Catalytic Effect of Two Shapes of Nano‐Fe2O3 on Hexanitrohexaazaisowurtzitane Using a Non‐Isothermal Decomposition Kinetic Method

Nanosized Fe₂O₃ particles (nano‐Fe₂O₃) with two shapes (tetrakaidecahedral and grainy) were synthesized by hydrothermal methods. The morphologies and structures were characterized using a combination of experimental techniques including X‐ray diffraction (XRD) and scanning electron microscopy (SEM). Two composites containing CL‐20 (hexanitrohexaazaisowurtzitane, HNIW) and tetrakaidecahedral nano‐Fe₂O₃ [nmT‐Fe₂O₃/CL‐20] or grainy nano‐Fe₂O₃/CL‐20 (nmG‐Fe₂O₃/CL‐20) were prepared. The thermal behaviors of the two composites and pure CL‐20 were investigated using differential scanning calorimetry (DSC). Non‐isothermal decomposition kinetic parameters and the thermal decomposition mechanism of the two composites and CL‐20 were obtained. The apparent activation energy (E_a) of the main thermal decomposition reaction of CL‐20, nmT‐Fe₂O₃/CL‐20 and nmG‐Fe₂O₃/CL‐20 are 181.94, 179.17, and 176.18 kJ mol⁻¹, respectively. The thermal decomposition mechanism of CL‐20 as well as nmT‐Fe₂O₃/CL‐20 was controlled by the Avrami‐Erofeev equation (n=2/5) assumed as random nucleation and subsequent growth, while, the reaction mechanism of the composite nmG‐Fe₂O₃/CL‐20 was controlled by the Mample Power law (n=1/2). The reason for this difference may be due to the different morphology and particle size of the two nano‐Fe₂O₃ particles.     

Synthesis and characterization of novel core‐shell magnetic nanogels based on 2‐acrylamido‐2‐methylpropane sulfonic acid in aqueous media

Ultrafine well‐dispersed Fe₃O₄ magnetic nanoparticles were directly prepared in aqueous solution using controlled coprecipitation method. The synthesis of Fe₃O₄/poly (2‐acrylamido‐2‐methylpropane sulfonic acid) (PAMPS), Fe₃O₄/poly (acrylamide‐co‐2‐acrylamido‐2‐methylpropane sulfonic acid) poly(AM‐co‐AMPS) and Fe₃O₄/poly (acrylic acid‐co‐2‐acrylamido‐2‐methylpropane sulfonic acid) poly(AA‐co‐AMPS) ‐core/shell nanogels are reported. The nanogels were prepared via crosslinking copolymerization of 2‐acrylamido‐2‐methylpropane sulfonic acid, acrylamide and acrylic acid monomers in the presence of Fe₃O₄ nanoparticles, N,N′‐methylenebisacrylamide (MBA) as a crosslinker, N,N,N′,N′‐tetramethylethylenediamine (TEMED) and potassium peroxydisulfate (KPS) as redox initiator system. The results of FTIR and ¹H‐NMR spectra indicated that the compositions of the prepared nanogels are consistent with the designed structure. X‐ray powder diffraction (XRD) and transmission electron microscope (TEM) measurements were used to determine the size of both magnetite and stabilized polymer coated magnetite nanoparticles. The data showed that the mean particle size of synthesized magnetite (Fe₃O₄) nanoparticles was about 10 nm. The diameter of the stabilized polymer coated Fe₃O₄ nanogels ranged from 50 to 250 nm based on polymer type. TEM micrographs proved that nanogels possess the spherical morphology before and after swelling. These nanogels exhibited pH‐induced phase transition due to protonation of AMPS copolymer chains. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

The Catalytic Asymmetric Addition of Diethylzinc to N‐(Diphenylphosphinoyl) Imines Catalyzed by Cu(OTf)2‐Chiral N‐(Binaphthyl‐2‐yl)thiophosphoramide Ligands

Chiral N‐(binaphthyl‐2‐yl)thiophosphoramide L7 [O,O‐diethyl 2′‐(ethylamino)‐1,1′‐binaphthyl‐2‐ylamidothiophosphate] prepared from the reaction of diethyl chlorothiophosphate with (R)‐(+)‐N‐ethyl‐1,1′‐binaphthyl‐2,2′‐diamine was used as a catalytic chiral ligand in the first Cu(OTf)₂‐promoted catalytic asymmetric addition of diethylzinc to N‐(diphenylphosphinoyl) imines in which ~85% ee can be realized.     

