A novel combustion process for the synthesis of fine particle α-alumina and related oxide materials

Synthesis of fine particle α-alumina and related oxide materials such as MgAl2O4, CaAl2O4, Y3Al5O12 (YAG), Image , β′-alumina, LaAlO3 and ruby powder (Image ) has been achieved at low temperatures (500°C) by the combustion of corresponding metal nitrate-urea mixtures. Solid combustion products have been identified by their characteristic X-ray diffraction patterns. The fine particle nature of α-alumina and related oxide materials has been investigated using SEM, TEM, particle size analysis and surface area measurements.

Complexes of Lanthanide Perchlorates with N-(2-Pyrimidyl)benzamide

New complexes of lanthanide perchlorates with N-(2-pyrimidyl)benzamide (BApymH) of the general formulae [Ln(BApymH)4](ClO4)3 (where Ln = La-Yb and Y) have been synthesised and characterised by chemical analysis, molar conductivity and physical methods such as infrared and electronic spectra in the visible region. Molar conductance and infrared data point to the ionic nature of the per-chlorate groups in the complexes. IR data unequivocally proves that the coordination of the ligand to the metal ion takes place in a bidentate fashion through the oxygen of the secondary amide and nitrogen of the pyrimidine ring. From a comparison of the visible electronic spectral shapes of the Nd3+ and Ho3+ complexes with those reported in the literature, an eight coordinate geometry around the metal ion has tentatively been assigned in all the complexes.

Infrared spectra of 1.3-dithiole-2-thione and its selenium analogues ând frequency assignment and molecular force constants

Infrared spectra of 1,3-dithiole-2-thione (DTT) and its four selenium analogues have been studied in the region 4000 to 20 cm�1. Assignment of all the fundamental frequencies was made by noting the band shifts on progressive selenation. Normal coordinate analysis procedures have been applied for both in-plane and out-of-plane vibrations to help the assignments. The Urey�Bradley force function supplemented with valence force constants for the out-of-plane vibrations was employed for coordinate calculations. A correlation of the infrared assignments of DTT with its different selenium analogues is accomplished. Further, the infrared assignments are compared with those of trithiocarbonate ion and its selenium analogues and other structurally related heterocyclic molecules.

Transient pulse evolution of active-mode locking in an intra-cavity frequency-doubled laser

The theory of transient mode locking for an active modulator in an intracavity frequency-doubled laser is presented. The theory is applied to mode-locked and intracavity frequency-doubled Nd:YAG laser and the mode-locked pulse width is plotted as a function of number of round trips inside the cavity. It is found that the pulse compression is faster and the system takes a very short time to approach the steady state in the presence of a second harmonic generating crystal inside the laser cavity. The effect of modulation depth and the second harmonic conversion efficiency on the temporal behavior of the pulse width is discussed.

Lanthanide perchlorate complexes of 4-cyano pyridine-N-oxide, 4-chloro 2-picoline-N-oxide and 4-dimethyl amino-2-picoline-N-oxide

Complexes of lanthanide perchlorates with 4-cyano pyridine-1-oxide, 4-chloro 2-picoline-1-oxide and 4-dimethyl-amino 2-picoline-1-oxide have been isolated for the first time and characterized by analysis, conductance, infrared, NMR and electronic spectra. The complexes of 4-cyano pyridine-1-oxides have the composition Ln(CyPO)6(ClO4)3. 2H2O (Ln=La, Sm, Dy and Ho); Ln(CyPO)7 (ClO4)3. 2H2O (Ln=Pr, Nd, Er and Yb); and Ln(CyPO)5 (ClO4)3. 2H2O (Ln=Gd and Tb). The complexes of 4-chloro 2-picoline-1-oxide analyse for the formulae Ln(CpicO)6 (ClO4)3 (Ln=La, Pr, Nd and Ho); and Ln (CpicO)5 (ClO4)3 (Ln=Er and Yb), and those of 4-dimethylamino 2-picoline-1-oxide for Ln(DMPicO)6 (ClO4)3 (Ln=La and Nd); Ln(DMPicO)7 (ClO4)3 (Ln=Gd, Er and Yb); and Ln(DMPicO)8 (ClO4)3 (Ln=Dy and Ho).

