Monolithic Hybrid Research Articles

FRACTURE RESISTANCE AND FAILURE MODE OF TWO RESTORATION DESIGNS MADE OF MONOLITHIC HYBRID AND GLASS MACHINABLE CERAMICS ; IN VITRO STUDY

Statement of the problem: Monolithic hybrid and glass ceramics are indicated for intracoronal and extracoronal ceramic restorations. Available data regarding selection of the appropriate ceramic type for each preparation design and its influence on fracture resistance of tooth restoration complex is still scarce.Purpose: The purpose of this study was to evaluate in vitro the fracture resistance and investigate failure mode of two restoration designs (crowns and inlays) made from lithium disilicate glass ceramic and hybrid ceramic constructed by the CAD /CAM technique.Materials and Methods: A total of twenty ceramic restorations restoring lower molars were designed and fabricated in this study. The restorations were divided into two groups; Group 1: Ten full coverage crowns and Group 2: Ten inlays. Each of the previous groups was further subdivided into two equal subgroups; Subgroup 1: Five restorations constructed from lithium disilicate glass ceramics (e.max CAD) and Subgroup 2: Five restorations constructed from hybrid ceramic (VITA ENAMIC) by the CAD/CAM technology. Two ivorine teeth were prepared following the guidelines for full coverage and inlay ceramic restorations, they were duplicated into stone dies followed by scanning, designing and milling of restorations. The stone dies were duplicated into epoxy dies where the restorations were adhesively cemented on them. All cemented samples were exposed to 2000 thermal cycles (5°C and 55°C in water) with a dwell time of 25 seconds in a computer controlled thermocycler. All specimens were loaded in a universal testing machine where fracture test was done by compressive mode of load applied occlusally using a metallic rod with round tip at cross-head speed of 1mm/min until fracture occurred. Fracture resistance values were recorded in Newtons then they were statistically evaluated and failure modes were analyzed. Results: For group 1 representing crown restorations, a statistically significant difference was found between (e.max CAD) and (VITA ENAMIC) subgroups at (p=0.05) where the highest mean value of maximum load was found in (VITA ENAMIC) (951.77 N ± 81.05) and the lowest mean value of maximum load was found in (e.max CAD) (709.35 N± 49.51). While for the second group representing inlay restorations, no statistically significant difference was found between (e.max CAD) and (VITA ENAMIC) subgroups at (p=0.307) where the highest mean value of maximum load was found in (e.max CAD) (627.71 N ± 80.01) and the lowest mean value of maximum load was found in (VITA ENAMIC) (581.26 N± 51.74). For the e.max CAD subgroup, a statistically significant difference was found between (Crown) and (Inlay) groups at (p=0.005) where the highest mean value of maximum load was found in the crown group (790.35 N± 49.51) and the lowest mean value of maximum load was found in the inlay group (627.71N ± 80.01).Regarding the VITA ENAMIC subgroup, a statistically significant difference was found between (Crown) and (Inlay) groups at (p<0.001) where the highest mean value of maximum load was found in the crown group (951.77 N ± 81.05) and the lowest mean value of maximum load was found in the inlay group (581.26N±51.74).Conclusions: 1. All inlays and crowns constructed from hybrid and glass ceramics in this study revealed fracture load values falling in the range of physiologic masticatory forces 2. When considering restoration of molars with full coverage crowns, VITA ENAMIC is more preferred than e.max CAD ceramic in terms of fracture resistance as it showed a higher statistical significant mean values.3. When planning to restore molars with minimally invasive intracoronal restorations, both ceramics can be used as there was insignificant statistical difference between them , however e.max CAD can be recommended due to its more favorable mode of fracture compared to VITA ENAMIC.4. Irrespective of preparation designs, both ceramics showed insignificant difference regarding fracture resistance mean values.

