We show that, by changing and tuning the direction of the As flux on a rippled substrate, at temperatures higher than 530 °C and high As/In flux ratio, a selective growth of InAs dots can be obtained on GaAs. This is an undisclosed effect related to the Arsenic flux in the molecular beam epitaxial growth of InAs quantum dots (QDs) on GaAs(001). This effect cannot be explained by a shadowing effect, due to the gentle slopes of the mounds (1–3°), and reveals instead that As plays a fundamental role at these growth conditions. We have developed a kinetic model, which takes into account the coupling between cations and anions, and found that the very small surface gradient in the anion flux, due to the oblique evaporation on the mounded surface, is responsible for a massive drain of cations toward the surface anion-rich areas, thus generating the selective growth of QDs.

Heteroepitaxial Ge quantum dots were grown on Si (001) by molecular beam epitaxy, with a Mn co-deposition flux giving a nominal composition of Ge0.9Mn0.1. At this large Mn flux, and with growth temperatures of 450 °C required for Ge quantum dot self-assembly, extensive second phase formation occurred. Atomic force microscopy reveals that quantum dots typical for the Ge/Si (001) system still form. In addition, copious formation of both rod-like and cluster-like morphologies is observed, with many of these structures conjoined to Ge dots. Extensive transmission electron microscopy identified several coexisting intermetallic phases, all based on Mn–silicide crystal structures, albeit with varying degrees of Ge substitution. The Ge quantum dots themselves appear to have little or no Mn incorporated in them, indicating that the intermetallic particles scavenge Mn from extended surface areas. Under these growth conditions, Mn is highly mobile, with surface diffusion lengths of the order of 800 nm, with significant bulk mobility as well, resulting in surface structures that also penetrate the Si substrate. A magnetic phase transition at 220 °C does not match known behavior of the bulk silicide phases but might result from extensive ternary alloying with Ge, especially into the cubic MnSi phase.

The graded composition buffer layers are very commonly used in the semiconductor triple-junction solar cell device. To grow a strain-free 1.0-eV In0.3Ga0.7As thin film on a GaAs substrate, a total of 2.2% misfit strain must be relaxed through well-designed buffer layer structures. In this work, a phase-field model of a multilayered system is developed to probe the roughness of top surface morphology and predict optimal buffer layer thickness. Our simulation shows time evolution of the thin film morphology and the root-mean-square roughness of the surface with different buffer layer thickness designs. The strain distribution is investigated to explain the surface morphology evolution with the effect of the buffer layer. The simulation results show that the buffer layer thickness is a key parameter that affects the quality of the In0.3Ga0.7As epilayers. The simulation results can be effective in improving the design of graded buffer layers.

Absorption losses in tellurite glasses due to OH− ions were reduced by melting the glasses under a reactive atmosphere of Cl2 + O2 gas. Incorporation of dry Cl2 + O2 gas has a major influence on the reduction of OH− species, which is found to be consistent with thermochemical data. Absorption loss due to OH− ions in bulk glasses prepared from the as-received raw materials and processed under a reactive atmosphere was 1000 and 60 dB/m, respectively. Gaussian fits have been used to identify the different species of OH− attached to the structural units present in the glass. All of the OH− species (free and bonded to Te), units can be reduced by melting the starting raw materials in a reactive atmosphere of Cl2 + O2. The net reduction in OH− absorbance at 3.2 µm was 1.1 cm−1, which is equivalent to 500 ppm. OH− reduction in tellurite glasses using O2 gas bubbling shows a reduction in the fundamental absorption band from 1.8 to 0.57 cm−1 after 75 min.

