Mechanochemical Synthesis of Visible-light Induced Photocatalyst with Nitrogen and Carbon Doping

Nitrogen and/or carbon doped titania photocatalysts were prepared by a novel mechanochemical method. The prepared powders possessed two absorption edges around 400 and 540 nm wavelengths and showed excellent photocatalytic ability for nitrogen monoxide oxidation under visible light irradiation. Under the irradiation of visible light of wavelength >510 nm,37% of nitrogen monoxide could be continuously removed by the carbon and nitrogen co-doped titania prepared by planetary ball milling of P-25 titania–10% hexamethylenetetramine mixture followed by calcination in air at 400-C.

Nonlinear Doping, Chemical Passivation and Photoluminescence Mechanism in Water-Soluble Silicon Quantum Dots by Mechanochemical Synthesis

A series of boron- and phosphorus-doped silicon wafers are used to prepare a series of doped silicon nanocrystals （nc-Si） by high-energy ball milling with carboxylic acid-terminated surface. The sizes of the nc-Si samples are demonstrated to be 〈 S nm. The doping levels of the nc-Si are found to be nonlinearly dependent on the original doping level of the wafers by x-ray photoelectron spectroscopy measurement. It is found that the nonlinear doping process will lead to the nonlinear chemical passivation and photoluminescence （I3L） intensity evolution. The doping, chemical passivation and PL mechanisms of the doped nc-Si samples prepared by mechanochemical synthesis are analyzed in detail.

Synthesis of Crystalline Hydroxyapatite from CaCO_3 and CaHPO_4·2H_2O by Mechanochemical Method

The mixture of CaHPO 4·2H 2O and CaCO 3 was ground in an aqueous system under appropriate conditions to investigate the mechanochemical reaction for the synthesis of crystalline hydroxyapatite (HA) powder. Hydroxyapatite of high crystallinity powder including trace Ca 10 (PO 4) 6CO 3(OH) and Ca 9HPO 4(PO 4) 6OH can be synthesized by mechanical activation without further thermal treatment at a high temperature. The synthesis reaction during the grinding process was almost completed within 1h. The as-ground powder exhibits a particle distribution of 20-100nm in size with a spherical or rodlike morphology. The composition and degree of crystallinity of the mechanochemical synthesized hydroxyapatite powders were coincident with the cement-type hydroxyapatite.

Mechanochemical redox-based synthesis of highly porous CoxMn1-xOy catalysts for total oxidation

A mechanochemical redox reaction between KMnO4 and CoCl2 was developed to obtain a CoxMn1-xOy catalyst with a specific surface area of 479 m^2 g^-1,which was higher than that obtained using a co-precipitation(CP)method(34 m2 g^-1),sol-gel(SG)method(72 m^2 g^-1),or solution redox process(131 m^2 g^-1).During catalytic combustion,this CoxMn1-xOy catalyst exhibited better activity(T100 for propylene=~200℃)than the control catalysts obtained using the SG(325℃)or CP(450℃)methods.The mechanical action,mainly in the form of kinetic energy and frictional heating,may generate a high degree of interstitial porosity,while the redox reaction could contribute to good dispersion of cobalt and manganese species.Moreover,the as-prepared CoxMn1-xOy catalyst worked well in the presence of water vapor(H2O 4.2%,>60 h)or SO2(100 ppm)and at high temperature(400℃,>60 h).The structure MnO2·(CoOOH)2.93 was suggested for the current CoxMn1-xOy catalyst.This catalyst could be extended to the total oxidation of other typical hydrocarbons(T90=150°C for ethanol,T90=225°C for acetone,T90=250℃for toluene,T90=120℃for CO,and T90=540℃for CH4).Scale-up of the synthesis of CoxMn1-xOy catalyst(1 kg)can be achieved via ball milling,which may provide a potential strategy for real world catalysis.

Advantageous mechanochemical synthesis of copper(Ⅰ)selenide semiconductor,characterization,and properties

Copper(I)selenide-nanocrystalline semiconductor was synthesized via one-step mechanochemical synthesis after 5 min milling in a planetary ball mill.The kinetics of synthesis was followed by X-ray powder diffraction analysis and specific surface area measurements of milled 2Cu/Se mixtures.The X-ray diffraction confirmed the orthorhombic crystal structure of Cu_(2)Se with the crystallite size∼25 nm.The surface chemical structure was studied by X-ray photoelectron spectroscopy,whereby the binding energy of the Cu 2p and Se 3d signals corresponded to Cu^(+)and Se^(2−)oxidation states.Transmission electron microscopy revealed agglomerated nanocrystals and confirmed their orthorhombic structure,as well.The optical properties were studied utilizing ultraviolet-visible spectroscopy and photoluminescence spectroscopy.The direct bandgap energy 3.7 eV indicated a blue-shift phenomenon due to the quantum size effect.This type of Cu_(2)Se synthesis can be easily adapted to production dimensions using an industrial vibratory mill.The advantages of mechanochemical synthesis represent the potential for inexpensive,environmentally-friendly,and waste-free manufacturing of Cu_(2)Se.

