Both synthesis and photocatalytic potential of an innovative catalyst-powder type composite material based on the Zn or/and ZnO dispersed in a matrix of amorphous-carbon have been investigated. Zn/ZnO/amorphous-carbon nanostructured-matrix composite was prepared by partial pyrolysis method based on the Pechini method. The amorphous character of composite was characterized X-ray diffraction, while chemical bond investigated by infrared spectroscopy. The photocatalytic activity directed to the degradation of the phenol red dye of small fraction of commercial ZnO, Zn/C and Zn/ZnO/C composites were evaluated as a function of the degradation reaction of the phenol red dye, in the alkaline medium pH = 9. A mass concentration of 1:10,000 was selected being considered 30 and 150 min of reaction A comparison between photocatalytic activity showed that the degradation rate of phenol red dye is more efficient at both ZnO/Zn/C and Zn/C amorphous composites when compared to the pristine ZnO. The efficiency obeys the following order C/Zn ≥ C/ZnO/Zn > commercial ZnO with conversion equal to 70% for C/Zn and C/ZnO/Zn, while for the ZnO is around 55%. The kinetic of degradation is discussed.

Several processing methods were developed and evaluated for synthesizing empty silicon clathrates. A solution synthesis method based on the Hofmann-elimination oxidation reaction was successfully utilized to produce 20 mg of empty Si46. Half-cells using the Si46 electrodes were successfully cycled for 1000 cycles at rate of 5.3C. The capacity of the Si46 electrode in long-term tests was 675 mAh/g at the 4th cycle, but increased to 809 mAh/g at 50 cycles. The corresponding Coulombic efficiency was better than 99%. The capacity dropped from 809 to 553 mAh/g after 1000 cycles while maintaining a 99% Coulombic efficiency. In comparison, a Ba8Al8Si38 electrode could be cycled for about 200 cycles with a lower capacity and Coulombic efficiency. Potential applications of empty silicon clathrates as anode materials in Li-ion batteries are discussed.

Boron sub-2,3-naphthalocyanine chloride (SubNc) was investigated as a potentialred-sensitive organic photoconductive film (OPF). A photoconductive cell wasfabricated, and its current–voltage characteristics, both with andwithout light irradiation, and external quantum efficiency (EQE) weredetermined. The structure of the photoconductive cell was as follows, withthicknesses in nm given in parentheses: glasssubstrate/In–Zn–O (100)/spiro-2CBP (30)/SubNc(50)/Alq3 (30)/Al (50) (spiro-2CBP =2,7-bis(carbazol-9-yl)-9,9-spirobifluorene; Alq3 =tris(8-hydroxyquinolinato)aluminum). The spiro-2CBP and Alq3 layerswere inserted between the SubNc layer and the electrodes to block dark currentinjection. The three organic layers were successively deposited by evaporationin a vacuum on the In–Zn–O-patterned substrate. SubNc filmabsorbed light in the red region well, with an absorption peak at 695 nm. TheEQE of the cell reached 80% when the applied bias was 15 V. In addition, theblocking layers effectively suppressed dark current in the OPF, whichcorresponded to a current density of 20 nA/cm2 at 15 V. These resultsindicate that SubNc is a promising candidate as a red-sensitive OPF.

Interfacial dislocations (IDs) and half-loop arrays (HLAs) present in theepilayers of 4H-SiC crystal are known to have a deleterious effect on deviceperformance. Synchrotron X-ray Topography studies carried out on n-type 4H-SiCoffcut wafers before and after epitaxial growth show that in many cases BPDsegments in the substrate are responsible for creating IDs and HLAs during CVDgrowth. This paper reviews the behaviors of BPDs in the substrate during theepitaxial growth in different cases: (1) screw-oriented BPD segmentsintersecting the surface replicate directly through the interface during theepitaxial growth and take part in stress relaxation process by creating IDs andHLAs (Matthews-Blakeslee model [1] ); (2) non-screw oriented BPD half loopintersecting the surface glides towards and replicates through the interface,while the intersection points convert to threading edge dislocations (TEDs) andpin the half loop, leaving straight screw segments in the epilayer and thencreate IDs and HLAs; (3) edge oriented short BPD segments well below the surfaceget dragged towards the interface during epitaxial growth, leaving two longscrew segments in their wake, some of which replicate through the interface andcreate IDs and HLAs. The driving force for the BPDs to glide toward theinterface is thermal stress and driving force for the relaxation process tooccur is the lattice parameter difference at growth temperature which resultsfrom the doping concentration difference between the substrate and epilayer.

