A comparative study of key properties of glycine glycinium picrate (GGP) and glycinium picrate (GP): A combined experimental and quantum chemical approach

Using experimental and computational techniques, a comparative study of electro-optical properties for glycine glycinium picrate (GGP) and glycinium picrate (GP) compounds has been performed. The single crystal of GGP has been grown using slow evaporation technique that was further subjected to experimental characterization of its electro-optical properties. The good optical transparency and mechanical strength at micro level was confirmed from optical and nanoindentation measurements using the Oliver–Pharr method of the grown single crystals. Differential scanning calorimetric (DSC) analysis was done to probe the thermal stability of the grown single crystals. Using the density functional theory (DFT) methods, we have not only investigated the GGP but also proposed GP molecule. Additionally, we have shed light on the molecular geometries, infrared and Raman spectra, linear and nonlinear optical properties of both GGP and GP at molecular level. The time dependent DFT (TD-DFT) approach was adopted to calculate the excitation energies of the molecules in different phases including gas, water, acetone, cyclohexane and chloroform as well. For GGP, its wavelength of maximum absorption is calculated to be ～390 nm at B3LYP/6-31G¹ level of theory. The calculated amplitudes of first hyperpolarizability (β_tot) for GGP and GP are found to be 712 and 970 a. u., respectively, which are about 16 and 23 times larger than that of the urea molecule (a prototype NLO molecule). Thus the present study not only brings to limelight the optical and nonlinear optical properties of GGP but also sheds light on the possible potential of GP as new NLO molecule.     

Electrical and positron annihilation study on epoxy and epoxy acrylate composites

Epoxy acrylate resin was prepared by endcapping the acrylic acid to epoxy resin backbone in the presence of triphenyl phosphene as catalyst. The structure was elucidated by IR and NMR spectroscopy. Epoxy and epoxy acrylate composites were prepared by mixing different concentrations of mica, magnesium hydroxide and calcium silicate with each epoxy/hardener and epoxy acrylate/styrene mixtures, respectively. The permittivity ε′, dielectric loss ε′′ and loss tangent tan δ were measured for these composites in the frequency range (10²-10⁶ Hz) and at 30 °C. The data obtained were analyzed into two absorption regions related to Maxwell-Wagner effect and to some local molecular motions rather than the main chain motion. The higher values of ε′ and the lower values of tan δ given for the composites containing the epoxy acrylate resin indicate some improvement in the dielectric properties when compared with those containing the epoxy resin. The effect of filler type and filler content on the positron annihilation lifetime and its intensity as well as S-parameter for epoxy and epoxy acrylate composites were also studied. The high values of S-parameter noticed by with increasing filler content indicates some increase in free electrons which lead to an increase in electrical conductivity. The highest value of hardness was obtained in the case of calcium silicate followed by mica and magnesium hydroxide.     

The directional crystallization of W-B-C-d-transition metal alloys

Crystallization from the melt during arc melting and directional solidification during induction zone melting of pseudo-alloys tungsten carbide (WC)-MeB₂ (Me—Ti, Zr, Cr) and a number of alloys of the W-B-C system (WB_0.12C_0.74; WB_0.25C_0.75; WB_0.34C_0.32; WB_0.49C_0.76; WB_0.59C_0.76; WB_0.89C_0.75; (WC)_0.9B_0.1) has been studied. It was shown that the alloys WC—80 mass%-ZrB₂—20 mass% and WC—72 mass%-WB—28 mass% are the closest ones to eutectic compositions. Investigation of the microstructure of eutectic alloys in the WC-WB system by thin foil method has revealed that both matrix and reinforcing phases are single crystalline.Hardness tests by indentation of the eutectic structure area (P=10.3 N) do not result in radial crack formation, which is evidence of the essential plasticity of the obtained composite material. It is established that new ceramic-ceramic eutectic composite materials based on WC with transition metal diborides and with a boride phase of tungsten may be created. Such materials can be successfully applied in contemporary high-temperature techniques.     

The effect of curing conditions on the physical and mechanical properties of styrenated polyester

The curing behavior of unsaturated polyester resin was investigated. In the present study, styrene, methyl ethyl keton peroxide (MEKP) and cobalt octoate (CO) have been selected as solvent (monomer), catalyst and accelerator, respectively. The effect of the concentration of both MEKP and CO on the curing exotherm, curing time, hardness and compressive strength of the prepared copolymers was investigated.     

