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At least 73 records · Page 4

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NASA NTRS1985

Surface effects of corrosive media on hardness, friction, and wear of materials

Hardness, friction, and wear experiments were conducted with magnesium oxide exposed to various corrosive media and also with elemental iron and nickel exposed to water and NaOH. Chlorides such as MgCl2 and sodium containing films were formed on cleaved magnesium oxide surfaces. The MgCl2 films softened the magnesium oxide surfaces and caused high friction and great deformation. Hardness was strongly influenced by the pH value of the HCl-containing solution. The lower the pH, the lower the microhardness. Neither the pH value of nor the immersion time in NaOH containing, NaCl containing, and HNO3 containing solutions influenced the microhardness of magnesium oxide. NaOH formed a protective and low friction film on iron surfaces. The coefficient of friction and the wear for iron were low at concentrations of NaOH higher than 0.01 N. An increase in NaOH concentration resulted in a decrease in the concentration of ferric oxide on the iron surface. It took less NaOH to form a protective, low friction film on nickel than on iron.

Miyoshi, K.↗

NASA NTRS1985

Surface effects of corrosive media on hardness, friction, and wear of materials

Miyoshi, K.↗

DOE OSTI2010

Experimental co-digestion of corn stalk and vermicompost to improve biogas production

Anaerobic co-digestion of corn stalk and vermicompost (VC) as well as mono-digestion of corn stalk were investigated. Batch mono-digestion experiments were performed at 35 {+-} 1 {sup o}C and initial total solid loading (TSL) ranged from 1.2% to 6.0%. Batch co-digestion experiments were performed at 35 {+-} 1 {sup o}C and initial TSL of 6% with VC proportions ranged from 20% to 80% of total solid (TS). For mono-digestion of corn stalk, a maximum methane yield of 217.60 {+-} 13.87 mL/g TS{sub added} was obtained at initial TSL of 4.8%, and acidification was found at initial TSL of 6.0% with the lowest pH value of 5.10 on day 4. Co-digestion improved the methane yields by 4.42-58.61% via enhancing volatile fatty acids (VFAs) concentration and pH value compared with mono-digestion of corn stalk. The maximum biogas yield of 410.30 {+-} 11.01 mL/g TS{sub added} and methane yield of 259.35 {+-} 13.85 mL/g TS{sub added} were obtained for 40% VC addition. Structure analysis by X-ray diffractometry (XRD) showed that the lowest crystallinity of 35.04 of digested corn stalk was obtained from co-digestion with 40% VC, which decreased 29.4% compared to 49.6 obtained from un-treated corn stalk. It is concluded that co-digestion with VC is beneficial for improving biodigestibility and methane yield from corn stalk.

09 BIOMASS FUELS↗

DOE OSTI2018

Influence of calcium ion in concrete pore solution on the passivation of galvanized steel bars

The addition of supplementary cementitious materials may affect the Ca{sup 2+} concentration and pH value of the concrete pore solutions. This work studied the influence of the calcium ion on the passivation of the galvanized steel bars in simulated concrete pore solutions with relatively low pH value of 12.5 and 13.15. The results showed that continuous protective layers were formed on the galvanized coating in the solutions with saturated Ca(OH){sub 2} at pH 12.5 and solutions with either KOH or NaOH at pH 13.15. The passive film formed in the saturated Ca(OH){sub 2} solution showed better protective properties than those in other solutions. In the solutions with lower concentrations of Ca{sup 2+} at pH 12.5, there was no obvious reaction and no protective layer was formed on the surface.

36 MATERIALS SCIENCE↗

DOE OSTI2017

Effect of magnesium on calcium silicate hydrate (C-S-H)

The addition of MgCl{sub 2} to synthetic calcium silicate hydrate (C-S-H) with Ca/Si = 0.8 lowers the pH values below 10. Experimental observations and thermodynamic calculations show the destabilization of C-S-H and the precipitation of magnesium silicate hydrate (M-S-H). In contrast, the addition of MgO to C-S-H increases the pH values up to 11.5 and the Ca/Si in C-S-H from 0.8 to ~ 1.0. At high pH, the formation of M-S-H and brucite is observed experimentally. Less brucite is present at 50 than at 20 °C indicating a slow dissolution kinetic of brucite at 20 °C. Thermodynamic modelling is in good agreement with the changes in C-S-H and M-S-H formation in the presence of MgO although no brucite is predicted. M-S-H is observed in the presence of both MgCl{sub 2} and MgO, is stable from pH 7.5 to 11.5 and has a structure comparable to the structure of M-S-H prepared from MgO and SiO{sub 2} only.

