In this paper, we will describe the nature of defects and impurities in thick epitaxial-Si layers and their influence on the cell efficiency. These wafers have very low average dislocation density. Stacking faults (SFs) are the main defect in epi layers. They can occur in many configurations—be isolated, intersecting, and nested. When nested, they can be accompanied by formation of coherent twins resulting in dendritic growth, with pyramids protruding out of the wafer surface. Such pyramids create large local stresses and punch out dislocations. The main mechanism of dislocation formation is through pyramids. Stacking faults degrade solar cell performance. Analyses of the solar cells have revealed that the nested SFs have a controlling effect on the solar cell performance. A well-controlled growth can minimize defect generation and produce wafers that can yield cell efficiencies close to 20%.

This paper describes the organometallic synthesis of pure rhenium nanoparticles (Re NPs) and their characterization by a combination of state-of-the art techniques (TEM, HAADF-STEM, EDX, WAXS, EA, FT-IR). The Re NPs synthesis is achieved by reducing the [Re2(C3H5)4] complex in solution under a dihydrogen atmosphere and in the presence of hexadecylamine or polyvinylpyrrolidone as stabilizing agents. The so-obtained Re NPs are monodisperse with a mean size of 1.1 nm (0.3) nm and display a spherical shape with a disordered hcp structure.

We analyze and compare optoelectronic properties and hot carrier relaxation dynamics in different forms of TiO2 anatase materials: nanowires and thin films. The models are chosen in such way that the same crystallographic surfaces are exposed and any difference in properties is attributed to the change of the dimensionality of the nanostructure. Specifically, we give a brief review of the electronic properties and non-adiabatic excited state dynamics of <001> anatase TiO2 nanowire as well as (100) and (001) anatase TiO2 surfaces. The calculated band gap of nanowire is larger than the ones of surfaces. The hole relaxation rate is higher than the electron relaxation rate for both the surfaces and nanowire, and the electron and hole relaxation rates of surfaces are larger than the ones of nanowire.

The Next Generation Science Standards make scientific discourse a vital part of the classroom and arguing with evidence needs to become a common practice for students. Analysis and interpretation of data are an integral part as well. We present an approach using 21st-century technology combined with collection of laboratory data that is suitable for middle school through college. In an experiment using common nuts and bolts first semester chemistry students form six groups and determine a bolt mass indirectly. They collect mass data; then enter the data into an online form that compiles the data into a spreadsheet in Google Drive, a free cloud-based application. Once all the groups have submitted their data, they access the spreadsheet online and start an emulated online discussion in the laboratory as if the groups were globally dispersed using the chat feature available in Google Drive. Each group is identified by a group number having a unique group email address so there is a semi-anonymous sense among the members that allows for a fairly free discussion among students.

CTGS (Ca3TaGa3Si2O14) is a commercially available, Czochralski-grown piezoelectric material from the langasite family that has an ordered crystal structure. It can be excited piezoelectrically up to at least 1285 °C, which is very close to the melting temperature of 1350 °C. In order to determine the loss at elevated temperatures, two different resonance techniques are used. A contactless transduction method is employed up to about 600 °C, whereas transduction involving standard keyhole-shaped film electrodes is employed up to 1285 °C. Comparison of the temperature-dependent inverse Q factor shows that contactless measurements are best suited for the lower temperature range, where sample clamping and losses caused by the electrodes contribute significantly to the total loss. However, at higher temperatures, measurement of the electrical impedance of samples with film electrodes in the vicinity of the resonance frequency proves to be suitable. Even at 1100 °C, 5 MHz CTGS resonators are found to have a Q factor of about 1200, which is great enough to enable numerous bulk-acoustic-wave applications. Further, a nearly linear temperature dependence of the resonance frequency with a temperature coefficient of 210 Hz/K makes Y-cut CTGS well suited for temperature-sensing applications.

Black liquor is a by-product of the paper mill Kraft process that deserves more valorization than its present use as low-grade fuel. In this work, SiC/C composite foams were prepared for the first time from concentrated emulsions by carbothermal reduction of bio-sourced precursors combining sodium silicate by lignin at 1400°C. The composition of the materials was determined by XRD, FTIR and Raman analyses. Their porous structure was characterized by SEM, mercury intrusion porosimetry, and nitrogen sorption, while their thermal properties were measured by TGA and dynamic DSC. Concerning their heat transport properties, we found out that when the starting lignin content was increased, the final C/Si ratio, the specific surface area and the heat diffusivity increased as well. Its high values were attributed to a cooperative effect between radiative heat transfer and the presence of partially graphitized carbon.