In this study, stimuli-responsive ionic poly(acrylamide–itaconic acid) (P(AAm–IA)) and poly(N,N-dimethylacrylamide–itaconic acid) (P(DMA–IA)) hydrogels have been prepared by free radical crosslinking copolymerization in aqueous solution using N,N-methylenebisacrylamide as the crosslinking agent. In particular, the swelling ratio and elasticity of both hydrogel systems including the effect of ionic comonomer itaconic acid (IA) content were investigated. In spite of the similarity in monomer/crosslinker ratio and the content of ionic comonomer in the hydrogel structures, comparable differences were observed in their swelling capacity and elasticity. Compared to P(DMA–IA) hydrogels, P(AAm–IA) hydrogels exhibit higher swelling capacity in water and a more pronounced dependency of the swelling ratio on the ionic comonomer content. The incorporation of a small amount of IA into the network structure causes the hydrogel system to exhibit polyelectrolyte type swelling behavior. P(AAm–IA) and P(DMA–IA) hydrogels showed good response to the valency of counterions and pH of the external solution.

Antiperovskite manganese nitrides Mn3MN (M = Zn, Ni, Cu…) have been extensively studied in the past decade due to their many interesting properties, such as negative thermal expansion. To get a better understanding of the origin of these phenomena, the information from the microscopic scale is necessary, so we performed systematic transmission electron microscopic study of Mn3Zn0.8Ni0.2N and found that the sample particle is wrapped in a thin MnO layer. The same result was also found in Mn3Zn0.5Ni0.5N and Mn3ZnN, indicating that it is a common phenomenon in this kind of compound. The presence of the MnO surface layer was also confirmed by the macroscopic XPS measurements. Our study suggests that M is easier to be lost than Mn in manganese nitrides Mn3MN (M = Zn, Ni, Cu…), and this character is much more obvious on the surface, i.e., this kind of compound has a strong surface activity. Figure 6 could best represent this manuscript.

Dielectric aging of Dy and Mn-codoped BaTiO3 multilayer ceramic capacitors was investigated. The increase of Dy concentration significantly decreased the aging rate and caused a disappearance of the thermally stimulated depolarization current peak associated with the defect dipole of Mn such as ${\rm{Mn}}_{{\rm{Ti}}}^{\prime \prime } {\rm{ - V}}_{\rm{O}}^{\cdot\cdot}$ or ${\rm{Mn}}_{{\rm{Ti}}}^\prime {\rm{ - V}}_{\rm{O}}^{\cdot\cdot}$, which was observed in low Dy-concentration specimens. These results experimentally demonstrate that the rare earth element, Dy, decreases the concentration of the defect dipoles and thereby controls dielectric aging.

Interfacial reactions at 100 and 150 °C in the Sn–20.48 at.% In–3.05 at.% Ag (Sn–20.0 wt% In–2.8 wt% Ag)/Ni couples are studied. Three unusual phenomena are observed. First, liquation is found in Sn–20.48 at.% In–3.05 at.% Ag (Sn–In–Ag)/Ni couples that are reacted at 150 °C, which is lower than the melting points of both the solder and the Ni substrate. In addition to the Ni3Sn4 phase, liquid phase is formed in the reaction layer. Second, the liquid phase disappears and isothermal solidification occurs when there is prolonged isothermal heat treatment at 150 °C. The results are similar to those for transient liquid phase bonding. Third, the thickness of the reaction layer in Sn–In–Ag/Ni couples that are reacted for 1440 h at 150 °C is 40 times thicker than that of those reacted at 100 °C. The reaction mechanisms for these three unusual phenomena: liquation, isothermal solidification, and an extraordinary increase in the reaction rate for only 50 °C difference in temperature are elaborated and are related to each other.

During peritectic solidification, besides the longitudinal remelting of the primary phase at the temperature of peritectic reaction $\left( {T_{\rm{p}}^K} \right)$, a lateral remelting phenomenon of the primary phase below $T_{\rm{p}}^K$ is observed under high velocity in directionally solidified Cu–Ge alloys. The lateral remelting occurs continuously along a liquid channel as temperature decreases, and the lateral remelting velocity is larger than that of peritectic transformation. The lateral remelting leads to the morphological change of the primary dendrites, even the fragmentation of dendrite arms. The phenomenon also means that the classical theory calculating the volume fraction of the primary phase during peritectic transformation can need to be modified under some conditions. However, under low velocity, the phenomenon is not so significant. The phenomenon is explained by means of solidification and remelting theory.

