Experimental Study of the Distribution of Au and Cu in Aqueous Vapor Phase at High Temperatures and Its Role on Ore-forming Transportation

This study focuses on experiments of Au and Cu dissolved in vapor phase in hydrothermal fluids. Experiments prove that Au and Cu can re-distribute in vapor phase and liquid phase during separation of Au- and Cu-bearing supercritical fluids to vapor and liquid phases. These experimental results can illustrate some ore geneses, where boiling phenomena of ore fluids were found. Au- and Cubearing NaHCO3-HCl solutions were heated up to more than 350℃ in the main vessel, and then passed through a phase separator in a temperature range from 250℃ to 300℃, separated into vapor and liquid phases. We collected and analyzed the liquid and vapor samples separately, and found that Au and Cu dissolved and distributed in vapor phase. In some cases, the concentrations of Au and Cu in vapor are higher than those in liquid phase. Those experiments are used to interpret field observations of fluid inclusion data of some Au and Cu deposits, and demonstrate that some Au and Cu ore deposits are derived from metals transportation in vapor phase.

Growth of β-Ga_2O_3 Films on Sapphire by Hydride Vapor Phase Epitaxy

Two-inch Ga_2O_3 films with（ˉ201）-orientation are grown on c-sapphire at 850–1050°C by hydride vapor phase epitaxy. High-resolution x-ray diffraction shows that pure β-Ga_2O_3 with a smooth surface has a higher crystal quality, and the Raman spectra reveal a very small residual strain in β-Ga_2O_3 grown by hydride vapor phase epitaxy compared with bulk single crystal. The optical transmittance is higher than 80% in the visible and near-UV regions, and the optical bandgap energy is calculated to be 4.9 e V.

The fabrication of AlN by hydride vapor phase epitaxy

Aluminum nitride(AlN)is the promising substrates material for the epitaxial growth ofⅢ-nitrides devices,such as high-power,high-frequency electronic,deep ultraviolet optoelectronics and acoustic devices.However,it is rather difficult to obtain the high quality and crack-free thick AlN wafers because of the low surface migration of Al adatoms and the large thermal and lattice mismatches between the foreign substrates and AlN.In this work,the fabrication of AlN material by hydride vapor phase epitaxy(HVPE)was summarized and discussed.At last,the outlook of the production of AlN by HVPE was prospected.

Influence comparison of N2 and NH3 nitrogen sources on AlN films grown by halide vapor phase epitaxy

A comparison of the nitrogen sources(N2 and NH3)influence on AlN films grown by high-temperature halide vapor phase epitaxy(HVPE)is reported.The x-ray rocking curves(XRCs)indicate that the full width at half maximum(FWHM)of(0002)plane for AlN films using N2 as nitrogen source is generally smaller than that using NH3.Optical microscope and atomic force microscope(AFM)results show that it is presently still more difficult to control the crack and surface morphology of AlN films with thicknesses of 5-10µm using N2 as the nitrogen source compared to that using NH3.Compared with one-step growth,two-step growth strategy has been proved more effective in stress control and reducing the density of threading dislocations for AlN epilayers using N2 as the nitrogen source.These investigations reveal that using N2 as nitrogen source in HVPE growth of AlN is immature at present,but exhibits great potential.

Optical properties of ZnO and Mn-doped ZnO nanocrystals by vapor phase transport processes

In this paper we investigated the optical properties of ZnO and Mn doped ZnO nanocrystals that were fabricated by a vapor phase transport growth process, using zinc acetate dihydrate with or without Mn in a constant O2/Ar mixture gas flowing through the furnace at 400600℃, respectively. The as grown ZnO nanocrystals are homogeneous with a mean size of 19 nm observed by scanning electron microscope（SEM）. The optical characteristics were analyzed by absorption spectra and photoluminescence（PL） spectra at room-temperature. For ZnO nanocrystals, a strong and predominant UV emission peaked at 377 nm was found in the PL spectra. For Mn doped ZnO nanocrystals, in addition to the strong UV emission, a strong blue emission peaked at 435 nm was observed as well. By doping Mn ions, the major UV emission shifts from 377 nm to 408 nm, showing that Mn ions were not only incorporated into ZnO Ncs, but also introduced an impurity level in the bandgap. Moreover, with the concentration of Mn increasing, the relative intensities of the two emissions change largely, and the photoluminescence mechanism of them is discussed.

