Longer Deposition Times Research Articles

Nano Copper Oxide-Modified Carbon Cloth as Cathode for a Two-Chamber Microbial Fuel Cell.

In this work, Cu2O nanoparticles were deposited on a carbon cloth cathode using a facile electrochemical method. The morphology of the modified cathode, which was characterized by scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) tests, showed that the porosity and specific surface area of the cathode improved with longer deposition times. X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry (CV) results showed that cupric oxide and cuprous oxide coexisted on the carbon cloth, which improved the electrochemical activity of cathode. The cathode with a deposition time of 100 s showed the best performance, with a power density twice that of bare carbon cloth. Linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) results revealed that moderate deposition of nano copper oxide on carbon cloth could dramatically reduce the charge transfer resistance, which contributed to the enhanced electrochemical performance. The mediation mechanism of copper oxide nanocatalyst was illustrated by the fact that the recycled conversion between cupric oxide and cuprous oxide accelerated the electron transfer efficiency on the cathode.

Nanostructure and Microstructure Evolution of D.C. Reactive Magnetron Sputtered CrN Thin Films

The CrN thin films were deposited on silicon (100) substrate using reactive magnetron sputtering technique. The films were characterized by XRD, FE-SEM, EDS and nanoindentation techniques to examine the effect of deposition time on crystal structure, compositions, microstructure and hardness. The crystal structure, microstructure, element composition and hardness. The higher crystallinity through longer deposition time were investigated. The grain aggregration with columnar structure were obtained from FE-SEM. The Cr and N contents were not direct relationship with deposition time. The CrN coated sample performed hardness varied between 9 - 16 GPa.

One-pot electrodeposition of cobalt flower-decorated silver nanotrees for oxygen reduction reaction

In this paper, we demonstrate a simple fabrication of bimetallic silver (Ag) and cobalt (Co) nanostructures (AgCo) with various Ag to Co relative contents via electrochemical co-deposition. A series of AgCo catalysts was electrodeposited on glassy carbon (GC) electrodes at −0.57V vs. SCE in the deposition solutions, containing Ag precursor, Co precursor, Triton X-100, and 0.3M KNO3 aqueous solution, with various Ag to Co precursor concentration ratios (1:x, x was varied from 3 to 11). The films, deposited with the total deposition charge of 0.042C, were denoted as Ag1Cox. SEM and TEM analyses showed that Ag1Cox formed a structure consisted of flower-like Co grown on tree-like Ag backbones while it had more Co flowers with a greater x. The ORR activities were examined in 0.1M NaOH solution with rotating disk electrode (RDE) voltammetry and Ag1Co7 showed the best catalytic activity. The co-deposition mechanism was further investigated by varying the deposition time of Ag1Co7. At the early stage of deposition, Ag-tree branches were formed predominantly, followed by the growth of flower-like Co nanostructures on the Ag nanotrees: More Co flowers were produced on Ag backbones with longer deposition time, being attributed to both a less negative reduction potential of Ag+ to Ag than Co2+ to Co and promoted Co2+ reduction on the initially formed Ag surface. Ag1Co7 electrodeposited for 200s, consisted of ∼14% Co, showed the greatest ORR catalytic activity which was better or comparable to noble metal Pt.

Oxygen reduction at electrodeposited ZnO layers in alkaline solution

Zinc oxide (ZnO) layers were electrodeposited from an aqueous nitrate bath at 62°C on copper substrates. At −0.9V (vs. saturated calomel reference electrode), the growth rate is 600nmmin−1 . In the early stages of the deposition, the layers are porous. At longer deposition times, the surface becomes dense and rough. The wurtzite crystalline structure is confirmed by XRD measurements and the chemical composition of the ZnO surface was assessed by EDX and XPS. The oxygen reduction reaction (ORR) was investigated at room temperature in a 10−3M KOH solution with KCl as supporting electrolyte. The ORR onset potential is found to be much larger than that of platinum taken as reference electrocatalyst. Rotating ring-disk electrode experiments evidence a negligible production of hydrogen peroxide as intermediate product of the reaction. The latter follows thus a direct four-electron pathway at pH ∼11.

