Poly(lactic acid)/Poly(butylene adipate-co-terephthalate)films with simultaneous high oxygen barrier and fast degradation properties

Although poly(lactic acid)(PLA)is a good environmentally-friendly bio-degradable polymer which is used to substitute traditional petrochemical-based polymer packaging films,the barrier properties of PLA films are still insufficient for high-barrier packaging applications.In this study,oxygen scavenger hydroxyl-terminated polybutadiene(HTPB)and cobalt salt catalyst were incorporated into the PLA/poly(butylene adipate-co-terephthalate)(PLA/PBAT),followed by melting extrusion and three-layer co-extrusion blown film process to prepare the composite films.The oxygen permeability coefficient of the composite film combined with 6 wt%oxygen scavenger and 0.4 wt%catalyst was decreased significantly from 377.00 cc·mil·m^(-2)·day^(-1)·0.1 MPa^(-1) to 0.98 cc·mil·m^(-2)·day^(-1)·0.1 MPa^(-1),showing a remarkable enhancement of 384.69 times compared with the PLA/PBAT composite film.Meanwhile,the degradation behavior of the composite film was also accelerated,exhibiting a mass loss of nearly 60%of the original mass after seven days of degradation in an alkaline environment,whereas PLA/PBAT composite film only showed a mass loss of 32%.This work has successfully prepared PLA/PBAT composite films with simultaneously improved oxygen barrier property and degradation behavior,which has great potential for high-demanding green chemistry packaging industries,including food,agricultural,and military packaging.

Preparation of Diamond-like Carbon Films on the Surface of Ti Alloy by Electro-deposition

In this paper, diamond-like carbon (DLC) films were deposited on Ti alloy by electro-deposition. DLC films were brown andcomposed of the compact grains whose diameter was about 400 nm. Examined by XPS, the main composition of the filmswas carbon. In the Raman spectrum, there were a broad peak at 1350 cm^(-1) and a broad peak at 1600 cm^(-1), which indicatedthat the films were DLC films.

Influence of Microwave Power on the Properties of Hydrogenated Diamond-Like Carbon Films Prepared by ECR Plasma Enhanced DC Magnetron Sputtering

Electron cyclotron resonance （ECR） plasma was applied to enhance the direct current magnetron sputtering to prepare hydrogenated diamond-like carbon （H-DLC） films. For different microwave powers, both argon and hydrogen gas are introduced separately as the ECR working gas to investigate the influence of microwave power on the microstructure and electrical property of the H-DLC films deposited on P-type silicon substrates. A series of characterization methods including the Raman spectrum and atomic force microscopy are used. Results show that, within a certain range, the increase in microwave power affects the properties of the thin films, namely the sp3 ratio, the hardness, the nanoparticle size and the resistivity all increase while the roughness decreases with the increase in microwave power. The maximum of resistivity amounts to 1.1×10^9 Ω.cm. At the same time it is found that the influence of microwave power on the properties of H-DLC films is more pronounced when argon gas is applied as the ECR working gas, compared to hydrogen gas.

Structure and Mechanical Performance of Nitrogen Doped Diamond-like Carbon Films

Nitrogen doped diamond-like carbon （DLC：N） films were prepared by electron cyclotron resonance chemical vapor deposition （ECR-CVD） on polycrystalline Si chips. Film thickness is about 50 nm. Auger electron spectroscopy （AES） was used to evaluate nitrogen content, and increasing N2 flow improved N content from 0 to 7.6%. Raman and X-ray photoelectron spectroscopy （XPS） analysis results reveal CN-sp^3C and N-sp^2C structure. With increasing the N2 flow, sp^3C decreases from 73.74% down to 42.66%, and so does N-sp^3C from 68.04% down to 20.23%. The hardness decreases from 29.18 GPa down to 19.74 GPa, and the Young＇s modulus from 193.03 GPa down to 144.52 GPa.

Fabrication of Diamond-like Carbon Films by Ion Assisted Middle Frequency Unbalanced Magnetron Sputtering

Diamond-like carbon （DLC） films are deposited by the Hall ion source assisted by the mid-frequency unbalanced magnetron sputtering technique. The effects of the substrate voltage bias, the substrate temperature, the Hall discharging current and the argon/nitrogen ratio on the DLC film＇s performance were studied. The experimental results show that the film＇s surface roughness, the hardness and the Young＇s modulus increase firstly and then decrease with the bias voltage incrementally increases. Also when the substrate temperature rises, the surface roughness of the film varies slightly, but its hardness and Young＇s modulus firstly increase followed by a sharp decrease when the temperature surpassing 120 ℃. With the Hall discharging current incrementally rising, the hardness and Young＇s modulus of the film decrease and the surface roughness of the film on 316L stainless steel firstly decreased and then remains constant.

