Fe_(2)O_(3)对ZrTiO_(4)载体NH_(3)-SCR催化性能的影响

NH_(3)-SCR催化剂主要用于工业生产和汽车尾气清洁,本研究采用“共沉淀-浸渍法”制备了新型α%Fe_(2)O_(3)/ZrTiO_(4)(α=0、8、12、15)催化剂。结果表明,α%Fe_(2)O_(3)/ZrTiO_(4)催化剂的最佳成分配比的12%Fe_(2)O_(3)/ZrTiO_(4)催化剂在250−400℃条件下NO_(x)转化率大于80%,在300℃时NO_(x)转化率接近100%,并且N2选择性在200−450℃大于90%。在ZrTiO_(4)表面负载Fe_(2)O_(3)后,催化剂的氧化还原性能、表面酸度和Oβ/(Oα+Oβ)比例都有所提高,这不仅归因于α%Fe_(2)O_(3)/ZrTiO_(4)催化剂具有多孔结构,还归因于活性组分Fe_(2)O_(3)和载体ZrTiO_(4)之间的电子相互作用。此外,原位DRIFTs反应表明,12%Fe_(2)O_(3)/ZrTiO_(4)催化剂的NH_(3)-SCR反应遵循Eley-Rideal机制。明确的反应机制有利于更深入了解SCR过程中NO_(x)转化的反应过程。这项工作为未来Fe基SCR催化剂在中温范围内替代V基催化剂提供了可行的策略。

Causes of Odor in Kitchens,Bathrooms,and Toilets of Multi-story Residential Apartments with Natural Ventilation

The causes of an offensive odor in the kitchens,bathrooms,and toilets of residential apartments in multi-story buildings with natural ventilation in Tomsk,Russia,are discussed in this paper.This problem exists in other cities and countries.Wall electric fans can be installed in ventilation grills in kitchens,bathrooms,and toilets of apartments in multi-story residential buildings.Typically,these fans turn on with the light in the bathroom or toilet,so the problem is periodic.Forced airflow from a fan in one apartment disrupts the natural outflow of air in the ventilation system of a residential building designed and built according to building codes and regulations and can cause an unpleasant smell in neighboring apartments.In many cases,it is difficult to determine which apartments have fans and force the neighbors to remove them.Locally,on the scale of one apartment,the problem is solved by installing an air check valve in the ventilation grill,which will block the nuisance airflow from the ventilation system into the bathroom.Globally,the problem is solved by modification and subsequent compliance with building codes and regulations,the implementation of which is controlled by local authorities.

Recycle of valuable products from oily cold rolling mill sludge

Oily cold rolling mill （CRM） sludge contains lots of iron and alloying elements along with plenty of hazardous organic components, which makes it as an attractive secondary source and an environmental contaminant at the same time. The compound methods of ＂vacuum distillation ＋ oxidizing roasting＂ and ＂vacuum distillation ＋ hydrogen reduction＂ were employed for the recycle of oily cold rolling mill sludge. First, the sludge was dynamically vacuum distilled in a rotating furnace at 50 r/rain and 600℃ for 3 h, which removed almost hazardous organic components, obtaining 89.2wt% ferrous resultant. Then, high purity ferric oxide powders （99.2wt%） and reduced iron powders （98.9wt%） were obtained when the distillation residues were oxidized and reduced, respectively. The distillation oil can be used for fuel or chemical feedstock, and the distillation gases can be collected and reused as a fuel.

Effects of laser pulse energy on surface microstructure and mechanical properties of high carbon steel

Surface microstructure and mechanical properties of pearlitic Fe–0.8%C(mass fraction) steel after laser shock processing(LSP) with different laser pulse energies were investigated by scanning electron microscopy(SEM),transmission electron microscopy(TEM),X-ray diffraction(XRD) and microhardness measurements.After LSP,the cementite lamellae were bent,kinked and broken into particles.Fragmentation and dissolution of the cementite lamellae were enhanced by increasing the laser pulse energy.Due to the dissolution of carbon atoms in the ferritic matrix,the lattice parameter of α-Fe increased.The grain size of the surface ferrite was refined,and the microstructure changed from lamellae to ultrafine micro-duplex structure(ferrite(α)+cementite(θ)) with higher laser pulse energy,accompanied by the residual stress and microhardness increase.

Review of the fatigue behavior of hard coating–ductile substrate systems

With the wide application of coating materials in aerospace and other fields, their safety under fatigue conditions in service is important.However, research on the fatigue properties of ceramic hard coatings started late, and a unified standard is yet to be established to evaluate the fatigue life of hard coating–ductile substrate systems.Studies also present different opinions on whether coatings can improve or reduce the fatigue life of substrates.In this paper, the influence of the properties of ceramic coatings on fatigue performance is reviewed, and the effects of coating on the mechanism of fatigue crack initiation in substrates are discussed, aiming to help readers understand the fatigue behavior of hard coating–ductile substrate systems.

