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Periodical dynamic characteristics induced by geometric parameters and operational variables of the self-excited pulsed cavitation jet under the optimum experimental condition is analyzed in the present study. The mechanism of cavitation jet occurrence is interpreted by combining the jet shape, the striking force, and the cavity pressure. With the increase of the inlet pressure, the pulsed frequency increases, and the amplitude decreases. Besides, the pulsed frequency decreases, and the amplitude increases as the oscillation chamber length gets much longer. It reflects that the shape and trend of the waveform are different under different structural parameters and the same operating pressure, while the waveform is the same with the same nozzle structure parameters and the various operating pressures. The peak bandwidth of the waveform is reduced with the increase of the pressure. A long enough peak bandwidth has an essential effect on the striking work operation. Only the peak value of the strike force is kept for an extended period so that it can get an effective strike. The waveform of all dynamic characteristics in the pulsed jet is harmonic. These harmonic waves can be seen as the superposition of several sine waves or cosine waves. It is required that the dominant frequency of pressure oscillation waves is single to avoid the negative influence of noise waves, and then a better effect of striking force is obtained.

The fatigue test was carried out by simplified lifting method, and the fatigue characteristic curve of X12Cr13 stainless steel at stress ratio of R = 0.1 was plotted at a single point, with the result that the fatigue strength is about 0.5 times the tensile strength. The normal stress ratio R has significant effects on the fatigue life of X12Cr13 stainless steel. As the stress ratio R increases, the fatigue life of the material increases significantly. At the same stress ratio R, the type of fracture morphology of the fatigue specimens is not significantly influenced by the variation of the maximum load. Under the same maximum load condition, larger stress ratio R leads to finer and smoother fatigue fracture surface.

Uniform experimental design method is applied to the slow strain rate testing of X12Cr13 stainless steel in natural gas environment. The influence of H2S concentration, CO2 concentration, ambient temperature and pressure on stress corrosion susceptibility are investigated. Through the observation of fracture morphology of the specimens, it is found that the fracture morphology of the specimens is stress corrosion fracture, and there are transgranular, intergranular and mixed fracture. In the fracture energy spectrum analysis, there are many oxides of S and C in the fracture composition, and the content of each element varies greatly with the corrosion environment.

The distribution and characteristics of internal flow field of the impeller with crack damage in service environment was investigated via numerical simulation with RNG k-ε turbulence model. The diffuser and volute are added based on the original impeller to simulate the internal flow field comprehensively. It was found that along the flow direction, the pressure, velocity, and temperature of the fluid increase continuously, and the maximum value appears near the outlet of the impeller. The maximum pressure and velocity in the crack area are distributed around the middle section and the trailing edge of the crack. Entropy production theory was applied in the study of internal flow, which reveals that the entropy production becomes larger around the crack. The further propagation of the crack is promoted by the opening force perpendicular to the entrance direction of the middle crack, the corrosion propagation at the rear edge of the crack, and the thermal deformation of the blade. The accelerated crack process will finally lead to the blade fracture accident.

The blending effect of gasoline is numerically simulated with different angles of nozzles and rotation speeds based on a rotary jet mixing (RJM) system. The outlet of the RJM system might destroy the components of gasoline, therefore an extra component is firstly added when the RJM system was established. In order to increase the accuracy of the simulation, sliding grid technology is applied and the meshes are divided into different sizes. The radial velocity attenuation curves and Center dynamic pressure attenuation curves of horizontal nozzles, the distribution curves of the cross-section velocity, and velocity nephograms of different blending flow fields were obtained. The results show that the jet property of nozzles and the mixing performance of the RJM system and it can effectively improve the mixing efficiency. Keywords: Gasoline blending, Numerical investigation, Rotary jet mixing system, Mixing time, Jet stirring

Tensile failure process of plane specimens and unilateral V-notched specimens is simulated basing on cohesive zone model (CZM). The internal stress in corrosion scales and film-induced stress in matrix increases with the increase of corrosion scale thickness. The thicker the corrosion scales are, the smaller the crack initiation strength is and the easier to initiate and propagate for stress corrosion cracks are. Meanwhile, with the thickness of corrosion scale increasing, the stress corrosion cracking (SCC) sensitivity of plane specimen increases and KISCC of unilateral V-notch specimens are reduced, making the stress corrosion cracks more likely to propagate. Simulation results show that the stress corrosion cracks nucleate on the surface of corrosion scale and propagate gradually until corrosion scale broke with the continuous tensile load. Finally, stress corrosion cracks propagate into the matrix. Keywords: FV520B stainless steel, Stress corrosion cracking, Slow strain rate tensile test, Cohesive zone model

