Effect of Sc_2O_3 addition on densification and microstructure of different spinelized magnesium aluminate spinels

The densification and microstructure of different spinelized magnesium aluminate spinels（MAS） were studied adding Sc_2O_3 as additive. Sintered products were then characterized in terms of densification, phase analysis, quantitative elemental analysis and microstructure. The results show that Sc_2O_3 is found to be beneficial for the densification of MAS. Sc_2O_3 has a more significant effect on the densification of partially spinelized MAS batch than that of fully spinelized MAS batch. At the sintering temperature of 1650 °C, the bulk density of sintered products of partially spinelized powders increases by 0.243 g/cm3 as the Sc_2O_3 content increases from 0 to 4%（mass fraction） and that of fully spinelized powder increases by 0.14 g/cm3. Compared with the sintered samples prepared from the fully spinelized powder, the sintered samples using the partially spinelized powders as raw materials have more compact microstructures.

Preparation of SO_4^(2-)/TiO_2-MoO_3 Solid Superacid and Its Catalytic Activity in Acetalation and Ketalation

SO4^2-/TiO2-MoO3, a novel solid superacid, has been prepared and its catalytic activity at different synthetic conditions was examined with esterification of n-butanoic acid and n-butyl alcohol as probing reaction.The optimum conditions were also found, that is, the mass ratio of MoO3 used in the compound is 25%, the calcination temperature 450℃, and the soaked consistency of H2SO4 is 0.5mol.L^-1. Then it was applied in the catalytic synthesis of six similar important ketals and acetals as catalyst and revealed high catalytic activity. Under the condition that the molar ratio of aldehyde/ketone to glycol was 1:1.5, the mass ratio of the catalyst to the reactants was 0.5% and the reaction time 1.0 h, the yield of ketals and acetals reached up to 63.2%. The catalyst can be easily recovered and reused.

Effects of Rare-Earth La_2O_3 Addition on Microstructures and Electrical Properties of SrTiO_3 Varistor-Capacitor Dual Functional Ceramics

The effects of rare-earth La_2O_3 addition on microstructures and electrical properties of SrTiO_3 ceramics were investigated. Semiconductor SrTiO_3-based voltage-sensing and dielectric dual functional ceramics was prepared by a single step sintering technology in this study, and the effects of the content of La_2O_3 on characteristics of the product were discussed in terms of microstructures and electrical properties of materials. The results show that SrTiO_3-based ceramics doped with La_2O_3 exhibits more homogeneous grain distribution, greater grain size, and excellent voltage sensing and dielectric characteristics than those without La_2O_3 doping. The samples doped with 1 1% La_2O_3 were sintered at 1420 ℃ in N_2+C weak reducing atmosphere. The average grain size of the samples doped with La_2O_3 is 40 μm, the breakdown voltage of 19.7 V·mm^(-1), the nonlinear exponent of 7.2, and dielectric constant of 22500. The results reveal that final products are suitable to use in low operating voltage.

Fabrication of an in-situ nanoAl_2O_3/Cu composite with high strength and high electric conductivity

A heat-resistant dispersion-strengthening nano-Al_2O_3/Cu composite with highstrength and high electric conductivity was fabricated in a multiplex medium. The internaloxidation product, microstructures and properties of the composite, and the process flow weresystematically studied. It is confirmed that this new technique simplifies the process and improvesthe properties of the composite. X-ray analysis indicates that the alumina particles formed duringinternal oxidation consist of a large mount of gamma-Al_2O_3 and a certain amount of theta-Al_2O_3and alpha-Al_2O_3. TEM observation shows that the obtained gamma-Al_2O_3 nano-particles areuniformly distributed in the copper grains; their mean size and space between particles are 7 runand 30 nm, respectively. The main properties of the composite with 50 percent cold deformation areas follows: the electric conductivity is 51 MS/m (87 percent IACS), sigma_b = 628 MPa, and thehardness is HRB86. After annealing at 1273 K, all or most of the above properties remain, and themicrostructures are still dependent on elongated fiber-form grains.

