中国MH-Ni电池封口化成机理的研究进展

综述了国内近几年对化成技术的应用与研究的若干进展 ,并提出了作者的一些看法。

铅酸电池管式正极化成的机理

通过观察铅酸电池管式正极板化成过程中二氧化铅(PbO2)的形成和两种晶型的分布,研究管式极板的化成机理。管式极板的化成从筋条圆翼处开始,并逐步向筋条的上下方延伸,与电解液距离较近的部位化成开始得较早。筋条圆翼处生成红棕色α-PbO2,远离圆翼的位置为黑褐色β-PbO2。两种晶型PbO2的分布与孔内铅膏的p H值有关,并提出相应的化学/电化学反应式。

Formation mechanism of nanopores in dense films of anodic alumina

Constant-current anodization of pure aluminum was carried out in non-corrosive capacitor working electrolytes to study the formation mechanism of nanopores in the anodic oxide films.Through comparative experiments,nanopores are found in the anodic films formed in the electrolytes after high-temperature storage(HTS)at 130°C for 240 h.A comparison of the voltage-time curves suggests that the formation of nanopores results from the decrease in formation efficiency of anodic oxide films rather than the corrosion of the electrolytes.FT-IR and UV spectra analysis shows that carboxylate and ethylene glycol in electrolytes can easily react by esterification at high temperatures.Combining the electronic current theory and oxygen bubble mold effect,the change in electrolyte composition could increase the electronic current in the anodizing process.The electronic current decreases the formation efficiency of anodic oxide films,and oxygen bubbles accompanying electronic current lead to the formation of nanopores in the dense films.The continuous electronic current and oxygen bubbles are the prerequisites for the formation of porous anodic oxides rather than the traditional field-assisted dissolution model.

Formation mechanism of MgB_2 in 2LiBH_4+MgH_2 system for reversible hydrogen storage

The formation conditions of MgB2 in 2LiBH4 ＋ MgH2 system during dehydrogenation were investigated and its mechanism was discussed. The results show that direct decomposition of LiBH4 is suppressed under relative higher initial dehydrogenation pressure of 4.0×10^5 Pa, wherein LiBH4 reacts with Mg to yield MgB2, and 9.16% （mass fraction） hydrogen is released within 9.6 h at 450 ℃. However, under relatively lower initial dehydrogenation pressure of 1.0×10^2 Pa, LiBH4 decomposes independently instead of reacting with Mg, resulting in no formation of MgB2, and 7.91% hydrogen is desorbed within 5.2 h at 450 ℃. It is found that the dehydrogenation of 2LiBH4 ＋ MgH2 system proceeds more completely and more hydrogen desorption amount can be obtained within a definite time by forming MgB2. Furthermore, it is proposed that the formation process of MgB2 includes incubation period and nucleus growth process. Experimental results show that the formation process of MgB2, especially the incubation period, is promoted by increasing initial dehydrogenation pressure at constant temperature, and the incubation period is also influenced greatly by dehydrogenation temperature.

Down-regulation of Wnt Antagonist,SFRP1 in Colorectal Tumorigenesis

OBJECTIVE To assess the functional change of SFRP1 （secreted frizzled-related protein1）, in colorectal tumorigenesis. METHODS Immunohistochemical investigation and the semiquantitative reverse transcription-polymerase chain reaction （RT-PCR） were used to assess the expression of SFRP1, β-catenin （β-cat） and E-caderin （E-cad） in matched samples of normal colorectal mucosa, adenomas and cancers. RESULTS SFRP1 mRNA expression was down-regulated in the neoplasms, and abnormal expressions of β-cat and E-cad were found in colorectal adenomas and colorectal cancers. CONCLUSION Down-regulation of SFRP1 observed is consistent with its acting as a tumor suppressor gene in colorectal tumorigenesis.

Formability and strengthening mechanism of AA6061 tubular components under solid granule medium internal high pressure forming

A new technological process of tube forming was developed, namely solution treatment → granule medium internal high pressure forming → artificial aging. During this process, the mechanical properties of AA6061 tube can be adjusted by heat treatment to satisfy the process requirements and the processing method can also be realized by granule medium internal high pressure forming technology with the features of convenient implementation, low requirement to equipment and flexible design in product. Results show that, at a solution temperature of 560 ℃ and time of 120 min, the elongation of AA6061 increases by 313%, but the strength and the hardness dramatically decrease. At an aging temperature of 180 ℃ and time of 360 min, the strength and hardness of AA6061 alloy are recovered to the values of the as-received alloy. The maximum expansion ratio（MER） of AA6061 tube increases by 25.5% and the material properties of formed tube reach the performances of raw material.

