Thomas R. Hess

An FTIR and XPS investigations of the effects of carbonation on the solidification/stabilization of cement based systems-Portland type V with zinc

The effects of carbonation on the solidification/stabilization (S/S) of zinc using Portland cement Type V (OPC) has been investigated by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). The FTIR results indicate that carbon dioxide reacts with the metal-bonded and hydrogen-bonded hydroxides [CaZn[sub 2](OH)[sub 6][center dot]2H[sub 2]O] generally present in zinc-doped Portland cement (Zn-OPC) samples. XPS examinations of the carbonated products of the undoped and doped (Zn-OPC) samples indicate that the resulting silica phases have chemical states different from standard silica gel. Both FTIR and XPS results suggest that carbonation promotes polymerization of the SiO[sub 4] units present in OPC matrix. The chemical states of the surface components obtained by XPS analysis are discussed in the light of polymerization of the silicates.

Chemical and physical effects of sodium lignosulfonate superplasticizer on the hydration of portland cement and solidification/stabilization consequences

Abstract The effects of sodium lignosulfonate superplasticizer on the hydration of Portland cement Type V have been investigated by XRD and FTIR techniques. The results of these studies indicate that the superplasticizer inhibits the hydration reaction as demonstrated by the reduced formation of Ca(OH) 2 as well as a lower degree of polymerization of the silicate anions. The hydration reaction seems to be controlled by dispersions of various charges present in hyperalkaline | solution in cement paste. The mechanism of inhibition is discussed and a ‘Charge Dispersed Tri-layer Model’ is proposed to explain the observed effects on the hydration reactions. According to this charge dispersal model, the Ca 2+ ions from initial hydration reactions go into the solution to form a tightly-bound bi-layer of counterions with the negatively charged calcium-silica-hydrate surface. Consequent to this intrinsic process, a tri-layer consisting of superplasticizer anions is immediately formed which inhibits further reactions. Possible consequences of the presence of superplasticizer on the solidification/stabilization of inorganic and organic pollutants by cementitious materials have also been discussed.

An XPS and SEM/EDS characterization of leaching effects on lead- and zinc-doped portland cement

Abstract The characterization of leaching effects on portland cement doped with lead and zinc has been carried out by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS). Evidence is presented from XPS and SEM/EDS results that the dopant metal ions are preferentially adsorbed on the surface of the cementitious materials. Leaching tests reveal that most of the Zn 2+ ions and some of the Pb 2+ ions are dissolved. A chemical shift with respect to the Si( 2p ) XPS peak occurs due to the increased polymerization of the silicates present in cement. The distribution of the cations before and after leaching is discussed in relation to the XPS and SEM/EDS results.

An FTIR, SEM and EDS investigation of solidification/ stabilization of chromium using portland cement Type V and Type IP

Abstract The characterization of chromium-doped ordinary portland cement (Cr-OPC) before and after leaching has been carried out using Fourier transform infrare

Fractionation and characterization of Texas lignite class F fly ash by XRD, TGA, FTIR and SFM

Fly ash is a complicated heterogeneous material and utilization of it requires a detailed knowledge of the physical and chemical characteristics. In the present study Texas lignite class ‘F’ ash was examined by X-ray diffractometer (XRD), thermogravimetric analyzer (TGA), Fourier transformed infrared spectrophotometer (FTIR) and scanning force microscopy (SFM). The XRD and FTIR data indicated that the bulk fly ash was composed of mullite, quartz, cristobalite and amorphous aluminosilicates. The TGA indicated a negligible amount of absorbed water, and an absence of structural water in the amorphous aluminosilicate phases. The magnetic component of the fly ash was made up of magnetite and present mostly in the coarser fractions ≥50 μm. The SFM of the bulk fly ash showed the presence of amorphous glassy surface and quartz. The fractionated samples indicated that about 90 wt% of the fly ash was composed of ≥50 μm particles. The amorphous component increased with the decreasing particle fractions. Hence, the chemical reactivity of fly ash will increase with the decreasing particle size.

Surface and bulk studies of leached and unleached fly ash using XPS, SEM, EDS and FTIR techniques

Abstract The effective chemical utilization of fly ash in environmental applications requires a detailed knowledge of the surface and bulk changes induced by leaching in acid solutions. The surface and bulk characteristics of fly ash from the combustion of Texas lignite have been examined by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and Fourier transform infrared spectroscopy (FTIR). The effects of leaching with acid solutions commonly used in environmental studies have been documented using these techniques. The results of these studies reveal that the fly ash particles are relatively resistant to either chemical or physical changes due to attack by acidic leaching solutions.

