Robust time-averaged molecular dynamics has been developed to calculate finite-temperature elastic constants of a single crystal. We find that when the averaging time exceeds a certain threshold, the statistical errors in the calculated elastic constants become very small. We applied this method to compare the elastic constants of Pd and PdH0.6 at representative low (10 K) and high (500 K) temperatures. The values predicted for Pd match reasonably well with ultrasonic experimental data at both temperatures. In contrast, the predicted elastic constants for PdH0.6 only match well with ultrasonic data at 10 K; whereas, at 500 K, the predicted values are significantly lower. We hypothesize that at 500 K, the facile hydrogen diffusion in PdH0.6 alters the speed of sound, resulting in significantly reduced values of predicted elastic constants as compared to the ultrasonic experimental data. Literature mechanical testing experiments seem to support this hypothesis.

Using ultrafast angle-resolved light scattering technique, we were able to trigger photoinduced phase transition processes in V2O3 film grown on a glass substrate. The phase transition is caused by photoacoustic wave in the film and appears as coherent oscillations of scattering signal at various time scales. These processes strongly depend on the size of microstructures constituting the V2O3 film. One of the key findings of our study is the presence of a size dependent phase transition threshold for V2O3 microstructures, where small size structures ( $\tilde <$ 0.5μm) have lowest contribution to the phase transition. The presence of this threshold can be well described by considering uneven internal strain in the films which is one of the key parameters controlling phase transition dynamics in various vanadium oxides.

Precision molding is a replicative production method for the mass production of complex glass optics in high precision. In contrast to the traditional material removal process, such as grinding and polishing, the surface as well as the entire shape of the optical component is created by deforming glass at elevated temperatures using precise molding tools with optical surfaces. The molded glass components present high shape accuracy and surface finish after the molding process, therefore no further processing is required. During the molding process, the glass is heated in the molding tool up to above the transition temperature Tg, then pressed into desired shape and cooled down to approximately 200 °C. The precision glass molding is therefore a complex thermo-mechanical process, in which the glass lens undergoes uneven cooling speed and stress distribution. These lead to several drawbacks on the molded glass optics, such as form deviation, index change and fracture. In this study, FEM simulation was employed in order to achieve preliminary understanding of the molding process. The FEM model included viscoelasticity behavior of glass material (stress-relaxation, structure-relaxation and thermos-rheological simplicity), as well as thermodynamics model of the molding machine. In the form of a case study of a real molding example, the form deviation, index change and fracture of the molded glass optic were predicted in advance of the molding experiment by means of the numerical calculation of thermal shrinkage, volume change and stress distribution respectively. The good agreement between simulation results and molding experiment results proves the accuracy of the developed FEM model.

The two-phase systems of pure diluent FS-13 – aqueous solution of 14 mol/L nitric acid and 0.02 mol/L solution of CMPO in diluent FS-13 – aqueous solution of 14 mol/L HNO3 were studied at autoclave temperatures 170 °C and 200 °C. The effect of pre-irradiation on the kinetics of thermolysis was determined. All samples were irradiated using an electron accelerator at a dose rate of 10 kGy/h up to absorbed doses of 0.1, 0.5 and 1 MGy. The parameters of heat and gas emissions were determined during thermolysis of the studied extraction system in a closed apparatus. It has been shown that the conditions required for the growth of autocatalytic oxidation are not created during heating of the two-phase systems in closed vessels even for the extraction systems contacted with 14 mol/l HNO3 for two weeks.

As an extension of our previous proving that ion beam synthesis is an efficient route to form doped silicon nanocrystals (nc’s) [1, 2], we show here that ion beam synthesis, by co-implantion of the dopant and of the constituents of the alloy, followed by a single high temperature anneal, is also a convenient way to grow more complex structures, such as As doped nc’s of Si1-xGex alloys.