WEAR PERFORMANCE OF THREE CAD/CAM MONOLITHIC RESTORATIONS: TWO-BODY WEAR AND SURFACE ROUGHNESS

Statement of the problem: The use of monolithic ceramic restorations is rapidly increasing. However, there is a rising concern about their wear performance against antagonist enamel.Objective: The present study aimed at ranking and comparing the wear performance of three CAD/CAM monolithic ceramic materials and their effect on the wear and surface roughness of their antagonist enamel.Materials and methods: Five cylindrical discs (n=5) were constructed from each of: BruxZir zirconia, IPS e.max CAD lithium disilicate based ceramic and Enamic hybrid ceramic representing three types of monolithic restorations (N=15). Ceramic samples were polished till obtaining convergent surface roughness values of the three materials. Enamel antagonists were prepared as sectioned buccal cusps of maxillary first premolars (N=15). Baseline surface roughness and weight values were obtained using optical surface profiler and sensitive balance, respectively, for all samples (ceramic discs and their antagonist cusps) prior to subjecting the samples to chewing simulation procedure test including the application of 5kg (49N) load for 120,000 cycle with vertical movement 1mm, horizontal movement 3mm and frequency 1.6Hz. Weight loss was calculated for all samples (ceramic discs and their antagonists) as an indication of wear. In addition, change in surface roughness was calculated using optical surface profiler. Obtained data were statistically analyzed.Results: The statistically significant highest mean material’s weight loss was recorded in Enamic group, whereas the statistically significant lowest mean weight loss was recorded in BruxZir group. The statistically significant greatest mean antagonist weight loss was recorded for e.max antagonist cusp, whereas the statistically significant lowest mean weight loss was recorded for Enamic antagonist cusp. Surface roughness increased after wear procedure in all samples.Conclusions: Monolithic hybrid ceramic (Enamic) and zirconia (BruxZir) produce less wear in opposing teeth compared to lithium disilicate based ceramics (e.max CAD). However, hybrid ceramic is more affected by wear compared to zirconia.

A monolithic hybrid finite element strategy for nonlinear thermoelasticity

SummaryThis work deals with the formulation and implementation of a mixed finite element formulation for nonlinear thermoelasticity. In the literature, a ‘consistent’ mixed formulation to reduce spurious oscillations in thermal stresses has been developed which involves the use of a temperature interpolation that is one order lower than the displacement interpolation functions. However, such a strategy would require a very fine mesh in problems where thermal gradients are high. In order to reduce the computational cost, we propose a new hybrid formulation for both the mechanical and thermal parts of the stress tensor, that not only overcomes membrane, shear, and volumetric locking but also eliminates thermal stress oscillations, even with the use of a coarse mesh. For transient problems, a new energy‐momentum conserving time stepping scheme is also proposed so that linear and angular momenta and energy are conserved exactly in the fully discrete hybrid framework in the absence of loading and dissipation. Several examples for the St. Venant–Kirchhoff and Ogden material models where the solutions are compared against either analytical or other numerical strategies show the efficacy of the developed procedure. Copyright © 2016 John Wiley &amp; Sons, Ltd.

Synthesis of silica-polybutadiene hybrid aerogels: The effects of reaction conditions on physical and mechanical properties

The aim of this study was to synthesize a novel organic-inorganic hybrid aerogel using silane functionalized polybutadiene latex nanoparticles to enhance their physical and mechanical properties by varying the synthesis conditions. The effect of silica sol concentration, pH of the mixture during gelation and silane grafting degree of polymer latex on the structure, morphology and compression strength properties of the aerogels were studied. The silane-modified rubber particles were combined with Tetraethoxysilane (TEOS) as silica precursor by two step acid-base catalyzed sol-gel process followed by drying in ambient pressure condition. The monolithic hybrid aerogels with different polymer latex content (0–70wt.%) were prepared. The aerogels containing up to 30wt.% of polybutadiene latex showed lower densities (ranging from 0.19 to 0.24g/cm3) and higher surface areas (from 763 to 461m2/g) with negligible volume shrinkages after drying. Increasing in polymer latex content (>30wt.%) resulted in lower surface area along with a sharp decrease in the porosity as evaluated by Nitrogen adsorption/desorption. The aerogel samples with compression strength varying from 262 to 14,450kPa were obtained. It was found that increasing the silane grafting degree of polybutadiene latex improved the compression strength properties >3× (from 262.4 to 853.6kPa), without decreasing in porosity.

