Fabrication of Free Standing Nanocellulose Film via Spray Coating and its Biomedical Application: A Review

Spraying nanocellulose onto films provides a quick and scalable way to create free-standing films with exceptional consistency and customizable thickness. This method increases the application of nanocellulose films in various industries and satisfies the requirements of large-scale production. In the field of biomedicine, spray-coated free-standing nanocellulose films hold great promise for applications such as drug delivery, tissue engineering, wound healing, device coatings, and biosensing. They are excellent nanomaterials for a variety of biomedical applications due to their special qualities, including biocompatibility, high mechanical strength, porous structure, large surface area, and adaptability. This paper reviewed the detailed exposure of the spray coating process of nanocellulose suspension onto free- standing films and its biomedical applications.

Growth of Free-standing Diamond Films on Graphite Substrates with Ti Interlayers

Free-standing diamond films, deposited using DC Arc Plasma Jet CVD method onto graphite substrates with titanium interlayers, have been investigated. The Ti interlayers were deposited by arc ion plating equipments. The thickness, morphology and composite phase of Ti interlayers were examined by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The titanium carbide (TiC) was detected in both sides of the interlayers, which played an important role with respect to reasonable adhesion with film and diamond nucleation. The semi-translucent diamond films were characterized by SEM and Raman spectrum. The sharp diamond peak with low intensity of amorphous carbon shows that diamond films have very high quality. The overall results suggest that plating Ti interlayer on graphite substrate is an effective way to obtain optical grade free-standing diamond films.

A review on polishing technology of large area free-standing CVD diamond films

Recently,with the rapid development of chemical vapor deposition(CVD)technology,large area free-standing CVD diamond films have been produced successfully.However,the coarse grain size on the surface and the non-uniform thickness of unprocessed CVD diamond films make it difficult to meet the application requirement.The current study evaluates several existing polishing methods for CVD diamond films,including mechanical polishing,chemical mechanical polishing and tribochemical polishing technology.

Synthesis of free-standing Ga_2O_3 films for flexible devices by water etching of Sr_3Al_2O_6 sacrificial layers

Flexible electronic devices have attracted much attention due to their practical and commercial value. Integration of thin films with soft substrate is an effective way to fabricate flexible electronic devices. Ga_2O_3 thin films deposited directly on soft substrates would be amorphous mostly. However, the thickness of the thin film obtained by mechanical exfoliation method is difficult to control and the edge of the film is fragile and easy to be damaged. In this work, we fabricated free-standing Ga_2O_3 thin films using the water-soluble perovskite Sr_3Al_2O_6 as a sacrificial buffer layer. The obtained Ga_2O_3 thin films were polycrystalline. The thickness and dimension of the films were controllable. A flexible Ga_2O_3solar-blind UV photodetector was fabricated by transferring the free-standing Ga_2O_3 film on a flexible polyethylene terephthalate substrate. The results displayed that the photoelectric performances of the flexible Ga_2O_3 photodetector were not sensitive to bending of the device. The free-standing Ga_2O_3 thin films synthesized through the method described here can be transferred to any substrates or integrated with other thin films to fabricate electronic devices.

Preparation of free-standing diamond films for high frequency SAW devices

Free-standing diamond films were prepared by hot filament chemical vapor deposition (HFCVD) method under different conditions. Inter-digital transducers (IDTs) were formed on the nucleation sides of free-standing diamond films by photolithography technique. Then piezoelectric ZnO films were deposited by radio-frequency(RF) reactive magnetron sputtering to obtain the ZnO/diamond film structures. Surface morphologies of the nucleation sides and the IDTs were characterized by means of scanning electron microscopy (SEM), atomic force microscope (AFM) and optical microscopy. The results indicate that the surfaces of nucleation sides are very smooth and the IDTs are of high quality without discontinuity and short circuit phenomenon. Raman spectra show the sharp diamond feature peak at about 1 334 cm?1 and the small amount of non-diamond carbon in the nucleation side. X-ray diffraction (XRD) patterns of the structure of ZnO/diamond films show a strong diffraction peak of ZnO (002), which indicates that as-sputtered ZnO films are highly c-axis oriented.