Structural studies of TiO2/wood coatings prepared by hydrothermal deposition of rutile particles from TiCl4 aqueous solutions on spruce (Picea Abies) wood

A low temperature approach was developed for the deposition of rutile TiO2 particles on a wood surface by hydrolysis of TiCl4 in aqueous solutions acidified with HCl, and crystallization at 75 and 90°C (1h). Prior to hydrothermal treatment, Picea Abies wood was first soaked in a 0.5mmol/l aqueous solution containing anionic surfactant sodium dodecyl sulphate (SDS, Sigma Aldrich) for 2h at 80°C. The crystal structure of the hydrothermally made rutile particles was determined with XRD, while the morphology of the deposited TiO2 particles and their distribution in the wood were examined with SEM and EDX measurements. The penetration and amount of deposited rutile particles could be modified by changing the deposition conditions. Thicker layers were obtained from more concentrated aqueous TiCl4 solutions with and without added HCl, and with longer deposition times and higher temperatures of the hydrothermal treatment.The interaction of TiO2 particles with hemicellulose and lignin in wood was established from infrared attenuated total reflection (FT-IR ATR) and Raman spectra measurements, from which the spectra of wood were subtracted. Analysis of the subtraction spectra showed the presence of titania particles on the wood surface, revealing also the establishment of TiO2-wood coordinative bonds of titanium ions with hemicellulose and lignin. The red frequency shift of the OH stretching modes suggested interaction of the TiO2 particles with water molecules of wood. TiO2 deposited on wood treated with SDS became hydrophobic (water contact angles (WCA) of 150°), contrasting the properties of untreated wood with a deposited TiO2 particle coating, which remained hydrophilic.

Silicanizing Process On Mild Steel Substrate by Using Tronoh Silica Sand: Microstructure, composition and coating growth

A new Silicanizing process on formation of coating on mild steel using Tronoh Silica Sand (TSS) is presented. The process was performed in the temperature range 1000- 1100°C and with varying deposition time of 1-4 hours. Influence of the layer and the substrate constituents on the coating compatibility of the whole silicanized layer is described in detail. Morphology and structure of the silicanized layer were investigated by XRF, XRD and SEM. It is observed that diffusion coatings containing high concentrations of silica which profile distribution of SiO2 in the silicanized layer was encountered and the depth from the surface to the substrate was taken as the layer thickness. The results also depicted that a longer deposition time have tendency to produce a looser and larger grain a hence rougher layer. The silicanized layer composed of FeSi and Fe2SiO4 phases with preferred orientation within the experimental range. It is also found that longer deposition time and higher temperature resulted in an increase in SiO2 concentration on the substrate (mild steel).

Synthesis and gas-sensing properties of the silicon nanowires/vanadium oxide nanorods composite

As air pollution is becoming more and more serious in recent years, gas-sensing devices have attracted intensive attention. In particular, NO2 is one of the most toxic gases in the atmosphere, which tends to produce acid rain and photochemical smog. Thus, there is a strong demand of cheap, reliable and sensitive gas sensors targeting NO2. Gas sensors fabricated on silicon substrates with room-temperature operation are very promising in power saving, integrated circuit processing and portable detectors. More important, the silicon nanowires (SiNWs)-based devices are compatible with very large scale integration processes and complementary metal oxide semiconductor technologies. In the present work, the novel nanocomposite structure of (SiNWs)/vanadium oxide (V2O5) nanorods for NO2 detection is successfully synthesized. The SiNWs are fabricated by a combination of nanosphere lithography and metal-assisted chemical etching. Vanadium films are deposited on SiNWs by DC magnetron sputtering, and then V2O5 nanorods are synthesized with subsequent thermal annealing process for full oxidation in air. The morphology and crystal structure of product obtained are characterized by field-emission scanning electron microscopy and X-ray diffraction. The characterization results indicate that V2O5 nanorods are uniformly distributed on the surfaces of SiNWs. The increased specific surface area of SiNWs/V2O5 nanocomposite provides more adsorption sites and diffusion conduits for gas molecules. Therefore, the novel structure of the nanocomposite is conducive to gas-sensing. In addition, the sputtering time has an obvious influence on the morphology of vanadium oxide. With the increase of the sputtering time, the specific surface area and the number of p-n heterojunctions formed in the nanocomposite are both less than those of nanocomposite with appropriate sputtering time. The gas-sensing properties are examined by measuring the resistance change towards 0.5-4 ppm NO2 gas at room temperature by the static volumetric method. Results show that the nanocomposite with shorter deposition time has better gas-sensing properties to low-concentration NO2 gas than those of bare SiNWs and nanocomposite with longer deposition time. On the contrary, the responses of the nanocomposite to other high-concentration reducing gases are very low, indicating good selectivity. The enhancement in gas sensing properties may be attributed to the change in width of the space charge region, which is similar to the behavior of p-n junction under forward bias, in the high-density p-n heterojunction structure formed between SiNWs and V2O5 nanorods. In conclusion, these results demonstrate that the SiNWs/V2O5 nanocomposite has great potential for future NO2 gas detection applications with low consumption and good performance.