This work presents a comparison of the structural, chemical and electronic properties of multi-layer graphene grown on SiC(000-1) by using two different growth approaches: thermal decomposition and chemical vapor deposition (CVD). The topography of the samples was investigated by using atomic force microscopy (AFM), and scanning electron microscopy (SEM) was performed to examine the sample on a large scale. Raman spectroscopy was used to assess the crystallinity and electronic behavior of the multi-layer graphene and to estimate its thickness in a non-invasive way. While the crystallinity of the samples obtained with the two different approaches is comparable, our results indicate that the CVD method allows for a better thickness control of the grown graphene.

Structural and magnetic properties of nanocrystalline P6/mmm R(Fe,M)9C are presented. Their structure is explained with a model based on the R1–s(Fe,M)5+2s formula (s = vacancy rate) where s R atoms are statistically substituted by s transition metal pairs. The maximum coercivity is obtained for low Ga/Si content for auto-coherent diffraction domain size 30 nm. This controlled microstructure might lead to hard permanent magnet materials. Furthermore, the influence of small amount of Dy substitution on magnetocaloric properties of R-Fe systme is reported. The potential for using these low-cost iron based nanostructured RFe9 powders in magnetic refrigeration at room temperature is also discussed.

Fiber optic temperature sensors are used in a variety of harsh environment applications. We have explored use of such temperature sensors in commercial gas turbines to measure the temperature at various regions of interest within the turbine system. More specifically, fiber optic temperature rakes were designed and installed on a commercial gas turbine under full load conditions. This work will focus on failure mechanisms observed at multiple length scales that impact the performance of high temperature optical fiber sensors. It was found that Au-coated silica fibers, which are a standard in the industry, undergo various failure modes when subjected to combinations of high temperature and high vibration. More specifically, the Au coating became soft/ductile as the temperature is increased. We also observed that the Au coating was not well bonded to the silica fiber, as expected since there were no adhesion layers present. These effects led to significant damage of the fiber optic under high vibrations. We also found that vibrations from the gas turbine coupled into fundamental modes of the fiber optic probe assembly, which were analyzed by detailed dynamic mechanical analysis. This led to the fiber impacting the internal wall of the probe assembly, which caused further damage and failure of the fiber and the Au coating. The silica fibers returned from the field also exhibited significant twisting throughout most of their length. This suggests the fibers reached temperatures above their strain point (about 1000 C for pure silica glass), which is explained by either a) the strain point had been significantly reduced by the presence of the Ge dopant, or b) the temperature was higher than expected in the gas turbine exhaust region. It was also hypothesized that complex anelastic effects may play a role under the high temperature, high vibration environment experienced by the probes. Detailed structural analysis of the fiber optic temperature sensors by scanning electron microscopy, ToF-SIMS, and X-ray microscopy will be presented to corroborate the above simulations and proposed damage mechanisms. Finally, we note that the fiber Bragg gratings (FBG) present within the temperature probes provided promising temperature data, and were in fact not damaged/erased by the high temperature environment.

We have synthesized and investigated electronic properties of several non-centrosymmetric actinide compounds, which do not have an inversion center in the crystal structure “globally” or “locally”, under high pressure. The Néel temperature of an antiferromagnet UIrSi3 with “globally” non-centrosymmetric structure increases with increasing pressure at a rate of 2.5 K/GPa up to 5 GPa. On the other hand, T Ns of U2Rh3Si5 and U2Ir3Si5, which are “locally” non-centrosymmetric compounds, decrease with -1 K/GPa and -0.5 K/GPa with increasing pressure, respectively. Here, U2Ir3Si5 is a new antiferromagnet crystallizing in the U2Co3Si5-type of orthorhombic structure. Below T N = 36.5 K, U2Ir3Si5 shows magnetic order-order transition at T 0 = 26.1 K with a first-order nature. Electrical resistivity in U2Ir3Si5 shows semiconducting-like behavior due to the formation of the super-zone gap in the antiferromagnetic state. T N and T 0 as well as semi-conducting-like behavior in resistivity are suppressed by external pressure.

Corrected scanning transmission electron microscopy (STEM) was used to characterise a novel thin film displaying a complex three dimensional nanostructure. The film was prepared by plasma deposition in such a way that it self-organises into layers of silver islands (each with typical dimensions of a few nanometres) within an aluminium nitride matrix. Successful application of STEM imaging and subsequent analysis was able to determine critical information about the material structure, namely island size, shape and crystalline orientation and the detection of island – matrix intermixing. Such information is essential in being able to predict the properties of this material and the approach adopted here is applicable to any similarly structured material.

We have investigated plant growth response to atmospheric air plasma treatments of seeds on their growth for 5 plant speces; Radish sprout (Raphanus sativus L.), rice (Oryza Sativa), Zinnia, Arabidopsis L. Thaliana and Plumeri. The average length of Radish sprout, rice, Arabidopsis Thaliana, Plumeria and Zinnia, are 250%, 80%, 60%, 30% and 20% longer than those without plasma treatments, respectively. We have obtained correlation between the growth enhancement and O3 and NOx concentration. The optimum radical dose for the growth enhancement depends on plant species.