Strain Coupling of a Mechanical Resonator to a Single Quantum Emitter in Diamond

The recent maturation of hybrid quantum devices has led to significant enhancements in the functionality of a wide variety of quantum systems. In particular, harnessing mechanical resonators for manipulation and control has expanded the use of two-level systems in quantum information science and quantum sensing. In this letter, we report on a monolithic hybrid quantum device in which strain fields associated with resonant vibrations of a diamond cantilever dynamically control the optical transitions of a single nitrogen-vacancy (NV) defect center in diamond. We quantitatively characterize the strain coupling to the orbital states of the NV center, and with mechanical driving, we observe NV-strain couplings exceeding 10 GHz. Furthermore, we use this strain-mediated coupling to match the frequency and polarization dependence of the zero-phonon lines of two spatially separated and initially distinguishable NV centers. The experiments demonstrated here mark an important step toward engineering a quantum device capable of realizing and probing the dynamics of non-classical states of mechanical resonators, spin-systems, and photons.

Preparation of cyclodextrin-modified monolithic hybrid columns for the fast enantioseparation of hydroxy acids in capillary liquid chromatography.

Cyclodextrins and their derivatives are one of the most common and successful chiral selectors. However, there have been few publications about the use of cyclodextrin-modified monoliths. In this study, organic hybrid monoliths were prepared by the immobilization of derivatized β-cyclodextrin alone or with l-2-allylglycine hydrochloride to the polyhedral oligomeric silsesquioxane methacryl substituted monolith. The main topic of this study is a combined system with dual chiral selectors (l-2-allylglycine hydrochloride and β-cyclodextrin) as monolithic chiral stationary phase. The effect of l-2-allylglycine hydrochloride concentration on enantioseparation was investigated. The enantioseparation of the four acidic compounds with resolutions up to 2.87 was achieved within 2.5 min on the prepared chiral monolithic column in capillary liquid chromatography. Moreover, the possible mechanism of enantioseparation was discussed.

Hierarchical emulsion based hybrid ceramics synthesized with different siloxane precursor and with embedded nickel nanoparticles

An emulsion-based synthesis route for the generation of organo-silica-based monolithic hybrid ceramics with a high content of different organic groups and embedded nickel nanoparticles is presented. By this route hybrid ceramics with a hierarchical pore size distribution and tailorable surface characteristics can be obtained. Mixtures of methyl polysiloxane (MK), tetraethyl orthosilicate (TEOS) and (3-aminopropyl)triethoxysilane (APTES) with varying ratios are selected as precursors, cross-linked, and subsequently pyrolyzed at 500 or 600 °C. In this way monolithic emulsion based hybrid ceramics with three different organo-functionalized siloxane precursor can be synthesized. Additionally, by adding the metal precursor NiCl2, metal-containing emulsion-based hybrid ceramics can be achieved. By adjusting the oil/water ratio and using high- or low internal phase emulsions (HIPEs or LIPEs), controlled micro-, meso-, and macropore distributions are obtained. After pyrolysis, materials achieve specific BET surface areas of up to 550 m2/g. Adjustable surface characteristics in terms of hydrophobicity and hydrophilicity of the material surface by thermal decomposition behavior of precursors is demonstrated. Nickel is incorporated through the formation of complexes with APTES, resulting in well-distributed metal nanoparticles with average particle sizes between 35 and 69 nm. The material properties are pivotal features for catalysis and gas separation applications.