Porous AlN films grown on C-face SiC by hydride vapor phase epitaxy

We report the growth of porous AlN films on C-face SiC substrates by hydride vapor phase epitaxy(HⅤPE).The influences of growth condition on surface morphology,residual strain and crystalline quality of Al N films have been investigated.With the increase of theⅤ/Ⅲratio,the growth mode of Al N grown on C-face 6H-SiC substrates changes from step-flow to pit-hole morphology.Atomic force microscopy(AFM),scanning electron microscopy(SEM)and Raman analysis show that cracks appear due to tensile stress in the films with the lowestⅤ/Ⅲratio and the highestⅤ/Ⅲratio with a thickness of about 3μm.In contrast,under the mediumⅤ/Ⅲratio growth condition,the porous film can be obtained.Even when the thickness of the porous Al N film is further increased to 8μm,the film remains porous and crack-free,and the crystal quality is improved.

Evolution of microstructure, stress and dislocation of AlN thick film on nanopatterned sapphire substrates by hydride vapor phase epitaxy

A crack-free AlN film with 4.5 μm thickness was grown on a 2-inch hole-type nano-patterned sapphire substrates(NPSSs) by hydride vapor phase epitaxy(HVPE). The coalescence, stress evolution, and dislocation annihilation mechanisms in the AlN layer have been investigated. The large voids located on the pattern region were caused by the undesirable parasitic crystallites grown on the sidewalls of the nano-pattern in the early growth stage. The coalescence of the c-plane AlN was hindered by these three-fold crystallites and the special triangle void appeared. The cross-sectional Raman line scan was used to characterize the change of stress with film thickness, which corresponds to the characteristics of different growth stages of AlN. Threading dislocations(TDs) mainly originate from the boundary between misaligned crystallites and the c-plane AlN and the coalescence of two adjacent c-plane AlN crystals, rather than the interface between sapphire and AlN.

Growth of a-Plane GaN Films on r-Plane Sapphire by Combining Metal Organic Vapor Phase Epitaxy with the Hydride Vapor Phase Epitaxy

Hydride vapor phase epitaxy （HVPE） is utilized to grow nonpolar a-plane GaN layers on r-plane sapphire templates prepared by metal organic vapor phase epitaxy （MOVPE）. The surface morphology and microstructures of the samples are characterized by atomic force microscopy. The full width at half maximum （FWHM） of the HVPE sample shows a W-shape and that of the MOVPE sample shows an M-shape plane with the degree of 0 in the high-resolution x-ray diffraction （HRXRD） results. The surface morphology attributes to this significant anisotropic. HRXRD reveals that there is a significant reduction in the FWHM, both on-axis and off-axis for HVPE GaN are compared with the MOVPE template. The decrease of the FWHM of E2 （high） Raman scat tering spectra further indicates the improvement of crystal quality after HVPE. By comparing the results of secondary- ion-mass spectroscope and photoluminescence spectrum of the samples grown by HVPE and MOVPE, we propose that C-involved defects are originally responsible for the yellow luminescence.

Optical and Electrical Properties of Polyimide Thin Films Doped-Cu-phthalocyanine Polymerized by Vapor Phase Deposition

Using Cu-phthalocyanine（CuPc）,4,4’-diaminodiphenyl ether and pyromellitic dianhydride as monomer materials, polyimide（PI） thin films doped-CuPc have been prepared onto glass substrate by vapor phase co-deposition polymerization under a vacuum of 2×10-3Pa and thermal curing of polyamic acid film in at temperature of 150-200℃ for 60min. In this process, the polymerization can be carried out through controlling the stoichiometric ratio, heating time and deposition rates of the three monomers. IR spectrum identifies the designed chemical structure of the polymer. The absorption of polyimide doped-CuPc is very intense in vis-range and near-infrared by UV-Vis spectrum. And, the PI films doped-CuPc polymerized by vapor phase deposition have uniformity, fine thermal stability and good nonlinear optical properties, and the third-order optical nonlinear susceptibility χ（3） with degenerate four-wave mixing can be 1.984×10-9ESU.

