Thermal Chemical Vapor Deposition Method Research Articles

Synthesis of Graphite on SiC Particles by Using the Thermal-Chemical Vapor-Deposition Method with and It?�s Dependence on Temperature and Time

Synthesis of Graphite on SiC Particles by Using the Thermal-Chemical Vapor-Deposition Method with and It?�s Dependence on Temperature and Time

Indium phosphide nanowires: Synthesis and integration into a gas sensing device

Abstract Indium phosphide nanowires (InPNWs) with an average diameter of 87 nm were successfully synthesised through thermal chemical vapour deposition (CVD) method. The smooth surface nanowires showed a relatively narrow size distribution of 70–105 nm. Temperature programmed desorption (TPD) was used to study the thermodynamic behaviour of gas desorption. The study revealed that gaseous CO and CH4 molecules bind to InPNW surface through chemical and physical adsorption, respectively. The Redhead method was used to estimate the enthalpy energy of desorption for CO and CH4 to be 142 kJ/mol and 38 kJ/mol. The sorption temperature ranges were found to be 220–260 C for CO and -50 to -20 C for CH4. InPNWs were used to fabricate a gas sensor electronic device and were tested for performance. The device showed a quick response time of 29.19 s for CO at 250 C, thus relatively faster than that of H2 and NO2.

One-step in-situ fabrication of carbon nanotube/stainless steel mesh membrane with excellent anti-fouling properties for effective gravity-driven filtration of oil-in-water emulsions

The occurrence of membrane fouling has resulted in limited wastewater treatment applications. The development of superhydrophilic-underwater superoleophobic materials has received significant attention owing to their good anti-fouling properties. However, to fabricate such materials need costly regents and tedious steps. Thus, developing a one-step process to prepare a low-cost material for oil/water separation is still desired. In this study, bio-inspired from an arachnid, inorganic carbon nanotube stainless steel meshes (CNT@SSMs) having superhydrophilic-underwater superoleophobic and excellent anti-fouling properties and a unique fiber structure were fabricated via a one-step thermal chemical vapor deposition method. The CNT@SSMs had a small pore size enabling a high water flux of 10,639 L m−2h−1 and the separation of oily wastewater, including various emulsions, at a high rejection ratio of >98.89%. As a result of its excellent chemical stability under high temperatures, a broad pH range, and saline environments, the CNT@SSM has the potential to be used in extreme conditions. In summary, these CNT@SSMs are easy to fabricate and are low-cost as a result of inexpensive reagents involved. Moreover, these novel superwetting membranes are promising candidates for treatment of hazardous oily wastewater.

Synthesis of nanostructured calcite thin film by additive-free carbonation reaction via thermal chemical vapor deposition method

There is new development in nanostructured calcite research offering high potential sensitive application due to its non-toxic inorganic metal properties. Previous research revolves around calcium carbonate in powder form and mainly used as fillers in industry. However, nanostructured calcite thin film synthesis is lacking reports despite its potential. This work offers novel information on the synthesis of calcite thin film by additive-free thermal chemical vapor deposition method. It discussed the effect of deposition temperature to the chemical reaction and composition of the produced nanostructured thin film. Nanostructured calcite thin film deposited at 400 °C has shown single crystalline phase at 29° with calculated crystallite size of 27.8 nm. This work proposes basic substantial parameters that enable future study on CaCO3 thin film for wider applications such as biosensor and photocatalyst.

