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A Pulsed Laser Deposition (PLD) technique is a type of physical vapor deposition (PVD) technology. This research is one of a series of PVD studies aimed at determining the best PLD coating that can minimize the damage of steel pins made of SKD61 with a hardness of 48±1 HRc. The study began with the dummy blocks from SKD61 as research samples, followed by PVD-PLD with three coating materials as alternatives: Al/Cr (70:30), Al/Ti1 (50:50), and Al/Ti2 (63:37), all without active gases (N and C). The procedures used to test the research findings were FESEM, SEM, XRF, EDS, Vickers, and Rockwell Microhardness. The experiments were conducted at the BRIN Fotonic Research Center and the PT AHM Laboratory. The PLD process lasted for 10 minutes and employed an Nd: YAG laser with a wavelength of 1064 nm, a Q-switch with a time delay of 180 s, a pulse energy of 70 mJ, and a vacuum pressure of 1.161.35 Torr. Based on the results of the coating study, an AlTi1 coating was found to be the most effective material coating. The coating consisted of amorphous particles with a size range of 10 nm to 20 nm The coating had a thickness of 23 µm, and the surface hardness was measured to be 474-523 mHv for the single-layer coating and 477-501 mHv for the multilayer coating. The materials in both single-layer and multilayer coating samples have the same hardness in ascending order: AlCr, AlTi2, AlTi1, with a Ti concentration rise from 0.7% to 3.7%. The impact of the Ti element is also crucial in increasing hardness, wear resistance, and roughness. [ABSTRACT FROM AUTHOR]

An experimental study was conducted in search of the experimental condition required for the much needed suppression of spectral interference caused by surface water in hydrogen analysis using laser-induced low-pressure helium plasma spectroscopy. The problem arising from the difficulty in distinguishing hydrogen emission from hydrogen impurity inside the sample and that coming from the water molecules was overcome by taking advantage of similar emission characteristics shared by hydrogen and deuterium demonstrated in this experiment by the distinct time-dependent and pressure-dependent variations of the D and H emission intensifies from the D-doped zircaloy-4 samples. This similarity allows the study of H impurity emission in terms of D emission from the D-doped samples and thereby separating it from the H emission originating from the water molecules. Employing this strategy has allowed us to achieve the large suppression of water induced spectral interference from the previous minimum of 400 [micro]g/g to the current value of 30 [micro]/g when a laser beam of 34 mJ under tight focusing condition was employed. Along with this favorable result, this experimental condition has also provided a much better (about 6-fold higher) spatial resolution, although these results were achieved at the expense of reducing the linear calibration range from the previous 4 300 [micro]g/g to the present 200 [micro]g/g.

It was proved that the analysis of deuterium can be conducted using laser-induced plasma spectroscopy. By selecting the appropriate surrounding gas, its pressure, and gating time of the detection system, it was shown that the emission lines of both hydrogen ([H.sub.[alpha]]) and deuterium ([D.sub.[alpha]]), separated by only 0.179 nm, can be fully resolved. A linear calibration curve was also obtained, indicating that this technique has the potential for quantitative analysis of deuterium. The minimum detection limit achieved in this stage of research was estimated to be 50 ppm. We have also shown that this technique can be used as a simple and rapid method for D and H analysis in solid samples.

An Nd-YAG laser was focused on various types of solid organic samples coated on the surface of a glass substrate surrounding air pressure of 2 Torr and a modulated technique was used to study the mechanism of excitation of the emission of the organic material. The results showed that ablated atoms and molecules are excited by a shock-wave mechanism.

