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The mixed ionic-electronic conducting perovskite La0.75Ca0.25FeO3-δ (LCF7525) was synthesized via a citric acid – ethylenediaminetetraacetate sol-gel route. Crystal structure, phase purity, and lattice constants were determined by powder X-ray diffraction and Rietveld refinement. The oxygen exchange kinetics (chemical surface exchange coefficients and chemical diffusion coefficients of oxygen) and the electronic conductivity were studied by in-situ dc-conductivity (relaxation) measurements at 600–800 °C and 1 × 10−3 ≤ pO2/bar ≤ 0.1. The thermal expansion coefficient was determined by dilatometry at 30–1000 °C and 1 × 10−3 ≤ pO2/bar ≤1. The oxygen nonstoichiometry was measured as a function of temperature and oxygen partial pressure by thermogravimetry and could be described by a point defect model. Experimental data of the chemical diffusion coefficient of oxygen and results from defect chemical modelling were used to estimate self-diffusion coefficients of oxygen and oxygen vacancies, as well as the ionic conductivity. Based on the results obtained for the mass and charge transport properties and the thermal expansion behaviour, it can be concluded that LCF7525 may be an attractive Sr- and Co-free material for air electrodes in intermediate temperature solid oxide fuel cells and solid oxide electrolyser cells.

The long-term stability of the oxygen exchange kinetics of the Sr- and Co-free solid oxide fuel cell (SOFC) and solid oxide electrolyser cell (SOEC) air electrode material Pr0.8Ca0.2FeO3-δ (PCF82) is investigated by in-situ dc-conductivity relaxation measurements. The chemical oxygen surface exchange coefficient kchem is determined as a function of time at 700 °C under ideal (O2-Ar atmosphere) and accelerated ageing conditions (O2-Ar with 2 ppm SO2). In pure O2-Ar PCF82 shows fast oxygen surface exchange kinetics with kchem = 6 × 10−4 cm s−1 and excellent stability for 1000 h. Due to the addition of 2 ppm SO2 to the test gas only a moderate degradation occurs with kchem decreasing to 8 × 10−5 cm s−1 during further 1000 h. Post-test analyses by scanning (transmission) electron microscopy and X-ray photoelectron spectroscopy show S-rich secondary phases in the near-surface region of the SO2-poisoned sample. These inactive phases occur in an island-like arrangement of relatively large crystals, whereas significant amounts of the surface remain unaffected. This effect explains the high stability of the oxygen exchange kinetics of PCF82 against SO2-poisoning in comparison to state-of-the art materials like La0.6Sr0.4CoO3-δ (LSC64).

The influence of simultaneous Cr- and Si-poisoning on the oxygen exchange kinetics of La2NiO4+δ was studied at 800 °C in dry and humid O2/Ar atmospheres over a period of 4000 h by means of dc-conductivity relaxation measurements. Chemical and morphological changes of the La2NiO4+δ surface exposed to increasingly harsh ambient conditions were investigated using X-ray photoelectron spectroscopy (XPS) depth profiling, scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDXS) and high-resolution scanning transmission electron microscopy with energy dispersive X-ray and electron energy loss spectroscopy (HR-STEM EDXS/EELS). In the presence of Cr/Si-sources and under dry conditions, La2NiO4+δ shows good stability for more than 1000 h. However, as soon as humidity is introduced into the system a strong decline of the oxygen exchange activity is observed. Post-test analyses reveal newly formed partially blocking Cr- and Si-rich secondary phases on the surface of La2NiO4+δ which impede the surface exchange of oxygen.

Pr2Ni0.9Co0.1O4 + δ (PNCO) powder was synthesized via a freeze drying process by mixing and shock freezing of aqueous metal acetate solutions, vacuum freeze drying of the resulting precursor and thermal treatment to obtain the complex oxide. X-ray powder diffraction and Rietveld refinement confirmed that the material was mainly single phase (

Five coordination polymers catena-[(3-Hampy)2[Zn7(N3)16(3-ampy)4]·3H2O] (1), catena-[Zn2(μ2-4-HO-py)(μ1,1-N3)4]·H2O (2), catena-[Zn2(μ2-4-amtz)(μ1,1-N3)4] (3), catena-[Zn(5-Et-2-Me-py)(μ1,1-N3)2] (4) and catena-[Zn(μ2-2-O-py-N-oxide)(μ1,1-N3)] (5), where 3-ampy = 3-aminopyridine, 4-HOpy = 4-hydroxypyridine, 4-amtz = 4-amino-4H-1,2,4-triazole, 5-Et-2-Mepy = 5-ethyl-2-methylpyridine and 2-HO-py-N-oxide = 2-hydroxypyridine-N-oxide were synthesized and structurally characterized by single crystal X-ray crystallography. The complexes display different dimensionality depending on the nature of the coligand. The anionic polymer in complex 1 consists of 1D system of defective dicubanes with two different azido-bridging μ1,1-N3 and μ1,1,1-N3 modes. Complexes 2 and 3 are isostructural and both exhibit 2D networks with μ(O,O)-pyridinone bridging molecule in 2 or μ(N,N′)-bridging 4-amtz in 3, and μ1,1,-azide bridging. Complex 4 reveals a zigzag chains of 1D polyhedral through a doubly bridged μ1,1-N3 bonding mode, whereas in complex 5 a 1D polymeric chain is generated via singly bridged μ1,1-N3 bonding and hydrogen bonding results in the formation of supramolecular 2D system. The emission spectral properties of the parent free ligands and their corresponding Zn(II) complexes were investigated where enhancement luminescence emissions with strong red shifts were observed in complexes 2, 4 and 5.