Manoeuvring Morphological, Optical and Electrical Properties of CVD-Grown Ba-Doped SnO2 Nanostructures via Mn Co-Doping

Barium and manganese (Ba and Mn) co-doped nanostructures of tin oxide (SnO2) are synthesized in situ using a thermal chemical vapour deposition method. The structural property correlation is established using X-ray diffraction, field emission scanning electron microscopy, high-resolution transmission electron microscopy, ultraviolet–visible light (UV–Vis), X-ray photoelectron spectroscopy and Hall measurements. The role of substrate type (n-type silicon and quartz) and catalyst layer thickness is also studied for detailed examination of the correlation with SnO2 properties at nanoscale. In this study, the significant role of Mn as co-dopant in Ba-doped SnO2 one-dimensional and two-dimensional nanostructures (nanowires and nanoflakes) is studied. Optical and room-temperature (RT) electrical measurements confirm the band gap tailoring from 3.2 eV to 3.6 eV relating to the Ba increase with Mn as co-dopant. Subsequently, the RT electron mobility changes from 46 cm2 s−1 V−1 to 88 cm2 s−1 V−1 as SnO2 changes from Ba-doped to Ba/Mn co-doped. The effective role of the co-dopant in band gap tailoring and the effects on morphology, optical and electrical properties are studied for SnO2 nanostructures. This study helps to gain a better understanding of the dopant population and the electrical and optical properties for transparent conducting oxides (TCOs), sensors, photocatalysis, solar cell materials and other applications.

Synthesis and plasma surface functionalization of carbon nanotubes for using in advanced epoxy-based nanocomposites

In this study, thermal chemical vapor deposition (CVD) method was utilized to fabricate carbon nanotubes (CNTs) using an Fe/Al catalyst. Plasma enhanced CVD (PECVD) was applied to coat CNTs surfaces with a hydrophobic poly(hexafluorobutyl acrylate) (PHFBA) thin film. Then pure CNT and surface-modified CNT (f-CNT) were used as nanofillers at 0.5–3 wt% in bisphenol-A (DGEBA) and phenolic novolac types epoxy (EPN) resins to produce composite materials with superior properties. For characterization of both types of CNTs, FTIR, XRD, SEM, TEM and TGA analyses were performed. The morphologies of composites were examined via XRD and SEM. Thermal properties of composites were revealed by TGA. The influences of CNT surface functionalization and matrix type on the thermal, mechanical, electrical conductivity and surface wettability properties of composites were investigated. EPN based composites exhibited higher mechanical properties than that DGEBA based ones. At 1.5 wt% f-CNTs, the Young's modulus and tensile strength of the nanocomposites were found 6.9 ± 0.50 GPa and 141.0 ± 7.8 MPa, respectively using DGEBA matrix; 8.7 ± 0.59 GPa and 153.4 ± 7.9 MPa respectively, using EPN matrix. Composites electrical conductivity increased with increasing both type CNTs amount and reached a maximum value of 10−4 S/m and 10−6 S/m at 3 wt% of neat and f-CNTs contents.

Effects of Experimental Configuration on the Morphology of Two-Dimensional ZnO Nanostructures Synthesized by Thermal Chemical-Vapor Deposition

Using two experimental configurations, self-assembled zinc oxide (ZnO) nanostructures including nanoplates, nanosaws, and nanobelts were synthesized by thermal chemical-vapor deposition (CVD), and their morphological properties were investigated. ZnO nanostructures grown on Au-coated Si substrates in a parallel setup revealed highly defined ZnO nanoplates and branched nanowires. ZnO nanostructures grown in a perpendicular setup using Si substrates with and without the Au catalyst exhibited vertically oriented ZnO nanosaws and randomly aligned nanobelts, respectively. In the thermal CVD method, experiment conditions such as oxygen-flow rate, growth temperature, and catalyst, and experimental configurations (i.e., parallel and perpendicular setups) were important parameters to control the morphologies of two-dimensional ZnO nanostructures showing platelike, sawlike, and beltlike shapes.

