DIAMOND FILMS DEPOSITED AT LOW TEMPERATURES MICROWAVE PLASMA-ASSISTED CVD METHOD

Low-temperature deposition of diamond thin films in the range of 280￣445℃ has been successfully carried out by microwave plasma-assisted CVD method.At lower deposition temperatures (280￣445℃),the large increase in the nucleation density and great improvement in the average surfae roughness of the diamond were observed. Results of low temperature deposition and characterization of diamond thin films obtained are presented.

Experimental Research of Inactivation Effect of Low-Temperature Plasma on Bacteria

The killing logarithms index in killing a vegetative form in an explosure of about 90s and a spore in an explosure of about 120s, by using a low-temperature plasma produced by dielectric barrier discharge （DBD）, reached 5. The speed in killing the strains tested, by using a low-temperature plasma, was the highest with E. Coli, then S. Aureus and B. Subtilis var niger spore. The results of the scanning electron microscope showed that the low-temperature plasma destroyed the outer structure of the bacteria and that the vegetative form was more susceptible to the inactivation effect of the low-temperature plasma than was the spore. This indicated that the effects of the high voltage and high velocity particle flow, in plasma, penetrating through the outer structure of the bacteria might play a dominant role during the inactivation of the bacteria.

Surface Modification of Polyvinylidene Fluoride (PVDF) Membranes by Low-Temperature Plasma with Grafting Styrene

In order to control the surface pore sizes of polyvinylidene fluoride membranes and their distribution, low temperature plasma-induced grafting modifications of PVDF were studied to prepare hydrophobe membranes. By argon （Ar） treating and subsequent grafting reaction, a hydrophobe monomer, styrene, was introduced into the PVDF membrane. Fourier transform infrared attenuated total reflection （FTIR-ATR） was utilized to characterize the chemical and physical changes in the Ar plasma modified membrane. The surface modifications of PVDF membranes were investigated by using scanning electron microscopy （SEM）, atomic force microscopy （AFM） and differential scanning calorimeter （DSC）. The water permeability and the solute rejection were measured by PVDF membrane modified in different graft conditions. Results demonstrated that the pores in the modified membranes get smaller and the distribution of pores gets narrowed with the increase in grafting reaction duration. Longer graft time caused the water flux of PVDF membrane to decrease from 578 kg/（m^2· h） to 23 kg/（m^2· h） and the solute rejection to increase from 73% to 92%.

Design and characteristics investigation of a miniature low-temperature plasma spark discharge device

Atmospheric pressure low-temperature plasma is a promising tool in biomedicine applications including blood coagulation,bacterial inactivation,sterilization,and cancer treatment,due to its high chemical activity and limited thermal damage.It is of great importance to develop portable plasma sources that are safe to human touch and suitable for outdoor and household operation.In this work,a portable and rechargeable low-temperature plasma spark discharge device(130 mm×80 mm×35 mm,300 g)was designed.The discharge frequency and plume length were optimized by the selection of resistance,capacitance,electrode gap,and ground electrode aperture.Results show that the spark plasma plume is generated with a length of 12 mm and a frequency of 10 Hz at a capacitance of 0.33μF.resistance of 1 MΩ,electrode gap of 2 mm,and ground electrode aperture of 1.5 mm.Biological tests indicate that the plasma produced by this device contains abundant reactive species,which can be applied in plasma biomedicine,including daily sterilization and wound healing.

Surface XPS-investigations of tobacco leaves treated with low-temperature plasma

The tobacco leaves were treated with low-temperature plasma in Ar, N2, O2, and air atmospheres at different powers (60―130 W). The surface-elemental components, their relative contents, and the functional groups of the surface components of the tobacco leaves were determined using XPS (X-ray photoelectron spectroscopy). The ex- perimental results showed that the percentage of the elements C, N, and O had changed considerably and a large number of polar functional groups containing oxygen atoms were incorporated into the components on the tobacco surfaces. The measurements of the surface contact angle showed that the surface contact angle of the modified tobacco leaves was 0 degree, whereas it was 110 degrees before the plasma treatment. These results indicate that the wettability of the modified tobacco leaves improved dramatically. This work may be significant for future researches on the surface modification of the tobacco leaves.

