Phase composition,conductivity,and sensor properties of cerium-doped indium oxide

The hydrothermal synthesis of In_(2)O_(3)and CeO_(2)–In_(2)O_(3)is investigated as well as the properties of sensor layers based on these compounds.During the synthesis of In_(2)O_(3),intermediate products In(OH)_(3)and InOOH are formed,which are the precursors of stable cubic(c-In_(2)O_(3))and metastable rhombohedral(rh-In_(2)O_(3))phases,respectively.A transition from c-In_(2)O_(3)to rh-In_(2)O_(3)is observed with the addition of CeO_(2).The introduction of cerium into rh-In_(2)O_(3)results in a decrease in the sensor response to hydrogen,while it increases in composites based on c-In_(2)O_(3).The data on the sensor activity of the composites correlate with XPS results in which CeO_(2)causes a decrease in the concentrations of chemisorbed oxygen and oxygen vacancies in rh-In_(2)O_(3).The reverse situation is observed in composites based on c-In_(2)O_(3).Compared to In_(2)O_(3)and CeO_(2)–In_(2)O_(3)obtained by other methods,the synthesized composites demonstrate maximum response to H_(2)at low temperatures by 70–100℃,and have short response time(0.2–0.5 s),short recovery time(6–7 s),and long-term stability.A model is proposed for the dependence of sensitivity on the direction of electron transfer between In_(2)O_(3)and CeO_(2).

Cerium Methacrylate Assisted Preparation of Highly Thermally Conductive and Anticorrosive Multifunctional Coatings for Heat Conduction Metals Protection

Preparing polymeric coatings with well corrosion resistance and high thermal conductivity(TC)to prolong operational life and ensure service reliability of heat conductive metallic materials has long been a substantive and urgent need while a difficult task.Here we report a multifunctional epoxy composite coating(F-CB/CEP)by synthesizing cerium methacrylate and ingeniously using it as a novel curing agent with corrosion inhibit for epoxy resin and modifier for boron nitride through"cation-π"interaction.The prepared F-CB/CEP coating presents a high TC of 4.29 W m^(−1)K^(−1),which is much higher than other reported anti-corrosion polymer coatings and thereby endowing metal materials coated by this coating with outstanding thermal management performance compared with those coated by pure epoxy coating.Meanwhile,the low-frequency impedance remains at 5.1×10^(11)Ωcm^(2)even after 181 days of immersion in 3.5 wt%NaCl solution.Besides,the coating also exhibits well hydrophobicity,self-cleaning properties,temperature resistance and adhesion.This work provides valuable insights for the preparation of high-performance composite coatings with potential to be used as advanced multifunctional thermal management materials,especially for heat conduction metals protection.

Cerium-tungsten oxides supported on activated red mud for the selective catalytic reduction of NO_(x)

Activated red mud(RM)has been proved to be a promising base material for the selective catalysis reduction(SCR)of NOx.The inherent low reducibility and acidity limited its low-temperature activity.In this work,molybdenum oxide,tungsten oxide,and cerium oxide were used to reconfigure the redox sites and acid sites of red mud based catalyst.When activated red mud was reconfigured by cerium-tungsten oxide(Ce-W@RM),the NOx conversion kept above 90%at 219-480℃.The existence of Ce^(3+)/Ce^(4+) redox electron pairs provided more surface adsorbed oxygen(O_(α)) and served as a redox cycle.Positive interactions between Ce,W species and Fe oxide in red mud occurred,which led to the formation of unsaturated chemical bond and promoted the activation of adsorbed NH_(3) species.WO_(3) and Ce_(2)(WO_(4))_(3)(formed by solid-state reaction between Ce and W species)could provide more Brønsted acid sites(W-O modes of WO_(3),W=O or W-O-W modes of Ce_(2)(WO_(4))_(3)).CeO_(2) species could provide more Lewis acid sites.The Langmuir-Hinshelwood(L-H)routes and Eley-Rideal(E-R)routes occurred in the low-temperature SCR reaction on the Ce-W@RM surface.NH_(4)^(+) species on Brønsted acid sites,NH_(3) species on Lewis acid sites,bidentate nitrate and bridging nitrate species were key active intermediates species.

