Secondary Ion Mass Spectrometry Spectra Research Articles

Hydrolysis of VX on concrete: rate of degradation by direct surface interrogation using an ion trap secondary ion mass spectrometer.

The nerve agent VX (O-ethyl S-2-diisopropylaminoethyl methylphosphonothiolate) is lethal at very low levels of exposure, which can occur by dermal contact with contaminated surfaces. Hence, behavior of VX in contact with common urban or industrial surfaces is a subject of acute interest. In the present study, VX was found to undergo complete degradation when in contact with concrete surfaces. The degradation was directly interrogated at submonolayer concentrations by periodically performing secondary ion mass spectrometry (SIMS) analyses after exposure of the concrete to VX. The abundance of the [VX + H]+ ion in the SIMS spectra was observed to decrease in an exponential fashion, consistent with first-order or pseudo-first-order behavior. This phenomenon enabled the rate constant to be determined at 0.005 min(-1) at 25 degrees C, which corresponds to a half-life of about 3 h on the concrete surface. The decrease in [VX + H]+ was accompanied by an increase in the abundance of the principal degradation product diisopropylaminoethanethiol (DESH), which arises by cleavage of the P-S bond. Degradation to form DESH is accompanied by the formation of ethyl methylphosphonic acid, which is observable only in the negative ion spectrum. A second degradation product was also implicated, which corresponded to a diisopropylvinylamine isomer (perhaps N,N-diisopropyl aziridinium) that arose via cleavage of the S-C bond. No evidence was observed for the formation of the toxic S-2-diisopropylaminoethyl methylphosphonothioic acid. The degradation rate constants were measured at four different temperatures (24-50 degrees C), which resulted in a linear Arrhenius relationship and an activation energy of 52 kJ mol(-1). This value agrees with previous values observed for VX hydrolysis in alkaline solutions, which suggests that the degradation of submonolayer VX is dominated by alkaline hydrolysis within the adventitious water film on the concrete surface.

Solution Assembled and Microcontact Printed Monolayers of Dodecanethiol on Gold: A Multivariate Exploration of Chemistry and Contamination

Self-assembled monolayers (SAMs) of dodecanethiol on gold formed by solution assembly and microcontact printing were compared using electron spectroscopy for chemical analysis (ESCA) and time-of-flight secondary ion mass spectrometry (SIMS). Both univariate (ESCA and TOF-SIMS) and multivariate (TOF-SIMS) analysis techniques were employed. Univariate analysis showed that samples stamped with a thiol concentration >10−50 mM produced SAMs comparable to long solution assembly times. Principal component analysis (PCA) of the SIMS spectra provided deeper insight into the two sets of samples. The scores from the first principal component (PC1) showed similarities between the samples prepared by the two methods, though there was more scatter in the microcontact printed samples. The second principal component (PC2) showed that differences exist between the solution assembled and stamped samples due mainly to a relative increase in the presence of oxidized species (SO3-, HSO4-, O-, OH-, (M−H)-oxidized) and silicone...

Gd 2 O 3 , Ga2O3(Gd2O3), Y2O3, and Ga2O3, as high-k gate dielectrics on SiGe: A comparative study

We report a comparative study of the electrical properties of some oxides e.g., Gd2O3, Ga2O3(Gd2O3), Y2O3, and Ga2O3 as gate dielectric for strained Si0.74Ge0.26 metal–oxide–semiconductor devices. Secondary ion mass spectroscopy spectra of the Ga2O3(Gd2O3)/SiGe sample showed a significant amount of GaO and GdO along with Ga and Gd signals. The depth profile taken for O, Si, SiO, Ga, Ge, Gd, and GdO showed sharp interface at about 20 nm. Though Gd2O3 and Y2O3 showed the highest resistivity and breakdown strength, Ga2O3(Gd2O3) was found to be most effective for surface passivation of SiGe giving lowest interface state density while pure Ga2O3 was incapable of passivating the SiGe surface. The positive fixed oxide charge and interface state density for Ga2O3(Gd2O3) film were found to be 8.4×1010 cm−2 and 4.8×1011 eV−1 cm−2, respectively, which are the lowest among all the oxide films of the present study.

