The effects of zinc bath temperature on the coating growth behavior of reactive steel

The purpose of this work is to identify the influence of zinc bath temperature on the morphology and the thickness of reactive steel (Fe–0.1 wt.%Si alloy) coatings. The Fe–0.1 wt.%Si samples were galvanized for 3 min at temperatures in the range of 450–530 °C in steps of 10 °C. The coatings were characterized by using scanning electron microscopy/energy dispersive X-rays analysis. It was found that the coating thickness reaches the maximum at 470 °C and the minimum at 500 °C, respectively. When the reactive steel is galvanized at temperatures in the range of 450–490 °C, the coatings have a loose ζ layer on the top of a compact δ layer. With the increase of the galvanizing temperature, the ζ layer becomes looser. When the temperature is at 500 °C, the ζ phase disappears. With the increase of temperature, the coatings change to be a diffuse-Δ layer (δ+ liquid zinc).     

Aligned tungsten oxide nanowires on tungsten (100) substrates

WO₃ nanowires in body center cubic structure were grown on W (100) substrates by heating in an argon atmosphere. Scanning electron microscope and transmission electron microscope characterizations show the WO₃ NWs grew along the [100] crystallographic orientation and were aligned in three directions. The diameter of WO₃ NWs is in the range of several to 20 nm and the length is up to 1 µm. Field emission measurements show that the field emission current density can reach 1.8 mA/cm² under electrical field 10 V/µm and the turn-on field can be as low as 2.6 V/µm.     

Characterization of precipitates in a 7.9Cr–1.65Mo–1.25Si–1.2V steel during tempering

In this paper, the precipitates formed during the tempering after quenching from temperature 1150 °C for 7.90Cr–1.65Mo–1.25Si–1.2V steels are investigated using an analytical transmission electron microscope (A-TEM).The study of this tempering is carried out in isothermal and anisothermal conditions, by comparing the results given by dilatometry and hot hardness.Tempering is performed in the range of 300–700 °C. Coarse primary carbides retained after heat treatment are V-rich MC and Cr–Mo-rich M₇C₃ types. In turn, it gives a significant influence on the precipitation of fine secondary carbides, that is, secondary hardening during tempering. The major secondary carbides are Cr–Mo–V-rich M′C (and/or) Cr–Mo-rich M₂C type. The peak hardness is observed in the tempering range of 450–500 °C. In the end, we observe between 600 and 700 °C, that this impoverished changes the phase. At these high temperatures of tempering, we observe that there is a carbide formation of the types M₆C developing at the expense of the fine M₇C₃ carbides previously formed.     

Fabrication of amperometric xanthine biosensors based on direct chemistry of xanthine oxidase

The construction of amperometric xanthine biosensor by immobilization of xanthine oxidase (XOD) on the multi-wall carbon nanotubes (CNTs) modified glassy carbon (GC) electrode surface was investigated. The direct chemistry of XOD was accomplished and the formal potential was about − 0.465 V (vs SCE). The heterogeneous electron transfer rate constant was evaluated to be 2.0 ± 0.3 s^− 1. The xanthine biosensor based on XOD entrapped in silica sol–gel (SG) thin film on CNTs-modified GC electrode surface was also investigated. The XOD still maintains its activity to xanthine. The amperometric response to xanthine showed a linear relation in the range from 0.2 µM to 10 µM and a detection limit of 0.1 µM (S/N = 3). The enzyme electrode retained 95% of its initial activity after 90 days of storage. The sensor exhibited high sensitivity, rapid response and good long-term stability.     

Analyses of nano-crystalline LiCoVO4 prepared by solvothermal reaction

LiOH·H₂O, Co(NO₃)₂·6H₂O and NH₄VO₃ were used to prepare nano-crystalline LiCoVO₄ by 150 °C solvothermal reaction in isopropanol for 10–360 h and subsequent calcination at 300–500 °C for 6 h. XRD, TEM and selected area electron diffraction (SAED) revealed the presence of nano-crystalline LiCoVO₄ with inverse spinel structure. The V–O stretching vibration modes of VO₄ tetrahedrons were detected by FTIR over the range 617–835 cm^− 1 and by Raman spectrometer at 805.7 and 783.1 cm^− 1. Co, V and O were detected by EDX. TGA of solvothermal products shows weight loss due to the evaporation and decomposition processes at 40–648 °C.     

