Mechanical behaviors of warm and ice-rich frozen soil stabilized with sulphoaluminate cement

The warm and ice-rich frozen soil is characterized by high unfrozen water content, low shear strength and large compressibility, which is unreliable to meet the stability requirements of engineering infrastructures and foundations in permafrost regions. In this study, a novel approach for stabilizing the warm and ice-rich frozen soil with sulphoaluminate cement was proposed based on chemical stabilization. The mechanical behaviors of the stabilized soil, such as strength and stress-strain relationship, were investigated through a series of triaxial compression tests conducted at -1.0℃, and the mechanism of strength variations of the stabilized soil was also explained based on scanning electron microscope test. The investigations indicated that the strength of stabilized soil to resist failure has been improved, and the linear Mohr-Coulomb criteria can accurately reflect the shear strength of stabilized soil under various applied confining pressure. The increase in both curing age and cement mixing ratio were favorable to the growth of cohesion and internal friction angle. More importantly, the strength improvement mechanism of the stabilized soil is attributed to the formation of structural skeleton and the generation of cementitious hydration products within itself. Therefore, the investigations conducted in this study provide valuable references for chemical stabilization of warm and ice-rich frozen ground, thereby providing a basis for in-situ ground improvement for reinforcing warm and ice-rich permafrost foundations by soil-cement column installation.

Experimental and numerical interpretation on composite foundation consisting of soil-cement column within warm and ice-rich frozen soil

Affected by climate warming and anthropogenic disturbances, the thermo-mechanical stability of warm and ice-rich frozen ground along the Qinghai-Tibet engineering corridor(QTEC) is continuously decreased, which may delay the construction of major projects in the future. In this study, based on chemical stabilization of warm and icerich frozen ground, the soil-cement column(SCC) for ground improvement was recommended to reinforce the foundations in warm and ice-rich permafrost regions. To explore the validity of countermeasures mentioned above, both the original foundation and the composite foundation consisting of SCC with soil temperature of -1.0℃ were prepared in the laboratory, and then the plate loading tests were carried out. The laboratory investigations indicated that the bearing capacity of composite foundation consisting of SCC was higher than that of original foundation, and the total deformation of original foundation was greater than that of composite foundation, meaning that overall stability of foundation with warm and ice-rich frozen soil can be improved by SCC installation. Meanwhile, a numerical model considering the interface interaction between frozen soil and SCC was established for interpretating the bearing mechanism of composite foundation. The numerical investigations revealed that the SCC within composite foundation was responsible for the more applied load, and the applied load can be delivered to deeper zone in depth due to the SCC installation, which was favorable for improving the bearing characteristic of composite foundation. The investigations provide the valuable guideline for the choice of engineering supporting techniques to major projects within the QTEC.

Effect of Molybdenum Doping on Oxygen Permeation Properties and Chemical Stability of SrCo0.8Fe0.2O3-δ

The phase composition, microstructure, thermal expansion coefficients, oxygen permeation properties and chemical stability of SrCo0.8Fe0.2O3-δ （SCFM） were investigated and compared with those of SrCo0.8Fe0.2O3-δ（SCF）. Single phase SCFM was successfully prepared by a combined EDTA-citric method. SCFM shows a lower thermal expansion coefficient （24× 10^-6-29× 10^-6/K） than SCF between 500 and 1050 ℃, indicating a more stable structure. SCFM shows a high oxygen permeation flux, although the oxygen flux of SCFM decreases slightly because of Mo dopant. Furthermore, it was demonstrated that the doping of Mo in SCF can prevent the order-disorder transition and improves the chemical stability to CO2.

Chemical stability of doped BaCeO_3-BaZrO_3 solid solutions in different atmospheres

BaCe0.45Zr0.45M0.1O3-δ （M=Y, In） and BaCe0.9Y0.1O3-δ were prepared through the conventional solid state reaction route. The chemical stability was investigated in hydrogen, carbon dioxide, and boiling water. Crystalline phase and microsa-ucture of the proton conductor before and after stability test were measured with X-ray diffraction （XRD） and scanning electron microscopy （SEM）, respectively. The results showed that all materials were quite stable in H2 atmosphere. In CO2 atmosphere, BaCe0.45Zr0.45M0.1O3-δ（M=Y, In） were relatively stable, while Bafe0.9Y0.1O3-δ decomposed. In boiling water, BaCe0.9Y0.1O3-δ was quickly decomposed into Ba（OH）2 and corresponding oxide. BaCe0.45Zr0.45M0.1O3-δ slightly reacted with boiling water and some amorphous phases were formed. However, BaCe0.45Zr0.45In0.1O3-δ was observed to exhibit better stability than BaCe0.45Zr0.45Y0.1O3-δ in water. The experimental results were interpreted in terms of thermodynamic data and tolerance factor.