36 MATERIALS SCIENCE↗

DOE OSTI2015

pH effect on structural and optical properties of nanostructured zinc oxide thin films

ZnO nanostructures were Deposited on Objekttrager glasses for various pH values by chemical bath deposition method using Zn (NO3)2·6H2O (zinc nitrate hexahydrate) solution at 75°C reaction temperature without any posterior treatments. The ZnO nanostructures obtained were characterized by X-ray Diffraction (XRD, UV). The structure was hexagonal and it was found that some peaks disappear with various pH values. The grain sizes of ZnO films increases from 22-to-29nm with increasing pH. The transmission of the films was (85-95%)

77 NANOSCIENCE AND NANOTECHNOLOGY↗

DOE OSTI2015

Structural characterization of nickel oxide/hydroxide nanosheets produced by CBD technique

Graphical abstract: SEM images of (a) as deposited β-Ni(OH)2 and (b) NiO samples deposited with pH 10 solution. The inset figures shows the absorbance spectra of (a) β-Ni(OH)2 and (b) NiO samples. - Highlights: • The formation of β-Ni(OH){sub 2} and NiO were confirmed with XRD, SEM, FT-IR and Raman. • Porous nickel oxide was synthesized after heat treatment of nickel hydroxide. • The increase in pH value changes the nanoflake structure to hexagonal nanosheet. • On increasing the pH from 8 to 11, the band gap decreases from 3.52 to 3.37 eV. - Abstract: Nickel hydroxide samples were deposited onto glass substrates using Ni(NO{sub 3}){sub 2}·6H{sub 2}O and aqueous ammonia by chemical bath deposition technique. The influence of pH of solution was investigated by means of X-ray diffraction, field emission scanning electron microscopy, Fourier transform infrared, Raman spectroscopy, optical absorption and BET analysis. The as-deposited samples were identified as β-Ni(OH){sub 2}, were transformed into NiO after heat treatment in air at 500 °C for 2 h. Porous nickel oxide nanosheets are obtained by heating nickel hydroxide nanosheets. The optical transitions observed in the absorbance spectra below optical band gap is due to defects or Ni{sup 2+} vacancies in NiO samples. The band gap energy of NiO samples changes between 3.37 and 3.52 eV depending on the pH values.

77 NANOSCIENCE AND NANOTECHNOLOGY↗

DOE OSTI2011

Thermodynamic Model for SnO 2 (cr) and SnO 2 (am) Solubility in the Aqueous Na+-H+ -OH- -Cl- -H 2 O System

The solubility of SnO 2 (cassiterite) was studied at 23 ± 2°C as functions of time (7 – 49 days) and pH value (0-14.5). Steady state concentrations were reached in < 7 days. The data were interpreted using the SIT model. The data shows that SnO 2 (cassiterite) is the stable phase at pH values of < ~11.7. These extensive data provided a log10 K 0 value of -64.39 ± 0.30 for the reaction (SnO 2 (cassiterite) + 2H 2 O = Sn 4+ + 4OH - ) and values of 1.86 ± 0.30, ≤ -0.62, -9.20 ± 0.34, and -20.28 ± 0.34 for the reaction (Sn 4+ + nH 2 O = Sn(OH)n 4- n + nH + ) with values of “n” equal to 1, 4, 5, and 6 respectively. These thermodynamic hydrolysis constants were used to reinterpret the extensive literature data for SnO 2 (am) solubility, which provided a log10 K 0 value of -61.80 ± 0.29 for the reaction (SnO 2 (am) + 2H 2 O = Sn 4+ + 4OH - ). SnO 2 (cassiterite) is unstable under highly alkaline conditions (NaOH concentrations > 0.003 mol.dm -3 ) and transforms to a double salt of SnO 2 and NaOH. Although additional well-focused studies will be required for confirmation, the experimental data in the highly alkaline region (0.003 to 3.5 mol.dm -3 NaOH) can be well described with log10 K 0 of -5.29 ± 0.35 for the reaction (Na 2 Sn(OH) 6 (s) = Na 2 Sn(OH) 6 (aq)).

