Larger Stabilizing Particles Make Stronger Liquid Marble

Understanding the mechanical stability of granular‐armored liquid marbles is prerequisite for their applications including encapsulation, sensors, microreactions, and miniaturized liquid storage. Most liquid marbles are armored with agglomerated granular structure which complicates the wetting and interacting states of particles, hence, impeding one from understanding the effect of granular size on the mechanical stability of marbles. In this work, using a custom‐built platform to examine the liquid marbles armored by a single layer of uniform grains, it is revealed that larger microsized grains produce stronger liquid marble. This finding is attributed to the gravity‐induced capillary attraction which dominates the interaction of particles and provides additional tension to the granular network of the marble surface, which enhances the mechanical stability of marbles. In addition, different granular network structures are formed at the marble surface by using a binary mixture of monodisperse grains, and their effect on the mechanical stability of marbles is explored. The understandings offer important insights for application involving liquid marbles and provides guideline to formulate robust marble‐based products.     

液体弹珠的微流体操作及工程应用

微流体技术是一种精确操控和检测微量流体的新兴技术,广泛应用于生物、化学、材料等领域的实验及工程中.液体弹珠作为一种新兴的数字微流体平台在近几年快速发展.它是一种将疏水的微纳米级颗粒包裹在液滴表面形成的软物质,体积通常在几微升到几百微升之间.区别于构建特殊表面微结构或化学改性制备的超疏水表面,液体弹珠是通过颗粒层阻隔内部液体与载体的微观接触,构建类似于莱顿弗罗斯特液滴的结构来实现微量液体在固体或液体表面不润湿且稳定存在的目的.目前的研究已经证明液体弹珠拥有独特优越的物理性能,如液体弹珠表面的颗粒层将固-液接触转化为固-固和固-气接触,因此具有不粘的特性,与载体表面的摩擦很小,在很小的外力作用下就可以实现灵活移动且不污染弹珠内的液体和载体.当表面颗粒呈多层且致密分布时也并非完全阻隔外界环境,在很大程度上能够减缓内部液体的蒸发且具有良好的气体渗透性,而且液体弹珠具有较好的稳固性,往往能够承受30％的可逆线性弹性形变,这些性能使液体弹珠可以作为理想的数字微流体平台.液体弹珠的原材料十分丰富,从而决定了其性状具有灵活的可调控性,所用颗粒的疏水性和形状会直接影响液体弹珠的力学性能,例如棒状颗粒包裹的液体弹珠具有更大的刚度,链状颗粒包裹的液体弹珠具有优越的弹性性能.颗粒的化学性质可以按需赋予液体弹珠不同的响应特性,从而衍生出多种操控手段,主要方式包括静电力、磁力、自推进、光辐射、温度、超声等,完成液体弹珠的精确移动、定位、颗粒层开启和关闭以及释放内部液体的操作.以上特性使液体弹珠能够应用于各种工程中,在细胞组织和微生物的培养以及微型化学反应器方面具有很好的应用前景,同时还被广泛应用于传感器、制药和精密仪器等领域,例如光电传感、污水检测、微型胶囊制备、构建纳米复合透镜以及精准电化学沉积等.同时液体弹珠制备方法较简单,无需复杂仪器设备,具有很高的经济效益.本文结合近年来液体弹珠相关研究的发展现状介绍了液体弹珠的制备方法、结构特点、材料和不同于纯液滴的性质主要包括有效表面张力、力学稳定性和蒸发速率,归纳了几种主流操作控制液体弹珠移动和释放的手段并分析优势与不足,总结了目前液体弹珠在工程上的主要应用并对其未来的发展趋势和应用前景进行展望.     

