光固化快速成型工艺过程分析及应用

光固化快速成型作为先进的制造技术的一部分,具有重要的应用价值。首先介绍了光固化快速成型工艺的基本原理,分析其存在的优点与缺点。论述了光固化快速成型设备的主要组成部分,如光学装置、容器系统、光敏材料、涂敷机构和控制系统等。以一个非标准圆柱齿轮为例,详细论述具体的加工过程并在SCPS350B成型机上加工出实物。探讨光固化成型技术在产品设计、模具制造、精密铸造、生物医学等方面的应用,展望该技术在未来的发展前景。     

Direct fabrication of deep x-ray lithography masks by micromechanical milling

Micromechanical milling has been shown to be a rapid and direct method for fabricating masks for deep x-ray lithography with lateral absorber features down to 10 micrometers. Conventional x-ray mask fabrication requires complex processes and equipment, and a faster and simpler method using micromechanical milling was investigated for larger microstructures for mesoscale applications. Micromilled x-ray masks consisting of a layered architecture of gold and titanium films on graphite yielded exposures in PMMA with accuracy and repeatability suitable for prototype purposes. A method for compensating milling tool radial runout was adapted, and the average accuracy of mask absorber features was 0.65 micrometers, with an average standard deviation of 0.55 micrometers. The milling process leaves some absorber burrs, and the absorber wall is tapered, which introduces an additional process bias. Mask fabrication by micromilling is fast and, therefore, less costly than conventional mask fabrication processes.     

Fabrication of conjugated polymers nanostructures via direct near-field optical lithography

We report our investigations into the fabrication of nanostructures of poly(p-phenylene vinylene) via direct scanning near-field lithography of its soluble precursor. Our technique is based on the spatially selective inhibition of the precursor solubility by exposure to the ultraviolet optical field present at the apex of commercially available, Au-coated near-field probes with aperture diameters between 40 and 80 nm (±5 nm). After development in methanol and thermal conversion under vacuum we obtain features with a minimum dimension of 160 nm. We analyse our results via tapping-mode atomic force microscopy, and find a clear phase contrast between the core and the centre of the lithographed features, corroborating the hypothesis that hard, fully insolubilised regions are surrounded by a gel-like phase, which we estimate of the order of 110–130 nm for the smallest features, by comparing our experiments with simulations carried out using a Bethe–Bouwkamp model. Use of such model also allows us to discuss the influence of probe size, tip–sample distance, and film thickness on the resolution of the lithographic process. We demonstrate the use of the technique for the direct writing of two-dimensional periodic structures with intentional defects and a periodicity relevant to applications in the visible range.     

Pulsed wire discharge apparatus for mass production of copper nanopowders

A pulsed wire discharge (PWD) apparatus for the mass production of nanopowders has been developed. The apparatus has a continuous wire feeder, which is operated in synchronization with a discharging circuit. The apparatus is designed for operation at a maximum repetition rate of 1.4 Hz at a stored energy of 160 J. In the present study, Cu nanopowder was synthesized using the PWD apparatus and the performance of the apparatus was examined. Cu nanopowder of 2.0 g quantity was prepared in N(2) gas at 100 kPa for 90 s. The particle size distribution of the Cu nanopowder was analyzed by transmission electron microscopy and the mean surface diameter was determined to be 65 nm. The ratio of the production mass of the powder to input energy was 362 g/kW h.     

Application of direct current comparator apparatus in combustion calorimetry

A method was developed for the application of direct current comparator apparatus in resistance thermometry and in voltage measurements in combustion calorimetry. The performance of the measuring system was checked by combustions of benzoic acid combined with electrical calibration of the calorimeter.     

