High-Quality Spherical Silver Alloy Powder for Laser Powder Bed Fusion Using Plasma Rotating Electrode Process.

The plasma rotating electrode process (PREP) is an ideal method for the preparation of metal powders such as nickel-based, titanium-based, and iron-based alloys due to its low material loss and good degree of sphericity. However, the preparation of silver alloy powder by PREP remains challenging. The low hardness of the mould casting silver alloy leads to the bending of the electrode rod when subjected to high-speed rotation during PREP. The mould casting silver electrode rod can only be used in low-speed rotation, which has a negative effect on particle refinement. This study employed continuous casting (CC) to improve the surface hardness of S800 Ag (30.30% higher than mould casting), which enables a high rotation speed of up to 37,000 revolutions per minute, and silver alloy powder with an average sphericity of 0.98 (5.56% higher than gas atomisation) and a sphericity ratio of 97.67% (36.28% higher than gas atomisation) has been successfully prepared. The dense S800 Ag was successfully fabricated by laser powder bed fusion (LPBF), which proved the feasibility of preparing high-quality powder by the "CC + PREP" method. The samples fabricated by LPBF have a Vickers hardness of up to 271.20 HV (3.66 times that of mould casting), leading to a notable enhancement in the strength of S800 Ag. In comparison to GA, the S800 Ag powder prepared by "CC + PREP" exhibits greater sphericity, a higher sphericity ratio and less satellite powder, which lays the foundation for dense LPBF S800 Ag fabrication.

Binding dynamics of cavity solitons in a Kerr resonator with high order dispersion.

Cavity solitons are persistent light pulses arising from the externally driven Kerr resonators. Thanks to the passive parametric gain, cavity soliton has been endowed with the natural advantage of the chip-scaled integration since it was first experimentally generated in the fiber-based platform. Deterministic single soliton with smooth spectrum is a preferred state for numerous applications. However, multiple solitons are more common in the resonators with anomalous dispersion. In this condition, adjacent solitons are easily perturbed to attract and collide with each other. Some experimental observations deviated from the aforementioned description have recorded the stable soliton intervals that can last for a long time scale. This phenomenon is known as soliton binding and is attributed to the presence of narrow resonant sidebands in the spectrum. While the stationary configuration of two binding solitons has been investigated, the dynamical evolution remains an area for further exploration. In this paper, we discuss the binding dynamics of the cavity solitons in the presence of high-order dispersion. The proposed theoretical predictions match well with the numerical results, encompassing both the stationary stable intervals and dynamic trajectories. Our research will provide a comprehensive insight into the soliton motion induced by the internal perturbations.

Tungstate removal from aqueous solution by nanocrystalline iowaite: An iron-bearing layered double hydroxide.

Tungstate enrichment in aquatic systems may cause negative environmental and health effects. This study addresses tungstate removal from aqueous solution by nanocrystalline iowaite, an iron-bearing layered double hydroxide, which has not been used for treatment of tungstate-rich waters so far. Tungstate sorption experiments were conducted with various contact times, temperatures, initial tungstate concentrations (0.001-2 mM), and solution pH values (2-13), the results indicating that iowaite sorbed aqueous tungstate effectively and quickly, and the sorption maximum can be up to 71.9 mg/g. Moreover, the tungsten sorption capacity keeps nearly constant at a wide pH range from 3 to 11. Duo to its pH buffering effect, the alkaline conditions were generated by the addition of iowaite, which are favorable for the removal of aqueous tungstate because the polymerization of tungstate can be prohibited at alkaline pH values. Zeta potential, XRD and XPS analyses were employed to clarify the sorption mechanisms, and it was concluded that tungstate was sorbed via its exchange with the chloride originally intercalated into iowaite interlayers as well as its stronger inner-sphere complexation with the Fe atoms located in iowaite layers. Nanocrystalline iowaite is suitable for treating both tungstate-bearing natural waters with moderately high tungstate concentrations and industrial wastewaters extremely rich in tungstate.

Enhanced Removal of Arsenic from Water by Synthetic Nanocrystalline Iowaite.