The synthesis and characterization of bismuth sulfide-cellulose nanocomposite thin films was explored. The films were prepared using organosoluble precursors, namely bismuth xanthates for Bi2S3 and trimethylsilyl cellulose (TMSC) for cellulose. Solutions of these precursors were spin coated onto solid substrates yielding homogeneous precursor films. Afterwards, a heating step under inert atmosphere led to the formation of thin nanocomposite films of bismuth sulfide nanoparticles within the TMSC matrix. In a second step, the silyl groups were cleaved off by vapors of HCl yielding bismuth sulfide/cellulose nanocomposite films. The thin films were characterized by a wide range of surface sensitive techniques such as atomic force microscopy, attenuated total reflection infrared spectroscopy, transmission electron microscopy and wettability investigations. In addition, the formation of the nanoparticle directly in the TMSC matrix was investigated in situ by GI-SWAXS using a temperature controlled sample stage.

A generic approach to design optoelectronic devices using renewable biopolymers is demonstrated. As a proof of principle, a biopolymer/CuInS2 nanocomponent-based solar cell has been assembled by using a cellulose derivative with a reasonable life cycle performance, namely, trimethylsilyl cellulose (TMSC). The solar cells are manufactured using a mixture of copper and indium xanthates as precursors, which decompose and form CIS nanoparticles within the biopolymer matrix during a thermal treatment, which was investigated by in situ combined grazing incidence small and wide-angle X-ray scattering experiments. The growth of the nanoparticles is thereby controlled by the TMSC matrix. The nanocrystals exhibit an average diameter of approximately 4 nm. Using this composite, it was possible to fabricate solar cells, generating current in a wide range of the solar spectrum and exhibiting power conversion efficiencies of ca. 1%.

Metal oxide nanostructures like tungsten oxide nanowires are intensively studied materials for sensor applications. In this work we report on tungsten oxide gas sensors integrated on a CMOS fabricated microhotplate chip. Tungsten oxide gas sensors were prepared by drop coating of a nanowire network suspension onto interdigitated electrodes prefabricated on the CMOS microhotplate chip. The tungsten oxide nanowire network was characterised by TEM and Raman spectroscopy, confirming their non-stoichiometric state. Using tungsten oxide nanowire networks as gas sensing material we observed high sensitivity to hydrogen sulphide: concentrations of 1 ppm have been detected with a sensor response up to 55%.

In this work, the mixed ionic-electronic conducting ceramic La 2 NiO 4 + δ is investigated with respect to its applicability as SOFC cathode as well as SOEC anode material on the basis of electrolyte-supported button cells. Results are obtained by electrochemical impedance spectroscopy and current-voltage analyses on symmetrical cells with screen printed La 2 NiO 4 + δ electrodes under both anodic and cathodic polarization, where special emphasis is put on the chromium tolerance of the material. The long-term behavior of electrodes in pure oxygen/argon as well as in humidified chromium-containing atmospheres is studied at 800 °C both under open circuit conditions and with applied current load. Once a chromium source is introduced in humid conditions, a strong decline in the cell performance occurs which can be mainly ascribed to a deactivation of the SOFC cathode layer. Post-test analytical investigations of cell cross sections by SEM and TEM suggest differences in the extent of Cr-contamination to be the main factor for the pronounced discrepancy between degradation rates of both electrodes.

We present the integration of thin film SnO 2 gas sensor on CMOS microchips. A spray pyrolysis process was used to deposit the gas sensitive film, with a thickness of 50 nm, on CMOS microhotplates. The exposure of the CMOS integrated gas sensor to carbon monoxide at different operating temperatures and humidity levels lead to a significant decrease in the sensor resistance. At an operating temperature of 375 °C a sensor response of almost 50% was achieved. The integration of the sensing material on CMOS microhotplates makes it possible to reduce the size and power consumption of metal oxide gas sensors.