Glass-forming Ability and Chemical Stability of Magneto-optical Glass Heavily Doped with Rare Earth Oxide

The glass-forming region of B2O3-Al2O3-SiO2 （BAS） glass heavily doped with rare earth oxides was investigated by an effective method, and the chemical stability was investigated by powder method. Influences of rare earth oxides on the glass-forming ability and the chemical stability of the BAS glass were also discussed. The experimental results show that the BAS glass-forming region expands firstly with the increase of the Tb2O3 content up to 30mol% and then shrinks. The acid-resistant capacity of the BAS glass doped with rare earth oxides is the lowest, the water-resistant capacity is secondary, and the alkali-resistant capacity is the best. Besides, the glass chemical stability can be improved by doping appropriate amount of rare earth oxides. Moreover, the stronger the ionic polarization ability of the rare earth ions is, the better the chemical stability of the BAS glass will be.

Improvements of marine clay slurries using chemicale-physical combined method(CPCM)

In this paper, the effectiveness, applicability and validity of chemicalephysical combined methods（CPCMs） for treatment of marine clay （MC） slurries were evaluated. The method CPCM1 combineschemical stabilization and vacuum preloading （VP）, while CPCM2 is similar to CPCM1 but includes boththe application of surcharge and use of geo-bags to provide confinement during surcharge preloading.The key advantage of CPCM2 using geo-bags is that the surcharge can be immediately applied on thechemically stabilized slurries. Two types of geo-bags were investigated under simulated land filling anddyke conditions, respectively. The test results show that the shear strength （cu） of treated slurry byCPCM2 is generally much higher than that by CPCM1. Besides, the use of CPCM2 can significantly reducethe treatment time due to the short drainage paths created by geo-bags. Overall, CPCM2 allows fasterconsolidation and higher preloading that help to achieve higher mechanical properties of the stabilizedslurry. There are consistent relationships between cU and water content of slurries treated by CPCM2.Several important observations were also made based on comparisons of experimental data. 2015 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting byElsevier B.V. All rights reserved.

NON-EQUILIBRIUM STATIONARY STATE IN CHEMICAL REACTION OF SiO_2/Fe AT INTERFACE OF SLAG/METAL AND ITS STABILITY DURING ARC WELDING

For characteristics of open and far from thermodynamic equilibrium in welding chemical reaction, a new kind of quantitative method, which is used to analyze direction and extent for chemical reaction of SiO2/Fe during quasi-steady state period, is introduced with the concept of non-equilibrium stationary state. The main idea is based on thermodynamic driving forces, which result in non-zero thermodynamic fluxes and lead to chemical reaction far away from thermodynamic equilibrium. There exists certain dynamic equilibrium relationship between rates of diffusion fluxes in liquid phase of reactants or products and the rate equation of chemical reaction when welding is in quasi-steady state. As result of this, a group of non-linear equations containing concentrations of all substances at interface of slag/liquid-metal may be established. Moreover the stability of this non-equilibrium stationary state is discussed using dissipative structure theory and it is concluded theoretically that this non-equilibrium stationary state for welding chemical reaction is of stability.

A new fluorescent particle prepared by chemical stabilized phycobilisome

Natural phycobilisomes （PBSs） were isolated and purified from a red macroalga, Polysiphonia urceolata, by multi-step of sucrose gradient centrifugation, and were chemically stabilized by small molecule cross-linker formaldehyde. The stabilized PBSs showed similar absorption and fluorescent properties at room temperature compared to natural PBSs and kept a steady F672/F580 value during more than 3 months of storage in 0.45 mol/L phosphate buffer （pH 6.8） or at low temperature at 77 K. The stabilized PBS migrated as a single band at mild PAGE and in 14-18 h of sucrose gradient centrifugation. All these characters indicated that the stabilized PBSs were stable, soluble, homogenous fluorescent particles with favorable spectroscopic features prepared under present conditions.

