Doping, as a primary technique to modify semiconductor transport, has achieved tremendous success in the past decades. For example, boron and phosphorus doping of Si modulates the dominant carrier type between p-type and n-type, serving as the backbone for the modern microelectronic technologies. Doped III-V semiconducting systems exhibit phenomenal optoelectronic properties. Magnesium doped gallium nitride plays an important role to build efficient blue light-emitting diode (LED), which won Nobel Prize in physics in 2014. The rise of two-dimensional (2D) materials sheds light on their potential in next generation electronic, optoelectronic, and quantum applications. These properties can further be controlled via doping of 2D materials, however, many challenges still remain in this field. Here, we present a rapid review on the recent achievements and challenges in the metastable and substitutional doping of 2D materials, followed by providing an outlook on integrating 2D materials into more advanced electronic architectures.

Bar codes and quick response codes are the standard methods of visual data storage. These codes rely on changes in visual patterns to encode data into a binary format. Problems with these methods include limited data storage capacity and poor visual appeal in product marketing. This work examined magnetic patterns as an alternative to visual patterns as a potential means to encode data. Using magnetic patterns it is theorized that data storage capacity can be improved, while embedding the code within a tagged object. Magnetic patterns were formed using neodymium magnets, which yielded results that are similar to a bar code. Lines of high magnetic field strength followed by regions of low magnetic field strength at different spacing produced different overall magnetic patterns. Next, magnetic patterns were 3-dimensionally printed using an iron and polylactic acid commercial filament. The effect of infill density and the print line of the magnetic regions were studied by measuring the attractive force between the sample and a neodymium magnet attached to a force gauge for different print configurations. As expected the infill density of 100% had the highest force, which was roughly 330 mN, while the 10% sample had the lowest force being about 120 mN. It was expected that print line should not have an influence on magnetic force, but in this experiment magnetic regions with print lines at 0° were about 10 mN higher than samples printed at 90°. The cause of this was likely due to the printer error. Future work will study print plane, which is another processing variable in 3-dimensional printing. The target goal of matching the data storage capability of QR codes will also be work towards.

Partial amount of austenite can be dynamically transformed into ferrite above the Ae3 temperature when it is being deformed. This happens by a displacive mechanism. On removal of the load, it retransforms back into the stable austenite by diffusional processes. Plate rolling simulation under continuous cooling conditions was carried out on a high Nb X70 steel. Pass strains of 0.2 together with interpass times of 10, 20 and 30 s were employed. The initial and final temperatures for the finishing simulation were 920 and 830 °C, respectively. The mean flow stresses (MFS`s) behaviour indicates that dynamic transformation (DT) and recrystallization (DRX) were taking place during straining. It is shown that ferrite is formed during the roughing passes and increases its volume fraction throughout the finishing rolling steps. The ferrite formation is favoured by strain accumulation, shorter time between passes and also when the temperature reaches the Ae3 line. The results obtained here can be used to design improved models for transformation on accelerated cooling.

The incorporation of triturated tire particles as an aggregate in the concrete mixture is one of the ways to take advantage of this Waste Rubber (WR) in order to improve concrete properties, such as mechanical behavior. In this research we evaluated mechanical behavior of concrete specimens prepared with different amounts WR, which partially substituted the fine aggregate, under an indirect tensile test. In contrast with other’s researcher’s findings, our results show that the specimens with 5% WR present the highest value of indirect tensile strength (TP) of 4.36 MPa. Polynomial relationships between TP and compression strength (f´c), where Tp ranges from 0.1f´c to 0.2f´c. Specimens with the 0, 5 and 10% WR content show two types of failure: normal tension and tiple-cleft failure, described in the norm ASTM 1144-89. Nevertheless, specimens with 15 and 20% WR show a new failure not described in the norm, which is thought to be occurring due to the high amount of WR used.

