Dali Mao

Luminescent properties of CaMgSi2O6 and Ca2MgSi2O7 phosphors activated by Eu2+, Dy3+and Nd3+

Long lasting alkaline earth silicates, CaMgSi2O6:Eu,Dy,Nd, Ca2MgSi2O7:Eu,Dy,Nd and Ca2MgSi2O7:Eu,Dy, were prepared under a reducing atmosphere by a solid-state reaction. The obtained phosphors were characterized by means of X-ray diffraction (XRD) and their photoluminescence spectrum (PLS). The Ca2MgSi2O7:Eu,Dy,Nd phosphor showed a two-peak emission at 447 and 516 nm, while the CaMgSi2O6:Eu,Dy,Nd phosphor generated only one peak emission at 447 nm. This phenomenon is due to the different lattice sites occupied by Eu2+ in the Ca2MgSi2O7 and CaMgSi2O6 lattices. The electron affinity (ea) values for Eu2+ in [EuO6] and [EuO8] were calculated to be 4.2 and 1.9 eV, respectively. The Nd co-doped phosphor revealed a better afterglow characteristic, indicating that a deeper trap center was formed in the phosphor by the doping of trivalent Nd ions.

Mechanical and histological evaluations of hydroxyapatite-coated and noncoated Ti6Al4V implants in tibia bone

This paper evaluates the behavior of hydroxyapatite (HAP) coated and noncoated Ti6Al4V implants in dog tibia after 3 and 5 months implantation. HPA-coated implants were obtained by plasma spraying. XRD, SEM, and EPMA were employed to estimate the coating characteristics and their behavior in vivo. Investigation of material characteristics showed that the as-received coatings consisted mainly of amorphism and HAP phase. Other phases such as TCP and CaO were identified due to thermal changes of HAP particles in plasma flame. SEM micrographs showed a typical microstructure of plasma-sprayed coating. The as-received coating was formed by well-melted pancake-like splats that lead to a dense coating with a rough surface. Lamellar structure, micropores, and microcracks, observed inside the coating, are characteristic of plasma spraying. Push-out tests revealed that HAP coating had a significant promotion of interfacial shear strength. The shear strength between bone and HAP-coated implants was much higher than that between bone and noncoated implants due to the different bone-implant interfaces formed after implantation. SEM observation revealed a direct attachment between HAP coating and newly formed bone. However, noncoated implants were separated from newly formed bone by fibrous tissues. Ti ions were found to be released into the surrounding environment after long time immersion in body fluid, and thus caused low shear strength. Prolongation of implantation time had different effects on shear strength. It improved the shear strength between HAP-coated implant and newly formed bone. However, it had little effect on that between noncoated implant and surrounding tissues.

Anodic fabrication and bioactivity of Nb-doped TiO2 nanotubes

We report anodic formation of Ti-Nb-O nanotubes on top of a Ti35Nb alloy, and in vitro bioactivity and stem cell response of the anodic nanotubes. It was found that the amorphous Ti-Nb-O nanotubes presented a significantly enhanced in vitro bioactivity (in simulated body fluids) compared to those of undoped TiO2 nanotubes and porous Ti-Nb-O without nanotubular structure. Similar to undoped TiO2 nanotubes, the Ti-Nb-O nanotubes also promote mesenchymal stem cell adhesion and fast formation of extracellular matrix (ECM) materials. The above findings make it possible to further explore the biological properties, such as cell proliferation and drug delivery, of a variety of Ti-alloy-based oxide nanotubes.

The hydrothermal preparation, crystal structure and photoluminescent properties of GdOOH nanorods

This paper reports the hydrothermal preparation of a new lanthanide compound, nanorod GdOOH, its crystal structure and related photoluminescent properties. Pure phase Gd(OH)3 nanorods were prepared through a hydrothermal method which later served as the precursor for GdOOH nanorods. HRTEM investigation showed a preferred growth along the c?axis for the precursor. GdOOH nanorods were obtained simply by calcinating the precursor at 600?K. Rietveld refinement revealed that the newly found phase belongs to the monoclinic system, with space group P 21/m (No.?11); cell parameter a = 6.086(1)??, b = 3.7289(8)??, c = 4.3465(8)??, and ? = 108.79(1)?. HRTEM also showed the single crystalline nature of the GdOOH nanorods, with a preferred growth also along the c?axis direction. When Eu3+ ions were introduced to GdOOH lattice sites which replace the original Gd3+ ions, a strong red emission centred at 615?nm was observed upon UV illumination, due to the intrinsic Eu3+ transition between5D0 and7F configurations.