Experimental Evaluation and Stabilization of Regional Kaolinite Clay and Mineral Soil by Use of Lime and Cement

Soil stabilization is a set of measurements and treatment which apply to soils. The main reason of the measurements is to prepare a soil type which covers the geotechnical engineering necessities like shear resistance, bearing capacity, compressibility, etc.. Stabilization methods are generally limited into mechanical and chemical properties of Kaolinite soil. Actually, the first method is by use of stabilization binding agents and the second one is done via construction machines like rollers and tampers. Generally, civil projects or earth projects are mostly getting along with clay soils. Therefore, a sufficient knowledge about the soil property is needed due to their special behavior beside sufficient stabilization methods. In the research, a comparison between lime and cement stabilization agents via proctor standard test is conducted to evaluate mechanical and chemical stabilization methods encountered clay soil sample with kaolinite mineral from Fars region, Iran.

Physico-Chemical and Microbiological Study for the Stability of Phenytoin Sodium Extemporaneously Compounded Suspension in Saudi Arabia Hospitals

Epilepsy is a chronic and the fourth most common neurological disorder which affects people of all age groups. Recently research and awareness on epilepsy-related deaths have rapidly grown over the past two decades. Many previous studies are attributed to the guidelines that apprise health care professionals in handling these deaths, but there is a relative scarcity of information accessible for clinicians and pharmacists who are responsible for manufacturing or preparing the extemporaneous anti-epileptic suspensions in the hospitals. Mostly in partial seizures, phenytoin is one of the first-choice drugs. In Saudi Arabian hospitals, the extemporaneous preparation of phenytoin suspension is common, but the hot climatic weather in Saudi Arabia possesses stability problems that should be tackled as the prepared suspension should pass all the stability tests to ensure uniform dosage of the extemporaneous formulation. In the current study, the commercial capsules were used to prepare the oral phenytoin sodium extemporaneous suspension. The physical, chemical and microbiological stability of phenytoin sodium suspension is analyzed at various temperatures.

Crystal Phases and Chemical Stabilities of YSi2 Powders Fabricated from Low and High Purity Si and Y Powders

Y-Si compounds with the composition of Y:Si = 1:2 were fabricated using Yttrium and Silicon raw powders with low and high purity in various atmospheres and temperatures. Although the latest Y-Si phase diagram shows that the α- and β-YSi2 phases are the stable phases for the stoichiometric composition of Y:Si = 1:2, the current experimental results suggest that the high temperature phase with the hexagonal structure, β-Y3Si5, would be the stable phase for this composition, and that the high temperature phase with the orthorhombic structure, β-YSi2, would be the meta-stable phase with high oxygen impurity content. It was demonstrated that YSi2 powders possess much superior chemical stability than Yttrium metal. It was found that the best dispersing solvent was 2-propanol for YSi2 powder.

Biomimetic chitin hydrogel via chemical transformation

Chitin hydrogel has been recognized as a promising material for various biomedical applications because of its biocompatibility and biodegradability.However,the fabrication of strong chitin hydrogel remains a big challenge because of the insolubility of chitin in many solvents and the reduced chain length of chitin regenerated from solutions.We herein introduce the fabrication of chitin hydrogel with biomimetic structure through the chemical transformation of chitosan,which is a water-soluble deacetylated derivative of chitin.The reacetylation of the amino group in chitosan endows the obtained chitin hydrogel with outstanding resistance to swelling,degradation,extreme temperature and pH conditions,and organic solvents.The chitin hydrogel has excellent mechanical properties while retaining a high water content(more than 95 wt.%).It also shows excellent antifouling performance that it resists the adhesion of proteins,bacteria,blood,and cells.Moreover,as the initial chitosan solution can be feasibly frozen and templated by ice crystals,the chitin hydrogel structure can be either nacre-like or wood-like depending on the freezing method of the precursory chitosan solution.Owing to these anisotropic structures,such chitin hydrogel can exhibit anisotropic mechanics and mass transfer capabilities.The current work provides a rational strategy to fabricate chitin hydrogels and paves the way for its practical applications as a superior biomedical material.

Enhanced H_(2) permeation and CO_(2) tolerance of self-assembled ceramic-metal-ceramic BZCYYb-Ni-CeO_(2) hybrid membrane for hydrogen separation

