Predicting the dislocation nucleation rate as a function of temperature and stress is crucial for understanding the plastic deformation of nanoscale crystalline materials. However, the limited time scale of molecular dynamics simulations makes it very difficult to predict the dislocation nucleation rate at experimentally relevant conditions. We recently develop an approach to predict the dislocation nucleation rate based on the Becker–Döring theory of nucleation and umbrella sampling simulations. The results reveal very large activation entropies, which originated from the anharmonic effects, that can alter the nucleation rate by many orders of magnitude. Here we discuss the thermodynamics and algorithms underlying these calculations in greater detail. In particular, we prove that the activation Helmholtz free energy equals the activation Gibbs free energy in the thermodynamic limit and explain the large difference in the activation entropies in the constant stress and constant strain ensembles. We also discuss the origin of the large activation entropies for dislocation nucleation, along with previous theoretical estimates of the activation entropy.

Calcium phosphates form a vast family of biominerals, which have attracted much attention in fields like biology, medicine, and materials science, to name a few. Solid state Nuclear Magnetic Resonance (NMR) is one of the few techniques capable of providing information about their structure at the atomic level. Here, examples of recent advances of solid state NMR techniques are given to demonstrate their suitability to characterize in detail synthetic and biological calcium phosphates. Examples of high-resolution 31P, 1H (and 17O), solid state NMR experiments of a 17O-enriched monocalcium phosphate monohydrate-monetite mixture and of a mouse tooth are presented. In both cases, the advantage of performing fast Magic Angle Spinning NMR experiments at high magnetic fields is emphasized, notably because it allows very small volumes of sample to be analyzed.

Bulk production of iron nanowire inside carbon nanotubes (CNTs) from iron phthalocyanine (FePc) polymer under 800 °C is presented for the first time. The bis-phthalonitrile was firstly reacted with iron nanoparticles to produce iron phthalonitrile oligomer, and heat treatments made the formation of CNTs occurred during the carbonization process of FePc polymer at ambient pressure in nitro atmosphere under 800 °C. The iron nanowire inside carbon tubes from the metal Pc polymer possessed excellent electromagnetic loss and magnetic loss properties.

Using a recently developed multidimensional nanocontact system designed for a quantitative measurement of lateral contact stiffness in the 10–106 N/m stiffness range (or 10–1000 nm contact size), we found a crystallographic-orientation-dependent lateral-stiffness reduction relative to the elastic prediction at contact sizes around 50 nm for polished Ni single crystal surface in air. The slidingless measurement is enabled by a frequency-specific, continuous stiffness measurement technique. Based on an interface microslip model and an anisotropic elastic contact analysis, the resulting friction stress is found to increase monotonically when the tested lateral direction rotates away from the closely packed direction.

A series of red-emitting phosphors with compositions of La2(Mo1−zSiz)2O9:0.05Eu3+ (0 ≤ z ≤ 0.10) with strong near-UV absorption were prepared by solid-state method. The structure and luminescence properties were investigated by x-ray powder diffraction, UV–vis diffuse reflectivity, and photoluminescence spectra. The luminescent properties as a function of Si4+ concentrations were systematically studied. Under excitation of a wide range near-UV (250–430 nm) or blue light, Si4+-doped series phosphors exhibit characteristic red emission of Eu3+ peaked at 615 nm. The incorporation of Si4+ into La2Mo2O9:0.05Eu3+ phosphor leads to the improvement of the excitation broad band and sharp peaks, as well as the broadening of charge transfer band. Appropriate amount of Si4+ doping can enhance the red luminescence intensity. Finally, the possible reasons for the luminescence enhancement via the corporation of Si4+ were explained.

In this study, bulk and multifoil diffusion couple experiments were conducted to examine the interdiffusion process in Ni–Pt and Co–Pt binary alloy systems. Inter-, intrinsic-, and tracer-diffusion coefficients at different temperatures, and as a function of the composition, were estimated by using the experimental data. Results show that in both the alloy systems, Pt is the slower diffusing species, and hence the interdiffusion process is controlled by either Ni or Co. The thermodynamic driving force makes the intrinsic diffusion coefficients of Co and Ni higher in the range of 30–70 at.%. The low activation energy for Co and Ni impurity diffusion in Pt compared with Pt in Ni and Co indicates that the size of the atoms plays an important role. The vacancy wind effects on the diffusion process are examined in detail, and it was demonstrated that its contribution falls within the experimental scatter and hence can be neglected.

ZnS:Cu,Cl,Mn,Te, which shows red AC powder electroluminescence (ACPEL) emission, was synthesized using a conventional wet synthesis and a sealed vessel method. The photoluminescence (PL) and ACPEL were characterized. After the second firing, 0.5 wt% tellurium (Te)-doped ZnS:Cu,Cl,Mn,Te phosphor shows almost red PL emission from the 4T1–6A1 transition of Mn2+ ions, which are affected by the Te. Extended x-ray absorption fine structure analysis on the Mn K edge proved that the substitution of sulfur (S) with Te changes the local crystal field of the Mn2+ ions and shifts an orange emission (∼588 nm) to a red emission (∼650 nm). A red ACPEL emission is first shown in 0.5 wt%Te-doped ZnS:Cu,Cl,Mn,Te after the third firing phosphor even though its luminance is not very high. The origin of the ACPEL emission is assumed to be not a CuxS–ZnS p–n junction but a CuxTe–ZnS p–n junction. Raman spectra were characterized to support that the red ACPEL emission is probably attributed to a CuxTe–ZnS p–n junction.

