Preparation and Characterization of Microcapsules for Self-healing Materials

The urea-formaldehyde（UF） capsules filled with a healing agent, a mixture of epoxy resins（epoxy 711 and E-51） as core material, were produced by means of one step in-situ polymerization. The characteristics of these microcapsules were studied via scanning electron microscopy（SEM）, particle size analysis, FTIR and DSC/TGA. The results show that the dispersed and integrated microcapsules of 5 μm in shell thickness were synthesized successfully. The capsules were produced with diameters ranging from 10 to 250 μm via controlling agitation rate. Young＇s modulus of the capsule was a little lower than those of the epoxy resins, but the microcapsules having such a shell thickness were robust enough to survive handling during manufacturing self-healing composites. When damage occurred in the epoxy matrix, the crack could rupture the microcapsule to make the repairing agent release.

Application Research on Self-healing Technology with Microcapsules for Automobile Brake Pad

In order to improve the performance of non-asbestos composite auto brake pads that are composed of matrix resin, reinforced material and fillers, a novel method with new technology of self-heal microcapsules was proposed. Nano reinforced fillers＇ effects were also considered in the experiment project. Five recipe designs for new composite auto brake pads were carried out and cor-responding samples were prepared as well. The friction coefficient and wearing properties at certain temperature, impact intensity and hardness were comparatively studied. Investigations indicate that properties of such composite auto brake pads meet the requirements of the national standards while microcapsule＇s weight content varies from 5.5wt%-1.09wt% of matrix resin and microcapsule＇s loca-tion varies in the pads. Nano reinforced fillers have the effects of increasing composites＇ impact in-tensity and hardness. Application of self-healing microcapsules in auto brake pads is feasible.

Characteristics of Self-Healing Microcapsules for Cementitious Composites

Urea formaldehyde/epoxy resin microcapsules were prepared by an in situ polymerization method and the effect of emulsifier on the syntheses process of the microcapsules was discussed. The surface morphology of the microcapsules was observed by optical microscopy and scanning electron microscopy（SEM）. Chemical structure was characterized by Fourier transform infrared spectroscopy（FTIR）. Thermal stability was obtained using simultaneous thermal analysis（STA）. The microcapsules were composed of urea-formaldehyde resin shell and epoxy resin core. Emulsifier played an important role in the polymerization process when the core material was packed by pre-polymer, so the effects of different emulsifiers（OP-10, SDS and SDBS） were discussed respectively. Results showed that the particle size of the microcapsules was uniform when SDBS as an emulsifier. Microcapsules showed good thermal stability below 240 ℃ and the initial decomposition temperature of the microcapsules was 265 ℃. The core materials released after microcapsules rupturing, which could be proven by the images of SEM. When implanted in cementitious composites, complete shape of microcapsules and good interface between microcapsules and cement specimen substrate could also be observed.

Self-Healable and Stretchable PAAc/XG/Bi_(2)Se_(0.3)Te_(2.7) Hybrid Hydrogel Thermoelectric Materials

Thermoelectric power generators have attracted increasing interest in recent years owing to their great potential in wearable electronics power supply.It is noted that thermoelectric power generators are easy to damage in the dynamic service process,resulting in the formation of microcracks and performance degradation.Herein,we prepare a new hybrid hydrogel thermoelectric material PAAc/XG/Bi_(2)Se_(0.3)Te_(2.7)by an in situ polymerization method,which shows a high stretchable and self-healable performance,as well as a good thermoelectric performance.For the sample with Bi_(2)Se_(0.3)Te_(2.7)content of 1.5 wt%(i.e.,PAAc/XG/Bi2Se0.3Te27(1.5 wt%)),which has a room temperature Seebeck coefficient of-0.45 mV K^(-1),and exhibits an open-circuit voltage of-17.91 mV and output power of 38.1 nW at a temperature difference of 40 K.After being completely cut off,the hybrid thermoelectric hydrogel automatically recovers its electrical characteristics within a response time of 2.0 s,and the healed hydrogel remains more than 99%of its initial power output.Such stretchable and self-healable hybrid hydrogel thermoelectric materials show promising potential for application in dynamic service conditions,such as wearable electronics.

一种高效的Long-Lived Self-Healing密钥分发机制

对Staddon等人提出的self-healing密钥分发方案作了3个方面的改进:第一,提出了一种更高效的无条件安全的long-lived方案取代基于计算安全的long-lived方案,降低了计算复杂度和通信复杂度;第二,增强了用户恢复合理密钥的能力,使得在某个特殊场景中,用户可以恢复出合理密钥;第三,降低了广播消息的次数和存储在用户端的私人密钥数目.