Bulk preparation and characterization of mesoporous carbon nanotubes by catalytic decomposition of cyclohexane on sol–gel prepared Ni–Mo–Mg oxide catalyst

Multiwalled carbon nanotubes were synthesized using Ni–Mo–Mg oxide catalyst prepared by sol–gel technique. Carbon nanotubes were formed in situ by the reduction of nickel oxide (NiO) and molybdenum oxide (MoO₃) to Ni and Mo by a gas mixture of nitrogen, hydrogen and cyclohexane at 750 °C. Scanning Electron Microscopy (SEM) was used to confirm the formation of carbon nanotubes (CNTs). The pore size distribution of carbon nanotubes (CNTs) was investigated by N₂ adsorption and desorption. It was found that the pore size fell into the mesopore range: 2 < d < 50 nm. Interpretation was also made using Raman spectroscopy, Diffuse reflectance spectroscopy, X-ray diffraction and ESR spectra. This method is found to produce a very high yield weighing over 20 times of the catalyst. Based on the experimental conditions and results obtained a possible growth mechanism of the carbon nanotubes is proposed.     

A novel method for synthesis of α-Si3N4 nanowires by sol–gel route

Silicon nitride (Si₃ N₄) nanowires have been prepared by carbothermal reduction followed by the nitridation (CTRN) of silica gel containing ultrafine excess carbon obtained by the decomposition of dextrose over the temperature range of 1200–1350 °C. This innovative process involves repeated evacuation followed by purging of nitrogen gas so that the interconnected nanopores of the gel are filled with nitrogen gas prior to heat treatment. During heat treatment at higher temperatures, the presence of nitrogen gas in the nanopores of the gel starts the CTRN reaction simultaneously throughout the bulk of the gel, leading to the formation of Si₃ N₄ nanowires. The in situ generated ultrafine carbon obtained by the decomposition of dextrose decreases the partial pressure of oxygen in the system to stabilize the nanowires. The nanowires synthesized by this process are of ∼500 nm diameter and ∼0.2 mm length. The product was characterized by scanning electron microscope (SEM), energy dispersive x-ray analysis (EDX), x-ray diffraction (XRD) and infrared (IR) spectra.     

SiOC ceramic nanotubes of ultrahigh surface area

Silicon oxycarbide ceramic nanotubes have been successfully synthesized by inert atmosphere pyrolysis of polysilicone nanotubes using a sacrificial alumina membrane as a template at different pyrolysis temperatures. Scanning electron microscopy images show that the silicon oxycarbide ceramic nanotubes have well-aligned tubular structures. X-ray diffraction patterns and Raman spectra reveal that the obtained silicon oxycarbide ceramic nanotubes are amorphous below 1200 °C and are mainly composed of SiO₂ crystallites and free carbon when the temperature exceeds 1300 °C. Nitrogen-sorption isotherms indicate that the silicon oxycarbide ceramic nanotubes have high Brunauer–Emmett–Teller (BET) specific surface areas (up to 1387 m²/g), large pore volumes (up to 1.82 cm³/g).     

CuO纳米线在碳纤维上的制备与表征

通过热氧化镀铜碳纤维,在碳纤维上制备了CuO纳米线。利用热重分析研究了镀铜碳纤维的热氧化过程。通过扫描电子显微镜、X射线衍射以及透射电子显微镜研究了退火温度、时间以及碳纤维对CuO纳米线生长的影响。结果表明,所制备的CuO纳米线为单斜型单晶结构,在碳纤维上制备CuO纳米线的最佳条件为400℃退火2h。并讨论了CuO纳米线在碳纤维上的生长机理。     

Solvent-induced growth of ZnO particles at low temperature

In this work, ZnO whiskers with different sizes and hexagonal ZnO platelets were successfully prepared by a simple solution route at low temperature (85 °C), using zinc chloride and sodium hydroxide as the reactants. The influence on the morphology of the products was investigated while the type of the alcohol solvent changed. It is believed that interface–solvent interaction is responsible for the evolution of ZnO crystals. Resultant products have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscope (HRTEM) and selected area electron diffraction (SAED).     

