Thermodynamics of some ZrO_2-containing ceramics

Thermodynamic assessment in the ternary systems ZrO2 -CeO2 -Y2 O3, ZrO2 -CeO2 -Ce2 03 and the limiting binaries ZrO2 -Y2 O3, ZrO2 -CeO2, CeO2 -Y2 03, ZrO2 -Ce2O3, CeO2 -Ce2O3 as well as the modeling for oxides are reviewed comprehensively. Based on the recent estimations on the YO1.5-CeO2, ZrO2-CeO2 and ZrO2 -YO1.6 systems, isothermal sections at 1273 and 1 973 K of the ternary CeO2- ZrO2-YO1.5system are calculated. In the system of ZrO2-CeO2-Ce2O3, the complex relation between the nonstoichiometry （y） in CeO2-x, the composition of the ZrO2 -CeO2 solid solution and the oxygen partial pressure （Po2 ） for different ZrO2 containing solid solutions CexZr1-xO2-x. are evaluated from 1 473 to 1 773 K. The relation between the degree of Ce^＋4 reduction to Ce.3 under different Po2 in the fluorite CeO2-xy and CexZr1-xOz-x solid solutions at different temperatures can be used as a guide in the development of functional ceramics.

Luminescence Spectra of YGG：RE^3＋, Bi^3＋ （RE = Eu and Tb） and Energy Transfer from Bi^3＋ to RE^3＋

We investigate the luminescence properties of Bi^3＋ and RE^3＋ （RE = Tb or Eu） in a Y3Ga5O12 （YGG） host system. The additional doping of Bi^3＋ can enhance the luminescence of Th^3＋ or Eu^3＋ in this host. Energy transfer from Bi^3＋ to Tb^3＋ and Eu^3＋ is observed and the mechanism of energy transfer is investigated. Mechanism of energy transfer can be explained as electric multipole interaction since the Bi^3＋ emission band and Tb^3＋ or Eu^3＋ excitation band overlaps and the Bi^3＋ emission intensity decreases while the intensity of Tb^3＋ or Eu^3＋ increases with the increase of Tb^3＋ or Eu^3＋ concentration. Therefore, Bi^3＋ ion is a kind of efficient sensitizer to the Tb^3＋ and Eu^3＋ activators in the Y3Ga5O12 host.

Improvement in Dielectric Tunability of Ba0.6Sr0.4TiO4-Mg2TiO4 Composite Ceramics via Heterogeneous Nucleation Processing

Dielectric tunable composite ceramics Ba0.6Sr0.4 TiO4-Mg2 TiO4 （BST-MT） are prepared with a heterogeneous nucleation sol-gel approach. The Mg2 TiO4 powders are synthesized by the conventionM solid-state reaction method. The micro-sized MT powders with dispersant Ciba-4010 are introduced into Ba-Sr-Ti sol to obtain uniform and homogeneous mixture compounds with nano-sized BST particles synthesized via heterogeneous nucleation （HN） in the sol-gel process. Thus, the mierostructural and dielectric properties can be tailored. The dielectric constants of BST-MT composite ceramics can be adjusted in a larg＇e range from 294 to 1790, and the dielectric tunability can be adjusted from 29.4% to 37.0% with different MT contents from 60wt% to 20wt%. Compared to the samples prepared by the conventional solid-state （SS） process, the BST-MT composite ceramics by the heterogeneous nucleation sol-gel process exhibit a more uniform microstructure, and improve dielectric properties.

Observation of Ferroelastic and Ferroelectric Domains in AgNbO_(3) Single Crystal

Compared to AgNbO_(3) based ceramics, the experimental investigations on the single crystalline AgNbO_(3), especially the ground state and ferroic domain structures, are not on the same level. Here, based on successfully synthesized AgNbO_(3) single crystal using a flux method, we observed the coexistence of ferroelastic and ferroelectric domain structures by a combination study of polarized light microscopy and piezoresponse force microscopy.This finding may provide a new aspect for studying AgNbO_(3). The result also suggests a weak electromechanical response from the ferroelectric phase of AgNbO_(3), which is also supported by the transmission electron microscope characterization. Our results reveal that the AgNbO_(3) single crystal is in a polar ferroelectric phase at room temperature, clarifying its ground state which is controversial from the AgNbO_(3) ceramic materials.

Orderedisorder transition and thermal conductivities of the(NdSmEuGd)_((1-x)/2)Dy_(2x)Zr_(2)O_(7)series

Rare-earth zirconates with pyrochlore and fluorite structures have recently been identified as promising thermal barrier coating materials owing to their low thermal conductivities.In this study,six samples with the general formula(NdSmEuGd)_((1-x)/2)Dy_(2x)Zr_(2)O_(7)were synthesized to further reduce the thermal conductivity.X-ray diffraction and Raman spectroscopy showed that the transition from an ordered pyrochlore to a disordered fluorite structure is due to cation and anion disorder.Transmission electron microscopy showed that anion disorder occurred before cation disorder.A modified mass disorder parameter was introduced into this system,which can describe the change in thermal conductivity well.This parameter can be a basis for designing more complex materials with lower thermal conductivities.

