Microtopographical studies of prism faces of potassium dihydrogen phosphate crystals

Surface structures on prism faces of potassium dihydrogen phosphate crystals grown from aqueous solutions and also by gel method are described and illustrated. Density of growth centres increases as the supersaturation of the mother liquor is increased. Gel grown crystals predominantly show rectangular growth hillocks on their prism faces. In the needle shaped crystals further nucleation extends predominantly along theC axis than at right angles to it. Influence of misoriented guest microcrystals on the growth of the prism faces is described.     

大口径氘化磷酸二氢钾晶体离线亚纳秒激光预处理技术

大口径氘化磷酸二氢钾(DKDP)晶体抗激光损伤性能偏低严重地制约着大型高功率激光装置输出水平.本研究利用离线亚纳秒激光预处理技术有效地提升了大口径DKDP晶体抗激光损伤性能.实际使用情况表明,采用离线亚纳秒激光预处理后,DKDP晶体在9 J/cm2激光通量辐照下的表面平均损伤密度得到大幅下降,由未处理前的5.02 pp...     

Multiwavelength investigation of laser-damage performance in potassium dihydrogen phosphate after laser annealing

The laser-induced damage performance of potassium dihydrogen phosphate and deuterated potassium dihydrogen phosphate nonlinear optical crystals after pre-exposure to lower-energy laser pulses (laser annealing, also known as laser conditioning) is investigated as a function of wavelength for both the damaging and conditioning pulses. We obtain a quantitative evaluation of the bulk damage performance of these materials by measuring the density of damage events as a function of laser parameters. This new method allows for a detailed assessment of the improvement of material performance from laser conditioning and reveals the key parameters for optimizing performance depending on the operational wavelength.     

Formation energies and electronic structures of native point defects in potassium dihydrogen phosphate

The formation energies and the equilibrium concentration of vacancies,interstitial H,K,P,O and antisite structural defects with P and K in KH 2 PO 4 (KDP) crystals are investigated by ab initio total-energy calculations.The formation energy of interstitial H is calculated to be about 2.06 eV and we suggest that it may be the dominant defect in KDP crystal.The formation energy of an O vacancy (5.25 eV) is much higher than that of interstitial O (0.60 eV).Optical absorption centres can be induced by defects of O vacancies,interstitial O and interstitial H.We suggest that these defects may be responsible for the lowering of the damage threshold of the KDP.A K vacancy defect may increase the ionic conductivity and therefore the laser-induced damage threshold decreases.     

Investigation of laser annealing parameters for optimal laser-damage performance in deuterated potassium dihydrogen phosphate

Laser annealing via preexposure to laser pulses at sub-damage-threshold fluences is known to improve the resistance of KDP crystals to laser-induced damage. Using a specific damage-testing method, we investigate the laser annealing process as a function of fluence and number of preexposure pulses (at 355 nm, 2.5 ns). Our aim is to reveal the key laser parameters in order to devise a practical and efficient protocol for optimizing performance of the material for operation in laser systems in the near UV. Results suggest that a near twofold improvement to the laser-damage performance can be achieved with a limited number of preexposure pulses.     

Effect of irradiation distance on degradation of phenol using indirect ultrasonic irradiation method

Ultrasound is used as degradation of hazardous organic compounds. In this study, indirect ultrasonic irradiation method was applied to the degradation process of phenol, the model hazardous organic compound, and the effects of irradiation distance on radical generation and ultrasonic power were investigated. The chemical effect estimated by KI oxidation dosimetry and ultrasonic power measured by calorimetry fluctuated for the irradiation distance, and there was a relationship between the period of the fluctuation of ultrasonic effect and the wavelength of ultrasound. The degradation of phenol was considered to progress in the zero-order kinetics, before the decomposition conversion was less than 25%. Therefore, the simple kinetic model on degradation of phenol was proposed, and there was a linear relation in the degradation rate constant of phenol and the ultrasonic power inside the reactor. In addition, the kinetic model proposed in this study was applied to the former study. There was a linear relation in the degradation rate constant of phenol and ultrasonic energy in the range of frequency of 20-30 kHz in spite of the difference of equipment and sample volume. On the other hand, the degradation rate constant in the range of frequency of 200-800 kHz was much larger than that of 20-30 kHz in the same ultrasonic energy, and this behaviour was agreed with the former investigation about the dependence of ultrasonic frequency on chemical effect.     

Synthesis of dinitrochalcones by using ultrasonic irradiation in the presence of potassium carbonate

The synthesis of dinitrochalcones was studied by using ultrasonic irradiation in the presence of potassium carbonate as a catalyst, which provided a conventional procedure with the advantages of a short reaction period and as high as 90% product yield.     