Rutherford backscattering spectrometry (RBS) is used to measure the impurity profiles and evaluate the average concentration of the various species (Si, Ge, As). The formation of the nc’s is evidenced by TEM observation and further confirmed by Raman and XRD analysis, which also allow us to estimate the Ge content of the nc’s.

The incorporation of As inside the Si1-xGex nc’s is attested by the presence of the characteristic Ge-As related line in the Raman spectra of the As-doped samples, and strengthened by the increased conductivity of MOS structure including such doped nc’s inside the dielectric film.

More than 50 high school students each year learn how to conduct science research at the Garcia Summer Scholars Program at Stony Brook University through hands-on, inquiry-based methods. Started in 1998, the program has already provided hundreds of students from diverse backgrounds a unique opportunity for outstanding scientific performance and achievement. In this paper, we present a brief overview of how the program operates as well as several case studies that display the effect of the Garcia Program on student accomplishment. The evidence provided demonstrates that the Garcia Program has had an overwhelmingly positive effect on its many student participants, regardless of their background or socio-economic status.

Microscopy studies were performed over a series of metal-organic-framework (MOF) imbedded electrospun fibers. Analysis of as-spun fibers revealed five different MOF particle-fiber imbedded morphologies including complete particle encasement, over-filled, surface-bound, welded, and agglomerated. To mitigate issues with fiber breakup during electrospinning (ES) due to MOF particle incorporation, secondary growth method was used. Secondary growth was performed on both Matrimid and polysulfone fibers impregnated with a MOF, ZIF-8, in either water or methanol solvents. Results show that when water was used, crystal formation was limited to formation on the top layer of the fiber mat due to hydrophobicity. When methanol was used in place of water, MOF crystal growth occurred in a patchwise manner, where crystals grow across fibers and span the entire fiber mat. From this work, it was determined that successful secondary growth of MOF imbedded electrospun fibers can be accomplished when particles are either highly exposed along the fiber surface for adequate exposure to solvent, or the solvent used promotes reactant penetration into the polymer to allow access to the seeded MOF crystals.

We report the temperature dependence of Er optical centers in GaN epilayers prepared by metal-organic chemical vapor deposition under the resonant excitation (4 I 15/2 → 4 I 9/2) excitation using a Ti:Sapphire laser (λexc = 809 nm). High resolution infrared spectroscopy and temperature dependence measurements of photoluminescence intensity from Er ions in GaN have been performed to identify the crystal filed splitting of the first excited state, 4 I 13/2. Here, we have employed a simple approach to determine activation energies which are related to the thermal population of electrons from the lowest level to the higher level of the crystal field splitting of the first excited state.

In this paper, we experimentally study the unique surface sensing property and enhanced sensitivity in subwavelength grating (SWG) based microring resonator biosensors versus conventional ring resonator biosensors. In contrast to a conventional ring, the effective sensing region in the SWG microring resonator includes not only the top and side of the waveguide, but also the space between the silicon pillars on the propagation path of the optical mode. It leads to an unique property of thickness-independent surface sensitivity versus common evanescent wave sensors; in other words, the surface sensitivity remains constantly high with progressive attachment of biomolecules to the sensor surface. To increase the robustness of performance of ring shaped circular SWG biosensors, we experimentally demonstrate silicon SWG racetrack resonators. A quality factor of 9800 and bulk sensitivity (S) is ∼429.7 nm/RIU (refractive index per unit) results in an intrinsic detection limit (iDL) 3.71×10-4 RIU in racetrack SWG biosensors while still retaining the accumulated surface thickness properties of circular rings.

