Crystallization of Mg-based bulk metallic glass

Mg-based bulk metallic glass fabricated by conventional copper mould method was aged at different temperatures. X-ray diffractometry(XRD), scanning electron microscopy(SEM), atomic force microscopy(AFM) and focused ion beam(FIB) miller were employed to examine specimens obtained under different conditions. The crystallization of Mg-based bulk metallic glass depends upon both the aging temperature and the aging time. As temperature increases or the holding time increases, the microstructure of the aged specimen varies from glassy one to crystalline one plus glassy phase and then to absolutely multiphase crystalline one. From the FIB images, it is clear that Mg-based bulk metallic glass could not only crystallize completely but also display dendrite-like growth style. From the AFM images, there are not only significant variations of microstructures but also surface morphology of specimens obtained under different conditions. It is proposed that the surface morphology varies as the treating temperature increases. The Vickers hardness of different specimens increases as the fraction of crystalline phase (s) increases.

Synthesis,Crystal Structure and Optical and Photocatalytic Properties of a Discrete Cuprous Iodide Compound with a Transition Metal Complex Cation

With transition metal complex, a discrete cuprous iodide compound, namely, [Ni（phen）3]2Cu6I10（1, phen = 1,10-phenanthroline） has been solvothermally synthesized and structurally characterized. Single-crystal X-ray diffraction studies revealed that compound 1 crystallizes in triclinic space group P1（No. 2） with a = 11.2694（2）, b = 12.3699（3）, c = 15.0387（3） ？, α = 102.840（2）, β = 105.215（2）, γ = 96.388（2）°, V = 1940.04（7） ^3, Z = 1, Dc = 2.438 g·cm^-3, F（000） = 1324, R = 0.0256 and w R = 0.0555（I 〉 2σ（I））. Compound 1 features a discrete anionic moiety of [Cu6I10]^4- charge-balanced by two metal complexes of [Ni（phen）3]2＋. The optical absorption edge of compound 1 was estimated to be 2.24 eV. Interestingly, nearly 95% of contaminant（crystal violet aqueous solution（CV）, 50 m L, 1.0 × 10^-5 M） could be decolorized after exposure to visible light within 30 min, illustrating an impressive photocatalytic activity of compound 1. The thermal stability of 1 has also been studied.

Comparative Study of the One Dimensional Dielectric and Metallic Photonic Crystals

The optical transmission properties of two types of photonic crystals have been analyzed by using the transfer matrix method. The first one is the dielectric photonic crystal (DPC), and the second is the metallic photonic crystal (MPC). We found the dielectric and metallic photonic crystals have different transmission spectra. The effect of the most prameters on the transmission spectra of the dielectric and metallic photonic crystals has been studied.

Synthesis and Crystal Structure of a Novel Chiral 3D Metal-organic Framework Based on an N-methyl Substituted Salan Ligand

A chiral 3D metal-organic framework [CdL].DMSO＇H20 （1） was constructed by an N-methyl substituted salan ligand （H2L）, and characterized by elemental analyses, IR, TGA, powder XRD and single-crystal X-ray crystallography. 1 crystallizes in the chiral hexagonal space group P6522 with a = b = 12.2175（3）, c = 51.450（3） A, V= 6650.9（4） A3, Z = 6, Mr = 883.45, Dc = 1.323 g.cm-3, F（000） = 2760, 2（CuKa） = 1.54178 A,β = 4.771 mm-1, GOOF = 1.041, R = 0.0313 for 3901 observed reflections with I 〉 20（/） and wR = 0.0773.1 consists of three identical sets of independent 3D frameworks interpenetrated with each other. In each set of such 3D frameworks, one half of the monomer （CdL）1/2 as the building unit forms double antiparrel helical chains which are further bridged together by other （CdL）1/2 units from adjacent helical chains. All CdL units in 1 adopt A geometry. DMSO and water guest molecules are found in the gap of the interpenetrated frameworks.

Synthesis and Crystal Structure of a Magnesium Metal-organic Framework

A magnesium metal organic framework, [N-H2（CH3）2][-N（CH3）4][Mgs（bpdc）3（O2CH）6]· 3H2O （1, bpdcH2 = 4,4＇-biphenyldicarboxylic acid）, has been solvothermally synthesized and structurally characterized. 1 crystallizes in the trigonal system, space group R-3, with a = 11.3427（3）, c = 41.5662（18） A, V = 4631.3（3） A^3, Z = 3 and the final R = 0.0457. Its structure features a pillared-layered three-dimensional network with 8.21 A cavities, in which cationic [NH2（CH3）2]^＋ or [N（CH3）4]^＋ and lattice water molecules are located. Thermal stability of the title compound has also been investigated.