Catalytic synthesis of toluene‐2,4‐diisocyanate from dimethyl carbonate

The process for catalytic synthesis of toluene‐2,4‐diisocyanate (TDI) from dimethyl carbonate (DMC) consists of two steps. Starting from the catalytic reaction between toluene‐2,4‐diamine (TDA) and DMC, dimethyl toluene‐2,4‐dicarbamate (TDC) is formed, and then decomposed to TDI. For the first step, the yield of TDC is 53.5% at a temperature of 250 °C, over Zn(OAc)₂/α–Al₂O₃ catalyst. For the second step, the yield of TDI is 92.6% at temperatures of 250–270 °C and under pressure of 2.7 kPa, over uranyl zinc acetate catalyst, when di‐n‐octyl sebacate(DOS) is used as heat‐carrier, and a mixture of tetrahydrofuran (THF) and nitrobenzene is used as solvent. © 2001 Society of Chemical Industry     

Catalytic Oxidative Dehydrogenation of n‐Butane on Gallium Nitride‐Containing Titanosilicate Catalyst

GaN‐containing titanosilicate catalysts were used for the first time for the oxidative dehydrogenation (ODH) of n‐butane at a relatively low reaction temperature (460 °C). Commercially available GaN powder with a wurtzite crystal structure showed superior reactivity and stability for the ODH of n‐butane. The catalytic property of GaN catalyst for ODH strongly depends on the GaN particle size. The effects of the GaN weight percentage and GaN particle size on the catalytic performance are investigated in a fixed bed reactor. Based on the physicochemical properties of the catalyst characterized via TEM, DLS, N₂ adsorption‐desorption, XRF, O₂‐TPD, XRD, XPS, and in‐situ FTIR, the textural and structural properties of catalyst were obtained. The catalytic results reveal that the presence of GaN increases the activity of the catalysts, indicating that GaN can be used as a new active phase for the ODH of n‐butane. XRD, XPS, O₂‐TPD, DLS, TEM, and in‐situ FTIR results show that activated O species exist on the surface of the GaN catalyst and enhance the catalytic performance with a decreasing GaN particle size, suggesting that smaller GaN particles possess a remarkable capability to activate O species in O₂ and C‐H bonds in light alkanes.     

Catalytic Effect of CeO2‐Stabilized ZrO2 Ceramics with Strong Shock‐Heated Mono‐ and Di‐Atomic Gases

The reducibility of synthesized ceria‐stabilized zirconia (CSZ) with strong shock‐heated test gases is investigated. Free piston‐driven shock tube operating at hypersonic speed at Mach number of 6–8 has been used to heat the ultrahigh pure test gases like Ar to ~12800 K, N₂ to ~7960 K, and O₂ to ~5500 K at a medium reflected shock pressure (5.0–7.4 MPa) for a short duration of 1–2 ms test time. Under this extreme thermodynamic condition, test gases undergo real gas effects. The structural and spectroscopic investigations of CSZ (Ce₂Zr₂O₈) after interaction with shock‐heated argon gas show pyrochlore structure of Ce₂Zr₂O_7?δ which is observed to be black in color. In presence of shock‐heated N₂ gas, CSZ remains in fluorite structure by changing its color to pale green as nitrogen atoms fill oxygen vacancies. After O₂ interaction with the shock wave, CSZ remains pale yellow but the X‐ray diffraction pattern shows the presence of monoclinic ZrO₂ due to phase separation. During reduction process, Ce⁴⁺ has been reduced to Ce³⁺ which is an unusual effect. In this study, the catalytic and surface recombination effects of CSZ due to shock‐induced compression in millisecond timescale are presented.     