SIMS study of adsorption of collectors on pyrite

Adsorption of sulfide collectors such as xanthate on pyrite has been studied extensively over several decades using a wide variety of techniques. In spite of this, there are unanswered questions as to the identity of adsorbed species on pyrite surfaces—dixanthogen vs. iron xanthate complexes. Far less is known in non-xanthate collector systems. We have used Secondary Ion Mass Spectroscopy (SIMS) successfully in the past to obtain direct evidence for the identity of the adsorbed collector species on copper sulfides, galena and Cu-activated quartz. The present study is an extension of the SIMS analysis to investigate the adsorption of xanthate, dithiophosphate, dithiocarbamate, and modified thionocarbamates and thioureas on pyrite. Adsorption of these collectors on chalcocite was also studied for comparison. An attempt was also made to obtain SIMS spectra for pure dixanthogens at room temperature. The collector molecular ion was detected for pure amyl dixanthogen, but only dixanthogen fragments were observed for the isobutyl and ethyl homologues. Only in the case of dithiocarbamate (DTC) was there direct evidence for the presence of not only the collector dimer, but also iron–DTC complexes. On chalcocite, only the copper–DTC complexes were detected (no dimer). In the case of xanthate, the collector molecular ion and its S adduct—which are possible fragments from dixanthogen—were detected on pyrite, along with a fragment peak suggesting Fe 2X. For dithiophosphate, the collector molecular ion and Fe(DTP)(OH) complex were detected (no dimer). For modified thionocarbamate and thiourea, adsorption on pyrite was negligible. SIMS results obtained in this study imply that one cannot subscribe only to collector dimers as the predominant species on pyrite under practical flotation conditions and rule out the formation of Fe-collector complexes for the adsorption of collectors on pyrite.

Investigation of tungsten cathodes activated with Ba 2CaWO 6

The investigation of chemical and topographic structure of activated tungsten cathodes has great importance in the optimisation of high pressure discharge lamps. In spite of the numerous investigations, there are many open questions in connection to the transport mechanism of the activator substances from the reservoir to the electron emitting tip. Investigations of tungsten cathodes activated by Ba 2CaWO 6 were performed by means of simultaneous surface analytical methods: scanning electron microscopy (SEM), electron microprobe (EMP), cathodoluminescence (CL) and secondary ion mass spectrometry (SIMS). The topography of the surface was studied by SEM and CL, giving the result that the activator substances are inhomogeneously distributed on the surface of the tip. According to the EMP analyses the chemical composition of the observed precipitates on the surface of the samples corresponds to the original activator compound with O excess. According to the SIMS spectra, parallel migration of atomic and oxide species is possible. Lateral and in-depth investigations show that the substances migrate mostly on the surface of the tungsten rod, but their minor quantity may migrate also along the grain boundaries. Ratio of fluxes of migration channels could be estimated from the crystal sizes determined and are compared to the heat of formation of the oxides.

Enhancement on field-emission characteristics of diamondlike coated Mo substrates by redox process

We have improved the emission characteristic of diamondlike carbon (DLC)-coated Mo substrates by using a reduction-oxidation (redox) process. The maximum emission current density of the DLC/Mo films increased substantially from 10 to 225 μA/cm2 with the turn-on field decreased from 12.4 to 6.4 V/μm due to redox treatment. Secondary-ion mass spectrometry spectra and x-ray diffraction patterns show that the structure of Mo films was insignificantly changed due to oxidation and reduction, whereas atomic force microscopy and transmission electron microscopy indicate that the roughness increased markedly. The electron emission characteristics of DLC films coated on redox Mo substrates are much better than those of the films coated on normal Mo film, which is ascribed to the increase in the field enhancement factor of the DC films.

