改性硝酸铵的热分析研究

改性硝酸铵的热分析研究雷芳龄（黎明化工研究院洛阳４７１００１）硝酸铵在温度自２５℃到１６９℃范围内，常压下有四种热力学稳定的结晶变体，每种变体仅在一定的温度范围内存在，当由一种变体转变成另一种变体（多晶转变）时，则伴随着晶体结构及体积的改变，同时也伴...

Antiphase boundary-like structure in α′′ martensite of TC21 titanium alloy

The morphology and formation mechanism of the substructure of martensite in TC21 alloy was investigated by XRD and TEM. The results showed that the martensitic transformation from β to α＂ occurs upon quenching after solution treatment between 960-1000 ℃. The antiphase boundary （APB）-like structure was observed clearly in the α＂ martensite plates. The APB-like contrasts exist along the （001） and （020） planes of α＂ martensite. This APB-like structure of α＂ martensite was identified as a kind of stacking fault with an APB-like morphology induced by martensitic transformation and not by order/disorder transition. During martensitic transformation, martensitic domains nucleate and grow, eventually encounter each other, resulting in the formation of the APBdike contrast.

Effect of rolling reduction on deformation mechanism and twinning behavior of WE43 magnesium alloy

The effect of rolling reduction of the last pass on the dislocation slip and twinning behavior during direct hot rolling of a cast WE43 magnesium alloy at 480℃ was investigated.The results showed that prismatic<á>slip was always the main deformation mode during rolling at 480℃.In addition,the activated twinning type was associated with rolling reduction.The{1012}extension twinning was activated at a slight rolling reduction(2%),while{1011}compression twinning and{1011}−{1012}double twinning were activated at larger rolling reduction(12%and 20%).Schmid factor calculation showed that the activation of{1012}extension twin variants followed the Schmid Law,whereas the activation of{1011}compression twin variants did not follow it.Even if the rolling reduction reached 20%,almost no dynamic recrystallization(DRX)grains were found,presumably because the amount of deformation required for DRX to occur was not reached.

Crystal Structure and Spectroscopic Properties of [Ni(phen)_3]Pic_2·2CH_3CN

The crystal structure of the title complex having the stoichiometric formula [Ni\|(phen) 3]Pic 2·2CH 3CN (Pic=picrate anion; phen=1,10\|phenanthroline) has been determined by single-crystal X-ray diffraction. The crystal (C 52 H 34 N 14 O 14 Ni, M r=1137.63) belongs to the triclinic system, space group P1(#2) with the following crystallographic parameters: a = 14\^130(1), b=15\^256(3), c=13.673(2); α=109.11(1), β =90.92(4), γ=66.75(3)°; V=2537\^72 3, D c=1.489g/cm 3, μ(MoKα)=4.66cm -1 , F(000)=1168, Z=2, and final R=0.062 and R w=0.078 for 4917 observed reflections (I>2.00σ(I)). The analytical results of crystal structure and spectroscopic properties show that nickel(II) cation coordination environment is a distorted octahedral geometry, the Ni 2+ ion is coordinated with six nitrogen atoms~ of three phen directly, while two picrate anions and two acetonitrile molecules do not take part in coordination~.

Simulation of strain induced abnormal grain growth in aluminum alloy by coupling crystal plasticity and phase field methods

A mesoscale modeling methodology is proposed to predict the strain induced abnormal grain growth in the annealing process of deformed aluminum alloys. Firstly, crystal plasticity finite element(CPFE) analysis is performed to calculate dislocation density and stored deformation energy distribution during the plastic deformation. A modified phase field(PF) model is then established by extending the continuum field method to consider both stored energy and local interface curvature as driving forces of grain boundary migration. An interpolation mapping approach is adopted to transfer the stored energy distribution from CPFE to PF efficiently. This modified PF model is implemented to a hypothetical bicrystal firstly for verification and then the coupled CPFE-PF framework is further applied to simulating the 2D synthetic polycrystalline microstructure evolution in annealing process of deformed AA3102 aluminum alloy.Results show that the nuclei with low stored energy embedded within deformed matrix tend to grow up, and abnormal large grains occur when the deformation is close to the critical plastic strain, attributing to the limited number of recrystallized nuclei and inhomogeneity of the stored energy.