Mid‐IR transparent TeO2‐TiO2‐La2O3 glass and its crystallization behavior for photonic applications

In this report, effect of enhanced rare earth (La₂O₃) concentration on substitution of TeO₂ within ternary TeO₂‐TiO₂‐La₂O₃ (TTL) glass system has been studied with respect to its thermal, structural, mechanical, optical, and crystallization properties with an aim to achieve glass and glass‐ceramics having rare‐earth‐rich crystalline phase for nonlinear optical and infrared photonic applications. DSC analysis (10°C/min) demonstrates a progressive increase in glass‐transition temperature (T_g) from 359 to 452°C with the increase in La₂O₃ content. Continuous glass network modification with transformation of [TeO₄] to [TeO₃/TeO₃₊₁] units is evidenced from Raman spectra which is corroborated with XPS studies. While mechanical properties demonstrate enhancement of cross‐linking density in the network. These glasses exhibit optical transmission window extended from 0.4 to 6 μm with calculated zero dispersion wavelength (λ_ZDW) varying from 2.41 to 2.28 μm depending upon La₂O₃ content. Crystallization kinetics of TTL10 (80TeO₂‐10TiO₂‐10La₂O₃ in mol%) glass has been studied via established models. Activation energy (E_a) has been evaluated and dimensionality of crystal growth (m) suggests formation of surface crystals. Glass‐ceramic with crystalline phase of La₂Te₆O₁₅ has been realized in heat‐treated TTL10 glass samples (at 450°C). As predicted from DSC analysis, FESEM study unveils the formation of surface crystallized glass‐ceramics.     

Synthesis and Biological Evaluation of Purine 2′‐Fluoro‐2′‐deoxyriboside ProTides as Anti‐influenza Virus Agents

2′‐Fluoro‐2′‐deoxyguanosine has been reported to have potent anti‐influenza virus activity in vitro and in vivo. Herein we describe the synthesis and biological evaluation of 6‐modified 2′‐fluoro‐2′‐deoxyguanosine analogues and their corresponding phosphoramidate ProTides as potential anti‐influenza virus agents. Whereas the parent nucleosides were devoid of antiviral activity in two different cellular assays, the 5′‐O‐naphthyl(methoxy‐L ‐alaninyl) ProTide derivatives of 6‐O‐methyl‐2′‐fluoro‐2′‐deoxyguanosine, 6‐O‐ethyl‐2′‐fluoro‐2′‐deoxyguanosine, and 2′‐deoxy‐2′‐fluoro‐6‐chloroguanosine, and the 5′‐O‐naphthyl(ethoxy‐L ‐alaninyl) ProTide of 6‐O‐ethyl‐2′‐fluoro‐2′‐deoxyguanosine displayed antiviral EC₉₉ values of ～12 μM . The antiviral results are supported by metabolism studies. Rapid conversion into the L ‐alaninyl metabolite and then 6‐modified 2′‐fluoro‐2′‐deoxyguanosine 5′‐monophosphate was observed in enzymatic assays with yeast carboxypeptidase Y or crude cell lysate. Evidence for efficient removal of the 6‐substituent on the guanine part was provided by enzymatic studies with adenosine deaminase, and by molecular modeling of the nucleoside 5′‐monophosphates in the catalytic site of a model of ADAL1, thus indicating the utility of the double prodrug concept.     