Delayed extraction for improved resolution of ion/surface collision products by time-of-flight mass spectrometry

A time-of-flight mass spectrometer is described which contains a collision surface located behind the reflectron. This collision device uses delayed extraction (DE) to improve the instrument resolving power for ion/surface collision products formed by secondary ion mass spectrometry (SIMS) and surface induced dissociation (SID). Comparisons are made between spectra acquired using delayed and continuous extraction. SIMS spectra were acquired by bombarding a perfluoropolyether (PFPE) surface with 1.5 keV ferrocene molecular ion projectiles. Sputtered fluorocarbon ions were detected with resolving powers ( m/Δ m, FWHM) of 150 and 950 using continuous and delayed extraction, respectively. SID spectra were acquired using naphthalene projectile ions which collide upon the PFPE surface at 50 eV. Naphthalene fragments were detected with a resolving power of 130 using continuous extraction and 350 with DE. For both the high- and low-energy experiments, the instrument resolving power showed a strong dependence on extraction delay. Energy resolved SID mass spectra collected using ferrocene molecular ions show that fragmentation of this projectile is similar to that observed while using other instrument geometries.

The annealing effects on ZnCdSe/ZnSe quantum wells and ZnSe/GaAs interfaces

This study investigated the thermally induced interdiffusion in ZnCdSe/ZnSe quantum wells and the outdiffusion of Ga atoms from the GaAs substrate by photoluminescence (PL), secondary ion mass spectrometry (SIMS), and contactless electroreflectance (CER) spectroscopy. The quantum well structures grown by molecular beam epitaxy were thermally annealed at temperatures between 250 and 700 °C. According to our results, the 15 K PL main peak disappeared when the annealing temperature reached 550 °C and above for samples grown with a 0.1 μm ZnSe buffer (sample A). In contrast, the PL main peak disappeared when the annealing temperature reached 600 °C and above for samples grown with 0.85 μm ZnSe buffer (sample C). In addition, for sample A, two extra PL peaks around 2.0 and 2.3 eV were observed when the annealing temperature reached 500 °C and above; those peaks were observed only when the annealing temperature reached 700 °C for sample C. SIMS results indicated the interdiffusion of Cd in the ZnCdSe/ZnSe quantum well regions in both samples. However, only sample A revealed a strong outdiffusion of Ga atoms from the substrate into the epilayer side, but a weaker one in sample C. The main peaks in PL spectra and the intersubband transitions in CER spectra disappeared owing to the Cd interdiffusion in the wells and the defect-related transitions introduced by the Ga outdiffusion onto the epilayer side. Based on the SIMS, PL, and CER spectra results, a thicker ZnSe buffer layer can increase the thermal stability of ZnCdSe/ZnSe quantum wells grown on GaAs substrates because of its effectiveness in mitigating the outdiffusion of Ga atoms into buffer layers and the interdiffusion of quantum well regions.

Hydrogen (deuterium) bonding properties in ZrV 2D x studied by SIMS and SNMS

Secondary ion mass spectrometry (SIMS) and secondary neutral mass spectrometry (SNMS) measurements on the Zr–V–H(D) system have been carried out to study the hydrogen bonding properties of the AB 2 Laves phase ZrV 2 in comparison to those of the pure components Zr and V. The SIMS spectra clearly show that Zr and V both keep their hydrogen bonding ability also in the Laves phase without clearly perceptible alterations. Only the hydrogen bonding character of Zr seems to be influenced a little, probably due to a weak electron transfer from zirconium.

Structure of the Monophosphoryl Lipid A Moiety Obtained from the Lipopolysaccharide of Chlamydia trachomatis