Microscale Infrared Observation of Liquid-Vapor Phase Change Process on the Surface of Porous Media for Loop Heat Pipe

Loop Heat Pipe (LHP) performance strongly depends on the performance of a wick that is porous media inserted in an evaporator. In this paper, the visualization results of thermo-fluid behavior on the surface of the wick with microscopic infrared thermography were reported. In this study, 2 different samples that simulated a part of wick in the evaporator were used. The wicks were made by different two materials: polytetrafluoroethylene (PTFE) and stainless steel (SUS). The pore radii of PTFE wick and SUS wick are 1.2 μm and 22.5 μm. The difference of thermo-fluid behavior that was caused by the difference of material was investigated. These two materials include 4 different properties: pore radius, thermal conductivity, permeability and porosity. In order to investigate the effect of the thermal conductivity on wick’s operating mode, the phase diagram on the q-keff plane was made. Based on the temperature line profiles, two operating modes: mode of heat conduction and mode of convection were observed. The effective thermal conductivity of the porous media has strong effect on the operating modes. In addition, the difference of heat leak through the wick that was caused by the difference of the material was discussed.

Application of halide vapor phase epitaxy for the growth of ultrawide band gap Ga_2O_3

Halide vapor phase epitaxy(HVPE) is widely used in the semiconductor industry for the growth of Si, GaAs, GaN, etc.HVPE is a non-organic chemical vapor deposition(CVD) technique, characterized by high quality growth of epitaxial layers with fast growth rate, which is versatile for the fabrication of both substrates and devices with wide applications. In this paper, we review the usage of HVPE for the growth and device applications of Ga_2O_3, with detailed discussions on a variety of technological aspects of HVPE. It is concluded that HVPE is a promising candidate for the epitaxy of large-area Ga_2O_3 substrates and for the fabrication of high power β-Ga_2O_3 devices.

Hydride vapor phase epitaxy for gallium nitride substrate

Due to the remarkable growth rate compared to another growth methods for gallium nitride(GaN)growth,hydride vapor phase epitaxy(HVPE)is now the only method for mass product GaN substrates.In this review,commercial HVPE systems and the GaN crystals grown by them are demonstrated.This article also illustrates some innovative attempts to develop homebuilt HVPE systems.Finally,the prospects for the further development of HVPE for GaN crystal growth in the future are also discussed.

Growth and doping of bulk GaN by hydride vapor phase epitaxy

Doping is essential in the growth of bulk GaN substrates,which could help control the electrical properties to meet the requirements of various types of GaN-based devices.The progresses in the growth of undoped,Si-doped,Ge-doped,Fedoped,and highly pure GaN by hydride vapor phase epitaxy(HVPE) are reviewed in this article.The growth technology and precursors of each type of doping are introduced.Besides,the influence of doping on the optical and electrical properties of GaN are presented in detail.Furthermore,the problems caused by doping,as well as the methods to solve them are also discussed.At last,highly pure GaN is briefly introduced,which points out a new way to realize high-purity semi-insulating(HPSI) GaN.

Vapor Phase Polymerization Deposition Conducting Polymer Nanocomposites on Porous Dielectric Surface as High Performance Electrode Materials

We report chemical vapor phase polymerization(VPP) deposition of poly(3,4-ethylenedioxythiophene)(PEDOT) and PEDOT/graphene on porous dielectric tantalum pentoxide(Ta_2O_5) surface as cathode films for solid tantalum electrolyte capacitors. The modified oxidant/oxidant-graphene films were first deposited on Ta_2O_5 by dip-coating, and VPP process was subsequently utilized to transfer oxidant/oxidant-graphene into PEDOT/PEDOT-graphene films. The SEM images showed PEDOT/PEDOT-graphene films was successfully constructed on porous Ta_2O_5 surface through VPP deposition, and a solid tantalum electrolyte capacitor with conducting polymer-graphene nano-composites as cathode films was constructed. The high conductivity nature of PEDOT-graphene leads to resistance decrease of cathode films and lower contact resistance between PEDOT/graphene and carbon paste. This nano-composite cathode films based capacitor showed ultralow equivalent series resistance(ESR) ca. 12 m? and exhibited excellent capacitance-frequency performance, which can keep 82% of initial capacitance at 500 KHz. The investigation on leakage current revealed that the device encapsulation process has no influence on capacitor leakage current, indicating the excellent mechanical strength of PEDOT/PEDOT-gaphene films. This high conductivity and mechanical strength of graphene-based polymer films shows promising future for electrode materials such as capacitors, organic solar cells and electrochemical energy storage devices.