Inhibitory effect of humanized anti-VEGFR-2 ScFv-As_2O_3-stealth nanoparticles conjugate on growth of human hepatocellular carcinoma:in vitro and in vivo studies

Objective:To investigate the inhibitory effect of humanized anti-VEGFR-2 ScFv-As2O3-stealth nanoparticles conjugate on growth of human hepatocellular carcinoma both in vitro and in vivo,which may be a potential agents with sensitivity and targeting ability for human hepatocellular cancer.Methods:Humanized anli-VECFR-2 ScFv-As2O3-stealth nanoparticles conjugate was previously constructed using ribosome display technology and antibody conjugate technology.In this combined in vitro and in vivo study,the inhibitory effects of anti-VEGFR-2 ScFv-As2O3-stealth nanoparticles conjugate on tumor growth,invasion,and metastasis was observed with human liver carcinoma cell line Bel7402 and normal cell L02 by MTT assay,Tanswell assay,Hochest33258 staining,and DNA ladder analysis.The anticancer activity and distribution of anti-VEGFR-2 ScFv-As2O3-stealth nanoparticles was then verified in a mouse model of Bel7402xenografts.Results:Anti-VEGFR-2 ScFv-As2O3-stealth nanoparticles significantly inhibited the proliferation of Bel7402 in the 3-(4,5-dimethylthiazol-2-yh-2,5-diphenyltetrazolium bromide assay while had almost no effects on L02 cells.And the apoptosis inducing effects were proved by Hochest33258 staining and DNA ladder analysis.Transwell assay found that the drug also inhibited the metastasis ability of tumor cells.Furthermore,anti-VEGFR-2 ScFv-As^-stealth nanoparticles significantly delayed the growth of Bel7402 xenografts after administration（92.9%）,followed by As2O3-stealth nanoparticles,anti-VEGFR-2 ScFv,and As203（61.4%,58.8%,20.5%,P【0.05）.The concentration of As2O3 in anti-VEGFR-2 ScFv-As2O3-steallh nanoparticles group was more selectively.Conclusions:Anti-VEGFR-2 ScFv-As2O3-stealth nanoparticles is a potent and selective anti-hepatocellular carcinoma agent which could inhibit the growth of liver cancer as a targeting agent both in vitro and in vivo and also significantly inhibit angiogenesis.

Abrasive wear characteristics and mechanisms of Al_2O_3/PA1010 composite coatings

The abrasive wear characteristics of Al_2O_3/PA1010 composite coatings on thesurface of quenched and low-temperature temper steel 45 were tested on the template abrasive weartesting machine and the same uncoated steel 45 was used as a reference material. Experimentalresults showed that the abrasive wear resistance of Al_2O_3/PA1010 composite coatings has a goodlinear relationship with the volume fraction of Al_2O_3 particles in Al_2O_3/PA1010 compositecoatings, and the linear correlative coefficient is 0.979. Under the experimental conditions, thesize of Al_2O_3 particles (40.5-161.0 μm) has little influence on the abrasive wear resistance ofAl_2O_3/PA1010 composite coatings. By treating the surface of Al_2O_3 particles with a suitablebonding agent, the distribution of Al_2O_3 particles in matrix PA1010 is more homogeneous and thebonding state between Al_2O_3 particles and matrix PA1010 is better. Therefore, the Al_2O_3particles in Al_2O_3/PA1010 composite coatings make the Al_2O_3/PA1010 composite coatings havebetter abrasive wear resistance than PA1010 coatings. The wear resistance of Al_2O_3/PA1010composite coatings is about 45% compared with that of steel 45.