Combination of superconducting (SC) and ferromagnetic (FM) sheets into layered SC/FM composites allows to obtain metamaterials with unusual magnetic properties: the effective magnetic permeability along the sheets could be much higher than in the perpendicular direction. One can design the magnetic cloak consisting of a shell from SC/FM composite protecting its inner space against the penetration of a static magnetic field. Difference between such a device and a usual SC or FM shield will be in its un-detectability by magnetic sensors checking the field distribution outside the cloak. Thus it could be considered a magnetic invisibility cloak and one can think about using it e.g. for protecting a sensitive electronic circuitry in an electric machine.

We have prepared a series of SC/FM cloaks using commercial coated conductors as the superconducting elements and various kinds of ferromagnetic sheets as the ferromagnetic elements. Finite element calculation was utilized to optimize the architecture. Experimental testing of the cloaking ability in static magnetic field was performed by scanning the field distribution in vicinity of the cloak. Detectability in low frequency (< 100 Hz) AC magnetic fields was tested in an AC magnetization set-up allowing to see both screening and dissipation signals. Recording of magnetization loops allowed to analyze in detail the dynamics of field interaction with the cloak. Reduction of the detected magnetic signature due to the cloak was confirmed, however it is still not complete. Tests of various arrangements of superconducting and ferromagnetic materials allowed to identify the main problems hindering to achieve a perfect cloaking.

Most of what is known about the Iron Age in Southeastern Kazakhstan has been learned from kurgan burials and historical accounts describing the largely nomadic lifestyle of steppe populations from the 8th century B.C.E. to the 5th century C.E. Recent archaeological surveys however, are revealing an unexpectedly large number of settlements at the edges of the steppe, along the northern slopes of the Tien Shan Mountains. One of these sites, Tuzusai, has provided a wealth of ceramic finds that offer insight into local pottery production traditions and their social and material contexts. Our preliminary analysis of both pottery and local clay and temper resources suggests that the community at Tuzusai engaged in feasting activities that incorporated a diverse vocabulary of pot forms. The overwhelming majority of these forms appear to have been locally produced using assembly strategies that responded to shortcomings in available raw materials. Given our current understanding of local production resources and the technical difficulty associated with the production of thin walled forms using these materials, we suggest that these ceramics may be high-status goods valued not solely for their function in feasting activities, but for the labor and skill required to produce them.

In this work, the exothermic reaction of the chemical energy storage material for stranded renewable energy, lithium is analyzed in carbon dioxide (CO2) and air. Spectroscopic techniques were used to characterize the reaction of bulk lithium pellets of up to 1 g weight. In comparison, power plant applicable combustion of atomized lithium spray was analyzed.

Electrical high voltage spark was used to overcome to activation energy of the combustion for the experiments with bulk lithium. The lithium spray was successfully ignited by pre-heating the reaction gases (air and CO2).

Radiation temperature of the bulk lithium during reaction in air was calculated to 2260 K. The observed green and red emission of the lithium combustion could be demonstrated in the spectral analysis.

In CO2 atmosphere the reaction products were found to be lithium carbonate with little lithium oxide. Beside, lithium carbide could be detected in the reaction product of the combustion of bulk lithium. The gaseous reaction product carbon monoxide (CO), which could be further converted with hydrogen from renewable sources to valuable methanol or gasoline, was detected online by gas analysis.

The present work addresses the systematic evaluation of the influence of the incorporation of dopant species (Ca+2, Ag+1) on the structural and functional properties of bismuth ferrite (BFO) nanocrystalline powders and films. Pure and doped BFO powders and thin films were synthesized by a modified sol-gel method. The concentration of the doping species varied from 0 up to 7 at %. The development of the host BFO structure was confirmed by XRD analyses of samples annealed at 700°C for one hour in air and nitrogen atmosphere. Thicknesses of films varied between 80 and 200 nm, depending on the concentration of Ca+2 species. Doped BFO exhibited a magnetic behavior that turned from paramagnetic into ferrimagnetic with the increase of Ca+2 concentrations.

Uniform and multilayered nanocomposites are of growing interest due to their desirable mechanical properties and their performance under high stress, wear, and impact conditions. Composite structures offer an opportunity to combine the useful properties from multiple materials. Controlled variations in composition and microstructure within a composite material allow for tunable local variations in properties. The simplest version of such a variation is to periodically change the composite volume fraction to create a multilayered composite material. Such structures would have hard layers to maintain strength and softer layers to allow for greater plasticity and prevent brittle failure. We are able to manufacture uniform and layered composites of nickel matrices embedded with alumina nanoparticles using electrodeposition. In this method a rotating disk electrode (RDE) is used to directly control the rate of particle incorporation. Uniform composites are made by holding a constant RDE rotation rate while layered composites are manufactured by periodically varying the rotation rate during deposition. We have demonstrated this novel manufacturing process for large-scale samples, several square centimeters in area and hundreds of microns thick, while maintaining submicron microstructural resolution.