Three-dimensional numerical simulation of heating and melting behaviors of cerium oxide powders in radio frequency thermal plasma

The present study aims at the numerical simulations of the melting process of cerium oxide particles in RF thermal plasma.The physical model and the calculating method were described firstly;the interaction between cerium oxide particles and plasma was analyzed;specific attention was given to the effects of particle initial size,injection velocity on the particle melting and trajectory in plasma.The influence of the temperature field and velocity field distribution of the plasma around the particle trajectory on the melting effect is analyzed,and the relationship between the heat absorption efficiency of the particles and the particle size reduction process is further determined.It is also found that there exists an optimal particle initial injection velocity which led to a more concentrated final particle size distribution and a more significant reduction of particle size.The results could provide effective guidance for understanding the plasma spheroidization process of uranium dioxide and cerium dioxide powder particles.

Nano transdermal system combining mitochondria-targeting cerium oxide nanoparticles with all-trans retinoic acid for psoriasis

Psoriasis is an inflammatory skin disease that is intricately linked to oxidative stress.Antioxidation and inhibition of abnormal proliferation of keratinocytes are pivotal strategies for psoriasis.Delivering drugs with these effects to the site of skin lesions is a challenge that needs to be solved.Herein,we reported a nanotransdermal delivery system composed of all-trans retinoic acid(TRA),triphenylphosphine(TPP)-modified cerium oxide(CeO2)nanoparticles,flexible nanoliposomes and gels(TCeO_(2)-TRA-FNL-Gel).The results revealed that TCeO_(2)synthesized by the anti-micelle method,with a size of approximately 5 nm,possessed excellent mitochondrial targeting ability and valence conversion capability related to scavenging reactive oxygen species(ROS).TCeO_(2)-TRA-FNL prepared by the film dispersion method,with a size of approximately 70 nm,showed high drug encapsulation efficiency(>96%).TCeO_(2)-TRA-FNL-Gel further showed sustained drug release behaviors,great transdermal permeation ability,and greater skin retention than the free TRA.The results of in vitro EGF-induced and H2O2-induced models suggested that TCeO_(2)-TRA-FNL effectively reduced the level of inflammation and alleviated oxidative stress in HaCat cells.The results of in vivo imiquimod(IMQ)-induced model indicated that TCeO_(2)-TRA-FNL-Gel could greatly alleviate the psoriasis symptoms.In summary,the transdermal drug delivery system designed in this study has shown excellent therapeutic effects on psoriasis and is prospective for the safe and accurate therapy of psoriasis.

Cerium-promoted conversion of dinitrogen into high-energy-density material CeN_(6) under moderate pressure

Synthesis pressure and structural stability are two crucial factors for highly energetic materials,and recent investigations have indicated that cerium is an efficient catalyst for N2 reduction reactions.Here,we systematically explore Ce–N compounds through first-principles calculations,demonstrating that the cerium atom can weaken the strength of the N≡N bond and that a rich variety of cerium polynitrides can be formed under moderate pressure.Significantly,P1-CeN_(6) possesses the lowest synthesis pressure of 32 GPa among layered metal polynitrides owing to the strong ligand effect of cerium.The layered structure of P1-CeN_(6) proposed here consists of novel N_(14) ring.To clarify the formation mechanism of P1-CeN_(6),the reaction path Ce+3N2→trans-CeN_(6)→P1-CeN_(6) is proposed.In addition,P1-CeN_(6) possesses high hardness(20.73 GPa)and can be quenched to ambient conditions.Charge transfer between cerium atoms and N_(14) rings plays a crucial role in structural stability.Furthermore,the volumetric energy density(11.20 kJ/cm^(3))of P1-CeN_(6) is much larger than that of TNT(7.05 kJ/cm^(3)),and its detonation pressure(128.95 GPa)and detonation velocity(13.60 km/s)are respectively about seven times and twice those of TNT,and it is therefore a promising high-energy-density material.