We report in this paper the results of an experimental study on the spectral and dynamical characteristics of plasma emission induced by 1 mJ picoseconds (ps) Nd-YAG laser using spatially resolved imaging and time resolved measurement of the emission intensities of copper sample. This study has provided the experimental evidence concerning the dynamical characteristics of the excitation mechanisms in various stages of the plasma formation, which largely consolidate the basic scenarios of excitation processes commonly accepted so far. However, it is also clearly shown that the duration of the shock wave excitation process induced by ps laser pulses is much shorter than those observed in laser induced breakdown spectroscopy employing nanosecond laser at higher output energy. This allows the detection of atomic emission due exclusively to He assisted excitation in low pressure He plasma by proper gating of the detection time. Furthermore, the triplet excited state associated with He I 587.6 nm is shown to be the one most likely involved in the process responsible for the excellent spectral quality as evidenced by its application to spectrochemical analysis of a number of samples. The use of very low energy laser pulses also leads to minimal destructive effect marked by the resulted craters of merely about 10 μm diameter and only 10 nm deep. It is especially noteworthy that the excellent emission spectrum of deuterium detected from D-doped titanium sample is free of spectral interference from the undesirable ubiquitous water molecules without a precleaning procedure as applied previously and yielding an impressive detection limit of less than 10 μg/g. Finally, the result of this study also shows a promising application to depth profiling of impurity distribution in the sample investigated. [ABSTRACT FROM AUTHOR]

We report the results of experimental study on CN 388.3 nm and C I 247.8 nm emission characteristics using 40 mJ laser irradiation with He and N2 ambient gases. The results obtained with N2 ambient gas show undesirable interference effect between the native CN emission and the emission of CN molecules arising from the recombination of native C ablated from the sample with the N dissociated from the ambient gas. This problem is overcome by the use of He ambient gas at low pressure of 2 kPa, which also offers the additional advantages of cleaner and stronger emission lines. The result of applying this favorable experimental condition to emission spectrochemical measurement of milk sample having various protein concentrations is shown to yield a close to linear calibration curve with near zero extrapolated intercept. Additionally, a low detection limit of 5 lg/g is found in this experiment, making it potentially applicable for quantitative and sensitive CN analysis. The visibility of laser induced breakdown spectroscopy with low pressure He gas is also demonstrated by the result of its application to spectrochemical analysis of fossil samples. Furthermore, with the use of CO2 ambient gas at 600 Pa mimicking the Mars atmosphere, this technique also shows promising applications to exploration in Mars. [ABSTRACT FROM AUTHOR]

A study is conducted on the detailed static and dynamic characteristics of plasma and the resulting emission spectral qualities generated by a femtosecond (fs) laser irradiation compared with those produced by nanosecond (ns) laser irradiation at a reduced ambient air pressure of 0.65 kPa. It is shown that both plasmas feature a tiny primary and a much larger secondary plasmas, which share the same hemispherical shape of roughly the same size at the appropriately chosen pulse energies. The resulted emission spectra in both cases exhibit one of the shock wave characteristics marked by a much stronger Zn triplet than its singlet emission lines. Further measurement of log(r)–log(t) of Cu I 521.8 nm emission line yields a slope of around 0.4, which is in good agreement with Sedov's equation derived for shock wave plasma. While exhibiting similar pressure-dependent emission intensities of Cu and Zn emission lines, the fs induced emission intensities are consistently lower than those induced by ns laser plasma. The estimated average temperature of the ns laser induced plasma (10 200 K) is only slightly higher than that induced by the fs laser (9800 K). The lower integrated emission intensity of fs plasma is related to previously reported lower electron density in fs laser-induced breakdown spectroscopy (fs-LIBS) and the faster decay of the associated continuum background, implying rapid diminution of ionized atoms and hence lower integrated emission intensity. Therefore, apart from cases demanding minimal surface damages, the simpler and less expensive ns-LIBS should be considered as a more favorable alternative for spectrochemical analysis. However, the applications to surface analysis do show that the fs laser offers higher detection sensitivity. A judicial selection is, therefore, strongly recommended. [ABSTRACT FROM AUTHOR]