Properties of fly‐ash bricks produced for environmental applications

Abstract The effects of pressure and temperature on preparation of bricks made from fly ash have been investigated. Bricks from Texas lignite fly ash and fly ash‐clay (kaolinite or montmorillonite) mixtures were prepared. It has been found that bricks with 20% kaolinite and 5% montmorillonite have green strengths high enough to handle without any additives. Samples were pressed under the pressure ranging from 35 MPa to 350 MPa. Lamination occurred at pressures higher than 270 MPa and plerospheres cracked under applied pressure. Fly ash with and without clay pellets were fired at 1000°C for 3 hours. Surface and bulk properties of fired and unfired samples were investigated and devitrification/sintering processes analyzed by x‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy‐energy dispersive spectroscopy (SEM‐EDS), and x‐ray photoelectron spectroscopy (XPS) techniques and the results are reported.

Effect of added lignosulfonate superplasticizer on the solidification/stabilization of phenol using Portland cement type‐V

Abstract This study explores the interaction of phenol, a significant organic pollutant, with cement and cement modified with a common superplasticizer, lignosulfonate. Samples of plain cement, cement doped with phenol, and superplasticized cement doped with phenol, have been examined by X‐ray diffraction (XRD), fourier transform infrared spectroseopy (FT‐IR) and scanning electron microscopy/ energy dispersive spectroseopy (SEM/EDS). Leachates of these samples have been examined by UV/VIS and GC/MS. Both phenol and (lignosulfonate + phenol) have been observed to retard the hydration of cement through specific surface chemical reactions. XRD and FT‐IR results are consistent with surface calcium diphenoxide formation. Both phenol and (lignosulfonate + phenol) have been found to retard formation of Ca(OH)2 and stabilize ettringite. Leaching of admixture doped cement by water removed the phenol and lignosulfonate and caused complete hydration of cement. The Charge Dispersal Model (CDM) has been used to explai...

Pulsed field desorption mass spectrometric study of the oxidation of hydrogen-doped Ni3Zr

Abstract The oxidation of a Ni 3 Zr field emitter, electrochemically doped with hydrogen, has been studied over a temperature range from 100°C to 250°C in an oxygen atmosphere with pressures ranging from 10 −4 Torr to 3 × 10 −1 Torr using PFDMS. Water was observed immediately after the first oxidation at 100°C and 10 −4 Torr O 2 and was observed throughout the series of oxidations. Pulse field desorption produced a wide range of ions: Ni + , Ni 2+ , H + , O + , O 2+ , O 2 + , H 2 O + , Ni(OH) 2 + , NiOH + , NiOH 2+ , NiOH 3+ , Ni 2 O 2+ , Ni(CO) + , Ni(CO) 2 + , Ni(CO) 3 + , Zr + , ZrO 2 3+ , ZrO 2 2+ , ZrO 2 + , Zr 2 O + , ZrO 3+ , ZrO 2+ and ZrO + ; which differ substantially from an atom probe investigation of the oxidation (dry, no H abs ) of the same alloy. The data show, for all oxidation temperatures and pressures, an initial strong enrichment of Ni at the surface. At lower temperatures and oxygen pressures this layer appears to be very thin. Previous low temperature/pressure thermal oxidation experiments performed on Ni 3 Zr (no H abs ) resulted in the preferential oxidation and segregation of Zr to the surface. Only at higher temperatures and/or oxygen pressures has preferential Ni oxidation and segregation been previously observed. This behavior is indeed observed during these experiments after the 250°C and 3 × 10 −1 Torr O 2 oxidation. The unusual H-doped Ni 3 Zr behavior at low temperatures/pressures appears to involve the formation of a thin layer of Ni(OH) x which is more stable than NiO. The results from the study of H-doped Ni 3 Zr yield some important new findings regarding the effect of hydrogen absorption on the alloy oxidation. In addition, the reaction of absorbed hydrogen with oxygen provides a unique way of introducing water on a sample in a UHV environment.

Prediction of alloy component oxidation order from a kinetic model using free energies of oxide formation

Described is a method based on the modified Cabrera–Mott model to predict the order of oxidation of alloy components under conditions of varying temperature and oxygen pressure.