Liquid marbles,formation and locomotion using external fields and forces

Liquid marbles may be traditionally formed by rolling a droplet on a bed of non-wetting particles resulting in encapsulation and stabilisation. Particles used in this process may range from nanometre to millimetre if handled with sufficient care. This method, however, runs the risk of droplet coalescence and is limited to non-wetting particles. Currently there exist some alternative methods of formulation including using electrostatics to either deliver a particle bed to the droplet or pull the droplet to the particles. The former has shown some promise in potential batch processes but is hindered by interparticle forces. Additional production methods include a form of blender, but this has shown to be unable to produce marbles of a narrow size distribution. Once formed, liquid marbles have demonstrated value as potential blood typing devices, as micro-reaction vessels due to the inherent barrier between the internal phase and the substrate whilst maintaining gas permeability, and as contaminant sensors. Liquid marbles also demonstrate a remarkable level of elasticity under compressive force and reduced evaporation rates when compared to bare water droplets, a function of the size and composition of the stabilising particles. In addition to this, liquid marbles have been proposed as actuators. Locomotion may easily be induced in these structures, using electrostatics, sound, magnetism or light depending on the particle/liquid combinations used in formation, and the environment of deployment. This review seeks to present and summarise recent advances in the field of liquid marble manufacture and methods for actuation. We also aim to highlight potential future avenues of further study within this arena.     

A Feasibility Study of Localized Electrochemical Deposition Using Liquid Marbles

A liquid marble is a droplet of liquid coated with microparticles or nanoparticles. A novel method of localized electrochemical deposition (LECD) using liquid marbles and the feasibility of application of this method in additive manufacturing/microrepair is studied. Controllability of the transportation of liquid marbles to any desired location by pick and place technique has been demonstrated by depositing a 3 × 3 grid pattern with 1 mm period using an in-house built CNC setup. Electrodeposition experiments performed at defective spots with liquid marbles confirm the feasibility of microrepair using this novel technique.     

Liquid marble interaction gate for collision-based computing

Liquid marbles are microliter droplets of liquid, encapsulated by self-organized hydrophobic particles at the liquid/air interface. They offer an efficient approach for manipulating liquid droplets and compartmentalizing reactions in droplets. Digital fluidic devices employing liquid marbles might benefit from having embedded computing circuits without electronics and moving mechanical parts (apart from the marbles). We present an experimental implementation of a collision gate with liquid marbles. Mechanics of the gate follows principles of Margolus’ soft-sphere collision gate. Boolean values of the inputs are given by the absence (FALSE) or presence (TRUE) of a liquid marble. There are three outputs: two outputs are trajectories of undisturbed marbles (they only report TRUE when just one marble is present at one of the inputs), one output is represented by trajectories of colliding marbles (when two marbles collide they lose their horizontal momentum and fall), this output reports TRUE only when two marbles are present at inputs. Thus the gate implements AND and AND-NOT logical functions. We speculate that by merging trajectories representing AND-NOT output into a single channel one can produce a one-bit half-adder. Potential design of a one-bit full-adder is discussed, and the synthesis of both a pure nickel metal and a hybrid nickel/polymer liquid marble is reported.     

切槽爆破技术在汉白玉石材开采中的应用研究

目前,随着世界高档石材市场的需求日益旺盛,控制爆破法切割汉白玉石材的应用研究得到了世界各石材大国的广泛重视.应用岩石断裂力学理论和爆生气体膨胀准静压理论,通过理论计算得到了适合切槽爆破切割汉白玉石材的基本爆破参数,并在现场实验中获得了较好的实验效果,对提高汉白玉石材开采效率起到了一定的指导作用.     

两条断续预制裂纹粗晶大理岩强度参数的研究

基于在岩石力学伺服试验机上得到的两条断续预制裂纹粗晶大理岩常规三轴压缩试验结果,采用Coulomb和Hoek-Brown强度准则,获得了断续预制裂纹粗晶大理岩的强度参数,评价了Coulomb和Hoek-Brown准则用于断续预制裂纹岩样强度分析的适用性。研究表明:完整岩样强度和围压之间的关系用Coulomb和Hoek-Brown准则均可以很好地表征,而断续预制裂纹岩样强度更好地符合Hoek-Brown强度准则。利用Hoek-Brown准则确定的粘聚力和内摩擦角也可以表征岩石材料真实的力学特性。断续预制裂纹岩样强度对围压的敏感程度高于完整岩样,计算得到的粘聚力显著低于完整岩样,而内摩擦角高于完整岩样。断续预制裂纹岩样的粘聚力以及内摩擦角与裂纹倾角关系复杂,单轴压缩强度是否参与回归影响较大。由Hoek-Brown准则得到的粗晶大理岩强度参数T(m,s)(联合回归均值)对完整岩样和断续预制裂纹岩样分别为T(6.542,0.99)和T(6.625,0.156),可知断续预制裂纹对岩石强度参数m(软硬程度)影响不大,而对参数s(破碎程度)存在较大影响。     