Self Healing Capacity of Asphalt Binders

To test self healing capability of asphalt binders,three asphalt specimens（pure asphalt,modified asphalt and aged asphalt） were prepared.Every specimen was tested by dynamic shear rheometer（DSR）.The temperature sweeps result indicates that both aging and SBS modifying influence the self healing capability of asphalt binder.The fatigue-heal-fatigue test was introduced to study the self healing capability of asphalt in its serving periods.Furthermore,three different periods（0.5 h,1 h,3 h） were set up to study the influence of rest time on fatigue time.It is concluded that longer rest time,less load will delay the appearance of cracks and extend the service life of asphalt binders.

Self-healing Action of Permeable Crystalline Coating on Pores and Cracks in Cement-based Materials

The self-healing action of a permeable crystalline coating on the po rous mortar was investigated by two times impermeability test. Moreover, the sel f-healing mechanism of cement-based materials with the permeable crystalline c oating was studied by SEM. The results indicate that the permeable crystalline c oating not only seals the pores and cracks in mortar during its curing process, but also heals the permeable pathway caused by first impermeability test or crac ks produced by freeze-thaw cycles. Therefore, cement-based materials can be im proved by the permeable crystalline coating for the self-healing function. SEM images prove that the self-healing function is realized by generating a great q uantity of non-soluble dendritic crystalline within the pores and cracks, which prevents the penetration of water and other liquids.

Distribution of Calcium Carbonate in the Process of Concrete Self-healing

The complete deposition distribution process of calcium carbonate is summarized in three directions of cracks. Distribution of calcium carbonate in the self-healing process of microbial concrete is studied in detail, with the help of a variety of analytical techniques. The results show that carbonate deposits along the x-axis direction of the cracks. The farther from the crack surfaces of concrete matrix in x-axis direction, the more the content of the substrate, the less content of calcium carbonate. Gradual accumulation of calcium carbonate along the y-axis direction is like building a house with bricks. Different repair points are gradually connected, and ultimately the whole of cracks are completely filled. In the z-axis direction, calcium deposits on the surface of fracture direction, when the crack is filled on the surface, because the internal crack hypoxia in the depths of cracks hardly produces calcium carbonate.

Self-healing of Cracks in Concrete with Various Crystalline Mineral Additives in Underground Environment

Cracks can deteriorate mechanical properties and/or durability of concrete. A few studies have shown that, cracks can autogenously heal under a certain conditions besides the traditional passive repair with a deliberate external intervention. For underground concrete structures, the presence of water, as a necessity for chemical reactions of the healing additives, is beneficial to healing concrete. In this paper, a natural healing method by mineral additives was developed according to the chemical and physical characteristics of underground environment. The healing capacity of three different crystalline mineral materials classified namely, carbonate, calcium sulphoaluminate expansive agent and natural metakaolin due to permeation- crystallization, expansion and pozzolanic reaction, has been assessed from the mechanical properties, referring to the relative elastic modulus, the strength restoration, and the water permeability of the healed specimens. In addition, the morphology of the healing products in the vicinity of the crack was observed. The results indicate that the specimens incorporated with the three mineral additives show different healing capacity according to the improved mechanical properties and permeability. The permeability of the host matrix decreased a lot after crack healing by natural metakaolin followed by carbonate whereas no noticeable improvement of water permeability has been observed for the specimens mixed with expansive agent. The specimens incorporated with carbonate show the best mechanical restoration in terms of relative elastic modulus and compressive strength. Although the dominate element is CaCO3 by reaction of CO32-, either from the dissolved CO2 or from the additives, and Ca2＋ in the cementitious system to fill the cracks, the healing capacity depends greatly on the morphology and the properties of the newly formed products.

Self-healing Performance of Composite Coatings Prepared by Phosphating and Cerium Nitrate Post-sealing

The phosphated and cerium nitrate post-sealed galvanized steel was firstly scratched to expose zinc layer and then placed in neutral salt spray （NSS） chamber for different durations. The microstructure and compositions of the scratches were investigated using SEM and EDS. The phases of the corrosion products were examined through XRD. The self-healing mechanism of the composite coatings was discussed. The experimental results show that the composite coatings have an excellent corrosion resistance. The corrosion products increase with corrosion time and finally cover the whole scratch. They contain phosphorous, cerium, oxygen, chloride and zinc, and are fine needle and exceedingly compact. The composite coatings are favorable self-healing. During corrosion, the self-healing ions such as Ce3＋, Ce4＋, PO43-, Zn2＋ in the composite coatings were dissolved, migrated, recombined, and covered the exposed zinc, impeding zinc corrosion. The self-healing process of the scratches on the composite coatings can be divided into three stages, about 2 h, 4 h, and 24 h, respectively.

