This paper presents an experimental study on the characteristics of earth cement blocks with Rice Husk Ash (RHA) as a partial replacement to cement. The replacement of RHA content is limited to 0%, 5%, 10%, 15% and 20% by mass of the total binder in the earth cement block. The experiments on earth cement blocks investigate the compressive strength and flexural tensile strength for mechanical properties and water absorption, sorption rate and erosion against water spray for its durability. Due to the high content of SiO2 in RHA with great reactivity, a significant increase in the compressive and flexural tensile strength of earth cement blocks was observed up to 10% RHA content. However, the durability of earth cement blocks becomes adverse with the increasing percentage of RHA replacement, but within the allowable limit. The experimental results indicate that to some extent, RHA based earth cement blocks have a significant potential for reduction in cement used in the construction industry.

Concrete is the most used material in the world after water because of its good mechanical characteristics and its reasonable cost. However, reinforced concrete structures can be damaged by corrosion or other chemical attacks and require repair and maintenance. The repair materials need to satisfy some mechanical and physico-chemical characteristics. Ready-made repair mortars are widely used. However, they are quite expensive, generally imported and they frequently incorporate low volume of synthetic fibers. This paper reports an experimental investigation designing an environmental friendly repair mortar made of local mineral addition (natural pozzolan (PN) and slag (SL)) and local natural fibers. The natural fibers used are Alfa fibers and date palm tree fibers at a volume ratio of 0.75%. The physical and mechanical properties studied are compressive strength, bending strength, total shrinkage and bond strength by slant shear and pull-off tests. The durability of the mortar was assessed by water capillary absorption. The results are compared to those of a reference mortar. The results showed that the substitution of cement by slag and natural pozzolan lead to a decrease in shrinkage (at 28 days of age). The use of date palm and alfa fibers improves the bending strength but reduces compressive strength. According to the results of the pull-off tests, only mortars containing slag meet the minimum value (1.5 MPa) required by EN1504-3. The types of failures observed for most composites show that they can be successfully applied with 20 mm thick layers.

In this work, we have investigated the structural and mechanical properties of a new class of soft and superelastic materials, called schwarzynes. These materials are obtained by inserting sp carbon atoms (acetylenic groups) into the schwarzite framework. Using fully atomistic molecular dynamics simulations with the AIREBO force field, our results show that schwarzynes are stable materials up to high temperatures (1000K). Schwarzynes exhibit a very wide elastic regime, some of them up to 70% strain without structural fractures. Our preliminary results show that the elastic properties can be easily engineered by tuning the number of acetylenic groups and the crystallographic directions where they are inserted.

Deep UV photoluminescence (PL) spectroscopy was employed to study optical properties of a sapphire substrate sample. The sample was photo-excited by the third harmonic laser of a Ti:sapphire pulse laser at wavelength ~ 266 nm which is a below bandgap excitation. In the low temperature (12 K) PL measurement, we observed two sharp atomic-like emissions in the ultraviolet region with peaks at 3.361 eV and 3.315 eV with spectral line-width of 0.85 and 3.30 nm respectively, in the PL spectrum. We performed temperature and power-dependent PL measurements of the sample and observed that the emission peak positions did not change with changing excitation power and sample temperature. We also performed X-ray photoelectron spectroscopy for chemical composition analysis of the sample to explore the origin of the atomic-like emission that could be used for single photon sources for quantum information technology. We will discuss a possible electronic transition and its origin in sapphire.