The Effect of Vanadium Content on Mechanical Properties and Structure of Self-Hardening Steel X 160C rMo 12-1

The aim of this research was to examine the influence of vanadium on the structure, hardness and tensile strength of X I60CrMo 12-1 self-hardened steels. It is known that vanadium affects the process of solidification of this alloy in a way that narrows temperature interval of crystallization. Vanadium, as an alloying element, moves liquidus and solidus lines toward higher temperatures, approximately for 25 to 30 ~C. In addition, vanadium forms V6C5 carbides, which, are partly distributed between present phases in the steel; carbide （Cr,Fe）7C3 and austenite. The presence of vanadium enables the formation of （Cr, Fe）23C6 carbide and its precipitation into austenite during the cooling process. In local areas around fine carbide particles, austenite is transformed into martensite, i.e., vanadium reduces remained austenite and improves steel air-hardening. Vanadium concentration over 2.5% significantly improves the impact toughness. The basic problem in the application of high alloyed Cr-Mo steels is to increase their impact toughness and thereby sustain a relatively high value of hardness. Recent studies, concerning to the chemical composition and heat treatment regime, show that it is possible to get a martensitic structure with a very small amount of retained austenite. Investigations are directed toward the testing of the influence of alloying elements such as molybdenum, manganese and especially vanadium. Vanadium has great influence to the crystallization process. With increasing of its content, the eutectic point moves toward lower carbon concentrations and the temperature interval of solidification is narrowing.

Novel Thermally-Accessible Structural Changes of Chiral and Some Related Cu（ll） Complexes

A mononuclear chiral copper（ll） complex, [Cu（RRchxn）2（C（CN）3）2]＇H20 （RRchxn = （1R, 2R）-diaminocyclohexane） （RRchxnH）, and its deuterated compound, [Cu（RRchxn）2（C（CN）3）z].D20 （RRchxnD）, and their isomers, [Cu（trchxn）2（C（CN）3）2]＇H20 （trchxn = trans-l,2-diaminocyclohexane） （trchxnH） and [Cu（trchxn）2（C（CN）3）2]＇D20 （trchxnD） have been prepared and characterized by means of 1R （infrared）, electronic, and CD （circular dichroism） spectra, magnetic susceptibility, and variable-temperature X-ray crystallography as single crystals or powder. Interestingly, depending on grain size of samples, RRchxnH exhibits the monoclinic form and the orthorhombic form, which are distinguished by systematic absence and powder XRD （X-ray diffraction） patterns clearly. Although single crystals did not exhibit phase transition, powder XRD patterns of RRchxnH and weakly hydrogen bonded RRchxnD emerged low-temperature phase of monoclinic in the orthorhombic patterns only around 200-220 K. However, as a control, powder XRD patterns of both trchxnH and trchxnD did not exhibit such phase transition clearly.

The Preparation of Ultra-fine Calcium Carbonate and Its properties Study

This article adopts the double decomposition method, select the appropriate experimental conditions and operation process, respectively add appropriate amount of sodium carboxymethyl cellulose （CMC） as crystal control agent to study the influence of crystalline of ultrafine calcium carbonate. The experimental results show that the different concentrations of CMC as crystal control agent on the morphology and crystal structure of calcium carbonate have obvious effect, which emerge morphology change from square to spherical, crystalline transition from calcite to aragonite. Thus, the results provide experimental data and theoretical basis for the use of different additives, and provide experimental basis and feasible solution for this kind of reaction.

Propagation characteristics of six-core photonic liquid crystal fibers

We demonstrate a new kind of multi-core photonic liquid crystal fibers (PLCFs) which have six liquid crystal cores arrayed in the ring-type geometry and separated by the air holes. Through analyzing the structure of this kind of PLCFs, it can be found that they have the ability to resist the structure deformation. Due to the effective index of the liquid crystal can be adjusted by temperature and wavelength, the energy in the six liquid crystal cores is increased with the temperature increasing and wavelength decreasing. The effective index of the PLCFs is decreased, the effective fundamental mode area is increased and the dispersion properties are gently affected with the wavelength increasing and temperature decreasing.