Shape-memory polymer actuators often contain crystallizable polyester segments. Here, the influence of accelerated hydrolytic degradation on the actuation performance in copolymer networks based on oligo(ε-caprolactone) dimethacrylate (OCL) and n-butyl acrylate is studied. The semi-crystalline OCL was utilized as crosslinker with molecular weights of 2.3 and 15.2 kg∙mol−1 (ratio: 1:1 wt%) and n-butyl acrylate (25 wt% relative to OCL content) acted as softening agent creating the polymer main chain segments within the network architecture. The copolymer networks were programmed by 50% elongation and were degraded by means of alkaline hydrolysis utilizing sodium hydroxide solution (pH = 13). Experiments were performed in the range of the broad melting range of the actuators at 40 °C. The degradation of test specimen was monitored by the sample mass, which was reduced by 25 wt% within 105 d. As degradation products, fragments of OCL with molecular masses ranging from 400 to 50.000 g·mol-1 could be detected by NMR spectroscopy and GPC measurements. The cleavage of ester groups included in OCL segments resulted in a decrease of the melting temperature (Tm) related to the actuator domains (amorphous at the temperature of degradation) and simultaneously, the Tm associated to the skeleton domain was increased (semi-crystalline at the temperature of degradation).

The alkaline hydrolysis decreased the polymer chain orientation of OCL domains until a random alignment of crystalline domains was obtained. This result was confirmed by cyclic thermomechanical actuation tests. The performance of directed movements decreased almost linearly as function of degradation time resulting in the loss of functionality when the orientation of polymer chains disappeared. Here, actuators were able to provide reversible movements until 91 d when the accelerated bulk degradation procedure using alkaline hydrolysis (pH = 13) was applied. Accordingly, a lifetime of more than one year can be guaranteed under physiological conditions (pH = 7.4) when, e.g., artificial muscles for biomimetic robots as potential application for these kind of shape-memory polymer actuators will be addressed.

Chemical vapor deposition (CVD) growth of two-dimensional molybdenum disulfide (MoS2) using molybdenum trioxide (MoO3) and sulfur (S) powder often results in intermediate molybdenum oxy-sulfide (MoOS2) species along with MoS2 due to a lack of control over the vapor pressure required for the clean growth. Much effort has been devoted in understanding and controlling of these intermediate MoOS2 specifies. Here, we show that with a second step sulfurization at moderate temperatures, these MoOS2 crystals can be transformed to monolayer MoS2 crystals. Scanning electron microscopy, Raman and photoluminescence spectroscopy and atomic force microscopy characterization carried out before and after re-sulfurization confirm the monolayer MoS2 growth via this route. This study shows that MoOS2 formed at the intermediate state can be successfully recycled to MoS2.

Thermoelectric (TE) generators, converting waste heat to electricity regain their attractiveness for reduction of fossil fuels’ reliance, and consequently minimizing adverse environmental effects. Such generators are based on an electrical series connection of TE couples, which consist n- and p- type semiconducting legs divided by metallic bridges. While for intermediate temperatures of up to 500°C, n-type PbTe was extensively studied and employed in commercial TE power generation applications, its maximal efficiency, as was reflected by the TE figure of merit, ZT, was in most of the cases maximized at a narrow temperature range for any given donor dopant concentration. The most commonly applied donor dopants are iodine and bismuth. Yet, some interesting characteristics were recently proposed upon using Ti as a donor dopant. Up to date an impressive maximal ZT of ∼1.2 was obtained at 500°C, upon doping of PbTe by 0.1 at.% Ti, while no lower concentrations were ever investigated. In the current research a lower, 0.05 at.% Ti doping level was applied, leading to the highest ever reported ZT values, for any given Ti doped PbTe, up to 350°C. Since the chemical compatibility of Ti with PbTe, as a metallic bridge in such couples, is well established, mainly due to its low diffusion rates, the potential of generating a stable Ti-doped functionally graded n-type PbTe material, with enhanced TE performance, is currently being proposed.