High-temperature and high-pressure pulsed synthesis apparatus for supercritical production of nanoparticles

In materials science continuous flow supercritical fluid reactors are widely used for highly controlled synthesis of nanoparticles. The major limitation of continuous flow reactors is that the inherent distribution of residence times leads to broadening of the corresponding size distribution of the nanoparticles, and in addition it is not possible to carry out synthesis with very short or very long reaction times. Here, we report a new synthesis concept that we call pulsed synthesis, which removes the limitations of flow synthesis at the expense of a more complex reactor design and extensive computer control. Another limitation of flow synthesis is that it is largely a black box, where limited direct information is available of the specific chemical reactions taking place, the particle nucleation, the particle growth, etc. Such information is commonly obtained from in situ synchrotron and neutron scattering studies, but transfer of information from in situ studies with static reactors to laboratory flow reactor conditions is highly non-trivial. The new pulse reactor provides superior heating rates, arbitrary residence times with narrow distribution limited only by the pulse duration, and the ability of using the same reactor both for nanoparticle production and in situ synchrotron studies; thus eliminating the need for transfer of in situ information to laboratory reactor designs.     

Characteristic X-ray production cross-sections for standardless elemental analysis in EDX

Measurements have been made of cross-sections for the production of X-rays following ionization of the K-shell by fast electrons for a range of elements and incident electron energies. These data have been fitted to a simple functional expression for the ionization cross-section. This model, the Bethe model, includes two empirical fitting parameters. We found that a single universal pair of parameters may be used to allow the model to predict cross-sections with a mean error of ～ 7% and a maximum error of ～ 20% over the range of conditions considered. A relativistic form of the Bethe model yields a small improvement in accuracy for higher incident electron energies. Measurements have also been made of L-shell production cross-sections. It is expected that the Bethe model will apply also to the L-shell. Comparison of experimental and calculated K/L-shell cross-section ratios generally supports this, but uncertainties in the values in the literature for L-shell fluorescence yields precludes the drawing of any firm conclusions here.     

Multilayer Fresnel zone plate for soft X-ray microscopy resolves sub-39nm structures

Best resolutions in X-ray focusing are obtained to date by using diffractive lenses called Fresnel zone plates (FZPs). Their further improvement is nevertheless hindered by fundamental limitations in the employed manufacturing techniques. Here, we show a novel method to fabricate FZPs based on multilayer deposition with atomic layer deposition (ALD) and subsequent sectioning with focused ion beam (FIB). For the first time a multilayer FZP working in the soft X-ray range was prepared and could achieve the best resolution obtained so far for multilayer FZPs by resolving features below 39 nm in size in a scanning soft X-ray microscope. The new technique presents high potential for high resolution microscopy in both the soft and hard X-ray range.     

Simple procedure for the production of carbon-polymer support grids for use in X-ray microanalysis

A simple and rapid procedure for the production of low-cost carbon-polymer support grids is described. These grids are particularly useful for X-ray microanalysis of thin specimens because of their low X-ray background properties. The grids can be prepared for immediate use, which guarantees constant quality.     

The efficiency of X-ray production at low energies

The absolute efficiency of X-ray production has been determined for the K-lines of Al, Si and Cu; for the L-lines of Fe, Co, Cu, Ge and As; and for the M-lines of Hf, Ir, Pt, Au and Bi, using overvoltage ratios in the range 1–10. These emissions, with the exception of the Cu K, have critical excitation energies below 2.6 keV and are therefore typical of the lines used for X-ray microanalysis at low beam energies. For K-lines it is found that the experimental results are in good agreement with a Bethe, or a Casnati, cross-section model. For the L- and M-lines a Monte Carlo technique has been used to find an effective X-ray generation cross-section for each of the elements. The functional forms of these cross-sections are found to be in general agreement with proposed theoretical models.     

基于深度强化学习的流水线预测性维护决策

预测性维护是一种以设备工作状态为依据的维护决策方式,旨在降低维护成本的同时提高设备乃至生产系统的运作效率.针对考虑机器劣化过程的多机流水线,以产线性能评估为基础,分析系统运行过程中机器的维护时机,研究流水线预测性维护决策问题.首先,分析了机器故障和维护活动对系统状态转移过程的影响,基于马尔科夫链构建了流水线瞬态性能评估模型,揭示了机器故障和维护活动对生产过程影响的作用机理,量化了系统瞬态产出和在制品水平等性能指标.其次,综合考虑在制品库存成本、缺货惩罚成本和预测性维护成本,以最小化系统总成本为目标,基于马尔科夫决策过程建立了流水线预测性维护决策模型.利用所提的瞬态性能评估模型模拟流水线的实时运行过程,产生神经网络训练所需的数据,利用深度强化学习算法对问题进行近似求解,获得了有效的流水线预测性维护策略.仿真实验结果表明,所提预测性维护决策方法既保证了流水线产出,又降低了在制品库存和维护成本.     

