Size Dependence of the Tetragonal to Orthorhombic Phase Transition of Ammonia Borane in Nanoconfinement.

We have investigated the thermodynamic property modification of ammonia borane via nanoconfinement. Two different mesoporous silica scaffolds, SBA-15 and MCM-41, were used to confine ammonia borane. Using in situ Raman spectroscopy, we examined how pore size influences the phase transition temperature from tetragonal () to orthorhombic () for ammonia borane.

The corrosion behavior of borosilicate glass in the presence of cementitious waste forms.

Borosilicate glasses are widely used for radioactive waste disposal due to their ability to incorporate a variety of contaminants and radionuclides while exhibiting high durability in various disposal scenarios. This research evaluated the dissolution of borosilicate glass using both single-pass-flow-through (ASTM C1662-18) and product consistency test (ASTM C1285-21) methods with different solutions, including a cementitious-contacted water (called grout-contacted, GC, from this point) and solutions with varying levels of dissolved cementitious species such as Si, Ca, Al. The results indicated that the presence of Ca plays a crucial role in suppressing glass corrosion, as evidenced by the slower normalized dissolution rates, which were one order of magnitude lower for boron and two orders of magnitude lower for rhenium, observed in both Ca-amended and GC solutions compared to the pH 12 buffer solution.

High-pressure high-temperature synthesis of NdRe.

In this study, we report the synthesis of a new cubic neodymium-rhenium metallic alloy NdRe through the utilization of high pressure and laser heating in a diamond anvil cell. NdRe crystallizes in the space group with a lattice parameter equal to 7.486 (2) Å and Z = 8 at 24 (1) GPa and 2,200 (100) K.

The synthesis of novel lanthanum hydroxyborate at extreme conditions.

The novel structure of lanthanum hydroxyborate LaBO(OH) was synthesized by the reaction of partially hydrolyzed lanthanum and boron oxide in a diamond anvil cell under high-pressure/high-temperature (HPHT) conditions of 30 GPa and ∼2,400 K. The single-crystal X-ray structure determination of the lanthanum hydroxyborate revealed: , = 6.555(2) Å, = 17.

Characterization of Nanodiamond-based anti-HIV drug Delivery to the Brain.

Human Immunodeficiency Virus Type 1 (HIV-1) remains one of the leading causes of death worldwide. Present combination antiretroviral therapy has substantially improved HIV-1 related pathology. However, delivery of therapeutic agents to the HIV reservoir organ like Central nervous system (CNS) remains a major challenge primarily due to the ineffective transmigration of drugs through Blood Brain Barrier (BBB).

Pressure-induced shear and interlayer expansion in TiC MXene in the presence of water.

Pseudo-negative compressibility in layered materials is a phenomenon typically limited to in situ high-pressure experiments in some clay minerals and carbon-based materials. We show that the MXene TiCT expands along its crystallographic direction when compressed in the presence of HO. This expansive effect occurs when a mixture of powders and excess water is quasi-hydrostatically compressed in a diamond anvil cell; it also occurs to a much larger extent when powders are pressed uniaxially into discs and, notably, persists after pressure is released.

Ammonia as a case study for the spontaneous ionization of a simple hydrogen-bonded compound.

Modern ab initio calculations predict ionic and superionic states in highly compressed water and ammonia. The prediction apparently contradicts state-of-the-art experimentally established phase diagrams overwhelmingly dominated by molecular phases. Here we present experimental evidence that the threshold pressure of ~120 GPa induces in molecular ammonia the process of autoionization to yet experimentally unknown ionic compound--ammonium amide.

An extended high pressure-temperature phase diagram of NaBH4.

We have studied the structural stability of NaBH(4) under pressures up to 17 GPa and temperatures up to 673 K in a diamond anvil cell and formed an extended high P-T phase diagram using combined synchrotron x-ray diffraction and Raman spectroscopy. Even though few reports on phase diagram of NaBH(4) are found in current literature, up to our knowledge this is the first experimental work using diamond anvil cell in a wide pressure/temperature range. Bulk modulus, its temperature dependence, and thermal expansion coefficient for the ambient cubic phase of NaBH(4) are found to be 18.

Raman spectroscopy study of ammonia borane at high pressure.

Ammonia borane, NH(3)BH(3), has attracted significant interest as a promising candidate material for hydrogen storage. The effect of pressure on the bonding in NH(3)BH(3) was investigated using Raman spectroscopy to over 20 GPa in a diamond anvil cell, and two new transitions were observed at approximately 5 and 12 GPa. Vibrational frequencies for the modes of the NH(3) proton donor group exhibited negative pressure dependence, which is consistent with the behavior of conventional hydrogen bonds, while the vibrational frequencies of the BH(3) proton acceptor group showed positive pressure dependence.