In recent times, nanotechnology has drawn the attention of the scientific community because of the wide variety of applications that can be done with it, from food packaging to targeted drug delivery; the use of nanoparticles has been a breakthrough in science that has now reached the market. Silver nanoparticles (Ag NPs) have unique properties due to the oscillation of electrons in the superficial plasmon. These nanostructures have been used in different applications in the area of nanomedicine, such as: targeted drug delivery, sensing and imaging, anti-fungal, anti-cancerous and biosensors. It has become evident that pathogenic bacteria are resisting antibiotics such as Penicillin becoming one of the most worrying topics in the world. People in the science community fear the day when we no longer can use these antibiotics, because the resistance of bacteria became too great, leaving us defenceless against any type of pathogens and possibly causing a catastrophe. However, we theorize that the possible solution to this problem could be the use of silver nanoparticles, given that there has not been a documented bacterial adaptation strategy that could give them resistance to Ag NPs. The purpose of this study is to find how the water-stable silver nanoparticles interact with different strains, including Gram negative and Gram-positive bacteria. The main objectives of our research were to synthesize and characterize water stable silver nanoparticles and test their potential bactericidal activity. We synthesized our Ag NPs using sodium citrate as a reducing agent. After synthesizing the nanoparticles, their optical properties were characterized by Ultraviolet-visible spectroscopy (UV-Vis); crystalline structure was evaluated with Electron Diffraction (ED) and X-Ray Diffraction (XRD); morphology was assessed by High Resolution Transmission Electron Microscopy (HR-TEM). Fourier Transform Infra-Red Spectroscopy (FT-IR) was used to indicate functional groups involved in the nanoparticle capping. Cultures were prepared with agarose and inoculated with the following bacterial strains: Bacillus cereus (Gram +), Micrococcus luteus (Gram +), Staphylococcus aureus (Gram +), Escherichia coli (Gram -), Citrobacter freundii (Gram -), Enterobacter aerogenes (Gram -), Klebsiella pneumoniae (Gram -), Proteus mirabilis (Gram -), Proteus vulgaris (Gram -) and Serratia marcescens (Gram -). Preliminary tests showed an inhibition diameter that surpassed 1.0 cm in all bacterial strains. We expect our Ag NPs to have a potential antibacterial activity towards all types of bacteria, due to oxidation of silver (Ag0 to Ag+).

Solar energy can alleviate our dependence on traditional energy sources like coal and petroleum. In this regard, the design and performance of solar absorbers are crucial for capturing energy from sunlight. Specifically, for applications relying on solar-thermal energy conversion, it is desirable to construct solar absorbers using scalable techniques that also allow a variation in optical properties. In this study, we demonstrate the ability to tune the spectral absorptance of nickel-infused nanoporous alumina using a scalable and inexpensive fabrication procedure. With simple variations in the geometry of the nanostructures, we enable broadband absorption with a net solar absorptance of 0.96 and thermal emittance of 0.98 and spectrally-selective absorption with a net solar absorptance of 0.83 and thermal emittance of 0.22. The simple manufacturing techniques presented in this study to generate nanoengineered surfaces can lead to further advancements in solar absorbers with well-controlled and application-specific optical properties.

The deficient disposition of the pruning waste, from grass (Poaceae), has been converted into a considerable environmental problem since it is discarded in common garbage dumps. As a result, gases and lixiviates are generated producing a negative impact on the environment. This project takes advantage of these residues to isolate their chloroplasts, with the aim of subsequently developing bioreactors that absorb CO2. The encapsulation of grass chloroplasts into silica monolith with a hierarchical texture, using high internal phase emulsion (HIPE) method was carried out. The isolated chloroplasts were analysed by UV-Vis spectroscopy to estimate the amount of chlorophylls a and b present in the grass. Moreover, the synthesized samples were characterized by fluorescence spectroscopy for monitoring their photosynthetic activity, having an activity up to at least 90 days.

The US Department of Energy Office of Nuclear Energy is conducting a brine availability heater test to characterize the thermal, mechanical, hydrological and chemical response of salt at elevated temperatures. In the heater test, brines will be collected and analyzed for chemical compositions. In order to support the geochemical modeling of chemical evolutions of the brines during the heater test, we are recalibrating and validating the solubility models for the mineral constituents in salt formations up to 100°C, based on the solubility data in multiple component systems as well as simple systems from literature.

In this work, we systematically compare the model-predicted values based on the various solubility models related to the constituents of salt formations, with the experimental data. As halite is the dominant constituent in salt formations, we first test the halite solubility model in the Na-Mg-Cl dominated brines. We find the existing halite solubility model systematically over-predict the solubility of halite. We recalibrate the halite model, which can reproduce halite solubilities in Na-Mg-Cl dominated brines well.

As gypsum/anhydrite in salt formations controls the sulfate concentrations in associated brines, we test the gypsum solubility model in NaCl solutions up to 5.87 mol•kg–1 from 25°C to 50°C. The testing shows that the current gypsum solubility model reproduces the experimental data well when NaCl concentrations are less than 1 mol•kg–1. However, at NaCl concentrations higher than 1, the model systematically overpredicts the solubility of gypsum.

