Cl Contamination Research Articles

Experimental constraints on the volatility of germanium, zinc, and lithium in Martian basalts and the role of degassing in alteration of surface minerals

AbstractThe surface of Mars is enriched in Cl and S which is linked to volcanic activity and degassing. Similarly, elevated Ge and Zn levels in Gale crater sedimentary bedrock indicate a magmatic source for these elements. To constrain the relative effects of Cl and S on the outgassing of these trace metals and chemical characteristics of primary magmatic vapor deposits incorporated to Martian surface, we conducted a set of degassing and fumarolic alteration experiments. Ge is found to be more volatile than Zn in all experiments. In S‐bearing runs, the loss of Ge and Zn was less than any other experiments. In Cl‐only runs, degassing of Zn was more than twice that of Ge within the first 10 min and percent loss increased for both elements with increasing time. In Cl + S runs, S‐induced reduction of GeO2 and ZnO to metallic Ge and Zn switches the preference of chloride formation from Zn to Ge. Up to 90% of Ge and Zn loss in the 1‐h no volatile‐added (NVA) experiments might be due to the small amounts of Cl contamination in NVA mixes via other oxides used for synthesis. Alteration experiments show different phases between 1‐h and 24‐/72‐h runs. In 1‐h runs, anhydrite and langbeinite dominate while in 24‐/72‐h runs halite and sylvite dominate the condensate assemblages. S‐bearing phases form as the intermediate products of fumarolic deposition, while chlorides are common when the system is allowed to cool gradually. One‐hour exposure was sufficient to form alteration phases and vapor deposits such as NaCl, KCl, CaSO4, and langbeinites on the Martian analog minerals. These salts were identified in Martian meteorites and in situ measurements. Our results provide evidence that volcanic degassing along with fumarolic alteration could be a potential source for the enrichment and varying abundances of Cl, S, Fe, Zn, Ge in Martian surface, as well as a cause for Ge depletion in shergottites.

Effect of Potassium Ferrate as a Dewatering Conditioner on Sludge Pyrolysis Characteristics and the Releasing Characteristics of Nitrogen, Sulfur, and Chlorine during Sewage Sludge Pyrolysis

Sludge pyrolysis is a promising method for treating excess sludge as a by-product of municipal sewage plants, allowing for energy self-sufficiency and resource recovery. Before sludge pyrolysis begins, a few conditioning agents are added to the sludge that promote sludge dewatering. Potassium ferrate (K2FeO4) is applied as a conditioning agent with both cracking and flocculation effects, but the effects of K2FeO4 on the release characteristics of nitrogen, sulfur, and chlorine during sludge pyrolysis have not been elucidated. In this study, we analyzed the sludge pyrolysis characteristics and chemical state changes of N, S, and Cl contaminants in the dewatered sludge after K2FeO4 conditioning before and after pyrolysis. Further, the release characteristics of condensable/noncondensable gases during pyrolysis were assessed using thermogravimetric mass spectrometry (TG-MS) and pyrolysis–gas chromatography/mass spectrometry (Py-GC/MS) analyses before and after conditioning. We found that potassium pertechnetate reduced the activation energy required for the sludge in the pyrolysis process. Noticeably this process made the sludge more susceptible to thermal decomposition leading to volatile production and also influenced the release of different contaminants generated by the pyrolysis process. Moreover, K2FeO4 promoted the release of C/H/O gases and reduced the release of N/S/Cl pollutant gases from the sludge. Overall, this study provides a theoretical basis for the selection of conditioning agents for the sludge conditioning and dewatering steps during the sludge pyrolysis process.