Experimental Structural Analysis of Hybrid Composite-Concrete Beams by Digital Image Correlation (DIC) and Acoustic Emission (AE)

The use of composites such as textile reinforced cements (TRCs) and fibre reinforced polymers (FRPs) enables the development of lightweight structures. Such a lightweight solution for floor renovation consists of a hybrid composite-concrete cross section: prefabricated beams (TRC–CFRP reinforced hollow boxes with concrete on top) support sandwich panels together with a finishing concrete compression layer creating a monolithic hybrid floor. As the hybrid beams are the main structural element of this floor system, their load-bearing and failure behaviour should be fully understood. In order to examine the optimal design of these structures in terms of load bearing capacity, the beams are separately tested in four point bending while the amount of CFRP reinforcement and the concrete thickness are varied. The digital image correlation (DIC) and acoustic emission (AE) measuring techniques are applied in a complimentary way to monitor the bending and failure behaviour of the full scale hybrid beams. DIC visualises the development of surface strain fields together with the exact cracking patterns in relation to the applied load. AE contributes in defining the load at the onset of serious cracking activity. Furthermore, AE characterizes the contribution of the different fracture modes that may vary from concrete cracking, delamination between the successive layers of the TRC or debonding at the interphase between the TRC hollow box and the concrete on the one hand and the CFRP on the other hand.

A Monolithic Hybrid Cellulose-2.5-Acetate/Polymer Bioreactor for Biocatalysis under Continuous Liquid-Liquid Conditions Using a Supported Ionic Liquid Phase.

Mesoporous monolithic hybrid cellulose-2.5-acetate (CA)/polymer supports were prepared under solvent-induced phase separation conditions using cellulose-2.5-acetate microbeads 8-14 μm in diameter, 1,1,1-tris(hydroxymethyl)propane and 4,4'-methylenebis(phenylisocyanate) as monomers as well as THF and n-heptane as porogenic solvents. 4-(Dimethylamino)pyridine and dibutyltin dilaurate (DBTDL), respectively, were used as catalysts. Monolithic hybrid supports were used in transesterification reactions of vinyl butyrate with 1-butanol under continuous, supported ionic liquid-liquid conditions with Candida antarctica lipase B (CALB) and octylmethylimidazolium tetrafluoroborate ([OMIM(+) ][BF4 (-) ]) immobilized within the CA beads inside the polymeric monolithic framework and methyl tert-butyl ether (MTBE) as the continuous phase. The new hybrid bioreactors were successfully used in dimensions up to 2×30 cm (V=94 mL). Under continuous biphasic liquid-liquid conditions a constant conversion up to 96 % was achieved over a period of 18 days, resulting in a productivity of 58 μmol mg(-1) (CALB) min(-1) . This translates into an unprecedented turnover number (TON) of 3.9×10(7) within two weeks, which is much higher than the one obtained under standard biphasic conditions using [OMIM(+) ][BF4 (-) ]/MTBE (TON=2.7×10(6) ). The continuous liquid-liquid setup based on a hybrid reactor presented here is strongly believed to be applicable to many other enzyme-catalyzed reactions.

Radical-mediated step-growth: Preparation of hybrid polymer monolithic columns with fine control of nanostructural and chromatographic characteristics

