Nitridation of chromium powder in ammonia atmosphere

CrN powder was synthesized by nitriding Cr metal in ammonia gas flow, and its chemical reaction mechanism and nitridation process were studied. Through thermodynamic calculations, the Cr-N-O predominance diagrams were constructed for different temperatures. Chromium nitride formed at 7002-1200℃ under relatively higher nitrogen and lower oxygen partial pressures. Phases in the products were then investigated using X-ray diffraction (XRD), and the Cr₂N content varied with reaction temperature and holding time. The results indicate that the Cr metal powder nitridation process can be explained by a diffusion model. Further, Cr₂N formed as an intermediate product because of an incomplete reaction, which was observed by high-resolution transmission electron microscopy (HRTEM). After nitriding at 1000℃ for 20 h, CrN powder with an average grain size of 63 nm was obtained, and the obtained sample was analyzed by using a scanning electron microscope (SEM).     

Intergranular corrosion behavior of high nitrogen austenitic stainless steel

The intergranular corrosion (IGC) behavior of high nitrogen austenitic stainless steel (HNSS) sensitization treated at 650-950℃ was investigated by the double loop electrochemical potentiodynamic reactivation (DL-EPR) method. The effects of the electrolytes, scan rate, sensitizing temperature on the susceptibility to IGC of HNSS were examined. The results show that the addi-tion of NaCl is an effective way to improve the formation of the cracking of a passive film in chromium-depleted zones during the reactivation scan. Decreasing the scan rate exhibits an obvious effect on the breakdown of the passive film. A solution with 2 mol/L H₂SO₄+1 mol/L NaCl+0.01 mol/L KSCN is suitable to check the susceptibility to IGC of HNSS at a sensitizing temperature of 650-950℃ at a suitable scan rate of 1.667 mV/s. Chromium depletion of HNSS is attributed to the precipitation of Cr₂N which results in the susceptibility to IGC. The synergistic effect of Mo and N is suggested to play an important role in stabilizing the passive film to prevent the attack of IGC.     

Synthesis,Structure and Antitumor Activities of [Ni（dien）2][Ni（CN）4] Complex

Ni(II)-dien complex was prepared and characterized by X-ray diffraction. The crystal belongs to triclinic system, space group P-1, with crystallographic parametersa=0.888 13(18) nm,b=0.890 10(18) nm,c=1. 591 8(3) nm, α=77.71(3)°, β=89.12(3)°, γ=61.24(3)°,Z=2. The two dien molecules coordinate to the central Ni atom, the six nitrogen atoms form a distorted octahedron. Preliminary pharmacological tests showed this complex had antitumor activity against HepG₂ and HL-60 cell linesin vitro. Foundation item, Supported by the National Natural Science Foundation of China (29972034) Biography: Li Tao (1976-), male, Ph. D candidate, research direction: ophthalmology and chemicalbiology.     

Synthesis and characterization of spinel Li_(1.05)Cr_(0.1)Mn_(1.9)O_(4-z)F_z as cathode materials for lithium-ion batteries

Samples with the nominal stoichiometry Li_1.05Cr_0.1Mn_1.9O_4−z F _z (z=0, 0.05, 0.1, 0.15, and 0.2) were synthesized via the solid-state reaction method and characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), galvanostatic charge/discharge, and slow rate cyclic voltammetry (SSCV) techniques. The results show that the pure spinel phase indexed to Fd3m can be obtained when z=0, 0.05, and 0.1. The substitution of F for O with z≤0.1 contributes to the increase of initial capacity compared with Li_1.05Cr_0.1Mn_1.9O₄ spinels. However, when the F-dopant content is designed to be 0.15 and 0.2, the Li_1.05Cr_0.1Mn_1.9O_4−z F _z samples deliver relatively low capacity and poor cycling properties at 55°C.     

Structure and properties of NASICON synthesized by two different zirconium salts

ZrOCl₂·8H₂O and ZrO(NO₃)₂·2H₂O were used respectively to synthesize a NASICON solid electrolyte by a sol-gel method. The structure and properties of two samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and electrochemical impedance spectroscopy (EIS). The crystal structure was investigated by the Rietveld refinement. It is found that both the samples contain a monoclinic C2/c phase as the main conductive phase with the lattice parameters of a=1.56312 nm, b=0.90784 nm and c=0.92203 nm, though a small amount of rhombohedral phase is also detected in the final product. The sample synthesized by ZrO(NO₃)2·2H₂O contains more monoclinic phase (89.48wt%) than that synthesized by ZrOCl₂·8H₂O (74.91wt%). As expected, the ionic conductivity of the latter is higher than that of the former; however, the activation energy of the latter (0.37 eV) is slightly higher than that of the former (0.35 eV).     