Synthesis of organic functional thin films and their application tests of graphene based FET

This study investigated on the effects of gate dielectrics for field effect transistors (FETs). The gate dielectrics with organic and inorganic layers were deposited on Si (100) substrates using cyclohexane and tetraethyl orthosilicate (TEOS) by plasma enhanced chemical vapor deposition (PECVD) method. After the Si (100) substrates were dry-cleaned by in situ Ar plasma bombardment with 60 W for 15 min., the gate dielectric plasma polymer thin films deposited under plasma power between 20 W and 60 W with different precursor flow ratio. Also, the active graphene layer was grown on a Ni substrate using CH4 by low-pressure thermal chemical vapor deposition (CVD) method, and the Ni substrate was then etched away. In order to fabricate a back-gate graphene-based FET, the graphene layer was adsorbed onto the plasma-polymer gate dielectric film, then 80 nm thick Au electrodes were finally evaporated onto the graphene using a mask with a gap of 370 nm, and a probe-station system was utilized to characterize the devices. As the plasma power and flow rate of TEOS increases, the gate voltage moves at a positive voltage, indicting p-doping by high fragmented Si and O elements under high plasma power and TEOS flow rate.

Vacancy-Assisted Selective Detection of Low-ppb Formaldehyde in Two-Dimensional Layered SnS2

A two-dimensional (2D) layered SnS2 film synthesized by the thermal-chemical vapor deposition method is utilized for detecting formaldehyde (HCHO), which causes a sick building syndrome. A back-gated field-effect transistor (FET)-based SnS2 sensor successfully detects HCHO with concentrations down to 1 ppb in a nitrogen atmosphere. Sensing measurements performed under dry air conditions also exhibit a clear response to 20 ppb of HCHO, which is more sensitive than the previously reported sensors based on other 2D-layered materials. Moreover, it is found that the sensor possesses a high selectivity for HCHO over other organic species. Theoretical calculations suggest that native sulfur vacancies existing in n-type SnS2 crystals play an important role in HCHO detection. Actually, oxygen atoms that are unexpectedly detached from HCHO molecules are found to fill the vacancies, giving rise to p-type doping in SnS2. As a result, decrease in the drain current of SnS2-FET can be found as a signal of HCHO detection. Furthermore, considering the future mass-production of sensors, we demonstrate large-scale growth of the SnS2 film by means of magnetron-sputtering deposition and subsequent annealing in a diluted hydrogen sulfide atmosphere. The sputtered film is also found to exhibit a good sensing ability to HCHO.

Study on the characteristics of nitrogen-doped activated carbon fibers to remove nitrate ions by multi-factor analysis

A type of rayon-based commercial activated carbon fibers (ACFs), named as KF1500, was modified by thermal chemical vapor deposition (CVD) method to remove nitrate in aqueous solution. Acetonitrile (vapor) was introduced to dope positive charge nitrogen species on it. The sample was ded as KF-8ST10-8AN20-9.5HT30-8ST30 (8ST10; steam activation at 800 °C with 10 mL water, 8AN20; thermal CVD treatment at 800 °C charging 20 mL acetonitrile, 9.5HT30; annealing at 950 °C for 30 min, 8ST30; steam activation at 800 °C with 30 mL water), obtaining great nitrate adsorption capacity of 0.74 mmol/g in 200 mg/L nitrate solution at pH 3.0. For deeply exploring the adsorption characteristics of this well-modified ACFs, in this study, the pH of point of zero charge (pHpzc) for KF8ST10-8AN20-9.5HT30-8ST30 as well as KF1500 has been explored to further understand the surface charge properties. The results indicated that pHpzc was 7.2 for KF1500 and that for modified ACFs KF-8ST10-8AN20-9.5HT30-8ST30 was about pHpzc 7.0. Effect of solution pH at various initial solution concentrations was also studied, and adsorption isotherms were well fitted by Langmuir model at pH 1.5–8, and adsorption capacity obtained from the fitting was 0.67 mmol/g (R2 = 0.993). In addition, the effect of temperature (15–35 °C) on nitrate adsorption was also tested. Moreover, desorption of nitrate hydrochloric acid solution proceeded for 3 h at pH 3. With the above results, the working condition of quaternary nitrogen (N–Q) and carbon π bond was investigated, and the contribution to nitrate adsorption by N–Q was also defined more clearly which was 22% at least.