The long-term stability of the mixed-conducting perovskite oxide La 0.6 Sr 0.4 CoO 3-δ (LSC) was investigated for 3400 h at 800 °C. The oxygen exchange kinetics of LSC was studied in-situ in dry and humidified atmospheres in the absence as well as the presence of Cr and Si sources. The chemical surface exchange coefficient (k chem ) and the chemical diffusion coefficient (D chem ) of oxygen were measured by the dc-conductivity relaxation method. Degraded samples were analyzed by scanning electron microscopy (SEM) with energy and wavelength dispersive X-ray spectroscopy (EDXS/WDXS), X-ray photoelectron spectroscopy (XPS), and analytical scanning transmission electron microscopy (STEM). In dry atmosphere with 10% O 2 high values of k chem = 1 × 10 − 3 cm s − 1 and D chem = 2 × 10 − 5 cm 2 s − 1 were found. A stable performance was observed during 1300 h without or with the presence of Cr- and Si-impurities. However, a significant decrease in k chem and D chem occurred when the atmosphere was humidified (30–60% relative humidity). XPS depth profiles showed Sr-enrichment and Co-depletion of the surface already during 1300 h in dry atmosphere. After the treatment in humidified atmospheres for additional 2100 h significant amounts of Cr and Si contaminations were found. SEM and STEM showed crystallites of SrCrO 4 and La-silicate on the surface. SrCrO 4 and Co 3 O 4 were also found at the grain boundaries in the near-surface region. It can be concluded that the observed decrease in the oxygen exchange kinetics is closely related to significant changes of the surface composition as a result of Cr and Si poisoning which leads to the decomposition of the oxygen exchange-active LSC phase into inactive secondary phases.

Chromium- and silicon-poisoned samples of the intermediate temperature solid oxide fuel cell (IT-SOFC) cathode materials La 0.6 Sr 0.4 CoO 3-δ (LSC) and La 2 NiO 4 + δ (LNO) were investigated by transmission electron microscopy (TEM) with energy dispersive X-ray spectroscopy (EDXS), electron energy loss spectroscopy (EELS), convergent beam electron diffraction (CBED), as well as by atomic force microscopy (AFM). Analytical TEM revealed phase decomposition of the original, oxygen exchange-active materials LSC and LNO, and the formation of secondary phases after 3500 h of testing at 700 °C. In the case of LSC, the phases SrCrO 4 , Co 3 O 4 , and CoCr 2-x Co x O 4 as well as a La‐chromate phase with unknown stoichiometry were found in the near-surface region and at the grain boundaries. Transport of cations, especially Sr and Cr, along the grain boundaries seems to play a key role in the degradation of LSC. AFM was used to determine the three-dimensional shape including interplanar facet angles of SrCrO 4 crystallites. In the case of the Sr-free material LNO, the formation of La‐silicate and La-Ni‐chromate phases was observed, which seems to proceed from the surface toward the bulk. Based on the experimental results, tentative mechanisms for the degradation processes are suggested.

The impact of silicon on the long-term stability of the intermediate temperature solid oxide fuel cell cathode material La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ (LSCF) was investigated during 2400 h at 700 °C. The area-specific resistance (ASR) of symmetric cells of LSCF on Gd 0.1 Ce 0.9 O 1.95-δ (GDC) was determined by electrochemical impedance spectroscopy (EIS) in ambient air without and with Si contamination of the electrodes. The ASR of the fresh LSCF electrode was 0.3 Ω cm 2 . During 1060 h without Si contamination, an increase in the cathode ASR by a factor of 4.5 was observed, which may be attributed to a decrease in the surface oxygen exchange coefficient of LSCF due to changes in the surface elemental composition. Subsequently, 10 nm thick silicon layers were sputtered onto the LSCF electrodes. This contamination resulted in a strong increase in the ASR by a factor of 5.9 during additional 1340 h at 700 °C. Post-test analyses by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed that the degradation of the cathode is caused by the phase decomposition of LSCF within an approximately 50 nm thick surface region. A continuous La-Sr-silicate layer is formed in addition to isolated (Co,Fe) x O y nanoparticles. In agreement with the changes in the shape of the impedance spectra, it is assumed that this impurity layer leads to limitations in the gas diffusion towards the electrode and/or oxygen adsorption on the surface of the electrode.

Tungsten oxide is an intensively studied semiconductor with the relevant application as H2S gas sensor. In this work we report on H2S gas sensor devices based on tungsten oxide nanowire networks, which are integrated on a CMOS fabricated microhotplate chip. Tungsten oxide gas sensors were prepared by the deposition of nanowire networks onto interdigitated electrodes on CMOS. The material properties of the tungsten oxide nanowires were investigated by TEM and Raman spectroscopy, confirming their non-stoichiometric state. Utilising WO3-x nanowire networks as gas sensing material we obtained extraordinary sensitivity to H2S: concentrations down to 10 ppb have been detected, even in the presence of 50% relative humidity.

An Al-Mn-Cu alloy was microalloyed with beryllium, scandium and zirconium, cast into a copper mould, and aged at different temperatures. It was characterised using X-Ray Diffraction, Differential Scanning Calorimetry and Transmission Electron Microscopy. The compression tests of samples aged at 400 °C for 1 h were performed at room temperature, 300 °C and 350 °C, while the accelerated creep tests were performed at 300 °C and 350 °C. Icosahedral QuasiCrystalline and L12 precipitates prevailed in the as-aged microstructure, while the fraction of decagonal precipitates was low. The precipitates possessed specific orientation relationships with the matrix. The alloy exhibited enhanced hardness, compressive strength, and creep resistance in comparison to the Al-Mn-Cu alloys.