氮含量对SWRH82B盘条组织和性能的影响

为了研究不同含氮量的SWRH82B盘条在组织和性能等方面的差异,利用液压万能试验机对盘条进行拉伸试验,利用扫描电镜（SEM）和透射电镜（TEM）观察盘条的微观组织、拉伸断口及第二相析出情况。结果表明：增氮使索氏体组织的层片间距更细小;增加1.38×10-4的氮可使盘条的屈服强度提高8 MPa、抗拉强度提高28 MPa、延伸率降低1.8%、断面收缩率降低5.8%;高氮盘条比低氮盘条的拉伸断口上有更多的夹杂物;高氮盘条中的析出物更多且分布较弥散,析出物主要集中在位错线或原奥氏体晶界上,经标定,析出物中含有细小的V(C,N)颗粒。     

Expression, purification and characterization of the soluble CuA domain of cytochrome c oxidase ofParacoccus versutus

The key subunit Ⅱ of cytochrome c oxidase (CcO) contains a soluble binuclear copper center (Cu_A) domain. The Cu_A domain of Paracoccus versutus was cloned, expressed, purified and characterized. The gene encoding the Cu_A domain in pET11d vector was expressed in E. coli BL21 (DE3). The results showed that the Cu_A domain was expressed mostly in inclusion bodies and the Cu_A domain protein synthesized in E. coli cells represents approximately 10 percent of the total cellular proteins. Dissolved in urea, dialyzed and recombined with Cu⁺/Cu²⁺ and purified by the Q-sepharose fast flow anion-exchange column and Sephadex G-75 gel filtration column, the soluble purple-colored protein, which shows a single band in electrophoresis, was obtained. The UV-visible absorption spectrum of Cu_A domain showed that there are intense band at 478 nm and a shoulder peak at 530 nm, and two weak bands at 360 and 806 nm respectively, which can be assigned to the charge transfer and the interactions of obitals of Cu—S and Cu——Cu in the mixed-valence binuclear metal center (Cu₂S₂R₂). The far-UV CD spectrum indicated that this domain is predominantly in β-sheet structure. The fluorescence spectra showed that its maximal excitation wavelength and maximal emission wavelength are at 280 and 345 nm, respectively.     

二苯环丙烷衍生物的晶体结构与分子结构

用Ｘ射线单晶衍射法测定二苯环丙烷衍生物Ｃ１６Ｈ１２ＮＣｌ晶体结构和分子结构,晶体属正交晶系空间群Ｐｚ１ｚ１ｚ１,晶胞参数ａ＝０．７６８１７（３）ｎｍ,ｂ＝１．１６３０７（４）ｎｍ,ｃ＝１．４２０５７（５）ｎｍ,ｖ＝１．２６９２（７）ｎｍ３,Ｚ＝４．Ｄｅ＝１．３２８ｇｃｍ－３,Ｒ＝０．０４７,ＲＷ＝０．０５０。并讨论了分子结构。     

Deformation mechanism of fine structure and its quantitative relationship with quasi-static mechanical properties in near β-type Ti-4.5Mo-5.1Al-1.8Zr-1.1Sn-2.5Cr −2.9Zn alloy

The deformation mechanism of the fine structure composed of primary α phase (α_p) and acicular secondary α phase (α_s) on quasi-static mechanical properties is still not very clear. The main controversy is focused on the role of α_p in the mechanical behavior. In this paper, the microstructure of the heat-treated near β-type Ti-4.5Mo-5.1Al-1.8Zr-1.1Sn-2.5Cr-2.9Zn alloy after tensile tests was observed by transmission electron microscopy (TEM). And the results showed that in the slight deformation region the dislocations were accumulated at the intersection of α_p and β matrix separated by α_s, while only a few dislocations nucleated in β matrix. In the severe deformation region, a large quantity of dislocations in both α_p and β matrix were observed. It can be inferred that α_p deformed firstly and then activated the deformation of β matrix, that is, the thickness of α_p and the inter-particle spacing of α_s played a dominant role in the deformation process. The quantitative relationship between the yield strength and the microstructure parameters is consistent with this inference. By adjusting the solution treatment parameters and the subsequent aging treatment, three fine structures were obtained, and the corresponding mechanical properties were determined. Furthermore, the yield strength can be described by the mathematical model σ_y ​= ​756.4 ​+ ​135.6/h_p^1/2 +32.2/d_s^1/2, where h_p and d_s are the thickness of α_p and the inter-particle spacing of α_s, respectively.     