The electronic properties of the interface between Rh clusters and CeO2 (111), (110) and (100) surfaces were studied using an isothermal-isobaric (NPT) ensemble at 773 K and 101.343 kPa using the tight binding-quantum chemical molecular dynamics (TB-QCMD) method. The amount of electronic exchange by interaction at the interface between the supported Rh55 clusters and each CeO2 surface was investigated quantitatively. A comparison of the mean square displacement (MSD) showed that the topmost oxygens on the Rh-supporting CeO2 surface exhibited higher mobility than those of the bare CeO2 surface. Although the mobility of the topmost oxygens on the bare CeO2 surface was in the order (100) > (110) > (111), this sequence was altered by the presence of Rh, so that the oxygen mobility for the more open (110) surface was the largest. The amount of electron exchange that occurred between Rh and the CeO2 (110) surface was also larger than for the (111) or (100) surface. The Ce 4f orbitals on the CeO2 (110) surface exhibited the strongest mixing with Rh 4d orbitals, which simultaneously caused restructuring and instability of the topmost Ce-O bonds. This enhancement of oxygen migration in the presence of Rh was occurred together with an increase in the number of oxygen vacancies on the ceria surface. This was because the topmost oxygens was shifted to have a stronger affinity with Rh and thus formed stronger bonds with Rh than with Ce.

Understanding crystal orientation at the ferroelectric domain level, using a non destructive technique, is crucial for the design and characterization of nano-scale devices. In this study, piezoresponse force spectroscopy (PFS) is used to identify ferroelectric domain orientation. The impact of crystal orientation on the switching field of ferroelectric BaTiO3 is also investigated at the domain level. The preferential domain orientations for BaTiO3 thin films prepared by pulsed laser deposition (PLD) in this study are [001], [101] and [111]. They have been mapped onto PFS spectra to show three corresponding switching fields of 460, 330 and 120 kV/cm respectively. In addition, the electric field at which the enhanced piezoresponse occurs was found to vary, due to a phase change. The polarization reversal occurs via a 2-step process (rotation and switching) for [101] and [111] orientations. The piezoresponse enhancement is absent for the [001] (pure switching) domains. The results demonstrate that an electric field induced phase change causes the [101] and [111] domains to reverse polarization at a lower field than the [001] domain.

The occurrence of Atmospheric chloride-Induced Stress Corrosion Cracking (AISCC) under wetted deposits of MgCl2 or sea-salt at 70°C has been investigated at various Relative Humidities (RH). The appearance of AISCC is a function of the environmental RH. At 33% RH (the deliquescence point of MgCl2), AISCC generated under MgCl2 or sea-salt deposits is of a similar appearance with regards to the number of cracks produced and average crack length. At 50% RH sea-salt seems to be more aggressive at least in terms of crack frequency. This observation may highlight the significance of carnallite (KMgCl3.6H2O) in promoting AISCC in types 304L and 316L stainless steels. The use of accelerated testing methods to validate apparent thresholds in chloride deposition density and other critical factors that influence the initiation and propagation of AISCC is briefly discussed.

Molecules such as dithiols are of significant interest for potential molecular electronics applications. To investigate their properties, an efficient method for measuring their electrical conductance is crucial. This research focuses on the time domain measurement, a novel technique capable of measuring hundreds of molecules within a matter of seconds. Measurements were conducted using STM with the tip positioned within tunneling distance over a SAM of 1,8-octanedithiol on Au(111)-mica substrate submerged in toluene. Bonding/debonding events between the tops of molecules and the tip were observed through jumps in the time domain current waveform. A new time-spent histogram data analysis technique was developed to extract conductance values from complex waveforms. Conductance of 2.6 nS was obtained for a single 1,8-octanedithiol molecule, consistent with results obtained from wellestablished but time consuming break junction technique, validating the new STM based time domain technique for fast measurement of molecular conductance.

In the present study a new sandwich laminate is designed and mechanically characterized. The laminate is elaborated with a core of particulate composite material consisting of recycled material from milk and juice cartons (multilayer laminate of Tetra Brik® ), and HDPE containers from Urban Solid Waste (USW). The elaborated material consists of aluminum facings with a particulate core, consolidated with a thermoplastic adhesive of polypropylene- maleic anhydride. The main properties under tension are evaluated under testing standards. Results show good compatibility in the union of elements, with potential applications in building facades and false walls for the construction and furnishing industries.

