Indentation size effect, indentation cracks and microhardness measurement of some brittle crystals are reviewed against the background of the existing concepts of indentation deformation of crystalline solids. Several approaches reported in the literature devoted to relationships between applied indentation test load P and indentation diagonal length d are applied to analyze the experimentally observed normal and reverse indentation size effect (ISE) in brittle compounds. Using typical examples of normal and reverse ISE it is shown that the indentation induced cracking model does not give load-independent hardness and the final expression describing the experimental data for various compounds is essentially another form of the Meyer law. Analysis of experiment data on crack lengths and indentation diagonals for different indentation loads suggests that the origin of ISE is associated with the processes of formation of indentation cracks following the general concepts of fracture mechanics. The load-independent hardness H0 may be determined reliably from plots of P /d against d of the proportional resistance model or of HV against 1/d as predicted by strain gradient plasticity theories. It was found that the load-independent hardness of depends on crystal orientation and state of the indented surface. Finally, some comments on determination of fracture toughness and brittle index of crystals are made. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Review: Indentation size effect, indentation cracks and microhardness measurement of brittle crystalline solids – some basic concepts and trends

Polyvinyl alcohol (PVA) nanocomposite films embedded with iron (Fe) nanoparticles were prepared via the solution cast technique. The effect of Fe nanoparticles on the structural and optical properties of PVA nanocomposite films were investigated using X-ray diffraction, a scanning electron microscope, and UV–Vis spectroscopy. The size of the Fe nanoparticles was calculated using the Debye–Scherrer equation, and it was found that there was an increase in nanoparticle size after dispersion in the polymer matrix due to aggregation. Optical parameters such as optical band gap, Urbach energy, refractive index and extinction coefficient were investigated. The transmittance of a pure PVA film decreases from 82% to 18% after 3 wt% Fe nanoparticle dispersion in a polymer matrix. The direct optical band gap was found to decrease whereas Urbach energy was found to increase with the increase in Fe nanoparticle concentration. In addition, the refractive index and extinction coefficient of polymer nanocomposite films were found to increase compared to those made of pure PVA. Also, the optical dielectric and optical conductivity were observed to increase with an increase in Fe nanoparticle concentration.

Effect of Fe nanoparticles on the structure and optical properties of polyvinyl alcohol nanocomposite films

Ensuring nuclear safety has become of great significance as nuclear power is playing an increasingly important role in supplying worldwide electricity. β-ray monitoring is a crucial method, but commercial organic scintillators for β-ray detection suffer from high temperature failure and irradiation damage. Here, we report a type of β-ray scintillator with good thermotolerance and irradiation hardness based on a two-dimensional halide perovskite. Comprehensive composition engineering and doping are carried out with the rationale elaborated. Consequently, effective β-ray scintillation is obtained, the scintillator shows satisfactory thermal quenching and high decomposition temperature, no functionality decay or hysteresis is observed after an accumulated radiation dose of 10 kGy (dose rate 0.67 kGy h-1). Besides, the two-dimensional halide perovskite β-ray scintillator also overcomes the notorious intrinsic water instability, and benefits from low-cost aqueous synthesis along with superior waterproofness, thus paving the way towards practical application.

/pdf/two-dimensional-halide-perovskite-as-b-ray-scintillator-for-2i7zm35kzh.pdf

Two-dimensional halide perovskite as β-ray scintillator for nuclear radiation monitoring

Good quality and optically transparent single crystals of pure and doped glycine phosphite (GPI) were grown by both solvent-evaporation and temperature-cooling techniques. Dopants were chosen in different categories, namely transition metals (Cr, Mn, Co, Ni, Zn, Mg, Cd), rare-earth metals (Ce, Nd, La), dyes (rhodamine B, malachite green, fluorescein) and an amino acid (l-proline). The concentration of dopants was chosen depending on the category of dopants and the quality of crystallization during the growth process. The crystalline perfection of the as-grown pure and doped GPI crystals was investigated by high-resolution X-ray diffraction at room temperature. A multicrystal X-ray diffractometer employing a well collimated and highly monochromated Mo Kα1 beam and set in the (+, −, −, +) configuration was employed. Most of the crystal specimens show excellent crystalline perfection. However, grain boundaries, low-angle tilt boundaries, and vacancy and interstitial point defects were observed in some crystal specimens.

/pdf/study-of-the-influence-of-dopants-on-the-crystalline-usxaox4meq.pdf

Study of the influence of dopants on the crystalline perfection of ferroelectric glycine phosphite single crystals using high-resolution X-ray diffraction analysis

Growth, spectral and optical characterization of a novel nonlinear optical organic material: d-Alanine dl-Mandelic acid single crystal

Crystal structure and characterization of a novel organic optical crystal: 2-Aminopyridinium trichloroacetate

https://cdn.intechopen.com/pdfs/42259/InTech-Studies_on_growth_crystal_structure_and_characterization_of_novel_organic_nicotinium_trifluoroacetate_single_crystals.pdf

Studies on growth, crystal structure and characterization of novel organic nicotinium trifluoroacetate single crystals

Growth and characterization of nonlinear optical γ-glycine single crystal from lithium acetate as solvent

Benzil single crystals have been grown by the modified vertical Bridgman technique using the double wall ampoule with nanotranslation for the first time. The characterization studies of benzil crystals grown by both single and double wall ampoules were analyzed. The grown benzil crystal was confirmed by single crystal and powder X-ray diffraction analyses. Fourier transform infrared analysis confirms the functional groups of the grown benzil. High resolution X-ray diffraction analysis indicates the crystalline perfection of the grown crystals. The UV-Vis-NIR studies show that the grown benzil crystals cutoff wavelength is around 434 nm. The green emission of the grown benzil was identified by photoluminescence studies. The thermal property of the grown benzil was studied by thermogravimetric and differential thermal analyses. The dielectric measurements of benzil crystals were carried out with different frequencies and temperatures and the results indicate an increase in dielectric and conductivity parameters with the increase of temperature at all frequencies. The second harmonic conversion efficiency of the grown benzil was determined.

/pdf/growth-and-characterization-of-benzil-single-crystals-using-ftmcdzgsz2.pdf

Growth and characterization of benzil single crystals using nanotranslation by the modified vertical Bridgman technique

https://cdn.intechopen.com/pdfs-wm/26410.pdf

P.V. Dhanaraj

Papers

Crystal structure and characterization of a novel organic optical crystal: 2-Aminopyridinium trichloroacetate

Studies on growth, crystal structure and characterization of novel organic nicotinium trifluoroacetate single crystals

Growth and characterization of nonlinear optical γ-glycine single crystal from lithium acetate as solvent

Growth and characterization of benzil single crystals using nanotranslation by the modified vertical Bridgman technique

Effect of amino acid additives on crystal growth parameters and properties of ammonium dihydrogen orthophosphate crystals