THE INVESTIGATION ON THE FORMATIONOF(K_(0.5)Na_(0.5))NbO_(3)PEROVSKITE PHASE IN MECHANOCHEMICAL SYNTHESIS

teviseuzobeptehberzoriLead-free(K_(0.5)Na_(0.5))NbO_(3)(KNN)nanopowder with perovskite structure was synthesized bymechanochemical synthesis method successfully.In order to investigate the perovskite phaseformation of KNN powders during the mechanochemical synthesis process,we set up three millingroutes with different transmission ratios(W_(v)/W_(p))acting on the mixed starting powders of Na_(2)CO_(3),K_(2)CO_(3)and Nb_(2)O_(5).KNN perovskite phase was not detected by XRD under the lowtransmission ratios-2 with the shock power of 273 W.When the transmission ratios wasincreased to-2.75 with the shock power of 683.4 W,KNN perovskite phase was formed aftermilling for 22 h.Based on these results it has been found,that in shock mode process(SMIP),thathigher shock power is helpful for the formation KNN perovskite phase.The critical shock powerPaitial and critical weight-normalized cumulative shock energy P^(*)_(critical)in KNN system are dis-cussed.Compared with SMP,when W_(v)/W_(p),=-3.5,in friction mode process(FMiP),KNN per-ovskite phase was formed after milling for 5 h.It implis that FMP benefit the formation of KNNperovslkite phase,The morphology of KNN powder was observed by transmsion electronmicroscopy(TEM).

Mechanochemical Synthesis and Characterization of Nanocrystalline Copper-Cobalt Ferrites

Nanocrystalline copper-cobalt ferrites with composition Cu_（1-x）Co_xFe_2O_4,where x = 0.2 and 0.8,were synthesized by mechanochemical treatment of co-precipitated precursors.The ferrite powders were characterized by XRD and Mossbauer spectroscopy.Results proved obtaining of spinel ferrites with crystallite size smaller than 10 nm.Increasing of crystallite size of samples with increasing of mechanochemical treatment duration was established,too.Catalytic properties of obtained ferrites were tested in reactions of oxidation of CO,methanol and dimethyl ether.High catalytic activity of nanocrystalline copper-cobalt ferrites toward CO and CH_3OH（about 100% conversions of CO and CH_3OH at 160 ℃）and moderate activity toward（CH_3）_2O oxidation were established.The results obtained revealed that the Co/Cu atomic ratio is an important factor determinant the behavior of catalysts toward methanol and DME oxidation.

Synthesis of niobium borides by powder metallurgy methods using Nb_(2)O_(5), B_(2)O_(3) and Mg blends

Niobium boride powders having NbB, NbB2 and Nb3B4 phases in various amounts and single phase NbB powders were successfully synthesized by using powder metallurgy methods from related metal oxide raw materials in the presence of a strong reducing agent. Nb2O5, B2O3 and Mg powder blends were milled at room temperature by a high-energy ball mill for different time. Subsequently, undesired MgO phase was removed from the milled powders by HCl leaching to constitute NbB?NbB2?Nb3B4 as final products and they were subjected to an annealing process at 1500 °C for 4 h to observe probable boride transformation. Characterization was carried out by XRD, DSC, PSA, SEM/EDX, TEM and VSM. The effects of milling time (up to 9 h) on the formation, microstructure and thermal behavior of the final products were investigated. Reduction reaction took place after milling stoichiometric powder blends for 2 h. Nano-sized NbB?NbB2?Nb3B4 powders in high purity were obtained in the absence of any secondary phase and any impurity via mechanochemistry by milling for 5 h and leaching with 4 mol/L HCl. After annealing, pure and nano-sized NbB?NbB2?Nb3B4 powders transformed to a single NbB phase without leaving behind NbB2 and Nb3B4 phases.

Solvent-free esterification of poly(vinyl alcohol) and maleic anhydride through mechanochemical reaction

A solid-state mechanochemical processing, that is, pan-milling, was used to conduct the esterification of poly（vinyl alcohol） （PVA） with maleic anhydride （MA） through stress-induced reaction. FTIR spectrum study indicated the presence of ester linkages and olefinic double bonds in maleic anhydride cross-linked PVA. Thermal properties of the cross-linked product were characterized by DSC. The results showed its glass transition temperature was 20 ℃ higher than the original linear PVA and the thermal stability was also improved.

Solar Photocatalysis of TiO2 Supported Natural Palygorskite Nanofibers Elaborated by a One_Pot Mechanochemical Route

This study reports the successful synthesis of supported TiO2_Palygorskite nanocomposites by a one-pot dry mechanochemical route. Indeed, the elaboration procedure involved an in-situ reaction between accessories carbonates present in raw fibrous palygorskite clay and titanyl sulfate (TiOSO4) precursor under variable grinding conditions, essentially ball/solid matter mass ratio and rotation velocity. This yielded after air annealing at 600%C for 1 h to the immobilization of anatase TiO2 nanoparticles (≈8 nm of average size) as evidenced by XRD and TEM analyses. Once the conditions of elaboration were optimized, the photocatalytic properties were evaluated under 3 conditions: artificial UV radiation, artificial solar radiation (UV + visible range) and under dynamic solar illumination taking into account the discontinuities of the solar resource. The results allowed the estimation and comparison of the catalyst’s capabilities and showed its ability to work under natural irradiation. The so developed supported photocatalysts TiO2/Palygorskite exhibited a good activity towards the removal of Orange G (OG) dye from aqueous media under artificial UV and natural solar radiations.