Monophosphoryl lipid A was prepared from the lipopolysaccharide of Chlamydia trachomatis, converted to the methyl ester, and fractionated by reverse-phase high-performance liquid chromatography. The peak fractions were collected and analyzed by mass spectrometry. Matrix-assisted laser desorption/ionization and liquid secondary ion mass spectrometry of the first of two major high-performance liquid chromatographic fractions showed multiple quasi-molecular ions of MNa+ at m/z 1780, 1794, 1808, 1822, and 1836. The positive-ion liquid secondary ion mass spectrometry spectrum also showed a minor series of peaks at m/z 1916, 1930, 1944, 1958, and 1971, consistent with the formation of matrix adducts with 3-nitrobenzyl alcohol. Oxonium ions representing the distal subunit were observed at m/z 1057, 1071, 1085, 1099, and 1113. The second fraction was similarly analyzed and found to contain structural homologs of the first fraction. Based on this study, the major lipid A component of chlamydial lipopolysaccharide is a glucosamine disaccharide that contains five fatty acids and a phosphate in the distal segment. Three fatty acyl groups are in the distal segment, and two are in the reducing end segment. The acyloxyacyl group is located in the distal segment in amide linkage. Two structural series, differing by 14 atomic mass units in the reducing subunit, were observed. Chlamydial lipid A is complex and consists of at least 20 homologous structural components. The relatively low potency of Chlamydia trachomatis lipopolysaccharide in activating lipopolysaccharide-responsive cells might be related to the unusual fatty acid composition of the lipid A moiety.

Secondary Ion Mass Spectrometry of Polymers: a ToF SIMS Study of Monodispersed PMMA Standards

This paper is concerned with the effects that polymer molecular weight, casting solvent, sonification (with a non-polymer solvent) and annealing have upon the secondary ion mass spectrometry (SIMS) of polymers. Films of a series of monodispersed poly(methyl methacrylate) (PMMA) standards, Mw 2965–1200000, were prepared by solution casting from four solvents (tetrahydrofuran (THF), 2-butanone, toulene and chloroform) onto clean aluminium (Al) substrates. The PMMA films were characterized by high- and unit-mass resolution time-of-flight secondary ion mass spectrometry (ToF-SIMS). To determine the significance of variations seen in ion intensities, one PMMA sample was re-analysed 24 times, and the scatter in the absolute counts and normalized and ratioed ion intensities for specific (termed ‘key’) positive and negative ions were calculated. This provided 95% confidence error bars, which were subsequently employed. The 95% confidence limits were significantly reduced by normalizing or ratioing. Molecular weight was found to have the greatest effect in the SIMS spectra obtained, with the differences being most marked between Mw=2965 and Mw=89100. This was seen in both the total negative ion counts (m/z 31–200) and the key negative ion ratios. An explanation based on the surface concentration of chain ends is presented. Negative ion ratios were shown to be very sensitive to trace amounts of residual solvents. By annealing above the PMMA glass transition temperature Tg solvent-free films were produced from three solvents and these were spectrally indistinguishable. Solvent-free films could not be produced from THF. Residual solvent was identified by high mass resolution ToF-SIMS. Sonification with hexane, a polymer non-solvent, had a considerable effect on the total negative ion counts (m/z 31–200). No concomitant chemical changes were detected, so this effect is thought to arise from a physical perturbation of the surface. © 1997 by John Wiley & Sons, Ltd.

A characterization of the β -glycidoxypropyltrimethoxysilane and aluminium interface by SIMS and XPS