Cerium Oxide Nanoparticles Protect against Oxaliplatin Induced Testicular Damage: Biochemical, Histological, Immunohistochemical, and Genotoxic Study

Oxaliplatin is a chemotherapeutic drug used for colorectal cancer treatment. The testicular toxic effect is one of its recorded toxicities which resulted in a few studies. Oxidative stress could be a direct cause of this testicular toxicity. Cerium oxide nanoparticles (CONPs) are optimistic antioxidants for applications in medicine. The aim of the work is to study the protective effect of CONPs on testicular toxicity induced by oxaliplatin in rats. Forty adult male albino rats were divided into 4 groups: Control group, CONPs group (60 mg/kg, 5 times/week), Oxaliplatin group (4 mg/kg, twice/week), and Oxaliplatin & CONPs group, for 4 weeks. Seventy-two hours after the last administration, blood samples were taken for hormonal levels and testes were used for both histopathology and immunohistochemical microscopic examination. Sperm smears were also performed and their results were statistically analyzed to detect any sperm abnormalities. Oxaliplatin increased MDA levels. SOD and GPx activity was decreased. GSH levels were decreased. Also, it decreased the sperm cell count and serum testosterone, and anti-Müllerian hormon. In the testicular sections, significant histopathology changes were seen and immunohistochemical examination confirmed these results. Upon supplementation of CONPs with oxaliplatin decreased MDA levels. SOD and GPx activity was increased, and GSH did not change. In testicular sections, normal morphology was seen. Also, there was an increase in the sperm cell count and serum testosterone anti-Müllerian with significant improvement of testicular architecture, and immunohistochemical examination confirmed these results. The utilization of CONPs produced significant protection against all of the above-mentioned changes.

Corrosion resistance of cerium-doped zinc calcium phosphate chemical conversion coatings on AZ31 magnesium alloy

Zinc calcium phosphate （Zn-Ca-P） coating and cerium-doped zinc calcium phosphate （Zn-Ca-Ce-P） coating were prepared on AZ31 magnesium alloy. The chemical compositions, morphologies and corrosion resistance of coatings were investigated through energy-dispersive X-ray spectroscopy （EDS）, X-ray photoelectron spectroscopy （XPS）, X-ray diffraction （XRD）, electron probe micro-analysis （EPMA） and scanning electron microscopy （SEM） together with hydrogen volumetric and electrochemical tests. The results indicate that both coatings predominately contain crystalline hopeite （Zn3（PO4）2·4H2O）, Mg3（PO4）2 and Ca3（PO4）2, and traces of non-crystalline MgF2 and CaF2. The Zn-Ca-Ce-P coating is more compact than the Zn-Ca-P coating due to the formation of CePO4, and displays better corrosion resistance than the Zn-Ca-P coating. Both coatings protect the AZ31 Mg substrate only during an initial immersion period. The micro-galvanic corrosion between the coatings and their substrates leads to an increase of hydrogen evolution rate （HER） with extending the immersion time. The addition of Ce promotes the homogenous distribution of Ca and formation of hopeite. The Zn-Ca-Ce-P coating has the potential for the primer coating on magnesium alloys.

Co-doping of Iron and Cerium in Titanium Dioxide: Observation of a Cooperative Effect

The co-doping of iron and cerium into TiO2 was studied by means of X-ray diffraction, Raman spectroscopy, UV Vis diffuse reflectance spectroscopy and X-ray photoelectron spectroscopy, when separately doping via the sol-gel method, iron was introduced in the fralnework of anatase TiO2 whereas cerium was not; interestingly, both iron and cerium were introduced in tile framework when co-doping by the sol-gel method. The co-doped TiO2 behaves much more intense surface hydroxyl concentration than the separately-doped and pure TiO2. This observation demonstrates for the first time a cooperative effect in the co-doping of transitional metals in the framework of TiO2.