Preparation of ZnO Thin Films on Free-Standing Diamond Substrates

Highly c-axis-oriented ZnO films were deposited successfully on the nucleation sides of free-standing diamond （FD） films by the direct current （DC） magnetron sputtering method. The effect of the sputtering parameters, such as power, gas pressure and sputtering plasma composition of Ar-to-O2, on the properties of ZnO thin films was investigated in detail. X-ray diffraction （XRD） measurements showed that, at a sputtering power of 200 W, gas pressure of 0.5 Pa and an Ar-to- O2 composition of 1：1, a higher intensity of the （002） diffraction peak and a narrower full width at half maximum （FWHM） were detected which meant high c-axis orientation and high quality of the ZnO films. To improve the quality of the ZnO film, a thin ZnO layer was pre-grown as a homo-buffer layer. XRD measurements showed that this buffer layer had a beneficial effect on the structural and morphological properties of the post-grown ZnO film.

Growth of Free-Standing Diamond Films on Stainless Steel

Free-standing diamond films have been successfully deposited on stainless steel substrates using microwave plasma-assisted chemical vapor deposition. Although iron, which is the main element of stainless steel, is known to inhibit the nucleation of diamond and enhance the formation of graphite, we were able to grow relatively thick films （-1.2 mm）. The films were easily detachable from the substrates. The poor adhesion made it possible to obtain free-standing diamond films without chemical etching. Raman spectroscopy showed the 1332 cm^-1 characteristic Raman peak of diamond and the 1580 cm^-1, 1350 cm^-1 bands of graphite on the growth surface and backside of the films, respectively. By energy dispersive X-ray spectroscopy it was only possible to detect iron on the back of the films, but not on the surface. The role of iron in the film growth is discussed.

Effect of working pressure and temperature on ZnO film deposited on free-standing diamond substrates

The structure characteristic and electric performance of ZnO film deposited on nucleation side of free-standing diamond substrates under different heating temperatures (Th) of substrate and working pressures (p) were studied. The structure of the ZnO films tested by X-ray diffraction shows that ZnO film of high c-axis orientation is deposited on the nucleation side of free-standing diamond substrate which is extremely smooth when Th=250 ℃ and p=0.4 Pa. After annealing at 480 ℃ in N2 atmosphere, the SEM and the AFM analyses demonstrate that the c-axis orientation of ZnO film is obviously enhanced. The resistivity of ZnO films also increases up to 8×105 ■·cm which is observed by I?V test.

Numerical Analysis of Nd:YAG Pulsed Laser Polishing CVD Self-standing Diamond Film

Chemical vapor deposited （CVD） diamond film has broad application foreground in high-tech fields. But polycrystalline CVD self-standing diamond thick film has rough surface and non-uniform thickness that adversely affect its extensive applications. Laser polishing is a useful method to smooth self-standing diamond film. At present, attentions have been focused on experimental research on laser polishing, but the revealing of theoretical model and the forecast of polishing process are vacant. The paper presents a finite element model to simulate and analyze the mechanism of laser polishing diamond based on laser thermal conduction theory. The experimental investigation is also carried out on Nd：YAG pulsed laser smoothing diamond thick film. The simulation results have good accordance with the results of experimental results. The temperature and thermal stress fields are investigated at different incidence angles and parameters of Nd：YAG pulsed laser. The pyramidal-like roughness of diamond thick film leads to the non-homogeneous temperature fields. The temperature at the peak of diamond film is much higher than that in the valley, which leads to the smoothing of diamond thick film. The effect of laser parameters on the surface roughness and thickness of graphite transition layer is also carried out. The results show that high power density laser makes the diamond surface rapid heating, evaporation and sublimation after its graphitization. It is also found that the good polish quality of diamond thick film can be obtained by a combination of large incident angle, moderate laser pulsed energy, large repetition rate and moderate laser pulse width. The results obtained here provide the theoretical basis for laser polishing diamond film with high efficiency and high quality.

