Surface treatment of new type aluminum lithium alloy and fatigue crack behaviors of this alloy plate bonded with Ti–6Al–4V alloy strap

Samples consisting of new aluminum lithium alloy (Al–Li alloy) plate developed by the Aluminum Company of America and Ti–6Al–4V alloy (Ti alloy) plate were investigated. Plate of 400 mm × 140 mm × 2 mm with single edge notch was anodized in phosphoric solution and Ti alloy plate of 200 mm × 20 (40) mm × 2 mm was anodized in alkali solution. Patterns of two alloys were studied at original/anodized condition. And then, aluminum alloy and Ti alloy plates were assembled into a sample with FM 94 film adhesive. Fatigue crack behaviors of the sample were investigated under condition of nominal stress σ = 36 MPa and 54 MPa, stress ratio of 0.1. Testing results show that anodization treatment modifies alloys surface topography. Ti alloy bonding to Al–Li alloy plate effectively retards crack growth than that of Al–Li alloy plate. Fatigue life of sample bonded with Ti alloy strap improves about 62.5% than that of non-strap plate.     

Effect of stitch density on fatigue characteristics and damage mechanisms of stitched carbon/epoxy composites

The effect of stitch density (SD) on fatigue life, stiffness degradation and fatigue damage mechanisms in carbon/epoxy (T800SC/XNRH6813) stitched using Vectran thread is presented in this paper. Moderately stitched composite (SD = 0.028/mm²; ‘stitched 6 × 6’) and densely stitched composite (SD = 0.111/mm²; ‘stitched 3 × 3’) are tested and compared with composite without stitch thread (SD = 0.0; ‘unstitched’). The experiments show that the fatigue life of stitched 3 × 3 is moderately better than that of unstitched and stitched 6 × 6. Stitched 3 × 3 pattern is also able to postpone the stiffness degradation onset. The improvement of fatigue properties and postponement of stiffness degradation onset in stitched 3 × 3 is primarily due to an effective impediment of edge-delamination. Quantification of damage at various cycles and stress levels shows that stitch density primarily affects the growth rate of delamination.     

Growth and dielectric,mechanical, thermal and etching studies of an organic nonlinear optical l-arginine trifluoroacetate (LATF) single crystal

l-arginine trifluoroacetate, an organic nonlinear optical material, has been synthesized from aqueous solution. Bulk single crystal of dimension 57 mm × 5 mm × 3 mm has been grown by temperature lowering technique. Powder X-ray diffraction studies confirmed the monoclinic structure of the grown l-arginine trifluoroacetate crystal. Linear optical property of the grown crystal has been studied by UV–vis spectrum. Dielectric response of the l-arginine trifluoroacetate crystal was analysed for different frequencies and temperatures in detail. Microhardness study on the sample reveals that the crystal possesses relatively higher hardness compared to many organic crystals. Thermal analyses confirmed that the l-arginine trifluoroacetate material is thermally stable upto 212 °C. The etching studies have been performed to assess the perfection of the l-arginine trifluoroacetate crystal. Kurtz powder second harmonic generation test confirms the nonlinear optical properties of the as-grown l-arginine trifluoroacetate crystal.     

Influence of air annealing temperature and time on the optical properties of Yb:YAG single crystal grown by HDS method

