Narrow Results

In order to study the protection behavior of brittle materials against a shaped charge jet, the jet penetration and the fracture behavior have been investigated by the series of photographs taken by the IMACON high speed camera. The examined materials were glass, fused silica, and single crystalline quartz. The trend of crack growth in BK7 glass and fused silica indicated conical shape. In the case of the single crystalline quartz, it was observed that the crack grows fast along the axis of crystal growth. The velocity of shock wave (~ 6km/sec) into glass and fused silica was faster than the sonic velocity. However, the velocity of shock wave in the single crystalline quartz showed to be similar to its sonic velocity. The ballistic protection capability of single crystalline quartz showing fast crack growth has been evaluated to be lower than that of fused silica which has relatively slow crack growth, although the quartz has higher physical and mechanical properties.

Tilt angle (order parameter) and the susceptibility are calculated as a function of temperature for the $\alpha$–$\beta$ transition in quartz using a Landau phenomenological model. The tilt angle as obtained from the model is fitted to the experimental data from the literature and the temperature dependence of the tilt angle susceptibility is predicted close to the $\alpha$–$\beta$ transition in quartz. Our results show that the mean field model explains the observed behavior of the $\alpha$–$\beta$ phase transition in quartz adequately and it can be applied to some related materials.

The main objective of this research is the explanation of the replacement of feldspar limestone imported from Spain with recycled automotive glass, in order to reduce waste and promote environmental sustainability. Details and efforts of making porcelain ceramics from local raw materials such as quartz, kaolin and glass are also given. Replacing the feldspar with reclaimed automotive glass shows the effect of the Na₂O and CaO solvents contained in the glass on the sintering and crystallization of the studied porcelain. The results showed that the added glass contributes to the reduction of the density and the acceleration of the sintering process, by occupying the sites of the open spaces, observed in the samples not containing feldspars. By reaching a nonporous ratio at a temperature of 1000^∘C, the melting of the material is accelerated due to the dissolved oxides it contains, in addition to the linear shrinkage rate in samples that contain a lot of glass reaching the normal level of porcelain (about 12%) at low temperature compared to ordinary porcelain.

Machining of hard and brittle materials such as engineering ceramics, glass, and silicon is a formidable task. Unlike cutting processes employing plasma and lasers, better machining capabilities of abrasive jet machining are characterized by thermally damaged free surface which is highly competitive as well as important for survival of materials in service. In this paper, an attempt has been made to combine hot abrasives and compressed air to form a hot abrasive air jet. This study aims to analyze the cutting performance in hot-abrasive jet machining (HAJM) of hardstone quartz concerning surface roughness, taper angle (TA), and material removal rate (MRR). Combined approach of Box–Behnken design — analysis of variance, response surface methodology, and statistical technique (here desirability function approach), followed by computational approach (here genetic algorithm), is, respectively, employed for experimental investigation, predictive modeling, and multi-response optimization. Thereafter, the effectiveness of proposed two multi-objective optimization techniques is evaluated by confirmation test and subsequently, the best optimal solution (i.e. at air pressure of 7kgf/cm², abrasive temperature of $64^{\circ }$C, stand-off distance of 4 mm) is used for economic analysis. Result shows that the most significant parameter is abrasive temperature for surface roughness, whereas it is pressure in case of both TA and MRR. Applications of hot abrasives in AJM process have shown attention in enhancing the cutting performance for material removal. Due to lower percentage contribution of error (6.68% to Rz, 9.89% to TA, and 6.42% in case of MRR), a higher correlation coefficient ($R^2$) was obtained with the quadratic regression model, which showed values of 0.92, 0.9, and 0.93 for surface roughness, TA, and MRR, respectively.

The goal of this paper is to improve the technical level of preparing composite photocatalysts with SiO₂-supported nano-TiO₂, expand the selection range of SiO₂ carriers, reduce expenses and understand the influence of SiO₂ crystallization behavior. Natural quartz (Q/SiO₂) powder was used as a carrier to prepare a Q/SiO₂-TiO₂ composite photocatalyst by hydrolyzing a butyl titanate solution and performing high-temperature calcination of the hydrolysate. The performance, morphology, structure and mechanism were tested and characterized. In addition, the as-prepared photocatalyst was compared with other amorphous SiO₂ carrier composite photocatalysts. The results showed that the Q/SiO₂ surface of Q/SiO₂-TiO₂ contained a uniform load of TiO₂ with a 26.98% proportion. Anatase-type TiO₂ was mainly present, and the size was 5–10nm. Moreover, Q/SiO₂ and TiO₂ were firmly combined in the form of Si–O–Ti bonds between the interfaces. The degradation rate of Q/SiO₂-TiO₂ to methyl orange solution was 99.59% under UV irradiation for 60min, which was equivalent to that of pure nano-TiO₂. The degradation performance remained stable after four cycles. Compared with other amorphous SiO₂ carriers, Q/SiO₂ exhibited a higher load of TiO₂. Furthermore, Q/SiO₂ played a more significant role in inhibiting the phase transition of TiO₂ to rutile and improving the photocatalytic performance.

Some people think that carbon and sustainable development are not compatible. This textbook shows that carbon dioxide (CO₂) from the air and bio-carbon from biomass are our best allies in the energy transition, towards greater sustainability. We pose the problem of the decarbonation (or decarbonization) of our economy by looking at ways to reduce our dependence on fossil carbon (coal, petroleum, natural gas, bitumen, carbonaceous shales, lignite, peat). The urgent goal is to curb the exponential increase in the concentration of carbon dioxide in the atmosphere and hydrosphere (Figures 1.1 and 1.2) that is directly related to our consumption of fossil carbon for our energy and materials The goal of the Paris agreement (United Nations COP 21, Dec. 12, 2015) of limiting the temperature increase to 1.5 degrees (compared to the pre-industrial era, before 1800) is becoming increasingly unattainable (Intergovermental Panel on Climate Change (IPCC), report of Aug. 6, 2021). On Aug. 9, 2021 Boris Johnson, prime minister of the United Kingdom, declared that coal needs to be consigned to history to limit global warming. CO₂ has an important social cost…

The chirality (of Greek χείρ, ch[e]ir: hand) is a fundamental symmetry property of three-dimensional objects. Your two hands are not superimposable. They are mirror images of each other. They are therefore chiral (Figure 10.1). The chirality of your right hand can be seen by trying to put it in a glove for your left hand. The same can be seen by trying to put your left hand into a glove for your right hand. The same experience can be done while putting on shoes. Normally you are not comfortable after exchanging the shoe for the left foot with the one for the right foot…