The currently most successful type of porous polymer monoliths utilized in chromatography is prepared by free-radical cross-linking (co)polymerization in porogenic solvents and a single-step molding process. Though such types of materials are well-recognized in the scientific community, they suffer from their multi-scale heterogeneity originating from the nanoscale through to their microscale and ultimately limited performance on their macroscale. This is in particular true when estimating their performance under equilibrium (i.e. isocratic) elution conditions for retained compounds.In this contribution, we study a new concept in the preparation of porous monolithic hybrid materials based on polyhedral oligomeric vinylsilsesquioxanes which undergo radical mediated step-growth cross-linking with thiol-linkers. Fundamental characterization of this new entry of materials is performed via a variety of characterization approaches including infrared and Raman spectroscopies, thermogravimetric analysis, gel fraction, dry-state surface area analysis, and visualization of the capillary-scale porous structure by scanning electron microscopy. This characterization identifies that a rational choice of experimental conditions in monolith preparation leads to destined and desirable materials’ properties, in particular with experimentally accessible near-ideal nanoscale network structures. With the obtained structural informations at hand, we finally evidence the monoliths’ tailored chromatographic performance by isocratic elution experiments of structurally similar small molecules under reversed-phase type of chromatographic conditions. This validates the fundamental origin for an improved performance of these types of monolithic materials under solvated conditions that has its foundation established in the creation of near-ideal nanoscale networks of material. This identified ideality is manifested in an enhanced and almost retention-insensitive performance in liquid chromatographic separations of small molecules across wide ranges of retention factors over at least two orders of magnitude and wide ranges of mobile phase compositions. Such experimental observation is explained by a more homogeneous energetic distribution of partition and adsorption sites. A reference analysis of normalized plate height data at varied retention was performed and set in context with data of state-of-the-art silica- and polymer-based monoliths. This analysis clearly identifies the present materials to display performance behavior clearly located in the domain of derivatized silica-based monoliths.

Hybrid Energy Storage Devices Based on Monolithic Electrodes Containing Well-defined TiO2 Nanotube Size Gradients

Well-defined TiO2 nanotube size gradient thin films, manufactured using a bipolar electrochemistry approach, can be used as versatile monolithic hybrid electrodes for energy storage devices. The nanotube size distribution within the gradients can readily be controlled by altering the bipolar current and/or the length of the bipolar titanium sheet. As the electrochemical properties of the gradient electrodes can be carefully tailored by modifying the nanotube size gradient, this approach provides new possibilities for the manufacturing of hybrid electrodes with integrated energy and power density gradients. The free-standing anatase TiO2 nanotube size gradient electrodes provide unprecedented capacities at cycling rates from C/5 (i.e. 162μAhcm−2 or 169mAhg−1) to 50C (i.e. 40μAhcm−2 or 42mAhg−1). It is likewise shown that the size gradient electrodes facilitate fundamental studies of the charge/discharge process of TiO2 based electrodes. The results demonstrate that the different shapes of charge and discharge curves of TiO2 nanotube electrode can be explained by inherent differences between the lithiation and delithiation processes.

Surfactant assisted syntheses of monolithic hybrid ceramics with hierarchical porosity

A surfactant assisted emulsion-based syntheses route is presented for obtaining organo-silica-based monolithic hybrid ceramics with a hierarchical pore size distribution and tailorable surface characteristics. Methyl polysiloxane (MK) and methyl-phenyl polysiloxane (H44) with varying mixing ratios are selected as precursors, cross-linked and subsequently pyrolyzed at 500°C or 600°C, respectively. By adjusting the oil/water ratio and by tailoring the surfactant concentration controlled micro and macropore distributions with mesoscopic cell windows are obtained. After pyrolysis, specific surface areas of up to 600m2/g are achieved. In addition, due to the distinguished pyrolysis decomposition behavior of MK and H44, the adjustment of the surface characteristics in terms of hydrophobicity or hydrophilicity is demonstrated. The presented surfactant assisted emulsion-based process is hence highly suitable for tailoring pore size distribution and surface characteristics at the same time. Both material properties are pivotal features for catalysis and gas separation applications.

Demonstration of the feasibility of large-port-count optical switching using a hybrid Mach-Zehnder interferometer-semiconductor optical amplifier switch module in a recirculating loop.