Inorganic-organic hybrid photocatalysts:Syntheses,mechanisms,and applications

Inorganic-organic hybrid materials are promising for application in the field of photocatalysis because of their excellent properties.Therefore,their syntheses,mechanisms,and applications are reviewed in this paper.First,we introduce the role of inorganic-organic photocatalysts,their advantages and disadvantages,and their design principles.Second,we present the top-down and bottom-up synthesis methods of the hybrid materials.The interaction between inorganic and organic components in hybrid materials is discussed,followed by how to improve inorganic-organic photocatalysts.Third,the applications of hybrid materials in the field of photocatalysis,such as realizing hydrogen evolution,organic pollutant degradation,heavy metals and CO_(2) reduction,sterilization,and nitrogen fixation,are examined.Finally,the application prospects and development directions of inorganic-organic hybrid materials are explored and the unsolved problems are described.

Effects of Activation Atmospheres on Structure and Activity of Mo-based Catalyst for Synthesis of Higher Alcohols

Activated carbon supported Mo-based catalysts were prepared and reduced under different activation atmospheres, including pure H2, syngas （H2/CO=2/1）, and pure CO. The cat- alysts structures were characterized by X-ray diffraction , X-ray absorption fine structure, and in situ diffuse reflectance infrared Fourier transform spectroscopy. The catalytic per- formance for the higher alcohol synthesis from syngas was tested. The pure H2 treatment showed a high reduction capacity. The presence of a large amount of metallic CoO and low valence state Mo^φ＋ （0〈φ〈2） on the surface suggested a super activity for the CO dissoci- ation and hydrogenation, which promoted hydrocarbons formation and reduced the alcohol selectivity. In contrast, the pure CO-reduced catalyst had a low reduction degree. The Mo and Co species at the catalyst mainly existed in the form of Mo^4＋ and Co^2＋. The syngas- reduced catalyst showed the highest activity and selectivity for the higher alcohols synthesis. We suggest that the syngas treatment had an appropriate reduction capacity that is between those of pure H2 and pure CO and led to the coexistence of multivalent Co species as well as the enrichment of Mo~＋ on the catalyst＇s surface. The synergistic effects between these active species provided a better cooperativity and equilibrium between the CO dissociation, hydrogenation and CO insertion and thus contributed beneficially to the formation of higher alcohols.

Effective siRNA targets screening for human telomerase reverse transcriptase

AIM: To study the inhibitory effects of siRNAs targeting different hTERT sequences and to screen the effective siRNA sequence.METHODS: Five double-stranded siRNAs targeting coding and non-coding regions of hTERT gene were designed and synthesized by T7 transcription system in vitro. siRNA4sequence was screened by full length gene targeting technique and the rest of the siRNA sequences were selected randomly. After being purified by ethanol precipitation, the siRNAs were transfected to the human hepatocellular carcinoma cell (HepG2) by Lipofectamine 2000TM. At 48-72 h after siRNAs transfection, MTT assay,RT-PCR and Western-blot were applied to evaluate the effects of siRNAs on cell growth, mRNA and protein expression level of hTERT gene, respectively.RESULTS: Compared to the control cells, the cells treated with the five double-stranded siRNAs exhibited different degrees of inhibition of cell proliferation in a dose-dependent manner. siRNA2 and siRNA4, exhibited obvious effects of inhibiting hTERT mRNA and protein expression in HepG2cells.CONCLUSION: siRNAs targeting different hTERT sequences have significantly various inhibitory effects on hTERT gene expression. The siRNA sequence screened by full length gene targeting technique has comparable inhibitory effect with the rest siRNA sequences screened by random selection, suggesting that siRNAs and antisense oligonucleic acids may have the same effective target sites. Compared with chemical synthesis method,synthesizing double-stranded siRNA by T7 transcription system in vitro is a rapid, simple, and inexpensive method suitable for screening high-effect siRNA targeting site for specific gene.

Side force formation mechanism and change law of TBM center cutter

The center cutter of a hard rock tunnel boring machine(TBM) is installed on the cutterhead at a small radius and thus bears complex side force.Given this fact,the formation mechanism and change law of the side force suffered by the center cutter were studied.Based on the rock shear failure criterion in combination with the lateral rolling width,a model for predicting the average side force was set up.Besides,a numerical analysis model of the rock fragmentation of the center cutter was established,and the instantaneous load changing features were investigated.Results shows that the inner side of the center cutter can form lateral rolling annulus in rock during the rotary cutting process.The smaller the installation radius is,the greater the cutter side force will be.In a working condition,the side force of the innermost center cutter is 11.66 k N,while it decreases sharply when installation radius increases.Variation tends to be gentle when installation radius is larger than 500 mm,and the side force of the outermost center cutter is reduced to 0.74 k N.