VAPOR PHASE PHOTOGRAFTING OF ACRYLIC ACID ON PE FIBERS

The surface of high strength and high modulus polyethylene (PE) fiber has been modified bygrafting with acrylic acid.Benzophenone and acrylic acid in vapor phase were UV-irradiated in thepresence of the PE tiber substrate.Grafting with acrylic acid took place in a thin layer on the sur-face,thus increasing the surface adhesion of PE fiber with epoxy resin.This paper dealt withphoto-polymerization reactions including the role of photoinitiator.The degree of graft increasedwith the enhancing of reaction time,reaction temperature and concentration of initiator.Acetonewas used as carriers of monomer and tiator and able to initiate and promote grafting to the sur-face.ATR-IR and SEM measurements on the grafted surface showed that some polar groups wereintroduced to the surface of PE fibers.Oligomer which existed during the polymerization could beremoved by washing with benzene.

Response time improvement of AlGaN photoconductive detectors by adjusting crystal-nuclei coalescence process in metal organic vapor phase epitaxy

AlGaN photoconductive ultraviolet detectors are fabricated to study their time response characteristics. Persistent photoconductivity, a deterring factor for the detector response time, is found to be strongly related to the grain boundary density in AlGaN epilayers. By improving the crystal-nuclei coalescence process in metal organic vapor phase epitaxy, the grain-boundary density can be reduced, resulting in an-order-of-magnitude decrease in response time.

NaA Zeolite Membrane with High Performance Synthesized by Vapor Phase Transformation Method

NaA zeolite membrane was synthesized with high permeance on porous alumina substrate by the vapor phase transformation method. The membranes were characterized by XRD and SEM techniques. The XRD results showed that the membranes after the synthesis time of 24 h consisted of the pure NaA zeolite crystals. The SEM results showed that the membranes after the synthesis time of 48 h consisted of intergrown zeolite crystals. The H_2 permeance of the NaA zeolite membranes was higher than 2.0×10 -6 mol/(Pa·m 2·s),and the maximum of the gas H_2/C_3H_8 permselectivity was 7.15,which is higher than the corresponding Knudsen diffusion selectivity of which is 4.69.

Halide vapor phase epitaxy of monolayer molybdenum diselenide single crystals

Single-crystalline transition metal dichalcogenides(TMD)films are of potential application in future electronics and optoelectronics.In this work,a halide vapor phase epitaxy(HVPE)strategy was proposed and demonstrated for the epitaxy of molybdenum diselenide(MoSe_(2))single crystals,in which metal halide vapors were in-situ produced by the chlorination of molybdenum as sources for the TMD growth.Combined with the epitaxial sapphire substrate,unidirectional domain alignment was successfully achieved and monolayer single-crystal MoSe_(2) films have been demonstrated on a 2-inch wafer for the first time.A series of characterizations ranging from centimeter to nanometer scales have been implemented to demonstrate the high quality and uniformity of the MoSe_(2).This work provides a universal strategy for the growth of TMD single-crystal films.

Mesoporous silicon sulfonic acid as a highly efficient and stable catalyst for the selective hydroamination of cyclohexene with cyclohexylamine to dicyclohexylamine in the vapor phase

In this work,a new mesoporous silicon sulfonic acid catalyst derived from silicic acid has been successfully prepared by the chemical bonding method.The physicochemical properties of mesoporous silicon sulfonic acid catalysts have been systematically characterized using various techniques.The results demonstrate that sulfonic acid groups have been grafted on silicic acid by forming a new chemical bond(Si-O-S).The mesoporous silicon sulfonic acid exhibits excellent catalytic performance and stability in the vapor phase hydroamination reaction of cyclohexene with cyclohexylamine.Cyclohexene conversion of 61% and 97% selectivity to dicyclohexylamine was maintained after running the reaction for over 350 h at 280℃.The developed mesoporous silicon sulfonic acid catalyst shows advantages of low cost,superior acid site accessibility,and long term reactivity stability.Moreover,a possible catalytic hydroamination reaction mechanism over silicon sulfonic acid was suggested.It has been demonstrated that the sulfonic acid groups of the catalyst play an important role in the hydroamination.The present work provides a simple,efficient,and environmentally friendly method for the hydroamination of cyclohexene to valuable dicyclohexylamine,which also shows important industrial application prospects.