Two-dimensional crystallization and preliminary electron crystallographic result of partially purified F<Subscript>0</Subscript> from porcine mitochondria

After removal of cytoplasmic sector F₁ from submitochondrial particles of F₀F₁-ATP synthase complex with guanidine hydrochloride, the transmembrane sector F₀ was specifically extracted from the stripped membranes in the presence of detergent CHAPS and partially purified. Two-dimensional crystals were produced by the reconstitution of the partially purified F₀ into asolectin and microdialysis. The obtained crystals are able to diffract to 2 nm. The projection map of the negatively stained crystal shows that the crystal has p42₁2 symmetry, lattice constant, a=b=14.4 nm. A unit cell contains four F₀ molecules.     

Synthesis and crystal structure of new supramolecular adducts of [PtCl6]2− with cucurbit [7] uril: [(H3O)2 (PtCl6)]3 (C42H42N28O14)2·H2O

A novel supramolecular adduct [(H₃O)₂ (PtCl₆)]₃ (C₄₂H₄₂N₂₈O₁₄)₂·H₂O (1) was synthesized by mixing [PtCl₆]²⁻ and cucurbit [7] uril in solution of hydrochloric acid. The crystal structure was determined by single crystal X-ray diffraction analysis. The crystal belongs to orthorhombic system and space group F dd2 with cell dimensions:a=4. 705 33 (5) nm,b=7. 153 80 (6) nm,c=1. 894 61 (2) nm,Z=16,V=63, 7744 (11) nm³,D _c =1.534 g/cm³, μ=3. 007 mm⁻¹,F(000)=29 120,R ₁=0.070 7,wR ₂=0. 169 2. In crystal, the cucurb [7] uril molecules from two zig-zag chains. Foundation item: Supported by the National Natural Science Foundation of China (20172040) Biography: Yan kun (1977-), female, Master, research direction: macrocyclic chemistry.     

Mesoporous fibrous silicon nitride by catalytic nitridation of silicon

The catalytic effect of metal oxide/alumina whiskers(CeO_2, Mn_3O_4, NiO, Co_3O_4, Fe_2O_3, Cr_2O_3/AW) was evaluated on their ability to drive the nitridation of silicon and to generate mesoporous fibrous silicon networks.Silicon powder with different particles size along with the catalyst was nitridized at 1300 °C for 5 h in nitrogen and nitrogen diluted with 10 vol% ammonia atmospheres. Nitridation degree of silicon up to 99% was recorded using 1.5 wt% CeO_2 and Fe_2O_3 catalysts in nitrogen-ammonia atmosphere. The catalyzed samples contain submicronic silicon nitride fibres with a diameter of 400–500 nm and a length of up to few micrometers. The compressive strength of 46 ± 1 MPa was measured for silicon samples catalyzed with nickel oxide/alumina whiskers and nitridized in N_2/10 vol%NH_3 atmosphere. Porous silicon nitride networks were produced with 45–52% porosity, pore sizes in the range of 370–1200 nm and median pore in the range of 495–1655 nm.     

<Emphasis Type="Italic">In situ</Emphasis> synthesis of TiC reinforced Cu<Subscript>47</Subscript>Ti<Subscript>34</Subscript>Zr<Subscript>11</Subscript>Ni<Subscript>8</Subscript> bulk metallic glass composites

In situ synthesized TiC particles and β-Ti dendrites reinforced Cu47Ti34Zr11Ni8 bulk metallic glass (BMG) composite ingots were prepared by the suction casting method.The ingots with diameters from 1 up to 4mm were successfully obtained. It was shown that introducing TiC micro-sized particles into the amorphous matrix did not disturb the glass forming ability (GFA) of the matrix,while the yield strength and ductility could be well improved.The phase constitution, microstructure and elements distribution in the composites were studied by OM, XRD, SEM and EDS.It was shown that the in situ synthesized TiC particles acting as heterogeneous nucleation sites promoted the precipitation of β-Ti dendrites, resulting in the formation of the TiC particles and β-Ti dendrites co-reinforced BMG composites. The compressive tests were employed to probe the yield strength and ductility of BMG composites.     