Prospect of vapor phase catalytic H2O2 production by oxidation of water

Vapor phase catalytic hydrogen peroxide production by oxidation of water is possible by coupling the reaction with oxidation of an organic sacrificial reductant. It is potentially a safer process than direct synthesis from H2 and O2. Based on mechanistic information available mostly for liquid phase catalytic processes, feasible reaction mechanisms for such coupled reactions are proposed based on which desirable catalyst properties are identified. It is found that the surface-adsorbed oxygen bond is an important parameter for identifying desirable catalysts. Thermodynamics can be used to identify the types of organic oxidation reactions that can couple with water oxidation such that H2O2 formation becomes thermodynamically favorable. Reactions such as epoxidation of alkenes and selective oxidation of alkanes to alcohols cannot provide sufficient thermodynamic driving force, whereas oxidation of alcohols to aldehydes and to acids can. Finally, further research is suggested to identify catalytic properties important for H2O2 decomposition and for coupling selective oxidation of organic compounds to oxidation of H2O in order to facilitate development of H2O2 production coupled with selective organic oxidation.

Pore structure of ore granular media by computerized tomography image processing

The pore structure images of ore particles located at different heights of leaching column were scanned with X-ray computerized tomography (CT) scanner, the porosity and pore size distribution were calculated and the geometrical shape and connectivity of pores were analyzed based on image process method, and the three dimensional reconstruction of pore structure images was realized. The results show that the porosity of ore particles bed in leaching column is 42.92%, 41.72%, 39.34% at top, middle and bottom zone, respectively. Obviously it has spatial variability and decreases appreciably along the height of the column. The overall average porosity obtained by image processing is 41.33% while the porosity gotten from general measurement method in laboratory is 42.77% showing the results of both methods are consistent well. The pore structure of ore granular media is characterized as a dynamical space network composed of interconnected pore bodies and pore throats. The ratio of throats with equivalent diameter less than 1.91 mm to the total pores is 29.31%, and that of the large pores with equivalent diameter more than 5.73 mm is 2.90%.

Formation mechanisms of Ni-Al intermetallics during heat treatment of Ni coating on 6061 Al substrate

The formation mechanisms and growth kinetics of Al3 Ni and Al3Ni2 in Ni-Al diffusion couple prepared by electrodeposition of Ni on Al substrate were investigated. The nickel coating with 20 μm thickness was applied on 6061 aluminum alloy by direct current electroplating. The samples were then heat-treated for different durations at 450, 500 and 550 °C under argon atmosphere. The intermetallic phases were identified by means of scanning electron microscopy（SEM）, energy dispersive spectrometry（EDS） and X-ray diffraction（XRD）. The results showed that the formation of intermetallic phases consisted of two important steps. The first step was the lateral growth of intermetallic phase from separate sites, resulting in the formation of a continuous layer. The second step was the growth of the continuous intermetallic layer in the direction perpendicular to the interface. However, excessive increase in thickness of intermetallic phases led to the detachment of reaction products, i.e., Al3 Ni and Al3Ni2, from the substrate. It was also observed that aluminum was the dominant diffusing element during Al3 Ni growth, while nickel diffusion was dominant during Al3Ni2 growth. The growth kinetics of both Al3 Ni and Al3Ni2 phases obeyed a parabolic law.

Transforming catalysis to produce e‐fuels:Prospects and gaps

After short introducing the crucial role of e‐fuels to meet net‐zero emissions targets,this perspective paper discusses the differences between reactive catalysis(electro‐,photo‐and plasma‐catalysis,with focus on the first for conciseness)and thermal catalysis used at most.The main point is to evidence that to progress in producing e‐fuels,the gap is not in terms of scaling‐up and pilot testing,but rather in the fundamental needs to turn the current approach and methodologies to develop reactive catalysis,including from a mechanistic perspective,to go beyond the current methods largely derived from thermal catalysis.Developing thus new fundamental bases to understand reactive catalysis is the challenge to accelerate the progress in this area to enable the potential role towards a sustainable net‐zero emissions future.Some novel aspects are highlighted,but the general aim is rather to stimulate discussion in rethinking catalysis from an alternative perspective.

Microscopic mechanism of perfluorocarbon gas formation in aluminum electrolysis process

In view of the unclear cause of perfluorocarbons(PFCs)emission in the anode effect stage of aluminum electrolysis,the microscopic formation mechanism of PFCs was studied by density functional theory calculation and X-ray photoelectron spectroscopy(XPS).It is found that the discharge of fluorine containing anions([F]−)on carbon anode first causes the substitution of C—H by C—F and further results in the saturation of aromatic C—C bonds,leading to the appearance of—CF_(3)or—C_(2)F_(5)group through six-carbon-ring opening.Elimination of—CF_(3)and—C_(2)F_(5) with F atom could be a likely mechanism of CF_(4) and C_(2)F_(6) formation.XPS results confirm that different types of—CF_(x) group can be formed on anode surface during electrolysis,and the possibility that[F]−discharges continuously at the C edge and finally forms different C—F bonds in quantum mechanical calculation was verified.