Graphical abstract, Highlights • Rapid disinfection of water containing E. coli is obtained by a pilot-scale ARHCR. • The ARHCR can cause serious cleavage and surface damages to E. coli. • Proposed disinfection mechanism includes hydrodynamical and sonochemical effects., Hydrodynamic cavitation is a promising technique for water disinfection. In the present paper, the disinfection characteristics of an advanced hydrodynamic cavitation reactor (ARHCR) in pilot scale were studied. The effects of various flow rates (1.4–2.6 m3/h) and rotational speeds (2600–4200 rpm) on the removal of Escherichia coli (E. coli) were revealed and analyzed. The variation regularities of the log reduction and reaction rate constant at various cavitation numbers were established. A disinfection rate of 100% was achieved in only 4 min for 15 L of simulated effluent under 4200 rpm and 1.4 m3/h, with energy efficiency at 0.0499 kWh/L. A comprehensive comparison with previously introduced HCRs demonstrates the superior performance of the presented ARHCR system. The morphological changes in E. coli were studied by scanning electron microscopy. The results indicate that the ARHCR can lead to serious cleavage and surface damages to E. coli, which cannot be obtained by conventional HCRs. Finally, a possible damage mechanism of the ARHCR, including both the hydrodynamical and sonochemical effects, was proposed. The findings of the present study can provide strong support to the fundamental understanding and applications of ARHCRs for water disinfection.

Graphical abstract, Highlights • Cavitation flow in an ARHCR is studied combining flow visualization and CFD. • Cavitation is characterized by the periodic motion of CGUs. • Cavitation development process shows high periodicity from flow visualization. • Vortex cavitation is generated at the vortex center of CGUs. • Sheet cavitation is induced in the flow separation region of downstream CGUs., Hydrodynamic cavitation (HC) has emerged as one of the most potential technologies for industrial-scale water treatment. The advanced rotational hydrodynamic cavitation reactors (ARHCRs) that appeared recently have shown their high effectiveness and economical efficiency compared with conventional devices. For the interaction-type ARHCRs where cavitation is generated from the interaction between the cavitation generation units (CGUs) located on the rotor and the stator, their flow field, cavitation generation mechanism, and interaction process are still not well defined. The present study experimentally and numerically investigated the cavitation flow characteristics in a representative interaction-type ARHCR which has been proposed in the past. The cavitation generation mechanism and development process, which was categorized into “coinciding”, “leaving”, and “approaching” stages, were analyzed explicitly with experimental flow visualization and computational fluid dynamics (CFD) simulations. The changes in the cavitation pattern, area ratio, and sheet cavitation length showed high periodicity with a period of 0.5 ms/cycle at a rotational speed of 3,600 rpm in the flow visualization. The experimental and CFD results indicated that sheet cavitation can be generated on the downstream sides of both the moving and the static CGUs. The sheet cavitation was induced and continuously enlarged in the “leaving” and “approaching” stages and was crushed after the moving CGUs coincided with the static CGUs. In addition, vortex cavitation was formed in the vortex center of each CGU due to high-speed rotating fluid motion. The shape and size of the vortex cavitation were determined by the compression effect produced by the interaction. The findings of this work are important for the fundamental understanding, design, and application of the ARHCRs in water treatment.

The rise of CO2 in the atmosphere, which results in severe climate change and temperature increase, is known as the major reason for the greenhouse effect. Reducing CO2 to value-added products is an attractive solution to this severe problem, along with addressing the energy crisis, to which the catalysts being employed are of vital importance. Due to their high porosity and tunable compositions, metal-organic frameworks (MOFs) show great potential in energy conversion systems. By thermal or chemical treatment methods, the MOFs are easily turned into MOF-derived carbon nanomaterials. The much higher level of conductivity enables MOF-derived carbon nanomaterials to be employed in CO2 conversion processes. The present review, discusses the state of the art of MOF-derived carbon nanomaterials in CO2 electrochemical, photocatalytic, and thermal reduction applications. The corresponding reaction mechanisms and influence of various factors on catalyst performance are elaborated. Finally, the deficiencies and recommendations are provided for future progress.

