Nature of heterophase inclusions in high-purity optical fiber materials as studied with 3D laser ultramicroscopy

3D laser ultramicroscopy (3D LUM) is intended specially for determining the concentration and size distribution of submicron inclusions in the bulk samples of high-purity materials for visible and IR fiber optics. In this work the 3D LUM technique is shown to be able to identify the nature of individual inclusions detected. The measurement of the light scattered by an inclusion at a varied probe beam wavelength and polarization and at a varied scattered light collection angle makes it possible to determine the inclusion refractive index. The 3D LUM possibilities are illustrated by the example of studying the inclusion nature in the As₂S₃ glass samples prepared by the direct synthesis from elements in a quartz container at elevated temperatures.     

一种基于传像束的新型微三维形貌测量系统

文章根据结构光的测量原理提出了一种基于传像束的微三维形貌检测系统。充分利用传像束自由度大、能弯曲、易实现长度超过1m的光路等优点，在投射结构光条纹及摄取变形条纹图像时用它来代替传统的光学系统，从而使该系统比一般的微三维形貌测量系统多了内腔测量和远距离测量的功能。文中给出了实验结果，该系统的可行性得到了验证。     

Precise measurement of refractive index spectral dependence of optical materials for laser,fiber, and integrated optics

An interferometric technique for measuring the spectral dependence of the refractive index of solid-state materials to an accuracy of 10^?5 over the entire transparency region is described. The possibilities of the technique are demonstrated by the example of new phosphate glasses formulated for laser and fiber optics. It is shown that, in the presence of absorption bands in the transmission spectrum, the technique allows their associated jumps in the refractive index values to be recorded on the order of 10^?4?10^?5 and below. The shift in the spectral dependence of the refractive index in the region of the absorption band with intensity at 1.7 cm^?1 is measured for the first time.     

Preparation and characterization of gypsum-based materials used for 3D robocasting

In this study, gypsum-based materials (GM) comprising mainly α-hemihydrate gypsum, polycarboxylate, hydroxypropyl methyl cellulose and starch ether were prepared and used for 3D robocasting (3DR). The setting time and rheological properties of the GM slurry and the physical properties of the GM sample, including bulk density, porosity and mechanical strength, were investigated. The results indicate that the GM slurry exhibits an obvious shear thinning behavior and a good shape fidelity. The measured dynamic yield stress, final viscosity and initial storage modulus of the GM slurry are as high as 420.73 Pa, 7.29 Pa s and 273.86 kPa, respectively. Meanwhile, the GM slurry presents an adequate initial setting time of 68 min compared with a printing time of 14 min. In addition, the GM sample prepared by 3DR has a high compressive strength of 64.96?±?5.98 MPa and a bending strength of 15.24?±?1.58 MPa. These mechanical strengths are comparable with those of the GM and pure gypsum plaster sample prepared by traditional molding. Generally, the 3DR of GM is a promising method to improve the mechanical strength of printed gypsum products and presents great application prospects in the building of complex large-scale structures.     

A review of patented works on the mechanical characterization of materials at micro- and nano-scale

In recent years, the development of cost-effective processing techniques, novel design concepts and new materials paved the way to a widespread diffusion of micro- and nano-electro-mechanical systems (NEMS/MEMS). Obviously, the reliability as well as the performance of NEMS/MEMS depend on the corresponding materials properties, which in turn should be determined using ad-hoc small samples fabricated at the relevant size-scale. For this reason, in the last decade research efforts have been devoted to the development of experimental techniques suitable for the mechanical characterization of materials at micro- and nano-scale. There are many contributions stemming from this research area, the purpose of the present work is to give an overview of the most recent patented works. The focus will be directed to selected patents on the mechanical characterization of both micro- and nanosamples, like nanotubes and nanowires. Special emphasis will be given to the methods suited for the determination of elastic properties, fracture resistance and residual stresses of materials.     