Preparation and Characterization of High Quality Diamond Films by DC ArcPlasma Jet CVD Method

Under optimal conditions free-standing high quality diamond films were prepared by DC arc plasma jet CVD method at a growth rate of 7-10 Pm/h. Surface and cross section morphologies of the diamond films were observed by SEM. Raman spectrometer wasused to characterize the quality of diamond films. The IR transmittivity measured by IR spectrometer is close to the theoretical value ofabout 71% in the far infrared band. The thermal conductivity measured by photothermal deflection exceeds 18 W/cm' K. <l 10> is thepreferential growth orientation of the films detected by X-ray diffractometer. As s result, the extremely high temperature of DC arc plasma jet can produce supersaturated atomic hydrogen, which played an important role in the process for the deposition of high quality diamond films.

FREE STANDING FILM OF POLYANILINE

A free standing film of polyaniline as large as 18 cm×18cm×0.002 cm can be obtained by evaporation of a solution of the chemically synthesized base in NMP. Its structure was examined by the elemental analysis, IR, U.V.-visible spectra, XPS, DSC, SEM and X-ray scattering and its conducting behavior as well as electrochemical properties were studied. Results show that the composition, structure of main chain, physical properties of the free standing film of polyanilme is similar to that of the powder. However, some differences in its electronic structure, conductivity at room temperature and potential of redox couple between the flee standing film and powder are observed, which may be due to cross-linking of the film of polyaniline.

Fabrication of Diamond Microstructures by Using Dry and Wet Etching Methods

Diamond films have great potential for micro-electro-mechanical system（MEMS） application.For device realization,precise patterning of diamond films at micrometer scale is indispensable.In this paper,simple and facile methods will be demonstrated for smart patterning of diamond films,in which two etching techniques,i.e.,plasma dry etching and chemical wet etching（including isotropic-etching and anisotropic-etching） have been developed for obtaining diamond microstructures with different morphology demands.Free-standing diamond micro-gears and micro-combs were achieved as examples by using the experimental procedures.It is confirmed that as-designed diamond structures with a straight side wall and a distinct boundary can be fabricated effectively and efficiently by using such methods.

基于玻璃碳基底的超薄自支撑多晶金刚石膜制备

选取Ti、Si、玻璃碳3种基底,采用微波等离子体化学气相沉积技术,以CH_(4)/H_(2)为反应源制备超薄多晶金刚石膜。通过SEM、Raman、台阶仪表征并分析所制备的金刚石薄膜整体形态、表面(断面)形貌、组成、应力状态等。结果表明:仅以玻璃碳为基体生长的金刚石膜能自动剥离形成完整自支撑体,且薄膜表面晶粒的晶面显形清晰,膜厚仅为10μm;Raman光谱表征表明薄膜呈强的尖锐金刚石特征峰,且计算的残余应力最低,仅有−0.2161 GPa。可为超薄自支撑CVD金刚石膜的一步法生长-剥离提供新的技术途径。

多色柔性自支撑胆甾相液晶薄膜反射器件

一维手性软光子晶体胆甾相液晶(CLC)在防伪标签、纳米激光器和传感等领域具有广泛的应用。本文采用多步图案化紫外固化方法并结合清洗-重填工艺,实现了多色的柔性自支撑CLC薄膜反射器件。采用标签打印机打印PET图案作为掩膜版,对可聚合的CLC材料进行紫外固化,得到图案化的柔性自支撑CLC薄膜反射器件。在此基础上,将非固化区域的液晶材料洗去并重新填充不同手性剂含量的CLC,再次图案化紫外曝光,即可实现多色的柔性自支撑CLC薄膜反射器件。研究了不同入射角、弯曲曲率半径和温度对反射器件光学性能的影响。实验结果表明,采用上述方法制备的多色可自支撑反射器件具有良好的柔性,不同曲率半径下的布拉格反射中心波长基本不变。随着温度升高,布拉格反射中心波长红移,且具有良好的线性度。多色的可自支撑柔性薄膜反射器件可拓展CLC在显示、传感、激光防护和微纳光学等领域的进一步应用。

ELECTROSYNTHESES OF FREE-STANDING POLY(THIOPHENE-3-ACETIC ACID) FILM IN MIXED ELECTROLYTES OF BORON TRIFLUORIDE DIETHYL ETHERATE AND TRIFLUOROACETIC ACID

High quality free-standing poly（thiophene-3-acetic acid） （PTAA）, a water-soluble polythiophene derivative, was uccessfully electrosynthesized in boron trifluoride diethyl etherate （BFEE） ＋ 25% （by volume） trifluoroacetic acid （TFA） at 9wer potential （0.38 V versus Pt）. The carboxyl group makes PTAA highly soluble in water, facilitating its potential pplication as a blue-light-emitting material. PTAA films with conductivity of 7 S cm-1 obtained from this medium showed ,etter redox activity and thermal stability. The structure and morphology of the polymer were studied by UV-Vis, FT-IR, H-NMR spectra and scanning electron microscopy, respectively.