One of the most challenging issues for the large-scale application of nanomaterials, especially nanocarbons, is the lack of industrial synthetic methods. Sonochemistry, which creates an extreme condition of high pressure and temperature, has been thereby applied for synthesizing a wide variety of unusual nanostructured materials. Hydrodynamic cavitation (HC), characterized by high effectiveness, good scalability, and synergistic effect with other physical and chemical methods, has emerged as the promising sonochemistry technology for industrial-scale applications. Recently, it was reported that HC can not only significantly enhance the performance of biochar, but also preserve or improve the respective chemical composition. Moreover, the economical efficiency was found to be as least one order of magnitude higher than that of conventional methods. Due to the great potential of HC in the industrial-scale synthesis of nanomaterials, the present perspective focuses on the mechanism of sonochemistry, advances in HC applications, and development of hydrodynamic cavitation reactors, which is supposed to contribute to the fundamental understanding of this novel technology.

For the welded joint specimens of the steel FV520B used in natural gas impellers, the uniform experimental method is applied in the experiment of electrochemical corrosion potential (ECP) under a certain concentration of H2S and CO2, temperature and pressure to get some test data including electrochemical corrosion potential, current density, Tafel slope and polarization resistance. In addition, the stress corrosion susceptibility index has been measured by the experimental of slow strain rate tensile (SSRT). Combined with observation of crack and fracture morphology, the stress corrosion cracking mechanism of the martensitic stainless steel FV520B welded joints in the service environment is explored. The experimental results show that there are obvious tendency of stress corrosion cracking in welded joints and the relatively significant effects of temperature and CO2 concentration on corrosion current density and stress corrosion susceptibility. In the environment of 98 °C, 6 MPa, 30% H2S and 65% CO2, the stress corrosion susceptibility of welded joint specimens is the highest, and the fracture surfaces display brittle fracture behavior.

The influence of pit shape and size on local stress concentration in the tensile specimen and the stress corrosion cracks inception was studied by employing the element remove technique. The maximum stress located in the bottom of pit on FV520B tensile specimen. The location of maximum strain was near the mouth of the pit or the shoulder and plastic strain existed in this region. Stress concentration factor and plastic deformation on four different geometrical shape pits of hemisphere, semi-ellipsoid, bullet and butterfly were numerically investigated, respectively. The simulation results showed that butterfly pit got the biggest stress concentration factor. The plastic strain rate during pit growth was in the sensitivity range of stress corrosion cracks inception, indicating that stress corrosion cracks were more likely to nucleate near the pit tip or the shoulder. Keywords: Stress corrosion crack, Pit shape, Stress concentration factor, FV520B, Element remove technique

Rotary jet agitator is an effective device for mixing, dispersing, dissolving, and suspending dispersed phases in liquid, and is particularly advantageous to the homogenization of oxygen-enriched air within the lime slurry desulfurization system. The distribution of oxygen-enriched air in agitators is vital for the process of gypsum crystallization and the homogeneous and sufficient oxygen-enriched air can promote the formation of an economically useful by-product. The present study investigated the diffusion performance of oxygen-enriched air in a rotary jet agitator during the wet flue gas desulfurization process by utilizing computational fluid dynamics. The consistency of numerical and experimental results is validated under identical conditions. Investigation results show that the rotation velocities and the inlet velocities of rotary jet machines significantly affect the distribution and homogeneity of the oxygen-enriched air distribution. However, these effects deteriorate with increasing rotation angular and jet outlet velocities. Under the optimal condition, the oxygen-enriched air concentration, within the cross-sections, fluctuates by approximately 20%. The Rotary jet agitator appears to be a remarkable method for the homogenization of oxygen-enriched air in the lime slurry tank, and in other gas-liquid stirring tanks, due to its high efficacy and good stirring effect.

A variety of geometric sizes of a self-excited pulsed jet such as the diameter of the suction and discharge nozzle, jet chamber length and diameter, and the collision angle are the main structural parameters. Under certain operating conditions at a given fluid flow rate, target space, and dynamic head, the jet strike force amplitude and frequency were significantly influenced by these structural sizes. Twenty five group orthogonal experiments were designed to explore the jet dynamic performance with structural sizes to find which group was the best combination. The experiment employed five levels of the diameter of the suction and discharge nozzles, three levels of the chamber diameter, and five levels of the length of the chamber and collision angles. Experimental results showed that the suction nozzle diameter was the most important parameter influencing the jet performance. The next was discharge nozzle diameter. The other three sizes of chamber diameter and length, and collision angle had the similar effect on the self-excited pulsed jet. The results can have guiding significance for the design of self-excited pulsed cavitation nozzles.