Investigation of the physical and chemical parameters affecting biodegradation of diesel and synthetic diesel fuel contaminating Alaskan soils

In cold regions, biodegradation of fuel spills can take a prolonged period of time. Conventional fuels and crude oil contain contaminants such as aromatics and PAH which can pose risks to humans and the environment. The goal of the present study was therefore to investigate the biological degradation of an alternative synthetic fuel, Syntroleum, which is less toxic and, as shown in this study, more easily biodegradable than conventional diesel fuel. Use of alternative fuels such as Syntroleum would be especially beneficial in sensitive regions where spills of conventional fuel are highly undesirable. Gravel and sand from Interior Alaska were spiked with diesel and synthetic diesel fuel (arctic-grade Syntroleum). After adding an inoculum, samples were incubated in the laboratory at different temperatures (6 °C and 20 °C), contamination levels (2000 mg and 4000 mg of fuel/kg dry soil), nutrient dosages (300 mg N/kg soil and 0 mg N/kg soil) and moisture contents (2%, 4%, 8% and 12% gravimetric water content). The objective of this research was to investigate the effect of physical and chemical environmental conditions on the biodegradability of contaminants and to determine optimal conditions for biodegradation by indigenous microorganisms. The respiration rate (CO₂ production) was measured as an indicator of microbial activity and mineralization of contaminants, and complemented by analysis for hydrocarbons at the end of the experiment by gas chromatography/mass spectrometry. Both fuel types were biodegraded, with up to 75% mineralization after 17 weeks. The faster degradation rate was achieved in Syntroleum-contaminated soils with a degradation-rate constant of 0.0064–0.0106 d^− 1 at 20 °C. At 6 °C, diesel fuel showed minimal degradation during several short-term studies (4–6 weeks), less than 5% total mineralization of the hydrocarbons in the fuel. The average degradation-rate constant for Syntroleum at 6 °C was 0.0016 d^− 1 during a 4-week study, while the degradation-rate constants became much higher (0.0045–0.005 d^− 1) for the long-term experiments (12–17 weeks), resulting in significant mineralization of total carbon present. The different moisture contents in the sandy soil showed no significant impact on respiration. The addition of fertilizer was essential to achieve good degradation rates. After the end of the 17-week experiment, the recovered contaminant was approximately 50% less in the case of Syntroleum when nutrients were added to the soil as compared with nutrient-deficient conditions. Respiration rates were higher in sand than in gravel, which may be due to differences in soil porosity and the available surface area for more even hydrocarbon distribution. Degradation rates varied significantly over time. A first-order model, which used different rate constants for three growth phases, was able to model cumulative carbon dioxide production quite well over a period of four months. In the carbon mass balance, the sum of the diesel range organics recovered from the soil plus the produced carbon dioxide accounted for approximately 30–85%. The remaining amount of carbon either was incorporated into biomass, degraded incompletely, or evaporated.     

Formation of ZnS nanorods entrapped in polyacrylic acid (PAA) film

A simplistic approach for synthesis of zinc sulphide (ZnS) nanorods is reported. The synthesis of ZnS nanoparticles involved mixing of zinc acetate, sodium sulphide and acrylic acid in appropriate ratio at proper conditions, which formed the core. These nanoparticles were trapped in PAA by in-situ polymerization of acrylic acid and carefully casted into the film which resulted into entrapped nanorods in the polymer matrix. The nanoparticles as well as nanorods entrapped in PAA were characterized using high resolution scanning electron microscopy (SEM) for morphological investigations; energy dispersive X-ray analysis (EDAX) for composition and its crystalinity was checked using X-ray diffraction (XRD). The length of nanorods was in the range of 2–4 μm and thickness between 50–200 nm.     