For what we believe is the first time, the feasibility of large-port-count nanosecond-reconfiguration-time optical switches is demonstrated using a hybrid approach, where Mach-Zehnder interferometric (MZI) switches provide low-loss, high-speed routing with short semiconductor optical amplifiers (SOAs) being integrated to enhance extinction. By repeatedly passing signals through a monolithic hybrid dilated 2×2 switch module in a recirculating loop, the potential performance of high-port-count switches using the hybrid approach is demonstrated. Experimentally, a single pass switch penalty of only 0.1 dB is demonstrated for the 2×2 module, while even after seven passes through the switch, equivalent to a 128×128 router, a penalty of only 2.4 dB is recorded at a data rate of 10 Gb/s.

Wide Bandgap Copper Chalcopyrite Materials for Photoelectrochemical Hydrogen Production

Photoelectrochemistry (PEC) is one of the most efficient methods to produce alternative fuels, although the efficiency, cost, and durability of lab-scale systems are currently not at the level required to make this technology economically feasible. The chalcopyrite material class, typically identified by its most popular alloy Cu(In,Ga)Se2, provides exceptionally good candidates to meet the requirements identified for cheap, sustainable solar fuels production. As we recently reported[1], co-evaporated 1.6 eV CuGaSe2 offers very high-saturated photocurrent densities (-16 mA.cm- 2 in 0.5M H2SO4 under AM1.5G illumination), long durability (up to 400 hours), and high Faradaic efficiency (>85% for non-catalyzed systems). Although CuGaSe2 has the highest bandgap of the copper chalcopyrite class, its optical characteristics are still too close to that of amorphous silicon (a-Si), a low-cost material our research team has identified as an ideal photovoltaic driverin a monolithic hybrid photoelectrode device. Nevertheless, a solar-to-hydrogen efficiency of 3.7% was achieved using a co-planar integration scheme. In order to improve the water-splitting efficiency further, novel chalcopyrite alloys with bandgap greater than 1.6 eV must be developed.In the present communication, we report on our efforts to synthesize 1.8-2.2 eV band-gap chalcopyrite materials for PEC water splitting. Specifically, we investigated the effect of sulfur on the optical and photoelectrochemical characteristics of the copper chalcopyrite material class. Using co-evaporated 1 μm-thick CuGaSe2 as baseline system, we demonstrate that the substitution of selenium with sulfur is accomplished through a simple annealing step. As a result, a dramatic change in optical properties was observed, with a bandgap increase from 1.6 eV (CuGaSe2) to 2.4 eV (CuGaS2), in good agreement with theoretical predictions[2]. Then, by simply adjusting the indium content in the film during the initial growth process, the bandgap of sulfurized copper chalcopyrite was decreased from 2.4 eV [GGI=Ga/(Ga+In)=1] to 2.2 eV (GGI»0.8) and finally to 2.0 eV (GGI»0.7). X-ray diffraction data indicated successful bulk sulfurization by the shift of the prominent (112), (220), and (312) reflections to higher angles. Preliminary PEC analyses revealed an anodic shift of the flatband potential with increasing bandgap when compared to CuGaSe2. This suggests that the bandgap modification in sulfurized films primarily stems from a downward shift of the valence band, an ideal situation for p-type PEC systems. Saturated photocurrent densities greater than -5 mA/cm2 were achieved with 2.0 eV red CuIn0.3Ga0.7S2 photocathodes in 0.5M H2SO4 under AM1.5G simulated illumination.[1] N. Gaillard, D. Prasher, J. Kaneshiro, S. Mallory, and M. Chong, MRS Spring Meeting, Z2.07 (2013).[2] M. Bär, W. Bohne, J. Rohrich, E. Strub et al., Appl. Phys. Lett. 96, 3857 (2004).