Bacterial infections are commonly found on paper towels and other paper products leading to the potential spread of bacteria and consequent health concerns. The objective of this in vitro study was to introduce antibacterial properties to paper towel surfaces by coating them with selenium nanoparticles. Results showed that the selenium nanoparticle coated paper towels inhibited the growth of S. Aureus and P. aeruginosa by 80%∼90% after 72 hours compared with the uncoated paper towels. Thus, the study showed that nano-selenium coated paper towels may lead to an increased eradication of bacteria to more effectively clean a wide-range of clinical environments, thus, improving health.

Fibrin hydrogels are an exciting platform for cell-based therapies, as they contain necessary cues for adhesion, can be remodeled by entrapped cells, and the biophysical properties can be modified with a plethora of strategies. Furthermore, fibrin acts as a provisional matrix in vivo for tissue regeneration. While the majority of studies seek to manipulate fibrin gel properties by changing the concentration of clotting proteins, these studies highlight our capacity to change bulk stiffness and fiber properties by supplementing the solutions with sodium chloride (NaCl). Physical properties including fiber thickness, porosity, compressive modulus, and fluid uptake capacity were dependent on NaCl content, with gels containing 2.60% (w/v) NaCl exhibiting compressive moduli threefold higher than gels without NaCl. These material properties, in turn, affected the gel morphology along with the osteogenic and pro-angiogenic response of entrapped mesenchymal stem/stromal cells (MSCs). The osteoconductivity of fibrin gels can be enhanced by inclusion of apatite-coated polymer substrata to nucleate mineral, while the efficacy of engineered fibrin gels to simultaneously deploy small molecules with cells to enhance endogenous angiogenic potential has been demonstrated. Collectively, these data demonstrate the broad capacity of engineered fibrin gels to regulate function of entrapped cells for use in tissue engineering and regenerative medicine.

A simple methodology to electrodeposit thin soft CoFe films with desirable microwave properties from simple salt solutions at room temperature is demonstrated. Plating solution parameters have diverse influences on real potentials of ion reductions and deposition behavior of the FeCo crystals, consequently affecting largely the particle size, crystal structure and chemical composition of the film fabricated. This in turn determines their static magnetism and dynamic microwave properties. Through optimizing solution additive, concentration and temperature from electrodeposition mechanism, the as-prepared nanofilms possess a low coercivity of < 30 Oe, moderate anisotropy of 60-90 Oe, high crystallinity and magnetic moment of ≥ 2.0 T, and hence readily display an ultrahigh magnetic permeability (up to 1128) and resonant frequency (up to 2.1 gigahertz) simultaneously, as well as other desirable physico-chemical properties. Thus the nanofilms can be applied to high gigahertz frequency applications.

This study demonstrates the development of a zinc oxide (ZnO) based microelectrode sensor for the ultra-sensitive detection of protein biomarkers. Our research focuses on utilizing a materials-based approach to achieve this objective by utilizing ZnO as part of our biosensor for (1) improved surface binding to enhance sensitivity and (2) creating a nanotextured surface for enhanced output signal response. Nanotextured ZnO thin films were integrated onto printed circuit boards using RF magnetron sputter deposition. Films sputtered with and without the presence of oxygen were examined for possible differences in biosensor efficacy. These fabrication conditions not only dictate the number of oxygen vacancies within the film but also regulate the amount of zinc and oxygen terminated ends occurring on the material surface. The correlation between the surface terminations of the nanotextured ZnO to its performance as a biosensor was evaluated using two cross-linker molecules, dithiobis succinimidyl propionate and (3-aminopropyl)triethoxysilane, that maintain different binding chemistries to ZnO. Qualitative and quantitative assessment of cross-linker binding was accomplished using fluorescent microscopy and fluorescent intensity measurements. Electrical impedance spectroscopy (EIS) was used as the transduction mechanism for detection of the well-established cardiac biomarker, troponin-T. Utilizing EIS with a functionalized immunoassay on the ZnO surface, troponin-T was detected as low as 10 fg/mL using ZnO films sputtered without oxygen. This enhanced detection of the cardiac biomarker can be directly attributed to 1) oxygen vacancies within the metal oxide film, 2) the nanotexturing of the sensing site surface, and 3) the ability to bind a significant amount of cross-linker molecules for immobilizing capture antibodies.