Crystallization Kinetics of Misch Metal Based Bulk Metallic Glasses

The crystallization kinetics of Mm55Al25Cu10Ni5Co5 bulk metallic glass （BMG） was investigated by means of differential scanning calorimetry （DSC） in the mode of continuous heating or isothermal annealing. It was found that the apparent activation energy Eg, Ex and Ep of the BMG calculated by Kissinger＇s method were 189.58, 170.68 and 170.41 kJ·mol^-1, respectively, which was bigger than those of La55Al25Cu10Ni5Co5 BMG indicating that thermal stability of the former was higher than that of the latter. The local activation energy obtained using Ozawa equation decreased as crystallization proceeded except for the initial stage. The Avrami exponents were calculated to be in the range of 3.26 - 5.23 for different crystallization stages and isothermal temperatures. This implied that crystallization of Mm55Al25Cu10Ni5Co2 BMG was governed by diffusion-controlled three-dimensional growth with either reduced or increased nucleation rate, depending on isothermal temperature. Inconsistency of thermal stability with glass-forming ability for Mm（La）-Al-Cu-Ni-Co BMGs was discussed.

Synthesis and Crystal Structure of the Novel Chiral o-Hydroxyphenyloxazoline Metal Complexes

The chiral o-hydroxyphenyloxazoline ligands were synthesized and their metal complexes with Cu, Ni and Ti were prepared. The crystal structure of complex 2a formed by ligand 1a with Cu (molar ratio 2:1) was determined by single-crystal X-ray diffraction analysis, and it belongs to monoclinic, space group P21 with a = 11.679(2), b = 17.681(4), c = 12.838(3) ? b = 106.50(3), C26H32N2O4Cu, Mr = 500.08, V = 2541.8(9) 3, Z = 4, F(000) = 1052, Dc = 1.307 g/cm3, m = 0.892 mm-1, the final R = 0.0448 and wR = 0.0930 (I > 2s(I)). In the asymmetric unit of complex 2a, there exist two types of molecules which are self-associated by intermolecular O…Cu interactions, and 揹imeric complex?is thus formed. The distances of the Cu and O atoms of a pair of intermolecular coordinated molecules are 2.828 ?for Cu(1)…O(21) and 2.776 ?for Cu(2)…O(13), respectively. The coordination N and O atoms and the central Cu are slightly deviated from coplanarity.

Solution-based metal induced crystallization of a-Si

This paper investigates a simplified metal induced crystallization （MIC） of a-Si, named solution-based MIC （SMIC）. The nickel inducing source was formed on a-Si from salt solution dissolved in de-ionized water or ethanol, a-Si thin film was deposited with low pressure chemical vapour deposition or plasma enhanced chemical vapour deposition as precursor material for MIC. It finds that the content of nickel source formed on a-Si can be controlled by solution concentration and dipping time. The dependence of crystallization rate of a-Si on annealing time illustrated that the linear density of nickel source was another critical factor that affects the crystallization of a-Si, besides the diffusion of nickel disilicide. The highest electron Hall mobility of thus prepared S-MIC poly-Si is 45.6 cm^2/（V· s）. By using this S-MIC poly-Si, thin film transistors and display scan drivers were made, and their characteristics are presented.

Formation and crystallization of Zr-Ni-Ti metallic glass

The metallic Zr65Ni25Ti10（mole fraction, %） glass has been fabricated by a single roller melt-spinning method. The glass forming ability（GFA） and thermal stability of the Zr65Ni25Ti10 melt-spun ribbons were investigated by using X-ray diffraction（XRD） and differential scanning calorimetry（DSC） in the mode of continuous heating. It is shown that the reduced glass transition temperature (Trg) is 0.506 and the supercooled liquid region （ΔTx） is 30 K. Two exothermic peaks were observed in the DSC curves of the as-quenched ribbon, which indicates that the crystallization process undergoes two different stages. The phase transformation during the isothermal annealing was investigated by X-ray diffraction（XRD） and transmission electronic microscope（TEM）. It is observed that the metastable FCC Zr2Ni（Fd3m, a=12.27 ） precipitated while annealing in the suppercooled region（615 K） and the stable BCT Zr2Ni（I4/mcm, a=6.499 , c=5.270 ） precipitated while annealing at higher temperature（673 K or 723 K）. The crystallines are on nanoscale, with grain size of 1530 nm. The reason for the precipitation of the different structural Zr2Ni from the glassy matrix under different annealing conditions was discussed based on the concept of multi-component chemical short range order（MCSRO）.

