AN EXPERIMENTAL STUDY ON POST-BUCKLING BEHAVIOR OF SLENDER COLUMN WITH FIBER REINFORCED COMPOSITE MATERIAL

Equilibrium paths of post-buckling are measured for large slenderness column specimensmade of the fiber reinforced composite material. The influence of the initial curvature is investigatedexperimentally and compared with the result of the initial post-buckling theory. Both the theoreticaland experimental results reveal that the column with the initial curvature has stable post-buckling be-haviors and is not sensitive to the imperfection in the form of initial curvature. The experimental re-sults show that when the lateral buckling displacement is less than 20 percent of the column length, theexperimental results agree with the results from the theory of initial post-buckling quite well, whilethey agree with the results from the large deflection theory in a quite large range.     

Soot formation in a steady, nonpremixed, recirculating flame

An inverted step burner has been designed in which a steady ethylene, recirculating flame is established. The burner was housed within a vertical wind tunnel. Laser extinction was used to determine the soot volume fraction in the recirculation zone. Temperatures were determined by a thermocouple. One-dimensional laser-Doppler velocity (LDV) measurements were obtained with a frequency shift system to measure the flow field in the recirculating flame. All the measurements were obtained for a fixed ethylene flow rate; a low and a high velocity in the approach flow were investigated.

Variation in air velocity changed the structure of the flame. At low flow conditions, the soot loading has two distinct peaks at the lower and upper edge of the flame. At the higher air velocity, the upper part of the flame has a much lower relative soot loading as a result of the shorter residence time. The location of the peak values of the soot also changed with the residence time. The peak temperature was of the order of 1600°C. The soot loading was low in the regions of high temperature and relatively high in regions of low temperatures, reflecting the important role of thermal radiation in these luminous flames. The LDV measurements were used to reveal the nature of the flow field. The local soot loading in the flame increased as the approach flow velocity increased; this result suggests the possibility that soot may continue to grow when it is recirculated to regions of growth in a flame.     

Oxygen isotopes of fuel pellets from the fifth collaborative materials exercise and uranium oxides reference materials determined by continuous flow laser fluorination mass spectrometry for nuclear forensic applications

Journal of Radioanalytical and Nuclear Chemistry - Uranium oxides are essential materials in the production process of nuclear fuel for civilian or military applications. As such, identifying their...     

Synthesis, structure, photophysics, electrochemistry, and ion-binding studies of ruthenium(II) 1,10-phenanthroline complexes containing thia-, selena-, and aza-crown pendants

A series of ruthenium(II) diimine complexes containing thia-, selena- and aza-crowns derived from 1,10-phenanthroline have been synthesized and characterized, and their photophysics and electrochemistry were studied. Their interaction with metal ions was investigated by UV-vis, luminescence, and 1H NMR spectroscopy. The crystal structures of [Ru(bpy)2(L1)](PF6)2, [Ru(bpy)2(L2)](ClO4)2, [Ru(bpy)2(L3)](ClO4)2, and [Ru(bpy)2(L4)](ClO4)2 have been determined. The luminescence properties of [Ru(bpy)2(L1)](ClO4)2 were found to be sensitive and selective toward the presence of Hg2+ ions in an acetonitrile solution. The addition of alkaline-earth metal ions, Zn2+, Cd2+, and Hg2+ ions, to the solution of [Ru(bpy)2(L6)](ClO4)2 in acetonitrile gave rise to large changes in the UV-vis and emission spectra. The binding of metal ions to [Ru(bpy)2(L6)](ClO4)2 was found to cause a strong enhancement in the emission intensities of the complex, with high specificity toward Hg2+ ions.     

Luminescent 1D chain of platinum(II) terpyridyl units with p-dithiobenzoquinone organometallic linker: self-aggregation imparted from Pt...Pt/pi-pi interactions

Unlike p-dithiobenzoquinone (), which is extremely reactive and has never been isolated, the metal-stabilised p-dithiobenzoquinone [Cp*Ir(eta4-C6H4S2)] () was prepared and used as an efficient organometallic linker to construct novel supramolecular assemblies. Treatment of with the electrophilic Pt(II)(terpy) building blocks produced the supramolecular assembly {[Pt(terpy){Cp*Ir-p-(eta4-C6H4S2)}Pt(terpy)][OTf]4}n (), which was fully characterised and its molecular structure was determined by X-ray crystallography. The structure of revealed the presence of pi-pi and Pt[dot dot dot]Pt interactions among individual molecules describing a 1D chain. Complex showed unusual UV/Vis absorption and luminescence behaviour at low temperature, imparted from self-aggregation mediated by pi-pi and Pt...Pt interactions.     