Tunable wettability on Pendelic marble: could an inorganic marble surface behave as a “self-cleaning” biological surface?

The sustainable protection of the Greek cultural heritage aims to strengthen Pendelic marble, to preserve its unique esthetic properties and its resistance to long weathering. Our main purpose was to design, apply, and study a system of controllable wettability appropriate to the hydrophilic nature of the surface of Pendelic marble. A very simple, cost effective, and easily reproducible method has been developed, to fabricate a composite protective hybrid nanostructured film via a bio-mimetic route. This is a modern technological method for self-cleaning surfaces mimicking nature’s phenomena and structures, such as the Lotus leaf hierarchical nano/microstructure. Our approach differs from the conventional conservation methods in that it is based on a top coating with nanostructured synthesis, consisting of a hydrophilic/hydrophobic silica mixture dispersed in organic solvents, applied by “alla prima” technique onto a fluorosilanic base matrix that has been coated onto Pendelic marble. The behavior of this new surface is critically examined in this document.     

Utilization of waste marble dust as an additive in cement production

In this experimental study, the usability of waste marble dust (WMD) as an additive material in blended cement has been investigated. For this purpose, waste marble dust added cements (WMDCs) have been obtained by intergrinding WMD with Portland cement clinker at different blend ratios: 2.5%, 5.0%, 7.5% and 10% by weight. 40 × 40 × 160 mm mortar prisms have been produced with the obtained cements. Strength tests have been carried out on mortar specimen at 7, 28, and 90 days. WMDCs have been compared to each other as well as to control cements of CEM I and CEM II with respect to their physical, chemical and mechanical properties. Obtained results showed that WMDCs conform to EN 197-1 standard and thus 10% WMD can be used as an additive material in cement manufacturing.     

Investigating the effect of using granite and marble as a building material on the radiation exposure of humans

The aim of this study was to comprehensively study the radiological hazards of granite and marble used as a building material in Egypt. The activity concentrations of (226)Ra, (232)Th and (40)K were determined using high-resolution hyper-pure germanium detectors in 25 samples of different types of commercially available granite and marble. The measured activity concentrations for these natural radionuclides were compared with the reported data for Egypt and other countries. In order to assess the radiological impact, the radiation hazard parameters such as radium equivalent activity (Ra(eq)) and hazard level index (I(γ)) were calculated. The internal and external dose rates due to natural radionuclides in granite and marble were also calculated. The data obtained were considered as helpful in regulating the use of building materials in Egypt.     

The Application of Critical Path Method (CPM) in Workflow Schema of Marble Processing Plants

The critical path method (CPM) is a widely applied technique in large-scale industrial project planning and control. Based on a detailed review of the current literature, no references have been found referring to the use of the CPM in marble processing plants and other industrial mineral plants. In this regard, this study proposes a new application area of CPM and suggests the implementation details of mineral processing workflows with particular emphasis on marble production facilities. In the study, the CPM is applied to marble processing plants for selecting an applicable production process and for determining the workflow schema in order to optimize the cost of operation and to effectively manage time. As a consequence of this analysis, a new production plan is proposed for medium-scale marble processing plants. A suitable marble processing plant has been built and taken into operation in accordance with the proposed plant plan. It has been observed that this plant has a higher production rate at a preferable capacity when compared to three other plants studied as a part of this research.     