In the Na+—Cl–—SO42–—CO32– system, the validation tests up to 100°C demonstrate that the model excellently reproduces the experimental data for the solution compositions equilibrated with one single phase such as halite (NaCl) or thenardite (Na2SO4), with deviations equal to, or less than, 1.5 %. The model is much less ideal in reproducing the compositions in equilibrium with the assemblages of halite + thenardite, and of halite + thermonatrite (Na2CO3•H2O), with deviations up to 31 %. The high deviations from the experimental data for the multiple assemblages in this system at elevated temperatures may be attributed to the facts that the database has the Pitzer interaction parameters for Cl–—CO32– and SO42–—CO32– only at 25°C.

In the Na+—Ca2+—SO42–—HCO3– system, the validation tests also demonstrate that the model reproduces the equilibrium compositions for one single phase such as gypsum better than the assemblages of more than one phase.

Copper is a candidate for use as an overpack material in deep underground nuclear waste disposal. Copper, however, is susceptible to corrosion following closure of the repository and migration of the corrosion products through the buffer material may affect the migration of redox-sensitive radionuclides. Electromigration experiments were performed whereby a copper coupon, which was in contact with compacted bentonite, served as the working electrode and was held at a constant potential of between +100 to +400 mV vs. Ag/AgCl electrode for up to 48 h. The amounts of copper that migrated into the bentonite specimens were found to be in good agreement with the calculated values based on the corrosion current flow for the assumption that copper underwent anodic dissolution as Cu(II). A model based on dispersion and electromigration was able to explain the measured copper profiles in the bentonite specimens. The fitted values of the dispersion coefficient did not depend on the applied potential and were about 10-12 m2/s.

In this work, low-Pt content nanocatalysts (≈ 5 wt. %) supported on Hollow Carbon Spheres (HCS) were synthesized by two routes: i) colloidal conventional polyol, and ii) surfactant-free Bromide Anion Exchange (BAE). The nanocatalysts were labelled as Pt/HCS-P and Pt/HCS-B for polyol and BAE, respectively. The physicochemical characterization of the nanocatalysts showed that by following both methods, a good control of chemical composition was achieved, obtaining in addition well dispersed nanoparticles of less than 3 nm TEM average particle size (d) on the HCS. Pt/HCS-B contained more Pt0 species than Pt/HCS-P, an effect of the synthesis method. In addition, the structure of the HCS remains more ordered after BAE synthesis, compared to polyol. Regarding the catalytic activity for the Oxygen Reduction Reaction (ORR) in 0.5 M KOH, Pt/HCS-P and Pt/HCS-B showed a similar performance in terms of current density (j) at 0.9 V vs. RHE than the benchmark commercial 20 wt. % Pt/C. However, Pt/HCS-P and Pt/HCS-B demonstrated a 6 and 5-fold increase in mass catalytic activity compared to Pt/C, respectively. A positive effect of the high specific surface area of the HCS and its interactions with metal nanoparticles and electrolyte, which promoted the mass transfer, increased the performance of Pt/HCS-P and Pt/HCS-B. The high catalytic activity showed by Pt/HCS-B and Pt/HCS-P for the ORR, even with a low-Pt content, make them promising cathode nanocatalysts for Anion Exchange Membrane Fuel Cells (AEMFC).

A student's t-test was applied in carbon nanospheres synthesis from cis-1,4-polyisoprene considering the green chemical principles. The synthesis was carried out by Chemical Vapor Deposition method with a quartz tube reactor using an AISI 304 steel bar as catalyst. It was possible to obtain two types of different samples, one from the surface of the steel bar (catalyst) and another from the quartz tube surface (without catalyst) in the same experiment. Carbon spheres were observed in both samples by micrographs obtained by FESEM. The Raman and FTIR spectroscopies shown characteristic bands of this carbon structures (G and D). The results obtained by student's t-test proved a statistical significance between spheres means of samples collected from steel bar and quartz tube surface.