Organosilanes are frequently applied as primers to oxide layers on aluminium and its alloys in order to improve adhesion to organic coatings, for example, for corrosion protection, although the bonding mechanism is not well understood [1, 2]. A common view has been that the adhesion involves formation of Si±O±Al type linkages, although direct evidence for this interfacial bonding has proved elusive [3±9]. Earlier work from this laboratory suggested that angle-dependent X-ray photoelectron spectroscopy (ADXPS), in combination with a bias-potential technique, may give a new way for probing the interfacial bonding between oxidized aluminium and silanes, and for aiding the identi®cation of relationships between atomic-level interfacial structure and macroscopic properties [10, 11]. For a thin layer of a-glycidoxypropyltrimethoxysilane (a-GPS) deposited on chemically etched aluminium, it was hypothesized that a new structure apparent in Al2p spectra for small exit angles in ADXPS, after applying a negative biasing potential, may indicate a ` chemical shift'' effect associated with the Si±O± Al bonding [10]. The evidence was indirect; it depended on the existence for some silane±aluminium systems of this additional structure in Al2p spectra, induced by differential charging, and an associated correlation with corrosion protection. This letter reports further observations on the same system, and includes an attempt at characterizing the interfacial bonding with secondary ion mass spectrometry (SIMS) in the static SIMS mode [12]. Following the earlier reports [10, 11], square panels of 7075-T6 aluminium (1 cm) were degreased and acid etched before coating with the silane solution (1 vol % formed by dissolving a-GPS monomer in an equi-volume mixture of distilled water and methanol). Three main samples are referred to below. Sample A was a blank sample prior to coating with aGPS (i.e. the alloy after etching); sample B was formed from sample A by applying the a-GPS solution drop-by-drop until a thick layer of polymer was formed; sample C gave the a-GPS=substrate interface formed by dipping sample A in the a-GPS solution for 5 min followed by air drying. X-ray photoelectron spectroscopy (XPS) spectra were measured with a Leybold MAX200 spectrometer [13] using the unmonochromatized AlKa source (1486.6 eV) operated at 15 kV, 20 mA with pressure in the analysis chamber around 6 3 10y7 Pa. The biased spectra were obtained by applying an external potential of y93 V through the sample holder, and then, after measurement, mathematically shifting the energy scale back by 93 eV [10]. Static SIMS was performed with a VG MM12-12S quadrupole mass spectrometer using a xenon primary beam (5 keV impact energy), for which a current of 0.2 nA irradiated a square area (6.25 mm) on the samples. XPS con®rms that the samples A, B and C had the expected compositions for the surface regions; also sample B was suf®ciently thick that Al signals were not detectable. Sample C showed the extra structure reported previously in the Al2p spectra from using the bias potential technique, and therefore it appeared to provide a suitable sample for probing the a-GPS=aluminium interface with SIMS. Relevant positive ion static SIMS spectra are reported in Fig. 1. Those for the acid-etched alloy (sample A) and the thick a-GPS layer (sample B) serve as references for interpreting that from the interface structure (sample C). The spectrum from sample A in Fig.1a is made up of Al‡ (mass 27) and CH fragments, the latter being indicative of the commonly observed hydrocarbon contamination. Since C2H3 ‡ and C2H5 ‡ fragments are usually comparable in intensity, only part of the mass 27 peak can be assigned to C2H3 ‡. The small peak at mass 28 may be AlH‡ (Si‡ is considered less likely since no Si was detected by XPS). Sample B experienced charging under ion bombardment, and the spectrum in Fig. 1b was obtained with operation of an electron ood gun (500 eV) to compensate. The signals obtained were fairly weak; nonetheless peaks from Si‡ and SiOH‡, and possibly SiCH3 ‡, were evident in the spectrum. The presence of SiOH‡ is consistent with expectation from the a-GPS polymerization [3]. There should be no contribution at mass 27 from Al‡ given the thickness of the a-GPS layer, but hydrocarbon fragments, in part from the a-GPS backbone, are clearly present. Fig. 1c shows the static SIMS spectrum for sample C. No sample charging was evident, thereby supporting the belief that the a-GPS layer was very thin. The most prominent peak was at mass 45 (SiOH‡ from the a-GPS polymerization), but there

SrTiO3 buffering effect on Pb1−xLaxTiO3 thin films prepared by pulsed laser deposition

Thin films of phase-pure perovskite PLT (Pb0.95La0.05Ti0.9875O3) were deposited in situ onto Si, Pt/Ti/SiO2/Si, and SrTiO3/Si substrates by pulsed laser deposition from stoichiometric targets. No Pb loss was observed in the near-surface region. The blocking of the interdiffusion between inner Si substrate and the outer PLT films by SrTiO3 buffer layer was evidenced using x-ray diffraction (XRD) and secondary ion mass spectrometry (SIMS) analyses. The formation of TiO2 second phase in PLT/Pt/Ti/SiO2/Si films was indicated by XRD and SIMS spectra to be the outward diffusion of Ti atoms from the underlying Ti layer through the Pt layer, reacting with ambient O2 at the PLT-to-Pt interface.