Characteristics of crystals precipitated in sintered apatite/wollastonite glass ceramics

In this paper, apatite/wollastonite (A/W) glass ceramics were obtained by sintering the A/W glass powder compact at 1200°C. XRD, TEM and EDX were used to identify the crystalline phase and determine the chemical composition. The results showed that, the precipitated crystals at 1200°C were wollastonite and whitlockite. The sintered A/W glass ceramics consisted of crystalline phases, while glass matrix was found on the grain boundary. Whitlockite crystal showed a hexagonal morphology, while wollastonite exhibited a column shape. The two crystals were non-stoichiometic, and certain amounts of Mg and Si were found in wollastonite and whitlockite. The existence of Si in whitlockite caused an increment in lattice volume while Mg did not change the lattice parameter of wollastonite due to different ion radius.

The preparation of LiCoO2 nanoplates via a hydrothermal process and the investigation of their electrochemical behavior at high rates

We report an alternative hydrothermal process for the preparation of pure phase LiCoO(2) cathode material for potential application under high rates. By adjusting the hydrothermal conditions, nanoplate-like LiCoO(2) crystals were obtained, with grain size about 200 nm. It was found in the experiment that the H(2)O(2) concentration and hydrothermal temperature were the two key factors that influence the phase purity and crystal shape, while LiOH concentration has only a slight effect on the crystal size of the product. The electrochemical test revealed a good rate behavior of the synthesized pure phase LiCoO(2) nanoplates, demonstrating a potential of the hydrothermal process for mass production.

Thermal stability and in vitro bioactivity of Ti–Al–V–O nanostructures fabricated on Ti6Al4V alloy

This work investigates the thermal stability and in vitro bioactivity of Ti-Al-V-O nanostructures grown on Ti6Al4V alloy through an anodization method. After anodization of the two-phase Ti6Al4V alloy, there were two different kinds of Ti-Al-V-O nanostructure (nanotube arrays grown in the alpha-phase region and irregular nanopores grown in the beta-phase region) that formed on the surface of the alloy. It was found that the Ti-Al-V-O nanotubes can withstand a high temperature of 675 degrees C in air without collapse, whereas the irregular Ti-Al-V-O nanopores presented a lower thermal stability. In vitro simulated body fluid (SBF) testing of heat-treated nanostructures indicated that a quick apatite formation on these nanostructures occurred after only several hours of sample immersion in the SBF.

Structural control of a cobalt nanocone array grown by directional electrodeposition

A metallic nanocone array by means of a directional electrodeposition method without any template is reported. With the crystallization modifier in the nickel electroplating solution, the cobalt conical structure can be deposited onto different metal substrates. The morphology of the nanocones can be controlled by changing the electroplating condition. The as-prepared Co nanocones grow preferentially along directions with very sharp tips. The conical structures are single crystalline without any disruption of the lattice planes. The growth mechanism is also briefly discussed.

Through silicon via filling by copper electroplating in acidic cupric methanesulfonate bath

Copper electrodeposition in acidic cupric methanesulfonate bath with organic additives is discussed in this paper. The influence of poly(ethylene glycol) (PEG) and bis-(3-sodiumsulfopropyl disulfide) (SPS) on copper deposition were studied by means of linear sweep voltammetry, cyclic voltammetry and chronoamperometry. These electrochemical analysises revealed a competition of PEG and SPS on electrode surface site. The swiftness of SPS chemisorption and the subsequent displacement by the passivating film of PEG exerted an extra wave at small overpotential on the negative-going sweep. The following polarization curve indicated the firmness of the passivating film. All these features of additives in acidic cupric methanesulfonate bath suggested a novel method to achieve superconformal or bottom-up filling which was proved by actual TSV plating.

Adhesion improvement of Epoxy Molding Compound – Pd Preplated leadframe interface using shaped nickel layers

The weak adhesion between the Epoxy Molding Compound (EMC) and Pd Preplated leadframes (Pd PPF’s) often causes delaminations and reduces the reliability of integrated circuit. This paper reports on a practical method of dramatically improving the adhesion between EMC and Pd PPF’s using electroplating of shaped nickel layers. Button shear tests indicate that the adhesions between the EMC and three different shaped PPF’s are 100%, 160%, 169% higher than that of conventional PPF’s. The mechanical interlocking effect caused by increased surface roughness is the major reason for the improved adhesion as well as for the failure mode transition from adhesive failure to cohesive failure.