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1.
An original setup combining a very stable loading stage, an atomic force microscope and an environmental chamber, allows to obtain very stable subcritical fracture propagation in oxide glasses under controlled environment, and subsequently to finely characterize the nanometric roughness properties of the crack surfaces. The analysis of the surface roughness is conducted both in terms of the classical root mean square roughness to compare with the literature, and in terms of more physically adequate indicators related to the self‐affine nature of the fracture surfaces. Due to the comparable nanometric scale of the surface roughness, the AFM tip size and the instrumental noise, a special care is devoted to the statistical evaluation of the metrologic properties. The roughness amplitude of several oxide glasses was shown to decrease as a function of the stress intensity factor, to be quite insensitive to the relative humidity and to increase with the degree of heterogeneity of the glass. The results are discussed in terms of several modeling arguments concerning the coupling between crack propagation, material's heterogeneity, crack tip plastic deformation and water diffusion at the crack tip. A synthetic new model is presented combining the predictions of a model by Wiederhorn et al (J Non‐Cryst Solids, 353, 1582‐1591, 2007) on the effect of the material's heterogeneity on the crack tip stresses with the self‐affine nature of the fracture surfaces.  相似文献   

2.
Crystallization, mechanical properties, and workability are all important for the commercialization and optimization of silicate glass compositions. However, the inter-relations of these properties as a function of glass composition have received little investigation. Soda-lime-silica glasses with Na2O-MgO-CaO-Al2O3-SiO2 compositions relevant to commercial glass manufacture were experimentally studied and multiple liquidus temperature and viscosity models were used to complement the experimental results. Liquidus temperatures of the fabricated glasses were measured by the temperature gradient technique, and Rietveld refinements were applied to X-Ray powder diffraction (XRD) data for devitrified glasses, enabling quantitative determination of the crystalline and amorphous fractions and the nature of the crystals. Structural properties were investigated by Raman spectroscopy. Acoustic echography, micro-Vicker's indentation, and single-edge-notched bend testing methods were used to measure Young's moduli, hardness, and fracture toughness, respectively. It is shown that it is possible to design lower-melting soda-lime-silica glass compositions without compromising their mechanical and crystallization properties. Unlike Young's modulus, brittleness is highly responsive to the composition in soda-lime-silica glasses, and notably low brittleness values can be obtained in glasses with compositions in the wollastonite primary phase field: an effect that is more pronounced in the silica primary phase field. The measured bulk crystal fractions of the glasses subjected to devitrification at the lowest possible industrial conditioning temperatures indicate that soda-lime-silica glass melts can be conditioned close to their liquidus temperatures within the compositional ranges of the primary phase fields of cristobalite, wollastonite, or their combinations.  相似文献   

3.
Lateral nanoindentation provides access to the scratch hardness of glass surfaces. The specific sensitivity of the scratching experiment to surface mechanical properties can be enhanced when the local load at the tip apex is reduced. Here, we report on ramp-load scratch tests on a range of silicate glasses using a sphero-conical tip shape. Similar as with regular scratching experiments using sharp indenters, such tests create a sequence of micro-ductile, micro-cracking, and micro-abrasive regimes. Detailed investigation of the indenter displacement h and of the lateral force FL as recorded in situ, however, reveals pronounced deviations in comparison to Vickers or Berkovich scratching experiments. Most notably, this includes an abrupt increase in both h and FL at moderate normal load, marking the onset of ductile fracture, and a yield point at the transition from fully elastic deformation to the elastic-plastic regime at low load. For the range of examined silicate glasses, we find that structural cohesion controls yielding, whereas scratch-induced fracture and micro-abrasion are dominated by the volume density of bond energy.  相似文献   