This manuscript aims at synthesizing Al2O3-de-ionized water nanofluid and constructing a practical design of self-cooling device that does not require any external power input. Crystalline phase of powder was confirmed by X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) showed the various functional groups and absorption bands and average particle size was calculated to be 58.608 nm by Field Emission Scanning Electron Microscopy (FESEM) annealed at 900K. Experimental investigations were carried out to determine the effect of volume fraction of Al2O3 nanoparticles in the nanofluid on the rate of heat transfer from heat load to heat sink. Temperature of heat load was taken as 80° C. According to our results, cooling by 15°C, 13°C and 12°C was attained when volume fraction of nanoparticles was 1.5%, 1% and 0.5% respectively. The thermal conductivity was also measured and found to be increasing with the concentration of nanoparticles in nanofluid. Hence, indicating the use of nanofluids with suitable concentration in various cooling applications.

Ultra deep desulfurization of liquid fuels such as gasoline/diesel has attracted considerable attention of modern clean fuel research due to strict environmental regulations. Apart from that, SOx produced during combustion, poison the catalytic converter and exhaust emission system. Comparing to conventional catalytic and hydrodesulfurization techniques, adsorptive method for removal of sulfur bearing compounds e.g. thiophene derivatives is a promising approach which does not require hydrogen gas and high temperature. In this study, we used nickel sulfide nanoparticles incorporated poly(methyl methacrylate)-zirconia membranes as potential affinity material for adsorptive extraction of dibenzothiophene from n-hexane. The functionality and surface morphology of synthesized material was examined by Fourier transformation infrared (FTIR) spectroscopy and atomic force microscopy (AFM) images, respectively. The quantitative data regarding adsorptive removal of dibenzothiophene was determined by monitoring the shift in absorbance values of standard solutions before and after treating with synthesized material under ambient conditions. Nickel sulphide nanoparticles exhibited suitable rebinding response for removal of dibenzothiophene down to 1 ppm due to affinity interactions which is useful concerning ultra deep desulfurization. Finally, nickel sulphide nanoparticles were incorporated in poly(methyl methacrylate)-zirconia membrane which showed potential application for adsorptive desulfurization of dibenzothiophene at ambient conditions.

MXenes are a novel class of two dimensional materials, discovered by Barsoum and Gogotsi [M. Naguib, J. Come, B. Dyatkin, V. Presser, P. Taberna, P. Simon, M. W. Barsoum, and Y. Gogotsi, Electrochemistry Communications 16, 61-64 (2012); B. Anasori, M. R. Lukatskaya, and Y. Gogotsi, Nature Reviews Materials vol. 2, 16098 (2017)]. Their large specific surface area and the tunability of their physicochemical properties as a function of the transition metal and surface terminal group make them a unique design platform for various applications, a primary example of which is pseudocapacitive energy storage. However, there is still incomplete understanding of how the transition metal chemistry and stoichiometry, and the surface termination affect charge storage mechanisms in MXene. In this study, we have performed systematic first-principles calculations for bulk MXene and found that the atomic charge of the metal cations, which is related to their valence, decreases across the d-electron metal series. Electronic-structure indicators of performance are examined to understand the energy storage behavior, whereby charges are stored between the terminal groups and adsorbing cations. Importantly, we found that the differential Bader charges show good agreement with theoretical capacitances and are useful in predicting charge storage trends in MXene-based pseudocapacitors. Furthermore, we have performed first-principles and grand canonical Monte Carlo calculations for the slab systems, finding that the solvent plays a critical role in enhancing the pseudocapacitive response.

Ternary Sn-Sb-S thin films with remarkable optical, electrical and structural properties were developed by chemical bath deposition. Tin and antimony chlorides and thioacetamide were used as tin, antimony, and sulfur ion sources, respectively, while tartaric acid was used as a complexing agent. XRD analysis of as-deposited films showed a combination of binary phases of SnS, Sn2S3, and Sb2S3, while after thermal treatment in nitrogen at 400 °C, the films became crystalline showing well-defined reflections of the ternary SnSb2S4. The heating also influenced the morphology, compactness, and thickness of the films. On the other hand, all the films showed an absorption coefficient higher than 104 cm-1, while the optical band gap of the as-deposited film decreased from 1.49 to 1.37 eV after heating at 400 °C. In addition, the photoconductivity of the films prior to heating was of 10-9 Ω-1 cm-1, while after that at 400 °C was of 10-7 Ω-1 cm-1. The evaluation of the ternary film in solar cells gave an open-circuit voltage Voc of 448 mV and short-circuit current density of Jsc of 2.4 mA/cm2.