Investigation of microstructure changes in Al_(2)O_(3)-YSZ coatings and YSZ coatings and their effect on thermal cycle life

Yttria-stabilized zirconia(YSZ)coatings and Al_(2)O_(3)–YSZ coatings were prepared by atmospheric plasma spraying(APS).Their microstructural changes during thermal cycling were investigated via scanning electron microscopy(SEM)equipped with electron backscatter diffraction(EBSD)and X-ray diffraction(XRD).It was found that the microstructure and microstructure changes of the two coatings were different,including crystallinity,grain orientation,phase,and phase transition.These differences are closely related to the thermal cycle life of the coatings.There is a relationship between crystallinity and crack size.Changes in grain orientation are related to microscopic strain and cracks.Phase transition is the direct cause of coating failure.In this study,the relationship between the changes in the coating microstructure and the thermal cycle life is discussed in detail.The failure mechanism of the coating was comprehensively analyzed from a microscopic perspective.

Hydrogen-assisted scalable preparation of ultrathin Pt shells onto surfactant-free and uniform Pd nanoparticles for highly efficient oxygen reduction reaction in practical fuel cells

Concentrating active Pt atoms in the outer layers of electrocatalysts is a very effective approach to greatly reduce the Pt loading without compromising the electrocatalytic performance and the total electrochemically active surface area(ECSA)for the oxygen reduction reaction(ORR)in hydrogen-based proton-exchange membrane fuel cells.Accordingly,a facile,low-cost,and hydrogen-assisted two-step method is developed in this work,to massively prepare carbon-supported uniform,small-sized,and surfactant-free Pd nanoparticles(NPs)with ultrathin~3-atomic-layer Pt shells(Pd@Pt_(3L) NPs/C).Comprehensive physicochemical characterizations,electrochemical analyses,fuel cell tests,and density functional theory calculations reveal that,benefiting from the ultrathin Pt-shell nanostructure as well as the resulting ligand and geometric effects,Pd@Pt_(3L) NPs/C exhibits not only significantly enhanced ECSA,electrocatalytic activity,and noble-metal(NM)utilization compared to commercial Pt/C,showing 81.24 m^(2)/gPt,0.710 mA/cm^(2),and 352/577 mA/mgNM/Pt in ECSA,area-,and NM-/Pt-mass-specific activity,respectively;but also a much better electrochemical stability during the 10,000-cycle accelerated degradation test.More importantly,the corresponding 25-cm^(2) H2-air/O_(2) fuel cell with the low cathodic Pt loading of~0.152 mgPt/cm^(2)geo achieves the high power density of 0.962/1.261 W/cm^(2)geo at the current density of only 1,600 mA/cm^(2)geo,which is much higher than that for the commercial Pt/C.This work not only develops a high-performance and practical Pt-based ORR electrocatalyst,but also provides a scalable preparation method for fabricating the ultrathin Pt-shell nanostructure,which can be further expanded to other metal shells for other energy-conversion applications.

Bacterial Metabolism-Initiated Nanocatalytic Tumor Immunotherapy

The low immunogenicity of tumors remains one of the major limitations of cancer immunotherapy.Herein,we report a bacterial metabolisminitiated and photothermal-enhanced nanocatalytic therapy strategy to completely eradicate primary tumor by triggering highly effective antitumor immune responses.Briefly,a microbiotic nanomedicine,designated as Cu_(2)O@ΔSt,has been constructed by conjugating PEGylated Cu_(2)O nanoparticles on the surface of an engineered Salmonella typhimurium strain(ΔSt).Owing to the natural hypoxia tropism ofΔSt,Cu_(2)O@ΔSt could selectively colonize hypoxic solid tumors,thus minimizing the adverse effects of the bacteria on normal tis-sues.Upon bacterial metabolism within the tumor,Cu_(2)O@ΔSt generates H_(2)S gas and other acidic substances in the tumor microenvironment(TME),which will in situ trigger the sulfidation of Cu_(2)O to form CuS facilitating tumor-specific photothermal therapy(PTT)under local NIR laser irradiation on the one hand.Meanwhile,the dissolved Cu+ions from Cu_(2)O into the acidified TME enables the nanocatalytic tumor therapy by catalyzing the Fenton-like reaction of decom-posing endogenous H_(2)O_(2) into cytotoxic hydroxyl radicals(·OH)on the other hand.Such a bacterial metabolism-triggered PTT-enhanced nanocatalytic treatment could effectively destroy tumor cells and induce a massive release of tumor antigens and damage-associated molecular patterns,thereby sensitizing tumors to checkpoint blockade(ICB)therapy.The combined nanocatalytic and ICB therapy results in the much-inhibited growth of distant and metastatic tumors,and more importantly,induces a powerful immunological memory effect after the primary tumor ablation.