Nanocrystalline iowaite, a Mg/Fe-based layered double hydroxide (LDH) intercalated with chloride, was synthesized to evaluate its performance for arsenic removal from water and to investigate the contributing dearsenication mechanisms. It is characterized by fast arsenic sorption rates and has a much higher arsenic uptake capacity than other LDHs that are commonly used for water dearsenication. The surface adsorption of the solution arsenic onto the iowaite samples and the anion exchange of the arsenic in solution with chloride, which is originally in the iowaite interlayers, are the primary mechanisms for the uptake of arsenic by iowaite. In addition to the Coulombic attraction between arsenate/arsenite and positively charged layers of iowaite, the inner-sphere complexation of arsenic with Fe (instead of Mg) in the iowaite layers is responsible for the formation of more stable and stronger arsenic bonds, as indicated by both XPS and EXAFS analyses. Specifically, bidentate-binuclear and monodentate-mononuclear As-Fe complexes were detected in the arsenate removal experiments, whereas bidentate-mononuclear, bidentate-binuclear, and monodentate-mononuclear As-Fe complexes were present for the arsenite-treated iowaite samples. This study shows that nanocrystalline iowaite is a promising, low-cost material for arsenic removal from natural arsenic-rich waters or contaminated high-arsenic waters.

[Spectroscopy Identification of Untreated and Heated Corundum].

Nowadays, a great quantity of heat treating corundums are emerging in our market. It is hard to distinguish them scientifically just by conventional methods. In order to accurately determine whether the corundums have been heated or not, we need to analyse their spectral characteristics. This paper describes the spectroscopy identification of untreated and heated corundum. The experiment is conducted as follows: First, We observed the inclusions of corundum samples, then measured and recorded their infrared spectra, UV-Vis spectra by Fourier Transform Infrared Spectrometer and Ultraviolet-visible Spectrophotometer respectively. Next we chose a part of samples to heat, after the heat treatment, we recorded their spectra and made a comparison with that of untreated corundums. The results showed that we can detect the absorption peaks at 1 980 and 2 110 cm(-1) which represent diaspore in untreated ruby. However, after heat treatment, the absorption peaks disappear which means the structure of AlO(OH) has been destroyed. The sapphires which grown in alkali basalt under reductive condition appear the absorption peak at 3 310 cm(-1). However, this peak vanishes after 18 h heat treatment when the temperature is 1 600 ℃. For UV-Vis spectra of ruby, after heat treatment, the slight shift occurs in strong, wide absorption band at around 555 nm, and this band becomes more pointed. In addition, absorption intensity difference between wave crest and wave hollow increases. The absorption bands at 375, 387, 454 nm of heated sapphires are more pointed than that of the untreated sapphires, and absorption intensity difference rises. These changes in spectral characteristics can help us to distinguish untreated corundum from heat treating corundum.

[The Gemological Characteristics of One Kind Turquoise Imitation].

It has been a long time that the imitations of turquoise appear in gem market. Pressed dyed carbonate in the early stage and dyed variscite, chalcedony as well as magnesite appeared in succession. These kinds of materials do not have the color and characteristics of natural turquoise. Their physical and optical properties are quite different from natural turquoise. One kind of turquoise imitation newly appears in market is selected to be studied in this paper. The conventional gemological method, infrared absorption spectroscopy and X-ray diffraction were employed to study its mineral compositions, gemological properties and structural characteristics. The results show that: the brecciated structure can be observed and the distribution of the iron wire is very simple on the surface of the sample. Deep blue granules are visible on the surface of blue samples and a few black spots can be observed on the surface of white ones, which are typical indication of pressing process. The blue imitations of turquoise has been stained and pressed. The index of this kind of turquoise imitation range from 1.54 to 1.58, which is lower than that of natural turquoise and it show bluish white fluorescence, which can be used as important evidence to distinguish it with natural turquoise. The data of X-ray diffraction shows the sample mainly consists of enstatite and quartz. The results of infrared absorption spectroscopy show that the absorption spectra of this kind of turquoise imitation is in accordance with the typical absorption peaks of enstatite: the absorption peaks which locates near 1 088 and 799 cm-1 are associated with Si­O, Si­O­Si stretching vibration in quartz; the absorption peaks near 2 947 and 2 882 cm-1 is related with stretching vibration of CH2 of exotic organic resin; the absorption peaks near 1 736 and 1 510 cm-1 are resulted from the bending and stretching vibration of CO and CH2.

[Vibrational spectra of Caesious nephrite from Qinghai Province].