Epidemiological and Therapeutic Profile of Leishmaniasis in the Province of Al Haouz-Morocco

The objectives of our study are to trace the epidemiological profile of cutaneous and visceral leishmaniasis in the province of al Haouz and to study the effectiveness of the national control program against leishmaniasis in this endemic area. It is a descriptive epidemiological study of cases recorded in public health facilities (health centers) and in the service of infrastructure and provincial ambulatory activities (SIAAP) of the province al Haouz between 2015 and 2019. Also it is an evaluative study of the provincial leishmaniasis control program. We found 264 cases of CL (94.96%) and 14 cases of VL (5.03%). The age groups most affected by CL were 0-5 years and pediatric cases (age less than 15 years) represented 74.62 percent of all CL cases. Females accounted for 61.15 percent of CL cases. The evolution of the number of notified cases of CL each year showed significant variations with a minimum value of 36 in 2015 and a maximum value of 70 in 2018 with an average number of CL cases recorded per year of 52 cases. The period at risk of CL contamination was the second and third quarter of the year with a percentage of 69.7 percent. 93.18 percent of communes affected by CL were rural communes. Passive screening was 96.59 percent with a number of LC cases of 255. 248 CL cases (93.93% of cases) were treated locally and 2 cases (0.75%) were treated systemically. 14 cases of VL were recorded, with a minimum value of 1 case in 2016 and a maximum value of 5 cases in 2017.All cases were treated by general route. In the present study, the analysis of the annual incidence of CL per 100,000 inhabitants showed a clear decrease in this indicator from 4.48 in 2015 to 1.65 in 2019.

Tuning the band gap and carrier concentration of titania films grown by spatial atomic layer deposition: a precursor comparison.

Spatial atomic layer deposition retains the advantages of conventional atomic layer deposition: conformal, pinhole-free films and excellent control over thickness. Additionally, it allows higher deposition rates and is well-adapted to depositing metal oxide nanofilms for photovoltaic cells and other devices. This study compares the morphological, electrical and optical properties of titania thin films deposited by spatial atomic layer deposition from titanium isopropoxide (TTIP) and titanium tetrachloride (TiCl4) over the temperature range 100–300 °C, using the oxidant H2O. Amorphous films were deposited at temperatures as low as 100 °C from both precursors: the approach is suitable for applying films to temperature-sensitive devices. An amorphous-to-crystalline transition temperature was observed for both precursors resulting in surface roughening, and agglomerates for TiCl4. Both precursors formed conformal anatase films at 300 °C, with growth rates of 0.233 and 0.153 nm s−1 for TiCl4 and TTIP. A drawback of TiCl4 use is the HCl by-product, which was blamed for agglomeration in the films. Cl contamination was the likely cause of band gap narrowing and higher defect densities compared to TTIP-grown films. The carrier concentration of the nanofilms was found to increase with deposition temperature. The films were tested in hybrid bilayer solar cells to demonstrate their appropriateness for photovoltaic devices.

Ni-Based Nanoparticles on Mesoporous Silica Supports for Single-Stage Arsenic and Chlorine Removal during Diesel Fraction Hydrotreating.

As- and Cl-containing impurities are highly detrimental to sulfided catalysts in hydrotreating processes. To prevent the irreversible loss of activity of the main sulfide catalysts by As and Cl contaminants, a protective double-layered guard bed catalyst is applied. Two types of mesoporous silica supports (SBA-15 and MCF) were used to obtain sorption-catalytic materials. The high specific surface area of the supports allowed for a significant increase in access to the active catalyst centers. The NiMo/SBA-15/Al2O3 and NiMg/MCF/Al2O3 sorption-catalytic materials demonstrated high activity and stability over 48 h for the simultaneous removal of As and Cl. The catalytic materials allowed for reducing the concentrations of As and Cl to less than 0.1 ppm in the diesel fraction under the following conditions: 5.0 MPa pressure, 2.0 h–1 LHSV, 300 L/L H2-to-substrate volume ratio, and 360 °C.

Thermal Isolation of a Clean Alloy from Waste Slag and Polymeric Residue of Electronic Waste

Unprecedented advances and innovation in technology and short lifespans of electronic devices have resulted in the generation of a considerable amount of electronic waste (e-waste). Polymeric components present in electronic waste contain a wide range of organic materials encompassing a significant portion of carbon (C). This source of carbon can be employed as a reducing agent in the reduction of oxides from another waste stream, i.e., steelmaking slag, which contains ≈20 wt%–40 wt% iron oxide. This waste slag is produced on a very large scale by the steel industry due to the nature of the process. In this research, the polymeric residue leftover from waste printed circuit boards (PCBs) after a physical-chemical recycling process was used as the source of carbon in the reduction of iron oxide from electric arc furnace (EAF) slag. Prior to the recycling tests, the polymer content of e-waste was characterized in terms of composition, morphology, thermal behavior, molecular structure, hazardous elements such as Br, the volatile portion, and the fixed carbon content. After the optimization of the ratio between the waste slag (Fe source) and the waste polymer (the carbon source), the microstructure of the recycled alloy showed no Br, Cl, S, or other contamination. Hence, two problematic and complex waste streams were successfully converted to a clean alloy with 4 wt% C, 4% Cr, 2% Si, 1% Mn, and 89% Fe.