Perovskite-type mixed protonic-electronic conducting membranes have attracted attention because of their ability to separate and purify hydrogen from a mixture of gases generated by industrial-scale steam reforming based on an ion diffusion mechanism.Exploring cost-effective membrane materials that can achieve both high H_(2) permeability and strong CO_(2)-tolerant chemical stability has been a major challenge for industrial applications.Herein,we constructed a triple phase(ceramic-metal-ceramic)membrane composed of a perovskite ceramic phase BaZr_(0.1)Ce_(0.7)Y_(0.1)Yb_(0.1)O_(3-δ)(BZCYYb),Ni metal phase and a fluorite ceramic phase CeO_(2).Under H_(2) atmosphere,Ni metal in-situ exsolved from the oxide grains,and decorated the grain surface and boundary,thus the electronic conductivity and hydrogen separation performance can be promoted.The BZCYYbNi-CeO_(2)hybrid membrane achieved an exceptional hydrogen separation performance of 0.53 mL min^(-1)cm^(-2) at 800℃ under a 10 vol% H_(2) atmosphere,surpassing all other perovskite membranes reported to date.Furthermore,the CeO_(2) phase incorporated into the BZCYYb-Ni effectively improved the CO_(2)-tolerant chemical stability.The BZCYYbNi-CeO_(2) membrane exhibited outstanding long-term stability for at least 80 h at 700℃ under 10 vol%CO_(2)-10 vol%H_(2).The success of hybrid membrane construction creates a new direction for simultaneously improving their hydrogen separation performance and CO_(2) resistance stability.

Polymer-to-Monomers Chemically Recyclable Poly(imide-imine)Plastics with Extreme-Condition Resistance and Flame Retardancy

Polyimides are a family of high-tech plastics that have irreplaceable applications in the fields of aerospace,defense,and opto-electronics,but polyimides are difficult to be reprocessed and recycled at the end of their service life,resulting in a significant waste of resources.Hence,it is of great significance to develop recyclable polyimides with comparable properties to the commercial products.Herein,we report a novel polymer-to-monomers chemically recyclable poly(imide-imine)(PtM-CR-PII)plastic,synthesized by cross-linking the amine-terminated aromatic bisimide monomer and the hexa-vanillin terminated cyclophosphazene monomer via dynamic imine bonds.The PtM-CR-PII plastic exhibits comparable mechanical and thermal properties as well as chemical stability to the commercial polyimides.The PtM-CR-PII plastic possesses a high Young’s modulus of≈3.2 GPa and a tensile strength as high as≈108 MPa,which also exhibits high thermal stability with a glass transition temperature of≈220℃.Moreover,the PtM-CR-PII plastic exhibits outstanding waterproofness,acid/alkali-resistance,and solvent-resistance,its appearance and mechanical properties can be well maintained after long-term soaking in water,highly concentrated acid and base,and various organic solvents.Furthermore,the cyclophosphazene moieties endow the PtM-CR-PII plastic with excellent flame retardancy.The PtM-CR-PII plastic exhibits the highest UL-94 flame-retarding rating of V-0 and a limiting oxygen index(LOI)value of 45.5%.Importantly,the PtM-CR-PII plastic can be depolymerized in an organic solvents-acid mixture medium at room temperature,allowing easy separation and recovery of both monomers in high purity.The recovered pure monomers can be used to regenerate new PtM-CR-PII plastics,enabling sustainable polymer-monomers-polymer circulation.

A new method of inhibiting pollutant release from source water reservoir sediment by adding chemical stabilization agents combined with water-lifting aerator

Source water reservoirs easily become thermally and dynamically stratified. Internal pollution released from reservoir sediments is the main cause of water quality problems. To mitigate the internal pollution more effectively, a new method, which combined chemical stabilization with water lifting aerator （WLA） technology, was proposed and its effciency in inhibiting pollutant release was studied by controlled sediment-water interface experiments. The results showed that this new method can inhibit pollutant release from sediment effectively. The values of mean effciency （E） in different reactors 2#–5# （1# with no agent, 2# 10 mg/L polymeric aluminum chloride （PAC） was added, 3# 20 mg/L PAC was added, 4# 30 mg/L PAC was added, 5# 20 mg/L PAC and 0.2 mg/L palyacrylamide （PAM） were added） for PO43- were 35.0%, 43.9%, 50.4% and 63.6%, respectively. This showed that the higher the PAC concentration was, the better the inhibiting effciency was, and PAM addition strengthened the inhibiting effciency significantly. For Fe2＋, the corresponding values of E for the reactors 2#–5# were 22.9%, 47.2%, 34.3% and 46.2%, respectively. The inhibiting effect of PAC and PAM on Mn release remained positive for a relatively short time, about 10 days, and was not so effective as for PO43- and Fe2＋. The average effciencies in inhibiting the release of UV254 were 35.3%, 25.9%, 35.5%, 38.9% and 39.5% for reactors 2#–5#, respectively. The inhibiting mechanisms of the agents for different pollutants varied among the conditions and should be studied further.