An experimental study on picosecond laser induced plasma spectroscopy of a zircaloy sample with low-pressure surrounding helium gas has been carried out to demonstrate its potential applicability to three-dimensional quantitative micro-analysis of deuterium impurities in zircaloy. This was achieved by adopting the optimal experimental condition ascertained in this study, which is specified as 7 mJ laser energy, 1.3 kPa helium pressure, and 50 μs measurement window, and which was found to result in consistent D emission enhancement. Employing these operational parameters, a linear calibration line exhibiting a zero intercept was obtained from zircaloy-4 samples doped with various concentrations of D impurity, regarded as surrogates for H impurity. An additional measurement also yielded a detection limit of about 10 μg/g for D impurity, well below the acceptable threshold of damaging H concentration in zircaloy. Each of these measurements was found to produce a crater size of only 25 μm in diameter, promising its application for performing less-destructive measurements. The result of this study has thus paved the way for conducting a further experiment with hydrogen-doped zircaloy samples and the further technical development of a three-dimensional quantitative micro-analysis of detrimental hydrogen impurity in zircaloy vessels used in nuclear power plants. [ABSTRACT FROM AUTHOR]

An experimental study was conducted on the spatial distributions of hydrogen emission intensities from low-pressure plasmas generated by laser ablation of zircaloy-4 and black stone targets in nitrogen and helium ambient gases. In addition to confirming the previously observed intensity enhancement effect in ambient helium gas, the hydrogen and helium emission intensities measured along the plasma expansion direction revealed remarkable extended spatial distributions featuring unexpected maxima near the far end of the plasma where the available shock-wave generated thermal excitation energy should have been significantly reduced. This “anomalous” feature necessarily implied the presence of an additional excitation process beside the well known shock-wave excitation process which is responsible for the plasma emission of heavy atoms in low-pressure ambient gas. Further analysis of the data led to a suggested physical mechanism explaining the possible contribution of a helium metastable excited state to the unusual phenomenon observed in this experiment. [ABSTRACT FROM AUTHOR]

A series of measurements have been performed on the time dependences of the intensities of helium, hydrogen, and deuterium emission lines from the corresponding laser-induced helium plasma at atmospheric pressure for two different He flow rates. The prolonged H¿ and H¿ emissions along with their constant intensity ratio over a relatively extended period indicate the need to provide an alternative excitation mechanism other than the well-known thermal excitation process in a hot plasma. This additional excitation mechanism is also related to the metastable excited state of a He atom as indicated by the similar characteristics of the observed time dependence of the emission intensities. The enhanced intensity and lifetime of He emission at a high He flow rate was explained in terms of the collision-induced increase in the number of He atoms excited to above the 2 1S0 metastable state, which was also responsible for the delayed excitation of H and D atoms via an energy transfer mechanism involving a Penning-like chemi-ionization process. Finally, the benefits of He-assisted delayed excitation of H and D atoms and the aforementioned enhanced intensity and lifetime at a high He flow rate were demonstrated by the achievement of clearly resolved H¿ and D¿ emission lines. [ABSTRACT FROM AUTHOR]

An experimental study was performed on the N2-induced quenching of He-induced intensity enhancement effect in reduced-pressure plasma emission produced by Nd-YAG irradiation on solid zircaloy and porous fossil samples. The spatial distributions and temporal variations in the emission intensities show pronounced intensity quenching effects on the He I 667.9 nm, H I 656.2 nm, and D I 656.1 nm emission lines in both samples when a tiny amount (5% by volume) of nitrogen was added to helium gas, while leaving the spatial and temporal intensity profiles of the heavier Zr and Ca atoms virtually unaffected. In both cases of different ambient gases, the spatial and temporal variations in the He, H, and D emission intensities exhibit distinct features and changes, which are clearly distinguishable from those observed on the Zr and Ca emission lines, which were mainly produced by the shock-wave induced thermal excitation process. The analysis of these data unambiguously revealed the presence of an additional and distinct “He-assisted” excitation mechanism in the He plasma, which was further suggested to be related to the He metastable excited state. The quenching effect was therefore explained as a consequence of energy depletion of the He metastable excited state triggered by the Penning ionization process induced by the presence of nitrogen. This also explains the relatively insensitive response of the Zr and Ca emission intensity profiles to nitrogen addition despite the increased plasma electron density resulting from the ionization process. [ABSTRACT FROM AUTHOR]