Destruction of Gaseous Styrene with a Low-Temperature Plasma Induced by a Tubular Multilayer Dielectric Barrier Discharge

The destruction of gaseous styrene was studied using a low-temperature plasma induced by tubular multilayer dielectric barrier discharge（DBD）.The results indicate that the applied voltage,gas flow rate,inlet styrene concentration and reactor configuration play important roles in styrene removal efficiency （ηstyrene） and energy yield（EY）.Values of ηstyrene and EY reached 96%and 15567 mg/kWh when the applied voltage,gas flow rate,inlet styrene concentration and layers of quartz tubes were set at 10.8 kV,5.0 m/s,229 mg/m^3 and 5 layers,respectively.A qualitative analysis of the byproducts and a detailed discussion of the reaction mechanism are also presented.The results could facilitate industrial applications of the new DBD reactor for waste gas treatment.

Remove of Phenolic Compounds in Water by Low-Temperature Plasma: A Review of Current Research

Phenolic compounds have very strong toxicity, so it has been paid sharply attention to find an effective way of controlling the wastewater containing phenolic compounds. The work on this subject done by domestic and overseas scholars is studied in this paper, and the progress of researches on low-temperature plasma treatment is summarized through the electrical discharge types, mechanism, kinetics of phenolic compounds decomposition and combination of several methods with low-temperature plasma treatment. In addition, the crucial problem and the developing tendency on low-temperature plasma treatment for phenol-bearing wastewater are briefly discussed.

The Application of Microwave Low Temperature Plasma in Pretr-eatment of Cotton Fabric

The effect of microwave low temperature plasma pretreatment on desizing and removing natural impurity of cellulose fiber was studied. The influencing factors of pretreatment such as treating power, gas pressures and time were discussed in detail and the final effect had been compared with that of traditional pretreating process of cotton fabric. The results showed that better capillary effect, strength, whiteness and dyeing K/S value could be given by means of microwave low temperature plasma treatment.

Silk fibroins modify the atmospheric low temperature plasma-treated poly (3-hydroxybutyrate-co-3-hydroxyhexanoate) film for the application of cardiovascular tissue engineering

Tissue engineered scaffold is one of the hopeful therapies for the patients with organ or tissue damages. The key element for a tissue engineered scaffold material is high biocompatibility. Herein the poly (3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) film was irradiated by the low temperature atmospheric plasma and then coated by the silk fibroins (SF). After plasma treatment, the surface of PHBHHx film became rougher and more hydrophilic than that of original film. The experiment of PHBHHx flushed by phosphate buffer solution (PBS) proves that the coated SF shows stronger immobilization on the plasma-treated film than that on the untreated film. The cell viability assay demonstrates that SF-coated PHBHHx films treated by the plasma significantly supports the proliferation and growth of the human smooth muscle cells (HSMCs). Furthermore, the scanning electron microscopy and hemotoylin and eosin (HE) staining show that HSMCs formed a cell sub-monolayer and secreted a large amount of extracellular matrix (ECM) on the films after one week's culture. The silk fibroins modify the plasma-treated PHBHHx film, providing a material potentially applicable in the cardiovascular tissue engi-neering.

Continuous Emission Spectrum Measurement for Electron Temperature Determination in Low-Temperature Collisional Plasmas

Continuous emission spectrum measurement is applied for the inconvenient diagnos- tics of low-temperature collisional plasmas. According to the physical mechanism of continuous emission, a simplified model is presented to analyze the spectrum in low temperature plasma. The validity of this model is discussed in a wide range of discharge parameters, including electron tem- perature and ionization degree. Through the simplified model, the continuous emission spectrum in a collisional argon internal inductively coupled plasma is experimentally measured to determine the electron temperature distribution for different gas pressures and radio-frequency powers. The inverse Abel transform is also applied for a better spatially resoluted results. Meanwhile, the result of the continuous emission spectrum measurement is compared to that of the electrostatic double probes, which indicates the effectiveness of this method.