Hard titanium nitride coating deposition inside narrow tubes using pulsed DC PECVD processes

In the present work, we reviewed and studied the fabrication process of hard erosion resistant TiN protective coatings on the inner surfaces of narrow tubes using a Non-Line-Of-Sight (NLOS) approach. Initially, while evaluating the growth of DLC and TiN by the CW RF PECVD process, we found that the use of a hydrocarbon precursor to obtain DLC provides uniform film thickness along the tube axis, while the use of the TiCl4 precursor for TiN leads to a significant thickness nonuniformity of 80% and large differences between the film properties in the middle of the tube compared to the edges. Following detailed plasma analysis, we demonstrate that the uniformity can be substantially enhanced by applying pulsed-DC PECVD, while uniform (better than 20%) hard TiN films were prepared by low-frequency (5 kHz) pulsed-DC PECVD. The TiN films (about 12 μm thick), systematically studied by SEM, XRD, and nanoindentation, when prepared under optimized conditions, exhibit high hardness and reduced Young's modulus (25 and 225 GPa, respectively) corresponding to the (111) preferred crystallographic orientation, and a very low Cl contamination (<3%). The film uniformity has been correlated to that of the discharge light emission intensity along the tube axis, and the microstructural evolution is interpreted in terms of surface densification due to substrate temperature and ion bombardment of the inner surface. The pulsed DC PECVD NLOS process providing TiN coatings with a hardness markedly higher than the hardness of the erodent particles and with a solid particle erosion resistance increased by a factor of >15 compared to the bare substrate is well suited for the protection of aerospace, manufacturing, and other critical components with a complex shape of inner surfaces.

Ductile electrodeposited Al from a dimethylsulfone bath with trace amounts of tin chloride

Al and Al alloys electrodeposited from a dimethylsulfone (DMSO2) bath are typically contaminated with S and Cl. Electrodeposited Al and Al alloys suffer from limited ductility since undesired impurities decrease plastic deformability. Herein, we report an electrodeposition process involving the use of a DMSO2 bath that realizes an Al product with tensile elongation as large as ∼30%. Doping of tin chloride in the DMSO2 bath resulted in a micrometer-scale grain microstructure with sub-µm Sn precipitates distributed along the grain boundaries of the electrodeposited Al. These Sn precipitates on the electrodeposits prevented S and Cl contamination, which is likely the main factor underlying the large tensile elongation in the electrodeposited Al. Furthermore, electrodeposition with varying concentrations of tin chloride pointed to that tin chloride showed enough impurities reducing ability even in trace amounts.

Reduction of impurity contents in aluminum plates electrodeposited from a dimethylsulfone-aluminum chloride bath

High productivity and bath stability of electrodeposition for Al and its alloys from a dimethylsulfone (DMSO2)-aluminum chloride bath are highly desirable characteristics for a wide range of critical applications. However, a long-standing problem for such electrodeposits is S and Cl contamination, which results in limited ductility. In this study, we explored a reduction method for S and Cl in Al electrodeposits from a DMSO2 bath to facilitate plastic elongation of the electrodeposited Al. For 2–5:10 M ratios of aluminum chloride to DMSO2, tailoring the conditions of electrodeposition decreased the S and Cl contents to ∼0.2 at%. The addition of various metal salts revealed that gallium chloride further reduced the S and Cl contents to less than 0.1 at%. This reduction permitted the electrodeposited Al–Ga alloys to exhibit plastic elongation in tensile tests. Based on the results of experiments and first-principles calculations, we discuss the role of Ga in the growth mode of electrodeposits and its effect on grain boundary cohesion. Thus, we elucidate the mechanisms for realizing high strength and ductility in electrodeposited Al alloys.