Carbon steel (C-steel) is studied to be the reference material for the metallic components in the high level waste (HLW) repository concepts of several European countries such as France, Switzerland, Belgium.

Electrochemical impedance spectroscopy (EIS) was performed over a period of 7 years, to determine the instantaneous corrosion rate (CR) of carbon steel (C-steel) in contact with clay porewater in diffusive regime. The study was conducted at the Mont Terri underground research laboratory (URL) located in Switzerland. The test chamber was at a depth of 8 m under anoxic conditions at 90°C in a vertical and descending borehole drilled in Opalinus clay (OPA). Microbial and chemical investigations were conducted on porewater in contact with C-steel as well as directly on C-steel surface further to dismantling.

The results showed clearly a decrease of the CR over time followed by a steady state below 1 µm/year. Sulphate and thiosulphate reducing bacteria were observed in porewater and at the metal surface, with a higher concentration of mesophilic and thermophilic bacteria respectively. The metal surface characterizations revealed the presence of magnetite, mackinawite, hydroxychloride and siderite with local traces of oxidizing species such as goethite.

Heteroepitaxial growth of high-quality II-VI-alloy materials on Si substrates is a well-established commercial growth process for infrared (IR) detector devices. However, it has only recently been recognized that these same processes may have important applications for production of high-efficiency photovoltaic devices. This submission reviews the process developments that have enabled effective heteroepitaxy of II-VI alloy materials on lattice-mismatched Si for IR detectors as a foundation to describe recent efforts to apply these insights to the fabrication of multijunction Si/CdZnTe devices with ultimate conversion efficiencies >40%. Reviewed photovoltaic studies include multijunction Si/CdZnTe devices with conversion efficiency of ∼17%, analysis of structural and optoelectrical quality of undoped CdTe epilayer films on Si, and the effect that a Te-rich growth environment has on the structural and optoelectronic quality of both undoped and As-doped heteroepitaxial CdTe.

Titanium dioxide (TiO2) loaded with gold (Au) as noble metal, acts as an efficient photocatalyst that has been extensively investigated for water splitting processes. In this paper, we report on the microstructure of atomic layer deposited titanium dioxide and the crystallinity modification of the material using energetic electron beam irradiation. A rapid high-energy electron beam induced crystallization of the nanostructures has been observed in-situ inside a High-Resolution Transmission Electron Microscope (HRTEM). The systematic crystallization of the nanomaterial occurring under the electron beam irradiation (300 KV) indicates the transformation of the near amorphous material into a mixture of two nuances of TiO2 polymorphs, namely rutile and anatase. We believe that this transformation will enhance the efficiency of water splitting process, as the mixed phases of rutile and anatase are known to possess better optical properties than the individual polymorphs of TiO2. This finding may be of particular interest in developing appropriate heat treatment methods for these nanostructures dedicated to water splitting to increase their efficiency.

Research in the field of phase change materials (PCMs) requires that the temperature dependence of the thermal storage capacity be well known for the selection of PCMs as well as for simulation input. A differential scanning calorimeter (DSC) is often used, but it substantially misrepresents the true heat capacity in the vicinity of large-enthalpy phase transitions. Therefore, other suitable experimental techniques should be applied for the determination of the thermal storage capacity. Peltier-element-based adiabatic scanning calorimetry (pASC) measures the heat capacity and the enthalpy of PCMs in thermodynamic equilibrium, thus removing the rate dependence and deformation that are inherent to DSC. The technique is illustrated here by measurements on the pure alkane tricosane (C23), the commercial alkane mixture RT42 and its bound counterpart PX42.

Here we discuss requirements for high performance and solution processable organic semiconductors, by presenting a systematic investigation of 7-alkyl-2-phenyl[1]benzothieno[3,2-b][1]benzothiophenes (Ph-BTBT-Cn ’s). We found that the solubility and thermal properties of Ph-BTBT-Cn ’s depend systematically on the substituted alkyl-chain length n. The observed features are well understood in terms of the change of molecular packing motif with n: The compounds with n ≤ 4 do not form independent alkyl chain layers, whereas those with n ≥ 5 form isolated alkyl chain layers. The latter compounds afford a series of isomorphous bilayer-type crystal structures that form two-dimensional carrier transport layers within the crystals. We also show that the Ph-BTBT-C10 afford high performance single-crystalline field-effect transistors the mobility of which reaches as high as 15.9 cm2/Vs. These results demonstrate a crucial role of the substituted alkyl chain length for obtaining high performance organic semiconductors and field-effect transistors.