The Feasibility of Applying AC Driven Low-Temperature Plasma for Multi-Cycle Detonation Initiation

Ignition is a key system in pulse detonation engines （PDE）. As advanced ignition methods, nanosecond pulse discharge low-temperature plasma ignition is used in some combustion systems, and continuous alternating current （AC） driven low-temperature plasma using dielectric barrier discharge （DBD） is used for the combustion assistant. However, continuous AC driven plasmas cannot be used for ignition in pulse detonation engines. In this paper, experimental and numerical studies of pneumatic valve PDE using an AC driven low-temperature plasma igniter were described. The pneumatic valve was jointly designed with the low-temperature plasma igniter, and the numerical simulation of the cold-state flow field in the pneumatic valve showed that a complex flow in the discharge area, along with low speed, was beneficial for successful ignition. In the experiments ethylene was used as the fuel and air as oxidizing agent, ignition by an AC driven low-temperature plasma achieved multi-cycle intermittent detonation combustion on a PDE, the working frequency of the PDE reached 15 Hz and the peak pressure of the detonation wave was approximately 2.0 MPa. The experimental verifications of the feasibility in PDE ignition expanded the application field of AC driven low-temperature plasma.

Plasma-assisted surface treatment for low-temperature annealed ohmic contact on AlGaN/GaN heterostructure field-effect transistors

In this study, a low-temperature annealed ohmic contact process was proposed on AlGaN/GaN heterostructure field effect transistors （HFETs） with the assistance of inductively coupled plasma （ICP） surface treatment. The effect of ICP treatment process on the 2DEG channel as well as the formation mechanism of the low annealing temperature ohmic contact was investigated. An appropriate residual AlGaN thickness and a plasma-induced damage are considered to contribute to the low-temperature annealed ohmic contact. By using a single Al layer to replace the conventional Ti/Al stacks, ohmic contact with a contact resistance of 0.35 Ω.mm was obtained when annealed at 575 ℃ for 3 min. Good ohmic contact was also obtained by annealing at 500 ℃ for 20 rain.

IMPROVEMENT OF MECHANICAL PROPERTIES OF MARTENSITIC STAINLESS STEEL BY PLASMA NITRIDING AT LOW TEMPERATURE

A series of experiments were carried out to study the influence of low temperature plasma nitriding on the mechanical properties of AISI 420 martensitic stainless steel. Plasma nitriding experiments were carried out for 15 h at 350℃ by means of DC- pulsed plasma in 25%N2＋ 75%H2 atmosphere. The microstructure, phase composition, and residual stresses profiles of the nitrided layers were determined by optical microscopy and X-ray diffraction. The microhardness profiles of the nitridied surfaces were also studied. The fatigue life, sliding wear, and erosion wear loss of the untreated specimens and plasma nitriding specimens were determined on the basis of a rotating bending fatigue tester, a ball-on-disc wear tester, and a solid particle erosion tester. The results show that the 350℃ nitrided surface is dominated by c-Fe3N and ON, which is supersaturated nitrogen solid solution. They have high hardness and chemical stabilities. So the low temperature plasma nitriding not only increases the surface hardness values but also improves the wear and erosion resistance. In addition, the fatigue limit of AISI 420 steel can also be improved by plasma nitriding at 350℃ because plasma nitriding produces residual compressive stress inside the modified layer.

Dyeing Behavior of Yak Hair Fiber Treated with Microwave Low Temperature Plasma

The scales on the surface of yak hair fiber act as barriers during the dyeing process. In order to solve the scale problem and to improve the dyeability of yak hair, yak hair fiber was treated by microwave low temperature plasma (MLTP) in this study. The weight loss and the dyeing properties of the yak hair fiber modified by MLTP were investigated. Scanning Electron Microscopy (SEM) photographs were taken to observe the changes in the surface shape of yak hair fiber before and after treatment. Results showed that after MLTP treatment, the scale structure of yak hair was weakened and damaged greatly and the noticeable changes on the surface shape took place. At the same time, a significant improvement in dyeing properties of yak hair fiber was exhibited.