This work addresses aspects for the analysis of industrial relevant materials via transmission electron microscopy (TEM). The complex phase chemistry and structural diversity of these materials require several characterization techniques to be employed simultaneously; unfortunately, different characterization techniques often lack connection to yield a complete and consistent picture. This paper describes a continuous path, starting with the acquisition of 3D diffraction data - alongside classical high-resolution imaging techniques - and linking the structural characterization of hard metal industrial samples with energy-loss fine-structure simulations, quantitative electron energy-loss (EEL) and energy-dispersive X-ray (EDX) spectroscopy. Thereby, the compositional analysis of a MAX phase indicated an offset of the hydrogenic, theoretical sensitivity factors, originating from poorly-adjusted screening factors. In a next step, these results were matched against quantitative compositions and parameters obtained from X-ray spectroscopy data, carried out synchronously with EELS.

Low-frequency noise properties of single CuO nanowire devices were investigated under gas sensor operation conditions in dry and humid synthetic air at 350¿°C. A 1/f noise spectrum was found with the normalized power spectral density of current fluctuations typically a factor of 2 higher for humid compared to dry atmosphere. A core-shell nanowire model is proposed to treat the noise as parallel combination of gas-independent bulk and gas-dependent surface noise components. The observed increase in 1/f noise in the presence of water vapor is explained in terms of Hooge's mobility fluctuation model, where the increased surface noise component is attributed to carrier scattering at potential fluctuations due to hydroxyl groups at the nanowire surface.

In this work, an Al–Mn–Be–Cu alloy was studied containing a primary and eutectic icosahedral quasicrystalline phase in the as-cast microstructure. Special attention was given to a transmission electron microscopy investigation of precipitates formed within the aluminium solid solution (Alss) at different temperatures. At 200 °C, only binary Al–Cu precipitates (θ′) were formed. At 300 °C, icosahedral quasicrystalline (IQC) precipitates prevailed with a crystallographic orientation relationship with the Alss. The rods of the T-phase (Al20Mn3Cu2) which were precipitated above 400 °C, also had a specific orientation relationship with the Alss. The primary and eutectic IQC microstructural constituent started to transform rapidly to the T-phase and Be4Al(Mn,Cu) at 500 °C.

The impact of long-term exposure of La 0.6 Sr 0.4 CoO 3 − δ to SO 2 -containing atmospheres was investigated. In-situ dc-conductivity relaxation measurements showed a decrease in the chemical surface exchange coefficient of oxygen (k chem ) during the course of 1000 h in an atmosphere with either a few ppb or 2 ppm SO 2 at 700 °C. Post-test analyses by scanning electron microscopy with energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and analytical transmission electron microscopy indicated that SrSO 4 crystals with diameters of 100 nm–1 μm are formed during the degradation, in addition to a nanocrystalline 100–300 nm thick multi-phase layer and LaCoO 3 − δ at grain boundaries. In order to regenerate the degraded sample, a thermal treatment was applied. It could be shown that a partial re-activation of the degraded specimen takes place at 750–850 °C even in an atmosphere with 2 ppm SO 2 . This regeneration is ascribed to the in-situ formation of catalytically active LaCoO 3 − δ nanoparticles at the surface. However, a subsequent degradation follows independently of the SO 2 content of the atmosphere when the sample is kept for 1000 h at 850–900 °C. Post-test analyses indicate that this effect is due to a strong grain growth of the LaCoO 3 − δ nanocrystals which leads to a loss in the catalytic activity.

Controlling magnetic properties on the nm-scale is essential for basic research in micro-magnetism and spin-dependent transport, as well as for various applications such as magnetic recording, imaging and sensing. This has been accomplished to a very high degree by means of layered heterostructures in the vertical dimension. Here we present a complementary approach that allows for a controlled tuning of the magnetic properties of Co/Pt heterostructures on the lateral mesoscale. By means of in-situ post-processing of Pt- and Co-based nano-stripes prepared by focused electron beam induced deposition (FEBID) we are able to locally tune their coercive field and remanent magnetization. Whereas single Co-FEBID nano-stripes show no hysteresis, we find hard-magnetic behavior for post-processed Co/Pt nano-stripes with coercive fields up to 850 Oe. We attribute the observed effects to the locally controlled formation of the CoPt L1$_{0}$ phase, whose presence has been revealed by transmission electron microscopy., Comment: Accepted for publication in Beilstein J. Nanotechnol

Simultaneous antibacterial and anticoagulant surfaces have been prepared by immobilization of engineered gold nanoparticles onto different kinds of surfaces. The gold nanoparticle core is surrounded by a hemocompatible, anticoagulant polysaccharide, 6-O chitosan sulfate, which serves as reduction and stabilizing agent for the generation of gold nanoparticles in a microwave mediated reaction. The particle suspension shows anticoagulant activity, which is investigated by aPTT and PT testing on citrated blood samples of three patients suffering from congenital or acquired bleeding disorders. The amount of nanoparticles deposited on the surfaces is quantified by a quartz crystal microbalance with dissipation unit. All gold containing surfaces exhibit excellent antimicrobial properties against the chosen model organism, Escherichia coli MG 1655 [R1-16]. Moreover, blood plasma coagulation times of the surfaces are increased after deposition of the engineered nanoparticles as demonstrated by QCM-D.

