Influence of Aging Time on the Properties of Precursors of CuO/ZnO Catalysts for Methanol Synthesis

The aging process of pure copper precursors and copper-zinc binary precursorswere studied by XRD, TG-DTG and TPR techniques. The catalytic activity and stability of CuO/ZnOwere tested using fixed-bed flow reactor, and the physical properties of the catalysts and Cuspecies were characterized with N_2 adsorption and N_2O passivation method, respectively. For theCu-Zn binary system prepared at the precipitating condition of pH=8.0 and temperature=80℃, theinitial phase was a mixture of copper nitrate hydroxide Cu_2(NO_3)(OH)_3, georgeite and hydrozinciteZn_5(CO_3)_2(OH)_6. By increasing the duration of its aging time, the phase of Cu_2(NO_3)(OH)_2first transited to georgeite, and then interdiffused into Zn_5(CO_3)_2(OH)_6 and resulted in two newphases: rosasite (Cu,Zn)_2CO_3(OH)_2 and au-richalcite (Zn,Cu)_5(CO_3)_2(OH)_6. The former phasewas much easier to be formed than the latter one, while the latter phase was more responsible forthe activity of methanol synthesis than the former one. It is found that the composition andstructure of the precursors altered obviously after the colour transition point. The experimentalresults showed that methanol synthesis is a structure-sensitive catalytic reaction.

Influence of concrete differential aging time on the construction phases analysis of the Fenghua River Bridge

The Fenghua River Bridge is a major structure on the highway between Hengzhang and Guojiachi, which is to be built with a four-span prestress concrete (PC) box girder and symmetrical cantilever castings. In this paper, a finite element method (FEM) model is set up to study the effects of concrete differential aging time on the construction phases of the Fenghua River Bridge by calculating the vertical displacement of the folding segment of the middle span and the longitudinal bending moment of Pier 12#. In the model, the girders are classified into 150 changing sections based on the desgn scheme, and their construction is to be carried in 16 phases respectively to build 12 blocks connected by a side folding segment and a middle folding segment, covered with a second dead load and in completion for 20 years. It is found that the internal forces and deformations of the concrete structures at the aging time of 60 d are quite different from those of 0 d aging time while the behaviors of the structures of 120 d aging time is nearly the same as those of 60 d aging time― the differences are so small that can be neglected, suggesting that the creep develops obviously about one month after the cement is hardened and the development fades later on.

Effects of precipitate aging time on the cerium-zirconium composite oxides

Cerium-zirconium composite oxides with high performance were synthesized by a co-precipitation method, using zirconium oxychloride and rare earth chloride as raw materials. The effects of precipitate aging time on the properties of cerium-zirconium composite oxides were investigated. The prepared cerium-zirconium composite oxides were characterized by X-ray diffraction（XRD）, BET specific surface area, pulsed oxygen chemical adsorption, H2 temperature-programmed-reduction（H2-TPR）, scanning electron microscopy（SEM）, etc. The results showed that the precipitate aging time caused great effects on the properties of cerium zirconium composite oxides. With the increase of aging time, the cerium zirconium composite oxides showed enhanced specific surface area, good thermal stability, and high oxygen storage capacity（OSC）. The best performance sample was obtained while the precipitate aging time up to 48 h, with the specific surface area of 140.7 m2/g, and OSC of 657.24 μmolO2/g for the fresh sample. Even after thermal aged under 1000 oC for 4 h, the aged specific surface area was 41.6 m2/g, moreover with a good OSC of 569.9 μmolO2/g.

Effect of ageing time on corrosion behavior of Mg-10Gd-4.8Y-0.6Zr extruded-alloy

The corrosion behaviors of Mg-10Gd-4.8Y-0.6Zr extruded-alloys with various ageing time were investigated by immersion test and electrochemical measurements.The results show that the corrosion rate of the experimental alloy decreases with the increase of ageing time from 0 to 108 h.The corrosion resistance of the experimental alloy was found to increase with the increase of the size of the precipitate phases.The open circuit potential of the experimental alloy increases with the increase of the ageing time.The potentiodynamic polarization curves show that the cathodic over-potential increases with the increase of ageing time,leading to a decrease in the current density of anodic current plateau with the increase of ageing time.

Microstructure and mechanical properties of high strength Al-Zn-Mg-Cu alloys used for oil drill pipes

Three Al?Zn?Mg?Cu alloys used for oil drill pipes (Alloy A: Al?6.9Zn?2.3Mg?1.7Cu?0.3Mn?0.17Cr; Alloy B: Al?8.0Zn?2.3Mg?2.6Cu?0.2Zr, Alloy C: Al?8.0Zn?2.3Mg?1.8Cu?0.18Zr) were studied by hardness tests, tensile tests and transmission electron microscopy (TEM). The results show that the ultimate tensile strength, yield strength and elongation for Alloys A, B and C are 736 MPa, 695.5 MPa and 7%; 711 MPa, 674 MPa and 12.5%; 740.5 MPa, 707.5 MPa and 13%, respectively after solid solution treatment ((450 °C, 2 h)+(470 °C, 1 h)) followed by aging at 120 °C for 12 h. The dominant strengthening phases in Alloy A are GPII zone andη′ phase, the main precipitate in Alloy B isη′ phase, and the main precipitates in Alloy C are GPI zone, GPII zone andη′ phase, which are the reason for better comprehensive properties of Alloy C. The increase of zinc content leads to the improvement of the strength. The increase of copper content improves the elongation but slightly decreases the strength. Large second-phase particles formed by the increase in the manganese content induce a decrease in the elongation of alloys.