Enthalpy-change driven synthesis of high-entropy perovskite nanoparticles

Due to their diverse and tunable composition,distorted lattice and excellent stability,high-entropy ceramics(HECs)hold great promise for catalysis,especially when they present as nanoparticles(NPs).However,current HECs are typically limited to bulky materials with none or fewer defects,because high synthetic temperature(e.g.,1,000–1,200°C)is usually required to highlight the entropic contribution(TΔS)inΔG=ΔH−TΔS.Being different with previous strategies,a negative Gibbs free energy for HECs crystallization is obtained by dramatically decreasing the mixing enthalpy(ΔH).Guided by this principle,single-phase highentropy La(Ni_(0.2)Mn_(0.2)Cu_(0.2)Fe_(0.2)Co_(0.2))O_(3−δ)perovskite(HE-LMO)NPs were prepared at a relatively low temperature(≤500°C).Interestingly,abundant oxygen vacancies were directly created within HE-LMO NPs,which exhibited good activity in catalytic oxidation.Meanwhile,the high-entropy structure endows as-made HE-LMO with robust stability even with 5 vol.%water in feeding gas.Density functional theory(DFT)calculations revealed that the defective sites in HE-LMO NPs facilitated the charge transfer from HE-LMO to CO,thus activating the adsorbed CO gas.The current work may inspire future design and synthesis of HECs NPs.

Nanocrystalline Growth Activation Energy of Zirconia Polymorphs Synthesized by Mechanochemical Technique

The synthesis of ZrO2 by mechanochemical reaction using ZrCI4 and CaO as raw materials and subsequent annealing of the products were investigated. The effect of thermal treatment on the structural evolution and morphological characteristics of the nanopowders was studied by X-ray diffractometry, Raman spectroscopy, transmission electron microscopy, scanning electron microscopy, differential thermal analysis and Rietveld refinement. The results showed that the average crystallite size of Zr02 was less than 100 nm up to around 1100 ℃. The activation energy for ZrO2 nanocrystallite growth during calcination was calculated to be about 13,715 and 27,333 J/too Mechanism of the nanocrysta for tetragonal （t-ZrO2） and monoclinic （m-Zr02） polymorphs, respectively. ite growth of the ZrO2 polymorphs during annealing is primarily investigated.

Role of MgF2 addition on high energy ball milled kalsilite:Implementation as dental porcelain with low temperature frit

Porcelain fused to metal(PFM)has received great attention over the last few years due to its importance in the dentistry.Kalsilite(K_(2)O·Al_(2)O_(3)·SiO_(2))is a high thermal expansion porcelain,suitable for bonding to metals.However,kalsilite is a metastable phase which gets converted into crystalline leucite upon heating.In the current work feasibility of developing stable kalsilite phase,dispersion of MgF2 in it as an additive and using mechanochemical synthesis are studied.Micro fine dental material has been formulated by mixing prepared kalsilite with low temperature frit(LTF)in different ratio.The crystalline phases evolved in fired powders are characterized by powder X-ray diffraction(XRD)technique.Kalsilite with different ratio of LTF has been cold pressed and heat treated to examine its coefficient of thermal expansion(CTE),flexural strength,apparent porosity(AP),bulk density(BD)and microstructure.Results indicate that MgF_(2) addition and high milling duration help in kalsilite stabilization.Temperature also plays an important role in this stabilization,and at 1100℃single phase kalsilite formation is observed.Present outcomes demonstrate that it is easily possible to synthesize a stable single phase kalsilite with desirable properties.

Cu/Ta sheaths for iron-based superconductors:First experimental findings in Ca/K-1144 wires

Iron based superconducting wires(IBSCs)produced by the Powder in Tube(PIT)method rely on the use of silver sheaths as chemical buffer between the outer metal and the superconducting core.The adoption of silver entails however some limitations,such as the viable temperature range when coupled with copper,and the incompatibility with calcium-based IBSCs already at 600℃,driving the research towards other wires architecture.Taking inspiration from the low temperature superconductors field,we decided to evaluate the adoption of tantalum as diffusion barrier in a layered Cu/Ta architecture,choosing a Ca/K-1144 IBSC as case study considering the high reactivity issues already reported in the case of silver sheaths for this compound.Squared wires were produced through a groove rolling lamination process coupled with a thermal treatment at 800℃.The microstructural analyses show the absence of interdiffusion between the different parts of the wire,and the magnetic characterization shows performance in line with similar polycrystalline manufacts,with margin of enhancement to be pursued via the optimization of the mechanical process and other experimental variables.The reported results suggest thus the effectiveness of tantalum as diffusion barrier for Ca/K-1144 PIT wires.