Influence of As_2O_3 combined with ginsenosides Rg3 on inhibition of lung cancer NCI-H1299 cells and on subsistence of nude mice bearing hepatoma

Objective:To study the effect of arsenic trioxide（As2O3）combined with ginsenosides Rg3 on inhibiting the NCI-H1299 lung cancer cells and subsistence in nude mice bearing hepatoma.Methods:MTT method was used to measure the inhibition effect of（As2O3）combined Rg3 on NC1-H1299 cells,and the proliferation inhibiting effect was observed via establishing the transplanted tumor model in vitro.A total of 40 tumor-bearing nude mice were randomly divided into normal saline group,（As2O3）,Rg3 and As2O3+Rg3 group.Transplantation tumor model of lung cancer in nude mice was constructed,followed by injection of certain concentrations of normal saline,As2O3,ginseng saponin Rg3 and As2O3+Rg3 every day.The survival duration and the tumors size of the mice were recorded and the Kaplan-Meier curve was made;microscopic observation of apoptosis of tumor cells in vivo was done using TUNEL staining.Results:After 72 h of injection.inhibition rate of tumor cell in normal saline group,As2O3 group.Rg3 group and As2O3+Rg3 group was（5.66±0.31）%,（65.58±4.75）%,（44.69±3.32）%and（82.67±5.43）%,respectively.Inhibition rate of tumor cell in As2O3 group.Rg3 groap and As2O3+Rg3 group was significantly higher than that of normal saline group（P【0.01）;inhibition rate of tumor cells of As2O3+Rg3 group was significantly higher than that of the two groups given As2O3 or Rg3 alone（P【0.01）.The tumor volume of As2O3 group,Rg3 group and As2O3+Rg3 group shrank to（65.38±3.25）%,（77.68±3.43）%and（42.65±3.55）%of the original,tumor volume of saline group was 1.21 times of the original size（P【0.01）;Median survival of saline group,Rg3 group,As2O3 group were significantly shorter than that of As2O3+Rg3 group（P【0.01）;co-ordinated intervention ability of As2O3+Rg3 on NCI-H1299 cell was significantly higher than that of As2O3 or Rg3,separately.Conclusions:As2O3 combined with Rg3 can significantly inhibit prolifaration of NCI-H1299 cells in lung cancer,prolong survival fo tumor-bearing nude mice,and promote tumor cell apoptosis,and have significant effect on lung cancer treatment.

Progress of power field effect transistor based on ultra-wide bandgap Ga_2O_3 semiconductor material

As a promising ultra-wide bandgap semiconductor, gallium oxide(Ga_2O_3) has attracted increasing attention in recent years. The high theoretical breakdown electrical field(8 MV/cm), ultra-wide bandgap(～ 4.8 eV) and large Baliga's figure of merit(BFOM) of Ga_2O_3 make it a potential candidate material for next generation high-power electronics, including diode and field effect transistor(FET). In this paper, we introduce the basic physical properties of Ga_2O_3 single crystal, and review the recent research process of Ga_2O_3 based field effect transistors. Furthermore, various structures of FETs have been summarized and compared, and the potential of Ga_2O_3 is preliminary revealed. Finally, the prospect of the Ga_2O_3 based FET for power electronics application is analyzed.

EFFECTS OF In_2O_3 DOPING AND SINTERING TEMPERATURE ON THE ELECTRICAL PROPERTIES OF ZnO VARISTORS

ZnO varistors are prepared using the 0.1-0.3mm ZnO powders. The effects of the sintering temperature, contents of In2O3 doping on the non-linear properties of ZnO varistors have been investigated. Theresults show that this kind of ZnO powder has a high sintering activity. It is suitable for making the low voltage varistors. The Vc decreases with the increase of sintered temperature, when the In2O3 content is fixed(0. 98 %, mass fraction), and increases with the increase of In2O3 contents when the temperature is steady.

A New Co-Activator Gd_2O_3 to Eu_2O_3 and Dy_2O_3 Doped Alkaline Earth Silicate Phosphors

Three alkaline earth silicate phosphors: Sr2MgSi2O7∶Eu, Dy, Gd, Sr3MgSi2O8∶Eu, Dy, Gd and Sr2MgSi2O7∶Eu, Dy were prepared and their luminescent properties were investigated. The Photoluminescence (PL) measurements indicated that the phosphors gave a longer emitting phosphorescence phenomenon by comparing with those without Gd2O3 activator, in which a better afterglow characteristic was observed by adding Gd2O3 to the phosphors. While little influence on the structure of luminescent materials was observed via XRD spectra, and obvious emission wavelength shift was exhibited due to the differences in the structure parameters of the two hosts. The results revealed that the improvement was due to nonequivalent substitution to produce more e-traps, and energy transfer from Gd3+ to Dy3+, to boost the performance of Sr2MgSi2O7∶Eu, Dy phosphor. Role of Gd3+ co-doped into Sr2MgSi2O7∶Eu, Dy matrix and the possible long-lasting phosphorescence progress were discussed.