The electrochemical corrosion of the FV520B stainless steel for natural gas compressor impeller is studied by means of the uniform experimental method. The electrochemical corrosion potential, current density and Tafel slope of the material are measured, and the polarization resistance is solved. The experimental results show that FV520B material does not appear passivation area in the presence of the natural gas environment with H2S, and the material has been in the activation and dissolved state. When the temperature is below 130 °C, the corrosion is dominated by the process of the anode reaction, the concentration of H2S is the decisive factor to determine the occurrence of stress corrosion, the increase of H2S concentration significantly accelerates the corrosion process of the specimen, CO2 inhibits the occurrence of the stress corrosion to a certain extent. Keywords: FV520B, Stress corrosion, Electrochemical corrosion, Natural gas

FV520B is a common stainless steel for manufacturing centrifugal compressor impeller and shaft. The internal metal flaw destroys the continuity of the material matrix, resulting in the crack propagation fracture of the component, which seriously reduces the service life of the equipment. In this paper, Abaqus software was used to simulate the prefabricated crack propagation of FV520B specimen with unilateral gap. The results of static crack propagation simulation results show that the maximum value of stress–strain located at the tip of the crack and symmetrical distributed like a butterfly along the prefabricated crack direction, the maximum stress is 1990 MPa and the maximum strain is 9.489 × 10−3. The Mises stress and stress intensity factor KI increases with the increase of the expansion step, the critical value of crack initiation is reached at the 6th extension step. The dynamic crack propagation simulation shows that the crack propagation path is perpendicular to the load loading direction. Similarly, the maximum Mises stress located at the crack tip and is symmetrically distributed along the crack propagation direction. The critical stress range of the crack propagation is 23.3–43.4 MPa. The maximum value of stress–strain curve located at the 8th extension step, that is, the crack initiation point, the maximum stress is 55.22 MPa, and the maximum strain is 2.26 × 10−4. On the crack tip, the stress changed as 32.24–40.16 MPa, the strain is at 1.292 × 10−4–1.897 × 10−4. Keywords: FV520B, Crack propagation, Mises stress, Stress–strain, Numerical investigation

The advanced rotational hydrodynamic cavitation reactors (ARHCRs) that appeared recently have shown obvious advantages compared with conventional devices in various process intensifications. In ARHCRs, the cavitation generation unit (CGU) located on the rotor and stator basically determines their performance. For the first time, the present study investigated the effect of the CGU structure on the performance of a representative ARHCR by utilizing computational fluid dynamics. The amount of generated cavitation and required torque of the axis for various shapes, diameters, interaction distances, heights, and inclination angles of the CGU were analyzed. The results indicate that the interaction-type ARHCR (cavitation is generated by stator-rotor interaction) was far superior to the non-interaction type one. In addition, the hemisphere-shaped CGU demonstrates the best performance compared with that with cone-cylinder, cone, and cylinder shapes. Moreover, by evaluating the effects of various geometrical factors, the hemisphere-shaped CGU with a diameter of 12 mm, an interaction distance of 1 mm, a height of 1 mm, and an inclination angle of 10° achieved the highest performance. The reasons leading to different performance were elaborated in accordance with the flow and pressure field distributions, as well as the generated cavitation patterns. The findings of this work can strongly support the fundamental understanding, design, and application of ARHCRs for process intensifications.

To clarify the effects of free stream turbulence and surfactant concentration, a systematic study was carried out using an advanced PIV/Shadowgraphy system. The experiments were carried out for the case of single bubbles as well as bubbles rising in chains in grid generated turbulence. The data on rise characteristics of the bubbles along with liquid flow pattern are reported for the first time for the bubbles rising in surfactant solution in presence of controlled turbulence. An oscillating grid apparatus was used to generate nearly isotropic flow with nearly zero mean flow. The in-house image processing routines were used to deduce the trajectory of the bubbles along with the parameters describing bubble shape characteristics like the eccentricity and interface wobbling. The results indicated that the modification of rising velocity was a function of the turbulent characteristics, the bubble frequency and the surfactant concentration. The maximum interactions between the continuous and dispersed phases occurred at higher bubble frequency and higher surfactant concentration. The increase in turbulence intensity was observed to increase the bubble rise velocity at higher surfactant concentration.

