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1.
Akhilesh Kumar Swarnakar Omer van der Biest Bernd Baufeld 《Journal of Materials Science》2011,46(11):3802-3811
Young’s modulus and damping behavior is investigated by the impulse excitation technique in vacuum up to 1100 °C for Ti–6Al–4V
components, fabricated by shaped metal deposition (SMD). This is a novel additive manufacturing technique where near net-shape
components are built layer by layer by tungsten inert gas welding. The Young’s modulus decreases linearly from 118 GPa at
room temperature to 72 GPa at 900 °C, followed by a stronger decrease up to 1000 °C and during the first heating a plateau
thereafter. The damping exhibits an exponential increase with temperature superimposed by two peaks around 700 and 900 °C
during the first heating. During cooling and follow-up cycles only the damping peak around 700 °C appears. The change in Young’s
modulus and the damping behavior is interpreted by different processes like α/β transformation, O alloying and grain boundary
sliding. These results indicate that components fabricated by SMD contain a non-equilibrium α phase which transforms to the
β phase at higher temperatures than the equilibrium α phase. Furthermore, the vacuum between 2.4 and 5.3 × 10−4 mbar proved at high temperatures to be not good enough to rule out the contamination by O, which leads to α casing, stiffening,
and hardening. 相似文献
2.
An experimental research was performed on the complete compressive stress–strain relationship for unconfined and confined
concrete after exposure to freeze–thaw cycles. For the unconfined concrete, tests were carried out on three series of prisms
specimens (100 mm × 100 mm × 300 mm) with water/cement ratio of 0.60, 0.54 and 0.48 respectively. While for confined concrete,
two series of tied columns (150 mm × 150 mm × 450 mm prisms) with confinement index of 0.317 and 0.145 were prepared. Analytical
models for the stress–strain relationship of frozen-thawed unconfined and confined concrete were empirically developed respectively.
Through the regression analysis, formulations for the main parameters were established, including the compressive strength,
peak strain and elastic modulus. Compared with the available experimental data, the proposed models were shown to be applicable
to concrete after different numbers of freeze–thaw cycles. 相似文献
3.
The aim of the present work is to study the mechanical properties of poly(vinyl chloride) (PVC)/poly(methyl methacrylate)
(PMMA) blends based polymer electrolytes for lithium ion batteries. The introduction of PVC into PMMA is found to increase
the Young’s modulus value from 5.19 MPa (in pure PMMA) to 6.05 MPa (in PVC:PMMA = 70:30). The different Young’s modulus values
in PVC blends is due to the difference in the cross-linking density provided by PVC with different weight fraction values.
The stress–strain analysis reveals that the mechanical strength of the polymer electrolyte system deteriorated with the incorporation
of LiCF3SO3. The results show that the introduction of salt decreases the Young’s modulus and stress at peak values along with higher
elongation at peak value. The addition of low molecular weight plasticizers to PVC–PMMA–LiCF3SO3 decreases the modulus and stress at peak of the complexes. To be applicable in practical applications, the mechanical strength
of the plasticized films is found to improve with the addition of silica as nanocomposite filler. 相似文献
4.
Synthesis and characteristics of monticellite bioactive ceramic 总被引:1,自引:0,他引:1
Chen X Ou J Kang Y Huang Z Zhu H Yin G Wen H 《Journal of materials science. Materials in medicine》2008,19(3):1257-1263
Mono-phase ceramics of monticellite (CaMgSiO4) were successfully synthesized by sintering sol–gel-derived monticellite powder compacts at 1,480 °C for 6 h. The mechanical
properties and the coefficient of thermal expansion (CTE) of the monticellite ceramics were tested. In addition, the bioactivity
in vitro of the monticellite ceramics was evaluated by investigating their bone-like apatite-formation ability in simulated
body fluid (SBF), and the biocompatibility in vitro was detected by osteoblast adhesion and proliferation assay. The results
showed that the bending strength, fracture toughness and Young’s modulus of the monticellite ceramics were about 159.7 MPa,
1.63 MPa m1/2 and 51 GPa, respectively. The CTE was 10.76 × 10−6 °C−1 and close to that of Ti-6Al-4V alloy (10.03 × 10−6 °C−1). Furthermore, the monticellite ceramics possessed bone-like apatite-formation ability in SBF and could release soluble ionic
products to significantly stimulate cell growth and proliferation. In addition, osteoblasts adhered and spread well on the
monticellite ceramics, which indicated good bioactivity and biocompatibility. 相似文献
5.