Luminescent Amphiphilic 2,6‐Bis(1,2,3‐triazol‐4‐yl)pyridine?Platinum(II) Complexes: Synthesis,Characterization, Electrochemical,Photophysical, and Langmuir–Blodgett Film‐Formation Studies

A new series of platinum(II) complexes with tridentate ligands 2,6‐bis(1‐alkyl‐1,2,3‐triazol‐4‐yl)pyridine and 2,6‐bis(1‐aryl‐1,2,3‐triazol‐4‐yl)pyridine (N7R), [Pt(N7R)Cl]X ( 1 – 7 ) and [Pt(N7R)(C?CR′)]X ( 8 – 17 ; R=n‐C₄H₉, n‐C₈H₁₇, n‐C₁₂H₂₅, n‐C₁₄H₂₉, n‐C₁₈H₃₇, C₆H₅, and CH₂‐C₆H₅; R′=C₆H₅, C₆H₄‐CH₃‐p_, C₆H₄‐CF₃‐p, C₆H₄‐N(CH₃)₂‐p, and cholesteryl 2‐propyn‐1‐yl carbonate; X=OTf^?, PF₆^?, and Cl^?), has been synthesized and characterized. Their electrochemical and photophysical properties have also been studied. Two amphiphilic platinum(II)? 2,6‐bis(1‐dodecyl‐1,2,3‐triazol‐4‐yl)pyridine complexes ( 3‐Cl and 8 ) were found to form stable and reproducible Langmuir–Blodgett (LB) films at the air/water interface. These LB films were characterized by the study of their surface‐pressure–molecular‐area (π–A) isotherms, XRD, and IR and polarized‐IR spectroscopy.     

Carbazolylgold(iii) complexes with thermally activated delayed fluorescence switched on by ligand manipulation as high efficiency organic light-emitting devices with small efficiency roll-offs

A series of carbazolyl ligands has been designed and synthesized through the integration of various electron-donating and electron-accepting motifs, including electron-donating 4-(diphenylamino)aryl and electron-accepting cyano and diphenylphosphine oxide moieties, for the development of a new class of gold(iii) complexes, where the energies of their triplet intraligand and ligand-to-ligand charge transfer excited states can be manipulated for the activation of thermally activated delayed fluorescence (TADF). Upon excitation, these complexes show high photoluminescence quantum yields of up to 80% in solid-state thin films, with short excited state lifetimes down to 1 μs. Vacuum-deposited and solution-processed organic light-emitting devices based on these complexes demonstrate promising electroluminescence (EL) performance with maximum external quantum efficiencies of 15.0% and 11.7%, respectively, and notably small efficiency roll-off values of less than 1% at the practical luminance brightness level of 1000 cd m⁻². These distinct EL performances are believed to be due to the occurrence of multichannel radiative decay pathways via both phosphorescence and TADF that significantly shorten the emission lifetimes and hence reduce the occurrence of the detrimental triplet–triplet annihilation in the gold(iii) complexes.

Switch on of TADF can be achieved by tuning the excited state energy levels via ligand manipulation of the carbazolylgold(iii) C^C^N complexes. The resulting OLEDs show maximum EQEs of over 11% and efficiency roll-offs of down to less than 1%.     

Proof of Potassium Ions by Luminescence Signaling Based on Weak Gold–Gold Interactions in Dinuclear Gold(I) Complexes

Two versatile luminescence ion probes for potassium ions have been designed based on the “switching on and off” of the gold–gold interaction. Addition of potassium ions to the gold(I ) complexes [Au₂(R₂PCH₂PR₂)(S-benzo[15]crown-5)₂] (see the picture; R=Ph, cyclohexyl; M⁺=K⁺) give rise to an intense red luminescence.     

Highly efficient carbazolylgold(iii) dendrimers based on thermally activated delayed fluorescence and their application in solution-processed organic light-emitting devices

A new class of C^C^N ligand-containing carbazolylgold(iii) dendrimers has been designed and synthesized. High photoluminescence quantum yields of up to 82% in solid-state thin films and large radiative decay rate constants in the order of 10⁵ s⁻¹ are observed. These gold(iii) dendrimers are found to exhibit thermally activated delayed fluorescence (TADF), as supported by variable-temperature emission spectroscopy, time-resolved photoluminescence decay and computational studies. Solution-processed organic light-emitting diodes (OLEDs) based on these gold(iii) dendrimers have been fabricated, which exhibit a maximum current efficiency of 52.6 cd A⁻¹, maximum external quantum efficiency of 15.8% and high power efficiency of 41.3 lm W⁻¹. The operational stability of these OLEDs has also been recorded, with the devices based on zero- and second-generation dendrimers showing maximum half-lifetimes of 1305 and 322 h at 100 cd m⁻², respectively, representing the first demonstration of operationally stable solution-processed OLEDs based on gold(iii) dendrimers.

A new class of carbazolylgold(iii) C^C^N dendrimers with thermally activated delayed fluorescence properties has been designed and synthesized for the realzaqtion of operationally stable solution-processed organic light-emitting devices.