One of the major concerns regarding the clinical translation of metal nanoparticles is related to the question of their persistence in organisms that can increase the likelihood of toxicity and the interaction/interference with common medical diagnoses.

In order to overcome these issues we have recently introduced a versatile 90 nm nano-architecture composed by: i) arrays of 3 nm gold nanoparticles, ii) functionalizable commercial polymers surrounding the gold nanoparticles, and iii) biodegradable and derivatizable silica shell embedding the polymer-nanoparticle assembly. These robust nanocapsules maintain the intriguing features of gold nanospheres but are biodegraded in physiological media to their potentially renal clearable building blocks.

The effects of TiCl4 post-treatment on the physicochemical properties of porous TiO2 (pTiO2) layers fabricated at 300 °C and 400 °C (denoted as pTiO2(300) and pTiO2(400), respectively) in CH3NH3PbI3 perovskite photovoltaic cells were investigated. Water contents (physisorbed water and water derived from surface hydroxyl groups) of pTiO2(300) and pTiO2(400) before and after TiCl4 post-treatment were measured by using temperature desorption spectroscopy (TDS). Moreover, structural analysis of the CH3NH3PbI3 perovskite part was performed by X-ray diffraction (XRD). In the case of pTiO2(300), the content of water was increased by the TiCl4 post-treatment due to the removal of residual organic compounds that existed before the treatment. It then caused a change in the surface activity of pTiO2(300) and enhancement of solar cell performance and photocurrent density, though suppression of CH3NH3PbI3 perovskite formation occurred. In comparison, contents of water were decreased for pTiO2(400), leading to enhancement of the conversion of PbI2 to CH3NH3PbI3 perovskite. As a result, there were significant increases in short circuit current density (Jscs) and PCEs. The results showed that TiCl4 post-treatment is an effective approach to prepare high-performance CH3NH3PbI3 perovskite solar cells without heat treatment at a very high temperature.

We studied MOCVD processing for direct growth of BN on 2” sapphire substrates as a template for heterostructures with two dimensional (2D) and three dimensional (3D) materials. The combined experimental evidence points to three growth modes for BN: self-terminating, 3D random, and layer-by-layer, all of which are dependent on V/III ratio, temperature, pressure, and substrate surface modification via nitridation. At moderate temperature (950-1050°C), BN growth using high V/III ratio is self-terminating, resulting in c-oriented films aligned in-plane with respect to the orientation of the sapphire substrate. BN films grown under low V/III ratios are 3D, randomly oriented, and nano-crystalline. At higher temperature (1100°C), self-terminating growth transitions to a continuous layer-by-layer growth mode. When BN growth is self-terminating, films exhibit atomically smooth surface morphology and highly uniform thickness over a 2” sapphire wafer. Using these BN/sapphire templates we studied the growth of 2D and 2D/3D heterostructures. To study direct growth of 2D on 2D layered material we deposited graphene on BN in a continued process within the same MOCVD system. Furthermore, we explore the growth and nucleation of 3D materials (GaN and AlN) on BN. AlGaN/GaN based high electron mobility transistor (HEMT) structures grown on BN/sapphire exhibited two-dimensional electron gas characteristics at the AlGaN/GaN heterointerface, with room-temperature electron mobility and sheet electron density about 1900cm2/Vs and 1x1013cm-2, respectively.

Resistive switching behaviors in Aloe vera films are being explored for nonvolatile memory applications. A simple structure in which the Aloe vera films sandwiched in between a top and bottom electrode are used. The switching behaviors of the devices in which the Aloe vera film is dried at different temperatures and the roles of top electrode materials (Al and Ag) are investigated. Current density–voltage measurements reveal that filamentary conduction is the dominant conduction process inducing resistive switching characteristics in Aloe vera films. Device with Al-top electrode requires a forming voltage higher than devices with Ag-top electrode, due to the tendency of oxide formation of these materials. The resistive switching behaviors are highly reproducible, as demonstrated by the data retention performance over an interval of 104 s and endurance capability of over 100 cycles.

Near real-time visualization of complex two-phase flow in a porous medium was demonstrated with dynamic 4-dimensional (4D) (3D + time) imaging at the 2-BM beam line of the Advanced Photon Source (APS) at Argonne National Laboratory. Advancing fluid fronts through tortuous flow paths and their interactions with sand grains were clearly captured, and formations of air bubbles and capillary bridges were visualized. The intense X-ray photon flux of the synchrotron facility made 4D imaging possible, capturing the dynamic evolution of both solid and fluid phases. Computed Tomography (CT) scans were collected every 12 s with a pixel size of 3.25 μm. The experiment was carried out to improve understanding of the physics associated with two-phase flow. The results provide a source of validation data for numerical simulation codes such as Lattice-Boltzmann, which are used to model multi-phase flow through porous media.