Erythropoietin in liver cirrhosis: Two questions without answers

TO THE EDITORIn a recent paper[1], and in a subsequent letter[2], Tacke et al. reported the investigation of plasma erythropoietin (Epo) levels in patients affected by chronic liver disease of various aetiologies. The authors also compared[2] their data to our previous work[3]. The results show a substantial agreement but also some important differences between the two works. We would like to highlight, from our point of view, this issue. Both the papers demonstrated increased Epo values in anaemic cirrhotic subjects when compared to healthy controls and non-anemic patients with liver disease.

The research on the thermal destruction of environment and controlling techniques of the No.4 outcrops fire in Haibaoqing

The coal fire is one of very serious disasters in natural, not only amount of coal resources was burned and some ecological environment problems such as ground subsidence, acid rain, pollution and vegetation died were caused serious. The No.4 coal seam outcrops fire in Haibaoqing was take as research object, based on the existing theory of mechanism and characteristics of coal outcrop fires, a new fire-fighting composite gel is applicated which fits in with extinguishment of outcrop coal fires well. The technology has many advantages in extinguishing coal fires including isolating the coal from oxygen and lowering the temperature of the high-temperature coal and rock. The structure and chemical composition as well as fires-fighting properties of the composite gel is analyzed profoundly, as a result, reduce and stop the environment destruction caused by the coal fire.

Perspectives in application of biosensors for the modernization of traditional Chinese medicine

Biosensor is an instrument which is sensitive to biological material and converts its concentration into electrical signals.Organisms such as enzymes, antibodies, tissues, cells and so on can selectively identify specific substances. Thesemolecular recognition functions can be combined with the target, such as the binding of antibodies and antigens, and thebinding of enzymes to the substrate through the recognition process. Biosensor has the advantages of high specificity,high sensitivity, fast reaction speed, low cost and easy operation. It has wide application prospect in food, pharmacy,chemical industry, clinical examination, biomedicine, environmental monitoring and so on, especially as a newtechnology means, in the field of modern herbal medicine research influence. Studies have demonstrated that thebiosensing technology has been applied to, traditional Chinese medicine （TCM） targets, isolation and purification ofTCM, the mechanism of TCM, quality control of TCM, the active ingredients detection of TCM and other basicresearches. Biosensor technology has made an important contribution to the research of modern herbal medicine, and hasbecome a Hot-spot in future research.

General trends in Horiuti-Polanyi mechanism vs non-Horiuti-Polanyi mechanism for water formation on transition metal surfaces

It is generally acknowledged in heterogeneous catalysis that hydrogenation follows the so-called Horiuti-Polanyi(HP) mechanism. In this work, a thorough investigation of the mechanism of hydrogenation of hydroxyl groups and O catalyzed by a series of transition metals was carried out through density functional theory calculations, as surface hydroxyls and O are very common species in many catalytic systems. It is found that different metal catalysts exhibit different mechanisms. On some metal catalysts, the non-HP mechanism is preferred, whereas the classic HP mechanism is favored on other catalysts. Detailed analyses of the metal-dependent mechanism shows that the activity toward the dissociation of H2 decides which mechanism is preferred. On active catalysts, such as Ni and Pt, H2 prefers to dissociate with strong H adsorption energies, which lead to the classic HP mechanism being favored. On inactive surfaces, on the other hand, the adsorption of H is weak, which results in the non-HP mechanism being preferred. The parameter η, which is a structural descriptor, was defined to understand the different mechanisms.

Ferronickel preparation using Ni-Fe co-deposition process

Nucleation mechanism and technological process for Ni-Fe co-deposition with a relatively high Fe^(2+)concentration surrounded were described,and the effects of Fe^(2+) concentration,solution pH,temperature,and sodium dodecyl sulfonate concentration were investigated.Electrochemical experiments demonstrate that iron's electrodeposition plays a leading role in the Ni-Fe co-deposition process,and the co-deposition nucleation mechanism accords with a progressive nucleation.Temperature increase does favor in increasing nickel content in the ferronickel(Ni-Fe co-deposition products),while Fe^(2+) concentration increase does not.When solution pH is higher than 3.5,nickel content in the ferronickel decreases with pH because of the hydrolysis of Fe^(2+).With the current density of 180 A/m^2,Na_2SO_4 concentration of 100 g/L and Ni^(2+) concentration of 60 g/L,a smooth ferronickel deposit containing 96.21% Ni can be obtained under the conditions of temperature of 60 °C,Fe^(2+) concentration of 0.3 g/L,solution pH of 3 and sodium dodecyl sulfonate concentration of 40 mg/L.