Edge-strengthening of flat glass with acrylate coatings

Edge-strengthening is a novel technology used to strengthen glass by applying a coating only on the edges. In this work, edge flaws of flat glass articles were examined in detail via scanning electron microscope (SEM) imaging. Then the effect of using weatherable acrylate coatings on edge-strengthening of flat glass was determined. Four-point bending measurement showed that the coatings provided more than twofold increase of the mean flexural strength and a factor of about two increase of the tensile stress needed to reach 0.8% cumulative probability of failure. The coatings were found to cover the flaw zone at the glass edges and partially fill in the cracks. Different surface treatments led to different levels of strengthening, indicating the importance of coating adhesion. The coating’s thermal and mechanical properties affected the extent of strengthening effect. A coating formulation with a higher glass transition temperature tended to provide a better strengthening effect, indicating the importance of closure stress within cracks generated during film curing process. Challenges of applying the edge-strengthening technology are also discussed.     

The effect of preflux bath additives on the morphology and structure of the hot‐dip galvanized coatings

The effect of CdCl₂, NiCl₂ and SnCl₂ on the morphology and on the structure of hot‐dip galvanized coatings was examined with optical microscopy, scanning electron microscopy and X‐ray diffraction, when these salts are added in the preflux bath. From this investigation it turned out, that the morphology of the coatings formed after fluxing in a preflux bath containing CdCl₂ is very similar to the morphology of the coatings formed in the usual flux, regardless of the concentration of the Cd salt and the solvent used (water or aqueous solution containing 50% ZnCl₂^.NH₄Cl) in the preflux bath. By contrast, Ni enhances the growth of small‐sized crystallites of the zeta‐phase instead of the columnar growth, and finally it results in reduction of the coating thickness. This phenomenon is likely to be affected by the NiCl₂ concentration but not by the solvent used (pure water or aqueous solution containing 50% ZnCl₂^.NH₄Cl). Finally, Sn addition seems to be inert with regard to the coating structure. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

AES and FTIR characterization of sol–gel alumina films

In this work we obtained sol–gel alumina coatings on AISI 304 stainless steel substrates. Alumina sols were prepared by using aluminum isopropoxide (AI) as precursor, acetic acid (HOAc) as catalyst, ethanol (C₂H₅OH) or isopropanol (C₃H₈O) as solvent, and water. The as-prepared solutions were deposited on stainless steel substrates by means of the dip-coating technique. The obtained composites were characterized by Fourier transform infrared spectroscopy (FTIR) and Auger electron spectroscopy (AES). We observed that the concentration of AlO type bonds in the obtained alumina coatings depends on the solvent type used, temperature and peptization state of the sol, withdrawal speed, and number of dipping cycles. AES experiments showed that the interface formed between the alumina coating and substrate surface is in general formed by several layers of different chemical compositions.     

Study of the mechanical properties of two organic–inorganic hybrid systems: GPTMS/colloidal silica and GPTMS/TEOS

This work investigates the mechanical properties of different scratch resistant coatings, namely, a mixture of 3-glycidoxypropyltrimethoxysilane (GPTMS) with either colloidal silica particles or tetraethoxysilane (TEOS). Coatings were prepared by the hydrolysis and the condensation of the precursor's alkoxide (sol–gel process) with thermally catalyzed polymerization of epoxy ring of GPTMS. Dip deposition techniques were used on silicon substrate.The nanoindentation technique was used to analyze the force required to indent the coating with a diamond tip. At low forces, this technique, based on indentation depth, predicts the hardness and the elastic modulus of the coating, while at higher forces, cracks appear. Another analysis based on geometric approach, namely, the crack length, allows the determination of both coating and interface toughness.     

Temperature dependence of the tribological properties of laser re-melted Al-Cu-Fe quasicrystalline plasma sprayed coatings

The aim of this study was to investigate the effect of temperature on tribological properties of plasma-sprayed Al-Cu-Fe quasicrystal (QC) coating after laser re-melting treatment. The laser treatment resulted in a more uniform, denser and harder microstructure than that of the as-sprayed coatings. Tribological experiments on the coatings were conducted under reciprocating motion at high frequency in the temperature range from 25 to 650 °C. Remarkable influence of temperature on the friction behavior of the coating was recorded and analyzed. Microstructural analysis indicated that the wear mechanisms of the re-melted QC coatings changed from abrasive wear at room temperature, to adhesive wear at 400 °C and severe adhesive wear at 650 °C owing to the material transfer of the counterpart ball. It was also observed that the ratio of the icosahedral (i)-phase to β-Al₅₀(Fe,Cu)₅₀ phase in the coating was higher after test at 400 °C than that at 650 °C. The variation of the ratio i/β of coating and of the property of the counterpart ball and coating with the temperature are the two main factors influencing the wear mechanisms and value of the friction coefficient.     

