Effect of humidity on friction,wear, and plastic deformation during nanoscratch of soda lime silica glass

Physical flaws and defects on glass surfaces are known to reduce the mechanical strength and chemical durability of glass. The formation of surface defects depends not only on the mechanical conditions of the physical contact but also on the environment in which the contact is made. In this study, the nanoscratch behavior of soda lime silica (SLS) glass was investigated in 10% and 60% relative humidity (RH) conditions. Based on the evolution of friction and scratch depth, the deformation of SLS glass surface could be divided into four regimes: elastic deformation and recovery (E), RH-independent mild plastic deformation (P-1), RH-dependent intermediate plastic deformation (P-2), and RH-independent severe plastic formation (P-3). It is quite surprising to observe that plastic deformation of the glass surface has dependence on RH of the environment (outside the glass) because plastic deformation is the process occurring below the surface (inside the glass) by the externally applied load. From this result, it can be inferred that frictional energy dissipation mode at the sliding interface, which is a function of adsorbed water molecules, influences the subsurface deformation mode. Although friction, wear, and subsurface deformation/damage are all coupled, there is no direct one-on-one correlation among them.     

Differences in indentation and wear behaviors between the two sides of thermally tempered soda lime silica glass

Thermal tempering is an industrial process widely used to make soda lime silica (SLS) glass panels stronger and tougher. During the tempering process, the upper and bottom sides of the glass may experience different cooling rates, and thus, their properties could be different. This study characterized changes in surface composition and subsurface glass network structures as well as indentation and wear resistance properties of the air- and tin-sides of 6-mm-thick SLS window panels faced toward the upper and sliding roller sides during thermal tempering. The results showed that although the chemical and structural differences detected with X-ray photoelectron spectroscopy and specular reflection infrared spectroscopy are subtle, there are large differences in nanoindentation behaviors and mechanochemical wear properties of the SLS glass surface. The findings of this study provide further insights into the performance difference between the air- and tin-sides of the SLS glass panel treated with thermal tempering.     

Synergy between surface mechanochemistry and subsurface dissolution on wear of soda lime silica glass in basic solution

The polishing of oxide glass in aqueous solution is sensitive to not only the mechanical conditions applied by abrasives but also the chemistry of solution. This study elucidates the synergistic interactions of mechanical and chemical effects—especially, the synergetic effects of surface mechanochemical wear and subsurface dissolution are studied by measuring the material removal rate of soda lime silica (SLS) glass upon rubbing with a Pyrex glass ball in noncorrosive (neutral pH) in corrosive solutions (pH 10 and 13 NaOH) as a function of sliding speed. Based on the synergetic model of surface wear and subsurface dissolution, it is found that the mechanochemical surface reaction dominates the wear behavior of SLS glass in neutral and pH 10 solution conditions; the wear of SLS glass in pH 10 is enhanced, compared to the neutral pH case, due to the presence of OH^- ions at the sliding interface. In the case of pH 13, the dissolution of the densified subsurface region, which is formed due to interfacial friction during the surface wear, becomes significant, further enhancing the material removal yield. The finding provides an insight for designing an efficient polishing process in manufacturing of oxide glass materials with a good surface finish.     

Cracking mechanism in laser directed energy deposition of melt growth alumina/aluminum titanate ceramics

Thanks to its advantages of high efficiency and near-net shaping, laser directed energy deposition (LDED) is rapidly becoming a remarkable preparation technology for high-purity ceramics. However, the cracking problem in shaping process is always a great challenge for LDED to achieve industrial application. For this purpose, alumina/aluminum titanate melt-growth ceramics (A/AT MGCs) were prepared using LDED system, and the corresponding finite element thermal analysis model was developed. The solidification behavior and cracking mechanism of A/AT MGCs were investigated based on the thermal analysis model, and the influence of process parameters on the cracking characteristics was revealed with experiments. Results show that the crack morphology and distribution are controlled by microstructure and temperature gradient together. The scanning speed of 100–150 mm/min, with better microstructure and lower temperature gradient, is a preferred process window. This study provides theoretical guidance and technical support for the cracking suppression during LDED shaping of ceramics.     