The challenges of a high temperature environment impose severe material performance constraints in terms of melting point, oxidation resistance and structural functionality. In metallic systems the multiphase microstructures that can be developed in the Mo-Si-B system and Nb silicide alloys offer useful options for high temperature applications. Since the alloy compositions that exhibit the lowest oxidation rate will most likely not yield optimum mechanical properties performance, it is important to develop robust and compatible oxidation resistant coatings. An effective strategy to achieve the necessary environmental resistance is based upon the use of an integrated Mo-Si-B based coating that is applied by a pack cementation process to develop an aluminoborosilica surface and in-situ diffusion barriers with self-healing characteristics for enhanced oxidation resistance. The environmental performance requires resistance not only to high temperature oxidation, but also resistance to water vapor, CMAS (calcia-magnesia-aluminosilica) attack, hot corrosion and thermal cycling. Under these extended environmental conditions the Mo-Si-B based coating exhibits robust performance.

We report on the establishment of a new lab-scale experimental capability for Spin and Angular Resolved Photoemission Spectroscopy (SARPES) for the study of valleytronics related materials. The ARPES capabilities of the system were demonstrated by measurement on gold [Au(111)] and molybdenum disulphide (MoS2) single crystals and the full functionality of the spin detector was also verified. Experimental results are compared with theoretical modeling by ab-initio band structure calculations. We discuss the potential scope of measurement that this experimental setup affords for investigating spin-related properties (e.g. spin-orbit coupling, valley transport, etc.) in layered materials.

The study of several types of plasma reactors used to obtain carbon nanostructures (CNS) is realized in the Laboratory of Plasma Applications. To obtain carbon nanotubes (CNT) thermal plasma was used and carbon nanofibers (CNF) were obtained with glow discharge. Optical emission spectroscopy was applied to correlate some plasma parameters with CNS growth. Several analytical techniques are used to study CNS obtained by both plasma techniques.

In this work, we present results concerning the use of CNS as harmful gases traps and some results of a CNT based supercapacitor prototype are also depicted.

Experimental results here detailed, show the capacity of CNF to absorb nitrogen oxides (NOx), sulfur dioxide (SO2) and, at less proportion, carbon dioxide (CO2).

CNF films were obtained by electrophoretic deposition technique and by adding CNT ink; preliminary results showed a capacitance value of 2.69 F/g. This value remains still low compared to some supercapacitors, therefore additional work has to be done in order to improve the capacitance value.

We are developing millimeter wave (mm-wave) components and circuits based on hydrogen-intercalated graphene. The development covers epitaxial graphene growth, device fabrication, modelling, integrated circuit design and fabrication, and circuit characterizations. The focus of our work is to utilize the distinctive graphene properties and realize new components that can overcome some of the main challenges of existing mm-wave technologies in term of linearity.

The CMP challenges for advanced technology nodes are discussed. Global and local uniformity challenges and their cumulative effects are presented. Uniformity improvements for advanced node integration were achieved through slurry, pad and platen optimization, innovative integration schemes, the reduction of incoming variation and the reduction of cumulative effects. We discuss reduction of typical CMP defect types. Defects resulting from simple mechanisms (foreign material, polish residues) and those resulting from chemical and physical interactions (corrosion, chemical attack, scratches, physical migration) and strategies for control are studied. Defectivity reduction measures include new post-CMP clean chemicals, new slurries and pads and reduction of incoming defectivity. Finally we discuss an observed tradeoff between good defectivity and good uniformity.

We report the use of a novel extrusion tip that allows for the omnidirectional printing of eutectic gallium-indium (eGaIn) alloy onto the surface of hydrogel materials into complex 2-dimensional patterns. The use of these printed soft “wires” as an electrothermal heating element for soft robotics purposes was explored. Heating of the eGaIn structures encapsulated in an alginate/acrylamide ionic-covalent entanglement hydrogel was measured by a thermal imaging camera. It was determined that eGaIn is a suitable material for use in future soft robotics applications as an electrothermal heating element to actuate thermally responsive N-isoproylacrylamide hydrogels.