Coupled annealing temperature and layer thickness effect on strengthening mechanisms of Ti/Ni multilayer thin films

A systematic study was performed on mechanical and microstructural properties of Ti/Ni multilayers with layer thickness from 200 nm to 6 nm and annealing temperature from room temperature to 500 °C. Based on the observed hardness evolution, a coupled layer-thickness and annealing-temperature dependent strengthening mechanism map is proposed. For as-deposited films, the deformation behavior follows the traditional trend of dislocation mediated strengthening to grain boundary mediated softening with decreasing layer thickness. For annealed films, grain boundary relaxation is considered to be the initial strengthening mechanism with higher activation temperature required for thicker layers. Under further annealing, solid solution hardening, intermetallic precipitation hardening, and fully intermixed alloy structure continue to strengthen the thin layered films, while recrystallization and grain-growth lead to the eventual softening of thick layered films. For the films with intermediate layer thickness, a strong orientation dependent hardness behavior is exhibited under high temperature annealing due to mechanism switch from grain growth softening to intermetallic precipitation hardening when changing the loading orientation from perpendicular to parallel to the layer interfaces.     

Ab initio SCRF study of solvent effect on the nonlinear polarizabilities of different intramolecular charge-transfer molecules

The macroscopic solvent effect on static nonlinear polarizabilities of a number of intramolecular charge-transfer (ICT) molecules have been studied by using the self-consistent-reaction field (SCRF) model in the framework of ab initio time-dependent-HF (TDHF) method using 3-21G basis set. The two-state model of static β and <γ> have been used to obtain their functional dependence on the ground-state hardness parameter, dipole moment and solvation energy. The methyl substituted 4-quinopyran and other zwitterionic molecules are found to exhibit strong diminution of both quadratic and cubic polarizabilities at higher solvent reaction field due to negative solvatochromic effect. However, molecules showing positive solvatochromism lead to strong enhancement of the NLO response on increase in solvent polarity. The evolution pattern of the solvent modulated static β and <γ> of 4-quinopyran (4QP) obtained for varying inter-ring torsion angle differ strikingly from that shown by p-amino p'-nitro biphenyl (ANB).     

Filling and wear behaviors of micro-molded parts made with nanomaterials

Microinjection molding technology and its various modifications represent established processes for micro-molded parts with high accuracy under large scale production. Recently, the use of plastic material with added reinforced fillers has become a potential alternative approach due to its high strength and the ease of batch fabrication. This paper investigates the moldability and wear properties of a polymer with added nanoceramic materials during microinjection molding. In this study, parts with micro-features were successfully manufactured using a custom-made injection machine. The results show that the polymer with added nanomaterials effectively increased the hardness achieved. In addition, a nanoceramic material, such as ZnO, improved wear resistance by 70% when nanoparticles were uniformly dispersed in the polymer and a suitable surfactant solvent was chosen. However, wear resistance decreased significantly if the nanoparticles were not processed well and a proper surfactant solvent was not chosen. The results also show that high hardness did not result in reinforced parts with high wear resistance.     

Empirical Correlations for Viscosity of Polyacrylamide Solutions with the Effects of Salinity and Hardness

A series of experiments have been conducted to characterize and quantify the effects of shear rate, salinity, and hardness on the viscosity of polymer solutions. A set of correlations were developed to predict the viscosity of polymer solutions. These correlations consider the individual and combined effects of shear rate, salinity, and hardness on the viscosity of polymer solutions. The power-law model for the viscosity behavior has been modified to accommodate the influence caused by these three factors. Nonlinear regression was performed on the experimental data to develop the proposed correlations. The proposed correlations can be integrated into any reservoir simulator for polymer injection and should prove useful for the initial screening for the selection of the polymer for enhanced oil recovery applications in oil reservoirs.      

两种T700碳纤维的微观结构与性能研究

采用原子力显微镜(AFM)、扫描电镜(SEM)、拉曼光谱(Raman)、X射线衍射(XRD)和透射电镜(TEM)对国产JHT45-T700和日本东丽T700两种碳纤维的硬度相对大小、表面和断面形貌、石墨化程度和微晶结构进行了表征,分析了其中的差异。结果表明,东丽T700微区硬度大于国产JHT45-T700;国产JHT45-T700表面存在大量沟槽,而东丽T700表面光滑。因此,国产JHT45-T700与树脂基体的浸润性优于东丽T700。Raman与XRD分析表明,东丽T700石墨化程度、微晶尺寸和结构的有序程度均高于国产JHT45-T700;TEM显示,东丽T700晶格条纹比国产JHT45-T700更规整些,晶相较多,石墨微晶发育相对更完善。