Despite the increasing economic impact of fat-filled dairy powders, their manufacture is still empirical. The aim of the study was to understand the mechanisms responsible for fat supramolecular structure in such a dry matrix. For the purpose, emulsions were obtained under controlled manufacturing conditions. Then, they were dried under different inlet air temperatures, leading to different drying kinetics. Fat droplet size was determined in both emulsions and powders. Free fat and surface fat were assessed to characterize fat in the resulting powders. Confocal laser scanning microscopy was used to characterize fat supramolecular structure in situ in the powder particles. Results showed that fat supramolecular structure in fat-filled dairy powders was connected with drying air temperatures, not necessarily with drying kinetics. Inlet air temperature and consequently temperature of the drying droplet had the most significant influence. Such a study considering drying air temperatures and kinetics is essential in elucidating the mechanisms of free fat formation and the presence of fat at the surface of powder particles. Mechanisms underlying fat supramolecular structure in fat-filled dairy powders are proposed: They can be used as a tool to adjust spray-drying air temperatures and kinetics.

Biotite is a constituent Fe-bearing mineral of Delta subsoils in India and Bangladesh and has been hypothesized as a primary source of arsenic (As). The adsorption behavior of As onto structural Fe(II, III)-bearing biotite fractions (<50μm) was investigated in the pH range of 4–8 under a CO2-free, anoxic condition (O2<1ppmv) using X-ray Photoelectron Spectroscopy (XPS) and X-ray Absorption Spectroscopy (XAS). The batch experiments indicate that As adsorption is strongly pH dependent and that As(V) adsorbs more efficiently than As(III). X-ray Absorption Near-Edge Structure (XANES) spectra show no oxidation or reduction of As by biotite after reaction with As(III) or As(V) solutions for 3days. Extended X-ray Absorption Fine Structure (EXAFS) spectroscopic results suggest that As(III) forms bidentate mononuclear edge-sharing (2E) and bidentate binuclear corner-sharing (2C) surface complexes at pH 7.7 as indicated by average As–Fe bond distances at 3.00±0.02Å and 3.37±0.03Å respectively. The surface speciation retrieved by XPS does not provide any evidence of reduction of As(V) on biotite after 30days further confirming the thermodynamic prediction and the XANES results. This study has therefore significant environmental implications for As contaminated areas, where biotite retards the release of As into reducing groundwater. The changes in soil redox conditions and weathering of biotite may likely contribute to the occurrence of high As in groundwater.

Adapting and combining specific biochemical and physical methods to investigate the properties of fat is the first step of an integrated approach conducted on fat-filled dairy powders, which have an economic and qualitative importance. The study includes the isolation, quantification and characterization of the free fat fraction, and the investigation of fat properties in situ in the powder. Free fat isolation is achieved by solvent extraction; the extracted fat can be quantified and further studied from thermal profile features by differential scanning calorimetry (DSC). Fat droplet sizes are investigated by laser light scattering: measurements are achieved on emulsions obtained after the rehydration of the powders. In situ methods mainly include investigation of the thermal properties by DSC, composition of the surface by X-ray photoelectron spectroscopy and qualitative observations by confocal laser scanning microscopy. After this study, reliable and connected methods are available (i) to quantify and locate the different types of fat within a powder particle and (ii) to investigate fat composition, structure and thermal properties. The need to combine several methods to conclude on a data set was demonstrated.

X-ray photoelectron and Raman spectroscopies were used to investigate the chemical and the structural properties of thin diamond films synthesised by Plasma Assisted Chemical Vapour Deposition (PACVD). Continuous polycrystalline diamond films were grown under different plasma conditions and based on the combination of detailed XPS and Raman spectroscopic analysis two main topics are highlighted (i) the stress measurements were discussed by distinguishing clearly the chemical effects from the mechanical effects; (ii) an electronic gap at 2.7eV probed by Raman resonance that corresponds to an energy loss peak on the XPS carbon signal, was related to the surface hydrogenation.

The relationships between powder surface composition and powder rehydration properties under variable conditions of storage are investigated in this paper. A rheological approach was used to evaluate the modifications induced by storage on the rehydration properties of native phosphocaseinate powder. Concurrently, the powder surface composition (i.e., lactose, proteins, and lipids) was evaluated by X-ray photoelectron spectroscopy (XPS). A strong correlation was found between the powder wetting time lengthening and the migration of lipids on the powder surface during storage. XPS studies indicated also an over-representation of lipids on the powder surface (6%) in comparison with total lipids (0.4%) even on fresh powder before storage. Detailed investigation of powder lipids revealed the presence of high levels of polar lipids (66% compared with < 1% in milk lipids). Their amphiphilic nature and their melting points could explain the extensive enrichment of lipids observed at the powder surface during processing and storage.