Cerium incorporation in zirconolite glass-ceramic systems, consolidated by hot isostatic pressing, was investigated. Samples were formulated to target Ce incorporation on the Ca and / or Zr sites. Results show successful incorporation of Ce into the ceramic phase although complete waste digestion was not achieved. The formation of a Ce-bearing perovskite phase when targeting Zr substitution, was associated with reduction of Ce4+ to Ce3+. This study is part of preliminary work towards fabricating Pu-bearing glass-ceramic HIP samples.

A TEM study of pure tantalum and tantalum-tungsten alloys explosively shocked at a peak pressure of 30 GPa (strain rate: ∼1 x 104 sec-1) is presented. While no ω (hexagonal) phase was found in shock-recovered pure Ta and Ta-5W that contain mainly a low-energy cellular dislocation structure, shock-induced ω phase was found to form in Ta-10W that contains evenly distributed dislocations with a stored dislocation density higher than 1 x 1012 cm-2. The TEM results clearly reveal that shock-induced α (bcc) → ω (hexagonal) shear transformation occurs when dynamic recovery reactions which lead the formation low-energy cellular dislocation structure become largely suppressed in Ta-10W shocked under dynamic (i.e., high strain-rate and high-pressure) conditions. A novel dislocation-based mechanism is proposed to rationalize the transition of dislocation glide to twinning and/or shear transformation in shock-deformed tantalum. Twinning and/or shear transformation take place as an alternative deformation mechanism to accommodate high-strain-rate straining when the shear stress required for dislocation multiplication exceeds the threshold shear stresses for twinning and/or shear transformation.

The consolidating adhesive project is an international collaboration which aims to develop a new adhesive with well characterized physical, optical, and ageing characteristics specific for the consolidation of painted layers. Since starting in 2010, many findings have been made, and new useful polymer-tackifier, and polymer-tackifier-wax blends have been tested. The concept of component miscibility and the effect it has on the final properties of the adhesive is complex, but fundamental to the development of a new product. To quantify the properties conservators most need, the initial focus was on understanding BEVA® 371, a widely used poly(ethylene vinyl acetate) based heat-seal adhesive. It was originally developed as a lining adhesive for paintings, and has been adapted by conservators for a variety of consolidating applications; however, its ideal consolidation performance properties are starting to be out-weighed by concerns regarding its long-term stability, as well as recent formulation changes. There is a need for a new adhesive tailored to the requirements of the conservation field. This paper will discuss the results obtained thus far, and the goals for the future. The project is entering a new phase, where we hope to continue to explore new blends, and have conservator testing on painting mock-ups.

The synthesis of a polyacetal-block-polyurethane copolymer was achieved which possesses the ability to depolymerize both selectively and in response to orthogonal stimuli, heat and pH. To utilize heat as a stimulus, poly(phthalaldehyde) (PPA) was used as a block of the copolymer, while poly(benzyl-4-hydroxymethylphenylcarbamate) (PPC) end-capped with a tert-butoxycarbonyl protecting group (Boc group) were explored for viability as a pH-responsive block. The stimulus-induced depolymerization was studied using nuclear magnetic resonance (NMR), gel permeation chromatography (GPC), and attenuated total reflectance infrared spectroscopy (ATR-IR). These techniques confirmed that the depolymerization event did not affect the nature of the neighboring polymeric block. Depolymerization kinetics were measured for various chain lengths of each block. The results are presented and discussed to explore the ability of these materials to depolymerize in a controlled manner depending on the magnitude of the stimulus, as well as the ability for the blocks to remain unaffected by the orthogonal stimulus. This work shows promise for the development of advanced coatings systems and drug delivery applications.

The influence of grain boundaries on the vibrational properties of nanoscale phononic crystals is studied with the help of molecular dynamics simulations. The low-frequency vibrational density of states of phononic crystals made from single crystal and polycrystalline silicon are derived from the simulations. The results show that the presence of grain boundaries leads to an increase of the density of states and a change of its peak structure at low frequencies. Calculations of the band structure of the model systems along one direction reveal that the grain boundaries affect the bands differently and in a non-uniform manner.