Sintering behavior of Cr in different atmospheres and its effect on the microstructure and properties of copper-based composite materials

Copper matrix composites consisting of chromium (Cr) or ferrochrome (Cr-Fe) as strengthening elements and molybdenum disulfide as a lubricant had been sintered in nitrogen and hydrogen atmosphere, respectively. Their morphology and energy-dispersive X-ray spectrometry (EDS) analysis showed that serious interaction occurred between MoS₂ and Cr (or Cr-Fe) particles when the samples were sintered in hydrogen atmosphere. Chromium sulfide compound (Cr_xS_y) was formed as a reaction product, which decreased the density and strength of the composites remarkably. This interaction was inhibited when the samples were sintered in nitrogen atmosphere; thus, the mechanical properties of the composites were improved.     

Microstruct ural evolution and mechanical behavior of metastable β -type Ti – 25Nb–2Mo – 4Sn alloy with high strength and low modulus

This paper presents a systematic study of newly developed metastable β-type Ti-25Nb-2Mo-4Sn (wt%) alloy with high strength and low elastic modulus, with focus on the microstructural evolution and mechanical behavior associated with aging. The pre-treatment (solution treatment or cold rolling) prior to aging exerts substantial influence on the subsequent aging response including microstructural evolution and mechanical behavior. Even under the same aging treatment, the aging products could be (β+ω), or alternatively (β+α), depending on the pre-treatments. This interesting aging response was discussed on the basis of the mechanism for ω formation. High-density dislocation tangles and grain boundaries induced by severe cold rolling play a key role in hindering the transition from β to isothermal ω, favoring the precipitation of α phase on aging. By aging cold-rolled specimen for short time, superior mechanical properties, i.e. high ultimate strength of ～1113 MPa and low elastic modulus of ～65 GPa, achieved in Ti-25Nb-2Mo-4Sn alloy. The characterization of microstructural evolution and compositional change indicated that the precipitation of fine α does not cause the enrichment of β-stabilizers in β matrix upon a short-time aging, guaranteeing low elastic modulus of the short-time aged specimen. Meanwhile, fine α precipitates as well as dislocations play a crucial part in strengthening, giving rise to its high yield strength and high ultimate tensile strength.     

The precipitation strengthening behavior of Cu-rich phase in Nb contained advanced Fe–Cr–Ni type austenitic heat resistant steel for USC power plant application

Copper has been used as a strengthening element in newly developed Fe–Cr–Ni type austenitic heat resistant steel for inducing Cu-rich phase precipitation to meet high temperature strength requirement for 60°C Ultra Super-Critical (USC) coal fired power plants for many years. However, the precipitation behavior and strengthening mechanism of Cu-rich phase in these advanced austenitic heat resistant steels is still unclear. In order to understand the precipitation strengthening behavior of Cu-rich phase and to promote high strength austenitic heat resistant steel development, 18Cr9 NiCuNb steel which is a Cu-added Nb contained advanced Fe–Cr–Ni type austenitic heat resistant steel has been selected for this study to be aged at 650°C till to 10,000 h. Micro-hardness and room temperature tensile test were conducted after long-time aging. SEM,TEM, HRTEM and three dimensional atom probe (3DAP) technology accompanying with thermodynamic calculation have been used to investigate the Cu-rich phase precipitation behavior during 650°C aging. The experimental results showed that Cu atoms can quickly concentrate in clusters at very early precipitation stage to form the fine nano-size Cu-rich ‘‘segregation areas’within less than 1 h at 650°C. With increasing aging time at 650°C Cu atoms continuously concentrate to Cu-rich segregation areas (clusters) and simultaneously other kinds of atoms such as Fe, Cr and Ni diffuse away from Cu-rich segregation areas to austenitic matrix, and finally to complete the transformation from Cu-rich segregation areas to Cu-rich phase. However, there is only Cu atoms concentration but not crystallographic transformation from early stage of Cu-rich clusters forming to the final Cu-rich phase formation. Even the Cu atom becomes the main composed element after 500 h aging at 650°C the Cu-rich phase still keeps coherent relationship with austenitic matrix. According the experimental results in this study, Cu-rich phase precipitation sequence which starts from the Cu atom segregation followed by the Cu diffusing from matrix to segregation areas and Fe, Cr and Ni atoms diffuse out from Cu-rich areas to matrix without crystallographic transformation is proposed. The Cu-rich phase is the most dispersed phase and contributes the most important strengthening effect among all precipitated phases (M23C6, MX and Cu-rich phase). It has been found that Cu-rich phase is very stable and still keeps in nano-size even for 10,000 h aging at 650°C. The unique precipitation strengthening of Cu-rich phase in combination with nano-size Nb-rich MX phase and grain-boundary M23C6carbide contributes excellent strengthening effect to 18Cr9 NiCuNb austenitic heat resistant steel.     

