Influence of Basicity on the Formation of Cluster Ions/Adduct Ions for Organic Ammonium Halides by Positive Secondary Ion Mass Spectrometry

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Feedback model of secondary electron emission in DC gas discharge plasmas

Feedback is said to exist in any amplifier when the fraction of output power in fed back as an input.Similarly,in gaseous discharge ions that incident on the cathode act as a natural feedback element to stabilize and self sustain the discharge.The present investigation is intended to emphasize the feedback nature of ions that emits secondary electrons（SEs）from the cathode surface in DC gas discharges.The average number of SEs emitted per incident ion and non ionic species（energetic neutrals,metastables and photons）which results from ion is defined as effective secondary electronemission coefficient（ESEEC,Eg）.In this study,we derive an analytic expression that corroborates the relation betweenEg and power influx by ion to the cathode based on the feedback theory of an amplifier.In addition,experimentally,we confirmed the typical positive feedback nature of SEEfrom the cathode in argon DC glow discharges.The experiment is done for three different cathode material of same dimension（tungsten（W）,copper（Cu）and brass）under identical discharge conditions（pressure：0.45 mbar,cathode bias：-600 V,discharge gab：15 cm and operating gas：argon）.Further,we found that theEg value of these cathode material controls the amount of feedback power given by ions.The difference in feedback leads different final output i.e the power carried by ion at cathode（Pi C￠∣）.The experimentally obtained value of Pi C￠∣is 4.28 W,6.87 W and9.26 W respectively for W,Cu and brass.In addition,the present investigation reveals that the amount of feedback power in a DC gas discharges not only affect the fraction of power fed back to the cathode but also the entire characteristics of the discharge.

A depressant for marmatite flotation:Synthesis,characterisation and floatation performance

This study synthesised a zincic salt(ZS)as a depressant for marmatite-galena separation.The effect of ZS on the flotation of marmatite and galena was investigated through micro-flotation tests.88.89%of the galena was recovered and 83.39%of the marmatite was depressed with ZS dosage of 750 mg·L^(−1)at pH=4.The depression mechanism of ZS on marmatite was investigated by a variety of techniques,including adsorption measurements,Fourier transform infrared(FTIR),X-ray photoelectron spectroscopic(XPS)analysis,and time of flight secondary ion mass spectrometry(ToF-SIMS).Results of adsorption tests and FTIR reveal that ZS adsorbed on marmatite surface and impeded the subsequent adsorption of butyl xanthate(BX).The results of XPS and ToF-SIMS indicate that the ZnO_(2)^(3-)released by ZS could be chemisorbed on the marmatite surface and depress marmatite flotation.

Low-resistance ohmic contacts on InAlN/GaN heterostructures with MOCVD-regrown n+-InGaN and mask-free regrowth process

This paper studied the low-resistance ohmic contacts on InAlN/GaN with metal–organic chemical vapor deposition(MOCVD)regrowth technique.The 150-nm regrown n-InGaN exhibits a low sheet resistance of 31Ω/□,resulting in an extremely low contact resistance of 0.102Ω·mm between n^(+)-InGaN and InAlN/GaN channels.Mask-free regrowth process was also used to significantly improve the sheet resistance of InAlN/GaN with MOCVD regrown ohmic contacts.Then,the diffusion mechanism between n^(+)-InGaN and InAlN during regrowth process was investigated with electrical and structural characterizations,which could benefit the further process optimization.

Strategies towards robust interpretations of in situ zircon oxygen isotopes

Oxygen isotopes are a versatile tool to address a wide range of questions in the Earth sciences.Applications include geothermometry,paleoclimatology,tracing of geochemical reservoirs,fluid-rock interaction,magmatic petrogenesis,and identification of extra-terrestrial materials.Zircon arguably provides one of the most robust records of primary magmatic O isotope ratio due to low diffusion rates in crystalline grains.The ability to correlate zircon O isotopes with temporal and petrogenetic information(e.g.U-Pb geochronology,Lu-Hf isotopes,and trace elements)makes this mineral a key archive for understanding Earth’s crustal evolution.Consequently,zircon O isotope geochemistry has found widespread usage to address fundamental questions across the earth and planetary sciences.The general apparent ease of O isotopic acquisition through the advancement of rapid in situ techniques(i.e.secondary ion mass spectrometry;SIMS)and associated dedicated national laboratories has led to the generation of large O isotopic data sets of variable quality,highlighting the importance of a coherent workflow for data collection,reduction,and presentation.This paper presents a set of approaches for measurement,assessment,and reporting of zircon O isotope data.The focus in this contribution is on in situ analysis via secondary ion mass spectrometry using large geometry instruments,but other commonly used techniques are briefly reviewed for context.This work aims to provide an analytical framework necessary for geologically meaningful interpretation of O isotope data.In addition,we describe inherent geological(e.g.radiation-induced disturbance of the zircon O isotopic system)and analytical(e.g.fractionation due to sample topography effects)challenges and outline means to identify and avoid such issues as a prerequisite to the generation of robust primary O isotopic signatures for geological interpretation.