2098. Reduction of Central-Line-associated Bloodstream Infection Rates: Impact of Minimizing Blood Cultures from Central Lines

BackgroundCLABSI surveillance at our institution indicated that a significant proportion of CLABSI had a positive blood culture drawn from central line (CL-BC) with corresponding negative BC done by venipuncture (VP-BC), suggesting possible CL contamination. The contribution of minimizing CL-BC on CLABSI rates remains unknown. This study evaluates the impact on CLABSI rates of reducing CL-BC in addition to standard CLABSI reduction strategies in adult intensive care units (ICUs).MethodsThe study was done from January 1, 2015 to August 31, 2017 in adult ICUs at a hospital with 164 ICU beds, in urban Detroit. Education initiatives to minimize CL-BC were implemented in the ICU. Internal metrics VP-BC ratio (No. VP-BC/total BC in patients with CL) and CL-BC ratio (No. CL-BC/total BC in patients with CL) were used to monitor effectiveness. Compliance audits of CL maintenance were done, i.e., CL dressing intact, proper use of chlorhexidine dressing, site without redness or drainage. Monthly unit-specific CLABSI rates, CL utilization ratios (CL-UR), and VP-BC and CL-BC ratios were provided as feedback to the ICUs. CLABSI rates and number of contaminated BC were monitored. Trends of the various metrics were analyzed using Kendall Tau’s correlation for continuous variables. The relationship between CLABSI rate, VP-BC ratios and CL-UR were examined using Spearman’s correlation coefficient. Statistical significance was set at P < 0.05.ResultsDuring the study period in the ICU there were 148,762 patient-days and 82,153 CL days. Trends over time of the metrics are shown (figure). There was significant improvement noted in CLABSI rates, CL-UR and VP-BC rates (Table 1). There was a significant correlation between the CLABSI rates with VP-BC −0.395 (P value = 0.025) and a not significant correlation with CL-UR 0.278 (P value = 0.123). The number of contaminated blood cultures were 29, 3, and 0 in 2015, 2016 and 2017, respectively.ConclusionMinimizing BC obtained from CL can significantly contribute to reduction in CLABSI rates when used in combination with standard best care practices for CL insertion and maintenance.Table 1:Correlation of Metrics Over TtimeVariableCorrelation with Time P-ValueCLABSI rate−0.2600.036CL-UR−0.520<0.001VP-BC ratio0.806<0.001CL care bundle compliance−0.0480.805 Disclosures All authors: No reported disclosures.

In situ XPS study of low temperature atomic layer deposition of B2O3 films on Si using BCl3 and H2O precursors

In this study, atomic layer deposition (ALD) of nanoscale boron oxide (B2O3) films on Si using BCl3/H2O precursors at room temperature was investigated using in situ x-ray photoelectron spectroscopy (XPS). B2O3 thin films are of considerable interest in ultra-shallow Si doping applications, including high aspect ratio FinFET structures, where film conformality and precise thickness control are crucial. ALD is therefore of particular interest for such applications. XPS data demonstrate that initial BCl3 exposures on Si at room temperature are self-limiting and are accompanied by partial B-Cl dissociation and Cl-Si formation. H2O exposures &amp;gt;1.7 × 108 Langmuir at room temperature removed Cl from B sites, but failed to remove Cl from the Cl-Si species. ALD-type growth of B2O3 was observed with an average growth rate of ∼2.5 Å/cycle and without further increase in the Cl content. The initial Cl contamination was due to Cl-Si bond formation at the interface, without Cl incorporation into the oxide film. The role of Cl in the inhibition of oxide film growth was further investigated by the reactions of BCl3/O2 on SiO2 at room temperature and 650 K. BCl3/O2 precursors exhibit negligible B2O3 growth at room temperature. At 650 K, B2O3 growth was observed with a decreasing growth rate per BCl3/O2 cycle, corresponding to an increase in the Cl:B atomic ratio. These data indicate that room temperature ALD using BCl3/H2O precursors is a potential route toward the formation of uniform B2O3 films for shallow Si doping applications, but that Cl-Si formation significantly impacts initial oxide nucleation and growth.