Growth and physical properties of a new chiral open-framework crystal for NLO applications: Cesium hydrogen l-malate monohydrate

Cesium hydrogen l-malate monohydrate, CsH(C4H4O5)·H2O, is a new chiral open-framework semi-organic crystalline material with a second-harmonic generation efficiency one order of magnitude greater than KDP. Single crystals of this new material have been grown by the conventional slow cooling technique from aqueous solution. Grown crystals display both platy and prismatic morphologies depending on the imposed supersaturation. Hardness values measured using Vickers hardness indenter show considerable anisotropy. The resistivity behavior at room temperature and above, places the crystal between an ionic conductor and a dielectric. The single-crystal SHG efficiency estimated through Maker fringes experiment gives deff which is 4.24 times that of KDP. Single and multiple shot experiments performed on the grown crystals for the fundamental and second harmonic of pulsed Nd:YAG laser (1064 and 532 nm) show that it exhibits a high laser damage threshold which is a favorable property for nonlinear optical applications.

Complexes of lanthanide iodides with 3-methylpyridine-1-oxide

Complexes of lanthanide iodides with 3-methylpyridine-1-oxide of the formula Ln(3-MePyO)8I3.xH2O where x = 0 for Ln = La and Tb, x = 1 for Ln = Pr, and x = 2 for Ln = Nd, Sm, Dy, Yb, and Y have been prepared and characterized by chemical analyses, conductance, infrared, proton nmr, and DTA data. Infrared and proton nmr data have been interpreted in terms of the coordination of the ligand to the metal ion through the oxygen of the N—O group. Proton nmr spectrum of the Yb(III) complex is indicative of a restricted rotation of the pyridine ring about the N—O bond.

Komplexe von Lanthanidnitraten mit 2-Methylpyridin-1-oxid

Complexes of lanthanide nitrates with 2-methylpyridine-1-oxide of the formuleLn(2-MePyO)3(NO3)3 whereLn=Nd, Sm, Tb, Dy and Yb and La(2-MePyO)3(NO3)3·2H2O have been prepared and characterized by chemical analyses, IR spectral, conductance andDTA data. IR spectral data have been interpreted in terms of the coordination of the ligand to the metal through the oxygen of the N–O group. Conductance and IR spectral data show that all the nitrate groups are bidentate and that two of the nitrate groups are bound to the metal in a different manner than the other.

Pyridine-1-oxide complexes of lanthanide iodides

Pyridine-1-oxide complexes of lanthanide iodides of the formulaLn(PyO)8I3 whereLn=La, Pr, Nd, Tb, Dy, Er, and Yb have been prepared and characterised by analyses, molecular weight, conductance, infrared and proton NMR data. Proton NMR and IR data have shown the coordination of the ligand to the metal through the oxygen atom of the N–O group. NMR data have been interpreted in terms of a distorted square antiprismatic geometry in solution.

3-Picoline-N-oxide complexes of rare-earth bromides

3-Picoline-N-oxide (3-PicNO) complexes of rare-earth bromides of the formulaMBr3(3-PicNO)8–n·nH2O wheren=0 forM=La, Pr, Nd, Sm Tb or Y andn=2 forM=Ho or Yb have been prepared. Infrared and proton NMR studies indicate that the coordination of the ligand is through oxygen. Conductance data in acetonitrile suggest that two bromide ions are coordinated to the metal ion. Proton NMR studies suggest a bicapped dodecahedral arrangement of the ligands around the metal ion in solution for Pr(III), Nd(III) and Tb(III) complexes.

Komplexe von 2,6-Dimethylpyridin-1-oxid mit Lanthanidjodiden

Complexes of 2,6-dimethylpyridine 1-oxide with lanthanide iodides of the formulaeLn(2,6-LTNO)5I3 whereLn=La, Tb and Yb,Ln(2,6-LTNO)4I3 whereLn=Pr and Nd and Er(2,6-LTNO)4.5I3 have been prepared and characterised by chemical analysis, infrared and conductance studies. Infrared and conductance data have been interpreted in terms of dimeric (or polymeric) structures involving bridging amine oxide groups.