Significant Improvement of Superconducting Properties in Nano‐NiFe2O4‐Doped Y–Ba–Cu–O Single‐Grain Superconductor

Introduction of refined second‐phase particles in superconducting YBa₂Cu₃O_7?x (Y‐123) matrix is known to be an effective route to improve the δl‐type pinning and the performance of Y–Ba–Cu–O (YBCO) single‐grain superconductors, while the δT_c‐type pinning induced by spatial fluctuations in matrix composition is also important and contributes to the in‐field J_c performance and high‐field applications of bulk superconductors. In this communication, chemical doping of nano‐sized NiFe₂O₄ (mean size 50 nm) in single‐grain YBCO superconductor is performed using a novel top‐seeded infiltration growth (TSIG) technique based on a solid source pellet (SSP) of nano‐Y₂O₃ + BaCuO₂. The results indicate that, significant improvement of bulk performances including levitation force (33.93 N) and trapped field (0.3628 T) has been observed in the 0.2 wt% nano‐NiFe₂O₄‐doped sample, which are much higher than the undoped sample (28.81 N and 0.2754 T). T_c measurement indicates that, a decreased onset T_c of about 87.5 K and a broadened transition width of about 5 K are observed in the NiFe₂O₄‐doped sample, indicating appearance of weak superconducting regions in superconducting matrix caused by Ni and Fe substitutions in Y‐123 crystal lattice. This study supplies a practical approach to increase the YBCO bulk performance significantly.     

Arabinosylated phenolics obtained from SO2‐steam‐pretreated sugarcane bagasse

A pentose‐rich hydrolysate fraction obtained by extraction of steam‐pretreated sugarcane bagasse was analysed with regard to dissolved phenolics. The liquid obtained after steam pretreatment (2% SO₂ (w/w) at 190 °C for 5 min) was divided into two parts: one containing dissolved compounds originating from hemicellulose (with xylose as the dominating compound), and the other containing predominantly dissolved compounds originating from lignin. Using nuclear magnetic resonance, the main dissolved compounds originating from lignin were identified as the glycosylated aromatics, 5‐O‐(trans‐feruloyl)‐L‐Arabinofuranose and 5‐O‐(trans‐coumaroyl)‐L‐Arabinofuranose, together with p‐coumaric acid and small amounts of more common free phenolics such as p‐hydroxybenzaldehyde, p‐hydroxybenzoic acid and vanillin. The phenolic compounds were analysed and quantified using reversed‐phase high‐performance liquid chromatography. The findings show that SO₂ steam explosion opened up new degradation pathways during lignin degradation. Copyright © 2012 Society of Chemical Industry     

Bio‐Based Hybrid Magnetic Latex Particles Containing Encapsulated γ ‐Fe2O3 by Miniemulsion Copolymerization of Soybean Oil‐Acrylated Methyl Ester and Styrene

This work reports the use of acrylated fatty acid methyl ester (AFAME) as a biomonomer for the synthesis of bio‐based hybrid magnetic particles poly(styrene‐co‐AFAME)/γ‐Fe₂O₃ produced by miniemulsion polymerization. Poly(styrene‐co‐AFAME)/γ‐Fe₂O₃ can be tailored for use in various fields by varying the content of AFAME. The strategy employed is to encapsulate superparamagnetic iron oxide nanoparticles (SPIONs) as γ‐Fe₂O₃ into a styrene/AFAME‐based copolymer matrix. Raman spectroscopy is employed to ensure the formation of the SPIONs (γ‐Fe₂O₃) obtained by a co‐precipitation technique followed by oxidation of Fe₃O₄. The functionalization of SPIONs with oleic acid (OA) is carried out to increase the SPIONs–monomer affinity. The presence of OA on the surface of γ‐Fe₂O₃ is certified by identification of main absorption bands by fourier‐transform infrared spectroscopy (FTIR). Thermal analysis (differential thermogravimetry/differential thermo analysis and differential scanning calorimetry) results of poly(styrene‐co‐AFAME)/γ‐Fe₂O₃ show an increase in AFAME content leading to a lower copolymer glass transition temperature (T _g). Dynamic light scattering (DLS) measurements result in poly(styrene‐co‐AFAME)/γ‐Fe₂O₃ particles with diameter in the range of 100–150 nm. It is also observed by transmission electron microscopy (TEM) and cryo‐TEM techniques that γ‐Fe₂O₃ particles are successfully encapsulated into the poly(styrene‐co‐AFAME) matrix.     