6.
Fine-grain SiC-based ceramics have been produced via infiltration of molten silicon into preforms fabricated from SiC and
graphite powders, with a phenol-formaldehyde resin as a binder. The materials thus prepared have a density of 2.70–3.15 g/cm3, dynamic modulus of elasticity from 200 to 400 GPa, compressive strength from 800 to 1900 MPa, bending strength from 150
to 315 MPa, thermal expansion coefficient (KTE) of 4.1 × 10−6 K−1, and thermal conductivity of 140–150 W/(m K). Their properties are compared to those of known silicon carbide materials fabricated
by other processes. The results indicate that the density and physicomechanical properties of the silicon carbide ceramics
depend little on the fabrication process and are determined primarily by the SiC content. Increasing the SiC content from
20 to 99.5 wt % increases the density of the ceramics from 2.2 to 3.15 g/cm3 and leads to an exponential rise in their physicomechanical parameters: an increase in modulus of elasticity from 95 to 430
GPa, in compressive strength from 120 to 4200 MPa, and in bending strength from 70 to 410 MPa. The thermal conductivity of
the ceramics depends very little on the fabrication process, falling in the range 100–150 W/(m K) over the entire range of
SiC concentrations. Their KTE decreases slightly, from 4.3 × 10−6 to 2.4 × 10−6 K−1, as the SiC content increases to 99–100 wt %. 相似文献
7.
T. Shimazu H. Maeda E. H. Ishida M. Miura N. Isu A. Ichikawa K. Ota 《Journal of Materials Science》2009,44(1):93-101
High-damping materials are widely used in engineering fields. In order to increase the precision of vibration control to different
levels, high-damping materials with high-rigidity are required. This study attempts to develop a new high-damping high-rigidity
material using ductile ceramics based on the Al2TiO5–MgTi2O5 system, which has many continuous microcracks along the grain boundaries. Ductile ceramics have high internal friction (Q
−1 = 0.01–0.037), but very low rigidity (<10 GPa). The rigidity of Al2TiO5–MgTi2O5 ceramics was improved by combining them with a polymer such as acrylic resin. The Young’s modulus and internal friction of
the composites of Al2TiO5–MgTi2O5 ceramics and acrylic resin are investigated. They show high-damping capacity (Q
−1 = 0.03–0.04) with high rigidity (E = 50–60 GPa), and their properties depend on those of the polymer. Thus, the composites fabricated using the above method
can serve as high-damping high-rigidity materials. 相似文献
8.
The evolution of Young’s modulus versus temperature has been evaluated in SiC-based hydraulically bonded refractories used
in waste-to-energy (WTE) plants. Two types of low cement castables (LCC) with 60 and 85 wt% of SiC aggregates have been considered.
The study was conducted by the way of a high temperature ultrasonic pulse-echo technique which allowed in situ measurement
of Young’s modulus during heat treatment starting from the as-cured state up to 1400 °C in air or in neutral atmosphere (Ar)
and during thermal cycles at intermediate temperatures (1000 and 1200 °C). For comparison in order to facilitate interpretation,
thermal expansion has also been followed by dilatometry performed in the same conditions. Results are discussed in correlation
with phase transformations occurring in the oxide matrix (dehydration at low temperature, crystallization of phases in the
CaO–Al2O3–SiO2 system) above 800 °C and damage occurring when cooling. The influence of oxidation of SiC aggregates on elastic properties
is also discussed. 相似文献
9.
Polycarbosilane (PCS) ceramic precursor fibers are irradiated in a nuclear reactor and pyrolyzed under inert atmosphere. Bridge
structure of Si–CH2–Si is formed in the irradiated products by the rupture of Si–H bonds and succeeding cross-linking. When irradiated at the
neutron fluence of 2.2 × 1017 cm−2 under N2 atmosphere, the gel content and ceramic yield at 1,273 K of PCS fibers are up to 80% and 94.3%, respectively, and their pyrolysis
products are still fibrous, which illuminates that the infusibility of PCS fibers has been achieved. FT-IR spectra indicate
that the chemical structure of pyrolysis products is very similar to that of pure SiC, while X-ray diffraction curves suggest
that β-SiC microcrystals are formed in the fibers, and their mean grain size is about 7.5 nm. The oxygen content (1.69–3.77 wt%)
is much lower than that of conventional SiC fibers by oxidation curing method (about 15 wt%). Tensile strength of the SiC
fibers is up to 2.72 GPa, which demonstrates that their mechanical properties are excellent. After heat-treated at 1,673 K
in air for an hour or at 1,873 K under Ar gas atmosphere for 0.5 h, their external appearance is still undamaged and dense,
and their tensile strength decreases to a small extent, which verifies that heat resistance of the SiC fibers is eximious. 相似文献
10.
