Effects of TiC addition on properties of laser particle deposited WC-Co-Cr and WC-Ni coatings

The mechanisms by which titanium carbide （TiC） improves the properties of tungsten carbide （WC） coatings deposited on duplex stainless steels using laser particle injection technique were investigated. The relationships between laser process parameters and the synthesized composite were studied. The morphologies and microstructures of the feedstock powders and composite coatings were characterized using scanning electron microscopy （SEM） and energy dispersive X-ray spectroscopy （EDX） techniques. Surface hardness of the composite layers was determined using the Vickers microhardness tester while its corrosion behaviour in 3.5%NaCl solution was investigated by potentiodynamic polarization curve measurement method. As a result of the laser treatment, microstructures characterized by hard ceramic particles with strong bonding to substrate were formed on the surface layer of the steels. The addition of TiC to WC resulted in microstructures free from cracks, pores and intermetallics which could be detrimental to the properties of the composites. High microhardness was observed and most of the coatings shifted the corrosion potential to more noble values with the pseudo-passive curve.

OMEC LS800 Laser Particle Sizer

Laser particle sizers (LPS’s) measure the size of smallparticles from the phenomenon of light scattering, whilescattering by large particles is considered to consists ofdiffraction. Mie’s Theory applies to small particles down tosubmicron dimensions. OMEC recognizes that the scat-tering theory should be used for both large and small par-ticles in order to have a precise description of the scat-

COMPARISON OF VARIOUS PARTICLE SIZING TECHNIQUES

SEM,TEM, gas absorption, X-ray Sedi-graph and laser particle sizing have been employed to analyse particle size distribution and powder agglomeration for Alcoa A16 and for Sumitomo AKS-53B and SKP-53 alpha - Al2O3 powders on several occasions as well. Comparison and evaluation of various particle-sizing techniques have been made.

Proton Acceleration with Nano-Scale Micro-Structured Target by Circularly Polarized Laser Pulse

Two dimensional particle-in-cell simulations are taken to study the interaction of a circularly polarized laser pulse with a nano-scale micro-structured target. The protons which are doped in the rear side of the target experience the electrostatic fields caused by both the radiation pressure driven shock and the target normal sheath at the rear side of the target. A quasimonoenergetic proton bunch with central energy of about 11MeV and energy spread of ＆#8710; ε/ε about 0.18 is achieved by using a 3.45×1019 W/cm2, 66fs laser pulse. A comparison with the case of linearly polarized laser pulse and the same target condition is considered.

Precise photoelectrochemical tuning of semiconductor microdisk lasers

Micro-and nanodisk lasers have emerged as promising optical sources and probes for on-chip and free-space applications.However,the randomness in disk diameter introduced by standard nanofabrication makes it challenging to obtain deterministic wavelengths.To address this,we developed a photoelectrochemical(PEC)etching-based technique that enables us to precisely tune the lasing wavelength with subnanometer accuracy.We examined the PEC mechanism and compound semiconductor etching rate in diluted sulfuric acid solution.Using this technique,we produced microlasers on a chip and isolated particles with distinct lasing wavelengths.These precisely tuned disk lasers were then used to tag cells in culture.Our results demonstrate that this scalable technique can be used to produce groups of lasers with precise emission wavelengths for various nanophotonic and biomedical applications.

Evaluating Low-Cost Commercially Available Sensors for Air Quality Monitoring and Application of Sensor Calibration Methods for Improving Accuracy

In this paper, we present the results of the evaluation of three low-cost laser sensors and comparison with the standard device Metone Aerocet 531s which is capable of counting dust particles as small as 0.3 μm. The sensors used in this study are PMS5003 (Plantower), SPS30 (Sesirion), SM-UART-04L (Amphenol). During the measurement, the overall trend of the outputs from the sensors was similar to that of the Aerocet 531s. The PMS5003 sensor has a relatively small standard error in the all particle measurement ranges (<15 μg/m3 in the low particle concentration range). All sensors have a high linearity compared to data from standard equipment, PMS5003: PM1.0 R2 = 0.89;PM2.5 R2 = 0.95;PM10 R2 = 0.87;SPS30 PM2.5 R2 = 0.95 and PM10 R2 = 0.99;SM-UART-04L PM1.0 R2 = 0.98. Three main sensor calibration methods (single-point calibration, two-point calibration and multi-point curve correction) with implementation steps for each method as well as their practical applications in calibrating low-cost air quality sensors according to standard measuring equipment are also detailed illustrated.

FUNCTIONS OF POLYAMINES IN ROSIN SIZING UNDER NEUTRAL PAPERMAKING CONDITIONS

Functions of the polyamines in neutral rosin sizing were investigated using X-ray photoelectron spectroscopy (XPS) and laser diffraction particle analysis. The polyamine with a higher charge density and a smaller unite size could retain more rosin and cover larger fiber surfaces. The XPS spectra demonstrated that polyallylamine (PAAm) and polyvinylamine (PVAm) could react with a rosin size to form a -OC-N-CO- structure, but polydimethylamino ethyl methacrylate (PDMAEMA) could not. The formation of this structure may be a key step for effective sizing.

Passively Q-switched ytterbium-doped fiber laser using the evanescent field interaction with bulk-like WTe_2 particles

The potential of bulk-like WTe2 particles for the realization of a passive Q-switch operating at the 1 μm wavelength was investigated. The WTe2 particles were prepared using a simple mechanical exfoliation method together with Scotch tape. By attaching bulk-like WTe2 particles, which remained on the top of the sticky surface of a small segment of the Scotch tape, to the flat side of a side-polished fiber, a saturable absorber（SA） was readily implemented. A strong saturable absorption was then readily obtained through an evanescent field interaction with the WTe2 particles. The modulation depth of the prepared SA was measured as ~2.18% at 1.03 μm. By incorporating the proposed SA into an all-fiberized ytterbium-doped fiber ring cavity, stable Qswitched pulses were readily achieved.

Characterizing THz Coherent Synchrotron Radiation at Femtosecond Linear Accelerator

The generation and observation of coherent THz synchrotron radiation from femtosecond electron bunches in the Shanghai Institute of Applied Physics femtosecond accelerator device is reported. We describe the experiment setup and present the first result of THz radiation properties such as power and spectrum.

Inversion of particle size distribution from light-scattering data using a modified regularization algorithm

A modified regularization algorithm with a more proper operator was proposed for the inversion of particle size distribution （PSD） from light-scattering data in a laser particle sizer based on the Mie scattering principle. The Generalized Cross-Validation （GCV） method and the L-curve method were used for deter- mining the regularization parameter. The Successive Over-Relaxation （SOR） iterative method was used to increase the exactness and stability of the converged result. The simulated results based on the modified algorithm are in a good agreement with the experimental data measured for nine standard particulate samples, their mixtures as well as three natural particulate materials with irregular shapes, indicating that this modified regularization method is not only feasible but also effective for the simulation of PSD from corresponding light-scattering data.

A 2D scintillator-based proton detector for high repetition rate experiments

We present a scintillator-based detector able to measure the proton energy and the spatial distribution with a relatively simple design.It has been designed and built at the Spanish Center for Pulsed Lasers(CLPU)in Salamanca and tested in the proton accelerator at the Centro de Micro-Análisis de Materiales(CMAM)in Madrid.The detector is capable of being set in the high repetition rate(HRR)mode and reproduces the performance of the radiochromic film detector.It represents a new class of online detectors for laser-plasma physics experiments in the newly emerging high power laser laboratories working at HRR.