Metal Release of Multilayer Coatings by Physical Vapour Deposition (PVD)

Orthopaedic implants are mostly fabricated by Stainless Steel, Titanium, and Ni-Cr Alloys that consist of Chromium (Cr), Cobalt (Co), Nickel (Ni) and Molybdenum (Mo). 10-15% of population are affected by metals (Ni, Co, Cr, Mo) hypersensitivity reaction. Multilayer coating by Physical Vapour Deposition (PVD) has been applied onto orthopedic implants to prevent metallic ions leaching into human body. This paper aims to study the metal ions leaching of Cr, Ni, Mo, and Co from multilayer coatings of Chromium (Cr), Chromium Nitride (CrN), Chromium Carbonitride (CrCN) and Zirconium Nitride (ZrN) by Physical Vapour Deposition (PVD). Cr, CrN, CrCN and ZrN have been successfully deposited onto stainless steel substrates by CAPVD. XRD analysis detected major peak in preferred orientation of (200) and other peaks with (111), (220), (311) for CrN cubic phase. For CrCN, XRD analysis detected only low intensity peaks of Cr7C3 and ZrN peaks with preferred orientation of (111), (200) with other peak (220), (311) and (222). A seven days metal released test by ICP-MS showed that generally all ions concentration for Ni, Co, Mo decreased from uncoated substrate to multilayer coatings except for Cr. Metal released showed higher concentration for coatings deposition with longer deposition time at 10minutes.

Martensitic transformation in as-grown and annealed near-stoichiometric epitaxial Ni2MnGa thin films

Magnetic shape memory nanostructures have a great potential in the field of the nanoactuators. The relationship between dimensionality, microstructure and magnetism characterizes the materials performance. Here, we study the martensitic transformation in supported and free-standing epitaxial Ni47Mn24Ga29 films grown by sputtering on (0 0 1) MgO using a stoichiometric Ni2MnGa target. The films have a Curie temperature of ~390 K and a martensitic transition temperature of ~120 K. Similar transition temperatures have been observed in films with thicknesses of 1, 3 and 4 μm. Thicker films (with longer deposition time) present a wider martensitic transformation range that can be associated with small gradients in their chemical concentration due to the high vapour pressure of Mn and Ga. The magnetic anisotropy of the films shows a strong change below the martensitic transformation temperature. No features associated with variant reorientation induced by magnetic field have been observed. Annealed films in the presence of a Ni2MnGa bulk reference change their chemical composition to Ni49Mn26Ga25. The change in the chemical composition increases the martensitic transformation temperature, being closer to the stoichiometric compound, and reduces the transformation hysteresis. In addition, sharper transformations are obtained, which indicate that chemical inhomogeneities and defects are removed. Our results indicate that the properties of Ni–Mn–Ga thin films grown by sputtering can be optimized (fixing the chemical concentration and removing crystalline defects) by the annealing process, which is promising for the development of micromagnetic shape memory devices.

Electrochemical and Photoelectrochemical Properties of Nano-Islands of Zinc and Niobium Oxides Deposited on Aluminum Thin Film by RF Magnetron Reactive Sputtering

Zinc oxide (ZnO) and niobium oxide (NbOx) with a nano-island structure were deposited by a sputtering method on Al-coated glass substrates. Cells with a (ZnO or NbOx)/Al/glass|KNO3aq.|Al/ glass structure were assembled, and electrochemical and photoelectrochemical properties were evaluated. The ZnO and NbOx electrodes had higher electrode potentials than the counter Al/glass electrode, and electron flows from the counter electrode to the ZnO and NbOx electrodes through the external circuit were commonly confirmed. In the ZnO-based cell, only faint photocurrent generation was seen, where Zn and Al elution from the ZnO electrode was found. In the NbOxbased cell, however, stable generation of electricity was successfully achieved, and electrode corrosion was not recognized even in microscopic observations. A photoelectrochemical conversion model was proposed based on potential-pH diagrams. In the case of nano-island structures formed at shorter NbOx deposition time, it was concluded that the photoelectrochemical reactions, which were proceeded in the immediate vicinity of the boundary among nano-islands, substrate, and electrolyte solution, were predominant for the photoelectrochemical conversion, and in the case of film structures with longer deposition time, the predominant reactions took place at the film surface.