Nucleation doping strategy is an effective doping method; herein the synthesis of MnSe/CdSe nanocrystals using this strategy with different anion precursors was demonstrated. The resulted nanocrystals were characterized by various test technology to confirm the composition and structure. Wurtzite CdSe shell was achieved without using alkylphosphine, this is meaningful for the development of green chemistry. It is argued that the shell growth is more like a second nucleation process, rather than the epitaxial growth; this conclusion is believed to shed some light on the nucleation doping process.

With 2 mol% Zn2+ codoping and 2 mol% K+ charge compensation, the red-emitting phosphor [K0.8Y0.63Eu3+0.08Zn0.02][Mo0.2W0.8O4] was synthesized by solid-state reaction. X-ray powder diffraction spectrum indicates that it owns single phase. Through its emission spectra, excitation spectra, and fluorescence decay curves measured, its emission mechanism was mentioned and it was calculated for its partial J-O parameters and quantum efficiency of Eu3+ 5D0 energy level under 395 nm excitation. The results indicate that Eu3+ 5D0 → 7F2 red luminescence in the host can be excited by 395 nm, but its quantum efficiency can be improved in space and it has potential applications for white light-emitting diode as the red luminescent materials.

The hexagonal mesoporous silica MCM-41 nanospheres with Au nanorods (AuNRs) as core have been synthesized via a modified Stöber method by a process of hydration and condensation of tetraethoxysilane in a water–ethanol mixture. The AuNR@MCM-41 nanocomposites combine the photothermal characteristic with the mesopore of MCM-41 in one body. We utilized these core–shell materials for ibuprofen encapsulation and release in the simulated body fluid (pH 7.4) for the first time. The results certificated AuNR@MCM-41 nanocomposites as novel dual-functional materials could realize the light-driven release of drug due to the photothermal effect of the AuNRs. Such novel nanomaterials offer a new way for cancer treatment which combine hyperthermia with the chemotherapeutic drugs by synergistic effect.

Physical aging induced by an exposure of As–Se, As–S, and Ge–Se glasses to the light of different discrete wavelengths is studied using differential scanning calorimetry technique. The value of this effect is compared to the physical aging caused by natural storage in the dark. It is shown that a choice of As or Ge atoms does not influence significantly the spectral dependence of light-assisted physical aging, whereas substitution of Se with S causes drastic changes in the magnitude of the effect. The mechanism of the observed light-induced phenomena is discussed in terms of transient and metastable displacements of network chalcogen atoms.

A contact for a micromechanical switch has been fabricated using electroplated gallium (Ga) on silicon to create an electrical switch contact that can be annealed to recover its original properties after mechanical damage. The resistivity of the electroplated Ga appears to be similar to pure Ga. The resistance increased with cycling but recovered to the original value after a thermal reflow process at 120 °C for 10 min. The hardness of thermally reflowed Ga droplets was 2 MPa when the droplets were unconstrained and was up to 95 MPa for constrained droplets, suggesting that all switching in this study caused permanent deformation at room temperature and that defects formed during plastic deformation are likely candidates for the increased resistance during cycling. Up to 300 switching cycles were investigated for contacts involving up to four Ga droplets to measure contact behavior under high-current and load-switching applications. Oxidation behavior was characterized for the thermal reflow process on the Ga droplets, suggesting a passivating 30-nm oxide form at 100 °C, and electrical contact resistance nanoindentation suggests the oxide breaks during mechanical contact.

Blister-actuated laser-induced forward transfer (BA-LIFT) is a direct-write technique, which enables high-resolution printing of sensitive inks for electronic or biological applications. During BA-LIFT, a polymer laser-absorbing layer deforms into an enclosed blister and ejects ink from an adjacent donor film. In this work, we develop a finite element model to replicate and predict blister expansion dynamics during BA-LIFT. Model inputs consist of standard mechanical properties, strain-rate-dependent material parameters, and a parameter encapsulating the thermal and optical properties of the film. We present methods to determine these material parameters from experimental measurements. The simulated expansion dynamics are shown to be in good agreement with experimental measurements using two different polymer layer thicknesses. Finally, the ability to model high-fluence blister rupture is demonstrated through a strain-based failure approach.

The effects of water vapor and oxygen on the cyclic fatigue behavior of oxygen-excess La0.8Sr0.2MnO3+δ (LSM) were investigated under three-point bending at 1273 K. Because the fatigue life did not obviously depend on the number of cycles, which also represented the effective time of the applied stress, the fracture was presumed to not be significantly controlled by stress-corrosion cracking. Under a low oxygen partial pressure (), however, wet exposure inhibited both fatigue fracture and permanent deformation, in which the LSM crystal lattice was distorted and the unit cell free volume was reduced. Under a high , on the contrary, the crystal symmetry was increased by the wet exposure. The inhibition of fatigue fracture and deformation at both high and low was probably caused by retardation of lanthanum diffusion through its vacancies.