Characterization and chemical durability of 70Ph2SiO·30TiO2 coating prepared by the sol-gel process

70Ph₂SiO·30TiO₂ coatings on slide glass and phosphate glass substrates have been prepared by the sol-gel process. Experimental results on the characterization and chemical durability of the coatings are presented. It is shown that the coatings heated at 150°C have reasonably good acid and water resistance while their alkali durability is very poor. The XPS results are used to verify the different corrosion behaviors of the coating in pure water and 1N HC1 solutions. The chemical durability of phosphate glass can be significantly improved by this coating.     

超声辅助脉冲电沉积Ni-TiN复合镀层制备工艺研究

采用超声辅助脉冲电沉积方法在45#钢表面制备NI-TiN复合镀层..利用X射线衍射仪(XRD)对复合镀层的物相组成进行检测分析,并利用原子力显微镜(AFM)、透射电镜(TEM)对Ni-TiN复合镀层的立体表面形貌及晶粒的分布进行观察分析.结果表明:当超声波功率为300 W时,所制备的Ni-TiN纳米复合镀层衍射峰强度最高,且含有Ni、TiN两相,Ni晶粒得到显著细化,TiN纳米颗粒分布较为均匀,无显著团聚现象发生.     

Performance and durability of octadecyltrichlorosilane coated borosilicate glass

While a coating may alter the surface properties and the performance of a material, it is unclear if these thin barrier layers can effectively inhibit environmentally-assisted cracking processes. In this research a nanoscale, hydrophobic film of octadecyltrichlorosilane was applied to bulk borosilicate glass rods. The resistance of the coated and uncoated rods to environmentally-assisted cracking was then evaluated in a room temperature, deionized water environment. While the coating procedure did not damage the glass surface or affect the probability of completing a successful test, it did not provide protection the glass samples against environmentally-assisted cracking. Analytical models based on linear elastic fracture mechanics suggest that the coating thickness must be on the order of the crack mouth opening displacement for the barrier layer to be effective. This finding suggests that nanoscale barrier coatings are best suited for micron and nanometer-scale substrates when superior structural performance is required.     

The theoretical growth form of potassium nitrate from an aqueous solution

The theoretical growth form the potassium nitrate, obtained from a PBC analysis, is compared to the growth forms obtained from aqueous solutions. The discrepancies are explained satisfactorily in a semi-quantitative way by taking the solvent interaction into account. It was assumed that the desolvation of the crystal surface determines the growth rate. The solvent interaction was obtained from molecular mechanics calculations on water molecules at the solvent accessible surfaces of the crystal faces. It was observed that the water molecules orient preferentially with their dipole moments parallel to the surface to form a “skin”, kept together by hydrogen bonds.     

Water diffusion coefficient measurements in deposited silica coatings by the substrate curvature method

The diffusion of water in silica coatings deposited by evaporation and physical vapor deposition (sputtering) is studied using the substrate curvature measurement technique. The diffusion of water into the coatings induced a swelling, which in turn caused bending (curvature) of the silicon substrate. The curvature change was measured in situ during a humidity increase from 0% to 95% at room temperature. The diffusivity of water in the sputtered silica coating was measured to be 10 × 10^?12 cm²/s and achieved equilibrium in about 10 min. The diffusion of water in the evaporated silica coating achieved equilibrium in about 2 min. Because the coatings exhibited very short equilibration times, the impact of a non-instantaneous humidity change on the calculated diffusion coefficients was also examined.     