Conductometric measurements were performed on a CMOS integrated SnO 2 – Au functionalized gas sensor. The sensor material was deposited by spray pyrolysis at 400 °C upon a microhotplate (a CMOS integrated structure to adjust the sensor's temperature). The sensing layers were structured by photolithography and ion etching. The functionalization of the SnO 2 layers was conducted by evaporation of a 2 nm thin gold film. In a subsequent step the sensing layers were tempered at 400 °C, which resulted in the formation of Au nanoparticles. The sensor performance is evaluated for ethanol, a hydrocarbon-mix (acetylene, ethane, ethene, and propene) and two relative humidity levels.

We report on the design and synthesis of high performance catalytic nanoparticles with a robust geometry via magnetron-sputter inert-gas condensation. Sputtering of Pd and Mg from two independent neighbouring targets enabled heterogeneous condensation and growth of nanoparticles with controlled Pd core-MgO porous shell structure. The thickness of the shell and the number of cores within each nanoparticle could be tailored by adjusting the respective sputtering powers. The nanoparticles were directly deposited on glassy carbon electrodes, and their catalytic activity towards methanol oxidation was examined by cyclic voltammetry. The measurements indicated that the catalytic activity was superior to conventional bare Pd nanoparticles. As confirmed by electron microscopy imaging and supported by density-functional theory (DFT) calculations, we attribute the improved catalytic performance primarily to inhibition of Pd core sintering during the catalytic process by the metal-oxide shell.

Proton (H+) implantations are used in power semiconductor devices to introduce recombination centers (Hazdra et al., Microelectron. J. 32(5), 449–456 (2001)) or to form hydrogen related donor complexes (Zohta et al., Jpn. J. Appl. Phys. 10, 532–533 (1991)). Proton implantations are also used in the 'smart cut' process to generate defects that can be used to cleave thin wafers (Romani and Evans, Nucl. Instrum. Methods Phys. Res. B 44, 313–317 (1990)). However, the implantation damage resulting from H+implantations is not completely understood. In this study, protons with energies from 400 keV up to 4 MeV and doses up to 1016 H+/cm² were implanted into highly ohmic boron doped m:Cz silicon (100). Electron Beam Induced Current (EBIC) measurements were performed to locally determine the minority charge carrier diffusion length. The diffusion length decreases with increasing implantation dose and incorporated damage. Spreading Resistance Profiling (SRP) measurements were performed to analyze the charge carrier concentration profiles for different annealing procedures. The electrical activation and growth of the defect complexes varies strongly with the annealing parameters. Transmission Electron Microscopy measurements were made to investigate the microscopic structures formed by the high dose implantation processes. Due to the high local damage density resulting from low energy and high dose H+ implants, platelet structures are formed. During high-energy high-dose H+implantations, the implanted hydrogen generates strain in the crystal lattice resulting in changes in the distances between atomic planes. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Focused electron beam induced deposition (FEBID) is an important synthesis method as it is an extremely flexible tool for fabricating functional (3D) structures with nanometer spatial resolution. However, FEBID has historically suffered from carbon impurities up to 90 at %, which significantly limits the intended functionalities. In this study we demonstrate that MeCpPtIVMe3 deposits can be fully purified by an electron-beam assisted approach using H2O vapor at room temperature, which eliminates sample and/or gas heating and complicated gas delivery systems, respectively. We demonstrate that local pressures of 10 Pa results in an electron-limited regime, thus enabling high purification rates of better than 5 min·nA–1·μm–2 (30 C·cm–2) for initially 150 nm thick deposits. Furthermore, TEM measurements suggest the purification process for the highly compact deposits occurs via a bottom-up process.

In order for the gas sensor devices to enjoy the miniaturization trend that has consumed much of the electronic device industry, major research in the field is undertaken. The bulky sensor devices of previous generations can not easily be incorporated into a CMOS processing sequence, because of their bulky nature and potential higher cost of production. More recently, materials such as zinc oxide and tin dioxide have shown powerful gas sensing capabilities. Among many potential deposition methods, spray pyrolysis has become a popular approach because of its ease of use and cost effectiveness. A model for spray pyrolysis deposition is developed and implemented within the level set framework. The implementation allows for a smooth integration of multiple processing steps for the manufacture of smart gas sensor devices. From the observations, it was noted that spray pyrolysis deposition, when performed with a gas pressure nozzle, results in good step coverage, analogous to a CVD process. This is mainly due to the atomizing nozzle being placed at a reasonable distance away from the wafer surface and reducing the droplets volume and mass in order to ensure they fully evaporate prior to contact with the substrate surface. A topography simulator for this deposition methodology is presented.