Fabrication of Au@SiO2 core–shell nanoparticles on conducting glass substrate by pulse electrophoresis deposition

Au@SiO2 core–shell nanoparticles (NPs) of 20±5nm Au core with 32 ±5nm silica shells were deposited on fluorine doped tin oxide (FTO) glass substrate by pulse electrophoresis deposition (PED). Field emissions scanning electron microscopy (FESEM) images reveal that the number of core–shell NPs deposited on the substrate increased at lower pH and longer deposition time. The deposited particles are more stable as compared to the bare NPs. The stability of the core–shell NPs at high temperature has been also investigated.

Self-assembly of large-scale gold nanoparticle arrays and their application in SERS

Surface-enhanced Raman scattering is an effective analytical method that has been intensively applied in the field of identification of organic molecules from Raman spectra at very low concentrations. The Raman signal enhancement that makes this method attractive is usually ascribed to the noble metal nanoparticle (NMNP) arrays which can extremely amplify the electromagnetic field near NMNP surface when localized surface plasmon resonance (LSPR) mode is excited. In this work, we report a simple, facile, and room-temperature method to fabricate large-scale, uniform gold nanoparticle (GNP) arrays on ITO/glass as SERS substrates using a promoted self-assembly deposition technique. The results show that the deposition density of GNPs on ITO/glass surface increases with prolonging deposition time, and nanochain-like aggregates appear for a relatively longer deposition time. It is also shown that these films with relatively higher deposition density have tremendous potential for wideband absorption in the visible range and exhibit two LSPR peaks in the extinction spectra because the electrons simultaneously oscillate along the nanochain at the transverse and the longitudinal directions. The SERS enhancement activity of these GNP arrays was determined using 10-6 M Rhodamine 6G as the Raman probe molecules. A SERS enhancement factor as large as approximately 6.76 × 106 can be obtained at 1,363 cm-1 Raman shift for the highest deposition density film due to the strong plasmon coupling effect between neighboring particles.

Synthesis of nitrogen-doped graphene by the thermal chemical vapor deposition method from a single liquid precursor

In this work we report the synthesis of nitrogen-doped graphene using an ambient pressure chemical vapor deposition technique on polycrystalline Ni substrates with a single liquid precursor, as the source of both carbon and nitrogen. Nitrogen atom substitution of the so-formed graphene was confirmed by X-ray photoelectron spectroscopy. The signal from sp2 bonded carbon atoms decreased in the nitrogen-doped graphene at longer deposition times. Spatially resolved Raman mapping results and transmission electron microscopy images show that the nitrogen-doped graphene formed with varying thickness from a monolayer to >10 layers. The effects of growth temperature and deposition time on the level of nitrogen doping, number of layers, and the quality of the nitrogen-doped graphene layer were investigated.

One- and two-dimensional cuprous oxide nano/micro structures fabricated on highly orientated pyrolytic graphite (HOPG) by electrodeposition

One- and two-dimensional cuprous oxide (Cu2O) nanostructures were fabricated on highly orientated pyrolytic graphite (HOPG) by electrodeposition in CuSO4 at room temperature (25°C) with no additives. For short deposition times, 1D Cu2O single nanocrystals were generally of an octahedral shape with sizes ranging from 50nm to 400nm, while 2D Cu2O nanowires with diameters ranging from 100nm to 300nm had lengths of more than 100μm. With longer deposition times, microwires were found to have diameters ranging from 1μm to 2μm with lengths up to 60μm, while microcrystals were also produced with sizes 1μm to 6μm. The highly aligned Cu2O nano/microwires were found to be deposited on the step edges of the HOPG substrate. Various crystal morphologies including flower-like and butterfly-like structures, and dendrites and truncated octahedra were observed on the working electrode of HOPG. Some of the morphologies are revealed for the first time by one step electrodeposition and these are confirmed to be single Cu2O crystals.

Effect of Deposition Time on Properties of ZrO<sub>2</sub> Coating Prepared Using Electrolytic Method

AISI 440C martensitic stainless steel is one of the most widely studied engineering materials for its tribological properties. It is capable of attaining the best mechanical properties such as high strength and hardness compared to other martensitic grades. Unfortunately, the corrosion resistance of this 440C steel is the lowest among the stainless group, which results in the precipitation of carbide phases. AISI 440C were coated using electrolytic ZrO2 layer deposition method in ZrO(NO3)2 aqueous solution. In order to preserve the high mechanical properties of this steel, various heat treatment processes applied to the coated samples. After drying and annealing, the ZrO2 coated samples were evaluated using SEM, hardness tests and corrosion tests. Some mud-crack had been indicated in all samples. However, it become more homogeneously on the sample which undergoes longer deposition time. This difference resulted in a significant improved on corrosion resistance of ZrO2 coated sample.