Qinghai caesious nephrite is discovered in the 1990s in the Golmud area of Qinghai Province. The conventional gemological testing methods, electron microprobe, infrared absorption spectroscopy and Raman spectroscopy were used in this study to analyze the chemical composition and infrared spectra characteristics of the caesious nephrite, selected from the jade mine of Xiaozhaohuo river in Golmud area. The results show that, the gemological physical properties of the Qinghai caesious nephrite are similar to other origin nephrite. Electron microprobe analysis indicates that the MgO, CaO and SiO2 are the major and stable composition for the caesious nephrite. The content of MgO and CaO are 18. 572%-23.603% and 12.333%-12.807% respectively. Moreover, the content of SiO2 is 56.799%-59.926%. In addition, it also contains a higher content of FeOr(Wt%: 1.924%-8.699%) and an amount of Al2O3, TiO2 and Na2O. Infrared absorption and Raman spectra show that the Qinghai caesious nephrite has a characteristic spectral features of tremolite indicating it is mainly composed of tremolite. The different frequency of the infrared absorption bands is due to the difference of Mg--Fe2+ isomorphous substitutionand Fe2+ content of the caesious nephrite. Comprehensive analysis of chemical composition and vibrational spectroscopy indicate that the color of dark gray blue for the Qinghai nephrite is mainly related to its high content of FeOr, and the Fe is a main coloring element.

[Spectroscopic characteristics study of morganite from Mozambique].

In recent years, morganite is becoming more and more popular due to its special color. The morganite samples located in the Republic of Mozambique were detailedly analyzed for its basic properties, chemical composition characteristics and spectroscopy properties by laser ablation plasma mass spectrometry (LA-ICP-MS), ultraviolet-visible absorption spectra (UV-Vis-NIR), infrared spectrum (IR) and Raman spectroscopy. The color parameters of morganite samples including the main wave- length, saturation, and lightness were got by UV-Vis-NIR Chemical composition test showed higher content of Li, Rb, Cs and Mn in samples and chemical formula was calculated as Be3.2090 Al2.0757 Li0.425 Si5.664 O18 (Na0.1420 Cs0.1316). Infrared spectroscopy showed that morganite structure vibration area is mainly in the fingerprint area 400-1200 and 900-1200 cm(-1) for the vibration of the ring Si--O--Si, 550-900 cm(-1) for Be-O vibration area, and 450-530 cm(-1) for Al--O vibration area. Because the Cs element content is higher in sample morganite and Cs belongs to higher atomic number elements, its existence may move the vibrationfrequency of Si--O--Si rings to the low position. Raman spectra showed 1065 cm(-1) for Si-O inner vibration of non bridge oxygen, around 1000 cm(-1) for Be--O outer vibration of non bridge oxygen, 685 cm(-1) for Si--O--Si inner vibration of deformation, 400 cm(-1) for O--Be--O outer vibration of bending, 390 cm(-1) for. Al--O outer vibration of deformation, 320 cm(-1) for Al--O outer vibration of bending.

[The spectrum characteristic analysis of mammoth ivory].

Due to the similarities between mammoth ivory ornaments and modern elephant ivory ones in the market, the spectral properties of the two kinds of ivories were analyzed and compared in the present paper through the gemological tests, infrared spectrum and X-ray powder diffraction, etc. The research found that the refractive index and specific gravity of the two ivories are very similar. The refractive index of mammoth ivory is 1.52-1.53 whereas that of elephant ivory is 1.54-1.55. The specific gravity of mammoth ivory is 1.77 and that of elephant ivory is 1.72. It should be careful that Schreger angles are used to distinguish the two kinds of ivories, because the angles of inner and middle layers in the two kinds of tusks are similar except the angles of elephant tusk out-layers are larger than those of mammoth (The Schreger angle of the sample mammoth ivory belonging to out-layer tusks is 100 degrees nd that of elephant ivory is 115 degrees). In addition, the out-layer Schreger angles of Asian elephants are normally less than 120 degrees, while those of Africa elephants are bigger than 120 degrees (This can be used to identify Asian and Africa elephant ivories). The infrared spectroscopy test shows that the water-molecule-related absorption peaks of 3319, 1642 and 1557 cm(-1) are more obvious in the modern elephant ivory samples than in the mammoth ivory samples; the collagen-related absorption peaks of 2927and 2855 cm(-1) are obvious in the modern elephant ivory but extremely weak in the mammoth ivory. The results indicate that collagen and crystallized water in mammoth ivory reduced to a very low level after having been buried for a long period. X-ray powder diffraction results show that the diffraction peak splits of mammoth ivories are more obvious and sharp than that of elephant ivories, which means hydroxyapatites crystallized better despite being buried for thousands of years. Hence, it is an important reference for identifying the two kinds of ivories that the ivory organic matter was losing and inorganic matter crystallized better at same time after having been buried.

[Mineralogical and spectral characteristics of copper pectolite].

