Evolution of M23C6 phase in HR3C steel aged at 650 °C

The evolution of the morphology, composition, and particle size of the M₂₃C₆ phase in HR3C steel aged at 650 °C was analysed, by means of metallographic microscopy, scanning electron microscopy, and transmission electron microscopy. The results showed that the Cr/Fe ratio in the M₂₃C₆ phase, in the form of irregular square and long strip, increased with the ageing time. Fe was gradually replaced by Cr in the M₂₃C₆ lattice. The M₂₃C₆ phase gradually evolved and then became stable after ageing for 2000 h.     

Cyclic behavior of 9–12% Cr steel under different control modes in low cycle regime: A comparative study

Cyclic behavior of 9–12% Cr steel under both stress and strain control modes was investigated at 873 K. Significant asymmetric deformation and cyclic softening were observed for both modes. Under the strain-controlled fatigue, a strain level-independent softening factor (SF) was observed. The SF was dependent on applied stress under the stress-controlled fatigue. For the strain-controlled fatigue, the magnitude of cyclic asymmetry decreases with the increase of strain amplitude, while under the stress-controlled fatigue, the asymmetry increases with the increase of stress amplitude. The anomalous ratcheting strain resulted from the asymmetry under the stress-controlled mode has a detrimental effect on fatigue life.     

A PLA/calcium phosphate degradable composite material for bone tissue engineering: an in vitro study

Biodegradable polymers reinforced with an inorganic phase such as calcium phosphate glasses may be a promising approach to fulfil the challenging requirements presented by 3D porous scaffolds for tissue engineering. Scaffolds’ success depends mainly on their biological behaviour. This work is aimed to the in vitro study of polylactic acid (PLA)/CaP glass 3D porous constructs for bone regeneration. The scaffolds were elaborated using two different techniques, namely solvent-casting and phase-separation. The effect of scaffolds’ micro and macrostructure on the biological response of these scaffolds was assayed. Cell proliferation, differentiation and morphology within the scaffolds were studied. Furthermore, polymer/glass scaffolds were seeded under dynamic conditions in a custom-made perfusion bioreactor. Results indicate that the final architecture of the solvent-cast or phase separated scaffolds have a significant effect on cells’ behaviour. Solvent-cast scaffolds seem to be the best candidates for bone tissue engineering. Besides, dynamic seeding yielded a higher seeding efficiency in comparison with the static method.     

In vitro and in vivo performance of Ti6Al4V implants with plasma-sprayed osteoconductive hydroxylapatite–bioinert titania bond coat “duplex” systems: an experimental study in sheep

To evaluate the in vivo performance of "duplex" hydroxylapatite top coat/TiO(2) bond coat systems, cylindrical Ti6Al4V rods of 130 mm in length and 11-13 mm in diameter were coated by atmospheric plasma spray (APS) technique with both a standard hydroxylapatite (HAp) layer and a HAp+TiO(2) bond coat "duplex" layer. In this pilot study coated and uncoated rods serving as controls were implanted into the femur of sheep so that their distal ends were freely suspended in the medulla of the femur. After an observation time of six months it was found that bone apposition and bone ingrowth were considerably increased in the presence of a osteoconductive coating. In particular, in vivo spalling and delamination frequently observed with HAp coatings was virtually absent in duplex coatings owing to the strong adhesion of the bond coat to the HAp top coat that anchored the latter solidly to the metallic surface of the implant. Some tentative mechanisms leading to this improved coating adhesion will be discussed.     

On the CVD of MoSi2: an experimental study from the MoCl4–SiCl4–H2–Ar precursor with a view to the preparation of C/MoSi2/SiC and SiC/MoSi2/SiC microcomposites

The chemical vapour deposition of MoSi2 on plane substrates (graphite or sintered-SiC) and ceramic fibres has been studied from MoCl4–SiCl4–H2–Ar gas mixtures at 900相似文献   

The δ value dependence of photoluminescence in green-emitting Ba3Si6O12−δN2+2/3δ:Eu2+ phosphors for white light-emitting diodes

Green emitting Eu²⁺-doped Ba₃Si₆O_12?δ N_2+2/3δ phosphors with δ value varying in the range of ?0.6 to 1.8 were synthesized by firing the raw materials of α-Si₃N₄, SiO₂, BaCO₃ and Eu₂O₃ at 1,350 °C for 12 h under a N₂/H₂ atmosphere. The solid-solution and luminescence properties of as-prepared Ba₃Si₆O_12?δ N_2+2/3δ :Eu²⁺ phosphors were investigated by XRD, O/N automatic analyzer and UV–Vis spectrophotometer. The composition-dependent solid solution of Ba₃Si₆O_12?δ N_2+2/3δ with small range of δ is established. The emission wavelength with a range of 522–545 nm by varying δ value as a function of dopant Eu²⁺ is observed in this phosphor. The emission band shows a shift to higher energy and a diverse quenching concentration with an increase of N/O ratio in Ba₃Si₆O_12?δ N_2+2/3δ :Eu²⁺ phosphors. The measured results suggest that Ba₃Si₆O_12?δ N_2+2/3δ :Eu²⁺ possesses broad applications as an effective green phosphor in producing white light-emitting diodes.     

Preparation and characterization of multi-walled carbon nanotube/hydroxyapatite nanocomposite film dip coated on Ti–6Al–4V by sol–gel method for biomedical applications: An in vitro study

In the present research, the introduction of multi-walled carbon nanotubes (MWCNTs) into the hydroxyapatite (HA) matrix and dip coating of nanocomposite on titanium alloy (Ti–6Al–4V) plate was conducted in order to improve the performance of the HA-coated implant via the sol–gel method. The structural characterization and electron microscopy results confirmed well crystallized HA–MWCNT coating and homogenous dispersion of carbon nanotubes in the ceramic matrix at temperatures as low as 500 °C. The evaluation of the mechanical properties of HA and HA/MWCNT composite coatings with different weight percentages of MWCNTs showed that the addition of low concentrations of MWCNTs (0.5 and 1 wt.%) had improved effect on the mechanical properties of nanocomposite coatings. Moreover, this in vitro study ascertained the biocompatibility of the prepared sol–gel-derived HA/MWCNT composite coatings.