The addition of Cr2O3 to modern UO2 fuel modifies the microstructure so that, through the generation of larger grains during fission, a higher proportion of fission gases can be accommodated. This reduces the pellet-cladding mechanical interaction of the fuel rods, allowing the fuels to be “burned” for longer than traditional UO2 fuel, thus maximising the energy obtained. We here describe the preparation of UO2 and Cr-doped UO2 using Hot Isostatic Pressing (HIP), as a potential method for fuel fabrication, and for development of analogue materials for spent nuclear fuel research. Characterization of the synthesised materials confirmed that high density UO2 was successfully formed, and that Cr was present as particles at grain boundaries and also within the UO2 matrix, possibly in a reduced form due to the processing conditions. In contrast to studies of Cr-doped UO2 synthesised by other methods, no significant changes to the grain size were observed in the presence of Cr.

Control and manipulation of residual stresses in thin films is a key for attaining coatings with high mechanical and tribological performance. It is therefore imperative to have reliable residual stress measurements methods to further understand the dynamics involved. The sin2ψ method of X-ray diffraction was used to investigate the residual stresses on the tungsten carbide cobalt thin films deposited on a mild steel surface to understand the how the deposition parameters influence the generation of residual stresses within the substrate surface. X-ray spectra of the surface revealed an amorphous phase of the thin film therefore the stress measured was of the substrate surface and the effects of sputtering parameters on residual stress were analysed. Compressive stresses were identified within all samples studied. The results reveal that as the sputtering parameters are varied, the residual stresses also change. Optimum deposition parameters in terms of residual stresses were suggested.

Nanocomposite hydrogels of poly-n-isopropyl were prepared by incorporating gold and magnetite nanoparticles. The nanocomposite-based hydrogels formed were geometrical, ∼7.3 mm in diameter and 5 mm thick (in the swollen state). Morphological analysis was characterized by a scanning electron microscope. Drug-loaded hydrogels were subjected to laser heating at 1 W, 1.5 W and 2 W for 20 min in each laser cycle. The metabolic activities of the cells were analysed. The photothermal conversion efficiency of the nanocomposite hydrogels was also evaluated for P(NIPA)-AuNP-PG and P(NIPA)-MNP-PG to be 36.93 and 32.57 %, respectively. The result was then discussed for potential applications whereby metal-based hydrogels can be employed in microfluidic devices for targeted cancer drug delivery.

Plants produce energy in a sustainable way, they are very effective in converting light energy into a useable form. Utilising certain parts of plants in technology could become an efficient way to enhance energy production and improve sustainability. Integrating plants with technology would offer a ‘green’ way of producing elements for electronic circuits and reduce heavy metal waste. In this paper, we demonstrate that conducting polymers can be incorporated into living system such as celery. Electrical impedance analysis was used to establish the conductivity of celery with a conducting polymer (PEDOT:PSS) into its vascular system. It was demonstrated that electronic celery exhibited conductivity values of up to 0.55 ± 0.03 S/cm. This conductivity value was sufficient to demonstrate the potential of celery electronics where celery stalks are used as electrodes in simple circuits.

Cellular senescence, a driver of aging and age-related diseases, is a stable state found in metabolically active cells characterized by irreversible cell growth arrest and dramatic changes in metabolism, gene expression and secretome profile. Endogenous regeneration efficacy of mesenchymal stem cells (MSCs) could be attenuated due to senescence. MSCs can be modulated by not only biochemical signals but also by physical cues such as substrate topography. To provide a cell culture substrate that can prevent MSC senescence over an extended period of in vitro cultivation, here, the cell- and immunocompatible poly(ether imide) (PEI) substrate was used. Two distinct levels of roughness were created on the bottom surfaces of PEI inserts via injection molding: Low-R (similar to the thickness of attached single MSC, Rq: 3.9 ± 0.2 µm) and High-R (larger than single MSC thickness. Rq: 22.7 ± 0.8 µm). Cell expansion, lysosomal enzymatic activity, apoptosis and paracrine effects of senescent MSCs were examined by cell counting, detection of senescence-associated β-galactosidase (SA β-gal), Caspase 3/7, and CFSE labeling. MSCs showed high cell viability and similar spindle-shaped morphology on all investigated surfaces. Cells on Low-R presented the highest expansion (80000 ± 1805 cells), as compared to cells on smooth PEI and High-R. The low apoptosis level (0.08 vs 0.12 from smooth PEI) and senescence ratio (35% vs. 54% from smooth PEI) were observed in MSCs cultured on Low-R. The secretome from Low-R effectively prevents senescence and supports the proliferation of neighboring cells (1.5-fold faster) as compared to the smooth PEI secretome. In summary, the Low-R PEI provided a superior surface environment for MSCs, which promoted proliferation, inhibited apoptosis and senescence, and effectively influenced the proliferation of neighboring cells via their paracrine effect. Such microroughness can be considered as a key parameter for improving the therapeutic potential of endogenous regeneration, anti-organismal aging and anti-age-related pathologies via directly promoting cell growth and modulating paracrine effects of the senescence associated secretome.