4.
The fictive temperature of glass characterizes the glass network structure and its thermal history, and thereby can influence ion and water transport in the glass surface. In this study, IR specular reflectance (SR), refractive index, and density measurements were used to characterize and confirm the effects of glass sample processing, especially the fictive temperature/thermal‐history variations. The subsequent acid leaching of these glasses created leached surface layers due to interdiffusion and reaction of hydrous species in the surface; the hydrogen depth profiles obtained with secondary ion mass spectrometry (SIMS) confirmed enhanced leaching with increasing fictive temperature. Attenuated total reflectance (ATR) in the mid‐ and near‐IR indicated increases in both SiOH and H2O species with increasing fictive temperature. The relative intensities and shapes of the ATR peaks were found to vary between the samples suggesting that speciation of the hydrous reaction products (eg, strong and weakly hydrogen‐bonded OH) is also influenced by the original fictive temperature of the glass, but could not be quantitatively determined.  相似文献   

5.
The fracture toughness and thermal conductivity of soda-lime glass were enhanced by an interfacial precipitation of Ag. Large quantities of silver nanoparticles (AgNPs) are formed on the surface and subsurface layers of the Ag–Na ion exchanged glass powders during the heat-treatment in H2 for various times, and are fully densified by subsequent spark plasma sintering (SPS). The AgNPs with particle sizes above 50 nm are mainly located near the interfaces with the original glass particles, whereas smaller AgNPs are observed inside the glass particles. Moreover, the thickness of the precipitated Ag layer is seen to increase with increasing heat-treatment time. The incorporation of AgNPs is shown to enhance the fracture toughness of the soda-lime glass due to ductile deformation, crack deflection, and crack bridging. Finally, a maximum fracture toughness of 1.14 MPa m1/2, and a maximum thermal conductivity of 1.20 W m?1K?1, are obtained for the glass powders that were subjected to the entire process of ion-exchange, heat-treatment, and SPS densification.  相似文献   

6.
The glass transition temperature of the hard‐segment phase and the storage modulus of segmented polyurethane increased substantially in the presence of a small amount of tethered nano‐sized layered silicates from montmorillonite compared with their pristine state (by 44°C and by 2.8‐fold, respectively). Furthermore, the heat resistance and degradation kinetics of these montmorillonite/polyurethane nanocomposites were enhanced, as shown by thermogravimetric analysis. In particular, a 40°C increase in the degradation temperature and a 14% increase in the degradation activation energy occurred in polyurethane containing 1 wt % trihydroxyl swelling agent‐modified montmorillonite compared to that of the pristine polyurethane. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1741–1748, 2002  相似文献   

7.
The thermal activation energy u1 characterizing changes in crack velocity with temperature for fused silica in water is determined. The determination is based on a new analysis that incorporates the familiar Arrhenius term for thermally activated processes and a term characterizing the departure of the propagating crack system from fracture equilibrium. In determining u1 from experimental data, the Arrhenius term and the nonequilibrium term are of approximately equal magnitude. The analysis is applied to an extensive compilation of crack velocity measurements in fused silica to arrive at an estimate of u1 = (69 ± 11) kJ mol−1, where the value represents the multi-laboratory mean ± variability. This value is greater than that assumed in some earlier works and characterizes a typical within-laboratory increase in crack velocity of a factor of approximately 102 in fused silica between freezing and boiling water conditions and a decrease of a factor of 103 in component time to failure for the same change in conditions. The multi-laboratory variation in velocity at fixed temperature is comparable to the within-laboratory maximum increase, perhaps obscuring temperature effects.  相似文献   

8.
Multi-step heterogeneous phase chemical reaction schemes were used to develop different surface chemistries on nonporous glass substrates. Reliable analysis of the products of reaction was needed, because many of the functional groups introduced to the surface were intended to serve as reactive sites for further chemical tailoring to meet specific applications. Because the mass of the surface derivatization layer was only parts per million of the substrate mass, analysis of the reaction products was daunting. However, surface evaluation was accomplished by using several analysis methods in combination and by using the particular glass geometry most suitable to each analysis method.  相似文献   