Copper pectolite, a type of pectolite with blue stripes, is a rare gem material with a great market prospect. Mineralogy and genesis were investigated using X-ray diffraction (XRD), Fourier infrared absorption spectroscopy (FTIR), Raman spectroscopy (Raman), scanning electron microscopes (SEM) and ultraviolet-visible spectrometer(UV-VIS) to understand the mineralogical compositions and characteristics of the parts with different color. XRD, FTIR and Raman result showed that copper pectolite is composed of pectolite and minor calcite, consistent with the result of SEM. FTIR showed that an obvious band at 1 500 cm(-1) with 883 and 710 cm(-1) occurred on the white part that contain minor calcite, while the band was absent on the blue part. UV-Vis absorption spectroscopy analysis showed that the blue part has 640 nm absorption band in the UV area that indicates containing elements Cu. The different mineralogical compositions of the white and blue part indicate their different geological conditions.

[Study on the vibrational spectra characterization of the "she tai cui" jade].

The gemological testing methods, infrared absorption spectrum, Raman spectrum and X-ray powder diffraction were employed to study the gemological characteristics, spectral characteristics and structural features of the "She tai cui" jade. It is indicated that most "She tai cui" jade has the refractive index in the range of 1.53 to 1.54, and a density of 2.65-2.79 cm(-1), and the hardness of 6.5 to 7 in addition to the low hardness (< 5) for the pure white one. The mineral constitution is dominated by quartz in most of the "She tai cui" jade, except the white one, which is dominated by dolomite (about 63.91%). The former may contain a certain amount of other impure minerals and is attributed to the quartzite jade, while the latter contains a certain amount of SiO2 (about 34.85%) and a trace amount of calcite and albite, and is attributed to the dolomite jade.

[Gemology and spectra characterization of gem garnet from Muling City, Heilongjiang Province].

Cenozoic basalts gem-garnets from Muling City, Heilongjiang Province were studied by using standard gemological methods, electron microprobe, Raman spectroscopy, infrared spectroscopy, and ultraviolet-visible spectroscopy to obtain the gemology and spectra characterization. Chemical composition analysis indicates that the garnets are pyropes with some impurity element Fe, Ca, Mn, Cr, and Ti. The average chemical structure formula of the gem-garnet is (Mn0.022 Ca0.455, Fe(2+)0.720, Mg1.793) sigma = 2.990 (Ti0.003 Cr0.009 Fe(3+)0.062 Al1.951) sigma = 2.025 (SiO4)3. Roman spectrum analysis suggests that there are mixed-phases in the garnet, which can be shown by the Roman shift which is caused by bridging oxygen vibration of garnet. The Roman shifts of bridging oxygen bending vibration of pyrope are at 560 cm(-1) (A(1g)), and 641 cm(-1) (E(g) + F(2g)), while the Roman shifts of bridging oxygen bending vibration caused by E(g) + F(2g) of almandine and grossular are at 507 and 486 cm(-1). IR functional group area indicates that the pyropes have no molecules water, but seldom pyropes have a little structure water, which forms three stepped weak absorption peaks at 3 585, 3 566 and 3 544 cm(-1) respectively. Most pyropes are brown-red, which is caused by electronic transitions of impurity ions Cr3+, Fe3+ and Mn2+. UV-Vis spectra show that absorption peaks caused by electron transition of Fe3+ are at 570, 521 and 502 nm, while absorption peaks caused by electron transition of Mn2+ are at 460 and 430 nm, and absorption peaks caused by electron transition of Cr3+ are at 690 and 367 nm.

[Study on XRD and infrared spectroscopy of nephrites from Xinjiang and Xiuyan, Liaoning].

The nephrite species with different colors from Xinjiang and Xiuyan, Liaoning, including gray nephrite, yellow nephrite, white nephrite, jasper and He-Mo nephrite, a special nephrite from Xiuyan, were selected for the present study. The gemological testing method, infrared absorption spectroscopy and X-ray powder diffraction were used to analyze and compare the gemological characteristics of the nephrite with different colors and textures from the above localities, in order to understand the similarities and differences between these nephrites with similar colors but different origin, and provide a theoretical basis for the identification of the nephrite origin. The results show that the nephrites from Xinjiang and Xiuyan, Liaoning province have similar gemological properties. They have similar refractive index of 1.60-1.62 and density of 2.660-3.020 g x cm(-3), and only the density has some differences with different colors. The fluorescence.characteristics are not obvious in these nephrites. The major constituent minerals for these nephrites are tremolite, and small amounts of clay minerals such as chlorite and illite are found in the jasper from Xinjiang. Based on the X-ray powder diffraction analysis on the different types of nephrite from two localities, it was shown that the character of spectra peaks and diffraction intensity of different types of nephrite can reflect the texture of the nephrite and the size of crystalline particles to some extent. The infrared absorption spectra are similar for the nephrites from two localities. The infrared absorption spectrum does not make sense to identify the origin and species of nephrites.