Deformation study of bicrystalline and nano-polycrystalline structures using phase field crystal method

Deformation behaviors of bicrystalline and nano-polycrystalline structures of various tilt angles and inclination angles in two dimensions are investigated in detail using a two-mode phase field crystal model.The interaction between grain boundary(GB)and dislocation is also examined in bicrystals and nano-polycrystals that both contain asymmetric and symmetric tilt GBs,with energy analysis being carried out to analyze these processes.During deformation simulations,we assume the volume of each simulation cell at every time step is coincident with that of the initial state just before deformation.Our simulation results show that the behaviors of symmetric and asymmetric GBs in bicrystals and nano-polycrystals differ from each other depending on tilt angle and inclination angle.A new dislocation emission mechanism of interest is observed in bicrystals which contain low angle symmetric tilt GBs.Low angle GB has a higher mobility relative to high angle GB in both bicrystalline and nano-polycrystalline structures,as does asymmetric GB to symmetric GB.The generation,motion,pileup and annihilation of dislocations,grain rotation and grain coalescence are observed,which is consistent with the simulation results obtained by molecular dynamics.These simulation results can provide strong guidelines for experimentation.

Glucose-sensitivity of core-shell microspheres and their crystalline colloidal arrays

Thermoresponsive core-shell microspheres are prepared and functionalized with 3-aminophenylboronic acid to make them responsive to glucose.The volume phase transition of the resulting particles is shifted to a lower temperature and a clear swelling is caused by the presence of glucose.The particles after the functionalization preserved their capability to form crystalline colloidal arrays.The changes of their properties may be used in the design of glucose sensors.

Hollow spherical rare-earth-doped yttrium oxysulfate： A novel structure for upconversion

A facile biomolecule-assisted hydrothermal route followed by calcination has been employed for the preparation of monoclinic yttrium oxysulfate hollow spheres doped with other rare-earth ions （Yb3＋ and Eu3＋ or Er3＋）. The formation of hollow spheres may involve Ostwald ripening. The resulting hybrid materials were used for upconversion applications. The host crystal structure allows the easy co-doping of two different rare-earth metal ions without significantly changing the host lattice. The luminescent properties were affected by the ratio and concentration of dopant rare-earth metal ions due to energy transfer and the symmetry of the crystal field. The type of luminescent center and the crystallinity of samples were also shown to have a significant influence on the optical properties of the as-prepared products.

Helix-sense-selective radical polymerization of bulky styrenic monomers: chiral induction and liquid crystallinity

Eight chiral vinylterphenyl monomers, （＋）-2,5-bis{4＇-[（S）-1＂-methylpropyloxy]phenyl}styrene （Ia）, （＋）-2,5-bis{4＇-[（S）-2＂- methylbutyloxy]phenyl}styrene （Ib）, （＋）-2,5-bis{4＇-[（S）-3＂-methylpentyloxy]phenyl}styrene （Ic）, （＋）-2,5-bis{4＇-[（S）-4＂- methylhexyloxy]phenyl}styrene （Id）, （-）-2,5-bis{4＇-[（R）-1＂-methylpropyloxy]phenyl}styrene （le）, （＋）-2-/4＇-[（S）-l＂-methyl- propyloxy]phenyl}-5-{4＇-[（R）-1＂-methylpropyloxy]phenyl}styrene （Ⅱa）, （-）-2-{4＇-[（R）-1＂-methylpropyloxy]phenyl}-5-{4＇- [（S）- 1 ＂-methylpropyloxy]phenyl } styrene （lib）, and （＋）-2- { 4＇-[（S）-2＂-methylbutyloxy]phenyl }-5- { 4＇-[（S）- 1＂-methylpropyl- oxy]phenyl}styrene （Ⅲ）, were synthesized and radically polymerized. These molecules were designed to further understand long-range chirality transfer in radical polymerization and to possibly tune the chiroptical properties of the polymers by varying the spatial configuration, position, and various combination of the stereogenic centers at the ends ofp-terphenyl pendants. The resultant polymers adopted helical conformations with a predominant screw sense. When the stereogenic centers ran away from the terphenyl group as in Ⅰb-d, the corresponding polymers changed the direction of optical rotation in an alternative way and showed no obvious stereomutation upon annealing in tetrahydrofuran. The two stereogenic centers of Ⅱa, Ⅱb, and Ⅲ acted concertedly in chiral induction, whereas those of la and Ie played a counteractive role. The five polymers derived from Ⅰa, Ⅰe, Ⅱa, Ⅱb, and Ⅲ underwent stereomutation when annealed in tetrahydrofuran. The polymers PIa-e had good thermal stability and high glass transition temperatures （Tgs）. They generated liquid crystalline phases at above Tgs that could be kept upon cooling, with the exception of Pie. This result was consistent with the extended helical structures.