9.
The effect of water contact on the propagation of microscale surface cracks is investigated in two types of glass: annealed and tempered glass. Initial flaw is artificially created on the glass surface using a Vickers indenter, and is covered with a water droplet for 20 min. Micrographs of the flaw taken before and after water contact confirms the increase in crack length from around 61–103 μm for thermally tempered glass. After water dipping, the maximum length to which the crack growth is approximately 57 % smaller in the thermally tempered glass than in the annealed glass. Despite the severe effect of water contact on crack propagation, it is found that the fracture strength is not substantially altered by water dipping; even though the crack length is enlarged, the fracture strength of glass is similar, and in the case of tempered glass, its fracture strength is slightly changed within 7% due to the blunting of the crack tip by water or others.  相似文献   

10.
In this work, the deformation and fracture behaviors of a commercial vinylester resin reinforced with fly ash were investigated. Tensile, compressive, and fracture tests were performed on the matrix and the composites with different ash content. Most composites exhibited improved stiffness, tensile strength, and fracture properties in comparison to the vinylester matrix. From scanning electron microscopic analysis of fracture surfaces, the toughening mechanisms of crack pinning, crack deflection, particle debonding, and localized shear yielding were identified. In addition, the dependence of tensile and compressive modulus and fracture energy toward ash content was adequately fitted by simple models available in the literature. From the results of these models and energy‐dispersive X‐ray spectroscopy analysis, some interaction between vinylester and ash seemed to exist. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013  相似文献   

11.
As a means to elucidate the mechanical stress effect on the durability of soda lime silicate (SLS) float glass, a thin glass plate under flexural stress was investigated with X-ray photoelectron spectroscopy (XPS), specular reflectance infrared (SR-IR) spectroscopy, nanoindentation, and tribo-testing. A lab-built four-point bending rig was employed to create compressive or tensile stress (around 40 MPa) on the air-side surface of SLS glass. XPS analysis showed that electric field-induced sodium ion migration is greatly enhanced in both compressive and tensile stress surfaces. The SR-IR analysis of the Si-O-Si stretch mode revealed that the structural distortion of the silicate network appears to be larger under compressive stress than tensile stress. The elastic and plastic responses of the SLS surface to nanoindentation were significantly altered under the flexural stress conditions even though the magnitude of the flexural stress was less than 0.7% of the applied indentation stress. Compared to the stress-free surface, the resistance to mechanochemical wear at 90% relative humidity deteriorated under the compressive stress condition, while it just became more scattered under the tensile stress condition. Even though the applied flexural stress was very small, its impact on chemical and structural properties could be surprisingly large. Combining all results in this study and previously published works suggested that the changes observed in nanoindentation and mechanochemical wear behaviors may be associated with the strain in the Si-O bonds of the silicate network.  相似文献   

12.
《Ceramics International》2022,48(5):6767-6779
The demands towards high precision and surface quality of ultra-thin glass for curved screens are continuously rising in the field of smart mobile terminals. Although the ultra-thin glass molding process (UTGMP) has the advantage of the shorter production cycle and higher efficiency, there are still typical forming defects in the molding process, namely crack, shape deviation, and large surface roughness. This paper aimed to investigate the influence mechanism of UTGMP molding temperature and pressure on the shape deviation, crack area, and surface quality of ultra-thin glass. In this study, a finite element model (FEM) was established to study typical forming defects of curved surfaces, and the effects of molding temperature and pressure on the shape deviation and crack area for ultra-thin glass were studied by the FEM simulation method. The simulation results revealed the molding temperature has a significant effect on the shape deviation, crack area and surface quality, while the molding pressure is only strongly correlated with shape deviation and crack area. In addition, the reliability of the model was verified by a series of five-level single factor experiments, and the shape deviation and crack area of ultra-thin glass were discussed in detail. Under the appropriate molding pressure and temperature range (0.45 MPa, 802–806 °C), the accuracy of curvature was improved by 33%, the roughness was reduced by 21%, and the probability of crack was also reduced. Thus, this study contributes to improving UTGMP's molding accuracy and reducing molding defects, and plays a positive role in reducing production costs and improving production efficiency.  相似文献   