Effect of compatibilizers on the crystallization kinetics of cellulose-filled high density polyethylene

High density polyethylene (HDPE) is a ubiquitous material with versatile properties. It is produced and used in greater volume than any other thermoplastic. HDPE is often filled with a variety of materials for various applications. Glass fiber and wood flour are two common fillers for HDPE. This study investigated microcrystalline cellulose (MCC) as a filler in HDPE. The use of compatibilizers, or coupling agents, was investigated as a means of improving the dispersion of the cellulose filler in the HDPE matrix and the mechanical properties of the resulting composites. One compatibilizer was shown to improve the strength of the resulting composite. The stiffness was unaffected, as expected. Thermal properties were measured by means of differential scanning calorimetry. Analysis of the crystallization kinetics indicated that the Avrami coefficient was altered by the filler and was also modified by the presence of the compatibilizer. The presence of cellulose and/or compatibilizer increased the matrix degree of crystallinity. The two compatibilizers studied did not behave similarly and may have different mechanisms of compatibilization.     

Electric field effect on crystallization kinetics

The effect of a dc electric field on the kinetics of dielectric crystallization is considered. It is shown that the electric field has a significant effect on the rate of nucleation, the linear rate of crystallization, and the time for complete crystallization of a given volume of mother liquor, and also leads to structural changes in the crystallizing solid phase.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 63–67, February, 1979.     

Phase matching characteristics of deuterated ammonium dihydrogen phosphate crystals

Refractive indices for crystals ammonium dihydrogen phosphate(ADP), 30% deuterated ADP(DADP), 50%DADP, and 70% DADP are measured from 253 to 1529 nm with 5 × 10-6accuracy. Numerical fits to modified double-pole Sellmeier equation are made. Second-harmonic generation, third-harmonic generation phase matching(PM) angles, and noncritical PM(NCPM) wavelengths are calculated using the Sellmeier parameters. The deuterated crystals show smaller PM angles than pure crystal. Fourth-harmonic generation process can be realized by DADP in smaller deuterium content than deuterated potassium dihydrogen phosphate(DKDP).The measured NCPM wavelengths are consistent with the calculated value. PM characteristics are compared between DADP and DKDP.     

Effect of operational parameters on degradation of Malachite Green by ultrasonic irradiation

The aim of the present study was to apply ultrasonic technique to remove Malachite Oxalate Green (MG) from aqueous solution. An ultrasonic bath with frequency of 35 kHz was used to investigate the effect of different operational parameters such as MG concentration, power density, temperature, mechanical agitation and addition of EtOH, 2-PrOH and iso-BuOH. Decolorization of MG follows a first order kinetics and hydroxyl radicals have an important role in degradation of MG. The apparent reaction rate constant (k(ap)) was influenced by variation of operational parameters. The activation energy was 30.95 kJ/mol in temperature range of 21-34 degrees C, suggesting a diffusion-controlled reaction. Alcohols act as hydroxyl radicals scavengers having undesirable contribution. UV-vis spectral change of MG showed hypsochromic shift occurred with increasing sonication time, proposing N-demethylation process of MG.     

Influence of shear on polypropylene crystallization kinetics

Isothermal crystallization kinetics under shear in the melt of iPP was investigated by optical microscopy. It appears that shearing from 200 to the crystallization temperatures enhanced the kinetics, but the shear effect was not obvious if the melt of iPP was sheared only at 200. The experiment results show that relaxation plays an important role during crystallization, and that spherulite growth rates increased with shear rates and were governed by relaxation. The effect of flow on the crystallization kinetics can be understood by considering that the increase of the degree of order due to flow results is an effective change of the melt free energy. The Laurizen-Hoffman theory and the DE-IAA model were used to describe the shear-induced crystallization kinetics of iPP excellently.Received: 30 August 2004, Published online: 19 October 2004PACS: 61.41. + e Polymers, elastomers, and plastics - 61.50.-f Crystalline state - 64.70.-p Specific phase transitions     

Bilinear optical susceptibilities of potassium dihydrogen phosphate and of III–V,II–VI and I–VII semiconductors

The approximate orbital-approach of Jha and Bloembergen is used to calculate the non-dispersive part of the bilinear optical susceptibility,χ ⁽²⁾, for various compounds. Using bonding and antibonding states of the molecular orbital theory it is shown thatχ ⁽²⁾ satisfies a simple relation in terms of other measurable physical quantities. This relation is used to calculateχ ⁽²⁾ for various III–V, II–VI and I–VII semiconductors, both with cubic zinc blende structure and with hexagonal wurtzite structure. The same procedure is used to obtainχ ⁽²⁾ for potassium dihydrogen phosphate (KDP). The calculated values are compared with the experimentally observed values and it is found that the present model gives excellent results for II–VI compounds and for KDP.     