Niobium carbide reinforced-Ti6Al4V composites via directed energy deposition

Directed energy deposition (DED) was used to produce niobium carbide (NbC)-reinforced Ti6Al4V (Ti64) metal–matrix-composite (MMC) structures. The objective was to improve upon Ti64's wear and oxidation resistance. The characterization techniques consisted of scanning electron microscopy (SEM), backscattered electron (BSE) imaging, energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction analysis (XRD), thermogravimetric analysis (TGA), Vickers micro- and nanoindentation-derived hardness, as well as tribological testing at varying normal loads. DED produced compositions were of Ti64, Ti64 + 5 wt.% NbC (5NbC), and Ti64 + 10 wt.% NbC (10NbC). Electron micrographs revealed crack- and delamination-free structures. Tribological analysis revealed a 25.1% reduction in specific wear rate. XRD and EDS results indicated the presence of a Ti-Nb solid solution. It was deduced that the NbC particles coupled with the Ti-Nb solid solution aided in increasing Ti64's resistance to plastic shear as the superficial microstructure remained unchanged compared to pure Ti64. Additionally, TGA displayed a reduction in total oxidation mass gain and suppressed oxidation kinetics to parabolic behavior with increased NbC. Application-based composite structures with site-specific mechanical properties were fabricated in the form of a composite cylinder, gear and compositionally graded cylinder. The graded cylinder displayed a 0%–45%NbC presence—end-to-end—equating to a hardness increase from 161.6 ± 4.0HV_0.2 to 1055.9 ± 157.4HV_0.2.     

Differences in surface failure modes of soda lime silica glass under normal indentation versus tangential shear: A comparative study on Na+/K+-ion exchange effects

The effects of exchanging Na⁺ with K⁺ on the mechanical and mechanochemical properties of a soda lime silica (SLS) glass were investigated. It is known that replacing smaller modifier ions with bigger ions in the silicate glass network, at temperatures below the glass transition (T_g), produces a compressive stress in the subsurface region that enhances resistance to mechanical damages. This study found that when Na⁺ ions in SLS are exchanged with K⁺ ions at 400°C, the hardness, indentation fracture toughness, and crack initiation load of the surface are increased, which is consistent with the chemical strengthening effect. However, the resistance to mechanochemical wear in a near-saturation humidity condition (relative humidity RH = 90%) is deteriorated. When K⁺ ions are exchanged back with Na⁺ ions at 350°C, the wear resistance in high humidity conditions is recovered. These results indicate that the improvement of mechanical properties under indentation normal to the surface is irrelevant with the resistance to mechanochemical wear under tangential shear at the surface. Based on the analysis of the surface chemical composition, silicate network structure, and hydrogen-bonding interactions of hydrous species in the subsurface region, it is proposed that the leachable Na⁺ associated with non-bridging oxygen and subsurface hydrous species in the silicate network play more important roles in the mechanochemical wear of SLS at high RH.     

Chemical structure and mechanical properties of soda lime silica glass surfaces treated by thermal poling in inert and reactive ambient gases

This study employed thermal poling at 200°C as a means to modify the surface mechanical properties of soda lime silica (SLS) glass. SLS float glass panels were allowed to react with molecules constituting ambient air (H₂O, O₂, N₂) while sodium ions were depleted from the surface region through diffusion into the bulk under an anodic potential. A sample poled in inert gas (Ar) was used for comparison. Systematic analyses of the chemical composition, thickness, silicate network, trapped molecular species, and hydrous species in the sodium‐depleted layers revealed correlations between subsurface structural changes and mechanical properties such as hardness, elastic modulus, and fracture toughness. A silica‐like structure was created in the inert gas environment through restructuring of Si–O–Si bonds at 200°C in the Na‐depleted zone; this occurred far below T_g. This silica‐like surface also showed enhancement of hardness comparable to that of pure silica glass. The anodic thermal poling condition was found so reactive that O₂ and N₂ species can be incorporated into the glass, which also alters the glass structure and mechanical properties. In the case of the anodic surfaces prepared in a humid environment, the glass showed an improved resistance against crack formation, which implies that abundant hydrous species incorporated during thermal poling could be beneficial to improve the toughness.     