Tribological Characteristic of Diamond-like Carbon Films Investigated by Lateral Force Microscope

Tribological characteristic of different thick diamond-like carbon (DLC) films was studied. A geometrical method was applied to calibrate the cantilever spring constant and to calculate the normal and lateral forces, respectively. Experimental results show that the lateral force under different applied loads is proportional to the normal force for the DLC films with the thickness of 153.4nm and 64.9nm. However, for the thickness of 4.48nm and 2.78nm DLC films, lateral force is nonlinear to normal force, which is opposed to the Amonton's law.The single asperity regime and the DMT model were put forward to predict the possible nanotribological mechanism between the probe and DLC film.

Studies of diamond-like carbon (DLC) films deposited on stainless steel substrate with Si/SiC intermediate layers

In this work, diamond-like carbon （DLC） films were deposited on stainless steel substrates with Si/SiC intermediate layers by combining plasma enhanced sputtering physical vapour deposition （PEUMS-PVD） and microwave electron cyclotron resonance plasma enhanced chemical vapour deposition （MW-ECRPECVD） techniques. The influence of substrate negative self-bias voltage and Si target power on the structure and nano-mechanical behaviour of the DLC films were investigated by Raman spectroscopy, nano-indentation, and the film structural morphology by atomic force microscopy （AFM）. With the increase of deposition bias voltage, the G band shifted to higher wave-number and the integrated intensity ratio ID/IG increased. We considered these as evidences for the development of graphitization in the films. As the substrate negative self-bias voltage increased, particle bombardment function was enhanced and the sp^3-bond carbon density reducing, resulted in the peak values of hardness （H） and elastic modulus （E）. Silicon addition promoted the formation of sp^3 bonding and reduced the hardness. The incorporated Si atoms substituted sp^2- bond carbon atoms in ring structures, which promoted the formation of sp^3-bond. The structural transition from C-C to C-Si bonds resulted in relaxation of the residual stress which led to the decrease of internal stress and hardness. The results of AFM indicated that the films was dense and homogeneous, the roughness of the films was decreased due to the increase of substrate negative self-bias voltage and the Si target power.

Tribological properties of diamond-like carbon films deposited bv pulsed laser arc deposition

A novel method, pulsed laser arc deposition combining the advantages of pulsed laser deposition and cathode vacuum arc techniques, was used to deposit the diamond-like carbon （DLC） nanofilms with different thicknesses. Spectroscopic ellipsometer, Auger electron spectroscopy, x-ray photoelectron spectroscopy, Raman spectroscopy, atomic force microscopy, scanning electron microscopy and multi-functional friction and wear tester were employed to investigate the physical and tribological properties of the deposited films. The results show that the deposited films are amorphous and the sp2, sp3 and C-O bonds at the top surface of the films are identified. The Raman peak intensity and surface roughness increase with increasing film thickness. Friction coefficients are about 0.1, 0.15, 0.18, when the film thicknesses are in the range of 17-21 nm, 30-57 nm, 67-123 nm, respectively. This is attributed to the united effects of substrate and surface roughness. The wear mechanism of DLC films is mainly abrasive wear when film thickness is in the range of 17-41 nm, while it transforms to abrasive and adhesive wear, when the film thickness lies between 72 and 123 nm.

Structures of Diamond-Like Carbon Films

The structures of diamond-like carbon （DLC） films, including a-C：H, a-C, ta-C：H and ta-C films have been investigated as a random covalent network with a dense film structure. The results show that sp2 C in a-C：H and a-C films tends to form olefinic and aromatic groups while sp^3 C in ta-C：H and ta-C films tends to form single or multiple sixfold groups. The hydrogen atoms in hydrogenated DLC films contribute to stabilizing the carbon skeletal networks. The film structures are well related to their properties such as optical gaps, density and hardness. The results also indicate that the high density and the extreme hardness of ta-C films are attributed to the forming of large sp^3 C bonded sixfold groups.

Influences of nitrogen flow rate on the structures and properties of Ti and N co-doped diamond-like carbon films deposited by arc ion plating

In this paper, Ti-C-N nanocomposite films are deposited under different nitrogen flow rates by pulsed bias arc ion plating using Ti and graphite targets in the Ar/N2 mixture gas. The surface morphologies, compositions, microstructures, and mechanical properties of the Ti-C-N films are investigated systematically by field emission scanning electron mi- croscopy （FE-SEM）, x-ray photoelectron spectroscopy （XPS）, grazing incident x-ray diffraction （GIXRD）, Raman spectra, and nano-indentation. The results show that the nanocrystalline Ti（C,N） phase precipitates in the film from GIXRD and XPS analysis, and Raman spectra prove the presence of diamond-like carbon, indicating the formation of nanocomposite film with microstructures comprising nanocrystalline Ti（C,N） phase embedded into a diamond-like matrix. The nitrogen flow rate has a significant effect on the composition, structure, and properties of the film. The nano-hardness and elastic modulus first increase and then decrease as nitrogen flow rate increases, reaching a maximum of 34.3 GPa and 383.2 GPa, at a nitrogen flow rate of 90 sccm, respectively.

