 and T12 sites linked to two Al atoms [Q4(2Al) silicons]. Tetrahedral and cavity cation site disorder are coupled so that Al mainly occupies T2 sites, with Ca in M12A and M12B being balanced by Al in T12A and T12B; T11A and T11B sites appear to only contain Si, in agreement with the M11 site being vacant. The crystal chemistries of the wide range of stoichiometries which crystallize with the leucite/pollucite structure-type are also reviewed, with particular attention being paid to the tetrahedral ordering configurations present in these phases, and the implications to crystallographic phase transitions.

scholarly journals Characterization of nucleosome sediments for protein interaction studies by solid-state NMR spectroscopy

2021 ◽  
Author(s):  
Ulric B. le Paige ◽  
ShengQi Xiang ◽  
Marco M. R. M. Hendrix ◽  
Yi Zhang ◽  
Markus Weingarth ◽  
...  
Keyword(s):  
Solid State ◽  
Nmr Spectroscopy ◽  
Solid State Nmr ◽  
Magic Angle Spinning ◽  
Magic Angle ◽  
Dense Phase ◽  
Binding Studies ◽  
Nmr Studies ◽  
Solid State Nmr Spectroscopy ◽  
Wide Range

Abstract. Regulation of DNA-templated processes such as gene transcription and DNA repair depend on the interaction of a wide range of proteins to the nucleosome, the fundamental building block of chromatin. Both solution and solid-state NMR spectroscopy have become an attractive approach to study the dynamics and interactions of nucleosomes, despite their high molecular weight of ~200 kDa. For solid-state NMR (ssNMR) studies, dilute solutions of nucleosomes are converted to a dense phase by sedimentation or precipitation. Since nucleosomes are known to self-associate, these dense phases may induce extensive interactions between nucleosomes, which could interfere with protein binding studies. Here, we characterized the packing of nucleosomes in the dense phase created by sedimentation using NMR and small-angle x-ray scattering (SAXS) experiments. We found that nucleosome sediments are gels with variable degrees of solidity, have nucleosome concentration close to that found in crystals, and are stable for weeks under high-speed magic angle spinning (MAS). Furthermore, SAXS data recorded on recovered sediments indicate that there is no pronounced long-range ordering of nucleosomes in the sediment. Finally, we show that the sedimentation approach can also be used to study low affinity protein interactions with the nucleosome. Together, our results give new insights into the sample characteristics of nucleosome sediments for ssNMR studies and illustrate the broad applicability of sedimentation-based NMR studies.

scholarly journals Fabrication and Characterization of Polylactic Acid Electrospun Scaffolds Modified with Multi-Walled Carbon Nanotubes and Hydroxyapatite Nanoparticles

Biomimetics ◽  
2020 ◽  
Vol 5 (3) ◽  
pp. 43
Author(s):  
Athanasios Kotrotsos ◽  
Prokopis Yiallouros ◽  
Vassilis Kostopoulos
Keyword(s):  
Mechanical Properties ◽  
Carbon Nanotubes ◽  
Polylactic Acid ◽  
Physical And Mechanical Properties ◽  
Polymeric Materials ◽  
Cost Effective ◽  
Electrospinning Process ◽  
Wide Range ◽  
Multi Walled Carbon Nanotubes ◽  
Walled Carbon Nanotubes

The solution electrospinning process (SEP) is a cost-effective technique in which a wide range of polymeric materials can be electrospun. Electrospun materials can also be easily modified during the solution preparation process (prior SEP). Based on this, the aim of the current work is the fabrication and nanomodification of scaffolds using SEP, and the investigation of their porosity and physical and mechanical properties. In this study, polylactic acid (PLA) was selected for scaffold fabrication, and further modified with multi-walled carbon nanotubes (MWCNTs) and hydroxyapatite (HAP) nanoparticles. After fabrication, porosity calculation and physical and mechanical characterization for all scaffold types were conducted. More precisely, the morphology of the fibers (in terms of fiber diameter), the surface properties (in terms of contact angle) and the mechanical properties under the tensile mode of the fabricated scaffolds have been investigated and further compared against pristine PLA scaffolds (without nanofillers). Finally, the scaffold with the optimal properties was proposed as the candidate material for potential future cell culturing.

scholarly journals A Novel Precipitate-Type Architected Metamaterial Strengthened via Orowan Bypass-Like Mechanism

2020 ◽  
Vol 10 (21) ◽  
pp. 7525
Author(s):  
Zhehao Lu ◽  
Wenyuan Yan ◽  
Pengfei Yan ◽  
Biao Yan
Keyword(s):  
Mechanical Properties ◽  
Volume Fraction ◽  
Deformation Mode ◽  
Strengthening Mechanism ◽  
Fused Deposition Modelling ◽  
Strengthening Effect ◽  
Fused Deposition ◽  
Structure Changes ◽  
The Difference ◽  
Bypass Mechanism

The objective of the study is to investigate the strengthening mechanism of embedded meta-precipitates in the design of architected metamaterials. Four precipitate-type architected metamaterials are designed and prepared by fused deposition modelling (FDM). The difference of mechanical properties and deformation mode of these structures is analyzed. The strengthening effect of the introduced meta-precipitates is then compared with Orowan bypass strengthening mechanism. The similarities and discrepancies of metallurgical hardening principles and that found in architected metamaterials are established. It is found that due to the introduction of embedded meta-precipitates, the deformation of the structure changes significantly from diagonal crushing to a meander route, thus improves the mechanical properties and energy absorption abilities. The hindering effect and the influence of volume fraction of meta-precipitates is similar to Orowan bypass mechanism.

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