Room-temperature phosphorescence materials from crystalline to amorphous state

Room temperature phosphorescence(RTP)in metal-free organic materials has attracted considerable attention due to its rich excited state properties,high quantum efficiency,long luminescence lifetimes,etc.,showing great potential in organic optoelectronic devices,bioimaging,information anti-counterfeiting,and so forth.The crystals have excellent rigidity and clear molecular packing patterns,which can effectively avoid non-radiative transitions of excitons for phosphorescence enhancement.In the early stages,researchers paid great attention to the regulation of RTP performance in crystalline states.However,due to the complex preparation and poor processability of crystals,amorphous materials with RTP features have become a new research topic recently.This perspective aims to summarize the recent advances of RTP materials from crystalline to amorphous states,and analyze their molecular design strategies and luminescence mechanisms in detail.Finally,we prospect the future research directions of amorphous RTP materials.This perspective will provide a guideline for the future study of advanced RTP materials.

Correlation between Structures of Bulk Amorphous Zr-Ti-Ni-Cu-Be Alloy in Different States

The structures of the bulk amorphous Zr41Ti14Cu12.5Nil0.0Be22.5 alloy have been analyzed in solid, supercooled liquid and liquid with X-ray diffraction. The first coordination sphere radii and the first coordination numbers are 0.312 um, 11.2 in solid state.10.932 nm, 10.932 in supercooled liquid region and 0.305 urn, 11.296 in liquid state. The structures are the same in different states. But it shows some tendency to crystallizing that the first coordination sphere radius and the first coordination number drop in supercooled liquid region.

Pressure-volume-temperature and excess molar volume prediction of amorphous and crystallizable polymer blends by equation of state

In this work the statistical mechanical equation of state was developed for volumetric properties of crystalline and amorphous polymer blends.The Ihm-Song-Mason equations of state(ISMEOS) based on temperature and density at melting point(T_m and ρ_m) as scaling constants were developed for crystalline polymers such as poly(propylene glycol) + poly(ethylene glycol)-200(PPG + PEG-200),poly(ethylene glycol) methyl ether-300(PEGME-350) + PEG-200 and PEGME-350 + PEG-600.Furthermore,for amorphous polymer blends containing poly(2,6-dimethyl-1,4-phenylene oxide)(PPO) + polystyrene(PS) and PS + poly(vinylmethylether)(PVME),the density and surface tension at glass transition(ρ_g and γ_g) were used for estimation of second Virial coefficient.The calculation of second Virial coefficients(B_2),effective van der Waals co-volume(b) and correction factor(α) was required for judgment about applicability of this model.The obtained results by ISMEOS for crystalline and amorphous polymer blends were in good agreement with the experimental data with absolute average deviations of 0.84%and 1.04%,respectively.

MAGNETIC PROPERTIES AND CRYSTALLIZATION OF AMORPHOUS ALLOYS Co_(90-x)Cr_xZr_(10)

Curie temperature of amorphous alloys Co_(90-x)Cr_x Zr_(10) decreases linearly with increas- ing x.Average magnetic moment per magnetic atom Co or Cr is 1.51 μB or -3.62 μB respectively.The temperature dependence of spontaneous magnetization at low temper- atures is in agreement with Bloch's T^(3/2) law.The spin wave stiffness constant decreases with increasing x from 4 to 20.The range of interaction is 2—3 atoms for x=4 and nearest neighbour atom for x=20.The crystallization temperature increases mono- tonically with increasing x.It may relate to the average number of outer electrons per atom.The crystalline phase components of heat-treated alloys were analyzed by X-ray diffration and thermomagnetic measurement.

Effect of Thermal Treatment on the PA-6 in the Blends

Aim To investigate the multiple melting behavior of polyamide 6(PA 6) in polyamide 6/linear low density polyethylene blends crystallized from the crystal amorphous state. Methods\ The effects of annealing temperature, annealing time, heating rate, and the step wise annealing were measured by DSC. Results and Conclusion\ There exists a critical heating rate affecting the middle temperature melting peak. When annealed at the temperature close to the melting peak, the main melting peak of PA 6 shifted to a higher temperature. Within a short time, annealing time has much effect on neat PA 6 but little effect on PA 6 in the blends. Addition of PE results in a decreasing in the height of melting peak. These phenomenon show that the melting behavior of PA 6 was affected by PE, compatibilizer, as well as thermal treatment.

Effects of Composition on the Structure and Capacitive Properties of Ti/(ZrO_2)_x(RuO_2)_(1-x) Electrodes

A series of nominal composition Ti/（ZrO2）x（RuO2）l-x （0.1≤x≤0.9） coatings chan-ged in 10% steps was deposited on titanium substrate from RuCl3·nH2O and ZrCl4 containing ethanol solution by thermal decomposition method. The X-ray diffraction （XRD）, high-resolution transmission electron microscopy （HR-TEM） and electrochemical tests were performed to clarify the effects of ZrO2 content on the structure and capacitive property of Ti/（ZrO2）x（RuO2）l-x. The results show that by adding ZrO2 into the coatings the degree of crystallization of RuO2 decreases. The specific capacitance firstly increases and then deceases with the increase of ZrO2 content in the mixed oxide coatings. The film of Ti/（ZrO2）0.6（RuO2）0.4 consisting of amorphous matrix and fine nano-crystalline RuO2 （about 4 nm） has the maximum specific capacitance of 713.27 F/g（RuO2）.

Structural transition and magnetic properties of evaporated Fe/Gd multilayers

Fe/Gd multilayers were prepared by alternate vapor deposition of pure Fe and Gd at a rate of 0.01-0.03 nm/s in an ultra-high-vacuum elec- tron-gun evaporation system. The effects of the constituent metal layer thickness on the microstructures and magnetic properties of the films were investigated by low angle X-ray diffraction, transmission electron microscopy, and vibrating sample magnetometer. The experimental results show that a transition from the polycrystalline to amorphous state in the Fe layers occurs with the decrease of Fe layer thickness in the Fe/Gd multilayers. The saturation magnetization of the multilayers reduces significantly with decreasing Fe layer thickness and increasing Gd layer thickness. A superparamagnetic behavior at room temperature is observed for the [Fe（0.6 nm）/Gd（4.0 nm）]15 multilayer due to the formation of discontinuous Fe layers.

Mechanical Alloying of Co and Al Powders

1.IntroductionMechanical alloying is one of the effec-tive methods to prepare amorphous alloys[1].This method was first used by Koch etal.to prepare the Ni;Nb;amorphous alloy[2].Since then many other amorphousbinary alloys have been prepared by the