Correlation between topographic structures and local field emission characteristics of graphene-sheet films

In an early report, some of us have demonstrated that graphene-sheet films prepared by electrophoretic deposition (EPD) method have great potential as high-performance field emission cathode. We report that the field emission performance from such graphene-sheet films may be enhanced. We have investigated the correlation between topographic structures and local field emission characteristics of graphene-sheet films, prepared with changing EPD deposition time. Detailed experiments show that samples prepared with longer deposition time have better field emission performance. Both scanning electron microscopy and high resolution transmission electron microscopy images show that the topographic structure of the surface layer of the samples deposited with longer time is formed with higher density of graphene sheets with shorter length and fewer graphene layers, in comparison with those with shorter deposition times. Such topographic structure is found experimentally to give large field enhancement. Computer simulation further confirms that a thinner graphene sheet will give more significant geometrical field enhancement at the corner of graphene sheet. Theoretical analysis shows that in an EPD process, longer-length graphene sheets will be deposited before shorter ones, explaining why with longer deposition time, the topographic structure of surface layer consists of shorter-length graphene sheets.

Structure Characterization of W-Doped Vanadium Oxide Thin Films Prepared by Reactive Magnetron Sputtering

W-doped Vanadium oxide thin films were prepared on the substrates of SiO2 glass, float glass and Si (100) by reactive magnetron sputtering after annealing in vacuum. The structure, morphology and phase transition were characterized by X-ray diffractometer, atomic force microscopy (AFM) and differential thermal analysis (DTA), respectively. The results show that, the major phase of W-doped films on SiO2 glass is VO2.Dopant reduce the phase transition temperature of VO2 thin films to 21.9°C. The root-mean-square roughness of the film increase for the longer deposition time.

Influence of Deposition Time on the Properties of Highly-Oriented SnS Thin Films Prepared Using the Thermal Evaporation Method

The influence of deposition time on the properties of SnS films grown using the thermal evaporation was reported. The deposition time was varied between 0.7 – 3 min, keeping other deposition variables constant. The layers showed single phase with orthorhombic crystal structure, exhibiting a strong (040) reflection. With an increase of deposition time, the Sn/S atomic ratio and grain size and the number of crystallites in the layers increased while the dislocation density and bulk resistivity decreased. The increase of crystallinity of the layers was confirmed by the change of strain from tensile to compressive with increasing deposition time. The transmittance of the films were > 70% for deposition time ≤ 1min and decreased drastically otherwise. The energy band gap varied in the range 1.80 - 1.30 eV with the lower values obtained at longer deposition times.

The Growth Mechanism of LSGM Thin Film Electrolyte by RF Magnetron Sputtering

In order to discuss the growth mechanism of LSGM films, La0.9Sr0.1Ga0.8Mg0.2O2.85 (LSGM) thin films electrolytes were fabricated on Si substrates by RF magnetron sputtering. The atomic force microscope (AFM) and X-ray diffraction analyzer (XRD) were used to analyze film surface morphology and phase components. The results show that LSGM films are grown with island structure. When the deposition time increases to 30min, the preferred growth orientations appears, which is (112) crystal face. The longer deposition time is, and the rougher the surface possesses.

Characterization of nanocrystalline PbS thin films prepared using microwave-assisted chemical bath deposition

Nanocrystalline lead sulfide (PbS) thin films were synthesized on glass substrates using microwave-assisted chemical bath deposition (CBD) method. Various deposition periods of time ranging from 30 to 120min were used. Results demonstrated that the thickness of the thin films increased with longer deposition time. X-ray diffraction (XRD) measurement revealed that all thin films have cubic rock salt (NaCl) type structure. The surface morphology studied using scanning electron microscopy (SEM) showed that the films have uniform surface morphology over the entire substrate and were of good quality. AFM images confirm that the films have a smooth surface with good adherence to the substrate, a narrow particle size distribution, and that the surface roughness increased with increasing deposition time. Energy gap Eg decreases as the deposition time increases. Electrical measurements revealed that all films were p-type and that the conductivity decreased as the deposition time increased.