13.
Poly(styrene‐co‐acylonitrile) was used to modify diglycedyl ether of bisphenol‐A type epoxy resin cured with diamino diphenyl sulfone and the modified epoxy resin was used as the matrix for fiber‐reinforced composites (FRPs) to get improved mechanical properties. E‐glass fiber was used as fiber reinforcement. The tensile, flexural, and impact properties of the blends and composites were investigated. The blends exhibited considerable improvement in mechanical properties. The scanning electron micrographs of the fractured surfaces of the blends and tensile fractured surfaces of the composites were also analyzed. The micrographs showed the influence of morphology on the properties of blends. Results showed that the mechanical properties of glass FRPs increased gradually upon fiber loading. Predictive models were applied using various equations to compare the mechanical data obtained theoretically and experimentally. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008  相似文献   

14.
The surfaces of glass fibers were sized by polyvinyl alcohol (PVA), polyester, and epoxy resin types in order to improve the mechanical interfacial properties of fibers in the unsaturated polyester matrix. The surface energetics of the glass fibers sized were investigated in terms of contact angle measurements using the wicking method based on the Washburn equation, with deionized water and diiodomethane as the wetting liquids. In addition, the mechanical behaviors of the composites were studied in the context of the interlaminar shear strength (ILSS), critical stress intensity factor (KIC), and flexural measurements. Different evolutions of the London dispersive and specific (or polar) components of the surface free energy of glass fibers were observed after different sizing treatments. The experimental result of the total surface free energies calculated from the sum of their two components showed the highest value in the epoxy‐sized glass fibers. From the measurements of mechanical properties of composites, it was observed that the sizing treatment on fibers could improve the fiber–matrix interfacial adhesion, resulting in improved final mechanical behaviors, a result of the effect of the enhanced total surface free energy of glass fibers in a composite system. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1439–1445, 2001  相似文献   

15.
The first step in accurately measuring the fracture toughness of a polymeric material is to generate a sharp crack in the sample. Often this is accomplished by tapping a razor blade into the sample, allowing a natural crack to grow; however, it can be difficult to control the crack propagation. Alternate methods for initial crack generation are investigated, including scoring the sample with a razor blade and inserting thin films or foils into the samples during cure. Fluoropolymer films and aluminum and stainless steel foils of various thicknesses are examined in a number of epoxy‐amine resins with a range of toughness and glass transition values. None of the alternative methods replicate the results of starting with a natural crack. Furthermore, it is difficult to form satisfactory test samples using fluoropolymer films. For relative toughness comparisons, either the scoring method or thin, ≤25.4 μm, foils can be used to initiate cracks with similar results. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44364.  相似文献   

16.
针状硅酸盐的表面改性及其橡胶复合材料的力学性能   总被引:2,自引:0,他引:2  
考察了不同改性剂及其用量对针状硅酸盐(FS)表面改性和FS/橡胶复合材料力学性能的影响。结果表明,FS存在结构羟基,其中一些羟基具有化学反应活性。硅烷偶联剂、钛酸酯偶联剂和十六烷基三甲基溴化铵对FS具有较好的改性效果。硅烷偶联剂Si69改性FS增强效果最好,其最佳用量为2.4质量份;改性FS用量的增加改善了复合材料的力学性能;改性FS对丁苯橡胶、三元乙丙橡胶、丁腈橡胶、羧基丁腈橡胶具有良好的增强效果。  相似文献   

17.
Acetyl tri‐n‐butyl citrate (ATBC) and poly(ethyleneglycol)s (PEGs) with different molecular weights (from 400 to 10000) were used in this study to plasticize poly(L‐lactic acid) (PLA). The thermal and mechanical properties of the plasticized polymer are reported. Both ATBC and PEG are effective in lowering the glass transition (Tg) of PLA up to a given concentration, where the plasticizer reaches its solubility limit in the polymer (50 wt % in the case of ATBC; 15–30 wt %, depending on molecular weight, in the case of PEG). The range of applicability of PEGs as PLA plasticizers is given in terms of PEG molecular weight and concentration. The mechanical properties of plasticized PLA change with increasing plasticizer concentration. In all PLA/plasticizer systems investigated, when the blend Tg approaches room temperature, a stepwise change in the mechanical properties of the system is observed. The elongation at break drastically increases, whereas tensile strength and modulus decrease. This behavior occurs at a plasticizer concentration that depends on the Tg‐depressing efficiency of the plasticizer. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1731–1738, 2003  相似文献   