Preparation and Thermal Characterization of Diamond-Like Carbon Films

Diamond-like carbon （DLC） films are prepared on silicon substrates by microwave electron cyclotron resonance plasma enhanced chemical vapor deposition. Raman spectroscopy indicates that the films have an amorphous structure and typical characteristics. The topographies of the films are presented by AFM images. Effective thermal conductivities of the films are measured using a nanosecond pulsed photothermal reflectance method. The results show that thermal conductivity is dominated by the microstructure of the films.

STUDY OF RAY IRRADIATION ON DIAMOND-LIKE CARBON FILMS

Diamond-like carbon (DLC) films have been deposited on glass substrates usingradio-frequency (rf) plasma deposition method. Gamma -ray, ultraviolet (UV) ray were used toirradiate the DLC films. Raman spectroscopy and infrared (IR) spectroscopy were use to characterizethe changing characteristics of SP^3 C-H bond and hydrogen content in the films due to theirradiations. The results show that, the damage degrees induced by the UV ray on the SP^3 C-H bondsare much stronger than that by the gamma -ray. When the irradiation dose of gamma -ray reaches 1 OX10^4 Gy, the SP^3 C-H bond reduces about 50 percent in number. The square electrical resistance ofthe films is reduced due to the irradiation of UV ray and this is caused by severe oxidation of thefilms. By using the results on optical gap of the films and the fully constrained network theory,the hydrogen content in the as-deposited films is estimated to be l0-25at. percent.

Surface properties of diamond-like carbon films prepared by CVD and PVD methods

Diamond-like carbon （DLC） films have been deposited using three different techniques： （a） electron cyclotron resonance——plasma source ion implantation, （b） low-pressure dielectric barrier discharge, （c） filtered——pulsed cathodic arc discharge, The surface and mechanical properties of these films are compared using atomic force microscopebased tests. The experimental results show that hydrogenated DLC films are covered with soft surface layers enriched with hydrogen and sp^3 hybridized carbon while the soft surface layers of tetrahedral amorphous carbon （ta-C） films have graphite-like structure, The formation of soft surface layers can be associated with the surface diffusion and growth induced by the low-energy deposition process. For typical CVD methods, the atomic hydrogen in the plasmas can contribute to the formation of hydrogen and sp^3 hybridized carbon enriched surface layers, The high-energy ion implantation causes the rearrangement of atoms beneath the surface layer and leads to an increase in film density. The ta-C films can be deposited using the medium energy carbon ions in the highly-ionized plasma.

Structural characteristics of surface-functionalized nitrogen-doped diamond-like carbon films and effective adjustment to cell attachment

Nitrogen-doped diamond-like carbon （DLC：N） films prepared by the filtered cathodic vacuum arc technology are functionalized with various chemical molecules including dopamine （DA）, 3-Aminobenzeneboronic acid （APBA）, and adenosine triphosphate （ATP）, and the impacts of surface functionalities on the surface morphologies, compositions, microstructures, and cell compatibility of the DLC：N films are systematically investigated. We demonstrate that the surface groups of DLC：N have a significant effect on the surface and structural properties of the film. The activity of PC12 cells depends on the particular type of surface functional groups of DLC：N films regardless of surface roughness and wettability. Our research offers a novel way for designing functionalized carbon films as tailorable substrates for biosensors and biomedical engineering applications.

A Study of Diamond-Like Carbon Thin Films Prepared by Microwave Plasma Chemical Vapour Deposition

In order to deposit good films, we need to study the uniformity of plasma density and the plasma density under different gas pressures and powers. The plasma density was diagnosed by a Langmuir probe. The optical emission spectroscopy （OES） of CH4 and H2 discharge was obtained with raster spectroscopy, with characteristic peaks of H and CH achieved. Diamond-like carbon films were achieved based on the study of plasma density and OES and characterized by atomic force microscope （AFM）, X-ray diffraction instrument （XRD）, Raman spectroscope and profiler.