Model of Diffusion of Sulfur in Soda-lime-silicate Glass:An Experimental and Comparative Study

The diffusion property of sulfur on the soda-lime-silicate float glass surface was studied by using secondary ion mass spectroscopy（SIMS）.According to the Fick＇s Second Law,two models of diffusion of sulfur on the glass surface were built.When the diffusion of sulfate（S^6＋） is considered uniquely,the concentration-depth profile of sulfur can not be fitted very well,especially on the top surfaces of the air side and tin side of float glass.So the diffusion of sulfide（S^2-） on the profile of sulfur can not be ignored.The concentration-depth profile of sulfur on both sides of glass can be fitted more exactly when both S^6＋ and S^2- are considerd.Based on the above-mentioned fitting results,it is concluded that the diffusion coefficents of S^6＋ and S^2- of tin side are larger than those of the air side.Moreover,the diffusion coefficents are related to the contacted medium.

Characterization of deep acceptor level in as-grown ZnO thin film by molecular beam epitaxy

We report deep level transient spectroscopy results from ZnO layers grown on silicon by molecular beam epitaxy （MBE）, The hot probe measurements reveal mixed conductivity in the as-grown ZnO layers, and the current-voltage （l-V） measurements demonstrate a good quality p-type Schottky device. A new deep acceptor level is observed in the ZnO layer having activation energy of 0.49 ± 0.03 eV and capture cross-section of 8,57 ×10^-18 cm^2. Based on the results from Raman spectroscopy, photoluminescence, and secondary ion mass spectroscopy （SIMS） of the ZnO layer, the observed acceptor trap level is tentatively attributed to a nitrogen-zinc vacancy complex in ZnO,

Layer-by-Layer Analysis of the Composition of Thin Films by SIMS and Raman Spectroscopy

In this study, thin films were produced by magnetron sputtering NC （nanocrystalline） specimens of titanium saturated in hydrogen and were evaluated by layer-by-layer SIMS （secondary ion mass spectrometry） and Raman spectroscopy. Due to magnetron sputtering, the chemical composition of the films was non-homogeneous and was variable among layers. Moreover, in the deposition of specimens saturated with hydrogen, hydrogen diffused throughout the depth of the film; diffusion, however, was restricted to the area near the film-substrate interface, affecting less than 50% of the thickness of the film.

Source Rock Classification and the Basic Structure of Coal and Kerogen

In accordance with the confusion on classification of source rocks, the authors raised a source rock classification for its enriched and dispersed organic matter types based on both Alpern’s idea and maceral genesis/composition. The determined rock type is roughly similar to palynofacies of Combaz , whereas it is "rock maceral facies (for coal viz. coal facies)" in strictly speaking. Therefore, it is necessary to use the organic ingredients classification proposed by the authors so that it can be used for both maceral analysis and environment research . This source rock classification not only shows sedimentology and diagenetic changes but also acquires organic matter type even if hydrocarbon potential derived from maceral’s geochemical parameters. So, it is considered as genetic classification. The "rock maceral facies" may be transformed to sedimentary organic facies , which is used as quantitative evaluation means if research being perfect.Now, there are many models in terms of structure either for coal or for kerogen. In our opinion, whatever coal or kerogen ought be polymer, then we follow Combaz’s thought and study structure of amorphous kerogens which are accordance with genetic mechanism showing biochemical and geochemical process perfectly. Here, we use the time of flight secondary ion mass spectrometry (TOFSIMS) to expand Combaz’s models from three to five. They are also models for coal.

Analysis of the linkage positions and isomers of monosaccharide units in oligosaccharides by negative secondary ion mass spectrometry in combination with the stereoselective reaction with substituted boronic acid

The negative secondary ion mass spectrometry,in combination with the stereoselective derivatizations with substituted boronic acid RB(OH)_2,was used in the analysis of fourteen oligosac- charides.The mass spectra of the derivatives provide information on their linkage Positions and iso- merism of the individual monoscaccharide units.The results indicated that among the derivatives of the oligosaccharides analyzed,those with 1—4 and 1—6 linkages all presented the ion peaks at m/z 287,sometimes one more peak at m/z 449.Furthermore,a relationship was found between the linkage positions and the intensity orders of the derivative ions.Finally,the derivatives of the disaccharides with a galactose presented an intense ion peak at m/z 347,and those of oligosaccharides with 1—6 linkage to a galactose at terminal presented the ion at m/z 317.In the case of oligosaccharides with a fructose residue,characteristic ion of m/z 155 was produced.The conditions of stereoselective derivatizations and mass spectrometry were studied,in order to obtain a better reproducibility of the mass spectra.