Evaluation of a gate-first process for AlGaN/GaN metal-oxide-semiconductor heterostructure field-effect transistors with low ohmic annealing temperature

In this paper, TiN/A1Ox gated A1GaN/GaN metal-oxide-semiconductor heterostructure field-effect transistors （MOS- HFETs） were fabricated for gate-first process evaluation. By employing a low temperature ohmic process, ohmic contact can be obtained by annealing at 600 ℃ with the contact resistance approximately 1.6 Ω.mm. The ohmic annealing process also acts as a post-deposition annealing on the oxide film, resulting in good device performance. Those results demonstrated that the TiN/A1Ox gated MOS-HFETs with low temperature ohmic process can be applied for self-aligned gate AIGaN/GaN MOS-HFETs.

LOW TEMPERATURE ALUMINUM FLOATING ELECTROLYSIS IN HEAVY ELECTROLYTE Na_3AlF_6-AlF_3-BaC1_2-NaCl BATH SYSTEM

Multiple regression equations of liquidus temperature, electrical conductivity and bath density of the Na_3AlF_6-AlF_3-BaC1_2-NaCl system were obtained from experiments by using orthogonal regression method. The experiments were carried out in 100A cell with low melting point electrolyte, the influences of cathodic current density, electrolytic temperature, density differences of bath and liquid aluminum on current efficiency (CE) were studied; when the electrolyte cryolite ratio was 2.5, w(BaC1_2) and w(NaCl) were 48% and 10%, respectively, CE reached 90% and specific energy consumption was 10.97k Wb/kg/kg. Because of the fact that aluminum metal obtained floated on the surface of molten electrolyte, this electrolysis method was then defined as low temperature aluminum floating electrolysis. The results showed that the new low temperature aluminum electrolysis process in the Na_3AlF_6-AlF_3-BaC1_2-NaCl bath system was practical and promising.

Applications and challenges of low temperature plasma in pharmaceutical field

Low temperature plasma(LTP)technology has shown an outstanding application value in the pharmaceutical filed in recent ten years.This paper reviews the research advances in LTP,including its effects on enhancing or inhibiting drug activity,its combined use with drugs to treat cancers,its effects on the improvement of drug delivery system,its use in preparation of new inactivated virus vaccines,its use with mass spectrometry for rapid detection of drug quality,and the anti-tumor and sterilization effects of plasma-activated liquids.The paper also analyzes the challenges of LTP in the pharmaceutical filed,hoping to promote related research.

BEHAVIOR OF CHO CELLS ON MODIFIED POLYPROPYLENE BY LOW TEMPERATURE AMMONIA PLASMA

The surface of polypropylene (PP) membrane was modified by low temperature plasma with ammonia. The effect of exposure time was investigated by means of contact angle measurement. The results show that low temperature ammonia plasma treatment can enhance its hydrophilicity. Chinese hamster ovary (CHO) cells attachment on the modified membrane was enhanced and the growth rate on the membrane was faster than unmodified one.

Study on Free Surface and Channel Flow Induced by Low Temperature Plasma via Lattice Boltzmann Method

Active boundary layer flow control and boundary layer manipulation in the channel flow that was based on low temperature plasma were studied by means of a lattice Boltzmann method. Two plasma actuators were placed in a row to obtain the influence rule of their separation distance on the velocity profile at three locations and maximum velocity in the flow field. Two plasma actuators were placed symmetrically inside a channel to examine the effect of channel height and voltage on the velocity profile and flow rate. It was found that the channel height controls the distribution of flow velocity, which affected the flow rate and its direction. Increasing plasma voltage had a negative effect on the flow rate due to the generation of a larger and stronger flow vortex.

Effect of processing temperatures on characteristics of surface layers of low temperature plasma nitrocarburized AISI 204Cu austenitic stainless steel

The influence of processing temperatures on the surface characteristics of AISI 204Cu austenitic stainless steel was investigated during a low temperature plasma nitrocarburizing.The resultant layer was a dual-layer structure,which comprises a N-enriched layer on the top of C-enriched layer.The surface hardness and the layer thickness increase up to about HV 0.05 1000 and 20μm with increasing temperature.The specimen treated at 400°C shows a much enhanced corrosion resistance compared to the untreated steel.A loss in corrosion resistance was observed for specimens treated at temperatures above 430°C due to the formation of Cr2N.