Atomic layer deposition of iron(III) oxide on zirconia nanoparticles in a fluidized bed reactor using ferrocene and oxygen

Conformal films of amorphous iron(III) oxide and α-Fe₂O₃ have been coated on zirconia nanoparticles (26 nm) in a fluidized bed reactor by atomic layer deposition. Ferrocene and oxygen were alternately dosed into the reactor at temperatures between 367 °C and 534 °C. Self-limiting chemistry was observed via in situ mass spectrometry, and by means of induced coupled plasma-atomic emission spectroscopy analysis. Film conformality and uniformity were verified by high resolution transmission electron microscopy, and the growth rate was determined to be 0.15 Å per cycle. Energy dispersive spectroscopy, X-ray diffractometry, and X-ray photoelectron spectroscopy were utilized as a means to determine film composition at each deposition temperature. Over all of the deposition temperatures investigated, films were deposited as amorphous iron(III) oxide. However, after heat treatment at 850 °C in air and N₂ atmospheres, α-Fe₂O₃ was the predominant species.     

Boriding of nickel in a fluidized bed reactor

Heat treatments of alloys in fluidized bed reactors have been carried out for more than 25 years. Recently, this technology has been used for surface engineering applications in the deposition of hard and/or corrosion resistant layers. In the present paper we used FBT to deposit boride coatings on nickel metal. The coatings were examined by means of optical microscopy, X-rays diffraction and Vickers microhardness in terms of the coating’s morphology, thickness, hardness and phase formation. The coating’s tribological properties were evaluated under dry wear. The as-produced coatings are characterized by good uniformity and it was found that only Ni₃B (space group Pnma) was formed during the treatment. Furthermore, the boride layer improved the tribological properties of nickel.     

Conformal atomic layer deposition of TA-based diffusion barrier film using a novel mono-guanidinate precursor

In this work, we present elaboration of Ta-based thin films by ALD from a novel tantalum precursor, the eta2-N,N'-isopropylethylguanidinato-tetra-diethylamino tantalum ([eta2-(i)PrNC(NEt2)NEt]Ta(NEt2)4, IEGTDEAT). Ammonia was used as reducing agents. The experimental conditions were optimized by quartz microgravimetry, studying the influence of duration of precursors and purge pulses and the substrate temperature. An optimal deposition temperature of 260 degrees C was showed. Ta-based thin films deposited on planar and patterned substrates showed a perfect conformality and continuity, even at low number of cycles.     

Determination of the mixing coefficient in a fluidized bed reactor

A method is presented for determination of the mixing coefficient in a fluidized bed by means of a mathematical model of the process. A numerical example is given for the case of an ore-drying process.     

致密SiC包覆层低温流化床化学气相沉积制备及形成机制

一般致密SiC材料的制备需要极高的温度,而降低制备温度一直是SiC制备领域的重要研究方向。采用流化床化学气相沉积法,在球形二氧化锆陶瓷颗粒上制备了厚度为几十微米的SiC包覆层。通过对不同温度SiC包覆层的显微形貌及微观结构变化规律研究,给出了沉积效率变化规律,发现低温产物富硅,而高温产物富碳。对不同氩气含量的实验研究发现,氩气的加入可以促进沉积反应向富碳方向移动,从而可以在显著降低温度的条件下制备出致密SiC包覆层。综合实验结果给出了流化床化学气相沉积方法在不同温度及氩气浓度条件下制备SiC的物相分布图。      