微波PCVD法大尺寸透明自支撑金刚石膜的制备及红外透过率(英文)

采用微波PCVD方法制备出直径50mm膜厚300μm的大尺寸透明自支撑金刚石膜。在甲烷体积分数2%的条件下制备的透明自支撑金刚石膜经过两面抛光后在500cm-1~4000cm-1红外波段范围内红外透过率达到70%,但是其生长速率只有1μm/h^2μm/h。在体积分数4%甲烷浓度下制备的自支撑透明金刚石膜,其生长速率达到7μm/h^8μm/h,经过两面抛光之后膜厚为260μm的金刚石膜的在500cm-1~4000cm-1红外波段范围内红外透过率达到60%左右,而且膜中心和边缘区的红外透过率基本相同。这些结果为大尺寸金刚石厚膜在红外窗口上的实际应用奠定了基础。

用人工神经网络预测电铸自支撑金刚石-镍复合膜沉积结果

用人工神经网络预测了电铸自支撑金刚石-镍复合膜中金刚石颗粒的含量、复合膜的厚度和表面微观形貌。结果表明,当阴极电流密度小于1.0A/dm2时,复合膜的表面均匀,无镍瘤;复合膜的沉积速率约为14μm/h。其预测的沉积结果与实际样品测量值接近,相对误差小于9.9%。人工神经网络能够充分体现电镀工艺参数与沉积结果之间的非线性关系和隐含关系,训练精度较高,具有较高的预测能力。

DC Plasma Jet CVD金刚石自支撑膜体结构的控制生长及其表面粗糙度的研究

在 100kW级DCPlasmaJetCVD设备上,采用Ar H2 CH4 混合气体,通过控制工艺参数,在Mo衬底上获得不同占优晶面和应力状态的膜体结构。研究表明:不同取向的晶面在膜体中的分布不同,但各晶面随沉积温度的变化规律是相似的,在 900℃左右容易获得较大的(220)晶面占优的膜体结构;薄膜的内应力沿晶体生长方向逐渐减小,且随沉积温度或甲烷浓度的增大而增大;具有高取向度的膜体将获得较为平整的表面。

金刚石自支撑膜的高温红外透过性能

由于金刚石具有低吸收和优异的力学与导热性能使其成为长波(8~12μm)红外光学窗口材料的重要选择。对于许多极端条件的应用,化学气相沉积(CVD)金刚石自支撑膜的高温光学性质至关重要。应用直流电弧等离子喷射法制备光学级金刚石自支撑膜进行变化温度的红外光学透过性能研究,采用光学显微镜、X射线衍射、激光拉曼和傅里叶变换红外-拉曼光谱仪检测CVD金刚石膜的表面形貌、结构特征和红外光学性能。结果表明:在27℃时金刚石膜长波红外8~12μm之间的平均透过率达到65.95%,在500℃时8~12μm处的平均透过率为52.5%。透过率下降可分为3个阶段。对应于透过率随温度的下降,金刚石膜的吸收系数随温度的升高而增加。金刚石自支撑膜表面状态的变化,对金刚石膜光学性能的影响显著大于内部结构的影响。

无支撑、光学级MPCVD金刚石膜的研制

利用引进的6 kW微波等离子体化学气相沉积设备,进行了无支撑金刚石膜工艺的初步研究。在800~1050℃的基片温度范围内,金刚石膜都呈（111）择优取向;基片相对位置对沉积较大面积、光学级金刚石膜至关重要。制出0.25 mm厚Φ50 mm的无支撑金刚石膜。拉曼光谱和X射线衍射分析表明,合成的金刚石膜晶体结构完整,sp2含量极低;透过率测试结果说明了优良的光学性能：截止波长225 nm,光学透过率（λ≥2.5μm）≥70%。