In this work, processing of molybdenum and tungsten by Selective Laser Melting (SLM) is analyzed. The study reveals the impact of the oxygen content of the powder, the process atmosphere and the temperature of the substrate plate on the structural and mechanical properties of the processed material. For clarifying the causes and mechanisms for the formation of defects in molybdenum and tungsten processed by SLM, the samples were examined by x-ray, scanning and transmission electron microscopy including elemental distribution maps and crystallographic analyses by electron backscatter diffraction. Impurities, mainly oxygen, were identified as cause for the predominant defect structure comprising cracks and residual porosity. During processing, oxygen in the form of molybdenum/tungsten oxide, segregates at the grain boundaries, thereby inducing hot cracking. This is due to the lower melting point of the eutectic compared to the matrix phase. Moreover, the oxygen impurities were found to weaken the grain boundaries and thus increasing the risk for cold cracking and leading to a higher Ductile-to-Brittle Transition Temperature (DBTT). Subsequently, the combination of cracks through hot cracking at planar solidified grain boundaries and cold cracking along weakened grain boundaries during rapid cooling from the melting point creates the crack network generally found in molybdenum and tungsten processed by SLM. Also a substrate plate temperature of 1000 °C does not prevent the formation of cracks in tungsten caused by oxygen segregations.

Transition areas in multilayer assemblies used for electronic structures are of vital importance for the characteristics of the final devices. In this study, the interfacial region between SiC and SiO2 was studied with atomic resolution scanning transmission electron microscopy and electron energy-loss spectroscopy in order to gain insight in the structural morphology and the chemical composition of the interface and the appearance of interfacial layers formed during passivation procedures. The annealing process in an N-rich atmosphere during fabrication of the multilayer stack leads to a (sub-)monolayer of nitrogen at the interface between the bulk material and the oxide that is illustrated and quantified. In addition, closer analysis of the EELS signal reveals a transition region that is 3 nm in width, extending approximately 1 nm further into the SiO2 than the N-peak.

We report on novel gas sensing devices based on cupric oxide (CuO) nanowires which are synthesized on-chip by thermal oxidation of electroplated copper microstructures. This technique enables the direct integration of a multitude of CuO nanowires, which bridge the electrical contacts of a conductometric gas sensor. The CuO nanowire bridges exhibit a huge surface-to-volume ratio and are entirely surrounded by the gas atmosphere, which is a highly favorable gas sensor configuration. As a result, the CuO nanowire gas sensor devices are able to detect carbon monoxide (CO) down to a concentration of 10 ppm and exhibit extraordinary sensitivity to hydrogen sulfide (H 2 S) where concentrations down to 10 ppb have been detected, even in the presence of humidity. For characterization of the CuO nanowires, X-ray diffraction measurements, transmission electron microscopy and electron energy loss spectroscopy are employed. As no process temperatures higher than 400 °C are required for the fabrication of the CuO nanowire devices, our approach can be employed in a CMOS backend process enabling the realization of a fully silicon integrated CuO nanowire gas sensing device.

A degraded sample of the solid oxide fuel cell cathode material La 0.58 Sr 0.4 Co 0.2 Fe 0.8 O 3 − δ (LSCF) is investigated by analytical transmission electron microscopy (TEM) with energy dispersive X-ray spectroscopy (EDXS) and electron energy loss spectroscopy (EELS). In the present study TEM is applied in order to analyse the relevant surface-near regions of an LSCF sample which was pre-treated for 1000 h in a dry O 2 –Ar atmosphere and an additional 1000 h in a humidified atmosphere in the vicinity of a silicon source. The results show that Si contamination occurs in an approximately 20 nm thick layer (with local variations from 4 to 35 nm) at the surface of the degraded LSCF sample. In addition, TEM gives evidence of isolated nanocrystals of SrSO 4 with diameters in the range of 200–500 nm. A local decomposition of the perovskite phase is found within depths of 500–600 nm from the surface. The decomposition products are ternary oxides which contain either Sr–La–O or Co–Fe–O.

In this contribution a nepheline like sample synthesized from the thermal transformation of zeolite Na LTA was investigated. In a previous work the product of the thermal treatment has been described to be a standard nepheline. Our TEM investigations conducted on the synthesized polycrystalline material proved the presence of a structure with a tripled c unit cell parameter compared to that observed in classical nepheline. Consequently we compared the theoretical X ray powder diagrams of all known trinepheline compounds with the experimental powder pattern and concluded that the material is actually a mixture of two phases. Rietveld refinement against XRPD data using structural models of (a) classical Na nepheline (S. G. P63 a = 9.971(3) c =8.349(2) ) and (b) monoclinic trinepheline (S. G. P1121 a = 9.995(4) b = 9.963(4) c = 24.988(7) ? = 119.75(3)) resulted in a satisfying agreement between calculated and observed step intensities (?2 = 1.96 Rwp = 11.3 Rp = 8.77). The additional quantitative analyses of the samples obtained in a temperature range of stability of nepheline (900 – 1100 ?C) showed the presence of both structures and also a gradual increase of the weight fraction of the monoclinic trinepheline phase with increasing temperature.