Hydrogen-dominated metal-free growth of graphitic-nitrogen doped graphene with n-type transport behaviors

Controllable nitrogen doping, an effective way to regulate the electronic property of graphene, has been achieved on metal catalyst which needs to be removed by additional processes when fabricating electronic devices, giving rise to structural damages and contaminations. Here, by using pyridine as the sole source of carbon and nitrogen, a metal-free thermal chemical vapor deposition method is demonstrated to synthesize nitrogen-doped graphene (NG) on dielectrics (SiO2/Si, quartz, rock crystal, and sapphire). It is discovered that increasing H2 flow could promote the quality of graphene and the proportion of graphitic-N. At an optimal growth temperature of 1000 °C, we realize the controllable synthesis of graphitic-N doped graphene. Impressively, field-effect transistors directly fabricated from the N-doped graphene (∼1.1%) films on SiO2/Si exhibit strong n-type semiconducting behaviors with electron mobilities of 110–283 cm2 V−1 s−1 in air, rivaling heavily doped NG grown on metals. As revealed by density functional theory calculations, compared with NG with multiple types of nitrogen atoms, single graphitic-N doping leads to more prominent n-type transport behaviors, owing to the absence of p-type pyrrolic-N and pyridinic-N.

Chemical vapor deposition synthesis of carbon spheres: Effects of temperature and hydrogen

Carbon spheres (CS) of relatively uniform size, ranging from 200 to 350 nm, were synthesized using the non-catalytic thermal Chemical Vapor Deposition (CVD) method. The effect of temperature (650 °C–1050 °C) along with hydrogen (H2) and argon (Ar) in acetylene (C2H2) on the carbon spheres were studied using Scanning Electron Microscopy (SEM) and Raman spectroscopy. Morphological studies show that relatively uniform carbon spheres can be synthesized by pyrolysis of acetylene under H2 and Ar at temperatures above 950 °C in an atmospheric pressure CVD. The broad peaks in the XRD spectrum and ID/IG ratio of 0.85 obtained from Raman Spectroscopy reveals that the carbon spheres synthesized are amorphous in nature. The morphological studies using SEM on different concentrations of Ar and H2 during the synthesis indicate that the concentration of carrier gases profoundly affects the morphology. The presence of Ar gives smooth carbon spheres and H2 contributes to the relative uniformity of the carbon spheres synthesized. A detailed study was carried out to analyze the influence of the concentration of H2 using SEM, Raman spectroscopy and FTIR. The effect of low concentration of H2 along with Ar and acetylene reduces the defects and the graphitization degree obtained was 0.85. The present study also infers that high concentrations of H2 deteriorates the morphology of carbon spheres due to the excess of C–H functional group formation.

Highly luminescent Alq3: Zn nanowires

The present paper deals with the synthesis and characterization of Alq3 and Zn doped Alq3 (Alq3: Zn) nanowires. Zn has been incorporated in Alq3 matrix using ultrasonic assisted incorporation using ZnCl2. Nanowires of Alq3 and Alq3: Zn are synthesized using Thermal Vapor Transport or Chemical Vapor Deposition (CVD) method. The morphological, structural and optical characteristics of these nanowires are studied using Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), Energy Dispersive X-ray Spectroscopy (EDAX), Fourier Transform Infrared (FTIR) Spectroscopy, UV-Visible Spectroscopy and Fluorescence Spectroscopy. These studies confirm the formation of fine and crystalline nanowires with the drastic enhancement in PL intensity on Zn incorporation. The PL intensity has been observed to increase with Zn concentration. The highest PL has been observed for Alq3: Zn nanowires having concentration ratio of Alq3: Zn = 1:0.9.