Germanium Redistribution Phenomena in the Synthesis of SiGe Layers

AbstractA unique germanium redistribution phenomenon occurs in the synthesis of SiGe by 74Ge+ ion implantation. A number of silicon samples were implanted with 74Ge+ ion using a range of substrate temperatures (R.T. to 600°C) with different germanium fluences (1.5 × 1016 cm-2 to 4 × 1016 cm-2) and implantation energies (100keV – 18OKeV). Samples were germanium profiled using Rutherford backscattering spectrometry (RBS) and secondary ion mass spectrometry (SIMS).The experimental results show that the peak range of the germanium implant increases progressively above 150°C and a shift of 40nm in the peak germanium range was measured for a sample implanted at 600°C. The ‘hot’ implants have an extended tail profile contrary to the Debye model for root-mean-square deviations of the lattice atoms from their equilibrium sites which should ideally contribute to dechanneling. The data suggest strongly that dynamic annealing related diffusion (DARD) processes exist, whereby mobile non-equilibrium point defects influence diffusion to take place at the elevated implantation temperature. The SIMS spectra of samples implanted with high Ge fluences at elevated temperature show “uphill” diffusion.

Germanium Redistribution Phenomena in the Synthesis of SiGe Layers

AbstractA unique germanium redistribution phenomenon occurs in the synthesis of SiGe by 74Ge+, ion implantation. A number of silicon samples were implanted with 74Ge+ ion using a range of substrate temperatures (R.T. to 600°C) with different germanium fluences (1.5 × 1016 cm-2 to 4 × 1016 cm-2) and implantation energies (100keV - 180KeV). Samples were germanium profiled using Rutherford backscattering spectrometry (RBS) and secondary ion mass spectrometry (SIMS).The experimental results show that the peak range of the germanium implant increases progressively above 150°C and a shift of 40nm in the peak germanium range was measured for a sample implanted at 600°C. The ‘hot’ implants have an extended tail profile contrary to the Debye model for root-mean-square deviations of the lattice atoms from their equilibrium sites which should ideally contribute to dechanneling. The data suggest strongly that dynamic annealing related diffusion (DARD) processes exist, whereby mobile non-equilibrium point defects influence diffusion to take place at the elevated implantation temperature. The SIMS spectra of samples implanted with high Ge fluences at elevated temperature show “uphill” diffusion.

Secondary-ion mass spectrometry of some catalpol and mussaenoside derivatives

The iridoid glycosides catalpol, veronicoside, catalposide, mussaenoside, and 8-epiloganin have been investigated by secondary-ion mass spectrometry (SIMS). A tendency of these compounds to give cationized1 form of the molecular ions in the SIMS regime has been shown. In the SIMS spectra of veronicoside and catalposide the maximum peaks were those of acyl cations, and in the cases of mussaenoside and 8-epilonganin they were the peaks of ions formed by the elimination of a glucose molecule.

Comparative study of incorporation of Cl and F into SiO 2 during the MCVD process

We report the results of examination of incorporation of chlorine and fluorine into silica as revealed from secondary ion mass spectroscopy (SIMS) and Raman spectroscopy measurements. The samples were preform-like rods made by the MCVD process. SIMS spectra were used for quantitative analysis of Cl concentration in glass. The concentrations of F were obtained from the Raman spectra. Both spectroscopic methods indicated the presence of SiCl groups in SiO 2 synthesized from chlorine-rich vapour gaseous blend. The difference in structural roles of Cl and F in chemically deposited silica manifests itself in the efficiency of their bonding to Si and in interaction with intrinsic structural defects.

Investigating the relationship between surface chemistry and endothelial cell growth: partial least-squares regression of the static secondary ion mass spectra of oxygen-containing plasma-deposited films.