基于HJC模型高温后大理岩SHPB实验数值模拟研究

为对高温后大理岩动态压缩实验结果进行验证并探索数值模拟方法,采用"参考-计算-试算-调整"的方法基于HJC本构模型对不同温度等级高温处理后大理岩材料模型参数进行确定,利用ANSYS/LS-DYNA数值模拟软件对高温处理后大理岩SHPB实验进行数值模拟,并将数值模拟结果与室内实验结果进行对比分析.结果表明,数值模拟结果与...     

Morphological and structural modulation of PbWO(4) crystals directed by dextrans

A facile, dextran-directed solution route for the morphology-?and structure-controlled synthesis of PbWO(4) crystals, such as monoclinic raspite PbWO(4) nanobelts and tetragonal stolzite PbWO(4) crystals with penniform and wheat-ear-like morphologies, has been demonstrated. Three differently charged dextrans were employed for the PbWO(4) crystallization and they turned out to be very effective in the morphological and structural modulation of PbWO(4) crystals, as evidenced by the scanning electron microscopy (SEM), transmission electron microscopy (TEM), x-ray diffraction (XRD) and Raman spectroscopy characterizations. In particular, novel monoclinic raspite PbWO(4) nanobelts were produced under the direction of anionic dextran with a suitable concentration, probably due to the specific interactions between SO(4)(2-) groups from anionic dextran molecules and Pb(2+) ions from PbWO(4) crystals. To the best of our knowledge, this is the first synthesis of monoclinic raspite PbWO(4) in the laboratory, which usually exists as a natural crystal. In addition, the photoluminescence properties of the obtained PbWO(4) crystals with different morphologies and crystal structures have been characterized and discussed, which provides useful information for the fundamental investigation and potential application of PbWO(4) crystals.     

Untersuchung des Erosionsverhaltens von silberbasierten Kontaktwerkstoffen mittels FIB‐Techniken

Microstructure investigations and arc erosion behaviour of silver‐based contact materials by focused ion beam technique The understanding of the degradation mechanisms of contact materials is a key issue for the development of new materials with enhanced durability. This can be achieved through the investigation of the microstructure modification caused by electrical arcs on the surface of contacts. In this work, the erosion behaviour of pure silver and silver based composites as well as the characterization in two or three dimensions is presented. Single breaking operations were performed with direct current. Using white light interferometry, the size of the craters on the surface as well as the volume of eroded material has been measured. By means of dual beam techniques, the microstructural modifications in the crater have been investigated and reconstructed in three dimensions.     

Microstructural study of material removal mechanisms observed in abrasive waterjet cutting of calcareous stones

An experimental study was conducted to determine the influence of material properties on the cutting mechanisms involved in abrasive waterjet (AWJ) of calcareous stones. SEM analysis was performed to investigate the material removal mechanisms. Two Portuguese calcareous stones were tested with different genesis and thus structural and mechanical characteristics.

It was found that rock hardness and porosity have a significant effect on the cutting mechanisms investigated. In harder homogeneous rocks, like marbles, cutting occurs due to intergranular cracking and cleavage of calcitic grains. In limestones, the material removal process mostly involves intergranular cracking and material sliding along the argilous matrix and between this and calcitic grains. Plastic deformation of the matrix can also be observed.     

A new hybrid photomultiplier tube as detector for scintillating crystals

In this work, we have attentively studied the performance of a new hybrid photomultiplier tube (HPMT) as detector for photons from scintillating crystals. The HPMT is equipped with a YAP window in order to improve light collection and increase measured light response from scintillating crystals. Several measurements have been performed on BGO, LSO, CsI(Tl) and NaI(Tl) planar crystals having three different surface treatments as well as on YAP : Ce and CsI(Tl) matrices. Such crystals have been coupled to two HPMTs, one equipped with a YAP window (Y-HPMT) and the other with a conventional quartz window (Q-HPMT). Measurements on crystals coupled to the Y-HPMT have shown a consistent improvement of the light response, thanks to the presence of the YAP window. Indeed, the light response measured with the Y-HPMT was on average equal to 1.5, 2.1 and 2.6 times that obtained with the Q-HPMT for planar crystals with white painted (diffusive), fine ground and polished rear surfaces, respectively. With regards to crystal matrices, we measured a light response increase of about 1.2 times.     