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2017

Carboxylated Fullerene at the Oil/Water Interface

The self-assembly of carboxylated fullerene with poly(styrene-b-2-vinylpyridine) (PS-b-P2VP) with different molecular weights, poly-2-vinylpyridine, and amine-terminated polystyrene, at the interface between toluene and water was investigated. For all values of the pH, the functionalized fullerene interacted with the polymers at the water/toluene interface, forming a nanoparticle network, reducing the interfacial tension. At pH values of 4.84 and 7.8, robust, elastic films were formed at the interface, such that hollow tubules could be formed in situ when an aqueous solution of the functionalized fullerene was jetted into a toluene solution of PS-b-P2VP at a pH of 4.84. Lastly, with variation of the pH, the mechanical properties of the fullerene/polymer assemblies can be varied by tuning the strength of the interactions between the functionalized fullerenes and the PS-b-P2VP.

36 MATERIALS SCIENCE↗

DOE OSTI2018

Spectroscopic and Theoretical Studies of Fluorescence Effects in 2-Methylamino-5-(2,4-dihydroxyphenyl)-1,3,4-thiadiazole Induced by Molecular Aggregation

The article presents the results of fluorescence analyses of 2-methylamino-5-(2,4-dihydroxyphenyl)-1,3,4-thiadiazole (MDFT) in an aqueous environment. MDFT dissolved in aqueous solutions with a pH value in the range from 1 to 4.5 yielded an interesting effect of two clearly separated fluorescence emissions. In turn, a single fluorescence was observed in MDFT dissolved in water solutions with a pH value from 4.5 to 12. As it was suggested in the previous investigations of other 1,3,4-thiadiazole compounds, these effects may be associated with conformational changes in the structure of the analysed molecule accompanied by aggregation effects. Crystallographic data showed that the effect of the two separated fluorescence emissions occurred in a conformation with the –OH group in the resorcyl ring bound on the side of the sulphur atom from the 1,3,4-thiadiazole ring. The hypothesis of aggregation as the mechanism involved in the change in the spectral properties at low pH is supported by the results of (Time-Dependent) Density Functional Theory calculations. The possibility of rapid analysis of conformational changes with the fluorescence spectroscopy technique may be rather important outcome obtained from the spectroscopic studies presented in this article. Additionally, the presented results seem to be highly important as they can be easily observed in solutions and biologically important samples.

74 ATOMIC AND MOLECULAR PHYSICS↗

DOE OSTI2019

Enrichment and Distribution of Pb 2+ Ions in Zwitterionic Poly(cysteine methacrylate) Brushes at the Solid–Liquid Interface

Cysteine-based polyzwitterionic brushes have been prepared via a two-step route. First, poly(allyl methacrylate) (PAMA) brushes have been grown from the surface of silicon substrates using surface-initiated atom transfer radical polymerization. The obtained PAMA brushes with free pendant vinyl groups were further modified via radical thiol-ene addition reaction to attach L-cysteine moieties. Surface zeta potential investigations on pH-responsiveness of these poly(cysteine methacrylate) (PCysMA) brushes confirm their zwitterionic character at intermediate pH range, while at pH values either below pH 3.50 or above pH 8.59, they exhibit polyelectrolyte character. Under acid (pH < 3.50) or base (pH > 8.59) conditions, they possess either cationic or anionic character, respectively. In the zwitterionic region, these PCysMA brushes show positive surface $\zeta$ potential in the presence of Pb(CH 3 COO) 2 solutions of various concentrations. The results are in line with microscopic investigations using anomalous X-ray reflectivity (AXRR) carried out along the absorption edge of Pb 2+ ions. When the photon energies were varied around the absorption L3 edge of lead (13037 eV), the Pb 2+ concentration normal to the silicon substrates, as a function of depth inside PCysMA brushes, could be revealed at the nanoscale. Both zeta potential and AXRR measurements confirm the enrichment of Pb 2+ ions inside PCysMA brushes, indicating the potential of PCysMA to be used as a water purification material.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2012