The relationship between endothelial cell growth and surface properties of plasma-deposited films (PDFs) was investigated using partial least-squares regression (PLS). PDFs of oxygen-containing precursors were prepared under various conditions, and bovine arterial endothelial cells (BAECs) were grown on these substrates. Secondary ion mass spectrometry (SIMS) in the static mode was used to characterize the surface chemistry of these substrates. The growth of BAECs on the PDFs was correlated to the positive and negative static SIMS spectra of the PDFs by PLS. A good correlation between the SIMS spectra of PDFs and endothelial cell growth was obtained. Qualitative information was also extracted from the multivariate model, giving some information as to the most important variables influencing BAEC growth.

Surface characterization of novel plasma‐polymerized primers for rubber‐to‐metal bonding

AbstractThin (750 Å) plasma‐polymerized films of acetylene were deposited onto polished steel substrates in an inductively coupled r.f. reactor. The films were characterized by x‐ray photoelectron spectroscopy (XPS), Fourier‐transform infrared spectroscopy (FTIR), Auger electron spectroscopy (AES) and secondary ion mass spectrometry (SIMS) immediately after deposition and after aging in the atmosphere. The FTIR spectra of the as‐deposited films were characterized by bands related to mono‐ and disubstituted acetylene groups and by bands related to methyl and methylene groups. During exposure to the atmosphere, bands related to acetylenic groups decreased in intensity while new bands due to carbonyl groups appeared. When XPS spectra were obtained from films that were exposed to the atmosphere, new components assigned to oxidation products were observed in the C 1s spectra that were not observed for as‐deposited films, verifying that oxidation had occurred. Numerous peaks related to aromatic structures were observed in positive SIMS spectra of as‐deposited films. Results obtained from AES showed that the plasma‐polymerized films were continuous and that the oxide on the substrate surface was partially reduced during deposition.Plasma‐polymerized acetylene films were excellent primers for rubber‐to‐steel bonding. Miniature lap joints were prepared by using rubber as an ‘adhesive’ to bond together pairs of polished steel adherends primed with plasma‐polymerized acetylene films. The force required to break the as‐prepared joints was ∼2000 N for a bonded area of 64 mm2 and failure was 100% cohesive in the rubber. Similar results were obtained for joints prepared using polished brass substrates.Because of the complexity of reactions between rubber and the plasma‐polymerized primer, a model ‘rubber’ consisting of a mixture of squalene, zinc oxide, carbon black, sulfur, stearic acid, cobalt naphthenate, N,N‐dicyclohexylbenzothiazole sulfenamide and diaryl‐p‐diphenyleneamine was used to simulate the cross‐linking reaction. The results obtained using XPS, SIMS, AES and FTIR showed that sulfur diffused through the primer to form a layer of sulfide at the primer/substrate interface. Zinc and cobalt sulfides and perthiomercaptides, which formed at the interface between squalene and the plasma‐polymerized acetylene primer, catalyzed the reaction between squalene and the primer. Cross‐links between squalene and the primer were mostly mono‐sulfidic, although some evidence for di‐ and trisulfidic cross‐links was observed.

A calculation method for analysis of SIMS spectra from oxidation of metals in H216O/H218O/16O2 gas mixtures

AbstractA calculation method for the secondary ion mass spectrometry (SIMS) analysis of the reaction of a pure metal with gas mixtures of water and oxygen is introduced. Equation systems are to be solved, each expressed as: Y = A × X, where Y is an amplitude column measured from the SIMS spectrum, A is a matrix constructed from the relative abundances of isotopes of the metal and X is an unknown amplitude column of the relevant species MeaOHb±(a = 1, 2; b = 0, 1, 2 and 3). The applicability of the calculation method has been tested in SIMS analysis of ex situ‐grown iron oxides with different and known 18O contents. In in situ oxidation, measurement of the ratio of H216O/H218O in the metal–water–oxygen reaction allows fractions of O in the species MeaOHb+ that originate from water to be calculated. Data from such calculations have been used to study the initial stage of the reaction of Fe and Cr in H216O/H218O/16O2 gas mixtures. The results are interpreted in terms of coupled/uncoupled reaction type, reactivity of metal to water relative to oxygen in the mixed gas and degree of dissociation of water.