Preparation and structure characteristics of nano-Bi_2O_3 powders with mixed crystal structure

The nano-Bi2O3 powders were prepared by a chemical precipitation method with Bi（NO3）3, HNO3 and NaOH as reactants. The structural characteristics and morphology of nano-Bi2O3 powders were investigated by X-ray diffraction and transmission electron microscopy, respectively. The results show that under the optimum condition that 300g/L Bi（NO3）3 reacts at 90℃ for 2h, the Bi2O3 powders with 60nm on the average and 99.5% in purity are obtained. The prepared nano-Bi2O3 powders contain a mixed crystal structure of monoclinic and triclinic instead of traditional structure of monoclinic α-Bi2O3. And the mixed crystal structure is stable in air. The reason for the appearance of the mixed crystal structure may be that the ionic radius ratio of Bi 3+ to O 2- changes easily during the formation of nano-Bi2O3 particles by a chemical precipitation method.

Investigation of Loss Weight and Densification of SiC-Al_2O_3-Y_2O_3 Ceramic Composite on Sintering

α-SiC, Al_2O_3 and Y_2O_3 powders were all used as raw materials. The SiC-Al_2O_3-Y_2O_3 ceramic composites were made by pressureless liquid phase sintering technology. The effects of sintering temperature, loss weight and coordination number on sintering densification were studied. The reason for producing loss weight on sintering was analysed. The results show that the primary reason for producing loss weight on sintering in SiC-Al_2O_3-Y_2O_3 ceramic composite was that chemical reactions between SiC and Al_2O_3 are happened during sintering, and given out volatile gases. If sintering temperature is excessively lower, grain size would be finer, and coordination number would be higher, well then material would be on no sintering densification. If sintering temperature is excessively higher, grains would grow up, though small coordination number would benefit to make pore eliminate and shrink, but coarse microstructure would also block gliding and resetting of grains, together affected by expansion stress from volatile gas, the material densification would instead go down. Only under the sintering process of 1850 ℃ for 30 min, material densification is better, and the mechanical property of ceramic composites is also improved.

Agglomeration Control of Ultrafine Y_2O_3-ZrO_2 and (MgO, Y_2O_3)-ZrO_2 Powders Synthesized by Coprecipitation Process

Chemical coprecipitation was used to produce ultrafine and easily sinterable Y2O3-stabilized and （Y2O3,MgO）-stabilized ZrO2 powders. Six precipitation processes for preparation of ZrO2-based ultrafine powders were designed separately, meanwhile different techniques used to control the agglomeration formation were proposed. By means of TEM, SEM, Raman spectroscopy and IR spectroscopy, the mechanisms of agglomeration control in the precipitation processes and post-precipitation and drying process were investigated. The experimental results show that adding appropriate anion surface active agents （such as PAA1460） or polymer （PEG1540 matching with PEG200） in aqueous solution systems during precipitation processes could reinforce charge effect and location effect for gel particles interface. Adding wetting agents to wet gels washing with distilled water during drying process could change interface structure of gel particles and decrease surface tension between gel particles. The agglomeration control in the precipitation, post-precipitation and drying processes had remarkable influence on the characteristics of powders. By adding various macromolecules in the processes, the agglomeration state could be controlled efficiently, and the characteristics of powders were improved.