Due to their excellent properties, aerogel has attracted the attention of the scientific community to use it in the biomedical area as a drug delivery system. This work reports on the synthesis and characterization of ZrO2 aerogels and cryogels obtained by the sol-gel method. The influence of different cetyltrimethylammonium bromide (CTAB) and the type of drying on structural, morphological and texture properties of ZrO2 aerogels and cryogels was investigated. SEM images reveal that a porous interconnected three-dimensional network was formed into aerogels due to supercritical drying. Zirconia aerogel sample has a specific surface area (SBET) larger than zirconia cryogels. Therefore, our results indicate that zirconia aerogel is an adequate material for applications in drug delivery systems.

Exact solution of the generalized Shockley – Queisser model provides simple and effective tool for modeling of photovoltaic (PV) and thermophotovoltaic (TPV) devices with advanced photonic management. This formalism takes into account spectral characteristics of absorption/emission and a variety of recombination processes in semiconductor cell. In the current work we generalize this formalism to devices with non-ideal light reflectors used for light recycling and trapping. As an example, we investigate effects of the light management in InGaAsSb TPV converters (0.53 eV bandgap) with back surface reflector and with an additional front surface scattering layer, which provides Lambertian trapping of photons. We calculate the output power (efficiency) and investigate tradeoff between photon absorption and Auger recombination processes as a function of the device thickness. Finally, we compare performance of these TPV devices with the performance of traditional devices.

Selective Laser Melting (SLM) involves numerous fabrication parameters, the interaction between those parameters determine the final characteristics of the resulting part and because of the latter, it is considered a complex process. Low-density components is one of the main issues of the SLM process, due to the incorrect selection of process parameters. These defects are undesired in high specialized applications (i.e. aerospace, aeronautic and medical industries). Therefore, the characterization of the defects (pores) found in aluminum parts manufacture by SLM and the relationship with fabrication parameters was performed. A robust orthogonal design of experiments was implemented to determine process parameters, and then parts were manufactured in SLM. Relative density of the samples was then characterized using the Archimedes principle and microscopy; the data was then statistically analyzed in order to determine the optimal process parameters. The main purpose of the present research was to establish the best processing parameters of an in-house SLM system, as well as to characterize the pore geometry in order to fully eliminate pores in a future research.

Semiconductor nanowires (NWs) have widely been studied as an ideal platform for developing electronic, photovoltaic, photonic devices and biological probes in the nanoscale. The ability to synthesize high-quality NWs of various materials with a precise control in shape, doping and crystal structure is the key to the growth of NW-based technologies. In the past decade, there has been growing interest in controllably creating NW heterojunctions and periodically-modulated superlattices (SLs) because it is expected to bring new functionalities that are not present in uniform NWs. In particular, the interaction of NW SLs with light has been one of the central interests because the diameter and modulation length scale are on the same order as the wavelength of light in the optical regime. Also, degenerately-doped semiconductor NWs exhibit localized surface plasmon resonances (LSPRs), which comprises unexpected long-range interactions when the plasmon resonators are regularly placed in NW SLs. In this review, I will summarize the recent progress in photonics research of NW SLs. The topics discussed include preparation and types of NW SLs, light-trapping and light-emission properties, and plasmonic optical- and thermal-transport properties.