Template-free synthesis of NiO hollow microspheres covered with nanoflakes

α-Ni(OH)₂ hollow microspheres precursors were synthesized without any template through a solvothermal method. Hydrolyzing NiCl₂ in alkaline solution, the Ni(OH)₂ hollow microspheres covered with a disordered covering of perpendicular nanoflakes were prepared. Subsequently, the similar microstructured NiO hollow microspheres with BET area around 222.8 m²/g and specific pore volume around 0.5 cm³/g were obtained by calcining the above precursor at 250–300 °C with a slow heating rate (about 1 K/min). The effects of the surfactant and the calcining temperature on the morphology and the mesostructure of the NiO hollow microspheres were also discussed.     

Fabrication of Ag and Cu nanowires by a solid-state ionic method and investigation of their third-order nonlinear optical properties

Ag and Cu nanowires were separately fabricated in a direct current electric field using a solid-state ionic method, and characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Their optical nonlinearities induced by 8 ns laser pulses from a frequency-doubled, Nd:YAG laser at 532 nm, were investigated using the Z-scan technique. Experimental results indicate the metal nanowires have obvious positive refractive nonlinearities and reverse saturated absorption behaviors. The self-focusing behaviors of Ag and Cu nanowires can be attributed to Kerr-induced self-focusing of laser radiation, the nonlinear refractive indexes of Ag and Cu nanowires are n₂ = 1.7 × 10^− 11 esu and n₂ = 2.4 × 10^− 11 esu respectively, and the two-photon process of Ag and the one-photon process of Cu are responsible for the difference between Ag and Cu nanowires suspended in de-ionized water in nanosecond nonlinear absorptions.     

New powellite type oxides in Ca–R–Nb–Mo–O system (R = Y, La, Nd, Sm or Bi)—Their synthesis, structure and dielectric properties

New complex oxides having powellite (CaMoO₄) type structure in the Ca–R–Nb–Mo–O system (R = Y, La, Nd, Sm or Bi) were prepared employing the method of solid state reaction between the component oxides at high temperature (1000–1100 °C). The new compounds, CaRNbMoO₈ (R = Y, La, Nd, Sm, Bi) are colorless and electrical insulators. The dielectric constants (K at 1 MHz) of these compounds are in the range 14–33 and K shows very little variation in the temperature range 30–100 °C. Their temperature coefficient of dielectric constant (TCK) is negative, which varies from − 21 to − 220 ppm/°C.     

Formation of hydroxyapatite on low Young's modulus Ti–30Nb–1Fe–1Hf alloy via anodic oxidation and hydrothermal treatment

Hydroxyapatite (HA) on the Ti–30Nb–1Fe–1Hf alloy has been fabricated via anodic oxidation followed with the hydrothermal treatment. The anodic oxide film (AOF) containing Ca and P was formed by anodic oxidation in a solution consisting of β-glycerophosphate disodium pentahydrate(β-GP), and calcium acetate monohydrate(CA). The AOF was formed by a 2-stage growth: (1) a thin oxide film that intimately contacted the substrate formed prior to sparking; (2) after sparking, the thickness of AOF increased rapidly, accompanying with the formation of numerous craters in the AOF. When anodizing to 300 V, the AOF had a glassy amorphous structure. Increasing anodizing potential increased the Ca/P ratio and contents of Ca and P, but decreased the adhesion strength between the AOF and the substrate. After 6 h of hydrothermal treatment at 250 °C, a great number of crystalline HA precipitated on the surface of AOF anodized to 300 V. The shapes and population density of HA crystals can be controlled by modifying the anodizing potential and the solution pH of hydrothermal treatment. Increasing the pH of the solution in hydrothermal treatment enhanced the precipitation of HA crystals. Numerous needle-like HA crystals that nearly covered the surface of AOF were obtained when hydrothermally treated in the pH 13 solution.     