Anaerobic treatment of pinkwater in a fluidized bed reactor containing GAC

Pinkwater is generated during the handling and demilitarization of conventional explosives. This listed hazardous waste contains dissolved trinitrotoluene (TNT) and cyclo trimethylene trinitramine (RDX), as well as some by-products. It represents the largest quantity of hazardous waste generated by the operations support command, and its treatment produces a by-product hazardous waste--spent granular activated carbon (GAC).Anaerobic treatment in a fluidized bed reactor (FBR) containing GAC is an emerging technology for organic compounds resistant to aerobic biological treatment. Bench scale batch studies using an anaerobic consortium of bacteria fed ethanol as the sole electron donor demonstrated the transformation of TNT to triaminotoluene (TAT), which then degrades to undetectable end products. RDX is sequentially degraded to nitroso-, dinitroso-, trinitroso- and hydroxylaminodinitroso-RDX before the triazine ring is presumably cleaved, forming methanol and formaldehyde as major end products. The bacterial members of the anaerobic consortia are typically found in sludge digesters at municipal or industrial wastewater treatment plants.The results of a pilot scale evaluation of this process that was conducted at McAlester Army Ammunition Plant (MCAAP, OK) over a 1 year period are reported in this paper. The pilot test experienced wide fluctuations in influent concentrations, representative of true field conditions. The FBR was a 20 in. (51 cm) diameter column with an overall height of 15 ft (4.9 m) and a bed of GAC occupying 11 ft (3.4m). Water was recirculated through the column continuously at 30 gpm (114 l/min) to keep the GAC fluidized, and pinkwater for treatment was pumped into the recirculation line. Several flowrates were evaluated to determine the proper mass loading rate (mass of TNT and RDX per reactor volume per time, kg/m(3) per day) which the reactor could handle while meeting the discharge limitations. Based on the tests performed, a 1 gpm (3.785 l/min) rate in the 188 gal (710 l) volume of the fluidized GAC bed was determined to consistently meet the discharge requirements.This information was used to develop a cost estimate for a system capable of treating the total effluent currently produced at MCAAP. The cost of installing and operating this system was compared to the cost of GAC adsorption for MCAAP at current pinkwater generation rates. The GAC-FBR system had an annual operating cost of approximately US$ 19K, compared to US$ 71 K annually for GAC adsorption. When including the amortization of the capital equipment required for the GAC-FBR, the payback period for installation of this new process was estimated at 3.7 years.     

流化床CVD法制备单壁碳纳米管:反应温度与时间的影响

基于负载法Fe—MgO体系催化剂研究了化学气相沉积（CVD）法在流化床反应器中反应温度和时间对单壁碳纳米管（SWCNTs）生长的影响。通过气相色谱对尾气进行实时在线分析，获得了CH4在反应过程中的转化率随时间的变化规律。并对不同反应温度和反应时间所获产品进行了TEM、Raman和TGA等表征。结果表明，900℃是最佳的反应温度，反应温度过低会降低催化剂活性，反应温度过高则容易使催化剂过快失活。在合适的反应温度下，反应前10min催化剂的平均活性较高，能够得到较高质量的SWCNTs，10min后催化剂基本失活。     

Nickel and copper deposition on fine alumina particles by using the chemical vapor deposition-circulation fluidized bed reactor technique

A Chemical Vapor Deposition-Circulation Fluidized Bed Reactor technique has been developed to deposit metallic Ni and Cu onto alumina particles of 45 m diameter. The furnaces consisted of upper and lower zones, and the deposition precursors were produced both in situ and by vaporization of chlorides. X-ray diffraction, metallographical examination, and compositional analysis were used to analyze the deposition layers. For both Ni and Cu deposition, the deposition rates increased with higher temperatures of the lower furnace. The rates increased with greater amounts of chloride addition as well, but they reached plateaus when the amounts of addition were more than 40%.     

Biodegradation of diesel fuel-contaminated wastewater using a three-phase fluidized bed reactor

Aerobic biodegradation of diesel fuel (DF)-contaminated wastewater is carried out in a three-phase fluidized bed reactor under unsteady and steady state conditions. The solid phase lava rock particles, which act as the support for the biomass, are fluidized by the upward flows of influent wastewater, and air. The results show that the reactor under unsteady state operation achieved 100% DF removal from synthetic wastewater loaded with 0.43-1.03 kg/m3 day of DF. An average of over 97% of the influent chemical oxygen demand (COD) was also removed from the wastewater with COD concentrations in the range, 547-4025 mg/L. For influent COD concentrations up to 1345 mg/L, the removal is greater than 90%. Under steady state operation, the reactor was able to remove 100% of the DF, and an average of 96% of the COD from the wastewater. It had approximately 200 mg/L of DF, and 1237 mg/L of COD at a low hydraulic residence time of 4 h. In general, the results demonstrate that the reactor is very efficient, and requires short residence times to remove both DF and COD from heavily contaminated wastewater.     