Cytochrome c Catalyzes the Hydrogen Peroxide‐Assisted Oxidative Desulfuration of 2‐Thiouridines in Transfer RNAs

The 5‐substituted 2‐thiouridines (R5S2Us) present in the first (wobble) position of the anticodon of transfer RNAs (tRNAs) contribute to accuracy in reading mRNA codons and tuning protein synthesis. Previously, we showed that, under oxidative stress conditions in vitro, R5S2Us were sensitive to hydrogen peroxide (H₂O₂) and that their oxidative desulfuration produced 5‐substituted uridines (R5Us) and 4‐pyrimidinone nucleosides (R5H2Us) at a ratio that depended on the pH and an R5 substituent. Here, we demonstrate that the desulfuration of 2‐thiouridines, either alone or within an RNA/tRNA chain, is catalyzed by cytochrome c (cyt c). Its kinetics are similar to those of Fenton‐type catalytic 2‐thiouridine (S2U) desulfuration. Cyt c/H₂O₂‐ and Fe^II‐mediated reactions deliver predominantly 4‐pyrimidinone nucleoside (H2U)‐type products. The pathway of the cyt c/H₂O₂‐peroxidase‐mediated S2U→H2U transformation through uridine sulfenic (U‐SOH), sulfinic (U‐SO₂H), and sulfonic (U‐SO₃H) intermediates is confirmed by LC–MS. The cyt c/H₂O₂‐mediated oxidative damage of S2U‐tRNA may have biological relevance through alteration of the cellular functions of transfer RNA.     

The Catalytic Diastereo‐ and Enantioselective Claisen Rearrangement of 2‐Alkoxycarbonyl‐Substituted Allyl Vinyl Ether

The catalytic asymmetric Claisen rearrangement of 2‐alkoxycarbonyl‐substituted allyl vinyl ethers that contain two stereogenic double bonds is described. A combination of the highly Lewis acidic [Cu{(S,S)‐tert‐Bu‐box}](H₂O)₂(SbF₆)₂ complex and molecular sieves served as catalyst and afforded the Claisen rearrangement products, substituted and functionalized α‐keto esters, in high yield with a remarkable diastereo‐ and enantioselectivity. The influence of ligand structure, counterion and allyl vinyl ether double bond configuration on the stereoselectivity of the rearrangement was briefly investigated. We propose an explanation for the rate accelerating effect of the Lewis acid as well as a stereochemical model which serve to explain and predict the stereochemical course of the copper bis(oxazoline) catalyzed Claisen rearrangement.     

Al2O3/Yttria‐Stabilized Zirconia Hollow‐Fiber Membrane Incorporated with Iron Oxide for Pb(II) Removal

Removal by absorptive ceramic membranes can simultaneously absorb and separate metal ions from water. Alumina/yttria‐stabilized zirconia (Al₂O₃/YSZ) hollow‐fiber membranes, fabricated using phase inversion and sintering process, were deposited with iron oxide by an in‐situ hydrothermal process. The results showed that α‐Fe₂O₃ was produced and incorporated across the membranes. A reduction in flux was recorded with the deposition of α‐Fe₂O_3. However, it improved the adsorption capacity for heavy metal adsorption. The adsorption‐separation test demonstrated that the optimized membrane is able to completely remove Pb(II) ions after two hours.     

Resistance of 2ZrO2·Y2O3 top coat in thermal/environmental barrier coatings to calcia‐magnesia‐aluminosilicate attack at 1500°C