Influence of synthesis parameters on the crystallinity and Si/Al ratio of NaY zeolite synthesized from kaolin

Well-crystallized high-silica NaY zeolites （Si/Al〉2.5） were prepared from a reaction mixture consisting of metakaolin, sodium silicate solution and seed solution via optimization of the mixture composition and reaction conditions. The transformation from kaolin to high-silica NaY zeolite was confirmed by XRD, SEM and IR techniques. Subsequently, the influence of synthesis parameters, i.e. initial SIO2/Al2O3, initial Na2O/SiO2, initial H2O/SiO2, aging time of the seed solution, crystallization temperature and crystallization time, on the NaY growth was investigated in terms of crystallinity and Si/Al ratio. The results showed that the effects of initial SiO2/Al2O3, initial Na2O/SiO2 and initial H2O/ SiO2 on the crystaIlinity and Si/Al ratio of NaY zeolite are similar to those observed in the conventional syntheses of NaY zeolites only using sodium silicate solution as silicon source. However, due to the use of metakaolin as the main silicon and aluminum sources in the present study, a long crystallization induction period of 20 h was achieved, which can be attributed to the dissolution of metakaolin. In addition, different from the conventional syntheses of zeolite NaY, pure NaY zeolites （i.e. without NaP zeolite impurity） were still obtained even at 120℃ because of the use of a large quantity of seed solution （23 wt%） in the reaction mixture. As the aging time of the seed solution increased from 3.5 h to 22 h, the relative crystallinity of the NaY zeolite first increased sharply and then reached a plateau, while the Si/Al ratio first increased rapidly up to a maximum value of 2.75 corresponding to an aging time of 6.5 h, and then decreased sharply with the aging time.

Aging process design based on the morphological evolution ofγprecipitates in a 4th generation nickel-based single crystal superalloy

In order to meet the design requirements of the aging treatment process of a 4th generation nickel-based single crystal superalloy(Ni-SX)developed independently,the effects of aging temperatures and aging times on the precipitation and morphological evolution ofγprecipitates are studied.The morphological evolution behavior ofγprecipitates during the aging process is summarized subsequently and the coarsening behavior ofγprecipitates is discussed by comparing with the Lifshitz-Slyozov-Wagner model(LSW)and the trans-interface diffusion-controlled model(TIDC).It is demonstrated that primary aging temperature and secondary aging time dominate the size and squareness ofγprecipitates respectively,a narrow primary aging temperature range and a suitable secondary aging time are allowed to obtain the optimized morphology ofγprecipitates.The optimal aging process of the Ni-SX investigated in the present work is obtained for 1100-1120°C/4 h and 870°C/16 h,confirmed by the corresponding creep tests.The coarsening growth ofγprecipitates in short-term aging also conforms to the LSW model well.Besides,the aging process design rules of various Ni-SXs of different generations are also summarized.

Optimization of the preparation process of nano TiO2 with sol-gel method at low temperature

In this paper, preparation process of nano TiO2 with sol-gel method at low temperature was optimized by response surface method. The nano TiO2 was analysised by DRS and XRD. Result show that： 20mL tetrabutyl titanate, 10mL acetic acid, 6mL ethanol dosage, aging time was 29h, aging temperature was 36℃, Nano TiO2 was prepared under the condition. Particle size of nano particles was 37.3nm, Photodegradation rate was 90.2%. It had good photocatalytic ability.

Morphology Controlling of the Ultrafine Cerium Dioxide (CeO_2) Precursor

The synthesis of ultrafine cerium dioxide precursor via homogeneous precipitation was studied. Mixed aqueous solution of anhydrous cerium nitrate and urea was first heated to 85℃ for 2 h, and the prepared suspension was then aged at room temperature for various periods of time. White precipitate was finally collected by centrifuging and washed with distilled water and anhydrous ethanol. The obtained cerium dioxide (CeO2) precursor was observed with SEM. It was found that the morphology and size of the precursor were strongly affected by aging time and stirring conditions (with or without stirring). The precipitated fine spherical particles of the precursor changed their shape from ellipse to slice or directly to slice. Fine spherical monodispersed (300 nm) precursor powders could be obtained by controlling the aging time. Stirring the solution also could change the reaction process and thus the morphology and size of the precursor were changed.

MORPHOLOGY CONTROL OF ULTRAFINE CeO_2 AND ITS POLISHING EFFICACY

Homogenous precipitation and subsequent calcination has been used tosynthesize ultrafine ceria from cerium nitrate and urea solution. The ceria calcined from theprecursor inherit the size and morphology of it. The size and morphology of the precursor areclosely related to the preparation process. The morphology, size and distribution of the precursorcould be tailored by changing the reaction condition and the ageing time. Monodispersed 200 nm sizedspherical particles is prepared by this method. The powder is used in the chemical-mechanicalpolishing of Si wafer. The average surface roughness of the polished Si wafer is 0.171 nm measuredby AFM.