Prostate cancer has a strong preference for metastasizing to bone which is the primary cause of prostate cancer-related morbidity and mortality. The complex nature of cancer metastasis requires the development of translational models that recapitulate a specific metastatic stage. Herein, we report the mimicking of mesenchymal to epithelial transition (MET) of prostate cancer cells using highly metastatic and a non-metastatic prostate cancer cell lines. A unique cell culture technique that we termed as ‘sequential culture’ was used to create a biomimetic bone microenvironment for metastasized prostate cancer cells by introducing bioactive factors from osteogenic induction of human mesenchymal stem cells (MSCs) within the porous 3D scaffolds. The in vitro 3D tumor model can be used as a testbed to study the interaction between prostate cancer and bone microenvironment and for the design of novel therapeutic studies.

Electrohydrodynamic (EHD) instabilities can be induced in polymers by placing a polymer film above its Tg in a strong electric field between two capacitor plates or electrodes. The polymer experiences an electrostatic stress at the interface between the polymer and air due to a mismatch in their dielectric constants. This stress, along with thermal fluctuations, induces small magnitude capillary waves in the polymer film, and the minima and maxima of those waves experience slightly different electric field strengths. In a sufficiently strong electric field, the capillary wave maxima, where the distances between the polymer film and the top electrode(s) are the smallest, are eventually drawn up to the top electrode. The wavelength of the instabilities in the film and the ability of the polymer to be drawn upward is a dependent on the competition between surface tension forces and the electrostatic stress imparted on the polymer. While EHD instabilities are typically used to pattern polymer surfaces on a nanometer-scale, instabilities have been induced in polymer films with air gaps up to 500 μm. Upper electrodes with non-planar structures have also been used to induce instabilities in polymer films, resulting in patterned polymer surfaces without contact. Size, shape, arrangement, and placement of the upper electrode relative to the polymer film and lower electrode, as well as the processing conditions such as temperature and applied voltage, can all be modified to produce a desired array of structures with tailored performance characteristics. Patterned polymer surfaces can provide high-index contrast over a periodic matrix with 3-dimensional element shapes. The dielectric contrast and array pitch and height can be tuned to control specular reflection and achieve specific scattering characteristics. Surfaces with tailored scattering characteristics in the aforementioned ranges could be useful in producing frequency-selective windows for glare reduction, anti-reflective solar cells with enhanced efficiency, surface waveguides and whispering gallery-mode resonator arrays for integrated photonics and sensors, and surfaces with controlled emissivity for directed heat dissipation.

Pure and Nb-doped zirconium germanate materials of composition K2-xZr1-xNbxGe3O9.H2O where x = 0, 0.1, 0.2 and 0.25 with the structure of the mineral umbite have been successfully synthesised. The parent material displays negligible ion exchange of K+ for Cs+ but the doped materials shows much improved exchange. Synchrotron X-ray diffraction shows substantial peak splitting which varies with increasing niobium content. Preliminary Rietveld refinements suggest a two phase model with a caesium and potassium rich doped umbite phase.

Using first-principles calculation, we investigate water-dissociation dynamics in a Σ5 tilt grain boundary (GB) of Methyl-Ammonium Lead Triiodide (MAPbI3) perovskite. We find that the water dissociation process undergoes with two-step reaction at the GB: one of H ions of a water molecule that segregates into the GB is dissociated, migrates along the GB, and is attracted by an N atom in the MAPbI3, following the H-ion release from the ammonium. The process thereby generates OH− ion and, in turn, leads to possible initiation of the degradation for crystallinity in the perovskite.

The discovery and optimization of phase-change and shape memory alloys remain a tedious and expensive process. Here a simple computational method is proposed to determine the ideal phase- change material for a given alloy composed of three elements. Using first-principles calculations, within a high-throughput framework, the ideal composition of a phase-change material between any two assumed phases can be determined. This ideal composition minimizes the interface strain during the structural transformation. Then one can target this ideal composition experimentally to produce alloys with low mechanical failure rates for a potentially wide variety of applications. Here we will provide evidence of the effectiveness of our calculations for a well-known phase- change material in which we predict the ideal composition and compare it to experimental results.