Effect of gamma-ray irradiation on isothermal crystallization of biodegradable poly(ethylene succinate)

The effects of gamma-ray irradiation on the isothermal crystallization of biodegradable poly(ethylene succinate) (PESu) and the growth behavior of PESu spherulites have been studied by differential scanning calorimetry and polarized optical microscopy. The irradiation doses used in the study are 0, 200, 400, and 600 kGy. The kinetic parameters for the isothermal crystallization have been determined, using the Avrami relationship. The nucleation constants and activation energy for the growth of the PESu spherulites have been analyzed, using the Lauritzen-Hoffman growth theory. Triple melting points have been observed for all the irradiated PESu. The gamma irradiation has no observable effect on the Avrami exponent, and the composite rate constant increases first with the increase of the crystallization temperature, reaches maximum at the crystallization temperature of ~35 °C, and then decreases with the increase of the crystallization temperature for both the non-irradiated and irradiated PESu. There exists a transition of the growth of the PESu spherulites from regime II to regime III. Both the nucleation constants and activation energy increase with increasing the irradiation dose. The gamma irradiation increases the energy barrier for the migration of polymer chains.     

Effect of condensation conditions on the kinetics of crystallization of films during isothermal annealing

A study was made of processes involved in the nucleation of Me-Ge films (Me: Ni, Co, Fe) containing 30 at. % transition metal. Conditions which affect the activation energy of the crystallization process and the structural state of the crystallized films were examined. It is established that crystallization energies are somewhat lower for condensation in an electric field than the energies for films deposited under normal conditions.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 52–55, November, 1990.     

Effect of coal ash on hydrazine degradation under stirring and ultrasonic irradiation conditions

The degradation of hydrazine (N(2)H(4)) with concentrations of 0.1-5.0 mmol/L was investigated as a function of amount of coal ash (0.0-5.0 wt%) under the stirring (300 rpm) and ultrasonic irradiation (200 kHz, 200 W) conditions. It was found that the rate of decrease in the hydrazine concentration depended upon an amount of coal ash under the stirring and ultrasonic irradiation condition. It was considered under the stirring condition that hydrazine was adsorbed and degraded partly on coal ash. Furthermore, the sonochemically formed OH radicals were more effective in the hydrazine degradation than stirring condition in the presence of an intermediate amount of coal ash (0.6-2.4 wt%), whereas the effect of OH radicals disappeared in the presence of coal ash more than 2.4 wt%.     

超声对硫酸钙结晶过程影响的研究

研究了超声对硫酸钙结晶过程的影响。实验表明，与对比样相比，超声可以明显缩短成核时间，改变结晶量，影响结晶在不同方向的成长速度，使结晶的形状比例(长／宽)减小。粒度分布的定量测定和计算显示，超声使硫酸钙结晶粒度分布范围由200μm缩小到100μm，体积平均直径从69．9μm降到26．59μm；硫酸钙的成核速率提高2．74倍，但结晶成长速率减少到对比样的40．9％。两者番加的结果体现为结晶过程总速率的增加。     

Effect of gamma ray irradiation on optical properties of Nd doped phosphate glass

The effect of gamma irradiation in the dose range of 5-500 kGy on the optical absorption and luminescence spectra of Nd doped phosphate glass is reported. The spectral absorption of this glass before and after gamma irradiation was measured in the spectral range 300-900 nm at room temperature using spectrophotometer and synchrotron beamline. Drastic increase in absorption was noted below 600 nm after gamma irradiation, which was dependent on the dose of irradiation. Additional absorption (AA) spectra of irradiated sample shows generation of two absorption bands below 600 nm, which finally became one very broad band peak with increased intensity at irradiation dose of 500 kGy. AA spectra also show the presence of negative peaks at the location of absorption peaks of Nd³⁺. Photoluminescence of Nd doped phosphate glass shows two strong bands which decreases to a very low intensity with a red shift after gamma irradiation. These results indicate that irradiation produces different kinds of defects in the glass material along with conversion of valence state of Nd³⁺ to Nd²⁺. This change was found irreversible at room temperature.     

Effect of ultrasound on the dissolution kinetics of phosphate rock in HNO3

Ultrasound is known to enhance solid/liquid reactions. This paper deals with the investigation of the dissolution of phosphate rock in nitric acid, in the absence and presence of ultrasound. The reaction is first-order with respect to H⁺ and activation energy equal to 16 kJ/mol in both cases. The effect of ultrasound is on the pre-exponential factor A. An empirical relation is given, which relates rate constant to ultrasound power.