Internally cooled, hollow SiC‐based ceramic matrix composites (CMCs) components that may replace metallic components in the hot section of future high‐efficiency gas‐turbine engines will require multilayered thermal/environmental barrier coatings (T/EBCs) for insulation and protection. In the T/EBC system, the thermally insulating outermost (top coat) ceramic layer must also provide resistance to attack by molten calcia‐magnesia‐aluminosilicate (CMAS) deposits. The interactions between a potential candidate for top coat made of air‐plasma‐sprayed (APS) 2ZrO₂·Y₂O₃ solid‐solution (ss) ceramic and two different CMASs (sand and fly ash) are investigated at a relevant high temperature of 1500°C. APS 2ZrO₂·Y₂O₃(ss) top coat was found to resist CMAS penetration at 1500°C for 24 hours via reaction products that block CMAS penetration pathways. In situ X‐ray diffraction (XRD) studies have identified the main reaction product to be an Ca‐Y‐Si apatite, and have helped elucidate the proposed mechanism for CMAS attack mitigation. Ex situ electron microscopy and analytical spectroscopy studies have identified the advantageous characteristics of the reaction products in helping the CMAS attack mitigation in the APS 2ZrO₂·Y₂O₃(ss) coating at 1500°C. Finally, the Y³⁺ solubility limit and transport behavior are identified as potential comparative tools for assessing the CMAS resistance ability of top‐coat ceramics.     

Template‐Free Synthesis of Porous Fe3O4/SiOC(H) Nanocomposites with Enhanced Catalytic Activity

We present a template‐free synthesis of Fe₃O₄/SiOC(H) nanocomposites with in situ formed Fe₃O₄ nanoparticles with a size of about 50 nm embedded in a nanoporous SiOC(H) matrix obtained via a polymer‐derived ceramic route. Firstly, a single‐source precursor (SSP) was synthesized by the reaction of allylhydridopolycarbosilane (AHPCS) with Fe‐acetylacetonate [Fe(acac)₃] at 140°C. The SSP was heat‐treated at 170°C to generate Fe₃O₄ nanocrystals in the cross‐linked polymeric matrix. Subsequently, the SSP was pyrolyzed at 600°C–700°C in argon atmosphere to yield porous Fe₃O₄/SiOC(H) nanocomposites with the high BET surface area up to 390 m²/g, a high micropore surface area of 301 m²/g, and a high micropore volume of 0.142 cm³/g. The Fe‐free SiOC(H) ceramic matrix derived from original AHPCS is nonporous. The in situ formation of Fe₃O₄ nanoparticles embedded homogeneously within a nanoporous SiOC(H) matrix shows significantly enhanced catalytic degradation of xylene orange in aqueous solution with H₂O₂ as oxidant as compared with pure commercial Fe₃O₄ nanoparticles.     

Er3+ ‐Doped Y2O3 Nanophosphors for Near‐Infrared Fluorescence Bioimaging Applications

Rare‐earth‐doped ceramic nanophosphor (RED‐CNP) materials are promising near‐infrared (NIR) fluorescence bioimaging (FBI) agents that can overcome problems of currently used organic dyes including photobleaching, phototoxicity, and light scattering. Here, we report a NIR–NIR bioimaging system by using NIR emission at 1550 nm under 980 nm excitation which can allow a deeper penetration depth into biological tissues than ultraviolet or visible light excitation. In this study, erbium‐doped yttrium oxide nanoparticles (Er³⁺:Y₂O₃) with an average particle size of 100 and 500 nm were synthesized by surfactant‐assisted homogeneous precipitation method. NIR emission properties of Er³⁺:Y₂O₃ were investigated under 980 nm excitation. The surface of Er³⁺:Y₂O₃ was electrostatically PEGylated using poly (ethylene glycol)‐b‐poly(acrylic acid) (PEG‐b‐PAAc) block copolymer to improve the chemical durability and dispersion stability of Er³⁺:Y₂O₃ under physiological conditions. In vitro cytotoxic effects of bare and PEG‐b‐PAAc‐modified Er³⁺:Y₂O₃ were investigated by incubation with mouse macrophage cells (J774). Microscopic and macroscopic FBI were demonstrated in vivo by injection of bare or PEG‐b‐PAAc‐modified Er³⁺:Y₂O₃ into C57BL/6 mice. The NIR fluorescence images showed that PEG‐b‐PAAc modification significantly reduced the agglomeration of Er³⁺:Y₂O₃ in mice and enhanced the distribution of Er³⁺:Y₂O₃.     

