HYDRIDE CRACKING IN ZIRCONIUM ALLOYS IS ONE OF THE MAJOR CAUSES OF FAILURE AND CONSIDERING THE IMPORTANCE OF THIS TYPE FAILURE WE HAVE REVIEWED THE SITUATION THAT MAKES ZIRCONIUM ALLOYS VULNERABLE TO CRACKING. THE RESULTS SHOW THAT MOST OF ATOMIC HYDROGEN IS PRODUCED IN NORMAL CORROSION PROCESS ALBEIT; ABSORPTION DEPENDS ON VARIOUS FACTORS. THE RECENT INVESTIGATIONS REVEALED THAT, RADIAL HYDRIDES ARE MORE DISASTROUS COMPARED TO CIRCUMFERENTIAL HYDRIDES.

IN THIS STUDY THE ELECTROCHEMICAL HYDRIDING IS USED FOR SYNTHESIS OF ZIRCONIUM HYDRIDE. THIS METHOD OVERCOMES MAJOR PROBLEMS OF CONVENTIONAL METHODS OF METAL HYDRIDE SYNTHESIS SUCH AS REQUIREMENT OF HIGH PRESSURE AND ELEVATED TEMPERATURE. ZIRCONIUM PLATE WAS APPLIED AS A CATHODE OF HYDROLYZES REACTION AND ATOMIC HYDROGEN PRODUCES BY THE ELECTROLYSIS OF A WATER SOLUTION THAT DIRECTLY DIFFUSES INTO THE CATHODE AND FORMS METAL HYDRIDE. THEN XRD ANALYSIS TOGETHER WITH THE SEM CHARACTERIZATION OF SURFACE CONFIRMS ZRH2 FORMATION ON THE ELECTRODE SURFACE.

A DIODE LASER BASED SYSTEM FOR DETECTION OF HYDRIDE FORMING ELEMENTS HAS BEEN DEVELOPED. THE SETUP USES A 405 NM DIODE LASER INITIALLY FOR DETECTION OF LEAD. THE WAVELENGTH WAS TUNED USING A LAB MADE TEMPERATURE CONTROLLER TO 405.78 NM AS THE OPTIMIZED WAVELENGTH. ...

SELENIUM AS A NONMETALLIC CHEMICAL ELEMENT, HAS RECEIVED HIGH ATTENTION OF BIOLOGISTS BECAUSE OF ITS DUAL ROLE AS AN ESSENTIAL TRACE NUTRIENT AND A TOXIC ELEMENT. THIS DUAL EFFECT HAS BEEN RECOGNIZED FOR MANY NATURALLY OCCURRING CHEMICAL DETERMINATIONS OF THESE ELEMENTS AT SUCH RANGES NEEDS A RELATIVE SENSITIVE TECHNIQUE WITH ENOUGH LOW DETECTION LIMIT. ATOMIC ABSORPTION SPECTROMETRY METHODS PROVIDE SIMPLE AND LOW COST TECHNIQUES FOR SUCH MEASUREMENTS. HOWEVER, THEIR DETECTION LIMITS IN SIMPLE INSTRUMENTATIONS LIES IN PPM RANGES. DIRECT SOLID SAMPLE SPECTROMETRY IS IMPORTANT BECAUSE IT DECREASES TIME CONSUMPTION FOR PREPARATION OF SAMPLE SOLUTIONS AND USE OF CONTAMINANTS REAGENTS LIKE ACIDS, FOR ANALYSIS OF SAMPLES.IN THE PRESENT WORK SELENIUM IS DETERMINED BY HYDRIDE GENERATION FLAME ATOMIC ABSORPTION SPECTROMETRY. SELENIUM AS A HEAVY METAL ELEMENT IS DETERMINED DIRECTLY BY ATOMIC ABSORPTION SPECTROMETRY IN SOLID SAMPLES. IN THIS METHOD SAMPLE DIGESTION AND PREPARATION STEPS ARE ELIMINATED. TO ACHIEVE THE BEST RESULTS, FIRST A SLOTTED QUARTZ TUBE IS FABRICATED AS AN ATOM TRAPPING DEVICE. THIS DEVICE IS THEN, EMPLOYED FOR DETERMINATION OF NANO AND MICROGRAM AMOUNTS OF SELENIUM IN SOLID SAMPLES. THE POWDER OF SOLID SAMPLES AND VISCOSE SOLUTIONS AFTER VAPORIZATION OF THEIR SOLVENTS CAN BE ANALYZED BY THIS METHOD DIRECTLY. RSD FOR 4 TIMES MEASUREMENT IS 5.44% AND LOD IS 5 PPM.

IN ORDER TO STUDY THE EFFECT OF HYDRIDE FORMATION ON THE CORROSION BEHAVIOR AND MECHANICAL PROPERTIES, THE DEVELOPMENT OF AN APPROPRIATE HYDROGEN CHARGING METHOD IS REQUIRED. IN THIS STUDY THE ELECTROCHEMICAL HYDRIDING IS USED FOR SYNTHESIS OF HYDRIDE PHASES ON THE SURFACE OF TITANIUM SAMPLE, AND THEN CONFIRMED BY XRD ANALYSIS.