8 at.% Yb:YAG plate single crystal with the dimension of 170 mm × 150 mm × 30 mm was grown in vacuum by Horizontal Directional Solidification method. Aimed at blue-green color centers, annealing treatments of 15 mm × 15 mm × 1 mm samples from 900 °C to 1400 °C for 5 h and at 900 °C from 5 h to 40 h in air were conducted. The absorption spectra, emission spectra, fluorescence lifetime and X-ray photoelectron spectroscopy of samples under different annealing conditions were measured at room temperature, respectively. Annealing at above 1000 °C for 5 h or at 900 °C for 40 h made the blue-green color centers disappear and the samples turned to transparent. Absorption coefficients decreased in the 300 nm–800 nm wavelength range, emission intensities increased and emission bands broadened around 486 nm and 1029 nm with increasing temperature up to 1200 °C, then varied inversely. These values decreased or increased monotonically with increasing annealing time at 900 °C. The maximal increases of fluorescence lifetime were 62.3% and 64.7%, respectively. The calculated emission cross section of 1200 °C for 5 h was up to 4.4 × 10⁻²⁰ cm². In X-ray photoelectron spectroscopy, the concentrations of oxygen vacancies reduced from 1.28% down to absence by annealing. These experiments show that color centers are detrimental to the optical properties of HDS-Yb:YAG laser crystal and optimal annealing treatments should be conducted.     

Effect of stitching on the low-velocity impact response of [03/903]s graphite/epoxy laminates

This study examines the effect of stitching on the impact performance of a class of graphite/epoxy cross-ply laminates with the aim of investigating the ability of through-thickness reinforcement to improve the delamination resistance of laminates.Unstitched and stitched rectangular specimens (65 mm × 87.5 mm) were simply supported by a steel plate having a rectangular opening 45 mm × 67.5 mm in size and impacted at the center with energies ranging between 1 and 13 J. Stitched and unstitched laminates revealed similar structural performances in terms of force versus displacement response, energy absorption and residual indentation depth. It was also observed that whereas stitching does not appear capable of preventing the initiation and spread of delaminations, it induces a clear reduction of damage area when stitches bridge delaminations sufficiently developed in length.     

Optical and thermal properties of crystalline Tb: KLu(WO4)2

A single crystal of Tb: KLu(WO₄)₂ with dimensions of 40 mm × 40 mm × 18 mm has been grown by the top-seeded solution growth (TSSG) method. The color of the crystal is brown. Absorption and fluorescence spectra were measured at room temperature. The measured specific heat is a little lower than that of Yb: KLW (0.365 J/g K) at 90 °C. The measured mean linear coefficients of thermal expansion are α_a = 17.1643 × 10^− 6 K^− 1_, α_a^⁎ = 14.0896 × 10^− 6 K^− 1, α_b = 8.7938 × 10^− 6 K^− 1, α_c = 23.1745 × 10^− 6 K^− 1, α_c^⁎ = 20.2866 × 10^− 6 K^− 1. The results indicate that the crystal has a large anisotropy. The refractive index was measured.     

Tritium digital autoradiography with a Medipix2 hybrid silicon pixel detector

We report on the first measurements of ³H beta autoradiography obtained using a room temperature hybrid pixel detector, consisting of the Medipix2 single particle counting read-out chip bump-bonded to a 300 μm thick silicon pixel detector. This system has 256×256 square pixels of 55 μm pitch for a total sensitive area of 14×14 mm². Each pixel contains a double threshold discriminator and a 13-bit counter. Using a detection threshold equivalent to less than 6 keV and a background count rate of 5×10⁻³ counts mm⁻² s⁻¹, with exposures up to several hours, real-time images have been obtained of tritium-labeled solution drops spotted on a thin mylar foil placed in contact with the continuous top electrode of the silicon detector, in open air condition.     

Studies on optical and mechanical properties of new organic NLO crystal: Guanidinium 4-aminobenzoate (GuAB)

Organic nonlinear optical crystal of guanidinium 4-aminobenzoate (GuAB) has been successfully grown by slow evaporation solution growth technique. The grown crystal is up to the dimension of 36 × 8 × 6 mm³. The crystal is characterized by single crystal XRD for obtaining unit cell parameters. Optical properties of the grown crystal have been studied by means of UV–Vis–NIR transmission and absorption spectra in the range of 200 to 1000 nm. The refractive index and band gap energy of the GuAB crystal are obtained as 1.68 and 3.73 eV respectively. Mechanical hardness has been carried out on the grown crystal.     