310S is an austenitic stainless steel for high temperature applications, having strong resistance of oxidation, hydrogen embrittlement and corrosion. Stress corrosion cracking(SCC) is the main corrosion failure mode for 310S stainless steel. Past researched about SCC of 310S primarily focus on the corrosion mechanism and influence of temperature and corrosive media, but few studies concern the combined influence of temperature, pressure and chloride. For a better understanding of temperature and pressure’s effects on SCC of 310S stainless steel, prepared samples are investigated via slow strain rate tensile test(SSRT) in different temperature and pressure in NACE A solution. The result shows that the SCC sensibility indexes of 310S stainless steel increase with the rise of temperature and reach maximum at 10MPa and 160°C, increasing by 22.3% compared with that at 10 MPa and 80 °C. Instead, the sensibility decreases with the pressure up. Besides, the fractures begin to transform from the ductile fracture to the brittle fracture with the increase of temperature. 310S stainless steel has an obvious tendency of stress corrosion at 10MPa and 160°C and the fracture surface exists cleavage steps, river patterns and some local secondary cracks, having obvious brittle fracture characteristics. The SCC cracks initiate from inclusions and tiny pits in the matrix and propagate into the matrix along the cross section gradually until rupture. In particular, the oxygen and chloride play an important role on the SCC of 310S stainless steel in NACE A solution. The chloride damages passivating film, causing pitting corrosion, concentrating in the cracks and accelerated SSC ultimately. The research reveals the combined influence of temperature, pressure and chloride on the SCC of 310S, which can be a guide to the application of 310S stainless steel in super-heater tube.

The stress corrosion cracking (SCC) behavior of AISI347 austenitic stainless steel exposed to acid solution containing chloride ion at different temperature and pressure is studied through slow strain rate testing (SSRT) at different test condition. The result of SSRT shows, with the pressure increasing, the SCC resistance is getting worse and the trend of brittle fracture presented by the fracture surface is more obvious. With the temperature rising, the mechanical properties of AISI347 getting worse first and then getting better, it gets to be the worst when the temperature is 260 °C. The result of significance effect analysis of temperature and pressure on SCC shows that the temperature has a greater effect on the resistance to SCC of AISI347 austenitic stainless steel than the pressure. The main component of passive film is analyzed and the mechanism of SCC is discussed. Chromium oxides soluble in the acidic chloride solution results in the forming of corrosion pits and the cracking of the passive film under stress. Keywords: Stress corrosion cracking, Chloride ion, Slow strain rate testing, AISI347

FV520B steel is a kind of precipitation hardening Martensitic stainless steel, it has high-strength, good plasticity and good corrosion resistance. Stress corrosion cracking (SCC) is one of the main corrosion failure mode for FV520B in industrial transportation of natural gas operation. For a better understanding the effect on SCC of FV520B, the improved wedge opening loading (WOL) specimens and constant displacement loading methods were employed in experimental research in carbon dioxide and hydrogen sulfide solution. The test results showed that the crack propagation rate is 1.941 × 10−7–5.748 × 10−7 mm/s, the stress intensity factor KISCC is not more than 36.83 MPa m. The rate increases with the increasing of the crack opening displacement. Under the condition of different initial loading, KISCC generally shows a decreasing tendency with the increase in H2S concentration, and the crack propagation rate showed an increasing trend substantially. For the enrichment of sulfur ion in the crack tip induced the generation of pitting corrosion, promoting the surrounding metal formed the corrosion micro batteries, the pit defects gradually extended and connected with the adjacent pit to form a small crack, leading to further propagation till cracking happened. Fracture microscopic morphology displayed typical brittle fracture phenomena, accompanying with trans-granular cracking, river shape and sector, many second cracks on the fracture surface. Keywords: FV520B, Wedge opening loading specimen, Stress corrosion cracking, Hydrogen sulfide