This study investigated the use of mixed weathered coal fine ash (MWA) and coal gasification ash (CGA), sourced from Sasol® Ltd, South Africa, as partial replacements (10%, 15% and 30% by mass) of Portland Cement (PC) in concrete. The objective was to assess the feasibility of using the ashes, which are generally of lower quality than FA, in concrete in order to avert their negative environmental impact i.e. disposal in heaps and landfills. Companion reference concretes were made using conventional fly ash (FA). Two water-to-binder (w/b) ratios (0.50 and 0.60) were used. The concretes were tested for compressive strength (7, 28 and 56 days) and durability (gas permeability and chloride resistance at 28 and 56 days). In general, the results strongly suggest that the ashes can be used in conventional structural concrete – both from strength and durability viewpoints. Aspects that require attention when they are used include decrease in both workability and rate of strength gain. The gas permeability of the CGA and MWA concretes were similar to those for FA at all replacement levels but a 15% replacement level gave higher chloride resistance.

Among different possible energy sources, in the search for fossil fuel substitutes, hydrogen and fuel cells are presented as one of the most promising alternatives, with great potential, in the development of devices for the generation of clean electrical energy. Recently, lanthanum based compounds have been studied due to their interesting transport properties, which led these products to be applied as possible cathode materials in a solid oxide fuel cell. In this work, a lanthanum based material with a perovskite structure, La0.7Sr0.3Fe0.7Co0.3O3±δ (LSFC), was synthesized, from nitrates, by sonochemistry. This product was structurally characterized by powder X-ray diffraction and morphological studies were obtained by scanning electron microscopy. Results showed a nanostructured material with a crystal size in de order of 14 nm and a cubic perovskite structure with cell parameters of a = 3.8927 Å. Morphological characterization indicated a porous material formed by grains of homogeneous size, pores had an average length of 17 nm and area of 36 nm2, showing a channel shape distribution.

The energy level alignment that occurs at the interfaces in planar-hetero structured perovskite photovoltaic devices strongly influences the charge transport across the interface, and thus plays a crucial role in overall device performance. To directly observe the energy level alignment requires pristine homogeneous surfaces that are free of contamination including adventitious carbon. Co-evaporation offers the ability to grow perovskite thin films in-situ, and the method involves thermally evaporating the perovskite precursors such as PbI2 and CH3NH3I. Early reports have shown that the perovskite film formation and stoichiometry are problematic at ultralow coverages. In particular, it was reported that there was excessive PbI2 and a deficiency in CH3NH3I. Using photoemission spectroscopy, we investigated the perovskite precursor PbI2 on gold and highly oriented pyrolytic graphite (HOPG) surfaces. Results show that the nature of the surface and the deposition conditions can strongly influence the film formation. Excessive iodine observed in the initial evaporation stages appears to be substrate dependent, and this may influence the overall energy level alignment.

Realization of the full potential of 2D nanosheet materials in energy storage and conversion devices requires heterogeneously structured electrodes having good electrical conductivity and large mean free paths for ion diffusion. Electrospinning of anisotropic objects usually obscures this anisotropy because of a large amount of carrier polymer typically required to form fibers. We demonstrate electrospinning of graphene with nearly quantitative retention of flake anisotropy to provide low to moderate density coatings of randomly oriented flakes having very large inter-flake mean free paths for ionic diffusion. Polyvinyl alcohol (PVA) is used as a carrier polymer and yields graphene anisotropy retention over an instability domain wherein electrospinning transitions to electrospraying. Graphene is deposited in polymer-encapsulated films at weight concentrations up to 50%, almost an order of magnitude higher than previously reported. Electrode applications will require at least partial replacement of PVA by electrically conducting polymers, and such polyelectrolytes should also suppress this electrospraying instability. We believe that large-scale electrospinning of graphene nanosheets will accelerate development of 2D materials in the fields of energy storage and conversion, catalysis, and tissue engineering.