A Nd:YAG laser (1064 nm, 120 mJ, and 8 ns) was focused on various types of fossil samples, including fossilized buffalo horns (around 400 000 and 1×106 yr old, respectively) found in Sangiran, Indonesia. Such fossils represent an important starting point for tracing man’s origin and evolution during the Pleistocene era. Carbon emission was found to decrease significantly with the degree of fossilization and no carbon emission was found in a horn fossil dated at 1×106 yr. Some molecular band spectra were also found in all the fossils examined in this study. It was assumed that by combining information on carbon emission, hydrogen emission, and molecular band spectra that the degree of fossilization might be quantitatively calculated. Further results showed that silicon emission is not detected in old fossils, but it is present as a major constituent. This is probably due to the fact that silicon is strongly bound to other elements in old fossils and is ablated in the form of clusters. In order to prove the above hypothesis, a thin film of an old fossil was deposited on a silver plate substrate by means of a laser ablation technique. The resulting film was then irradiated and atomic emission lines of silicon were clearly detected. A comparative study of the low-pressure plasma introduced in this study was conducted using the well-known laser-induced breakdown spectroscopy technique and the results confirmed that operating conditions at atmospheric pressure are unfavorable for a fossil analysis. [ABSTRACT FROM AUTHOR]

Several experimental studies are conducted to explain the spatial densities and the intensity distribution of the enhanced hydrogen emission from low-pressure He plasmas. A new mechanism describing the contribution of helium metastable excited state to the experimental phenomenon is also discussed.

A series of measurements were performed on the time dependences of the intensities of helium, hydrogen, and deuterium emission lines from the corresponding laser-induced helium plasma at atmospheric pressure for two different He flow rates is presented. The resolved [H.sub.[alpha]] and [D.sub.[alpha]] emission lines demonstrated the benefits of He-assisted delayed excitation of H and D atoms and the enhanced intensity and lifetime at a high He flow rate.

The [N.sub.2]-induced quenching of He-induced intensity enhancement effect is studied in reduced-pressure plasma emission produced by Nd-YAG irradiation on solid zircaloy and porous fossil samples. The quenching effect is explained as a consequence of energy depletion of the He metastable excited state triggered by the Penning ionization process induced by the presence of nitrogen.

A study on gas analysis by means of laser-induced breakdown spectroscopy is conducted using a Nd-yttrium aluminum garnet laser and helium host gas at atmospheric pressure on a sample of mixed water (H2O) and heavy water (D2O) in vapor form. It is argued that the helium metastable excited state plays an important role in the hydrogen excitation process.

In this study, we used laser ablation to fabricate toluene-soluble carbon nanoparticles from coconut fiber. In response to excitations at various wavelengths, the fabricated carbon nanoparticles exhibit three distinctive emission peaks at wavelengths of 300 nm, 440 nm, and 540 nm. These three emission peaks correspond to the π orbital state, σ orbital state, and surface state, respectively. Photoluminescence excitation measurements indicate a high probability of energy transfer between the surface state and σ orbital state, whereas the π orbital state is likely independent of the other states. The results of time-resolved photoluminescence measurements indicate that electrons are likely to remain longer in higher-energy states. Given that the carbon dots fabricated in this study were made from natural resources, these findings may find application in photonic devices that feature tunable emissions. [ABSTRACT FROM AUTHOR]

It was proved that the analysis of deuterium can be conducted using laser-induced plasma spectroscopy. By selecting the appropriate surrounding gas, its pressure, and gating time of the detection system, it was shown that the emission lines of both hydrogen (Hα) and deuterium (Dα), separated by only 0.179 nm, can be fully resolved. A linear calibration curve was also obtained, indicating that this technique has the potential for quantitative analysis of deuterium. The minimum detection limit achieved in this stage of research was estimated to be 50 ppm. We have also shown that this technique can be used as a simple and rapid method for D and H analysis in solid samples. [ABSTRACT FROM AUTHOR]