The synthesis and characterization of bismuth sulfide-cellulose nanocomposite thin films was explored. The films were prepared using organosoluble precursors, namely bismuth xanthates for Bi

We present H 2 S gas sensor devices based on tungsten oxide nanowire networks, which are integrated on CMOS fabricated microhotplate chips. Such CMOS integrated systems are promising candidates for realizing smart sensor devices for consumer market applications. The CMOS tungsten oxide gas sensors were prepared by the deposition of nanowire networks onto interdigitated electrodes on CMOS microhotplates via drop-coating. Drop-coating of a nanowire suspension represents a simple and cost-effective technique for mass production of tungsten oxide nanowire network gas sensors. Utilizing this tungsten oxide nanowire network as gas sensing material we could obtain extraordinary sensitivity to H 2 S: concentrations down to 100 ppb have been detected at different humidity levels. An optimum operating temperature could be determined, where the different humidity levels do not affect the sensor performance.

A new mechanism for twin nucleation in the eutectic Al-Si alloy with trace Sr impurities is proposed. Observations made by sub-angstrom resolution scanning transmission electron microscopy and X-ray probing proved the presence of Sr columns located preferentially at twin boundaries. Density functional theory simulations indicate that Sr atoms bind in the Si lattice only along the direction, with preferential positions at first and second nearest neighbors for interstitial and substitutional Sr, respectively. Density functional theory total energy calculations confirm that twin nucleation at Sr columns is energetically favorable. Hence, twins may nucleate in Si precipitates after solidification, which provides a different perspective to the currently accepted mechanism which suggests twin formation during precipitate growth.

Aluminum quasicrystalline alloys present a novel class of high-strength alloys. They possess a high potential for practical applications in many fields. In this study, we used a quasicrystalline Al-alloy with a copper addition to achieving strengthening by heat treatment. The alloys were prepared by melt-spinning and by casting into a copper mold. In both cases, quasicrystals formed during solidification either as a primary phase or as a part of a quasicrystal-containing eutectic. Afterward, the samples were subjected to T5 heat treatment. The hardness of the melt-spun ribbons increased considerably while the hardness of the gravitationally cast samples did not change noticeably. A detailed investigation using transmission electron microscopy (TEM) showed that different types of precipitates can form. At lower temperatures, binary Al-Cu precipitates formed, in the intermediate region prevailed the quasicrystalline precipitates, while at higher temperatures formed T-precipitates (Al20Mn3Cu2). Particular attention was given to determination of their orientation relationships with the Al-rich matrix.

In order to optimize the performance of gas sensor devices, nanocrystalline SnO2 thin film and single crystalline SnO2 nanowire sensors have been characterized for the target gases CO, CH4, H2, CO2, SO2 and H2S. At optimum operating temperature – varying from 250 °C to 400 °C – the SnO2 thin film sensor detects CO, CH4, CO2 and SO2 with responses in the range of 23–34%, H2 and H2S with responses above 80%. The SnO2 nanowire sensor shows responses in the range of 1–8% for CO, H2 and SO2, 29% for H2S, while CH4 and CO2 are not detected. Taking into account that the exposed surface area of the thin film sensor is 800 times larger than that of the single nanowire, we have correlated the number of CO gas molecules impinging the sensors’ surface with the number of electrons, which are actually detected as sensors’ response for the target gas CO. In case of the thin film sensor a single detected electron requires ∼2760 gas molecules impinging the sensor's surface. For the nanowire sensor only ∼86 gas molecules are required for a single detected electron. The SnO2 nanowire sensor thus has a detection efficiency more than 30 times higher than the SnO2 thin film sensor, which we attribute to a lack of grain boundaries. From our measurements we conclude that single crystalline SnO2 nanowire sensors provide a higher sensitivity and an improved cross-sensitivity than their nanocrystalline counterpart.

The "direct-on-barrier" electroplating of copper on ruthenium from a 1 mol dm−3 solution of CuCl in the ionic liquid 1-ethyl-3-methylimidazolium dicyanamide, [C2mim][N(CN)2], is reported. Continuous layers of copper with a preferential Cu(111) orientation were obtained from this electrolyte. The copper coatings were investigated by top view scanning electron microscopy (SEM), X-ray diffraction (XRD), and focused ion beam transmission electron microscopy (FIB-TEM). The nucleation density was both theoretically and experimentally evaluated by the Scharifker-Hills model and transmission electron microscopy, respectively. The direct plating of copper on resistive substrates for advanced interconnects and package is a promising new application of ionic liquids.