Nickel and copper deposition on Al2O3 and SiC particulates by using the chemical vapour deposition–fluidized bed reactor technique

A chemical vapour deposition–fluidized bed reactor technique was developed to perform metal deposition on ceramic particulates. Experiments of nickel and copper deposition on Al₂O₃ and SiC particulates were conducted. Argon was used as the carrier gas to fluidize the ceramic particulates. The metal–H–Cl system was selected for the chemical vapour deposition. The volumetric ratios of the inlet gas were 3.5% HCl, 20.0% H₂, and 76.5% Ar. The deposition reactions were carried out at four different temperatures: 500, 600, 700 and 800 °C. Successful deposition of metallic nickel and copper on the ceramic particulates was observed. It was also noticed that the deposition rates varied with the types of substrates and deposited metals. This revised version was published online in November 2006 with corrections to the Cover Date.     

Numerical simulation of gas-solid flows in fluidized bed gasification reactor

A numerical model for simulating a fluidized bed gasifier should include appropriate parameters to capture the dynamics of gas-solid flows, gasification kinetics and the interaction between these two. The focus of the present study is to analyze the effects of coal gasification chemistry models reported in literature on the prediction of product gas composition in a fluidized bed gasification reactor. Numerical results are validated against the experimental data available in literature. The validated model is used to examine the available chemical kinetics schemes for water gas shift reaction, steam methane reforming reaction and char heterogeneous reactions. It is also used to assess the effects of hydrodynamic models parameters such as drag model, particle-particle restitution coefficient and specularity coefficient on exit gas composition. Results show that the predictions of product gas composition are notably affected by the choices of the kinetics schemes for water gas shift and steam methane reforming reactions. Systematic analysis using the available choices to simulate initial processes such as moisture removal, volatile and tar cracking is reported. Drag models and the value of specularity coefficient are shown to have no effect on product gas composition, and the particle-particle restitution coefficient slightly influences the predicted gas composition.     

Ultrathin oxide films by atomic layer deposition on graphene

In this paper, a method is presented to create and characterize mechanically robust, free-standing, ultrathin, oxide films with controlled, nanometer-scale thickness using atomic layer deposition (ALD) on graphene. Aluminum oxide films were deposited onto suspended graphene membranes using ALD. Subsequent etching of the graphene left pure aluminum oxide films only a few atoms in thickness. A pressurized blister test was used to determine that these ultrathin films have a Young's modulus of 154 ± 13 GPa. This Young's modulus is comparable to much thicker alumina ALD films. This behavior indicates that these ultrathin two-dimensional films have excellent mechanical integrity. The films are also impermeable to standard gases suggesting they are pinhole-free. These continuous ultrathin films are expected to enable new applications in fields such as thin film coatings, membranes, and flexible electronics.     

Monocrystalline zinc oxide films grown by atomic layer deposition

In the present work we report on the monocrystalline growth of (00.1) ZnO films on GaN template by the Atomic Layer Deposition technique. The ZnO films were obtained at temperature of 300 °C using dietylzinc (DEZn) as a zinc precursor and deionized water as an oxygen precursor. High resolution X-ray diffraction analysis proves that ZnO layers are monocrystalline with rocking curve FWHM of the 00.2 peak equals to 0.07°. Low temperature photoluminescence shows a sharp and bright excitonic line with FWHM of 13 meV.     