Effects of crystallization on corrosion behaviours of a Ni-based bulk metallic glass

The effects of microstructure change on the corrosion behaviours of Ni55Nb20Ti10Zr8Co7 bulk glass-forming alloy were investigated in 1 mol/L HCl and 0.5 mol/L H2SO4 solutions. Different microstructures of the Ni-based alloy were achieved by annealing the bulk glassy rod prepared by copper mould casting. The microstructure, grain size, grain distribution, and phase composition were characterized. Electrochemical behaviours of the Ni-based alloy were revealed by static immersion and anodic potentiodynamic polarization tests. It is indicated that the corrosion behaviours of the Ni-based bulk glass-forming alloy are related to its microstructures, while the fully crystallized alloy exhibits a relatively lower corrosion resistance than those of the amorphous states.

CRYSTALLIZATION OF Fe_(38)Ni_(39)Si_(10)B_(13) METALLIC GLASS UNDER HELIUM ION IRRADIATION

he crystallization features of Fe38Hi39Si10B13 metallic glass under 100 keV and 6μA/cm2 helium ion irradiation with different doses are reported. It is found that the Fe38 Ni39Si10 B13 metallic glass crystallized under the helium ion irradiation at the temperature lower than the ordinary thermal crystallization temperature. The preferential precipitation phase is FeSi, and followed by the eutectic phase α-Fe. The critical dose for the formation of helium bubbles in the material is around 5x10￣16/cm2. The sensitivity of crystallization due to the temperature rising under helium ion irradiation and the mechanism of the sequence of precipitated phase are briefly discussed.

Crystallization of amorphous silicon beyond the crystallized polycrystalline silicon region induced by metal nickel

Crystallization of amorphous silicon（a-Si） which starts from the middle of the a-Si region separating two adjacent metal-induced crystallization（MIC） polycrystalline silicon（poly-Si） regions is observed. The crystallization is found to be related to the distance between the neighboring nickel-introducing MIC windows. Trace nickel that diffuses from the MIC window into the a-Si matrix during the MIC heat-treatment is experimentally discovered, which is responsible for the crystallization of the a-Si beyond the MIC front. A minimum diffusion coefficient of 1.84×10^-9cm^2/s at 550℃ is estimated for the trace nickel diffusion in a-Si.

Micromechanism of Crystallization in Multicomponent Metallic Glass

A micromechanism in an atomic level of crystallization of transition metal-metalloid TM(80)M(20) metallic glass is thermodynamically proposed by taking Bernal polyhedra as the starting structure of metallic glass. It is composed of two competitively processes: (i) densification process of atom cluster leads to the formation of the precursor in amorphous matrix; (ii) the growth of atom cluster leads to the decreasing packing density. The preferential precipitation sequence of metastable phase is bcc, bet, cpc (close-packed crystal, hcp or fee structure). A metastable phase decomposition (Fe,Mo)(23)B-6 (fcc)-Fe2B highly strained bet phase was observed during crystallization of (Fe(0.99)M(0.01))(78)Si9B13 metallic glass, which is related to the occurrence of nanocrystalline.

Crystallization Behavior of Metallic GlassCo_（65．1）Fe_（4．7）Ni_（4．6）Si_（10．2）B_（15．4）

The in situ observation of crystallization behavior of metallic glass Co_(65.1) Fe_(4.7)Ni_(4.6)Si_(10.2) B_(15.4)during heat-ing in an electron microscope is carried out. The three crystalline phases correlated with the exothermalpeaks on the DSC profiles are identified by means of electron diffraction. and they are all stable phasesfrom room temperature to 1000 K.Besides.an anomalous crystalline phase with long spikes along the direction in the reciprocal lattice space is found during crystallization. and its structural model is also discussed.

Transitional Metal Complexes with 1,2,4-Triazole Ligand:Syntheses and Crystal Structures

Four novel transitional metal complexes with 3-（4-pyridly）-4-phenyl-5-sulfhydryl- 1,2,4- triazole （HL1） and 3-（3-pyridly）-4-phenyl-5-sulfhydryl-l,2,4-triazole （HLz） were synthesized and characterized by elemental analysis, IR and X-ray diffraction. Complexes 1, 3 and 4 have two-dimensional （2-D） neutral rhombohedral grid with a （4, 4） topology. In 1, 3 and 4, all the metal ions are six-coordinated to four nitrogen atoms of four distinct ligands and two O atoms from water molecules. Complex 2 has tetranuclear CuaCI4 units which are interconnected by four desulfuri- zation ligands （L1-S） via Cu-N bonds to form a 2-D layer with （4,4） topology.