Interfacial Stress Analysis on Skutterudite-based Thermoelectric Joints under Service Conditions

In thermoelectric(TE)devices,the interfacial reliability greatly influenced devices’durability and power output.For skutterudites(SKD)devices,TE legs and electrodes are bonded together with diffusion barrier layer(DBL).At elevated temperatures,DBL react with SKD matrix or electrode to generate complex interfacial microstructures,which often accompanies evolutions of the thermal,electrical and mechanical properties at the interfaces.In this work,a finite element model containing the interfacial microstructure characteristics based on the experimental results was built to analyze the interfacial stress state in the skutterudite-based TE joints.A single-layer model was applied to screen out the most important parameters of the coefficient of thermal expansion(CTE)and the modulus of DBL on the first principle stress.The multilayer model considering the interfacial microstructures evolution was built to quantitively simulate the stress state of the TE joints at different aging temperatures and time.The simulation results show that the reactive CoSb2 layer is the weakest layer in both SKD/Nb and SKD/Zr joints.And by prolonging the aging time,the thickness of the reaction layer continuously increased,leading to a significant raising of the interfacial stress.The tensile testing results of the SKD/Nb joints match the simulation results well,consolidating accuracy and feasibility of this multilayer model.This study provides an important guidance on the design of DBL to improve the TE joints’mechanical reliability,and a common method to precisely simulate the stress condition in other coating systems.

Development of sandwich joining piece to fabricate segmented half-Heusler/skutterudite thermoelectric joints

Sn/Ni-Sn/Sn sandwich joining piece was developed and applied to fabricate segmented half-Heusler/skutterudite thermoelectric joints,and high-temperature service behavior of the joints was studied.The microstructure and contact resistance of the joint before and after aging were investigated.The joints are well bonded and no cracks appear at the interfaces of the joint before and after aging,which can be attributed to the formation of high-melting point intermetallic compounds.The electrical resistance crosses the joining layer smoothly and the contact resistance is low.These results show that the sandwich joining piece is effective and flexible,and promising for the preparation of segmented thermoelectric devices.

Plasma-induced nanowelding of a copper nanowire network and its application in transparent electrodes and stretchable conductors

铜 nanowires (Cu NW ) 由于他们的突出的电的性质和低费用为电子学作为积木吸引了增加的注意。然而，无所不在地在 Cu NW 的表面上存在的器官的残余和氧化物层阻碍好内部电线的接触。象热退火和酸处理那样的通常使用的方法经常导致 nanowire 损坏。此处，在房间温度的氢血浆处理被表明了为同时的表面在连接清洗并且选择焊接 Cu NW 有效。有优秀光电的性能的透明电极(19 O 汯獹獩琠浥数慲畴敲漠 ??? ‰ ???????璪？？

Starvation-Sensitized and Oxygenation-Promoted Tumor Sonodynamic Therapy by a Cascade Enzymatic Approach

The therapeutic outcomes of noninvasive sonodynamic therapy(SDT)are always compromised by tumor hypoxia,as well as inherent protective mechanisms of tumor.Herein,we report a simple cascade enzymatic approach of the concurrent glucose depletion and intratumoral oxygenation for starvation-sensitized and oxygenation-amplified sonodynamic therapy using a dual enzyme and sonosensitizer-loaded nanomedicine designated as GOD/CAT@ZPF-Lips.In particular,glucose oxidase-(GOD-)catalyzed glycolysis would cut off glucose supply within the tumor,resulting in the production of tumor hydrogen peroxide(H_(2)O_(2))while causing tumor cells starvation.The generated H_(2)O_(2)could subsequently be decomposed by catalase(CAT)to generate oxygen,which acts as reactants for the abundant singlet oxygen(^(1 O_(2))production by loaded sonosensitizer hematoporphyrin monomethyl ether(HMME)upon the US irradiation,performing largely elevated therapeutic outcomes of SDT.In the meantime,the severe energy deprivation enabled by GOD-catalyzed glucose depletion would prevent tumor cells from executing protective mechanisms to defend themselves and make the tumor cells sensitized and succumbed to the cytotoxicity of^(1 O_(2)).Eventually,GOD/CAT@ZPF-Lips demonstrate the excellent tumoral therapeutic effect of SDT in vivo without significant side effect through the cascade enzymatic starvation and oxygenation,and encouragingly,the tumor xenografts have been found completely eradicated in around 4 days by the intravenous injection of the nanomedicine without reoccurrence for as long as 20 days.