In the present study, the characteristics of a representative advanced rotational hydrodynamic cavitation reactor (ARHCR) in pilot scale were experimentally investigated. The cavitation generation mechanism was analyzed with respects to experimental flow visualization. The variation regularity of the thermal performance under a full range of operational conditions (i.e., various rotational speeds (2600 to 4200 rpm) and flow rates (1 to 2.6 m3/h)) was analyzed by establishing polynomial model and response surface. A critical flow rate of 1.2 (≤2800 rpm) or 1.4 m3/h (>2800 rpm) was found out for the present ARHCR for the first time, the thermal performance can be greatly enhanced when the critical flow rate was reached. The achieved heat generation rate and thermal efficiency can be as high as 57.21 MJ/h and 79.99%, respectively. The effects of the operational conditions on the thermal performance were evaluated and discussed. Finally, the thermal and disinfection performance of the present ARHCR was compared with that of previous devices. The ARHCR achieved a disinfection rate of 100% for Escherichia coli with an expense of $2.72/m3 at the optimal condition. The disinfection result indicated that the treatment rate of the present ARHCR was approximately 140 times higher than that of the recently reported ARHCR, with 50 times lower expenses. The findings of this work can strongly contribute to the fundamental understanding, design, and application of ARHCRs in water treatment.

The charging flow rate fluctuation of the coal slurry pump was caused by the ball valve. In this study, the reconstruction was established to increase the circulation area surrounding the valve ball, the valve limiter was redesigned. The numerical simulation of the structure and performance of the ball valve is carried out with the new limiter structure, getting the flow resistance and the operational parameters The simulation results showed that the new limiter can effectively eliminate the flow fluctuation caused by the old limiter, the reform was successful to bring huge economic benefits to the plant.

Even the vapor vulcanization technology has developed a lot. The uneven temperature distribution caused by the condensation water inside the capsule still exists. In this paper, a numerical simulation study was conducted on vapor condensation of tyre capsule. Using a simplified two-dimensional model, after the 240s calculation, we analysed the result. The result shows that there was flow inside, and it was mainly induced by the condensation water flowing down the wall after it had been produced on the wall. The height of the condensed water layer is about 4.0mm. The volume of condensed water in three dimensions is about 240ml, which results in uneven temperature distribution. The temperature of the wall area with condensed water is about 3 to 13 lower than other wall areas, and the maximum °C°C temperature difference occurs at the deepest part of the condensate layer.

Corrosion failure, especially stress corrosion cracking and corrosion fatigue, is the main cause of centrifugal compressor impeller failure. And it is concealed and destructive. This paper summarizes the main theories of stress corrosion cracking and corrosion fatigue and its latest developments, and it also points out that existing stress corrosion cracking theories can be reduced to the anodic dissolution (AD), the hydrogen-induced cracking (HIC), and the combined AD and HIC mechanisms. The corrosion behavior and the mechanism of corrosion fatigue in the crack propagation stage are similar to stress corrosion cracking. The effects of stress ratio, loading frequency, and corrosive medium on the corrosion fatigue crack propagation rate are analyzed and summarized. The corrosion behavior and the mechanism of stress corrosion cracking and corrosion fatigue in corrosive environments, which contain sulfide, chlorides, and carbonate, are analyzed. The working environments of the centrifugal compressor impeller show the behavior and the mechanism of stress corrosion cracking and corrosion fatigue in different corrosive environments. The current research methods for centrifugal compressor impeller corrosion failure are analyzed. Physical analysis, numerical simulation, and the fluid-structure interaction method play an increasingly important role in the research on impeller deformation and stress distribution caused by the joint action of aerodynamic load and centrifugal load.

Decomposition of CO2 over reduced MFe2O4 (M = Ni, Co, Cu, Zn) was studied by H2–TPR, H2–TG, and CO2–TG. XRD Rietveld analysis was used for determining phase composition and crystallite size of reduced and oxidized samples. The results indicate that spinel CoFe2O4 and CuFe2O4 are reduced to metals by H2, while ZnFe2O4 and NiFe2O4 only partly reduced at 350 °C. The CoFe2O4 spinel ferrite shows the best activity in decomposing CO2 and the ZnFe2O4 shows the best recovery ability in the process of redox.