Spheroidization of molybdenum powder by radio frequency thermal plasma

To control the morphology and particle size of dense spherical molybdenum powder prepared by radio frequency（RF） plasma from irregular molybdenum powder as a precursor, plasma process parameters were optimized in this paper. The effects of the carrier gas flow rate and molybdenum powder feeding rate on the shape and size of the final products were studied. The molybdenum powder morphology was examined using high-resolution scanning electron microscopy. The powder phases were analyzed by X-ray diffraction. The tap density and apparent density of the molybdenum powder were investigated using a Hall flow meter and a Scott volumeter. The optimal process parameters for the spherical molybdenum powder preparation are 50 g/min powder feeding rate and 0.6 m^3/h carrier gas rate. In addition, pure spherical molybdenum powder can be obtained from irregular powder, and the tap density is enhanced after plasma processing. The average size is reduced from 72 to 62 μm, and the tap density is increased from 2.7 to 6.2 g/cm^3. Therefore, RF plasma is a promising method for the preparation of high-density and high-purity spherical powders.

Current-voltage characteristics of lead zirconate titanate/nickel bilayered hollow cylindrical magnetoelectric composites

Current--voltage measurements obtained from lead zirconate titanate/nickel bilayered hollow cylindrical magnetoelectric composite showed that a sinusoidal current applied to the copper coil wrapped around the hollow cylinder circumference induces voltage across the lead zirconate titanate layer thickness. The current--voltage coefficient and the maximum induced voltage in lead zirconate titanate at 1~kHz and resonance （60.1~kHz） frequencies increased linearly with the number of the coil turns and the applied current. The resonance frequency corresponds to the electromechanical resonance frequency. The current--voltage coefficient can be significantly improved by optimizing the magnetoelectric structure geometry and/or increasing the number of coil turns. Hollow cylindrical lead zirconate titanate/nickel structures can be potentially used as current sensors.

Nd_2Fe_(17) nanograins effect on the coercivity of HDDR NdFeB magnets with low boron content

Relationships between the coercivity of hydrogenation disproportionation desorption recombination （HDDR） Nd12.5Fe81.5-xfo6Bx bonded magnets and boron content were investigated. Nd2Fe17 phase with planar magnetic anisotropy is present in the microstructure when x= 4at%-5.88at%, which does not reduce the coercivity of the bonded magnets. High-resolution transmission electron microscopy （TEM） images show that Nd2Fe17 phase exists in the form of nanocrystals in the Nd2Fe14B matrix. There is an exchange-coupling interaction between the two phases so that the coercivity of HDDR Nd12.5Fe81.5-xCo6Bx bonded magnets is hardly reduced with a decrease in boron content.

Recent advances and perspective in metal coordination materialsbased electrode materials for potassium-ion batteries

Recently,to ameliorate the forthcoming energy crisis,sustainable energy conversion and storage devices have been extensively investigated.Potassium-ion batteries(KIBs)have aroused widespread attention in these very active research applications due to their earth abundance and similar low redox potential compared to Li-ion batteries(LIBs).It is critical to develop electrode materials with large ion diffusion channels and robust structures for long cycling performance in KIBs.Metal coordination materials,including metal-organic frameworks,Prussian blue,and Prussian blue analogue,as well as their composites and derivatives,are known as promising materials for high-performance KIBs due to their open frameworks,large interstitial voids,functionality and tailorability.In this review,we give an overview of the recent advances on the application of metal coordination materials in KIBs.In addition,the methods to enhance their K-ion storage properties are summarized and discussed,such as morphology engineering,doping,as well as compositing with other materials.Ultimately,some prospects for future research of metal coordination materials for KIBs are also proposed.

One-step Crystallization Kinetic Parameters of the Glass-ceramics Prepared from Stainless Steel Slag and Pickling Sludge

One-step crystallization is one of the most energy conserving methods for glass-ceramics preparation.However,only a few kinetics studies focused on the glass-ceramics prepared by the one-step crystallization.The onestep crystallization kinetic parameters were studied using differential scanning calorimetry.The activation energy（Ea）and the Avrami parameter（n）were calculated as 152.79kJ·mol-1 and 4.39,respectively.These parameters indicate that continuous nucleation and three-dimensional crystal growth are the dominating mechanisms in the one-step crystallization process of the parent glass.The properties of the obtained glass-ceramics can be compared to the glass-ceramics prepared by the two-stage heat treatment and sintering method.This crystallization kinetics research can be used to evaluate the one-step crystallization potential of a parent glass.