Maricela Lizcano Hyun Soo Kim Sandip Basu Miladin Radovic 《Journal of Materials Science》2012,47(6):2607-2616
In this study, a set of mechanical properties of geopolymers, synthesized by alkali (NaOH or KOH) activation of metakaolin
and SiO2 mixture, were characterized at ambient temperature. Samples with K/Al or Na/Al atomic ratios equal to 1, Si/Al atomic ratios
in the 1.25–2.5 range and H2O/Al2O3 molar ratios of 11 or 13 are cured at 80 °C for 24 and 48 h before characterization, to determine effect of Si/Al ratio and
curing time on the structure and mechanical properties of geopolymers. The structure of synthesized geopolymers characterized
using XRD, NMR, SEM, and density measurements was correlated to their mechanical properties, including compressive strength,
Young’s modulus, hardness, and fracture toughness. The results of this study suggest a strong effect of Si/Al ratios (in the
1.5–2 range), density, and microstructure on the maximum strength, Young’s modulus, and hardness of geopolymers. There were
also notable differences in strength between samples cured for 24 and 48 h, suggesting that the degree of geopolymerization
reaction also plays important role in mechanical properties of this new class of inorganic polymers. 相似文献
11.
He Ming Zhang Shu Ren Zhou Xiao Hua 《Journal of Materials Science: Materials in Electronics》2011,22(4):389-393
The dielectric, thermal and mechanical properties of CaO–SiO2–B2O3 ternary system ceramics by solid-phase method have been carried out and quantitive analysis been examined by X-ray diffraction
(XRD) patterns. The results showed that the major crystalline phase of CaO–SiO2–B2O3 ternary system ceramics was wollastonite (about 90 wt%) which existed at the temperature ranging from 950 to 1,100 °C. It
is also observed that wollastonite could be transformed to pseudowollastonite at 1,200 °C. In addition, with increase in calcination
temperature, the amount of wollastonite increases. When the sintering temperature is at 1,100 °C, the amount of wollastonite
has a maximum value of 92.7 wt%. Accordingly, CaO–SiO2–B2O3 ternary system ceramics achieved excellent properties at 1,100 °C, such as dielectric constant of 8.38, dielectric loss of
1.51 × 10−3 at 1 MHz, linear thermal-expansion coefficient (300 K) of 6.68 × 10−6/K, bending strength of 121.75 Mpa. Analysis of the mechanical and dielectric properties showed that the measured bending
strength, dielectric constant and loss of CaO–SiO2–B2O3 ternary system ceramics can be substantially modified and improved by controlling the sintering temperature, in particular
due to the amount of wollastonite crystalline phase and size of grains. 相似文献
12.
S. Biswas T. Nithyanantham N. T. Saraswathi S. Bandopadhyay 《Journal of Materials Science》2009,44(3):778-785
Elastic properties of Ni-8YSZ anode-supported bi-layer SOFC structures were studied at elevated temperatures up to 1,000 °C
in both ambient air and H2 environments. The anode samples with desired porosity and microstructure were fabricated by reducing a NiO-8YSZ anode precursor
structure in a gas mixture of 5% H2–95% Ar at 800 °C for selected time periods up to 8 h. The development of the essential porous microstructure in forming the
Ni-8YSZ cermet phase was analyzed with SEM. It was observed that the room temperature elastic moduli and hardness of the anode
samples decrease significantly with increasing fraction of reduced NiO. Since the elastic properties of fully dense Ni, NiO,
and 8YSZ are comparable to each other, the decrease in the magnitude in elastic moduli and hardness is evidently due to the
colossal increase in porosity in the reduced Ni-8YSZ cermet anodes because of the reduction of NiO to Ni. At elevated temperatures,
the Ni-8YSZ anodes show a complex profile of Young’s modulus as a function of temperature, which is significantly different
from the unreduced NiO-8YSZ samples. When studied in ambient air, the Young’s modulus of the Ni-8YSZ samples decrease slowly
up to ~250 °C, then more rapidly from 250 to 550 °C, and finally it increases monotonically with the increase in temperature.