溶液等离子喷涂氧化锆涂层力学性能的研究

采用溶液等离子喷涂技术(SPPS)制备了氧化钇部分稳定氧化锆(7YSZ)热障涂层(TBCs).热障涂层剥落失效的影响因素众多,其中很多都与涂层的力学性能相关.利用扫描电镜(SEM)、X射线衍射仪(XRD)和硬度计等研究了涂层的力学性能.结果表明,SPPS涂层的弹性模量约为58 GPa,硬度约为7 GPa,比大气等离子喷涂(APS)涂层高了15;左右;SPPS涂层的断裂韧性为1.8~2 MPa·m1/2,结合强度约为25 MPa.SPPS涂层因为低的孔隙率和更好的板条之间的结合带来了力学性能的提升.     

Investigation on sol–gel silica coatings for the protection of ancient glass: Interaction with glass surface and protection efficiency

To hinder the phenomenon of weathering of ancient stained glass, the present work proposes the application of sol–gel coatings to the glass surface. Previous investigations [1], [2], [3], [4], [5] and [6], in fact, show that sol–gel silica coatings do not change the appearance of artistic glasses when deposited on their surface. Moreover, the film thickness is so small (around 200 nm) and its composition and structure so compatible with that of the original glass, that the characteristics of the coating and original glass are not distinguishable. In this work, several recipes used to produce sol–gel coatings have been tested in order to understand their behavior when adopted for covering ancient weathered glass. The coatings are made of sol–gel silica prepared with two different catalysts: H⁺, Pb²⁺ and without catalyst. All the investigated samples show a good adhesion of the coating to the glasses used to simulate the behavior of ancient artefacts. The sol–gel silica coatings have been studied before and after accelerated ageing to test the resistance of the protective coatings to weathering. Another important index to test of the efficiency of the sol–gel coatings for the protection of an ancient glass is the lead ion mobility. In ancient stained glass, in fact, this element is present in the metallic lead network, in the grisaille paintings and constitutes a main component of many glass tesserae. The action of water on this highly mobile ion involves the degradation of the glass itself and the release of the ion in the rain solution. Ageing tests show the efficiency of H⁺ and Pb²⁺ catalyzed coatings and the inefficiency of the non-catalyzed sol–gel layers.     

MoB/CoCr金属陶瓷涂层的制备、组织结构及性能研究

利用低压等离子喷涂(LPPS)制备了MoB/CoCr金属陶瓷涂层.通过X射线衍射(XRD)分析物相组成、扫描电镜(SEM)、能谱(EDAX)对涂层的微观组织和成分进行分析,并对涂层的结合强度和抗热震性能进行研究.研究结果表明:粉末与喷涂后涂层物相差异不大,涂层为层状结构,随压力越高,粉末熔化越充分;涂层与基体结合良好,涂层致密;涂层喷涂后主要成分保持不变,且具有良好的结合强度和抗热震性能,经过1080 h熔融Al-12.07;Si腐蚀后,涂层完好,具有很好的抗腐蚀性能.     

Correlation between the substrate roughness and light loss for interference mirror coatings

The correlation between the parameters of multilayer mirror coatings used in ring laser gyroscopes with the roughness height of the substrate and top surface of mirror coating is investigated. A complex approach is applied to analysis of the roughness of substrates and mirror coatings, which is based on the use of atomic force microscopy and X-ray scattering. A correlation between the roughness of substrates and mirror coatings is established. In addition, the correlation between the scattering coefficient, reflectance, and transmittance of multilayer mirror coatings and the roughness of the substrates used is investigated.     

Effect of laser‐induced nanocrystallisation on the properties of electroless Ni‐P/Ni‐W‐P duplex coatings

This paper presents a comparative study of nanocrystallisation and the wear resistance of electroless plated Ni‐P/Ni‐W‐P duplex coatings with a single Ni‐W‐P coating before and after high‐ power diode laser treatment. Effects of the laser operating parameters on microstructures, in terms of crystallisation, porosity formation, phase transformation and grain growth, were investigated using scanning electron microscopy (SEM) with energy dispersive X‐ray spectroscopy (EDX) and quantitatively X‐ray Diffraction (XRD). Microhardness and wear behaviour of the coatings before and after laser treatment were evaluated by measurement of coating surface and cross‐section hardness as well as un‐lubricated friction and wear tests. The results revealed that in the case of laser treatment, the Ni‐P/Ni‐W‐P duplex coatings offered better wear resistance than the single Ni‐W‐P coating, while the as‐plated, single Ni‐W‐P coating showed better wear resistance than the Ni‐P/Ni‐W‐P duplex coatings. Adhesive wear mechanism prevails in the laser‐treated coatings when subjected to wear test against hardened steel material. The effects of microstructural characteristics in the coatings, in particularly the grain size of Ni₃P phase and the degree of crystallisation, on the adhesive wear behaviour have been investigated and found to be dominant besides the effect of hardness.     