The sorption of europium(III) species from EuCl3 solution at pH = 5.4 onto dickite particles is investigated using spectroscopic methods. Thanks to the neutrality of phyllosilicate sheets of dickite, cation exchange is prevented. X-ray photoelectron spectroscopy reveals that chloride atoms probably remain in the ligand sphere of the europium(III) cation. The edge site-specific reactivity is evidenced by epifluorescence microscopy and Raman spectroscopy. Comparison between dickite/europium(III) samples rinsed or not with distilled water shows that the surface processes not only involve inner-sphere complex formation, but also either outers-sphere complex or surface precipitation. Raman spectra also indicate that europium(III) surface complexes are preferentially localised at the edge of tetrahedral silica sheets.

Sorption of mercury(II) onto well-characterized samples of pyrite was studied between DH 2 and 12 using X-ray photoelectron spectroscopy for surface analysis and extended X-ray absorption fine structure fur surface speciation. In the presence of Hg, the surface oxidation of pyrite was strongly decreased. Even if the sorption capacity of pyrite for Hg was high, the sorption reversibility was possible by adding some strong ligands, such as I-, S2O32-, and CN-, to the aqueous phase. Spectroscopic studies showed the absence of Hg(0) and S(-II) and evidenced the formation of a surface complex between S(-I) and Hg(II). At low pH, ternary surface complexes =S-1-Hg-OH or =S-1-Hg-Cl were formed with the following distances: R=S-Hg = 2.40 Angstrom, RHg-OH = 2.25 Angstrom, and RHg-Cl = 2.33 Angstrom if Cl- was present. At high pH, the spectroscopic signals of Hg, S, or Fe decreased, possibly because of the presence at the surface of a solid solution constituted of Fe (hydr)oxides and surface complexes between Hg and both oxides and pyritic sulfur.

Hydrogen adsorption on Pt80Fe20(111) has been investigated mainly by TDS and UPS. It has been compared to hydrogen adsorption on Pt(111) as the composition of the first layer of this alloy is almost pure platinum due to a strong surface segregation. It appears that the valence band of both clean surfaces is different and that the work function is lowered by 0.2 eV on the alloy compared to Pt(111). The work function changes induced by hydrogen adsorption are of the same sign and the same order of magnitude on both surfaces. Finally the activation energy for desorption of hydrogen is lower by about 2 kcal/mol on the alloy. Results are discussed in relation with the catalytic properties of this alloy in hydrogenation reactions.

La vitesse d’adsorption du monoxyde d'azote sur ruban polycristallin de platine a été étudiée entre 300 et 1 500 K. A des températures inférieures à 400 K, cette adsorption est non dissociative; au-dessus de cette température, on observe une décomposition partielle dont les produits sont exclusivement de l’azote qui désorbe immédiatement et de l’oxygène qui contamine la surface. Le spectre de désorption thermique programmé est complexe : une fraction du monoxyde d’azote est décomposée au cours du chauffage et on détecte, en plus, deux étals de désorption dont les énergies de désorption peuvent être estimées à 24 et 28 kcal/mole.

Temperature programmed desorption (2.65 Ksec) has been used to study carbon monoxide and mixed layers of carbon monoxide and oxygen on rhenium ribbons, strongly oriented parallel to the (0001) plane. Four binding states, populated in decreasing energy have been detected. Interpretation of the results on β states agrees qualitatively with King's model postulating dissociation of carbon monoxide molecules and a repulsive interaction energy between carbon and oxygen atoms. However, in the coadsorbed layers studies, it is shown that all the oxygen atoms do not play a part in the recombination process, during desorption, and that when oxygen is adsorbed after carbon monoxide, a displacement reaction occurs, due to apparent transfer from β states towards molecular α states. Optimization of the results on pure carbon monoxide layers leads to an interactional energy ω, equal to 3 kcalmole, and is only possible if is assumed that β states are formed on alternatively filled and empty rows.

Temperature programmed desorption ( 2.65 K sec ) has been used to study carbon monoxide and mixed layers of carbon monoxide and oxygen on rhenium ribbons, strongly oriented parallel to the (0001) plane. Four binding states, populated in decreasing energy have been detected. Interpretation of the results on β states agrees qualitatively with King's model postulating dissociation of carbon monoxide molecules and a repulsive interaction energy between carbon and oxygen atoms. However, in the coadsorbed layers studies, it is shown that all the oxygen atoms do not play a part in the recombination process, during desorption, and that when oxygen is adsorbed after carbon monoxide, a displacement reaction occurs, due to apparent transfer from β states towards molecular α states. Optimization of the results on pure carbon monoxide layers leads to an interactional energy ω, equal to 3 kcal mole , and is only possible if is assumed that β states are formed on alternatively filled and empty rows.