18.
This work deals with surface modification of soda‐lime glass slides which, by itself, does not have hydroxyl groups at the surface. So, a glass surface pretreatment is needed, to create hydroxyl groups onto it, before carrying out the polypropylene (PP) grafting reaction. Different acid/base pretreatments were performed to develop an adequate concentration of superficial hydroxyl groups. Subsequently, a metallocenic polymerization (propylene‐α olefin graft reaction, catalyzed by EtInd2ZrCl2/methylaluminoxane), was carried out to provide graft‐PP chains chemically linked to the glass surface. The surface so modified can be further functionalized and tailored for different applications, including polymer composites. The pretreatment conditions that best preserved homogeneity and caused less damage to the glass surface resulted from a step of contact with dilute HF/NH4F buffer, a washing step with distilled water, and a final exposure to KOH. After the propylene copolymerization was performed, part of the graft copolymer formed remained chemically bonded to the glass slide surface. The presence of grafted PP at the surface was confirmed by SEM, FTIR, and EDAX characterization, even after the physically adsorbed polymer was excluded by a severe solvent extraction treatment. From these results, the copolymerization of a hydroxy α‐olefin, grafted on a MAO‐pretreated glass slide, is foreseen as a possible way to graft polymers onto inorganic solids. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008  相似文献   

19.
The mechanical and thermal properties of glass bead–filled nylon‐6 were studied by dynamic mechanical analysis (DMA), tensile testing, Izod impact, thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) tests. DMA results showed that the incorporation of glass beads could lead to a substantial increase of the glass‐transition temperature (Tg) of the blend, indicating that there existed strong interaction between glass beads and the nylon‐6 matrix. Results of further calculation revealed that the average interaction between glass beads and the nylon‐6 matrix deceased with increasing glass bead content as a result of the coalescence of glass beads. This conclusion was supported by SEM observations. Impact testing revealed that the notch Izod impact strength of nylon‐6/glass bead blends substantially decreased with increasing glass bead content. Moreover, static tensile measurements implied that the Young's modulus of the nylon‐6/glass bead blends increased considerably, whereas the tensile strength clearly decreased with increasing glass bead content. Finally, TGA and DSC measurements indicated that the thermal stability of the blend was obviously improved by incorporation of glass beads, whereas the melting behavior of the nylon‐6 remained relatively unchanged with increasing glass bead content. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1885–1890, 2004  相似文献   

20.
The dynamic mechanical properties of A‐glass bead filled polypropylene (PP)/ethylene–propylene–diene monomers polymer (EPDM) ternary composites have been measured over a temperature range from −80 °C to 100 °C and at a fixed frequency of 1 Hz, using a dynamic mechanical analyser (DMA), to identify the effects of the filler content and its surface treatment with a silane coupling agent on the dynamic viscoelastic behaviour. The results show that the storage modulus (Ec) and loss modulus (Ec) of these composites with 10% volume fraction of EPDM at 25 °C increase non‐linearly with increasing volume fraction of glass beads (ϕg). At the same test conditions, the Ec value of the PP/EPDM filled with pretreated glass beads is higher than that of the uncoated glass bead filled PP/EPDM system, especially at higher ϕg, while the difference in Ec between both systems is very small. The mechanical damping for the former decreases with increasing ϕg, but the opposite is true for the latter. The glass transition temperature of these composites varies irregularly with ϕg. The dynamic complex viscosity increases nonlinearly with an increase of ϕg. In addition, the interfacial structure between the matrix and inclusions has been observed by means of a scanning electron microscope. © 1999 Society of Chemical Industry  相似文献   

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