Laboratory-Grown Diamond:A Gemological Laboratory Perspective

This article provides an overview of the laboratory-grown diamonds seen at GIA over the last 15 years.During that time,the diamond industry has witnessed an exponential increase in the quantity and quality of laboratory-grown diamonds and,therefore,these products’ability to be commercialized on a large scale.It presents a brief summary of the HPHT and CVD growth processes and then explores some of the major trends observed since GIA began providing synthetic diamond grading reports in 2007.These trends include the shift towards larger and colorless stones.It also shows a shift towards CVD diamonds dominating the supply of laboratory-grown diamonds submitted for grading reports and that the majority of these have been subjected to post-growth HPHT treatment.In addition,we briefly discuss some methods and strategies used for identification such as the distinguishing gemological characteristics and some recent approaches in advanced testing.Finally,we present an array of laboratory-grown diamonds that are currently unusual,however,these may become more common in the future.

Non-destructive Testing Method for Crack Based on Diamond Nitrogen-vacancy Color Center

Magnetic field measurement plays an extremely important role in material science,electronic en-gineering,power system and even industrial fields.In particular,magnetic field measurement provides a safe and reliable tool for industrial non-destructive testing.The sensitivity of magnetic field measurement deter-mines the highest level of detection.The diamond nitrogen-vacancy(NV)color center is a new type of quan-tum sensor developed in recent years.The external magnetic field will cause Zeeman splitting of the ground state energy level of the diamond NV color center.Optical detection magnetic resonance(ODMR),using a mi-crowave source and a lock-in amplifier to detect the resonant frequency of the NV color center,and finally the change of the resonant frequency can accurately calculate the size of the external magnetic field and the sensi-tivity of the external magnetic field change.In the experiment,a diamond containing a high concentration of NV color centers is coupled with an optical fiber to realize the preparation of a magnetic field scanning probe.Then,the surface cracks of the magnetized iron plate weld are scanned,and the scanning results are drawn into a two-dimensional magnetic force distribution map,according to the magnetic field gradient change of the magnetic force distribution map,the position and size of the crack can be judged very accurately,which pro-vides a very effective diagnostic tool for industrial safety.

An Emerging Testing Method for Metallics Based on NV Center in the Diamond

Metal substance detection plays an extremely important role in daily life,industrial manufacturing and even industrial security.The traditional methods include optical detection,X-ray detection,microwave detection and ultrasonic detection.These methods,playing a vital role in the field of non-destructive testing,can not only judge the presence or absence of metal,but also accurately detect the type and size of metal defects.For microwave detection,the detection efficiency of metal materials is limited by the response sensitivity of the detector to microwaves.In recent years,scientists have discovered a quantum sensing system based on the diamond nitrogen-vacancy(NV)color center.The system obtains optical detection magnetic resonance(ODMR)fluorescence spectra under the combined action of a 532nm laser and a certain frequency band of microwaves,and the signal contrast changes significantly with the microwave power.Based on the NV color center quantum sensing system,this paper studies its application in the field of metal detection,and takes steel detection as an example to detect the size of steel bars according to the changes in the spectral line,providing a new method for non-destructive testing such as metal substance detection.