In the present work, it has been suggested that the gene expression programing is a good tool for determination of hardness of metal matrix nanocomposite produced by mechanical alloying (MA). For example, we studied the Al matrix nanocomposite, and to build the models, 35 input-target data were gathered from the literature, randomly divided into 28 and 7 data sets and then were respectively trained and tested by the proposed models. The differences between the models were in their gene number, chromosomes, and head size. The amount of reinforcement, ball to powder ratio, compaction pressure, milling time, reinforcement hardness, sintering temperature, sintering time, and vial speed were 8 independent input parameters. The output parameter was mean hardness of nanocomposites. The results indicate that gene expression programing is a powerful tool for predicting the hardness of the nanocomposite produced by MA.

To clarify the underlying mechanism of formation and growth of aluminum coating, the interface microstructures of as-prepared aluminum coating iron were investigated using various experimental methods. The liquid Al–Si, Al–Ge alloys were chosen as the dipping baths. In both cases, the total thickness of the reaction layer is controlled mainly by the well-known diffusion growth of η-Al5Fe2. The melt environment of the Al bath plays a decisive role in the formation and growth of the diffusion layer. The results show that Ge atoms could also decelerate reaction layer growth like Si atoms, which mainly restrain the diffusion of Al atoms. Meanwhile, Ge element represents an abnormal concentration gradient in the η-Al5Fe2 phase. The diverse growth behavior of the diffusion layer is attributed to the strong controlling role of the alloying element in Al baths based on the atomic diffusion and activity analysis.

Zr-based bulk metallic glasses (BMGs) exhibit superior physical and chemical properties in comparison to their crystalline counterparts. In the present work, drilling behavior of Zr57.5Cu11.2Ni13.8Al17.5 BMG was investigated at various operating conditions. Drilling was performed using high-speed steel (HSS) and carbide bits. Chip morphology, chip light emission, and burr formation at various drilling parameters were studied to achieve a feasible operating condition for drilling hole without light emission, chip clogging, and debris accumulation. Short spiral chip morphology which is considered ideal in the drilling process was observed at relatively low feed rate (1.5 mm/min) and medium spindle speed (1500 rpm). This also resulted in a small amount of molten debris around the entry hole. It was observed that at the same feed rate, the gradual increase in the speed of the HSS drill bit results in more light emission from the machining surface, whereas no light emission was observed in the case of the carbide drill bit at all drilling parameters.

A series of Ni/C catalysts with different Ni content (15, 20, and 30 wt% Ni) were prepared by the wet incipient impregnation method. Their textural properties were studied by surface fractal dimension (Ds) and nonlocal density functional theory using nitrogen sorption data. Their structural properties were studied by x-ray diffraction, Rietveld refinement, radial distribution functions (RDFs), and electron density maps of Fourier. Surface areas of Ni/C catalysts decreases slightly from 614 to 533 m2/g as Ni content increases from 15 to 30 wt%; however, the Ni crystallite size (5.1–31.4 nm) increases as the nickel content increases. Many point defects were found by Rietveld refinement in nickel nanostructures of Ni/C catalysts with 20 and 30 wt% Ni. This was confirmed by RDFs and electronic density maps. On the other hand, the hydrogen production via the photodehydrogenation of ethanol is very sensitive to the nickel crystallite size and the number Ni atoms in nickel nanostructures. The maximum reaction rate (363.64 μmol/h) is achieved on Ni/C catalyst with 15 Wt% Ni content which has the smallest crystallite size (5.1 nm) and less point defects in its nickel nanostructures. Ab initio calculations were performed to propose a reaction mechanism in the photodehydrogenation of ethanol.