Initial formation of corrosion products on pure zinc in simulated body fluid

Zinc was recently suggested to be a potential candidate material for degradable coronary artery stent.The corrosion behavior of pure zinc exposed to r-SBF up to 336 h was investigated by electrochemical measurements and immersion tests. The morphology and chemical composites of the corrosion products were investigated by scanning electron microscope, grazing-incidence X-ray diffraction, X-ray photoelectron spectroscopy and Fourier transform infrared spectrometer. The results demonstrate that the initial corrosion products on the pure zinc mainly consist of zinc oxide/hydroxide and zinc/calcium phosphate compounds. The pure Zn encounters uniform corrosion with an estimated corrosion rate of 0.02-0.07 mmy;during the immersion, which suggests the suitability of pure Zn for biomedical applications.

Characterization of the Hot Deformation Behavior of Cu–Cr–Zr Alloy by Processing Maps

Hot deformation behavior of the Cu-Cr-Zr alloy was investigated using hot compressive tests in the tem- perature range of 650-850℃ and strain rate range of 0.001-10 s-1. The constitutive equation of the alloy based on the hyperbolic-sine equation was established to characterize the flow stress as a function of strain rate and deformation temperature. The critical conditions for the occurrence of dynamic recrystallization were determined based on the alloy strain hardening rate curves. Based on the dynamic material model, the processing maps at the strains of 0.3, 0.4 and 0.5 were obtained. When the true strain was 0.5, greater power dissipation efficiency was observed at 800-850 ℃ and under 0.001-0.1 s-1, with the peak efficiency of 47%. The evolution of DRX microstructure strongly depends on the deformation temperature and the strain rate. Based on the processing maps and microstructure evolution, the optimal hot working conditions for the Cu-Cr-Zr alloy are in the temperature range of 800-850 ℃ and the strain rate range of 0.001-0.1 s-1.

Initial formation of corrosion products on pure zinc in saline solution

Corrosion product formed on zinc sample during 2 weeks immersion in saline solution has been investigated.The corrosion layer morphology as well as its chemical composition,was analyzed using scanning electron microscopy(SEM),x-ray diffraction(XRD),x-ray photoelectron spectroscopy(XPS)and Fourier transform infrared spectroscopy(FTIR).Electrochemical measurement was used to analyze the corrosion behavior.Zinc oxide,zinc hydroxide and zinc hydroxide chloride were formed on zinc surface in saline solution.The thickness of corrosion layer increased with the time increased.The pure Zn has an estimated corrosion rate of 0.063mmy^−1 after immersion for 336 h.Probable mechanisms of zinc corrosion products formation are presented.

Properties and precipitates of the high strength and electrical conductivity Cu-Ni-Co-Si-Cr alloy

In this paper,a novel Cu-1.5 Ni-1.1 Co-0.6 Si-0.1 Cr(wt.%)alloy with high strength and electrical conductivity was designed.After aging,excellent properties of 857±12 MPa yield strength,300±8 HV microhardness,42.8±2.5%IACS conductivity,and 7±0.5%elongation were obtained.According to the atomic structure,part of Ni atoms in Ni_(2)Si can be replaced by Co atoms to form nano-precipitates(Ni,Co)_(2)Si.The alloy’s high strength and conductivity are mainly attributed to the fine and uniformly distributed(Ni,Co)_(2)Si and Cr nano precipitates.The alloy strength was also enhanced by twins,dislocations,and grain refining strengthening.Based on the investigations of deformation microstructure and the orientation relationship between the(Ni,Co)_(2)Si precipitates and the Cu matrix,the main reason for elongation increase is attributed to the formation of deformation twins and the small lattice mismatch strain at the coherent interfaces of precipitates and the Cu matrix.

Microstructure Evolution and Microhardness of Ultrafine-grained High Carbon Steel during Multiple Laser Shock Processing

Surface microstructure and microhardness of （ferrite＋ cementite） microduplex structure of the ultrafine- grained high carbon steel after laser shock processing （LSP） with different impact times were investigated by means of scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, X-ray diffraction （XRD） and microhardness measurements. Equiaxed ferrite grains were refined from 400 to 150 nm, and the cementite lamellae were fully spheroidized, with a decrease of the particle diameter from 150 to 100 nm as the impact times increased. The cementite dissolution was enhanced significantly. Correspondingly, the lattice parameter of α-Fe and microhard- hess increased with the impact times.

Mechanism of CeMgAl_(11)O_(19):Tb^(3+) alkaline fusion with sodium hydroxide

Comprehensive CeMgA111O19： Tb3＋ （CTMA） disintegration via alkaline fusion was discussed. The rare earth （RE） elements in CTMA were dissolved by HC1 completely after alkaline fusion. Relationships between the alkaline fusion temperature and various properties of the compounds were examined by various techniques to elu- cidate their roles in the expected CTMA disintegration. X-ray diffraction （XRD） analysis indicates the phase transformation sequence. A scientific hypothesis of crystal structure disintegration presents that sodium ions substitute for the europium and barium ions in the mirror plane and magnesium ions in the spinel block successively, resulting in that more oxygen vacancies and interstitial sodium ions appear. The unit cell [P63/mmc （194）] breaks from the mirror plane. Then it is decomposed into NaA102, and magnesium, cerium, and terbium ions combine with free OH- into MgO, Tb2O3 and CeO2; Tb2O3 and CeO2 change into Ceo.6Tbo.O2-x. In the end, the rare earth oxide is recycled easily by the acidolysis. The mechanism provides fundamental basis for recycling of REEs from waste phosphors.