Cupric oxide (CuO) nanowires were synthesized by thermal oxidation of resistively heated copper wires in ambient air conditions. Aspect ratios up to 1000 have been achieved with this easy growth method that requires only standard laboratory equipment. The as-synthesized nanowires were subsequently transferred to silicon substrates and contacted by a structured metallization layer. These devices were used for conductometric gas sensing as nanowire conductivity is strongly dependent on the surrounding gas atmosphere. The sensitivity of a single CuO nanowire towards water vapour and hydrogen sulfide (H 2 S) was investigated regarding a possible application in hydrogen fuel cells.

In this paper we report on a new approach for the fabrication of ultra-long single crystalline SnO2-nanowires for gas sensing applications based on a combined spray pyrolysis and annealing process. The SnO2-nanowires are grown on SiO2-coated Si-substrates and exhibit diameters of 30–400 nm and lengths up to several 100 μm. The whole SnO2-nanowire fabrication procedure is performed at atmospheric pressure and requires no vacuum. The experimental results suggest a competing evaporation and condensation process, which converts the nanocrystalline SnO2-films into single crystalline SnO2-nanowires directly on the chip. For the realization of gas sensors the SnO2-nanowires are transferred to another SiO2-coated Si-substrate. Evaporation of Ti/Au contact pads on both ends of single SnO2-nanowires enables their direct use as sensing elements. The devices are very sensitive, are able to detect humidity, and concentrations of CO and CH4 as low as a few ppm at operating temperatures of 200–250 °C. We believe that our fabrication procedure might be the technology of choice for the controlled fabrication of SnO2-nanowires as highly sensitive gas sensing elements on a wafer scale.

The structure of the oxygen-deficient perovskite La{sub 0.4}Sr{sub 0.6}CoO{sub 3-{delta}} ({delta}=0.29) was investigated by transmission electron microscopy (TEM) and X-ray powder diffraction (XRD). Domains between 50 and 250 nm in size were observed in the electron microscope. Weak superstructure reflections were found with both X-ray and electron diffraction. Investigations of these superstructure reflections by selected area electron diffraction (SAED) and convergent beam electron diffraction (CBED) showed that the domains in a crystal are orientated in a 90 deg. relationship. High-resolution transmission electron microscopy (HRTEM) images from the domain boundary also revealed a 90 deg. orientation dependency. Using the symmetry of CBED patterns, the point group 4/mmm was determined. By comparing reflections from the SAED pattern with possible reflections, the space group I4/mmm (No. 139) could be isolated and finally the crystal structure was refined by Rietveld refinement. - Graphical abstract: Two adjacent domains show different orientation of the c-axis of the tetragonal unit cell in the according convergent beam electron diffraction patterns.

Three new polymeric zinc(II) azido complexes, namely [Zn(N 3 ) 2 (3-Brpy)] n ( 1 ), [Zn(N 3 ) 2 (4-Etpy)] n ( 2 ) and [Zn 2 (N 3 ) 4 (2,5-dmpyz)] n ( 3 ), where Brpy = bromopyridine, Etpy = ethylpyridine and dmpyz = dimethylpyrazine have been prepared and structurally characterized. The IR spectra of these complexes are measured and discussed. The structures of 1 and 2 are similar and feature one-dimensional zigzag chain of [Zn(N 3 ) 2 ] n in which each zinc atom is surrounded by double di-end on (EO) bridging azido ligands forming cyclic Zn 2 N 2 units. Furthermore, each zinc atom links a N hetero atom of the pyridine moiety leading to ZnN 5 chromophore. The geometry around the zinc center is best described as distorted trigonal bipyramid. Although complex 3 consists of the 1D chain of [Zn(N 3 ) 2 ] n with double di-EO azido bridges around each zinc center with almost planar Zn 2 N 2 cyclic units, the pyrazinic moiety behaves as a bidentate bridging N , N ′-ligand that binds the zinc centers across the [Zn 2 (N 3 ) 2 ] n chains extending the structure to be two-dimensional sheets. The Zn … Zn distances within the Zn 2 N 2 units are similar, fall within the range of 3.20–3.26 A, and the azido ligands are asymmetric and linear within experimental error in all of these three complexes.

Attempts to introduce rare earth elements other than Eu as guest atoms into intermetallic clathrates have remained elusive to date. Besides fundamental interest, their motivation is to create “strongly correlated” clathrates with correlation-enhanced “giant” thermopower values in addition to the much discussed low thermal conductivities, and thus with enhanced thermoelectric figures-of-merit. In Eu clathrates no sizeable hybridization of the 4f electrons with the conduction electrons is observed. Here we present our attempts to incorporate Yb in Eu8Ga16Ge30. Yb leads to strong correlation effects in many intermetallic compounds. Along with the standard melting and annealing procedure an alternative route, namely quick quenching of the melt by melt spinning, was tested. Samples obtained in both ways were investigated by XRD, SEM/EDX, and TEM/EDX techniques. No sizable substitution of Eu by Yb in the clathrate phase was found.