Effects of Additive Nd_2O_3 on Varistor Voltage and Microstructure of ZnO Varistor

The influence of additive Nd_2O_3 on varistor voltage and microstructure of ZnO varistor was studied,and its mechanism was proposed from theoretical analysis. The results show that the varistor voltage of ZnO varistor increases with the content of Nd_2O_3 in the range of 0～0.04 (%,mol fraction). However when the content of Nd_2O_3 is more than 0.04 (%,mol fraction),the varistor voltage of ZnO varistor decreases with the content increase. The microstructure analysis indicates that a small amount of new compound with Nd exists at ZnO grain boundary and hinders the movement of grain boundary,which decreases the size of ZnO grain and makes the grain size and distribution homogeneous,as a result,additive (Nd_2O_3) raises the varistor voltage of the varistor greatly.

Sol-Gel Derived SiO_2-Y_2O_3∶Eu^(3+) Nanocomposites and Their PL Properties

An improved sol-gel method was used to prepare Eu3+ ions doped SiO-Y2O3 nanocomposites. Systematic study on the effect of post-annealling treatment on photoluminescence (PL) properties of the samples under various europium ions doping concentrations were carried out. XRD patterns indicate that the samples show an amorphous matrix structure, and the SEM patterns show that the samples present a multi-hole loosen structure, and a rod structure after high-temperature annealling treatment (800 ℃) for 3 h. Raman spectra demonstrate that Y3+ and Eu3+ ions were incorporated into the composites successfully through the sol-gel and post-anneal process. Under the excitation of 387 nm (7F0→5G2) violet light (but not 394 nm (7F0→5L6)), the strongest emission spectrum, the red light, was observed at around 616 nm (5D0→7F2) when the samples were re-treated by annealing at high temperature after 3 months laying aside. Without annealing treatment, the optimized doping mole ratio of Eu ions is about 9%, which is much higher than that doped in SiOglass with the concentration of 3.5%, and it then becomes 5% when the samples are treated by high temperature annealing. In addition, the excitation of 532 nm (7F0→5D1) light can also arouse a comparatively strong emission.

Theoretical Prediction of Gibbs Free Energies of Formation for Crystallineα-MOOH andα-M_2O_3 Based on a Linear Free-Energy Relationship

In the present study,the modified Sverjensky-Molling equation,derived from a linear-free energy relationship,is used to predict the Gibbs free energies of formation of crystalline phases ofα-MOOH （with a goethite structure）andα-M_2O_3（with a hematite structure）from the known thermodynamic properties of the corresponding aqueous trivalent cations（M^（3＋））.The modified equation is expressed asΔG_（f,M_VX）~0=a_（M_VX）ΔG_（0,M^（3＋））^（0）＋b_（M_VX）＋β_（M_VXγM^（3＋））,where the coefficients a_（M_VX）,b_（M_VX）,andβ_（M_VX） characterize a particular structural family of M_VX（M is a trivalent cation[M^（3＋）]and X represents the remainder of the composition of solid）;γ^（3＋）is the ionic radius of trivalent cations（M^（3＋））;ΔG_（f,M_VX）~0 is the standard Gibbs free energy of formation of M_vX;andΔG_（n,M^（3＋））~0 is the non-solvation energy of trivalent cations（M^（3＋））.By fitting the equation to the known experimental thermodynamic data,the coefficients for the goethite family（α-MOOH）are a_（M_VX）=0.8838,b_（M_VX）=-424.4431（kcal/mol）,andβ_（M_VX）=115（kcal/ mol.（？））,while the coefficients for the hematite family（α-M_2O_3）are a_（M_VX）=1.7468,b_（M_VX）=-814.9573（kcal/ mol）,andβ_（M_VX）=278（kcal/mol.（？））.The constrained relationship can be used to predict the standard Gibbs free energies of formation of crystalline phases and fictive phases（i.e.phases that are thermodynamically unstable and do not occur at standard conditions）within the isostructural families of goethite（α-MOOH）and hematite（α-M_2O_3）if the standard Gibbs free energies of formation of the trivalent cations are known.