However, in reducing environment, the Young’s moduli values decrease continuously throughout the temperature range. Two sets
of samples of different thicknesses were studied simultaneously to highlight the effects of the sample thickness on the elastic
properties of the anodes. 相似文献
13.
M. Alfano G. Di Girolamo L. Pagnotta D. Sun J. Zekonyte R. J. K. Wood 《Journal of Materials Science》2010,45(10):2662-2669
In this study, ceria–yttria co-stabilized zirconia (CYSZ) free-standing coatings, deposited by air plasma spraying (APS),
were isothermally annealed at 1315 °C in order to explore the effect of sintering on the microstructure and the mechanical
properties (i.e., hardness and Young’s modulus). To this aim, coating microstructure, before and after heat treatment, was
analyzed using scanning electron microscopy, and image analysis was carried out in order to estimate porosity fraction. Moreover,
Vickers microindentation and depth-sensing nanoindentation tests were performed in order to study the evolution of hardness
and Young’s modulus as a function of annealing time. The results showed that thermal aging of CYSZ coatings leads to noticeable
microstructural modifications. Indeed, the healing of finer pores, interlamellar, and intralamellar microcracks was observed.
In particular, the porosity fraction decreased from ~10 to ~5% after 50 h at 1315 °C. However, the X-ray diffraction analyses
revealed that high phase stability was achieved, as no phase decomposition occurred after thermal aging. In turn, both the
hardness and Young’s modulus increased, in particular, the increase in stiffness (with respect to “as produced” samples) was
equal to ~25%, whereas the hardness increased to up to ~60%. 相似文献
14.
The present study intends to investigate the effect of temperature on cumulative fatigue damage (D) of laminated fibre-reinforced polymer (FRP) composites. The effect of temperature on fatigue damage is formulated based
on Ramkrishnan–Jayaraman and Varvani-Farahani–Shirazi residual stiffness fatigue damage models. The models are further developed
to assess the fatigue damage of FRP composites at various temperatures (T). This task is fulfilled by formulating the temperature dependency of Young’s modulus (E) and ultimate tensile strength (σult) as the inputs of the models. Temperature-dependant parameters of Young’s modulus and ultimate tensile strength are found
to be in good agreement with the experimentally obtained data when used for unidirectional, cross-ply and quasi-isotropic
FRP laminates. The proposed fatigue damage model is evaluated using six sets of fatigue damage data. The proposed temperature-dependent
model was also found promising to predict the fatigue damage of unidirectional (UD) and orthogonal woven FRP composites at
different temperatures. 相似文献
15.
To investigate the possibility and problems in recycling techniques for wood powder compacted material (WPCM) obtained by
steam compression, a dynamic mechanical thermal analysis (DMTA) was conducted in dry and wet conditions. The results obtained
show that mechanical properties such as the static Young’s modulus and bending strength of WPCM increased with an increasing
steam temperature up to 170 °C during the compression of the wood powder. It is emphasized that WPCM having a bending strength
of 80 MPa with a Young’s modulus of 8 GPa can be prepared by steam compressing of wood powder only due to a auto-condensation
of wood components. The DMTA showed that the relative storage Young’s modulus of WPCM dramatically decreased in water exposure
by heating, although it slightly increased in the dry condition. This indicates that WPCM is softened under heat in the presence
of water, but it becomes harder by heating without water. The loss tangent peaks showed that the softening behavior of WPCM
seems to result from lignin. Consequently, it is thought that WPCM can be shaped by compressing in water, and after obtaining
the desired shape, the drying process should be conducted to fix the shape and harden the WPCM. 相似文献
16.
Zongbo Zhang Fan Zeng Juanjuan Han Yongming Luo Caihong Xu 《Journal of Materials Science》2011,46(18):5940-5947
A new liquid polyborosilazane precursor for Si–B–C–N ceramic was synthesized by co-condensation reaction of boron trichloride,
organodichlorosilanes, and hexamethyldisilazane. The structure and properties of polyborosilazane were studied by means of
Fourier transform-infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR), rheology, and thermogravimetric analysis
(TGA). The conversion of polymer to ceramic and the high-temperature behavior of the new polymer-derived ceramic were investigated
by TG–MS, FT-IR, X-ray diffraction (XRD) and high-temperature TGA (HTGA). The ceramics showed good oxidative resistance and
thermal stability with weight gain of 1.8 wt% at 1350 °C under air atmosphere and weight loss of 2.6% at 1900 °C under Ar
atmosphere. 相似文献
17.