Effect of Synthesis Temperature on the Growth of Carbon-based Materials from Waste Engine Oil Precursor

Different stuctures of carbon material were succesfully synthesized from waste engine oil (WEO) as carbon source using double-stage thermal chemical vapor deposition method. In this work, 5.33 wt% ferrocene was used as catalyst, precursor temperature at 450°C and the synthesis temperatures were varied from 600-1000°C with 100°C increament. The prepared samples were characterized using field emission scanning electron microscopy and micro-Raman spectroscopy. Below 700°C, amorphous structure of carbon was formed. Well growth carbon spheres were produced at 800°C while at 900°C, bigger diameter and lower crystallinity of carbon spheres were resulted. At very high temperature, 1000°C, a highly defective structure of carbon was produced. These results show that the structure of carbon materials from WEO precursor was highly affected by synthesis temperature changes

Surface modified mechanism of activated carbon fibers by thermal chemical vapor deposition and nitrate adsorption characteristics in aqueous solution

In this study, commercial activated carbon fibers (ACFs) KF1500 was modified by thermal chemical vapor deposition (CVD) method using acetonitrile and steam to adsorb nitrate ions in aqueous solution. Physical properties and surface chemical characteristics of each modified ACF were examined to reveal the surface modification mechanism of modified ACFs. Adsorption kinetics and influence of solution pH were also examined to investigate the adsorption properties. The sample of KF-8ST10-8AN20-9.5HT30-8ST30 showed maximal nitrate adsorption capacity of 0.74 mmol/g at solution pH 3, and surface area was calculated to be 1358 m2/g and 1483 m2/g by Brunauer-Emmett-Teller (BET) method and subtracting pore effect (SPE) method using αs plots, respectively. By means of modification, the quaternary N (or graphitic N) (N–Q) configuration, which is a strong site to adsorb nitrate ion, represented nearly 5 times greater value than that of KF1500. The N–Q configuration reached up to 1.86% in total elemental composition from 0.4% of KF1500. The adsorptive kinetic data of KF-8ST10-8AN20-9.5HT30-8ST30 ACFs were highly well described with pseudo-second-order (R2 = 0.998) model. The adsorption capacity of nitrate decreased rapidly with the increase of the alkalinity in nitrate solution, which indicated that hydroxyl groups rather than nitrate ions in the aqueous solution were more attractive and competitive to the N-Q and other adsorptive sites on the surface of ACFs.

Turn-Number-Dependent Motion Behavior of Catalytic Helical Carbon Micro/Nanomotors.

Helical micro/nanomotors (MNMs) can be propelled by external fields to swim through highly viscous fluids like complex biological environments, which promises miniaturized robotic tools to perform assigned tasks at small scales. However, the catalytic propulsion method, most widely adopted to drive MNMs, is seldom studied to actuate helical MNMs. Herein, we report catalytic helical carbon MNMs (CHCM) by sputtering Pt onto helical carbon nano-coils (HCNC) that are in bulk prepared by a thermal chemical vapor deposition method. The Pt-triggered H2 O2 decomposition can drive the MNMs by an electrokinetic mechanism. The MNMs demonstrate versatile motion behaviors including both directional propulsion and rotation depending on the turn number of the carbon helix. Besides, due to the ease of surface functionalization on carbon and other properties such as biocompatibility and photothermal effect, the helical carbon MNMs promise multifunctional applications for biomedical or environmental applications.

A Study of the Wettability of Single-Walled Carbon Nanotube Films on Flat and Textured Si Substrates.

Contact angle measurements are investigated on the surface of single-walled carbon nanotube (SWNT) films directly formed on flat and textured Si substrates using a thermal chemical vapor deposition method. The SWNT films on the textured Si consist of a multiscale structure composed of nanoscale SWNTs and a microscale textured Si. They show superhydrophobic properties in which the water contact angle was around 161°. A direct surface treatment to them increase the contact angle to 174°. The reversible wettability of the SWNT films formed on the textured Si substrates is confirmed through the oxidation process using an acid mixture of nitric and sulfuric acids and a successive reduction procedure via heating treatment in an NH₃ environment.