Effect of Zr addition on precipitates in K4169 superalloy

In order to investigate the effect of Zr addition on the precipitations of K4169 superalloy, a manual electric arc furnace was used to prepare the superalloy with different Zr addition from 0.03wt.% to 0.07wt%. After standard heat treatment and long-time aging, the microstructures of the alloys were observed using XRD, SEM and TEM. The results show that Zr not only inhibits the precipitation of Laves phase at the grain boundary, but also significantly promotes the precipitation of earlobe-like γ＇ and γ＂ phases. After long time aging at 680 ℃ for 500 h, the γ＂ phase grows up obviously and forms a γ＇/γ＂ clad microstructure when the Zr addition is 0.03 wt.%. A large number of fine orbed γ＇ particles precipitate in the grains and some γ＂ phase transforms to disk-like c5 phase when the Zr addition increases to 0.05wt.%. The nano-polycrystalline γ＇ phase precipitates in the grains and there is a little δ phase when the Zr addition is 0.07wt.%. As the Zr addition increases, the amount of Laves phase at the grain boundary decreases at first, and then increases and forms flaky morphology.

Analysis of geological conditions and thermal reservoir characteristics of Guantao Formation in new coastal region

Geothermal resources is one of the most practical and competitive new energy at present,and there is abundant geothermal resources in the new coastal region.The article get the three following conclusion through the geothermal geological condition by the drilling strata and the condition of the reducing test:stratigraphic division is done by the analysis of formation lithology and the drilling aging;the water yield is higher than 100m3/h,the flow temperature is 67℃--71℃;the average geothermal gradient of the overlying strata is 3.08℃--3.33℃/100 m.

The Study on the Mechanical Properties of Optical Fiber With Long-Term Time Aging

The fiber properties depending on the coating thickness and long-term time aging were investigated. The coating strip forces of optical fiber were strongly increased with secondary coating thickness. But it did not change with time aging up to 90 days. The tensile strength and stress corrosion parameters of coated fiber were increased with time aging also but the increasing rate was quite different depending on the coating

Impact of sol aging on TiO_2 compact layer and photovoltaic performance of perovskite solar cell

Perovskite solar cells are known to have a power conversion efficiency dependent on subtle variation in chemical composition and crystal and microstructures of materials,processing conditions,and device fabrication procedures and conditions.The present work demonstrates such strong dependence of power conversion efficiency on a TiO_2 film made of the same sol with various aging time.A dense and conformal TiO_2 film was prepared by sol-gel method,and the influences of its surface morphology and thickness on performance of perovskite solar cells have been investigated.The surface morphology and thickness of the TiO_2 film were tuned by adjusting the aging time of sol,resulting in enhanced short-circuit current density and fill factor of the perovskite solar cells due to increased coverage and roughness of perovskite films,light refraction,and effective charge recombination blocking effect,which were verified by means of the light absorption spectra,photoluminescence of perovskite films with and without hole transport layer,cyclic voltammogram,and electrochemical impedance spectra.The cells with a dense and conformal TiO_2 compact layer derived from the sol aged for 4 h exhibit a power conversion efficiency of 15.7%,50% higher than the efficiency based on TiO_2 layer derived from 0 h aging sol and 3 times of the efficiency with TiO_2 layer made from 8 h aged sol.

Investigation of radionuclide～(63)Ni(Ⅱ) sequestration mechanisms on mordenite by batch and EXAFS spectroscopy study

The sorption behavior and microscopic sequestration mechanisms of radionuclide 63Ni（II） on mordenite as a function of aging time, ionic srength, initial 63Ni（II） concentrations, solid content and coexistent electrolyte ions were investigated by the combination of batch and EXAFS techniques. Macroscopic experiment results show that the sorption of 63Ni（II） is dependent on ionic strength at pH〈7, and independent of ionic strength at pH〉7. The sorption percentage of 63Ni（II） on mordenite increases with increasing solid content, while the sorption capacity decreases as solid content increases. The presence of different electrolyte ions can enhance or inhibit the sorption of Ni（II） on mordenite in various degrees. EXAFS analysis results of the sam- ples under three different ionic strengths suggest that the retained 63Ni（II） in these samples exists in an octahedral environment with six water ligands. In the initial period of rapid uptake, the sorption of 63Ni（II） is dominated by the formation of innersphere surface complexes. As aging time increases, 63Ni（II） sequestration behavior tends to be mainly controlled by the formation of Ni phyllosilicate coprecipitates and/or Ni（OH）2（s） precipitates. Results for the second shell fit of the sample prepared at an initial 63Ni（II） concentration of 100 mg/L indicate the possible formation of Ni polynuclear surface complexes. Both the macroscopic sorption data and the molecular level evidence of 63Ni（II） surface speciation at the mordenite/water interfaces should be factored into better predictions of the mobility and bioavailability of 63Ni（II） in environment mediums.