Phases in the crystallization process of Zr_(65)Al_(7.5)Ni_(10)Cu_(17.5)metallic glass

The crystallization process of metallic glass Zr_(65)Al_(7.5)Ni_(10)Gu_(17.5)(atom fraction in percent) were studied by transmission electron microscopy and X-ray diffraction.Two stages of crystallization process, which are indicated by the two exothermic peaks in thedifferential scanning calorimetry diagram, were studied separately. It is found that the phases inthe various stage of the crystallization are different. In the first stage, it consists mainly oftI-CuZr_2 and tP-Al_2Zr_3 phases, between which a definite orientation relationship is found. Whilein the second stage, in addition to the above phases, phase hP^2-Al_2NiZr_6 and phase hP^3-alpha-Zrappear, between which another orientation relationship is also found. At the same time, a comparisonis made based on the study of the phases exist in the arc-melted master ingot. The latticeparameters of the identified phases were determined and some interesting similarities were found.According to these similarities, all the phases were classified into two groups. The first is: oB,tI-CuZr_2 and hP^3-alpha-Zr; the other is: hP^2, tP-Al_2NiZr_3 and hP^1-Al_2NiZr_6. Therelationships between phases in these two groups were investigated and the probable reasons that mayresult in these relationships were discussed.

Crystallization of Pd_40Cu_30Ni_10P_20 bulk metallic glass with and without pressure

The glass-transition behavior of Pd40Cu30Ni10P20 bulk metallic glass was investigated by differential scanning calorimetry （DSC） and X-ray powder diffraction （XRD）. The effect of pressure on the crystallization behavior of Pd40Cu30Ni10P20 bulk glass was studied by in situ high-pressure and high-temperature X-ray powder diffraction using synchrotron radiation. Phase analyses show at least six crystalline phases in the crystallized sample, namely, monoclinic, tetragonal CuaPd-like, rhombohedral, fcc-Ni2Pd2P, fcc-（Ni, Pd） solid solution, and body-centered tetragonal （bct） NiaP-like phases. The onset crystallization temperature increases with pressure having a slope of 1 1 K/GPa in the range of 0 to 4 GPa. The results are attributed to the competing process between the thermodynamic potential barrier and the diffusion activation energy under pressure.

Kinetics of Glass Transition and Crystallization in Carbon Nanotube Reinforced Mg-Cu-Gd Bulk Metallic Glass

Mg65Cu25Gd10 bulk metallic glass and its carbon nanotube reinforced composite were prepared. Differential scanning calorimeter （DSC） was used to investigate the kinetics of glass transition and crystallization processes. The influence of CNTs addition to the glass matrix on the glass transition and crystallization kinetics was studied. It is shown that the kinetic effect on glass transition and crystallization are preserved for both the monothetic glass and its glass composite. Adding CNTs in to the glass matrix reduces the influence of the heating rate on the crystallization process. In addition, the CNTs increase the energetic barrier for the glass transition. This results in the decrease of GFA. The mechanism of the GFA decrease was also discussed.

Low Frequency Dispersion Law for Two-Dimensional Metallic Photonic Crystals

Using the rigorous multiple-scattering theory, we study the dispersion relation of electromagnetic （EM） waves in two dimensional dielectric photonic crystals （PCs） and metallic photonic crystals （MPCs） in the low-frequency limit. Analytic formula for the effective velocity of EM waves in PCs and MPCs is obtained. Accuracy of our formula is checked by comparing the results with rigorous calculations. For PCs, our result is exactly the same as the coherent potential approximation （CPA）, which is accurate even when the filling fraction is high. But for MPCs, our approach demonstrates special advantages, while the CPA theory fails, in predicting the effective velocity of EM waves in MPCs at low frequency.

Pressure Effect on Crystallization of Zr_(55)Cu_(30)Al_(10)Ni_5 Bulk Metallic Glass

The effect of pressure on the variation of the crystallization phases of the Zr55Cu30Al10Ni5 bulk glass and its thermal stability under high pressure annealing was investigated by X-ray diffraction (XRD) and differential scanning calorimeter (DSC). The mode of crystallization and products of crystallization of the Zr55Cu30Al10Ni5 bulk glass were quite different under different pressure. At ambient pressure, the crystallization products consisted of NiZr2 and CuZr2, while at pressure of 1 GPa and 3 GPa, the alloys crystallized into NiZr2 and Cu10Zr7, respectively. The alloy was nearly not crystallized and only a small amount of Cu10Zr7 was precipitated under 5 GPa. DSC proved that the mode of the crystallization under high pressure was different from that at ambient pressure.