Copper nanowire-TiO2-polyacrylate composite electrodes with high conductivity and smoothness for flexible polymer solar cells

Copper nanowire （Cu NW） transparent electrodes have attracted considerable attention due to their outstanding electrical properties, flexibility and low cost. However, complicated post-treatment techniques are needed to obtain good electrical conductivity, because of the organic residues and oxide layers on the surface of the Cu NWs. In addition, commonly used methods such as thermal annealing and acid treatment often lead to nanowire damage. Herein, a TiO2 sol treatment was introduced to obtain Cu NW transparent electrodes with superb performance （13 Ω/sq @ 82% T） at room temperature within one minute. Polymer solar ceils with excellent flexibility were then fabricated on the copper nanowire- TiO2-polyacrylate composite electrode. The power conversion efficiency （PCE） of the cells based on a blend of poly（3-hexylthiophene） （P3HT） and phenyl-C61- butyric acid methyl ester （PC61BM） reached 3.11%, which was better than the control devices that used indium tin oxide （ITO）-PET electrodes, and outperforms other Cu NW based organic solar cells previously reported. The PCE of the solar cells based on Cu NW electrodes remained at 90% after 500 cycles of bending, while the PET/ITO solar cells failed after 20 and 200 cycles, with sheet resistance of 35 and 15 Ω/sq, respectively.

Water vapor corrosion behaviors of high-entropy pyrosilicates

In this study,the water vapor corrosion resistance of two types of high-entropy pyrosilicates((Yb_(0.2)Y_(0.2)Lu_(0.2)Ho_(0.2)Er_(0.2))_(2)Si_(2)O_(7)((5RE1/5)_(2)Si_(2)O_(7))and(Yb_(0.2)5Lu_(0.2)5Ho_(0.2)5Er_(0.2)5)_(2)Si_(2)O_(7)((4RE_(1/4))_(2)Si_(2)O_(7)))and two single-component pyrosilicates(Yb_(2)Si_(2)O_(7) and Lu_(2)Si_(2)O_(7))were evaluated at 1350℃ for 50e100 h,and the initial corrosion behaviors of these pyrosilicates were studied.The results showed that the final corrosion products of the four types of pyrosilicates were all X2-type monosilicates,exhibiting similar corrosion phenomena.However,(4RE_(1/4))_(2)Si_(2)O_(7) generated many nanoscale monosilicate grains during corrosion.The corrosion resistance of Lu_(2)Si_(2)O_(7) was clearly better than those of the others,and(4RE_(1/4))_(2)Si_(2)O_(7) exhibited the worst corrosion resistance.The corrosion mechanism of the pyrosilicate blocks was analyzed from the perspectives of grain size,bulk hydrophobicity,and binding energy.This study potentially provides a theoretical basis for the preparation of high-entropy pyrosilicates with different atomic ratios according to the different properties of the various rare earth elements.

Transparent heaters based on highly stable Cu nanowire films

尽管有灵活、透明的电影加热器的最近的成功的示范，有高光的发射度和低应用直接电流(DC ) 的大多数加热器电压是基于的银 nanowire (Ag NW ) 或银基于格子。在这研究，灵活、可拉长的铜 nanowire (Cu NW ) 基于透明电影加热器通过一个基于答案的过程，恐水病的聚合物的薄层在 Cu NW 电影上在被包含被制作。薄聚合物层在严厉严峻的条件下面保护了这些电影免受氧化的伤害，即，高温度，高湿度，和酸、碱的环境。这些电影展出了显著性能，一个宽操作温度范围(多达 150 

Semi-transparent polymer solar cells with all-copper nanowire electrodes

Transparent electrodes based on copper nanowires （Cu NWs） have attracted significant attention owing to their advantages including high optical transmittance, good conductivity, and excellent mechanical flexibility. However, low-cost, high-performance, and environmental friendly solar cells with all-Cu NW electrodes have not been realized until now. Herein, top and bottom transparent electrodes based on Cu NWs with low surface roughness and homogeneous conductivity are fabricated. Then, semi-transparent polymer solar cells （PSCs） with the inverted structure of polyacrylate/Cu NWs/poly（3,4- ethylenedioxythiophene）：poly（styrenesulfonate） （PEDOT：PSS） （PH1000）/Y-TiO2/ poly（3-hexylthiophene）：[6,6]-phenyl-C61-butyric acid 3,4,5-tris（octyloxy）benzyl/ PEDOT：PSS （4083）/Cu NWs/polyimide/polydimethylsiloxane are constructed; these could absorb light from both sides with a power conversion efficiency reaching 1.97% and 1.85%. Furthermore, the PSCs show an average transmittance of 42% in the visible region, which renders them suitable for some specialized applications such as power-generating windows and building-integrated photovoltaics. The indium tin oxide （ITO）- and noble metal-free PSCs could pave new pathways for fabricating cost-effective semi-transparent PSCs.