Preparation and Characterization of Cerium Doped Ti/SnO_2-Mn_2O_3/PbO_2 Electrode

The acid-proof anode Ti/SnO2+Mn2O3/PbO2 doped with Ce was prepared by thermal decomposition and electrodeposition combination technology, the effect of Ce on the morphology and structure of anode was also studied in this paper. The results obtained by cyclic voltammetry (CV), electrochemical impedance spectroscopic (EIS), X-ray Diffraction (XRD) and scanning electron microscopy (SEM) indicated that PbO2 crystal grains presented honeycomb structure were formed on the electrode surface by doping with Ce. The specific surface areas and catalytic active sites of the Ce-PbO2 doped electrode were increased and the catalytic activity was evidently greater than the undoped one. However, when Ce was doped into the intermediate layer (SnO2+Mn2O3), a more cracked surface structure formed, thus leading electrode deactivation by passivation of the Ti-substrate. So the anodic stability was decreased according to the accelerated life tests.

FT-IR Spectroscopic Investigation of Co-adsorption of Acetonitrile and CO on Fresh Mo_2C/Al_2O_3 Catalyst

The adsorption of acetonitrile and its co-adsorption with CO on fresh Mo_2C/Al_2O_3 catalyst have been studied by insitu FT-IR spectroscopy.Linearly adsorbed CH_3CN and CH_3CH_2NH_2 were formed after CH_3CN adsorption on the Mo_2C/ Al_2O_3 catalyst.The appearance of a strong band at 1578 cm^(-1) indicates that CH_3CN was reactive with hydrogen on the Mo_2C/Al_2O_3 catalyst.

Unraveling the role of dual Ti/Mg metals on the ignition and combustion behavior of HTPB-boron-based fuel

Metal additives play an essential role in explosive and propellant formulations. Boron(B) is widely used in propellant applications owing to its high energetic content. The addition of B to explosives and propellants increases their energy density, making them more efficient and powerful. Nevertheless, B forms oxide layers on its surface during combustion, slowing down the combustion rate and reducing rocket motor efficiency. To overcome this issue, other metal additives such as aluminum(Al), magnesium(Mg),and titanium(Ti) are revealed to be effective in boosting the combustion rate of propellants. These additives may improve the combustion rate and therefore enhance the rocket motor’s performance. The present study focused on preparing and investigating the ignition and combustion behavior of pure hydroxyl-terminated polybutadiene(HTPB)-B fuel supplemented with nano-titanium and nanomagnesium. The burn rates of HTPB-B fuel samples were evaluated on the opposed flow burner(OFB)under a gaseous oxygen oxidizer, for which the mass flux ranges from 22 kg/(m^(2)·s) to 86 kg/(m^(2)·s). The addition of Ti and Mg exhibited higher regression rates, which were attributed to the improved oxidation reaction of B due to the synergetic metal combustion effect. The possible combustion/oxidation reaction mechanism of B-Mg and B-Ti by heating the fuel samples at 900℃ and 1100℃ was also examined in a Nabertherm burnout furnace under an oxygen atmosphere. The post-combustion products were collected and further subjected to X-ray diffraction(XRD) and field emission scanning electron microscopy(FE-SEM) analyses to inspect the combustion behavior of B-Ti and B-Mg. It has been observed that the B oxide layer at the interface between B-Ti(B-Mg) is removed at lower temperatures, hence facilitating oxygen transfer from the surroundings to the core B. Additionally, Ti and Mg decreased the ignition delay time of B, which improved its combustion performance.

Microstructure and Fracture Toughness of Al_2O_3/3Y-TZP Composites

The composites were prepared by ball-milling ZrO_2(3%Y_2O_3) and γ-Al_2O_3 nanoparticles, pressing unidirectionally, cold-pressing isostatically and pressurelessly sintering in air. The phases of ZrO_2 in composites were examined by X-ray diffraction. The microstructure of Al_2O_3/3Y-TZP composites was observed by scanning electron microscope (SEM) and transmission electron microscopy (TEM) respectively. The X-ray analysis reveals that ZrO_2 of both surface and fracture surface is mainly t-ZrO_2. The SEM image shows that there are some intragranular particles in large granulars. The fracture toughness K_ 1c of Al_2O_3/70%ZrO_2(3%Y_2O_3(mole fraction)) composite tested by single-edge notched bending is 13.5 MPa·m 1/2. Being toughened by the ferroelastic domain switching and the intragranular microstructure explains high toughness of the composite.