Investigation on third order nonlinear optical,electrical and surface properties of organic stilbazolium crystal of 4-N,N-dimethylamino-N′-methylstilbazolium p-methoxybenzenesulfonate

The third order nonlinear optical, electric and dielectric properties of an organic stilbazolium derivative of 4-N,N-dimethylamino-N′-methylstilbazolium p-methoxybenzenesulfonate (DSMOS) crystal are reported. The nonlinear refractive index (n₂), two photon absorption coefficient (β) and third order optical susceptibility χ⁽³⁾ have been measured by Z-scan technique using Gaussian beam from the Nd:YAG laser at 1064 nm. The results show a large negative nonlinear refractive index (n₂ = −1.122 × 10−9 cm²/W) with a molecular two photon absorption coefficient β value of 3.625 × 10⁻⁶ cm/W. The low dielectric constant observed in the high frequency region indicates the suitability of the sample for electro-optic applications. The surface features are also investigated by atomic force microscopy (AFM).     

Flexural properties loss of unidirectional epoxy/fique composites immersed in water and alkaline medium for construction application

Epoxy fique composites were evaluated for construction applications and compared with conventional wood used in construction. The composites studied were made with fique fibers treated using Na(OH) solution at 18 w/v%, untreated fique fibers were also used. The matrices were epoxy and epoxy with 5 wt.% of chemically modified C30B montmorillonite. Unidirectional composites of 90 mm × 20 mm × 4 mm were elaborated by pultrusion processing technique. The flexural properties loss occurred over 20 days of composites submitted to three types of environments: (i) water, (ii) saturated calcium hydroxide solution and (iii) mortar with w/c ratio of 0.45 and 540 kg/m³ of cement, cured in a saturated solution of lime stone at 50 °C. Results showed that fiber treatment and montmorillonite addition improved the flexural modulus and strength of composites in 40% and 34% respectively. Moreover the flexural properties of composites before and after ageing resulted comparable or even better than conventional wood used in construction.     

Impact strength of a few natural fibre reinforced cement mortar slabs: a comparative study

This paper presents the experimental investigations of the resistance to impact loading of cement mortar slabs (1:3, size: 300 mm × 300 mm × 20 mm) reinforced with four natural fibres, coir, sisal, jute, hibiscus cannebinus and subjected to impact loading using a simple projectile test. Four different fibre contents (0.5%, 1.0%, 1.5% and 2.5%—by weight of cement) and three fibre lengths (20 mm, 30 mm and 40 mm) were considered. The results obtained have shown that the addition of the above natural fibres has increased the impact resistance by 3–18 times than that of the reference (i.e. plain) mortar slab. Of the four fibres, coir fibre reinforced mortar slab specimens have shown the best performance based on the set of chosen indicators, i.e. the impact resistance (R_u), residual impact strength ratio (I_rs), impact crack-resistance ratio (C_r) and the condition of fibre at ultimate failure.     

Flexural properties loss of unidirectional epoxy/fique composites immersed in water and alkaline medium for construction application

Epoxy fique composites were evaluated for construction applications and compared with conventional wood used in construction. The composites studied were made with fique fibers treated using Na(OH) solution at 18 w/v%, untreated fique fibers were also used. The matrices were epoxy and epoxy with 5 wt.% of chemically modified C30B montmorillonite. Unidirectional composites of 90 mm × 20 mm × 4 mm were elaborated by pultrusion processing technique. The flexural properties loss occurred over 20 days of composites submitted to three types of environments: (i) water, (ii) saturated calcium hydroxide solution and (iii) mortar with w/c ratio of 0.45 and 540 kg/m³ of cement, cured in a saturated solution of lime stone at 50 °C. Results showed that fiber treatment and montmorillonite addition improved the flexural modulus and strength of composites in 40% and 34% respectively. Moreover the flexural properties of composites before and after ageing resulted comparable or even better than conventional wood used in construction.     