One-pot preparation and applications of self-healing,self-adhesive PAA-PDMS elastomers

A new family of transparent,biocompatible,self-adhesive,and self-healing elastomer has been developed by a convenient and efficient one-pot reaction between poly(acrylic acid)(PAA)and hydroxyl-terminated polydimethylsiloxane(PDMSOH).The condensation reaction between PAA and PDMS-OH has been confirmed by attenuated total reflection Fourier transform infrared(ATR-FTIR)spectra.The prepared PAA-PDMS elastomers possess robust mechanical strength and strong adhesiveness to human skin,and they have fast self-healing ability at room temperature(in^10 s with the efficiency of 98%).Specifically,strain sensors were fabricated by assembling PAA-PDMS as packaging layers and polyetherimide-reduced graphene oxide(PEI-rGO)as strain-sensing layers.The PAA-PDMS/PEI-rGO sensors are stably and reliably responsive to slight physical deformations,and they can be attached onto skin directly to monitor the body’s motions.Meanwhile,strain sensors can self-heal quickly and completely,and they can be reused for the motion detecting after shallowly scratching the surface.This work provides new opportunities to manufacture high performance self-adhesive and self-healing materials.

Evaluation on Self-healing Mechanism and Hydrophobic Performance of Asphalt Modified by Siloxane and Polyurethane

In order to inhibit and remove the thin ice and extend the lifetime of the damaged bridge, the self-healing mechanism and hydrophobic performance of asphalt modified by siloxane and polyurethane (ASP) were studied by dynamic shear rheology (DSR), fluorescence microscope (FM), atomic force microscope (AFM), the fracture-healing-re-fracture test and molecular simulations. The experimental results indicated that the selfhealing capability of ASP increased with increasing heating time and temperature. Furthermore, the addition of siloxane could improve the reaction energy barrier and complex modulus, and it is believed that the self-healing is a viscosity driven process, consisting of two parts namely crack closure and properties recovery. Contact angle of ASP increased with the increasing siloxane content and it deduced that the siloxane could improve the hydrophobic performance of ASP and the ASP molecule model could simulate well the self-healing mechanism and hydrophobic performance of ASP.

A Survey about Self-Healing Systems (Desktop and Web Application)

The complexity of computer architectures, software, web applications, and its large spread worldwide using the internet and the rapid increase in the number of users in companion with the increase of maintenance cost are all factors guided many researchers to develop software, web applications and systems that have the ability of self-healing. The aim of the self healing software feature is to fast recover the application and keep it running and available for 24/7 as optimal as possible. This survey provides an overview of self-healing software and system that is especially useful in all of those situations in which the involvement of humans is costly and hard to recover and needs to be automated with self healing. There are different aspects which will make us understand the different benefits of these self-healing systems. Finally, the approaches, techniques, mechanisms and individual characteristics of self healing are classified in different tables and then summarized.

Epoxy Thermosets with Self-Healing Ability

A hybrid epoxy resin with intrinsic self healing properties has been prepared from a bifunctional Diels-Alder (DA) adduct. The obtained network, based on conventional Diglycidyl ether of BisphenolA (DGEBA) and DA epoxy, leads to simultaneous tuning of physical-chemical properties and healing capability. The self-repairing behavior has been verified by means of scratch recovery observation and micromechanical analysis. A satisfactory morphological and mechanical recovery has been achieved by thermal stimulus, leading to very promising application in the field of adhesives and structural applications.

Design of an Intelligent Self-Healing Smart Grid using a Hybrid Multi-Agent Framework

This paper discusses the applications of a hybrid multi-agent framework for self-healing applications in an intelligent smart grid system following catastrophic disturbances such as loss of generators or during system fault.The proposed hybrid multi-agent framework is a hybrid of both centralized and decentralized scheme to allow distributed intelligent agent in the smart grid system to make fast local decision while allowing the slower central controller to judge the effectiveness of the decision made by the local agents and to suggest more optimal solutions.