Characterization of ion beam sputtered ZrN coatings prepared at different substrate temperatures

Zirconium nitride (ZrN) coatings were prepared on Si (100) by single ion beam sputtering in N₂ and Ar mixture at different substrate temperatures. Structure and morphology of the ZrN coatings were analyzed using X‐ray diffraction and atomic force microscopy. Rutherford backscattering technique was utilized for the determination of composition and thickness of the coatings. Electrical properties of the ZrN coatings were determined by four point‐ probe and Hall test. The results showed that the growth of ZrN with a preferred (111) orientation was achieved. The coating thickness depended on the substrate temperature and coating surface roughly remained smooth. The resistivity of the coatings varied from 1× 10^‐3 to 14× 10^‐3 Ω cm depending on the substrate temperature. A correlation between resistivity and charge carrier density was established to explain the electrical behavior of the coatings. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Relation between substrate surface morphology and microcrystalline silicon solar cell performance

In the present paper, the structural and electrical performances of microcrystalline silicon (μc-Si:H) single junction solar cells co-deposited on a series of substrates having different surface morphologies varying from V-shaped to U-shaped valleys, are analyzed. Transmission electron microscopy (TEM) is used to quantify the density of cracks within the cells deposited on the various substrates. Standard 1 sun, variable illumination measurements (VIM) and Dark J(V) measurements are performed to evaluate the electrical performances of the devices. A marked increase of the reverse saturation current density (J₀) is observed for increasing crack densities. By introducing a novel equivalent circuit taking into account such cracks as non-linear shunts, the authors are able to relate the magnitude of the decrease of V_oc and FF to the increasing density of cracks.     

Preparation and thermal properties of fire resistant metakaolin-based geopolymer-type coatings

Geopolymer-type coatings prepared by using an industrially available sodium silicate solution (SiO₂:Na₂O = 3.1) and metakaolin were applied to steel substrates. The coatings exhibited excellent adhesion to steel substrates achieving greater than 3.5 MPa tensile stress. Dissolution of the coating in water after 72 h of static testing varied between 12.8 and 34.5 wt.% depending on the water content of initial formulations. Coating formulations showed up to 3% thermal expansion after heating to 800 °C. Coatings maintained high structural integrity with steel substrates when subjected to a heat treatment by a gas torch and formulations calcined at 1000 °C for 1 h showed an X-ray amorphous structure.     

Influence of humidity on the electrical charging properties of cork agglomerates

Cork is a natural cellular and electrically insulating material which may have the capacity to store electric charges on or in its cell walls. Since natural cork has many voids, it is difficult to obtain uniform samples with the required dimensions. Therefore, a more uniform material, namely commercial cork agglomerate, usually used for floor and wall coverings, is employed in the present study. Since we know from our previous work that the electrical properties of cork are drastically affected by absorbed and adsorbed water, samples were protected by means of different polymer coatings (applied by spin-coating or soaking). Corona charging and isothermal charging and discharging currents were used to study the electrical trapping and detrapping capabilities of the samples. A comparison of the results leads to the conclusion that the most promising method for storing electric charges in this cellular material consists of drying and coating or soaking with a hydrophobic, electrically insulating polymer such as polytetraflouroethylene (Teflon^®).     

Charge separation at evaporation and vapor growth of ice and water

A mathematical model of the interface charging at evaporation and growth of ice and water phases from vapor is proposed. This model takes into account the competition between the two mechanisms of charge separation, one of which is based on protons and the other involves orientational defects. The first mechanism leads to the accumulation of a positive charge by ice and water during evaporation, while the second one provides negative charge accumulation. The protonic mechanism dominates at low velocities of the evaporation front with respect to the condensed phase material (lower than 10^?11–10^?9 m/s). At high rates, the mechanism based on orientational defects is dominant. When vapor is condensed, and, correspondingly, the ice and water phases grow, the charge polarity is opposite to the polarity in the case of evaporation. The proposed model adequately describes the experimentally observed interface electric current and the signs of phase charges during evaporation and condensation.