Electric field-assisted ion exchange strengthening of borosilicate and soda lime silicate glass

In this study, we investigate the effects of electric field-assisted ion exchange (EF-IE) on potassium for sodium ion exchanges of soda borosilicate and soda lime silicate glasses. The results show that applying an electric field (E-field) with the intensity of 1000 V cm⁻¹ for few minutes produces an exchanged layer with a thickness comparable to the conventional chemical strengthening for 4 hours. There is a critical E-field that increases the mobility and, therefore, the diffusion coefficient of the potassium ions in the glasses. The increase is, perhaps, related to the evolution of the glass structure due to the penetration of potassium ions under an E-field. Vickers indentations showed that strong compression is generated in the glass by EF-IE; however, the bending strength improvement is limited because of the presence of large surface defects and the stress distribution inhomogeneity.     

Effects of fictive temperature on the leaching of soda lime silica glass surfaces

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.     

Direct additive manufacturing of TiCp reinforced Al2O3-ZrO2 eutectic functionally graded ceramics by laser directed energy deposition

Laser directed energy deposition (LDED) provides an ideal manufacturing technique to produce ceramic matrix composites, which are endows with superior and customizable mechanical properties by the reinforcement of gradient distribution of rigid particles. In this paper, we for the first time manufactured TiCp reinforced Al₂O₃-ZrO₂ eutectic functionally graded ceramics with two different transition modes using LDED. The results show that the gradient transition realizes gradually increase of TiCp particles in Al₂O₃-ZrO₂ eutectic matrix. With the increase of TiCp content, the morphology of Al₂O₃-ZrO₂ eutectic matrix changes from lamellar or rod-shaped to irregular shape. Meanwhile, LDED realizes controllable fabrication of properties in different positions of gradient materials, and the wear resistance of TiCp rich regions has increased by 43.4% compared with pure Al₂O₃-ZrO₂ region.     

Reduction of coal-water mixture consistency with soda ash and lime

The addition of soda ash and lime to improve the Theological properties of a 60 wt % bituminous coal-water mixture (CWM) was investigated. Soda ash and lime were used to precipitate calcium and magnesium cations naturally present in the aqueous phase of the CWM. Addition of the required amounts of soda ash and lime alone, based on analyses of the total Ca²⁺ and Mg²⁺ burdens in the CWM, using standard water softening technology as well as addition of soda ash and lime along with an ionic dispersant were studied. Significant reduction in consistency was measured following soda ash and lime addition alone, and marked reduction in consistency resulted when both soda ash and lime and dispersant were used. Additive costs to obtain a given degree of consistency reduction were lowered by factors ranging from 3 to 15 with soda ash and lime, either alone or in concert with an anionic dispersant, relative to the use of anionic dispersant alone.     

合理利用我国硅质原料节能节碱降低生产成本

通过对我国玻璃生产及硅质原料的使用情况分析,阐述合理利用资源,节能、节碱、降低生产成本.     

Aluminum‐enhanced alkali diffusion from float glass to PVD‐sputtered silica thin films

Interdiffusion processes between aluminum enriched PVD‐sputtered silica thin films and industrial float soda‐lime silicate glass substrates are quantitatively studied using SIMS analysis. Heat treatments are performed at temperatures close or above the glass transition temperature of the float glass. Aluminum doping of the film is shown to strongly increase the migration of alkali from the glass substrate to the silica thin film. In particular the final alkali content in the film exhibits a linear scaling with the aluminum concentration. An interdiffusion process is evidenced between bulk alkali ions and protons originating from a significant water content in the as‐deposited silica film. Experimental measurements of sodium concentration are shown to be consistent with a simple thermodynamic model based on the equilibration of the activity of sodium between the film and the glass substrate.     

钠钙玻璃熔窑应慎用全氧燃烧技术

通过对普通空气助燃熔窑和全氧燃烧熔窑的对比分析,指出在国内以火力发电为主的现状下,对熔化率高、熔化能耗低及产品产值不高的普通钠钙玻璃熔窑,采用全氧燃烧技术后不能节能,氮氧化物减排效果不明显,成本也有所提高,目前应慎重选用全氧燃烧技术;对于熔制质量要求高、熔化能耗较大及产品产值高的特种玻璃,采用全氧燃烧技术后节能和NOx减排明显,成本降低,经济效益和社会效益好,可考虑逐步推行全氧燃烧技术。     