纺染用烘干设备内筒的设计与制造

某纺机制造企业生产纺染用烘干设备,其内筒在设计与制造方面具有以下特点：封头直边加长且与筒体板厚悬殊又不同材质;制造了专用压头机预弯钢板;筒体与封头阍的连接采用搭接方式。由于简化了工艺降低了成本,从而提高了产品的经济性,可供相关厂家参考、借鉴。     

Photovoltaic X-ray detectors on the basis of GaAs epitaxial structures

The results of investigations of the properties of a new photovoltaic X-ray detector are presented. The detector was manufactured on the basis of a GaAs (p ⁺-n-n′-n ⁺) epitaxial structure, which was grown using the vapor-phase epitaxy method. The detector sensitivity to X-rays in a range of effective energies of 7–120 keV was measured. Multichannel linear X-ray detectors were developed and used in obtaining high-quality digital images.     

Microstructuring of optical surfaces: Technology and device for direct laser writing of diffractive structures

Results of development and testing of a scanning system of interference lithography are presented. The system is designed to form diffractive microstructures consisting of microgratings with a specified orientation, a size of 5–10 µm, and a period ranging from 0.6 to 1.5 µm. The total writing field of the system is 300 × 300 mm. The system is used to study direct laser writing of microgratings on chromium and amorphous silicon films applied by the method of magnetron sputtering onto the glass substrate surfaces. The device and technology of direct writing of microgratings can be further used to form antireflective subwave coatings of optical elements and graphical microstructured identification marks for product protection and also to manufacture diffractive attenuators of laser radiation.     

Composite replicas: Methodologies for direct evaluation of the relationship between intramembrane and extramembrane structures

Electron microscopic studies of membrane structure have been facilitated by the recent development of the composite replica technique in which the membrane is freeze-fractured, then inverted and the surface deep-etched and replicated. Examination in stereo of this composite preparation of two replicas with interposed half-membrane and associated surface elements reveals the physical relationship between structures on the surface and within the membrane. Composite replicas of the toad urinary bladder surface demonstrated connections of filamentous glycocalyx elements to intramembrane particles (IMPs). Using a bidirectional shadowing technique, many membrane surface particles also are shown to be associated with underlying IMPs, suggesting that these membrane surface particles are projections of the IMPs above the surface of the membrane. There is evidence that elements whose attachment sites relate to the half-membrane fractured away can be displaced from the membrane surface and lost. Labelling studies using colloidal gold-labelled antibodies were carried out to assess loss of surface mesh from fractured membrane. Gold distributions and amounts were similar in labelled surface replicas, label-fracture specimens, and labelled composite replicas, yet the amount of mesh detected in the composite replicas was less than in the surface replicas. This suggests that while some unlabelled or lightly labelled surface elements can be lost from fractured membranes, ligands stabilize elements and reduce their loss apparently by cross-linking them.     

Maskless laser direct imaging lithography using a 355-nm UV light source in manufacturing of flexible fine dies

This paper describes the results of the application of laser direct imaging (LDI) lithography for dimensional tolerance improvement through surface treatment of cutting edge in the flexible fine dies (FFD). Laser direct imaging lithography was successfully performed on AISI W1-8 substrates by a specifically designed laser system using UV 355 nm light source. The characteristics of patterned line width according to conditions such as scan speed and multi pass were investigated by optical microscope. The average line width of LDIed patterns was observed to be about 1 mm. The experimental results show that the line width of patterned samples was reduced with increasing scan speed and decreasing repetition number (R/N) of scanning. This conclusion proves the feasibility in the selectively application for manufacturing flexible fine die.