Photosensitivity in GeO2–SiO2 glasses and optical waveguides

Permanent refractive index changes caused by a KrF excimer laser operating at 248 nm in GeO₂–SiO₂ glasses deposited on Si (100) substrates using flame hydrolysis deposition (FHD) are presented. The sample was amorphouslike investigated by X-ray diffraction (XRD), and the ratio of Ge:Si is 14:86 from X-ray photoelectron spectroscopy (XPS) analysis. The 10-min irradiation with a KrF excimer laser (10 Hz, 187 mJ/cm²) induced a positive refractive index change of 0.341% at 1550 nm, which has achieved an international level of this field. An innovative photomask with a Cr-loaded structure coated on a UV quartz glass, was used to fabricate a 50 μm gap with a period of 100 μm waveguide grating under 1460 mJ/cm²/pulse at 6 Hz, and the diffraction patterns were observed clearly. The extinction coefficients of the samples are also measured over the range 250–1600 nm.     

Preparation temperature effect on the synthesis of various carbon nanostructures

Various carbon nanostructures (CNs) have been prepared by a simple deposition technique based on the pyrolysis of a new carbon source material tetrahydrofuran (THF) mixed with ferrocene using quartz tube reactor in the temperature range 700–1100 °C. A detailed study of how the synthesis parameter such as growth temperature affects the morphology of the carbon nanostructures is presented. The obtained CNs are investigated by scanning electron microscope (SEM), X-ray diffraction (XRD), electron dispersive scattering (EDS), thermogravimetry analysis (TGA), Raman and transmission electron microscope (TEM). It is observed that at 700 °C, normal CNTs are formed. Iron filled multi-walled carbon nanotubes (MWCNTs) and carbon nanoribbons (CNRs) are formed at 950 °C. Magnetic characterization of iron filled MWCNTs and CNRs studied at 300 K by superconducting quantum interference device (SQUID) reveals that these nanostructures have an enhanced coercivity (Hc = 1049 Oe) higher than that of bulk Fe. The large shape anisotropy of MWCNTs, which act on the encapsulated material (Fe), is attributed for the contribution of the higher coercivity. Coiled carbon nanotubes (CCNTs) were obtained as main products in large quantities at temperature 1100 °C.     

Controlled growth of CuO nanowires on woven carbon fibers and effects on the mechanical properties of woven carbon fiber/polyester composites

The effect of CuO nanowires on the improvement of the mechanical properties of woven carbon fiber (WCF)-based polyester resin composite was studied. The composite was manufactured by the vacuum-assisted resin transfer molding (VARTM) process. CuO nanowires were grown on woven carbon fiber sheets in subsequent steps of seeding followed by growth. Scanning electron microscopy (SEM) showed the growth of CuO nanowires on the surface of the carbon fibers; this growth increased with the number of seeding cycles and the length of the growth time. The concentration of the growth solution did not have a significant effect. The maximum amount of growth occurred for 8 seeding cycles with a 60 mM growth solution and a growth time of 8 h. An analysis of the percent weight change, along with X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy, supported the above findings. The crystalline peak height of the CuO nanowires increased with the nanowire growth. The new absorption peaks arising in the FTIR spectra also indicated growth of CuO nanowires on the WCF. The mechanical properties in terms of tensile strength, modulus, and impact resistance improved significantly after the growth of nanowires on the carbon fibers: the modulus and strength improved by up to 33.1% and 42.8%, while the impact energy absorption increased by 136.8% relative to bare WCF.     

Dielectric and ferroelectric properties of Ba3M3Ti5Nb5O30 (M=Sm or Y) ceramics

(M=Sm or Y) compounds were synthesized by the conventional powder compaction and high temperature solid state reaction technique. The calcined compounds were pelletized and sintered in the range 1275–1325 °C for 4 h. The dielectric and ferroelectric properties of the sintered pellets were measured and further characterised by X-ray diffraction and scanning electron microscopy (SEM). Sm and Y substituted compounds were found to have tetragonal structure and shown dielectric constants of 145 and 49 respectively at 1 MHz. The dielectric loss increases with frequency. Samarium compound had undergone a diffuse phase transition in the temperature range 195–210 °C whereas the same with Yttrium had shown the transition at around 25 °C.