Peculiar aging response of near b Ti–25 Nb–2Mo–4Sn alloy for biomedical applications

In this paper,aging response of a recently developed near β Ti-25Nb-2Mo-4Sn(wt%) alloy with high strength and low modulus was investigated intensively.The experimental results from X-ray diffraction and transmission electron microscopy showed that the aging production of the Ti-2524 alloy was(β+ω) or(β+α) even under the same aging treatment condition,depending on the pre-treatments prior to the aging.Solid evidence confirmed the competition between stable α phase and metastable ω phase during the decomposition of β phase on aging.Different aging response of Ti-2524 alloy can be attributed to high-density dislocations and grain boundaries which suppress the formation of ω,and alternatively promote a phase formation.This provides a thermo-mechanical approach to inhibit deleterious ω phase formation and assist fine α phase precipitation.Upon an appropriate aging treatment,superior mechanical properties of high ultimate tensile strength(1233 MPa) and low elastic modulus(77 GPa) were achieved in Ti-2524 alloy.     

New crystal structure of molecular complex 1-piperidine carboxylate-piperidinium-H<Subscript>2</Subscript>O studied by X-ray single crystal diffraction

Piperidine absorbs CO2 and H2O in air to form a molecular complex： piperidium-l-piperidinecarboxylate-H2O. The structure of the complex was characterized by X-ray single crystal diffraction. The crystal structure was determined to be triclinic, space group P1^-with a=0.648 6（8） nm, b=0.809 200） nm, c= 1.357 1（16） nm, a=96.96706）°, β =102.506（15）°,γ=104.202 05）°, Z=2. The complex is stabilized via five hydrogen bonds between the three components, N-O electrostatic interaction and O-O interaction （electron transfer） betweenl-piperidinecarboxylate and H2O. Due to electron transference of carbamate ion, the oxygen atom in water molecule is strongly negatively charged and the O-H bond is considerably shorter than that of the free molecule of water. The formation of the molecular complex is a reversible process and will decompose upon heating. The mechanism of formation and stabilization is further investigated herein.     

Effects of metal binder on the microstructure and mechanical properties of Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-based micro-nanocomposite ceramic tool material

The Al₂O₃-(W,Ti)C composites with Ni and Mo additions varying from 0vol% to 12vol% were prepared via hot pressing sintering under 30 MPa. The microstructure was investigated via X-ray diffraction (XRD) and scanning electron microscopy (SEM) equipped with energy dispersive spectrometry (EDS). Mechanical properties such as flexural strength, fracture toughness, and Vickers hardness were also measured. Results show that the main phases Al₂O₃ and (W,Ti)C were detected by XRD. Compound MoNi also existed in sintered nanocomposites. The fracture modes of the nanocomposites were both intergranular and transgranular fractures. The plastic deformation of metal particles and crack bridging were the main toughening mechanisms. The maximum flexural strength and fracture toughness were obtained for 9vol% and 12vol% additions of Ni and Mo, respectively. The hardness of the composites reduced gradually with increasing content of metals Ni and Mo.     

The ring-substituted phthalo-cyanines and its metal com-plexes: Crystal structure of 1,4, 8,11,15,18,22,25-octa-butoxyphthalocyani-natocopper(Ⅱ)

Crystal structure of 1, 4, 8, 11, 15, 18, 22, 25-octa-butoxyphthalocyaninato- copper (Ⅱ) (1) was determined by X-ray diffraction methods. The crystal system is mono-clinic, space group is P2₁/c, Z = 4, a = 1.3741(1) nm, b = 2.6737(1) nm, c = 1.6690(1) nm, β= 101.278(1)°. The steric congestion between the neighbouring butoxyl groups causes the distortion of the ring core of phthalocyanine (Pc) into a saddle shape conformation. In the crystal structure, molecules stack along a axis forming one-dimensional packing structure and there are two molecular overlap types which appear in turn with different distances between molecules, overlap area and angle.