Oxygen permeability and CO_2-tolerance of Ce_(0.8)Gd_(0.2)O_(2-δ)-Ln BaCo_2O_(5+δ) dual-phase membranes

A series of oxygen permeable dual-phase composite oxides 60 wt% Ce0.8Gd0.2O2-δ-40 wt% LnBaCo2O5＋δ （CGO-LBCO, Ln = La, Pr, Nd, Sin, Gd and Y） were synthesized through a sol-gel route and effects of the Ln3＋ cations on their phase structure, oxygen permeability and chemical stability against CO2 were investigated systemically by XRD, SEM, TG-DSC and oxygen permeation experiments. XRD patterns reveal that the larger Ln3＋ cations （La3＋, Pr3＋ and Nd3＋） successfully stabilized the double-layered perovskite structure of sintered LBCO, while the smaller ones （Sm3＋, Gd3＋, and Y3＋） resulted in the partial decomposition of LBCO with some impurities formed. CGO-PBCO yields the highest oxygen permeation flux, reaching 2.8× 10^-7 mol.s-1.cm-2 at 925 ℃ with 1 mm thickness under air/He gradient. The TG-DSC profiles in 20 mol% CO2/N2 and oxygen permeability experiments with CO2 as sweep gas show that CGO-YBCO demonstrates the best chemical stability against CO2, possibly due to its minimum basicity. The stable oxygen permeation flux of CGO-YBCO under CO2 atmosphere reveals its potential application in the oxy-fuel combustion route for CO2 capture.

Three-Dimensional Cu-Ni Composite Superamphiphobic Surface via Electrodeposition and Fluorosilane Modification

A superamphiphobic(SAP)surface was fabricated by electrodepositing Cu-Ni micro-nano particles on aluminum substrate and modifying via 1 H,1 H,2 H,2 Hperfluorodecyltrimethoxysilane.Scanning electron microscopy,X-ray diffraction,energydispersive X-ray spectroscopy,and Fourier-transform infrared spectroscopy were employed to investigate the morphology and chemical composition.The results showed that the SAP surface had three-dimensional micro-nano structures and exhibited a maximum water contact angle of 160.0°,oil contact angle of 151.6°,a minimum water slide angle of 0°and oil slide angle of 9°.The mechanical strength and chemical stability of the SAP surface were tested further.The experimental results showed that the SAP surface presented excellent resistance to wear,prominent acid-resistance and alkali-resistance,self-cleaning and anti-fouling properties.

Preparation of Stable CaS∶Eu^(2+), Tm^(3+) Phosphor

Different fluxes were used to synthesize long persistence phosphors, calcium sulfides activated by Eu 2+ and Tm 3+ , by convenient solid state method. The phosphor using NH 4F as a flux has good crystallinity and large particle size, its stability against water and other atmospheric components is enhanced, and its afterglow is longer and fluorescent intensity is more intense than those of the phosphor using NH 4Cl as flux. Their PL intensities varied with time in moist air were measured, no remarkable change was found for those prepared with NH 4F flux in contrast with NH 4Cl as flux. So using NH 4F as flux is a good method to enhance the stability of alkaline earth sulfides.

COPOLYMERIZATION OF PROPYLENE WITH HINDERED PIPERIDINE MONOMER OVER A HIGH ACTIVITY SUPPORTED ZIEGLER-NATTA CATALYST

Copolymerization of propylene and hindered piperidine monomers was carried out over a high activity supported Ziegler-Natta catalyst, using Al(C2H5)(3) as cocatalyst. Factors which affect the copolymerization were studied, The copolymers exhibited high light stability without adding extra light stabilizers. A self-stabilized polypropylene was prepared.

A Comparative Study of the Performance of Symmetric and Asymmetric Mixed-conducting Membranes

According to the configuration,mixed-conducting membranes are classified as symmetric membranes and asymmetric membranes consisting of a thin dense layer and a porous support.In this study,these two kinds of SrCo0.4Fe0.5Zr0.1O3-δ oxide-based membranes were systematically compared in terms of oxygen permeability and chemical stability,and their differences were elucidated by means of the theoretical calculation.For the oxygen permeability,the asymmetric membrane was greater than the symmetric membrane due to the significant decrease of bulk diffusion resistance in the thin dense layer of the asymmetric membrane.In regard to the chemical stability,the increase of oxygen partial pressure on the asymmetric membrane surface at CH4 side produced the stable time of over 1032h in partial oxidation of methane at 1123K,while the symmetric membrane was only of 528h.This study demonstrated that the asymmetric membrane was a promising geometrical configuration for the practical application.