Self‐catalysed growth of InAs nanowires on bare Si substrates by droplet epitaxy

AbstractWe demonstrate the self‐catalyst growth of vertically aligned InAs nanowires on bare Si(111) by droplet epitaxy. The growth conditions of indium droplets suitable for nucleation and growth of nanowires have been identified. We have then realized vertically aligned and non‐tapered InAs nanowires on bare Si(111) substrates through optimal indium droplets. It was found that the lateral dimensions and density of nano‐wires are defined by the indium droplets. This technique unravels a controllable, cost‐effective and time‐efficient route to fabricating functional monolithic hybrid structures of InAs nanowires on silicon.magnified image(© 2014 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Bandgap Optimization of Copper Indium Gallium Disulfide Chalcopyrites for Solar-Assisted Water Splitting

Photoelectrochemistry (PEC) is an attractive method for producing hydrogen as an alternative fuel to oil. Limitations arising from device efficiencies, cost, and durability demonstrated in laboratories prevent the implementation of this technology on a larger scale. The chalcopyrite material class, exemplified by its most popular alloy Cu(In,Ga)Se2, encompasses some of the most promising candidates to meet the criteria for cheap, sustainable solar fuel production. As we recently reported[i], co-evaporated 1.6 eV CuGaSe2 offers very high-saturated photocurrent densities (20 mA.cm- 2 in pH 0 under AM1.5G illumination), long durability (up to 400 hours), and relatively high Faradaic efficiency (>85% for non-catalyzed systems). Although CuGaSe2 has the highest bandgap of the copper chalcopyrite class, its optical characteristics are still too close to that of amorphous silicon (a-Si), a low-cost material our research team has identified as an ideal photovoltaic driver in a monolithic hybrid photoelectrode device. Nevertheless, a solar-to-hydrogen efficiency of 3.7% was achieved using a co-planar integration scheme, where CuGaSe2 was connected in series with three a-Si solar cells. In order to increase the water-splitting efficiency, novel chalcopyrite alloys with bandgaps greater than 1.6 eV must be developed.In the present communication, we report on our efforts to synthesize 1.8-2.2 eV band-gap chalcopyrite materials for PEC water splitting. Specifically, we investigated the effect of sulfur on the optical and photoelectrochemical characteristics of the copper chalcopyrite material class. Using co-evaporated 1 μm-thick CuGaSe2 as baseline system, we demonstrate that the substitution of selenium with sulfur is accomplished through a simple annealing step. As a result, a dramatic change in optical properties was observed, with a bandgap increase from 1.6 eV (CuGaSe2) to 2.4 eV (CuGaS2), in good agreement with theoretical predictions[ii]. Then, by simply adjusting the indium content in the film during the initial growth process, the bandgap of sulfurized copper chalcopyrite was decreased from 2.4 eV [GGI=Ga/(Ga+In)=1] to 2.2 eV (GGI»0.8) and finally to 2.0 eV (GGI»0.7), as presented in Fig. 1. X-ray diffraction data (Fig. 2) indicated successful bulk sulfurization by the shift of the prominent (112), (220), and (312) reflections to higher angles. Preliminary PEC analyses revealed an anodic shift of the flatband potential with increasing bandgap, when compared to CuGaSe2. This suggests that the bandgap modification in sulfurized films primarily stems from a downward shift of the valence band, an ideal situation for p-type PEC systems. Saturated photocurrent densities greater than -5 mA/cm2 were achieved with 2.0 eV red CuIn0.3Ga0.7S2 photocathodes in 0.5M H2SO4 under AM1.5G simulated illumination.[i] N. Gaillard, D. Prasher, J. Kaneshiro, S. Mallory, and M. Chong, MRS Spring Meeting, Z2.07 (2013).[ii] M. Bär, W. Bohne, J. Rohrich, E. Strub et al., Appl. Phys. Lett. 96, 3857 (2004).