Fabrication of doxorubicin-loaded monodisperse spherical micro-mesoporous silicon particles for enhanced inhibition of cancer cell proliferation

Spherical micro-mesoporous silicon (mSi) particles were fabricated by thermal decomposition of monosilane (SiH4) within the mesopores of monodisperse silica particles (MSP) and subsequent etching out of the template material. The thermal destruction of SiH4 occurs within the whole pore volume uniformly because in the thermal chemical vapor deposition method we developed, the limiting stage of the process in which MSP pores are filled with silicon is the reaction in which monosilane is decomposed, rather than its diffusion within template mesopores. The porosity of the mSi particles synthesized can be varied without changes in the shape and outer diameter of the particles by varying the parameters of the technological process of silane decomposition. The particles have large Brunauer-Emmett-Teller specific surface area (250–350 m2 g−1) and pore volume (0.3–0.5 cm3 g−1). For the first time the obtained submicron spherical porous silicon particles are monodisperse with a size scatter not exceeding 10%, which provides the identity of their hydrodynamic and adsorption properties so important for biomedical applications. We introduced the cytostatic drug doxorubicin (DOX) into mSi pores by the physical adsorption method. It was shown that DOX is desorbed from the mSi pores and penetrates into K-562 cancer cells, with local DOX concentration maxima observed in the intracellular space. The cytotoxicity of the mSi and mSi/DOX particles was studied, and the inhibition capacities of the cancer-cell proliferation by doxorubicin adsorbed by mSi particles and a DOX solution were compared in vitro. It was shown that the half-maximal inhibitory concentration (IC50) is four times lower under the action of DOX-loaded mSi particles as compared with free doxorubicin.

Synthesis of CNTs on stainless steel microfibrous composite by CVD: Effect of synthesis condition on carbon nanotube growth and structure

CNT-microfibrous (CNT-MF) composites are synthesized by thermal chemical vapor deposition (CVD) method. The effects of deposition temperature, deposition time, gas flow rate and acid pretreatment on the structure of CNT-MF are investigated. Results show that with increase of temperature, the yield of CNT is increased due to the increasing CNT growth rate and the evolution of surface roughness of the composite. The quality of the CNT is increased first and then decreased. With increase of gas flow rate, the yield of CNT is increased first and then decreased due to the increase of carbon diffusion rate and decrease of contact time between carbon precursor and catalysts. The CNT crystalline perfection is improved. With increase of deposition time, the yield and quality of CNT is increased and the CNT growth form changes as deposition time increases. Acid pretreatment can change the surface structure of the support. 1 mol/L HCl pretreatment forms uniform small particles so the yield of CNT is increased, but the quality of CNT is decreased. When the acid concentration is increase to 2 mol/L, the mechanical strength of the substrate is destroyed badly and flaky grains are formed, causing the decrease of the CNT yield and quality.

Improving the electrochemical properties of SiO@C anode for high-energy lithium ion battery by adding graphite through fluidization thermal chemical vapor deposition method

A series SiO/graphite@C (SGC) composites electrode are successfully prepared by a fluidization thermal chemical vapor deposition (FTCVD) route in a kilogram-scale fluidized bed CVD equipment. This strategy can avoid the effect of particle agglomeration on carbon coating during heating reaction. The phase composition, element distribution, particle appearance and electrochemical properties of the as-obtained SGC composite is investigated in detail. The charge specific capacity of SGC-37 is close to 799.1 mAh g−1 after 100 cycles at 200 mA g−1. The SGC-37 shows a high capacity retention of 93.7% after 100 cycles, which much higher than that of SiO, SiO@C, SGC-73 and SGC-55 (the retention rates are 26.3%, 56.8%, 75.5% and 89.6%, respectively). The reason is mainly because improve Li ion diffusion coefficient, shorten transfer pathway of Li ion and ease to the volume change of SiO due to surface carbon coating and graphite addition. The FTCVD methods is not only an efficient method to prepared SGC anode, but also is may easy to apply to surface carbon coating of another particle material.