Fast in situ 3D nanoimaging: a new tool for dynamic characterization in materials science

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Fabrication and mechanical characterization of 3D woven Cu lattice materials

3D metallic lattices designed to have two distinctly different material architectures have been woven with metallic Cu wires. A vacuum soldering technique was employed to metallurgically bond the wire nodes and form stiff 3D lattice materials. The structures and mechanical properties of the as-woven and soldered lattices were characterized by optical microscopy and micro-scale mechanical property experiments. The measured in-plane shear stiffness shows good agreement with predictions from finite element (FE) models that account for variations in the manufacturing and solder bonding. The study indicates that stiffness is influenced by the percentage of bonded nodes and the location of bonding. The 3D woven lattice materials manufactured in this study exhibited a very high percentage (80%) of bonded nodes and a unique combination of stiffness and density as compared to that typically reported for ultra lightweight lattice materials.     

A method to quantify the 3D microstructure of fibrous materials containing mineral fillers using X-ray microtomography: application to paper materials

This article proposed and validated an original and automatic method based on synchrotron X-ray microtomography to characterise non-destructively, in 3D, the mineral fillers that may be present in fibrous composite materials. The approach consists of (i) obtaining the 3D internal structure of the sample in a non invasive way, (ii) identifying the fillers in the 3D microstructure using appropriate image processing tools, (iii) calculating the filler content on the numerical data, and (iv) validating the representativity of the data sets by evaluating the representative elementary volume. This method was successfully applied in the case of paper samples. The numerical filler content were in good agreement with standards. This method opens new perspectives in terms of characterisation of filler spatial repartition.     

3D printing of smart materials: A review on recent progresses in 4D printing

ABSTRACT

Additive manufacturing (AM), commonly known as three-dimensional (3D) printing or rapid prototyping, has been introduced since the late 1980s. Although a considerable amount of progress has been made in this field, there is still a lot of research work to be done in order to overcome the various challenges remained. Recently, one of the actively researched areas lies in the additive manufacturing of smart materials and structures. Smart materials are those materials that have the ability to change their shape or properties under the influence of external stimuli. With the introduction of smart materials, the AM-fabricated components are able to alter their shape or properties over time (the 4th dimension) as a response to the applied external stimuli. Hence, this gives rise to a new term called ‘4D printing’ to include the structural reconfiguration over time. In this paper, recent major progresses in 4D printing are reviewed, including 3D printing of enhanced smart nanocomposites, shape memory alloys, shape memory polymers, actuators for soft robotics, self-evolving structures, anti-counterfeiting system, active origami and controlled sequential folding, and some results from our ongoing research. In addition, some research activities on 4D bio-printing are included, followed by discussions on the challenges, applications, research directions and future trends of 4D printing.     

A new method for meshless integration in 2D and 3D Galerkin meshfree methods

A method for the evaluation of regular domain integrals without domain discretization is presented. In this method, a domain integral is transformed into a boundary integral and a 1D integral. The method is then utilized for the evaluation of domain integrals in meshless methods based on the weak form, such as the element-free Galerkin method and the meshless radial point interpolation method. The proposed technique results in truly meshless methods with better accuracy and efficiency in comparison with their original forms. Some examples, including linear and large-deformation problems, are also provided to demonstrate the usefulness of the proposed method.     

Contactless nondestructive inspection method and measuring system for the thermophysical characteristics of materials, with adaptive compensation for heat loss

A new method with loss compensation is proposed for contactless measurements of thermal conductivity and heat capacity. A microprocessor unit for implementing the method is described in detail. Translated from Izmeritel'naya Tekhnika, No. 8, pp. 49–52, August, 1997.     

Scanning near-field optical nanotomography: a new method of multiparametric 3D investigation of nanostructural materials

A new experimental approach to multiparametric three-dimensional (3D) investigation of a broad class of composite nanostructural materials is developed on the basis of scanning near-field optical nanotomography (SNONT). Using this method, it is possible to simultaneously study the optical properties, 3D morphology, and distribution of the mechanical and electrical properties of the same region of a sample. The proposed method combines features of the confocal and near-field optical microspectroscopy (fluorescence and Raman spectroscopy) with a lateral resolution of up to 50 nm and scanning-probe microscopy. The possibility of studying the volume distribution of optical, morphological, electrical, and mechanical characteristics of a material with nanoscale resolution is related to the probing of sequential layers at a step of up to 20 nm and a total Z-scan depth of up to 3 mm. In particular, the SNONT method has been used to study a liquid-crystalline polymer doped with fluorescent nanocrystals.     