Synthesis of pH-Responsive Particles with Shape Anisotropy

Seeded emulsion polymerization is used to produce large quantities of shape anisotropic, amphoteric particles in a size range of about 1 μm. Here, copolymer dicolloids (CDCs) containing pyridine groups are synthesized by swelling spherical, lightly cross-linked polystyrene seeds with a mixture of styrene and pH-responsive monomer 2-vinyl pyridine followed by secondary polymerization to contrast with their analogue homopolymer dicolloids (HDCs) where the swelling step is carried out with styrene alone. After the particles are coated with a nonionic surfactant to minimize van der Waals attractions, surface potentials and aggregation properties of dilute suspensions are studied as functions of pH and ionic strength. Compared to HDCs, which remain stable at all pH values studied (3 < pH < 9) up to an ionic strength of 5 M, the CDC particles show amphoteric behavior with strong attractions under conditions where dipolar interactions are expected to dominate.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

NASA NTRS1998

Tetragonal Chicken Egg White Lysozyme Solubility in Sodium Chloride Solutions

The solubility of chicken egg white lysozyme, crystallized in the tetragonal form was measured in sodium chloride solutions from 1.6 to 30.7 C, using a miniature column solubility apparatus. Sodium chloride solution concentrations ranged from 1 to 7% (w/v). The solutions were buffered with 0.1 M sodium acetate buffer with the solubility being measured at pH values in 0.2 pH unit increments in the range pH 4.0 to 5.4, with data also included at pH 4.5. Lysozyme solubility was found to increase with increases in temperature and decreasing salt concentration. Solution pH has a varied and unpredictable effect on solubility.

Forsythe, Elizabeth L.↗

DOE OSTI2015

Fabrication of single phase p-CuInSe{sub 2} nanowire arrays by electrodeposited into anodic alumina templates

Single-phase CuInSe{sub 2} nanowire (NW) arrays were prepared at various pH values in a heated electrolyte by using pulse electrodeposition techniques and an anodized aluminum oxide template. X-ray diffraction showed that the CuInSe{sub 2} NW nucleation mechanism received H{sup +} constraints when the NWs were deposited at pH 1.7 with a (112) orientation and annealed at 550 °C. The CuInSe{sub 2} NW band gap was determined to be approximately 1 eV through optical measurements. Transmission electron microscopy showed that at the pH value of 1.7, small particles of the single-phase CuInSe{sub 2} NWs aligned along the crystallographic direction are nucleated to form large particles. Scanning electron microscopy revealed that the NW diameter and the length were 80 nm and 2.3 μm, respectively. From Mott–Schottky and Ohmic contact plots, the CuInSe{sub 2} NWs were found to be p-type semiconductors, and their work function was estimated to be approximately 4.69 eV.

36 MATERIALS SCIENCE↗

DOE OSTI2013

Synthesis and structural characterization of CZTS nanoparticles

The CZTS nanoparticles were successfully synthesized by Chemical co-precipitation method with different pH values in the range of 6 to 8. The synthesized nanoparticles were characterized by X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. XRD studies revealed that the CZTS nanoparticles exhibited Kesterite Structure with preferential orientation along the (112) direction. Sample at pH value of 7 reached the nearly stoichiometric ratio.