Third-order nonlinear optical properties of bis(tetrabutylammonium)bis(4,5-dithiolato-1,3-dithiole-2-thione)copper

Bis(tetrabutylammonium)bis(4,5-dithiolato-1,3-dithiole-2-thione)copper (BCDT) was synthesized and its third-order optical nonlinearity was characterized using picosecond Z-scan at 1064 nm. The Z-scan spectra reveal a large negative nonlinear refraction coefficient n₂ as high as 4.0 × 10⁻¹⁸ m²/W and a slight two-photon absorption β, which is determined to be 3.4 × 10⁻¹² m/W. The molecular second-order hyperpolarizability γ was calculated to be 6.5 × 10⁻³² esu. All these results suggest that this material has potential for the application of all-optical switching.     

Bridgman growth of large-aperture yttrium calcium oxyborate crystal

Large-aperture yttrium calcium oxyborate YCa₄O(BO₃)₃ (YCOB) crystals with 3 in. in diameter were grown with modified vertical Bridgman method, and the large crystal plate (63 mm × 68 mm × 20 mm) was harvested for high-average power frequency conversion system. The crack, facet growth and spiral growth can be effectively controlled in the as-grown crystal, and Bridgman method displays more effective in obtain large size and high quality YCOB crystal plate than Czochralski technique.     

Characteristics of Al-doped c-axis orientation ZnO thin films prepared by the sol–gel method

Transparent conducting ZnO thin films doped with Al have been prepared by sol–gel method, which were characterized by X-ray diffraction, atomic force microscopy and ultra-violet spectrometer. The films showed a hexagonal wurtzite structure and high preferential c-axis orientation. The optical transmittance spectra of the films showed the transmittance higher than 85% within the visible wavelength region. A minimum resistivity of 6.2 × 10⁻⁴ Ω cm was obtained for the film doped with 1.5 mol.% Al, preheated at 300 °C for 15 min and post-heated at 530 °C for 1 h.     

Optical investigations on Tb3+ doped l-Histidine hydrochloride mono hydrate single crystals grown by low temperature solution techniques

The potential nonlinear optical material of Terbium (Tb³⁺) ion doped l-Histidine hydrochloride monohydrate (LHHC) single crystals were successfully grown. Tb³⁺:LHHC crystals of 7 mm × 5 mm × 3 mm and 59 mm length and 15 mm diameter have been grown by the slow solvent evaporation and Sankaranarayanan-Ramasamy (SR) techniques respectively. The grown crystals were characterized by single crystal X-ray diffraction analysis to confirm the crystalline structure and morphology. High resolution X-ray diffraction (HRXRD) studies revealed that the SR grown sample shows relatively good crystalline nature with 9″ full-width at half-maximum (FWHM) for the diffraction curve. Functional groups were identified by Fourier transform infra-red spectroscopy (FTIR). The optical transparency and band gaps of grown crystals were measured by UV–Vis spectroscopy. Thermogravimetric and differential thermal analysis (TG/DTA) studies reveal that the crystal was thermally stable up to 155 °C in SR grown crystal. Surface morphology of the growth plane was observed using scanning electron microscopy (SEM). The incorporation of Tb ion was estimated by EDAX. The frequency-dependent dielectric properties of the crystals were carried out for different temperatures. Vickers hardness study carried out on (1 0 0) face at room temperature shows increased hardness of the SR method grown crystal. Second harmonic generation efficiency of SEST and SR grown crystals are 3.2 and 3.5 times greater than that of pure KDP. The Photoluminescence (PL) studies of Tb³⁺ ions result from the radiative intra-configurational f-f transitions that occur from the ⁵D₄ excited state to the ⁷F_j (j = 6, 5, 4, 3) ground states. The decay curve of the ⁵D₄ level of emission was observed with a long life time of 319.2041 μs for the SR grown Tb³⁺:LHHC crystal.     