Cerium Separation from Light Rare Earth Concentrate by Liquid-Liquid Extraction

This work presents an investigation of solvent extraction parameters in order to obtain high purity cerium from a mixture containing other rare earths elements, as an alternative to oxidation and selective precipitation or dissolution. The study was carried out using a sample of sulfuric liquor obtained from the leaching of monazite rich in light rare earth elements (La, Ce, Pr, Nd) provided by INB (Indústrias Nucleares do Brasil S.A.). Experiments were carried out in chloridric, nitric and sulfuric media. The nitric and hydrochloric solutions were prepared by precipitation of the REE from the sulfuric liquor as rare earths oxalate, calcining the precipitate and dissolving it with nitric or hydrochloric acid. The separation of cerium was investigated in its trivalent and tetravalent forms. The parameters investigated were: type and concentration of extractant, type and amount of the oxidizing agent, liquor acidity, and volumetric ratio between organic and aqueous phases. The preference of the organic phase to extract cerium in its oxidized form (IV) over the other rare earths elements was confirmed, allowing the obtainment of a high purity cerium solution. The best results were achieved in nitric medium, with cerium in its tetravalent form, using cationic extractants (P507 or D2EHPA) and a mixture of potassium persulfate and silver chloride as oxidizing agents, yielding over 99% of cerium extraction with over 99% of purity.

Direct fabrication of cerium oxide hollow nanofibers by electrospinning

Electrospinning technique was used to fabricate PVP/Ce（NO3）3 composite microfibers. Different morphological CeO2 nanofibers were obtained by calcination of the PVP/Ce（NO3）3 composite microfibers and were characterized by scanning electron microscopy （SEM）, Transmission electron microscopy （TEM）, X-ray diffraction （XRD）, thermal gravimetric and differential thermal analysis （TG-DTA）, and （FTIR）. SEM micrographs indicated that the surface of the composite fibers was smooth and became coarse with the increase of calcination temperatures. The diameters of CeO2 hollow nanofibers （300 nm at 600 ℃ and 600 nm at 800 ℃ ） were smaller than those of PVP/Ce（NO3）3 composite fibers （1-2 um ）. CeO2 hollow nanofibers were obtained at 600 ℃ and CeO2 hollow and porous nanofibers formed by nanoparti- cles were obtained at 800 ℃. The length of the CeO2 hollow nanofibers was greater than 50 um. XRD analysis revealed that the composite microfibers were amorphous in structure and CeO2 nanofibers were cubic in structure with space group O^5H - FM3m when calcination tem- peratures were 600-800 ℃. TG-DTA and FTIR revealed that the formation of CeO2 nanofibers was largely influenced by the calcination temperatures. Possible formation mechanism of CeO2 hollow nanofibers was proposed.

Influences of Cerium and Carbide on Mechanical Properties of Steels

s: The influences of cerium and cerium carbide on the strength, plasticity, impact toughness and other mechanical properties of steels were investigated by means of metallography, scanning electron microscopy, impact test, tensile test and other experimental methods. The results show that cerium in solid solution of the steel matrix can inhibit the grain growth of austenite and enhance the temperature of grain coarsening by fifty degrees at least. An excess of cerium addition will segregate to grain boundaries, and considerably reduce the impact toughness of the steel. The cerium carbide can obviously improve the plasticity and toughness of steels, but does not noticeably affect the yield strength of steels.