36 MATERIALS SCIENCE↗

DOE OSTI2015

Effects of pH on deposition rate of supersaturated silicic acid around geological disposal system - 15245

For the migration assessment of radionuclides around geological repository, it is important to estimate the dynamic behavior of silicic acid under a high alkalinity condition due to the cementitious materials for the construction of the repository. This study examined the pH dependencies of the deposition behavior of supersaturated silicic acid in the co-presence of solid phase. The parameters for the deposition experiments were as follow: the pH was set to 8, 9 and 10, the initial saturated concentration was set to 2-8 mM, the amount of amorphous silica (350 m{sup 2}/g) as solid phase was set to 0.1-1.0 g. The experimental results showed that the initial supersaturated concentrations strongly affected the formation of colloidal silicic acid, increasing the deposition amount of silicic acid and decreasing the soluble silicic acid with time. In other words, the polymerization and the deposition of silicic acid simultaneously arose in these experiments. Furthermore, this study evaluated the apparent deposition rates of silicic acid by assuming the first-order reaction equation considering the specific surface area. As a result, the deposition rate constants, k, were in a narrow range of 10{sup -11} to 10{sup -10} m/s under all experimental conditions in this study. This means that the deposition rate constants do not depend both on pH-value (in the range from 8 to 10) and the initial concentration of supersaturated silicic acid. That is, the estimated deposition rate constants are useful in estimation of the deposition behavior of supersaturated silicic acid, such as the clogging in fractures (flow-paths) around the repository, even if the pH-value of groundwater gradually or dramatically changes. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2014

Remediation of AMD using natural and waste material

Acid Mine Drainage (AMD) is highly acidic, sulphate rich and frequently carries a high transition metal and heavy metal burden. These AMD's eventually migrate into streams and rivers and impact negatively on the quality of these water bodies. So it is dire necessary to treat this AMD. Various materials such as ladle furnace slag (LFS), bentonite, zeolite, active carbon and kaolinite are currently available to remove heavy metals from contaminated water. All these materials are capable to rise up the pH value and adsorb heavy metals. The process is divided into two stages; screening test and tank experiment. Screening test is conduct by using Batch Equilibrium Test (BET), X-Ray Fluorescene (XRF) identification also Scanning Electron Microscopic (SEM) characteristic. The results showed that all the concentration of heavy metal are decreasing extremely and pH value rise up except for kaolinite. From screening test only ladle furnace slag, bentonite, zeolite and active carbon are chosen for the tank experiment. Tank experiment design with 18cm (H) X 15cm (L) X 15cm (H) was made by silica glass. All these treatment materials were stirred in the tank for 30 days. Initial pH for all tanks is 2.4 and after 30 days is changing into 6.11, 3.91, 2.98 and 2.71 for LFS, bentonite, active carbon as well as zeolite respectively. LFS is the best material for absorption of Zn, Mn and Cu in the synthetic solution. Meanwhile, bentonite is the best absorbent for Ni, Fe and Cd. The conclusion shows that LFS might have big potentials to control AMD pollution base on neutralize pH resulting in a great improvement in the quality of the water.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2016

Morphology modification of gold nanoparticles from nanoshell to C-shape: Improved surface enhanced Raman scattering

Morphology modification of nanostructures is of great interest, because it can be used to fabricate nanostructures which are hard to be done using other methods. Different from traditional lithographic technique which is slow and expensive, morphology modification is easy, cheap, and reproducible. In this paper, modification of the optical and morphological properties of a hollow gold nanoshell (HGNS) is achieved by using H{sub 2}O{sub 2} as an oxidizer. The reshaping of these nanostructures has been demonstrated as a consequence of an oxidation process in which HGNSs are dissolved by H{sub 2}O{sub 2} under the acidic conditions provided by HCl. We investigate the oxidation process by a transmission electron microscope and propose a reshaping model involving four different shapes (HGNS, HGNS with hole, gold nanoring, and C-shaped gold nanoparticle) which are corresponding to the oxidation products of HGNSs at different pH values. Besides, the surface enhanced Raman scattering (SERS) activity of each oxidation product has been evaluated by using rhodamine 6G as the Raman active probe. It has been observed that the C-shaped gold nanoparticles which are corresponding to the oxidation products at the minimum pH value have the highest SERS activity and this result can also be interpreted by discrete-dipole approximation simulations. We demonstrate that the morphology modification of HGNSs becomes possible in a controlled manner using wet chemistry and can be used in preparation of gold nanoparticles such as HGNS with hole, gold nanoring, and C-shaped gold nanoparticle with large SERS activity. These nanostructures must have potential use in many plasmonic areas, including sensing, catalysis, and biomedicine.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