Thermal atomic layer deposition of tungsten carbide films from WCl6 and AlMe3

The atomic layer deposition (ALD) of tungsten carbide films is described with a thermal process employing WCl6 and AlMe3 as precursors. WCl6 has not been previously reported as an ALD precursor. Furthermore, WCl6 has favorable precursor characteristics and advantages over the widely used WF6, which is corrosive and toxic. The process displays an ALD window between 275 and 350 °C and a high growth rate of 1.5–1.8 Å/cycle within the ALD window. High purity tungsten carbide films with low Al and Cl contaminants were deposited at 300 °C. Film resistivities decreased with increasing growth temperature, reaching a minimum value of 1500 μΩ cm at 375 °C. The as-deposited films are amorphous, which could indicate superior performance as a Cu diffusion barrier over previously studied polycrystalline tungsten carbide barrier layers.

Lower crustal hydrothermal circulation at slow-spreading ridges: evidence from chlorine in Arctic and South Atlantic basalt glasses and melt inclusions

Hydrothermal circulation at slow-spreading ridges is important for cooling the newly formed lithosphere, but the depth to which it occurs is uncertain. Magmas which stagnate and partially crystallize during their rise from the mantle provide a means to constrain the depth of circulation because assimilation of hydrothermal fluids or hydrothermally altered country rock will raise their chlorine (Cl) contents. Here we present Cl concentrations in combination with chemical thermobarometry data on glassy basaltic rocks and melt inclusions from the Southern Mid-Atlantic Ridge (SMAR; ~ 3 cm year−1 full spreading rate) and the Gakkel Ridge (max. 1.5 cm year−1 full spreading rate) in order to define the depth and extent of chlorine contamination. Basaltic glasses show Cl-contents ranging from ca. 50–430 ppm and ca. 40–700 ppm for the SMAR and Gakkel Ridge, respectively, whereas SMAR melt inclusions contain between 20 and 460 ppm Cl. Compared to elements of similar mantle incompatibility (e.g. K, Nb), Cl-excess (Cl/Nb or Cl/K higher than normal mantle values) of up to 250 ppm in glasses and melt inclusions are found in 75% of the samples from both ridges. Cl-excess is interpreted to indicate assimilation of hydrothermal brines (as opposed to bulk altered rock or seawater) based on the large range of Cl/K ratios in samples showing a limited spread in H2O contents. Resorption and disequilibrium textures of olivine, plagioclase and clinopyroxene phenocrysts and an abundance of xenocrysts and gabbroic fragments in the SMAR lavas suggest multiple generations of crystallization and assimilation of hydrothermally altered rocks that contain these brines. Calculated pressures of last equilibration based on the major element compositions of melts cannot provide reliable estimates of the depths at which this crystallization/assimilation occurred as the assimilation negates the assumption of crystallization under equilibrium conditions implicit in such calculations. Clinopyroxene–melt thermobarometry on rare clinopyroxene phenocrysts present in the SMAR magmas yield lower crustal crystallization/assimilation depths (10–13 km in the segment containing clinopyroxene). The Cl-excesses in SMAR melt inclusions indicate that assimilation occurred before crystallization, while also homogeneous Cl in melts from Gakkel Ridge indicate Cl addition during magma chamber processes. Combined, these observations imply that hydrothermal circulation reaches the lower crust at slow-spreading ridges, and thereby promotes cooling of the lower crust. The generally lower Cl-excess at slow-spreading ridges (compared to fast-spreading ridges) is probably related to them having few if any permanent magma chambers. Magmas therefore do not fractionate as extensively in the crust, providing less heat for assimilation (on average, slow-spreading ridge magmas have higher Mg#), and hydrothermal systems are ephemeral, leading to lower total degrees of crustal alteration and more variation in the amount of Cl contamination. Hydrothermal plumes and vent fields have samples in close vicinity that display Cl-excess, mostly of > 25 ppm, which thus can aid as a guide for the exploration of (active or extinct) hydrothermal vent fields on the axis.

X-ray spectroscopy for chemistry in the 2-4 keV energy regime at the XMaS beamline: ionic liquids, Rh and Pd catalysts in gas and liquid environments, and Cl contamination in γ-Al2O3.