[Raman spectroscopy study on the mineral composition of the Guatemalan jade].

Guatemala is another jade commercial origin in addition to the Myanmar. The Guatemalan jade is usually an assemblage of a variety of mineral compositions, and the mineral composition is unique and different from the Myanmar jade. The characteristics of the structures and paragenetic minerals of the purple and gray-green jade from Guatemala were studied by laser Raman spectroscopy analysis. The results show that the jadeite is a major constituent mineral in Guatemala jade, associated by a variety of coexisting minerals. The paragenetic minerals in Guatemalan jade can be divided into five categories, including the dark minerals hornblende, dolomite, omphacite, chlorite, and light-colored mineral apatite. The hornblende, dolomite, omphacite and chlorite are also the paragenetic minerals in the Myanmar jade, but the apatite is almost invisible in the Myanmar jadeite.

[Infrared spectroscopy and XRD studies of coral fossils].

Coral fossil is an old remain of multicellular animal on the earth, and formed by various geological processes. The structural characteristics and compositions of the coral fossils with different color and radial texture on the surface were studied by infrared absorption spectroscopy and X-ray powder diffraction analyses. The results show that the studied coral fossils mainly are composed of SiO2, and the radial microstructure characterized by the calcareous coral cross-section is preserved. It is formed by metasomatism by SiO2. The infrared absorption spectra of the coral fossil with different color and texture are essentially the same, showing typical infrared absorption spectra of the quartz jade. XRD analysis shows that the main components of the coral fossils with different color and texture are consistent and mainly composed of SiO2 with a trace amount of other minerals and without CaCO3.

Simple hybrid wire-wireless fiber laser sensor by direct photonic generation of beat signal.

Based on direct photonic generation of a beat signal, a simple hybrid wire-wireless fiber laser sensor is proposed. In the sensor, an improved multilongitudinal modes fiber laser cavity is set up by only a fiber Bragg grating, a section of erbium-doped fiber, and a broadband reflector. A photodetector is used to detect the electrical beat signal. Next, the beat signal including the sensor information can access the wireless network through the wireless transmission. At last, a frequency spectrum analyzer is used to demodulate the sensing information. With this method, the long-distance real-time monitor of the fiber sensor can be realized. The proposed technique offers a simple and cheap way for sensing information of the fiber sensor to access the wireless sensor network. An experiment was implemented to measure the strain and the corresponding root mean square deviation is about -5.7 µÎµ at 916 MHz and -3.8 µÎµ at 1713 MHz after wireless transmission.

Dual-wavelength distributed feedback fiber laser based on double exposure and equivalent phase shift method.

A special sampling structure based on double exposure technology is proposed to achieve dual-wavelength lasing in the distributed feedback fiber laser. This structure is composed of two grating pitches in one sampling period, which could be realized by changing the fiber's length in the fabrication. Through employing an equivalent phase shift, only a submicrometer-level precision is required for precise phase control. Then a stable dual-wavelength laser with the spacing of 400 pm is obtained in the experiment successfully. The output power is 30.46 µW and the sidemode suppression ratio is 46 dB under a pumped power of 146 mW.

Multilongitudinal mode fiber laser for strain measurement.

A multilongitudinal mode fiber laser sensor formed by two fiber Bragg gratings and a piece of erbium-doped fiber is first proposed and validated experimentally. When the strain is applied on the sensor, the laser cavity is stretched, which leads to a change of round-trip frequency. Thus the strain can be obtained by measuring the beat frequency of the resonant cavity. The proposed sensor is found to be characterized with simplicity, easy setup, high resolution, low-cost demodulation, and good stability. Experimental results show that the sensor has a sensitivity of -1.1 KHz/microepsilon and the root-mean-square deviation of 3.6 microepsilon.

Experimental demonstration of distributed feedback semiconductor lasers based on reconstruction-equivalent-chirp technology.

In this paper we report, to the best of our knowledge, the first experimental realization of distributed feedback (DFB) semiconductor lasers based on reconstruction-equivalent-chirp (REC) technology. Lasers with different lasing wavelengths are achieved simultaneously on one chip, which shows a potential for the REC technology in combination with the photonic integrated circuits (PIC) technology to be a possible method for monolithic integration, in that its fabrication is as powerful as electron beam technology and the cost and time-consuming are almost the same as standard holographic technology.