4-Nitro and 4-chloro pyridine-N-oxide complexes of lanthanide perchlorates

Adducts of lanthanide perchlorates with 4-nitro and 4-chloro pyridine-Noxides (4-NPNO and 4-CPNO respectively) have been synthesised for the first time and characterised by analysis, electrolytic conductance, infrared, proton-NMR and electronic spectral data. The complexes are of the compositions Ln2(NPNO)15 (ClO4)6 (Ln = La, Pr, Nd and Gd), Tb(NPNO), (C1O4)6), Ln2(NPNO)13 (C1O4)6) (Ln = Dy, Ho, and Yb); Ln (CPNO)8 (C104)3) (Ln = La, Pr, Nd, Tb, Dy, Ho and Yb) and Ln(CPNO), (C1O4)3) (Ln = Sm and Gd). Conductivity and IR data provide evidence for the non-coordinated nature of the perchlorate groups. IR and NMR spectra suggest coordinationvia the oxygen of the N-oxide group. Electronic spectral shapes of the Nd+3 and Ho+3 complexes are interpreted in terms of eight-and seven-coordinate environments in the case of 4-NPNO complexes and eight-coordination in the case of 4-CPNO complexes. IR data indicate bridged structure in NPNO complexes of lanthanides other than Tb.

Implantation Induced Hardening of Nanocrystalline Titanium Thin Films

Formation of nanocrystalline TiN at low temperatures was demonstrated by combining Pulsed Laser Deposition (PLD) and ion implantation techniques. The Ti films of nominal thickness similar to 250 nm were deposited at a substrate temperature of 200 degrees C by ablating a high pure titanium target in UHV conditions using a nanosecond pulsed Nd:YAG laser operating at 1064 nm. These films were implanted with 100 keV N+ ions with fluence ranging from 1.0 x 10(16) ions/cm(2) to 1.0 x 10(17) ions/cm(2). The structural, compositional and morphological evolutions were tracked using Transmission Electron Microscopy (TEM), Secondary Ion Mass Spectrometry (SIMS) and Atomic Force Microscopy (AFM), respectively. TEM analysis revealed that the as-deposited titanium film is an fcc phase. With increasing ion fluence, its structure becomes amorphous phase before precipitation of nanocrystalline fcc TiN phase. Compositional depth profiles obtained from SIMS have shown the extent of nitrogen concentration gradient in the implantation zone. Both as-deposited and ion implanted films showed much higher hardness as compared to the bulk titanium. AFM studies revealed a gradual increase in surface roughness leading to surface patterning with increase in ion fluence.

Laser damage studies in nonlinear optical crystal sodium p-nitrophenolate dihydrate

We report the surface laser damage threshold in sodium p-nitrophenolate dihydrate, a nonlinear optical crystal. The experiment is performed with a pulsed Nd:YAG laser in TEM00 mode. The single shot damage thresholds are 11.16 +/- 0.28GWcm(-2) and 1.25 +/- 0.02GWcm(-2) for 1064 nm and 532 nm laser wavelengths respectively. A close correlation between the laser damage threshold and mechanical hardness is observed. A possible mechanism of laser damage is discussed.

Effect of laser surface treatment on microstructure and properties of MRI 230D Mg alloy

A creep resistant Mg alloy MRI 230D was subjected to laser surface treatment using Nd:YAG laser equipped with a fiber optics beam delivery system in argon atmosphere. The laser surface treatment produced a fine dendritic microstructure and this treatment was beneficial for the corrosion and wear resistance of the alloy. Long-term linear polarisation resistance and Electrochemical Impedance Spectroscopy measurements confirmed that the polarisation resistance values of laser treated material were twice as high as that for the untreated material. This improved behaviour was due to the finer and more homogenous microstructure of the laser treated surface. The laser treatment also increased surface hardness two times and reduced the wear rate by 25% due to grain refinement and solid solution strengthening.