The 2-4 keV energy range provides a rich window into many facets of materials science and chemistry. Within this window, P, S, Cl, K and Ca K-edges may be found along with the L-edges of industrially important elements from Y through to Sn. Yet, compared with those that cater for energies above ca. 4-5 keV, there are relatively few resources available for X-ray spectroscopy below these energies. In addition, in situ or operando studies become to varying degrees more challenging than at higher X-ray energies due to restrictions imposed by the lower energies of the X-rays upon the design and construction of appropriate sample environments. The XMaS beamline at the ESRF has recently made efforts to extend its operational energy range to include this softer end of the X-ray spectrum. In this report the resulting performance of this resource for X-ray spectroscopy is detailed with specific attention drawn to: understanding electrostatic and charge transfer effects at the S K-edge in ionic liquids; quantification of dilution limits at the Cl K- and Rh L3-edges and structural equilibria in solution; in vacuum deposition and reduction of [Rh(I)(CO)2Cl]2 to γ-Al2O3; contamination of γ-Al2O3 by Cl and its potential role in determining the chemical character of supported Rh catalysts; and the development of chlorinated Pd catalysts in `green' solvent systems. Sample environments thus far developed are also presented, characterized and their overall performance evaluated.

Efficient Pt/carbon electrocatalysts for proton exchange membrane fuel cells: Avoid chloride-based Pt salts!

The catalytic layers of Proton Exchange Membrane (PEM) fuel cells use carbon-supported Pt-based nanoparticles, which are classically synthesized by impregnation with a metal precursor usually based on chloride counter-ions. However, the literature points out that chloride ions poison the catalytic activity. The purpose of this work is to compare the surface reactivity and the electrocatalytic activity of Pt/carbon xerogel nanoparticles contaminated with different amount of chlorine. The catalysts were synthesized using the Strong Electrostatic Adsorption (SEA) method and H2PtCl6 as a metal precursor. The Cl content in the catalysts was changed by varying the gas atmosphere and the duration of the reduction step. The effect of Cl contamination was investigated on two model reactions: the electrochemical COads oxidation and the O2 reduction. Evidences are provided that the Cl− ions issued from the incomplete decomposition/removal of the metal precursor partially block the Pt catalytic sites, and limit the rate of the COads + OHads recombination and of the diffusion of COads molecules in CO stripping experiments. The adsorption of Cl− ions also depreciates the ORR kinetics. In search for efficient catalysts, chloride-containing metal precursors must therefore be avoided.

Influence of precursor chemistry on CVD grown TiO2 coatings: differential cell growth and biocompatibility

Nanocrystalline titanium oxide (TiO2) coatings with different phases and surface topographies were deposited using chemical vapor deposition (CVD) of different homo- and heteroleptic titanium precursors of general formula [XTi(OiPr)3] (X = Cl (1), –NEt2 (2), –N(SiMe3)2 (3), –C5H5 (4), –OiPr (5) and –OtBu (6)) to elucidate the influence of molecular configuration on resulting material properties. The interdependence of precursor chemistry and materials features of the CVD deposits was verified by performing film growth under similar conditions using different precursor molecules (1–6). Studies on composition (XPS), structure (SEM, XRD) and bio-functional properties (cell tests) revealed that the decomposition process is markedly influenced by the auxiliary ligands, which led to incorporation of heteroelements (Si, Cl, N) in the films. Cell tests performed to evaluate the biocompatibility of the coatings towards the growth of bone cells showed a pronounced correlation between cell adhesion and surface morphology as well as the chemical composition. Growth of osteoblast cells was strongly enhanced on films obtained using [Ti(OiPr)4] and [CpTi(OiPr)3], whereas TiO2 coatings produced by [ClTi(OiPr)3] significantly inhibited the cell growth and their proliferation due to Cl contamination. Also, the nanomorphological features of the films were found to stimulate the cell adhesion and growth.

Atomic Layer Deposition of Tantalum Oxide and Tantalum Silicate from Chloride Precursors

AbstractThe atomic layer deposition (ALD) of Ta2O5 and TaSiOx from TaCl5, SiCl4, and H2O is reported. Both processes are influenced by the concomitant etching of Ta2O5 and TaSiOx by TaCl5. The optimum deposition temperature is found to be 250 °C for both Ta2O5 and TaSiOx. For lower deposition temperatures, the large Cl contamination leads to poor dielectric properties of the films, whereas higher temperatures lead to poor within‐wafer (WiW) thickness non‐uniformity due to etching. Si incorporation is limited to Si/(Si + Ta) ∼ 0.65 because of the slow adsorption kinetics of SiCl4 on SiOH‐terminated surfaces. Under optimum conditions, amorphous films with good dielectric quality are obtained.