In Situ Modification of the Silica Backbone leading to Highly Porous Monolithic Hybrid Organic–Inorganic Materials via Ambient Pressure Drying

We report the synthesis of monolithic porous hybrid organic-inorganic materials based on tetraethoxysilane (TEOS) and a bifunctional precursor synthesized from 3-aminopropyltriethoxysilane (APTES) and 3-glycidoxypropyltrimethoxysilane (GLYMO) via base catalysis. To compensate for the slower hydrolysis and condensation rate of the organically modified silane in basic media, it was prehydrolysed prior to adding it to the silane solution. This process leads to a lower shrinkage and stable monoliths with densities as low as 200 kg/m(3). Analysis of the samples supports the assumption that the porous monolithic materials derived via ambient pressure drying of the gels consist of a network of homogeneous hybrid primary particles. These particles are larger than their inorganic counterparts in classical silica gels and therefore the capillary forces while drying the gels at ambient pressure are reduced. This leads to less shrinkage and thus lower densities of the materials derived via ambient pressure drying. An inorganic xerogel with the same low density can be achieved by a subsequent oxidation step that decomposes the organic moieties.

Hybrid Transformer-Based Tunable Differential Duplexer in a 90-nm CMOS Process

Practical implementation of monolithic hybrid transformer duplexers have been limited by the poor common-mode isolation. In this paper, a differential hybrid transformer duplexer that covers 3GPP bands I, II, III, and IX between 1.7 and 2.2 GHz is introduced. It achieves a differential to differential isolation of 60 dB in the transmit (TX) band and 40 dB in the receive (RX) band, and a differential to common-mode isolation of 60 dB in both bands. The duplexer with a cascaded low-noise amplifier (LNA) achieves a noise figure of 5.6 dB in the RX path and an insertion loss of 3.7 dB in the TX path. The duplexer and LNA are implemented in a 90-nm CMOS process, consume 20 mA, and occupy an active area of 0.6 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> .

Nitride Nanoparticle Addition to Beneficially Reinforce Hybrid Magnesium Alloys

This study is aimed at understanding the function of two nitride nanoparticles regarding altering the mechanical properties of hybrid magnesium alloys in relation to nanoparticle-matrix reactivity. Nitride nanoparticles were selected for reinforcement purposes due to the affinity between magnesium and nitrogen (in parallel with the well-known magnesium-oxygen affinity). AZ91/ZK60A and AZ31/AZ91 hybrid magnesium alloys were reinforced with AlN and Si3N4 nanoparticles (respectively) using solidification processing followed by hot extrusion. Each nitride nanocomposite exhibited higher tensile strength than the corresponding monolithic hybrid alloy. However, AZ91/ZK60A/AlN exhibited slightly lower tensile ductility than AZ91/ZK60A, while AZ31/AZ91/Si3N4 exhibited higher tensile ductility than AZ31/AZ91. The formation of high strain zones (HSZs) (from particle surfaces inclusive) during tensile deformation as a significant mechanism supporting ductility enhancement was addressed. AZ91/ZK60A/AlN exhibited lower and higher compressive strength and ductility (respectively) compared to AZ91/ZK60A, while AZ31/AZ91/Si3N4 exhibited higher and unchanged compressive strength and ductility (respectively) compared to AZ31/AZ91. Nanograin formation (recrystallization) during room temperature compressive deformation (as a toughening mechanism) in relation to nanoparticle-stimulated nucleation (NSN) ability was also discussed. The beneficial (as well as comparative) effects of the respective nitride nanoparticle on each hybrid alloy are studied in this article.

Complex monolithic and InP hybrid integration on high bandwidth electro-optic polymer platform

We report on the monolithic integration of multimode interference couplers, Bragg gratings, and delay-line interferometers on an electro-optic polymer platform capable of modulation directly at 100 Gb/s. We also report on the hybrid integration of InP active components with the polymer structure using the butt-coupling technique. Combining the passive and the active components, we demonstrate a polymer-based, external cavity laser with 17 nm tuning range and the optical assembly of an integrated 100 Gb/s transmitter, and we reveal the potential of the electro-optic polymer technology to provide the next generation integration platform for complex, ultra-high-speed optical transceivers.