Gas anti-solvent precipitation assisted salt leaching for generation of micro- and nano-porous wall in bio-polymeric 3D scaffolds

The mass transport through biocompatible and biodegradable polymeric 3D porous scaffolds may be depleted by non-porous impermeable internal walls. As consequence the concentration of metabolites and growth factors within the scaffold may be heterogeneous leading to different cell fate depending on spatial cell location, and in some cases it may compromise cell survival.In this work, we fabricated polymeric scaffolds with micro- and nano-scale porosity by developing a new technique that couples two conventional scaffold production methods: solvent casting-salt leaching and gas antisolvent precipitation. 10–15 w/w solutions of a hyaluronic benzyl esters (HYAFF11) and poly-(lactic acid) (PLA) were used to fill packed beds of 0.177–0.425 mm NaCl crystals. The polymer precipitation in micro and nano-porous structures between the salt crystals was induced by high-pressure gas, then its flushing extracted the residual solvent. The salt was removed by water-wash. Morphological analysis by scanning electron microscopy showed a uniform porosity (~ 70%) and a high interconnectivity between porous. The polymeric walls were porous themselves counting for 30% of the total porosity. This wall porosity did not lead to a remarkable change in compressive modulus, deformation, and rupture pressure. Scaffold biocompatibility was tested with murine muscle cell line C2C12 for 4 and 7 days. Viability analysis and histology showed that micro- and nano-porous scaffolds are biocompatible and suitable for 3D cell culture promoting cell adhesion on the polymeric wall and allowing their proliferation in layers. Micro- and nano-scale porosities enhance cell migration and growth in the inner part of the scaffold.     

Electrodeposition in capillaries: bottom-up micro- and nanopatterning of functional materials on conductive substrates

A cost-effective and versatile methodology for bottom-up patterned growth of inorganic and metallic materials on the micro- and nanoscale is presented. Pulsed electrodeposition was employed to deposit arbitrary patterns of Ni, ZnO, and FeO(OH) of high quality, with lateral feature sizes down to 200-290 nm. The pattern was defined by an oxygen plasma-treated patterned PDMS mold in conformal contact with a conducting substrate and immersed in an electrolyte solution, so that the solid phases were deposited from the solution in the channels of the patterned mold. It is important that the distance between the entrance of the channels, and the location where deposition is needed, is kept limited. The as-formed patterns were characterized by high resolution scanning electron microscope, energy-dispersive X-ray analysis, atomic force microscopy, and X-ray diffraction.     

溶胶-凝胶法纳米WO3材料的合成、表征及气敏性能

采用溶胶-凝胶法制备了一系列掺杂有SiO2的WO3纳米粉体,通过TEM、XRD等分析手段对产物粉体的粒度、晶相结构进行了表征,测试了材料的气敏性能,探讨了煅烧温度、掺杂量、工作温度对材料气敏性能的影响。结果表明：适量SiO2的掺杂有利于提高WO3对NO2气体的灵敏度,其中掺杂量为3％（质量分数）的气敏元件在较低的工作温度下气敏性能突出。     

3D printing in X-ray and Gamma-Ray Imaging: A novel method for fabricating high-density imaging apertures

Advances in 3D rapid-prototyping printers, 3D modeling software, and casting techniques allow for cost-effective fabrication of custom components in gamma-ray and X-ray imaging systems. Applications extend to new fabrication methods for custom collimators, pinholes, calibration and resolution phantoms, mounting and shielding components, and imaging apertures. Details of the fabrication process for these components, specifically the 3D printing process, cold casting with a tungsten epoxy, and lost-wax casting in platinum are presented.     

X-ray computed microtomography and 2D image analysis for morphological characterization of short lignocellulosic fibers raw materials: A benchmark survey

Optimizing the performance of lignocellulosic fibers often requires relating mechanical behavior or morphological characteristics to microstructure. X-ray computed microtomography (X-ray CT), which provides 3D images with a high level of detail at both the micro- and macro-scales, may overcome these difficulties. This work provides a comparative analysis of the potential of X-ray CT (3D) and an office scanner (2D) for morphological characterization of lignocellulosic fibers. To this end, three specimens of lignocellulosic fiber materials obtained after the first decortication of the plant were retained. X-ray CT and 2D scanning correlations of sample diameter distributions are presented. The general aspects of the fibers diameter correlation are discussed. Image analysis was used to assess the potential and limitations of both the X-ray CT and 2D scanning methods based on the experimental work, and the main conclusions of the benchmark study are given in a table.