Surface characterization of zirconia dental implants

Objectives The aim of the study was to characterize the chemical composition, microstructure and roughness of two commercially available zirconia dental implants (WhiteSky and Zit-Z). Methods The chemical composition of the cervical collar and threaded root parts of the implants ( n = 2) were studied by XPS and HV-EDX. LV-SEM was used for morphological assessment, Raman microanalysis for microstructural characterization and optical profilometry for surface roughness measurements. XRD, HV-EDX and Raman microanalysis of bulk regions (longitudinal sections) were used as reference. Results XPS showed the presence of C, O, Zr and Y (collar) plus Al (root) at implant surfaces. More C (10–26 at%) and a lower Al/Zr ratio were found in WhiteSky (1.05 vs 1.26 in Zit-Z). Zr, Y and Al were detected in single, fully oxidized states. The same elements, plus Hf, were identified by HV-EDX at bulk and surface regions, with a Al/Zr ratio higher in WhiteSky (0.17 vs 0.09 in Zit-Z). Na, K and Cl contaminants were traced at implant root parts by both methods. XRD analysis of cross-sectioned specimens revealed the presence of monoclinic and tetragonal zirconia along with cubic yttria phases. Raman microanalysis showed that the monoclinic zirconia volume fraction was higher at root surfaces than the collar. No monoclinic phase was found at bulk regions. Significantly higher Sa and Sq values were recorded in WhiteSky than Zit-Z, whereas Zit-Z showed higher Rt value. Significance The differences found between the implants in the extent of carbon contamination, residual alumina content, tetragonal to monoclinic ZrO 2 phase transformation and 3D-roughness parameters may contribute to a substantial differentiation in the cellular and tissue response.

Hf O 2 ∕ Si interface formation in atomic layer deposition films: An in situ investigation

The authors have studied the initial stages of the atomic layer deposition (ALD) of HfO2 onto Si by means of x-ray photoelectron spectroscopy using synchrotron radiation. The ALD was obtained using HfCl4 and H2O as precursors. The investigation was carried out in situ giving the possibility to determine the properties of the grown film after each ALD cycle. The Si 2p, O 1s, and Hf 4d+Cl 2p spectra show the growth of HfO2 in a smooth way until the complete formation of two oxide layers. The averaged growth rate is found to be 0.33 (one layer after three cycles) in accordance with previous works but, within the formation of one oxide layer, each ALD cycle behaves in a distinct way: the oxidation step in the various cycles shows a different efficiency leading to the inclusion of Cl impurities into the Hf oxide. In relation to the experimental results we discuss the origin of the Cl contamination proposing a mechanism based on the adsorption geometry of HfCl4 onto the–OH terminated substrate.

Influence of calcination temperature of IrO 2/Ti electrodes on oxygen reduction

IrO 2-coated titanium plate electrocatalysts prepared by a dip-coating method (IrO 2/Ti) with different calcination temperatures are characterized by scanning electron microscope, X-ray diffraction and X-ray photoelectron spectroscopy. The electrocatalytic behavior of the oxygen reduction reaction (ORR) is evaluated by cyclic voltammetry and galvanostatic electrolysis in 1 mol dm −3 KOH solution. The effects of calcination temperature on the oxygen reduction pathway are examined. Galvanostatic electrolysis results show that the reaction pathway on the IrO 2/Ti electrode prepared at high calcination temperature is mainly a two-electron pathway producing H 2O 2. It is observed that higher calcination temperatures produce: a more uniform fault-free surface; reduced levels of Cl contamination (residual Cl presumably from incomplete IrCl 3 decomposition during the coating process); higher levels of rutile character of the IrO 2 layer; lower hydration levels. It is confirmed that ORR electrocatalytic behavior on highly hydrated IrO 2 is better than on slightly hydrated IrO 2.