O4‐Alkylated‐2‐Deoxyuridine Repair by O6‐Alkylguanine DNA Alkyltransferase is Augmented by a C5‐Fluorine Modification

Oligonucleotides containing various adducts, including ethyl, benzyl, 4‐hydroxybutyl and 7‐hydroxyheptyl groups, at the O⁴ atom of 5‐fluoro‐O⁴‐alkyl‐2′‐deoxyuridine were prepared by solid‐phase synthesis. UV thermal denaturation studies demonstrated that these modifications destabilised the duplex by approximately 10 °C, relative to the control containing 5‐fluoro‐2′‐deoxyuridine. Circular dichroism spectroscopy revealed that these modified duplexes all adopted a B‐form DNA structure. O⁶‐Alkylguanine DNA alkyltransferase (AGT) from humans (hAGT) was most efficient at repair of the 5‐fluoro‐O⁴‐benzyl‐2′‐deoxyuridine adduct, whereas the thymidine analogue was refractory to repair. The Escherichia coli AGT variant (OGT) was also efficient at removing O⁴‐ethyl and benzyl adducts of 5‐fluoro‐2‐deoxyuridine. Computational assessment of N1‐methyl analogues of the O⁴‐alkylated nucleobases revealed that the C5‐fluorine modification had an influence on reducing the electron density of the O⁴?C_α bond, relative to thymine (C5‐methyl) and uracil (C5‐hydrogen). These results reveal the positive influence of the C5‐fluorine atom on the repair of larger O⁴‐alkyl adducts to expand knowledge of the range of substrates able to be repaired by AGT.     

Oxygen Isotope Transport Properties of Yttria‐Stabilized Zirconia (YSZ) in O2‐ and H2O‐Containing Atmospheres

Oxygen isotope exchange experiments, H₂¹⁸O/H₂¹⁶O (”wet” anneals) and ¹⁸O₂/¹⁶O₂ (”dry” anneals), were performed on single crystal samples of yttria‐stabilized zirconia (YSZ) at a temperature of T = 1073 K with subsequent determination of the oxygen isotope profiles in the solid by time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS). Such experiments yielded oxygen tracer diffusion coefficients (D*) and oxygen tracer surface exchange coefficients (k*), from both the polished (smooth) and unpolished (rough) sides of single crystal samples, as a function of water partial pressure pH₂O and oxygen partial pressure pO₂. Isothermal values of D* were found to depend on neither pO₂ nor pH₂O (nor surface roughness). Isothermal values of k*, in contrast, displayed a strong dependence on pO₂ or pH₂O; k*_wet was, in addition, 2–3 orders of magnitude higher than k*_dry. Surprisingly, surface roughness had little effect on k*_wet, whereas rough surfaces exhibited much higher k*_dry values than smooth surfaces. Data for k*_wet obtained as a function of temperature at pH₂O = 18 mbar show a change in activation enthalpy at T ≈ 973 K. The behavior of k* is discussed in terms of surface composition, surface area and surface reaction mechanisms.     

POEGMA‐b‐PAA comb‐like polymer dispersant for Al2 suspensions

POEGMA‐b‐PAA comb‐like polymer is synthesized through RAFT polymerization, and it is employed as an efficient dispersant for Al₂O₃ suspensions. The POEGMA‐b‐PAA polymer consists of PAA chains and POEGMA comb‐like chains. The former provide electrostatic attraction between Al₂O₃ particles and polymer, while the latter extend to solution and maintain the stability of suspension due to strong steric hindrance. The adsorption is proven and the rheology behaviors of Al₂O₃ suspensions are strongly improved. Different POEGMA‐b‐PAA polymers with different length of side chains have similar but not identical rheological properties. The polymer with the appropriate length of side chain provides the biggest improvement to rheological properties of Al₂O₃ suspensions, such as apparent viscosity and granularity. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43352.