A. Seal A. K. Dalui M. Banerjee A. K. Mukhopadhyay K. K. Phani 《Bulletin of Materials Science》2001,24(2):151-155
The biaxial flexural strength, Young’s modulus, Vicker’s microhardness and fracture toughness data for very thin, commercial,
soda-lime-silica cover slip glass (diameter, D-18 mm, thickness, T-0.3 mm; T/D ≈ 0.02) are reported here. The ball on ring
biaxial flexure tests were conducted at room temperature as a function of the support ring diameter (≈ 10–20 mm) and cross
head speed (0.1–10 mm min−1). In addition, the Weibull modulus data were also determined. The Young’s modulus data was measured using a linear variable
differential transformer (LVDT) from biaxial flexure tests and was checked out to be comparable to the data obtained independently
from the ultrasonic time of flight measurement using a 15 MHz transducer. The microhardness data was obtained for the applied
load range of 0.1–20 N. The fracture toughnessK
IC data was obtained by the indentation technique at an applied load of 20 N. 相似文献
18.
Wave-transparent materials used at high temperature environment generated by high supersonic and hypersonic speeds must possess
excellent mechanical property. In this paper, porous Si3N4 ceramics with high strength were fabricated by low molding pressure (10 MPa) and pressureless sintering process, without
any other pore forming agents. The sintering behavior and the effect of porosity on the mechanical strength and dielectric
properties were investigated. The flexural strength of porous Si3N4 ceramics was up to 57–176 MPa with porosity of 45–60%, dielectric constant of 2.35–3.39, and dielectric loss of 1.6–3.5 × 10−3 in the frequency range of 8–18 GHz, at room temperature. With the increase of porosity, the flexural strength, dielectric
constant, and dielectric loss all decreased. 相似文献
19.
The relationship between microstructure and Young’s modulus of thermally sprayed ceramic coatings 总被引:1,自引:0,他引:1
An idealized model for the microstructure of thermally sprayed ceramic coatings, consisting of the stacking of lamellae a
few micrometres thick, has been used to estimate Young’s modulus of the coating perpendicular to the coating plane. A theoretical
relationship between Young’s modulus and the microstructural parameters has been established. There are two components of
elastic strain of the coating under tensile stress, one arising from localized elastic strain at the regions of real-bonded
area between lamellae, and the other arising from elastic bending of the lamellae between bonded regions. The bending component
only becomes significant for a percentage bonding ratio between lamellae of less than 40%. The bending strain contribution
depends strongly upon geometrical parameters of the coating microstructure. The estimated Young’s modulus for a typical alumina
coating, based on quantitative microstructural data, was about 24% of that for the fully dense material. Taking into account
the variable proportion of α-Al2O3 and γ-Al2O3 forms in an alumina coating, the comparison of the estimated Young’s modulus
with published data gives reasonable agreement for the coating prepared over a wide range of processes and experimental conditions.
This revised version was published online in November 2006 with corrections to the Cover Date. 相似文献
20.
Shigeru Hanzawa 《Journal of Materials Science》2012,47(2):833-844
The following technique is known to synthesize C/C (carbon fiber-reinforced carbon) composites. The organic matter in the
preformed yarn (plastic straw covered yarn including bundles of long carbon fibers, carbon powder, and organic binder) is
pyrolyzed at 500 °C and concurrently hot-pressed. Then, the carbon ingredient is graphitized in an atmosphere of nitrogen
at 2000 °C. The authors used the above mentioned C/C composites as a starting material and developed a dense Si–SiC matrix
C/C composites in which most long carbon fibers remain without reacting with Si which is infiltrated in argon at 1600 °C and
100 Pa. As a result, production of 1 × 2 m large size plates free from warps and cracks was attained in NGK Insulators, Ltd.
This mechanism consists of three steps. First, a trunk-shaped Si–SiC matrix is synthesized between yarn and yarn. Then a trunk-shaped
Si–SiC matrix extends a yarn by force. Only differential gap is made in a yarn surface. Finally, branch-shaped Si–SiC matrix
is synthesized so that a trunk-shaped Si–SiC matrix leads to the yarn inside. 相似文献