Preparation,characterization and micromolding of multi-walled carbon nanotube polydimethylsiloxane conducting nanocomposite polymer

We present the preparation, characterization and micromolding of a flexible electrically conducting nanocomposite polymer which has been prepared by ultrasonic agitation with multi-walled carbon nanotubes (MWCNT) in polydimethylsiloxane (PDMS). We demonstrate microfabrication of the conducting nanocomposite through soft lithography micromolding of hole and post structures (minimum feature size of 200 ± 10 μm, with a height of approximately 200 μm) against a polymer master. We characterize and compare the current–voltage characteristics of films 1 mm × 1 mm × 200 µm in size as a function of different weight percentages of MWCNT (ranging from 0.8 to 2.5 wt.%) with the result that the conductivity remains low until approximately 1.5 wt.%.     

Low energy implantation to inhibit wear in N+ ions implanted WC–Co composite

This work discusses the influence of nitrogen ion (N⁺) implantation on wear resistance of WC–Co composite. The WC–Co samples were bombarded at low N⁺ ions energies of 20 and 30 keV and doses of 10¹⁷ and 2 × 10¹⁷ ions cm⁻². Tribological tests were conducted against cylindrical 100Cr6 pin at 200 N load and 180 mm s⁻¹ speed. The tests use water lubrication and four sample types with Co binder content ranging in 6.5–25%. The X-ray spectra reveal that implantation is able to transform the original [CFC] Co structure of virgin surface to harder amorphous phase. However, it was found that excessive low binder content alters the wear behavior on non-implanted samples since it causes wear rate transition from 0.59 × 10⁻⁷ to 2.1 × 10⁻⁷ mm³/(mm² s) imposing hence instable wear regime. The SEM micrographs confirm the formation of transferred film within the implanted worn surface owing to (i) an enhancement in Co flow and (ii) a generation of oxides (Fe₂O₃, Fe₃O₄, Co₂O₃, WO₂). While the formed film acts to inhibit severe abrasion, the material removal process combining cobalt flow and carbide grains pull-out seems to be associated with oxidation mechanisms to be accentuated with energy increase. The most improvements in wear resistance were observed on samples with the highest Co content and the results were found more sensitive to N⁺ ions implantation energy than dose.     

Nonlinear optical properties of the PbS nanorods synthesized via surfactant-assisted hydrolysis

PbS nanorods were synthesized by surfactant-assisted homogenous hydrolysis. The products were characterized by UV–vis spectrophotometer, X-ray powder diffraction (XRD) and transmission electron microscope (TEM). PbS nanorods were measured by the Z-scan technique to investigate the third-order nonlinear optical (NLO) properties. The result of the NLO measurements shows that the PbS nanorods have the third-order nonlinear optical properties of both NLO absorption and NLO refraction with self-focusing effects. The nonlinear absorption coefficient and refractive index of the PbS nanorods are 2.16 × 10^− 9 m/W and 3.52 × 10^− 16 m²/W respectively.     

Photodegradation of pyrene on soil surfaces under UV light irradiation

The rates of photodegradation of pyrene (Pyr) on soil surfaces under UV light have been studied. Different parameters such as temperature, soil particle sizes, soil depth, and humic acid (HA) concentration responsible for photodegradation have been monitored. The results obtained indicated that Pyr photodegradation follows pseudo-first-order kinetics. Pyr degradation was fastest at 30 °C, while the photodegradation rate was increased with the temperature from 20 to 30 °C. The degradation loss was about 35% at 30 °C, 30% at 25 °C and 25% at 20 °C, respectively. The rates of Pyr photodegradation at different soil particle sizes followed the order: less than 1 mm > less than 0.45 mm > less than 0.25 mm. The results showed that the relationship of Pyr half-life with soil depth was linear (significant correlation, p < 0.01). When the soil depth increased from 1 to 4 mm, the half-life increased from 19.80 to 37.46 d. HA treatments significantly increased the photodegradation of Pyr on soil surfaces under UV light. However the concentration of HA increased from 5 to 40 mg kg^?1, the pseudo-first-order rates of Pyr decreased due to the shielding effect of HA.