Effect of Core Material on Breaking Behavior of Self-Bursting Microcapsules

Self-bursting microcapsules, which retain their shape when suspended in water but burst quickly after the water evaporates, were proposed in a previous report. In this report, the effect of core materials on the bursting mechanism was studied. Five kinds of solvents were used as core materials, microencapsulated with polyurethane via an interfacial polymerization method. It was found that the self-bursting ratio was proportional to the measured dielectric constant of the core material. Thus, the solvents with a higher dielectric constant had an effect on the wall material to a greater extent. Furthermore, the self-bursting ratio was able to be predicted using the “organic conceptual diagram.”

An Average Distance Based Self-Relocation and Self-Healing Algorithm for Mobile Sensor Networks

The sensing coverage of a wireless sensor network is an important measure of the quality of service. It is desirable to develop energy efficient methods for relocating mobile sensors in order to achieve optimum sensing coverage. This paper introduces an average distance based self-relocation and self-healing algorithm for randomly deployed mobile sensor networks. No geo-location or relative location information is needed by this algorithm thereby no hardware such as GPS is required. The tradeoff is that sensors need to move longer distance in order to achieve certain coverage. Simulations are conducted in order to evaluate the proposed relocation and self-healing algorithms. An average of 94% coverage is achieved in the cases that we are examined with or without obstacles.

Towards a self healing information system for digital libraries

An important area of focus in complex systems development is the capability to adapt to variable runtime environmental resources and to accommodate runtime system failures. The research in this area is broadly termed as “Self Healing” and has recently aroused increasing attention to complex systems. Digital libraries have gained popularity because of the richer features they provide compared to traditional libraries. As more users begin to use digital libraries, addressing downtimes of these valuable resources has become a high priority. Operating and providing access to digital content to anyone, anytime from anywhere in the world, results in a continued rise of administrative overhead for system monitoring and needs continuous human intervention. Given the volume of information and the huge infrastructure of modem libraries, continuous manual system administration is quite costly and not feasible. In this paper we propose a self healing digital library system as the solution to this problem and present the approach of adding self healing capabilities to an existing digital library project, the Digital Library of India （DLI）. We also propose a self healing framework that enables successful reuse of our approach to other architecturally similar digital library systems.

Experimental Studies of Self Healing Behaviour of Under-Aged Al-Mg-Si Alloys and 60Sn-40Pb Alloy Reinforced Aluminium Metal-Metal Composites

Experimental studies to demonstrate self healing potentials of Al-Mg-Si alloy were undertaken in this research work. Self healing exploring secondary precipitation in the Al-Mg-Si alloy and use of low melting metallic alloy reinforcement (60Sn-40Pb alloy) were used as basis for the investigation. For the precipitation study, the Al-Mg-Si alloy was under-aged at temperature of 160oC for 10 minutes and then subjected to second step ageing treatment at four different temperatures within the range of 25oC and 70oC. In the 60Sn-40Pb alloy reinforced Al-Mg-Si alloy study, the samples were prepared in pre-cracked state and then subjected to healing heat-treatment at 250oC. For all cases tensile test and healing efficiency was used to analyze the results generated. It was observed that a second step thermal ageing at 50oC resulted in peak improvement in tensile strength, yield strength, toughness and percent elongation while ageing above this temperature lead to a drop in the tensile properties in comparison to that of the sample not subjected to a second ageing treatment. Also the use of 60Sn-40Pb alloy as reinforcement in the Al-Mg-Si alloy resulted in a healing efficiency of 91% after pre-cracking and heat-treatment. The satisfactory bonding between the 60Sn-40Pb alloy and the Al-Mg-Si alloy matrix contributed to the high healing efficiency observed.

Usage as Complementary Correspondence Analysis and Logistic Regression in a Scientific Survey on Self Healing Methods

The aim of this study is to show complementary usage of logistic and correspondence analysis in a research subject to self-healing methodologies. Firstly, the number of the variables is reduced by logistic regression according to relationship between dependent and independent variables and then research carries on searching variables. The relationship among the behaviours of individuals and their demographic characteristics is modelled by logistic regression and shown graphically by correspondence analysis. In application, first of all, the effect of age, sex, marital status, education level, occupation and income level and present health condition, on appreciating self-health, is explained by a model. As a result of that model, it can be said that the effect of age, occupation and present health condition is reasonable. After analysing that model, the relationship between categorical variables (age, sex, occupation, preferred precautions, and worth of personal health) is shown graphically by multiple correspondence analysis.