烧碱生产系统能效水平对标初探

介绍了河北盛华化工有限公司开展生产系统能效水平对标活动的具体内容。通过现场对标、对标培训、成立对标组织机构、明确对标组织职责、制定对标工作计划、健全能源管理制度、完善计量手段、投入节能技改资金等一系列措施,使烧碱能效对标工作取得了良好的效果,烧碱生产各工序能耗均有不同程度下降,烧碱综合能耗明显降低,达到了对标标杆值。     

Direct additive manufacturing of melt growth Al2O3-ZrO2 functionally graded ceramics by laser directed energy deposition

Functionally graded ceramics (FGC), which combine properties of different ceramics in one part, usually have better comprehensive function and structural efficiency. In this study, four different gradient transition Al₂O₃-ZrO₂ FGC samples were prepared by laser directed energy deposition (LDED) method. The results show that there is an obvious interface in direct transition sample. The transition section bears tensile stress caused by difference of thermophysical properties of materials, resulting in significant longitudinal cracks. Element transition in interface region shows a step sharp transition. The direct transition sample shows intergranular fracture and the bonding strength is very low. Gradient transition mode can effectively suppress cracks, and avoid the step transition of microstructure and elements. Elements, microhardness of 25, 20 wt% FGC samples realized a nearly linear smooth transition. The interface fracture of FGC samples changed to transgranular fracture, bonding strength was significantly improved, and the maximum flexural strength reached 160.19 MPa.     

Effect and mechanism of ZrO2 doping on the cracking behavior of melt-grown Al2O3 ceramics prepared by directed laser deposition

Directed laser deposition (DLD) is a new method for rapidly preparing melt-grown ceramics, but cracking problem greatly limited its application. In this study, cracking behavior of Al₂O₃ ceramics was suppressed by doping ZrO₂. Crack suppression mechanism of ZrO₂ doping in melt-grown ceramics was also analyzed. Process parameters which are prone to generating cracks were adopted in the experiments, and they contribute to showing the crack clearly. Results show that ZrO₂ doping has remarkable crack suppression effects. It is most obvious when ZrO₂ content is 37 mol%. Compared with those of pure Al₂O₃ ceramics, crack density reduces by 43.2%, and the number of longitudinal main cracks reduces by 63.2%. Doping of ZrO₂ forms dense composite microstructure with primary α-Al₂O₃ grains discretely distributing in eutectic continuous matrix. Therefore, initial crack sources are effectively reduced. Morphology of primary Al₂O₃ grains transforms from cellular to dendritic, which changes crack propagation mode from inter-granular to trans-granular. Mismatch of thermo-physical properties of different phase promotes the arrest, deflection, and bridging phenomena in crack propagation, contributing to crack suppression. On the basis of ZrO₂ doping, we have realized the preparation of crack-free eutectic ceramic (37 mol%ZrO₂) samples through further process optimization. The maximum size of the sample reaches 230 mm.     

Molecular dynamics study on nano‐particles reinforced oxide glass

Energy release rate and fracture toughness of amorphous aluminum nanoparticles reinforced soda‐lime silica glass (SLSG) were measured by performing fracture simulations of a single‐notched specimen via molecular dynamics simulations. The simulation procedure was first applied to conventional oxide glasses and the accuracy was verified with comparing to experimental data. According to the fracture simulations on three models of SLSG/‐Al₂O₃ composite, it was found that the crack propagation in the composites is prevented through following remarkable phenomena; one is that a‐Al₂O₃ nanoparticles increase fracture surface area by disturbing crack propagation. The other is that the deformation of a‐Al₂O₃ nanoparticle dissipates energy through cracking. Moreover, one of the models shows us that the crack cannot propagate if the initial notch is generated inside a‐Al₂O₃ nanoparticle. Such strengthening is partly due to the fact that the strength of the interface between nanoparticle and SLSG matrix is comparable to that of SLSG matrix, implying that their interface does not reduce crack resistance of the oxide glass.     

石灰竖窑热平衡及节能技术改造

针对石灰竖窑运行中存在产量低、能耗高、操作环境恶劣、热效率过低等问题,对竖窑进行了全面的热平衡测试,找出影响竖窑热损失的主要原因,提出具体炉窑改造方案,并进行了竖窑的改造;通过改造前后的热平衡测试数据的对比,竖窑的热效率提高了4倍,单位成品热耗降为原来的1 6,成品率提高,节能效果显著。