The ultra-fine Ni 0.49 Cu 0.24 Zn 0.24 Fe 2 O 4 was prepared as a novel material for decomposing CO 2 which is the main gas causing “green house effect”. The relationships between the microstructure and CO 2 decomposition activity of Ni 0.49 Cu 0.24 Zn 0.24 Fe 2 O 4 were investigated. The results showed that H 2 -reduced Ni 0.49 Cu 0.24 Zn 0.24 Fe 2 O 4 had higher decomposition performance than MFe 2 O 4 (M = Ni, Cu, Zn) at 310 °C. The study of cycle decomposition activity found that Ni 0.49 Cu 0.24 Zn 0.24 Fe 2 O 4 can be used repeatedly at 310 °C. Moreover, the analysis of phases and morphology of products by XRD Rietveld analysis, TEM, and Raman, respectively, demonstrated that Ni 0.49 Cu 0.24 Zn 0.24 Fe 2 O 4 was destroyed to carbide, ZnO, and metal alloy and the activity phase changed from spinel structure to metal alloys during the decomposition of CO 2 . The deposited carbon was in the form of amorphous.

A Gd and Mg co-doped ceria electrolyte Ce0.85Gd0.1Mg0.05O1.9 (CGM) was prepared by sol–gel method. Its conductivity behavior was studied and compared with those of singly doped ceria electrolytes Ce0.9Mg0.1O1.9 (CM10) and Ce0.9Gd0.1O1.95 (CGO). By using CGM as the electrolyte, a fuel cell was fabricated with a Ni/CGM anode and a La0.6Sr0.4Co0.2Fe0.8O3 (LSCF)/CGM composite cathode. Its performance was compared with that of CGO based fuel cells. Both the CM10 and CGM electrolytes were ceria based solid solutions. The dopant Mg2+ might be situated in the interstitials of the crystal lattice of CeO2. The co-doped CGM showed a higher conductivity in air at 773–973 K in comparison to that of CGO and CMO. The CGM based fuel cell also showed higher open circuit voltage (OCV) and higher maximum power density (MPD) than the CGO based cell at 773–973 K. The MPD of the fuel cells were improved further by using composite cathode of LSCF/CGO (or CGM). With Ni/CGM anode and LSCF/CGM cathode, the MPD of the CGM based fuel cell at 873 K reached 202.5 mW cm−2.

A low temperature CO sensor has been made by the use of ultrafine tin oxide as the base material. The gas sensor performance is correlated with the effects of different adsorbed CO species. A mechanism for the low temperature sensing is proposed and discussed.

Surface-covered nanometer-sized CuO/Al2O3, CuO-ZnO/Al2O3, and CuO/ZnO catalysts were prepared by phase transfer with carboxylate. The surface-covered structure was studied using XPS, XRD, TEM, and high-resolution electron microscope. The results indicated that amorphous CuO and ZnO were dispersed on the surface of nanometer-sized Al2O3 particles in catalysts CuO-ZnO/Al2O3 and CuO/Al2O3, respectively. The thickness of its surface layer is about several angstroms. No spinel structure was found in the catalyst. The particle size of the surface-covered CuO/Al2O3 catalyst was about 2-3 nm. Al2O3 in the catalyst was amorphous. Surface-covered material CuO in the catalyst with low CuO content was also armophous. A large amount of copper carboxylate resulted in crystalline CuO and Cu2O. The protective ability of carboxylate to sol particles differs from the metal element of carboxylate. Copyright 1997 Academic Press. Copyright 1997Academic Press

Publisher Summary Zirconium oxychloride (or zirconium oxynitrate) was mixed with urea, nitric acid, and water in an evaporating dish, and then thermolyzed in a muffle furnace at a fixed temperature for about 10 minutes. This led to samples with a foam structure. Zirconium oxides are extensively used in many fields (such as ceramic, refractory, sensor and catalysis) because of their properties. Many methods have been developed for the production of such materials. Samples from zirconium oxychloride show higher surface area than those from zirconium oxynitrate. Furthermore, Brunauer, Emmett, and Teller (BET) surface area for ZrO(NO 3 ) 2 + urea system are lower than those for ZrOCI 2 + HNO 3 + urea system. This is in good agreement with the one reported by kingsley, in which BET surface area of pure Al 2 O 3 sample was 8.30 m 2 /g and that of 50 wt% ZrO 2 in Al 2 O 3 sample only 3.12 m 2 /g when zirconium oxynitrate was employed. These indicate that nitric acid plays important roles in the formation of the foam. Obviously, the foam structure and high BET surface area should be attributed to the synergetic effect of the decomposition of precursor and the combustion of fuel.