Crystal structure of histidine-containing phosphocarrier protein from Thermoanaerobacter tengcongensis MB4 and the implications for thermostability

Protein thermostability is an inherent characteristic of proteins from thermophilic microorganisms,and therefore enables these organisms to survive at extreme temperatures.Although it is well-known that thermostable proteins are critical for the growth of thermophilic organisms,the structural basis of protein thermostability is not yet fully understood.The histidine-containing phosphocarrier (HPr) protein,a phosphate shuttle protein in the phosphoenolpyruvate-dependent sugar transport system (PTS) of bacterial species,is an ideal model for investigating protein thermostability with respect to its small size and deficiency in disulphide bonds or cofactors.In this study,the HPr protein from Thermoanaerobacter tengcongensis (TtHPr) is cloned and purified.Crystal structure with good quality has been determined at 2.3 resolution,which provides a firm foundation for exploring the thermostable mechanism.However,it shows that the crystal structure is conserved and no clue can be obtained from this single structure.Furthermore,detailed comparison of sequence and structure with the homologs from mesoor thermophilic bacteria shows no obvious rule for thermostability,but the extra salt-bridge existing only in thermophilic bacteria might be a better explanation for thermostability of HPr.Thus,mutations are performed to interrupt the salt-bridge in HPrs in thermophilic bacteria.Using site-directed mutations and the circular dichroism method,thermostability is evaluated,and the mutational variations are shown to have a faster denaturing rate than for wild-type viruses,indicating that mutations cause instability in the HPrs.Understanding the higher-temperature resistance of thermophilic and hyperthermophilic proteins is essential to studies on protein folding and stability,and is critical in engineering efficient enzymes that can work at a high temperature.

Superconductivity in two-dimensionalη-Mo3C2 films

Two-dimensional(2D)superconductors have intriguing physical properties and abundant potential applications.Recently,2D superconductingα-Mo2C and facecentered cubic Mo2C have been controllably prepared and they bring new viewpoints to carbon-based superconductivity.Although molybdenum carbides(Mo-Cs)have multiple crystalline stacking orders,there are still few structures reported for the lack of higher energy supply during growth.In this study,we report a two-step vapor deposition method to grow superconducting η-Mo3C2 films with different thicknesses,with the assistance of controllable plasma power.The grownη-Mo3C2 films show polycrystalline characteristics,but they still present superior superconductivity.The 3.0-nm-thick film has the superconducting transition temperature of 5.38 K,and its electrical performances follow truly 2D superconducting transitions.This study will not only exhibit a robust superconductingη-Mo3C2 ultrathin film,but also provides a convenient growth way to realize more carbide-based heterostructures for future device applications.

Reversible phase transition of the 1:1 complex between 18-crown-6 and n-propylammonium triiodide

Solid-state structure of the crystalline 1：1 complex [C3H10N（18-crown-6）]＋[I3] （1） between 18-crown-6 and n-propylammonium triiodide has been determined at 293 and 93 K, respectively, showing a change from monoclinic P21/m to monoclinic P21/a. Crystal structural analysis shows that in addition to van der Waals＇ forces, conventional N-H..-O hydrogen bonds are the key interactions. Measurements of unit cell parameters versus temperature show that the values of one of the three axes and the crystal volume change abruptly and remarkably at 220 K, indicating a first-order phase transition. The lack of the mirror plane in the low temperature structure is the most important differences between the two structural forms. Dif- ferential scanning calorimetry （DSC） measurement confirms that I undergoes a reversible phase transition at about 220 K with a thermal hysteresis of 3.5 K. The relatively large latent heat makes 1 a good candidate for phase change materials. The phase transition is accompanied by an anomaly of dielectric constant during heating and cooling process near the phase transition temperature.