Characteristics on Cerium Promoted Iron Based Catalyst forDehydrogenation Ethylbenzene to Styrene

it was found by XPS and XRD that cerium existed as CeO_2 in iron based catalyst for dehydrogenation of ethylbenzene to styrene. and CeO_2 can be partly reduced under the reaction conditions to create Ce(3+)/Ce(4+) redox couples in the catalyst. The experiment of XPS and TPR-GC showed that there is an interaction between Ce oxide and Fe oxide, resulting in the shift of negative charge from iron to cerium and in the difficulty of Fe_2O_3 reduction to Fe_3O_4 in Fe_2O_3-CeO_2 system.The role of cerium promoter in the catalytic process was supposed to enhance the electron transfer among neighboring Fe active-sites of the catalyst and to improve the redox process of ethylbenzene dehydrogenation in the presence of steam by transferring oxygen from water to the active phase of the catalyst.

Effect of cerium ion(Ⅲ) on corrosion resistance of organic-inorganic hybrid coating on surface of aluminum-tube used in refrigeration equipment

Organic?inorganic hybrid coating on the surface of aluminum-tube used in refrigeration equipment using cerium ion (III) as the additive was fabricated by sol?gel method, and the structure of the coating was confirmed by FT-IR. The results of the characterization show that the corrosion resistance of the coating with 1.5 mmol/L cerium ion (III) gains significant improvement, in which the colour retention time of CuSO4 extends to 500 s, the anti-acid and alkali corrosion rates reduce by 67% and 70% compared with the blank one, respectively, and the salt spray tests also show good corrosion resistance. The electrochemical tests demonstrate that the self-corrosion current density and potential of the sample with hybrid coating are about 2.877×10?7 A/cm2 and?0.550 V, respectively. The metallographic and SEM images show that the hybrid coating is uniform and dense, and the EDS analysis confirms that the coating is mainly composed of Al, Si and Ce elements.

Study on corrosion resistance of the BTESPT silane cooperating with rare earth cerium on the surface of aluminum-tube

Bis-3-(triethoxysilyl)propyltetrasulfide(BTESPT) silane-rare earth cerium composite coatings on aluminum-tube were prepared at 60 °C by immersion method.The performance of composite coatings to protect the aluminum-tube against corrosion was investigated with potentiodynamic polarization curves,electrochemical impedance spectroscopy(EIS),and salt spray test(SST).The results of potentiodynamic polarization curves and EIS indicated that the self-corrosion current decreased by two orders of magnitude and the i...

Preparation of Nano-TiO_2 Doped with Cerium and Its Photocatalytic Activity

Cerium-doped titanium dioxide nano-powders were prepared through the sol-gel method and the compound sampies were characterized by X-ray diffraction （XRD）, transmission electron microscopy （TEM）, and UV/Vis diffuse reflectance spectra （DRS）. The photocatalytic activity was evaluated by photocatalytic degradation of phenol in water. The results of XRD, TEM, and DRS show that pure TiO2 and Ce-doped TiO2 powder crystallines are a mixture of anatase and rutile ; the doping can retard the development of the grain size of TiO2 and decrease the diameter of TiO2 from more than 20 nm of pure TiO2 to about 10 nm; the doped TiO2 can improve the light absorption of TiO2 and suitable doping content tends to move the DRS spectrum of TiO2 towards visible light, but too much doping is not good for the light absorption ability. The results of the photocatalytic experiments show that doping with Ce content of 0.08% -0.4% can increase the photocatalytic activity of TiO2; however, doping with Ce content of 0.5% -2.5% can significantly decrease the photocatalytic activity of TiO2. The favorite doping content is 0.4% in the range of our experiments.