Effect of Hydrogen on Corrosion and Stress Corrosion Cracking of AZ91 Alloy in Aqueous Solutions

The effect of hydrogen on the corrosion and stress corrosion cracking of the magnesium AZ91 alloy has been investigated in aqueous solutions. Hydrogen produced by corrosion in water diffuses into, and reacts with the Mg matrix to form hydride. Some of the hydrogen accumulates at hydride/Mg matrix （or secondary phase） interfaces as a consequence of slow hydride formation and the incompatibility of the hydride with the Mg matrix （or secondary phase）, and combines to form molecular hydrogen. This leads to the development of a local pressure at the hydride/Mg matrix （or secondary phase） interface. The expansion stress caused by hydride formation and the local hydrogen pressure due to its accumulation result in brittle fracture of hydride. These two combined effects promote both the corrosion rate of the AZ91 alloy, and crack initiation and propagation even in the absence of an external load. Hydrogen absorption leads to a dramatic deterioration in the mechanical properties of the AZ91 alloy, indicating that hydrogen embrittlement is responsible for transgulanar stress corrosion cracking in aqueous solutions.

Stratigraphic analysis of intercalated graphite electrodes in aqueous inorganic acid solutions

A detailed stratigraphic investigation of the intercalation mechanism when graphite electrodes are immersed inside diluted perchloric(HClO_(4))and sulfuric(H_(2)SO_(4))electrolytes is obtained by comparing results when graphite crystals are simply immersed in the same acid solutions.By combining time-of-flight secondary ion mass spectrometry(ToF-SIMS)and in-situ atomic force microscopy(AFM),we provide a picture of the chemical species involved in the intercalation reaction.The depth intensity profile of the ion signals along the electrode crystal clearly shows a more complex mechanism for the intercalation process,where the local morphology of the basal plane plays a crucial role.Solvated anions are mostly located within the first tens of nanometers of graphite,but electrolytes also diffuse inside the buried layers for hundreds of nanometers,the latter process is also aided by the presence of mesoscopic crystal defects.Residual material from the electrolyte solution was found localized in well-defined circular spots,which represent preferential interaction areas.Interestingly,blister-like micro-structures similar to those observed on the highly oriented pyrolytic graphite(HOPG)surface were found in the buried layers,confirming the equivalence of the chemical condition on the graphite surface and in the underneath layers.

Probing the Proteolysis of Melittin Using Liquid Secondary Ion Mass Spectrometry

Liquid secondary ion mass spectrometry(LSIMS) was used to probe the proteolysis of melittin by trypsin and pepsin. The results showed that LSIMS is good for monitoring proteolytic reactions. It can not only identify the proteolytic products of proteins, but also be used to research the dynamics of proteolytic reactions. The proteolysis of melittin by trypsin gave seven main peptide fragments: 1, AA 1 AA 7 ; 2, AA 1 AA 21 ;3, AA 1 AA 22 ; 4, AA 1 AA 23 ; 5, AA 1 AA 24 ; 6, AA 8 AA 21 ; 7, AA 8 AA 22 . The proteolysis of melittin with pepsin gave thirteen peptide fragments: 1, AA 1 AA 3; 2, AA 4 AA 6;3, AA 1 AA 4;4, AA 1 AA 5 ;5, AA 1 AA 6 ;6, AA 1 AA 8;7, AA 7 AA 13 ;8, AA 10 AA 13 ;9, AA 14 AA 16 ;10, AA 14 AA 26 ;11, AA 15 AA 26 ;12, AA 17 AA 26 ;13, AA 20 AA 26 .