Copper nanoparticles deposited inside the pores of anodized aluminium oxide using atomic layer deposition

Equally sized copper nanoparticles were deposited in the pores (200 nm) of anodic alumina membranes (Whatman Anodisc) using a low-temperature Atomic Layer Deposition technique. Copper was deposited from gas pulses of copper chloride and a water/hydrogen gas mixture. By employing long gas pulse lengths (30 s) it was possible to obtain an equal coverage of copper particles throughout the pores of the membrane. The aspect ratio (length of pores over width of pores) was 350. By varying the number of cycles, the size of the particles could be varied from a few nanometers up to 60–70 nm. Scanning electron microscopy was used to estimate the size and distribution of the copper particles. X-ray diffraction confirmed that the particles consisted of metallic copper.     

Boride coatings on non-ferrous materials in a fluidized bed reactor and their properties

Fluidized bed technology has been successfully used in the formation of different types of coatings, e.g. aluminizing [Surf. Coat. Technol. 120 (1999) 151; Steel Res. 66 (1995) 318; J. Mater. Sci. 35 (2000) 5493], chromizing [Surf. Coat. Technol. 120 (1999) 151; Steel Res. 66 (1995) 318; J. Mater. Sci. 35 (2000) 5493], nitriding [Heat treatment in fluidized bed furnaces, 1993], carburizing [Heat treatment in fluidized bed furnaces, 1993], carbonitriding [Heat treatment in fluidized bed furnaces, 1993]. Recently, this technology has been used for the deposition of hard boride layers onto ferrous substrates [Mater. Lett. 51 (2001) 156; Fifth International Conference on Heat Treatment Materials, Budapest, Hungary, vol. 3, 1986]. In the present paper, we used fluidized bed technology to deposit boride coatings onto non-ferrous metals and alloys. The coatings were examined by means of optical microscopy, Vickers microhardness and X-ray diffraction, to determine thickness and morphology, phase formation and properties. The properties of dry wear and thermal cycling oxidation of the coatings were evaluated. The as-produced coatings were characterized by adequate thickness and improved wear and oxidation resistance.     

Boride coatings on non-ferrous materials in a fluidized bed reactor and their properties

Fluidized bed technology has been successfully used in the formation of different types of coatings, e.g. aluminizing [Surf. Coat. Technol. 120 (1999) 151; Steel Res. 66 (1995) 318; J. Mater. Sci. 35 (2000) 5493], chromizing [Surf. Coat. Technol. 120 (1999) 151; Steel Res. 66 (1995) 318; J. Mater. Sci. 35 (2000) 5493], nitriding [Heat treatment in fluidized bed furnaces, 1993], carburizing [Heat treatment in fluidized bed furnaces, 1993], carbonitriding [Heat treatment in fluidized bed furnaces, 1993]. Recently, this technology has been used for the deposition of hard boride layers onto ferrous substrates [Mater. Lett. 51 (2001) 156; Fifth International Conference on Heat Treatment Materials, Budapest, Hungary, vol. 3, 1986]. In the present paper, we used fluidized bed technology to deposit boride coatings onto non-ferrous metals and alloys. The coatings were examined by means of optical microscopy, Vickers microhardness and X-ray diffraction, to determine thickness and morphology, phase formation and properties. The properties of dry wear and thermal cycling oxidation of the coatings were evaluated. The as-produced coatings were characterized by adequate thickness and improved wear and oxidation resistance.     

Characterizations of NbAlO thin films grown by atomic layer deposition

Niobium-aluminate (NbAlO) thin films have been prepared on silicon (100) with different Nb₂O₅:Al₂O₃ growth cycle ratio by atomic layer deposition (ALD) technology. The structural, chemical and optical properties of NbAlO thin films are investigated using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and spectroscopic ellipsometry (SE). The results show that all the obtained NbAlO films are amorphous and fully oxidized. It is also found that the proportion of components in the NbAlO film can be well-controlled by varying the ALD growth cycles of the independent oxides. Furthermore, the refraction index of the prepared films is observed to increase with an increase of the concentration of Nb in the mixtures.