Behaviors of Lanthanum and Cerium on Grain Boundaries in Carbon Manganese Clean Steel

The behaviors of La and Ce on gram boundaries in carbon manganese clean steel were investigated by high-reso- lution transmission elecetron microscope （HRTEM）, scanning elecetron microscopy（SEM ）, energy dispersive spectrometer （EDS） and X-ray diffraction（XRD） analysis. The existing forms of rare earths （RE） in clean steel were as follows： dissolved in sohd solution, forming inclusion or second phase containing RE （RE-Fe-P, La-P, Fe-La eutectic and Fe-Ce phase）. The dissolved La or Ce segregated at grain boundaries. The segregation of both S and P at gram boundaries was reduced with suitable RE content. The impact toughness of the steel was improved obviously. La and Ce had effecets on purifying molten steel and modifying inclusions in clean steel, whereas with excessive La or Ce, La-Fe-P, La-P and Fe-La eutecetic phase or Ce-Fe-P and Fe-Ce intermetallic compound would form along grain boundaries, causing the impact energy to decrease significantly.

Post treatment of silane and cerium salt as chromate replacers on galvanized steel

A complex film on hot-dip galvanized steel sheet（HDG） was prepared by immersing the sheet in 0.1wt.% Ce（NO3）3 solution and 5vol.% silane solution in turn.The corrosion protection of the complex film was evaluated by potentiodynamic linear polarization（LPR）, electrochemical impendence spectra（EIS） and natural salt spray（NSS） tests and compared with that of single cerium film and silane film.The results showed that, the presence of these films on the zinc coating hindered corrosion reaction by reducing the rate of both anodic and cathodic reaction in the corrosion process, and the corrosion protection of the complex film was much better than that of single cerium film or silane film and closed to that of chromate film, because the polarization resistance Rp and electrochemical impendence were increased markedly.Microstructure and chemical composition of these pretreated films were also investigated by scanning electron microscopy（SEM） and AES.

Toxic Effects of Lanthanum, Cerium, Chromium and Zinc on Potamogeton Malaianus

The toxic effects of rare earth elements such as lanthanum, cerium and heavy metal elements such as chromium, zinc on Potamogeton malaianus Miq. were studied. The results show that the contents of chlorophyll and soluble protein increase to a certain degree and then decrease under La3+ Ce3+ Zn2+ stress, while there is a constantly dropping tendency under Cr6+ stress. The four ions have different effects on protective enzyme systems of Potamogeton malaianus. They can induce rises of the activities of catalase (CAT) and peroxides (POD) at lower concentration, however, with the increase of ions concentration, the activities decline. The change of SOD activity is exactly opposite to that of CAT and POD activity. It falls at first and rises later. An increasing tendency of MDA content appears with the increasing concentration. The toxicities of La3+, Zn2+, Ce3+ and Cr6+ become more serious in the order. The lethal concentration of Cr6+ to Potamogeton malaianus ranges from 0.5 to I mg(-1) that of Ce3+ and Zn2+ ranges from 3 to 5 mg(-1) and that of La3+ ranges from 7 to 10 mg(.)L(-1). The toxic mechanism of La3 + and Ce3+ is similar to that of Cr6+ and Zn2+.

Effects of Cerium on Accumulation of Anthocyanins and Expression of Anthocyanin Biosynthetic Genes in Potato Cell Tissue Cultures

The effects of Ce （Ⅳ） on callus growth, anthocyanin content, and expression of anthocyanin biosynthetic genes in callus suspension cultures of Solanum tuberosum cv. Chieftain were studied by the measurement of fresh weight, spectrophotometric assays, and semiquantitative RT-PCR. The results indicate that 0.1 mmol·L^- 1 Ce （ Ⅳ ） can promote callus growth, increase the accumulation of anthocyanins, and enhance the expression of five anthocyanin biosynthetic genes （ CHS, F3H, F3＇5＇H, DFR, and 3 GT） most efficiently. At high concentrations of 1 mmol·L^- 1, Ce （Ⅳ） partially inhibits callus growth and at 2 mmol· L^-1 eventually lends to cell death. The results show that Ce（ Ⅳ ） can induce the expression of anthocyanin biosynthetic genes to produce and accumulate anthocyanins and increase the yield of anthocyanins.