Accuracy of LA-ICPMS zircon U-Pb age determination:An inter-laboratory comparison

LA-ICPMS zircon U-Pb dating has been greatly advanced and widely applied in the past decade because it is a cheap and fast technique.The internal error of LA-ICPMS zircon U-Pb dating can be better than 1%,but reproducibility(accuracy)is relatively poor.In order to quantitatively assess the accuracy of this technique,zircons from two dioritic rocks,a Mesozoic dioritic microgranular enclave(FS06)and a Neoproterozoic diorite(WC09-32),were dated independently in eight laboratories using SIMS and LA-ICPMS.Results of three SIMS analyses on FS06 and WC09-2 are indistinguishable within error and give a best estimate of the crystallization age of 132.2 and 760.5 Ma(reproducibility is^1%,2RSD),respectively.Zircon U-Pb ages determined by LA-ICPMS in six laboratories vary from 128.3±1.0 to 135.0±0.9 Ma(2SE)for FS06 and from 742.9±3.1 to777.8±4.7 Ma(2SE)for WC09-32,suggesting a reproducibility of^4%(2RSD).Uncertainty produced during LA-ICPMS zircon U-Pb analyses comes from multiple sources,including uncertainty in the isotopic ratio measurements,uncertainty in the fractionation factor calculation using an external standard,uncertainty in the age determination as a result of common lead correction,age uncertainty of the external standards and uncertainty in the data reduction.Result of our study suggests that the uncertainty of LA-ICPMS zircon U-Pb dating is approximately 4%(2RSD).The uncertainty in age determination must be considered in order to interpret LA-ICPMS zircon U-Pb data rationally.

Influence of kaolinite and montmorillonite on benzo[a]pyrene biodegradation by Paracoccus aminovorans HPD-2 and the underlying interface interaction mechanisms

Clay minerals play an important role in biogeochemical cycling.Here,kaolinite and montmorillonite,the two most abundant and widespread clay minerals with typical layered structures,were selected to investigate and compare their effects on the biodegradation of benzo[a]pyrene(BaP)by Paracoccus aminovorans HPD-2 and to investigate the underlying interface mechanisms.Overall,the BaP degradation efficiency was significantly higher 7 d after montmorillonite addition,reaching 68.9%(P<0.05),when compared with that of the control without addition of clay minerals(CK,61.4%);however,the addition of kaolinite significantly reduced the BaP degradation efficiency to 45.8%.This suggests that kaolinite inhibits BaP degradation by inhibiting the growth of strain HPD-2,or its strong hydrophobicity and readily agglomerates in the degradation system,resulting in a decrease in the bio-accessibility of BaP to strain HPD-2.Montmorillonite may buffer some unfavorable factors,and cells may be fixed on the surface of montmorillonite colloidal particles across energy barriers.Furthermore,the adsorption of BaP on montmorillonite may be weakened after swelling,reducing the effect on the bio-accessibility of BaP,thus promoting the biodegradation of BaP by strain HPD-2.The experimental results indicate that differential bacterial growth,BaP bio-accessibility,interface interaction,and the buffering effect may explain the differential effects of the different minerals on polycyclic aromatic hydrocarbon biodegradation.These observations improve our understanding of the mechanisms by which clay minerals,organic pollutants,and degrading bacteria interact during the biodegradation process and provide a theoretical basis for increasing the biodegradation of soil pollutants by native microorganisms under field conditions.

Chemical characteristics and source apportionment of PM_(2.5) between heavily polluted days and other days in Zhengzhou, China

PM（2.5） samples were collected in Zhengzhou during 3 years of observation, and chemical characteristics and source contribution were analyzed. Approximately 96% of the daily PM（2.5） concentrations and annual average values exceeded the Chinese National Ambient Air Quality Daily and Annual Standards, indicating serious PM（2.5） pollution. The average concentration of water-soluble inorganic ions was 2.4 times higher in heavily polluted days（daily PM32.5 concentrations ＆gt; 250 μg/mand visibility ＆lt; 3 km） than that in other days, with sulfate, nitrate, and ammonium as major ions. According to the ratio of NO-3/SO2-4,stationary sources are still the dominant source of PM（2.5） and vehicle emission could not be ignored. The ratio of secondary organic carbon to organic carbon indicated that photochemical reactivity in heavily polluted days was more intense than in other days.Crustal elements were the most abundant elements, accounting for more than 60% of 23 elements. Chemical Mass Balance results indicated that the contributions of major sources（i.e., nitrate, sulfate, biomass, carbon and refractory material, coal combustion, soil dust,vehicle, and industry） of PM（2.5） were 13%, 16%, 12%, 2%, 14%, 8%, 7%, and 8% in heavily polluted days and 20%, 18%, 9%, 2%, 27%, 14%, 15%, and 9% in other days, respectively.Extensive combustion activities were the main sources of polycyclic aromatic hydrocarbons during the episode（Jan 1-9, 2015） and the total benzo[a]pyrene equivalency concentrations in heavily polluted days present significant health threat. Because of the effect of regional transport, the pollution level of PM（2.5） in the study area was aggravated.