Improvement of Thermal Stability and Tribological Performance of Diamond-Like Carbon Composite Thin Films

Diamond-like carbon (DLC) is a metastable amorphous film that exhibits unique properties. However, many limitations exist regarding the use of DLC, for example, its tribological characteristics at high temperature, as well as its limited thermal stability. In this study, silicon/oxygen and silicon/nitrogen co-incorporated diamond-like carbon (Si-O-DLC and Si-N-DLC) films are studied, taking into account the thermal stability and tribological performance of these films compared with pure DLC. All the films were prepared on Si wafers, WC-Co materials, and aluminum foils using a plasma-based ion implantation (PBII) technique using acetylene (C2H2), tetramethylsilane (TMS, Si(CH3)4), oxygen (O2) and nitrogen (N2) as plasma sources. The structure of the films was characterized using Raman spectroscopy. The thermal stability of the films was measured using thermogravimetric and differential thermal analysis (TG-DTA). The friction coefficient of the films was assessed using ball-on-disk friction testing. The results indicate that Si-N-DLC films present better thermal stability due to the presence of Si-O networks in the films. The Si-N-DLC (23 at.%Si, 8 at.%N) film was affected using thermal annealing in an air atmosphere with increasing temperature until 500°C. The film can also resist thermal shock by cycling 10 times between the various temperatures and air atmosphere until 500°C. Further, Si-O-DLC and Si-N-DLC films exhibit excellent tribological performance, especially the Si-N-DLC (23 at.%Si, 8 at.%N) film, which exhibits excellent tribological performance at 500°C in an air atmosphere. It is concluded that Si-O-DLC and Si-N-DLC films improve upon the thermal stability and tribological performance of DLC.

ION IMPLANTATION OF DIAMOND-LIKE CARBON FILMS

Diamond-like carbon (DLC) films (a-C:H) were implanted by 140 keV and 110 keV Ar ion beams. The resistivities of the implanted films decreased dramatically under a dose of 2×1016 Ar/cm2 . IR spectra and optical gap Eopt were measured. It was found that the sp2 and sp3 components decreased due to the loss of hydrogen during implantation, and the ratio of components sp bonds to sp bonds increased with the ion dose. And the optical gap Eopt decreased from 1.46 eV to 0.83 eV. The hydrogen (bonded and unbonded) contents in the films were measured with the nuclear resonant reaction 1H(19 F, x 7) 16O. It is shown that hydrogen plays an important role in affecting some properties of DLC fims.

Mechanism of high growth rate for diamond-like carbon films synthesized by helicon wave plasma chemical vapor deposition

A high growth rate fabrication of diamond-like carbon（DLC）films at room temperature was achieved by helicon wave plasma chemical vapor deposition（HWP-CVD）using Ar/CH4gas mixtures.The microstructure and morphology of the films were characterized by Raman spectroscopy and scanning electron microscopy.The diagnosis of plasma excited by a helicon wave was measured by optical emission spectroscopy and a Langmuir probe.The mechanism of high growth rate fabrication for DLC films by HWP-CVD has been discussed.The growth rate of the DLC films reaches a maximum value of 54μm h^-1at the CH4flow rate of 85 sccm,which is attributed to the higher plasma density during the helicon wave plasma discharge.The CH and Hαradicals play an important role in the growth of DLC films.The results show that the Hαradicals are beneficial to the formation and stabilization of C=C bond from sp^2to sp^3.

Adhesion Studies of Diamond-Like Carbon Films Deposited on Ti6Al4V Alloy after Carbonitriding

Diamond-like Carbon (DLC) coatings have attracted significant attention due to their low friction coefficient, high degree of hardness, chemical inertness, and high wear resistance as well as and their many possible uses in metallurgical, aeronautical, and biomedical applications. However, DLC has low adhesion strength to metallic substrates. Carbonitriding was performed before DLC deposition to improve this adherence. Different concentration of nitrogen in the gas mixture was used during the carbonitriding of Ti6Al4V alloy. DLC films were subsequently grown from methane using plasma enhanced chemical vapor deposition. The samples were characterized with Raman scattering spectroscopy, nanoindentation, and tribological tests. Films from 80.0% N2 had the best friction coefficient (0.07) and a critical load of ~22 N. In the scratching test, these films had adhesive failure and they completely detached from the substrate only in the end of the tests. SEM images show carbonitring promoted a significant increase in the surface defects (homogeneously distributed) but without the presence of microcracks. EDX analysis indicated that nitrogen element was diffused throughout the thickness of the samples. Hydrogen and carbon atoms from carbonitriding formed a diffusion-barrier layer that can be used as the first step for DLC deposition. This carbonitriding can also provide a carbide layer, which serves as the precursor for the nucleation and growth of DLC films.

Characterization and Application of Diamond-like Carbon Films

Diamond like carbon films were synthesized by the pulsed laser deposition method under a magnetic filed. The magnetic field was used to enhance the hardness of the films. Analysis with transmission electron microscopy and atomic force microscopy were carried out to characterize the films. As a protective coating, the film was deposited on porous silicon. The influence of the coating on the photoluminescence properties of porous silicon was studied.