Treatment method of hazardous pickling sludge by reusing as glass–ceramics nucleation agent

Heavy metal containing pickling sludge（PS） is one of the by-products of the stainless-steel-making industry,which has been considered hazardous due to contained chromium and nickel.Traditional methods of PS disposing are landfill and cement solidification.This research is aimed at disposing PS by solidification/stabilization and reusing it as a nucleation agent of glass–ceramics.The crystallization behavior and the properties of a glass in the CaO–MgO–SiO2–Al2O3 system were studied by considering PS as the nucleation agent.Experimental results confirm that introducing 14 wt% PS as the nucleation agent of glass–ceramics can decrease crystallization temperature by 110.8 °C,refine the grain size by forming isometric crystals with size of 2 lm,enhance Vickers hardness by 2690 MPa and decrease water absorption from（1.21 ± 0.10） wt% to（0.04 ± 0.01） wt%.Therefore,it is reasonable to conclude that PS can be utilized as a nucleation agent to improve the crystallization and mechanical properties of the glass–ceramics.The testing results of US EPA toxicity characteristic leaching procedure（TCLP）confirm the safety of this reusing method.

Fabrication and characterization of anodic oxide nanotubes on TiNb alloys

Titanium and its alloys have been extensively used as implant materials owing to their high specific strength, good biocompatibility and excellent corrosion resistance. Oxide nanotubular array layer can be formed on Ti alloy surface by electrochemical anodization treatment. In this work, the morphology of nanotubes formed on Ti-Nb alloys（Nb content of 5 wt%, 10 wt%, 20 wt%, 30 wt% and40 wt%） was investigated using an electrolyte containing ethylene glycol and NH_4 F. Oxide layers consisting of highly ordered nanotubes with a range of diameters（approximately40-55 nm for the inner diameter and 100-120 nm for the outer diameter） and lengths（approximately 10-20 lm） can be formed on alloys in the Ti-x Nb system, independent on the Nb content. The nanotubes formed on the Ti-Nb alloy surface were transformed from the anatase to rutile structure of titanium oxide. The oxide nanotubular surface is highly hydrophilic compared with the intact Ti Nb foil. The surface wettability varies with the nanotube diameter. As the nanotube diameter increases while the nanotube layer thickness remains constant, the capillary wetting of the nanotube surface decreases and the surface becomes less hydrophilic.Annealing changes the nanotubular surface wettability further and establishes less hydrophilic surface conditions due to the removal of hydroxyl groups and residue fluoridecontaining species. It is believed that the surface wettability is changed due to the decreasing content of hydroxyl groups in ambient atmosphere. This work can provide guidelines for improving structural and environmental conditions responsible for changing surface wettability of Ti Nb surfaces for biomedical applications.

Microstructure and Hardness of Laser Shocked Ultra-fine-grained Aluminum

Ultra-fine-grained commercial purity aluminum was produced by severe cold rolling, annealing and then strain- ing at ultra-high rate by a single pass laser shock. Resulted microstructure was investigated by transmission electron microscopy. Microhardness of annealed 0.6μm ultra-fine grained aluminum increased by 67% from 24 to 40 HV. Many 0.3 μm sub-grains appeared at the shock wave center after a single pass laser shock, while high density dislocation networks were observed in some grains at the shock wave edges. Accordingly, microhardness at the impact center increased by 37.5% from 40 to 55 HV. From the impact center to the edge, microhardness decreased by 22% from 55 to 45 HV.

Mechanism and kinetics of the BaMgAl_(10)O_(17):Eu^(2+) alkaline fusion reaction

Knowledge of the kinetics and mechanism of BaMgAl10017：Eu2＋ （BAM） fusion with sodium hydroxide will benefit recy- cling rare earth elements （REEs） from the waste phosphors. The reaction temperature range of 290-375 ~C and the reaction mecha- nism were determined using X-ray diffraction, scanning electron microscopy and differential scanning calorimetry. Activation energy was determined by the four model-free methods, and calculated results showed that the Kissinger method value of 579.5 KJ/mol was close to the average value of the Kissinger-Akahira-Sunose （KAS） and the Flynn-Wall-Ozawa （FWO） methods of 563.5 kJ/mol. The calculated activation energy variation tendency versus conversion factor agreed with the proposed mechanism.