Influence of purity of HfO_2 on reflectance of ultraviolet multilayer

The impurities in two kinds of HfO2 materials and in their corresponding single layer thin films were determined through glow discharge mass spectrum technology and secondary ion mass spectrometry （SIMS） equipment respectively. It was found that ZrO2 was the main impurity in the two kinds of HfO2 either in the original HfO2 materials or in the electron beam deposited films. In addition, the difference of Zr content in the two kinds of HfO2 single layer films was much larger than that of the other impurities such as Ti and Fe, which showed that it was just ZrO2 that made the difference between the optical performance of the film products including the two kinds of HfO2. With these two kinds of HfO2 and the same kind of SiO2, we deposited HfO2/SiO2 multilayer reflective coatings at the wavelength of 266 nm. Experimental results showed that the reflectances of these two mirrors were about 99.85% and 99.15% respectively, which agreed well with the designed results what were based on the optical constants obtained from the corresponding single layer thin films.

Effect of the Addition of High Li Concentration on the Microstructure and Mechanical Properties of Al-Mg-Si Alloys with Different Mg Contents

In the present work,the microstructural characteristics and mechanical properties of Al-1.5 Mg-0.6Si and Al-3.0 Mg-0.6Si alloy containing 3 wt%Li were investigated by optical microscopy(OM),X-ray diffraction analysis(XRD),scanning electron microscopy(SEM),time of flight-secondary ion mass spectrometry(SIMS),transmission electron microscopy(TEM),and mechanical performance testing.The addition of Li reduces the density of the base alloy by up to 8.4%.The residual second phases contain Mg and Si in the hot-rolled condition,but the Mg/Si atomic ratio decreases after quenching,which means that Li substitute some of the Mg and convert Mg_(2)Si into a(Mg,Li)_(2)Si phase during solution treatment.The results of SIMS observations confirm this.The high Mg-containing alloy has a more rapid hardening response compared to the low Mg-containing alloy.TEM observation reveals that theδ′-Al3Li+β′′-Mg_(2)Si dual phases can be observed in the high Mg-containing alloy after aging for 100 h at 170°C.The higher Mg content enhances the precipitation of theδ′phase,which results in the high Mg-containing alloy having a larger average diameter size ofδ′particles and widerδ′-precipitate-free zones(δ′-PFZs).The mechanical properties are significantly improved with the elastic modulus increasing by more than 16.5%.However,the existence of large second phases and wideδ′-PFZs in Li-containing alloys is detrimental to their ductility;as a result,their elongation is much lower than that of the base alloy.

Effect of boron addition on the microstructure and mechanical properties of K4750 nickel-based superalloy

The effect of boron addition at 0,0.007 wt.% and 0.010 wt.% on the microstructure and mechanical properties of K4750 nickel-based superalloy was studied.The microstructure of the as-cast and heat-treated alloys was analyzed by SEM,EPMA,SIMS and TEM.Lamellar M_(5) B_(3)-type borides were observed in boroncontaining as-cast alloys.After the full heat treatment,boron atoms released from the decomposition of M_(5) B_(3) borides were segregated at grain boundaries,which inhibited the growth and agglomeration of M_(23)C_(6) carbides.Therefore,the M_(23)C_(6) carbides along grain boundaries were granular in boron-containing alloys,while those were continuous in boron-free alloys.The mechanical prope rty analysis indicated that the addition of bo ron significantly improved the tensile ductility at room tempe rature and stress rupture properties at 750℃/430 MPa of K4750 alloy.The low tensile ductility at room temperature of 0 B alloy was attributed to continuous M_(23)C_(6) carbides leaded to stress concentration,which provided a favorable location for crack nucleation and propagation.The improvement of the stress rupture properties of boron-containing alloys was the result of the combination of boron segregation increased the cohesion of grain boundaries and granular M_(23)C_(6) carbides suppressed the link-up and extension of micro-cracks.

Synthesis and Electrochemical Performance of Spinel LiMn_2O_(4-x )(SO_4)_x Cathode Materials

The spinel LiMn_2O_(4-x)(SO_4)_x compound cathode materials were synthesizedby solid-state reaction of the calculated amounts of LiOH · H_2O, MnO_2 and MnSO_4. The results ofthe electrochemical test demonstrated that these materials exhibited excellent electrochemicalproperties. The highest reversible capacity of these series of cathode materials was ～120 mAh/g,and after 50 cycles, this reversible capacity was still around 116 mAh/g with nearly 100% reversibleefficiency, which revealed that doped sulfate ion could improve the structural stability of spinel.