Electrochemical behaviour of molybdenum coated with flame CVD polycrystalline diamond film

Although natural diamond is a complete chemically-inert material for a wide range of aggressive environments, its comparative scarcity and problems for coating design have hampered its utility as a corrosion protective coating. The recent discovery and development of chemical vapour deposition methods for growing diamond crystals and polycrystalline diamond films has opened up a wide range of applications thanks to their excellent tribological, electronic and optical properties. Various applications are in progress for corrosion and combined wear and corrosion protection. This paper presents the first study of the corrosion behaviour of continuous polycrystalline diamond films using electrochemical impedance electroscopy. Diamond films have been deposited on molybdenum substrates by means of the acetylene flame combustion method (FCVD). Electrochemical behaviour has been studied in a 0.6 M NaCl solution, it being seen that despite the inert character and apparent continuity of the film, there are areas of the base material which are exposed to the electrolyte. This behaviour has been modelled by means of an equivalent circuit which allows for the corroboration of the proposed mechanism.     

Application of orientation imaging microscopy to study phase transformations in steels

In this investigation, the methodology, advantages, and limitations of using Orientation Imaging Microscopy (OIM) to study microstructures in multiphase steels are examined. In particular, proeutectoid ferrite precipitation has been investigated in a hypoeutectoid steel (Fe–0.12%C–3%Ni), while the proeutectoid cementite transformation has been studied in a hypereutectoid steel (Fe–1.3%C–13%Mn). By utilizing misorientation maps and inverse pole figure maps to determine the orientation differences between individual crystals, the internal morphology of the solid-state precipitates has been determined. What appear by other types of imaging to be monolithic single crystals are shown to be aggregates of finer crystals with misorientations between them. The relative quality of the Electron Backscatter Diffraction (EBSD) patterns has been correlated to specific phases and to interphase and grain boundaries using pattern quality maps (also referred to as image quality maps). These techniques have been adapted for quantitative identification of different microconstituents, including volume fraction measurements. By making comparisons among optical micrographs, conventional SEM micrographs, pattern quality maps, inverse pole figure maps, and misorientation maps, the advantages and limitations of different types of OIM mapping for studying different aspects of phase transformations in steels are elucidated.     

CO2 Laser Cutting of Calcareous Stones

Portugal is one of the major European producers of natural stones. In the last decade, transformation of stones has been privileged in most of the companies and the quantity of finished product for exportation increased with a major added value. New technologies and processes have been investigated. For example, CO₂ laser has been used for cutting, marking, and drilling. The major advantage of this tool is its flexibility, and thus, it improved the working environment significantly. This article presents a report on the use of CO₂ lasers in the cutting process of marbles and limestones. The cut quality was evaluated by adjusting the laser output power and assist gas type and pressure. The CO₂ laser can be used as a feasible tool for cutting ornamental stones. Due to the economic reasons, it is specially adequate for cutting nonlinear shapes where conventional cutting tools, such as the diamond wires and saws, have limitations on both the shape and the dimensions to be cut.     

An investigation on chain mobility in solid state polymer systems

In this paper we have investigated chain mobility in polyethylene below its melting temperature. The investigation techniques like atomic force microscopy (AFM), transmission electron microscopy (TEM), time-resolved small/wide angle X-ray scattering (SAXS/WAXS), time-resolved longitudinal acoustic mode (LAM) Raman spectroscopy have been used to follow the chain mobility within individual single crystals and regularly stacked crystals, as a function of temperature and time. Our observations on single crystals are that crystal thickness increases immediately on heating just above the crystallization temperature. In the regularly stacked polyethylene single crystals wherever the overlapping of at least two lamellae arises, thickening occurs during annealing via a mutual chain rearrangement between the adjacent crystals, which leads (ultimately) to a quantum increase, i.e., doubling, of the lamellar thickness. A model has been proposed to explain this quantum increase in the lamellar thickness. The fundamental findings have been extended for some applications.